Optical glass

Abstract

Provided is an optical glass that contains TiO2 and Nb2O5 as the glass composition, can achieve high light transmittance and has excellent mass productivity.　This optical glass is characterized by containing TiO2 and Nb2O5 in a total amount of 20 mol% or more as the glass composition and having a basicity of 12 or higher.

Description

Technical Field

[0001] The present invention relates to an optical glass used as a light guide plate or the like of a wearable image display device.

Background Art

[0002] A glass plate is used as a component of a wearable image display device such as glasses with a projector, a glasses-type or goggles-type display, a virtual reality (VR) or augmented reality (AR) display device, or a virtual image display device. The glass plate functions as, for example, a see-through light guide plate, and it is possible to view an image displayed on the glass plate while viewing an external scene through the glass plate. Further, it is also possible to realize a 3D display by using a technique of projecting different images on the left and right of the glasses, or to realize a virtual reality space by using a technique of coupling to the retina by utilizing the crystalline lens of the eye. The glass plate is required to have a high refractive index in terms of widening the angle of an image, increasing the brightness and contrast, and improving the light guiding characteristics (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to improve the refractive index of glass, it is effective to contain components that contribute to a high refractive index, such as TiO2 and Nb2O5, in the glass. On the other hand, when TiO2 and Nb2O5 are contained in the glass, the light transmittance of the glass tends to decrease. In order to solve such problems, a method has been proposed in which the glass is annealed for a long time after melting and forming to improve the light transmittance of the glass (see, for example, Patent Document 2). However, this method has the problem of requiring cost and time.

[0005] In view of the above, an object of the present invention is to provide an optical glass having a glass composition containing TiO2 and Nb2O5 and excellent mass productivity capable of obtaining a high light transmittance.

Means for Solving the Problems

[0006] As a result of intensive studies by the present inventors, in an optical glass containing a certain amount or more of high refractive index components TiO2 and Nb2O5, by providing a ligand field that allows Ti ions and Nb ions in the glass to stably exist in a high valence state, it has been found that high transmittance characteristics can be easily obtained.

[0007] That is, the optical glass of the present invention is characterized in that, as a glass composition, it contains TiO2 and Nb2O5 in a total amount of 20 mol% or more in mol%, and has a basicity of 12 or more. In this way, Ti ions and Nb ions in the glass can be stably present in a high valence state with less absorption, and as a result, high transmittance characteristics can be obtained without performing a long annealing treatment.

[0008] The optical glass of the present invention preferably contains TiO2 of 8 to less than 40% and Nb2O5 of 1 to 11% in mol%.

[0009] The optical glass of the present invention preferably has a refractive index nd of 1.8 to 2.3.

[0010] The optical glass of the present invention preferably has an Abbe number (νd) of 20 to 35.

[0011] The optical glass of the present invention preferably has an internal transmittance of 80% or more at 450 nm with a thickness of 10 mm.

[0012] Another aspect of the present invention is an optical glass whose glass composition contains 20 mol% or more of TiO2 and Nb2O5 in total, with (B2O3+La2O3+ZnO)-(SiO2+Y2O3+ZrO2) making up 10-40%, and the number of bubbles and foreign matter present inside is 1 / cm³. 3 The following characteristics apply:

[0013] The optical glass of the present invention preferably contains, in mol%, 10-30% B2O3, 3% or more SiO2, 0-5% RO (R is at least one selected from Mg, Ca, Sr, and Ba), 50-5% Ta2O, 10-50% Ln2O3 (Ln is at least one selected from La, Gd, Y, and Yb), 0-1% ZnO, 30-1% Al2O, and 30-0.2% WO.

[0014] The optical glass of the present invention preferably exhibits a change in internal transmittance at 450 nm with a thickness of 10 mm when heat-treated for 72 hours at a temperature within ±200°C of the glass transition temperature, which is less than 10%. The optical glass of the present invention can achieve high transmittance characteristics regardless of whether or not long-term annealing treatment is performed. In other words, it has the characteristic of having a small change in internal transmittance when subjected to long-term annealing treatment.

[0015] The optical glass plate of the present invention is characterized by being made of any of the above-mentioned optical glasses.

[0016] The optical glass plate of the present invention preferably has a thickness of 0.01 to 5 mm.

[0017] The light guide plate of the present invention is characterized by being made of any of the optical glass plates described above.

[0018] The light guide plate of the present invention is preferably 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.

[0019] The wearable image display device of the present invention is characterized by comprising any of the above-described light guide plates.

[0020] The present invention relates to a method for manufacturing optical glass, which includes a step of obtaining molten glass by melting raw materials, and then cooling the molten glass to obtain a molded body, characterized in that the molded body is not subjected to heat treatment for 48 hours or more at a temperature within ±200°C of the glass transition point of the molded body. As described above, the optical glass of the present invention can obtain high transmittance properties regardless of whether or not a long-term annealing treatment is performed. Therefore, the manufacturing method of the present invention has the advantage of being able to omit a long-term heat treatment step of, for example, 48 hours or more at a temperature within ±200°C of the glass transition point of the molded body, and is characterized by its excellent mass productivity.

[0021] In the optical glass manufacturing method of the present invention, it is preferable that the melting temperature of the raw materials is 1400°C or lower. This makes it less likely for components of the molten container (such as Pt) to dissolve into the molten glass during melting, thereby increasing the light transmittance of the resulting optical glass. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide an optical glass that contains TiO2 or Nb2O5 as part of its glass composition, and that is highly mass-producible and can achieve high light transmittance. [Brief explanation of the drawing]

[0023] [Figure 1] The graph shows the relationship between the basicity and the change in internal transmittance for the glass samples obtained in the examples. [Modes for carrying out the invention]

[0024] The optical glass of the present invention contains at least one selected from TiO2 and Nb2O5 as its glass composition. The preferred content of these components is described below. In the following descriptions of the content of each component, unless otherwise specified, "%" means "molar percent".

[0025] TiO2 and Nb2O5 are components that significantly increase the refractive index of glass. However, if these components are present in excessive amounts, vitrification becomes difficult, and the light transmittance in the visible range tends to decrease. Therefore, the lower limit of the TiO2 + Nb2O5 content is preferably 20% or more, 25% or more, 27% or more, 29% or more, and particularly preferably 30% or more, and the upper limit is preferably 40% or less, 38% or less, and particularly preferably 35% or less. The lower limit of the TiO2 content is preferably 8% or more, 10% or more, 15% or more, 18% or more, 22% or more, and particularly preferably 23% or more, and the upper limit is preferably less than 40%, 35% or less, 32% or less, and particularly preferably 29% or less. The lower limit of the Nb2O5 content is preferably 1% or more, 2% or more, 2.5% or more, and particularly preferably 3% or more, and the upper limit is preferably 11% or less, 8% or less, 6% or less, and particularly preferably 5% or less. In this invention, "x + y + ..." represents the total amount of each component.

[0026] In this invention, in order to obtain glass with 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 molar ratio of TiO2 / Nb2O5 is 3 or more, 4 or more, and particularly 5 or more. There is no particular upper limit, but in reality it is less than 40, and even less than 30.

[0027] In addition to TiO2 and Nb2O5, the optical glass of the present invention may also contain the following components.

[0028] B2O3 is a component that particularly contributes to the stability of vitrification in glasses containing TiO2 or Nb2O5. In particular, vitrification tends to be unstable when the refractive index nd is high, such as 1.9 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 10% or more, 14% or more, 15% or more, 16% or more, and particularly 18% or more, and the upper limit is preferably 28% or less, 25% or less, 23% or less, 22% or less, and particularly 21% 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 basicity and refractive index tend to decrease. In this invention, by including B2O3 and increasing the basicity of the glass, it is possible to obtain properties that are easy to mass-produce and have high transmittance.

[0029] 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. As a result, Nb and Ti are more easily reduced, which tends to decrease the internal transmittance. Also, the refractive index tends to decrease. The lower limit of the SiO2 content is preferably 3% or more, 5% or more, 8% or more, 9% or more, and especially 10% or more, and the upper limit is preferably 25% or less, 22% or less, 21% or less, 20% or less, 19% or less, and especially 18% or less.

[0030] 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 molar ratio of B2O3 / SiO2 is preferably 0.5 or higher, 0.6 or higher, particularly 0.8 or higher, and 10 or lower, particularly 8 or lower. In this invention, "x / y" means the value obtained by dividing the content of x by the content of y.

[0031] Furthermore, in the present invention, Si is present in cation%. 4+ +B 3+ The content of is preferably 30% or more, 32% or more, and especially 33% or more. This improves the stability of vitrification. Si 4+ +B3+ 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 50% or less, 45% or less, and especially 40% or less.

[0032] The alkaline earth component RO (where R is at least one selected from Mg, Ca, Sr, and Ba) is a component that stabilizes vitrification. If its content is too high, the refractive index tends to decrease and the liquidus temperature tends to increase. In particular, with respect to BaO, if its content is high, the density of the glass tends to increase, and the weight of the optical element made of the optical glass of the present invention tends to increase. For this reason, it is undesirable for applications such as wearable image display devices. Accordingly, the RO content is preferably 5% or less, 2% or less, 1% or less, and especially 0.5% or less. The preferred ranges for the content of each component MgO, CaO, SrO, and BaO, and the preferred range for the combined amount of two or three selected from these, are also preferably the same as above.

[0033] 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.

[0034] 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 10%, 14%, 19%, 20%, 21%, and especially preferably 21.5%, while the upper limit is preferably 35% or less, 30% or less, 28% or less, 26% or less, 24%, and especially preferably 23.5% 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, which tends to make mass production difficult.

[0035] 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 1% or more, 2% or more, and particularly preferably 3% or more, and the upper limit is preferably 10% or less, 7% or less, and particularly preferably 5% or less.

[0036] While Y2O3 is a component that enhances refractive index and chemical durability, if its content is too high, the melting temperature tends to become extremely high, and vitrification becomes unstable. Therefore, the lower limit of the Y2O3 content is preferably 0%, 0.1%, and especially 0.5%, and the upper limit is preferably 8% or less, 7% or less, 5% or less, less than 4%, and especially 2.5% or less.

[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] Furthermore, the content of Ln2O3 (where Ln is at least one selected from La, Gd, Y, and Yb) is preferably 11% or more, 15% or more, 20% or more, and particularly 22% or more. This increases the basicity of the glass, making it possible to improve the refractive index and visible light transmittance. There is no particular upper limit to the Ln2O3 content, but if it is too high, devitrification is likely to occur, so it is preferably 50% or less, 40% or less, and particularly 30% or less.

[0039] In order to obtain a glass with a high refractive index and excellent vitrification stability in the present invention, it is preferable to appropriately adjust the ratio of the total amount of SiO2 and B2O3 to Ln2O3. Specifically, the lower limit of (SiO2 + B2O3) / Ln2O3 is preferably 0.5 or more, 0.8 or more, and particularly 1 or more, and the upper limit is preferably 2 or less, 1.6 or less, and particularly 1.4 or less.

[0040] ZnO is a component that promotes solubility (solubility of raw materials) in the composition system of the present invention. However, if its content is high, it becomes difficult to obtain high refractive index properties, and it also promotes devitrification and reduces acid resistance, so a low content is preferable. Specifically, the ZnO content is preferably 1% or less, 0.5% or less, or less than 0.1%, and it is particularly preferable that it is not present at all.

[0041] Al2O3 is an ingredient that improves water resistance. However, if its content is too high, devitrification becomes more likely. Therefore, the Al2O3 content is preferably 1% or less, or 0.5% or less, and it is particularly preferable that it is not included at all.

[0042] WO3 is a component that increases the refractive index, but it absorbs light in the visible region and reduces light transmittance. Therefore, the WO3 content is preferably 0.2% or less, 0.1% or less, and it is particularly preferable that it is not present at all.

[0043] 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. The lower limit of the ZrO2 content is preferably 0% or more, greater than 0%, 1% or more, 3% or more, 4% or more, and especially 5% or more, while the upper limit is preferably 15% or less, 12% or less, 10% or less, 9% or less, and especially 8% or less. If the ZrO2 content is too high, devitrification becomes more likely.

[0044] In the present invention, in order to obtain glass with a high refractive index and excellent transmittance in the visible range, it is preferable to appropriately adjust the ratios of TiO2, Nb2O5, and ZrO2. Specifically, the lower limit of the molar ratio of Nb2O5 / (TiO2+Nb2O5+ZrO2) is preferably 0.05 or higher, 0.06 or higher, and particularly preferably 0.8 or higher, while the upper limit is preferably 0.2 or lower, 0.15 or lower, and particularly preferably 0.13 or lower.

[0045] In the present invention, in order to obtain glass with excellent transmittance in the visible range, it is preferable to appropriately adjust the combined amounts of TiO2, Nb2O5, and WO3. Specifically, the content of TiO2 + Nb2O5 + WO3 is preferably 41% or less, 38% or less, and particularly preferably 35% or less. However, if the content of these components is too low, it becomes difficult to obtain the desired high refractive index characteristics, so it is preferable that the lower limit of the TiO2 + Nb2O5 + WO3 content be 20% or more.

[0046] In the present invention, in order to obtain glass with a high refractive index and excellent transmittance in the visible range, it is preferable to appropriately adjust the ratios of TiO2, Nb2O5, and WO3. Specifically, the lower limit of the molar ratio of Nb2O5 / (TiO2+Nb2O5+WO3) is preferably 0.05 or higher, 0.07 or higher, and particularly preferably 0.08 or higher, while the upper limit is preferably 0.3 or lower, 0.25 or lower, and particularly preferably 0.2 or lower.

[0047] In the present invention, in order to obtain glass with good solubility and excellent quality, it is preferable to appropriately adjust the combined amounts of B2O3, La2O3, and ZnO. These components promote initial melt formation and can particularly increase solubility at low temperatures. However, if too much is included, it becomes difficult to obtain high refractive index properties. In view of the above, the lower limit of B2O3 + La2O3 + ZnO is preferably 35% or more, 38% or more, and especially 41% or more, and the upper limit is preferably 50% or less, 48% or less, and especially 46.5% or less.

[0048] In the present invention, in order to obtain glass with good solubility and excellent quality, it is preferable to appropriately adjust the combined amounts of SiO2, Y2O3, and ZrO2. These components are poorly soluble, and if they are included in too large an amount, melt formation is impaired, and solubility tends to decrease, especially at low temperatures. Specifically, the lower limit of SiO2 + Y2O3 + ZrO2 is preferably 10% or more, 11% or more, and particularly 12% or more, and the upper limit is preferably 25% or less, 22% or less, and particularly 19.5% or less.

[0049] In the present invention, in order to obtain glass having good solubility and excellent quality, it is preferable to appropriately adjust the difference between the total content of B2O3, La2O3 and ZnO and the total content of SiO2, Y2O3 and ZrO2. Specifically, the lower limit of (B2O3 + La2O3 + ZnO) - (SiO2 + Y2O3 + ZrO2) is preferably 10% or more, 15% or more, 20% or more, particularly preferably 25% or more, and the upper limit is preferably 40% or less, 35% or less, particularly preferably 30% or less.

[0050] As described above, by appropriately adjusting the content of B2O3 + La2O3 + ZnO, the content of SiO2 + Y2O3 + ZrO2, and further the difference between them, the solubility can be increased and internal defects such as bubbles and foreign matters in the optical glass can be reduced. The number of bubbles and foreign matters present inside the optical glass is 1 piece / cm 3 Hereinafter, 0.5 piece / cm 3 Hereinafter, 0.3 piece / cm 3 Hereinafter, particularly 0.2 piece / cm 3 It is preferably below.

[0051] 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 Y2O3 to Ln2O3. Specifically, the lower limit of Y2O3 / Ln2O3 is preferably 0 or more, 0.005 or more, particularly preferably 0.01 or more, and the upper limit is preferably 0.3 or less, 0.25 or less, particularly preferably 0.2 or less.

[0052] 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 Gd2O3 to Ln2O3. Specifically, the lower limit of Gd2O3 / Ln2O3 is preferably 0.05 or more, particularly preferably 0.1 or more, and the upper limit is preferably 0.25 or less, particularly preferably 0.2 or less.

[0053] In the present invention, in order to increase the refractive index and visible light transmittance, 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 5 or more, 6 or more, and particularly 8 or more, and the upper limit is preferably 30 or less, 20 or less, and particularly 15 or less.

[0054] Li2O, Na2O, and K2O are components that lower the softening point, but if their content is too high, devitrification becomes more likely. Therefore, the content of these components is preferably 10% or less, 5% or less, and 1% or less, respectively, and it is particularly preferable that they are not included. Furthermore, if two or more of Li2O, Na2O, and K2O are included, their combined amounts are preferably 10% or less, 5% or less, and 1% or less, and it is particularly preferable that they are not included.

[0055] Furthermore, it is preferable to substantially omit the presence of As components (As2O3, etc.), Pb components (PbO, etc.), and fluorine components (F2, etc.) due to their significant environmental impact. Additionally, Bi2O3 and TeO2 are coloring components and tend to reduce visible light transmittance, so it is preferable to substantially omit their presence. Here, "substantially omitted" means intentionally omitting them from the raw materials, and does not eliminate the possibility of unavoidable impurities. Objectively, this means that the content of each of the above components is less than 0.1%.

[0056] Pt, Rh, and Fe2O3 are coloring components, and their content should be low as they tend to reduce the transmittance in the visible range. Specifically, the Pt content should be 10 ppm or less, particularly 5 ppm or less; the Rh content should be 0.1 ppm or less, particularly 0.01 ppm or less; and the Fe2O3 content should be 1 ppm or less, particularly 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 should be 0.1 ppm or more, particularly 0.5 ppm or more.

[0057] The optical glass of the present invention may contain the clarifying agent components Cl, CeO2, SO2, Sb2O3, or SnO2 in amounts of 0.1% or less, respectively.

[0058] The optical glass of the present invention has a basicity of 12 or higher, defined as (sum of moles of oxygen atoms / sum of field strengths (cation fields) of cations) × 100, and preferably 12.5 or higher, 13.3 or higher, 13.5 or higher, and particularly 14 or higher. In the present invention, "Field Strength (hereinafter referred to as FS)" is determined by the following formula.

[0059] FS = Z / r 2 (Z represents the ionic charge, and r represents the ionic radius (Å)).

[0060] In this invention, the values ​​of Z and r are those shown in Table 1. For r, the values ​​listed in "Chemical Handbook Basic Edition, Revised 2nd Edition (published by Maruzen Co., Ltd. in 1975)" are used. However, B 3+ and P 5+ Regarding the ionic radius, it adopts a tetrahedral structure together with oxygen ions in glass (specifically, B 3+ or P 5+ With four O's at the center, 2- The value of 0.315 is used, which is the value assumed to be the tetrahedral structure formed by the coordination of ions.

[0061] For example, in the case of a composition of SiO2 15%, B2O 320%, TiO2 30%, Nb2O 55%, and La2O 330% in mole percent, the basicity can be calculated as follows.

[0062] First, the sum of the FS of the cations can be calculated as follows. Si 4+ The FS per mole of Z(Si) is 4+ ) / r(Si 4+ ) 2 =4 / (0.4) 2=25.00, B 3+ The FS per 1 mol is Z(B 3+ ) / r(B 3+ ) 2 =3 / (0.315) 2 =30.23, Ti 4+ The FS per 1 mol of Z(Ti) is 4+ ) / r(Ti 4+ ) 2 =4 / (0.75) 2 =7.11, Nb 5+ The FS per 1 mol of is Z(Nb 5+ ) / r(Nb 5+ ) 2 = 5 / (0.78) 2 =8.22, La 3+ The FS per 1 mol of is Z(La 3+ ) / r(La 3+ ) = 3 / (1.32) 2 = 1.72, The sum of the product of the FS and moles of each ion is 25.00 × 15 + 30.23 × 2 × 20 + 7.11 × 30 + 8.22 × 2 × 5 + 1.72 × 2 × 30 = 1982.9.

[0063] Furthermore, the oxygen atoms contained in one mole of glass are 15 × 2 from SiO2, 3 × 20 from B2O3, 2 × 30 from TiO2, 5 × 5 from Nb2O5, and 3 × 30 from La2O3, totaling 265.

[0064] Therefore, the basicity is (265 / 1982.9) × 100 ≈ 13.4.

[0065] [Table 1]

[0066] Basicity is an indicator of the state of constraint on electrons and oxygen by cations. The higher the basicity, the weaker the constraint on electrons and oxygen by cations, meaning that electrons and oxygen move more easily within the glass. By designing for high basicity, it becomes possible to easily position electrons or oxygen around Ti ions or Nb ions. As a result, the Ti and Nb ions in the glass can be placed in a less absorbent high-number state (Ti). 4+ Ya Nb 5+ This allows for stable existence and enables the acquisition of high permeability characteristics. However, if the constraint of electrons or oxygen by the cation becomes too weak, vitrification becomes unstable and chemical durability tends to decrease, so a basicity of 16 or less, and particularly 15 or less, is preferable.

[0067] Furthermore, in the case of high refractive index glass, specifically glass with a refractive index nd of 1.9 or higher, Nb 5+ Compared to Ti 4+ Discoloration due to Ti tends to be particularly noticeable. 4+ / Nb 5+ This tendency becomes stronger when the basicity is 2.1 or higher, 2.5 or higher, or even 3 or higher. Even in that case, as mentioned above, increasing the basicity will increase Ti 4+ This makes it possible to arrange electrons or oxygen around the element, making it easier to obtain high transmission properties. Thus, when the refractive index nd is 1.9 or higher and Ti 4+ / Nb 5+ When the basicity is 2.1 or higher, it becomes easier to enjoy the effects obtained by increasing the basicity.

[0068] As described above, the optical glass of the present invention can obtain high transmittance characteristics regardless of whether or not it undergoes long-term annealing treatment. In other words, it has the characteristic of having a small change in internal transmittance when subjected to long-term annealing treatment. Specifically, when the optical glass of the present invention is heat-treated for 72 hours at a temperature within ±200°C of the glass transition temperature, it is preferable that the change in internal transmittance at 450 nm with a thickness of 10 mm is less than 10%, 5% or less, less than 2%, 1.5% or less, 1% or less, or 0.5% or less, and it is particularly preferable that it is 0% (i.e., the internal transmittance does not change before and after heat treatment).

[0069] The lower limit of the refractive index (nd) of the optical glass of the present invention is preferably 1.8 or higher, 1.85 or higher, 1.90 or higher, 1.95 or higher, and particularly preferably 1.98 or higher, and the upper limit is preferably 2.3 or lower, 2.1 or lower, 2.05 or lower, 2.03 or lower, and particularly preferably 2.01 or lower. 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.

[0070] The Abbe number (νd) of the optical glass of the present invention is not particularly limited, but considering the stability of vitrification, the lower limit is preferably 20 or more, 22 or more, and particularly preferably 25 or more, and the upper limit is preferably 35 or less, 32 or less, and particularly preferably 30 or less.

[0071] The internal transmittance of the 10mm thick optical glass of the present invention at 450nm is preferably 80% or more, and more preferably 90% 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 of the present invention.

[0072] The liquidus temperature of the optical glass of the present invention is preferably 1300°C or lower, 1250°C or lower, 1150°C or lower, 1100°C or lower, and particularly preferably 1070°C or lower. This makes it less likely to devitrify during melting and molding, thus improving mass production efficiency.

[0073] The optical glass 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 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.

[0074] The optical glass of the present invention has a thermal expansion coefficient of 95 × 10 at 30 to 300°C. -7 / ℃ or below, 91×10 -7 / ℃ or lower, especially 88×10 -7 It is preferable that the coefficient of thermal expansion is below / °C. If the coefficient of thermal expansion is too high, the glass becomes more prone to cracking due to thermal shock. There is no particular lower limit to the coefficient of thermal expansion, but if it is too low, other properties such as optical properties tend to deteriorate, so 75 × 10⁻⁶ is preferable. -7 / ℃ or higher, especially 80×10 -7 It is preferable that the temperature is above / ℃.

[0075] 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 tends 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 discomfort when the device is worn.

[0076] 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 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 especially 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.

[0077] The optical glass of the present invention includes the step of obtaining molten glass by melting raw materials that have been blended to obtain a predetermined glass composition (a glass composition having the predetermined basicity described above), and then cooling the molten glass to obtain a molded body. Here, it is not necessary to further heat treat the molded body for 48 hours or more at a temperature within ±200°C of the glass transition point of the molded body. As described above, the optical glass of the present invention can obtain high transmittance properties regardless of whether or not a long-term annealing treatment is performed. Therefore, in the manufacturing method of the present invention, for example, a long-term heat treatment step of 48 hours or more at a temperature within ±200°C of the glass transition point of the molded body can be omitted, and it has the advantage of being able to mass-produce. The glass transition point of the optical glass of the present invention is approximately 650 to 800°C.

[0078] 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 (such as Pt) tend to dissolve into the molten glass, and the light transmittance of the resulting optical glass 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.

[0079] As described above, by appropriately adjusting the content of B2O3+La2O3+ZnO, the content of SiO2+Y2O3+ZrO2, or the difference in their content, solubility can be increased, and bubbles and foreign matter can be reduced even when melted at low temperatures. As a result, optical glass with excellent light transmittance and fewer bubbles and foreign matter can be obtained.

[0080] 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, the surface of the light guide plate is provided with a diffraction grating for diffracting the light emitted from the image display element into the light guide plate. [Examples]

[0081] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0082] Tables 2-8 show examples of the present invention. Tables 2-5 are mainly intended to compare the change in internal transmittance, which will be discussed later, and compositions with the same total amount of TiO2 and Nb2O5, which greatly affect internal transmittance, are grouped together.

[0083] [Table 2]

[0084] [Table 3]

[0085] [Table 4]

[0086] [Table 5]

[0087] [Table 6]

[0088] [Table 7]

[0089] [Table 8]

[0090] The raw materials were mixed to achieve the compositions shown in Tables 2-8, and the resulting batches were placed in a platinum crucible and melted at 1350°C for 2 hours. The molten glass was poured onto a carbon plate and shaped. After holding it at 700-800°C for 1 hour, it was cooled to room temperature at -1°C / min and annealed to obtain glass samples. The water resistance, acid resistance, liquidus temperature, liquidus viscosity, refractive index, Abbe number, density, glass transition temperature, thermal expansion coefficient, and internal transmittance of the obtained glass samples were measured. The results are shown in Tables 2-8.

[0091] Water resistance and acid resistance were measured according to the powder method specified in JOGIS.

[0092] The liquidus temperature and liquidus viscosity were measured as follows.

[0093] After remelting the glass sample in an electric furnace at 1200°C for 0.5 hours, it was held in an electric furnace with a temperature gradient for 18 hours. The sample was then removed from the furnace and allowed to cool in air. The liquidus temperature was measured by determining the deposition location of devitrified material using an optical microscope.

[0094] Separately, glass samples were 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 viscosity curves. Using the obtained viscosity curves and the liquidus temperatures determined above, the viscosity corresponding to the liquidus temperature (liquidus viscosity) was determined.

[0095] The refractive index is shown as a measurement for the d-line (587.6 nm) of a helium lamp. 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 a hydrogen lamp, and the refractive index of the C-line (656.3 nm) of a hydrogen lamp, using the formula (νd) = [(nd-1) / (nF-nC)].

[0096] The density was measured using the Archimedes method with a glass sample weighing approximately 10 g.

[0097] The glass transition point was defined as the point where the straight line on the low-temperature side and the straight line on the high-temperature side of the thermal expansion curve, measured by a dilatometer, intersect.

[0098] The coefficient of thermal expansion was measured using a dilatometer in a temperature range of 30 to 300°C with a cylindrical glass sample measuring 5 mm in diameter and 20 mm in size.

[0099] The internal transmittance was measured as follows: Optically polished glass samples with thicknesses of 10 mm ± 0.1 mm and 5 mm ± 0.1 mm were measured at 0.5 nm intervals using a spectrophotometer (Shimadzu UV-3100). Based on the obtained measurements, the internal transmittance τ at a thickness of 10 mm was calculated using the following formula. 10 I calculated it.

[0100] logτ 10 =-{(logT5-logT 10 ) / Δd}×10(%) T5: Light transmittance of a glass sample with a thickness of 5 mm ± 0.1 mm T 10Light transmittance of a glass sample with a thickness of 10 mm ± 0.1 mm Δd: Thickness difference between the two glass samples

[0101] Furthermore, glass samples obtained by heat-treating them at 700-800°C for 72 hours and then cooling them to room temperature at -1°C / min were also measured for internal transmittance in the same manner. The internal transmittance values ​​before and after heat treatment, and the change in internal transmittance before and after heat treatment are shown in Tables 2 to 8. In addition, Figure 1 shows graphs plotting the relationship between basicity and the change in internal transmittance for No. 1-1 to 1-5, No. 2-1 to 2-5, No. 3-1 to 3-3, No. 4-1 to 4-2, No. 5-1 to 5-5, No. 6-1 to 6-2, and No. 7-1. Note that in Figure 1, compositions with the same total amount of TiO2 and Nb2O5 are shown on the same plot.

[0102] Furthermore, for samples No. 8-1 to No. 8-17, the solubility and external transmittance were evaluated or measured according to the melting temperature.

[0103] Solubility was measured as follows: The raw materials were mixed to achieve the compositions shown in Tables 6-8, and the resulting batches were placed in a platinum crucible and melted at 1270°C to 1330°C for 90 minutes. The molten glass was poured onto a carbon plate and shaped, then held at 700-800°C for 1 hour, cooled to room temperature at -1°C / min for annealing, and then machined to obtain glass samples measuring 10 mm × 50 mm × 100 mm. The number of bubbles and foreign matter present inside the obtained glass samples was counted by microscopic observation at 50x magnification, and measured by 1 cm². 3 The number of winning items was calculated.

[0104] External transmittance was measured as follows: The obtained glass sample was optically polished to a thickness of 10 mm, and the light transmittance (linear transmittance) at a wavelength of 450 nm, including surface reflection loss, was measured using a spectrophotometer (Shimadzu UV-3100).

[0105] Furthermore, water resistance, acid resistance, refractive index, Abbe number, density, and internal transmittance were measured using the methods described above. In addition, the content of Pt, Rh, and Fe2O3 was also measured. The Pt and Rh content was measured by ICP mass spectrometry after decomposing the crushed glass sample with a mixed acid containing HF, HClO4, HNO3, and HCl. The Fe2O3 content was measured by ICP mass spectrometry after decomposing the crushed glass sample with a mixed acid containing HF, H2SO4, HNO3, and HCl. The evaluation of these properties was performed using glass samples obtained by melting at 1270°C for Nos. 8-8 to 8-10 and 8-16 to 8-17, glass samples obtained by melting at 1300°C for Nos. 8-1, 8-3 to 8-7, and 8-11 to 8-15, and glass samples obtained by melting at 1330°C for No. 8-2.

[0106] As shown in Tables 2-8 and Figure 1, the glass samples in the examples had a high basicity of 12.1-15.4, and the difference in internal transmittance before and after heat treatment at a wavelength of 450 nm was 0-9%. From this, it can be seen that the glass samples in the examples exhibit excellent light transmittance in the visible range even without prolonged heat treatment.

[0107] Furthermore, as shown in Tables 6-8, higher melting temperatures tend to result in fewer internal defects such as bubbles and foreign matter, but also a decrease in external permeability. Conversely, lower melting temperatures tend to improve external permeability, but also increase the number of internal defects. However, it can be seen that even at low melting temperatures, increasing the (B2O3+La2O3+ZnO)-(SiO2+Y2O3+ZrO2) ratio can reduce internal defects. [Industrial applicability]

[0108] The optical glass 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. The glass composition is TiO in mol%. ２ and Nb ２ O ５ It contains 20 mol% or more of the total amount, Furthermore, in mole percent, TiO ２ 8 to 28.0%, Nb ２ O ５ 2 to 11%, B ２ O ３ 19% or less, Ln ２ O ３ (Ln is at least one selected from La, Gd, Y and Yb) contains 26.0% or more, and the molar ratio TiO ２ / Nb ２ O ５ is 5.8 or more, and the basicity is 12 or more, characterized by an optical glass.

2. The optical glass according to claim 1, characterized in that the refractive index nd is 1.8 to 2.

3.

3. The optical glass according to claim 1 or 2, characterized in that its Abbe number (νd) is 20 to 35.

4. The optical glass according to any one of claims 1 to 3, characterized in that it has a thickness of 10 mm and an internal transmittance of 80% or more at 450 nm.

5. Furthermore, in mol%, B ２ O ３ 10-19%, SiO ２ 3% or more, RO (R is at least one selected from Mg, Ca, Sr and Ba) 0-5%, Ta ２ O ５ 0-5%, Ln ２ O ３ (Ln is at least one selected from La, Gd, Y, and Yb) 26.0–50%, ZnO 0–1%, Al ２ O ３ 0-1%, and WO ３ The optical glass according to any one of claims 1 to 4, characterized in that it contains 0 to 0.2%.

6. The optical glass according to any one of claims 1 to 5, characterized in that when heat-treated at a temperature within ±200°C of the glass transition temperature for 72 hours, the change in internal transmittance at 450 nm with a thickness of 10 mm is less than 10%.

7. The glass composition is TiO in mol%. ２ and Nb ２ O ５ It contains 20 mol% or more of the total amount, Furthermore, in mol%, TiO ２ 8-28.0%, Nb ２ O ５ 2-11%, B ２ O ３ 19% or less, Ln ２ O ３ (Ln is at least one selected from La, Gd, Y, and Yb) Contains 26.0% or more, molar ratio TiO ２ / Nb ２ O ５ (B ２ O ３ +La ２ O ３ +ZnO) -(SiO ２ +Y ２ O ３ +ZrO ２ The percentage is 10-40%, and the number of bubbles and foreign matter present inside is 1 / cm². ３ An optical glass characterized by the following:

8. An optical glass plate characterized by being made of optical glass according to any one of claims 1 to 7.

9. The optical glass plate according to claim 8, characterized in that the plate thickness is 0.01 to 5 mm.

10. A light guide plate characterized by being made of an optical glass plate as described in claim 8 or 9.

11. The light guide plate according to claim 10, 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.

12. A wearable image display device characterized by comprising a light guide plate according to claim 10 or 11.

13. A method for manufacturing optical glass according to any one of claims 1 to 7, The process includes obtaining molten glass by melting raw materials, and then cooling the molten glass to obtain a molded body. A method for manufacturing optical glass, characterized in that the molded body is not subjected to heat treatment for 48 hours or more at a temperature within ±200°C of the glass transition temperature of the molded body.

14. The method for producing optical glass according to claim 13, characterized in that the melting temperature of the raw material is 1400°C or lower.

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