Patent ID: 7151063

Claim:
Glass for a multilayer film filter comprising: SiO 2 , B 2 O 3 , Na 2 O, K 2 O, MgO and Al 2 O 3 , wherein a SiO 2 content is not less than 37 mol % nor more than 43 mol %; a B 2 O 3 content is not less than 2 mol % nor more than 5 mol %; Na 2 O content is not less than 5 mol % nor more than 20 mol %; a K 2 O content is not less than 7 mol % nor more than 20 mol %; a sum of the Na 2 O content and the K 2 O content is not less than 21 mol % nor more than 27 mol %; a MgO content is not less than 21 mol % nor more than 37 mol %; and a Al 2 O 3 content is not less than 3 mol % nor more than 10 mol %; and the glass contains a partial crystal, and a mean linear expansion coefficient of the glass is not lower than 125×10 −7 K −1 in a temperature range of 50° C. to 150° C.