JP2011219278A - Optical glass - Google Patents

Abstract

Provided is a phosphate-based optical glass having an optical constant having a refractive index of 1.9 or more, an Abbe number of 19 to 22, and excellent light transmission characteristics.
A in mol% on an oxide basis, in mol% based on _{oxides, P 2 O 5 20.0-30.0B 2 O} 3 3.5-10.0SiO 2 0-5.0BaO 0-5 0.0Na ₂ O 16.2-25.0 K ₂ O 0-8.0 Bi ₂ O ₃ 10.0-20.0 TiO ₂ 3.0-15.0 Nb ₂ O ₅ 10.0-20.0 WO ₃ 0-15.0ZnO 0-5.0, substantially free of Li ₂ O, liquid phase viscosity (η _TL ) of 7 dPa · s or more, refractive index n _d : 1.90 or more, Optical glass that is.
[Selection figure] None

Description

  The present invention relates to a phosphate optical glass having a high refractive index, capable of precision press molding, and excellent in gob moldability for preforms.

High refractive index, an optical glass of high dispersion region, those lead-free, Patent Document 1, although the system in which the phosphate-based in Patent Document 2 has been proposed a refractive index (n _d) No specific composition has been proposed that exceeds 1.90.

As a high refractive index optical glass having a refractive index (n _d ) exceeding 1.90, a system based on phosphate is proposed in Patent Document 3. Patent Document 3 proposes a phosphate-based optical glass that has a high refractive index, a low-temperature softening property, and a lead-free material, but is sufficiently satisfactory in terms of preform gob moldability. It is not a thing.

  Preform gob molding is a method for manufacturing precision press-molding preforms. The molten glass flows out from the tip of the nozzle, separates the molten glass lump of the desired mass, and floats on the mold with nitrogen gas. It is a process to produce a glass lump with a full fire making surface. In the gob molding for preforms, if the viscosity of the glass is lower than 7 dPa · s, the glass lump that flows out and separates from the nozzle becomes small, and the size required for a product such as a lens cannot be satisfied.

  Moreover, when the viscosity of the glass is lower than 7 dPa · s, the yield is such that when the glass is floated with nitrogen gas, the nitrogen gas is taken into the glass lump or the surface shape is distorted and the desired shape cannot be obtained. Will fall. Although it is possible to compensate for these defects to some extent by devising the size and shape of the nozzle and devising the mold, essentially lower the liquidus temperature of the glass and increase the viscosity. Therefore, it is most important to increase the liquid phase viscosity. By the way, even if the liquid phase viscosity is too high, there is a problem that the outflow amount from the nozzle is reduced and the productivity is lowered, but in general, there is little possibility that the liquid phase viscosity is too high in this region of phosphate glass. .

Therefore, a high refractive index (n _d ) of 1.90 or higher, precision press molding, and excellent preform gob moldability have not been proposed yet.

JP 2003-321245 A JP 2005-8518 A JP 2006-111499 A

The present invention has an optical constant having a refractive index (n _d ) of 1.9 or more, an Abbe number (ν _d ) of 19 to 22, and a low glass transition point. An object of the present invention is to provide an optical glass having a liquid phase viscosity suitable for gob moldability.

In mol% of oxide basis,
P ₂ O ₅ 20.0-30.0
B ₂ O ₃ 3.5-10.0
SiO ₂ 0-5.0
BaO 0-5.0
Na ₂ O 16.2-25.0
K ₂ O 0-8.0
Bi ₂ O ₃ 10.0-20.0
TiO ₂ 3.0-15.0
Nb ₂ O ₅ 10.0-20.0
WO ₃ 5.0-15.0
ZnO 0-5.0
And substantially free of Li ₂ O, the liquid phase viscosity (η _TL ) is 7 dPa · s or more,
An optical glass having a refractive index n _{d of} 1.90 or more is provided.

The phosphate-based optical glass of the present invention (hereinafter referred to as the present glass) requires P ₂ O ₅ , B ₂ O ₃ , Na ₂ O, Bi ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and WO ₃ as essential. Since it is a component, the refractive index n _{d is} 1.9 or more, and an optical characteristic with an Abbe number ν _{d of} 19 to 22 is preferably obtained.

According to the present glass, Li ₂ O is not substantially contained, and since an appropriate amount of Na ₂ O is contained instead of Li ₂ O, the liquid phase viscosity is 7 dPa · s or more, and the gob moldability for preforms is excellent. Therefore, the precision press preform has a high degree of freedom in shape and can be produced efficiently, so that the productivity of optical elements such as lenses can be increased.

According to the present glass, since the glass transition temperature (T _g ) can be 500 ° C. or less, the degree of deterioration of the protective film and the release film normally formed on the mold surface is reduced, and as a result, the durability of the mold. As a result, productivity is greatly improved.

  The present invention provides a liquid phase of phosphate optical glass for the purpose of providing a phosphate optical glass having a refractive index of 1.9 or more, excellent gob moldability for preforms, and easy to precision press molding. This is based on the results of various studies to increase the viscosity.

As a result of the examination, P ₂ O ₅ , B ₂ O ₃ , Na ₂ O, Bi ₂ O ₃ , TiO ₂ , Nb ₂ O _5, WO _3, etc. should be contained in a balanced manner, and Li ₂ O should not be substantially contained. Thus, it has been found that this purpose can be achieved.

The present glass is characterized by containing P ₂ O ₅ , B ₂ O ₃ , Na ₂ O, Bi ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ and WO ₃ . The reason why each component range of the glass is set is as follows. In the present specification, “%” means “mol%” unless otherwise specified. The chemical composition is based on oxide.

In the present glass, P ₂ O ₅ is an essential component, and is a main component (glass-forming oxide) that forms glass and a component that increases the viscosity of the glass. In the present glass, if the P ₂ O ₅ content is too small, the glass becomes unstable and the viscosity at the time of preform gob molding may be lowered. Therefore, in the present glass, the P ₂ O ₅ content is 20. 0% or more. The P ₂ O ₅ content is preferably 24.0% or more, and the P ₂ O ₅ content is more preferably 25.0% or more. On the other hand, when the P ₂ O ₅ content is increased, the refractive index is lowered. Therefore, in the present glass, the P ₂ O ₅ content is 30.0% or less. The P ₂ O ₅ content is preferably 28.0% or less, and the P ₂ O ₅ content is more preferably 27.0% or less.

In the present glass, B ₂ O ₃ is an essential component and a component that forms glass. If the content is too small, the glass becomes unstable and the viscosity at the time of preform gob molding may be lowered. Therefore, the B ₂ O ₃ content of the present glass is 3.5% or more. The B ₂ O ₃ content is preferably 4.0% or more, and the B ₂ O ₃ content is more preferably 4.5% or more. On the other _hand, since the content of B 2 _{O 3} is too large, the refractive index is lowered, in the present _glass, the content of B 2 _{O 3} is 10.0%. The B ₂ O ₃ content is preferably 7.0% or less, and the B ₂ O ₃ content is more preferably 6.0% or less.

In the present glass, SiO ₂ is not an essential component, but is a component that forms glass. If added from the viewpoint of the glass transition point and refractive index, preferably a SiO ₂ content of 5.0% or less. More preferably, the SiO ₂ content is 4.0% or less. It is particularly preferable that the SiO ₂ content is 3.0% or less.

  In the present glass, BaO is not an essential component but is a component that softens the glass. When added, the BaO content is preferably 5.0% or less from the viewpoint of viscosity and refractive index. More preferably, the BaO content is 4.0% or less. The BaO content is particularly preferably 3.0% or less.

In the present glass, Na ₂ O is an essential component, a component that softens the glass, and at the same time, one of components that stabilize the glass. In the glass, when the content of Na 2 _O is too small, there is a risk that the glass becomes unstable, the present glass content of Na 2 _O is 16.2% or more. The Na ₂ O content is preferably 17.0% or more, and the Na ₂ O content is more preferably 17.5% or more. The Na ₂ O content is particularly preferably 18.0% or more. On the other hand, when the Na ₂ O content is increased, the refractive index is lowered. Therefore, in the present glass, the Na ₂ O content is 25.0% or less. The Na ₂ O content is preferably 23.0% or less, and the Na ₂ O content is more preferably 20.0% or less.

In the present glass, Li ₂ O is not substantially contained. “Substantially not contained” means that it is contained as an unavoidable impurity but is not actively added. In this specification, the content is 0.1% or less. In the present glass, since an appropriate amount of Na ₂ O is contained instead of substantially containing Li ₂ O, the liquid phase viscosity is 7 dPa · s or more, and the optical glass is optimum for preform gob molding.

In the present glass, K ₂ O is not an essential component but is a component that softens the glass. In the present glass, when K ₂ O is contained, if the content is too small, the glass transition point may be increased. Therefore, the K ₂ O content is preferably 2.5% or more. More preferably, the K ₂ O content is 3.0% or more. The K ₂ O content is particularly preferably 3.5% or more.

On the other hand, when the K ₂ O content increases, the refractive index decreases and the glass becomes unstable. Therefore, in the present glass, the K ₂ O content is preferably 8.0% or less. The K ₂ O content is more preferably 5.0% or less, and the K ₂ O content is more preferably 4.0% or less.

In the present glass, Bi ₂ O ₃ is an essential component and has an effect of increasing the refractive index of the glass and softening the glass. Since there is a possibility that the effect as the content is too small may be insufficient, Bi ₂ O ₃ content of the glass is 10.0% or more. The Bi ₂ O ₃ content is preferably 14.0% or more, and the Bi ₂ O ₃ content is more preferably 15.0% or more. On the other hand, if the Bi ₂ O ₃ content is increased, the light transmission characteristics in the visible range are lowered and the viscosity is lowered. Therefore, the Bi ₂ O ₃ content of the present glass is 20.0% or less. The Bi ₂ O ₃ content is preferably 18.0% or less, and the Bi ₂ O ₃ content is more preferably 17.0% or less.

In the present glass, TiO ₂ is an essential component and has an effect of increasing the refractive index of the glass. If the content is too small, the above effect may be insufficient, so the TiO ₂ content of the present glass is 3.0% or more. The TiO ₂ content is preferably 4.0% or more, and the TiO ₂ content is more preferably 5.0% or more. On the other hand, when the TiO ₂ content is increased, the light transmission characteristics in the visible region are lowered and the glass transition point is increased, so that the TiO ₂ content of the present glass is 15.0% or less. The TiO ₂ content is preferably 12.0% or less, and the TiO ₂ content is more preferably 10.0% or less. The TiO ₂ content is particularly preferably 8.0% or less.

In the present glass, Nb ₂ O ₅ is an essential component and has an effect of increasing the refractive index of the glass. Since there is a possibility that the effect as the content is too small may be insufficient, Nb ₂ O ₅ content of the glass is 10.0% or more. The Nb ₂ O ₅ content is preferably 13.0% or more, and the Nb ₂ O ₅ content is more preferably 14.0% or more. On the other hand, if the Nb ₂ O ₅ content is increased, the light transmission characteristics in the visible region are lowered and the glass becomes unstable. Therefore, the Nb ₂ O ₅ content of the present glass is 20.0% or less. The Nb ₂ O ₅ content is preferably 17.0% or less, and the Nb ₂ O ₅ content is more preferably 16.0% or less.

In the present glass, WO ₃ is an essential component and has an effect of increasing the refractive index of the glass. Since there is a possibility that the effect as the content is too small may be insufficient, WO ₃ content of the glass is 5.0% or more. The WO ₃ content is preferably 8.0% or more, and the WO ₃ content is more preferably 9.0% or more. On the other hand, if the WO ₃ content is increased, the light transmission characteristics in the visible range are deteriorated and the glass becomes unstable, so the WO ₃ content of the present glass is 15.0% or less. The WO ₃ content is preferably 12.0% or less, and the WO ₃ content is more preferably 11.0% or less.

  In the present glass, ZnO is not an essential component but is a component that softens the glass. When added, the ZnO content is preferably 5% or less from the viewpoint of viscosity and refractive index. More preferably, the ZnO content is 3% or less.

  In the present glass, the total of the above components is preferably 95% or more because various properties can be balanced. The total of the above components is more preferably 98% or more, and the present glass is particularly preferably composed of the above components.

In this glass, in order to adjust optical characteristics, Al ₂ O ₃ , GeO ₂ , Ga ₂ O ₃ , ZrO ₂ , Gd ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , Ta ₂ O ₅ , TeO _{2 are used.} Any one or more of MgO, CaO, and SrO can be added as an optional component. Since the effect of adjusting optical properties is hardly obtained when the content is small, each content is preferably 0.1% or more each independently, and the content is 1.0% or more. More preferably, the content is particularly preferably 2% or more. On the other hand, since the glass becomes unstable or the raw materials are relatively expensive when the content of each component increases, it is preferable to suppress the content of these elements as much as possible in the industry. Accordingly, it is preferably 5.0% or less each independently, more preferably 4.0% or less, and particularly preferably 3.0% or less.

Further, in the present glass, PbO, F, As ₂ O ₃ is not substantially contained, that is, the content of PbO, F, As ₂ O ₃ is less than 0.05%, in view of molding temperature. It is preferable from the viewpoint of environmental impact.

In the present glass, Sb ₂ O ₃ is not an essential component, but can be added as a clarifier during glass melting. The content is preferably 1% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less. In the present glass, the lower limit when adding is preferably 0.01% or more, more preferably 0.05% or more, and further preferably 0.1% or more.

As an optical characteristic of the present glass, the refractive index (n _d ) is 1.90 or more. The refractive index (n _d ) of the present glass is preferably 1.91 or more, and the refractive index (n _d ) of the present glass is more preferably 1.92 or more. On the other hand, in order to balance various properties, the refractive index (n _d ) of the present glass is preferably 2.00 or less, and for the same reason, the refractive index (n _d ) is 1.98 or less. Is more preferable, and the refractive index (n _d ) is more preferably 1.96 or less.

In addition, the Abbe number (ν _d ) of the present glass is preferably 22 or less, and the Abbe number (ν _d ) of the present glass is more preferably 21 or less. On the other hand, since it is difficult to make the Abbe number (ν _d ) of the present glass less than 19, it is preferably 19 or more.

The glass transition point (T _g ) of the present glass is preferably 500 ° C. or lower because the molding temperature can be lowered and the durability of the protective film formed on the mold surface is improved. The glass transition point of the present glass is more preferably 495 ° C. or less, and the glass transition point is more preferably 490 ° C. or less.

  The yield point (At) of the present glass is preferably 550 ° C. or lower because the molding temperature can be lowered and the durability of the protective film formed on the mold surface is improved. More preferably, the yield point is 540 ° C. or lower. The yield point of the present glass is particularly preferably 530 ° C. or lower.

Further, the liquid phase temperature (T _L ) of the present glass is preferably 900 ° C. or lower because the liquid phase viscosity becomes high and the gob moldability for preforms is excellent. The liquidus temperature is more preferably 890 ° C. or lower, and the liquidus temperature of the present glass is further preferably 885 ° C. or lower. On the other hand, if the liquidus temperature (T _L ) is less than 700 ° C., glass may not be obtained, and therefore the liquidus temperature (T _L ) is preferably 700 ° C. or higher.

The liquid phase viscosity (η _TL ) of the present glass is 7 dPa · s or more. The liquid phase viscosity (η _TL ) of the present glass is preferably 10 dPa · s or more, since the degree of freedom in shape and yield in the gob molding for preforms is improved, more preferably 15 dPa · s or more, and 20 dPa · s. The above is more preferable. A liquid phase viscosity of 10 dPa · s or higher and a liquid phase temperature of 890 ° C. or lower are particularly preferable because the preform gob moldability and the precision press moldability of the preform are balanced.

  On the other hand, when the liquid phase viscosity of the present glass is too high, the amount of molten glass flowing out from the nozzle is reduced, which is not preferable because the productivity is lowered. Therefore, the liquid phase viscosity is preferably 100 dPa · s or less, and more preferably 80 dPa · s or less.

  The method for producing this glass is not particularly limited. For example, platinum, platinum, and the like are used by weighing and mixing raw materials used in ordinary optical glass such as oxides, hydroxides, carbonates, nitrates, and phosphates. Put in a crucible usually used in optical glass such as crucible, gold crucible, quartz crucible, alumina crucible, etc., cast into a mold preheated to 400 to 500 ° C after melting, clarifying and stirring at about 850 to 1100 ° C for 2 to 10 hours. It can be manufactured by slow cooling after squeezing.

  As a method of preform gob molding using this glass, the molten glass flows out from the nozzle tip, a molten glass lump of a desired mass is separated, received while being floated with nitrogen gas on the mold, the entire surface Although the method of manufacturing the glass lump of the surface made with fire is mentioned as an example, it is not limited to this.

In addition, the method of molding the present glass into an optical element is not particularly limited, but a preform produced by gob molding for a preform based on the glass liquidus temperature ( _TL ) of the present glass. Is placed in a high-precision processed mold (for example, SiC, carbide, etc.) with a protective film formed on the mold surface and pressed at a predetermined pressure and time in a non-oxidizing atmosphere. Thus, a method of obtaining a desired shape is given as an example, but the method is not limited thereto.

Examples of the present invention will be described below. Example 1 is a comparative example of the present invention, and Examples 2 to 10 are examples of the present invention. In addition, Example 1 is Example 6 which is an Example described in Japanese Patent Application Laid-Open No. 2006-111499 [Chemical Composition / Sample Preparation Method]
The raw materials were weighed so that the chemical composition (%) shown in Table 1 was obtained. The raw materials of each glass are H ₃ PO ₄ , BPO ₄ , BaP ₂ O ₆ , LiPO ₃ , NaPO ₃ , KPO ₃ in the case of P ₂ O ₅ , and H ₃ BO ₃ or BPO _{4 in} the case of B ₂ O _3. and the BaCO ₃ or _BaP 2 _{O 6} in the case of BaO, the _Li 2 CO ₃ or LiPO ₃ for Li ₂ O, in the case of Na ₂ O and _Na 2 CO ₃ or NaPO _3, the case of _{K 2} O Used K ₂ CO ₃ or KPO ₃ , and in the case of SiO ₂ , Bi ₂ O ₃ , Nb ₂ O ₅ , WO ₃ , ZnO, an oxide was used. Weighed raw materials were mixed, put into a platinum crucible with an internal volume of about 300 cc, melted at about 850 to 1100 ° C. for 1 to 3 hours, clarified and stirred, then preheated to about 400 to 5000 ° C. After casting into a rectangular mold, it was gradually cooled at about 0.5 ° C./min to prepare a sample.

[Evaluation methods]
Refractive index (n _d) is the refractive index with respect to the helium d line, refractometer (Kalnew Optical Industry Co., Ltd., trade name: KRP-2) was measured in. The refractive index value was measured to the fifth decimal place and rounded to the fifth decimal place and listed as the fourth decimal place.
The Abbe number (ν _d ) was calculated by ν _d = (n _d −1) / (n _F −n _C ), and the second decimal place was rounded off to the first decimal place. _However, n F, _{n C} is the refractive index for each of the hydrogen F line and C line.
Glass transition temperature (T _g ) and yield point (At) are obtained by processing each obtained glass into a rod shape, and by thermal expansion using a thermal analyzer (Bruker AXS, trade name: TMA4000SA). The measurement was performed at a heating rate of 5 ° C./min.
・ Liquid phase temperature (T _L ) is about 5 g of glass sample in a platinum dish, each of which is held at 800 ° C. to 900 ° C. in increments of 10 ° C. for 1 hour. Was observed with a microscope, and the lowest temperature at which no crystals were observed was defined as the liquidus temperature.
Liquid phase viscosity (η _TL ) Viscosity was measured by the rotating cylinder method, and the viscosity at the liquid phase temperature (L _T ) was determined.
-About the solubility of glass, etc., as a result of visual observation at the time of the above sample preparation, for Examples 1 to 10, there is no problem in solubility, and the obtained glass sample has no bubbles or striae confirmed.

  This glass is an optical glass having a refractive index of 1.90 or more, and is suitable for precision press molding because of its low glass transition point. Moreover, since it has a high liquidus viscosity, it has excellent preform gob moldability. Therefore, it is useful as an optical glass for precision press molding having a high refractive index and high properties.

Claims (5)

In mol% of oxide basis,
P ₂ O ₅ 20.0-30.0
B ₂ O ₃ 3.5-10.0
SiO ₂ 0-5.0
BaO 0-5.0
Na ₂ O 16.2-25.0
K ₂ O 0-8.0
Bi ₂ O ₃ 10.0-20.0
TiO ₂ 3.0-15.0
Nb ₂ O ₅ 10.0-20.0
WO ₃ 5.0-15.0
ZnO 0-5.0
And substantially free of Li ₂ O, the liquid phase viscosity (η _TL ) is 7 dPa · s or more,
An optical glass having a refractive index n _{d of} 1.90 or more. Na ₂ O and 17.0-23.0Mol% including claim 1, wherein the optical glass.   The optical glass according to claim 1 or 2, wherein the total of the components is 95 mol% or more. The optical glass according to claim 1, 2 or 3, wherein the Abbe number ν _d is 19 to 22. Liquid phase temperature ( _TL ) is 900 degrees C or less, Optical glass in any one of Claims 1-4.