Electrophotography – Image formation – Fixing
Reexamination Certificate
2003-02-21
2004-01-20
Pendegrass, Joan (Department: 2852)
Electrophotography
Image formation
Fixing
C399S329000, C430S097000
Reexamination Certificate
active
06681095
ABSTRACT:
FIELD OF THE INVENTION AND RELATED ART STATEMENT
The present invention relates to a transparent coat layer forming apparatus for forming a transparent coat layer made of transparent toner on a surface of a color image formed by a copying machine or a printer adopting an electrophotographic system, an electrostatic recording system, and the like, or an image forming apparatus such as a facsimile, and a color image forming apparatus using the transparent coat layer forming apparatus.
Conventionally, in the case where a color image is formed on a transfer material in a copying machine or a printer adopting an electrophotographic system, an electrostatic recording system, and the like, or an image forming apparatus such as a facsimile, a color original is copied, for example, as follows. In the image forming apparatus, a color original is set on a color scanner, the color original is illuminated with light, and light reflected from the color original is split to three colors (e.g., RGB) by the color scanner and read. Image data of the color original read by the color scanner is subjected to predetermined image processing by an image processing device. Thereafter, an image signal of plural colors (e.g., Y (yellow), M (magenta), C (cyan), and K (black)) obtained by color correction is sent to an image exposure device on a color basis. Then, in the image forming apparatus, the image is exposed to light based on the image signal of plural colors sent from the image processing device by the image exposure device. In the image exposure device, for example, a laser light source such as a semiconductor laser is modulated, and a laser beam modulated based on the image signal is emitted from the semiconductor laser. The laser beam is irradiated onto an inorganic photosensitive member such as Se and amorphous silicon or an organic photosensitive member using a phthalocyanine pigment, a bis-azo pigment, or the like as a charge generating layer in plural times for each color. Consequently, plural electrostatic latent images are successively formed for each color on a photosensitive drum made of an inorganic photosensitive member or an organic photosensitive member, every time the photosensitive drum is rotated. The plural electrostatic latent images successively formed on the photosensitive drum are successively developed, for example, with toner of four colors (Y, M, C, and K). The first electrostatic latent image is Y, the second electrostatic latent image is M, and the like. Then, the toner images of the respective colors (Y, M, C, and K) successively formed on the photosensitive drum are finally transferred together in an overlapped state onto a transfer material such as a sheet. Thereafter, the toner images of the respective colors transferred together in an overlapped state onto the transfer material are pressurized by heating to be fixed onto the transfer material with a heat-fixing roller or the like. Thus, a color image is formed.
The color toner used in the above-mentioned image forming apparatus is composed of particles containing, for example, binding resin (e.g., polyester resin, an ethylene/acrylic copolymer, and a styrene/butadiene copolymer) in which a colorant is dispersed, and having an average particle size of 1 to 15 &mgr;m. Fine particles having an average particle size of about 5 to 100 nm (e.g., inorganic fine particles such as silicon oxide, titanium oxide, and aluminum oxide or resin fine particles such as PMMA and PVDF) adhere to the particles of the color toner. Examples of the above-mentioned colorant will be given below. As the Y (yellow) colorant, for example, benzidine yellow, quinoline yellow, Hansa yellow, and the like are used. As the M (magenta) colorant, rhodamine B, rose Bengal, pigment red, and the like are used. As the C (cyan) colorant, phthalocyanine blue, aniline blue, pigment blue, and the like are used. As the K (black) colorant, carbon black, aniline black, a blend of color pigments, and the like are used.
A color image made of the color toner thus formed has its surface fixed and smoothed by heating when being nipped between a heating roller and a pressurizing roller. Therefore, the color image has glossiness different from that of the surface of a sheet. Furthermore, the viscosity of the color toner is varied during fixing by heating, depending upon the kind of binding resin, a method for fixing by heating, and the like. Thus, it is known that the glossiness of a color image is varied.
The preference for the glossiness of a color image is varied depending upon the kind of an image, the purpose of use, and the like. However, in the case of a photographic original of a person, a scene, or the like, an image with high glossiness is preferred so as to obtain a clear image.
As a technique of obtaining an image with high glossiness by using an image forming apparatus such as a color copying machine, for example, those which are disclosed in JP 5-142963 A, JP 3-2765 A, JP63-259575A, and the like have already been proposed. According to the techniques disclosed in these publications, it is attempted to obtain an image with high glossiness by selecting the material for toner, fixing conditions thereof, and the like.
In the case of the techniques disclosed in these publications, although the glossiness of an image part made of toner can be enhanced, the glossiness of a non-image part composed of a surface of a transfer material cannot be enhanced. Therefore, these techniques have a problem that the glossiness of the surface of a transfer material cannot be enhanced and made uniform. Furthermore, in the case of the, techniques disclosed in the above publications, in an image part made of color toner, the layer thickness of a color toner image is varied depending upon the number of colors of color toner forming the image part. Therefore, the unevenness caused by the difference in layer thickness of a toner image remains on the surface of an image, which prevents the surface of an image from being smooth as in a photograph or printed matter and makes it impossible to obtain smooth texture.
In order to solve the above-mentioned problem, the technique disclosed in JP 3-130791 A has already been proposed. According to the technique disclosed in JP 3-130791 A, a transparent resin layer is formed on a fixing belt, and the transparent resin layer is overlapped to be fixed to a transfer material with a toner image adhering thereto, whereby the glossiness on the transfer material is made uniform.
However, the above-mentioned conventional technique has the following problem. That is, in the case of the conventional technique disclosed in JP 3-130791 A, transparent resin is developed on a photosensitive drum in a contact portion between an apparatus for forming a transparent resin layer and a fixing belt at start-up of an apparatus. The development of the transparent resin on the photosensitive drum is caused by the difference between the charge potential of the photosensitive drum at start-up of an apparatus and the potential of a DC bias of a developing device as shown in FIG.
9
. Furthermore, if the transparent resin is developed on the photosensitive drum at start-up of an apparatus, i.e., in the absence of a transfer material, the transparent resin developed on the photosensitive drum is transferred to and accumulated on the fixing belt to some degree due to the absence of the transfer material. As a result, the transparent resin accumulated on the fixing belt is diffused on its periphery to adhere to the reverse surface of a recording sheet and contaminates it. Furthermore, the transparent resin accumulated on the fixing belt is transferred to the surface of the recording sheet in some cases, thereby causing a step or a difference in glossiness.
In order to solve the above-mentioned problem, the inventors of the present invention have studied a configuration in which a photosensitive drum
100
used for forming a transparent resin layer and a fixing belt
101
are retracted from each other while an image is not being formed, as shown in FIG.
10
.
However, in th
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Pendegrass Joan
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