Optical Glass and Optical Elements

Abstract

To provide an optical glass having medium dispersion characteristics and excellent weather resistance.SOLUTION: In a glass composition, in terms of cation%, an optical glass comprises B3+, Si4+, Al3+, Li+ and Zn2+ as essential components, and Al3+ content is 5 cation% or more, Li+ content is 10 cation% or more, Ba2+ content is 10 cation% or less, total content (Al3++Zn2++Y3++La3++Gd3++Ti4++Nb5++Zr4++Ta5+) is 12 cation% or more, and a cation ratio {(Al3++Zn2++Y3++La3++Gd3++Ti4++Nb5++Zr4++Ta5+) / (Mg2++Ca2+++Sr2++Ba2+)} is 0.80 or more, a total content (Li++Na++K+) is 10 to 30 cation%, a cation ratio (Si4+ / B3+) is 3.0 or less, and an Abbe number ν d is 55 or more and 65 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical glass and an optical element. [Background technology]

[0002] Optical glasses with medium dispersion characteristics are useful as materials for optical elements. For example, Patent Document 1 discloses optical glasses with such optical constants. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-174791 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable for optical glass to be resistant to surface deterioration due to atmospheric moisture, i.e., to have excellent weather resistance. One example of the reason why excellent weather resistance is desirable is that when glass with an altered surface is pressed, phenomena such as cloudiness becoming apparent after pressing and scratches occurring in the altered areas can occur.

[0005] In view of the above, an object of one aspect of the present invention is to provide an optical glass that has medium dispersion characteristics and excellent weather resistance. [Means for solving the problem]

[0006] One aspect of the present invention is In the glass composition expressed in cation %, B 3+ , Si 4+ , Al 3+ , Li + and Zn 2+ Contains as an essential ingredient, Al 3+ Content is 5% or more cations, Li + Content is 10% or more of cations, Ba 2+ Content is 10% or less of cations, Al 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is 12% or more of cations, Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ Al content relative to the total content 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The cation ratio of the total content of {(Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) / (Mg 2+ +Ca 2+ ++Sr 2+ +Ba 2+ )} is 0.80 or more, Li + , Na + and K. + The total content of (Li + +Na + +K + ) is 10-30% cation, B3+ Si content 4+ Cation ratio of content (Si 4+ / B 3+ ) is 3.0 or less, and an optical glass having an Abbe number νd of 55 or more and 65 or less; Regarding.

[0007] The optical glass has the above glass composition and thus has medium dispersion characteristics and exhibits excellent weather resistance. [Effects of the Invention]

[0008] According to one aspect of the present invention, an optical glass having medium dispersion characteristics and excellent weather resistance can be provided, and an optical element made of such an optical glass can be provided. [Brief explanation of the drawings]

[0009] [Figure 1] 1 shows a schematic cross-sectional view of a precision press molding device. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Optical glass] In the present invention and this specification, unless otherwise specified, the refractive index refers to the refractive index nd at the d line of helium (wavelength 587.56 nm).

[0011] In the present invention and this specification, the Abbe number νd is used as a value that indicates the properties related to dispersion, and is expressed by the following formula. νd=(nd-1) / (nF-nC) In the above formula, nF is the refractive index at the F line (wavelength 486.13 nm) of blue hydrogen, and nC is the refractive index at the C line (656.27 nm) of red hydrogen.

[0012] In the present invention and this specification, the meltability of glass refers to the ease with which a single liquid phase is formed when various glass raw materials are weighed and mixed in a predetermined ratio and placed at a predetermined temperature, and the devitrification resistance of glass refers to the resistance to crystal precipitation when molten glass solidifies.

[0013] In the present invention and this specification, the content and total content of cationic components are expressed in cation % unless otherwise specified, and the content and total content of anionic components are expressed in anion % unless otherwise specified. Here, "cation %" is a value calculated by "(number of cations of interest / total number of cations in the glass components) x 100" and means the molar percentage of the amount of cations of interest relative to the total amount of cationic components. Furthermore, "anion %" is a value calculated by "(number of anions of interest / total number of anions in the glass components) x 100" and means the molar percentage of the amount of anions of interest relative to the total amount of anion components. The molar ratio of the contents of the cationic components to each other is equal to the ratio of the contents, expressed as cationic %, of the cationic components in question. The content of each component can be determined by known methods, such as inductively coupled plasma atomic emission spectrometry (ICP-AES), inductively coupled plasma mass spectrometry (ICP-MS), and ion chromatography. In the present invention and this specification, the content of a component being 0%, not containing, or not incorporating a component means that the component is substantially not contained, and the content of the component is at or below the impurity level, for example, less than 0.01%.

[0014] The optical glass (sometimes simply referred to as "glass") will be described in more detail below.

[0015] <Glass composition> The glass composition of the optical glass, expressed in cation % will be explained below.

[0016] The above optical glass is B 3+ , Si 4+ , Al 3+ , Li + and Zn 2+ The optical glass contains as an essential component the content of which in the optical glass is greater than 0%.

[0017] Al 3+ From the viewpoint of improving weather resistance and acid resistance, the content is 5% or more, and more preferably 6% or more, 7% or more, 8% or more, and 9% or more in that order. 3+ From the viewpoint of improving meltability and devitrification resistance, the content is preferably 15% or less, more preferably 14% or less, and even more preferably 13% or less.

[0018] Li + The content is 10% or more, preferably 11% or more, 12% or more, 13% or more, 14% or more, and 15% or more in that order, from the viewpoint of suppressing an increase in the glass transition temperature. + From the viewpoint of suppressing deterioration of weather resistance and / or acid resistance, the content is preferably 30% or less, more preferably 29% or less, 28% or less, 27% or less, and 26% or less in that order.

[0019] Li + , Na + and K. + is an alkali metal cation. + , Na + and K. + The total content of (Li + +Na + +K + From the viewpoint of improving weather resistance and acid resistance, the total content (Li) is 30% or less, and more preferably 29% or less, 28% or less, and 27% or less in that order. + +Na + +K + ) is 10% or more, and is preferably 11% or more, 12% or more, 13% or more, 14% or more, 15% or more, 16% or more, and 17% or more in that order from the viewpoint of suppressing an increase in the glass transition temperature.

[0020] Na + From the viewpoint of preventing deterioration of weather resistance and / or acid resistance, the content is preferably 10% or less, and more preferably 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, and 2% or less in that order. + It can be a glass that does not contain Na + The optical glass may also contain Na. + The content can be 0%, 0% or more, greater than 0%, 0.5% or more, or 1% or more.

[0021] K + From the viewpoint of preventing deterioration of weather resistance and / or acid resistance, the content is preferably 10% or less, and more preferably 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, and 2% or less in that order. + The content may be 0%, or may be 0% or more, or may exceed 0%. However, from the viewpoint of the devitrification resistance of the glass, the content is preferably 0.5% or more, or 1% or more.

[0022] B 3+ Since B is an essential component of the optical glass, its content is greater than 0%. 3+ From the viewpoint of improving meltability, the content is 10% or more, and more preferably 11% or more, 12% or more, 13% or more, 14% or more, and 15% or more in that order. 3+ From the viewpoint of further improving weather resistance and acid resistance, the content is preferably 25% or less, more preferably 22% or less, even more preferably 20% or less, still more preferably 19% or less, even more preferably 18% or less, and still more preferably 17% or less.

[0023] Si 4+ Since Si is an essential component of the above optical glass, its content is greater than 0%. 4+The content can be, for example, 5% or more, 10% or more, 15% or more, 20% or more, or 25% or more. From the viewpoint of improving acid resistance, the content is preferably 30% or more, more preferably 31% or more, 32% or more, and 33% or more in that order. 4+ From the viewpoint of improving meltability, the content is preferably 40% or less, more preferably 39% or less, 38% or less, and 37% or less in that order.

[0024] B 3+ Si content 4+ Cation ratio of content (Si 4+ / B 3+ From the viewpoint of improving meltability and suppressing the occurrence of striae, the cation ratio (Si 4+ / B 3+ ) is preferably 1.2 or more, more preferably 1.3 or more, 1.4 or more, 1.5 or more, and 1.6 or more in that order, from the viewpoint of improving weather resistance and acid resistance.

[0025] Zn 2+ Since Zn is an essential component of the optical glass, its content is greater than 0%. 2+ tends to increase the refractive index and make the glass more highly dispersive. 2+ From the above viewpoint, Zn has the effect of lowering the glass transition temperature. 2+ The content is preferably 0.5% or more, and more preferably 1% or more. 2+ From the viewpoint of preventing a decrease in Abbe number and / or deterioration of acid resistance, the content is preferably 10% or less, more preferably 9% or less, 8% or less, and 7% or less in that order.

[0026] Ba 2+ , Mg 2+ , Ca 2+ and Sr 2+ is an alkaline earth metal cation. Among the alkaline earth metal cations, the optical glass contains Ba. 2+ The glass may be Ba-free. 2+The above optical glass may also be a glass containing Ba. 2+ From the viewpoint of improving weather resistance, the content is 10% or less, and more preferably 9% or less, 8% or less, and 7% or less in that order. 2+ The content can be 0%, or can be 0% or more, or can be more than 0%. 2+ From the viewpoint of increasing the refractive index of the glass, the content is preferably 1% or more, 2% or more, and 3% or more, in that order.

[0027] Mg 2+ Regarding the above optical glass, Mg 2+ It can be a glass that does not contain Mg 2+ The optical glass may also contain Mg. 2+ From the viewpoint of improving the meltability and / or devitrification resistance of the glass, the content is preferably 5% or less, and more preferably 4% or less, 3% or less, and 2% or less in that order. 2+ The content can be 0%, or can be equal to or greater than 0%.

[0028] Ca 2+ Regarding the above optical glass, Ca 2+ It can be a glass that does not contain Ca. 2+ The optical glass may also contain Ca. 2+ From the viewpoint of improving the meltability and / or devitrification resistance of the glass, the content is preferably 15% or less, and more preferably 14% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, and 8% or less in that order. 2+ The content can be 0%, or can be equal to or greater than 0%.

[0029] Sr 2+ Regarding the above optical glass, Sr 2+ The glass may be free of Sr 2+ The optical glass may also contain Sr. 2+From the viewpoint of improving weather resistance, the content is preferably 8% or less, more preferably 7% or less, and even more preferably 6% or less. 2+ The content can be 0%, or can be equal to or greater than 0%.

[0030] The above optical glass Al 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ From the viewpoint of improving weather resistance and acid resistance, the total content (Al) is 12% or more, preferably 13% or more. 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ From the viewpoint of improving the meltability and / or devitrification resistance of the glass, it is preferred that the content of Cr is 25% or less, 24% or less, 23% or less, 22% or less, 21% or less, 20% or less, 19% or less, and 18% or less, in that order.

[0031] Mg in the above optical glass 2+ , Ca 2+ , Sr 2+ and Ba 2+ Al content relative to the total content 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta5+ The cation ratio of the total content of {(Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) / (Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ From the viewpoint of improving weather resistance, the cation ratio {(Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) / (Mg 2+ +Ca 2+ +Sr 2+ +Ba 2+ )} is preferably 3.00 or less, 2.80 or less, 2.60 or less, or 2.40 or less, from the viewpoint of improving meltability and / or devitrification resistance.

[0032] Y 3+ , La 3+ and Gd 3+ is a rare earth cation. In one embodiment, the optical glass is 3+ , La 3+ and Gd 3+ In another embodiment, the rare earth cation Y 3+ , La 3+ and Gd 3+ The rare earth cation may contain at least one kind, and may contain two or more kinds, selected from the group consisting of Y 3+ , La 3+ and Gd 3+ is a component that functions to increase the refractive index and also to increase the weather resistance and / or acid resistance. 3+ , La 3+ and Gd3+ The total content (Y 3+ +La 3+ +Gd 3+ ) can be 0%, 0% or more, more than 0%, 0.1% or more, or 0.5% or more. On the other hand, from the viewpoint of improving the meltability and / or devitrification resistance of the glass, the total content (Y 3+ +La 3+ +Gd 3+ ) is preferably 5% or less, more preferably 4% or less, and more preferably 3% or less in that order.

[0033] Y 3+ Regarding the above optical glass, Y 3+ The glass may be free of Y. 3+ The optical glass may also contain Y. 3+ From the viewpoint of improving the meltability and / or devitrification resistance of the glass, the content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. 3+ The content can be 0%, or can be equal to or greater than 0%.

[0034] La + Regarding the above optical glass, La 3+ The glass may be free of La. 3+ The optical glass may also contain La. 3+ From the viewpoint of improving the meltability and / or devitrification resistance of the glass, the content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. 3+ The content can be 0%, 0% or more, greater than 0%, 0.1% or more, or 0.5% or more.

[0035] Gd 3+ Regarding the above optical glass, Gd 3+ The glass may be free of Gd. 3+ The optical glass may also contain Gd. 3+From the viewpoint of improving the meltability and / or devitrification resistance of the glass, the content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. 3+ The content can be 0%, or can be equal to or greater than 0%.

[0036] Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ is a component that functions to increase the refractive index and also to increase the weather resistance and / or acid resistance of the glass, but tends to significantly decrease the Abbe number of the glass. 4+ , Nb 5+ , Zr 4+ and Ta 5+ In another embodiment, the cations may be free of Ti. 4+ , Nb 5+ , Zr 4+ and Ta 5+ The optical glass may contain at least one cation selected from the group consisting of Ti, TiN, TiNb ... 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) can be 0%, 0% or more, more than 0%, 0.1% or more, or 0.5% or more. On the other hand, from the viewpoint of suppressing a decrease in the Abbe number of the glass, the total content (Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is preferably 5% or less, more preferably 4% or less, and more preferably 3% or less in that order. Ti 4+ Regarding the above optical glass, Ti 4+ The glass may be free of Ti. 4+ The optical glass may also contain Ti. 4+From the viewpoint of suppressing a decrease in the Abbe number of the glass, the content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. 4+ The content can be 0%, or can be equal to or greater than 0%. Nb 5+ Regarding the above optical glass, Nb 5+ The glass may be free of Nb. 5+ The optical glass may also contain Nb. 5+ From the viewpoint of suppressing a decrease in the Abbe number of the glass, the content is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less. 5+ The content can be 0%, or can be equal to or greater than 0%.

[0037] Zr 4+ is a component that functions to increase the refractive index and also to improve weather resistance and / or acid resistance, but it also significantly reduces the Abbe number of the glass and deteriorates the devitrification resistance of the glass. 4+ The glass may be free of Zr. 4+ The optical glass may also contain Zr. 4+ The content of Zr is preferably 3% or less, more preferably 2% or less, and even more preferably 1% or less, from the viewpoints of suppressing a decrease in the Abbe number of the glass and enhancing the devitrification resistance of the glass. 4+ The content can be 0%, or can be equal to or greater than 0%.

[0038] Ta 5+ is a component that acts to increase the refractive index. 5+ The glass may be free of Ta. 5+ Among glass raw materials, Ta compounds are relatively expensive. From the viewpoint of reducing the cost of glass, the Ta content of the above optical glass can be 5+The content is preferably 3% or less, more preferably 2% or less, even more preferably 1% or less, and even more preferably 0%. 5+ The content can be equal to or greater than 0%.

[0039] In one embodiment, a glass having excellent acid resistance is desirable. This is because a glass having excellent acid resistance is suitable as a glass for optical elements to be mounted in equipment that may be exposed to an acidic environment, such as a surveillance camera installed outdoors or an in-vehicle camera. From the viewpoint of improving acid resistance, the Al content of the above optical glass is 3+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is preferably 7 cation % or more, more preferably 8% or more. 3+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is preferably 15% or less, more preferably 14% or less.

[0040] Pb, As, Cd, Tl, Be, and Se are all toxic, and therefore it is preferable not to include these elements, i.e., not to introduce these elements into the glass as glass components. U, Th, and Ra are all radioactive elements, and therefore it is preferable not to include these elements, i.e., not to introduce these elements into the glass as glass components. V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce are undesirable elements to be contained in glass for optical elements because they can increase the coloration of the glass or be a source of fluorescence. Therefore, it is preferable not to contain these elements, i.e., not to introduce these elements into the glass as glass components.

[0041] Sb and Sn are optional elements that function as fining agents. The Sb content of the optical glass can be, for example, 0.40% or less, 0.20% or less, 0.10% or less, 0.05% or less, 0.02% or less, or 0.01% or less, expressed as a mass fraction (%) of Sb2O3 when the mass of the glass is taken as 100. On the other hand, the Sb content can be 0.00% or more, or even 0.00%, expressed as a mass fraction (%) of Sb2O3 when the mass of the glass is taken as 100. The Sn content of the optical glass can be, for example, 0.40% or less, 0.20% or less, 0.10% or less, 0.05% or less, 0.02% or less, or 0.01% or less, expressed as a mass fraction (%) of SnO2 when the mass of the glass is taken as 100. On the other hand, the Sn content can be 0.00% or more, or even 0.00%, expressed as a mass fraction (%) of SnO2 when the mass of the glass is taken as 100.

[0042] Now that the cationic component has been described, the anionic component will be described.

[0043] The optical glass may be an oxide glass, and may contain O as an anion component. 2- It can include 2- The content is preferably 95.0 anion % or more, more preferably 97.0 anion % or more, even more preferably 98.0 anion % or more, even more preferably 99.0 anion % or more, still more preferably 99.5 anion % or more, and may be 100 anion %.

[0044] O2- Other anion components include F - , Cl - , Br - and I - However, F - , Cl - , Br - and I - Both of these components are prone to volatilization during glass melting. The volatilization of these components tends to change the physical properties of the glass, reducing the homogeneity of the glass and causing significant wear on the melting equipment. - , Cl - , Br - and I - The total content of 100% anion is calculated as follows: 2- It is preferable to reduce the content of

[0045] <Glass properties> (refractive index nd) From the viewpoint of usefulness as a material for optical elements, the refractive index nd of the optical glass is preferably 1.55 or more, and can be 1.56 or more or 1.57 or more. From the viewpoint of usefulness as a material for optical elements, the refractive index nd of the optical glass is preferably 1.65 or less, and can be 1.64 or less, 1.63 or less, 1.62 or less, 1.61 or less, 1.60 or less, or 1.59 or less.

[0046] (Abbe number νd) The optical glass has an Abbe number νd of 55 or more and 65 or less, and is useful as a material for optical elements having medium dispersion characteristics. The Abbe number νd of the optical glass can be 56 or more, 57 or more, or 58 or more, or can be 64 or less, 63 or less, or 62 or less.

[0047] (DH 96 ) DH 96 is the difference in haze amount before and after the weather resistance test, and can be used as an index of weather resistance. The weather resistance test is a weather resistance test for optical glass specified in ISO22531, but with the treatment time changed to 96 hours. A typical method for evaluating weather resistance is the weather resistance test for optical glass specified in ISO 22531. In this weather resistance test, a glass sample with polished surfaces measuring 30 mm x 30 mm x 3 mm is subjected to a temperature cycle test under high temperature and high humidity conditions as specified in ISO 22531, and the difference in the haze amount (cloudiness, %) of the glass sample before and after the test is determined. The smaller this difference, the better the weather resistance. Haze measurement can be performed using a haze meter specified in ISO 14782. ISO 22531 specifies that the processing time for temperature cycle testing should be 24 cycles, with each cycle lasting two hours, for a total of 48 hours. However, depending on the application of the optical glass, stricter weather resistance standards may be required. In such cases, it is preferable to evaluate under more severe test conditions, such as extending the processing time to 48 cycles, or 96 hours. The optical glass has the glass composition described above in detail, and thus can exhibit very excellent weather resistance. Specifically, in one embodiment, the optical glass has a haze difference DH of the optical glass sample before and after the test when the high-temperature, high-humidity temperature cycle test specified in ISO22531 is carried out with 48 cycles, i.e., the treatment time is changed to 96 hours, with one cycle being 2 hours. 96 (unit: %) is 3.0% or less. 96 is more preferably 2.9% or less, more preferably 2.5% or less, 2.0% or less, 1.5% or less, 1.0% or less, 0.5% or less, and 0.3% or less in that order, and the smaller the value, the more preferable it is.

[0048] (mass reduction rate DA) In one embodiment, the optical glass can also exhibit excellent acid resistance. Acid resistance can be evaluated according to the Japan Optical Glass Industry Association standard JOGIS06-2019 "Method for measuring chemical durability of optical glass (powder method)." The specific measurement method is as follows. Mass equivalent to specific gravity (Mbefore Powdered glass (particle size 425 μm to 600 μm) weighing (unit: g) is placed in a platinum cage, which is then immersed in 80 ml of a 0.01 mol / l aqueous solution of nitric acid contained in a round-bottom flask made of quartz glass or borosilicate glass-1 as specified in JIS R 3503, and treated in a boiling water bath for 60 minutes. The mass M of the powdered glass after treatment is after When the mass loss rate (DA) is measured (unit: g), the mass loss rate DA (%) is DA(%)=[(M before -M after ) / M before ] × 100, The acid resistance can be evaluated based on the magnitude of this DA. As one embodiment of the optical glass, the glass having excellent acid resistance may have the DA value of 0.35% or less, or may be less than 0.35%.

[0049] (glass transition temperature Tg) From the viewpoint of precision pressing suitability, a glass having a low glass transition temperature Tg is preferred. From this viewpoint, the glass transition temperature Tg of the optical glass is preferably 535°C or lower, more preferably 530°C or lower, even more preferably 525°C or lower, and even more preferably 520°C or lower.

[0050] The glass transition temperature Tg can be determined as follows. In differential scanning calorimetry, when a glass sample is heated, an endothermic behavior associated with a change in specific heat, i.e., an endothermic peak, appears, and when the temperature is further increased, an exothermic peak appears. In differential scanning calorimetry, a differential scanning calorimetry curve (DSC curve) is obtained, with the horizontal axis representing temperature and the vertical axis representing quantities corresponding to the heat generation and endothermic heat of the sample. The glass transition temperature Tg is determined by the intersection of the tangent to the point where the slope of this curve becomes maximum when an endothermic peak appears from the baseline and the baseline. The glass transition temperature Tg can be measured by using glass that has been thoroughly crushed in a mortar or the like as a sample, using a differential scanning calorimeter, and at a heating rate of 10°C / min.

[0051] (specific gravity) The refractive power of the optical elements that make up an optical system is determined by the refractive index of the glass that makes up the optical element and the curvature of the optically functional surface of the optical element (the surface through which the light rays to be controlled enter and exit). Increasing the curvature of the optically functional surface also increases the thickness of the optical element. As a result, the optical element becomes heavier. In contrast, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface. From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, it will be possible to reduce the weight of an optical element having a certain refractive power. From the above viewpoints, the specific gravity d of the optical glass is preferably 3.5 or less, with 3.4 or less, 3.3 or less, 3.2 or less, and 3.1 or less being more preferred in that order. Since a lower specific gravity is preferable from the viewpoint of reducing the weight of optical elements, there is no particular lower limit for the specific gravity of the optical glass. In one embodiment, the specific gravity can be 2.5 or more, 2.6 or more, or 2.7 or more.

[0052] (Coloring degree λ5, λ 70 , λ 80 ) The light transmittance of the glass, specifically, the suppression of the shift of the light absorption edge on the short wavelength side to longer wavelengths, is a factor that determines the coloring degree λ5, λ 70 and λ 80 The coloring degree λ5 represents the wavelength at which the spectral transmittance (including surface reflection loss) of a 10 mm thick glass becomes 5% from the ultraviolet region to the visible region. 70 represents the wavelength at which the spectral transmittance measured by the method described for λ5 is 70%. 80 represents the wavelength at which the spectral transmittance measured by the method described for λ5 is 80%. 70 and λ 80 is a value measured in the wavelength range of 250 to 700 nm. The spectral transmittance T (%) of glass in the present invention and this specification is calculated by dividing the intensity of light incident perpendicularly on one of two optically polished planes parallel to each other by I in The intensity of the light that passes through the glass sample and emerges from the other surface is I outWhen T(%)=I out / I in ×100 It is expressed as: Coloring degree λ5, λ 70 and λ 80 According to this method, the absorption edge on the short wavelength side of the spectral transmittance can be quantitatively evaluated. When lenses are bonded together with an ultraviolet-curable adhesive to produce a cemented lens, the adhesive is cured by irradiating it with ultraviolet light through an optical element. From the viewpoint of efficiently curing the ultraviolet-curable adhesive, it is preferable that the absorption edge on the short wavelength side of the spectral transmittance is in a short wavelength range. As an index for quantitatively evaluating the absorption edge on the short wavelength side, the coloring degree λ5, λ 70 and λ 80 One or more of the following can be used. The optical glass preferably exhibits a λ5 of 360 nm or less. λ5 is more preferably 350 nm or less, 340 nm or less, and 330 nm or less, in that order. λ5 is more preferably a shorter wavelength, and there is no particular lower limit. The optical glass preferably has a λ of 400 nm or less. 70 It can be shown that λ 70 is more preferably 390 nm or less, 380 nm or less, 370 nm or less, and 360 nm or less, in that order. 70 The shorter the wavelength, the more preferable it is, and there is no particular lower limit. The optical glass preferably has a λ of 420 nm or less. 80 It can be shown that λ 80 is more preferably 410 nm or less, 400 nm or less, 390 nm or less, 380 nm or less, and 370 nm or less, in that order. 80 The shorter the wavelength, the more preferable it is, and there is no particular lower limit.

[0053] <Glass manufacturing method> The optical glass can be obtained by weighing, blending, and thoroughly mixing raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides to obtain the desired glass composition, heating and melting the mixture in a melting vessel, degassing, and stirring to produce a homogeneous, bubble-free glass melt, and then molding the resulting glass. Specifically, the glass can be produced using a known melting method.

[0054] [Glass material for press molding, its manufacturing method, and manufacturing method of glass molded body] According to one aspect of the present invention, there are provided a press-molding glass material made of the above optical glass, a glass molded article made of the above optical glass, and methods for producing them. The glass material for press molding means a glass lump that is heated and subjected to press molding. Examples of glass materials for press molding include glass gobs having a mass equivalent to the mass of press-molded products such as precision press molding preforms and glass materials (press molding glass gobs) for press molding optical element blanks. The glass material for press molding can be produced through a process of processing a glass molded body. The glass molded body can be produced by heating and melting a glass raw material as described above, and molding the resulting glass melt. Examples of processing methods for the glass molded body include cutting, grinding, polishing, etc.

[0055] [Optical element blank and its manufacturing method] According to one aspect of the present invention, an optical element blank made of the above optical glass can be provided. The optical element blank is a glass molded body having a shape similar to that of the optical element to be manufactured. The optical element blank can be produced by a method of molding glass into a shape that is the shape of the optical element to be manufactured plus a processing allowance to be removed by processing. For example, the optical element blank can be produced by a method of heating and softening a glass material for press molding and press-molding it (reheat press method), or a known method of supplying a molten glass gob to a press mold and press-molding it (direct press method).

[0056] [Optical elements and their manufacturing methods] According to one aspect of the present invention, an optical element made of the above optical glass can be provided. Examples of the types of optical elements include lenses such as spherical lenses and aspherical lenses, prisms, and diffraction gratings. Examples of the lens shapes include biconvex lenses, plano-convex lenses, biconcave lenses, plano-concave lenses, convex meniscus lenses, and concave meniscus lenses.

[0057] One embodiment of the method for manufacturing an optical element is a method for manufacturing an optical element by heating a precision press molding preform and precision press molding. A known press mold can be used for precision press molding, and a known molding method can be applied. The method for manufacturing an optical element by precision press molding is suitable for manufacturing aspherical lenses, microlenses, diffraction gratings, etc.

[0058] Another embodiment of the method for manufacturing an optical element is a method for manufacturing an optical element by machining an optical element blank. Examples of machining include cutting, milling, rough grinding, fine grinding, and polishing. This manufacturing method is suitable for manufacturing spherical lenses, prisms, etc.

[0059] As a result of quantitative analysis of glass composition, the glass components are sometimes expressed in terms of oxides, and the content of the glass components is expressed in mass%. The composition expressed in mass% on an oxide basis can be converted to a composition expressed in cation% and anion% using, for example, the following method. If N kinds of glass components are contained in the glass, the kth glass component is A(k). m O n Here, k is an integer between 1 and N. A(k) is a cation, O is oxygen, and m and n are stoichiometric integers. For example, in the oxide-based notation of B2O3, m=2 and n=3, and in the case of SiO2, m=1 and n=2. Next, A(k) m O nThe content of A(k) is X(k) [mass %]. Here, if the atomic weight of A(k) is P(k) and the atomic number of oxygen O is Q, then A(k) m O n The formal molecular weight R(k) of R(k)=P(k)×m+Q×n This becomes: Furthermore, B=100 / {Σ[m×X(k) / R(k)]} Then, the cationic component A(k) s+ The content (cation %) of is [X(k) / R(k)] × m × B (cation %). Here, Σ means the sum of m × X(k) / R(K) for k = 1 to N. m changes depending on k. s is 2n / m. The molecular weight R(k) can be calculated by rounding off the fourth decimal place and displaying the value to three decimal places. The molecular weights of several glass components and additives expressed on an oxide basis are shown in Table 1 below.

[0060] [Table 1] [Example]

[0061] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the embodiments shown in the examples.

[0062] <Examples 1 to 31 and Comparative Examples 1 to 6> To obtain the glass compositions shown in the table below, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component, and the raw materials were weighed and thoroughly mixed to obtain blended raw materials. The raw materials were placed in a platinum crucible and heated to melt. After melting, the molten glass was poured into a mold and allowed to cool to near the glass transition temperature. It was then immediately placed in an annealing furnace and held at a temperature close to the glass transition temperature for about 1 hour, after which it was slowly cooled at a rate of -30°C / hour for 4 hours, and then allowed to cool to room temperature in the furnace to obtain the optical glasses (oxide glasses) shown in Table 1. The anion components of each optical glass shown in the table below are O 2- The content is 100% anion. The physical properties of the optical glass thus obtained are shown in the table below. The physical properties of the optical glass were measured by the following methods.

[0063] <Evaluation of the physical properties of optical glass> (1) Refractive index nd Abbe number νd The refractive index nd and Abbe number vd of the obtained glass were measured by the refractive index measurement method specified by the Japan Optical Glass Industry Association standard.

[0064] (2) Glass transition temperature Tg The glass was thoroughly crushed in a mortar and used as a sample, and the glass transition temperature Tg was measured using a differential scanning calorimeter (DSC3300SA) manufactured by NETZSCH at a heating rate of 10°C / min.

[0065] (3) Specific gravity Specific gravity was measured by Archimedes' method.

[0066] (4) Coloring degree λ5, λ 70 , λ 80 A 10±0.1 mm thick glass sample with two optically polished flat surfaces facing each other was used to measure the spectral transmittance T (%) using a spectrophotometer. The wavelength (nm) at which T is 5% is defined as λ5, and the wavelength (nm) at which T is 70% is defined as λ. 70 The wavelength (nm) at which T is 80% is λ 80 It was decided.

[0067] (5)DH 96 As an index of weather resistance, DH was measured by the method detailed above. 96Specifically, a glass sample of 30 mm x 30 mm x 3 mm polished on both sides was subjected to a high temperature and high humidity temperature cycle test specified in ISO 22531, with 48 cycles of 2 hours per cycle, i.e., a treatment time of 96 hours. The haze amount (%) before and after the test was measured using a haze meter based on ISO 17482, and the difference in haze amount before and after the test, DH 96 (%) was calculated.

[0068] (6) Mass reduction rate DA As an indicator of acid resistance, the mass loss rate DA (%) was determined using the method described in detail above. Specifically, a mass (g) of powdered glass (particle size 425 μm to 600 μm) equivalent to the specific gravity was placed in a platinum cage, which was then immersed in 80 ml of a 0.01 mol / l aqueous nitric acid solution placed in a round-bottom flask and treated in a boiling water bath for 60 minutes. The mass of the powdered glass was measured before and after treatment, and the mass loss rate DA (%) was calculated.

[0069] The evaluation results are shown in the following table, in which the content of each component and the total content are expressed in units of cation %, and the ratios are cation ratios. In Comparative Example 6, the refractive index and Abbe number could not be measured because a large amount of striae was contained in the glass. This is because the cation ratio (Si 4+ / B 3+ ) exceeds 3.0. In the following table, the columns for nd and νd for Comparative Example 6 are marked with "Striae NG." As shown in the table below, the glasses of Comparative Examples 1 to 5 were inferior in weather resistance to the glasses of Examples 1 to 31. This is because the total content (Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is thought to be below 12 cation %. From the comparison between the examples, Al 3+ , Y 3+ , La3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ It can be seen that Examples 3 to 31, in which the total content is 7 cation % or more and 15 cation % or less, have superior acid resistance compared to Examples 1 and 2, in which the total content is outside the above range.

[0070] [Table 2-1]

[0071] [Table 2-2]

[0072] [Table 2-3]

[0073] [Table 2-4]

[0074] [Table 3-1]

[0075] [Table 3-2]

[0076] [Table 3-3]

[0077] [Table 3-4]

[0078] [Table 4-1]

[0079] [Table 4-2]

[0080] [Table 4-3]

[0081] [Table 4-4]

[0082] [Table 5-1]

[0083] [Table 5-2]

[0084] [Table 5-3]

[0085] [Table 5-4]

[0086] [Preparation of precision press molding preforms] For each of Examples 1 to 31, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component so as to obtain the glass composition shown in the above table, and the raw materials were weighed and thoroughly mixed to prepare a compounded raw material. This blended raw material was placed in a platinum crucible and heated to melt. The clarified and homogenized glass melt was then discharged at a constant flow rate from a platinum alloy pipe whose temperature was adjusted to a temperature range that allowed stable flow without devitrification of the glass, and separated into molten glass gobs of the desired preform mass by a drip or drop-cutting method. The separated molten glass gobs were received in a mold with a gas outlet at the bottom, and gas was ejected from the gas outlet to float the glass gobs, thereby forming a preform for precision press molding. By adjusting and setting the separation distance between the molten glass gobs, a flattened spherical preform was obtained.

[0087] [Fabrication of optical elements (aspherical lenses)] FIG. 1 shows a schematic cross-sectional view of a precision press molding device. The preform obtained above was precision press-molded using the precision press-molding device shown in FIG. 1 to obtain an aspherical lens. Specifically, the preform was placed between the lower mold 2 and the upper mold 1 that constituted the press mold, and then the inside of the quartz tube 11 was filled with nitrogen and the heater (not shown) was energized to heat the inside of the quartz tube 11. The temperature inside the press mold was adjusted to the temperature at which the glass to be formed was 10 6 ~10 10 The temperature was set to a temperature at which the viscosity of the glass was 10 dPa·s, and while maintaining this temperature, the push rod 13 was lowered to press the upper mold 1 and press the preform set in the mold. The pressure of the press was 8 MPa, and the pressing time was 30 seconds. After pressing, the pressure of the press was released, and the press-molded glass product was left in contact with the lower mold 2 and the upper mold 1 until the viscosity of the glass reached 10 12The glass molded product is slowly cooled to a temperature of at least dPa·s, and then rapidly cooled to room temperature, and removed from the mold to obtain an aspherical lens. In Figure 1, holding member 10 holds lower mold 2 and barrel mold 3, and support rod 9 supports upper mold 1, lower mold 2, barrel mold 3, and holding member 10, and also bears the pressing pressure from push rod 13. A thermocouple 14 is inserted inside lower mold 2 to monitor the temperature inside the press mold. When the surfaces of the lenses obtained in Examples 1 to 31 were visually inspected, no cloudiness or scratches were found.

[0088] Finally, the above-mentioned aspects will be summarized.

[0089] According to one embodiment, in the glass composition expressed in cation %, B 3+ , Si 4+ , Al 3+ , Li + and Zn 2+ Contains as an essential component, Al 3+ Content is 5% or more of cations, Li + Content is 10% or more of cations, Ba 2+ Content is 10% or less of cations, Al 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is 12% or more of cations, Mg 2+ , Ca 2+ , Sr 2+ and Ba 2+ Al content relative to the total content 3+ , Zn 2+ , Y 3+ , La 3+ , Gd 3+, Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The cation ratio of the total content of {(Al 3+ +Zn 2+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) / (Mg 2+ +Ca 2+ ++Sr 2+ +Ba 2+ )} is 0.80 or more, Li + , Na + and K. + The total content of (Li + +Na + +K + ) is 10-30% cation, B 3+ Si content 4+ Cation ratio of content (Si 4+ / B 3+ ) is 3.0 or less and the Abbe number νd is 55 to 65 or less.

[0090] The optical glass can exhibit excellent weather resistance.

[0091] In one embodiment, B of the optical glass 3+ The content can be 10 cation % or more and 25 cation % or less.

[0092] In one embodiment, the Si of the optical glass 4+ The content can be 30 cation % or more and 40 cation % or less.

[0093] In one embodiment, the Al of the optical glass 3+ The content can be 5 cation % or more and 15 cation % or less.

[0094] In one embodiment, the Al of the optical glass 3+ , Y 3+ , La 3+ , Gd3+ , Ti 4+ , Nb 5+ , Zr 4+ and Ta 5+ The total content of Al 3+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) can be greater than or equal to 7 cation % and less than or equal to 15 cation %.

[0095] Total content (Al 3+ +Y 3+ +La 3+ +Gd 3+ +Ti 4+ +Nb 5+ +Zr 4+ +Ta 5+ ) is preferably 7 cation % or more and 15 cation % or less from the viewpoint of improving acid resistance.

[0096] The glass transition temperature Tg of the optical glass can be 535° C. or lower.

[0097] It is preferable that the glass transition temperature Tg of the optical glass is 535° C. or less from the viewpoint of suitability for precision pressing.

[0098] In one embodiment, the difference DH of the haze amount of the optical glass before and after the weather resistance test 96 The above weather resistance test is a weather resistance test for optical glass specified in ISO 22531, but with the treatment time changed to 96 hours.

[0099] In one embodiment, the mass loss rate DA of the optical glass after an acid resistance test specified in JOGIS06:2019 is carried out can be 0.35% or less.

[0100] According to one embodiment, there is provided an optical element made of the above optical glass.

[0101] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. For example, by adjusting the composition as described in the specification for the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be obtained. Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges. [Explanation of symbols]

[0102] 1: Upper mold 2: Lower mold 3: Body type 4:Precision press molding preforms 9: Support rod 10: Holding member 11:Quartz tube 13: Push stick 14: Thermocouple

Claims

1. In the glass composition expressed in cation %, B ３＋ , Si ４＋ , Al ３＋ , Li ＋ and Zn ２＋ Contains as an essential ingredient, B3+ content is 25 cation % or less; a Si 4+ content of 30 cation % or more and 40 cation % or less; Al ３＋ The content is 5% or more of cations, Li ＋ The content is 10% or more of cations, Ba ２＋ The content is 10% or less of cations, Al ３＋ , Zn ２＋ , Y ３＋ , La ３＋ , Gd ３＋ , Ti ４＋ , Nb ５＋ , Zr ４＋ and Ta ５＋ The total content (Al ３＋ +Zn ２＋ +Y ３＋ +La ３＋ +Gd ３＋ +Ti ４＋ +Nb ５＋ + Zr ４＋ +Ta ５＋ ) is 12 cation % or more, Mg ２＋ , Ca ２＋ , Sr ２＋ and Ba ２＋ Al relative to the total content ３＋ , Zn ２＋ , Y ３＋ , La ３＋ , Gd ３＋ , Ti ４＋ , Nb ５＋ , Zr ４＋ and Ta ５＋ The cation ratio of the total content of {(Al ３＋ +Zn ２＋ +Y ３＋ +La ３＋ +Gd ３＋ +Ti ４＋ +Nb ５＋ + Zr ４＋ +Ta ５＋ ) / (Mg ２＋ + Ca ２＋ + Sr ２＋ +Ba ２＋ )} is 0.95 or more, Li ＋ , Na ＋ and K. ＋ The total content (Li ＋ +Na ＋ +K ＋ ) is 10 to 28 cation %, B ３＋ Si content ４＋ The cation ratio of the content (Si ４＋ / B ３＋ ) is 2.5 or less, and An optical glass having an Abbe number νd of 55 or more and 65 or less.

2. Al ３＋ 2. The optical glass according to claim 1, wherein the content is 5 cation % or more and 15 cation % or less.

3. Al ３＋ , Y ３＋ , La ３＋ , Gd ３＋ , Ti ４＋ , Nb ５＋ , Zr ４＋ and Ta ５＋ The total content (Al ３＋ +Y ３＋ +La ３＋ +Gd ３＋ +Ti ４＋ +Nb ５＋ + Zr ４＋ +Ta ５＋ 3. The optical glass according to claim 1, wherein the content of ZnO is 7 cation % or more and 15 cation % or less.

4. 4. The optical glass according to claim 1, which has a glass transition temperature Tg of 535° C. or lower.

5. Difference in haze amount before and after weather resistance test DH ９６ is 3.0% or less, 5. The optical glass according to claim 1, wherein the weather resistance test is a weather resistance test performed in accordance with ISO 22531, except that the treatment time is changed to 96 hours.

6. 6. The optical glass according to claim 1, wherein the mass loss rate DA after carrying out an acid resistance test specified in JOGIS06:2019 is 0.35% or less.

7. An optical element made of the optical glass according to any one of claims 1 to 6.

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