US3928036A

US3928036A - Flexible xerographic photoreceptor element

Info

Publication number: US3928036A
Application number: US518554A
Authority: US
Inventors: Robert N Jones
Original assignee: Xerox Corp
Current assignee: Xerox Corp
Priority date: 1974-10-29
Filing date: 1974-10-29
Publication date: 1975-12-23
Anticipated expiration: 1992-12-23

Abstract

A seamless flexible photoreceptor device which comprises a conductive substrate made up of an elastomeric material formed in the shape of a continuous belt with the elastomer containing a second phase which results in electrical conductivity. A photoconductive layer overlays and is bonded to the substrate. The photoconductive layer comprises a polymeric matrix of an electrically insulating elastomeric resin containing an interlocking network of photoconductive material in the form of continuous chains which pass through the photoconductive layer thickness. The photoconductor is present in a volume concentration of from about 1 to 15 percent by volume of the binder layer.

Description

[451 Dec. 23, 1975 Jones FLEXIBLE XEROGRAPHIC PHOTORECEPTOR ELEMENT [75] Inventor: Robert N. Jones, Fairport, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Oct. 29, 1974 [21] Appl. No.: 518,554

[52] US. Cl. 96/15; 96/l.8; 252/501 [51] Int. Cl. 603G 5/04; 6036 5/08 [58] Field of Search 96/15, 1.8; 252/501 [56] References Cited UNITED STATES PATENTS 3,787,208 l/l974 Jones 96/15 X 3,837,906 9/1974 Jones 96/15 X Primary Examiner-Roland E. Martin, Jr.

[57] ABSTRACT A seamless flexible photoreceptor device which comprises a conductive substrate made up of an elastomeric material formed in the shape of a continuous belt with the elastomer containing a second phase which results in electrical conductivity. A photoconductive layer overlays and is bonded to the substrate. The photoconductive layer comprises a polymeric matrix of an electrically insulating elastomeric resin containing an interlocking network of photoconductive material in the form of continuous chains which pass through the photoconductive layer thickness. The photoconductor is present in a volume concentration of from about 1 to 15 percent by volume of the binder layer.

3 Claims, 2 Drawing Figures U.S. Patant Dec. 23, 1975 3,928,036

FIG. 2

BACKGROUND OF THE INVENTION This invention relates to xerography and more specifically to a novel flexible elastomeric photoreceptor member.

The art of xerography involves the use of a photosenl sitive element or member containing a photoconductive insulating layer which is first uniformly electrostatically charged in order to sensitize its surface. The plate is then exposed to an image of activating electromagnetic radiation, such as light, x-ray, or the like, which selectively dissipates the charge in the exposed areas of the photoconductive insulator while leaving behind a latent electrostatic image in the nonexposed areas. This latent electrostatic image may then be developed and made visible by depositing finely divided electroscopic marking particles on the surface of the photoconductive layer. This concept was originally disclosed by Carlson in U.S. Pat. No. 2,297,691, and is further amplified and described by many related patents in the field.

One type of photoconductive layer used in xerography is illustrated by U.S. Pat. No. 3,121,006, to Middleton et al which describes a number of binderlayers comprising finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. In one commercial form, the binder layer contains particles of photoconductive zinc oxide dispersed in an insulating resin binder which is coated on a paper backing. In the Middleton et al Patent, a relatively high volume concentration of photoconductor, up to about 50 percent or more by volume is usually necessary in order to obtain sufficient photoconductor particle-to-particle contact for rapid discharge. Such high loadings of photoconductor in a binder layer, result in the physical continuity of the resin being destroyed, thereby significantly reducing the mechanical properties of the binder layer. In addition, the utilization of high photoconductor volume loadings, and correspondingly low binder concentrations, results in poor mechanical properties in terms of cohesion, adhesion, flexibility, toughness, and- /or results in a porous film which can result in undesirable humidity sensitivity and fatigue effects. At the same time, surface porosity tends to negate residual toner removal and therefore, the capability of repeated cycling of the photoreceptor in the xerographic imaging mode.

In U.S. Pat. No. 3,787,208, to R. N. Jones, the above high photoconductor concentration disadvantages were overcome by the discovery ofa method of making a novel photoconductive binder layer which enables the use of relatively low photoconductor volume concentrations. In addition to excellent mechanical properties, such a binder layer also exhibits excellent electrical characteristics which enable the photoreceptor to be used in a cycling manner. The photoreceptor of the present invention provides further improvements in the mechanical properties, and in particular with respect to the flexibility and elastomeric properties of the photoreceptor over those exhibited by the photoreceptor made by the U.S. Pat. No. 3,787,208 cited above.

OBJECTS OF THE INVENTION It is therefore an object of this invention to provide a flexible elastomeric photoreceptor device.

It is another object of this invention to provide a seamless, flexible, photoreceptor belt. It is another object of this invention to provide a novel photoreceptor binder layer in the form of a flexible elastomeric endless belt.

SUMMARY OF THE INVENTION The foregoing objects and others are accomplished in accordance with this invention by providing a flexible, elastomeric photoreceptor device. More specifically, the invention comprises an elastomeric photoreceptor device having a rubber or other elastomeric substrate in the form of a continuous belt. The elastomeric material contains a second conductive phase which results in providing electrical conductivity to ground. A photoconductive binder layer is fused or bonded to the conductive elastomeric substrate material. The photoconductor may consist of a polymeric matrix, which is preferably an elastomer, or at least a material having high flexibility and elongation, which will bond to the substrate material. In order to insure the desired physical characteristics of high flexibility, the photoconductor is dispersed in a low volume concentration of less than 15 percent by volume in the form of an interlocking network of photoconductive chains which pass through the binder layer thickness. The present invention provides a continuous seamless belt photoreceptor capable of being elongated up to about 10 percent or more without detrimentally effecting mechanical integrity of the photoconductive coating. Such a photoreceptor reduces tracking problems and concentricity deviation when mounted on a roller assembly.

An important step in making the binder layer of the instant invention involves the photoconductor geometry control which is achieved by employing a particulate binder material having a correct size distribution. The instant concept may be illustrated by the following example:

A photoconductive binder layer is made by forming a particulate mixture of photoconductive particles having a size distribution of about 0.001 to 2.0 microns with a thermoplastic resin binder having a particle size distribution of about 1 to microns. The photoconductor is present in a concentration from about 1 to 15 percent by volume. The mixture is dispersed in a suitable fluid carrier in which neither the photoconductor nor binder is soluble. The dispersion is coated onto an elastomeric substrate and the carrier fluid allowed to evaporate. The dried layer may then heated to fuse the binder particles into a binder matrix containing photoconductor particles in the form of continuous paths in particle-to-particle contact throughout the thickness of the binder layer. The size of the resin particles should, in general, be at least about 5 times that of the photo conductor particles. It should be noted that if the particle size of the photoconductor approaches that of the binder, the desired geometry of the photoconductor particles cannot be achieved and the photoconductor particles become completely encased in the binder matrix. In this case, the desirable results of the Applicants invention are not achieved, as will be shown later.

Binder layers of the controlled dispersion type described above exhibit a combination of electrical characteristics and mechanical properties which are superior to those of the binder systems of the uniform dispersion type as exemplified by the examples described in the Middleton et al Patent.

DETAILED DESCRIPTION OF THE DRAWINGS FIG. 1 represents an imaging device of the present invention containing a flexible conductive substrate 11 having thereon a photoconductive binder layer 14.

Flexible electrically conductive substrate 11 comprises a rubber, or other elastomeric material, which is formed by well known techniques in the form of a continuous belt, and which contains a second phase which results in electrical conductivity. Reference character 12 represents a rubber or other flexible elastomeric material which comprises the major phase and provides for the flexibility of the imaging member. Any synthetic or natural occurring rubber having these properties may be used. A particularly preferred group of materials comprises elastomers including styrene butadiene, polybutadiene, neoprene, butyl, polyisoprene, nitrile, and ethylenepropylene rubbers. Conductive phase 13 represents a separate phase of conductive material dispersed in the rubber or elastomeric matrix. The conductive phase may comprise any material such as conductive metals, carbon or graphite. Flexible material 12 should comprise a major proportion of the substrate in order to insure the desired degree of flexibility.

Photoconductive binder layer 14, comprises an interlocking network of photoconductive particles 15 contained in a substantially electrically insulating organic matrix material 16. Matrix 16 may comprise an elastomer, rubber or other insulating resin. Thus the photoconductive layer consists of a polymeric matrix which is preferably elastomeric, or at the very least flexible, and chosen from materials which will bond to the substrate material. The photoconductor phase is maintained in the form of a series or network of contacting chains which pass through the binder layer thickness. In order to insure the flexible properties of the device, the photoconductor material is maintained in a concentration of about 1 to 15 percent by volume or less and fabricated according to the concepts disclosed in U.S. Pat. No. 3,787,208, which is incorporated herein by reference.

The binder layers of the instant invention may utilize any suitable photoconductive material. These include both inorganic and organic photoconductors or mixtures thereof.

Typical inorganic photoconductors suitable for use in the instant invention comprises cadmium sulfide, cadmium sulf-selenide, cadmium selenide, trigonal selenium, zinc sulfide, lead oxide, zinc oxide, antimony trisulfide and mixtures thereof. U.S. Pat. No. 3,121,006 to Middleton et al provides a more complete listing of inorganic photoconductors suitable for use in the instant invention. Inorganic photoconductive glasses may also be used as the photoconductor. Typical materials include vitreous or amorphous selenium, alloys of selenium, with materials such as arsenic, tellurium, thallium, bismuth, sulfur, antimony, and mixtures thereof. Typical organic photoconductors suitable for use in the instant invention include the X-form of metal-free phthalocyanine described in U.S. Pat. No. 3,357,989, anthracene, anthraquinones, and metal and metal-free phthalocyanines.

In addition, various additives, activators, dopants and/or sensitizers may also be used to enhance the photoconductivity of the above photoconductive materials. For example, the addition of halogens to arsenicselenium alloys is known to increase photosensitivity. Similarly, zinc oxide exhibits enhanced spectral response when sensitized with a suitable dye. It is also well known that increased photosensitivity is obtained when photoconductors such as cadmium sulfide are reacted with a very small amount of an activator material such as copper.

The matrix material may comprise any electrically insulating resin which can be obtained or made in particulate form, cast into a film from a dispersion, and later processed to form a smooth continuous binder layer. Typical resins include polysolfones, acrylates, polyethylene, styrene, diallyphthalate, polyphenylene sulfide, melamine formaldehyde, epoxies, polyesters, polyvinyl chloride, nylon, polyvinyl fluoride and mixtures thereof. Thermoplastic and thermosetting resins are preferred in that they may be easily formed or coalesced into the final binder layer by simply heating the particulate layer. As stated above, a particularly preferred group of matrix materials comprise elastomeric materials of the type listed for use for the substrate in that these materials provide the greatest degree of mechanical flexibility.

FIG. 2 illustrates a preferred embodiment of the present invention in which reference character 20 designates a xerographic member in the form of a flexible belt 21 having the flexible rubberized substrate described above in FIG. 1, having thereon a photoconductive coating 22 similar to that illustrated and described for FIG. 1 above. The photoreceptor is normally mounted over pulleys or rollers 23 and 24.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples further specifically define the present invention with respect to a method of making and testing a flexible photoreceptor member. Examples below are intended to illustrate varioius preferred embodiments of the present invention.

EXAMPLE I Ten parts by volume of a cadmium sulfoselenide (CdSSe) photoconductive pigment having a size distribution of from .03 to 0.5 microns are dispersed in a carrier liquid of cyclohexanol with parts by volume of a particulate polyester having a size distribution of from about 1 to 10 microns. A film of the dispersion is coated onto a conductive neoprene belt material available from Goodyear Rubber Company, and fused at 400F to form a photoconductive coating 25 microns thick. This photoreceptor member approximates the configuration illustrated in FIG. 1 of the drawings. The resultant device is extremely flexible and could be elongated about 10 percent without detrimentally affecting the photoconductor coating. This photoreceptor member was imaged in the conventional xerographic manner including charging, exposure to form an image, and development of the image. Satisfactory visible images were formed using this photoreceptor member.

Other modifications and ramifications of the present invention would appear to those skilled in the art upon reading the disclosure. These are also intended to be within the scope of the invention.

What is claimed is:

l. A flexible photoreceptor member comprising:

a. aconductive Substrate comprising an elastomeric material formed in the shape of a continuous belt, said elastomer containing a second phase which results in electrical conductivity; and

b. a photoconductive layer overlying and bonded to said substrate, said photoconductive layer comprising a polymeric matrix of an electrically insulating elastomeric resin containing therein an interlocking network ofphotoconductive material in the form of continuous chains which pass through the photoconductive layer thickness, said photoconductor being present in a volume concentration from about 1 to percent by volume of said binder layer, with the outer surface of said layer I comprises a major proportion of neoprene containing a minor proportion of a conductive phase.

Claims

1. A FLEXIBLE PHOTORECEPTOR MEMBER COMPRISING: A. A CONDUCTIVE SUBSTRATE COMPRISING AN ELASTOMERIC MATERIAL FORMED IN THE SHAPE OF A CONTINUOUS BELT, SAID ELASTOMER CONTAINING A SECOND PHASE WHICH RESULTS IN ELECTRICAL CONDUCTIVITY; AND B. A PHOTOCONDUCTIVE LAYER OVERLYING AND BONDED TO SAID SUBSTRATE, SAID PHOTOCONDUCTIVE LAYER COMPRISING A POLYMERIC MATRIX OF AN ELECTRICALLY INSULATING ELASTOMERIC RESIN CONTAINING THEREIN AN INTERLOCKING NETWORK OF PHOTOCONDUCTIVE MATERIAL IN THE FORM OF CONTINUOUS CHAINS WHICH PASS THROUGH THE PHOTOCONDUCTIVE LAYER THICKNESS SAID PHOTOCONDUCTIVE BEING PRESENT IN A VOLUME CONCENTRATION FROM ABOUT 1 TO 15 PERCENT BY VOLUME OF SAID BINDER LAYER, WITH THE OUTER SURFACE OF SAID LAYER COMPRISING ELASTOMERIC RESIN MATERIAL.

2. The device of claim 1 in which the photoconductive material comprises at least one material selected from the group consisting of trigonal selenium, vitreous selenium, selenium alloys, cadmium sulfide, cadmium selenide and cadmium sulfoselenide.

3. The device of claim 1 in which a substrate material comprises a major proportion of neoprene containing a minor proportion of a conductive phase.