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Description  |
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BACKGROUND OF THE INVENTION
(a) Field of the Invention
This invention relates to photosensitive materials for use in
electrophotography which comprise a conductive support coated with a
photoconductive layer and a protective layer wherein said protective layer
formed on said photoconductive layer comprises specifically selected
components which improve the light-decay property, mechanical strength and
image formability of said photosensitive materials.
(B) Description of the Prior Art
Photosensitive materials for use in electrophotography have benerally been
provided by forming a photocontive layer consisting of an inorganic
semi-conductor or an organic semi-conductor on a conductive support. To
form an electrostatic latent image on such photosensitive materials, the
so-called Carlson's process has been employed. This process comprises
charging of the photoconductive layer side of the photosensitive material
and image-like exposure. However, photosensitive materials of this type
lack mechanical strength in the photoconductive layer and break easily
when used repeatedly. To avoid this defect, there have hitherto been
proposed a variety of photosensitive materials aimed at improving
durability by providing a transparent protective film of resin formed on
the photoconductive layer. Such photosensitive materials are disclosed in
Japanese Patent Publication No. 23910/1967, Japanese Patent Publication
No. 19748/1967, Japanese Patent Publication No. 24748/1968, Japanese
Patent Publication No. 2965/1974, Japanese Patent Publication No.
15446/1963, Japanese Patent Publication No. 3713/1971, Laid-open
Application No. 22036/1973 and U.S. Pat. No. 3,140,174. These proposed
photosensitive materials are defective in that the provision of a
protective layer has caused a deterioration of the light-decay property
(sensitivity) inherent in the photoconductive layer, and a tendency to
give rise to blurred images. Moreover, their mechanical strength is
unsatisfactory. These deficiencies have been considered attributable to
the insufficiency of the insulating property or the physical properties of
the resin employed for the protective layer.
The present inventors have found that, by forming said protective layer
utilizing specifically selected resins, or selected resins together with a
silane-coupling agent, not only can the mechanical strength of the
protective layer be improved, but also the adhesive property thereof to
the photoconductive layer can be enhanced. Moreover, in neither case is
there an insulating property of the protective layer, and in both cases
the aforesaid defects of the conventional photosensitive materials are
substantially eliminated.
SUMMARY OF THE INVENTION
The principal object of the present invention is to provide photosensitive
materials for use in electrophotography which are superior in durability
to conventional photosensitive materials.
Another object of the present invention is to provide photosensitive
materials which do not cause deterioration of the light-decay property
inherent in the photoconductive layer despite the provision of a
protective layer and can produce an image free of any disorder or blur.
More specifically, the present invention provides photosensitive materials
for use in electrophotography which comprises, as shown in FIG. 1 of the
accompanying drawings, a photoconductive layer 2, a protective layer 1,
and a conductive support 3, wherein said protective layer is composed of
either (1) a member selected from the group of resins consisting of
polyvinyl butyral, polyvinyl acetate, acrylic or derivative resins
thereof, copolymers of styrene and maleic anhydride or alkyl esters
thereof, copolymers of vinyl acetate or derivatives thereof (such as alkyl
derivatives) and vinyl pyrrolidone, copolymers of butyl vinyl ether and
maleic anhydride or alkyl monoesters thereof, polyamides, polyvinyl
pyrrolidones, polyvinyl alcohols, polyvinyl acetals, cellulose and
shellac, or composed mainly of (2) a resin selected from the
above-mentioned resins or other resins together with a silane-coupling
agent. By applying an adhesive to the interspaces of said support,
photoconductive layer and protective layer, the strata can be
strengthened.
Conventional materials may be used to form the photoconductive layer in the
present invention. These include plates or cylinders made of aluminum,
copper, stainless steel and the like, paper or plastic film deposited with
such metals through vacuum evaporation, conductive glass, etc.
Typical photoconductive substances which may be employed in the
photoconductive layer in the present invention include inorganic
semi-conductors such as zinc oxide, titanium oxide, cadmium sulfide, and
film-forming organic semi-conductors such as poly-N-vinyl carbazole,
poly-N-vinyl-3,6-dibromocarbazole, pyrene-formaldehyde resins, polyvinyl
dibenzothiophene and polyvinyl anthracene. Inorganic semi-conductors such
as selenium which can be used independently, and CdS and ZnO which are
used together with resinous binders can be utilized. These binders
include, for example, acrylic resins, silicone resins, alkyd resins,
epoxide resins, styrene-butadiene resins and melamine resins. Sensitizers,
coloring materials, or electron acceptors such as Rose Bengal,
fluorescene, Methylene Blue, benzopyrylium, 2,4,7-trinitrofluorenone may
be employed in the conventional manner. Selenium may be doped with
telurium.
In order to prepare the photosensitive materials for use in
electrophotography according to the present invention, a photoconductive
layer is first formed on a conductive support and dried in the
conventional manner. The protective layer is formed from a solution of the
aforesaid specific resin or a resin and a silane-coupling agent by coating
with the knife coater, blade or the like or impregnating and drying
thereafter. Typically, the thickness of the protective layer is from about
0.1-30.mu., preferably 0.1-25.mu.. The solvent utilized in forming the
protective layer should not dissolve or otherwise affect the
photoconductive layer. Solvents having an SP value (solubility parameter
value) of more than 11 or less than 8 are particularly useful. These
include, for example, alcohols such as methanol and ethanol, ethylene
glycol, water, carbon tetrachloride, n-hexane, and the like.
All of the aforesaid specific resins for use in the protective layers of
the present invention have sufficient insulating ability and are superior
in such physical properties as film-formability, adhesive strength, so
that they do not adversely affect the electrophotographic properties of
the photoconductive layer. Moreover, they are readily available
commercially or can be prepared utilizing known methods of synthesis.
The protective layer may also contain such additives as adhesives,
cross-linking agents (including those which also function as adhesives),
curing catalysts and/or wetting agents to the extent of up to 50% by
weight based on the total weight of the protective layer in order to
improve abrasion resistance, resistance to wetting and adhesive strength.
Typical adhesives which can be employed for this purpose include vinyl
resins as polyvinyl butyral, polyvinyl alcohol, polyvinyl chloride,
polyvinyl acetate, acrylic resins, epoxide resins, urethane resins and the
like.
Useful cross-linking agents include, for example, aminotriazines, urea
resins, epoxide resins, urethane resins, and the like. Amino triazines are
especially effective. Typical aminotriazines which may be mentioned by way
of example include butyrated melamine, hexamethoxymethylol melamine,
acetoquanamine, benzoquanamine, formquanamine, N-(t-butyl)melamine,
N-(t-octyl)melamine, 2-phenyl-P-oxy-4,6 diamino-1,3,5-triazine,
6-methyl-2,4-diamino-1,3,5-triazine, 2,4,6-trihydrazine-1,3,5-triazine,
N,N-dialkyl melamine and the like.
Curing catalysts which may be utilized include acid catalysts such as
sulfuric acid, paratoluene sulfonic acid, 1-naphthalene sulfonic acid and
the like. Paratoluene sulfonic acid is most effective. In addition to the
above, there are potassium persulfate, ammonium persulfate, hydrogen
peroxide solution and the like.
Various commercial silicone oils are applicable as wetting agents.
Cross-linking agents which concurrently act as adhesives include
silane-coupling agents which can effect adhesion between the
photoconductive layer and the protective layer through chemical reaction
and form a firm coating film. Such silane-coupling agents are readily
available on the market. They include, for instance, vinyl chlorosilane,
vinyl triethoxysilane, vinyl trimethoxysilane,
vinyltris(.beta.-methoxyethoxy)silane, .gamma.-methacryloxypropyl
trimethoxysilane, .gamma.-methacryloxypropyl
tris(.beta.-methoxyethoxy)silane, .beta.-(3,4-epoxycyclohexyl)ethyl
trimethoxysilane, .gamma.-glydicoxypropyl trimethoxysilane, vinyl
triacetoxysilane, .gamma.-mercaptopropyl trimethoxysilane,
.gamma.-aminopropyl triethoxysilane,
N-.beta.-(aminoethyl)-.gamma.-aminopropyltrimethoxysilane,
N-.beta.-(aminoethyl)-.gamma.-aminopropyl methyl dimethoxysilane,
N,N-bis(.beta.-hydroxyethyl)-.gamma.-aminopropyl triethoxysilane,
.gamma.-chloropropyl trimethoxysilane and the like.
Because of reaction between various functional groups such as epoxide
groups and carboxyl or hydroxyl groups, melamine and carboxyl group,
present in the above-mentioned adhesive, cross-linking agents, curing
agents, a three-dimensional structure is formed so that the abrasion
resistance, resistance to wetting and adhesive strength of the protective
layer is remarkably improved.
The silane-coupling agents contain two or more reactive groups of different
reactivity in the same molecule. One is a reactive group capable of
effecting film coupling by chemically bonding with inorganic matter (e.g.,
methoxyl group and silanol group) and the other is a reactive group
capable of effecting chemical bonding with organic matter (e.g., vinyl
group, epoxide group, methacryl group and amino group). As a result, the
silane-coupling agent not only enhances the binding property of organic
materials but also functions as a mediator between the organic materials
and inorganic materials, so that it renders it possible to mix those
inorganic materials which will increase the mechanical strength and those
organic materials which will result in a three-dimensional structure in
the protective layer of the present invention. Useful inorganic materials
include, for instance, quartz sand, glass fiber, amorphous silica, crystal
silica and metal oxides such as Al.sub.2 O.sub.3, ZnO, MgO. Useful organic
materials include, for instance, cross-linking agents or adhesives such as
the aforesaid epoxide resins, polyamide resins, urea resins, urethane
resins and amino triazines.
When a resin is used together with a silane-coupling agent, the quantity of
said agent utilized in the protective layer is from about 0.01 wt% to 10
wt.%. Increased quantities of silane-coupling agents tend to reduce the
cohesive strength of the protective layer. The preferred quantity is from
0.1 wt.% to 0.24 wt.%.
It is not essential to employ a silane-coupling agent in the protective
layer, as has been suggested above. It is, however, preferred to do so.
With conventional resins such as polyamides, polyvinyl pyrrolidones,
polyvinyl alcohols, polyvinyl acetals, and cellulose, the silane-coupling
agent is indispensable.
In order to form an electrostatic latent image on the photosensitive
material prepared as above, the Carlson's process or modifications thereof
such as the processes disclosed in Japanese Patent Publication No.
2965/1973 and Japanese Patent Publication No. 37,959/1970 are applicable.
In other words, it suffices to apply either a process comprising, in
order, subjecting the protective layer side to a primary charging,
charging elect ricity having a polarity opposite to that of said primary
charging or applying AC corona discharge simultaneously with the
image-like exposure, and subsequently effecting an overall exposure, an
occasion demands, or a process comprising subjecting the protective layer
side to a primary charging, applying an overall exposure simultaneously
with or immediately after said primary charging, subsequently charging
electricity having a polarity opposite to that of said primary charging,
and thereafter effecting the image-like exposure to thereby form an
electrostatic latent image, followed by development, transfer and fixing
according to the conventional methods.
Inasmuch as the photosensitive material for use in electrophotography
according to the present invention is provided with a protective layer, it
can be used repeatedly. Moreover, it is free of deterioration of the
electrophotographic properties of photoconductive layer thereof despite
the provision of a protective layer thereon.
BRIEF DESCRIPTION OF THE DRAWING
In the accompanying drawings:
FIG. 1 is a cross-sectional view of a photosensitive material according to
the present invention, wherein 1 denotes the protective layer, 2 denotes
the photoconductive layer and 3 denotes the conductive support; and
FIGS. 2 and 3 are respectively a curve showing the surface potential
difference between the exposed area and the non-exposed area of the
photosensitive material according to the present invention used in Example
1 and Example 3, respectively.
The following nonlimiting examples are given by way of illustration only.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
EXAMPLE 1
______________________________________
Poly-N-vinyl carbazole 2.0 g
2,4,7-Trinitrofluorenone
3.3 g
Polyester Adhesive 49,000
0.472 g
(the manufacture of DuPont Co.)
Silicone Oil Ak-1,000 0.014 g
(the manufacture of Worker
Chemical GMBH)
Tetrahydrofuran 41.7 g
______________________________________
A solution having the above composition was coated on a polyester film
deposited with aluminum through vacuum evaporation by the use of a doctor
blade and was dried at a temperature of 60.degree. C. for 10 minutes and
at a temperature of 100.degree. C. for 2 minutes in succession, whereby a
20.mu.-thick organic photoconductive layer was formed. Next, a 10 wt.%
methanol solution of butyral resin (a manufacture of SEKISUI KAGAKU K.K.;
trade name: S-LEC BM-2) was coated on the thus prepared photoconductive
layer to the extent of 10-20.mu. in dry thickness, whereby a transparent
protective layer was formed. The resulting photosensitive material was so
superior in flexibility that it could be easily fastened around a
cylinder.
The thus prepared photosensitive material was charged with positive
electricity by corona discharge of 6.5 KV and was subjected to overall
exposure simultaneously with or immediately after said charging. The
surface potential at this time was +1000 V. Subsequently, by charging
negative electricity by corona discharge of 5.3 KV in the dark (the
surface potential at this time was -700 V) and subjecting to image-like
exposure under the condition of 18 lux.sec, an electrostatic latent image
was formed on the photosensitive material. The surface potential at this
time was +100 V, and the potential difference between the non-exposed area
and the exposed area was 800 V as shown in FIG. 2 of the accompanying
drawings.
Next, when the image produced through dry-developing process or
wet-developing process according to the known methods was
electrostatically transferred to a slick paper and fixed, there was
obtained a positive image in which the background was free of stains and
faithful to the original image. Even after producing 5,000 copies by
repeating the above procedures, there was observed no deterioration of
sensitivity or image.
EXAMPLE 2
By coating a solution having the same composition and under the same
condition of coating as in Example 1, a 2.mu.-thick organic
photoconductive layer was formed on a polyester film deposited with
aluminum through vacuum evaporation. Next, a 10 wt.% methanol solution of
polyvinyl acetate resin (a manufacture of Daicel Co.; trade name: SEVIAN
A-001) was coated on the thus prepared photoconductive layer to the extent
of 12-15.mu. in dry thickness by the use of a doctor blade, whereby a
transparent protective layer was formed. The resulting photosensitive
material was so superior in flexibility that it could be easily fastened
round on a cylinder.
This photosensitive material was then charged with positive electricity by
corona discharge of 6.5 KV and was subjected to overall exposure
simultaneously with or immediately after said electrification. The surface
potential at this time was +800 V. Subsequently, by charging negative
electricity by corona discharge of 4.7 KV in the dark (the surface
potential at this time was -500 V) and then subjecting to image-like
exposure under the condition of 18 lux.sec, an electrostatic latent image
was formed on the photosensitive material. The surface potential at this
time was +200 V, and the potential difference between the non-exposed area
and the exposed area was 700 V as shown in FIG. 2. Next, when a positive
image was formed in the same way as in Example 1 and the test copying was
repeated, the result was the same as in Example 1.
EXAMPLE 3
By coating a solution having the same composition and under the same
condition of coating as in Example 1, a 20.mu.-thick organic
photoconductive layer was formed on a polyester film deposited with
aluminum through vacuum evaporation. Next, a 10 wt.% methanol solution of
acryl polyol (a manufacture of SOKEN KAGAKU K.K. having hydroxyl group
value of 30; trade name: THERMOLAC U-230A) was coated on the foregoing
photoconductive layer to the extent of 12-16.mu. in dry thickness by the
use of a doctor blade, wherety a transparent protective layer was formed.
The resulting photosensitive material was so superior in flexibility that
it could be easily fastened round on a cylinder.
The thus prepared photosensitive material was then charged with positive
electricity by corona discharge of 6.5 KV and was subjected to overall
exposure simultaneously with or immediately after said electrification.
The surface potential at this time was +900 V. Subsequently, by charging
negative electricity by corona discharge of 4.7 KV in the dark (the
surface potential on this occasion was -700 V) and then subjecting to
image-like exposure under the condition of 18 lux.sec, an electrostatic
latent image was formed on the photosensitive material. The surface
potential between the non-exposed area and the exposed area was 1,000 V as
shown.
Next, when a positive image was formed in the same way as in Example 1 and
the test copying was repeated, the result was equal to that in Example 1.
EXAMPLE 4
By applying the same procedure as in Example 3, a 20.mu.-thick organic
photoconductive layer and a 10-15.mu.-thick transparent protective layer
were formed on a polyester film deposited with aluminum through vacuum
evaporation.
The thus prepared photosensitive material was then charged with positive
electricity by corona discharge of 6.5 KV and was subjected to overall
exposure simultaneously with or immediately after said electrification.
The surface potential at this time was +750 V. Subsequently, by charging
negative electricity by corona discharge of 5.3 V in the dark (the surface
potential at this time was -800 V) and then subjecting to image-like
exposure under the condition of 18 lux.sec, an electrostatic latent image
was formed on the photosensitive material. The surface potential of the
exposed area at this time was +100 V and the potential difference between
the non-exposed area and the exposed area was 900 V. Next, when a positive
image was formed in the same way as in Example 1 and the test copying was
repeated, the result was equal to that in Example 1.
______________________________________
Poly-N-vinyl carbazole 2.0 g
2,4,7-Trinitrofluorenone
3.3 g
Polyester Adhesive 49,000
0.472 g
(the manufacture of DuPont Co.)
Silicone Oil Ak-1,000 0.014 g
(the manufacture of Worker
Chemical GMBH)
Tetrahydrofuran 41.7 g
______________________________________
A solution having the above composition was coated on a polyester film
deposited with aluminum through vacuum evaporation by the use of a doctor
blade and was dried at a temperature of 60.degree. C. for 10 minutes and
at a temperature of 100.degree. C. for 2 minutes in succession, whereby a
20.mu.-thick organic photoconductive layer was formed. Meanwhile, upon
putting 300 ml of benzene, 10.4 g (0.1 mole) of styrene, 9.8 g (0.1 mole)
of maleic anhydride and 0.1 g of benzoyl peroxide in a 4-nozzled flask
having the capacity of 500 ml as equipped with the agitator, thermometer,
reflux cooling pipe and nitrogen-inducing pipe, agitation was carried out
at room temperature until a transparent solution was obtained. While thus
agitating, the mixture was heated to boil in water bath, whereby copolymer
was gradually formed. After one hour's reaction, the mixture was cooled
and the solid polymer was separated therefrom by filtration, whereby 200 g
of white powder were yielded. When 10 g of the thus obtained copolymer
were taken into a 4-nozzled flask having the capacity of 300 ml, 90 g of
methyl alcohol were added thereto, and the resulting mixture was refluxed
on water bath for 5 hours, said copolymer dissolved in methyl alcohol to
produce a transparent methyl ester compound.
A 5-10 wt.% methanol solution of the thus obtained methyl ester of
copolymer of styrene and maleic anhydride was coated on the aforesaid
photoconductive layer to the extent of 0.1-15.mu. in dry thickness,
whereby two varieties of photosensitive materials having a 2.1.mu.-thick
protective layer and a 13.4.mu.-thick protective layer, respectively, were
prepared. The thus prepared photosensitive materials were so superior in
flexibility that they could be easily fastened on a cylinder.
These photosensitive materials were then charged with negative electricity
by corona discharge of 6.0 KV, exposed to the light of white tungsten lamp
of 20 luxes, and subjected to measurement for determining the amount of
exposure E 1/2 (lux.sec) required for decay of the surface potential to
1/2, the amount of exposure E 1/5 (lux.sec) required for decay of the
surface potential to 1/5 and the amount of exposure E 1/10 (lux.sec)
required for decay of the surface potential to 1/10, after applying the
light. And, the values obtained from this measurement, which represent the
sensitivity of the photosensitive materials, were compared with the
counterpart of a photosensitive material having no protective layer. The
result was as shown in the following Table 1.
Table 1
______________________________________
light-decay property
photosensitive layer
E 1/2 E 1/5 E 1/10
______________________________________
none 4.6 12.0 20.6
2.1 .mu.-thick layer
4.6 12.1 20.5
13.4 .mu.-thick layer
4.6 12.0 22.3
______________________________________
As is evident from the showing in this table, the sensitivity of the
photosensitive materials according to the present invention was
practically equal to that of the photosensitive material having no
protective layer.
Next, when the image produced through the known dry-developing process or
wet-developing process was electrostatically transferred to a slick paper
and fixed, there was obtained a positive image having a background free of
stains and faithful to the original image. Even after producing 30,000
copies by repeating the foregoing procedures, there was observed no
deterioration of the sensitivity nor occurrence of any disorder of image.
Meanwhile, as for the photosensitive material having no protective layer,
when the image test was conducted in the same way as above, it was
observed that the sensitivity deteriorated, the background became stained,
and the image became disordered when only 5,000 copies were produced.
EXAMPLE 6.
______________________________________
poly-N-vinyl carbazole 2.0 g
2,4,7-trinitrofluorenone
3.3 g
polycarbonate 0.472 g
Silicone Oil Ak-1,000 0.014 g
(the manufacture of Worker
Chemical GMBH)
tetrahydrofuran 41.7 g
______________________________________
A solution having the above composition was coated on a polyester film
deposited with aluminum through vacuum evaporation by the use of a doctor
blade and was dried at a temperature of 60.degree. C. for 10 minutes and
at a temperature of 100.degree. C. for 2 minutes in succession, whereby an
18.mu.-thick organic photoconductive layer was formed.
Meanwhile, by putting 10 g of the styrene-maleic anhydride copolymer
obtained in Example 5 in a 4-nozzled flask having the capacity of 300 ml,
adding 90 g of ethyl alcohol thereto and refluxing the resulting mixture
on water bath for 5 hours, said copolymer was dissolved in ethyl alcohol
and a transparent ester compound was prepared.
A 5-10 wt.% methanol solution of the thus prepared ethyl ester of
styrene-maleic anhydride copolymer was coated on the foregoing
photoconductive layer to the extent of 0.1-20.mu. in dry thickness,
whereby two varieties of photosensitive materials having a 5.4.mu.-thick
protective layer and an 18.2.mu.-thick protective layer, respectively,
were prepared. These photosensitive materials were so superior in
flexibility that they could be easily fastened on a cylinder. When the
light-decay property of these photosensitive materials was measured in the
same way as in Example 5, the results were shown in the following Table 2.
Table 2
______________________________________
light-decay property
photosensitive layer
E 1/12 E 1/5 E 1/10
______________________________________
none 4.8 12.5 21.4
5.4 .mu.-thick layer
4.8 12.4 21.6
18.2 .mu.-thick layer
4.8 13.0 22.0
______________________________________
As is evident from the showing in this table, the sensitivity of the
photosensitive materials according to the present invention was
practically equal to that of the photosensitive material having no
protective layer.
Next, when the image test of the present photosensitive materials was
conducted in the same way as in Example 5, it was possible to obtain a
positive image having a background free of stains and being faithful to
the original image. There was no deterioration of iamge even after
producing 25,00 copies.
EXAMPLE 7
By coating a solution having the same composition and under the same
condition of coating as in Example 5, a 20.mu.-thick organic
photoconductive layer was formed on a polyester film deposited with
aluminum through vacuum evaporation. Meanwhile, by putting 10 g of the
styrene-maleic anhydride copolymer obtained in Example 5 in a 4-nozzled
flask having the capacity of 300 ml, adding 90 g of isopropyl alcohol
thereto and refluxing the mixture on oil bath for 5 hours, said copolymer
was dissolved in isopropyl alcohol and a transparent isopropyl ester
compound was prepared.
A 5-10 wt.% methanol solution of the thus prepared isopropyl ester of
styrene-maleic anhydride copolymer was coated on the foregoing
photoconductive layer to the extent of 0.1-20.mu. in dry thickness,
whereby two varieties of photosensitive materials having a 2.5.mu.-thick
protective layer and a 16.7.mu.-thick protective layer, respectively, were
prepared. These photosensitive materials were so superior in flexibility
that they could be easily fastened on a cylinder. When the light-decay
property of these photosensitive materials was measured in the same way as
in Example 5, the results were as shown in the following Table 3.
Table 3
______________________________________
light-decay property
protective layer
E 1/2 E 1/5 E 1/10
______________________________________
none 4.6 12.0 20.6
2.5 .mu.-thick layer
4.6 12.0 21.3
16.7 .mu.-thick layer
4.6 11.9 21.9
______________________________________
As is evident from the showing in this table, the sensitivity of the
photosensitive materials according to the present invention was
practically equal to that of the photosensitive material having no
protective layer.
Next, when the image test of the present photosensitive materials was
conducted in the same way as in Example 5, it was possible to obtain a
positive image having a background free of stains and being faithful to
the original image. There was no deterioration of image even after the
production of 30,000 copies.
EXAMPLE 8
By depositing amorphous selenium containing 10% of tellurium to the extent
of 50.mu. thickness through vacuum evaporation on a polyester film
deposited with aluminum through vacuum evaporation, an organic
photoconductive layer was formed. Next, a 5-10 wt.% methanol solution of
methyl ester of styrene-maleic anhydride copolymer obtained in Example 5
was coated on the foregoing photoconductive layer to the extent of
0.1-30.mu. in dry thickness, whereby two varieties of photosensitive
materials having a 3.3.mu.-thick protective layer and a 25.6.mu.-thick
protective layer, respectively, were prepared. When the light-decay
property of these photosensitive materials was measured in the same way as
in Example 5, the result was as shown in the following Table 4.
Table 4
______________________________________
light-decay property
protective layer
E 1/2 E 1/5 E 1/10
______________________________________
none 2.0 3.8 7.0
3.3 .mu.-thick layer
2.0 3.6 7.1
25.6 .mu.-thick layer
2.0 3.6 7.1
______________________________________
As is evident from the showing in this table, the sensitivity of the
photosensitive materials according to the present invention was
practically equal to that of the photosensitive material having no
protective layer.
Next, when the image test of the present photosensitive materials was
conducted in the same way as in Example 5, it was possible to obtain a
positive image having a background free of stains and being faithful to
the original image. There was no deterioration of image even after
producing 28,000 copies.
EXAMPLE 9
______________________________________
Poly-N-vinyl carbazole 2.0 g
2,4,7-Trinitrofluorenone
3.3 g
Polyester Adhesive 49,000
0.472 g
(the manufacture of DuPont Co.)
Silicone Oil Ak-1,000 0.014 g
(the manufacture of Worker
Chemical GMBH)
Tetrahydrofuran 41.7 g
______________________________________
A solution having the above composition was coated on a polyester film
deposited with aluminum through vacuum evaporation by the use of a doctor
blade and was dried at a temperature of 60.degree. C. for 10 minutes and
at a temperature of 100.degree. C. for 2 minutes in succession, whereby a
20.mu.-thick organic photoconductive layer was formed.
Meanwhile, by dissolving 10 g of ethyl acrylate-acrylic acid copolymer
(molar ratio = 90:10) in 90 g of isopropanol and then adding 3.5 g of
hexamethoxymethylol melamine, 0.35 g of p-toluene sulfonic acid and 0.5 g
of .beta.(3,4-epoxycyclohexyl)ethyl trimethoxy silane thereto, an overcoat
solution was prepared. Further, after adjusting the concentration (in
terms of said copolymer) of this solution to be in the range of 5-10%, by
coating the thus adjusted solution on the foregoing photoconductive layer,
two varieties of photosensitive materials having a 1.5.mu.-thick
protective layer and a 6.5.mu.-thick protective layer, respectively, were
prepared. The thus prepared photosensitive materials were so superior in
flexibility that they could be easily fastened on a cylinder.
These photosensitive materials were charged | | |
