An electrophotographic imaging member is characterized by a halogenindium phthalocyanine produced by dry milling and treating with an organic amine solvent.

FIELD OF THE INVENTION 
This invention relates to halogenindium phthalocyanine crystals having 
improved photosensitivity as charge generating pigments and to an 
electrophotographic photoreceptor containing the halogenindium 
phthalocyanine as a charge generating material. 
BACKGROUND OF THE INVENTION 
Chloroindium phthalocyanine is useful as a charge carrier generating 
pigment in electrophotographic photoreceptors. Chloroindium phthalocyanine 
is characterized by long wavelength infrared absorption at about 780 nm. 
Hence, chloroindium phthalocyanine crystals and halogenindium 
phthalocyanine crystals in general are candidates for use as charge 
generating pigments in photoreceptors that are used in printers having 780 
nm laser diode exposure systems. However, photoreceptors that contain 
generating layers with chloroindium phthalocyanine are characterized by 
low sensitivity. 
U.S. Pat. No. 4,471,039 to Borsenberger et al., teaches photoconductive 
elements containing the .beta.-phase form of an indium phthalocyanine. 
U.S. Pat. No. 4,555,463 to Hor et al. teaches a photoresponsive imaging 
member comprised of a chloroindium phthalocyanine photogenerating 
composition. U.S. Pat. No. 4,587,188 to Kato et al. and U.S. Pat. No. 
4,731,312 to Karo et al. teach a photoconductor with a chloroindium 
phthalocyanine and a method for electrophotography with a light source 
having a wavelength of about 650 nm or greater. 
U.S. Pat. No. 5,302,710 to Nukada et al. teaches a phthalocyanine mixed 
crystal comprising a halogenated indium phthalocyanine and a halogenated 
gallium phthalocyanine. Nukada et al. discloses an electrophotographic 
photoreceptor containing the phthalocyanine mixed crystal. The mixed 
crystal is prepared by dry milling and treatment with an organic solvent. 
Electrophotographic photoreceptors containing the mixed crystal are 
characterized by improved stability upon repeated use. 
Loutfy et al., "Near-Infrared Photoreceptor Devices Incorporating 
Chloroindium Phthalocyanine," Journal of Imaging Science, Volume 29, No. 
4, July/August 1985, pp. 148-153 teaches the synthesis and purification of 
organic photoconductor chloroindium phthalocyanine. Loutfy et al. teaches 
the determination of X-ray diffraction characteristics of crystals of the 
choloroindium phthalocyanine and xerographic measurements of photoreceptor 
compositions containing chloroindium phthalocyanine. The disclosure of 
this reference is incorporated herein by reference. 
The present invention relates to halogenindium phthalocyanines that are 
characterized by improved sensitivity. The improved sensitivity enables 
the halogenindium phthalocyanine to be used in high speed printers. 
SUMMARY OF THE INVENTION 
The present invention provides a chloroindium phthalocyanine crystal that 
has substantially improved sensitivity in an electrophotographic imaging 
member. The improved chloroindium phthalocyanine is prepared by a process 
of dry milling a chloroindium phthalocyanine and treating the chloroindium 
phthalocyanine with an amine solvent. The present invention provides an 
electrophotographic imaging member comprising the improved chloroindium 
phthalocyanine with increased sensitivity.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A representative structure of an electrophotographic imaging member of the 
present invention is shown in FIG. 1. This imaging member is provided with 
an anti-curl layer 1, a supporting substrate 2, an electrically conductive 
ground plane 3, a charge blocking layer 4, an adhesive layer 5, a charge 
generating layer 6, a charge transport layer 7 and an overcoating layer 8. 
The Supporting Substrate 
The supporting substrate 2 may be opaque or substantially transparent and 
may comprise numerous suitable materials having the required mechanical 
properties. An aluminum drum is the preferred substrate. 
The substrate may further be provided with an electrically conductive 
surface (ground plane 3). Accordingly, the substrate may comprise a layer 
of an electrically non-conductive or conductive material such as an 
inorganic or an organic composition. As electrically non-conducting 
material, there may be employed various resins known for this purpose 
including polyesters, polycarbonates, polyamides, polyurethanes, and the 
like. For a belt-type imaging member, the electrically insulating or 
conductive substrate should be flexible and may have any number of 
different configurations such as, for example, a sheet, a scroll, an 
endless flexible belt, and the like. Preferably, the substrate is in the 
form of an endless flexible belt and comprises a commercially available 
biaxially oriented polyester known as Mylar, available from E.I. du Pont 
de Nemours & Co., or Melinex available from ICI Americas Inc. 
The preferred thickness of the substrate layer depends on numerous factors, 
including economic considerations. The thickness of this layer may range 
from about 65 micrometers to about 150 micrometers, and preferably from 
about 75 micrometers to about 125 micrometers for optimum flexibility and 
minimum induced surface bending stress when cycled around small diameter 
rollers, e.g., 19 millimeter diameter rollers. The substrate for a 
flexible belt may be of substantial thickness, for example, 200 
micrometers, or of minimum thickness, for example, 200 micrometers, or of 
minimum thickness, for example 50 micrometers, provided there are no 
adverse effects on the final photoconductive device. The surface of the 
substrate layer is preferably cleaned prior to coating to promote greater 
adhesion of adjacent layer. Cleaning may be effected by exposing the 
surface of the substrate layer to plasma discharge, ion bombardment and 
the like. 
The Electrically Conductive Ground Plane 
The electrically conductive ground plane 3 (if needed) may be an 
electrically conductive layer such as a metal layer which may be formed, 
for example, on the substrate 2 by any suitable coating technique, such as 
a vacuum depositing technique. Typical metals include aluminum, zirconium, 
niobium, tantalum, vanadium, hafnium, titanium, nickel, stainless steel, 
chromium, tungsten, molybdenum, and the like, and mixtures and alloys 
thereof. The conductive layer may vary in thickness over substantially 
wide ranges depending on the optical transparency and flexibility desired 
for the electrophotoconductive member. Accordingly for a flexible 
photoresponsive imaging device, the thickness of the conductive layer is 
preferably between about 20 .ANG. to about 750 .ANG., and more preferably 
from about 50 .ANG. to about 200 .ANG. for an optimum combination of 
electrical conductivity, flexibility and light transmission. 
Regardless of the technique employed to form a metal layer, a thin layer of 
metal oxide generally forms on the outer surface of most metals upon 
exposure to air. Thus, when other layers overlying the metal layer are 
characterized as "continuous" layers, it is intended that these overlying 
contiguous layers may, in fact, contact a thin metal oxide layer that has 
formed on the outer surface of the oxidizable metal layer. Generally for 
rear erase exposure, a conductive layer light transparency of at lest 
about 15 percent is desirable. The conductive layer need not be limited to 
metals. Other examples of conductive layers may be combinations of 
materials such as conductive indium tin oxide as a transparent layer for 
light having a wavelength between about 4000 .ANG. and about 9000 .ANG. or 
a conductive carbon black dispersed in a plastic binder as an opaque 
conductive layer. The conductive ground plane 3 may be omitted if a 
conductive substrate is used. 
The Charge Blocking Layer 
After deposition of any electrically conductive ground plane layer, the 
charge blocking layer 4 may be applied thereto. Electron blocking layers 
for positively charged photoreceptors allow holes from the imaging surface 
of the photoreceptor to migrate toward the conductive layer. For 
negatively charged photoreceptors, any suitable hole blocking layer 
capable of forming a barrier to prevent hole injection from the conductive 
layer to the opposite photoconductive layer may be utilized. 
The blocking layer 4 may include polymers such as polyvinylbutyral, epoxy 
resins, polyesters, polysiloxanes, polyamides, polyurethanes and the like; 
nitrogen-containing siloxanes or nitrogen-containing titanium compounds 
such as trimethoxysilyl propyl ethylene diamine, N-beta-(aminoethyl) 
gamma-amino-propyl trimethoxy silane, isopropyl 4-aminobenzene sulfonyl 
titanate, di(dodecylbenzene sulfonyl) titanate, isopropyl 
di(4-aminobenzoyl)isostearoyl titanate, isopropyl tri(N-ethylamino) 
titanate, isopropyl trianthranil titanate, isopropyl 
tri(N,N-dimethyl-ethylamino) titanate, titanium-4-amino benzene sulfonate 
oxyacetate, titanium 4-aminobenzoate isostearate oxyacetate, [H.sub.2 
N(CH.sub.2).sub.4 ]CH.sub.3 Si(OCH.sub.3).sub.2 (gamma-aminobutyl methyl 
dimethoxy silane), [H.sub.2 N(CH.sub.2).sub.3 ]CH.sub.3 
Si(OCH.sub.3).sub.2 (gamma-aminopropyl methyl dimethoxy silane), and 
[H.sub.2 N(CH.sub.2).sub.3 ]Si(OCH.sub.3).sub.3 (gamma-aminopropyl 
trimethoxy silane) as disclosed in U.S. Pat. Nos. 4,338,387, 4,286,033 and 
4,291,110. 
A preferred hole blocking layer comprises a reaction product of a 
hydrolyzed silane or mixture of hydrolyzed silanes and the oxidized 
surface of a metal ground plane layer. The oxidized surface inherently 
forms on the outer surface of most metal ground plane layers when exposed 
to air after deposition. This combination enhances electrical stability at 
low relative humidity. The hydrolyzed silanes that can be used are 
hydrolyzed silanes that are well known in the art. For example, see U.S. 
Pat. No. 5,091,278 to Teuscher et al. 
The blocking layer 4 should be continuous and may have a thickness of up to 
2 micrometers depending on the type of material used. A blocking layer of 
between about 0.005 micrometer and about 0.3 micrometer is satisfactory 
because charge neutralization after the exposure step is facilitated and 
good electrical performance is achieved. A thickness between about 0.03 
micrometer and about 0.06 micrometer is preferred for blocking layers for 
optimum electrical behavior. 
The blocking layer 4 may be applied by any suitable 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 layer is 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. 
Generally, a weight ratio of blocking layer material and solvent of 
between about 0.5:100 to about 5.0:100 is satisfactory for spray coating. 
The Adhesive Layer 
An intermediate layer 5 between the blocking layer and the charge 
generating or photogenerating layer may be provided to promote adhesion. 
However in the present invention, a dip coated aluminum drum is the 
preferred substrate and is utilized without an adhesive layer. When an 
adhesive layer is utilized, it can be characterized by a dry thickness 
between about 0.01 micrometer to about 0.3 micrometer, more preferably 
about 0.05 to about 0.2 micrometer. 
An adhesive layer, if utilized, may comprise any known adhesive for layers 
of an electrophotographic imaging member. The adhesive layer may comprise 
a film-forming polyester resin adhesive such as du Pont 49,000 resin 
(available from E.I. du Pont de Nemours & Co.), Vitel 1200 (available from 
Goodyear Rubber & Tire Co.), or the like. Both the du Pont 49,000 and 
Vitel 1200 adhesive layers provide reasonable adhesion strength and 
produce no deleterious electrophotographic impact on the resulting imaging 
member. 
Another copolyester resin adhesive is available from Goodyear Tire & Rubber 
Co. as Vitel 2200. This polyester resin is a linear saturated copolyester 
of two diacids and two diols. The molecular structure of this linear 
saturated copolyester is represented by the following: 
##STR1## 
where the ratio of diacid to ethylene glycol in the copolyester is 1:1. 
The diacids are terephthalic acid and isophthalic acid in a ratio of 
1.2:1. The two diols are ethylene glycol and 2,2-dimethyl propane diol in 
a ratio of 1.33:1. The Goodyear Vitel 2200 linear saturated copolyester 
consists of randomly alternating monomer units of the two diacids and the 
two diols and has a weight average molecular weight of about 58,000 and a 
Tg of about 67.degree. C. 
Other suitable copolyesters include Goodyear Vitel 1710, Vitel 1870, Vitel 
3300, Vitel 3550 and Vitel 5833. Vitel 5833 is a short chained branched 
polymer having cross-linkable hydroxyl and carboxylic acid functional 
groups. Vitel 5833 is particularly useful by itself or blended with other 
polyesters in applications requiring an increase of adhesive layer 
cross-linking density. 
The Charge Generating Layer 
The charge generating layer 6 comprises a polymer binder and a 
photoconductive pigment. The photoconductive pigment is a halogenindium 
phthalocyanine or mixtures of halogenindium phthalocyanine with at least 
one other metal-containing phthalocyanine pigment. The halogenindium 
phthalocyanine can be halogenated with chlorine, bromine or iodine. 
Chloroindium phthalocyanine is the preferred pigment. In another preferred 
embodiment, the pigment includes a mixture of chloroindium phthalocyanine 
and a second metal-containing phthalocyanine. The second metal-containing 
phthalocyanine is preferably a TiO phthalocyanine (IV) or an 
hydroxygallium phthalocyanine (V) pigment. 
The halogenindium phthalocyanine according to the present invention is in 
the form of small particles that characteristically scatter light 
differently from larger particles. The particles of the present invention 
exhibit characteristic light scattering indices. 
The ratio of the halogenindium phthalocyanine crystal (I)/second 
metal-containing phthalocyanine pigment component (II) in the preferred 
mixed pigment of the present invention is a ratio of from about 5/95 to 
95/5 by weight and preferably from 10/90 to 90/10 by weight. 
A halogenindium phthalocyanine crystal can be synthesized by known 
processes, such as a process comprising reacting a trihalogenated indium 
with phthalocyanine or diiminoisoindoline in an appropriate organic 
solvent. See Loutfy et al., supra. In the preparation of the halogenindium 
phthalocyanine crystal (I) of the present invention, a halogenindium 
phthalocyanine is ground by dry grinding or milling (e.g., salt milling) 
in a ball mill, a sand mill, a kneader, a mortar, attritor, etc. followed 
by treatment with an organic amine solvent. Examples of useful organic 
solvents include triethanol amine, N,N-dimethylacetamide, 
dimethylformamide and diethylformamide. A particular preferred solvent is 
N,N-dimethylformamide (DMF). The phthalocyanine crystal (I) of the present 
invention is useful as a charge generating material for electrophotography 
and provides an electrophotographic photoreceptor that exhibits excellent 
sensitivity. The dry grinding or milling step (A) can be carried out for a 
period of 24 to 100 hours preferably 72 to 96 hours. In solvent treating 
step (B), proportion of the solvent to phthalocyanine is generally from 
1/1 to 200/1, preferably from 10/1 to 100/1. 
The halogenindium phthalocyanine crystal (I) is characterized by improved 
purity. The grinding step may produce an extremely small particle having 
high surface area. Smaller, high surface area particles may permit 
substantially improved efficiency in the solvent treatment steps. Prior to 
the treatment process of the invention, the halogenindium phthalocyanine 
has a particle size in the range of 50 to 1000 nm. After grinding or 
milling, the particle size is significantly reduced to the range of 50 to 
250 nm. 
The photoreceptor of the present invention preferably uses a blend of TiO 
phthalocyanine (IV) and chloroindium phthalocyanine to achieve a balanced 
sensitivity. Surprisingly, the pretreated chloroindium phthalocyanine 
contributes a sensitivity to the mixture so that less TiO phthalocyanine 
(IV) pigment is required to provide a resulting photoreceptor having 
satisfactory sensitivity. For example, a mixture of pretreated 
chloroindium phthalocyanine with about 15-20% TiO phthalocyanine (IV) has 
about the same sensitivity as a mixture of untreated chloroindium 
phthalocyanine with about 20-25% TiO phthalocyanine (IV). Additionally, 
pretreated chloroindium phthalocyanine can be used as a low sensitivity 
component in other photoreceptor designs. A pretreated chloroindium 
phthalocyanine can be mixed with a higher sensitivity pigment such as 
hydroxygallium phthalocyanine. 
The charge generating layer is formed by coating on a conductive substrate, 
a coating composition prepared by dispersing the phthalocyanine crystal 
(I) of the present invention in a solution of the binder resin in an 
organic solvent. A compounding ratio of the phthalocyanine crystal to the 
binder resin generally ranges from 40/1 to 1/10, and preferably from 10/1 
to /1:4, by weight. If the ratio of the phthalocyanine mixed crystal is 
too high, the stability of the coating composition tends to be reduced. If 
it is too low, the sensitivity of the charge generating layer tends to be 
reduced. 
The solvents to be used in the coating compositions are preferably selected 
from those incapable of dissolving the lower layer, i.e., the layer on 
which the charge generating layer is applied. Examples of the organic 
solvents include alcohols, e.g., methanol, ethanol, and isopropanol; 
ketones, e.g., acetone, methyl ethyl ketone, and cyclohexanone; amides, 
e.g., N,N-dimethylformamide and N,N-dimethylacetamide; dimethyl 
sulfoxides; ethers, e.g., tetrahydrofuran, dioxane, and ethylene glycol 
monomethyl ether; esters, e.g., methyl acetate and ethyl acetate; 
halogenated aliphatic hydrocarbons, e.g., chloroform, methylene chloride, 
dichloroethylene, carbon tetrachloride, and trichloroethylene; and 
aromatic hydrocarbons, e.g., benzene, toluene, xylene, ligroin, 
monochlorobenzene, and dichlorobenzene. 
The coating composition for a charge generating layer can be coated by any 
known coating technique, such as dip coating, spray coating, spin coating, 
bead coating, wire bar coating, blade coating, roller coating, and curtain 
coating. Drying after coating is preferably carried out first by drying at 
room temperatures to the touch and then heat-drying. Heat-drying may be 
performed at a temperature of from 50.degree. to 200.degree. C. for a 
period of from 5 minutes to 2 hours in still air or in an air flow. The 
charge generating layer usually has a thickness of from about 0.05 to 5 
.mu.m. 
The Charge Transport Layer 
The charge transport layer 7 may comprise any suitable transparent organic 
polymer or non-polymeric material capable of supporting the injection of 
photogenerated holes or electrons from the charge generating layer 6 and 
allowing the transport of these holes or electrons to selectively 
discharge the surface charge. The charge transport layer not only serves 
to transport holes or electrons, but also protects the charge generating 
layer from abrasion or chemical attack and therefore extends the operating 
life of the imaging member. 
The charge transport layer is substantially transparent to radiation in a 
region in which the imaging member is to be used. The charge transport 
layer is normally transparent when exposure is effected therethrough to 
ensure that most of the incident radiation is utilized by the underlying 
charge generating layer. When used with a transparent substrate, imagewise 
exposure or erase may be accomplished through the substrate with all light 
passing through the substrate. In this case, the charge transport material 
need not transmit light in the wavelength region of use. 
The charge transport layer may comprise activating compounds dispersed in 
normally electrically inactive polymeric materials for making these 
materials electrically active. These compounds may be added to polymeric 
materials that are incapable of supporting the injection of photogenerated 
charge and incapable of allowing the transport of this charge. An 
especially preferred transport layer employed in multilayer 
photoconductors comprises from about 25 percent to about 75 percent by 
weight of at least one charge transporting aromatic amine compound, and 
about 75 percent to about 25 percent by weight of a polymeric film-forming 
resin in which the aromatic amine is soluble. 
The charge transport layer is preferably formed from a mixture comprising 
one or more compounds having the general formula: 
##STR2## 
wherein R.sub.1 and R.sub.2 are selected from the group consisting of 
substituted or unsubstituted phenyl groups, naphthyl groups, and 
polyphenyl groups and R.sub.3 is selected from the group consisting of 
substituted or unsubstituted aryl groups, alkyl groups having from 1 to 18 
carbon atoms and cycloaliphatic groups having from 3 to 18 carbons atoms. 
The substituents should be free from electron-withdrawing groups such as 
NO.sub.2 groups, Cn groups, and the like. 
Examples of charge transporting aromatic amines represented by the 
structural formula above include triphenylmethane, 
bis(4-diethylamine-2-methylphenyl)-phenylmethane; 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane; 
N,N'-bis(alkyl-phenyl)-(1,1'-biphenyl)-4,4'-diamine wherein the alkyl is, 
for example methyl, ethyl, propyl, n-butyl, etc., 
N,N'-diphenyl-N,N'-bis(3-methylphenyl)-(1,1'-biphenyl)-4,4'-diamine; and 
the like, dispersed in an inactive resin binder. 
Any suitable inactive resin binder soluble in methylene chloride or other 
suitable solvent may be employed. Typical inactive resin binders soluble 
in methylene chloride include polycarbonate resin, polyvinylcarbazole, 
polyester, polyacrylate, polyether, polysulfone, and the like. Molecular 
weights can vary from about 20,000 to 1,500,000. Other solvents that may 
dissolve these binders include tetrahydrofuran, toluene, 
trichloroethylene, 1,1,2-trichloroethane, 1,1,1-trichloroethane, and the 
like. 
The preferred electrically inactive resin materials are polycarbonate 
resins having a 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 resin materials are 
poly(4,4'-dipropylidene-diphenylene carbonate) with a 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 
molecular weight of from about 40,000 to about 45,000, available as Lexan 
141 from General Electric Company; a polycarbonate resin having a 
molecular weight of from about 50,000 to about 100,000, available as 
Makrolon from Farbenfabricken Bayer A.G.; a polycarbonate resin having a 
molecular weight of from about 20,000 to about 50,000, available as Merlon 
from Mobay Chemical Company; polyether carbonates; and 
4,4'-cyclohexylidene diphenyl polycarbonate. Methylene chloride solvent is 
a desirable component of the charge transport layer coating mixture for 
adequate dissolving of all the components and for its low boiling point. 
The thickness of the charge transport layer may range from about 10 
micrometers to about 50 micrometers, and preferably from about 20 
micrometers to about 35 micrometers. Optimum thicknesses may range from 
about 23 micrometers to about 31 micrometers. 
The Ground Strip 
Ground strip 9 may comprise a film-forming binder and electrically 
conductive particles. Cellulose may be used to disperse the conductive 
particles. Any suitable electrically conductive particles may be used in 
the electrically conductive ground strip layer 9. The ground strip 9 may 
comprise materials which include those enumerated in U.S. Pat. No. 
4,664,995. Typical electrically conductive particles include carbon black, 
graphite, copper, silver, gold, nickel, tantalum, chromium, zirconium, 
vanadium, niobium, indium tin oxide and the like. The electrically 
conductive particles may have any suitable shape. Typical shapes include 
irregular, granular, spherical, elliptical, cubic, flake, filament, and 
the like. Preferably, the electrically conductive particles should have a 
particle size less than the thickness of the electrically conductive 
ground strip layer to avoid an electrically conductive ground strip layer 
having an excessively irregular outer surface. An average particle size of 
less than about 10 micrometers generally avoids excessive protrusion of 
the electrically conductive particles at the outer surface of the dried 
ground strip layer and ensures relatively uniform dispersion of the 
particles through the matrix of the dried ground strip layer. 
Concentration of the conductive particles to be used in the ground strip 
depends on factors such as the conductivity of the specific conductive 
particles utilized. 
The ground strip layer may have a thickness from about 7 micrometers to 
about 42 micrometers, and preferably from about 14 micrometers to about 27 
micrometers. 
The Anti-Curl Layer 
The anti-curl layer 1 is optional, and may comprise organic polymers or 
inorganic polymers that are electrically insulating or slightly 
semi-conductive. The anti-curl layer provides flatness and/or abrasion 
resistance. 
Anti-curl layer 1 may be formed at the back side of the substrate 2, 
opposite to the imaging layers. The anti-curl layer may comprise a 
film-forming resin and an adhesion promoter polyester additive. Examples 
of film-forming resins include polyacrylate, polystyrene, 
poly(4,4'-isopropylidene diphenyl carbonate), 4,4'-cyclohexylidene 
diphenyl polycarbonate, and the like. Typical adhesion promoters used as 
additives include 49,000 (du Pont), Vitel PE-100, Vitel PE-200, Vitel 
PE-307 (Goodyear), and the like. Usually from about 1 to about 15 weight 
percent adhesion promoter is selected for film-forming resin addition. The 
thickness of the anti-curl layer is about 3 micrometers to about 35 
micrometers, and preferably about 14 micrometers. 
The anti-curl coating may be applied as a solution prepared by dissolving 
the film forming resin and the adhesion promoter in a solvent such as 
methylene chloride. The solution is applied to the rear surface of the 
supporting substrate (the side opposite to the imaging layers) of the 
photoreceptor device by hand coating or by other methods known in the art. 
The coating wet film is then dried to produce the anti-curl layer 1. 
The Overcoating Layer 
The optional overcoating layer 8 may comprise organic polymers or inorganic 
polymers that are capable of transporting charge through the overcoat. The 
overcoating layer may range in thickness from about 2 micrometers to about 
8 micrometers, and preferably from about 3 micrometers to about 6 
micrometers. An optimum range of thickness is from about 3 micrometers to 
about 5 micrometers. 
The invention will further be illustrated in the following, non-limiting 
examples, 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 
therein. 
Chloroindium phthalocyanine is useful as a xerographic charge generator 
pigment in applications requiring about 780 nm infrared sensitivity. 
However, low sensitivity to light at 780 nm wavelength has limited the use 
of chloroindium phthalocyanine pigment. For example, dispersions of 
chloroindium phthalocyanine usually has a sensitivity of only about 15-25 
volts/erg/cm squared. The following example describes the preparation of a 
chloroindium phthalocyanine pigment according to the present invention 
that results in a pigment with a increased sensitivity to light at 780 nm 
wavelength of between 35-45 volts/erg cm.sup.2. 
EXAMPLE 
Chloroindium phthalocyanine (CllnPc) crude pigment, 300 g, is placed in a 
4L polypropylene jar containing 2.65 kg of glass beads of 6 mm diameter. 
The jar is closed and placed on a roll mill at 50-60 rpm (jar speed) for 
96 hours. Dimethyl formamide (DMF), 1.5L, is added to the jar and milling 
is continued for an additional 48 hours. The pigment is separated from the 
glass beads by filtration using a Buchner funnel and rinsing with DMF. The 
pigment is removed from the Buchner funnel and a reslurry is washed in 3L 
of hot (75.degree. C.) DMF for 1 hour in a 4L beaker and then filtered 
again in the Buchner funnel. The hot DMF slurry wash process is repeated 
three additional times. Finally, the pigment is slurried in 3L of 
methanol, followed by filtration four times to remove the DMF. The final 
filtered pigment is dried at 80.degree.-85.degree. under vacuum to remove 
residual methanol. 
Particle size of CllnPc materials before and after treatment is examined 
using electron microscopy. Prior to treatment, particle size is from 50 to 
1000 nm. After treatment, the particle size of the ClinPc materials are 
significantly reduced to vary from 50 to 250 nm. Larger particles are no 
longer present. 
The pigment is dispersed as follows: A solution of n-butyl acetate, 900 g, 
and polyvinyl butyral, 32 g is prepared. The CllnPc pigment, 68 g, is 
added and the mixture stirred for 1 hour using a high shear Silverson 
mixer. The mixture is then circulated through a Dynomill dispersing 
apparatus containing 0.4 mm ZrO media to reduce particle size to about 
0.1-0.2 .mu.m. An additional 900 g of n-butyl acetate is added to the 
dispersion to prepare a coating composition. 
The dispersion composition prepared above is added to a small dip tank. A 
drum that has have been precoated with a 1.5 .mu.m Luckamide (polyamide) 
undercoat layer is dip coated to apply the charge generation layer (CGL). 
The drum is dried and overcoated with a charge transport layer (CTL) to a 
thickness between 15-20 .mu.m. 
Table 1 illustrates the beneficial effects of the pretreated CllnPc 
compared to the untreated CllnPc. Increased sensitivity is demonstrated by 
both the dV/dX number, which represents initial slope of the Photo Induced 
Discharge Curve (PIDC). PIDC is used to characterize photoresponse of a 
photoreceptor by plotting surface potential versus exposed energy. A steep 
initial dV/dX slope indicates high sensitivity. Sensitivity is further 
demonstrated by the 7 erg and 25 erg exposure voltages, which are 
significantly lower when using the treated pigment. Plotted dV/dX values 
indicate that sensitivity is increased by 53% by the treatment of the 
present invention. 
TABLE 1 
______________________________________ 
Untreated Treated 
Xerographic Characteristic 
CllnPc CllnPc 
______________________________________ 
Vddp 350 350 
Sensitivity dV/dX 26 40 
dark decay % 4 6 
7 erg exposure voltage 
259 210 
25 erg exposure voltage 
131 90 
Residual voltage 45 44 
______________________________________ 
While the invention has been described with reference to a particular 
preferred embodiment, the invention is not limited to the specific Example 
given, and other embodiments and modifications can be made by those 
skilled in the art without departing from the spirit and scope of the 
invention and claims.