Generator layer sensitization through transport layer doping

An electrophotographic imaging member including PA1 a supporting substrate, PA1 an undercoat layer, PA1 a charge generating layer comprising PA2 photoconductive pigment particles, PA2 film forming binder and PA1 a charge transport layer formed from a coating solution, the coating solution comprising charge transporting molecules, the charge transporting molecules comprising a major amount of a first charge transport molecule comprising an alkyl derivative of an arylamine and a minor amount of second transport molecule comprising an alkyloxy derivative of an arylamine. the charge generating layer being located between the substrate and the charge transport layer. A process for fabricating this imaging member is also disclosed.

BACKGROUND OF THE INVENTION 
This invention relates in general to electrophotography and more 
specifically, to an improved electrophotographic imaging member having an 
a more sensitive charge generating layer through transport layer doping. 
In the art of electrophotography, an electrophotographic plate comprising a 
photoconductive insulating layer on a conductive layer is imaged by first 
uniformly electrostatically charging surface of the photoconductive 
insulating layer. The plate is then exposed to a pattern of activating 
electromagnetic radiation such as light, which selectively dissipates the 
charge in the illuminated areas of the photoconductive insulating layer 
while leaving behind an electrostatic latent image in the non-illuminated 
areas. This electrostatic latent image may then be developed to form a 
visible image by depositing finely divided electroscopic toner particles 
on the surface of the photoconductive insulating layer. The resulting 
visible toner image can be transferred to a suitable receiving member such 
as paper. This imaging process may be repeated many times with reusable 
photoconductive insulating layers. 
Electrophotographic imaging members are usually multilayered photoreceptors 
that comprise a substrate support, an electrically conductive layer, an 
optional hole blocking layer, an adhesive layer, a charge generating 
layer, and a charge transport layer in either a flexible belt form or a 
rigid drum configuration. For most multilayered flexible photoreceptor 
belts, an anti-curl layer is usually employed on the back side of the 
substrate support, opposite to the side of the electrically active layers, 
to render the desired photoreceptor flatness. One type of multilayered 
photoreceptor comprises a layer of finely divided particles of a 
photoconductive inorganic compound dispersed in an electrically insulating 
organic resin binder. In U.S. Pat. No. 4,265,990 a layered photoreceptor 
is disclosed having separate charge generating (photogenerating) and 
charge transport layers. The charge generating layer is capable of 
photogenerating holes and injecting the photogenerated holes into the 
charge transport layer. The photogenerating layer utilized in multilayered 
photoreceptors include, for example, inorganic photoconductive particles 
or organic photoconductive particles dispersed in a film forming polymeric 
binder. Inorganic or organic photoconductive material may be formed as a 
continuous, homogeneous photogenerating layer. Many suitable 
photogenerating materials known in the art can be utilized, if desired. 
As more advanced, higher speed electrophotographic copiers, duplicators and 
printers were developed, degradation of image quality was encountered 
during extended cycling. Moreover, complex, highly sophisticated, 
duplicating and printing systems employed flexible photoreceptor belts, 
operating at very high speeds, have also placed stringent mechanical 
requirements and narrow operating limits as well on photoreceptors. 
Advanced photoreceptors have excellent electrical and mechanical 
properties. Some have very stable electrical performance over long life, 
for example, up to at least 200K cycles. However, many photoreceptors 
exhibit fluctuations in photosensitivity from batch to batch even where 
every effort is made to ensure identical processing conditions such as the 
milling of charge generation layer pigment dispersion under the same 
conditions. For example, when extrinsic photosensitive pigments are 
employed, the photogenerated carriers must be brought out of the surface 
of pigment particles before the carriers recombine and move into the 
charge transport layer under the applied electric field. This process 
slows down considerably in binders containing dispersed extrinsic 
photosensitive pigment particles such as benzimidazole perylene particles, 
especially at low applied electric fields. Under these conditions, the 
photoinduced discharged curve (PIDC) becomes softer at low field. Such a 
soft PIDC curve requires more powerful, bulky and expensive laser light 
sources for imaging in an electrophotographic printer or duplicator. The 
expression photoinduced discharged curve (PIDC) as employed herein is 
defined as a relationship between the potential as a function of exposure 
and is a measure of the sensitivity of the device. It generally represents 
the supply efficiency (number carriers injected from the generator layer 
into the transport layer per incident photon) as a function of the field 
across the device. 
INFORMATION DISCLOSURE STATEMENT 
U.S. Pat. No. 5,863,686 to Yuh et al., issued Jan. 26, 1999--An 
electrophotographic member comprising a supporting substrate, an undercoat 
layer doped with a donor molecule, a charge generator layer comprising 
photoconductive pigment particles, film forming binder and a donor 
molecule dissolved in the film forming binder and a charge transport layer 
the charge generating layer being located between the substrate and the 
charge transport layer. The donor molecule dissolved in the film forming 
binder comprising poly vinyl butyral is selected from the group consisting 
of N,N'-diphenyl-N,N'bis(3-hydroxyphenyl)-[1,1'-biphenyl]-4,4'diamine, 
N,N'-di(3-methoxyphenyl)-N,N'-diphenyl -[1,1'-biphenyl]-4,4'diamine and 
mixtures thereof. 
U.S. Pat. No. 5,992,498 to Yuh et al., issued Jul. 13, 1999--An 
electrophotographic member including a supporting substrate, an undercoat 
doped with an acceptor molecule, a charge generator layer comprising 
photoconductive pigment particles, film forming binder and an acceptor 
molecule represented by a specific structure dissolved in the film forming 
is binder and a charge transport layer. 
U.S. Pat. No. 5,437,950 issued to Yu et al. on Aug. 1, 1995--An 
electrophotographic imaging member is disclosed including a substrate, an 
optional blocking layer, an optional thermoplastic adhesive interface 
layer, a thin charge generation layer comprising pigment particles 
dispersed in a film forming polymer binder having dissolved or molecularly 
dispersed therein an electron accepting/transporting compound, and a 
charge transport layer. 
U.S. Pat. No. 4,725,518 issued to Carmichael et al. on Feb. 16, 1988--An 
electrophotographic imaging device comprising a charge generating layer 
and charge transport layer is disclosed in which an aromatic amine 
compound and a protonic acid or Lewis acid is added to the charge 
transport layer to control the dark development and background potentials 
of the imaging device. 
U.S. Pat. No. 5,342,719 to Pai et al., on Aug. 30, 1994--an 
electrophotographic imaging member including a charge generator layer, a 
charge transport layer with a charge transport molecules and as 
sensitizing additive or dopant a hydroxy derivative of the transport 
molecule. 
U.S. Pat. No. 5,356,741 issued to Carmichael et al. in Oct. 10, 1994--An 
electrophotographic imaging device comprising a charge generating layer 
and charge transport layer is disclosed involving the incorporation of at 
least weak acid or a weak base and the conjugated salt of the weak acid or 
weak base to reduce variations in the dark development potential an the 
background potential of the imaging device. 
U.S. Pat. No. 4,874,682 issued to Scott et al. on Oct. 1989--An 
electrophotographic imaging device comprising a charge generating layer 
and charge transport layer is disclosed in which a monomeric or polymeric 
non-volatile basic amine is incorporated in the charge transport layer to 
eliminate the fatigue effects of acids. 
U.S. Pat. No. 5,792,582 to Yuh et al., issued August 11, 1998--An 
electrophotographic member including a supporting substrate, a charge 
generator layer comprising photoconductive pigment particles, a first film 
forming binder and 2,6-di-tert-butyl-4-methylphenol, and a charge 
transport layer. 
Thus, there is a continuing need for photoreceptors having improved 
sensitivity, and for tools or controls to adjust the sensitivity of the 
photoreceptor to meet consistently meet exacting specifications in spite 
of batch to batch variations in the quality of the various component 
materials, especially the photoconductive pigment. 
BRIEF SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide an improved 
electrophotographic imaging member and process for fabricating the imaging 
member. 
It is another object of the present invention to provide an improved 
electrophotographic imaging member having greater sensitivity. 
It is yet another object of the present invention to provide a quality 
control tool or solution to bring the sensitivity of an 
electrophotographic imaging member within narrow specifications in spite 
of quality variations between component materials from batch to batch, 
especially photoconductive pigments. 
It is still another object of the present invention to provide a quality 
control tool or knob to bring the sensitivity of an electrophotographic 
imaging member within narrow specifications without major changes in the 
dispersion quality of charge generator layer dispersion or without any 
major changes to the fabrication process of the device. 
The foregoing objects and others are accomplished in accordance with this 
invention by providing an electrophotographic imaging member comprising 
a supporting substrate, 
an undercoat layer, 
a charge generating layer comprising 
photoconductive pigment particles, 
film forming binder and 
a charge transport layer comprising charge transporting molecules, the 
charge transporting molecules comprising a major amount of a first charge 
transport molecule comprising an alkyl derivative of an arylamine and a 
minor amount of second transport molecule comprising an alkyloxy 
derivative of an arylamine, 
the charge generating layer being located between the substrate and the 
charge transport layer. 
This imaging member may be fabricated by 
forming an undercoat layer from a coating solution, 
forming a charge generating layer from a coating dispersion comprising 
photoconductive pigment particles dispersed in 
a solution of a film forming binder dissolved in a solvent for the binder, 
forming a charge transport layer from a coating solution comprising 
charge transport molecules, 
a film forming binder, 
solvent for the binder, and 
drying the coating to form a charge transport layer overlying the charge 
generating layer, the charge transporting molecules comprising a major 
amount of a first charge transport molecule comprising an alkyl derivative 
of an arylamine and a minor amount of second transport molecule comprising 
an alkyloxy derivative of an arylamine. 
Generally, electrophotographic imaging members comprise a supporting 
substrate, having an electrically conductive surface or coated with an 
electrically conductive layer, an optional charge blocking layer, an 
undercoat layer, a charge generating layer, a charge transport layer and 
an optional overcoating layer. 
The substrate may be opaque or substantially transparent and may comprise 
numerous suitable materials having the required mechanical properties. 
Accordingly, this substrate may comprise a layer of an electrically 
non-conductive or conductive material such as an inorganic or an organic 
composition. The electrically conductive layer may comprise the entire 
supporting substrate or merely be present as a coating on an underlying 
rigid or flexible web member. Any suitable electrically conductive 
material may be utilized. Typical electrically conductive materials 
include, for example, aluminum, titanium, nickel, chromium, brass, gold, 
stainless steel, copper iodide, and the like. When the conductive layer is 
to be flexible, it may vary in thickness over substantially wide ranges 
depending on the desired use of the electrophotoconductive member. 
Accordingly, the conductive layer can generally range in thicknesses of 
from about 50 Angstrom units to about 150 micrometers. As electrically 
non-conducting materials there may be employed various thermoplastic and 
thermoset resins known for this purpose including polyesters, 
polycarbonates, polyamides, polyurethanes, and the like. The substrate may 
have any suitable shape such as, for example, a flexible web, rigid 
cylinder, sheet and the like. 
The thickness of a flexible substrate support depends on numerous factors, 
including economical considerations, and thus this layer for a flexible 
belt may be of substantial thickness, for example, over 200 micrometers, 
or of minimum thickness less than 50 micrometers, provided there are no 
adverse affects on the final photoconductive device. 
Any suitable hole blocking layer capable of forming an electronic barrier 
to holes between the adjacent photoconductive layer and the underlying 
conductive layer may be utilized. A hole blocking layer may comprise any 
suitable material. Typical hole blocking layers utilized for the 
negatively charged photoreceptors may include, for example, Luckamide, 
hydroxy alkyl methacrylates, nylons, gelatin, hydroxyl alkyl cellulose, 
organopolyphosphazines, organosilanes, organotitanates, organozirconates, 
silicon oxides, zirconium oxides, and the like. Preferably, the hole 
blocking layer comprises nitrogen containing siloxanes. Typical nitrogen 
containing siloxanes are prepared from coating solutions containing a 
hydrolyzed silane. Typical hydrolyzable silanes include 3-aminopropyl 
triethoxysilane, (N,N'-dimethyl 3-amino) propyl triethoxysilane, 
N,N-dimethylamino phenyl triethoxy silane, N-phenyl aminopropyl trimethoxy 
silane, trimethoxy silylpropyldiethylene triamine and mixtures thereof. 
During hydrolysis of the amino silanes described above, the alkoxy groups 
are replaced with hydroxyl group. An especially preferred blocking layer 
comprises a reaction product between a hydrolyzed silane and the oxidized 
surface of an underlying conductive layer which inherently forms on the 
surface of conductive a metal layer when exposed to air after deposition. 
This combination reduces spots at time 0 and provides electrical stability 
at low RH. The imaging member is prepared by depositing on the conductive 
layer of a coating of an aqueous solution of the hydrolyzed silane at a pH 
between about 4 and about 10, drying the reaction product layer to form a 
siloxane film and applying electrically active layers, such as a 
photogenerator layer and a hole transport layer, to the siloxane film. 
The blocking layer may be applied by any suitable conventional technique 
such as spraying, dip coating, draw bar coating, gravure coating, silk 
screening, air knife coating, reverse roll coating, vacuum deposition, 
chemical treatment and the like. For convenience in obtaining thin layers, 
the blocking layers are preferably applied in the form of a dilute 
solution, with the solvent being removed after deposition of the coating 
by conventional techniques such as by vacuum, heating and the like. This 
siloxane coating is described in U.S. Pat. No. 4,464,450, the disclosure 
of thereof being incorporated herein in its entirety. After drying, the 
siloxane reaction product film formed from the hydrolyzed silane contains 
larger molecules. The reaction product of the hydrolyzed silane may be 
linear, partially crosslinked, a dimer, a trimer, and the like. 
A preferred charge blocking layer may be fabricated from a solution of 
zirconium butoxide and gamma-amino propyl tri-methoxy silane in a suitable 
solvent such as anisisopropyl alcohol, butyl alcohol and water mixture. 
Generally, a preferred solution comprises between about 70 and about 90 by 
weight of zirconium butoxide and between about 30 and about 10 by weight 
of gamma-amino propyl tri-methoxy silane, based on the total weight of 
solids in the solution. 
The blocking layer should be continuous and have a thickness of less than 
about 0.5 micrometer because greater thicknesses may lead to undesirably 
high residual voltage. A blocking layer of between about 0.005 micrometer 
and about 0.3 micrometer (50 Angstroms-3000 Angstroms) is preferred 
because charge neutralization after the exposure step is facilitated and 
optimum electrical performance is achieved. A thickness of between about 
0.03 micrometer and about 0.06 micrometer is preferred for metal oxide 
layers for optimum electrical characteristics. 
Any suitable undercoat layer may be applied to the charge blocking layer. 
Undercoat layer materials are well known in the art. Typical undercoat 
layer materials include, for example, polyesters, MOR-ESTER 49,000 
(available from Morton International Inc.), Vitel PE-100, Vitel PE-200, 
Vitel PE-200D, and Vitel PE-222 (all Vitels available from Goodyear Tire 
and Rubber Co.), polyarylates (Ardel, available from AMOCO Production 
Products), polysulfone (available from AMOCO Production Products), 
polyurethanes, and the like. The MOR-ESTER 49000 polyester resin is a 
linear saturated copolyester reaction product of ethylene glycol with 
terephthalic acid, isophthalic acid, adipic acid and azelaic acid. Other 
polyester resins which are chemically similar to the 49000 polyester resin 
and which are also suitable for a photoreceptor undercoat layer coating 
include Vitel PE-100 and Vitel PE-200, both of which are available from 
Goodyear Tire & Rubber Co. An especially preferred undercoat layer 
material is a polyamide such as Luckamide 5003 from Dai Nippon Ink, Nylon 
8 with methylmethoxy pendant groups, CM 4000 and CM 8000 from Toray 
Industries Ltd and other N-methoxymethylated polyamides, such as those 
prepared according to the method described in Sorenson and Campbell 
"Preparative Methods of Polymer Chemistry" second edition, pg 76, John 
Wiley and Sons Inc., 1968 and the like and the mixtures thereof. These 
polyamides can be alcohol soluble, for example, with polar functional 
groups, such as methoxy, ethoxy and hydroxy groups, pendant from the 
polymer backbone. Any suitable alcohol solvent or solvent mixtures may be 
employed to form a coating solution. Typical solvents include methanol, 
ethanol, propanol and mixtures thereof. Water may optionally be added to 
the solvent mixture. Satisfactory results may be achieved with a dry 
undercoat layer thickness between about 0.05 micrometer and about 0.3 
micrometer. Conventional techniques for applying an undercoat layer 
coating mixture to the charge blocking layer include spraying, dip 
coating, roll coating, wire wound rod coating, gravure coating, Bird 
applicator coating, and the like. Drying of the deposited coating may be 
effected by any suitable conventional technique such as oven drying, infra 
red radiation drying, air drying and the like. In some embodiments, the 
undercoat layer functions as a blocking layer and there is no need for a 
separate blocking layer beneath the undercoat layer. 
Photoconductive particles for charge generating binder layer such vanadyl 
phthalocyanine, metal free phthalocyanine, metal phthalocyanines, 
benzimidazole perylene, trigonal selenium, are especially sensitive to 
white light. 
Any suitable polymeric film forming binder material may be employed as the 
matrix in the charge generating (charge generation) binder layer. Typical 
polymeric film forming materials include those described, for example, in 
U.S. Pat. No. 3,121,006, the entire disclosure of which is incorporated 
herein by reference. Thus, typical organic polymeric film forming binders 
include thermoplastic and thermosetting resins such as polycarbonates, 
polyesters, polyamides, polyurethanes, polystyrenes, polyarylethers, 
polyarylsulfones, polybutadienes, polysulfones, polyethersulfones, 
polyethylenes, polypropylenes, polyimides, polymethylpentenes, 
polyphenylene sulfides, polyvinyl acetate, polysiloxanes, polyacrylates, 
polyvinyl acetals, polyamides, polyimides, amino resins, phenylene oxide 
resins, terephthalic acid resins, phenoxy resins, epoxy resins, phenolic 
resins, polystyrene and acrylonitrile copolymers, polyvinylchloride, 
vinylchloride and vinyl acetate copolymers, acrylate copolymers, alkyd 
resins, cellulosic film formers, poly(amideimide), styrene-butadiene 
copolymers, vinylidenechloride-vinylchloride copolymers, 
vinylacetate-vinylidenechloride copolymers, styrene-alkyd resins, 
polyvinylcarbazole, and the like. These polymers may be block, random or 
alternating copolymers. The preferred binders for benzamidazole perylene 
pigment particles for adequate to good dispersion (of the pigment in the 
binder) are polyvinyl butyral (PVB) and poly 
(4,4'-diphenyl-1,1'-cyclohexane carbonate) (PCZ). However, although PVB is 
a good binder for applications employing drum substrates, PVB is not 
preferred for belt applications because it usually does not adhere as well 
to the other layers. PCZ is the preferred binder for belt applications. 
The choice of generator layer binder also determines the sensitivity and 
the shape of the Photo-induced Discharge Characteristics. One factor in 
this may be due to the solubility considerations of the transport layer 
molecule in the generator layer binder. The transport layer molecules 
diffuse into the generator layer during the transport layer coating. From 
the point of view of transport layer molecular solubility in the generator 
layer binder, PCZ is far superior to PVB. 
Any suitable organic solvent may be utilized to dissolve the film forming 
binder. Typical solvents include n-butyl acetate, cyclohexanone, methyl 
ethyl ketone (MEK) and the like. The solvent n-butyl acetate is preferred 
because the dispersion quality of the coating mixture is superior. Coating 
dispersions for charge generating layer may be formed by any suitable 
technique using, for example, attritors, ball mills, Dynomills, paint 
shakers, homogenizers, microfluidizers, and the like. 
The charge generation layer containing photoconductive pigments and the 
resinous binder material generally has a thickness of between about 0.1 
micrometer and about 5 micrometers, and preferably has a thickness of 
between about 0.3 micrometer and about 2 micrometers. The charge 
generation layer thickness is related to binder content. Higher binder 
content compositions generally require thicker layers for photogeneration. 
Thicknesses outside these ranges can be selected providing the objectives 
of the present invention are achieved. Typical charge generating layer 
thicknesses have an optical density of between about 1.7 and about 2.1. 
Any suitable and conventional technique may be utilized to mix and 
thereafter apply the charge generation layer coating mixture. Typical 
application techniques include slot coating, gravure coating, roll 
coating, spray coating, spring wound bar coating, dip coating, draw bar 
coating, reverse roll coating, and the like. 
Any suitable drying technique may be utilized to solidify and dry the 
deposited coatings. Typical drying techniques include oven drying, forced 
air drying, infrared radiation drying, and the like. 
The charge generation composition or pigment is present in the resinous 
binder composition in various amounts. Generally, however, from about 5 
percent by volume to about 90 percent by volume of the charge generation 
pigment is dispersed in about 10 percent by volume to about 95 percent by 
volume of the resinous binder, and preferably from about 20 percent by 
volume to about 30 percent by volume of the charge generation pigment is 
dispersed in about 70 percent by volume to about 80 percent by volume of 
the resinous binder composition. 
The charge generating layer of the photoreceptor of this invention 
preferably comprises a perylene pigment as a solution coated layer 
containing the pigment dispersed in a film forming resin binder. For 
photoreceptors utilizing a perylene charge generating layer, the perylene 
pigment is preferably benzimidazole perylene which is also referred to as 
bis(benzimidazole). This pigment exists in the cis and trans forms. The 
cis form is also called bis-benzimidazo(2,1-a-1', 1'-b) anthra 
(2,1,9-def:6,5,10-d'e'f') disoquinoline-6,11-dione. The trans form is also 
called bisbenzimidazo (2,1-a1', 1'-b) anthra (2,1,9-def:6,5,10-d'e'f') 
disoquinoline-10,21-dione. This pigment may be prepared by reacting 
perylene 3,4,9,10-tetracarboxylic acid dianhydride with 1,2-phenylene. 
Benzimidazole perylene compositions are well known and described, for 
example, in U.S. Pat. Nos. 5,019,473 and 4,587,189, the entire disclosures 
thereof being incorporated herein by reference. Benzimidazole perylene may 
be ground into fine particles having an average particle size of less than 
about 1 micrometer. Optimum results are achieved with a pigment particle 
size between about 0.2 micrometer and about 0.3 micrometer. Other suitable 
charge generation materials known in the art may also be utilized, if 
desired. 
Any suitable charge transport layer containing the charge transport 
materials of this invention may be utilized on the charge generator layer. 
The active charge transport layer may comprise any suitable transparent 
organic polymer of non-polymeric material capable of supporting the 
injection of photo-generated holes and electrons from the charge 
generating layer and allowing the transport of these holes or electrons 
through the organic layer to selectively discharge the surface charge. The 
charge transport layer in conjunction with the generation layer in the 
instant invention is a material which is an insulator to the extent that 
an electrostatic charge placed on the transport layer is not conducted in 
the absence of activating illumination. Thus, the active charge transport 
layer is a substantially non-photoconductive material which supports the 
injection of photogenerated holes from the generation layer. 
An especially preferred transport layer employed in one of the two 
electrically operative layers in the multilayer photoconductor of this 
invention comprises from about 25 to about 75 percent by weight of the 
charge transporting materials of this invention, and about 75 to about 25 
percent by weight of a polymeric film forming resin in which the aromatic 
amine is soluble. A dried charge transport layer containing between about 
40 percent and about 50 percent by weight of the charge transporting 
materials of this invention based on the total weight of the dried charge 
transport layer is preferred. 
The charge transport materials preferably comprises an alkyl derivative of 
an aryl amine compound and an alkoxy derivative of an arylamine compound. 
Typical arylamine compounds include triphenyl amines, bis and poly 
triarylamines, bis arylamine ethers, bis alkyl-arylamines and the like. 
One of the preferred charge transporting compounds in the charge transport 
layer are alkyl derivatives of arylamines capable of supporting the 
injection of photogenerated holes of a charge generating layer and 
transporting the holes through the charge transport layer. Typical charge 
transporting alkyl derivatives of arylamines include, for example, 
N,N'-bis(alkylphenyl)-[1,1'-biphenyl]-4,4'-diamine wherein the alkyl is, 
for example, methyl, ethyl, propyl, n-butyl and the like, 
N,N'-diphenyl-N,N'-bis(chlorophenyl)-[1,1'-biphenyl]-4,4'-diamine, 
N,N'-diphenyl-N,N'-bis(3"-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine, and 
the like dispersed in an inactive film forming resin binder. Some of these 
charge transporting aromatic amines are represented by the formula: 
##STR1## 
wherein X.sub.1 and X.sub.2 are independently selected from alkyl groups 
containing from 1 to 4 carbon atoms, or chlorine or hydrogen with at least 
one being alkyl or chlorine. 
Although photoreceptor embodiments prepared with a charge generating layer 
comprising benzimidazole perylene dispersed in various types of film 
forming resin binders give reasonably good results, the sensitivity of the 
photoreceptor is found to be significantly improved, particularly, with 
the use of charge generating layers comprising benzimidazole perylene 
dispersed in poly(4,4'-diphenyl-1,1'-cyclohexane carbonate) (PCZ) when the 
charge transporting layer contains both an alkyl substituted diarylamine 
and an alkoxy substituted diarylamine or arylamine. Some of these alkoxy 
substituted diamines or amines are represented by the formula: 
##STR2## 
and or 
##STR3## 
wherein X.sub.3 is and X.sub.4 are independently selected from the group 
consisting of OCH.sub.3 and H with at least one being OCH.sub.3, and 
X.sub.5, X.sub.6 and X.sub.7 are independently selected from the group 
consisting of H and OCH.sub.3 with at least one being an OCH.sub.3 group. 
Typical molecules represented by the above formulae include, for example, 
N,N'-diphenyl -N,N'bis[3-methoxyphenyl]-1,1'-biphenyl]-4,4'diamine, 
N,N'-diphenyl-N,N'bis[4-methoxyphenyl]-1,1'-biphenyl]-4,4'diamine, 
4-methoxyphenyldiphenylamine, bis[4-methoxyphenyl]phenylamine, 
tris[4-methoxyphenyl]amine, and the like. For convenience, the expressions 
"diarylamine" and "arylamine" will frequently collectively be referred to 
herein as "arylamine". 
The charge transport materials in the charge transport layer coating 
solution preferably comprise a major amount of a between about 30 percent 
by weight and about 50 percent by weight alkyl substituted diarylamine and 
a minor amount of between about 5 percent by weight and about 25 percent 
by weight alkoxy substituted arylamine, based on the total weight of 
solids in the coating solution. 
Without being restricted by the theory, it is believed that a small 
fraction of the alkoxy containing amine or diamine migrates to the 
generator layer during fabrication of the transport layer and sensitizes 
the benzimidazole perylene in the charge generating layer. The amount of 
alkoxy containing amine or diamine that migrates to the generator layer 
varies depending upon the specific materials and proportions used in the 
charge transport layer coating solution. Since benzamidazole perylene is 
an extrinsic pigment, the photogeneration process within the generator 
layer requires the presence of transport layer molecules in the generator 
layer. The transport layer molecules migrate into the generator layer 
during the transport layer coating. An extrinsic pigment is one where 
photoabsorption within the pigment creates an exciton (a hole-electron 
pair) which dissociates into a free hole and an electron only when the 
transport molecules is present on the pigment surface. The choice of 
generator layer binder therefore determines the sensitivity and the shape 
of the Photo-induced Discharge Characteristics. One factor in this may be 
due to the solubility considerations of the transport layer molecule in 
the generator layer binder. The sensitization (increased sensitivity) with 
alkyloxy arylamine molecules in the transport layer must also mean that 
alkyloxy arylamine molecules migrate into the transport layer during the 
transport layer fabrication. A preferred method of sensitization is 
through transport layer doping. Generator layer doping of molecules 
through generator layer coating dispersions is not preferred since adding 
molecules into the generator layer coating dispersion may lead to changes 
in the dispersion quality. Migration of molecules during the transport 
layer coating process avoids changes in the dispersion quality of the 
generator layer coating dispersions and is easily employed as a quality 
control tool during the manufacturing process to obtain the desired 
sensitivity. From the point of view of transport layer molecular 
solubility in the generator layer binder, poly 
(4,4'-diphenyl-1,1'-cyclohexane carbonate) (PCZ) is superior to polyvinyl 
butyral (PVB). 
Any suitable inactive film forming resin binder soluble in methylene 
chloride or other suitable solvent may be employed in the process of 
forming the charge transport layer of this invention. Typical inactive 
solvent soluble resin binders include, for example, polycarbonate resin, 
polyester, polyarylate, polyacrylate, polyether, polysulfone, and the 
like. Weight average molecular weights can vary, for example, from about 
20,000 to about 1,500,000. 
Preferred electrically inactive resin materials include polycarbonate 
resins have a weight average molecular weight from about 20,000 to about 
120,000, more preferably from about 50,000 to about 100,000. The materials 
most preferred as the electrically inactive film forming resin material is 
poly(4,4'-dipropylidene-diphenylene carbonate) with a weight average 
molecular weight 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 weight average molecular weight of from about 40,000 to 
about 45,000, available as Lexan 141 from the General Electric Company; a 
polycarbonate resin having a weight average molecular weight of from about 
50,000 to about 100,000, available as Makrolon from Farbenfabricken Bayer 
A. G., a polycarbonate resin having a weight average molecular weight of 
from about 20,000 to about 50,000 available as Merlon from Mobay Chemical 
Company and poly(4,4'-diphenyl-1,1'-cyclohexane carbonate) with a 
molecular weight of from about 35,000 to about 40,000, available as PCZ 
400 available from Mitsubishi Chemical Co. Excellent results are achieved 
when the charge transport layer comprises 
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine and 
one or more of 
N,N'-diphenyl-N,N'bis[3-methoxyphenyl]-1,1'-biphenyl]-4,4'diamine, 
N,N'-diphenyl -N,N'bis[4-methoxyphenyl]-1,1'-biphenyl]-4,4'diamine, 
4-methoxyphenyidiphenylamine, bis[4-methoxyphenyl]phenylamine, 
tris[4-methoxyphenyl]amine, in poly(4,4'-dipropylidene-diphenylene 
carbonate) binder. 
Examples of photosensitive members having at least two electrically 
operative layers include the charge generator layer and diamine containing 
transport layer members disclosed in U.S. Pat. Nos. 4,265,990, 4,233,384, 
4,306,008, 4,439,507. The disclosures of these patents are incorporated by 
reference herein in their entirety. 
Any suitable and conventional technique may be utilized to mix and 
thereafter apply the charge transport layer coating mixture to the charge 
generating layer. Typical application techniques include spraying, dip 
coating, roll coating, wire wound rod coating, and the like. Drying of the 
deposited coating may be effected by any suitable conventional technique 
such as oven drying, infra red radiation drying, air drying and the like. 
Generally, the thickness of the transport layer is between about 5 
micrometers to about 100 micrometers, but thicknesses outside this range 
can also be used. A dried thickness of between about 18 micrometers and 
about 35 micrometers is preferred with optimum results being achieved with 
a thickness between about 20 micrometers and about 29 micrometers. 
Preferably, the charge transport layer comprises an arylamine small 
molecule dissolved or molecularly dispersed in a polycarbonate. 
Other layers such as conventional ground strips comprising, for example, 
conductive particles disposed in a film forming binder may be applied to 
one edge of the photoreceptor in contact with the conductive surface or 
layer, blocking layer, adhesive layer or charge generating layer. 
Optionally, an overcoat layer may also be utilized to improve resistance to 
abrasion. In some cases a back coating may be applied to the side opposite 
the photoreceptor to provide flatness and/or abrasion resistance. These 
overcoating and backcoating layers may comprise organic polymers or 
inorganic polymers that are electrically insulating or slightly 
semi-conductive. 
The improved electrophotographic imaging members of this invention exhibit 
greater sensitivity. Further it is believed that diffusion of the alkoxy 
amine or diamine molecule from the transport layer causes this increase in 
sensitivity. The alkoxy containing amine or diamine molecule dopant in the 
transport layer does not cause any residual potential or cycle-up 
problems. Cycle-up is a phenomenon in which the residual potential keeps 
increasing with cycles. 
PREFERRED EMBODIMENT OF THE INVENTION 
The invention will now be described in detail with respect to the specific 
preferred embodiments thereof, it being understood that these examples are 
intended to be illustrative only and that the invention is not intended to 
be limited to the materials, conditions, process parameters and the like 
recited herein. All parts and percentages are by weight unless otherwise 
indicated.

EXAMPLE I 
Several photoreceptors were prepared by forming coatings using conventional 
techniques on a substrate comprising vacuum deposited titanium layer on a 
polyethylene terephthalate film. The first coating was a siloxane barrier 
layer formed from hydrolyzed gamma-aminopropyltriethoxysilane having a 
thickness of 0.005 micrometer (50 Angstroms). The barrier layer coating 
composition was prepared by mixing 3-aminopropyltriethoxysilane (available 
from PCR Research Center Chemicals of Florida) with ethanol in a 1:50 
volume ratio. The coating composition was applied by a multiple clearance 
film applicator to form a coating having a wet thickness of 0.5 mil. The 
coating was then allowed to dry for 5 minutes at room temperature, 
followed by curing for 10 minutes at 110.degree. C. in a forced air oven. 
The second coating was an adhesive layer of polyester resin (49,000, 
available from E.I. duPont de Nemours & Co.) having a thickness of 0.005 
micrometer (50 Angstroms). The second coating composition was applied 
using a 0.5 mil bar and the resulting coating was cured in a forced air 
oven for 10 minutes. The next coating was a charge generator layer of 
benzamidazole perylene (BzP) containing 40 percent by volume BzP, and 60 
percent by volume of polycarbonate (PCZ) is coated on the adhesive layer. 
This photogenerating layer is prepared by introducing 0.45 grams PCZ and 
50 mis of tetrahydrofuran into a 4 oz. amber bottle. To this solution is 
added 2.4 grams of BzP and 300 grams of 1/8 inch (3.2 millimeter) diameter 
stainless steel shot. This mixture is then placed on a ball mill for 72 to 
96 hours. Subsequently, 2.25 grams of PCZ is dissolved in 46.1 gm of 
tetrahydrofuran, then added to this BzP slurry. This slurry is then placed 
on a shaker for 10 minutes. The resulting slurry is thereafter applied to 
the adhesive interface layer by using a 1/2 mil gap Bird applicator to 
form a coating layer having a wet thickness of 0.5 mil (12.7 micrometers). 
This photogenerating layer is dried at 125.degree. C. for 1 minute in a 
forced air oven to form a dry photogenerating layer having a thickness of 
1.0 micrometer. 
COMATIVE EXAMPLE II 
On the generator layer of one of the photoreceptors of Example I a 
transport layer of the prior art was coated. A charge transport layer 
solution was prepared by dissolving 1.2 grams of Makrolon.RTM. 
polycarbonate in 13 grams of methylene chloride. Added to this polymer 
solution was 1.2 gram of 
N,N'-diphenyl-N,N'-bis[3-methylphenyl]-[1,1'-biphenyl]-4,4'-diamine (TPD). 
After dissolution, the mixture was coated on the substrate containing the 
generator layer using a 3 mil Bird film applicator. The resulting film was 
dried in a forced air oven at 100.degree. C. for 20 minutes to form a 25 
micrometer thick dried layer of charge transport material. 
EXAMPLE III 
On the generator layer another of the photoreceptors of Example I, a 
transport layer of this invention was coated. A charge transport layer 
solution was prepared by dissolving 1.2 grams of Makrolon.RTM. 
polycarbonate in 13 grams of methylene chloride. Added to this polymer 
solution was one gram 
N,N'-diphenyl-N,N'-bis[3-methylphenyl]-[1,1'-biphenyl]-4,4'-diamine and 
0.2 gram of 
N,N'-diphenyl-N,N'-bis[3-methoxyphenyl]-[1,1'-biphenyl]-4,4'-diamine. 
After dissolution, the mixture was coated on the substrate containing the 
generator layer using a 3 mil Bird film applicator. The film was dried in 
a forced air oven at 100.degree. C. for 20 minutes to form a 25 micrometer 
thick dried layer of charge transport material. 
EXAMPLE IV 
On the generator layer of one of the photoreceptors of Example I, a 
transport layer of this invention was coated. A charge transport layer 
solution was prepared by dissolving 1.2 grams of Makrolon.RTM. 
polycarbonate in 13 grams of methylene chloride. Added to this polymer 
solution was 0.8 gram 
N,N'-diphenyl-N,N'-bis[3-methylphenyl]-[1,1'-biphenyl]-4,4'-diamine and 
0.4 gram of 
N,N'-diphenyl-N,N'-bis[3-methoxyphenyl]-[1,1'-biphenyl]-4,4'-diamine. 
After dissolution, the mixture was coated on the substrate containing the 
CGL using a 3 mil Bird film applicator. The resulting film was dried in a 
forced air oven at 100.degree. C. for 20 minutes to form a 25 micrometer 
thick dried layer of charge transport material. 
EXAMPLE V 
Electrical Scanning Test 
Each photoreceptor device of Examples II, III and IV was mounted on a 
cylindrical aluminum drum substrate which was rotated on a shaft of a 
scanner. Each photoreceptor was charged by a corotron mounted along the 
periphery of the drum. The surface potential was measured as a function of 
time by capacitively coupled voltage probes placed at different locations 
around the shaft. The probes were calibrated by applying known potentials 
to the drum substrate. The photoreceptors on the drums were exposed by a 
light source located at a position near the drum downstream from the 
corotron. As the drum was rotated, the initial (pre-exposure) charging 
potential was measured by voltage probe 1. Further rotation leads to the 
exposure station, where the photoreceptor was exposed to monochromatic 
radiation of known intensity. The photoreceptor was erased by a light 
source located at a position upstream of charging. The measurements made 
included charging of the photoreceptor in a constant current or voltage 
mode. The photoreceptor was charged to a negative polarity corona. As the 
drum was rotated, the initial charging potential was measured by voltage 
probe 1. Further rotation lead to the exposure station, where the 
photoreceptor was exposed to monochromatic radiation of known intensity. 
The surface potential after exposure was measured by voltage probes 2 and 
3. The photoreceptor was finally exposed to an erase lamp of appropriate 
intensity and any residual potential was measured by voltage probe 4. The 
process was repeated with the magnitude of the exposure automatically 
changed during the next cycle. The photodischarge characteristics were 
obtained by plotting the potentials at voltage probes 2 and 3 as a 
function of light exposure. The charge acceptance and dark decay were also 
measured in the scanner. The photoreceptors were then subjected to charge, 
discharge and erase cycles for 10,000 cycles and all the potentials were 
plotted to determine the cyclic stability. The sensitivity of the three 
devices are shown in Table I and the increases are considered very 
significant for devices employing benzamidazole perylene pigment. 
TABLE I 
______________________________________ 
TL dopant Ergs/cm.sup.2 
Ergs/cm.sup.2 
Device concentration (800 to 200 V) (800 to 100 V) 
______________________________________ 
Example I 
Control (0% dopant) 
8.16 11.28 
Example II 8.5 wt. % 7.92 11.06 
Example III 17 wt. % 7.47 10.41 
______________________________________ 
The TL dopant in Examples II and III was 
N,N'-diphenyl-N,N'-bis[3-methoxyphenyl]-[1,1'-biphenyl]-4,4'-diamine. 
The dopant concentration percentage was calculated based on the total 
weight of transport layer. 
When cycled for 10,000 cycles there was no residual cycle-up in any of the 
three devices. 
EXAMPLE VI 
Devices as described in Examples III and IV were also fabricated wherein 
N,N'-diphenyl-N,N'-bis[3-methoxyphenyl]-[1,1'-biphenyl]-4,4'-diamine was 
replaced by 
N,N'-diphenyl-N,N'-bis[4-methoxyphenyl]-[1,1'-biphenyl]-4,4'-diamine, 4- 
methoxyphenyldiphenylamine, bis[4-methoxyphenyl]phenylamine, 
tris[4-methoxyphenyl]amine and tested as described in Example V. Sensivity 
increases in the range of 8 to 10 percent were observed. These increases 
are considered very significant for devices employing benzamidazole 
perylene pigment. When cycled for 10,000 cycles there was no residual 
cycle-up in any of these devices. 
Although the invention has been described with reference to specific 
preferred embodiments, it is not intended to be limited thereto, rather 
those having ordinary skill in the art will recognize that variations and 
modifications may be made therein which are within the spirit of the 
invention and within the scope of the claims.