Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Process of making developer composition
Reexamination Certificate
2001-05-29
2003-09-30
Dote, Janis L. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Process of making developer composition
C430S137100
Reexamination Certificate
active
06627374
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a process for producing toner particles of toners used in processes of rendering latent images visible and in toner jet recording processes, and a system for producing such toner particles.
2. Related Background Art
A number of methods as disclosed in U.S. Pat. No. 2,297,691 and so forth are conventionally known as electrophotography. In general, copied images are obtained by forming an electrostatic latent image on a photosensitive member by utilizing a photoconductive material and by various means, subsequently developing the latent image by the use of a toner to form a toner image, and transferring the toner image to a transfer medium such as paper as occasion calls, followed by fixing by the action of heat, pressure or solvent vapor. As methods for developing electrostatic latent images by the use of toners or methods for fixing toner images, a variety of methods have been proposed, and methods suited for the corresponding image-forming processes are employed.
Toners used for such purpose have commonly been produced by melt-kneading colorants such as dyes and/or pigments into thermoplastic resins to effect uniform dispersion, followed by pulverization and classification to produce toners having the desired particle diameters.
Reasonably good toners can be produced by such a production method, but there is a certain limit, i.e., a limit to the range in which toner materials are selected. For example, resin-colorant dispersions must be brittle enough to be pulverizable by means of economically available production apparatus. However, resin-colorant dispersions made brittle in order to meet such a requirement tend to result in a broad particle size range of the particles formed when actually pulverized at a high speed, especially causing such a problem that fine particles tend to be included in the particles in a relatively large proportion. Moreover, such highly brittle materials tend to be further pulverized or powdered when used in development in, e.g., copying machines. Also, in this method, it is difficult to perfectly uniformly disperse solid fine particles of colorants and so forth in the resin, and, depending on the degree of their dispersion, toners may cause an increase in fog, a decrease in image density and a lowering of color mixing properties or transparency. Accordingly, care must be taken when they are dispersed. Also, colorants may come bare at rupture sections of toner particles, and may cause fluctuations in developing performance of toners.
Meanwhile, in order to overcome the problems of the toners produced by such pulverization, various polymerization toners and methods of producing such toners are proposed, including toners produced by suspension polymerization as disclosed in Japanese Patent Publications No. 36-10231, No. 43-10799 and No. 51-14895. For example, in the suspension polymerization, a polymerizable monomer, a colorant and a polymerization initiator, and also optionally a cross-linking agent, a charge control agent and other additives are uniformly dissolved or dispersed to form a monomer composition. Thereafter, this monomer composition is dispersed in a continuous phase, e.g., an aqueous medium, containing a dispersion stabilizer, by means of a suitable agitator, and is simultaneously subjected to polymerization to obtain toner particles having the desired particle diameters.
Since this method has no step of pulverization at all, the toner particles are not required to be brittle, and hence soft materials can be used. Also, since it is possible to omit the step of classification, this method is greatly effective for cost reduction on account of energy saving, reduction of production time, improvements in process yield and so forth.
Toner itself is also required to be made multifunctional because copying machines and printers are made to satisfy demands for high-image-quality, full-color and energy-saving in recent years. For example, in order to make toner particles with finer particle diameters so as to be adaptable to high-resolution digital systems corresponding to higher image quality, to improve the transparency of OHP images corresponding to full-color image formation and to make toners fixable at a lower energy saving temperature, toners are required to contain low-softening materials and to have toner particle shapes effective for improving transfer efficiency to transfer materials. As a means for meeting such requirements, the toners produced by polymerization are useful.
On the other hand, the polymerization causes an increase in viscosity of polymerization systems with progress of polymerization in its reaction form inclusive of that for polymerization toners, to make it difficult for radicals and polymerizable monomers to move, so that unreacted polymerizable monomer components tend to remain in a large quantity. Especially in the case of suspension polymerization toners, components having a possibility of inhibiting polymerization reaction as exemplified by dyes, pigments (in particular, carbon black), charge control agents and magnetic materials are present in polymerizable monomer systems in a large quantity in addition to the polymerizable monomers, and hence the unreacted polymerizable monomers much more tend to remain.
Then, where any components acting as solvents for binder resins without limitation to the polymerizable monomers are present in such toner particles, they may lower the fluidity of toner to make image quality poor and besides cause a lowering of anti-blocking properties. Besides performances which correlate directly as those of toners, especially when organic semiconductors are used as photosensitive members, problems caused by phenomena of deterioration of photosensitive members as exemplified by memory ghost and blurred images may occur in addition to a phenomenon of melt-adhesion of toner to photosensitive drums. In addition to such matters concerning the performances of products, there is such a problem that the polymerizable monomer components volatilize at the time of fixing to give off a bad smell.
To improve the matters stated above, it is proposed as disclosed in Japanese Patent Application Laid-open No. 7-92736 that any unreacted polymerizable monomers present in toner particles are reduced to a residue of 500 ppm or less to bring about the effect of more improving image quality.
In addition, as copying machines and printers are made compact and personal, restrictions are more placed on apparatus and a greater load is imposed on the above problems. Also, there is an increasing interest in environment, and it is demanded to reduce VOC (volatile organic compounds) arising from toner particles, generated at the time of, e.g., fixing. Accordingly, the unreacted polymerizable monomers present in toner particles may preferably be reduced to a residue of 100 ppm or less.
As methods by which the unreacted polymerizable monomers present in toner particles are reduced to a much smaller residue, any known means for accelerating the consumption of polymerizable monomers may be used which are used when binder resins are produced by polymerization. For example, methods of removing unreacted polymerizable monomers may include a method in which they are washed with a highly volatile organic solvent capable of dissolving toner binder resins but not dissolving polymerizable monomers and/or organic solvents; a method in which they are washed with an acid or an alkali; a method in which a solvent component which does not dissolve foaming agents and polymers is put into a polymer system and the resultant toner is made porous to enlarge the area where the inside polymerizable monomer and/or organic solvent components volatilize; and a method in which polymerizable monomer and/or organic solvent components are volatilized under dry conditions. Because it is difficult to select solvents, e.g., due to the point that toner constituents may dissolve out as a result of deterioration of toner encapsulation or the solvent may remain, most preferred
Fumita Hidekazu
Kanda Hitoshi
Koyama Hiroshi
Omura Minoru
Canon Kabushiki Kaisha
Dote Janis L.
Fitzpatrick ,Cella, Harper & Scinto
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