Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-07-22
2004-11-02
Goodrow, John L (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C110S105500
Reexamination Certificate
active
06811941
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an electrostatic image developing toner which is employed in copiers and printers, a production method of said toner, and an image forming method using said toner.
BACKGROUND OF THE INVENTION
Recently, Japanese Patent Publication Open to Public Inspection No. 2000-214629 disclosed that since it is possible to control the diameter as well as the shape of polymerization toner particles, prepared utilizing a suspension polymerization method or an emulsion polymerization method, during the polymerization process in a water based medium, it is possible to prepare minute spherical toner particles having no corners as well as having a narrow size distribution. Said toner has received attention as a toner which makes it possible to reproduce minute dot images for the use of digital images due to its fine line reproducibility as well as excellent definition.
It is known that the dispersibility of coloring agents, which are incorporated into said polymerization toner, is inferior to those of a pulverized toner. This is due to the following factors. In said suspension polymerization method, polymerization is carried out after dispersing pigments as the coloring agents into a monomer. As said polymerization proceeds, said coloring agents coagulate due to an increase in the viscosity of monomer droplets. Further, in said emulsion polymerization method, during polymerization, namely coagulation process, since the effects of the pH accelerate coagulation, said coloring agents coagulate.
As mentioned above, said polymerization toner exhibits problems such that dispersibility is degraded due to the occurrence of the coagulation of coloring agents during the production processes. Therefore, techniques to improve the dispersion of said coloring agents have been increasingly investigated, however a technique, which overcomes dispersion problems of said coloring agents, has not been found yet. In a multicolor image forming method, color images are formed by superimposing a plurality of toner images, whereby a certain degree of transparency is required. Therefore, when images are formed on film for overhead projectors, said problems become critical.
Further, in said polymerization toner, surface active agents, as dispersing agents, and the like, which are employed in production processes, remain on the surface of toner particles as the final product. As a result, these residual materials cause problems such that the charge holding function of toner varies and toner results in brittleness due to the fact that said residual particles absorb moisture from the ambient air; particularly at high temperature and high humidity, fogging occurs; and resolution is degraded due to dust formed by the destruction of toner during development as well as transfer.
Further, when at high temperature and high humidity, an image forming apparatus is not operated for an extended period of time, a state is formed in which a toner having a varied amount of static charge due to the absorption of moisture and a fresh toner are mixed. As a result, problems occur in which uneven density results on halftone images comprised of halftone dots, and in multicolor image formation, color difference is increased due to difference in developability between developers of each color, which are further affected by said coloring agents incorporated in the toner of said developers.
In order to overcome said problems with residual materials on the surface of toner particles, Japanese Patent Publication Open to Public Inspection No. 57-15085 discloses a technique to decrease the amount of impurities on the surface of toner particles to less than or equal to the specified amount by repeatedly washing the prepared toner. However, the process, which employs a large amount of water for said washing, is not preferred because said process makes the toner production processes more complicated, and in addition, new problems occur in regard to the environmental protection.
It is generally well known that the state of coloring agents incorporated in a toner particle affects the performance of the toner such as resolution. For example, Japanese Patent Publication Open to Public Inspection Nos. 2000-81735 and 2000-284540 disclose that excellent color reproduction as well as static charge stabilizing properties is obtained by improving the dispersibility of a coloring agent in a toner by specifying the ratio of the length to breadth of the particle of said coloring agent as well as the number average diameter of said coloring agent particles employed in a pulverized toner. However, said patents only specify the coloring agent prior to incorporation into toner particles and do not suggest the state of said coloring agent in the toner particle.
Further, when a coloring agent is uniformly dispersed in a toner particle without resulting in a phase separation structure such as a domain structure or a coagulation structure, the resultant transparency is superior, while the resultant static charge holding function tends to be degraded. On the other hand, when said coloring agent is dispersed so as to result in phase separation structure or coagulation, the resultant static charge holding function is excellent, while light transmission is degraded. Japanese Patent Publication Open to Public Inspection No. 5-88409 discloses a capsule toner in which a coloring agent is coagulated into one lump in a particle and a resin covers the resultant lump so as to form a capsule. From the disclosed structure, it was expected that the desired light transmission as well as the desired static charge holding function would be exhibited. However, the desired transparency was not obtained due to the fact that light was scattered at the interface between the coloring agent region and the resin. As noted, a polymerization toner, which exhibits the desired static charge holding function as well as the desired transparency, has not yet been introduced into the market.
SUMMARY OF THE INVENTION
A first object of the present invention is to provide an electrostatic image developing toner which is not affected by a residual material present on the surface of toner particles and does not result in variation of the amount of static charge at high temperature as well as at high humidity.
A second object of the present invention is to provide an electrostatic image developing toner to form multicolor images, which results in suitable dispersibility of a coloring agent into a toner particle and also results in light transmission images with high transparency, and results in especially high quality images for overhead projectors.
A third object of the present invention is to provide an electrostatic image developing toner which results in uniform density of halftone images under such operation conditions, of an image forming apparatus, as repetition of non-operation over a relatively long period.
A fourth object of the present invention is to provide an electrostatic image developing toner capable of invariably producing multicolor images with minimal color difference while being not affected by a coloring agent incorporated in each color developer, at high temperature as well as at high humidity, and in an image forming apparatus which has not been operated over an extended period of time.
A fifth object of the present invention is to provide an electrostatic image developing toner capable of consistently producing, over an extended period of time, high quality images which do not exhibit blocked text but exhibit excellent developability as well as excellent reproducibility of fine lines, irrespective of the environment and conditions in which an image forming apparatus is employed.
A sixth object of the present invention is to provide a method for specifically forming digital multicolor images while employing said electrostatic image developing toner.
The present invention not only has simply improved the dispersibility of said coloring agent in toner particles, but has also made it possible to achieve the aforesaid objects. Namely, att
Hirano Shiro
Horiuchi Kazuhisa
Matsushima Asao
Nagase Tatsuya
Nishimori Yoshiki
Goodrow John L
Konica Corporation
Squire Sanders & Dempsey
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