Optical glass plate

Abstract

Provided is an optical glass plate having a higher refraction index characteristic than conventional optical glass plates. This optical glass plate is characterized by containing 0-12% of SiO2, 0-10% of B2O3, 0-9% of BaO, 0-5% of ZnO, 2-10% of ZrO2, 15-45% of La2O3, 0-15% of Gd2O3, 0-15% of Nb2O5, 0-10% of WO3, 15-50% of TiO2, and 0.1-10% of Y2O3 by mass% and characterized in that the ratio Y3+ / (Gd3+ + Y3+ + Yb3+) is 0.2 or more in terms of cation%, the refraction index nd is 2.01 or more, and the Abbe number νd is 35 or less.

Description

[Technical Field]

[0001] This invention relates to an optical glass plate used as a light guide plate or the like in a wearable image display device. [Background technology]

[0002] Glass plates are used as components of wearable image display devices such as projector-equipped glasses, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. These glass plates function, for example, as see-through light guide plates, allowing users to view the external scenery through the glass plate while simultaneously viewing the image displayed on it. Furthermore, it is possible to achieve 3D display by utilizing technology that projects different images onto the left and right sides of the glasses, or to realize a virtual reality space by utilizing technology that fuses the image to the retina using the lens of the eye. These glass plates are required to have a high refractive index for aspects such as wide-angle image enhancement, high brightness and contrast, and improved light guide characteristics (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-32673 [Patent Document 2] Patent No. 6517411 [Overview of the project] [Problems that the invention aims to solve]

[0004] To improve the performance of wearable image display devices, there is a need for even higher refractive indices in glass plates. To improve the refractive index of glass plates, it is effective to incorporate components that contribute to a high refractive index, such as TiO2, into the glass. However, incorporating large amounts of such high refractive index components into the glass can make vitrification difficult.

[0005] In view of the above, an object of the present invention is to provide an optical glass plate having higher refractive index characteristics than conventional ones. [Means for Solving the Problem]

[0006] As a result of intensive studies by the present inventors, it has been found that an optical glass plate having a predetermined composition can solve the above problem. Hereinafter, each aspect of the optical glass plate that solves the above problem will be described.

[0007] That is, the optical glass plate of aspect 1 contains, in mass%, 0 to 12% of SiO2, 0 to 10% of B2O3, 0 to 9% of BaO, 0 to 5% of ZnO, 2 to 10% of ZrO2, 15 to 45% of La2O3, 0 to 15% of Gd2O3, 0 to 15% of Nb2O5, 0 to 10% of WO3, 15 to 50% of TiO2, and 0.1 to 10% of Y2O3, wherein the cation percentage ratio of Y 3+ / (Gd 3+ +Y 3+ +Yb 3+ ) is 0.2 or more, a refractive index nd is 2.01 or more, and an Abbe number νd is 35 or less.

[0008] The optical glass plate of aspect 2, in aspect 1, preferably has an internal transmittance τ at a wavelength of 450 nm for a thickness of 10 mm 450 of 70% or more.

[0009] The optical glass plate of aspect 3, in aspect 1 or aspect 2, preferably has a thickness of 1 mm or less.

[0010] The optical glass plate of aspect 4, in any one of aspects 1 to 3, preferably has a major axis of a main surface of 100 mm or more.

[0011] The optical glass plate of aspect 5, in any one of aspects 1 to 4, preferably has a liquid phase viscosity of 10 0.1 dPa·s or more.

[0012] The optical glass plate of aspect 6, in any one of aspects 1 to 5, has a density of 5.5 g / cm 3It is preferably as follows.

[0013] The light guide plate of aspect 7 is characterized by being composed of the optical glass plate according to any one of aspects 1 to 6.

[0014] The light guide plate of aspect 8 is preferably used, in aspect 7, in a wearable image display device selected from the group consisting of glasses with a projector, a glasses-type or goggle-type display, a virtual reality (VR) or augmented reality (AR) display device, and a virtual image display device.

[0015] The wearable image display device of aspect 9 is characterized by comprising the light guide plate of aspect 7 or aspect 8. Effects of the Invention

[0016] According to the present invention, it is possible to provide an optical glass plate having higher refractive index characteristics than conventional optical glass plates. Mode for Carrying Out the Invention

[0017] The optical glass plate of the present invention contains, by mass%, 0 to 12% of SiO₂, 0 to 10% of B₂O₃, 0 to 9% of BaO, 0 to 5% of ZnO, 2 to 10% of ZrO₂, 15 to 45% of La₂O₃, 0 to 15% of Gd₂O₃, 0 to 15% of Nb₂O₅, 0 to 10% of WO₃, 15 to 50% of TiO₂, and 0.1 to 10% of Y₂O₃, and the ratio of Y in cation% 3+ / (Gd 3+ +Y 3+ +Yb 3+ ) is 0.2 or more. The reason for limiting the glass composition as described above will be explained below. In the following description of the content of each component, "%" means "mass%" unless otherwise specified.

[0018] SiO2 is a component of the glass skeleton and improves the stability of vitrification and chemical durability. However, if its content is too high, the melting temperature becomes extremely high. When the melting temperature is high, transition metal components such as Nb and Ti are reduced, causing absorption in the visible range and making it easier for the internal transmittance to decrease. In addition, the refractive index tends to decrease. The lower limit of the SiO2 content is preferably 0%, 3%, 5%, 5.5%, and especially 6% or more, and the upper limit is preferably 12% or less, 11% or less, 10% or less, 9.5%, and especially 9% or less.

[0019] B2O3 is a component that contributes to the stability of vitrification. In particular, vitrification tends to be unstable when the refractive index nd is high, such as 2.00 or higher, but the stability of vitrification can be improved by including an appropriate amount of B2O3. The lower limit of the B2O3 content is preferably 0%, 0.1%, 0.2%, 0.5%, 1%, 2%, and especially 3% or higher, and the upper limit is preferably 10% or less, 8% or less, 7% or less, 6% or less, and especially 5% or less. If the B2O3 content is too low, it becomes difficult to obtain the above effects. On the other hand, if the B2O3 content is too high, the refractive index tends to decrease.

[0020] Furthermore, in order to improve the stability of vitrification and enhance mass productivity, it is preferable to appropriately adjust the ratio of SiO2 to B2O3. Specifically, the mass ratio of B2O3 / SiO2 is preferably 0.003 or higher, 0.005 or higher, 0.02 or higher, 0.04 or higher, 0.05 or higher, 0.1 or higher, 0.3 or higher, and particularly preferably 0.4 or higher, and 3 or lower, 2 or lower, 1.5 or lower, 1.2 or lower, 1 or lower, 0.8 or lower, 0.6 or lower, and particularly preferably 0.5 or lower. In this invention, "x / y" means the value obtained by dividing the content of x by the content of y.

[0021] Furthermore, in the present invention, Si is used in cation%. 4+ +B 3+ Si content 4+ and B 3+The total amount of Si is preferably 5% or more, 6% or more, and especially 7% or more. This improves the stability of vitrification. 4+ +B 3+ There is no particular upper limit to the content, but if it is too high, the refractive index tends to decrease and the melting temperature tends to increase, so it is preferable that it be 40% or less, 35% or less, 30% or less, 25% or less, 20% or less, 19% or less, 15% or less, and especially 14% or less.

[0022] The SiO2+B2O3 content (total amount of SiO2 and B2O3) is preferably 5% or more, 6% or more, or 7% or more. This enhances vitrification stability. If the SiO2+B2O3 content is too high, the refractive index decreases, so it is preferable to have a content of 10.4% or less, 9.7% or less, and especially 8% or less.

[0023] BaO is a component that stabilizes vitrification. However, as the BaO content increases, the density of the glass increases, and the weight of the optical glass plate tends to increase. Therefore, it is undesirable, especially for applications such as wearable image display devices. Accordingly, the lower limit of the BaO content is preferably 0%, 0.1%, 0.3%, and especially 1% or more, and the upper limit is preferably 9% or less, 8% or less, 5% or less, and especially 3% or less. When prioritizing weight reduction of the optical glass plate, the BaO content is preferably 1% or less, especially 0.5% or less, and most preferably no BaO at all.

[0024] ZnO is a component that promotes solubility (solubility of raw materials) in the composition system of the present invention. However, if the content is too high, it becomes difficult to obtain high refractive index properties, and devitrification resistance and acid resistance tend to decrease. Therefore, the lower limit of the ZnO content is preferably 0%, 0.3%, 0.5%, and particularly 1% or more, and the upper limit is preferably 5% or less, 4% or less, 3% or less, 2.8% or less, 2.5% or less, and particularly 2% or less.

[0025] ZrO2 is a component that enhances refractive index and chemical durability. However, if its content is too high, the melting temperature tends to become extremely high. Therefore, the lower limit of the ZrO2 content is preferably 2%, 3%, 4%, and especially 5%, and the upper limit is preferably 10% or less, 9.5%, 9%, and especially 8% or less.

[0026] La2O3 is a component that significantly increases the refractive index and improves the stability of vitrification. The lower limit of the La2O3 content is preferably 15%, 25%, 30%, and especially 35% or more, and the upper limit is preferably 45% or less, and especially 43% or less. If the La2O3 content is too low, it becomes difficult to obtain the above effects. On the other hand, if the La2O3 content is too high, the resistance to devitrification decreases, and mass production tends to be poor.

[0027] Gd2O3 is also a component that increases the refractive index and improves the stability of vitrification. The lower limit of the Gd2O3 content is preferably 0%, 1%, and especially 2% or more, and the upper limit is preferably 15% or less, 13% or less, 10% or less, 7% or less, and especially 6% or less. If the Gd2O3 content is too low, it becomes difficult to obtain the above effects. On the other hand, if the Gd2O3 content is too high, the resistance to devitrification decreases, which tends to make mass production difficult.

[0028] Nb2O5 is a component that significantly increases the refractive index of glass. However, if its content is too high, it can make vitrification difficult and reduce the light transmittance in the visible range. Therefore, the lower limit of the Nb2O5 content is preferably 0%, 3%, and especially 5%, and the upper limit is preferably 15% or less, 12%, 10%, and especially 8% or less.

[0029] WO3 is a component that increases the refractive index, but it tends to absorb visible light and reduce light transmittance. Therefore, the lower limit of the WO3 content is preferably 0%, 0.1%, and especially 1%, and the upper limit is preferably 10%, 9%, 8%, 6%, 5%, 3%, and especially 2%. From the viewpoint of increasing transmittance in the visible range, the WO3 content is preferably 1% or less, especially 0.5%, and most preferably no WO3 at all.

[0030] TiO2 is a component that significantly increases the refractive index of glass. However, if the content is too high, it becomes difficult to vitrify the glass, and the light transmittance in the visible range tends to decrease. Therefore, the lower limit of the TiO2 content is preferably 15% or more, 18% or more, 20% or more, 21% or more, 22% or more, and especially preferably 23% or more, and the upper limit is preferably 50% or less, 40% or less, 35% or less, 30% or less, 29% or less, and especially preferably 28% or less.

[0031] The upper limit of the TiO2+WO3 content (total amount of TiO2 and WO3) is preferably 60% or less, 50% or less, 40% or less, 35% or less, 30% or less, 29% or less, 28% or less, and especially preferably 25% or less, while the lower limit is preferably 15% or more, 18% or more, and especially preferably 20% or more. This makes it easier to increase the light transmittance in the visible range.

[0032] Y2O3 is a component that enhances refractive index and chemical durability, but if its content is too high, the melting temperature tends to become extremely high or the vitrification process becomes unstable. Therefore, the lower limit of the Y2O3 content is preferably 0.1% or more, 1% or more, 2% or more, 2.5% or more, and especially preferably 3% or more, and the upper limit is preferably 10% or less, 7% or less, 6% or less, 5% or less, and especially preferably 4% or less.

[0033] In addition to the above components, the optical glass plate of the present invention may also contain the following components.

[0034] Ga2O3 acts as an intermediate oxide, forming a glass skeleton and expanding the vitrification range. It also has the effect of increasing the refractive index. However, if the Ga2O3 content is too high, vitrification becomes difficult, and raw material costs tend to increase. Therefore, the lower limit of the Ga2O3 content is preferably 0%, 1%, and especially 2% or more, and the upper limit is preferably 10% or less, 7%, 6%, 5%, and especially 4% or less.

[0035] MgO, CaO, and SrO are components that stabilize vitrification. If their content is too high, the refractive index tends to decrease and the liquidus temperature tends to increase. The content of these components is preferably 5% or less, 2% or less, 1% or less, and especially 0.5% or less, respectively.

[0036] Ta2O5 is a component that increases the refractive index. However, if its content is too high, phase separation and devitrification are likely to occur. Also, since Ta2O5 is a rare and expensive component, a high content leads to higher raw material batch costs. In light of the above, the Ta2O5 content is preferably 5% or less, 3% or less, or 1% or less, and is particularly preferably absent.

[0037] Yb2O3 is also a component that increases the refractive index. However, if its content is too high, devitrification and striations are more likely to occur. Therefore, it is preferable that the Yb2O3 content be 10% or less, 8% or less, 5% or less, 3% or less, and especially 1% or less.

[0038] In the present invention, in order to increase the refractive index and visible light transmittance, and to improve the stability of vitrification, Y 3+ and Gd 3+ +Y 3+ +Yb 3+ It is preferable to appropriately adjust the ratio (cation ratio) of Y. 3+ / (Gd 3+ +Y 3+ +Yb 3+) is preferably 0.2 or higher, 0.25 or higher, 0.3 or higher, 0.4 or higher, 0.5 or higher, 0.52 or higher, 0.55 or higher, and especially preferably 0.61 or higher. The upper limit is preferably 1 or lower, 0.9 or lower, and especially preferably 0.8 or lower. Note that "Y 3+ / (Gd 3+ +Y 3+ +Yb 3+ )」 is Y 3+ The content of Gd 3+ , Y 3+ and Yb 3+ It means the value obtained by dividing by the total amount.

[0039] Al2O3 is an ingredient that improves water resistance. However, if its content is too high, devitrification is likely to occur. Therefore, the content of Al2O3 is preferably 5% or less, 3% or less, 1% or less, or 0.5% or less, and it is particularly preferable that it is substantially absent. In this specification, "substantially absent" means intentionally omitting it as a raw material, and does not exclude its inclusion as an unavoidable impurity. More specifically, in this specification, it means that the content of each component is less than 0.1%.

[0040] Li2O, Na2O, and K2O are components that lower the softening point, but if their content is too high, devitrification becomes more likely. Therefore, it is preferable that the content of these components be 10% or less, 5% or less, and 1% or less, respectively, and it is especially preferable that they are substantially absent. Furthermore, if two or more types of Li2O, Na2O, and K2O are included, it is preferable that their combined amounts be 10% or less, 5% or less, and 1% or less, respectively.

[0041] Furthermore, it is preferable to substantially omit the presence of As components (such as As2O3), Pb components (such as PbO), and fluorine components (such as F2) due to their significant environmental impact. Additionally, it is preferable to substantially omit Bi2O3 and TeO2, as these are coloring components that tend to reduce the transmittance in the visible spectrum.

[0042] Pt, Rh, and Fe2O3 are coloring components, and their content is preferable to be low because they tend to reduce the transmittance in the visible range. Specifically, for Pt, it is preferable to have a content of 10 ppm or less, 9 ppm or less, and especially 5 ppm or less; for Rh, it is preferable to have a content of 0.1 ppm or less, and especially 0.01 ppm or less; and for Fe2O3, it is preferable to have a content of 1 ppm or less, and especially 0.5 ppm or less. From the viewpoint of suppressing coloring, a lower Pt content is better, but this requires lowering the melting temperature, which tends to reduce solubility. Therefore, considering solubility, the lower limit of the Pt content is preferably 0.1 ppm or more, and especially 0.5 ppm or more.

[0043] The optical glass plate of the present invention may contain the clarifying agent components Cl, CeO2, SO2, Sb2O3, or SnO2 in amounts of 0.1% or less, respectively.

[0044] The refractive index (nd) of the optical glass plate of the present invention is preferably 2.01 or higher, 2.02 or higher, 2.04 or higher, 2.05 or higher, 2.06 or higher, 2.07 or higher, 2.09 or higher, 2.10 or higher, and particularly preferably 2.12 or higher. If the refractive index is too low, the field of view tends to be narrow when used as a light guide plate for wearable image display devices such as projector-equipped glasses, spectacle-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. On the other hand, if the refractive index is too high, defects such as devitrification and striations are more likely to occur, so the upper limit is preferably 2.3 or lower, and particularly preferably 2.2 or lower.

[0045] The Abbe number (νd) of the optical glass plate of the present invention is preferably 35 or less, 34 or less, 33 or less, 30 or less, 28 or less, and particularly 25 or less, taking into consideration the stability of vitrification. On the other hand, the lower limit is preferably 15 or more, 18 or more, and particularly 20 or more.

[0046] The internal transmittance of the 10mm thick optical glass plate of the present invention at 450nm is preferably 70% or more, 75% or more, 80% or more, and particularly preferably 85% or more. This makes it easier to increase the brightness of the image seen by the user in a wearable image display device using the optical glass plate of the present invention.

[0047] The liquidus temperature of the optical glass plate of the present invention is preferably 1350°C or lower, 1330°C or lower, and particularly preferably 1300°C or lower. Furthermore, the liquidus viscosity of the optical glass plate of the present invention is 10 0.1 dPa·s or higher, 10 0.2 dPa·s or higher, especially 10 1 It is preferable that the concentration be dPa·s or higher. This makes it less likely for devitrification to occur during melting and molding, thus improving mass production efficiency.

[0048] The optical glass plate of the present invention has a density of 5.5 g / cm³. 3 Below, 5.3g / cm 3 The following, in particular, is 5.1 g / cm³. 3 The following is preferable. If the density is too high, the weight of the wearable device using the optical glass plate of the present invention will increase, increasing discomfort when wearing the device. There is no particular lower limit to the density, but if it is too low, other properties such as optical properties tend to deteriorate, so 4 g / cm³ is preferable. 3 In particular, 4.5 g / cm³ 3 It is preferable that the above conditions are met.

[0049] The upper limit of the thickness of the optical glass plate of the present invention is preferably 1 mm or less, 0.8 mm or less, 0.6 mm or less, and particularly preferably 0.3 mm or less. If the thickness of the optical glass plate is too large, the weight of the wearable image display device using the optical glass plate will increase, increasing discomfort when the device is worn. On the other hand, if the thickness of the optical glass plate is too small, the mechanical strength tends to decrease, so the lower limit is preferably 0.01 mm or more, 0.02 mm or more, 0.03 mm or more, 0.04 mm or more, and particularly preferably 0.05 mm or more.

[0050] The shape of the optical glass plate of the present invention is, for example, a plate shape with a planar shape such as a circle, ellipse, or polygon such as a rectangle. In this case, the major axis (diameter in the case of a circle) of the optical glass plate is preferably 100 mm or more, 120 mm or more, 150 mm or more, 160 mm or more, 170 mm or more, 180 mm or more, 190 mm or more, and particularly 200 mm or more. If the major axis of the optical glass plate is too small, it becomes difficult to use it for applications such as wearable image display devices. It also tends to be difficult to mass-produce. There is no particular upper limit to the major axis of the optical glass plate, but in reality it is 1000 mm or less.

[0051] The optical glass plate of the present invention can be manufactured by first melting raw materials that have been blended to obtain a predetermined glass composition, then shaping the molten glass, and subsequently performing post-processing such as cutting and polishing as necessary. For melting, platinum crucibles, aluminal crucibles, quartz crucibles, aluminum nitride crucibles, boron nitride crucibles, zirconium crucibles, silicon carbide crucibles, molybdenum crucibles, tungsten crucibles, etc. The form of the raw materials is not particularly limited, and for example, powdered raw materials or glass cullet can be used.

[0052] Alternatively, an optical glass plate may be manufactured by first producing glass cullet by melting raw materials that have been blended to obtain a predetermined glass composition, and then reheating only the glass cullet.

[0053] The melting temperature is preferably 1400°C or lower, 1350°C or lower, 1300°C or lower, and particularly 1280°C or lower. If the melting temperature is too high, components of the molten container (Pt, Rh, etc.) tend to dissolve into the molten glass, and the light transmittance of the resulting optical glass plate tends to decrease. On the other hand, if the melting temperature is too low, bubbles and foreign matter (for example, foreign matter derived from undissolved material) tend to be generated. Therefore, in order to reduce bubbles and foreign matter in the glass, the melting temperature is preferably 1200°C or higher, and particularly 1250°C or higher.

[0054] The optical glass plate of the present invention is suitable as a light guide plate, which is a component of a wearable image display device selected from projector-equipped glasses, spectacle-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. The light guide plate is used in the so-called spectacle lens portion of the wearable image display device and plays the role of guiding the light emitted from the image display element of the wearable image display device and directing it toward the user's pupil. Preferably, a diffraction grating is provided on the surface of the light guide plate to diffract the light emitted from the image display element into the light guide plate. [Examples]

[0055] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0056] Tables 1-9 show examples of the present invention (No. 1-10, No. 13-49) and comparative examples (No. 11, 12).

[0057] [Table 1]

[0058] [Table 2]

[0059] [Table 3]

[0060] [Table 4]

[0061] [Table 5]

[0062] [Table 6]

[0063] [Table 7]

[0064] [Table 8]

[0065] [Table 9]

[0066] Glass raw materials, prepared to match the compositions shown in Tables 1-9, were melted in a platinum crucible at 1250-1400°C for 2 hours. Subsequently, the molten glass was poured onto a carbon plate and annealed for 2-48 hours to obtain glass samples.

[0067] The refractive index (nd), Abbe number (νd), internal transmittance (τ450), liquidus temperature, liquidus viscosity, and density of the obtained glass samples were measured as follows. The results are shown in Tables 1 to 9.

[0068] The refractive index is shown as a measurement for the d-line (587.6 nm) of a helium lamp.

[0069] The Abbe number was calculated using the refractive index of the d line mentioned above, the refractive index of the F line (486.1 nm) of the hydrogen lamp, and the refractive index of the C line (656.3 nm) of the hydrogen lamp, using the formula (νd) = [(nd-1) / (nF-nC)].

[0070] The internal transmittance was measured as follows: Optically polished samples with thicknesses of 10 mm ± 0.1 mm and 3 mm ± 0.1 mm were prepared, and the optical transmittance (linear transmittance), including surface reflection loss, was measured at 1 nm intervals using a spectrophotometer (Shimadzu UV-3100). The internal transmittance curve for the 10 mm thick sample was obtained from the optical transmittance data for the 10 mm and 3 mm thick samples. The internal transmittance at a wavelength of 450 nm was read from the obtained internal transmittance curve.

[0071] The liquidus temperature and liquidus viscosity were determined as follows.

[0072] The crushed glass sample was melted at 1350°C and cooled at a rate of -1.5°C / min while being observed with a high-temperature observation microscope (MS-18SP, manufactured by Yonekura Seisakusho). The temperature at which precipitated crystals were confirmed was defined as the liquidus temperature (crystal precipitation temperature).

[0073] Separately, a block of glass sample was placed in an alumina crucible and heated and melted. The viscosity of the resulting glass melt was determined at multiple temperatures using the platinum ball pulling method. Subsequently, the constants of the Vogel-Fulcher equation were calculated using the measured glass viscosity values ​​to create a viscosity curve. In the created viscosity curve, the viscosity corresponding to the liquidus temperature determined above was defined as the liquidus viscosity.

[0074] The density was measured using the Archimedes method with a glass sample weighing approximately 10 g.

[0075] As shown in Tables 1-9, the glass samples No. 1-10 and No. 13-49, which are examples, had the desired optical constants, with refractive indices of 2.06-2.15 and Abbe numbers of 20.5-32.7. On the other hand, the glass sample No. 11, which is a comparative example, devitrified. Also, the glass sample No. 12, which is a comparative example, had a low refractive index of 2.00. [Industrial applicability]

[0076] The optical glass plate of the present invention is suitable as a light guide plate used in wearable image display devices selected from projector-equipped glasses, spectacle-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices.

Claims

1. In mass%, SiO ２ 0 to 12%, B ２ O ３ 0 to 10%, BaO 0 to 9%, ZnO 0 to 5%, ZrO ２ 2 to 10%, La ２ O ３ 15 to 45%, Gd ２ O ３ 0 to 15%, Nb ２ O ５ 0 to 15%, WO ３ 0 to 10%, TiO ２ 15 to 50%, and Y ２ O ３ 0.1 to 10%, wherein the cation percentage ratio Y ３＋ / (Gd ３＋ +Y ３＋ +Yb ３＋ ) is 0.2 or more, a refractive index nd is 2.01 or more, an Abbe number νd is 35 or less, and an internal transmittance τ450 at a wavelength of 450 nm for a thickness of 10 mm is 70% or more. An optical glass plate characterized by the above.

2. The optical glass plate according to claim 1, characterized in that its thickness is 1 mm or less.

3. The optical glass plate according to claim 1 or 2, characterized in that the major axis of the main surface is 100 mm or more.

4. Liquid phase viscosity is 10 ０．１ The optical glass plate according to claim 1 or 2, characterized in that it is dPa·s or higher.

5. Density is 5.5 g / cm³ ３ The optical glass plate according to claim 1 or 2, characterized in that it is as follows:

6. A light guide plate characterized by being made of an optical glass plate as described in claim 1 or 2.

7. The light guide plate according to claim 6, characterized in that it is used in a wearable image display device selected from projector-equipped glasses, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices.

8. A wearable image display device characterized by comprising the light guide plate described in claim 6.

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