Method for producing optical glass

Abstract

Provided is a method for producing optical glass with which it is possible to stably obtain optical glass having few bubbles and high light transmittance even when the refractive index of the resulting optical glass is raised.　This method for producing optical glass has a mixing step for mixing a plurality of glass-component-containing raw materials to obtain a mixed raw material, a melting step for melting and refining the mixed raw material to form molten glass, and a molding step for molding and cooling the molten glass to obtain optical glass. The mixed raw material contains a defoaming agent containing at least a carbonate. The mixed raw material contains, in cation% (mol%): 0.01-20.00% of B3+; 20.50% or more in total of one or more selected from the group consisting of La3+, Gd3+, Y3+, and Yb3+; and 35.00% or more in total of one or more selected from the group consisting of Nb5+, Ti4+, W6+, and Zr4+.

Description

Optical glass manufacturing method

[0001] The present invention relates to a method for producing optical glass.

[0002] In recent years, there has been rapid progress in the digitalization and high definition of devices that use optical systems. In the field of various optical devices, such as photographing devices such as digital cameras and video cameras, and image reproduction (projection) devices such as projectors and projection televisions, there is a growing demand to reduce the number of optical elements used in an optical system by adopting optical glass having a high refractive index for optical elements such as lenses and prisms, thereby making the entire optical system lighter and more compact.

[0003] As a method for producing optical glass having such a high refractive index, for example, Patent Document 1 describes a method for producing optical glass, which includes a step of mixing raw materials and a step of melting the glass without supplying water, characterized in that the raw materials contain at least a reducing agent.The method employs such a configuration, and by suppressing coloration of the glass due to platinum dissolved into the glass from a crucible or the like due to oxidation during the glass melting process, it is possible to obtain optical glass in which the transmittance of light on the short wavelength side of visible light is increased and the defoaming properties are improved by the reducing agent.

[0004] Japanese Patent Application Laid-Open No. 2020-169116

[0005] Furthermore, in the field of optical equipment in recent years, there has been an increasing demand for lighter and smaller optical systems, and in order to meet this demand, optical glasses with even higher refractive indices have been sought.

[0006] The conventional method for increasing the refractive index of optical glass is to use Nb as a raw material. ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ However, it is useful to include a large amount of one or more selected from the group consisting of Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ When one or more elements selected from the group consisting of Nb are contained in a large amount, the resulting optical glass tends to contain bubbles more easily as the refractive index increases.５＋ , Ti ４＋ , W ６＋ , Zr ４＋ Components such as these increase the melting temperature, which increases the amount of platinum that dissolves into the glass from the crucible, etc., and this increases the coloring caused by the increase in platinum, which tends to reduce the transmittance of light on the short wavelength side of visible light. In the method for producing optical glass described in Patent Document 1, particularly when producing optical glass with an even higher refractive index, it is necessary to include large amounts of these components, so the suppression of bubble formation is insufficient, and optical glass with high light transmittance cannot be stably obtained without devitrification, leaving room for improvement.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for producing optical glass that can stably produce optical glass with few bubbles and high light transmittance, even when the refractive index of the resulting optical glass is increased.

[0008] In order to solve the above problems, the present inventors have conducted extensive research and experimentation, and as a result, have discovered that a defoaming agent containing at least a carbonate is added to the mixed raw material obtained in the mixing step, and that the mixed raw material contains B ３＋ 0.01% or more and 20.00% or less, La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ The present inventors have found that even when obtaining high refractive index glass containing at least 35.00% in total of one or more types selected from the group consisting of:

[0009] (1) A method for producing optical glass, comprising a mixing step of mixing a plurality of raw materials containing glass components to obtain a mixed raw material, a melting step of melting and refining the mixed raw material to form molten glass, and a forming step of forming and cooling the molten glass to obtain optical glass, wherein the mixed raw material contains a defoaming agent containing at least a carbonate, and the mixed raw material has, in terms of cation % (mol %), the following: B ３＋ 0.01% or more and 20.00% or less, La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ One or more selected from the group consisting of: a total of 20.50% or more, and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ A method for producing an optical glass, characterized in that the optical glass contains at least one kind selected from the group consisting of:

[0010] (2) The method for producing optical glass according to (1) above, wherein the defoaming agent has reducing power.

[0011] (3) The method for producing an optical glass according to (1) or (2) above, wherein the defoaming agent is a carbonate.

[0012] (4) The mixed raw material has a cationic percentage (mol%) of: B ３＋ 0.01% or more and 20.00% or less, Si ４＋ 1.00% or more and 20.00% or less, La ３＋ 5.00% or more and 35.00% or less, Ti ４＋ 25.00% or more and 45.00% or less, Zr ４＋ 1.00% or more and 10.00% or less, Nb ５＋ 1.00% or more and 20.00% or less and Ba ２＋ The content of Y is in the range of 1.00% or more and 20.00% or less. ３＋ The content of is 15.00% or less, and Zn ２＋ The method for producing an optical glass according to (1), (2) or (3) above, wherein the content of is 10.00% or less.

[0013] According to the present invention, it is possible to provide a method for producing optical glass that can stably produce optical glass with few bubbles and high light transmittance, even when the refractive index of the resulting optical glass is increased.

[0014] The method for producing an optical glass of the present invention comprises a mixing step [Step 1] of mixing a plurality of raw materials containing glass components to obtain a mixed raw material, a melting step [Step 2] of melting and refining the mixed raw material to form molten glass, and a forming step [Step 3] of forming and cooling the molten glass to obtain an optical glass. Here, the mixed raw material obtained in the mixing step [Step 1] contains a defoaming agent containing at least a carbonate, and has a cation % (mol %) of B ３＋ 0.01% or more and 20.00% or less, La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ The composition contains at least one selected from the group consisting of:

[0015] Hereinafter, embodiments of the method for producing optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be practiced with appropriate modifications within the scope of the object of the present invention. Note that redundant explanations may be omitted where appropriate, but this does not limit the spirit of the invention.

[0016] In this specification, unless otherwise specified, the content of each component is expressed as cation % or anion % based on a molar ratio. Here, "cation %" and "anion %" (hereinafter sometimes referred to as "cation % (mol %)" and "anion % (mol %)") refer to the composition expressed by the content of each component contained in the mixed raw material obtained in the mixing step [Step 1] described below or the constituent components of the optical glass produced by the production method of the present invention, when the components are separated into cation components and anion components, and the sum of the cation components and anion components is taken as 100 mol %.

[0017] The ionic valence of each component is merely a representative value used for convenience, and is not intended to distinguish it from components with other ionic valences. The ionic valence of each component present in optical glass may be other than the representative value. For example, B (boron) is usually contained in mixed raw materials and optical glass in a trivalent ionic valence state, and therefore in this specification it is referred to as "B ３＋ Although the components are expressed as "," they may be contained in other ionic valence states. Thus, even if strictly speaking they may be contained in other ionic valence states, in this specification each component is treated as being contained in the mixed raw material or optical glass in the ionic valence state of a representative value.

[0018] (i) Mixing Step [Step 1] The method for producing optical glass of the present invention involves a mixing step [Step 1] in which a plurality of raw materials containing glass components are mixed to obtain a mixed raw material. In the mixing step [Step 1], high-purity raw materials such as oxides, hydroxides, nitrates, and metaphosphate compounds are selected as raw materials for each component that makes up the optical glass, and these raw materials are mixed uniformly so that the content of each component falls within a predetermined range.

[0019] The mixed raw material obtained in the mixing step [Step 1] is B ３＋ In addition, La is contained in the range of 0.01% or more and 20.00% or less. ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ Contains a total of 20.50% or more of one or more selected from the group consisting of Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ The composition contains at least one selected from the group consisting of: ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋Optical glass obtained from a mixed raw material containing a large amount of one or more selected from the group consisting of Nb, which is a component that is prone to generating bubbles during melting and is prone to coloring, has an extremely high refractive index. ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ Since the raw materials contain a large amount of platinum, the resulting optical glass is prone to contain bubbles and also tends to have a low transmittance for light in the short wavelength region of visible light. In this regard, in the method for producing optical glass of the present invention, by including at least a carbonate as a defoaming agent in the mixed raw materials, even when obtaining optical glass with such an extremely high refractive index, coloration due to components that reduce the light transmittance of the glass and coloration due to the inclusion of platinum in the glass can be suppressed, and devitrification of the glass can be made less likely to occur. As a result, optical glass with few bubbles and high transmittance for light in the short wavelength region of visible light can be consistently obtained.

[0020] Here, it is preferable that the defoaming agent contained in the mixed raw material has reducing power. That is, it is preferable that a defoaming agent having reducing power is contained in the mixed raw material as a part or all of the defoaming agent. By using a defoaming agent having reducing power, Nb ５＋ , Ti ４＋ , W ６＋ , Zr ４＋ When these reducing agents are added, the optical glass is melted at high temperatures, which suppresses coloration of the optical glass caused by oxidized platinum being mixed into the glass. This makes it possible to reduce the amount of reducing agent used and to obtain an optical glass with even higher light transmittance in the short wavelength range of visible light.

[0021] Examples of the defoaming agent include compounds that are solid at room temperature (e.g., 25°C), such as carbonates, sulfates, fluorides, and antimony oxide (Sb ２ O ３ ), arsenic oxide (As ２ O ３Among them, from the viewpoint of not affecting the composition of the optical glass to be obtained and not worsening the coloring of the optical glass, it is preferable to use, for example, one or both of carbonates and sulfates as the defoaming agent. On the other hand, fluorides, antimony oxide (Sb ２ O ３ ) and arsenic oxide (As ２ O ３ ) is preferably used in combination with one or both of a carbonate and a sulfate, but some or all of these compounds may not be used. In particular, it is more preferable to use a carbonate as the defoaming agent, and thereby, in the melting step [Step 2] described later, the carbonate releases carbon dioxide to defoam and clarify the molten glass, and Ti ４＋ This can suppress coloration of the optical glass due to oxidation of the above-mentioned elements and the inclusion of platinum. Furthermore, since the melting temperature in the melting step [Step 2] described below can be lowered, coloration of the optical glass due to the inclusion of platinum can be further suppressed. Furthermore, by using carbonate as a defoaming agent, CO ３ ２－ Since it contains, the resulting glass is less likely to devitrify.

[0022] Carbonates used as defoaming agents include barium carbonate (BaCO ３ ), calcium carbonate (CaCO ３ ), magnesium carbonate (MgCO ３ ), lithium carbonate (Li ２ CO ３ ), sodium carbonate (Na ２ CO ３ ), potassium carbonate (K ２ CO ３ ), lanthanum carbonate (La ２ (CO ３ ) ３ ) can be used. Among them, Ba ２＋ From the viewpoint of being able to further increase the refractive index by ３ ) is preferably used.

[0023] The content of carbonate, which is a defoaming agent, is ３ ２－ In particular, from the viewpoint of further enhancing the effect of degassing and clarifying the molten glass and making the resulting glass less susceptible to devitrification, the content of carbonate is preferably in the range of 1.00% to 50.00% by mass of carbonate ions (CO ３ ２－ On the other hand, the upper limit of the content of the carbonate as a defoaming agent is not particularly limited, but may be, for example, carbonate ions (CO ３ ２－ The upper limit of the content of ZnO in mass % may be 40.00%, or 30.00%.

[0024] In particular, barium carbonate (BaCO ３ ), the content of barium carbonate in the mixed raw material is ３ ２－ The content of calcium carbonate (CaCO ) in mass % is preferably in the range of 1.00% to 30.00%. ３ ), the content of calcium carbonate in the mixed raw material is ３ ２－ The amount of magnesium carbonate (MgCO ) in terms of mass % is preferably in the range of 1.00% to 30.00%. ３ ), the content of magnesium carbonate in the mixed raw material is ３ ２－ ) in the range of 1.00% to 10.00% in terms of mass %. ２ CO ３ ), the content of lithium carbonate in the mixed raw material is ３ ２－ The amount of sodium carbonate (Na ) in terms of mass % is preferably in the range of 0.10% to 10.00%. ２ CO ３), the content of sodium carbonate in the mixed raw material is ３ ２－ The amount of potassium carbonate (K) in terms of mass % is preferably in the range of 0.50% to 15.00%. ２ CO ３ ), the content of potassium carbonate in the mixed raw material is ３ ２－ The amount of anion % (mol %) of lanthanum carbonate (La(CO)) is preferably in the range of 0.50% to 10.00%. ３ ) ２ When using lanthanum carbonate, the content of lanthanum carbonate in the mixed raw material is ３ ２－ The amount of the hydroxybenzoates is preferably in the range of 1.00% to 50.00% by mass. These may be selected individually or in combination.

[0025] Here, CO is used as an anion component of the mixed raw material. ３ ２－ In the case where the molten metal is contained in the molten metal, in the melting step [Step 2] described later, ３ ２－ releases carbon dioxide to form oxides, so the O ２－ The content of O in the mixed raw material ２－ Therefore, the content of SO can be increased to a level higher than that of the glass, and no unnecessary components can be left in the glass. ２ , Na ２ SO ４ Sulfates such as Sn ４＋ , Sb ３＋ In this case, the devitrification of the glass can be made less likely to occur than when the defoaming effect is obtained by the above-mentioned methods.

[0026] The content of sulfate, which is a defoaming agent, is determined by the sulfate ion (SO ４ ２－ In particular, from the viewpoint of further increasing the light transmittance of the molten glass, more specifically, the shortest wavelength (λ ) at which the spectral transmittance of 70% is exhibited is preferably 0.5% or less. ７０In order to further shorten the time required for the saturation period, the content of sulfate is ４ ２－ ) is more preferably 0.20% or less, and further preferably 0.10% or less, in terms of mass%.

[0027] Carbonate ions (CO ３ ２－ ) and sulfate ions (SO ４ ２－ The content of carbonate ions (CO ) in mass% is the percentage of carbonate ions (CO ) when the total mass of the mixed raw material is 100%. ３ ２－ ) and sulfate ions (SO ４ ２－ ) expressed in units of mass% (mass% divided by the mass of the oxides; hereinafter, sometimes simply referred to as "mass% divided by the mass").

[0028] Furthermore, from the viewpoint of further enhancing the effect of degassing and fining the molten glass and making the resulting glass less susceptible to devitrification, the total content of the degassing agent in the mixed raw material is preferably 0.50% or more, more preferably 1.00% or more, even more preferably 2.00% or more, even more preferably 3.00% or more, and even more preferably 4.00% or more, when the total mass of the mixed raw material is taken as 100%. On the other hand, the upper limit of the total content of the degassing agent in the mixed raw material is not particularly limited, but may be, for example, 50.00%, 40.00%, or 30.00%, when the total mass of the mixed raw material is taken as 100%. Here, the total content of the degassing agent in the mixed raw material is determined by the ratio of carbonate ions (CO 2 ) in carbonates, sulfates, and fluorides contained in the mixed raw material to the total content of the degassing agent in the mixed raw material. ３ ２－ ), sulfate ions (SO ４ ２－ ) and fluoride ions (F － ) content in mass% and antimony oxide (Sb ２ O ３ ) and arsenic oxide (As ２ O ３ ) and the contents of antimony and arsenic in mass %.

[0029] The anion component of the mixed raw material contains at least O ２－ Contains. ２－ From the viewpoint of making devitrification less likely to occur, the content of O may be preferably 10.00% or more, more preferably 20.00% or more, and even more preferably 30.00% or more, expressed in anion % (mol %). ２－ The content of may be 100%. ２－ When the content of is less than 100%, the anion component may be the above-mentioned CO ３ ２－ and SO ４－ , F － In addition to the above, Cl, which is a component that does not fall under either the defoaming agent or the reducing agent, － It may contain the following:

[0030] On the other hand, the mixed raw material contains, as the cationic component, B ３＋ In addition, La is contained in the range of 0.01% or more and 20.00% or less. ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ Among them, the cationic % (mol %) of at least one selected from the group consisting of B ３＋ 0.01% or more and 20.00% or less, Si ４＋ is 1.00% or more and 20.00% or less, La ３＋ 5.00% or more and 35.00% or less, Ti ４＋ 25.00% or more and 45.00% or less, Zr ４＋ 1.00% or more and 10.00% or less, Nb ５＋ 1.00% or more and 10.00% or less and Ba ２＋ in the range of 1.00% or more and 20.00% or less, and Y ３＋ The content of is 15.00% or less, and Zn ２＋ The content is preferably 10.00% or less.

[0031] B３＋ is a component that promotes the formation of stable glass, making devitrification less likely to occur, and is an essential component contained in the mixed raw materials. ３＋ The content of B is set to 0.01% or more, preferably 3.00% or more, and more preferably 5.00% or more. ３＋ By making the content of B 20.00% or less, ３＋ Since the decrease in the refractive index due to B is suppressed, a higher refractive index can be obtained. ３＋ The content of B is 20.00% or less, preferably 17.00% or less, and more preferably 14.00% or less. ３＋ is, for example, H ３ BO ３ , Na ２ B ４ O ７ , Na ２ B ４ O ７ ・10H ２ O, BPO ４ It can be included in the mixed raw material in the form of

[0032] Si ４＋ When Si is contained in an amount of more than 0%, it reduces the coloring of the optical glass, thereby increasing the transmittance of short-wavelength visible light, and also promotes stable glass formation, making devitrification less likely to occur. Therefore, Si is an optional component in the mixed raw materials. ４＋ The content of Si may be preferably 1.00% or more, more preferably 3.00% or more, and further preferably 5.00% or more. ４＋ By making the content of Si 20.00% or less, ４＋ Therefore, a higher refractive index can be obtained. ４＋ The Si content is preferably 15.00% or less, more preferably 12.00% or less, and further preferably 10.00% or less. ４＋ is a material containing, for example, SiO ２ , K. ２ SiF ６ , Na ２ SiF ６It can be included in the mixed raw material in the form of

[0033] La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ The total content of one or more selected from the group consisting of is 20.50% or more in terms of cationic % (mol %). In particular, by making this total content 20.50% or more, an optical glass having a higher refractive index can be obtained. This also makes it possible to increase the Abbe number and reduce coloration. Therefore, the La content in the mixed raw material is ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ The total content of one or more selected from the group consisting of La is 20.50% or more, preferably 21.00% or more, and more preferably 21.50% or more. ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ From the viewpoint of making devitrification of the optical glass less likely to occur, the total content of one or more selected from the group consisting of is preferably 35.00% or less, more preferably 30.00% or less, and even more preferably 25.00% or less.

[0034] La ３＋ is a component that increases the refractive index of the optical glass and improves the chemical durability of the optical glass when contained in an amount exceeding 0%, and is an optional component in the mixed raw material. ３＋ The content of La may be preferably 5.00% or more, more preferably 10.00% or more, and further preferably 15.00% or more. ３＋ By making the content of La 35.00% or less, it is possible to make the optical glass less susceptible to devitrification. ３＋ The content of La may be preferably 33.00% or less, more preferably 30.00% or less, and further preferably 25.00% or less. ３＋ is, for example, La as a raw material. ２ (CO ３ ) ２ , La ２ O３ , La(NO ３ ) ３ ・XH ２ O (X is any integer) can be contained in the mixed raw material.

[0035] Gd ３＋ is a component that increases the refractive index of optical glass and increases the Abbe number when contained in an amount exceeding 0%, and is an optional component in the mixed raw material. ３＋ By making the content of Gd 30.00% or less, it is possible to make the optical glass less susceptible to devitrification. ３＋ The content of Gd may be preferably 20.00% or less, more preferably 10.00% or less, and further preferably 5.00% or less. ３＋ is, for example, Gd ２ O ３ , GdF ３ It can be included in the mixed raw material in the form of

[0036] Y ３＋ is a component that increases the refractive index of the optical glass and increases the Abbe number when contained in an amount exceeding 0%, and is an optional component in the mixed raw material. ３＋ The content of Y may be 0%, but from the viewpoint of increasing the refractive index of the optical glass and increasing the Abbe number, it may be preferably 0.10% or more, and more preferably 2.00% or more. ３＋ By making the content of Y in the mixed raw material 20.00% or less, it is possible to make the optical glass less susceptible to devitrification. ３＋ The content of Y is preferably 15.00% or less, more preferably 10.00% or less, and further preferably 5.00% or less. ３＋ is, for example, Y ２ O ３ , Y.F. ３ It can be included in the mixed raw material in the form of

[0037] Yb ３＋ is a component that, when contained in an amount of more than 0%, increases the refractive index of the optical glass, increases the Abbe number, and makes the optical glass less susceptible to devitrification, and is an optional component in the mixed raw material.３＋ By making the content of Yb 10.00% or less, ３＋ This can reduce devitrification due to excessive inclusion of Yb, and can reduce the material cost and specific gravity of the glass. This also prevents increases in the glass transition temperature and deformation temperature. ３＋ The content of Yb is preferably 7.00% or less, more preferably 5.00% or less, even more preferably 3.00% or less, and even more preferably 1.00% or less. ３＋ is a raw material Yb ２ O ３ , YbF ３ It can be included in the mixed raw material in the form of

[0038] Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ The total content of one or more selected from the group consisting of Nb is 35.00% or more in terms of cationic % (mol %). In particular, by making this total content 35.00% or more, the refractive index of the optical glass can be increased, and an optical glass with a particularly high refractive index can be obtained. This also makes it possible to adjust the Abbe number low. Therefore, the Nb content in the mixed raw material ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ The total content of one or more selected from the group consisting of Nb and Nb+ is 35.00% or more, preferably 38.00% or more, and more preferably 40.00% or more. ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ From the viewpoint of making devitrification of the optical glass less likely to occur, the total content of one or more selected from the group consisting of is preferably 60.00% or less, more preferably 55.00% or less, and even more preferably 53.00% or less.

[0039] In addition, Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ B relative to the total content of one or more selected from the group consisting of ３＋It is preferable that the ratio of the contents of Nb (cation % (mol %) ratio) is 0.50 or less. By making this cation % (mol %) ratio 0.50 or less, devitrification can be suppressed without deteriorating the transmittance. ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ B relative to the total content of one or more selected from the group consisting of ３＋ The ratio of the contents (cation % (mol %)) may be preferably 0.50 or less, more preferably 0.45 or less, and further preferably 0.40 or less. ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ B relative to the total content of one or more selected from the group consisting of ３＋ The lower limit of the ratio of the contents (cation % (mol %)) is not particularly limited, but from the viewpoint of obtaining a stable glass, for example, it may be preferably 0.10 or more, more preferably 0.13 or more, and even more preferably 0.15 or more.

[0040] Nb ５＋ When the content of Nb exceeds 0%, it increases the refractive index of the optical glass and adjusts the Abbe number to a low level, and is an optional component in the mixed raw material. ５＋ The content of Nb may be 0%, but from the viewpoint of increasing the refractive index of the optical glass and adjusting the Abbe number to a low level, it may be preferably 1.00% or more, and more preferably 3.00% or more. ５＋ By making the content of Nb 20.00% or less, the stability of the optical glass can be improved, making it difficult for devitrification to occur. ５＋ The Nb content may be preferably 17.00% or less, more preferably 15.00% or less, and further preferably 10.00% or less. ５＋ is, for example, Nb ２ O ５ It can be included in the mixed raw material in the form of

[0041] Ti ４＋When Ti is contained in an amount of more than 0%, it increases the refractive index of the optical glass, adjusts the Abbe number to a low value, and increases the chemical durability of the glass, and is an optional component in the mixed raw materials. ４＋ The content of Ti may be preferably 25.00% or more, more preferably 27.50% or more, and further preferably 30.00% or more. ４＋ By making the content of 45.00% or less, Ti, which can generate crystal nuclei in the glass, can be suppressed. ４＋ Therefore, it is possible to suppress devitrification of the glass due to the excessive content of Ti. ４＋ The Ti content may be preferably 42.00% or less, more preferably 41.00% or less. ４＋ is a material containing, for example, TiO ２ It can be included in the mixed raw material in the form of

[0042] W ６＋ When the content of W exceeds 0%, it increases the refractive index of the optical glass and adjusts the Abbe number to a low level, and is an optional component in the mixed raw material. ６＋ By making the content of W in the mixed raw material 10.00% or less, it is possible to make the optical glass less susceptible to devitrification and also reduce the raw material cost. ６＋ The content of W may be preferably 5.00% or less, more preferably 3.00% or less, and further preferably 1.00% or less. ６＋ is obtained by using, for example, WO ３ It can be included in the mixed raw material in the form of

[0043] Zr ４＋ is a component that promotes stable glass formation and makes devitrification of optical glass less likely to occur when it is contained in excess of 0%, and is an optional component in the raw material mixture. ４＋ The content of Zr may be 0%, but from the viewpoint of promoting stable glass formation and making devitrification of the optical glass less likely to occur, it may be preferably 1.00% or more, and more preferably 3.00% or more. ４＋ By making the content of Zr 15.00% or less, it is possible to form crystal nuclei in the glass. ４＋Therefore, the amount of Zr in the mixed raw material can be reduced. ４＋ The content of Zr may be preferably 10.00% or less, more preferably 5.00% or less. ４＋ is made by using, for example, ZrO ２ , ZrF ４ It can be included in the mixed raw material in the form of

[0044] Zn ２＋ is a component that makes optical glass less susceptible to devitrification when contained in an amount exceeding 0%, and is an optional component in the raw material mixture. ２＋ The content of may be 0%, but from the viewpoint of making the optical glass less susceptible to devitrification, it may be preferably 0.10% or more, and more preferably 0.20% or more. ２＋ By making the content of Zn in the mixed raw material 10.00% or less, the decrease in the refractive index and Abbe number can be suppressed, and therefore a higher refractive index and Abbe number can be obtained. ２＋ The content of Zn may be preferably 5.00% or less, more preferably 3.00% or less, and further preferably 2.00% or less. ２＋ is made of raw materials such as ZnO and ZnF ２ It can be included in the mixed raw material in the form of

[0045] Mg ２＋ , Ca ２＋ , Sr ２＋ and Ba ２＋ The total content of one or more selected from the group consisting of is preferably 20.00% or less in terms of cationic % (mol %). In particular, by making this total content 8.00% or less, it is possible to suppress a decrease in the refractive index and Abbe number. Therefore, Mg in the mixed raw material ２＋ , Ca ２＋ , Sr ２＋ and Ba ２＋ The total content of one or more selected from the group consisting of may be preferably 20.00% or less, more preferably 15.00% or less, and even more preferably 10.00% or less. ２＋ , Ca ２＋ , Sr２＋ and Ba ２＋ The total content of one or more elements selected from the group consisting of may be 0%, but, particularly from the viewpoint of making devitrification of the optical glass less likely to occur, may be preferably 1.00% or more, more preferably 3.00% or more, and even more preferably 5.00% or more.

[0046] Mg ２＋ is a component that makes optical glass less susceptible to devitrification when contained in an amount of more than 0%, and is a component that further increases the transmittance of visible light, and is an optional component in the mixed raw material. ２＋ By making the content of Mg in the mixed raw material 20.00% or less, it is possible to suppress the decrease in the refractive index and the Abbe number. ２＋ The content of Mg may be preferably 15.00% or less, more preferably 10.00% or less, and further preferably 5.00% or less. ２＋ is, for example, MgCO ３ , MgF ２ In this case, MgCO ３ When MgCO is included in the mixed raw material, ３ is Mg ２＋ It is a raw material for the above and also acts as a defoamer.

[0047] Ca ２＋ is a component that makes optical glass less susceptible to devitrification when contained in an amount of more than 0%, and is an optional component in the mixed raw materials. ２＋ By making the content of Ca 20.00% or less, it is possible to suppress a decrease in the refractive index and the Abbe number. ２＋ Therefore, it is possible to suppress devitrification and deterioration of chemical durability due to excessive content of Ca in the mixed raw material. ２＋ The content of Ca may be preferably 15.00% or less, more preferably 10.00% or less, and further preferably 5.00% or less. ２＋ is, for example, CaCO as a raw material. ３ , CaF ２ In this case, CaCO ３ When included in the mixed raw material, CaCO ３ is Ca２＋ It is a raw material for the above and also acts as a defoaming agent with reducing power.

[0048] Sr ２＋ is a component that makes optical glass less susceptible to devitrification when contained in an amount exceeding 0%, and is an optional component in the mixed raw materials. ２＋ By making the content of Sr 20.00% or less, it is possible to suppress the decrease in the refractive index and the Abbe number. ２＋ Therefore, it is possible to suppress devitrification and deterioration of chemical durability due to excessive Sr content in the mixed raw material. ２＋ The content of Sr may be preferably 15.00% or less, more preferably 10.00% or less, and further preferably 5.00% or less. ２＋ is a material such as Sr(NO ３ ) ２ , SrF ２ It can be included in the mixed raw material in the form of

[0049] Ba ２＋ When Ba is contained in an amount of more than 0%, it is a component that further increases the refractive index of the optical glass and makes devitrification less likely to occur, and further increases the transmittance of visible light, and is an optional component in the raw material mixture. ２＋ The content of Ba may be preferably 1.00% or more, more preferably 3.00% or more, and further preferably 5.00% or more. ２＋ By making the content of Ba 20.00% or less, ２＋ It is possible to suppress the decrease in refractive index and Abbe number due to the excessive content of Ba. ２＋ Therefore, it is possible to suppress devitrification and deterioration of chemical durability due to excessive content of Ba. ２＋ The content of Ba may be preferably 15.00% or less, more preferably 10.00% or less, and further preferably 9.00% or less. ２＋ is, for example, BaCO ３ , Ba(NO ３ ) ２ , BaF ２ In this case, BaCO３ When included in the mixed raw material, Ba ２＋ This further increases the refractive index of the optical glass, and BaCO ３ From the viewpoint of making it act as a defoaming agent with reducing power, BaCO ３ Ba ２＋ It is preferable to use it as a raw material for

[0050] La ３＋ , Y ３＋ , Gd ３＋ and Yb ３＋ Ba relative to the total content of one or more selected from the group consisting of ２＋ It is preferable that the ratio of the contents of La (cation % (mol %) ratio) is 0.40 or less. By making this cation % (mol %) ratio 0.40 or less, it is possible to reduce the specific gravity of the obtained glass and improve the devitrification resistance. ３＋ , Y ３＋ , Gd ３＋ and Yb ３＋ Ba relative to the total content of one or more selected from the group consisting of ２＋ The ratio of the contents of La (cation % (mol %)) may be preferably 0.40 or less, more preferably 0.39 or less, and even more preferably 0.38 or less. ３＋ , Y ３＋ , Gd ３＋ and Yb ３＋ Ba relative to the total content of one or more selected from the group consisting of ２＋ The lower limit of the ratio of the contents (cation % (mol %)) is not particularly limited, but from the viewpoint of making devitrification less likely to occur and increasing the transmittance to visible light, it may be preferably 0.20 or more, more preferably 0.25 or more, and even more preferably 0.30 or more.

[0051] Li ＋ is a component that lowers the melting temperature of the mixed raw material when contained in an amount of more than 0%, and is an optional component in the mixed raw material. ＋ By making the content of Li 5.00% or less, it is possible to suppress the decrease in the refractive index. ２＋ Therefore, the devitrification caused by the excessive content of Li in the mixed raw material can be suppressed.＋ The content of Li may be preferably 3.00% or less, more preferably 2.00% or less, and further preferably 1.00% or less. ＋ is, for example, Li as a raw material ２ CO ３ , LiNO ３ , LiF, etc. can be contained in the glass.

[0052] Na ＋ is a component that lowers the melting temperature of the mixed raw material when contained in an amount exceeding 0%, and is an optional component in the mixed raw material. ＋ By making the content of Li 5.00% or less, it is possible to suppress the decrease in the refractive index. ２＋ Therefore, the devitrification caused by the excessive content of Na in the mixed raw material can be suppressed. ＋ The content of Na may be preferably 3.00% or less, more preferably 2.00% or less, and further preferably 1.00% or less. ＋ is, for example, Na ２ CO ３ , NaNO ３ , NaF, Na ２ SiF ６ It can be included in the mixed raw material in the form of

[0053] K ＋ is a component that lowers the melting temperature of the mixed raw material when contained in an amount of more than 0%, and is an optional component in the mixed raw material. ＋ By making the content of Li 5.00% or less, it is possible to suppress the decrease in the refractive index. ２＋ Therefore, the devitrification caused by the excessive content of K in the mixed raw material can be suppressed. ＋ The content of K may be preferably 3.00% or less, more preferably 2.00% or less, and further preferably 1.00% or less. ＋ is, for example, K ２ CO ３ , KNO ３ , KF, KHF ２ , K. ２ SiF ６ It can be included in the mixed raw material in the form of

[0054] Al３＋ is a component that, when contained in an amount of more than 0%, improves the chemical durability of the optical glass while increasing the viscosity of the molten glass when the mixed raw materials are melted, and is an optional component in the mixed raw materials. ３＋ By making the content of Al in the mixed raw material 10.00% or less, devitrification of the optical glass can be made less likely to occur. ３＋ The Al content may be preferably 5.00% or less, more preferably 3.00% or less, and further preferably 1.00% or less. ３＋ is, for example, Al as a raw material. ２ O ３ , Al(OH) ３ , AlF ３ It can be included in the mixed raw material in the form of

[0055] Bi ３＋ When Bi is contained in an amount of more than 0%, it increases the refractive index of the optical glass and adjusts the Abbe number to a low value, and is an optional component in the mixed raw material. ３＋ By making the content of Bi 15.0% or less, it is possible to make the optical glass less susceptible to devitrification. ３＋ The content of Bi may be preferably 10.0% or less, more preferably 5.0% or less, and further preferably 3.0% or less. ３＋ is, for example, Bi as a raw material ２ O ３ It can be included in the mixed raw material in the form of

[0056] Ta ５＋ When contained in an amount of more than 0%, Ta is a component that further increases the refractive index of the optical glass and also makes the optical glass less susceptible to devitrification, and is an optional component in the mixed raw materials. ５＋ By limiting the content to 7.00% or less, Ta, a rare mineral resource, can be ５＋ The amount of Ta used is reduced and the mixed raw materials are more easily melted at a lower temperature, which reduces the production cost of the optical glass. ５＋ Therefore, it is possible to suppress devitrification caused by an excessive content of Ta in the mixed raw material. ５＋The content of Ta may be preferably 5.00% or less, more preferably 3.00% or less, and further preferably 1.00% or less. ５＋ is Ta as a raw material ２ O ５ It can be included in the mixed raw material in the form of

[0057] Sn ４＋ When the content of Sn exceeds 0%, it has a defoaming effect when melting glass, and is an optional component in the mixed raw materials. ４＋ When Sn is contained in the mixed raw material, there are disadvantages in that the specific gravity of the optical glass becomes heavy and the risk of alloying with Pt increases. ４＋ The content of Sn is preferably 3.00% or less, more preferably 1.00% or less, and further preferably Sn ４＋ The mixed raw material does not contain Sn ４＋ When Sn is included in the mixed raw material, ４＋ is a material containing, for example, SnO, SnO ２ , SnF ２ , SnF ４ It can be included in the form of

[0058] Sb ３＋ When the content of Sb exceeds 0%, it is a component that has a defoaming effect when melting glass, and is an optional component in the mixed raw materials. ３＋ When Sb is contained in the mixed raw material, the optical glass is easily colored and foreign matter is easily generated in the glass. ３＋ The content of Sb is preferably 2.00% or less, more preferably 1.00% or less, and further preferably Sb ３＋ The mixed raw material does not contain Sn ４＋ When Sb is included in the mixed raw material, ３＋ is, for example, Sb ２ O ３ It can be included in the form of

[0059] Cations other than those mentioned above can also be added as needed within the range that does not impair the properties of the optical glass. ４＋ , Zr ４＋ , Nb５＋ , W ６＋ , La ３＋ , Gd ３＋ , Y ３＋ , Yb ３＋ , Lu ３＋ Cations of transition metals other than those mentioned above, more specifically cations such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, have the property of coloring the glass and causing absorption at specific wavelengths in the visible range even when contained in small amounts, either alone or in combination, and therefore it is preferable that they are not substantially contained in the mixed raw material.

[0060] In addition, lead compounds such as PbO and As ２ O ３ Arsenic compounds such as PbO are components that have a high environmental impact. Therefore, it is desirable that lead compounds such as PbO are not substantially contained, that is, that they are not contained at all in the mixed raw material except for unavoidable contamination. ２＋ It is desirable that As is not substantially contained in the mixed raw material. ２ O ３ For the same reason, it is desirable that the mixed raw material does not substantially contain arsenic compounds such as As. ３＋ It is desirable that the mixed raw material is substantially free of these substances.

[0061] Furthermore, in recent years, there has been a trend to refrain from using Th, Cd, Tl, Os, Be, and Se cations as harmful chemical substances, and environmental measures are required not only in the glass manufacturing process but also in the processing process and disposal after commercialization. Therefore, when environmental impact is important, it is preferable that these cations are substantially not included in the mixed raw materials.

[0062] In the manufacturing method of the present invention, from the viewpoint of further increasing the light transmittance of the molten glass, more specifically, the shortest wavelength (λ ) at which the spectral transmittance of the molten glass is 70% is selected. ７０) further shortens the glass transition time. A reducing agent may be contained in the mixed raw material. Here, the content of the reducing agent in the mixed raw material may be more than 0% or may be 0.10% or more, relative to the total mass of the mixed raw material. On the other hand, in the manufacturing method of the present invention, it is preferable that the mixed raw material contains a small amount of reducing agent. More specifically, the content of the reducing agent in the mixed raw material is preferably 5.00 mass% or less, more preferably 3.00 mass% or less, even more preferably 1.00 mass% or less, even more preferably less than 0.50 mass%, and even more preferably less than 0.3 mass%, relative to the total mass of the mixed raw material. In the manufacturing method of the present invention, the mixed raw material does not need to contain a reducing agent. Examples of reducing agents include simple substances such as carbon (C) and sulfur (S), and organic compounds such as sucrose. By reducing the content of such reducing agents, it is possible to prevent excess components from remaining in the glass, thereby making it less likely for devitrification of the glass to occur.

[0063] (ii) Melting Step [Step 2] The melting step [Step 2] is a step of melting and refining the mixed raw materials to form a glass melt. More specifically, the mixed raw materials are placed in a platinum crucible, and melted in an electric furnace at a temperature range of 1100°C to 1500°C for 1 hour to 10 hours, depending on the melting difficulty of the raw materials, followed by stirring and homogenization, to form a glass melt. By forming a glass melt through this melting step [Step 2], the defoaming action of the defoaming agent can defoam and refine the glass melt.

[0064] (iii) Molding Step [Step 3] The molding step [Step 3] is a step in which the glass melt is molded and cooled to obtain optical glass. In this step, the glass melt is cooled to an appropriate temperature, cast into a mold, and slowly cooled to obtain optical glass with few bubbles and high light transmittance.

[0065] (iv) Physical Properties of the Resulting Optical Glass The optical glass obtained by the manufacturing method of the present invention preferably has a particularly high refractive index. More specifically, the lower limit of the refractive index (nd) of the optical glass obtained by the manufacturing method of the present invention is preferably 1.95, more preferably 2.00, and even more preferably 2.05. On the other hand, the upper limit of the refractive index (nd) may be preferably 2.18, more preferably 2.16, and even more preferably 2.14. Such a high refractive index makes it possible to obtain a large amount of light refraction even when the optical element is made thin, thereby contributing to further weight and size reduction of optical systems.

[0066] Furthermore, the optical glass obtained by the manufacturing method of the present invention preferably has high dispersion (low Abbe number). More specifically, the lower limit of the Abbe number (νd) of the optical glass obtained by the manufacturing method of the present invention is preferably 10, more preferably 15, and even more preferably 20. On the other hand, the upper limit of the Abbe number (νd) may be preferably 35, more preferably 25, and even more preferably 21. By having such low dispersion, when used as a single lens, it is possible to reduce the focus shift (chromatic aberration) due to the wavelength of transmitted light. Therefore, for example, by constructing an optical system using optical elements having high dispersion (low Abbe number), it is possible to reduce aberrations throughout the optical system and achieve high imaging characteristics, etc.

[0067] Furthermore, it is preferable that the optical glass obtained by the manufacturing method of the present invention has a high visible light transmittance, particularly a high transmittance for light on the short wavelength side of visible light, and thus has little coloring. More specifically, the optical glass obtained by the manufacturing method of the present invention has a spectral transmittance of 70% at the shortest wavelength (λ ７０ ) may be preferably 500 nm or less, more preferably 480 nm or less, even more preferably 470 nm or less, and even more preferably 460 nm or less. This brings the absorption edge of the glass into the ultraviolet region or its vicinity, thereby increasing the transparency of the glass to visible light and reducing coloration, and therefore the optical glass can be preferably used for optical elements that transmit light, such as lenses.

[0068] The optical glass obtained by the manufacturing method of the present invention preferably has a small amount of platinum, and therefore is less colored. In particular, the platinum content in the optical glass of the present invention is preferably 15.0 ppm or less, more preferably 10.0 ppm or less, even more preferably 5.0 ppm or less, even more preferably 4 ppm or less, and even more preferably 3 ppm or less. The manufacturing method of the present invention makes it difficult for oxidation of the crucible and other components during the glass melting process, thereby suppressing coloration of the glass due to platinum dissolved in the molten glass due to oxidation of the crucible and other components, and thereby increasing the transmittance of the glass for light on the short wavelength side of the visible range, making the optical glass suitable for use in optical elements that transmit light, such as lenses.

[0069] The optical glass of the present invention preferably contains few bubbles. The degree of bubbles in the glass can be graded based on the Japan Optical Glass Industry Association standard JOGIS12-2012, "Method for measuring bubbles in optical glass." The grade based on this measurement method preferably falls into any of Grades 1 to 3, more preferably Grade 1 or 2, and most preferably Grade 1.

[0070] The optical glass of the present invention preferably exhibits little devitrification due to crystal formation. The degree of devitrification in the glass can be graded based on the number of microcrystals, which are crystals with a maximum length of 4 μm or more, contained in 100 ml of glass, in accordance with the Japan Optical Glass Industry Association standard JOGIS13-2019, "Method for Measuring Foreign Matter in Optical Glass." The grade based on this measurement method preferably falls into any of Classes A to C, more preferably Class A or Class B, and most preferably Class A.

[0071] (v) Production of Preforms and Optical Elements Using Optical Glass A glass molded body can be produced from the optical glass produced by the production method of the present invention using, for example, polishing means or mold press molding means such as reheat press molding or precision press molding. For example, a glass molded body can be produced by performing mechanical processing such as grinding and polishing on the optical glass. A glass molded body can also be produced by performing reheat press molding on a preform for mold press molding formed from the optical glass and then polishing. A glass molded body can also be produced by performing precision press molding on a preform produced by mechanical processing such as grinding and polishing on the optical glass, or a preform molded by known floating molding or the like. Note that the means for producing a glass molded body are not limited to these means.

[0072] The glass molded body produced in this manner is useful as an optical element. Among them, it is particularly preferable to form a preform from the optical glass produced by the production method of the present invention and use this preform to perform reheat press molding, precision press molding, or the like to form a glass molded body that will become an optical element such as a lens or a prism. This makes it possible to form a preform with a large diameter, and while increasing the size of the resulting optical element, it is possible to achieve high-definition and high-precision imaging and projection characteristics when used in optical equipment such as a camera or projector.

[0073] Next, in order to further clarify the effects of the present invention, examples of the present invention and comparative examples will be described, but the present invention is not limited to these examples of the present invention.

[0074] The composition of the mixed raw materials obtained in the mixing step [Step 1] of the manufacturing methods of the present invention and comparative examples, the refractive index (nd), Abbe number (νd), and the shortest wavelength (λ ) at which the spectral transmittance of the glass obtained by the manufacturing methods of the present invention and comparative examples is 70%. ７０The evaluation results for the glass thickness, the platinum content (ppm) in the glass, and bubbles (air bubbles) and devitrification in the glass are shown in Tables 1 and 2. The following examples of the present invention are for illustrative purposes only, and the present invention is not limited to these examples.

[0075] In the manufacturing methods of the present invention examples and comparative examples, in the mixing step [Step 1], high-purity raw materials used in ordinary optical glass, such as oxides, hydroxides, nitrates, and metaphosphate compounds, were selected as raw materials for each component constituting the optical glass, and the raw materials containing the glass components were weighed out to obtain the composition ratios shown in Tables 1 and 2, and then uniformly mixed to obtain a mixed raw material. At this time, in present invention examples 1 to 11 and comparative example 2, high-purity (purity 99% or more) barium carbonate (BaCO ３ ), lanthanum carbonate (La ２ (CO ３ ) ３ ) and zinc sulfate (ZnSO ４ ) were weighed out so as to have the composition ratios shown in Tables 1 and 2, and were added to the mixed raw material. In Examples 10 and 11 of the present invention and Comparative Example 2, high-purity (purity of 99% or more) zinc sulfate (ZnSO ４ ) were weighed out to achieve the compositional ratios shown in Table 2 and incorporated into the mixed raw materials. In addition, in Inventive Examples 6 to 9 and Comparative Example 1, carbon (C) and sulfur (S) were weighed out as reducing agents to achieve the compositional ratios shown in Tables 1 and 2 and incorporated into the mixed raw materials. The total contents of the defoaming agents and the total contents of the reducing agents in Inventive Examples 1 to 11 and Comparative Examples 1 to 3 are shown in Tables 1 and 2. Next, in the melting step [Step 2], the mixed raw materials were placed in a platinum crucible and melted in an electric furnace at a temperature range of 1100°C to 1500°C for 2 to 5 hours depending on the melting difficulty of the raw materials, and then stirred and homogenized to form a glass melt. Thereafter, in the molding step [Step 3], the glass melt was cooled to an appropriate temperature, poured into a mold, and slowly cooled to produce an optical glass.

[0076] The refractive index (nd) of the glasses obtained by the methods of the present invention and comparative examples was shown as a measurement value for the d-line (587.56 nm) of a helium lamp in accordance with the V-block method specified in JIS B 7071-2: 2018. The Abbe number (νd) was calculated from the formula (νd) = [(nd-1) / (nF-nC)] using the refractive index for the d-line, the refractive index (nF) for the F-line (486.13 nm) of a hydrogen lamp, and the refractive index (nC) for the C-line (656.27 nm).

[0077] The transmittance of the glasses obtained by the methods of the present invention and comparative examples was measured in accordance with the Japan Optical Glass Industry Association standard JOGIS02. In the present invention, the presence and degree of coloration of the glass was determined by measuring the transmittance of the glass. Specifically, bulk glass materials obtained by the methods of the present invention and comparative examples were polished parallel to each other to form samples with a thickness of 10±0.1 mm. After annealing these samples, the light transmittance (spectral transmittance) for light with wavelengths of 200 nm to 800 nm was immediately measured by the method specified in JOGIS02-1975, and from the results, λ ７０ The shortest wavelength at which the transmittance was 70% was determined. ７０ The smaller the value, the higher the light transmittance for light on the short wavelength side of the visible light wavelength range, and the less coloring of the glass.

[0078] The platinum content (ppm) in the glasses obtained by the methods of the present invention and comparative examples was measured using an ICP-MS (inductively coupled plasma mass spectrometer).

[0079] The evaluation of bubbles in the glasses obtained by the methods of the present invention and the comparative examples was based on the Japan Optical Glass Industry Association standard JOGIS12-2012 "Method for measuring bubbles in optical glass" and was carried out by measuring the total cross-sectional area (mm ２ The total cross-sectional area of ​​bubbles contained in a 100 ml glass was 0.03 mm ２ When the total cross-sectional area of ​​bubbles contained in a 100 ml glass was less than 0.03 mm, the glass was evaluated as being particularly excellent in terms of the number of bubbles in the glass. ２ More than 0.1 mm２ When the total cross-sectional area of ​​bubbles contained in a 100 ml glass was less than 0.1 mm, it was evaluated as "Grade 2," which is excellent in that there were few bubbles in the glass. ２ 0.25mm or more ２ On the other hand, when the total cross-sectional area of ​​bubbles contained in a 100 ml glass was less than 0.25 mm, it was evaluated as "Grade 3" as being good in terms of the number of bubbles in the glass. ２ More than 0.5 mm ２ If the total cross-sectional area of ​​bubbles contained in a 100 ml glass is less than 0.5 mm, it is classified as "Class 4." ２ If the glass was more than this, it was rated as "grade 5" and in these cases it was rated as poor because there were many bubbles in the glass.

[0080] The evaluation of devitrification in the glasses obtained by the methods of the present invention and comparative examples was based on the Japan Optical Glass Industry Association standard JOGIS13-2019 "Method for measuring foreign matter in optical glass," and was graded based on the number of microcrystals, which are crystals with a maximum length of 4 μm or more, contained in 100 ml of glass. Of these, when the number of microcrystals contained in 100 ml of glass was less than 10, it was evaluated as "Grade A," which is particularly excellent in terms of low devitrification due to crystal formation. Furthermore, when the number of microcrystals contained in 100 ml of glass was 10 to 100, it was evaluated as "Grade B," which is excellent in terms of low devitrification due to crystal formation. Furthermore, when the number of microcrystals contained in 100 ml of glass was 100 to 500, it was evaluated as "Grade C," which is good in terms of low devitrification due to crystal formation. On the other hand, when the number of microcrystals contained in 100 ml of glass was 500 or more but less than 1000, it was rated as "Grade D," and when the number of microcrystals contained in 100 ml of glass was 1000 or more, it was rated as "Grade E." These cases were rated as poor because there was a lot of devitrification due to the formation of crystals in the glass.

[0081]

[0082]

[0083] As shown in the table, the optical glasses obtained by the manufacturing methods of Examples 1 to 11 of the present invention all had a λ ７０In contrast, the glasses obtained by the manufacturing methods of Comparative Examples 1 to 3 had a λ ７０ This demonstrates that the optical glasses obtained by the manufacturing methods of Examples 1 to 11 of the present invention are less susceptible to coloration than the glasses obtained by the manufacturing methods of Comparative Examples 1 to 3.

[0084] Furthermore, the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 all had bubble ratings of Grades 1 to 3. In contrast, the glasses obtained by the manufacturing methods of Comparative Examples 1 and 3 had a bubble rating of Grade 5. This demonstrates that the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 have bubbles removed more sufficiently than the glasses obtained by the manufacturing methods of Comparative Examples 1 and 3, and have a higher degassing effect.

[0085] Furthermore, the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 were all rated as Class A or Class B for devitrification. In contrast, the glasses obtained by the manufacturing methods of Comparative Examples 1 and 2 were rated as Class E for devitrification. This demonstrates that the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 are less susceptible to devitrification than the glasses obtained by the manufacturing methods of Comparative Examples 1 and 2, and that optical glasses can be reliably obtained.

[0086] Furthermore, the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 all had platinum amounts of 3.0 ppm or less. In contrast, the glasses obtained by the manufacturing methods of Comparative Examples 2 and 3 had platinum amounts exceeding 3.0 ppm. This demonstrates that the optical glasses obtained by the manufacturing methods of Inventive Examples 1 to 11 have lower platinum contents than the glasses obtained by the manufacturing methods of Comparative Examples 2 and 3.

[0087] Furthermore, the optical glasses obtained by the manufacturing methods of Examples 1 to 11 of the present invention all had a refractive index (nd) of 1.95 or more, which was within the desired range.

[0088] From the above, in the manufacturing method of the optical glass of Examples 1 to 11 of the present invention, the mixed raw material contains, in cationic % (mol %), La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ It has become clear that when one or more types selected from the group consisting of are contained in a total amount of 35.00% or more, by adding a defoaming agent containing at least a carbonate, it is possible to stably obtain optical glass with few bubbles and high light transmittance, even when the refractive index of the obtained optical glass is increased.

[0089] In contrast, in the manufacturing methods of the optical glasses of Comparative Examples 1 and 3, the mixed raw materials contained, in cationic % (mol %), La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ No defoaming agent was added when the glass contained a total of 35.00% or more of one or more selected from the group consisting of: As a result, the optical glasses obtained in Comparative Examples 1 and 3 were inferior to the optical glasses obtained in Invention Examples 1 to 11 in that they contained more bubbles and had lower light transmittance.

[0090] Among these, in the manufacturing method of the optical glass of Comparative Example 1, the mixed raw material contained, in cationic % (mol %), La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ A reducing agent was used instead of a defoaming agent when the glass contained a total of 35.00% or more of one or more selected from the group consisting of: Therefore, the optical glass obtained in Comparative Example 1 was inferior to the optical glasses obtained in Invention Examples 1 to 11 in that it was evaluated as having a lower degree of devitrification than the optical glasses obtained in Invention Examples 1 to 11.

[0091] On the other hand, in the manufacturing method of the optical glass of Comparative Example 2, the mixed raw material contained, in cationic % (mol %), La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ In the case where one or more kinds selected from the group consisting of: were contained in a total of 35.00% or more, the defoaming agent did not contain carbonate, but contained sulfate instead of carbonate. Therefore, the optical glass obtained in Comparative Example 2 had a spectral transmittance of 70% at the shortest wavelength (λ ７０ ) was long, and therefore the optical glass obtained in Comparative Example 2 was inferior in that it received a low evaluation for devitrification, and was therefore inferior to the optical glasses obtained in Inventive Examples 1 to 11.

[0092] Although the present invention has been described in detail for purposes of illustration, it will be understood that the examples are for illustrative purposes only and that many modifications may be made by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A method for producing optical glass, comprising: a mixing step of mixing a plurality of raw materials containing glass components to obtain a mixed raw material; a melting step of melting and refining the mixed raw material to form a glass melt; and a shaping step of shaping and cooling the glass melt to obtain an optical glass, wherein the mixed raw material contains a defoaming agent containing at least a carbonate, and the mixed raw material has, in terms of cation % (mol %), the following: B ３＋ 0.01% or more and 20.00% or less, La ３＋ , Gd ３＋ , Y ３＋ and Yb ３＋ One or more selected from the group consisting of: a total of 20.50% or more, and Nb ５＋ , Ti ４＋ , W ６＋ and Zr ４＋ A method for producing an optical glass, characterized in that the optical glass contains at least one kind selected from the group consisting of:

2. The method for producing optical glass according to claim 1, wherein the defoaming agent has reducing power.

3. The method for producing optical glass according to claim 1, wherein the defoaming agent is a carbonate.

4. The mixed raw material is expressed as follows in cationic percentage (mol%): B ３＋ 0.01% or more and 20.00% or less, Si ４＋ 1.00% or more and 20.00% or less, La ３＋ 5.00% or more and 35.00% or less, Ti ４＋ 25.00% or more and 45.00% or less, Zr ４＋ 1.00% or more and 10.00% or less, Nb ５＋ 1.00% or more and 20.00% or less and Ba ２＋ The content of Y is in the range of 1.00% or more and 20.00% or less. ３＋ The content of is 15.00% or less, and Zn ２＋ 4. The method for producing an optical glass according to claim 1, 2 or 3, wherein the content of is 10.00% or less.

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