Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2000-09-14
2002-04-02
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S190000
Reexamination Certificate
active
06365311
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to electrostatographic developers and toners containing charge-control agents.
BACKGROUND OF THE INVENTION
In electrography, image charge patterns are formed on a support and are developed by treatment with an electrographic developer containing marking particles which are attracted to the charge patterns. These particles are called toner particles or, collectively, toner. Two major types of developers, dry and liquid, are employed in the development of the charge patterns.
In electrostatography, the image charge pattern, also referred to as an electrostatic latent image, is formed on an insulative surface of an electrostatographic element by any of a variety of methods. For example, the electrostatic latent image may be formed electrophotographically, by imagewise photo-induced dissipation of the strength of portions of an electrostatic field of uniform strength previously formed on the surface of an electrophotographic element comprising a photoconductive layer and an electrically conductive substrate. Alternatively, the electrostatic latent image may be formed by direct electrical formation of an electrostatic field pattern on a surface of a dielectric material.
One well-known type of electrostatographic developer comprises a dry mixture of toner particles and carrier particles. Developers of this type are employed in cascade and magnetic brush electrostatographic development processes. The toner particles and carrier particles differ triboelectrically, such that during mixing to form the developer, the toner particles acquire a charge of one polarity and the carrier particles acquire a charge of the opposite polarity. The opposite charges cause the toner particles to cling to the carrier particles. During development, the electrostatic forces of the latent image, sometimes in combination with an additional applied field, attract the toner particles. The toner particles are pulled away from the carrier particles and become electrostatically attached, in imagewise relation, to the latent image bearing surface. The resultant toner image can then be fixed, by application of heat or other known methods, depending upon the nature of the toner image and the surface, or can be transferred to another surface and then fixed.
Toner particles often include charge control agents that desirably provide uniform net electrical charge to toner particles. Many types of positive charge control agents, materials which impart a positive charge to toner particles in a developer, have been used and are described in the published patent literature. In contrast, relatively few negative charge control agents, materials which impart a negative charge to toner particles in a developer, are known.
Prior negative charge-control agents have a variety of shortcomings. Many charge-control agents are dark colored and cannot be readily used with pigmented toners, such as cyan, magenta, yellow, red, blue, and green. Some are highly toxic or produce highly toxic by-products. Some are highly sensitive to environmental conditions such as humidity. Some exhibit high throw-off or adverse triboelectric properties in some uses. Use of charge-control agents requires a balancing of shortcomings and desired characteristics to meet a particular situation.
U.S. Pat. No. 5,332,637 describes the use of phthalimide and derivatives thereof as negative charge control agents for electrostatographic developers. U.S. Pat. No. 5,332,637 described electrostatographic dry toner and developer compositions with N-hydroxyphthalimide.
The present invention is directed to the use of 2,4 dicyanoglutarimides as negative charge control agents. The synthesis of 2,4-dicyanoglutarimides is known, as disclosed in Guareschi, I.,
Chem. Zbl.,
1901, 579 and
Organic Syntheses, IV,
463, 662 (John Wiley & Sons 1963). The prior disclosure or use of 2,4-dicyanoglutarimides as charge control agents for electrostatographic toners and developers, however, is unknown.
Currently there is a dearth of commercially available colorless, metal-free free negative charge control agents for electrophotographic toners and developers. In order to provide consistently good print to print image quality with electrophographic printers, it is imperative that toner charge remain fairly constant over the life of the developer. Hence the need for new charge control agents. It would be highly desirable to obtain negative charge control agents useful in electrostatographic toners and developers which agents have favorable charging and other relevant characteristics.
SUMMARY OF THE INVENTION
The invention provides an electrophotographic toner having a polymeric binder and a charge control agent selected from the group consisting of 2,4-dicyanoglutarimides of the following general structure:
where R
1
and R
2
are the same or different and may be hydrogen; unsubstituted or substituted alkyl containing from 1-18 carbon atoms; unsubstituted or substituted aryl containing from 6 to 14 carbon atoms, unsubstituted or substituted heterocyclic ring Systems; or wherein R
1
and R
2
form an unsubstituted or substituted ring system, wherein the aforementioned substituted moieties have one or more substituents independently selected from the group consisting of halo, hydroxyl, alkyl, alkoxy, thioalkyl, amino, nitro, unsubstituted or substituted aryl (using the same substituents), unsaturated hydrocarbon groups, and combinations thereof.
When reference in this application is made to a particular moiety or group that is substituted, this means with one or more substituents (up to the maximum possible number), for example, substituted benzene (with up to five substituents), substituted heteroaromatic, and substituted heterocyclic. Generally, unless otherwise specifically stated, substituent groups usable on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for the electrostatic utility. Examples of substituents on any of the mentioned groups can include known substituents, such as: halogen, for example, chloro, fluoro, bromo, iodo; alkoxy, particularly those “lower alkyl” (that is, with 1 to 6 carbon atoms), for example, methoxy, ethoxy; substituted or unsubstituted alkyl, particularly lower alkyl (for example, methyl, trifluoromethyl); thioalkyl (for example, methylthio or ethylthio), particularly either of those with 1 to 6 carbon atoms; substituted and unsubstituted aryl, particularly those having from 6 to 20 carbon atoms (for example, phenyl); and substituted or unsubstituted heteroaryl, particularly those having a 5 or 6-membered ring containing 1 to 3 heteroatoms selected from N, O, or S (for example, pyridyl, thienyl, furyl, pyrrolyl). Alkyl substituents may specifically include “lower alkyl” (that is, having 1-6 carbon atoms), for example, methyl, ethyl, and the like. Further, with regard to any alkyl group or alkylene group, it will be understood that these can be branched, unbranched or cyclic. The charge-control agents are useful in electrostatographic toners and developers. An advantageous effect of the present invention is that negatively charging toners can be provided that have comparatively favorable charging characteristics. Other advantageous properties of these materials include their thermal stability in air which permits their use in toners which are melt compounded and their low color which permits their use in color toners without adversely affecting the toner hue. Further advantages include ease of synthesis from readily available starting materials and the absence of environmentally undesirable toxic metals.
DETAILED DESCRIPTION OF THE INVENTION
The term “particle size” as used herein, or the term “size,” or “sized” as employed herein in reference to the term “particles,” means the median volume weighted diameter as measured by conventional diameter measuring devices, such as a Coulter Multisizer, sold by Coulter, Inc. of Hialeah, Fla. Median volume weighted diameter is an equivalent weight spherical particle which represents the median fo
Mcgrath Gretchen S.
Srinivsan Satyanarayan A.
Wilson John C.
Eastman Kodak Company
Goodrow John
Konkol Chris P.
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