Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/062—Glass compositions containing silica with less than 40% silica by weight
  • C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
  • C03C3/068—Glass compositions containing silica with less than 40% silica by weight containing boron containing rare earths
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B1/00—Optical elements characterised by the material of which they are made; Optical coatings for optical elements

Definitions

• the present invention relates to glass, optical glass and optical elements.
• In-vehicle glass which may be installed in multiple locations, is exposed to various impacts.
• the size of flying objects such as dust and pebbles caught in the air by the tires and the speed of the vehicle change the impact on the glass, so it is necessary to have extremely high strength.
• the Knoop hardness of JOGIS is known as an indicator of the hardness of glass, and can also be used as an indicator of glass with high mechanical durability.
• a glass composition as typified by Patent Document 1 is known.
• the glass disclosed in Patent Document 1 is an invention in which it was found that the moldability of the lens can be improved by increasing the Knoop hardness, and the increased hardness of the glass makes the glass lens less likely to be scratched. However, it cannot be said that the impact resistance is sufficient.
• Tempered glass is an example of glass with high strength. Tempered glass has excellent strength because it has a compressive stress layer on the glass surface. Chemical strengthening or the like is required, which complicates the manufacturing process. Also, it is necessary to introduce an alkaline component for ion exchange, which deteriorates the impact resistance.
• the present invention has been made in view of the above problems, and its purpose is to simply produce glass with higher impact resistance than conventional glass and to stably provide it.
• the present inventors have conducted intensive testing and research, and found that while suppressing the contents of the SiO 2 component and the BaO component, the SiO 2 component, the B 2 O 3 component, and the Al 2 O 3 component , La 2 O 3 component, Y 2 O 3 component, and Gd 2 O 3 component, and adjusting the mass ratio of Al 2 O 3 component to SiO 2 component and B 2 O 3 component to 0.01 or more,
• ⁇ the average linear expansion coefficient
• ⁇ / ⁇ which is the ratio of ⁇ to ⁇ , to 7.80 or more
• a highly stable and impact-resistant glass material found that it is possible to create, and completed the present invention.
• the present invention provides the following.
• mass sum of SiO 2 +B 2 O 3 +Al 2 O 3 +La 2 O 3 +Y 2 O 3 +Gd 2 O 3 is 50.0% or more (however, the SiO 2 component is 22.0% or less); mass ratio Al 2 O 3 /(SiO 2 +B 2 O 3 ) is 0.01 or more; BaO content is 10.0% or less, and
• ⁇ / ⁇ which is the ratio of ⁇ to ⁇ , is 7.80 or more.
• Mass ratio Gd 2 O 3 /Ln 2 O 3 is 0.10 or less (Ln is one or more selected from the group consisting of La, Y, Gd and Yb) The glass according to (1) to (3).
• Knoop hardness is grade 6 or higher, The glass according to (1) to (4), which has an average linear expansion coefficient ⁇ of 90 ⁇ 10 -7 ° C. -1 or less at 100 to 300°C.
• the present invention provides a glass, optical glass, and optical element having better impact resistance than conventional glass by adjusting each component and adjusting the ratio between the average linear expansion coefficient ⁇ and the Knoop hardness at 100 to 300 ° C. can be obtained.
• composition converted to oxide means that, when it is assumed that oxides, composite salts, metal fluorides, etc. used as raw materials for the constituent components of the glass of the present invention are all decomposed and changed into oxides when melted, It is a composition in which each component contained in the glass is expressed with the total mass of the produced oxide being 100% by mass.
• the SiO2 component is a component that can increase the viscosity of the molten glass and increase the hardness of the glass. It is also a component that enhances the stability of the glass and makes it easier to obtain a glass that can withstand mass production. Therefore, the lower limit of the content of the SiO2 component is preferably more than 0%, more preferably 2.0% or more, more preferably 4.0% or more. On the other hand, by setting the content of the SiO 2 component to 22.0% or less, the deterioration of the impact resistance of the glass can be suppressed. In particular, the SiO 2 component is inferior to the B 2 O 3 component and the Al 2 O 3 component, which will be described later, in impact resistance. Therefore, the upper limit of the content of the SiO2 component is preferably 22.0% or less, more preferably 21.0% or less, still more preferably 18.0% or less, still more preferably 16.0% or less.
• the B 2 O 3 component is a component that becomes a glass-forming oxide in the glass of the present invention containing a large amount of rare earth oxides.
• the lower limit of the content of the B 2 O 3 component is preferably more than 0%, more preferably 1.5% or more, still more preferably 2.0% or more, and still more preferably 3.5% or more.
• the content of the B 2 O 3 component is preferably 20.0% or less, more preferably 18.0% or less, more preferably 16.0% or less, and still more preferably 15.0% or less. do.
• the Al 2 O 3 component is a component that, when included, forms a strong bond, suppresses the thermal expansion of the glass, and improves the devitrification resistance of the molten glass.
• the Al 2 O 3 component is the component that maximizes the impact resistance when compared with the SiO 2 component and the B 2 O 3 component. Therefore, the lower limit of the content of the Al 2 O 3 component is preferably 0.1% or more, more preferably 0.3% or more, still more preferably 0.5% or more, and still more preferably 0.8% or more. .
• the content of the Al 2 O 3 component is preferably 15.0% or less, more preferably 13.0% or less, even more preferably 12.0% or less, still more preferably 10.0% or less, and even more preferably is 7.0% or less, more preferably 6.0% or less, more preferably 5.0% or less.
• the TiO 2 component is a component that increases the refractive index of the glass, increases the Abbe's number, and increases the hardness of the glass. In particular, by adjusting the content of the TiO 2 component, devitrification due to excessive content can be reduced, and the transmittance in the infrared region can be increased. Cameras for in-vehicle use should preferably have high transmittance in the infrared region because they need to be used day and night.
• the lower limit of the TiO 2 component content is preferably 3.0% or more, more preferably 4.5% or more, still more preferably 6.0% or more, and still more preferably 7.0% or more.
• the upper limit of the content of the TiO 2 component is preferably 28.0% or less, more preferably 26.0% or less, still more preferably 24.0% or less, and even more preferably 22.0% or less.
• the La 2 O 3 component is a component that increases the refractive index and Abbe number of the glass while increasing the Knoop hardness. Therefore, the content of the La 2 O 3 component is preferably 18.0% or more, more preferably 20.0% or more, still more preferably 24.0% or more, and still more preferably 30.0% or more. .
• the content of the La 2 O 3 component is preferably 18.0% or more, more preferably 20.0% or more, still more preferably 24.0% or more, and still more preferably 30.0% or more. .
• by setting the content of the La 2 O 3 component to 55.0% or less devitrification can be reduced by increasing the stability of the glass, and an unnecessary increase in the Abbe number can be suppressed.
• the upper limit is 55.0% or less, more preferably 53.0% or less, still more preferably 51.0% or less, still more preferably 48.0% or less, and even more preferably 45.0% or less.
• the Y 2 O 3 component is a component capable of increasing the stability of the glass by improving the meltability of the raw material for glass while suppressing the material cost of the glass while maintaining the desired refractive index and Abbe number.
• the upper limit of the content of the three Y 2 O components is preferably 15.0% or less, more preferably 12.0% or less, and still more preferably 10.0% or less.
• the lower limit of the content of the Y 2 O 3 component is preferably 0.1% or more, preferably 0.5% or more, and more preferably 1.0% or more.
• the Gd 2 O 3 component and the Yb 2 O 3 component are components capable of increasing the refractive index of the glass.
• the Gd 2 O 3 component and the Yb 2 O 3 component are expensive as raw materials, and if the content is large, the production cost will be high. Therefore, the contents of the three Gd 2 O components and the three Yb 2 O components are each preferably 3.0% or less, more preferably 2.0% or less, still more preferably 1.0% or less, still more preferably 0.0% or less. 8% or less, more preferably 0.5% or less, still more preferably 0.3% or less, further preferably 0.1% or less. In particular, from the viewpoint of reducing material costs, it is most preferable not to contain these components.
• the ZnO component is a component that increases the meltability of the raw material, increases the hardness of the glass, and increases the stability of the glass. It is also a component that contributes to the improvement of impact resistance.
• the lower limit of the ZnO component content is preferably more than 0%, more preferably 0.5% or more, and still more preferably 1.0% or more.
• the upper limit of the content of the ZnO component is preferably 25.0% or less, more preferably 23.0% or less, and more preferably 21.0% or less.
• the MgO component is an optional component that can improve the meltability of glass raw materials and the devitrification resistance of glass.
• the upper limit of the content of the MgO component is preferably 8.0% or less, more preferably 6.0% or less, still more preferably 4.0% or less, still more preferably 3.0% or less.
• the CaO component is an optional component capable of increasing the hardness and impact resistance of the glass and improving the meltability of the glass raw material.
• the alkaline earth components it is the most effective component for improving impact resistance.
• the lower limit of the CaO component content is preferably more than 0%, more preferably 0.5% or more, and still more preferably 1.0% or more.
• the upper limit of the CaO content is preferably 20.0% or less, more preferably 18.0% or less, still more preferably 15.0% or less, still more preferably 13.0% or less.
• the SrO component is an optional component that can improve the meltability of glass raw materials and the devitrification resistance of glass.
• the upper limit of the SrO component content is preferably 8.0% or less, more preferably 6.0% or less, still more preferably 4.0% or less, and still more preferably 3.0% or less.
• the BaO component is a component that increases the refractive index and Abbe number of the glass and lowers the liquidus temperature.
• the BaO component reduces the impact resistance of the glass the most among the alkaline earth metals. Therefore, the content of the BaO component is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 1.0%. % or less is the upper limit.
• the Li 2 O component, Na 2 O component and K 2 O component are components capable of improving the meltability of the glass and lowering the glass transition point.
• the Li 2 O component, the Na 2 O component, and the K 2 O component each 5.0% or less, it becomes difficult to lower the refractive index of the glass, and the devitrification of the glass can be reduced. decrease in hardness can be suppressed.
• the contents of the Li 2 O component, the Na 2 O component and the K 2 O component are each preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, still more preferably is 2.0% or less, more preferably 1.0% or less, more preferably 0.8% or less, still more preferably 0.6% or less, and still more preferably 0.3% or less.
• the ZrO 2 component is a component capable of increasing the refractive index Abbe number while suppressing coloration. Therefore, the lower limit is preferably more than 0%, more preferably 0.5% or more, and still more preferably 1.0% or more. On the other hand, the ZrO 2 component causes devitrification when contained excessively. Therefore, the upper limit of the content of the ZrO 2 component is preferably 8.0% or less, more preferably 6.0% or less, and still more preferably 4.0% or less.
• the Nb 2 O 5 component is an optional component that can increase the refractive index of the glass.
• the content of the Nb 2 O 5 component is preferably 5.0% or less, more preferably 4.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, further preferably
• the upper limit is 1.0% or less, more preferably 0.8% or less, more preferably 0.5% or less, still more preferably 0.3% or less, and even more preferably 0.1% or less.
• the Nb 2 O 5 component may not be contained.
• the WO 3 component is a component that can increase the refractive index, improve the resistance to devitrification, and increase the meltability in a small amount.
• the content of the three WO components is preferably 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, still more preferably 2.0% or less, and still more preferably 1.0% or less.
• the upper limit is 0% or less, more preferably 0.8% or less, more preferably 0.5% or less, still more preferably 0.3% or less, and even more preferably 0.1% or less.
• the Ta 2 O 5 component is an optional component that can increase the refractive index of the glass and improve the devitrification resistance. Also, by setting the content of the Ta 2 O 5 component to 5.0% or less, the melting temperature of the raw material is lowered, and the energy required for melting the raw material is reduced, so that the manufacturing cost of the glass can be reduced. Therefore, the content of the Ta 2 O 5 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, further preferably 0.1% or less. In particular, from the viewpoint of reducing material costs, it is most preferable not to contain the Ta 2 O 5 component.
• the P 2 O 5 component is a component capable of lowering the liquidus temperature of the glass to improve devitrification resistance.
• the upper limit of the content of the P 2 O 5 component is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, and still more preferably 0.8% or less.
• the content of the three Bi 2 O components is preferably 3.0% or less, more preferably 1.0% or less, still more preferably 0.8% or less, still more preferably 0.5% or less, still more preferably 0.5% or less.
• the upper limit is 3% or less, most preferably 0.1% or less.
• the content of component F is preferably 5.0% or less, more preferably 3.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, and still more preferably 0.3% or less. is the upper limit, but it may be 0%.
• the content of TeO 2 component is preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, but the upper limit is 0% may be
• the upper limit of the content of Ga 2 O 3 component is preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, and still more preferably 0.5% or less, It may be 0%.
• the content of GeO 2 component is preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, but the upper limit is 0% may be
• the content of the CeO 2 component is preferably 3.0% or less, more preferably 2.0% or less, more preferably 1.0% or less, still more preferably 0.5% or less, but the upper limit is 0% may be
• the content of the HfO 2 component is preferably 0.5% or less, more preferably 0.1% or less, more preferably 0.05% or less, and most preferably substantially free.
• the upper limit of the SnO 2 component content is preferably 2.0% or less, more preferably 1.0% or less, and still more preferably 0.5% or less, but may be 0%.
• the Sb 2 O 3 component is an optional component capable of defoaming the glass melt when it is contained in an amount exceeding 0.0%.
• the content of the Sb 2 O 3 component is preferably 1.0% or less, more preferably 0.5% or less, still more preferably 0.3% or less.
• the component for fining and defoaming the glass is not limited to the above Sb 2 O 3 component, and any known fining agent, defoaming agent or combination thereof in the field of glass production can be used.
• the structure of the glass can be strengthened and the hardness of the glass can be increased.
• the SiO2 component is a component that lowers the impact resistance of the glass compared to B2O3 and Al2O3 .
• the content is preferably 22.0% or less. The preferred range of the content of the SiO2 component is as described above.
• the mass sum of SiO 2 +B 2 O 3 +Al 2 O 3 +La 2 O 3 +Y 2 O 3 +Gd 2 O 3 is preferably 50.0% or more, more preferably 53.0% or more, still more preferably 55.0%. Above, preferably 57.0% or more, more preferably 58.0% or more, is the lower limit.
• the mass ratio Al 2 O 3 /(SiO 2 +B 2 O 3 ) is preferably 0.01 or more, more preferably 0.015 or more, still more preferably 0.02 or more, still more preferably 0.03 or more, and still more preferably has a lower limit of 0.04 or more.
• the upper limit of the mass ratio Al 2 O 3 /(SiO 2 +B 2 O 3 ) is preferably 0.500 or less, more preferably 0.400 or less, and still more preferably 0.350 or less.
• Nb 2 O 5 +WO 3 is preferably 10.0% or less, more preferably 5.0% or less, still more preferably 3.0% or less, still more preferably 2.0% or less, further preferably 1.0% or less.
• the upper limit is 0% or less.
• the mass ratio TiO 2 /(SiO 2 +B 2 O 3 +Al 2 O 3 ) is preferably 0.20 or more, more preferably 0.25 or more, still more preferably 0.29 or more, still more preferably 0.35 or more, More preferably, the lower limit is 0.40 or more.
• the mass ratio TiO 2 /(SiO 2 +B 2 O 3 +Al 2 O 3 ) is preferably 1.20 or less, more preferably 1.00 or less, still more preferably 0.90 or less, still more preferably 0.90 or less.
• the upper limit is 75 or less.
• the mass ratio Gd 2 O 3 /Ln 2 O 3 is preferably 0.10 or less, more preferably 0.07 or less, still more preferably 0.06 or less, still more preferably 0.03 or less, still more preferably 0.02. Up to the following.
• the meltability can be improved and the rare earth oxide can be stably introduced.
• the lower limit of the mass ratio B 2 O 3 /(SiO 2 +B 2 O 3 +Al 2 O 3 ) is preferably 0.10 or more, more preferably 0.15 or more, and still more preferably 0.17 or more.
• the mass ratio B 2 O 3 /(SiO 2 +B 2 O 3 +Al 2 O 3 ) is 2.00 or less, deterioration of acid resistance can be suppressed.
• the mass ratio B 2 O 3 /(SiO 2 +B 2 O 3 +Al 2 O 3 ) is preferably 2.00 or less, more preferably 1.96 or less, still more preferably 1.93 or less, still more preferably 1.90. Up to the following.
• the lower limit of the mass sum CaO+ZnO is preferably 5.0% or more, more preferably 7.0% or more, still more preferably 10.0% or more, and still more preferably 13.0% or more.
• the upper limit of the mass sum CaO+ZnO is preferably 23.0% or less, more preferably 21.0% or less, and even more preferably 20.0% or less.
• the coefficient of thermal expansion can be reduced while maintaining the refractive index. It becomes possible to increase the hardness of the glass. Although the B 2 O 3 component and the Al 2 O 3 component can increase the hardness of the glass, it becomes difficult to maintain the refractive index when the content is large. Therefore, by including La 2 O 3 and Y 2 O 3 and adjusting the contents of the components, it is possible to increase the hardness of the glass with a small coefficient of thermal expansion while maintaining the refractive index.
• the mass ratio (B 2 O 3 +Al 2 O 3 )/(La 2 O 3 +Y 2 O 3 ) is preferably 0.300 or more, more preferably 0.315 or more, still more preferably 0.320 or more, still more preferably has a lower limit of 0.325 or more.
• the mass ratio (B 2 O 3 +Al 2 O 3 )/(La 2 O 3 +Y 2 O 3 ) is preferably 0.450 or less, more preferably 0.440 or less, still more preferably 0.420 or less. , more preferably 0.418 or less.
• each transition metal component such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu, is Even if a small amount of is contained alone or in combination, the glass will be colored and have the property of causing absorption at specific wavelengths in the visible range. preferable.
• lead compounds such as PbO and arsenic compounds such as As 2 O 3 are components with a high environmental load, it is desirable that they are not substantially contained, that is, they are not contained at all except for unavoidable contamination.
• Th, Cd, Tl, Os, Be, and Se components have recently tended to refrain from being used as hazardous chemical substances.
• Environmental measures are required up to the present. Therefore, it is preferable not to contain these substantially when environmental influence is emphasized.
• the glass of the present invention is preferably grade 6 or higher in a measuring method according to "JOGIS09-2019 Method for measuring Knoop hardness of glass".
• the Knoop hardness of the glass of the present invention is preferably grade 6 or higher, more preferably grade 7 or higher.
• the Knoop hardness of the glass of the present invention is preferably 600 or more.
• the Knoop hardness can be represented by a grade, and even in the range of 550 to 650 where the Knoop hardness is grade 6, it is more preferably 600 or more.
• the lower limit of the Knoop hardness of the glass of the present invention is preferably 600 or higher, more preferably 620 or higher, and still more preferably 650 or higher.
• the upper limit of the Knoop hardness of the glass of the present invention is not particularly limited, the upper limit of the Knoop hardness of the glass of the present invention may be, for example, 780 or less, 760 or less, 740 or less, or 720 or less.
• the glass of the present invention preferably has an average linear expansion coefficient ⁇ of 90 ⁇ 10 ⁇ 7 ° C. ⁇ 1 or less at 100 to 300° C.
• the glass of the present invention has an average coefficient of linear expansion ⁇ at 100 to 300 ° C. specified in Japan Optical Glass Industry Standard JOGIS08-2003, preferably 90 ⁇ 10 -7 ° C. -1 , more preferably 88 ⁇ 10
• the upper limit is -7 ° C. -1 , more preferably 86 ⁇ 10 -7 ° C. -1 .
• the lower limit of the average linear expansion coefficient ⁇ of the glass of the present invention is not particularly limited, the average linear expansion coefficient ⁇ of the glass of the present invention is, for example, 60 ⁇ 10 ⁇ 7 ° C. ⁇ 1 or more, 65 ⁇ 10 ⁇ 7 ° C. ⁇
• the lower limit may be 1 or more and 70 ⁇ 10 ⁇ 7 ° C. ⁇ 1 or more.
• the glass of the present invention preferably has a ratio of ⁇ to ⁇ , ⁇ / ⁇ , of 7.80 or more, where ⁇ is the average coefficient of linear expansion at 100 to 300°C and the Knoop hardness.
• Glass has the property that even if there is a minute scratch on the surface of the glass, the scratch will grow, and when an impact is applied, the scratch will grow further and the glass will break.
• it is effective to increase the hardness of the glass and suppress scratches on the glass surface.
• the inventors have found that even if the hardness of the glass is the same, the glass does not necessarily withstand the impact of the same degree.
• the glass of the present invention has an average linear expansion coefficient ⁇ at 100 to 300 ° C. and a Knoop hardness as ⁇ . You can get strong glass.
• ⁇ / ⁇ is preferably 7.80 or more, more preferably 7.83 or more, still more preferably 7.85 or more, still more preferably 7.88 or more, still more preferably 7.90 or more, still more preferably 7.93 or more is the lower limit.
• the upper limit of ⁇ / ⁇ is preferably 9.50 or less, more preferably 9.30 or less, and still more preferably 9.10 or less.
• the lower limit of the refractive index (n d ) of the glass of the present invention is preferably 1.80000 or more, more preferably 1.81000 or more, and still more preferably 1.82000 or more.
• the refractive index (n d ) of the glass of the present invention may be preferably 1.95000 or less, more preferably 1.94000 or less, and more preferably 1.93000 or less.
• the Abbe number ( ⁇ d ) of the glass of the present invention is preferably 23.00 or more, more preferably 25.00 or more, still more preferably 28.00 or more.
• the Abbe number ( ⁇ d ) is preferably 40.00 or less, more preferably 38.00 or less, and even more preferably 36.00 or less.
• the glass of the present invention is produced, for example, as follows. That is, high-purity raw materials used in ordinary glasses such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphoric acid compounds are used as raw materials for each of the above components, and each component is contained within a predetermined content range.
• the resulting 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, and stirred and homogenized. After that, it is cooled to an appropriate temperature, cast into a mold, and slowly cooled.
• a glass molded body can be produced from the produced glass by, for example, polishing means or mold press molding means such as reheat press molding or precision press molding.
• the means for producing the glass molded body is not limited to these means.
• the glass of the present invention can be used as optical glass and is useful for various optical elements and optical designs.
• the glass molded body made of the glass of the present invention can be used, for example, for optical elements such as lenses, prisms, and mirrors, and is also used for applications requiring impact resistance, such as vehicle-mounted optical devices such as vehicle-mounted cameras. be able to.
• compositions of Examples 1 to 15 of the present invention and Comparative Examples 1 to 3, and refractive index (n d ), Abbe number ( ⁇ d ), Knoop hardness, average linear expansion coefficient at 100 to 300 ° C. of these glasses Tables 1 and 2 show the results of ⁇ . It should be noted that the following examples are for the purpose of illustration only, and the present invention is not limited only to these examples.
• the glasses of the examples of the present invention use high-purity raw materials such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc., which are used in ordinary glasses, as raw materials for each component. After selecting, weighing and mixing uniformly so that the composition ratio of each example shown in the table is obtained, it is put into a platinum crucible and heated to 1000 to 1400 ° C. in an electric furnace depending on the melting difficulty of the glass raw material. After being melted for 1 to 10 hours in a temperature range, it was stirred and homogenized, cast into a mold or the like, and slowly cooled.
• high-purity raw materials such as corresponding oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphate compounds, etc.
• the refractive index (n d ) and Abbe number ( ⁇ d ) of the glasses of Examples and Comparative Examples were measured according to the V-block method defined in JIS B 7071-2:2018.
• the refractive index (n d ) is shown as a measured value for the d-line (587.56 nm) of a helium lamp.
• the Abbe number ( ⁇ d ) is 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 C-line (656.27 nm).
• Knoop hardness (Hk) of the glass of Examples and Comparative Examples was measured based on the Japan Optical Glass Industry Association Standard (JOGIS09-2019). Specifically, a diamond rhombic indenter (diagonal angles of 172.5° and 130°) on the flat polished surface of the sample was pressed for 15 seconds under a load of 0.98 N (0.1 kgf) to make an indentation, and the longer diagonal of the indentation was measured and obtained by the formula (1).
• Knoop hardness 1.451 F/l 2 (1)
• a grade of 650 or higher is defined as grade 7, and the higher the grade, the harder the glass.
• the average linear expansion coefficient ⁇ of the glasses of Examples and Comparative Examples at 100 to 300 ° C. was determined according to the Japan Optical Glass Industry Standard JOGIS08-2003 "Method for measuring thermal expansion of optical glass" using a vertical expansion measuring instrument (Bruker (manufactured by the company).
• a sample having a diameter of 4.5 mm and a length of 20 mm was used for the measurement, and the heating rate was 4° C./min.
• the glass of the example had a Knoop hardness of grade 6 or higher and 600 or higher.
• the glass of the example of the present invention had an average coefficient of linear expansion ⁇ of 90 ⁇ 10 -7 ° C. -1 or less at 100 to 300°C.
• all the glasses of Examples had a refractive index (n d ) of 1.80000 or more and 1.95000 or less, which was within the desired range.
• the Abbe number ( ⁇ d ) of the glass of the examples of the present invention was within the range of 23.00 or more and 40.00 or less.
• a steel ball of 71.7 g (about 2.6 cm in diameter) made of SUJ2 was prepared, and on a SUS plate, a SUS ball with a diameter of 35 mm was hollowed out in the center so that the opening had a circular diameter of 30 mm.
• a cylindrical body is installed, and a double-sided optically polished glass with a diameter of 35 mm and a thickness of 2 mm is installed on it, and it is fixed with a SUS lid cut out so that the opening has a circular opening with a diameter of 30 mm. did.
• the glasses of Examples 3 and 10 of the present invention having ⁇ / ⁇ of 7.80 or more have higher impact resistance than the glass of Comparative Example 2 having ⁇ / ⁇ of less than 7.80. was glass. Furthermore, when the glasses of Example 3 and Example 10 were compared, the glass of Example 3, which had a larger ⁇ / ⁇ , had higher impact resistance. Therefore, it was found that glass having high impact resistance can be obtained by adjusting ⁇ / ⁇ .

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