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US 8,541,326 B2Granted
Optical member for deep ultraviolet and process for producing same
AssigneeAsahi Glass Company, Limited
InventorsRyusuke Morita, Takuya Nakagawa, Kei Iwata, Masaaki Takata
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Abstract
The present invention relates to an optical member for deep ultraviolet having a wavelength of 250 nm or shorter, containing a synthetic silica glass which does not substantially contain a halogen element, has a maximum OH group content of less than 10 ppm by weight, has contents of ODC (oxygen deficient centers) and E-prime center of each less than 1×1014 cm−3, does not substantially contain SiH and peroxy linkage, and has a fictive temperature of 1,050° C. or lower.
Claims20
An optical member comprising:
- a synthetic silica glass which does not substantially contain a halogen element, has a maximum OH group content of less than 10 ppm by weight, has contents of an oxygen deficient center and an E-prime center of each less than 1×1014 cm−3, does not substantially contain SiH and peroxy linkage, and has a fictive temperature of 1,050° C. or lower,
- wherein the synthetic silica glass is transparent to a deep ultraviolet light having a wavelength of 250 nm or shorter.
A process for producing an optical member, comprising:
- synthesizing a porous synthetic silica glass body having a volume average bulk density of 0.33 g·cm−3 or more, the synthesizing comprising growing glass fine particles by a flame hydrolysis reaction of a raw material comprising a silicon compound;
- pre-sintering the porous synthetic silica glass body after the synthesizing;
- subjecting the porous synthetic silica glass body to a heat treatment at a temperature in a range of from 1,050 to 1,250° C. for more than 90 hours in vacuum at a pressure of 1×10−2 Pa or less;
- and
- performing a transparent vitrification of the porous synthetic silica glass body to obtain a synthetic silica glass.
2 more elements
Dependencies are inferred from the claim text.