Monomer mixture and curable composition containing same

A monomer mixture comprising two or more types of cationically polymerizable monomers,

• the monomer mixture comprising:
• not less than 10 wt. %, based on a total amount of the monomer mixture, of a compound (I);
• not less than 5 wt. %, based on the total amount of the monomer mixture, of a compound (b);
• and
• 15 to 50 wt. %, based on the total amount of the monomer mixture, of a compound (b′), and
• the monomer mixture having a weight ratio of the compound (I) to the compound (b) of from 1.1 to 5.5,
• where:
• the compound (I) has at least one cationically polymerizable group selected from the group consisting of a vinyl ether group, an epoxy group, and an oxetanyl group, and at least one hydroxy group in a molecule,
• the compound (b) is represented by Formula (b):
• where R represents an s-valent straight-chain or branched saturated aliphatic hydrocarbon group or an s-valent group having two or more straight-chain or branched saturated aliphatic hydrocarbon groups bonded to each other through an ether bond, and s represents an integer of 2 or greater, and
• the compound (b′) is represented by Formula (b′):
• where X represents a single bond or a linking group;
• the monomer mixture further comprising:
• at least one of a compound represented by Formula (a-1) and a compound represented by Formula (a-2):