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JP-7856945-B2 - Optical glass

JP7856945B2JP 7856945 B2JP7856945 B2JP 7856945B2JP-7856945-B2

Inventors

  • 此下 聡子
  • 籔内 浩一

Assignees

  • 日本電気硝子株式会社

Dates

Publication Date
20260512
Application Date
20210329
Priority Date
20200406

Claims (14)

  1. The glass composition contains 20 mol% or more of TiO₂ and Nb₂O₅ in total, Furthermore, the optical glass is characterized by containing, in mol% terms, TiO2 8-28.0 %, Nb2O5 2-11 %, B2O3 19 % or less, and Ln2O3 (where Ln is at least one selected from La, Gd, Y , and Yb) 26.0% or more, with a molar ratio of TiO2 / Nb2O5 of 5.8 or higher, and a basicity of 12 or higher.
  2. The optical glass according to claim 1, characterized in that its 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 an internal transmittance of 80% or more at 450 nm with a thickness of 10 mm.
  5. Furthermore, the optical glass according to any one of claims 1 to 4 is characterized by containing, in mol%, 10-19 % B₂O₃ , 3% or more SiO₂ , 0-5% RO (where R is at least one selected from Mg, Ca, Sr, and Ba), 0-5% Ta₂O₅, 26.0-50% Ln₂O₃ (where Ln is at least one selected from La, Gd , Y, and Yb), 0-1% ZnO, 0-1 % Al₂O₃, and 0-0.2% WO₃ .
  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 contains 20 mol% or more of TiO₂ and Nb₂O₅ in total, Furthermore, the optical glass is characterized by containing, in molar percentages, 8 to 28.0 % TiO2 , 2 to 11% Nb2O5 , 19 % or less B2O3 , and 26.0% or more Ln2O3 (where Ln is at least one selected from La, Gd, Y , and Yb), with a molar ratio of TiO2 / Nb2O5 of 5.8 or more, a ( B2O3 + La2O3 + ZnO)-( SiO2 + Y2O3 + ZrO2 ) content of 10 to 40%, and having an internal number of bubbles and foreign matter of 1 or less per cm³ .
  8. An optical glass plate characterized by being made of optical glass as described in 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 as described in 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 materials is 1400°C or lower.

Description

This invention relates to optical glass used as a light guide plate or the like in wearable image display devices. Glass plates are used as components in wearable image display devices such as projector-equipped glasses, eyeglass-type or goggle-type displays, virtual reality (VR) or augmented reality (AR) display devices, and virtual image display devices. These glass plates function, for example, as see-through light guide plates, allowing the user to view the external scenery through the glass plate while simultaneously viewing the image displayed on it. Furthermore, it is possible to achieve 3D display by utilizing technology to project different images onto the left and right sides of the glasses, or to realize a virtual reality space by utilizing technology to fuse the image to the retina using the eye's lens. These glass plates are required to have a high refractive index for aspects such as wide-angle image enhancement, high brightness and contrast enhancement, and improved light guide characteristics (see, for example, Patent Document 1). Japanese Patent Publication No. 2017-32673Patent No. 6517411 The graph shows the relationship between the basicity and the change in internal transmittance for the glass samples obtained in the examples. 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 "mol%". 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. 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. In addition to TiO₂ and Nb₂O₅ , the optical glass of the present invention may also contain the following components. 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. 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. 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 hi