Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2001-09-26
2003-07-22
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C523S340000
Reexamination Certificate
active
06596453
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a production process of a toner for development of electrostatic images for developing electrostatic latent images formed by an electrophotographic process, electrostatic recording process or the like, and more particularly to a process for producing a polymerized toner for development of electrostatic images, which is markedly reduced in the content of a residual polymerizable monomer, prevented from emitting offensive odor upon fixing of the toner and excellent in environmental safety.
BACKGROUND OF THE INVENTION
In an image forming apparatus such as an electrophotographic apparatus or electrostatic recording apparatus, the formation of an image is conducted through (1) an exposure step of conducting exposure to a light pattern of the image on a photosensitive member uniformly and evenly charged to form an electrostatic latent image (electrostatic image), (2) a development step of applying a toner to the electrostatic latent image to form a toner image (visible image), (3) a transfer step of transferring the toner image to a transfer medium such as paper or OHP film, and (4) a fixing step of fusion-bonding the toner image to the transfer medium by heating and pressing, or the like.
In order to develop the electrostatic latent image formed on the photosensitive member, a developer composed mainly of a toner for development of telectrostatic images (hereinafter referred to as “toner” merely) is used. As the toner, are used colored resin particles containing at least a binder resin and a colorant, and additionally containing various kinds of additives such as a charge control agent as needed.
Processes for producing a toner are roughly divided into a grinding process and a polymerization process. The grinding process is a process of producing colored resin particles by melting a binder resin synthesized by polymerization in advance and kneading it with additive components such as a colorant, a charge control agent and a parting agent, and then grinding and classifying the kneaded product. The colored resin particles are generally called “ground toner”.
The polymerization process is a process of producing colored polymer particles (i.e., colored resin particles) by mixing a polymerizable monomer with additive components such as a colorant, a charge control agent and a parting agent to prepare a polymerizable monomer composition and then polymerizing the polymerizable monomer composition by suspension polymerization, emulsion polymerization, dispersion polymerization or the like. The colored polymer particles are generally called “polymerized toner”. In the polymerization process, the polymer component formed by the polymerization becomes a binder resin to directly form the colored polymer particles. Incidentally, the colored polymer particles obtained by the polymerization process may be referred to as “polymer particles” merely in some cases in the present specification.
In any technique of the grinding process and the polymerization process, it is difficult to completely react the polymerizable monomer in the polymerization step for forming the binder resin. Therefore, an unreacted polymerizable monomer remains. As a result, such a monomer comes to be contained in the toner. When the toner containing the polymerizable monomer is used in an image forming apparatus, the polymerizable monomer is vaporized out of the toner by heating in a fixing step, or the like to worsen a working environment or emit offensive odor. When the content of the polymerizable monomer in the toner is high, the toner tends to undergo blocking during its storage to aggregate or to cause an offset phenomenon or toner filming on individual members in the image forming apparatus.
In the grinding process, a polymerizable monomer is polymerized in advance to synthesize a binder resin. Therefore, an unreacted polymerizable monomer can be removed with relative ease by a washing treatment or heat treatment after the polymerization. Thereafter, the binder resin is melted and kneaded with various kinds of additive components, and the resulting mixture is ground and classified, whereby a ground toner low in content of the residual polymerizable monomer can be provided. On the other hand, in the polymerization process, a polymerized toner is obtained as polymer particles containing the various kinds of additive components by polymerizing the polymerizable monomer. Therefore, it is difficult to remove the residual unreacted polymerizable monomer.
The residual polymerizable monomer in the polymerized toner is easy to be adsorbed on the various kinds of additive components, so that its removal is difficult compared with the case of the binder resin alone. Even when the polymerized toner is fully washed after the polymerization, it is difficult to remove the residual polymerizable monomer adsorbed within the polymerized toner. The attempt to remove the residual polymerizable monomer by the heat treatment of the polymerized toner results in aggregation of the polymerized toner.
In recent years, there has been a demand for development of toners capable of being fixed at a temperature lower than before for the purpose of achieving the speeding-up of copying or printing and energy saving. There has also been a demand for development of color toners for color output, which are low in melt viscosity and easy to be uniformly melted upon fixing. As described above, there is an increasing demand in market for development of toners (hereinafter referred to as “low-temperature fixing toner”) capable of being fixed at a temperature lower than before. When the glass transition temperature or melt viscosity of a binder resin component is lowered for meeting such requirements, however, it is more and more difficult to reduce the content of the residual polymerizable monomer while preventing aggregation of the resulting polymerized toner.
Many of polymerized toners are produced by a process of suspension-polymerizing a polymerizable monomer composition containing a polymerizable monomer and various kinds of additive components in an aqueous medium. In the production steps of a toner by the polymerization process, general post-treatment steps after a polymerization step include washing, dewatering and drying steps. Many processes of conducting a removing treatment of an unreacted polymerizable monomer in a post-treatment step after polymerization for the purpose of reducing the content of the unreacted polymerizable monomer remaining in the resulting polymerized toner have heretofore been investigated.
Specifically, for example, (1) a process of treating a polymerized toner after a drying step, (2) a process of treating a polymerized toner after a dewatering step, and (3) a process of treating a suspension containing a polymerized toner formed by suspension polymerization are known.
As the process (1) of treating the polymerized toner after the drying step, there is known a process in which a dry polymerized toner is heated and subjected to a deaerating treatment under reduced pressure (Japanese Patent Application Laid-Open No. 92736/1995). However, this process is difficult to reduce the content of the polymerizable monomer remaining in the polymerized toner to an extent lower than 150 ppm. In addition, the heat treatment of the dry polymerized toner shows a tendency for polymerized toner particles to aggregate to one another. In the case of low-temperature fixing toners suitable for use in high-speed printing or as color toners, the tendency to aggregate upon the heat treatment becomes particularly strong. The reason for it is that those having a low glass transition temperature, melting point or softening point are used as a polymer component, which will become a binder resin, and various kinds of additive components in the low-temperature fixing toner for the purpose of lowering the fixing temperature thereof. When the polymerized toner is heat-treated in the post-treatment step after the polymerization, these components are softened to become liable to aggregate. Accordingly,
Fujino Takeo
Funakura Seiji
Sato Kazuhiro
Dinsmore & Shohl LLP
Goodrow John
Zeon Corporation
LandOfFree
Production process of polymerized toner does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Production process of polymerized toner, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Production process of polymerized toner will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3095375