Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2000-04-14
2001-08-21
Rodee, Christopher (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S131000
Reexamination Certificate
active
06277535
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention is generally directed to imaging members for electrophotography. More specifically, this invention is directed to a multilayer imaging photoreceptor having a mechanically and electrically robust undercoating layer.
2. Description of Related Art
In electrophotography, an electrophotographic imaging member, also commonly referred to as a photoreceptor, containing a photoconductive layer on a conductive layer, is imaged by first uniformly electrostatically charging the surface. The substrate is then exposed to a pattern of activating electromagnetic radiation, such as light. The light or other electromagnetic radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided electrostatically charged marking particles, generally referred to as toner particles, on the surface of the photoconductive layer. The resulting visible image may then be transferred from the electrophotographic imaging member to a support such as paper. This image developing is repeated as many times as necessary with reusable photoconductive layers.
An electrophotographic imaging member may take one of many different forms. For example, layered photoresponsive imaging members are known in the art. U.S. Pat. No. 4,265,990, which is incorporated herein by reference in its entirety, describes an exemplary layered photoreceptor having separate photogenerating and charge transport layers. The photogenerating layer is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
More advanced photoreceptors contain highly specialized component layers. For example, a multilayered photoreceptor that can be employed in electrophotographic imaging systems can include a substrate, a charge blocking undercoating layer, a charge generating layer (including photogenerating material in a binder) over the undercoating layer, and a charge transport layer (including charge transport material in a binder). Additional layers such as an overcoating layer or layers can also be included.
The photoconductors currently used are susceptible to carrier injection from the substrate into the photosensitive layer such that the charge on the surface of the photoconductor may be microscopically dissipated or decayed. This can result in production of a defective image. The interposition of an undercoating layer between the substrate and the photosensitive layer has been suggested to overcome this problem, and improve the chargeability of the photoconductor and enhance adhering and coating properties of the photosensitive layer with respect to the substrate.
U.S. Pat. No. 5,958,638, which is incorporated herein by reference in its entirety, discloses known materials used for undercoat layers. For example, such materials have included a resin material alone, such as polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyurethane, epoxy resin, polyester, melamine resin, silicone resin, polyvinyl butyryl, polyamide and copolymers containing two or more of repeated units of these resins. The resin materials further have included casein, gelatin, polyvinyl alcohol, ethyl cellulose, etc.
The undercoat layers are typically formed by a dip coating method. See, for example, U.S. Pat. No. 5,958,638 and U.S. Pat. No. 5,891,594.
In photoreceptors of the above type, the photogenerating material generates electrons and holes when subjected to light. In the case of a hole blocking undercoating layer, the undercoating layer prevents holes in the conductive ground plane from passing into the photogenerator from which they would be conducted to the photoreceptor surface, thus dissipating the surface charge of the photoconductor. The undercoating layer does permit electrons generated in the photogenerator to pass to the conductive ground plane, preventing an undesirably high electric field from building up across the generator upon repeated usage or cycling of the photoconductive imaging member.
SUMMARY OF THE INVENTION
Despite the above and other photoconductor and imaging member designs, a need continues to exist in the art for electrophotographic imaging members, and processes for making such imaging members, that provide improved operational performance. The present invention meets these needs.
This invention provides a crosslinked polysiloxane undercoating layer (UCL) derived from crosslinking a silyl-functionalized hydroxyalkyl acrylate and/or methacrylate polymer with silane coupling agents, bis(alkoxysilyl)alkane such as 1,2-bis (triethoxysilyl)ethane and/or bis(trialkoxysilyl)arene such as 1,4-bis(trimethoxysilyl)benzene and an optional aminoalkylalkoxysilane such as &ggr;-aminopropylsilane, or an optional mixture of an alkylalkoxysilane such as methyltrimethoxysilane and a crosslinking catalyst such as triethylamine or acetic acid.
The present invention also provides a photoconductive imaging member having at least the following sequence of layers:
(A) a substrate;
(B) a charge blocking undercoating layer; and
(C) a photosensitive component comprising a charge generating layer and a charge transport layer.
The photoconductive imaging member of the present invention may be utilized in an electrophotographic apparatus.
The present invention also provides a method of making a photoconductive imaging member that incorporates a crosslinked polysiloxane undercoating layer derived from crosslinking a silylfinctionalized hydroxyalkyl acrylate and/or methacrylate polymer with a silane coupling agent, bis(alkoxysilyl)alkane such as 1,2- bis(triethoxysilyl)ethane or bis(alkoxysilyl)arene such as 1,4-bis(trimethoxysilyl)benzene and an optional aminoalkyltrialkoxysilane such as &ggr;-aminopropylsilane or an optional mixture of an alkylalkoxysilane such as methyltrimethoxysilane and a crosslinking catalyst such as triethylamine or acetic acid.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
In an exemplary embodiment of an electrophotographic imaging member in accordance with this invention, the imaging member includes a substrate; an undercoating layer formed on the substrate; and a photoconductor layer formed on the undercoating layer, comprising a photogenerating layer and a charge transport layer. Other optional layers such as an adhesive layer may also be included, as desired.
The undercoating layer is generally located between the substrate and the photosensitive layer, although additional layers may be present and located between these layers. According to the present invention, the undercoating layer is formed by crosslinking a silylfunctionalized hydroxyalkyl acrylate and/or methacrylate polymer with a silane coupling agent, bis(alkoxysilyl)alkane or bis(alkoxysilyl)arene and an optional aminoalkyltrialkoxysilane or an optional mixture of an alkylalkoxysilane and a crosslinking catalyst such as triethylamine or acetic acid. The present inventors have found that such materials provide a more readily crosslinkable composition that cures at a faster rate, providing a solvent resistant and mechanically robust undercoating layer. Thus, in embodiments of the present invention, the silane coupling agents, bis(alkoxysilyl)alkane and bis(trialkoxysilyl)arene can be represented by formula (I):
(RO)
3
Si—A—Si(OR)
3
(I)
wherein R is an alkyl, substituted alkyl, aryl, or substituted aryl, acyl, and the like, preferably containing from about 1 to 24 carbon atoms, or some range therebetween; and A is selected from the group of divalent linkages such as alkylene, arylene, and alkylenearyl, preferably containing from about 1 to 24 carbon atoms, or some range therebetween. The different “R”s are preferably the same, but in embodiments can be different, if desired.
Illustrative examples of bis(alkoxysilyl)alkanes include, but are not limited to, 1,2-bis(trimethoxylsilyl)ethane, 1,
Cherniack Helen R.
Hsiao Cheng-Kuo
Liu Ping
Ong Beng S.
Qi Yu
Oliff & Berridg,e PLC
Rodee Christopher
Xerox Corporation
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