Patent ID: 8034171

Claim:
A water base ink for ink-jet recording comprising a coloring agent, water, a penetrant, and a surfactant, wherein: the penetrant includes diethylene glycol n-hexyl ether (A); the surfactant includes an acetylene glycol-based surfactant (B 1 ) and sodium polyoxyethylene alkyl ether sulfate (B 2 ); and (A), (B 1 ), and (B 2 ) are blended at ratios respectively to fulfill at least one condition of the following conditions (a) to (d): condition (a): all of expressions (a1) to (a5) hold: x≧ 0.05 (a1) 40.3 x+ 228.15 y− 146.25 z+ 81.9325≧0 (a2) 124.6 x+ 22.05 y− 78.75 z− 6.0725≦0 (a3) y≧ 2 x/ 9+3.05/9 (a4) y≦−x/ 3+1.85/3 (a5) condition (b): all of expressions (b1) to (b5) hold: x≦ 0.50 (b1) 56 x+ 63 y− 112.5 z+ 101.15≧0 (b2) 2.002 x+ 2.646 y− 1.575 z− 0.8687≦0 (b3) y≧−x/ 3+1.1/3 (b4) y≦ 2 x/ 9+3.05/9 (b5) condition (c): all of expressions (c1) to (c5) hold: x≧ 0.50 (c1) 2.8 x− 14 y+ 25 z− 30.1≦0 (c2) 12.6 x+ 42 y− 25 z− 4.2≦0 (c3) y≧x/ 5+0.1 (c4) y≦− 3 x/ 10+0.6 (c5) condition (d): all of expressions (d1) to (d5) hold: x≦ 1.00 (d1) 14 x− 70 y+ 75 z− 87.5≦0 (d2) 1.4 x+ 14 y− 5 z− 1.4≦0 (d3) y≧−x/ 10+0.25 (d4) y≦x/ 5+0.1 (d5) wherein: x: blending amount (% by weight) of (A) with respect to a total amount of the ink; y: blending amount (% by weight) of (B 1 ) with respect to the total amount of the ink; z: blending amount (% by weight) of (B 2 ) with respect to the total amount of the ink.