Patent ID: 8133957

Claim:
A resin composition for encapsulating an optical semiconductor element, comprising components (A), (B), (C), and (D) described below: (A) a branched silicone resin containing 2 to 6 epoxy groups, one or more (R 1 SiO 3/2 ) units, two or more (R 2 R 3 SiO) n structures and 3 or more (R 4 3-x R 5 x SiO 3/2 ) units per molecule, in an amount of 100 parts by weight, wherein R 1 , R 2 , R 3 , R 4 and R 5 each represents a hydrogen atom, a hydroxyl group or a monovalent organic group of 1 to 20 carbon atoms which monovalent organic group may or may not contain an oxygen atom, provided that at least two of the R 5 groups within each molecule represent an epoxy group and/or an epoxy group-containing non-aromatic group, n represents an integer of 3 to 20, and x represents an integer of 1 to 3, (B) a curing agent, in such an amount that a content of epoxy reactive groups in the component (B) ranges from 0.4 to 1.5 moles per 1 mol of epoxy groups within component (A), (C) a curing catalyst, in an amount within a range from 0.01 to 3 parts by weight per 100 parts by weight of a combination of component (A) and component (B) and (D) a diepoxy carboxylate.