CN114105470A

CN114105470A - Manufacturing method of optical glass

Info

Publication number: CN114105470A
Application number: CN202110979983.8A
Authority: CN
Inventors: 桃野净行
Original assignee: Ohara Inc
Current assignee: Ohara Inc
Priority date: 2020-08-26
Filing date: 2021-08-25
Publication date: 2022-03-01
Also published as: JP7429622B2; JP2022038465A

Abstract

本发明提供一种玻璃的制造方法，能够抑制在熔解玻璃的过程中氧化并熔解入玻璃中的铂导致的玻璃的着色，并且能够抑制微细的泡产生。本发明的光学玻璃的制造方法，包括对玻璃原料进行熔融，其特征在于，所述玻璃原料，以氧化物换算的质量％，含有30.0～65.0％的La₂O₃成分、3.0～25.0％的B₂O₃成分，并且添加还原剂以及氯。The present invention provides a method for producing glass that can suppress coloration of glass due to platinum that is oxidized and melted into glass in the process of melting glass, and can suppress the generation of fine bubbles. The method for producing an optical glass of the present invention includes melting a glass raw material, wherein the glass raw material contains 30.0 to 65.0% of La ₂ O ₃ component and 3.0 to 25.0% of La 2 O 3 in mass % in terms of oxides. B ₂ O ₃ component, and a reducing agent and chlorine are added.

Description

Method for producing optical glass

Technical Field

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

Background

In recent years, digitalization and high definition of devices using an optical system have been rapidly advanced, and in the fields of various optical devices such as imaging devices such as digital cameras and video cameras, and image display (projection) devices such as projectors and projection televisions, there has been an increasing demand for reducing the number of optical elements such as lenses and prisms used in the optical system, and for reducing the weight and size of the entire optical system.

In the production of optical glass, platinum, which is commonly used in crucibles and the like, has a melting point as high as over 1700 ℃, and is suitable for melting glass, but platinum and platinum ions after oxidation are easily dissolved in glass because platinum is easily reacted with oxygen and deteriorated. Platinum dissolved in the glass absorbs visible light and thus causes coloration of the optical glass of the final product.

In addition, it is desirable that few bubbles are mixed in the final product of the optical glass. For example, when an optical glass containing bubbles is used as a lens, the bubbles are also displayed on a projected picture, and image distortion occurs due to the influence of scattered light caused by the bubbles.

As an index indicating the degree of bubbles contained in the optical glass, japanese optical glass industry standard JOGIS 12-2012 "method for measuring bubbles in optical glass" was used.

In "method for measuring bubbles of optical glass" of japan optical glass industry standard JOGIS 12-2012, bubbles having a diameter of 30 μm or more existing in the optical glass are regarded as bubbles.

However, fine bubbles having a diameter of less than 30 μm, which have no problem in the standards, deteriorate in internal quality when the number thereof is large, and affect the final product as much as or even more than 30 μm in diameter.

On the other hand, in order to reduce the coloration of the optical glass by platinum and to reduce bubbles in the glass, the following methods have been proposed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2019-019050

Patent document 2: japanese patent laid-open publication No. 2016-074558

Disclosure of Invention

Technical problem to be solved by the invention

Patent document 1 discloses that a glass with reduced coloration due to platinum can be obtained by increasing the water content in the melting step.

Patent document 2 discloses that a glass having a good defoaming effect can be obtained by using a sulfur component as an oxidizing agent in melting the glass.

When melting optical glass, the optimum method for suppressing the coloration of glass by platinum and the generation of bubbles in glass varies depending on the amount of glass melted, raw materials used, production equipment, melting conditions, and the like, and it is necessary for a person skilled in the art to be able to appropriately select various methods.

However, a method for reducing fine bubbles that does not have a problem in terms of standards has not been found in the conventional invention.

The present invention has been made in view of the above circumstances, and an object thereof is to obtain an optical glass which can suppress coloring of the glass due to platinum which is oxidized and dissolved in the glass during melting and can reduce generation of fine bubbles.

Means for solving the problems

The present inventors have made extensive and intensive studies to solve the above-mentioned problems and as a result, have found a process for producing an optical glass containing B₂O₃Component (A) and La₂O₃The addition of the reducing agent and chlorine to the raw materials of the component (a) can suppress coloration due to platinum which is oxidized and dissolved in the glass during the process of melting the glass, and can reduce the generation of fine bubbles.

Specifically, the present invention provides the following method.

(1) A process for producing an optical glass, which comprises melting a glass raw material,

the glass raw material contains, in terms of mass% in terms of oxides:

30.0-65.0% of La₂O₃The components of the components are mixed and stirred,

3.0 to 25.0% of B₂O₃The components of the components are mixed and stirred,

and, the method comprises adding a reducing agent and an antifoaming agent.

(2) The process for producing an optical glass as described in (1),

the glass raw material contains, in terms of mass% in terms of oxides:

SiO of 20.0% or less₂The components of the components are mixed and stirred,

TiO₂component (B) and Nb₂O₅Component (I) and WO₃At least one of the components.

(3) The process for producing an optical glass according to (1) or (2),

more than 0.01 percent of chlorine is added.

(4) The process for producing an optical glass according to any one of (1) to (3),

the optical glass has a platinum content of 8ppm or less.

ADVANTAGEOUS EFFECTS OF INVENTION

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 an optical glass including La₂O₃Component (A) and (B)₂O₃The addition of the reducing agent and chlorine to the raw materials of the component (a) can suppress coloration of the glass due to platinum which is oxidized and dissolved in the glass during the process of melting the glass, and can reduce the generation of fine bubbles.

Detailed Description

According to the method for producing an optical glass of the present invention, 30.0 to 65.0% by mass of La is contained in terms of oxides₂O₃Component (B) 3.0 to 25.0%₂O₃The reducing agent and chlorine are added to the raw materials of the glass of component (A), so that the optical glass can be obtained, wherein the coloration of the glass caused by platinum which is oxidized and dissolved in the glass in the process of melting the glass is inhibited, and the generation of fine bubbles is inhibited.

Embodiments of the optical glass and the method for producing an optical glass according to the present invention will be described in detail below. The present invention is not limited to the following embodiments, and can be carried out with appropriate modifications within the intended scope of the present invention. Note that, description of parts overlapping with the description may be omitted as appropriate, and this does not limit the interest of the invention.

[ glass composition ]

In the present specification, the content of each component is expressed as mass% of the total mass of the composition in terms of oxide unless otherwise specified. Here, the "composition in terms of oxide" means that, assuming that all of oxides, complex salts, metal fluorides, and the like used as raw materials of the glass composition components of the present invention are decomposed and converted into oxides during melting, the total mass of the generated oxides is referred to as 100 mass%, and the composition of each component contained in the glass is expressed.

La₂O₃Component (b) is an essential component in the glass of the present invention, and can increase the refractive index of the glass and can improve the chemical durability of the glass. In particular, by subjecting La₂O₃The content of the component (B) is 65.0% or less, and the devitrification resistance of the glass can be improved and the Abbe number can be increased. Thus, La₂O₃The upper limit of the content of the component (B) is preferably 65.0% or less, more preferably 62.0% or less, and most preferably 59.0% or less, based on the total mass of the glass in terms of oxide. On the other hand, La₂O₃The lower limit of the content of the component (b) is preferably 30.0% or more, more preferably 35.0% or more, and most preferably 40.0% or more, based on the total mass of the glass in terms of oxide.

B₂O₃Component (b) is an essential component in the glass of the present invention, and can promote stable glass formation and improve resistance to devitrification. In particular, by causing B to₂O₃The content of component (B) is less than 25.0%, and B can be inhibited₂O₃The refractive index is lowered by the components, and thus a high refractive index is easily obtained. Thus, B₂O₃The upper limit of the content of the component (b) is preferably 25.0% or less, more preferably 20.0% or less, and still more preferably 15.0% or less, based on the total mass of the glass in terms of oxide. On the other hand, B₂O₃The lower limit of the content of the component (b) is preferably 3.0% or more, more preferably 4.0% or more, and most preferably 5.0% or more, based on the total mass of the glass in terms of oxide.

Nb₂O₅When the content of the component (B) is more than 0%, the refractive index and Abbe number of the glass can be increased, and Nb is added₂O₅The content of the component (A) is 15.0% or less, and the stability of the glass and resistance to devitrification can be improved. Thus, Nb₂O₅The upper limit of the content of the component (B) is preferably 15.0% or less based on the total mass of the glass in terms of oxideMore preferably 13.0% or less, and most preferably 11.0% or less.

SiO₂When the content is more than 0%, the coloring of the glass can be reduced to improve the transmittance of visible light having a short wavelength, and the devitrification resistance of the glass can be improved by promoting the stable glass formation. In particular, by making SiO₂The content of the component is less than 20.0%, and SiO can be inhibited₂The refractive index is lowered by the component, and thus a high refractive index can be easily obtained. Thus, SiO₂The upper limit of the content of the component (b) is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 12.0% or less, and most preferably 9.0% or less, based on the total mass of the glass in terms of oxide. On the other hand, SiO₂The lower limit of the content of the component (b) is preferably more than 0%, more preferably 1.0% or more, and most preferably 2.0% or more, based on the total mass of the glass in terms of oxide.

TiO₂When the content of the component (b) is more than 0%, the refractive index of the glass can be increased and the chemical durability of the glass can be improved. In particular, by containing TiO₂Component (b), a high refractive index can be obtained. On the other hand, by making TiO₂The content of the component (A) is 25.0% or less, and devitrification due to an excessive content can be suppressed and deterioration of the transmittance can be suppressed. TiO 2₂The lower limit of the content of the component (b) is preferably more than 0%, more preferably 3.0% or more, and most preferably 6.0% or more, based on the total mass of the glass in terms of oxide. On the other hand, TiO₂The upper limit of the content of the component (B) is preferably 25.0% or less, more preferably 20.0% or less, and most preferably 15.0% or less, based on the total mass of the glass in terms of oxide.

Al₂O₃When the content of the component (b) is more than 0%, the chemical durability of the glass can be improved and the viscosity of the glass at the time of melting can be improved. In particular, by making Al₂O₃The content of the component is 10.0% or less, and can be increasedThe meltability of the glass and the tendency of the glass to devitrify can be reduced. Thus, Al₂O₃The upper limit of the content of the component (B) is preferably 10.0% or less, more preferably 5.0% or less, and most preferably 3.0% or less, based on the total mass of the glass in terms of oxide.

Y₂O₃When the content of the component (b) is more than 0%, the refractive index of the glass can be increased and the Abbe number can be increased. In particular, by making Y₂O₃The content of the component (A) is 15.0% or less, and the devitrification resistance of the glass can be improved and a desired optical coefficient can be obtained. Thus, Y₂O₃The upper limit of the content of the component (B) is preferably 15.0% or less, more preferably 12.0% or less, and most preferably 11.0% or less, based on the total mass of the glass in terms of oxide. On the other hand, Y₂O₃The lower limit of the content of the component (b) is preferably more than 0%, more preferably 3.0% or more, and most preferably 5.0% or more, based on the total mass of the glass in terms of oxide.

Gd₂O₃When the content of the component (b) is more than 0%, the refractive index of the glass can be increased and the Abbe number can be increased. In particular, by reacting Gd₂O₃The content of the component (A) is 20.0% or less, and the devitrification resistance of the glass can be improved and a desired optical coefficient can be obtained. Thus, Gd₂O₃The upper limit of the content of the component (b) is preferably 20.0% or less, more preferably 15.0% or less, still more preferably 10.0% or less, further preferably 5.0% or less, and most preferably 3.0% or less, based on the total mass of the glass in terms of oxide.

ZrO₂When the content of the component (b) is more than 0%, the coloring of the glass can be reduced, the transmittance of the glass to short-wavelength visible light can be improved, and stable glass formation can be promoted to improve the devitrification resistance of the glass. On the other hand, by causing ZrO₂The content of the component (A) is 15.0% or less, and ZrO can be reduced₂Devitrification due to excessive content of ingredients. Thus, ZrO₂The upper limit of the content of the component (B) is preferably 15.0% or less, more preferably 12.0% or less, and most preferably 9.0% or less, based on the total mass of the glass in terms of oxide. On the other hand, ZrO₂The lower limit of the content of the component (b) is preferably more than 0%, more preferably 1.0% or more, and most preferably 3.0% or more, based on the total mass of the glass in terms of oxide.

WO₃The component (b) is an optional component in the glass of the present invention, and when the content is more than 0%, the refractive index of the glass can be increased. In particular, by making WO₃The content of the component (A) is 15.0% or less, whereby the glass can have improved devitrification resistance and can be inhibited from lowering in transmittance to short-wavelength visible light. Thus, WO₃The upper limit of the content of the component (B) is preferably 15.0% or less, more preferably 10.0% or less, and most preferably 5.0% or less, based on the total mass of the glass in terms of oxide.

The ZnO component is an optional component in the glass of the present invention, and when the content is more than 0%, the liquidus temperature of the glass can be lowered and the devitrification resistance of the glass can be improved. In particular, by setting the content of the ZnO component to 15.0% or less, a high refractive index and low dispersion can be easily obtained. Therefore, the content of the ZnO component in the total mass of the glass in terms of oxides is preferably 15.0% or less, more preferably 12.0% or less, and most preferably 9.0% or less.

The MgO component is an arbitrary component in the glass of the present invention, and when the content is more than 0%, the liquidus temperature of the glass can be lowered, the devitrification resistance of the glass can be improved, and the transmittance for visible light is hardly lowered. In particular, by setting the content of the MgO component to 10.0% or less, a high refractive index and low dispersion can be easily obtained. Therefore, the upper limit of the content of the MgO component in relation to the total mass of the glass in terms of oxides is preferably 10.0% or less, more preferably 5.0% or less, and most preferably 3.0% or less.

The CaO component is an optional component in the glass of the present invention, and when the content is more than 0%, the liquidus temperature of the glass can be lowered and the devitrification resistance of the glass can be improved. In particular, by setting the content of the CaO component to 20.0% or less, a high refractive index and a low dispersion can be easily obtained, and the devitrification resistance and the decrease in chemical durability of the glass can be suppressed. Therefore, the upper limit of the content of the CaO component in terms of oxides in the total mass of the glass is preferably 20.0% or less, more preferably 15.0% or less, and most preferably 10.0% or less.

The SrO component is an optional component in the glass of the present invention, and when the content is more than 0%, the liquidus temperature of the glass can be lowered and the devitrification resistance of the glass can be improved. In particular, by setting the content of the SrO component to 10.0% or less, a high refractive index and low dispersion can be easily obtained, and the devitrification resistance and the reduction in chemical durability of the glass can be suppressed. Therefore, the upper limit of the content of the SrO component in the total mass of the glass in terms of oxides is preferably 10.0% or less, more preferably 5.0% or less, and most preferably 3.0% or less.

The BaO component is an arbitrary component in the glass of the present invention, and when the content is more than 0%, the refractive index of the glass is increased, the devitrification resistance of the glass is improved, and the transmittance for visible light is hardly lowered. In particular, by setting the content of the BaO component to 20.0% or less, a high refractive index and low dispersion can be easily obtained, and the resistance to devitrification and the decrease in chemical durability can be suppressed. Therefore, the upper limit of the content of the BaO component in the total mass of the glass in terms of oxides is preferably 20.0% or less, more preferably 15.0% or less, and most preferably 10.0% or less.

Li₂The O component is an optional component in the glass of the present invention, and when the content is more than 0%, the melting temperature of the glass can be lowered. In particular, by reacting Li₂The content of the O component is 10.0% or less, a high refractive index can be easily obtained, and the stability of the glass can be improved and the occurrence of devitrification and the like can be reduced. Thus, Li₂The upper limit of the content of the component O in the total mass of the glass in terms of oxide is preferably 10.0% or less, and more preferably 5.0% or less, and most preferably 3.0% or less.

Na₂The O component is an optional component in the glass of the present invention, and when the content is more than 0%, the melting temperature of the glass can be lowered. In particular, by reacting Na₂The content of the O component is 10.0% or less, a high refractive index can be easily obtained, and the stability of the glass can be improved and the occurrence of devitrification and the like can be reduced. Thus, Na₂The upper limit of the content of the component O in the total mass of the glass in terms of oxides is preferably 10.0% or less, more preferably 5.0% or less, and most preferably 3.0% or less.

K₂The O component is an optional component in the glass of the present invention, and when the content is more than 0%, the melting temperature of the glass can be lowered. In particular, by making K₂The content of the O component is 10.0% or less, a high refractive index can be easily obtained, and the stability of the glass can be improved and the occurrence of devitrification and the like can be reduced. Thus, K₂The upper limit of the content of the O component in the total mass of the glass in terms of oxide is preferably 10.0% or less, more preferably 5.0% or less, and still more preferably 3.0% or less.

Ta₂O₅When the content is more than 0%, the refractive index of the glass is increased and resistance to devitrification is improved. Ta₂O₅The upper limit of the content of the component (b) is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

P₂O₅When the content is more than 0%, the liquidus temperature of the glass can be lowered and the devitrification resistance can be improved. P₂O₅The upper limit of the content of the component (b) is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

GeO₂When the content is more than 0%, the refractive index of the glass is increased and high resistance to devitrification is improved. GeO₂The upper limit of the content of the component (C) is preferably 5.0% or less, more preferablyIt is preferably 3.0% or less, more preferably 1.0% or less, and still more preferably 0.5% or less.

Ga₂O₃When the content is more than 0%, the chemical durability of the glass can be improved and the devitrification resistance of the molten glass can be improved. Ga₂O₃The upper limit of the content of the component (b) is 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

Bi₂O₃The component is a component which can increase the refractive index and lower the glass transition point in the case where the content is more than 0%. Bi₂O₃The upper limit of the content of the component (b) is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

TeO₂The component is a component which can increase the refractive index and lower the glass transition point in the case where the content is more than 0%. TeO₂The upper limit of the content of the component (b) is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

SnO₂When the content is more than 0%, the component can reduce the oxidation of the molten glass to clarify the molten glass and can improve the visible light transmittance of the glass. SnO₂The upper limit of the content of the component (b) is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

The component F is a component which can improve the meltability of the glass when the content is more than 0%, but on the other hand, when the content is large, the component F volatilizes to cause devitrification. The upper limit of the content of the component F is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, and further preferably 0.5% or less.

Sb₂O₃The component (b) is a component capable of defoaming the molten glass when the content is more than 0%.

On the other hand, when Sb is₂O₃When the content of (b) is too large, the transmittance in the short wavelength region of the visible light region is deteriorated. Thus, Sb₂O₃The upper limit of the content of the component (b) is preferably 1.0% or less, more preferably 0.5% or less, and still more preferably 0.3% or less.

At Ln₂O₃When the sum (mass sum) of the contents of the components (in the formula, Ln is1 or more selected from the group consisting of La, Y, Gd, and Yb) is 30.0% or more and 65.0% or less, the devitrification resistance can be improved.

Thus, Ln₂O₃The lower limit of the sum of the components is preferably 30.0% or more, more preferably 32.0% or more, still more preferably 35.0% or more, still more preferably 38.0% or more, still more preferably 42.0% or more, still more preferably 45.0% or more, and still more preferably 47.5% or more.

Ln, on the other hand₂O₃The upper limit of the sum (mass sum) of the contents of the components is preferably 65.0% or less, more preferably 62.0% or less, and still more preferably 60.0% or less.

By making SiO₂Component (B)₂O₃Component (C) and Al₂O₃The total content of the components, i.e. mass and SiO₂+B₂O₃+Al₂O₃The content of the glass is 8.0% or more and 28.0% or less, and the stability of the glass can be improved.

Therefore, mass and SiO₂+B₂O₃+Al₂O₃The lower limit is preferably 8.0% or more, more preferably 9.0% or more, still more preferably 10.0% or more, further preferably 11.5% or more, and further preferably 13.0% or more.

On the other hand, mass and SiO₂+B₂O₃+Al₂O₃The upper limit thereof is preferably 28.0% or less, more preferably 26.0% or less, and still more preferably 24.0% or less.

By making Ln₂O₃The sum of the contents of the components and SiO₂Component (B)₂O₃Component (C) and Al₂O₃Total of ingredientsRatio of quantity to quantity, i.e. mass ratio Ln₂O₃/(SiO₂+B₂O₃+Al₂O₃) Being 6.0 or less, resistance to devitrification can be improved.

Therefore, mass ratio Ln₂O₃/(SiO₂+B₂O₃+Al₂O₃) The upper limit thereof is preferably 6.0 or less, more preferably 5.5 or less, still more preferably 5.0 or less, and further preferably 4.5 or less.

By making TiO₂Component (B) and Nb₂O₅Component (I) and WO₃The total content of the components, i.e. mass and TiO₂+Nb₂O₅+WO₃5.0% or more and 35.0% or less, and the refractive index (n) can be increased_d) And the reduction color due to the high refractive index component can be reduced.

Therefore, mass and TiO₂+Nb₂O₅+WO₃The lower limit is preferably 5.0% or more, more preferably 7.0% or more, still more preferably 12.0% or more, further preferably 15.5% or more, and further preferably 20.0% or more.

On the other hand, mass and TiO₂+Nb₂O₅+WO₃The upper limit thereof is preferably 35.0% or less, more preferably 30.0% or less, and still more preferably 27.0% or less.

In the present invention, the following components are contained preferably in a total amount of 95.0% or more, more preferably 97.0% or more, and still more preferably 98.0% or more.

La₂O₃Component (A) Y₂O₃Component (b) Gd₂O₃Component Yb₂O₃Component (B) SiO₂Component B₂O₃Component (C) Al₂O₃Component (C) TiO₂Component (B) Nb₂O₅Component (A) WO₃Component (B) of Bi₂O₃Component (b), ZnO component, ZrO₂Component (B), MgO component, CaO component, SrO component, BaO component, Li₂O component, Na₂Component O, K₂O component, Ta₂O₅And (3) components.

< about an ingredient which should not be contained >

Next, components that should not be contained in the optical glass of the present invention and components that are preferably not contained therein will be described.

Other components may be added as necessary within a range not impairing the characteristics of the glass of the present invention. However, in addition to Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, various transition metal components such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, if contained individually or in a composite form, have a property of coloring the glass even if contained in a small amount and absorbing light of a specific wavelength in a visible light region, and therefore, it is preferable that the optical glass, particularly, using a wavelength in the visible light region, is substantially not contained.

Lead compounds such As PbO and As₂O₃The arsenic compound is preferably not substantially contained, that is, not contained at all except for unavoidable mixing, because it is a component having a high environmental load.

Further, each of Th, Cd, Tl, Os, Be and Se components tends to Be avoided as harmful chemical substances in recent years, and measures for environmental countermeasures are required not only in the glass production step but also in the processing step and the disposal after the product formation. Therefore, when importance is attached to the environmental influence, it is preferable that these components are not substantially contained.

The optical glass of the present invention is characterized by adding a reducing agent. By adding the reducing agent, mixing of platinum into the glass can be suppressed, and the transmittance can be improved. The upper limit of the content of the reducing agent is preferably 3.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less, and most preferably 0.8% or less in terms of an incremental ratio (a ratio of an amount which is additionally increased when the total ratio of the glass components is 100%). On the other hand, the lower limit of the content of the reducing agent is preferably 0.01% or more, more preferably 0.05% or more, still more preferably 0.1% or more, further preferably 0.2% or more, and most preferably 0.3% or more in terms of an incremental ratio. Examples of the reducing agent include simple substances such as carbon and S, organic compounds such as sucrose, and raw materials such as ammonium sulfate that generate a reducing gas upon thermal decomposition.

The optical glass of the present invention is characterized by adding chlorine. In an optical glass in which a platinum crucible is frequently used, chlorine reacts with platinum to form platinum chloride, and therefore chlorine is a component that conversely causes an increase in the amount of platinum.

In the present invention, chlorine is added together with a reducing agent, whereby mixing of platinum can be suppressed and generation of fine bubbles can be suppressed. The upper limit of the chlorine content is preferably 2.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, still more preferably 0.4% or less, and most preferably 0.3% or less in terms of an incremental ratio. On the other hand, the lower limit of the chlorine content is preferably 0.01% or more, more preferably 0.03% or more, still more preferably 0.05% or more, further preferably 0.08% or more, and most preferably 0.1% or more in terms of an incremental ratio. By adjusting the chlorine content, the optical properties and the transmittance lambda can be controlled without affecting₇₀In the case of (3), fine bubbles are reduced. The chlorine is not particularly limited, and examples thereof include a chloride raw material and a chlorinated gas.

[ production method ]

The optical glass of the present invention can be produced, for example, as follows. That is, the above raw materials are uniformly mixed so that the respective components are within the predetermined content range, and the resulting mixture is placed in a platinum crucible, and can be produced by a known glass production method according to the degree of difficulty in melting and the melting scale of the glass raw materials. The time at which the reducing agent and chlorine are added may be a method of adding the reducing agent and chlorine as raw materials, or a method of blowing a reducing atmosphere or chlorine in a melting step of the glass raw material.

[ Properties ]

The optical glass of the present invention has a refractive index (n)_d) Preferably 1.75000 or more. Refractive index (n) of glass of the present invention_d) The lower limit thereof is preferably 1.75000 or more, more preferably 1.80000 or more, and still more preferably 1.85000 or more. The refractive index (n)_d) The upper limit thereof is preferably 2.10000 or less, more preferably 2.07000 or less, and still more preferably 2.05000 or less. Further, Abbe of the glass of the present inventionNumber (v)_d) The lower limit thereof is preferably 20.00 or more, more preferably 23.00 or more, and still more preferably 25.00 or more. The Abbe number (v)_d) The upper limit thereof is preferably 45.00 or less, more preferably 40.00 or less, and still more preferably 37.00 or less.

The optical glass of the present invention is preferably less colored because of high visible light transmittance, particularly high transmittance of light on the short wavelength side of visible light.

A sample of the glass of the present invention having a thickness of 10mm shows the shortest wavelength (. lamda.) at a spectral transmittance of 70%₇₀) The upper limit is preferably 470nm or less, more preferably 450nm or less, still more preferably 430nm or less, and further preferably 420nm or less.

The optical glass of the present invention preferably has a small platinum content and thus is less colored.

In particular, the upper limit of the platinum content in the optical glass of the present invention is preferably 8ppm or less, more preferably 7ppm or less, and still more preferably 6ppm or less. This can suppress coloration due to platinum and can improve the transparency of the glass to visible light, and therefore the optical glass can be preferably used as an optical element that transmits light, such as a lens.

The optical glass of the present invention is characterized by containing few fine bubbles. In the present invention, fine bubbles mean bubbles having a diameter of less than 30 μm.

In particular, the number of fine bubbles in the optical glass of the present invention is preferably 53.5 or less, more preferably 45.0 or less, still more preferably 35.0 or less, and further preferably 25.0 or less. The number of fine bubbles was calculated by using a glass having a length of 1.4cm, a width of 2.4cm and a thickness of 1.0 cm. Thereby, deterioration of internal quality can be suppressed, and thus the optical glass can be preferably used as an optical element that transmits light such as a lens.

[ preform and optical element ]

The glass shaped body can be produced from the optical glass produced by, for example, polishing or press molding such as reheat press molding or precision press molding. That is, the glass molded body can be produced in the following manner: machining optical glass by grinding, polishing and the like to produce a glass molded body; or, a preform for press molding is made of optical glass, and after the preform is subjected to reheat press molding, a glass molded body is produced by grinding; alternatively, a glass shaped body or the like is produced by precision press molding of a preform obtained by polishing or a preform obtained by known float molding or the like. The method for producing the glass shaped material is not limited to the above-mentioned methods.

Thus, the optical glass of the present invention can be used in various optical elements and optical designs. Among these, it is preferable to form a preform from the optical glass of the present invention, and to use the preform for reheat press molding, precision press molding, or the like to produce an optical element such as a lens or a prism. This enables the formation of a preform having a large diameter, which enables the size of an optical element to be increased, and enables high-precision and high-definition image forming characteristics and projection characteristics to be achieved when the preform is used in an optical device such as a camera or a projector.

[ examples ] A method for producing a compound

Compositions of examples and comparative examples of the glasses of the present invention, and refractive indices (n) of these glasses_d) Abbe number (v)_d) The wavelengths (lambda) at which the spectral transmittances are 70% and 5%, respectively₇₀、λ₅) The results of (a) and (b) are shown in the table, together with the platinum content (ppm) in the glass and the measured value of bubbles (blisters) in the glass. The following embodiments are intended to be illustrative only and are not intended to be limiting.

The glasses of examples and comparative examples of the present invention were prepared by selecting, as raw materials of each component, a high-purity raw material, a reducing agent, and a chloride raw material, which were used for general optical glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphoric acid compounds, and then weighing and uniformly mixing these raw materials so as to obtain the composition ratios of each example shown in the table and the ratio of the reducing agent to chlorine, and then charging the mixture into a platinum crucible, melting the mixture for 30 minutes to 2 hours at 1100 to 1500 ℃ using an electric furnace according to the degree of difficulty of melting the glass raw material, stirring the mixture to homogenize the mixture, casting the homogenized mixture into a mold, and gradually cooling the cast mixture.

In examples and comparative examples of the glass of the present invention, reducing agents, chlorine and sulfuric acid were added in amounts shown in the table. Here, sulfuric acid functions as an antifoaming agent.

Refractive index (n) of glasses of examples and comparative examples_d) In accordance with JIS B7071-2: 2018, as measured on the d-line (587.56nm) of a helium lamp. In addition, Abbe number (. nu.)_d) The refractive index of d-line and the refractive index (n) of F-line (486.13nm) of hydrogen lamp were used_F) Refractive index (n) to C line (656.27nm)_C) According to Abbe number (v)_d)＝[(n_d－1)/(n_F－n_C)]The equation (2) is calculated. Then, the refractive index (n) is calculated_d) And Abbe number (v)_d) To find the relation n_d＝－a×ν_dAnd the intercept b at which the slope a is 0.01 in + b.

The transmittances of the glasses of examples and comparative examples were measured according to the Japanese society for optical glass Standard JOGIS 02-2003. In the present invention, the presence or absence and the degree of coloring of the glass can be determined by measuring the transmittance of the glass. Specifically, the light transmittance (spectral transmittance) and λ were determined by measuring the spectral transmittance of 200nm to 800nm of a facing parallel polishing member having a thickness of 10. + -. 0.1mm in accordance with JIS Z8722₇₀(wavelength at a transmittance of 70%).

The platinum content (ppm) in the glasses of examples and comparative examples was measured by using ICP-MS (inductively coupled plasma mass spectrometer).

The bubbles in the glasses of examples and comparative examples were measured based on "method for measuring bubbles in optical glass" of japanese optical glass industry association standard JOGIS 12-2012.

The number of fine bubbles in the glasses of examples and comparative examples was calculated by using a glass sample having a length of 1.4cm, a width of 2.4cm and a thickness of 1.0cm, and using a stereomicroscope SZ61 manufactured by olympus corporation.

Glass samples having fine bubbles with a diameter of less than 30 μm of 53.5 or less are referred to as "good" and glass samples having a fine bubble number of more than 53.5 are referred to as "poor".

[ TABLE 1 ]

Glass of the invention, lambda, of the examples of the invention₇₀(wavelength at a transmittance of 70%) of 450nm or less. In more detail, the glass of the invention, lambda, of the examples of the invention₇₀(wavelength at a transmittance of 70%) of 420nm or less. On the other hand, the glass of comparative example B, containing only chlorine,. lambda.₇₀Greater than 450 nm. Therefore, it is found that the optical glass of the examples of the present invention is less likely to be colored than the glass of the comparative example.

The optical glasses of the examples of the present invention each had a platinum content of 8ppm or less. On the other hand, the glass of comparative example B containing only chlorine had a platinum content of more than 8 ppm. Therefore, it is understood that the glasses of examples of the present invention have a smaller platinum content than the glasses of comparative examples.

The optical glasses of the examples of the present invention were all rated at 1 bubble, and it is understood that the optical glasses of the examples of the present invention have fewer fine bubbles than the glasses of the comparative examples and have better internal quality.

Therefore, it is understood that the optical glass of the examples of the present invention can suppress the coloring of the glass due to platinum which is oxidized and dissolved in the glass in the process of melting the glass and the generation of fine bubbles by adding the reducing agent and chlorine.

Although the present invention has been described in detail for the purpose of illustration, the present embodiment is for illustrative purposes only, and it is to be fully understood that many modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. A method for producing an optical glass, comprising melting glass raw material, wherein the glass raw material, in terms of mass % in terms of oxide, contains:

30.0-65.0% La ₂ O ₃ composition,

3.0 to 25.0% B ₂ O ₃ composition,

Also, the method includes adding a reducing agent and chlorine.

2. The method for producing an optical glass according to claim 1, wherein

The glass raw material, in terms of mass % in terms of oxides, contains:

20.0% or less _SiO2 composition,

At least one or more of the TiO ₂ component, the Nb ₂ O ₅ component, and the WO ₃ component.

3. The manufacturing method of optical glass according to claim 1 or 2, wherein,

Add more than 0.01% chlorine.

4 . The method for producing an optical glass according to claim 1 , wherein the optical glass has a platinum content of 8 ppm or less. 5 .