Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2001-04-13
2002-02-26
Goodrow, John (Department: 1753)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S059400
Reexamination Certificate
active
06350550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates in general to electrophotographic imaging members and more specifically to an improved electrophotographic imaging member having a charge generation section comprised of a mixture of two different photoconductive pigments. The mixture is comprised of hydroxygallium phthalocyanine photoconductive pigment and benzimidazole perylene photoconductive pigment.
2. Description of Related Art
In the art of electrophotography, an electrophotographic plate comprising a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging the imaging surface of the photoconductive insulating layer. The plate is then exposed to a pattern of activating electromagnetic radiation such as light, which selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated area This electrostatic latent image may then be developed to form a visible image by depositing finely divided electroscopic toner particles on the surface of the photoconductive insulating layer. The resulting visible toner image can be transferred to a suitable receiving member such as paper. This imaging process may be repeated many times with reusable electrophotographic imaging members.
The electrophotographic imaging members may be in the form of plates, drums or flexible belts. These electrophotographic members are usually multilayered photoreceptors that comprise a substrate, a conductive layer, an optional hole blocking layer, an optional adhesive layer, a charge generating layer, a charge transport layer, an optional overcoating layer and, in some belt embodiments, an anticurl backing layer. One type of multilayered photoreceptor comprises a layer of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. In U.S. Pat. No. 4,265,990 a layered photoreceptor is disclosed having separate charge generating (photogenerating) sections and charge transport layers. The charge generation section is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer.
The charge generating section utilized in multilayered photoreceptors include, for example, inorganic photoconductive particles or organic photoconductive particles dispersed in a film forming polymeric binder. Inorganic or organic photoconductive material may be formed as a continuous, homogeneous charge generation section. Many suitable photogenerating materials known in the art may be utilized, if desired.
Electrophotographic imaging members or photoreceptors having varying and unique properties are needed to satisfy the vast demands of the xerographic industry. The use of organic photogenerating pigments such as perylenes, bisazos, perinones, and polycyclic quinones in electrophotographic applications is well known. Generally, layered imaging members with the aforementioned pigments exhibit acceptable photosensitivity in the visible region of the light spectrum, and hence they are particularly suitable for use in electrophotographic processes where visible light sources such as tungsten, fluorescent, and xenon lamps are used.
However, these classes of pigments in many instances have low or negligible photosensitivity in the near infrared region of the spectrum, for example between about 750 and 970 nanometers, thereby preventing their selection for photoresponsive imaging members in electronic printers wherein electronic light emitting devices, such as GaAs diode lasers, are commonly used as a light source to create an electrostatic image on the imaging members. Also, some of the above mentioned organic pigments have a narrow and restricted spectral response range such that they cannot reproduce certain colors present in the original documents, thus resulting in inferior copy quality.
To satisfy these demands, photoreceptors with different charge generation section formulations providing varying photo-sensitivities may be utilized. Charge generation sections are often formed by layering a dispersion of photoconductive pigments on to the photoreceptor. The cost to develop different photoconductive pigments and different charge generation section coating dispersion formulations and to change dispersion solutions for different products in the manufacturing process greatly increases the costs to manufacture photoreceptors.
The process of making a photoreceptor using dispersions is strongly susceptible to many variables, such as: materials variables, including contents and purity of the material; process variables, including milling time and milling procedure; and coating process variables, including web coating, dip coating, the drying process of several layers, the time interval between the coatings of successive layers etc. The net outcome of all these variables is that the electrical characteristics of photoreceptors may be inconsistent during the manufacturing process.
Sensitivity is a very important electrical characteristic of electrophotographic imaging members or photoreceptors. Sensitivity may be described in two aspects. The first aspect of sensitivity is spectral sensitivity, which refers to sensitivity as a function of wavelength. An increase in spectral sensitivity implies an appearance of sensitivity at a wavelength in which previously no sensitivity was detected. The second aspect of sensitivity, broadband sensitivity, is a change of sensitivity (e.g., an increase) at a particular wavelength previously exhibiting sensitivity, or a general increase of sensitivity encompassing all wavelengths previously exhibiting sensitivity. This second aspect of sensitivity may also be described as change of sensitivity, encompassing all wavelengths, with a broadband (white) light exposure. A common problem encountered in the manufacturing of photoreceptors is maintaining consistent spectral and broadband sensitivity from batch to batch.
A conventional technique for coating cylindrical or drum shaped photoreceptor substrates to form charge generation sections involves dipping the substrates in coating baths. The bath used for preparing charge generation sections is prepared by dispersing photoconductive pigment particles in a solvent solution containing a film forming binder. Unfortunately, some photoconductive pigments cannot be applied by dip coating and still obtain high quality photoconductive coatings due to settling, shear thinning, etc. in the solvent solution and other problems associated with dip coating.
Some pigments tend to settle in the solvent solution of the film forming binder. This may cause a lower than expected amount of photoconductive pigment to be dispersed onto the charge generation section and thus affect the sensitivity of the coated web or other substrate to be coated. Attempting to offset the tendency to settle requires constant stirring which may lead to the entrapment of air bubbles. Such air bubbles may be carried over into the final charge generation section deposited on a photoreceptor substrate resulting in defects in print quality and/or non-uniform charge generation sections. The settling of the pigments may also result in pigment agglomerates which likewise may lead to defects in print quality and/or non-uniform charge generation sections. The settling of the pigments may also cause streak surface coating defects in the charge generation section through the depositing of pigments in a concentration level other than a desired concentration level in localized portions of the charge generation section.
Shear thinning is another common problem in the development of charge generation sections. Shear thinning occurs when forces of varying magnitudes are applied to a non-Newtonian solution resulting in disparate changes in the nature of the non-Newtonian solution. Newtonian solutions are preferred for dip coating since uniform results in the charge generation section are more likely to occur.
Typically, flexible photor
Carmichael Kathleen M.
Horgan Anthony M.
Mishra Satchidanand
Nonkes Steven
Sullivan Donald P.
Goodrow John
Oliff & Berridg,e PLC
Xerox Corporation
LandOfFree
Photoreceptor with adjustable charge generation section does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Photoreceptor with adjustable charge generation section, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Photoreceptor with adjustable charge generation section will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2963289