JP7662985B2 - Optical Glass - Google Patents

Description

The present invention relates to optical glass used as a light guide plate for wearable image display devices.

Glass plates are used as components of wearable image display devices such as glasses with projectors, eyeglasses or goggles, virtual reality (VR) or augmented reality (AR) displays, and virtual image displays. The glass plate functions as a see-through light guide plate, for example, and allows the user to see the image displayed on the glass plate while looking at the outside scenery through the glass plate. It is also possible to realize a 3D display using a technology that projects different images on the left and right sides of the glasses, or to realize a virtual reality space using a technology that uses the crystalline lens of the eye to connect to the retina. The glass plate is required to have a high refractive index in terms of widening the angle of the image, increasing brightness and contrast, improving light guide properties, etc. (see Patent Document 1, for example)

JP 2017-32673 A

In order to improve the refractive index of glass, it is effective to include _TiO2 or _{Nb2O5 ,} which are components that contribute to a high refractive index, in the glass. On the other hand, when _TiO2 or _Nb2O5 is included in the glass, the liquidus temperature may decrease and the vitrification _{may become unstable. Therefore, it is considered to include B2O3 in} order to stabilize the vitrification. However, when _{B2O3 is} included in the glass, there is a problem that _the chemical durability is easily decreased.

In view of the above, an object of the present invention is to provide an optical glass that contains B ₂ O ₃ in addition to TiO ₂ and Nb ₂ O ₅ as part of its glass composition and that has a high refractive index and excellent chemical durability.

As a result of intensive research, the present inventors have found that the above-mentioned problems _can be solved by specifying the basicity, which is an index showing the state of non- _bridging oxygen (NBO) in optical glass containing _{B2O3 together with TiO2 and Nb2O5} , within a predetermined range.

That is, the optical glass of the present invention _is characterized by comprising at least one selected from _TiO2 and _Nb2O5 , _{and B2O3} as a glass composition, having a refractive index nd of 1.95 or more, and a basicity of 11 or more.

The optical glass of the present invention preferably has a coloring degree λ ₇₀ of 470 nm or less. In the present invention, the "coloring degree λ ₇₀ " means the wavelength at which the light transmittance, including reflection loss, is 70% at a thickness of 10 mm.

The optical glass of the present invention preferably has water resistance and acid resistance of grade 1 or 2 according to JOGIS.

The optical glass of the present invention preferably contains, by mass%, 10-31% TiO ₂ +Nb ₂ O ₅ , 4-15% B ₂ O ₃ , 3% or more SiO ₂ , 0-15% RO (R is at least one selected from Mg, Ca, Sr and Ba), and 0-5% Ta ₂ O ₅ .

The optical glass of the present invention preferably contains, in mass %, 8 to less than 20% TiO ₂ , 40 to 65% Ln ₂ O ₃ (Ln is at least one selected from La, Gd, Y and Yb), 0 to 0.5% ZnO, 0 to 1% Al ₂ O ₃ , and 0 to 0.2% WO ₃ .

The optical glass of the present invention preferably contains substantially no Bi ₂ O ₃ , TeO ₂ and PbO.

The optical glass of the present invention preferably has a Pt content of 10 ppm or less.

The optical glass of the present invention preferably has an Abbe number (νd) of 20 to 35.

The optical glass of the present invention preferably has a liquidus temperature of 1250°C or less.

The optical glass plate of the present invention is characterized by being made of the optical glass described above.

The optical glass plate of the present invention preferably has a plate thickness of 0.01 to 5 mm.

The light guide plate of the present invention is characterized by being made of the above-mentioned optical glass plate.

The light guide plate of the present invention is preferably used in a wearable image display device selected from 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.

The wearable image display device of the present invention is characterized by having the above-mentioned light guide plate.

According to the present invention, it is possible to provide an optical glass that contains B ₂ O ₃ in addition to TiO ₂ and Nb ₂ O ₅ as a glass composition and has a high refractive index and excellent chemical durability.

_{The optical glass of the present invention contains at least one selected from TiO2 and Nb2O5, and B2O3 as a glass composition} . The preferred contents of these components are described below. In the following description of the contents of each component, "%" means "mass%" unless otherwise specified.

_TiO2 and _Nb2O5 are components that significantly increase the refractive index of glass. They also have the effect of improving chemical durability. However, if these components are too much, the transmittance in the visible range may decrease or vitrification may become difficult. Therefore, _the lower limit of the content _{of TiO2} + _Nb2O5 is preferably 10% or more, 11% or more, 12% or more, 14% or more, and particularly 16% or more, and the upper limit is particularly preferably 31% or less, 29% or less, 25% or less, and particularly preferably 20% or less. The lower limit of the content of _TiO2 is preferably 8% or more, 9% or more, 11% or more, and particularly preferably 12% or more, and the lower limit is preferably less than 20%, 18% or less, 17% or less, and particularly preferably 16% or less. The lower limit of _{the Nb2O5} content is preferably 1% or more, 1.7% or more, 2% or more, 2.5% or more, 3.3% or more, 4.4% or more, 5.3% or more, particularly preferably 6.1 or more, and the upper limit is preferably 25% or less, 22% or less, 20% or less, 18% or less, 15% or less, 14% or less, 10% or less, particularly preferably 9% or less. In the present invention, "x+y+..." means the total amount of each component.

In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible range, it is preferable to appropriately adjust the ratio of _TiO2 to _Nb2O5 . Specifically, it is preferable that the mass ratio _{of TiO2} / _Nb2O5 is 0.3 or more, 0.5 or _more , 0.8 or more, and particularly 1 or more. There is no particular upper limit, but in reality it is 29 or less, 20 or less, or even 10 or less.

B ₂ O ₃ is a component that contributes to the stability of vitrification in particular in glasses containing TiO ₂ or Nb ₂ O _5. The lower limit of the content of _{B 2} O ₃ is preferably 4% or more, 5% or more, 6.5% or more, 7% or more, 7.5% or more, 8% or more, 8.3% or more, and particularly 9% or more, and the upper limit is preferably 15% or less, 13% or less, 12% or less, 11.5% or less, 11% or less, 10.5 _{% or less, and particularly less than 10.5%. If the content of B 2 O 3} is too small, it is difficult to obtain the above effect. On the other hand, if the content of _{B 2} O ₃ is too large, the refractive index tends to decrease. In addition to containing B 2 O 3, the basicity of the glass can be set to 11 or more to improve chemical durability, particularly acid resistance.

The optical glass of the present invention may contain the following components in addition to TiO ₂ , Nb ₂ O ₅ and B ₂ O ₃ .

_SiO2 is a glass skeleton component, and is a component that improves the stability of vitrification and chemical durability. However, if the content is too high, the melting temperature becomes extremely high. As a result, Nb and Ti are easily reduced, and the internal transmittance is easily reduced. In addition, the refractive index tends to decrease. The lower limit of the content of _SiO2 is preferably 3% or more, 3.5% or more, 4% or more, and particularly 4.5% or more, and the upper limit is preferably 20% or less, 18% or less, 15% or less, 13% or less, 12% or less, 11% or less, 10% or less, 9% or less, and particularly 8% or less.

The alkaline earth component RO (R is at least one selected from Ca, Sr, and Ba) is a component that stabilizes vitrification. If the content is too high, the refractive index tends to decrease and the liquidus temperature tends to increase. In particular, with regard to BaO, if the content is high, the density of the glass increases, and the weight of the optical element made of the optical glass of the present invention tends to increase. For this reason, it is particularly undesirable for applications such as wearable image display devices. Therefore, the content of RO is preferably 0-15%, 0-10%, 0-5%, 0-2%, 0-1%, and especially 0-0.5%. The preferred ranges of the contents of each of the CaO, SrO, and BaO components are also preferably the same as above.

Ta ₂ O ₅ is a component that increases the refractive index. However, if the content is too high, phase separation and devitrification are likely to occur. In addition, since Ta ₂ O ₅ is a rare and expensive component, if the content is high, the raw material batch cost will increase. In view of the above, the content of Ta ₂ O ₅ is preferably 0 to 5%, 0 to 3%, or 0 to 1%, and it is particularly preferable that it is not contained.

In order to increase the stability of vitrification and improve _mass productivity, it is preferable to appropriately adjust the ratio of _{SiO2 to B2O3} . Specifically, the mass ratio _B2O3 / _SiO2 is preferably 1 or more, 1.3 or more, particularly 1.5 or more, and is preferably 2.5 or less, 2 or less, particularly 1.96 or less. In the present invention, "x/y" means the value obtained by dividing the content of x by the content of y.

Al ₂ O ₃ is a component that improves water resistance. However, if the content is too high, the glass is prone to devitrification. Therefore, the content of Al ₂ O ₃ is preferably 0 to 1%, 0 to 0.5%, and it is particularly preferable that no Al 2 O 3 is contained.

_La2O3 is _a component that significantly increases the refractive index and improves the stability of vitrification.The lower limit of the content _{of La2O3} is preferably 27% or more, 30% or more, 35% or more, 38% or more, 40% or more, 42% or more, and particularly 45% or more, and the upper limit is preferably 50% or less, 49.8% or less, 49.5% or less, 49% or less, and particularly 48.5% or less.If the _content of _La2O3 is too small, it is difficult to obtain the above effects.On the other hand, if the content of _La2O3 is too large, _the devitrification resistance decreases and mass productivity tends to be poor.

_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 6% or more, particularly preferably 6.5% or more, and the upper limit is preferably 25% or less, 20% or less, 14% or less, 10% or less, particularly preferably 9% or less.

_Y2O3 is also _a component that increases the refractive index, but if its content is too high, vitrification tends to become unstable. Therefore, the lower limit of the _Y2O3 content is preferably 0% or more, particularly 0.1% or more, and the _upper limit is preferably 8% or less, 5% or less, 3% or less, particularly less than 1%.

Yb ₂ O ₃ is also a component that increases the refractive index. However, if the content is too high, devitrification and striae tend to occur. Therefore, the content of Yb ₂ O ₃ is preferably 0 to 10%, particularly 0 to 8%.

The content of _Ln2O3 (wherein Ln is at least one selected from La, Gd, Y, and Yb) _is preferably 40% or more, 45% or more, and particularly preferably 48% or more. This makes it possible to increase the refractive index and light transmittance in the visible range. There is no particular upper limit to the content of _Ln2O3 , but if it is too high, devitrification is likely to occur, so _it is preferably 65% or less, and particularly preferably 60% or less.

In the composition of the present invention, ZnO is a component that promotes devitrification and reduces acid resistance, so its content is preferably low. Specifically, the ZnO content is preferably 0.5% or less, 0.1% or less, and it is particularly preferable that no ZnO is contained.

_WO3 is a component that increases the refractive index, but absorbs light in the visible region and reduces the transmittance. The content of _WO3 is preferably 0 to 0.2%, more preferably 0 to 0.1%, and particularly preferably zero.

_ZrO2 is a component that increases the refractive index and chemical durability. The lower limit of the content of _ZrO2 is preferably 0% or more, more than 0%, 1% or more, 3% or more, 4% or more, and particularly 5% or more, and the upper limit is preferably 10% or less, 9% or less, 8% or less, 7.5% or less, and particularly 7% or less. If the content of _ZrO2 is too high, devitrification is likely to occur.

Li ₂ O, Na ₂ O, and K ₂ O are components that lower the softening point, but if the content is too high, devitrification tends to occur. Therefore, the content of these components is preferably 0 to 3%, and 0 to 1%, respectively, and it is particularly preferable that they are not contained.

In the present invention, in order to obtain a glass having a high refractive index and excellent vitrification stability, it is preferable to appropriately adjust _the total amount _{of SiO2} and _B2O3 and the ratio of _Ln2O3 . Specifically, the lower limit of ( _SiO2 + _B2O3 )/ _Ln2O3 is preferably 0.15 or more, 0.2 or more, and particularly preferably 0.25 or more, and _the upper limit is preferably 0.9 or less, 0.6 or less, _and particularly preferably 0.5 or less.

In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible range, it is preferable to appropriately adjust the ratios of TiO ₂ , Nb ₂ O ₅ and ZrO _2. Specifically, the lower limit of the mass ratio Nb ₂ O ₅ /(TiO ₂ +Nb ₂ O ₅ +ZrO ₂ ) is preferably 0.1 or more, 0.15 or more, and particularly preferably 0.2 or more, and the upper limit is preferably 0.46 or less, 0.4 or less, and particularly preferably 0.37 or less.

In the present invention, in order to obtain a glass having excellent transmittance in the visible region, it is preferable to appropriately adjust the total amount of TiO ₂ , Nb ₂ O ₅ and WO _3. Specifically, the content of TiO ₂ + Nb ₂ O ₅ + WO ₃ is preferably 31% or less, 29% or less, 25% or less, and particularly preferably 20% or less. However, if the contents of these components are too small, it becomes difficult to obtain the desired high refractive index characteristics, so the lower limit of the content of TiO ₂ + Nb ₂ O ₅ + WO ₃ is preferably 10% or more, 11% or more, and particularly preferably 12% or more.

In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible range, it is preferable to appropriately adjust the ratios of TiO ₂ , Nb ₂ O ₅ and WO _3. Specifically, the lower limit of the mass ratio Nb ₂ O ₅ /(TiO ₂ +Nb ₂ O ₅ +WO ₃ ) is preferably 0.15 or more, 0.2 or more, and particularly preferably 0.3 or more, and the upper limit is preferably 0.8 or less, 0.6 or less, and particularly preferably 0.5 or less.

In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, it is preferable to appropriately adjust the ratio of Y ₂ O ₃ to Ln ₂ O _3. Specifically, the lower limit of Y ₂ O ₃ /Ln ₂ O ₃ is preferably 0 or more, 0.005 or more, and particularly preferably 0.01 or more, and the upper limit is preferably 0.1 or less, 0.05 or less, and particularly preferably 0.3 or less.

In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, it is preferable to appropriately adjust the ratio of Gd ₂ O ₃ to Ln ₂ O _3. Specifically, the lower limit of Gd ₂ O ₃ /Ln ₂ O ₃ is preferably 0.1 or more, particularly preferably 0.12 or more, and the upper limit is preferably 0.25 or less, particularly preferably 0.2 or less.

In the present invention, in order to increase the refractive index and the light transmittance in the visible range and to improve the stability of vitrification, it is preferable to appropriately adjust the ratio of _the total amount of _TiO2 and _B2O3 to the total _amount of _Nb2O5 and _WO3 . Specifically, the lower limit of ( _TiO2 + _B2O3 )/( _Nb2O5 + _{WO3 )} is preferably _1.6 or more, 1.8 or more, and particularly preferably 2 or more, and the upper limit is preferably 10 or less, 4 or less, and particularly preferably 3.5 or less.

In addition, it is preferable that As components (As ₂ O ₃ , etc.), Pb components (PbO, etc.) and fluorine components (F ₂ , etc.) are not substantially contained because they have a large environmental load. In addition, Bi ₂ O ₃ and TeO ₂ are coloring components, and are likely to reduce the transmittance in the visible range, so it is preferable that they are not substantially contained. Here, "substantially not contained" means that they are not intentionally contained as raw materials, and does not exclude the inclusion of unavoidable impurities. Objectively, it means that the content of each of the above components is less than 0.1%.

Pt is a coloring component that tends to reduce transmittance in the visible range, so its content is preferably 10 ppm or less.

The optical glass of the present invention may contain fining components Cl, _CeO2 , _SO2 , _Sb2O3 , or _SnO2 in a proportion of 0.1% or less _each .

The optical glass of the present invention has a glass basicity defined as (sum of moles of oxygen atoms/sum of field strengths of cations) x 100 of 11 or more, preferably 12 or more, and particularly preferably 12.5 or more. In the present invention, "field strength (hereinafter abbreviated as F.S.)" is calculated by the following formula:

F.S.=Z/ ^r2 (Z is the ionic valence, and r is the ionic radius (Å))

In the present invention, the values of Z and r are those in Table 1. For r, reference is made to the value described in "Chemical Handbook, Basic Edition, Revised 2nd Edition (published by Maruzen Co., Ltd. in 1975)" and the like. However, the ionic radius of B3 ⁺ and P5 ⁺ is set to 0.32, which is a value assuming that they form a tetrahedral structure together with oxygen ions in glass (specifically, a tetrahedral structure is formed by coordinating four ^O2- ions around B3 ⁺ or P5 ⁺ at the center).

Basicity is an index showing the state of electron or oxygen binding by cations. The higher the basicity, the weaker the binding of electrons or oxygen by cations. Oxygen is likely to be arranged around boron, which has low chemical durability, and boron is stable in the glass, which makes it easier to improve chemical durability. If the binding of electrons or oxygen by cations becomes too weak, vitrification becomes unstable and, conversely, chemical durability tends to decrease, so the basicity is preferably 17 or less, 16 or less, and particularly 15 or less.

Furthermore, when the binding of electrons or oxygen by cations is weakened, Ti ions and Nb ions are more likely to be oxidized, and the proportion of Ti4 ⁺ and Nb5 ⁺ , which do not reduce the visible light transmittance, tends to increase, thereby improving the visible light transmittance of the optical glass of the present invention.

The lower limit of the refractive index (nd) of the optical glass of the present invention is 1.95 or more, preferably 1.96 or more. 1.965 or more, 1.966 or more, 1.97 or more, and particularly preferably 1.98 or more, and the upper limit is preferably 2.05 or less, 2.04 or less, 2.03 or less, 2.01 or less, and particularly preferably 2.00 or less. If the refractive index is too low, the viewing angle tends to be narrow when used as a light guide plate for wearable image display devices such as glasses with projectors, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) displays, and virtual image displays. On the other hand, if the refractive index is too high, the glass is more likely to have defects such as devitrification and striae.

The coloring degree _λ70 of the optical glass of the present invention is preferably 470 nm or less, particularly preferably 460 nm or less. In this way, in a wearable image display device using the optical glass of the present invention, the brightness of the image seen by the user tends to be increased.

The Abbe number (νd) of the optical glass of the present invention is not particularly limited, but in consideration of the stability of vitrification, it is preferable that the lower limit is 20 or more, 22 or more, and particularly 25 or more, and the upper limit is 35 or less, 32 or less, and particularly 30 or less.

The liquidus temperature of the optical glass of the present invention is preferably 1250°C or less, 1200°C or less, 1150°C or less, 1100°C or less, and particularly preferably 1070°C or less. This makes it less susceptible to devitrification during melting or molding, which makes it easier to improve mass productivity.

The optical glass of the present invention preferably has a density of 5.5 g/cm3 or ^less , 5.3 g/ ^cm3 or less, and particularly preferably 5.1 g/cm3 or ^less . If the density is too high, the weight of a wearable device using the optical glass of the present invention increases, 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 decrease, so it is preferably 4.0 g/cm3 or ^more , and particularly preferably 4.5 g/ ^cm3 or more.

The optical glass of the present invention preferably has a thermal expansion coefficient at 30 to 300° C. of 95×10 ⁻⁷ /° C. or less, 91×10 ⁻⁷ /° C. or less, and particularly preferably 88×10 ⁻⁷ /° C. or less. If the thermal expansion coefficient is too high, the glass is more likely to break due to thermal shock. There is no particular lower limit for the thermal expansion coefficient, but if it is too low, other properties such as optical properties are reduced, so it is preferably 75×10 ⁻⁷ /° C. or more, and particularly preferably 80×10 ⁻⁷ /° C. or more.

The lower limit of the thickness of the optical glass plate made of the optical glass of the present invention 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, and the upper limit is preferably 5 mm or less, 3 mm or less, 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 small, the mechanical strength is likely to decrease. On the other hand, if the thickness of the optical glass plate is too large, the weight of the wearable image display device using the optical glass plate increases, increasing the discomfort when wearing the device.

The shape of the optical glass plate of the present invention is, for example, a plate shape having a planar shape of a circle, an ellipse, or a polygon such as a rectangle. In this case, the major axis of the optical glass plate (diameter in the case of a circle) is preferably 50 mm or more, 80 mm or more, 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. In addition, mass productivity tends to be poor. There is no particular limit to the upper limit of the major axis of the optical glass plate, but in reality it is 1000 mm or less.

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 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. The light guide plate is used in the so-called glasses lens portion of the wearable image display device, and serves to guide light emitted from an image display element provided in the wearable image display device and emit it toward the user's pupil. It is preferable that a diffraction grating is provided on the surface of the light guide plate to diffract the light emitted from the image display element inside the light guide plate.

The present invention will be described in detail below using examples, but the present invention is not limited to these examples.

Table 2 shows examples of the present invention (No. 1 to 9) and a comparative example (No. 10).

First, the glass raw materials were mixed to obtain the compositions shown in Table 2, and melted in a platinum crucible at 1200-1350°C for 2 hours. The molten glass was poured onto a carbon plate and further annealed to prepare samples suitable for each measurement.

The Pt content, water resistance, acid resistance, coloring degree λ ₇₀ , liquidus temperature, liquidus viscosity, refractive index (nd), Abbe number (νd), density, and thermal expansion coefficient of the obtained sample were measured. The results are shown in Table 2.

The Pt content was measured by an ICP mass spectrometer after decomposing the crushed glass sample with a mixed acid containing HF, HClO ₄ , HNO ₃ and HCl.

Water resistance and acid resistance were measured using the powder method specified in JOGIS.

The coloring degree λ ₇₀ was measured as follows. For an optically polished sample having a thickness of 10 mm±0.1 mm, the light transmittance (linear transmittance) including the surface reflection loss was measured at intervals of 0.5 nm using a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation). The wavelength at which the light transmittance became 70% was read from the light transmittance curve obtained by the measurement.

The liquidus temperature and liquidus viscosity were measured as follows:

The glass was remelted in an electric furnace at 1200°C for 0.5 hours, then held in an electric furnace with a temperature gradient for 18 hours, then removed from the furnace and allowed to cool in air, and the positions of devitrified matter were measured using an optical microscope.

Separately, a lump glass sample was placed in an alumina crucible and heated to melt. The viscosity of the resulting molten glass was measured at multiple temperatures using the platinum ball pulling method. Next, the measured glass viscosity was used to calculate the constants of the Vogel-Fulcher equation and create a viscosity curve.

The liquidus temperature and viscosity curve obtained in the above manner were used to determine the viscosity corresponding to the liquidus temperature (liquidus viscosity).

The refractive index is shown as a measured value for the d line (587.6 nm) of a helium lamp. The Abbe number was calculated from the Abbe number (νd) = [(nd-1)/(nF-nC)] using the refractive index of the d line, the F line (486.1 nm) of a hydrogen lamp, and the C line (656.3 nm) of a hydrogen lamp.

The density was measured by Archimedes' method using a glass sample weighing approximately 10 g.

The thermal expansion coefficient was measured using a dilatometer over a temperature range of 30 to 300°C using glass samples molded to approximately 5φ x 20 mm.

As shown in Table 2, the samples No. 1 to No. 9, which are examples, had a basicity of 11.6 to 17, and were both Class 1 in terms of water resistance and acid resistance. They also had high refractive indices of 1.952 to 2.04. On the other hand, the sample No. 10, which is a comparative example, had a basicity of 9.3, poor Class 4 acid resistance, and a low refractive index of 1.81.

The optical glass of the present invention is suitable as a light guide plate for use in a wearable image display device selected from 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.

Claims (14)

An optical glass comprising, as a glass composition, at least one selected _{from TiO2} and _Nb2O5 , _{and B2O3} , and containing, by mass%, 35-46.9 % _La2O3 , ₁₁ -less than 20% _TiO2 , 1-7.6 % _Nb2O5 , 0-7.9% _Gd2O3 , _0-0.2 % _WO3 , _and 0.5% or less ZnO, and having a refractive index nd of 1.95 or more and a basicity of 11 or more. 2. The optical glass according to claim 1, wherein the color degree λ ₇₀ is 470 nm or less. The optical glass according to claim 1 or 2, characterized in that its water resistance and acid resistance according to JOGIS are class 1 or 2. The optical glass according to any one of claims 1 to 3, characterized in that it contains, by mass%, 12 to 25% TiO ₂ +Nb ₂ O ₅ , 4 to 15% B ₂ O ₃ , 3% or more SiO ₂ , 0 to 15% RO (R is at least one selected from Mg, Ca, Sr and Ba), and 0 to 5% Ta ₂ O ₅ . 5. The optical glass according to claim ₄ , containing, by mass % , 40 to 65% _Ln2O3 (Ln is at least one selected from La, Gd, Y and Yb) and ₀ to 1% _Al2O3 . 6. The optical glass according to claim 1, which is substantially free of Bi ₂ O ₃ , TeO ₂ and PbO. The optical glass according to any one of claims 1 to 6, characterized in that the Pt content is 10 ppm or less. The optical glass according to any one of claims 1 to 7, characterized in that the Abbe number (νd) is 20 to 35. The optical glass according to any one of claims 1 to 8, characterized in that the liquidus temperature is 1250°C or less. An optical glass plate comprising the optical glass according to any one of claims 1 to 9. The optical glass plate according to claim 10, characterized in that the plate thickness is 0.01 to 5 mm. A light guide plate comprising the optical glass plate according to claim 10 or 11. The light guide plate according to claim 12, characterized in that it is used in a wearable image display device selected from 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. A wearable image display device comprising the light guide plate according to claim 12 or 13.