Chemically strengthened optical glass

Abstract

To provide a high hardness chemically reinforced optical glass improved in impact resistance while maintaining a refractive index, an Abbe number, and a transmission factor required for a prior optical glass.SOLUTION: A chemically reinforced optical glass has a compressive stress layer on the surface, contains in mass% in terms of oxides, 20.0-50.0% of a SiO2 constituent, 10.0-45.0% of a TiO2 constituent, and 0.1-20.0% of a Na2O constituent, has a refractive index (nd) of 1.65-1.85, and an impact resistance of 8 cm or more by a sand paper falling ball test of falling a SUS ball having a weight of 16.0 g.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a chemically strengthened optical glass having a compressive stress layer on its surface. [Background technology]

[0002] In recent years, wearable devices used for AR (virtual reality) and VR (virtual reality), such as projector glasses, eyeglass-type displays, goggle-type displays, virtual reality displays, augmented reality displays, and virtual image displays, as well as in-vehicle cameras, have been attracting attention.

[0003] Such wearable devices, in-vehicle cameras, and the like are expected to be used in harsh external environments, and therefore there is a demand for optical glass that is highly impact-resistant, shatter-resistant, and has higher hardness so that these devices can withstand even harsher use, while maintaining the high refractive index and Abbe number required of conventional optical glass.

[0004] Patent Document 1 discloses high-refractive-index, high-dispersion glass with a refractive index (nd) of 1.7 or more and an Abbe number (νd) of 20 to 30, which addresses the challenges of digitalization and high-definition optical devices, but does not disclose optical glass with high hardness for which impact resistance is an issue, as it is not intended for use in harsh external environments. Furthermore, at the time of filing of Patent Document 1, modern cutting-edge technologies such as VR and AR had not yet become widespread, and furthermore, the use of in-vehicle cameras, which play a key role in "surrounding recognition sensors" for autonomous driving and ensuring safety, has rapidly increased in recent years. Therefore, at the time of filing of Patent Document 1, optical glass with high hardness and improved impact resistance was not anticipated.

[0005] Furthermore, if high-strength optical glass with improved impact resistance is used, it will be possible to make the glass used in optical lenses thinner, thereby enabling optical lenses to be made thinner and more compact. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2009-203134 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to obtain an optical glass having high hardness and improved impact resistance while maintaining the refractive index and Abbe number required of conventional optical glasses. [Means for solving the problem]

[0008] The inventors of the present invention have conducted extensive testing and research in order to solve the above-mentioned problems. As a result, they have discovered a glass composition and blend suitable for obtaining high-hardness optical glass that has an impact resistance of 8 cm or more in a sandpaper drop ball test in which a 16.0 g stainless steel ball is dropped on a glass substrate having a compressive stress layer on the surface by chemically strengthening the optical glass, and have thus completed the present invention. Furthermore, the present inventors have conducted extensive testing and research in order to solve the above problems, and as a result have found that a glass substrate having a compressive stress layer on its surface by chemically strengthening an optical glass exhibits the following properties in a sandpaper drop ball test in which a 16.0 g stainless steel ball is dropped: [Height at which the glass substrate does not break (after chemical strengthening)] - [Height at which the glass substrate does not break (before chemical strengthening)] ≥ 2.0 cm The inventors have discovered a glass composition and blending suitable for obtaining a high-hardness optical glass, which has led to the completion of the present invention. Specifically, the present invention provides the following:

[0009] (1) It has a compressive stress layer on the surface, In terms of oxide, mass % SiO2 content: 20.0-50.0%, TiO2 component 10.0 to 45.0%, Contains 0.1 to 20.0% Na2O. The refractive index (nd) is 1.65 to 1.85, Chemically strengthened optical glass characterized by its impact resistance of 8cm or more in a sandpaper drop test in which a 16.0g stainless steel ball is dropped.

[0010] (2) It has a compressive stress layer on the surface, In terms of oxide, mass % SiO2 content: 20.0-50.0%, TiO2 component 10.0 to 45.0%, Contains 0.1 to 20.0% Na2O. The refractive index (nd) is 1.65 to 1.85, In a sandpaper drop test in which a 16.0g SUS ball was dropped, [Height at which the glass substrate does not break (after chemical strengthening)] - [Height at which the glass substrate does not break (before chemical strengthening)] ≥ 2.0 cm A chemically strengthened optical glass characterized by having impact resistance of 1000 MPa or less.

[0011] (3) In terms of oxide, mass % Nb2O5 component 3.0 to 20.0%, The chemically strengthened optical glass according to (1) or (2), further containing 0 to 20.0% of BaO.

[0012] (4) In terms of oxide, mass % Al2O3 0-15.0%, ZrO2 0-15.0%, Li2O 0 to 10.0%, K2O 0 to 15.0%, The chemically strengthened optical glass according to any one of (1) to (3), further containing 0 to 1.0% of Sb2O3.

[0013] (5) The chemically strengthened optical glass according to any one of (1) to (4), characterized in that the Abbe number (νd) is 20.0 to 33.0. [Effects of the Invention]

[0014] According to the present invention, it is possible to provide a chemically strengthened optical glass having a compressive stress layer, which has high hardness and improved impact resistance while maintaining a high refractive index and Abbe number. [Brief explanation of the drawings]

[0015] [Figure 1] EDX analysis results of the fracture surface of Example 5-A [Figure 2] EDX analysis results of the fracture surface of Example 7-B DETAILED DESCRIPTION OF THE INVENTION

[0016] The composition ranges of each component constituting the chemically strengthened optical glass of the present invention are described below. In this specification, unless otherwise specified, the content of each component is expressed as mass% relative to the total mass of the composition converted into oxides. Here, the "composition converted into oxides" refers to the composition of each component contained in the glass, assuming that the oxides, composite salts, metal fluorides, etc. used as raw materials for the glass components of the present invention are all decomposed and converted into oxides during melting, with the total mass of the resulting oxides being 100 mass%.

[0017] [Glass components] The chemically strengthened optical glass of the present invention has a compressive stress layer on its surface and is characterized by containing, in mass % converted to oxides, 20.0 to 50.0% of an SiO2 component, 10.0 to 45.0% of a TiO2 component, and 0.1 to 20.0% of a Na2O component.

[0018] [Required and optional ingredients] The SiO2 component forms the network structure of the glass and reduces devitrification (the generation of crystals), which is undesirable in optical glass, and is an essential component for the chemically strengthened optical glass of the present invention. In particular, by making the content of the SiO2 component 20.0% or more, it is possible to produce a stable optical glass with high strength. Therefore, the lower limit of the content of the SiO2 component is preferably 20.0% or more, more preferably 23.0% or more, and even more preferably more than 25.0%. On the other hand, by keeping the SiO2 content at 50.0% or less, excessive increases in viscosity and deterioration of meltability can be suppressed, and a decrease in refractive index can be suppressed. Furthermore, a decrease in chemical strengthening can be suppressed. Therefore, the upper limit of the SiO2 content is preferably set to 50.0% or less, more preferably 47.0% or less, and even more preferably 43.0% or less.

[0019] The TiO2 component is a component that increases the refractive index and chemical durability (acid resistance), and is an essential component of the chemically strengthened optical glass of the present invention. In particular, by making the content of the TiO2 component 10.0% or more, the desired refractive index, Abbe number, etc. of the glass can be achieved. Therefore, the lower limit of the content of the TiO2 component is preferably 10.0% or more, more preferably 13.0% or more, and even more preferably more than 15.0%. On the other hand, by keeping the content of the TiO2 component at 45.0% or less, it is possible to suppress devitrification of the glass and a decrease in the transmittance of the glass to visible light (particularly wavelengths of 500 nm or less). Therefore, the upper limit of the content of the TiO2 component is preferably 45.0% or less, more preferably 40.0% or less, even more preferably 35.0% or less, and even more preferably 33.0% or less.

[0020] The Na2O component is a component that improves the meltability of the glass and is also a component that is used for ion exchange during chemical strengthening as described below, and is an essential component in the chemically strengthened optical glass of the present invention. In particular, by setting the content of the Na2O component to 0.1% or more, an exchange reaction between the potassium component (potassium ion) with a large ionic radius in the molten salt and the sodium component (sodium ion) with a small ionic radius in the substrate proceeds, resulting in the formation of compressive stress on the substrate surface. Therefore, the lower limit of the content of the Na2O component is preferably 0.1% or more, more preferably 0.5% or more, and even more preferably 5.0% or more. On the other hand, by keeping the content of the Na2O component at 20.0% or less, it is possible to prevent the refractive index of the glass from decreasing and to reduce devitrification of the glass. Therefore, the upper limit of the content of the Na2O component is preferably set to 20.0% or less, more preferably 17.0% or less, more preferably 15.0% or less, and even more preferably less than 14.0%.

[0021] The Nb2O5 component is a component that increases the refractive index and stabilizes the glass, and is an optional component of the chemically strengthened optical glass of the present invention. In particular, by making the Nb2O5 content 3.0% or more, it is possible to improve devitrification resistance. Also, it is possible to suppress a decrease in hardness due to a salt bath during chemical strengthening. Therefore, the lower limit of the Nb2O5 content is preferably 3.0% or more, more preferably 4.0% or more, more preferably more than 5.0%, and even more preferably 6.0% or more. On the other hand, by keeping the content of the Nb2O5 component at 20.0% or less, devitrification due to excessive content can be reduced. Therefore, the upper limit of the content of the Nb2O5 component is preferably set to 20.0% or less, more preferably 17.0% or less, more preferably 15.0% or less, and even more preferably 13.0% or less.

[0022] When the K2O content exceeds 0%, it adjusts the refractive index and Abbe number while adjusting the meltability of the glass, and in chemical strengthening, it is a component that can improve the surface compressive stress. Therefore, the lower limit of the K2O content is preferably 0% or more, more preferably more than 0%, more preferably 0.5% or more, and even more preferably 2.0% or more. On the other hand, by keeping the content of the K2O component at 15.0% or less, it is possible to prevent the refractive index of the glass from decreasing and to reduce devitrification of the glass. Therefore, the upper limit of the content of the K2O component is preferably set to 15.0% or less, more preferably 10.0% or less, more preferably 8.0% or less, and even more preferably 7.5% or less.

[0023] When the Li2O component is contained in an amount exceeding 0%, it adjusts the refractive index and Abbe number while adjusting the meltability of the glass, and is also used for ion exchange in chemical strengthening. Therefore, the lower limit of the Li2O component content is preferably 0% or more, more preferably more than 0%, more preferably 0.1% or more, more preferably 0.3% or more, and even more preferably 0.5% or more. On the other hand, by keeping the content of the Li2O component at 10.0% or less, it is possible to prevent a decrease in the refractive index and reduce devitrification due to excessive content. Therefore, the upper limit of the content of the Li2O component is preferably set to 10.0% or less, more preferably 8.0% or less, and even more preferably 7.5% or less.

[0024] The BaO component is an optional component in the chemically strengthened optical glass of the present invention, which increases the refractive index of the glass when contained in an amount greater than 0%. Furthermore, a BaO content greater than 0% can suppress a decrease in hardness due to the salt bath during chemical strengthening. Therefore, the lower limit of the BaO content is preferably 0% or more, more preferably greater than 0%, more preferably 1.0% or more, and even more preferably 2.0% or more. On the other hand, by keeping the content of the BaO component at 20.0% or less, it is possible to suppress deterioration of devitrification and chemical strengthening resistance, and to prevent the glass surface from becoming brittle. Therefore, the upper limit of the content of the BaO component is preferably set to 20.0% or less, more preferably 15.0% or less, and even more preferably 12.0% or less.

[0025] MgO, CaO and SrO are components that increase the refractive index of the glass when their content exceeds 0%, and are optional components in the chemically strengthened optical glass of the present invention. On the other hand, by limiting the content of each of the MgO, CaO, and SrO components to 20.0% or less, it is possible to suppress a decrease in hardness due to the salt bath during chemical strengthening. Therefore, the upper limit of each of the MgO, CaO, and SrO contents is preferably 20.0% or less, more preferably 15.0% or less, and even more preferably 10.0% or less. In particular, from the viewpoint of productivity, it is desirable to set the CaO content to preferably less than 0.5%, more preferably less than 0.3%, in order to prevent deterioration of devitrification.

[0026] ZnO is a component that increases the refractive index of the glass when its content exceeds 0%, and is an optional component in the chemically strengthened optical glass of the present invention. On the other hand, by limiting the ZnO content to 15.0% or less, it is possible to suppress the decrease in hardness due to the salt bath during chemical strengthening. Therefore, the upper limit of the ZnO content is preferably 15.0% or less, more preferably 10.0% or less, and even more preferably less than 8.0%.

[0027] When the Al2O3 content exceeds 0%, it is an effective component for increasing the chemical durability of the glass and improving the devitrification resistance of the glass melt, and is an optional component in the chemically strengthened optical glass of the present invention. On the other hand, by keeping the content of the Al2O3 component at 15.0% or less, the liquidus temperature of the glass can be lowered and devitrification due to excessive content can be reduced. Therefore, the upper limit of the content of the Al2O3 component is preferably set to 15.0% or less, more preferably 10.0% or less, and even more preferably 5.0% or less.

[0028] The ZrO2 component is a component that increases the refractive index of the glass when its content exceeds 0%, and is an optional component in the chemically strengthened optical glass of the present invention. On the other hand, by keeping the content of the ZrO2 component at 15.0% or less, it is possible to reduce devitrification due to excessive inclusion of the ZrO2 component. Therefore, the upper limit of the content of the ZrO2 component is preferably set to 15.0% or less, more preferably to 10.0% or less, and even more preferably to 5.0% or less.

[0029] The B2O3 component is an optional component that, when contained in an amount exceeding 0%, can promote the formation of stable glass and improve devitrification resistance. On the other hand, by keeping the B2O3 content at 15.0% or less, devitrification due to excessive B2O3 content can be reduced. Therefore, the upper limit of the B2O3 content is preferably set to 15.0% or less, more preferably 10.0% or less, and even more preferably 5.0% or less.

[0030] The La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component are optional components that can increase the refractive index and decrease the partial dispersion ratio by containing at least any one of them in an amount exceeding 0%. On the other hand, when the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component are contained in large amounts, the liquidus temperature decreases, causing the glass to devitrify. In particular, by keeping the content of each of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component at 10.0% or less, devitrification and coloration can be reduced. Therefore, the upper limit of each of the La2O3 component, Gd2O3 component, Y2O3 component, and Yb2O3 component is preferably 10.0% or less, more preferably 8.0% or less, even more preferably 5.0% or less, and most preferably 3.0% or less.

[0031] The WO3 component is an optional component that increases the refractive index, decreases the Abbe number, and improves the meltability of the glass raw material. On the other hand, by keeping the content of the WO3 component at 10.0% or less, it is possible to make it difficult for the partial dispersion ratio of the glass to increase, and also to reduce coloration of the glass and increase the internal transmittance. Therefore, the upper limit of the content of the WO3 component is preferably set to 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and most preferably 1.0% or less.

[0032] The P2O5 component is an optional component that can increase the stability of the glass. On the other hand, by keeping the P2O5 content at 5.0% or less, it is possible to reduce an increase in the partial dispersion ratio due to an excessive P2O5 content. Therefore, the upper limit of the P2O5 content is preferably set to 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0033] The Ta2O5 component is an optional component that can increase the refractive index, decrease the Abbe number and partial dispersion ratio, and increase the devitrification resistance. In particular, by limiting the content of the Ta2O5 component to 10.0% or less, the amount of Ta2O5 component, a rare mineral resource, used can be reduced, and the glass can be more easily melted at lower temperatures, thereby reducing glass production costs. This also reduces devitrification of the glass due to excessive inclusion of the Ta2O5 component. Therefore, the upper limit of the content of the Ta2O5 component is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and even more preferably 1.0% or less. In particular, from the perspective of reducing glass material costs, the Ta2O5 component may not be included.

[0034] The GeO2 component is an optional component that can increase the refractive index and reduce devitrification. By setting the GeO2 component content to 10.0% or less, the amount of expensive GeO2 component used can be reduced, thereby reducing the material cost of the glass. Therefore, the upper limit of the GeO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and even more preferably 1.0% or less.

[0035] The Ga2O3 component is an optional component that can increase the refractive index and improve the resistance to devitrification. On the other hand, by keeping the Ga2O3 content at 10.0% or less, devitrification due to excessive Ga2O3 content can be reduced. Therefore, the upper limit of the Ga2O3 content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, and even more preferably 1.0% or less.

[0036] The Bi2O3 component is an optional component that can increase the refractive index, decrease the Abbe number, and lower the glass transition temperature. By keeping the Bi2O3 component content at 10.0% or less, it is possible to make it difficult for the partial dispersion ratio to increase, reduce coloration of the glass, and increase the internal transmittance. Therefore, the upper limit of the Bi2O3 component content is preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less.

[0037] The TeO2 component is an optional component that can increase the refractive index, decrease the partial dispersion ratio, and lower the glass transition temperature. By keeping the content of the TeO2 component at 10.0% or less, it is possible to reduce the coloration of the glass and increase the internal transmittance. Furthermore, by reducing the use of the expensive TeO2 component, it is possible to obtain glass with lower material costs. Therefore, the upper limit of the content of the TeO2 component is preferably 10.0% or less, more preferably 5.0% or less, more preferably 3.0% or less, and even more preferably 1.0% or less. In particular, from the viewpoint of reducing the material costs of the glass, it is not necessary to contain the TeO2 component.

[0038] SnO2 is an optional component that can clarify (degass) molten glass and increase the visible light transmittance of the glass. By keeping the SnO2 content at 1.0% or less, it is possible to prevent the glass from becoming discolored or devitrified due to reduction of the glass melt. Furthermore, alloying of SnO2 with the melting equipment (especially precious metals such as Pt) is reduced, thereby extending the life of the melting equipment. Therefore, the upper limit of the SnO2 content is preferably 1.0% or less, more preferably 0.5% or less, and even more preferably 0.1% or less.

[0039] The Sb2O3 component is an optional component that can degas the glass melt when its content exceeds 0%. On the other hand, by keeping the content of Sb2O3 at 1.0% or less, it is possible to suppress a decrease in transmittance in the short wavelength region of the visible light spectrum, solarization of the glass, and a deterioration in internal quality. Therefore, the content of Sb2O3 may be preferably 1.0% or less, more preferably less than 1.0%, more preferably less than 0.7%, even more preferably 0.5% or less, and most preferably 0.4% or less.

[0040] The meltability of glass can be improved when the sum of the contents (sum by mass) of the Rn2O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is 5.0% or more. Therefore, the lower limit of the sum of the Rn2O component is preferably 5.0% or more, more preferably 7.0% or more, and even more preferably 10.0% or more. On the other hand, by setting the sum (mass sum) of the RnO components to 30.0% or less, the decrease in refractive index can be suppressed and devitrification due to excessive content can be reduced. Therefore, the upper limit is preferably set to 30.0% or less, more preferably 25.0% or less, even more preferably 23.0% or less, and most preferably 20.0% or less.

[0041] When the sum of the contents of RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) exceeds 0%, the low-temperature meltability can be improved. Therefore, the lower limit of the sum of the contents of RO components is preferably more than 0%, more preferably 1.0% or more, and even more preferably 2.0% or more. On the other hand, the total content of RO components is preferably 20.0% or less to prevent deterioration of devitrification resistance due to excessive content. Therefore, the upper limit of the total mass of RO components is preferably 20.0% or less, more preferably 15.0% or less, more preferably 14.0% or less, and even more preferably 13.0% or less.

[0042] When the sum of the contents (sum of mass) of the Ln2O3 component (wherein Ln is one or more selected from the group consisting of La, Gd, Y, and Yb) exceeds 0%, a high refractive index can be easily obtained. On the other hand, by setting the total content (mass sum) of the Ln2O3 component to 15.0% or less, devitrification due to excessive content can be reduced. Therefore, the upper limit is preferably set to 15.0% or less, more preferably 10.0% or less, and even more preferably 5.0% or less.

[0043] The refractive index can be increased when the mass sum of TiO2 + BaO + Nb2O5 is 30.0% or more. Therefore, the lower limit of the mass sum of TiO2 + BaO + Nb2O5 is preferably 30.0% or more, more preferably 33.0% or more, and even more preferably 35.0% or more. On the other hand, by setting the mass sum of TiO2 + BaO + Nb2O5 to 60.0% or less, it is possible to suppress a decrease in the transmittance of the glass to visible light (particularly wavelengths of 500 nm or less). Therefore, the mass sum of TiO2 + BaO + Nb2O5 is preferably set to an upper limit of 60.0% or less, more preferably 57.0% or less, even more preferably 55.0% or less, and most preferably less than 50.0%.

[0044] Chemical strengthening can be facilitated when the mass ratio K2O / Na2O exceeds 0. Therefore, the lower limit of the mass ratio K2O / Na2O is preferably greater than 0, more preferably 0.10 or more, and even more preferably 0.20 or more. On the other hand, by setting the mass ratio K2O / Na2O to 1.00 or less, devitrification of the glass can be reduced. Therefore, the upper limit of the mass ratio K2O / Na2O is preferably 1.00 or less, more preferably 0.95 or less, and even more preferably 0.90 or less.

[0045] When the mass sum of Nb2O5 + BaO is 8.0% or more, it is possible to suppress a decrease in hardness due to a salt bath during chemical strengthening. Therefore, the mass sum of Nb2O5 + BaO is preferably 8.0% or more, more preferably more than 10.0%, more preferably 13.0% or more, and even more preferably 15.0% or more as the lower limit. On the other hand, by setting the mass sum of Nb2O5+BaO to 30.0% or less, deterioration of devitrification tendency of the glass can be reduced. Therefore, the upper limit of the mass sum of Nb2O5+BaO is preferably set to 30.0% or less, more preferably to 27.0% or less, and even more preferably to 25.0% or less.

[0046] When the mass sum of SiO2 + R0 is 35.0% or more, a stable optical glass can be produced. Therefore, the lower limit of the mass sum of SiO2 + R0 is preferably 35.0% or more, more preferably 38.0% or more, and even more preferably 40.0% or more. On the other hand, by setting the mass sum of SiO2 + RO to 60.0% or less, it is possible to suppress the decrease in refractive index and facilitate chemical strengthening. Therefore, the upper limit of the mass sum of SiO2 + RO is preferably 60.0% or less, more preferably 57.0% or less, and even more preferably 54.0% or less.

[0047] When the mass sum of SiO2 + TiO2 + Na2O is 50.0% or more, a glass that has a high refractive index and can be chemically strengthened can be stably produced. Therefore, the mass sum of SiO2 + TiO2 + Na2O is preferably 50.0% or more, more preferably 55.0% or more, more preferably 60.0% or more, and even more preferably 63.5% or more as the lower limit. On the other hand, by setting the mass sum of SiO2 + TiO2 + Na2O to 90.0% or less, deterioration of devitrification tendency of the glass can be reduced. Therefore, the upper limit of the mass sum of SiO2 + TiO2 + Na2O is preferably set to 90.0% or less, more preferably to 85.0% or less, and even more preferably to 81.0% or less.

[0048] When the mass sum of SiO2 + Na2O + BaO is 45.0% or more, chemically strengthenable optical glass can be stably produced. Therefore, the mass sum of SiO2 + Na2O + BaO is preferably 45.0% or more, more preferably 48.0% or more, more preferably 50.0% or more, and even more preferably 51.5% or more as the lower limit. On the other hand, by setting the mass sum of SiO2 + Na2O + BaO to 70.0% or less, the decrease in refractive index can be suppressed. Therefore, the upper limit of the mass sum of SiO2 + Na2O + BaO is preferably set to 70.0% or less, more preferably to 68.0% or less, and even more preferably to 65.0% or less.

[0049] When the mass ratio (ZrO2+Na2O) / BaO is 0.20 or more, the meltability is improved and the devitrification resistance is good. Therefore, the mass ratio (ZrO2+Na2O) / BaO has a lower limit of preferably 0.20 or more, more preferably 0.50 or more, even more preferably 0.60 or more, and even more preferably 0.80 or more. On the other hand, by setting the mass ratio (ZrO2 + Na2O) / BaO to 20.0 or less, it is possible to prevent deterioration of devitrification due to excessive addition of components. Therefore, the upper limit of the mass ratio (ZrO2 + Na2O) / BaO is preferably set to 20.0 or less, more preferably 18.0 or less, more preferably 15.0 or less, and even more preferably 13.0 or less. Particularly from the viewpoint of chemical strengthening, it is desirable to set the mass ratio (ZrO2+Na2O) / BaO to more than 0.86, since an increase in hardness due to chemical strengthening is likely to occur.

[0050] When the mass sum of SiO2 + Na2O is 33.0% or more, chemically strengthenable optical glass can be stably produced. Therefore, the lower limit of the mass sum of SiO2 + Na2O is preferably 33.0% or more, more preferably 35.0% or more, and even more preferably 38.0% or more. On the other hand, by setting the mass sum of SiO2 + Na2O to 65.0% or less, the decrease in refractive index can be suppressed. Therefore, the upper limit of the mass sum of SiO2 + Na2O is preferably 65.0% or less, more preferably 60.0% or less, even more preferably 58.0% or less, and most preferably 55.0% or less.

[0051] [Manufacturing method] The chemically strengthened optical glass of the present invention is produced, for example, as follows: Raw materials such as oxides, carbonates, nitrates, and hydroxides are mixed uniformly so that the contents of each component are within a predetermined range, the mixture is placed in a platinum crucible, and melted in an electric furnace at a temperature ranging from 1200 to 1500°C for 1 to 4 hours depending on the melting difficulty of the glass composition. After stirring and homogenization, the mixture is cooled to an appropriate temperature, poured into a mold, and slowly cooled, followed by chemical strengthening.

[0052] [Chemical strengthening] Chemically strengthened glass is glass that has been strengthened by a method for strengthening the surface of glass, such as chemical strengthening, chemical strengthening, or ion exchange strengthening. In the chemically strengthened optical glass of the present invention, the glass surface is strengthened by subjecting the glass surface to an ion exchange treatment to form a surface layer (compressive stress layer) in which compressive stress remains. Ion exchange generally occurs at a temperature below the glass transition point, replacing alkali metal ions (typically lithium ions or sodium ions) with small ionic radii on the glass surface with alkali ions (typically sodium ions or potassium ions for lithium ions, and potassium ions for sodium ions) with larger ionic radii. This leaves compressive stress on the surface of the glass, improving its strength.

[0053] The chemical strengthening method can be carried out, for example, by the following steps: The glass base material is brought into contact with or immersed in a molten salt of a salt containing potassium or sodium, such as potassium nitrate (KNO3), sodium nitrate (NaNO3), or a mixed or composite salt thereof. This treatment of contacting or immersing in the molten salt (chemical strengthening treatment) may be carried out in one step or two steps.

[0054] For example, in the case of a two-stage chemical strengthening treatment, first, the steel is contacted with or immersed in sodium salt or a mixed salt of potassium and sodium heated at 370°C to 550°C for 1 to 1440 minutes, preferably 90 to 800 minutes, followed by second, the steel is contacted with or immersed in potassium salt or a mixed salt of potassium and sodium heated at 350°C to 550°C for 1 to 1440 minutes, preferably 60 to 800 minutes. In the case of one-stage chemical strengthening treatment, the material is contacted with or immersed in a salt containing potassium or sodium or a mixed salt thereof heated at 370°C to 550°C for 1 to 1440 minutes, preferably 60 to 800 minutes.

[0055] The thermal strengthening method is not particularly limited, but for example, a compressive stress layer can be formed by heating a glass base material to 300°C to 600°C and then rapidly cooling it by water cooling and / or air cooling, due to the temperature difference between the surface and the interior of the glass substrate. Note that by combining this with the above-mentioned chemical treatment method, the compressive stress layer can be formed more effectively.

[0056] The ion implantation method is not particularly limited, but for example, ions are implanted into the surface of the glass base material by bombarding the surface with an acceleration energy and acceleration voltage that are not enough to destroy the surface of the base material. By subsequently performing a heat treatment as necessary, a compressive stress layer can be formed on the surface in the same way as with other methods.

[0057] [Refractive index and Abbe number] The chemically strengthened optical glass of the present invention preferably has a high refractive index. In particular, the refractive index (nd) of the chemically strengthened optical glass of the present invention preferably has a lower limit of 1.65 or more, more preferably 1.67 or more, and even more preferably 1.68 or more. On the other hand, the upper limit of this refractive index is preferably 1.85 or less, more preferably 1.83 or less, more preferably 1.80 or less, and even more preferably 1.79 or less. The Abbe number (νd) of the chemically strengthened optical glass of the present invention has a lower limit of preferably 20.0 or more, more preferably 22.0 or more, and even more preferably 23.0 or more. On the other hand, the upper limit of this Abbe number is preferably 33.0 or less, more preferably 30.0 or less, and even more preferably 28.0 or less.

[0058] The optical glass of the present invention preferably has high visible light transmittance, particularly high transmittance for light on the short wavelength side of visible light, and therefore is less colored. In particular, the shortest wavelength (λ5) at which a 10 mm thick sample of the optical glass of the present invention exhibits a spectral transmittance of 5% is preferably 400 nm or less, more preferably 390 nm or less, and even more preferably 380 nm or less. These properties bring the absorption edge of the glass into the ultraviolet region or nearby, increasing the transparency of the glass to visible light, making this optical glass suitable for use in optical elements that transmit light, such as lenses.

[0059] [specific gravity] The upper limit of the specific gravity of the optical glass of the present invention is preferably 4.00 or less, more preferably 3.80 or less, more preferably 3.50 or less, and even more preferably 3.30 or less, from the viewpoint of contributing to weight reduction of optical elements and optical instruments. On the other hand, the specific gravity of the optical glass of the present invention is generally 2.00 or more, more specifically 2.50 or more, and even more specifically 3.00 or more.

[0060] The crystallized glass substrate was subjected to a ball drop test using sandpaper in the following manner, which simulates a drop onto asphalt. A SUS base was laid with #180 sandpaper and a crystallized glass substrate (φ36 × 2 mm) was placed on it. A 16.0 g SUS iron ball was then dropped onto the substrate from a height of 60 mm (6 cm) from the substrate. If the substrate did not break after the drop, the height was increased by 20 mm (2 cm) and the same test was continued until the crystallized glass substrate broke, followed by visual observation. Breakage here refers to the visual presence of splits, cracks, chips, or cracks. Each test was performed three times, and the average height before breakage was calculated. From the viewpoint of contributing to the impact resistance of wearable devices, in-vehicle cameras, etc., in the present invention, the glass substrate preferably has an impact resistance of 8 cm or more in a sandpaper drop test in which a 16.0 g SUS ball is dropped. Therefore, the chemically strengthened optical glass of the present invention has an impact resistance of 8 cm or more, more preferably 12 cm or more, and even more preferably 14 cm or more in a sandpaper drop test in which a 16.0 g SUS ball is dropped. Furthermore, the chemically strengthened optical glass of the examples of the present invention has the following characteristics in a sandpaper drop test in which a 16.0 g SUS ball is dropped: [Height at which the glass substrate does not break (after chemical strengthening)] - [Height at which the glass substrate does not break (before chemical strengthening)] ≥ 2.0 cm It is preferable that the impact resistance is 100% or less. Therefore, in the chemically strengthened optical glass of the present invention, [height at which the glass substrate does not break (after chemical strengthening)] - [height at which the glass substrate does not break (before chemical strengthening)] is preferably 2.0 cm or more, more preferably 2.5 cm or more, more preferably 3.0 cm or more, and even more preferably 4.0 cm or more.

[0061] The following examples are provided to illustrate the present invention in detail for illustrative purposes, but it should be noted that these examples are for illustrative purposes only and that many modifications may be made by those skilled in the art without departing from the spirit and scope of the present invention.

[0062] Glasses with various compositions, as listed in Table 1, were prepared as Examples (Nos. 1 to 9) and Comparative Example 1. High-purity raw materials typically used in chemically strengthened optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, were selected as the raw materials for each component. These were weighed and mixed to achieve the compositional ratios shown in Table 1 for each example. The mixture was then placed in a platinum crucible and melted in an electric furnace at a temperature ranging from 1200 to 1400°C for 1 to 4 hours, depending on the melting difficulty of the glass composition. The mixture was then stirred and homogenized, cooled to an appropriate temperature, and poured into a mold or other suitable container. The refractive index (nd), Abbe number (νd), transmittance (λ5), and specific gravity of each glass were measured and are shown in Table 1.

[0063] The refractive index (nd) and Abbe number (νd) of the glass were measured using the V-block method specified in JIS B 7071-2:2018 for the d-line (587.56 nm) of a helium lamp. The Abbe number (νd) is calculated by multiplying the refractive index of the d-line and the refractive index (n F ), refractive index for C line (656.27 nm) (n C ) value, Abbe number (νd) = [(nd-1) / (n F -n C )] was calculated using the formula: Here, the refractive index (nd) and Abbe number (νd) were determined by measuring the glass obtained by slow cooling at a temperature decreasing rate of −25° C. / hr.

[0064] The transmittance of the glass was measured in accordance with the Japan Optical Glass Industry Association standard JOGIS02-2019. In the present invention, the presence and degree of coloration of the glass was determined by measuring the transmittance of the glass. Specifically, a 10±0.1 mm thick, parallel-polished specimen was measured for spectral transmittance from 200 to 800 nm in accordance with JIS Z8722, and the wavelength (λ5) at which the spectral transmittance reached 5% was determined.

[0065] The specific gravity ρ of the glasses in the examples and comparative examples was measured based on the Japan Optical Glass Industry Association standard JIS Z8807:2012 "Method for measuring the specific gravity of optical glass."

[0066] Glass substrates were immersed in a potassium nitrate (KNO3) bath (K bath) or a sodium nitrate (NaNO3) bath (Na bath) at the temperatures and times listed in Table 2. Subsequently, EDX analysis was performed in the vertical depth direction from the outermost surface to the interior of the glass substrate to confirm whether a surface compressive stress layer had formed on the surface of the glass substrate. A JEOL scanning electron microscope (JSM-IT700HR) was used for the EDX analysis. The EDX analysis results for Example 5-A and Example 7-B were shown in Figures 1 and 2, respectively, showing the change in the characteristic X-ray intensity ratio (ratio) due to sodium and potassium. In each of Figures 1 and 2, the horizontal axis indicates the depth from the surface of the glass substrate. It can be seen that the characteristic X-ray intensity ratio (ratio) due to potassium is highest at the outermost surface of the glass substrate and decreases down to a depth of about 10 μm. On the other hand, it can be seen that the characteristic X-ray intensity due to sodium increases from the outermost surface to a depth of about 10 μm. From the change in the characteristic X-ray intensity ratio due to potassium and sodium in FIGS. 1 and 2, it was confirmed that ion exchange was taking place on the outermost surface of the glass substrate in the salt bath.

[0067] Table 2 also shows the results of a sandpaper ball drop test in which a 16.0 g SUS ball was dropped on each of these glasses.

[0068] [Table 1]

[0069] [Table 2]

[0070] The chemically strengthened optical glasses of the examples of the present invention exhibited a high refractive index, and were found to have impact resistance of 8 cm or more in a sandpaper drop test in which a 16.0 g stainless steel ball was dropped. Furthermore, the chemically strengthened optical glass of the examples of the present invention exhibits a high refractive index, and in a sandpaper drop test in which a 16.0 g stainless steel ball is dropped, [Height at which the glass substrate does not break (after chemical strengthening)] - [Height at which the glass substrate does not break (before chemical strengthening)] ≥ 2.0 cm It was revealed that it has impact resistance of 100mW.

Claims

1. It has a compressive stress layer on the surface, In terms of oxide, mass % SiO ２ The content of the ingredients is 20.0 to 50.0%, TiO ２ The content of the ingredients is 21.88 to 45.0%, Na ２ The content of O component is 0.1 to 20.0%, The content of BaO component is 7.77% or more, The content of Nb 2 O 5 component is 3.0% or more, The content of the La 2 O 3 component is less than 3% (but PbO is not contained), The refractive index (nd) is 1.65 to 1.85, A chemically strengthened optical glass characterized by having an impact resistance of 8 cm or more in a sandpaper drop test in which a 16.0 g SUS ball is dropped.

2. It has a compressive stress layer on the surface, In terms of oxide, mass % SiO ２ The content of the ingredients is 20.0 to 50.0%, TiO ２ The content of the ingredients is 21.88 to 45.0%, Na ２ The content of O component is 0.1 to 20.0%, The content of BaO component is 7.77% or more, The content of Nb 2 O 5 component is 3.0% or more, The content of the La 2 O 3 component is less than 3% (but PbO is not contained), The refractive index (nd) is 1.65 to 1.85, In a sandpaper drop test in which a 16.0 g SUS ball is dropped, [Height at which the glass substrate does not break (after chemical strengthening)] - [Height at which the glass substrate does not break (before chemical strengthening)] ≥ 2.0 cm A chemically strengthened optical glass characterized by having impact resistance of 1000 MPa or less.

3. In terms of oxide, mass % Nb ２ O ５ The content of the component is 3.0 to 20.0%, 3. The chemically strengthened optical glass according to claim 1, wherein the BaO content is 7.77 to 20.0%.

4. In terms of oxide, mass % Al ２ O ３ The content of the component is 0 to 15.0%, ZrO ２ The content of the component is 0 to 15.0%, Li ２ The content of O component is 0 to 10.0%, K ２ The content of O component is 0 to 15.0%, Sb ２ O ３ 4. The chemically strengthened optical glass according to claim 1, wherein the content of the component is 0 to 1.0%.

5. 5. The chemically strengthened optical glass according to claim 1, having an Abbe number (νd) of 20.0 to 33.0.

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