ELECTROPHOTOGRAPHY PHOTOSENSITIVE COMPOSITION

COMPOSE PHOTOSENSIBLE POUR ELECTROPHOTOGRAPHIE

English Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides a photosensitive
composition which comprises an electron donative organic photo-
conductive compound and a sensitizer having the formula
<IMG>
wherein A represents an aromatic group or heterocyclic group
which may be substituted by an inert group; R represents cyano,
nitro, alkoxycarbonyl, aryl or carbamoyl group; and n is 0 or 1.

Claims

THE EMBODIMENT OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A photosensitive composition which comprises an
electron donative organic photoconductive compound selected from
the group consisting of aromatic hydrocarbons, heterocyclic
compounds and polymers and copolymers having a monomer unit
derived therefrom and a sensitizer having the formula
<IMG>
wherein A represents an aromatic group or heterocyclic group
which may be substituted by an inert group; R represents cyano,
nitro, alkoxycarbonyl, aryl or carbamoyl group; and n is 0 or 1
said sensitizer being present in an amount from 0.1 to 100 mole
based on the organic photoconductive compound as monomer units.
2. A composition as claimed in Claim 1 in which the
electron donative organic photoconductive compound is selected
from naphthalene, anthracene, acenaphthene, pyrene, perillene,
tetraphene, 2,3-benzochrycene, 6,7-benzopyrene, tetracene,
chrycene, fluorene, phenanthrene, triphenylene, carbazole,
indole, acridine, dibenzothiophene, phenazine, benzofuran,
phenothiazine, pyrazoline, benzotriazole, benzimidazole, poly-
viny-anthracene, polyacenaphthylene, polyvinylpyrene, poly-
vinylcarbazole, polyvinylacridine, polypyrenylmethyl vinyl
ether, polyglycidylcarbazole, polymethylenepyrene, and poly-
carbazolylethyl vinyl ether.
3. A composition according to Claim 1, wherein A
represents phenyl, naphthyl, anthryl, acenaphthyl, furyl or
thienyl group or said group having substituent group selected
from chloro, bromo, alkoxy nitro, cyano and alkoxycarbonyl
group; and R represents cyano, nitro, alkoxycarbonyl, aryl or
carbamoyl group.
-16-

4. A composition as claimed in Claim 1, 2 or 3 in
which R is cyano.
5. A composition as claimed in Claim 1, or 2 in which
R is cyano and A is phenyl, naphthyl, furyl or thienyl.
6. A composition as claimed in Claim 1 or 2 in which
the sensitizer is a malonic nitrile, an acrylic acid ester
derivative, an ethylene derivative, or an acrylamide derivative.
7. A composition as claimed in Claim 1 or 2, in which
the sensitizer is selected from benzal malononitrile, p-chloro-
benzal malononitrile, p-bromobenzal malononitrile, p-methylbenzal
malononitrile, p-methoxybenzal malononitrile, p-cyanobenzal
malononitrile, p-nitrobenzal malononitrile, m-nitrobenzal
malononitrile, m-cyanobenzal malononitrile, p-methoxycarbonyl-
benzal malononitrile, 2-chloro-5-nitrobenzal malononitrile,
2,4-dichlorobenzal malononitrile, 2-thienylmethylene malononitrile,
5-nitro-2-thienylmethylene malononitrile, 1-naphthylmethylene
malononitrile, 2-naphthylmethylene malononitrile, 5-acenaphthyl-
methylene malononitrile, 9-anthracenylmethylene malononitrile,
2-furfurylidene malononitrile, 5-nitro-2-furfurylidene malono-
nitrile, cinnamylidene malononitrile; .alpha.-cyano - .beta.-phenyl acrylic
acid ethyl ester, .alpha.-cyano-.beta.-(p-cyanophenyl)acrylic acid ethyl
ester, .alpha.-cyano, .beta.-(p-nitrophenyl) acrylic acid ethyl ester,
.alpha.-cyano- .beta.-(p-chlorophenyl) acrylic acid methyl ester, .alpha.-cyano-
.beta.-(1-naphthyl acrylic acid ethyl ester; 1-cyano-1-nitro-2-
phenylethylene, 1-cyano-1,2-bis(p-nitrophenyl) ethylene, 1-cyano-
1-(p-nitrophenyl)-2-(p-cyanophenyl) etllylene, 1-cyano-1,2-bis
(p-cyanophenyl) ethylen,.alpha.-cyano- .beta.-(p-nitrophenyl) acryliamide,
.alpha.-cyano-.beta.-(p-cyanopherlil)acrylarlide, .alpha.-cyano-.beta.-(2-chloro-5-
nitrophenyl) acrylamide, .alpha.-cyano-.beta.-naphthyl acrylamide, .alpha.-cyano-
.beta.-(p-nitrophenyl)-N-phenylacrylamide and .alpha.-cyano-.beta.-(p-cyano-
phenyl)-N-ethylacrylamide.
8. A composition as claimed in Claim 1 or 2 in which
17

the sensitizer is selected from 2-naphthylmethylene malononitrile,
2-furfurylidene malononitrile, cinnarylidene malononitrile, p-
methoxycarbonylbenzal malononitrile, p-nitrobenzal malononitrile,
p-cyanobenzal malononitrile, 2-chloro-5-nitrobenzal malononitrile
and 1-cyano-1,2-bis (p-nitrophenyl) ethylene.
9. A composition as claimed in Claim 1, 2
or 3 in which the organic photoconductive compound is present
in a concentration of 1 to 80 wt%.
10. A composition as claimed in Claim 1, 2 or 3
in which the organic photoconductive compound is present
in a concentration of 5 to 60 wt%.
18

Description

~6s
The present invention relates to an electrophotography
photosensitive composition. More particularly, the present
invention relates to a sensitizer capable of improving sensitivity
of a photosensitive composition in addition to an organic photo-
conductive compound.
Heretofore, inorganic compounds such as selenium,
zinc oxide and cadmium sulfide have been used as photosemicon-
ductors for electrophotography. More recently, organic photo-
semiconductors (organic photoconductive compounds) such as poly-
vinyl carbazoles have been considered. However, these organicphotosemiconductors usually have low sensitivity, and accordingly,
it is necessary to increase the sensitivity for satisfactory
practical use by adding a sensitizer thereto. Sensitizers have
been classified to certain groups depending upon sensitizing
mechanism. Typical groups are sensitizers which impart sensiti-
vity in absorption bands of the sensitizer such as dyes; and
sensitizers which impart sensitivity by charge transfer inter-
action with an organic photosemiconductor. The latter group is
particularly superior than the former group with respect to
photoresistance. However, a practical sensitivity has not been
attained by using these conventional sensitizers.
The inventors have studied the latter sensitizers
which effect charge transfer interactions with an organic photo-
semiconductor, and have found that certain cyanovinyl derivatives
provide a remarkable sensitizing effect.
The present invention provides an electrophotography
photosensitive composition which has remarkable sensitivity.
According to the present invention therefore there is
provided an electrophotography photosensitive composition which
comprises an electron donative organic photoconductive compound
and a compound having the formula

~4~2~5
/ CN
A (- CH = CH )n CH = C \ ..... [ 1 ]
R
wherein A represents an aromatic group or heterocyclic group which
can be substituted by an inert group; R represents cyano, nitro,
alkoxycarbonyl, aryl or carbamoyl group; and n is O or 1.
The photosensitive composition of the present invention
thus comprises a first component of sensitizer having the
formula [ 1 ].
In formula I, A may be an aromatic group such as phenyl,
naphthyl, anthryl and acenaphthyl group; or a heterocyclic group
such as furyl and thienyl group. It is especially preferable
that A is phenyl, naphthyl, furyl or thienyl group. The aromatic
group or the heterocyclic group can be substituted by an inert
group such as chloro, bromo, alkoxy, nitro, cyano and alkoxy-
carbonyl group; preferably chloro, nitro, cyano, alkoxy or
carbonyl group. R can be cyano, nitro, alkoxycarbonyl, aryl
or carbamoyl group preferably cyano group. The aryl or carbamoyl
group can have a substituent of nitro, a lower alkyl or a phenyl
group.
Typical compounds having the formula [ 1 ] include
malonic nitriles such as benzal malononitrile, p-chlorobenzal
malononitrile, p-bromobenzal malononitrile, p-methylbenzal
malononitrile, p-methoxybenzal malononitrile, p-cyanobenzal
malononitrile, p-nitrobenzal malononitrile, m-nitrobenzal
malononitrile, m-cyanobenzal malononitrile, p-methoxycarbonyl-
benzal malononitrile, 2-chloro-5-nitrobenzal malononitrile,
2,4-dichlorobenzal malononitrile, 2-thienylmethylene malononitrile,
5-nitro-2-thienylmethylene malononitrile, l-naphthylmethylene
malononitrile, 2-naphthylmethylene malononitrile, 5-acenaphthyl-
methylene malononitrile, 9-anthracenylmethylene malononitrile,
2-furfurylidene malononitrile, 5-nitro-2-furfurlidene

10~;4~S
malononitrile, and cinnamylidene malononitrile; acrylie acid
ester derivatives sueh as ~-cyano- ~-phenyl acrylic aeid ethyl
ester, ~-cyano- ~-(p-cyanophenyl)aerylic acid ethyl ester,
~-cyano- ~-(p-nitrophenyl)aerylic aeid ethyl ester, ~-cyano- ~-
(p-chlorophenyl)-aerylic acid methyl ester, and ~-cyano, ~-
(l-naphthyl) acrylic acid ethyl ester; and ethylene derivatives
such as l-cyano-l-nitro-2-phenylethylene, l-cyano-1,2-bis-(p-
nitrophenyl) ethylene, l-eyano-l-(p-nitrophenyl)-2-(p-cyano-
phenyl)-ethylene, and l-cyano-1,2-bis(p-cyanophenyl)-ethylene,
and acrylamide derivatives sueh as ~-eyano- ~-(p-nitrophenyl)
aerylamide, ~-cyano- ~-(p-cyanophenyl)aerylamide, ~-cyano, ~~
(2-ehloro-5-nitrophenyl)acrylamide, ~-cyano- ~-naphthyl
acrylamide, ~-cyano- ~-(p-nitrophenyl)-N-phenylacrylamide and
~-eyano- ~-(p-cyanophenyl)-N-ethylacrylamide. Preferable
compounds of formula I include l-naphthylmethylene malononitrile,
2-naphthylmethylene malononitrile, 2-furfurylidene malononitrile,
cinnamilidene malononitrile, p-methoxycarbonylbenzal malononitrile,
and especially p-nitrobenzal malononitrole, p-eyanobenzal
malononitrile, 2-chloro-5-nitrobenzal malononitrile, and l-
cyano-1,2-bis(p-nitrophenyl) ethylene. These compounds ean
be usually produced by a eondensation reaetion of an aromatic
aldehyde with an active methylene compound, in high yield. The
eonventional proeess for produeing these eompounds is diselosed
in Zikken Kagaku Koza Vol. 18 "Reaetion of organie compound II"
(Nippon Kagaku-kai) (Published by Maruzen).
The photosensitive composition of the present invention
comprises as a second component an electron donative organic
photoconductive compound which imparts eharge transfer inter-
action with the first component of the sensitizer. The charge
transfer interaction causes a new charge transfer absorption
band by the eharge transfer force between an electron donative

~s
compound and an electron acceptive compound. Typical electron
donative organic photoconductive compounds include aromatic
hydrocarbons such as naphthalene, anthracene, acenaphthene,
pyrene, perillene, tetraphene, 2,3-benzochrycene, 6,7-benzo-
ch~y.~ene
pyrene, tetracene, chryacnc, fluorene, phenanthrene and tri-
phenylene; and heterocyclic compounds such as carbazole, indole,
acridine, dibenzothiophene, phenazine, benzofuran, phenothiazine,
pyrazoline, benzotriazole, and benzimidazole and derivatives
thereof substituted with one or more halogen, alkyl, aryl,
alkoxy, aryloxy or amino group polymers and copolymers having
a monomer unit derived from said compound, such as polyvinyl
anthracene, polyacenaphthylene, polyvinylpyrene, polyvinyl-
carbazole, polyvinylacridine, polypyrenylmethyl vinyl ether,
polyglycidylcarbazole, polymethylénepyrene, polycarbazolylethyl
vinyl ether; and derivatives thereof substituted with chloro,
bromo, methyl and dimethylamino group. It is preferable to use
a polymer having a monomer unit of carbazole such as polyvinyl-
carbazole, polyglycidylcarbazole, a polymer prepared by substi-
tuting a part of chlorine atoms of polyepichlorohydrin. It
is especially preferable to use a combination of the first
component of sensitizer and the second component of electron
donative organic photoconductive compound to provide charge
transfer absorption bands caused by the charge transfer inter-
action in the visible range.
The photosensitive composition of the present invention
is usually formed by dissolving the first component of the
S~co~d
sensitizer and the Ecaom~ component of the electron donative
organic photoconductive compound in a solvent and coating the
solution on a desirable substrate to form a photoconductive layer.
The concentration of the organic photoconductive oompound in the
photosensitive composition is usually 1 - 80 wt.% preferably
5 - 60 wt.~. The quantity of the sensitizer to the organic

109:6Z65
photoconductive compound is not limited and is dependent upon
sensitivity, color depth of photoconductive layer and miscibility,
and is usually 0.1 - lO0 mole% to the organic photoconductive
compound as monomer unit in the case of a polymeric photocon-
ductive compound.
The solvent is usually selected from those capable of
dissolving both of the sensitizer and the organic photoconductive
compound, such as tetrahydrofuran, 1,2-dichloroethane, mono-
chlorobenzene, toluene and dimethylformamide. The quantity of
the solvent is sufficient to dissolve both of the first and
second components. The substrates include zinc plate, copper
plate, paper and plastic film or sheet.
The photosensitive compositions of the present inven-
tion can include other additives such as a conventional sensiti-
zer, a binder, plasticizer, a dye and a pigment.
The photoconductive layer prepared by coating the
composition, has usually color given by shifting charge transfer
absorption bands to the visible range caused by the charge trans-
fer interaction of the combination of the first and second com-
ponen~s, though the sensitizer and the organic photoconductivecompound are colorless or pale yellow. ~he shift of charge trans-
fer absorption bands caused by the mixing corresponds substan-
tially to the shift of photocurrent to the longer wavelength side
in the comparison of the electronic spectrum of the photoconduc-
tive layer and its photocurrent. Accordingly, it is clear that
the improvement of the sensitivity by the sensitizer of the
present invention is dependent upon the charge transfer inter-
action. The photosensitive composition of the present invention
has high sensitivity and can be used in electrophotography field
such as photocopy, microfilm, and photographic paper.
The present invention will be further illustrated by
way of the following Examples inconjunction with the accompanying

~04~26S
drawings in which
Figure 1 is a graph of absorbance-wavelength against
optical density illustrating the electronic spectrum of the
polymer, the sensitizer and the photosensitive composition.
Figure 2 is a graph of absorbance-wavelength against
optical density illustrating the photocurrent spectrum of the
polymer, the photosensitive composition and electronic spectrum
of the polymer.
Figure 3 is a graph of transmission % against wave-
length illustrating absorption spectrum of samples.
[Preparation 1]
Preparation of sensitizer of l-cyano-1,2-bis(p-nitrophenyl)
ethylene
A 1.5 g of p-nitrobenzaldehyde and 1.7 g of p-nitro-
benzylcyanide were dissolved in 5 mQ of ethanol in hot condition
and 0.05 mQ pyridine was added and th~ mixture was heated for
10 minutes. After cooling overnight, the precipitated crystals
were filtered and recrystallized from a mixture of acetone and
ethanol to obtain l-cyano-1,2-bis(p-nitrophenyl)ethylene having
a melting point of 216.5 - 217.5C.
The elementary analysis of the product was as follows.
C H N
Found (wt.%) 60.78 3.31 14.41
Calculated (wt.%) 61.02 3.07 14.23
[Example 1]
A 5.0 g of polyvinylcarbazole (manufactured by B A S F)
and 0.25 g of each of various sensitizers were dissolved in 50
mQ of 1,2-dichloroethane. The solution was coated by a Baker
(a trademark) applicator on an aluminum plate having thickness of
0.3 mm which was treated by sand blasting, to provide a layer
having a dry thickness of 15~, whereby a photoconductive layer
was formed. After drying it, positive charge was charged on
the surface of the photoconductive layer by a Corona
-- 6 --

1046~65
discharge in the dark.
The charged photoconductive layer was exposed to
a light of halogen lamp to measure an exposure period for half
decay of surface potential.
The relative sensitivity was calculated on the basis
that the sensitivity of polyvinylcarbazole is 1.
Table 1
SensitizerRelative sensitivity
1 benzalmalononitrile 114
2 p-nitrobenzalmalononitrile308
3 m-nitrobenzalmalononitrile247
4 p-methoxybenzalmalonitrile 95
p-chlorobenzalmalononitrile154
6 2,4-dichlorobenzalmalononitrile 238
7 p-cyanobenzalmalononitrile370
8 2-chloro-5-nitrobenzalmalononitrile 667
9 9-anthracenylmethylenemalononitrile 105
10 2-naphthylmethylenemalononitrile 278
11 ~-cyano- ~-(p-cyanopheny) acrylic ethyl ether 154
12 1-cyano-1,2-bis(p-nitrophenyl)ethylene 351
13 cinnamylidenemalononitrile 267
14 2-furfurylidenemalononitrile 118
15 ~-cyano- ~-(p-nitrophenyl)acrylamide 154
.
50 wt. parts of the sensitizer of benzalmalononitrile
or 2-chloro-5-nitrobenzalmalononitrile and 100 wt. parts of a
binder polymer of cellulose acetate (manufactured by Junsei
~agaku Co.) were dissolved in tetrahydrofuran.
In accordance with said process, the solution was
coated to form a layer and the layer was charged and exposed
to the light.
_ q _

~04t;~6S
However, no attenuation of the surface potential was
found. The sensitivity of the sensitizer itself to the halogen
lamp was substantially zero.
[Example 2]
1.0 g of polyvinyl carbazole and 0.05 g of p-nitro-
benzalmalononitrile were dissolved in 10 mQ of 1,2-dichloroethane.
In accordance with Example 1, the solution was coated on an
aluminum plate. After drying, positive charge was charged by
the Corona discharge.
The charged layer was exposed for 0.2 second under 400
lux from a tungsten-filament lamp, passed through a transparent
positive original, and the exposed layer was developed with a
commercial developer to obtain a clear image which corresponds
to the original.
[Example 3]
_
1.0 g of polyvinylcarbazole and 0.2 g of p-cyanobenzal-
malononitrile were dissolved in 10 mQ of 1,2-dichloroethane. In
accordance with the process of Example 1, the solution was coated
on an aluminum plate. After drying it, positive charge was
charged on the layer by the Corona discharge.
The charged layer was exposed for 0.4 second under 400
lux from a tungsten-filament lamp, passed through a transparent
positive original, and the exposed layer was developed by a
magnetic brush method.
A paper was put on the layer and Corona discharge was
applied from the back of the paper to transfer the image on the
paper, and the image was fixed by heating with an infrared lamp,
to obtain a sharp image.
[Example 4]
Polyvinyl carbazole was brominated with N-bromosucci-
nimide to give a 188% brominated polymer. 10 g of the brominated
polymer and 0.1 g of cinnamylidene malononitrile were dissolved

lQ4~Z65
in 10 ml of monochlorobenzene.
In accordance with the process of Example 2, the solu-
tion was coated and the layer was charged, exposed and developed,
to obtain a sharp image.
[Example 5]
Polyacenaphthylene (~ sp/c = 0.052 c=0.200 g/dl, benz- ~;
ene solution at 30C) was produced by polymerizing acenaphthylene
in the presence of a boron trifluoride-diethyletherate catalyst
in benzene.
A 1.0 g of polyacenaphthylene and 0.1 g of p-cyano-
benzal malononitrile and 0.1 g of a plastizer of chlorinated
paraffin (manufactured by Adeka-Argus Chem. Co.) were dissolved
in 10 ml of tetrahydrofuran.
In accordance with the process of Example 2, the solu-
tion was coated and the layer was charged and exposed for 1.5 -~
seconds and developed to obtain a sharp image.
[Example 6]
1.0 g of a polymer prepared by substituting 85% of
chlorine atoms of polyepichlorohydrin with carbazole, and 0.2 g
of p-cyanobenzal malononitrile were dissolved in 1,2-dichloro-
ethane.
The solution was coated by a casting method, on a
quarts plate having a transparent electrode made of tin oxide s
membrane.
In accordance with the process of Example 3, the layer
was charged, exposed, developed and transferred to obtain a
sharp image. An aluminum electrode was formed by a vapor deposi-
tion on the layer coated on the quartz plate. The spectral light
passed from an Xenon lamp through a spectrograph (suppled under
the trademark Narumi R-23 type), was exposed from the transparent
electrode (positiveelectrode) sideof theproduct to measure photo-
current. In Figuresl and2, the results of the measurements ofthe

6s
photocurrent and the electronic spectrum of the polymer, the
sensitizer and the photosensitive composition of the present
invention.
As it is clear from the results, in the wavelength
dependency of the photocurrent, the photocurrent is extended
to the longer wavelength side corresponding to the charge
transfer absorption bands extended to the visible range by
mixing the sensitizer with the polymer.
Accordingly, it is found that the sensitizing effect
of the sensitizer is increased by the charge transfer inter-
action. In Figure 1, a designates the electronic spectrum of
the polymer itself; b designates the electronic spectrum of the
sensitizer itself and d designates the electronic spectrum
of the photosensitive composition of the present invention.
In Figure 2, c designates the photocurrent spectrum
of the photosensitive composition of the present invention;
d designates the electronic spectrum thereof; and e designates
the photocurrent spectrum of the polymer itself.
[Example 7]
Polyglycidylcarbazole (n sp/c = 0.030, c = 0.199
g/dQ in tetrahydrofuran at 30C) was produced by polymerizing
N-glycidylcarbazole in toluene in the presence of a boron tri-
fluoride-diethyl etherate catalyst. 1.0 g of the polyglycidyl-
carbazole and 0.05 g of 2-chloro-5-nitrobenzalmalononitrile
were dissolved in 10 mQ of tetrahydrofuran. The solution was
coated on a polyester film having thickness of 100~ which
was treated to give electroconductivity.
In accordance with the process of Example 2, the layer
was charged, exposed and developed. The resulting film was
used for a slide-projection to obtain sharp image without fog.
[Example 8]
1.0 g of polyvinylcarbazole, 0.1 g of
-- 10 --

2-naphthylmethylene malononitrile and 0.005 g of Crystal Violet
were dissolved in 1,2-dichloroethane. In accordance with the
process of Example 7, the solution was coated and the layer was
charged, exposed and developed, to obtain a sharp image without
fog.
[Example 9]
0.3 g of 2-chloro-5-nitrobenzal-malononitrile; 3.0 g
of fluorene and 5.0 g of polyvinylacetate were dissolved in 35
mQ of tetrahydrofuran. The solution was coated by a Baker
(a trademark) applicator on an aluminum plate having thickness
of 0.3 mm which was treated by sand blasting, to provide a layer
having a dry thickness of 15~, whereby a photoconductive layer
was formed.
The positive charge ~as charged on the surface of
the photosensitive plate by Corona discharge in dark place. The
charged photosensitive plate was exposed for 25 seconds at 15
cm distance from a light source of fluorescent lamp of 15 W
(manufactured by Mitsubishi Denki K.K. under the trade mark
F L 155 BL-360), through a transparent original, and then the
layer was developed with a liquid developer to obtain a sharp
image. As the reference, the process was repeated without
fluorene. The exposure time required for forming the image
was 1 minute 20 seconds. The process was also repeated without
benzal-malononitrile. Any image was not obtained even though
the light was exposed for 10 minutes.
[Example 10]_
A solution of 1.0 g of polyvinylcarbazole and 0.2 g
of chlorinated paraffin having chlorine content of 40~ in 10
mQ of monochlorobenzene was admixed with 0.1 g of p-cyanobenzal-
malononitrile. The solution was coated by a Baker applicatoron an electroconductive polyester film (manufactured by Toray
Co.) to provide a layer having a dry thickness of lOu, and it

~s
was dried.
A reference sample was also prepared in accordance with
the above-mentioned process except using 0.1 g of 2,4,7-tri-
nitrofluorenone which is a known sensitizer having a very high
sensitizing effect, instead of p-cyanobenzalmalononitrile.
The film coated with thecomposition containingp-cyanobenzalmalono-
nitrile was a transparent film having pale yellow color. The
film coated with the composition containing 2,4,7-trinitrofluor-
enone was a transparent film having chocolate color. Each
absorption spectrum of each sample is shown in Figure 3, wherein
f is an absorption spectrum of the sample using p-cyanobenzal-
malononitrile and g is an absorption spectrum of the sample using
2,4,7-trinitrofluorenone.
Each projection density of each sample was measured
by Transmission Densitometer (manufactured under the trademark
~uanta Log Model TD-102 by Macbeth Corp.). The projection density
was 0.22 of the sample of the invention and 0.44 of the sample
of the reference. The projection density of the polyester film
substrate was 0.16. Accordingly, the density of the coated
layer itself was 0.06 (the sample of the invention) and 0.28
(the sample of the reference). As it is clear that the sample
of the invention had excellent transmission comparing to the
sample of the reference.
When a sample having higher transmission is developed
with black toner, a contrast of an image is higher so as to give
an excellent film having high contrast.
Each sample was exposed to monochromatic light through
an interference filter (manufactured by Toshiba Co.), to
compare sensitivities of the samples. The sensitivity was
measured by a dose to give 1/3 of the initial surface potential
by the exposure. The sensitivity of the sample of the invention
to the light of 450 mm or 500 mm was 1.5 times of that of the
- 12 -

;~s
sample of the reference. When p-nitrobenzalmalononitrile was
used instead of p-cyanobenzalmalononitrile, similar results were
given.
[Ex _ple 11]
The polymer of Exampl~ 6 was admixed with 5 wt.~ of
each of the following sensitizers, and treated in accordance
with the procesc. of Example 6. The relative sensitivity was
calculated on the basis that the sensitivity of polyvinylcarbazole
is 1.
The results are shown in Table 2.

l~;~S
Table 2
_
SensitizerRelative sensitivity
1 benzalmalononitrile 60
2 p-nitrobenzalmalononitrile 177
3 m-nitrobenzalmalononitrile 81
4 p-cyanobenzalmalononitrile 245
5 p-chlorobenzalmalononitrile 65
6 2,4-dichlorobenzalmalononitrile120
7 2-chloro-5-nitrobenzalmalononitrile 231
8 4-acetoxybenzalmalononitrile 63
9 2-fluoromalononitrile 74
10 ~-cyano- ~-(p-cyanophenyl) acrylic acid
ethyl ester 98
11 1-cyano-1,2-bis(p-nitrophenyl) ethylene270
12 2-furfurylidenemalononitrile 44
13 cinnamylidenemalononitrile 165
14 ~-cyano-~-(p-nitrophenyl) acrylic acid
ethyl ester 107
15 ~-cyano-~-(m-nitrophenyl) acrylic acid
ethyl ester 36
16 l-naphthylmethylenemalononitrile 114
17 2-naphthylmethylenemalononitrile 147
18 1,1-dicyano-4-(p-cyanophenyl)-
1,3-butadiene 143
19 1,1-dicyano-4-(p-chlorophenyl)-
1,3-butadiene 150
20 1,1-dicyano-4-(p-nitrophenyl)-
1,3-butadiene 300
21 1,1-dicyano-4-(m-nitrophenyl)-
1,3-butadiene 157
_ . . _ . .

[Example 12]
1.0 g of the polymer of Example 6 and 0.3 g of 1,1-
dicyano-4-(p-cyanophenyl)-1,3-butadiene were dissolved in 10
mQ of 1,2-dichloroethane. The solution was coated by a Baker
(a trademark) applicator on an aluminum foil having thickness of
20~ laminated on polyester film having thickness of 100~ to
provide a layer having a dry thickness of 12~.
After drying it, positive charge was charged on the
surface of the photoconductive layer by a Corona discharge ( +
6KV applied voltage) in the dark.
The charged photoconductive layer was exposed for 1
second under 30 lux from a tungsten filament lamp, passed through
a transparent positive original, and the exposed layer was
developed with a commercial developer to obtain a clear image
which corresponds to the original.