Photocopying – Contact printing – Light boxes
Patent
1994-01-12
1995-08-29
Grimley, A. T.
Photocopying
Contact printing
Light boxes
355282, 430 99, 430124, G03G 1320
Patent
active
054465273
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of forming fixed images used for plain paper copying machines, laser printers, plain paper facsimiles, etc. More particularly, the present invention relates to a method of forming images in which transfer and fixing are simultaneously carried out on the surface of the heat-resistant photoconductor covered with a transfer film using a recording medium whose surface is heated in advance.
BACKGROUND ART
Conventionally, when images are formed with copying machines, laser beam printers, etc., the Carlson Method has been generally used (U.S. Pat. Nos. 2,221,776, 2,297,691 and 2,357,809, "Electrophotography," p22-p41, R. M. Shaffert, 1965, The Focal Press).
FIG. 2 shows a schematic view of an apparatus used in a conventional method of forming fixed images. In the conventional method, after an electrostatic latent image formed on a photoconductor by optical means is developed in a developing process, it is transferred to a recording medium such as a recording paper in a transfer process and then fixed into the final image generally with heat and pressure in a fixing process. As the photoconductor is repeatedly used, a cleaning device is provided for cleaning the residual toner after the transfer process with its rotation.
In the conventional method of forming fixed images, however, the processes from the formation of the electrostatic latent image up to its fixing onto the recording medium are time consuming, which makes the apparatus used therein not only complicated but also large. In addition, since the transfer efficiency of the toner is poor in the transfer process, it poses such problems as extra labor needed for the disposal of the toner collected by cleaning the residual toner, and pollution due to the scattering of the toner in and out of the apparatus.
Therefore, a method of simultaneously conducting transferring and fixing has been proposed (U.S. Pat. No. 4,448,872). In this method, since the transferring and fixing are simultaneously carried out by pressing the toner image developed on the dielectric drum to the recording medium, the simplification of the apparatus can be surely achieved. However, since only pressure is applied at fixing, the fixing ability is poor, and little improvement is achieved in transfer efficiency.
The fixing of the toner should be generally conducted at a high temperature due to the high melting temperature of the toner, thereby requiring an apparatus with high thermal efficiency. The fixing process usually works independently, and is carried out at such a high temperature of around 200.degree. C. Accordingly, expensive heat-resistant materials such as heat-resistant resins, heat-resistant rubbers, etc. have to be provided in the periphery of the fixing device.
In addition, when the fixing is carried out at a high temperature, it is subject to problems such as curling and jamming of the paper, etc. Therefore, taking into consideration of the radiation from the apparatus, a device highly capable of radiating heat is in demand. Further, if the fixing requires a high temperature, it takes more time to reach the set temperature so that a quick printing becomes impossible. In such a case, therefore, this method is unsuitable for devices such as a facsimile which requires quick printings.
Further, in view of solving the problems, there has been proposed a method of forming fixed images, wherein the transfer and fixing process is simultaneously carried out by adhering the toner onto a transfer film, which rotates while keeping it partly in close contact with a photoconductor to form a toner image, and putting the recording paper and the transfer film between a pressure roller and a heat roller provided away from the photoconductor (Japanese Patent Laid-Open No. 197884/1990).
According to this method, however, when the transfer film is wound around the pressure roller, one of the pair of rollers for transfer and fixing, and a heat roller is arranged on the outside of the transfer film, the recording medium, which is heated
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Kawabe Kuniyasu
Sasaki Mitsuhiro
Yamasaki Harumasa
Yasuda Shin-ichiro
Dang Thu
Grimley A. T.
Kao Corporation
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