| abstract |
Disclosed is a sealing agent for an optical semiconductor element, which has excellent transparency, heat resistance, light resistance and adhesiveness, has a stably controlled shape when used for sealing a light-emitting element for an optical semiconductor element, and can prevent the precipitation of a phosphor. Also disclosed is an optical semiconductor element which is produced by using the sealing agent. Specifically disclosed is a sealing agent for an optical semiconductor element, which comprises a silicone resin having a cyclic-ether-containing group in the molecule, a thermosetting agent capable of reacting with the cyclic-ether-containing group and a silicon oxide microparticle, which has a viscosity of 500 to 10,000 mPa s as measured on an E-type viscometer at 25˚C and at 5 rpm, which has a thixotropic value of 1.2 to 2.5 [wherein the thixotropic value is calculated by dividing a viscosity measured on an E-type viscometer at 25˚C and at 1 rpm by a viscosity measured under the same conditions except that 10 rpm is employed in place of 1 rpm (i.e., a (viscosity at 1 rpm)/(viscosity at 10 rpm) value), and which has a minimum viscosity of 100 mPa s or more as measured on a parallel-plate rheometer at 1 s-1 in the temperature range from 25˚C to a curing temperature. |