White heat-curable epoxy resin composition for optical semiconductor element encapsulation and optical semiconductor device using same

A white heat-curable epoxy resin composition comprising:

• (A) a prepolymer as a molten mixture of
• (A-1) an epoxy resin:
• a triazine derivative epoxy resin and/or an alicyclic epoxy compound having an epoxy group and an alicyclic structure in one molecule and being non-fluid at 25° C.,
• (A-2) an acid anhydride having no carbon-carbon double bond and
• (A-3) an acrylic resin-based modifier having an epoxy group and a weight-average molecular weight of 1,000 to 30,000, wherein
• a ratio of [equivalent of epoxy groups in (A-1) and (A-3)]/[equivalent of acid anhydride groups in (A-2)] is 0.6 to 2.0, and an amount of the component (A-3) added is 2 to 30 parts by mass per a total of 100 parts by mass of the components (A-1) and (A-2);
• (B) a white pigment containing a titanium oxide by an amount of not smaller than 10% by mass, the white pigment being in an amount of 3 to 350 parts by mass per the total of 100 parts by mass of the components (A-1) and (A-2);
• (C) an inorganic filler in an amount of 80 to 600 parts by mass per the total of 100 parts by mass of the components (A-1) and (A-2);
• (D) a curing accelerator in an amount of 0.05 to 5 parts by mass per the total of 100 parts by mass of the components (A-1) and (A-2);
• and
• (E) an antioxidant in an amount of 0.1 to 12 parts by mass per the total of 100 parts by mass of the components (A-1) and (A-2).