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

摘要

Disclosed is a one-component type magnetic developer for development of positively charged images and transfer of developed images, which comprises particles of a composition comprising a finely divided magnetic material dispersed in a binder medium comprising a vinyl aromatic polymer or acrylic polymer in an amount of 45 to 95% by weight based on the magnetic material, said particles of the magnetic material having a bulk density of at least 0.42 g/ml, a number average maximum size of 0.35 mu m as measured by an electron microscope and a maximum size/minimum size ratio of from 1.0 to 5.5, especially from 1.0 to 3, wherein said composition further comprises an aliphatic carboxylic acid 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 and a negative charge controlling agent consisting of an alcohol-soluble metal-containing dye in an amount of 0.5 to 5% by weight based on said polymer. This magnetic developer provides an excellent transferred image having high image density and image sharpness on a plain paper as a transfer sheet without fogging or broadening of the contour of the image. This image is excellent in reproducibility of fine lines, solid black portions and half tones.