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US 5,290,653 AGranted
Block copolymer amine salts as charge directors for negative electrostatic liquid developer
AssigneeE. I. Du Pont de Nemours and Company
InventorKathryn A. Pearlstine
Life of this patent
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Abstract
A negative-working electrostatic liquid developer consists essentially of a nonpolar liquid having Kauri-butanol value less than 30; thermoplastic resin particles having an average particle size by area of less than 10 .mu.m; a salt of an AB diblock copolymer charge director compound as defined; and optionally a colorant and charge adjuvant; and process of making same.
Claims16
An improved negative electrostatic liquid developer consisting essentially of
- (A) a nonpolar liquid having a Kauri-butanol value of less than 30,
- (B) thermoplastic resin particles having an average by area particle size of less than 10 .mu.m, and
- (C) a salt of an AB diblock copolymer charge director substantially soluble in component (A), wherein the B block is a polymer substantially soluble in component (A) having a number average molecular weight range of 2,000 to 50,000, and the A block is a trialkyl amino polymer having a number average molecular weight range of 200 to 10,000, the number average degree of polymerization (DP) ratio of the B block to the A block being in the range of 10:2 to 100:20, and wherein the salt is formed by neutralizing the AB diblock copolymer with an acid.
A process for preparing a negative-working electrostatic liquid developer for electrostatic imaging comprising
- (A) dispersing at an elevated temperature in a vessel a thermoplastic resin and a dispersant nonpolar liquid having a Kauri-butanol value of less than 30, while maintaining the temperature in the vessel at a temperature sufficient to plasticize and liquify the resin and below that at which the dispersant nonpolar liquid degrades and the resin decomposes,
- (B) cooling the dispersion, either
- (1) without stirring to form a gel or solid mass, followed by shredding the gel or solid mass and grinding by means of particulate media;
- (2) with stirring to form a viscous mixture and grinding by means of particulate media;
- or
- (3) while grinding by means of particulate media to prevent the formation of a gel or solid mass;
- (C) separating the dispersion of toner particles having an average by area particle size of less than 10 .mu.m from the particulate media, and
- (D) adding to the dispersion during or subsequent to Step (A) a salt of an AB diblock copolymer charge director substantially soluble in the nonpolar dispersant liquid, wherein the B block is a polymer substantially soluble in the nonpolar dispersant liquid having a number average molecular weight range of 2,000 to 50,000, and the A block is a trialkyl amino polymer having a number average molecular weight range of 200 to 10,000, the number average degree of polymerization (DP) ratio of the B block to the A block being in the range of 10:2 to 100:20, and wherein the salt is formed by neutralizing the AB diblock copolymer with an acid.
5 more elements
Dependencies are inferred from the claim text.