Provided are: a radical polymerization initiator which has excellent sensitivity and solubility in water; a composition containing the same; a cured product of the composition; a method of producing the cured product; and a compound. The radical polymerization initiator contains a compound represented by Formula (A) below (wherein Z
1
represents a direct bond or the like; Z
2
represents >CR
102
2
or the like; R
1
to R
8
each represent a hydrogen atom or the like, or a group containing a salt-forming group, which is represented by Formula (B1) below (wherein L
1
represents a direct bond or the like, B represents an acidic group salt or the like, b represents 1 to 10, and the asterisk (*) represents a binding site); at least one of R
1
to R
8
is the group containing a salt-forming group; R
101
and the like each represent a hydrogen atom or the like; one or more hydrogen atoms in the alkyl group and the like used as R
1
to R
8
and the like are optionally substituted with an ethylenically unsaturated group or the like; one or more methylene groups in R
1
to R
8
and the like are optionally substituted with a double bond or the like; adjacent groups such as R
1
and R
2
are optionally bound together to form a ring and optionally form a fused ring with a benzene ring in Formula (A); and R′ represents a hydrogen atom or the like).
提供了:具有优异灵敏度和
水溶性的自由基聚合
引发剂;含有该
引发剂的组合物;该组合物的固化产物;生产该固化产物的方法;以及一种化合物。自由基聚合
引发剂包含以下式(A)所代表的化合物(其中Z1代表直接键或类似物;Z2代表>CR1022或类似物;R1至R8各自代表氢原子或类似物,或者包含盐形成基团的群,该基团由下式(B1)代表(其中L1代表直接键或类似物,B代表酸性基团盐或类似物,b代表1至10,星号(*)代表结合位);R1至R8中至少有一个是包含盐形成基团的群;R101等各自代表氢原子或类似物;R1至R8等中所用的烷基群等中的一个或多个氢原子可以选择性地被
乙烯不饱和基团等替代;R1至R8等中的一个或多个亚甲基群可以选择性地被双键等替代;相邻的群,如R1和R2,可以选择性地结合在一起形成环,并且可以选择性地与式(A)中的苯环形成融合环;R′代表氢原子或类似物)。