Optical glass, optical element, light guide plate, and image display device

Abstract

To provide optical glass having a high refractive index and a low specific gravity.SOLUTION: An optical glass contains, on a mass basis, 1.00% or more of SiO2, 1.00% or more of B2O3, 1.00% or more of CaO, 15.00% or more of TiO2, and 10.00% or more of La2O3, wherein a total content of SiO2 and B2O3 (SiO2+B2O3) is 22.00% or less, a total content of TiO2 and Nb2O5 (TiO2+Nb2O5) is 20.00% or more, a total content of MgO, CaO, SrO, and BaO (MgO+CaO+SrO+BaO) is 18.00% or less, a mass ratio of BaO to the total content of MgO, CaO, SrO, and BaO (BaO / (MgO+CaO+SrO+BaO)) is 0.50 or less, a mass ratio of TiO2 to CaO (TiO2 / CaO) is 1.50 or more and 15.00 or less, and a mass ratio of TiO2 to the total content of TiO2 and Nb2O5 (TiO2 / (TiO2+Nb2O5)) is 0.50 or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to an optical glass, an optical element, a light guide plate, and an image display device. [Background technology]

[0002] For example, Patent Document 1 discloses an optical glass with a high refractive index. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2024-3105 Summary of the Invention [Problem to be solved by the invention]

[0004] Optical glasses with high refractive indices can correct chromatic aberration and enable compact optical systems, for example by combining a lens made of such glasses with another lens made of glasses with different dispersion properties to form a cemented lens. Therefore, such optical glasses are useful as materials for optical elements that constitute imaging optical systems and projection optical systems such as projectors.

[0005] Light guide plates, which are components of image display devices, are also made from optical glass. Optical glass with a high refractive index allows the manufacture of light guide plates with a wide viewing angle.

[0006] Furthermore, a low specific gravity is also a desirable physical property for optical glass for the following reasons. The refractive power of the optical elements that make up an optical system is determined by the refractive index of the glass that makes up the optical element and the curvature of the optically functional surface of the optical element (the surface through which the light rays to be controlled enter and exit). Increasing the curvature of the optically functional surface also increases the thickness of the optical element. As a result, the optical element becomes heavier. In contrast, if glass with a high refractive index is used, a large refractive power can be obtained without increasing the curvature of the optically functional surface. From the above, if the refractive index can be increased while suppressing an increase in the specific gravity of the glass, it will be possible to reduce the weight of an optical element having a certain refractive power. Furthermore, it is also preferable that the glass constituting the light guide plate has a low specific gravity from the viewpoint of reducing the weight of the light guide plate and the image display device.

[0007] In view of the above, an object of one aspect of the present invention is to provide an optical glass having a high refractive index and a low specific gravity. [Means for solving the problem]

[0008] One aspect of the present invention is as follows. [1] By mass, SiO2 content is 1.00% or more, B2O3 content is 1.00% or more, CaO content is 1.00% or more, TiO2 content is 15.00% or more, La2O3 content is 10.00% or more, The total content of SiO2 and B2O3 (SiO2 + B2O3) is 22.00% or less, The total content of TiO2 and Nb2O5 (TiO2 + Nb2O5) is 20.00% or more, The total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is 18.00% or less, The mass ratio of the BaO content to the total content of MgO, CaO, SrO, and BaO (BaO / (MgO+CaO+SrO+BaO)) is 0.50 or less; The mass ratio of the TiO2 content to the CaO content (TiO2 / CaO) is 1.50 or more and 15.00 or less, and An optical glass (hereinafter simply referred to as "optical glass" or "glass") in which the mass ratio of the TiO2 content to the total content of TiO2 and Nb2O5 (TiO2 / (TiO2+Nb2O5)) is 0.50 or more. [2] The optical glass according to [1], wherein the mass ratio of the SiO2 content to the total content of SiO2 and B2O3 (SiO2 / (SiO2+B2O3)) is 0.05 or more and 0.80 or less. [3] The optical glass according to [1] or [2], wherein the total content of Li2O, Na2O and K2O (Li2O + Na2O + K2O) is 5.00% or less. [4] The optical glass according to any one of [1] to [3], wherein the total content of MgO, CaO, SrO, BaO and ZnO (MgO+CaO+SrO+BaO+ZnO) is 20.00% or less. [5] The optical glass according to any one of [1] to [4], wherein the mass ratio of the CaO content to the total content of MgO, CaO, SrO and BaO (CaO / (MgO+CaO+SrO+BaO)) is 0.50 or more. [6] The optical glass according to any one of [1] to [5], wherein the total content of Y2O3, La2O3 and Gd2O3 (Y2O3 + La2O3 + Gd2O3) is 10.00% or more. [7] The optical glass according to any one of [1] to [6], wherein the mass ratio of the Y2O3 content to the total content of Y2O3, La2O3 and Gd2O3 (Y2O3 / (Y2O3+La2O3+Gd2O3)) is 0.00 or more and 0.80 or less. [8] The optical glass according to any one of [1] to [7], wherein the mass ratio of the total content of TiO2 and Nb2O5 to the total content of Y2O3, La2O3 and Gd2O3 ((TiO2+Nb2O5) / (Y2O3+La2O3+Gd2O3)) is 0.50 or more and 2.00 or less. [9] The mass ratio of the SiO2 content to the total content of SiO2 and B2O3 (SiO2 / (SiO2+B2O3)) is 0.20 or more and 0.80 or less; the total content of LiO, NaO and KO (LiO + NaO + KO) is 5.00% or less, The total content of MgO, CaO, SrO, BaO and ZnO (MgO + CaO + SrO + BaO + ZnO) is 20.00% or less, the mass ratio of the CaO content to the total content of MgO, CaO, SrO, and BaO (CaO / (MgO+CaO+SrO+BaO)) is 0.50 or more; The total content of Y2O3, La2O3 and Gd2O3 (Y2O3 + La2O3 + Gd2O3) is 10.00% or more, The mass ratio of the Y2O3 content to the total content of Y2O3, La2O3, and Gd2O3 (Y2O3 / (Y2O3+La2O3+Gd2O3)) is 0.00 or more and 0.80 or less, and The optical glass according to [1], wherein the mass ratio of the total content of TiO2 and Nb2O5 to the total content of Y2O3, La2O3 and Gd2O3 ((TiO2+Nb2O5) / (Y2O3+La2O3+Gd2O3)) is 0.50 or more and 2.00 or less.

[10] An optical element made of the optical glass according to any one of [1] to [9].

[11] A light guide plate made of the optical glass according to any one of [1] to [9].

[12] An image display element; a light guide plate that guides light emitted from the image display element; Including, The image display device, wherein the light guide plate is the light guide plate according to

[11] . [Effects of the Invention]

[0009] According to one aspect of the present invention, an optical glass having a high refractive index and a low specific gravity can be provided. According to another aspect of the present invention, there are provided an optical element and a light guide plate made of the above optical glass, and an image display device including the light guide plate. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating an example of an image device (head-mounted display) including an image display element and a light guide plate. [Figure 2]FIG. 2 is a side view schematically showing the configuration of the head mounted display 1 shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Optical glass] <Glass composition> In the present invention and this specification, the glass composition is expressed as a glass composition based on oxides. Here, "glass composition based on oxides" refers to a glass composition obtained by converting the glass raw materials into oxides that are present in the glass after they are all decomposed during melting. Furthermore, unless otherwise specified, the glass composition is expressed on a mass basis (mass %, mass ratio). The glass composition of the present invention and the present specification can be determined by a method such as ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometry). Quantitative analysis is performed for each element using ICP-AES. The analytical values ​​are then converted into oxide notation. The analytical values ​​obtained by ICP-AES may contain a measurement error of, for example, about ±5% of the analytical value. Therefore, the oxide notation values ​​converted from the analytical values ​​may also contain an error of about ±5%. In the present invention and this specification, the content of a component being 0%, 0.0%, 0.00%, or not containing or not incorporating means that the component is substantially not contained, and that the content of the component is at or below the impurity level, for example, less than 0.01%.

[0012] The glass composition of the optical glass will now be described in more detail.

[0013] From the viewpoints of maintaining glass stability, maintaining a viscosity suitable for forming the glass melt, and suppressing a decrease in chemical durability, the SiO content is 1.00% or more, preferably 1.10% or more, more preferably 1.20% or more, even more preferably 1.30% or more, and more preferably 2.00% or more, 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, and 7.00% or more in that order. From the viewpoint of suppressing a decrease in the refractive index and maintaining glass meltability, the SiO content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, 10.00% or less, and 8.00% or less in that order.

[0014] From the viewpoints of maintaining glass stability and maintaining a viscosity suitable for forming the glass melt, the B2O3 content is 1.00% or more, preferably 2.00% or more, and more preferably 3.00% or more, 4.00% or more, 5.00% or more, 6.00% or more, 7.00% or more, and 8.00% or more in that order. From the viewpoint of suppressing a decrease in the refractive index and a decrease in chemical durability, the B2O3 content is preferably 30.00% or less, and more preferably 25.00% or less, 20.00% or less, 18.00% or less, 16.00% or less, 14.00% or less, 12.00% or less, and 10.00% or less in that order.

[0015] The total content of SiO2 and B2O3 (SiO2 + B2O3) is 22.00% or less, preferably 21.00% or less, and more preferably 20.00% or less, 19.00% or less, and 18.00% or less in that order, from the viewpoint of suppressing a decrease in the refractive index. From the viewpoint of maintaining glass stability, the total content (SiO2 + B2O3) is preferably 2.00% or more, and more preferably 4.00% or more, 6.00% or more, 8.00% or more, 10.00% or more, 11.00% or more, 12.00% or more, 13.00% or more, 14.00% or more, and 15.00% or more in that order.

[0016] From the viewpoint of maintaining the thermal stability of the glass, the mass ratio of the SiO2 content to the total content of SiO2 and B2O3 (SiO2 / (SiO2+B2O3)) is preferably 0.05 or more, and more preferably 0.07 or more, 0.09 or more, 0.10 or more, 0.12 or more, 0.14 or more, 0.16 or more, 0.18 or more, 0.20 or more, 0.22 or more, 0.24 or more, 0.26 or more, 0.28 or more, 0.30 or more, 0.31 or more, 0.32 or more, 0.33 or more, 0.34 or more, 0.35 or more, 0.36 or more, 0.37 or more, 0.38 or more, 0.39 or more, and 0.40 or more, in that order. From the viewpoint of maintaining the thermal stability of the glass, the mass ratio (SiO2 / (SiO2+B2O3)) is preferably 0.80 or less, and more preferably 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.59 or less, 0.58 or less, 0.57 or less, 0.56 or less, 0.55 or less, 0.54 or less, 0.53 or less, 0.52 or less, 0.51 or less, 0.50 or less, 0.49 or less, 0.48 or less, 0.47 or less, 0.46 or less, 0.45 or less, and 0.44 or less, in that order.

[0017] From the viewpoint of improving the thermal stability and meltability of the glass, the CaO content is 1.00% or more, preferably 2.00% or more, and more preferably 2.50% or more, 3.00% or more, 3.50% or more, 4.00% or more, 4.50% or more, and 5.00% or more in that order. From the viewpoint of suppressing a decrease in the refractive index, the CaO content is preferably 20.00% or less, and more preferably 18.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, and 10.00% or less in that order.

[0018] The mass ratio of the BaO content to the total content of MgO, CaO, SrO, and BaO (BaO / (MgO+CaO+SrO+BaO)) can be, for example, 0.00, 0.00 or more, more than 0.00, or 0.01 or more. From the viewpoint of lowering the specific gravity while improving the meltability of the glass, the mass ratio (BaO / (MgO+CaO+SrO+BaO)) is 0.50 or less, and preferably 0.48 or less, and more preferably 0.45 or less, 0.43 or less, 0.40 or less, 0.38 or less, 0.35 or less, 0.33 or less, 0.30 or less, 0.28 or less, 0.25 or less, 0.23 or less, and 0.20 or less, in that order.

[0019] From the viewpoint of lowering the specific gravity while improving the meltability of the glass, the mass ratio of the CaO content to the total content of MgO, CaO, SrO, and BaO (CaO / (MgO+CaO+SrO+BaO)) is preferably 0.50 or more, and more preferably 0.52 or more, 0.55 or more, 0.60 or more, 0.65 or more, and 0.70 or more in that order. The mass ratio (CaO / (MgO+CaO+SrO+BaO)) can be, for example, 1.00, 1.00 or less, or less than 1.00, and can also be 0.90 or less, 0.80 or less, or 0.70 or less.

[0020] From the viewpoint of improving the thermal stability of the glass and suppressing a decrease in the refractive index, the total content of MgO, CaO, SrO and BaO (MgO+CaO+SrO+BaO) is preferably 1.00% or more, and more preferably 2.00% or more, 3.00% or more, 4.00% or more, and 5.00% or more in that order. From the viewpoint of improving the thermal stability of the glass and suppressing a decrease in the refractive index, the total content (MgO+CaO+SrO+BaO) is 18.00% or less, preferably 17.00% or less, and more preferably 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, and 10.00% or less, in that order.

[0021] From the viewpoint of improving the thermal stability of the glass and suppressing a decrease in the refractive index, the total content of MgO, CaO, SrO, BaO and ZnO (MgO + CaO + SrO + BaO + ZnO) is preferably 20.00% or less, and more preferably 19.00% or less, 18.00% or less, 17.00% or less, 16.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, and 10.00% or less in that order. The total content (MgO+CaO+SrO+BaO+ZnO) can be, for example, 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, or 5.00% or more.

[0022] The content of each of MgO, SrO, and BaO may be 0.00%, 0.00% or more, more than 0.00%, 0.05% or more, or 0.10% or more. In addition, the content of each of MgO, SrO, and BaO may be, for example, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, or 1.00% or less. Although MgO, SrO, and BaO all function to improve the thermal stability of the glass, increasing their contents tends to decrease the refractive index, so the contents of MgO, SrO, and BaO are preferably within the above-mentioned ranges.

[0023] The ZnO content can be 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, or 0.10% or more. The ZnO content can be, for example, 10.00% or less, 9.00% or less, 8.00% or less, 7.00% or less, 6.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, or 2.00% or less. ZnO has the function of improving the thermal stability of the glass, but a high ZnO content tends to increase the specific gravity, so the ZnO content is preferably within the above range.

[0024] From the viewpoint of increasing the refractive index of the glass and improving the chemical durability, the TiO2 content is 15.00% or more, preferably 18.00% or more, and more preferably 20.00% or more, 21.00% or more, 22.00% or more, 23.00% or more, 24.00% or more, 25.00% or more, 26.00% or more, and 27.00% or more in that order. From the viewpoint of suppressing a decrease in glass stability, the TiO2 content is preferably 50.00% or less, and more preferably 45.00% or less, 40.00% or less, 38.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 33.00% or less, 32.00% or less, 31.00% or less, and 30.00% or less in that order.

[0025] From the viewpoint of increasing the refractive index of the glass and improving the thermal stability, the mass ratio of the TiO2 content to the CaO content (TiO2 / CaO) is 1.50 or more, and preferably 1.80 or more, and more preferably 1.90 or more, 2.00 or more, 2.10 or more, 2.20 or more, 2.30 or more, 2.40 or more, 2.50 or more, 2.60 or more, 2.70 or more, 2.80 or more, 2.90 or more, 3.00 or more, 3.10 or more, 3.20 or more, 3.30 or more, 3.40 or more, 3.50 or more, 3.60 or more, 3.70 or more, 3.80 or more, 3.90 or more, and 4.00 or more in that order. From the viewpoint of increasing the refractive index of the glass and improving the thermal stability, the mass ratio (TiO2 / CaO) is 15.00 or less, preferably 14.00 or less, and more preferably 13.00 or less, 12.00 or less, 11.00 or less, 10.00 or less, 9.00 or less, 8.00 or less, 7.00 or less, 6.00 or less, and 5.00 or less, in that order.

[0026] From the viewpoint of suppressing a decrease in the refractive index, the total content of TiO2 and Nb2O5 (TiO2 + Nb2O5) is 20.00% or more, preferably 21.00% or more, and more preferably 22.00% or more, 23.00% or more, 24.00% or more, 25.00% or more, 26.00% or more, and 27.00% or more in that order. From the viewpoint of maintaining glass stability, the total content (TiO2 + Nb2O5) is preferably 50.00% or less, and more preferably 45.00% or less, 40.00% or less, 39.00% or less, 38.00% or less, 37.00% or less, 36.00% or less, 35.00% or less, 34.00% or less, 33.00% or less, 32.00% or less, and 31.00% or less in that order.

[0027] The mass ratio of the TiO2 content to the total content of TiO2 and Nb2O5 (TiO2 / (TiO2+Nb2O5)) is 0.50 or more, preferably 0.55 or more, and more preferably 0.60 or more, 0.65 or more, 0.70 or more, 0.75 or more, 0.80 or more, 0.82 or more, 0.84 or more, 0.86 or more, 0.88 or more, and 0.90 or more, in that order, from the viewpoint of further increasing the refractive index and further decreasing the specific gravity of the glass. The mass ratio (TiO2 / (TiO2+Nb2O5)) can be, for example, 1.00, less than or equal to 1.00, or less than 1.00.

[0028] The Nb2O5 content can be 0.00%, 0.00% or more, greater than 0.00%, 0.10% or more, 0.50% or more, 1.00% or more, 1.50% or more, 2.00% or more, 2.50% or more, 3.00% or more, 3.50% or more, 4.00% or more, 4.50% or more, or 5.00% or more. The Nb2O5 content can be, for example, 20.00% or less, 18.00% or less, 15.00% or less, 14.00% or less, 13.00% or less, 12.00% or less, 11.00% or less, or 10.00% or less. The Nb2O5 content is preferably within the above range from the viewpoint of increasing the refractive index of the glass and improving the chemical durability.

[0029] From the viewpoints of increasing the refractive index of the glass, maintaining low dispersion, and improving chemical durability, the La2O3 content is 10.00% or more, preferably 15.00% or more, and more preferably 18.00% or more, 20.00% or more, 22.00% or more, 24.00% or more, 26.00% or more, 28.00% or more, 30.00% or more, 31.00%, 32.00% or more, 33.00% or more, 34.00% or more, and 35.00% or more in that order. From the viewpoint of suppressing a decrease in glass stability, the La2O3 content is preferably 60.00% or less, and more preferably 55.00% or less, 50.00% or less, 48.00% or less, 46.00% or less, 44.00% or less, 42.00% or less, and 40.00% or less in that order.

[0030] The Y2O3 content can be 0.00%, 0.00% or more, or more than 0.00%. The Y2O3 content can be, for example, 15.00% or less, 13.00% or less, 10.00% or less, 8.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, 0.50% or less, or 0.10% or less, or can be 0.00%. The Y2O3 content is preferably within the above range from the viewpoints of increasing the refractive index of the glass, maintaining low dispersion, and improving chemical durability. Furthermore, Y2O3 has a low specific gravity among rare earth oxides. From the viewpoint of lowering the specific gravity of the glass, the Y2O3 content is preferably within the above range.

[0031] The Gd2O3 content can be 0.00%, 0.00% or more, or more than 0.00%. The Gd2O3 content can be, for example, 10.00% or less, 8.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, 0.50% or less, or 0.10% or less, or can even be 0.00%. The Gd2O3 content is preferably within the above range from the viewpoints of increasing the refractive index of the glass, maintaining low dispersion, and improving chemical durability.

[0032] The Yb2O3 content can be 0.00%, 0.00% or more, or more than 0.00%. The Yb2O3 content can be, for example, 10.00% or less, 8.00% or less, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, 1.00% or less, 0.50% or less, or 0.10% or less, or can be 0.00%. The Yb2O3 content is preferably within the above range from the viewpoints of increasing the refractive index of the glass, maintaining low dispersion, and improving chemical durability.

[0033] From the viewpoint of increasing the refractive index while maintaining the low dispersion of the glass, the total content of Y2O3, La2O3 and Gd2O3 (Y2O3 + La2O3 + Gd2O3) is preferably 10.00% or more, and more preferably 15.00% or more, 20.00% or more, 23.00% or more, 25.00% or more, 28.00% or more, 30.00% or more, 33.00% or more, and 35.00% or more in that order. The total content (Y2O3 + La2O3 + Gd2O3) can be, for example, 70.00% or less, 60.00% or less, 55.00% or less, 50.00% or less, 45.00% or less, 44.00% or less, 43.00% or less, 42.00% or less, 41.00% or less, or 40.00% or less.

[0034] The mass ratio of the Y2O3 content to the total content of Y2O3, La2O3, and Gd2O3 (Y2O3 / (Y2O3+La2O3+Gd2O3)) can be 0.00 or more, and is preferably 0.01 or more, and more preferably 0.02 or more, 0.03 or more, 0.04 or more, 0.05 or more, 0.08 or more, 0.10 or more, 0.13 or more, 0.15 or more, 0.18 or more, and 0.20 or more, in that order. The mass ratio (Y2O3 / (Y2O3+La2O3+Gd2O3)) is preferably 0.80 or less, and more preferably 0.75 or less, 0.70 or less, 0.65 or less, 0.60 or less, 0.55 or less, 0.50 or less, 0.48 or less, 0.45 or less, 0.43 or less, 0.40 or less, 0.38 or less, 0.35 or less, 0.33 or less, and 0.30 or less, in that order. From the viewpoint of increasing the refractive index of the glass while decreasing the specific gravity, it is preferable that the mass ratio (Y2O3 / (Y2O3+La2O3+Gd2O3)) be in the above range.

[0035] The mass ratio of the total content of TiO2 and Nb2O5 to the total content of Y2O3, La2O3, and Gd2O3 ((TiO2+Nb2O5) / (Y2O3+La2O3+Gd2O3)) is preferably 0.50 or more, and more preferably 0.53 or more, 0.55 or more, 0.58 or more, 0.60 or more, 0.63 or more, 0.65 or more, 0.68 or more, 0.70 or more, 0.73 or more, 0.75 or more, 0.78 or more, 0.80 or more, 0.83 or more, and 0.85 or more in that order. The mass ratio ((TiO2+Nb2O5) / (Y2O3+La2O3+Gd2O3)) is preferably 2.00 or less, and more preferably 1.90 or less, 1.80 or less, 1.70 or less, 1.60 or less, 1.55 or less, 1.50 or less, 1.45 or less, 1.40 or less, 1.35 or less, 1.30 or less, 1.25 or less, 1.20 or less, 1.15 or less, 1.10 or less, 1.05 or less, and 1.00 or less, in that order. From the viewpoint of increasing the refractive index while maintaining the thermal stability of the glass, it is preferable that the mass ratio ((TiO2+Nb2O5) / (Y2O3+La2O3+Gd2O3)) be in the above range.

[0036] The total content of Li2O, Na2O and K2O (Li2O + Na2O + K2O) can be 0.00%, 0.00% or more, or greater than 0.00%. From the viewpoint of suppressing a decrease in the refractive index and a decrease in chemical durability, the total content (Li2O+Na2O+K2O) is preferably 5.00% or less, more preferably 4.00% or less, 3.00% or less, 2.00% or less, and 1.00% or less in that order, and may be 0.00%.

[0037] The LiO content can be 0.00%, 0.00% or more, or more than 0.00%. The LiO content can be, for example, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, or 1.00% or less, or can be 0.00%.

[0038] The NaO content can be 0.00%, 0.00% or more, or more than 0.00%. The NaO content can be, for example, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, or 1.00% or less, or can be 0.00%.

[0039] The K2O content can be 0.00%, 0.00% or more, or more than 0.00%. The K2O content can be, for example, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, or 1.00% or less, or can be 0.00%.

[0040] The ZrO2 content can be 0.00% or 0.00% or more, and from the viewpoint of increasing the refractive index of the glass and improving chemical durability, it is preferably more than 0.00%, and more preferably 0.50% or more, 1.00% or more, 2.00% or more, 3.00% or more, 4.00% or more, and 5.00% or more in that order. Furthermore, from the viewpoint of suppressing a decrease in glass stability, the ZrO2 content is preferably 15.00% or less, and more preferably 13.00% or less, 10.00% or less, and 8.00% or less in that order.

[0041] The Ta2O5 content may be 0.00%, 0.00% or more, more than 0.00%, 0.10% or more, or 0.10% or more. The Ta2O5 content may be, for example, 5.00% or less, 4.00% or less, 3.00% or less, 2.00% or less, or 1.00% or less, or may be 0.00%. Ta2O5 can contribute to increasing the refractive index of glass and improving chemical durability. However, Ta2O5 is expensive, and glass stability tends to decrease as the Ta2O5 content increases. From these perspectives, the Ta2O5 content is preferably within the above range.

[0042] The optical glass may further contain one or more of P2O5, Al2O3, and the like in addition to the above components. The P2O5 content can be 0.00% or more, preferably 10.00% or less, and more preferably 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%. The Al2O3 content can be 0.00% or more, and is preferably 10.00% or less, and is more preferably 8.00% or less, 6.00% or less, 4.00% or less, 2.00% or less, 1.00% or less, and 0.50% or less in that order, and may be 0.00%.

[0043] Pb, As, Cd, Tl, Be, and Se are all toxic, and therefore it is preferable not to include these elements, i.e., not to introduce these elements into the glass as glass components. U, Th, and Ra are all radioactive elements, and therefore it is preferable not to include these elements, i.e., not to introduce these elements into the glass as glass components. V, Cr, Mn, Fe, Co, Ni, Cu, Pr, Nd, Pm, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Ce are undesirable elements to be contained in glass for optical elements because they increase the coloration of the glass or are sources of fluorescence. Therefore, it is preferable not to contain these elements, i.e., not to introduce these elements into the glass as glass components.

[0044] Sb and Sn are elements that can be added as desired and function as fining agents. The amount of Sb added is converted to Sb2O3 and, when the total content of glass components other than Sb2O3 is taken as 100 mass%, is preferably in the range of 0.000 to 0.100 mass%, more preferably in the range of 0.001 to 0.020 mass%, and even more preferably in the range of 0.001 to 0.010 mass%. The amount of Sn added is converted to SnO2 and, when the total content of glass components other than SnO2 is taken as 100 mass%, is preferably in the range of 0.000 to 0.100 mass%, more preferably in the range of 0.000 to 0.020 mass%, even more preferably in the range of 0.000 to 0.010 mass%, and still more preferably in the range of 0.000 to 0.005 mass%.

[0045] <Glass properties> (refractive index nd) The refractive index nd of the optical glass is preferably greater than 1.90000, more preferably 1.95000 or greater, 1.96000 or greater, and more preferably 1.97000 or greater, 1.98000 or greater, 1.99000 or greater, and 2.00000 or greater in that order. The refractive index nd of the optical glass can be, for example, 2.20000 or less, 2.15000 or less, 2.14000 or less, 2.13000 or less, 2.12000 or less, 2.11000 or less, or 2.10000 or less. In the present invention and this specification, "refractive index" means "refractive index nd."

[0046] (Abbe number νd) The Abbe number vd is a value that represents the dispersibility properties, and is expressed as vd = (nd - 1) / (nF - nC) where nd, nF, and nC are the refractive indices at the d-line, F-line, and C-line, respectively. From the viewpoint of usefulness as a material for optical elements and light guide plates, the Abbe number vd of the optical glass is preferably 20.00 or more, more preferably 21.00 or more, and even more preferably 22.00 or more and 23.00 or more in that order. From the same viewpoint, the Abbe number vd is preferably 30.00 or less, more preferably 29.00 or less, and even more preferably 28.00 or less, 27.00 or less, 26.00 or less, 25.00 or less, and 24.00 or less in that order.

[0047] (specific gravity) The specific gravity of the optical glass is preferably 5.00 g / cc or less, more preferably 4.80 g / cc or less, and even more preferably 4.60 g / cc to 4.50 g / cc, or 4.40 g / cc or less. Since a lower specific gravity is preferable from the viewpoint of reducing the weight of optical elements, there is no particular lower limit for the specific gravity of the optical glass. In one embodiment, the specific gravity can be 4.00 g / cc or more, 4.10 g / cc or more, or 4.20 g / cc or more.

[0048] The optical glass described above is useful as a glass material for optical elements and a glass material for light guide plates.

[0049] <Optical glass manufacturing method> The above optical glass can be obtained, for example, by the following method. Raw materials such as oxides, carbonates, sulfates, nitrates, and hydroxides are weighed, blended, and thoroughly mixed to obtain the desired glass composition. This mixed batch is heated and melted in a melting vessel, degassed, and stirred to produce a homogeneous, bubble-free glass melt. Specifically, the glass melt can be produced using a known melting method. The above optical glass can be obtained by molding the glass melt thus obtained.

[0050] [Glass materials for press molding, optical element blanks, and their manufacturing methods] Another aspect of the present invention is a glass material for press molding comprising the optical glass; an optical element blank made of the optical glass; Regarding.

[0051] According to another aspect of the present invention, a method for producing a glass material for press molding, comprising a step of molding the optical glass into a glass material for press molding; a method for producing an optical element blank, comprising a step of press-molding the glass material for optical glass press molding using a press mold to produce an optical element blank; a method for manufacturing an optical element blank, comprising a step of molding the optical glass into an optical element blank; is also provided.

[0052] An optical element blank is an optical element base material that approximates the shape of the desired optical element, with polishing allowances (surface layers to be removed by polishing) and, if necessary, grinding allowances (surface layers to be removed by grinding) added to the shape of the optical element. The optical element is finished by grinding and polishing the surface of the optical element blank. In one embodiment, the optical element blank can be produced by a method (called a direct press method) in which a molten glass obtained by melting an appropriate amount of the above glass is press-molded. In another embodiment, the optical element blank can also be produced by solidifying a molten glass obtained by melting an appropriate amount of the above glass.

[0053] In another embodiment, an optical element blank can be produced by preparing a glass material for press molding and press-molding the prepared glass material for press molding.

[0054] Press molding of a glass material for press molding can be carried out by a known method in which a glass material for press molding in a heated and softened state is pressed in a press mold. Both heating and press molding can be carried out in the atmosphere. After press molding, the glass is annealed to reduce internal strain, thereby obtaining a homogeneous optical element blank.

[0055] Glass materials for press molding include not only glass gobs for press molding that are used for press molding as they are to produce optical element blanks, but also glass gobs for press molding that are machined by cutting, grinding, polishing, etc. and then used for press molding. Cutting methods include forming a groove in the area of ​​the surface of the glass plate to be cut by a method called scribing, applying local pressure to the grooved area from the back side of the surface where the groove was formed, thereby breaking the glass plate at the grooved area, and cutting the glass plate with a cutting blade. Grinding and polishing methods include barrel polishing, etc.

[0056] A glass material for press molding can be produced, for example, by casting molten glass into a mold to form a glass plate, and then cutting this glass plate into a plurality of glass pieces. Alternatively, a suitable amount of molten glass can be molded to produce a glass gob for press molding. An optical element blank can also be produced by reheating, softening, and press-molding a glass gob for press molding. The method of producing an optical element blank by reheating, softening, and press-molding glass is called a reheat press method, as opposed to a direct press method.

[0057] [Optical element and its manufacturing method] Another aspect of the present invention is Optical elements made of the above optical glass Regarding. The optical element is manufactured using the optical glass. In the optical element, the glass surface may be coated with one or more layers, such as a multilayer film including an anti-reflection film.

[0058] According to another aspect of the present invention, a method for manufacturing an optical element, comprising a step of manufacturing an optical element by grinding and / or polishing the optical element blank described above; is also provided.

[0059] In the above-mentioned method for manufacturing optical elements, known methods may be used for grinding and polishing, and by thoroughly cleaning and drying the surface of the optical element after processing, optical elements with high internal and surface quality can be obtained. In this way, optical elements made of the above-mentioned glass can be obtained. Examples of optical elements include various lenses such as spherical lenses, aspherical lenses, and microlenses, as well as prisms.

[0060] Optical elements made of the above optical glass are also suitable as lenses constituting cemented optical elements. Examples of cemented optical elements include those in which lenses are cemented together (cemented lenses) and those in which a lens and a prism are cemented together. For example, a cemented optical element can be produced by precisely machining (e.g., spherical polishing) the cementing surfaces of two optical elements to be cemented so that their shapes are inverted, applying an ultraviolet-curing adhesive used for bonding cemented lenses, bonding them together, and then irradiating ultraviolet light through the lenses to cure the adhesive. The above glasses are preferred for producing cemented optical elements in this way. By producing multiple optical elements to be cemented using multiple types of glass with different Abbe numbers νd and cementing them together, an element suitable for correcting chromatic aberration can be produced.

[0061] [Light guide plate, image display device] Another aspect of the present invention is a light guide plate made of the optical glass; an image display device comprising an image display element and a light guide plate for guiding light emitted from the image display element, the light guide plate being made of any one of the optical glasses described above; A specific embodiment of the image display device will be described later. [Example]

[0062] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the embodiments shown in the examples.

[0063] [Example 1] To obtain the glass compositions shown in the table below, the corresponding nitrates, sulfates, carbonates, hydroxides, oxides, boric acid, etc. were used as raw materials for introducing each component, and the raw materials were weighed and thoroughly mixed to obtain blended raw materials. The blended raw materials were placed in a platinum crucible and heated to melt. After melting, the molten glass was poured into a mold and allowed to cool to near the glass transition temperature. It was then immediately placed in an annealing furnace and annealed within the glass transition temperature range for about 1 hour, and then allowed to cool to room temperature in the furnace, yielding the optical glasses Nos. 1 to 51 shown in the table below. In the table below, the units of content are % by mass. The Sb2O3 content is the content when the total content of the glass components other than Sb2O3 is taken as 100% by mass.

[0064] The following table shows the physical properties of each optical glass of Example 1. The physical properties of the optical glasses were measured by the methods shown below.

[0065] [Evaluation of physical properties of optical glass] (1) Refractive index nd Abbe number νd The glass was cooled at a cooling rate of -30°C / hour, and the refractive index nd and Abbe number vd were measured by the refractive index measurement method specified by the Japan Optical Glass Industry Association standard.

[0066] (2) Specific gravity Specific gravity was measured by Archimedes' method.

[0067] The results are shown in the table below.

[0068] [Table 1]

[0069] [Table 2]

[0070] [Table 3]

[0071] [Table 4]

[0072] [Table 5]

[0073] [Table 6]

[0074] [Table 7]

[0075] [Table 8]

[0076] [Table 9]

[0077] [Example 2] Glass gobs for press molding (glass gobs) were prepared using each of the optical glasses obtained in Example 1. These glass gobs were heated and softened in the atmosphere and press-molded in a press mold to produce lens blanks (optical element blanks). The produced lens blanks were removed from the press mold, annealed, and subjected to machining including polishing to produce spherical lenses made of each of the optical glasses of Example 1.

[0078] [Example 3] A desired amount of the molten glass produced in Example 1 was press-molded in a press mold to produce a lens blank (optical element blank). The produced lens blank was removed from the press mold, annealed, and subjected to machining including polishing to produce a spherical lens made of each of the optical glasses of Example 1.

[0079] [Example 4] The glass melt produced in Example 1 was solidified to produce a glass lump (optical element blank), which was then annealed and subjected to machining including polishing to produce spherical lenses made of the optical glasses of Example 1.

[0080] [Example 5] The spherical lenses produced in Examples 2 to 4 were bonded to spherical lenses made of other types of glass to produce cemented lenses.

[0081] [Example 6] 1 is a schematic diagram of a head-mounted display, which is an example of an image device including an image display element and a light guide plate. A head-mounted display 1 having the configuration shown in FIG. 1 was fabricated by the following method. Each optical glass of Example 1 was processed into a rectangular thin plate having a length of 50 mm, a width of 20 mm, and a thickness of 1.0 mm, to obtain a light guide plate 10. This light guide plate was attached to a head-mounted display 1 (hereinafter abbreviated as "HMD1") shown in FIG. 1. FIG. 1(a) is a front perspective view of the HMD 1, and FIG. 1(b) is a rear perspective view of the HMD 1. As shown in FIGS. 1(a) and 1(b), eyeglass lenses 3 are attached to the front of an eyeglass-type frame 2 worn on the user's head. A backlight 4 for illuminating images is attached to a mounting portion 2a of the eyeglass-type frame 2. A signal processing device 5 for displaying images and a speaker 6 for reproducing sound are provided on the temples of the eyeglass-type frame 2. Flexible printed circuits (FPCs) 7, which constitute wiring drawn from the circuit of the signal processing device 5, are routed along the eyeglass-type frame 2. A display element unit (e.g., a liquid crystal display element) 20 is routed by the FPC 7 to the center position of the user's eyes, and is held so that the approximate center of the display element unit 20 is positioned on the optical axis of the backlight 4. The imager unit 20 is fixed relatively to the light guide plate 10 so as to be located approximately in the center of the light guide plate 10. Furthermore, HOEs (Holographic Optical Elements) 32R and 32L (first optical elements) are closely fixed to the first surface 10a of the light guide plate 10 by adhesive or the like at locations located in front of the user's eyes. HOEs 52R and 52L are stacked on the second surface 10b of the light guide plate 10 at positions facing the imager unit 20 across the light guide plate 10. FIG. 2 is a side view schematically illustrating the configuration of the HMD 1 shown in FIG. 2. To clarify the drawing, FIG. 2 shows only the main components, and the eyeglass-type frame 2 and the like are omitted. As shown in FIG. 2, the HMD 1 has a bilaterally symmetrical structure with respect to a center line X connecting the center of the image display element 24 and the light guide plate 10. Furthermore, light of each wavelength incident on the light guide plate 10 from the image display element 24 is split into two and guided to the right eye and left eye of the user, as will be described later. The optical paths of the light of each wavelength guided to each eye are also approximately bilaterally symmetrical with respect to the center line X. As shown in FIG. 2, the backlight 4 includes a laser light source 21, a diffusion optical system 22, and a microlens array 23. The display element unit 20 is an image generating unit including an image display element 24, and is driven, for example, by a field sequential method. The laser light source 21 includes laser light sources corresponding to the wavelengths of B (wavelength 436 nm), G (wavelength 546 nm), and R (wavelength 633 nm), and sequentially irradiates light of each wavelength at high speed. The light of each wavelength is incident on the diffusion optical system 22 and the microlens array 23, where it is converted into a uniform, highly directional parallel beam of light with no unevenness in light intensity, and is then incident perpendicularly on the display panel surface of the image display element 24. The image display element 24 is, for example, a transmissive liquid crystal (LCDT-LCOS) panel driven by a field sequential method. The image display element 24 modulates light of each wavelength in accordance with an image signal generated by an image engine (not shown) of the signal processing device 5. The light of each wavelength modulated by the pixels in the effective area of ​​the image display element 24 is incident on the light guide plate 10 with a predetermined beam cross section (approximately the same shape as the effective area). Note that the image display element 24 can also be replaced with other types of display elements, such as a DMD (Digital Mirror Device), a reflective liquid crystal (LCOS) panel, a MEMS (Micro Electro Mechanical Systems), an organic EL (Electro-Luminescence), or an inorganic EL. The image generating unit of the image display element 20 is not limited to a field sequential type image display element, but may be a simultaneous type image display element (a display element having a predetermined arrangement of RGB color filters in front of the light emitting surface). In this case, for example, a white light source is used as the light source. As shown in Fig. 2, light of each wavelength modulated by the image display element 24 is sequentially incident on the first surface 10a into the light guide plate 10. HOEs 52R and 52L (second optical elements) are stacked on the second surface 10b of the light guide plate 10. HOEs 52R and 52L are, for example, rectangular reflective volume phase HOEs, each composed of three stacked photopolymer sheets on which interference fringes corresponding to light of each wavelength of R, G, and B are recorded. In other words, HOEs 52R and 52L are configured to have a wavelength selection function that diffracts light of each wavelength of R, G, and B and transmits light of other wavelengths. The HOEs 32R and 32L are also reflective volume phase HOEs and have the same layer structure as the HOEs 52R and 52L. The HOEs 32R and 32L and the HOEs 52R and 52L may have, for example, approximately the same pitch of the interference fringe patterns. The HOEs 52R and 52L are stacked with their centers aligned and with their interference fringe patterns inverted by 180°. They are then tightly fixed by adhesive or the like onto the second surface 10b of the light guide plate 10 so that their centers are aligned with the center line X. The light of each wavelength modulated by the image display element 24 is incident sequentially on the HOEs 52R and 52L via the light guide plate 10. HOEs 52R and 52L each diffract light of each wavelength incident sequentially at a predetermined angle to guide it to the right eye and left eye. The light of each wavelength diffracted by HOEs 52R and 52L undergoes repeated total reflection at the interface between light guide plate 10 and air, propagates within light guide plate 10, and is incident on HOEs 32R and 32L. HOEs 52R and 52L impart the same diffraction angle to light of each wavelength. Therefore, light of all wavelengths incident at approximately the same position on light guide plate 10 (or, in other words, emitted from approximately the same coordinates within the effective area of ​​image display element 24) propagates along approximately the same optical path within light guide plate 10 and is incident on HOEs 32R and 32L at approximately the same position. From another perspective, HOEs 52R and 52L diffract light of each wavelength of RGB so that the pixel positional relationship within the effective area of ​​image display element 24 is faithfully reproduced on HOEs 32R and 32L. Thus, in this embodiment, HOEs 52R and 52L each diffract light of all wavelengths emitted from approximately the same coordinates within the effective area of ​​image display element 24 so that the light is incident at approximately the same position on HOEs 32R and 32L. Alternatively, HOEs 52R and 52L may be configured to diffract light of all wavelengths that would originally form the same pixel but are relatively shifted within the effective area of ​​image display element 24 so that the light is incident at approximately the same position on HOEs 32R and 32L. The light of each wavelength incident on the HOEs 32R and 32L is diffracted by the HOEs 32R and 32L and sequentially emitted approximately perpendicularly to the outside from the second surface 10b of the light guide plate 10. The light of each wavelength emitted as approximately parallel light in this manner forms a virtual image I of the image generated by the image display element 24 on the retina of the user's right eye and left eye, respectively. Alternatively, to allow the user to observe the virtual image I of the enlarged image, the HOEs 32R and 32L may be given a condenser effect. That is, light incident on the peripheral regions of the HOEs 32R and 32L may be emitted at an angle closer to the center of the pupil and formed on the user's retina. Alternatively, to allow the user to observe the virtual image I of the enlarged image, the HOEs 52R and 52L may diffract the light of each wavelength of RGB so that the pixel positional relationship on the HOEs 32R and 32L forms an enlarged, similar shape to the pixel positional relationship within the effective area of ​​the image displayed on the image display element 24. Since the air-equivalent optical path length of light traveling through the light guide plate 10 becomes shorter as the refractive index increases, the use of the above optical glasses with a high refractive index makes it possible to increase the apparent viewing angle relative to the width of the image display element 24. Furthermore, because the specific gravity of the glass is kept low despite its high refractive index, it is possible to provide a light guide plate that is lightweight yet provides the above effects. The light guide plate 10 thus obtained was incorporated into the HMD 1, and the image was evaluated at the eyepoint position. As a result, it was possible to observe a high-brightness, high-contrast image over a wide viewing angle. The light guide plates made of the above optical glasses can be used in see-through transmissive head-mounted displays and non-transmissive head-mounted displays. These head-mounted displays have a light guide plate made of high-refractive-index glass, which provides a wide viewing angle and a sense of immersion, making them ideal as image display devices for use in combination with information terminals, for providing AR (Augmented Reality), and for watching movies, playing games, and VR (Virtual Reality). In this embodiment, a head-mounted display has been described as an example, but the light guide plate may be attached to other image display devices.

[0082] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. For example, by adjusting the composition as described in the specification for the glass compositions exemplified above, an optical glass according to one aspect of the present invention can be obtained. Furthermore, it is of course possible to arbitrarily combine two or more of the items described in the specification as examples or preferred ranges.

Claims

1. By mass, SiO ２ Content is 1.00% or more, B ２ O ３ Content is 1.00% or more, CaO content is 1.00% or more, TiO ２ The content is 15.00% or more, La ２ O ３ The content is 10.00% or more, SiO ２ and B ２ O ３ and the total content (SiO ２ +B ２ O ３ ) is 22.00% or less, TiO ２ and Nb ２ O ５ The total content of TiO ２ +Nb ２ O ５ ) is 20.00% or more, the total content of MgO, CaO, SrO and BaO (MgO + CaO + SrO + BaO) is 18.00% or less; the mass ratio of the BaO content to the total content of MgO, CaO, SrO, and BaO (BaO / (MgO+CaO+SrO+BaO)) is 0.50 or less; TiO relative to CaO content ２ Mass ratio of content (TiO ２ / CaO) is 1.50 or more and 15.00 or less, and TiO ２ and Nb ２ O ５ TiO relative to the total content of ２ Mass ratio of content (TiO ２ / (TiO ２ +Nb ２ O ５ )) is 0.50 or more.

2. SiO ２ and B ２ O ３ SiO relative to the total content of ２ Mass ratio of content (SiO ２ / (SiO ２ +B ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.05 or more and 0.80 or less.

3. Li ２ O, Na ２ O and K ２ The total content of O (Li ２ O + Na ２ O+K ２ 2. The optical glass of claim 1, wherein O is 5.00% or less.

4. 2. The optical glass according to claim 1, wherein the total content of MgO, CaO, SrO, BaO, and ZnO (MgO + CaO + SrO + BaO + ZnO) is 20.00% or less.

5. 2. The optical glass according to claim 1, wherein the mass ratio of the CaO content to the total content of MgO, CaO, SrO, and BaO (CaO / (MgO+CaO+SrO+BaO)) is 0.50 or more.

6. Y ２ O ３ , La ２ O ３ and Gd ２ O ３ The total content (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ 2. The optical glass according to claim 1, wherein the content of C is 10.00% or more.

7. Y ２ O ３ , La ２ O ３ and Gd ２ O ３ Y relative to the total content of ２ O ３ Mass ratio of content (Y ２ O ３ / (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.00 or more and 0.80 or less.

8. Y ２ O ３ , La ２ O ３ and Gd ２ O ３ TiO relative to the total content ２ and Nb ２ O ５ The mass ratio of the total content of (TiO ２ +Nb ２ O ５ ) / (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.50 or more and 2.00 or less.

9. SiO ２ and B ２ O ３ SiO relative to the total content of ２ Mass ratio of content (SiO ２ / (SiO ２ +B ２ O ３ ) is 0.20 or more and 0.80 or less, Li ２ O, Na ２ O and K ２ The total content of O (Li ２ O + Na ２ O+K ２ O) is 5.00% or less, the total content of MgO, CaO, SrO, BaO and ZnO (MgO + CaO + SrO + BaO + ZnO) is 20.00% or less; the mass ratio of the CaO content to the total content of MgO, CaO, SrO, and BaO (CaO / (MgO+CaO+SrO+BaO)) is 0.50 or more; Y ２ O ３ , La ２ O ３ and Gd ２ O ３ The total content (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ ) is 10.00% or more, Y ２ O ３ , La ２ O ３ and Gd ２ O ３ Y relative to the total content of ２ O ３ Mass ratio of content (Y ２ O ３ / (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ )) is 0.00 or greater and 0.80 or less, and Y ２ O ３ , La ２ O ３ and Gd ２ O ３ TiO relative to the total content ２ and Nb ２ O ５ The mass ratio of the total content of (TiO ２ +Nb ２ O ５ ) / (Y ２ O ３ +La ２ O ３ +Gd ２ O ３ 2. The optical glass according to claim 1, wherein σ is 0.50 or more and 2.00 or less.

10. An optical element made of the optical glass according to any one of claims 1 to 9.

11. A light guide plate made of the optical glass according to any one of claims 1 to 9.

12. an image display element; a light guide plate that guides light emitted from the image display element; Including, An image display device, wherein the light guide plate is the light guide plate according to claim 11.

Images