Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-08-26
2004-05-04
Chapman, Mark A. (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S124300, C430S126200, C430S058200, C399S159000
Reexamination Certificate
active
06730448
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image forming method utilizing electrophotography and electrostatic recording, to a process cartridge and to an image forming apparatus. In particular, the present invention relates to an image forming method, a process cartridge and an image forming apparatus using a compound having an acid-adsorbing ability.
2. Description of the Related Art
The Karlson method has been generally used when an image is formed in copier or a laser beam printer. In conventional image forming methods, an image is formed by developing an electrostatic latent image formed on a photoreceptor by optical means, transferring the electrostatic latent image to an image receiving member such as recording paper, and next fixing to the image receiving member using heat and pressure. Because the photoreceptor is used repeatedly, a cleaning device is disposed to remove residual toner left on the photoreceptor after the transfer.
A structure referred to as a function-separating type, in which a charge generation layer is isolated from a charge transfer layer, has been devised and put to practical use in recent years as an electrophotographic photoreceptor in view of sensitivity and stability. Electrophotographic photoreceptors having such a structure comprise two layers consisting of a charge generation layer, which is produced by binding a charge generation material using a suitable resin as a binding material (binder resin), and a charge transfer layer, which is produced by dispersing or dissolving a charge transfer material in a binder resin. The layer containing a charge transfer material contains a positive hole transfer material in many cases. As the binder resin, thermoplastic resins such as polycarbonate resins, polyester resins, acryl resins and polystyrene resins, and heat-curable resins such as polyurethane resins and epoxy resins are under study.
In this case, the surface of the charge transfer layer must be negatively charged by corona charging or roller charging. This gives rise to problems in that the characteristics of the photoreceptor are adversely affected due to various causes, such as resin deterioration caused by ozone generated when the charge surface layer is negatively charged, wear, reduced sensitivity and reduced charging ability caused by the electrical impact of discharging at the photoreceptor surface, and mechanical breakdown resulting from friction during subsequent toner development, transfer to paper, and cleaning.
Various studies such as those listed below have been made in relation to the foregoing problems. Attempts have made to blend a polysiloxane resin with a copolymer component or other resins, and studies have been made with respect to improve the quality, life and cleaning characteristics of photoreceptors using the characteristics of polysiloxane, as can be seen in Japanese Patent Application Laid-open (JP-A) No. 61-238062, which discloses a photoreceptor that uses a heat-curable resin containing a polysiloxane resin for a charge transfer layer; in JP-A No. 62-108260, which discloses a photoreceptor including a protective layer containing a polysiloxane resin; in JP-A No. 4-346356, which discloses a photoreceptor disposed with a protective layer formed by dispersing silica gel, a urethane resin or a fluororesin in a heat-curable polysiloxane resin; and in JP-A No. 4-273252, which discloses a photoreceptor in which a resin obtained by dispersing a heat-curable polysiloxane resin in a thermoplastic resin is used for a protective layer or as a charge transfer binder resin.
Although polysiloxane has excellent thermal and mechanical strength, it is quite incompatible with organic compounds that function as electronic devices. For this reason, studies have been with respect to photoreceptors in which a charge transfer material having an unsaturated bond is bound directly with polysiloxane such as poly(hydrogen methylsiloxane) to make a resin, which is used as a binder resin for a protective layer or charge transfer material (JP-A No. 8-319353); photoreceptors in which a thin film produced using a sol gel method is used as a protective layer (
Proceedings of IS
&
T's Eleventh International Congress on Advances in Non
-
Impact Printing Technologies,
pp. 57-59); and photoreceptors in which an organic silicon modified positive positive hole transfer compound obtained by directly introducing silicon having a hydrolyzable group into a charge transfer material is used for an electrophotographic photoreceptor (JP-A No. 9-190004). In the photoreceptors described in
Proceedings of IS
&
T's Eleventh International Congress on Advances in Non
-
Impact Printing Technologies,
pp. 57-59, and in JP Nos. 2575536 and 9-190004, a firm film is formed because siloxane forms a three-dimensional network. As a result, these photoreceptors have attracted considerable attention because mechanical strength is largely improved.
As disclosed in JP-A Nos. 11-38656, 11-184106 and 11-316468, we developed novel materials previously and demonstrated that these materials have superior characteristics. We found that when a series of these materials is used as the surface layer of an electrophotographic photoreceptor, the surface layer had overwhelmingly superior thermal and mechanical strength with respect to conventional surface layers, whereby deterioration of the surface layer caused by wear can be significantly reduced and longevity can be improved.
However, it was found that when the surface layer is used for a long period of time, especially in a humid environment, image defects including image flow are caused.
As a result of investigating the cause of this problem, the following is surmised. It is known that, when a photoreceptor is charged by charging means such as corona charging or a conductive roller, discharge products (active products) such as ozone and NOx are produced in the process. Ozone and NOx produced in the above step not only pose a problem in terms of environmental sanitation, but they also act on the surface of the photoreceptor to increase potential fluctuation and residual potential, and impact photographic characteristics and images (e.g., image flow), thus reducing the durability of the photoreceptor. Therefore, the surface of the photoreceptor is occasionally denatured by the action of the ozone and NOx. Moreover, when the surface of the photoreceptor is hydrophilic, ozone and NOx adhere to the surface, whereby moisture in the atmosphere also tends to adhere to the surface, with the result being that electrical resistance of the surface is microscopically reduced and it is difficult to maintain the charge generated by the charging.
The surface of the photoreceptor comprising the aforementioned series of materials has overwhelmingly superior mechanical strength and significantly small abrasion loss. On the other hand, a conventional surface layer is abraded to some extent. Taking this phenomenon into account, it is surmised that a certain degree of abrasion of the surface layer can suppress the renewal of a deteriorated surface and the progress of the adhesion of products created by discharge. Accordingly, it is believed that it is difficult for the aforementioned phenomenon (suppression the adhesion of products created by discharging) to occur and easy for image defects such as image flow to be generated on a surface layer that has superior mechanical strength and small abrasion loss.
Various studies have been made to suppress these image defects. For instance, a method in which fine particles (abrasives) having an abrasive function are incorporated into a developing agent for the purpose of properly abrading the surface of a photoreceptor (JP-A No. 5-188630) and a method in which a thin film of a fatty acid metal salt is formed on the surface of a photoreceptor to protect the surface layer from adverse effects of discharge products (JP-A No. 2001-5207) have been proposed. Also, for example, a method in which a hydrotalcite compound that adsorbs anions is incorporated into a
Hodumi Masahiko
Yoshihara Koutarou
Yoshino Susumu
Chapman Mark A.
Fuji 'Xerox Co., Ltd.
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