WO2007116943A1 - Optical glass for mold press molding - Google Patents

Abstract

Disclosed is a lead-free optical glass for mold press molding which has characteristics required for optical glasses for mold press molding, especially a refractive index (nd) of 1.57-1.62 and an Abbe number (νd) of not less than 55, while being excellent in weather resistance. The lead-free optical glass for mold press molding is characterized by having a composition containing, in mass%, 41-56% of SiO2, 1.5-5% of Al2O3, 7-16% of B2O3, 0.1-10% of CaO, 0-10% of BaO, 0-10% of SrO, 0-5% of ZnO, 1-10% of Li2O, 0-5% of Na2O and 5-15% of La2O3. Preferably, the composition of the optical glass further satisfies the following conditions: MgO + CaO + BaO + SrO is 10-20%, Li2O + Na2O + K2O is 5-12% and 3.2 ≤ SiO2/La2O3 ≤ 15.0.

Description

 Specification

 Optical glass for mold press molding

 Technical field

 [0001] The present invention relates to an optical glass for mold press molding.

 Background art

 [0002] Refractive index (nd) for optical lenses such as optical pickup lenses for various optical disk systems such as CD, MD, DVD, and video cameras, etc. for ordinary cameras is 1.57 to L 62, Abbe An optical glass having a number (vd) of 55 or more, more specifically a refractive index (nd) of 1.5575-1.610 and an Abbe number (vd) of 58.5-62.0 is used. Conventionally, as such glass, lead-containing glass based on SiO 2 —PbO—R ′ 0 (R and O are alkali metal oxides) has been used.

2 2 2

 Widely used force In recent years, SiO—B O—RO (RO is

 2 2 3

 Potassium earth metal oxides) R'O-based non-lead glass is being switched (for example,

 2

 Patent Documents 1 and 2).

 Patent Document 1: JP-A-6-107425

 Patent Document 2: JP 2000-302479 A

 Patent Document 3: Japanese Patent Application Laid-Open No. 2004-328068

 Disclosure of the invention

 Problems to be solved by the invention

 [0003] These optical pickup lenses and photographing lenses are molded as follows. First, molten glass is dripped from the tip of the nozzle to produce a glass droplet once, then polished I ”, polished and washed to produce a preform glass. Alternatively, rapidly cool and forge molten glass and make glass blocks, and also polish and wash them to make preform glass. After that, the preform glass that has been softened again is pressed with a precision-processed mold, and the surface shape of the mold is transferred to the glass. Such a method is called a so-called mold press molding method and is widely used.

[0004] Glass that is molded by mold press molding not only satisfies the required optical constants (refractive index, Abbe number), but also has a low soft spot so as not to deteriorate the mold. ,Money It is required that fusion with the mold does not occur easily and weather resistance is high.

 [0005] In addition, the conventional lead-free preform glass as described above often does not have sufficient weather resistance. If the weather resistance of the glass is not sufficient, glass components will elute into the polishing cleaning water and various cleaning solutions during the cutting and cleaning processes, and the surface will be altered. As a result, defects are generated in the glass where devitrification is easily generated in the molding process, and mass production becomes difficult. Even in the final product, when exposed to high temperature and humidity for a long time, the surface of the glass is altered, and there is a problem that the reliability is impaired.

 [0006] An object of the present invention is to satisfy various properties required for optical glass for mold press molding, and particularly, the refractive index (nd) is 1.57 to L 62, and the Abbe number (vd) is 55 or more (preferably Is a refractive index (nd) force S1. 575 to 1.610, Abbe number (vd) force 58.5 to 62.0) It is to be.

 Means for solving the problem

[0007] As a result of various experiments conducted by the present inventors, SiO-BO-RO-R'O-LaO-based glass

 We have found that the above objective can be achieved by strictly limiting the composition of 2 2 3 2 2 3 and propose it as the present invention.

[0008] That is, a mold for press molding an optical glass of the present invention, the mass _^0/0, SiO ^41~56%

 2

 , Al O 1.5-5%, B O 7-16%, CaO 0.1-10%, BaO 0-10%, SrO

2 3 2 3

 0-10%, ZnO 0-5%, Li O 1-10%, Na O 0-5%, La O 5-15% included

 2 2 2 3

 It is characterized by having.

 The invention's effect

[0009] The optical glass of the present invention is used for optical lenses such as optical pickup lenses for CD, MD, DVD and other various optical disk systems, and photographing lenses for video cameras and general cameras. And an Abbe number (vd) of 55 or more. In addition, since the soft point is low and the glass component is difficult to volatilize, the molding accuracy is not lowered and the mold is not deteriorated or contaminated. In addition to excellent mass productivity of preform glass with a wide working temperature range and good weather resistance, it does not cause deterioration of physical properties or surface deterioration during the manufacturing process or use of products. Therefore, it is suitable as an optical glass for mold press molding. BEST MODE FOR CARRYING OUT THE INVENTION [0010] mold for press molding an optical glass of the present invention, the mass _^0/0, SiO 41

 2 to 56%, Al O

 2

1. 5-5%, B O 7-16%, CaO 0.1-10%, BaO 0-10%, SrO 0-1

3 2 3

 0%, ZnO 0-5%, Li O 1

 2-10%, Na O 0

 2-5%, La O 5

 This glass has a basic composition of 2 3 to 15%. In general, lead-free glass contains a large amount of alkaline earth metal oxide RO in order to obtain a high refractive index, which is a cause of lowering the weather resistance of this glass. Yes. Therefore, the glass of the present invention contains La O, which is a component that increases the refractive index, and Al O, which is a component that improves weather resistance, and contains RO.

 2 3 2 3

 By reducing the amount and containing CaO as an essential component as RO, the weather resistance of the glass is improved while maintaining the refractive index. In addition, when La O is contained, the Abbe number is low.

 twenty three

 By including the force B O that tends to decrease, the Abbe number is prevented from decreasing. This

 twenty three

 With excellent weather resistance, 1. 57 ~: Refractive index (nd) of L62, Abbé number (vd) greater than 55, especially 1.575 ~ 1.610 refractive index ( nd), 58.5 to 62.0 Abbe number (vd) of mold press molding optical glass can be obtained and used as an optical lens for high-performance and small-sized optical elements with little chromatic dispersion be able to. Further, in the optical glass for mold press molding of the present invention, the softening point of the glass is preferably 650 ° C. or lower (preferably 640 ° C. or lower, more preferably 630 ° C. or lower). When the soft spot of the glass is lowered, press molding can be performed at a low temperature, and fusing between the glass and the mold can be suppressed if the mold is contaminated due to oxidation of the mold and volatilization of the glass component.

[0011] The reason for limiting the range of each component as described above will be described.

 [0012] SiO is a component constituting the skeleton of glass, and has an effect of improving weather resistance. That

 2

 The content is 41 to 56%, preferably 42 to 53%, more preferably 43 to 50.5%. If the amount of SiO increases, the refractive index tends to decrease and the soft spot tends to increase. Devitrification

 2

 The tendency becomes stronger. On the other hand, when the amount of SiO decreases, the weather resistance such as acid resistance and water resistance deteriorates.

 2

[0013] B 2 O is a skeletal component of glass and is effective in improving devitrification resistance. Also increase the Abbe number

 twenty three

Therefore, it is a component that lowers the soft saddle point. It also has the effect of reducing the basicity of the glass, and is effective in preventing fusion between the glass and the mold in mold press molding. Its content is 7-16%, preferably 9-16%, particularly preferably 10-15. 5%, more preferably 12-15. %. When BO increases, the volatiles formed by BOR 'O when the glass melts

 2 3 2 3 2

 Increases and encourages the generation of striae. Furthermore, the weather resistance is poor. On the other hand, if B O is low

 twenty three

There is a possibility that the devitrification resistance is lowered and a sufficient working temperature range cannot be secured. Also, it becomes easy to fuse with the mold. Furthermore, in a composition range with a small amount of SiO, a small amount of B 2 O increases the Abbe number

 2 2 3

 It becomes difficult to maintain above 55.

[0014] Al 2 O is a component that constitutes the glass skeleton together with SiO, and has the effect of improving weather resistance

 2 3 2

 There is. Especially for SiO -B O -RO-R and O La O glass,

 2 2 3 2 2 3

 It has a remarkable effect of suppressing selective elution into water, and its content is 1.5 to 5%, preferably 2 to 4.5%, more preferably 2.7 to 4.5%. . If there is too much Al O, devitrification

 twenty three

 It becomes easy. In addition, if the meltability is poor, bubbles remain in the glass and may not satisfy the required quality of glass for lenses. On the other hand, when AlO is low, water resistance and acid resistance

 twenty three

 Is reduced to obtain a glass having very high weather resistance.

 [0015] Alkaline earth metal oxides (RO) such as CaO, BaO, and SrO act as fluxes, and do not reduce the Abbe number in SiO-BO-RO R'OLaO-based glasses.

 2 2 3 2 2 3

 There is an effect of increasing the refractive index. The total amount of CaO, BaO, and SrO is preferably 10 to 30%, particularly 10 to 20%, and more preferably 12 to 18%. In addition, when RO increases, devitrification black tends to precipitate during the melting and forming process of the preform glass, and the liquidus temperature rises, so that the working range becomes narrow and mass production tends to be difficult. Furthermore, elution from the glass into polishing cleaning water and various cleaning solutions increases, and the surface of the glass changes significantly in a hot and humid state. On the other hand, when RO decreases, inconveniences such as a decrease in refractive index and an increase in softening point are likely to occur.

[0016] CaO is a component that increases the refractive index without decreasing the Abbe number. In addition, it is an essential component for improving the weather resistance because the effect of preventing precipitation of alkali or alkaline earth on the surface in a high temperature and high humidity state is enhanced. The CaO content is preferably 0.1 to 10%, particularly 0.5 to 5%, and more preferably 1 to 4%. When CaO is increased, the liquidus temperature rises and devitrification easily occurs.

[0017] BaO is a component that increases the refractive index, and this glass system also has the effect of lowering the liquidus temperature and improving workability. However, the amount of precipitation from the glass surface in a hot and humid state Is significantly higher than other RO components, so adding a large amount may impair the weather resistance of the final product. The BaO content is preferably 0 to 10%, more preferably 0.5 to 9.5%, and even more preferably 4 to 9%.

 [0018] SrO is a component that increases the refractive index. Compared with BaO, the amount of precipitation from the glass surface in a high temperature and high humidity state is small. Therefore, by using SrO actively, a product with excellent weather resistance can be obtained. Its content is 0 to 10%, preferably 0.5 to 9%, more preferably 3 to 8%. As SrO increases, the liquidus temperature rises and the working range tends to narrow.

 In addition to CaO, BaO, or SrO, MgO may be added to increase the refractive index. When MgO is added, its content is preferably 0 to 5%, particularly preferably 0 to 3%. It becomes easy to devitrify when the amount of MgO increases.

 [0020] ZnO has the effect of increasing the refractive index and improving the weather resistance. Further, since the tendency to devitrification is not strong, a homogeneous glass can be obtained even if it is contained in a large amount. Its content is 0 to 5%, preferably 0.5 to 4%, more preferably 1 to 3%. As the amount of ZnO increases, the number of hot stones tends to decrease.

 [0021] Alkali metal oxides (R, O) such as Li 2 O and Na 2 O are components for lowering the softening point.

 2 2 2

 Minutes. Li 2 O and Na 2 O are combined in 5 to 12%, especially 6 to: L l%, further 7 to 10%

 twenty two

 It is desirable. As R'O increases, the liquidus temperature rises and the working temperature range becomes narrower.

 2

 easy. In this case, the mass productivity may be adversely affected. In addition, the weather resistance tends to be poor. Conversely, the soft spot increases as R'O decreases.

 2

 [0022] Among R'Os, LiO has the greatest effect of lowering the soft saddle point. Its content is 1 ~

 twenty two

 10%, preferably 3 to 9%, more preferably 5 to 8.5%. However, Li O is phase separation

 2

 Therefore, if added in a large amount, the liquidus temperature tends to be high and workability tends to deteriorate. In addition, it has a low field strength (hereinafter referred to as F. S.) and increases the basicity of the glass, which will be described later. On the other hand, the soft saddle point increases as Li O decreases.

 2

 [0023] Na O has the effect of lowering the soft saddle point.

 2 2 3

'More volatiles are formed in o, which promotes the formation of striae. Also molding Sometimes volatilization occurs and contaminates the mold, greatly reducing the life of the mold. Na O

 The content of 2 is preferably 0 to 5%, particularly preferably 0.5 to 3%.

In addition to Li 2 O and Na 2 O, K 2 O may be added to lower the softening point. K O

 When 2 2 2 2 is added, its content is preferably 0 to 7%, particularly preferably 0 to 5%. K O

 2 Weather resistance deteriorates when the amount increases.

 [0025] Since La O has the effect of increasing the refractive index without decreasing the Abbe number, a large amount of R

 twenty three

 There is no need to contain o, which is effective in improving weather resistance. In addition, it has the effect of improving devitrification resistance and can expand the working temperature range, but if it is contained in a large amount, the phase separation tendency of the glass becomes strong and a homogeneous glass can be obtained. . La O content is 5-1

 twenty three

 5%, preferably 6 to 12%, more preferably 7 to 10%.

[0026] Further, the content of SiO and La 2 O is such that the value of SiO 2 / La 2 O is 3.2 to 15.0 on a mass% basis.

 2 2 3 2 2 3

 In particular, it is preferable to adjust so as to be within the range of 3.2-10. By setting this ratio to 3.2-15.0, it is possible to maintain high devitrification resistance without lowering the refractive index. When this ratio decreases, the devitrification resistance decreases, and when it increases, the refractive index tends to decrease.

[0027] Sb 2 O can be added as a fining agent. However, excessive coloration on the glass

 twenty three

 To avoid this, the Sb 2 O content should be 1% or less.

 twenty three

 [0028] It should be noted that TiO and NbO reduced the force Abbe number, which is a component that increases the refractive index of glass.

 2 2 5

 As a result, the absorption in the ultraviolet region is large, the transmittance at 390 to 440 nm is reduced, and the use as a short wavelength lens may be hindered.

 [0029] In addition, PbO, Bi 2 O and As 2 O are light for Ag and halogens for environmental reasons.

 2 3 2 3

 Substantial introduction into glass should be avoided as it is a reverse color carrier.

 In the present invention, “substantially avoid introduction into glass” means that the content is 0.1% or less.

[0031] In addition to the above features, the basicity of the glass can be used to prevent the glass and mold from being fused at the time of mold press molding in the optical glass for mold press molding of the present invention. Is 11 or less (preferably 9.5 or less).

[0032] In the present invention, the basicity means (total number of moles of oxygen atoms Z d Sum of Strength) Defined as X 100, and Field Strength (hereinafter referred to as FS) is calculated by Equation 1 below.

[0033] Equation 1 FS = Z / r ²

 Z is the ion valence, and r is the ion radius. In the present invention, the values of Z and r used the values in Table 1 (values described in “Science Manual Basic Bias Revised 2nd Edition (issued by Maruzen Co., Ltd., 1975)”) According to the knowledge of the present inventor, the lower the basicity, the harder it is to fuse with the mold. The mechanism by which the basicity of the glass controls the fusion will be described below.

[0034] [Table 1]

z r

S i ^{4 +} 4 0. 4 0

A 1 ^{3 +} 3 0. 5 3

B ³ + 3 0. 3 2

M g ^{2 +} 2 0 .8 6

C a ^{2 +} 2 1. 1 4

B a ^{2 +} 2 1 .5 0

S r ^{2 +} 2 1. 3 9

Z n ^{2 +} 2 0. 8 9 and i ¹ + 1 0. 8 8

N a ^{1 +} 1 1. 1 6

K ¹ + 1 1 .5 2 τ i ⁴ + 4 0 .7 5

Z r ^{4 +} 4 0. 8 6

N b ^{5 +} 5 0. 7 8 and a ^{3 +} 3 1. 3 2

 G d 3 + 3 1. 0 8

T a ^{5 +} 5 0. 8 3

W ^{6 +} 6 0. 7 2

B i ^{3 +} 3 0. 8 6

S b ^{3 +} 3 0. 7 5 p 5 + 5 0. 3 2

[0035] Here, taking SiO as an example, how to determine the basicity of glass will be described.

 2

 [0036] First, the number of moles of oxygen atoms is determined. lmol of SiO contains 2 mol of oxygen atoms

 2

 It is. Therefore, multiply this 2 mol of oxygen by the mol% of SiO in the glass composition.

 2

 Thus, the number of moles of oxygen atoms possessed by SiO in the glass is obtained. Similarly oxygen of each component

 2

 The number of moles of atoms is obtained, and the total is defined as “sum of moles of oxygen atoms”.

[0037] Next, FS is obtained. The cation Si ⁴⁺ has Z = 4 and r = 0.4, so FS = 25 . Since Si ⁴⁺ is contained in lmol in SiO, FS in the glass is 25 X l (mol) X (composition

2

It is obtained as a mole _^0/0) of SiO in.

 2

 [0038] This is obtained for each component, and the sum is taken as the "total cation FS". The value obtained by multiplying the “sum of the number of moles of oxygen atoms” by the “sum of positive F.S.” and multiplying by 100 is the “basicity of the glass”.

 [0039] Next, a mechanism in which the basicity of the glass controls the fusion will be described.

 [0040] The basicity of glass is an index indicating how much oxygen electrons in glass are attracted to cations in glass. High basicity! In glass, oxygen is not attracted by cations in glass. Therefore, when a glass having a high basicity is in contact with a cation (mold component) that has a strong tendency to demand electrons, a cation from the mold enters into the glass compared to a glass having a low basicity. Easy! When the cation, which is a mold component, penetrates (diffuses) into the glass, the concentration of the mold component in the glass phase near the interface increases. This reduces the compositional difference between the glass phase and the mold phase, increasing the affinity between the two and making it easier for the glass to wet the mold. It is considered that the glass and the mold are fused by such a mechanism. Therefore, as the basicity decreases, the mold components enter the glass and the glass and the mold are not fused.

 [0041] Specifically, if the basicity of the glass is 11 or less, preferably 9.5 or less, it is considered that fusion does not occur. If the basicity of the glass exceeds 9.5, there is a tendency to fuse with the mold, and if it exceeds 11, the surface accuracy of the product is impaired due to fusion between the glass and the mold, and the mass productivity is markedly deteriorated. There is a tendency to.

 [0042] Next, a method for producing an optical pickup lens, a photographing lens or the like using the glass of the present invention will be described.

 [0043] First, a glass raw material is prepared so as to have a desired composition, and then melted in a glass melting furnace.

 [0044] Next, molten glass is dripped from the tip of the nozzle to temporarily produce glass droplets to obtain preform glass. Alternatively, the molten glass is rapidly cooled and fabricated to once produce a glass block, which is then ground, polished and washed to obtain a preform glass.

[0045] Subsequently, it is placed in a preform glass in a precision-processed mold until it is in a soft wrinkle state. The mold is pressure-formed while being heated to transfer the surface shape of the mold to glass. This molding method is called a mold press molding method and is widely used. In this way, an optical pickup lens can obtain a photographing lens.

 Example

 Hereinafter, the present invention will be described based on examples.

[0047] [Table 2]

1 2 3 4 Composition (mass%)

S i O ₂ 4 8. 0 5 0. 2 4 8. 0 4 8. 1

A 1 ₂ O 2. 7 2. 7 3. 7 3. 7

B ₂ 0 ₃ 1 3. 0 1 3. 0 1 5. 0 1 4.0

C a O 5. 0 9. 0 2. 0 2. 0

B a O 5. 0 0. 5 6. 5 8. 0

S r O 8-0 7. 0 5. 0 5. 0

Z n O 1-2. 0

L i ₂ O 7. 4 7-9 7. 9 7. 9

N a O 2. 7 1-7 1. 2 1. 2

L a ₂ O 8. 0 8. 0 1 0. 5 8. 0

S b ₂ O 0. 2 One 0. 2 0. 1

 O 1 8. 0 1 5. 0 1 3. 5 1 5. 0

R ' ₂ O 1 0. 1 9. 1 9. 1 9. 1

S i O ₂ / LaO 6.0 0 6. 3 4. 6 6. 0 Refractive index nd 1. 5 3 8 7 1. 5 8 8 9 1. 5 8 5 1 1. 5 3 5 5 Abbe number vd 5 9. 6 5 9. 6 6 0. 5 6 0. 1 Softening point (° C) 5 9 9 6 0 1 6 0 2 6 0 5 Liquidus temperature (° C) 8 4 5 8 5 5 8 6 5 8 4 4 Weather resistance

 1. 5 1. 4 1. 3 1.1 (Transmittance difference Δ T%)

 Basicity 8.5 3 8. 5 8 8. 2 4 8. 3 4

[0048] [Table 3] 5 6 Composition (mass%)

S i O ₂ 5 1. 0 4 9. 0

A i ₂ O 3 0. 7 2. 5

B ₂ O 3 1 3. 0 1 3. 0

C a O 5.0

B a O 5. 0 8. 0

S r O 9. 0 9. 0

Z n O —— 2. 7

L i ₂ O 6. 4 7. 5

N a ₂ O 2 .7 0 .9

L a 2 O 3 7. 0 7. 4

S b ₂ O 3 0 .2 ―

R O 1 9. 0 1 7. 0

R ' ₂ 9. 1 8. 4

S i O 2 / Laa O 3 7. 3 6. 6 Refractive index nd 1.5 Β 3 7 1. 5 8 5 1 Abbe number vd 6 0. 5 6 0. 4 Softening point (° C) 6 1 7 6 0 6 Liquidus temperature (.C) 8 6 6 8 4 0 Weather resistance

 4Q

 Ο. 丄

(Transmittance difference Δ Τ%)

Basicity 8. 3 6 8. 3 6

7 8 9 1 0 Composition (mass%)

S i 0 ₂ 4 3. 1 5 0. 0 4 8. 6 4 2. 0

A 1 ₂ 0 ₃ 4. 5 3. 0 3. 5 4. 8

B ₂ O ₃ 1 5. 0 1 5. 0 1 3. 5 1 6. 0

C a O 4.0 0 2. 0 1. 3 0. 6

B a O 9. 0 6. 0 9. 0 9. 0

S r O 4. 8 4. 0 4. 0 8. 0

Z n O 3. 0 1. 0 3. 0 3. 0 and i ₂ O 7.5 5. 9. 0 8. 0 8. 0

N a O 1. 0 0. 5 1. 0

 L a O 8. 0 9. 3 8. 0 8. 4

S b ₂ O 0. 1 0. 2 0. 1 0. 2

R O 1 7. 8 1 2. 0 1 4. 3 1 7. 6

R 'O 8. 5 9. 5 9. 0 8. 0

S i O ₂ / L a O ₃ 5. 4 5. 4 6. 1 5. 0 Refractive index nd 1. 5 9 5 9 1. 5 8 3 0 1. 5 8 5 9 1. 5 9 6 2 Number of Abbe d 5 9. 3 6 0. 7 5 9. 9 5 9. 6 Softening point (V) 6 0 1 6 0 0 6 0 4 5 9 8 Liquidus temperature (° C) 8 6 8 8 5 8 8 4 5 8 5 2 Weather resistance

 1.5 1.5 3 1.1 1.2 (Transmittance difference Δ T%)

Basicity 8. 4 0 8. 2 3 8. 3 6 8. 2 6

Five]

Composition (mass%)

S i O ₂ 5 5. 3 4 6. 8 4 1. 0

A 1 ₂ O a 1.7 1 .6 4 .0

B ₂ O ₃ 7. 2 7. 4 1 5. 0

C a O 4. 2 9. 7 5. 0

B a O 9. 6 1 0. 0

S r O 5. 0 5. 0

Z n O 5. 0 3. 0 5. 0

L i ₂ O 9 .8 7 .0 ₂ .5

N a ₂ O 2. 0 4. 9 4. 9

L a 2 O a 5. 2 1 4. 6 7. 6

S b ₂ O 3

R O 1 3. 8 1 4. 7 2 0. 0

R '2 O 1 1. 8 1 1. 9 7. 4

S i O ₂ / L 2 O 3 1 0 .6 3 .2 5 .4 Refractive index nd 1.5 8 2 1 1 .6 0 6 1 1.5 5 9 4 8 Abbe number vd 5 8. 7 5 6. 6 5 8. 6 Softening point (.c) 5 7 6 5 9 9 6 4 8 Liquidus temperature (° C) 8 7 5 8 Β 7 8 3 8 Weather resistance

 1. 6 1. 5 1. 1

(Transmittance difference Δ T%)

 Basicity 9 .0 9 9 .5 5 8 .2 7

[0051] Tables 2, 4 and 5 show examples of the present invention (sample Nos. 1 to 4 and 7 to 13), and Table 3 shows comparative examples (samples No. 5 to 6).

[0052] Each sample was prepared as follows. First, glass raw materials were adjusted so as to have the composition shown in the table, and were melted at 1400 ° C for 3 hours using a platinum crucible. After melting, the melt was poured onto a carbon plate, and after annealing, samples suitable for each measurement were prepared.

[0053] The obtained sample was measured for refractive index (nd), Abbe number d), softening point (Ts), and weather resistance. The basicity was calculated. The results are shown in each table.

As is apparent from the table, the samples No. 1 to 4 and 7 to 13 which are examples of the present invention have a refractive index of 1.5821-1.6061 and an Abbe number force of 6.6 or more. , Softening point below 648 ° C, liquidus temperature The degree was 887 ° C or less. In addition, the change in transmittance before and after the exposure test in a hot and humid state was 1.6% or less, and the weather resistance was small. It contains a lot of BO and has a basicity of 9.5.

 twenty three

 It is thought that fusion with the mold is difficult to occur!

[0055] On the other hand, each of the samples No. 5 and No. 6 which are comparative examples had a low weather resistance with a large change in transmittance of 3.1% or more before and after the exposure test.

Note that the refractive index (nd) is a measured value with respect to d-line (587.6 nm) of a helium lamp.

[0057] The Abbe number (Vd) is obtained by using the refractive index values of the d-line and the F-line (486. lnm) of the hydrogen lamp and the C-line (656.3nm) of the hydrogen lamp. Number (vd) = {(nd— 1) / (n

F—nC)} formula force was also calculated.

 [0058] The softening point T is determined by the fiber elongation method based on Japanese Industrial Standard R-3104.

 Therefore, it measured.

 The liquid phase temperature T is 297 to 500 / ζ πι, and the sample is pulverized and classified before platinum.

 Shi

 Put it in a boat made of steel, hold it in an electric furnace with a temperature gradient for 24 hours, and let it cool in the air

The measurement was performed by determining the deposition position of devitrification with an optical microscope.

[0059] The weather resistance was evaluated by measuring the transmittance of the glass before and after the exposure test in a hot and humid state with a spectrophotometer, and evaluating the difference in the transmittance of the glass at a wavelength of 590 nm in the visible region. The exposure test was conducted under the conditions of temperature 60 ° C, humidity 90%, and 300 hours.

X 25mm optically polished on both sides and 10mm thick was used.

[0060] Basicity is (total number of moles of oxygen atoms Z total field strength of cations) X

It is calculated based on 100 formulas. The field strength (hereinafter referred to as F. S.) in the formula is obtained by the following formula.

[0061] FS = Z / r ²

 Z is the ion valence, and r is the ion radius.

[0062] Although the invention has been described in detail and with reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention. is there.

This application is based on a Japanese patent application filed on April 5, 2006 (Japanese Patent Application 2006-103806) and a Japanese patent application filed on March 29, 2007 (Japanese Patent Application 2007-86412). The contents are incorporated herein by reference.

Claims

The scope of the claims [1] in a weight _{^{0/0, SiO 41~56%,}} A1 0 1. 5~5%, BO 7~16%, CaO 0. 1~  2 2 3 2 3  10%, BaO 0-10%, SrO 0-10%, ZnO 0-5%, Li O 1-10%, Na O  twenty two Optical glass for mold press molding characterized by containing 0 to 5% and La O 5 to 15%  twenty three  Su.  [2] In the optical glass for mold press molding according to claim 1, the total amount of Li 2 O and Na 2 O  Optical glass for mold press molding characterized by 2 2 power ~ 12%. [3] The optical glass for mold press molding according to claim 1 or 2, wherein the total amount of CaO, BaO and SrO is 10 to 20%. [4] The optical glass for mold press molding according to any one of claims 1 to 3, which further contains substantially no TiO and NbO.  2 2 5  Academic glass.  [5] In the optical glass for mold press molding according to any one of claims 1 to 4, the content of SiO 2 and La 2 O is 3.2 ≦ SiO 2 / La 2 O ≦ 15.0 on a mass% basis. There is 2 2 3 2 2 3  Optical glass for mold press molding characterized by these.