TWI707834B - Phosphate optical glass, glass materials for pressing and optical components - Google Patents

Abstract

The present invention provides a phosphate optical glass which is excellent in transmittance and suppresses the increase in refractive index with high dispersion. In addition, optical elements and optical glass materials formed of such phosphate optical glass are provided. A phosphate optical glass with Abbe number (νd) below 16.70 and refractive index (nd) below 2.1000, containing P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ , the content of TiO _{2 and} the content of Nb ₂ O ₅ The mass ratio [TiO ₂ /Nb ₂ O ₅ ] is 0.15 or more.

Description

Phosphate optical glass, glass materials for pressing and optical components

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

A lens made of high-dispersion glass is combined with a lens made of low-dispersion glass to form a pair of lenses to correct chromatic aberrations. High-dispersion glass usually has a high refractive index, and low-dispersion glass usually has a low refractive index. Therefore, if the two are combined to form a pair lens, there is a problem that the curvature of field is strongly expressed due to the large difference in refractive index.

For example, Patent Document 1 discloses a high-dispersion glass having a low Abbe number (νd). However, the refractive index is too high, which causes a problem of curvature of field when used for the aforementioned pair of lenses.

[Prior Technical Literature]

[Patent Literature]

Patent Document 1: JP 2013-212935 A.

The present invention has been completed in view of such actual circumstances, and its object is to provide a phosphoric acid with excellent transmittance and high dispersion that suppresses the increase in refractive index. Salt optical glass. Furthermore, an object of the present invention is to provide an optical element and an optical glass material formed of such a phosphate optical glass.

The inventors of the present invention have repeatedly studied in order to achieve the above-mentioned object. As a result, they have found that the object can be achieved by adjusting the content ratios of various glass components (hereinafter referred to as glass components) constituting the glass. Based on this knowledge, the present invention has been completed. invention.

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

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

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

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

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

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

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

According to the present invention, since the difference in Abbe number is large when combined with a low-dispersion glass lens to form a pair of lenses, it has a high effect in correcting chromatic aberrations. In addition, even when it is combined with a low-dispersion glass lens with a low refractive index to form a pair of lenses, since the difference in refractive index is small, curvature of field can be suppressed.

Hereinafter, a mode for implementing the present invention (hereinafter simply referred to as "embodiment") will be described in detail. The following embodiment is an example for explaining the present invention, and its purpose is not to limit the present invention to the following content. The present invention can be suitably modified and implemented within the scope of its gist. Furthermore, the description of the repeated description may be omitted as appropriate, but it does not limit the spirit of the invention. It should be noted that, in this specification, "optical glass" is a glass composition containing a plurality of glass constituents (glass components), and unless otherwise specified, it is used as a shape (block, plate, spherical, etc.), use ( Materials for optical elements, optical elements, etc.), and general terms irrelevant to size are used. That is, the shape, use, and size of the optical glass are not limited, and optical glass of any shape, optical glass of any other purpose, and optical glass of any size are included in the optical glass of the present invention. In addition, in this specification, optical glass may be simply referred to as "glass".

In addition, in this manual, (numerical value 1) is sometimes used with "(numerical value 1) The numerical range is expressed in the form of "below". The range expressed in this way is the numerical range less than (numerical value 1) plus the numerical range of (numerical value 1). The numerical range represented by "less than (numerical value 1)" is less than (numerical value The numerical range of 1) does not include (numerical value 1). Sometimes (numerical value 2) is used to express the numerical range as "(numerical value 2) or more". The range expressed in this way is the numerical range greater than (numerical value 2) plus The numerical range of (numerical value 2). Sometimes the numerical range is expressed as "exceeding (numerical value 2)". The range expressed in this way is a numerical range greater than (numerical value 2), not including (numerical value 2).

In the first embodiment and the second embodiment, the optical glass according to the present invention will be described mainly based on the content of each glass component expressed in mass %. Hereinafter, unless otherwise specified, "%" means mass%. In addition, some glass components are also recorded as the content expressed in cationic %.

In this specification, the term "expressed in mass%" means that for each glass component expressed in oxides and fluorides, the content of each glass component is expressed in mass percentage when the total content of all glass components is 100% by mass To represent. In addition, the so-called total content expressed in mass% refers to the total amount of the content of a plurality of glass components (including the case where the content is 0%). In addition, the mass ratio refers to the ratio (ratio) of the contents of the glass components (including the total contents of a plurality of components) expressed in mass %.

In addition, in this specification, the term "expressing in cationic %" means the molar percentage when the total content of all cationic components is set to 100%. The total content expressed in cationic% refers to the total amount of the content of a plurality of cationic components (including the case where the content is 0%). In addition, the "cation ratio" refers to the ratio (ratio) of the contents of the cation components (including the total contents of a plurality of cation components) when expressed in cation %.

It should be noted that the valence of the cation component (for example, the valence of P ⁵⁺ is +5, the valence of Si ⁴⁺ is +4, and the valence of La ³⁺ is +3) are the values determined according to conventional methods, and the When P, Si, and La as glass components are expressed on a physical basis, it is the same as expressing 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 cationic component. In addition, the valence of the anion component (for example, the valence of O ^2- is -2) is also a value conventionally determined, and the oxide-based glass component as described above is expressed as, for example, P ₂ O ₅ , SiO ₂ , La ₂ O ₃ is the same. Therefore, it is not necessary to analyze the valence of the anion component when analyzing the glass composition.

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

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

The first embodiment

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

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

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

By setting the Abbe number (νd) to 16.70 or less, when it is combined with a low-dispersion glass lens to form a pair lens, the difference in Abbe number becomes large, and a high effect is achieved in the correction of chromatic aberration.

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

By setting the refractive index (nd) to 2.1000 or less, even when it is combined with a low-dispersion glass lens with a low refractive index to form a pair lens, the curvature of field can be suppressed due to the difference in refractive index.

The optical glass according to the first embodiment contains P ₂ O ₅ , TiO _2, and Nb ₂ O ₅ . By including P ₂ O ₅ , TiO _2, and Nb ₂ O ₅ , it is possible to obtain an optical glass that suppresses the increase in refractive index (nd) with high dispersion.

In the optical glass according to the first embodiment, the mass ratio [TiO ₂ /Nb ₂ O ₅ ] of the content of TiO _{2 to} the content of Nb ₂ O ₅ is 0.15 or more. As described above, the optical glass according to the first embodiment contains P ₂ O ₅ and TiO ₂ , but the increase in P ₂ O ₅ and TiO ₂ causes problems in that the solubility of the glass decreases and the liquidus temperature rises. Therefore, Nb ₂ O ₅ , which contributes to high dispersion, is contained in a specific ratio with respect to TiO ₂ to prevent an increase in the liquidus temperature and eliminate this problem.

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

In addition, in the optical glass according to the first embodiment, when the content of the glass component is expressed in cationic %, the upper limit of the cationic ratio [Ti ⁴⁺ /Nb ⁵⁺ ] of the Ti ⁴⁺ content to the Nb ⁵⁺ content Preferably, it is 6.00, and is more preferably 5.90, 5.80, 5.70, 5.65, 5.60 in order. The lower limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42 in order.

Ti ⁴⁺ tends to decrease the solubility of glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ suppresses the decrease in liquidus temperature and the increase in refractive index, and contributes to high dispersion. Therefore, by containing Nb ⁵⁺ in a certain ratio with respect to Ti ⁴⁺ , 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 cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably set to the above range.

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

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

P ₂ O ₅ is a component necessary to suppress the increase in refractive index (nd) and to contain a large amount of high-dispersion components in the glass. On the other hand, if P ₂ O ₅ is contained excessively, the solubility will deteriorate. Therefore, in the optical glass according to this embodiment, it is preferable to set the content of P ₂ O ₅ in the above-mentioned range.

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

P ⁵⁺ is a component necessary to suppress the increase in refractive index (nd) and to contain a large amount of high-dispersion components in the glass. On the other hand, if P ⁵⁺ is contained excessively, the solubility will deteriorate. Therefore, in the optical glass according to this embodiment, it is preferable to set the content of P ⁵⁺ in the aforementioned range.

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

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

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

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

In the optical glass according to the first embodiment, the lower limit of the mass ratio of the total content of TiO ₂ and WO _{3 to} the content of Nb ₂ O ₅ [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 0.15 , And 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, 0.64, 0.65. In addition, the upper limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 8.00, and more preferably 7.90, 7.80, 7.70, 7.60, 7.40, 7.20, and 7.00 in order.

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

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

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

In the optical glass according to the first embodiment, the mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ and WO _{3 to} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [(TiO The lower limit of ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] is preferably 0.45, and more preferably 0.50, 0.55, 0.60, 0.65, 0.70. , 0.75, 0.80, 0.85. In addition, 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 mass ratio [(TiO ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ + WO ₃ +Bi ₂ O ₃ )] within the above range, the change in transmittance can be suppressed. Poor, and suppress the increase in refractive index and specific gravity.

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

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

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

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to the first embodiment, W ⁶⁺ as a high-dispersion component relative to the content of Ba ²⁺ is contained so as to have the above-mentioned cation ratio, so that the desired high-dispersibility can be maintained.

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

In the case where the content of W ⁶⁺ is 0 cationic% and the content of Ba ²⁺ exceeds 0 cationic %, Ti ⁴⁺ , which is second only to W ⁶⁺ in the high-dispersion components, contributes to high-dispersion, and has improved By setting the total content of Bi ³⁺ as a function of thermal stability in the above range, it is possible to suppress low dispersion due to Ba ²⁺ .

(Glass composition)

The optical glass according to the above-mentioned first embodiment can contain the following glass components.

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

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

B ₂ O ₃ is a network-forming component of glass, and has functions of improving the meltability of glass and suppressing the increase in refractive index. On the other hand, if the content of B ₂ O ₃ is high, the decrease in Abbe number is suppressed, high dispersion is prevented, and chemical durability tends to decrease. Therefore, from the viewpoint of suppressing the increase in the refractive index and improving the thermal stability, meltability, and moldability of the glass, the upper limit of the content of B ₂ O ₃ is preferably the above range. On the other hand, from the viewpoint of obtaining a desired Abbe number and maintaining good chemical durability, the lower limit of the content of B ₂ O ₃ is preferably the above range.

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

SiO ₂ is a network forming component of glass, which has the functions of improving the thermal stability, chemical durability and weather resistance of glass, increasing the viscosity of molten glass, and facilitating molding of molten glass. On the other hand, if the content of SiO ₂ is large, the meltability and low-temperature softening properties of the glass will decrease, and the glass raw material will tend to remain molten. Therefore, the upper limit of the content of SiO ₂ is preferably in the above-mentioned range from the viewpoint of improving the meltability and low-temperature softening properties of the glass.

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

Al ₂ O ₃ is a glass component that has the effect of suppressing the increase in refractive index and 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, problems such as a decrease in the thermal stability of the glass, an increase in the glass transition temperature (Tg), and a decrease in meltability are likely to occur. From the viewpoint of avoiding such problems, the upper limit of the content of Al ₂ O ₃ is preferably the above range.

In the optical glass according to the present embodiment, the total content of P ₂ O ₅ , B ₂ O ₃ , SiO ₂ and Al ₂ O ₃ as the network forming components of the glass [P ₂ O ₅ +B ₂ O ₃ +SiO The upper limit of ₂ +Al ₂ O ₃ ] is preferably 45.0%, and more preferably 43.0%, 41.0%, 39.0%, 37.0%, 35.0%, 33.0% in order. In addition, 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% in order , 15.0%.

By setting the upper limit of the total content [P ₂ O ₅ +B ₂ O ₃ +SiO ₂ +Al ₂ O ₃ ] to the above range, the refractive index can be easily maintained in 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 ] to the above range, the thermal stability of the glass can be easily improved and the devitrification of the glass can be further suppressed ( Devitrification).

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

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

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

Compared with Nb ₂ O ₅ and Bi ₂ O ₃ , TiO ₂ suppresses the increase in refractive index and greatly contributes to high dispersion. On the other hand, TiO ₂ is easier to increase the coloring of glass. In addition, TiO ₂ promotes the formation of crystals in the glass during the process of molding and gradual cooling of molten glass to obtain optical glass, and reduces the transparency of the glass (white turbidity). Therefore, in the optical glass according to this embodiment, the content of TiO ₂ is preferably within the above-mentioned range.

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

Compared with Nb ⁵⁺ and Bi ³⁺ , Ti ⁴⁺ suppresses the increase in refractive index and greatly contributes to high dispersion. On the other hand, Ti ⁴⁺ is easier to increase the coloring of the glass. In addition, Ti ⁴⁺ promotes the formation of crystals in the glass during the process of molding and slow cooling of the molten glass to obtain the optical glass, and reduces the transparency of the glass (white turbidity). Therefore, in the optical glass according to this embodiment, the content of Ti ⁴⁺ is preferably within the above-mentioned range.

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

In the optical glass according to the present embodiment, since TiO _{2 is} contained, there is a problem of promoting crystal formation in the glass and lowering the transparency of the glass (white turbidity). This problem can be solved by containing P ₂ O ₅ as a network forming component with respect to TiO ₂ in a ratio within the above-mentioned range.

In addition, in the optical glass according to this embodiment, when the content of the glass component is expressed in cation %, the upper limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] of the Ti ⁴⁺ content to the P ⁵⁺ content is preferable It is 1.50, and more preferably 1.40, 1.30, 1.29, 1.28, 1.27, 1.26, 1.25, 1.24, 1.23, 1.22 in order. The lower limit of the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] is preferably 0.50, and more preferably 0.51, 0.52, 0.53 in order.

In the optical glass according to the present embodiment, Ti ^{4+ is} contained, so there is a problem of promoting crystal formation in the glass and lowering the transparency of the glass (white turbidity). This problem can be eliminated by containing P ⁵⁺ as a network forming component with respect to Ti ⁴⁺ in the above-mentioned range.

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

Nb ₂ O ₅ is a component that contributes to high dispersion. Moreover, it is also a glass component that improves the thermal stability and chemical durability of glass. On the other hand, if the content of Nb ₂ O ₅ becomes too large, the thermal stability of the glass decreases and the coloring of the glass tends to increase. Therefore, in the optical glass according to this embodiment, the content of Nb ₂ O ₅ is preferably within the above-mentioned range.

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

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

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

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

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

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

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

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

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

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

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

Li ₂ O plays a role of suppressing the increase in refractive index and improving the meltability of glass. Therefore, from the viewpoint of maintaining required optical properties and ensuring meltability, the content of Li ₂ O is preferably within the above-mentioned range.

In the optical glass according to this embodiment, the upper limit of the Na ₂ O content is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, 3.5%, and 3.0% in this order. In addition, 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 this embodiment, the upper limit of the K ₂ O content is preferably 12.0%, and more preferably 11.0%, 10.0%, 9.0%, 8.5%, and 8.0% in this order. In addition, in order to maintain the thermal stability of the glass well and suppress the rise in the liquidus temperature, the lower limit of the content of K ₂ O is preferably 0.1%, and more preferably 0.3%, 0.5%, 1.0%, 1.5%. , 2.0%, 2.5%. The content of K ₂ O may be 0%.

Both Na ₂ O and K ₂ O have the effects of suppressing the increase in refractive index and improving the meltability of the glass, but when their content increases, the thermal stability, chemical durability, and weather resistance of the glass will decrease. Therefore, each content of Na ₂ O and K ₂ O is preferably set to the aforementioned range.

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

Li ₂ O, Na ₂ O, and K ₂ O all have the effect of suppressing the increase in refractive index and improving the meltability of glass. But when their content increases, the thermal stability, chemical durability, and weather resistance of the glass will 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 aforementioned range.

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

In the optical glass according to the present embodiment, the upper limit of the content of Cs ₂ O is preferably 6.0%, and more preferably 5.0%, 4.5%, 4.0%, and 3.5% in this order. In addition, 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 effect of suppressing the increase in refractive index and improving the meltability of the glass, but when their content increases, the thermal stability, chemical durability, and weather resistance of the glass will decrease. Therefore, each content of Rb ₂ O and Cs ₂ O is preferably set to the aforementioned range.

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

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

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

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

MgO, CaO, SrO, and BaO are all glass components that have the effect of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, the high dispersion will be impaired, and the thermal stability of the glass will decrease. Low, glass is prone to devitrification. Therefore, each content of these glass components is each preferably in the above-mentioned range.

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

Mg ²⁺ , Ca ²⁺ , Sr ²⁺ , and Ba ²⁺ are all glass components that have an effect of improving the thermal stability and meltability of glass. However, when the content of these glass components increases, the high dispersion property is impaired, and the thermal stability of the glass decreases, and the glass tends to devitrify. Therefore, each content of these glass components is each preferably in the above-mentioned range.

In the optical glass of this 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] Preferably it is 10.0%, and more preferably is 9.0%, 8.0%, 7.0%, 6.0%, 5.5%, 5.0% in order. In addition, the lower limit of the total content [MgO+CaO+SrO+BaO] is preferably 0%. The total content [MgO+CaO+SrO+BaO] can be 0%.

In the optical glass according to this embodiment, the upper limit of the content of ZnO is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0% in this order. In addition, the lower limit of the content of ZnO is preferably 0%. The content of ZnO can be 0%.

ZnO is a glass component that has a function of promoting the melting of the raw material of the glass (that is, a function of improving the meltability) when the glass is melted. In addition, ZnO has a stronger effect on improving the thermal stability of glass and lowering the liquidus temperature than 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 content of ZnO is preferably the above range. In addition, from the viewpoint of suppressing the low dispersion of the glass, the upper limit of the content of ZnO is preferably within the above range.

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

ZrO ₂ is a glass component that has a function of improving the thermal stability of glass. However, when the content of ZrO ₂ is too large, the refractive index increases and the thermal stability of the glass tends to decrease. In addition, the glass raw material becomes easy to melt and remain. Therefore, the upper limit of the content of ZrO ₂ is preferably in the above-mentioned range from the viewpoint of maintaining the meltability and thermal stability of the glass well and achieving the required optical properties. On the other hand, from the viewpoint of achieving required optical properties and improving the thermal stability of the glass, the lower limit of the content of ZrO ₂ is preferably the above range.

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

Ta ₂ O ₅ is a glass component having an effect of improving the thermal stability of glass. On the other hand, Ta ₂ O ₅ increases the refractive index and lowers the dispersion of the glass. In addition, Ta ₂ O ₅ is an extremely expensive component compared to other glass components. If the content of Ta ₂ O ₅ increases, the production cost of the glass increases. Furthermore, Ta ₂ O ₅ has a higher molecular weight than other glass components, and therefore increases the specific gravity of the glass. As a result, the weight of the glass optical element increases. In addition, when the content of Ta ₂ O ₅ increases, the meltability of the glass is lowered, and melting residue of the glass raw material is likely to occur when the glass is melted. Therefore, the content of Ta ₂ O ₅ is preferably within the above range.

In the optical glass according to this embodiment, the upper limit of the Ga ₂ O ₃ content is preferably 4.0%, and more preferably 3.5%, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5%. , 0.1%. In addition, 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 this embodiment, the upper limit of the content of In ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, and 3.0% in this order. In addition, the lower limit of the content of In ₂ O ₃ is preferably 0%. The content of In ₂ O ₃ may be 0%.

In the optical glass according to the present embodiment, the upper limit of the content of Sc ₂ O ₃ is preferably 5.0%, and more preferably 4.0%, 3.0%, 2.0%, and 1.0% in this order. In addition, 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 this embodiment, the upper limit of the content of HfO ₂ is preferably 8.0%, and more preferably 7.0%, 6.5%, 6.0%, 5.5%, 5.0%, 4.5%, 4.0%, 3.5 %, 3.0%, 2.5%, 2.0%, 1.5%, 1.0%, 0.5%, 0.1%. In addition, the lower limit of the content of HfO ₂ is preferably 0%. The content of HfO ₂ may be 0%.

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

In the optical glass according to this embodiment, the upper limit of the content of Lu ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, and 3.0% in this order. In addition, 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 effect of increasing the refractive index (nd). And because of its high molecular weight, it is also a glass component that increases the specific gravity of glass. Accordingly, it is preferable that the content of Lu ₂ O ₃ is decreased, the content of Lu ₂ O ₃ is preferably in the above range.

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

GeO ₂ has the effect of increasing the refractive index (nd), and is a component that stands out as a high-priced 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 this embodiment, the upper limit of the content of La ₂ O ₃ is preferably 5.0%, and more preferably 4.5%, 4.0%, 3.5%, 3.0%, 2.5%, 2.0%, 1.5%. , 1.0%, 0.5%. In addition, 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 tends to lose clarity during manufacturing. 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-mentioned range.

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

When the content of Gd ₂ O ₃ is too large, the thermal stability of the glass is reduced, and the glass is likely to lose clarity during manufacturing. In addition, when the content of Gd ₂ O ₃ is excessively increased, the specific gravity of the glass increases, which is not preferable. Therefore, from the viewpoint of maintaining the thermal stability of the glass well and suppressing an increase in specific gravity, the content of Gd ₂ O ₃ is preferably within the above-mentioned range.

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

When the content of Y ₂ O ₃ is too large, the thermal stability of the glass is reduced, and the glass is likely to lose clarity during manufacturing. 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-mentioned range.

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

Yb ₂ O ₃ has a higher molecular weight than La ₂ O ₃ , Gd ₂ O ₃ , and Y ₂ O ₃ and therefore increases the specific gravity of the glass. When the specific gravity of the glass increases, the quality of the optical element increases. For example, if a high-quality lens is assembled into an auto-focus type photographic lens, the power required to drive the lens during auto-focusing will increase, and battery consumption will increase. Therefore, it is desirable to reduce the content of Yb ₂ O ₃ to suppress an increase in the specific gravity of the glass.

In addition, when the content of Yb ₂ O ₃ is too large, the thermal stability of the glass decreases, and the glass tends to devitrify during production. From the viewpoints 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-mentioned range.

The optical glass involved in this embodiment preferably mainly consists of 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 , the total content of the above glass components is preferably more than 95 %, more preferably more than 98%, further preferably more than 99%, still further preferably more than 99.5%.

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

TeO ₂ is a component that increases the refractive index (nd), and because it 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 this embodiment, the anion component (that is, the anion component) is mainly oxygen ions, and as other anions, halogen ions such as chloride ions, iodide ions, and bromide ions can be contained in a small amount.

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

That is, in the optical glass according to this embodiment, the content of oxides in all glass components is preferably more than 95% by mass. Furthermore, the lower limit of the content of oxides in all glass components is more preferably 97% by mass and 99% by mass in this order. %, 99.5% by mass, 99.9% by mass, 99.95% by mass, and 99.99% by mass, and the content of oxides in all glass components may be 100% by mass. The glass in which the oxide content in all glass components is 100% by mass does not substantially contain halide.

In addition, in the optical glass according to this embodiment, the upper limit of the content of halogen ions is preferably 4 anion%, and more preferably 3 anion%, 2 anion%, 1 anion%, and 0.5 anion% in this order. The content of halide ions can be 0 anion%. The term "anion %" is the molar percentage when the total content of all anion components contained in the glass is 100%.

It should be noted that the optical glass according to the present embodiment is preferably basically composed of the above-mentioned glass components, but may contain other components within a range that does not hinder the effects of the present invention. In addition, in the present invention, the inclusion of unavoidable impurities is not excluded.

<Other ingredients composition>

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

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

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

Sb (Sb ₂ O ₃ ), Sn (SnO ₂ ), and Ce (CeO ₂ ) are elements that can be optionally added that function as a fining agent. Among them, Sb (Sb ₂ O ₃ ) is a clarifying agent with a large clarifying effect. However, Sb (Sb ₂ O ₃ ) is highly oxidizing. If the amount of Sb (Sb ₂ O ₃ ) added is increased, light absorption by Sb ions will increase the coloration of the glass, which is not preferable. In addition, if Sb is present in the melt when the glass is melted, the platinum constituting the glass melting crucible is promoted to dissolve into the melt, and the platinum concentration in the glass increases. If platinum exists as an ion in the glass, the coloration of the glass increases due to the absorption of light. In addition, if platinum is present as a solid substance in the glass, it becomes a scattering source of light and degrades the quality of the glass. Sn(SnO ₂ ) and Ce(CeO ₂ ) have a smaller clarifying effect than Sb(Sb ₂ O ₃ ). When Sn(SnO ₂ ) and Ce(CeO ₂ ) are added in large amounts, the coloring of the glass will be enhanced. Therefore, in the case of adding a clarifying agent, it is better to pay attention to the addition amount while adding Sb (Sb ₂ O ₃ ).

The content of Sb ₂ O ₃ is expressed in an additive manner. That is, the range of the content of Sb ₂ O ₃ when the total content of all glass components other than Sb ₂ O ₃ , SnO ₂ and CeO ₂ is 100% by mass is preferably less than 1% by mass, more preferably less than 0.5 The mass% is more preferably less than 0.1 mass %. The content of Sb ₂ O ₃ may be 0% by mass.

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

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

When the upper limit of the glass transition temperature (Tg) satisfies the above range, the increase in the annealing temperature of the glass can be suppressed, and the annealing equipment such as the continuous annealing furnace called "lehr" and the batch annealing furnace can be reduced. damage.

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

<Light Transmittance of Glass>

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

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

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

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

By using an optical glass whose wavelength is shortened to λ5, it is possible to provide an optical element that can reproduce colors ideally.

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

<Specific gravity of glass>

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

<Liquid temperature>

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

(Manufacture of optical glass)

The optical glass according to the embodiment of the present invention may be prepared by blending glass raw materials so as to have the aforementioned predetermined composition and using the blended glass raw materials according to a known glass manufacturing method. For example, a variety of compounds are blended and thoroughly mixed to prepare batch materials, and the batch materials are put into a quartz crucible or a platinum crucible for rough melt. The melt obtained by rough melting is quenched and pulverized to produce cullet. Furthermore, the cullet was put into a platinum crucible, heated and remelted (remelt) to prepare a molten glass, and after further clarification and homogenization, the molten glass was molded and slowly cooled to obtain an optical glass. The molding and slow cooling of the molten glass may be performed by applying a known method.

It should be noted that as long as the desired glass component can be introduced into the glass at the desired content, the compound used when preparing the batch material is not particularly limited. Examples of such a compound include oxides, Phosphoric acid, metaphosphate, phosphorus pentoxide, carbonate, nitrate, hydroxide, fluoride, etc.

(Manufacture of optical components, etc.)

To produce an optical element using the optical glass according to the embodiment of the present invention, it is only necessary to apply a known method. For example, the glass raw material is melted into molten glass, and the molten glass is poured into a mold and molded into a plate shape to produce a glass material formed of the optical glass according to the present invention. The obtained glass material is appropriately cut, ground, and polished to produce a glass material for press molding of a size and shape suitable for press molding. The glass material for press molding is heated and softened, and press-molded by a known method to produce an optical element blank having a shape similar to the optical element. The optical element blank is annealed, ground and polished by a well-known method to make the light Learn components.

The optical function surface of the produced optical element can be coated with an anti-reflection film, a total reflection film, etc. according to the purpose of use.

As an optical element, various lenses, such as a spherical lens, a prism, a diffraction grating, etc. can be illustrated.

Second embodiment

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

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

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

By setting the Abbe number (νd) to 16.70 or less, when it is combined with a low-dispersion glass lens to form a pair lens, the difference in Abbe number becomes large, and a high effect is achieved in the correction of chromatic aberration.

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

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

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

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

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

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

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

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

The optical glass according to the second embodiment is a phosphate optical glass. The so-called phosphate optical glass refers to an optical glass mainly containing phosphate as a glass network forming component. Therefore, the optical glass according to the second embodiment contains phosphate as a network forming component, and the content thereof is expressed as the content of P ₂ O ₅ . As a network forming component of glass, P ₂ O ₅ , Al ₂ O ₃ , B ₂ O ₃ , SiO ₂ and the like are known. Here, the so-called glass mainly containing phosphate as a network forming component means that the content of P ₂ O ₅ expressed by mass% is greater than the content of any one of Al ₂ O ₃ , B ₂ O ₃ , and SiO ₂ .

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

P ₂ O ₅ is a component necessary for the glass to contain a large amount of high dispersion components. On the other hand, if P ₂ O ₅ is contained excessively, the meltability will deteriorate. Therefore, in the glass according to this embodiment, it is preferable to set the content of P ₂ O ₅ in the above-mentioned range.

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

P ⁵⁺ is a component necessary to suppress the increase in refractive index (nd) and to contain a large amount of high-dispersion components in the glass. On the other hand, if P ⁵⁺ is contained excessively, the solubility will deteriorate. Therefore, in the optical glass according to this embodiment, it is preferable to set the content of P ⁵⁺ in the aforementioned range.

In the optical glass according to the second embodiment, the mass ratio of the total content of TiO ₂ , Nb ₂ O ₅ and WO _{3 to} the total content of TiO ₂ , Nb ₂ O ₅ , WO ₃ and Bi ₂ O ₃ [(TiO The lower limit of ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] is preferably 0.45, and more preferably 0.50, 0.55, 0.60, 0.65, 0.70. , 0.75, 0.80, 0.85. In addition, 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 mass ratio [(TiO ₂ +Nb ₂ O ₅ +WO ₃ )/(TiO ₂ +Nb ₂ O ₅ +WO ₃ +Bi ₂ O ₃ )] within the above range, it is possible to suppress deterioration in transmittance , And suppress the increase in refractive index.

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

TiO ₂ tends to decrease the solubility of glass and increase the liquidus temperature. On the other hand, Nb ₂ O ₅ suppresses the decrease in liquidus temperature and the increase in refractive index, and contributes to high dispersion. Therefore, by containing Nb ₂ O ₅ at a certain 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 set to the above range.

In addition, in the optical glass according to the second embodiment, when the content of the glass component is expressed in cation %, the upper limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] of the Ti ⁴⁺ content to the Nb ⁵⁺ content Preferably, it is 6.00, and is more preferably 5.90, 5.80, 5.70, 5.65, 5.60 in order. The lower limit of the cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably 0.40, and more preferably 0.41 and 0.42 in order.

Ti ⁴⁺ tends to decrease the solubility of glass and increase the liquidus temperature. On the other hand, Nb ⁵⁺ suppresses the decrease in liquidus temperature and the increase in refractive index, and contributes to high dispersion. Therefore, by containing Nb ⁵⁺ in a certain ratio with respect to Ti ⁴⁺ , 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 cation ratio [Ti ⁴⁺ /Nb ⁵⁺ ] is preferably set to the above range.

In the optical glass according to the second embodiment, the lower limit of the mass ratio of the total content of TiO ₂ and WO _{3 to} the content of Nb ₂ O ₅ [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 0.15, Further 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, 0.64 , 0.65. In addition, the upper limit of the mass ratio [(TiO ₂ +WO ₃ )/Nb ₂ O ₅ ] is preferably 8.00, and more preferably 7.90, 7.80, 7.70, 7.60, 7.40, 7.20, and 7.00 in order.

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

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

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

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

Ba ²⁺ is a component that contributes to low dispersion. Therefore, in the optical glass according to the second embodiment, W ⁶⁺ as a high-dispersion component relative to the content of Ba ²⁺ is contained so as to have the above-mentioned cation ratio, so that the desired high-dispersibility can be maintained.

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

When the content of W ⁶⁺ is 0 cationic% and the content of Ba ²⁺ exceeds 0 cationic %, Ti ⁴⁺ , which is second only to W ⁶⁺ in the high-dispersion components, contributes to high-dispersion and has improved The total content of Bi ³⁺ , which acts as a thermal stability, is within the above-mentioned range, so that it is possible to suppress the low dispersion caused by Ba ²⁺ .

In the optical glass according to the second embodiment, the upper limit of the refractive index (nd) is preferably 2.1500, and more preferably 2.1300, 2.1100, 2.1000, 2.0900, 2.0700, 2.0500, 2.0300, 2.0140, 2.0000 in order. In addition, the lower limit of the refractive index (nd) is preferably 1.8800, and the smaller the value in the order of 1.9000, 1.9200, 1.9400, and 1.9600, the better.

By setting the refractive index (nd) in the above range, even when it is combined with a low-dispersion glass lens with a low refractive index to form a pair of lenses, the curvature of field can be suppressed due to the difference in refractive index.

The composition of glass components other than the above in the second embodiment can be the same as in the first embodiment. In addition, the glass characteristics, the manufacture of optical glass, the manufacture of optical elements, etc. in the second embodiment can also be the same as those in the first embodiment.

Example

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

(Example 1)

Weigh and each component so that it becomes a glass with the composition of numbers 1 to 129 shown in Table 1-1, Table 1-4, and Table 1-5, Table 2-1, Table 2-3, and Table 2-4 The corresponding compound raw materials, namely phosphates, carbonates, oxides and other raw materials, are fully mixed to make the preparation raw materials.

Here, Table 1-1, Table 1-4, and Table 1-5 are expressed in mass %, and Table 2-1, Table 2-3, and Table 2-4 are expressed in cation% to show the glass compositions numbered 1 to 129. That is, although Table 1-1, Table 1-4, and Table 1-5 are different from Table 2-1, Table 2-3, and Table 2-4, although the glass composition representation method is different, the optical glass with the same number has the same composition . Therefore, Table 1-1, Table 1-4, Table 1-5 and Table 2-1, Table 2-3, and Table 2-4 substantially represent the same optical glass.

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

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

Put the above blended raw materials into a platinum crucible and heat to 1200 ℃~1350℃, after melting, stirring, and clarification, the molten glass is poured from the crucible into the mold and formed into a glass block.

Observation of the obtained glass blocks revealed that no impurities such as crystals and molten residues of raw materials were seen in the glass, and high-homogeneity and high-quality optical glass could be obtained. In addition, optical glass numbers 1 to 6, 12 to 129 are examples of the first embodiment, and optical glass numbers 1 to 129 are examples of the second embodiment.

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

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

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

(2) Glass transition temperature (Tg)

The glass transition temperature is measured based on the endothermic curve when the glass in a solid state is heated up with a differential scanning calorimeter DSC8270. The glass transition temperature (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 3, Table 4-1, and Table 4-2.

(3) Wavelength (λ5)

λ5 is measured in the following way. Using a 10 mm thick glass sample having planes that are parallel to each other and optically polished, the spectral transmittance in the wavelength range from 280 nm to 700 nm is measured. For the spectral transmittance, the light of intensity A is incident perpendicular to a plane that has been optically polished, and the light emitted from another plane is measured. The intensity B of the output light is calculated by B/A. Therefore, the spectral transmittance also includes the reflection loss of light on the sample surface. The wavelength at which the spectral transmittance is 5% is λ5. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(4) Specific gravity

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

(5) Liquidus temperature (LT)

Put the glass sample into a furnace heated to a predetermined temperature and keep it for 2 hours. After cooling, observe the inside of the glass with a 100-fold optical microscope, and determine the liquidus temperature based on the presence or absence of crystals. The measurement results are shown in Table 3, Table 4-1, and Table 4-2.

(Example 2)

In the same manner as in Example 1, the optical glass numbers 1 to 129 were obtained. The glass raw materials were heated, melted, clarified, and homogenized, and the obtained molten glass was poured into a mold to be quenched and molded into a glass block. Next, after annealing the glass block, cutting and grinding are performed to produce a glass material for press molding.

(Example 3)

The press-forming glass material made of various optical glasses produced in Example 2 was heated and softened, and press-molded by a known method using a press-forming mold to produce optical element blanks such as lens blanks and prism blanks.

After the optical element blank is precisely annealed, the refractive index is precisely adjusted to the required refractive index, and then concave lenses, convex lenses, and prisms are made by well-known grinding and polishing methods.

The resultant lens is combined with a low-dispersion glass lens with a large Abbe number (νd). As a result, chromatic aberration can be corrected well and curvature of field can be reduced.

Claims (10)

A phosphate optical glass, comprising: Abbe number (νd) of 16.70 or less; refractive index (nd) of 2.1000 or less; containing P ₂ O ₅ , TiO ₂ and Nb ₂ O ₅ ; and TiO ₂ , Nb ₂ O ₅ and the total content of WO ₃ of _{[TiO 2 + Nb 2 O 5 +} WO 3 ] 65.3 mass% content of TiO ₂ and the content of P ₂ O ₅ mass ratio of [TiO ₂ / P ₂ O _5] is 0.70 or more . For the phosphate optical glass described in item 1 of the scope of patent application, the mass ratio of the content of TiO _{2 to} the content of Nb ₂ O ₅ [TiO ₂ /Nb ₂ O ₅ ] is 0.45 or more. In the phosphate optical glass described in item 1 of the scope of the patent application, the mass ratio of the content of TiO _{2 to} the content of Nb ₂ O ₅ [TiO ₂ /Nb ₂ O ₅ ] is 0.74 or more. The phosphate optical glass as described in any one of items 1 to 3 in the scope of patent application, wherein the content of Nb ₂ O ₅ is 45.1% by mass or less, and the content of WO ₃ is 21.0% by mass or less. The phosphate optical glass described in any one of items 1 to 3 in the scope of patent application, wherein the total content of Li ₂ O, Na ₂ O and K ₂ O [Li ₂ O+Na ₂ O+K ₂ O] is 5.4% by mass or less. The phosphate optical glass described in any one of items 1 to 3 in the scope of patent application, wherein the content of Bi ₂ O ₃ is 29.0% by mass or less. A phosphate optical glass, comprising: Abbe number (νd) of 16.70 or less; Bi ₂ O ₃ content of 29.0 mass% or less; and the total content of Ti ⁴⁺ , Nb ⁵⁺ , W ⁶⁺ and Bi ³⁺ [Ti ⁴⁺ +Nb ⁵⁺ +W ⁶⁺ +Bi ³⁺ ] is 54.45 cation% or more, and the cation ratio of the content of Ba ^{2+ to} the content of W ⁶⁺ [Ba ²⁺ /W ⁶⁺ ] is 0.073 or less. For the phosphate optical glass described in item 7 of the scope of patent application, the cation ratio [Ti ⁴⁺ /P ⁵⁺ ] of the content of Ti ^{4+ to} the content of P ⁵⁺ is 0.625 or more. A glass material for press molding, which is formed of the phosphate optical glass described in any one of the patent applications from 1 to 8. An optical element, formed of the phosphate optical glass described in any one of the patent applications from 1 to 8.