An ultraviolet curable resin composition comprises (A) an ultraviolet curable
resin obtained by reacting an epoxy group containing polymer (a), which is prepared
by polymerizing an ethylenically unsaturated monomer component including an ethylenically
unsaturated monomer (i) having an epoxy group, with an ethylenically unsaturated
monomer (b) having a carboxyl group, and then reacting a resultant intermediate
product with a saturated or unsaturated polybasic acid anhydride (c); (B) an epoxy
compound having at least two epoxy groups in molecule; (C) a photopolymerization
initiator; and (D) a diluent The ultraviolet curable resin includes 0.3 to 10 mol
of a polymerizable unsaturated group in 1 kg thereof. A photo solder resist ink
containing this resin composition has the capability of providing a permanent film
with excellent flexibility and solder heat resistance, and is preferably used to
manufacture flexible printed circuit boards.
