TWI881051B - Glass material for molding - Google Patents

Abstract

The present invention provides a glass material for molding that has excellent stability during reheating. The glass material for molding of the present invention has a maximum linear expansion coefficient α _max and a total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass %, satisfying the following formula (1): α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ··· (1)

Description

Glass material for molding

The present invention relates to a glass material for molding.

Optical glass not only has specific optical constants such as refractive index and Abbe value, but also has characteristics such as high light transmittance and homogeneity of optical properties. It is different from the commonly known silicate glass such as window glass and can glass.

In recent years, in response to the high-precision imaging equipment, the demand for higher performance of imaging equipment has also increased, and the demand for low-profile optical components has also increased. Therefore, optical glass with a high refractive index and excellent stability is expected.

Here, the manufacturing method of optical glass includes, for example, a reheating press method, a round rod molding method, an extrusion molding method, etc. In such manufacturing methods, when a silicate optical glass is introduced _with a large amount of _Nb2O5 , _TiO2 , or _{La2O3 ,} which are components that improve optical properties, the stability of the glass is easily reduced, and in particular, crystallization is easily carried out when reheating.

It is known that a molten inorganic compound that is easily crystallized can be vitrified by rapid cooling. Therefore, the inorganic glass to which the present invention is directed is prepared by cooling a molten inorganic compound at a faster rate than the rate at which crystallization proceeds, thereby maintaining/freezing the disordered atomic configuration of the molten state even at room temperature.

However, optical glass that does not absorb visible light at least has low thermal conductivity even in the molten state, so the cooling rate of the entire glass decreases as the glass thickness increases, and the rapid cooling effect is limited. For example, as shown in Non-Patent Document 1, if a 0.5mm thick molten glass is pressed using a metal plate, even if a cooling rate of 10 ² ~10 ³ ℃/sec can be obtained, the cooling rate of a 5mm thick molten glass when pressed using a metal plate remains at 10~20℃/sec. For this reason, the glass obtained by rapid cooling is a "thin sheet" as shown in Non-Patent Document 2.

Furthermore, the thickness of glass used for forming optical elements is about 10 mm, and 30 mm or 40 mm thick glass is produced by continuous melting. However, if there are crystals inside the glass, it will cause light scattering, so this kind of glass cannot be used as an optical element. Even if the surface of glass with such a thickness is quenched to obtain glass, the inside of the glass is not sufficiently quenched, which will cause crystals to appear inside the glass. In addition, if the cooling conditions are too strong to avoid such crystallization inside the glass, the surface of the glass will solidify before the inside of the glass, resulting in problems such as cracking or glass breakage.

In this way, when manufacturing glass with a certain thickness, the situation where it can be vitrified without crystallization by ordinary rapid cooling operation is limited to the vicinity of the surface. In addition, even if the glass that has already crystallized inside is reheated, the crystallization tendency will not disappear, and the possibility of vitrification again during molding is quite high. Therefore, the glass material obtained in this way cannot obtain the required shape even if it is heated and softened, and cannot be used as optical glass used in the general industry.

On the other hand, Patent Document 1 discloses a prior art that proposes cooling conditions different from ordinary cooling conditions for optical glass. That is, it discloses that for silicate-based glass containing a large amount of _TiO2 , the molten glass is cooled to room temperature, and then annealed at a temperature lower than the glass transition temperature Tg to remove strain, thereby obtaining a glass material that can suppress the formation of crystals when reheated.

However, the optical glass obtained from the glass material of Patent Document 1 cannot meet the requirements for optical design in recent years, such as low light transmittance in the short-wavelength region of visible light (especially blue light) and large partial dispersion ratio Pg,F value. [Prior Technical Document] [Patent Document]

[Patent document 1] Japanese Patent Publication No. 2003-192384 [Non-patent document]

[Non-patent document 1] Tsukio Sakuha, "Glass Amorphous Science" (1983) p.23 [Non-patent document 2] New Glass Forum (company) "New Glass Basics Lecture" (1983) p.2-6

[The problem that the invention wants to solve]

This invention was made in view of this reality, and its purpose is to provide a glass material for molding that has excellent stability when reheated. [Means for solving the problem]

The gist of the present invention is as follows. [1] A glass material for molding, wherein the maximum linear expansion coefficient α _max and the total content of SiO ₂ and ZrO ₂ expressed in mass % [SiO ₂ +ZrO ₂ ] satisfy the following formula (1): α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ... (1)

[2] A glass material for molding, wherein the maximum linear expansion coefficient α _max , the average linear expansion coefficient α _100-300 at 100-300°C, and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % satisfy the following formula (4): α _max /α _100-300 × [SiO ₂ +ZrO ₂ ] ≦ 264 ···(4)

[3] A glass material for molding, wherein the maximum linear expansion coefficient α _max is less than the maximum linear expansion coefficient α _max (Tg) of the glass material obtained by homogenizing the glass material for molding at a glass transition temperature Tg, cooling at -30°C/hr for 4 hours, and then cooling.

[4] For the glass material for molding as described in [1] to [3], when a sample of 11 mm × 11 mm × 10.5 mm is heat treated at a temperature 200°C higher than the glass transition temperature Tg for 5 minutes, the crystal number density D per 1 g of glass is less than 10/g.

[5] The glass material for molding as described in [1] to [4], wherein the TiO ₂ content [TiO ₂ ] and the Nb ₂ O ₅ content [Nb ₂ O ₅ ] expressed in terms of mass % satisfy the following formula (7): {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]}≦3 ···(7)

[6] The glass material for molding as described in [1] to [5], wherein the wavelength λτ ₈₀ at which the internal transmittance of 10 mm thick glass is 80% within the wavelength range of 280 to 700 nm is below 395 nm.

[7] The glass material for molding as described in [1] to [6], wherein the Abbe number νd and the partial dispersion ratio Pg,F satisfy the following formula (8): Pg,F≦-0.00286×νd+0.68700 ・・・(8)

[8] An optical glass is formed from the molding glass material described in [1] to [7]. [Effect of the invention]

According to the present invention, a glass material for molding having excellent stability during reheating can be provided.

In the present invention and this specification, the glass composition is expressed on an oxide basis unless otherwise specified. The "glass composition on an oxide basis" referred to herein refers to the glass composition obtained by converting the glass raw materials into oxide forms when they are completely decomposed during melting. The expression of each glass component follows the conventional description of SiO ₂ , TiO ₂ , etc. The content and total content of the glass components are on a mass basis unless otherwise specified, and "%" means "mass %". In addition, "glass material for molding" may be abbreviated as "glass" or "glass material".

The content of glass components can be quantified by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), etc. In addition, in this specification and the present invention, the so-called "content of a constituent is 0%" means that the constituent is not substantially contained, and the constituent is allowed to be contained to a certain extent as unavoidable impurities.

Hereinafter, the glass material for molding of the present invention will be described according to the first embodiment, the second embodiment, and the third embodiment. In addition, the glass properties of the second and third embodiments are the same as those of the first embodiment. Furthermore, the functions and effects of each glass component of the second and third embodiments are the same as those of each glass component of the first embodiment. Therefore, in the second and third embodiments, the relevant description and repeated matters of the first embodiment are appropriately omitted.

First Embodiment The maximum linear expansion coefficient α _max of the molding glass material of the first embodiment and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % satisfy the following formula (1): α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ··· (1)

In the first embodiment, the maximum linear expansion coefficient α _max and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % satisfy the following formula (1), preferably the following formula (2), and more preferably the following formula (3). By satisfying the following formula, a molding glass material having excellent stability during reheating can be obtained. α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ・・・(1) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27500 ・・・(2) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27000 ・・・(3)

The maximum value of the linear expansion coefficient α _max can be controlled by adjusting the conditions for cooling the molten glass in the manufacturing step of the glass material described later.

The linear expansion coefficient is measured in accordance with the provisions of the Japan Institute of Technology standard JOGIS08. The sample is a round bar with a length of 20mm±0.5mm and a diameter of 5mm±0.5mm. Under a load of 98mN, the sample is heated at a constant rate of 4℃ per minute, and the temperature and sample extension are measured every 1 second. Because the maximum linear expansion coefficient α _max is the maximum linear expansion coefficient between room temperature and yield point temperature (the temperature at which the sample yields and stops extending on the surface), it is sufficient to obtain the linear expansion coefficient at the temperature at which the sample elongates to the maximum for each unit temperature rise. The maximum linear expansion coefficient α _max can also be obtained by moving the linear expansion coefficients of 31 measurement locations and obtaining the maximum value. The average linear expansion coefficient α _100-300 described below is an average value of the linear expansion coefficient at 100 to 300°C.

In addition, in this specification, the maximum linear expansion coefficient α _max and the average linear expansion coefficient α _100-300 are expressed to the first integer in the unit of 10 ^-7 ℃ ^-1 according to the JOGIS08 specification. That is, the maximum linear expansion coefficient α _max and the average linear expansion coefficient α _100-300 are expressed in the unit of [10 ^-7 ‧℃ ^-1 ] and in integers.

In this specification, the mean linear expansion coefficient α is expressed in [°C ^-1 ], but even when the unit is [K ^-1 ], it is still the same as the value of the mean linear expansion coefficient α.

For the glass material used for molding in this embodiment, the properties and glass composition other than those mentioned above are shown below as non-limiting examples.

The maximum linear expansion coefficient α _max , the average linear expansion coefficient α _100-300 °C at 100-300°C, and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % of the molding glass material of the first embodiment preferably satisfy the following formula (4), more preferably satisfy the following formula (5), and particularly preferably satisfy the following formula (5). In order to obtain a molding glass material having excellent stability during reheating, it is best to satisfy the following formula.

α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦264‧‧‧(4)

α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦260‧‧‧(5)

α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦255‧‧‧(6)

The maximum linear expansion coefficient α _max and the average linear expansion coefficient α _100-300 can be controlled by adjusting the conditions for cooling the molten glass in the manufacturing step of the glass material described later.

The maximum linear expansion coefficient α _max of the molding glass material of the first embodiment is preferably less than the maximum linear expansion coefficient α _max (Tg) of the glass material obtained by homogenizing the molding glass material at the glass transition temperature Tg, cooling at -30°C/hr for 4 hours, and then cooling. However, the maximum linear expansion coefficient α _max may be only slightly greater than the maximum linear expansion coefficient α _max (Tg). Therefore, the difference between α _max and α _max (Tg) [α _max (Tg)-α _max ], when expressed in 10 ^-7・℃ ^-1 units to the first integer, is preferably -9 or more, and more preferably -4 or more, 0 or more, 5 or more, 10 or more, 20 or more, 40 or more, 60 or more, 80 or more, 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 250 or more, 300 or more, 350 or more, and 400 or more. In addition, although the upper limit of the difference is not particularly limited, it is usually α _max (Tg), preferably about α _max (Tg)-100.

The maximum linear expansion coefficient α _max (Tg) is the maximum linear expansion coefficient of the glass obtained by holding the molding glass material at the glass transition temperature Tg and then cooling it at -30°C/hr for 4 hours. In addition, the molding glass material of the first embodiment has the maximum linear expansion coefficient α _max but does not have the maximum linear expansion coefficient α _max (Tg). As described later, the molding glass material of the first embodiment is obtained by holding at a temperature lower than the glass transition temperature Tg, and therefore has α _max that is smaller than α _max (Tg).

When the homogenization is performed at the glass transition temperature Tg, the glass material for molding is heated to a temperature higher than Tg, and thus the temperature can be lowered to the same temperature as Tg. Alternatively, the glass material for molding can be gradually heated to the same temperature as Tg.

FIG. 1 shows a glass temperature diagram in a manufacturing step of an example of a molding glass material according to the present embodiment. The molding glass material according to the present embodiment is maintained at a temperature lower than the glass transition temperature Tg in step 2 as described later. Here, the maximum linear expansion coefficient α _max (Tg) is obtained by maintaining the glass transition temperature Tg in step 2 as in the comparative example (Tg1) in FIG. 1 . Alternatively, the maximum linear expansion coefficient α _max (Tg) can also be obtained by heating the molding glass material from room temperature, homogenizing it at a temperature equal to the glass temperature Tg, and then cooling it as in the comparative example (Tg2) in FIG. 1 .

When the glass material for molding is heated to a temperature higher than the glass transition temperature Tg and then cooled, the lower limit of the time required for equalization at the glass transition temperature Tg varies according to the sample size, and is about 30 minutes after the glass surface temperature reaches Tg, and can also be 1 hour, 2 hours, or 4 hours. The upper limit is not particularly limited, but is usually within 24 hours, preferably within 12 hours. In addition, the equalization time of the glass interior after reaching the Tg temperature is preferably about 10 minutes.

When the glass material for molding is homogenized, for example, even if the surface temperature of the glass reaches the glass transition point Tg, it does not necessarily mean that the internal temperature reaches Tg. Here, whether the homogenization is sufficient can be determined by the specific gravity. The specific gravity of the glass obtained after being homogenized sufficiently at the glass transition temperature Tg and then cooled will hardly change even if the holding time at Tg is prolonged. On the other hand, the specific gravity of the glass obtained before homogenization at the glass transition temperature Tg, for example, before the inside of the glass reaches the glass transition temperature Tg, will be different from that of the glass obtained after the inside of the glass is sufficiently homogenized at Tg and then cooled.

Therefore, for example, the absolute value of the change [d(t 1 )-d(t ₁ +K)] between the specific gravity d(t ₁ ) of the glass obtained by heating the glass material for molding in a furnace and maintaining the holding time t ₁ (hr) and then cooling the glass material for molding in _a furnace and maintaining the holding time t ₁ +K (hr) and then cooling the glass is preferably 0.002 or less. Here, the lower limit of the K value is preferably 4, more preferably 8, _and particularly preferably 12.

When the above variation is satisfied, it can be determined that the glass heated at the holding time _t1 is sufficiently homogenized. In this case, the time required for homogenization at the glass transition temperature Tg is preferably greater than _t1 .

The method of cooling the glass homogenized at the glass transition temperature Tg is based on the premise that the glass is cooled at a cooling rate of -30°C/hr for 4 hours after homogenization, and there is no particular limitation. For example, a gradual cooling furnace capable of temperature program control can be used. In addition, if the strain point of the glass does not decrease even if the glass is cooled at a cooling rate of -30°C/hr for 4 hours from the maintained temperature Tg, the glass can be cooled at a cooling rate of -30°C/hr for 5 to 6 hours from the maintained temperature Tg.

The heating temperature during reheating is usually a temperature at which the glass softens and deforms. Specifically, the heating temperature is about 50°C higher than the glass transition temperature Tg in the case of a lower heating temperature, and about 200-300°C higher than the glass transition temperature Tg in the case of a higher heating temperature. When the heating temperature during reheating is low, that is, heating is performed at a temperature about 50°C higher than the glass transition temperature Tg, it is easy to ensure the stability of the glass and suppress the occurrence of crystallization and devitrification.

However, if the heating temperature during reheating is low, a higher pressure needs to be applied during molding. As a result, the molded glass products (such as lenses, lens blanks, round rods, extruded products, etc.) are more likely to crack or break. Therefore, if the heating temperature during reheating is low, it is easy to reduce the production yield and the shape of the glass products that can be molded is also easily limited.

On the other hand, when the heating temperature during reheating is relatively high, that is, when heating is performed at a temperature higher than the glass transition temperature Tg by about 200 to 300°C, deformation can be achieved in a shorter time and the shape freedom of the molded product can be increased, but it is difficult to ensure the stability of the glass, and crystallization and devitrification are likely to occur. From these phenomena, the glass having the composition of the present invention is likely to precipitate crystals if the molding temperature is increased. In order to avoid the precipitation of crystals, the molding temperature must be set lower than that of conventional glass, thereby increasing the possibility of deformation defects such as cracking and breaking.

When a 11mm×11mm×10.5mm sample of the first embodiment is heat treated at a temperature 200°C higher than the glass transition temperature Tg for 5 minutes, the crystal number density D per 1g of glass is preferably less than 10 pieces/g, and the upper limit is more preferably 9 pieces/g, 8 pieces/g, 7 pieces/g, 6 pieces/g, 5 pieces/g, 4 pieces/g, 3 pieces/g, 2 pieces/g, and 1 piece/g. The best crystal number is 0 pieces/g.

The number of crystals at the above number density D is obtained by the number of bright spots of crystals confirmed by an optical microscope (100 times).

The above number density D is calculated according to the following sequence.

[Sample preparation] First, observe with an optical microscope (100 times) to confirm that there are no identifiable foreign matter or crystals inside the glass. Then, cut the glass and cut it to obtain a cubic sample of about 11mm×11mm×10.5mm. The surface of the sample is all sanded using the grinding stones of number ♯80~400.

[Heat treatment furnace] Set the temperature to 200℃ higher than the glass transition temperature Tg, and after the temperature inside the furnace reaches Tg+200℃, perform heat treatment for more than 15 minutes, and place in a heat treatment furnace with an internal space volume of about 25cm×about 10cm×about 10cm for heating.

At this time, the temperature controller of the heat treatment furnace is set at the approximate center of the internal space, and when the glass sample is heat treated, the glass sample is set at a position within 3 cm from the sensor part of the temperature controller.

[Preheating of receiving dish] A cubic hexahedral alumina ceramic plate of about 10.5cm×about 3cm×about 1cm is used as a receiving dish. 0.01~0.3g, preferably 0.5g~0.15g, and more preferably 0.1g of anti-welding agent such as powdered alumina or solid lubricant such as BN is applied to the front end of the receiving dish, and a glass sample is placed on it. Each receiving dish is placed in a heat treatment furnace for heating. The above-mentioned receiving dish is placed in a heat treatment furnace for preheating for more than 15 minutes before the test.

[Heat treatment of glass samples] The receiving dish is taken out of the heat treatment furnace just before the glass sample is put in, and the glass sample is immediately placed on the position of the receiving dish where the anti-melting agent or solid lubricant is applied, and then the glass sample and the receiving dish are returned to the original position in the furnace. The time from taking out the receiving dish to returning to the original position is preferably within 10 seconds, more preferably within 8 seconds, and particularly preferably within 6 seconds to avoid the temperature of the receiving dish from decreasing. After 5 minutes from the time the glass sample is put in, the above-mentioned glass is taken out from each receiving dish, and after the glass sample is taken out from the receiving dish, it is cooled at a cooling rate that does not cause cracking. At this time, in order not to affect the stability of the glass and to cool it efficiently, it is best to roll the glass sample in ceramic fibers immediately (about 3±1 seconds) after taking it out of the furnace, so that the sample is also covered with ceramic fibers without pressure, and then cool it to room temperature. The end of the cooled glass sample is optically polished, and the inside of the glass sample is observed using an optical microscope (100 times). During optical polishing, the softened glass sample preferably retains more than 80% and more preferably more than 85% of the observed volume. Count the number of crystals (bright spots) inside the glass sample, and measure the weight of the sample after optical polishing, and convert it to the number per 1g.

The TiO ₂ content [TiO ₂ ] and the Nb ₂ O ₅ content [Nb ₂ O ₅ ] of the first embodiment of the molding glass material preferably satisfy the following formula (7) in terms of mass %: {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]}≦3 ···(7)

The upper limit of the above-mentioned {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} is preferably 2, and more preferably 1.25, 1.1, 1.0, 0.9, 0.8, 0.7, 0.6, and 0.5 in order to further reduce Pg, F and achieve glass stability and/or high refractive index. On the other hand, from the viewpoint of particularly reducing Pg, F and further improving the blue region transmittance λτ80, the upper limit of the above-mentioned 5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} is preferably 0.4, and more preferably 0.3, 0.2, and 0.1 in order. The above-mentioned 5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} may also be set to 0.0.

The above {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} represents the existence ratio of Ti ions and Nb ions in the glass material for molding. If the Ti ions are too much, there is a concern that the partial dispersion ratio Pg,F will increase. In addition, there is a concern that fine crystal nuclei will be generated when the molten glass is cooled, and this may cause crystal growth and optical quality to deteriorate depending on the subsequent molding conditions, which may hinder glass production. Therefore, in order to suppress the increase of the partial dispersion ratio Pg,F and suppress glass crystallization, it is best to satisfy the above formula.

In the first embodiment of the glass material for molding, the partial dispersion ratio Pg,F preferably satisfies the following formula (8), preferably satisfies the following formula (9), particularly preferably satisfies the following formula (10), best satisfies the following formula (11), and most best satisfies the following formula (12). By satisfying the following formula, an optical glass suitable for chromatic aberration correction can be provided. Pg,F≦-0.00286×νd+0.68700・・・(8) Pg,F≦-0.00286×νd+0.68600・・・(9) Pg,F≦-0.00286×νd+0.68500・・・(10) Pg,F≦-0.00286×νd+0.68400・・・(11) Pg,F≦-0.00286×νd+0.68300・・・(12)

The partial dispersion ratio Pg,F is expressed by the following formula (13) using the refractive indices ng, nF, and nC of the g-line, F-line, and C-line: Pg,F=(ng-nF)/(nF-nC) ・・・(13)

The partial dispersion ratio Pg,F is obtained by adjusting the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (SiO ₂ + P ₂ O ₅ + B ₂ O ₃ )], the mass ratio [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )], the mass ratio [(SiO ₂ + P ₂ O ₅ + B ₂ O ₃ ) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )], the mass ratio [ZrO ₂ / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )], the mass ratio [P ₂ O ₅ / (SiO ₂ + P ₂ O ₅ + B ₂ O ₃ )] and mass ratio [Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] can be controlled.

Furthermore, ΔPg,F is the deviation of Pg,F from the normal line, which is obtained according to formula (14): ΔPg,F=Pg,F-(0.6483-0.001802×νd) ・・・(14)

The glass material for molding of the first embodiment can be a high-dispersion glass with a smaller partial dispersion ratio Pg,f. In high-dispersion glass, by reducing the Pg,f value, when achromatization (focal distance adjustment) focusing on the F line and the C line is usually performed, it is easy to suppress the focus distance shift near the g line, that is, it is easy to suppress the chromatic aberration in the short wavelength domain. In addition, when the image taken by the camera is enlarged, the contrast can be easily improved. In addition, when the digital image is electronically viewed, the edge of the object can be easily viewed, and it is expected to suppress the calculation load of the image engine.

The molding glass material of this embodiment may have glass composition A, glass composition B, or glass composition C as described in detail below.

(Glass composition A)

Hereinafter, the content and ratio of the glass components and the glass properties will be described in the case where the glass material for molding of this embodiment has a glass composition A.

In the glass material for molding of the present embodiment, when the glass composition A is used, it is preferably a silicate glass in which the glass network forming component mainly contains _SiO2 . The lower limit of the _SiO2 content is preferably 6%, and more preferably 11%, and 16% in sequence, and the larger the value, the better. In particular, when the thermal stability is more important than the glass refractive index, the lower limit of the _SiO2 content is preferably 21%, and can also be set to 24%, 26%, or 28%. In addition, the upper limit of the _SiO2 content is preferably 40%, and more preferably 38%, 35%, and 33% in sequence, and the smaller the value, the better. In particular, when the refractive index is more important than the glass stability, the upper limit of the _SiO2 content is preferably 30%, and can also be set to 28%, 26%, or 25%.

_SiO2 is a network-forming component of glass in glass composition A. It has the following effects: improving the thermal stability, chemical durability and weather resistance of glass, increasing the viscosity of molten glass and making it easier to shape molten glass. It also has the effect of improving thermal stability during reheating and reducing the crystal number density D. On the other hand, if the _SiO2 content is too high, the glass's resistance to devitrification tends to decrease, resulting in an increase in Pg, F. Therefore, the _SiO2 content is preferably within the above range.

When the glass material for molding of the present embodiment is glass composition A, it preferably contains _P2O5 . The lower limit of _{the P2O5} content is preferably 0%, and more preferably 0.2%, 0.4%, and 0.6% in sequence. Moreover, the upper limit of _{the P2O5} content is preferably 10%, _and more preferably 8%, 7%, 6%, 5%, and 4% in sequence.

In glass composition A, when the lower limit of _{the P2O5} content satisfies the above, the thermal stability during reheating is improved, _which has the effect of reducing the number density D of crystals. Furthermore, when the upper limit of the _P2O5 content satisfies the above, the increase of the partial dispersion ratio Pg,F is suppressed, and the stability during reheating can be maintained.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the B ₂ O ₃ content is preferably 20%, and more preferably 14%, 9%, and 4% in that order. The _{B 2} O ₃ content may also be 0%.

_B2O3 is a network _- forming component of glass in glass composition A, and has the effect of increasing the solubility of glass and improving thermal stability. On the other hand, if the _B2O3 content is too high, there is a concern that the volatility of glass components _will increase when the glass is melted, and there is a tendency to hinder high dispersion and reduce resistance to devitrification. In addition, compared with the case where the same amount of _SiO2 is replaced, there is a concern that the viscosity of the glass _{will be further reduced. And if excessively introduced, there is also a concern that the thermal stability during reheating will be reduced. Therefore, the B2O3 content} is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Al ₂ O ₃ content is preferably 20%, and more preferably 9%, 4%, 2%, and 1% in sequence. The lower limit of the Al ₂ O ₃ content is preferably 0%, and more preferably 0.02%, 0.04%, 0.08%, 0.12%, 0.14%, 0.16%, 0.2%, and 0.3% in sequence. The _{Al 2} O ₃ content may also be 0%.

In glass composition A, Al ₂ O ₃ is a glass component that improves the chemical durability and weather resistance of glass, and can be considered to be a network-forming component. On the other hand, if the Al ₂ O ₃ content is too high, the devitrification resistance of the glass decreases. In addition, the higher the glass transition temperature Tg, the more likely it is that the thermal stability will decrease when the molten glass is cooled. From the perspective of avoiding such problems, the Al ₂ O ₃ content is preferably within the above range. In addition, when a refractory brick container and/or a ladle is used for melting and transporting the molten glass, the Al ₂ O ₃ content can also be set to 0.02% or more.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the total content of SiO ₂ and P ₂ O ₅ [SiO ₂ +P ₂ O ₅ ] is preferably 5%, and more preferably 11%, 16%, and 21% in that order. In particular, when stability is important, the lower limit of the total content is preferably 24%, and can also be set to 27% or 30%. In addition, the upper limit of the total content is preferably 40%, and more preferably 38%, 36%, 34%, and 33% in that order.

In glass composition A, when the lower limit of the total content of SiO ₂ and P ₂ O ₅ [SiO ₂ +P ₂ O ₅ ] satisfies the above, the thermal stability during reheating can be improved and the number density D of crystals can be reduced. Moreover, when the upper limit of the total content satisfies the above, the decrease in refractive index and the increase in partial dispersion ratio Pg,F can be suppressed, and the thermal stability of the glass can be maintained.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the total content of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ [SiO ₂ + P ₂ O ₅ + B ₂ O ₃ ] is preferably 5%, and more preferably 10%, 15%, 18%, 21%, 22%, and 23% in that order. Moreover, the upper limit of the total content is preferably 50%, and more preferably 45%, 40%, 37%, 35%, 34%, and 33% in that order. In particular, when the refractive index is taken into consideration, the upper limit of the total content is preferably 30%, and may also be set to 28%, 26%, or 25%.

In the glass composition A, from the viewpoint of maintaining stability during reheating, the total content [SiO ₂ + P ₂ O ₅ + B ₂ O ₃ ] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of B ₂ O ₃ content to SiO ₂ content [B ₂ O ₃ /SiO ₂ ] is preferably 0.80, more preferably 0.70, 0.60, 0.50, 0.40, 0.30, 0.20, 0.10, 0.05, 0.03 in sequence. Moreover, the lower limit of the mass ratio is preferably 0, more preferably 0.005, 0.01, 0.015, 0.02 in sequence. The mass ratio may also be 0.

In the glass composition A, from the viewpoint of suppressing an increase in the specific gravity of the glass and suppressing an increase in the coloring of the glass, the mass ratio [B ₂ O ₃ /SiO ₂ ] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the mass ratio of the content _{of P2O5} to the total content _{of SiO2} and _P2O5 [ _P2O5 / _{( SiO2} + _{P2O5 )} ] is preferably 0.00, and more preferably 0.006, 0.011, 0.016, and 0.021 in sequence. The upper limit of the mass ratio is preferably 0.20, and more preferably 0.18, 0.16, 0.14, 0.12, and 0.11 in sequence.

In glass composition A, if the mass ratio [P ₂ O ₅ /(SiO ₂ +P ₂ O ₅ )] is too low, there is a concern that stability may deteriorate upon reheating, and if it is too high, there is a concern that the partial dispersion ratio Pg,F may increase. Therefore, the mass ratio is preferably within the above range.

_In the glass material for molding of the present embodiment, in the case of glass composition A, the mass ratio of the content _{of P2O5} to the total content _{of SiO2, P2O5 and B2O3 [ P2O5 / ( SiO2} + _P2O5 + _{B2O3 )} ] is preferably _0.00 , more preferably 0.006, 0.011, 0.016, 0.021 in order. The upper limit of the mass ratio is preferably 0.20, more preferably 0.18, 0.16, 0.14, 0.12 _, 0.11 in order.

In glass composition A, if the mass ratio [P ₂ O ₅ /(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )] is too high, there is a concern that the partial dispersion ratio Pg,F may increase. Therefore, the mass ratio is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the mass ratio of SiO ₂ content to the total content of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ [SiO ₂ /(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )] is preferably 0.100, and more preferably 0.200, 0.300, 0.400, 0.500, 0.600, 0.700, 0.800, 0.820, 0.840, 0.860 in order. In addition, the upper limit of the mass ratio is preferably 1.000, and more preferably 0.995, 0.990, 0.985, 0.980, 0.978 in order.

In the glass composition A, from the viewpoint of maintaining stability during reheating, the mass ratio [SiO ₂ /(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )] is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the lower limit of the ZrO ₂ content is preferably 0%, and more preferably 2%, 3%, 4%, and 5% in sequence. In particular, when stability is more important than the refractive index, the lower limit of the ZrO ₂ content is preferably 6%, or it can also be set to 8%. In addition, the upper limit of the ZrO ₂ content is preferably 15%, and more preferably 14%, 13%, 12%, 11%, and 10% in sequence. In particular, when stability is more important than the refractive index, the upper limit of the ZrO ₂ content is preferably 9%, and it can also be set to 8%, 7%, or 6%.

In glass composition A, by satisfying the above lower limit of the ZrO ₂ content, a glass having both high refractive index, high dispersion and high internal transmittance λτ ₈₀ can be obtained. Furthermore, by satisfying the above upper limit of the ZrO ₂ content, in addition to suppressing the increase of the partial dispersion ratio Pg,F and suppressing the occurrence of defects when forming an optical element, the meltability and thermal stability of the glass can be maintained.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the Nb ₂ O ₅ content is preferably 1%, and more preferably 11%, 21%, 26%, 31%, 34%, and 36% in this order. In particular, when stability is more important than refractive index, the lower limit of the Nb ₂ O ₅ content is preferably 39%, and can also be set to 41%, 46%, 49%, or 50%. In addition, the upper limit of the Nb ₂ O ₅ content is preferably 80%, and more preferably 70%, 64%, 59%, 56%, and 54% in this order. In particular, when stability is more important than refractive index, the upper limit of the Nb ₂ O ₅ content is preferably 51%, and can also be set to 47%, 44%, 43%, or 38%.

In glass composition A, by satisfying the above lower limit of the Nb ₂ O ₅ content, a high refractive index and high dispersion glass with a reduced partial dispersion ratio of Pg, F can be obtained. In addition, Nb ₂ O ₅ is also a glass component that improves the thermal stability and chemical durability of the glass. If the content is too low, there is a concern that Pg, F will increase, and if it is excessively contained, there is a concern that the thermal stability of the glass will deteriorate. Therefore, by satisfying the above upper limit of the Nb ₂ O ₅ content, the thermal stability and chemical durability of the glass can be well maintained, and the formability during reheating can be improved.

In the glass material for molding of the present embodiment, when the glass composition A is used, the lower limit of the _TiO2 content is preferably 0%, and more preferably 1%, 2%, 3%, and 4% in sequence. In addition, the upper limit of the _TiO2 content is preferably 20%, and more preferably 15%, 11%, 8%, and 6% in sequence.

_TiO2 is a component that contributes to high refractive index and high dispersion in glass composition A. By coexisting with _Nb2O5 , the stability of the glass can be improved while maintaining a high refractive index, thereby enhancing the stability during reheating. On the other hand, if _TiO2 is excessively _introduced , there is a concern that the partial dispersion ratio Pg,F will rise and the transmittance of the glass in the short wavelength region will decrease. In addition, crystals will form in a temperature range lower than the yield point of the glass, which may hinder the productivity of the glass. Therefore, the _TiO2 content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the total content of Nb ₂ O ₅ and TiO ₂ [Nb ₂ O ₅ +TiO ₂ ] is preferably 10%, and more preferably 20%, 30%, 35%, 38%, 39%, 40%, and 41% in this order. In particular, when stability is more important than refractive index, the lower limit of the total content is preferably 45%, and can also be set to 48%, 51%, 53%, or 55%. In addition, the upper limit of the total content is preferably 80%, and more preferably 75%, 70%, 65%, 62%, 59%, and 56% in this order. In particular, when stability is more important than refractive index, the upper limit of the total content is preferably 53%, and can also be set to 50%, 47%, 44%, or 43%.

In the glass composition A, from the viewpoint of improving the glass stability while maintaining a high refractive index and enhancing the stability during reheating, the total content of [Nb ₂ O ₅ +TiO ₂ ] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of TiO ₂ content to Nb ₂ O ₅ content [TiO ₂ /Nb ₂ O ₅ ] is preferably 0.50, and more preferably 0.40, 0.30, 0.20, 0.18, and 0.16 in sequence. The lower limit of the mass ratio is preferably 0, and more preferably 0.02, 0.04, 0.06, 0.08, and 0.10 in sequence. The mass ratio may also be 0.

In the glass composition A, from the viewpoint of suppressing the increase of the partial dispersion ratio Pg,F and improving λτ80, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the mass ratio of the content _{of P2O5} to the content _{of Nb2O5} [ _P2O5 / _Nb2O5 ] is preferably 0.000, more preferably 0.005, 0.010, 0.015, 0.020 in sequence. The upper limit of the mass ratio is preferably 0.200, more preferably 0.150, _{0.100 ,} 0.090, 0.080 in sequence.

In the glass composition A, from the viewpoint of suppressing an increase in the partial dispersion ratio Pg,F, the mass ratio [P ₂ O ₅ /Nb ₂ O ₅ ] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the mass ratio of the content _{of P2O5} to the total content _{of Nb2O5} and _TiO2 [ _P2O5 /( _Nb2O5 + _TiO2 )] is preferably _0.000 , more preferably 0.005, 0.010, 0.015, _0.018 in sequence. The upper limit of the mass ratio is preferably 0.200, more preferably 0.150, 0.100, 0.090, 0.080 in sequence.

In the glass composition A, from the viewpoint of obtaining the desired high dispersibility, the mass ratio [P ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ )] is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the WO ₃ content is preferably 20%, and the more preferred ranges are 17%, 14%, 11%, 8%, 6%, 4%, 3%, 2%, 1%, 0.5%, and 0.2% in that order. In addition, the lower limit of the WO ₃ content is preferably 0%. The WO ₃ content may also be 0%.

WO ₃ is a component that improves stability during reheating in glass composition A. On the other hand, WO ₃ increases the partial dispersion ratio Pg,F. Also, it is easy to cause glass coloring and reduce λτ80. Therefore, the WO ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Bi ₂ O ₃ content is preferably 20%, and more preferably 17%, 14%, 11%, 8%, 6%, 4%, 3%, 2%, 1%, 0.5%, and 0.2% in sequence. In addition, the lower limit of the Bi ₂ O ₃ content is preferably 0%. The _{Bi 2} O ₃ content may also be 0%.

Bi ₂ O ₃ has the effect of improving the thermal stability of glass by containing an appropriate amount in glass composition A. On the other hand, if the Bi ₂ O ₃ content is too high, the partial dispersion ratio Pg,F will increase. In addition, there is a concern that the glass coloring will increase and λτ80 will decrease. Therefore, the Bi ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ ] is preferably 80%, and more preferably 75%, 70%, 65%, 62%, 59%, and 56% in that order. In particular, when stability is more important than refractive index, the upper limit of the total content is preferably 53%, and can also be set to 50%, 47%, 44%, or 43%. In addition, the lower limit of the total content is preferably 10%, and more preferably 20%, 30%, 35%, 38%, 39%, 40%, and 41% in that order. In particular, when stability is more important than refractive index, the lower limit of the total content is preferably 45%, and may also be set to 48%, 51%, 53%, or 55%.

In glass composition A, TiO ₂ , WO ₃ and Bi ₂ O ₃ are components that contribute to high refractive index and high dispersion together with Nb ₂ O _5. Therefore, the total content [Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the Nb ₂ O ₅ content to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [Nb ₂ O ₅ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is preferably 1, and more preferably 0.98, 0.96, 0.94, and 0.92 in order from the viewpoint of maintaining the thermal stability of the glass, improving the λτ80 of the glass, and enhancing the stability during reheating. The lower limit of the mass ratio is preferably 0.1, and more preferably 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.8 in order.

Furthermore, in the molding glass material of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the ZrO ₂ content to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [ZrO ₂ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is preferably 1 from the perspective of maintaining the thermal stability of the glass, and the more preferred order is 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, and 0.25. Furthermore, from the viewpoint of increasing λτ80 of the glass, the lower limit of the mass ratio [ZrO ₂ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is preferably 0.01, and more preferably 0.03, 0.05, 0.08, 0.09, 0.10, and 0.11, respectively. Furthermore, from the viewpoint of maintaining high dispersibility of the glass, the upper limit of the mass ratio [ZrO ₂ /(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] may be set to 0.02, 0.01, or 0.00.

Furthermore, in the case of glass composition A of the present embodiment, the upper limit of the mass ratio of the total content of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )/(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is preferably 5, and more preferably 4, 3, 2, 1.5, 1.3, 1.1, 1.0, 0.9, and 0.8 in this order. When paying special attention to the refractive index, the upper limit of the mass ratio is preferably 0.7, and can also be set to 0.6, 0.5, or 0.45. Furthermore, the lower limit of the mass ratio is preferably 0.013, and more preferably 0.10, 0.20, 0.30, 0.35, and 0.40, respectively. When stability is particularly important, the lower limit of the mass ratio is preferably 0.50, and can also be set to 0.60, 0.70, or 0.75.

In the glass composition A, by setting the mass ratio [(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )/(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] within the above range, the refractive index of the glass can be adjusted and the thermal stability can be maintained.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Ta ₂ O ₅ content is preferably 20%, and more preferably 15%, 10%, 8%, 6%, 4%, 2%, and 1% in sequence. In addition, the lower limit of the Ta ₂ O ₅ content is preferably 0%. The _{Ta 2} O ₅ content may also be 0%.

Ta ₂ O ₅ is a glass component that improves the thermal stability of glass in glass composition A. On the other hand, if the content of Ta ₂ O ₅ is too high, the thermal stability of glass decreases, and when the glass is melted, glass raw material melt residues are likely to occur. In addition, it is a high-priced component, which may increase the cost of glass production. Therefore, the content of Ta ₂ O ₅ is preferably within the above range.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the content _{of Ta2O5} to the total content _{of Ta2O5, Nb2O5 , TiO2 , WO3} and _Bi2O3 [ _{Ta2O5 /} ( _Ta2O5 + _Nb2O5 + _TiO2 + _WO3 + _Bi2O3 )] is preferably 0.9, and more preferably _0.7 , 0.5, 0.3 _, 0.2 _{, 0.1} and _0.05 in that order. The lower limit of the mass ratio is preferably 0.000.

_In the glass composition A, from the viewpoint of suppressing an increase _{in specific gravity and suppressing an increase in glass production cost, the mass ratio [Ta2O5/(Ta2O5+Nb2O5 + TiO2 + WO3 + Bi2O3 )} ] is preferably within the _above range.

In the glass material for molding of this embodiment, when the glass composition A is used, the upper limit of the Li ₂ O content is preferably 10%, and more preferably 9%, 8%, 7%, and 6% in sequence. The lower limit of the Li ₂ O content is preferably 0%, and more preferably 1%, 2%, 3%, 3.5%, 4%, and 4.5% in sequence.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Na ₂ O content is preferably 30%, and more preferably 25%, 20%, 18%, 16%, 14%, and 12% in sequence. The lower limit of the _{Na 2} O content is preferably 0%, and more preferably 1%, 2%, 3%, 3.5%, 4%, 4.5%, and 5% in sequence.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the _K2O content is preferably 30%, and more preferably 20%, 15%, 10%, 7%, and 4% in sequence. The lower limit of the _K2O content is preferably 0%, and more preferably 0.1%, 0.2%, 0.3%, 0.4%, and 0.5% in sequence.

In glass composition A, Li ₂ O, Na ₂ O and K ₂ O all have the effect of lowering the liquidus temperature and improving the thermal stability of glass. If their contents are too high, the chemical durability and weather resistance will be reduced. Therefore, the contents of Li ₂ O, Na ₂ O and K ₂ O are preferably within the above ranges.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the total content of _Li2O , _Na2O and _K2O [ _Li2O + _Na2O + _K2O ] is preferably 1%, and more preferably 5%, 8%, 10%, 12%, 13%, and 14% in sequence. Moreover, the upper limit of the total content is preferably 40%, and more preferably 35%, 30%, 25%, 22%, 20%, 19%, 18%, and 17% in sequence.

In glass composition A, when the lower limit of the total content [ _Li2O + _Na2O + _K2O ] satisfies the above, the glass meltability can be improved and the liquidus temperature rise can be suppressed. When the upper limit of the total content satisfies the above, the glass viscosity can be increased, the crystallization rate of the glass melt can be reduced, and the stability during reheating can be improved.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the mass ratio of the total content of _Li2O , _Na2O and _K2O to the total content of _{Nb2O5 and TiO2} [( _Li2O + _Na2O + _K2O )/( _Nb2O5 + _TiO2 )] is preferably 0.10, and more preferably 0.15, 0.18, 0.21, 0.23, and 0.25 in order. In addition, the upper limit of the mass ratio is preferably 0.70, and more preferably 0.65, _0.60 , 0.55, 0.50, and 0.45 in order.

In the glass composition A, from the viewpoint of obtaining the desired optical constants while maintaining the glass melting characteristics and thermal stability, the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O)/(Nb ₂ O ₅ +TiO ₂ )] is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the content _{of P2O5} to the total content _{of Li2O} , _Na2O , _K2O and _Nb2O5 [ _{P2O5 /} ( _Li2O + _Na2O + _K2O + _Nb2O5 )] is preferably 0.500, and more preferably 0.400, 0.300, 0.200, 0.100, 0.080, 0.070, 0.060 in order. In addition, the lower limit of the mass ratio is preferably 0, and more preferably 0.005, _0.010 , 0.011, 0.012, 0.013, 0.014 in order.

In the glass composition A, from the viewpoint of stabilizing the glass and suppressing an increase in the partial dispersion ratio _Pg ,F, the mass ratio [ _P2O5 /( _Li2O + _Na2O + _K2O + _Nb2O5 )] is preferably within the above _range .

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Cs ₂ O content is preferably 10%, and more preferably 8%, 6%, 4%, 3%, 2%, and 1% in that order. The lower limit of the Cs ₂ O content is preferably 0%.

Cs ₂ O has the effect of improving the thermal stability of glass in glass composition A, but if its content is too high, chemical durability and weather resistance will decrease. Therefore, the Cs ₂ O content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the lower limit of the total content of _Li2O , _Na2O , _K2O and _Cs2O [ _Li2O + _Na2O + _K2O + _Cs2O ] is preferably 1%, and more preferably 5%, 8%, 10%, 12%, 13%, and 14% in that order. Moreover, the upper limit of the total content is preferably 40%, and more preferably 35%, 30%, 25%, 22%, 20%, 19%, 18%, and 17% in that order.

In the glass composition A, from the viewpoint of maintaining stability during reheating, the total content [Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O] is preferably within the above range.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the content of _Li2O to the total content of _Li2O , _Na2O , _K2O , and _Cs2O [ _Li2O /( _Li2O + _Na2O + _K2O + _Cs2O )] is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, 0.45, and 0.4 in order from the viewpoint of suppressing the increase in liquidus temperature and suppressing the decrease in weather resistance. Moreover, the lower limit of the mass ratio is preferably 0, and more preferably 0.1, 0.2, 0.25, 0.29, 0.31, and 0.33 in order.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the content of _Na2O to the total content of _Li2O , _Na2O , _K2O , and _Cs2O [ _Na2O /( _Li2O + _Na2O + _K2O + _Cs2O )] is preferably 1, and more preferably 0.95, 0.9, 0.85, 0.80, 0.75, 0.70, and 0.66 in order from the viewpoint of suppressing the increase in liquidus temperature and suppressing the decrease in weather resistance. Moreover, the lower limit of the mass ratio is preferably 0, and more preferably 0.1, 0.2, 0.25, 0.29, 0.31, 0.33, and 0.34 in order.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the _K2O content to the total content of _Li2O , _Na2O , _K2O , and _Cs2O [ _K2O /( _Li2O + _Na2O + _K2O + _Cs2O )] is preferably 1, and more preferably 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.28, and 0.27 in order from the viewpoint of suppressing the increase in liquidus temperature and suppressing the decrease in weather resistance. The lower limit of the mass ratio is preferably 0, and more preferably 0.1, 0.15, 0.20, 0.22, 0.24, and 0.25 in order.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the content _{of P2O5} to the total content of _Li2O , _Na2O , _K2O , _Cs2O , _{Nb2O5 , TiO2} , _WO3 and _Bi2O3 [ _P2O5 /( _Li2O +Na2O+K2O+ _Cs2O + _Nb2O5 +TiO2+ _WO3 + _{Bi2O3 ) ]} is preferably 1, and more preferably 0.5, 0.3 _, 0.1, _0.08 , 0.07, 0.06 in order. _Moreover , the lower limit of the mass ratio is preferably 0, _and more preferably 0.005, _0.008 , 0.011, 0.012 in order.

In glass composition A, by appropriately introducing the glass components Li ₂ O, Na ₂ O, K ₂ O, Cs ₂ O, Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ , the required Abbe number νd and partial dispersion ratio Pg,F can be obtained. However, if these components are introduced into silicate glass, there is a concern that the stability during reheating will deteriorate. On the other hand, P ₂ O ₅ is a component that improves the stability during reheating. Therefore, if the mass ratio _{[ P2O5} /( _Li2O + _Na2O + _K2O + _Cs2O + _Nb2O5 + _TiO2 + _WO3 + _Bi2O3 )] is too _high , there is a concern that the glass stability may deteriorate and _the partial dispersion ratio Pg,F may increase. On the other hand, if it is too low, there is a concern that the stability may deteriorate during reheating. Therefore, it is best that the mass ratio is within the above range.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the total content of _Li2O , _Na2O , _K2O and _Cs2O to the total content of _SiO2 , _P2O5 and _B2O3 [( _Li2O + _Na2O + _K2O + _Cs2O )/( _SiO2 + _P2O5 + _B2O3 )] is preferably 5, and more preferably 4, ₃ , 2, 1.5, ₁ , 0.9, 0.8, _0.7 , _0.6 in order. Moreover, the lower limit of the mass ratio is preferably 0.02, and more preferably 0.1, 0.2, 0.3, 0.4, 0.45 in order.

In glass composition A, if the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)/(SiO ₂ +P ₂ O ₅ +B ₂ O ₃ )] is too low, the glass transition point Tg may increase, and there may be concerns that solubility may deteriorate and the partial dispersion ratio Pg,F may increase. On the other hand, if it is too high, the viscosity of the glass during melting may decrease, the thermal stability of the melt may decrease, and there may be concerns that the stability may deteriorate during reheating.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 4, and more preferably 3, 2, 1.5, 1, 0.9, 0.8, 0.7, 0.6, and 0.5 in this order. In addition, the lower limit of the mass ratio is preferably 0.015, and more preferably 0.100, 0.200, and 0.300 in this order.

In glass composition A, if the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)/(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is too low, the partial dispersion ratio Pg,F may increase and the transmittance may deteriorate. If it is too high, the Abbe number may increase, the refractive index may decrease, and the stability may deteriorate during reheating.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the MgO content is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. In addition, the lower limit of the MgO content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, the lower limit of the MgO content is preferably 1%, and may also be set to 2%, 4%, or 6%.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the CaO content is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. In addition, the lower limit of the CaO content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, the lower limit of the CaO content is preferably 1%, and may also be set to 2%, 4%, 6%, or 8%.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the SrO content is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. In addition, the lower limit of the SrO content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, the lower limit of the SrO content is preferably 1%, and may also be set to 2%, 4%, 6%, or 8%.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the BaO content is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. In addition, the lower limit of the BaO content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, the lower limit of the BaO content is preferably 1%, and may also be set to 2%, 4%, 6%, or 8%.

In glass composition A, MgO, CaO, SrO, and BaO are glass components that improve the thermal stability and devitrification resistance of glass. However, if the content of these glass components is too high, the specific gravity will increase and the high dispersibility will be damaged, and the thermal stability and devitrification resistance of the glass will decrease. Therefore, the content of each of these glass components is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the ZnO content is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. In addition, the lower limit of the ZnO content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, or when the glass transition point is lowered, the lower limit of the ZnO content is preferably 1%, and may also be set to 2%, 4%, or 6%.

ZnO is a glass component that improves the thermal stability of glass in glass composition A. However, if the ZnO content is too high, there is a concern that the specific gravity will increase. Therefore, the ZnO content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the total content of MgO and CaO [MgO+CaO] is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. Moreover, the lower limit of the total content is preferably 0%. From the viewpoint of not hindering high dispersion and maintaining thermal stability, the total content is preferably within the above range.

Furthermore, in the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the total content of MgO, CaO, SrO, BaO and ZnO [MgO+CaO+SrO+BaO+ZnO] is preferably 20%, and more preferably 14%, 9%, 4%, 2%, and 1% in that order. The upper limit may also be 0%. Moreover, the lower limit of the total content is preferably 0%. In particular, when the specific resistivity of the glass is increased to improve the melting efficiency, the lower limit of the total content is preferably 1%, and may also be set to 2%, 4%, 6%, or 8%. From the perspective of suppressing the increase in specific gravity, not hindering high dispersion, and maintaining thermal stability, the total content is preferably within the above range.

Furthermore, in the glass material for molding of the present embodiment, in the case of glass composition A, the upper limit of the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of _Li2O , _Na2O , _K2O and _Cs2O [(MgO+CaO+SrO+BaO+ZnO)/( _Li2O + _Na2O + _K2O + _Cs2O )] is preferably 20, and more preferably 18, 16, and 14 in that order. The lower limit of the mass ratio is preferably 0, and more preferably 5, 8, 10, 12, and 13 in that order. The mass ratio may also be 0. The mass ratio is preferably within the above range from the viewpoints of suppressing an increase in the specific gravity of the glass, improving the melting property while achieving high refractive index and high dispersion by increasing the glass filling rate, and appropriately maintaining the specific resistivity of the glass.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the La ₂ O ₃ content is preferably 20%, and more preferably 17%, 14%, and 12% in that order. When stability is more important than the refractive index, the upper limit of the La ₂ O ₃ content may be set to 9%, 7%, 5%, 3%, 2%, or 1%. The upper limit may also be 0%. In addition, the lower limit of the La ₂ O ₃ content is preferably 0%. In particular, when the refractive index is increased while maintaining the content of the glass-forming components, the lower limit of the La ₂ O ₃ content is preferably 1%, and may also be set to 2%, 4%, or 6%.

In glass composition A, if the La ₂ O ₃ content is too high, the high dispersion of the glass will be inhibited and the thermal stability will be reduced. Therefore, the La ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Y ₂ O ₃ content is preferably 20%, and more preferably 17%, 14%, and 12% in that order. When stability is more important than the refractive index, the upper limit of the Y ₂ O ₃ content may be set to 9%, 7%, 5%, 3%, 2%, or 1%. The upper limit may also be 0%. In addition, the lower limit of the Y ₂ O ₃ content is preferably 0%. In particular, when the refractive index is increased while maintaining the content of the glass-forming components, the lower limit of the Y ₂ O ₃ content is preferably 1%, and may also be set to 2%, 3%, or 5%.

In glass composition A, if the Y ₂ O ₃ content is excessively increased, the high dispersion of the glass will be inhibited, the thermal stability will be reduced, and the glass will be easily devitrified during production. Therefore, the Y ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Sc ₂ O ₃ content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. In addition, the lower limit of the Sc ₂ O ₃ content is preferably 0%.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the _HfO2 content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. In addition, the lower limit of the _HfO2 content is preferably 0%.

Sc ₂ O ₃ and HfO ₂ have the function of improving the high dispersibility of the glass in the glass composition A, but they are expensive components. Therefore, the contents of Sc ₂ O ₃ and HfO ₂ are preferably within the above ranges.

In addition, HfO ₂ is contained in a certain amount in the ZrO ₂ raw material. Therefore, the glass containing ZrO ₂ will contain a certain amount of HfO _2. Therefore, in the case of the glass composition A of the molding glass material of the first embodiment, the mass ratio of the HfO ₂ content to the ZrO ₂ content [HfO ₂ /ZrO ₂ ] should also be set within a predetermined range. For example, the lower limit of the mass ratio [HfO ₂ /ZrO ₂ ] may be 0.005, or 0.010, 0.013, or 0.015. On the other hand, the upper limit of the mass ratio may be 0.05, or 0.040, 0.030, 0.020, or 0.018. From the viewpoint of suppressing the melting of refractory brick components into glass, the glass preferably contains a small amount of ZrO ₂ , and therefore the HfO ₂ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the Lu ₂ O ₃ content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. In addition, the lower limit of the Lu ₂ O ₃ content is preferably 0%.

Lu ₂ O ₃ has the function of improving the high dispersibility of glass in glass composition A, but because of its large molecular weight, it is also a glass component that causes the specific gravity of glass to increase. Therefore, the Lu ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of the _GeO2 content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. In addition, the lower limit of the _GeO2 content is preferably 0%.

GeO ₂ has the function of improving the high dispersibility of glass in glass composition A, but it is an extremely expensive component among the glass components generally used. Therefore, from the perspective of reducing the cost of glass manufacturing, the GeO ₂ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of _{the Gd2O3} content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. In addition, the lower limit of _{the Gd2O3} content is preferably 0%.

In glass composition A, if _{the Gd2O3} content is excessively increased, the thermal stability of the glass will be reduced. Also, if the _Gd2O3 content is excessively increased, the specific gravity of the glass _will increase, which is not desirable. Therefore, from the perspective of suppressing the increase in specific gravity while maintaining the thermal stability of the glass, _{the Gd2O3} content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of _{the Yb2O3} content is preferably 3%, and more preferably 2%, 1.5%, 1%, and 0.5% in that order. The upper limit may also be 0%. Moreover, the lower limit of _{the Yb2O3} content is preferably 0%.

In glass composition A, since the molecular weight of Yb ₂ O ₃ is greater than that of La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ , the specific gravity of the glass increases. If the specific gravity of the glass increases, the mass of the optical element will increase. For example, if a large mass lens is assembled in an autofocus camera lens, the power required to drive the lens during autofocus will increase, resulting in intense battery consumption. Therefore, it is best to reduce the Yb ₂ O ₃ content to suppress the increase in the specific gravity of the glass.

Furthermore, if _{the Yb2O3} content in glass composition A is too high, the thermal stability of the glass will decrease and absorption will occur easily in the near-infrared region. From the perspective of maintaining the transmittance of the glass in the near-infrared region, preventing the decrease in thermal stability, and suppressing the increase in specific gravity, _{the Yb2O3} content is preferably within the above range.

In the case of the glass composition A of the present embodiment, the molding glass material is preferably mainly composed of the above-mentioned glass components ₍ i.e., _{SiO2 , P2O5} , _B2O3 , _Al2O3 , _ZrO2 , _TiO2 , _Nb2O5 , _{WO3 , Bi2O3 , Ta2O5} , _Li2O , _Na2O , _K2O , _Cs2O , _MgO , CaO, _SrO , _BaO , _ZnO , _La2O3 , _Y2O3 , _{Sc2O3 , HfO2} , _Lu2O3 , _GeO2 , _Gd2O3 , _{and Yb2O3 ) .} ), and the lower limit of the total content of the above glass components is preferably 95.5%, and the more preferred order is 96.0%, 96.5%, 97.0%, 97.5%, 98.0%, 98.5%, and 99.0%.

In addition, the glass material for molding of the present embodiment is preferably basically composed of the above-mentioned glass components, but may also contain other components within the range that does not hinder the effect of the present invention. In addition, the present invention does not exclude the inclusion of inevitable impurities.

(Other components) Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, the glass components of the glass material used for forming the present embodiment should preferably not contain these elements.

U, Th, and Ra are all radioactive elements. Therefore, it is best not to contain these elements in the glass component of the glass material for molding in this embodiment.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm will cause the coloring of the glass to increase and become a source of fluorescence. Therefore, it is best not to contain these elements in the glass composition of the glass material for molding in this embodiment.

Sb (Sb ₂ O ₃ ) and Ce (CeO ₂ ) are optional elements that have the function of clarifiers. Among them, Sb (Sb ₂ O ₃ ) is not only a clarifier with a greater clarification effect, but also has the effect of increasing λτ80 because a small amount of it can promote the oxidation of easily reduced components. The clarification effect of Ce (CeO ₂ ) is smaller than that of Sb (Sb ₂ O ₃ ). If Ce (CeO ₂ ) is added in large quantities, the coloring of the glass will tend to be enhanced.

The Sb ₂ O ₃ content is expressed as an outer percentage. That is, when the total content of all glass components other than Sb ₂ O ₃ and CeO ₂ is set to 100 mass %, the upper limit of the Sb ₂ O ₃ content is preferably 1.000 mass %, and more preferably 0.500 mass %, 0.300 mass %, 0.100 mass %, 0.080 mass %, 0.060 mass %, and 0.040 mass %. In addition, the lower limit of the Sb ₂ O ₃ content is preferably 0.000 mass %, and more preferably 0.001 mass %, 0.003 mass %, 0.005 mass %, 0.010 mass %, 0.015 mass %, and 0.020 mass %. In addition, because _Sb2O3 itself will shift the penetration absorption edge of the glass toward the long wavelength, from the perspective of maximizing the transmittance of the glass in the short wavelength region, _{the Sb2O3} content _can be below 0.008 mass%, below 0.004 mass%, and even 0.000 mass%.

The CeO ₂ content is also expressed as an additional ratio. That is, when the total content of all glass components other than CeO ₂ and Sb ₂ O ₃ is set to 100 mass%, the upper limit of the CeO ₂ content is preferably 1.000 mass%, and more preferably 0.500 mass, 0.300 mass, 0.100 mass, 0.080 mass, 0.060 mass, and 0.040 mass in sequence. In addition, the lower limit of the CeO ₂ content is preferably 0.000 mass%, and more preferably 0.005 mass, 0.010 mass, 0.015 mass, and 0.020 mass in sequence. The _{CeO 2} content may also be 0 mass%.

(Glass properties when having glass composition A) <Abbe number νd> In the case of the glass material for molding of the present embodiment, when the glass composition is A, the upper limit of the Abbe number νd is preferably 50, and may also be 45, 40, 35, 33, 31, or 30. In addition, the lower limit of the Abbe number νd is preferably 15, and may also be 17, 18, 19, 20, 21, 22, 23, or 24.

By setting the Abbe number νd to the above range, a glass with high dispersion can be obtained. The Abbe number νd can be controlled by adjusting the contents of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ , which are glass components that contribute to high dispersion.

<Refractive index nd> In the case of glass composition A in the molding glass material of the present embodiment, the lower limit of the refractive index nd can be set to 1.65, and can also be set to 1.70, 1.72, 1.74, 1.76, or 1.80. In addition, the upper limit of the refractive index nd can be set to 2.30, and can also be set to 2.10, 2.00, or 1.90. The refractive _index can be controlled by adjusting the content of _Nb2O5 , _TiO2 , _WO3 , and _Bi2O3 , _which are glass components that contribute to high refractive index.

<Glass transition temperature Tg> When the glass material for molding of the present embodiment has glass composition A, the upper limit of the glass transition temperature Tg is preferably 700°C, 680°C, 670°C, 660°C, 650°C, 640°C, 630°C, 620°C, 610°C, 600°C, 590°C, and 580°C in this order. The lower limit of the glass transition temperature Tg is not particularly limited, but is preferably 200°C, more preferably 300°C, 400°C, and 450°C in this order. The glass transition temperature Tg can be controlled by adjusting the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)/(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )], etc.

By satisfying the above upper limit of the glass transition temperature Tg, the increase in the forming temperature and the annealing temperature during the reheating of the glass can be suppressed, thereby reducing the thermal damage to the reheating forming equipment and the annealing equipment.

By satisfying the above lower limit of the glass transition temperature Tg, the glass of the present invention can maintain good formability and glass thermal stability during reheating while having the required Abbe number, refractive index or transmittance.

<Specific gravity> In the glass material for molding of this embodiment, when the glass composition A is used, the upper limit of the specific gravity is preferably 4.3, and the more preferred order is 4.1, 4.0, 3.9, 3.8, 3.7, and 3.6. There is no particular restriction on the lower limit of the specific gravity, which is usually 2.0, and preferably 2.5.

The specific gravity is measured by a method with a repeated measurement accuracy of ±0.001 to ±0.002.

＜λτ80＞ In the case of glass composition A, glass samples with thicknesses of 2.0mm±0.1mm and 10.0mm±0.1mm were used to measure the spectral transmittance in the wavelength range of 200~700nm according to JOGIS17 (method for measuring internal transmittance of optical glass). The wavelength when the internal transmittance of the glass with a thickness of 10mm becomes 80% was set as λτ80.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of λτ80 is preferably 395nm, and the upper limit is preferably 390nm, 385nm, 380nm, 375nm, and 370nm in order, and the smaller the value, the better. The lower limit of λτ80 is not particularly limited, and is usually 250nm. From the perspective of suppressing the transmittance of ultraviolet light, it can also be set to 300nm or 320nm.

<λ70> For glass composition A, the spectral transmittance of a glass sample with a thickness of 10.0mm±0.1mm was measured in the wavelength range of 200~700nm, and the wavelength when the external transmittance became 70% was set as λ70.

In the glass material for molding of the present embodiment, when the glass composition A is used, the upper limit of λ70 is preferably 445nm, and more preferably 440nm, 430nm, 420nm, 410nm, 400nm, 390nm, and 380nm in that order. The lower limit of λ70 is not particularly limited, and is usually 255nm. From the perspective of suppressing the transmittance of ultraviolet light, it can be set to 305nm or 325nm.

In addition, in the case of the glass composition A of the present invention, it has a high refractive index and a small partial dispersion ratio Pg,f. Therefore, even if the glass cooling rate of the later-described step 3 is set to one-tenth, the dispersion change of the glass can still be suppressed. For example, when comparing the glass obtained in step 3 at the later-described cooling rate with the glass obtained at one-tenth of the cooling rate, the change Δνd of the Abbe number is preferably greater than -0.10, more preferably greater than -0.09, and the lower limit is preferably -0.08, -0.07, -0.06, -0.05, -0.04, and -0.03 in order. In addition, when combined with a low-dispersion lens, from the perspective of effectively correcting chromatic aberration, the Abbe number νd of the glass material of this embodiment is preferably less than 50. Therefore, the upper limit of the above Δνd is +0.10, and the more preferred values are +0.08, +0.06, +0.04, +0.02, and +0.01, respectively. In particular, when the Abbe number is below 35, preferably below 30, the upper limit of the above Δνd is preferably +0.005, and more preferably can be set to +0.00, -0.01, -0.02, or -0.03.

<Average linear expansion coefficient α _L > In the molding glass material of the present embodiment, when the glass composition A is used, the lower limit of the average linear expansion coefficient α _L at -30 to 70°C is preferably 0.70×10 ^-5 ℃ ^-1 , and more preferably 0.71×10 ^-5 ℃ ^-1 , 0.72×10 ^-5 ℃ ^-1 , 0.73×10 ^-5 ℃ ^-1 , 0.74×10 ^-5 ℃ ^-1 , 0.75×10 ^-5 ℃ ^-1 , 0.76×10 ^-5 ℃ ^-1 , 0.77×10 ^-5 ℃ ^-1 , 0.78×10 ^-5 ℃ ^-1 , and 0.79×10 ^-5 ℃ ^-1 . From the viewpoint of maintaining glass stability and obtaining desired optical properties, the upper limit of the mean linear expansion coefficient α _L is 1.10×10 ^-5 ℃ ^-1 , preferably 1.05×10 ^-5 ℃ ^-1 or less, and more preferably 1.00×10 ^-5 ℃ ^-1 , 0.96×10 ^-5 ℃ ^-1 , 0.92×10 ^-5 ℃ ^-1 , 0.88×10 -5 ℃ ^-1 , and 0.84× ^{10 -5 ℃ -1} , in that order.

In the case of glass composition A, by setting the average linear expansion coefficient α _L from -30 to 70°C within the above range, a glass material for molding that can be used in a wide temperature environment can be obtained.

The average linear expansion coefficient α _L is measured according to the provisions of JOGIS16. The sample is a round bar with a length of 20mm±0.5mm and a diameter of 5mm±0.5mm. Under a load of 98mN, the sample is heated at a constant rate of 4℃ per minute, and the temperature and sample extension are measured every 1 second. The average linear expansion coefficient α _L is the average value of the linear expansion coefficients from -30 to 70℃.

In addition, although JOGIS16 stipulates that "the mean linear expansion coefficient is expressed in units of 10 ^-7 ℃ ^-1 to the first integer", in this manual, the mean linear expansion coefficient α _L is expressed in units of [10 ^-5・℃ ^-1 ].

In this specification, the unit of the mean linear expansion coefficient α _L is [10 ^-5・℃ ^-1 ], but even if the unit is [10 ^-5・K ^-1 ], the value of the mean linear expansion coefficient α _L is the same.

(Glass composition B) Next, in the case where the molding glass material of this embodiment has glass composition B, the content and ratio of the glass components and the glass properties are explained.

In the case of the present embodiment having glass composition B, the glass components are C(SiO _{2 )} , C(B ₂ O ₃ ), C(Al _{2 O 3 )} , C(Li ₂ O ₎ , C( _{Na 2 O} ), C( _{K 2 O), C(Cs 2 O ) , C (} MgO ₎ , C( _CaO ), C( _{SrO ), C(BaO), C(ZnO), C(La 2 O 3 ), Gd 2 O 3 , Y 2 O 3 , ZrO} 2 , TiO 2 , Nb ₂ O 5 , WO 3 , and Bi ₂ O ₃ , expressed in terms _of mass %, _respectively . O ₃ ), C(Gd ₂ O ₃ ), C(Y ₂ O ₃ ), C(ZrO ₂ ), C(TiO ₂ ), C(Nb ₂ O ₅ ), C(WO ₃ ), and C(Bi ₂ O ₃ ).

The glass components other than the above are represented by _their mass % as _C ( _{Ta2O5 )} , C( _{Sc2O3 )} , _C ( _HfO2 ), _C ( _{Lu2O3 )} , C _{( GeO2} ), and _{C ( Yb2O3 ) , respectively .}

In the case of the present embodiment having glass composition B, the chemical formula weights of SiO ₂ , BO _1.5 , AlO _1.5 , LiO _0.5 , NaO _0.5 , KO _0.5 , CsO _0.5 , MgO, CaO, SrO, BaO, ZnO, LaO _1.5 , GdO _1.5 , YO _1.5 , ZrO ₂ , TiO ₂ , NbO _2.5 , WO ₃ , and BiO _1.5 are respectively M(SiO ₂ ), M(BO _1.5 ), M(AlO _1.5 ), M(LiO _0.5 ), M(NaO _0.5 ), M(KO _0.5 ), M(CsO _0.5 ), M(MgO), M(CaO), M(SrO), M(BaO), M(ZnO), M(LaO _1.5 ), M(GdO _1.5 ), M(YO _1.5 ), M(ZrO ₂ ), M(TiO ₂ ), M(NbO _2.5 ), M(WO ₃ ), and M(BiO _1.5 ).

The chemical formulas of the glass components TaO _2.5 , ScO _1.5 , HfO ₂ , LuO _1.5 , GeO ₂ , and YbO _1.5 other than the above are represented by M(TaO _2.5 ), M(ScO _1.5 ), M(HfO ₂ ), M(LuO _1.5 ), M(GeO ₂ ), and M(YbO _1.5 ), respectively.

That is, in the case of the present embodiment having a glass composition B, for example, the content of the relevant oxide _{XyOz can} be set as C( _XyOz ) in terms of mass % _. Furthermore, the chemical formula weight of the _cation (cation "X") of _the oxide _XyOz per 1 mol (i.e., the chemical formula weight of XOz _/y ) can be set as M(XOz _/y ). When expressed by the formula {C( _XyOz )/M(XOz _/y )}, it is the content of the cation "X" expressed in terms of mole %, i.e., the content of "X" expressed in terms of cation %.

In the case of the glass material for molding of the present embodiment, when the glass composition B is A1={C(B ₂ O ₃ )/M(BO _1.5 )}/{C(B ₂ O ₃ )/M(BO _1.5 )+C(SiO ₂ )/M(SiO ₂ )}, the lower limit of A1 is preferably 1/3, and more preferably 1.1/3, 1.2/3, 1.3/3, 1.4/3, 1.5/3, 1.6/3, 1.7/3, 1.8/3, and 1.9/3. The upper limit of A1 is preferably 3.0/3, and more preferably 2.9/3, 2.8/3, 2.7/3, 2.6/3, 2.5/3, 2.4/3, and 2.3/3.

In glass composition B, by setting A1 to the above range, a glass material for molding with a large average linear expansion coefficient α _L at -30 to 70°C and low dispersion can be obtained. In addition, the temperature coefficient of the relative refractive index of the glass (dn/dT) can be reduced. In addition, even if a large amount of La ₂ O ₃ is contained, the reduction in thermal stability of the glass can be suppressed. On the other hand, if A1 is too small, when a large amount of La ₂ O ₃ and Y ₂ O ₃ , which are glass components for increasing the refractive index nd and preventing the average linear expansion coefficient α _L from being reduced, are contained, there is a concern that the glass may become unstable. In addition, if A1 is too large, there is a concern that the stability, chemical durability, and mechanical properties of the glass may be reduced.

In the case of the glass composition B of the molding glass material of the present embodiment, B1={C(BaO)/M(BaO)+C(SrO)/M(SrO)}/{C(Li ₂ O)/M(LiO _0.5 )+C(Na ₂ O)/M(NaO _0.5 )+C(K ₂ O)/M(KO _0.5 )+C(Cs ₂ O)/M(CsO _0.5 )+C(MgO)/M(MgO)+C(CaO)/M(CaO)+C(SrO)/M(SrO)+C(BaO)/M(BaO)}, the lower limit of B1 is preferably 0.62, and the more preferred sequences are 0.63, 0.65, 0.67, 0.69, 0.71, 0.73, 0.75, 0.77, 0.79, 0.81, 0.83, 0.85, and 0.87. In addition, the upper limit of B1 is preferably 1.00, and the more preferred sequences are 0.99 and 0.98. B1 may also be 1.00.

In the glass composition B, by setting B1 to the above range, a molding glass material having a large average linear expansion coefficient α _L and a high refractive index can _be obtained. In addition, the decrease in thermal stability can be suppressed while the average linear expansion coefficient α L is increased. On the other hand, if B1 is too small, the average linear expansion coefficient α _L and the refractive index nd may decrease, thereby damaging the stability of the glass.

In the case of glass composition B, the molding glass material of the present embodiment is C1={C(BaO)/M(BaO)+C(Li ₂ O)/M(LiO _0.5 )}/{C(Na ₂ O)/M(NaO _0.5 )+C(K ₂ O)/M(KO _0.5 )+C(SiO ₂ )/M(SiO ₂ )+C(TiO ₂ )/M(TiO ₂ )+C(Nb ₂ O ₅ )/M(NbO _2.5 )+C(WO ₃ )/M(WO ₃ )}, the lower limit of C1 is preferably 8/9, and the more preferred order is 8.2/9, 8.4/9, 8.6/9, 8.8/9, 9.0/9, 9.2/9, 9.4/9, 9.5/9. Moreover, the upper limit of C1 is preferably 27/9, and the more preferred order is 25/9, 23/9, 21/9, 19/9, 17/9, 15/9, 13/9, 12/9.

In glass composition B, by setting C1 to the above range, a molding glass material having a large average linear expansion coefficient α _L and a high refractive index and low dispersion can be obtained. In addition, the temperature coefficient of the relative refractive index of the glass (dn/dT) can be reduced. On the other hand, if C1 is too small, there is a concern that the average linear expansion coefficient α _L is reduced and the glass loses its high refractive index and low dispersion. In addition, if C1 is too large, there is a concern that the stability of the glass is reduced.

In the glass material for molding of the present embodiment, when the glass composition B is D1=C( _Gd2O3 )+C( _ZnO )+C(TiO2)+C( _Nb2O5 )+C( _WO3 )+C( _ZrO2 ), _the upper limit of D1 is preferably 13.50, and more preferably 12.00, 11.00, _10.50 , 10.00, 9.50, 9.00, 8.50 in that order. The lower limit of D1 is preferably 0, and more preferably 1, 2, 3, 4, 5, 6, 7, 8 in that order. D1 may also be 0.

In glass composition B, by setting D1 to the above range, the average linear expansion coefficient α _L can be suppressed from decreasing. In addition, a glass material for molding with high refractive index and low dispersion can be obtained, which suppresses high dispersion. In addition, it also has the effect of not increasing the temperature coefficient (dn/dT) of the relative refractive index of the glass. D1 can also be set to 0, and D1 can also be set to be greater than 0 to adjust optical constants such as the Abbe number νd. On the other hand, if D1 is too large, there is a concern that the average linear expansion coefficient α _L will decrease and the glass will lose its high refractive index and low dispersion.

In the molding glass material of the present embodiment, when the glass composition B is E1={C(La ₂ O ₃ )+C(Gd ₂ O ₃ )+C(Y ₂ O ₃ )}/{C(SiO ₂ )+C(B 2 O 3 )+C(Al ₂ O ₃ )}, the lower limit of E1 is preferably 1.25, and more preferably 1.30, _1.35 , 1.40, 1.45, 1.50, 1.55, 1.60, 1.65, and 1.70, respectively. The upper limit of E1 is preferably 3.00, and more preferably 2.80, _2.60 , 2.40, 2.20, and 2.10, respectively.

In glass composition B, by setting E1 to the above range, a high refractive index and low dispersion glass material for molding can be obtained. On the other hand, if E1 is too small, the glass may lose its high refractive index and low dispersion, and the average linear expansion coefficient α _L may decrease. Moreover, if E1 is too large, the thermal stability of the glass may decrease.

In the molding glass material of the present embodiment, in the case of glass composition B, when F1={C(Gd ₂ O ₃ )/M(GdO _1.5 )+C(ZnO)/M(ZnO)+C(TiO ₂ )/M(TiO ₂ )+C(Nb ₂ O ₅ )/M(NbO 2.5 )+C(WO 3 )/M(WO ₃ )+C(Bi _{2 O 3} )/M(BiO 1.5 )}/{C(Y _{2 O 3} )/M(YO _1.5 )}, the upper limit of F1 is preferably 2.0, and more preferably 1.8, _{1.6 ,} 1.4, 1.2, 1.1, 1.0, 0.9, 0.8, and 0.6 in this order. Furthermore, the lower limit of F1 is preferably 0, and more preferably 0.1, 0.2, 0.3, and 0.4 in that order. F1 may also be 0.

In the glass composition B, by setting F1 to the above range, a molding glass material having a large average linear expansion coefficient α _L can be obtained. In addition, the thermal stability of the glass can be suppressed from being degraded. F1 may be 0, but in order to adjust optical constants such as the Abbe number νd, F1 may be set to be greater than 0. On the other hand, if F1 is too large, the average linear expansion coefficient α _L may be reduced, and the glass may lose its high refractive index and low dispersion.

In the case of the glass material for molding of the present embodiment, when the glass composition B is G1=C(BaO)/M(BaO)+C(La ₂ O ₃ )/M(LaO _1.5 )+C(Li ₂ O)/M(LiO _0.5 )+C(Y ₂ O ₃ )/M(YO _1.5 ), the lower limit of G1 is preferably 0.47, and more preferably 0.475, 0.48, and 0.485 in that order. The upper limit of G1 is preferably 0.60, and more preferably 0.59, 0.58, 0.57, 0.56, 0.55, 0.54, and 0.53 in that order.

In the glass composition B, it is preferable to set G1 to the above range from the viewpoint of obtaining a glass material for molding with a high refractive index and low dispersion while suppressing the decrease of the average linear expansion coefficient _αL. On the other hand, if G1 is too small, there is a concern that the average linear expansion coefficient _αL decreases and the glass loses its high refractive index and low dispersion. Moreover, if G1 is too large, there is a concern that the thermal stability of the glass decreases.

In the present embodiment, when the glass composition is B, the lower limit of {C(B ₂ O ₃ )/M(BO _1.5 )+C(SiO ₂ )/M(SiO ₂ )} is preferably 0.35, and more preferably 0.37, 0.39, 0.41, 0.43, 0.45, and 0.47, respectively. The upper limit is preferably 0.75, and more preferably 0.73, 0.71, 0.69, 0.67, 0.65, 0.63, 0.61, and 0.59, respectively.

In the glass composition B, {C(B ₂ O ₃ )/M(BO _1.5 )+C(SiO 2 )/M(SiO ₂ )} is preferably set to the _above range from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient α _L and low dispersion.

In the present embodiment, when the glass composition is B, the lower limit of {C(BaO)/M(BaO)+C(SrO)/M(SrO)} is preferably 0.15, and more preferably 0.16, 0.17, 0.18, 0.19, and 0.20 in sequence. Moreover, the upper limit is preferably 0.30, and more preferably 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, and 0.23 in sequence.

In the glass composition B, from the viewpoint of obtaining a high refractive index molding glass material with a large average linear expansion coefficient _αL , {C(BaO)/M(BaO)+C(SrO)/M(SrO)} is preferably set to the above range.

In the present embodiment, in the case of glass composition B, the lower limit of {C( _Li2O )/M( _LiO0.5 )+C( _Na2O )/M( _NaO0.5 )+C( _K2O )/M( _KO0.5 )+C( _Cs2O )/M( _CsO0.5 )+C(MgO)/M(MgO)+C(CaO)/M(CaO)+C(SrO)/M(SrO)+C(BaO)/M(BaO)} is preferably 0.15, and more preferably 0.16, 0.17, 0.18, 0.19, and 0.20, respectively. Moreover, the upper limit is preferably 0.35, and the more preferred order is 0.34, 0.33, 0.32, 0.31, 0.30, 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, and 0.23.

In the glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _αL and a high refractive index, {C( _Li2O )/M( _LiO0.5 )+C( _Na2O )/M( _NaO0.5 )+C( _K2O )/M( _KO0.5 )+C( _Cs2O )/M( _CsO0.5 )+C(MgO)/M(MgO)+C(CaO)/M(CaO)+C(SrO)/M(SrO)+C(BaO)/M(BaO)} is preferably set to the above range.

In the present embodiment, when the glass composition is B, the lower limit of {C(BaO)/M(BaO)+C(Li ₂ O)/M(LiO _0.5 )} is preferably 0.15, and more preferably 0.16, 0.17, 0.18, 0.19, and 0.20, respectively. The upper limit is preferably 0.35, and more preferably 0.34, 0.33, 0.32, 0.31, 0.30, 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, and 0.23, respectively.

In the glass composition B, {C(BaO)/M(BaO)+C(Li ₂ O)/M(LiO _0.5 )} is preferably within the above range from the viewpoint of obtaining a molding glass material having a large average _linear expansion coefficient α L and a high refractive index and low dispersion.

In the present embodiment, when the glass composition is B, the lower limit of {C( _Na2O )/M( _NaO0.5 )+C( _K2O )/M( _KO0.5 )+C(SiO2)/M( _SiO2 )+C( _TiO2 )/M(TiO2)+C( _Nb2O5 )/M( _NbO2.5 )+C( _WO3 )/M( _WO3 )} is preferably 0.05, and more preferably 0.06, 0.07 _, 0.08, 0.09, _0.10 , _0.11 , 0.12, 0.13, 0.14, 0.15, and 0.16, respectively. Moreover, the upper limit is preferably 0.30, and the more preferable order is 0.29, 0.28, 0.27, 0.26, 0.25, 0.24, 0.23, 0.22, and 0.21.

In the glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _αL , a high refractive index and low dispersion, it is preferable to set the composition of C( _Na2O )/M( _NaO0.5 )+C( _K2O )/M( _KO0.5 )+C( _{SiO2 )} /M( _SiO2 )+C( _TiO2 )/M( _TiO2 )+C( _Nb2O5 )/M( _NbO2.5 )+C( _WO3 )/M( _WO3 ) to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [C(BaO)/{C(SiO ₂ )+C(TiO ₂ )+C(Nb ₂ O ₅ )+C(WO ₃ )}] is preferably 1.0, and more preferably 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, and 2.4 in order. The upper limit of the mass ratio is preferably 5.5, and more preferably 5.3, 5.1, 4.9, 4.7, 4.5, 4.3, 4.1, 3.9, 3.7, and 3.5 in order.

In glass composition B, it is preferable to set the mass ratio [C(BaO)/{C( _SiO2 )+C(TiO2)+C( _Nb2O5 )+C(WO3 ₎ }] to the above range from the viewpoint of obtaining a molding glass material having _a large average linear expansion coefficient αL, a high refractive index and low dispersion, and from the viewpoint of reducing the temperature coefficient of _relative refractive index (dn/ _dT ).

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [C(BaO)/{C(SiO ₂ )+C(B ₂ O ₃ )+C(TiO ₂ )+C(Nb ₂ O ₅ )+C(WO ₃ )}] is preferably 0.80, and more preferably 0.85, 0.90, 0.95, 1.00, 1.05, 1.10, 1.15, and 1.20, respectively. The upper limit of the mass ratio is preferably 1.70, and more preferably 1.65, 1.60, 1.55, 1.50, 1.45, 1.40, and 1.35, respectively.

In glass composition B, it is preferable to set the mass ratio [C( _BaO) /{C(SiO 2 )+C(B 2 O 3 )+C(TiO 2 )+C(Nb ₂ O 5 )+C(WO ₃ )}] to the above range from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _{α L} , _a high refractive index and low _dispersion , and from the viewpoint of reducing the temperature dependence of _the temperature coefficient of relative refractive index (dn/dT).

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [{C(BaO)+C(Li ₂ O)+C(SrO)}/{C(SiO ₂ )+C(TiO ₂ )+C(Nb ₂ O ₅ )+C(WO ₃ )}] is preferably 0.5, more preferably 1.0, 1.5, 2.0, 2.2, 2.4 in that order. The upper limit of the mass ratio is preferably 7.0, more preferably 6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5 in that order.

In glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _αL , a high refractive index and low dispersion, it is preferable to set the mass ratio [{C(BaO)+C( _Li2O )+C(SrO)}/{C( _SiO2 )+C( _TiO2 )+ _C ( _Nb2O5 )+C( _WO3 )}] to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [{C( _Li2O )+C( _Na2O )+C( _K2O )+C(Cs2O)+C( _CaO )+C(SrO)+C(BaO)}/{C(SiO2)+C( _TiO2 )+C( _Nb2O5 )+C( _WO3 )}] is preferably 0.5, more preferably 1.0, 1.5, _2.0 , 2.2 _, 2.4 in that order. The upper limit of the mass ratio is preferably 7.0, more preferably 6.5, 6.0, 5.5, 5.0, 4.5, 4.0, 3.5 in that order.

In glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _αL , a high refractive index and low dispersion, it is preferable to set the mass ratio [{C( _Li2O )+C( _Na2O )+C( _K2O )+C( _Cs2O )+C(CaO)+C(SrO)+C(BaO)} _/ {C( _SiO2 )+C( _TiO2 )+C( _Nb2O5 )+C( _WO3 )}] to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the total content [C(ZnO)+C(Gd ₂ O ₃ )+C(TiO ₂ )+C(Nb ₂ O ₅ )+C(WO ₃ )] is preferably 0, and more preferably in the order of 1, 2, 3, 4, and 5. The total content may also be 0. Moreover, the upper limit of the total content is preferably 15, and more preferably in the order of 14, 13, 12, 11, 10, 9, 8, 7, and 6.

In the glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion _{coefficient αL} and _small dispersion, it is preferable that the total content [C(ZnO)+C( _Gd2O3 )+C( _TiO2 )+C( _Nb2O5 )+C( _WO3 )] is within the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, the lower limit of the total content [C(SiO ₂ )+C(ZnO)+C(Gd ₂ O ₃ )+C(TiO ₂ )+C(Nb ₂ O ₅ )+C(WO ₃ )] is preferably 5, more preferably 6, 7, 8, and 9 in order. The upper limit of the total content is preferably 25, more preferably 24, 23, 22, 21, 20, 19, 18, 17, 16, 15, and 14 in order.

In glass composition B, the total content [C( _SiO2 )+C( _ZnO )+C(Gd2O3)+ _C (TiO2)+C(Nb2O5)+C( _{WO3 )} ] is preferably within the above range from the viewpoint of obtaining a molding glass material _{having a large} average linear expansion coefficient αL and _a high refractive index and low dispersion.

In the molding glass material of the present embodiment, in the case of glass composition B, the lower limit of the total content [C(SiO ₂ )+C(ZnO)+C(Gd ₂ O ₃ )+C(ZrO _{2 )+C(TiO 2 )} +C(Nb ₂ O ₅ )+C(WO ₃ )] is preferably 5, more preferably 6, 7, 8, and 9 in order. The upper limit of the total content is preferably 25, more preferably 24, 23, 22, 21, 20, 19, 18, 17, and 16 in order.

In glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient _αL and a high refractive index and low dispersion, it is preferable that the total content [C( _SiO2 )+C( _ZnO )+C( _Gd2O3 )+C( _ZrO2 )+C( _TiO2 )+C( _Nb2O5 )+C( _WO3 ) _] be within the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, the lower limit of the total content [C( _Al2O3 )+C _{( SiO2} )+C(ZnO)+C( _Gd2O3 )+C( _ZrO2 )+C( _TiO2 )+C( _Nb2O5 )+C( _WO3 )] is preferably 5, more preferably 6, _{7 ,} 8, and 9 in order. The upper limit of the total content is preferably 25, more preferably 24, 23, 22, 21, 20, 19, 18, 17, and 16 in order.

In glass composition B, from the viewpoint of obtaining a molding glass material having a large average linear expansion _{coefficient αL} and a high refractive index and low dispersion, it is preferable to set the total content [C( _Al2O3 )+C( _SiO2 )+C( _{ZnO )} +C( _Gd2O3 )+C(ZrO2)+C( _TiO2 )+C _{( Nb2O5} )+C( _WO3 )] to the above range.

In the present embodiment, in the case of glass composition B, the lower limit of the total content [C(La ₂ O ₃ )+C(Gd ₂ O ₃ )+C(Y ₂ O ₃ )] is preferably 25, and more preferably 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38. Moreover, the upper limit of the total content is preferably 50, and more preferably 49, 48, 47, 46, 45, 44, 43.

In the glass composition B, from the viewpoint of obtaining a high refractive index and low dispersion molding glass material, the total content [C(La ₂ O ₃ )+C(Gd ₂ O ₃ )+C(Y ₂ O ₃ )] is preferably set to be within the above range.

In this embodiment, when the glass composition is B, the lower limit of the total content [C(SiO ₂ )+C(B ₂ O ₃ )+C(Al ₂ O ₃ )] is preferably 15, more preferably 16, 17, 18, 19. The upper limit of the total content is preferably 30, more preferably 29, 28, 27, 26, 25.

In the glass composition B, from the viewpoint of obtaining a high refractive index and low dispersion molding glass material without reducing the refractive index as much as possible, the total content [C(SiO ₂ )+C(B ₂ O ₃ )+C(Al ₂ O ₃ )] is preferably set to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [{C(La ₂ O ₃ )+C(Gd ₂ O ₃ )+C(Y ₂ O ₃ )}/{2×C(SiO ₂ )+C(B ₂ O ₃ )+C(Al ₂ O ₃ )}] is preferably 1.00, and more preferably 1.05, 1.10, 1.15, 1.16, 1.17, 1.18, 1.19, 1.20, and 1.21, respectively. The upper limit of the mass ratio is preferably 1.80, and more preferably 1.75, 1.70, 1.65, 1.60, 1.55, 1.54, 1.53, 1.52, 1.51, and 1.50, respectively.

In glass composition B, from the viewpoint of obtaining a high refractive index _and low dispersion molding glass material _, the mass ratio [{C( _La2O3 )+C( _Gd2O3 )+ _{C(Y2O3 )} }/{2xC( _SiO2 )+C( _{B2O3 )} + _{C(Al2O3 )} }] is preferably within the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, the lower limit of the total content [2×C(SiO ₂ )+C(B ₂ O ₃ )+C(Al ₂ O ₃ )] is preferably 20, and more preferably 21, 22, 23, 24, 25, and 26 in order. The upper limit of the total content is preferably 45, and more preferably 44, 43, 42, 41, 40, 39, 38, 37, 36, and 35 in order.

In the glass composition B, the total content [2×C(SiO ₂ )+C(B 2 O 3 )+C(Al _{2 O 3} )] is preferably within _the above range from the viewpoint of obtaining a molding glass material having a large average linear expansion coefficient α L and a high refractive index _and low dispersion.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the mass ratio [{C(La ₂ O ₃ )+C(Y ₂ O ₃ )}/{C(B ₂ O ₃ )+C(BaO)}] is preferably 0.50, and more preferably 0.55, 0.60, 0.65, 0.70, 0.75, and 0.80, respectively. The upper limit of the mass ratio is preferably 1.30, and more preferably 1.25, 1.20, 1.15, 1.10, 1.05, 1.00, 0.95, and 0.92, respectively.

In the glass composition B, from the viewpoint of obtaining a high refractive index and low dispersion molding glass material, the mass ratio [{C(La ₂ O ₃ )+C(Y ₂ O ₃ )}/{C(B ₂ O ₃ )+C(BaO)}] is preferably set to the above range.

In the present embodiment, when the glass composition is B, the lower limit of [C(Gd ₂ O ₃ )/M(GdO _1.5 )+C(ZnO)/M(ZnO)+C(TiO ₂ )/M(TiO ₂ )+C(Nb ₂ O ₅ )/M(NbO _2.5 )+C(WO ₃ )/M(WO ₃ )+C(Bi ₂ O ₃ )/M(BiO _1.5 )] is preferably 0, and more preferably 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06, respectively. This value may also be 0. Moreover, the upper limit is preferably 0.30, and more preferably in the order of 0.25, 0.20, 0.18, 0.16, 0.14, 0.12, 0.10, and 0.08.

In glass composition B, from the viewpoint of increasing _the average linear expansion coefficient _αL and suppressing the decrease in thermal _stability of glass, [C( _Gd2O3 )/M( _GdO1.5 )+C(ZnO)/M(ZnO)+C( _TiO2 )/M( _TiO2 )+C( _Nb2O5 )/M( _NbO2.5 )+C( _WO3 )/M( _WO3 )+C( _{Bi2O3 )} /M( _BiO1.5 )] is preferably within the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, _the lower limit of the mass ratio [C( _Y2O3 )/{C( _La2O3 )+C( _{Y2O3 )} +C( _Gd2O3 )}] is preferably 0.20, and more preferably 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, _0.29 , 0.30, 0.31, 0.32, 0.33 _, and 0.34, in order. Moreover, the upper limit of the mass ratio is preferably 0.60, and the more preferred order is 0.59, 0.58, 0.57, 0.56, 0.55, 0.54, 0.53, 0.52, 0.51, 0.50, 0.49, 0.48, 0.47, and 0.46.

In the glass composition B, from the viewpoint of increasing the average linear expansion coefficient _αL and suppressing the decrease in the thermal _stability of the _glass , it is preferable to set the mass ratio [C( _Y2O3 )/{C( _La2O3 )+C( _{Y2O3 )} + _C ( _Gd2O3 )}] to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, _the lower limit of the mass ratio [C( _Y2O3 )/{ _C ( _La2O3 )+C( _{Y2O3 )} +C( _TiO2 )}] is preferably 0.20, and more preferably 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.30, 0.31, and 0.32, respectively. The upper limit of the mass ratio is preferably 0.50, and more preferably 0.49, 0.48, 0.47, 0.46, and 0.45, respectively.

In the glass composition B, from the viewpoint of increasing the average linear expansion coefficient _αL and suppressing the decrease in the thermal stability of _{the glass} , it is preferable to set the mass ratio [C( _Y2O3 )/{C( _La2O3 )+C _{( Y2O3} )+C( _TiO2 )}] to the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, _the lower limit of the total content [C(BaO)+C( _La2O3 )+C( _Y2O3 )] is preferably 50, and more preferably 52, ₅₄ , 56, 58, 60, 62, 64, 66, 68, 70. The upper limit of the total content is preferably 85, and more preferably 83, 81, 79, 77, 76.

In the glass composition B, from the viewpoint of obtaining a molding glass material having a high refractive index and low dispersion while suppressing a decrease in the mean linear expansion coefficient _αL , it is preferable that the total content [C(BaO)+C(La ₂ O ₃ )+C(Y ₂ O ₃ )] be within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the lower limit of the _SiO2 content is preferably 3.0%, and more preferably 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%, and 7.0% in sequence. In addition, the upper limit of the _SiO2 content is preferably 15.0%, and more preferably 14.5%, 14.0%, 13.5%, 13.0%, 12.5%, 12.0%, 11.5%, 11.0%, 10.5%, and 10.0% in sequence.

_SiO2 is a network-forming component of glass in glass composition B, and has the effect of improving the thermal stability, chemical durability, and weather resistance of glass, as well as increasing the viscosity _of molten glass and making it easier to shape molten glass. Moreover, _SiO2 has a stronger effect of increasing the ΔPg,F value than _La2O3 , BaO, and _Y2O3 , which are contained in large amounts in glass composition B. On _the other hand, if the _SiO2 content is too high, in addition to the average linear expansion coefficient _αL being more likely to decrease, there is also a concern that the refractive index nd will decrease. Moreover, if the _SiO2 content is too low, there is a concern that the stability will deteriorate during reheating. Therefore, the _SiO2 content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition is B, the lower limit of _{the B2O3} content is preferably 8.0%, and more preferably 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, and 12.0% in sequence. In addition, the upper limit of _{the B2O3} content is preferably 20.0%, and more preferably 19.5%, 19.0%, 18.5%, 18.0%, 17.5%, 17.0%, 16.5%, 16.0%, 15.5%, and 15.0% in sequence.

_B2O3 is a network-forming component of glass in glass composition B and has the effect of improving the thermal stability of glass. _It is also a component that is less likely to reduce the average linear expansion coefficient _αL among network-forming components. In addition, from the perspective of obtaining a high refractive index nd glass without damage and low dispersion, the _B2O3 content can be set to the above range. On the other hand, if _{the B2O3} content is too high, there is a concern that _the refractive index nd will be reduced. In addition, if the _B2O3 content is too low, there is a concern that the stability during reheating _will deteriorate.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the Al ₂ O ₃ content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. In addition, the lower limit of the Al ₂ O ₃ content is preferably 0%. The _{Al 2} O ₃ content may also be 0%.

In glass composition B, Al ₂ O ₃ is a glass component that improves the chemical durability and weather resistance of glass, and can also be considered a network-forming component. On the other hand, if the Al ₂ O ₃ content is too high, there will be concerns about a decrease in the refractive index nd, and a decrease in the thermal stability and melting properties of the glass. Therefore, the Al ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of _{the P2O5} content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. In addition, the lower limit of _{the P2O5} content is preferably 0%. _{The P2O5} content may also be 0%.

_P2O5 is _a component that lowers the refractive index nd and also lowers the thermal stability of the glass in the glass composition B. Therefore, _{the P2O5} content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the Li ₂ O content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. Moreover, the lower limit of the Li ₂ O content is preferably 0%. The _{Li 2} O content may also be 0%.

_Li2O is a component that contributes to lowering the specific gravity of glass in glass composition B, improves the glass meltability, and increases the average linear expansion coefficient _αL . It is also a component that contributes to lowering the glass transition temperature Tg, and contributes to improving the formability when precision press molding is performed. In addition, from the perspective of obtaining a glass with a high refractive index nd without compromising low dispersibility, the _Li2O content can be set to the above range. On the other hand, if the _Li2O content is too high, there is a concern that the devitrification resistance and acid resistance will be reduced. There is also a concern that the low dispersibility will be compromised.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the Na ₂ O content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. Moreover, the lower limit of the Na ₂ O content is preferably 0%. The _{Na 2} O content may also be 0%.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the K ₂ O content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in this order. The lower limit of the K ₂ O content is preferably 0%. The _{K 2} O content may also be 0%.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the total content of _Na2O and _K2O is preferably 10%, more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, 0.1%, respectively. The lower limit of the total content is preferably 0%, more preferably 0.001%, 0.01%, 0.05%, respectively.

In glass composition B, Na ₂ O and K ₂ O both have the effect of improving glass melting properties. They also have the effect of increasing the mean linear thermal expansion coefficient. On the other hand, if their contents are too high, thermal stability, devitrification resistance, chemical durability, and weather resistance will be reduced. Therefore, the individual contents and total contents of Na ₂ O and K ₂ O are preferably within the above ranges.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the Cs ₂ O content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. Moreover, the lower limit of the Cs ₂ O content is preferably 0%. The _{Cs 2} O content may also be 0%.

Cs ₂ O in glass composition B has the effect of improving the melting property of glass, but if the content is too high, it will reduce the thermal stability and refractive index nd of the glass, and increase the volatility of glass components during melting, resulting in the concern that the desired glass cannot be obtained. Therefore, the Cs ₂ O content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in that order. Moreover, the lower limit of the total content is preferably 0%. The total content may also be 0%. From the viewpoint of suppressing the increase in the liquidus temperature of the glass, the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O is preferably set to the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the MgO content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. In addition, the lower limit of the MgO content is preferably 0%. The MgO content may also be 0%.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the CaO content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.2%, and 0.1% in sequence. In addition, the lower limit of the CaO content is preferably 0%. The CaO content may also be 0%.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the SrO content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.4%, and 0.3% in sequence. In addition, the lower limit of the SrO content is preferably 0%, and more preferably 0.05%, 0.10%, 0.15%, and 0.20% in sequence.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the total content of MgO, CaO, and SrO is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.4%, and 0.3% in that order. Moreover, the lower limit of the total content is preferably 0%, and more preferably 0.05%, 0.10%, 0.15%, and 0.20% in that order. The total content may also be 0%.

In glass composition B, MgO, CaO, and SrO are glass components that improve the glass's meltability and also have a larger average linear expansion coefficient. However, if the content of these glass components is too high, the thermal stability and devitrification resistance of the glass will decrease. Therefore, the content of each of these glass components and the total content are preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the lower limit of the BaO content is preferably 20%, and more preferably 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, and 31% in sequence. In addition, the upper limit of the BaO content is preferably 45%, and more preferably 44%, 43%, 42%, 41%, 40%, 39%, 38%, 37%, 36%, 35%, and 34% in sequence.

BaO is a glass component that does not damage the high refractive index and low dispersion characteristics, but increases the average linear expansion coefficient α _L in glass composition B, and is also a component that reduces the ΔPg,F value. By setting the BaO content within the above range, a molding glass material with high refractive index and low dispersion and improved average linear expansion coefficient α _L can be obtained. On the other hand, if the BaO content is too high, the thermal stability of the glass will be reduced, and there will be a concern that the glass will devitrify, and there will be a concern that the stability will deteriorate when reheated.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the total content of _{SiO2 and B2O3} is preferably 30%, and more preferably 29%, 28%, 27%, 26%, 25%, 24%, 23%, 22%, 21%, and 20% in sequence. In addition, the lower limit of the total content is preferably 13%, and more preferably 14%, 15%, 16%, 17%, and 18% in sequence.

In the glass composition B, from the viewpoint of maintaining the stability of the glass and suppressing the decrease in the refractive index, the total content of SiO ₂ and B ₂ O ₃ is preferably set to the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the mass ratio of BaO content to the total content of SiO ₂ and B ₂ O ₃ [BaO/(SiO ₂ +B ₂ O ₃ )] is preferably 3.00, and more preferably 2.80, 2.60, 2.40, 2.20, 2.00, 1.80, and 1.70 in sequence. In addition, the lower limit of the mass ratio is preferably 0.60, and more preferably 0.80, 0.90, 1.00, 1.10, 1.20, and 1.30 in sequence.

In glass composition B, from the perspective of obtaining glass having a large mean linear expansion coefficient α _L while maintaining glass stability, the mass ratio is preferably set to the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the ZnO content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, 0.4%, 0.3%, 0.2%, 0.1%, 0.05%, 0.03%, 0.02%, 0.01% in this order. In addition, the lower limit of the ZnO content is preferably 0%. The ZnO content may also be 0%.

ZnO is a glass component in glass composition B that improves the melting property of glass. However, if the ZnO content is too high, there is a concern that the specific gravity of the glass increases and the average linear expansion coefficient α _L decreases. There is also a concern that the low dispersibility of the glass is impaired. There is also a concern that the glass transition temperature Tg decreases. Therefore, the ZnO content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of _{the La2O3} content is preferably 15%, and more preferably 16%, 17%, 18%, 19%, 20%, 21%, and 22% in sequence. Moreover, the upper limit of _{the La2O3} content is preferably 40%, and more preferably 39%, 38%, 37%, 36%, 35%, 34%, 33%, 32%, 31%, 30%, 29%, and 28% in sequence.

La ₂ O ₃ is a glass component that suppresses the decrease of the Abbe number νd and increases the refractive index in glass composition B. It is also a component that reduces the partial dispersion ratio Pg,F, and has a stronger effect of reducing the ΔPg,F value than BaO. Therefore, by setting the La ₂ O ₃ content within the above range, a molding glass material with high refractive index and low dispersion, suppressed decrease in the average linear expansion coefficient α _L , and suppressed increase in the temperature coefficient of relative refractive index (dn/dT) can be obtained. On the other hand, if the La ₂ O ₃ content is excessively increased, there is a concern that the thermal stability and devitrification resistance of the glass will be reduced, and there is also a concern that the stability will deteriorate during reheating.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of _{the Gd2O3} content is preferably 20%, and more preferably 15%, 10%, 5%, 4%, 3%, 2%, 1%, and 0.5% in sequence. In addition, the lower limit of _{the Gd2O3} content is preferably 0%. _{The Gd2O3} content may also be 0%.

_Gd2O3 is _a component with high refractive index and low dispersion in glass composition B, and can suppress the decrease of average linear expansion coefficient _αL . However, in the glass of the present embodiment in which BaO is introduced in large amounts, if the _Gd2O3 content is _excessively increased, the thermal stability and devitrification resistance of the glass _will be reduced, and the glass will easily devitrify during manufacturing. In addition, if the _Gd2O3 content is excessively increased, the specific gravity of the glass will increase, which is not desirable. Moreover, it is disadvantageous from the perspective of reducing the cost of raw materials. Therefore, _{the Gd2O3} content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the lower limit of _{the Y2O3} content is preferably 5%, and more preferably 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, and 14% in sequence. In addition, the upper limit of _{the Y2O3} content is preferably 25%, and more preferably 24%, 23%, 22%, 21%, 20%, and 19% in sequence.

In glass composition B, Y ₂ O ₃ is a component that has the effect of suppressing the decrease of Abbe number νd and increasing the refractive index. In addition, the glass of this embodiment in which a large amount of BaO or SrO is introduced into the alkali component or the alkali earth component is also an effective component for suppressing the decrease of the average linear expansion coefficient α _L and imparting high refractive and low dispersion characteristics. It also has the effect of improving the chemical durability and weather resistance of the glass and increasing the glass transition temperature. It is a component that reduces the partial dispersion ratio Pg,F and also has the effect of reducing the ΔPg,F value. On the other hand, if the Y ₂ O ₃ content is excessively increased, there is a concern that the thermal stability and devitrification resistance of the glass will be reduced. There is also a concern that the stability will deteriorate during reheating. Therefore, the Y ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the ZrO ₂ content is preferably 10%, and more preferably 9%, 8%, 7%, 6%, 5%, 4%, 3%, and 2.5% in sequence. In addition, the lower limit of the ZrO ₂ content is preferably 0%, and more preferably 0.005%, 0.01%, 0.05%, 0.1%, 0.5%, 1.0%, 1.5%, and 2.0% in sequence. The _{ZrO 2} content may also be 0%.

_ZrO2 in glass composition B is a component that has the effect of increasing the refractive index. When contained in an appropriate amount, it also has the effect of improving the thermal stability of the glass. However, _ZrO2 is not only a component that makes the average linear expansion coefficient _αL smaller, but also a component that increases the temperature dependence of the temperature coefficient of relative refractive index (dn/dT). Moreover, if the content is too high, there is a concern that the thermal stability will be significantly reduced. Therefore, the _ZrO2 content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the _TiO2 content is preferably 15%, and the more preferred sequence is 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, and 6%. In addition, the lower limit of the _TiO2 content is preferably 0%, and the more preferred sequence is 1%, 2%, 3%, 4%, and 5%. The _TiO2 content may also be 0%.

_TiO2 is a component that increases the refractive index in glass composition B. When contained in an appropriate amount, it also improves the thermal stability of the glass. _TiO2 is a component that increases the partial dispersion ratio Pg,F, and its effect of increasing Pg,F and ΔPg,F values is stronger than that _{of Nb2O5} . On the other hand, if the _TiO2 content is too high, in addition to the concern of decreasing the average linear expansion coefficient _αL , there is also the concern of decreasing the Abbe number νd, and there is the concern of increased glass coloring and deterioration of melting properties. There is also the concern of deterioration of stability during reheating. Therefore, the _TiO2 content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the Nb ₂ O ₅ content is preferably 20%, and more preferably 19%, 18%, 17%, 16%, 15%, 14%, 13%, 12%, 11%, 10%, 5%, 3%, 2%, and 1% in sequence. In addition, the lower limit of the Nb ₂ O ₅ content is preferably 0%, and more preferably 0.001%, 0.003%, 0.005%, 0.010%, 0.050%, 0.080%, and 0.100% in sequence. The _{Nb 2} O ₅ content may also be 0%.

Nb ₂ O ₅ is a component that increases the refractive index in glass composition B. When contained in an appropriate amount, it also improves the thermal stability of the glass. In addition, Nb ₂ O ₅ is a component that increases the partial dispersion ratio Pg,F and ΔPg,F. On the other hand, if the Nb ₂ O ₅ content is too high, in addition to the concern of reducing the average linear expansion coefficient α _L , there is also the concern of increased coloring of the glass. There is also the concern of deterioration of stability during reheating. Therefore, the Nb ₂ O ₅ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the WO ₃ content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, and 0.1% in sequence. In addition, the lower limit of the WO ₃ content is preferably 0%. The WO ₃ content may also be 0%.

WO ₃ in glass composition B has the effect of lowering the glass transition temperature Tg of other highly dispersed components. Therefore, when the glass is softened and molded, especially when precision pressing is performed, it can be introduced for the purpose of protecting the molding mold, protective film, and molding machine and lowering the molding temperature. On the other hand, from the perspective of improving the glass transmittance and suppressing the increase in the temperature coefficient of the glass relative refractive index (dn/dT), the WO ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the Bi ₂ O ₃ content is preferably 10%, and more preferably 8%, 6%, 4%, 2%, 1%, 0.5%, and 0.1% in this order. In addition, the lower limit of the Bi ₂ O ₃ content is preferably 0%. The _{Bi 2} O ₃ content may also be 0%.

Bi ₂ O ₃ is a component that increases the refractive index nd and reduces the Abbe number νd in glass composition B. It is also a component that tends to enhance the coloring of glass. Therefore, the Bi ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the Ta ₂ O ₅ content is preferably 20%, and more preferably 15%, 13%, 10%, 5%, 3%, and 1% in that order. Moreover, the lower limit of the Ta ₂ O ₅ content is preferably 0%. The _{Ta 2} O ₅ content may also be 0%.

Ta ₂ O ₅ is a glass component in glass composition B that improves the thermal stability and resistance to devitrification of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and makes the glass highly dispersed. Moreover, if the content of Ta ₂ O ₅ is too high, the thermal stability of the glass decreases, and when the glass is melted, melt residues of the glass raw materials are likely to occur. Moreover, it is a component that lowers the average linear expansion coefficient α _L. Therefore, the content of Ta ₂ O ₅ is preferably within the above range. Moreover, compared with other glass components, Ta ₂ O ₅ is a component with a very high unit price. If the content of Ta ₂ O ₅ is too high, the production cost of the glass will increase. Moreover, because the molecular weight of Ta ₂ O ₅ is larger than that of other glass components, the specific gravity of the glass will increase, resulting in an increase in the weight of the optical element.

In the molding glass material of the present embodiment, in the case of glass composition B, the upper limit of the Sc ₂ O ₃ content is preferably 2%. Also, the lower limit of the Sc ₂ O ₃ content is preferably 0%.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the _HfO2 content is preferably 2%. In addition, the lower limit of the _HfO2 content is preferably 0%.

In the glass composition B, Sc ₂ O ₃ and HfO ₂ are both components that have the function of increasing the refractive index nd and are high in unit price. Therefore, the contents of Sc ₂ O ₃ and HfO ₂ are preferably within the above ranges.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the Lu ₂ O ₃ content is preferably 2%. Also, the lower limit of the Lu ₂ O ₃ content is preferably 0%.

Lu ₂ O ₃ has the effect of increasing the refractive index nd in glass composition B. Also, because of its large molecular weight, it is also a glass component that increases the specific gravity of the glass. Therefore, the Lu ₂ O ₃ content is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the GeO ₂ content is preferably 2%. In addition, the lower limit of the GeO ₂ content is preferably 0%.

GeO ₂ has the function of increasing the refractive index nd in glass composition B, and is a very expensive component among commonly used glass components. Therefore, from the perspective of reducing the cost of glass manufacturing, the GeO ₂ content is preferably within the above range.

In the glass material for molding of the present embodiment, in the case of glass composition B, the upper limit of the La ₂ O ₃ content is preferably 2%. Moreover, the lower limit of the La ₂ O ₃ content is preferably 0%. The _{La 2} O ₃ content may also be 0%.

In glass composition B, if the La ₂ O ₃ content is too high, the thermal stability and devitrification resistance of the glass will be reduced, and the glass will easily devitrify during production. Therefore, from the viewpoint of suppressing the reduction of thermal stability and devitrification resistance, the La ₂ O ₃ content is preferably within the above range.

In the molding glass material of the present embodiment, in the case of glass composition B, the upper limit of the Yb ₂ O ₃ content is preferably 2%. Also, the lower limit of the Yb ₂ O ₃ content is preferably 0%.

In glass composition B, if the _Yb2O3 content is too high, there is a concern that the thermal stability and devitrification resistance of the glass _may be reduced. Moreover, it is a high-priced component among the glass components generally used. From the perspective of preventing the thermal stability of the glass from being reduced, suppressing the increase in specific gravity, and suppressing the glass manufacturing cost, _{the Yb2O3} content is preferably within the above range.

In the case of glass composition B, the molding glass material of the present embodiment is preferably mainly composed of the above-mentioned glass components _SiO2 , _B2O3 , _Al2O3 , _P2O5 , _Li2O , _Na2O , _K2O , _Cs2O , _MgO , CaO, _SrO , _BaO , _ZnO , _{La2O3 , Gd2O3} , _Y2O3 , ZrO2, _TiO2 , _{Nb2O5 , WO3 , Bi2O3} , _{Ta2O5 , Sc2O3 , HfO2 , Lu2O3 , GeO2} , _{and Yb2O3 . 3} , and the total content of the above glass components is preferably 95% or more, more preferably 98% or more, particularly preferably 99% or more, and most preferably 99.5% or more.

In the glass material for molding of this embodiment, the upper limit of the _TeO2 content is preferably 2%. In addition, the lower limit of the _TeO2 content is preferably 0%.

Since TeO ₂ is toxic, it is better to reduce the content of TeO _2. Therefore, the content of TeO ₂ is preferably within the above range.

In the glass material for molding of the present embodiment, when the glass composition B is used, the content of fluorine F is preferably less than 3%, and the upper limit is 1%, 0.5%, and 0.3%. The lower the F content, the better, and the lower limit is preferably 0%. The F content may also be 0%. In addition, it is best not to contain fluorine F substantially.

In the glass composition B, by setting the F content within the above range, volatility of the glass during melting can be suppressed, thereby suppressing the change in refractive index and the formation of streaks.

In addition, the glass material for molding of the present embodiment is preferably basically composed of the above-mentioned glass components, but may also contain other components within the range that does not hinder the effect of the present invention. In addition, the present invention does not exclude the inclusion of inevitable impurities.

<Other components> Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, the glass component of the glass material used for forming the present embodiment preferably does not contain these elements.

U, Th, and Ra are all radioactive elements. Therefore, the glass component of the glass material for molding in this embodiment preferably does not contain these elements.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm will cause the coloring of the glass to increase and become a source of fluorescence. Therefore, the glass composition of the glass material for molding in this embodiment preferably does not contain these elements.

Sb (Sb ₂ O ₃ ) and Ce (CeO ₂ ) are elements that can be added arbitrarily and have the function of clarifiers. Among them, Sb (Sb ₂ O ₃ ) is a clarifier with a greater clarification effect.

The Sb ₂ O ₃ content is expressed as an additional ratio. That is, when the total content of all glass components except Sb ₂ O ₃ and CeO ₂ is set to 100 mass%, the Sb ₂ O ₃ content is preferably less than 1 mass%, more preferably less than 0.1 mass%. Moreover, it is particularly preferably less than 0.05 mass%, less than 0.03 mass%, less than 0.02 mass%, and less than 0.01 mass%, in that order. The _{Sb 2} O ₃ content may also be 0 mass%.

The CeO ₂ content is also expressed as an additional ratio. That is, when the total content of all glass components except CeO ₂ and Sb ₂ O ₃ is set to 100 mass%, the CeO ₂ content is preferably less than 2 mass%, more preferably less than 1 mass%, particularly preferably less than 0.5 mass%, and most preferably less than 0.1 mass%. The CeO ₂ content may also be 0 mass%. By setting the CeO ₂ content to the above range, the clarity of the glass can be improved.

(Glass properties with glass composition B)

<Refractive index nd>

In the glass material for molding of this embodiment, when the glass composition B is used, the refractive index nd is not particularly limited, and can be exemplified as 1.60 to 2.10, preferably 1.65 to 2.00, more preferably 1.70 to 1.88, and more preferably 1.73 to 1.85. The lower limit of the refractive index nd can also be 1.65, 1.74, 1.75, 1.76, 1.77, 1.78, or 1.79, and the upper limit of the refractive index nd can also be 2.0, 1.9, 1.84, 1.83, or 1.82.

The refractive index nd can be set to a desired value by appropriately adjusting the content of each glass component in the glass composition B. Components that have the effect of relatively increasing the refractive index nd (high refractive index components) include Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ , Bi ³⁺ , Ta ⁵⁺ , Zr ⁴⁺ , La ³⁺ , etc. (i.e., if expressed in terms of oxides, they are Nb ₂ O ₅ , TiO ₂ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , La ₂ O ₃ , etc.). On the other hand, components that have the effect of relatively lowering the refractive index nd (refractive index lowering components) include P ⁵⁺ , Si ⁴⁺ , B ³⁺ , Li ⁺ , Na ⁺ , K ⁺ , etc. (i.e., if expressed as oxides, they are P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, etc.).

<Abbe value νd>

In the glass material for molding of the present embodiment, when the glass composition B is used, the Abbe number νd can be exemplified as 20 to 70, preferably 25 to 65, more preferably 30 to 60, and particularly preferably 35 to 55. The lower limit of the Abbe number νd can be 23, 28, 32, 36, 37, 38, 39, or 40, and the upper limit of the Abbe number νd can be 67, 63, 57, 53, 51, 49, 47, 45, 43, or 42.

The Abbe number νd can be made a desired value by appropriately adjusting the content of each glass component in the glass composition B. Components that relatively reduce the Abbe number νd (i.e., highly dispersed components) include, for example, Nb ⁵⁺ , Ti ⁴⁺ , W ⁶⁺ , Bi ³⁺ , Ta ⁵⁺ , Zr ⁴⁺ , etc. (i.e., if expressed in terms of oxides, they are Nb ₂ O ₅ , TiO ₂ , WO ₃ , Bi ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , etc.). On the other hand, components that relatively increase the Abbe number νd (i.e., low-dispersion components) may be, for example, P ⁵⁺ , Si ⁴⁺ , B ³⁺ , Li ⁺ , Na ⁺ , K ⁺ , La ³⁺ , Ba ²⁺ , Ca ²⁺ , Sr ²⁺ , etc. (i.e., if expressed in terms of oxides, they are P ₂ O ₅ , SiO ₂ , B ₂ O ₃ , Li ₂ O, Na ₂ O, K ₂ O, La ₂ O ₃ , BaO, CaO, SrO, etc.).

In the glass material for molding of this embodiment, when the glass composition B is used, the refractive index nd and the Abbe number νd preferably satisfy the following formula (1), more preferably satisfy the following formula (2), more preferably satisfy the following formula (3), and particularly preferably satisfy the following formula (4). By satisfying the following formula with the refractive index nd and the Abbe number νd, a molding glass material having high refractive index and low dispersion characteristics can be obtained. nd-(-0.0183×Abbe value νd+2.502)≧0 …(1) nd-(-0.0183×Abbe value νd+2.512)≧0 …(2) nd-(-0.0183×Abbe value νd+2.522)≧0 …(3) nd-(-0.0183×Abbe value νd+2.532)≧0 …(4)

<Average linear expansion coefficient α _L > In the molding glass material of the present embodiment, in the case of glass composition B, the lower limit of the average linear expansion coefficient α _L at -30 to 70°C is preferably 0.80×10 ^-5 ℃ ^-1 , and more preferably 0.81×10 ^-5 ℃ ^-1 , 0.82×10 ^-5 ℃ ^-1 , 0.83×10 ^-5 ℃ ^-1 , 0.84×10 ^-5 ℃ ^-1 , 0.85×10 ^-5 ℃ ^-1 , 0.86×10 ^-5 ℃ ^-1 , 0.87×10 ^-5 ℃ ^-1 , and 0.88×10 ^-5 ℃ ^-1 , in that order. From the viewpoint of maintaining the stability of the glass and obtaining the desired optical properties, the upper limit of the mean linear expansion coefficient α _L is 1.20×10 ^-5 ℃ ^-1 , preferably 1.10×10 ^-5 ℃ ^-1 or less, and more preferably 1.00×10 ^-5 ℃ ^-1 , 0.98×10 ^-5 ℃ ^-1 , 0.96×10 ^-5 ℃ ^-1 , 0.95×10 ^-5 ℃ ^-1 , 0.94×10 ^-5 ℃ ^-1 , and 0.93×10 ^-5 ℃ ^{-1 ,} in that order.

In the case of glass composition B, by setting the average linear expansion coefficient α _L between -30 and 70°C to the above range, a molding glass material that can be used in a wide temperature environment can be obtained.

The average linear expansion coefficient α _L is measured according to the provisions of JOGIS16. The sample is a round bar with a length of 20mm±0.5mm and a diameter of 5mm±0.5mm. Under a load of 98mN, the sample is heated at a constant rate of 4℃ per minute, and the temperature and sample extension are measured every 1 second. The average linear expansion coefficient α _L is the average value of the linear expansion coefficients from -30 to 70℃.

In addition, JOGIS16 stipulates that "the average linear expansion coefficient is expressed in units of 10 ^-7 ℃ ^-1 to the first integer digit", but the average linear expansion coefficient α _L in this manual is expressed in units of [10 ^-5・℃ ^-1 ].

In this specification, the unit of the mean linear expansion coefficient α _L is [10 ^-5・℃ ^-1 ], but even if the unit is [10 ^-5・K ^-1 ], the value of the mean linear expansion coefficient α _L is the same.

<Average linear expansion coefficient α _100-300 > In the glass material for molding of the present embodiment, in the case of glass composition B, the lower limit of the average linear expansion coefficient α _100-300 at 100-300°C is preferably 90, more preferably 92, 94, and 95 in that order. In addition, the upper limit of the average linear expansion coefficient α _100-300 can be exemplified as 130, preferably 115, and more preferably 110, 106, and 104 in that order from the viewpoint of maintaining the stability of the glass and obtaining the desired optical properties.

The average linear expansion coefficient α _100-300 is measured according to the provisions of JOGIS08. The sample is set as a round bar with a length of 20mm±0.5mm and a diameter of 5mm±0.5mm. Under the condition of applying a load of 98mN to the sample, the temperature is increased at a constant rate of 4℃ per minute, and the temperature and sample extension are measured every 1 second. The average linear expansion coefficient α _100-300 is the average value of the linear expansion coefficient of 100~300℃.

In this specification, the average linear expansion coefficient α _100-300 is expressed in units of 10 ^-7 ℃ ^-1 to the first integer according to the provisions of JOGIS08. That is, the average linear expansion coefficient α _100-300 is set to [10 ^-7・℃ ^-1 ] units and expressed as an integer.

<Temperature coefficient of relative refractive index dn/dT> The temperature coefficient of relative refractive index (dn/dT) of glass is measured by changing the temperature from -40℃ to 110℃ for light with a wavelength of 632.8nm using Japanese Industrial Standard JIS B7072-2 (Determination of temperature coefficient of refractive index of optical glass - Part 2: Interference method). In this manual, the temperature coefficient of relative refractive index (dn/dT) is expressed in units of [10 ^-6・℃ ^-1 ]. Even if the unit is [10 ^-6・K ^-1 ], the value of the temperature coefficient of relative refractive index dn/dT remains the same.

In the molding glass material of the present embodiment, when the glass composition is B, the upper limit of the temperature coefficient of relative refractive index dn/dT is within the range of He-Ne laser wavelength (633nm to 632.8nm) and temperature 20~40℃, preferably 2.0× ^10-6 ℃ ^-1 , and more preferably 1.5× ^10-6 ℃ ^-1 , 1.0× ^10-6 ℃ ^-1 , 0.5× ^10-6 ℃ ^-1 , 0.0× ^10-6 ℃ ^-1 , -0.5× ^10-6 ℃ ^-1 , -1.0× ^10-6 ℃ ^-1 . Moreover, although the lower limit of the temperature coefficient of relative refractive index dn/dT is not clearly limited, within the range of He-Ne laser wavelength (633nm to 632.8nm) and temperature of 20~40℃, the optimal value is -13.0× ^10-6 ℃ ^-1 , and the more preferred values are -10.0× ^10-6 ℃ ^-1 , -9.0× ^10-6 ℃ ^-1 , -8.0× ^10-6 ℃ ^-1 , -7.0× ^10-6 ℃ ^-1 , and -6.5× ^10-6 ℃ ^-1 , respectively.

By setting dn/dT within the above range and combining it with an optical element with a positive dn/dT value, or an optical element with a negative dn/dT value and a lens focal distance with a different sign, the refractive index change is reduced even in an environment where the temperature of the optical element varies greatly, so that the required optical characteristics can be exerted with high precision over a wider temperature range.

On the other hand, when light with high energy, such as laser light, is incident on glass at a wavelength equivalent to that absorbed by glass, the temperature rise of the glass varies depending on the light intensity and exposure time. In this case, the glass of this embodiment is also required to reduce the temperature change of the refractive index.

The upper limit of the temperature coefficient of relative refractive index dn/dT in this case, taking the He-Ne laser wavelength (633nm to 632.8nm) and the temperature range of 20~40℃ as an example, is preferably 2.0×10 ^-6 ℃ ^-1 , and more preferably 1.5×10 ^-6 ℃ ^-1 , 1.0×10 ^-6 ℃ ^-1 , 0.5×10 ^-6 ℃ ^-1 , 0.3×10 ^-6 ℃ ^-1 , and 0.1×10 ^-6 ℃ ^-1 . The lower limit of the temperature coefficient of the relative refractive index dn/dT is preferably -2.0×10 ^-6 ℃ ^-1 , and more preferably -1.5×10 ^-6 ℃ ^-1 , -1.0×10 ^-6 ℃ ^-1 , -0.5×10 ^-6 ℃ ^-1 , -0.3×10 ^-6 ℃ ^-1 , and -0.1×10 ^-6 ℃ ^-1 . The temperature coefficient of the relative refractive index dn/dT may also be set to 0.0×10 ^-6 ℃ ^-1 . In addition, the temperature coefficient of the relative refractive index (dn/dT) of the glass material for molding of the present embodiment may also be appropriately selected from the above preferred range according to the wavelength of the laser used, with reference to the description of this specification.

<Method for measuring the temperature dependence of the temperature coefficient of relative refractive index dn/dT> The glass of this embodiment has a relatively small temperature dependence of the temperature coefficient of relative refractive index (dn/dT) when the glass composition is B. The measuring method is as follows.

The measurement was performed using the interference method according to the method described in the Japan Optical Glass Industry Association Standard JOGIS18 "Measurement Method for Temperature Coefficient of Refractive Index of Optical Glass". The temperature was changed from -40°C to 80°C, and dn/dT at a wavelength of 632.8nm (hereinafter referred to as "dn/dT@632.8") was measured at -30°C, -10°C, +10°C, +30°C, +50°C, and +70°C. The approximate straight line of the dn/dT@632.8 value versus temperature was obtained using the least squares method, and the slope of the straight line was set as a, and the intercept at 0°C was set as b.

The closer the slope a is to 0, the smaller the dn/dT change caused by temperature. This means that even in different temperature ranges, the dn/dT value change per temperature change is small. In other words, the focal distance shifts in response to the temperature change per unit of the optical element and remains constant regardless of the temperature. Therefore, the position adjustment mechanism of the light-receiving element can be simplified, effectively making it an optical element that achieves high-precision imaging.

Therefore, in the molding glass material of the present embodiment, when the glass composition is B, the range of the slope a value is preferably 10.0×10 ^-9 to -10.0×10 ^-9 , and more preferably 8.0×10 ^-9 to -8.0×10 ^-9 , 6.0×10 ^-9 to -6.0×10 ^-9 , 4.0×10 ^-9 to -4.0×10 ^-9 , and 3.0×10 ^-9 to -3.0×10 ^-9 , in that order.

Furthermore, the closer the intercept b is to 0.0×10 ^-6 , the smaller the dn/dT@632.8 value of the approximate straight line at 0°C, which means that the absolute value of the dn/dT value is smaller. Therefore, since the focal distance offset itself becomes smaller relative to the unit temperature change of a single optical element, it effectively becomes an optical element for high-precision imaging.

Therefore, in the glass material for molding of the present embodiment, when the glass composition B is used, the intercept b value preferably ranges from 3.0×10 ^-6 to -3.0×10 ^-6 , and more preferably from 2.0×10 ^-6 to -2.0×10 ^-6 , 1.0×10 ^-6 to -1.0×10 ^-6 , and 0.5×10 ^-6 to -0.5×10 ^-6 , in that order. In addition, if the slope a value is set below a certain value (preferably controlled to be near 0), the intercept b does not necessarily have to be 0. The intercept b may also be set to be near 0.

<Glass transition temperature Tg> In the glass material for molding of the present embodiment, when the glass composition B is used, the upper limit of the glass transition temperature Tg is preferably 730°C, and more preferably 720°C, 710°C, and 700°C in that order. In addition, the lower limit of the glass transition temperature Tg is preferably 500°C, and more preferably 550°C, 560°C, 570°C, and 580°C in that order.

By making the upper limit of the glass transition temperature Tg satisfy the above range, the increase in the glass forming temperature and annealing temperature can be suppressed, and the thermal damage to the press forming equipment and annealing equipment can be reduced. In addition, by making the lower limit of the glass transition temperature Tg satisfy the above range, the thermal stability of the glass can be well maintained while maintaining the required Abbe value and refractive index. In addition, when used as a precision press material, good formability can be obtained.

On the other hand, the higher the glass transition temperature Tg, the smaller the amount of expansion per unit temperature change tends to be, and thus the degree of shape change caused by thermal expansion per unit temperature change tends to be reduced. Also, if the temperature of the glass is raised to near Tg or above the strain point by heating, there is a concern that the optical performance will not return to the original state even if the glass is cooled later. Therefore, the lower limit of Tg is preferably within the above range.

<Glass Specific Gravity> In the glass material for molding of this embodiment, when the glass composition B is used, the specific gravity is preferably 5.50 or less, and more preferably 5.00 or less, and 4.80 or less in that order. If the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, the power consumption of the camera lens equipped with the lens during autofocus drive can be reduced.

<Light transmittance of glass> The light transmittance of the glass material used for molding in this embodiment can be evaluated using the coloring indexes λ5, λ70, and λ80. In the case of glass composition B, for a glass sample with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance is measured in the wavelength range of 200 to 700 nm, and the wavelength at which the external transmittance becomes 5% is set as λ5, the wavelength at which the external transmittance becomes 70% is set as λ70, and the wavelength at which the external transmittance becomes 80% is set as λ80.

In the molding glass material of the present embodiment, when the glass composition B is used, λ5 is preferably 400 nm or less, preferably 380 nm or less, more preferably 360 nm or less, and particularly preferably 350 nm or less.

In the molding glass material of the present embodiment, in the case of glass composition B, λ70 is preferably 440 nm or less, more preferably 430 nm or less, and even more preferably 420 nm or less.

In the molding glass material of the present embodiment, in the case of glass composition B, λ80 is preferably 510 nm or less, more preferably 500 nm or less, and even more preferably 490 nm or less.

By using λ5, λ70, and λ80 as the molding glass material with the wavelength shortened as described above, an optical element capable of better color reproduction can be provided.

(Glass composition C) Next, in the case where the glass material for forming the present embodiment has glass composition C, the content and ratio of the glass components and the glass properties are explained.

In the glass material for molding of the present embodiment, when the glass composition is C, _SiO2 is a network-forming component of the glass and is an essential component that has the functions of improving the thermal stability, reheating devitrification, chemical durability and weather resistance of the glass, increasing the viscosity of the molten glass and _making the molten glass easier to mold. From the above viewpoints, the _SiO2 content is preferably greater than the total content _{of B2O3} and _P2O5 in terms of mass%. In the case of glass composition C, silicate glass is preferred. In the case of glass composition C, the _SiO2 content is preferably 8.0% or more, and more preferably 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 14.00% or more, 14.50% or more, 15.00% or more, 15.50% or more, 16.00% or more, 16.50% or more, and 16.60% or more. In the molding glass material of the present embodiment, when the glass composition C is used, from the viewpoint of improving the devitrification resistance of the glass, improving the solubility, and improving the partial dispersion characteristics, the _SiO2 content is preferably 50.00% or less, and more preferably, in order, 45.00% or less, 40.00% or less, 35.00% or less, 30.00% or less, 28.00% or less, 26.00% or less, 25.00% or less, 24.50% or less, 24.00% or less, 23.50% or less, 23.00% or less, 22.75% or less, 22.50% or less, and 22.00% or less.

In the glass material for molding of the present embodiment, when the glass composition C is used, the total content of SiO ₂ and B ₂ O ₃ (SiO ₂ + B ₂ O ₃ ) is preferably 10.00% or more, and more preferably 12.00% or more, 14.00% or more, 15.00% or more, 16.00% or more, 17.00% or more, 17.75% or more, 18.00% or more, 18.25% or more, 18.50% or more, in order of improving the thermal stability of the glass, lowering the specific gravity, and obtaining better optical constants. The above percentages are 18.60% or more and preferably 35.00% or less. The more preferred percentages are 32.00% or less, 30.00% or less, 28.00% or less, 27.00% or less, 26.50% or less, 26.00% or less, 25.50% or less, 25.00% or less, 24.50% or less, 24.40% or less and 24.30% or less.

In the case of glass composition C in the molding glass material of the present embodiment, although SiO ₂ and B ₂ O ₃ have the effect of improving the thermal stability of the glass, if the SiO ₂ content is too high, it tends to reduce the meltability of the glass. From the above viewpoints, the mass ratio of SiO ₂ to the total content of SiO ₂ and B ₂ O ₃ (SiO ₂ /(SiO ₂ +B ₂ O ₃ )) is preferably above 0.50, and more preferably above 0.55, above 0.60, above 0.65, above 0.70, above 0.75, above 0.77, and above 0.80, and is preferably below 1.00, and more preferably below 0.99, below 0.98, below 0.97, below 0.96, below 0.95, below 0.94, below 0.93, below 0.92, below 0.91, below 0.90, below 0.89, and below 0.88.

In the molding glass material of the present embodiment, when the glass composition C is used, the mass ratio of the B ₂ O ₃ content to the SiO ₂ content (B ₂ O ₃ /SiO ₂ ) is preferably less than 1.00 from the viewpoint of improving chemical durability, reducing α _max , and improving reheating devitrification resistance, and more preferably is 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.35 or less, 0.32 or less, 0.31 or less, 0.30 or less, 0.29 or less, 0.28 or less, 0.27 or less, 0.26 or less, and 0.25 or less. From the viewpoint of improving thermal stability, the mass ratio (B ₂ O ₃ /SiO ₂ ) is preferably 0.00 or more, and more preferably 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, and 0.15 or more.

In the molding glass material of the present embodiment, when the glass composition is C, _{the B2O3} content is preferably 0.00% or more, more preferably more than 0.00%, and particularly preferably 0.10% or more, 0.20% or more, 0.30% or more, 0.35% or more, 0.37% or more, 0.39% or more, 0.40% or more, 0.41% or more, 0.42% or more, 0.43% or more, 0.44% or more, 0.45% or more, 0.46% or more, 0.47% or more, 0.48% or more, and 0.49% or more. Furthermore, _{the B2O3} content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.50% or less, 5.20% or less, 5.10% or less, 5.00% or less, 4.90% or less, and _{4.80% or less. By setting the B2O3 content} within the above range, the specific gravity of the glass can be further reduced, and the thermal stability of the glass can be improved.

In the molding glass material of the present embodiment, when the glass composition is C, the CaO content is preferably 3.00% or more, more preferably 4.00% or more, and particularly preferably 5.00% or more, 5.10% or more, 5.20% or more, 5.30% or more, 5.40% or more, 5.50% or more, 5.60% or more, 5.70% or more, 5.80% or more, and 5.90% or more from the viewpoint of improving the meltability and thermal stability of the glass. Furthermore, from the same point of view, the CaO content is preferably less than 40.00%, and more preferably less than 35.00%, less than 30.00%, less than 28.00%, less than 26.00%, less than 24.00%, less than 22.00%, less than 21.50%, less than 21.00%, less than 20.50%, less than 20.25%, less than 20.00%, and less than 19.50%.

In the molding glass material of the present embodiment, when the glass composition C is used, the total content of MgO, CaO, SrO and BaO, which are alkali earth metal oxides, and ZnO (MgO+CaO+SrO+BaO+ZnO) is preferably 5.00% or more, and more preferably, in this order, 7.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 13.50% or more, 14.00% or more, 14.50% or more, 15.00% or more, 15.30% or more, 15.50% or more, and 16.00% or more. Furthermore, the total content (MgO+CaO+SrO+BaO+ZnO) is preferably 50.00% or less, and more preferably 45.00% or less, 40.00% or less, 39.00% or less, 38.00% or less, 37.00% or less, 36.50% or less, 36.00% or less, 35.50% or less, 35.00% or less, 34.50% or less, and 34.00% or less. If the total content (MgO+CaO+SrO+BaO+ZnO) is within the above range, it is preferred from the viewpoints of lowering the specific gravity, not hindering high dispersion, and maintaining thermal stability.

In the glass material for molding of the present embodiment, when the glass composition is C, among MgO, CaO, SrO, BaO and ZnO, MgO and CaO are more effective components than SrO, BaO and ZnO in terms of suppressing the specific gravity of the glass. Therefore, from the perspective of further suppressing the increase in specific gravity, the mass ratio of the total content of ZnO, SrO and BaO to the total content of MgO and CaO ((ZnO+SrO+BaO)/(MgO+CaO)) is preferably 2.78 or less, and more preferably 2.77 or less, 2.76 or less, 2.75 or less, 2.74 or less, and 2.73 or less in that order. On the other hand, the effect of SrO, BaO and ZnO in improving partial dispersion characteristics is greater than that of MgO and CaO. Therefore, from the perspective of improving partial dispersion characteristics, the mass ratio ((ZnO+SrO+BaO)/(MgO+CaO)) is preferably greater than 0.17, and more preferably greater than 0.18, greater than 0.19, and greater than 0.20, in that order.

In the molding glass material of the present embodiment, when the glass composition is C, the mass ratio of the CaO content to the total content of MgO, CaO, SrO, BaO and ZnO (CaO/(MgO+CaO+SrO+BaO+ZnO)) is preferably 0.35 or more, and more preferably 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, 0.40 or more, 0.41 or more, and 0.42 or more, in this order. From the perspective of improving thermal stability, the mass ratio (CaO/(MgO+CaO+SrO+BaO+ZnO)) is preferably less than 1.00, and more preferably less than 0.95, less than 0.90, less than 0.89, less than 0.88, less than 0.87, less than 0.86, less than 0.85, less than 0.84, less than 0.83, less than 0.80, and less than 0.78.

In the molding glass material of the present embodiment, when the glass composition is C, the mass ratio of the total content of CaO and MgO to the total content of MgO, CaO, SrO, BaO and ZnO ((CaO+MgO)/(MgO+CaO+SrO+BaO+ZnO)) is preferably 0.35 or more from the viewpoint of lowering the specific gravity, and more preferably 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, 0.40 or more, 0.41 or more, and 0.42 or more in this order. From the perspective of improving thermal stability, the mass ratio ((CaO+MgO)/(MgO+CaO+SrO+BaO+ZnO) is preferably less than 1.00, and more preferably less than 0.95, less than 0.90, less than 0.89, less than 0.88, less than 0.87, less than 0.86, less than 0.85, less than 0.84, less than 0.83, less than 0.80, and less than 0.78.

In the molding glass material of the present embodiment, when the glass composition is C, MgO, CaO, SrO and BaO, which are alkali earth metal oxides, and ZnO have the effect of lowering the liquidus temperature and improving thermal stability. On the other hand, if their content is too high, there is a tendency to reduce chemical durability and/ _or weather resistance. In addition, although _SiO2 and _B2O3 have the effect of improving thermal stability and reheating devitrification, if _their content is too high, there is a tendency to reduce solubility. From the above viewpoints, the mass ratio of the total content of _SiO2 and _B2O3 to the total content of MgO, CaO, SrO, BaO and ZnO ₍ ( _SiO2 + _B2O3 )/(MgO+CaO+SrO+BaO+ZnO)), preferably 0.40 or more, more preferably 0.45 or more, 0.50 or more, 0.52 or more, 0.54 or more, 0.56 or more, 0.57 or more, 0.58 or more, 0.59 or more, 0.60 or more, 0.61 or more, 0.70 or more, 0.80 or more, 0.90 or more, 1.00 or more, 1.10 or more, preferably 2.00 or less, more preferably 1.80 or less, 1.60 or less, 1.55 or less, 1.50 or less, 1.45 or less, 1.40 or less, 1.35 or less.

In the glass material for molding of the present embodiment, when the glass composition C is used, the MgO content is preferably 0.00% or more. Furthermore, the MgO content is preferably 15.00% or less, and more preferably 12.00% or less, 9.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.50% or less, 3.00% or less, 2.50% or less, and 2.10% or less.

In the glass material for molding of the present embodiment, when the glass composition C is used, the SrO content is preferably 0.00% or more, more preferably 0.10% or more, 0.20% or more, 0.25% or more, 0.26% or more, 0.27% or more, 0.28% or more, 0.29% or more, 0.30% or more, 0.31% or more. In addition, the SrO content is preferably 15.00% or less, more preferably 12.00% or less, 10.00% or less, 9.00% or less, 8.50% or less, 8.00% or less, 7.50% or less, 7.00% or less, 6.50% or less, 6.00% or less.

In the molding glass material of the present embodiment, when the glass composition is C, the BaO content is preferably 0.00% or more, and more preferably 0.10% or more, 0.20% or more, 0.30% or more, 0.40% or more, 0.50% or more, 0.60% or more, 0.70% or more, 0.80% or more, 0.90% or more, 1.00% or more, 1.10% or more, 1.20% or more, and 1.30% or more. Moreover, the BaO content is preferably 25.00% or less, and more preferably 22.00% or less, 20.00% or less, 19.00% or less, 18.00% or less, 17.00% or less, 16.50% or less, 16.00% or less, 15.50% or less, 15.25% or less, and 15.00% or less, in that order.

MgO, CaO, SrO and BaO are glass components that improve the thermal stability and devitrification resistance of glass. From the perspective of high dispersibility and lower specific gravity, and from the perspective of improving the thermal stability and devitrification resistance of glass, the contents of each of these glass components are preferably within the above ranges.

In the glass material for molding of the present embodiment, when the glass composition C is used, the ZnO content is preferably 0.00% or more. In addition, the ZnO content is preferably 10.00% or less, and more preferably 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less. ZnO is a glass component that improves the thermal stability of glass. From the perspective of lowering the specific gravity, improving the thermal stability of glass, and obtaining better optical constants, the ZnO content is preferably within the above range.

In the molding glass material of the present embodiment, when the glass composition C is used, the total content of _{La2O3 , Gd2O3} and _{Y2O3 ( La2O3} + _Gd2O3 + _{Y2O3 )} which are rare earth oxides is preferably more than 0% from the viewpoint of high refractive index and _low dispersion, and more preferably is _0.50 % or more, 1.00% or more, 1.33% or more, 1.50% or more, 2.00% or more, 2.50% or more, and 3.00% or more _, in this order. From the perspective of lowering specific gravity, the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ ) is preferably less than 30.00%, and more preferably less than 29.00%, less than 28.00%, less than 26.00%, less than 24.00%, less than 22.00%, less than 20.00%, less than 18.00%, less than 16.00%, less than 15.00%, less than 14.50%, less than 14.00%, less than 13.50%, less than 13.00%, less than 12.50% and less than 12.00%, respectively.

_{In the molding glass material of the present embodiment, when the glass composition is C, BaO and rare earth oxides La2O3, Gd2O3 and Y2O3 are components that contribute} to low dispersibility (i.e., increase _the Abbe number νd), but if their contents are too high, the specific gravity of the glass tends to increase. From the above viewpoints, in the case of glass composition C, the total content of BaO, and rare earth oxides La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (BaO + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is preferably less than 30.00%, and more preferably less than 29.00%, less than 28.00%, less than 27.00%, less than 26.00%, less than 25.00%, less than 24.50%, less than 24.00%, less than 23.50%, and less than 23.00%, respectively. Furthermore, from the viewpoint of increasing the Abbe number νd, the total content of BaO, La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (BaO + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ ) is preferably more than 0%, and more preferably 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, 7.50% or more, 8.00% or more, and 8.50% or more, in that order.

In the glass material for molding of the present embodiment, when the glass composition is C, both BaO and La ₂ O ₃ are low-dispersibility components, but in terms of the effect of increasing the refractive index, BaO is smaller than La ₂ O _3. Therefore, from the viewpoint of increasing the refractive index, the mass ratio of the BaO content to the La ₂ O ₃ content (BaO/La ₂ O ₃ ) is preferably 8.30 or less, and more preferably in the order of 8.00 or less, 7.50 or less, 7.00 or less, 6.50 or less, 6.00 or less, 5.50 or less, 5.40 or less, 5.30 or less, 5.20 or less, 5.10 or less, 5.00 or less, 4.90 or less, 4.80 or less, and 4.70 or less. In the glass material for molding of the present embodiment, when the glass composition is C, the mass ratio (BaO/La ₂ O ₃ ) may be 0 or may be greater than 0.00. From the viewpoint of maintaining the thermal stability of the glass, the mass ratio (BaO/La ₂ O ₃ ) is preferably greater than 0.00, and more preferably is, in order, greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09, greater than 0.10, and greater than 0.11.

In the glass material for molding of the present embodiment, when the glass composition is C, _La2O3 , _Gd2O3 and _{Y2O3 , which} are rare earth _oxides , contribute to improving the refractive index and low dispersibility, but if their contents are too high, the thermal stability tends to be reduced. Moreover, although _SiO2 and _{B2O3 have} the effect of improving thermal stability, if their contents are too high, the solubility tends to be reduced and the refractive index tends to be reduced. From the above viewpoints, the mass ratio of the total content of SiO ₂ and B ₂ O ₃ to the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ ((SiO ₂ +B ₂ O ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably greater than 0.00, and more preferably is, in order, greater than 0.25, greater than 0.50, greater than 0.75, greater than 1.00, greater than 1.25, greater than 1.50, greater than 1.75, greater than 1.80, and greater than 1.85. Furthermore, it is preferably less than 7.47, and more preferably is less than 7.40, less than 7.35, less than 7.30, and less than 7.25.

_{In the molding glass material of the present embodiment, when the glass composition C is used, La2O3, Gd2O3 and Y2O3 are all components that} can increase the refractive index of the glass. However, in terms of increasing the specific gravity, _Gd2O3 and _{Y2O3 are} components _that can increase _the specific gravity ratio more _{than La2O3} . Therefore, from the perspective of further reducing specific gravity, the mass ratio of La ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (La ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably greater than 0.00, and more preferably in order of 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, and 0.75 or more. The mass ratio (La ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) can be set to 1.00 or less. From the same point of view, when the glass composition is C, the mass ratio of the Gd ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (Gd ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably less than 1.00, and more preferably is 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, 0.25 or less, and 0.20 or less, in that order. The mass ratio (Gd ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) can be set to be greater than 0.00. Furthermore, from the same point of view, in the case of glass composition C, the mass ratio of the Y ₂ O ₃ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (Y ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably less than 1.00, and more preferably is 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, and 0.25 or less, in that order. The mass ratio (Y ₂ O ₃ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) can be set to be greater than 0.00.

In the glass material for molding of the present embodiment, when the glass composition C is used, from the above viewpoint, the contents of the above components belonging to the rare earth oxides are preferably within the following ranges. The _La2O3 content is preferably 0.00% _or more, and more preferably, in this order, more than 0.00%, more than 0.50%, more than 1.00%, more than 1.33%, more than 1.50%, more than 2.00%, more than 2.50%, more than 2.75%, more than 3.00%. Furthermore, the La ₂ O ₃ content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.50% or less, 13.00% or less, 12.50% or less, and 12.00% or less. The Gd ₂ O ₃ content is preferably 0.00% or more. Furthermore, the Gd ₂ O ₃ content is preferably 10.00% or less, and more preferably 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less. The Y ₂ O ₃ content is preferably 0.00% or more. Furthermore, _{the Y2O3} content is preferably 10.00% or less, and more preferably 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less, in that order.

In the glass material for molding of the present embodiment, when the glass composition is C, La ₂ O ₃ has the effect of increasing the refractive index of the glass, and B ₂ O ₃ has the tendency to decrease the refractive index of the glass. Therefore, from the viewpoint of further increasing the refractive index, the mass ratio of the La ₂ O ₃ content to the B ₂ O ₃ content (La ₂ O ₃ /B ₂ O ₃ ) is preferably 1.30 or more, and more preferably 1.35 or more, 1.40 or more, 1.45 or more, 1.50 or more, 1.55 or more, 1.60 or more, 1.65 or more, 1.70 or more, and 1.72 or more. From the viewpoint of further lowering specific gravity, the mass ratio (La ₂ O ₃ /B ₂ O ₃ ) is preferably 20.00 or less, and more preferably 18.00 or less, 16.00 or less, 14.00 or less, 13.00 or less, 12.00 or less, 11.50 or less, 11.00 or less, 10.50 or less, and 10.00 or less.

In the glass material for molding of the present embodiment, when the glass composition is C, the mass ratio of the B ₂ O ₃ content to the La ₂ O ₃ content (B ₂ O ₃ /La ₂ O ₃ ) is preferably 0.79 or less, more preferably 0.78 or less, 0.77 or less, 0.76 or less, 0.75 or less, 0.70 or less, 0.65 or less, 0.64 or less, 0.62 or less, 0.61 or less, 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, and 0.50 or less. The mass ratio (La ₂ O ₃ /B ₂ O ₃ ) is preferably 0.00 or more, more preferably more than 0.00.

In the case of the glass composition C in the molding glass material of the present embodiment, although the rare earth oxides can increase the refractive index of the glass, if the content of the rare earth oxides is too high, there is a tendency for the thermal stability to decrease and the melting property of the glass to decrease. Therefore, from the viewpoint of maintaining the thermal stability of the glass and further improving the refractive index, the mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ to the total content of BaO, La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )/(BaO+La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably less than 1.00, less than 0.99, less than 0.98, less than 0.97, less than 0.96, less than 0.95, less than 0.94, less than 0.93, less than 0.92, less than 0.91 and less than 0.90, in this order. The mass ratio ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )/(BaO+La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably more than 0.00, and more preferably in order of 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.10 or more, 0.11 or more, 0.12 or more, 0.13 or more, 0.14 or more, 0.15 or more, 0.16 or more, 0.17 or more, 0.18 or more, and 0.20 or more.

In the case of the glass composition C in the molding glass material of the present embodiment, although rare earth oxides can increase the refractive index of the glass, if the content is too high, the glass meltability tends to decrease. On the other hand, although alkali earth metal oxides can increase the meltability of the glass, if the content is too high, the refractive index tends to decrease. Therefore, from the perspective of further increasing _the refractive index while maintaining the melting property of the _glass , the mass ratio of the total content _{of La2O3} , _Gd2O3 and _Y2O3 to the total content of _{MgO ,} CaO, SrO, BaO, ZnO, _{La2O3 , Gd2O3 and Y2O3} is ₍ ( _{La2O3 +Gd2O3 + Y2O3} )/(MgO+ _CaO + _SrO + _BaO + _{ZnO + ...} )), preferably more than 0.00, more preferably in order of 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, and preferably below 0.85, and more preferably below 0.80, 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.45 or less, 0.44 or less, 0.43 or less, 0.42 or less, 0.41 or less, 0.40 or less.

In the case of the glass material for molding of the present embodiment, when the glass composition is C, although rare earth oxides can increase the refractive index of the glass, if the content _is too high, the thermal stability of the glass tends to be reduced. On the other hand, although _B2O3 can increase the thermal stability of the glass, if the content is too high, the refractive index tends to be reduced. Therefore, from the perspective of further improving the refractive index while maintaining the thermal stability of the glass, the mass ratio of B ₂ O ₃ content to the total content of BaO, La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (B ₂ O ₃ /(BaO+La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably greater than 0.00, more preferably greater than 0.00, greater than 0.01, greater than 0.02, and greater than 0.03, in that order; further, it is preferably less than 1.00, and more preferably less than 0.90, less than 0.80, less than 0.70, less than 0.60, less than 0.55, less than 0.50, less than 0.45, less than 0.40, and less than 0.35, in that order.

In the glass material for molding of the present embodiment, when the glass composition is C, although _{La2O3 , Gd2O3} and _Y2O3 have the effect of increasing the refractive index _of the glass, if the total content of these elements is too high, the thermal stability tends to decrease. On the other hand, although _B2O3 has _the effect of improving the thermal stability _of the glass, it tends to decrease the refractive index. Therefore, from the perspective of maintaining the thermal stability of the glass while improving the refractive index, the mass ratio of the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ to the total content of B ₂ O ₃ , La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )/(B ₂ O ₃ +La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably not less than 0.57, and more preferably not less than 0.58, not less than 0.59, not less than 0.60, not less than 0.61, not less than 0.62, not less than 0.63 and not less than 0.64, in this order. From the viewpoint of further lowering specific gravity, the mass ratio ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )/(B ₂ O ₃ +La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably less than 1.00, and more preferably in the order of less than 1.00, less than 0.99, less than 0.98, less than 0.97, less than 0.96, less than 0.95, less than 0.94, less than 0.93, less than 0.92, less than 0.91, less than 0.90, less than 0.89, less than 0.88, less than 0.87, less than 0.86, and less than 0.85.

_In the case of glass composition C in the molding glass material of the present embodiment, although _{La2O3 , Gd2O3} , _Y2O3 and _ZrO2 have the effect of increasing the refractive index and improving the partial dispersion characteristics, if the _ZrO2 content is too high, the glass _meltability tends to decrease. From the above viewpoints, the mass ratio of ZrO ₂ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and ZrO ₂ (ZrO ₂ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +ZrO ₂ )) is preferably greater than 0.01, more preferably greater than 0.02, greater than 0.03, and greater than 0.04, in that order; and preferably less than 5.00, and more preferably less than 4.00, less than 3.00, and less than 2.00, in that order.

_In the molding glass material of the present embodiment, when the glass composition is C, _{La2O3 , Gd2O3} , _Y2O3 and _ZrO2 are all components that increase the refractive index, but _ZrO2 has a greater effect of increasing the refractive index and a greater effect of increasing dispersion (reducing _the Abbe value) _{than La2O3} , _{Gd2O3 and Y2O3 .} From the perspective of maintaining low dispersion, the mass ratio of ZrO ₂ content to the total content of La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (ZrO ₂ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) is preferably less than 3.30, and more preferably less than 3.00, less than 2.90, less than 2.80, less than 2.70, less than 2.60, less than 2.50, less than 2.40, less than 2.30, less than 2.20, less than 2.10, less than 2.00, less than 1.90, less than 1.80, less than 1.70, less than 1.60, less than 1.50, less than 1.40, less than 1.30, and less than 1.25. The mass ratio (ZrO ₂ /(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )) can be set to 0.00 or more. From the viewpoint of further increasing the refractive index, it is preferably more than 0.00, and more preferably 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, and 0.06 or more.

In the glass material for molding of this embodiment, when the glass composition C is used, ZrO ₂ content from the viewpoint of achieving better optical constants and improving partial dispersion characteristics, preferably it is 7.63% or less, more preferably less than 7.63%, more preferably 7.60 or less, 7.50 or less, 7.40 or less, 7.30 or less, 7.20 or less, 7.10 or less, 7.00 or less, 6.90 or less, 6.80 or less, 6.70 or less, 6.60 or less, 6.50 or less, 6.40 or less, 6.30 or less, 6.20 or less, 6.10 or less, 6.00 or less, 5.95 or less, 5.90 or less, particularly from the viewpoint of improving reheating devitrification, preferably it is 6.00 or less, more preferably 5.50 or less, 5.00 or less, 4.00 or less, 3.00 or less, 2.50 or less. In addition, from the perspective of achieving better optical constants and further improving partial dispersion characteristics, the _ZrO2 content is preferably above 0.00%, and the better order is above 0.00%, above 0.10%, above 0.20%, above 0.30%, above 0.40%, above 0.50%, above 0.60%, above 0.65%, above 1.10%, and above 1.60%.

In the glass material for molding of the present embodiment, when the glass composition is C, although MgO, CaO, SrO, BaO and ZnO have the effect of improving the thermal stability of the glass, if the content _of these is too high, there is a tendency to reduce the refractive index. On the other hand, although _La2O3 , _Gd2O3 and _Y2O3 have the effect of increasing the refractive index, if the content of these is too high, there is _a tendency to reduce _the thermal stability. From the above viewpoints, the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of _{La2O3 , Gd2O3} and _Y2O3 ((MgO+CaO+SrO+BaO+ZnO)/( _{La2O3 +} Gd2O3+ _Y2O3 ) is ((MgO+CaO+ _SrO +BaO+ZnO)/(La2O3+ _Gd2O3 + _{Y2O3 )} ) _. )), preferably it is more than 0.00, and the more preferred order is 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, 0.50 or more, 0.60 or more, 0.70 or more, 0.80 or more, 0.90 or more, 1.00 or more, 1.10 or more, 1.20 or more, 1.30 or more, 1.40 or more, and preferably it is less than 20.00, and the more preferred order is 18.00 or less, 16.00 or less, 14.00 or less, 11.09 or less, 11.08 or less, 11.07 or less, 11.06 or less, 11.05 or less, 11.04 or less, 11.03 or less, 11.02 or less, 11.01 or less, and 11.00 or less.

In the glass material for molding of the present embodiment, when the glass composition is C, SrO, BaO, La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ are all effective components that can maintain low dispersibility. Therefore, from the viewpoint of maintaining lower dispersibility, the total content of SrO, BaO, La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ (SrO+BaO+La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ ) is preferably 9.00% or more, and more preferably 9.50% or more, 10.00% or more, 10.50% or more, 11.00% or more, 11.50% or more, 12.00% or more, 12.50% or more, 13.00% or more, and 13.50% or more, in that order.

Furthermore, in the molding glass material of the present embodiment, when the _glass composition C is used, from the viewpoint of further lowering the specific gravity, the total content (SrO+BaO+ _La2O3 + _Gd2O3 + _Y2O3 ) is preferably 45.00% or less, _and more preferably 40.00% or less, 35.00% or less, 30.00% or less, 29.00% or less, 28.00% or less, 27.00% or less, 26.00% or less, _and 25.00% or less, in this order.

In the glass material for molding of the present embodiment, when the glass composition is C, _La2O3 , _Gd2O3 and _Y2O3 are components that have the effect of increasing the refractive index, and _SiO2 is _{a component that maintains the thermal stability of the glass. The mass ratio of the total content of La2O3, Gd2O3 and Y2O3 to the total content of La2O3 , Gd2O3 , Y2O3 and SiO2 ( ( La2O3 + Gd2O3 + Y2O3 ) / ( La2O3 + Gd2O3 + Y2O3 + SiO2} )) is preferably _0.12 or more, and more preferably 0.13 _or more _, from the viewpoint of further increasing _the refractive index. From the viewpoint of maintaining thermal stability of glass, the mass ratio ((La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ )/(La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +SiO ₂ )) is preferably less than 0.70, and more preferably less than 0.60, less than 0.50, less than 0.49, less than 0.48, less than 0.47, less than 0.46, less than 0.45, less than 0.44, less than 0.43, less than 0.42, and less than 0.41, in this order.

In the molding glass material of the present embodiment, when the glass composition is C, with respect to the mass ratio of the total content of _SiO2 and CaO to the total content _{of TiO2} , _Nb2O5 , _Ta2O5 , _{WO3 and Bi2O3} (( _SiO2 + _CaO )/ _{( TiO2} + _Nb2O5 + _Ta2O5 + _{WO3 +Bi2O3 )} ), the denominator is the total content of the components having a greater effect of increasing _the refractive index, and the numerator is the total content of the components effective in low dispersion and low specific gravity. From the perspective of maintaining a high refractive index and low dispersibility, and maintaining a low specific gravity and thermal stability, the mass ratio ((SiO ₂ +CaO)/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably less than 1.20, and more preferably less than 1.09, less than 1.08, less than 1.07, less than 1.06, less than 1.05, less than 1.04, less than 1.03, less than 1.02, less than 1.01, less than 0.99, less than 0.94, less than 0.89, and less than 0.86. Furthermore, from the viewpoint of maintaining a higher refractive index, lower dispersibility, and lower specific gravity, the mass ratio ((SiO ₂ +CaO)/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 0.25 or more, and more preferably 0.30 or more, 0.35 or more, 0.40 or more, 0.42 or more, 0.44 or more, 0.46 or more, 0.48 or more, 0.50 or more, 0.52 or more, 0.54 or more, and 0.55 or more, in this order.

In the glass material for molding of the present embodiment, when the glass composition C is used, among the components for increasing the refractive index, namely, ZrO ₂ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ , the effect of ZrO ₂ on improving dispersion is relatively small. Therefore, from the viewpoint of maintaining lower dispersion, the mass ratio of the ZrO ₂ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ (ZrO ₂ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 0.00 or more, more preferably 0.01 or more, and 0.02 or more, in that order. From the viewpoint of maintaining the thermal stability of the glass and maintaining the resistance to devitrification when the glass is heated to soften it and then press-formed (stability during reheat press-forming: also called "reheat press-forming property"), the mass ratio (ZrO ₂ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably less than 0.21, and more preferably less than 0.20, less than 0.19, less than 0.18, less than 0.17, less than 0.16, less than 0.15, less than 0.12, less than 0.10, less than 0.08, and less than 0.06, in this order.

In the glass material for molding of the present embodiment, when the glass composition is C, the lower limit of the total content of _Li2O , _Na2O and _K2O [ _Li2O + _Na2O + _K2O ] is preferably 0.1%, more preferably 0.2%, 0.5%, 1.0%, 1.2%, 1.5% in that order. The upper limit of the total content is preferably 20%, more preferably 15%, 10%, 8%, 6%, 4%, 2% in that order.

In glass composition C, when the lower limit of the total content [ _Li2O + _Na2O + _K2O ] satisfies the above, the glass meltability can be improved and the liquidus temperature rise can be suppressed. When the upper limit of the total content satisfies the above, the glass viscosity can be increased, the crystallization rate of the glass melt can be reduced, and the stability during reheating can be improved.

In the glass material for molding of the present embodiment, when the glass composition is C, Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O, which are alkali metal oxides, have the effect of improving partial dispersion characteristics, and also have the effect of lowering the liquidus temperature and improving the thermal stability of the glass. From these viewpoints, the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O (Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O) is preferably 0.00% or more, and more preferably, in this order, more than 0.00%, 0.05%, 0.10%, 0.15%, 0.20%, 0.25%, 0.28%, 0.60%, 1.10%, 1.30%, 1.60%. From the perspective of improving chemical durability and weather resistance, the total content (Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O) is preferably less than 20.00%, and more preferably less than 18.00%, less than 16.00%, less than 14.00%, less than 12.00%, less than 10.00%, less than 9.00%, less than 8.00%, less than 7.00%, less than 6.50%, less than 6.00%, less than 5.50%, less than 5.00%, less than 4.50%, less than 3.90%, less than 2.90%, and less than 2.40%.

In the glass material for molding of the present embodiment, when the glass composition is C, the upper limit of the mass ratio of the total content of _Li2O , _Na2O , _K2O and _Cs2O to the total content of _SiO2 , _P2O5 and _B2O3 [ _{( Li2O} + _Na2O + _K2O +Cs2O)/( _SiO2 + _P2O5 + _{B2O3 )} ] is preferably 1.0, and more preferably 0.7, _0.5 , _0.4 , _0.3 , 0.2, 0.1, 0.09, 0.08 in order. In addition, the lower limit of the mass ratio is preferably 0.001, and more preferably 0.01, 0.02, 0.03, 0.04, 0.05, 0.06 in order.

In glass composition C, if the mass ratio [( _Li2O + _Na2O + _K2O + _Cs2O )/( _SiO2 + _P2O5 + _B2O3 )] is too low, the solubility may be deteriorated. If it is too high, the viscosity of the glass may be reduced during melting, the thermal stability of the melt _may be reduced, and _the stability may be deteriorated during reheating.

In the glass material for molding of the present embodiment, when the glass composition is C, the upper limit of the mass ratio of the total content of Li ₂ O, Na ₂ O, K ₂ O and Cs ₂ O to the total content of Nb ₂ O ₅ , TiO ₂ , WO ₃ and Bi ₂ O ₃ [(Li ₂ O + Na ₂ O + K ₂ O + Cs ₂ O) / (Nb ₂ O ₅ + TiO ₂ + WO ₃ + Bi ₂ O ₃ )] is preferably 1.0, and more preferably 0.5, 0.3, 0.2, 0.1, 0.09, 0.08, 0.07, 0.06, 0.05 in order. In addition, the lower limit of the mass ratio is preferably 0.005, and more preferably 0.01, 0.02, 0.03, 0.04 in order.

In glass composition C, if the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O+Cs ₂ O)/(Nb ₂ O ₅ +TiO ₂ +WO ₃ +Bi ₂ O ₃ )] is too low, the partial dispersion ratio Pg,F may increase and the transmittance may deteriorate. If it is too high, the Abbe number may increase, the refractive index may decrease, and the stability may deteriorate when reheated.

In the glass material for molding of the present embodiment, when the glass composition is C, although alkali metal oxides and alkali earth metal oxides contribute to maintaining the glass meltability and thermal stability, if their contents are too high, the glass meltability and thermal stability tend to be reduced. Therefore, from the viewpoint of maintaining the glass meltability and thermal stability, the total content of _Li2O , _Na2O , _K2O and _Cs2O belonging to alkali metal oxides and MgO, CaO, SrO and BaO belonging to alkali earth metal oxides ( _Li2O + _Na2O + _K2O +Cs2O ₎ is preferably 0.1%. O+MgO+CaO+SrO+BaO), preferably 5.00% or more, more preferably 7.00% or more, 9.00% or more, 10.00% or more, 12.00% or more, 14.00% or more, 15.00% or more, 16.00% or more, 17.00% or more, 18.00% or more, 18.50% or more, and preferably 50.00% or more. Below, the better order is below 48.00%, below 46.00%, below 44.00%, below 43.00%, below 42.00%, below 41.00%, below 40.00%, below 39.00%, below 38.00%, below 37.00%, below 36.00%, below 35.00%, below 34.50%, below 34.00%.

In the glass material for molding of the present embodiment, when the glass composition is C, although alkali metal oxides and alkali earth metal oxides have the effect of lowering the liquidus temperature and improving thermal stability, if their content is too high relative to the network forming components of the glass, there is a tendency for chemical durability and weather resistance to decrease. In addition, although _{SiO2 and B2O3} have the effect of improving thermal stability, if their content is too high, there is a tendency for melting properties to decrease. From these viewpoints, the mass ratio of the total content of _Li2O , Na2O, _K2O , _Cs2O , _MgO , CaO, SrO and BaO to the total content _{of SiO2} and _B2O3 (( _Li2O + _Na2O + _K2O + _Cs2O +MgO+CaO+SrO+BaO) _/ ( _SiO2 + _B2O3 )), preferably it is above 0.50, and more preferably in order of above 0.52, above 0.54, above 0.56, above 0.58, above 0.60, above 0.62, above 0.64, above 0.66, above 0.68, above 0.70, above 0.72, above 0.74, above 0.75, above 0.76, above 0.77, above 0.78, above 0.79, and more preferably in order of below 5.00, and more preferably in order of below 4.50, below 4.00, below 3.50, below 3.00, below 2.50, below 2.00, below 1.90, below 1.80, below 1.70, below 1.65, and below 1.60.

In the glass material for molding of the present embodiment, when the glass composition is C, among Li ₂ O, Na ₂ O and K ₂ O, Li ₂ O is the component that is least likely to lower the refractive index. Therefore, from the viewpoint of further increasing the refractive index, the mass ratio of the content of Li ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O (Li ₂ O/(Li ₂ O+Na ₂ O+K ₂ O)) is preferably 0.00 or more, and more preferably, in this order, more than 0.00, 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, and 0.45 or more. On the other hand, the mass ratio ( _Li2O /( _Li2O + _Na2O + _K2O )) can be, for example, 1.00 or less, and from the viewpoint of suppressing a decrease in reheating devitrification, can be 0.99 or less, 0.98 or less, 0.95 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.65 or less, 0.60 or less, or 0.50 or less.

In the glass material for molding of the present embodiment, when the glass composition is C, although Li ₂ O, Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO and ZnO have the effect of improving the thermal stability and melting property of the glass, if the total content of Li ₂ O, Na ₂ O and K ₂ O is too high, the glass tends to be highly dispersible. Therefore, from the viewpoint of obtaining better dispersibility, the mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of MgO, CaO, SrO, BaO and ZnO ((Li ₂ O+Na ₂ O+K ₂ O)/(MgO+CaO+SrO+BaO+ZnO)), preferably 0.00 or more, more preferably more than 0.00, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, preferably 4.00 or less, more preferably 3.50 or less, 3.00 or less, 2.50 or less, 2.00 or less, 1.50 or less, 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.35 or less.

In the molding glass material of the present embodiment, when the glass composition C is used, the mass ratio of the total content of _Li2O , _Na2O and _K2O to the total content of _{SiO2 and B2O3 (} ( _Li2O + _Na2O + _K2O )/ _{( SiO2} + _B2O3 )) is preferably 1.00 or less, and more preferably 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.35 or less, 0.30 or less, and 0.25 or less, in order of maintaining thermal stability and/or maintaining rehot press formability. From the viewpoint of maintaining melting properties and/or reducing the partial dispersion ratio to provide glass suitable for high-order chromatic aberration correction, the mass ratio (( _Li2O + _Na2O + _K2O )/( _SiO2 + _B2O3 )) is preferably 0.00 or more, _and more preferably more than 0.00, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, and 0.05 or more.

In the glass material for molding of the present embodiment, when the glass composition C is used, the Li ₂ O content is preferably 0.00% or more, more preferably 0.05% or more, 0.10% or more, 0.15% or more, 0.20% or more, 0.25% or more, 0.30% or more, 0.40% or more, 0.50% or more, 0.60% or more. Furthermore, the Li ₂ O content is preferably 14.00% or less, more preferably 12.00% or less, 10.00% or less, 8.00% or less, 7.00% or less, 6.50% or less, 6.00% or less, 5.50% or less, 5.00% or less. From the viewpoint of achieving better optical constants and from the viewpoint of maintaining chemical durability, weather resistance, and stability during reheating, it is preferable to set the Li ₂ O content to the above range.

In the glass material for molding of the present embodiment, when the glass composition C is used, the Na ₂ O content is preferably 0.00% or more. Furthermore, the Na ₂ O content is preferably 10.00% or less, and more preferably 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less. Setting the Na ₂ O content within the above range is preferred from the viewpoint of improving partial dispersion characteristics.

In the molding glass material of the present embodiment, when the glass composition is C, the K ₂ O content is preferably 0.00% or more. Furthermore, the K ₂ O content is preferably 10.00% or less, and more preferably 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, and 2.00% or less. Setting the K ₂ O content within the above range is preferred from the viewpoint of improving the thermal stability of the glass.

In the molding glass material of the present embodiment, when the glass composition is C, the Cs ₂ O content is preferably 5.00% or less, more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, 0.50% or less, and may be 0%.

In the molding glass material of the present embodiment, when the glass composition is C, the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is preferably 30.00% or more, and more preferably 31.00% or more, 32.00% or more, 33.00% or more, 34.00% or more, 35.00% or more, 36.00% or more, 36.50% or more, 37.00% or more, and 37.55% or more, in this order. From the perspective of lowering specific gravity and improving thermal stability, the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is preferably less than 60.00%, and more preferably less than 58.00%, less than 56.00%, less than 54.00%, less than 52.00%, less than 51.00%, less than 50.00%, less than 49.50%, less than 49.00% and less than 48.50%, respectively.

In the molding glass material of the present embodiment, when the glass composition C is used, the mass ratio of the total content of _SiO2 and _B2O3 to _the total content _{of TiO2} , _Nb2O5 , _Ta2O5 , _{WO3 and Bi2O3} (( _SiO2 + _B2O3 )/ _{( TiO2} + _Nb2O5 + _Ta2O5 + _WO3 + _{Bi2O3 )} ) is preferably 0.75 or less from the viewpoint of obtaining _a high _refractive index glass while _suppressing an increase in specific gravity. In addition to the above, from the viewpoint of achieving the required Abbe number νd, improving the partial dispersion characteristics, and enhancing the devitrification resistance, the mass ratio ((SiO ₂ + B ₂ O ₃ )/(TiO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )) is preferably above 0.16, and more preferably in order of above 0.20, above 0.25, above 0.30, above 0.35, above 0.36, above 0.37, above 0.38, above 0.39, above 0.40, above 0.41, and above 0.42; and preferably below 0.75, and more preferably in order of below 0.74, below 0.73, below 0.72, below 0.71, below 0.70, below 0.69, below 0.68, below 0.67, below 0.66, below 0.65, and below 0.64.

_In the molding glass material of this embodiment, when the glass composition is C, _SiO2 and _B2O3 have the effect of lowering _the refractive index and reducing dispersion (increasing the Abbe number). On the other hand, _TiO2 , _Nb2O5 , _Ta2O5 , _WO3 , _Bi2O3 , _{and ZrO2} are high refractive index _and high dispersion components. From the perspective of further improving the refractive index, the mass ratio of the total content of SiO ₂ and B ₂ O ₃ to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and ZrO ₂ ((SiO ₂ +B ₂ O ₃ )/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O _{5 +WO 3 +} Bi ₂ O ₃ +ZrO ₂ )) is preferably less than 0.64, and more preferably less than 0.63, less than 0.62, less than 0.61, less than 0.60, less than 0.59 and less than 0.58, in this order. On the other hand, in the case of glass composition C, from the viewpoint of suppressing high dispersion, the mass ratio ((SiO ₂ +B ₂ O ₃ )/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +ZrO ₂ )) is preferably 0.13 or more, and more preferably 0.15 or more, 0.20 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more, 0.35 or more, 0.36 or more, 0.37 or more, and 0.38 or more.

In the molding glass material of the present embodiment, when the glass composition C is used, the mass ratio of the total content of Li ₂ O, Na ₂ O and K ₂ O to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ ((Li ₂ O+Na ₂ O+K ₂ O)/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 0.00 or more, and more preferably 0.01 or more, in order of improving partial dispersion characteristics and transmittance. From the perspective of maintaining thermal stability of glass and/or re-hot press formability, the mass ratio ((Li ₂ O+Na ₂ O+K ₂ O)/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably less than 0.67, and more preferably less than 0.60, less than 0.50, less than 0.40, less than 0.30, less than 0.20, less than 0.15, and less than 0.10, in that order.

In the glass material for molding of the present embodiment, when the glass composition is C, although MgO, CaO, SrO, BaO and ZnO have the effect of improving the thermal stability of the glass, if their contents are too high, the refractive index tends to decrease and the glass tends to have a lower dispersion. On the other hand, although _TiO2 , _Nb2O5 , _{WO3 and Bi2O3} have the tendency to increase _the refractive index and make the glass more dispersed, if their contents are too high, the thermal stability tends to decrease. From the above point of view, the mass ratio of the total content of MgO, CaO, SrO, BaO and ZnO to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ ((MgO+CaO+SrO+BaO+ZnO)/(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )), preferably 0.09 or more, more preferably in order of 0.10 or more, 0.15 or more, 0.20 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.35 or more, 0.40 or more, 0.45 or more, and preferably 1.66 or less, more preferably in order of 1.60 or less, 1.50 or less, 1.40 or less, 1.30 or less, 1.20 or less, 1.10 or less, 1.00 or less, 0.95 or less, 0.90 or less, 0.88 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less.

In the molding glass material of the present embodiment, when the glass composition C is present, among MgO, CaO, SrO, BaO and ZnO, MgO and CaO are less effective than SrO, BaO and ZnO in suppressing the increase in the specific gravity of the glass and reducing α _100-300 and α _max . Therefore, from the perspective of suppressing the increase in specific gravity, the mass ratio of the total content of ZnO, SrO and BaO to the total content of MgO and CaO ((ZnO+SrO+BaO)/(MgO+CaO)) is preferably less than 1.98, and the more preferred ratios are, in order, less than 1.96, less than 1.94, less than 1.92, less than 1.90, less than 1.88, less than 1.86, less than 1.85, less than 1.84, less than 1.83, less than 1.82, less than 1.81, less than 1.80, less than 1.79, less than 1.78, less than 1.50, less than 1.20, less than 0.95, less than 0.80, less than 0.70, less than 0.60, and less than 0.50.

On the other hand, in the glass material for molding of the present embodiment, when the glass composition is C, SrO, BaO, and ZnO can improve the stability of the glass by introducing a small amount, and also have the effect of increasing the refractive index. Therefore, from the perspective of maintaining low dispersion, the mass ratio ((ZnO+SrO+BaO)/(MgO+CaO)) is preferably 0.17 or more, and more preferably 0.18 or more, 0.19 or more, 0.20 or more, 0.25 or more, and 0.30 or more in this order.

In the glass material for molding of the present embodiment, when the glass composition is C, the lower limit of the mass ratio of the total content of _Li2O , _Na2O and _K2O to the total content of _{Nb2O5 and TiO2} [( _Li2O + _Na2O + _K2O )/( _Nb2O5 + _TiO2 )] is preferably 0.001, more preferably 0.01, 0.02, _0.03 , 0.04 in order. In addition, the upper limit of the mass ratio is preferably 1.00, more preferably 0.50, 0.30, 0.20, 0.10, 0.08, 0.06 in order.

In glass composition C, from the viewpoint of obtaining desired optical constants while maintaining glass melting characteristics, thermal stability, and stability during reheating, the mass ratio [(Li ₂ O+Na ₂ O+K ₂ O)/(Nb ₂ O ₅ +TiO ₂ )] is preferably within the above range.

In the molding glass material of the present embodiment, when the glass composition C is present, as far as dispersibility is concerned, if TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ are compared with La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ tend to make the glass less dispersible, while La ₂ O ₃ , Gd ₂ O ₃ and Y ₂ O ₃ tend to make the glass more dispersible. From the perspective of obtaining the desired dispersibility, the mass ratio of the total content of _La2O3 , _{Gd2O3 and Y2O3} to _{the total content of TiO2, Nb2O5, Ta2O5 , WO3 and Bi2O3 ( ( La2O3 + Gd2O3 + Y2O3 )} / _{( TiO2 + Nb2O5} + _Ta2O5 + _{WO3 + Bi2O3 ) ) is} )), preferably more than 0.00, more preferably in order of 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, and preferably below 1.00, and more preferably in order of 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.45 or less, 0.40 or less, 0.35 or less, 0.32 or less.

In the molding glass material of the present embodiment, when the glass composition is C, the mass ratio of the TiO ₂ content relative to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (TiO ₂ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 0.00 or more from the viewpoint of high refractive index and low specific gravity, and more preferably, in order, more than 0.00, 0.01 or more, 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.06 or more, 0.07 or more, 0.08 or more, 0.09 or more, 0.15 or more, 0.20 or more, 0.25 or more, and 0.30 or more. On the other hand, from the perspective of suppressing glass coloring and improving glass stability, the preferred value is 1.00 or less, and the more preferred order is less than 1.00, 0.95 or less, 0.90 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.73 or less, 0.60 or less, 0.50 or less, 0.45 or less, and 0.40 or less.

In the molding glass material of the present embodiment, when the glass composition is C, the mass ratio of the Nb ₂ O ₅ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (Nb ₂ O ₅ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 0.00 or more from the viewpoint of improving partial dispersion characteristics, and more preferably, in order, more than 0.00, 0.01 or more, 0.05 or more, 0.10 or more, 0.15 or more, 0.20 or more, 0.21 or more, 0.22 or more, 0.23 or more, 0.24 or more, 0.25 or more, 0.26 or more, and 0.27 or more. On the other hand, in order to enhance the thermal stability of the glass and improve the reheating devitrification, the preferred value is 1.00 or less, and the more preferred values are, in this order, less than 1.00, 0.99 or less, 0.98 or less, 0.97 or less, 0.96 or less, 0.95 or less, 0.94 or less, 0.93 or less, 0.92 or less, 0.91 or less, 0.85 or less, 0.80 or less, 0.75 or less, 0.70 or less, and 0.66 or less.

In the molding glass material of the present embodiment, when the glass composition is C, the mass ratio of the Ta ₂ O ₅ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (Ta ₂ O ₅ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably 1.00 or less, and more preferably 0.80 or less, 0.60 or less, 0.40 or less, 0.30 or less, 0.20 or less, 0.10 or less, and most preferably 0, in order of reducing the cost of glass raw materials and further lowering the specific gravity.

In the case of glass composition C in the molding glass material of the present embodiment, among TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ which are high refractive index and high dispersion components, WO ₃ and Bi ₂ O ₃ have a greater effect of increasing the specific gravity. Therefore, from the perspective of further lowering specific gravity, the mass ratio of WO ₃ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (WO ₃ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably less than 1.00, and more preferably less than 0.80, less than 0.60, less than 0.40, less than 0.30, less than 0.20, less than 0.10, in that order, and particularly preferably 0. From the same point of view, in the case of glass composition C, the mass ratio of Bi ₂ O ₃ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (Bi ₂ O ₃ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )) is preferably less than 1.00, more preferably less than 0.80, less than 0.60, less than 0.40, less than 0.30, less than 0.20, less than 0.10, and particularly preferably 0.

In the molding glass material of the present embodiment, when the glass composition is C, _Li2O , _La2O3 , _{Gd2O3 , Y2O3} , _ZrO2 , _TiO2 , _Nb2O5 , _Ta2O5 , _WO3 and _Bi2O3 have the effect of increasing the refractive _index . On the other hand, _{SiO2 , B2O3} , _{Na2O , K2O} , _MgO , CaO, SrO, _BaO and _ZnO have the tendency to reduce the refractive index. From the perspective of higher refractive index, the mass ratio of the total content of SiO ₂ , B ₂ O ₃ , Na ₂ O, K ₂ O, MgO, CaO, SrO, BaO and ZnO to the total content of Li ₂ O, La ₂ O ₃ , Gd ₂ O ₃ , Y _{2 O 3 ,} ZrO ₂ , TiO 2 , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ is ((SiO ₂ + B ₂ O ₃ + Na ₂ O + K ₂ O + MgO + CaO + SrO + BaO + ZnO) / (Li ₂ O + La ₂ O ₃ + Gd ₂ O ₃ + Y ₂ O ₃ + ZrO ₂ + TiO ₂ + Nb ₂ O ₅ + Ta ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )), preferably it is above 0.12, and more preferably it is above 0.15, above 0.20, above 0.30, above 0.35, above 0.40, above 0.45, above 0.50, and above 0.55, and more preferably it is below 2.83, and more preferably it is below 2.80, below 2.60, below 2.40, below 2.20, below 2.00, below 1.80, below 1.70, below 1.60, below 1.50, below 1.40, below 1.30, below 1.26, below 1.25, and below 1.24.

In the case of the glass composition C in the molding glass material of the present embodiment, although _TiO2 , _Nb2O5 , _{Ta2O5 , WO3} , _Bi2O3 and _ZrO2 have the effect of increasing the refractive index _of the glass, if the _ZrO2 content _is too high, the glass meltability tends to decrease. From the above viewpoints, the mass ratio of ZrO ₂ content to the total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , Bi ₂ O ₃ and ZrO ₂ (ZrO ₂ /(TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ +ZrO ₂ )) is preferably greater than 0.00, more preferably greater than 0.01 and greater than 0.02, respectively, and preferably less than 0.17, and more preferably less than 0.16, less than 0.15, less than 0.14 and less than 0.13, respectively.

In the glass material for molding of the present embodiment, when the glass composition is C, although TiO ₂ , Nb ₂ O ₅ , WO ₃ and ZnO tend to increase the refractive index and make the glass more highly dispersible, if they are contained in large amounts, the thermal stability of the glass tends to decrease. On the other hand, MgO, CaO, SrO and BaO tend to make the glass less dispersible and have the effect of improving the thermal stability, but if they are contained in large amounts, the refractive index tends to decrease. From the above viewpoints, the mass ratio of the total content of MgO, CaO, SrO and BaO to the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and ZnO ((MgO+CaO+SrO+BaO)/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +ZnO)) is preferably 0.10 or more, and more preferably 0.15 or more, 0.20 or more, 0.25 or more, 0.26 or more, 0.27 or more, 0.28 or more, 0.29 or more, 0.30 or more, 0.31 or more, and 0.32 or more, and preferably 1.50 or less, and more preferably 1.30 or less, 1.20 or less, 1.10 or less, 1.00 or less, 0.95 or less, 0.90 or less, and 0.87 or less, in that order.

In the molding glass material of the present embodiment, when the glass composition C is used, the _TiO2 content is preferably 0.00% or more, and more preferably more than 0.00%, 0.50% or more, 1.00% or more, 1.50% or more, 2.00% or more, 2.50% or more, 3.00% or more, 3.50% or more, and 4.00% or more. Furthermore, it is preferably 50.00% or less, and more preferably 45.0% or less, 40.00% or less, 38.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 32.00% or less, 31.00% or less, 30.00% or less, 29.50% or less, and 29.00% or less. The _TiO2 content within the above range is preferred from the perspective of achieving better optical constants and reducing the cost of glass raw materials.

In the molding glass material of the present embodiment, when the glass composition is C, _{the Nb2O5} content is preferably 0.00% or more, and more preferably, in order of more than 0.00%, more than 1.00%, more than 2.00%, more than 3.00%, more than 4.00%, more than 5.00%, more than 6.00%, more than 7.00%, more than 8.00%, more than 9.00%, more than 10.00%, and more than 10.50%. Furthermore, the Nb ₂ O ₅ content is preferably 60.00% or less, and more preferably 58.00% or less, 56.00% or less, 54.00% or less, 52.00% or less, 50.00% or less, 49.00% or less, 48.00% or less, 47.00% or less, 46.00% or less, 45.00% or less, and 44.00% or less. _{The Nb 2} O ₅ content within the above range is preferred from the viewpoint of achieving better optical constants, lower specific gravity, and improved partial dispersion characteristics.

In the glass material for molding of the present embodiment, when the glass composition is C, the Ta ₂ O ₅ content can be set to 0.00% or more. In addition, the Ta ₂ O ₅ content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less. The _{Ta 2} O ₅ content within the above range is preferred from the perspective of improving the thermal stability of the glass, improving the melting property, and further reducing the specific gravity.

In the glass material for molding of the present embodiment, when the glass composition C is used, the WO ₃ content can be set to 0.00% or more. In addition, the WO ₃ content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less. The WO ₃ content within the above range is preferred from the perspective of increasing glass transmittance, improving partial dispersion characteristics, and further reducing specific gravity.

In the glass material for molding of the present embodiment, when the glass composition is C, the Bi ₂ O ₃ content can be set to 0.00% or more. In addition, the Bi ₂ O ₃ content is preferably 5.00% or less, and more preferably 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less. The _{Bi 2} O ₃ content within the above range is preferred from the viewpoints of improving the thermal stability of the glass, improving the partial dispersion characteristics, and further reducing the specific gravity.

In the glass material for molding of the present embodiment, when the glass composition C is used, although GeO ₂ has the effect of increasing the refractive index, it is a very expensive component. From the perspective of reducing the glass manufacturing cost, the GeO ₂ content can be set to be greater than 0.00% and less than 2.00%, and more preferably less than 1.50%, less than 1.00%, and less than 0.50%, in that order.

In the glass material for molding of the present embodiment, when the glass composition C is used, in addition to the _above components, one or more of _P2O5 , _{Al2O3 , etc.} may be contained. The content _{of P2O5} may be set to be 0.00% or more, and preferably 10.00% or less, and more preferably 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less. The content _{of P2O5} within the above range is preferred from the viewpoint of improving the thermal stability of the glass and improving the partial dispersion characteristics. The _Al2O3 content can be set _to be 0.00% or more, and preferably 10.00% or less, and more preferably 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and _0.50 % or less. The _Al2O3 content within the above range is preferred from the perspective of improving the devitrification resistance and thermal stability of the glass.

Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, it is best not to contain these elements, that is, it is best not to introduce these elements into the glass as glass components.

U, Th, and Ra are all radioactive elements. Therefore, it is best not to contain these elements, that is, it is best not to introduce these elements into the glass as glass components.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, Ce are elements that will increase the color of the glass or become a source of fluorescence, and it is best not to be contained in the glass used for optical components. Therefore, it is best not to contain these elements, that is, it is best not to introduce these elements into the glass as glass components.

Sb and Sn are elements that can be added arbitrarily and have the function of clarifiers.

The amount of Sb added is preferably in the range of 0 to 0.11 mass %, more preferably in the range of 0.01 to 0.08 mass %, and particularly preferably in the range of 0.02 to 0.05 mass % when converted into _{Sb 2} O ₃ and _the total content of glass components other than Sb 2 O 3 is assumed to be 100 mass %.

The amount of Sn added _is preferably in the range of 0 to 0.50 mass %, more preferably in the range of 0 to 0.20 mass %, and particularly preferably 0 mass %, when the total content of glass components other than SnO ₂ is 100 mass %.

<Glass properties>

(refractive index nd)

In the glass material for molding of the present embodiment, when the glass composition C is used, it can become a high refractive index glass. In the case of glass composition C, the refractive index nd is preferably 1.860 or more, and more preferably 1.865 or more, 1.870 or more, 1.875 or more, 1.880 or more, 1.885 or more, 1.890 or more, 1.895 or more, and 1.900 or more. In addition, the refractive index nd is, for example, set to 1.950 or less, 1.945 or less, 1.940 or less, 1.935 or less, 1.930 or less, or 1.925 or less. In the present invention and this specification, "refractive index" refers to "refractive index nd".

(Abbe value νd)

The Abbe value νd is a value indicating a property related to dispersion, and is expressed by νd=(nd-1)/(nF-nC) using the refractive indices nd, nF, and nC of the d-line, F-line, and C-line, respectively. In the case of the glass material for molding of the present embodiment, when the glass composition is C, the Abbe value νd is preferably 22.00 or more, and more preferably 22.50 or more, 23.00 or more, 23.50 or more, 24.00 or more, 24.20 or more, 24.40 or more, 24.60 or more, 24.70 or more, 24.80 or more, 25.00 or more, 25.50 or more, 25.60 or more, 25.80 or more, and 26.00 or more in order of usefulness as a material for optical elements. From the same point of view, the Abbe number νd is preferably below 30.00, and more preferably below 29.50, below 29.00, below 28.50, below 28.40, below 28.30, below 28.20, below 28.10, below 28.00, below 27.90, below 27.80, and below 27.70.

Furthermore, in the glass material for molding of the present embodiment, when the glass composition C is used, from the perspective of the usefulness of the material for optical elements, the refractive index nd and the Abbe value νd preferably satisfy at least one of the following relationships: nd≧-0.0025νd+1.925 nd≧-0.0025νd+1.935 nd≦-0.0025νd+1.995 nd≦-0.0025νd+2.005

(Specific gravity d) The refractive power of the optical element constituting the optical system is determined by the refractive index of the glass constituting the optical element and the curvature of the optical functional surface (the surface for controlling the incidence and emission of light) of the optical element. If the curvature of the optical functional surface is increased, the thickness of the optical element will also increase. As a result, the optical element becomes heavier. In contrast, if a glass with a higher refractive index is used, a greater refractive power can be obtained even without increasing the curvature of the optical functional surface. As mentioned above, if the refractive index can be increased while suppressing the increase in the specific gravity of the glass, the optical element with a certain refractive power can be made lightweight. From the above viewpoints, in the glass material for molding of the present embodiment, when the glass composition C is used, the specific gravity d is preferably 4.100 or less, and more preferably 4.095 or less, 4.090 or less, 4.085 or less, 4.080 or less, 4.050 or less, 4.000 or less, 3.995 or less, 3.990 or less, and 3.985 or less. From the viewpoint that the lower the specific gravity, the lighter the optical element, the lower the specific gravity is, and the lower limit of the specific gravity is not particularly limited. In one embodiment, the specific gravity can be set to 3.400 or more, 3.450 or more, 3.500 or more, 3.550 or more, 3.600 or more, 3.650 or more, 3.700 or more, or 3.750 or more.

(d/nd) From the same perspective as the above-mentioned items concerning specific gravity d, in the glass material for molding of the present embodiment, when the glass composition C is used, the quotient (d/nd) of specific gravity d divided by refractive index nd is preferably 4.35 or less, and more preferably 4.00 or less, 3.50 or less, 3.00 or less, 2.90 or less, 2.80 or less, 2.70 or less, 2.60 or less, 2.50 or less, 2.40 or less, 2.30 or less, 2.20 or less, and 2.15 or less. From the perspective that the smaller the (d/nd) value, the lighter the optical element, the smaller the (d/nd) value is, and there is no particular lower limit for the relevant (d/nd). The (d/nd) of a form can be set to, for example, 1.74 or more, 1.76 or more, 1.78 or more, 1.80 or more, 1.82 or more, 1.84 or more, 1.85 or more, 1.86 or more, 1.87 or more, 1.88 or more, 1.89 or more, 1.90 or more, 1.91 or more, 1.92 or more, 1.93 or more, 1.94 or more, or 1.95 or more.

(Coloring λ5) In the glass material for molding of the present embodiment, in the case of glass composition C, the light transmittance of the glass, in detail, suppresses the light absorption end on the short wavelength side from becoming longer wavelength, and can be evaluated using the coloring λ5. The so-called "coloring λ5" means the wavelength when the spectral transmittance (including surface reflection loss) of 10mm thick glass from the ultraviolet region to the visible region becomes 5%. In the case of glass composition C, the so-called "spectral transmittance" is, for example, the spectral transmittance obtained when light is incident on the above-mentioned polished surface from a vertical direction using a glass sample with a thickness of 10.0±0.1mm and a plane parallel to the polished direction, that is, when the light intensity incident on the above-mentioned glass sample is set to Iin and the light intensity penetrating the above-mentioned glass sample is set to Iout, it means Iout/Iin. The absorption end of the spectral transmittance on the short wavelength side can be quantitatively evaluated based on the coloring index λ5. When using a UV-curing adhesive to join lenses together to make a double lens, the adhesive is cured by irradiating UV light through an optical element. From the perspective of efficiently curing the UV-curing adhesive, the absorption end of the spectral transmittance on the short wavelength side is preferably in the shorter wavelength range. The coloring index λ5 can be used as a quantitative evaluation index for the absorption end on the short wavelength side. In the case of glass composition C, a λ5 of less than 400nm is preferred. The more preferred order of λ5 is less than 395nm, less than 390nm, less than 385nm, and less than 380nm. The lower the λ5, the better, and there is no particular lower limit.

(Glass transition temperature Tg) In the glass material for molding of this embodiment, when the glass composition C is used, the glass transition temperature Tg is preferably 560°C or higher from the perspective of mechanical workability. Glass with a higher glass transition temperature is more likely to be less damaged when glass mechanical processing such as cutting, cutting, grinding, and polishing is performed, so it is more preferred. From the perspective of mechanical workability, the glass transition temperature Tg is more preferably 570°C or higher, and more preferably 580°C or higher, 590°C or higher, and 600°C or higher in that order. On the other hand, from the perspective of reducing the burden on the annealing furnace and the molding die, the glass transition temperature Tg is preferably below 800°C, and more preferably below 790°C, below 780°C, below 770°C, below 760°C, below 750°C, and below 740°C, in that order.

The glass transition temperature Tg is obtained as follows. In differential scanning calorimetry, if the temperature of a glass sample is increased, endothermic behavior will occur with a change in specific heat, that is, an endothermic peak will appear. If the temperature is further increased, a heat generation peak will appear. In differential scanning calorimetry, a differential scanning calorimetry curve (DSC curve) with temperature on the horizontal axis and the vertical axis corresponding to the heat generation and endothermic amount of the sample can be obtained. The intersection of the tangent line from the base line at the point where the endothermic peak appears in the curve is the largest is set as the glass transition temperature Tg. When measuring the glass transition temperature Tg, the glass can be fully crushed using a mortar or the like and used as a sample, and then a differential scanning calorimeter can be used to perform the measurement at a heating rate of 10°C/min.

(Liquid phase temperature) The thermal stability of glass includes resistance to devitrification when the molten glass is formed, and resistance to devitrification when the solidified glass is reheated. The resistance to devitrification when the molten glass is formed can be measured by the liquid phase temperature LT. It can be said that the lower the liquid phase temperature, the better the resistance to devitrification. In order to prevent devitrification of glass with a higher liquid phase temperature, the temperature of the molten glass (i.e. molten glass) must be kept at a high temperature, but this may cause problems such as volatility of volatile components, corrosion of the crucible, and especially in the case of a crucible made of precious metals, the glass may be colored due to the dissolution of precious metal ions in the molten glass, and the viscosity during forming may decrease, making it difficult to form a highly homogeneous glass. Therefore, in the case of glass composition C, the liquidus temperature is preferably 1400°C or lower, and more preferably 1370°C or lower, 1340°C or lower, 1310°C or lower, 1280°C or lower, 1270°C or lower, 1260°C or lower, and 1250°C or lower. The liquidus temperature may be, for example, 1000°C or higher, 1050°C or higher, or 1100°C or higher, but may also be higher than the values exemplified here.

The "liquidus temperature" in the present invention and this specification can be obtained according to the following method. Using a differential scanning calorimeter, while nitrogen at a flow rate of 0.3L/min is flowing, about 0.02ml of crushed glass sample is heated to 1350℃ at a heating rate of 10℃/min in a nitrogen environment. When crystallization occurs in the glass generated during the heating process and melting occurs in a temperature range higher than the glass transition temperature or crystallization temperature, the end point of the generated endothermic peak is set as the liquidus temperature. Figure 1 shows a schematic diagram of a differential scanning calorimetry curve (DSC curve). The horizontal axis is temperature, and the more to the right on the horizontal axis, the higher the temperature, and the more to the left, the lower the temperature. The vertical axis corresponds to the heat generation and absorption of the sample. The area above the baseline (dashed line) is heat generation, and the area below is absorption. The crystal precipitation during the temperature rise process corresponds to the heat generation peak, and the melting of the precipitated crystals corresponds to the endothermic peak. The temperature at which the crystals melt and become molten is the liquidus temperature. The liquidus temperature is the temperature at which the tangent to the endothermic peak on the high temperature side intersects with the baseline.

(Manufacturing of glass materials) The glass of the embodiment of the present invention is prepared by mixing glass raw materials in a manner to form the above-mentioned predetermined composition, and then can be produced from the prepared glass raw materials. For example, a plurality of compounds are mixed and fully mixed to form a master batch, and the master batch is placed in a quartz crucible or a platinum crucible for rough melting. The molten material obtained by the rough melting is cooled and crushed to produce glass scraps. The glass scraps are further placed in a platinum crucible for heating and remelting (remelting) to form molten glass, and after cooling, clarifying, and homogenizing, the molten glass is cast into a mold whose temperature is adjusted to a temperature Tx that is less than Tg (step 1), and maintained at the temperature Tx (step 2). Then, in order to reduce the strain point temperature of the glass, cooling is performed at -30°C/hr for 4 hours (step 3), and the glass is cooled to a temperature that can be taken out of the furnace at a gradual cooling rate that does not cause cracking (step 4).

In addition, under the premise that the desired glass components can be introduced into the glass in the desired content, there is no particular limitation on the compounds used in preparing the masterbatch. Such compounds can be exemplified by oxides, carbonates, nitrates, hydroxides, fluorides, etc.

The following describes steps 1 to 4.

(Step 1) In step 1, molten glass is cast into a mold whose temperature is adjusted to a temperature Tx that is less than the glass transition temperature Tg. By controlling the temperature of the molten glass as described above, the thermal energy applied to the glass can be suppressed, so that the movement of atoms in the glass can be suppressed. As a result, the movement of atoms can be regulated before the structural factors inside the glass such as the bond distance and bond angle between atoms in the glass are homogenized. Therefore, by maintaining a chaotic glass structure like a molten state, a glass material with excellent stability when reheated can be obtained.

In addition, the temperature of the molten glass before step 1 is usually the liquidus temperature of the glass ~ the melting temperature of the glass. In addition, in step 1, the temperature of the glass when the molten glass is cast into the mold is the temperature of the glass when it is melted, which is about 1500℃~1100℃, preferably in the range of 1400℃~1200℃. Therefore, in step 1, the molten glass will be cooled when it is cast into the mold. The cooling at this time is usually carried out by cooling in the atmosphere. However, if the cooling speed is not fast enough, a part of the inside of the glass will show a high viscosity or solidification without flow. This will hinder the homogenization of the glass, and there will also be a concern that the glass will crack or break. Therefore, the lower limit of the cooling rate in step 1 is preferably about 1°C/second, and more preferably 3°C/second and 6°C/second, respectively. The upper limit of the cooling rate is preferably 20°C/second, and more preferably 15°C/second, 12°C/second, and 10°C/second, respectively.

(Step 2) In step 2, the molten glass is maintained at a temperature Tx. The maintenance temperature Tx of step 2 is preferably less than the glass transition temperature Tg, and the upper limits are preferably Tg-1℃, Tg-5℃, Tg-10℃, Tg-15℃, and Tg-20℃. By setting the upper limit of the maintenance temperature Tx to the above range, the complexity of the glass structure can be improved, so that a glass material with excellent stability when reheated can be obtained.

The lower limit of the holding temperature Tx in step 2 is preferably Tg-100°C, and more preferably Tg-90°C, Tg-80°C, Tg-70°C, Tg-60°C, and Tg-50°C in that order. It is particularly preferred that Tx is not excessively lower than the strain point, and the best is to be above the strain point. By setting the lower limit of the holding temperature Tx to the above range, the excessive internal strain of the glass can be removed, so that the deterioration of the glass processability can be suppressed in the subsequent steps, or the glass block material can be prevented from being damaged. When the subsequent steps belong to the process that is not related to whether the glass processability is deteriorated, there is no special regulation for the lower limit of the temperature of step 2.

The holding time of step 2 is to make the high temperature glass cooled from the molten state uniform. The thicker the glass is and the larger the glass volume is, the longer the holding time tends to be. It is preferably more than 10 minutes, and can also be set to more than 20 minutes, or more than 30 minutes. From the perspective of productivity and the perspective of maintaining the thermal stability of the glass, the upper limit of the holding time is less than 3 hours, and the more preferably less than 2 hours, less than 1.5 hours, or less than 1.0 hours. If the holding time is too long, the disordered atomic configuration of the molten state cannot be maintained, and the thermal stability of the glass is reduced due to the structural ordering of the atomic configuration, and α _max tends to increase.

(Step 3) In step 3, the glass is cooled at -30℃/hr for 4 hours so that the strain point temperature can be reduced during gradual cooling. The cooling time is preferably 4 hours or more, more preferably 5 hours or more, and particularly preferably 6 hours or more when the temperature Tx is higher than the strain point. If the temperature Tx is lower than the strain point, the cooling time may be less than 4 hours.

(Step 4) In step 4, the glass is cooled to a temperature that can be taken out of the furnace at a gradual cooling rate that does not cause cracking. The gradual cooling rate of step 4 is preferably less than about -50℃/hr, and more preferably is set to about -10℃/hr or -30℃/hr. If it is less than -1℃/hr, there is a concern that productivity will be hindered. In addition, the temperature of the glass that can be taken out of the furnace varies depending on the insulation condition outside the furnace, and is preferably below about 100℃, and more preferably below 80℃, below 60℃, below 40℃, and below 20℃ in that order. If expressed as a difference from room temperature, the upper limit of the temperature of the glass that can be taken out of the furnace is preferably room temperature + 50°C, and more preferably room temperature + 40°C, room temperature + 30°C, room temperature + 20°C, and room temperature + 10°C. The lower limit of the temperature of the glass that can be taken out of the furnace can be set to room temperature.

When the glass is gradually cooled, any known method that can obtain the above-mentioned temperature distribution (such as a temperature-programmable gradual cooling furnace, etc.) can be adopted.

By setting the cooling rate of step 1 and the holding temperature Tx of step 2 within the above range, a glass material with high structural complexity and excellent stability when reheated can be obtained. In addition, by cooling and gradually cooling the glass as in steps 3 and 4, the strain of the glass can be removed, so that the workability of the glass can be maintained in the subsequent steps.

The optical glass of the embodiment of the present invention can be directly used as the glass material for molding of the embodiment of the present invention.

(Manufacturing of optical elements, etc.) When using the molding glass material of the embodiment of the present invention to manufacture optical elements, it is sufficient to adopt a known method. For example, when manufacturing the above-mentioned glass material, molten glass is poured into a casting mold and molded into a plate to manufacture the molding glass material of the present invention. The obtained glass material is appropriately cut, ground, and polished to manufacture a molding precursor (also called a "slice") having a size and shape suitable for molding after reheating. The slice is heated and softened, and molded using a known method (reheat stamping, round rod molding, extrusion molding, etc.) to obtain an optical element blank that is approximately the shape of an optical element. The optical element blank is annealed, and cut, ground, and polished using a known method to manufacture an optical element.

The optical functional surface of the manufactured optical element can also be coated with an anti-reflection film, a total reflection film, etc. according to the purpose of use.

According to one aspect of the present invention, an optical element composed of the above optical glass can be provided. Examples of the types of optical elements include lenses such as spherical lenses, aspherical lenses, prisms, diffraction gratings, etc. Examples of the shapes of lenses include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, concave meniscus lenses, etc. The optical element can be manufactured using a method including the step of processing a glass molded body composed of the above optical glass. Examples of processing include cutting, cutting, rough grinding, fine grinding, grinding, etc. By using the above-mentioned glass during this processing, damage can be reduced, so that high-quality optical components can be stably supplied.

Second Embodiment The molding glass material of the second embodiment has a maximum linear expansion coefficient α _max , an average linear expansion coefficient α _100-300 at 100-300°C, and a total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass %, satisfying the following formula (4): α _max /α _100-300 × [SiO ₂ +ZrO ₂ ] ≦ 264 ... (4)

In the second embodiment, the maximum linear expansion coefficient α _max , the average linear expansion coefficient α _100-300 at 100-300°C, and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % satisfy the following formula (4), more preferably the following formula (5), and particularly preferably the following formula (6). By satisfying the following formula, a molding glass material having excellent stability during reheating can be obtained. α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦264 ・・・(4) α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦260 ・・・(5) α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ]≦255 ・・・(6)

The maximum linear expansion coefficient α _max and the average linear expansion coefficient α _100-300 can be controlled by adjusting the conditions for cooling the molten glass in the manufacturing step of the glass material described later.

The maximum linear expansion coefficient α _max and the average linear expansion coefficient α _100-300 can be measured in the same manner as in the first embodiment.

In the molding glass material of the second embodiment, the maximum linear expansion coefficient α _max and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % preferably satisfy the following formula (1), more preferably satisfy the following formula (2), and particularly preferably satisfy the following formula (3). From the viewpoint of obtaining a molding glass material excellent in stability during reheating, it is preferably satisfied the following formula: α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ···(1) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27500 ···(2) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27000 ···(3)

The maximum value of the linear expansion coefficient α _max can be controlled by adjusting the conditions for cooling the molten glass in the manufacturing step of the glass material described later.

In the second embodiment, the properties and glass composition other than those described above can be the same as those of the first embodiment. In addition, the production of the glass material and the production of the optical element of the second embodiment can also be the same as those of the first embodiment.

Third Implementation Form In the third implementation form, the maximum linear expansion coefficient α _max of the molding glass material is smaller than the maximum linear expansion coefficient α _max (Tg), and the maximum linear expansion coefficient α _max (Tg) is the maximum linear expansion coefficient α _max (Tg) of the glass material obtained by homogenizing the molding glass material at a glass transition temperature Tg, cooling at -30°C/hr for 4 hours, and then cooling.

In the molding glass material of the third embodiment, the maximum linear expansion coefficient α _max is smaller than the maximum linear expansion coefficient α _max (Tg) of the glass material obtained by homogenizing the molding glass material at the glass transition temperature Tg, cooling at -30°C/hr for 4 hours, and then cooling. However, the maximum linear expansion coefficient α _max may be slightly larger than the maximum linear expansion coefficient α _max (Tg). Therefore, the difference between α _max and α _max (Tg) [α _max (Tg)-α _max ], when expressed as an integer in the unit of 10 ^-7・℃ ^-1 , is preferably -9 or more, and more preferably -4 or more, 0 or more, 5 or more, 10 or more, 20 or more, 40 or more, 60 or more, 80 or more, 100 or more, 120 or more, 140 or more, 160 or more, 180 or more, 200 or more, 250 or more, and 300 or more. The upper limit of the difference is not particularly limited, and is usually α _max (Tg), preferably about α _max (Tg)-100.

In the molding glass material of the third embodiment, the method for measuring the maximum value α _max (Tg) is the same as that of the first embodiment.

In the molding glass material of the third embodiment, the maximum linear expansion coefficient α _max and the total content of SiO ₂ and ZrO ₂ [SiO ₂ +ZrO ₂ ] expressed in mass % preferably satisfy the following formula (1), more preferably satisfy the following formula (2), and particularly preferably satisfy the following formula (3). From the viewpoint of obtaining a molding glass material having excellent stability during reheating, it is most preferable to satisfy the following formula: α _max × [SiO ₂ +ZrO ₂ ] ≦ 27900 ···(1) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27500 ···(2) α _max × [SiO ₂ +ZrO ₂ ] ≦ 27000 ···(3)

The maximum value of the linear expansion coefficient α _max can be controlled by adjusting the conditions for cooling the molten glass in the manufacturing step of the glass material described later.

In the glass material for molding of the third embodiment, the properties and glass composition other than those mentioned above can be set to be the same as those of the first embodiment. In addition, the manufacturing of the glass material and the manufacturing of the optical element, etc. of the third embodiment can also be set to be the same as those of the first embodiment. [Example]

The present invention is described in more detail below using embodiments. However, the present invention is not limited to the embodiments shown in the embodiments.

(Example 1-1) Glass samples having the glass composition I shown in Table 1(1) were prepared according to the following procedure, and various evaluations were performed on the obtained glass samples. The results are shown in Tables 2(1) and 2(2).

[Manufacturing of glass samples] First, the raw materials are prepared in the form of oxides, hydroxides, carbonates, and nitrates corresponding to the glass components. The raw materials are weighed and mixed in such a way that the glass composition of the optical glass obtained becomes the composition I shown in Table 1 (1), and then the raw materials are fully mixed. The prepared raw materials (master batch) obtained in this way are put into a platinum crucible and heated at 1350℃~1450℃ for 2 hours to obtain molten glass, which is stirred to be homogenized and clarified. The molten glass is then cast into a mold preheated to an appropriate temperature and rapidly cooled (step 1). The cast glass is maintained at a holding temperature Tx that is 25℃ lower than the glass transition temperature Tg for 30 minutes (step 2). Then, the glass sample was obtained by cooling at a rate of -30°C/hr to a temperature 120°C lower than the holding temperature Tx in step 2 (step 3), and then cooling in a furnace to room temperature (step 4). The amount of glass here was set to 150 g.

Here, the holding temperature Tx in step 2 is the value of the glass transition temperature Tg (unit: °C) rounded to the first decimal place as the Tg of the glass sample, and then the value 25°C lower than the temperature is set as the holding temperature Tx. Table 2 (2) records the difference between the rounded Tg equivalent to this temperature difference and the holding temperature Tx. In this way, although the measured value of Tg varies to some extent, it can be set to the same holding temperature Tx, so that multiple samples can be held at one time, thereby improving the production efficiency of the glass of the present invention.

[Confirmation of glass component composition] The content of each glass component was measured using inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the obtained glass sample. Composition I was confirmed as shown in Table 1 (1).

[Glass transition temperature Tg] The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH JAPAN at a heating rate of 10°C/min.

[Stability Test] After confirming that there is no foreign matter inside the obtained glass sample using an optical microscope (100 times), it is cut and cut to obtain a sample of 11mm×11mm×10.5mm. The sample is placed in a heat treatment furnace set at a temperature 200℃ higher than Tg and heated. After 5 minutes, it is taken out and the glass sample is cooled. The end of the cooled glass sample is optically polished, and the inside of the glass sample is observed using an optical microscope (100 times). The number of crystals (bright spots) observed from the entire glass sample is counted and converted to the number per 1g. The crystals are set to a size range of 1~300μm. In addition, no cracks or lines were found in the glass sample.

[Linear expansion coefficient] The average linear expansion coefficient of the obtained glass samples was measured in accordance with the provisions of JOGIS08. The sample was set as a round bar with a length of 20mm±0.5mm and a diameter of 5mm±0.5mm. Under a load of 98mN, the sample was heated at a constant rate of 4°C per minute, and the temperature and sample extension were measured every 1 second. Between room temperature and yield point temperature (the temperature at which the sample yields and stops extending on the surface), when the sample extension becomes maximum per unit temperature rise, the maximum linear expansion coefficient at this temperature is set as α _max . In addition, α _max is the maximum value of the linear expansion coefficient obtained by moving average processing using the linear expansion coefficients of 31 measurement points. Furthermore, the average value of the linear expansion coefficients at 100-300°C is defined as the average linear expansion coefficient α _100-300 .

The maximum linear expansion coefficient α _max and the maximum linear expansion coefficient α _max (Tg) of the glass when the holding temperature Tx in step 2 is set to the glass transition temperature are measured, and the difference Q: α _max (Tg)-α _max is calculated.

[Average linear expansion coefficient α _L ] The average linear expansion coefficient of the obtained glass sample was measured in accordance with the provisions of JOGIS16. The average linear expansion coefficient was measured using a thermomechanical analyzer (TMA4000SE) manufactured by NETZSCH JAPAN. The sample used was a round bar with a length of 20 mm ± 0.5 mm and a diameter of 5 mm ± 0.5 mm. First, the sample temperature was cooled to below -80°C using liquid nitrogen, and after being kept for 20 minutes, the measurement was started. During the measurement, a load of 98 mN was applied to the sample, and the temperature was raised to 320°C at a constant rate of 4°C per minute, while the temperature and sample extension were measured every 1 second. The average value of the linear expansion coefficient from -30 to 70°C was set as the average linear expansion coefficient α _L .

[Measurement of optical properties] For the obtained glass samples, the refractive indices nd, ng, nF and nC, the Abbe number νd, the partial dispersion ratio Pg,F, ΔPg,F were measured. The results are shown in Tables 2(1) and 2(2).

(i) Refractive index nd, ng, nF, nC and Abbe number νd For the above glass samples, the refractive index nd, ng, nF, nC were measured using the refractive index measurement method of Japanese industrial standard JIS B 7071-1, and the Abbe number νd was calculated according to the following formula. νd=(nd-1)/(nF-nC)

(ii) Partial dispersion ratio Pg,F, ΔPg,F Using the refractive indices ng, nF, and nC of the g-line, F-line, and c-line, the partial dispersion ratio Pg,F and ΔPg,F are calculated according to the following formula. Pg,F=(ng-nF)/(nF-nC) ・・・(13) ΔPg,F=Pg,F-(0.6483-0.001802×νd) ・・・(14)

[Evaluation of light transmittance] (i)λτ80 Using glass samples with thicknesses of 2.0mm±0.1mm and 10.0mm±0.1mm, the spectral transmittance was measured in the wavelength range of 200~700nm according to JOGIS17 (Internal transmittance measurement method of optical glass). The wavelength at which the internal transmittance of the glass with a thickness of 10mm becomes 80% is set as λτ80. The results are shown in Table 2(1).

(ii) λ70 For a glass sample with a thickness of 10.0 mm ± 0.1 mm, the spectral transmittance was measured in the wavelength range of 200 to 700 nm. The wavelength at which the internal transmittance becomes 70% is set as λ70. The results are shown in Table 2 (1).

[Specific gravity] Specific gravity was measured using the Archimedean method. The results are shown in Table 2(1).

(Example 1-2) In the manufacture of the glass sample, except that the holding temperature Tx in step 2 is set to a temperature 50°C lower than the glass transition temperature Tg, the rest is the same as in Example 1-1 to obtain the glass sample. Various evaluations are carried out in the same manner as in Example 1-1.

(Example 1-3) In the manufacture of the glass sample, except that the holding temperature Tx in step 2 is set to a temperature 100°C lower than the glass transition temperature Tg, the rest is the same as in Example 1-1 to obtain the glass sample. Various evaluations are performed in the same manner as in Example 1-1.

(Example 2-1) A glass sample having glass composition II shown in Table 1 (1) was manufactured. In manufacturing the glass sample, the raw materials were prepared in a manner to obtain glass composition II and the holding temperature Tx in step 2 was set to a temperature 60°C lower than the glass transition temperature Tg. The glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1.

(Comparative Example 1-1) In the manufacture of the glass sample, except that the holding temperature Tx in step 2 is set to a temperature 30°C higher than the glass transition temperature Tg, the glass sample is obtained in the same manner as in Example 1-1. Various evaluations are performed in the same manner as in Example 1-1.

(Comparative Example 1-2) In the manufacture of the glass sample, the glass sample was obtained in the same manner as in Example 1-1 except that the holding temperature Tx in step 2 was set to the glass transition temperature Tg. Various evaluations were performed in the same manner as in Example 1-1. In addition, the maximum value of the linear expansion coefficient of Comparative Example 1-2 was set to α _max (Tg) and compared with the maximum values of the linear expansion coefficients α _max of Examples 1-1, 1-2, and 1-3.

(Comparative Example 1-3) In the manufacture of glass samples, except for setting the holding time of step 2 to 72 hours, the glass samples were obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1. In addition, although glass was obtained in Comparative Example 1-3, obvious devitrification occurred during the stability test. In addition, the refractive index nd, Abbe number νd, partial dispersion ratio Pg,F, and ΔPg,F could not be measured.

(Comparative Example 2-1) In the manufacture of the glass sample, the glass sample was obtained in the same manner as in Example 2-1 except that the holding temperature Tx in step 2 was set to the glass transition temperature Tg. Various evaluations were performed in the same manner as in Example 2-1. In addition, the maximum value of the linear expansion coefficient of Comparative Example 2-1 was set to α _max (Tg) and compared with the maximum value of the linear expansion coefficient α _max of Example 2-1.

(Example 3-1) A glass sample having glass composition III shown in Table 1 (2) was manufactured. In manufacturing the glass sample, the raw materials were prepared in a manner to obtain glass composition III and the holding temperature Tx in step 2 was set to a temperature 60°C lower than the glass transition temperature Tg. The glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1.

(Example 3-2) A glass sample having glass composition III shown in Table 1 (2) was manufactured. In manufacturing the glass sample, the raw materials were prepared in a manner to obtain glass composition III and the holding temperature Tx in step 2 was set to a temperature 100°C lower than the glass transition temperature Tg. The glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1.

(Example 4-1) A glass sample having glass composition IV shown in Table 1 (3) was manufactured. In the manufacture of the glass sample, except that the raw materials were prepared in a manner to obtain glass composition III and the holding temperature Tx in step 2 was set to a temperature 100°C lower than the glass transition temperature Tg, the glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1. A glass sample having glass composition IV shown in Table 1 (3) was manufactured. In the manufacture of the glass sample, except that the raw materials were prepared in a manner to obtain glass composition IV and the holding temperature Tx in step 2 was set to the same temperature as the glass transition temperature Tg, the glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1.

(Example 4-2) A glass sample having glass composition IV shown in Table 1 (3) was manufactured. In manufacturing the glass sample, except for preparing the raw materials in a manner to obtain glass composition IV, the rest of the glass sample was obtained in the same manner as in Example 1-1. Various evaluations were performed in the same manner as in Example 1-1.

[Table 1(1)] Composition (mass%) I II _{P2O5 ​} 1.10 0.76 SiO ₂ 23.27 31.91 _Li2O 5.66 5.26 _Na2O 5.15 11.06 _K2O 3.79 0.71 ZrO ₂ 5.82 8.75 _{Nb2O5 ​} 50.14 35.79 _TiO2 5.07 5.77 Total 100 100 _{Sb2O3 ​} 0.02 0.02 {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} 0.169 0.269

[Table 1(2)] Composition (mass%) III SiO ₂ 7.20 _{B2O3 ​} 12.40 SrO 0.29 BaO 31.94 La ₂ O ₃ 22.01 _{Y2O3 ​} 17.99 ZrO ₂ 2.35 _TiO2 5.82 Total 100.00 {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} -

[Table 1(3)] Composition (mass%) IV SiO ₂ 19.94 _{B2O3 ​} 3.11 _Li2O 1.76 CaO 14.78 SrO 1.69 BaO 3.36 La ₂ O ₃ 11.99 ZrO ₂ 2.34 _{Nb2O5 ​} 26.58 _TiO2 14.45 Total 100 _{Sb2O3 ​} 0.050 {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]} 0.91

[Table 2(1)] Glass composition SiO ₂ (mass%) ZrO ₂ (mass%) nd νd Pg_F ⊿Pg_F -0.00286×νd+0.68700 proportion α _L (10 ^-5 ℃ ^-1 ) λτ80 (nm) λ70 (nm) Glass transition temperature Tg(℃) Step 2 holding temperature Tx (℃) Holding time t ₁ (hr) in step 2 Difference between Tx and Tg (℃) Comparison Example 1-1 I 23.27 5.82 1.85455 25.18 0.610 0.007 0.615 3.486 0.81 389 395 553 580 0.5 +30 Comparison Example 1-2 I 23.27 5.82 1.85403 25.18 0.610 0.007 0.615 3.487 0.81 389 395 553 550 0.5 0 Comparison Example 1-3 I 23.27 5.82 Unable to determine Unable to determine Unable to determine Unable to determine Unable to determine 3.488 0.81 389 395 553 525 72 -25 Embodiment 1-1 I 23.27 5.82 1.85355 25.19 0.610 0.007 0.615 3.486 0.81 389 395 553 525 0.5 -25 Embodiment 1-2 I 23.27 5.82 1.85217 25.25 0.610 0.007 0.615 3.483 0.81 389 395 553 500 0.5 -50 Embodiment 1-3 I 23.27 5.82 1.85116 25.26 0.610 0.007 0.615 3.480 0.81 389 395 553 450 0.5 -100 Comparison Example 2-1 II 31.91 8.75 1.77090 29.26 0.598 0.002 0.603 3.267 0.82 369 372 562 560 0.5 0 Example 2-1 II 31.91 8.75 1.76788 29.34 0.598 0.002 0.603 3.264 0.82 369 372 562 500 0.5 -60 Example 3-1 III 7.20 2.35 1.80515 40.58 0.572 -0.003 0.571 4.607 0.90 688 630 0.5 -60 Example 3-2 III 7.20 2.35 0.572 -0.003 4.608 0.90 688 590 0.5 -100 Example 4-1 IV 19.99 2.35 1.9003 27.1 0.607 0.007 0.609 3.833 －－－ 429 445 640 640 0.5 0 Example 4-2 IV 19.99 2.35 1.90025 27.14 0.607 0.007 0.609 3.834 －－－ 428 445 640 615 0.5 -25

[Table 2(2)] Stability test crystal number density D (pieces/g) Maximum linear expansion coefficient α _max (10 ^-7 ℃ ^-1 ) (the bottom line is α _max (Tg)) Average linear expansion coefficient α _100-300 (10 ^-7 ℃ ^-1 ) α _max ×[SiO ₂ +ZrO ₂ ] α _max /α _100-300 ×[SiO ₂ +ZrO ₂ ] α _max (Tg)-α _max (10 ^-7 ℃ ^-1 ) Comparison Example 1-1 5.5×10 ⁴ 974 106 28333 266 -10 Comparison Example 1-2 10 964 105 28043 268 0 Comparison Example 1-3 9.5×10 ⁵ 1077 106 31335 295 -113 Embodiment 1-1 2 925 106 26906 253 39 Embodiment 1-2 - 720 107 20945 196 244 Embodiment 1-3 0 631 106 18346 172 333 Comparison Example 2-1 2.5×10 ³ 880 111 35764 321 0 Example 2-1 0 615 111 25006 224 265 Example 3-1 0 495 103 4728 46 67 Example 3-2 0 471 103 4499 44 91 Example 4-1 6 848 91 18942 208 0 Example 4-2 0 837 91 18696 205 11

(Example 3) Using the glass samples made in Examples 1-1, 1-2, 1-3, 2-1, 3-1, 3-2, 4-1, and 4-2, lens blanks are made by known methods, and then the lens blanks are processed by known methods such as grinding to make various lenses. The optical lenses made are various lenses such as: biconvex lenses, biconcave lenses, plano-convex lenses, plano-concave lenses, concave meniscus lenses, convex meniscus lenses, etc. Various lenses can be combined with lenses composed of other types of optical glass to correct secondary chromatic aberration well.

Similarly, prisms are manufactured using various optical glasses manufactured in Examples 1-1, 1-2, 1-3, 2-1, 3-1, 3-2, 4-1, and 4-2.

The embodiments disclosed herein are all for illustration only and should not be considered as limiting. The scope of the present invention is not limited to the above description, but is as shown in the scope of the patent application, and all modifications within the scope and meaning equivalent to the scope of the patent application are included.

For example, by adjusting the composition of the glass composition described in the specification, an optical glass of one embodiment of the present invention can be produced. Furthermore, of course, any combination of two or more items described in the specification or in the preferred range can be made.

without.

[Fig. 1] Fig. 1 is a diagram showing the glass temperature during the manufacturing step of an example of a glass material for molding according to the present embodiment; the vertical axis is the glass temperature and the horizontal axis is the time (seconds) expressed logarithmically.

Claims (6)

A glass material for molding has a _SiO2 content of 3 mass % or more, a _ZrO2 content of 0.005 mass % or more, a maximum linear expansion coefficient α _max and a total content of _SiO2 and _ZrO2 [ _SiO2 + _ZrO2 ] expressed in mass % satisfying the following formula (1): α _max × [ _SiO2 + _ZrO2 ] ≦ 27900 ... (1), and _{a Bi2O3} content of 10 mass % or less. The glass material for molding as described in claim 1, wherein a sample of 11 mm×11 mm×10.5 mm is subjected to a heat treatment at a temperature 200°C higher than the glass transition temperature Tg for 5 minutes, and the crystal number density D per 1 g of the glass is less than 10/g. The molding glass material as recited in claim 1 contains TiO ₂ and Nb ₂ O ₅ , wherein the TiO ₂ content [TiO ₂ ] and the Nb ₂ O ₅ content [Nb ₂ O ₅ ] expressed in mass % satisfy the following formula (7): {5×[TiO ₂ ]}/{3×[Nb ₂ O ₅ ]}≦3 ···(7). For the glass material for molding as described in claim 1, the wavelength λτ ₈₀ at which the internal transmittance of 10 mm thick glass is 80% within the wavelength range of 280-700 nm is below 395 nm. For the glass material for molding as described in claim 1, the Abbe number νd and the partial dispersion ratio Pg,F satisfy the following formula (8): Pg,F≦-0.00286×νd+0.68700 ···(8). An optical glass is formed from the molding glass material described in any one of claims 1 to 5.

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