JP7194082B2 - Reheat-pressed glass material, reheat-pressed glass material, polished glass, and manufacturing method thereof - Google Patents

Description

The present invention relates to a reheat-pressed glass material having a glass surface treated, a reheat-pressed glass material, a polished glass, and production methods thereof.

Conventionally, as a method for molding optical glass, a glass material having a predetermined shape (reheat press glass material) is supplied to a mold having a lower mold and an upper mold, and the glass material is heated and softened, and then the mold is heated and softened. A reheat press method is widely known, in which the glass is press-molded at a high temperature and the molded glass is taken out. In addition, it is difficult to manufacture a large-diameter optical lens by other methods, and the reheat press method is generally adopted.

However, when a glass material is placed in a reheat press type mold and heated, a hard layer resulting from crystals of the glass is formed on the surface, making it difficult to soften in some cases. If pressing is performed in this state, if the glass material has a shape with corners, the edges and corners that are hard crystals will enter the inside of the lens material and cannot be removed by subsequent polishing. . In the worst case, crystals are precipitated inside the glass material, making it impossible to obtain a homogeneous glass material.

In addition, if the optical glass material has a composition that easily crystallizes, the crystal layer formed on the surface of the glass material during heat softening is thick, and many crystal layers must be removed in order to make the final product. , more material is lost and wasted. In addition, since the thermal conductivity of glass is lower than that of general mold materials, the degree of crystallization of the glass differs depending on the temperature distribution in the glass material during the reheat press process, even if the glass material is the same. (For example, when increasing the processing size to increase the diameter of the lens, when trying to improve the processing accuracy of the glass, when processing a shape with a thickness distribution, etc.) However, even if one attempts to suppress the crystallization of a specific portion of the glass, it may not be possible to suppress the crystallization of another portion of the glass, or the desired shape may not be obtained. yes it gets more serious.

As described above, there are various problems in reheat press-type glass molding, and the degree of difficulty has increased in recent years. As a technique related to such a reheat press method, for example, Patent Literature 1 discloses a technique of applying a coating film for release to a glass material. Further, Patent Document 2 discloses a technique that eliminates the need for a protective film on the mold surface by using a glass molding mold containing carbon atoms.

However, these documents do not discuss a technique for avoiding the edge of the crystal layer of the optical glass material for reheat press from penetrating inside.

Japanese Patent Laid-Open No. 9-227136 Japanese Patent Application Laid-Open No. 2002-356334

In the present invention, the glass material is heated and softened, and when the glass material is pressed, part of the surface crystal layer, such as edges and corners, enters the inside of the glass material, preventing foreign matter from entering the glass material, and the amount of grinding and polishing. To provide a glass material for reheat press capable of reducing the

The present inventor modified the glass surface of glass having a total content of Li component, Na component, K component, Rb component, Cs component and Fr component of 1.2% by mass or less and/or lanthanum borate glass. By doing so, the formation of a crystal layer on the surface of the glass is suppressed, and a method for facilitating the softening of the glass has been investigated, leading to the present invention. The present invention includes the following.
[1] glass containing Li component, Na component, K component, Rb component, Cs component and Fr component in a total content of 1.2% by mass or less;
and a surface modification layer covering the glass,
Glass for reheat press, wherein the content of at least one component selected from the Li component, Na component, K component, Rb component, Cs component and Fr component in the surface modified layer is higher than the content of the component in the glass. material.
[2] Lanthanum borate-based glass;
and a surface modification layer covering the glass,
Glass for reheat press, wherein the content of at least one component selected from the Li component, Na component, K component, Rb component, Cs component and Fr component in the surface modified layer is higher than the content of the component in the glass. material.
[3] The glass material for reheat press according to [1] or [2], wherein the surface modified layer has a thickness of 1000 nm or less.
[4] Any one of [1] to [3], wherein the glass contains 0.1% by mass or less of Li component, Na component, K component, Rb component, Cs component, and Fr component. glass material for reheat press.
[5] A reheat-pressed glass material derived from the reheat-press glass material according to any one of [1] to [4].
[6] Polished glass derived from the reheat-pressed glass material of [5].
[7] Glass raw materials are melted so that the total content of Li component, Na component, K component, Rb component, Cs component and Fr component is 1.2% by mass or less, and then cooled to form glass. a manufacturing process;
forming a surface modified layer on the surface of the glass by immersing the glass in a molten salt containing at least one of Li component, Na component, K component, Rb component, Cs component and Fr component. A method for manufacturing a glass material for reheat press.
[8] a step of producing a lanthanum borate glass by melting raw materials for the lanthanum borate glass and then cooling;
A step of forming a surface modified layer on the surface of the glass by immersing the lanthanum borate-based glass in a molten salt containing at least one of Li, Na, K, Rb, Cs and Fr components. and a method for manufacturing a glass material for reheat press.
[9] A method for producing a reheat-pressed glass material, comprising a step of reheat-pressing the glass material for reheat-press obtained by the production method according to [7] or [8].
[10] A method for producing polished glass, comprising grinding and polishing the reheat-pressed glass material obtained by the production method of [9].

Even if the glass material for reheat press of the present invention is heated and softened, the formation of a hard surface crystal layer is suppressed, and part of the surface crystal layer at the edges and corners is prevented from entering the interior of the glass material during pressing. can be prevented and the amount of grinding and polishing can be reduced.

FIG. 1 is a schematic diagram of a reheat press without a surface modification layer. FIG. 2 is a schematic diagram of a reheat press with a surface modified layer. FIG. 3 is a photograph of the manufacturing conditions of the reheat-press glass materials 1 to 4 and the comparative reheat-press glass material, and the appearance when heated for a predetermined time. FIG. 4 is a photograph of the manufacturing conditions of the reheat-press glass materials 5 to 8 and the comparative reheat-press glass material, and the appearance when heated for a predetermined time. FIG. 5 is a photograph of the manufacturing conditions of the reheat-press glass materials 9 to 12 and the comparative reheat-press glass material, and the appearance when heated for a predetermined time. FIG. 6 is a photograph of the manufacturing conditions of the reheat-press glass materials 13 to 15 and the comparative reheat-press glass material, and the appearance when heated for a predetermined time. FIG. 7 is a photograph of the manufacturing conditions of the reheat-press glass materials 16 to 17 and the comparative reheat-press glass material, and the appearance when heated for a predetermined time. FIG. 8 shows the results of measurement of the reheat press glass material 7 using LIBS (Laser Induced Breakdown Spectroscopy).

[Glass material for reheat press]
The glass material for reheat press will be described below. In this specification, unless otherwise specified, "%" used when indicating the glass composition means "% by mass". In addition, in this specification, "-" used when specifying a numerical range includes both the upper limit and the lower limit. For example, when "10 to 20%" is indicated as the content of a glass constituent, it means that the content is 10% by mass or more and 20% by mass or less. Moreover, let content of a glass component be the amount converted into the oxide. Furthermore, the content (content rate) of the glass constituents is quantified by a known method such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), or the like. In the present invention, the content of a glass component of 0% means that this component is not substantially contained, and it is allowed that the component is contained at the level of unavoidable impurities. be.
Moreover, in this specification, "alkali metal" refers to Li (lithium), Na (sodium), K (potassium), Rb (rubidium), Cs (cesium), and Fr (furandium).

Further, in this specification, the glass material for reheat press is a material for obtaining glass as a final product by using the material and going through a reheat press process.

[Mother glass]
(First aspect)
A first aspect of the glass material for reheat press of the present invention includes alkali metal components (Li component (Li ₂ O), Na component (Na ₂ O), K component (K ₂ O), Rb component (Rb ₂ O), Glass having a total content of Cs component (Cs ₂ O) and Fr component (Fr ₂ O) of 1.2% by mass or less (including 0% by mass) is used as mother glass.
The type of the glass of the first embodiment is not particularly limited as long as it contains 1.2% by mass or less of an alkali metal component as an oxide.

The content of each alkali metal component in the base glass of the first aspect is 1.2% or less, preferably 1.1% or less, 0.8% or less, based on the total amount of the glass, based on metal oxides. , 0.5% or less, 0.3% or less, 0.1% or less, 0.08% or less, 0.05% or less, 0.03% or less, 0.01% or less, and all The content of alkali metal components can also be 0%. When the content of the alkali metal component is small, there is an advantage that it is easy to increase the refractive index. The present invention may also be applied to glass that becomes unstable as glass (it does not turn into glass, but forms crystals) if it contains an alkali metal component.

Other glass components of the mother glass of the first aspect are as follows.

The base glass of the first aspect can contain one or more of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ components. These components are components that constitute the skeleton of the glass, and are components that improve the thermal stability of the glass. It is also a component that contributes to low refractive index and low dispersion. The contents of the SiO ₂ , P ₂ O ₅ and B ₂ O ₃ components are not particularly limited, and can be arbitrarily set. The upper limits of SiO ₂ , P ₂ O ₅ and B ₂ O ₃ components are, for example, 99% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, and 40%, respectively. 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, or 5% or less, and the lower limits are, for example, 0% or more, 5% or more, and 10%, respectively. 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80%, 90% or more may

Also, the total content of the SiO ₂ , P ₂ O ₅ and B ₂ O ₃ components (SiO _{2 +} P ₂ O ₅ +B ₂ O ₃ ) is not particularly limited and can be any value. The upper limit of +P ₂ O ₅ +B ₂ O ₃ is, for example, 99% or less, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, It may be 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, or 5% or less. The lower limit is, for example, 0% or more, 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% It may be 70% or more, 80% or more, or 90% or more.

The base glass of the first embodiment can contain at least one of Li component, Na component, K component, Rb component, Cs component and Fr component, and the total content of these components is As shown, it is 1.2% by mass or less (including 0% by mass). Li ₂ O, Na ₂ O, and K ₂ O are components that improve the meltability of the glass, and may improve the thermal stability of the glass. It is also a component that lowers the glass transition temperature.

Among alkali metals, Li ₂ O and Na ₂ O components are components that increase the refractive index more than K ₂ O, Rb ₂ O and Cs ₂ O components and contribute to high dispersion. The upper limit of the total content of Li ₂ O and Na ₂ O components (Li ₂ O + Na ₂ O) is preferably 1.2% or less, 1.1% or less, 0.8%, 0.8%, 0 .5% or less, 0.3% or less, 0.1% or less, 0.08% or less, 0.05% or less, 0.03% or less, 0.01% or less, and all alkali metal The content of the component can also be 0%.

The K ₂ O component is a component that may increase the refractive index and contribute to high dispersion more than the Rb ₂ O and Cs ₂ O components. Regarding the upper limit of the total content of Li ₂ O, Na ₂ O and K ₂ O (Li ₂ O + Na ₂ O + K ₂ O) obtained by adding K ₂ O to the above-mentioned total content of Li ₂ O and Na ₂ O , preferably 1.2% or less, 1.1% or less, 0.8%, 0.5% or less, 0.3% or less, 0.1% or less, 0.08% or less, 0 0.05% or less, 0.03% or less, 0.01% or less, or the content of all alkali metal components can be 0%.

MgO, CaO, SrO, BaO, and ZnO components are components that improve the meltability of the glass, and may improve the thermal stability of the glass. Also, MgO, CaO, SrO, BaO, and ZnO components are components that lower the glass transition temperature, and may increase the refractive index more than Na ₂ O, K ₂ O, and Cs ₂ O components. The content of each of the MgO, CaO, SrO, BaO, and ZnO components is also not particularly limited, and the upper limit of the content of each of the MgO, CaO, SrO, BaO, and ZnO components is 90% or less and 80% or less. , 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5 % or less, 3% or less, 1% or less, or 0.5% or less.

The lower limit of the content of each of the MgO, CaO, SrO, BaO, and ZnO components is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more.

The total content of each of the MgO, CaO, SrO, BaO, and ZnO components (MgO + CaO + SrO + BaO + ZnO) is not particularly limited, and the upper limit of MgO + CaO + SrO + BaO + ZnO is, for example, 90% or less, 80% or less, 70% or less, or 60% or less. , 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1 % or less, or 0.5% or less.

The lower limit of the total content of each of the MgO, CaO, SrO, BaO, and ZnO components (MgO + CaO + SrO + BaO + ZnO) is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more. , 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80% or more, 90% or more may

La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ components are components that increase the refractive index compared to the MgO, CaO, SrO, and BaO components, and have a high refractive index and low dispersion. It is a contributing component. In some cases, the thermal stability of the glass is improved by introducing La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components. _The content of _each of the _{La2O3 , Gd2O3 ,} Y2O3 _, and Yb2O3 components is not particularly limited _, and _{La2O3 , Gd2O3 , Y2O3 ,} and _Yb2 . The upper limit of _each content of O3 is, for example, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, % or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ , and Yb ₂ O ₃ The lower limit of the content of each component is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80% or more There may be.

The total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components (La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ ) is also not particularly limited, The upper limit of La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

The _lower limit of the _total content of the _three components _{La2O3 , Gd2O3 ,} Y2O3 _, and Yb2O3 _{( La2O3 + Gd2O3 +} Y2O3 _{+ Yb2O3} ) is ₀ % 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, It may be 50% or more, 60% or more, 70% or more, 80% or more, or 90% or more.

TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ are components that contribute to high refractive index and high dispersion, and their introduction improves the thermal stability of the glass. Sometimes. Each content of _TiO2 , _{Nb2O5 , Ta2O5} , _{WO3 ,} and _{Bi2O3 components} is not particularly _limited , and _TiO2 , _Nb2O5 , _Ta2O5 , _{WO3 ,} and The upper limit of each content of Bi ₂ O ₃ is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% % or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

The lower limits of the contents of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O are 0% or more, 1% or more, ₃ % or more, 5% or more, and 7% or more. , 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80% or more may

The total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is also particularly limited. However, the upper limit of TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ is, for example, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, 0.5% or less good too.

The lower limit of the total content of each of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ components (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is , for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more , 45% or more, 50% or more, 60% or more, 70% or more, or 80% or more.

The ZrO ₂ and Al ₂ O ₃ components are components that improve the chemical durability, and their introduction may improve the thermal stability of the glass. The contents of each of the ZrO ₂ and Al ₂ O ₃ components are also not particularly limited, and the upper limits of the respective contents of ZrO ₂ and Al ₂ O ₃ are, for example, 30% or less, 20% or less, 15% or less, 14% % or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7%, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, It may be 1% or less, or 0.5% or less.

The lower limit of the content of each of the ZrO ₂ and Al ₂ O ₃ components is, for example, 0% or more, 1% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more. , 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 20% or more, 25% or more.

If desired, at _{least one} of _{As2O3 , Sb2O3} and SnO2 can be added to the glass. As ₂ O ₃ , Sb ₂ O ₃ , and SnO ₂ have a fining effect during melting of the glass and an effect of reducing platinum specks (platinum foreign matter) in the resulting glass. In some cases, the oxidized/reduced state of the glass can be adjusted. The content of Ab ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ is not particularly limited, but the upper limit of the content of each of Ab ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ is 1% or less. , 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0 .1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, 0.04% or less, 0.03% or less, 0.02% % or less, 0.01% or less, 0.009% or less, 0.008% or less, 0.007% or less, 0.006% or less, 0.005% or less, 0.004% or less, 0.003% or less , 0.002% or less, or 0.001% or less. In addition, the lower limits of the contents of As ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ are 0% or more, 0.001% or more, 0.002% or more, 0.003% or more, and 0.004% or more. , 0.005% or more, 0.006% or more, 0.007% or more, 0.008% or more, 0.009% or more, 0.01% or more, 0.02% or more, 0.03% or more, 0 .04% or more, 0.05% or more, 0.06% or more, 0.07% or more, 0.08% or more, 0.09% or more, 0.1% or more, 0.2% or more, 0.3% % or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, or 0.9% or more.

In addition, if the inclusion of radioactive substances in the material is a problem depending on the application, it is preferable to keep the content of radioactive isotopes below a certain amount or not to contain them intentionally (however, contamination as impurities is not prevented). ).

(Second aspect)
In a second aspect of the glass material for reheat press of the present invention, the base glass is lanthanum borate glass.
The type of mother glass of the second aspect is not particularly limited as long as it is a lanthanum borate glass. Lanthanum borate-based glasses are generally high-refractive-index, low-dispersion glasses and the like in optical glass applications, and the present invention can target such glasses.

In this specification, lanthanum borate glass means glass containing a B component (B ₂ O ₃ ) and an La component (La ₂ O ₃ ) as glass components.

In the second aspect, the content of B ₂ O ₃ is not particularly limited, but the lower limit is 1.0% or more, 5.0% or more, 7.0% or more, 8.0% or more , 9.0% or more, or 10.0% or more. On the other hand, the upper limit of the B ₂ O ₃ component can be 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 40% or less, 30% or less, and 20% or less. From the viewpoint of maintaining the thermal stability of the glass, the content of B ₂ O ₃ in mass% is greater than the content of SiO ₂ , and the content of B ₂ O ₃ is greater than the content of P ₂ O ₅ are preferred respectively. Similarly, from the viewpoint of maintaining the thermal stability of the glass, it is preferable that the content of B ₂ O ₃ expressed in mass% is greater than the total content of SiO ₂ and B ₂ O ₃ .

In the second aspect, the content of La ₂ O ₃ is not particularly limited, but the lower limit may be 10% or more, 12% or more, 15% or more, 17% or more, and 20% or more. can.

The upper limit of La ₂ O ₃ can be 90% or less, 80% or less, 75% or less, 70% or less, 68% or less, 65% or less, 63% or less, and 60% or less.

In the second aspect, the SiO ₂ and P ₂ O ₅ components are optional components that constitute the framework of the glass, and are components that improve the thermal stability of the glass. It is also a component that contributes to low refractive index and low dispersion. The content of the SiO ₂ and P _{2 O} components is not particularly limited, and can be set to any content. The upper limits of the _five components of SiO ₂ and P ₂ O are, for example, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, and 25% or less. , 20% or less, 15% or less, 10% or less, or 5% or less, and the lower limits are, for example, 0% or more, 5% or more, 10% or more, 15% or more, 20% or more, and 25% or more. , 30% or more, 35% or more, 40% or more, or 45% or more.

The lanthanum borate glass in the second aspect can contain at least one of Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O components. Among them, Li ₂ O, Na ₂ O, and K ₂ O are components that improve the meltability of the glass, and may improve the thermal stability of the glass. It is also a component that lowers the glass transition temperature. The contents of the Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O components when contained in the mother glass are not particularly limited and can be set to any content. The upper limits of the contents of Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O are, for example, 50% or less, 45% or less, 40% or less, 35% or less and 30%. 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less, 5.0% or less, 4.0% or less, 3.5% or less, 3.0% or less; 5% or less, 2.0% or less, 1.5% or less, 1.0% or less, or 0.5% or less. The lower limit is, for example, 0% or more, 0.1% or more, 0.5% or more, 1.0% or more, 1.5% or more, 2.0% or more, 2.5% or more, 3.0% or more , 3.5% or more, 4.0% or more, 5.0% or more, 7.5% or more, 10.0% or more, 15.0% or more, 20.0% or more, 25.0% or more, 30 0% or more, 35.0% or more, 40.0% or more, 45.0% or more, and contains all of Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O and Cs ₂ O components It doesn't have to be.

Among alkali metals, Li ₂ O and Na ₂ O components are components that increase the refractive index more than K ₂ O, Rb ₂ O and Cs ₂ O components and contribute to high dispersion. Regarding the total content of Li ₂ O and Na ₂ O components (Li ₂ O + Na ₂ O), when these components are included, for example, 0.1% or less, 0.5% or less, 1.0% or less, 1.5% or less, 2.0% or less, 2.5% or less, 3.0% or less, 3.5% or less, 4.0% or less, 5.0% or less, 7.5% or less, 10. 0% or less, 15.0% or less, 20.0% or less, 25.0% or less, 30.0% or less, 35.0% or less, 40.0% or less, 45.0% or less, 50.0% It may be below.

The lower limit of the total content of Li ₂ O and Na ₂ O (Li ₂ O + Na ₂ O) is, for example, 0% or more, 0.1% or more, 0.5% or more, 1.0% or more, 1. 5% or more, 2.0% or more, 2.5% or more, 3.0% or more, 3.5% or more, 4.0% or more, 5.0% or more, 7.5% or more, 10.0% 15.0% or more, 20.0% or more, 25.0% or more, 30.0% or more, 35.0% or more, 40.0% or more, or 45.0% or more.

The K ₂ O component is a component that may increase the refractive index and contribute to high dispersion more than the Rb ₂ O and Cs ₂ O components. The sum of the contents of Li ₂ O, Na ₂ O, and K ₂ O (Li ₂ O + Na ₂ O + K ₂ O), which is the sum of the contents of Li ₂ O and Na ₂ O described above and K ₂ O is added, is also particularly limited. The upper limit is, for example, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7.5% or less , 5.0% or less, 4.0% or less, 3.5% or less, 3.0% or less, 2.5% or less, 2.0% or less, 1.5% or less, 1.0% or less, 0 It may be 0.5% or less.

Regarding the lower limit of the total amount of Li ₂ O, Na ₂ O and K ₂ O components (Li ₂ O + Na ₂ O + K ₂ O), for example, 0% or more, 0.1% or more, 0.5% or more, 1.0% 1.5% or more, 2.0% or more, 2.5% or more, 3.0% or more, 3.5% or more, 4.0% or more, 5.0% or more, 7.5% or more, 10.0% or more, 15.0% or more, 20.0% or more, 25.0% or more, 30.0% or more, 35.0% or more, 40.0% or more, 45.0% or more good too.

MgO, CaO, SrO, BaO, and ZnO components are components that improve the meltability of the glass, and may improve the thermal stability of the glass. Also, MgO, CaO, SrO, BaO, and ZnO components are components that lower the glass transition temperature, and may increase the refractive index more than Na ₂ O, K ₂ O, and Cs ₂ O components. The content of each of the MgO, CaO, SrO, BaO, and ZnO components is also not particularly limited, and the upper limit of the content of each of the MgO, CaO, SrO, BaO, and ZnO components is 50% or less and 45% or less. , 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, 0.5% or less may be

The lower limit of the content of each of the MgO, CaO, SrO, BaO, and ZnO components is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 15% or more, It may be 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, or 45% or more.

The total content of each of the MgO, CaO, SrO, BaO, and ZnO components (MgO + CaO + SrO + BaO + ZnO) is not particularly limited, and the upper limit of MgO + CaO + SrO + BaO + ZnO is, for example, 50% or less, 45% or less, 40% or less, or 35% or less. , 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

The lower limit of the total content of each of the MgO, CaO, SrO, BaO, and ZnO components (MgO + CaO + SrO + BaO + ZnO) is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more. , 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more.

The Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components are components that increase the refractive index compared to the MgO, CaO, SrO and BaO components and contribute to high refractive index and low dispersion. . In some cases, the thermal stability of the glass is improved by introducing Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components. _The content of _each of the La ₂ O _{3 , Gd 2} O _{3 ,} Y ₂ O ₃ and _{Yb 2} O ₃ components is not particularly limited. The upper limit of the content is, for example, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% It may be 3% or less, 1% or less, or 0.5% or less.

The lower limit of the content of each of Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components is, for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more. , 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more.

The total content of La ₂ O ₃ , Gd ₂ O ₃ , Y ₂ O ₃ and Yb ₂ O ₃ components (La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ ) is also not particularly limited, The upper limit of La ₂ O ₃ +Gd ₂ O ₃ +Y ₂ O ₃ +Yb ₂ O ₃ is 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

The _lower limit of the _total content of the _three components _{La2O3 , Gd2O3 ,} Y2O3 _, and Yb2O3 _{( La2O3 + Gd2O3 +} Y2O3 _{+ Yb2O3} ) is ₅ % 7% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more.

TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ , and Bi ₂ O ₃ are components that contribute to high refractive index and high dispersion, and their introduction improves the thermal stability of the glass. Sometimes. Each content of _TiO2 , _{Nb2O5 , Ta2O5} , _{WO3 ,} and _{Bi2O3 components} is not particularly _limited , and _TiO2 , _Nb2O5 , _Ta2O5 , _{WO3 ,} and The upper limit of each content of Bi ₂ O ₃ is 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 25% % or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, or 0.5% or less.

The lower limits of the contents of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O are 0% or more, 1% or more, ₃ % or more, 5% or more, and 7% or more. , 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 60% or more, 70% or more, 80% or more may

The total content of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is also particularly limited. However, the upper limit of TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ is, for example, 90% or less, 80% or less, 70% or less, 60% or less, 50% or less, 45% or less, 40% or less. , 35% or less, 30% or less, 25% or less, 20% or less, 15% or less, 10% or less, 7% or less, 5% or less, 3% or less, 1% or less, 0.5% or less good.

The lower limit of the total content of each of TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , WO ₃ and Bi ₂ O ₃ components (TiO ₂ +Nb ₂ O ₅ +Ta ₂ O ₅ +WO ₃ +Bi ₂ O ₃ ) is , for example, 0% or more, 1% or more, 3% or more, 5% or more, 7% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more , 45% or more, 50% or more, 60% or more, 70% or more, or 80% or more.

The ZrO ₂ and Al ₂ O ₃ components are components that improve the chemical durability, and their introduction may improve the thermal stability of the glass. The contents of each of the ZrO ₂ and Al ₂ O ₃ components are also not particularly limited, and the upper limits of the respective contents of ZrO ₂ and Al ₂ O ₃ are, for example, 30% or less, 20% or less, 15% or less, 14% % or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, 8% or less, 7%, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, It may be 1% or less, or 0.5% or less.

The lower limit of the content of each of the ZrO ₂ and Al ₂ O ₃ components is, for example, 0% or more, 1% or more, 3% or more, 4% or more, 5% or more, 6% or more, 7% or more, 8% or more. , 9% or more, 10% or more, 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 20% or more, 25% or more.

If desired, at _{least one} of _{As2O3 , Sb2O3} and SnO2 can be added to the glass. As ₂ O ₃ , Sb ₂ O ₃ , and SnO ₂ have a fining effect during melting of the glass and an effect of reducing platinum specks in the obtained glass. In some cases, the oxidized/reduced state of the glass can be adjusted. The content of Ab ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ is not particularly limited, but the upper limit of the content of each of Ab ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ is 1% or less. , 0.9% or less, 0.8% or less, 0.7% or less, 0.6% or less, 0.5% or less, 0.4% or less, 0.3% or less, 0.2% or less, 0 .1% or less, 0.09% or less, 0.08% or less, 0.07% or less, 0.06% or less, 0.05% or less, 0.04% or less, 0.03% or less, 0.02% % or less, 0.01% or less, 0.009% or less, 0.008% or less, 0.007% or less, 0.006% or less, 0.005% or less, 0.004% or less, 0.003% or less , 0.002% or less, or 0.001% or less. In addition, the lower limits of the contents of As ₂ O ₃ , Sb ₂ O ₃ and SnO ₂ are 0% or more, 0.001% or more, 0.002% or more, 0.003% or more, and 0.004% or more. , 0.005% or more, 0.006% or more, 0.007% or more, 0.008% or more, 0.009% or more, 0.01% or more, 0.02% or more, 0.03% or more, 0 .04% or more, 0.05% or more, 0.06% or more, 0.07% or more, 0.08% or more, 0.09% or more, 0.1% or more, 0.2% or more, 0.3% % or more, 0.4% or more, 0.5% or more, 0.6% or more, 0.7% or more, 0.8% or more, or 0.9% or more.

(preferred mode)
According to the present invention, the total content of the Li component, Na component, K component, Rb component, Cs component and Fr component in the base glass is 1.2% by mass or less, which is the feature of the first aspect, and the second It is preferable that the embodiment satisfies both of the characteristics of the embodiment, that the base glass is a lanthanum borate-based glass. That is, the present invention uses a lanthanum borate base glass in which the total content of Li, Na, K, Rb, Cs, and Fr components is 1.2% by mass or less (including 0% by mass). It is preferable to use as

When the base glass is a lanthanum borate-based glass in which the total content of the Li, Na, K, Rb, Cs, and Fr components is 1.2% by mass or less, the glass component is an alkali metal component. can be the content described in the first embodiment, and the content of the other glass components can be the content described in the second embodiment.

[Glass characteristics]

The glass material for reheat press of the present invention is a material suitable for molding by pressing in a state of being softened by heating.

The shape of the glass material for reheat press is not particularly limited, but examples thereof include polygons such as rectangular parallelepipeds and cubes, and cylinders. All of these shapes have edges and corners. If the edge or corner of the glass material is crystallized, it becomes difficult to soften, and the shape of the edge or corner remains as it is. However, by having the surface modified layer of the present invention, the edges and corners do not solidify as they are, but are softened by heating and the glass material becomes rounded. becomes difficult to enter the inside of the glass. As the glass material for reheat press, gobs obtained directly from molten glass can also be used.

The glass serving as the matrix of the glass material for reheat press is preferably optical glass, and is preferably optical glass intended for lens molding. The refractive index nd of the glass is not particularly limited. It may be 1.90 or more, 2.00 or more, 2.10 or more, or 2.20 or more. The upper limit of the refractive index nd may be 2.70 or less, 2.60 or less, 2.50 or less, 2.40 or less, 2.30 or less, 2.20 or less, 2.10 or less. 00 or less, 1.90 or less, 1.80 or less, 1.70 or less, 1.60 or less, 1.50 or less, or 1.40 or less. The Abbe number νd is not particularly limited, and the lower limit may be 10 or more, 15 or more, 20 or more, 25 or more, 30 or more, 35 or more, 40 or more, 45 or more, 50 or more, 55 or more, 60 or more. , 65 or more, 70 or more, 75 or more, 80 or more, 85 or more, 90 or more, 95 or more, or 100 or more. The upper limit of the Abbe number νd may be 150 or less, 140 or less, 130 or less, 120 or less, 110 or less, 100 or less, 95 or less, 90 or less, 85 or less, 80 or less, 75 or less, 70 or less, 65 60 or less, 55 or less, 50 or less, 45 or less, 40 or less, 35 or less, 30 or less, 25 or less, or 20 or less.

In addition, if the inclusion of radioactive substances in the material is a problem depending on the application, it is preferable to keep the content of radioactive isotopes below a certain amount or not to contain them intentionally (however, contamination as impurities is not prevented). ).

[Surface modification layer]
The surface-modified layer is characterized in that the content of at least one component selected from the Li component, Na component, K component, Rb component, Cs component, and Fr component is higher than the content of the component in the base glass. do. Since the surface-modified layer is also glass, it is difficult to confirm the boundary with the base glass. In this case, the content of at least one of Li component, Na component, K component, Rb component, Cs component and Fr component in the portion near the surface is higher than the Li component, Na component, K component and Rb component of the base glass. , Cs component or Fr component content, and this portion is referred to as a surface modified layer in this specification.

The lower limit of the thickness of the surface modified layer is not particularly limited, but from the results of component analysis, it is preferably 5000 nm or less, more preferably 3000 nm or less, and further preferably 1000 nm or less from the surface of the glass material for reheat press. A thickness of 500 nm or less is more preferable, and a thickness of 300 nm or less is particularly preferable. If the thickness is 5000 nm or less, the surface modified layer can be removed by grinding and polishing after pressing.
Although the lower limit of the thickness of the surface modified layer is not particularly limited, it is preferably 1 nm or more, more preferably 10 nm or more. When the thickness is 10 nm or more, the stability of the surface portion of the glass material for reheat press is increased, and the surface portion is easily softened by heating.
Note that the thickness of the surface-modified layer is the same as that of the untreated glass, as measured by LIBS (Laser Induced Breakdown Spectroscopy) of a portion containing a large amount of alkali metal contained in the surface-modified layer. The boundary is defined as the point where the intensity is the same as the maximum intensity of LIBS. For example, in FIG. 8, the boundary of the LIBS of the glass treated with _NaNO3 is the same as the untreated maximum intensity at the 5-shot position, so the boundary between the glass and the surface modification layer is 500 nm. can be done.

[Reheat-pressed glass material and polished glass]
The glass material for reheat press of the present invention is suitable as a material for producing polished glass, particularly optical elements made of glass, such as optical lenses. In order to produce polished glass from the reheat-press glass material, first, the reheat-press glass material is reheat-pressed to produce a reheat-pressed glass material. Next, the reheat-pressed glass material is ground and polished to produce polished glass. Production using the glass material for reheat press of the present invention is high in quality and high yield because the crystal layer is not mixed into the inside of the glass by reheat press, and the crystal layer formed by heating can be made thinner. The amount of glass removed by polishing can be reduced.

[Manufacturing method of glass material for reheat press]
(Immersion process)
A method for manufacturing a glass material for reheat press will be described. The glass material for reheat press is obtained by cutting a plate-shaped or rod-shaped glass material (mother glass) to a predetermined size (in this specification, sometimes referred to as a "cut piece"), or Produced by immersing gobs directly obtained from molten glass in molten salt of alkali metal (molten salt containing at least one of Li, Na, K, Rb, Cs and Fr components) can do.

The molten salt containing at least one of the Li component, Na component, K component, Rb component, Cs component and Fr component includes at least one of the Li component, Na component, K component, Rb component, Cs component and Fr component. Although it is not particularly limited as long as it is a molten salt containing the components, from the viewpoint of ease of handling, lithium nitrate (LiNO ₃ ), sodium nitrate (NaNO ₃ ), potassium nitrate (KNO ₃ ), cesium nitrate (CsNO ₃ ) ), sodium carbonate (Na ₂ CO ₃ ), potassium carbonate (K ₂ CO ₃ ), rubidium carbonate (Rb ₂ CO ₃ ), cesium carbonate (Cs ₂ CO ₃ ), and two selected from the molten salts thereof Or a mixture consisting of three kinds. The mixing ratio of the mixture can be determined arbitrarily. As a component, the Na component is preferable, and in the case of a mixture of the Na component and the K component, it is preferable that the Na component is large.

The temperature during immersion is not particularly limited as long as the molten salt containing at least one of Na component, K component, Rb component, Cs component and Fr component is in a molten state, but the lower limit is The temperature is above the melting point of each salt. It is preferably 308° C. or higher, more preferably 320° C. or higher, and the upper limit temperature is preferably 800° C. or lower, more preferably 600° C. or lower.

The immersion time should be sufficient so long as the alkali component of the molten salt penetrates into the glass, but if it is too long, the production efficiency may deteriorate. For example, the lower limit of the immersion time is preferably 10 minutes, more preferably 30 minutes, and the upper limit of the immersion time is preferably 24 hours or less, more preferably 12 hours or less, and even more preferably 6 hours or less. More preferably, it is 2 hours or less.

Formation of the surface-modified layer by the immersion step is considered to be the formation of a relatively highly stable surface-modified layer in which alkali metal components from the molten salt enter only the surface layer of the glass. In addition, it can be considered that when the alkali metal salt penetrates, it becomes difficult to form a hard crystal layer even when heated to near the glass softening temperature. It should be noted that even a glass that is rather unstable when it contains an alkali metal component may form a relatively highly stable surface modified layer by the immersion process.

[Reheat press process, grinding and polishing process]
Next, the molding of glass will be explained. The glass material for reheat press of the present invention is suitable for reheat press.

(Reheat press process)
The reheat press will be described with reference to the drawings. FIG. 1 is a conceptual diagram when reheat-pressing a material that does not have a surface modified layer.

A glass 11 of a predetermined shape is placed in a lower die 13 of a press and heated to soften it (FIG. 1(a)). At this time, if the heating temperature is too high, the glass melts and liquefies in the mold, making it impossible to mold. On the other hand, if the heating temperature is too low, the glass material remains hard and cannot be molded. Therefore, the softening temperature is preferably in the range from 100° C. lower than the softening point of the glass to be molded to 300° C. higher than the softening point of the glass. Here, the softening point of glass is a value measured by the method specified in JIS R 3103-1:2001.

However, at a temperature near the softening point, depending on the type of glass, a hard surface crystal layer 11a is formed on the surface, leaving corners of the surface crystal layer of the glass material (FIG. 1(b)). When pressed with the upper mold 12 and the lower mold 13 in this state, the hardened corners intrude into the inside of the glass material (FIGS. 1(c) to 1(d)). However, it is impossible to remove the corner portion (intruded crystal layer 11(b)) that has penetrated inside (FIG. 1(e)).

On the other hand, in the case of glass having a surface treatment layer (see FIG. 2, however, the surface modification layer is not shown because there is no clear boundary with the glass), the surface stability of the glass 21 is high, and the temperature near the softening point is low. The surface crystal layer 21a formed at temperature is thinner than in the case of FIG. 1 without the surface treatment layer. Further, the reheat press glass material 21 having corners is softened by heating, and the corners disappear (FIG. 2(b)). Even if the upper mold 22 and the lower mold 23 are pressed in this state, no interstitial crystal layer as shown in FIG. )). Therefore, the surface crystal layer 21a can be completely removed by grinding and polishing after reheat pressing (see FIG. 2(e)).

(Grinding and polishing process)
After reheat-pressing, the reheat-pressed glass material can be ground and polished to produce the finished polished glass. The resulting polished glass is suitable as an optical lens. Grinding and polishing can be performed by conventional methods.

Grinding and polishing are usually carried out through various grinding and polishing steps to obtain glass as a final product. When the glass material for reheat press of the present invention is used, the thickness of the surface crystal layer is thin and the crystal surface layer does not penetrate inside, so the amount of grinding and polishing can be reduced.
Conventional materials can be used for grinding and polishing.

EXAMPLES The present invention will be further described with reference to examples below. In addition, the present invention is not limited to the examples. In this example, an optical glass lens material for reheat press was manufactured as a glass material for reheat press, and an optical glass lens was molded.

[Manufacturing optical glass cut pieces]
First, glass raw materials (content ratio is mass %, glass composition No. 1) are mixed so as to obtain a glass having the following composition, melted at 1400 ° C., cast in a mold, and annealed at 730 ° C. Thus, a plate-like optical glass was obtained.
_{B2O3 8.1} %
_SiO2 6.1%
_{La2O3 45.7} %
_{Gd2O3 10.6} %
_{Y2O3 0.3} %
_ZrO2 5.8%
_TiO2 13.9%
_{Nb2O5 7.9} %
ZnO 1.6%
As properties of the glass, Tg (glass transition point) was 709° C., nd (refractive index) was 2.001, and νd (Abbe number) was 29.13.

The resulting plate-shaped optical glass was cut into a rectangular parallelepiped shape of 10 mm (length) x 10 mm (width) x 9.0 mm (height) to obtain a plurality of cut pieces of the same shape.

[Manufacture of optical glass lens material for reheat press]
(Example 1)
The entire cut piece was immersed in 70 ml of 100 mol % NaNO ₃ molten salt heated to 350° C. for 60 minutes to obtain optical glass lens material 1 for reheat press.

(Examples 2 to 13)
The type of molten salt (NaNO ₃ or a 1:1 mixture of NaNO ₃ and KNO ₃ ), immersion temperature (Immersion temp. (° C.)) and immersion time (Immersion time (min)) are shown in FIGS. The cut pieces were immersed in the same manner as in Example 1, except that the numerical values were changed to obtain optical glass lens materials 2 to 13 for reheat press.

[Thickness measurement after reheating (reheating) experiment]
Reheat press optical glass lens materials 1 to 13 are held in an annealing furnace at 700° C. for 10 minutes, then heated at 880° C. for 10 minutes, then taken out. Heights of reheat press optical glass lenses 1 to 13 after heating was measured, and the amount of decrease (Δt) from the height (9.0 mm) before heating was calculated (described in FIGS. 3 to 7). In addition, it was confirmed that the surfaces of all the optical glass lenses 1 to 13 for reheat press after heating turned white, and were covered with a surface crystal layer. Similarly, a cut piece that was not immersed (optical glass lens material for reheat press for comparison) was subjected to the same reheating experiment, and the thickness of the cut piece was measured. It was confirmed that the cut pieces that were not immersed were also covered with a surface crystal layer. Photographs of optical glass lens materials for reheat press 1 to 13 after the reheat experiment and materials for comparative optical glass lenses for reheat press are also shown in FIGS.

[Thickness of surface crystal layer]
The optical glass lens material 7 for reheat press after heating was cut, and the thickness of the surface crystal layer was measured by photography or the like to find that it was 20 μm. Similarly, the optical glass lens for reheat press for comparison was cut, and the thickness of the surface crystal layer was measured by photography or the like to find that it was 50 μm. The composition of the surface portion including the modified surface layer changed, and the cut piece was covered with a surface crystal layer that was not a hard crystal, and the cut piece was in a nearly spherical shape with rounded corners. With such a cut piece, the corners did not penetrate into the middle glass during reheat pressing, and the thin surface crystal layer had a thickness sufficient to be removed by grinding and polishing the glass.

[Ingredients of Surface Modified Layer]
For measurement of the Na component in the surface modified layer of the optical glass lens material for reheat press (before reheat press), for example, LIBS (Laser Induced Breakdown Spectroscopy), Applied Spectra, is used. ) can be used. LIBS was used in the following measurements.
The components of the surface-modified layer of optical glass lens material for reheat press 7 (before reheat press) were measured using such an apparatus. The results are shown in FIG. It was found that a predetermined distance (approximately 500 nm) from the surface contains a large amount of Na although the base glass does not contain Na. It is presumed that this is because the Na component penetrated into the glass due to the immersion.

As in the above examples, the glass composition No. 1 in place of glass composition No. 1 listed in Table 1. 2 to 31, and the temperature was appropriately changed according to the properties of the glass, and the same experiment as in Example 1 was performed. The composition of the crystal changed, and instead of hard crystals, the cut pieces became nearly spherical with rounded corners. With such a cut piece, the corners did not penetrate into the middle glass during reheat pressing, and the thin surface crystal layer had a thickness sufficient to be removed by grinding and polishing the glass.

By immersing each cut piece in molten alkali metal salt, the thickness of the surface crystal layer can be reduced. It was confirmed that a nearly spherical shape can be obtained. With such a cut piece, it is possible to prevent the corners from penetrating into the middle glass during reheat pressing. Also, the thin surface crystal layer of these examples has a thickness that can be sufficiently removed by grinding and polishing the glass.

Various glass materials for reheat press thus produced were heated, softened, and reheat press molded to produce lens blanks having shapes similar to optical lenses. Observation of the lens blank revealed no penetration of the surface crystal layer at the edges and corners of the glass material into the interior of the glass.
The surface of the reheat-pressed glass material after reheat-press molding is subjected to surface analysis in the same manner as the surface analysis of the reheat-press glass material, and the presence of a surface-modified layer similar to that of the reheat-press glass material. Confirmed to do.
Then, the lens blank was ground and polished to produce various optical lenses. Since the lens blank does not have a surface crystal layer at the edges and corners of the glass material that penetrates into the inside of the glass, the amount of grinding and polishing can be reduced.
In addition, the said reheat press molding, grinding, and polishing can apply a well-known method.
Although the production of optical lenses has been described above, the present invention can also be applied to the production of various optical elements made of glass such as prisms, and the production of glass articles other than optical elements.

INDUSTRIAL APPLICABILITY The present invention is useful in the technical field of optical glasses. In particular, since the glass of the present invention has the feature of reducing surface devitrification during reheating, it is particularly suitable for manufacturing glass including a reheating process, but it can be used for many applications other than reheat press. can.

Reference numerals 11, 21 Glass 11a, 21a Crystal layer 11b Intrusion crystal layer 12, 22 Upper mold 13, 23 Lower mold

Claims (10)

a glass containing the total content of Li component, Na component, K component, Rb component, Cs component and Fr component at 1.2% by mass or less;
and a surface modification layer covering the glass,
Glass for reheat press, wherein the content of at least one component selected from the Li component, Na component, K component, Rb component, Cs component and Fr component in the surface modified layer is higher than the content of the component in the glass. material. lanthanum borate-based glass;
and a surface modification layer covering the glass,
Glass for reheat press, wherein the content of at least one component selected from the Li component, Na component, K component, Rb component, Cs component and Fr component in the surface modified layer is higher than the content of the component in the glass. material. The glass material for reheat press according to claim 1 or 2, wherein the thickness of the surface modification layer is 1000 nm or less. The glass for reheat press according to any one of claims 1 to 3, wherein the glass contains 0.1 mass% or less of each of Li component, Na component, K component, Rb component, Cs component and Fr component. material. A reheat-pressed glass material derived from the reheat-press glass material according to any one of claims 1 to 4. A polished glass derived from the reheat-pressed glass material of claim 5 . A step of melting glass raw materials so that the total content of Li component, Na component, K component, Rb component, Cs component and Fr component is 1.2% by mass or less, and then cooling to produce glass. When,
forming a surface modified layer on the surface of the glass by immersing the glass in a molten salt containing at least one of Li component, Na component, K component, Rb component, Cs component and Fr component. A method for manufacturing a glass material for reheat press. a step of producing a lanthanum borate glass by melting raw materials for the lanthanum borate glass and then cooling the raw material;
A step of forming a surface modified layer on the surface of the glass by immersing the lanthanum borate-based glass in a molten salt containing at least one of Li, Na, K, Rb, Cs and Fr components. and a method for manufacturing a glass material for reheat press. A method for producing a reheat-pressed glass material, comprising the step of reheat-pressing the glass material for reheat-press obtained by the production method according to claim 7 or 8. A method for producing polished glass, comprising the steps of grinding and polishing the reheat-pressed glass material obtained by the production method of claim 9 .

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