Electrophotographic photoconductor containing fluorenyl-azine derivatives as charge transport additives

A photoconductor for use in electrophotographic reproduction devices is disclosed. This photoconductor exhibits reduced room light and cycling fatigue without any corresponding negative impact on the sensitivity of the photoconductor. The photoconductor of the present invention includes specifically defined fluorenyl-azine derivatives in its charge transport layer. These materials have the formula: ##STR1## wherein R.sub.1 and R.sub.2 independently selected from C.sub.1 -C.sub.4 alkyl and phenyl, and R.sub.3 is selected from hydrogen, C.sub.1 -C.sub.4 alkyl, and phenyl.

TECHNICAL FIELD 
The present invention relates to an improved photoconductor, used in 
electrophotographic reproduction devices, having a charge generating layer 
and a charge transport layer, which exhibits reduced room light and 
cycling fatigue without negatively impacting on the sensitivity of the 
photoconductor. 
BACKGROUND OF THE INVENTION 
The present invention is a layered electrophotographic photoconductor, 
i.e., a photoconductor having a metal ground plane member on which a 
charge generation layer and a charge transport layer are coated, in that 
order. Although these layers are generally separate from each other, they 
may be combined into a single layer, which provides both charge generation 
and charge transport functions. Such a photoconductor may optionally 
include a barrier layer located between the metal ground plane member and 
the charge generation layer, and/or an adhesion-promoting layer located 
between the barrier (or ground plane member) and charge generation layer, 
and/or an overcoat layer on the top surface of the charge transport layer. 
In electrophotography, a latent image is created on the surface of an 
insulating, photoconducting material by selectively exposing an area of 
this surface to light. A difference in electrostatic charge density is 
created between the areas on the surface exposed and those unexposed to 
the light. The latent electrostatic image is developed into a visible 
image by electrostatic toners containing pigment components and 
thermoplastic components. The toners, which may be liquids or powders, are 
selectively attracted to the photoconductor surface, either exposed or 
unexposed to light, depending upon the relative electrostatic charge on 
the photoconductor surface and the toner. The photoconductor may be either 
positively or negatively charged, and the toner system similarly may 
contain negatively- or positively-charged particles. 
A sheet of paper or intermediate transfer medium is given an electrostatic 
charge opposite that of the toner and then passed close to the 
photoconductor's surface, pulling the toner from the photoconductor 
surface onto the paper or the transfer medium still in the pattern of the 
image developed from the photoconductor surface. A set of fuser rolls 
melts and fixes the toner on the paper, subsequent to direct transfer or 
indirect transfer when an intermediate transfer medium is used, producing 
the printed image. 
The electrostatic printing process, therefore, comprises an on-going series 
of steps in which the photoconductor surface is charged and discharged as 
the printing takes place. It is important to keep the charge voltage on 
the surface of the photoconductor relatively constant as different pages 
are printed to make sure that the quality of the images produced is 
uniform (cycling stability). If the charge/discharge voltage is changed 
significantly each time the drum is cycled, i.e., if there is fatigue or 
other significant change in the photoconductor surface, the quality of the 
pages printed will not be uniform and will not be satisfactory. 
Hydrazone derivatives, which have frequently been employed as charge 
transfer molecules and organic photoconductors for electrophotography, 
possess interesting photochemical properties which are known to connect 
closely with the so-called fatigue phenomenon of photoconductors. A good 
deal of research supports the fact that photoisomerization and 
photochemical reactions are responsible in large part for the fatigue 
phenomenon. For example, p-(diethylamino) benzaldehyde diphenyl hydrazone 
(DEH) undergoes a photochemically-induced unimolecular rearrangement to 
the indazole derivative, 
1-phenyl-3-(4-(diethylamino)-1-phenyl)-1,3-indazole. The following 
articles give an overview of the mechanism of photo-induced fatigue in 
electrophotographic conductors: J. Pacansky, et al., Chem. Mater. 
4:401(1992); T. Nakazawa, et al, Chem. Lett. 1992, 1125; and E. Matsuda, 
et al., Chem. Lett. 1992, 1129. 
In order to use hydrazones as charge transport molecules for 
electrophotographic applications, photo-induced fatigue has to be reduced 
to an acceptable level. There are two major paths to minimize 
photo-induced chemical changes in hydrazone molecules such that 
photo-induced fatigue of photoconductors can be improved: (1) introducing 
appropriate substitution on the hydrazone molecules to increase rigidity 
such that photo-induced cyclization or isomerization can be hindered; and 
(2) formulating with additives, e.g., a light absorber, in the charge 
transport layer to filter away the harmful wavelength light (See, for 
example, U.S. Pat. No. 4,362,798, Anderson, et al.). The former approach 
will inevitably increase the cost to produce the molecules as compared 
with the corresponding unsubstituted hydrazones. Therefore, the approach 
of current choice is the use of additives, such as Acetosol Yellow, to 
serve as a light filter. Although this approach is effective in reducing 
room light fatigue of the photoconductor to a certain degree, it also 
negatively effects the electrical properties of the photoreceptor by 
increasing discharge voltage and dark decay. 
Azines, which are the product of condensing the remaining NH.sub.2 of a 
hydrazone with a carbonyl compound, have been disclosed for use in 
electrophotographic applications, both as transport molecules and as 
dopants in charge transport layers. Several series of hydrazones and 
azines are disclosed as charge transport materials in DE3716982, 
JP62006262 and JP61209456. In addition, some azines have been taught to be 
used in combination with hydrazones in electrophotographic conductors 
(see, for example, JP61043752, JP61043753, and JP61043754). It is 
important to note that these azines are not the fluorenyl-azine 
derivatives used in the present invention. 
Fluorenyl-azines are known in the art. For example, 9-[p-(diethylamino) 
benzylidenehydrazono)] fluorene has been disclosed in JP57138644 and 
JP59195659 as a charge transport agent. 
U.S. Pat. No. 4,415,640, Goto, et al, issued Nov. 15, 1983, discloses 
flourenyl-azines of the type utilized in the present development. The 
materials are disclosed as charge transport materials, not as adjunct 
materials used together with another charge transport molecule (see, for 
example, column 6, lines 52-54; column 7, lines 30-32; and column 8, lines 
62-68). The use of these fluorenyl-azines as charge transport materials is 
taught to minimize photoconductor fatigue. 
It has now unexpectedly been found that addition to a DEH-containing 
charge-transport layer of a flourenyl-azine material provides elimination 
of room light fatigue and cycling fatigue in the resulting photoconductor. 
For example, a photoconductor containing a DEH-charge transport layer 
doped with 2-5% azine, exhibits no fatigue after four hours of fluorescent 
light exposure, while the same photoconductor containing the standard 
Acetosol Yellow filtering agent exhibits negative fatigue. Increasing the 
Acetosol Yellow concentration in the charge transport layer, results in 
negative affects on the sensitivity of the photoconductor and dark decay, 
while no such effects are observed with the azine material. 
SUMMARY OF THE INVENTION 
The present invention relates to an electrophotographic imaging member 
comprising a charge transport layer comprised of a hydrazone charge 
transport molecule, such as p-(diethylamino) benzaldehyde diphenyl 
hydrazone (DEH), a polymeric binder, and an additive having the formula: 
##STR2## 
wherein R.sub.1 and R.sub.2 are independently selected from C.sub.1 
-C.sub.4 alkyl and phenyl, and R.sub.3 is selected from hydrogen, C.sub.1 
-C.sub.4 alkyl and phenyl. 
More specifically, the present invention relates to an electrophotographic 
member comprising: 
(a) a ground plane member; 
(b) a charge generating layer carried by said ground plane member 
comprising an effective amount of a photosensitive dye dispersed in a 
binder; and 
(c) a charge transport layer carried by said charge generating layer 
comprising from about 25% to about 65% by weight of a hydrazone charge 
transport molecule, such as DEH; from about 34.5% to about 65% by weight 
of a polymeric binder; and from about 0.5% to about 10% by weight of an 
additive having the formula: 
##STR3## 
wherein R.sub.1 and R.sub.2 are independently selected from C.sub.1 
-C.sub.4 alkyl and phenyl, and R.sub.3 is selected from hydrogen, C.sub.1 
-C.sub.4 alkyl and phenyl. 
As used herein, all percentages, ratios and parts are "by weight", unless 
otherwise specified. 
DETAILED DESCRIPTION OF THE INVENTION 
Photoconductors of the present invention find utility in 
electrophotographic reproduction devices, such as copiers and printers, 
and may be generally characterized as layered photoconductors wherein one 
layer (the charge generating layer) absorbs light and, as a result, 
generates an electrical charge carrier, while a second layer (the charge 
transport layer) transports the charged carriers to the exposed surface of 
the photoconductor. 
While these devices frequently have separate charge generation and charge 
transport layers with the charge transport layer being overlaid on the 
charge generating layer, it is also possible to combine the charge 
generator and charge transport functions into a single layer in the 
photoconductor. 
In the photoconductor structure, a substrate, which may be flexible (such 
as a flexible web or a belt) or inflexible (such as a drum), is uniformly 
coated with a thin layer of metallic aluminum. The aluminum layer 
functions as an electrical ground plane. In a preferred embodiment, the 
aluminum is anodized which turns the aluminum surface into a thicker 
aluminum oxide surface (having a thickness of about 2 to about 12.mu., 
preferably from about 4 to about 7.mu.). The ground plane member may be a 
metallic plate (made, for example, from aluminum or nickel), a metallic 
drum or a foil, a plastic film on which, for example, aluminum, tin oxide 
or indium oxide is vacuum-evaporated, or a conductive substance-coated 
paper, plastic film or drum. 
The aluminum layer is then coated with a thin, uniform thickness 
charge-generating layer comprising a photosensitive dye material dispersed 
in a binder. Finally, the uniform thickness charge transport layer is 
coated onto the charge generating layer. The charge transport layer 
comprises a thermoplastic film-forming binder, a hydrazone charge 
transport molecule, and an effective amount of a specific fluorenyl-azine 
additive material. 
In the case of a single layer structure, the photosensitive layer comprises 
a charge generating material, a hydrazone charge transport material, a 
binder resin, and the fluorenyl-azine material. 
The thickness of the various layers in the structure is important and is 
well known to those skilled in the art. In an exemplary conductor, the 
ground plane layer has a thickness of from about 0.01 to about 0.07.mu.; 
the charge generating layer has a thickness of from about 0.5 to 5.0.mu., 
preferably from about 0.1 to 2.0.mu., most preferably from about 0.1 to 
about 0.5.mu.; and the charge transport layer has a thickness of from 
about 10 to about 25.mu., preferably from about 20 to about 25.mu.. If a 
barrier layer is used between the ground plane and the charge generating 
layer, it has a thickness of from about 0.05 to 2.0.mu.. Where a single 
charge generating/charge transport layer is used, that layer generally has 
a thickness of from about 10 to about 25.mu.. 
In forming a charge generating layer utilized in the present invention, a 
fine dispersion of a small particle photosensitive dye material is formed 
in the binder material, and this dispersion is coated onto the ground 
plane member. This is generally done by preparing the dispersion 
containing the photosensitive dye and the binder in a solvent, coating the 
dispersion onto the ground plane member, and drying the coating. 
Any organic photosensitive dye material known in the art to be useful in 
photoconductors may be used in the present invention. Examples of such 
materials belong to any of the following classes: 
(a) polynuclear quinones, e.g., anthanthrones; 
(b) quinacridones; 
(c) naphthalene 1, 4, 5, 8-tetracarboxylic acid-derived pigments, such as 
perinones; 
(d) phthalocyanines and naphthalocyanines, e.g., H.sub.2 -phthalocyanine in 
X crystaline form (see, for example, U.S. Pat. No. 3,357,989); metal 
phthalocyanines and naphthalocyanines (including those having additional 
groups binded to the central metal); 
(e) indigo- and thioindigo dyes; 
(f) benzothioxanthene derivatives; 
(g) perylene 3, 4, 9, 10-tetracarboxylic acid-derived pigments, including 
condensation products with amines (perylene diimides) and o-diamines 
(perylene bisimidazoles); 
(h) polyazo-pigments, including bisazo-, trisazo-, and 
tetrakisazo-pigments; 
(i) squarylium dyes; 
(j) polymethine dyes; 
(k) dyes containing quinazoline groups (see, for example, U.K. Patent 
Specification 1,416,602); 
(l) triarylmethane dyes; 
(m) dyes containing 1, 5-diamino-anthraquinone groups; 
(n) thiapyrylium salts; 
(o) azulenium salts; 
(p) pyrrolo-pyrrole pigments. 
Such materials are described in greater detail in U.S. Pat. No. 5,190,817, 
Terrell, et al, issued Mar. 2, 1993, incorporated herein by reference. 
The preferred photosensitive dyes for use in the present invention are 
phthalocyanine dyes, which are well-known to those skilled in the art. 
Examples of such materials are taught in U.S. Pat. No. 3,816,118, Byrne, 
issued Jun. 11, 1974, incorporated herein by reference. Any suitable 
phthalocyanine may be used to prepare the charge generating layer portion 
of the present invention. The phthalocyanine used may be in any suitable 
crystalline form. It may be unsubstituted either (or both) in the 
six-membered aromatic rings and at the nitrogens of the five-membered 
rings. Useful materials are described, and their syntheses given, in Moser 
& Thomas, Phthalocyanine Compounds, Reinhold Publishing Company 1963, 
incorporated herein by reference. Particularly preferred phthalocyanine 
materials are those in which the metal central in the structure is 
titanium (i.e., titanyl phthalocyanines) and metal-free phthalocyanines. 
The metal-free phthalocyanines are also particularly preferred, especially 
the X-crystalline form, metal-free phthalocyanines. Such materials are 
disclosed in U.S. Pat. No. 3,357,989, Byrne, et al, issued Dec. 12, 1967; 
U.S. Pat. No. 3,816,118, Byrne, issued Jun. 11, 1974; and U.S. Pat. No. 
5,204,200, Kobata, et al, issued Apr. 20, 1993, all of which are 
incorporated herein by reference. The X-type non-metal phthalocyanine is 
represented by the formula: 
##STR4## 
Such materials are available in an electrophotographic grade of very high 
purity, for example, under the trade name Progen-XPC from Zeneca Colours 
Company. 
As the binder, a high molecular weight polymer having hydrophobic 
properties and good film-forming properties for an electrically insulating 
film is preferably used. These high molecular weight film-forming polymers 
include, for example, the following materials, but are not limited 
thereto: polycarbonates, polyesters; methacrylic resins, acrylic resins, 
polyvinyl chlorides, polyvinylidene chlorides, polystyrenes, 
polyvinylbutyrals, ester-carbonate copolymers, polyvinyl acetates, 
styrene-butadiene copolymers, vinylidene chloride-acrylonitrile 
copolymers, vinyl chloride-vinyl acetate copolymers, vinyl chloride-vinyl 
acetate-maleic anhydride copolymers, silicone resins, silicone alkyd 
resins, phenyl-formaldehyde resins, styrene-alkyd resins, and 
poly-N-vinylcarbazoles. These binders can be used in the form of a single 
resin or in a mixture of two or more resins. 
Preferred materials include the bisphenol A and bisphenol A--bisphenol TMC 
copolymers described below, medium molecular weight polyvinyl chlorides, 
polyvinylbutyrals, ester-carbonate copolymers, and mixtures thereof. The 
polyvinyl chloride compounds useful as binders have an average molecular 
weight (weight average) of from about 25,000 to about 300,000, preferably 
from about 50,000 to about 125,000, most preferably about 80,000. The PVC 
material may contain a variety of substituents including chlorine, 
oxirane, acrylonitrile or butyral, although the preferred material is 
unsubstituted. Polyvinyl chloride materials useful in the present 
invention are well-known to those skilled in the art. Examples of such 
materials are commercially available as GEON 110X426 from the GEON 
Company. Similar polyvinyl chlorides are also available from the Union 
Carbide Corporation. 
Bisphenol A, having the formula given below, is a useful binder herein: 
##STR5## 
wherein each X is a C.sub.1 -C.sub.4 akyl and n is from about 20 to about 
200. 
The bisphenol copolymer binders referred to above are copolymers of 
bisphenol A and bisphenol TMC. This copolymer has the following formula: 
##STR6## 
wherein a and b are selected such that the weight ratio of bisphenol A to 
bisphenol TMC is from about 30:70 to about 70:30, preferably from about 
35:65 to about 65:35, most preferably from about 40:60 to about 60:40. The 
molecular weight (weight average) of the polymer is from about 10,000 to 
about 100,000, preferably from about 20,000 to about 50,000, most 
preferably from about 30,000 to about 40,000. 
In forming the charge-generating layer, a mixture of the photosensitive dye 
is formed in the binder material. The amount of photosensitive dye used is 
that amount that is effective to provide the charge generation function in 
the photoconductor. This mixture generally contains from about 10 parts to 
about 50 parts, preferably from about 10 parts to about 30 parts, most 
preferably about 20 parts of the photosensitive dye component, and from 
about 50 parts to about 90 parts, preferably from about 70 parts to about 
90 parts, most preferably about 80 parts of the binder component. 
The photosensitive dye-binder mixture is then mixed with a solvent or 
dispersing medium for further processing. The solvent selected should: (1) 
be a true solvent for high molecular weight polymers; (2) be non-reactive 
with all components; and (3) have low toxicity. Examples of dispersing 
media/solvents that may be utilized in the present invention, used either 
alone or in combination with preferred solvents, include hydrocarbons, 
such as hexane, benzene, toluene, and xylene; halogenated hydrocarbons, 
such as methylene chloride, methylene bromide, 1,2-dichloroethane, 
1,1,2-trichloroethane, 1,1,1-trichloroethane, 1,2-dichloropropane, 
chloroform, bromoform, and chlorobenzene; ketones, such as acetone, 
methylethyl ketone, and cyclohexanone; esters, such as ethyl acetate and 
butyl acetate; alcohols, such as methanol, ethanol, propanol, butanol, 
cyclohexanol, heptanol, ethylene glycol, methyl cellosolve, ethyl 
cellosolve, and cellosolve acetate, and derivatives thereof; ethers and 
acetals, such as tetrahydrofuran, 1,4-dioxane, furan and furfural; amines, 
such as pyridine, butylamine, diethylamine, ethylene diamine, and 
isopropanolamine; nitrogen compounds, including amides, such as N, 
N-dimethylformamide; fatty acids and phenols; and sulfur and phosphorous 
compounds, such as carbon disulfide and triethylphosphate. The preferred 
solvents for use in the present invention are methylethyl ketone, 
methylene chloride, cyclohexanone and tetrahydrofuran (THF). The mixtures 
formed include from about 1% to about 50%, preferably from about 2% to 
about 10%, most preferably about 5%, of the photosensitive dye/binder 
mixture, and from about 50% to about 99%, preferably from about 90% to 
about 98%, most preferably about 95%, of the solvent/dispersing medium. 
The entire mixture is then ground, using a conventional grinding 
mechanism, until the desired dye particle size is reached and is dispersed 
in the mixture. The organic pigment may be pulverized into fine particles 
using, for example, a ball mill, homogenizer, paint shaker, sand mill, 
ultrasonic disperser, attritor or sand grinder. The preferred device is a 
sand mill grinder. The photosensitive dye has a particle size (after 
grinding) ranging from sub-micron (e.g., about 0.01.mu.) to about 5.mu., 
with a particle size of from about 0.05.mu. to about 0.5.mu. being 
preferred. The mixture may then be "let down" or diluted with additional 
solvent to from about 2% to about 5% solids , providing a viscosity 
appropriate for coating, for example, by dip-coating. 
The charge-generating layer is then coated onto the ground plan member. The 
dispersion from which the charge generating layer is formed is coated onto 
the ground plane member using methods well-known in the art, including 
dip-coating, spray coating, blade coating or roll coating, and is then 
dried. The preferred method for use in the present invention is dip 
coating. The thickness of the charge generating layer formed should 
preferably be from about 0.1 to about 2.0.mu., preferably about 0.5.mu.. 
The thickness of the layer formed will depend upon the percent solids of 
the dispersion into which the ground plane member is dipped, as well as 
the time and temperature of the process. Once the ground plane member has 
been coated with the charge-generating layer, it is allowed to dry for a 
period of from about 10 to about 100 minutes, preferably from about 30 to 
about 60 minutes, at a temperature of from about 60.degree. C. to about 
160.degree. C., preferably about 100.degree. C. 
The charge transport layer is then prepared and coated on the ground plane 
member so as to cover the charge generating layer. The charge transport 
layer is formed from a solution containing a hydrazone charge transport 
molecule in a thermoplastic film-forming binder, including therein a 
specifically defined group of fluorenyl-azine materials, coating the 
solution onto the charge-generating layer and drying the coating. 
In principle, a large class of known whole or electron transport molecules 
may be used in the transport layer of an electrophotographic 
photoconductor. However, since the purpose the present invention is to 
eliminate the fatigue problems seen when hydrazone materials are used as 
the charge transport molecule, the charge transport molecule used in the 
present invention is selected from the class of hydrazone materials having 
the following general formula: 
##STR7## 
wherein R.sup.1, R.sup.8 and R.sup.9, independently from each other, 
represent a hydrogen or a lower alkyl (C.sub.1 -C.sub.4), and R.sup.15 and 
R.sup.16, independently from each other, represent a lower alkyl (C.sub.1 
-C.sub.4) or aryl. 
The most preferred charge transport molecule is known as DEH, having the 
chemical name p-diethylaminobenzaldehyde-N,N-diphenylhydrazone. This 
compound has the following structural formula: 
##STR8## 
The binders used in the charge transport layer of the present invention are 
the binders described above which are used in the charge generating layer. 
The charge transport layer also contains specifically defined 
fluorenyl-azine materials having the following formula: 
##STR9## 
wherein R.sub.1 and R.sub.2 are independently selected from C.sub.1 
-C.sub.4 alkyl and phenyl, and R.sub.3 is selected from hydrogen, C.sub.1 
-C.sub.4 alkyl, and phenyl. In preferred compounds, R.sub.1 and R.sub.2 
are selected from ethyl and phenyl, while R.sub.3 is selected from 
hydrogen and phenyl. Particularly preferred compounds are the ones in 
which both R.sub.1 and R.sub.2 are ethyl and R.sub.3 is hydrogen, as well 
as the one in which both are R.sub.1 and R.sub.2 are phenyl and R.sub.3 is 
hydrogen. 
9-(p-diethylaminobenzylidenehydrazono) fluorene (R.sub.1 =R.sub.2 =ethyl 
and R.sub.3 =hydrogen) may be synthesized in the following manner. A 
mixture of 9H-fluorenohydrazone (19.4 g, 0.1 mol), 
p-diethylaminobenzaldehyde (19.4 g, 0.11 mol), benzene (200 ml) and a 
catalytic amount of p-tolylsulfonic hydrate is stirred at ambient 
temperature for about three hours. Water (100 ml) is then added. The 
organic layer is separated, washed with water twice, washed with brine, 
and dried over sodium sulfate. The solvent is removed and an orange solid 
recrystallized from a mixture of acetone and hexane to yield the title 
compound (orange needles at 92%). 9-(p-diphenylaminobenzylidenehydrazono) 
fluorene (R.sub.1 =R.sub.2 =phenyl and R.sub.3 =hydrogen) may be prepared 
in an analogous manner. 
The mixture of hydrazone charge transport molecule (as disclosed), binder 
and fluorenyl-azine derivatives having a composition of from about 25% to 
about 65%, preferably from about 30% to about 50%, most preferably from 
about 35% to about 45% of the hydrazone charge transport molecule; from 
about 34.5% to about 65%, preferably from about 50% to about 65%, most 
preferably from about 55% to about 65% of the binder; and from about 0.5% 
to about 10%, preferably from about 1% to about 5%, most preferably from 
about 2% to about 5% of the fluorenyl-azine derivative is then formulated. 
The amount of charge transport molecule utilized is that amount that is 
effective to perform the charge transport function in the 
photoconconductor. The binders are used, both in the charge transport and 
charge generating layers, in an amount effective to perform their binder 
function. Fluorenyl-azine materials are preferably added to the organic 
solvent before the other components are added. 
The mixture is added to a solvent, such as those discussed above for use in 
forming the charge generation layer. Preferred solvents are THF, 
cyclohexanone, and methylene chloride. It is preferred that the solution 
contain from about 10% to about 40%, preferably about 25% of the 
binder/transport molecule/fluorenyl-azine mixture, and from about 60% to 
about 90%, preferably about 75% of the solvent. The charge transport layer 
is then coated onto the charge generating layer and the ground plane 
member using any of the conventional coating techniques discussed above. 
Dip coating is preferred. The thickness of the charge transport layer is 
generally from about 10 to about 25.mu., preferably from about 20 to about 
25.mu.. The percentage of solids in the solution, viscosity, the 
temperature of the solution, and the withdrawal speed control the 
thickness of the transport layer. The layer is usually heat dried for from 
about 10 to about 100 minutes, preferably from about 30 to about 60 
minutes, at a temperature of from about 60.degree. C. to about 160.degree. 
C., preferably about 100.degree. C. Once the transport layer is formed on 
the electrophotographic member, pretreatment of the layer by either using 
UV curing or thermal annealing is preferred in that it further reduces the 
rate of transport molecule leaching, especially at higher transport 
molecule concentrations. 
In addition to the layers discussed above, an undercoat layer may be placed 
between the ground plane member (substrate) and the charge generating 
layer. This is essentially a primer layer which covers over any 
imperfections in the substrate layer, and improves the uniformity of the 
thin charge layer formed. Materials that may be used to form this 
undercoat layer include epoxy, polyamide and polyurethane. It is also 
possible to place an overcoat layer (i.e., a surface protecting layer) on 
top of the transport layer. This protects the charge transport layer from 
wear and abrasion during the printing process. Materials which may be used 
to form this overcoat layer include polyurethane, phenolic, polyamide, and 
epoxy resins. These structures are well-known to those skilled in the art. 
The following example illustrates the photoconductors of the present 
invention. The example is intended to be illustrative only and not 
limiting of the scope of the present invention.

EXAMPLE 
In order to provide a basis of comparison, drum and web photoconductors, 
which contain DEH with Acetosol Yellow in the charge transport layer and 
DEH with fluorenyl-azine derivative in the charge transport layer are made 
and tested under similar conditions. 
Formulation 
The charge generation (CG) dispersion consists of titanyl phthalocyanine 
and polyvinylbutyral (BX-55Z, Sekisui Chemical Co.) in a weight ratio of 
45/55 in a mixture of 2-butanone and cyclohexanone. The CG dispersion is 
dip coated on the aluminum substrate and dried at 100.degree. C. for 15 
minutes or blade coated on mylar film to give a thickness less than 1.mu., 
and more preferably, 0.2-0.3.mu.. 
A standard charge transport formulation (CT) containing DEH is prepared in 
the following manner. DEH (27.0 g), bisphenol-A (39.7 g, Makrolon 5208, 
Bayer AG) and Acetosol Yellow (0.48 g) are mixed in a solvent mixture 
which includes tetrahydrofuran and 1,4-dioxane. The CT layer is dip coated 
on the CG coated drum or blade coated on the CG coated film, which are 
then dried at 100.degree. C. for 60 minutes. Similar charge transport 
layers were formulated as above, except that in place of the Acetosol 
Yellow, azine-1 (0.48 g, R.sub.1 =R.sub.2 =ethyl, R.sub.3 =hydrogen) and 
azine-2 (0.48 g, R.sub.1 =R.sub.2 =phenyl, R.sub.3 =hydrogen) are used in 
place of Acetosol Yellow. 
Testing 
The layered photoconductors, prepared as described above, are then tested 
either by parametric tester or by Shogun tester. The web films are 
measured for initial electrical properties with and without room light 
exposure for a certain period of time. Cycling fatigue is evaluated by 
measuring the electricals of the samples directly before and after cycling 
in the Shogun tester. The light fatigue of the drums is induced by 
exposing the drum to a fluorescent light source. The results of the 
testing is summarized in the following table: 
______________________________________ 
Initial Initial 
V.sub.0.25 
2-hr light 
Fatigue 
V.sub.res 
2-hr light 
Fatigue 
Drum (-V) V.sub.0.25 (-V) 
(-V) (-V) V.sub.res (-V) 
(-V) 
______________________________________ 
Acetosol 
386 432 46 166 275 109 
Yellow 
Azine 1 
402 433 31 167 217 50 
Azine 2 
395 381 -14 172 171 -1 
______________________________________ 
The azine derivatives, as defined in the present application, clearly acted 
to reduce room light and cycling fatigue without negatively impacting on 
the sensitivity of the photoconductor itself.