Carrier particles

Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...

Reexamination Certificate

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C430S111400, C430S111410

Reexamination Certificate

active

06511780

ABSTRACT:

RELATED PATENTS AND COPENDING APPLICATIONS
Illustrated in copending application U.S. Ser. No. 09/037,555, and U.S. Pat. No. 5,998,076, the disclosures of which are totally incorporated herein by reference are, for example, a carrier comprised of a soft or hard magnetic core, a number of, or all of the pores thereof being filled with polymer, and thereover a coating and a carrier comprised of a porous hard magnetic core and wherein the pores thereof are filled with a polymer and which carrier contains a coating thereover of a polymer, or a polymer mixture. Also, illustrated in U.S. Pat. No. 6,004,712, the disclosure of which is totally incorporated herein by reference, are carriers, coated carriers, and developers thereof. The carrier coatings of the above application and patents may contain a conductive component, such as carbon black therein.
Illustrated in U.S. Pat. No. 6,358,659, the disclosure of which is totally incorporated herein by reference, is, for example, a carrier comprised of a core and thereover a polymer, and wherein the polymer contains a conductive polymer dispersed therein.
Illustrated in U.S. Pat. No. 6,391,509, the disclosure of which is totally incorporated herein by reference, is, for example, a carrier comprised of a core, a polymer coating and wherein the coating contains a conductive polymer.
The appropriate components of the above patents and copending applications may be selected for the present invention in embodiments thereof.
BACKGROUND OF THE INVENTION
This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions containing carriers. In embodiments of the present invention the carrier particles can be generated from a mixture of an insulating carrier and a conductive carrier inclusive of mixtures of coated insulating and coated conductive carriers, and wherein insulating refers, for example, to a conductivity of from about 10
−13
to about 10
−18
(ohm-cm)
−1
, and conducting refers, for example, to conductivities of about 10
5
to about 10
−9
(ohm-cm)
−1
. Thus, for example, there can be provided in accordance with aspects of the present invention carrier particles with a conductivity of from about 10
−6
to about 10
−15
(ohm-cm)
−1
, and more specifically, wherein the carriers possess semiconductive characteristics, that is wherein the conductivity of the carrier particles are in between conductive and insulative carriers, and more specifically, wherein semiconductive refers, for example, to a carrier with a conductivity of from about 10
−9
to about 10
−13
(ohm-cm)
−1
. The carriers of the present invention may be mixed with a toner of resin, colorant, and optional toner additives to provide developers that can be selected for the development of images in electrostatographic, especially xerographic, imaging systems, printing processes and digital systems.
Examples of conductive carriers are comprised, for example, of a carrier core and a polymer coating of, for example, polyacetylene, poly(p-phenylene), poly(p-phenylene sulfide), polyvinylenephenylene, poly(vinylene sulfide), polyaniline, polypyrrole, polythiophene and derivatives thereof, and a class of components with conjugated Π-electron backbones, which when oxidized or reduced with charge transfer agents, or dopants in suitable amounts of, for example, from about 0.1 to about 20 weight percent, can convert an insulating polymer to a conductive polymer. The electrical conductivity of the conducting polymer is usually measured using a 4 point probe according to ASTM-257, and which conductivity can vary widely depending, for example, primarily on the oxidizing or reducing power of the dopant. Conductivities of about 1,100 (ohm-cm)
−1
have been reported for polyacetylene, 100 (ohm-cm)
−1
for polypyrrole and 10 (ohm-cm)
−1
for polythiophene with AsF
6

as the dopant ion. Using other doping agents, such as BF
4

, I
2
, FeCl
4

, HCl, ClO
4

, conductivities of from about 500 to about 7,500 (ohm-cm)
−1
S/cm have been reported for polypyrrole, 1,000 (ohm-cm)
−1
for polythiophene, about 1,000 to about 10,000 (ohm-cm)
−1
for poly(3-alkylthiophene) and 200 (ohm-cm)
−1
for polyaniline, however, many of the commercial polymer materials have conductivities between 10
−12
and 100 (ohm-cm)
−1
. Other doping agents include sulfuric acid, methanesulfonic acid, trifluoromethane sulfonic acid, benzenesulfonic acid, p-toluene sulfonic acid, p-ethylbenzene sulfonic acid, 1,3 benzenedisulfonic acid, 2-naphthalene sulfonic acid, 1,5 naphthalene sulfonic acid, 2-anthraquinone sulfonic acid. Conductive carriers can also include a carrier core, a polymer thereover and a conductive component, such as a conductive carbon black dispersed in the polymer coating.
Examples of insulating carriers include carriers comprised of a carrier core and a polymer thereover, such as polymethylmethacrylate (PMMA), polyvinylidenefluoride, polyethylene, copolyethylene vinylacetate, copolyvinylidenefluoride tetrafluoroethylene, polystyrene, polytetrafluoroethylene, polyvinylchloride, polyvinylfluoride, polylbutylacrylate, copolybutylacrylate methacrylate, polytrifluoroethylmethacrylate, and polyurethanes.
Advantages of the carriers of the present invention in embodiments include controlling and preselecting the triboelectric charge and conductivity of the carrier, the formation of homogenous mixtures, excellent carrier coating adherence, stable charging characteristics, carrier design flexibility and freedom, economical carrier formation, avoidance or minimization of two or more polymer coatings, excellent stable charging characteristics, and the like.
PRIOR ART
Developer compositions with coated carriers that contain conductive components like carbon black are known. Disadvantages associated with these prior art carriers may be that the carbon black can increase the brittleness of the polymer matrix, which causes the separation of the coating from the core, and thereby contaminates the toner and developer causing, for example, instabilities in the charging level of the developer as a function of a number of factors, such as the developer age in the xerographic housing and the average toner area coverage of a printed page, or instabilities in the color gamut of the developer set. In addition, with carbon black it is difficult to tune, or preselect the carrier conductivity. These and other disadvantages are avoided, or minimized with the carriers of the present invention in embodiments thereof.
The conductivity of carbon blacks is generally independent of the type of carbon black used, and in carbon black composites there is usually formed a filamentary network above a certain concentration, referred to as the “percolation” threshold. At concentrations of up to about 30 weight percent, conductivities of 10
−2
(ohm-cm)
−1
have been reported. The resistivity thereof, measured with a standard 4-pin method according to ASTM-257, is observed to increase with decreasing carbon black concentration.
Carrier particles for use in the development of electrostatic latent images are illustrated in many patents including, for example, U.S. Pat. No. 3,590,000. These carrier particles may contain various cores, including steel, with a coating thereover of fluoropolymers, or terpolymers of styrene, methacrylate, and silane compounds. Recent efforts have focused on the attainment of coatings for carrier particles, for the primary purpose of improving development quality; and also to permit carrier particles that can be recycled, and which do not adversely effect the imaging member in any substantial manner. Some of the present commercial coatings can deteriorate, especially when selected for a continuous xerographic process where the entire coating may separate from the carrier core in the form of chips or flakes, and fail upon impact, or abrasive contact with machine parts and other carrier parti

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