Optical glass and optical element

Abstract

The invention provides optical glass which has excellent formability, high stability in a manufacturing process and an excellent color correction function in a wide area, and an optical element using the optical glass. In the optical glass, the refractive index (nd) at the d-line wavelength (587.6 nm) of helium is in the range of 1.45000-1.65000, in the ISO color characteristic index ISO / CCI, the blue color (B) is 0.00, the green color (G) is 0.80 or less, the red color (R) is 0.80 or less, and the S value calculated according to the formula S = E * alpha / (1-v) is in the range of 0.70 * 10 ^ 6 or more and less than 1.03 * 10 ^ 6 (Pa / DEG C). Wherein E is the Young's modulus (unit: GPa), alpha is the average linear expansion coefficient (unit: 10 ^-7 DEG C ^-1) within the temperature range of 100-300 DEG C, and v is the Poisson's ratio.

Description

Technical Field

[0001] The present disclosure relates to an optical glass and an optical element, and in particular to an optical glass having a refractive index within a relatively lower range than that of conventional glass and a color characteristic index with a low degree of color variation, the optical glass having excellent formability, high stability in the manufacturing process, and excellent color correction performance in a wide range of fields, and to an optical element using the optical glass. Background Art

[0002] In the past, when manufacturing optical elements, optical glass was used as its raw material. However, as a method for manufacturing optical elements from optical glass, conventionally known methods include, for example, a method of grinding and polishing a frit or glass block formed of optical glass to obtain an optical element shape (for example, Japanese Patent Publication No. 2001-1661 17), a method of reheating and molding a frit or glass block formed of optical glass (re-hot press molding) and grinding and polishing the obtained glass molded body (for example, Japanese Patent Publication No. 2001-19446), and a method of molding a preformed material obtained from a frit or glass block in an ultra-precision mold (precision press molding) to obtain an optical element shape (for example, Japanese Patent Publication No. 2005-281106).

[0003] In addition, as a method for manufacturing optical elements in recent years, there is also a method of manufacturing optical elements by grinding and coating glass plates formed of optical glass, and then stacking them through cutting steps, cleaning steps, grinding steps, molding steps, etc.

[0004] However, when manufacturing optical elements from optical glass through multiple processes, changes in the original properties of the optical glass occur, resulting in changes in various physical properties of the optical element. In particular, the cutting process and the molding process not only have a great influence on various physical properties of the optical element, but also easily cause cracks and chipping. For these reasons, optical glass with excellent moldability and high stability in the manufacturing process is required.

[0005] In addition, in recent years, optical components are increasingly used in wearable applications and mobile device applications such as AR (augmented reality), VR (virtual reality), and MR (mixed reality). For example, glasses with projectors, glasses-type or goggle-type displays, virtual reality and augmented reality display devices, virtual image display devices, etc. for wearable applications, as well as mobile phones and smartphones for mobile device applications.

[0006] As an example of an invention of optical glass disclosed for wearable purposes, for example, Japanese Patent Publication No. 2019-511449 discloses a high refractive index optical glass with a refractive index exceeding 1.65 at a wavelength λ=587.6nm, which can be used in virtual or augmented reality devices. In addition, Japanese Patent Publication No. 2021-102549 discloses an invention of an optical glass having a refractive index nd of 1.95 or more, the glass composition of which contains at least one selected from TiO2 and Nb2O5 and contains B2O3. In addition, Japanese Patent Publication No. 2021-31378 discloses an invention of a high refractive index optical glass having a refractive index in the range of 1.90 to 2.10, which contains SiO2: 9.0 to 11.0%, B2O3: 22.0 to 24.0%, La2O3: 18.0 to 20.0%, and TiO2: 30.0 to 31.0% in terms of molar percentage based on oxides.

[0007] These inventions are all based on the view that optical glass for wearable purposes requires a high refractive index, and provide inventions of optical glass with a high refractive index. However, in order to increase the refractive index, it is necessary to contain a high proportion of components that significantly increase the refractive index of the glass, such as TiO2 or Nb2O5, in the glass. If the glass contains a high proportion of components that significantly increase the refractive index of the glass, the vitrification will become unstable, so it is necessary to contain a high proportion of B2O3 in the glass to stabilize the vitrification. For example, in the above-mentioned Japanese Patent Gazette No. 2021-31378, 30.0-31.0% of TiO2 is contained in the molar percentage representation based on the oxide, and further 22.0-24.0% of B2O3 is contained, thereby obtaining a high refractive index optical glass with a refractive index in the range of 1.90 to 2.10.

[0008] However, depending on the structure and design freedom of optical elements used in wearable devices or mobile devices, a high refractive index is not necessarily required. Moreover, optical glass used to produce optical elements that do not require a high refractive index does not necessarily have to have a high refractive index. If the optical glass does not require a high refractive index, it is not necessary to contain a component that significantly increases the refractive index of the glass, such as TiO2 or Nb2O5, in the glass at a high ratio. As a result, it is not necessary to contain B2O3 in the glass at a high ratio in order to stabilize vitrification.

[0009] For optical glass used in the manufacture of wearable devices or mobile devices, which do not necessarily require a high refractive index, a color characteristic index with a low degree of color variation and excellent color correction performance over a wide area (wide range) are more required than the refractive index itself.

[0010] Prior art literature

[0011] Patent Literature

[0012] Patent Document 1: Japanese Patent Application Publication No. 2001-166117

[0013] Patent Document 2: Japanese Patent Application Publication No. 2001-19446

[0014] Patent Document 3: Japanese Patent Application Publication No. 2005-281106

[0015] Patent Document 4: Japanese Patent Application No. 2019-511449

[0016] Patent Document 5: Japanese Patent Application Publication No. 2021-102549

[0017] Patent Document 6: Japanese Patent Application Publication No. 2021-31378

[0018] Patent Document 7: Japanese Patent No. 4537317 Summary of the invention

[0019] Problems to be solved by the invention

[0020] The present invention is proposed in view of the above problems, and its purpose is to provide a refractive index (n d The present invention discloses an optical glass having a color characteristic index of relatively low color (color property index) but low color variation, the optical glass has excellent formability and high stability in the manufacturing process, and has excellent color correction performance in a wide range. At the same time, the present invention also provides an optical element using the optical glass.

[0021] Solutions for solving problems

[0022] In order to solve the above problems, the present invention provides an optical glass characterized in that the refractive index (nd) at the d-line wavelength (587.6 nm) of helium is in the range of 1.45000 to 1.65000, the blue (B) is 0.00, the green (G) is 0.80 or less, and the red (R) is 0.80 or less in the ISO color characteristic index ISO / CCI, and the S value calculated by the following formula (1) is in the range of 0.70×10^6 or more and less than 1.03×10^6 (Pa / °C). Wherein: E: Young's modulus (unit: GPa), α: average linear expansion coefficient in the temperature range of 100°C to 300°C (unit: 10^-7°C^-1), ν: Poisson's ratio.

[0023] S=E·α / (1-ν)……Formula (1)

[0024] The upper limit of the refractive index (nd) is preferably 1.64000.

[0025] It is preferable that the ISO color characteristic index ISO / CCI is within the range of 0.00 for blue (B), 0.70 or less for green (G), and 0.70 or less for red (R).

[0026] The S value is preferably in the range of 0.73×10^6 or more and less than 1.00×10^6 (Pa / °C).

[0027] Preferably, the total content of the TiO2 component, the Nb2O5 component, the Bi2O3 component and the WO3 component is less than 10.0% in terms of molar percentage based on oxides.

[0028] Preferably, the SiO2 component contains 30.0 to 80.0% and the B2O3 component contains 0.00 to 30.0% in molar percentage based on oxides, and the total of the SiO2 component and the B2O3 component does not exceed 100.0%.

[0029] The optical element of the present invention is composed of the above-mentioned optical glass.

[0030] The optical element also uses a transparent resin plate or a curable resin material.

[0031] The optical element is suitable for a wearable device or a mobile device.

[0032] Effects of the Invention

[0033] According to the present invention, there is provided a d ) is an optical glass with a color characteristic index that is relatively lower than that of conventional glass and has a low degree of color variation, the optical glass has excellent formability and high stability in the manufacturing process, and has superior color correction performance over a wide area. This optical glass is very suitable for wearable applications such as AR (augmented reality), VR (virtual reality), MR (mixed reality), and mobile device applications. DETAILED DESCRIPTION

[0034] The optical glass of the present invention and an optical element using the same will be described in detail below.

[0035] (A: optical glass of the present invention)

[0036] 1. Color Characteristic Index (ISO / CCI)

[0037] As described above, the optical glass of the present invention is an optical glass having a color characteristic index with a low degree of color change (low degree of color change). Specifically, when the color characteristic is expressed by the ISO color characteristic index (ISO / CCI) specified in the Japanese Industrial Standards, when converted to a flat plate with a thickness of 10 mm, the ISO color characteristic index ISO / CCI has a color characteristic within the range of 0.00 for blue (B), 0.80 or less for green (G), and 0.80 or less for red (R).

[0038] The Color Condition Index (CCI) is an index that predicts how much the color of a color photo taken with a certain lens system will change compared to the original color due to the spectral characteristics of the lens. The index is expressed as a set of numerical values, including three numerical values ​​for each of blue (B), green (G), and red (R). The ISO / CCI can be used to predict the degree of color change as a single glass material. In addition, JIS B 7097 can be used as a reference for measurement and calculation.

[0039] Generally speaking, the ISO / CCI value of optical glass indicates that the glass has good light transmittance in the short wavelength region of visible light, and when the B value of ISO / CCI is 0, its G value and R value are small. However, in order to obtain optical glass with a high refractive index, the resistance to devitrification and melting properties will decrease. Moreover, in order to improve the resistance to devitrification and melting properties, increasing the melting temperature or extending the melting time will increase the ISO / CCI G value and R value of the glass material, resulting in the disadvantage of deteriorating color balance. In addition, high refractive index glass with a refractive index (nd) of more than 1.78, for example, has poor light transmittance in the short wavelength region, so the ISO / CCI G value and R value of the glass material are large, and the color balance is poor.

[0040] However, for optical glass used in the manufacture of wearable devices or mobile devices that do not necessarily require a high refractive index, since a high refractive index is not required, not only the ISO / CCI B value of the glass material can be reduced, but also the G value and R value can be reduced, thereby ensuring good color balance and being able to manufacture optical glass with a color characteristic index with a low degree of color change. Moreover, optical elements manufactured with such optical glass with a color characteristic index with a low degree of color change can provide users with images or videos that are closer to real colors, and are therefore suitable for wearable applications such as AR, VR, and MR, as well as mobile device applications.

[0041] Therefore, the color characteristics of the optical glass of the present invention expressed by ISO / CCI in a flat plate having a thickness of 10 millimeters (mm) are: blue (B) is 0.00, and green (G) is 0.80 or less. In addition, the value of green (G) is preferably 0.70 or less, and more preferably 0.60 or less. In addition, red (R) is 0.80 or less, and this value is preferably 0.70 or less, and more preferably 0.60 or less.

[0042] 2. Mechanical properties (thermal shock resistance)

[0043] In general, the stress (σ) generated in a glass material by thermal shock can be predicted by the following equation:

[0044] σ=λ·E·α·ΔT / (1-ν)

[0045] Where λ is a constant related to the shape and thermal conductivity of the glass, E is the Young's modulus (GPa), and α is the average linear expansion coefficient in the temperature range of 100°C to 300°C (10 －7 ℃ －1 ), ΔT is the temperature difference, and ν is the Poisson's ratio.

[0046] As mentioned above, ΔT is the temperature difference and is a parameter of the manufacturing process, not a characteristic (performance) of the glass material. Therefore, the values ​​that mainly depend on the glass composition are the following three values, namely Young's modulus (E), the average linear expansion coefficient (α) in the temperature range of 100°C to 300°C, and Poisson's ratio (ν).

[0047] In order to improve the heat shock resistance of optical glass, it is particularly desirable that the value of S=E·α / (1-ν) is low. The applicant pointed out in the specification of Japanese Patent No. 4537317 that obtaining a glass material with a small Young's modulus (E) and an average linear expansion coefficient (α) is an important point in manufacturing optical glass with high heat shock resistance. The specification discloses the invention of an optical glass with high heat shock resistance, in which the value of S=E·α / (1-ν) is 1.00×10^6~1.35×10^6 (Pa·℃^-1). Such high heat shock resistance is required because in the manufacturing process of optical elements such as compression molding, even when there are drastic temperature changes such as rapid heating and cooling, high heat shock resistance of optical glass is required to avoid cracks and gaps in the process.

[0048] In recent years, wearable devices and mobile devices will generate heat rapidly during operation, so the thermal shock resistance of traditional glass cannot meet the current situation, and glass with higher thermal shock resistance is needed.

[0049] Therefore, the present invention improves the production stability and formability of the optical glass by adjusting the composition so that the S value calculated by the following formula (1) is within the range of 0.70×10^6 to 1.03×10^6 (Pa / ℃). By designing this value within this range, a suitable thermal expansion coefficient is obtained, so that the optical glass has excellent formability and is not prone to cracking or breaking during the manufacturing process. On the other hand, if this value is too large, the risk of cracking or breaking during the manufacturing process is likely to increase significantly, so the upper limit is set to 1.03×10^6 (Pa / ℃).

[0050] The optical glass of the present invention can be preferably used as a light guide plate. When the glass of the present invention is used as a light guide plate, the glasses will be bonded together for use, and the difference in average linear expansion coefficient between the bonded glasses (hereinafter referred to as substrate 1, substrate 2...substrate n) is preferably not more than ±3.0×10^-7. The difference in average linear expansion coefficient between substrates 1 to substrates n is preferably not more than ±3.0×10^-7, more preferably not more than ±2.0×10^-7, and further preferably not more than ±1.0×10^-7. When the expansion difference between substrates 1 to substrates n is small, even if the light guide plate is affected by heat, the expansion difference between the glasses can be suppressed to prevent dislocation or peeling.

[0051] S=E·α / (1-ν) Formula (1)

[0052] In formula (1), E is Young's modulus (unit: GPa), α is the average linear expansion coefficient in the temperature range of 100°C to 300°C (unit: 10^-7°C^-1), and ν is Poisson's ratio.

[0053] The S value is 0.70×10^6 or more and less than 1.03×10^6 (Pa / °C), which is lower than the S value (1.00×10^6 to 1.35×10^6 (Pa·°C^-1)) of the high heat shock resistant optical glass disclosed in Japanese Patent No. 4537317. Therefore, the optical glass of the present invention is not prone to cracking and breaking during the manufacturing process, thereby improving the production stability and formability of the optical glass.

[0054] As described above, the present invention adjusts the components so that the above-mentioned S value is within the range of 0.70×10^6 or more and less than 1.03×10^6 (Pa / ℃). The lower limit of the above-mentioned S value is preferably 0.73×10^6 (Pa / ℃) or more, more preferably 0.75×10^6 (Pa / ℃) or more, and further preferably 0.80×10^6 (Pa / ℃) or more. In addition, the upper limit of the above-mentioned S value is preferably less than 1.00×10^6 (Pa / ℃), more preferably less than 0.98×10^6 (Pa / ℃). For example, in a preferred case, the range of the above-mentioned S value is 0.73×10^6 or more and less than 1.00×10^6 (Pa / ℃).

[0055] 3. Refractive index (n d )

[0056] The lower limit of the refractive index (nd) of the optical glass of the present invention at the d-line wavelength (587.6nm) of helium is 1.45000, and the upper limit is 1.65000, that is, the range of 1.45000 to 1.65000. As mentioned above, the refractive index of the optical glass disclosed in Japanese Patent Gazette No. 2021-102549 is above 1.95, while the refractive index of the optical glass disclosed in Japanese Patent Gazette No. 2021-31378 is in the range of 1.90 to 2.10. Therefore, the refractive index (nd) value of the optical glass of the present invention is significantly lower than the refractive index (nd) value of conventional optical glass for wearable applications. This is because, as mentioned above, for optical glass used in the manufacture of wearable devices or mobile devices that do not necessarily require a high refractive index, a color characteristic index with a low degree of color change and superior color correction performance in a wide range are more required than the refractive index itself, and the present invention is also made based on the above-mentioned demand point of view.

[0057] In addition, according to the structure and design freedom of the optical element used in the optical glass of the present invention, the lower limit of the refractive index (nd) can be above 1.48000, can be above 1.50000, and can even be above 1.51000. In addition, the upper limit of the refractive index (nd) can be below 1.64000, can be below 1.63000, can even be below 1.62000, or below 1.61000.

[0058] 4. Optical uniformity

[0059] The inhomogeneity of the refractive index within the optical glass can have a significant impact on the optical properties and lead to a degradation of the characteristics of the optical element. In this regard, the optical glass of the present invention has high homogeneity and thus has an excellent refractive index distribution.

[0060] The refractive index distribution of the optical glass of the present invention is preferably within 0.00050, more preferably within 0.00030, further preferably within 0.00010, further preferably within 0.00007, and most preferably within 0.00005. The refractive index uniformity can be measured using a Fizeau interferometer, and the PV value of the refractive index fluctuation amplitude excluding the refractive index linear variation component in the refractive index variation in the measured surface can be obtained by an oil plate method or a polishing average method: ΔnPV.

[0061] 5. Abbe number

[0062] The Abbe number (inverse dispersion) is an indicator for evaluating the dispersion of a transparent body (refractive index varies with wavelength), and the larger the Abbe number, the smaller the dispersion. The Abbe number of the optical glass of the present invention is larger than that of the conventional one and has low dispersion, and its lower limit is preferably above 35.00, more preferably above 38.00, further preferably above 40.00, and most preferably above 42.00. On the other hand, the upper limit of the Abbe number is preferably below 70.00, more preferably below 68.00, further preferably below 67.00, and most preferably below 65.00.

[0063] 6. Specific gravity

[0064] The specific gravity of the optical glass of the present invention is not particularly limited, but from the viewpoint of reducing the weight of optical elements, the specific gravity is preferably 4.50 or less, more preferably 4.00 or less, further preferably 3.80 or less, and most preferably 3.50 or less.

[0065] 7. Ratio of specific gravity to refractive index

[0066] In the optical glass of the present invention, the specific gravity d and the refractive index n d The ratio of d / n is preferably d <2.1, more preferably d / n d <2.0, more preferably d / n d <1.9. Glass materials that meet these requirements are advantageous as glass materials for optical elements of the present invention, such as smartphone lenses and periscope camera prisms. For example, there are two ways to reduce the weight of a prism: one is to use glass with a higher refractive index to reduce the volume of the prism, and the other is to use glass with a lighter specific gravity. The present invention adopts the latter method. In this case, d / n d The preferred range of is less than 2.1, more preferably less than 2.0, further preferably less than 1.9, and most preferably less than 1.85.

[0067] 8. Composition

[0068] The composition of the optical glass of the present invention is described below. Unless otherwise specified, the content of each component below is expressed in molar percentage (mol%). In addition, in this specification, "substantially free of" means that it is not mixed as a raw material component, that is, it is not intentionally contained, but does not exclude the situation of being mixed as an impurity.

[0069] In addition, as described later, in the optical glass of the present invention, the total content of TiO2, Nb2O5, Bi2O3 and WO3 components, based on the molar percentage of oxides, is less than 10.0%, and in the molar percentage of oxides, the content of SiO2 is 30.0-80.0%, and the content of B2O3 is 0.00-30.0% (but the total of SiO2 and B2O3 does not exceed 100.0%).

[0070] Here, in this specification, "oxide basis" means that under the assumption that the oxides, complex salts, metal fluorides, etc. used as raw materials for the glass components of the present invention are all decomposed and converted into oxides when melted, the total weight of the generated oxides is taken as 100 mole percent and the content of each component in the glass is expressed in this way.

[0071] SiO2 component: SiO2 component is a component that forms glass, giving glass high strength, stability and chemical durability, and improving formability, while reducing expansion rate. The preferred lower limit of the content of SiO2 component is 40% or more, more preferably 43% or more, 45% or more, 48% or more, or 50% or more. The preferred upper limit of the content of SiO2 component is 90% or less, more preferably 85% or less, 80% or less, 78% or less, or 75% or less.

[0072] Na2O component: Na2O component is a component that improves the melting property and formability of glass. On the other hand, too high a content will reduce the impact resistance. The optical glass of the present invention may be an optical glass that does not contain Na2O component (0%), but if it contains, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. The preferred upper limit of the content of Na2O component is 20% or less, more preferably 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less.

[0073] BaO component: BaO component is a component that improves the melting property of optical glass and increases the refractive index of glass. On the other hand, too high a content will reduce the impact resistance. The optical glass of the present invention can be an optical glass without BaO component (0%), but if it is contained, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. The preferred upper limit of the content of BaO component is 30% or less, more preferably 28% or less, 25% or less, or 20% or less.

[0074] B2O3 component: B2O3 component is a component that forms glass, which can improve the resistance to devitrification and formability, and can reduce the expansion rate. The optical glass of the present invention can be an optical glass that does not contain B2O3 component (0%), but if it contains B2O3 component, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, 0.8% or more, or 1.0% or more. The preferred upper limit of the content of B2O3 component is 30% or less, more preferably 25% or less, 23% or less, or 20% or less.

[0075] K2O component: K2O component is a component that improves the meltability and formability of optical glass. On the other hand, too high a content will reduce impact resistance. The optical glass of the present invention may be an optical glass that does not contain K2O component (0%), but if it contains K2O component, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. The preferred upper limit of the content of K2O component is 20% or less, more preferably 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less.

[0076] Li2O component: Li2O component is a component that improves the meltability and formability of optical glass. On the other hand, too high a content of Li2O will reduce impact resistance. The optical glass of the present invention may be an optical glass that does not contain Li2O component (0%), but if it contains it, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. The preferred upper limit of the content of Li2O component is 20% or less, more preferably 15% or less, 14% or less, 13% or less, 12% or less, 11% or less, or 10% or less.

[0077] Al2O3 component: Al2O3 component is a component that improves the impact resistance and devitrification resistance of optical glass and reduces glass expansion. In addition, Al2O3 can also inhibit glass phase separation and further improve devitrification resistance. The optical glass of the present invention can be an optical glass that does not contain Al2O3 component (0%), but if it contains, the preferred lower limit is 0% or more, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. The preferred upper limit of the content of Al2O3 component is 10% or less, more preferably 8% or less, 6% or less, or 5% or less.

[0078] TiO2 component: TiO2 component is a component that increases the refractive index of glass. On the other hand, too high a content will cause the glass to be colored. The optical glass of the present invention may be an optical glass that does not contain TiO2 component (0%), but if it contains it, the preferred lower limit is more than 0%, more preferably more than 0.1%, more than 0.5% or more than 1.0%. In addition, the content of TiO2 component preferably has an upper limit of less than 20%, more preferably less than 15%, less than 14%, less than 13%, less than 12%, less than 11% or less than 10%.

[0079] The components Nb2O5, Bi2O3, and WO3 are components that increase the refractive index of the glass. On the other hand, too high a content will cause the glass to be colored. The optical glass of the present invention may be an optical glass that does not contain Nb2O5, Bi2O3, and WO3 components (0%), but if contained, the lower limit of each component is preferably more than 0%, more preferably more than 0.1%, more than 0.5%, or more than 1.0%. In addition, the upper limit of the content of each component is preferably less than 10%, more preferably less than 8%, less than 5%, less than 3%, less than 2%, or less than 1%.

[0080] CaO component: CaO component is a component that improves the glass's meltability and refractive index. On the other hand, too high a content will reduce impact resistance. The optical glass of the present invention may be an optical glass that does not contain a CaO component (0%), but if it contains a CaO component, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. In addition, the upper limit of the content of the CaO component is preferably 30% or less, more preferably 28% or less, 25% or less, or 20% or less.

[0081] ZnO component: ZnO component is a component that improves the glass's meltability and refractive index. On the other hand, too high a content will reduce impact resistance. The optical glass of the present invention may be an optical glass that does not contain a ZnO component (0%), but if it contains it, the preferred lower limit is more than 0%, more preferably 0.1% or more, 0.5% or more, or 1.0% or more. In addition, the upper limit of the content of the ZnO component is preferably less than 10%, more preferably less than 8%, less than 5%, less than 3%, less than 2%, or less than 1%.

[0082] ZrO2 component: ZrO2 component can be added to adjust the optical constants and improve the durability of the glass. However, since it may reduce the stability of the glass, it is preferably substantially free of ZrO2 component, but if it is included, the upper limit is preferably 5.0% or less, more preferably 4.0% or less, 3.0% or less, 2.0% or less, or 1.0% or less.

[0083] F component: The F component is effective for obtaining high transmittance, and can also obtain an optical glass having a low transition temperature (Tg).

[0084] In the optical glass of the present invention, the F component is considered to exist in the form of replacing part or all of the oxygen atoms of one or more oxides of silicon or other metal elements. If the total amount of fluoride as F replacing part or all of the oxygen atoms in the oxide is too much, the volatilization amount of the fluorine component increases, and it is difficult to obtain a homogeneous glass, which may hinder stable manufacturing. In this case, it is not added. Therefore, in the present invention, the oxide reference upper limit is preferably 5.0% or less, more preferably 3.0% or less, 1.0% or less, 0.5% or less, or 0.3% or less, and the F component may be substantially absent.

[0085] Ta2O5 component: Ta2O5 component is a component that improves the refractive index and resistance to devitrification of glass. On the other hand, by limiting the content of Ta2O5 component to less than 5.0%, the usage of Ta2O5 component as a rare mineral resource can be reduced, and the glass is more easily melted at a lower temperature, thereby reducing the production cost of the glass. In addition, by the above-mentioned control amount, the devitrification of glass caused by excessive inclusion of Ta2O5 component can be reduced. Therefore, the content of Ta2O5 component is preferably less than 5.0%, more preferably less than 3.0%, further preferably less than 1.0%, and can also be 0%.

[0086] P2O5 component: The content of P2O5 component is preferably 5.0% or less, more preferably 3.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and may be 0%.

[0087] TeO2 component: The content of TeO2 component is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and may also be 0%.

[0088] Ga2O3 component: The content of Ga2O3 component is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and may also be 0%.

[0089] GeO2 component: The content of GeO2 component is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and may also be 0%.

[0090] CeO2 component: The content of CeO2 component is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, further preferably 0.5% or less, and may also be 0%.

[0091] Er2O3 component, Pr2O3 component: The content of Er2O3 component and Pr2O3 component is preferably 1.0% or less, more preferably 0.5% or less, further preferably 0.1% or less, and most preferably substantially free of them.

[0092] SnO2 component: The content of SnO2 component is preferably 2.0% or less, more preferably 1.0% or less, further preferably 0.5% or less, and may also be 0%.

[0093] Sb2O3 component: Sb2O3 component is an optional component that promotes clarification and degassing when melting glass. Controlling the content of Sb2O3 to less than 0.1% can particularly suppress the coloring of high refractive index glass. In addition, by controlling the content to less than 0.1%, the problem of excessive foaming during glass melting can be reduced, making it difficult to alloy Sb2O3 with melting equipment (especially precious metals such as Pt). Therefore, the content of Sb2O3 is preferably less than 0.1%, more preferably less than 0.08%, and further preferably less than 0.05% as the upper limit, but it can also be 0%.

[0094] In addition, the components used for clarification and degassing are not limited to the above-mentioned Sb2O3, and a clarifier, a degassing agent, or a combination thereof known in the field of glass manufacturing can be used.

[0095] C component: C component is a component that can maintain the reducing atmosphere in the platinum crucible, inhibit platinum from mixing into the glass due to oxidation, and improve the transmittance. However, if the content is too high, it will cause the cationic components in the glass to be reduced, thereby coloring the glass. Therefore, the content of C component is preferably 10.0% or less, more preferably 8.0% or less, further preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of C component is preferably more than 0%, more preferably 0.5% or more, further preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but it can also be 0%.

[0096] S component: The S component is a component that can maintain the reducing atmosphere in the platinum crucible, inhibit platinum from mixing into the glass due to oxidation, and improve the transmittance. However, if the content is too high, it will cause the cationic components in the glass to be reduced, thereby coloring the glass. Therefore, the content of the S component is preferably 10.0% or less, more preferably 8.0% or less, further preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of the S component is preferably more than 0%, more preferably 0.5% or more, further preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but it can also be 0%.

[0097] Sucrose and other organic components: Sucrose and other organic components can maintain the reducing atmosphere in the platinum crucible, inhibit platinum from mixing into the glass due to oxidation, and thus improve the light transmittance. However, if the content is too high, the cationic components in the glass will be reduced, thereby coloring the glass. Therefore, the content of sucrose and other organic components is preferably 10.0% or less, more preferably 8.0% or less, further preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of sucrose and other organic substances is preferably more than 0%, more preferably 0.5% or more, further preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but it can also be 0%.

[0098] In addition, the component for reducing the cations in the glass is not limited to the above-mentioned C component, S component and organic components such as sucrose, and a reducing agent known in the field of glass manufacturing or a combination thereof may be used.

[0099] By controlling the total content of TiO2, Nb2O5, Bi2O3 and WO3 to 10.0% or less, the refractive index can be reduced without increasing the specific gravity. Therefore, the total content of TiO2, Nb2O5, Bi2O3 and WO3 is preferably 10.0% or less, more preferably 8.0% or less, further preferably 5.0% or less, further preferably 3.0% or less, and further preferably 1.0% or less as the upper limit.

[0100] The sum (molar sum) of the contents of Ln2O3 components (wherein Ln is one or more selected from La, Y, Gd, and Yb) can increase the refractive index of the glass, but if the content is too much, the devitrification of the glass will increase. Therefore, the sum of the contents of the Ln2O3 components is preferably 5.0% or less, more preferably 4.0% or less, further preferably 3.0% or less, further preferably 2.0% or less, and further preferably 1.0% or less as the upper limit.

[0101] The sum (molar sum) of the contents of Rn2O components (in the formula, Rn is one or more selected from Li, Na, and K) is a component that can improve the solubility of the glass, but if the content is too much, the resistance to devitrification during processing decreases. By improving the solubility of the glass, glass with good production performance can be obtained. Therefore, the sum of the contents of Rn2O components is preferably 20.0% or less, more preferably 18.0% or less, and further preferably 16.0% or less as the upper limit. On the other hand, the sum of the contents of Rn2O components is preferably more than 0%, more preferably 0.1% or more, further preferably 0.2% or more, further preferably 0.3% or more, and further preferably 0.4% or more as the lower limit.

[0102] The sum (molar sum) of the contents of RO components (in the formula, R is one or more selected from Mg, Ca, Sr, and Ba) is a component that can improve the stability of the glass, but if the content is too high, it will lead to a decrease in the refractive index. Therefore, the sum of the contents of RO components is preferably 30.0% or less, more preferably 28.0% or less, further preferably 26.0% or less, and further preferably 25.0% or less as the upper limit. On the other hand, the sum of the contents of RO components is preferably more than 0%, more preferably 0.1% or more, further preferably 0.3% or more, further preferably 0.4% or more, and further preferably 0.5% or more as the lower limit.

[0103] By setting the total content of the Rn2O component and the RO component (molar sum Rn2O+RO) to 10.0% or more, a glass with high melting point and stability can be obtained. Therefore, the molar sum Rn2O+RO is preferably 10.0% or more, more preferably 12.0% or more, further preferably 13.0% or more, further preferably 14.0% or more, and further preferably 15.0% or more as the lower limit. On the other hand, by setting the molar sum Rn2O+RO to 40.0% or less, an excessive decrease in the refractive index can be suppressed. Therefore, the molar sum Rn2O+RO is preferably 40.0% or less, more preferably 38.0% or less, further preferably 35.0% or less, further preferably 33.0% or less, and further preferably 30.0% or less as the upper limit.

[0104] Chemical durability can be improved by setting the molar ratio (SiO2+B2O3+Al2O3) / (Rn2O+RO) of the total molar content of SiO2, B2O3 and Al2O3 relative to the total molar content of Rn2O and RO to 1.00 or more. Therefore, the molar ratio (SiO2+B2O3+Al2O3) / (Rn2O+RO) is preferably 1.00 or more, more preferably 1.30 or more, further preferably 1.50 or more, further preferably 1.80 or more, and further preferably 2.00 or more as the lower limit. On the other hand, the meltability can be maintained by setting the molar ratio (SiO2+B2O3+Al2O3) / (Rn2O+RO) to 7.00 or less. Therefore, the molar ratio (SiO2+B2O3+Al2O3) / (Rn2O+RO) is preferably 7.00 or less, more preferably 6.80 or less, further preferably 6.50 or less, further preferably 6.30 or less, and further preferably 6.00 or less as the upper limit.

[0105] <Ingredients that should not be contained>

[0106] Next, components that should not be contained in the optical glass of the present invention and components that are not preferably contained will be described.

[0107] Other components may be added as needed within a range that does not impair the characteristics (properties) of the glass of the present invention. However, each transition metal component other than Ti, Zr, Nb, W, La, Gd, Y, Yb and Lu, such as Nd, V, Cr, Mn, Fe, Co, Ni, Cu, Ag and Mo, will color the glass and have the property of absorbing specific wavelengths in the visible light range even if a small amount of these substances is contained alone or in combination, so it is best not to substantially contain these components in optical glasses using visible light wavelengths.

[0108] In addition, lead compounds such as PbO and arsenic compounds such as As2O3 should be substantially avoided due to their high environmental load, that is, these components should not be contained at all except for unavoidable mixing.

[0109] In addition, in recent years, since Th, Cd, Tl, Os, Be and Se are harmful chemical substances, their use is being restricted, and environmental measures are required not only in the glass manufacturing process, but also in the processing process and post-product handling. Therefore, if environmental impact is important, it is preferred that these components are not substantially contained.

[0110] The optical glass of the present invention, in one form, has a total content of TiO2, Nb2O5, Bi2O3 and WO3 not exceeding 10.0% calculated as a molar percentage on an oxide basis.

[0111] In addition, the optical glass of the present invention, in another form, contains 30.0-80.0% SiO2 and 0.00-30.0% B2O3 in terms of oxide-based molar percentage, but the total of SiO2 and B2O3 does not exceed 100.0%.

[0112] 9. Manufacturing method

[0113] The optical glass of the present invention can be manufactured, for example, by the following method: that is, after the above raw materials are uniformly mixed according to the content of each component within a predetermined range, the mixture is placed in a platinum crucible, and melted in an electric furnace at a temperature range of 1100 to 1500° C. for 2 to 5 hours according to the melting difficulty of the glass raw materials, and stirred and homogenized, and then cooled to an appropriate temperature, poured into a mold and slowly cooled to form. In particular, from the viewpoint of reducing deformation, the optical glass of the present invention is preferably manufactured by reducing the layer speed in the forming process. Specifically, it is preferably 400 mm / min, more preferably 300 mm / min, and further preferably 220 mm / min.

[0114] The above-mentioned optical glass provides an optical glass having a color characteristic index with a lower refractive index (nd) than conventional glass and a low degree of color variation, and an optical glass having excellent production stability and formability and excellent color correction function in a wide area.

[0115] (B: Optical element composed of the optical glass of the present invention)

[0116] The optical glass of the present invention is suitable for optical elements that do not require a high refractive index, and is particularly suitable for wearable devices such as AR, VR, and MR, as well as mobile device applications. For example, it is suitable for wearable devices such as glasses with projectors, glasses-type or goggle-type displays, virtual reality and augmented reality display devices, virtual display devices, and mobile devices such as mobile phones and smart phones. These optical elements may be used together with a transparent resin plate or a curable resin material.

[0117] The compositions of the optical glasses of Examples 1 to 9 are shown in Table 1, and the physical property data are shown in Table 2.

[0118] The glasses in the embodiments of the present invention all adopt high-purity raw materials commonly used in ordinary optical glass, such as oxides, hydroxides, carbonates, nitrates, fluorides, metaphosphates, etc. corresponding to the raw materials of each component, and are weighed and evenly mixed according to the composition ratios of Examples 1 to 9 shown in Table 1, and then put into a platinum crucible. Depending on the melting difficulty of the glass composition, they are melted in an electric furnace at a temperature range of 1000 to 1500° C. for 2 to 4 hours, and then after stirring and homogenizing, they are poured into a mold for casting, and slowly cooled to produce glass.

[0119] The refractive index (nd) and Abbe number (νd) of the glasses of Examples 1 to 9 were measured according to the V-block method specified in JIS B7071-2:2018. The refractive index (nd) is expressed as a measured value for the d-line (587.56nm) of a helium lamp. The Abbe number (νd) is calculated by the formula Abbe number (νd) = [(nd-1) / (nF-nC)] using the refractive index (nd) for the d-line of a helium lamp, the refractive index (nF) for the F-line (486.13nm) of a hydrogen lamp, and the refractive index (nC) for the C-line (656.27nm). These data of the refractive index (nd) and the Abbe number (νd) were obtained by measuring the glasses obtained under the condition of a slow cooling rate of -25°C / hr.

[0120] The ISO color characteristic index (ISO / CCI) of the example glass was measured with reference to JIS B7097 (Photographic color characteristics expressed by the ISO color characteristic index (ISO / CCI)). When the B (blue) value was set to 0, the G value (green) and the R value (red) were calculated to two decimal places.

[0121] Regarding the measurement of the Young's modulus and Poisson's ratio of the example glass, the Young's modulus (E), shear modulus (G), and Poisson's ratio (ν) were measured by an ultrasonic pulse method using a sample of 100×10×10 mm.

[0122] The average linear expansion coefficient (α) of the example glass was measured in the range of -30 to 70°C and 100 to 300°C in accordance with Japan Optical Glass Industry Association Standard JOGIS 16-2019 “Method for measuring the average linear expansion coefficient of optical glass near room temperature”.

[0123] The specific gravity of the glass in the examples was measured according to the method for measuring density and specific gravity by the floating body method in liquid described in JIS Z 8807:2019.

[0124] Table 2 summarizes the physical property data of the optical glasses of Examples 1 to 9 obtained by the above method.

[0125] Table 1

[0126]

Table 1

[0127]

[0128] Table 2

[0129]

Table 2

[0130]

[0131] As described above, in the optical glass for manufacturing wearable devices and mobile devices that do not necessarily require a high refractive index, since a high refractive index is not required, the optical glass of the present invention can reduce the B value, G value and R value of ISO / CCI, thereby ensuring good color balance and having a color characteristic index with a low degree of color variation. Optical elements manufactured using optical glass having such a color characteristic index with a low degree of color variation can provide users with images or videos that are closer to actual colors, and are therefore very suitable for wearable applications such as AR, VR, and MR, as well as mobile device applications.

[0132] (Industrial Application Possibility)

[0133] The present invention provides an optical glass with a relatively low refractive index (nd) and a color characteristic index with a low degree of color variation, which has production stability, formability, and color correction advantages in a wide range of fields. This optical glass is very suitable for wearable applications such as AR, VR, MR, and mobile device applications.

Claims

1. An optical glass, characterized in that: The refractive index (n) at the d-line wavelength (587.6 nm) of helium d ) is in the range of 1.45000 to 1.65000, The ISO color characteristic index ISO / CCI ranges from 0.00 for blue (B), 0.80 or less for green (G), and 0.80 or less for red (R). The S value calculated by the following formula (1) is in the range of 0.70×10^6 or more and less than 1.03×10^6 (Pa / ℃). S=E·α / (1-ν)……Formula (1) Where: E: Young's modulus (unit: GPa), α: average linear expansion coefficient in the temperature range of 100°C to 300°C (unit: 10^-7°C^-1), ν: Poisson's ratio.

2. The optical glass according to claim 1, wherein: The refractive index (n d ) has an upper limit of 1.64000.

3. The optical glass according to claim 1, wherein: The range of the ISO color characteristic index ISO / CCI is that blue (B) is 0.00, green (G) is 0.70 or less, and red (R) is 0.70 or less.

4. The optical glass according to claim 1, wherein: The S value is in the range of 0.73×10^6 or more and less than 1.00×10^6 (Pa / °C).

5. The optical glass according to claim 1, wherein: The total content of the TiO2 component, the Nb2O5 component, the Bi2O3 component and the WO3 component is less than 10.0% in molar percentage based on oxides.

6. The optical glass according to claim 1, wherein: In terms of molar percentage based on oxides, it contains 30.0 to 80.0% SiO2 and 0.00 to 30.0% B2O3. Furthermore, the total amount of the SiO2 component and the B2O3 component does not exceed 100.0%.

7. An optical element, characterized in that: The optical element is composed of the optical glass according to any one of claims 1 to 6.

8. The optical element according to claim 7, wherein: The optical element also uses a transparent resin plate or a curable resin material.

9. The optical element according to claim 7, wherein: The optical element is suitable for a wearable device or a mobile device.

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