PURPOSE: To reduce the amount of gas emitted from hard glass at high temp. and provide a high transition point and superior meltability to the glass by specifying the contents of SiO2, Al2O3 and alkaline earth metal oxides (RO) in the glass and adding an adequate amount of ZnO.
CONSTITUTION: This hard glass has a composition 98wt% of which consists of 48W62% SiO2, 10W20% Al2O3, 20W30% RO and 2W10% ZnO (where RO is alkaline earth metal oxides composed of 10W23% BaO and 5W10% SrO+CaO+ MgO). This glass has characteristics such as ≥720°C transition point and ≤52× 10-7 thermal expansion coefft. at 0W300°C. It does not contain B2O3 and Na2O substantially, the content of an alkaline earth metal oxide is restricted to a low level, and ZnO is added in an adequate amount, so the glass has superior suitability to seal bonding to metal. Accordingly, it is fit for the bulb of a halogen lamp, etc.
KIMURA KAZUHISA
OOTA SHIYUNICHI
MIWA OSAMI
