Liquid developing method and liquid developing apparatus

Abstract

A liquid developing method and a liquid developing apparatus that use a highly-concentrated liquid developing agent to develop an electrostatic latent image A highly-concentrated liquid developing agent with a viscosity of 100 to 1,000 mPa.s can be used. Therefore, a film of developing agent from 5 to 40 .mu.m thick can be formed on the surface of the developing roller or developing belt (510) and this provides a soft contact with the photosensitive member surface where the electrostatic latent image has been formed. If the surface of the photosensitive member does not have good release properties, a film of pre-wet liquid can be formed on the surface of the photosensitive member (10). A gap which is larger than the thickness of the liquid developing agent film and smaller than the sum of the thicknesses of the liquid developing agent film and the pre-wet liquid film is maintained between the surfaces of the photosensitive member and the developing roller or other developing agent bearing member such that the pre-wet liquid is always interposed between the two surfaces. Extremely good copies can be obtained if a 5 to 40 .mu.m thin film of liquid developing agent with a viscosity of 100 to 10,000 mPa.s and containing toner with an average particle size of 1 to 5.0 .mu.m at a concentration of 5 to 40% is used with a 30 .mu.m or less thin film of pre-wet liquid with a viscosity of 0.5 to 5.0 mPa.s and the gap between the photosensitive member and the developing agent roller or other developing agent bearing member is set at 5 to 60 .mu.m.