U.S. patent number 3,819,370 [Application Number 05/301,051] was granted by the patent office on 1974-06-25 for photoconductive element and process of preparing same using thermo-shrinkable material.
This patent grant is currently assigned to Canon Kabushiki Kaisha. Invention is credited to Takashi Ihara, Takao Komiya, Takehiko Matsuo, Hirokazu Negishi, Katsunobu Ohhara, Umi Tosaka.
United States Patent |
3,819,370 |
Komiya , et al. |
June 25, 1974 |
**Please see images for:
( Certificate of Correction ) ** |
PHOTOCONDUCTIVE ELEMENT AND PROCESS OF PREPARING SAME USING
THERMO-SHRINKABLE MATERIAL
Abstract
A photosensitive member for electrophotography comprising an
endless substrate, a photoconductive layer overlying the substrate
and a seamless insulative layer overlying the photoconductive
layer, is produced by applying a photoconductive layer to the
substrate, loosely encircling such applied photoconductive layer
and substrate with a thermally-shrinkable endless resin film and
heating the film into continuous contacting relation with the
photoconductive layer.
Inventors: |
Komiya; Takao (Yokohama,
JA), Ihara; Takashi (Kawasaki, JA), Matsuo;
Takehiko (Tokyo, JA), Tosaka; Umi (Tokyo,
JA), Negishi; Hirokazu (Yokohama, JA),
Ohhara; Katsunobu (Kawasaki, JA) |
Assignee: |
Canon Kabushiki Kaisha (Tokyo,
JA)
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Family
ID: |
27564456 |
Appl.
No.: |
05/301,051 |
Filed: |
October 26, 1972 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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828658 |
May 28, 1969 |
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Foreign Application Priority Data
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Jun 4, 1968 [JA] |
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43-37748 |
Jun 6, 1968 [JA] |
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43-39133 |
Aug 21, 1968 [JA] |
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43-59755 |
Aug 21, 1968 [JA] |
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43-59762 |
Aug 22, 1968 [JA] |
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43-60161 |
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Current U.S.
Class: |
430/67; 156/86;
156/165; 430/132 |
Current CPC
Class: |
B29C
63/20 (20130101); G03G 5/0525 (20130101); G03G
5/147 (20130101); B29C 63/42 (20130101); B29C
63/0069 (20130101); B29L 2031/324 (20130101); B29C
35/04 (20130101) |
Current International
Class: |
B29C
63/20 (20060101); B29C 63/42 (20060101); B29C
63/38 (20060101); B29C 63/00 (20060101); G03G
5/05 (20060101); G03G 5/147 (20060101); B29C
35/04 (20060101); G03g 005/08 () |
Field of
Search: |
;96/1R,1.5,1.8,115P
;156/86,165 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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1,078,560 |
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Aug 1967 |
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GB |
|
730,965 |
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Mar 1966 |
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CA |
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Primary Examiner: Martin, Jr.; Roland E.
Attorney, Agent or Firm: Watson Leavenworth Kelton &
Taggart
Parent Case Text
This is a continuation of application Ser. No. 828,658 filed May
28, 1969, now abandoned.
Claims
We claim:
1. A method for producing a photosensitive body having a
photoconductive layer and an insulative layer overlying said
photoconductive layer comprising the steps of:
a. applying to a surface of an endless substrate a mixture
including particulate photoconductive material;
b. arranging an endless thermally-shrinkable resin film in loosely
encircling relation with said photoconductive material; and
c. heating said film, thereby shrinking said film into contacting
relation with said applied photoconductive material.
2. The method claimed in claim 1 wherein said substrate comprises a
conductive member.
3. The method claimed in claim 1 wherein said substrate comprises
an insulative member.
4. The method claimed in claim 1 wherein said substrate comprises a
conductive member overlying an insulative member.
5. The method claimed in claim 1 wherein said resin film comprises
polyester resin.
6. The method claimed in claim 1 wherein said heating step is
practiced under sub-atmospheric pressure, said photosensitive body
being subjected to atmospheric pressure following practice of said
heating step.
7. The method claimed in claim 1 wherein said heating step is
practiced by applying heated water to said resin film.
8. The method claimed in claim 1 wherein said heating step is
practiced by applying heated gas to said resin film.
9. A method of producing a photosensitive body having a
photoconductive layer and an insulative layer overlying said
photoconductive layer comprising the steps of:
a. applying to the interior surface of a tubular
thermally-shrinkable resin film a mixture including particulate
photoconductive material;
b. disposing a cylindrical substrate interiorly of said tubular
film with said photoconductive material in loosely-encircling
relation with said substrate; and
c. heating said film, thereby shrinking said film and disposing
said photoconductive material in contacting relation with said
substrate.
10. The method claimed in claim 9 wherein said substrate comprises
a conductive member.
11. The method claimed in claim 9 wherein said substrate comprises
an insulative member.
12. The method claimed in claim 9 wherein said substrate comprises
a conductive member overlying an insulative member.
13. The method claimed in claim 9 wherein said substrate comprises
an insulative member overlying a conductive member.
14. The method claimed in claim 9 wherein said resin film comprises
polyester resin.
15. The method claimed in claim 9 wherein said mixture comprises a
dispersion of said photoconductive material in a thermoplastic
resin.
16. The method claimed in claim 9 wherein said mixture comprises a
dispersion of said photoconductive material in a thermosetting
resin.
17. The method claimed in claim 1 including the further step of
smoothening the surface of said applied mixture prior to practice
of said heating step by rubbing said surface with a member
substantially non-adhesive to said mixture.
18. The method claimed in claim 17 wherein said mixture comprises a
dispersion of said photoconductive material in a solution of a
synthetic resin monomer or a synthetic resin of low polymerization
degree and a polymerization accelerator.
19. A method for producing a photosensitive body having a
photoconductive layer and an insulative layer overlying said
photoconductive layer comprising the steps of:
a. aplying to a surface of an endless substrate a mixture
comprising a dispersion of particulate photoconductive material in
a solution of a synthetic resin monomer or a synthetic resin of low
polymerization degree and a polymerization accelerator;
b. arranging an endless thermally-shrinkable resin film in
loosely-encircling relation with said photoconductive material;
and
c. heating said film, thereby shrinking said film into contacting
relation with said applied photoconductive material,
said arranging and heating steps being practiced prior to
completion of polymerization of said synthetic resin.
20. The method claimed in claim 19 wherein said resin film includes
a heat-absorbing coating on a surface thereof.
21. The method claimed in claim 10 wherein said resin film
comprises polyester resin.
22. The method claimed in claim 1 including the further step,
practiced intermediate said applying and arranging steps, of
overlaying on said applied mixture a layer comprising a resin
rendered adhesive during said heating step.
23. The method claimed in claim 9 including the terminal step of
removing said substrate.
24. The method claimed in claim 1 wherein said resin film includes
a heat-absorbing coating on a surface thereof.
25. A photosensitive member comprising an endless substrate, a
photoconductive layer overlying said substrate and an insulative
layer overlying said photoconductive layer, said insulative layer
comprising a thermally-shrunk endless film of thermoplastic
resin.
26. The photosensitive member claimed in claim 25 wherein said
substrate comprises a conductive material.
27. The photosensitive member claimed in claim 25 wherein said
substrate comprises an insulative material.
28. The photosensitive member claimed in claim 25 wherein said
substrate comprises a conductive layer overlying an insulative
layer.
29. The photosensitive member claimed in claim 25 wherein said
substrate comprises an insulative layer overlying a conductive
layer.
30. The method claimed in claim 1 wherein said substrate comprises
an insulative member overlying a conductive member.
Description
This invention relates to a process for producing a photosensitive
body for electrophotography and an apparatus for producing the
photosensitive body. More particularly, this invention relates to a
process for producing an excellent seamless photosensitive member
of uniform thickness used for electrophotography, said
photosensitive member being composed of a photoconductive layer and
an insulating layer provided on a conductive center member and to
an apparatus therefor.
In electrophotography, images are produced generally through
various stages such as electrostatic latent image formation,
developing, fixing, etc., each affected by the photosensitive body
which is based on a conductive substrate.
As the photosensitive body, those in flat form and cylindrical
shape are already in widespread use. They are, however, selected
according to the respective electrophotographic systems to which
they are to be applied, and satisfactory results are obtained in
accordance with the respective system objects.
There have been introduced hitherto various systems of
electrophotography, but we will explain hereunder specifically
those systems which are particularly effective.
To a photosensitive body which is composed basically of an
electrically conductive layer, a photoconductive layer and an
insulating layer, primary charge is applied and then secondary
charge or an alternating current corona discharge is applied at the
same time as irradiation of an original image is performed, if
desired, followed by further entire exposure, so as to form an
electrostatic image. After this procedure, the electrostatic latent
image is developed, transferred to a specific transfer paper and
fixed. In this system, an electrostatic image is not directly
formed on the photoconductive layer, unlike in the case of
conventional so-called Carlson process, but is formed on the
insulating layer which is in close contact with the photoconductive
layer. This system is, therefore, characterized not only in
protection of the photoconductive body, but also in attainment of
clear image of high contrast, as well as in making good transfer
onto paper, metal, wood, cloth, etc., since the efficiency of the
transfer is very good in this case.
The systems of this type are described in U.S. application Ser. No.
563,899, filed on July 8, 1966 and No. 571,538, filed on Aug. 10,
1966, now abandoned.
For constructing a copier for the formation of electrophotographic
images based on the above-mentioned system, it is advantageous that
the photosensitive body be in a drum shape and not in the form of a
flat plate. That is, it is possible for charge, exposure,
developing, transfer and remnant toner cleaning apparatus to be
arranged around a photosensitive drum, such that a copier is so
constructed as to produce copied images in a rotary system with the
different process steps performed one after another, with copying
speed increased.
In this case, it is necessary for the structure of the copier that
the photosensitive drum be seamless. With seams on the drum, the
copier has to be so constructed as to enable it to produce images
on the unseamed parts of the drum, disadvantages not presented by a
seamless drum.
The photosensitive drums of this seamless type, however, have not
been developed practically hitherto, as no adequate manufacturing
method has yet been discovered, and only photosensitive plates of
flat form are being used today.
The present invention provides photosensitive drums in cylindrical
shape, belt form, etc., which are seamless and are composed of the
aforesaid different layers, and which are able to act very
effectively in the electrophotographic systems described above.
Another object of the present invention is to provide very easy and
simple methods for making seamless photosensitive drums.
One more object of the present invention is to provide apparatus
for making seamless photosensitive drums.
The present invention further aims at obtaining all advantages of
the following explanations, practical examples, etc.
The above and other objects, aspects and advantages will become
apparent by reading the following description taken in conjunction
with the accompanying drawing, in which:
FIG. 1 is a cross sectional view of an embodiment of a
photosensitive body of this invention;
FIG. 2 shows an embodiment of the coating apparatus of this
invention;
FIG. 3 shows a thermal shrinking technique;
FIG. 4 schematically illustrates a system for forming a
photoconductive layer;
FIGS. 5 and 6 explain the process step of inserting a cylinder
member;
FIG. 7 schematically illustrates a method for smoothing the surface
of the photosensitive body; and
FIGS. 8 and 9 show an embodiment of the apparatus of this
invention.
The photosensitive drum obtained by the present invention is
basically composed of a substrate layer 1, photoconductive layer 2
and insulating (insulative) layer 3, as shown in FIG. 1. The
substrate layer can be in the form of a conductive layer or an
insulating layer, or a combination thereof.
Methods for making such electrophotographic photosensitive drums in
general, comprises a first process step of forming a
photoconductive layer on the surface of the drum and a second
process step of producing an insulating layer thereupon. In this
case, the conditions required for the first process step are:
1. to reduce as far as possible the proportion of binder resin in
the photoconductive body, so as to improve photoconductivity and to
increase sensitivity;
2. to finish the photoconductive layer in specific thickness evenly
all over the drum, thus enabling it to receive good images;
3. to make smooth the finish of the surface of the photoconductive
layer, so that in the next process step the insulating layer can be
formed throughout in specific uniform thickness. With unevenness in
the surface of the photoconductive layer, projecting parts on the
surface of the photoconductive layer cause thinness and indented
parts cause thickness in the insulating layer, thus permitting no
uniform finish; and
4. to finish the photoconductive layer sufficiently firm and strong
to ensure no change in the thickness and flatness of the
photoconductive layer in the process step of producing the
insulating layer.
Next, the conditions to be met in the process step of forming the
insulating layer are:
1. to finish the insulating layer in specific thickness evenly all
over, thus enabling it to receive good images. It is essential for
obtaining a better image that the insulating layer be kept as thin
and even as possible. It is absolutely essential for this condition
to be met that the photoconductive layer be finished smoothly as
described above;
2. to finish flat and even the surface of the insulating layer, so
that there can be no stain by the adhesion of toner, and also that
remnant toner left after the transfer can be cleaned easily;
3. and to finish the insulating layer with enough durability to
withstand repeated uses and with chemical resistance, etc.
For satisfying the above various conditions at the same time, it is
necessary in general to manufacture the photosensitive drum by the
method as described in the following.
The first process step of forming the photoconductive layer can be
carried out, for instance, in the following manner. That is, fine
powder for the photoconductive body is first dispersed in a binder
resin (monomer of epoxy resin) and then this is kneaded thoroughly
with a curing agent in order to prepare a mixture in paste form,
followed immediately by coating of this paste on the surface of a
revolving drum in uniform thickness by means of a doctor blade.
Since the surface of this photoconductive layer cannot be finished
flat and even, and exhibits much unevenness, the surface is rubbed
until flat and even with a substance of low adhesion, for example,
fluorine resin, prior to onset of the curing reaction of epoxy
resin and then the said curing reaction of epoxy resin is completed
under specific conditions, thus completing preparation of the
photoconductive layer. By this method, the unevenness of the
surface can be kept below 10 .mu. and a photoconductive layer with
a flat and firm surface can thus be produced, and consequently the
following process step of forming the insulating layer can be
carried out more advantageously.
Next, as to forming the insulating layer, in general this step
involves coating and drying a lacquer, but an inevitable obstacle
is presented where this method is employed. That is, in the case of
producing a photoconductive layer by the method described above or
by another coating method, there are formed numerous fine pinholes
or uneven parts on the photoconductive layer, and after coating the
lacquer thereon, foams may appear in the coated layer and the
insulating layer may become uneven in its thickness. Accordingly
after completion of such foaming, there may be parts where no
insulating layer is present.
In order to remove this disadvantage to some extent, the lacquer is
diluted enough for its application in liquid form, thus allowing it
to flow more readily into the pinholes or uneven parts and at the
same time accelerating the completion of foaming, such that after
the completion of foaming, the lacquer around such parts is still
able to flow easily and form a flat and even coated layer. When a
single coating does not attain thickness after drying, this process
step may be repeated as necessary. In this way, however, there may
still result disadvantages such as the need for more working, and
an increase in dirt adhering to the coated layer between coating
and drying.
The present invention aims at excellent methods for the solution of
these disadvantageous problems. That is, in the process step of
producing the insulating layer, a so-called thermo-shrinkable tube,
which is composed of thermoplastic resin of high insulating
property (thermoplastic resin in chargeable insulating film form),
is loosely encircled over the drum on which the photoconductive
layer has been formed, instead of applying a lacquer coat thereto,
and by utilization of its thermo-shrinkable property, the surface
of the photoconductive layer is covered, so as to build an
insulating layer. The thermoshrinkable tube is composed of film of
thermoplastic resin and is in form pre-extended circumferentially.
When heated and softened, it shrinks to assume its original shape
by reducing its diameter. It is possible to make it shrink very
easily if it is heated by subjecting it to hot air for a short time
or by pouring hot water over it.
When the insulating layer is produced in this way, the surface of
the thermo-shrinkable tube pre-formed in flat shape can be made use
of as it is, and it is thus possible to manufacture an
electrophotosensitive drum which has a level surface superior to
the insulating layer produced by the lacquer coating method.
As a result of research conducted to provide apparatus to produce a
good insulating layer by practice of this method, it has become
evident that apparatus as shown in, for instance, FIG. 2 is useful,
and that the method may be practiced generally in the following
manner. That is, over the photoconductive layer 2 formed on the
surface of the drum 1, the thermo-shrinkable tube 3 is laid, and
the whole assembly is moved axially of the drum along the guide
prop 15 by making use of wind-up mechanism 14. At the same time,
hot air prepared by heating the air from the fan 16 by electric
heater 17 is blown onto the surface of the thermo-shrinkable tube,
over the whole part thereof within a plane which is perpendicular
to the drum axis. Thus, the thermo-shrinkable tube is made to
shrink gradually, beginning from its top part, and there is formed
by a single operation an insulating layer which completely covers
the photoconductive layer. In this case, the mechanism for hot air
blowing may alternatively be arranged for movement.
The points that require special care in the practice of this method
are two, one being that the thermoshrinkable tube is made to shrink
evenly all over and to adhere perfectly onto the photoconductive
layer in uniform thickness, and the other being that no foaming is
allowed to be involved therein. To completely satisfy these
conditions, it is necessary that the hot air be blown evenly all
over and that shrinking is made to proceed successively from an end
part.
As for the thermo-shrinkable tube to form the insulating layer, it
is necessary, in view of the special character of the
photosensitive drum, to use a tube which is composed of the
thinnest possible film, and in order to make it perform thermal
shrinkage evenly circumferentially, it is advisable not to use a
thermo-shrinkable tube which is thicker than necessary.
Accordingly, it is necessary that air be blown in between the
photoconductive layer and the thermo-shrinkable tube, so that the
thermo-shrinkable tube is swollen and the distance between the
layer and tube is kept equal all over the circumference.
As a result of research conducted to provide the simplest and
surest method to obtain uniform heat shrinkage, it has become clear
that the simplest and most certain method is to lay the
thermo-shrinkable tube, with its one end 18 sealed, over the
surface of the photosensitive layer 2 formed on the drum 1 and to
dip the whole assembly into hot water 19 gradually, beginning from
the end part of the sealed end side, along the guide prop 15, as
shown in FIG. 3. In this method, there is merit in that the desired
object can be accomplished simply by mechanism to dip the drum and
the thermo-shrinkable tube gradually into hot water beginning from
the end part.
In order to prevent foaming completely in the shrinkage, heating is
by means of an infrared lamp or electric heater instead of heating
by blowing hot air and the whole body is placed in a vacuum to
perform heat shrinkage. With a vacuum degree higher than about 300
mmHg by mercury column, it is possible to form a light-permeable
insulating layer which is entirely free from foams. It is not
particularly necessary in this case to heat the thermo-shrinkable
tube successively from an end part.
Next, as another different method, we will present a method for
coating the photoconductive material beforehand on the insulating
film and then providing it on the drum.
The conventional photoconductive materials are all in the form of
crystals of large particle size and thus render very difficult
making the surface flat and smooth and thus the image produced
thereby is not good in quality. The present invention provides
improvement in this respect.
In providing a photoconductive layer, the photoconductive substance
is dispersed in a binder resin and cured, and the binder resin to
be used in this case may be either thermoplastic resin or
thermo-setting resin.
First, we will explain about a manufacturing method in which a
thermosetting resin is used. A photoconductive material is kneaded
well in 5 - 20 percent by weight of the binder resin, and then this
photoconductive substance in paste form is coated evenly to a
thickness of 50 - 200 .mu. inside the thermo-shrinkable tube
film.
An example of this method of coating is shown in FIG. 4. Inside the
thermo-shrinkable tube-form film 3 which is held by the roller 21,
the spacer 22 is placed facing the film 3, and then cadmium
sulphide well mixed and kneaded with the resin 2 is applied to the
inside of the tube-form film 3 and the film or metal foil 23 is
laid over its surface, and then the coating is made in uniform
thickness by rubbing the film 23 with the blade 24. Then, the film
23 is removed. In the case where metal foil is used, it is left in
place.
Next, into the tube-form film 3 inside which the photoconductive
layer 2 has been formed, the cylinder 25 is inserted as shown in
FIG. 5. Then, the thermo-shrinkable tube film is shrunk by heating
and the photoconductive layer is adhered compactly to the cylinder
25. After levelling the unevenness that occurred in the
photoconductive layer upon the shrinkage of the film 3, it is
heated further to cure the binder resin, and thus three different
layers, i.e., the highly insulating layer 3, the photoconductive
layer 2 and the cylindrical central substrate 25, are combined in a
single body. Thus, an electrophotographic photosensitive body in
cylindrical form is manufactured. In this case, it is also possible
to make it into other optional shapes, for instance, belt form, by
removing the central member.
When using thermoplastic resin, 5 - 20 percent by weight of a
binder resin is dissolved in a solvent, in which the
photoconductive material is dispersed thoroughly, and this is then
applied evenly to the inside of the thermo-shrinkable tube film to
a thickness of 50 - 200 .mu. by the method shown in FIG. 4. After
complete evaporation of the solvent and drying, it is laid over the
outside of the cylindrical central member, and then the
photoconductive layer is softened by heating and at the same time
the thermoshrinkable tube film is made to shrink. Unevenness of the
photoconductive layer occurring on this occasion is eliminated in
the course of softening of the binder resin and then the resin is
hardened by cooling at room temperature. Thus, there is produced an
electrophotographic photosensitive body of cylindrical shape
comprising three layers, i.e., a highly insulating lyaer, a
photoconductive layer and a cylindrical central substrate.
On the other hand, where the photoconductive layer is a coated
layer comprising a mixture of dispersed photoconductive material
and resin, the layer becomes porous since foams are involved in the
mixture, and its surface is uneven and cannot be flat and smooth.
Therefore, when lacquer is applied to such surface, the thickness
of the insulating layer 3 becomes uneven and also foams float up
from the cavities of the photoconductive layer 2, thus causing the
formation of cavities in the surface of the insulating layer or
pinholes in the insulating layer. It is thus hard to form an
insulating layer of uniform thickness and homogeneous quality.
Furthermore, in order to provide print contrast and clearness in
use of the photosensitive body on which the surface insulating
layer 3 has been formed, it is desirous that the surface insulating
layer is made as thin as possible. However, the thinner it becomes,
the more conspicuous are the above problems. In addition, it is
difficult to render the surface of the insulating layer 3 formed by
such lacquer coating method flat and smooth, since it has uneven
parts, and the cleaning of remnant toner cannot be readily
accomplished. The faults described above are unavoidable in the
case of formation of the surface insulating layer by the lacquer
coating method. The present invention, therefore, also provides
another way to form the surface insulating layer 3, characterized
in that the surface insulating layer is produced by covering the
photoconductive layer 2 with a tube which is composed of insulating
material formed in specific thickness beforehand with an inside
diameter large enough for compactly covering the photoconductive
layer 2.
As for the tube of insulating material mentioned above, there can
be used tubes of various thermoplastic resins which are
manufactured by, for instance, the inflation method. By the use of
a tube stable in quality, it can be in fixed thickness and also can
be uniform in quality and satisfactory in surface flatness and
smoothness.
It is a matter of course that the inside diameter of the tube 3 as
described above is selected to cover the photoconductive layer 2
compactly, and in the case when its inside diameter is somewhat
smaller, this diameter of the tube is made larger by passing
through it a mould in conical shape which has its maximum outside
diameter larger than th inside diameter of the tube, and then this
tube is laid over the photoconductive layer.
In the cylindrical, electrophotographic photosensitive body of the
present invention, the surface insulating layer is formed by a
separate tube as described above, and hence all of the faults which
are found in the above-mentioned method of formation by coating can
be eliminated. In addition, it has merit in that when the
insulating layer has been harmed or damaged in long use, it can be
replaced easily by a new tube.
The present invention further provides other different methods of
obtaining a seamless photosensitive body in cylindrical shape. As
shown in FIG. 6, the insulating layer 32 is formed by coating,
according to necessity, electric insulating lacquer, etc. on the
outer surface of the cylindrical body 31 which is made in perfect
circular shape by shaving.
A mixture in paste or paint form is prepared by dispersing fine
photoconductive powder in a solution of a synthetic resin monomer
or a synthetic resin of low polymerization degree and a
polymerization accelerator.
Then, this photoconductive material is applied by knife coating or
roller coating on the above-mentioned cylindrical body 31 while it
is maintained horizontal and rotating. In this case, the coating is
made in even thickness all over the circumference by removing
surplus portions of the photoconductive body by setting a knife at
a proper angle. The photoconductive layer 2 in this case remains in
an uncured condition.
Next, it is encircled with a previously produced tube of synthetic
resin which is high in electric insulating property and is also of
thermosetting nature, and then this is made to shrink with heat and
to cover compactly the photoconductive layer 2, thus forming the
insulating layer 3.
After the heat shrinkage and covering as described above, the whole
cylindrical body is maintained at a specific temperature and the
polymerization reaction of the monomer of synthetic resin or the
synthetic resin of low polymerization degree in the photoconductive
layer 2 is completed.
By the method described above, the photoconductive layer 2 is
combined compactly with the electric insulating layer 3, and there
is formed a seamless electric insulating layer 3 which is uniform
in thickness and has a smooth and flat surface, thus yielding the
desired product. This flat and smooth surface is dependent on the
flat and smooth surface of the photoconductive layer 2, and
therefore, the coating finishing of the photoconductive layer 2 is
an important process step. However, since the photoconductive layer
2 immediately after coating is still in uncured and viscous
condition as described above, levelling of its surface is quite
difficult.
The present inventors made studies and consequently succeeded in
levelling the surface by a step of rubbing the surface with a
material having low adhesion to the viscous photoconductive layer
2, i.e., by a levelling spatula or roller 34 on the surface of
which is provided a substance such as fluorine resin film 33. By
this process step, the border between members 2 and 3 is flattened
and levelled, so that the surface of the electric insulating layer
3 can be formed fully flat and also in uniform thickness all
over.
By having this tube circumferentially extended beforehand (and also
somewhat axially) and by utilizing its characteristic of reducing
its diameter (and its length also) by assuming its original form
upon softening under heating, the photoconductive layer 2 is
compactly adhered to the center member. As the means of heating
either hot air or hot water is employed. In this thermo-shrinking
and covering process, attention should be paid to the following
matters:
1. to accomplish shrinkage evenly and in uniform thickness;
2. to take caution to prevent foams from occurring in and between
layers 2 and 3; and
3. to prevent scratching of the uncured photoconductive layer
2.
As the means for attending to these matters, effective examples are
shown in FIGS. 8 and 9. Therein the shaft 35 is fitted to the
cylinder on whose surface the photoconductive layer 2 has been
coated, then the shaft 35 is placed in springs 36.sub.1 and
36.sub.2 at both sides of the cylinder 31, and circular plates
37.sub.1 and 37.sub.2 are fixed loosely about the shaft 35. The
thermo-shrinkable tube 3.sub.1 is laid over and fixed onto the
circular plates 37.sub.1 and 37.sub.2 with the rings 38.sub.1 and
38.sub.2.
The space between members 3.sub.1 and 37.sub.1 and between members
3.sub.1 and 37.sub.2 is rendered air-tight by grease coating,
etc.
With the cock 40 open and the ventilation pipe 39 fixed onto the
circular plate 37.sub.1, the assembly is placed in a vacuum tank,
and when the vacuum tank is evacuated, the space intervening the
thermo-shrinkable tube 3.sub.1 and layer 2 is evacuated. As the
cock 40 is closed at a certain specific degree of reduced pressure
(if located inside the vacuum tank, the cock is closed by remote
operation) and the thermo-shrinkable tube 3.sub.1 shrinks under
heating by an electric heater placed in the vacuum tank, the tube
3.sub.1 adheres compactly to the photoconductive layer 2 as seen in
FIG. 9, and thus the insulating layer 3 is formed.
Upon this thermal shrinkage, axial shrinkage is absorbed by the
compression of the springs 36.sub.1 and 36.sub.2. In order to
prevent the photoconductive layer 2 from being scratched by the
thermo-shrinkable tube 3.sub.1 in its axial shrinkage, it is ideal
that the shrinkage occur gradually from the central part of the
tube 3.sub.1 to its outer side and also gradually from one end
towards the other side. For this purpose, a narrow width electric
heater capable of local heating, which can be freely moved by
remote control, is located inside the vacuum tank. This is
necessary particularly when the photosensitive cylindrical body is
very long.
After shrinkage performed as above, air is admitted into the vacuum
tank, and then the whole body is taken from the vacuum tank and
placed in ambient air. Since the tube 3.sub.1 is further strongly
pressed by the atmospheric pressure since its interior is still
subjected to vacuum, both the surface insulating layer 3.sub.1 and
the photoconductive layer 2 are adhered compactly enough.
There is thus insured ideally compact adhesion and a flat and
smooth border. The insulating layer 3 is in uniform thickness all
over. It is possible to further improve such compact adhesion by
rotating a pressure roller on the surface of the insulating layer
3.
The heat shrinkage in the vacuum described above is performed
mainly by the radiant heat. The thermoshrinkable tube 3.sub.1
permits heat to pass through it easily and is thus heated slowly,
while the photoconductive cylinder 31 is heated more quickly.
Consequently, the photoconductive layer 2 is heated, rapidly
advancing the binder resin to its curing reaction, and the
photoconductive layer 2 itself gels. Its adhesion to the surface
insulating layer 3 is, therefore, reduced, and border flatness may
not possibly be maintained. Therefore, a paint containing black
inorganic pigment which easily absorbs the heat rays, such as, for
example, carbon black, tri-iron tetroxide, and the like is applied
previously to the surface of the thermo-shrinkable tube 3.sub.1,
and it is removed with a solvent after completion of final
product.
Excessive parts of the layer 3.sub.1 are cut off and finally it is
put into a bath at constant temperature, so as to complete the
polymerization reaction of the binder resin and to thus obtain a
final finished product.
For the adhesion of different layers as described above, it is also
possible to adhere the photoconductive layer and the insulating
film by laying between them an intervening cementing layer.
However, the adhesive generally used in one which is cohesive at
room temperature, and hence it is very difficult to affix a thin
insulating film onto the surface of photoconductive layer in such a
way as to prevent formation of wrinkles and foams. Particularly, in
the case when an insulating film in tube form is made to shrink by
heat and laminated on drum photoconductive layer by a cohesive
bonding agent, thermal shrinkage of the insulating film is always
accompanied by local unevenness, and consequently this cohesive
bonding agent can act to fix the wrinkles and foams that they
formed. A drum in which the wrinkles and foams have formed once, is
not good for practical use because elimination of such faults is
difficult.
In order to eliminate the aforesaid defects and to manufacture
wrinkleless and foamless photosensitive bodies at a high
efficiency, so-called hot melting type resin, which is a resin of
low softening point may be used.
The resins of hot melting type are resins which are transparent and
high in insulating property, having a softening point of
approximately 70.degree. - 150.degree.C, such as polyvinyl butyral,
polyvinyl acetate, copolymer of vinyl chloride and vinyl acetate,
copolymer of vinyl acetate and polyethylene, acrylic resin, rosin,
phenol resin, modified phenol resin, maleic resin, modified fumaric
resin, dammar gum, and the like. These low softening resins are not
cohesive at the room temperature, but when heated up to the
above-mentioned temperature by infrared rays, etc., they melt and
exhibit their bonding agent characteristics.
In the present invention, the aforesaid resins of low softening
point are dissolved in an adequate solvent, and the solution is
either applied or sprayed onto the surface of photoconductive layer
or the surface of insulating film, followed by drying the
evaporation of the solvent. An adhesive layer is thus produced,
which does not have the cohesive property of low softening point
resins.
Next, with this adhesive layer in between, both the photoconductive
layer and the insulating film are laid one above the other, then
the adhesive layer is melted by heating and is made to act as a
bonding agent, and finally the photoconductive layer and the
insulating film are adequately pressed to accomplish their adhesion
and lamination.
In other conventional methods, insulating film is adhered directly
on the photoconductive layer by using a bonding agent which is
cohesive at room temperature. When an insulating film, which is so
thin as 20 .mu. or so, is spread over a photoconductive layer, the
formation of wrinkles and foams is inevitable. On the contrary, the
present invention as explained above, involves laying a
photoconductive layer and an insulating layer one above the other
with an intervening adhesive layer non-cohesive at room
temperature, and to render the adhesive layer cohesive and
effective as a bonding agent by heating. It is thus possible to
spread a thin insulating film over a photoconductive layer in such
a way as to cause neither wrinkles nor foams, and then the agent
provides its bond. In addition, this method has merit in that the
bonding process can be carried out easily.
This is particularly advantageous for a photosensitive body in a
drum form. In this case, a tube form insulating film is bonded on
the drum form photoconductive layer by thermal shrinkage, and if a
conventional bonding agent which is cohesive at the room
temperature is used, local uneven shrinkage, which is unavoidable
because of physical phenomena of tube form film, is fixed as it is
by the bonding agent, and the formation of correct cylindrical form
is difficult. With the above-mentioned other bonding agent used in
this case, such local uneven shrinkage described above is still not
fixed, since the bonding agent is non-adhesive at the time of
thermal shrinkage of the tube form film. As the bonding agent is
next melted by heating to exhibit its cohesive properties for
bonding, the aforesaid uneven shrinkage is reformed naturally by
its internal stress at the time of bonding and thus becomes flat
and smooth, eliminating all wrinkles and foams.
As to photoconductive materials to be used for the cylindrical
photosensitive bodies manufactured by the different methods
mentioned above, it is possible to employ various photoconductive
substances which are in general use. As inorganic photoconductive
substances, such as, for instance, CdS, CdSe, Se SeTe, ZnO, etc.
can be used, and as organic photoconductive substances, such as,
for example, those having a heterocyclic ring, those having
condensation cycles, those having double bond, those having amino,
or nitrole, condensation products, polyvinyl carbazole, vinyl
polymer, condensation polymer, etc. can be used. Besides these,
other substances which are rendered conductive with light can also
be used without limit.
These photoconductive substances can be individually formed into
tube or insulating layer directly, for instance, by spattering,
etc., or used in form dispersed in binder resin.
As for the binder resins, there may be mentioned, for example,
thermoplastic copolymer of vinyl chloride and vinyl acetate,
polyvinyl chloride, polyvinyl acetate, cellulose acetate,
nitrocellulose, methacryl resin, phenol resin, P.V.A., polyvinyl
butyral and the like and thermosetting resins such as epoxy resin,
unsaturated polyester resin, and the like.
As to the drums, those in hollow form or hermetically sealed ones
can be used. In case of hollow drums, those in endless belt form or
in tube form, etc. can also be used. It is also possible to employ
drums in polygonal form, etc. in addition to those in cylindrical
or tube form.
Further, as to structural materials, metals, nonmetals, alloys
thereof, etc. can be used as electroconductive materials, and, for
example, wood, paper, resin, cloth, etc. can be used as insulating
materials.
These drums or tubes are effective, for example, where insulating
material is set on an electroconductive substrate, where an
electroconductive substrate is used alone or where an
electroconductive material is provided on an insulating base. With
respect to insulating materials, inorganic insulating material such
as Al.sub.2 0.sub.3, SiO.sub.2, silica glass, TiO.sub.2, BN and the
like, as well as organic insulating materials mentioned previously,
may be employed. The thermo-shrinkable tube film must be a material
which can retain electrostatic charge and is highly insulating, for
example, polyester, polyvinyl chloride, polyvinylidene chloride,
Teflon, polyethylene, bridged polyethylene, polypropylene, fluorine
resin, etc. In this case, light permeability, electric charge
retention and other factors are decided relative to another
insulating layer which, if desired, is placed between the
cylindrical substrate and the photoconductive layer. In such case,
at least the tube film or the substrate and the other insulating
layer should be light permeable.
Light permeability as mentioned here means such permeability as to
permit radiation to permeate to the photoconductive body. That is,
if either insulating layer is light permeable, the original image
light is projected through its surface, and it is not always
necessary that both insulative layers be light permeable.
Examples for practicing the present invention follow.
Example 1
By fully mixing and kneading 40 g. of cadmium sulphide activated by
copper, 5 g. of Epikote 815 (product of Shell Petroleum Co.) which
is an epoxy resin and 0.6 g. of epoxy resin hardener K 61B (product
of Anchor Chemical Co.), a mixture in paste form was obtained. This
paste was then applied by a doctor blade to a drum made of
aluminum, 15 cm. in diameter and 22 cm. in length, while rotating
the drum, to form a coating of 100 .mu. thickness and a
photoconductive coating was thus formed. Then, immediately, a film
of ethylene tetrafluoride resin was applied to the surface of the
photoconductive layer by pressure while rotating the drum and its
surface was flattened by rubbing. Then, the whole of this drum was
placed in ambient atmosphere at 70.degree.C for 4 hrs. and the
epoxy resin was thus hardened. A photoconductive layer was formed
thereby.
Next, a thermo-shrinkable tube having an inner diameter of about
15.5 cm. and composed of polyvinyl chloride film of approximately
20 .mu. thickness was laid over the drum, and while applying hot
air at about 80.degree.C thereto by the apparatus shown in FIG. 2,
the assembly was moved upwardly at a speed of 5 mm. per second and
thermal shrinkage was effected. As a result, a polyvinyl chloride
film covered the whole surface of the photoconductive layer in
uniform thickness of about 25 .mu., thus forming a good light
permeable insulating layer, and an electrophotographic
photosensitive drum was obtained.
This photosensitive drum was used in, for example, the rotary
copier practicing the electrophotographic method disclosed in
Japanese Patent Publication No. 23910/1967, and thereby a good copy
print was obtained. The sensitivity of the photosensitive drum was
as high as 2 - 3 Lux.sec., and the light permeable insulating layer
of polyvinyl chloride resin proved durable and adapted for repeated
use, and its surface was very flat and smooth.
EXAMPLE 2
Over a photoconductive layer produced on the surface of an
electroconductive drum by the same method as in Example 1 above,
was laid a thermo-shrinkable tube composed of polyvinyl chloride
film, and the assembly was placed in the vacuum of about 50 mm Hg.
Next, by an electric heater, this tube was heated over its whole
circumference, and the thermo-shrinkable tube shrunk so as to form
a light permeable insulating layer. It was thus possible to produce
a good light permeable insulating layer which contained enitrely no
air foams. In reproduction using this sensitive drum, good images
were obtained.
EXAMPLE 3
To provide thermal shrinkage in Example 1 above, the method shown
in FIG. 3 was practiced by covering a conductive drum having a
photoconductive layer with a thermo-shrinkable tube composed of
polyvinyl chloride film, then sealing an end of the tube, and
dipping the whole body gradually into hot water at 80.degree.C,
beginning from the sealed end of the tube. As a result, there was
obtained good even thermal shrinkage, containing no foams. This
photosensitive drum also gave very satisfactory reproduction
images.
EXAMPLE 4
By mixing and kneading thoroughly 40 g. of cadmium sulphide
activated by copper, 5 g. of Acmex R-11 (product of Nihon Gosei
Kako Co.) which is an epoxy resin and 1 g. of H-92 (product of
Nihon Gosei Kako Co.) which is a hardener for the above epoxy
resin, a mixture in homogeneous paste form was prepared. By a
doctor blade, this mixture was applied to the surface of aluminum
drum, 15 cm. in diameter and 22 cm. length, to a thickness of
80.mu., with the drum rotating. Then, the drum was allowed to stand
for 24 hours at room temperature, was then heated for 2 hours in an
air drier at 50.degree.C and was finally cooled to form a
photoconductive layer.
Next, polyester tube (HS Diafoil manufactured by Mitsubishi Resin
Co.), having a folded diameter of 25 cm. (about 16 cm. in diameter)
and a thickness of 0.03 mm., was laid over this drum, and an end of
the tube was sealed. The assembly was then soaked in hot water at
90.degree.-95.degree.C at a speed of 1 mm. per second, beginning
from the sealed end. Thereby, the polyester tube was adhered to the
photoconductive layer without introducing any foams inside the
tube. After cutting off the excessive portions of the polyester
tube at both ends of the drum, the product was used for
reproduction in the same way as in Example 1 above, and good
reproduction prints were obtained. The sensitivity of the
photoconductive drum in this Example was 2 - 3 Lux. sec. and the
film formed by the polyester tube was good in light permeability,
very tough and strong, and also good in electrical property, thus
being adapted for repeated use.
EXAMPLE 5
To epoxy resin (Epikote 815) as binder was added 12 percent by
weight of hardener K 61B and the mixture was stirred thoroughly.
The resulting mixture was then mixed in and kneaded well with 40 g.
of cadmium sulphide. This photoconductive substance (containing 13
percent by weight of CdS) in paste form was next applied evenly, to
a thickness of about 100.mu., to the inner side of a
thermo-shrinkable tube film (HHS Diafoil, a polyester 15.mu. in
thickness), and this was then laid over a cylinder made of
aluminum. After shrinkage by heating, the uneven surface of the
photoconductive layer was levelled and then the binder was cured.
Thus, there was produced a cylindrical electrophotographic
photosensitive body comprising three layers. In reproduction using
this photosensitive body, it was possible to obtain very
satisfactory images.
EXAMPLE 6
Cadmium sulphide was dispersed in a copolymer of vinyl chloride and
vinyl acetate as binder, diluted adequately with a thinner such
that the copolymer could be 10 percent by weight ratio. This
dispersion was then applied, by a sprayer, to the inner side of
thermo-shrinkable tube film (HHS Diafoil 15.mu.), to form a film of
100.mu. thickness and, after drying, an aluminum cylinder was
inserted in the tube. Since the resin was thermo-plastic, the
photoconductive layer was next shrunk by heating. Thereby, the
dried photoconductive layer was softened and followed the shrinkage
of the film. The surface of the photoconductive layer, which
thereby became uneven, was levelled while the resin was in a
softened condition. It was then cooled for curing, and there was
produced a cylindrical electrophotographic photosensitive body
comprising three layers. Very good images were obtained when
reproduction was carried out with this photosensitive body.
EXAMPLE 7
Cadmium sulphide (40 g.) was mixed with 5.2 g. of epoxy resin
(Epikote 815 plus hardener K 61B), kneaded well and dispersed
homogeneously. This dispersion was then applied evenly to a
thickness of 80.mu. to the inner side of a polyester film tube, 15
cm. in diameter, by the method shown in FIG. 4, and after curing of
the resin, an aluminum cylinder having a cut made thereon was
inserted in the tube to form a cylindrical photosensitive body
comprising three layers. In testing reproduction by using this
sensitive body, it was possible to get good reproduction
images.
EXAMPLE 8
By mixing and kneading well 40 g. of CdS with average diameter of
2.mu., which was activated by copper, 20 g. of clear lacquer
containing 20 percent solid of copolymer of vinyl chloride and
vinyl acetate and 10 cc. of a thinner for the above-mentioned
lacquer composed mainly of ketone, a yellow mixture in paint form
was prepared. This was then applied to an aluminum cylinder, 20 cm.
in diameter and 22 cm. in length, by a knife coating method such
that the thickness after drying was 60 - 80.mu., and upon drying, a
photoconductive layer was produced. By covering this assembly with
polyvinyl chloride resin film, 20.mu. in thickness and about 20 cm.
in inner diameter and produced by an inflation method, there was
obtained a cylindrical electrophotographic photosensitive body.
This photosensitive body was utilized in an electrophotographic
copier disclosed in Japanese Patent Publication No. 23910/1967 and
good images were obtained. Furthermore, the surface of the
insualting layer withstood repeated use for several thousand times
and remnant toner was easily removed therefrom.
EXAMPLE 9
By fully mixing 40 g. of zinc oxide, 20 g. of copolymer styrene and
butadiene and 40 cc. of xylol by a ball mill and then adding
thereto 2 cc. of 1.0 percent ethanol solution of Rose Bengal, a
light pink mixture in paint form was prepared. Next, to an aluminum
cylinder of the same size as in Example 1 above, epoxy resin
lacquer was applied such that after drying, it was in a thickness
of about 50.mu.. Upon drying, an insulating layer was produced. The
above-mentioned mixture in paint form was applied to this
insulating layer such that its thickness after drying was about
60.mu. and upon drying, a photoconductive layer was provided. By
then employing a tube made of polyester resin of about 25.mu.
thickness and about 20 cm. inner diameter, there was obtained a
cylindrical electrophotographic photosensitive body.
In the use of this sensitive body in the same copier as in Example
1 above, it was possible also to obtain good and clear images. The
surface insulating layer was durable exhibiting no insulation
breakdown, and could be used repetitively.
When the above-mentioned tube of light permeable insulating
substance in the present invention was formed by using a
thermo-shrinkable tube comprising thermo-plastic resin and this was
laid over the photoconductive layer and shrunk by heating, it was
possible to make the adhesion still better.
EXAMPLE 10
In place of the polyvinyl resin tube or polyester resin tube
referred to in Example 8 above, a slightly larger thermo-shrinkable
tube composed of such resins was used for covering, and it was
shrunk by pouring thereover hot water at 90.degree.-95.degree. C.
By this procedure, the photoconductive layer was covered compactly
and a cylindrical electrophotographic sensitive body could be
produced. The thickness of the insulating layer formed by shrinkage
was approximately 25.mu..
This member also gave good images as in Examples 8 and 9 above.
EXAMPLE 11
A mixture in paste form was prepared by fully mixing 40 g. of
cadmium sulphide activated by copper, 5.0 g. of epoxy resin monomer
Epikote 815 (product of Shell Petroleum Co.) and 0.6 g. hardener K
61B (product of Anchor Chemical Co.) for said resin.
This was coated on the surface of an aluminum cylinder, 16 cm. in
diameter and 22 cm. in length, to a thickness of about 80.mu. by a
knife coating method using two knives, and a photoconductive layer
was formed.
Next, by means of the apparatus shown in FIG. 8, a
thermo-shrinkable tube made of polyester film, about 20.mu. in
thickness and 27 cm. in folded diameter (54 cm. circumference and
about 17 cm. diameter), was laid over the above-mentioned cylinder
and was also fixed to a flange of about 17 cm. diameter. Within
about a 10 cm. distance between the cylinder and the flange, a coil
spring having a strength of 2 kg/cm was inserted. Next, the
assembly was placed in a vacuum tank, the pressure was reduced to
about 100mmHg. by a rotary pump, and the cock of an exhaust pipe
was closed by means of a rotary solenoid. Upon heating for about 4
minutes in the vacuum tank by a nichrome wire heater of 1 KW.
arranged at 1 cm. distance from the thermo-shrinkable tube, the
tube shrunk. After the shrinking, the flange compressed the springs
and the springs consequently moved about 2 cm. toward the cylinder,
respectively.
Then, the cylinder covered with the thermo-shrinkable tube was
taken out of the vacuum tank and this cylinder was placed for 3
hours in a constant temperature bath at about 70.degree.C to
complete the curing of the epoxy resin. Finally, excessive portions
of the thermo-shrinkable tube at both ends of the cylinder were cut
off and a cylindrical electrophotographic photosensitive body was
obtained. The surface insulating layer formed by the shrinkage of
the thermo-shrinkable tube was approximately 25.mu. in
thickness.
To this photosensitive body, a corona discharge of (+) 6KV was
applied by the same electrophotographic copier as in Example 1
above, and then the image was irradiated thereon while a corona
discharge of AC 6KV was simultaneously applied followed by light
irradiation all over the surface. Developing was then made with a
toner of negative charge. It was possible in this way to obtain
images of excellent quality.
In this case, nearly the same good result was obtained by using a
direct current corona discharge of (-) 6KV instead of the
above-mentioned alternating current corona discharge.
EXAMPLE 12
After the photoconductive layer was formed as in Example 11 above,
this cylinder was rotated 120 times per minute (about 100 cm. per
second in circumferential speed), and to the surface of the
photoconductive layer a Teflon FEP film of 25.mu. thickness (Trade
name of a fluorine resin manufactured by Du Pont Co.) was pressed,
with its flat and smooth face in contact with the layer surface at
slight pressure. The photoconductive layer, still in uncured
condition, was thus flattened and smoothened by the rubbing action
of the film. This levelled surface was very flat and smooth and
also exhibited strong adhesion.
Then, in the same way as in Example 11 above, the shrinkable tube
was shrunk to form an insulating layer. As a result, it exhibited
very good adhesion, with no foams present between the
photoconductive layer and the insulating layer, and there was
obtained an excellent cylindrical electrophotographic
photosensitive body which provided very good images.
EXAMPLE 13
By mixing thoroughly 40 g. of cadmium sulphide activated by copper,
55 g. of styrene monomer solution of polyester resin, named Ester
G-10 (product of Tokyo Koatsu Co., Ltd.), 0.04 g. of methyl ethyl
ketone peroxide and 0.03 g. of cobalt naphthenate, a mixture in
paste form was prepared.
Subsequently, following the method of Example 11 above, a
cylindrical photosensitive body was manufactured. The curing
reaction was completed in 2 - 3 hours at room temperature. The
photosensitive body thus produced also gave images of good
quality.
EXAMPLE 14
Over the surface of the thermo-shrinkable tube referred to in
Example 11 above, a paint of good heat absorbing property, which
was composed mainly of natural rubber and chlorinated rubber and
which also contained 20 - 30 percent of carbon black and tri-iron
tetroxide, respectively, was coated. It was possible in this way to
get complete shrinkage in about 3 minutes. This black film was
later removed with ketone.
EXAMPLE 15
A photoconductive layer, in which CdS was dispersed in epoxy resin,
was coated with a 10 percent ethanol solution of polyvinyl butyral
(for example, Esleck BM-2 of Sekisui Co.) and dried to form a
hot-melt bond layer. By laying it over a polyester film of 25.mu.
in thickness, followed by heating and pressing, an
electrophotographic photosensitive body in the form of a flat plate
was obtained.
Reproducing was carried out by using this electrophotographic
photosensitive body in flat plate form in the copier for
electrophotography described in Example 1 above, and very good
reproduction images were obtained.
EXAMPLE 16
A photoconductive layer was obtained by coating a conductive
cylinder with a photoconductive material obtained by dispersing ZnO
in silicon resin.
A solution of natural resin modified fumaric resin (for example,
10% MIBK butanol solution of Beccasite 1127 manufactured by
Dainippon Ink) was applied to the inside of a thermo-shrinkable
tube of polyester, and after drying, it was laid over the
cylindrical photoconductive layer. Tying both tube ends, hot water
(below 100.degree.C) was poured on it and it shrunk until it
adhered compactly onto the cylindrical photoconductive layer.
In this case Beccasite 1127 does not soften with hot water.
After this shrinkage, the insulating layer was adhered jointly by
an infrared heater and a pressure roller.
On the surface of this cylindrical electrophotographic
photosensitive body, corona discharge of + 6KV was applied and then
the image was irradiated while corona discharge of alternating
current of 6KV was simultaneously carried out, followed by light
irradiation all over the surface. There was obtained a sharp image
of high contrast by developing with negative toner according to a
known method.
As explained above, the present invention provides excellent
manufacturing methods, as well as apparatus for providing a
seamless electrophotographic photosensitive drum which has a
photoconductive layer incorporating photoconductive material in a
resin dispersion on a conductive layer and also has thereon a light
permeable insulating layer. This invention therefore can contribute
very much to the development of electrophotographic copiers.
Further, according to the methods of the present invention, since
no solvent whatever is used in the process step of forming the
light permeable insulating layer, there can be no degradation of
the photoconductive layer even where solvent-soluble resin is used
as a binder resin in the photoconductive layer. Thus
advantageously, binder resins can be selected from wide ranges. The
present invention has further merits in that a light permeable
insulating layer, damaged as a result of repeated uses of the
sensitive drum, can be replaced easily by other new ones according
to the method of the present invention.
* * * * *