Photoconductive imaging members

A photoconductive imaging member comprised of a hydroxygallium phthalocyanine photogenerator layer, a charge transport layer, a barrier layer, a photogenerator layer comprised of a mixture of bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline -6,11-dione and bisbenzimidazo(2,1 -a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline-10,21-dione, and thereover a charge transport layer.

COPENDING APPLICATIONS AND PATENTS 
Disclosed in copending application U.S. Ser. No. 700,326, now U.S. Pat. No. 
5,645,965, the disclosure of which is totally incorporated herein by 
reference, are photoconductive imaging members with perylenes and a number 
of charge transports, such as amines. These charge transports may be 
selected for the imaging members of the present invention. 
Illustrated in U.S. Pat. No. 5,493,016, the disclosure of which is totally 
incorporated herein by reference, are imaging members comprised of a 
supporting substrate, a photogenerating layer of hydroxygallium 
phthalocyanine, a charge transport layer, a photogenerating layer of BZP 
perylene, which is preferably a mixture of 
bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-6,11-dione and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10, 21-dione, reference U.S. Pat. No. 4,587,189, the disclosure of which 
is totally incorporated herein by reference; and as a top layer a second 
charge transport layer. 
Also, in U.S. Pat. No. 5,473,064, the disclosure of which is totally 
incorporated herein by reference, there is illustrated a process for the 
preparation of hydroxygallium phthalocyanine Type V, essentially free of 
chlorine, whereby a pigment precursor Type I chlorogallium phthalocyanine 
is prepared by reaction of gallium chloride in a solvent, such as 
N-methylpyrrolidone, present in an amount of from about 10 parts to about 
100 parts, and preferably about 19 parts with 1,3-diiminoisoindolene 
(Dl.sup.3) in an amount of from about 1 part to about 10 parts, and 
preferably about 4 parts of Dl.sup.3, for each part of gallium chloride 
that is reacted; hydrolyzing said pigment precursor chlorogallium 
phthalocyanine Type I by standard methods, for example acid pasting, 
whereby the pigment precursor is dissolved in concentrated sulfuric acid 
and then reprecipitated in a solvent, such as water, or a dilute ammonia 
solution, for example from about 10 to about 15 percent; and subsequently 
treating the resulting hydrolyzed pigment hydroxygallium phthalocyanine 
Type I with a solvent, such as N,N-dimethylformamide, present in an amount 
of from about 1 volume part to about 50 volume parts and preferably about 
15 volume parts for each weight part of pigment hydroxygallium 
phthalocyanine that is used by, for example, ball milling the Type I 
hydroxygallium phthalocyanine pigment in the presence of spherical glass 
beads, approximately 1 millimeter to 5 millimeters in diameter, at room 
temperature, about 25.degree. C., for a period of from about 12 hours to 
about 1 week, and preferably about 24 hours. 
BACKGROUND OF THE INVENTION 
This invention is generally directed to imaging members, and, more 
specifically, the present invention is directed to improved multilayered 
imaging members with two photogenerating layers, one of which is sensitive 
to a wavelength of from about 500 to about 800 nanometers, such as BZP, 
reference U.S. Pat. No. 4,587,189, the disclosure of which is totally 
incorporated herein by reference, and one of which is sensitive to a 
wavelength of from about 550 to about 950 nanometers, reference for 
example U.S. Pat. No. 5,482,811, the disclosure of which is totally 
incorporated herein by reference, especially Type V hydroxygallium 
phthalocyanine, and situated therebetween, and more specifically between 
the charge transport layer with the hydroxygaliium phthalocyanine and the 
BZP layer, a suitable barrier layer of, for example, a polyester, such as 
MOR-ESTER 49,000.RTM. available from Norton International, and wherein 
there is enabled a number of advantages for the resulting imaging member, 
such as improving the BZP coating quality, and the photoconductive imaging 
member electricals of photosensitivity, and cycling stability. The 
photogenerating layers can be exposed to light of the appropriate 
wavelengths simultaneously, sequentially, or alternatively only one of the 
photogenerating layers can be exposed. The imaging members of the present 
invention in embodiments exhibit excellent cyclic stability, independent 
layer discharge, and substantially no adverse changes in performance over 
extended time periods. The aforementioned photoresponsive, or 
photoconductive imaging members can be negatively charged when the 
photogenerating layers are situated between the hole transport layers and 
the substrate. Processes of imaging, especially xerographic imaging and 
printing, including digital, are also encompassed by the present 
invention. More specifically, the layered photoconductive imaging members 
can be selected for a number of different known imaging and printing 
processes including, for example, electrophotographic imaging processes, 
especially xerographic imaging and printing processes wherein negatively 
charged or positively charged images are rendered visible with toner 
compositions of an appropriate charge polarity. The imaging members as 
indicated herein are in embodiments sensitive in the wavelength region of, 
for example, from about 550 to about 900 nanometers, and in particular, 
from about 700 to about 850 nanometers, thus diode lasers can be selected 
as the light source. Moreover, the imaging members of this invention are 
preferably useful in color xerographic applications where several color 
printings can be achieved in a single pass. 
Photoresponsive imaging members with BZP alone, and hydroxygallium alone as 
a photogenerator pigment are known. These photoresponsive imaging members 
are usually comprised of a single generator and a single transport layer, 
and they can be selected in xerographic printing processes to perform one 
pass/one color printing. Multiple color printing requires repeating the 
process several times depending on the number of colors selected. Also, in 
the known trilevel xerographic process, conventional photoresponsive 
imaging members are used in one pass/two color printing processes. The 
imaging member is selectively discharged with a single laser source to 
create three potential levels and later toned to create two color printing 
processes. 
Thus, there remains a need for improving the color printing capability of 
xerographic processes, and in particular, to print more colors with a 
minimum number of passes, and therefore, improve the productivity of the 
printing process, and moreover, there is a need for improved 
photoconductive imaging members with excellent BZP coating qualities, and 
improved photoconductor electricals. This can be achieved with the imaging 
members of the present invention wherein there are sequentially arranged, 
for example, five layers. These imaging members can be referred to as a 
multilayered two-tier photoresponsive imaging member. The photodischarge 
behavior of two-tier imaging members can be selectively controlled by the 
wavelengths of exposure light and hence the member can be fully 
discharged, partially discharged or zero discharged. There can be two 
partially discharged areas depending, for example, on the location of the 
photodischarge, top tier discharge or bottom tier discharge. The fully 
discharged and zero discharged areas can be developed with appropriate 
toners to provide two different colors. Also, a flood exposure with a 
light effective on only the top tier can be selected to remove its partial 
charge to zero. The zero charge area can then be developed with another 
color toner. With two lasers of selected wavelengths, one effective on the 
top tier, the other on the bottom tier, and applying a further flood 
discharge on the top tier, three color printing in a single pass is 
achieved. 
PRIOR ART 
Layered photoresponsive imaging members have been described in a number of 
U.S. patents, such as U.S. Pat. No. 4,265,990, the disclosure of which is 
totally incorporated herein by reference, wherein there is illustrated an 
imaging member comprised of a photogenerating layer, and an aryl amine 
hole transport layer. Examples of photogenerating layer components include 
trigonal selenium, metal phthalocyanines, vanadyl phthalocyanines, and 
metal free phthalocyanines. Additionally, there is described in U.S. Pat. 
No. 3,121,006 a composite xerographic photoconductive member comprised of 
finely divided particles of a photoconductive inorganic compound dispersed 
in an electrically insulating organic resin binder. The binder materials 
disclosed in the '006 patent comprise a material which is incapable of 
transporting for any significant distance injected charge carriers 
generated by the photoconductive particles. 
The use of certain perylene pigments as photoconductive substances is also 
known. There is thus described in Hoechst European Patent Publication 
0040402, DE3019326, filed May 21, 1980, the use of N,N'-disubstituted 
perylene-3,4,9,10-tetracarboxyldiimide pigments as photoconductive 
substances. Specifically, there is, for example, disclosed in this 
publication 
N,N'-bis(3-methoxypropyl)perylene-3,4,9,10-tetracarboxyldiimide dual 
layered negatively charged photoreceptors with improved spectral response 
in the wavelength region of 400 to 700 nanometers. A similar disclosure is 
revealed in Ernst Gunther Schlosser, Journal of Applied Photographic 
Engineering, Vol. 4, No. 3, page 118 (1978). There are also disclosed in 
U.S. Pat. No. 3,871,882 photoconductive substances comprised of specific 
perylene-3,4,9,10-tetracarboxylic acid derivative dyestuffs. In accordance 
with the teachings of this patent, the photoconductive layer is preferably 
formed by vapor depositing the dyestuff in a vacuum. Also, there are 
specifically disclosed in this patent dual layer photoreceptors with 
perylene-3,4,9,10-tetracarboxylic acid diimide derivatives, which have 
spectral response in the wavelength region of from 400 to 600 nanometers. 
Also, in U.S. Pat. No. 4,555,463, the disclosure of which is totally 
incorporated herein by reference, there is illustrated a layered imaging 
member with a chloroindium phthalocyanine photogenerating layer. In U.S. 
Pat. No. 4,587,189, the disclosure of which is totally incorporated herein 
by reference, there is illustrated a layered imaging member with, for 
example, a BZP perylene, pigment photogenerating component. Both of the 
aforementioned patents disclose an aryl amine component as a hole 
transport layer. 
The disclosures of all of the aforementioned publications, laid open 
applications, copending applications and patents are totally incorporated 
herein by reference. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide imaging members thereof 
with many of the advantages illustrated herein. 
Another object of the present invention relates to the provision of 
improved layered photoresponsive imaging members with photosensitivity to 
near infrared radiations. 
It is yet another object of the present invention to provide improved 
layered photoresponsive imaging members with a sensitivity to visible 
light, and which members possess improved electricals and improved coating 
characteristics, especially for BZP, and wherein the charge transport 
molecules do not diffuse, or there is minimum diffusion thereof into the 
BZP layer. 
Moreover, another object of the present invention relates to the provision 
of improved layered photoresponsive imaging members with simultaneous 
photosensitivity to near infrared radiations, for example from about 550 
to about 950 nanometers, and to light of a wavelength of from about 500 to 
about 800 nanometers. 
It is yet another object of the present invention to provide 
photoconductive imaging members with two photogenerating layers, and two 
charge transport layers, and a barrier layer. 
In a further object of the present invention there are provided imaging 
members containing as one of the photogenerating pigments Type V 
hydroxygallium phthalocyanine, especially with XRPD peaks at, for example, 
Bragg angles (2 theta.+-.0.20.degree.) of 7.4, 9.8, 12.4, 16.2, 17.6, 
18.4, 21.9, 23.9, 25.0, 28.1, and the highest peak at 7.4 degrees. The 
X-ray powder diffraction traces (XRPDs) were generated on a Philips X-Ray 
Powder Diffractometer Model 1710 using X-radiation of CuK-alpha wavelength 
(0.1542 nanometer). The diffractometer was equipped with a graphite 
monochrometer and pulse-height discrimination system. Two-theta is the 
Bragg angle commonly referred to in x-ray crystallographic measurements. I 
(counts) represents the intensity of the diffraction as a function of 
Bragg angle as measured with a proportional counter. 
In still a further object of the present invention there are provided 
multilayered two-tier photoresponsive, or photoconductive imaging members 
which can be selected for imaging processes including color xerography, 
such as xerocolography, and three color printing by selectively 
discharging the two-tier imaging member wherein, for example, three 
different surface potentials can be obtained after exposure to light, that 
is for example zero voltage when both tiers are discharged; partial 
voltage when one tier is discharged, or full voltage when neither tier is 
discharged. 
In embodiments the present invention relates to the provision of imaging 
members with, for example, a two-tier design. More specifically, the 
photoconductive imaging members of the present invention are comprised of 
an optional supporting substrate, a photogenerating layer of 
hydroxygallium phthalocyanine, a charge transport layer, a barrier layer, 
a photogenerating layer of BZP perylene, which is preferably a mixture of 
bisbenzim 
idazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline-6,11-dio 
ne and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10,21-dione, reference U.S. Pat. No. 4,587,189, the disclosure of which is 
totally incorporated herein by reference; and as a top layer a second 
charge transport layer. In embodiments, it is preferred that the BZP layer 
possess an optical density of at least 2 to absorb about 99 percent or 
more of the about 500 to about 700 nanometers radiation, thus the lower 
tier (HOGaPc generator and bottom transport layer) will not be discharged 
by such a radiation or any monochromatic light with, for example, 
wavelengths within the range of about 500 to about 700 nanometers. 
The two-tier imaging member can be selected in color xerographic printing 
processes. More specifically, when selectively imaged with two laser 
lights of different wavelengths, color xerographic printing enables 
printing of three colors in a single pass process. After being charged to 
about -800 volts, the imaging member is selectively discharged by exposure 
to a suitable type of light. The top tier comprising BZP and top transport 
layer is discharged by about 680 nanometers of radiation. The bottom tier 
is discharged by about 830 nanometers of radiation. Thus, four resultant 
areas on the imaging member are created after passing an imaging station; 
and (a) the unexposed area retains the original surface potential, about 
-800 volts, (b) the area exposed with about 680 nanometers, which is 
discharged to about one-half of the original surface voltage, about -400 
volts, (c) the area exposed with about 830 nanometers, which is also 
discharged to about one-half of the original surface voltage, that is 
about. -400 volts; and (d) the area exposed with both about 680 and about 
830 nanometers which is fully discharged to about 0 (zero) volts. While 
only three potential levels are present on the imaging member at this 
stage immediately after exposure, there will be four distinctively 
different areas on the surface of the imaging member after xerographic 
development as indicated herein. After toning the area (a) with charge 
area development (CAD), the surface potential of (a) is changed to -400 
volts by a positively charged black toner. Then, applying discharge area 
development step (DAD) and toning area (b), the surface potential is 
changed to -400 volts by negatively charged toners. As a result, the four 
areas are at equal potential (-400 volts) at this stage. By exposing the 
imaging member with a broad band exposure 500 to 700 nanometers, only area 
(c) is further discharged to 0 volts as the BZP layer is photoactive in 
this wavelength range. Area (a) is not discharged as the toners on it 
block this radiation. Area (b) is not discharged because the top BZP 
generator layer completely absorbs the radiation. By applying a (DAD) 
step, area (c) is now toned with another color toner. Area (b) remains 
untoned. Therefore, three color toners can be deposited in a single pass. 
Embodiments of the present invention include a method of imaging which 
comprises generating an electrostatic latent image on the imaging member 
comprised in the following order of a supporting substrate, a 
hydroxygallium phthalocyanine photogenerator layer, a first charge 
transport layer, a barrier layer, a photogenerator layer comprised of a 
mixture of 
bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-6,11-dione and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10,21-dione, and as a top layer a second charge transport layer; 
developing the latent image; and transferring the developed electrostatic 
image to a suitable substrate; and wherein the imaging member is first 
exposed to light of a wavelength of from about 500 to about 800 
nanometers, and then is exposed to light of a wavelength of from about 550 
to about 950 nanometers; and a method of imaging which comprises 
generating an electrostatic latent image on an imaging member comprised of 
a supporting substrate, a hydroxygallium phthalocyanine photogenerator 
layer, a first charge transport layer, a polyester barrier layer, a 
photogenerator layer comprised of a mixture of 
bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-6,11-dione and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10,21-dione, and as a top layer a second charge transport layer, 
developing the latent image; and transferring the developed electrostatic 
image to a suitable substrate; and wherein the imaging member is 
simultaneously exposed to light of a wavelength of from about 500 to about 
800 nanometers; and a wavelength of from about 550 to about 950 
nanometers. 
Of importance with respect to the present invention is the selection of a 
suitable barrier layer, examples of which include polyesters, such as 
VITAL.RTM. PE100 and PE200 available from Goodyear Chemicals, and 
especially MOR-ESTER 49,000.RTM. available from Norton International. The 
barrier layer can be coated on to the first charge transport layer from a 
tetrahydrofuran and/or dichloromethane solution with a thickness ranging 
from 0.1 to 3.0 microns. The main function of the barrier layer is to 
prevent the diffusion of transport molecules from the first transport 
layer into the top BZP layer, which otherwise results in charge leakage 
and cross talk. Cross talk refers, for example, to the undesirable 
discharge of one generator layer when the second generator layer is 
exposed to laser light. For example, if a two-tier imaging member is 
charged to -800V, ideally a 400V (50 percent) discharge with no cross talk 
is expected from each tier when they are sequentially exposed to light. 
However, in a non-ideal situation, the first tier might be photodischarged 
to, for example, -400V followed by a voltage drop of 200V, due to charge 
leakage, followed by the photodischarge of the second tier to zero volt. 
In this situation, the imaging member can possess a 25 percent cross talk. 
Cross talks of, for example, less than 3 percent are acceptable and will 
not, it is believed, adversely affect developability. The incorporation of 
the barrier layer significantly improves the discharge split of the 
two-tier imaging member and reduced cross talk from about 17 to 21 percent 
to about 2 to 4 percent. Also, in embodiments there may be selected, it is 
believed, in place of the barrier layer known blocking layer components. 
The hydroxygallium photogenerating layer, which is preferably comprised of 
hydroxygallium phthalocyanine Type V, is in embodiments comprised of, for 
example, about 50 weight percent of the Type V and about 50 weight percent 
of a resin binder like polystyrene/polyvinylpyridine; and the BZP layer is 
in embodiments comprised of, for example, about 80 weight percent of BZP 
dispersed in a resin binder like polyvinylbutyral. The photoconductive 
imaging member with two photogenerating layers and two charge transport 
layers can be prepared by a number of methods, such as the coating of the 
layers, and more specifically as illustrated herein. Thus, the 
photoresponsive imaging members of the present invention can in 
embodiments be prepared by a number of known methods, the process 
parameters and the order of coating of the layers being dependent, for 
example, on the member desired. The photogenerating and charge transport 
layers of the imaging members can be coated as solutions or dispersions 
onto a selective substrate by the use of a spray coater, dip coater, 
extrusion coater, roller coater, wire-bar coater, slot coater, doctor 
blade coater, gravure coater, and the like, and dried at from 40 to about 
200.degree. C. for from 10 minutes to several hours under stationary 
conditions or in an air flow. The coating can be accomplished to provide a 
final coating thickness of from about 0.01 to about 30 microns after 
drying. The fabrication conditions for a given photoconductive layer can 
be tailored to achieve optimum performance and cost in the final members. 
Imaging members of the present invention are useful in various 
electrostatographic imaging and printing systems, particularly those 
conventionally known as xerographic processes. Specifically, the imaging 
members of the present invention are useful in xerographic imaging 
processes wherein the Type V hydroxygallium phthalocyanine pigment absorbs 
light of a wavelength of from about 550 to about 950 nanometers, and 
preferably from about 700 to about 850 nanometers; and wherein the second 
BZP layer absorbs light of a wavelength of from about 500 to about 800 
nanometers, and preferably from about 600 to about 750 nanometers. In 
these processes, electrostatic latent images are initially formed on the 
imaging member followed by development, and thereafter, transferring the 
image to a suitable subpresent invention the imaging members of the 
present invention can be selected for electronic printing processes with 
gallium arsenide diode lasers, light emitting diode (LED) arrays which 
typically function at wavelengths of from 660 to about 830 nanometers. 
In embodiments, the photoconductive imaging member comprised in sequence of 
a conductive supporting substrate, a hydroxygallium phthalocyanine 
photogenerating layer thereover, a first transport layer, a blocking 
layer, a BZP photogenerating layer thereover, and a second top transport 
layer, can be initially charged with red light, about 670 nanometers, IR, 
about 830 nanometers, and subsequently charged with red light at 670 
nanometers, and IR at 830 nanometers, and which subsequent charges are 
applied to a portion of the member not initially charged. 
The negatively charged photoresponsive imaging member of the present 
invention in embodiments is comprised, in the following sequence, of a 
supporting substrate, a barrier layer comprised of, for example, MOR-ESTER 
49,000.RTM., a photogenerator layer comprised of Type V hydroxygallium 
phthalocyanine, optionally dispersed in an inactive polymer binder, a 
first hole transport layer thereover comprised of 
N,N'-diphenyl-N,N'-bis(3-methyl phenyl)-1,1'-biphenyl-4,4'-diamine 
dispersed in a polycarbonate binder, a barrier layer thereover, thereover 
a photogenerating layer of BZP, and a top layer of 
N,N'-diphenyl-N,N'-bis(3-methyl phenyl)-1,1'-biphenyl-4,4'-diamine 
dispersed in a polycarbonate binder. Embodiments of the present invention 
also include a photoconductive imaging member comprised of a 
hydroxygallium phthalocyanine photogenerator layer, a charge transport 
layer, a barrier layer, a photogenerator layer comprised of a mixture of 
bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-6,11-dione and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10,21-dione, and thereover a charge transport layer. 
Examples of substrate layers selected for the imaging members of the 
present invention can be opaque or substantially transparent, and may 
comprise any suitable material having the requisite mechanical properties. 
Thus, the substrate may comprise a layer of insulating material including 
inorganic or organic polymeric materials, such as MYLAR.RTM. a 
commercially available polymer, MYLAR.RTM. containing titanium, a layer of 
an organic or inorganic material having a semiconductive surface layer, 
such as indium tin oxide, or aluminum arranged thereon, or a conductive 
material inclusive of aluminum, chromium, nickel, brass or the like. The 
substrate may be flexible, seamless, or rigid, and many have a number of 
many different configurations, such as for example a plate, a cylindrical 
drum, a scroll, an endless flexible belt, and the like. In one embodiment, 
the substrate is in the form of a seamless flexible belt. In some 
situations, it may be desirable to coat on the back of the substrate, 
particularly when the substrate is a flexible organic polymeric material, 
an anticurl layer, such as for example polycarbonate materials 
commercially available as MAKROLON.RTM.. 
The thickness of the substrate layer depends on many factors, including 
economical considerations, thus this layer may be of substantial 
thickness, for example over 3,000 microns, or of minimum thickness 
providing there are no adverse effects on the system. In one embodiment, 
the thickness of this layer is from about 75 microns to about 300 microns. 
Generally, the thickness of each of the photogenerator layers depends on a 
number of factors, including the thicknesses of the other layers and the 
amount of photogenerator material contained in these layers. Accordingly, 
each layer can be of a thickness of, for example, from about 0.05 micron 
to about 10 microns, and more specifically, from about 0.25 micron to 
about 1 micron when, for example, each of the photogenerator compositions 
is present in an amount of from about 30 to about 75 percent by volume. 
The maximum thickness of the layers in an embodiment is dependent 
primarily upon factors, such as photosensitivity, electrical properties 
and mechanical considerations. The photogenerating layer binder resin, 
present in various suitable amounts, for example from about 1 to about 20, 
and more specifically from about 1 to about 10 weight percent, may be 
selected from a number of known polymers such as poly(vinyl butyral), 
poly(vinyl carbazole), polyesters, polycarbonates, poly(vinyl chloride), 
polyacrylates and methacrylates, copolymers of vinyl chloride and vinyl 
acetate, phenoxy resins, polyurethanes, poly(vinyl alcohol), 
polyacrylonitrile, polystyrene, and the like. In embodiments of the 
present invention, it is desirable to select a coating solvent that does 
not disturb or adversely effect the other previously coated layers of the 
device. Examples of solvents that can be selected for use as coating 
solvents for the photogenerator layers are ketones, alcohols, aromatic 
hydrocarbons, halogenated aliphatic hydrocarbons, ethers, amines, amides, 
esters, and the like. Specific examples are cyclohexanone, acetone, methyl 
ethyl ketone, methanol, ethanol, butanol, amyl alcohol, toluene, xylene, 
chlorobenzene, carbon tetrachloride, chloroform, methylene chloride, 
trichloroethylene, tetrahydrofuran, dioxane, diethyl ether, dimethyl 
formamide, dimethyl acetamide, butyl acetate, ethyl acetate, methoxyethyl 
acetate, and the like. 
The coating of the photogenerator layers in embodiments of the present 
invention can be accomplished with spray, dip or wire-bar methods such 
that the final dry thickness of the photogenerator layer is, for example, 
from about 0.01 to about 30 microns and preferably from about 0.1 to about 
15 microns after being dried at, for example, about 40.degree. C. to about 
150.degree. C. for about 5 to about 90 minutes. 
Illustrative examples of polymeric binder materials that can be selected 
for the photogenerator pigments are as indicated herein, and include those 
polymers as disclosed in U.S. Pat. No. 3,121,006, the disclosure of which 
is totally incorporated herein by reference. 
As adhesives usually in contact with the supporting substrate, there can be 
selected various known substances inclusive of polyesters, polyamides, 
poly(vinyl butyral), poly(vinyl alcohol), polyurethane and 
polyacrylonitrile. This layer is of a thickness of from about 0.001 micron 
to about 1 micron. Optionally, this layer may contain effective suitable 
amounts, for example from about 1 to about 10 weight percent, conductive 
and nonconductive particles, such as zinc oxide, titanium dioxide, silicon 
nitride, carbon black, and the like, to provide, for example, in 
embodiments of the present invention further desirable electrical and 
optical properties. 
Aryl amines selected for the hole transporting layers, which generally is 
of a thickness of from about 5 microns to about 75 microns, and preferably 
of a thickness of from about 10 microns to about 40 microns, include 
molecules of the following formula 
##STR1## 
dispersed in a highly insulating and transparent polymer binder, wherein X 
is an alkyl group, a halogen, or mixtures thereof, especially those 
substituents selected from the group consisting of Cl and CH.sub.3. 
Examples of specific aryl amines are 
N,N'-diphenyl-N,N'-bis(alkylphenyl)-1,1-biphenyl-4,4'-diamine wherein 
alkyl is selected from the group consisting of methyl, ethyl, propyl, 
butyl, hexyl, and the like; and 
N,N'-diphenyl-N,N'-bis(halophenyl)-1,1'-biphenyl-4,4'-diamine wherein the 
halo substituent is preferably a chloro substituent. Other known charge 
transport layer molecules can be selected, reference for example U.S. Pat. 
Nos. 4,921,773 and 4,464,450, the disclosures of which are totally 
incorporated herein by reference. 
Examples of the highly insulating and transparent polymer binder material 
for the transport layers include components, such as those described in 
U.S. Pat. No. 3,121,006, the disclosure of which is totally incorporated 
herein by reference. Specific examples of polymer binder materials include 
polycarbonates, acrylate polymers, vinyl polymers, cellulose polymers, 
polyesters, polysiloxanes, polyamides, polyurethanes and epoxies as well 
as block, random or alternating copolymers thereof. Preferred electrically 
inactive binders are comprised of polycarbonate resins having a molecular 
weight of from about 20,000 to about 100,000 with a molecular weight of 
from about 50,000 to about 100,000 being particularly preferred. 
Generally, the transport layer contains from about 10 to about 75 percent 
by weight of the charge transport material, and preferably from about 35 
percent to about 50 percent of this material. 
Also, included within the scope of the present invention are methods of 
imaging and printing with the photoresponsive devices illustrated herein. 
These methods generally involve the formation of an electrostatic latent 
image on the imaging member, followed by developing the image with a toner 
composition comprised, for example, of thermoplastic resin, colorant, such 
as pigment, charge additive, and surface additives, reference U.S. Pat. 
Nos. 4,560,635; 4,298,697 and 4,338,390, the disclosures of which are 
totally incorporated herein by reference, subsequently transferring the 
image to a suitable substrate, and permanently affixing the image thereto. 
In those environments wherein the device is to be used in a printing mode, 
the imaging method involves the same steps with the exception that the 
exposure step can be accomplished with a laser device or image bar.

The following Examples are being submitted to illustrate embodiments of the 
present invention. These Examples are intended to be illustrative only and 
are not intended to limit the scope of the present invention. Also, parts 
and percentages are by weight unless otherwise indicated. A comparative 
Example is also provided. 
All XRPDs were determined as indicated herein. 
EXAMPLE I 
Alkoxy-bridged Gallium Phthalocyanine Dimer Synthesis Using Gallium 
Methoxide Obtained From Gallium Chloride and Sodium Methoxide In Situ 
To a 1 liter round bottomed flask were added 25 grams of GaCl.sup.3 and 300 
milliliters of toluene, and the mixture was stirred for 10 minutes to form 
a solution. Then, 98 milliliters of a 25 weight percent sodium methoxide 
solution (in methanol) were added while cooling the flask with an ice bath 
to keep the contents below 40.degree. C. Subsequently, 250 milliliters of 
ethylene glycol and 72.8 grams of o-phthalodinitrile were added. The 
methanol and toluene were quickly distilled off over 30 minutes while 
heating from 70.degree. C. to 135.degree. C., and then the phthalocyanine 
synthesis was performed by heating at 195.degree. C. for 4.5 hours. The 
alkoxy-bridged gallium phthalocyanine dimer was isolated by filtration at 
120.degree. C. The product was then washed with 400 milliliters DMF at 
100.degree. C. for 1 hour and filtered. The product was then washed with 
600 milliliters of deionized water at 60.degree. C. for 1 hour and 
filtered. The product was then washed with 600 milliliters of methanol at 
25.degree. C. for 1 hour and filtered. The product was dried at 60.degree. 
C. under vacuum for 18 hours. The alkoxy-bridged gallium phthalocyanine 
dimer, 1,2-di(oxogallium phthalocyaninyl) ethane, was isolated as a dark 
blue solid in 77 percent yield. The dimer product was characterized by 
elemental analysis, infrared spectroscopy, .sup.1 H NMR spectroscopy and 
X-ray powder diffraction. Elemental analysis showed the presence of only 
0.10 percent of chlorine. Infrared spectroscopy: major peaks at 573, 611, 
636, 731, 756, 775, 874, 897, 962, 999, 1069, 1088, 1125, 1165, 1289, 
1337, 1424, 1466, 1503, 1611, 2569, 2607, 2648, 2864, 2950, and 3045 
cm.sup.-1 ; .sup.1 H NMR spectroscopy (TFA-d/CDCl.sub.3 solution, 1:1 v/v, 
tetramethylsilane reference): peaks at 4.00 (4H), 8.54 (16H), and 9.62 
(16H); X-ray powder diffraction pattern: peaks at Bragg angles (2 
theta.+-.0.2.degree.) of 6.7, 8.9, 12.8, 13.9, 15.7, 16.6, 21.2, 25.3, 
25.9, and 28.3 with the highest peak at 6.7 degrees. 
EXAMPLE II 
Hydrolysis of Alkoxy-bridged Gallium Phthalocyanine to Hydroxygallium 
Phthalocyanine (Type I) 
The hydrolysis of alkoxy-bridged gallium phthalocyanine synthesized in 
Example I to hydroxygallium phthalocyanine was performed as follows. 
Sulfuric acid (94 to 96 percent, 125 grams) was heated to 40.degree. C. in 
a 125 milliliter Erlenmeyer flask, and then 5 grams of the chlorogallium 
phthalocyanine were added. Addition of the solid was completed in 
approximately 15 minutes, during which time the temperature of the 
solution increased to about 48.degree. C. The acid solution was then 
stirred for 2 hours at 40.degree. C., after which it was added in a 
dropwise fashion to a mixture comprised of concentrated (30 percent) 
ammonium hydroxide (265 milliliters) and deionized water (435 
milliliters), which had been cooled to a temperature below 5.degree. C. 
The addition of the dissolved phthalocyanine was completed in 
approximately 30 minutes, during which time the temperature of the 
solution increased to about 40.degree. C. The reprecipitated 
phthalocyanine was then removed from the cooling bath and allowed to stir 
at room temperature for 1 hour. The resulting phthalocyanine was then 
filtered through a porcelain funnel fitted with a Whatman 934-AH grade 
glass fiber filter. The resulting blue solid was redispersed in fresh 
deionized water by stirring at room temperature for 1 hour and filtered as 
before. This process was repeated at least three times until the 
conductivity of the filtrate was &lt;20 .mu.S. The filter cake was oven dried 
overnight at 50.degree. C. to give 4.75 grams (95 percent) of Type I 
HOGaPc, identified by infrared spectroscopy and X-ray powder diffraction, 
XRPD. The X-ray powder diffraction traces (XRPDs) were generated on a 
Philips X-Ray Powder Diffractometer Model 1710 using X-radiation of 
CuK-alpha wavelength (0.1542 nanometers). The diffractometer was equipped 
with a graphite monochrometer and pulse-height discrimination system. 
Two-theta is the Bragg angle commonly referred to in x-ray 
crystallographic measurements. I (counts) represents the intensity of the 
diffraction as a function of Bragg angle as measured with a proportional 
counter. Infrared spectroscopy: major peaks at 507, 573, 629, 729, 756, 
772, 874, 898, 956, 984, 1092, 1121, 1165, 1188, 1290, 1339, 1424, 1468, 
1503, 1588, 1611, 1757, 1835, 1951, 2099, 2207, 2280, 2384, 2425, 2570, 
2608, 2652, 2780, 2819, 2853, 2907, 2951, 3049 and 3479 (broad) cm.sup.-1 
; X-ray diffraction pattern: peaks at Bragg angles of 6.8, 13.0, 16.5, 
21.0, 26.3 and 29.5 with the highest peak at 6.8 degrees (2 
theta.+-.0.2.degree.). 
EXAMPLE III 
Conversion of Type I Hydroxygallium Phthalocyanine to Type V 
The Type I hydroxygallium phthalocyanine pigment obtained in Example II was 
converted to Type V HOGaPc as follows. The Type I hydroxygallium 
phthalocyanine pigment (3.0 grams) was added to 25 milliliters of 
N,N-dimethylformamide in a 60 milliliter glass bottle containing 60 grams 
of glass beads (0.25 inch in diameter). The bottle was sealed and placed 
on a ball mill overnight (18 hours). The solid was isolated by filtration 
through a porcelain funnel fitted with a Whatman GF/F grade glass fiber 
filter, and washed in the filter using several 25 milliliter portions of 
acetone. The filtered wet cake was oven dried overnight at 50.degree. C. 
to provide 2.8 grams of Type V HOGaPc which was identified by infrared 
spectroscopy and X-ray powder diffraction. Infrared spectroscopy: major 
peaks at 507, 571, 631, 733, 756, 773, 897, 965, 1067, 1084, 1121, 1146, 
1165, 1291, 1337, 1425, 1468, 1503, 1588, 1609, 1757, 1848, 1925, 2099, 
2205, 2276, 2384, 2425, 2572, 2613, 2653, 2780, 2861, 2909, 2956, 3057 and 
3499 (broad) cm.sup.-1 ; X-ray diffraction pattern: peaks at Bragg angles 
of 7.4, 9.8, 12.4, 12.9, 16.2, 18.4, 21.9, 23.9, 25.0 and 28.1 with the 
highest peak at 7.4 degrees (2 theta.+-.0.20.degree.). 
EXAMPLE IV 
Fabrication and Testing of Two-Tier Imaging Member Without Barrier Layer 
A two-tier imaging member was prepared by sequentially coating the four 
layers: 1) HOGaPC generator of Example III, 2) charge transport, 3) BZP 
generator, and 4) charge transport all contained on a supporting substrate 
of a titanized MYLAR.RTM., which was precoated with a thin 0.025 micron 
silane blocking layer and a thin 0.1 micron polyester adhesive layer. The 
first photogenerating layer was hydroxygallium phthalocyanine as prepared 
above. The BZP for the second photogenerating layer was as illustrated in 
U.S. Pat. No. 4,587,189, and more specifically, was comprised of a mixture 
of about 50/50 weight percent of 
bisbenzimidazo(2,1-a-1',2'-b)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-6,11-dione and 
bisbenzimidazo(2,1-a:2',1'-a)anthra(2,1,9-def:6,5,10-d'e'f')diisoquinoline 
-10,21-dione. The dispersion of Type V hydroxygallium phthalocyanine 
(HOGaPC) was prepared by milling 0.125 gram of the HOGaPC, prepared as 
described in Example III, from a precursor pigment, which was prepared as 
described in Example I, and 0.125 gram of polystyrene-b-polyvinylpyridine 
in 9.0 grams of chlorobenzene in a 30 milliliter glass bottle containing 
70 grams of 1/8 inch stainless steel balls. The bottle was put on a Norton 
roller mill running at 300 rpm for 20 hours. The dispersion was coated on 
the titanized MYLAR.RTM. substrate using 1 mil film applicator to form a 
photogenerator layer. The formed photogenerating layer HOGaPc was dried at 
135.degree. C. for 20 minutes to a final thickness of about 0.3 micron. 
A hole transporting layer solution was prepared by dissolving 2.64 grams of 
N,N'-diphenyl-N,N-bis(3-methyl phenyl)-1,1'-biphenyl-4,4'-diamine, and 3.5 
grams of polycarbonate in 40 grams of dichloromethane. The solution was 
coated onto the HOGaPc generator layer using a 6 mil film applicator. The 
charge transporting layer thus obtained was dried at from 100.degree. C. 
to 135.degree. C. for 20 minutes to provide a final thickness of about 15 
microns. 
Thereafter, the BZP generator layer was coated thereover as illustrated 
above. The BZP dispersion was prepared by milling 0.40 gram of BZP pigment 
mixture, 0.1 gram of polycarbonate, and 8.00 grams of tetrahydrofuran in a 
30 milliliter bottle containing 70 grams of 1/8 inch stainless steel 
balls. The milling time was for 5 days. The BZP dispersion was diluted and 
coated with a 2 mil applicator and the coated device was dried at from 
100.degree. C. to 135.degree. C. for 20 minutes. The optical density of 
the BZP layer was greater than 2.0. Finally, a transport layer comprised 
of a second diamine hole transport layer identified above was coated on 
top of the BZP layer and dried as illustrated before. The resulting device 
was comprised of four sequentially deposited layers, bottom HOGaPc 
generator layer/bottom charge transport layer/top BZP generator layer/top 
charge transport layer, and all contained on a titanized MYLAR.RTM. 
conductive substrate. 
The xerographic electrical properties of the imaging member can be 
determined by known means, including as indicated herein electrostatically 
charging the surfaces thereof with a corona discharge source until the 
surface potentials, as measured by a capacitively coupled probe attached 
to an electrometer, attained an initial value V.sub.o of about -800 volts. 
After resting for 0.5 second in the dark, the charged members attained a 
surface potential of V.sub.ddp, dark development potential. Each member 
was then exposed to light from a filtered Xenon lamp with a XBO 150 watt 
bulb, thereby inducing a photodischarge which resulted in a reduction of 
surface potential to a V.sub.bg value, background potential. The percent 
of photodischarge was calculated as 100.times.(V.sub.ddp 
-V.sub.bg)/V.sub.ddp. The desired wavelength and energy of the exposed 
light was determined by the type of filters placed in front of the lamp. 
The monochromatic light photosensitivity was determined using a narrow 
band-pass filter. 
When exposing the charged imaging member with 680 nanometers of light at an 
intensity of 30 ergs/cm.sup.2, a photodischarge of 54 percent and a cross 
talk of 17 percent were obtained. Cross talk in a two-tier imaging member 
reduces developability and is undesirable discharge of a charge generating 
layer when the second generator layer is exposed to the laser light. 
When exposing the charged imaging member with the 830 nanometers of light 
at an intensity of 10 ergs/cm.sup.2, a photodischarge of 73 percent and a 
cross talk of 21 percent were observed. The imaging member was fully 
discharged when it was exposed to both 680 and 830 nanometers of light. 
The charged imaging members showed a significant amount of aging after six 
months. The cross talks measured (as above) at 680 nanometers and 830 
nanometers increased, respectively, to 36 percent and 33 percent. These 
results indicate that the photodischarge behavior of the two charge 
imaging members are not independent and that there is a cross talk between 
them. 
EXAMPLE V 
Fabrication and Testing of Two-Tier Imaging Member With Barrier Layer 
A two-tier imaging member was prepared by sequentially coating the five 
layers: 1) HOGaPC generator, 2) charge transport, 3) barrier layer, 4) BZP 
generator, and 5) charge transport all contained on a supporting substrate 
of a titanized MYLAR.RTM., which was precoated with a thin 0.025 micron 
silane blocking layer and a thin 0.1 micron polyester adhesive layer. The 
first and second photogenerating layers were, respectively, hydroxygallium 
phthalocyanine and BZP as prepared above. 
A hole transporting layer solution was prepared by dissolving 2.28 grams of 
N,N'-diphenyl-N,N-bis(3-methyl phenyl)-1,1'-biphenyl-4,4'-diamine, and 
4.23 grams of polycarbonate in 40 grams of dichloromethane. The solution 
was coated onto the HOGaPc generator layer using a 6 mil film applicator. 
The charge transporting layer thus obtained was dried at from 100.degree. 
C. to 135.degree. C. for 20 minutes to provide a final thickness of about 
15 microns. 
A barrier layer was prepared by dissolving 0.2 gram of MOR-ESTER 
49,000.RTM. polyester in 10 grams of dichloromethane. The solution was 
then coated onto the first charge transporting layer. The barrier layer 
thus obtained was dried at 100.degree. C. for 20 minutes to provide a 
final thickness of about 0.8 micron. 
Thereafter, the BZP generator layer was coated thereover as illustrated 
above. The optical density of the BZP layer was greater than about 2.0, 
for example about 2.5. Finally, the amine transport layer was prepared and 
coated on top of the BZP layer and dried as illustrated before. The 
resulting device was comprised of five sequentially deposited layers, 
bottom HOGaPc Type V generated from Example III, photogenerator 
layer/first charge transport layer/barrier layer/top BZP generator 
layer/second charge transport layer, and all contained on a titanized 
MYLAR.RTM. supporting conductive substrate. 
The xerographic electrical properties of the imaging member were determined 
by repeating the process of Example IV. 
When exposing the charged imaging member with the 680 nanometers of light 
at an intensity of 30 ergs/cm.sup.2, a photodischarge of 48 percent and a 
cross talk of 2 percent were obtained. When exposing the charged imaging 
member with the 830 nanometers of light at an intensity of 10 
ergs/cm.sup.2, a photodischarge of 46 percent and a cross talk of 4 
percent were observed. The two-tier imaging member with the barrier layer 
tested showed no sign of aging, and the cross talk and discharge 
characteristics were maintained; in contrast with the imaging member 
prepared without the barrier layer which evidenced substantial increase in 
cross talk with aging. 
These results indicated that by incorporating a barrier layer, the 
photodischarge behavior of the two-tier imaging member significantly 
improved, and compared with Example IV independent photodischarge from 
each tier with substantial decrease in cross talk was achieved. 
Furthermore, the barrier layer prevented the degradation of the two-tier 
imaging member with time. 
EXAMPLE VI 
Stability of Two-Tier Imaging Member with Barrier Layer 
The electrical stability of the two-tier imaging member of Example V was 
monitored by repeating the charging and discharging steps 10,000 times. In 
the first cycle, the member was charged to V.sub.ddp, about -800 volts, it 
was exposed to 670 nanometers light to have the top tier partially 
discharged to V2 (about -450 volts) due to light absorption by BZP, and 
then further discharged by 825 nanometers of light (absorbed by HOGaPc in 
the bottom tier) to V3 (at about -80 volts). The variations in V.sub.ddp, 
V2 and V3 and represented as .DELTA.V.sub.ddp, .DELTA.V2, .DELTA.V3 
provided an indication of the stability of the imaging member. In 10,000 
cycles, the changes .DELTA.V.sub.ddp, .DELTA.V2, .DELTA.V3 were only 23, 
20 and 27 volts indicating excellent electrical stability. The stability 
test was repeated again with charging, and discharging the bottom tier, 
and then the top tier using lights of 825 nanometers, and 670 nanometers, 
respectively. The variations of .DELTA.V.sub.ddp, .DELTA.V2 and .DELTA.V3 
were measured to be 16, 18 and 13 volts, and an excellent stability was 
observed. Whether the top or bottom tier of imaging member was the first 
to be discharged, the stability of the member was maintained for extended 
imaging cycles, for example 300,000 cycles. 
EXAMPLE VII 
Adhesive Strength of Two-Tier Imaging Member With Barrier Layer 
The adhesion of the multilayer imaging member was determined by peel 
strength measurements using an INSTRON.RTM. Tensile Tester. The procedure 
used was the standard test method for peel strength of adhesive bonds and 
identified as method ASTM D903 (American Society for Testing of 
Materials). The average load per unit width required to separate 
progressively one layer from the other over the adhered surfaces at a 
separation angle of 180.degree. C. was determined. It was expressed in 
units of grams/centimeter. The samples used were 15 centimeters 
(length).times.2.5 centimeters (width) and mounted on an aluminum backing 
plate. One end of the sample with the aluminum plate was held in the upper 
jaw of the INSTRON while the other end of the sample was peeled and held 
on the lower jaw of the INSTRON. During the test, the upper jaw was fixed 
while the lower jaw with the peeled sample was lowered at a speed of 30 
centimeters/minute. The testing machine was retained in an environmentally 
controlled room at a temperature of 50.degree. C. and a relative humidity 
of 23 percent. A two-tier imaging member of Example V with a barrier layer 
of MOR-ESTER 49,000.RTM. polyester and a thickness of 0.8 micron had a 
peel strength of 162 grams/centimeter. By comparison, a two-tier imaging 
member of Example IV with no barrier layer had a much lower peel strength 
of 67 grams/centimeter. 
Other embodiments and modifications of the present invention may occur to 
those skilled in the art subsequent to a review of the information 
presented herein; these embodiments and modifications, as well as 
equivalents thereof, are also included within the scope of this invention.