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JP-7857122-B2 - Synthetic silica glass for optical components, method for manufacturing synthetic silica glass for optical components, and optical components

JP7857122B2JP 7857122 B2JP7857122 B2JP 7857122B2JP-7857122-B2

Inventors

  • 茶谷 直
  • 木村 康宏
  • 宮芝 一磨

Assignees

  • 株式会社オハラ

Dates

Publication Date
20260512
Application Date
20220314

Claims (8)

  1. A synthetic silica glass for optical components, in which chlorine and hydrogen are introduced, with a chlorine concentration of 9000 ppm or higher and a hydrogen molecule concentration of 1.0 × 10¹⁷ molecules/ cm³ or higher.
  2. The synthetic silica glass for optical components according to claim 1, wherein the peak intensity ratio (D2/SiO) of the peak originating from the three-membered ring structure of the silica glass (D2) to the peak originating from the skeletal vibration (SiO) in the Raman spectrum is 0.13 or less.
  3. A synthetic silica glass for optical components according to claim 1 or 2, used in the wavelength range of 175 nm to 3000 nm.
  4. A synthetic silica glass for optical components according to any one of claims 1 to 3, wherein the OH group concentration is 0 ppm or more and 30 ppm or less.
  5. A synthetic silica glass for optical components according to any one of claims 1 to 4, wherein the birefringence at 632.8 nm is 10 nm/cm or less.
  6. A synthetic silica glass for optical components according to any one of claims 1 to 5, wherein the decrease in transmittance at 193 nm before and after irradiation with a 100 kJ ArF laser is 1.0% or less.
  7. An optical component formed using synthetic silica glass for optical components as described in any one of claims 1 to 6.
  8. A method for producing synthetic silica glass for optical components according to any one of claims 1 to 6, A method for producing synthetic silica glass for optical components, comprising a hydrogen introduction step in which hydrogen is introduced into silica glass into which chlorine has been introduced, in a hydrogen gas-containing atmosphere at a temperature of 360°C to 600°C and a pressure of 0.9 MPa or less.

Description

This invention relates to synthetic silica glass for optical components, a method for producing synthetic silica glass for optical components, and optical components. There is a technique to increase the refractive index of silica glass by introducing chlorine into it. For example, Patent Document 1 describes a method for producing synthetic silica glass by depositing silica glass fine particles obtained by flame hydrolysis or oxidation of gaseous silicon compounds, and then heat-treating the porous glass body to produce transparent glass. In this method, chlorine is added to produce transparent glass in a gas atmosphere consisting of a mixed gas of 3-20% silicon tetrachloride ( SiCl₄ ) and the remainder being an inert gas, thereby increasing the refractive index and flattening the refractive index distribution. Publication No. 3845906 This is a schematic diagram illustrating the method for preparing sample A of the embodiment and the measurement locations.This is a schematic diagram illustrating the method for preparing sample B of the example and the measurement locations.This is a schematic diagram illustrating the method for preparing sample C in the example and the measurement locations.This figure shows the results of the transmittance measurement.This figure shows the results of the transmittance measurement. The embodiments of the present invention will be described in detail below. However, the present invention is not limited to the embodiments described below. <Synthetic silica glass for optical components> The synthetic silica glass for optical components according to this embodiment has chlorine and hydrogen introduced into it, with a chlorine concentration of 500 ppm or more and a hydrogen molecule concentration of 1.0 × 10¹⁷ molecules/ cm³ or more. When chlorine is introduced (doped) into silica glass, the hydrogen atoms in the OH groups are replaced by chlorine, resulting in a reduction in light absorption at longer wavelengths, such as in the near-infrared region. However, chlorine doping causes absorption at shorter wavelengths (e.g., around 200 nm), thus reducing the transmittance of short-wavelength light such as ultraviolet light. Therefore, chlorine-doped silica glass has been difficult to use in optical components that utilize short-wavelength light such as ultraviolet light. However, in this embodiment, by setting the chlorine concentration to 500 ppm or higher and the hydrogen molecule concentration to 1.0 × 10¹⁷ molecules/ cm³ or higher, absorption occurring on the short-wavelength side, such as ultraviolet light, is suppressed, thus suppressing the decrease in transmittance of short-wavelength light, such as ultraviolet light, caused by chlorine doping. Therefore, it becomes a synthetic silica glass for optical components that also has excellent transmittance of light on the short-wavelength side (for example, wavelengths of 175 nm to 280 nm, preferably wavelengths of 175 nm to 220 nm). Thus, it is suitable for optical components used in a wide wavelength range, for example, from 175 nm to 3000 nm. However, the present invention is not limited thereto, and can also be used as a material for optical components used in wavelength ranges shorter than 175 nm and longer than 3000 nm. Furthermore, Patent Document 1, which introduces chlorine, aims to increase the refractive index and flatten the refractive index distribution. The technology described in Patent Document 1 does not involve introducing hydrogen in addition to chlorine. In this specification, chlorine concentration in ppm refers to ppm by mass. The chlorine concentration should be 500 ppm or higher, but it may also be 1000 ppm or higher, or even 9000 ppm or higher. There is no particular upper limit to the chlorine concentration, but for example, it should be 15000 ppm or lower, and 11000 ppm or lower is also acceptable. The hydrogen molecule concentration is 1.0 × 10¹⁷ molecules/ cm³ or higher, preferably 5.0 × 10¹⁷ molecules/ cm³ or higher, and more preferably 7.0 × 10¹⁷ molecules/ cm³ or higher. The upper limit of the hydrogen molecule concentration is not particularly limited, but for example, it is 6.5 × 10¹⁸ molecules/ cm³ or lower, preferably 5.0 × 10¹⁸ molecules/ cm³ or lower, and more preferably 3.0 × 10¹⁸ molecules/ cm³ or lower. Furthermore, the synthetic silica glass for optical components according to this embodiment has a peak intensity ratio (D2/SiO) of 0.13 or less between the peak (D2) originating from the three-membered ring structure of the silica glass and the peak (SiO) originating from skeletal vibrations in the Raman spectrum. However, the D2/SiO ratio in this invention may be greater than 0.13. Skeletal vibrations are Si-O bond vibrations in the Si-O network structure of silica glass, and the peak (SiO) originating from skeletal vibrations is observed at 425–445 cm⁻¹ . The peak (D2) originating from the three-membered ring structure of silica glass, that is, the peak originating from the three-member