US3870516A - Method of imaging photoconductor in change transport binder - Google Patents

Abstract

A photosensitive member having a binder layer comprising photoconductive particles dispersed in an electrically insulating active organic matrix material. The photoconductor comprises a material which exhibits the capability of photo-excited hole generation and injection, with the active organic matrix being substantially transparent and nonabsorbing in the wavelength region of use and capable of supporting the injection and transport of photo-excited holes from the photoconductive particles. The member may be imaged in the conventional zerographic mode which includes charging, exposure to light, followed by development.

Description

United States Patent [191 Smith et al. I

[ METHOD OF IMAGING PHOTOCONDUCTOR IN CHANGE TRANSPORT BINDER [75] Inventors: Michael Smith, Rochester; Charles F. Hackett, Williamson; Richard W. Radler, Marion, all of NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: June 20, 1973 [21] App]. No.: 371,646

Related U.S. Application Data [63] Continuation-in-part of Ser. No. 93,994, Dec. 1, 1970, abandoned, which is a continuation-in-part of Ser. No. 14,281, Feb. 26, 1970, abandoned.

UNITED STATES PATENTS 3,037,861 6/1962 Hoegl 96/1.5

Primary Examiner-Roland E. Martin, Jr.

[57] ABSTRACT A photosensitive member having a binder layer comprising photoconductive particles dispersed in an electrically'insulating active organic matrix material. The photoconductor comprises a material which exhibits the capability of photo-excited hole generation and injection, with the active organic matrix being substantially transparent and nonabsorbing in the. wavelength region of use and capable of supporting the injection and transport of photo-excited holes from the photoconductive particles. The member may be imaged in the conventional zerographic mode which includes charging, exposure to light, followed by development.

13 Claims, 10 Drawing Figures SHEET 1 [If 6 FATENTED H97 ,ngmggmx 1 I975 SHEET 3 [IF 6 AMORPHOUS Se/ PVK SANDWICH LAYER FIELD= 5O VOLTS/ MICRON SELENIUM F|ELD= 5O VOLTS MICRON A BINDER LAYER 0F X-FORM METAL FREE PHTHALOCYANINE FIELD= 5o VOLTS/MICRON A BINDER LAYER OF TRIGONAL 2E6 oint mwomux WAVELENGTH A 20 wdz 5b o x ENGINES zofiozixm E302 WAVELENGTH -X PATENT D sum 5 or g IOOO POSITIVE CORONA CHARGING O o w m w NEGATIVE CORONA CHARGING BINDER TO PIGMENT RATIO (BY VOL.) POLYVINYL CARBAZOLE' TRIGONAL SELENIUM I 59x IOIZ PHOTONS- CM2 SEC 5 VOLT E, 3 x IO CM d IZFSAMPLES REY/U516 PATENT DHAR] H975 SHEET 8 0F 6 WKOFlU Q Gt Ooh

1 METHOD OF IMAGING PHOTOCONDUCTOR IN CHANGE TRANSPORT BINDER This application is a continuation-in-part of copending application, Ser. No. 93,994, filed Dec. 1, 1970, now abandoned, which is a continuation-in-part of application, Ser. No. 14,28l,f1led Feb. 26, 1970, and now abandoned.

BACKGROUND OF THE INVENTION This invention relates in general to xerography and more specifically to a novel photosensitive device and method of use.

In the art of xerography, a xerographic plate containing a photoconductive insulating layer is imaged byfirst uniformly electrostatically charging its surface. 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 insulator while leaving behind a latent electrostatic image in the nonilluminated areas. This latent electrostatic image may then be developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer.

A photoconductive layer for use in xerography may be a homogeneous layer of a single material such as vitreous selenium or it may be a composite layer containing a photoconductor and another material. One type of composite photoconductive layer used in xerography is illustrated by US. Pat. No. 3,121,006 to Middleton and Reynolds which describes a number of binder layers comprising finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. In its present commercial form, the binder layer contains particles of zinc oxide uniformly dispersed in a resin binder and is coated on a paper backing.

1n the particular examples of binder systems described in Middleton et al, the binder comprises a material which is incapable of transporting injected charge carriers generated by the photoconductor particles for any significant distance. As a result, with the particular materials disclosed in the Middleton et al. patent, the photoconductor particles must be in substantially continuous particle-to-particle contact throughout the layer in order to permit the charge dissipation required for stable cyclic operation. With the uniform dispersion of photoconductor particles described in Middleton et al., therefore, 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. It has been found, however, that high photoconductor loadings in the binder layers of the resin type result in the physical continuity of the resin being destroyed, thereby significantly reducing the mechanical properties of the binder layer. Layers with high photoconductor loadings are often characterized by a brittle binder layer having little or no flexibility. On the other hand, when the photoconductor concentration is reduced appreciably below about 50 percent by volume, the discharge rate is reduced, making high speed cyclic or repeated imaging difficult or impossible.

US. Pat. No. 3,121,007 to Middleton et al. teaches another type of photoconductor which includes a two phase photoconductive binder layer comprising photoconductive insulating particles dispersed in a homogeneous photoconductive insulating matrix. The photoconductor is in the form of a particulate photoconductive inorganic crystalline pigment broadly disclosed as being present in an amount from about 5 to percent .by weight. Photodischarge is said to be caused by the combination of charge carriers generated in the photoconductive insulating matrix material and charge carriers injected from the photoconductive crystalline pigment into the photoconductive insulating matrix.

US. Pat. No. 3,037,861 to Hoegl et al. teaches that polyvinyl carbazole exhibits some long-wave U.V. sensitivity and suggests that its spectral sensitivity be extended into the visible spectrum by the addition of dye sensitizers. Hoegl et al further suggests that other additives such as zinc oxide or titanium dioxide may also be used in conjunction with polyvinyl carbazole. ln Hoegl et al., it is clear that the polyvinyl carbazole is intended to be used as a photoconductor, with or without additive materials which extend its spectral sensitivity.

In addition, certain specialized. layer structures particularly designed for reflex imaging have been proposed. For example, US. Pat. No. 3,165,405 to Hoesterey utilizes a two layered zinc oxide binder structure for reflex imaging. The Hoesterey patent utilizes two separate contiguous photoconductive layers having different spectral sensitivities in order to carry out a particular reflex imaging sequence. The Hoesterey device utilizes the properties of multiple photoconductive layerss in order to obtain the combined advantages of the separate photoresponse of the respective photoconductive layers. I

It can be seen from a review of the conventional composite photoconductive layers cited above, that upon exposure to light, photoconductivity in the layer structure is accomplished by charge transport through the bulk of the photoconductive layer, as in the case of vitreous'selenium (and other homogeneous layer modifications). ln devices employing photoconductive binder structures, which include inactive electrically insulating resins such as those described in the Middleton et al,, US. Pat. No. 3,121,006 conductivity or charge transport is accomplished through high loadings of the photoconductive pigment allowing particle-to-particle contact of the photoconductive particles. 1n the case of photoconductive particles dispersed in a photoconductive matrix, such as illustrated by the Middleton et al., US. Pat. No. 3,121,007, photoconductivity occurs through the generation of charge carriers in both the photoconductive matrix and the photoconductor pigment particles.

Although the above patents relay upon distinct mechanisms of discharge throughout the photoconductive layer, they generally suffer from common deficiencies in that the photoconductive surface during operation is exposed to the surrounding environment, and particularly in the case of cycling xerography, susceptible to abrasion, chemical attack, heat, and multiple exposures to light during cycling. These effects are characterized by a gradual deterioration in the electrical characteristics of the photoconductive layer resulting in the printing out of surface defects and scratches, l0- calized areas of persistent conductivity which fail to retain an electrostatic charge, and high dark discharge.

In addition to the problems noted above, these photoconductive layers require that the photoconductor comprise either a hundred percent of the layer, as in the case of the vitreous selenium layer, orthat they preferably contain a high proportion of photoconduc-. tive material in the binder configuration. The requirements of a photoconductive layer containing all or a major proportion of a photoconductive material further restricts the physical characteristics of the final plate, drum or belt in that the physical characteristics such as flexibility and adhesion of the photoconductor to a supporting substrate are primarily dictated by the physical properties of the photoconductor, and not by the resin or matrix material which is preferably present in a minor amount.

Another form of composite photosensitive layer which has also been considered by the prior art includes a layer of photoconductive material which is covered with a relatively thick plastic layer and coated on a supporting substrate.

US. Pat. No. 3,041,166 to Bardeen describes such a configuration in which a transparent plastic material overlays a layer of vitreous selenium which is contained on a supporting substrate. The plastic material is described as one having a long range for charge carriers of the desired polarity. In operation, the free surface of the transparent plastic is electrostatically charged to a given polarity. The device is then exposed to activating radiation which generates a hole-electron pair in the photoconductive layer. The electron moves through the plastic layer and neutralizes a positive charge on the free surface of the plastic layer thereby creating an electrostatic image. Bardeen, however, does not teach any specific plastic materials which will function in this manner, and confines his examples to structures which use a photoconductor material for the top layer.

French Pat. No. 1,577,855 to Herrick et a1 describes a special purpose composite photosensitive device adapted for reflex exposure by polarized light. One embodiment which employs a layer of dichroic organic photoconductive particles arrayed in oriented fashion on a supporting substrate and a layer of polyvinyl carbazole formed over the oriented layer of dichroic material. When charged and exposed to light polarized perpendicularly to the orientation of the dichroic layer, the oriented dichroic layer and polyvinyl carbazole layer are both substantially transparent to the initial exposure light. When the polarized light hits the white background of the document being copied, the light is depolarized, reflected back through the device and absorbed by the dichroic photoconductive material. In another embodiment, the dichroic photoconductor is dispersed in oriented fashion througout the layer of polyvinyl carbazole.

In view of the state of the art, it can readily be seen that there is a need for a general purpose photoreceptor exhibiting acceptable photoconductive characteristics and which additionally provides the capability of exhibiting outstanding physical strength and flexibility to be reused under rapid cyclic conditions without the progressive deterioration of the xerographic properties dueto wear, chemical attack, and light fatigue MW OBJECTS OF THE INVENTION It is, therefore, an object of this invention to provide a novel photosensitive device adapted for cyclic imaging which overcomes the above noted disadvantages.

It is a further object of this invention to provide a novel imaging system.

It is a further object of this, invention to provide a photosensitive member which exhibits facile hole generation and transport.

It is another objectof this invention to provide a method of imaging a photosensitive member.

It is a further object of this invention to provide a novel photosensitive binder structure.

It is another object of this invention to provide a novel binder structure characterized by an extremely low ratio of photoconductor to binder.

It is yet another object of this invention to provide a novel photosenstive member which is capable of exhibiting outstanding physical properties.

SUMMARY OF THE INVENTION The foregoing objects and others are accomplished in accordance with this invention by providing a photosensitive member having a composite photosensitive layer which comprises substantially unoriented photoconductive particles utilized in conjunction with an electrically active organic binder or matrix. The photoconductive particles must be capable of generating and injecting photoexcited holes into the electrically active organic material which comprises a transparent organic polymer or nonpolymeric material which is substantially nonabsorbing to radiation in .the spectral region of intended use, but which is active in that it allows the injection of photoexcited holes from the photoconductive particles and allows these holes to be transported through the active matrix. In a preferred form of the in vention, the photoconductive particles are dispersed throughout the active matrix material. I

It should be understood that the active organic matrix material does not function as a photoconductor in the wavelength region of use. As stated above, holeelectron pairs are photogenerated in the photoconductive particles and the holes are then injected into the active matrix with hole transparent occurring through the active matrix.

One embodiment of a typical application of the instant invention consists of a supporting substrate such as a conductor containing a binder layer thereon. For example, the binder layer may comprise particles of trigonal selenium contained in a transparent polymeric layer which allows for hole injection and transport. The transparent active (polymer) matrix allows oneto take advantage of extremely low photoconductor loading not previously available to the art and preferably certain selected matrix materials having high charge injection and transparent efficiency are utilized. In addition, the structure can function effectively for repetitive use or cycling. This structure can be imaged in the conventional xerographic manner which usually includes charging, optical projection exposure, and development.

In general, the advantages of the improved structure and method of imaging will become appparent upon consideration of the following disclosure of the invention; especially when taken in conjunction with the accompanying drawings wherein:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a plot of photosensitivity versus field dependence for an active material alone, and in conjunction with a photoconductor.

FIG. 2 is a plot similar to FIG. 1 for a second active material.

FIG. 3 represents a plot of the absorption spectrum for polyvinyl carbazole.

FIG. 4 represents a plot of the absorption spectrum for pyrene.

FIG. 5 illustrates the spectral response toconductor materials.

FIG. 6 represents a plot of the absorption spectrum for perylene.

FIG. 7 is a schematic illustration ofone embodiment of a device of the instant invention.

FIG. 8 represents a plot of the discharge characteristics for positive and negative corona charging one embodiment of a binder layer of the instant invention.

FIG. 9 represents a plot of the discharge characteristies for positive and negative corona charging a second embodiment of a binder layer of the instant invention.

FIG. 10 illustrates the cycling characteristics at various exposure wavelengths for a device employing an active layer.

DETAILED DESCRIPTION OF THE DRAWINGS As defined herein, a photoconductor is a material which is electrically photoresponsive to light in the wavelength region in which it is to be used. More specifically, it is a material whose electrical conductivity increases significantly in response to the absorption of electromagnetic radiation in a wavelength region in which it is to be used. This definition is necessitated by the fact that a vast number of aromatic organic compounds are known or expected to be photoconductive when irradiated with strongly absorbed ultraviolet, x-ray or gamma-radiation. Photoconductivity in orfor three phoganic materials is a common phenomenon. Practically all highly conjugated organic compounds exhibit some degree of photoconductivity under appropriate conditions. Most of these organic materials have their prime wavelength response in the ultraviolet. However, little commercial utility has been found for ultraviolet responsive materials, and their short wavelength response is not particularly suitable for document copying or color reproduction. In view of the general prevalence of photoconductivity. it is therefore necessary that for the instant invention. the term photoconductor or photoconductive be understood to include only those materials which are in fact substantially photoresponsive in the wavelength region in which they are to be used.

The active material, which is also referred to as the active matrix material when used as a matrix for the binder layer, is a substantially nonphotoconductive material which supports an injection efficiency of photoexcited holes from the photoconductive particles of at least about 10 percent at fields of about 2 X 10 volts/cm. This material is further characterized by the ability to transport the carrier at least 10' cm. at a field of no more than about 10 volts/cm. In addition, the active matrix material is substantially transparent in the wavelength region in which the device is to be used.

As can be seen from the above discussion, most materials which are useful active matrices for binder layers of the instant invention are incidentally also photoconductive when radiation of wavelengths suitable for electronic excitation is absorbed by them. However, photoresponse in the short wavelength region, which falls outside the spectral region for which the photoconductor is to be used, is irrelevant to the performance of the device. It is well known that radiation must be absorbed in order to excite photoconductive response, and the transparency criteria stated above for the active matrix materials implies that these materials do not contribute significantly to the photoresponse of 5 the photoreceptor in the wavelength region of use. The active transport material which is employed in conjunction with the photoconductive layer in the instant invention is a material which is an insulator to the extent that an electrostatic charge placed on said 0 active binder material is not conducted in the absence of illumination at a rate sufficient to prevent the formation and retention of an electrostatic latent image thereon. In general, this means that the specific resistivity of the active transport material should be at least 10" ohm-ems.

The reason forthe requirement that the active materials must be transparent is based upon the discovery that under all practical conditions, the efficiency of photoinjection from the photoconductor into the active materials, for visible radiation absorbed by the photoconductor, far exceeds the intrinsic photosensitivity of the active material in any wavelength region-visible or otherwise. This situation is illustrated by FIGS. 1 and 2 which shows a comparison of the field dependence of the injection sensitivity of the photoconductor selenium into typical active materials and the intrinsic photosensitivity of two active materials-polyvinyl carbazole and polyvinyl pyrene, each measured at wavelengths of high response. The polyvinyl carbazole and polyvinyl pyrene curves of FIG. 1 and 2, respectively, are measured on samples 20 microns thick contained on an aluminum substrate and prepared by the method of Example I of Applicants copending application entitled Layered Imaging I Member and Method" filed concurrently with the instant application. The curves for the layered structures of the same materials having a 0.4 micron layer of vitreous selenium formed between the layer of active material and substrate are similar to the structure illustrated by FIG. 9 and are made by the method set forth in Example III of the above mentioned copending application. The data of FIGS. 1 and 2 is determined by plotting the'initial xeroxgraphic gain (G) as a function of the applied field. The xerographic gain was calculated from the initial discharge rate.

Where I is the incident photon flux, d the thickness of the layer, It the electric permittivity, and e the electronic charge. A xerographic gain of unity would be observed if one charge carrier per'incident photon were excited and moved across the layer. It is clear from FIGS. 1 and 2 that the intrinsic photoconductivity of the active materials at their peak wavelength of absorption (U.V. excitation) leads to gains considerably lower than the two phase structures incorporating efficient photoconductive materials, such as illustrated by the layered structures employing the 0.4 micron thick selenium layers with suitable active materials. These structures can achieve gains of approximately 0.70 at a field of about 10 volts/cm, using a I excitation wavelength within the visible spectrum (4,000A8,000A). It is also clear from FIGS. 3 and 4 that the typical active materials mentioned above will exhibit negligible, if any, discharge when exposed to a wavelength of light useful in xcrography, i.e., 4,000A'-8,000A. The obvious improvement in performance which results from the use of thetwo phase systems can best be realized if the active material is substantiallytransparent to radiation in a region in which the photoconductor is to be used; for any absorption of desired radiation by the active material will prevent this radiation from reaching the photoconductive particles or pigment where it is much more effectively utilized. It therefore follows that it is advantageous to use active matrix materials which are transparent in the wavelength in which the photoconductor or pigment has its main response, and more particularly in the wavelength region in which the photoconductor is to be used.

Applications where complete transparency in the visible region is not required for the active material include the selective recording of narrow-band radiation such as that emitted from lasers, spectral pattern recognition, color coded form duplication, and possible functional color xerography.

FIGS. 3, 4, and 6 represent the well known absorption efficiency for'active matrix materials polyvinyl carbazole, pyrene, and perylene, respectively. FIG. represents the xerographic response spectra for three typical photoconductor-active matrix material combinations. The amorphous selenium-PVK response is for a 0.4 micron layer of amorphous selenium contained on a micron layer 'of PVK. The X-form of metal free phthalocyanine and trigonal selenium are contained in a polyvinyl carbazole binder in a concentration of about'30 to l (by volume) for thephthalocyanine and about l00'to l (by volume) for the trigonal selenium. Both binder layers are about 20 microns in thickness. As can be seen from FIGSLS, 4, 5, and 6, it may be deduced that certain combinations of active matrix materials and various photoconductors would be of particular use for selective spectral response.

Referringto FIG. 7, reference character 11 illustrates a preferred embodiment of the instant invention which comprises a photosensitive member in the form of a plate having a supporting substrate 11 coated witha binder layer 12. Substrate 11 preferably comprises any suitable conductive material. Typical conductors comprise aluminum, steel, brass, or the like. The substrate may be rigid or flexible and of any convenient thickness. Typical substrates include flexible belts or sleeves, sheets, webs, plates, cylinders, and drums. The

substrate or support may also comprise a composite,

structure such as a thin conductive coating contained on a paper base; a plastic coated with a thin conductive layer such as aluminum or copper iodide; or glass coated with a thin conductive coating of chromium or tin oxide. When using a transparent substrate it should be understood that imagewise exposure may optionally be carried out through the substrate or back of the imaging member.

Binder layer 12 contains photoconductive particles 13 dispersed in an unoriented fashion in an electricallyactive matrix or binder material 14. The photoconductive particles may consist of any suitable inorganic or organic photoconductor, and mixtures thereof, which are capable of injecting photoexcited holes into the m atrix. Typical inorganic materials include inorganic crystalline compounds and inorganic photoconductive selenium alloys such as selenium-tellurium and seleniu-' marsenic. Selenium may also be used as a crystalline form known as trigonal selenium. Typical organic materials include phthalocyanine pigments such as the X- form of metal free phthalocyanine described in U.S.

Pat. No. 3,357,989 to Bryne et al, metal phthalocyanines, such as copper phthalocyanine; quinacridones available from DuPont under the tradename Monastral Red, Monastral Violet, and Monastral Red Y; substituted 2,4-diamino-triazines disclosed by Weinberger in U.S. Pat. No. 3,445,227; triphenodioxazines disclosed by Weinberger in U.S. Pat. No. 3,442,781; polynuclear aromatic quinones available from Allied Chemical Corp. under the tradename lndofast Double Scarlet, lndofast Violet Lake B, lndofast Brilliant Scarlet, and lndofast Orange. The above list of photoconductors should in'no way be taken as limiting, but is merely illustrative of suitable materials. The size of the photoconductive particles is not critical, but particles in a size range of about 0.01 to 1.0 microns yield particularly satisfactory results.

As previously stated, the photoconductive material of the instant'invention is employed in an unoriented manner. By unoriented, it is meant that the pigment or photoconductive material is isotropic with respect to the exciting electromagnetic radiation, in that it is equally sensitive to any polarization of the exciting radiation.

The active matrix material 14 may compriseany suitable transparent organic polymer or nonpolymeric material capable of supporting the injection of photoexcited holes from the photoconductive pigment and allowing the transport of these holes through the active matrix to selectively discharge a surface charge. Polymers having this characteristic have been found to contain repeating units of a polynuclear aromatic hydro-- carbon which may also contain heteroatoms such as; for example, nitrogen, oxygen, or sulfur. Typical polymers include poly-N-vinyl carbazole (P-VK), poly-lvinyl pyrene (PVP), poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)-carbazole, poly-9-(5-hexyl)-carbazole, polymethylene pyrene, poly-l-(- pyrenyl)-butadiene and N-substituted polymeric acrylic acid amides of pyrene. Also included are derivatives of such polymers including alkyl, nitro, amino, halogen, and hydro'xy substituted polymers. Typical examines are p oly-il-amino carbazole, l,3- dibromo-poly-N-vinyl carbazole and 3,6-dibromo-poly- N-vinyl carbazole in particular derivatives of the formula where Y Asmara "s'ab timais"55516755 mega;

' Also included are structural isomers of these polymers,

pyrene/bu ta diene ABA, and AB block polymers. Typical nonpolymeric materials include carbazole, N-

ethylcarbazole, N-phe'nylcarbazole, pyrene, tetraphene, l-acetylpyrene, 2,3-benzochrysene, 6,7- benzopyrene, l-bromopyrene, l-ethylpyrene, 1-

methylpyrene, perylene, 2-phenylindole, tetracene, picene, l,3,6,8-tetraphenyl-pyrene chrysene, fluorene, fluorenone, phenanthrene, triphenylene, l,2,5,6- dibenzanthracene, 1,2,3,4-dibenzanthracene, 2,3- benzopyrene, anthraquinone, dibenzothiophene, naphthalene, and l-phenylnaphthalene. Due to the poor mechanical properties of the non-polymer materials they are preferably used in conjunction with either an active polymer material or a non-active polymeric binder. Typical examples include suitable mixtures of carbazole in poly-N-vinyl carbazole as an active polymer and carbazole in a non-active binder. Such non-active binder materials include polycarbonates, acrylate polymers, poly amides, polyesters, polyurethanes, and cellulose polymers.

It should be understood that the use of any polymer (a polymer being a large molecule built up by the repetition of small, simple chemical units) whose repeat unit contains the appropriate aromatic hydrocarbon, such as carbazole, and which supports hole injection and transport, may be used. It is therefore not the intent of the invention to restrict the type of polymer which can be employed as the matrix material. Polyesters, polysiloxanes, polyamides, polyurethanes and epoxies as well as block, random, or graft co-polymers (containing the aromatic repeat unit) are exemplary of the various types of polymers which can be employed. In addition suitable mixtures of active polymers with inactive polymers or non-polymeric materials may be employed. One action of certain non-active material is to act as a plasticizer to improve the mechanical properties of the active polymer layer. Typical plasticizers include epoxy resins, polyester resins, polycarbonate resins, l-phenyl naphthalene and chlorinated diphenyl.

In general, the active layer is substantially transparent or non-absorbing in at least some significant portion of the range from about 4,000-8,000 Angstroms, but will still function to allow injection and transport of holes generated within this wavelength range by the photoconductive pigment particles.

An upper limit on photoconductor volume concentration or occupancy is governed by various factors: Notably (l) the stageat which the physical properties of the polymer are seriously impaired; 2 the stage at which there is significant transport through particle-toparticle contacts; and (3) the stage at which, with conductive pigments such as trigonal selenium, there is ex-. cessive hole sweep out during charging. The latter two factors frequently lead to a lack of cycling ability. ln general, to attain the best combination of physical and electrical properties, the upper limit for the photoconductive pigment or particles must be no greater than about 5 percent by volume of the binder layer. A lower limit for the photoconductive particles of about 0.1 percent by volume of the binder layer is required to insure that the light absorption coefficient is sufficient to give appreciable carrier generation. In order to achieve a closely equivalent discharge rate under both charging conditions, it is necessary to work in a volume occupancy region where the average depth of light penetration is near the center ofthe layer. Thus for two exam- Pl6S Show" aEKi-j 4 .19.21 wh qht nrsse itlt ndst layers of the X-form of metal free phthalocyanine and trigonal selenium contained in a PVK binder, reasonably equivalent discharge is obtained in the volume ranges of above about 1 part in 84 parts by volume for the X-form of metal free phthalocyanine and above about 1 part in 190 by volume for trigonal selenium. It should be noted that these preferred volume ranges are dependent upon the layer thickness. These figures also illustrate that although under positive charging conditions there is a steady increase in discharge rate with increased pigment loading, due to the increased light absorption coefficient, the performance is still very high even at loadings in the 1 percent by volume range.

It can be seen from the above that a critical range of about 0.1 to 5 percent by volume of the photoconductor is required to achieve the advantages of the instant invention. in addition, a preferred range for optimum mechanical properties has been established in the region of about 0.1 to 1.0 percent by volume for the photoconductor material.

The thickness of the binder layer is not particularly critical. Layer thicknesses from about 2 to microns have been found satisfactory, with a preferred thickness of about 5 to 50 yielding particularly good results.

Another variation of the structure described in FIG.

7 consists of the use of a blocking layer at the substratebinder layer interface. The blocking layer functions to prevent the injection of charge carriers from the sub strate into the photoconductive layer. Any suitable blocking material may be used. Typical materials in clude nylon, epoxy, and aluminum oxide.

Although the active material may comprise any suitable polymer or nonpolymeric material having the required properties, polymeric materials are preferred in that their physical properties such as flexibility, are superior to the physical properties of the nonpolymeric materials.

Although the instant invention has been described above in terms of the preferred embodiment, i.e., the binder configuration, it should be understood that the structure may take other forms. For example, the layered configuration described in Applicants copending application entitled Layered Imaging Member and Method filed concurrently with the instant application, illustrates a second basic embodiment of the instant invention. One embodiment of the layered configuration comprises a substrate having a photoconductive layer thereon which in turn is overcoated with a relatively thick layer of an active organic material. It should be understood that various modifications of the layered and binder configuration are also included within the scope of the instant invention. These alternative embodiments may include structural modifications of either the layered or binder configuration as well as combinations of the two.

In order to demonstrate the improvement provided by the instant invention over the particular binder layer disclosed in the Middleton et al., U.S. Pat. No. 3,121,006 the following tests are carried out. Three typical resin binder materials disclosed by US. Pat. No. 3,121,006 to Middleton et al are tested in order to determine the characteristics of these resins in comparison with the active materials of the instant invention. The resins include polystryrene, polyisobutylmethacrylate, and a silicone resin available under the tradename SR82 from General Electric. The results of the test demonstrate that these resin binder materials cannot support any practically useful level of charge displacement when used with a vitreous selenium photoreceptor. The polyisobutylmethacrylate and silicone resin are tested in a layered plate configuration by first form- The values for the experimental slope are calculated using the Method of Least Squares from the experimental data points. The Method of Least Squares is fully described by J. Topping in the book Errors f0h- Selenium ing a thin nylon blocking layer about 0.1 microns thick servation And Their Treatment published by Reinhold over two 4 X 4 inch aluminum substrates from a liquid Publishing Corp. of New York, 1955. The small stansolution using conventional coating techniques. A 1.0 dard error of the slopes indicate that the data points do micron layer of each resin respectively, is then formed not scatter significantly about the best straight line. The over the blocking layers of the two plates. A 0.5 micron comparison between the experimental and calculated layer of vitreous selenium is then formed over the resin or theoretical slope must next be considered. Although layers by vacuum evaporation. A third plate is formed the experimental and calculated slopes are not the by the above method using polystyrene as the resin same, they compare favorably when all the errors are layer without a nylon blocking layer. considered. Although the random errors of the meas- The three plates are each tested by charging to a urements are small (i.e., the standard error of the known potential, illuminating the charged layer, and slope), large systematic errors can arise because of the measuring the residual potential. If there is no charge difficulty in making thickness measurements of the laydisplacement across'the plastic layer then the residual ers. potential can be calculated from the known properties It may, e o be Concluded from the p m nof the resin, the thickness of the layers, the dielectric tal a in Table I that there is a negligible amount of constant of the materials, and the initial potential. The charge displacement through the three resin layer calculated residual potential should be the same as the fivenwhen their thickness is n y 1 micron, p t0 ds measured residual, within experimental error, until the Of abo t 5 ts/m c o t fi S eX flg abO 5 electrical breakdown point of the plastic layer occurs, voltslmicrons. th hin lay r xhi i iele ri eak- If it is assumed that the initial field distribution is caq This experimental test does'not Show h e pacitive, then h id potential V ill b 1 this lack of charge displacement derives from an inabilfined by the following formula: ity to support hole injection from vitreous selenium or from a very small hole transport range. When all the error limits are considered, it is safe to say that these M. a l [1 f u plastics act as insulators under the experimental conditions; that is, the charge is either not injected from the If he Charge is transported across the resin layer, the selenium into the plastic or, if injected, not transported plot of the experimental V,,. should be proportional toth h th l ti at th fi 1d 0 initial pp Potential) with a Slope of In order to show the advantages of the instant inven- "Tmwwwmi tion with respect to the prior art which uses a combinal (kidfiflkzdl) tion of at least two or more photosensitive materials, #MM t such as US. Pat. No. 3,212,007 to Middleton, and US. Pat. No. 3,037,861 to Hoegl et al., additional tests are P h above h dlelecmc constantjof h carried out. If during use, the active matrix material of resm l k1 and the resm thlcknes? d1; h selemum the instant invention absorbs some of the incident exf f f collstant the Selemum thlckness The 40 posure illumination, the photoreceptor, whether it be initial applied voltage 1s V in particulate form in a binder or as a separate photoinh ,ixpenments are earned out 3 e t jeETiifgTay ei, becomes less sensitive. in addition to a mahe hght Source Of 9 Ahgstroms ah lhtehslty decrease in discharge sensitivity, the utilization of the of 2 photohs/cmz/sec' Each Plate charged to photoconductive nature of the active matrix material serles of Selected Voltages between aboht 0 to 100 leads to serious problems in continuous use such as in e (abouf to 65 v ma The reslchlal P .copy machine cycling. Normally it is desirable that a e y the lheldeht hght slhee under photoreceptor have stable or consistent electrical propah Conditions of the experhheht enough hght used to erties during cycling to allow for proper design of other generate a sufficient number of carriers in the selenium components i h System h as, f example d to reduce the field across the selenium layer essentially jopmem, exposure, and background control If these to Zero- The thlekhess of layers are p ihtehtiohconditions cannot be maintained substantially conihy. mal e eh, Ehhg thlh Samples P some stant, it becomes difficult, if not impossible, to design measurement problems, in order to approximate th a reliable automatic copy machine that does not reactual Shuahee blhder 5mlethre Ph0l0FeeePl0T$i quire constant servicing and adjustments. In order to I the f- P p e of the {hm films of P demonstrate the criticality of imaging structures of the tie between the pigment particles are controlling. The instant invention only within wavelengths in which resules of these calculations and experiments are set charge carriers are generated by the photoconductor. forth in Table l below: and in which the surrounding matrix or active material TABLE 1 Electrical Properties of Layered Structures Experimental Calculated k (I ope Slope Polystyrene 2.4 1.0 0.77 (i) 0.01 0.83 Polylsobutylmethacrylate 2.7 1.0 0.79 (i) 0.02 0.82 Silicone Resin 2 s 1.2 0.70 (i) 0.02 0.8]

13 is substantially transparent, the following test is carried out.

A plate is made for test purposes. The plate @551- prises a conductive tin oxide coated quartz substrate. A 0.1 micron epoxy blocking layer is formed over the tin oxide, followed by a 0.5 micron layer of amorphous selenium which is formed by vacuum evaporation. A micron testing of PVK is then formed over the selenium layer. In order to illustrate the fact that the active mate- 'rial should be transparent to radiation in order to attain maximum efficiency for the device, the following test is carried out:

The plate is charged to a negative potential of about 200 volts and tested at four different wavelengths by exposure through the top surface of the PVK layer. Upon illumination, through the top, the plate exhibits a characteristic electrical discharge curve. The xerographic speed of the plate can be compared by determining graphically the slope of the discharge curve at the instant of illumination, i.c., (a'V/dr) at i=0, normalized to the thickness of the sample and to incident flux of l X 10' photons/cm lsec. This calculation is defined as the discharge sensitivity and is shown in Table ll below:

TABLE II Dependence on Discharge Rate on Absorption by PVK Wavelength V,, (dV/dt) t=o A (Volts) (volts/sec) coated with a 0.2 micron layer of epoxy to form a blocking layer, a 0.5 micron layer of vitreous selenium is then formed over the blocking layer by vacuum deposition, the selenium layer is then overcoated with a 12 micron layer of PVK. This plate is then taped to an 8 inch diameter aluminum drum, charged to a negative potential of 900 volts, and exposed to light to obtain 200 volts of contrast potential. The plate is then erased to a negative potential of 40 volts or less by exposure with a quartz iodine lamp, and charged again to 900 volts negative potential. The cycle is then repeated at a peripheral drum speed of about 6 inches per second. For all tests, the starting potential is adjusted to 900 volts by adjusting the corona current at the beginning of the test. The experiments were carried out at exposures of 4,000, 3450, and 2537 Angstroms, respectively. In each case, the intensity is adjusted at the beginning to create 200 volts of contrast potential. The results of the test are illustrated in FIG. 10.

As shown in FIG. 10, at 4,000 Angstroms, where the PVK is transparent to the incident light and not being tial potential, resulting in a constant contrast potential.

Although it would be possible to develop such an image, the change in potential with constant contrast would lead to difficulties in development and background control and be unsuitable for automatic cycling in the xerographic mode. a

It should be understood that the results of the above tests are readily applicable to structures in which the photoconductor particles are dispersed in an active binder matrix as well as to layered configurations, since the layered case may simply be considered as representative of the events that occur around each pigment particle surrounded by the active matrix.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following examples further specifically define the present invention with respect to a method of making a photosensitive member containing a binder layer having photoconductive particles dispersed in an active organic matrix. The percentages are by weight unless otherwise indicated. The examples below are intended to illustrate various preferred embodiments of the instant invention.

EXAMPLE I A photosensitive binder plate similar to that shown in FIG. 7 and containing unoriented photoconductive particles of the X-form of metal free phthalocyanine dispersed in a polyvinyl carbazole (PVK) binder in a ratio of 48 to l PVK by weight (60 to l by volume) to the photoconductive pigment particles is prepared by the following technique: 31 grams ofa 16.7 weight percent PVK stock solution is formed by dissolving the appropriate amount of Luvican M170 grade poly-N-vinylcarbazole, available from BASF, in 180 grams of toluene and 20 grams of cyclohexanone. This solution is added to 0.108 grams of X-form'metal free phthalocyanine and 10 grams of toluene. This mixture is milled with steel milling shot for 15 to 60 minutes until a well dispersed suspension is formed. A coating is then formed on an aluminum substrate utilizing a Gardner Laboratory Bird Applicator. The final thickness after air drying at C for 1 to 24 hours is about 24 microns.

EXAMPLE 11 Three plates are made by the method of Example I except that the phthalocyanine concentration is varied to ratios of:

a. 72/1 by weight (90/1 by volume) PVK phthalocyanine with a binder layer thickness of about 20 microns.

b. 24/1 by weight (30/1 by volume) PVK to phthalocyanine with a binder layer thickness of about 20 microns. s

c. 96/] by weight (/1 by volume) PVK to phthalocyanine with a binder layer thickness of about 20 microns.

EXAMPLE 111 Three plates are made by the method of Example 1 except that in plate of phthalocyanine, a polynuclear aromatic quinone available frm Allied Chemical Corporation under the tradename lndofast Orange is used as the photoconductive pigment in ratios of:

a. 24/1 by weight (30/1 by volume) PVK to pigment with a binder layer thickness of about 13 microns.

b. 48/1 by weight (60/1 by volume) PVK to pigment with a binder layer thickness of about 15 microns.

c. 72/1 PVK by weight (72/1 by volume) to pigment with a binder layer thickness of about 14 microns.

EXAMPLE 1V Two plates are made by the method of Example I except that trigonal selenium is used as pigment in ratios of:

a. 24/1 by weight (96/1 by volume) PVK to trigonal EXAMPLE Vlll A plate is made by the method of-Example 1 except that trigonal selenium is used as the pigment with the ratio of PVK to trigonal selenium being 6/1 by weight (24/1 by volume). The binder layer has a thickness of about 10 microns.

Each of the plates of Examples lVlll exhibits excellent electrical properties which are characterized by good charge acceptance and photoresponse upon exposure to light. The gain or maximum efficiency for 7 of the plates of Examples l-Vlll is shown in Table 111.

The plates of Table 111 are electrostatically charged to a positive potential to the field values indicated (a field of 50 X 10 volts/cm. represents a voltage of 50 X 10 volts for each cm. of layer thickness) using a corona charging device. Each sample was then exposed to monochromatic light of wavelength near the peak absorption for the photoconductor pigment being used. The resulting discharge (voltage versus time) are reselenium with a binder layer thickness of about mlcorded. For this data the xerographic gain was calcucrons. lated using the formulas previously defined.

TABLE 111 Gain or Max. Efficiency (Charge Exposure Field Carriers Col Plate Wavelength Photon Flux Range lected Per of In Angstrom (Photons/cm Tested Absorbed Exam Units Sec.) (V/Cm X 10') Photon) I ,ple

l 6200 6.5 X 10' 50 .26 11a 6200 6.5 x 10'-' 50 .23 [lb 6200 8.0 x to 8-95 .35 lVu 4000 3.8 x 10 10-70 .25 lVu 4000 2.0 x 10' .20 WI: 4000 5.9 x 10"-' 30 .22 V111 4000 5.9 x 10 30 3a b. 48/1 by weight 192/1 by volume) PVK to trigonal In addition to the testing described above in Table 111,

three of the plates are used to reproduce an original imselenium with a binder layer thickness of about 12 microns.

EXAMPLE V A plate is made by the method of Example I except that cadmium sulfoselenide is used as the pigment with the ratio of PVKto cadium sulfoselenide being 24/] by weight (105/1 by volume). The binder layer has a th s snsssyig misr n EXAMPLE VI 7 the plate in a solution of nylon (sold by DuPont under the tradename Zytel) dissolved in methyl alcohol.

EXAMPLE Vll A plate is made by the method of Example 1 except that trigonal selenium is used as the pigment with the ratio of PVK to trigonal selenium being 24/1 by weight (96/1 by volume). The binder layer has a thickness of about 9 'microns.

age. The plate of Example lVa is electrostatically charged to about 800 volts positive potential using a corona charging device. The plate is then exposed to a pattern of white light, from a quartz iodine source filtered to eliminate all radiation below 4,000 Angstrom Units, which selectively dissipates the charge in the illuminated areas. The latent electrostatic image which is formed is then developed using a liquid development system in which electrostatically negative charged toner particles dispersed in kerosene are allowed to flow over the above latent image. The electrostatically charged areas of the latent image attract the toner particles and form a visible image. The toner image is then transferred to a sheet of paper and fixed to form a permanent copy.

The plate of Example V1 is imaged by the method described above for the plate of Example lVa, except that the plate is charged to a potential of about 500 volts.

The plate of Example V is also imaged by the method described for the plate of Example lVa except that the plate is charged to a potential of 500 volts and the latent electrostatic image is developed using cascade development with Xerox 914 toner particles. Each of the above three plates produced an excellent reproduction of an original image.

In order to demonstrate the cycling capability of the device of the instant invention, the plates of Examples 1, 111a, and 1V a are cycled electrically by first electrostatically charging the plates in the dark to a field of about 30 volts/micron of binder layer thickness. Plates l, llla and Wu are then exposed to wavelengths of 6200, 4,000 and 4,000 Angstrom Units, respectively with a photon flux of about 2 X l photons/cm /sec. to discharge the plate. Following this, the plates were each flood illuminated with white light to remove any residual charge left on the surface of the plate. This entire cycle is repeated 200 times for plate land Wu and 250 times for the plate llla. Each of the plates exhibits excellent charge acceptance and photodischarge at the end of the cyclic testing. The initial potential. contrast potential, and residual potential were essentially the same at the end of cycling as compared with these properties after the first cycle.

EXAMPLE IX A source of vitreous selenium shot having a purity of 99.999 percent (available from American Smelting and Refining Co.) is sealed in a quartz ampule and placed in a vacuum chamber at a pressure of about Torr. The selenium is heat treated at 100C for 16 hours to convert the vitreous selenium to the crystalline trigonal form.

A mixture of 1 part by volume trigonal to 1 part by volume poly-1-vinylpyrene (PVP) is dispersed in 100 parts of reagent grade chloroform. This mixture is milled on a paint shaker for 1 hour with Vs inch diameter steel balls until the selenium particles are ground to a maximum size of no greater than about l micron. Enough PVP is then added to achieve a 24/1 ratio of PVP to selenium. This mixture is milled for about 30 minutes and coated onto 3 aluminum alloy substrates to form a dried layer thickness of 25 microns for each plate. Each substrate has a 0.2 micron epoxy barrier formed over the substrate prior to coating with the binder mixture.

Each of the above plates is tested electrically. All 3 plates exhibit good electrical discharge.

Although specific components and proportions have been stated in the above description of the preferred embodiments of the instant invention, other suitable material and procedures such as those listed above may be used with similar results. in addition. other materials and modifications may be utilized which synergize, enhance, or otherwise modify the photosensitive member and. method of use. For example, when using a transparent substrate such as a plastic coated with a transparent thin conductive coating of aluminum or tin oxide, the structure may be imaged by exposure through the substrate. In addition, if desired, an electrically insulating substrate may also be used. In this instance, the charge may be placed upon the photosensitive member by simumtaneously double corona charging the surface and insulating substrate with charges of the opposite polarity. Other modifications using an insulating substrate or no substrate at all, involve placing the photosensitive member or place on a conductive backing member and charging the surface of the photosensitive member while in contact with said backing member. Subsequent to imaging, the photoreceptor member may then be stripped from the conductive backing.

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 method of imaging which comprises:

a. providing an imaging member having a binderlayer contained on a supporting substrate. said binder layer having a thickness from about 3 to I00 microns comprising photoconductive particles dispersed in an unoriented fashion in an electrically active organic matrix material, said photoconductive particles having the facility for photo-excited hole generation and injection, said active matrix material exhibiting a facility for supporting hole injection from said photoconductive particles and ca pable of facile hole transport, said photoconductive particles being present in an amount from about 0.1 to 5 percent by volume of said binder layer, and wherein said active matrix comprises at least one material selected from the group consisting of poly-l-vinylpyrene, polymethylene pyrenc, N-substituted polymeric acrylic acid amides of pyrene, pyrene, tetraphene, l-acetylpyrene, 2.3- benzochrysene, 6,7-benzopyrene, l-bromopyrene, l-ethylpyrene, l-methylpyrene, 'perylene, 2- phenylindole, tetracene, picene, l,3,6,8-tetraphcnylpyrene, chrysene, fluorene, fluorenone, phenanthrene, triphenylene, l,2,5,6-dibenzanthracene, l,2,3,4-dibenzanthracene, 2,3-benzopyrene, 2,3- benzochrysene, anthraquinone, dibenzothiophene and naphthalene;

b. uniformly electrostatically charging said binder layer, followed by:

c. exposing said charged layer to a source of activating radiation to which the photoconductor particles are absorbing and to which the active organic matrix material is non-absorbing, the exposure being in the form of a pattern of light and shadow optically projected toward the layer, whereby the photo-excited holes generated by said photoconductive particles are injected into and are transported through said active matrix material to form a latent electrostatic image on the surface of said binder layer.

2. The method of claim 1 in which the latent electrostatic image is developed to form a visible image.

3. The method of claim 1 in which the activating radiation is within the visible spectrum.

4. The method of claim 1 in which the exposure radiation is in the range of about 4,000 to 8,000 Angstrom Units.

5. The method of claim 1 in which the binder layer is contained on an electrically conductive substrate.

6. The method of claim 1 in which the binder layer is contained on a transparent substrate and exposure to activating radiation is through said substrate.

7. The method of claim ,1 in which the binder layer comprises photoconductive particles in an amount from about 0.1 to L0 percent by volume of said binder layer.

8. The method of claim 1 in which the active matrix material is selected from the group consisting of poly N-vinyl carbazole, poly-l-vinyl pyrene, poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)- carbazole, poly-9-(5-hexyl)-carbazole, polymethylene pyrene, poly-l-(-a-pyrenyl)-butadienc, Nsubstituted polymeric acrylic acid amides of pyrene, poly-3-amino carbazole, l,3-dibromo-poly-N-vinyl carbazole, 3,6-

dibromo-poly-N-vinyl carbazole, poly-2-vinyl carbazole, poly-3-vinyl carbazole, N-vinyl carbazole/methyl acrylate copolymers, l-vinyl pyrene/bu'tadiene ABA, and AB block polymers, carbazole, N-ethylcarbazole, N-phenylearbazole pyrene, tetraphene, l-acetylpyrene N-benzochrysene, 6,7-benzopyrene, l-bromopyrene, l-ethylpyrene, l-methylpyrene, perylene, 2- phenylindole, tetracene, picene, l,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene triphenylen'e, l,2,5,6-dibenzanthracene, 1,23,4- dibenzanthracene, 2,3-benzopyrene, 2,3- benzochrysene, anthranquinone, dibenzothiophene,

naphthalene and l-phenylnaphthalene.

9. A method of imaging which comprises:

a. providing an imaging member having a binder layer contained on a supporting substrate, said binder layer having a thickness from about 2 to 100 microns comprising photoconductive particles dispersed in an unoriented fashion in an electrically active organic matrix material, said photoconductive particles having the facility for photo-excited hole generation and injection, said active matrix material exhibiting a facility for supporting hole injection from said photoconductive particles and capable of facile hole transport, said photoconductive particles being present in an amount from about 0.1 to 5 percent by volume of said binder layer, and wherein said active matrix comprises at least one material selected from the group consisting of polyvinyl carbazole, poly-l-vinylpyrene, polymethylene pyrene, carbazole, N- ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, l-acetylpyrene, 2,3-benzochrysene, 6,7- benzopyrene, l-bromopyrene, l-ethylpyrene, lmethylpyrene, perylene, Z-phenylindole, tetracene, picene, l,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene, triphenylene, 1,2,5 ,b-dibenzanthraeene, 1,2,3 ,4- dibenzanthracene, 2,3-

2,3-benzopyrene, V

benzochrysenc, anthraquinone, dibenzothiophene, and naphthalene;

b. uniformly electrostatically charging said binder layer, followed by;

c. exposing said charged layer to a source of activating radiation to which the photoconductive particles are absorbing and to which the active organic matrix material is non-absorbing, the exposure being in the form of a pattern of light and shadow optically projected toward said layer, whereby the photo-excited holes generated by said photoconductive particles are injected into and are transported through said active matrix material to form a latent electrostatic image on the surface of said binder layer.

10. The method of claim 9 which further includes developing the latent image to form a visible image.

11. The method of claim 10 in which the charging, exposing, and developing steps are repeated at least one additional time.

12. The method of claim 9 in which the exposure radiation is in the range of about 4,000 to 8,000 Angstrom Units.

13. The imaging member ofclaim 11 in which the active matrix comprises a material selected from the group consisting of alkyl. nitro, amino, halogen and hydroxy substituted polymers, said polymer selected from the group consisting of poly-l-vinylpyrene, polymethylenepyrene, N-substituted polymeric acrylic acid amides of pyrene, poly-N-vinylcarbazole, poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pcntenyl)- carbazole, poly-9-(5-hexyl)-carbazole, poly-l.- (pyrenyl)-butadiene, p0ly-3-amino carbazole, 1,3- dibromo-poly-N-vinyl carbazole, 3,6-dibronio-poly-N- vinyl carbazole, poly-2-vinyl carbazole, poly-3-vinyl carbazole, N-vinyl carbazole/methyl aerylate eopolymer, l-vinyl pyrene/butadiene ABA block polymer'and l-vinyl pyrene/butadiene AB block polymer.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3, 870 516 DATED March 11, 1975 INVENTOR(S) M. Smith, C. F. Hackett R. W. Radler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In the title line 2, delete "CHANGE" and insert CHARGE-.

In the ABSTRACT, line ll, last sentence,

delete "zerographic" and insert xerographic.

Column 2, lines 30 & 31, delete "lay-erss" and insert layers-.

Column 2, line 53, delete "relay" and insert rely-.

Column 3, line 52, delete "througout" and insert -throughout-.

Column 6, line 45, delete "xeroxgraphic" and insert xerographic.

column 7. line 22, delete "possible" and insert -possibly.

Column 8, lines 5 & 6 delete "seleniu-marsenic and insert seleniumarsenic.

Column 8, line 48, delete pyrenyl) and-insert (-0 py y UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3 870, 516

DATED March 11, 1975 lN\/ ENTOR(S) M. Smith C. F. Hackett, R. W. Radler Page 2 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 11, line 57, delete "resules and insert -results-.

Column 13, line 8, delete "testing" and insert coating-.

Column 13, line 28, delete "on" and insert of--.

Column 14, line 61 insert to between PVK and phthalocyanine.

Column 14, lines 64 & 65, delete "mi-crons.s" and insert microns-.

Column 15, line 3, delete "plate" and insert place-.

Column 15, line 5, delete "frm and insert from.

Column 15, line 47 delete "cadium" and insert -cadmium.

Column 17, line 201 delete "ampule and insert --ampoule--.

Column 17 line 55 delete "simumtaneously" and insert -simultaneously--.

Column 17 line 59, delete "place" and insert --plate-.

. UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,870,516 Page 3 DATED March 11, 1975 0 INV ENTOR(S): M. Smith, c. F. Hackett R. W. Radler It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

. Claim 1, line 31 after the word by, delete "z" and insert Claim 13 line 24, delete the word "member" and insert the word method-.

Signed and Sealed thls twenty-eight Day Of October 1975 i [SEAL] Attest.

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner nfParents and Trademarks

Claims (13)

1. A method of imaging which comprises: a. providing an imaging member having a binder layer contained on a supporting substrate, said binder layer having a thickness from about 2 to 100 microns comprising photoconductive particles dispersed in an unoriented fashion in an electrically active organic matrix material, said photoconductive particles having the facility for photo-excited hole generation and injection, said active matrix material exhibiting a facility for supporting hole injection from said photoconductive particles and capable of facile hole transport, said photoconductive particles being present in an amount from about 0.1 to 5 percent by volume of said binder layer, and wherein said active matrix comprises at least one material selected from the group consisting of poly-1-vinylpyrene, polymethylene pyrene, N-substituted polymeric acrylic acid amides of pyrene, pyrene, tetraphene, 1-acetylpyrene, 2,3-benzochrysene, 6,7-benzopyrene, 1-bromopyrene, 1-ethylpyrene, 1-methylpyrene, perylene, 2-phenylindole, tetracene, picene, 1,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene, triphenylene, 1,2,5,6-dibenzanthracene, 1,2,3,4-dibenzanthracene, 2,3-benzopyrene, 2,3-benzochrysene, anthraquinone, dibenzothiophene and naphthalene; b. uniformly electrostatically charging said binder layer, followed by: c. exposing said charged layer to a source of activating radiation to which the photocOnductor particles are absorbing and to which the active organic matrix material is non-absorbing, the exposure being in the form of a pattern of light and shadow optically projected toward the layer, whereby the photo-excited holes generated by said photoconductive particles are injected into and are transported through said active matrix material to form a latent electrostatic image on the surface of said binder layer.

1. A METHOD OF IMAGING WHICH COMPRISES: A. PROVIDING AN IMAGING MEMBER HAVING A BINDER LAYER CONTAINED ON A SUPPORTING SUBSTRATE, SAID BINDER LAYER HAVING A THICKNESS FROM ABOUT 2 TO 100 MICRONS COMPRISING PHOTOCONDUCTIVE PARTICLES DISPERSED IN AN UNORIENTED FASHION IN AN ELECTRICALLY ACTIVE ORGANIC MATRIX MATERIAL, SAID PHOTOCONDUCTIVE PARTICLES HAVING THE FACILITY FOR PHOTO-EXCITED HOLE GENERTION AND INJECTION, SAID ACTIVE MATRIX MATERIAL EXHIBITING A FACILITY FOR SUPPORTING HOLE INJECTION FROM SAID PHOTOCONDUCTIVE PARTICLES AND CAPABLE OF FACILE HOLE TRANSPORT, SAID PHOTOCONDUCTIVE PARTICLES BEING PRESENT IN AN AMOUNT FROM ABOUT 0.1 TO 5 PERCENT BY VOLUME OF SAID BINDER LAYER, AND WHEREIN SAID ACTIVE MATRIX COMPRISES AT LEAST ONE MATERIAL SELECTED FROM THE GROUP CONSISTING OF POLY-1-VINYLPYRENE, POLYMETHYLENE PYRENE, N-SUBSTITUTED POLYMERIC ACRYLIC ACID AMIDES OF PYRENE, PYRENE, TETRAPHENE, 1-ACETYLPYRENE, 2,3-BENZOCHRYSENE, 6,7-BENZOPYRENE, PERYLENE, 21-ETHYLPYRENE, 1-METHYLPYRENE, PERYLENE 2PHENYLINDOLE, TETRACENE, PICENE, 1,3,6,8TETRAPHENYLPYRENE, CHRYSENE, FLUORENE, FLUORENONE, PHENANTHRENE, TRIPHENYLENE, 1,2,5,6-DIBENZANTHRACENE, 1,2,3,4-DIBENZANTHRACENE, 2,3-BENZOPYRENE, 2,3BENZOCHRYSENE, ANTHRAQUINONE, DIBENZOTHIOPHENE AND NAPTHALENE; B. UNIFORMLY ELECTROSTATICALLY CHARGING SAID BINDER LAYER, FOLLOWED BY: C. EXPOSING SAID CHARGED LAYER TO A SOURCE OF ACTIVATING RADIATION TO WHICH THE PHOTOCONDUCTOR PARTICLES ARE ABSORBING AND TO WHICH THE ACTIVE ORGANIC MATRIX MATERIAL IS NON-ABSORBING, THE EXPOSURE BEING IN THE FORM OF A PATTERN OF LIGHT AND SHADOW OPTICALLY PROJECTED TOWARD THE LAYER, WHEREBY THE PHOTO-EXCITED HOLES GENERATED BY SAID PHOTOCONDUCTIVE PARTICLES ARE INJECTED INTO AND ARE TRANSPORTED THROUGH SAID ACTIVE MATRIX MATERIAL TO FORM A LATENT ELECTROSTATIC IMAGE ON THE SURFACE OF SAID BINDER LAYER.

2. The method of claim 1 in which the latent electrostatic image is developed to form a visible image.

3. The method of claim 1 in which the activating radiation is within the visible spectrum.

4. The method of claim 1 in which the exposure radiation is in the range of about 4,000 to 8,000 Angstrom Units.

5. The method of claim 1 in which the binder layer is contained on an electrically conductive substrate.

6. The method of claim 1 in which the binder layer is contained on a transparent substrate and exposure to activating radiation is through said substrate.

7. The method of claim 1 in which the binder layer comprises photoconductive particles in an amount from about 0.1 to 1.0 percent by volume of said binder layer.

8. The method of claim 1 in which the active matrix material is selected from the group consisting of poly-N-vinyl carbazole, poly-1-vinyl pyrene, poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)-carbazole, poly-9-(5-hexyl)-carbazole, polymethylene pyrene, poly-1-(- Alpha pyrenyl)-butadiene, N-substituted polymeric acrylic acid amides of pyrene, poly-3-amino carbazole, 1,3-dibromo-poly-N-vinyl carbazole, 3,6-dibromo-poly-N-vinyl carbazole, poly-2-vinyl carbazole, poly-3-vinyl carbazole, N-vinyl carbazole/methyl acrylate copolymers, 1-vinyl pyrene/butadiene ABA, and AB block polymers, carbazole, N-ethylcarbazole, N-phenylcarbazole pyrene, tetraphene, 1-acetylpyrene, N-benzochrysene, 6,7-benzopyrene, 1-bromopyrene, 1-ethylpyrene, 1-methylpyrene, perylene, 2-phenylindole, tetracene, picene, 1,3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene triphenylene, 1,2,5,6-dibenzanthracene, 1,2,3,4-dibenzanthracene, 2,3-benzopyrene, 2,3-benzochrysene, anthraquinone, dibenzothiophene, naphthalene and 1-phenylnaphthalene.

9. A method of imaging which comprises: a. providing an imaging member having a binder layer contained on a supporting substrate, said binder layer having a thickness from about 2 100 microns comprising photoconductive particles dispersed in an unoriented fashion in an electrically active organic matrix material, said photoconductive particles having the facility for photo-excited hole generation and injection, said active matrix material exhibiting a facility for supporting hole injection from said photoconductive particles and capable of facile hole transport, said photoconductive particles being present in an amount from about 0.1 to 5 percent by volume of said binder layer, and wherein said active matrix comprises at least one material selected from the group consisting of polyvinyl carbazole, poly-1-vinylpyrene, polymethylene pyrene, carbazole, N-ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, 1-acetylpyrene, 2,3-benzochrysene, 6,7-benzopyrene, 1-bromopyrene, 1-ethylpyrene, 1-methylpyrene, perylene, 2-phenylindole, tetracene, picene, 1, 3,6,8-tetraphenylpyrene, chrysene, fluorene, fluorenone, phenanthrene, triphenylene, 1,2,5,6-dibenzanthracene, 1,2,3,4-dibenzanthracene, 2,3-benzopyrene, 2,3-benzochrysene, anthraquinone, dibenzothiophene, and naphthalene; b. uniformly electrostatically charging said binder layer, followed by; c. exposing said charged layer to a source of activating radiation to which the photoconductive particles are absorbing and to which the active organIc matrix material is non-absorbing, the exposure being in the form of a pattern of light and shadow optically projected toward said layer, whereby the photo-excited holes generated by said photoconductive particles are injected into and are transported through said active matrix material to form a latent electrostatic image on the surface of said binder layer.

10. The method of claim 9 which further includes developing the latent image to form a visible image.

11. The method of claim 10 in which the charging, exposing, and developing steps are repeated at least one additional time.

12. The method of claim 9 in which the exposure radiation is in the range of about 4,000 to 8,000 Angstrom Units.

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