Patent ID: 6812175
Filing Date: 2004-11-02
Classification: C03C

Abstract:
A glass composition for an electric lamp comprising, expressed in mol %:SiO2â€‰70 to 85%,Al2O3â€‚â€‰0 to 10%,B2O3â€‚â€‰0 to 10%,Li2Oâ€‚â€‰0 to 6%,Na2Oâ€‚â€‰1 to 7%,K2Oâ€‚â€‰5 to 15%,MgOâ€‚â€‰0 to 5%,CaOâ€‚â€‰0 to 5%,SrOâ€‚â€‰0 to 0.5%,BaO0.1 to 1%ZnOâ€‚â€‰0 to 2%,PhOâ€‚â€‰0 to 8.5%,wherein a total amount of MgO, CaO, SrO, BaO, ZnO and PbO constitutes 2 to 8.5%; wherein K2O is contained in a larger amount than an amount of Na2O; wherein a total amount of Li2O, Na2O and K2O constitutes 12 to 17%; wherein a brittleness index value B of the glass composition that is determined by the Vickers hardness test is 7,000 mâˆ’1/2 or lower; and wherein a thermal expansion coefficient &agr; of the glass composition is 91Ã—10âˆ’7 Kâˆ’1 to 97Ã—107âˆ’Kâˆ’1, where the thermal expansion coefficient &agr; is determined by a measurement performed at a temperature of 30 to 380Â° C.