Optical glass and optical element

Abstract

To provide an optical glass excellent in light weight and transmittance while having a high refractive index (nd), and low in temperature dependence of a refractive index.SOLUTION: An optical glass of the present invention includes: B2O3, La2O3, TiO2, Nb2O5, and BaO as essential constituents, and has a small temperature coefficient (Δn / ΔT) of a refractive index of the optical glass by incorporating a BaO constituent. The optical glass has a refractive index (nd) to a d line of 2.08000 or higher, and the temperature coefficient (Δn / ΔT) of a relative refractive index to light (D line) of a wave length of 589.29 nm when a temperature is varied from 40°C to 60°C is 7.0[10-6 / K] or lower. The optical glass of the present invention is an optical glass having a low specific gravity and a high transmission while having a high refractive index, and in addition, is an optical glass having a low temperature dependence of a refractive index so as to be suitable for an optical element such as a wearable instrument and a mobile instrument.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to optical glass and optical elements, and particularly to optical glass suitable for wearable device applications and mobile device applications.

Background Art

[0002] Optical glass and optical elements can be used for applications such as improving the optical characteristics of cameras and imaging devices by combining lenses in different optical regions, and for applications such as being mounted in optical devices to realize various optical designs. In particular, reducing the weight of optical glass and optical elements leads to the compactification and weight reduction of the optical device body, modules, etc. For example, in a camera with a zoom function or an autofocus function, the light weight of the optical element enables smooth transmission of power between the actuator and the lens, thereby enhancing performance.

[0003] In recent years, with the explosive spread of wearable devices and mobile devices, research and development of optical glass suitable for these devices have been underway. For example, glasses-type devices called AR / MR glasses that support the display of augmented reality (AR) and mixed reality (MR) have attracted attention, and the market for these AR / MR glasses has been expanding as the next-generation devices following smartphones.

[0004] In such technical fields related to wearable devices, for the purpose of providing users with an immersive visual experience, new glass compositions of high refractive index optical glass that ensure a larger field of view (FOV) and enable the formation of large and clear images have been proposed. For example, Patent Document 1 (CN102745894) discloses La-based high refractive index glass, Patent Document 2 (Japanese Patent No. 4262256) discloses P-Nb-based high refractive index glass, and Patent Document 3 (Japanese Unexamined Patent Application Publication No. 2020-19710) discloses an invention of Bi-based high refractive index glass.

[0005] Thus, for optical glasses used in wearable devices and mobile devices, weight reduction (low specific gravity) and a high refractive index are required to enable a lighter and more sophisticated device design, and optical transparency such as a high transmittance for light in the blue wavelength range is also required. That is, optical glasses for wearable devices and mobile devices are required to have a higher refractive index, a lower specific gravity, and a higher transmittance.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] However, physical properties such as low specific gravity and high transmittance are in a trade-off relationship with a high refractive index. Under this trade-off relationship, how to obtain an optical glass with a higher refractive index, a lower specific gravity, and a higher transmittance becomes an issue in development.

[0008] For example, in the production of glass, as the content of components that increase the refractive index is increased to increase the refractive index, the specific gravity tends to increase. The glasses disclosed in Patent Document 1 and Patent Document 2 described above contain a large amount of components with a large specific gravity such as rare earth components and Bi 2 O 3 components. Therefore, while the refractive index can be increased, the specific gravity increases, which is a problem from the perspective of weight reduction of optical glasses.

[0009] Also, in order to reduce the material cost of optical glasses, the raw material cost of optical glasses is preferably as inexpensive as possible. However, the glass described in Patent Document 3 uses Nb, which is an expensive raw material 2O 5 Since it contains a large amount of [O], it is difficult to say that it fully meets such requirements.

[0010] Furthermore, hitherto, the temperature dependence of the refractive index of optical glass for wearable device applications has hardly been noticed. However, in the future, as wearable devices become more widespread, it is expected that their usage environments will become more diverse. Also, in addition to wearable device applications, it is expected that optical glass suitable for devices used in various temperature environments will be desired. In view of such circumstances, it is expected that a low temperature dependence of the refractive index of optical glass will also be an important factor so that the original device characteristics can be ensured regardless of the temperature in the usage environment.

[0011] The present invention has been made in view of the above problems, and an object thereof is to provide an optical glass that has a high refractive index, a low specific gravity, a high transmittance, and in addition, a low temperature dependence of the refractive index.

Means for Solving the Problems

[0012] As a result of intensive experimental research to solve the above problems, the inventors have completed an invention of an optical glass that has a high refractive index, a low specific gravity, a high transmittance, and in addition, a low temperature dependence of the refractive index. Specifically, the present invention provides the following.

[0013] (1) B 2 O 3 , La 2 O 3 , TiO 2 , Nb 2 O 5 , and BaO as essential components, and the refractive index (n d ) of the d-line is 2.08000 or more, and the temperature coefficient of the relative refractive index (Δn / ΔT) when the temperature is changed from 40°C to 60°C for light of wavelength 589.29 nm (D-line) is 7.0 [10 -6 / K] or less. An optical glass characterized by this.

[0014] (2) SiO 2 The ratio (SiO 2 / RO) of the mass % based on oxides of the SiO component and the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is 10.0 or less. The optical glass according to (1).

[0015] (3) TiO 2 The ratio (TiO 2 O 3 ) of the mass % based on oxides of the TiO component and the lanthanoid component (Ln 2 / Ln 2 O 3 ) is greater than 0 and 1.50 or less. The optical glass according to (1).

[0016] (4) The ratio (BaO / Ln 2 O 3 ) of the mass % based on oxides of the BaO component and the lanthanoid component (Ln 2 O 3 ) is greater than 0. The optical glass according to (1).

[0017] (5) An optical element comprising the optical glass according to any one of (1) to (4).

[0018] (6) The optical element according to (5), wherein the optical element is used in a wearable device or a mobile device.

Embodiments for Carrying Out the Invention

[0019] The optical glass of the present invention contains B 2 O 3 , La 2 O 3 , TiO 2 , Nb 2 O 5 , and BaO as essential components, and the refractive index (n d ) of the d-line is 2.08000 or more, and the temperature coefficient of the relative refractive index (Δn / ΔT) when the temperature is changed from 40 °C to 60 °C for light with a wavelength of 589.29 nm (D-line) is 7.0 [10 -6 / K] is as follows. According to the present invention, there is provided an optical glass which has a high refractive index, a low specific gravity, a high transmittance, and in addition, a low temperature dependence of the refractive index.

[0020] Hereinafter, embodiments of the optical glass of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention. Note that, for parts where the description is repetitive, the description may be omitted as appropriate, but it does not limit the gist of the invention.

[0021] <Glass components> The composition ranges of the respective components constituting the optical glass of the present invention are described below. In this specification, unless otherwise specified, the content of each component is expressed as mass% with respect to the total mass of the glass in terms of oxide composition. Here, the "oxide-equivalent composition" is a composition in which, assuming that oxides, double salts, metal fluorides, etc. used as raw materials for the glass constituent components of the present invention are all decomposed into oxides during melting, the total amount of the generated oxides is 100 mass%, and each component contained in the glass is described.

[0022] [BaO component] When the BaO component is contained in an amount exceeding 0%, it is a component that can adjust the refractive index, meltability, and devitrification resistance of the glass. In addition to this, as a result of investigations, the present inventors have obtained the finding that the BaO component is also a component that can adjust the temperature coefficient (Δn / ΔT) of the refractive index of the optical glass. Specifically, it has been found that by increasing the content of the BaO component, the temperature coefficient (Δn / ΔT) of the refractive index can be decreased. Therefore, the content of the BaO component is preferably more than 0%, more preferably 3.00% or more, still more preferably 5.00% or more, even more preferably 7.00% or more, and even more preferably 8.00% or more.

[0023] On the other hand, by setting the content of the BaO component to 20.00% or less, a decrease in the refractive index can be suppressed, and devitrification due to an excessive content of this component can be reduced. Therefore, the content of the BaO component is preferably 20.00% or less, more preferably 18.00% or less, still more preferably 16.00% or less, and even more preferably 14.00% or less.

[0024] [B 2 O 3 component] B 2 O 3 The B 2 O 3 component is an oxide that can form a network by itself (a network-forming component of the glass) in the optical glass of the present invention containing a large amount of rare earth oxides, and is a component that enhances the stability of the glass. Therefore, it is an essential component that cannot be dispensed with as a glass-forming oxide. In particular, by containing more than 0% of the B 2 O 3 component, the devitrification resistance of the glass can be enhanced, and the specific gravity can be reduced. Therefore, the content of the B 2 O 3 component is preferably more than 0%, more preferably 1.00% or more, still more preferably 2.00% or more, and even more preferably 3.00% or more.

[0025] On the other hand, since the B 2 O 3 component is a component that lowers the refractive index of the optical glass, in order to obtain an optical glass with a high refractive index, it is necessary to suppress its content to a predetermined amount or less. By setting the content of the B 2 O 3 component to 15.00% or less, a decrease in the refractive index and an increase in the Abbe number can be suppressed, and a deterioration in chemical durability can be suppressed. Therefore, the content of the B 2 O 3 component is preferably 10.00% or less, more preferably 9.00% or less, and still more preferably 8.00% or less.

[0026] [La 2 O 3 component] La 2 O 3The component is an essential component that can increase the refractive index and is also a component that makes it difficult to color the glass. Therefore, La 2 O 3 The content of the component is preferably more than 0%, more preferably 10.00% or more, more preferably 15.00% or more, more preferably 20.00% or more, still more preferably more than 25.00%, and still more preferably 28.00% or more.

[0027] On the other hand, by setting the content of the La 2 O 3 component to 40.00% or less, the stability of the glass can be increased, devitrification can be reduced, and an increase in specific gravity can be suppressed. Therefore, the content of the La 2 O 3 component is preferably 40.00% or less, more preferably 38.00% or less, still more preferably 36.00% or less, and still more preferably 35.00% or less.

[0028] [TiO 2 component] The TiO 2 component is an essential component that can increase the refractive index of the optical glass, reduce the specific gravity, and improve the devitrification resistance. Therefore, the content of the TiO 2 component is preferably more than 0%, more preferably 10.00% or more, more preferably 15.00% or more, still more preferably 20.00% or more, still more preferably 25.00% or more, and still more preferably 27.00% or more.

[0029] On the other hand, the TiO 2 component is also a component that deteriorates the transmittance of the glass. By setting the content of the TiO 2 component to 40.00% or less, deterioration of the transmittance and devitrification due to excessive content of the TiO 2 component can be suppressed. Therefore, the content of the TiO 2 component is preferably 40.00% or less, more preferably 38.00% or less, still more preferably 36.00% or less, still more preferably 34.00% or less, and still more preferably 32.00% or less.

[0030] [Nb 2 O5 Component Nb 2 O 5 When the component is contained in an amount exceeding 0%, it is a component that can increase the refractive index of the glass and lower the liquidus temperature of the glass, thereby enhancing the devitrification resistance. Therefore, Nb 2 O 5 The content of the component is preferably more than 0%, more preferably 2.00% or more, still more preferably 4.00% or more, and even more preferably 6.00% or more.

[0031] On the other hand, by setting the content of the Nb 2 O 5 component to 18.0% or less, the material cost of the glass can be suppressed and the decrease in the Abbe number can be suppressed. Also, excessive content of the Nb 2 O 5 component can reduce devitrification and suppress the decrease in the transmittance of the glass to visible light (especially light with a wavelength of 500 nm or less). Therefore, the content of the Nb 2 O 5 component is preferably 18.00% or less, more preferably 15.00% or less, still more preferably 13.00% or less, and even more preferably 11.00% or less.

[0032] [ZrO 2 Component ZrO 2 The ZrO component can increase the refractive index and Abbe number of the glass and improve the devitrification resistance. Therefore, the content of the ZrO 2 component may be preferably more than 0%, more preferably 1.00% or more, still more preferably 2.00% or more, even more preferably 3.00% or more, and even more preferably 4.00% or more.

[0033] On the other hand, since the ZrO 2 component serves as a nucleating agent for the crystallization of the glass, if the content is high, the glass is likely to crystallize. Therefore, the content of the ZrO 2 component is preferably 10.00% or less, more preferably 9.00% or less, and still more preferably 8.00% or less.

[0034] [Gd2 O 3 Component Gd 2 O 3 The component is not only a component that can increase the refractive index and Abbe number of the glass, but also a component that can reduce the temperature coefficient of the refractive index (Δn / ΔT). However, Gd 2 O 3 The component has a high raw material price. When its content is large, the production cost increases, and the specific gravity of the glass also increases. Therefore, Gd 2 O 3 The content of the component is preferably 10.00% or less, more preferably 8.00% or less, still more preferably 7.00% or less, and even more preferably 5.00% or less. Especially from the viewpoint of reducing material costs, it is most preferable not to contain the Gd 2 O 3 component.

[0035] [SiO 2 Component SiO 2 The component can increase the viscosity of the molten glass, reduce the coloring of the glass, and enhance the devitrification resistance. On the other hand, the SiO 2 component is a component that increases the liquidus temperature and also reduces the refractive index. Therefore, by setting the content of the SiO 2 component to 15.0% or less, the decrease in the refractive index can be suppressed, and the specific gravity can be reduced. Therefore, the content of the SiO 2 component is preferably 15.00% or less, more preferably 13.00% or less, still more preferably 11.00% or less, and even more preferably 9.00% or less, and even more preferably 7.00% or less.

[0036] [Y 2 O 3 Component Y 2 O 3 When the component contains more than 0%, it is a component that can suppress the material cost of the glass and reduce the specific gravity of the glass while maintaining a high refractive index and a high Abbe number. Therefore, the content of the Y 2 O 3 component is preferably more than 0%. On the other hand, Y2 O 3 By setting the content of the component to 10.00% or less, a decrease in the refractive index of the glass can be suppressed, the stability of the glass can be enhanced, and in addition, a deterioration in the meltability of the glass raw material can be suppressed. Therefore, Y 2 O 3 The content of the component is preferably 10.00% or less, more preferably 9.00% or less, still more preferably 8.00% or less, and even more preferably 7.00% or less.

[0037] [Ta 2 O 5 component] Ta 2 O 5 When the Ta 2 O 5 component contains more than 0%, it is a component that can increase the refractive index of the glass and enhance the devitrification resistance. However, the Ta 2 O 5 component has a high raw material price, and when its content is large, the production cost increases. Also, by setting the content of the Ta 2 O 5 component to 10.00% or less, the melting temperature of the raw material becomes lower and the energy required for melting the raw material is reduced, so the manufacturing cost of the optical glass can also be reduced. Therefore, the content of the Ta 2 O 5 component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 2.50% or less. Particularly from the viewpoint of reducing the material cost, it is most preferable not to contain the Ta

[0038] [WO 3 component] WO 3 When the WO 3 component contains more than 0%, it is a component that can increase the refractive index while reducing the coloring of the glass by other high-refractive-index components, can lower the glass transition point, and can enhance the devitrification resistance. On the other hand, by setting the content of the WO 3Coloring of the glass due to components can be reduced to increase the visible light transmittance. Therefore, WO 3 The content of the component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 2.50% or less.

[0039] [ZnO component] When the ZnO component is contained in an amount exceeding 0%, it is a component that can enhance the stability of the glass and reduce coloring. It is also a component that can lower the glass transition point and improve chemical durability. On the other hand, by setting the content of the ZnO component to 15.00% or less, a decrease in the refractive index of the glass can be suppressed, and devitrification due to an excessive decrease in viscosity can be reduced. Therefore, the content of the ZnO component is preferably 15.00% or less, more preferably 12.00% or less, still more preferably 10.00% or less, even more preferably 8.00% or less, still more preferably 6.00% or less, still more preferably 3.00% or less, and even more preferably 2.50% or less.

[0040] [MgO component, CaO component, SrO component] When the MgO component, CaO component, and SrO component are contained in an amount exceeding 0%, they are components that can adjust the refractive index, fusibility, and devitrification resistance of the glass. On the other hand, they are components that lower the refractive index, and when contained in excess, they cause devitrification. Therefore, the content of the MgO component, CaO component, and SrO component is preferably 18.0% or less, more preferably 16.0% or less, still more preferably 14.0% or less, and even more preferably 12.0% or less, respectively.

[0041] [Li 2 O component, Na 2 O component, K 2 [O component] Li 2 O component, Na 2 O component, K 2 When the O component is contained in an amount exceeding 0%, it is a component that can improve the fusibility of the glass and lower the glass transition point. On the other hand, the Li 2 O component, Na 2 O component and K 2By making each of the O components 10.00% or less, it becomes difficult to lower the refractive index of the glass and devitrification of the glass can be reduced. Therefore, Li 2 O component, Na 2 O component and K 2 The content of the O component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less, respectively.

[0042] [Sb 2 O 3 component] Sb 2 O 3 When the Sb component contains more than 0%, it is a component that can defoam the molten glass. On the other hand, if the amount of Sb 2 O 3 is too large, the transmittance in the short wavelength region of the visible light region deteriorates. Therefore, the content of the Sb 2 O 3 component is preferably 1.00% or less, more preferably 0.50% or less, and still more preferably 0.30% or less.

[0043] Note that the components for clarifying and defoaming the glass are not limited to the above-mentioned Sb 2 O 3 component, and known fining agents, defoaming agents or combinations thereof in the field of glass manufacturing can be used.

[0044] [P 2 O 5 component] P 2 O 5 When the P component contains more than 0%, it can act as a glass-forming component and can lower the liquidus temperature of the glass and enhance the devitrification resistance. On the other hand, by making the content of the P 2 O 5 component 10.00% or less, a decrease in the chemical durability of the glass, particularly the water resistance, can be suppressed. Therefore, the content of the P 2 O 5 component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less.

[0045] [GeO 2 Component GeO 2 When the component contains more than 0%, it can increase the refractive index of the glass and improve the devitrification resistance. However, GeO 2 has a high raw material price, and its production cost will increase when its content is high. Therefore, the content of the GeO 2 component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less. In particular, from the perspective of reducing material costs, the GeO 2 component may not be contained.

[0046] [Al 2 O 3 Component and Ga 2 O 3 Component Al 2 O 3 Component and Ga 2 O 3 When the component contains more than 0%, it can improve the chemical durability of the glass and improve the devitrification resistance of the glass. On the other hand, Al 2 O 3 Component and Ga 2 O 3 By setting the content of each of the components to 10.00% or less, devitrification due to excessive content can be suppressed. Therefore, the content of the Al 2 O 3 component and the Ga 2 O 3 component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less, respectively.

[0047] [Bi 2 O 3 Component Bi 2 O 3 When the component contains more than 0%, it can increase the refractive index and lower the glass transition point. On the other hand, Bi 2 O 3By setting the content of the component to 10.00% or less, an increase in specific gravity can be suppressed. Therefore, Bi 2 O 3 The content of the component is preferably 10.00% or less, more preferably 8.00% or less, still more preferably 7.00% or less, and even more preferably 6.00% or less. In particular, from the viewpoint of reducing specific gravity, Bi 2 O 3 The component may not be contained.

[0048] [TeO 2 component] TeO 2 When the TeO component is contained in an amount exceeding 0%, it is a component that can increase the refractive index and lower the glass transition point. On the other hand, TeO 2 has a problem that it can alloy with platinum when melting glass raw materials in a platinum crucible or a melting tank whose part in contact with molten glass is formed of platinum. Therefore, the content of the TeO 2 component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less.

[0049] [SnO 2 component] SnO 2 When the SnO component is contained in an amount exceeding 0%, it is a component that can reduce the oxidation of molten glass to clarify it and increase the visible light transmittance of the glass. On the other hand, by setting the content of the SnO 2 component to 3.00% or less, coloring of the glass due to reduction of molten glass and devitrification of the glass can be reduced. Also, since alloying of the SnO 2 component with melting equipment (especially noble metals such as Pt) is reduced, the long life of the melting equipment can be achieved. Therefore, the content of the SnO 2 component is preferably 3.00% or less, more preferably 2.00% or less, and still more preferably 1.00% or less.

[0050] [F component] When the F component is contained in an amount exceeding 0%, it is a component that can increase the Abbe number of the glass, lower the glass transition point, and improve the devitrification resistance. However, if the content of the F component, that is, the total amount of fluoride substituted for part or all of one or more oxides of the above-mentioned metal elements as F, exceeds 10.0%, the volatilization amount of the F component increases, making it difficult to obtain stable optical constants and homogeneous glass. Therefore, the content of the F component is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less.

[0051] [Sb 2 O 3 component] Sb 2 O 3 The component is a component that promotes clarification and defoaming when melting the glass and is an optional component. Here, by setting the content of the Sb 2 O 3 component to 0.1% or less, it is possible to suppress coloring, particularly in high refractive index glass. Also, by setting it to 0.1% or less, excessive foaming during glass melting is less likely to occur, so it is possible to make it difficult for the Sb 2 O 3 component to alloy with the melting equipment (especially precious metals such as Pt). Therefore, the content of the Sb 2 O 3 component is preferably 0.1% or less, more preferably 0.08% or less, still more preferably 0.05% or less as the upper limit, but it may be 0%.

[0052] Note that the components for clarifying and defoaming the glass are not limited to the above-mentioned Sb 2 O 3 component, and known fining agents, defoaming agents or combinations thereof in the field of glass manufacturing can be used.

[0053] [C component] Component C can keep the inside of the platinum crucible in a reducing atmosphere, suppress the mixing of platinum into the glass due to oxidation, and improve the transmittance. However, if the content is too high, the cation components in the glass will be reduced, causing the glass to become colored. Therefore, the content of Component C is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of Component C is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but 0% is also acceptable.

[0054] [Component S] Component S can keep the inside of the platinum crucible in a reducing atmosphere, suppress the mixing of platinum into the glass due to oxidation, and improve the transmittance. However, if the content is too high, the cation components in the glass will be reduced, causing the glass to become colored. Therefore, the content of Component S is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of Component S is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but 0% is also acceptable.

[0055] [Organic components such as sucrose] Organic components such as sucrose can keep the inside of the platinum crucible in a reducing atmosphere, suppress the mixing of platinum into the glass due to oxidation, and improve the transmittance. However, if the content is too high, the cation components in the glass will be reduced, causing the glass to become colored. Therefore, the content of organic components such as sucrose is preferably 10.0% or less, more preferably 8.0% or less, still more preferably 6.0% or less, and most preferably 5.0% or less as the upper limit. On the other hand, the content of organic components such as sucrose is preferably more than 0%, more preferably 0.5% or more, still more preferably 1.0% or more, and most preferably 2.0% or more as the lower limit, but 0% is also acceptable.

[0056] [Rn 2 O component] Rn 2The O component (wherein Rn is one or more selected from the group consisting of Li, Na, and K) not only enhances the stability of the glass and improves the transmittance but also reduces the temperature coefficient of refractive index (Δn / ΔT). In particular, 2 By setting the sum of the masses of the Rn 2 O components to more than 0%, the meltability during glass production can be improved, and the devitrification resistance can be enhanced. Therefore, this sum of masses is preferably more than 0%, more preferably 3.00% or more, still more preferably 5.00% or more, even more preferably 7.00% or more, and even more preferably 8.00% or more. On the other hand, 2 By setting the sum of the masses of the Rn 2 O components to 10.00% or less, it becomes difficult to lower the refractive index of the glass, and devitrification of the glass can be reduced. Therefore, 2 The sum of the masses of the Rn 2 O components is preferably 10.00% or less, more preferably 5.00% or less, still more preferably 3.00% or less, and even more preferably 1.00% or less, respectively.

[0057] [RO component] The RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) not only enhances the stability of the glass and improves the transmittance but also reduces the temperature coefficient of refractive index (Δn / ΔT). In particular, by setting the sum of the masses of the RO components to more than 0%, the meltability during glass production can be improved, and the devitrification resistance can be enhanced. Therefore, this sum of masses is preferably more than 0%, more preferably 3.00% or more, still more preferably 5.00% or more, even more preferably 7.00% or more, and even more preferably 8.00% or more.

[0058] On the other hand, the RO component not only reduces the refractive index of the glass but also tends to increase the specific gravity. Therefore, this sum of masses is preferably 20.00% or less, more preferably 18.00% or less, still more preferably 16.00% or less, even more preferably 14.00% or less, and even more preferably 13.50% or less.

[0059] [Ln 2 O 3 component] Ln 2 O 3The component (wherein Ln is one or more selected from the group consisting of La, Y, Gd, and Yb) is a component that can increase the refractive index. Therefore, Ln 2 O 3 The sum of the masses of the components is preferably more than 0%, more preferably 10.00% or more, more preferably 15.00% or more, more preferably 20.00% or more, still more preferably more than 25.00%, still more preferably 28.00% or more, and still more preferably 30.00% or more.

[0060] On the other hand, Ln 2 O 3 The component can enhance the stability of the glass, reduce devitrification, and suppress an increase in specific gravity. Therefore, the sum of the masses of this Ln 2 O 3 component is preferably 50.00% or less, more preferably 48.00% or less, still more preferably 45.00% or less, still more preferably 43.00% or less, and still more preferably 40.00% or less.

[0061] [The ratio of the mass % on an oxide basis of the [SiO 2 component to the RO component]] As described above, the SiO 2 component can increase the viscosity of the molten glass, reduce the coloring of the glass, and enhance the devitrification resistance, but it is a component that increases the liquidus temperature and also decreases the refractive index. Further, the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) not only enhances the stability of the glass and improves the transmittance but also is a component that reduces the temperature coefficient of the refractive index (Δn / ΔT).

[0062] SiO 2 The ratio of the mass % on an oxide basis of the SiO 2 component to the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, Ba, and Zn) (SiO

[0063] / RO) is preferably 10.00 or less. More preferably 5.00 or less, still more preferably 2.00 or less, still more preferably 1.00 or less, and still more preferably 0.80 or less. On the other hand, SiO2 The ratio (SiO 2 / RO) of the mass % based on oxides of the Si component and the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) is preferably more than 0. More preferably, it is 0.10 or more, still more preferably 0.15 or more, still more preferably 0.20 or more, still more preferably 0.25 or more, and still more preferably 0.30 or more.

[0064] [TiO 2 component and the Ln 2 O 3 component in terms of mass % based on oxides] As described above, the TiO 2 component is a component that can increase the refractive index of the optical glass, reduce the specific gravity, and improve the devitrification resistance, while also being a component that deteriorates the transmittance of the glass. Also, the Yb 2 O 3 component and lanthanoid components such as the Lu 2 O 3 component (Ln 2 O 3 ) are components that can stabilize the glass while increasing the refractive index when contained in a certain amount, while being components that reduce the transmittance and increase the specific gravity when the content is increased. That is, increasing the content of the Ln component can stabilize the glass while increasing the refractive index, while decreasing the content of the Ln component can decrease the specific gravity while increasing the transmittance.

[0065] TiO 2 component and the Ln 2 O 3 component in terms of mass % based on oxides (TiO 2 / Ln 2 O 3 ) is preferably more than 0, while preferably being 1.50 or less. More preferably, it is 1.00 or less, and still more preferably 0.95 or less.

[0066] On the other hand, the ratio (TiO 2 component and the Ln 2 O 3 component in terms of mass % based on oxides (TiO 2 / Ln 2 O3 ) is preferably greater than 0. More preferably 0.10 or more, still more preferably 0.20 or more, still more preferably 0.30 or more, still more preferably 0.40 or more, still more preferably 0.50 or more, and still more preferably 0.60 or more.

[0067] [Mass% ratio of BaO component to Ln 2 O 3 component based on oxide] As described above, the BaO component can adjust the refractive index, fusibility, and devitrification resistance of the glass. In addition, according to the research results of the present inventors, it is also a component that can adjust the temperature coefficient of the refractive index (Δn / ΔT) of the optical glass. However, when a certain amount of BaO component is contained, if the content of the Ln component is large, the glass becomes unstable. Therefore, the mass% ratio (BaO / Ln 2 O 3 ) is preferably greater than 0, more preferably greater than 0.15, still more preferably 0.18 or more, and still more preferably 0.20 or more. On the other hand, if the content of the BaO component is large, it causes a decrease in refractive index and devitrification. Therefore, the mass% ratio (BaO / Ln 2 O 3 ) of the Ba component and the lanthanoid component (Ln 2 O 3 ) based on oxide is preferably 2.00 or less, preferably 1.00 or less, preferably 0.80 or less, and more preferably 0.50 or less.

[0068] [B 2 O 3 component and SiO 2 component mass% ratio based on oxide] When the optical glass contains a relatively large amount of the TiO 2 component, the coloring becomes strong and the devitrification during pressing becomes high. Therefore, it is necessary to contain a certain amount of Si component. By adjusting the mass% ratio of this B 2 O 3 component and the SiO 2 component based on oxide, a stable and high-viscosity glass can be obtained, and the formability can be improved. B2 O 3 component and SiO 2 component and B 2 O 3 Sum of components (SiO 2 +B 2 O 3 )) in terms of mass % on an oxide basis, the ratio of B 2 O 3 / (SiO 2 +B 2 O 3 )) is preferably greater than 0, more preferably 0.10 or more, still more preferably 0.20 or more, still more preferably 0.30 or more, and even more preferably greater than 0.35. Also, this ratio of mass % on an oxide basis of B 2 O 3 / (SiO 2 +B 2 O 3 )) is preferably 1.00 or less, more preferably 0.90 or less, and still more preferably 0.80 or less.

[0069] [Regarding components that are preferably not contained] Next, components that are preferably not contained in the optical glass of the present invention will be described.

[0070] Each transition metal component such as V, Cr, Mn, Fe, Co, Ni, Cu, Ag, and Mo, excluding Ti, Zr, Nb, W, La, Gd, Y, Yb, and Lu, has the property that even when contained in a small amount alone or in combination, the glass is colored and absorption occurs at specific wavelengths in the visible region. Therefore, in optical glass that uses wavelengths in the visible region, it is preferably substantially free of them.

[0071] Also, lead compounds such as PbO and arsenic compounds such as As 2 O 3 etc. are components with a high environmental load, so it is desirable to be substantially free of them, that is, to contain none at all except for unavoidable contamination.

[0072] Furthermore, each component of Th, Cd, Tl, Os, Be, and Se has been showing a tendency to refrain from use as harmful chemical substances in recent years, and environmental measures are required not only in the manufacturing process of glass but also in the processing process and disposal after productization. Therefore, when emphasizing environmental impact, it is preferable not to substantially contain these substances.

[0073] <Manufacturing Method> The optical glass of the present invention is produced, for example, as follows. That is, the above raw materials are uniformly mixed so that each component is within a predetermined content range, the prepared mixture is put into a platinum crucible, 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, stirred and homogenized, then cooled to an appropriate temperature and cast into a mold, and gradually cooled to produce.

[0074] <Physical Properties> The optical glass of the present invention is an optical glass having a high refractive index, a low specific gravity, and a high transmittance, and in addition, has a low temperature dependence of the refractive index. Specifically, it has the following physical properties.

[0075] [Refractive Index] The optical glass of the present invention preferably has a high refractive index. Also, although there is no special limitation on the Abbe number (ν d ), it preferably has a high Abbe number (low dispersion). In particular, the refractive index (n d ) of the d-line of the optical glass of the present invention has a lower limit of 2.08000. This refractive index (n d ) is preferably 2.08000 or more, more preferably 2.09000 or more, still more preferably 2.10000 or more, still more preferably 2.10200 or more, still more preferably 2.10400 or more, still more preferably 2.10600 or more, still more preferably 2.10800 or more.

[0076] [Abbe Number] As described above, in the optical glass of the present invention, although there is no special limitation on the Abbe number (ν d ), it preferably has a high Abbe number (low dispersion). The Abbe number (νd ) is preferably 20.00 or more, more preferably 21.00 or more, and even more preferably 21.50 or more.

[0077] [Temperature coefficient of refractive index (Δn / ΔT)] In addition to being an optical glass having a high refractive index, a low specific gravity, and a high transmittance, the optical glass of the present invention is an optical glass having a low temperature dependence of the refractive index. When constructing an optical system in which the influence on imaging performance and the like due to temperature fluctuations is unlikely to occur, when the temperature rises, the refractive index decreases, and the optical element is composed of a glass having a negative temperature coefficient of the relative refractive index, and when the temperature rises, the refractive index increases, and the relative refractive index The combined use of an optical element composed of a glass having a positive temperature coefficient can correct the influence on imaging characteristics and the like due to temperature changes, which is preferable.

[0078] The optical glass of the present invention has a low value for the temperature coefficient of the relative refractive index (Δn / ΔT). More specifically, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably +10.0×10 -6 °C -1 , more preferably +8.0×10 -6 °C -1 , even more preferably +6.0×10 -6 °C -1 is the upper limit value, and can take a value equal to or lower (negative side) than this upper limit value.

[0079] On the other hand, the temperature coefficient of the relative refractive index of the optical glass of the present invention is preferably -1.0×10 -6 °C -1 , more preferably 0×10 -6 °C -1 , even more preferably +1.0×10 -6 °C -1 is the lower limit value, and can take a value equal to or higher (positive side) than this lower limit value.

[0080] In such glass with a low temperature coefficient of relative refractive index, the options for correcting image displacement and the like due to temperature changes can be expanded, and such correction can be made more easily. Therefore, by setting the temperature coefficient of relative refractive index within such a range, it is possible to contribute to the correction of image displacement and the like due to temperature changes.

[0081] Note that the temperature coefficient of the relative refractive index of the optical glass of the present invention is the temperature coefficient of the refractive index for light (D line) with a wavelength of 589.29 nm in air at the same temperature as the optical glass, and is the amount of change per 1 °C (°C -1 ) when the temperature is changed from 40 °C to 60 °C.

[0082] [Specific gravity] The specific gravity (g / cm 3 ) of the optical glass of the present invention is preferably 5.50 or less, more preferably 5.20 or less, still more preferably 5.00 or less, and even more preferably 4.90 or less as the upper limit from the viewpoint of contributing to the weight reduction of optical elements and optical devices.

[0083] [Relationship between specific gravity (d) and refractive index (n d )] The optical glass of the present invention satisfies the relationship between the refractive index (n d ) and the specific gravity (d) of d ≦ 1.4286 × n d + 2.0786. Glasses having a refractive index (n d ) of 2.08000 or more and a low specific gravity have conventionally been known only as those with high material costs. In contrast, the present invention satisfies the above relational expression, and thereby, by using an optical glass having a small specific gravity (d) with respect to the refractive index (n d ), it is possible to contribute to the weight reduction of optical elements and optical devices. More specifically, the relationship between the refractive index (n d ) and the specific gravity (d) in the optical glass of the present invention preferably satisfies the relationship of d ≦ 1.4286 × n d + 2.0786, more preferably satisfies the relationship of d ≦ 1.4286 × n d + 2.0286, and even more preferably satisfies the relationship of d ≦ 1.4286 × n dSatisfies the relationship of +1.9786, and more preferably d ≦ 1.4286 × n d Satisfies the relationship of +1.9286.

[0084] [Transmittance] The optical glass of the present invention is an optical glass having a high refractive index, a low specific gravity, and a high transmittance. The optical glass of the present invention has a transmittance of 60% or more with respect to visible light having a wavelength of 500 nm or less. More specifically, λ70 (nm: wavelength at which the transmittance becomes 70%) of the optical glass of the present invention is preferably 520 nm or less, more preferably 510 nm or less, still more preferably 500 nm or less, and even more preferably 495 nm or less. Further, λ5 (nm: wavelength at which the transmittance becomes 5%) of the optical glass of the present invention is preferably 400 nm or less, and even more preferably 390 nm or less.

[0085] [Preform and optical element] A glass molded body can be produced from the produced optical glass by means such as polishing, or mold press forming means such as reheat press forming or precision press forming. That is, a glass molded body can be produced by performing machining such as grinding and polishing on the optical glass, or a preform for mold press forming can be produced from the optical glass, and after performing reheat press forming on this preform, polishing is performed to produce a glass molded body, or a preform produced by polishing or a preform molded by known floating forming or the like can be precision press formed to produce a glass molded body. Note that the means for producing the glass molded body is not limited to these means.

[0086] Thus, the optical glass of the present invention is useful for various optical elements and optical designs. Among them, in particular, it is preferable to form a preform from the optical glass of the present invention and perform reheat pressing, precision pressing, etc. using this preform to produce optical elements such as lenses and prisms. As a result, since it becomes possible to form a preform with a large diameter, while increasing the size of the optical element, high-definition and high-precision imaging characteristics and projection characteristics can be realized when used in optical devices such as cameras and projectors.

[0087] In addition to being an optical glass having a high refractive index, a low specific gravity, and a high transmittance, the optical glass according to the present invention has a low temperature dependence of the refractive index, and thus is suitable for use in wearable devices or mobile devices.

Examples

[0088] The compositions of Examples (No. 1 to No. 123) of the present invention, and the refractive indices (n d ), Abbe numbers (ν d ), transmittances, specific gravities, and temperature coefficients of refractive index (Δn / ΔT) of these glasses are shown in Tables 1 to 13. Table 13 shows the compositions of Examples 1 to 123 above and the maximum values (Max) and minimum values (Min) of each characteristic. The unit of the temperature coefficient of refractive index (Δn / ΔT) shown in each table is 10 -6 °C -1 (also expressed as [10 -6 / K]). Note that Example 117 contains 0.61% by mass of Cs 2 O, and Example 118 contains 0.78% by mass of P 2 O 5 . These examples are for illustrative purposes only and are not limited to only these examples.

[0089] The glasses of the examples were all selected from high-purity raw materials such as the corresponding oxides, hydroxides, carbonates, sulfates, nitrates, fluorides, metaphosphate compounds, etc. commonly used in optical glasses as raw materials for each component, weighed to the proportions of the compositions of the respective examples shown in the table, uniformly mixed, then put into a platinum crucible, 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, stirred and homogenized, and then cast into a mold or the like and slowly cooled to produce.

[0090] The refractive index (n d ) and Abbe number (ν d ) of the glasses of the examples were measured in accordance with the V-block method specified in JIS B 7071-2:2018. Here, the refractive index (n d ) was shown as the measured value for the d-line (587.56 nm) of a helium lamp. Also, the Abbe number (ν d ) was calculated from the formula of Abbe number (ν C ) = [(n d - 1) / (n d - n F - n C )] using the value of the refractive index for the above d-line, the refractive index (nF) for the F-line (486.13 nm) of a hydrogen lamp, and the refractive index (n d ) for the C-line (656.27 nm). Also, using the measured value of n d , the relational expression of d ≦ 7.494×n

[0091] - 10.961 was calculated. 5 (wavelength at 5% transmittance) and λ 70 (wavelength at 70% transmittance) were obtained.

[0092] In addition, the specific gravity of the glass in the examples and comparative examples was measured in accordance with the Japan Optical Glass Industry Association Standard JOGIS05-2019 "Method for Measuring the Specific Gravity of Optical Glass".

[0093] The temperature coefficient (Δn / ΔT) of the relative refractive index of the glass in the examples and comparative examples was measured by the interference method among the methods described in the Japan Optical Glass Industry Association Standard JOGIS18-2019 "Method for Measuring the Temperature Coefficient of the Refractive Index of Optical Glass". The value of the temperature coefficient of the relative refractive index was measured for light with a wavelength of 589.29 nm (D line) when the temperature was changed from 40°C to 60°C.

[0094] [Table 1]

[0095] [Table 2]

[0096] [Table 3]

[0097] [Table 4]

[0098] [Table 5]

[0099] [Table 6]

[0100] [Table 7]

[0101] [Table 8]

[0102]

Table 9

[0103]

Table 10

[0104]

Table 11

[0105]

Table 12

[0106]

Table 13

[0107] Any of the examples shown in Tables 1 to 13 contains B 2 O 3 , La 2 O 3 , TiO 2 , Nb 2 O 5 , and BaO as essential components. By containing the BaO component, the temperature coefficient (Δn / ΔT) of the refractive index of the optical glass is reduced. Such an optical glass has a refractive index (n d ) of 2.08000 or more, and the temperature coefficient (Δn / ΔT) of the relative refractive index when the temperature is changed from 40 °C to 60 °C for light with a wavelength of 589.29 nm (D line) is 7.0 [10 -6 / K] or less. Such an optical glass is an optical glass having a high refractive index, low specific gravity, and high transmittance, and in addition, has a low temperature dependence of the refractive index, and is suitable for optical elements such as wearable devices and mobile devices.

[0108] As described above, all of the optical glasses according to the present invention contain B 2 O 3 , La 2 O 3 , TiO 2 , Nb 2 O 5 , and BaO as essential components, and the refractive index (n d ) of the d-line is 2.08000 or more. According to the study by the present inventors, the BaO component is not only a component that can adjust the refractive index, fusibility, and devitrification resistance of the glass, but also a component that can adjust the temperature coefficient (Δn / ΔT) of the refractive index of the optical glass. Based on the new finding that the temperature coefficient (Δn / ΔT) of the refractive index can be reduced by increasing the content of the BaO component, the BaO component is used as an essential component, and thereby, the temperature coefficient (Δn / ΔT) of the relative refractive index when the temperature is changed from 40°C to 60°C for light with a wavelength of 589.29 nm (D-line) is 7.0 [10 -6 / K] or less, and an optical glass is obtained.

[0109] As described above, it has been found that the present invention is an optical glass having a high refractive index, a low specific gravity, and a high transmittance, and in addition, having a low temperature dependence of the refractive index.

Industrial Applicability

[0110] According to the present invention, there is provided an optical glass having a high refractive index, a low specific gravity, and a high transmittance, and in addition, having a low temperature dependence of the refractive index. The optical glass according to the present invention is suitable for use in wearable devices and mobile devices.

Claims

1. B ２ O ３ , La ２ O ３ , TiO ２ , Nb ２ O ５ and BaO as essential components, and has a refractive index of d line (n ｄ ) is 2.08000 or more, and the temperature coefficient of the relative refractive index (Δn / ΔT) when the temperature is changed from 40° C. to 60° C. for light (D line) with a wavelength of 589.29 nm is 7.0 [10 －６ / K] or less.

2. SiO ２ The ratio of mass % of the oxide-based oxide of the component and the RO component (wherein R is one or more selected from the group consisting of Mg, Ca, Sr, and Ba) (SiO ２ 2. The optical glass according to claim 1, wherein R(.alpha. / RO) is 10.0 or less.

3. TiO ２ component and lanthanide component (Ln ２ O ３ ) based on oxide mass % (TiO ２ / Ln ２ O ３ 2. The optical glass according to claim 1 , wherein n is greater than 0 and is equal to or less than 1.

50.

4. BaO component and lanthanide component (Ln ２ O ３ ) based on oxide mass% ratio (BaO / Ln ２ O ３ 2. The optical glass of claim 1 , wherein n is greater than 0.

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

6. The optical element according to claim 5 , which is used in a wearable device or a mobile device.

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