| abstract |
(57) [Summary] Excellent repetition bending resistance and adhesiveness used for flexible printed wiring board, cover lay material and bonding sheet which are flexible printed wiring board materials. An epoxy resin composition having heat resistance, moisture resistance and electrical reliability, and a substrate for flexible printed wiring, a coverlay material and a bonding sheet using the same. An epoxy resin (a) and a curing agent (b) obtained by modifying a bifunctional glycidyl ether type epoxy resin having an epoxy equivalent of 150 to 3000 eq / g with a butadiene-acrylonitrile copolymer having carboxyl groups at both terminals. An epoxy resin composition comprising an ion scavenger (c) and a crosslinked rubber (d) having an average particle size of 1 μm or less. |