Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Radiation-sensitive composition or product
Reexamination Certificate
2002-10-31
2004-02-10
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Radiation-sensitive composition or product
C430S058600, C430S079000, C430S117200, C548S440000
Reexamination Certificate
active
06689523
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to organophotoreceptors suitable for use in electrophotography and, more specifically, to flexible organophotoreceptors having novel charge transport compounds comprising bis(3-formylcarbazolyl)-1,1′-(sulfonyldi-4,1-phenylene)bis-hydrazones.
2. Background of the Art
In electrophotography, an organophotoreceptor in the form of a plate, a flexible belt, a disk, a rigid drum, or a sheet around a rigid or compliant drum having an electrically insulating photoconductive element on an electrically conductive substrate is imaged by first uniformly electrostatically charging the surface of the photoconductive layer, and then exposing the charged surface to a pattern of light. The light exposure selectively dissipates the charge in the illuminated areas, thereby forming a pattern of charged and uncharged areas (referred to as latent image). A liquid toner or solid toner is then provided in the vicinity of the latent image, and the toner particles depositing in either the charged or uncharged areas to create a toned image on the surface of the photoconductive layer. The resulting visible toner image can be transferred to a suitable receiving surface such as paper, or the photoconductive layer can operate as a permanent receptor for the image. The imaging process can be repeated many times.
Both single layer and multilayer photoconductive elements have been used. In the single layer embodiment, a charge transport material and charge generating material are combined with a polymeric binder and then deposited on an electrically conductive substrate. In the multilayer embodiment, the charge transport material and charge generating material are in the form of separate layers, each of which can optionally be combined with a polymeric binder and deposited on the electrically conductive substrate. Two arrangements are possible. In one arrangement (the “dual layer” arrangement), the charge generating layer is deposited on the electrically conductive substrate and the charge transport layer is deposited on top of the charge generating layer. In an alternate arrangement (the “inverted dual layer” arrangement), the order of the charge transport layer and charge generating layer is reversed.
In both the single and multilayer photoconductive elements, the purpose of the charge generating material is to generate charge carriers (i.e., holes or electrons) upon exposure to light. The purpose of the charge transport material is to accept these charge carriers and transport them through the charge transport layer in order to discharge a surface charge on the photoconductive element.
To produce high quality images, particularly after multiple cycles, it is desirable for the charge transport material to form a homogeneous solution (usually a solid-in-solid, or solid state solution) with the polymeric binder and remain in solution. In addition, it is desirable to maximize the amount of charge which the charge transport material can accept (indicated by a parameter known as the acceptance voltage or “V
acc
”), and to minimize retention of that charge upon discharge (indicated by a parameter known as the residual voltage or “V
res
”).
There are many charge transport materials available for electrophotography. The most common charge transport materials are pyrazoline derivatives, fluorene derivatives, oxadiazole derivatives, stilbene derivatives, hydrazone derivatives, carbazole hydrazone derivatives, triphenylamine derivatives, julolidine hydrazone derivatives, polyvinyl carbazole, polyvinyl pyrene, or polyacenaphthylene. However, each of the above charge transport materials suffer some disadvantages. There is always a need for novel charge transport materials to meet the various requirements of electrophotography applications.
SUMMARY OF THE INVENTION
In a first aspect, the invention features an organophotoreceptor that includes:
(a) a charge transport compound having the formula
where R
1
and R
2
are, independently, a carbazolyl group or its derivatives;
R
3
and R
4
are, independently, hydrogen, an alkyl group, an aryl group, or a heterocyclic group; and
X is a sulfonyldiphenylene group or its derivatives;
(b) a charge generating compound; and
(c) an electrically conductive substrate.
The charge transport compound may or may not be symmetrical. Thus, for example, R
1
for any given “arm” of the compound may be the same or different from R
2
in the other “arm” of the compound. Similarly, R
3
for any given “arm” of the compound may be the same or different from R
4
in the other “arm” of the compound. In addition, the above-described formula for the charge transport compound is intended to cover isomers.
The organophotoreceptor may be provided in the form of a plate, a flexible belt, a disk, a rigid drum, or a sheet around a rigid or compliant drum. In one embodiment, the organophotoreceptor includes: (a) a charge transport layer comprising the charge transport compound and a polymeric binder; (b) a charge generating layer comprising the charge generating compound and a polymeric binder; and (c) the electrically conductive substrate. The charge transport layer may be intermediate between the charge generating layer and the electrically conductive substrate. Alternatively, the charge generating layer may be intermediate between the charge transport layer and the electrically conductive substrate.
In a second aspect, the invention features an electrophotographic imaging apparatus that includes (a) a plurality of support rollers; and (b) the above-described organophotoreceptor in the form of a flexible belt threaded around the support rollers. The apparatus preferably further includes a toner dispenser and especially a liquid toner dispenser.
In a third aspect, the invention features an electrophotographic imaging process that includes (a) applying an electrical charge to a surface of the above-described organophotoreceptor; (b) imagewise exposing the surface of the organophotoreceptor to radiation to dissipate charge in selected areas and thereby form a pattern of charged and uncharged areas on the surface; (c) contacting the surface with a toner and especially a liquid toner that includes a dispersion of colorant particles in an organic liquid to create a toned image; and (d) transferring the toned image to a substrate.
In a fourth aspect, the invention features a novel charge transport material having the formula
where R
1
and R
2
are, independently, a carbazolyl group or its derivatives;
R
3
and R
4
are, independently, hydrogen, an alkyl group, an aryl group, or a heterocyclic group; and
X is a sulfonyldiphenylene group or its derivatives.
In one embodiment, a charge transport compound is selected in which R
1
and R
2
are a 9-ethyl-3-carbazolyl group, R
3
and R
4
are hydrogen, and X is 1,1′-sulfonyldi-4,1-phenylene group. Non-limiting examples of such charge transport compound have the following structures.
These photoreceptors can be used successfully with toners and especially liquid toners to produce high quality images. The high quality of the images is maintained after repeated cycling.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.
DETAILED DESCRIPTION OF THE INVENTION
The invention features organophotoreceptors that include charge transport compounds having the formulae set forth in the Summary of the Invention above.
The organophotoreceptor may be in the form of a plate, a flexible belt, a disk, a rigid drum, or a sheet around a rigid or compliant drum, with flexible belts and rigid drums being preferred. The organophotoreceptor may include an electrically conductive substrate and a photoconductive element in the form of a single layer that includes both the charge transport compound and charge generating compound in a polymeric binder. Preferably, however, the organophotoreceptor includes an electrically conductive substrate and a photoconductive element that is a bilayer construction
Jubran Nusrallah
Law Kam W.
Tokarski Zbigniew
Goodrow John
Mark A. Litman & Assoc. P.A.
Samsung Electronics Co,. Ltd.
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