TW201710205A - Glass, optical glass, phosphate optical glass, polishing glass, glass material for press molding, and optical element - Google Patents

Abstract

To provide a phosphate optical glass which has excellent transmissivity and which, through high dispersion, suppresses an increase in the refractive index. Further, to provide an optical element and an optical glass material comprising the phosphate optical glass. A phosphate optical glass which has an Abbe number, νd, of 16.70 or lower, a refractive index, nd, of 2.1000 or lower, and which includes P2O5, TiO2 and Nb2O5, wherein, the mass ratio (TiO2/Nb2O5) of the content of TiO2 to the content of Nb2O5 is 0.15 or higher.

Description

Phosphate optical glass and optical components

The present invention relates to a phosphate optical glass which is excellent in transmissivity and suppresses an increase in refractive index with high dispersion. Further, the present invention relates to an optical element formed of such a phosphate optical glass.

A lens made of a high dispersion glass is formed into a pair of lenses by a lens made of a low dispersion glass to be used for correction of chromatic aberration. High dispersion glass is usually a high refractive index, and low dispersion glass is usually a low refractive index. Therefore, if the two are combined to form a pair of lenses, there is a problem that the field curvature is strongly expressed due to the large difference in refractive index.

For example, Patent Document 1 discloses a high-dispersion glass having a low Abbe number (νd), but since the refractive index is too high, it is used for the above-described problem of curvature of field when the lens is applied.

[Previous Technical Literature]

[Patent Literature]

Patent Document 1: Japanese Laid-Open Patent Publication No. 2013-212935.

The present invention has been made in view of such circumstances, and an object thereof is to provide a phosphoric acid which is excellent in transmissivity and suppresses an increase in refractive index with high dispersion. Salt optical glass. Further, it is an object of the invention to provide an optical element and an optical glass material formed of such phosphate optical glass.

The inventors of the present invention have conducted intensive studies in order to achieve the above object, and as a result, it has been found that the object can be achieved by adjusting the content ratio of various glass constituent components (hereinafter referred to as glass components) constituting the glass, and based on this knowledge, the present invention is completed. invention.

That is, the gist of the present invention is as follows.

(1) A phosphate optical glass having an Abbe number (νd) of 16.70 or less; a refractive index (nd) of 2.1000 or less; containing P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ; content of TiO ₂ and Nb ₂ O the mass content ratio _[5 TiO ₂ / Nb ₂ O _5] is 0.15 or more.

(2) The phosphate optical glass according to (1), wherein the content of Bi ₂ O ₃ is 29.0% by mass or less.

(3) A phosphate optical glass having an Abbe number (νd) of 16.70 or less; a content of Bi ₂ O ₃ of 29.0% by mass or less; and a total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ of 45.0% by mass or more.

(6) The phosphate optical glass according to any one of (1) to (3), wherein a mass ratio of the total content of TiO ₂ and WO _{3 to} the content of Nb ₂ O ₅ [(TiO ₂ + WO ₃ ) /Nb ₂ O ₅ ] is 0.15 or more.

(5) A glass material for press molding, which is any one of the above (1) to (4) The phosphate optical glass is formed.

(6) An optical element formed of the phosphate optical glass according to any one of the above (1) to (4).

According to the present invention, since the difference in the Abbe number is large when the lens is combined with the lens made of low dispersion glass, the effect of correcting the chromatic aberration is high. Further, even in the case of combining a low-dispersion glass lens having a low refractive index to form a pair of lenses, since the difference in refractive index is small, curvature of field can be suppressed.

Hereinafter, a mode for carrying out the invention (hereinafter simply referred to as "embodiment") will be described in detail. The following embodiments are illustrative of the invention, and the invention is not intended to limit the invention to the following. The present invention can be suitably modified and implemented within the scope of the gist of the invention. Further, the description of the portions that are repeatedly described will be appropriately omitted, but the purpose of the invention is not limited. In the present specification, the "optical glass" is a glass composition containing a plurality of glass constituent components (glass components), and is used as a shape (block shape, plate shape, spherical shape, etc.) and use unless otherwise specified. For optical elements, optical elements, etc., and the size-independent general term. That is, the shape, use, and size of the optical glass are not limited, and any shape of optical glass, optical glass of any other use, and optical glass of any size are included in the optical glass of the present invention. Further, in the present specification, the optical glass is sometimes simply referred to as "glass".

In addition, in this manual, (value 1) is sometimes used to "(value 1) The following numerical values are used to indicate the range of values. The range thus expressed is a range of values smaller than (value 1) plus a range of values of (value 1). The range of values represented by "insufficient (value 1)" is less than (value) The numerical range of 1) does not include (value 1). Sometimes the value range is expressed by "(value 2) or more" using the value (value 2). The range represented by this is a numerical range larger than (value 2) plus The numerical range of (value 2). The numerical range is sometimes expressed by "exceeding (value 2)". The range thus expressed is a numerical range larger than (value 2), and does not include (value 2).

In the first embodiment and the second embodiment, the optical glass according to the present invention will be mainly described based on the content of each glass component expressed by mass%. Hereinafter, "%" means mass% unless otherwise specified. Further, a part of the glass component is also referred to as a content represented by a cationic %.

In the present specification, the mass percentage of each glass component in the case where the total content of all the glass components is 100% by mass is expressed as a percentage by mass of each of the glass components represented by the oxide or the fluoride. To represent. In addition, the total content represented by mass % means the total amount of the content of various glass components (including the case where the content is 0%). In addition, the mass ratio means the ratio (ratio) of the content of the glass component (including the total content of the plurality of components) expressed by mass%.

In addition, in this specification, the term "cation %" means the percentage of moles when the total content of all the cationic components is 100%. The total content represented by the cationic % means the total amount of the content of a plurality of cationic components (including the case where the content is 0%). In addition, the cation ratio means a ratio (ratio) of the content of the cation components (including the total content of the plurality of cation components) when expressed by the cation %.

It should be noted that the valence of the cationic component (for example, the valence of P ⁵⁺ is +5, the valence of Si ⁴⁺ is +4, and the valence of La ³⁺ is +3) is a value determined according to conventionally, for oxidation. When the material reference is expressed as P, Si or La as a glass component, it is the same as P ₂ O ₅ , SiO ₂ or La ₂ O ₃ . Therefore, when analyzing the glass composition, the valence of the cationic component may not be analyzed. Further, the valence of the anion component (for example, the valence of O ^2- is -2) is also a value determined according to a conventional value, and the glass component based on the oxide as described above is expressed as, for example, P ₂ O ₅ , SiO ₂ , La _{2 .} O ₃ is the same. Therefore, when analyzing the glass composition, the valence of the anion component may not be analyzed.

As described later, Sb ₂ O ₃ , SnO ₂ , and CeO _{2 may} be added in a small amount to the glass as a clarifying agent. However, in the present specification, the content of Sb ₂ O ₃ , SnO _{2 ,} and CeO ₂ is not included in the total content of all the glass components. That is, the glass component of _{Sb 2 O 3, SnO 2,} CeO ₂ content is represented by each of Sb ₂ O _3, the total amount of all the components other than the glass of SnO ₂ and CeO ₂ in the Sb ₂ O _3, SnO ₂ And the content of CeO ₂ . Such expressions are referred to as additions in this specification.

The glass composition of the optical glass according to the embodiment of the present invention can be quantified by ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry) or ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). The analysis value obtained by ICP-AES may include, for example, a measurement error of about ±5% of the analysis value. Further, in the present specification and the present invention, the content of the constituent component of the glass of 0% or not means that the constituent component is not substantially contained, and the content of the constituent component is not more than the impurity level.

First embodiment

The optical glass according to the first embodiment of the present invention is a phosphate optical glass having an Abbe number (νd) of 16.70 or less; a refractive index (nd) of 2.1000 or less; and P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ; The mass ratio [TiO ₂ /Nb ₂ O ₅ ] of the content of TiO _{2 to} the content of Nb ₂ O ₅ is 0.15 or more.

Hereinafter, the optical glass according to the first embodiment will be described in detail.

In the optical glass according to the first embodiment, the Abbe number (νd) is 16.70 or less. The upper limit of the Abbe number (νd) is preferably 16.68, and more preferably 16.66, 16.64, 16.62, 16.60, 16.58, 16.56, 16.54. Further, the lower limit of the Abbe number is preferably 15.50, and the larger the value in the order of 15.55, 15.60, 15.65, and 15.70, the better.

By setting the Abbe number (νd) to 16.70 or less, when the lens is combined with a lens made of a low dispersion glass, the difference in the Abbe number becomes large, and the chromatic aberration is improved.

In the optical glass according to the first embodiment, the refractive index (nd) is 2.1000 or less. The upper limit of the refractive index is preferably 2.0950, and more preferably 2.0900, 2.0850, 2.0800, 2.0750, 2.0500, 2.0300, 2.0100, 2.000. Further, the lower limit of the refractive index is preferably 1.8800, and the larger the value in the order of 1.9000, 1.920, 1.940, and 1.960, the better.

By setting the refractive index (nd) to 2.1000 or less, even when a lens is formed by combining a low-dispersion glass lens having a low refractive index, the field curvature can be suppressed due to the difference in refractive index.

The optical glass according to the first embodiment contains P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ . By including P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ , it is possible to obtain an optical glass which suppresses an increase in refractive index (nd) with high dispersion.

In the optical glass according to the first embodiment, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] of the content of TiO _{2 to} the content of Nb ₂ O ₅ is 0.15 or more. As described above, the optical glass according to the first embodiment contains P ₂ O ₅ and TiO ₂ . However, when P ₂ O ₅ and TiO _{2 are} increased, the meltability of the glass is lowered and the liquidus temperature is increased. Therefore, this problem is eliminated by preventing Nb ₂ O ₅ which contributes to high dispersion from being contained in a specific ratio with respect to TiO ₂ to prevent an increase in the liquidus temperature.

In the optical glass according to the first embodiment, the lower limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] of the content of TiO _{2 to} the content of Nb ₂ O ₅ is preferably 0.16, and more preferably 0.17 or 0.18 in this order. , 0.19, 0.20, 0.23. Further, the upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.50, and more preferably 4.40, 4.30, 4.20, 4.10, 4.00, 3.80, 3.60.

Further, in the optical glass according to the first embodiment, when the content of the glass component is represented by the cation %, the upper limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] of the content of Ti ^{4+ and} the content of Nb ⁵⁺ is higher. Good is 6.00, and then more preferably 5.90, 5.80, 5.70, 5.65, 5.60. The lower limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42, respectively.

Ti ⁴⁺ tends to lower the meltability of the glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ inhibits the decrease in liquidus temperature and the increase in refractive index, contributing to high dispersion. Therefore, by including Nb ⁵⁺ in a certain ratio with respect to Ti ⁴⁺ , it is possible to suppress a decrease in the meltability of the glass and an increase in the liquidus temperature. Therefore, in the optical glass according to the embodiment, the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably in the above range.

The optical glass according to the first embodiment is a phosphate optical glass. The phosphate optical glass refers to an optical glass mainly containing phosphate as a network forming component of glass. Therefore, the optical glass according to the first embodiment contains phosphate as a network forming component, and its content is represented by the content of P ₂ O ₅ . As a network forming component of glass, P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known. Here, the glass mainly contains phosphate as a network forming component, and means that the content of P ₂ O ₅ in terms of % by mass is more than that of any of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ . .

In the optical glass according to the first embodiment, the lower limit of the content of P ₂ O ₅ is preferably 7.0%, and more preferably 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 12.5%, and 13.0. %. Further, the upper limit of the content of P ₂ O ₅ is preferably 35.0%, and more preferably 34.5%, 34.0%, 33.5%, and 33.0%, respectively.

P ₂ O ₅ is a component necessary for suppressing an increase in the refractive index (nd) and containing a large amount of a high dispersion component in the glass. On the other hand, if P ₂ O ₅ is contained in excess, the meltability may be deteriorated. Therefore, in the optical glass according to the embodiment, the content of P ₂ O ₅ is preferably in the above range.

In the optical glass according to the first embodiment, when the content of the glass component is represented by cation %, the upper limit of the content of P ⁵⁺ is preferably 45.00 cation %, and more preferably 44.50 cation %, 44.00 cationic %. 43.50% cationic, 43.00 cationic %, 42.50 cationic %, 42.00 cationic %, 41.50 cationic %, 41.00 cationic %, 40.50 cationic %, 40.00 cationic %, 39.50 cationic %, 39.00 cationic %, 38.50 cationic %. The lower limit of the content of P ⁵⁺ is preferably 20.00 cationic %, and more preferably 20.50 cationic %, 21.00 cationic %, 21.50 cationic %, 22.00 cationic %, 22.50 cationic %, 23.00 cationic %, 23.50 cationic %, 24.00 cationic %. 24.50% cationic, 25.00 cationic %, 25.50 cationic %.

P ⁵⁺ is a component necessary for suppressing an increase in the refractive index (nd) and containing a large amount of a high dispersion component in the glass. On the other hand, if P ⁵⁺ is excessively contained, the meltability may be deteriorated. Therefore, in the optical glass according to the embodiment, the content of P ⁵⁺ is preferably in the above range.

In the optical glass according to the first embodiment, the upper limit of the content of Bi ₂ O ₃ is preferably 29.0%, and more preferably 28.5%, 28.0%, 27.5%, 27.0%, 25.0%, 20.0%, 15.0. %, 10.0%, 6.0%, 5.0%. Further, the lower limit of the content of Bi ₂ O ₃ is preferably 0%. The content of Bi ₂ O ₃ may be 0%.

Bi ₂ O ₃ has an effect of improving the thermal stability of the glass by containing it in an appropriate amount. On the other hand, if the content of Bi ₂ O ₃ is increased, the refractive index is increased and the coloration of the glass is increased. Therefore, the content of Bi ₂ O ₃ is preferably set to the above range.

In the optical glass according to the first embodiment, when the content of the glass component is represented by the cation %, the upper limit of the content of Bi ³⁺ is preferably 20.00 cationic %, and more preferably 19.50 cationic %, 19.00 cationic %. 18.50% cationic, 18.00 cationic %, 17.50 cationic %, 17.00 cationic %, 16.50 cationic %. The lower limit of the content of Bi ³⁺ is preferably 3.00 cation %, and more preferably 1.50 cation %, 1.00 cation %, and 0.40 cation % in this order. The content of Bi ³⁺ may be 0 cationic %.

Bi ³⁺ has an effect of improving the thermal stability of the glass by making it contain an appropriate amount. On the other hand, if the content of Bi ³⁺ is increased, the refractive index is increased and the coloration of the glass is increased. Therefore, the content of Bi ³⁺ is preferably set to the above range.

In the optical glass according to the first embodiment, the lower limit of the mass ratio of the total content of TiO ₂ and WO _{3 to} the content of Nb ₂ O ₅ [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] is preferably 0.15. Further preferably, it is 0.17, 0.19, 0.20, 0.21, 0.23, 0.25, 0.26, 0.28, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64, 0.65. Further, the upper limit of the mass ratio [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] is preferably 8.00, and more preferably 7.90, 7.80, 7.70, 7.60, 7.40, 7.20, 7.00.

By setting the value of the mass ratio [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] to the above range, it is possible to obtain a glass which suppresses an increase in the refractive index and has high dispersion property suitable for chromatic aberration correction.

In the optical glass according to the first embodiment, when the content of the glass component is represented by the cation %, the cation ratio of the total content of Ti ⁴⁺ and W ^{6+ to} the content of Nb ⁵⁺ [(Ti ⁴⁺ + W) The upper limit of ⁶⁺ )/Nb ⁵⁺ ] is preferably 7.70, and more preferably 7.60, 7.50, 7.40, 7.35, 7.30, 7.28, 7.26. The lower limit of the cation ratio [(Ti ⁴⁺ + W ⁶⁺ ) / Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42, respectively.

By setting the value of the cation ratio [(Ti ⁴⁺ + W ⁶⁺ ) / Nb ⁵⁺ ] to the above range, it is possible to obtain a glass having a high dispersion property which is suitable for suppressing an increase in refractive index and having chromatic aberration correction. .

In the optical glass according to the first embodiment, the mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ and WO _{3 to} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [(TiO The lower limit of ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.45, and more preferably 0.50, 0.55, 0.60, 0.65, 0.70 in this order. , 0.75, 0.80, 0.85. Further, the upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 1.00. The content of Bi ₂ O ₃ may be 0%.

By setting the value of the mass ratio [(TiO ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] to the above range, it is possible to suppress the change in transmittance. It is poor, and it suppresses the increase of the refractive index and the increase of the specific gravity.

In the optical glass according to the first embodiment, the lower limit of the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably 43.0%, and more preferably 45.0%, 46.0%, 47.0%, 48.0%, 49.0%, 50.0%, 52.0%. Further, the upper limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably 85.0%, and more preferably 84.0%, 83.0%, 82.0%, 81.0%, 79.0%, and 77.0%, respectively.

Both TiO ₂ , Nb ₂ O ₅ and WO ₃ are glass components which contribute to high dispersion, but also cause coloring. Therefore, the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably set to the above range.

In the optical glass according to the first embodiment, when the content of the glass component is represented by the cation %, when the content of W ⁶⁺ exceeds 0 cation %, the cation ratio of the content of Ba ^{2+ to} the content of W ⁶⁺ is The upper limit of Ba ²⁺ /W ⁶⁺ ] is preferably 0.14, and more preferably 0.13, 0.12, 0.11, and 0.10 in this order.

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to the first embodiment, W ⁶⁺ which is a high dispersion component is contained so as to have the cation ratio with respect to the content of Ba ²⁺ , whereby desired high dispersion property can be maintained.

In the optical glass according to the first embodiment, when the content of the glass component is represented by the cation %, when the content of W ⁶⁺ is 0 cation % and the content of Ba ²⁺ exceeds 0 cation %, Ti ⁴ The upper limit of the total content of ⁺ and Bi ³⁺ [Ti ⁴⁺ +Bi ³⁺ ] is preferably 35.00 cationic %, and more preferably 34.00 cationic %, 33.00 cationic %, 32.50 cationic %, 32.30 cationic %, 32.00 cationic %. 31.80% cationic, 31.60 cationic %, 31.40 cationic %, 31.20 cationic %, 31.00 cationic %, 30.80 cationic %, 30.60 cationic %, 30.40 cationic %, 30.20 cationic %, 30.10 cationic %, 30.00 cationic %. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cationic %, and more preferably 21.20 cationic %, 21.40 cationic %, 21.60 cationic %, 21.80 cationic %, 22.00 cationic %, 22.20 cationic %, 22.40. Cationic %, 22.60 cationic %, 22.80 cationic %, 23.00 cationic %, 23.10 cationic %, 23.20 cationic %, 23.30 cationic %, 23.40 cationic %, 23.50 cationic %.

When the content of W ⁶⁺ is 0 cation % and the content of Ba ²⁺ exceeds 0 cation %, Ti ⁴⁺ which contributes to high dispersion after the high dispersion component is second only to W ⁶⁺ , and has an improvement. The total content of Bi ³⁺ which acts as a thermal stability is in the above range, and it is possible to suppress low dispersion due to Ba ²⁺ .

(glass composition)

In the optical glass according to the first embodiment, the following glass components can be contained.

The optical glass according to the present embodiment can contain B ₂ O ₃ , SiO ₂ , and Al ₂ O ₃ as a network forming component of glass other than P ₂ O ₅ .

In the optical glass according to the present embodiment, the upper limit of the content of B ₂ O ₃ is preferably 4.0%, and more preferably 3.0%, 2.0%, or 1.0%. The content of B ₂ O ₃ may be 0%.

B ₂ O ₃ is a network forming component of glass, and has an effect of improving the meltability of the glass and suppressing an increase in the refractive index. On the other hand, when the content of B ₂ O ₃ is large, there is a tendency that the decrease in the Abbe number is suppressed, the high dispersion is hindered, and the chemical durability is lowered. Therefore, from the viewpoint of suppressing an increase in the refractive index and improving the thermal stability, the meltability, the moldability, and the like of the glass, the upper limit of the content of B ₂ O ₃ is preferably in the above range. On the other hand, from the viewpoint of obtaining a desired Abbe number and maintaining chemical durability well, the lower limit of the content of B ₂ O ₃ is preferably in the above range.

In the optical glass according to the embodiment, the upper limit of the content of SiO ₂ is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.5%, 5.0%, 4.5%, 4.0%, 3.5%, or 3.0. %. The content of SiO ₂ may be 0%.

SiO ₂ is a network forming component of glass, and has an effect of improving the thermal stability, chemical durability, and weather resistance of the glass, improving the viscosity of the molten glass, and easily molding the molten glass. On the other hand, when the content of SiO ₂ is large, the meltability of the glass and the low-temperature softening property are lowered, and the glass raw material tends to remain molten. Therefore, from the viewpoint of improving the meltability of the glass, the low-temperature softening property, and the like, the upper limit of the content of SiO ₂ is preferably in the above range.

In the optical glass according to the embodiment, the upper limit of the content of Al ₂ O ₃ is preferably 5.0%, and more preferably 4.0%, 3.5%, 2.5%, 2.0%, 1.5%, 1.0%, or 0.5%. . The content of Al ₂ O ₃ may be 0%.

Al ₂ O ₃ is a glass component having an action of suppressing an increase in refractive index, improving chemical durability of glass, and weather resistance, and can be considered as a network forming component. On the other hand, when the content of Al ₂ O ₃ is increased, problems such as a decrease in thermal stability of the glass, an increase in glass transition temperature (Tg), and a decrease in meltability are liable to occur. From the viewpoint of avoiding such a problem, the upper limit of the content of Al ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ as a network forming component of glass [P ₂ O ₅ + B ₂ O ₃ + SiO The upper limit of ₂ + Al ₂ O ₃ ] is preferably 45.0%, and more preferably 43.0%, 41.0%, 39.0%, 37.0%, 35.0%, and 33.0%, respectively. Further, the lower limit of the total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] is preferably 10.0%, and more preferably 11.0%, 12.0%, 12.5%, 13.0%, and 14.0%, respectively. , 15.0%.

By setting the upper limit of the total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] to the above range, it is easy to maintain the refractive index within a desired range. In addition, by setting the lower limit of the total content [P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ ] to the above range, it is easy to improve the thermal stability of the glass and further suppress the devitrification of the glass ( Devitrification).

Further, the optical glass according to the present embodiment is directed to the, P ₂ O ₅ content relative to the _{P 2 O 5, B 2 O} 3, the quality of the total content of SiO ₂ and Al ₂ O ₃ ratio of [P ₂ O ₅ / The lower limit of (P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferably 0.70, and more preferably 0.75, 0.80, 0.85, and 0.90 in this order. The mass ratio [P ₂ O ₅ /(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] can also be set to 1.00.

If the mass ratio [P ₂ O ₅ /(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is small, the thermal stability of the glass is lowered, and the meltability is also lowered. Therefore, from the viewpoint of maintaining high dispersion of the glass and good meltability, the lower limit of the mass ratio [P ₂ O ₅ /(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )] is preferable. For the above range.

In the optical glass according to the present embodiment, the lower limit of the content of TiO ₂ is preferably 1.0%, and more preferably 3.0%, 5.0%, 6.0%, 7.0%, 8.0%, 9.0%, and 10.0%. Further, the upper limit of the content of TiO ₂ is preferably 45.0%, and more preferably 44.0%, 43.0%, 42.0%, 41.0%, 40.0%, and 39.0%, respectively.

TiO ₂ suppresses an increase in refractive index compared to Nb ₂ O ₅ and Bi ₂ O ₃ , and contributes greatly to high dispersion. On the other hand, TiO _{2 is} relatively easy to increase the coloration of the glass. Further, in the process of molding the molten glass and slow-cooling to obtain an optical glass, TiO ₂ promotes crystal formation in the glass and lowers transparency (white turbidity) of the glass. Therefore, in the optical glass according to the embodiment, the content of TiO ₂ is preferably in the above range.

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by cation %, the upper limit of the content of Ti ⁴⁺ is preferably 48.00 cationic %, and more preferably 47.00 cationic %, 46.00 cationic %, and more preferably 45.50% cationic, 45.00 cationic %, 44.50 cationic %, 44.00 cationic %, 43.50 cationic %, 43.00 cationic %, 42.50 cationic %, 42.00 cationic %. The lower limit of the content of Ti ⁴⁺ is preferably 10.00 cationic %, and more preferably more preferably 11.00 cationic %, 11.50 cationic %, 12.00 cationic %, 12.50 cationic %, 13.00 cationic %, 13.50 cationic %, 14.00 cationic %, 14.50 cationic %. , 15.00 cationic %, 15.50 cationic %.

Ti ⁴⁺ suppresses an increase in refractive index compared to Nb ⁵⁺ and Bi ³⁺ , and contributes greatly to high dispersion. On the other hand, Ti ^{4+ is} relatively easy to increase the color of the glass. In addition, Ti ⁴⁺ accelerates the formation of crystals in the glass during the process of molding the molten glass and slowly cooling to obtain an optical glass, thereby lowering the transparency (white turbidity) of the glass. Therefore, in the optical glass according to the embodiment, the content of Ti ⁴⁺ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the mass ratio [TiO ₂ /P ₂ O ₅ ] of the content of TiO _{2 to} the content of P ₂ O ₅ is preferably 4.50, and more preferably 4.00 and 3.50 in order. 3.00, 2.50, 2.00, 1.50. Further, the lower limit of the mass ratio [TiO ₂ /P ₂ O ₅ ] is preferably 0.04, and more preferably 0.08, 0.12, 0.16, 0.20, 0.24, 0.28, 0.32, 0.36, 0.40, 0.44, 0.48, and 0.52.

In the optical glass according to the present embodiment, since TiO _{2 is} contained, there is a problem that crystal formation in the glass is promoted and transparency (white turbidity) of the glass is lowered. This problem can be eliminated by including P ₂ O ₅ as a network forming component in a ratio of the above range with respect to TiO ₂ .

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by the cation %, the upper limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] of the content of Ti ^{4+ and} the content of P ⁵⁺ is preferably. It is 1.50, and more preferably 1.40, 1.30, 1.29, 1.28, 1.27, 1.26, 1.25, 1.24, 1.23, 1.22. The lower limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] is preferably 0.50, and more preferably 0.51, 0.52, and 0.53.

In the optical glass according to the present embodiment, since Ti ^{4+ is} contained, there is a problem that crystal formation in the glass is promoted and transparency (white turbidity) of the glass is lowered. This problem can be eliminated by including P ⁵⁺ as a network forming component in a ratio of the above range with respect to Ti ⁴⁺ .

In the optical glass according to the present embodiment, the lower limit of the content of Nb ₂ O ₅ is preferably 5.5%, and more preferably 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, or 8.5%. Further, the upper limit of the content of Nb ₂ O ₅ is preferably 55.0%, and more preferably 54.0%, 53.0%, 52.0%, 51.0%, 50.0%, 49.0%, and 48.0%, respectively.

Nb ₂ O ₅ is a component that contributes to high dispersion. Moreover, it is also a glass component which improves the thermal stability and chemical durability of the glass. On the other hand, when the content of Nb ₂ O ₅ is too large, the thermal stability of the glass is lowered, and the coloring of the glass tends to be enhanced. Therefore, in the optical glass according to the embodiment, the content of Nb ₂ O ₅ is preferably in the above range.

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by the cation %, the upper limit of the content of Nb ⁵⁺ is preferably 45.00 cation %, and more preferably 44.00 cation %, 43.50 cation %, and more preferably 43.00 cationic %, 42.50 cationic %, 42.00 cationic %, 41.50 cationic %, 41.00 cationic %, 40.50 cationic %, 40.00 cationic %, 39.50 cationic %, 39.00 cationic %, 38.50 cationic %. The lower limit of the content of Nb ⁵⁺ is preferably 1.00 cationic %, and more preferably 2.00 cationic %, 2.50 cationic %, 3.00 cationic %, 3.50 cationic %, 4.00 cationic %, 4.50 cationic %, 5.00 cationic %, 5.50 cationic %. , 6.00 cationic %, 6.50 cationic %.

Nb ⁵⁺ is a component that contributes to high dispersion. Moreover, it is also a glass component which improves the thermal stability and chemical durability of the glass. On the other hand, when the content of Nb ⁵⁺ is excessive, the thermal stability of the glass is lowered, and the coloring of the glass tends to be enhanced. Therefore, in the optical glass according to the embodiment, the content of Nb ⁵⁺ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of WO ₃ is preferably 45.0%, and more preferably 44.5%, 44.0%, 43.5%, 43.0%, 42.0%, 41.0%, and 40.0%. Further, the lower limit of the content of WO ₃ is preferably 9.0%, and more preferably 7.0%, 5.0%, 3.0%, 1.0%, 0.5%, 0.3%, or 0.1% in this order. The content of WO ₃ may be 0%.

WO ₃ suppresses an increase in the refractive index and greatly contributes to high dispersion. However, compared with TiO ₂ , Nb ₂ O ₅ and Bi ₂ O ₃ , WO ₃ tends to cause coloring of the glass and deteriorates transmittance. Therefore, the content of WO ₃ is preferably set to the above range.

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by the cation %, the upper limit of the content of W ⁶⁺ is preferably 30.00 cation %, and more preferably 29.00 cation %, 28.50 cation %, and more preferably 28.00 cationic %, 27.50 cationic %, 27.00 cationic %, 26.50 cationic %, 26.00 cationic %, 25.50 cationic %, 25.00 cationic %, 24.50 cationic %. The lower limit of the content of W ⁶⁺ is preferably 0.40 cation %, and more preferably 0.20 cation % and 0.10 cation % in this order. The content of W ⁶⁺ may be 0 cation %.

W ⁶⁺ suppresses the increase in the refractive index and greatly contributes to high dispersion. However, compared with Ti ⁴⁺ , Nb ⁵⁺ and Bi ³⁺ , it tends to cause coloring of the glass to deteriorate the transmittance. Therefore, the content of W ⁶⁺ is preferably set to the above range.

In the optical glass according to the present embodiment, the upper limit of the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably It is 86.0%, and more preferably 85.5%, 85.0%, 84.5%, 84.0%, 83.5%, and 83.0%. Further, the lower limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably 55.0%, and more preferably 55.5%, 56.0%, 56.5%, 57.0%, 57.5%, 58.0. %, 58.5%, 59.0%, 59.5%, 60.0%, 60.5%, 61.0%, 61.5%, 62.0%, 62.5%, 63.0%, 63.5%, 64.0%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to high dispersion of the glass. Further, by containing them in an appropriate amount, it also has an effect of improving the thermal stability of the glass. However, Bi ₂ O ₃ has a stronger effect of increasing the refractive index than TiO ₂ , Nb ₂ O ₅ and WO ₃ . Therefore, from the viewpoint of suppressing an increase in the refractive index and an increase in the color of the glass, the upper limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably in the above range. In addition, from the viewpoint of the high dispersion of the glass and the improvement of the thermal stability of the glass, the lower limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ ] is preferably in the above range.

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by the cation %, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ [Ti ⁴⁺ + Nb ⁵⁺ + The upper limit of W ⁶⁺ +Bi ³⁺ ] is preferably 75.00 cationic %, and more preferably 74.50 cationic %, 74.00 cationic %, 73.50 cationic %, 73.00 cationic %, 72.50 cationic %, 72.00 cationic %, 71.50 cationic %, 71.00 cationic %, 70.50 cationic %. The lower limit of the total content [Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ ] is preferably 52.00 cation %, and more preferably 52.10 cation %, 52.15 cation %, 52.20 cation %, 52.25 cation %, 52.30. cation%.

In the optical glass according to the embodiment, Ti ⁴⁺ , Nb ⁵⁺ , W ^{6+ ,} and Bi ³⁺ contribute to high dispersion of the glass. Further, by containing it in an appropriate amount, it also has an effect of improving the thermal stability of the glass. Therefore, the lower limit of the total content [Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ ] is preferably in the above range. On the other hand, Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ increase the coloration of the glass. Therefore, the upper limit of the total content [Ti ⁴⁺ + Nb ⁵⁺ + W ⁶⁺ + Bi ³⁺ ] is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Li ₂ O is preferably 1.2%, and more preferably 1.1%, 1.0%, 0.8%, 0.6%, or 0.4%. The content of Li ₂ O may be 0%.

Li ₂ O functions to suppress an increase in the refractive index and to improve the meltability of the glass. Therefore, the content of Li ₂ O is preferably in the above range from the viewpoint of maintaining desired optical characteristics and ensuring meltability.

In the optical glass according to the present embodiment, the upper limit of the content of Na ₂ O is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3.5%, or 3.0%. Further, the lower limit of the content of Na ₂ O is preferably 0%. The content of Na ₂ O may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of K ₂ O is preferably 12.0%, and more preferably 11.0%, 10.0%, 9.0%, 8.5%, or 8.0%. Further, in order to maintain the thermal stability of the glass well and suppress the increase in the liquidus temperature, the lower limit of the content of K ₂ O is preferably 0.1%, and more preferably 0.3%, 0.5%, 1.0%, 1.5% in order. , 2.0%, 2.5%. The content of K ₂ O may be 0%.

Both Na ₂ O and K ₂ O have an effect of suppressing an increase in the refractive index and improving the meltability of the glass. However, when the content thereof is increased, the thermal stability, chemical durability, and weather resistance of the glass are lowered. Therefore, the respective contents of Na ₂ O and K ₂ O are preferably set to the above ranges.

In the optical glass according to the present embodiment, the upper limit of the total content of Li ₂ O, Na ₂ O, and K ₂ O [Li ₂ O+Na ₂ O+K ₂ O] is preferably 15.0%, and more preferably sequentially. It is 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, and 9.0%. Further, in order to maintain the thermal stability of the glass and suppress the increase in the liquidus temperature, the lower limit of the total content [Li ₂ O+Na ₂ O+K ₂ O] is preferably 0.1%, and more preferably 0.3 in turn. %, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%. The total content [Li ₂ O+Na ₂ O+K ₂ O] may be 0%.

Each of Li ₂ O, Na ₂ O, and K ₂ O has an effect of suppressing an increase in refractive index and improving the meltability of the glass. However, when their content is increased, the thermal stability, chemical durability, and weather resistance of the glass are lowered. Therefore, the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O+Na ₂ O+K ₂ O] is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Rb ₂ O is preferably 2.0%, and more preferably 1.0%, 0.5%, or 0.1% in this order. Further, the lower limit of the content of Rb ₂ O is preferably 0%. The content of Rb ₂ O may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of Cs ₂ O is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, or 3.5%. Further, the lower limit of the content of Cs ₂ O is preferably 0%. The content of Cs ₂ O may be 0%.

Both Rb ₂ O and Cs ₂ O have an effect of suppressing an increase in refractive index and improving the meltability of the glass. However, when the content thereof is increased, the thermal stability, chemical durability, and weather resistance of the glass are lowered. Therefore, the respective contents of Rb ₂ O and Cs ₂ O are preferably set to the above ranges.

In the optical glass according to the present embodiment, the upper limit of the content of MgO is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, or 1.0%. Further, the lower limit of the content of MgO is preferably 0%. The content of MgO may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of CaO is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, or 1.0% in this order. Further, the lower limit of the content of CaO is preferably 0%. The content of CaO may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of SrO is preferably 6.0%, and more preferably 5.8%, 5.7%, 5.6%, 5.5%, 5.0%, 4.5%, 4.0%, or 3.5%. , 3.0%, 2.5%. Further, the lower limit of the content of SrO is preferably 0%. The content of SrO may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of BaO is preferably 6.0%, and more preferably 5.8%, 5.7%, 5.6%, 5.5%, 5.0%, 4.5%, or 4.0%. Further, the lower limit of the content of BaO is preferably 0%. The content of BaO may be 0%.

Each of MgO, CaO, SrO, and BaO has a glass component which serves to improve the thermal stability and meltability of the glass. However, when the content of these glass components is increased, high dispersion is impaired, and the thermal stability of the glass is lowered. Low, the glass is easy to devitrify. Therefore, the respective contents of these glass components are preferably in the above ranges.

Further, in the optical glass according to the present embodiment, when the content of the glass component is represented by cation %, the upper limit of the content of Ba ²⁺ is preferably 13.00 cation %, and more preferably 12.00 cation %, 11.00 cation %, and more preferably 10.00 cationic %, 9.00 cationic %, 8.00 cationic %, 7.50 cationic %, 7.00 cationic %, 6.50 cationic %, 6.00 cationic %, 5.50 cationic %, 5.00 cationic %, 4.50 cationic %, 4.00 cationic %, 3.50 cationic %. Further, the lower limit of the content of Ba ²⁺ is preferably 0 cation %. The content of Ba ²⁺ may be 0 cation %.

Each of Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ is a glass component having an effect of improving the thermal stability and meltability of the glass. However, when the content of these glass components is increased, high dispersion property is impaired, and the thermal stability of the glass is lowered, and the glass is easily devitrified. Therefore, the respective contents of these glass components are preferably in the above ranges.

In the optical glass according to the present embodiment, the upper limit of the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is considered from the viewpoint of maintaining thermal stability without impairing high dispersion. It is preferably 10.0%, and more preferably 9.0%, 8.0%, 7.0%, 6.0%, 5.5%, and 5.0% in this order. Further, the lower limit of the total content [MgO + CaO + SrO + BaO] is preferably 0%. The total content [MgO + CaO + SrO + BaO] may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of ZnO is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, or 1.0%. Further, the lower limit of the content of ZnO is preferably 0%. The content of ZnO may be 0%.

ZnO is a glass component which has an action of promoting melting of a raw material of glass (that is, an effect of improving meltability) when the glass is melted. Further, ZnO has a stronger effect of improving the thermal stability of the glass and lowering the liquidus temperature than other divalent metal components such as an alkaline earth metal. Therefore, from the viewpoint of improving the meltability and thermal stability of the glass, the lower limit of the content of ZnO is preferably in the above range. Further, from the viewpoint of suppressing the low dispersion of the glass, the upper limit of the content of ZnO is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of ZrO ₂ is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3.0%, or 2.0%. Further, the lower limit of the content of ZrO ₂ is preferably 0%. The content of ZrO ₂ may be 0%.

ZrO ₂ is a glass component having an effect of improving the thermal stability of the glass. However, when the content of ZrO ₂ is too large, the refractive index is increased and the thermal stability of the glass tends to be lowered. In addition, the glass raw material becomes easy to melt and remain. Therefore, from the viewpoint of satisfactorily maintaining the meltability and thermal stability of the glass and achieving desired optical characteristics, the upper limit of the content of ZrO ₂ is preferably in the above range. On the other hand, from the viewpoint of realizing the required optical characteristics and improving the thermal stability of the glass, the lower limit of the content of ZrO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Ta ₂ O ₅ is preferably 9.0%, and more preferably 8.0%, 7.0%, 6.0%, 5.0%, 4.0%, or 3.0%. Further, the lower limit of the content of Ta ₂ O ₅ is preferably 0%. The content of Ta ₂ O ₅ may be 0%.

Ta ₂ O ₅ is a glass component having an effect of improving the thermal stability of the glass. On the other hand, Ta ₂ O ₅ raises the refractive index to lower the dispersion of the glass. Further, Ta ₂ O ₅ is an extremely expensive component compared to other glass components, and if the content of Ta ₂ O ₅ is increased, the production cost of glass increases. Further, since Ta ₂ O ₅ has a larger molecular weight than other glass components, the specific gravity of the glass is increased, and as a result, the weight of the glass optical element is increased. Further, when the content of Ta ₂ O ₅ is increased, the meltability of the glass is lowered, and the melting of the glass raw material tends to occur when the glass is melted. Therefore, the content of Ta ₂ O ₅ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Ga ₂ O ₃ is preferably 4.0%, and more preferably 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, or 0.5%. , 0.1%. Further, the lower limit of the content of Ga ₂ O ₃ is preferably 0%. The content of Ga ₂ O ₃ may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of In ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, or 3.0%. Further, the lower limit of the content of In ₂ O ₃ is preferably 0%. The content of In ₂ O ₃ may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of Sc ₂ O ₃ is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, or 1.0%. Further, the lower limit of the content of Sc ₂ O ₃ is preferably 0%. The content of Sc ₂ O ₃ may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of HfO ₂ is preferably 8.0%, and more preferably 7.0%, 6.5%, 6.0%, 5.5%, 5.0%, 4.5%, 4.0%, or 3.5. %, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5%, 0.1%. Further, the lower limit of the content of HfO ₂ is preferably 0%. The content of HfO ₂ may be 0%.

Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , and HfO ₂ all have an effect of increasing the refractive index (nd) and are expensive components. Therefore, the content of each of Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , and HfO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Lu ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, or 3.0%. Further, the lower limit of the content of Lu ₂ O ₃ is preferably 0%. The content of Lu ₂ O ₃ may be 0%.

Lu ₂ O ₃ has an effect of increasing the refractive index (nd). Further, since the molecular weight is large, it is also a glass component which increases the specific gravity of the glass. Accordingly, it is preferable that the content of Lu ₂ O ₃ is decreased, the content of Lu ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of GeO ₂ is preferably 6.0%, and more preferably 5.0%, 4.0%, 3.0%, 2.0%, 1.5%, 1.0%, 0.5%, 0.1 in order. %. Further, the lower limit of the content of GeO ₂ is preferably 0%. The content of GeO ₂ may be 0%.

GeO ₂ has an effect of increasing the refractive index (nd), and is a component which is prominent in the glass component which is generally used. Therefore, from the viewpoint of reducing the production cost of the glass, the content of GeO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of La ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, or 1.5%. , 1.0%, 0.5%. Further, the lower limit of the content of La ₂ O ₃ is preferably 0%. The content of La ₂ O ₃ may be 0%.

When the content of La ₂ O ₃ is increased, the thermal stability of the glass is lowered, and the glass is easily devitrified during production. Therefore, from the viewpoint of suppressing the decrease in thermal stability of the glass, the content of La ₂ O ₃ is preferably in the above range.

In the optical glass according to the embodiment, the upper limit of the content of Gd ₂ O ₃ is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.0%, 4.0%, 3.0%, 2.0%, or 1.5%. 1.0%. Further, the lower limit of the content of Gd ₂ O ₃ is preferably 0%. The content of Gd ₂ O ₃ may be 0%.

When the content of Gd ₂ O ₃ is excessively increased, the thermal stability of the glass is lowered, and the glass is easily devitrified during production. Further, when the content of Gd ₂ O ₃ is excessively increased, the specific gravity of the glass is increased, which is not preferable. Therefore, from the viewpoint of maintaining the thermal stability of the glass satisfactorily and suppressing an increase in the specific gravity, the content of Gd ₂ O ₃ is preferably in the above range.

In the optical glass according to the present embodiment, the upper limit of the content of Y ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, or 2.0%. Further, the lower limit of the content of Y ₂ O ₃ is preferably 0%. The content of Y ₂ O ₃ may be 0%.

When the content of Y ₂ O ₃ is excessively increased, the thermal stability of the glass is lowered, and the glass is easily devitrified during production. Therefore, from the viewpoint of suppressing the decrease in the thermal stability of the glass, the content of Y ₂ O ₃ is preferably in the above range.

In the optical glass according to the embodiment, the upper limit of the content of Yb ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.0%, 1.0%, or 0.5%. , 0.1%. Further, the lower limit of the content of Yb ₂ O ₃ is preferably 0%. The content of Yb ₂ O ₃ may be 0%.

Since Yb ₂ O ₃ has a larger molecular weight than La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ , the specific gravity of the glass is increased. As the specific gravity of the glass increases, the quality of the optical element increases. For example, if a large-quality lens is assembled to an autofocus type photographic lens, the power required to drive the lens during autofocus increases, and battery consumption increases. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.

Further, when the content of Yb ₂ O ₃ is too large, the thermal stability of the glass is lowered, and the glass is easily devitrified during production. The content of Yb ₂ O ₃ is preferably in the above range from the viewpoint of preventing a decrease in thermal stability of the glass and suppressing an increase in specific gravity.

The optical glass according to the present embodiment is preferably mainly composed of the above glass components, that is, P ₂ O ₅ , B ₂ O ₃ , SiO ₂ , Al ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , WO ₃ , Bi _{2 .} O ₃ , Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, Cs ₂ O, MgO, CaO, SrO, BaO, ZnO, ZrO ₂ , Ta ₂ O ₅ , Ga ₂ O ₃ , In ₂ O ₃ And Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O _{3 are} formed, and the total content of the above glass components is preferably more than 95 %, more preferably more than 98%, further preferably more than 99%, still more preferably more than 99.5%.

In the optical glass according to the present embodiment, the upper limit of the content of TeO ₂ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0 in order. %, 0.5%, 0.1%. Further, the lower limit of the content of TeO ₂ is preferably 0%. The content of TeO ₂ may be 0%.

TeO ₂ is a component which raises the refractive index (nd), and since it is toxic, it is preferable to lower the content of TeO ₂ . Therefore, the content of TeO ₂ is preferably in the above range.

In the optical glass according to the present embodiment, the anion component (that is, the anion component) is mainly oxygen ions, and as the other anion, halogen ions such as chloride ions, iodide ions, and bromide ions can be contained in a small amount.

In the case where a halide is contained as a glass component, the content of the halide is preferably kept in a small amount so that the ratio (mass ratio) of the oxide in all the glass components is not 95% by mass or less.

In other words, in the optical glass according to the embodiment, the content of the oxide in all the glass components is preferably more than 95% by mass. Further, the lower limit of the content of the oxide in all the glass components is more preferably 97% by mass or 99% by mass. %, 99.5% by mass, 99.9% by mass, 99.95 mass%, and 99.99 mass%, and the content of the oxide in all the glass components may be 100% by mass. The glass in which the content of the oxide in all the glass components is 100% by mass does not substantially contain a halide.

Further, in the optical glass according to the present embodiment, the upper limit of the content of the halogen ions is preferably 4 anionic %, and more preferably 3 anionic %, 2 anionic %, 1 anionic %, or 0.5 anionic %. The content of the halogen ion may be 0 anion%. The anion % is the percentage of mole when the total content of all the anion components contained in the glass is 100%.

In addition, it is preferable that the optical glass of the present embodiment is basically composed of the above glass component, but other components may be contained in a range that does not impair the effects of the present invention. Further, in the present invention, the inclusion of unavoidable impurities is not excluded.

<Other ingredients>

Pb, As, Cd, Tl, Be, Se are all toxic. Therefore, the optical glass according to the embodiment preferably does not contain these elements as a glass component.

U, Th, and Ra are all radioactive elements. Therefore, the optical glass according to the embodiment preferably does not contain these elements as a glass component.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm increase the color of the glass and may become a source of fluorescence. Therefore, it is preferable that the optical glass according to the present embodiment does not contain these elements as a glass component.

Sb(Sb ₂ O ₃ ), Sn(SnO ₂ ), and Ce(CeO ₂ ) are elements which can be optionally added as a clarifying agent. Among them, Sb(Sb ₂ O ₃ ) is a clarifying agent having a large clarifying effect. However, Sb(Sb ₂ O ₃ ) is highly oxidizing, and when the amount of Sb(Sb ₂ O ₃ ) added is increased, light absorption by Sb ions causes an increase in coloring of the glass, which is not preferable. Further, when Sb is present in the molten material when the glass is melted, the platinum constituting the glass melting ruthenium is promoted to be eluted into the molten material, and the platinum concentration in the glass is increased. If platinum is present as ions in the glass, the coloration of the glass increases due to absorption of light. Further, if platinum is present as a solid in the glass, it becomes a source of light scattering, and the quality of the glass is lowered. Sn (SnO ₂ ) and Ce (CeO ₂ ) have a smaller clarifying effect than Sb (Sb ₂ O ₃ ). When Sn(SnO ₂ ) and Ce(CeO ₂ ) are added in a large amount, the color of the glass is enhanced. Therefore, in the case where a clarifying agent is added, it is preferable to add Sb(Sb ₂ O ₃ ) while adding the amount.

The content of Sb ₂ O ₃ is represented by an addition method. In other words, the content of the content of Sb ₂ O ₃ when the total content of all the glass components other than Sb ₂ O ₃ , SnO ₂ and CeO ₂ is 100% by mass is preferably less than 1% by mass, more preferably less than 0.5. The mass % is further preferably less than 0.1% by mass. The content of Sb ₂ O ₃ may be 0% by mass.

The content of SnO ₂ is also expressed in addition. In other words, the content of the content of SnO ₂ when the total content of all the glass components other than SnO ₂ , Sb ₂ O ₃ and CeO ₂ is 100% by mass is preferably less than 2% by mass, more preferably less than 1% by mass. Further, it is preferably less than 0.5% by mass, and still more preferably less than 0.1% by mass. The content of SnO ₂ may be 0% by mass. By setting the content of SnO ₂ to the above range, the clarity of the glass can be improved.

The content of CeO ₂ is also expressed in addition. In other words, the content of the content of CeO ₂ when the total content of all the glass components other than CeO ₂ , Sb ₂ O ₃ and SnO ₂ is 100% by mass is preferably less than 2% by mass, more preferably less than 1% by mass. Further, it is preferably less than 0.5% by mass, and still more preferably less than 0.1% by mass. The content of CeO ₂ may be 0% by mass. By setting the content of CeO ₂ to the above range, the clarity of the glass can be improved.

(glass characteristics)

<Glass transition temperature Tg>

The upper limit of the glass transition temperature (Tg) of the optical glass according to the present embodiment is preferably 750 ° C, and more preferably 740 ° C, 730 ° C, 720 ° C, 710 ° C, and 700 ° C in this order. Further, the lower limit of the glass transition temperature Tg is preferably 520 ° C, and more preferably 540 ° C, 560 ° C, 580 ° C, and 600 ° C in this order.

By satisfying the above range by the upper limit of the glass transition temperature (Tg), it is possible to suppress an increase in the annealing temperature of the glass, and it is possible to reduce the heat of the annealing apparatus, for example, a continuous annealing furnace called a "lehr", and a batch annealing furnace. damage.

The lower limit of the glass transition temperature (Tg) satisfies the above range, so that it is easy to maintain the desired Abbe number, the refractive index, and it is easy to maintain the thermal stability of the glass well.

<Light transmittance of glass>

In the present embodiment, the light transmittance can be evaluated by the degree of coloration (λ5).

A glass having a plane which is optically polished parallel to each other (having a thickness of 10.0 mm ± 0.1 mm) is used, and light rays are incident perpendicularly to the plane from one of the above two planes. Then, the ratio (Iout/Iin) of the intensity (Iout) of the transmitted light emitted from the other plane to the intensity (Iin) of the incident light is calculated, that is, the external transmittance is calculated. The external transmittance is measured while scanning the wavelength of the incident light in a range of, for example, 280 to 700 nm using a spectrophotometer, thereby obtaining a spectral transmittance curve.

The external transmittance increases as the wavelength of the incident light moves from the absorption end on the short wavelength side of the glass to the long wavelength side, showing a high value.

Λ5 is a wavelength at which the external transmittance is 5%, and in the wavelength region of 280 to 700 nm, the external transmittance of the glass on the long wavelength side longer than λ5 shows a value larger than 5%.

By using an optical glass that has a short wavelength of λ5, it is possible to provide an optical element that can ideally reproduce color.

For this reason, the range of λ5 is preferably 440 nm or less, and more preferably 435 nm or less, 430 nm or less, 425 nm or less, 420 nm or less, 415 nm or less, or 410 nm or less. The target of the lower limit of λ5 is 380 nm.

<specific gravity of glass>

The optical glass according to the present embodiment is a high-dispersion glass that suppresses an increase in refractive index and has a small specific gravity. Generally, the weight of the lens can be reduced as long as the specific gravity of the glass can be lowered. As a result, the power consumption of the autofocus drive of the camera lens on which the lens is mounted can be reduced. On the other hand, when the specific gravity is excessively decreased, the thermal stability is lowered. Therefore, the upper limit of the specific gravity (d) is preferably 5.80, and more preferably 5.60, 5.30, 5.00, 4.80, 4.60, 4.40, 4.20, 4.00, 3.80, 3.70. Further, from the viewpoint of improving thermal stability, the lower limit of the specific gravity (d) is preferably 2.80, and more preferably 2.90, 3.00, 3.10, and 3.20 in this order.

<liquidus temperature>

The upper limit of the liquidus temperature of the optical glass according to the present embodiment is preferably 1350 ° C, and more preferably 1340 ° C, 1330 ° C, 1320 ° C, 1310 ° C, and 1300 ° C in this order. Further, the lower limit of the liquidus temperature is preferably 1000 ° C, and more preferably 1020 ° C, 1040 ° C, 1060 ° C, 1080 ° C, 1100 ° C, 1130 ° C, 1150 ° C. According to the optical glass of the present embodiment, a high-dispersion glass in which the thermal stability of the glass is improved and the increase in the refractive index is suppressed can be obtained.

(Manufacture of optical glass)

The optical glass according to the embodiment of the present invention may be prepared by blending a glass raw material so as to have a predetermined composition, and using a prepared glass raw material in accordance with a known glass production method. For example, a plurality of compounds are formulated and thoroughly mixed to prepare a batch raw material, and the batch raw materials are placed in a quartz crucible or a platinum crucible for rough melt. The melt obtained by the crude melting was rapidly cooled and pulverized to prepare cullet. Further, the cullet is placed in a platinum crucible, heated, and remelted to obtain a molten glass, which is further clarified and homogenized, and then the molten glass is molded and slowly cooled to obtain an optical glass. The molding and slow cooling of the molten glass may be carried out by a known method.

In addition, as long as the desired glass component can be introduced into the glass so as to have a desired content, the compound to be used in the preparation of the batch raw material is not particularly limited, and examples of such a compound include oxides and positive Phosphoric acid, metaphosphate, phosphorus pentoxide, carbonate, nitrate, hydroxide, fluoride, and the like.

(Manufacture of optical components, etc.)

The optical element for producing an optical glass according to the embodiment of the present invention may be a known method. For example, a glass raw material is melted into a molten glass, and the molten glass is poured into a mold to form a plate material, thereby producing a glass material formed of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to prepare a glass material for press molding of a size and shape suitable for press molding. The glass material for press molding is heated and softened, and press-molded by a known method to produce an optical element blank which approximates the shape of the optical element. The optical element blank is annealed, ground and polished by a known method to produce light. Learning components.

The optical functional surface of the produced optical element can be coated with an antireflection film, a total reflection film, or the like according to the purpose of use.

As the optical element, various lenses such as a spherical lens, a prism, a diffraction grating, and the like can be exemplified.

Second embodiment

The optical glass of the second embodiment of the present invention is a phosphate optical glass having an Abbe number (νd) of 16.70 or less and a content of Bi ₂ O ₃ of 29.0% by mass or less; and TiO ₂ , Nb ₂ O ₅ and WO ₃ The total content is 45.0% by mass or more.

Hereinafter, the optical glass according to the second embodiment will be described in detail.

In the optical glass according to the second embodiment, the Abbe number (νd) is 16.70 or less. The upper limit of the Abbe number (νd) is preferably 16.68, and more preferably 16.66, 16.64, 16.62, 16.60, 16.58, 16.56, 16.54. Further, the lower limit of the Abbe number is preferably 15.50, and the larger the value in the order of 15.55, 15.60, 15.65, and 15.70, the better.

By setting the Abbe number (νd) to 16.70 or less, when the lens is combined with a lens made of a low dispersion glass, the difference in the Abbe number becomes large, and the chromatic aberration is improved.

In the optical glass according to the second embodiment, the content of Bi ₂ O ₃ is 29.0% or less.

In the optical glass according to the second embodiment, the upper limit of the content of Bi ₂ O ₃ is preferably 28.5%, and more preferably 28.0%, 27.5%, 27.0%, 25.0%, 20.0%, 15.0%, 10.0. %, 6.0%, 5.0%. Further, the lower limit of the content of Bi ₂ O ₃ is preferably 0%. The content of Bi ₂ O ₃ may be 0%.

Bi ₂ O ₃ has an effect of improving the thermal stability of the glass by containing it in an appropriate amount. On the other hand, if the content of Bi ₂ O ₃ is increased, the refractive index will increase and the color of the glass will increase. Therefore, the content of Bi ₂ O ₃ is set to the above range.

In the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, the upper limit of the content of Bi ³⁺ is preferably 20.00 cationic %, and more preferably 19.50 cationic %, 19.00 cationic %. 18.50% cationic, 18.00 cationic %, 17.50 cationic %, 17.00 cationic %, 16.50 cationic %. The lower limit of the content of Bi ³⁺ is preferably 3.00 cation %, and more preferably 1.50 cation %, 1.00 cation %, and 0.40 cation % in this order. The content of Bi ³⁺ may be 0 cationic %.

Bi ³⁺ has an effect of improving the thermal stability of the glass by making it contain an appropriate amount. On the other hand, if the content of Bi ³⁺ is increased, the refractive index will increase and the color of the glass will increase. Therefore, the content of Bi ³⁺ is preferably set to the above range.

In the optical glass according to the second embodiment, the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is 45.0% or more.

In the optical glass according to the second embodiment, the lower limit of the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably 46.0%, and more preferably 47.0%, 48.0%, 49.0%, 50.0%. Further, the upper limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably 85.0%, and more preferably 84.0%, 83.0%, 82.0%, 81.0%, 79.0%, and 77.0%, respectively.

TiO ₂ , Nb ₂ O ₅ and WO ₃ suppress the increase in refractive index (nd), contributing to high dispersion of the glass. Further, by containing it in an appropriate amount, it also has an effect of improving the thermal stability of the glass. The lower limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is in the above range from the viewpoint of the high dispersion of the glass and the improvement of the thermal stability of the glass. In addition, from the viewpoint of suppressing an increase in the refractive index and an increase in the color of the glass, the upper limit of the total content [TiO ₂ + Nb ₂ O ₅ + WO ₃ ] is preferably in the above range.

The optical glass according to the second embodiment is a phosphate optical glass. The phosphate optical glass refers to an optical glass mainly containing phosphate as a network forming component of glass. Therefore, the optical glass according to the second embodiment contains phosphate as a network forming component, and its content is represented by the content of P ₂ O ₅ . As a network forming component of glass, P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known. Here, the glass mainly contains phosphate as a network forming component, and means that the content of P ₂ O ₅ in terms of % by mass is more than that of any of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ . .

In the optical glass according to the second embodiment, the lower limit of the content of P ₂ O ₅ is preferably 7.0%, and more preferably 8.0%, 9.0%, 10.0%, 10.5%, and 11.0% in this order. Further, the upper limit of the content of P ₂ O ₅ is preferably 35.0%, and more preferably 34.5%, 34.0%, 33.5%, and 33.0%, respectively.

P ₂ O ₅ is a component necessary for making the glass contain a large amount of a high dispersion component. On the other hand, if P ₂ O ₅ is contained in excess, the meltability may be deteriorated. Therefore, in the glass according to the present embodiment, the content of P ₂ O ₅ is preferably in the above range.

Further, in the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, the upper limit of the content of P ⁵⁺ is preferably 45.00 cation %, and more preferably 44.50 cation %, 44.00 cation %. 43.50% cationic, 43.00 cationic %, 42.50 cationic %, 42.00 cationic %, 41.50 cationic %, 41.00 cationic %, 40.50 cationic %, 40.00 cationic %, 39.50 cationic %, 39.00 cationic %, 38.50 cationic %. The lower limit of the content of P ⁵⁺ is preferably 20.00 cationic %, and more preferably 20.50 cationic %, 21.00 cationic %, 21.50 cationic %, 22.00 cationic %, 22.50 cationic %, 23.00 cationic %, 23.50 cationic %, 24.00 cationic %. 24.50% cationic, 25.00 cationic %, 25.50 cationic %.

P ⁵⁺ is a component necessary for suppressing an increase in the refractive index (nd) and containing a large amount of a high dispersion component in the glass. On the other hand, if P ⁵⁺ is excessively contained, the meltability may be deteriorated. Therefore, in the optical glass according to the embodiment, the content of P ⁵⁺ is preferably in the above range.

In the optical glass according to the second embodiment, the mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ and WO _{3 to} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [(TiO The lower limit of ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 0.45, and more preferably 0.50, 0.55, 0.60, 0.65, 0.70 in this order. , 0.75, 0.80, 0.85. Further, the upper limit of the mass ratio [(TiO ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] is preferably 1.00. The content of Bi ₂ O ₃ may be 0%.

By setting the value of the mass ratio [(TiO ₂ + Nb ₂ O ₅ + WO ₃ ) / (TiO ₂ + Nb ₂ O ₅ + WO ₃ + Bi ₂ O ₃ )] to the above range, it is possible to suppress the deterioration of the transmittance. And suppress the increase in refractive index.

In the optical glass according to the second embodiment, the lower limit of the mass ratio of the content of TiO _{2 to} the content of Nb ₂ O ₅ [TiO ₂ /Nb ₂ O ₅ ] is preferably 0.15, and more preferably 0.16 or 0.17. , 0.18, 0.19, 0.20, 0.23. Further, the upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.50, and more preferably 4.40, 4.30, 4.20, 4.10, 4.00, 3.80, 3.60.

TiO ₂ tends to lower the meltability of the glass and increase the liquidus temperature. On the other hand, Nb ₂ O ₅ suppresses a decrease in liquidus temperature and an increase in refractive index, contributing to high dispersion. Therefore, by containing Nb ₂ O ₅ in a certain ratio with respect to TiO ₂ , it is possible to suppress a decrease in the meltability of the glass and an increase in the liquidus temperature. Therefore, in the optical glass according to the embodiment, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably in the above range.

Further, in the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, the upper limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] of the content of Ti ^{4+ and} the content of Nb ⁵⁺ is higher. Good is 6.00, and then more preferably 5.90, 5.80, 5.70, 5.65, 5.60. The lower limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42, respectively.

Ti ⁴⁺ tends to lower the meltability of the glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ inhibits the decrease in liquidus temperature and the increase in refractive index, contributing to high dispersion. Therefore, by including Nb ⁵⁺ in a certain ratio with respect to Ti ⁴⁺ , it is possible to suppress a decrease in the meltability of the glass and an increase in the liquidus temperature. Therefore, in the optical glass according to the embodiment, the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably in the above range.

In the optical glass according to the second embodiment, the lower limit of the mass ratio of the total content of TiO ₂ and WO _{3 to} the Nb ₂ O ₅ content [(TiO ₂ + WO ₃ )/Nb ₂ O ₅ ] is preferably 0.15. Further preferably, it is 0.17, 0.19, 0.20, 0.21, 0.23, 0.25, 0.26, 0.28, 0.30, 0.35, 0.40, 0.45, 0.50, 0.55, 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63, 0.64. , 0.65. Further, the upper limit of the mass ratio [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] is preferably 8.00, and more preferably 7.90, 7.80, 7.70, 7.60, 7.40, 7.20, 7.00.

By setting the value of the mass ratio [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] to the above range, it is possible to obtain a glass which suppresses an increase in refractive index and has high dispersion property suitable for chromatic aberration correction.

In the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, the cation ratio of the total content of Ti ⁴⁺ and W ^{6+ to} the content of Nb ⁵⁺ [(Ti ⁴⁺ + W) The upper limit of ⁶⁺ )/Nb ⁵⁺ ] is preferably 7.70, and more preferably 7.60, 7.50, 7.40, 7.35, 7.30, 7.28, 7.26. The lower limit of the cation ratio [(Ti ⁴⁺ + W ⁶⁺ ) / Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42, respectively.

By setting the value of the cation ratio [(Ti ⁴⁺ + W ⁶⁺ ) / Nb ⁵⁺ ] to the above range, it is possible to obtain a glass having a high dispersion property which is suitable for suppressing an increase in refractive index and having chromatic aberration correction. .

In the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, when the content of W ⁶⁺ exceeds 0 cation %, the cation ratio of the content of Ba ^{2+ to} the content of W ⁶⁺ is The upper limit of Ba ²⁺ /W ⁶⁺ ] is preferably 0.14, and more preferably 0.13, 0.12, 0.11, and 0.10 in this order.

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to the second embodiment, W ⁶⁺ which is a high dispersion component is contained so as to have the cation ratio with respect to the content of Ba ²⁺ , whereby desired high dispersion property can be maintained.

In the optical glass according to the second embodiment, when the content of the glass component is represented by the cation %, when the content of W ⁶⁺ is 0 cation %, when the content of Ba ²⁺ exceeds 0 cation %, Ti ⁴ The upper limit of the total content of ⁺ and Bi ³⁺ [Ti ⁴⁺ +Bi ³⁺ ] is preferably 35.00 cationic %, and more preferably 34.00 cationic %, 33.00 cationic %, 32.50 cationic %, 32.30 cationic %, 32.00 cationic %. 31.80% cationic, 31.60 cationic %, 31.40 cationic %, 31.20 cationic %, 31.00 cationic %, 30.80 cationic %, 30.60 cationic %, 30.40 cationic %, 30.20 cationic %, 30.10 cationic %, 30.00 cationic %. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cationic %, and more preferably 21.20 cationic %, 21.40 cationic %, 21.60 cationic %, 21.80 cationic %, 22.00 cationic %, 22.20 cationic %, 22.40. Cationic %, 22.60 cationic %, 22.80 cationic %, 23.00 cationic %, 23.10 cationic %, 23.20 cationic %, 23.30 cationic %, 23.40 cationic %, 23.50 cationic %.

In the case where the content of W ⁶⁺ is 0 cation % and the content of Ba ²⁺ exceeds 0 cation %, Ti ⁴⁺ which contributes to high dispersion is second only to W ⁶⁺ in the high dispersion component and has an improvement. The total content of Bi ³⁺ which acts as a thermal stability is in the above range, and it is possible to suppress low dispersion due to Ba ²⁺ .

In the optical glass according to the second embodiment, the upper limit of the refractive index (nd) is preferably 2.1500, and more preferably 2.1300, 2.1100, 2.1000, 2.0900, 2.0700, 2.0500, 2.0300, 2.0140, 2.000. Further, the lower limit of the refractive index (nd) is preferably 1.8800, and the smaller the value in the order of 1.9000, 1.920, 1.940, and 1.960, the better.

By setting the refractive index (nd) to the above range, even when a lens is formed by combining a low-dispersion glass lens having a low refractive index, the field curvature can be suppressed due to the difference in refractive index.

The glass component composition other than the above in the second embodiment can be the same as that of the first embodiment. In addition, the glass characteristics in the second embodiment, the production of optical glass, and the production of an optical element can be the same as in the first embodiment.

Example

Hereinafter, the present invention will be described by way of examples, but the present invention is not limited to the following examples.

(Example 1)

Weighing and each component in the form of a glass having the composition of Nos. 1 to 129 shown in Table 1-1, Table 1-4, and Table 1-5 and Table 2-1, Table 2-3, and Table 2-4 Raw materials such as phosphates, carbonates, and oxides, which are corresponding raw materials, are thoroughly mixed to prepare a raw material.

Here, Table 1-1, Table 1-4, and Table 1-5 are represented by mass%, and Table 2-1, Table 2-3, and Table 2-4 show the glass composition of the numbers 1 to 129 by the cation %. That is, although Table 1-1, Table 1-4, and Table 1-5 and Table 2-1, Table 2-3, and Table 2-4 show different glass compositions, the same number of optical glasses have the same composition. . Therefore, Table 1-1, Table 1-4, Table 1-5, and Table 2-1, Table 2-3, and Table 2-4 substantially represent the same optical glass.

In addition, in Table 2-1, Table 2-3, and Table 2-4, the glass composition is represented by the cation % in the case where the total amount of an anion component is O ^2- . That is, in Table 2-1, Table 2-3, and Table 2-4, the content of O ^2- is 100 anionic %.

In addition, the ratio of the total content of the glass component and the content of the glass component described in Table 1-2, Table 1-3, and Tables 1-6 to 1-9 are shown in Table 1-1, Table 1-4, and Table 1. The value calculated based on the content of each glass component described in -5. Similarly, the ratio of the total content of the glass components and the content of the glass components described in Table 2-2, Table 2-5, and Table 2-6 are shown in Table 2-1, Table 2-3, and Table 2-4. The value calculated based on the content of each glass component described.

Put the above ingredients into a platinum crucible and heat to 1200 After melting, stirring, and clarification at °C to 1350 ° C, the molten glass is cast from a crucible into a mold to form a glass block.

As a result of observing each of the obtained glass blocks, impurities such as crystals and molten residue of the raw materials were not observed in the glass, and an optical glass having high homogeneity and high quality could be obtained. Incidentally, the optical glass numbers 1 to 6 and 12 to 129 are examples of the first embodiment, and the optical glass numbers 1 to 129 are examples of the second embodiment.

The refractive index (nd), Abbe number (νd), glass transition temperature, specific gravity, λ5, and liquidus temperature of the obtained optical glass Nos. 1 to 129 are shown in Table 3, Table 4-1, and Table 4-2. . The refractive index (nd), the Abbe number (νd), the glass transition temperature, the specific gravity, λ5, and the liquidus temperature were measured in the following manner. It should be noted that the blank column in Table 3 indicates that it was not measured.

(1) Refractive index (nd) and Abbe number (νd)

It is measured based on the Japan Optical Glass Industry Association standard JOGIS-01. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(2) Glass transition temperature (Tg)

The glass transition temperature was measured based on the endothermic curve when the glass in a solid state was heated by a differential scanning calorimeter DSC8270. The glass transition temperature (Tg) using this measurement shows a correspondence relationship with Tg measured based on the Japan Optical Glass Industry Association standard JOGIS-08. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(3) Wavelength (λ5)

Λ5 was measured in the following manner. The spectral transmittance of the wavelength region from the wavelength of 280 nm to 700 nm was measured using a glass sample having a plane of 10 mm thick and optically polished parallel to each other. For spectral transmittance, the light of incident intensity A is incident perpendicular to a plane where optical polishing is performed, and the measurement is shot from another plane. The intensity B of the emitted light is calculated by B/A. Therefore, the spectral transmittance also includes the reflection loss of the light on the surface of the sample. The wavelength at which the spectral transmittance is 5% is λ5. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(4) Specific gravity

It is determined based on the Japan Optical Glass Industry Association standard JOGIS-05. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(5) Liquidus temperature (LT)

The glass sample was placed in a furnace heated to a predetermined temperature and held for 2 hours. After cooling, the inside of the glass was observed with a 100-fold optical microscope, and the liquidus temperature was determined based on the presence or absence of the crystal. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(Example 2)

The glass raw material was heated, melted, clarified, and homogenized in the same manner as in Example 1 to obtain optical glass Nos. 1 to 129, and the molten glass was poured into a mold and quenched to form a glass block. Next, the glass block was annealed, and then cut and ground to prepare a glass material for press molding.

(Example 3)

The glass material for press molding formed of the various optical glasses produced in Example 2 was heated and softened, and press-molded by a known method using a press molding die to prepare an optical element blank such as a lens blank or a prism blank.

After the optical element blank is precisely annealed, the refractive index is precisely adjusted to a desired refractive index, and a concave lens, a convex lens, and a prism are produced by a known grinding and polishing method.

When the obtained lens is combined with a low-dispersion glass lens having a large Abbe number (νd), chromatic aberration can be satisfactorily corrected, and field curvature can be reduced.

Claims (6)

A phosphate optical glass having an Abbe number (νd) of 16.70 or less; a refractive index (nd) of 2.1000 or less; comprising P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ; and a content of TiO ₂ and Nb ₂ the mass content ratio [O ₅ TiO ₂ / Nb ₂ O _5] is 0.15 or more. The phosphate optical glass according to claim 1, wherein the content of Bi ₂ O ₃ is 29.0% by mass or less. A phosphate optical glass having an Abbe number (νd) of 16.70 or less; a content of Bi ₂ O ₃ of 29.0% by mass or less; and a total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ of 45.0% by mass or more. . The phosphate optical glass according to any one of claims 1 to 3, wherein the mass ratio of the total content of TiO ₂ and WO _{3 to} the content of Nb ₂ O ₅ [(TiO ₂ + WO ₃ ) / Nb ₂ O ₅ ] is 0.15 or more. A glass material for press molding, which is formed from the phosphate optical glass of any one of claims 1 to 4. An optical element formed from the phosphate optical glass of any one of claims 1 to 4.