Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-04-25
2004-05-18
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100, C430S110100
Reexamination Certificate
active
06737211
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a color toner, and more particularly, to a color toner exhibiting not only a clear hue, but also excellent fluidity and dispersibility of colorants.
In recent years, color photographs as well as colorful documents and data have been increasingly used for both domestic and business purposes. With the wide spread of personal computers, there have been many opportunities for directly editing color photographs and color images. When these color photographs and color images are printed or copied, there have been increased needs for producing color prints or color copies with clear hues rather than monochromic ones.
Upon color printing, exact and faithful reproduction of images and colors, high image quality of obtained color prints and high-speed printers have been required. In addition, it has also been required that the printed image quality can be maintained for a long period of time without deterioration.
As conventional color electrophotographic developing methods, there are known a two-component developing method and a non-magnetic one-component developing method. In the two-component developing method, respective toners of cyan, magenta, yellow and black colors are brought into frictional contact with a carrier in order to impart an electric charge having a sign opposite to that of an electrostatic latent image to the toners, and cause the toners to adhere to the latent image by electrostatic attraction force therebetween and neutralize the electric charge, thereby developing the latent image into visual color image. As the toners used in such a developing method, there have been widely used composite particles obtained by mixing and dispersing organic pigments having respective colors in a binder resin.
Since the color printing is performed by overlapping a plurality of the color toners to obtain a desired color, it is required to more strictly control qualities of the respective color toners than black toner upon monochromic printing, in order to exactly reproduce a clear color image. Therefore, it has been strongly required to improve properties of the color toners.
It is known that the color toners are produced by blending organic pigments as colorants in resins. In addition, there is known a color toner containing magnetic particles coated with white pigments or color pigments (Japanese Patent Application Laid-Open (KOKAI) Nos. 58-25643(1983), 60-173553(1985) and 7-90310(1995)).
It is also known that developing characteristics are largely influenced by the colorant exposed to the surface of each color toner particle. Thus, there is a close relationship between various properties of the color toner and those of the colorant mixed and dispersed therein.
Namely, since hues and densities of the color toner largely depend upon those of the colorant contained therein, the colorant itself has been strongly required to show an excellent hue.
To satisfy the needs for high image quality, there is an increasing tendency that the color toner becomes finer. Such a fine color toner is also required to show the same hue between the color toners by uniformly blending a colorant therein. Therefore, the colorant must have an excellent dispersibility in the toner.
Further, in order to obtain clear color images, the color toner is required to act as independent particles without agglomeration. For this reason, conventional color toners ensure fluidity by adhering external additives, e.g., fine inorganic particles such as silica and alumina, to the surface of the toner. Thus, it has been strongly required to improve the fluidity of the color toner itself.
At present, it has been strongly required to provide colorants for color toner exhibiting excellent fluidity and dispersibility in binder resin. However, such colorants satisfying these properties have not been obtained yet.
When organic pigments are used as the colorants, it has been difficult to readily obtain a color toner having a uniform hue because of poor dispersibility of the organic pigments in resins, and the color toner has failed to show a good fluidity without addition of the external additives.
In Japanese Patent Application Laid-Open (KOKAI) Nos. 58-25643(1983), 60-173553(1985) and 7-90310(1995), it is described that the surface of magnetic particles is coated with white pigments or color pigments. However, since it is difficult to completely hide inherent hue of the magnetic particles as core particles, it is difficult to obtain color toners having a clear hue.
Also, in Japanese Patent Application Laid-Open (KOKAI) Nos. 11-338191(1999), 2001-5222 and 2001-13730, there are described black non-magnetic composite particles comprising black iron oxide particles or black iron oxide hydroxide particles; a coating layer formed on the surface of the black iron oxide particles or black iron oxide hydroxide particles which comprise organosilane compounds obtainable from alkoxysilanes, or polysiloxanes; and a carbon black coat formed on the coating layer comprising the organosilane compounds or polysiloxanes. However, these techniques described in these prior arts aim at fixedly adhering carbon black onto the black inorganic particles. Therefore, the objects and effects of these prior arts are quite different from those of the present invention relating to a colorant for color toner having a clear hue and a high chroma.
As a result of the present inventors', earnest studies, it has been found that by mixing extender pigments with a gluing agent to coat the surface of individual extender pigments with the gluing agent, and then mixing the gluing agent-coated extender pigments with organic pigments, the obtained colorant can exhibit a good fluidity and an excellent dispersibility in binder resin upon production of toner because the organic pigments can be effectively prevented from being desorbed or fallen-off from the surface of the extender pigments, and show a clear hue. The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a color toner having a clear hue and an excellent fluidity.
Another object of the present invention is to provide a colorant for color toner capable of exhibiting not only a clear hue, but also an excellent dispersibility in toner because of effectively preventing organic pigments from being desorbed or fallen-off from the surface of respective extender pigments.
To accomplish the aims, in a first aspect of the present invention, there is provided a color toner comprising: a binder resin, and
a colorant having an average particle diameter of 0.005 to 0.30 &mgr;m, comprising:
extender pigments,
a gluing agent-coating layer formed on surface of the extender pigment, and
an organic pigment coat formed onto the gluing agent-coating layer in an amount of 1 to 500 parts by weight based on 100 parts by weight of the extender pigments.
In a second aspect of the present invention, there is provided a colorant for color toner, having an average particle diameter of 0.005 to 0.30 &mgr;m, comprising:
extender pigments,
a gluing agent-coating layer formed on surface of the extender pigment, and
an organic pigment coat formed onto the gluing agent-coating layer in an amount of 1 to 500 parts by weight based on 100 parts by weight of the extender pigments.
In a third aspect of the present invention, there is provided a color toner having an average particle diameter of preferably 3 to 25 &mgr;m, a C* value of not less than 20, and a fluidity index of 76 to 100, and comprising: a binder resin, and
a colorant having an average particle diameter of 0.005 to 0.30 &mgr;m, comprising:
extender pigments,
a gluing agent-coating layer formed on surface of the extender pigment, and
an organic pigment coat formed onto the gluing agent-coating layer in an amount of 1 to 500 parts by weight based on 100 parts by weight of the extender pigments.
In a fourth aspect of the present invention, there is provided an electrostatic developing system for developing an electrostatic latent ima
Hayashi Kazuyuki
Iwasaki Keisuke
Morii Hiroko
Chapman Mark A.
Nixon & Vanderhye P.C.
Toda Kogyo Corporation
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