Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-04-10
2002-06-11
Chapman, Mark (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S108100
Reexamination Certificate
active
06403274
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a toner for developing an electrostatic image of an electrophotographic process, a process for preparation of the same, and a two-component toner.
BACKGROUND OF THE INVENTION
Various processes have been know as an electrophotographic process as described in U.S. Pat. Nos. 2,297,691 and 3,666,363, and in general, it is constituted by basic steps including an exposing step of forming an electric latent image on a photosensitive layer utilizing a photoconductive substance by various means, a step of developing with a toner, a step of transferring the toner to a recording material, such as paper, a step of fixing the toner image to the recording material by heating, pressure heat and pressure, or vapor of a solvent, a step of removing a toner remaining on a photosensitive layer.
In recent years, a duplicator or a printer using an electrophotographic process is being demanded to have a moderate price and a small size, and it is important to simplify a fixing process to design that kind of duplicators and printers. As a method for fixing a toner to paper, a heat roll fixing method is currently employed as the most popular method.
A monochrome duplicator or printer generally uses a system, in which oil need not be supplied to a fixing device (heat roll) (hereinafter sometimes referred to as “oilless fixing”), but with respect to a color toner, a unit for supplying an oil is necessary to prevent offset to the roll, and it becomes a factor of inhibiting the design of a system having a small size and a moderate price. This is because in a full color system, which requires to provide a multi-color image of clear colors using cyan, yellow and magenta toners among color toners, the respective toner layers must be sufficiently fused, and the fixing temperature of the heat roll must be increased to a value above the temperature at which fixing to paper is generally conducted. The fixing characteristics that should be owned by the color toner are extremely important in a color electrophotographic image that requires such a process that plural numbers of development are conducted to superpose several kinds of toner layers having different colors on the same support as the fixing step. That is, the fixed color toner necessarily has diffused reflection due to toner particles that is suppressed as possible to have moderate gloss. Polyester having sufficient flexibility even when it has a low molecular weight is often employed in a toner as a resin that is quickly fused on fixing to form a smooth image surface. However, since the polyester resin for a color toner having a small internal cohesive force is difficult to be released from the roll on fusing, it is important in a color toner using polyester to provide a toner that solves offset at high temperatures or is free of oil coating, and thus a releasing agent such as wax is necessarily contained in the color toner.
However, when a considerable amount of wax is used, a such problem arises that transmittance of a transparency for an OHP is decreased or unevenness is formed on color formation due to fusing unevenness of wax or unevenness of wax remaining on a heat roll caused by lapse of time, and another problem arises in that the toner is liable to be broken when the toner is agitated in a developing device to attain sufficient charge. On the other hand, a toner using a small amount of wax having a low melting point can be produced by a so-called submerged drying process, in which an oleophilic component liquid having a toner component dissolved therein is formed into particles in an aqueous medium, and is powdered after removing the solvent. However, a finger is necessarily provided in the fixing device to forcedly peel the fixed image support for preventing involution, and when the fixing temperature is increased to obtain sufficient coloring, a problem is caused in that it is liable that the fixed image is in contact with the peeling finger to deteriorate image quality.
SUMMARY OF THE INVENTION
The invention is to solve the problems associated with the conventional techniques to provide an electrophotographic toner excellent in coloring property, fixing property, OHP transmittance and charging property, a process for producing the same, and a two-component developer.
According to an aspect of the invention, the electrophotographic toner contains at least a binder resin, a colorant, a releasing agent and inorganic fine particles, in which the toner has a conglobation degree of about from 100 to 130, the releasing agent has an average particle diameter of about from 0.1 to 1 &mgr;m, a ratio of a major axis and a minor axis of about from 1.1 to 10, and the inorganic fine particles are dispersed in the toner particles.
According to another aspect of the invention, the process for producing the electrophotographic toner of the invention contains,
a step of mixing a binder resin, a colorant, a releasing agent and inorganic fine particles in an organic solvent that dissolves the binder resin to prepare an oleophilic component,
a step of suspending the oleophilic component in an aqueous medium and forming into particles, to prepare a suspension, and
a step of removing the organic solvent from the suspension.
According to still another aspect of the invention, the two-component developer contains a carrier and a toner, in which the toner is the electrophotographic toner according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
(Electrophotographic Toner)
The electrophotographic toner of the invention contains at least a binder resin, a colorant, a releasing agent and inorganic fine particles, and the toner has a conglobation degree of about from 100 to 130, and the releasing agent has an average particle diameter of about from 0.1 to 1 &mgr;m and a ratio of a major axis and a minor axis of about from 1.1 to 10. Since the electrophotographic toner of the invention has the specific conglobation degree, and the releasing agent has the specific average particle diameter and the specific major axis/minor axis ratio, it is excellent in a coloring property, a fixing property, an OHP transmittance and a charging property, and particularly, it can be easily released from a fixing device, such as a fixing roll, so as to provide an excellent coloring property (reproducibility) of additive colors. The materials will be described in detail below.
As the binder resin, known resins for fixing can be used, and specific examples thereof include polyester obtained by condensation polymerization of an alcohol component and a carboxylic acid component (examples of the alcohol component include a two or more valent alcohol and a derivative thereof, such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexane dimethanol, xylylene glycol, dipropylene glycol, polypropylene glycol, bisphenol A, hydrogenated bisphenol A, bisphenol A ethyleneoxide, bisphenol A propyleneoxide, sorbitol and glycerin, and examples of the carboxylic acid component include a two or more valent carboxylic acid, a carboxylic acid derivative and a carboxylic anhydride, such as maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, adipic acid, trimellitic acid, pyromellitic acid, cyclopentane dicarboxylic acid, succinic anhydride, trimellitic anhydride and dodecenyl succinic anhydride, provided that the alcohol component and the carboxylic acid component each may be a combination of two or more of them), an acrylate polymer (for example, polymethyl acrylate, polyethyl acrylate, polybutyl acrylate, poly-2-ethylhexyl acrylate and polylauryl acrylate), a methacrylate polymer (for example, polymethyl methacrylate, polyethyl methacrylate, polybutyl methacrylate, poly-2-ethylhexyl methacrylate and polylauryl methacrylate), a copolymer of an acrylate and a methacrylate, a copolymer of a styrene series monomer and an acrylate or a methacrylate, an ethylene series polymer (for example, polyvinyl acetate, polyvinyl propyo
Lee Teigen
Matsuoka Hirotaka
Takagi Seiichi
Tanaka Hiroyuki
Tomita Kazufumi
Chapman Mark
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
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