Liquid developer for electrostatic latent image

Claim 1

A liquid developer for developing electrostatic latent images consisting essentially of: (a) an electrically insulating isoparaffinic hydrocarbon carrier liquid having a volumetric resistance of at least 10 9 ohm-cm and a dielectric constant no greater than 3; (b) a toner insoluble in said carrier liquid composed of a pigment or dye and a light transmitting thermoplastic resin having a softening point range from 50°-130° C.; (c) a surface active agent soluble in said carrier liquid in amounts between 10 -3 and 10 gm. per liter of liquid developer selected from the group consisting of lecithin, cephalin, an alkyl alanine containing an alkyl group having 8-20 carbon atoms; a metal salt of naphthenic acid wherein the metal is Ca, Mn, Pb, Zn, Fe, Al or Ni; a fatty acid zirconium salt containing an alkyl group having 2-30 carbon atoms; a metal salt of an alkyl benzene sulfonate containing an alkyl group having 8-20 carbon atoms, a dialkyl sulfosuccinate containing an alkyl group having 8-20 carbon atoms, a dialkyl naphthalene sulfonate containing an alkyl group having 8-20 carbon atoms, a polyoxyethylene sulfate and a dialkyl phosphate containing an alkyl group having 8-20 carbon atoms, wherein the metal is Na, K, Mg, Co, Ba, Al or Zn; and mixtures thereof; and (d) a terpene resin having a repeating unit of the formula: ##STR2## said terpene resin (i) having a softening point of at least 50° C, (ii) being partially soluble in the carrier liquid, and (iii) being present in amounts between 5-50% by weight based on the total weight of the toner, said terpene resin at least partially encapsulating the toner to provide a surface to absorb said surface active agent to promote the charged state of the toner, the remaining portion of said terpene resin tending to dissolve into said carrier liquid to enhance dispersability of said toner.