JP2023139100A - Glass, optical glass, phosphate optical glass, and optical element - Google Patents

Abstract

To provide a glass, an optical glass, a glass material for polishing, a glass material for press molding, and an optical element that enable the reduction color to be reduced easily.SOLUTION: A phosphate optical glass has an Abbe number νd of 18.10 or less and contains at least one oxide selected from TiO2, Nb2O5, WO3 and Bi2O3. The phosphate optical glass can reduce the coloring due to the reduction color in a short time.SELECTED DRAWING: None

Description

The present invention consists of a first invention and a second invention. The first invention relates to a phosphate optical glass that has excellent transparency, high dispersion, and suppresses an increase in refractive index, and an optical element made of the phosphate optical glass. Further, the second invention relates to a glass, an optical glass, and an optical element that can easily reduce reduced color.

A lens made of high dispersion glass is used to correct chromatic aberration by combining it with a lens made of low dispersion glass to form a pair of lenses. High dispersion glasses generally have a high refractive index, and low dispersion glasses generally have a low refractive index. For this reason, when the two lenses are combined to form a pair lens, there is a problem that a strong curvature of field appears due to the large difference in refractive index.

For example, Patent Document 1 discloses a glass with a low Abbe number νd, that is, a high dispersion glass, but since the refractive index is too high, a problem of field curvature occurs when used in the above-mentioned pair lens.

In addition, high-dispersion glass usually contains a large amount of glass components such as TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (hereinafter sometimes referred to as "high-dispersion components"). are doing. These highly dispersed components are easily reduced during the glass melting process. When the high-dispersion component is reduced, it absorbs light on the short wavelength side of the visible light range, causing the glass to be colored (hereinafter sometimes referred to as "reduced color").

In Patent Document 2, such coloring of the glass is reduced by heat-treating the glass. This is thought to be because ions such as Ti, Nb, W, and Bi in a reduced state are oxidized by heating, which weakens visible light absorption.

In other words, in high-dispersion glass containing a large amount of high-dispersion components such as TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ as glass components, the required transparency can be achieved by reducing the reduced color through heat treatment. Obtainable. However, since this heat treatment requires heating the glass for a long time, improvements are required from the viewpoints of productivity and economy. In particular, high-dispersion glass with an Abbe number ν _d of 18.1 or less is more deeply colored, and therefore requires a long time for heat treatment to reduce coloring.

Japanese Patent Application Publication No. 2013-212935 Japanese Patent Application Publication No. 6-345481

In view of these circumstances, the first object of the first invention is to provide a phosphate optical glass that has excellent transparency, high dispersion, and suppresses an increase in refractive index; The purpose of the present invention is to provide an optical element made of optical glass and an optical glass material. A second object of the second invention is to provide a glass that can shorten the heat treatment time when reducing reduced color by heat treatment.

As a result of extensive research in order to achieve the above object, the present inventors have found that, in response to the first problem, the content ratio of various glass components (hereinafter referred to as glass components) constituting the glass must be adjusted. It was discovered that the object could be achieved by this, and based on this knowledge, the first invention was completed. In addition, with respect to the second problem, it was discovered that the objective could be achieved by incorporating Li ₂ O in a predetermined ratio to the high dispersion component, and based on this knowledge, the second invention was completed. I ended up doing it.

That is, the gist of the present invention is as follows.
(1) Abbe number νd is 16.70 or less,
The refractive index nd is 2.1000 or less,
Contains P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ,
A phosphate optical glass in which the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of 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) Abbe number νd is 16.70 or less,
The content of Bi ₂ O ₃ is 29.0% by mass or less,
A phosphate optical glass having a total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ of 45.0% by mass or more.
(4) 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 (1) to ( The phosphate optical glass according to any one of 3).
(5) A glass material for press molding comprising the phosphate optical glass according to any one of (1) to (4) above.
(6) An optical element made of the phosphate optical glass according to any one of (1) to (4) above.
(7) Abbe number ν _d is 18.10 or less,
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 30% by mass or more, and the content of Bi ₂ O ₃ is 38% by mass % or less of phosphate glass,
Mass ratio of Li ₂ O content to total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] Glass whose value obtained by multiplying by 100 is 0.015 to 0.770.
(8) Abbe number ν _d is 18.10 or less,
A phosphate glass containing at least one oxide selected from TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ ,
Remelt and mold for 90 minutes at a temperature 110 to 120°C higher than the liquidus temperature LT in an air atmosphere,
The glass obtained by keeping it at a holding temperature 0 to 20°C lower than the glass transition temperature Tg for 15 minutes in an air atmosphere and slowly cooling it at a cooling rate of 30°C/h to a temperature 120°C lower than the holding temperature, 17 mm long, For those processed to 13 mm in width and 10 mm in thickness,
When viewed from above, a portion within a distance of 0 to 5 mm from the end in the vertical direction and a distance of 0 to 5 mm from the end in the horizontal direction is defined as the glass end;
When the center of the glass is defined as a portion that is 6 to 11 mm from the vertical edge and 4 to 9 mm from the horizontal edge when viewed from above,
When light is incident parallel to the thickness direction, the external transmittance T _A of the edge of the glass and the external transmittance T _B of the center of the glass at a wavelength of 656 nm are greater than or equal to the value T ₁ calculated by the following formula (2). ,and,
Until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less,
Heat treatment in the air at a temperature increase rate of 100 °C/h and holding at a heat treatment temperature 5 to 15 °C lower than the glass transition temperature Tg, and a temperature decrease rate of 30 °C/h to a temperature 120 °C lower than the heat treatment temperature. When repeating the slow cooling process once or multiple times,
A glass whose total holding time at the heat treatment temperature in the heat treatment is 48 hours or less.
T ₁ =0.83×[1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (2)
[In formula (2), n _C is the heat treatment performed until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less. and the refractive index at a wavelength of 656.27 nm when subjected to slow cooling treatment. ]
(9) The glass according to (7) or (8), wherein the content of Li ₂ O is 0.010% by mass or more.
(10) The glass according to any one of (7) to (9), wherein the content of Li ₂ O is 0.640% by mass or less.
(11) The glass according to any one of (7) to (10), wherein the value of βOH shown in the following formula (1) is 0.05 mm-1 or more.
βOH=-[ln(D/C)]/t...(1)
[In formula (1), t represents the thickness (mm) of the glass used to measure the external transmittance, and C represents the external transmission at a wavelength of 2500 nm when light is incident on the glass parallel to its thickness direction. D represents the external transmittance (%) at a wavelength of 2900 nm when light is incident on the glass in parallel to its thickness direction. ]
(12) The glass according to any one of (7) to (11), containing Nb ₂ O ₅ as a glass component.
(13) The glass according to any one of (7) to (12), which contains TiO ₂ as a glass component.
(14) Optical glass comprising the glass described in any one of (7) to (13) above.
(15) A polishing glass material made of the glass according to any one of (7) to (13) above.
(16) A glass material for press molding made of the glass according to any one of (7) to (13) above.
(17) A polishing glass material comprising the optical glass described in (14) above.
(18) A press-molding glass material comprising the optical glass described in (14) above.
(19) An optical element made of the glass according to any one of (7) to (13) above.
(20) An optical element made of the optical glass described in (14) above.
(21) An optical element made of the polishing glass material described in (15) or (17) above.
(22) An optical element made of the press-molding glass material according to (16) or (18) above.

According to the first aspect of the invention, when a pair of lenses is made in combination with a low-dispersion glass lens, since the difference in Abbe number is large, a high effect is achieved in correcting chromatic aberration. Further, even when a pair lens is formed by combining the lens with a low-dispersion glass lens having a low refractive index, curvature of field is suppressed because the difference in refractive index is small.
According to the second invention, when reducing reduced color by heat treatment in a highly dispersible glass, the heat treatment time can be shortened.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter simply referred to as "embodiments") will be described in detail. The present embodiment below is an illustration for explaining the present invention, and is not intended to limit the present invention to the following content. The present invention can be implemented with appropriate modifications within the scope of its gist. Furthermore, the description may be omitted as appropriate for parts where the description overlaps, but this does not limit the gist of the invention. In this specification, "optical glass" refers to a glass composition containing multiple types of glass constituents (glass components), and unless otherwise specified, the term "optical glass" refers to a glass composition that includes multiple types of glass constituents (glass components), and unless otherwise specified, the term "optical glass" refers to a glass composition that includes multiple types of glass constituents (glass components), and unless otherwise specified, the term "optical glass" refers to a glass composition that includes multiple types of glass constituents (glass components). It is used as a general term regardless of use (materials for optical elements, optical elements, etc.) or size. That is, there are no restrictions on the form, use, or size of optical glass, and optical glass in any form, for any purpose, and in any size is included in the optical glass in the present invention. Moreover, in this specification, optical glass may be simply referred to as "glass."

Further, in this specification, (numerical value 1) may be used to represent a numerical range such as "(numerical value 1) or less". The range expressed in this way is the numerical range that is the sum of the numerical range smaller than (numerical value 1) and (numerical value 1). A numerical range expressed as "less than (numerical value 1)" is a numerical range smaller than (numerical value 1) and does not include (numerical value 1). (Number 2) may be used to express a numerical range, such as "(Number 2) or more". The range expressed in this way is a numerical range that is a combination of a numerical range larger than (numerical value 2) and (numerical value 2). A numerical range may be expressed, such as "more than (number 2)". The range expressed in this way is a numerical range larger than (numerical value 2) and does not include (numerical value 2).

In this specification, the optical glass according to the present invention will be explained mainly based on the content of each glass component expressed in mass %. Hereinafter, "%" represents mass % unless otherwise specified. In addition, for some glass components, the content expressed in cation percentage is also described.

In this specification, mass % display refers to the content of each glass component expressed as a mass percentage when the total content of all glass components is 100 mass% for each glass component represented by oxide or fluoride. It means to display by. Further, the total content expressed in mass % refers to the total content of multiple types of glass components (including cases where the content is 0%). Moreover, the mass ratio refers to the ratio (ratio) between the contents of glass components (including the total content of multiple types of components) expressed in mass %.

Moreover, in this specification, the cation % display refers to the molar percentage when the total content of all cation components is taken as 100%. The total content in terms of cation percentage refers to the total content of multiple types of cation components (including cases where the content is 0%). In addition, the cation ratio refers to the ratio (ratio) of the contents of cation components (including the total content of multiple types of cation components) in cation percentage display.

Note that the valences of cationic components (for example, the valence of P ⁵⁺ is +5, the valence of Si ⁴⁺ is +4, and the valence of La ³⁺ is +3) are values determined by custom, and are used as glass components. When P, Si, and La are expressed on an oxide basis, they are expressed as P ₂ O ₅ , SiO ₂ , and La ₂ O ₃ . Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of the cation component. In addition, the valence of the anion component (for example, the valence of O ^2- is -2) is a value determined by custom, and as mentioned above, the glass component on an oxide basis is replaced with, for example, P ₂ O ₅ , SiO ₂ , La This is the same as writing ₂ O ₃ . Therefore, when analyzing the glass composition, it is not necessary to analyze the valence of the anion component.

As described below, Sb ₂ O ₃ , SnO ₂ , and CeO ₂ are sometimes added in small amounts to glass as refining agents. However, in this specification, the total content of all glass components does not include the content of Sb ₂ O ₃ , SnO ₂ and CeO ₂ . That is, the respective contents of Sb ₂ O ₃ , SnO ₂ and CeO ₂ in the glass component are the Sb ₂ O ₃ , SnO ₂ in the total content of all glass components other than Sb ₂ O ₃ , SnO ₂ and CeO ₂ , CeO ₂ content. In this specification, such a notation is referred to as ``towari''.

Hereinafter, a first embodiment and a second embodiment of the present invention will be described. Note that the first embodiment is an embodiment of the first invention, and the second embodiment is an embodiment of the second invention.

First Embodiment Embodiment 1-1 and Embodiment 1-2 (hereinafter sometimes collectively referred to as "first embodiment") will be described in detail.

The glass composition of the optical glass according to the first embodiment can be determined 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 a measurement error of about ±5% of the analysis value, for example. Furthermore, in this specification and the present invention, 0% or no content of a glass component means that the component is not substantially included, and the content of this component is approximately at the impurity level. Refers to the following.

1-1 Embodiment The optical glass of 1-1 embodiment of the present invention is
Abbe number νd is 16.70 or less,
The refractive index nd is 2.1000 or less,
Contains P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ,
It is a phosphate optical glass in which the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of Nb ₂ O ₅ is 0.15 or more.

The optical glass according to Embodiment 1-1 will be described in detail below.

In the optical glass according to the 1-1 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 in the order of 16.66, 16.64, 16.62, 16.60, 16.58, 16.56, and 16.54. Further, the lower limit of Abbe's number is preferably 15.50, and more preferably, the larger the value is in the order of 15.55, 15.60, 15.65, and 15.70.

By setting the Abbe number νd to 16.70 or less, when the lens is combined with a low-dispersion glass lens to form a pair lens, the difference in Abbe numbers becomes large, resulting in a high effect in correcting chromatic aberration.

In the optical glass according to the 1-1 embodiment, the refractive index nd is 2.1000 or less. The upper limit of the refractive index is preferably 2.0950, and more preferably in the order of 2.0900, 2.0850, 2.0800, 2.0750, 2.0500, 2.0300, 2.0100, and 2.0000. more preferred. Further, the lower limit of the refractive index is preferably 1.8800, and more preferably the larger the value is in the order of 1.9000, 1.9200, 1.9400, and 1.9600.

By setting the refractive index nd to 2.1000 or less, even when combined with a low-dispersion glass lens having a low refractive index to form a pair lens, the difference in refractive index is small, so field curvature is suppressed.

The optical glass according to Embodiment 1-1 contains P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ . By containing P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ , an optical glass with high dispersion and suppressed increase in refractive index nd can be obtained.

In the optical glass according to the 1-1 embodiment, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of Nb ₂ O ₅ is 0.15 or more. As mentioned above, the optical glass according to Embodiment 1-1 contains P ₂ O ₅ and TiO ₂ , but by increasing P ₂ O ₅ and TiO ₂ , the solubility of the glass decreases and the liquidus temperature increases. The problem arises of rising. Therefore, this problem was solved by containing Nb ₂ O ₅ , which contributes to high dispersion, in a specific ratio to TiO ₂ to prevent the liquidus temperature from increasing.

In the optical glass according to the 1-1 embodiment, the lower limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of Nb ₂ O ₅ is preferably 0.16, Furthermore, the order of 0.17, 0.18, 0.19, 0.20, and 0.23 is more preferable. The upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.50, more preferably 4.40, 4.30, 4.20, 4.10, 4.00, 3.80. , 3.60 is more preferable.

Furthermore, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the cation ratio between the Ti ⁴⁺ content and the Nb ⁵⁺ content [Ti ⁴⁺ /Nb ^{5 +} ] is preferably 6.00, and more preferably in the order of 5.90, 5.80, 5.70, 5.65, and 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 in that order.

Ti ⁴⁺ tends to reduce the solubility of glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ suppresses a decrease in liquidus temperature and an increase in refractive index, contributing to high dispersion. Therefore, by containing Nb ⁵⁺ in a constant ratio 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 this embodiment, the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably within the above range.

The optical glass according to the 1-1 embodiment is a phosphate optical glass. Phosphate optical glass refers to optical glass that mainly contains phosphate as a network forming component of the glass. Therefore, the optical glass according to the 1-1 embodiment contains phosphate as a network forming component, and the content thereof is expressed as the content of P ₂ O ₅ . P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known as glass network forming components. Here, "containing mainly phosphate as a network-forming component of the glass" means that the content of P ₂ O ₅ in mass % is higher than the content of any of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ . Also means a lot of glass.

In the optical glass according to Embodiment 1-1, the lower limit of the P ₂ O ₅ content is preferably 7.0%, and more preferably 8.0%, 9.0%, 10.0%, The order of 11.0%, 12.0%, 12.5%, and 13.0% is more preferable. Further, the upper limit of the content of P ₂ O ₅ is preferably 35.0%, and more preferably in the order of 34.5%, 34.0%, 33.5%, and 33.0%.

P ₂ O ₅ is an essential component for suppressing an increase in the refractive index nd and for containing a large amount of highly dispersible components in the glass. On the other hand, if P ₂ O ₅ is included excessively, the solubility will deteriorate. Therefore, in the optical glass according to this embodiment, the content of P ₂ O ₅ is preferably within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the P ⁵⁺ content is preferably 45.00 cation%, and more preferably 44.00%. 50 cation%, 44.00 cation%, 43.50 cation%, 43.00 cation%, 42.50 cation%, 42.00 cation%, 41.50 cation%, 41.00 cation%, 40.50 cation %, 40.00 cation%, 39.50 cation%, 39.00 cation%, and 38.50 cation%. The lower limit of the content of P ⁵⁺ is preferably 20.00 cation%, more preferably 20.50 cation%, 21.00 cation%, 21.50 cation%, 22.00 cation%, 22.50 cation%. %, 23.00 cation%, 23.50 cation%, 24.00 cation%, 24.50 cation%, 25.00 cation%, and 25.50 cation%.

P ⁵⁺ is an essential component for suppressing an increase in the refractive index nd and for containing a large amount of highly dispersible components in the glass. On the other hand, when P ⁵⁺ is included excessively, solubility deteriorates. Therefore, in the optical glass according to this embodiment, the content of P ⁵⁺ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Bi ₂ O ₃ content is preferably 29.0%, and more preferably 28.5%, 28.0%, 27.5%, The preferred order is 27.0%, 25.0%, 20.0%, 15.0%, 10.0%, 6.0%, and 5.0%. Moreover, 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 the function of improving the thermal stability of glass by containing it in an appropriate amount. On the other hand, increasing the content of Bi ₂ O ₃ increases the refractive index and increases the coloring of the glass. Therefore, it is preferable that the content of Bi ₂ O ₃ is within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Bi ³⁺ content is preferably 20.00 cation%, and more preferably 19.00%. The preferred order is 50 cation%, 19.00 cation%, 18.50 cation%, 18.00 cation%, 17.50 cation%, 17.00 cation%, and 16.50 cation%. The lower limit of the Bi ³⁺ content 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 cation%.

Bi ³⁺ has the function of improving the thermal stability of glass by containing it in an appropriate amount. On the other hand, increasing the Bi ³⁺ content increases the refractive index and increases the coloring of the glass. Therefore, it is preferable that the content of Bi ³⁺ is within the above range.

In the optical glass according to the 1-1 embodiment, the lower limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] between the total content of TiO ₂ and WO ₃ and the Nb ₂ O ₅ content is as follows: Preferably it is 0.15, more preferably 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 The order of .64 and 0.65 is more preferable. Further, the upper limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 8.00, more preferably 7.90, 7.80, 7.70, 7.60, 7. The preferred order is 40, 7.20, and 7.00.

By setting the value of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] within the above range, it is possible to obtain a glass having high dispersion suitable for correcting chromatic aberration while suppressing an increase in the refractive index.

In addition, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the cation ratio of the total content of Ti ⁴⁺ and W ⁶⁺ and the content of Nb ⁵⁺ [( The upper limit of Ti ⁴⁺ +W ⁶⁺ )/Nb ⁵⁺ is preferably 7.70, more preferably 7.60, 7.50, 7.40, 7.35, 7.30, 7.28, The order of 7.26 is more preferable. 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 in that order.

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

In the optical glass according to the 1-1 embodiment, the mass of the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ and the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ The lower limit of the ratio [(TiO ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] is preferably 0.45, more preferably 0.50, 0.55. , 0.60, 0.65, 0.70, 0.75, 0.80, 0.85 in this order. 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%.

Mass ratio [(TiO ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )]
By setting the value within the above range, deterioration of transmittance can be suppressed, and increase in refractive index and specific gravity can also be suppressed.

In the optical glass according to the 1-1 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 are more preferable in the order of 45.0%, 46.0%, 47.0%, 48.0%, 49.0%, 50.0%, and 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%, and 81.0%. , 79.0%, and 77.0%.

TiO ₂ , Nb ₂ O ₅ and WO ₃ are all glass components that contribute to high dispersion, but they also cause increased discoloration. Therefore, the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ ] is preferably within the above range.

In the optical glass according to Embodiment 1-1, when the content of glass components is expressed in cation%, if the W ⁶⁺ content exceeds 0 cation%, the Ba ²⁺ content and W The upper limit of the cation ratio [Ba ²⁺ /W ⁶⁺ ] with respect to the content of ⁶⁺ is preferably 0.14, and more preferably in the order of 0.13, 0.12, 0.11, and 0.10. preferable.

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to the 1-1 embodiment, desired high dispersion can be achieved by containing W ⁶⁺ , which is a high dispersion component, at the above cation ratio with respect to the Ba ²⁺ content. can be maintained.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the content of W ⁶⁺ is 0 cation%, and the content of Ba ²⁺ is 0 cation%. cation%, the upper limit of the total content of Ti ⁴⁺ and Bi ³⁺ [Ti ⁴⁺ +Bi ³⁺ ] is preferably 35.00 cation%, more preferably 34.00 cation%, 33 .00 cation%, 32.50 cation%, 32.30 cation%, 32.00 cation%, 31.80 cation%, 31.60 cation%, 31.40 cation%, 31.20 cation%, 31.00 The preferred order is cation%, 30.80 cation%, 30.60 cation%, 30.40 cation%, 30.20 cation%, 30.10 cation%, and 30.00 cation%. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cation%, and more preferably 21.20 cation%, 21.40 cation%, 21.60 cation%, and 21.80 cation%. , 22.00 cation%, 22.20 cation%, 22.40 cation%, 22.60 cation%, 22.80 cation%, 23.00 cation%, 23.10 cation%, 23.20 cation%, 23 The preferred order is .30 cation%, 23.40 cation%, and 23.50 cation%.

When the W ⁶⁺ content is 0 cation% and the Ba ²⁺ content exceeds 0 cation%, Ti, which has the second largest contribution to high dispersion after W ⁶⁺ among high dispersion components, By setting the total content of ⁴⁺ and Bi ³⁺ , which has the function of improving thermal stability, within the above range, low dispersion caused by Ba ²⁺ can be suppressed.

(Glass component)
The optical glass according to Embodiment 1-1 above may contain the following glass components.

The optical glass according to the 1-1 embodiment can contain B ₂ O ₃ , SiO ₂ , and Al ₂ O ₃ as glass network forming components other than P ₂ O ₅ .

In the optical glass according to Embodiment 1-1, the upper limit of the B ₂ O ₃ content is preferably 4.0%, and more preferably 3.0%, 2.0%, and 1.0%. The order is more preferable. The content of B ₂ O ₃ may be 0%.

B ₂ O ₃ is a network forming component of glass, and has the function of improving the meltability of glass and suppressing an increase in refractive index. On the other hand, if the content of B ₂ O ₃ is high, it tends to suppress the decrease in Abbe's number and prevent high dispersion, and also tends to reduce chemical durability. Therefore, from the viewpoint of improving the thermal stability, meltability, moldability, etc. of the glass while suppressing an increase in the refractive index, the upper limit of the content of B ₂ O ₃ is preferably within the above range. On the other hand, from the viewpoint of maintaining good chemical durability while obtaining the desired Abbe number, the lower limit of the content of B ₂ O ₃ is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the upper limit of the SiO ₂ content is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.5%, and 5.0%. The preferred order is 0%, 4.5%, 4.0%, 3.5%, and 3.0%. The content of SiO ₂ may be 0%.

SiO ₂ is a network-forming component of glass, and has the function of improving the thermal stability, chemical durability, and weather resistance of glass, increasing the viscosity of molten glass, and making it easier to shape molten glass. On the other hand, if the content of SiO ₂ is high, the melting properties and low-temperature softening properties of the glass decrease, and the glass raw materials tend to remain unmelted. Therefore, from the viewpoint of improving the melting properties, low-temperature softening properties, etc. of the glass, the upper limit of the content of SiO ₂ is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the upper limit of the Al ₂ O ₃ content is preferably 5.0%, and more preferably 4.0%, 3.5%, 2.5%, The preferred order is 2.0%, 1.5%, 1.0%, and 0.5%. The content of Al ₂ O ₃ may be 0%.

Al ₂ O ₃ is a glass component that suppresses the increase in refractive index and improves the chemical durability and weather resistance of glass, and can be considered as a network-forming component. On the other hand, when the content of Al ₂ O ₃ increases, the thermal stability of the glass decreases, which tends to cause problems such as an increase in the glass transition temperature Tg and a decrease in meltability. From the viewpoint of avoiding such problems, the upper limit of the content of Al ₂ O ₃ is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ which are network forming components of the glass [P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ] is preferably 45.0%, more preferably 43.0%, 41.0%, 39.0%, 37.0%, 35.0%, 33.0%. The order of percentage is more preferable. 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%, 14.0%, 15.0% in that order.

By setting the upper limit of the total content [P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ] within the above range, it becomes easier to maintain the refractive index within the 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 ] within the above range, the thermal stability of the glass is improved and devitrification of the glass is further suppressed. It becomes easier.

Further, in the optical glass according to the 1-1 embodiment, the mass ratio of the content of P ₂ O ₅ to the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ [P ₂ O ₅ /(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )], the lower limit is preferably 0.70, and more preferably 0.75, 0.80, 0.85, and 0.90. The order is more preferable. 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 will decrease, and the meltability will also decrease. Therefore, from the viewpoint of maintaining high dispersion and good meltability of the glass, 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 within the above range. It is preferable that there be.

In the optical glass according to the 1-1 embodiment, the lower limit of the TiO ₂ content is preferably 1.0%, and more preferably 3.0%, 5.0%, 6.0%, and 7.0%. The preferred order is 0%, 8.0%, 9.0%, and 10.0%. Further, the upper limit of the content of TiO ₂ is preferably 45.0%, and furthermore, 44.0%, 43.0%, 42.0%, 41.0%, 40.0%, 39.0%. The order of 0% is more preferable.

TiO ₂ suppresses the increase in refractive index compared to Nb ₂ O ₅ and Bi ₂ O ₃ and greatly contributes to high dispersion. On the other hand, TiO ₂ is relatively easy to increase the coloration of glass. Furthermore, TiO ₂ promotes crystal formation within the glass during the process of forming and slowly cooling molten glass to obtain optical glass, thereby reducing the transparency of the glass (clouding). Therefore, in the optical glass according to this embodiment, the content of TiO ₂ is preferably within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Ti ⁴⁺ content is preferably 48.00 cation%, and more preferably 47.00%. 00 cation%, 46.00 cation%, 45.50 cation%, 45.00 cation%, 44.50 cation%, 44.00 cation%, 43.50 cation%, 43.00 cation%, 42.50 cation %, and 42.00 cation%. The lower limit of the content of Ti ⁴⁺ is preferably 10.00 cation%, and more preferably 11.00 cation%, 11.50 cation%, 12.00 cation%, 12.50 cation%, and 13.00 cation%. %, 13.50 cation%, 14.00 cation%, 14.50 cation%, 15.00 cation%, and 15.50 cation%.

Ti ⁴⁺ suppresses the increase in refractive index compared to Nb ⁵⁺ and Bi ³⁺ and greatly contributes to high dispersion. On the other hand, Ti ⁴⁺ relatively tends to increase the coloration of glass. Furthermore, Ti ⁴⁺ promotes crystal formation within the glass during the process of forming and slowly cooling molten glass to obtain optical glass, thereby reducing the transparency of the glass (clouding). Therefore, in the optical glass according to this embodiment, the content of Ti ⁴⁺ is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the upper limit of the mass ratio [TiO ₂ /P ₂ O ₅ ] between the content of TiO ₂ and the content of P ₂ O ₅ is preferably 4.50, Furthermore, the order of 4.00, 3.50, 3.00, 2.50, 2.00, and 1.50 is more preferable. 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. The preferred order is 28, 0.32, 0.36, 0.40, 0.44, 0.48, and 0.52.

In the optical glass according to the 1-1 embodiment, the inclusion of TiO ₂ promotes crystal formation within the glass, resulting in a problem that the transparency of the glass decreases (cloudiness). This problem can be solved by containing P ₂ O ₅ , which is a network forming component, in a ratio within the above range to TiO ₂ .

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the cation ratio between the Ti ⁴⁺ content and the P ⁵⁺ content [Ti ⁴⁺ /P ^{5 +} ] is preferably 1.50, and more preferably 1.40, 1.30, 1.29, 1.28, 1.27, 1.26, 1.25, 1.24, 1. The order of 23 and 1.22 is more preferable. The lower limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] is preferably 0.50, and more preferably in the order of 0.51, 0.52, and 0.53.

In the optical glass according to the 1-1 embodiment, the inclusion of Ti ⁴⁺ promotes crystal formation within the glass, resulting in a problem that the transparency of the glass decreases (cloudiness). This problem can be solved by containing P ⁵⁺ , which is a network forming component, in a ratio within the above range to Ti ⁴⁺ .

In the optical glass according to Embodiment 1-1, the lower limit of the Nb ₂ O ₅ content is preferably 5.5%, and more preferably 6.0%, 6.5%, 7.0%, The order of 7.5%, 8.0%, and 8.5% is more preferable. 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%, The order of 49.0% and 48.0% is more preferable.

Nb ₂ O ₅ is a component that contributes to high dispersion. It is also a glass component that improves the thermal stability and chemical durability of the glass. On the other hand, when the content of Nb ₂ O ₅ becomes too large, the thermal stability of the glass tends to decrease and the coloring of the glass tends to become stronger. Therefore, in the optical glass according to this embodiment, the content of Nb ₂ O ₅ is preferably within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Nb ⁵⁺ content is preferably 45.00 cation%, and more preferably 44.00%. 00 cation%, 43.50 cation%, 43.00 cation%, 42.50 cation%, 42.00 cation%, 41.50 cation%, 41.00 cation%, 40.50 cation%, 40.00 cation %, 39.50 cation%, 39.00 cation%, and 38.50 cation%. The lower limit of the content of Nb ⁵⁺ is preferably 1.00 cation%, more preferably 2.00 cation%, 2.50 cation%, 3.00 cation%, 3.50 cation%, 4.00 cation%. %, 4.50 cation%, 5.00 cation%, 5.50 cation%, 6.00 cation%, and 6.50 cation%.

Nb ⁵⁺ is a component that contributes to high dispersion. It is also a glass component that improves the thermal stability and chemical durability of the glass. On the other hand, if the content of Nb ⁵⁺ becomes too large, the thermal stability of the glass tends to decrease and the coloring of the glass tends to become stronger. Therefore, in the optical glass according to this embodiment, the content of Nb ⁵⁺ is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the upper limit of the WO ₃ content is preferably 45.0%, and more preferably 44.5%, 44.0%, 43.5%, 43.0%. The preferred order is 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. The order of 3% and 0.1% is more preferable. The content of WO ₃ may be 0%.

Although WO ₃ suppresses the increase in the refractive index and greatly contributes to high dispersion, it is more likely to cause coloring of the glass than TiO ₂ , Nb ₂ O ₅ and Bi ₂ O ₃ and deteriorates the transmittance. Therefore, the content of WO ₃ is preferably within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass component is expressed in cation%, the upper limit of the content of W ⁶⁺ is preferably 30.00 cation%, and more preferably 29.00%. 00 cation%, 28.50 cation%, 28.00 cation%, 27.50 cation%, 27.00 cation%, 26.50 cation%, 26.00 cation%, 25.50 cation%, 25.00 cation %, and 24.50 cation%. 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 that order. The content of W ⁶⁺ may be 0 cation%.

Although W ⁶⁺ suppresses the increase in the refractive index and greatly contributes to high dispersion, it is more likely to cause coloring of the glass than Ti ⁴⁺ , Nb ⁵⁺ and Bi ³⁺ and deteriorates the transmittance. Therefore, the content of W ⁶⁺ is preferably within the above range.

In the optical glass according to the 1-1 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 is 86.0%, and more preferably in the order of 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%, The preferred order is 62.0%, 62.5%, 63.0%, 63.5%, and 64.0%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. 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 coloring of the glass, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range. Further, from the viewpoint of highly dispersing the glass and improving 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 within the above range.

Furthermore, in the optical glass according to the 1-1 embodiment, when the content of glass components is expressed in cation%, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is preferably 75.00 cation%, more preferably 74.50 cation%, 74.00 cation%, 73.50 cation%, 73.00 cation%, 72 The preferred order is .50 cation%, 72.00 cation%, 71.50 cation%, 71.00 cation%, and 70.50 cation%. 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%, and 52.20 cation%. , 52.25% cations, and 52.30% cations in that order.

In the optical glass according to the 1-1 embodiment, Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. Therefore, the lower limit of the total content [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is preferably within 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 within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Li ₂ O content is preferably 1.2%, and more preferably 1.1%, 1.0%, 0.8%, 0. The order of .6% and 0.4% is more preferable. The content of Li ₂ O may be 0%.

Li ₂ O suppresses an increase in the refractive index and functions to improve the meltability of glass. Therefore, from the viewpoint of ensuring meltability while maintaining required optical properties, the content of Li ₂ O is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Na ₂ O content is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3. The order of .5% and 3.0% is more preferable. 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 Embodiment 1-1, the upper limit of the content of K ₂ O is preferably 12.0%, and more preferably 11.0%, 10.0%, 9.0%, 8. The order of .5% and 8.0% is more preferable. Further, the lower limit of the K ₂ O content is preferably 0.1%, more preferably 0.3%, in order to maintain good thermal stability of the glass and suppress the increase in liquidus temperature. , 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%. The content of K ₂ O may be 0%.

Both Na ₂ O and K ₂ O have the function of suppressing the increase in the refractive index and improving the meltability of glass, but when their content increases, the thermal stability and chemical durability of the glass deteriorate. properties and weather resistance decrease. Therefore, it is preferable that the respective contents of Na ₂ O and K ₂ O are within the above ranges.

In the optical glass according to Embodiment 1-1, 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 are more preferable in the order of 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, and 9.0%. In addition, the lower limit of the total content [Li ₂ O + Na ₂ O + K ₂ O] is preferably 0.1% in order to maintain good thermal stability of the glass and suppress the increase in liquidus temperature, and are more preferable in the order of 0.3%, 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%. The total content [Li ₂ O+Na ₂ O+K ₂ O] may be 0%.

Li ₂ O, Na ₂ O and K ₂ O all have the function of suppressing an increase in the refractive index and improving the meltability of glass. However, when these contents increase, the thermal stability, chemical durability, and weather resistance of the glass decrease. 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 within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Rb ₂ O content is preferably 2.0%, and more preferably in the order of 1.0%, 0.5%, and 0.1%. more preferred. Moreover, 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 Embodiment 1-1, the upper limit of the Cs ₂ O content is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3. The order of .5% is more preferable. 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 the function of suppressing the increase in the refractive index and improving the meltability of glass, but when their contents increase, the thermal stability and chemical durability of the glass deteriorate. properties and weather resistance decrease. Therefore, it is preferable that the respective contents of Rb ₂ O and Cs ₂ O are within the above ranges.

In the optical glass according to Embodiment 1-1, the upper limit of the MgO content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0%. The order of percentage is more preferable. Further, the lower limit of the MgO content is preferably 0%. The content of MgO may be 0%.

In the optical glass according to Embodiment 1-1, the upper limit of the CaO content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0%. The order of percentage is more preferable. Further, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

In the optical glass according to Embodiment 1-1, the upper limit of the SrO content is preferably 6.0%, and more preferably 5.8%, 5.7%, 5.6%, and 5.5%. %, 5.0%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%. Further, the lower limit of the SrO content is preferably 0%. The content of SrO may be 0%.

In the optical glass according to Embodiment 1-1, the upper limit of the BaO content is preferably 6.0%, and more preferably 5.8%, 5.7%, 5.6%, and 5.5%. %, 5.0%, 4.5%, 4.0% in that order. Further, the lower limit of the BaO content is preferably 0%. The content of BaO may be 0%.

MgO, CaO, SrO, and BaO are all glass components that have the function of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, high dispersibility is impaired, the thermal stability of the glass is reduced, and the glass is likely to devitrify. Therefore, the content of each of these glass components is preferably within the above range.

Further, in the optical glass according to the 1-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Ba ²⁺ content is preferably 13.00 cation%, and more preferably 12.00%. 00 cation%, 11.00 cation%, 10.00 cation%, 9.00 cation%, 8.00 cation%, 7.50 cation%, 7.00 cation%, 6.50 cation%, 6.00 cation %, 5.50 cation%, 5.00 cation%, 4.50 cation%, 4.00 cation%, and 3.50 cation%. Further, the lower limit of the Ba ²⁺ content is preferably 0 cation%. The content of Ba ²⁺ may be 0 cation%.

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ are all glass components that have the function of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, high dispersibility is impaired, the thermal stability of the glass is reduced, and the glass is likely to devitrify. Therefore, the content of each of these glass components is preferably within the above range.

In the optical glass according to Embodiment 1-1, from the viewpoint of maintaining thermal stability without hindering high dispersion, the upper limit of the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is preferably 10 0%, and more preferably in the order of 9.0%, 8.0%, 7.0%, 6.0%, 5.5%, and 5.0%. 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 Embodiment 1-1, the upper limit of the ZnO content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0%. The order of percentage is more preferable. Further, the lower limit of the ZnO content is preferably 0%. The content of ZnO may be 0%.

ZnO is a glass component that has the function of promoting the melting of glass raw materials (that is, the function of improving meltability) when melting glass. Moreover, ZnO has a strong effect of improving the thermal stability of glass and lowering the liquidus temperature compared to other divalent metal components such as alkaline earth metals. Therefore, from the viewpoint of improving the meltability and thermal stability of the glass, the lower limit of the ZnO content is preferably within the above range. Further, from the viewpoint of suppressing the dispersion of the glass, the upper limit of the ZnO content is preferably within the above range.

In the optical glass according to the 1-1 embodiment, the upper limit of the ZrO ₂ content is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3. The order of 0% and 2.0% is more preferable. Further, the lower limit of the ZrO ₂ content is preferably 0%. The content of ZrO ₂ may be 0%.

ZrO ₂ is a glass component that functions to improve the thermal stability of glass. However, if the content of ZrO ₂ is too large, the refractive index tends to increase and the thermal stability of the glass tends to decrease. Moreover, the glass raw material tends to remain unmelted. Therefore, from the viewpoint of maintaining good meltability and thermal stability of the glass and achieving desired optical properties, the upper limit of the ZrO ₂ content is preferably within the above range. On the other hand, from the viewpoint of improving the thermal stability of the glass while realizing the required optical properties, the lower limit of the ZrO ₂ content is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Ta ₂ O ₅ content is preferably 9.0%, and more preferably 8.0%, 7.0%, 6.0%, The order of 5.0%, 4.0%, and 3.0% is more preferable. 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 that functions to improve the thermal stability of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and lowers the dispersion of the glass. Further, Ta ₂ O ₅ is an extremely expensive component compared to other glass components, and as the content of Ta ₂ O ₅ increases, the production cost of the glass increases. Furthermore, since Ta ₂ O ₅ has a larger molecular weight than other glass components, it increases the specific gravity of the glass, resulting in an increase in the weight of the glass optical element. Moreover, when the content of Ta ₂ O ₅ increases, the meltability of the glass decreases, and unmelted glass raw materials tend to remain when melting the glass. Therefore, the content of Ta ₂ O ₅ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the content of Ga ₂ O ₃ is preferably 4.0%, and more preferably 3.5%, 3.0%, 2.5%, The preferred order is 2.0%, 1.5%, 1.0%, 0.5%, and 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 Embodiment 1-1, the upper limit of the content of In ₂ O ₃ is preferably 5.0%, more preferably 4.5%, 4.0%, 3.5%, The order of 3.0% is more preferable. 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 Embodiment 1-1, the upper limit of the content of Sc ₂ O ₃ is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, The order of 1.0% is more preferable. 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 1-1 embodiment, the upper limit of the HfO ₂ content is preferably 8.0%, and more preferably 7.0%, 6.5%, 6.0%, and 5.0%. 5%, 5.0%, 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, 0. The order of 5% and 0.1% is more preferable. 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 the function of increasing the refractive index nd, and are expensive components. Therefore, each content of Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , and HfO ₂ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the content of Lu ₂ O ₃ is preferably 5.0%, more preferably 4.5%, 4.0%, 3.5%, The order of 3.0% is more preferable. 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 the function of increasing the refractive index nd. Moreover, since it has a large molecular weight, it is also a glass component that increases the specific gravity of glass. Therefore, it is preferable to reduce the content of Lu ₂ O ₃ , and the content of Lu ₂ O ₃ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the content of GeO ₂ is preferably 6.0%, and more preferably 5.0%, 4.0%, 3.0%, 2. The preferred order is 0%, 1.5%, 1.0%, 0.5%, and 0.1%. Further, the lower limit of the content of GeO ₂ is preferably 0%. The content of GeO ₂ may be 0%.

GeO ₂ has the function of increasing the refractive index nd, and is by far the most expensive component among commonly used glass components. Therefore, from the viewpoint of reducing the manufacturing cost of glass, the content of GeO ₂ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the content of La ₂ O ₃ is preferably 5.0%, more preferably 4.5%, 4.0%, 3.5%, The preferred order is 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, and 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 increases, the thermal stability of the glass decreases, and the glass becomes more likely to devitrify during production. Therefore, from the viewpoint of suppressing a decrease in the thermal stability of the glass, the content of La ₂ O ₃ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Gd ₂ O ₃ content is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.0%, The preferred order is 4.0%, 3.0%, 2.0%, 1.5%, and 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%.

If the content of Gd ₂ O ₃ becomes too large, the thermal stability of the glass will decrease, and the glass will be more likely to devitrify during production. Moreover, if the content of Gd ₂ O ₃ is too large, the specific gravity of the glass will increase, which is not preferable. Therefore, from the viewpoint of suppressing an increase in specific gravity while maintaining good thermal stability of the glass, the content of Gd ₂ O ₃ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Y ₂ O ₃ content is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, The order of 3.0%, 2.5%, and 2.0% is more preferable. 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%.

If the content of Y ₂ O ₃ becomes too large, the thermal stability of the glass will decrease, and the glass will be more likely to devitrify during production. Therefore, from the viewpoint of suppressing a decrease in the thermal stability of the glass, the content of Y ₂ O ₃ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the upper limit of the Yb ₂ O ₃ content is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, The preferred order is 3.0%, 2.0%, 1.0%, 0.5%, and 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 , it increases the specific gravity of the glass. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus type imaging lens, the power required to drive the lens during autofocus increases, resulting in rapid battery consumption. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.

Moreover, if the content of Yb ₂ O ₃ is too large, the thermal stability of the glass will decrease, and the glass will be more likely to devitrify during production. From the viewpoint of preventing a decrease in the thermal stability of the glass and suppressing an increase in specific gravity, the content of Yb ₂ O ₃ is preferably within the above range.

The optical glass according to the 1-1 embodiment mainly contains the above-mentioned glass components, namely 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 , 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 , and the above-mentioned glass components The total content of is preferably more than 95%, more preferably more than 98%, even more preferably more than 99%, even more preferably more than 99.5%. .

In the optical glass according to Embodiment 1-1, the upper limit of the content of TeO ₂ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3. The preferred order is 0%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5%, and 0.1%. Further, the lower limit of the content of TeO ₂ is preferably 0%. The content of TeO ₂ may be 0%.

Since TeO ₂ is a component that increases the refractive index nd and is toxic, it is preferable to reduce the content of TeO ₂ . Therefore, the content of TeO ₂ is preferably within the above range.

In the optical glass according to Embodiment 1-1, the anion component, that is, the anion component is mainly oxygen ions, but contains a small amount of halogen ions such as chloride ions, iodine ions, bromide ions, etc. as other anions. be able to.

Even when a halide is contained as a glass component, it is preferable to keep the content of the halide to a small amount so that the proportion (mass ratio) of oxides in all glass components does not become 95% by mass or less.

That is, in the optical glass according to Embodiment 1-1, the content of oxides in all glass components is preferably greater than 95% by mass. Furthermore, the lower limit of the oxide content in all glass components is preferably in the order of 97% by mass, 99% by mass, 99.5% by mass, 99.9% by mass, 99.95% by mass, and 99.99% by mass. , the content of oxides in the total glass components may be 100% by mass. A glass with an oxide content of 100% by mass in all glass components is substantially free of halides.

Further, in the optical glass according to the 1-1 embodiment, the upper limit of the content of halogen ions is preferably 4 anion%, furthermore, 3 anion%, 2 anion%, 1 anion%, 0.5 anion%. The order of percentage is more preferable. The content of halogen ions may be 0% anion. Anion % is a molar percentage when the total content of all anion components contained in the glass is taken as 100%.

The optical glass according to Embodiment 1-1 is preferably basically composed of the above-mentioned glass components, but it is also possible to contain other components within the range that does not impede the effects of the present invention. be. Furthermore, the present invention does not exclude the inclusion of unavoidable impurities.

<Other component composition>
Pb, As, Cd, Tl, Be, and Se are all toxic. Therefore, it is preferable that the optical glass according to Embodiment 1-1 does not contain these elements as glass components.

U, Th, and Ra are all radioactive elements. Therefore, it is preferable that the optical glass according to Embodiment 1-1 does not contain these elements as glass components.

V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, and Tm increase the coloring of the glass and can be a source of fluorescence. Therefore, it is preferable that the optical glass according to Embodiment 1-1 does not contain these elements as glass components.

Sb (Sb ₂ O ₃ ), Sn (SnO ₂ ), and Ce (CeO ₂ ) are elements that function as refining agents and can be added arbitrarily. Among these, Sb (Sb ₂ O ₃ ) is a clarifying agent with a large clarifying effect. However, Sb (Sb ₂ O ₃ ) has strong oxidizing properties, and as the amount of Sb (Sb ₂ O ₃ ) added increases, coloring of the glass increases due to light absorption by Sb ions, which is not preferable. Further, when glass is melted, if Sb is present in the melt, the elution of platinum constituting the glass melting crucible into the melt is promoted, increasing the platinum concentration in the glass. When platinum is present as an ion in glass, the coloring of the glass increases due to absorption of light. Furthermore, if platinum is present as a solid substance in glass, it becomes a source of light scattering and deteriorates the quality of the glass. Sn (SnO ₂ ) and Ce (CeO ₂ ) have a smaller refining effect than Sb (Sb ₂ O ₃ ). When Sn (SnO ₂ ) and Ce (CeO ₂ ) are added in large amounts, the coloring of the glass becomes stronger. Therefore, when adding a clarifier, it is preferable to add Sb (Sb ₂ O ₃ ) while paying attention to the amount added.

The content of Sb ₂ O ₃ is expressed on an external basis. That is, when the total content of all glass components other than Sb ₂ O ₃ , SnO ₂ and CeO ₂ is 100% by mass, the content of Sb ₂ O ₃ is preferably less than 1% by mass, more preferably 0. The range is less than 5% by weight, more preferably less than 0.1% by weight. The content of Sb ₂ O ₃ may be 0% by mass.

The content of SnO ₂ is also expressed as an external value. That is, the content of SnO ₂ is preferably less than 2% by mass, more preferably less than 1% by mass when the total content of all glass components other than SnO ₂ , Sb ₂ O ₃ and CeO ₂ is 100% by mass. , more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass. The content of SnO ₂ may be 0% by mass. By setting the SnO ₂ content within the above range, the clarity of the glass can be improved.

The content of CeO ₂ is also expressed on an external basis. That is, the content of CeO ₂ is preferably less than 2% by mass, more preferably less than 1% by mass when the total content of all glass components other than CeO ₂ , Sb ₂ O ₃ , and SnO ₂ is 100% by mass. , more preferably less than 0.5% by mass, even more preferably less than 0.1% by mass. The content of CeO ₂ may be 0% by mass. By setting the CeO ₂ content within 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 1-1 embodiment is preferably 750°C, and more preferably in the order of 740°C, 730°C, 720°C, 710°C, and 700°C. Further, the lower limit of the glass transition temperature Tg is preferably 520°C, and more preferably in the order of 540°C, 560°C, 580°C, and 600°C.

When the upper limit of the glass transition temperature Tg satisfies the above range, it is possible to suppress the increase in the annealing temperature of the glass, and reduce thermal damage to annealing equipment, such as continuous annealing or batch annealing furnaces called rare. can do.

When the lower limit of the glass transition temperature Tg satisfies the above range, it becomes easier to maintain good thermal stability of the glass while maintaining the desired Abbe number and refractive index.

<Light transmittance of glass>
In the 1-1 embodiment, the light transmittance can be evaluated by the degree of coloration λ5.
Using a glass (thickness 10.0 mm ± 0.1 mm) that has two optically polished planes that are parallel to each other, a light beam is incident perpendicularly to one of the two planes. let 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, that is, the external transmittance is calculated. A spectral transmittance curve is obtained by measuring external transmittance using a spectrophotometer while scanning the wavelength of incident light in a range of, for example, 280 to 700 nm.

The external transmittance increases and shows a high value as the wavelength of the incident light goes from the short wavelength absorption edge of the glass to the long wavelength side.

λ5 is a wavelength at which the external transmittance is 5%. In the wavelength range of 280 to 700 nm, the external transmittance of glass on the wavelength side longer than λ5 exhibits a value greater than 5%.

By using optical glass whose wavelength λ5 is shortened, it is possible to provide an optical element that enables suitable color reproduction.

For these reasons, the range of λ5 is preferably 440 nm or less, and more preferably in the order of 435 nm or less, 430 nm or less, 425 nm or less, 420 nm or less, 415 nm or less, and 410 nm or less. The lower limit of λ5 is approximately 380 nm.

<Specific gravity of glass>
The optical glass according to the 1-1 embodiment is a high dispersion glass that suppresses an increase in refractive index, but does not have a large specific gravity. Generally, if the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, it is possible to reduce power consumption for autofocus driving of a camera lens equipped with a lens. On the other hand, reducing the specific gravity too much leads to a decrease in thermal stability. Therefore, the upper limit of 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, and 3.70 in that order. Further, from the viewpoint of improving thermal stability, the lower limit of 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 Embodiment 1-1 is preferably 1350°C, and more preferably in the order of 1340°C, 1330°C, 1320°C, 1310°C, and 1300°C. Further, the lower limit of the liquidus temperature is preferably 1000°C, and more preferably in the order of 1020°C, 1040°C, 1060°C, 1080°C, 1100°C, 1130°C, and 1150°C. According to the optical glass according to this embodiment, a high dispersion glass with improved thermal stability and suppressed increase in refractive index can be obtained.

Note that the liquidus temperature is determined as follows. 10 cc (10 ml) of glass is placed in a platinum crucible and melted at 1250°C to 1350°C for 20 to 30 minutes, then cooled to below the glass transition temperature Tg, and the glass is placed together with the platinum crucible in a melting furnace at a predetermined temperature and held for 2 hours. do. The holding temperature is 1000°C or higher in 5°C or 10°C increments, and after holding for 2 hours, it is cooled and the presence or absence of crystals inside the glass is observed using a 100x optical microscope. The lowest temperature at which no crystals precipitate is defined as the liquidus temperature.

(manufacture of optical glass)
The optical glass according to the embodiment of the present invention may be produced by blending glass raw materials to have the above-mentioned predetermined composition, and using the blended glass raw materials according to a known glass manufacturing method. For example, a plurality of compounds are prepared and sufficiently mixed to form a batch raw material, and the batch raw material is put into a quartz crucible or a platinum crucible and roughly melted (rough melted). The molten material obtained by rough melting is rapidly cooled and pulverized to produce cullet. Further, the cullet is placed in a platinum crucible, heated and remelted to obtain molten glass, and after further clarification and homogenization, the molten glass is shaped and slowly cooled to obtain optical glass. A known method may be applied to forming and slowly cooling the molten glass.

Note that the compounds used when preparing the batch raw materials are not particularly limited as long as the desired glass components can be introduced into the glass at the desired content, but examples of such compounds include oxides, positive Examples include phosphoric acid, metaphosphates, diphosphorous pentoxide, carbonates, nitrates, hydroxides, and fluorides.

(Manufacture of optical elements, etc.)
In order to produce an optical element using the optical glass according to the embodiment of the invention No. 1-1, a known method may be applied. For example, a glass material made of the optical glass according to the present invention is produced by melting glass raw materials to obtain molten glass, and pouring this molten glass into a mold to form it into a plate shape. The obtained glass material is appropriately cut, ground, and polished to produce a glass material for press molding having a size and shape suitable for press molding. A glass material for press molding is heated and softened, and then press molded by a known method to produce an optical element blank that approximates the shape of the optical element. An optical element blank is annealed, ground and polished by a known method to produce an optical element.

The optically functional surface of the manufactured optical element may be coated with an antireflection film, a total reflection film, etc. depending on the purpose of use.

Examples of optical elements include various lenses such as spherical lenses, prisms, and diffraction gratings.

1-2 Embodiment The optical glass of 1-2 embodiment of the present invention is
Abbe number νd is 16.70 or less,
The content of Bi ₂ O ₃ is 29.0% by mass or less,
This is a phosphate optical glass in which the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ is 45.0% by mass or more.

The optical glass according to Embodiment 1-2 will be described in detail below.

In the optical glass according to the 1-2 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 in the order of 16.66, 16.64, 16.62, 16.60, 16.58, 16.56, and 16.54. Further, the lower limit of Abbe's number is preferably 15.50, and more preferably, the larger the value is in the order of 15.55, 15.60, 15.65, and 15.70.

By setting the Abbe number νd to 16.70 or less, when the lens is combined with a low-dispersion glass lens to form a pair lens, the difference in Abbe numbers becomes large, resulting in a high effect in correcting chromatic aberration.

In the optical glass according to Embodiment 1-2, the content of Bi ₂ O ₃ is 29.0% or less.

In the optical glass according to Embodiment 1-2, the upper limit of the Bi ₂ O ₃ content is preferably 28.5%, and more preferably 28.0%, 27.5%, 27.0%, The preferred order is 25.0%, 20.0%, 15.0%, 10.0%, 6.0%, and 5.0%. Moreover, 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 the function of improving the thermal stability of glass by containing it in an appropriate amount. On the other hand, increasing the content of Bi ₂ O ₃ increases the refractive index and increases the coloring of the glass. Therefore, the content of Bi ₂ O ₃ is within the above range.

Furthermore, in the optical glass according to the 1-2 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Bi ³⁺ content is preferably 20.00 cation%, and more preferably 19.00%. The preferred order is 50 cation%, 19.00 cation%, 18.50 cation%, 18.00 cation%, 17.50 cation%, 17.00 cation%, and 16.50 cation%. The lower limit of the Bi ³⁺ content 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 cation%.

Bi ³⁺ has the function of improving the thermal stability of glass by containing it in an appropriate amount. On the other hand, increasing the Bi ³⁺ content increases the refractive index and increases the coloring of the glass. Therefore, it is preferable that the content of Bi ³⁺ is within the above range.

In the optical glass according to Embodiment 1-2, 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 Embodiment 1-2, 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 are more preferable in the order of 47.0%, 48.0%, 49.0%, and 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%, and 81.0%. , 79.0%, and 77.0%.

TiO ₂ , Nb ₂ O ₅ and WO ₃ suppress the increase in the refractive index nd and contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. From the viewpoint of highly dispersing the glass and improving the thermal stability of the glass, the lower limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ ] is within the above range. Further, from the viewpoint of suppressing an increase in the refractive index and an increase in coloring of the glass, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ ] is preferably within the above range.

The optical glass according to Embodiment 1-2 is a phosphate optical glass. Phosphate optical glass refers to optical glass that mainly contains phosphate as a network forming component of the glass. Therefore, the optical glass according to Embodiment 1-2 contains phosphate as a network forming component, and the content thereof is expressed as the content of P ₂ O ₅ . P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known as glass network forming components. Here, "containing mainly phosphate as a network-forming component of the glass" means that the content of P ₂ O ₅ in mass % is higher than the content of any of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ . Also means a lot of glass.

In the optical glass according to Embodiment 1-2, the lower limit of the P ₂ O ₅ content is preferably 7.0%, and more preferably 8.0%, 9.0%, 10.0%, The order of 10.5% and 11.0% is more preferable. Further, the upper limit of the content of P ₂ O ₅ is preferably 35.0%, and more preferably in the order of 34.5%, 34.0%, 33.5%, and 33.0%.

P ₂ O ₅ is a necessary component because glass contains a large amount of highly dispersed components. On the other hand, if P ₂ O ₅ is included excessively, the meltability will deteriorate. Therefore, in the glass according to this embodiment, the content of P ₂ O ₅ is preferably within the above range.

Furthermore, in the optical glass according to Embodiment 1-2, when the content of the glass components is expressed in cation%, the upper limit of the P ⁵⁺ content is preferably 45.00 cation%, and more preferably 44.00%. 50 cation%, 44.00 cation%, 43.50 cation%, 43.00 cation%, 42.50 cation%, 42.00 cation%, 41.50 cation%, 41.00 cation%, 40.50 cation %, 40.00 cation%, 39.50 cation%, 39.00 cation%, and 38.50 cation%. The lower limit of the content of P ⁵⁺ is preferably 20.00 cation%, more preferably 20.50 cation%, 21.00 cation%, 21.50 cation%, 22.00 cation%, 22.50 cation%. %, 23.00 cation%, 23.50 cation%, 24.00 cation%, 24.50 cation%, 25.00 cation%, and 25.50 cation%.

P ⁵⁺ is an essential component for suppressing an increase in the refractive index nd and for containing a large amount of highly dispersible components in the glass. On the other hand, when P ⁵⁺ is included excessively, solubility deteriorates. Therefore, in the optical glass according to this embodiment, the content of P ⁵⁺ is preferably within the above range.

In the optical glass according to Embodiment 1-2, the mass of the total content of TiO ₂ , Nb ₂ O ₅ and WO ₃ and the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ The lower limit of the ratio [(TiO ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] is preferably 0.45, more preferably 0.50, 0.55. , 0.60, 0.65, 0.70, 0.75, 0.80, 0.85 in this order. 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, deterioration of transmittance is suppressed and refraction is increase in rates can be suppressed.

In the optical glass according to Embodiment 1-2, the lower limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of Nb ₂ O ₅ is preferably 0.15, Furthermore, the order of 0.16, 0.17, 0.18, 0.19, 0.20, and 0.23 is more preferable. The upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.50, more preferably 4.40, 4.30, 4.20, 4.10, 4.00, 3.80. , 3.60 is more preferable.

TiO ₂ tends to reduce the solubility of 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 constant ratio to TiO ₂ , it is possible to suppress a decrease in the solubility of the glass and an increase in the liquidus temperature. Therefore, in the optical glass according to this embodiment, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably within the above range.

Furthermore, in the optical glass according to the 1-2 embodiment, when the content of the glass components is expressed in cation%, the cation ratio between the Ti ⁴⁺ content and the Nb ⁵⁺ content [Ti ⁴⁺ /Nb ^{5 +} ] is preferably 6.00, and more preferably in the order of 5.90, 5.80, 5.70, 5.65, and 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 in that order.

Ti ⁴⁺ tends to reduce the solubility of glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ suppresses a decrease in liquidus temperature and an increase in refractive index, contributing to high dispersion. Therefore, by containing Nb ⁵⁺ in a constant ratio 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 this embodiment, the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably within the above range.

In the optical glass according to Embodiment 1-2, the lower limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] between the total content of TiO ₂ and WO ₃ and the Nb ₂ O ₅ content is as follows: Preferably it is 0.15, more preferably 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 The order of .64 and 0.65 is more preferable. Further, the upper limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 8.00, more preferably 7.90, 7.80, 7.70, 7.60, 7. The preferred order is 40, 7.20, and 7.00.

By setting the value of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] within the above range, it is possible to obtain a glass having high dispersion suitable for correcting chromatic aberration while suppressing an increase in the refractive index. .

In addition, in the optical glass according to Embodiment 1-2, when the content of glass components is expressed in cation%, the cation ratio of the total content of Ti ⁴⁺ and W ⁶⁺ and the content of Nb ⁵⁺ [( The upper limit of Ti ⁴⁺ +W ⁶⁺ )/Nb ⁵⁺ is preferably 7.70, more preferably 7.60, 7.50, 7.40, 7.35, 7.30, 7.28, The order of 7.26 is more preferable. 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 in that order.

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

In the optical glass according to Embodiment 1-2, when the content of glass components is expressed in cation%, if the W ⁶⁺ content exceeds 0 cation%, the Ba ²⁺ content and W The upper limit of the cation ratio [Ba ²⁺ /W ⁶⁺ ] with respect to the content of ⁶⁺ is preferably 0.14, and more preferably in the order of 0.13, 0.12, 0.11, and 0.10. preferable.

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to Embodiment 1-2, the desired high dispersion can be achieved by containing W ⁶⁺ , which is a high dispersion component, at the above cation ratio with respect to the Ba ²⁺ content. can be maintained.

In the optical glass according to Embodiment 1-2, when the content of the glass components is expressed in cation%, the content of W ⁶⁺ is 0 cation%, and the content of Ba ²⁺ is 0 cation%. In the case where the total content of Ti ⁴⁺ and Bi ³⁺ [Ti ⁴⁺ + Bi ³⁺ ] is preferably 35.00 cation%, the upper limit is preferably 34.00 cation%, 33.00 cation%. cation%, 32.50 cation%, 32.30 cation%, 32.00 cation%, 31.80 cation%, 31.60 cation%, 31.40 cation%, 31.20 cation%, 31.00 cation% , 30.80% cations, 30.60% cations, 30.40% cations, 30.20% cations, 30.10% cations, and 30.00% cations in this order. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cation%, and more preferably 21.20 cation%, 21.40 cation%, 21.60 cation%, and 21.80 cation%. , 22.00 cation%, 22.20 cation%, 22.40 cation%, 22.60 cation%, 22.80 cation%, 23.00 cation%, 23.10 cation%, 23.20 cation%, 23 The preferred order is .30 cation%, 23.40 cation%, and 23.50 cation%.

When the W ⁶⁺ content is 0 cation% and the Ba ²⁺ content exceeds 0 cation%, Ti, which has the second largest contribution to high dispersion after W ⁶⁺ among high dispersion components, By setting the total content of ⁴⁺ and Bi ³⁺ , which has the function of improving thermal stability, within the above range, low dispersion caused by Ba ²⁺ can be suppressed.

In the optical glass according to Embodiment 1-2, the upper limit of the refractive index nd is preferably 2.1500, and further preferably 2.1300, 2.1100, 2.1000, 2.0900, 2.0700, The order of 2.0500, 2.0300, 2.0140, and 2.0000 is more preferable. Further, the lower limit of the refractive index nd is preferably 1.8800, and more preferably, the smaller the value is in the order of 1.9000, 1.9200, 1.9400, and 1.9600.

By setting the refractive index nd within the above range, even when combined with a low-dispersion glass lens with a low refractive index to form a pair lens, the difference in refractive index is small, so field curvature can be suppressed.

The glass component composition in the 1-2 embodiment other than the above may be the same as in the 1-1 embodiment. Further, the glass properties, the production of optical glass, the production of optical elements, etc. in Embodiment 1-2 can be the same as in Embodiment 1-1.

Embodiment 2-1 and Embodiment 2-2 (hereinafter may be collectively referred to as "Second Embodiment") below the second embodiment are glass, optical glass, etc. that can easily reduce reduced color. The present invention relates to a glass material for polishing, a glass material for press molding, and an optical element.

A second embodiment of the present invention aims to provide a glass that can shorten the heat treatment time when reducing reduced color by heat treatment.

When Li ₂ O is included as a glass component, the Abbe number ν _d increases and the thermal stability of the glass decreases. Therefore, high dispersion glass usually does not contain Li ₂ O.

In the high dispersion glass of the second embodiment of the present invention, while maintaining high dispersion by lowering the Abbe number ν _d , by containing Li ₂ O as a glass component, TiO ₂ , Nb ₂ O ₅ , WO The heat treatment time required to reduce the reduced color caused by highly dispersed components such as ₃ and Bi ₂ O ₃ can be shortened.

When an alkali metal oxide such as Li ₂ O is contained as a glass component, the melting temperature is lowered, and the glass transition temperature Tg is accordingly lowered. Some conventional precision press glasses contain Li ₂ O in order to lower the glass transition temperature Tg and make processing easier. Here, in a glass containing Li ₂ O to lower the glass transition temperature Tg, the reduction reaction of the high dispersion component does not proceed much during the melting process due to the low melting temperature, so the degree of coloring of the glass is light. Does not require long heat treatment. Therefore, when Li ₂ O is contained in order to lower the melting temperature as in conventional glass, it does not require a long heat treatment that would affect the production process, so the heat treatment required to reduce the reduced color is The problem of shortening the heat treatment time was not recognized.

The second embodiment of the present invention is a high-dispersion glass in which reduced color caused by high-dispersion components such as TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ is a problem. This is based on the _{discovery that the heat treatment time required to reduce reduced color can be shortened by including Li 2 O} , which is not normally included. This is an extremely innovative effect.

According to the second embodiment of the present invention, when reducing reduced color by heat treatment in high dispersion glass, the heat treatment time can be shortened.

In the glass according to the second embodiment of the present invention, the content of Li ₂ O was determined by ICP-MS (Inductively Coupled Plasma - Mass Spectrometry), and the content of glass components other than Li ₂ O was determined by ICP-AES. (Inductively Coupled Plasma - Atomic Emission Spectrometry). The analysis value obtained by ICP-AES may include a measurement error of about ±5% of the analysis value, for example. Furthermore, in this specification and the present invention, 0% or no content of a glass component means that the component is not substantially included, and the content of this component is approximately at the impurity level. Refers to the following.

2-1 Embodiment The glass of 2-1 embodiment of the present invention is
Abbe number ν _d is 18.10 or less,
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 30% by mass or more, and the content of Bi ₂ O ₃ is 38% by mass % or less of phosphate glass,
Mass ratio of Li ₂ O content to total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] The value obtained by multiplying by 100 is 0.015 to 0.770.

The glass according to the 2-1 embodiment will be described in detail below.

In the glass according to the 2-1 embodiment, the Abbe number ν _d is 18.10 or less. The upper limit of the Abbe number ν _d is preferably 18.05, and more preferably 18.00, 17.90, 17.80, 17.70, 17.60, 17.50, 17.40, 17.30. , 17.20, 17.10, 17.00, 16.90, 16.80, 16.78. Further, the lower limit of Abbe's number is preferably 15.00, and more preferably 15.10, 15.20, 15.25, 15.30, 15.35, 15.40, 15.45, 15.50. , 15.52, 15.54, 15.56, 15.58, 15.60.

By setting the Abbe number ν _d to 18.10 or less, when the lens is combined with a low-dispersion glass lens to form a pair lens, the difference in Abbe numbers becomes large, resulting in a high effect in correcting chromatic aberration.

In the glass according to the 2-1 embodiment, 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 30% or more . The lower limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably 35%, and more preferably 36%, 38%, 40%, 42%, 44%, 46%, 48%. %, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%. Further, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably 90%, and more preferably 88%, 86%, 85%, 84%, 83%, 82%. , 81%, 80%, 79%, 78%, and 77%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. Therefore, the lower limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range. On the other hand, TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ increase the coloration of the glass. Therefore, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range.

Furthermore, in the glass according to the 2-1 embodiment, when the content of glass components is expressed in cation%, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ [Ti ⁴⁺ +Nb ^{5 +} +W ⁶⁺ +Bi ³⁺ ] is preferably 75.00 cation%, more preferably 74.50 cation%, 74.00 cation%, 73.50 cation%, 73.00 cation%, 72. The preferred order is 50 cation%, 72.00 cation%, 71.50 cation%, 71.00 cation%, and 70.50 cation%. 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%, and 52.20 cation%. , 52.25% cations, and 52.30% cations in that order.

Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. Therefore, the lower limit of the total content [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is preferably within 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 within the above range.

In the glass according to Embodiment 2-1, the content of Bi ₂ O ₃ is 38% or less. The upper limit of the content of Bi ₂ O ₃ is preferably 35%, and more preferably in the order of 33%, 30%, 28%, 25%, 23%, and 20%. Moreover, 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 is a component that contributes to high dispersion. Further, by setting the content of Bi ₂ O ₃ within the above range, it is possible to suppress an increase in specific gravity and a decrease in glass transition temperature Tg. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus type imaging lens, the power required to drive the lens during autofocus increases, resulting in significant battery consumption. Therefore, it is preferable that the content of Bi ₂ O ₃ is within the above range.

Moreover, Bi ₂ O ₃ has the function of significantly increasing the refractive index compared to other high dispersion components TiO ₂ , Nb ₂ O ₅ , and WO ₃ . When the refractive index increases significantly, when used in combination with a low-dispersion glass lens with a low refractive index to correct chromatic aberration, a strong curvature of field tends to appear due to the large refractive index difference. Therefore, it is preferable that the content of Bi ₂ O ₃ is within the above range.

Further, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Bi ³⁺ content is preferably 10.00 cation%, and more preferably 9.00%. cation%, 8.00 cation%, 7.00 cation%, 6.00 cation%, 5.00 cation%, 4.50 cation%, 4.00 cation%, 3.50 cation%, 3.00 cation% , 2.50 cation%, 2.00 cation%, 1.50 cation%, and 1.00 cation% in this order. The content of Bi ³⁺ may be 0 cation%.

Bi ³⁺ is a component that contributes to high dispersion. Further, by setting the content of Bi ³⁺ within the above range, an increase in specific gravity and a decrease in glass transition temperature Tg can be suppressed. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus type imaging lens, the power required to drive the lens during autofocus increases, resulting in significant battery consumption. Therefore, it is preferable that the content of Bi ³⁺ is within the above range.

Furthermore, Bi ³⁺ has the function of significantly increasing the refractive index compared to other high dispersion components Ti ⁴⁺ , Nb ⁵⁺ , and W ⁶⁺ . When the refractive index increases significantly, when used in combination with a low-dispersion glass lens with a low refractive index to correct chromatic aberration, a strong curvature of field tends to appear due to the large refractive index difference. Therefore, it is preferable that the content of Bi ³⁺ is within the above range.

The glass according to Embodiment 2-1 is phosphate glass. Phosphate glass refers to glass that mainly contains phosphate as a network forming component of the glass. Therefore, the glass according to the 2-1 embodiment mainly contains phosphate as a network forming component, and the content thereof is expressed as the content of P ₂ O ₅ . P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known as glass network forming components. Here, "containing mainly phosphate as a network-forming component of the glass" means that the content of P ₂ O ₅ in mass % is higher than the content of any of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ . Also means a lot of glass.

In the glass according to Embodiment 2-1, 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%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, 20.0% more preferred. Further, the upper limit of the content of P ₂ O ₅ is preferably 37.0%, and more preferably 36.0%, 35.0%, 34.5%, 34.0%, 33.5%, The preferred order is 33.0%, 32.5%, 32.0%, 31.5%, 31.0%, 30.5%, and 30.0%.

P ₂ O ₅ is a necessary component because glass contains a large amount of highly dispersed components. On the other hand, if P ₂ O ₅ is included excessively, the meltability will deteriorate. Therefore, in the glass according to this embodiment, the content of P ₂ O ₅ is preferably within the above range.

Furthermore, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the P ⁵⁺ content is preferably 42.00 cation%, and more preferably 41.50 cation%. cation%, 41.00 cation%, 40.50 cation%, 40.00 cation%, 39.50 cation%, 39.00 cation%, 38.50 cation%, 38.00 cation%, 37.50 cation% , 37.00% cations, 36.50% cations, and 36.00% cations in this order. The lower limit of the content of P ⁵⁺ is preferably 25.00 cation%, more preferably 25.50 cation%, 26.00 cation%, 26.50 cation%, 27.00 cation%, 27.50 cation%. %, 28.00 cation%, 28.50 cation%, 29.00 cation%, and 29.30 cation%.

P ⁵⁺ is an essential component for suppressing an increase in the refractive index nd and for containing a large amount of highly dispersible components in the glass. On the other hand, when P ⁵⁺ is included excessively, solubility deteriorates. Therefore, in the optical glass according to this embodiment, the content of P ⁵⁺ is preferably within the above range.

In _the glass according to _{the 2-1 embodiment} , the _mass ratio [ _{Li 2 O} /(TiO _{2 +} Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] multiplied by 100 is 0.015 to 0.770. The lower limit of the mass ratio [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] multiplied by 100 is preferably 0.017, and more preferably 0.019, 0.021. , 0.023, 0.025, 0.027, 0.030 in this order. Further, the upper limit of the value obtained by multiplying the mass ratio [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] by 100 is preferably 0.750, and furthermore, 0.730, 0 The preferred order is .710, 0.700, 0.680, 0.650, 0.600, and 0.550.

By setting the value obtained by multiplying the mass ratio [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] by 100 to the above range, the reduction in coloration due to heat treatment is sufficiently promoted. If the value obtained by multiplying the mass ratio [Li ₂ O / (TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] by 100 exceeds 0.750, the desired high dispersion characteristics cannot be obtained, and the glass Stability is compromised.

In the glass according to Embodiment 2-1, when the content of glass components is expressed in cation%, if the W ⁶⁺ content exceeds 0 cation%, the Ba ²⁺ content and W ⁶ The upper limit of the cation ratio [Ba ²⁺ /W ⁶⁺ ] with the content of ⁺ is preferably 0.14, and more preferably in the order of 0.13, 0.12, 0.11, and 0.10. .

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the glass according to the 2-1 embodiment, desired high dispersibility can be achieved by containing W ⁶⁺ , which is a high dispersion component, at the above cation ratio with respect to the ^{Ba 2+} content. can be maintained.

Furthermore, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the content of W ⁶⁺ is 0 cation%, and the content of Ba ²⁺ is 0 cation%. %, the upper limit of the total content of Ti ⁴⁺ and Bi ³⁺ [Ti ⁴⁺ +Bi ³⁺ ] is preferably 35.00 cation %, more preferably 34.00 cation %, 33. 00 cation%, 32.50 cation%, 32.30 cation%, 32.00 cation%, 31.80 cation%, 31.60 cation%, 31.40 cation%, 31.20 cation%, 31.00 cation %, 30.80 cation%, 30.60 cation%, 30.40 cation%, 30.20 cation%, 30.10 cation%, and 30.00 cation%. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cation%, and more preferably 21.20 cation%, 21.40 cation%, 21.60 cation%, and 21.80 cation%. , 22.00 cation%, 22.20 cation%, 22.40 cation%, 22.60 cation%, 22.80 cation%, 23.00 cation%, 23.10 cation%, 23.20 cation%, 23 The preferred order is .30 cation%, 23.40 cation%, and 23.50 cation%.

When the W ⁶⁺ content is 0 cation% and the Ba ²⁺ content exceeds 0 cation%, Ti, which has the second largest contribution to high dispersion after W ⁶⁺ among high dispersion components, By setting the total content of ⁴⁺ and Bi ³⁺ , which has the function of improving thermal stability, within the above range, low dispersion caused by Ba ²⁺ can be suppressed.

(Glass component)
Preferred aspects of the glass according to Embodiment 2-1 above will be described in detail below.

In the glass according to Embodiment 2-1, the lower limit of the Li ₂ O content is preferably 0.010%, more preferably 0.012%, 0.014%, 0.016%, 0. The order of 0.018% and 0.020% is more preferable. The upper limit of the Li ₂ O content is preferably 0.640%, and more preferably 0.630%, 0.620%, 0.610%, 0.600%, 0.580%, 0.560%. %, 0.540%, 0.520%, 0.500%, 0.490%, 0.480%, 0.470%, 0.460%, 0.450%, 0.440%, 0.430 %, 0.420%, 0.410%, 0.400%, 0.390%, 0.380%, 0.370%, 0.360%, 0.350%, 0.340% in this order. .

By setting the Li ₂ O content within the above range, the heat treatment time required to reduce reduced color caused by highly dispersed components such as TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ can be shortened. . Further, a decrease in glass transition temperature Tg can be suppressed. On the other hand, if the content of Li ₂ O is too large, the Abbe number ν _d may increase and the thermal stability of the glass may decrease.

In the glass according to Embodiment 2-1, the lower limit of the value of βOH expressed by the following formula (1) is preferably 0.05 mm ^-1 , and more preferably 0.10 mm ^-1 and 0.15 mm ^{- 1} , 0.20 mm ^-1 , 0.25 mm ^-1 , 0.30 mm ^-1 , and 0.35 mm ^-1 in this order. Further, the upper limit of the value of βOH is preferably 4.00 mm ^-1 , and more preferably 3.90 mm ^-1 , 3.80 mm -1 , 3.70 mm ^-1 , 3.60 mm ^-1 , 3.50 ^{mm - 1} , 3.40mm ^-1 , 3.30mm ^-1 , 3.20mm ^-1 , 3.10mm ^-1 , 3.00mm ^-1 , 2.90mm ^-1 , 2.80mm ^-1 , 2.70.mm ^{- 1} , 2.60mm ^-1 , 2.50mm ^{-1 , 2.40mm -1 ,} 2.30mm ^-1 , 2.25mm ^-1 , 2.20mm ^-1 , 2.10mm ^-1 , 2.00mm ^-1 The order is more preferable.

βOH=-[ln(D/C)]/t...(1)
Here, in the above formula (1), t represents the thickness (mm) of the glass used to measure external transmittance, and C is the wavelength of 2500 nm when light is incident on the glass parallel to its thickness direction. D represents the external transmittance (%) at a wavelength of 2900 nm when light is incident on the glass in parallel to its thickness direction. Moreover, ln is a natural logarithm. The unit of βOH is mm ^-1 .

Note that "external transmittance" is the ratio of the intensity Iout of the transmitted light that passes through the glass to the intensity Iin of the incident light that enters the glass (Iout/Iin), that is, the transmittance that also takes into account surface reflection on the surface of the glass. It is. Transmittance is obtained by measuring the transmission spectrum using a spectrophotometer. As the spectrometer, "UV-3100 (Shimadzu)" can be used.

βOH represented by the above formula (1) is defined based on the fact that the transmittance changes due to absorption of light caused by hydroxyl groups. Therefore, by evaluating βOH, the concentration of water (and/or hydroxide ions) contained in the glass can be evaluated. That is, a glass with high βOH means that the concentration of water (and/or hydroxide ions) contained in the glass is high.

By setting the value of βOH within the above range, it is possible to reduce the amount of noble metals such as platinum derived from the glass melting container dissolved into the glass, and also improve the transmittance after reducing reduced color, that is, after heat treatment. can. Furthermore, the heat treatment time required to reduce reduced color can be further reduced. On the other hand, if the value of βOH is too large, the devitrification resistance of the glass may decrease and the amount of volatile matter from the molten glass may increase.

The method for increasing the βOH value of the glass is not particularly limited, but preferably includes a method of increasing the water content in the molten glass in the melting step. Examples of methods for increasing the water content in the molten glass include adding water vapor to the melting atmosphere, bubbling a gas containing water vapor into the molten glass, and the like.

The glass according to Embodiment 2-1 preferably contains Nb ₂ O ₅ . In the glass according to this embodiment, the lower limit of the Nb ₂ O ₅ content is preferably 5.0%, and more preferably 5.5%, 6.0%, 6.5%, and 7.0%. , 7.5%, 8.0%, 8.5%, 9.0%, 9.5%, 10.0%, 10.5%, 11.0%, 11.5%, 12.0% , 12.5%, 13.0%, 13.5%, 14.0%, 14.5%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5% , 18.0%, 18.5%, 19.0%, 19.5%, 20.0%, 20.5%, 21.0%, 21.5%, 22.0%, 22.5% , 23.0%. Further, the upper limit of the content of Nb ₂ O ₅ is preferably 60.0%, and more preferably 59.0%, 58.0%, 57.0%, 56.0%, 55.0%, 54.0%, 53.0%, 52.0%, 51.0%, 50.0%, 49.0%, 48.0%, 47.0%, 46.0%, 45.0%, The preferred order is 44.0%, 43.0%, 42.0%, 41.0%, 40.0%, 39.0%, 38.0%, and 37.0%.

Nb ₂ O ₅ is a component that contributes to high dispersion. It is also a glass component that improves the thermal stability and chemical durability of the glass. On the other hand, if the content of Nb ₂ O ₅ is too large, the thermal stability of the glass tends to decrease and the coloring of the glass tends to become stronger. Therefore, in the glass according to this embodiment, the content of Nb ₂ O ₅ is preferably within the above range.

Further, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Nb ⁵⁺ content is preferably 30.00 cation%, and more preferably 29.00 cation%. cation%, 28.50 cation%, 28.00 cation%, 27.50 cation%, 27.00 cation%, 26.50 cation%, 26.00 cation%, 25.50 cation%, 25.00 cation% , 24.50 cation%. The lower limit of the Nb ⁵⁺ content is preferably 10.00 cation%, more preferably 11.00 cation%, 12.00 cation%, 12.50 cation%, 13.00 cation%, 13.50 cation%. %, 14.00 cation%, 14.50 cation%, 15.00 cation%, 15.50 cation%, 16.00 cation%, 16.50 cation%, 17.00 cation%, 17.50 cation% The order is more preferable.

Nb ⁵⁺ is a component that contributes to high dispersion. It is also a glass component that improves the thermal stability and chemical durability of the glass. On the other hand, if the content of Nb ⁵⁺ is too high, the thermal stability of the glass tends to decrease and the coloring of the glass tends to become stronger. Therefore, in the glass according to this embodiment, the content of Nb ⁵⁺ is preferably within the above range.

The glass according to Embodiment 2-1 preferably contains TiO ₂ . In the glass according to the present embodiment, the lower limit of the TiO ₂ content is preferably 5.0%, and more preferably 6.0%, 7.0%, 8.0%, 9.0%, and 10%. .0%, 11.0%, 12.0%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%. more preferred. Further, the upper limit of the content of TiO ₂ is preferably 50.0%, and more preferably 49.0%, 48.0%, 47.0%, 46.0%, 45.0%, 44.0%. 0%, 43.0%, 42.0%, 41.0%, 40.0%, 39.0%, 38.0%, 37.0%, 36.0%, 35.0%, 34. The preferred order is 0%, 33.0%, 32.0%, and 31.0%.

TiO ₂ , like Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ , greatly contributes to high dispersion. On the other hand, TiO ₂ is relatively easy to increase the coloration of glass. Therefore, in the glass according to this embodiment, the content of TiO ₂ is preferably within the above range.

Furthermore, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Ti ⁴⁺ content is preferably 40.00 cation%, and more preferably 39.00 cation%. cation%, 38.00 cation%, 37.50 cation%, 37.00 cation%, 36.50 cation%, 36.00 cation%, 35.50 cation%, 35.00 cation%, 34.50 cation% This order is more preferable. The lower limit of the content of Ti ⁴⁺ is preferably 20.00 cation%, and further 21.00 cation%, 21.50 cation%, 22.00 cation%, 22.50 cation%, 23.00 cation%. %, 23.50 cation%, 24.00 cation%, 24.50 cation%, and 25.00 cation%.

Ti ⁴⁺ , like Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ , greatly contributes to high dispersion. On the other hand, TiO ₂ is relatively easy to increase the coloration of glass. Therefore, in the glass according to this embodiment, the content of Ti ⁴⁺ is preferably within the above range.

In the glass according to the 2-1 embodiment, the lower limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] between the content of TiO ₂ and the content of Nb ₂ O ₅ is preferably 0.16, and are more preferable in the order of 0.17, 0.18, 0.19, 0.20, and 0.23. The upper limit of the mass ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably 4.50, more preferably 4.40, 4.30, 4.20, 4.10, 4.00, 3.80. , 3.60 is more preferable.

TiO ₂ tends to reduce the solubility of 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 NNb ₂ O ₅ in a constant ratio 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 glass according to this embodiment, the cation ratio [TiO ₂ /Nb ₂ O ₅ ] is preferably within the above range.

Further, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the cation ratio between the Ti ⁴⁺ content and the Nb ⁵⁺ content [Ti ⁴⁺ /Nb ⁵⁺ The upper limit of ] is preferably 6.00, and more preferably in the order of 5.90, 5.80, 5.70, 5.65, and 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 in that order.

Ti ⁴⁺ tends to reduce the solubility of glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ suppresses a decrease in liquidus temperature and an increase in refractive index, contributing to high dispersion. Therefore, by containing Nb ⁵⁺ in a constant ratio 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 glass according to this embodiment, the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably within the above range.

The glass according to the 2-1 embodiment can contain B ₂ O ₃ , SiO ₂ , and Al ₂ O ₃ as glass network forming components other than P ₂ O ₅ .

In the glass according to the 2-1 embodiment, the upper limit of the B ₂ O ₃ content is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.0%, 4. The preferred order is .0%, 3.0%, 2.0%, and 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 the function of improving the meltability of glass. On the other hand, if the content of B ₂ O ₃ is high, the decrease in Abbe's number is suppressed, high dispersion is hindered, and chemical durability tends to decrease. Therefore, from the viewpoint of improving the thermal stability, meltability, moldability, etc. of the glass, the upper limit of the content of B ₂ O ₃ is preferably within the above range.

In the glass according to Embodiment 2-1, the upper limit of the SiO ₂ content is preferably 8.0%, and more preferably 7.0%, 6.0%, 5.0%, and 4.0%. %, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%. The content of SiO ₂ may be 0%.

SiO ₂ is a network-forming component of glass, and has the function of improving the thermal stability, chemical durability, and weather resistance of glass, increasing the viscosity of molten glass, and making it easier to shape molten glass. On the other hand, if the content of SiO ₂ is large, the meltability of the glass decreases, and the glass raw materials tend to remain unmelted. Therefore, from the viewpoint of improving the meltability of the glass, the upper limit of the content of SiO ₂ is preferably within the above range.

In the glass according to Embodiment 2-1, the upper limit of the Al ₂ O ₃ content is preferably 5.0%, and more preferably 4.0%, 3.5%, 3.0%, 2. The preferred order is .5%, 2.0%, 1.5%, 1.0%, and 0.5%. The content of Al ₂ O ₃ may be 0%.

Al ₂ O ₃ is a glass component that has the function of improving the chemical durability and weather resistance of glass, and can be considered as a network-forming component. On the other hand, when the content of Al ₂ O ₃ increases, the thermal stability of the glass decreases, the glass transition temperature Tg increases, and the meltability tends to decrease. Therefore, the upper limit of the content of Al ₂ O ₃ is preferably within the above range.

In the glass according to the 2-1 embodiment, the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ which are network forming components of the glass [P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ] is preferably 45.0%, more preferably 44.0%, 43.0%, 42.0%, 41.0%, 40.0%, 39.0% , 38.0%, 37.0%, 36.0%, 35.0%, 34.0%, 33.0%, 32.0%, 31.0%, 30.0%. 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%, 13.0%. %, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, 20.0% in that order.

By setting the total content [P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ] within the above range, the thermal stability of the glass can be improved and devitrification of the glass can be suppressed.

Furthermore, in the glass according to the 2-1 embodiment, the mass ratio of the content of P ₂ O ₅ to the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ [P ₂ O ₅ /(P ₂ O ₅ + B ₂ O ₃ + SiO ₂ + Al ₂ O ₃ )], the lower limit is preferably 0.55, and more preferably 0.60, 0.65, 0.70, 0.75, 0 The order of .80, 0.85, 0.90, and 0.95 is more preferable. 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 will decrease, and the meltability will also decrease. Therefore, from the viewpoint of maintaining high dispersion and good meltability of the glass, 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 within the above range. It is preferable that there be.

In the glass according to the 2-1 embodiment, the upper limit of the mass ratio [TiO ₂ /P ₂ O ₅ ] between the content of TiO ₂ and the content of P ₂ O ₅ is preferably 4.50, and are more preferable in the order of 4.00, 3.50, 3.00, 2.50, 2.00, and 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. The preferred order is 28, 0.32, 0.36, 0.40, 0.44, 0.48, and 0.52.

In the glass according to the 2-1 embodiment, the inclusion of TiO ₂ promotes crystal formation within the glass, resulting in a problem that the transparency of the glass decreases (cloudiness). This problem can be solved by containing P ₂ O ₅ , which is a network forming component, in a ratio within the above range to TiO ₂ .

Furthermore, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation %, the cation ratio between the Ti ⁴⁺ content and the P ⁵⁺ content [Ti ⁴⁺ /P ⁵⁺ ] is preferably 1.50, more preferably 1.40, 1.30, 1.29, 1.28, 1.27, 1.26, 1.25, 1.24, 1.23 , 1.22 is more preferable. The lower limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] is preferably 0.50, and more preferably in the order of 0.51, 0.52, and 0.53.

In the glass according to the 2-1 embodiment, the inclusion of Ti ⁴⁺ promotes crystal formation within the glass, resulting in a problem that the transparency of the glass decreases (cloudiness). This problem can be solved by containing P ⁵⁺ , which is a network forming component, in a ratio within the above range to Ti ⁴⁺ .

In the glass according to Embodiment 2-1, the upper limit of the WO ₃ content is preferably 50.0%, and more preferably 49.0%, 48.0%, 47.0%, and 46.0%. %, 45.0%, 44.0%, 43.0%, 42.0%, 41.0%, 40.0%, 39.0%, 38.0%, 37.0%, 36.0 %, 35.0%, 34.0%, 33.0%, 32.0%, 31.0%, 30.0%. Further, the lower limit of the content of WO ₃ is preferably 0.01%, and further in the order of 0.1%, 0.3%, 0.5%, 0.7%, and 1.0%. preferable. The content of WO ₃ may be 0%.

WO ₃ greatly contributes to high dispersion, but is more likely to cause coloring of the glass than TiO ₂ , Nb ₂ O ₅ and Bi ₂ O ₃ and deteriorates transmittance. Therefore, the content of WO ₃ is preferably within the above range.

Furthermore, in the glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the content of W ⁶⁺ is preferably 20.00 cation%, and more preferably 19.00%. cation%, 18.50 cation%, 18.00 cation%, 17.50 cation%, 17.00 cation%, 16.50 cation%, 16.00 cation%, 15.50 cation%, 15.00 cation% , 14.50% cations, 14.00% cations, and 13.50% cations in this order. 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 that order. The content of W ⁶⁺ may be 0 cation%.

Although W ⁶⁺ greatly contributes to high dispersion, it is more likely to cause coloring of the glass than Ti ⁴⁺ , Nb ⁵⁺ and Bi ³⁺ and deteriorates transmittance. Therefore, the content of W ⁶⁺ is preferably within the above range.

In the glass according to the 2-1 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 is 0.15, and furthermore, 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. The order of 64 and 0.65 is more preferable. Further, the upper limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 8.00, more preferably 7.90, 7.80, 7.70, 7.60, 7. The preferred order is 40, 7.20, and 7.00.

By setting the value of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] within the above range, it is possible to obtain a glass having high dispersion suitable for correcting chromatic aberration while suppressing an increase in the refractive index.

Furthermore, in the glass according to the 2-1 embodiment, when the content of glass components is expressed in cation%, the cation ratio of the total content of Ti ⁴⁺ and W ⁶⁺ and the content of Nb ⁵⁺ [(Ti ⁴⁺ +W ⁶⁺ )/Nb ⁵⁺ ] is preferably 7.70, more preferably 7.60, 7.50, 7.40, 7.35, 7.30, 7.28, 7 The order of .26 is more preferable. 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 in that order.

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

In the glass according to the 2-1 embodiment, the upper limit of the Na ₂ O content is preferably 10.0%, and more preferably 9.0%, 8.0%, 7.0%, and 6.0%. The preferred order is 0%, 5.0%, 4.0%, and 3.0%. The content of Na ₂ O may be 0%.

Furthermore, in the optical glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Na ⁺ content is preferably 13.00 cation%, and more preferably 12.00 cation%. cation%, 11.50 cation%, 11.00 cation%, 10.50 cation%, 10.00 cation%, 9.50 cation%, 9.00 cation%, 8.50 cation%, 8.00 cation% This order is more preferable. The lower limit of the Na ⁺ content is preferably 1.50 cation%, more preferably 1.30 cation%, 1.00 cation%, 0.70 cation%, 0.50 cation%, 0.30 cation%. This order is more preferable. The content of Na ⁺ may be 0 cation%.

In the glass according to the 2-1 embodiment, the upper limit of the K ₂ O content is preferably 15.0%, and more preferably 14.0%, 13.0%, 12.0%, 11. The preferred order is 0%, 10.0%, 9.0%, 8.0%, 7.0%, 6.0%, and 5.0%. Further, the lower limit of the K ₂ O content is preferably 0.01%, and more preferably 0.1%, 0.3%, and 0.4% in this order. The content of K ₂ O may be 0%.

Further, in the optical glass according to the 2-1 embodiment, when the content of the glass component is expressed in cation%, the upper limit of the K ⁺ content is preferably 15.00 cation%, and more preferably 14.50 cation%. The preferred order is cation%, 14.00 cation%, 13.50 cation%, 13.00 cation%, 12.50 cation%, 12.00 cation%, 11.50 cation%, and 11.00 cation%. The lower limit of the K ⁺ content is preferably 1.00 cation%, and more preferably 0.70 cation%, 0.50 cation%, and 0.30 cation% in this order. The content of K ⁺ may be 0 cation%.

Na ₂ O and K ₂ O, or alternatively Na ⁺ and K ⁺ , have the effect of helping to reduce the heat treatment time required to reduce reduced color due to highly dispersed components. Between Na ₂ O and K ₂ O, Na ₂ O has a higher effect, and between Na ⁺ and K ⁺ , Na ⁺ has a higher effect. Further, the higher the content of these elements, the greater the effect, but if the content is too high, the thermal stability, chemical durability, and weather resistance of the glass will decrease. Therefore, it is preferable that the respective contents of Na ₂ O, K ₂ O, Na ⁺ and K ⁺ are within the above ranges.

In the glass according to the 2-1 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 20.0%, and , 19.0%, 18.0%, 17.0%, 16.0%, 15.0%, 14.0%, 13.0%, 12.0%, 11.0%, 10.0% , 9.0%, 8.0%, 7.0%, and 6.0% in that order. Further, the lower limit of the total content [Li ₂ O + Na ₂ O + K ₂ O] is preferably 0.01%, and furthermore, 0.02%, 0.03%, 0.04%, 0.05%, The preferred order is 0.06%, 0.07%, 0.08%, 0.09%, 0.10%, 0.20%, 0.30%, 0.40%, and 0.50%.

Li ₂ O, Na ₂ O and K ₂ O have the function of shortening the heat treatment time required to reduce reduced color caused by highly dispersed components, and also improving the meltability of the glass. However, when these contents increase, the thermal stability, chemical durability, and weather resistance of the glass decrease. 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 within the above range.

Furthermore, in the optical glass according to the 2-1 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the total content of Li ⁺ , Na ⁺ and K ⁺ [Li ⁺ +Na ⁺ +K ⁺ ] is Preferably it is 22.00 cation%, more preferably 21.00 cation%, 20.00 cation%, 19.00 cation%, 18.00 cation%, 17.00 cation%, 16.50 cation%, 16. 00 cation%, 15.50 cation%, 15.00 cation%, 14.50 cation%, 14.00 cation%, 13.50 cation%, 13.00 cation%, 12.50 cation% 12.00 cation% , 11.50 cation%. The lower limit of the total content [Li ⁺ +Na ⁺ +K ⁺ ] is preferably 1.00 cation%, and more preferably 0.70 cation%, 0.50 cation%, and 0.30 cation% in that order. The total content [Li ⁺ +Na ⁺ +K ⁺ ] may be 0 cation%.

Li ⁺ , Na ⁺ and K ⁺ have the function of shortening the heat treatment time required to reduce reduced color caused by highly dispersed components and improving the meltability of the glass. However, when these contents increase, the thermal stability, chemical durability, and weather resistance of the glass decrease. Therefore, the total content of Li ⁺ , Na ⁺ and K ⁺ [Li ⁺ +Na ⁺ +K ⁺ ] is preferably within the above range.

In the glass according to the 2-1 embodiment, the mass ratio of the content of Li ₂ O to the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O/(Li ₂ O + Na ₂ O + K ₂ O )] is preferably 0.0012, and more preferably 0.0013, 0.0014, 0.0015, 0.0016, 0.0017, 0.0018, 0.0019, 0.0020, 0 .0021, 0.0022, 0.0023, 0.0024, 0.0025, 0.0026, 0.0027, 0.0028, 0.0029, 0.0030, 0.0032, 0.0035, 0.0037 , 0.0040 is more preferable. The upper limit of the mass ratio [Li ₂ O/(Li ₂ O+Na ₂ O+K ₂ O)] is preferably 1.00, and more preferably 0.80, 0.60, 0.50, 0.40, 0. The preferred order is 30, 0.20, 0.18, and 0.16.

In the glass according to Embodiment 2-1, the upper limit of the Rb ₂ O content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, 1. The preferred order is 0%, 0.7%, 0.5%, 0.3%, and 0.1%. Moreover, the lower limit of the content of Rb ₂ O is preferably 0%. The content of Rb ₂ O may be 0%.

In the glass according to Embodiment 2-1, the upper limit of the Cs ₂ O content is preferably 10.0%, and more preferably 9.0%, 8.0%, 7.0%, 6.0%. The preferred order is 0%, 5.0%, 4.5%, 4.0%, 3.5%, and 3.0%. Further, the lower limit of the content of Cs ₂ O is preferably 0%. The content of Cs ₂ O may be 0%.

Rb ₂ O and Cs ₂ O, like Na ₂ O and K ₂ O, have the effect of helping to shorten the heat treatment time required to reduce reduced color caused by highly dispersed components, but the effect is Smaller than Na ₂ O and K ₂ O. Moreover, when the content of these increases, the thermal stability, chemical durability, and weather resistance of the glass decrease. Therefore, it is preferable that the respective contents of Rb ₂ O and Cs ₂ O are within the above ranges.

In the glass according to Embodiment 2-1, the upper limit of the MgO content is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0%. This order is more preferable. Further, the lower limit of the MgO content is preferably 0%. The content of MgO may be 0%.

In the glass according to Embodiment 2-1, the upper limit of the CaO content is preferably 6.0%, and more preferably 5.0%, 4.0%, 3.0%, and 2.0%. , 1.0% is more preferable. Further, the lower limit of the CaO content is preferably 0%. The content of CaO may be 0%.

In the glass according to Embodiment 2-1, the upper limit of the SrO content is preferably 7.0%, and more preferably 6.0%, 5.0%, 4.0%, and 3.0%. , 2.0%, and 1.0% in that order. Further, the lower limit of the SrO content is preferably 0%. The content of SrO may be 0%.

In the glass according to Embodiment 2-1, the upper limit of the BaO content is preferably 10.0%, and more preferably 9.0%, 8.0%, 7.0%, and 6.0%. , 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%. Further, the lower limit of the BaO content is preferably 0%. The content of BaO may be 0%.

MgO, CaO, SrO, and BaO are all glass components that have the function of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, high dispersibility is impaired, the thermal stability of the glass is reduced, and the glass is likely to devitrify. Therefore, the content of each of these glass components is preferably within the above range.

Furthermore, in the glass according to Embodiment 2-1, when the content of the glass components is expressed in cation%, the upper limit of the Ba ²⁺ content is preferably 10.00 cation%, and more preferably 9.00 cation%. cation%, 8.00 cation%, 7.00 cation%, 6.00 cation%, 5.00 cation%, 4.50 cation%, 4.00 cation%, 3.50 cation%, 3.00 cation% , 2.50 cation%, 2.00 cation%, 1.50 cation%, 1.00 cation%, and 0.70 cation%. Further, the lower limit of the Ba ²⁺ content is preferably 0 cation%. The content of Ba ²⁺ may be 0 cation%.

Ba ²⁺ is a glass component that has the function of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, high dispersibility is impaired, the thermal stability of the glass is reduced, and the glass is likely to devitrify. Therefore, the content of each of these glass components is preferably within the above range.

In the glass according to the 2-1 embodiment, from the viewpoint of maintaining thermal stability without hindering high dispersion, the upper limit of the total content of MgO, CaO, SrO, and BaO [MgO+CaO+SrO+BaO] is preferably 17. 0%, furthermore, 16.0%, 15.0%, 14.0%, 13.0%, 12.0%, 11.0%, 10.0%, 9.0%, 8. The preferred order is 0%, 7.0%, 6.0%, 5.0%, 4.0%, 3.0%, 2.0%, and 1.0%. 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%.

ZnO, ZrO ₂ , Ta ₂ O ₅ , Ga ₂ O ₃ , In ₂ O ₃ , Sc ₂ O ₃ , HfO ₂ , Lu ₂ O ₃ , GeO ₂ , La ₂ O ₃ , Gd in Embodiment 2-1 The contents of ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ can be the same as in the 1-1 embodiment.

The glass according to the 2-1 embodiment mainly contains the above-mentioned glass components, namely 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 , _Li2O , Na2O, _{K2O , Rb2O} , _Cs2O , MgO, CaO, SrO, BaO, ZnO, _ZrO2 , _{Ta2O5 , Ga2O3 , In2O3 ,} It is preferably composed of a component selected from 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 , and the above-mentioned The total content of glass components is preferably more than 95%, more preferably more than 98%, even more preferably more than 99%, even more preferably more than 99.5%.

The other glass component compositions in the 2-1 embodiment can be the same as in the 1-1 embodiment.

(Glass characteristics)
<Glass transition temperature Tg>
The upper limit of the glass transition temperature Tg of the glass according to the 2-1 embodiment is preferably 750°C, and more preferably in the order of 740°C, 730°C, 720°C, 710°C, and 700°C. Further, the lower limit of the glass transition temperature Tg is preferably 500°C, and further preferably 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, The order of 610°C, 620°C, and 630°C is more preferable.

When the upper limit of the glass transition temperature Tg satisfies the above range, an increase in the heat treatment temperature of the glass can be suppressed, and thermal damage to annealing equipment such as a continuous annealing furnace called RARE or a batch annealing furnace can be reduced. It is also possible to reduce the power consumption of the furnace.

When the lower limit of the glass transition temperature Tg satisfies the above range, it becomes easy to maintain good thermal stability of the glass while maintaining a desired Abbe number.

<Refractive index n _d >
In the glass according to the 2-1 embodiment, the upper limit of the refractive index n _d at a wavelength of 587.56 nm is preferably 2.1500, and more preferably 2.1400, 2.1300, 2.1200, and 2.1100. , 2.1000, 2.0900, 2.0800, 2.0700, 2.0600, 2.0500, and 2.0400. Further, the lower limit of n _d is preferably 1.8800, and furthermore, 1.8900, 1.9000, 1.9100, 1.9200, 1.9300, 1.9350, 1.9400, 1.9450, 1 The larger the value is in the order of .9500, 1.9600, and 1.9700, the more preferable it is.

<Refractive index n _C >
In the glass according to the 2-1 embodiment, the upper limit of the refractive index n _C at a wavelength of 656.27 nm is preferably 2.1350, and more preferably 2.1250, 2.1150, 2.1050, and 2.0950. , 2.0850, 2.0750, 2.0650, 2.0550, 2.0450, 2.0350, 2.0250, 2.0150 in this order. Further, the lower limit of the refractive index is preferably 1.8650, and more preferably 1.8750, 1.8850, 1.8950, 1.9050, 1.9150, 1.9200, 1.9250, 1.9350. , 1.9400, 1.9450, and 1.9550, the larger the value is, the more preferable it is.

<Light transmittance of glass>
In the 2-1 embodiment, the light transmittance can be evaluated by the degree of coloration λ5, as in the 1-1 embodiment.

In the 2-1 embodiment, the upper limit of λ5 is preferably 460 nm, and more preferably in the order of 455 nm, 450 nm, 445 nm, 440 nm, 435 nm, 430 nm, 425 nm, and 420 nm. The lower limit of λ5 is 360 nm.

<Specific gravity of glass>
Although the glass according to the 2-1 embodiment is a high dispersion glass, its specific gravity is not large. Generally, if the specific gravity of the glass can be reduced, the weight of the lens can be reduced. As a result, it is possible to reduce power consumption for autofocus driving of a camera lens equipped with a lens. On the other hand, reducing the specific gravity too much leads to a decrease in thermal stability. Therefore, the upper limit of specific gravity d is preferably 5.60, and more preferably 5.50, 5.40, 5.30, 5.20, 5.10, 5.00, 4.90, 4.80. , 4.70, 4.60, 4.50, 4.40, 4.30, 4.20, 4.10, 4.00, 3.90, 3.80, 3.70. Further, from the viewpoint of improving thermal stability, the lower limit of 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 glass according to the 2-1 embodiment is preferably 1400°C, and more preferably 1390°C, 1380°C, 1370°C, 1360°C, 1350°C, 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 furthermore, 1010°C, 1020°C, 1030°C, 1040°C, 1050°C, 1060°C, 1070°C, 1080°C, 1090°C, 1100°C, 1110°C. ℃, 1120°C, 1130°C, 1140°C, 1150°C, 1160°C, 1170°C, and 1180°C. According to the glass according to this embodiment, a high dispersion glass with improved thermal stability of the glass can be obtained.

Note that the liquidus temperature is determined as follows. 10 cc (10 ml) of glass is placed in a platinum crucible and melted at 1250°C to 1350°C for 20 to 30 minutes, then cooled to below the glass transition temperature Tg, and the glass is placed together with the platinum crucible in a melting furnace at a predetermined temperature and held for 2 hours. do. The holding temperature is 1000°C or higher in 5°C or 10°C increments, and after holding for 2 hours, it is cooled and the presence or absence of crystals inside the glass is observed using a 100x optical microscope. The lowest temperature at which no crystals precipitate is defined as the liquidus temperature.

(manufacture of glass)
The glass according to the 2-1 embodiment of the present invention may be produced by blending glass raw materials to have the above-described predetermined composition, and using the blended glass raw materials according to a known glass manufacturing method. For example, a plurality of compounds are prepared and sufficiently mixed to form a batch raw material, and the batch raw material is put into a melting container and melted, clarified, and homogenized, and then a molten glass is formed and slowly cooled to obtain glass. Alternatively, the batch raw materials are put into a melting container and roughly melted. The molten material obtained by rough melting is rapidly cooled and pulverized to produce cullet. Furthermore, the cullet can be placed in a melting container, heated and remelted to obtain molten glass, and after further clarification and homogenization, the molten glass can be shaped and slowly cooled to obtain glass. A known method may be applied to forming and slowly cooling the molten glass.

In the production of glass according to Embodiment 2-1, when batch raw materials are roughly melted (rough melted) to produce cullet, the lower limit of the melting temperature during rough melting is preferably 1000°C, and further, The order of 1050°C, 1100°C, 1150°C, 1200°C, 1250, and 1300°C is more preferable. Further, the upper limit of the melting temperature is preferably 1500°C, and more preferably 1450°C, 1400°C, and 1350°C in this order.

When producing the glass according to Embodiment 2-1 by melting, refining, and molding the cullet, the lower limit of the melting temperature of the cullet is preferably 1000°C, and more preferably 1050°C, 1100°C, and 1150°C. ℃, 1200℃, 1250, and 1300℃ are more preferable in that order. Further, the upper limit of the melting temperature is preferably 1500°C, and more preferably 1450°C, 1400°C, and 1350°C in this order.

When manufacturing the glass according to Embodiment 2-1 by melting, refining, and molding batch raw materials without culleting, the lower limit of the melting temperature of the batch raw materials is preferably 1000°C, and further, The order of 1050°C, 1100°C, 1150°C, 1200°C, 1250, and 1300°C is more preferable. Further, the upper limit of the melting temperature is preferably 1500°C, and more preferably 1450°C, 1400°C, and 1350°C in this order.

In the production of glass according to Embodiment 2-1, the lower limit of the refining temperature when refining the molten glass is preferably 1000°C, more preferably 1050°C, 1100°C, 1150°C, 1200°C, 1250°C. , 1300°C are preferred in this order. Further, the upper limit of the fining temperature is preferably 1500°C, and more preferably 1450°C, 1400°C, and 1350°C in this order.

In manufacturing the glass according to the 2-1 embodiment, the lower limit of the outflow temperature when pouring the molten glass into the mold is preferably 1000°C, and more preferably 1050°C, 1100°C, 1150°C, 1200°C. , 1250°C, and 1300°C are preferred in this order. Further, the upper limit of the outflow temperature is preferably 1500°C, and more preferably 1450°C, 1400°C, and 1350°C in this order.

Note that the compound used when preparing the batch raw material is not particularly limited as long as the desired glass component can be introduced into the glass in a desired content. Examples of such compounds include oxides, orthophosphoric acid, metaphosphates, diphosphorous pentoxide, carbonates, nitrates, hydroxides, and fluorides.

(manufacture of optical glass)
The glass according to Embodiment 2-1 of the present invention can be used as is as the optical glass according to Embodiment 2-1 of the present invention.

When the glass according to Embodiment 2-1 of the present invention exhibits a reduced color, the glass according to this embodiment can be heat-treated to reduce the reduced color and can be made into optical glass. As the heat treatment method, a known method can be used. For example, there is a method in which glass is heated to a temperature 5 to 20° C. lower than the glass transition temperature Tg and held until the coloration is sufficiently reduced. Note that after the heat treatment, distortion of the glass can be removed by slow cooling treatment. As the slow cooling method, a known method can be used. For example, a method may be used in which the temperature is gradually lowered to a temperature 100 to 150° C. lower than the heating temperature in the above heat treatment.

(Manufacture of glass materials for polishing and glass materials for press molding)
The glass material for polishing and the glass material for press molding according to the 2-1 embodiment of the present invention can be manufactured from both the glass and the optical glass according to the 2-1 embodiment.

Glass materials for polishing are made by dividing glass or optical glass into cut pieces, and if necessary, rough polishing each cut piece (barrel polishing) to equalize the weight and attaching a mold release agent to the surface. It can be manufactured by softening, reheating, and press-molding the softened glass into a desired shape. Alternatively, in the manufacturing process of glass or optical glass, a predetermined weight of molten glass may be separated onto a mold and directly press-molded.

A glass material for press molding can be manufactured by dividing glass or optical glass into predetermined volumes and grinding and polishing the surface. Alternatively, in the manufacturing process of glass or optical glass, molten glass may be dropped and the molten glass droplets may be shaped.

In manufacturing glass materials for polishing and glass materials for press molding, heat treatment may be performed to reduce reduced color. The heat treatment method is the same as the heat treatment method used in manufacturing the optical glass described above. Heat treatment can be performed either after molding or before or after grinding and polishing.

(Manufacture of optical elements, etc.)
The optical element according to Embodiment 2-1 of the present invention can be manufactured from any of the glass, optical glass, glass material for polishing, and glass material for press molding according to Embodiment 2-1 of the present invention.

The optical element according to Embodiment 2-1 of the present invention can be manufactured by dividing glass or optical glass into predetermined volumes and grinding and polishing the surface. In addition, glass or optical glass is divided into pieces to create cut pieces, and if necessary, each cut piece is roughly polished (barrel polishing) to equalize the weight and to make it easier to attach a mold release agent to the surface. It is also possible to manufacture the optical element by press-molding the softened glass by reheating it into a shape approximating the shape of the desired optical element, and finally grinding and polishing it. Alternatively, in the manufacturing process of glass or optical glass, a predetermined weight of molten glass may be separated onto a mold, directly press-molded, and finally ground and polished.

The optical element according to the 2-1 embodiment of the present invention can be manufactured by grinding and polishing the above polishing glass material. Further, the optical element according to the 2-1 embodiment of the present invention can be manufactured by precision pressing the above-mentioned glass material for press molding. The glass material for press molding may be manufactured by precision pressing after heating.

In manufacturing the optical element according to Embodiment 2-1 of the present invention, heat treatment may be performed to reduce reduced color. The heat treatment method is the same as the heat treatment method used in manufacturing the optical glass described above. Heat treatment can be performed after press molding or precision pressing, and can also be performed before or after grinding and polishing.

Furthermore, in manufacturing the optical element according to the 2-1 embodiment of the present invention, centering processing may be performed as necessary.

The optical functional surface of the produced optical element can be coated with an antireflection film, a total reflection film, etc. depending on the purpose of use.

Examples of optical elements include various lenses such as aspherical lenses, microlenses, and lens arrays, and diffraction gratings.

2-2 Embodiment The glass of 2-2 embodiment of the present invention is
Abbe number ν _d is 18.10 or less,
A phosphate glass containing at least one oxide selected from TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ ,
Remelt and mold for 90 minutes at a temperature 110 to 120°C higher than the liquidus temperature LT in an air atmosphere,
The glass obtained by keeping it at a holding temperature 0 to 20°C lower than the glass transition temperature Tg for 15 minutes in an air atmosphere and gradually cooling it at a cooling rate of 30°C/h to a temperature 120°C lower than the holding temperature above is 17 mm long and wide. In those processed to 13mm and 10mm thick,
When viewed from above, a portion within a distance of 0 to 5 mm from the end in the vertical direction and a distance of 0 to 5 mm from the end in the horizontal direction is defined as the glass end;
When the center of the glass is defined as a portion that is 6 to 11 mm from the vertical edge and 4 to 9 mm from the horizontal edge when viewed from above,
When light is incident parallel to the thickness direction, the external transmittance T _A of the edge of the glass and the external transmittance T _B of the center of the glass at a wavelength of 656 nm are greater than or equal to the value T ₁ calculated by the following formula (2) ,and,
Until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less,
Heat treatment in the air at a heating rate of 100°C/h and holding at a heat treatment temperature 5 to 15°C lower than the glass transition temperature Tg, and a cooling rate of 30°C/h to a temperature 120°C lower than the above heat treatment temperature. When repeating the slow cooling process once or multiple times,
Glass whose total holding time at the heat treatment temperature in the heat treatment is 48 hours or less.
T ₁ =0.83×{1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (2)
(In formula (2), n _C is the heat treatment described above until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less. and the refractive index at a wavelength of 656.27 nm when subjected to slow cooling treatment.)

The glass according to the 2-2 embodiment will be described in detail below.

In the glass according to the 2-2 embodiment, the Abbe number ν _d is 18.10 or less. The upper limit of the Abbe number ν _d is preferably 18.05, and more preferably 18.00, 17.90, 17.80, 17.70, 17.60, 17.50, 17.40, 17.30. , 17.20, 17.10, 17.00, 16.90, 16.80, 16.78, 16.76, 16.74, 16.72, 16.70, 16.68, 16.66, 16 The preferred order is .64, 16.62, 16.60, 16.58, 16.56, 16.54, 16.52, 16.50. Further, the lower limit of Abbe's number is preferably 15.00, and more preferably 15.10, 15.20, 15.25, 15.30, 15.35, 15.40, 15.45, 15.50. , 15.52, 15.54, 15.56, 15.58, 15.60.

The glass according to the 2-2 embodiment contains at least one oxide selected from TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ .

The glass according to the 2-2 embodiment is phosphate glass. Therefore, the glass according to the 2-2 embodiment mainly contains phosphate as a network forming component, and the content thereof is expressed as the content of P ₂ O ₅ .

In the glass according to Embodiment 2-2, 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%, 13.0%, 14.0%, 15.0%, 16.0%, 17.0%, 18.0%, 19.0%, 20.0% more preferred. Further, the upper limit of the content of P ₂ O ₅ is preferably 37.0%, and more preferably 36.0%, 35.0%, 34.5%, 34.0%, 33.5%, The preferred order is 33.0%, 32.5%, 32.0%, 31.5%, 31.0%, 30.5%, and 30.0%.

P ₂ O ₅ is a necessary component because glass contains a large amount of highly dispersed components. On the other hand, if P ₂ O ₅ is included excessively, the meltability will deteriorate. Therefore, in the glass according to this embodiment, the content of P ₂ O ₅ is preferably within the above range.

Furthermore, in the glass according to Embodiment 2-2, when the content of glass components is expressed in cation%, the upper limit of the P ⁵⁺ content is preferably 42.00 cation%, and more preferably 41.50 cation%. cation%, 41.00 cation%, 40.50 cation%, 40.00 cation%, 39.50 cation%, 39.00 cation%, 38.50 cation%, 38.00 cation%, 37.50 cation% , 37.00% cations, 36.50% cations, and 36.00% cations in this order. The lower limit of the content of P ⁵⁺ is preferably 25.00 cation%, more preferably 25.50 cation%, 26.00 cation%, 26.50 cation%, 27.00 cation%, 27.50 cation%. %, 28.00 cation%, 28.50 cation%, 29.00 cation%, and 29.30 cation%.

P ⁵⁺ is an essential component for suppressing an increase in the refractive index nd and for containing a large amount of highly dispersible components in the glass. On the other hand, when P ⁵⁺ is included excessively, solubility deteriorates. Therefore, in the optical glass according to this embodiment, the content of P ⁵⁺ is preferably within the above range.

The glass according to the 2-2 embodiment can relatively uniformly reduce reduced color caused by highly dispersed components such as TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ , and can also reduce reduced color. It is a glass that can shorten the heat treatment time required for Specifically, when glass is heat-treated in a prescribed manner, the retention time at the heat treatment temperature (hereinafter sometimes referred to as "fading time") is 48 hours or less to reduce the reduced color to a problem-free level. It is a glass that can reduce The details are explained below.

In heat treatment for reducing reduced color, the fading time until the transmittance of the glass reaches a predetermined range varies depending on the coloring state of the glass and the size of the glass.

Therefore, in the 2-2 embodiment, the glass according to the present embodiment is reduced and colored under certain conditions, and the fading time is evaluated using a reduced glass sample processed into a predetermined size. The reduced glass sample used in the measurement is formed by remelting the glass according to the present embodiment at a temperature 110 to 120°C higher than the liquidus temperature LT for 90 minutes in an air atmosphere, and then forming the glass at a glass transition temperature in the air atmosphere. The glass obtained by holding at a holding temperature 0 to 20°C lower than Tg for 15 minutes and slowly cooling it to a temperature 120°C lower than the above holding temperature at a cooling rate of 30°C/h was processed into a length of 17 mm, width of 13 mm, and thickness of 10 mm. get it.

In order to remelt glass at a temperature 110 to 120° C. higher than the liquidus temperature LT in the atmosphere, the glass may be placed in a platinum crucible, heated, and remelted to form molten glass. At this time, coloration occurs due to highly dispersed components.

The molten glass is poured into a mold and formed into a plate shape. This was held in the air at a holding temperature 0 to 20°C lower than the glass transition temperature Tg for 15 minutes, and then slowly cooled to a temperature 120°C lower than the holding temperature at a cooling rate of 30°C/h to remove distortion of the glass. remove.

After removing the distortion, the glass is divided into pieces, polished, and processed into pieces measuring 17 mm long, 13 mm wide, and 10 mm thick. At this time, the upper and lower surfaces (surfaces measuring 17 mm in length and 13 mm in width) are optically polished to obtain a reduced glass sample.

The thus obtained reduced glass sample is subjected to heat treatment and slow cooling treatment under the following conditions, and the fading time is evaluated.
That is, a heat treatment in which heating is performed at a temperature increase rate of 100 °C/h in an atmospheric atmosphere and held at a heat treatment temperature 5 to 15 °C lower than the glass transition temperature Tg, and a temperature decrease rate of 30 °C/h is 120 °C lower than the above heat treatment temperature. Perform slow cooling treatment to gradually cool down to temperature. The heat treatment reduces coloring caused by highly dispersed components.

The above heat treatment and slow cooling treatment are performed until the reduced glass sample is discolored to a level that causes no practical problems. That is, when light is incident parallel to the thickness direction of the sample after treatment, the external transmittance T _A of the glass edge and the external transmittance T _B of the glass center at a wavelength of 656 nm are calculated using the following formula (2). The process is continued until the value T ₁ or more is reached and the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass is 5% or less.
T ₁ =0.83×{1-{(n _C -1)/(n _C +1)} ² } ² ×98 ... (2)

Note that n _C in the above formula (2) is determined by heat treatment until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less. and the refractive index at a wavelength of 656.27 nm when subjected to slow cooling treatment. The refractive index n _C is measured based on the Japan Optical Glass Industry Association standard (JOGIS 01-2003).

The above heat treatment and slow cooling treatment may be performed once or multiple times. When the heat treatment and slow cooling treatment are performed multiple times, the fading time may be different each time.

In the glass according to Embodiment 2-2, the total fading time in the heat treatment is within 48 hours, preferably within 46 hours, more preferably within 44 hours, within 42 hours, within 40 hours, within 38 hours, The preferred time is within 36 hours, within 34 hours, within 32 hours, within 30 hours, within 29 hours, within 28 hours, within 27 hours, within 26 hours, within 25 hours, and within 24 hours.

The total fading time is the fading time for one time when the above heat treatment and slow cooling treatment are performed, and the total fading time for each time when the above heat treatment and slow cooling treatment are performed multiple times. is the sum of For example, if the first fading time is 12 hours and the second fading time is 6 hours, the total fading time is 18 hours.

Note that in the above heat treatment, the heat treatment temperature is set to be 5 to 15° C. lower than the glass transition temperature Tg, considering that a plurality of glasses having different glass transition temperatures Tg are heat treated at once. Therefore, in the glass according to the present embodiment, if the reduced glass sample obtained as described above is heat treated at a heat treatment temperature 5 to 15 degrees Celsius lower than the glass transition temperature Tg, the color fading time is within 48 hours and sufficient reduction is achieved. In other words, if the heat treatment is performed at a heat treatment temperature that is at least 15° C. lower than the glass transition temperature Tg, the reduced color can be sufficiently reduced within 48 hours.

Here, the edge of the glass is a portion that is within a distance of 0 to 5 mm from the edge in the vertical direction and 0 to 5 mm from the edge in the horizontal direction when viewed from above, and is defined as the center of the glass. , when viewed from above, is a distance of 6 to 11 mm from the end in the vertical direction and a distance of 4 to 9 mm from the end in the horizontal direction.

In the heat treatment and slow cooling treatment, when light is incident parallel to the thickness direction, the external transmittance T _A of the glass edge and the external transmittance T _B of the glass center at a wavelength of 656 nm are calculated using the above formula (2). The process is continued until the value T ₁ or higher is reached. The external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass at a wavelength of 656 nm are preferably equal to or greater than the value T ₂ calculated by the following formula (3), and more preferably by the following formula (4). It is more preferable to have the value T ₃ or more calculated by the following formula (5), more preferably the value T ₄ or more calculated by the following formula (5).
T ₂ =0.84×{1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (3)
T ₃ =0.85×{1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (4)
T ₄ =0.86×{1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (5)

Furthermore, if the difference between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass (TA _- T _B ) is 5% or less, the reduced color of the entire glass is reduced almost uniformly. means that

During heat treatment, the reduction of the reduced color of the glass progresses from the surface to the center of the glass. Therefore, during the heat treatment, the center of the glass is colored more deeply than the edges of the glass. When the reduced color at the center of the glass is reduced to the same extent as at the edges of the glass, that is, when the reduced color is reduced uniformly, the external transmittance T _A at the glass ends and the external transmittance T at the center of the glass are The difference from _B (T _A - T _B ) is 5% or less.

In the glass according to the 2-2 embodiment, the heat treatment and slow cooling treatment reduce the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass by 5%. The content is preferably 4% or less, more preferably 3% or less, even more preferably 2% or less, even more preferably 1% or less, even more preferably 0.5% or less.

That is, in the glass according to the 2-2 embodiment, the heat treatment and slow cooling treatment are such that the external transmittance T _A of the glass edge and the external transmittance T _B of the glass center at a wavelength of 656 nm are calculated using the above formula (2). The process is continued until the value T ₁ is greater than or equal to the value T 1 and the difference (T _A -T _B ) is 5% or less. Preferably, in the heat treatment and slow cooling treatment, the external transmittance T _A and the external transmittance T _B are equal to or greater than the value T ₁ calculated by the above formula (2), and the difference ( _TA − T _B ) is 4% or less. Further, the process is continued until it becomes 3% or less, 2% or less, 1% or less, or 0.5% or less. The smaller the difference (T _A −T _B ) is, the more preferable it is.

Preferably, in the glass according to Embodiment 2-2, the heat treatment and slow cooling treatment are such that the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass at a wavelength of 656 nm are expressed by the above formula (3). ) is greater than or equal to the value T ₂ calculated by T 2 and the difference ( _TA - T _B ) is 5% or less. More preferably, in the heat treatment and slow cooling treatment, the external transmittance T _A and the external transmittance T _B are equal to or greater than the value T ₂ calculated by the above formula (3), and the difference ( _TA − T _B ) is 4%. Further, it is continued until it becomes 3% or less, 2% or less, 1% or less, or 0.5% or less. The smaller the difference (T _A −T _B ) is, the more preferable it is.

Preferably, in the glass according to Embodiment 2-2, the heat treatment and slow cooling treatment are performed such that the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass at a wavelength of 656 nm are expressed by the above formula (4). This is repeated until the calculated value T ₃ or more is reached and the difference ( _TA - T _B ) is 5% or less. More preferably, in the heat treatment and slow cooling treatment, the external transmittance T _A and the external transmittance T _B are equal to or greater than the value T ₃ calculated by the above formula (4), and the difference ( _TA − T _B ) is 4%. Further, it is continued until it becomes 3% or less, 2% or less, 1% or less, or 0.5% or less. The smaller the difference (T _A −T _B ) is, the more preferable it is.

Preferably, in the glass according to Embodiment 2-2, the heat treatment and slow cooling treatment are performed such that the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass at a wavelength of 656 nm are expressed by the above formula (5). This is repeated until the calculated value T ₄ or more is reached and the difference ( _TA - T _B ) is 5% or less. More preferably, in the heat treatment and slow cooling treatment, the external transmittance T _A and the external transmittance T _B are equal to or higher than the value T ₄ calculated by the above formula (5), and the difference ( _TA − T _B ) is 4%. Further, it is continued until it becomes 3% or less, 2% or less, 1% or less, or 0.5% or less. The smaller the difference (T _A −T _B ) is, the more preferable it is.

In the glass according to Embodiment 2-2, the fading time is preferably as short as possible. Therefore, in the most preferred embodiment, in the heat treatment and the slow cooling treatment, the fading time is within 24 hours, and the external transmittance T _A of the glass edge and the external transmittance T _B of the glass center at a wavelength of 656 nm satisfy the above formula (5). The value calculated by T ₄ is greater than or equal to the value T 4 , and the difference ( _TA − T _B ) is 0.5% or less.

The external transmittance is measured based on the Japan Optical Glass Industry Association standard (JOGIS 02-2003). In measuring the external transmittance, incident light is irradiated perpendicularly to the upper surface (a surface measuring 17 mm in length and 13 mm in width). Further, the incident light is applied so as to fall within the area of the glass edge and the center of the glass, that is, a range of 5 mm x 5 mm.

In the glass according to the 2-2 embodiment, the lower 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 35%, and furthermore, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, The order of 64% is more preferable. Further, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably 90%, and more preferably 88%, 86%, 85%, 84%, 83%, 82%. , 81%, 80%, 79%, 78%, and 77%.

TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. Therefore, the lower limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range. On the other hand, TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ increase the coloration of the glass. Therefore, the upper limit of the total content [TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ] is preferably within the above range.

Furthermore, in the glass according to the 2-2 embodiment, when the content of glass components is expressed in cation%, the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ [Ti ⁴⁺ +Nb ^{5 +} +W ⁶⁺ +Bi ³⁺ ] The lower limit is preferably 52.00 cation%, and further 52.10 cation%, 52.15 cation%, 52.20 cation%, 52.25 cation%, 52. The order of 30% cation is more preferable. The upper limit of the total content [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is preferably 75.00 cation%, and more preferably 74.50 cation%, 74.00 cation%, and 73.50 cation%. , 73.00% cations, 72.50% cations, 72.00% cations, 71.50% cations, 71.00% cations, and 70.50% cations in this order.

Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ contribute to high dispersion of the glass. It also has the effect of improving the thermal stability of glass by containing it in an appropriate amount. Therefore, the lower limit of the total content [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is preferably within 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 within the above range.

In the glass according to Embodiment 2-2, the upper limit of the content of Bi ₂ O ₃ is preferably 38%, and furthermore, 35%, 33%, 30%, 28%, 25%, 23%, The order of 20% is more preferable. Moreover, 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 is a component that contributes to high dispersion. Further, by setting the content of Bi ₂ O ₃ within the above range, it is possible to suppress an increase in specific gravity and a decrease in glass transition temperature Tg. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus type imaging lens, the power required to drive the lens during autofocus increases, resulting in significant battery consumption. Therefore, it is preferable that the content of Bi ₂ O ₃ is within the above range.

Furthermore, in the glass according to the 2-2 embodiment, when the content of the glass components is expressed in cation%, the upper limit of the Bi ³⁺ content is preferably 10.00 cation%, and more preferably 9.00 cation%. cation%, 8.00 cation%, 7.00 cation%, 6.00 cation%, 5.00 cation%, 4.50 cation%, 4.00 cation%, 3.50 cation%, 3.00 cation% , 2.50 cation%, 2.00 cation%, 1.50 cation%, and 1.00 cation% in this order. The content of Bi ³⁺ may be 0 cation%.

Bi ³⁺ is a component that contributes to high dispersion. Further, by setting the content of Bi ³⁺ within the above range, an increase in specific gravity and a decrease in glass transition temperature Tg can be suppressed. As the specific gravity of the glass increases, the mass of the optical element increases. For example, if a lens with a large mass is incorporated into an autofocus type imaging lens, the power required to drive the lens during autofocus increases, resulting in significant battery consumption. Therefore, it is preferable that the content of Bi ³⁺ is within the above range.

In the glass according to the 2-2 embodiment, the mass ratio of the content of Li ₂ O to the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] multiplied by 100 is preferably 0.017, and more preferably 0.019, 0.021, 0.023, 0.025, 0. The order of 0.027 and 0.030 is more preferable. Further, the upper limit of the value obtained by multiplying the mass ratio [Li ₂ O/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] by 100 is preferably 0.750, and furthermore, 0.730, 0 The preferred order is .710, 0.700, 0.680, 0.650, 0.600, and 0.550.

In the glass according to Embodiment 2-2, when the content of glass components is expressed in cation%, if the W ⁶⁺ content exceeds 0 cation%, the Ba ²⁺ content and W ⁶ The upper limit of the cation ratio [Ba ²⁺ /W ⁶⁺ ] with the content of ⁺ is preferably 0.14, and more preferably in the order of 0.13, 0.12, 0.11, and 0.10. .

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the glass according to Embodiment 2-2, desired high dispersibility can be achieved by containing W ⁶⁺ , which is a high dispersion component, at the above cation ratio with respect to the ^{Ba 2+} content. can be maintained.

Furthermore, in the glass according to the 2-2 embodiment, when the content of the glass components is expressed in cation%, the content of W ⁶⁺ is 0 cation%, and the content of Ba ²⁺ is 0 cation%. %, the upper limit of the total content of Ti ⁴⁺ and Bi ³⁺ [Ti ⁴⁺ +Bi ³⁺ ] is preferably 35.00 cation %, more preferably 34.00 cation %, 33. 00 cation%, 32.50 cation%, 32.30 cation%, 32.00 cation%, 31.80 cation%, 31.60 cation%, 31.40 cation%, 31.20 cation%, 31.00 cation %, 30.80 cation%, 30.60 cation%, 30.40 cation%, 30.20 cation%, 30.10 cation%, and 30.00 cation%. The lower limit of the total content [Ti ⁴⁺ +Bi ³⁺ ] is preferably 21.00 cation%, and more preferably 21.20 cation%, 21.40 cation%, 21.60 cation%, and 21.80 cation%. , 22.00 cation%, 22.20 cation%, 22.40 cation%, 22.60 cation%, 22.80 cation%, 23.00 cation%, 23.10 cation%, 23.20 cation%, 23 The preferred order is .30 cation%, 23.40 cation%, and 23.50 cation%.

When the W ⁶⁺ content is 0 cation% and the Ba ²⁺ content exceeds 0 cation%, Ti, which has the second largest contribution to high dispersion after W ⁶⁺ among high dispersion components, By setting the total content of ⁴⁺ and Bi ³⁺ , which has the function of improving thermal stability, within the above range, low dispersion caused by Ba ²⁺ can be suppressed.

Other glass components in the 2-2 embodiment can be the same as in the 2-1 embodiment. Further, the glass properties, the glass, the optical glass, the glass material for polishing, the glass material for press molding, the optical element, etc. in the 2-2 embodiment can be manufactured in the same manner as in the 2-1 embodiment.

EXAMPLES The present invention will be explained below with reference to examples, but the present invention is not limited to the following examples.

Examples 1-1 to 1-3 are examples corresponding to the first embodiment described above. Further, Examples 2-1 to 2-4 are examples corresponding to the second embodiment.

(Example 1-1)
No. shown in Tables 1-1-1, 1-1-4, and 1-1-5, and in Tables 1-2-1, 1-2-3, and 1-2-4. Compound raw materials corresponding to each component, ie, raw materials such as phosphates, carbonates, oxides, etc., were weighed so as to obtain a glass having a composition of 1 to 129, and mixed thoroughly to obtain a blended raw material.

Here, Table 1-1-1, Table 1-1-4 and Table 1-1-5 are expressed in mass%. No. is expressed in cation percentage. Glass compositions from 1 to 129 are displayed. That is, Table 1-1-1, Table 1-1-4, Table 1-1-5 and Table 1-2-1, Table 1-2-3, and Table 1-2-4 indicate the glass composition. The method is different, but the same No. The optical glasses of have the same composition. Therefore, Table 1-1-1, Table 1-1-4, Table 1-1-5 and Table 1-2-1, Table 1-2-3 and Table 1-2-4 are substantially the same. Showing optical glass.

Note that in Tables 1-2-1, 1-2-3, and 1-2-4, the glass composition is expressed in cation percentage when the total amount of anion components is O ^2- . That is, in Tables 1-2-1, 1-2-3, and 1-2-4, the content of O ^2- is 100% anion.

In addition, the total content of the glass components listed in Table 1-1-2, Table 1-1-3, and Tables 1-1-6 to 1-1-9, and the ratio between the contents of the glass components are , is a value calculated based on the content of each glass component listed in Table 1-1-1, Table 1-1-4, and Table 1-1-5. Similarly, the total content of glass components listed in Table 1-2-2, Table 1-2-5, and Table 1-2-6 and the ratio between the contents of glass components are as shown in Table 1-2-2. -1, which is a value calculated based on the content of each glass component listed in Tables 1-2-3 and 1-2-4.

The above-mentioned raw materials were put into a platinum crucible, heated to 1200° C. to 1350° C., melted, stirred and clarified, and then the molten glass was poured from the crucible into a mold to form a glass block.

When each of the obtained glass blocks was observed, no foreign matter such as crystals or unmelted raw materials was observed in the glass, and it was possible to obtain highly homogeneous, high-quality optical glass. In addition, optical glass No. 1 to 6 and 12 to 129 are examples of the 1-1 embodiment, and optical glasses No. 1 to 6 and 12 to 129 are examples of the 1-1 embodiment. 1 to 129 are examples of the 1st-2nd embodiment.

The obtained optical glass No. The refractive index nd of 1 to 129, Abbe number νd, glass transition temperature, specific gravity, λ5, and liquidus temperature are shown in Tables 1-3, 1-4-1, and 1-4-2. The refractive index nd, Abbe number νd, glass transition temperature, specific gravity, λ5, and liquidus temperature were measured as follows. Note that blank columns in Table 1-3 indicate that they have not been measured.

(1) Refractive index nd and Abbe number νd
Measurement was performed based on the Japan Optical Glass Industry Association standard JOGIS-01. The measurement results are shown in Table 1-3, Table 1-4-1 and Table 1-4-2.

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

(3) λ5
λ5 was measured as follows. Spectral transmittance in the wavelength range from 280 nm to 700 nm was measured using a glass sample having a thickness of 10 mm and parallel to each other and optically polished planes. The spectral transmittance was calculated by entering a light beam of intensity A perpendicularly into one optically polished plane, measuring the intensity B of the light beam emerging from the other plane, and calculating it by B/A. Therefore, the spectral transmittance also includes reflection loss of light rays at the sample surface. The wavelength at which the spectral transmittance is 5% is λ5. The measurement results are shown in Table 1-3, Table 1-4-1 and Table 1-4-2.

(4) Specific gravity Measured based on the Japan Optical Glass Industry Association standard JOGIS-05. The measurement results are shown in Table 1-3, Table 1-4-1 and Table 1-4-2.

(5) Liquidus temperature LT
A glass sample was placed in a furnace heated to a predetermined temperature and held for 2 hours, and after cooling, the inside of the glass was observed with a 100x optical microscope, and the liquidus temperature was determined from the presence or absence of crystals. The measurement results are shown in Table 1-3, Table 1-4-1 and Table 1-4-2.

(Example 1-2)
Optical glass No. 1 was prepared in the same manner as in Example 1-1. The glass raw materials were heated, melted, clarified, and homogenized so as to obtain 1 to 129, and the resulting molten glass was poured into a mold, rapidly cooled, and formed into a glass block. Next, the glass block was annealed, then cut and ground to produce a glass material for press molding.

(Example 1-3)
Glass materials for press molding made of various optical glasses produced in Example 1-2 were heated and softened, and press molded using a press mold by a known method to produce optical element blanks such as lens blanks and prism blanks. did.

After precision annealing the optical element blank and precisely adjusting the refractive index to the required refractive index, concave lenses, convex lenses, and prisms were produced by known grinding and polishing methods.

When the obtained lens was combined with a low-dispersion glass lens having a large Abbe number νd, chromatic aberration could be favorably corrected and field curvature could be reduced.

Examples 2-1 and 2-2 below are examples corresponding to the 2-1 embodiment, and Examples 2-3 and 2-4 are examples corresponding to the 2-2 embodiment.

Here, in Example 2-1, Table 2-1A shows the glass compositions of glass samples A to D in mass %, and Table 2-1B shows cation %. That is, although the display methods of glass compositions are different between Table 2-1A and Table 2-1B, glasses with the same number have the same composition. Therefore, Tables 2-1A and 2-1B represent substantially the same glass.

Similarly, in Example 2-2, Tables 2-3A-1 to 2-3A-8 are expressed in mass %, and Tables 2-3B-1 to 2-3B-8 are expressed in cation %. Glass compositions from 1 to 109 are displayed. That is, although the display method of glass composition is different between Tables 2-3A-1 to 2-3A-8 and Tables 2-3B-1 to 2-3B-8, glasses with the same number have the same composition. Therefore, Tables 2-3A-1 to 2-3A-8 and Tables 2-3B-1 to 2-3B-8 represent substantially the same glasses.

Note that in Table 2-1B and Tables 2-3B-1 to 2-3B-8, the glass composition is expressed in cation percentage when the total amount of anion components is O ^2- . That is, in Table 2-1B and Tables 2-3B-1 to 2-3B-8, the content of O ^2- is 100% anion.

(Example 2-1)
[Preparation of glass sample]
The raw materials were weighed and mixed so that the composition of the resulting glass would be as shown in Table 2-1A and Table 2-1B, and the resulting blended raw materials (batch raw materials) were put into a platinum crucible and heated at 1300 ~ The glass was melted by heating at 1350° C. for 90 minutes in an air atmosphere, and homogenized and refined by stirring to obtain a molten glass. The molten glass was cast into a mold and formed, slowly cooled, and ground and polished to a size of 17 mm in length, 12 mm in width, and 10 mm in thickness to obtain a glass sample. At this time, the upper and lower surfaces (surfaces measuring 17 mm in length and 12 mm in width) were optically polished.
The obtained glass sample exhibited a reduced color.

[Evaluation of glass sample]
Regarding the obtained glass sample, the glass composition was confirmed, the refractive index ( _nd and _nc ), the Abbe number ( _νd ), the glass transition temperature (Tg), the liquidus temperature (LT), The βOH value was measured, and the holding time at the heat treatment temperature required to sufficiently reduce the reduced color and the transmittance after the heat treatment were measured.

[1] Confirmation of glass composition An appropriate amount _{of the glass sample obtained as described above was taken, treated with acid and alkali, and the content of Li 2 O} was measured by ICP-MS. The content of the components was measured by ICP-AES and confirmed to be consistent with each oxide composition shown in Table 2-1A and Table 2-1B.

[2] Refractive index (n _d and n _c ), Abbe number (ν _d )
The glass sample was held in the air at around the glass transition temperature Tg for 48 hours, then slowly cooled at a cooling rate of 30° C./hour, and then left to cool to reduce coloration. The obtained sample was processed to produce a prism, and the refractive indices n _d , n _F , and n _C were measured based on the refractive index measurement method specified by the Japan Optical Glass Industry Association. Further, the Abbe number ν _d was calculated using each measured value of the refractive index _nd , n _F , and n _C . The results are shown in Table 2-1A.

[3] Glass transition temperature (Tg)
Measurement was performed using a thermomechanical analyzer manufactured by Rigaku Corporation at a temperature increase rate of 10° C./min. The results are shown in Table 2-1A.

[4] Liquidus temperature A 10 cc (10 ml) glass sample was placed in a platinum crucible and melted at 1250°C to 1350°C for 20 to 30 minutes, then cooled to below the glass transition temperature Tg, and the glass was heated to a predetermined temperature in the platinum crucible. It was placed in a melting furnace and held for 2 hours. The holding temperature was set at 1000°C or higher in 10°C increments, and the lowest temperature at which no crystals precipitated after holding for 2 hours was defined as the liquidus temperature. The results are shown in Table 2-1A.

[5] βOH
The glass sample was processed into a 1 mm thick plate whose both sides were optically polished so that they were parallel to each other and flat. Light was incident perpendicularly to the optically polished surface, and the external transmittance C at a wavelength of 2500 nm and the external transmittance D at a wavelength of 2900 nm were measured using a spectrophotometer (UV-3100, manufactured by Shimadzu), and the following results were obtained. βOH was calculated using equation (1).
βOH=-[ln(D/C)]/t...(1)
In the above formula (1), ln is a natural logarithm, and the thickness t corresponds to the distance between the two planes. The results are shown in Table 2-1A.

[6] Holding time at heat treatment temperature The glass sample exhibiting a reduced color was heat treated. That is, in an atmospheric atmosphere, heating is performed at a temperature increase rate of 100°C/hour, heat treatment is performed at a heat treatment temperature 5 to 15°C lower than the glass transition temperature Tg for a predetermined time, and the temperature is reduced to 120°C below the above heat treatment temperature at a temperature decrease rate of 30°C/hour. It was slowly cooled to a low temperature. The heat treatment and slow cooling were repeated until the reduced color of the glass sample was sufficiently reduced. When the reduced color was reduced and the color became uniform, it was evaluated that the reduced color was sufficiently reduced. Table 2-2 shows the total holding time at the heat treatment temperature required to sufficiently reduce the reduced color.

[7] Transmittance after heat treatment The external transmittance of a glass sample whose reduced color was reduced and the color became uniform by heat treatment was measured. Light was incident perpendicularly to the optically polished surface, and the external transmittance at a wavelength of 656 nm was measured using a spectrophotometer (UV-3150, manufactured by Shimadzu). The results are shown in Table 2-2.

(Example 2-2)
[Preparation of glass sample]
Glass samples were produced in the same manner as in Example 2-1, except that the composition of the resulting glass was as shown in Table 3, and the molten glass was obtained by adding water vapor to the melting atmosphere.
The obtained glass sample exhibited a reduced color.

[Evaluation of glass sample]
Regarding the obtained glass sample, the glass composition was confirmed, the refractive index (n _d and n _c ), the Abbe number (ν _d ), the glass transition temperature (Tg), and the liquidus temperature were determined in the same manner as in Example 2-1. The values of (LT) and βOH were measured, and the holding time at the heat treatment temperature required to sufficiently reduce the reduced color and the transmittance after the heat treatment were measured. The results are shown in Tables 2-3A, 2-3B, and 2-4.

(Example 2-3)
[Preparation of reduced glass sample]
The glass samples (samples A to D) obtained in Example 2-1 were remelted by heating at 1300° C. for 90 minutes in an air atmosphere, and homogenized and refined by stirring to obtain molten glass. Molten glass was poured into a mold and molded, and each sample was kept at a holding temperature of 0 to 20°C lower than the glass transition temperature Tg for 15 minutes in an air atmosphere, and the temperature was lowered to 120°C below the above holding temperature at a cooling rate of 30°C/h. It was slowly cooled to a low temperature and ground and polished to a length of 17 mm, width of 12 mm, and thickness of 10 mm to obtain a reduced glass sample. At this time, the upper and lower surfaces (surfaces measuring 17 mm in length and 12 mm in width) were optically polished.
The obtained reduced glass sample exhibited a reduced color.

[Evaluation of reduced glass sample]
The obtained reduced glass sample was heated in an atmospheric atmosphere at a temperature increase rate of 100 °C/hour, heat treated at a heat treatment temperature 5 to 15 °C lower than the glass transition temperature Tg for a predetermined time, and then heated at a temperature decrease rate of 30 °C/hour. A slow cooling treatment was performed to a temperature 120° C. lower than the above heat treatment temperature. The heat treatment and slow cooling treatment were repeated until the difference between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass ( _TA − T _B ) became 5% or less. The external transmittances T _A and T _B were measured using a spectrophotometer (UV-3150, manufactured by Shimadzu) at a wavelength of 656 nm with light incident perpendicularly to the optically polished surface. .

The total holding time and external transmission at the heat treatment temperature required until the difference between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass ( _TA - T _B ) becomes 5% or less. The rates T _A and T _B are shown in Table 2-5.

(Example 2-4)
[Preparation of reduced glass sample]
The glass samples obtained in Example 2-2 (sample Nos. 1 to 20, 22 to 32, 42, 44 to 52, 54, 57 to 80, 88 to 95) were treated in the same manner as in Example 2-3. It was remelted to obtain a reduced glass sample.
The obtained reduced glass sample exhibited a reduced color.

[Evaluation of reduced glass sample]
Regarding the obtained reduced glass sample, the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass was determined by the same method as in Example 2-3. % or less and the external transmittances T _A and T _B were measured. The results are shown in Table 2-6.

Claims (1)

Abbe number ν _d is 18.10 or less,
A phosphate glass containing at least one oxide selected from TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ ,
Remelt and mold for 90 minutes at a temperature 110 to 120°C higher than the liquidus temperature LT in an air atmosphere,
The glass obtained by keeping it at a holding temperature 0 to 20°C lower than the glass transition temperature Tg for 15 minutes in an air atmosphere and slowly cooling it at a cooling rate of 30°C/h to a temperature 120°C lower than the holding temperature, 17 mm long, For those processed to 13 mm in width and 10 mm in thickness,
When viewed from above, a portion within a distance of 0 to 5 mm from the end in the vertical direction and a distance of 0 to 5 mm from the end in the horizontal direction is defined as the glass end;
When the center of the glass is defined as a portion that is 6 to 11 mm from the vertical edge and 4 to 9 mm from the horizontal edge when viewed from above,
When light is incident parallel to the thickness direction, the external transmittance T _A of the edge of the glass and the external transmittance T _B of the center of the glass at a wavelength of 656 nm are greater than or equal to the value T ₁ calculated by the following formula (2). ,and,
Until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less,
Heat treatment in the air at a temperature increase rate of 100 °C/h and holding at a heat treatment temperature 5 to 15 °C lower than the glass transition temperature Tg, and a temperature decrease rate of 30 °C/h to a temperature 120 °C lower than the heat treatment temperature. When repeating the slow cooling process once or multiple times,
A glass whose total holding time at the heat treatment temperature in the heat treatment is 48 hours or less.
T ₁ =0.83×[1-[(n _C -1)/(n _C +1)] ² ] ² ×98 ... (2)
[In formula (2), n _C is the heat treatment performed until the difference (T _A - T _B ) between the external transmittance T _A at the edge of the glass and the external transmittance T _B at the center of the glass becomes 5% or less. and the refractive index at a wavelength of 656.27 nm when subjected to slow cooling treatment. ]