Optical glass

Abstract

To provide a method for producing optical glass which has high transmittance of light on the short wavelength side of visible light and improved defoaming property while suppressing coloration of glass due to platinum oxidized and dissolved in the glass during the process of melting the glass. [Solution] A method for producing optical glass, comprising the steps of: mixing raw materials; and melting glass without supplying moisture, wherein the raw materials contain a reducing agent.

Description

[Technical Field]

[0001] This invention relates to optical glass. [Background technology]

[0002] In recent years, the digitalization and high-definition capabilities of devices using optical systems have progressed rapidly. In the fields of various optical equipment, such as photographic equipment like digital cameras and video cameras, and image playback (projection) equipment like projectors and projection televisions, there is a growing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, thereby making the entire optical system lighter and smaller.

[0003] Platinum, commonly used in crucibles and other components during the manufacturing of optical glass, has a high melting point exceeding 1700°C, making it suitable for melting glass. However, it is also prone to degradation through reaction with oxygen, resulting in oxidized platinum or platinum ions dissolving into the glass. This dissolved platinum absorbs visible light, leading to discoloration of the final optical glass product. In response to this, Patent Document 1 describes a glass in which reduction of reduction coloration and improved degassing properties are achieved by supplying water vapor during the melting process or by bubbling water vapor into the molten material. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-19050 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, in the glass disclosed in Patent Document 1, water must be added in the melting process, which complicates the glass manufacturing process. Further, for the glass produced by adding a reducing agent, it was difficult to obtain an optical glass with a high visible light transmittance, a reduced reduction color, and improved defoaming properties, unless the content of TiO2 was reduced or the once-obtained glass was reheated.

[0006] The present invention has been made in view of the above problems, and an object thereof is to obtain an optical glass with a high visible light transmittance and improved defoaming properties while suppressing the coloring of the glass due to platinum dissolved in the glass by oxidation during the melting process by an extremely simple method.

Means for Solving the Problems

[0007] As a result of intensive test studies to solve the above problems, the present inventors have found an extremely simple method of suppressing the coloring of glass due to platinum dissolved in the glass by oxidation during the melting process, while obtaining an optical glass with a high visible light transmittance, by including a reducing agent in the raw materials of lanthanum-based and Si-Ti-based glass in an environment where no moisture is added. What can be obtained was found.

[0008] Further, as a result of intensive test studies to solve the above problems, the present inventors have found that an optical glass with improved defoaming properties can be obtained by an extremely simple method of including a reducing agent and a defoaming agent in the raw materials of lanthanum-based and Si-Ti-based glass in an environment where no moisture is added, and have thus completed the present invention. Specifically, the present invention provides the following.

[0009] (1) In mass%, 、 the Nb2O5 component is 15% or less or the TiO2 component is 40% or less 、 substantially contains the PbO component Without doing so, Refractive index (n d ) is 1.75 or higher, Optical glass characterized by containing 1% or less of a reducing agent in its raw materials (however, the glass is melted) (Excluding the supply of moisture during the process.)

[0010] (2) In mass%, La 2 O 3 Ingredients: 30-65% B 2 O 3 Ingredients 1-25%, SiO 2 Ingredients 15% or less, TiO 2 Ingredients 25% or less, Y 2 O 3 Ingredients 15% or less, The optical glass described in (1).

[0011] (3) In mass%, SiO 2 Ingredients 5-75%, The optical glass described in (1).

[0012] (4) The method for producing an optical glass according to (1) or (2), wherein the optical glass is in mass % based on the total mass of the glass in terms of oxide composition, SiO2 component: 5 to 75%, TiO2 component: 3 to 40%, and characterized by containing, a method for producing an optical glass.

Advantages of the Invention

[0013] The present invention has been made in view of the above problems, and the object thereof is to obtain an optical glass having a high transmittance of light on the short wavelength side of visible light and improved defoaming properties while suppressing the coloring of the glass due to platinum dissolved in the glass by oxidation during the melting process of the glass by an extremely simple method.

Embodiments for Carrying Out the Invention

[0014] According to the present invention, the lanthanum-based glass contains 30-65% La2O3, 1-25% B2O3, 15% or less Nb2O5, 15% or less SiO2, 25% or less TiO2, and 15% or less Y2O3 by mass%, and the Si-Ti-based glass contains 5-75% SiO2 and 3-40% TiO2 by mass%, and by adding a reducing agent to the glass raw materials and mixing them, and melting the glass without supplying water, it is possible to obtain optical glass with high transmittance of short-wavelength visible light and improved degassing properties while suppressing discoloration of the glass due to platinum that oxidizes and dissolves into the glass during the melting process.

[0015] The optical glass of the present invention will now be described in detail. The present invention is not limited in any way to the embodiments described below, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, explanations may be omitted where necessary to avoid repetition, but this does not limit the spirit of the invention.

[0016] [Glass components] The optical glass of the present invention has two embodiments: a first glass and a second glass. The composition range of each component constituting the first glass and the second glass is described below. In this specification, unless otherwise specified, the content of each component is expressed as a mass % of the total mass of the oxide-equivalent composition. Here, "oxide-equivalent composition" is the composition expressed by assuming that the oxides, composite salts, metal fluorides, etc., used as raw materials for the glass components of the present invention are all decomposed into oxides during melting, and the total mass of the resulting oxides is set to 100% by mass, with each component contained in the glass being expressed.

[0017] <Regarding the composition of the first glass> The La2O3 component is an essential component in the first glass, as it increases the refractive index of the glass and improves its chemical durability. In particular, by reducing the La2O3 content to 65% or less, the Abbe number can be increased while improving the devitrification resistance of the glass. Therefore, the La2O3 content relative to the total mass of the glass in terms of oxide composition is preferably limited to 65% or less, more preferably to 62% or less, and most preferably to 59% or less. On the other hand, the La2O3 content relative to the total mass of the glass in terms of oxide composition is preferably limited to 30% or more, more preferably to 35% or more, and most preferably to 40% or more. The La2O3 component can be incorporated into the glass using raw materials such as La2O3, La(NO3)3·XH2O (where X is any integer), etc.

[0018] The B2O3 component is an essential component in the first glass, as it promotes the formation of stable glass and enhances devitrification resistance. In particular, by limiting the B2O3 content to 25% or less, the decrease in refractive index due to the B2O3 component is suppressed, making it easier to obtain a high refractive index. Therefore, the B2O3 content relative to the total mass of glass in terms of oxide composition is preferably 25% or less, more preferably 20% or less, and even more preferably 15% or less as the upper limit. On the other hand, the B2O3 content relative to the total mass of glass in terms of oxide composition is preferably 1% or more, more preferably 3% or more, and most preferably 5% or more as the lower limit. The B2O3 component can be incorporated into the glass using raw materials such as H3BO3, Na2B4O7, Na2B4O7·10H2O, BPO4, etc.

[0019] The Nb2O5 component, when present in amounts exceeding 0%, increases the refractive index and Abbe number of the glass. On the other hand, by limiting the Nb2O5 content to 15% or less, the stability of the glass and its resistance to devitrification can be improved. Therefore, the Nb2O5 content relative to the total mass of the glass in terms of oxide composition is preferably 15% or less, more preferably 13% or less, and most preferably 11% or less. The Nb2O5 component can be incorporated into the glass using, for example, Nb2O5 as a raw material.

[0020] The SiO2 component, when present in amounts exceeding 0%, is an optional component in the first glass that reduces the coloration of the glass, thereby increasing the transmittance to short-wavelength visible light, and also promotes stable glass formation, thereby improving the devitrification resistance of the glass. In particular, by limiting the SiO2 component content to 15% or less, the decrease in refractive index due to the SiO2 component is suppressed, making it easier to obtain a high refractive index. Therefore, the SiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 15% or less, more preferably 12% or less, and most preferably 9% or less as the upper limit. On the other hand, the SiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably more than 0%, more preferably 1% or more, and most preferably 2% or more as the lower limit. The SiO2 component can be incorporated into the glass using raw materials such as SiO2, K2SiF6, Na2SiF6, etc.

[0021] The TiO2 component, when present in amounts exceeding 0%, increases the refractive index and Abbe number of the glass, and also enhances the chemical durability of the glass. It is an optional component of the first glass. In particular, including the TiO2 component allows for obtaining a high refractive index and a desired Abbe number. On the other hand, by limiting the TiO2 component content to 25% or less, devitrification due to excessive content can be suppressed, and the deterioration of transmittance can be reduced. From the viewpoint of particularly increasing the Abbe number of the glass, the TiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably greater than 0%, more preferably 3% or more, and most preferably 6% or more as the lower limit. On the other hand, the TiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 25% or less, more preferably 20% or less, and most preferably 15% or less as the upper limit. The TiO2 component can be incorporated into the glass using, for example, TiO2 as a raw material.

[0022] The Al2O3 component, when present in amounts greater than 0%, improves the chemical durability of the glass while increasing its viscosity during melting, and is an optional component in the first glass. In particular, by reducing the Al2O3 content to 10% or less, the meltability of the glass can be improved while weakening the devitrification tendency of the glass. Therefore, the Al2O3 content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The Al2O3 component can be incorporated into the glass using raw materials such as Al2O3, Al(OH)3, AlF3, etc.

[0023] The Y2O3 component, when present in amounts exceeding 0%, increases the refractive index of the glass and raises the Abbe number, and is an optional component in the first glass. In particular, by limiting the Y2O3 component content to 15% or less, it is possible to obtain the desired optical number while improving the devitrification resistance of the glass. Therefore, the Y2O3 component content relative to the total mass of the glass in terms of oxide composition is preferably 15% or less, more preferably 12% or less, and most preferably 11% or less as the upper limit. On the other hand, the Y2O3 component content relative to the total mass of the glass in terms of oxide composition is preferably more than 0%, more preferably 3% or more, and most preferably more than 5% as the lower limit. The Y2O3 component can be incorporated into the glass using raw materials such as Y2O3 and YF3.

[0024] The Gd2O3 component, when present in amounts greater than 0%, increases the refractive index of the glass and raises the Abbe number; it is an optional component in the first glass. In particular, by reducing the Gd2O3 content to 20% or less, it is possible to obtain the desired optical number while improving the devitrification resistance of the glass. The Gd2O3 component can be incorporated into the glass using raw materials such as Gd2O3 and GdF3.

[0025] The ZrO2 component, when present in amounts exceeding 0%, reduces the coloration of the glass, increases the transmittance to short-wavelength visible light, and promotes stable glass formation, thereby improving the glass's resistance to devitrification. It is an optional component in the first glass. On the other hand, by limiting the ZrO2 content to 15% or less, devitrification due to excessive ZrO2 content can be reduced. Therefore, the ZrO2 content relative to the total mass of the glass in terms of oxide composition is preferably capped at 15%, more preferably 12%, and most preferably 9%. Conversely, the ZrO2 content relative to the total mass of the glass in terms of oxide composition is preferably capped at over 0%, more preferably 1% or more, and most preferably 3% or more. The ZrO2 component can be incorporated into the glass using, for example, ZrO2, ZrF4, etc., as raw materials.

[0026] The WO3 component, when present in amounts exceeding 0%, increases the refractive index of the glass and raises the Abbe number, and is an optional component in the first glass. In particular, by limiting the WO3 component content to 15% or less, the devitrification resistance of the glass can be improved, and the decrease in the transmittance of the glass to short-wavelength visible light can be suppressed. Therefore, the WO3 component content relative to the total mass of the glass in terms of oxide composition is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less.

[0027] The ZnO component, when present in amounts exceeding 0%, lowers the liquidus temperature of the glass and enhances its resistance to devitrification; it is an optional component in the first glass. In particular, by limiting the ZnO content to 15% or less, it is easier to obtain a high refractive index and low dispersion. Therefore, the ZnO content relative to the total mass of the glass in terms of oxide composition is preferably 15% or less, more preferably 12% or less, and most preferably 9% or less. The ZnO component can be incorporated into the glass using raw materials such as ZnO and ZnF2.

[0028] The MgO component is an optional component in the first glass that, when present in amounts greater than 0%, lowers the liquidus temperature of the glass and enhances its resistance to devitrification, and also makes it less likely to reduce the transmittance to visible light. In particular, by limiting the MgO component content to 10% or less, it is easier to obtain a high refractive index and low dispersion. Therefore, the MgO component content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The MgO component can be incorporated into the glass using raw materials such as MgCO3 and MgF2.

[0029] The CaO component, when present in amounts exceeding 0%, lowers the liquidus temperature of the glass and enhances its devitrification resistance; it is an optional component in the first glass. In particular, by limiting the CaO content to 20% or less, it is easier to obtain a high refractive index and low dispersion, while suppressing a decrease in the glass's devitrification resistance and chemical durability. Therefore, the CaO content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 15% or less, and most preferably 10% or less. The CaO component can be incorporated into the glass using raw materials such as CaCO3 and CaF2.

[0030] The SrO component, when present in amounts greater than 0%, lowers the liquidus temperature of the glass and enhances its devitrification resistance; it is an optional component in the first glass. In particular, by limiting the SrO content to 10% or less, it is easier to obtain a high refractive index and low dispersion, and the decrease in the glass's devitrification resistance and chemical durability can be suppressed. Therefore, the SrO content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The SrO component can be incorporated into the glass using raw materials such as Sr(NO3)2 and SrF2.

[0031] The BaO component, when present in amounts exceeding 0%, increases the refractive index of the glass, enhances its resistance to devitrification, and minimizes the decrease in transmittance to visible light. It is an optional component in the first glass. In particular, by limiting the BaO component content to 20% or less, it is possible to easily obtain a high refractive index and low dispersion, while suppressing a decrease in devitrification resistance and chemical durability. Therefore, the BaO component content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 15% or less, and most preferably 10% or less. The BaO component can be incorporated into the glass using raw materials such as BaCO3, Ba(NO3)2, BaF2, etc.

[0032] The Li2O component, when present in amounts exceeding 0%, lowers the melting temperature of the glass and is an optional component in the first glass. In particular, by limiting the Li2O content to 10% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the content of the Li2O component relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The Li2O component can be incorporated into the glass using raw materials such as Li2CO3, LiNO3, and LiF.

[0033] The Na2O component, when present in amounts greater than 0%, lowers the melting temperature of the glass and is an optional component in the first glass. In particular, by limiting the Na2O content to 10% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the content of the Na2O component relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The Na2O component can be incorporated into the glass using raw materials such as Na2CO3, NaNO3, NaF, Na2SiF6, etc.

[0034] The K2O component, when present in amounts greater than 0%, lowers the melting temperature of the glass and is an optional component in the first glass. In particular, by limiting the K2O content to 10% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the K2O content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and even more preferably 3% or less. The K2O component can be incorporated into the glass using raw materials such as K2CO3, KNO3, KF, KHF2, K2SiF6, etc.

[0035] The Sb2O3 component is an optional component in the first glass, as it increases the transmittance of the glass to short-wavelength visible light and also has a degassing effect when the glass is melted. Here, by limiting the Sb2O3 content to 0.1% or less, it is possible to suppress discoloration, especially in high refractive index glass. Therefore, the content of the Sb2O3 component relative to the total mass of the glass in terms of oxide composition is limited to 0.1% or less, preferably 0.05% or less.

[0036] The SnO2 component, when present in amounts exceeding 0%, acts as a defoaming agent, clarifying the molten glass, and is an optional component of the first glass. In particular, the inclusion of the SnO2 component provides the aforementioned effect and makes devitrification of the glass less likely. Therefore, the SnO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 2% or less, more preferably 1% or less. The SnO2 component can be incorporated into the glass using raw materials such as SnO, SnO2, SnF2, SnF4, etc.

[0037] <Regarding the second component of glass> The SiO2 component, when present in a concentration of 5% or more, reduces the coloration of the glass, thereby increasing its transmittance to short-wavelength visible light, and promotes stable glass formation, thereby improving the glass's resistance to devitrification. It is an essential component in the second type of glass. In particular, by keeping the SiO2 component content at 75% or less, the decrease in refractive index due to the SiO2 component is suppressed, making it easier to obtain a high refractive index. Therefore, the upper limit of the SiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 75% or less, more preferably 73% or less, and most preferably 71% or less. On the other hand, the lower limit of the SiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 5% or more, more preferably 6% or more, and most preferably 7% or more. The SiO2 component can be incorporated into the glass using raw materials such as SiO2, K2SiF6, Na2SiF6, etc.

[0038] The TiO2 component, when present in a concentration of 3% or more, increases the refractive index and Abbe number of the glass, and also enhances its chemical durability. It is an essential component of the second type of glass. In particular, including the TiO2 component allows for obtaining a high refractive index and a desired Abbe number. On the other hand, by keeping the TiO2 component content below 40%, devitrification due to excessive content can be suppressed, and the deterioration of transmittance can be minimized. Therefore, the TiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 40% or less, more preferably 38% or less, and most preferably 35% or less. On the other hand, from the viewpoint of particularly increasing the Abbe number of the glass, the TiO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 3% or more, more preferably 4% or more, and most preferably 5% or more. The TiO2 component can be incorporated into the glass using, for example, TiO2 as a raw material.

[0039] The Nb2O5 component is a component that increases the refractive index and Abbe number of the glass, and is an optional component of the second glass. In particular, by including the Nb2O5 component, a high refractive index and a desired Abbe number can be obtained. On the other hand, by reducing the Nb2O5 component content to 25% or less, the stability of the glass can be increased, thereby improving its resistance to devitrification. Therefore, the Nb2O5 component content relative to the total mass of the glass in terms of oxide composition is preferably 1% or more, more preferably 2% or more, most preferably 3% or more as the lower limit, preferably 25% or less, more preferably 22% or less, and most preferably 19% or less as the upper limit. The Nb2O5 component can be incorporated into the glass using, for example, Nb2O5 as a raw material.

[0040] The B2O3 component, when present in amounts exceeding 0%, promotes the formation of stable glass and enhances devitrification resistance; it is an optional component in the second glass. In particular, by limiting the B2O3 content to 20% or less, the decrease in refractive index due to the B2O3 component is suppressed, making it easier to obtain a high refractive index. Therefore, the content of the B2O3 component relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 17% or less, and even more preferably 15% or less. The B2O3 component can be incorporated into the glass using raw materials such as H3BO3, Na2B4O7, Na2B4O7·10H2O, BPO4, etc.

[0041] The BaO component, when present in a concentration exceeding 0%, increases the refractive index of the glass, enhances its resistance to devitrification, and minimizes the decrease in transmittance to visible light. It is an optional component in the second glass. In particular, by limiting the BaO component content to 25% or less, it is possible to easily obtain a high refractive index and low dispersion, while suppressing a decrease in devitrification resistance and chemical durability. Therefore, the BaO component content relative to the total mass of the glass in terms of oxide composition is preferably 25% or less, more preferably 23% or less, and most preferably 20% or less as the upper limit. On the other hand, the BaO component content relative to the total mass of the glass in terms of oxide composition is preferably more than 0%, more preferably 3% or more, even more preferably 5% or more, and most preferably 8% or more as the lower limit. The BaO component can be incorporated into the glass using raw materials such as BaCO3, Ba(NO3)2, BaF2, etc.

[0042] The Na2O component, when present in amounts exceeding 0%, lowers the melting temperature of the glass and is an optional component in the second glass. In particular, by limiting the Na2O content to 20% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the Na2O content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 17% or less, and most preferably 14% or less as the upper limit. On the other hand, the Na2O content relative to the total mass of the glass in terms of oxide composition is preferably more than 0%, more preferably 3% or more, even more preferably 5% or more, and most preferably 8% or more as the lower limit. The Na2O component can be incorporated into the glass using raw materials such as Na2CO3, NaNO3, NaF, Na2SiF6, etc.

[0043] The Al2O3 component, when present in amounts greater than 0%, improves the chemical durability of the glass while increasing its viscosity during melting, and is a second optional component in the glass. In particular, by reducing the Al2O3 content to 10% or less, the meltability of the glass can be improved while weakening the devitrification tendency of the glass. Therefore, the Al2O3 content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The Al2O3 component can be incorporated into the glass using raw materials such as Al2O3, Al(OH)3, AlF3, etc.

[0044] The La2O3 component, when present in amounts exceeding 0%, increases the refractive index of the glass and improves its chemical durability; it is a second optional component in the glass. In particular, by reducing the La2O3 content to 20% or less, the Abbe number can be increased while improving the glass's resistance to devitrification. Therefore, the La2O3 content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 17% or less, and most preferably 15% or less. The La2O3 component can be incorporated into the glass using raw materials such as La2O3, La(NO3)3·XH2O (where X is any integer), etc.

[0045] The Y2O3 component, when present in amounts greater than 0%, increases the refractive index of the glass and increases the Abbe number; it is a second optional component in the glass. In particular, by limiting the Y2O3 content to 30% or less, it is possible to obtain the desired optical number while improving the devitrification resistance of the glass. Therefore, the content of the Y2O3 component relative to the total mass of the glass in terms of oxide composition is preferably 30% or less, more preferably 20% or less, even more preferably 17% or less, and most preferably 14% or less. The Y2O3 component can be incorporated into the glass using raw materials such as Y2O3 and YF3.

[0046] The Gd2O3 component, when present in amounts greater than 0%, increases the refractive index of the glass and increases the Abbe number; it is a second optional component in the glass. In particular, by limiting the Gd2O3 content to 20% or less, it is possible to obtain the desired optical number while improving the devitrification resistance of the glass. Therefore, the Gd2O3 content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 17% or less, and most preferably 14% or less. The Gd2O3 component can be incorporated into the glass using raw materials such as Gd2O3 and GdF3.

[0047] Yb2O3 is a component that, when present in amounts greater than 0%, enhances devitrification resistance while maintaining a high refractive index and high Abbe number, and is an optional component in the second glass. By reducing the Yb2O3 content to 10% or less, devitrification due to excessive Yb2O3 content can be reduced, and the material cost and specific gravity of the glass can be reduced. This also suppresses the increase in the glass transition temperature and flexure temperature. Therefore, the Yb2O3 content is preferably 10% or less, more preferably 5% or less, more preferably 2.5% or less, and still preferably 1% or less as the upper limit. Yb2O3 can be obtained as a raw material from Yb2O3, YbF3, etc.

[0048] The ZrO2 component, when present in amounts exceeding 0%, reduces the coloration of the glass, increases the transmittance to short-wavelength visible light, and promotes stable glass formation, thereby improving the glass's resistance to devitrification. It is a second optional component in the glass. On the other hand, by limiting the ZrO2 content to 10% or less, devitrification due to excessive ZrO2 content can be reduced. Therefore, the ZrO2 content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 8% or less, and most preferably 7% or less. The ZrO2 component can be incorporated into the glass using raw materials such as ZrO2 and ZrF4.

[0049] The WO3 component, when present in amounts exceeding 0%, increases the refractive index of the glass and raises the Abbe number, and is an optional component in the second glass. In particular, by limiting the WO3 component content to 10% or less, the devitrification resistance of the glass can be improved, and the decrease in the transmittance of the glass to short-wavelength visible light can be suppressed. Therefore, the WO3 component content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 7% or less, and most preferably 5% or less.

[0050] The Ta2O5 component, when present in amounts exceeding 0%, can increase the refractive index of the glass and enhance its resistance to devitrification; it is a second optional component in the glass. On the other hand, by reducing the Ta2O5 content to 10% or less, the amount of Ta2O5, a rare mineral resource, used is reduced, and the glass becomes easier to melt at lower temperatures, thus lowering the production cost of the glass. Furthermore, this reduces the devitrification of the glass due to excessive Ta2O5 content. Therefore, the Ta2O5 content is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. Ta2O5 can be used as a raw material for the Ta2O5 component.

[0051] The ZnO component, when present in amounts greater than 0%, lowers the liquidus temperature of the glass and enhances its resistance to devitrification; it is an optional component in the second glass. In particular, by limiting the ZnO content to 20% or less, it is easier to obtain a high refractive index and low dispersion. Therefore, the ZnO content relative to the total mass of the glass in terms of oxide composition is preferably 20% or less, more preferably 10% or less, and most preferably 5% or less. The ZnO component can be incorporated into the glass using raw materials such as ZnO and ZnF2.

[0052] The MgO component is an optional component that, when present in amounts greater than 0%, lowers the liquidus temperature of the glass and enhances its resistance to devitrification, and also makes it less likely to reduce the transmittance to visible light. In particular, by limiting the MgO content to 10% or less, it is easier to obtain a high refractive index and low dispersion. Therefore, the MgO content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The MgO component can be incorporated into the glass using raw materials such as MgCO3 and MgF2.

[0053] The CaO component, when present in amounts exceeding 0%, lowers the liquidus temperature of the glass and enhances its devitrification resistance; it is a second optional component in the glass. In particular, by limiting the CaO content to 12% or less, it is easier to obtain a high refractive index and low dispersion, while suppressing a decrease in the glass's devitrification resistance and chemical durability. Therefore, the CaO content relative to the total mass of the glass in terms of oxide composition is preferably 12% or less, more preferably 10% or less, and most preferably 8% or less. The CaO component can be incorporated into the glass using raw materials such as CaCO3 and CaF2.

[0054] The SrO component, when present in amounts greater than 0%, lowers the liquidus temperature of the glass and enhances its devitrification resistance; it is a second optional component in the glass. In particular, by limiting the SrO content to 10% or less, it is possible to easily obtain a high refractive index and low dispersion, while suppressing a decrease in the glass's devitrification resistance and chemical durability. Therefore, the SrO content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The SrO component can be incorporated into the glass using raw materials such as Sr(NO3)2 and SrF2.

[0055] The Li2O component, when present in amounts exceeding 0%, lowers the melting temperature of the glass and is an optional component in the second glass. In particular, by limiting the Li2O content to 10% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the content of the Li2O component relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 5% or less, and most preferably 3% or less. The Li2O component can be incorporated into the glass using raw materials such as Li2CO3, LiNO3, and LiF.

[0056] The K2O component, when present in amounts exceeding 0%, lowers the melting temperature of the glass and is an optional component in the second glass. In particular, by limiting the K2O content to 10% or less, it is possible to easily obtain a high refractive index and improve the stability of the glass, thereby reducing the occurrence of devitrification and other issues. Therefore, the K2O content relative to the total mass of the glass in terms of oxide composition is preferably 10% or less, more preferably 7% or less, and even more preferably 5% or less. The K2O component can be incorporated into the glass using raw materials such as K2CO3, KNO3, KF, KHF2, K2SiF6, etc.

[0057] The Sb2O3 component is an optional component in the second glass, which increases the transmittance of glass to short-wavelength visible light and also has a degassing effect when the glass is melted. By limiting the Sb2O3 content to 0.1% or less, it is possible to suppress discoloration, especially in high-refractive-index glass. Furthermore, by limiting it to 0.1% or less, excessive foaming during glass melting is less likely to occur, making it less likely for the Sb2O3 component to alloy with melting equipment (especially precious metals such as Pt). Therefore, the content of the Sb2O3 component relative to the total mass of glass in terms of oxide composition is limited to 0.1% or less, preferably 0.05% or less.

[0058] The SnO2 component, when present in amounts exceeding 0%, acts as a defoaming agent, clarifying the molten glass, and is an optional component of the second glass. In particular, the inclusion of the SnO2 component provides the aforementioned effect and makes devitrification of the glass less likely. Therefore, the SnO2 component content relative to the total mass of the glass in terms of oxide composition is preferably 2% or less, and more preferably 1% or less. The SnO2 component can be incorporated into the glass using raw materials such as SnO, SnO2, SnF2, SnF4, etc.

[0059] <Regarding ingredients that should not be included> Next, components that should not be included in the optical glass of the present invention, and components that are not preferable to include. Let me explain the ingredients.

[0060] Other components may be added as needed, as long as they do not impair the properties of the glass of the present invention. However, each transition metal component, such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo (excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu), has the property of causing the glass to color and producing absorption at specific wavelengths in the visible range, even when present in small amounts, either individually or in combination. Therefore, it is preferable that they be substantially omitted, especially in optical glass used with wavelengths in the visible range.

[0061] Furthermore, lead compounds such as PbO and arsenic compounds such as As2O3 are components with a high environmental impact, so it is desirable that they be substantially omitted, that is, completely omitted except for unavoidable contamination.

[0062] Furthermore, the components Th, Cd, Tl, Os, Be, and Se have recently been increasingly discouraged from use as hazardous chemicals, requiring environmental measures not only in the glass manufacturing process but also in the processing and disposal of the finished product. Therefore, when environmental impact is a major concern, it is preferable to substantially omit these components.

[0063] <About reducing agents> The optical glass of the present invention is characterized by the addition of a reducing agent as part of the glass raw material. By adding a reducing agent, the inclusion of platinum in the glass can be suppressed and the transmittance can be improved. The content of the reducing agent relative to the total mass of the glass in terms of oxide composition is preferably 5% or less, more preferably 3% or less, more preferably 2% or less, and most preferably 1% or less. Examples of reducing agents include single elements such as carbon and sulfur, organic compounds such as sucrose, and raw materials that generate reducing gases during thermal decomposition, such as ammonium sulfate.

[0064] <About defoaming agents> The optical glass of the present invention is characterized by the addition of a defoaming agent as part of the glass raw material. By adding a defoaming agent together with a reducing agent, glass with improved defoaming properties can be obtained compared to adding a defoaming agent alone. The content of the defoaming agent relative to the total mass of the glass in terms of oxide composition is preferably 3% or less, more preferably 2% or less, and most preferably 1% or less. Examples of defoaming agents include sulfates such as SO2 and Na2SO4, and Sb2O3 components.

[0065] The optical glass melting process of the present invention is characterized by the absence of water supply. In the present invention, the absence of water supply means that no water vapor is added to the molten atmosphere, no bubbling is performed, or any other special process is not carried out. Other methods of not supplying water may include adding a drying gas during the melting process, or performing the melting process in an inert gas atmosphere.

[0066] [Manufacturing method] The optical glass of the present invention is manufactured, for example, as follows: The above raw materials are uniformly mixed so that each component is within a predetermined content range, the resulting mixture is placed in a platinum crucible, and the mixture is melted in an electric furnace at a temperature range of 1100 to 1500°C for 2 to 5 hours, depending on the difficulty of melting the glass raw materials, and then stirred and homogenized. After lowering to an appropriate temperature, it is cast into a mold and slowly cooled.

[0067] [Physical properties] The optical glass of the present invention preferably has a high refractive index and a high dispersion (low Abbe number). The refractive index (n d ) of the first glass is preferably 1.75 or more, more preferably 1.80 or more, and still more preferably 1.85 or more as the lower limit. This refractive index (n d ) may be preferably 2.10 or less, more preferably 2.07 or less, and still more preferably 2.05 or less as the upper limit. Also, the Abbe number (ν d ) of the first glass is preferably 20 or more, more preferably 23 or more, and still more preferably 25 or more as the lower limit. This Abbe number (ν d ) is preferably 45 or less, more preferably 40 or less, and still more preferably 37 or less as the upper limit. The refractive index (n d ) of the second glass is preferably 1.50 or more, more preferably 1.52 or more, and still more preferably 1.53 or more as the lower limit. This refractive index (n d ) may be preferably 2.10 or less, more preferably 2.07 or less, and still more preferably 2.05 or less as the upper limit. Also, the Abbe number (ν d ) of the second glass is preferably 15 or more, more preferably 17 or more, and still more preferably 19 or more as the lower limit. This Abbe number (ν d ) is preferably 53 or less, more preferably 51 or less, and still more preferably 50 or less as the upper limit. By having such a high refractive index, a large amount of light refraction can be obtained even when the optical element is thinned. Also, by having such a low dispersion, the deviation of the focus (chromatic aberration) due to the wavelength of light can be reduced when used as a single lens. Therefore, for example, when an optical system is configured in combination with an optical element having a high dispersion (low Abbe number), the aberration of the entire optical system can be reduced and high imaging characteristics can be achieved. As described above, the optical glass of the present invention is useful in optical design. In particular, when an optical system is configured, while achieving high imaging characteristics and the like, the miniaturization of the optical system can be achieved, and the degree of freedom in optical design can be expanded.

[0068] The optical glass of the present invention preferably has high visible light transmittance, particularly transmittance of light on the short wavelength side of the visible light spectrum, and as a result has less coloration. The shortest wavelength (λ) that shows a spectral transmittance of 70% in the first glass sample with a thickness of 10 mm 70 The wavelength is preferably 470 nm or less, more preferably 450 nm or less, and even more preferably 430 nm or less. Furthermore, the shortest wavelength (λ5) at which a 10 mm thick sample of the optical glass of the present invention exhibits a spectral transmittance of 5% is preferably 390 nm or less, more preferably 380 nm or less, and even more preferably 370 nm or less. The shortest wavelength (λ) that shows a spectral transmittance of 70% in the second glass sample with a thickness of 10 mm 70 The wavelength of the second glass of the present invention is preferably 500 nm or less, more preferably 490 nm or less, and even more preferably 480 nm or less. Furthermore, the shortest wavelength (λ5) at which a 10 mm thick sample of the optical glass of the present invention exhibits a spectral transmittance of 5% is preferably 390 nm or less, more preferably 385 nm or less, and even more preferably 370 nm or less. As a result, the absorption edge of the glass is in or near the ultraviolet region, and the transparency of the glass with respect to visible light is enhanced, making this optical glass suitable for use in optical elements that transmit light, such as lenses.

[0069] The optical glass of the present invention preferably has a low platinum content, which results in less coloration. In particular, the amount of platinum in the optical glass of the present invention is preferably 10 ppm or less, more preferably 9 ppm or less, and even more preferably 8 ppm or less. This suppresses coloration due to platinum and enhances the transparency of the glass to visible light, so this optical glass can be preferably used in optical elements that transmit light, such as lenses.

[0070] [Preforms and optical elements] Glass molded bodies can be produced from the manufactured optical glass using, for example, polishing, or mold press molding methods such as reheat press molding or precision press molding. In other words, glass molded bodies can be produced by machining optical glass such as grinding and polishing, or by producing a preform for mold press molding from optical glass, then performing reheat press molding on this preform and polishing to produce a glass molded body, or by performing precision press molding on a preform produced by polishing or a preform formed by known methods such as floating molding. The means for producing glass molded bodies are not limited to these methods.

[0071] As described above, the optical glass of the present invention is useful for various optical elements and optical designs. In particular, it is preferable to form a preform from the optical glass of the present invention and use this preform to manufacture optical elements such as lenses and prisms by performing reheat press molding or precision press molding. This makes it possible to form preforms with a large diameter, so that even while increasing the size of the optical element, high-definition and high-precision imaging and projection characteristics can be achieved when used in optical equipment such as cameras and projectors. [Examples]

[0072] The composition of the first example and comparative example of the glass of the present invention, and the refractive index (n) of these glasses. d ), Abbe number (ν d ), wavelengths (λ) at which spectral transmittances are 70% and 5%. 70 Based on the results of λ5), Table 1 shows the measured amount of platinum in the glass (ppm) and the number of bubbles in the glass, the composition of the second example of glass, and the refractive index (n) of these glasses. d ), Abbe number (ν d ), wavelengths (λ) at which spectral transmittances are 70% and 5%. 70Table 2 shows the measured values ​​of platinum content (ppm) and bubbles (air bubbles) in the glass, based on the results of λ5). Note that if the compositions of the first and second glass examples contain Sb2O3, it also serves as a defoaming agent. The following examples are for illustrative purposes only and are not the only examples to which the method is applicable.

[0073] The glasses of the examples and comparative examples of the present invention were all prepared by selecting high-purity raw materials commonly used in optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, corresponding to each component as raw materials. These materials were weighed to the proportions of the composition shown in the table for each example, mixed uniformly, and then placed in a platinum crucible. Depending on the difficulty of melting the glass raw materials, the mixture was melted in an electric furnace at a temperature range of 1100 to 1500°C for 2 to 5 hours. After stirring and homogenization, the mixture was cast into a mold or the like and slowly cooled to produce the finished product.

[0074] Refractive index (n) of the glass in the examples and comparative examples. d The values ​​were measured 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 (ν) was also calculated. d ) is the refractive index of the d line mentioned above and the refractive index (n) relative to the F line (486.13 nm) of the hydrogen lamp. F ), refractive index (n) for the C line (656.27 nm) C Using the value of ), the Abbe number (ν d )=[(n d -1) / (n F -n C It was calculated from the formula (n). Then the refractive index (n) was obtained. d ) and Abbe number (ν d From the value of ), the relationship n d =-a × ν d We found the y-intercept b at +b when the slope a is 0.01.

[0075] The transmittance of the glass in the examples and comparative examples was measured in accordance with the Nippon Optical Glass Manufacturers Association standard JOGIS02. In this invention, the presence and degree of coloration of the glass was determined by measuring the transmittance of the glass. Specifically, a glass bulk material was prepared as a sample with a thickness of 10 ± 0.1 mm, polished with parallel faces, and immediately after annealing, the light transmittance (spectral transmittance) and λ were measured using the method specified in JOGIS02-1975. 70 We determined the wavelength at 70% transmittance and λ5 at 5% transmittance.

[0076] The amount of platinum (ppm) in the glass of the examples and comparative examples was measured using ICP-MS (inductively coupled plasma mass spectrometer).

[0077] The measurement of bubbles in the glass of the examples and comparative examples was performed in accordance with the Nippon Optical Glass Manufacturers Association standard JOGIS12-2012, "Method for measuring bubbles in optical glass."

[0078] [Table 1]

[0079] [Table 2]

[0080] As shown in the table, the first glass of the embodiment of the present invention all have a refractive index (n d ) is 1.75 or higher, more specifically 1.90 or higher, and this refractive index (n d The value was 2.10 or less, more specifically 2.05 or less, which was within the desired range. Furthermore, the second glass in the embodiment of the present invention has a refractive index (n d The value was 1.75 or higher, more specifically 1.80 or higher, which was within the desired range.

[0081] The first glass in the embodiment of the present invention all have an Abbe number (ν d ) is 25 or more, more specifically 26 or more, and this Abbe number (ν dThe value was 45 or less, more specifically 40 or less, which was within the desired range. Furthermore, the second glass in the embodiment of the present invention all have an Abbe number (ν d The result was 15 or higher, more specifically 23 or higher, which was within the desired range.

[0082] The first glass in the embodiments of the present invention is λ 70 The wavelength (at a transmittance of 70%) was 450 nm or less. On the other hand, the comparative glass had a wavelength of λ 70 The wavelength was greater than 450 nm. Therefore, it became clear that the optical glass of the embodiment of the present invention is less susceptible to staining than the glass of the comparative example.

[0083] The optical glasses in the examples of the present invention all had a platinum content of 9 ppm or less. In contrast, the glass in the comparative example had a platinum content of 11.1 ppm. Therefore, it became clear that the glass in the examples of the present invention had a lower platinum content than the glass in the comparative example.

[0084] All of the optical glasses in the embodiments of the present invention had a bubble rating of 3 or lower. In contrast, the glass in the comparative example had a bubble rating of 5. Therefore, it was clear that the optical glass in the embodiments of the present invention had significantly more bubbles removed compared to the glass in the comparative example, demonstrating a higher degassing effect.

[0085] Therefore, the optical glass of the embodiment of the present invention, by containing a predetermined amount of reducing agent, has a refractive index (n d ) and Abbe number (ν d It was found that the optical glass of the present invention exhibited high transmittance and was difficult to color with platinum, while remaining within the desired range. Furthermore, it was found that the defoaming properties of the optical glass of the present invention were improved by including predetermined amounts of reducing agent and defoaming agent.

[0086] Although the present invention has been described in detail above for illustrative purposes, it will be understood that these embodiments are for illustrative purposes only, and that many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

[Claim 1] In terms of mass % relative to the total mass of glass with oxide-based composition, La 2 O 3 Composition 48.100~65%, B 2 O 3 Ingredients 1 to 25%, SiO 2 Ingredients less than 15%, TiO 2 Ingredients: 9.3% or more, 25% or less Y 2 O 3 Ingredients 3% to 15% Nb 2 O 5 Ingredients less than 15%, WO 3 Ingredients 0% to less than 5% And, PbO component and Al 2 O 3 It contains virtually no ingredients, Refractive index (n ｄ ) is between 1.85 and 2.10, Abbe number (ν ｄ ) is between 20 and 37, For a sample with a thickness of 10 mm, the shortest wavelength (λ) that shows a spectral transmittance of 70% is measured. 70 ) is 421 nm or less and the shortest wavelength (λ) that shows a spectral transmittance of 5% 5 ) is 370 nm or less, Optical glass characterized by containing 1% or less of a reducing agent in its raw materials.

Images