PURPOSE: To prevent a photosensitive silver halide from being released from a fine particle even in the case of heat fixing, to prevent an unexposed ink particle from coming into contact with a coloring developer and to prevent the unexposed ink particle from coloring at the time of heat fixing.

CONSTITUTION: The ink particle is obtained by dispersing fine particles 2, 7 containing at least a color latent image forming material 4 having an outer shell layer 6 composed of a resin having ≥200°C m.p. and 7.5-12 solubility parameter or a porous outer shell layer 8 having 0.05-0.5μm pore diameter in a binder resin. And in a binding composition, at least the color latent image forming material 4 and thermosetting agent 10 are contained and a fine particle 9 having an outer shell layer composed of a resin is dispersed.