Coating composition and coating film

An antifouling coating composition comprising a silicon atom-containing resin,

• wherein
• the silicon atom-containing resin includes:
• a constituent unit (A) derived from a monomer (a) having at least one kind of silicon atom-containing group selected from the group consisting of a group represented by a formula (I) below, a group represented by a formula (II) below, a group represented by a formula (III) below, and a group represented by a formula (IV) below;
• a constituent unit (B) derived from a monomer (b) which is a (meth)acrylic acid ester represented by a formula (b) below;
• and
• a constituent unit (C) derived from a monomer (c) other than the monomer (a) and the monomer (b),
• the monomer (a) has a number average molecular weight of greater than 2500,
• a content of the constituent unit (A) is greater than 20% by mass in all constituent units contained in the silicon atom-containing resin,
• the monomer (c) is a monomer having a homopolymer solubility parameter SP of greater than or equal to 9.0 (cal/cm3)1/2 and less than or equal to 9.5 (cal/cm3)1/2 and having no cyclic structure, and
• a content of the constituent unit (C) is greater than 2% by mass in all constituent units contained in the silicon atom-containing resin:
• [in the formula (I), a and b each independently represent an integer of 2 to 5, m represents an integer of 0 to 50, and n represents an integer of 3 to 270;
• and R1 to R5 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group, or a substituted phenoxy group];
• [in the formula (II), c and d each independently represent an integer of 2 to 5, and p represents an integer of 0 to 50;
• R6, R7, and R8 each independently represent an alkyl group, Ra, or Rb;
• Ra is
• (in the formula, x represents an integer of 0 to 200, and R23 to R27 are the same or different and each represent an alkyl group);
• Rb is
• (in the formula, y represents an integer of 1 to 200, and R28 and R29 are the same or different and each represent an alkyl group)];
• [in the formula (III), e, f, g, and h each independently represent an integer of 2 to 5, q and s each independently represent an integer of 0 to 50, and r represents an integer of 3 to 270;
• R9 to R12 each independently represent an alkyl group, an alkoxy group, a phenyl group, a substituted phenyl group, a phenoxy group, or a substituted phenoxy group];
• [in the formula (IV), i, j, k, and 1 each independently represent an integer of 2 to 5, t and u each independently represent an integer of 0 to 50, and v and w each independently represent an integer of 0 to 70;
• and R13 to R22 are the same or different and each represent an alkyl group];
• and
• CH2═C(RA)(COORB) (b)
• [in the formula (b), RA represents a hydrogen atom or a methyl group;
• and RB represents a monovalent group including one or more kinds selected from the group consisting of a hydroxyl group, a carboxy group, and an oxyalkylene chain], and
• wherein
• the antifouling coating composition further comprises at least one kind of solvent selected from the group consisting of hydrocarbons, ethers, esters, ketones and alcohols, and
• the silicon atom-containing resin is dissolved in the solvent.