Epoxy composition for encapsulating an optical semiconductor element

A composition comprising:

• (i) a curable blend formed by mixing (A), (B), and (C) at a temperature of 40 to 100° C. for 1 to 100 hours, causing at least a portion of (C) to react with (A), (B) or both (A) and (B);
• and
• (ii) (D) 0.1 to 3 parts by mass of a curing catalyst per total 100 parts by mass of the aforesaid components (A) and (B);
• wherein
• (A) is a silicone-modified epoxy compound represented by the following formula (1)
• wherein R1 is, independently of each other, a substituted or unsubstituted monovalent hydrocarbon group having 1 to 20 carbon atoms, R2 is a group represented by the following formula (2), X is a group represented by the following formula (3), c is an integer of from 0 to 10, a and b are, independently of each other, an integer of from 0 to 100, provided that 0≦a+b≦100, and α is, independently of each other, 0 or 1, provided that the aforesaid formula (1) has at least one R2,
• wherein d and e are, independently of each other, an integer of from 0 to 100, provided that 0≦d+e≦100, and α is as defined above;
• (B) is a curing agent provided in an amount of 0.5 to 1.5 equivalents per epoxy equivalent of the component (A);
• and
• (C) is a polyhydric alcohol provided in an amount of 0.01 to 1.0 equivalents per equivalent of the curing agent (B).