INK-JET INK SET FOR CARDBOARD, AND IMAGE FORMATION METHOD

WIPO Patent Application WO/2017/061507

A1

Provided is an ink-jet ink set for cardboard, said set comprising the five color inks of cyan ink, magenta ink, yellow ink, black ink, and an α ink, wherein, when an image having a halftone dot area ratio of 100% is formed on a cardboard substrate using each of the five color inks separately, a hue angle h, a chroma saturation C*, and a lightness L* of the formed image in the CIE 1976 L*a*b* color space satisfy the relationships in formulas (1)-(3). Also provided is an image formation method. In formula (1), hM, hα, and hY represent the hue angle h of each ink. In formula (2), C*M, C*α, and C*Y represent the chroma saturation C* of each ink. In formula (3), L*M and L* α represent the lightness L* of each ink. Formula (1): hM