Optical glass, preform, and optical element

Abstract

To provide an optical glass which has optical properties such as high refractive index and high dispersibility, corresponds to class 1 to 3 acid resistance in a powder method, has Knoop hardness of class 6 or higher and is inexpensive.SOLUTION: An objective optical glass is characterized in that the glass includes in mass%: 0.0-10.0% of ZrO2, more than 0.0% to 20.0% of B2O3, more than 0.0% to 30.0% of SiO2, 0.0-40.0% of ZnO and 5.0-35.0% of La2O3; the sum of mass, Ta2O5+Nb2O5+WO3+Gd2O3 is 5.0 or less; a mass ratio, SiO2 / (SiO2+B2O3+TiO2) is in a range pf 0.15 to 0.45; the measurement result of acid resistance by a powder method set up in a specification of Japan optical glass industrial association (JOGIS06-2006) is in a range of class 1 to 3; and the measurement result of Knoop hardness by a measurement method set up in the specification of the Japan optical glass industrial association (JOGIS09-1975) is class 6 or higher.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to optical glass, preforms, and optical elements.

Background Art

[0002] In addition to digital cameras, projectors, and surveillance cameras, optical glass is increasingly used as an optical element such as an imaging lens mounted on in-vehicle cameras as autonomous driving technology advances. Among in-vehicle cameras, for example, in applications used outdoors, the front lens that is exposed to the outside air needs to have excellent chemical durability. By having good chemical durability, cloudiness due to corrosion of the lens surface is less likely to occur, and long-term use becomes possible. In addition, in-vehicle cameras require optical glass that is less likely to be scratched by impacts caused by collisions with small stones entrained by dust or tires in the atmosphere. Furthermore, it is desirable that the optical elements incorporated in in-vehicle optical devices be inexpensive.

[0003] As a material for lenses for in-vehicle cameras, there is a very high demand for a so-called high refractive index and high dispersion optical characteristic having a refractive index (n d ) of 1.75000 or more and an Abbe number (ν d ) of 20.00 or more and 40.00 or less, as well as a class 6 glass material having excellent chemical durability and mechanical properties such as Knoop hardness. As materials used for such in-vehicle optical devices, glass compositions represented by Patent Documents 1 and 2, for example, are known.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, the optical glass shown in Patent Document 1 has a chemical durability (acid resistance) of grades 1 to 3 by the powder method while maintaining a high refractive index, and has a Vickers hardness of grade 6 or more in a measurement method according to "JOGIS09-1975 Method for Measuring Vickers Hardness of Optical Glass". However, since it contains Nb2O5 and Gd2O3 with high raw material costs, there is a problem that the cost is high.

[0006] In addition, the optical glasses shown in Patent Documents 1 and 2 contain a large amount of ZrO2 component in order to have a high refractive index and obtain acid resistance of grades 1 to 3 by the powder method. However, the ZrO2 component is a component that deteriorates devitrification resistance and increases the liquidus temperature, and there is a problem that it reduces the melting and forming yield of the glass.

[0007] The present invention has been made in view of the above problems, and an object thereof is to provide an optical glass having optical characteristics of high refractive index and high dispersion, acid resistance of grades 1 to 3 by the powder method, a Vickers hardness of grade 6 or more, and being cheaper.

Means for Solving the Problems

[0008] As a result of intensive experimental research to solve the above problems, the present inventors have found that by reducing the Nb2O5 component and the ZrO2 component as much as possible and adjusting the contents of each component including the B2O3 component, the SiO2 component, the ZnO component, and the La2O3 component, a glass material having good chemical durability and mechanical properties at low cost can be created, and the present invention has been completed. Specifically, the present invention provides the following.

[0009] (1) In mass%, ZrO2 component: 0.0 to 10.0%, B2O3 component: more than 0.0% to 20.0%, SiO2 component: more than 0.0% to 30.0% ZnO component: 0.0 to 40.0%, La2O3 component: 5.0 to 35.0%, containing Ta2O5+Nb2O5+WO3+Gd2O3 with a total mass of 5.0% or less, the mass ratio of SiO2 / (SiO2+B2O3+TiO2) being 0.15 to 0.45 or less, and the measurement result of acid resistance by the powder method defined in the Japan Optical Glass Industry Association Standard (JOGIS06-2006) being grades 1 to 3, and the measurement result of Vickers hardness by the measurement method defined in the Japan Optical Glass Industry Association Standard (JOGIS09-1975) being grade 6 or higher. An optical glass characterized by this.

[0010] (2) the total mass of CaO+ZnO+TiO2 being 10.0 to 50.0% or less, the optical glass of (1) where the mass ratio of (BaO+ZnO) / La2O3 is 0.5 to 2.1 or less.

[0011] (3) having a refractive index (n d ) of 1.78000 or more and 1.98000 or less, and having an Abbe number (ν d ) of 20.00 or more and 40.00 or less, the optical glass of (1) or (2) where the mass ratio of (CaO+ZnO+Li2O) / BaO is 0.022 or more.

[0012] (4) A preform made of any of the optical glasses from (1) to (3).

[0013] (5) An optical element made of any of the optical glasses from (1) to (3).

[0014] (6) An optical device including the optical element of (5).

Advantages of the Invention

[0015] According to the present invention, there can be obtained an optical glass having optical properties of high refractive index and high dispersion, with the measurement result of acid resistance (JOGIS06-2006) by the powder method defined in the Japan Optical Glass Industry Association standard being grade 1 to 3, the measurement result of Vickers hardness (JOGIS09-1975) by the measurement method defined in the Japan Optical Glass Industry Association standard being a value of grade 6 or higher, excellent chemical durability, strong resistance to impact, etc., and being inexpensive, as well as a preform and an optical element using the same.

Embodiment for Carrying Out the Invention

[0016] The optical glass of the present invention contains, by mass%, 0.0 to 10.0% of a ZrO2 component, more than 0.0% to 20.0% of a B2O3 component, more than 0.0% to 30.0% of a SiO2 component, 0.0 to 40.0% of a ZnO component, and 5.0 to 35.0% of a La2O3 component. By adjusting the content of each component including the ZrO2 component, B2O3 component, SiO2 component, ZnO component, and La2O3 component, values of high refractive index and high dispersion can be obtained, the acid resistance by the powder method is grade 1 to 3, the measurement result of Vickers hardness is grade 6 or higher, it is inexpensive and has a low liquidus temperature, and an optical glass particularly suitable for in-vehicle glass materials can be obtained. Also, by setting the mass sum Ta2O5+Nb2O5+WO3+Gd2O3 to 5.0% or less, the raw material cost can be suppressed. By setting the mass ratio SiO2 / (SiO2+B2O3+TiO2) to 0.15 to 0.45 or less, the liquidus temperature of the glass becomes low, and a stable glass can be obtained while satisfying the desired refractive index and Abbe number.

[0017] Hereinafter, embodiments of the optical glass of the present invention will be described in detail. The present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that, for parts where the description overlaps, the description may be omitted as appropriate, but it does not limit the gist of the invention.

[0018] [Glass Components] The composition ranges of the components constituting the optical glass of the present invention are described below. In this specification, unless otherwise specified, the content of each component is expressed as mass% based on the total mass of the oxide-converted composition. Here, the "oxide-converted composition" is the composition in which each component contained in the glass is expressed with the total mass number of the generated oxides as 100 mass%, assuming that oxides, double salts, metal fluorides, etc. used as raw materials for the glass constituent components of the present invention are all decomposed into oxides during melting.

[0019] <Regarding essential components and optional components> In the optical glass of the present invention containing a large amount of rare earth oxides, the B2O3 component is an essential component as a glass-forming oxide. In particular, by setting the content of the B2O3 component to more than 0.0%, the devitrification resistance of the glass can be enhanced, and the meltability of the glass can also be enhanced. Therefore, the content of the B2O3 component is preferably more than 0%, more preferably 1.5% or more, and even more preferably 2.0% or more as the lower limit. On the other hand, by setting the content of the B2O3 component to 20.0% or less, it becomes easier to obtain a larger refractive index, and the deterioration of chemical durability can be suppressed. Therefore, the content of the B2O3 component is preferably 20.0% or less, more preferably 18.0% or less, and even more preferably 15.0% or less as the upper limit. As the B2O3 component, H3BO3, Na2B4O7, Na2B4O7·10H2O, BPO4, etc. can be used as raw materials.

[0020] When the SiO2 component is contained in an amount exceeding 0.0%, it is an essential component that can increase the viscosity of the molten glass and increase the hardness of the glass. It is also a component that can enhance the stability of the glass and make it easier to obtain a glass that can withstand mass production. Therefore, the content of the SiO2 component is preferably more than 0.0%, more preferably 2.0% or more, and even more preferably 4.0% or more as the lower limit. On the other hand, by setting the content of the SiO2 component to 30.0% or less, a viscosity suitable for glass forming can be obtained, and a decrease in the refractive index can be suppressed. Therefore, the content of the SiO2 component is preferably 30.0% or less, more preferably 27.0% or less, and even more preferably 25.0% or less as the upper limit. As the SiO2 component, SiO2, K2SiF6, Na2SiF6, etc. can be used as raw materials.

[0021] When the TiO2 component contains 5.0% or more, it is a component that increases the refractive index of the glass, increases the Abbe number, and raises the hardness of the glass. Therefore, the content of the TiO2 component preferably has a lower limit of 5.0% or more, more preferably 6.5% or more, and even more preferably 8.0% or more. On the other hand, by setting the content of the TiO2 component to 40.0% or less, devitrification due to excessive content of the TiO2 component can be reduced, and a decrease in the transmittance of the glass to visible light (especially light with a wavelength of 500 nm or less) can be suppressed. Also, a decrease in the Abbe number can be suppressed thereby. Therefore, the content of the TiO2 component preferably has an upper limit of 40.0% or less, more preferably 38.0% or less, and even more preferably 35.0% or less. As the TiO2 component, TiO2, etc. can be used as raw materials.

[0022] When the ZnO component contains more than 0.0%, it is an optional component that enhances the meltability of the raw materials, increases the hardness of the glass, and also enhances the stability of the glass. It is also a component that can improve chemical durability. Therefore, the content of the ZnO component preferably has a lower limit of more than 0.0%, more preferably 0.5% or more, and even more preferably 1.0% or more. On the other hand, by setting the content of the ZnO component to 40.0% or less, a decrease in the refractive index of the glass can be suppressed, and devitrification due to excessive decrease in viscosity can be reduced. Therefore, the content of the ZnO component preferably has an upper limit of 40.0% or less, more preferably 38.0% or less, and even more preferably 35.0% or less. As the ZnO component, ZnO, ZnF2, etc. can be used as raw materials.

[0023] When the La2O3 component contains more than 0.0%, it is an optional component that increases the refractive index and Abbe number of the glass. Therefore, when it is desired to obtain an optical glass having a refractive index of 1.75 or more, the content of the La2O3 component preferably has a lower limit of 5.0% or more, more preferably 8.0% or more, and even more preferably 10.0% or more. On the other hand, by setting the content of the La2O3 component to 35.0% or less, devitrification can be reduced by enhancing the stability of the glass, and an excessive increase in the Abbe number can be suppressed. Therefore, the upper limit is preferably 35.0% or less, more preferably 33.0% or less, and still more preferably 30.0% or less.

[0024] The ZrO2 component is an optional component that can suppress a decrease in acid resistance and increase the refractive index and Abbe number of the glass when its content exceeds 0.0%. The content of the ZrO2 component is preferably more than 0.0%, more preferably 0.5% or more, and still more preferably 1.0% or more as the lower limit. On the other hand, by setting the content of the ZrO2 component to 10.0% or less, devitrification due to excessive content of the ZrO2 component can be reduced. Therefore, the content of the ZrO2 component is preferably 10.0% or less, more preferably 8.0% or less, and still more preferably 5.3% or less as the upper limit. As the ZrO2 component, ZrO2, ZrF4, etc. can be used as raw materials.

[0025] The Nb2O5 component is an optional component that can increase the refractive index of the glass when its content exceeds 0.0%. On the other hand, by setting the content of the Nb2O5 component to 5.0% or less, the material cost of the glass can be suppressed. Also, devitrification due to excessive content of the Nb2O5 component can be reduced, and a decrease in the transmittance of the glass for visible light (especially light with a wavelength of 500 nm or less) can be suppressed. Further, a decrease in the Abbe number can be suppressed thereby. Therefore, the content of the Nb2O5 component is preferably 5.0% or less, more preferably 4.0% or less, and still more preferably 3.0% or less as the upper limit. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain the Nb2O5 component. As the Nb2O5 component, Nb2O5, etc. can be used as raw materials.

[0026] The WO3 component is an optional component that can increase the refractive index and enhance the devitrification resistance while reducing the coloring of the glass by other high refractive index components when its content exceeds 0.0%. On the other hand, by setting the content of the WO3 component to 5.0% or less, the material cost of the glass can be suppressed. In addition, the coloring of the glass by the WO3 component can be reduced to increase the visible light transmittance. Therefore, the content of the WO3 component is preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less as the upper limit. In particular, from the perspective of reducing the material cost, it is most preferable not to contain the WO3 component. As the WO3 component, WO3 or the like can be used as a raw material.

[0027] When the content of the Y2O3 component exceeds 0.0%, it is an optional component that can suppress the material cost of the glass while maintaining the desired refractive index and Abbe number. On the other hand, by setting the content of the Y2O3 component to 10.0% or less, a decrease in the refractive index of the glass can be suppressed, and the stability of the glass can be enhanced. In addition, deterioration of the meltability of the glass raw material can be suppressed. Therefore, the content of the Y2O3 component is preferably 10.0% or less, more preferably 5.0% or less, and even more preferably 3.5% or less as the upper limit. As the Y2O3 component, Y2O3, YF3 or the like can be used as a raw material.

[0028] The Gd2O3 component and the Yb2O3 component are optional components that can increase the refractive index of the glass when the content exceeds 0.0%. However, the raw material prices of the Gd2O3 component and the Yb2O3 component are high, and if their contents are large, the production cost will increase, so the effects of reducing the Nb2O5 component, the WO3 component, etc. will be diminished. In addition, by reducing the contents of the Gd2O3 component and the Yb2O3 component, an increase in the Abbe number of the glass can be suppressed. Therefore, the contents of the Gd2O3 component and the Yb2O3 component are each preferably 4.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.5% or less, and even more preferably 0.1% or less as the upper limit. In particular, from the perspective of reducing the material cost, it is most preferable not to contain these components. As the Gd2O3 component and the Yb2O3 component, Gd2O3, GdF3, Yb2O3 or the like can be used as a raw material.

[0029] The Ta2O5 component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when it contains more than 0.0%. However, since the Ta2O5 component has a high raw material price and the production cost increases when its content is high, the effects of reducing the Nb2O5 component, WO3 component, etc. are diminished. Also, by setting the content of the Ta2O5 component to 5.0% or less, the melting temperature of the raw material becomes lower and the energy required for melting the raw material is reduced, so the manufacturing cost of the optical glass can also be reduced. Therefore, the content of the Ta2O5 component is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less, still more preferably 0.5% or less, and still more preferably 0.1% or less as the upper limit. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain the Ta2O5 component. As the Ta2O5 component, Ta2O5 or the like can be used as the raw material.

[0030] The MgO component is an optional component that can improve the meltability of the glass raw material and the devitrification resistance of the glass. On the other hand, by setting the content of the MgO component to 10.0% or less, the decrease in refractive index and the decrease in devitrification resistance due to the excessive content of these components can be suppressed. Therefore, the content of the MgO component is preferably 10.0% or less, more preferably 9.0% or less, and more preferably 8.0% or less as the upper limit. preferably 10.0% or less, more preferably 9.0% or less, and more preferably 8.0% or less as the upper limit.

[0031] The CaO component is an optional component that can increase the hardness of the glass and improve the meltability of the glass raw material. On the other hand, by setting the content of the CaO component to 20.0% or less, the decrease in refractive index and the decrease in devitrification resistance due to the excessive content of these components can be suppressed. Therefore, the content of the CaO component is preferably 20.0% or less, more preferably 18.0% or less, and most preferably 15.0% or less as the upper limit.

[0032] The SrO component is an optional component that can improve the meltability of the glass raw material and the devitrification resistance of the glass. On the one hand, by setting the content of the SrO component to 10.0% or less, a decrease in refractive index and a decrease in devitrification resistance due to excessive content of these components can be suppressed. Therefore, the content of the SrO component is preferably 10.0% or less, more preferably 9.0% or less, and most preferably 8.0% or less as the upper limit.

[0033] When the BaO component contains more than 0.0%, it is an optional component that can increase the refractive index and Abbe number of the glass and lower the liquidus temperature. The content of the BaO component is preferably more than 0.0%, more preferably 1.0% or more, and still more preferably 1.5% or more as the lower limit. By setting the content of the BaO component to 40.0% or less, a decrease in refractive index, a decrease in devitrification resistance, and a deterioration of chemical durability (acid resistance) due to excessive content of these components can be suppressed. Therefore, the content of the BaO component is preferably 40.0% or less, more preferably 35.0% or less, and most preferably 31.0% or less as the upper limit.

[0034] The Li2O component, Na2O component, and K2O component are optional components that can improve the meltability of the glass and lower the glass transition temperature when they contain more than 0.0%. On the other hand, by setting the Li2O component, Na2O component, and K2O component to 10.0% or less respectively, it is difficult to lower the refractive index of the glass, and devitrification of the glass can be reduced. Also, deterioration of chemical durability (acid resistance) and decrease in hardness can be suppressed. Therefore, the content of the Li2O component, Na2O component, and K2O component is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, and most preferably 1.5% or less as the upper limit respectively. As raw materials for the Li2O component, Na2O component, and K2O component, Li2CO3, LiNO3, Li2CO3, Na2CO3, NaNO3, NaF, Na2SiF6, K2CO3, KNO3, KF, KHF2, K2SiF6, etc. can be used.

[0035] When the P2O5 component contains more than 0.0%, it is an optional component that can lower the liquidus temperature of the glass and enhance the devitrification resistance. On the other hand, by setting the content of the P2O5 component to 10.0% or less, a decrease in the chemical durability of the glass, particularly the water resistance, can be suppressed. Therefore, the content of the P2O5 component preferably has an upper limit of 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less. As the P2O5 component, Al(PO3)3, Ca(PO3)2, Ba(PO3)2, BPO4, H3PO4, etc. can be used as raw materials.

[0036] The GeO2 component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance when its content exceeds 0.0%. However, GeO2 has a high raw material cost, and when its content is large, the production cost increases, so the effects of reducing the Gd2O3 component, Ta2O5 component, etc. are diminished. Therefore, the content of the GeO2 component preferably has an upper limit of 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, even more preferably 1.0% or less, and even more preferably 0.1% or less. From the perspective of reducing material costs, the GeO2 component may not be contained. As the GeO2 component, GeO2, etc. can be used as raw materials.

[0037] The Al2O3 component is an optional component that can improve the chemical durability of the glass and the devitrification resistance of the molten glass when its content exceeds 0.0%. Therefore, the content of the Al2O3 component preferably has a lower limit of more than 0.0%, more preferably 0.5% or more. On the other hand, by setting the content of the Al2O3 component to 15.0% or less, the liquidus temperature of the glass can be lowered to enhance the devitrification resistance. Therefore, the content of the Al2O3 component preferably has an upper limit of 15.0% or less, more preferably 10.0% or less, still more preferably 9.0% or less, and even more preferably 8.0% or less. As the Al2O3 component, Al2O3, Al(OH)3, AlF3, etc. can be used as raw materials.

[0038] The Ga2O3 component is an optional component that can improve the chemical durability of the glass and the devitrification resistance of the molten glass when its content exceeds 0.0%. On the other hand, by setting the content of the Ga2O3 component to 15.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be enhanced. Therefore, the content of the Ga2O3 component is preferably 15.0% or less, more preferably 10.0% or less, still more preferably 5.0% or less, and even more preferably 3.0% or less as the upper limit. As the Ga2O3 component, Ga2O3, Ga(OH)3, etc. can be used as raw materials.

[0039] The Bi2O3 component is an optional component that can increase the refractive index and lower the glass transition point when its content exceeds 0.0%. On the other hand, by setting the content of the Bi2O3 component to 5.0% or less, the liquidus temperature of the glass can be lowered and the devitrification resistance can be enhanced. Also, since the raw material price is high, the production cost can be suppressed. Therefore, the content of the Bi2O3 component is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less as the upper limit. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain the Bi2O3 component. As the Bi2O3 component, Bi2O3, etc. can be used as raw materials.

[0040] The TeO2 component is an optional component that can increase the refractive index and lower the glass transition point when its content exceeds 0.0%. On the other hand, TeO2 has a problem that it can alloy with platinum when melting glass raw materials in a platinum crucible or a melting tank where the part in contact with the molten glass is formed of platinum. Therefore, the content of the TeO2 component is preferably 5.0% or less, more preferably 3.0% or less, still more preferably 1.0% or less as the upper limit. In particular, from the viewpoint of reducing the material cost, it is most preferable not to contain the TeO2 component. As the TeO2 component, TeO2, etc. can be used as raw materials.

[0041] The SnO2 component is an optional component that can reduce the oxidation of molten glass and clarify it, and increase the visible light transmittance of the glass when its content exceeds 0.0%. On the other hand, by setting the content of the SnO2 component to 3.0% or less, coloring of the glass due to reduction of the molten glass and devitrification of the glass can be reduced. In addition, since alloying of the SnO2 component and the melting equipment (especially noble metals such as Pt) is reduced, the service life of the melting equipment can be extended. Therefore, the content of the SnO2 component is preferably 3.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, and even more preferably 0.1% or less as the upper limit. As the SnO2 component, SnO, SnO2, SnF2, SnF4, etc. can be used as raw materials.

[0042] The Sb2O3 component is an optional component that can defoam the molten glass when contained in an amount exceeding 0.0%. On the other hand, if the amount of Sb2O3 is too large, the transmittance in the short wavelength region of the visible light region deteriorates. Therefore, the content of the Sb2O3 component is preferably 1.0% or less, more preferably 0.5% or less, and still more preferably 0.3% or less as the upper limit. As the Sb2O3 component, Sb2O3, Sb2O5, Na2H2Sb2O7·5H2O, etc. can be used as raw materials.

[0043] Note that the components for clarifying and defoaming the glass are not limited to the above-mentioned Sb2O3 component, and known fining agents, defoaming agents in the field of glass manufacturing, or combinations thereof can be used.

[0044] The F component is an optional component that can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance when contained in an amount exceeding 0.0%. However, when the content of the F component, that is, the total amount of F of the fluoride substituted for a part or all of one or more oxides of the above-mentioned metal elements exceeds 15.0%, the volatilization amount of the F component increases, so it becomes difficult to obtain stable optical constants and it becomes difficult to obtain a homogeneous glass. In addition, the Abbe number rises more than necessary. Therefore, the content of the F component is preferably 15.0% or less, more preferably 10.0% or less, still more preferably 5.0% or less, and even more preferably 3.0% or less as the upper limit. Component F can be contained in the glass by using, for example, ZrF4, AlF3, NaF, CaF2, etc. as raw materials.

[0045] By setting the mass ratio SiO2 / (SiO2 + B2O3 + TiO2) to 0.15 to 0.45 or less, the liquidus temperature of the glass can be lowered and a stable glass can be obtained. Therefore, the mass ratio SiO2 / (SiO2 + B2O3 + TiO2) preferably has a lower limit of 0.15 or more, more preferably 0.16 or more, and even more preferably 0.17 or more. On the other hand, by setting the mass ratio SiO2 / (SiO2 + B2O3 + TiO2) to 0.45 or less, the desired refractive index and Abbe number can be obtained. Therefore, the mass ratio SiO2 / (SiO2 + B2O3 + TiO2) preferably has an upper limit of 0.45 or less, more preferably 0.44 or less, and even more preferably 0.43 or less.

[0046] The total content of the Ta2O5 component, Nb2O5 component, WO3 component and Gd2O3 component is preferably 5.0% or less. In particular, by setting this total content to 5.0% or less, the content of these expensive components is reduced, so that the raw material cost can be suppressed. Therefore, the mass sum (Ta2O5 + Nb2O5 + WO3 + Gd2O3) preferably has an upper limit of 5.0% or less, more preferably 4.5% or less, and even more preferably 4.0% or less.

[0047] The total content of the CaO component, ZnO component and TiO2 component is preferably 10.0 to 50.0%. By setting the total content to 10.0% or more, the Knoop hardness can be increased. Therefore, the total content of the CaO component, ZnO component and TiO2 component preferably has a lower limit of 10.0% or more, more preferably 10.5% or more, and even more preferably 11.0% or more. On the other hand, by setting the total content of the CaO component, ZnO component and TiO2 component to 50.0% or less, the deterioration of devitrification resistance can be suppressed. Therefore, the total content of the CaO component, ZnO component and TiO2 component preferably has an upper limit of 50.0% or less, more preferably 49.0% or less, and even more preferably 48.0% or less.

[0048] The ratio of the total amount of the BaO component and the ZnO component to the content of the La2O3 component is preferably 0.5 to 2.1. In particular, by setting the mass ratio (BaO + ZnO) / La2O3 to 0.5 or more, the liquidus temperature of the glass becomes lower, and a desired refractive index and Abbe number can be obtained. Therefore, the mass ratio (BaO + ZnO) / La2O3 preferably has a lower limit of 0.5 or more, more preferably 0.55 or more, and even more preferably 0.6 or more. On the other hand, by setting the mass ratio (BaO + ZnO) / La2O3 to 2.1 or less, deterioration of the acid resistance by the powder method can be suppressed. Therefore, (BaO + ZnO) / La2O3 preferably has an upper limit of 2.1 or less, more preferably 2.06 or less, and even more preferably 2.02 or less.

[0049] The ratio of the total amount of the CaO component, the ZnO component, and the Li2O component to the BaO component is preferably 0.022 or more. In particular, by setting the mass ratio (CaO + ZnO + Li2O) / BaO to 0.022 or more, deterioration of the acid resistance by the powder method can be suppressed, and a glass having a large Knoop hardness can be obtained. Therefore, the mass ratio (CaO + ZnO + Li2O) / BaO preferably has a lower limit of 0.022 or more, more preferably 0.023 or more, and even more preferably 0.024 or more. On the other hand, the ratio of the total amount of the CaO component, the ZnO component, and the Li2O component to the BaO component is preferably 20.0 or less in order to suppress deterioration of the stability of the glass and reduction of the refractive index. Therefore, the mass ratio (CaO + ZnO + Li2O) / BaO preferably has an upper limit of 20.0 or less, more preferably 18.0 or less, and even more preferably 16.0 or less.

[0050] <Components that should not be contained> Next, components that should not be contained in the optical glass of the present invention and components that are preferably not contained will be described.

[0051] Other components can be added as necessary within a range that does not impair the properties of the glass of the present invention. However, each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, has the property that even when contained in a small amount alone or in combination, the glass is colored and absorbs at specific wavelengths in the visible region. Therefore, in particular, in optical glass that uses wavelengths in the visible region, it is preferably substantially free of them. Also, for each component of Rb and Cs, from the viewpoint of suppressing glass coloring, it is preferably not contained.

[0052] In addition, lead compounds such as PbO and arsenic compounds such as As2O3 are components with a high environmental load. Therefore, it is desirable that they are substantially not contained, that is, not contained at all except for unavoidable contamination.

[0053] Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has a tendency to refrain from being used as harmful chemical substances in recent years. Measures for environmental protection are required not only in the glass manufacturing process but also in the processing process and disposal after productization. Therefore, when emphasizing environmental impact, it is preferably substantially free of these.

[0054] [Manufacturing Method] The optical glass of the present invention is produced, for example, as follows. That is, as raw materials for the above respective components, high-purity raw materials used in ordinary optical glass such as oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc. are uniformly mixed so that each component is within a predetermined content range, and the prepared mixture is put into a platinum crucible and melted in an electric furnace at a temperature range of 1000 to 1400 °C for 1 to 10 hours according to the melting difficulty of the glass raw materials, stirred and homogenized, then cooled to an appropriate temperature and cast into a mold, and gradually cooled to produce it.

[0055] At this time, it is preferable to use a glass raw material with high fusibility. This enables melting at a lower temperature and in a shorter time, thereby enhancing the productivity of the glass and reducing the production cost. In addition, since the volatilization of components and the reaction with the crucible or the like are reduced, it becomes easier to obtain glass with less coloring.

[0056] <Physical properties> The optical glass of the present invention has a high refractive index and high dispersion. In particular, the refractive index (n d ) of the optical glass of the present invention preferably has a lower limit of 1.78000 or more, more preferably 1.78500 or more, and still more preferably 1.79000 or more. This refractive index (n d ) may preferably have an upper limit of 1.98000 or less, more preferably 1.97000 or less, and still more preferably 1.96500 or less. Also, the Abbe number (ν d ) of the optical glass of the present invention preferably has a lower limit of 20.00 or more, more preferably 21.00 or more, and still more preferably 22.00 or more. This Abbe number (ν d ) may preferably have an upper limit of 40.00 or less, more preferably 39.00 or less, and still more preferably 38.00 or less.

[0057] The optical glass of the present invention preferably has a high visible light transmittance, particularly the transmittance of light on the short wavelength side of visible light, and thereby has less coloring. In particular, for the optical glass of the present invention, when expressed by the transmittance of the glass, the wavelength (λ 70 ) at which a 10-mm-thick sample shows a spectral transmittance of 70% preferably has an upper limit of 480 nm or less, preferably 460 nm or less, more preferably 450 nm or less, and still more preferably 440 nm or less. Also, the shortest wavelength (λ5) at which a 10-mm-thick sample of the optical glass of the present invention shows a spectral transmittance of 5% preferably has an upper limit of 400 nm or less, more preferably 385 nm or less, and still more preferably 370 nm or less.

[0058] The glass of the present invention has high devitrification resistance, more specifically, it has a low liquidus temperature. This is preferable. That is, the liquidus temperature of the glass of the present invention is preferably 1300 ° C or lower, more preferably 1250 ° C or lower, and still more preferably 1200 ° C or lower as the upper limit. Thereby, even when the molten glass flows out at a lower temperature, the crystallization of the produced glass is reduced, so that devitrification particularly when forming glass from the molten state can be reduced. In addition, since the glass can be formed even when the melting temperature of the glass is lowered, the manufacturing cost of the glass can be reduced by suppressing the energy consumed during the forming of the glass. On the other hand, the lower limit of the liquidus temperature of the glass of the present invention is not particularly limited, but the liquidus temperature of the glass obtained by the present invention may preferably be 950 ° C or higher, more preferably 980 ° C or higher, and still more preferably 1000 ° C or higher as the lower limit. In addition, the "liquidus temperature" in this specification means that a 30 cc carrot-shaped glass sample is placed in a platinum crucible with a capacity of 50 ml and completely melted at 1350 ° C, cooled to a predetermined temperature and held for 12 hours, taken out of the furnace and cooled, and then immediately observe the presence or absence of crystals on the glass surface and in the glass and represents the lowest temperature at which no crystals are observed.

[0059] The acid resistance of the glasses of the examples and comparative examples is measured according to the Japan Optical Glass Industry Association standard "Method for Measuring Chemical Durability of Optical Glass" JOGIS06-2006. That is, a glass sample crushed to a particle size of 425 to 600 μm was placed in a specific gravity bottle and put into a platinum basket. The platinum basket was placed in a quartz glass round-bottom flask containing a 0.01N nitric acid aqueous solution and treated in a boiling water bath for 60 minutes. The weight loss rate (mass%) of the glass sample after the treatment is calculated, and when this weight loss rate (mass%) is less than 0.20, it is classified as Class 1, when the weight loss rate is 0.20 to less than 0.35, it is classified as Class 2, when the weight loss rate is 0.35 to less than 0.65, it is classified as Class 3, when the weight loss rate is 0.65 to less than 1.20, it is classified as Class 4, when the weight loss rate is 1.20 to less than 2.20, it is classified as Class 5, and when the weight loss rate is 2.20 or more, it is classified as Class 6. At this time, the smaller the number of classes, the better the acid resistance of the glass. In the optical glass of the present invention, it is preferably of grade 1 to 3, more preferably of grade 1 to 2.

[0060] In the measurement method according to "JOGIS09-1975 Method for Measuring the Knoop Hardness of Optical Glass", the optical glass of the present invention is preferably of grade 6 or higher. As a result, it becomes difficult for scratches and cracks to occur during the polishing of the glass, and for scratches on the surface to occur during the transportation of the glass, etc. Therefore, an optical glass having a desired surface state and being able to easily maintain that surface state can be obtained. Accordingly, the Knoop hardness of the optical glass of the present invention is preferably grade 6 or higher.

[0061] [Preform and Optical Element] From the produced optical glass, a glass formed body can be produced using, for example, means of polishing or means of mold press forming such as reheat press forming or precision press forming. That is, a glass formed body can be produced by performing machining such as grinding and polishing on the optical glass, or a preform for mold press forming can be produced from the optical glass, and after performing reheat press forming on this preform, polishing is performed to produce a glass formed body, or a preform produced by polishing or a preform formed by known floating forming or the like is subjected to precision press forming to produce a glass formed body. Note that the means for producing the glass formed body is not limited to these means.

[0062] Thus, the optical glass of the present invention is useful for various optical elements and optical designs. Among them, in particular, it is preferable to form a preform from the optical glass of the present invention and perform reheat press forming, precision press forming, etc. using this preform to produce optical elements such as lenses and prisms. As a result, it becomes possible to form a preform with a large diameter, so that while increasing the size of the optical element, high-definition and high-precision imaging characteristics and projection characteristics can be realized when used in an optical device.

[0063] The glass molded body made of the optical glass of the present invention can be used for applications of optical elements such as lenses, prisms, mirrors, etc., and can also be used for applications that require good hardness and chemical durability, such as in-vehicle optical devices such as in-vehicle cameras.

Examples

[0064] The compositions of Examples (No. 1 to No. 29) of the present invention, and the refractive index (n d ), Abbe number (ν d ), chemical durability (acid resistance) by the powder method, Vickers hardness, transmittance (λ5, λ 70 ) and liquidus temperature results are shown in Tables 1 to 4. The following examples are for illustrative purposes only and are not limited to these examples.

[0065] The glasses of the examples of the present invention were all selected from high-purity raw materials commonly used in optical glasses, such as the corresponding oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc. as raw materials for each component, weighed to the proportions of the compositions of the respective examples shown in the table and uniformly mixed, then put into a platinum crucible, melted in an electric furnace at a temperature range of 1000 to 1400 °C for 1 to 10 hours according to the melting difficulty of the glass raw materials, stirred and homogenized, and then cast into a mold or the like and slowly cooled to produce.

[0066] The refractive index (n d ) and Abbe number (ν d ) of the glasses of the examples and comparative examples were measured according to the V-block method specified in JIS B 7071-2:2018. Here, the refractive index (n d ) was shown as the measured value for the d-line (587.56 nm) of the helium lamp. Also, the Abbe number (ν d ) was calculated using the refractive index (n d ) for the d-line of the helium lamp, the refractive index (n F ) for the F-line (486.13 nm) of the hydrogen lamp, and the refractive index (n C ) for the C-line (656.27 nm), and the Abbe number (ν d ) = [(n d - 1) / (n F - nC ) were calculated from the formula. These refractive indices (n d ), Abbe numbers (ν d ) were determined by measuring the glass obtained with a slow cooling rate of -25 °C / hr.

[0067] The transmittance of the glass of the examples was measured in accordance with the Japan Optical Glass Industry Association Standard JOGIS02-2003. In the present invention, the presence and degree of coloring of the glass were determined by measuring the transmittance of the glass. Specifically, for a parallel-plane polished product with a thickness of 10 ± 0.1 mm, the spectral transmittance from 200 to 800 nm was measured in accordance with JIS Z8722, and λ5 (wavelength at 5% transmittance) and λ 70 (wavelength at 70% transmittance) were determined.

[0068] The liquidus temperature of the examples was obtained by putting 30 cc of a cullet-shaped glass sample into a platinum crucible with a capacity of 50 ml, completely melting it at 1350 °C, cooling it to a predetermined temperature, holding it for 12 hours, taking it out of the furnace and cooling it, and then immediately observing the presence or absence of crystals on the glass surface and in the glass to determine the lowest temperature at which no crystals were observed.

[0069] The chemical durability of the glasses of the examples and comparative examples was measured in accordance with the Japan Optical Glass Industry Association Standard "Method for Measuring the Chemical Durability of Optical Glass" JOGIS06-2006. That is, a glass sample crushed to a particle size of 425 - 600 μm was placed in a specific gravity bottle and put into a platinum basket. The platinum basket was placed in a quartz glass round-bottom flask containing a 0.01 N nitric acid aqueous solution and treated in a boiling water bath for 60 minutes. The weight loss rate (mass %) of the glass sample after the treatment was calculated. When the weight loss rate (mass %) was less than 0.20, it was classified as grade 1; when the weight loss rate was 0.20 to less than 0.35, it was classified as grade 2; when the weight loss rate was 0.35 to less than 0.65, it was classified as grade 3; when the weight loss rate was 0.65 to less than 1.20, it was classified as grade 4; when the weight loss rate was 1.20 to less than 2.20, it was classified as grade 5; when the weight loss rate was 2.20 or more, it was classified as grade 6. At this time, the smaller the number of grades, the better the acid resistance of the glass.

[0070] Also, the Vickers hardness (Hk) of the glasses in Examples (No. 1 to No. 29) and Comparative Example (A) was measured based on the standard of the Japan Optical Glass Industry Association (JOGIS09 - 1975). Specifically, a diamond rhombic indenter (opposite prism angles of 172°30´ and 130°) was pressed onto the flat polished surface of the sample with a load of 0.98 N (0.1 kgf) for 15 seconds to create an indentation, and the length of the longer diagonal of the indentation was measured, and it was determined by Equation (1).

[0071] Vickers hardness = 1.451F / l 2 (1) F: Load (N) l: Length of the longer diagonal (mm) When the Vickers hardness is less than 150, it is classified as Grade 1, when it is 150 or more and less than 250, it is Grade 2, when it is 250 or more and less than 350, it is Grade 3, when it is 350 or more and less than 450, it is Grade 4, when it is 450 or more and less than 550, it is Grade 5, when it is 550 or more and less than 650, it is Grade 6, and when it is 650 or more, it is Grade 7. The larger the grade, the harder the glass.

[0072]

Table 1

[0073]

Table 2

[0074]

Table 3

[0075]

Table 4

[0076] As shown in the table, the optical glasses of the examples had a chemical durability (acid resistance) of Grade 3 or higher by the powder method and were within the desired range. On the other hand, the optical glass of the comparative example was Grade 4.

[0077] Also, all of the optical glasses of the examples had a refractive index (nd ) was 1.80000 or more and within the desired range. Also, for all of the optical glasses of the examples of the present invention, the Abbe number (ν d ) was within the range of 20.00 or more and 40.00 or less.

[0078] Also, the liquidus temperature of the optical glasses of the examples of the present invention was 1200°C or lower. For this reason, it became clear that the optical glasses of the examples of the present invention are stable glasses excellent in devitrification resistance.

[0079] Also, the Vickers hardness of the optical glasses of the examples of the present invention was grade 6 or higher. For this reason, it became clear that the optical glasses of the examples of the present invention are hard glasses.

[0080] Furthermore, using the optical glasses of the examples of the present invention, glass blocks were formed, and these glass blocks were ground and polished to be processed into the shapes of lenses and prisms. As a result, it was possible to stably process them into various lens and prism shapes.

[0081] Although the present invention has been described in detail for illustrative purposes, it should be understood that these examples are for illustrative purposes only and that those skilled in the art can make many modifications without departing from the spirit and scope of the present invention.

Claims

1. By mass percentage, ZrO 2 component 0.0 to 5.3%, B 2 O 3 Component: more than 0.0% to 15.0%, SiO 2 Component 0.0% or more to 30.0%, ZnO component: 0.0 - 40.0%, La 2 O 3 Component 5.0 to 30.0%, TiO 2 Component 8.0 to 40.0%, CaO component: 0.00 - 18.0%, BaO component: over 0.0 - 30.39% and does not contain PbO, and Mass and Ta 2 O 5 + Nb 2 O 5 + WO 3 + Gd 2 O 3 is 5.0% or less, Mass ratio of SiO 2 / (SiO 2 + B 2 O 3 + TiO 2 is 0.18 to 0.45 or less, Mass ratio (CaO + ZnO + Li 2 O) / BaO is 0.024 or more is such that the measurement result of acid resistance by the powder method defined in the Japan Optical Glass Industry Association Standard (JOGIS06 - 2006) is grade 1 to 3, and the measurement result of Vickers hardness by the measurement method defined in the Japan Optical Glass Industry Association Standard (JOGIS09 - 1975) is grade 6 or higher. An optical glass characterized by this.

2. Mass and CaO + ZnO + TiO 2 is 10.0 to 50.0% or less, and the mass ratio (BaO + ZnO) / La 2 O 3 is 0.5 to 2.1 or less. The optical glass according to claim 1.

3. 1. A refractive index (n) of 1.78000 or more and 1.98000 or less ｄ and an Abbe number (ν) ｄ of 20.00 or more and 40.00 or less, the optical glass according to claim 1 or 2

4. A preform made of the optical glass according to any one of Claims 1 to 3.

5. An optical element made of the optical glass according to any one of Claims 1 to 3.

6. An optical device comprising the optical element according to Claim 5.

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