Electrophotography – Image formation – Transfer
Reexamination Certificate
1998-05-19
2001-08-21
Braun, Fred L. (Department: 2852)
Electrophotography
Image formation
Transfer
C399S308000
Reexamination Certificate
active
06278858
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming method, and an intermediate transfer member using an electrophotographic process. In particular, the present invention relates to an image forming apparatus, an image forming method, and an intermediate transfer member, in which a toner image formed on a first image holding member is transferred onto an intermediate transfer member and then retransferred onto a second image holding member.
2. Description of the Related Art
Image forming apparatuses having intermediate transfer members have the following advantages compared with image forming apparatuses that perform a direct transfer of an image from a first image holding member onto a second image holding member which is gripped or adsorbed onto a transfer drum (as described in, for example, Japanese Patent Laid-Open No. 63-301960). There will not be any significant registration occur when different color images are overlapped; and the selection of possible materials and the shapes of the second image holding member have high versatility since it can be used without additional treatment and control, for example, being fixed with a gripper, by adsorption, or by curling itself. For example, a usable second image holding member ranges from a thin paper sheet of 40 g/m
2
to a thick paper sheet of 200 g/m
2
. Further, its length and width are not limited. Envelopes, postcards and labels can therefore be used as a second image holding member. Full-color copying machines and printers provided with intermediate transfer systems having such advantages are spreading.
The recent rapid spread of image readers for personal computers, digital cameras and image scanners has led to a great demand for full-color printers and copying machines. These printers and copying machines must be applicable to a variety of users and environments. Other requirements are that the costs of producing, operating and maintaining are low, that maintenance is easy, that the apparatus itself is miniaturized, and that stability of the image quality is not affected by environmental factors, such as temperature and humidity.
Key factors for satisfying such requirements are the characteristics involved in transferring images from an intermediate transfer member to a second image holding member such as a paper sheet (hereinafter the transfer is referred to as secondary transfer), and cleaning characteristics of a developer remaining on the intermediate transfer member after the secondary transfer. The cleaning characteristics greatly affect the life of the intermediate transfer member, the configuration of the apparatus body, and the maintenance operation. Further, the transfer characteristics greatly affect the quality of the image and la the cleaning operation. The transfer characteristics will deteriorate significantly under a high-temperature, high-humidity environment.
A means for improving the transfer characteristics is disclosed in Japanese Patent Laid-Open No. 7-234592, in which fine particles being less than half the size of toner particles, are fixed onto the elastic surface of the intermediate transfer member in order to improve releasability. In Japanese Patent Laid-Open No. 9-230717, an intermediate transfer member which is coated with beads having a certain diameter is disclosed. Other means include the formation of a coating layer composed of water-repellent resin and the use of a water-repellent resin belt. Another means for improving the transfer characteristics is to use a copying machine provided with a coating unit which applies a lubricant onto the intermediate transfer member as disclosed in Japanese Patent Laid-Open No. 8-248776.
None of these means, however, have a countermeasure to the deterioration of transfer characteristics under high-temperature, high-humidity environments.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an image forming apparatus, an image forming method, and an intermediate transfer member having excellent transfer characteristics under high-temperature, high-humidity environments from the beginning of use.
It is another object of the present invention to provide an image forming apparatus, an image forming method, and an intermediate transfer member having a prolonged life and a capability of reducing the operational costs.
It is a further object of the present invention to provide an image forming apparatus, an image forming method, and an intermediate transfer member permitting simplified body configuration, improved maintenance, and high-speed printing.
A first aspect of the present invention is an image forming apparatus including a first image holding member, and an intermediate transfer member for holding by primary transfer a toner image formed on the first image holding member and for retransferring by secondary transfer the transferred toner image onto a second image holding member, wherein the contact angle between the surface layer of the intermediate transfer member and water is 50° to 120°, and transfer-promoting particles are loaded onto the surface layer.
A second aspect of the present invention is an image forming method including the following steps of a primary transfer of a toner image from a first image holding member onto an intermediate transfer member having a contact angle to water of 50° to 120° and having a surface layer provided with transfer-promoting particles loaded thereon, and a secondary transfer of the transferred toner image onto a second image holding member.
A third aspect of the present invention is an intermediate transfer member for holding by primary transfer a toner image formed on a first image holding member, and for retransferring by secondary transfer the transferred toner image onto a second image holding member, comprising a surface layer having a contact angle to water of 50° to 120°, and transfer-promoting particles loaded onto the surface layer.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.
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Kusaba Takashi
Nakazawa Akihiko
Takamori Toshio
Braun Fred L.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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