Patent ID: 8795425

Claim:
An ink for an ink-jet recording apparatus, comprising water, a pigment dispersion, a super-penetrating agent, and a high SP organic solvent, wherein the super-penetrating agent comprises at least one compound selected from the group consisting of 1,2-hexylene glycol, 2,4-diethyl-1,5-pentanediol, 2-ethyl-1,3-hexanediol, and 2-butyl-2-ethyl-1,3-propanediol, the high SP organic solvent is an organic solvent having an SP value of 13 or greter and less than 23 and comprises at least 1,3-propanediol, glycerin and diethylene glycol diethyl ether, a content of 1,3-propanediol is from 10% to 20% by mass based on a mass of the ink, all of ΔSPs which are differences between SP values of neighboring organic solvents in order of SP values thereof are from 0.5 to 5.0, and difference of SP max −SP min is 12 or less, in which SP max is the highest SP value of an organic solvent among organic solvents in the high SP organic solvent and SP min is the smallest SP value of an organic solvent among organic solvents in the super-penetrating agent.