Patent ID: 8304357

Claim:
A ceramic material composition comprising from 20 to 50 mass % of a borosilicate glass powder, from 25 to 55 mass % of an alumina filler powder and from 10 to 45 mass % of a filler powder (a high refractive index filler powder) having a refractive index higher than the alumina filler powder, wherein the borosilicate glass powder comprises, as calculated as oxides, from 30 to 70 mass % of SiO 2 , from 5 to 28 mass % of B 2 O 3 , from 5 to 30 mass % of Al 2 O 3 , from 3 to 35 mass % of CaO, from 0 to 25 mass % of SrO, from 0 to 25 mass % of BaO, from 0 to 10 mass % of Na 2 O, from 0 to 10 mass % of K 2 O, from 0.5 to 10 mass % of Na 2 O+K 2 O and from 3 to 40 mass % of CaO+SrO+BaO, and satisfies the following conditions: in the borosilicate glass powder, as represented by mass %, the value of “three times the B 2 O 3 content”+“twice (the CaO content+the SrO content+the BaO content)”+“ten times (the Na 2 O content+the K 2 O content)”, is within a range of from 105 to 165.