Apparatus for color development with a magnetic separator containing a stationary shell with rotating magnets

An improved apparatus for causing the development of electrostatic latent images on an imaging member consisting essentially of providing a moving deflected flexible imaging member, a moving toner transporting means, a development zone situated between said members, with the distance between the flexible imaging member and the transporting member being from about 0.05 millimeters to about 1.5 millimeters, a first developer reservoir with magnetic developer particles, a second developer reservoir with colored developer particles, and a magnetic separator comprised of a stationary shell with rotating magnets therein.

BACKGROUND OF THE INVENTION 
This invention generally relates to a process and an apparatus for 
effecting the development of color images. More specifically the present 
invention is directed to an improved process, and an improved apparatus 
for use in a single pass two-color development system, wherein 
contamination of the color developer is substantially eliminated. In one 
embodiment of the present invention there is provided in the development 
process and apparatus a magnet system which enables the removal of 
undesirable black toner particles from the color developer mixture. There 
is thus provided in an embodiment of the present invention an improved 
process, and an improved apparatus for obtaining color images by providing 
development zones encompassed by a moving deflected flexible imaging 
member and a moving transporting member, and wherein at one of the 
developer stations there is situated a magnet system for the purpose of 
removing black toner particles from the color developer composition 
reservoir thereby preventing contamination thereof. In this manner the 
process and apparatus of the present invention provides for the continual 
uncontaminated development of high quality images, particularly images of 
different colors, such as black and red, including the efficient and 
effective development of solid areas. Therefore, the problem of causing 
undesirable contamination of the colored toner composition black toner 
composition, for example, is uniquely solved in accordance with the 
process and apparatus of the present invention by positioning a magnet 
within the development apparatus. 
The development of images by electrostatographic means is well known. 
Generally in these processes toner particles are applied to an 
electrostatic latent image by various methods including cascade 
development, reference U.S. Pat. 3,618,552; magnetic brush development, 
U.S. Pat. Nos. 2,874,063; 3,251,706 and 3,357,402; powder cloud 
development, U.S. Pat. No. 2,217,776; and touchdown development, U.S. Pat. 
No. 3,166,432. Cascade development and powder cloud development are 
especially well suited for the development of line images common to 
business documents, however, images with solid areas are not faithfully 
reproduced by these methods. Magnetic brush development systems, however, 
provided an improved method for reproducing both line images and solid 
areas. 
In magnetic brush development systems, it is usually desirable to attempt 
to regulate the thickness of the developer composition, which is 
transported on a roller, by moving the roller past a metering blade. The 
adjustment of the metering blade is important, since in the development 
zone the flow of developer material is determined by a narrow restrictive 
opening situated between the transport roller and the imaging surface. 
Accordingly, in order to provide sufficient toner particles to the imaging 
surface, it is generally necessary to compress the developer bristles, 
thereby allowing toner particles adhering to the carrier particles near 
the ends of the bristle to be available for development. Any variation, or 
non-uniformity in the amount of developer metered onto the transport 
roller, or into the spacing between the transport roller and imaging 
member can result in undesired developer flow, and non-uniform image 
development. Non-uniform development is usually minimized by carefully 
controlling developer runout on the transport roller, and on the imaging 
member, and by providing a means for side-to-side adjustment in the 
relative positions of the metering blade, development roller and imaging 
member. 
While several improved toner and carrier materials as well as processes 
have been developed for the purpose of obtaining images, many difficulties 
existed in designing a simple, inexpensive and reliable two-component 
development system which will provide high solid area development rates, 
low background deposition, and long term stability. This was accomplished 
with the process and apparatus as described in U.S. Pat. No. 4,394,429 
entitled Development Process and Apparatus, the disclosure of which is 
totally incorporated herein by reference. There is illustrated in this 
patent a self-agitated two-component development process and apparatus 
wherein toner is continuously available immediately adjacent to a flexible 
deflected imaging member, and toner particles transfer from one layer of 
carrier particles to another layer of carrier particles in a development 
zone. More specifically, in one embodiment of the invention described in 
the 4,394,429 patent there is described an improved process for causing 
the development of electrostatic latent images on an imaging member 
comprising providing a development zone, ranging in length of from about 
0.5 centimeters to about 5 centimeters, encompassed by a tensioned 
deflected flexible imaging member and a transporting member, wherein the 
flexible imaging member is comprised of a supporting substrate, a 
photogenerating layer, and a diamine hole transport layer. The deflected 
flexible imaging member and transporting member can be caused to move in 
opposite directions at certain specific speeds; and furthermore, there is 
usually maintained a distance of from about 0.05 millimeters to about 1.5 
millimeters, between the flexible imaging member and the transporting 
member. 
Furthermore, it is known that color images can be obtained in xerographic 
imaging systems. Specifically, two-color reproduction systems serving 
distinct needs are generally known; representational wherein the colors of 
the reproduction are equivalent to those of the original document; and 
functional wherein the color to be reproduced merely serves to mark, 
distinguish or highlight portions of a document such as a text, graphs, or 
line drawings. In representational color processes, images are 
xerographically produced, for example by three successive color filter 
exposures, followed by an in-register transfer of toner images produced by 
three toners of the appropriate primary attractive colors. These processes 
are complex in that they require the superimposition of images on three 
separate exposures, either in three successive cycles, or on a 
photoreceptor of sufficient circumference or length to accommodate the 
images prior to transfer. Also, it is known to use in such processes a 
series of three separate in-register photoreceptor drums each contributing 
one image to the final transfer sheet. However, these processes can be 
costly, and can result in images of poor resolution in view of their 
complexity, and the necessity of using three separate photoreceptor drums. 
In the simpler highlight color imaging systems, to which the present 
invention relates, generally only two colors need to be reproduced. 
Specifically, in highlight color processes there are produced two color 
documents wherein, for example black may be used to represent the main 
text, and red, blue, or other color selected portions of the text, which 
are to be directed to the users attention by means of the highlight color. 
Accordingly, there can be generated images in two colors, such as red and 
black, by desirably employing only one imaging operation. 
Moreover, there is disclosed in U.S. Pat. No. 4,188,213, a method for 
producing color copies involving a number of complex steps including, for 
example, the recording of successive single color electrostatic latent 
images on an image bearing member, followed by developing each color 
electrostatic latent image with particles containing a predetermined 
dominant colorant therein corresponding to each recorded single color 
electrostatic latent image, transferring layers of the developed particles 
to a sheet of support material, and regulating electrically the transfer 
step in order that the successive thinner layers of particles are 
transferred from the image bearing member to a sheet of support material. 
Disclosed in this patent is a development method involving the deposition 
of particles containing a dominant cyan colorant with a minor magenta 
colorant impurity, on an electrostatic latent image formed from a red 
filtered image, depositing particles with a dominant magenta colorant with 
a minor yellow impurity on the electrostatic latent image formed from a 
green filtered light image, and depositing particles with a dominant 
yellow colorant on the electrostatic latent image formed from a blue 
filtered light image. Each successive layer of toner particles, which are 
transferred to a sheet of support material, is of a color corresponding to 
the color of impurity in the previously transferred layer of toner 
particles. Thus, successive layers of toner particles are transferred in 
superimposed registration with one another, with each successive 
transferred layer of toner particles correcting for the impurities in the 
colorant of the previously transferred layer of toner particles, thus 
producing a combination of toner particles substantially approximately the 
desired color. 
The invention disclosed in U.S. Pat. No. 4,189,224 solves some of the 
problems of the process of the 4,188,213 patent, in that the method 
described therein requires only a single exposure to derive a two color 
image. Therefore, registration and multiple cycling steps are eliminated. 
More specifically, there is described in U.S. Pat. No. 4,189,224 a two 
color electrostatic copying apparatus which can be operable for one color 
positive or negative copying. In accordance with the teachings of this 
patent, a photoconductive material with a conductive substrate, an inner 
photoconductive layer sensitive to visible light, and an outer 
photoconductive layer insensitive to red light, is subjected to an 
electrostatic charge applied to the outer layer, while at the same time 
irradiating the device with light so as to render one of the layers 
conductive. Subsequently, an electrostatic charge of opposite polarity is 
applied to the outer layer of the photoresponsive member, this step being 
accomplished in the dark. A light image of an original document is then 
projected onto the outer layer of the photoresponsive device, wherein 
white areas of the image cause photoconduction of both layers and red 
areas thereof, enabling photoconduction of only the inner layer. As a 
result, white areas are of zero surface potential, while red and black 
areas have non-zero surface potentials of opposite polarities. The images 
can then be developed with red and black toner particles of opposite 
charge. Thus, for example, red particles which are charged positively will 
be caused to adhere to negatively charged image areas, while black toner 
particles which are charged negatively will adhere to the black image 
areas which are charged positively. 
Also, disclosed in U.S. Pat. No. 4,078,929 is a single step 
electrostatographic copying process in which two different potential 
levels on a photoresponsive device may be developed in immediate sequence 
subsequent to a single exposure, by means of two differentially colored 
xerographic toners. The two potential levels may be of the same polarity 
or preferably of opposite polarities. In one embodiment of the invention 
disclosed in the 4,078,929 patent, positively charged toner particles of a 
first color, and negatively charged toner particles of a second color are 
about evenly concentrated in the relatively negative, and relatively 
positive areas of the imaging surface, thus allowing the positively 
charged toner particles to be attracted to the imaging surface with a 
negative charge pattern, while the negatively charged toner particles of a 
second color are attracted to the imaging surface with a positive charge 
pattern. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide an improved process and 
apparatus for effecting development of color images. 
In another object of the present invention there is provided an improved 
process and apparatus for single cycle two-color xerographic processes, 
such as the process as disclosed in U.S. Pat. No. 4,078,929, the subject 
matter of which is totally incorporated herein by reference. 
In yet another object of the present invention there is provided an 
improved process and apparatus which enables red intelligence on an 
original document to be distinguished from black intelligence on a 
relatively white colored background. 
In a further object of the present invention there is provided a process 
and apparatus wherein single cycle two-color imaging is affected and there 
is included in the development system magnets for the purpose of removing 
black toner particles from the reservoir with the color developer 
component thereby substantially eliminating contamination of this 
component. 
In yet another object of the present invention there is provided a process 
and apparatus useful for producing images in a two-color system, for 
example black and red, black and green, or black and blue, all on a white 
background, and wherein there is included in the development system a 
magnetic separator, enabling the removal of black toner particles, and 
thus avoiding contamination of the color developer mixture. 
In still another object of the present invention there is provided an 
improved process and apparatus with a moving deflected flexible imaging 
member, and a moving transporting member, reference U.S. Pat. No. 
4,394,429, the disclosure of which is totally incorporated herein by 
reference, and a magnetic separator for the purpose of removing black 
toner particles, thereby preventing contamination of the color developer 
mixture. 
These and other objects of the present invention are accomplished by 
providing a color development process and apparatus wherein toner is 
available continuously immediately adjacent to a flexible deflected 
imaging surface, and toner particles are transferred from one layer of 
carrier particles to another layer of carrier particles in a development 
zone. More specifically, there is provided in accordance with the present 
invention an improved process and apparatus for affecting the development 
of color images, especially black and red, comprising a transporting 
member, and a moving tensioned deflected flexible imaging member, a 
magnetic toner/developer reservoir, a reservoir with a colored developer 
mixture, and a separator means wherein black toner particles are attracted 
thereto enabling the substantial elimination of contamination of the color 
developer mixture. The developer particles are caused to be desirably 
agitated in a development zone situated between the deflected flexible 
imaging member and a transporting member, this agitation being dependent 
primarily on the arc or degree of deflection of the flexible imaging 
member, and the relative speeds of, and the distance between the flexible 
imaging member and the transporting member, while migration of the toner 
particles depends primarily on the magnitude of the electric field in the 
development zone. The details of this process and apparatus are described 
in U.S. Pat. No. 4,394,429, the disclosure of which is totally 
incorporated herein by reference. More specifically, there is described in 
this patent a process for causing the development of electrostatic latent 
images on an imaging member, comprising providing a development zone 
encompassed by a tensioned deflected flexible imaging member and a 
transporting member; causing the flexible imaging member to move at a 
speed of from about 5 cm/sec to about 50 om/sec; causing the transporting 
member to move at a speed of from about 6 cm/sec to about 100 cm/sec, said 
flexible member and said transporting member moving at different speeds; 
maintaining a distance between the flexible imaging member and the 
transporting member of from about 0.05 millimeters to about 1.5 
millimeters; adding developer particles to the development zone, which 
particles are comprised of electrically insulating toner particles and 
magnetic carrier particles, wherein the developer particles in the 
development zone are agitated; and the insulating toner particles migrate 
from one layer of carrier particles to another layer of carrier particles 
in the development zone, the carrier particles rotating in one direction 
then subsequently in another direction whereby toner particles are 
continuously made available immediately adjacent the flexible imaging 
member, said process being accomplished in the absence of a magnetic 
field. 
In another embodiment of the present invention there is provided an 
electrostatographic color imaging process and apparatus comprised of an 
imaging member means, a charging means, an exposure means, a development 
means, a transfer means and a fixing means, the improvement residing in 
the development means containing a deflected flexible imaging means; a 
transporting means; means for causing movement of the flexible imaging 
member means and the transporting means, which means are moving at 
different rates of speed; developer reservoir means containing therein 
magnetic developer particles; and a second developer reservoir with 
colored developer particles; and provided in close proximity to the second 
developer reservoir a magnetic separator means for affecting removal of 
black toner particles, enabling the substantial elimination of 
contamination of the color developer mixture. 
The apparatus and process of the present invention is particularly useful 
for obtaining colored image copies in two colors such as red and black as 
disclosed hereinbefore. Illustrative examples of documents that may be 
subjected to the highlight color process of the present invention include 
technical journals such as Scientific American, a large portion of whose 
pages are printed in black and highlight color; engineering drawings, 
letters, reports, and a variety of other documents created by color inks, 
crayons, signature impression stamps, and typewriter ribbons.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Illustrated in FIG. 1 is one embodiment of the development process and 
apparatus of the present invention designated 7, and comprised of a 
positively charged, deflected flexible imaging member 1, a developer 
transporting member 4, a developer reservoir 6, a developer reservoir 8, a 
paddlewheel 10, a paddlewheel 12, developer particles with positively 
charged black magnetic toner 14, color developer particles 16, magnetic 
separating apparatus 18, with a stationary shell 19, multiple rotating 
magnets 20, chutes 21, and a scrapper 22, reservoir 24, a positive 
precharge corotron 26, a paper substrate 28, a negative transfer corotron 
30, a voltage source means, not shown, for the transporting means 4, and a 
voltage source means, not shown, for the transporting means 5. In 
operation subsequent to biasing the members 4 and 5, and after causing the 
formation of an electrostatic latent image on the flexible imaging member 
1, magnetic developer particles are caused to migrate to the flexible 
imaging member 1 by paddlewheel 10, and the movement between the flexible 
imaging member and the transporting member. Thereafter, color developer 
particles in reservoir 16 are caused to deposit on the latent image 
contained on the flexible imaging member 1 by paddlewheel 12, and biased 
roll 5. Any black toner particles on transporting means 5 are removed 
therefrom by attraction to the rotating magnets 20 in the stationary shell 
19; therefore, black toner particles are prevented from entering into the 
color developer mixture reservoir 8. The black toner particles are 
retained on the shell and transported away from the color developer by 
rotation of the magnets. Susequently, the black toner particles can be 
removed from the stationary shell and deposited in the reservoir 24 for 
later reuse in the system. The scrapper blade 22 assists in the removal of 
the black toner particles from the stationary shell. 
With further reference to FIG. 1, the electrostatic image generally 
consists of three voltages, which are generated by varying the intensity 
from a laser exposure, or with a special document and light lens copying. 
Typically, black information to be printed is at about -800 volts; 
unprinted information (white) is at about -400 volts; and information to 
be printed in a color is more exposed to light, and is at zero (0) volts. 
Accordingly, in this embodiment, since the magnetic fields are relatively 
low black development can be easily achieved with a toner composition 
comprised of resin particles and a major amount of magnetite, exceeding 40 
percent by weight. Also, a bias of about -450 volts on roll 4 prevents 
black toner deposition in color information areas, that is those with zero 
(0) volts thereon, and in white information areas with about -400 volts 
thereon. However, black toner particles are caused to deposit in the black 
information areas, which are at about -800 volts. Thereafter, the black 
developed image, and color electrostatic image is then transported through 
color development station 18. At this station, a developer is selected 
wherein the color toner is negatively charged. Further the bias on the 
transporting roll 5 is fixed at about -300 volts. This prevents 
development in white information areas, about -400 volts, as the toner is 
negatively charged, and it also prevents further color development in the 
previously printed black area, which remains at about -800 volts. These 
parameters also enable the color toner to develop in color information 
areas, that is those at about zero (0) volts. While the electrostatics on 
the imaging member are arranged to maintain the black toner on the 
photoconductive imaging member as it passes through the housing with color 
toner particles therein, mechanical scrubbing by the color developer 
composition causes undesirable black toner contamination thereof. 
Accordingly, with the process and apparatus as illustrated in FIG. 1 the 
undesirable black toner is removed from the color developer composition 
enabling the achievement of images with the appropriate color. Also, black 
toner is prevented from adversely affecting the color toner charge level. 
Illustrated in FIG. 2 is the magnetic separator 18 of FIG. 1. There is thus 
illustrated in FIG. 2 a black toner magnetic separator comprised of a 
shell 19, rotating magnets 20, blade 22, a housing wall 41, a reservoir 24 
comprised of the collected black toner particles 43, red toner particles 
45, black magnetic toner particles 47, carrier beads 49, inclined chute 
51, and spacing gap 53. Generally, in operation the contaminated developer 
composition comprised of red toner particles 45, black magnetic toner 
particles 47, and carrier beads 49, is removed downward along the incline 
chute 51 subsequent to removal from the transporting roll 5 of FIG. 1. The 
stationary shell 19, with internal rotating magnets 20 therein, 
magnetically extracts black magnetic toner from the contaminated color 
developer composition. The black toner collection reservoir 24 is spaced 
slightly from the shell enabling the toner to pass therethrough. The 
rotating magnets then transport black magnetic toner along the shell 
surface until removal thereof by scrapper blade 22 held in contact with 
the shell. Thereafter, the black magnetic toner removed is collected in 
reservoir 24 and can be discarded or reused. Clean color developer 
particles can also be continuously cycled into the color housing 8. 
Alternatively, the shell 19 can be caused to rotate if desired. 
With further reference to FIG. 1, there is present in the developer 
reservoir 6 magnetic toner particles comprised of toner resin particles, 
and magnetite in an amount of from about 65 percent by weight to about 50 
percent by weight. Illustrative examples of magnetites that can be 
selected for incorporation into the toner resin particles include those 
commercially available such as Mapico Black, which is believed to be a 
mixture of iron oxides, hard irons, MO 4232, and the like. Generally, the 
magnetite is present in the toner resin particles in an amount of from 
about 15 percent by weight to about 50 percent by weight, and preferably 
in an amount of from about 20 percent by weight to about 40 percent by 
weight. It is important that a magnetic toner be selected for the 
development of black images since in the subsequent development step 
wherein a color developer mixture is applied the black toner can be 
desirably attracted to the rotating magnets contained in the stationary 
shell, reference FIG. 1 described in detail herein. 
Examples of toner resin particles that can be selected for the black 
developer mixture include polyimides, epoxies, diolefins, vinyl resins and 
polymeric esterification products of a dicarboxylic acid and a diol 
comprising a diphenol. Any suitable vinyl resin may be selected for the 
toner resins of the present application including homopolymers or 
copolymers of two or more vinyl monomers. Typical of such vinyl monomeric 
units include: styrene, p-chlorostyrene, unsaturated mono-olefins such as 
ethylene, propylene, butylene, isobutylene and the like; vinyl esters 
inclusive of esters of monocarboxylic acids including methyl acrylate, 
ethyl acrylate, n-butylacrylate, isobutyl acrylate, dodecyl acrylate, 
n-octyl acrylate, 2-chloroethyl acrylate, phenyl acrylate, 
methylalpha-chloroacrylate, methyl methacrylate, ethyl methacrylate, butyl 
methacrylate, and the like; acrylonitrile, and the like; vinyl ketones 
such as vinyl methyl ketone, vinyl hexyl ketone, methyl isopropenyl ketone 
and the like; styrene butadiene copolymers, and mixtures thereof. 
As one preferred toner resin there can be selected the esterification 
products of a dicarboxylic acid and a diol comprising a diphenol. These 
materials are illustrated in U.S. Pat. No. 3,590,000, the disclosure of 
which is totally incorporated herein by reference. Other preferred toner 
resins include styrene/methacrylate copolymers, and styrene/butadiene 
copolymers, polyester resins obtained from the reaction of bis-phenol A 
and propylene oxide, followed by the reaction of the resulting product 
with fumaric acid, and branched polyester resins resulting from the 
reaction of dimethylterephthalate, 1,3-butanediol, 1,2-propanediol, and 
pentaerthriol. These toner resin particles are also selected for 
incorporation into the color developer mixture for reservoir 8. 
Included in reservoir 8, in addition to the toner resin particles, are 
color pigment particles, including magenta, cyan, yellow, red, or green, 
and the like, as well as mixtures thereof. More specifically, with regard 
to obtaining color images with the developer mixture as contained in 
reservoir 8, illustrative examples of magenta materials that may be 
selected as pigments include 2,9-dimethyl-substituted quinacridone and 
anthraquinone dye, identified in the color index as Cl 26050; Cl Dispersed 
Red 14, a diazo dye identified in the color index as Cl 26050; Cl Solvent 
Red 19; and the like. Illustrative examples of cyan materials that may be 
used as pigments include copper tetra-4(octadecyl 
sulfonamido)phthalocyanine; X-copper phthalocyanine pigment, listed in the 
color index as Cl 74160; Cl Pigment blue; and Anthrathrene Blue, 
identified in the color index as Cl 69810; Special Blue X-2137; and the 
like; while illustrative examples of yellow pigments that may be selected 
include diarylide yellow 3,3-dichlorobenzidene acetoacetanilides, a 
monoazo pigment identified in the color index as Cl 12700, Cl Solvent 
Yellow 16, a nitrophenyl amine sulfonimide identified in the color index 
as Foron yellow SE/GLN, Cl dispersed yellow 33, 
2,5-dimethoxy-4-sulfonanilide phenylazo-4'-chloro-2,5-dimethoxy 
aceto-acetanilide, permanent yellow FGL, and the like. 
These pigment particles are generally present in the toner composition in 
an amount of from about 2 weight percent to about 20 weight percent, and 
preferably in an amount of from about 2 weight percent to about 10 weight 
percent. Other pigments not specifically mentioned herein can be selected 
providing the objectives of the present invention are achieved, these 
pigments including, for example, lithol scarlet red, reference U.S. Pat. 
No. 4,410,617, the disclosure of which is totally incorporated herein by 
reference. 
Illustrative examples of carrier particles that can be selected for mixing 
with the toner particles of the present invention include those that are 
capable of triboelectrically obtaining a charge thereon in relationship to 
the toner composition. Therefore, the carrier particles are selected, for 
example, enabling the black magnetic toner to be positively charged and 
enabling the toner compositions with colored pigments thereon to be 
negatively charged. Alternatively, the black magnetic toner particles may 
be negatively charged and the color toner composition may be positively 
charged. Illustrative examples of carrier substances selected include 
glass, steel, nickel, iron ferrites, and the like. Additionally, there can 
be selected as carrier particles nickel berry carriers as disclosed in 
U.S. Pat. No. 3,847,604, the disclosure of which is totally incorporated 
herein by reference, which carriers are comprised of nodular carrier beads 
of nickel, characterized by surfaces of reoccurring recesses and 
protrusions thereby providing particles with a relatively large external 
area. The selected carrier particles can be used with or without a 
coating, the coating generally containing fluoropolymers, such as 
methylmethacrylate, and a silane, such as triethoxy silane, 
tetrafluoroethylenes, other known coatings and the like. 
The diameter of the carrier particles can vary, generally the diameter is 
from about 50 microns to about 300 microns, thus allowing these particles 
to possess sufficient density and inertia to avoid adherence to the 
electrostatic images during the development process. The carrier particles 
can be mixed with the toner particles in various suitable combinations, 
however, best results are obtained when about 1 part to about 10 parts 
toner to about 200 parts by weight of carrier are mixed. 
Various suitable imaging members can be selected for the process and 
apparatus of the present invention such as those described in U.S. Pat. 
No. 4,265,990, the disclosure of which is totally incorporated herein by 
reference. Thus, for example, layered photoresponsive imaging members 
containing a photogenerating layer and a diamine hole transport layer can 
be selected as the deflected flexible imaging member. Examples of 
photogenerating compositions include metal phthalocyanines, metal-free 
phthalocyanines, vanadyl phthalocyanines, squaryliums, amorphous selenium, 
trigonal selenium, selenium alloys, and the like. One specific layered 
photoresponsive imaging device preferred for the process and apparatus of 
the present invention is comprised of a photogenerating layer of trigonal 
selenium, and coated thereover, a hole transport layer comprised of the 
diamine N,N'-diphenyl-N,N'-bis(methylphenyl)-[1,1-biphenyl-4,4'diamine], 
dispersed in an amount of about 40 percent in a resinous polycarbonate 
binder. 
Other modifications of the present invention may occur to those skilled in 
the art based upon a reading of the present disclosure. These are intended 
to be included within the scope of the present invention including 
equivalents thereof.