A polymerization initiator system for reactive monomers and unsaturated polymers which is contains a Group 4 transition metal or Group 4 transition metal-containing compound, peroxide or diazo compound that is capable of being reduced by the Group 4 transition metal or Group 4 transition metal-containing compound, and pinacol compound is disclosed. Further disclosed are methods for preparing the polymerization initiator and using the polymerization initiator for low temperature curing.

A photocurable composition exhibits favorable adhesion force to an adherend, and favorable durability upon compression of a cured product thereof. A photocurable composition contains the following components (A) to (D), component (A): a polyisobutylene compound having a (meth)acryloyl group in a molecule; component (B): a urethane-modified (meth)acrylate oligomer, excluding the component (A); component (C): a monomer having a (meth)acryloyl group, excluding the component (A) and the component (B); and component (D): a photoinitiator. A content of a monomer having an alicyclic structure and a (meth)acryloyl group is 6 to 20 mass % based on 100 mass % of a total amount of the component (C).

An optical film includes: a transparent substrate; and a colored layer laminated on at least one side of the transparent substrate, the colored layer containing a dye (A), the dye (A) containing a colorant having a wavelength of maximum absorption in the range of 470 nm to 530 nm, the colorant containing a dipyrromethene cobalt complex having a structure represented by formula (I), in which R.sup.1 to R.sup.7 are combined such that a free energy change between before and after the reaction, calculated by applying R.sup.1 to R.sup.7 in the formula (I) to a predetermined reaction formula (II) using a quantum chemical calculation program Gaussian 16 with a calculation method B3LYP and a basis function 6-31G (d,p) (however, a basis function LanL2DZ is assigned to elements having an atomic number greater than that of Kr in the periodic table), is 0.92 kcal/mol or greater.

An example of a bottlebrush polymer has a polymer backbone and a plurality of individual brush moieties bonded to the polymer backbone. The individual brush moieties respectively include a crosslinked oxyamine moiety, a hydrophilic segment, and a surface adhesive terminal group.

An example of a bottlebrush polymer has a polymer backbone and a plurality of individual brush moieties bonded to the polymer backbone. The individual brush moieties respectively include a crosslinked oxyamine moiety, a hydrophilic segment, and a surface adhesive terminal group.