Curable composition, cured product, and compound

A curable composition comprising a heterocyclic compound (A), an initiator (C), and a solvent (S), wherein the heterocyclic compound (A) is a compound represented by the following formula (A1):

• wherein RA1, RA2, and RA3 are each independently an optionally substituted monocyclic aromatic group or an optionally substituted condensed aromatic group, when the monocyclic aromatic group or the condensed aromatic group has a substituent, the substituent does not contain an aromatic ring, and three —NH— groups bonded to the triazine ring each are bonded to the aromatic ring in the RA1, the RA2, and the RA3;
• when the heterocyclic compound (A) has a polymerizable group, the curable composition comprises or does not comprise a polymerizable compound (B) other than the heterocyclic compound (A);
• when the heterocyclic compound (A) has no polymerizable group, the curable composition comprises a polymerizable compound (B) other than the heterocyclic compound (A);
• the polymerizable group is a radically polymerizable group-containing group or a cationically polymerizable group-containing group;
• when the curable composition comprises the heterocyclic compound (A) having the polymerizable group and the polymerizable compound (B), the polymerizable group possessed by the heterocyclic compound (A) and the polymerizable group possessed by the polymerizable compound (B) each is a radically polymerizable group-containing group or a cationically polymerizable group-containing group;
• and
• the solvent (S) comprises triethylene glycol dimethyl ether.