Optical glass

Abstract

Disclosed is an optical glass having optical constants, namely a refractive index (nd) of 1.50-1.65 and an Abbe number (gamma d) of 50-65, while having a glass transition temperature (Tg) of not more than 400 DEG C. In this optical glass, the shortest wavelength at which the light transmittance reaches 80% (lambda 80) is not more than 370 nm.

Description

technical field [0001] The present invention relates to an optical glass having a refractive index (nd) of 1.50 to 1.65, an Abbe number (νd) of optical constants in the range of 50 to 65, and a glass transition temperature (Tg) of 400°C or lower. Background technique [0002] Since very high temperatures are required to manufacture glass molded products by secondary hot press molding, the heat treatment furnace is prematurely degraded, which hinders stable production. Therefore, the lower the viscous flow temperature of the glass material, that is, the lower the glass transition temperature (Tg), the easier it is to carry out secondary hot pressing at a low temperature, which can reduce the load on the heat treatment furnace. The "viscous flow temperature" here refers to the temperature at which viscous flow occurs, which is approximately the same temperature as the glass transition temperature, and is well known in the art. [0003] When obtaining glass molded products suc...

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Problems solved by technology

[0004] At present, as a glass with a lower glass transition temperature, PbO or TeO 2 The glass is well known, but these components are environmentally unfavorable components, and the Abbe number (νd) tends to become small

In addition, as a glass that does not contain PbO and realizes a low glass transition temperature, for example, PbO 2 o 5 -RO-R 2 O system, which is due to the low glass transition temperature of R 2 The composition of O increases, so there is a disadvantage of poor chemical durability

[0005] In order to improve the above-mentioned shortcomings, Japanese Patent Application Laid-Open No. 60-171244 records that it contains La 2 o 3 while improving the chemical durability of P 2 o 5 -B 2 o 3 -Al 2 o 3 -RO-R 2 O-based glass, from the viewpoint of moldability, is not necessarily suitable for the purpose of molding because the numerical values ​​are not sufficiently limited, and examples of compositions satisfying the above-mentioned various conditions are not disclosed.

[0006] P is described in Japanese Patent Laid-Open No. 2004-217513 2 o 5 -R 2 O(R=Li, Na, K)-ZnO-BaO system, but the content of ZnO in the optical glass specifically disclosed in the publication is large, so it lacks thermal stability. For example, when making a preform for molding with molten glass, Devitrification is easy to occur, so there is a disadvantage that work efficiency deteriorates

Moreover, since the glass described in the gazette contains a lot of Nb 2 o 5 、 Bi 2 o 3 、WO 3 , so it has the disadvantages of more coloring and easy deterioration of light transmittance

[0007] P is described in Japanese Patent Laid-Open No. 2004-315324 2 o 5 -R 2 O(R=Li, Na, K)-BaO system, but the optical glass specifically disclosed in this gazette has a large content of MgO, so there is a disadvantage that only glass with a relatively high glass transition temperature (Tg) can be obtained

[0008] P is described in Japanese Patent Laid-Open No. 2002-211949 2 o 5 -BaO system, but this optical glass contains a lot of B 2 o 3 、Al 2 o 3 , RO, etc., and ZnO, R 2 O component is small, so there is a disadvantage that the softening point rises

[0009] P is described in Japanese Patent Laid-Open No. 2004-168593 2 o 5 -ZnO-BaO system, but this optical glass contains a large amount of rare earth oxides, so there is a disadvantage that only glass with a large refractive index can be obtained

[0010] P is described in Japanese Patent Application Laid-Open No. 2-124743 2 o 5 -ZnO system, this optical glass uses Al to improve chemical durability 2 o 3 The content of components is too high, so there is a defect that only glass with a high yield point (At) can be obtained

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