One-component type magnetic developer for development and transfer of positively charged images

Claim 1

In an electrostatic photographic reproduction process which includes the steps of forming a positively charged latent image on a photosensitive plate having a p-type photoconductive layer on an electrically conductive substrate, contacting a magnetic brush of a dry one-component magnetic developer with the surface of the plate carrying the latent image thereon to form a visable image of the developer, contacting the developer image with a transfer sheet and applying corona discharge with the same polarity as that of the electrostatic latent image to transfer the developer image onto the transfer sheet, and fixing the transferred image on the transfer sheet, the improvement comprising using as said magnetic brush a dry one-component magnetic developer which comprises a finely divided magnetic material dispersed in a medium, said medium consisting essentially of (A) a vinyl aromatic polymer or acrylic polymer in an amount of 45 to 95% by weight based on the magnetic material, (B) an aliphatic carboxylic acid or metal salt thereof having a total carbon number (inclusive of the carbon atom of the carboxyl group) of at least 14 per carboxyl group in an amount of 0.2 to 4% by weight based on said magnetic material and (C) a negative charge controlling agent consisting of an alcohol-soluble complex salt azo dye containing chromium, iron or cobalt in an amount of 0.5 to 5% by weight based on said polymer, said magnetic material being triiron tetroxide having a bulk density of at least 0.42 g/ml, a number average maximum size of at least 0.35 μm as measured by an electron microscope and a maximum size/minimum size ratio of 1.0 to 5.5.