Patent ID: 6420290
Filing Date: 2002-07-16
Classification: C03C,Y10S

Abstract:
Colourless inorganic glasses containing copper halides or copper cadmium halides and having a sharp optical absorption cutoff between 370 nm and 425 nm;consisting essentially of, expressed in cationic percentages: 23-73%SiO215-45%B2O3â€‚0-24%Al2O3â€‚0-12%Li2Oâ€‚0-20%Na2Oâ€‚0-12%K2O0-5%CaO + BaO + SrO0.125-1%â€ƒâ€‚â€‰Cu2O0-1%CdO0-5%ZrO2withâ€ƒâ€‰0-1.75%Cl0.25-2% Cl + Br andthe weight content of0-2%Br BR exceeding that ofCl (Br > Cl)and0-2%F;the Cl, Br and F contents being expressed in percentages by weight of the total composition; with an effective amount of at least one reducing agent selected from SnO2, As2O3, Sb2O3 , and mixtures thereof, in order to have mainly, in said glasses, the copper in the form of cuprous ions (Cu+), and thereby providing glasses which have neither a red coloration, nor a blue green coloration; and having a minimal yellow coloration whereby they have, according to the Standard T 51-067 (NF): a yellow index of less than 1.3 for a 2 mm. thick glass having a UV cutoff wavelength at 1% transmission between 370 and 395 nm; a yellow index of less than 2.3 for a 2 mm. thick glass having a UV cutoff wavelength at 1% transmission at 400 nm; a yellow index of less than 4 for a glass having a UV cutoff wavelength at 1% transmission, at 405 nm; a yellow index of less than 20 for a glass having a UV cutoff wavelength at 1% transmission at 411 nm; a yellow index of less than 50 for a 2 mm. thick glass having a UV cutoff wavelength at 1% transmission at 415 nm.