Liquid electrophotographic toner
AssigneeMinnesota Mining and Manufacturing Company
InventorsMohamed A. Elmasry, Kevin M. Kidnie
Life of this patent
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Abstract
Liquid toners for developing electrophotographic images contain dispersed toner particles which are based on a polymer with multiple characteristics. These particles comprise a thermoplastic resinous core with a T.sub.g below room temperature which is chemically anchored to an amphipathic copolymer steric stabilizer containing covalently attached groups of organic acid containing moieties having pKa's less than 4.5 which in turn are chemically bonded to metal soap containing compounds derived from organic acids having a pKa greater than 4.5. The toner particles so formed have advantageous properties of high charge/mass, and good charge and dispersion stability.
Claims30
A liquid toner for developing an electrostatic image comprising copolymer particles dispersed in a non-polar carrier liquid, said copolymer particles comprising a thermoplastic resinous core substantially insoluble in said carrier liquid, and chemically anchored to said core a copolymeric steric stabilizer soluble in said carrier liquid and having chemically bonded thereto moieties containing organic acids having a pKa less than 4.5 to which acids are chemically bonded metal soap compounds derived from organic acids with a pKa of greater than 4.5, said metal soap compounds imparting a positive charge to said liquid toner.
A method of making a liquid toner comprising the steps of
- A. preparing a comonomeric stablizer precursor by free radical catalyzed polymerization of three ethylenically unsaturated monomers, one selected from each of groups I, II, and III, said group I comprising an alkenylazlactone, a glycidylmethacrylate, methacrylic acid, and allylmethacrylate, said group II comprising octadecyl methacrylate, lauryl methacrylate, 2-ethylhexylacrylate, poly(12-hydroxystearic acid), and a monomer of 0.5-0.6 mole % methacryloxypropylmethyl polydimethylsiloxane which is trimethylsiloxy terminated;
- and
- and said group III comprising moieties containing organic acids having a pKa of less than 4.5,
- B. carrying out reactions on said group I comonomer selected from:
- i) condensing said azlactone moiety with an ethylenically unsaturated nucleophile chosen from the group containing a reactive group chosen from hydroxyl, amino, and mercaptan;
- ii) condensing said glycidyl moiety with a reactant chosen from acrylic acid and methacrylic acid;
- iii) condensing said acrylic acid moiety with glycidylmethacrylate;
- and
- iv) carrying out no reaction with the moiety derived from said allylmethacylate;
- C. preparing a latex by copolymerizing the stabilizer precursor from the reaction of step B above in an aliphatic hydrocarbon solvent with a comonomer selected from the group consisting of:
- ethylacrylate, methylacrylate, and vinylacetate,
- D. adding the latex of step C above to a hot solution in said aliphatic hydrocarbon of a metal soap selected from the group consisting of the salt of a fatty acid having a pKa of greater than 4.5 with a metal selected from the group consisting of Al, Ca, Co, Cr, Fe, Zn, and Zr;
- and
- E. dispersing a colorant in the latex of step D.
A liquid toner for use in developing an electrostatic image comprising an electrically insulating non-polar carrier liquid having dispersed therein toner particles comprising pigment particles having on their exterior surfaces polymer particles, said polymer particles having positive charge carrying metal soap compounds derived from organic acids with a pKa greater than 4.5 chemically bonded to the surface of said polymer particles by way of organic acid containing moieties which have a pKa of less than 4.5.
Dependencies are inferred from the claim text.