Block copolymer

A cured product of a curable resin composition, wherein the curable resin composition comprises a block copolymer comprising:

• a hard segment having a glass transition temperature of 25° C. or more;
• and
• a soft segment having a glass transition temperature of 10° C. or less,
• wherein the soft segment comprises a polymerization unit derived from a cross-linkable monomer, and
• the polymerization unit derived from the cross-linkable monomer has a higher concentration in a region adjacent to the hard segment than in a region which is not adjacent to the hard segment,
• wherein the cured product of the curable resin composition has a phase-separated structure comprising a shell layer and a spherical domain, wherein the shell layer comprises the soft-segment, and the spherical domain comprises the hard segment, and the shell layer has a higher cross-linking density in a region adjacent to the hard segment than in a region which is not adjacent to the hard segment.