Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2003-01-15
2004-11-23
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
Reexamination Certificate
active
06821702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of forming images, such as an electrophotographic method or an electrostatic recording method used in devices utilizing an electrophotographic process, such as a copy machine, a printer, a facsimile or the like, particularly a color copy machine.
2. Description of the Related Art
Methods of visualizing image information via an electrostatic image, such as an electrophotographic method, are used in various fields. In the electrophotographic method, electrostatic images are formed on a photoreceptor in a charging and light-exposure step, the electrostatic latent images are then developed with a toner-containing developer to form visible images, and the visible images are transferred to a recording material and then fixed. The developer used herein includes a two-component developer containing a carrier and a toner and a one-component developer using a magnetic or non-magnetic toner alone. The toner is usually produced by a kneading and milling process in which a thermoplastic resin is melt-kneaded with a pigment, a charge control agent, and a releasing agent such as wax, and the resultant mixture is then cooled, pulverized, and classified. Fine inorganic or organic particles for improving fluidity and cleaning properties may be added to the surfaces of such toner particles, if necessary.
Copy machines using a color electrophotographic method, printers, or combinations thereof such as facsimiles have become prevalent in recent years, but if gloss suitable for reproduction of color images and transparency for achieving excellent images for an overhead projector (OHP) are to be realized, use of a releasing agent such as wax is generally difficult. Accordingly, a large amount of oil is applied onto fuser rolls to facilitate release of a toner from the fuser rolls. However, this causes reproduced images, such as OHP images, to become sticky and makes writing on the images with a pen difficult, and uneven gloss may often occur. Application of generally used polyethylene, polypropylene, and wax, such as paraffin, to ordinary black and white copies is more difficult because OHP transparency is deteriorated.
Even if transparency is sacrificed, a toner produced by the conventional kneading and milling process hardly prevents exposure of the wax to the toner surface, so that when the toner is used as a developer, problems arise, such as a significant deterioration in fluidity and filming on a developing machine and a photoreceptor.
As a method for essentially solving these problems, a polymerization process in which a toner is produced by dispersing an oil phase containing a monomer (starting material of a resin) and a colorant in an aqueous phase and then polymerizing the monomer directly, thereby allowing the wax to be included inside of the toner to control exposure of the wax to the surface, has been proposed.
A method of producing a toner by an emulsion polymerization flocculation method is proposed in Japanese Patent Application Laid-Open (JP-A) Nos. 63-282752and 6-250439 as another means of enabling intentional regulation of the shape and surface structure of a toner. These publications disclose production processes which include steps of preparing a dispersion of fine resin particles generally by emulsion polymerization while separately preparing a dispersion having colorant particles dispersed in a solvent, mixing the dispersions to form flocculated particles having a size corresponding to the particle diameter of an intended toner, and fusing the particles by heating to form the toner.
Such production processes cannot only realize inclusion of wax inside of a toner but also facilitate a smaller diameter of the toner to achieve reproduction of sharp images of higher resolution.
As color copy machines and printers have become faster in recent years, they have been expected to fulfill a role as printing machines for small numbers of copies. When they are used as printers, longer-term storage ability of documents and greater applicability to various kinds of paper than for office use are required, and even if highly glossy paper used in pamphlets is used, kinship of gloss of the paper and developed images is essential. Conventional machines intended for use in offices can give gloss to images by reducing a feeding speed of paper in a thick-paper mode, but such approach cannot be applied at present to machines expected to achieve high productivity.
SUMMARY OF THE INVENTION
Accordingly, the present invention is to solve the problems in the prior art described above, to achieve the following object. That is, the object of the invention is to provide a method of forming images which are highly glossy, are excellent in storage ability and have excellent transmission when formed on OHP sheets with high productivity.
The invention provides a method of forming images, the method comprising the steps of: forming electrostatic latent images on an electrostatic image carrier, forming toner images with a toner-containing developer by developing the electrostatic latent images on the electrostatic image carrier, transferring the toner images onto transfer materials, and thermally fixing the toner images, wherein an electrophotographic toner comprising at least a binder resin, a colorant, and a releasing agent in the range of 10 to 25% by mass relative to toner particles and having a shape factor SF1 of 140 or less is used as the toner, and the thermal fixing step is carried out so as to satisfy, at a process speed of at least 170 mm/sec., the relationship (A): 200<0.7×&agr;+2000×&bgr; wherein &agr; is a fixing temperature (° C.), &bgr; is a heating time (second), and &agr; is 160° C. or higher.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, the present invention is described in more detail.
The method of forming images according to the invention is characterized in that an electrophotographic toner comprising at least a binder resin, a colorant, and a releasing agent in the range of 10 to 25% by mass relative to toner particles and having a shape factor SF1 of 140 or less is used as the toner, and the thermal fixing step is carried out so as to satisfy, at a process speed of at least 170 mm/sec., the relationship (A): 200<0.7×&agr;+2000×&bgr; wherein &agr; is a fixing temperature (° C.), &bgr; is a heating time (second), and &agr; is 160° C. or higher.
To achieve high gloss, the surface of fixed images should have excellent smoothness, and such smoothness can be easily obtained when the viscoelasticity of the toner is decreased by increasing the fixing temperature, and how the releasing agent is allowed to ooze out onto toner images (fixed images) to give smooth toner images is important at high process speed. Further, unless the releasing agent oozes out on the surface of toner images, the storageability and transmission of the toner images are adversely affected. As a result of intensive study in view of this aspect, the present inventors found that although the fixing temperature has an effect on oozing of the releasing agent onto the surface of the toner image, the heating time is more important. Accordingly, the method of forming images according to the invention can form images which permit a releasing agent to ooze out suitably onto the surface of toner images even at a high process speed, are highly glossy, are excellent in storage ability and have excellent transmission when formed on OHP sheets while maintaining high productivity, by using a toner containing a suitable amount of a releasing agent and by carrying out the fixing step so as to satisfy, at a process speed of at least 170 mm/sec., the relationship between the fixing temperature and the heating time (fixing time) when heat is applied to an unfixed image.
In the method of forming images according to the invention, the thermal fixing step (fixing step) is carried out so as to satisfy, at a process speed of at least 170 mm/sec., the relationship (A) 200<0.7×&agr;+2
Fujii Takahisa
Matsumura Yasuo
Nakajima Tomohito
Yaguchi Hidekazu
Yoshida Satoshi
Fuji 'Xerox Co., Ltd.
Oliff & Berridg,e PLC
Rodee Christopher
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