PURPOSE: To obtain a small-size printer applying printing to plain paper with high image quality, generating no environmental pollution and reduced in noise by using a photochromic material whose surface hydrophilicity is reversively changed by the irradiation with light as a latent image forming material.
CONSTITUTION: A shutter 6 is opened after a latent image forming process is completed. A thin membrane surface is formed on a photochromic sheet l by the rotation of a drum 2 in a clockwise direction. The exposed part of the photochromic sheet 1 shows hydrophilicity but the flocculation force of ink is low because of low viscosity and the ink is in a state non-separable between the hydrophilic part and hydrophobic part on the photochromic sheet l. Next, an electric field is formed by a power supply 11 so as to go toward the photochromic sheet 1 and the drum 2 from a transfer roller 7, an electrode 9 and a fixing roller 10. The viscosity of the ink at this part changes to one hundred and several tens P. The ink increased in viscosity of a non-image part is peeled off by the transfer roller 7 and the ink bonded to the transfer roller 7 becomes low in viscosity in a region of a non-strong electric field to be separated.