Process for producing polysilsesquioxane graft polymer, pressure-sensitive adhesive, and pressure-sensitive adhesive sheet

A process for producing a polysilsesquioxane graft polymer including a repeating unit shown by the following formula (1) in the molecule,

• wherein A represents a linking group, R1 represents a hydrocarbon group which may have a substituent, R2 represents a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, R3 represents a polar group or an aryl group which may have a substituent, R4 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an ester group, or an acyl group, k1, k2, and k3 individually represent arbitrary positive integers, provided that, when k1, k2, and k3 respectively represent two or more, the groups shown by the formula:
• —CH2—C(R2)(R3)— may be the same or different, and l, m, and n individually represent zero or an arbitrary positive integer, provided that the case where “m=n=0” is excluded, the process comprising applying ionizing radiation or heat to a mixture including a polysilsesquioxane compound including a repeating unit shown by the following formula (2),
• wherein A, R1, R4, l, m, and n have the same meanings as defined above, and Q represents an iniferter group, and a vinyl compound shown by the following formula (3):
• CH2═C(R2)—R3 (wherein R2 and R3 have the same meanings as defined above).