Polymerization initiator, polymerizable composition, cured product, and hydroperoxide having thioxanthone skeleton

The present invention pertains to a polymerization initiator (A) that contains a dialkyl peroxide (a-1) having a thioxanthone skeleton represented by general formula (1) and a hydroperoxide (a-2) having a thioxanthone skeleton represented by general formula (2), the amount of the dialkyl peroxide (a-1) being 100 parts by mass of the polymerization initiator (A), and the amount of the hydroperoxide (a-2) being 100 parts by mass of the polymerization initiator (A). The amount of the hydroperoxide (a-2) having a thioxanthone skeleton is 30 parts by mass or less. The polymerization initiator is capable of obtaining a polymerizable composition which exhibits excellent curability with respect to light having a wavelength of 365 nm or the like and which has excellent long-term storage stability at high temperatures. 本发明涉及一种聚合引发剂，其为含有由通式(1)表示的具有噻吨酮骨架的二烷基过氧化物(a-1)与由通式(2)表示的具有噻吨酮骨架的氢过氧化物(a-2)的聚合引发剂(A)，在100质量份的所述聚合引发剂(A)中，所述具有噻吨酮骨架的氢过氧化物(a-2)为30质量份以下。该聚合引发剂可得到相对于波长为365nm等的光表现出优异的固化性且在高温下的长期保存稳定性优异的聚合性组合物。