JP2021102549A - Optical glass - Google Patents

Abstract

To provide optical glass containing TiO2 or Nb2O5 and B2O3 as glass composition, having high refractive index and excellent chemical resistance.SOLUTION: Optical glass characterized by a glass composition comprising at least one selected from TiO2 and Nb2O5 and B2O3, having a refractive index nd of 1.95 or larger, and a basicity of 11 or larger.SELECTED DRAWING: None

Description

The present invention relates to optical glass used as a light guide plate or the like of a wearable image display device.

Glass plates are used as components of wearable image display devices such as eyeglasses with projectors, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. The glass plate functions as, for example, a see-through light guide plate, and the image displayed on the glass plate can be seen while looking at the outside scenery through the glass plate. In addition, it is also possible to realize 3D display by using the technology of projecting different images on the left and right of the glasses, and to realize the virtual reality space by using the technology of connecting to the retina using the crystalline lens of the eye. is there. The glass plate is required to have a high refractive index in terms of wide-angle image, high brightness / high contrast, improved light guide characteristics, and the like (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2017-32673

In order to improve the refractive index of the glass, it is effective to contain _{TiO 2} and Nb ₂ O ₅ which are components contributing to the high refractive index in the glass. On the other hand, if TiO ₂ or Nb ₂ O ₅ is contained in the glass, the liquidus temperature may decrease and the vitrification may become unstable. Therefore, it is conceivable to contain _{B 2} O ₃ in order to stabilize vitrification. However, when B ₂ O ₃ is contained in the glass, there is a problem that the chemical durability tends to decrease.

In view of the above, it is an object of the present invention _{to provide an optical glass containing B 2} O ₃ together with _{TiO 2} and N _{b 2} O ₅ as a glass composition, having a high refractive index and excellent chemical durability.

As a result of diligent studies by the present inventors, in _{an optical glass containing B 2} O ₃ together with _{TiO 2} and Nb ₂ O ₅ , the basicity, which is an index indicating the state of non-crosslinked oxygen (NBO) in the glass, is determined. It was found that the above-mentioned problems can be solved by defining the above range.

That is, the optical glass of the present invention contains at least one selected from _{TiO 2} and Nb ₂ O _{5 and B 2} O ₃ as a glass composition, has a refractive index of 1.95 or more, and has a basicity of 11 or more. It is characterized by being.

The optical glass of the present invention _{preferably has a coloration degree λ 70} of 470 nm or less. In the present invention, the “coloring degree λ ₇₀ ” means a wavelength at which the light transmittance including the reflection loss becomes 70% at a thickness of 10 mm.

The optical glass of the present invention preferably has water resistance and acid resistance according to JOBIS of 1st to 2nd grade.

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

The optical glass of the present invention, in _mass% TiO 2 less than _8-20%, (at least one Ln is selected La, Gd, Y and _{Yb) Ln 2 O 3 40~65%} , ZnO 0~0 It preferably contains 5.5%, Al ₂ O _{30 to 1} %, and WO _{30 to 0.2%.}

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 liquid phase temperature of 1250 ° C. or lower.

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

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 comprising the above-mentioned optical glass plate.

The light guide plate of the present invention is used in glasses with a projector, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and wearable image display devices selected from virtual image display devices. Is preferable.

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

According to the present invention, _{it is possible to provide an optical glass containing B 2} O ₃ together with _{TiO 2} and Nb ₂ O ₅ as a glass composition, having a high refractive index and excellent chemical durability.

The optical glass of the present invention contains at least one selected from _{TiO 2} and Nb ₂ O _{5 as a glass composition and B 2} O _3. The preferable contents of these components and the like will be described below. In the following description of the content of each component, "%" means "mass%" unless otherwise specified.

TiO ₂ and Nb ₂ O ₅ are components that significantly increase the refractive index of glass. It also has the effect of improving chemical durability. However, if these components are too large, the transmittance in the visible region may decrease or it may be difficult to vitrify. Therefore, _{the lower limit of the content of TiO 2} + Nb ₂ O ₅ is preferably 10% or more, 11% or more, 12% or more, 14% or more, particularly 16% or more, and the upper limit is 31% or less, 29% or less. It is particularly preferably 25% or less, particularly 20% or less. The lower limit of the TiO ₂ content is preferably 8% or more, 9% or more, 11% or more, particularly 12% or more, and the lower limit is less than 20%, 18% or less, 17% or less, particularly 16% or less. Is preferable. The lower limit of the content of Nb ₂ O ₅ is 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, especially 6.1 or more. The upper limit is 25% or less, 22% or less, 20% or less, 18% or less, 15% or less, 14% or less, 10% or less, and 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 region, it is preferable to appropriately adjust the ratio of _{TiO 2} and Nb ₂ O _5. Specifically, the mass ratio of TiO ₂ / Nb ₂ O ₅ is preferably 0.3 or more, 0.5 or more, 0.8 or more, and particularly preferably 1 or more. The upper limit is not particularly limited, but in reality, it is 29 or less, 20 or less, and further 10 or less.

B ₂ O ₃ is a component that contributes to the stability of vitrification in glass containing _{TiO 2} or Nb ₂ O _5. The lower limit of the content of B ₂ O ₃ is 4% or more, 5% or more, 6.5% or more, 7% or more, 7.5% or more, 8% or more, 8.3% or more, especially 9% or more. 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 preferably less than 10.5%. If _{the content of B 2} O ₃ is too small, it becomes 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. It should be noted that the chemical durability, particularly the acid resistance, can be improved by containing the _{B 2} O _{3 content and setting the basicity of the glass to 11 or more.}

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.

SiO ₂ is a glass skeleton component, which is a component that improves the stability of vitrification and the chemical durability. However, if the content is too high, the melting temperature becomes extremely high. As a result, Nb and Ti are likely to be reduced, so that the internal transmittance is likely to decrease. In addition, the refractive index tends to decrease. The lower limit of the content of SiO ₂ is preferably 3% or more, 3.5% or more, 4% or more, particularly 4.5% or more, and the upper limit is 20% or less, 18% or less, 15% or less, 13%. Below, it is preferably 12% or less, 11% or less, 10% or less, 9% or less, and particularly preferably 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 large, the refractive index tends to decrease and the liquidus temperature tends to increase. In particular, with respect to BaO, as the content thereof increases, 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. Therefore, it is not particularly preferable for applications such as wearable image display devices. Therefore, the RO content is preferably 0 to 15%, 0 to 10%, 0 to 5%, 0 to 2%, 0 to 1%, and particularly preferably 0 to 0.5%. The preferable range of the content of each component of CaO, SrO and BaO is also preferably the same as described above.

Ta ₂ O ₅ is a component that increases the refractive index. However, if the content is too large, phase separation and devitrification are likely to occur. Further, since Ta ₂ O ₅ is a rare and expensive component, the higher the content thereof, the higher the raw material batch cost. In view of the above, _{the content of Ta 2} O ₅ is preferably 0 to 5%, 0 to 3%, and 0 to 1%, and it is particularly preferable that the content is not contained.

In order to improve the stability of vitrification and improve mass productivity, it is preferable to appropriately adjust the ratio of _{SiO 2} and B ₂ O _3. Specifically, the mass ratio of B ₂ O ₃ / SiO ₂ is preferably 1 or more, 1.3 or more, particularly 1.5 or more, and 2.5 or less, 2 or less, particularly 1.96 or less. Is preferable. In the present invention, "x / y" means a 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 large, the glass tends to be devitrified. Therefore, Al ₂ O ₃ is preferably 0 to 1% and 0 to 0.5%, and particularly preferably not contained.

La ₂ O ₃ is a component that remarkably increases the refractive index and improves the stability of vitrification. The lower limit of the content of La ₂ O ₃ is preferably 27% or more, 30% or more, 35% or more, 38% or more, 40% or more, 42% or more, particularly 45% or more, and the upper limit is 50% or less. It is preferably 49.8% or less, 49.5% or less, 49% or less, and particularly preferably 48.5% or less. If _{the content of La 2} O ₃ is too small, it becomes difficult to obtain the above effect. On the other hand, _{if the content of La 2} O ₃ is too large, the devitrification resistance tends to decrease and the mass productivity tends to be inferior.

Gd ₂ O _{3 is} also a component that increases the refractive index and improves the stability of vitrification. The lower limit of the content of Gd ₂ O ₃ is preferably 6% or more, particularly 6.5% or more, and the upper limit is 25% or less, 20% or less, 14% or less, 10% or less, particularly 9% or less. Is preferable.

Y ₂ O _{3 is} also a component that increases the refractive index, but if the content is too large, vitrification tends to be unstable. Therefore, _{the lower limit of the content of Y 2} O ₃ is preferably 0% or more, particularly 0.1% or more, and the upper limit is 8% or less, 5% or less, 3% or less, particularly less than 1%. preferable.

Yb ₂ O _{3 is} also a component that increases the refractive index. However, if the content is too large, devitrification and veining are likely to occur. Therefore, _{the content of Yb 2} O ₃ is preferably 0 to 10%, particularly preferably 0 to 8%.

The content of Ln ₂ O ₃ (where 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. In this way, it is possible to increase the refractive index and the light transmittance in the visible region. The upper limit of the content of Ln ₂ O ₃ is not particularly limited, but if it is too large, devitrification is likely to occur, so that it is preferably 65% or less, particularly 60% or less.

ZnO is a component that promotes devitrification and lowers acid resistance in the composition system of the present invention, and it is preferable that the content thereof is small. Specifically, the content of ZnO is preferably 0.5% or less, 0.1% or less, and particularly preferably not contained.

WO ₃ is a component that increases the refractive index, but absorbs light in the visible region and lowers the transmittance. The content of WO ₃ is preferably 0 to 0.2%, more preferably 0 to 0.1%, and particularly preferably not contained.

ZrO ₂ is a component that enhances the refractive index and chemical durability. The lower limit of the content of ZrO ₂ is preferably 0% or more, more than 0%, 1% or more, 3% or more, 4% or more, particularly 5% or more, and the upper limit is 10% or less, 9% or less, 8%. Hereinafter, it is preferably 7.5% or less, particularly preferably 7% or less. If _{the content of ZrO 2} is too large, 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 large, devitrification is likely to occur. Therefore, the contents of these components are preferably 0 to 3% and 0 to 1%, respectively, and it is particularly preferable that they are not contained.

In order to obtain a glass having a high refractive index and excellent vitrification stability in the present invention, it is preferable to appropriately adjust the total amount of _{SiO 2} and B ₂ O _{3 and the ratio of Ln 2} O _3. Specifically, _{the lower limit of (SiO 2} + B ₂ O ₃ ) / Ln ₂ O ₃ is preferably 0.15 or more, 0.2 or more, particularly 0.25 or more, and the upper limit is 0.9 or less, 0. It is preferably 6.6 or less, particularly 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 region, it is preferable to appropriately adjust the ratios of _{TiO 2} , Nb ₂ O ₅ , and ZrO _{2. Specifically, the lower limit of Nb 2} O ₅ / (TiO ₂ + Nb ₂ O ₅ + ZrO ₂ ) in terms of mass ratio is preferably 0.1 or more, 0.15 or more, particularly 0.2 or more, and the upper limit is 0. It is preferably .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 content of these components is too small, it becomes difficult to obtain the desired high refractive index characteristics. Therefore _{, the lower limit of the content of TiO 2} + Nb ₂ O ₅ + WO ₃ is 10% or more, 11% or more, particularly 12%. The above is preferable.

In the present invention, in order to obtain a glass having a high refractive index and excellent transmittance in the visible region, it is preferable to appropriately adjust the ratios of _{TiO 2} , Nb ₂ O ₅ and WO _{3. Specifically, the lower limit of Nb 2} O ₅ / (TiO ₂ + Nb ₂ O ₅ + WO ₃ ) in terms of mass ratio is preferably 0.15 or more, 0.2 or more, particularly 0.3 or more, and the upper limit is 0. It is preferably 8.8 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 region and improve the stability of vitrification, it is preferable to appropriately adjust the ratio of _{Y 2} O ₃ and 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, particularly 0.01 or more, and the upper limit is 0.1 or less, 0.05 or less, particularly 0. It is preferably 0.3 or less.

In the present invention, in order to increase the refractive index and the light transmittance in the visible region and improve the stability of vitrification, it is preferable to appropriately adjust the ratio of _{Gd 2} O ₃ and 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 0.2 or less. ..

In the present invention, in order to increase the refractive index and the light transmittance in the visible region and improve the stability of vitrification, the _{total amount of TiO 2} and B ₂ O _{3 and} the total amount of Nb ₂ O ₅ and WO ₃ are used. It is preferable to adjust the ratio of Specifically, _{the lower limit of (TiO 2} + B ₂ O ₃ ) / (Nb ₂ O ₅ + WO ₃ ) is preferably 1.6 or more, 1.8 or more, particularly 2 or more, and the upper limit is 10 or less, 4 Below, it is particularly preferable that it is 3.5 or less.

It is preferable that the As component (As ₂ O _3, etc.), the Pb component (PbO, etc.) and the fluorine component (F _2, etc.) are substantially not contained because they have a large environmental load. Further, Bi ₂ O ₃ and Te _{O 2} are coloring components, and the transmittance in the visible region tends to decrease. Therefore, it is preferable that Bi 2 O 3 and Te O 2 are not substantially contained. Here, "substantially not contained" means that it is intentionally not contained as a raw material, and does not exclude unavoidable contamination of impurities. Objectively, it means that the content of each of the above components is less than 0.1%.

Since Pt is a coloring component and the transmittance in the visible region tends to decrease, its content is preferably 10 ppm or less.

The optical glass of the present invention may contain the clarifying agent components Cl, CeO ₂ , SO ₂ , Sb ₂ O ₃ or SnO ₂ at a ratio of 0.1% or less, respectively.

The optical glass of the present invention has a glass basicity of 11 or more, which is defined by (total number of moles of oxygen atoms / total number of cation Field Strength) × 100, and is 12 or more, especially 12.5 or more. It is preferable to have. In the present invention, "Field Strength (hereinafter referred to as F.S.)" is calculated by the following formula.

F. S. = Z / r ² (Z is the ionic valence and r is the ionic radius (Å))

The values in Table 1 are used as the values of Z and r in the present invention. For r, the values described in "Chemical Handbook Basic Edition Revised 2nd Edition (published by Maruzen Co., Ltd. in 1975)" etc. are referred to. However, ^{regarding the ionic radii of B 3+} and P ^5+, a tetrahedral structure is adopted together with oxygen ions in the glass (specifically, ^{around B 3+} or P ^{5+ , four O 2-} ions are arranged around it. It is set to 0.32, which is a value assuming that a tetrahedral structure is adopted by coordinating.

Basicity is an index showing the restraint state of electrons or oxygen by cations. The higher the basicity, the weaker the binding of electrons or oxygen by cations. Oxygen is likely to be arranged around the element of boron having low chemical durability, and boron is stably present in the glass, so that the chemical durability is easily improved. If the binding of electrons or oxygen by cations becomes too weak, vitrification becomes unstable and the chemical durability tends to decrease. Therefore, the basicity is 17 or less, 16 or less, especially 15 or less. Is preferable.

Further, when the binding of electrons or oxygen by cations is weakened, Ti ions and Nb ions are likely to be in an oxidized state, and ^{the proportion of Ti 4+} and Nb ⁵⁺ that do not reduce the visible light transmittance tends to increase. Thereby, the visible light transmittance of the optical glass of the present invention can be improved.

The lower limit of the refractive index (nd) of the optical glass of the present invention is 1.95 or more, and 1.96 or more. It is preferably 1.965 or more and 1.966 or more, 1.97 or more, particularly 1.98 or more, and the upper limit is 2.05 or less, 2.04 or less, 2.03 or less, 2.01 or less, especially 2. It is preferably 0.00 or less. If the refractive index is too low, when used as a light guide plate for wearable image display devices such as eyeglasses with projectors, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices, The viewing angle tends to be narrow. On the other hand, if the refractive index is too high, defects such as devitrification and veining tend to increase in the glass.

_{The degree of coloration λ 70} of the optical glass of the present invention is preferably 470 nm or less, particularly preferably 460 nm or less. In this way, in the wearable image display device using the optical glass of the present invention, the brightness of the image seen by the user tends to increase.

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

The liquidus temperature of the optical glass of the present invention is preferably 1250 ° C. or lower, 1200 ° C. or lower, 1150 ° C. or lower, 1100 ° C. or lower, and particularly preferably 1070 ° C. or lower. In this way, devitrification is unlikely to occur during melting or molding, and mass productivity is likely to be improved.

The optical glass of the present invention preferably has a density of 5.5 g / cm ³ or less, 5.3 g / cm ³ or less, and particularly preferably 5.1 g / cm ³ or less. If the density is too high, the weight of the wearable device using the optical glass of the present invention becomes heavy, and the discomfort when wearing the device increases. The lower limit of the density is not particularly limited, but if it is too low, other characteristics such as optical characteristics are deteriorated, so that it is preferably ^{4.0 g / cm 3} or more, particularly 4.5 g / cm ^{3 or more.}

The optical glass of the present invention preferably has a coefficient of thermal expansion 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 coefficient of thermal expansion is too large, the glass is liable to break due to thermal shock. The lower limit of the coefficient of thermal expansion is not particularly limited, but if it is too low, other characteristics such as optical characteristics deteriorate. Therefore, it is preferably ^{75 × 10 -7} / ° C. or higher, particularly 80 × 10 ^{-7 / ° C. or higher.}

The lower limit of the wall 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, particularly 0.05 mm or more, and the upper limit is 5 mm. Below, it is preferably 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 wall thickness of the optical glass plate is too small, the mechanical strength tends to decrease. On the other hand, if the wall thickness of the optical glass plate is too large, the weight of the wearable image display device using the optical glass plate becomes large, and the discomfort when the device is attached increases.

The shape of the optical glass plate of the present invention is, for example, a plate shape such as a polygon whose plane shape is circular, elliptical, or rectangular. In this case, the major axis (diameter in the case of a circle) of the optical glass plate may be 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, particularly 200 mm or more. preferable. 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. Moreover, it tends to be inferior in mass productivity. The upper limit of the major axis of the optical glass plate is not particularly limited, but is practically 1000 mm or less.

The optical glass plate of the present invention is a component of a wearable image display device selected from glasses with a projector, eyeglass-type or goggle-type displays, a virtual reality (VR) or augmented reality (AR) display device, and a virtual image display device. It is suitable as a light guide plate. The light guide plate is used for a so-called spectacle lens portion of a wearable image display device, and plays a role of guiding light emitted from an image display element included in the wearable image display device and emitting it toward the user's pupil. .. It is preferable that the surface of the light guide plate is provided with a diffraction grating for diffracting the light emitted from the image display element inside the light guide plate.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

Table 2 shows Examples (No. 1 to 9) and Comparative Examples (No. 10) of the present invention.

First, glass raw materials were prepared so as to have each composition shown in Table 2, and melted at 1200 to 1350 ° C. for 2 hours using a platinum crucible. The molten glass was poured onto a carbon plate, and after annealing, a sample suitable for each measurement was prepared.

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

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

Water resistance and acid resistance were measured based on the powder method specified in JOBIS.

The degree of coloration λ ₇₀ was measured as follows. For an optically polished sample with a thickness of 10 mm ± 0.1 mm, a spectrophotometer (UV-3100 manufactured by Shimadzu Corporation) was used to measure the light transmittance (linear transmittance) including surface reflection loss at intervals of 0.5 nm. Measured in. From the light transmittance curve obtained by the measurement, the wavelength at which the light transmittance was 70% was read.

The liquidus temperature and the liquidus viscosity were measured as follows.

After remelting the glass under the condition of 1200 ° C.-0.5 hours in an electric furnace, holding it in an electric furnace having a temperature gradient for 18 hours, removing it from the electric furnace, allowing it to cool in air, and devitrifying it with an optical microscope. It was measured by determining the precipitation position of.

Separately, a lumpy glass sample was put into an alumina crucible and heated and melted. For the obtained glass melt, the viscosity of the glass at a plurality of temperatures was determined by the platinum ball pulling method. Subsequently, the constant of the Vogel-Fulcher equation was calculated using the measured value of the glass viscosity to create a viscosity curve.

Using the liquidus temperature and viscosity curve obtained as described above, the viscosity (liquidus viscosity) corresponding to the liquidus temperature was obtained.

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

The density was measured by the Archimedes method using a glass sample weighing about 10 g.

The coefficient of thermal expansion was measured in a temperature range of 30 to 300 ° C. with a dilatometer using a glass sample formed to about 5φ × 20 mm.

As shown in Table 2, No. 1 of Examples. The samples 1 to 9 had a basicity of 11.6 to 17, and were first-class in both water resistance and acid resistance. The refractive index was as high as 1.952 to 2.04. On the other hand, No. The 10 samples had a basicity of 9.3, an inferior acid resistance of 4th grade, and a low refractive index of 1.81.

The optical glass of the present invention is used in glasses with a projector, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and wearable image display devices selected from virtual image display devices. Suitable as a light plate.

Claims (14)

An optical glass containing at least one selected from _{TiO 2} and Nb ₂ O ₅ as a glass composition _{and B 2} O ₃ , having a refractive index nd of 1.95 or more and a basicity of 11 or more. .. The optical glass according to claim 1, wherein the degree of coloring λ _{70 is 470 nm or less.} The optical glass according to claim 1 or 2, wherein the water resistance and acid resistance according to JOGIS are 1st and 2nd grade. By _{mass%, TiO 2 + Nb 2 O} 5 10~31%, B 2 O 3 4~15%, SiO 2 3% or more, RO (at least one R is selected from Mg, Ca, Sr and Ba) 0 15%, and _optical glass according to any one of claims 1 to 3, characterized in that it contains Ta ₂ O 5 0~5%. By _mass%, TiO 2 less than _{8~20%, Ln 2 O 3 (} Ln is La, Gd, at least one selected from Y and Yb) 40~65%, 0~0.5% ZnO , Al 2 O ₃ 0 to 1%, _and, the optical glass according to claim 4, characterized in that it contains WO 3 0 to 0.2%. The optical glass according to any one of claims 1 to 5, wherein the optical glass is substantially free of Bi ₂ O ₃ , TeO _{2 and PbO.} The optical glass according to any one of claims 1 to 6, wherein the content of Pt is 10 ppm or less. The optical glass according to any one of claims 1 to 7, wherein the Abbe number (νd) is 20 to 35. The optical glass according to any one of claims 1 to 8, wherein the liquidus temperature is 1250 ° C. or lower. 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, wherein the plate thickness is 0.01 to 5 mm. A light guide plate comprising the optical glass plate according to claim 10 or 11. 12. A wearable image display device selected from projector-equipped eyeglasses, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. The light guide plate described in. A wearable image display device comprising the light guide plate according to claim 12 or 13.