Camphorquinone derivative of acylphosphine oxide group, photopolymerization initiator and photo-/ chemical polymerization initiator and curable composition containing this derivative

Camphorquinone derivative having an acylphosphine oxide group [- (C = O) - (P = O) <] in each molecule, represented by the following general formula (I) is represented: [Chemical Formula 1] [wherein R R represented by the following general formula (II) ...