Process for producing glass product having gradient of refractive index

Claim 1

A process for producing a glass product having a gradient of refractive indices and transparent without turbidity which comprises: (a) producing a porous glass body by: (1) heating a glass body to effectuate a phase separation; (2) leaching out the acid-soluble phase from said glass body; and then (3) recovering therefrom the porous glass body; (b) premeating a solution of dopant into the micropores of said porous glass product wherein said dopant is selected from the group consistin of (1) TlNO 3 , the concentration of TlNO 3 in the dopant solution being about 80 g/100 ml of H 2 O or less, (2) TlNO 3 and an alkali metal compound, the concentration of TlNO 3 in the dopant solution being about 100 to 400 g/100 ml of H 2 O, and (3) TlNO 3 , Pb(NO 3 ) 2 and an alkali metal compound, the concentration of TlNO 3 in the dopant solution being about 100 to 400 g/100 ml of H 2 O, (c) leaching out a portion of the dopant from the micropores with or without solidifying the dopant in the micropores to form a concentration gradient of the dopant in said porous glass product; (d) solidifying the dopant in the micropores, (e) drying the porous glass product, (f) heat treating said porous glass product to collapse the micropores, and (g) recovering a glass having Δn greater than 0.04 wherein Δn is the difference between the central and peripheral portions of the glass.