Composite photosensitive material for use in electrophotography

A composite photosensitive material for use in electrophotography which comprises a conductive substrate on which there is laminated a first photoconductive layer having a sensitivity to at least a part (Light A) of the chromatic light of visible light region and a second photoconductive layer capable of transmitting said Light A as well as having a sensitivity to another chromatic light (Light B), characterized in that said photoconductive layers are each capable of holding the electric charge of a polarity opposite to each other and additionally accepting as well as retaining a surface potential enough to develop an electrostatic latent image, which is formed by said electric charge, with a toner.

BACKGROUND OF THE INVENTION 
(a) Field of the Invention 
The present invention relates to a photosensitive material for use in 
electrophotography, in particular a laminate-type electrophotographic 
photosensitive material capable of obtaining a dichromatic (two colors, 
such as black and red) reproduction from a multi-color original through 
only one exposure process, as well as the usual monochromatic 
reproduction. 
(b) Description of the Prior Art 
As typical photosensitive materials for use in conventional Carlson process 
(photosensitive materials for use in electrophotography) there are well 
known photosensitive materials comprising a selenium photoconductive layer 
on a conductive substrate, a charge transfer layer made of polyvinyl 
carbazole or the like on said selenium photoconductive layer, and so 
forth. 
These photosensitive materials are devised so that the surface potential 
thereof may hold a single positive or negative polarity in compliance with 
an electrostatic latent image to be formed through 
electrification-exposure processes. In order to obtain dichromatic 
reproductions using such photosensitive materials, therefore, it is 
ordinarily required to repeat the cycle of 
electrification-exposure-development-transfer. However, by the mere 
repetition of this cycle there can not be obtained a distinct dichromatic 
image owing to the occurrence of mixed colors, fog, shear in position, 
etc. 
Reflecting this actual condition, there has been proposed a process of 
obtaining a dichromatic copy (Japanese Open Patent Application No. 
144737/1978) which comprises the steps of carrying out a first corona 
electrification of a photosensitive material prepared by forming an 
insulating layer and a photoconductive layer, in that order, on a 
conductive substrate, performing the overall radiation of the thus 
electrified material with a light belonging to the sensitive region of 
said photoconductive layer either simultaneously with or after the first 
corona electrification, carrying out a second corona electrification of 
this material with a polarity opposite to that in the first 
electrification simultaneously with the imagewise exposure of the original 
having white, black and red areas (namely, the dichromatic original with 
red and black image areas) through a red complementary color filter, and 
performing the imagewise exposure again through a red filter, whereby 
there is created in the material wherein a condition the charged polarity 
of the electrostatic latent images formed on the red and black areas 
corresponding to the original has become opposite. Thereafter, these 
latent images are successively developed with toners of opposite polarity 
and different colors, and the resulting toner images are transferred onto 
image-receiving papers such as paper and are fixed thereon. However, this 
process is still defective in that considerably large quantities of 
exposure light are required in addition to the trouble of utilizing 
different filters two times. 
SUMMARY OF THE INVENTION 
One object of the present invention is to provide a novel composite 
photosensitive material for use in electrophotography which is widely 
different in photo-electric property as compared with conventional 
photoconductive materials which may be utilized in the Carlson process. 
Another object of the present invention is to provide a photosensitive 
material which can always obtain a distinct, dichromatic image. 
More specifically, the present invention relates to composite 
photosensitive materials for use in electrophotography which comprise a 
conductive substrate on which there is laminated a first photoconductive 
layer having a sensitivity to at least a part (Light A) of the chromatic 
light of the visible light region and a second photoconductive layer 
capable of transmitting said Light A as well as having a sensitivity to 
another chromatic light (Light B), characterized in that said 
photoconductive layers are each capable of holding an electric charge of a 
polarity opposite to the polarity of the other and additionally are 
capable of accepting as well as retaining a surface potential sufficient 
to develop an electrostatic latent image, which is formed by said electric 
charge, with a toner. 
The photosensitive material according to the present invention is 
conspicuously characterized in the following two points: 
(1) Each image portion of a multi-color original can be reproduced to a 
mutually fully discriminative extent with a monochromatic toner in 
accordance with the conventional Carlson process, and 
(2) A dichromatic image can be formed from a dichromatic original in 
accordance with a dichromatic electrophotographic process as described 
hereinafter. 
The aforesaid feature (1) can be attained only by the above-mentioned 
performances of the first and second photoconductive layers of the 
photosensitive material according to the present invention, specifically, 
the specific wavelength absorbing ability and the chargeability. In the 
photosensitive material of the present invention, since the upper layer, 
i.e., the second photoconductive layer absorbs Light B in this case, even 
if the light comprising Light A and Light B (namely, Light A+B) is 
radiated onto the surface of the photosensitive material, Light B does not 
reach the lower layer, i.e., the first photoconductive layer, and even if 
it reaches the lower layer, the quantity of light is very little. Due to 
this, the first photoconductive layer should not be restricted to one 
having a sensitivity to Light A alone but may be one having a sensitivity 
to both Light A and Light B. 
On the other hand, the aforesaid feature (2) can be attained by imparting a 
both-chargeability to at least one of the first and second photoconductive 
layers or imparting a commutating ability to the first photoconductive 
layer with relation to the conductive substrate in addition to the 
aforesaid basic performances. 
The term "both-chargeability" referred to herein means a property in which 
the layer can be electrified both positively and negatively and further 
does permit light-decay. The term "commutating ability" used herein means 
a property in which the layer can be electrified only either positively or 
negatively and further does permit the occurrence of light-decay in the 
electrifying polarity.

DETAILED DESCRIPTION OF THE INVENTION 
The photosensitive material according to the present invention, as 
illustrated in FIG. 1, comprises a conductive substrate 11 on which there 
is laminated a first photoconductive layer 12 having a sensitivity to at 
least Light A and a second photoconductive layer 13 capable of 
transmitting Light A as well as having a sensitivity to Light B, in that 
order. 
The first photoconductive layer 12 or the second photoconductive layer 13 
possesses the basic performances as described above, and additionally the 
photoconductive layer 12 or 13 may be allowed to have a both-chargeability 
concretely by using a composition consisting essentially of the 
under-mentioned combination 1 or 2. 
1. Combinations of a substance generating charge (positive or negative 
conductive carrier) on absorbing Light A or Light B (namely; (1) coloring 
pigment, (2) coloring dye, (3) a combination of donor with acceptor 
causing the absorption of a charge transfer complex at a chromatic area or 
(4) a combination of non-coloring pigment with coloring dye) with a 
substance capable of transferring either positive or negative charge 
(namely; (a) P-type photoconductor or donor as a positive charge transfer 
substance or (b) N-type photoconductor or acceptor as a negative charge 
transfer substance). In this case, it is necessary for the above-mentioned 
combinations to meet the following conditions such as (i) high efficiency 
of generating charge on absorbing Light A or Light B, in other words high 
quantum efficiency, (ii) high efficiency of injecting either positive or 
negative charge to a charge transfer substance and (iii) high charge 
mobility of a charge transfer substance. In this connection it is to be 
noted that every substance referred to hereinafter can meet the 
above-mentioned conditions. 
2. Co-existence of two kinds of charge transfer substances capable of 
transferring both positive and negative charges, namely a combination of 
N-type photoconductor with P-type photoconductor or a combination of donor 
with acceptor wherein either of the two is present in an excess quantity. 
In this instance, an excess donor or P-type photoconductor is required to 
possess a high hole mobility, while an excess acceptor or N-type 
photoconductor is required to possess a high electron mobility. The 
substances to be referred to hereinafter can meet this requirement. 
The coloring pigments, non-coloring pigments, coloring dyes, donors, 
acceptors, P-type photoconductors and N-type photoconductors used herein 
will be exemplified as follows: 
Coloring pigments (Group A) 
Amorphous Se and same containing incorporated therein spectral sensitizers 
such as As, Te, etc.; cadmium sulfide and same doped with Cu; cadmium 
selenide, zinc sulfide; trigonal system selenium; azo pigments such as 
Sudan Red, Dian Blue, Genus Green B, etc.; quinone pigments such as Algol 
Yellow, pyrenequinone, Indanthrene Brilliant Violet RRP, etc.; indigo 
pigments such as indigo and thioindigo; bisbenzimidazole pigments such as 
Indo Fast Orange toner; phthalocyanine pigments such as Cu-phthalocyanine, 
etc.; quinacridone pigments; perylene pigments; etc. 
Non-coloring pigments (Group A') 
titanium dioxide, zinc oxide, etc. 
Coloring dyes (Group B) 
diphenylmethane dyes such as Oramin, etc.; triphenylmethane dyes such as 
Tetrabromophenol Blue, Crystal Violet, Malachite Green, etc.; xanthene 
dyes such as fluorescein, Rose Bengal, Rhodamine B, etc.; acridine dyes 
such as Acridine Orange, Acridine Yellow, etc.; azine dyes such as 
phenosafranine, Methylene Violet, etc.; thiazine dyes such as 
phenothiazine, Methylene Blue, etc.; pyrylium salts such as 
1,3,5-triphenylpyrylium perchlorate, etc.; selena pyrylium salts such as 
4-(4-dimethylaminophenyl)-2-phenylbenzo[b]selena pyrylium perchlorate, 
etc.; thia pyrylium salts such as 1,3,5-triphenyl thiapyrylium 
perchlorate, etc.; and so forth. 
Acceptors (Group C) 
This group includes carboxylic acid anhydrides; compounds having an 
electron-acceptable structure such as ortho or paraquinoid structure or 
the like; aliphatic cyclic compounds having electron-acceptable 
substituents such as nitro, nitroso, cyano groups; aliphatic compounds; 
heterocyclic compounds, etc., in more particular maleic anhydride, 
phthalic anhydride, tetrachlorophthalic anhydride, tetrabromophthalic 
anhydride, naphthalic anhydride, pyromellitic anhydride, 
chloro-p-benzoquinone, 2,5-dichlorobenzoquinone, 2,6-dichlorobenzoquinone, 
5,8-dichloronaphthoquinone, O-chloranil, O-bromanil, p-chloranil, 
p-bromanil, p-iodanil, tetracyanoquinodimethane, 5,6-quinoline-dione, 
coumarin-2, 2-dione, oxyindirubin, oxyindigo, 1,2-dinitroethane, 
2-dinitropropane, 2-nitro-2-nitrosopropane, iminodiacetonitrile, 
succinonitrile, tetracyanoethylene, 1,1,3,3-tetracyanopropenyde, O-, m- or 
p-dinitrobenzene, 1,2,3-trinitrobenzene, 1,2,4-trinitrobenzene, 
1,3,5-trinitrobenzene, dinitrodibenzil, 2,4-dinitroacetophenone, 
2,4-dinitrotoluene, 1,3,5-trinitrobenzophenone, 1,2,3-trinitroanisole, 
.alpha.,.beta.-dinitronaphthalene, 1,4,5,8-tetranitronaphthalene, 
3,4,5-trinitro-1,2-dimethylbenzene, 3-nitroso-2-nitrotoluene, 
2-nitroso-3,5-dinitrotoluene, O-, m- or p-nitronitrosobenzene, 
phthalonitrile, terephthalonitrile, isophthalonitrile, benzoyl cyanide, 
bromobenzyl cyanide, quinoline cyanide, O-xylylene cyanide, O-, m- or 
p-nitrobenzil cyanide, 3,5-dinitropyridine, 3-nitro-2-pyridine, 
3,4-dicyanopyridine, .alpha.-, .beta.- or .gamma.-pyridine cyanide, 
4,6-dinitroquinone, 4-nitroxanthone, 9,10-dinitroanthracene, 
1-nitroanthracene, 2-nitrophenanthrenequinone, 2,5-dinitrofluorenone, 
2,6-dinitrofluorenone, 3,6-dinitrofluorenone, 2,7-dinitrofluorenone, 
2,4,7-trinitrofluorenone, 2,4,5,7-tetranitrofluorenone, 
3,6-dinitrofluorenone-mandenonitrile, 3-nitrofluorenone-mandenonitrile, 
tetracyanopyrene, etc. 
Low molecular weight donors (Group D) 
This group includes compounds containing at least one group selected from 
an alkyl group such as a methyl group or the like, an alkoxy group, an 
amino group, an imino group and an imido group; or compounds having, at 
the main chain or side chain, polycyclic aromatic compounds such as 
anthracene, pyrene, phenanthrene, coronene etc. or nitrogen-containing 
cyclic compounds such as indole, carbazole, isooxazole, thiazole, 
imidazole, pyrazole, oxadiazole, thiadiazole, thiazole, etc.; in more 
particular as low molecular weight compounds, hexamethylenediamine, 
N-(4-aminobutyl)cadaverine, as-didodecyl hydrazine, p-toluidine, 
4-amino-O-xylene, N,N'-diphenyl-1,2-diaminoethane, O-, m- or 
p-ditolylamine, triphenylamine, triphenylmethane such as 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenylmethane, durene, 
2-bromo-3,7-dimethylnaphthalene, 2,3,5-trimethylnaphthalene, 
N'-(3-bromophenyl)-N-(.beta.-naphthyl)urea, 
N'-methyl-N-(.alpha.-naphthyl)urea, N,N'-diethyl-N-(.alpha.-naphthyl)urea, 
2,6-dimethylanthracene, anthracene, 2-phenyl anthracene, 
9,10-diphenylanthracene, 9,9'-bianthranil, 2-dimethylaminoanthracene, 
phenanthrene, 9-aminophenanthrene, 3,6-dimethylphenanthrene, 
5,7-dibromo-2-phenylindole, 2,3-dimethylindoline, 3-indolylmethylamine, 
carbazole, 2-methylcarbazole, N-ethylcarbazole, 9-phenylcarbazole, 
1,1'-dicarbazole, 3-(p-methoxyphenyl)oxazolidine, 
3,4,5-trimethylisooxazole, 2-anilino-4,5-diphenylthiazole, 
2,4,5-triaminophenylimidazole, 4-amino-3,5-dimethyl-1-phenylpyrazole, 
2,5-diphenyl-1,3,4-oxadiazole, 1,3,5-triphenyl-1,2,4-triazole, 
1-amino-5-phenyltetrazole, bis-diethylaminophenyl-1,3,6-oxadiazole, etc. 
High molecular weight donors (Group E) 
This group includes poly-N-vinylcarbazole and its derivatives (for example, 
those having halogen such as chlorine, bromine or the like and 
substituents such as methyl group, amino group, etc. at the carbazole 
structure), polyvinylpyrene, polyvinylanthracene, pyrene-formaldehyde 
condensation polymer and its derivatives (for example, those having 
halogen such as bromine or the like and subsituents such as nitro group, 
etc. at the pyrene structure) 
P-type photoconductors utilized in the present invention include amorphous 
Se and phthalocyanine pigment, and as N-type photoconductors utilized in 
the present invention can be exemplified zinc oxide and cadmium sulfide. 
Reference will be made to the quantities of aforesaid raw materials used. 
With reference to the charge generating substance in the preceding 1, in 
the case of the combination of donor with acceptor the suitable molar 
ratio is about 1:1, and in the case of the combination of non-coloring 
pigment with coloring dye the suitable weight ratio of dye to pigment is 
about 1:0.3-10.sup.-5 (by weight). On the other hand, the ratio of N-type 
photoconductor to P-type photoconductor in the case of the preceding 2 is 
preferred to be about 1:0.1-10 (by weight), and the ratio of acceptor to 
donor is preferred to be about 1:0.1-10 (by weight). 
In this connection, the first and/or second photoconductive layer, which 
may be both chargeable or not, can be added with a binder and a 
plasticizer or with the spectral sensitizer selected from Group B and/or 
chemical sensitizers selected from Groups C and D in order to discriminate 
or separate the photosensitive wavelength regions of these photoconductive 
layers from each other. 
The quantities of those agents used will be given below. The quantities of 
the coloring agents belonging to Group A (or A') to be used in the first 
and second photoconductive layers suitably are in the range of 1-70% by 
weight, preferably 5-40% by weight (wherein the evaporation products such 
as Se and Se-base alloys may be used in the percentage of 100). The weight 
ratio of the overall composition including the coloring or non-coloring 
pigment together with the spectral sensitizer belonging to Group B or 
chemical sensitizer belonging to Groups C and D to the photoconductive 
layer should be less than 70% by weight, the balance being the high 
molecular weight donor belonging to Group E which also acts as a binder or 
a usual binder. As the binder utilized herein, there can be enumerated 
polyethylene, polystyrene, polybutadiene, styrene-butadiene copolymer, 
acrylic ester or methacrylic ester polymer and copolymer, polyester, 
polyamide, polyimide, polycarbonate, epoxy resin, urethane resin, silicone 
resin, alkyd resin, vinyl-type resins such as polyvinyl chloride, 
polyvinyl acetate, polyvinyl pyrrolidone, etc., cellulose type resins such 
as nitrocellulose, acetylcellulose, etc., and a resin selected from the 
blend of these resins. The usual plasticizers such as dibutyl phthalate, 
dioctyl phthalate, etc. may be added in a quantity less than 30% by weight 
relative to the photoconductive layer. 
As the exemplary both-chargeable photoconductive layers employed in the 
present invention can be enumerated those comprising the co-existence of 
the substances belonging to Group C with the substances belonging to Group 
D or Group E, preferably Group E, for instance, such as a photoconductive 
layer composed of substances constituting a charge transfer complex 
containing 2,4,7-trinitrofluorenone belonging to Group C and 
poly-N-vinylcarbazole belonging to Group E; a photoconductive layer 
comprising the co-existence of a substance belonging to Group A (or A') or 
Group B with that belonging to Group D or Group E; a photoconductive layer 
containing a cocrystalline complex composed of a pyrylium type dye such as 
pyrylium salt, thiapyrylium salt and selenapyrylium salt together with the 
triphenylmethane derivative belonging to Group D; a photoconductive layer 
comprising the co-existence of two kinds or more of substances belonging 
to Group A (or A'), for instance, such as zinc oxide and 
Cu-phthalocyanine; and so forth. Moreover, these photoconductive layers 
may be formed in the laminate type comprising a charge generating layer 
and a charge transfer layer, wherein each of the above photoconductive 
layers can be employed as the charge generating layer and a charge 
transfer layer is laminated thereon in which the compound belonging to 
Group C, D or E, i.e., a charge transfer substance is in the range of 
about 30-95% by weight, the balance being the aforesaid usual binder and 
plasticizer. In this instance, the charge generating layer may be formed 
into an evaporating or spattering layer of an inorganic photoconductive 
substance such as amorphous selenium or the like belonging to Group A and 
an organic photoconductive substance such as Cu-phthalocyanine and the 
like, or may be formed in the laminate type comprising the co-crystalline 
complex photoconductive layer utilized as the charge generating layer and 
a charge transfer layer, laminated thereon, which consists of the 
triphenylmethane derivative belonging to Group D such as 
bis-diethylaminophenyl-1,3,6-oxadiazole and the substance belonging to 
Group E or said usual binder such as poly-N-vinylcarbazole or polyester 
resin. 
The first and second photoconductive layers are formed by dissolving or 
dispersing the above-mentioned constituents of each layer in toluene, 
tetrahydrofurane, 1,2-dichloroethane, benzene, methanol or the like, 
applying the resulting organic solvent onto the conductive substrate (or 
the first photoconductive layer) by means of a coating method such as 
air-knife coating, blade coating, dipping or the like, and drying. 
On the other hand, for the purpose of imparting the commutating ability to 
the first photoconductive layer 12 in relation to the substrate, the 
substrate and/or photoconductive layer may be composed of the following 
specific raw materials: Se photoconductive layer evaporation-deposited 
onto an Al plate under specific conditions; As.sub.2 Se.sub.3 
evaporation-deposited onto the conductive substrate or conductive layer 
comprising a metal having 4.7 eV or more of work function, for instance, 
such as Pt, Au or Pd; and co-crystalline complex layer formed onto 
CuI-conductive substrate. 
In this case, the use of the metal having 4.7 eV or more of work function 
permits a thorough injection of positively or negatively polarized charge 
from the substrate to the first photoconductive layer when effecting the 
first electrification, whereby there can be obtained a high electric 
potential capable of selectively separating colors from each other. 
The composite photosensitive material according to the present invention, 
as hitherto explained, is a laminate type one which comprises the first 
photoconductive layer and the second photoconductive layer. With reference 
to the combination of these layers, even when either photoconductive layer 
has the both-chargeability or commutating ability, it is necessary that 
the first photoconductive layer should have a sensitivity to at least the 
chromatic light A, and the second photoconductive layer should be capable 
of transmitting said chromatic light A as well as have a sensitivity to 
another chromatic light B. On the supposition that the chromatic light A 
is red light and the chromatic light B is non-red visible light in this 
case, the photoconductive layers being sensitive to the respective lights 
can be classified as follows: 
a. Red color-sensitive photoconductive layers (.lambda..ltoreq.600 nm) 
Photoconductive layers using blue photoconductive substances such as Dian 
Blue from among organic azo pigments, indigo from among indigo pigments, 
copper phthalocyanine from among phthalocyanine pigments, etc. belonging 
to Group A; photoconductive layers using, as spectral sensitizers for 
photoconductive substances, blue dyes such as Methylene Blue of thiazine 
dyes, 1,3,5-triphenylthiapyrylium perchlorate, Tetrabromophenol Blue, etc. 
of pyrylium type dyes belonging to Group B, for instance 
spectral-sensitizing of polyvinyl carbazole, etc. with said pyrylium type 
dyes and spectral-sensitizing of zinc oxide with Tetrabromophenol Blue of 
triphenylmethane dyes; and photoconductive layers composed of raw 
materials containing the co-crystalline complexes comprising pyrylium type 
dyes and polycarbonate. 
b. Non-red color sensitive photoconductive layer (.lambda.&lt;600 nm) 
Photosensitive layers using inorganic photoconductive substances such as 
amorphous Se, cadmium sulfide, cadmium selenide, zinc oxide, zinc sulfide, 
titanium dioxide (in particular, of rutile type), etc. or yellow, red 
organic photoconductive substances such as Algol Yellow of quinone 
pigments, Indo Fast Orange toner of bis-benzimidazole pigments, 
quinacridone pigments, part of perillene pigments, etc. belonging to Group 
1; photosensitive layers containing, as spectral sensitizers for 
photoconductive substances, yellow and red dyes such as Oramin of 
diphenylmethane dyes, fluorescein and Rose Bengal of xanthene dyes, 
Acridine Orange, Acridine Yellow, etc. of acridine dyes, for instance 
those obtained by sensitizing zinc oxide with Rose Bengal; and further 
photosensitive layers composed of raw materials containing weak charge 
transfer complexes consisting of poly-N-vinylcarbazole, 
pyrene-formaldehyde condensates, etc. of the substances belonging to Group 
E and 2,6-dinitrofluorenone, etc. of the substances belonging to Group C. 
c. Red color and non-red color sensitive photoconductive layers 
(c-1) Inorganic photoconductive layers comprising copper-doped cadmium 
sulfide, As- or Te-doped amorphous selenium, As.sub.2 Se.sub.2, etc., and 
(c-2) Photoconductive layers composed of raw materials containing strong 
charge transfer complexes comprising the combinations of 
2,4,7-trinitrofluorenone and 3,6-dinitrofluorenonemandenonitrile from 
among the substances belonging to Group C with poly-N-vinylcarbazole and 
pyreneformaldehyde condensate from among the substances belonging to Group 
E. 
Accordingly, either a or b is selected for the second photoconductive layer 
13. On the other hand, for the first photoconductive layer 12 there is 
selected c, or b in case the second photoconductive layer 13 is a, or a in 
case the second photoconductive layer 13 is b. Still further, the concrete 
instances for imparting to the photoconductive layers a both-chargeability 
taking the above specific wavelength absorbability (wavelength separation 
ability or chromato-sensitivity) and a commutating ability with relation 
to the substrate will be shown as follows. 
As the instances where the second photoconductive layer has a sensitivity 
to red light as well as a both-chargeability and where the first 
photoconductive layer has a sensitivity to nonred light there can be 
enumerated in the case of the second photoconductive layer the 
combinations of co-crystalline complex with polyacrylalkane such as 
triphenylmethane derivatives; blue pigment (for instance, 
Cu-phthalocyanine) with acceptor (for instance, 2,4,7-trinitrofluorenone), 
etc. In the case of the first photoconductive layer, on the other hand, 
there can be enumerated the aforesaid substances having a sensitivity to 
red light, for instance, such as amorphous Se, zinc sulfide and as forth. 
In the application of the two-color process it is desirable for the purpose 
of better clarifying the difference between the surface potentials 
(electrostatic latent images), opposite in polarity to each other, 
corresponding to the two colored images of the two-color original that the 
sensitivity ratio of the second photoconductive layer whose surface was 
radiated with white light to the first photoconductive layer should be in 
the range between 1 or more and 20 or less, wherein the sensitivity of the 
second photoconductive layer is evaluated based on the white light per se 
but that of the first photoconductive layer is evaluated based on the 
white light whose partial wavelength has been absorbed when passing or 
filtering through the second photoconductive layer. 
According to the present invention, at any rate, the composite 
photosensitive material for use in electrophotography is prepared by 
employing, as a conductive substrate, a conductor having a volume 
resistivity of less than 10.sup.10 .OMEGA.cm, for instance, a metal plate 
of Al, Cu, Pb or the like, a plate comprising metal oxide such as 
SnO.sub.2, In.sub.2 O.sub.3, CuI, CuO.sub.2 or the like, or any one of 
glass, plastic film, paper and the like whose surface has been coated with 
said compound by evaporation or sputtering; and providing thereon a first 
photoconductive layer and a second photoconductive layer by means of the 
method of coating, evaporating or the like. The thickness of the first 
photoconductive layer, apart from its characteristics, suitably is in the 
range of 3-180 .mu.m, preferably about 5-150 .mu.m, and the thickness of 
the second photoconductive layer suitably is in the range of 3-50 .mu.m, 
preferably about 5-30 .mu.m. The organic solvent to be used in the course 
of preparation of the photosensitive material according to the present 
invention should be one capable of dissolving a binder. The organic 
solvent suitably used in the present invention includes for instance 
toluene, tetrahydropuran, dichloroethane, benzene, methanol, etc. 
The electrophotographic process to be applied in the photosensitive 
material according to the present invention may be classified into the 
following three processes: 
Process-I 
The photosensitive material applied to this process comprises the first 
photoconductive layer 12 having a sensitivity to Light A and the second 
photoconductive layer 13 which is capable of transmitting Light A as well 
as has a sensitivity to Light B. 
First, the first photoconductive layer 12 is subjected to the positive or 
negative first corona electrification with a polarity opposite to that to 
which the first photoconductive layer 12 has a sensitivity or with a 
polarity opposite to that of a charge injected from the substrate 11 to 
the first photoconductive layer 12, and thereafter is uniformly exposed to 
Light A alone or a light containing Light A but not Light B. This uniform 
exposure may be carried out simultaneously with the first electrification, 
but in case where the first photoconductive layer 12 is disposed to accept 
a charge injected from the substrate 11 at the time of said first 
electrification, the first electrification may be effected in the dark, 
dispensing the uniform exposure (FIG. 2-(a)). 
Next, the light image of the original 2 subjected to the second corona 
electrification with a polarity opposite to that in the first 
electrification (FIG. 2-(b)) is imparted to this photosensitive material. 
In this case, the second electrification is effected with an electric 
potential somewhat lower than that in the first electrification. At this 
time, the portion of the photosensitive material corresponding to the 
black area of the original 2 does not undergo any change in the charge 
distribution but the charge distribution at the portion of the 
photosensitive material corresponding to the white area of the original 
changes to render both the first and second photoconductive layers 12, 13 
conductive, whereby the charge thereat dissipates. On the other hand, at 
the portion of the photosensitive material corresponding to the chromatic 
area of the original 2, for instance, Color A area, although the first 
photoconductive layer 12 is rendered conductive, there remains on the 
second photoconductive layer a part of the charge (FIG. 2-(c)). Thus, on 
each of the photoconductive layers 12 and 13 of the photosensitive 
material are formed electrostatic latent images which correspond to the 
black and chromatic areas of the original 2 and have a polarity different 
from each other. These latent images are successively developed with 
chromatic toner 3 and black toner 4, whereby a two-color copy is obtained 
(FIG. 2-(d)). In this connection, FIG. 3 illustrates the conditions of 
surface potential of the photosensitive material with the passing of time. 
In the above explanation, the polarity of the first electrification is 
negative and that of second electrification is positive, but the same 
results may be obtained when the charge polarity is the inverse. 
Process-II 
The photosensitive material applied to this process comprises the first 
photoconductive layer 12 having a sensitivity to Light B and the second 
photoconductive layer 13 which is capable of transmitting Light B as well 
as has a sensitivity to Light A. 
The photosensitive material having such a disposition is subjected to 
positive or negative first corona electrification with the same polarity 
as that to which the second photoconductive layer 13 exhibits a 
sensitivity. At this time, the uniform exposure for rendering the second 
photoconductive layer 13 conductive with Light A is carried out 
simultaneously with or just after the electrification. In case where the 
second photoconductive layer 13 has a property of transferring the charge 
at the time of the first electrification, however, the first 
electrification may be effected in the dark, dispensing the uniform 
exposure (FIG. 4-(a)). 
Next, the photosensitive material is subjected to the second corona 
electrification with a polarity opposite to that in the first 
electrification (FIG. 4-(b)), and thereafter the light image of the 
original is imparted to this photosensitive material. In this case, the 
second electrification is effected with an electric potential somewhat 
lower than that in the first electrification. At this time, the portion of 
the photosensitive material corresponding to the black area of the 
original 2 does not undergo any change in the charge distribution but the 
charge distribution at the portion of the photosensitive material 
corresponding to the white area of the original changes to render both the 
first and second photoconductive layers 12, 13 conductive, whereby the 
charge thereat dissipates. On the other hand, at the portion of the 
photosensitive material corresponding to the chromatic area of the 
original 2, for instance, Color A area, although the second 
photoconductive layer 13 is rendered conductive, there remains onto the 
first photoconductive layer a part of the charge (FIG. 4-(c)). Thus, on 
the photosensitive material there are formed electrostatic latent images 
which correspond to the black and chromatic areas of the original 2 and 
have a polarity different from each other. These latent images are 
successively developed with chromatic toner 3 and black toner 4, whereby a 
two-color copy is obtained (FIG. 4-(d)). This process is advantageous in 
that the black image area takes the form of external latent image (latent 
image formed on the second photoconductive layer). In this connection, 
FIG. 5 illustrates the conditions of surface potential of the 
photosensitive material with the lapse of time throughout this process. 
Process-III 
The photosensitive material applied to this process comprises the first 
photoconductive layer 12 which has a sensitivity to Light B as well as is 
devised to accept the injection of charge to one charge polarity at the 
time of electrification, and the second photoconductive layer 13 which is 
capable of transmitting Light B as well as has a sensitivity to Light A. 
Accordingly, the thus constructed photosensitive material is subjected to 
the first corona electrification in the dark with a polarity opposite to 
that of a charge from the substrate 11 to the first photoconductive layer 
12 and to which the second photoconductive layer 13 exhibits a sensitivity 
(FIG. 6-(a)). Next, the photosensitive material is subjected to the second 
corona electrification with a polarity opposite to that in the first 
electrification (FIG. 6-(b)), and thereafter the light image of the 
original 2 is imparted to this photosensitive material. In this case, the 
second electrification is effected with an electric potential somewhat 
lower than that in the first electrification. At this time, the portion of 
the photosensitive material corresponding to the black area of the 
original 2 does not undergo any change in the charge distribution but the 
charge distribution at the portion of the photosensitive material 
corresponding to the white area of the original changes to render both the 
first and second photoconductive layers 12, 13 conductive, whereby the 
charge thereat dissipates. On the other hand, at the portion of the 
photosensitive material corresponding to the chromatic area of the 
original 2, for instance, Color A area, although the second 
photoconductive layer 13 is rendered conductive, there remains onto the 
first photoconductive layer a part of the charge (FIG. 6-(c)). Thus, on 
the photosensitive material there are formed electrostatic latent images 
which correspond to the black and chromatic areas of the original and have 
a different polarity respectively. These latent images are successively 
developed with chromatic toner 3 and black toner 4 to thereby obtain a 
two-color copy (FIG. 6-(d)). This process is advantageous in that the 
black image area takes the form of an external latent image. In this 
connection, FIG. 7 illustrates the conditions of surface potential of the 
photosensitive material with the passing of time throughout this process. 
In explaining the above three processes, the polarity of the first 
electrification is negative and that of the second electrification is 
positive, but if the conditions are satisfied, even when the charge 
polarity is made inverse there may be obtained the same results. 
Furthermore, the photosensitive material according to the present invention 
is applicable to not only said Processes-I, II and III as above-mentioned 
but also conventional Carlson process. The original employed herein may be 
not only the two-color original revealed in the aforesaid embodiments but 
also multicolor ones such as three-color or more. When copying is effected 
using this multi-color original through the above-mentioned two-color 
reproduction process, there can be obtained a two-colored copy, although a 
shade of color is caused between the respective chromatic areas. On the 
other hand, when this multi-color original is applied to Carlson process 
(monochro reproduction) there can be obtained a white and black 
image-carrying copy with a conspicuous difference in image density between 
the respective chromatic areas. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the Examples given hereinafter, the parts are by weight. 
EXAMPLE 1 
An aluminum evaporation-coated polyester film was employed as a conductive 
substrate, and a first conductive layer was formed on this aluminum 
evaporation coated surface in the following manner. First, amorphous Se 
was coated on the evaporation-coated surface by evaporation, thereby 
obtaining a charge generating layer having a thickness of 1 .mu.m. 
Then, on this layer was applied a solution obtained by 5 parts of 
polycarbonate resin and 5 parts of 
1,1-bis(P-N,N-dibenzylaminophenyl)propane in 90 parts of methylene 
chloride, and the same was dried at 80.degree. C. for 10 minutes, whereby 
a charge transfer layer having a thickness of about 5 .mu.m was formed to 
be a first photoconductive layer. 
Next, 25 parts of .beta. type copper phthalocyanine, 68 parts of 
poly-N-vinylcarbazole and 7 parts of polyester resin were added to 90 
parts of tetrahydrofuran, and the mixture was subjected to 5 hours' 
pulverizing and stirring treatment in a ball mill, and then was 
extensively applied onto the first photoconductive layer. The same was 
air-dried for 5 minutes and thereafter thermally dried for 10 minutes in 
an air bath heated to 110.degree. C., thereby obtaining a second 
photoconductive layer having a thickness of about 4 .mu.m. 
A composite photosensitive material comprising the above-mentioned first 
and second photoconductive layers was electrified in the dark with -6.3 KV 
corona discharge by means of a modified copying machine FT-6400 
(manufactured by Ricoh Co., Ltd. wherein the exposure slit width and drum 
linear speed have been changed so that the quantity of exposure light 
required for a halogen lamp may be 30 lux.sec.), and was subjected to 
imagewise exposure using an original comprising black, red, blue and white 
areas, followed by an automatic developing operation with a black toner. 
As a result, the red and blue areas of the original were also reproduced 
as a black image having a lower concentration as compared with that of the 
black area, while the white area was reproduced as a white image freed 
from background stains, whereby there was formed a distinct white and 
black colored image having a high contrast as a whole. 
EXAMPLE 2 
An aluminum evaporation-coated polyester film was employed as a conductive 
substrate, and a first conductive layer was formed on this aluminum 
evaporation-coated surface in the following manner. 25 parts of .beta. 
type copper phthalocyanine, 68 parts of poly-N-vinylcarbazole and 7 parts 
of polyester resin were added to 900 parts of tetrahydrofuran, and the 
mixture was subjected to 5 hours' pulverizing and stirring treatment in a 
ball mill, and then was extensively applied onto the conductive substrate. 
The same was air-dried for 5 minutes and thereafter thermally dried for 10 
minutes in an air bath heated to 110.degree. C., thereby obtaining a first 
photoconductive layer having a thickness of 8 .mu.m. Next, 1 hour's 
ultrasonic dispersion was effected for the purpose of dissolving or 
dispersing 5 parts of conductive CdS and 5 parts of styrene-butadiene 
copolymer resin in 100 parts of toluene. The resulting coating liquid was 
extensively applied onto the first photoconductive layer, thereby forming 
a charge generating layer having a thickness of about 4 .mu.m. 
Furthermore, onto this layer was extensively applied a solution obtained by 
dissolving 5 parts of 2,5-bis(P-diethylaminophenyl)-1,3,4-oxadiazole and 5 
parts of polyester resin in 90 parts of tetrahydrofuran and stirring. The 
same was air-dried for 5 minutes, and then thermally dried for 10 minutes 
in an air bath heated to 110.degree. C., whereby a charge transfer layer 
having a thickness of about 10 .mu.m was formed to be a second 
photoconductive layer. 
A composite photosensitive material comprising the above-mentioned first 
and second photoconductive layers was subjected to -6.3 KV corona 
electrification in the dark by means of the copying machine utilized in 
Example 3, and was further subjected to imagewise exposure using an 
original comprising black, red, blue and white areas, followed by an 
automatic developing operation with a black toner. As a result, the red 
and blue areas of the original were also reproduced as a black image 
having a lower concentration as compared with that of the black area, 
while the white area was reproduced as a white image freed from background 
stains, whereby there was formed a distinct white and black colored image 
having a high contrast as a whole. 
EXAMPLE 3 
An amorphous selenium having a purity of 99.99% was coated on an aluminum 
substrate at 65.degree. C. by evaporation to thereby obtain a first 
photoconductive layer being 15 .mu.m in thickness. 
Next, 1 part of .beta.-copper phthalocyanine and 4 parts of acrylic resin 
were added to 95 parts of tetrahydrofuran, and the same was pulverized and 
stirred for 5 hours in a ball mill. Then, it was extensively coated on the 
first photoconductive layer, air-dried for 5 minutes, and thereafter 
thermally dried for 30 minutes in an air bath heated to 50.degree. C., 
thereby forming a second photoconductive layer having a thickness of about 
7 .mu.m. Subsequently, the thus obtained composite photosensitive material 
was subjected to +6.3 KV corona electrification in the dark by means of 
the copying machine utilized in Example 1, and was further subjected to 
imagewise exposure using an original comprising black, red, blue, and 
white areas, followed by an automatic developing operation with a black 
toner. As a result, the red and blue areas of the original were also 
reproduced as a black image having a lower concentration as compared with 
that of the black area, while the white area was reproduced as a white 
image freed from background stains, whereby there was formed a distinct 
white and black colored image having a high contrast as a whole. 
EXAMPLE 4 
A co-crystalline complex was prepared by mixing a solution comprising 0.2 g 
of 4-(4-dimethylaminophenyl)-2,6-diphenylpyrylium perchlorate, 0.2 g of 
polycarbonate, 15 g of 1,2-dichloromethane and 5 g of dichloroethane. 
Next, 0.1 g of this co-crystalline complex was mixed with 0.3 g of 
vinylbutyral resin and 2 g of toluene, and the same was kneaded for 23 
hours in a ball mill. Moreover, this kneaded product was added to a 
solution obtained by adding 0.2 g of 
1-phenyl-3-(p-dimethylaminostyryl)pyrazoline to 2 g of 1,2-dichloroethane, 
and the same was kneaded for 5 hours to prepare a photosensitive 
composition. 
On the other hand, on an aluminum substrate was formed a first 
photoconductive layer which has scarcely a sensitivity to red color by 
coating said substrate with Se to a thickness of 50 .mu.m. 
Next, said photosensitive composition was applied onto this photoconductive 
layer with a blade and dried to thereby form a second photoconductive 
layer having a thickness of 15 .mu.m. Thus, there was obtained an 
electrophotographic photosensitive material comprising the first and 
second photoconductive layers. 
The thus obtained photosensitive material was stored in the dark for a 
whole day and night, then subjected to +6 KV corona discharge to the 
surface of the photosensitive material and successively -6 KV corona 
discharge to same thereby to positively electrify both the first and 
second photoconductive layers as a whole. Thereafter by employing, as an 
original, a red and black characters-carrying film, a tungsten light of 20 
lux was radiated onto the photosensitive material for 1 second from above 
this film. The surface potential Vo of the photosensitive material at this 
time, the potential corresponding to the white area after the lapse of 15 
seconds Vw, the potential corresponding to the red area after the lapse of 
15 seconds Vr and the potential corresponding to the black area after the 
lapse of the photosensitive material respectively are as shown in Table-1. 
TABLE 1 
______________________________________ 
V.sub.O (V) 
V.sub.W (V) V.sub.R (V) 
V.sub.B (V) 
______________________________________ 
-950 +20 +300 -900 
______________________________________ 
Next, the photosensitive material in these potential conditions was 
developed with a two component type black developer and successively a red 
developer in accordance with the magnet brush method and was uniformly 
electrified so as to have a negative polarity. Thereafter, the images were 
transferred onto a common paper according to the corona transfer method, 
thereby obtaining images having the density and resolving power as shown 
in Table-2. 
TABLE 2 
______________________________________ 
Black image Red image Resolving power 
density density (lines/mm) 
______________________________________ 
1.2 1.0 7 
______________________________________ 
EXAMPLE 5 
1 part of CdS, 1 part of polyester and 10 parts of tetrahydrofuran were 
subjected to ultrasonic dispersion. This dispersion was applied onto a 0.2 
mm-thick Al plate by means of a blade, and the same was hot air-dried at 
150.degree. C. for 30 minutes to form a 10.mu.-thick first photoconductive 
layer. On the other hand, 1 part of copper phthalocyanine, 3 parts of 
polyester and 10 parts of tetrahydrofuran were dispersed in a ball mill. 
This dispersion was applied onto said first photoconductive layer by means 
of a blade, and was dried at 100.degree. C. for 1 hour to form a 
20.mu.-thick second photoconductive layer. 
The thus obtained electrophotographic photosensitive material was subjected 
to a first electrification with +6.0 KV while exposing it to the light 
from a 100 W tungsten lamp through a red filter, and thereafter to a 
second electrification with -4.5 KV in the dark. Successively, a red, 
white and black images-carrying original is overlapped thereon, and the 
same was exposed to the light from a 100 W tungsten lamp, and thereafter 
was developed with a two component system positively charged dry black 
developer and then a two component system negatively charged dry red 
developer in the dark, whereby images were reproduced corresponding to the 
red, white and black images carried on the original. 
EXAMPLE 6 
A 10.mu.-thick selenium layer which is scarcely sensitive to red color was 
formed on a 0.2 mm-thick Al plate by evaporation at normal temperature to 
be a first photoconductive layer. Thereafter, the same was applied by 
means of a blade with a mixed liquid comprising 1 part of 
polyvinylcarbazole, 0.2 part of 2,4,7-trinitrofluorenone (TNF), 0.5 part 
of polyester, 5 parts of tetrahydrofuran and 0.001 part of silicone oil, 
and the same was dried at 50.degree. C. for 2 hours, whereby a second 
photoconductive layer having a thickness of 10 .mu.m was formed. 
As the result of having developed the obtained electrophotographic 
photosensitive material through the same procedure as Example 1 there were 
obtained the red, white and black copied images corresponding to those 
carried on the original. Referring to the surface potential of the 
photosensitive material at this time, the surface potentials at the black, 
red and white areas were -450 V, +250 V and +50 V respectively. 
EXAMPLE 7 
An Al substrate was coated with selenium to a thickness of about 20 .mu.m 
by vacuum evaporation while holding the substrate temperature at 
45.degree. C. to thereby form a first photoconductive layer. This one does 
not exhibit a photoconductivity to the long wavelength region over 600 nm. 
Next, onto the first photoconductive layer was applied a solution of the 
following composition by means of the blade method: 
4-p-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate: 0.2 part 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenyl methane: 2.0 parts 
polycarbonate resin: 2.8 parts 
methylene chloride: 55 parts 
The same was dried at 50.degree. C. for 5 minutes to thereby form a 2 
.mu.m-thick charge generating layer for use in a second photoconductive 
layer. Onto this layer, further, was applied a solution of the following 
composition by means of the blade method: 
4,4'-bis(dimethylamine)-2,2'-dimethyltriphenyl methane: 2.0 parts 
polycarbonate resin: 2.0 parts 
methylene chloride: 36 parts 
This was dried at 50.degree. C. for 20 minutes to form a charge transfer 
layer having a thickness of about 50 .mu.m, whereby a second 
photoconductive layer was obtained. 
The thus prepared composite photosensitive material was subjected to a 
first positive electrification (+6.0 KV) while exposing it to the light 
from a 100 W tungsten lamp through a red filter, and thereafter to a 
second negative electrification (-4.5 KV). Additionally, a pattern 
comprising red, white and black areas was radiated with a 100 W tungsten 
lamp to thereby form electrostatic latent images. These were developed 
successively with a black developer and then a red developer, whereby on 
the surface of the photosensitive material were formed red and black toner 
images corresponding to the red and black areas of original. These toner 
images were transferred to a common paper and fixed by heating, thereby 
obtaining a distinct two-colored image on the common paper. 
EXAMPLE 8 
A composite photosensitive material was prepared by repeating the same 
procedure as Example 7 except that a charge generating layer for use in 
the second photoconductive layer was made to have a thickness of about 1.5 
.mu.m by applying a solution of the following composition by means of the 
blade method and drying at 50.degree. C. for 5 minutes and the thickness 
of the first photoconductive layer (selenium layer) was about 7 .mu.m: 
4-p-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate: 0.3 part 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenyl methane: 1.9 parts 
polycarbonate resin: 2.8 parts 
dichloroethane: 55 parts 
This photosensitive material was subjected to the same copying operation as 
Example 7 to obtain the substantially same results. 
EXAMPLE 9 
A composite photosensitive material was prepared by repeating the same 
procedure as Example 7 except that a first photoconductive layer was made 
to have a thickness of about 20 .mu.m by applying a solution of the 
following composition by means of a blade method and drying at 100.degree. 
C. for 10 minutes. This photosensitive material was subjected to the same 
copying operation as Example 7 except that it was firstly electrified 
negatively (-6 KV) with exposure to a red light and secondarily 
electrified positively (+4.5 KV) in the dark to thereby obtain the 
substantially same results. 
CdS powder: 10 parts 
styrene-butadiene copolymer: 5 parts 
toluene: 20 parts 
EXAMPLE 10 
Dian Blue (Color Index CI 21180): 15 parts 
2,5-bis-diethylaminophenyl-1,3,5-oxadiazole: 32 parts 
poly-.gamma.-carbazolylethyl-L-glutamate: 53 parts 
tetrahydrofuran: 950 parts 
The above components were prepared for a first photoconductive 
layer-forming liquid. First, Dian Blue was mixed with tetrahydrofuran, and 
this mixture was pulverized more than 3 hours in a ball mill. This was 
applied onto an Al plate by means of the blade method, and air-dried for 5 
minutes and further dried at 100.degree. C. for 10 minutes, whereby there 
was formed a layer having a thickness of 10 .mu.m. Next, a composition of 
the undermentioned components was dispersed for 10 minutes by means of a 
homogenizer, then the resulting dispersion was applied onto said first 
photoconductive layer by means of the blade method, and dried at 
100.degree. C. for 10 minutes, thereby forming a second photoconductive 
layer having a thickness of about 15.mu.: 
zinc oxide: 40 g 
acrylic resin: 40 g 
Rose Bengal (4.times.10.sup.-5 mole/ml methane solution): 8 g 
toluene: 200 ml 
Upon measuring the properties of the thus obtained first photoconductive 
layer by means of a paper analyzer, it exhibited a high sensitivity, 
showing that the saturated potential Vs was 1080 V and the quantity of 
exposure light E 1/2 required for until the potential at the time of 
exposure Vo=760 V was reduced to 1/2 was 2.3 lux.sec. 
Next, the thus obtained photosensitive material was uniformly exposed to 
the light from a 100 W red fluorescent lamp and thus subjected to a first 
negative electrification (-6.2 KV) and then to a second positive 
electrification (+6.2 KV). The first and second charged potentials of the 
photosensitive material at this time were -1100 V and +800 V respectively. 
Next, an original obtained by entering red-and black-inked informations on 
a white common paper was exposed to a white light, and the reflected light 
was focussed on the photosensitive material through a lens system to 
thereby effect the radiation of the light image carried on the original. 
Consequently, on the photosensitive material was formed the following 
surface potential distribution, that is, the surface potential 
distribution at the area corresponding to the red color was -250 V, that 
corresponding to the black color +300 V, and that corresponding to the 
white color -50 V respectively. 
Further, the latent images having the above development potentials were 
developed with a negatively charged black developer and a positively 
charged red developer in that order by means of the magnet brush method. 
The thus obtained visible images were transferred onto a transfer sheet 
and fixed to obtain a distinct two-colored (red and black) image which was 
high in tone and freed from mixed-color. 
EXAMPLE 11 
A co-crystalline complex solution comprising the undermentioned components 
was applied onto an Al plate by means of the blade method, and dried at 
80.degree. C. for 2 minutes, thereby forming a first photoconductive layer 
having a thickness of 25 .mu.m: 
4-p-dimethylaminophenyl-2,6-diphenylthiapyrylium perchlorate: 4 parts 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenyl methane: 40 parts 
polycarbonate (Panlite K-1300 manufactured by TEIJIN K.K.): 56 parts 
dichloromethane: 1000 parts 
Next, 5 parts of CdS, 5 parts of styrene-butadiene copolymer and 100 parts 
of toluene were subjected to ultrasonic dispersion for 1 hour. Then, the 
resulting dispersion was applied extensively onto said first 
photoconductive layer air-dried for 5 minutes, and successively thermally 
dried at 100.degree. C. for 30 minutes, whereby there was formed a charge 
generating layer having a thickness of about 3 .mu.m. On this layer, 
furthermore, was extensively applied a solution comprising the 
undermentioned components: 
Polyester adhesive 49000 (manufactured by Du Pont): 5 parts 
2,5-bis-diethylaminophenyl-1,3,5-oxadiazole: 5 parts 
tetrahydrofuran: 90 parts 
The same was then air-dried for 5 minutes and further thermally dried at 
110.degree. C. for 1 hour to form a charge transfer layer having a 
thickness of about 10 .mu.m, whereby a composite photosensitive material 
was prepared. 
For comparison sake, on the other hand, a control composite photosensitive 
material was prepared by repeating the procedure of the present Example 
except that the first photoconductive layer was formed by 
evaporation-coating of Se (94 wt.%)--Te (6 wt.%) alloy. 
Next, the photosensitive material of this Example was negatively 
electrified (-6.2 KV) while exposing it uniformly to the light from a 10 W 
red fluorescent lamp. And the control one was also negatively electrified 
(-6.2 KV) under the same conditions. Subsequently, both photosensitive 
materials were subjected to a second positive electrification (+5.4 KV), 
wherein the charged potential of the photosensitive material was +650 V in 
the present Example and +800 V in the control case. 
These photosensitive materials were subjected to imagewise exposure through 
the same procedure as Example 7. The obtained surface potential 
distribution of each photosensitive material was as shown below: 
______________________________________ 
The area The area The area 
corresponding corresponding 
corresponding 
to red color to black to white 
(V) color (V) background 
______________________________________ 
Example 
-400 +600 -50 
11 
Control 
-200 +760 -60 
______________________________________ 
It was proved that a higher red development potential was applicable to the 
co-crystallizing complex type photoconductive layer-provided 
photosensitive material disclosed in this Example than the Se-Te alloy 
type photoconductive layer-provided control one. Further, it was found 
that the same results as Example 10 were obtained when the electrostatic 
latent images formed on the photosensitive material of this Example were 
made visible with a developer prepared by dispersing a negatively charged 
black toner and a positively charged red toner in a dispersion medium and 
said visible images were transferred onto a transfer sheet and fixed. 
EXAMPLE 12 
40 g of zinc oxide, 8 g of Rose Bengal (4.times.10.sup.-5 mole/50 ml 
methanol solution), 200 ml of toluene and 40 g of acrylic resin were 
dispersed for 10 minutes in a homogenizer. The resulting dispersion was 
applied onto the first photoconductive layer formed in Example 11 by means 
of the blade method and dried at 100.degree. C. for 10 minutes to form a 
second photoconductive layer having a thickness of about 20 .mu.m. 
The resulting photosensitive material was electrified and exposed through 
the same procedure as Example 11 with the result that at the time when 10 
seconds had passed after said exposure the charged potential corresponding 
to the white area was -80 V, the charged potential corresponding to the 
red area was -200 V and that corresponding to the black area was 600 V. 
Next, the latent images formed on this photosensitive material were 
developed under this condition and through the same procedure as Example 
11 to thereby obtain a two-colored image having a black concentration of 
0.8 and a red concentration of 0.6. 
EXAMPLE 13 
1 part of 8-hydroxyquinoline with Bi.sup.3+, 1 part of acrylic resin and 18 
parts of toluene were dispersed for 2 hours in a ball mill. The resulting 
dispersion was applied onto the first photoconductive layer formed in 
Example 11 by means of the blade method, and the same was dried at 
50.degree. C. for 1 hour to thereby form a second photoconductive layer 
having a thickness of about 15 .mu.m. The thus obtained photosensitive 
material was left standing in the dark for 12 hours, and then was 
subjected to a first negative electrification (-6 KV) so as to have a 
charged potential of -1200 V. This photosensitive material was subjected 
to a second positive electrification (+6 KV) so as to have a charged 
potential of +600 V, and then was subjected to a cycle of exposure, 
development, transfer and fixation according to the same procedure as 
Example 10, whereby there were obtained good results as seen in Example 
10. 
EXAMPLE 14 
Au was vacuum-evaporated on a 0.5 mm-thick Al plate to a thickness of 0.5 
.mu.m to prepare a conductive substrate. On the resulting substrate held 
at 230.degree. C. was vacuum-evaporated As.sub.2 Se.sub.3 to form a first 
photoconductive layer having a thickness of 45 .mu.m. Next, for the 
purpose of measuring the dark decay characteristic of this first 
photoconductive layer, it was subjected to -5.5 KV corona discharge by 
means of a commercially available paper analyzer so as to have a charged 
potential of -200 V and left standing in the dark. As a result, the 
initial charged potential became zero volt before the passage of 2 
seconds, exhibiting its superior dark decay characteristic. 
Next, on this substrate, while held at 50.degree. C., was spattered CdS to 
a thickness of 0.8 .mu.m, whereby there was formed a charge generating 
layer for use in a second photoconductive layer. Further, a 5 wt.% 
methylene chloride solution of polyvinylcarbazole was applied onto this 
layer and dried to form a 13 .mu.m-thick charge transfer layer for use in 
a second photoconductive layer, whereby there was prepared a composite 
photosensitive material. 
For comparison sake, on the other hand, an As.sub.2 Se.sub.3 alloy-made 
first photoconductive layer was provided directly on a 0.5 mm-thick Al 
plate according to the aforesaid procedure. The thus prepared one was 
subjected to corona discharge with -5.5 KV so as to have a charged 
potential of -290 V, but due to its inferior dark decay characteristic it 
was left standing for 20 seconds in the dark with the result that the 
initial potential was only lowered to -112 V. A control composite 
photosensitive material was prepared in the manner of providing, on this 
first photoconductive layer, a second photoconductive layer comprising a 
charge generating layer and a charge transfer layer through the same 
procedure as the present Example. 
Next, these photosensitive materials were respectively subjected a first 
corona discharge with -6.0 KV and then a second corona discharge with +5.5 
KV. Successively, each of them was subjected to each process of (1) 2 
seconds' dark decay, (2) 2 seconds' radiation of a light of 7 lux and (3) 
2 seconds' radiation of a light of 7 lux through a red filter so as to 
correspond to the black area, red area and white area of the original 
after the completion of imagewise exposure. And the surface potential at 
each time was measured. The obtained results were as shown in the 
following table. 
______________________________________ 
Process Control Example 
Example 14 
______________________________________ 
(1) +260 +280 
(2) -20 -10 
(3) -240 -350 
______________________________________ 
It is seen from this table that the separation potential [in the table, the 
difference between (1) and (2) and the difference between (2) and (3)] in 
the case of the present Example is high as compared that in the control 
one. The reason therefor is considered to consist in that the use of a 
metal having 4.7 eV or more of work function in the photoconductive layer 
of the substrate according to the present Example has permitted the 
sufficient injection of positively polarized carriers from the substrate 
to the first photoconductive layer at the time of effecting the first 
electrification. 
Next, using either Pd or Pt in place of Au of the present Example, two 
photosensitive materials were prepared. The thus obtained photosensitive 
material each was left standing in the dark for 12 hours, and then was 
subjected to a first negative electrification (-6 KV) so as to have a 
charged potential of -1350 V. This photosensitive material was subjected 
to a second positive electrification (+6 KV) so as to have a charged 
potential of +580 V, and then was subjected to a cycle of exposure, 
development, transfer and fixation according to the same procedure as 
Example 10, whereby there were obtained good results as seen in Example 
10. 
EXAMPLE 15 
An aluminum evaporation-coated polyester film was employed as a conductive 
substrate, and on this aluminum evaporation-coated surface was formed a 
first photoconductive layer in the following manner. 
The electrophotographic sensitivity E 1/10 (the quantity of exposure light 
required until the saturated surface potential is reduced to 1/10) of the 
first photoconductive layer in the case where the second photoconductive 
layer was allowed be present together with the first photoconductive layer 
at the time of exposure, namely when exposure is effected by using, as a 
filter the one comprising a glass substrate and the second photoconductive 
layer provided thereon was measured under the conditions: photosensitive 
surface intensity 20 lux, corona discharge -6 KV, and was evaluated to be 
72 lux.sec. 
A mixture of the undermentioned components was dissolved in 90 parts of 
tetrahydrofuran and stirred. The resulting solution was extensively 
applied onto a conductive substrate, air-dried for 5 minutes and thermally 
dried for 10 minutes in an air bath heated to 90.degree. C., thereby 
obtaining a first photoconductive layer having a thickness of about 17 
.mu.m: 
poly-N-vinylcarbazole: 54 parts 
2,4,7-trinitrofluorenone: 40 parts 
polyester resin: 6 parts 
Further, 8 parts of .beta.-copper phthalocyanine and 1 part of polyester 
resin were added to 96 parts of tetrahydrofuran. The same was pulverized 
and stirred for 5 hours in a ball mill. Then, it was applied extensively 
onto the first photoconductive layer, air-dried for 5 minutes, and 
thereafter thermally dried for 10 minutes in an air bath heated to 
90.degree. C., thereby forming a charge generating layer having a 
thickness of about 0.5 .mu.m. Finally, onto this layer was extensively 
applied a solution obtained by dissolving 5 parts of polyvinylcarbazole 
and 5 parts of 
##STR1## 
in 90 parts of tetrahydrofuran and stirred, air-dried for 5 minutes and 
subjected to 10 minutes' thermal drying in an air bath heated to 
90.degree. C., whereby there was formed a charge transfer layer having a 
thickness of about 16 .mu.m to be a second photoconductive layer. The 
second photoconductive layer alone was measured in respect of E 1/10 under 
the conditions where the first photoconductive layer had been subjected to 
exposure and electrification (wherein, however, the filter was absent and 
the charged polarity was plus) with the result that E 1/10 was 27 lux.sec. 
and the ratio of sensitivity between both photoconductive layers was 2.7. 
The composite photosensitive material comprising the first and second 
photoconductive layers was subjected to corona discharge with -6.3 KV 
while undergoing the overall exposure to a blue light, and successively 
corona discharge with +5.2 KV in the dark for reducing the surface 
potential to zero substantially. Thereafter, the white area of the 
photosensitive material was subjected to 1 second's imagewise exposure 
through an original comprising red, blue, black and white patterns by 
means of a 100 W halogen lamp, and then developed with a positively 
charged blue toner and a negatively charged red toner. The result was that 
the distinct and high-contrast blue and red colored images were obtained 
corresponding to the blue and red areas of the original, but the black and 
white areas of the original were reproduced as a background stain-free 
white area. 
Furthermore, the photosensitive material was subjected to the same 
electrification process, then was imagewisely exposed for 1 second to the 
light from a 100 W halogen lamp using an original comprising white and 
black negative patterns through a blue filter, and was developed with a 
positively charged black toner, whereby there was obtained a distinct and 
high-contrast reversal positive image freed from background stains. 
The same procedure as above-mentioned was repeated except that the blue 
filter was replaced by a red filter and the positively charged black toner 
was replaced by a negatively charged black toner to thereby obtain a 
distinct and high-contrast reversal positive image freed from background 
stains. 
EXAMPLE 16 
An aluminum evaporation-coated polyester film was employed as a conductive 
substrate. Then, on this aluminum evaporation-coated surface was formed a 
first photoconductive layer in the following manner. The first 
photoconductive layer was measured in respect of the electrophotographic 
sensitivity E 1/10 under the same conditions as Example 15 inclusive of a 
filter comprising the provision of a second photoconductive layer to be 
referred to hereinafter on a glass substrate (wherein, the charged 
polarity is plus) to find that the E 1/10 value was 30 lux.sec. 
20 parts of .beta. type-copper phthalocyanine and 40 parts of acrylic resin 
were added to 540 parts of tetrahydrofuran and the same was pulverized and 
stirred for 5 hours in a ball mill. 30 parts of zinc oxide and further 270 
parts of tetrahydrofuran were added to 300 parts of this dispersion, and 
the mixture was dispersed and stirred for 10 minutes by means of a 
homogenizer. This was extensively coated on the photoconductive substrate, 
air-dried for 5 minutes and then thermally dried for 10 minutes in an air 
bath heated to 90.degree. C., thereby obtaining a first photoconductive 
layer having a thickness of about 80 .mu.m. 
Amorphous Se was coated thereon by evaporation to a thickness of 1 .mu.m, 
thereby obtaining a charge generating layer. Moreover, a solution obtained 
by dissolving 5 parts of polycarbonate resin and 5 parts of 
1,1-bis(p-N,N-dibenzylaminophenyl)propane in 90 parts of methylene 
chloride was applied onto said layer, and dried at 80.degree. C. for 10 
minutes, whereby a charge transfer layer having a thickness of about 10 
.mu.m was formed to be a second photoconductive layer. The second 
photoconductive layer alone was measured in respect of E 1/10 under the 
same exposure and electrification conditions for the first photoconductive 
layer (wherein, however, the charged polarity is minus) to find that the E 
1/10 value was 82.1 lux.sec., and the ratio of sensitivity between both 
photoconductive layers was 1.1. 
The thus obtained electrophotographic composite photosensitive material was 
electrified with -6.3 KV while undergoing the overall exposure, through a 
red filter, to the light from a 100 W halogen lamp, and successively 
subjected to corona discharge with +5.2 KV in the dark. Thereafter, the 
photosensitive material was measured in respect of the surface potential. 
The measured surface potential was +540 volt. 
The photosensitive material, after having been electrified with +5.2 KV 
through the same procedure, was exposed imagewise, through an original 
comprising red, black and white patterns, to the light from a 100 W 
halogen lamp for 1 second, and then was developed with a positively 
charged red toner and a negatively charged black toner, whereby there were 
obtained red, black and white images corresponding to the red, black and 
white colors of the original. 
The photosensitive material was subjected to the same procedure except that 
the corona discharge potential in the dark +5.2 KV was replaced by +4.8 
KV, and then was measured in respect of the surface potential. The 
measured potential was -480 volt. 
After the completion of corona discharge with +4.8 KV by repeating this 
procedure, the photosensitive material was image-wisely exposed for 1 
second to the light from a 100 W halogen lamp using an original comprising 
blue, black and white patterns, and then was developed with a positively 
charged black toner and a negatively charged blue toner, whereby there 
were obtained the blue and black images corresponding to the blue and 
black patterns of the original. 
EXAMPLE 17 
An aluminum evaporation-coated polyester film was employed as a conductive 
substrate. Then, on this aluminum evaporation-coated surface was formed a 
first photoconductive layer in the following manner. 
A dispersion was obtained by adding 20 parts of indigo and 10 parts of 
polycarbonate resin in 570 parts of methylene chloride and pulverizing the 
same for 5 hours in a ball mill. 150 parts of this dispersion was mixed 
with a solution obtained by dissolving 4 parts of 
4-p-diethylaminophenyl-2,6-diphenylthiapyrylium perchlorate, 40 parts of 
4,4-bis(diethylamino)-2,2'-dimethyltriphenylmethane and 50 parts of 
polycarbonate resin in 800 parts of methylene chloride and stirring. This 
mixture was stirred again and then was extensively applied onto the 
conductive substrate. The same was air-dried for 5 minutes, and then 
thermally dried for 10 minutes in an air bath heated to 80.degree. C., 
whereby there was obtained a first photoconductive layer having a 
thickness of 30 .mu.m. The electrophtographic sensitivity E 1/10 of said 
first photoconductive layer was measured under the same conditions as 
Example 15 wherein an element comprising the provision of a second 
photoconductive layer to be referred to hereinafter on a glass substrate 
was employed as a filter (however, the charged polarity is plus) to find 
that the E 1/10 value was 13.5 lux.sec. 
Next, in order that 5 parts of photoconductive CdS and 5 parts of 
styrene-butadiene resin may be dispersed or dissolved in 100 parts of 
toluene, ultrasonic dispersion was carried out for 1 hour. The resulting 
coating liquid was extensively applied onto the first photoconductive 
layer to thereby form a charge generating layer having a thickness of 
about 4 .mu.m. 
Further, onto this layer was extensively applied a solution obtained by 
dissolving 5 parts of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole and 5 
parts of polyester resin in 90 parts of tetrahydrofuran and stirring. 
Then, the same was air-dried for 5 minutes and then thermally dried for 10 
minutes in an air bath heated to 110.degree. C., whereby there was formed 
a charge transfer layer having a thickness of about 20 .mu.m to be made a 
second photoconductive layer. The E 1/10 value of the second 
photoconductive layer alone was measured under the exposure and 
electrification conditions for the first photoconductive layer (wherein, 
however, the filter was absent and the charged polarity was minus) with 
the result that the E 1/10 value was 23 lux.sec. and the ratio of 
sensitivity between both photoconductive layers was 1.8. 
The thus obtained electrophotographic composite photosensitive material was 
electrified with -6.3 KV while undergoing the overall exposure, through a 
red filter, to the light from a 100 W halogen lamp, and successively 
subjected to corona discharge with +5.2 KV in the dark. Thereafter, the 
photosensitive material was measured in respect of the surface potential. 
It was +630 volt. 
The photosensitive material was subjected to corona discharge with +5.2 KV 
through the same procedure, then was imagewisely exposed for 1 second to 
the light from a 100 W halogen lamp using an original comprising red and 
grey scale patterns, and then was developed with a positively charged red 
toner and a negatively charged black toner, whereby there were obtained 
red and black images corresponding to the red and grey scale patterns of 
the original. 
EXAMPLE 18 
A substrate was prepared by coating an aluminum plate with gold by 
evaporation to a thickness of 0.5 .mu.m. Said substrate was 
evaporation-coated with As.sub.2 Se.sub.3 alloy to a thickness of 55 .mu.m 
while maintaining the substrate temperature at 230.degree. C. to thereby 
obtain a first photoconductive layer. The electrophotographic sensitivity 
E 1/10 (quantity of exposure light required until the saturated surface 
potential is reduced to 1/10) of the first photoconductive layer in case 
where a second photoconductive layer referred to hereinafter co-existed 
with this first photoconductive layer at the time of exposure, in other 
words, an element comprising the provision of said second photoconductive 
layer on a glass substrate was employed as a filter was measured under the 
conditions: photosensitive surface intensity=20 lux, corona discharge=+6 
KV. The thus measured E 1/10 was 7.8 lux.sec. 
Ultrasonic dispersion was carried out in order to disperse or dissolve 5 
parts of photoconductive CdS and 5 parts of polyester resin in 100 parts 
of tetrahydrofuran. The thus obtained coating liquid was applied 
extensively onto the first photoconductive layer to form a charge 
generating layer having a thickness of about 4 .mu.m. Onto this layer, 
furthermore, was extensively applied a solution obtained by dissolving 5 
parts of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole and 5 parts of 
polyester resin in 90 parts of tetrahydrofuran. The same was air-dried for 
5 minutes and then thermally dried for 10 minutes in an air bath heated to 
110.degree. C., whereby a charge transfer layer having a thickness of 
about 18 .mu.m was formed to be a second photoconductive layer. The E 1/10 
value of the second photoconductive layer alone was measured under the 
same exposure and electrification conditions for the first photoconductive 
layer (wherein, however, the filter is absent and the charged polarity is 
minus). Consequently, it was found that the thus measured E 1/10 was 10.8 
and the ratio of sensitivity between both photoconductive layers was 1.4. 
The thus obtained composite photosensitive material was subjected to corona 
discharge with -6.3 KV in the dark, and again corona discharge with +5.2 
KV so that the surface potential may be reduced to substantially zero. 
Then, the thus treated photosensitive material was subjected to 1 second's 
imagewise exposure, through an original carrying red, blue, black and 
white patterns on the white area, to the light from a 100 W halogen lamp, 
and then was developed with a positively charged blue toner and a 
negatively charged red toner, whereby there were obtained distinct and 
high-contrast blue and red colored images corresponding to the blue and 
red area of the original, but the black and white areas of the original 
were reproduced as a white area freed from background stains. 
Then, the photosensitive material, after the completion of the same 
electrification process, was exposed imagewise, using an original carrying 
a black-and-white negative pattern and through a blue filter, to the light 
from a 100 W halogen lamp for 1 second, and thereafter was developed with 
a positively charged black toner, whereby there was obtained a distinct 
and high-contrast reversal positive image freed from background stains. 
When the same procedure as above-mentioned operation was repeated except 
that the blue filter was replaced by a red filter and the positively 
charged black toner was replaced by a negatively charged one, there was 
likewise obtained a distinct and high-contrast reversal positive image 
freed from background stains. 
EXAMPLE 19 
An amorphous selenium containing 6 parts of Te was applied onto an aluminum 
substrate by evaporation while maintaining the substrate temperature at 
65.degree. C. to obtain a 60 .mu.m-thick first photoconductive layer. The 
electrophotographic sensitivity E 1/10 of this first photoconductive layer 
was measured under the same conditions as Example 18 where an element 
comprising the provision of a second photoconductive layer referred to 
hereinafter on a glass substrate was employed as a filter. The thus 
evaluated E 1/10 was 9.7 lux.sec. 
##STR2## 
and 1 part of polyester resin were added to 96 parts of tetrahydrofuran 
and the same was pulverized and stirred for 5 hours in a ball mill. Then, 
it was extensively applied onto the first photoconductive layer, air-dried 
for 5 minutes and thereafter thermally dried for 15 minutes in an air bath 
heated to 50.degree. C., thereby forming a charge generating layer having 
a thickness of about 0.8 .mu.m. Onto this layer, furthermore, was 
extensively applied a solution obtained by dissolving 5 parts of 
##STR3## 
resin in 90 parts of tetrahydrofuran and stirring, air-dried for 5 
minutes, and then thermally dried for 30 minutes in an air bath heated to 
50.degree. C., whereby a charge transfer layer having a thickness of about 
14 .mu.m was obtained to be a second photoconductive layer. The E 1/10 
value of the second photoconductive layer alone was measured under the 
exposure and electrification conditions for the first photoconductive 
layer (wherein, however, the filter was absent and the charged polarity 
was minus) to find that E 1/10 was 7.3 lux.sec. and the ratio of 
sensitivity between both photoconductive layers was 1.3. 
The thus obtained electrophotographic photosensitive material was 
electrified with -6.3 KV in the dark, and successively was subjected to 
corona discharge with +5.2 KV. Thereafter, the thus treated photosensitive 
material was measured to find that the surface potential was +620 volt. 
The photosensitive material, after the completion of corona discharge with 
+5.2 KV through the same operation, was exposed imagewise, through an 
original comprising red, black and white patterns, to the light from a 100 
W halogen lamp for 1 second, and then was developed with a positively 
charged red toner and a negatively charged black toner, whereby there were 
obtained red, black and white images corresponding to each of the red, 
black and white colors of the original. 
And, the photosensitive material was subjected to the same operation as 
above-mentioned except that the corona discharge potential +5.2 KV was 
replaced by +4.8 KV. Thereafter, this material was measured in respect of 
the surface potential. The measured surface potential was -510 volt. This 
photosensitive material, after the repetition of this operation and the 
completion of corona discharge with +4.8 KV, was exposed imagewise, 
through an original comprising blue, black and white patterns, to the 
light from a 100 W halogen lamp for 1 second, and then was developed with 
a positively charged red toner and a negatively charged black toner, 
whereby there were obtained blue and black images corresponding to each of 
the blue and black colors of the original. 
EXAMPLE 20 
An amorphous selenium with a purity of 99.99% was applied onto an aluminum 
substrate by evaporation while maintaining the substrate temperature at 
65.degree. C. to thereby obtain a 50 .mu.m-thick first photoconductive 
layer. The electrophotographic sensitivity E 1/10 of the first 
photoconductive layer was measured under the same conditions as Example 18 
where an element comprising the provision of a second photoconductive 
layer referred to hereinafter on a glass substrate was employed as a 
filter. The thus evaluated E 1/10 was 67 lux.sec. 
Next, onto the first photoconductive layer was extensively applied a 
solution obtained by adding 25 parts of .beta.-type copper phthalocyanine, 
10 parts of Permanent Red, 60 parts of poly-N-vinylcarbazole and 5 parts 
of polyester resin to 900 parts of tetrahydrofuran and subjecting the same 
to 5 hours' pulverization and stirring in a ball mill. The resulting 
solution was extensively applied onto the first photoconductive layer, 
air-dried, and then thermally dried for 30 minutes in an air bath heated 
to 50.degree. C., thereby obtaining a second photoconductive layer having 
a thickness of about 16 .mu.m. The E 1/10 value of the second 
photoconductive layer alone was measured under the exposure and 
electrification conditions for the first photoconductive layer (wherein, 
however, the filter was absent and the charged polarity was minus) to find 
that the measured E 1/10 was 54 lux.sec. and the ratio of sensitivity 
between both photoconductive layers was 1.2. 
The thus obtained electrophotographic composite photosensitive material was 
electrified with -6.3 KV in the dark and successively subjected to corona 
discharge with +5.2 KV. Thereafter, this photosensitive material was 
measured in respect of the surface potential. The measured surface 
potential was +610 volt. 
The photosensitive material was subjected to corona discharge with +5.2 KV 
through the same procedure, and thereafter was exposed imagewise, through 
an original comprising a grey scale pattern, to the light from a 100 W 
halogen lamp for 1 second. Then, the thus treated photosensitive material 
was developed with a positively charged red toner and a negatively charged 
black toner, whereby there were obtained red and black-and-white gradation 
reproduced images corresponding to each of the red and grey scale of the 
original. 
EXAMPLE 21 
Ultrasonic dispersion was effected for 1 hour in order that 5 parts of 
photoconductive CdS and 5 parts of polyester resin may be dispersed or 
dissolved in 100 parts of toluene. The resulting coating liquid was 
extensively applied onto the aluminum evaporation-coated surface of a 
conductive substrate comprising an aluminum evaporation-coated polyester 
film, thereby forming a charge generating layer having a thickness of 
about 4 .mu.m. 
Onto this layer was extensively applied a solution obtained by dissolving 5 
parts of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole and 5 parts of 
polyester resin in 90 parts of tetrahydrofuran and stirring. And the thus 
treated layer was air-dried for 5 minutes and then thermally dried for 10 
minutes in an air bath heated to 110.degree. C., whereby there was formed 
a charge transfer layer having a thickness of about 18 .mu.m to be a first 
photoconductive layer. The electrophotographic sensitivity E 1/10 
(quantity of exposure light required until the saturated surface potential 
is reduced 1/10) of the first photoconductive layer in case where a second 
photoconductive layer referred to hereinafter co-existed with this first 
photoconductive layer at the time of exposure, in other words, an element 
comprising the provision of said second photoconductive layer on a glass 
substrate was employed as a filter was measured under the conditions: 
photosensitive surface intensity=20 lux, corona discharge=-6 KV. The thus 
measured E 1/10 was 15.1 lux.sec. Furthermore, 2 parts of 
4-p-diethylaminophenyl-2,6-diphenylthiapyrylium perchlorate, 40 parts of 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenyl methane and 58 parts of 
polycarbonate resin were dissolved in 800 parts of methylene chloride and 
stirred. The resulting solution was applied extensively onto the first 
photoconductive layer, air-dried for 5 minutes and then thermally dried 
for 10 minutes in an air bath heated to 80.degree. C. to thereby obtain a 
20 .mu.m-thick second photoconductive layer. The E 1/10 value of the 
second photoconductive layer alone was measured under the exposure and 
electrification conditions for the first photoconductive layer (wherein, 
however, the filter was absent and the charged polarity was plus) to find 
that the measured E 1/10 was 14.3 lux.sec. and the ratio of sensitivity 
between both photoconductive layers was 1.1. 
The thus obtained composite photosensitive material was electrified with 
-6.3 KV while undergoing the overall radiation, through a red filter, of 
the light from a 100 W halogen lamp, and was successively subjected to 
corona discharge with +5.2 KV in the dark. The measured surface potential 
of the thus electrified photosensitive material was +570 volt. The 
photosensitive material was subjected to corona discharge with +5.2 KV 
following the same procedure, and thereafter was exposed image-wise, 
through an original comprising red, black and white patterns, to the light 
from a 100 W halogen lamp for 1 second. Then, the thus treated 
photosensitive material was developed with a positively charged red toner 
and a negatively charged black toner, whereby there were obtained red and 
black images corresponding to each of the red and black colors of the 
original. 
And, the photosensitive material was subjected to the same operation as 
above-mentioned except that the corona discharge potential in the dark 
+5.2 KV was replaced by +4.8. Thereafter, this photosensitive material was 
measured in respect of the surface potential. This measured value was -450 
volt. 
This photosensitive material, after the repetition of this operation and 
the completion of corona discharge with +4.8 KV, was exposed imagewise, 
through an original comprising blue, black and white patterns, to the 
light from a 100 W halogen lamp for 1 second, and then was developed with 
a negative charged blue toner and a positively charged black toner, 
whereby there were obtained blue and black images corresponding to each of 
the blue and black colors of the original. 
EXAMPLE 22 
3 parts of .beta.-copper phthalocyanine and 1 part of polyester resin were 
added to 96 parts of tetrahydrofuran, and the same was subjected to 5 
hours' pulverization and stirring in a ball mill. Thereafter, this was 
extensively applied onto the aluminum evaporation-coated surface of a 
conductive substrate comprising an aluminum evaporation-coated polyester 
film, air-dried for 5 minutes and then thermally dried in an air bath 
heated to 90.degree. C., thereby forming a charge generating layer having 
a thickness of about 0.5 .mu.m. 
Onto this layer, furthermore, was extensively applied a solution obtained 
by dissolving 5 parts of polyvinylcarbazole and 5 parts of 
##STR4## 
of tetrahydrofuran and stirring. The same was air-dried for 5 minutes, and 
then subjected to 10 minutes' thermal drying in an air bath heated to 
90.degree. C., whereby there was formed a charge transfer layer having a 
thickness of about 16 .mu.m to be a first photoconductive layer. The 
electrophotographic sensitivity E 1/10 of this first photoconductive layer 
was measured under the same conditions as Example 21 wherein an element 
comprising the provision of said second photoconductive layer on a glass 
substrate was employed as a filter. The evaluated E 1/10 was 81 lux.sec. 
Further, a solution obtained by dissolving 54 parts of 
poly-N-vinylcarbazole, 40 parts of 2,4,7-trinitrofluorenone and 6 parts of 
polyester resin were added to 90 parts of tetrahydrofuran and stirring was 
applied extensively onto the first photoconductive layer. And, the same 
was air-dried for 5 minutes and then subjected to 10 minutes' thermal 
drying in an air bath heated to 90.degree. C., thereby obtaining a second 
photoconductive layer having a thickness of about 17 .mu.m. The E 1/10 
value of this second photoconductive layer alone was measured under the 
exposure and electrification conditions for said first photoconductive 
(wherein, however, the filter was absent and the charged polarity was 
plus). The obtained E 1/10 was 45 lux.sec. and the ratio of sensitivity 
between both photoconductive layers was 1.8. 
The thus obtained composite photosensitive material was subjected to corona 
discharge with +6.3 KV while undergoing the overall exposure to a blue 
light, and successively corona discharge with -5.2 KV in the dark for 
reducing the surface potential to about zero. Then, the thus treated 
photosensitive material was subjected to 1 second's imagewise exposure, 
through an original carrying red, blue, black and white patterns on the 
white area, to the light from a 100 W halogen lamp, and then was developed 
with a positively charged blue toner and a negatively charged red toner, 
whereby there were obtained distinct and high-contrast blue and red images 
corresponding to the blue area and the red area of the original, but the 
black and white areas of the original were reproduced as a white area 
freed from background stains. 
And, the photosensitive material, after having been electrified by means of 
the same process as above-mentioned, was subjected to 1 second's imagewise 
exposure, using an original carrying a black-and-white negative pattern 
and through a blue filter, to the light from a 100 W halogen lamp, and 
then was developed with a positively charged black toner, thereby 
obtaining a distinct and high-contrast reversal positive image freed from 
background stains. 
EXAMPLE 23 
Ultrasonic dispersion was carried out for 1 hour so that 5 parts of 
photoconductive CdS and 5 parts of styrene-butadiene resin may be 
dispersed or dissolved in 100 parts of toluene, and the resulting coating 
liquid was applied extensively onto the aluminum evaporation-coated 
surface of a conductive substrate comprising an aluminum 
evaporation-coated polyester film to thereby form a charge generating 
layer having a thickness of about 4 .mu.m. 
Onto this layer, furthermore, was extensively applied a solution obtained 
by dissolving 5 parts of 2,5-bis(p-diethylaminophenyl)-1,3,4-oxadiazole 
and 5 parts of polyester resin in 90 parts of tetrahydrofuran and 
stirring. The same was air-dried for 5 minutes, and then thermally dried 
for 10 minutes in an air bath heated to 110.degree. C., whereby a charge 
transfer layer having a thickness of about 20 .mu.m was formed to be a 
first photoconductive layer. The electrophotographic sensitivity E 1/10 of 
this first photoconductive layer was measured under the same conditions as 
Example 21 wherein an element comprising the provision of a second 
photoconductive layer referred to hereinafter on a glass substrate was 
employed as a filter. The thus measured E 1/10 was 14.0 lux.sec. 
Next, 20 parts of indigo and 10 parts of polycarbonate resin were added to 
570 parts of methylene chloride, and the same was pulverized for 25 hours 
in a ball mill. 150 parts of the resulting dispersion was mixed with a 
solution obtained by dissolving 4 parts of 
4-p-diethylaminophenyl-2,6-diphenylthiapyrylium perchlorate, 40 parts of 
4,4'-bis(diethylamino)-2,2'-dimethyltriphenyl methane and 57 parts of 
polycarbonate resin in 800 parts of methylene chloride and stirring. This 
mixed solution was stirred again and then extensively applied onto the 
first photoconductive layer. The thus treated layer was air-dried for 5 
minutes, and then thermally dried for 10 minutes in an air bath heated to 
80.degree. C., thereby obtaining a second photoconductive layer having a 
thickness of 30 .mu.m. The E 1/10 value of said second photoconductive 
layer alone was measured under the exposure and electrification conditions 
for the first photoconductive layer (wherein, however, the filter was 
absent and the charged polarity was plus). The measured E 1/10 was 13.7 
lux.sec., and the ratio of sensitivity between both photoconductive layers 
was 1.02. 
The thus obtained composite photosensitive material was electrified with 
-6.3 KV while undergoing the overall radiation, through a red filter, to 
the light from a 100 W halogen lamp, and successively subjected to corona 
discharge with +5.2 KV in the dark. Thereafter, the surface potential 
measured thereof was +570 volt. 
The photosensitive material, after having been subjected to corona 
discharge with +5.2 KV through the same operation, was exposed imagewise, 
through an original comprising red and grey scale patterns, to the light 
from a 100 W halogen lamp for 1 second, and thereafter was developed with 
a positively charged red toner and a negatively charged black toner to 
thereby obtain red and black-and white gradation reproduced images 
corresponding to each of the red and grey scale of the original.