Composition for producing resin

A composition comprising:

• (a) 30 to 95% by weight of a compound having, in one molecule, one or more structures represented by the following formula (1):
• wherein R1 is a single bond or a divalent hydrocarbon group having 1 to 10 carbon atoms, R2, R3 and R4 are each hydrogen or a hydrocarbon group having 1 to 10 carbon atoms, Y is O, S, Se or Te, m is an integer of 1 to 5 and n is an integer of 0 to 5;
• (b) 1 to 40% by weight of a compound having at least one group selected from the group consisting of isocyanate group and isothiocyanate group in one molecule;
• and
• (c) 1 to 50% by weight of a compound having at least one mercapto group in one molecule,
• the weight percentages of the compounds (a), (b) and (c) being selected from the respective weight percentage ranges so that the total of the weight percentages of the compounds (a), (b) and (c) adds up to 100% by weight.