TWI887211B - Optical glass, glass raw materials for press molding, optical element blanks, and optical elements - Google Patents

Abstract

The present invention provides an optical glass having a low ratio of expensive glass components in the glass composition, a high refractive index and low dispersion. In the glass composition of the optical glass expressed in cation %, the Ta ⁵⁺ content is 0-5 cation %, the cation ratio (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 0.60-1.00, the cation ratio ((Si 4+ +B 3+ )/(La 3+ +Gd 3+ +Y 3+ )) is 0.50-2.50, the cation ratio ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W 6+ +Bi ³⁺ )) is 0.50-40.00, the cation ratio ((La 3+ +Gd 3+ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 0.60-1.00, the cation ratio ((Si ⁴⁺ +B 3+ )/(La ³⁺ +Gd ³⁺ +Y ³⁺ )) is 0.50-2.50, the cation ratio ((Si 4+ +B 3+ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi 3+ )) is 0.60-1.00 ³⁺ )) is 0.50~30.00, the cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(La ³⁺ +Y ³⁺ )) is 0.00~1.50, the cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(Si ⁴⁺ +B ³⁺ )) is 0.00~1.00, the cation ratio ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is 0.000~0.080, the refractive index nd of the optical glass is 1.8000~2.0000, and the Abbe number νd is 25.0~45.0.

Description

Optical glass, glass raw materials for press molding, optical element blanks, and optical elements

The present invention relates to optical glass, a glass raw material for press molding, an optical element blank and an optical element.

Optical glass with a high refractive index and low dispersion (high refractive index low dispersion glass) is useful as a material for optical elements. Such high refractive index low dispersion glass is disclosed in Patent Document 1, for example. [Prior Art Document] [Patent Document]

Patent document 1: Japanese Patent Application Publication No. 55-60039

[Problem to be solved by the invention]

The high refractive index and low dispersion glass disclosed in Patent Document 1 can be combined with a lens formed of the glass and a lens formed of ultra-low dispersion glass to form a bonded lens, thereby correcting chromatic aberration and realizing miniaturization of the optical system. However, the optical glass described in Patent Document 1 contains a large amount of expensive components (such as Ta ₂ O ₅ and WO ₃ ) among various glass components. However, in order to realize the cost reduction of optical elements formed of high refractive index and low dispersion glass, it is desired to reduce the proportion of expensive glass components in the glass composition of the optical glass.

One embodiment of the present invention provides an optical glass having a low proportion of expensive glass components in the glass composition, a high refractive index, and low dispersion. Solution to the problem

One embodiment of the present invention relates to an optical glass, in which, in a glass composition expressed in cation %, the Ta ⁵⁺ content is in the range of 0-5 cation %, the cation ratio of the Ti ⁴⁺ content relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.60-1.00, the cation ratio of the total content of Si ⁴⁺ and B ³⁺ relative to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ +B ³⁺ )/(La ³⁺ +Gd ³⁺ +Y ³⁺ )) is in the range of 0.50-2.50, the total content of Si ⁴⁺ and B ³⁺ relative to the total content of Ti 3+ The cation ratio of the total content of ^{Ti 4+} , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.50~40.00. The cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.50~30.00. The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of La ³⁺ and Y The cation ratio of the total content of Mg ^{2+ +} Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ / (La ³⁺ +Y ³⁺ )) is in the range of 0.00~1.50. The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ) / (Si ⁴⁺ +B ³⁺ )) is in the range of 0.00~1.00. The total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr The cation ratio of the total content of O ⁴⁺ and Ti ⁴⁺ ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ + Ti ⁴⁺ )) is in the range of 0.000~0.080, the refractive index nd of the optical glass is in the range of 1.8000~2.0000, and the Abbe number νd is in the range of 25.0~45.0.

Among the raw material compounds of optical glass, Ta compounds, Gd compounds, Nb compounds and W compounds are relatively expensive. In contrast, in the above optical glass, the Ta ⁵⁺ content is suppressed within the above range. Furthermore, the proportions of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ in the glass composition are also suppressed. Specifically, with respect to Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , the cation ratio ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is within the above range. That is, in the glass composition of the above optical glass, the proportions of Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , which are expensive glass components, are low. By adjusting the glass composition in such a glass composition so as to satisfy the above-mentioned various cation ratios, an optical glass having a high refractive index nd within the above-mentioned range and an Abbe number νd within the above-mentioned range (i.e., low dispersion) can be obtained. [Effect of the Invention]

According to one embodiment of the present invention, an optical glass having optical properties (nd and νd) useful as a material for an optical element and contributing to the cost reduction of an optical element can be provided. In addition, according to one embodiment, an optical glass having one or more physical properties of high glass stability, low specific gravity, and low coloring (high transmittance) can be provided. In addition, according to one embodiment of the present invention, a glass raw material for press molding, an optical element blank, and an optical element formed of the optical glass can be provided.

[Optical glass] In the present invention and the specification, unless otherwise specified, the content and total content of cationic components are expressed as cation %, and unless otherwise specified, the content and total content of anionic components are expressed as anion %. Here, "cation %" is a value calculated by "(the number of cations of concern/the total number of cations of glass components) × 100", which indicates the molar percentage of the amount of cations of concern relative to the total amount of cationic components. In addition, "anion %" is a value calculated by "(the number of anions of concern/the total number of anions of glass components) × 100", which indicates the molar percentage of the amount of anions of concern relative to the total amount of anionic components. The molar ratio of the contents of the cationic components is equal to the content ratio of the cationic component of interest expressed in cation %, and the molar ratio of the contents of the anionic components is equal to the content ratio of the anionic component of interest expressed in anion %. The molar ratio of the content of the cationic component to the content of the anionic component is the ratio of the contents of the components of interest (expressed in mol %) when the total amount of all cationic components and all anionic components is set to 100 mol %. The content of each component can be quantified by a known method, such as inductively coupled plasma emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), ion chromatography, etc. In the present invention and this specification, the content of a constituent is 0%, or it is not contained or not introduced, which means that the constituent is not substantially contained, and the content of the constituent is below the impurity level. Below the impurity level means, for example, less than 0.01%.

Hereinafter, the above-mentioned optical glass (sometimes simply referred to as "glass") will be described in more detail.

<Glass composition> In the above optical glass, the Ta ⁵⁺ content is in the range of 0~5 cation %, and the content of Ta ^5+, which is an expensive glass component, is small. From the perspective of further cost reduction of optical elements, the Ta ⁵⁺ content is preferably 4% or less, more preferably 3% or less, further preferably 2% or less, further preferably 1% or less, and further preferably no Ta ⁵⁺ is contained.

In the optical glass, the cation ratio of the total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ⁴⁺ ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ + La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is in the range of 0.000 to 0.080. That is, the proportion of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ in the glass composition of the optical glass is low. From the perspective of further reducing the cost of optical components, the above cation ratio ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is preferably 0.070 or less, more preferably 0.060 or less, further preferably 0.050 or less, further preferably 0.045 or less, further preferably 0.040 or less, further preferably 0.035 or less, further preferably 0.030 or less, further preferably 0.025 or less, 0.020 or less, 0.015 or less, 0.010 or less, 0.007 or less, 0.005 or less, 0.004 or less, 0.003 or less, 0.002 or less, or 0.001 or less, and further preferably 0.000. That is, it is further preferably free of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ .

From the viewpoint of reducing the cost of optical elements and reducing the specific gravity of glass, in the above optical glass, the total content of Gd ³⁺ and W ⁶⁺ (Gd ³⁺ +W ⁶⁺ ) is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The above total content (Gd ³⁺ +W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

In addition, in the above-mentioned optical glass, the cation ratio of the total content of Gd ³⁺ and W ⁶⁺ to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr ⁴⁺ and Ti ⁴⁺ ((Gd ³⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ + La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is preferably in the range of 0.000~0.080. From the perspective of further cost reduction of optical elements and low specific gravity of glass, the above-mentioned cation ratio ((Gd ³⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is preferably 0.070 or less, more preferably 0.060 or less, further preferably 0.050 or less, further preferably 0.045 or less, further preferably 0.040 or less, further preferably 0.035 or less, further preferably 0.030 or less, further preferably 0.025 or less, further preferably 0.020 or less, further preferably 0.015 or less, further preferably 0.010 or less, particularly preferably 0.007 or less, further particularly preferably 0.005 or less, further particularly preferably 0.004 or less, further particularly preferably 0.003 or less, further particularly preferably 0.002 or less, further particularly preferably 0.001 or less. The cation ratio ((Gd ³⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is particularly preferably 0.000. That is, the optical glass particularly preferably does not contain Gd ³⁺ and W ⁶⁺ .

Si ⁴⁺ and B ³⁺ are network-forming components of glass. From the viewpoint of improving glass stability, the total content of Si ⁴⁺ and B ³⁺ (Si ⁴⁺ +B ³⁺ ) is preferably 25% or more, more preferably 27% or more, further preferably 30% or more, further preferably 33% or more, further preferably 35% or more, further preferably 37% or more, further preferably 38% or more, further preferably 39% or more, further preferably 40% or more, further preferably 41% or more, further preferably 42% or more. On the other hand, from the perspective of suppressing the decrease in refractive index, the above-mentioned total content (Si ⁴⁺ +B ³⁺ ) is preferably less than 55%, more preferably less than 53%, further preferably less than 50%, further preferably less than 49%, further preferably less than 48%, further preferably less than 47%, further preferably less than 46%, further preferably less than 45%, and further preferably less than 44%.

From the viewpoint of further improving the glass stability of the above optical glass as a high refractive index and low dispersion glass, and from the viewpoint of further improving the refractive index, the cation ratio of the B ³⁺ content to the total content of Si ⁴⁺ and B ³⁺ (B ³⁺ /(Si ⁴⁺ +B ³⁺ )) is preferably 0.20 or more, more preferably 0.30 or more, further preferably 0.40 or more, further preferably 0.50 or more, further preferably 0.55 or more, further preferably 0.60 or more, further preferably 0.65 or more, further preferably 0.67 or more, further preferably 0.69 or more, further preferably 0.70 or more, further preferably 0.71 or more, particularly preferably 0.72 or more, and further particularly preferably 0.73 or more. In addition, from the same viewpoint, the above-mentioned cation ratio (B ³⁺ /(Si ⁴⁺ +B ³⁺ )) is preferably 0.95 or less, more preferably 0.90 or less, further preferably 0.85 or less, further preferably 0.83 or less, further preferably 0.80 or less, further preferably 0.79 or less, further preferably 0.78 or less, further preferably 0.77 or less, further preferably 0.76 or less, further preferably 0.75 or less, and particularly preferably 0.74 or less. From the viewpoint of improving the solubility of the glass, it is also preferred that the above-mentioned cation ratio (B ³⁺ /(Si ⁴⁺ +B ³⁺ )) is above the lower limit exemplified above. In terms of increasing the viscosity of the glass during melting, it is also preferred that the cation ratio (B ³⁺ /(Si ⁴⁺ +B ³⁺ )) be below the upper limit listed above. Furthermore, from the viewpoint of reducing changes in the glass composition due to volatility during melting and changes in optical properties caused thereby, from the viewpoint of improving one or more of the chemical durability, weather resistance and machinability of the glass, and from the viewpoint of reducing coloration, it is preferred that the cation ratio (B ³⁺ /(Si ⁴⁺ +B ³⁺ )) be below the upper limit listed above.

The total content of Si ⁴⁺ and B ³⁺ as network-forming components of glass is as described above. From the viewpoint of improving the stability, melting property, formability, chemical durability, weather resistance, machinability, etc. of the glass and reducing coloring, the preferred ranges of the Si ⁴⁺ content and the B ³⁺ content are as follows. The Si ⁴⁺ content is preferably 2% or more, more preferably 4% or more, further preferably 6% or more, further preferably 8% or more, further preferably 10% or more. In addition, the Si ⁴⁺ content is preferably 20% or less, more preferably 18% or less, further preferably 16% or less, further preferably 14% or less, further preferably 12% or less. The B ³⁺ content is preferably 20% or more, more preferably 22% or more, further preferably 24% or more, further preferably 26% or more, further preferably 28% or more, further preferably 29% or more. In addition, the B ³⁺ content is preferably 50% or less, more preferably 45% or less, further preferably 40% or less, further preferably 38% or less, further preferably 36% or less, further preferably 34% or less, further preferably 32% or less.

La ³⁺ , Gd ³⁺ and Y ³ are components that have the effect of suppressing the decrease of Abbe number and increasing the refractive index. In addition, these components also have the effect of improving the chemical durability and/or weather resistance of glass and increasing the glass transition temperature. From the viewpoint of suppressing the decrease of refractive index, the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ (La ³⁺ +Gd ³⁺ +Y ³⁺ ) is preferably 20% or more, more preferably 22% or more, further preferably 24% or more, further preferably 26% or more, further preferably 28% or more, further preferably 30% or more, further preferably 31% or more, further preferably 32% or more, further preferably 33% or more, further preferably 34% or more. In addition, from the viewpoint of suppressing the reduction of the chemical durability and/or weather resistance of the glass, and from the viewpoint of suppressing the reduction of the glass transition temperature, it is also preferred that the total content (La ³⁺ +Gd ³⁺ +Y ³⁺ ) is greater than the lower limit exemplified above. If the glass transition temperature is reduced, the glass becomes easily broken when mechanical processing (cutting, cutting, grinding, polishing, etc.) is performed on the glass (reduction of machinability). Therefore, suppressing the reduction of the glass transition temperature will lead to improvement of machinability. From the above viewpoints, it is also preferred that the total content (La ³⁺ +Gd ³⁺ +Y ³⁺ ) is greater than the lower limit exemplified above. On the other hand, from the perspective of improving glass stability, the above total content (La ³⁺ +Gd ³⁺ +Y ³⁺ ) is preferably less than 60%, more preferably less than 55%, further preferably less than 50%, further preferably less than 47%, further preferably less than 45%, further preferably less than 44%, further preferably less than 43%, further preferably less than 42%, further preferably less than 41%, further preferably less than 40%, further preferably less than 39%, particularly preferably less than 38%, and further preferably less than 37%.

From the perspective of improving glass stability and lowering specific gravity, in the above-mentioned optical glass, the cation ratio of the total content of Si ⁴⁺ and B ³⁺ as network-forming components of the glass relative to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ +B ³⁺ )/(La ³⁺ +Gd ³⁺ +Y ³⁺ )) is greater than 0.50, preferably greater than 0.60, more preferably greater than 0.70, further preferably greater than 0.80, further preferably greater than 0.90, further preferably greater than 0.95, further preferably greater than 0.97, and further preferably greater than 1.00. From the perspective of high refractive index, the above-mentioned cation ratio ((Si ⁴⁺ +B ³⁺ )/(La ³⁺ +Gd ³⁺ +Y ³⁺ )) is less than 2.50, preferably less than 2.40, more preferably less than 2.30, further preferably less than 2.20, further preferably less than 2.10, further preferably less than 2.00, further preferably less than 1.90, further preferably less than 1.80, further preferably less than 1.70, further preferably less than 1.60, further preferably less than 1.50, further preferably less than 1.40, and particularly preferably less than 1.30.

The preferred ranges of the contents of each component of La ³⁺ , Gd ³⁺ and Y ³⁺ are as follows: The La ³⁺ content is preferably 20% or more, more preferably 21% or more, further preferably 22% or more, further preferably 23% or more, further preferably 24% or more, further preferably 25% or more, further preferably 26% or more. In addition, the La ³⁺ content is preferably less than 60%, more preferably less than 57%, further preferably less than 55%, further preferably less than 53%, further preferably less than 50%, further preferably less than 47%, further preferably less than 45%, further preferably less than 43%, further preferably less than 40%, further preferably less than 37%, further preferably less than 35%, particularly preferably less than 34%, more particularly preferably less than 33%, further particularly preferably less than 32%, further particularly preferably less than 31%, and further particularly preferably less than 30%. The Gd ³⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The Gd ³⁺ content can be 0% or more. From the perspective of further reducing the cost and lowering the specific gravity of the optical element, the particularly preferred Gd ³⁺ content is 0%, that is, it does not contain Gd ³⁺ . From the perspective of improving solubility and improving glass stability, the Y ³⁺ content is preferably 0% or more, more preferably 1% or more, further preferably 2% or more, further preferably 3% or more, further preferably 4% or more, further preferably 5% or more, further preferably 6% or more, further preferably 7% or more. In addition, the Y ³⁺ content is preferably 30% or less, more preferably 25% or less, further preferably 20% or less, further preferably 17% or less, further preferably 15% or less, further preferably 14% or less, further preferably 13% or less, further preferably 12% or less, further preferably 11% or less, further preferably 10% or less, further preferably 9% or less.

Yb has a large atomic weight among rare earth elements and tends to increase the specific gravity of glass. In addition, Yb has absorption in the near-infrared region. On the other hand, replacement lenses for single-lens reflex cameras and surveillance camera lenses are expected to have high transmittance in the near-infrared region. Therefore, in order to produce glass useful for the production of these lenses, it is desired to have a low Yb ³⁺ content. From the above viewpoints, the Yb ³⁺ content is preferably less than 10%, more preferably less than 5%, further preferably less than 3%, and further preferably less than 1%. In addition, the Yb ³⁺ content can be greater than 0%, and the most preferred Yb ³⁺ content is 0%, that is, no Yb ³⁺ is contained.

Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ are components that have the effect of increasing the refractive index, and when contained in an appropriate amount, they also have the effect of improving the glass stability. From the viewpoint of improving the glass stability, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ) is preferably 0% or more, more preferably 1% or more, further preferably 3% or more, further preferably 5% or more, further preferably 7% or more, further preferably 8% or more, further preferably 9% or more, further preferably 10% or more, further preferably 11% or more. On the other hand, from the perspective of maintaining glass stability and suppressing the decrease in Abbe number, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ) is preferably less than 30%, more preferably less than 25%, further preferably less than 20%, further preferably less than 17%, further preferably less than 16%, further preferably less than 15%, further preferably less than 14%, further preferably less than 13%, and further preferably less than 12%.

From the viewpoint of maintaining glass stability and suppressing high dispersion and reducing coloring, in the above optical glass, the cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 0.50 or more, preferably 0.60 or more, further preferably 1.00 or more, further preferably 1.40 or more, further preferably 1.80 or more, further preferably 2.00 or more, further preferably 2.20 or more, further preferably 2.40 or more, further preferably 2.50 or more, further preferably 2.60 or more, further preferably 2.70 or more, further preferably 2.80 or more, and particularly preferably 2.90 or more. On the other hand, from the viewpoint of suppressing the decrease in refractive index and maintaining glass stability and the viewpoint of low specific gravity, in the above-mentioned optical glass, the above-mentioned cation ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 30.00 or less, preferably 25.00 or less, more preferably 20.00 or less, further preferably 15.00 or less, further preferably 10.00 or less, further preferably 8.00 or less, further preferably 7.00 or less, further preferably 6.00 or less, further preferably 5.00 or less, further preferably 4.00 or less, further preferably 3.50 or less, and particularly preferably 3.20 or less.

From the viewpoint of increasing the refractive index, in the above optical glass, the cation ratio of the total content of Si ⁴⁺ and B ³⁺ as the network forming components of the glass relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 40.00 or less, preferably 35.00 or less, more preferably 30.00 or less, further preferably 25.00 or less, further preferably 20.00 or less, further preferably 15.00 or less, further preferably 10.00 or less, further preferably 7.00 or less, further preferably 6.00 or less, further preferably 5.00 or less, further preferably 4.50 or less, further preferably 4.00 or less, particularly preferably 3.90 or less, and further preferably 3.80 or less. On the other hand, from the viewpoint of suppressing high dispersion, maintaining glass stability and reducing coloration, the above cation ratio ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 0.50 or more, preferably 0.80 or more, more preferably 1.00 or more, further preferably 1.40 or more, further preferably 1.80 or more, further preferably 2.20 or more, further preferably 2.60 or more, further preferably 2.80 or more, further preferably 2.90 or more, further preferably 3.00 or more, further preferably 3.10 or more, particularly preferably 3.20 or more, more particularly preferably 3.30 or more, further particularly preferably 3.40 or more, further particularly preferably 3.50 or more, further particularly preferably 3.60 or more.

From the viewpoint of maintaining glass stability and reducing coloring, in the above-mentioned optical glass, the cation ratio of Ti ⁴⁺ content relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.60~1.00. The above-mentioned cation ratio (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is preferably 0.70 or more, more preferably 0.75 or more, further preferably 0.80 or more, further preferably 0.85 or more, further preferably 0.90 or more, further preferably 0.95 or more, and further preferably 1.00.

The preferred ranges of the contents of each component of Ti ⁴⁺ , Nb ⁵⁺ and W ⁶⁺ are as follows. The Ti ⁴⁺ content is preferably 0% or more, more preferably 2% or more, further preferably 4% or more, further preferably 5% or more, further preferably 6% or more, further preferably 7% or more, further preferably 8% or more, further preferably 9% or more, further preferably 10% or more. In addition, the Ti ⁴⁺ content is preferably 30% or less, more preferably 25% or less, further preferably 23% or less, further preferably 20% or less, further preferably 18% or less, further preferably 16% or less, further preferably 15% or less, further preferably 14% or less, further preferably 13% or less, further preferably 12% or less. The Nb ⁵⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The Nb ⁵⁺ content may be 0% or more. From the perspective of further reducing the cost of optical components, the Nb ⁵⁺ content is preferably 0%, i.e., Nb ⁵⁺ is not contained. The W ⁶⁺ content is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The ^{W 6+} content may be 0% or more. From the perspective of further reducing the cost of optical components, reducing the specific gravity of glass, and reducing coloring, the W ⁶⁺ content is preferably 0%, i.e., W ⁶⁺ is not contained.

From the perspective of reducing the cost of optical components and reducing the specific gravity of glass, the total content of Nb ⁵⁺ and W ⁶⁺ (Nb ⁵⁺ +W ⁶⁺ ) is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The above total content (Nb ⁵⁺ +W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

From the perspective of reducing the cost of optical elements and reducing the specific gravity of glass, the total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ (Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ ) is preferably 8% or less, more preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. The above total content (Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ ) can be 0% or more, and particularly preferably 0%.

Bi ³⁺ is a component that increases the refractive index and decreases the Abbe number. In addition, it is also a component that easily causes an increase in specific gravity and coloring. From the perspective of producing glass having the above-mentioned optical properties with less coloring and low specific gravity, the preferred range of Bi ³⁺ content is as follows. The Bi ³⁺ content is preferably less than 20%, more preferably less than 15%, further preferably less than 10%, further preferably less than 7%, further preferably less than 5%, further preferably less than 3%, further preferably less than 1%. In addition, the Bi ³⁺ content can be greater than 0% or 0%.

From the viewpoint of maintaining glass stability, as well as the viewpoint of high refractive index and low dispersion, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ) is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the above-mentioned total content (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ) may be 0% or more. In one embodiment, the above total content (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ ) is preferably 0%.

From the perspective of improving the solubility of glass, maintaining glass stability and inhibiting an excessive increase in the glass transition temperature, the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ (Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ) is preferably above 0%, more preferably above 1%, further preferably above 2%, further preferably above 3%, and further preferably above 4%. On the other hand, from the perspective of maintaining glass stability, as well as the perspective of high refractive index and low dispersion, the above total content (Mg2 ⁺ +Ca2 ⁺ + ^Sr2+ +Ba2 ⁺ +Zn2 ⁺ ) is preferably less than 30%, more preferably less than 25%, further preferably less than 20%, further preferably less than 15%, further preferably less than 13%, further preferably less than 10%, further preferably less than 9%, further preferably less than 8%, further preferably less than 7%, and further preferably less than 6%.

From the viewpoint of maintaining glass stability, increasing the refractive index and reducing the dispersion, in the above optical glass, the cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of La ³⁺ and Y ³⁺ ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(La ³⁺ +Y ³⁺ )) is 1.50 or less, preferably 1.30 or less, more preferably 1.00 or less, further preferably 0.70 or less, further preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.35 or less, further preferably 0.30 or less, further preferably 0.25 or less, further preferably 0.24 or less, further preferably 0.23 or less, further preferably 0.22 or less, particularly preferably 0.21 or less, more particularly preferably 0.20 or less, further particularly preferably 0.19 or less, further particularly preferably 0.18 or less, further particularly preferably 0.17 or less. In addition, the above cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(La ³⁺ +Y ³⁺ )) is 0.00 or more. From the viewpoint of improving the solubility of the glass, maintaining the glass stability and suppressing the excessive increase in the glass transition temperature, it is preferably 0.00 or more, more preferably 0.01 or more, further preferably 0.02 or more, further preferably 0.03 or more, further preferably 0.04 or more, further preferably 0.05 or more, further preferably 0.06 or more, further preferably 0.07 or more, further preferably 0.08 or more, further preferably 0.09 or more, further preferably 0.10 or more, particularly preferably 0.11 or more, more particularly preferably 0.12 or more, further particularly preferably 0.13 or more.

From the perspective of maintaining glass stability and reducing specific gravity, in the above optical glass, the cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(Si ⁴⁺ +B ³⁺ )) is 1.00 or less, preferably 0.70 or less, more preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.35 or less, further preferably 0.30 or less, further preferably 0.25 or less, further preferably 0.24 or less, further preferably 0.23 or less, further preferably 0.22 or less, further preferably 0.21 or less, further preferably 0.20 or less, particularly preferably 0.19 or less, more particularly preferably 0.18 or less, further particularly preferably 0.17 or less, further particularly preferably 0.16 or less. In addition, the above-mentioned cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(Si ⁴⁺ +B ³⁺ )) is greater than 0.00. From the viewpoint of improving the solubility of the glass and suppressing the excessive increase in the glass transition temperature, it is preferably greater than 0.01, more preferably greater than 0.02, further preferably greater than 0.03, further preferably greater than 0.04, further preferably greater than 0.05, further preferably greater than 0.06, further preferably greater than 0.07, further preferably greater than 0.08, and further preferably greater than 0.09.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ and Ba ²⁺ are all components that have the effect of improving the solubility of glass. However, when the content of these components increases, there is a tendency for the glass stability to decrease. From the above viewpoints, the preferred range of the content of each of these components is as follows. The Mg ²⁺ content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the Mg ²⁺ content can be 0% or more, or 0%. The ^Ca2 + content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the ^Ca2 + content may be 0% or more. The Sr ² + content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the Sr ² + content may be 0% or more. The ^Ba2 + content is preferably 20% or less, more preferably 15% or less, further preferably 10% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the ^Ba2 + content may be 0% or more.

From the perspective of improving the melting property, stability, formability, machinability, etc. of the glass and realizing the above-mentioned optical properties, the preferred range of the Zn ²⁺ content is as follows. The Zn ²⁺ content can be 0% or more, preferably 1% or more, more preferably 2% or more, further preferably 3% or more, and further preferably 4% or more. In addition, the Zn ²⁺ content is preferably 30% or less, more preferably 25% or less, further preferably 20% or less, further preferably 15% or less, further preferably 13% or less, further preferably 10% or less, further preferably 9% or less, further preferably 8% or less, further preferably 7% or less, and further preferably 6% or less.

Regarding Zn ²⁺ , from the perspective of improving glass stability and achieving the above-mentioned optical properties, the cation ratio of Zn ²⁺ content to the total content of La ³⁺ and Y ³⁺ (Zn ²⁺ /(La ³⁺ +Y ³⁺⁾ )) is preferably 0.66 or less, more preferably 0.60 or less, further preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.35 or less, further preferably 0.30 or less, further preferably 0.25 or less, further preferably 0.23 or less, further preferably 0.22 or less, further preferably 0.21 or less, further preferably 0.20 or less, particularly preferably 0.19 or less, more particularly preferably 0.18 or less, further particularly preferably 0.17 or less. In addition, from the viewpoint of suppressing the decrease in glass transition temperature (and the improvement in machinability based on this) and improving chemical durability, it is also preferred that the above-mentioned cation ratio (Zn ²⁺ /(La ³⁺ +Y ³⁺ )) is small. The above-mentioned cation ratio (Zn ²⁺ /(La ³⁺ +Y ³⁺ )) may be greater than 0.00, and is preferably greater than 0.00 from the viewpoint of improving solubility and suppressing an excessive increase in glass transition temperature. The above-mentioned cation ratio (Zn ²⁺ /(La ³⁺ +Y ³⁺ )) is preferably 0.02 or more, further preferably 0.04 or more, further preferably 0.06 or more, further preferably 0.07 or more, further preferably 0.08 or more, further preferably 0.09 or more, further preferably 0.10 or more, further preferably 0.11 or more, further preferably 0.12 or more, further preferably 0.13 or more.

From the perspective of improving glass stability and achieving the above-mentioned optical properties, the cation ratio of the total content of Zn ²⁺ and Ba ²⁺ to the content of La ³⁺ ((Zn ²⁺ +Ba ²⁺ )/La ³⁺ ) is preferably above 0.00, more preferably above 0.02, further preferably above 0.04, further preferably above 0.06, further preferably above 0.08, further preferably above 0.10, further preferably above 0.11, further preferably above 0.12, further preferably above 0.13, further preferably above 0.14, further preferably above 0.15, and particularly preferably above 0.16. From the viewpoint of improving solubility, lowering specific gravity and suppressing an excessive increase in the glass transition temperature, the above-mentioned cation ratio ((Zn ²⁺ +Ba ²⁺ )/La ³⁺ ) is preferably 0.66 or less, more preferably 0.60 or less, further preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.35 or less, further preferably 0.30 or less, further preferably 0.27 or less, further preferably 0.25 or less, further preferably 0.24 or less, further preferably 0.23 or less, further preferably 0.22 or less, particularly preferably 0.21 or less, and further preferably 0.20 or less.

From the perspective of improving glass stability and achieving the above-mentioned optical properties, the cation ratio of the total content of Zn ²⁺ and Ba ²⁺ to the total content of La ³⁺ and Y ³⁺ ((Zn ²⁺ +Ba ²⁺ )/(La ³⁺ +Y ³⁺ )) is preferably above 0.00, more preferably above 0.02, further preferably above 0.04, further preferably above 0.06, further preferably above 0.07, further preferably above 0.08, further preferably above 0.09, further preferably above 0.10, further preferably above 0.11, further preferably above 0.12, further preferably above 0.13. From the viewpoint of improving solubility, lowering specific gravity and suppressing an excessive increase in the glass transition temperature, the above-mentioned cation ratio ((Zn ²⁺ +Ba ²⁺ )/(La ³⁺ +Y ³⁺ )) is preferably 0.66 or less, more preferably 0.60 or less, further preferably 0.50 or less, further preferably 0.40 or less, further preferably 0.35 or less, further preferably 0.30 or less, further preferably 0.25 or less, further preferably 0.23 or less, further preferably 0.22 or less, further preferably 0.21 or less, particularly preferably 0.20 or less, more particularly preferably 0.19 or less, further particularly preferably 0.18 or less, further particularly preferably 0.17 or less.

Li ⁺ has a strong effect of lowering the glass transition temperature. Therefore, when its content increases, the machinability tends to decrease. In addition, the glass stability, chemical durability and weather resistance also tend to decrease. Therefore, the Li ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the Li ⁺ content can be 0% or more.

Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ all have the effect of improving the melting property of glass, but when their contents increase, the glass stability, chemical durability, weather resistance and machinability tend to decrease. Therefore, the preferred ranges of the contents of Na ⁺ , K ⁺ , Rb ⁺ and Cs ⁺ are as follows. The Na ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the Na ⁺ content may be 0% or more, or 0%. The K ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the K ⁺ content may be 0% or more or 0%. The Rb ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the Rb ⁺ content may be 0% or more or 0%. The Cs ⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, further preferably 3% or less, further preferably 2% or less, further preferably 1% or less. In addition, the Cs ⁺ content may be 0% or more, or 0%.

Al ³⁺ is a component that improves the chemical durability and weather resistance of glass. However, when the Al ³⁺ content increases, a tendency of a decrease in the refractive index, a decrease in the glass stability, and a decrease in the solubility is sometimes observed. Taking the above aspects into consideration, the preferred range of the Al ³⁺ content is as follows. The Al ³⁺ content is preferably less than 10%, more preferably less than 8%, further preferably less than 6%, further preferably less than 4%, further preferably less than 3%, further preferably less than 2%, and further preferably less than 1%. In addition, the Al ³⁺ content can be greater than 0% or 0%.

Zr ⁴⁺ is a component that has the effect of increasing the refractive index. When contained in an appropriate amount, it also has the effect of improving the stability of the glass. In addition, Zr ⁴⁺ also has the effect of making the glass less likely to break during mechanical processing by increasing the glass transition temperature. From the perspective of obtaining these effects well, the Zr ⁴⁺ content is preferably 0% or more, more preferably 1% or more, further preferably 2% or more, further preferably 3% or more, and further preferably 4% or more. From the viewpoint of improving glass stability, the Zr ⁴⁺ content is preferably 15% or less, more preferably 13% or less, further preferably 10% or less, further preferably 9% or less, further preferably 8% or less, further preferably 7% or less, further preferably 6% or less, further preferably 5% or less.

P5 ⁺ is a component that lowers the refractive index and also a component that lowers the glass stability, but if introduced in a very small amount, it may improve the glass stability. From the perspective of obtaining a glass having the above-mentioned optical properties and excellent glass stability, the preferred range of the P5 ⁺ content is as follows. The P5 ⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the P5 ⁺ content may be 0% or more, or 0%.

Ga ³⁺ , In ³⁺ , Sc ³⁺ and Hf ⁴⁺ all have the function of increasing the refractive index. However, these components are not necessary components for obtaining the above-mentioned glass. The preferred ranges of the contents of Ga ³⁺ , In ³⁺ , Sc ³⁺ and Hf ⁴⁺ are as follows. The Ga ³⁺ content is preferably less than 5%, more preferably less than 4%, further preferably less than 3%, further preferably less than 2%, and further preferably less than 1%. In addition, the Ga ³⁺ content can be greater than 0% or 0%. The In ³⁺ content is preferably less than 5%, more preferably less than 4%, further preferably less than 3%, further preferably less than 2%, and further preferably less than 1%. In addition, the In ³⁺ content can be greater than 0% or 0%. The Sc ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the Sc ³⁺ content may be 0% or more, or 0%. The Sc ³⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the Sc ³⁺ content may be 0% or more, or 0%. The Hf ⁴⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and further preferably 2% or less. In addition, the Hf ⁴⁺ content may be 0% or more, or 0%.

Lu ³⁺ has the effect of increasing the refractive index, but it is also a component that causes the specific gravity of the glass to increase. In addition, Lu is a heavy rare earth element like Gd and Yb. Therefore, from the perspective of stable supply of glass, it is desired that the Lu ³⁺ content is small. From the above perspectives, the Lu ³⁺ content is preferably less than 10%, more preferably less than 8%, further preferably less than 6%, further preferably less than 4%, and further preferably less than 2%. In addition, the Lu ³⁺ content can be more than 0% or 0%.

Ge ⁴⁺ has the effect of increasing the refractive index, but from the perspective of further reducing the cost of optical elements, the Ge ⁴⁺ content is preferably 10% or less, more preferably 8% or less, further preferably 6% or less, further preferably 4% or less, and further preferably 2% or less. In addition, the Ge ⁴⁺ content can be 0% or more, or 0%.

Te ⁴⁺ is a component that increases the refractive index, but from the perspective of environmental concerns, it is preferred that the Te ⁴⁺ content is low. The Te ⁴⁺ content is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further preferably 2% or less, and further preferably 1% or less. In addition, the Te ⁴⁺ content may be 0% or more, or 0%.

Pb, As, Cd, Tl, Be and Se are toxic. Therefore, it is preferred not to contain these elements, that is, not to introduce these elements into the glass as glass components. U, Th and Ra are all radioactive elements. Therefore, it is preferred not to contain these elements, that is, not to introduce these elements into the glass as glass components. V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm and Ce will increase the coloring of the glass or become a source of fluorescence, and are not preferred as elements contained in glass for optical components. Therefore, it is preferred not to contain these elements, that is, not to introduce these elements into the glass as glass components.

Sb and Sn are optional elements that function as clarifiers. The Sb content of the optical glass can be, for example, less than 0.40%, less than 0.20%, less than 0.10%, less than 0.05%, less than 0.02%, or less than 0.01% in terms of the content of Sb ³⁺ . ^The Sb ³⁺ content can be greater than or equal to 0.00%. The Sn content of the optical glass can be, for example, less than 0.40%, less than 0.20%, less than 0.10%, less than 0.05%, less than 0.02%, or less than 0.01% in terms of the content of Sn 2+. The Sb ³⁺ content can be greater than or equal to 0.00%.

The above describes the cationic components. Next, the anionic components will be described.

The optical glass may be an oxide glass, and may contain O ^2- as an anion component. The O ^2- content is preferably 95.0 anion % or more, more preferably 97.0 anion % or more, further preferably 98.0 anion % or more, further preferably 99.0 anion % or more, further preferably 99.5 anion % or more, further preferably 100 anion %.

As anion components other than ^{O2- , F-} , ^Cl- , ^Br- , and ^I- can be exemplified. However, ^F- , ^Cl- , ^Br- , and ^I- are all easily volatilized during melting of glass. Due to the volatilization of these components, there is a tendency to cause changes in the physical properties of the glass, decrease the homogeneity of the glass, or increase the consumption of the melting equipment. Therefore, it is preferred to suppress the total content of ^F- , ^Cl- , Br- ^, and ^I- to an amount obtained by subtracting the content of ^O2- from 100% of anions.

<Glass properties> (Refractive index nd, Abbe number νd) The above optical glass is a high refractive index, low dispersion glass having a refractive index nd in the range of 1.8000 to 2.0000 and an Abbe number νd in the range of 25.0 to 45.0. From the perspective of usefulness as a material for optical elements, the preferred ranges of the refractive index nd and the Abbe number νd are as follows. The refractive index nd is 1.8000 or more, preferably 1.8500 or more, more preferably 1.8600 or more, further preferably 1.8700 or more, further preferably 1.8800 or more, further preferably 1.8850 or more, further preferably 1.8900 or more, further preferably 1.8950 or more, further preferably 1.9000 or more, further preferably 1.9050 or more, further preferably 1.9070 or more, further preferably 1.9100 or more. In addition, the refractive index nd is 2.0000 or less, preferably 1.9800 or less, more preferably 1.9700 or less, further preferably 1.9600 or less, further preferably 1.9500 or less, further preferably 1.9400 or less, further preferably 1.9300 or less, further preferably 1.9250 or less, further preferably 1.9200 or less, further preferably 1.9150 or less, further preferably 1.9120 or less. The Abbe number νd is a value indicating a property related to dispersion, and is expressed as νd=(nd-1)/(nF-nC) using the refractive indices nd, nF, and nC under d-rays, F-rays, and C-rays, respectively. The Abbe number is 45.0 or less, preferably 40.0 or less, more preferably 38.0 or less, further preferably 37.0 or less, further preferably 36.0 or less, further preferably 35.8 or less, further preferably 35.6 or less, further preferably 35.4 or less. In addition, the Abbe number νd is 25.0 or more, preferably 27.0 or more, more preferably 30.0 or more, further preferably 32.0 or more, further preferably 33.0 or more, further preferably 34.0 or more, further preferably 34.6 or more, further preferably 34.8 or more, further preferably 35.0 or more, further preferably 35.1 or more, further preferably 35.2 or more. In addition, the refractive index nd and the Abbe number νd preferably satisfy one or more of the following relationships. nd≥2.3700-0.0140×νd nd≥2.1450-0.0070×νd nd≥2.3900-0.0140×νd nd≥2.1510-0.0070×νd nd≥2.3960-0.0140×νd nd≥2.1550-0.0070×νd nd≥2.4000-0.014 0×νd nd≤2.4900-0.0140×νd nd≤2.4500-0.0140×νd nd≤2.4300-0.0140×νd nd≤2.4200-0.0140×νd In the present invention and this specification, unless otherwise specified, "refractive index" means "refractive index nd" and "Abbe number" means "Abbe number νd".

(Partial dispersion characteristics Pg, F) From the perspective of chromatic aberration correction, the above optical glass is preferably a glass with a small partial dispersion ratio when the Abbe number νd is fixed.

Here, the partial dispersion ratio Pg,F can be expressed as (ng-nF)/(nF-nc) using the refractive indices ng, nF, and nc under g-ray, F-ray, and c-ray.

From the perspective of providing high-refractive-index, low-dispersion glass suitable for high-level chromatic aberration correction, the preferred range of the partial dispersion ratio Pg,F of the above optical glass is as follows.

The partial dispersion ratio Pg,F is preferably less than 0.6000, more preferably less than 0.5950, further preferably less than 0.5900, further preferably less than 0.5900, further preferably less than 0.5880. In addition, the partial dispersion ratio Pg,F is preferably greater than 0.5700, more preferably greater than 0.5800, further preferably greater than 0.5820, further preferably greater than 0.5830, further preferably greater than 0.5840.

(Liquid phase temperature LT)

From the perspective of inhibiting crystallization during glass manufacturing, the liquidus temperature LT of the optical glass is preferably below 1350°C, more preferably below 1300°C, further preferably below 1280°C, further preferably below 1270°C, further preferably below 1260°C, further preferably below 1250°C, further preferably below 1240°C, further preferably below 1230°C, further preferably below 1220°C, further preferably below 1210°C, further preferably below 1200°C. The liquidus temperature LT may be, for example, above 1150°C. It should be noted that the liquidus temperature is preferably low, so the liquidus temperature may also be less than 1150°C, and its lower limit is not particularly limited.

(Glass transition temperature Tg)

The glass transition temperature Tg of the optical glass is not particularly limited, but is preferably 630°C or higher from the viewpoint of machinability. By setting the glass transition temperature to 630°C or higher, the glass can be less likely to be broken during mechanical processing of the glass such as cutting, cutting, grinding, and polishing. From the viewpoint of machinability, the glass transition temperature Tg is preferably 640°C or higher, more preferably 650°C or higher, more preferably 660°C or higher, more preferably 670°C or higher, more preferably 680°C or higher, more preferably 690°C or higher, and more preferably 695°C or higher. On the other hand, from the viewpoint of reducing the burden on the annealing furnace and the forming mold, the glass transition temperature Tg is preferably below 800°C, more preferably below 780°C, further preferably below 760°C, further preferably below 740°C, further preferably below 730°C, further preferably below 720°C, further preferably below 710°C.

(Specific gravity, specific gravity/nd) In an optical element (lens) constituting an optical system, the refractive power is determined by the refractive index of the glass constituting the lens and the curvature of the optical functional surface of the lens (the surface where the light is incident and emitted to be controlled). If the curvature of the optical functional surface is to be increased, the thickness of the lens must also be increased. As a result, the lens becomes heavier. In contrast, if glass with a high refractive index is used, a large refractive power can be obtained even without increasing the curvature of the optical functional surface. It can be seen that if the refractive index can be increased while suppressing the increase in the specific gravity of the glass, it is possible to achieve a lightweight optical element with a certain refractive power. From the above viewpoints, the specific gravity of the optical glass is preferably 5.20 or less, more preferably 5.10 or less, further preferably 5.00 or less, further preferably 4.95 or less, further preferably 4.93 or less, further preferably 4.90 or less, further preferably 4.88 or less, further preferably 4.87 or less, further preferably 4.86 or less, further preferably 4.85 or less. The lower the specific gravity, the better from the viewpoint of lightening the optical element, and therefore, there is no particular lower limit on the specific gravity of the optical glass. In one embodiment, the specific gravity of the optical glass may be, for example, 4.30 or more, 4.40 or more, 4.50 or more, 4.60 or more, 4.70 or more, 4.75 or more, 4.77 or more, or 4.80 or more. In addition, from the same point of view, the value obtained by dividing the specific gravity of the optical glass by the refractive index nd (specific gravity/nd) is preferably 2.80 or less, more preferably 2.70 or less, further preferably 2.65 or less, further preferably 2.60 or less, further preferably 2.58 or less, further preferably 2.57 or less, further preferably 2.56 or less, and further preferably 2.55 or less. The smaller the value of "specific gravity/nd", the better it is from the viewpoint of reducing the weight of the optical element. Therefore, there is no particular lower limit on the value of "specific gravity/nd" of the optical glass. In one embodiment, the "specific gravity/nd" of the optical glass may be, for example, 2.20 or more, 2.30 or more, 2.40 or more, 2.45 or more, 2.47 or more, 2.48 or more, 2.49 or more, 2.50 or more, or 2.51 or more.

(Coloring λ5, λ70) The light transmittance of glass can be evaluated based on the coloring λ5, specifically, it refers to the suppression of the long wavelength of the light absorption end on the short wavelength side. Coloring λ5 refers to the wavelength at which the spectral transmittance (including surface reflection loss) of glass with a thickness of 10 mm from the ultraviolet region to the visible region reaches 5%. The λ5 shown in the embodiment described below is a value measured in the wavelength range of 250~700nm. In more detail, the spectral transmittance refers to, for example, the spectral transmittance obtained by incident light from a perpendicular direction to a glass sample with parallel planes polished to a thickness of 10.0±0.1mm, that is, Iout/Iin when the intensity of light incident on the glass sample is set to Iin and the intensity of light after passing through the glass sample is set to Iout. The absorption end on the short wavelength side of the spectral transmittance can be quantitatively evaluated based on the chromaticity λ5. When lenses are bonded together using a UV-curing adhesive to produce a bonded lens, the following operation can be performed: UV rays are irradiated to the adhesive through an optical element to cure the adhesive. From the perspective of efficiently curing the UV-curing adhesive, it is preferred that the absorption end on the short wavelength side of the spectral transmittance is within the short wavelength region. The chromaticity λ5 can be used as an indicator for quantitatively evaluating the absorption end on the short wavelength side. The optical glass may show a λ5 of preferably 370 nm or less, more preferably 367 nm or less, further preferably 365 nm or less, further preferably 363 nm or less, further preferably 362 nm or less, further preferably 361 nm or less, further preferably 360 nm or less, further preferably 359 nm or less, further preferably 358 nm or less. The lower the λ5, the better, and its lower limit is not particularly limited. In one embodiment, the λ5 of the optical glass may be 330 nm or more, 340 nm or more, 345 nm or more, 346 nm or more, 347 nm or more, 348 nm or more, 349 nm or more, or 350 nm or more.

On the other hand, as an index of the coloration of glass, the coloration λ70 can also be cited. λ70 represents the wavelength at which the spectral transmittance reaches 70% as measured by the method described for λ5. From the viewpoint of producing glass with less coloration, λ70 is preferably 450nm or less, more preferably 440nm or less, further preferably 430nm or less, further preferably 425nm or less, further preferably 420nm or less, further preferably 415nm or less, further preferably 413nm or less, further preferably 410nm or less, further preferably 407nm or less, further preferably 405nm or less. The lower the λ70, the better, and there is no particular lower limit. In one embodiment, the λ70 of the optical glass may be greater than 370 nm, greater than 375 nm, greater than 380 nm, greater than 385 nm, greater than 390 nm, or greater than 395 nm.

(λ5/nd, λ5/νd, λ70/nd, λ70/νd) Regarding chromaticity, it is preferred to suppress the increase in chromaticity of the glass and increase the refractive index. It is also preferred to suppress the increase in chromaticity of the glass and reduce the dispersion. From the above viewpoints, the value (λ5/nd) obtained by dividing the λ5 of the optical glass by the refractive index nd is preferably 195.00 nm or less, more preferably 190.00 nm or less, further preferably 188.00 nm or less, further preferably 187.50 nm or less, further preferably 187.00 nm or less, further preferably 186.50 nm or less, further preferably 186.00 nm or less, further preferably 185.55 nm or less, further preferably 185.00 nm or less. In addition, the lower the λ5/nd, the better, and its lower limit is not particularly limited. In one embodiment, the λ5/nd of the optical glass may be greater than 170.00nm, greater than 175.00nm, greater than 177.00nm, greater than 179.00nm, greater than 180.00nm, greater than 181.00nm, greater than 182.00nm, greater than 183.00nm, greater than 183.50nm, or greater than 184.00nm. The value (λ5/νd) obtained by dividing λ5 of the above optical glass by the Abbe number νd is preferably 14.50nm or less, more preferably 13.50nm or less, further preferably 13.00nm or less, further preferably 12.50nm or less, further preferably 12.00nm or less, further preferably 11.50nm or less, further preferably 11.00nm or less, further preferably 10.75nm or less, further preferably 10.50nm or less, further preferably 10.40nm or less, further preferably 10.30nm or less, particularly preferably 10.20nm or less, further particularly preferably 10.10nm or less, further particularly preferably 10.05nm or less. In addition, the lower the λ5/νd, the better, and its lower limit is not particularly limited. In one embodiment, the λ5/νd of the optical glass can be 8.00nm or more, 8.50nm or more, 8.70nm or more, 9.00nm or more, 9.20nm or more, 9.40nm or more, 9.50nm or more, 9.60nm or more, 9.70nm or more, 9.80nm or more, 9.90nm or more, or 9.95nm or more. The value (λ70/nd) obtained by dividing the λ70 of the above optical glass by the refractive index nd is preferably 240.00nm or less, more preferably 230.00nm or less, further preferably 225.00nm or less, further preferably 220.00nm or less, further preferably 217.00nm or less, further preferably 215.00nm or less, further preferably 214.50nm or less, further preferably 214.00nm or less. In addition, the lower the λ70/nd, the better, and its lower limit is not particularly limited. In one embodiment, the λ70/nd of the above optical glass can be 190.00nm or more, 200.00nm or more, 205.00nm or more, 210.00nm or more, 211.00nm or more, or 212.00nm or more. The value (λ70/νd) obtained by dividing the λ70 of the above optical glass by the Abbe number νd is preferably 18.00nm or less, more preferably 15.00nm or less, further preferably 13.00nm or less, further preferably 12.50nm or less, further preferably 12.00nm or less, further preferably 11.80nm or less, further preferably 11.60nm or less. In addition, the lower the λ70/νd, the better, and its lower limit is not particularly limited. In one embodiment, the λ70/νd of the above optical glass can be 8.00nm or more, 9.00nm or more, 10.00nm or more, 11.00nm or more, 11.20nm or more, or 11.40nm or more.

<Glass Manufacturing Method> The above optical glass can be obtained by, for example, mixing, melting, and forming glass raw materials in a manner to obtain the desired characteristics. As glass raw materials, for example, phosphates, fluorides, alkali metal compounds, alkali earth metal compounds, etc. can be used. Regarding the melting method and forming method of glass, known methods can be used.

[Glass raw material for press molding, optical element blank, and their manufacturing method] Another embodiment of the present invention relates to: Glass raw material for press molding formed from the above optical glass; and Optical element blank formed from the above optical glass.

According to another embodiment of the present invention, there are also provided: A method for manufacturing a glass raw material for press molding, which has a process for molding the optical glass into a glass raw material for press molding; A method for manufacturing an optical element blank, which has a process for molding the glass raw material for press molding using a press molding mold to mold an optical element blank; and A method for manufacturing an optical element blank, which has a process for molding the optical glass into an optical element blank.

An optical element blank refers to an optical element base material that is similar in shape to a target optical element and to which a polishing material (a surface layer to be removed by polishing) and a grinding material (a surface layer to be removed by grinding) are added as needed. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) of press-forming molten glass obtained by melting an appropriate amount of the above optical glass. In another embodiment, the optical element blank can also be produced by solidifying molten glass obtained by melting an appropriate amount of the above glass.

In another embodiment, an optical element blank can be manufactured by manufacturing a press-molding glass material and press-molding the manufactured press-molding glass material.

The press-forming of the glass raw material for press-forming can be performed by a known method of pressing the glass raw material for press-forming in a heated and softened state using a press-forming mold. Both heating and press-forming can be performed in the atmosphere. By annealing after press-forming to reduce the strain inside the glass, a homogeneous optical element blank can be obtained.

As for the glass raw materials for press forming, in addition to the raw materials which are directly provided to the press forming for manufacturing the optical element blank in the original state and are called the glass gob for press forming, it also includes the raw materials which are provided to the press forming after being subjected to mechanical processing such as cutting, grinding, polishing, etc. and passing through the glass gob for press forming. As the cutting method, there are the following methods: a method of forming a groove on the portion to be cut on the surface of the glass plate by a method called scribing, a method of applying a local pressure to the groove portion from the back side of the grooved surface, and cutting the glass plate at the grooved portion; or a method of cutting the glass plate with a cutting knife, etc. In addition, as the grinding and polishing methods, roller polishing, etc. can be cited.

For example, a glass raw material for press molding can be produced by pouring molten glass into a casting mold and forming it into a glass plate, and then cutting the glass plate into a plurality of glass sheets. Alternatively, a glass drop for press molding can be produced by forming an appropriate amount of molten glass. It is also possible to produce an optical element blank by reheating and softening the glass drop for press molding and then press molding it. The method of reheating and softening the glass and then press molding it to produce an optical element blank is called a reheat press method in contrast to the direct press method.

[Optical element and method for manufacturing the same] Another embodiment of the present invention relates to: An optical element formed by the above optical glass. The above optical element is manufactured using the above optical glass. In the above optical element, one or more coating layers such as a multi-layer film such as an anti-reflection film can be formed on the glass surface.

In addition, according to an embodiment of the present invention, it is also possible to provide: A method for manufacturing an optical element having a process for manufacturing the optical element by grinding and/or polishing the optical element blank.

In the manufacturing method of the optical element, grinding and polishing can be performed by known methods. By fully cleaning and drying the surface of the optical element after processing, an optical element with high internal and surface quality can be obtained. In this way, an optical element formed of the optical glass can be obtained. As optical elements, various lenses such as spherical lenses, aspherical lenses, micro lenses, prisms, etc. can be exemplified.

In addition, the optical element formed by the above optical glass is also suitable for use as a lens constituting a bonded optical element. As a bonded optical element, there can be exemplified an element formed by bonding lenses to each other (bonded lens), an element formed by bonding a lens and a prism, and the like. For example, a bonded optical element can be produced by the following method: the bonding surfaces of the two optical elements to be bonded are precisely processed in such a way that their shapes become inverted shapes (for example, spherical polishing), and a UV-curable adhesive for bonding the bonding lenses is applied, and after they are bonded, ultraviolet rays are irradiated through the lens to cure the adhesive, thereby producing a bonded optical element. As a material for optical elements used to produce bonded optical elements in this way, the above optical glass is preferably used. Multiple optical glasses with different Abbe numbers νd can be used to make multiple optical elements to be joined, and by joining them, an element suitable for correcting chromatic aberration can be made.

In the results of quantitative analysis of glass composition, glass components are sometimes expressed on an oxide basis, and the content of glass components is expressed as mass %. In this way, a composition expressed as mass % on an oxide basis can be converted into a composition expressed as cation % and anion % by, for example, the following method. When a glass contains N glass components, the kth glass component is expressed as A(k) _m O _n . Here, k is an arbitrary integer greater than 1 and less than N. A(k) is a cation, O is oxygen, and m and n are integers that can be determined by stoichiometric methods. For example, in the case of B ₂ O ₃ expressed on an oxide basis, m=2 and n=3, and in the case of SiO ₂ , m=1 and n=2. Next, the content of A(k) _m O _n is represented as X(k) [mass %]. Here, when the atomic weight of A(k) is P(k) and the atomic number of oxygen O is Q, the formal molecular weight R(k) of A(k) _m O _n is R(k) = P(k) × m + Q × n. Furthermore, when B = 100/{Σ[m×X(k)/R(k)]}, the content (cation %) of the cation component A(k) ^s+ is [X(k)/R(k)]×m×B(cation %). Here, Σ represents the sum of m×X(k)/R(K) for k=1 to N. m varies depending on k. s is 2n/m. In addition, for the molecular weight R(k), the fourth decimal place is rounded off and the value expressed to the third decimal place can be used for calculation. In addition, regarding several glass components and additives, molecular weights expressed on the basis of oxides are shown in the following Table 1.

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

<Example 1> In order to obtain the glass composition shown in the table below, corresponding nitrates, sulfates, carbonates, hydroxides, oxides, borics, etc. are used as raw materials for introducing each component, the raw materials are weighed, and they are fully mixed to prepare a prepared raw material. The prepared raw material is placed in a platinum crucible, heated, and melted. After melting, the molten glass is poured into a casting mold, naturally cooled to near the glass transition temperature, and immediately placed in an annealing furnace. After annealing treatment within the glass transition temperature range for about 1 hour, it is naturally cooled to room temperature in the furnace, thereby obtaining each optical glass (oxide glass) shown in Table 1. Regarding the anion composition of each optical glass shown in the table below, the ^O2- content is 100 anion %. When the obtained optical glass was observed under magnification using an optical microscope, no crystal precipitation, foreign matter such as platinum particles, bubbles, or streaks were observed. The various physical properties of the optical glass obtained in this way are shown in the table below. The various physical properties of the optical glass were measured by the methods shown below.

<Evaluation of physical properties of optical glass> (1) Refractive index nd, ng, nF, nC and Abbe number νd The refractive index nd, ng, nF, nC and Abbe number νd of the glass obtained by cooling at a cooling rate of -30°C/hour were measured using the refractive index measurement method of the Japan Optical Glass Industry Association standard.

(2) Partial dispersion ratio Pg,F The partial dispersion ratio Pg,F was calculated from the refractive indices ng, nF, and nC obtained in (1) above.

(3) Glass transition temperature Tg The glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300) manufactured by NETZSCH with a heating rate of 10°C/min.

(4) Liquidus temperature LT A glass sample (volume: 10 cm ³ ) made of each glass shown in the table below was placed in a platinum crucible and kept in a glass melting furnace set at 1400°C for 20 minutes. After the glass sample was fully melted and molten, the platinum crucible was taken out of the glass melting furnace and the glass sample was left to cool in the platinum crucible until the temperature of the glass sample reached 500°C or less. Then, the platinum crucible was placed in a glass melting furnace set at a temperature of T°C and kept for 2 hours. After being taken out of the furnace, the platinum crucible containing the glass sample was immediately (within 8 seconds) placed on a refractory (brick, etc.) at room temperature and the glass sample was cooled to room temperature. The room temperature here is in the range of -10~80℃. Then, the surface and interior of the glass sample are observed with the naked eye to confirm the presence or absence of crystallization. The above experiment is repeated by changing the temperature T℃ in 10℃ increments within the range of 1100~1350℃, and the lowest temperature at which no crystallization is confirmed on the surface and interior of the glass sample is set as the liquidus temperature LT.

(5) Specific gravity, specific gravity/nd The specific gravity was measured by the Archimedean method. The value (specific gravity/nd) was calculated by dividing the measured specific gravity by the refractive index nd obtained by (1) above.

(6) Coloring λ5, λ70 A glass sample with a thickness of 10±0.1 mm and two optically polished surfaces facing each other was used. A spectrophotometer was used to measure the intensity of light Iout after passing through the glass sample when light with an intensity of Iin was incident from a direction perpendicular to the polished surface. The spectral transmittance Iout/Iin was calculated. The wavelength at which the spectral transmittance reached 5% was set as λ5, and the wavelength at which the spectral transmittance reached 70% was set as λ70.

(7) λ5/nd, λ5/νd, λ70/nd, λ70/νd Calculate λ5/nd, λ5/νd, λ70/nd, and λ70/νd based on the above-calculated nd, νd, λ5, and λ70.

The above results are shown in the following Table 2 (Table 2-1 to Table 2-4).

[Table 2-1]

[Table 2-2]

[Table 2-3]

[Table 2-4]

<Evaluation of glass stability> Glass is obtained by shaping molten glass. When the glass stability is low, the number of crystal grains contained in the glass obtained by pouring the molten glass into a casting mold and shaping it increases. Therefore, the glass stability, especially the resistance to devitrification when the glass melt is shaped, can be evaluated by the number of crystals contained in the glass after melting and shaping under certain conditions. An example of the evaluation method is shown below. Using nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. as raw materials, weighing each raw material powder and mixing them thoroughly to prepare a prepared raw material, the prepared raw material is placed in a platinum crucible with a capacity of 300 ml, and heated and melted in a glass melting furnace set at 1400°C for 2 hours to prepare 150g of homogeneous molten glass. During this period, the molten glass is stirred and vibrated several times. After 2 hours, the crucible with molten glass was taken out from the above furnace, stirred and vibrated for 15-20 seconds, and then the molten glass was poured into a carbon casting mold (50mm×40mm×8mm~12mm), and placed in a slow cooling furnace to eliminate strain. The inside of the glass was observed using an optical microscope (magnification 100 times), the number of precipitated crystals was counted, and the number of crystals contained in 1kg of glass was calculated as the number density of crystals (pieces/kg). The number density of crystals evaluated by the above method is preferably 2000 pieces/kg or less, more preferably 1000 pieces/kg or less, further preferably 800 pieces/kg or less, further preferably 600 pieces/kg or less, further preferably 400 pieces/kg or less, further preferably 200 pieces/kg or less, further preferably 100 pieces/kg or less, further preferably 50 pieces/kg or less, further preferably 30 pieces/kg or less, and particularly preferably 0 pieces/kg. The number density of crystals of each glass shown in Table 2 evaluated by the above method is all 0 pieces/kg.

<Example 2> Using the various glasses obtained in Example 1, a glass block (glass drop) for press molding was produced. The glass block was heated and softened in the atmosphere, and then press molded using a press mold to produce a lens blank (optical element blank). The produced lens blank was taken out of the press mold, annealed, and subjected to mechanical processing including polishing to produce a spherical lens formed of the various glasses produced in Example 1.

<Example 3> A desired amount of molten glass produced in Example 1 was press-formed using a press-forming mold to produce a lens blank (optical element blank). The produced lens blank was taken out of the press-forming mold, annealed, and subjected to machining including polishing to produce a spherical lens formed of various glasses produced in Example 1.

<Example 4> The glass block (optical element blank) produced by solidifying the molten glass produced in Example 1 was annealed and subjected to mechanical processing including polishing to produce a spherical lens formed of various glasses produced in Example 1.

<Example 5> A spherical lens produced in Examples 2 to 4 is bonded to a spherical lens formed of another type of glass to produce a bonded lens. The bonding surface of the spherical lens produced in Examples 2 to 4 is a convex surface, and the bonding surface of the spherical lens formed of another type of optical glass is a concave surface. The two bonding surfaces are produced in such a way that the absolute values of the curvature radii are equal to each other. An ultraviolet curing adhesive for bonding optical elements is applied to the bonding surface, and the two lenses are bonded to each other on the bonding surface. Then, ultraviolet rays are irradiated to the adhesive applied to the bonding surface through the spherical lens produced in Examples 2 to 4 to solidify the adhesive. A bonded lens is produced as described above.

Finally, the above implementation methods are summarized.

According to one embodiment, an optical glass can be provided, wherein in a glass composition expressed in cation %, the Ta ⁵⁺ content is in the range of 0-5 cation %, the cation ratio of the Ti ⁴⁺ content relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.60-1.00, the cation ratio of the total content of Si ⁴⁺ and B ³⁺ relative to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ +B ³⁺ )/(La ³⁺ +Gd ³⁺ +Y ³⁺ )) is in the range of 0.50-2.50, the total content of Si 4+ and B 3+ relative to the total content of Ti 3+ , Nb 5+ , W ⁶⁺ and Bi ³⁺ is in the range of 0.60-1.00, The cation ratio of the total content of ^{Ti 4+} , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.50~40.00, the cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.50~30.00, and the cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of La ³⁺ and Y The cation ratio of the total content of Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ / ( ^{La 3+ +} Y ³⁺ )) is in the range of 0.00~1.50. The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ) / (Si ⁴⁺ +B ³⁺ )) is in the range of 0.00~1.00. The total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr 4+ is 2.34~2.13. The cation ratio of the total content of O ⁴⁺ and Ti ⁴⁺ ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is in the range of 0.000~0.080, the refractive index nd of the optical glass is in the range of 1.8000~2.0000, and the Abbe number νd is in the range of 25.0~45.0.

The optical glass has optical properties (nd and νd) useful as a material for optical elements. In addition, the proportion of Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ , which are expensive glass components, in the optical glass is low, and therefore, it is an optical glass that can contribute to the cost reduction of optical elements.

In one embodiment, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ in the optical glass may be in the range of 0 to 30 cation %.

In one embodiment, the total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ in the optical glass may be in the range of 0-8 cation %.

In one embodiment, the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ in the optical glass may be in the range of 20-60 cation %.

According to one embodiment, a glass material for press molding formed of the above-mentioned optical glass can be provided.

According to one embodiment, an optical element blank formed of the above-mentioned optical glass can be provided.

The press-molding glass material and the optical element blank are formed of the optical glass in which the proportion of expensive glass components such as Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ is low, and thus can contribute to the cost reduction of optical elements.

According to one embodiment, an optical element formed of the above-mentioned optical glass can be provided.

The optical element is formed of the optical glass in which the proportion of Ta ⁵⁺ , Gd ³⁺ , Nb ⁵⁺ , and W ⁶⁺ , which are expensive glass components, is low, and can therefore be manufactured at low cost.

It should be understood that the embodiments disclosed this time are all exemplary and do not constitute limitations. The scope of the present invention is defined by the scope of the invention application, not the above description, and is intended to include all variations within the meaning and scope equivalent to the scope of the invention application. For example, for the glass composition exemplified above, by adjusting the composition described in the specification, an optical glass of an embodiment of the present invention can be obtained. In addition, of course, any combination of two or more of the items exemplified in the specification or described as a preferred scope can be used.

without.

without.

Claims (16)

An optical glass, in which, in a glass composition expressed in cation %, the Ta ⁵⁺ content is in the range of 0-5 cation %, the cation ratio of the Ti ⁴⁺ content relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.60-1.00, the cation ratio of the total content of Si ⁴⁺ and B ³⁺ relative to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ +B ³⁺ )/(La 3+ +Gd 3+ +Y ³⁺ )) is in the range of 0.50-2.50, the total content of Si ⁴⁺ and B 3+ relative to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ is in the range of 0.60-1.00, The cation ratio of the total content of La ³⁺ , Gd ³⁺ , and Y ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ , and Bi 3+ ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W 6+ +Bi ³⁺ )) is in the range of 0.50~40.00, the cation ratio of the total content of La 3+ , Gd 3+ , and Y ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ , and Bi ³⁺ ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 2.70~30.00, and the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ , and Zn ²⁺ to the total content of La ³⁺ and Y The cation ratio of the total content of Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ / ( ^{La 3+ +} Y ³⁺ )) is in the range of 0.00~1.50. The cation ratio of the total content of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , Ba ²⁺ and Zn ²⁺ to the total content of Si ⁴⁺ and B ³⁺ ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ ) / (Si ⁴⁺ +B ³⁺ )) is in the range of 0.00~1.00. The total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ to the total content of Si ⁴⁺ , B ³⁺ , Zn ²⁺ , La ³⁺ , Y ³⁺ , Zr 4+ is 2.34~2.13. The cation ratio of the total content of O ⁴⁺ and Ti ⁴⁺ ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is in the range of 0.000~0.035, the refractive index nd of the optical glass is in the range of 1.8000~2.0000, and the Abbe number νd is in the range of 25.0~45.0. The optical glass as described in item 1 of the patent application, wherein the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ is in the range of less than 30 cation %. The optical glass as described in item 1 or 2 of the patent application, wherein the total content of Gd ³⁺ , Nb ⁵⁺ and W ⁶⁺ is in the range of 0-8 cation %. The optical glass as described in item 1 or 2 of the patent application, wherein the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ is in the range of 20~60 cation %. The optical glass as described in item 1 of the patent application scope, wherein the cation ratio ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is greater than 1.80, the cation ratio ((Gd ³⁺ +Nb ⁵⁺ +W ⁶⁺ )/(Si ⁴⁺ +B ³⁺ +Zn ²⁺ +La ³⁺ +Y ³⁺ +Zr ⁴⁺ +Ti ⁴⁺ )) is less than 0.035, the cation ratio ((Zn ²⁺ +Ba ²⁺ )/La ³⁺ ) is less than 0.25, and the refractive index nd is less than 1.9500. The optical glass as described in item 1 of the patent application, wherein the cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(Si ⁴⁺ +B ³⁺ )) is 0.00~0.70. The optical glass as described in item 1 of the patent application, wherein the cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(La ³⁺ +Y ³⁺ )) is 0.00~1.30. The optical glass as described in item 1 of the patent application, wherein the cation ratio (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 0.70~1.00. The optical glass as described in item 1 of the patent application, wherein the cation ratio ((La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is 2.70~5.00. The optical glass as described in item 1 of the patent application, wherein the cation ratio ((Mg ²⁺ +Ca ²⁺ +Sr ²⁺ +Ba ²⁺ +Zn ²⁺ )/(La ³⁺ +Y ³⁺ )) is 0.00~0.21. The optical glass as described in item 1 of the patent application, wherein the Ge ⁴⁺ content is 0-2 cation %. The optical glass as described in item 1 of the patent application, wherein the Yb ³⁺ content is 0-1 cation %. The optical glass as described in item 1 of the patent application scope, in which, in the glass composition expressed as cation %, the Ta ⁵⁺ content is in the range of 0-2 cation %, the Ge ⁴⁺ content is in the range of 0-2 cation %, the Ti ⁴⁺ content is less than 14 cation %, the cation ratio of the Ti ⁴⁺ content to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ (Ti ⁴⁺ /(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 0.70-1.00, and the cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ ((Si ⁴⁺ +B ³⁺ )/(La ³⁺ +Gd 3+ The cation ratio of the total content of Si ⁴⁺ and B ³⁺ to the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ ((Si ⁴⁺ +B ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 2.60~10.00. The cation ratio of the total content of La ³⁺ , Gd ³⁺ and Y ³⁺ to the total content of ^{Ti 4+} , Nb ⁵⁺ , W ⁶⁺ and Bi ^{3+ (} (La ³⁺ +Gd ³⁺ +Y ³⁺ )/(Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ )) is in the range of 2.70~8.00. The cation ratio of the total content of ^{Zn 2+} and Ba ²⁺ to the content of La ³⁺ ((Zn ²⁺ +Ba ²⁺ )/La ³⁺ ) is in the range of 0.00~0.25, the refractive index nd is in the range of 1.8000~1.9400, and the Abbe number νd is in the range of 25.0~38.0. A glass raw material for press molding, which is formed from an optical glass as described in any one of items 1 to 13 of the patent application scope. An optical element blank, which is formed from the optical glass as described in any one of items 1 to 13 of the patent application scope. An optical element formed of the optical glass as described in any one of items 1 to 13 of the patent application scope.