Optical glass, preforms, and optical elements

Abstract

To provide an optical glass that allows a temperature coefficient of a relative refractive index to take a value of 0 or more and can contribute to compensating for the effects of temperature changes on image-forming properties, and a preform and an optical element including the same.SOLUTION: An optical glass contains, on an oxide basis in mass%, a P2O5 component of 55.0-85.0%, an Al2O3 component of 3.0-30.0%, and a ZnO component of 6.0% or more and has a temperature coefficient (40-60°C) of a relative refractive index (589.29 nm) of 0×10-6 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to optical glass, preforms, and optical elements. [Background technology]

[0002] In recent years, the digitalization and high-definition capabilities of devices using optical systems have progressed rapidly. In the fields of various optical equipment, such as photographic equipment like digital cameras and video cameras, and image playback (projection) equipment like projectors and projection televisions, there is a growing demand to reduce the number of optical elements such as lenses and prisms used in the optical system, thereby making the entire optical system lighter and smaller.

[0003] On the other hand, optical elements incorporated into automotive optical equipment such as in-car cameras, and optical elements incorporated into optical equipment that generates a lot of heat, such as projectors, copiers, laser printers, and broadcasting equipment, are increasingly being used in higher temperature environments. In such high-temperature environments, the temperature of the optical elements constituting the optical system tends to fluctuate greatly, often reaching temperatures of 100°C or higher. At this time, the adverse effects of temperature fluctuations on the imaging characteristics of the optical system become too large to ignore, so there is a need to construct an optical system that is less susceptible to the effects of temperature fluctuations on imaging characteristics.

[0004] In constructing an optical system that is less susceptible to the effects of temperature fluctuations on imaging performance, it is preferable to use in combination optical elements made of glass whose refractive index decreases as the temperature rises and whose relative refractive index temperature coefficient becomes negative, and optical elements made of glass whose refractive index increases as the temperature rises and whose relative refractive index temperature coefficient becomes positive, as this can compensate for the effects of temperature changes on imaging characteristics.

[0005] Here, glass compositions developed by focusing on the temperature coefficient of the relative refractive index are known, such as those represented in Patent Documents 1 and 2. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2020-132510 [Patent Document 2] WO2007 / 049622 publication [Overview of the project] [Problems that the invention aims to solve]

[0007] The glass described in Patent Document 1 relates to a phthalic acid-based glass that focuses on the temperature coefficient of the relative refractive index, but the temperature coefficient of the relative refractive index is limited to -3.8 to -2.3, and the glass described in Patent Document 2 has a high transition point, so it cannot be said to have good press formability.

[0008] The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide an optical glass that has a relative refractive index temperature coefficient of 0 or greater, has good press formability, and can contribute to correcting the effect of temperature changes on imaging characteristics, as well as a preform and an optical element using the same. [Means for solving the problem]

[0009] In order to solve the above problems, the inventors conducted extensive testing and research, and as a result, found that the P2O5 component was 55.0-85.0% by mass percentage based on oxides, the Al2O3 component was 3.0-30.0%, and the ZnO component was 6.0% or more, and the temperature coefficient (40-60°C) of the relative refractive index (589.29 nm) was 0 × 10⁻⁶ -6 Having discovered that such optical glass can be obtained, we have completed the present invention. Specifically, the present invention provides the following:

[0010] (1) Based on the mass percentage of oxides, The P2O5 component is 55.0-85.0%. Al2O3 component: 3.0-30.0% ZnO content of 6.0% or more Contains, The temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or higher optical glass.

[0011] (2) In terms of mass% based on oxides, the P2O5 component is 55.0 to 85.0%, the Al2O3 component is 3.0 to 30.0%, the ZnO component is less than 6.0% the MgO component is more than 0%, contains, the mass sum Li2O×5 + Na2O + (K2O / 2) is more than 4.0%, the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is 0×10 -6 or higher optical glass.

[0012] (3) The optical glass according to (1) or (2), wherein the mass ratio Al2O3 / Rn2O is 0.5 or more (Rn is one or more selected from the group consisting of Li, Na, and K).

[0013] (4) The optical glass according to any one of (1) to (3), wherein the mass ratio Al2O3 / (SiO2 + B2O3 + P2O5) is more than 0.

[0014] (5) The optical glass according to any one of (1) to (4), wherein the glass transition point (Tg) is 600 °C or lower and the glass yield point (At) is 650 °C or lower.

[0015] (6) An optical element made of the optical glass according to any one of (1) to (5).

[0016] (7) A preform for polishing and / or precision press molding made of the optical glass according to any one of (1) to (5).

Advantages of the Invention

[0017] According to the present invention, it is possible to provide an optical glass having good press formability and contributing to the correction of the influence on imaging characteristics due to temperature changes, a preform, and an optical element using the same. [Modes for carrying out the invention]

[0018] The embodiments of the optical glass of the present invention will be described in detail below. The present invention is not limited in any way to the embodiments described below, and can be implemented with appropriate modifications within the scope of the object of the present invention. In addition, explanations may be omitted where necessary to avoid repetition, but this does not limit the spirit of the invention.

[0019] [Glass components] The optical glass of the present invention has two embodiments: a first glass and a second glass. The composition range of each component constituting the first glass and the second glass is described below. In this specification, unless otherwise specified, the content of each component is expressed as a mass % of the total mass of the oxide-equivalent composition. Here, "oxide-equivalent composition" is the composition expressed by assuming that the oxides, complex salts, metal fluorides, etc., used as raw materials for the glass components of the present invention all decompose into oxides during melting, and the total mass number of the generated oxides is set to 100% by mass, with each component contained in the glass being expressed.

[0020] <Regarding the essential and optional components of the first glass> The P2O5 component is an essential component of the present invention as a glass-forming oxide. In particular, by including 55.0% or more of the P2O5 component, the stability of the glass can be increased while lowering the transition temperature. Therefore, the lower limit of the P2O5 component content is preferably 55.0% or more, more preferably 58.0% or more, even more preferably 60.0% or more, and most preferably 63.0% or more. On the other hand, by reducing the P2O5 content to 85.0% or less, devitrification of the glass can be reduced. Therefore, the upper limit of the P2O5 content is preferably 85.0% or less, more preferably 82.0% or less, even more preferably 80.0% or less, even more preferably 78.0% or less, and most preferably 75.0% or less.

[0021] The Al2O3 component is an essential component of the present invention that increases the temperature coefficient of the relative refractive index. Therefore, the content of the Al2O3 component is preferably 3.0% or more, more preferably 4.0% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, and most preferably 5.5% or more as the lower limit. On the other hand, by limiting the Al2O3 content to 30.0% or less, the deterioration of devitrification resistance and the rise in the transition temperature due to excessive content can be suppressed. Therefore, the Al2O3 content is preferably limited to 30.0% or less, more preferably to 25.0% or less, even more preferably to 20.0% or less, and most preferably to 18.0% or less.

[0022] The ZnO component is an essential component of the present invention that can improve the temperature coefficient of the relative refractive index and meltability, thereby improving press formability. Including the Rn2O component, described later, is effective in improving press formability, but the Rn2O component is also a component that lowers the relative refractive index. Equivalent meltability can be obtained by increasing the ZnO component content to 6.0% or more. Therefore, the ZnO component content is preferably 6.0% or more, more preferably 6.5% or more, even more preferably 7.5% or more, and most preferably 8.0% or more as the lower limit. On the other hand, by limiting the ZnO content to 25.0% or less, the increase in dispersion and decrease in devitrification resistance due to excessive content can be suppressed. Therefore, the ZnO content is preferably limited to 25.0% or less, more preferably 22.0% or less, even more preferably 18.0% or less, even more preferably 15.0% or less, and most preferably 12.0% or less.

[0023] The MgO component is an optional component of this invention that, when present in amounts exceeding 0%, increases the temperature coefficient of the relative refractive index. Among the RO components described later, the MgO component has the greatest effect in increasing the temperature coefficient of the relative refractive index. Therefore, the MgO content is preferably greater than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and most preferably 1.5% or more as the lower limit. On the other hand, by limiting the MgO content to 10.0% or less, the decrease in devitrification resistance due to excessive MgO content can be suppressed. Therefore, the MgO content is preferably limited to 10.0% or less, more preferably 8.0% or less, even more preferably 5.0% or less, and most preferably 4.0% or less.

[0024] The CaO component is an optional component of the present invention that, when present in amounts exceeding 0%, improves low-temperature meltability while increasing the temperature coefficient of the relative refractive index. Therefore, the lower limit of the CaO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by limiting the CaO content to 10.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the CaO content is preferably limited to 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, even more preferably 4.0% or less, and most preferably 3.0% or less.

[0025] The SrO component is an optional component of the present invention that, when present in amounts exceeding 0%, improves low-temperature meltability while increasing the temperature coefficient of the relative refractive index. Therefore, the SrO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the SrO content to 10.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the SrO content is preferably limited to 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, even more preferably 4.0% or less, and most preferably 3.0% or less.

[0026] The BaO component is an optional component of the present invention that, when present in amounts exceeding 0%, enhances the stability of the glass while increasing the temperature coefficient of the relative refractive index. Therefore, the BaO component content is preferably greater than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the BaO content to 15.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the BaO content is preferably limited to 15.0% or less, more preferably 13.0% or less, even more preferably 11.0% or less, and most preferably 9.0% or less.

[0027] The Li2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the lower limit of the Li2O component content is preferably more than 0%, more preferably 0.1% or more, even more preferably 0.3% or more, and most preferably 0.5% or more. On the other hand, by limiting the Li2O content to 10.0% or less, devitrification of the glass due to excessive Li2O content can be suppressed. Therefore, the Li2O content is preferably limited to 10.0% or less, more preferably 8.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

[0028] The Na2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the lower limit of the Na2O component content is preferably more than 0%, more preferably 0.01% or more, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by limiting the Na2O content to 15.0% or less, devitrification of the glass due to excessive Na2O content can be suppressed. Therefore, the Na2O content is preferably limited to 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 7.0% or less, and most preferably 5.5% or less.

[0029] The K2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the K2O component content is preferably greater than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the K2O content to 15.0% or less, devitrification of the glass due to excessive K2O content can be suppressed. Therefore, the K2O content is preferably limited to 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 6.0% or less, and most preferably 5.5% or less.

[0030] The B2O3 component is an optional component that promotes stable glass formation when present in amounts greater than 0%. On the other hand, if the B2O3 component is present in excess, it can lead to devitrification of the glass and a decrease in the glass transition temperature. Therefore, the content of the B2O3 component should preferably be 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, and most preferably 1.0% or less.

[0031] The SiO2 component, when present in amounts exceeding 0%, is a glass-forming oxide component that can improve the viscosity of molten glass. On the other hand, excessive SiO2 content can lead to devitrification of the glass and a decrease in the glass transition temperature. In particular, in the present invention, the SiO2 component is more likely to cause devitrification than the B2O3 component. Therefore, the content of the SiO2 component is preferably limited to 10.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.0% or less.

[0032] The La2O3, Gd2O3, Y2O3, and Yb2O3 components are optional components that can be used to obtain a high refractive index when present in amounts greater than 0%. In particular, by limiting the content of each component, La2O3, Gd2O3, Y2O3, and Yb2O3, to 15.0% or less, the decrease in the Abbe number can be suppressed, devitrification can be reduced, and discoloration can be reduced. Therefore, the content of each component, La2O3, Gd2O3, Y2O3, and Yb2O3, is preferably 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and most preferably 5.0% or less.

[0033] The TiO2 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. If the TiO2 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the TiO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0034] The Ta2O5 component is an optional component that can increase the refractive index of the glass when present in amounts greater than 0%. Since it becomes difficult to achieve the desired refractive index when the Ta2O5 content exceeds 10.0%, the Ta2O5 content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the Ta2O5 component may be omitted.

[0035] The WO3 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. If the WO3 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the WO3 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0036] The ZrO2 component is an optional component that, when present in amounts greater than 0%, can enhance the refractive index and dispersion of the glass. If the ZrO2 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the ZrO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0037] The Nb2O5 component is an optional component that, when present in amounts greater than 0%, can enhance the refractive index and dispersion of the glass. If the Nb2O5 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the Nb2O5 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0038] The Bi2O3 component is an optional component that, when present in amounts greater than 0%, can increase the refractive index and lower the glass transition temperature. If the Bi2O3 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the Bi2O3 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0039] The TeO2 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. Since it becomes difficult to achieve the desired refractive index when the TeO2 content exceeds 10.0%, the TeO2 content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the TeO2 component may be omitted.

[0040] Component F is an optional component that, when present in amounts greater than 0%, can provide a defoaming effect while minimizing dispersion. In particular, the glass of the present invention contains large amounts of P2O5 and Al2O3 components, so bubbles tend to remain during melting. Therefore, the content of component F is preferably greater than 0%, more preferably 0.1% or more, even more preferably 0.2% or more, even more preferably 0.5% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the content of component F to 5.0% or less, the decrease in the temperature coefficient of the relative refractive index due to component F can be suppressed. Therefore, the content of component F is preferably limited to 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

[0041] The Sb2O3 component is an optional component that can degas molten glass when present in a concentration greater than 0%. In particular, in the glass of the present invention, the presence of the Sb2O3 component not only provides a degassing effect but also improves filtrates, which are platinum crystals eroded from the crucible. Fibre, like bubbles, degrades the internal quality of the glass and is a particular problem when used in optical elements for automotive and projector applications. On the other hand, by reducing the Sb2O3 content to 1.0% or less, a decrease in transmittance in the short-wavelength region of the visible light range, solarization of the glass, and a decrease in internal quality can be suppressed. Therefore, the Sb2O3 content may preferably be 1.0% or less, more preferably less than 0.7%, even more preferably 0.4% or less, and most preferably 0.3% or less.

[0042] The sulfur (hereinafter referred to as S) component is an optional component that can degas molten glass when it is present in a concentration greater than 0 ppm. It is preferable to include the S component by adding a sulfate component as a glass raw material, for example. The sulfate component is one selected from among lithium sulfate hydrate (Li2SO4·H2O), sodium sulfate (Na2SO4), potassium sulfate (K2SO4), magnesium sulfate (MgSO4), calcium sulfate hydrate (CaSO4·1 / 2H2O), strontium sulfate (SrSO4), zinc sulfate hydrate (ZnSO4·7H2O), and lanthanum sulfate hydrate (La2(SO4)3·9H2O). The content of component S is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more as the lower limit. On the other hand, by limiting the sulfur content to 300 ppm or less, alloying and discoloration that can occur when sulfur is present in excess can be prevented. Therefore, the sulfur content is preferably limited to 300 ppm or less, more preferably to 200 ppm or less, and even more preferably to 100 ppm or less.

[0043] While the degassing effect can be obtained by including the Sb2O3 component and the S component individually, they may also be included together. In particular, in the glass of the present invention, including the Sb2O3 component and / or the S component not only provides a degassing effect but also improves the knots, which are platinum crystals eroded from the crucible. Knots, like bubbles, degrade the internal quality of the glass and become a problem when used in optical elements for automotive and projector applications. When both Sb2O3 and S components are present, the content of Sb2O3 is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and most preferably 0.1% or less. On the other hand, the content of S component is preferably 1 ppm or more, more preferably 10 ppm or more, even more preferably 20 ppm or more as the lower limit, and preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less as the upper limit.

[0044] When the sum of the Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is greater than 0%, it has the effect of improving low-temperature meltability while lowering dispersion. Therefore, the sum of the Rn2O components is preferably greater than 0%, more preferably 1.0% or more, even more preferably 2.0% or more, and most preferably 2.5% or more as the lower limit. On the other hand, the sum of the Rn2O components should preferably be 15.0% or less, as excessive content can worsen the resistance to devitrification. Therefore, the sum of the Rn2O components should preferably be 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, and most preferably 9.0% or less.

[0045] Low-temperature meltability can be improved when the sum of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is greater than 0%. Therefore, the sum of the RO components is preferably greater than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, and most preferably 2.0% or more as the lower limit. On the other hand, the sum of the RO components should preferably be 20.0% or less in order to suppress the decrease in glass stability. Therefore, the sum of the RO components by mass is preferably 20.0% or less, more preferably 18.0% or less, even more preferably 15.0% or less, and most preferably 12.0% or less.

[0046] The sum of the Ln2O3 components (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is an optional component that can obtain a high refractive index if it is greater than 0%. Therefore, the sum of the Ln2O3 components is preferably 10.0% or less, more preferably 7.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.0% or less as the upper limit.

[0047] When the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is within a desired range, it is possible to reduce the specific gravity while increasing the temperature coefficient of the relative refractive index. Therefore, the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is preferably 1.00 or higher, more preferably 1.50 or higher, even more preferably 1.80 or higher, even more preferably 2.00 or higher, and most preferably 2.10 or higher as the lower limit. On the other hand, the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is preferably 7.00 or less, more preferably 6.00 or less, even more preferably 5.50 or less, even more preferably 5.00 or less, and most preferably 4.50 or less.

[0048] By keeping the mass sum Ka2O + Na2O to 10.0% or less, the temperature coefficient of the relative refractive index can be increased. Therefore, the mass sum Ka2O + Na2O is preferably 10.0% or less, more preferably 9.0% or less, and most preferably 8.0% or less.

[0049] When the mass ratio of Al2O3 / Rn2O is 0.5 or higher, the elution of the Rn2O component after vitrification can be suppressed, and the temperature coefficient of the relative refractive index can be increased. Therefore, the mass ratio of Al2O3 / Rn2O is preferably 0.5 or higher, more preferably 0.7 or higher, even more preferably 0.8 or higher, even more preferably 0.9 or higher, and most preferably 1.0 or higher as the lower limit. On the other hand, by setting the mass ratio Al2O3 / Rn2O to infinite, the deterioration of devitrification resistance due to the excessive addition of Al2O3 can be suppressed. Therefore, the mass ratio Al2O3 / Rn2O is preferably set to infinite, more preferably 10.0 or less, more preferably 7.0 or less, even more preferably 5.0 or less, and most preferably 4.0 or less as the upper limit.

[0050] When the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is within a desired range, it is possible to increase the meltability while raising the temperature coefficient of the relative refractive index. Therefore, the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is preferably greater than 0, more preferably 0.01 or greater, and most preferably 0.02 or greater as the lower limit. On the other hand, the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.50 or less, even more preferably 0.30 or less, and most preferably 0.20 or less.

[0051] The Al2O3 component is necessary to improve the temperature coefficient of the relative refractive index, but depending on the ratio with the network-forming oxides SiO2, B2O3, and P2O5, it can affect the melting properties and stability of the glass. The mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably greater than 0, more preferably 0.05 or greater, even more preferably 0.08 or greater, and most preferably greater than 0.10 as the lower limit. On the other hand, the mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.5 or less, and most preferably 0.3 or less.

[0052] In the present invention, it is preferable that the following components are contained in total in the following order: 98.0% or more, 99.0% or more, 99.5% or more, and 99.8% or more. P2O5 component, SiO2 component, B2O3 component, Al2O3 component, MgO component, CaO component, SrO component, BaO component, Li2O component, Na2O component, K2O component, La2O3 component, Y2O3 component, Gd2O3 component, Yb2O3 component, TiO2 component, Nb2O5 component, WO3 component, Bi2O3 component, ZnO component, ZrO2 component, Ta2O5 component, Sb2O3 component, F component.

[0053] <Regarding the essential and optional components of the second type of glass> The P2O5 component is an essential component of the present invention as a glass-forming oxide. In particular, by including 55.0% or more of the P2O5 component, the stability of the glass can be increased while lowering the transition temperature. Therefore, the lower limit of the P2O5 component content is preferably 55.0% or more, more preferably 58.0% or more, even more preferably 60.0% or more, and most preferably 63.0% or more. On the other hand, by reducing the P2O5 content to 85.0% or less, devitrification of the glass can be reduced. Therefore, the upper limit of the P2O5 content is preferably 85.0% or less, more preferably 82.0% or less, even more preferably 80.0% or less, even more preferably 78.0% or less, and most preferably 75.0% or less.

[0054] The Al2O3 component is an essential component of the present invention that increases the temperature coefficient of the relative refractive index. Therefore, the content of the Al2O3 component is preferably 3.0% or more, more preferably 4.0% or more, even more preferably 4.5% or more, even more preferably 5.0% or more, and most preferably 5.5% or more as the lower limit. On the other hand, by limiting the Al2O3 content to 30.0% or less, the deterioration of devitrification resistance and the rise in the transition temperature due to excessive content can be suppressed. Therefore, the Al2O3 content is preferably limited to 30.0% or less, more preferably to 25.0% or less, even more preferably to 20.0% or less, and most preferably to 18.0% or less.

[0055] The MgO component is an essential component of this invention for increasing the temperature coefficient of the relative refractive index. Among the RO components described later, the MgO component has the greatest effect in increasing the temperature coefficient of the relative refractive index, and can suppress the decrease in the relative refractive index even when the ZnO component content is low. Therefore, the MgO content is preferably greater than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, and most preferably 1.2% or more as the lower limit. On the other hand, by limiting the MgO content to 10.0% or less, the decrease in devitrification resistance due to excessive MgO content can be suppressed. Therefore, the MgO content is preferably limited to 10.0% or less, more preferably 8.0% or less, even more preferably 7.0% or less, and most preferably 6.0% or less.

[0056] The ZnO component is an optional component of the present invention that, when present in amounts exceeding 0%, can increase the temperature coefficient of the relative refractive index and the moltenness. Therefore, the lower limit of the ZnO component content is preferably more than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 2.0% or more, and most preferably 3.0% or more. On the other hand, by keeping the ZnO content below 6.0%, the increase in dispersion and decrease in devitrification resistance due to excessive content can be suppressed. Therefore, the ZnO content is preferably limited to less than 6.0%, more preferably 5.5% or less, even more preferably 5.0% or less, and most preferably 4.5% or less.

[0057] The CaO component is an optional component of the present invention that, when present in amounts exceeding 0%, improves low-temperature meltability while increasing the temperature coefficient of the relative refractive index. Therefore, the lower limit of the CaO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by limiting the CaO content to 10.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the CaO content is preferably limited to 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, even more preferably 4.0% or less, and most preferably 3.0% or less.

[0058] The SrO component is an optional component of the present invention that, when present in amounts exceeding 0%, improves low-temperature meltability while increasing the temperature coefficient of the relative refractive index. Therefore, the SrO component content is preferably more than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the SrO content to 10.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the SrO content is preferably limited to 10.0% or less, more preferably 9.0% or less, even more preferably 7.0% or less, even more preferably 4.0% or less, and most preferably 2.0% or less.

[0059] The BaO component is an optional component of the present invention that, when present in amounts exceeding 0%, enhances the stability of the glass while increasing the temperature coefficient of the relative refractive index. Therefore, the BaO component content is preferably greater than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the BaO content to 15.0% or less, increases in refractive index and dispersion can be suppressed. Therefore, the BaO content is preferably limited to 15.0% or less, more preferably 13.0% or less, even more preferably 11.0% or less, and most preferably 9.0% or less.

[0060] The Li2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the lower limit of the Li2O component content is preferably more than 0%, more preferably 0.1% or more, even more preferably 0.3% or more, and most preferably 0.5% or more. On the other hand, by limiting the Li2O content to 10.0% or less, devitrification of the glass due to excessive Li2O content can be suppressed. Therefore, the Li2O content is preferably limited to 10.0% or less, more preferably 8.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

[0061] The Na2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the lower limit of the Na2O component content is preferably more than 0%, more preferably 0.01% or more, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more. On the other hand, by limiting the Na2O content to 15.0% or less, devitrification of the glass due to excessive Na2O content can be suppressed. Therefore, the Na2O content is preferably limited to 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 7.0% or less, and most preferably 5.5% or less.

[0062] The K2O component is an optional component that improves low-temperature meltability when present in amounts exceeding 0%. Therefore, the K2O component content is preferably greater than 0%, more preferably 0.3% or more, even more preferably 0.5% or more, even more preferably 0.8% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the K2O content to 15.0% or less, devitrification of the glass due to excessive K2O content can be suppressed. Therefore, the K2O content is preferably limited to 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, even more preferably 8.0% or less, even more preferably 6.0% or less, and most preferably 5.5% or less.

[0063] The B2O3 component is an optional component that promotes stable glass formation when present in amounts greater than 0%. On the other hand, excessive amounts of the B2O3 component can lead to devitrification of the glass and a decrease in the transition temperature. Therefore, the content of the B2O3 component should preferably be 10.0% or less, more preferably 7.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, and most preferably 1.0% or less.

[0064] The SiO2 component, when present in amounts exceeding 0%, is a glass-forming oxide component that can improve the viscosity of molten glass. On the other hand, excessive SiO2 content can lead to devitrification of the glass and a decrease in the transition temperature. In particular, in the present invention, SiO2 is more likely to cause devitrification than B2O3. Therefore, the content of SiO2 is preferably limited to 10.0% or less, more preferably 7.0% or less, even more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.0% or less.

[0065] The La2O3, Gd2O3, Y2O3, and Yb2O3 components are optional components that can be used to obtain a high refractive index when present in amounts greater than 0%. In particular, by limiting the content of each component, La2O3, Gd2O3, Y2O3, and Yb2O3, to 15.0% or less, the decrease in the Abbe number can be suppressed, devitrification can be reduced, and discoloration can be reduced. Therefore, the content of each component, La2O3, Gd2O3, Y2O3, and Yb2O3, is preferably 15.0% or less, more preferably 10.0% or less, even more preferably 8.0% or less, and most preferably 5.0% or less.

[0066] The TiO2 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. If the TiO2 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the TiO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0067] The Ta2O5 component is an optional component that can increase the refractive index of the glass when present in amounts greater than 0%. Since it becomes difficult to achieve the desired refractive index when the Ta2O5 content exceeds 10.0%, the Ta2O5 content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the Ta2O5 component may be omitted.

[0068] The WO3 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. If the WO3 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the WO3 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0069] The ZrO2 component is an optional component that, when present in amounts greater than 0%, can enhance the refractive index and dispersion of the glass. If the ZrO2 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the ZrO2 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0070] The Nb2O5 component is an optional component that, when present in amounts greater than 0%, can enhance the refractive index and dispersion of the glass. If the Nb2O5 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index and Abbe number. Therefore, the Nb2O5 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0071] The Bi2O3 component is an optional component that, when present in amounts greater than 0%, can increase the refractive index and lower the glass transition temperature. If the Bi2O3 component content exceeds 10.0%, it becomes difficult to achieve the desired refractive index. Therefore, the Bi2O3 component content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%.

[0072] The TeO2 component is an optional component that can increase the refractive index of the glass when it is present in amounts greater than 0%. Since it becomes difficult to achieve the desired refractive index when the TeO2 content exceeds 10.0%, the TeO2 content is preferably 10.0% or less, more preferably 5.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably less than 1.0%. From the viewpoint of reducing material costs, the TeO2 component may be omitted.

[0073] Component F is an optional component that, when present in amounts greater than 0%, can provide a defoaming effect while minimizing dispersion. In particular, the glass of the present invention contains large amounts of P2O5 and Al2O3 components, so bubbles tend to remain during melting. Therefore, the content of component F is preferably greater than 0%, more preferably 0.1% or more, even more preferably 0.2% or more, even more preferably 0.5% or more, and most preferably 1.0% or more as the lower limit. On the other hand, by limiting the content of component F to 5.0% or less, the decrease in the temperature coefficient of the relative refractive index due to component F can be suppressed. Therefore, the content of component F is preferably limited to 5.0% or less, more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.5% or less.

[0074] The Sb2O3 component is an optional component that can degas molten glass when present in a concentration greater than 0%. In particular, in the glass of the present invention, the presence of the Sb2O3 component not only provides a degassing effect but also improves filtrates, which are platinum crystals eroded from the crucible. Fibre, like bubbles, degrades the internal quality of the glass and is a particular problem when used in optical elements for automotive and projector applications. On the other hand, by reducing the Sb2O3 content to 1.0% or less, a decrease in transmittance in the short-wavelength region of the visible light range, solarization of the glass, and a decrease in internal quality can be suppressed. Therefore, the Sb2O3 content may preferably be 1.0% or less, more preferably less than 0.7%, even more preferably 0.4% or less, and most preferably 0.3% or less.

[0075] Sulfur (hereinafter referred to as S) is an optional component that, when present in amounts exceeding 0%, can degas molten glass. It is preferable to include the S component by adding a sulfate component as a glass raw material, for example. The sulfate component is one selected from among lithium sulfate hydrate (Li2SO4·H2O), sodium sulfate (Na2SO4), potassium sulfate (K2SO4), magnesium sulfate (MgSO4), calcium sulfate hydrate (CaSO4·1 / 2H2O), strontium sulfate (SrSO4), zinc sulfate hydrate (ZnSO4·7H2O), and lanthanum sulfate hydrate (La2(SO4)3·9H2O). The content of component S is preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 20 ppm or more as the lower limit. On the other hand, by limiting the sulfur content to 300 ppm or less, alloying and discoloration that can occur when sulfur is present in excess can be prevented. Therefore, the sulfur content is preferably limited to 300 ppm or less, more preferably to 200 ppm or less, and even more preferably to 100 ppm or less.

[0076] While the degassing effect can be obtained by including the Sb2O3 component and the S component individually, they may also be included together. In particular, in the glass of the present invention, including the Sb2O3 component and / or the S component not only provides a degassing effect but also improves the knots, which are platinum crystals eroded from the crucible. Knots, like bubbles, degrade the internal quality of the glass and become a problem when used in optical elements for automotive and projector applications. When both Sb2O3 and S components are present, the content of Sb2O3 is preferably 0.5% or less, more preferably 0.3% or less, even more preferably 0.2% or less, and most preferably 0.1% or less. On the other hand, the content of S component is preferably 1 ppm or more, more preferably 10 ppm or more, even more preferably 20 ppm or more as the lower limit, and preferably 300 ppm or less, more preferably 200 ppm or less, and even more preferably 100 ppm or less as the upper limit.

[0077] When the sum of the Rn2O components (wherein Rn is one or more selected from the group consisting of Li, Na, and K) is greater than 0%, it has the effect of improving low-temperature meltability while lowering dispersion. Therefore, the sum of the Rn2O components is preferably greater than 0%, more preferably 1.0% or more, even more preferably 2.0% or more, and most preferably 2.5% or more as the lower limit. On the other hand, the sum of the Rn2O components is preferably 15.0% or less, as excessive content can worsen the resistance to devitrification. Therefore, the sum of the Rn2O components is preferably 15.0% or less, more preferably 12.0% or less, even more preferably 10.0% or less, and most preferably 8.0% or less.

[0078] Low-temperature meltability can be improved when the sum of the RO components (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is greater than 0%. Therefore, the sum of the RO components is preferably greater than 0%, more preferably 0.5% or more, even more preferably 1.0% or more, even more preferably 1.5% or more, and most preferably 2.0% or more as the lower limit. On the other hand, the sum of the RO components should preferably be 20.0% or less in order to suppress the decrease in glass stability. Therefore, the sum of the RO components by mass is preferably 20.0% or less, more preferably 18.0% or less, even more preferably 15.0% or less, and most preferably 12.0% or less.

[0079] The sum of the Ln2O3 components (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is an optional component that can obtain a high refractive index if it is greater than 0%. Therefore, the sum of the Ln2O3 components is preferably 10.0% or less, more preferably 7.0% or less, even more preferably 4.0% or less, even more preferably 3.0% or less, even more preferably 2.0% or less, and most preferably 1.0% or less as the upper limit.

[0080] In this invention, the glass transition temperature can be lowered by making the mass sum Li2O×5 + Na2O + (K2O / 2), which is obtained by adding the value of the Li2O component multiplied by 5, the Na2O component content, and the Ka2O component content halved, greater than 4.0%. Therefore, the mass sum Li2O×5 + Na2O + (K2O / 2) is preferably greater than 4.0%, more preferably 4.5% or more, even more preferably 5.0% or more, and most preferably 5.5% or more as the lower limit.

[0081] When the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is within a desired range, it is possible to reduce the specific gravity while increasing the temperature coefficient of the relative refractive index. Therefore, the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is preferably 1.00 or higher, more preferably 1.50 or higher, even more preferably 1.80 or higher, even more preferably 2.00 or higher, and most preferably 3.00 or higher as the lower limit. On the other hand, the mass ratio (P2O5+MgO) / (Al2O3+ZnO) is preferably 10.00 or less, more preferably 9.00 or less, even more preferably 8.00 or less, even more preferably 7.50 or less, and most preferably 7.00 or less.

[0082] By keeping the mass sum Ka2O + Na2O to 10.0% or less, the temperature coefficient of the relative refractive index can be increased. Therefore, the mass sum Ka2O + Na2O is preferably 10.0% or less, more preferably 9.0% or less, and most preferably 8.0% or less.

[0083] When the mass ratio of Al2O3 / Rn2O is 0.5 or higher, the elution of the Rn2O component after vitrification can be suppressed, and the temperature coefficient of the relative refractive index can be increased. Therefore, the mass ratio of Al2O3 / Rn2O is preferably 0.5 or higher, more preferably 0.7 or higher, even more preferably 1.0 or higher, even more preferably 1.2 or higher, and most preferably 1.5 or higher as the lower limit. On the other hand, by setting the mass ratio Al2O3 / Rn2O to infinite, the deterioration of devitrification resistance due to the excessive addition of Al2O3 can be suppressed. Therefore, the mass ratio Al2O3 / Rn2O is preferably set to infinite, more preferably 8.0 or less, more preferably 6.0 or less, even more preferably 4.0 or less, and most preferably 3.0 or less as the upper limit.

[0084] When the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is within a desired range, it is possible to increase the meltability while raising the temperature coefficient of the relative refractive index. Therefore, the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is preferably greater than 0, more preferably 0.01 or greater, and most preferably 0.02 or greater as the lower limit. On the other hand, the mass ratio RO / (SiO2+B2O3+P2O5+Rn2O) is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.50 or less, even more preferably 0.30 or less, and most preferably 0.20 or less.

[0085] The Al2O3 component is necessary to improve the temperature coefficient of the relative refractive index, but depending on the ratio with the network-forming oxides SiO2, B2O3, and P2O5, it can affect the melting properties and stability of the glass. The mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably greater than 0, more preferably 0.05 or greater, even more preferably 0.10 or greater, and most preferably 0.12 or greater as the lower limit. On the other hand, the mass ratio Al2O3 / (SiO2+B2O3+P2O5) is preferably 1.0 or less, more preferably 0.8 or less, even more preferably 0.5 or less, and most preferably 0.3 or less.

[0086] In the present invention, it is preferable that the following components are contained in total in the following order: 98.0% or more, 99.0% or more, 99.5% or more, and 99.8% or more. P2O5 component, SiO2 component, B2O3 component, Al2O3 component, MgO component, CaO component, SrO component, BaO component, Li2O component, Na2O component, K2O component, La2O3 component, Y2O3 component, Gd2O3 component, Yb2O3 component, TiO2 component, Nb2O5 component, WO3 component, Bi2O3 component, ZnO component, ZrO2 component, Ta2O5 component, Sb2O3 component, F component.

[0087] <Regarding ingredients that should not be included> Next, we will describe the components that should not be included in the optical glass of the present invention, and components that are undesirable to include.

[0088] Other components may be added as needed, as long as they do not impair the properties of the glass of the present invention. However, each transition metal component, such as Cu, Nd, Er, Cs, V, Cr, Mn, Fe, Co, Ni, Ag, and Mo (excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu), has the property of causing the glass to color and absorbing at specific wavelengths in the visible range, even when present in small amounts, either individually or in combination. Therefore, it is preferable that they are substantially omitted, especially in optical glass used with wavelengths in the visible range.

[0089] In this specification, "substantially absent" preferably means having a content of less than 0.1%, and more preferably being absent except for unavoidable impurities. Here, the content of components included as unavoidable impurities may be, for example, less than 0.01% or less than 0.001%, but is not limited to these.

[0090] Furthermore, lead compounds such as PbO and arsenic compounds such as As2O3 are components with a high environmental impact, so it is desirable to omit them entirely, except in cases of unavoidable contamination.

[0091] Furthermore, the components Th, Cd, Tl, Os, Be, and Se have recently been increasingly discouraged from use as hazardous chemicals, requiring environmental measures not only in the glass manufacturing process but also in the processing and disposal of the finished product. Therefore, when environmental impact is a major concern, it is preferable to substantially omit these components.

[0092] <Physical properties> The physical properties of the optical glass of the present invention will be described. The optical glass of the present invention preferably has a low refractive index and a high Abbe number (low dispersion). In particular, the refractive index (n d The refractive index (n) is preferably 1.50000 or higher, more preferably 1.51000 or higher, and most preferably 1.52000 or higher as the lower limit. d The upper limit of the value is preferably 1.56000 or less, more preferably 1.55000 or less, and even more preferably 1.54000 or less. Furthermore, the Abbe number (ν) of the optical glass of the present invention d The lower limit of this Abbe number (ν) is preferably 60.00 or higher, more preferably 62.00 or higher, even more preferably 63.00 or higher, and most preferably 64.00 or higher. d The upper limit of the coefficient is preferably 75.00 or less, preferably 73.00 or less, more preferably 72.00 or less, and even more preferably 71.00 or less. The optical glass of the present invention having such a refractive index and Abbe number is useful in optical design. In particular, while achieving high imaging characteristics and the like, it is possible to miniaturize the optical system, thereby expanding the degree of freedom in optical design.

[0093] The optical glass of the present invention preferably has a temperature coefficient (40 to 60 °C) of relative refractive index (589.29 nm) of 0×10 -6 or more. In particular, the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) of the optical glass of the present invention is preferably 0×10 -6 or more, more preferably 0.5×10 -6 or more, still more preferably 1.0×10 -6 or more as the lower limit. Also, although the upper limit of the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) of the optical glass of the present invention is not particularly defined, it is preferably 10.0×10 -6 or less, more preferably 7.0×10 -6 or less, still more preferably 5.0×10 -6 or less, and even more preferably 4.5×10 -6 or less. The optical glass of the present invention having such a temperature coefficient (40 to 60 °C) of relative refractive index (589.29 nm) can constitute an optical system in which imaging characteristics and the like are hardly affected by temperature fluctuations, and thus can be suitably used for optical elements for in-vehicle applications and projector applications. In the present invention, there are places where the temperature coefficient (40 to 60 °C) of the relative refractive index (589.29 nm) is described as the relative refractive index.

[0094] The optical glass of the present invention preferably has a glass transition point (Tg) of 600 °C or lower. In particular, the glass transition point (Tg) of the optical glass of the present invention is preferably 600 °C or lower, more preferably 580 °C or lower, still more preferably 550 °C or lower, and most preferably 520 °C or lower as the upper limit. The optical glass of the present invention having such a glass transition point (Tg) is excellent in melting property, and thus can suppress devitrification during pressing.

[0095] The optical glass of the present invention preferably has a glass bending point (At) of 650°C or lower. In particular, the glass bending point (At) of the optical glass of the present invention is preferably 650°C or lower, more preferably 620°C or lower, even more preferably 600°C or lower, and most preferably 590°C or lower as the upper limit. The optical glass of the present invention, having such a glass bending point (At), has excellent meltability, and therefore can suppress devitrification during pressing.

[0096] The optical glass of the present invention preferably has a low specific gravity. In particular, the specific gravity of the optical glass of the present invention is preferably 3.50 or less, more preferably 3.30 or less, even more preferably 3.10 or less, and most preferably 3.00 or less. Such low-density optical glass is useful in optical design, and in particular, it allows for miniaturization of optical systems, thereby expanding the freedom of optical design.

[0097] [Manufacturing method] The optical glass of the present invention can be manufactured, for example, as follows: The above raw materials are uniformly mixed so that each component is within a predetermined content range, the resulting mixture is placed in a platinum crucible, and the glass is manufactured according to known glass manufacturing methods depending on the difficulty of melting the glass raw materials and the melting scale.

[0098] [Glass molding] The glass of the present invention can be melted and molded by known methods. The means for molding the molten glass are not limited.

[0099] [Preforms and optical elements] Glass molded bodies can be produced from the manufactured optical glass using, for example, polishing, or mold press molding methods such as reheat press molding or precision press molding. In other words, glass molded bodies can be produced by machining optical glass such as grinding and polishing, or by producing a preform for mold press molding from optical glass, then performing reheat press molding on this preform and polishing to produce a glass molded body, or by performing precision press molding on a preform produced by polishing or a preform formed by known methods such as floating molding. The means for producing glass molded bodies are not limited to these methods. [Examples]

[0100] Composition of the glass examples and comparative examples of the present invention, and refractive index (n) of these glasses. d ), Abbe number (ν d Tables 1 to 4 show the temperature coefficient (40-60°C) of the relative refractive index (589.29 nm), the transition point (Tg), the flexing point (At), and the specific gravity. Examples 1 to 7 use the first glass component, Examples 8 to 15 use the second glass component, Comparative Example A is Example 44 of WO2018 / 211861, and Comparative Example B is Example 12 of WO2007 / 049622. Note that the following examples are for illustrative purposes only and are not the only examples to which the invention is based.

[0101] In the examples of the present invention, high-purity raw materials commonly used in optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, and metaphosphate compounds, were selected as raw materials for each component. These raw materials were weighed to the proportions shown in the table for each example, and then uniformly mixed. The mixture was then placed in a quartz or platinum crucible and melted in an electric furnace at a temperature range of 1100-1400°C for 1-5 hours, depending on the difficulty of melting the glass composition. After stirring and homogenizing and removing bubbles, the temperature was lowered to 1000-1300°C, stirring and homogenizing again before being cast into a mold and slowly cooled to produce the glass.

[0102] Refractive index (n) of the glass in the example dThe values ​​were measured for the d-line (587.56 nm) of a helium lamp, in accordance with the V-block method specified in JIS B 7071-2:2018. The Abbe number (ν) was also calculated. d ) is the refractive index of the d line mentioned above and the refractive index (n) relative to the F line (486.13 nm) of the hydrogen lamp. F ), refractive index (n) for the C line (656.27 nm) C Using the value of ), the Abbe number (ν d )=[(n d -1) / (n F -n C It was calculated from the formula ).

[0103] The relative refractive index of the glass in the examples was determined by measuring the temperature coefficient of the relative refractive index at 40-60°C for light with a wavelength of 589.29 nm, in accordance with the interferometry method specified in JIS B 7072-2:2020.

[0104] The glass transition temperature (Tg) and flexing point (At) of the glass in the examples were determined from the thermal expansion curve obtained by measuring the relationship between temperature and the elongation of the sample, in accordance with the Nippon Optical Glass Manufacturers Association standard JOGIS08-2019 "Method for measuring thermal expansion of optical glass".

[0105] The specific gravity of the glass in the examples was determined based on the method for measuring density and specific gravity using the liquid weighing method as specified in JIS Z 8807:2012.

[0106] [Table 1]

[0107] [Table 2]

[0108] [Table 3]

[0109] [Table 4]

[0110] The optical glass in the embodiments of the present invention all have a relative refractive index (589.29 nm) and a temperature coefficient (40-60°C) of 0 × 10⁻¹⁰. -6 That was all.

[0111] Furthermore, all of the optical glasses in the examples had a glass transition temperature (Tg) of 600°C or lower and a glass flexing point (At) of 650°C or lower.

[0112] Furthermore, all of the optical glasses used in the examples had a specific gravity of 3.5 or less.

[0113] Furthermore, the optical glass in the examples formed a stable glass, and devitrification was less likely to occur during the glass manufacturing process.

[0114] Therefore, the optical glass of the example has a relative refractive index (589.29 nm) with a temperature coefficient (40-60°C) of 0 × 10⁻¹⁰. -6 The optical glass described above had few bubbles and a low specific gravity. From this, it can be inferred that the optical glass of the embodiment of the present invention has a high relative refractive index (589.29 nm) and a high temperature coefficient (40-60°C), and good internal quality, making it suitable for use in automotive cameras and projectors.

[0115] Furthermore, using the optical glass of the embodiment of the present invention, glass blocks were formed, and these glass blocks were ground and polished to process them into the shapes of lenses and prisms. As a result, it was possible to reliably process them into various lens and prism shapes.

[0116] Although the present invention has been described in detail above for illustrative purposes, it will be understood that these embodiments are for illustrative purposes only, and that many modifications can be made by those skilled in the art without departing from the spirit and scope of the present invention.

Claims

1. In terms of mass percentage based on oxides, P 2 O 5 The ingredients make up 66.37-72.63% Al 2 O 3 The ingredients are present in concentrations of 3.0-14.89%. ZnO content: 6.0% to 15.0% Contains, The B2O3 component is 3.0% or less. The SrO component is 3.0% or less. Cu and Nd components are not included except for unavoidable impurities. The glass transition temperature (Tg) is 509°C or lower. The temperature coefficient (40-60°C) of the relative refractive index (589.29 nm) is 0 × 10⁻⁶ -6 That concludes the description of optical glass.

2. Mass ratio Al 2 O 3 / Rn 2 The optical glass according to claim 1, wherein O is 0.5 or more (wherein Rn is one or more selected from the group consisting of Li, Na, and K).

3. Mass ratio of Al 2 O 3 / (SiO 2 + B 2 O 3 + P 2 O 5 is 0.05 or more, the optical glass according to claim 1 or 2.

4. The optical glass according to any one of claims 1 to 3, wherein the glass bending point (At) is 650°C or less.

5. An optical element made of optical glass according to any one of claims 1 to 4.

6. A preform for polishing and / or precision press molding, made of optical glass according to any one of claims 1 to 4.

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