Shielding coat membrane for discharge lamp and manufacturing process thereof

摘要

A conventional black oxide colorant used for the shielding coat membrane of the D2R type discharge lamps for automobiles has a problem that its wettablity with the granulated glass is not good so that a strong membrane is difficult to be obtained.A paint for the shielding coat membrane comprises polycrystalline silica and Mn-doped ferric oxide as a black colorant, which has a good wettability with the granulated glass and a shielding characteristics so as to improve the membrane strength, thereby providing a lamp with the shielding coat membrane that passes all evaluation test in the view point of the membrane strength, the light transmissivity, the discoloration, the suppression of pealing-off and cracking.