(Meth)acrylic copolymer, pressure-sensitive adhesive composition, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet

A pressure-sensitive adhesive composition comprising a (meth)acrylic copolymer, the (meth)acrylic copolymer comprising a constituent unit a derived from a macromonomer, a constituent unit b derived from a monomer represented by Formula (b), and a constituent unit c:

• wherein the macromonomer comprises two or more of a constituent unit X1 represented by formula X1:
• in formula (X1),
• R1 represents a hydrogen atom, a methyl group, or CH2OH, and
• R2 represents OR3, a halogen atom, COR4, COOR5, CN, CONR6R7, NHCOR8 or R9,
• R3 to R8 each independently represent a hydrogen, a substituted or unsubstituted alkyl group, a substituted or unsubstituted alicyclic group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted nonaromatic heterocyclic group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted alkaryl group, a substituted or unsubstituted organosilyl group, or a substituted or unsubstituted polyorganosiloxane, and
• R9 represents a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, or a substituted or unsubstituted nonaromatic heterocyclic group,
• in Formula (b),
• RA and RB each independently represent an alkyl group, a carboxyl group, or a halogen atom,
• n represents 0,
• m represents 0, and
• X represents a (meth)acryloyloxy group or a (meth)acryloyloxyalkyleneoxy group,
• the constituent unit c comprises the constituent unit X1,
• an amount of the constituent unit b is 0.01 to 25 wt % with respect to a total amount of the (meth)acrylic copolymer, and
• the glass transition temperature of the (meth)acrylic copolymer is −5° C. or lower.