Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-11-06
2001-04-17
Dote, Janis L. (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S106100, C430S106100, C430S109500, C430S110100
Reexamination Certificate
active
06218067
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to toner and developer compositions containing chargeable modified pigment particles.
2. Discussion of the Related Art
Electrophotographic processes and image-forming apparatus are currently widespread Particularly, aspects of the xerographic process are set forth in R. M. Schaffert “Electrography,” the Focal Press, London & N.Y., enlarged and revised edition, 1975. In electrophotography, an image comprising an electrostatic field pattern (also referred to as an electrostatic latent image), usually of nonuniform sgth, is formed on an insulative surface of an electrophotographic element. The insulative surface comprises a photoconductive layer and an electrically conductive substrate. The electrostatic latent image may be formed by imagewise photo-induced dissipation of the strength of portions of an electrostatic field of uniform strength previously formed on the insulative surface. Typically, the electrostatic latent image is then visualized by contacting the latent image with an oppositely charged toner powder generally containing a colorant. This process of visualization of a latent image is known as development, and the composition containing the dry toner powder is known as the developer. The toned image is then transferred onto a transfer medium such as paper and fixed thereon by heating and/or pressure. The last step involves cleaning residual toner from the electrophotographic element.
Developer compositions used in dry electrophotography to visualize latent electrostatic images are divided into one-component systems composed of a dry toner powder, generally including a binder resin having a colorant dispersed therein, and two-component systems composed of a dry toner powder and carrier particles. Charge control agents are often melt mixed with the toner resin to control the chargeability of the toner during use. Known positive charge controlling compounds for use in dry toners are dye bases and salts thereof such as nigrosine dye base and salts. In order that toner compositions have process suitability in copying, they are required to be excellent in fluidity, anti-caking properties, fixability, chargeability, cleaning properties, and the like. To improve these properties, particularly fluidity, anti-caking properties, and chargeability, extraparticulate inorganic fine particles are frequently added to toner compositions. The components of the toner are dispersed or dissolved in the toner resin vehicle during the compounding step of the preparation process. The degree of dispersion has an effect on the performance of the toner material in the printing process. Inadequate dispersion can in many instances lead to a lack of consistency of homogeneity in the toner particle to particle. This can lead to a broad spread in charge distribution of the toner because of the dissimilarity of composition of the particulate toner. The electrostatic printing process is best performed when the toner used has a uniform charging behavior which will minimize the occurrence of print defects such as fogging, background, halloing, character spread, and dust contamination of the internal parts of the printing apparatus.
Development of a latent electrostatic image requires that a charge be developed on the toner particles prior to their deposition on the latent image, and that this charge be opposite to the charge of the latent image. All components of a toner, including binder resin, colorants, charge control agents, waxes and the like, can influence the development of charge on the toner particles. The influence of the colorants on the charging behavior of toner compositions is seldom considered, as there are few known methods to change and control the natural charging behavior of colorants such as carbon black. Thus an unmet need in dry toner technology is for pigments which have certain unique and predictable tribocharging properties.
One approach to meeting this need is to surface-modify known pigments to enhance or change their natural tribocharging properties. For example, Japanese Patent Application Hei 3[1991]-197961 relates to surface treatment of carbon blacks with amine-functional silane coupling agents which can, to some extent, overcome the natural tendency of carbon blacks to tribocharge negatively, which makes the carbon blacks more useful as pigments in positive-charging toners. However, it is believed that for such treatments to be effective, the silane coupling agents must form a covalent bond to the surface of the carbon black. The chemical groups believed to be present on the surface of normal carbon black are oxygen-containing groups. Silane coupling agents can form covalent bonds with these groups. Such groups are normally present on the surface of carbon black at low and poorly-controlled levels, making such treatment with silane coupling agents of limited scope and value.
SUMMARY OF THE INVENTION
A feature of the present invention is to provide alternative additives which impart or assist in imparting a positive or negative charge to the toner particles in toner and developer compositions.
Another feature of the present invention is to provide a colorant for use in toner and developer compositions.
Additional features and advantages of the present invention will be set forth in part in the description which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The objectives and other advantages of the present invention will be realized and attained by means of the elements and combinations particularly pointed out in the written description and appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, the present invention relates to a toner composition which includes the product of the mixture of resin particles and at least one chargeable modified pigment particle, The chargeable modified pigment particle comprises at least one organic ionic group attached to the pigment particle and at least one amphiphilic counterion, wherein the amphiphilic counterion has a charge opposite to that of the organic ionic group.
The present invention also relates to a developer composition which includes carrier particles and the toner composition described above.
In addition, the present invention flier relates to a method of imaging which includes the steps of formulating an electrostatic latent image on a charged photoconductive imaging member, effecting the development thereof with a toner composition which includes the product of the mixture of: a) resin particles and b) at least one chargeable modified pigment particle, and thereafter transferring the developed image onto a suitable substrate. As described above, the chargeable modified pigment particle comprises at least one organic ionic group attached to the pigment particle and at least one amphiphilic counterion, wherein the amphiphilic counterion has a charge opposite to that of the organic ionic group.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the present invention, as claimed.
DETAILED DESCRIPTION OF THE INVENTION
The present invention relates to toner and developer compositions which include the product of the mixture of resin particles and at least one chargeable modified pigment particle. The chargeable modified pigment particle comprises at least one organic ionic group attached to the pigment particle and at least one amphiphilic counterion, wherein the amphiphilic counterion has a charge opposite to that of the organic ionic group. By “chargeable” is meant that the modified pigment particle will alter or change the tribocharging characteristics of a toner formulation.
The pigment particles that are modified can be carbon black, cyan pigment, magenta pigment, yellow pigment, blue pigment, green pigment, brown pigm
Cabot Corporation
Dote Janis L.
LandOfFree
Toners containing chargeable modified pigments does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Toners containing chargeable modified pigments, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Toners containing chargeable modified pigments will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441504