JP2012224501A - Optical glass, optical element and preform - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide optical glass whose optical constants are in such ranges that the refractive index (nd) is ≥1.85 and that the Abbe number (νd) is ≤25, and which is suitable for precision mold press forming.SOLUTION: This optical glass contains PO, BiO, NbOand TiOas indispensable components, and also contains in terms of mass, with respect to the glass total mass of the composition in terms of oxides, a 10.0-44.0% POcomponent, a 0.1-50.0% BiOcomponent, a 20.0-60.0% NbOcomponent and a 0.1-20.0% TiOcomponent. An optical element and a preform for precision press forming comprise the optical glass.

Description

  The present invention relates to an optical glass having an optical constant having a refractive index (nd) of 1.85 or more and an Abbe number (νd) of 25 or less, which is suitable for precision mold press molding.

  In recent years, digitization and high definition of devices using optical systems have been rapidly progressing, and various optical devices such as photographing devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions. In order to reduce the number of optical elements such as lenses and prisms used in the optical system, and to reduce weight and size, optical design using aspherical lenses using high refractive index and high dispersion glass is the mainstream. It is becoming.

  In particular, it is expensive and low-efficiency to produce an aspheric lens by grinding or polishing methods. Therefore, as a method for manufacturing an aspheric lens, a preform material obtained by cutting and polishing a gob or a glass block is heated and softened. By pressing this with a mold with a high-precision surface, the grinding / polishing process is omitted, and low-cost and mass production is realized. As such a high refractive index and high dispersion glass, glass compositions as described in Patent Documents 1 to 3 are known.

  JP-A-8-157231 discloses an optical glass which does not contain lead oxide and has a low yield point. However, the refractive index (nd) of the optical glass disclosed herein is in the range of 1.70 to 1.77 (first aspect) and 1.77 to 1.85 (second aspect).

  Japanese Patent Application Laid-Open No. 2001-58845 discloses an optical glass that does not contain lead oxide, has a refractive index (nd) of 1.83 or more, and has a yield point of 550 ° C. or less. However, a high refractive index composition having a refractive index (nd) of 1.88 or more tends to be milky without vitrification.

  Japanese Unexamined Patent Application Publication No. 2009-132610 discloses an optical glass having a refractive index (nd) of 1.90 or more and an Abbe number (νd) of 22 or less. However, a high refractive index and high dispersion composition having a refractive index (nd) of 1.90 or more and an Abbe number (νd) of 22 or less tends to deteriorate the light transmittance (coloring degree) in the visible light region.

JP-A-8-157231 JP 2001-58845 A JP 2009-132610 A

  The present invention provides an optical glass having an optical constant having a refractive index (nd) of 1.85 or more and an Abbe number (νd) of 25 or less, which is suitable for precision mold press molding. For the purpose.

  The lenses used in the optical system include a spherical lens and an aspheric lens. If an aspheric lens is used, the number of optical elements can be reduced. In addition, various optical elements other than lenses are known which have a complicatedly shaped surface. However, in order to obtain an aspherical surface or a complicatedly shaped surface by conventional grinding and polishing processes, a high-cost and complicated work process is required. Therefore, a method of obtaining a shape of an optical element by directly press-molding a preform material obtained from a gob or a glass block with an ultra-precision processed mold, that is, a method of precision mold press molding is currently mainstream.

  Preform material used for precision mold press molding is produced by a method of directly manufacturing from molten glass by the dropping method, a method of grinding and polishing a processed product obtained by reheating a glass block or grinding into a ball shape. Is done. In any method, in order to obtain an optical element by forming a molten glass into a desired shape, it is required to reduce devitrification of the formed glass.

  In addition to the method of precision mold press molding a preform material, the glass molded body obtained by reheating and molding (reheat press molding) a gob or glass block formed from a glass material is ground and polished to optically A method for obtaining the shape of an element is also known.

  The present invention improves various disadvantages found in the conventional optical glass, and has an index of refraction (nd) of 1.85 or more and an Abbe number (νd) of 25 or less, and is suitable for precision mold press molding. The object is to provide glass.

As a result of intensive studies and studies to solve the above problems, the present inventor has found that glass containing P ₂ O ₅ component, Bi ₂ O ₃ component, Nb ₂ O ₅ component, and TiO ₂ component in a predetermined ratio. In the present invention, an optical glass having a refractive index (nd) of 1.85 or more and an Abbe number (νd) of 25 or less and having extremely good precision mold pressability has been found, and the present invention has been achieved. .

The present invention includes the following (1) to (10).

(1) As an essential component, it contains P ₂ O ₅ , Bi ₂ O ₃ , Nb ₂ O ₅ , and TiO ₂ , and the P ₂ O ₅ component is 10% by mass with respect to the total glass mass of the oxide conversion composition. 0-60.0%, Bi ₂ O ₃ component 0.1-60.0%, Nb ₂ O ₅ component 5.0-60.0%, TiO ₂ component 0.1-35.0% Optical glass.

(2) The optical glass according to (1), which contains 20% or less of WO ₃ component by mass% with respect to the total mass of the glass having an oxide equivalent composition.

(3) as oxide entire mass of the glass composition, the weight ratio _{Nb 2 O 5 / Bi 2 O} 3 is 1.00 or less (1) an optical glass to (2).

(4) The total amount of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ is 50.0 to 95.0% by mass% with respect to the total glass mass of the oxide equivalent composition (1). Optical glass of (3).

(5) SiO ₂ component 0 to 20.0% by weight with respect to the total amount of glass in oxide-converted composition
B ₂ O ₃ component 0 to 30.0%
GeO ₂ component 0-50.0%
TeO ₂ component 0 to 30.0%
Li ₂ O component 0 to 20.0%
Na ₂ O component 0 to 25.0%
K ₂ O component 0 to 20.0%
Cs ₂ O component 0 to 20.0%
MgO component 0 to 15.0%
CaO component 0 to 20.0%
SrO component 0 to 20.0%
BaO component 0-40.0%
ZnO component 0-40.0%
Al ₂ O ₃ component 0 to 20.0%
ZrO ₂ component 0 to 20.0%
La ₂ O ₃ component 0 to 20.0%
Gd ₂ O ₃ component 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0%
Ta ₂ O ₅ component 0 to 20.0%
In ₂ O ₃ component 0 to 20.0%
Yb ₂ O ₃ component 0 to 20.0%
Sb ₂ O ₃ component 0-5.0%
CeO ₂ component 0-5.0%
Optical glass of Claim (1)-(4) which further contains each component of these.

(6) It has a refractive index (nd) of 1.85 or more, an Abbe number (νd) of 25 or less, and a wavelength (λ ₇₀ ) showing a spectral transmittance of 70% is 500 nm or less. The optical glass of claims (1) to (5).

(7) The optical glass of (1) to (6), wherein the glass transition temperature (Tg) is 640 ° C. or lower.

(8) A precision press-molding preform comprising the optical glass according to any one of (1) to (7).

(9) An optical element comprising the optical glass according to any one of (1) to (7).

(10) An optical element formed by precision pressing the preform of (8).

According to the present invention, in a glass containing P ₂ O ₅ component, Bi ₂ O ₃ component, Nb ₂ O ₅ component, and TiO ₂ component in a predetermined ratio, the refractive index (nd) is 1.85 or more. The Abbe number (νd) is in the range of 25 or less, and an optical glass suitable for precision mold press molding can be obtained.

  Each component of the optical glass of the present invention will be described. Hereinafter, embodiments of the optical glass of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and may be implemented with appropriate modifications within the scope of the object of the present invention. be able to. Unless otherwise specified, the content (%) of each component means mass% based on oxide.

The P ₂ O ₅ component is an important component as a glass forming oxide and an effective component for imparting high dispersibility to the glass. Accordingly, the P ₂ O ₅ component can be preferably contained at an upper limit of 60.0%, more preferably 50.0%, still more preferably 45.0%, preferably 20.0%, more preferably It can be contained at a lower limit of 15.0%, more preferably 10.0%.
The P ₂ O ₅ component can be contained in the glass using, for example, orthophosphoric acid, phosphate, or the like as a raw material.

The Bi ₂ O ₃ component has the effects of increasing the refractive index, increasing dispersion, and decreasing the glass transition temperature (Tg). However, if the amount is too large, the devitrification resistance tends to deteriorate, and solarization tends to deteriorate. Therefore, the Bi ₂ O ₃ component can be contained with an upper limit of preferably 60.0%, more preferably 55.0%, and still more preferably 50.0%. However, if the amount is too small, the desired refractive index and dispersion cannot be obtained, the glass transition temperature (Tg) is increased, and the precision mold pressability is deteriorated. Therefore, the lower limit of the amount of this component should preferably be 0.1%, more preferably 7.0%, still more preferably 10.0%, and most preferably 15.0%.
The Bi ₂ O ₃ component can be contained in the glass using, for example, Bi ₂ O ₃ as a raw material.

The Nb ₂ O ₅ component is an essential component effective for increasing the refractive index, increasing the dispersion, and improving the chemical durability and devitrification resistance. However, if the amount is too small, the effect becomes insufficient. On the other hand, if the amount is too large, the devitrification resistance is deteriorated, and the transmittance in the visible light short wavelength region is likely to be deteriorated. Therefore, the Nb ₂ O ₅ component can preferably contain 5.0%, more preferably 10.0%, more preferably 15.0% as a lower limit, preferably 60.0%, more preferably 55.0%, more preferably 50.0% can be contained as the upper limit.
The Nb ₂ O ₅ component can be contained in the glass using, for example, Nb ₂ O ₅ as a raw material.

The TiO ₂ component has the effect of increasing the refractive index. However, when the amount is too large, the transmittance and solarization in the visible light short wavelength region are deteriorated. Therefore, the TiO ₂ component can be contained with an upper limit of preferably 35.0%, more preferably 30.0%, still more preferably 25.0%, and most preferably 20.0%. However, if the amount is too small, the desired refractive index and dispersion cannot be obtained. Therefore, it can contain more than 0.1%, more preferably more than 3.0%, still more preferably 4.0%, and most preferably 5.0% as a lower limit.
TiO ₂ component as a raw material for example with TiO ₂ or the like can be contained in the glass.

The WO ₃ component has the effect of adjusting the optical constant, lowering the glass transition temperature (Tg), and improving devitrification resistance. However, if the amount is too large, the devitrification resistance and the light transmittance in the short wavelength region of the visible light region are adversely affected. Accordingly, the WO ₃ component may preferably contain 20.0%, more preferably 15.0%, even more preferably 10.0%, and most preferably less than 8.0% as the upper limit. However, if the amount is too small, the glass transition temperature (Tg) rises and the devitrification resistance improving effect cannot be obtained. Accordingly, the lower limit can be preferably 1.0%, more preferably 2.0%, and most preferably 3.0%.
The WO ₃ component can be contained in the glass using, for example, WO ₃ as a raw material.

In the optical glass of the present invention, the ratio of the content of the Nb ₂ O ₅ component to the content of the Bi ₂ O ₃ component is preferably 1.00 or less. By making this substance amount ratio 1.00 or less, the refractive index and precision mold pressability can be improved, and the glass transition temperature (Tg) can be lowered. Accordingly, the mass cost Nb ₂ O ₅ / Bi ₂ O ₃ of the oxide conversion composition is preferably 1.00%, more preferably 0.80%, and even more preferably 0.45%. .

In the optical glass of the present invention, the total content of TiO ₂ component, Nb ₂ O ₅ component, WO ₃ component and Bi ₂ O ₃ component is preferably 50.0% or more and 95.0% or less. In particular, when the content is 50.0% or more, the refractive index and dispersion of the glass can be increased. On the other hand, by being 95.0% or less, devitrification resistance can be enhanced while increasing the refractive index and dispersion of the glass. Therefore, the total content of these components with respect to the total amount of glass in terms of oxide composition is preferably 50.0%, more preferably 55.0% or more, and even more preferably 60.0% or more. On the other hand, the total content of these components with respect to the total amount of glass in terms of oxide composition is preferably 95.0%, more preferably 90.0%, and even more preferably 85.0%.

The SiO ₂ component is an optional component that acts as a glass-forming oxide, and is effective in increasing the viscosity of glass and improving devitrification resistance and chemical durability. Accordingly, the SiO ₂ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The SiO ₂ component can be contained in the glass using, for example, SiO ₂ as a raw material.

The B ₂ O ₃ component is an optional component that acts as a glass-forming oxide, and is effective in improving the devitrification resistance of the glass and lowering the glass transition point (Tg). In addition, in the P ₂ O ₅ —Nb ₂ O ₅ series glass, the SiO ₂ component tends to be left unmelted, but the meltability is improved by the coexistence of the B ₂ O ₃ component, and chemical It is effective for improving durability. Therefore, the upper limit of the amount of this component is preferably 30.0%, more preferably 15.0%, and still more preferably 7.5%. Incidentally, B ₂ O ₃ component is for an optional component, it is possible to produce glass of the present invention without containing, by including a predetermined amount, to improve the meltability. Accordingly, the lower limit of the content is preferably more than 0%, more preferably 1.0%, still more preferably 2.0%, and most preferably 3.0%.
B ₂ O ₃ can be contained in the glass using, for example, H ₃ BO ₃ , B ₂ O ₃ or the like as a raw material.

The GeO ₂ component is an optional component having an effect of increasing the refractive index and improving the devitrification resistance, and acts as a glass forming oxide. However, if the amount is too large, the raw material is very expensive, which increases the cost. Therefore, the GeO ₂ component can be contained preferably at an upper limit of 50.0%, more preferably 30.0%, and even more preferably 15.0%.
The GeO ₂ component can be contained in the glass using, for example, GeO ₂ as a raw material.

The TeO ₂ component is a component that has an effect of increasing the refractive index. When melting a glass raw material in a platinum crucible or a melting tank in which a portion in contact with molten glass is formed of platinum, tellurium and platinum are alloyed. Since the heat resistance is likely to deteriorate in the alloyed part, there is a concern about the risk of an accident that a hole is opened in the part and the molten glass flows out. Therefore, the TeO ₂ component can preferably contain 30.0%, more preferably 20.0%, and still more preferably 10.0% as the upper limit.
The TeO ₂ component can be contained in the glass using, for example, TeO ₂ as a raw material.

The Li ₂ O component has the effect of significantly lowering the glass transition temperature (Tg) and promoting the melting of the mixed glass raw material, and the effect of suppressing devitrification during reheat press molding in the composition system of the present invention. There is. However, if the amount is too large, the devitrification resistance tends to deteriorate rapidly. Therefore, the Li ₂ O component can be contained preferably at an upper limit of 20.0%, more preferably 15.0%, and still more preferably 10.0%. In addition, since the Li ₂ O component is an optional component, it is possible to produce the glass of the present invention even if it is not contained. However, in order to easily exhibit the effect, it preferably exceeds 0%, more The lower limit is preferably 0.1%, more preferably 1.0%.
The Li ₂ O component can be contained in the glass using, for example, Li ₂ O or a carbonate, nitrate, hydroxide, or the like as a raw material.

The Na ₂ O component has the effect of lowering the glass transition temperature (Tg) and promoting the melting of the mixed glass raw material. Moreover, there exists an effect which improves precision mold press property. Therefore, the Na ₂ O component can be contained with an upper limit of preferably 25.0%, more preferably 20.0%, and still more preferably 15.0%. Since the Na ₂ O component is an optional component, it is possible to produce the glass of the present invention even if it is not contained. However, by including a predetermined amount, the glass transition temperature (Tg) is lowered, and a precision mold press is used. Improve sexiness. Therefore, the lower limit is preferably more than 0%, more preferably 0.1%, and still more preferably 1.0%.
The Na ₂ O component can be contained in the glass using, for example, Na ₂ O or its carbonate, nitrate, hydroxide, etc. as a raw material.

The K ₂ O component has an effect of lowering the glass transition temperature (Tg) and promoting the melting of the mixed glass raw material. However, when the amount is too large, the devitrification resistance deteriorates rapidly, and in the composition system of the present invention, the devitrification property at the time of reheat press molding tends to deteriorate rapidly. Therefore, the K ₂ O component can be contained preferably at an upper limit of 20.0%, more preferably 15.0%, still more preferably 10.0%, and most preferably 5%. In addition, since the K ₂ O component is an optional component, it is possible to produce the glass of the present invention even if it is not contained. However, in order to easily exhibit the effect, it preferably exceeds 0%, more The lower limit is preferably 0.1%, more preferably 1.0%.
The K ₂ O component can be contained in the glass using, for example, K ₂ O or a carbonate, nitrate, hydroxide, or the like as a raw material.

The Cs ₂ O component has an effect of lowering the glass transition temperature (Tg) and promoting the melting of the mixed glass raw material. Therefore, the Cs ₂ O component can be contained at an upper limit of preferably 20.0%, more preferably 19.0%, and still more preferably 18.0%.
Cs 2 _O component, the raw material as for example Cs 2 _O or a carbonate, nitrate, hydroxide and the like can be contained in the glass by using.

The MgO component is effective for adjusting the optical constant. However, if the amount is too large, the devitrification resistance tends to deteriorate. Accordingly, the MgO component can be contained preferably at an upper limit of 15.0%, more preferably 14.0%, and still more preferably 13.0%.
The MgO component can be contained in the glass using, for example, MgO or a carbonate, nitrate, hydroxide, or the like as a raw material.

The CaO component is effective for adjusting the optical constant. However, if the amount is too large, the devitrification resistance tends to deteriorate. Therefore, the CaO component can be contained with an upper limit of preferably 20.0%, more preferably 19.5%, and still more preferably 19.0%.
The CaO component can be contained in the glass using, for example, CaO or a carbonate, nitrate, hydroxide, or the like as a raw material.

The SrO component is effective for adjusting the optical constant. However, if the amount is too large, the devitrification resistance tends to deteriorate. Accordingly, the SrO component can be contained with an upper limit of preferably 20.0%, more preferably 19.5%, and still more preferably 19.0%.
The SrO component can be contained in the glass using, for example, SrO or a carbonate, nitrate, hydroxide, or the like as a raw material.

The BaO component is effective for lowering the glass transition temperature (Tg), improving devitrification resistance, and adjusting optical constants. Accordingly, the BaO component can be contained preferably at an upper limit of 40.0%, more preferably 30.0%, still more preferably 25.0%, and most preferably 17.0%. Since the BaO component is an optional component, it is possible to produce the glass of the present invention even if it is not contained, but by including a predetermined amount, the glass transition temperature (Tg) is lowered and a precision mold press is used. Improve sexiness. Therefore, it is preferable that the lower limit of the content be preferably more than 0%, more preferably 0.5%, and most preferably 1.0%.
The BaO component can be contained in the glass using, for example, BaO or a carbonate, nitrate, hydroxide, or the like as a raw material.

The ZnO component has the effect of lowering the glass transition temperature (Tg) and improving chemical durability. Accordingly, the ZnO component can be contained preferably at an upper limit of 40.0%, more preferably 30.0%, still more preferably 20.0%, and most preferably 10.0%. Since the ZnO component is an optional component, it is possible to produce the glass of the present invention even if it is not contained, but by including a predetermined amount, the glass transition temperature (Tg) is lowered and the precision mold press Improve sexiness. Accordingly, the lower limit of the content is preferably more than 0%, more preferably 1.0%, still more preferably 2.0%, and most preferably 3.0%.
The ZnO component can be contained in the glass using, for example, ZnO as a raw material.

The Al ₂ O ₃ component is an optional component effective for improving chemical durability. However, if the amount is too large, the devitrification resistance tends to deteriorate. Therefore, the Al ₂ O ₃ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The Al ₂ O ₃ component can be contained in the glass using, for example, Al ₂ O ₃ , Al (OH) ₃ or the like as a raw material.

The ZrO ₂ component has the effect of increasing the refractive index and improving the chemical durability. However, if the amount is too large, the devitrification resistance tends to deteriorate. Therefore, the ZrO ₂ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The ZrO ₂ component can be contained in the glass using, for example, ZrO ₂ as a raw material.

The La ₂ O ₃ component is an effective component for increasing the refractive index of glass and reducing the dispersion. However, if the amount is too large, the devitrification resistance tends to deteriorate. Accordingly, the La ₂ O ₃ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The La ₂ O ₃ component can be contained in the glass using, for example, La ₂ O ₃ , lanthanum nitrate or a hydrate thereof as a raw material.

The Gd ₂ O ₃ component is effective in increasing the refractive index of the glass and lowering the dispersion. However, if the amount is too large, the devitrification resistance tends to deteriorate. Therefore, the Gd ₂ O ₃ component can preferably contain 20.0%, more preferably 15.0%, and even more preferably 10.0%.
Gd ₂ O ₃ can be contained in the glass using, for example, Gd ₂ O ₃ as a raw material.

The Y ₂ O ₃ component increases the refractive index of the glass, and the Y ₂ O ₃ component is effective for low dispersion. However, if the amount is too large, the devitrification resistance tends to deteriorate. Accordingly, the upper limit is preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The Y ₂ O ₃ component can be contained in the glass using, for example, Y ₂ O ₃ as a raw material.

The Ta ₂ O ₅ component is effective in increasing the refractive index and improving chemical durability and devitrification resistance. However, if the amount is too large, the devitrification resistance tends to deteriorate. Accordingly, the Ta ₂ O ₅ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The Ta ₂ O ₅ component can be contained in the glass using, for example, Ta ₂ O ₅ as a raw material.

The In ₂ O ₃ component is effective in increasing the refractive index of glass and reducing the dispersion. Therefore, the In ₂ O ₃ component can be contained with an upper limit of preferably 20.0%, more preferably 15.0%, and still more preferably 10.0%.
The In ₂ O ₃ component can be contained in the glass using, for example, In ₂ O ₃ , In ₂ F ₃ or the like as a raw material.

The Yb ₂ O ₃ component is effective in increasing the refractive index of the glass and lowering the dispersion. However, if the amount is too large, devitrification resistance and chemical durability are likely to deteriorate. Therefore, the Yb ₂ O ₃ component can be contained with an upper limit of preferably 20.0%, preferably 15.0%, more preferably 10.0%.
The Yb ₂ O ₃ component can be contained in the glass using, for example, Yb ₂ O ₃ as a raw material.

The Ga ₂ O ₃ component is a component having an effect of increasing the refractive index, but the raw material is very expensive. Therefore, the Ga ₂ O ₃ component can be contained with 10.0% as the upper limit, more preferably 8.0%, and even more preferably 5.0% as the upper limit.
The Ga ₂ O ₃ component can be contained in the glass using, for example, Ga ₂ O ₃ as a raw material.

The Sb ₂ O ₃ component can be optionally added for defoaming when the glass is melted, but if the amount is too large, the transmittance in the short wavelength region of the visible light region tends to deteriorate. Accordingly, the Sb ₂ O ₃ component can be contained preferably at an upper limit of 5.0%, more preferably 2.5%, and still more preferably 0.5%.

The CeO ₂ component is a component having an effect of improving devitrification resistance. However, if the amount is too large, the light transmittance in the short wavelength region is likely to deteriorate. Accordingly, the CeO ₂ component can be contained preferably at an upper limit of 5.0%, more preferably 2.5%, still more preferably 0.5%.
The CeO2 component can be contained in the glass using, for example, CeO2 as a raw material.

Lu ₂ O 3 _, SnO ₂ , and BeO can be contained, but Lu ₂ O ₃ is a high-priced raw material, so the raw material cost increases and is not practical in actual production. SnO ₂ is platinum. When a glass raw material is melted in a melting vessel in which the part in contact with the molten glass is made of platinum when the glass raw material is melted, an alloy formed by alloying tin and platinum becomes poor in heat resistance. There is a concern that there is a risk of an accident in which the molten glass flows and the molten glass flows out, and there is a problem that BeO is a component that has a harmful effect on the environment and a very large environmental load. Therefore, each component of Lu ₂ O 3 _, SnO ₂ and BeO is preferably contained in an amount of less than 0.1%, more preferably 0.05%, and further preferably not contained.

  Next, components that should not be contained in the optical glass of the present invention will be described.

  Since lead compounds are a component that has a large environmental impact, not only for glass production, but also for cold processing of glass such as polishing and disposal of glass. It should not be included in the optical glass of the invention.

As ₂ O ₃ , cadmium, thorium, and thallium all have harmful effects on the environment and are extremely heavy components of the environment, and therefore should not be contained in the optical glass of the present invention.

  Furthermore, it is preferable that the optical glass of the present invention does not contain coloring components such as V, Cr, Mn, Fe, Co, Ni, Cu, Mo, Eu, Nd, Sm, Tb, Dy, and Er. However, the term “not contained” means that it is not contained artificially unless it is mixed as an impurity.

In addition, the notation on the basis of oxides of the content of each component used in this specification is that all oxides, composite salts, metal fluorides, etc. used as raw materials for the glass constituents of the present invention are melted. When it assumes that it decomposes | disassembles and changes to an oxide, the mass% of the said production | generation oxide of each component with respect to the whole composition is represented.
[Production method]

The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible or the like, and 1000 to 1300 in an electric furnace according to the melting difficulty of the glass composition. It is produced by melting in the temperature range of 0 ° C. for 2 to 5 hours, homogenizing with stirring, lowering to an appropriate temperature, casting into a mold, and slow cooling.
[Physical properties]

  Next, the physical properties of the optical glass of the present invention will be described.

  The optical glass of the present invention needs to have a high refractive index (nd) and low dispersibility. In particular, the refractive index (nd) of the optical glass of the present invention is preferably 1.85, more preferably 1.88, and most preferably 1.90, preferably 2.05, more preferably 2.04. Most preferably, the upper limit is 2.03. The Abbe number (νd) of the optical glass of the present invention is preferably 17, more preferably 18, most preferably 19, the lower limit, preferably 25, more preferably 22, most preferably 20. As a result, the degree of freedom in optical design is increased, and a large amount of light refraction can be obtained even if the device is made thinner.

Further, the optical glass of the present invention has a better transmittance. The wavelength (λ ₇₀ ) at which the transmittance is 70% is preferably 500 nm or less, more preferably 470 nm or less, still more preferably 450 nm or less, and most preferably 440 nm or less. The wavelength (λ ₅ ) at which the transmittance is 5% is preferably 450 nm or less, more preferably 420 nm or less, and still more preferably 400 nm or less.
Incidentally, the transmittance is relative to the incident light intensity when irradiated perpendicularly to one of the optically polished surfaces of a glass sample subjected to parallel and flat optical polishing having a thickness of 10.0 ± 0.1 mm. It is represented by the ratio of the intensity of transmitted light transmitted through the glass sample and emitted from the other optical polishing surface (transmitted light intensity / incident light intensity). The wavelength at which the transmittance is 70% is λ ₇₀ , and the wavelength at which the transmittance is 5% is λ ₅ .

  In the optical glass of the present invention, when the glass transition temperature (Tg) becomes too high, as described above, when precision press molding is performed, deterioration of the mold tends to occur. Therefore, Tg of the optical glass of the present invention is preferably 640 ° C, more preferably 600 ° C, and further preferably 550 ° C.

  The optical glass of the present invention preferably has a yield point (At) of 700 ° C. or lower. Like the glass transition point (Tg), the yield point (At) is one of indices indicating the softening property of glass, and is an index indicating a temperature close to the press molding temperature. Therefore, by using a glass having a yield point (At) of 700 ° C. or lower, press molding at a lower temperature becomes possible, and therefore press molding can be performed more easily. Therefore, the upper limit of the yield point (At) of the optical glass of the present invention is preferably 700 ° C., more preferably 630 ° C., and most preferably 600 ° C. The lower limit of the yield point (At) of the optical glass of the present invention is not particularly limited, but the yield point (At) of the glass obtained by the present invention is generally 150 ° C. or higher, specifically 200 ° C. or higher, more specifically. Specifically, it is often 250 ° C. or higher.

  The optical glass of the present invention is useful for various optical elements and optical designs. For example, the optical glass of the present invention can be ground and polished to obtain an optical glass. Further, for example, an optical glass for precision press molding can be obtained from the optical glass of the present invention. Among them, it is particularly preferable to form a preform from the optical glass of the present invention, and to produce optical elements such as lenses, prisms, mirrors and the like by using means such as polishing and precision press molding for the preform. . As a result, when used in optical devices that transmit visible light to optical elements such as cameras and projectors, the optical system in these optical devices can be miniaturized while realizing high-definition and high-precision imaging characteristics. Can be planned. Here, the method for producing the preform material is not particularly limited. For example, a glass gob forming method described in JP-A-8-319124 and an optical glass manufacturing method and manufacturing apparatus described in JP-A-8-73229 are disclosed. Thus, a method of manufacturing a preform material directly from molten glass can also be used, and a method of manufacturing by performing cold processing such as grinding and polishing on a strip material formed from optical glass can also be used.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  Compositions of Examples 1 to 17 and comparative examples of the glass of the present invention, refractive index (nd), Abbe number (νd), spectral transmittance of these glasses 5%, 70%, glass transition temperature (Tg), deformation The point (At) is shown in Table 1. In the table, the composition of each component is expressed in wt%.

  Here, as for the optical glass of the Example (Examples 1-17) of this invention, and the glass of a comparative example, each composition which showed the raw material for normal optical glass, such as an oxide, composite salt, carbonate, nitrate, in the table | surface. Weigh and mix at a predetermined ratio so as to achieve a ratio, and then put into a platinum crucible, etc., melt, clarify and stir for 2 to 5 hours at a temperature of 1000 to 1300 ° C., then lower to an appropriate temperature. It was obtained by casting into a mold or the like and gradually cooling.

The refractive index (nd) and Abbe number (ν _d ) were measured based on Japan Optical Glass Industry Association Standard JOGIS01-2003. Here, the refractive index (nd) and the Abbe number (ν _d ) were determined by measuring the glass obtained at a slow cooling rate of -25 ° C./hr.

Moreover, the transmittance | permeability of the optical glass of an Example (Examples 1-17) and the glass of a comparative example was measured according to Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the presence / absence and degree of coloration of the glass were determined by measuring the transmittance of the glass. More specifically, a face parallel polished product having a thickness of 10 ± 0.1 mm was measured for a spectral transmittance of 200 to 800 nm in accordance with JISZ8722, and λ ₅ (wavelength when the transmittance was 5%), λ ₇₀ (transmittance). Wavelength at 70%).

  Moreover, the glass transition point (Tg) and the yield point (At) of the optical glass of an Example (Examples 1-17) and the glass of a comparative example were calculated | required by measuring using a thermal dilatometer. Here, the sample at the time of measurement used the thing of (phi) 5mm and length 20mm, and the temperature increase rate was 4 degrees C / min.

Each preform was press-molded with a mold composed of an upper mold, a lower mold, and a sleeve mold. The mold is made of Pt, Au, Ir, Ni, Cr, Mo, Rh, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Re, and C. The molding surface of the upper mold and the lower mold has a spherical shape with a diameter of 9 mm, a depth of 0.5 mm, and a curvature radius of 20 mm, and the molding surface of the mold has a surface roughness. An optical mirror-finished surface having a smoothness of Rmax 0.03 μm was used. Here, the preform is placed at the center of the molding surface of the lower mold inserted into the sleeve mold, the upper mold is inserted into the through hole of the sleeve mold, and the molding surface of the lower mold and the molding surface of the upper mold are To face each other. The preform placed in the mold is heated to 300 to 700 ° C. together with the mold, and when the glass of the preform is softened, the preform is pressed with the upper mold and the lower mold to perform press molding. Was made.
The MP (mold press) property of the optical glass of Examples (Examples 1 to 17) and the glass of Comparative Examples is free from devitrification / can / fogging in the glass after press molding, and the mold haze and release film. The case where there was no peeling was marked with ◎, the case where some of the molded glass had some deterioration was marked with ○, the portion with some defects was marked with Δ, and the case with defects was marked with ×.

As can be seen from Tables 1 to 5, the optical glasses of Examples of the present invention (Examples 1 to 17) all have a refractive index (nd) of 1.85 or more, more specifically 1.88 or more. The refractive index (nd) was 2.05 or less, more specifically 2.04 or less, and was within the desired range. In both cases, the Abbe number (ν _d ) is 25 or less, more specifically 22 or less, and the Abbe number (ν _d ) is 17 or more, more specifically 18 or more. there were.

In addition, the optical glasses of the examples of the present invention each had a λ ₇₀ (wavelength at a transmittance of 70%) of 500 nm or less, more specifically 470 nm or less. In addition, in the optical glasses of the examples of the present invention, λ ₅ (wavelength at 5% transmittance) was 450 nm or less, more specifically 420 nm or less. For this reason, it became clear that the optical glass of the Example of this invention was hard to color.

In addition, as shown in Tables 1 to 5, all of the optical glasses of the examples of the present invention have a glass transition temperature (Tg) of 640 ° C. or lower, more specifically 600 ° C. or lower, and a desired range. It was in. For this reason, it became clear that the optical glass of the Example of this invention has a low glass transition point (Tg). Further, the optical glasses of the examples of the present invention all had a yield point (At) of 700 ° C. or less, more specifically 650 ° C. or less, and were within a desired range.
On the other hand, the optical glass of Comparative Example 1 had a glass transition point (Tg) of 644 ° C. and a yield point (At) of 701 ° C. For this reason, it became clear that the optical glass of the Example of this invention is easy to soften at low temperature compared with the glass of the comparative example 1.

In addition, as shown in Tables 1 to 5, the optical glass of the examples of the present invention is free from devitrification / can / fogging in the glass after press molding, and the mold haze and the release film are peeled off. There is no. Alternatively, some of the glass after molding is somewhat deteriorated. For this reason, it became clear that the optical glass of the Example of this invention is suitable for precision press molding.
On the other hand, the optical glass of Comparative Example 1 had a glass transition point (Tg) of 644 ° C. and a yield point (At) of 701 ° C. As described above, when precision press molding is performed, if the glass transition temperature (Tg) becomes too high, the mold tends to deteriorate. Therefore, the optical glass of Comparative Example 1 is not suitable for precision press molding.

Therefore, the optical glass of the embodiment of the present invention can be manufactured at a low cost while having a refractive index (nd) and an Abbe number (ν _d ) within desired ranges, has high devitrification resistance, and can be press-molded by heat softening. It has become clear that it is easy to perform and has little coloration.

Furthermore, using the optical glass of the example of the present invention, after forming a preform for polishing, grinding and polishing were performed to form lenses and prisms. In addition, a precision press-molding preform was formed using the optical glass of the example of the present invention, and the precision press-molding preform was precision press-molded into a lens and a prism. In either case, it could be processed into various lens and prism shapes.

  Although the present invention has been described in detail for the purpose of illustration, this embodiment is only for the purpose of illustration, and many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention. Will be understood.

Claims (10)

As an essential component, it contains P ₂ O ₅ , Bi ₂ O ₃ , Nb ₂ O ₅ , and TiO ₂ , and the P ₂ O ₅ component is 10.0 to 60% by mass based on the total glass mass of the oxide conversion composition. Optical glass containing 0.0%, 0.1% to 60.0% Bi ₂ O ₃ component, 5.0 to 60.0% Nb ₂ O ₅ component, and 0.1 to 35.0% TiO ₂ component . The entire mass of the glass in terms of oxide composition, the optical glass of claim 1 containing 20% or less of WO ₃ components in mass%. _3. The optical glass according to claim 1, wherein the weight ratio Nb ₂ O ₅ / Bi ₂ O ₃ is 1.00 or less with respect to the total glass mass of the oxide equivalent composition. The total amount of TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi ₂ O ₃ is 50.0 to 95.0% by mass% with respect to the total glass mass of the oxide equivalent composition. Optical glass. SiO ₂ component 0 to 20.0% by weight with respect to the total amount of glass of oxide conversion composition
B ₂ O ₃ component 0 to 30.0%
GeO ₂ component 0-50.0%
TeO ₂ component 0 to 30.0%
Li ₂ O component 0 to 20.0%
Na ₂ O component 0 to 25.0%
K ₂ O component 0 to 20.0%
Cs ₂ O component 0 to 20.0%
MgO component 0 to 15.0%
CaO component 0 to 20.0%
SrO component 0 to 20.0%
BaO component 0-40.0%
ZnO component 0-40.0%
Al ₂ O ₃ component 0 to 20.0%
ZrO ₂ component 0 to 20.0%
La ₂ O ₃ component 0 to 20.0%
Gd ₂ O ₃ component 0 to 20.0%
Y ₂ O ₃ component 0 to 20.0%
Ta ₂ O ₅ component 0 to 20.0%
In ₂ O ₃ component 0 to 20.0%
Yb ₂ O ₃ component 0 to 20.0%
Sb ₂ O ₃ component 0-5.0%
CeO ₂ component 0-5.0%
The optical glass of Claims 1-4 which further contains each component of these. A wavelength (λ ₇₀ ) having a refractive index (nd) of 1.85 or more, an Abbe number (νd) of 25 or less, and a spectral transmittance of 70% is 500 nm or less. Item 5. Optical glass according to items 1 to 5. The glass transition temperature (Tg) is 640 ° C. or lower, and the optical glass according to claim 1.   A precision press-molding preform comprising the optical glass according to claim 1.   An optical element comprising the optical glass according to claim 1.   An optical element formed by precision pressing the preform of claim 8.