Methacrylic acid ester polymer, method for producing same, active energy ray-curable composition, and optical recording medium

An active energy ray-curable resin composition comprising:

• 100 parts by mass of a resin composition comprising:
• 5 to 50 parts by mass of a methacrylic acid ester polymer having an acid value of no higher than 50 mg KOH/g and a transition metal content of no more than 1 ppm, wherein the methacrylic acid ester polymer comprises at least 80% by mole of a polymer having a terminal double-bond structure represented by Formula (1), and 50 to 95 parts by mass of a radical-polymerizable compound comprising a compound having at least two (meth)acryloyl groups per molecule;
• and
• 1 to 20 parts by mass of a photopolymerization initiator,
• wherein R in Formula (1) represents an alkyl group, a cycloalkyl group or an aryl group.

An active energy ray-curable resin composition comprising:

• 100 parts by mass of a resin composition comprising 5 to 50 parts by mass of a methacrylic acid ester polymer having an acid value of no higher than 50 mg KOH/g and a mass average molecular weight of 3000 to 30000, and 50 to 95 parts by mass of a radical-polymerizable compound comprising a compound having at least two (meth)acryloyl groups per molecule;
• and
• 1 to 20 parts by mass of a photopolymerization initiator,
• wherein an organic solvent content is no more than 1% by mass.