CA1121203A - Imaging system containing trigonal selenium and a group ia hydroxide, carbonate, bicarbonate, acetate or selenite - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
An imaging member having a layer of particulate photo-conductive material which may be dispersed in an organic resinous binder either randomly or geometrically is disclosed. This photoconductive layer may also be used as a photogenerating layer in a composite photoconductive member which contains at least two electrically operative layers one of which is a charge carrier photogenerating layer and the other being a charge carrier transport layer. The photogenerating layer may also be used with an overlayer and underlayer of charge carrier transport material. The particulate photoconductive material consists essentially of trigonal selenium doped with from about 0 01 to about 12.0% by weight based on the weight of the trigonal selenium of a material selected from the group consisting of sodium, lithium, potassium, rubidium and cesium.

Description

)3 BACKGROUND OF THE INVENTION
-This invention relates in general to xerography and more specifically to a novel photosensitive device and a method of use.
Vitreous and amorphous selenium is a photoconductive material which has had wide use as a reusable photoconductor in commercial xerography. However, its spectral response is limited largely to the blue-green portion of the visible spectrum, i.e.
below 52 angstrom units.
Selenium also exists in a crystalline form known as trigonal or hexagonal selenium. Trigonal selenium is well known in the semiconductor art for use in the manufacture of selenium rectifiers.
In the past, trigonal selenium was not normally used in xerography as a photoconductive layer because of its relatively high electrical conductivity in the dark, although in some instances, trigonal selenium can be used in a binder configuration in which the trigonal selenium particles are dispersed in the matrix of another material such as an electrically active organic material or a photoconductive material such as vitreous selenium.
It is also known that a thin layer of trigonal selenium overcoated with a relatively thick layer of electrically active.
organic material, forms a useful composite photosensitive member which exhibits improved spectral response and increased sensitivity over conventional vitreous selenium-type photoreceptors.
This device and method are described in U.S. Patent 3,961,953.
It is known that when using trigonal selenium whether it be dispersed in a binder or used as a generation material in a composite photoconductive device that the trigonal selenium exhibits a high dark decay and high dark decay after the .

Z~)3 photoreceptor has been cycled in a xerographic process. This is referred to as fatigue dark decay. Also, after cycling the photoreceptor in a xerographic process, the photoreceptor will not accept as much charge as it did initially.
As mentioned, fatigue dark decay is defined as after the member, i.e. photoreceptor, has been erased at least one time during a xerographic cycle, then the member is recharged and the dark decay is again examined. This dark decay is called fatigued dark decay.
U.S. Patent 3,685,989 discloses a photoconductive layer which comprises vitreous selenium or a selenium-arsenic alloy which is doped with a small amount of sodium, lithium, potassium, rubidium or cesium. This is done in this photoreceptor in order to convert an essentially bipolar photoreceptor to an essentially ambipolar photoreceptor.
As taught in the prior art, trigonal selenium used as a photoconductive material in a xerographic process is not predictable from knowing that vitreous or amorphous selenium is a good photoconductive material. As taught in Keck, U.S.

2,739,079, trigonal selenium is quite conductive and would be unsuitable as a generating material. Japanese Publication No.
16,198 of 1968 of Japanese (M. Hayashi) application 73,753 of November 29, 1968, assigned to Matsushita Electric Industrial Company also discloses that one should not use a highly conductive photoconductive layer as a charge generation material in a multi-layered device comprising a charge generation layer and an overlayer of charge transport material. Therefore, since Keck U.S. 2,739,079 teaches that trigonal selenium is highly conductive, it was unobvious that trigonal selenium could be used as a photoconductive material in a xerographic device merely --3~

f~3 because vitreous or amorphous selenium was a good photoconductive material for use in a xerographic device. Therefore, the vitreous or amorphous selenium prior art is not analogous prior art for use in teaching that trigonal selenium may act as vitreous or amorphous selenium when used in xerographic devices.
U.S. 3,312,548 dicloses a xerographic plate having a photoconductive insulating layer o~ a composition of selenium, arsenic and doped with a halogen in a concentration of from about 10 to 10,000 parts per million.
Belgium Patent 763,540 issued ~ugust 26, 1971 (U.S.
application Serial No. 94,139, filed December 1, 1970, now abandoned) discloses an electrophotographic member having at least two electrically operative layers. The first layer comprises a photoconductive layer which is capable of photo~
generating charge carriers and injecting the photogenerated holes into a contiguous active layer. The active layer comprises a transparent organic material which is substantially nonabsorbing in the spectral region of intended use, but which is "active"
in that it allows injection of photogenerated holes from the photoconductive layer, and allows these holes to be transported through the active layer. The active polymers may be mixed with inactive polymers or nonpolymeric material.
U.S. Patent 3,926,762 discloses a method of making a photoconductive imaging deviGe which comprises directly depositing a thin layer of trigonal selenium onto a supporting conductive substrate.
U.S. 3,954,464 discloses a method of making a photo-sensitive imaging device which comprises vacuum evaporating a thin layer of vitreous selenium over a layer of electrically active organic material which is contained on a supporting .

substrate, forming a relatively thin layer of electrically insulating or electrically active organic material over the trigonal selenium layer. This is followed by heating khe device to an elevated temperature for a sufficient time to convert the vitreous selenium to the crystalline trigonal form.
U.S. Patent 3,961,953 discloses a method of making a photosensitive imaging device which comprises vacuum evapora-ting a thin layer of vitreous selenium onto a supporting substrate, forming a relatively ~hicker layer of electrically active organic material over the vitreous selenium layer.
This step if followed by heating the member to an elevated temperature for a sufficient time to convert the vitreous selenium into the crystalline trigonal form.
OBJECTS OF THE INVENTION
It is, therefore, an object of this invention to provide a novel photosensitive device adapted for cyclic imaging by the xerographic process which overcomes the above-noted disadvantages.
It is a further object of this invention to provide a process of doping trigonal selenium in order to control dark decay.
It is a further object of this invention to utilize this doped trigonal selenium in photosensitive devices in order to improve cyclic charge acceptance and control and improve dark decay both initially and after cycling the member in a xerographic process.
SUMMARY OF THE INVENTION
The foregoing objects and others are accomplished in accordance with this invention by providing a photosensitive member, i.e. imaging member, which comprises a layer of particulate photoconductive material dispersed in an organic resinous binder. The particulate photoconductive material comprises trigonal selenium doped with from about 0.01 to about 12.0~ by weight based on the weight of the trigonal selenium of a material comprising sodium, lithium, potassium, rubidium and cesium. The trigonal selenium doped with a dopant, i.e.
sodium, lithium, potassium, rubidium and cesium, prevents the trigonal selenium when the trigonal selenium is being used as a photoconductive material dispersed in a binder from exhibiting unacceptable and undesirable amounts of dark decay either initially, i.e. before charging and discharging of the member, or fatigue dark decay, i.e. after the member has been through a complete xerographic process, that is, charged and erased and then recharged in the dark. The sensitivity and dark decay of the trigonal selenium photoreceptor may be decreased or increased, respectively, by washing the dopant in or out of the trigonal selenium, e.g. see Fig. 5 and Fig. 6.
Typical applications of the invention include as mentioned above a single photoconductive layer having trigonal selenium in particulate form doped with sodium, lithium, potassium, rubidium or cesium or mixtures thereof dispersed in an organic resinous binder. This may be used as a photosensitive device itself. ~nother typical application of the invention includes a photosensitive member which has at least two operative 'ayers. The first layer comprises a layer of photoconductive material, i.e. trigonal selenium in particulate form doped with sodium, lithium, potassium, rubidium or cesium or mixtures thereof dispersed in an organic resinous binder. This layer is capable of photogenerating charge ' V ~

carriers and injecting these photogenerated charge carriers into a contiguous or adjacent charge carrier transport layer. The charge carrier transport layer may comprise a transparent organic polymer or a nonpolymeric material which when dispersed in an organic polymer results in the organic polymer becoming active, i.e. capable of transporting charge carriers. The charge carrier transport material should be substantially nonabsorbing to visible light or radiation in the region of intended use, but which is "active" in that it allows the injection of photogenerated charge carriers e.g. holes, from the particulate trigonal selenium layer and allows these charge carriers to be transported through the active layer to selectively discharge the surface charge on the free surface of the active layer.
It is not the intent of this invention to restrict the choice of active materials to those which are transparent in the entire visible region. For example, when used with a transparent substrate, imagewise exposure may be accomplished through the substrate without the light passing through the layer of active material, i.e. charge transport layer. In this case, the active layer need not be non-absorbing in the wavelength region of use.
Other applications where complete transparency is not required for the active material in the visible region include the selective recording of narrow-band radiation such as that emitted from lasers, spectral pattern recognition, and possible functional color xerography such as color coded form duplication.
Another embodiment of the instant invention may include an imaging member having a first layer of electrically active charge transport material contained on a supporting substrate, a photoconductive layer of the instant invention overlying the active layer and a second layer of electrically active charge transport

3;3 material overlying the photoconductive layer. Thls member i~
more fully described in U.S. Patent 3,953,207.
Another typical application of the invention in-cludes a photosensitive member which may comprise a photo-conductive insulating layer comprising a matrix material of insulating organic resinous material and particulate trigonal selenium doped with either sodium, lithium, potassium, rubidium and cesium. Substantially all of the doped particulate trigonal selenium in the layer is in substantially particle-to-particle contact forming a multiplicity of interlocking trigonal selenium paths through the thickness of the layer. The trigonal selenium paths being present in a volume concentration, based on the volume of the layer, of from about 1 to 25 percent.
In general, the advantages of the invention will become apparent upon consideration of the following dis-closure of the invention; especially when taken in conjunction with the accompanying drawings wherein:
BRIEF DESCRIPTION OF THE DRA~INGS
Fig. 1 is a schematic illustration of one of the members of the instant invention which comprises particulate trigonal selenium dispersed in a resinous binder overlying a substrate.
Fig. 2 is a schematic illustration of one of the members of the instant invention wherein the particulate trigonal selenium is geometrically dispersed within an electrically insulating organic binder. This layer overlies the substrate.
Fig. 3 is a schematic illustration of one of the members of the instant invention illustrating a composite , , ~ . .

photoreceptor comprising a charge carrier generation layer overcoated with a charge carrier transport layer. The charge carrier generation layer comprises doped trigonal selenium dispersed in an organic resinous binder as the charge carrier generation layer.
Fig. 4 is a schematic illustration of one embodiment of a device of the instant invention. A composite photoreceptor is disclosed comprising a charge carrier transport layer and a charge carxier generation layer. The charge carrier generation layer comprises sodium doped particulate trigonal selenium geometrically dispersed n an insulating binder.
Fig. 5 illustrates rested dark decay and fatigue dark decay of photoreceptors containing trigonal selenium both doped and undoped as the photoconductive material.
Fig. 6 illustrates the photoinduced discharge curves ~PIDC) of the members illustrated in Fig. 5.
DETAILED ~ESCRIPTION OF T~E DRAWINGS
-For a bet-ter understanding of the Figures, several terms should be defined. The term "rested dark decay" when used in this application means that it is the amount of voltage drop, i.e. surface potential drop, of a member which has been rested and then charged initially to an initial surface potential, measured in voltage, and then allowed to remain in the dark. The drop in potential is measured 0.06 seconds after charging, 0.22 seconds after charging, and 0.66 seconds after charging. This "rested dark decay" means that the photoreceptor has been rested in the dark for at least 30 minutes prior to testing i.e. cycling in a xerographic mode.
"Fatigue dark decay" means, for purpose of this application, a drop in surface potential 0.06 seconds after charging, then after 0.22 seconds and then after 0.66 seconds.

, . .. .

These measurements are made while the photoreceptor remains in the dark. "Fatigue dark decay" further means that the photoreceptor has been cycled at least one time through a xerographic cycle and then discharged, i.e. erased, and then is being tested before the photoreceptor has rested, preferably before 30 minutes has passed after charging the photoreceptor. The process speed of the photo-receptor is 30 inches per second.
Referring to Fig. 1, reference character 10 designates an imaging member which comprises a supporting substrate 11 having a binder layer 12 thereon. Substrate 11 is preferably comprised of any suitable conductive material. Typical conductors comprise aluminum, steel, nickel, brass or the like. The substrate may be rigid or flexible and of any conventional thickness. Typical substrates includes flexible belts of 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, nickel or copper iodine; or glass coated with a thin conductive coating or chromium or tin oxide.
In addition, if desired, an electrically insulating substrate may be used. In this instant, the charge may be placed upon the insulating member by double corona charging techni~ues well known or disclosed in the art. Other modifications using an insulating substrate or no substrate at all include placing the imaging member on a conductive backing member or plate in charging the surface while in contact with said backing member. Subsequent to imaging, the imaging member may then be stripped from the conductive backing.
Binder layer 12 contains trigonal selenium particles 13 which have been doped with from about 0.01 to about 12.0% by z~3 weight based on the weight of the trigonal selenium of any one of the following materials or mixtures thereof, i.e. sodium, lithium, potassium, rubidium and cesium. The doped trigonal selenium particles are dispersed randomly without orientation in binder 14-.
Binder material 14 may comprise any electrically insulating resin such as those disclosedin Middleton et al U.S. Patent 3,121,006. When using an electrically inactive or insulating resin, it is essential that there be particle-to-particle contact between the photoconductive particles. Thisnecessitates that the photoconductive material be present in an amount of at least about 15% by volume of the binder layer with no limit on the maximum amount of photoconductor in the binder layer. If the matrix or binder comprises an active material, the photoconductive material need only to comprise about 1% or less by volume of the binder layer with no limita-tion on the maximum amount of photoconductor in the binder layer.
Binder layer 12's thickness is not critical. Layer thicknesses from about 0.05 to 40.0 microns have been found to be satisfactory.
Binder material 14 may also comprise Saran ~, available from Dow Chemical Company, which is a copolymer of polyvinyl chloride and polyvinylidene chloride; polystyrene and poly-vinyl buty~al polymers.
The trigonal selenium 13 used in binder layer 12 as illustrated in Fig. 1 is doped wlth from about 0.01 to about 12.0~ by weight based on the weight of the trigonal selenium of a material selected from the group consisting of sodium, lithium, potassium, rubidium and cesium. The preferred doping ~ ;
material X

: . - -: -: .
: . ,. ;: i . ,., is sodium. The most preferred amount o dopant is present in from about 0.1 to abou~ 1.0~ by weight. This is the most preferred amounts when using binders, such as PVX. ~owever, this amount may vary if binders, such as electrically inactive binders, are used. Preferably there may be an adhesive charge blocking layer between the substrate and the charge generation layer, i.e.
doped trigonal selenium layer.
The preferred size of the doped particulate trigonal selenium particles is from about 0.01 micron to about 10 microns in diameter. The more preferred size of the doped particulate trigonal selenium particles is from about 0.1 microns to about 0.5 microns in diameter.
The member 10 as shown in Fig. 1 may optionally be overcoated with an electrically insulating organic resinous lS material.
In another embodiment of the instant invention, the structure of Fig. 1 is modified to insure that the doped trigonal selenium particles are in the form of continuous paths or particle-to-particle chains through the thickness of binder layer 12. This embodiment it is illustrated by Fig. 2 which shows the doped trigonal selenium particles 13 in the form of particle-to-particle chains. Layer 12 of Fig. 2 more specifically may comprise doped trigonal selenium particles in a multiplicity of interlocking photoconductive continuous paths through the thickness of layer 14, the photoconductive paths being present in a volume concentration based on the volume of the layer, of from about 1-25%. A further alternative for layer 14 of Fig. 2 comprises doped trigonal selenium material in substantially particle-to-particle contact in the layer in a multiplicity of interlocking photoconductive paths through the .

thickness of the member, the photoconductive paths being present in a volume concentration, based on the volume of the layer, of from about 1-25~.
Fig. 3 designates imaging member 30 in the form o~
an imaging member which comprises a supporting substrate 11 having a binder layer 12 thereon, and a charge transport layer 15 positioned over binder layer 12. Substrate 11 may be of the same material as described for use in Fig. 1. Binder layer 12 may be of the same configuration as and contain the same material as binder layer 12 described in Fig. 1.
Active layer 15 may comprise any suitable transparent organic polymer or nonpolymeric material capable of supporting the injection of photogenerated holes and electrons from the doped trigonal selenium binder layer and allowing the transport of these holes or electrons through the organic layer to selectively discharge the surface charge.
Polymers having this characteristic, i.e. capability of transporting holes have been found to contain repeating units of a polynuclear aromatic hydrocarbon which may also contain heteroatoms such as for example, nitrogen, oxygen or sulphur. Typical polymers include poly-N-vinyl carbazole (PVK), poly-l-vinyl pyrene (PVP), poly-9-vinyl anthracene, polyacenaphthalene, poly-9-(4-pentenyl)-carbaæole, poly-9-(5-hexyl)-carbazole, polyme~hylene 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 hydroxy substituted polymers. Typical examples are poly-3-amino carbazole, 1,3-dibromo-poly-N-vinyl carbazole and 3,6-dibromo-poly-N-vinyl carbazole in particular derivatives of the formula LY~ ,X1 -CH-CH2- n where X and Y are substituents and N is an integer. Also included are structural isomers of these polymers, typical examples include poly-N-vinyl carbazole, poly-2-vinyl carbazole and poly-3-vinyl carba~ole. ~lso included are copolymers; typical examples are N-vinyl carbazole/methyl acrylate copolymer and l-vinyl pyrene/butadiene ABA, and AB block polymers.
Typical nonpolymeric materials include carbazole, N-ethylcarbazole, N-phenylcarbazole, pyrene, tetraphene, l-acetylpyrene, 2,3-benzochrysene, 6,7-benzopyrene, l-bromopyrene, l-ethylpyrene, l-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, anthraquinone, dibenzothiophene, and naphthalene and l-phenylnaphthalene. Due to the poor mechanical properties of the nonpolymer materials they are preferably used in conjunction with either an active polymeric material or a nonac~ive polymeric binder. Typical examples include suitable mixtures of carbazole in poly-N-vinyl carbazole as an active polymer and carbazole in a nonactive binder. Such nonactive binder materials include polycarbonates, acrylate poly-mers, polyamides, 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 )3 of small, simple chemical units), whose repeat unit contains the appropriate aromatic hydrocarbon, such as carbazole, and which supports hole lnjection and transport, may be used. It is not the intent of the invention to restrict the type of polymer which can be employed as the transport layer. Polyesters, polysiloxanes, polyamides, polyurethanes and epoxies as well as block, random or graft copolymers (containing the aromatic repeat unit) are exemplary of the various types of polymers which can be employed as the active material. In addition, suitable mixtures of active polymers with inactive polymers or nonpolymeric materials may be employed. One action of certain nonactive 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 napthalene and chlorinated diphenyl.
The above transport layer 15 may comprise aromatic or heterocyclic electron acceptor materials which have been found to exhibit negative charge carrier transport properties as well ~0 as the requisite transparency characteristics~ Typical electron acceptor materials included within the scope of the instant invention include phthalic anhydride, tetrachlorophthalic anhydride, benzil, mellitic anhydride, S-tricyanobenzene, picryl chloride, 2,4-dinitrochlorobenzene, 2,4-dinitrobromobenzene,

4-nitrobiphenyl, 4,4-dinitrobiphenyl, 2,4,6-trinitroanisole, trichlorotrinitrobenzene, trinitro-o-toulene, 4,6-dichloro-1,3-dinitrobenzene, 4,6-dibromo-1,3-dinitrobenzene, P-dinitrobenze, chloranil, bromanil, and mixtures thereof. It is further intended to include within the scope of those materials suitable for use in active transport layer 15, other reasonable structural or chemical 2~3 modifications of the above-described materials provided that the modified compound exhibits the desired charge carrier transport characteristics.
While any and all aromatic or heterocyclic electron acceptors having the requisite transparency characteristic are within the purview of the instant invention, particularly good electron transport properties are found with aromatic or hetero-cyclic compounds having more than one substituent of the strong electron withdrawing substituents such as nitro(-N02), sulfonate ion (-S03), carboxyl-(-COOH) and cyano-(CH) groupings. From this class of materials, 2,4,7-trinitro-9-fluorenone (TNF), 2,4,5,7-tetranitrofluorenone, trinitroanthracene, dinitroacridene, tetracyanopyrene, and dinitroanthraquinone are preferred materials because of the availability and superior electron transport properties.
It will be obvious to those skilled in the art that the use of any polymer having the described aromatic or heterocyclic electron acceptor moiety as an integral portion of the polymer structuxe will function as an active transport material. It is ~ not the intent of the invention to restrict the type of polymer which can be employed as the transport material, provided it has an active electron acceptor moiety to provide the polymer with electron transport characteristics. Polyesters, polysiloxanes, polyamides, polyurethanes, and epoxies, as well as block, random or graft copolymers containing the aromatic moiety are therefore exemplary of the various types of polymers which could be employed.
In addition, electronically inactive polymers in which the active electron acceptor or material is dispersed at high concentration can be employed as hereina~ter described.

z~

The active layer not only serves to transport holes or electrons, but also protects the photoconductive layer from abrasion or chemical attack and therefore extends the operating life of the photoreceptor imaging member.
Electrically active layer or active layer when used herein to define layer 15 of Figs. 3 and 4 means that the material is capable of supporting the injection of photogenerated holes or electrons from the generating material, i.e. layer 12 and is capable of allowing the transport of these holes or electrons through the active layer 15 in order to discharge a surface charge on active layer 15.
The reason for the requirement that active layer, i.e.
charge transport layer 15, should be transparent is that most of the incident radiation is utilized by the charge carrier generator layer 12 for efficient photogeneration.
Charge transport layer 15 will exhibit negligible, if any, discharge when exposed to a wavelength of light useful in xerography, i.e., 4000 angstroms to 8000 angstroms. Therefore, charge transport layer 15 is substantially transparent to radiation in a region in which the photoconductor i5 to be used;
as mentioned, for any absorption of desired radiation by the active material 15 will prevent this radiation from reaching the photogeneration layer 12 where it is more effectively utilized.
Therefore, active layer 15 is a substantially nonphotoconductive material which supports an injection of photogenerated holes from the generation layer 12.
As mentioned, it is not the intent of this invention to restrict the choice of active materials to those which are trans-parent in the entire visible region. For example, when used with a transparent substrate, imagewise exposure may be accomplished ! ~ -. ' ' .

z~)3 through the substrate without light passing through the layer of active material. In this case, the active material need not be non-absorbing in the wavelength region of use.
The active layer 15 which is employed in conjunction with the generation layer 12 in the instant invention is a material which is an insulator to the extent that electrostatic charge placed on the active transport layer is not conducted in the absence of illumination, i.e. rate sufficient to prevent the formation and retention of an electrostatic latent image thereon.
In general, the thickness of the active layer should be from about 5-100 microns, but thicknesses outside this range can also be used. The ratio of the thickness of the active layer 15 to the charge generation layer 12, should be maintained from about 2:1 to 200:1 and in some instances as great as 400:1.
However, ratios outside this range can also be used.
In another embodiment of the instant invention, the structure of Fig. 3 is modified to insure that the sodium doped trigonal selenium particulate material is in the form of continuous chain through the thickness of binder layer 12. This embodiment is illustrated by Fig. 4 in which the basic structure and materials are the same as those of Fig. 3, except the doped trigonal selenium particulate material 13 is in the form of continuous chains. The same as illustrated in Fig. 2 for the particulate material 13.
In another embodiment, the various embodiments of this invention, i.e. members, may be overcoated with electrically insulating material. ~owever, it should be understood that when using such overlayers, then instead of using an electrical blocking layer between the substrate and the photoconductive or f~2~3 charge generation layer there should be used a charge injecting layer in place of this electrical blocking layer. There must be charge injecting contact between the substrate and the photo-conductive layer when using the electrically insulating overlayers.
In another embodiment o~ the present invention, a photogenerating layer comprising a layer of material similar to layer 12 illustrated in Fig. l and layer 12 illustrated in Fig. 2 may be sandwiched between an electron transporting material such as TNF in an electrically inactive binder or a complex of PVK/TNF
(polyvinyl carbazole/2,4,7-trinitro-9-fluorenone) alone and a layer of hole transport material. Therefore, when TNF alone is used, it is preferably blended with an inactive polymeric material in order to enhance the mechanical properties of the layer. This con~iguration is suitable for use in xerographic imaging with positive charging. If the position of the transport layer are reversed, the device then becomes suitable for use with negative charging. Therefore, in a broader sense, this embodiment may comprise a three layered composite photoreceptor device. The device may comprise a photogenerating layer such as layer 12 in Figs. 1 and 2, i.e. doped trigonal selenium dispersed randomly or geometrically in a binder, sandwiched~between two electrically active layers. As mentioned in one embodiment, the photoconductive layer is sandwiched or laminated between a positive or hole transport layer on one side and an electron or negative transport layer on the other side.
In another embodiment, both sides may be hole and electron transporting, e.g. PVK/TNF complex on both sides (one side thin enough to allow light ahsorption to the generation layer).

Z~3 "Electrically active" when used herein means that the material is capable of supporting the injection of photogenerated charge carriers from the generating material and is capable of allow;ng the transport of these charge carriers through the active layer in order to discharge a surface charge on the active layer.
"Electrically inactive" when used herein means that the material is not capable of supporting the injection of photo-generated charge carriers from the ~enerating material and is not capable of allowing the transport of these charge carriers through the material.
When the term "charge carrier" is used herein it refers to both photogenerated holes and electrons.
In reference to Figs. 3 and 4, the active layer 15 may comprise an activating compound useful as an additive to electri-cally inactive polymeric materials making these materials electrically active. The following compounds may be added to the electrically inactive polymeric materials, i.e. materials which are incapable of supporting the injection of photogenerated holes from the generation material and incapable of allowing the transport of these holes therethrough, in order to make the electrically inactive polymeric material, electrically active i.e. capable of supporting the injection of photogenerated holes from the generation material and capable of allowing the transport of these holes through the active layer in order to discharge the surface charge on the active layer.
One of the preferred embodiments of this invention comprise active layer 15 of Figures 3 and 4 as an electrically active layers which comprises an electrically inactive resinous . . : ,.; :
, Z~3 material made electrically active by the addition of certain activating compounds added thereto which comprise:
(1) N,N'-diphenyl-N,N'-bis(phenylmethyl)-[l,l'-biphenyl~-4,4'-diamine with the following formula:

( \
~CH2 CH2 ~ ~

It was found that N,N'-diphenyl-N,N'-bis(phenylmethyl)-~l,l'-biphenyl]-4,4'-diamine dispersed in an organic binder transports charge very efficiently without any trapping when this layer is used contiguous a generation layer, i.e. photo-conductive layer, and subjected to charge light discharge cycles in an electrophotographic mode. There is no buildup of the residual potential over many thousands of cycles.
Furthermore, when N,N'-diphenyl-N,N'-bis(phenylmethyl)-[l,l'-biphenyl]-4,4'-diamine dispersed in a binder is used as a transport layer contiguous a charge generation layer, i.e. photo-conductive layer, there is no interfacial trapping of the charge photogenerated in and injected from the generating layer.
No deterioration in charge transport was observed when these transport layers containing N,N~-diphenyl-N,N~-bis(phenylmethyl) ~l,l'-biphenyl]-4,4'-diamine dispersed in a binder subjected to ultraviolet radiation.
(2) Another activating compound useful as an additive 2~3 to the electrically inactive polymeric material making it electrically active is:

~)S C~

wherein Rl is selected from the group consisting of hydrogen, (ortho) CH3, (meta) CH3 or (para) C~3, and R2 is selected from the group consisting of (ortho) CH3, (meta) CH3 and (para) CH3.
The preferred materials are N,N'-diphenyl-N,N'-bis-(2-methylphenyl)-~2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine;
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N'-diphenyl-N,N'-bis(4-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; ~,N,N',N'-tetra(2-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N'-bis(2-methylphenyl)-N,N'-bis(3-methylphenyl)-[2,2'~dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N'-bis(2-methylphenyl)-N,N'-bis(4-methylphenyl)-2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine;
N,N'-bis(3-methylphenyl)-N,N'-bis(2-methylphenyl)-2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N,N',N'-tetra(3-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N' bis(3-methyl-phenyl)-N,N'-bis(4-methylphenyl)-~2,2'-dimethyl-1,1'-bipheny].]-4,4'-diamine; N,N'-bis(4-methylphenyl)-N,N'-bis(2-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine; N,N'-bis(4-methylphenyl)-N,N'-bis(3-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl[-4,4'-diamine and N,N,N',N'-tetra(4~methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine.

: .

The most prefexred materials are;
N,N,N',N'-Tetraphenyl-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine;

_N - N_~

N,N,N',N'-Tetra-(3-methylphenyl)-[2,2'-dimethyl-1,1'-biphenyl]-4,4'-diamine:

~ f H3 (~ ~ N

N,N'-Diphenyl-N,N'~bis(3-methylphenyl)-2,2'-dimethyl-1,1'-biphenyl[4,4'-diamine:

,~ r~
(~ 3 N._ ~ ~9 N~

The electrically active layer, i.e., the photogenerated hole transport layer 15, is substantially nonabsorbing to visible light or radiation in the region of intended use, but is "active"
in that is allows the injection of photogenerated holes from the photoconductive layer, i.e. charge generation layer, and allows these photogenerated holes to be transported through the electrically active charge transport layer to selectively discharge a surface charge on the surface of the active layer or at the interface between the substrate and the transport layer.
It was found that, unlike the prior art, when the N,N,N',N'-tetraaryl-bitolyldiamines of the instant invention were dispersed in an organic binder this layer transports charge very efficiently without any trapping of charges when this layer is used contiguous to a generator layer and subjected to charge/light discharge cycles in an electrophotographic mode. There is no buildup of the residual potential over many thousands of cycles.
(3) Another activating compound which may be added to the electrically inactive polymeric material in order to make the material electrically active is as follows:
~0 X ~ ~ X

wherein X is selected from the group consisting of (or~ho) CH3, (meta) CH3, tPara) CH3, (ortho) Cl, (meta) C1 and (para) C1. The chemical name of the above formula is N,N'-diphenyl-N,N'-bis-(alkylphenyl)-[l,l'-biphenyl]-4,4'-diamine wherein the alkyl is ~:. ., , ; . . .. . .

selected from the group consisting of 2-methyl, 3-methyl and 4-methyl or the compound may be N,N'-diphenyl-N,N'-bis(halo phenyl)-[l,l'-biphenyl]-4,4'-diamino wherein the halo is selected from the group consisting of 2-chloro, 3-chloro and 4-chloro.
Furthermore, when the substituted ~J,N,N',N'-tetraphenyl-[l,l'-biphenyl]-4,4'-diamines of the instant invention dispersed in a binder are used as transport layers contiguous a charge generation layer, there is no interfacial trapping of the charge photogenerated in and injected from the generating layer. When subjected to ultraviolet radiation, no deterioration in charge transport was observed in these transport layers containing the substituted N,N,N',N'-tetraphenyl-ll,l'-biphenyl]-4,4'-diamines of the instant invention.
Furthermore, the transport layers comprising substituted N,N,N',N'-tetraphenyl-[l,l'-biphenyl]-4,4'-diamines of the instant invention dispersed in a binder were found to have sufficiently high (Tg) even at high loadings, thereby eliminating the problems associated with low (Tg) as discussed above.
(4) Another activating compound which may be added ~ to the electrically inactive polymeric material to make it electrically active is bis-(4-diethylamino-2-methylphenyl)phenyl-methane which has the formula:

~ I ~
(C2H5)2~ C2H5)2 ~J

In all of the above charge transport layers, the - : ... .

~ r' ~ , .

activating compound which m~kes the electrically inactive polymeric material eleetrically active should be present in amounts of from about 15 to about 75 percent by weight, preferably ~rom about 25 to 50 percent by weight.
Active layer 15 may comprise any transport electrically inactive resinous material sueh as those described in Middleton et al, U.S. Patent 3,121,006.
The preferred electrically inactive resinous mater-ials are polycarbonate resins. The preferred polycarbonate resins have a molecular weight (Mw) from about 20,000 to about 100,000, more preferably from about 50,000 to about 100,000.
The materials most preferred as the electrically inactive resinous material is poly(4,4'-isopropylidene-diphenylene carbonate) with a molecular weight (Mw) of from about 35,000 to about 40,000, available as Lexan~ 145 from General Electric Company; poly(4,4'-isopropylidene-diphenylene carbonate) with a molecular weight (Mw) of from about 40,000 to about 45,000, available as Lexan~ 141 from the General Electric Company; a polycarbonate resin having a molecular weight (Mw) of from about 50,000 to about 100,000, available as Makrolon~ from Farbenfabricken Bayer A.G. and a polycar-bonate resin having a moleeular weight (Mw~ of from about 20,000 to about 50,000, available as Merlon~ from Mobay Chemical Company.
Alternatively, as mentioned, active layer 15 may comprise a photogenerated electron transport material.
Fig. 5 (sample 13 shows the rested dark deeay and the fatigue dark decay of a photoreceptor containing trigonal selenium undoped as the photoconductive material dispersed in an electrically active binder as the generator layer which is X , ~,~Z~LZ~)3 overcoated wi~h a transport layer. This member was made by the process as set forth in Example IX. The negative corona charge density was about 1.2 x 10 3 C/m2 and the thickness of the member was about 25 microns. The member was rested in the dark for 15 hours prior to charging. Then the member was charged to a maximum of 1280 volts initially measured 0.06 seconds charging. After 0.22 seconds, while the photoreceptor remained in the dark, its rested dark decay was 60 volts, i.e. the surface potential had dropped to 1220 volts. After 0.66 seconds the surface potential was 1140 volts indicating a dark decay of 140 volts.
As shown in Fig. 5, the fatigue dark decay was obtained by charging the member initially to a maximum of 1100 volts measured 0.06 seconds after charging. This is 180 volts less than the member was capable of being charged initially in the rested dark decay test. After the member remained in the dark for 0.22 seconds, it discharged to 920 volts which represents a fatigued dark decay of 180 volts. After 0.66 seconds the member discharged to 770 volts, indicating a fatigue dark decay of 330 volts.
It is convenient to express this fatigue dark decay as a percentage of the ratio of the surface potential change between 0.22 seconds and 0.66 seconds and the surface potential at 0.22 seconds after charging, e.g. in sample 1, 8% and 16~ for the rested and fatigued dark decay, respectively.
As can be seen from Fig. 5 the volts of charge on the surface of the member initially, i.e. after 15 hours dark rest, is almost the same as the volts of charge on the surface of the member after a xerographic cycle for the doped members. However, there is a measurable difference in these surface potential values for the undoped trigonal selenium. In other words, the drop between i :, .

)3 the rested and the fatigued dark decay is high in the undoped and low in the doped.
In Fig. 5 (sample 1), i.e. undoped trigonal selenium, shows 180, 300 and 370 volts difference, respectively, in the surface potential at 0.06, 0.22 and 0.66 seconds after charging of the rested, i.e. the member had not been xerographically cycled in at least 15 hours, versus the fatigued member, i.e. the member had been xerographically cycled and discharged (erased) in at least a 30 minute period. However, the doped samples, i.e. Fig. 5 (samples 2-8), showed almost no differences within the experimental measurement error.
From Fig. 5 (samples 1-8), it is shown by doping trigonal selenium with sodium for use as a photoconductive material in a photoreceptor that (1) the surface potential after fatigue of the undoped trigonal selenium containing photoreceptor was less than the surface potential of the doped fatigued trigonal selenium containing photoreceptor. That is, the fatigued doped members accepted more charge, almost as much charge as these members accepted when rested, as compared to the fatigued undoped member which accepted much less charge. The surface potential of the undoped member becomes much less, much faster, than the surface potential of the doped members. (2) Also both the rested and fatigued dark decay are more in the undoped member after 0.06 seconds, 0.22 seconds and 0.66 seconds in the dark as compared to the rested and fatigued dark decay in the doped members.
Referring now to Fig. 6, which shows the photo-induced discharge curves (PIDC) of members containing doped and undoped trigonal selenium as the photoconductive material, these PIDC's show surface potential versus the exposure at the photoreceptor . . . . . .

in ErgS/cm2. The PIDC of each sample was taken at two different times, i.e. 0.06 seconds after exposing and 0.5 seconds after exposing. The exposure station is loca~ed 0.16 seconds after charging for a photoreceptor process speed of 30 inches per second. The PIDC's of sample 1 of Fig. 5 are shown as the bottom two PIDC's on the graph. The next two PIDC's up the graph are for sample 3 from Fig. 5. The next two PIDC's are for sample 4 from Fig. 5. The next two PIDC's are for sample 6. The next PIDC is for sample 7 and the top PIDC is for sample 8.
The square points represent PIDC points (0.5 seconds after exposing) and the round points represent PIDC points (0.06 seconds after exposing).
Upon examining Fig. 6, it is clear that the PIDC's of number 1, i.e. sample #1 from Fig. 5 (photoreceptor containing undoped trigonal selenium), are unstable since the 0.06 seconds after exposing, PIDC, and the 0.5 seconds after exposing, PIDC, have changed with time. However, the PIDC's for number 3 (sample #3, Fig. 5) photoreceptor containing doped trigonal selenium, number 4 (sample #4, Fig. 5) photoreceptor containing doped trigonal selenium as well as number 6, 7, and 8 are stable. That is, the PIDC's vary only slightly with time between 0.06 seconds after exposing and 0.5 seconds after exposing. In fact, in number 7 and 8 the PIDC's show no variance since the PIDC for 0.06 seconds after exposing and the PIDC for 0.5 seconds after exposing were about the same. These curves are superimposed on each other. There-fore, by doping the trigonal selenium contained in the photo-receptors, the dark decay is removed from the photoreceptors or at the least controlled resulting in the stablization of the PIDC's of these doped members. Most importantly, in the doped members the PIDC's do not change as a function of time. However, in the undoped members the PIDC ' s do change as a function of time. This greatly affects image quality. For example, if a machine were to use a photoreceptor in belt form and the photoreceptor being used was undoped trigonal selenium and the member was flash exposed, then the belt would normally move into the development zone. The leading edge of the latent image on the belt would go into the develop-ment ~one before the trailing edge of the image. The PIDC
at the leading edge of the photoreceptor will be different from the PIDC at the trailing edge, since the PIDC of this undoped member changes as a func-~ion of time. Therefore, the latent image when developed would be unacceptable. The PIDC would unacceptably vary from one end of the image to the other.
However, this effect will vary as a function of the photoreceptor process speed, i.e. the greater the speed, the greater the effect.
Therefore, this would not happen when using a photoreceptor containing doped trigonal selenium as the photoconductive material, since the PIDC's of these members do not change as a function of time. The latter situation leads to good print characteristics.
As can be seen from the PIDC's of all the samples, i.e.
Fig. 6, all the sensitivities of the samples are a function of Na doping level. In addition, the dark decay is also a function of Na doping level, i.e. Fig. 5. Hence, depending on the Na doping level the PIDC's are stable and do not change with time.
However, as mentioned, in the undoped member even though the sensitivity is acceptable the members, i.e. sample #1, PIDC is unstable and changes with time. Furthermore, the dark decay is unacceptable.
One preferred embodiment involves exposing the particulate trigonal selenium to sodium. A preferred method involves washing the trigonal selenium with sodium hydroxide.

The trigonal selenium may be washed with water then with the sodium solution. The amount of sodium on the external surface of each particle of trigonal selenium may be varied by varying the sodium hydroxide concentration. This procedure may also vary the amount of sodium on the internal surface of the trigonal selenium particles. The excess sodium, e.g. sodium hydroxide, is removed and depending on the amount of sodium left, this varies the electrical properties of the trigonal selenium. Preferred amounts of sodium range from about 0.01 percent by weight to 1.0 percent by weight sodium based on the total weight of trigonal selenium present. However, 0.01 to 12.0~ by weight may be used. In addition to sodium hydroxide, sodium carbonate (Na2C03), sodium bicarbonate (NaHC03) and sodium acetate (NaC2H302) and sodium selenite (Na2SeO3) may be used to introduce the sodium into the solution. In addition, other sodium salts may be used. Similarly, the hydroxides and the salts of lithium, potassium, rubidium and cesium may be used.
Preferably, the particulate trigonal selenium should be in the size range from about 0.01 micron to about 10 microns ~ in diameter with the most preferred size being about 0.1 micron to 0.5 micron in diameter. This size is important in the sense that these particles of trigonal selenium have a high surface to volume ratio. A relatively large amount of sodium may be placed on the surface of these relatively small particles. This ~5 will control the surface component of dark decay. However, it is preferable that these particles also contain small cracks and crevasses. It is preferred that the dopants, e.g. sodium, - lithium, potassium, rubidium and cesium, be deposited in these cracks or crevasses. This helps control the bulk dark decay of the trigonal selenium particles. That is, getting the dopants `:

Z`~3 into these cracks and crevasses helps control and relieve bulk charge trapping. Therefore, both the external and internal surface of the particles of trigonal selenium are being doped.
Another possible explanation for doping the internal surface, i.e cracks and crevasses, of the particles o~ trigonal selenium particles is that all of the light does not stop at the surface of the particles but goes into the inside or inner portion of the particle and excites the material, i.e. trigonal selenium, at that point. When the dopants are located in the cracks and crevasses then these dopants help relieve the dark discharge.
That is, the dopants help with bulk discharge of each particle of trigonal selenium. As mentioned, it is believed that both the surfacc and the internal portion o~ particles of trigonal selenium are helped by the dopants being on both the surface and in the cracks and crevasses of the particles.
The salts, such as ~aOH, NaHCO3, NaCO3 and CH3COONa, and Na2SeO3 may also serve to neutralize any residual selenious acid (H2SeO3) left from the preparation formed by Se reacting with water.
The following examples further specifically define the present invention with respect to a method of making the doped trigonal selenium containing photoconductive members.
The percentages are by weight unless otherwise indicated.
The examples below are intended to illustrate various preferred embodiments of the instant invention.
EX~MP~ I
Preparation of undoped trigonal_selenium - Into a 500 milliliter Erlenmeyer flask fitted with a magnetic stirrer is placed 100 gms. of reagent grade sodium hydroxide (NaOH) dissolved in 100 milliliters of deionized water. When the solution is complete, then 23.7 gms. of X-grade amorphous selenium beads available from Canadian Copper Refineries are added. The solution is stirred at 85C for fi~e hours. Then deionized water is added to bring the total volume up to 300 milliliters. The solution is stirred for one minute. The heat is then removed and the solution allowed to digest at least for 18 hours.
The above solution is then filtered through a coarse fritted glass funnel into a vacuum glass containing 3700 milliliters of deionized water. The water should be swirling.
The total volume is 4 liters. The solution is stirred for five minutes. Then 10 milliliters of 30 percent reagent grade hydrogen peroxide (H2O2) is added dropwise to the solution over a period of two minutes. The solution is stirred for an additional 30 minutes. Trigonal selenium is then precipitated out of the solution resulting in the proper size of particulate trigonal selenium being formed. The precipitated trigonal selenium, i.e. solids, may be allowed to settle out. Then decant the supernatent and replace this with deionized water.
This washing procedure is repeated until the resistivity of the supernatent equals that of the deionized water. Then the trigonal selenium (undoped) is filtered out on a ~o~ 2 filter paper. The undoped trigonal selenium is dried at 60C
in a forced air oven for 18 hours. The sodium content of the final undoped trigonal selenium powder is 20 ppm (parts per million) other metal impurities are less than 20 ppm. The yield is 80 percent.
EXAMPLE II
Th`e preparation of undoped trigonal selen m - Into a 500 millil~ter Erlenmeyer flask fitted with a magnetic stirrer .

and a dropping funnel is placed 100 gms. of reagent grade sodium hydroxide (NaOH) and dissolved in 100 milliliters of deionized water. When the solution is complete, 23.7 gms. of X-grade amorphous selenium beads available from CCR (Canadian Copper Refineries) is added. Then the solu-tion is heated to 85C and stirred for five hours. Then deionized water is added to bring the total volume of the solution up to 300 milliliters. The solution is stirred for one minute. The heat is removed and the solution is allowed to digest at least 18 hours. The above solution is filtered through a coarse fritted glass funnel into a flask containing deionized water. The water should be swirling during the addition. The quantity of the water is such that upon precipitation, the final volume of slurry is 4 liters. The solution is stirred for five minutes. Stoichiometric amounts of either one of the following acids may be added: either 208 milliliters of 12 normal (N) HC1, 150 milliliters of 16 normal (N) HNO3 or 70 milliliters of 36 normal (N) H2SO4 or 133 ml of 17.4 (N) CH3COOH or 155 gm of H2SeO3. These are diluted to the desired concentrations which is usually 1.2 normal (N). Then these solutions are added to the polyselenide solution as rapidly as possible. A procedure that may be used to dilute the acid to 2 liters [1.2 normal (N)] and add to 2 liters of polyselenide solution. After the addition, the solution is stirred for 1/2 hour. The particulate size is as desired.
A particular procedure which may be followed is to allow the solids, i.e. precipitated trigonal selenium, to settle out. Then decant the supernatent and replace it with deionized water. This washing procedure is repeated until the resistivity of the supernatent equals that of the )3 deionized water. Then the trigonal selenium is filtered on a No. 2 filter paper. The selenium is dried at 60C
in a forced air oven for 18 hours. The sodium content of the undoped final trigonal selenium powder is 20 ppm. The other me~al impurities are less than 20 ppm. The yield is 95 percent.
EX~MPLE III
P'reparation of so'dium doped 'tr'igonal selenium -_ Trigonal selenium made by either Example I or Example II
may be used. The trigonal selenium must be thoroughly washed and before filtering, decant as much of the supernatent as possible. Then refill the solution to a volume of four liters with a 0.6 normal (N) solution of sodium hydroxide (NaOH).
Alternatively, 0.6 N, Na2CO3, NaHCO3, CH3COONa, Na2SeO3 may be used. This solution should be swirled for 1/2 hour. Tlle solids should be allowed to settle out and remain in contact with the sodium hydroxide (NaOH) or Na2CO3, NaHCO3, CH3COONa, Na2SeO3 solution for 18 hours. The solution is decanted and the supernatent is retained. The doped trigonal selenium is filtered on a No. 2 filter paper. The retained supernatent is used to rinse the beaker and funnel. The doped trigonal selenium is dried at 60C
in a forced air oven for 18 hours. The sodium levels average approximately 1.0 percent by weight based on the total weight of the trigonal selenium. All other metal impurities are less than 30 ppm.
'EXAMPLE IV
Prepara'tion of' a member cont'ain'.in'~ 'undoped tr'igonal selenium d'i'sp-ers'ed' in an' electrical'ly ac'tive' r'esih'ous binder - A
five mil aluminized Myla ~ substrate is rinsed with CH2C12 methylene chloride. The aluminized Myla ~ substrate is allowed to dry at ambient temperatures. In a glove box with the humidity less than 20 percent and the temperature at 82F, a layer of l/2 percent DuPont 49,000 adhesive, a polyester available from DuPont, in CHC13 (chloroform~ and trichloroethane 4 to 1 volume is coated onto the substrate with a Bird applicator. The wet thickness of the layer is l/2 mil. This layer is allowed to dry for one minute in the glove box and ten minutes in a 100C oven.
Alternatively, the aluminized Myla ~ may be coated with a layer of l/2~ Monsanto B72A (polyvinylbutyrol~ in ethanol with a Bird applicator. The wet thickness is 1/2 mil. The layer is allowed to dry in a glove box for 1 minute and lO minutes in 100C oven.
A generator layer containing 20~ by volume undoped trigonal selenium is prepared as follows:
Into a 2 ounce amber bottle is added 0.8 grams purified PVK and 14 ml. of l:l THF/toluene. Added to this solution is 100 grams of l/8 inch stainless steel shot and 0.8 grams undoped trigonal selenium. The above mixture is placed on a ball mill for 72 hours. Then the solution is coated on the above interface layer with a Bird applicator.
The wet thickness is ]/2 mil~ Then this member is annealed at 100C in a vacuum for 13 hours. The dry thickness is 2 microns.
EXAMPLE V
Preparation of a member contain~ing undoped trigonal selenium dispersed i_ an active binder - A five mil aluminized Myla ~ substrate is rinsed with CH2C12 methylene chloride. The aluminized Myla ~ substrate is allowed to dry at ambient tempera-ture. In a glove box with the humidity less than 20 percent and the temperature at ~2F, a layer of one percent Hytre ~, a polyester blocked polymer available from DuPont, in CHC13 (chloroform~ is coated onto the substrate with a l/2 mil Bird applicator. The ; -36-:

wet thickness of the layer is 1/2 mil. This layer is allowed to dry for one minute in the glove box and five minutes in a 100C oven. Then this is coated with a second layer of 1 percent PVK in benzene with a Bixd applicator. A 1/2 mil wet layer is applied. This layer is allowed to dry for one minute in the glove box and 5 minutes in a 100C oven.
A layer containing 25 percent by volume based on the total volume of the member of undoped trigonal selenium is prepared as follows: In a two ounce amber bottle is placed 0.328 grams of PVK, 0.0109 grams of TNF and 14 ml of benzene. 100 grams of stainless steel shot is added and 0.44 grams o~ undoped trigonal selenium as prepared in Example I or Example II is added. The above solution is placed on a paint shaker for one hour. Then 7 ml of benzene is added. The solution is placed on a roller mill for 1 minute. The solution is then coated on the above-prepared aluminized Myla ~ substrate by making 3 passes with a 1/2 mil Bird applicator on the above-prepared aluminumed Myla ~
substrate. The solution is allowed to dry for 1 minute between each pass. Then this member is annealed at 100C in a vacuum ~0 for 18 hours. The dried thickness is 2 microns.
' EXAMP'LE VI
Pr'epa'ra'tion of a me'mber 'conta'ining doped trigonal selenium `dispersed in an electri_ally ~ac'tive' re's no'us binder -A five mil aluminized Myla ~ substrate is rinsed with methylene chloride (CH2C12). The aluminized Myla ~ is allowed to dry at ambient temperature. In a glove box with humidity less than 20 percent and the temperatuxe at 82F r a layer of 1/2 percent DuPont 49,000 adhesive in CHC13 (chloroform~ and trichloroethane 4 to 1 volume, is coated onto the aluminized Myla ~ with a Bird applicator to a wet thickness of 1/2 mil. The coating is dried for 1 minute in the glove box and 10 minutes in a 100C
oven. Alternatively, the aluminized Myla ~ may be coated with a layer of 1/2 percent Monsanto B72A (polyvinylbutyral) in ethanol with a Bird applicator. The wet thickness is 1/2 mil. The layer is allowed to dry in a glove box for 1 minute and lO minutes in 100C oven.
A generator layer containing 20 percent by volume doped trigonal selenium is prepared as follows: I~to a 2 ounce amber bottle is added 0.8 grams purified PVK and 14 ml of 1:1 THF/
toluene. Added to this solution is 100 grams of 1/8 inch stain-less steel shot and 0.8 grams doped trigonal selenium as prepared in Example III. The above mixture is placed on a ball mill for 72 hours. Then the solution is coated on the above interface layer with a Bird applicator. The wet thickness is 1/2 mil.
Then this member is annealed at 100C in a vacuum for 18 hours~
The dry thickness is 2 microns.
EX~MPLE VII
Prepar'ation of a s'o'dium'doped'trigonal`selenium member where-in` the'dope'd trig~nal selenium i-s dispersed 'in 'an electrically active resinous bi~der - A ~ive mil aluminized Myla ~ substrate is rinsed with methylene chloride (CH2C12). The aluminized Myla is allowed to dry at ambient temperature. In a glove box with humidity less than 20 percent and the temperature at 82F, a layer of one percent Hytre ~, a polyester blocked polymer available from DuPont, in CHC13 (chloroform) is coated onto the aluminized Myla ~ with a Bird applicator to a dry thickness of 1/2 mil.
The coating is dried for one minute in the glove box and five minutes in a 100C oven. A second coating is applied to the member which is one percent PVK in benzene ~C6H6~ with a Bird applicator resulting in a dry thickness of lJ2 mil. This layer is allowed f~3 to dry for one minute in the glove box and 5 minutes in a 100C
oven.
A 25 percent by volume doped trigonal selenium containing member is prepared by placing into a two ounce amber bottle 0.328 gm. of P~K, 0.0109 gm. of ~NF and 14 milliliters of benzene (C6H6). Added to this is one hundred gms. of stainless steel shot and 0.44 gms. of doped trigonal selenium as prepared in Example III. The above solution is placed on a paint shaker for one hour. Then 7 milliliters of benzene (C6H6) is added. This 10 solution is placed on a roller mill for one minute. Then the solution is coated by making three passes with a Bird applicator.
The solution is allowed to dry for one minute between each pass.
The member is annealed at 100C in a vacuum oven for 18 hours.
The dried layer is about two microns thick.
E'XAMPLE VIII
Prepar _ion of'N,N'-dipheny'l-N,N''-bis('3-me't lphenyl) [l,l'-biphenyl]-4,4'-diamine - In a 500 milliliter, round bottom, 3-necked flask fitted with a mechanical stirrer and blanketed with Argon, is placed 360 gms. (1 mole) of N,N'-biphenylbenzidene, 20 550 gms. (2.5 moles) of m-iodotoluene, 550 gms. (4 moles) potassium carbonate (anhydrous) and 50 gms. of copper bronze catalysts and 1,500 milliliters of dimethylsulfoxide (anhydrous).
The heterogeneous mixture is refluxed for 6 days. The mixture is allowed to cool. 2000 milliliters of benzene is added. The 25 dark slurry is then filtered. The filtrate is extracted 4 times with water. Then the filtrate is dried with magnesium sulfate and filtered. The benzene is taken off under reduced pressure.
The black produce is column chromatographed using ~oelm neutral alumina. ~olorless crystals of the'product are obtained by )3 recrystallizin~ the product from n-octane. The melting point is 167-169C. The yield is 360 gms. (65 percent~.
E AMPL~ IX
A co~posite~photoconductive member is prepared which s comprises a genera~or lay~r which is overcoated with a transport layer - ~ five mil aluminized Myla ~ substrate is rinsed with CH2C12. This substrate is allowed to dry at ambient temperature.
In a glove box with humidity less than 20 percent and the temperature at 82F the aluminized Myla ~ substrate is coated with a layer of 1/2 percent Dupont 49,000 adhesive in CHC13 and trichloroethane at 4:1 volume with a Bird applicator. The wet thickness is 1/2 mil. The layer is allowed to dry for 1 minute in a glove box and 10 minutes in 100C oven. Alternatively, the aluminized Myla ~ may be coated with a layer of 1/2 percent Monsanto B72A (polyvinylbutyral) in ethanol with a Bird applicator. The wet thickness is 1/2 mil. The layer is allowed to dry in a glove box for 1 minute and 10 minutes in 100C oven.
A generator layer containing 20% by vol~me undoped trigonal selenium is prepared as follows: Into a 2 ounce amber bottle is added 0.8 grams purified PVK and 14 ml of 1:1 THF/
toluene. Added to this solution is 100 grams of 1/8 inch stainless steel shot and 0.8 grams undoped trigonal selenium as prepared in Example I or IIo The above mixture is placed on a ball mill ~or 72 hours. Then the solution is coated on the above interface layer with a Bird applicator. The wet thickness is 1/2 mil. Then this member is annealed at 100C in a vacuum for 18 hours. The dry thickness is 2 microns.
; The above generator layer is overcoated with a charge transport layer which i5 prepared as follows: A transport layer containing 50 percent by weight Makrolon~, a polycarbonate resin . . .

having a molecular weight (Mw) of from about 50,000 to about 100,000, available from Larbensabricken Bayer A.G., is mixed with 50 percent by weight N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[l,l'-biphenyl]-4,4'-diamine as prepared in Example VIII. This solution is mixed in 15 percent by weight methylene chloride. All of these components are placed into an amber bottle and dissolved.
The mixture is coated to a dr~ 25 micron thickness layer on top of the generator layer using a Bird applicator. ~he humidity is equal to or less than 15 percent. The solution is annealed at 70C
in a vacuum for 18 hours. The member is tested the same as the members as shown in Fig. 5 and Fig. 6. The rested dark decay and the fatigue dark decay o~ this photoreceptor containing undoped trigonal selenium as a photoconductive material dispersed in an electrically insulating resinous binder as a generating material overcoated with a charge transport material is tested as follows. The member is rested in the dark for 15 hours prior to charging. Then the member is charged to a maximum of 1280 volts initially measured at 0.06 seconds after charging. After 0.22 seconds while the photoreceptor remains in the dark, its rested dark decay is 60 volts, i.e. the surface potential dropped to 1220 volts. After 0.66 seconds the surface potential is 1140 volts indicating a dark decay of 140 volts.
The fatigued dark decay is obtained by charging the member initially to a maximum of 1100 volts measured at 0.06 secGnds after charging. This is 180 volts less than the member was capable of being initially in the rested dark decay test.
After the member is retained in the dark for 0.22 seconds, it discharges to 920 volts, which represents a fatigued dark decay of 180 volts. After 0.66 seconds, the member discharges to 770 volts indicating a fatigued dark decay of 330 volts.

.

EXAMPLE X
A composite photoconductive member is prep~ared which comprises a generation layer which is overcoated with a transport layer - The generation layer comprises undoped trigonal selenium dispersed in a resinous binder.
A five mil aluminized Myla ~ substrate is rinsed with methylene chloride. This substrate is allowed to dry at ambient temperature. In a glove box with the humidity less than 20 percent and the temperature at 82F, the aluminized Myla ~
substate is coated with a layer of one percent Hytrel~ in chloroform with a Bird applicator. The wet thickness of this layer is 1/2 mil. The layer is allowed to dry for one minute in a glove box and five minutes in 100C oven. This layer is coated with a second layer of one percent PVK in benzene with the sird applicator.
The wet thickness of this layer is 1/2 mil. This layer is allowed to dry for one minute in the glove box and 5 minutes in a 100C
oven.
A generation layer containing 25 percent by volume undoped trigonal selenium is prepared as follows. Into a 2 ounce amber bottle is added 0.328 gm~ PVK, 0.0109 gm. TNF and 14 milliliter of benzene. Added to this solution is 100 gms. of stainless steel shot and 0.44 gm. undoped trigonal selenium.
The above mixture is placed on a paint shaker for one hour. Then 7 milliliters of benzene is added. Then the solution is placed on a roller mill for one minute. Then the solution is coated by making three passes with the slurry with a Bird applicator.
One minute is allowed between passes in order for the solution to dry. The solution is annealed at 100C in ~acuum for 18 hours.
The dry thickness of the layer is 2 microns.

The above generator layer is overcoated with a charge transport layer which is prepared as follows. A transport layer containing 50 percen~ by weight o Makrolon~, a polycarbona~e resin having a molecular weight (Mw) of from about 50,000 to about lO0,000, available from Larbensabricken Bayer A. G., is mixed with 50 percent by weight of N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[l~l'-biphenyl~-4~4'-diamine as prepared in Example VIII. This solution is mixed in 15 percent by weight methylene chloride.
All of these components are placed into an amber bottle and dissolved. The mixture is coated to a dry 25 micron thickness layer on top of the generator layer using a Bird Applicator.
The humidity is equal to or less than 15 percent. The solution is annealed at 70C in a vacuum for 18 hours. The member is tested as in Fig. 5 and Fig. 6.
EXAMPLE XI
-Preparation of a multilayered -imaging member c mprising a generation layer over'coated with a' transpor't'layer - A five mil aluminized Myla ~ substrate is rinsed with methylene chloride.
The substrate is allowed to dry at ambient temperature. In a glove box with the humidity less than 20 percent and the temperature at 82F, the substrate is coated with a layer of l/2 percent DuPont 49,000 adhesive in a 4:1 by volume chloroform and trichloroethane with a Bird applicator to a wet thickness of 1/2 mil. The layer is allowed to dry in a glove box for one minute and in a 100C
oven for lO minutes. Alternatively, the aluminized Myla ~ may be coated with a layer of l/2 percent ~onsanto B72~ (polyvinyl~
butyral) in ethynal with a Bird applicator. The wet thickness is l/2 mil. The layer is allowed to dry in a glove box for l minute and 10 minutes in a 100C oven.
A charge generation layer containing 20 percent by volume ,, ; , :

Z~33 of sodium doped trigonal selenium is prepared as follows. ~ 2 ounce amber bottle is provided and 0.8 gram purified ~VK, and 14 ml of 1:1 THF/toluene is added to the bottle. To this solution is added 100 gms. of 1/2 inch stainless steel shot and 0.8 gm.
sodium doped trigonal selenium as prepared in Example III.
This solution is placed on a ball mill for 72 hours.
Then the solution is coated on the above interface layer with a sird applicator. The wet thickness is 1/2 mil. Then this member is annealed at 100C in a vacuum for 18 hours. A dry thickness is formed which is 2 microns thick.
A charge transport layer is formed on the above charged generating layer. The charge transport layer comprises a 50-50 by weight solution of ~akrolo ~, a polycarbonate resin having a molecular weight (Mw) of from about 50,000 to about 100,000 ~5 available from Larbenfabricken Bayer A. G., and N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl~-4,4'-diamine as prepared in Example VIII. This solution is placed into 15 percent by weight methylene chloride. All of these ingredients are placed in an amber bottle and dissolved. The components are coated with a Bird applicator to form a dry coating of 25 microns on top of the charge generation layer. The humidity is equal to or less than 15 percent. The solution is annealed at 70C
in a vacuum for 18 hours.
The member is tested as in Fig. 5 and Fig. 6, sample 6.
The rested dark decay and fatigue dark decay in the photoconductive which contains doped trigonal selenium is tested. In order to illustrate the rested dark decay, the member is charged to a maximum of 1260 volts initially measured at 0.06 seconds after charging and after 0.22 seconds it discharges to 1200 volts, representing a rested dark decay of 60 volts. After 0.66 seconds it 2~3 discharges to 1190 volts, representing a rested dark decay of 70 volts. The fatigue dark decay is shown by initially charging the member to a maximum of 1300 volts measured at 0.06 seconds after charging and after 0.22 seconds in the dark, the member discharges to 1210 voltsr representing a fatigue dark decay of 90 volts. After 0.66 seconds the member discharges to 1190 volts, representing a fatigue dark decay of 110 volts.
EXAMPLE XII
Fabrication of undoped; trigonal seleni-um binder layer -A trigonal selenium binder layer containing 30 percent by volume trigonal selenium is prepared as follows: Into a 2 ounce clear glass bottle is added 1 ounce (vol.) 1/8 inch stainless steel shot, 7.5 grams Flexclad~ cubes, a polyester available from Goodyear, 11.5 grams trigonal selenium as prepared in Example I or II, and 21.0 ml chloroform. The jar is placed on a paint shaker for 1 hour. The slurry is then placed in a vacuum desiccator and a vaccum pulled to remove air bubbles in the slurry. The slurry is coated on a 5 mil aluminum substrate with a multiple clearance bar.
The wet thickness is 10 mil. The la~er is dried for 2 hours at ~ 60C and heated to 150C for 20 minutes.
The plate is tested electrically b~ charging the plate to a field of 20 volts/micron and discharging it at a wavelength of 5800 angstrom units at 8 x 1012 photons/cm2 second. The plate exhibits satisfactory discharge at the above fields and is capable of use in forming visible images.
The member is also tested as illustrated in Figs. 5 and 6. However, this member is charged with positive corona. The undoped trigonal selenium containing member has a high dark discharge and an unstable PIDC as compared to members containing doped trigonal selenium as the photoconductive material.

EXAMPLE XIII
Fabrication of doped trigonal selenium binder layer -A trigonal selenium binder layer containing 30 percent by volume doped trigonal selenium as prepared in Example III is prepared as follows: Into a 2 ounce clear glass bottle is added 1 ounce (vol.) 1/8 inch stainless steel shot, 7.5 grams Flexcla ~ polyester cubes available from Goodyear, 11.5 grams doped trigonal selenium prepared as in Example III and 21.0 ml chloroform. The jar is placed on a paint shaker for 1 hour. The slurry is then placed in a vacuum desiccator and a vacuum is pulled to remove air bubbles in the slurry. The slurry is coated on a 5 mil aluminum substrate with a multiple clearance bar. The wet thickness is 10 mil. The layer is dried for 2 hours at 60~C and heated to 150C for 20 minutes.
The plate is tested electrically by charging the plate to a field of 30 volts/micron and discharging it at a wavelength of 5800 angstrom units at 8 x 1012 photons/cm2 second. The plate exhibits satisfactory discharge at the above fields and is capable of use in forming visible images.
The member is also tested as illustrated in Figs~ 5 and 6. However, this member is charged with positive corona. The doped trigonal selenium containing member has a low dark discharge as compared to the member as prepared in Example XII, i.e. undoped trigonal selenium, and has a stable PIDC as compared to the member as prepared in Example XII.
EXAMPLE XIV
Fabrication of undoped_trigonal selenium contained in a geometrically controlled ph t_receptor - A photoreceptor with geometricall~ controlled photoconductive material, i.e.
undoped trigonal selenium, contained therein is prepared as follows:

2~3 The member contains 8 percent by volume undoped trigonal selenium. Into a 4 ounce clear glass bottle is added 2 ounces (vol.) 1/8 inch stainless steel shot, 4.5 grams o~
undoped trigonal selenium as prepared in Examples I or II and 18.75 ml of a 1:1 isopropyl alcohol/isobutylalcohol~ This is placed on a ball mill for 6 hours at lS0 RPM. To this slurry is added 14.4 grams of spray dried Flexcla ~, a polyester available from Goodyear, and 30 ml of a 1:1 isopropylalcohol/isobutyl-alcohol. This is ball milled for 18 hours at 150 RPM.
The slurry is filtered through a 100 mesh screen, then allowed to stand for 10 minutes to remove air bubbles. The slurry is coated on a 5 mil aluminum substrate with a 10 mil multiple clearance bar. This layer is dried for 3 hours at 50C. It is then fused for 20 minutes at 175C.
The trigonal selenium is in substantially particle-to-particle contact in said member in a multiplicity of interlocking paths or chains through the thickness of the layer. The undoped trigonal selenium paths or chains are present in a volume concentration, as mentioned, as 8 percent based on the volume of the layer.
The member is tested as illustrated in Figs. 5 and 6.
However, this member is charged with positive corona.
The undoped trigonal selenium containing member has a high dark discharge and an unstable PIDC as compared to members containing doped trigonal selenium as the photoconductive material.
~XAMPLE ~V
Fabricatio'n of dcp~ed trigonal selenium ontained in a geomet-rical'l controlled ph'otorec'ept'or - A phbtoreceptor with - --Y - -- .
geometrically controlled photoconductive material, i.e. doped trigonal selenium, contained therein is prepared as follows:

The member contains 8 percent by volume doped trigonal selenium. Into a 4 ounce clear glass bottle is added 2 ounces (vol.) 1/8 inch stainless steel shot, 4.5 grams of doped trigonal selenium as prepared in Examples III and 18.75 ml o~ a 1:1 isopropylalcohol/isobutylalcohol. This is placed on a ball mill for 6 hours at 150 RPM. To this slurry is added 14.4 grams of spray dried Flexcla ~, a polyester available from Goodyear, and 30 mil of a 1:1 isopropylalcohol/isobutylalcohol. ThiS is ball milled from 18 hours at 150 RPM.
The slurry is filtered through a 100 mesh screen, then allowed to stand for 10 minutes to remove air bubbles. The slurry is coated on a 5 mil aluminum substrate with a 10 mil multiple clearance bar. This layer is dried for 3 hours at 50C. It is then fused for 20 minutes at 175C.
The trigonal selenium is in substantailly particle-to-particle contact in said member in a multiplicity of interlocking paths or chains through the thickness of the layer. The doped trigonal selenium paths or chains are present in a volume concentration, as mentioned, as 8 percent based on the volume of the layer.
The member is tested as illustrated in Figs. 5 and 6.
However, this member is charged with positive corona. The doped trigonal selenium containing member has a low dark discharge and a stable PIDC as compared to members containing undoped trigonal selenium as the photoconductive material.

Claims (14)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An imaging device comprising a layer of particulate photoconductive material dispersed in an organic resinous binder said particulate photoconductive material consisting essentially of trigonal selenium treated with the hydroxide, carbonate, bicarbonate, acetate or selenite of a member of the group consisting of sodium, lithium, potassium, rubidium and cesium so as to contain from 0.01 to about 12.0% by weight of said member based on the weight of said trigonal selenium.

2. The device according to claim 1 wherein said member is sodium.

3. The device according to claim 1 wherein said member is present about 0.01 to about 1.0%.

4. The device according to claim 1 wherein the size of the particulate trigonal selenium is from about 0.01 micron to about 10 microns in diameter.

5. The device according to claim 4 wherein the size of the particulate trigonal selenium is from about 0.1 micron to about 0.5 micron in diameter.

6. The device according to claim 1 wherein the binder layer is overcoated with an electrically insulating organic resinous material.

7. An imaging device comprising a charge generation layer comprising a particulate photoconductive material consisting essentially of trigonal selenium dispersed in an organic resinous binder, said trigonal selenium being treated with the hydroxide, carbonate, bicarbonate, acetate or selenite of a member of the group consisting of sodium, lithium, potassium, rubidium and cesium so as to contain from 0.01 to about 12% by weight of said member based on the weight of said trigonal selenium and a contiguous charge transport layer, said photoconductive material exhibiting the capability of photogeneration of charge carriers and injection of said charge carriers and said charge transport layer being sub-stantially non-absorbing in the spectral region at which the photoconductive material generates and injects photogenerated charge carriers but being capable of supporting the injection of photogenerated charge carriers from said photoconductive material and transporting said charge carriers through said charge transport layer.

8. The device according to claim 7 wherein the photogenerated charge carriers are photogenerated holes.

9. The device according to claim 7 wherein the photogenerated charge carriers are photogenerated electrons.

10. The device according to claim 7 wherein said member is sodium.

11. The device according to claim 7 wherein said member is present in about 0.01 to about 1.0% by weight.

12. The device according to claim 7 wherein the size of the trigonal selenium is from about 0.01 micron to about 10 microns in diameter.

13. The device according to claim 12 wherein the size of the trigonal selenium is from about 0.1 micron to about 0.5 microns in diameter.

14. The device according to claim 7 wherein the charge transport layer is overcoated with an electrally insulating organic resinous material.