Abstract: A large sized opaque quartz glass ingot having an excellent heat ray shielding property, an outstanding light blocking property, high mechanical strength and small roughness of a baked finished smooth surface. The shape of bubbles inside the quartz glass are almost complete spheres and the average particle size of the bubbles is 1 ?m or less, such that the strength of the opaque quartz glass ingot is increased as the stress concentration at the edges of the bubbles is eliminated and an increase of surface roughness caused by baking is alleviated.

Abstract: Flame-retardant adhesives for circuit materials which are harmless to the environment, show excellent thermo-humidity resistant electrical characteristics and have high flame retardancy. These flame-retardant adhesives contain a saturated polyester resin and a flame retarder containing a component having P—C bond in its molecule and a component having nitrogen in its molecule, and the content of the flame retardant amounts to 90 parts by weight or more per 100 parts by weight of the saturated polyester resin.