Electrophotography – Image formation – Transfer
Reexamination Certificate
2001-10-11
2003-11-18
Brase, Sandra (Department: 2852)
Electrophotography
Image formation
Transfer
C399S324000, C430S124300
Reexamination Certificate
active
06650860
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an image reproduction system such as a printer or a copier and particularly to the transfuse member which is part of such a system and is intended for transfusing toner on the receptor material.
BACKGROUND OF THE INVENTION
In a typical image reproduction system such as a printing or a copying system, a latent image is formed on an image-forming member by image-wise exposure using a known graphical process. The image-forming member can be an endless member such as a drum or a belt. Typical graphical processes include amongst others magnetography, ionography, and electrography, particularly electrophotography. At present electrophotography is the most widespread. In the latter process, a charged latent image is formed on a pre-charged photosensitive member by image-wise exposure to light. The latent image is subsequently made visible on the image-forming member with charged toner at a development zone. After the development of the latent image, the developed toner image is transferred directly or via one or more intermediate transfer members to a receptor material. The receptor material can be in the form of a web or in sheet form. In the latter case, the receptor material is preferably carried on a conveyor. In general however, to enable the ability to print on a wide range of receptor materials without having to go first through an elaborate medium qualification procedure and thereafter through a demanding medium conditioning procedure, intermediate transfer members are introduced. These intermediate transfer members are usually in the form of endless belts or drums. Furthermore, where in a system without intermediate transfer members the images are first transferred to the receptor material and thereafter fused using non-contact fusing, e.g. using radiant heating, or contact fusing. In contact fusing a nip zone is usually created between the receptor material and a heated member by pressure. In this nip zone the toner images are fused to the receptor material by pressure and heating to temperatures well above 150 degrees Centigrade, usually above 170 degrees Centigrade. In systems having at least one intermediate transfer member, one can opt to simultaneously transfer and fuse the toner images to the receptor material. This principle is hereinafter referred to as transfuse, while the intermediate transfer member in contact with the receptor material is referred to as the transfuse member. The contact zone between the transfuse member and the receptor material is hereinafter referred to as the final transfer zone. A typical example of such a system is disclosed in U.S. Pat. No. 6,047,156. In a multi-color reproduction system the configuration is such that in operation the heated transfuse member carries a registered composite multi-color toner image which is subsequently transfused to the receptor material in the final transfer zone.
There are two general approaches known in the art to facilitate the transfer, more particularly the release, of the composite multi-toner image from the heated transfuse member to the receptor material. In a first approach, use is made of a release agent metering system such a system is described in EP 09977944A1, EP 0997795A3, and EP 1004944A1 (Xeikon N.V.) which are hereby incorporated by reference in order to apply typical amounts of a release agent, e.g. silicone oil, on the outermost layer of the transfuse member. In another approach, use is made of an outermost layer where the release agent is inherent or built-in, such as certain silicone layers. Particularly silicone layers with a high swelling factor are preferred as the inherent or built-in release agent in such layers can easily migrate to the outermost surface. Such a layer is e.g. described in EP1014220 (Xeikon N.V.) which is hereby incorporated by reference. Optionally, a top coating is provided on such a layer with inherent or built-in release agent provided that this top coating is permeable for this release agent. In both approaches an amount of release agent is applied to the outermost surface of the transfuse member corresponding to an amount of at least 10 mg release agent per printed A4 side of receptor material. Although the introduction of a release agent on the outermost surface of the transfuse member, according to the afore-mentioned approaches, can be beneficial for the release, it has been determined experimentally that the presence of such amounts of release agents on the transfuse member is detrimental for the print quality due to back propagation of this release agent to the photosensitive element, directly or via one or more intermediate transfer members.
SUMMARY OF CERTAIN INVENTIVE ASPECTS
One aspect of the invention includes a transfusing member that can be used in hot-pressure fixing of toner particles to a substrate while avoiding the use of substantial amounts of release agents on the surface of the transfuse member.
Another aspect of the invention includes an outermost layer for the transfuse member and a toner composition associated therewith that combine good hot offset properties with low temperature fixability, particularly for temperatures in the range from 80 to 140 degrees Centigrade.
The present invention is particularly relevant to printers and copiers where, to enable printing on a wide variety of receptor materials, at least one intermediate transfer member is provided to transfer a developed toner image from an image forming station to a receptor material. The intermediate transfer member contacting the receptor material constitutes the transfuse member referred to herein. The transfer of the developed toner image from the transfuse member to the receptor material and the simultaneous fixing thereof, hereinafter referred to as transfuse, is by means of heat and pressure. In particular, the transfuse member may be in the form of a belt or drum heated to a temperature typically in the range from 80 to 140 degrees Centigrade. The surface of the transfuse member carrying the unfixed composite toner image contacts one face of the receptor material in the final transfer nip where the toner image is transfused. In case the transfuse member is in the form of a belt, this final transfer nip may be created by feeding the heated transfuse member and the recording material simultaneously between a first guide roller contacting the back of the heated transfuse member and a second guide roller contacting the back of the receptor material while pressure is exerted on at least one of these guide rollers to define the contact. Alternately, in case the transfuse member is in the form of a drum, the final transfer nip may e.g. be created by feeding the recording material between the transfuse drum and a counter roller contacting the back of the receptor material while pressure is exerted on the drum and/or the counter roller to define the contact.
According to the present invention, a fixing device for fixing toner images onto a receptor material is disclosed comprising:
an endless transfuse member urged into contact with an endless backing member to form a final transfer zone there-between through which a receptor material path extends, said endless transfuse member having an outermost layer of a material selected from the group of polyorganosiloxanes, fluorosilicones, phenylsilicones, fluoro-elastomers, and mixtures or hybrid compositions thereof, said outermost layer having a peel force, being measured according to Finat No 3, with tape TESA 4163 at a peeling speed of 30 cm/min, above 7 N/m or from 25 N/m to 200 N/m, or from 40 to 140 N/m or from 20 N/m to 100 N/m or from 40 N/m to 100 N/m; and
at least one heating device for heating said endless transfuse member to a temperature from 80 to 140 degrees Centigrade.
The fixing device may further comprise a release agent metering system contacting said outermost layer of said transfuse member for applying an amount of release agent on the outermost surface of said outermost layer corresponding to an amount of 0.5 mg per side A4 of paper or below. The release a
Broddin Dirk
Eelen Peter
Vangenechten Hans
Vrindts Paul
Brase Sandra
Knobbe Martens Olson & Bear LLP
Xeikon International N.V.
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