| 摘要 |
PROBLEM TO BE SOLVED: To provide optical quartz glass for UV which shows excellent initial transmittance and smaller transmittance reduction by irradiation with respect to an excimer laser beam such as that of KrF or ArF and also to provide a process for producing the optical quartz glass. SOLUTION: This optical quartz glass has a 10-30 ppm OH group concentration expressed in terms of a mass ratio, a <=10 ppm difference between the maximum and minimum OH group concentrations within the glass, a <=0.10 ppm/mm concentration gradient, a >=1018 mol/cm3 hydrogen content and a refractive index of 1.50860 at 248.25 nm wavelength. The production process comprises steps of preparing a synthetic quartz glass material by subjecting a silica porous body to OH group removal treatment at 1,100-1,500 deg.C under reduced pressure and thereafter subjecting the treated material to sintering to make a material transparent, subjecting the prepared synthetic quartz glass material to compression at 1,500-1,700 deg.C so as to provide a >=40% degree of compression, subjecting, after completion of the compression, the compressed material to strain removal treatment that comprises cooling the compressed material to <=600 deg.C at a 1-10 deg.C/hr cooling rate, and subsequently subjecting the cooled material to hydrogen-doping treatment in a hydrogen atmosphere under a <=1 MPa pressure at 400-1,000 deg.C for 10-200 hr. |
