Electrophotographic photoconductor and electrophotographic copying process and apparatus using the photoconductor

An electrophotographic photoconductor comprises (a) an electroconductive support, (b) a photoconductive layer formed thereon comprising a selenium alloy, and (c) a protective layer which is formed on the photoconductive layer, contains a binder resin component and an anti-oxidizing agent. In an electrophotographic copying process and an electrophographic copying apparatus using this photoconductor, the protective layer is abraded at a predetermined rate during the copying process in such a fashion that the anti-oxidizing agent contained in the protective layer is always present at the surface of the protective layer, thereby protecting the photoconductor from ozone and ions which are generated during corona charging of the photoconductor.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrophotographic photoconductor 
comprising a photoconductive layer of a selenium alloy and a protective 
layer formed thereon containing an anti-oxidizing agent, and an 
electrophotographic copying process and an apparatus using the particular 
electrophographic photoconductor. 
2. Discussion of Background 
Conventionally, a variety of electrophotographic photoconductors are known. 
For instance, there are known an electrophotographic photoconductor in 
which a photoconductive layer consisting essentially of selenium or a 
selenium alloy is formed on an electroconductive support; an 
electrophotographic photoconductor prepared by dispersing an inorganic 
photoconductive material, such as zinc oxide or cadmium sulfide, in a 
binder agent and coating the dispersion on an electroconductive support; 
and an electrophotographic photoconductor comprising a photoconductive 
layer which contains an organic photoconductive material such as a mixture 
of poly-N-vinylcarbazole and trinitrofluorenone, an azo pigment or 
amorphous silicon. 
Recently a demand for an electrophotographic photoconductor having high 
reliability, capable of producing high quality images for a long period of 
time is increasing. In the case of an electrophotographic photoconductor 
with its photoconductive layer unprotected and exposed, the 
photoconductive layer is gradually damaged by corona charges applied 
thereto in the course of a charging process. Furthermore the 
photoconductive layer is physically and chemically deteriorated in a 
copying process while it is brought into contact with other members of an 
electrophotographic copying apparatus. There are the main factors for 
shortening the life of the electrophotographic photoconductor. 
To solve the above-mentioned problem, methods of covering the surface of an 
electrophotographic photoconductor with a protective layer are known. More 
specifically, there are disclosed a method of forming an organic film on 
the surface of a photoconductive layer of an electrophotographic 
photoconductor in Japanese Patent Publication 38-015446; a method of 
providing an inorganic oxide layer on the surface of a photoconductive 
layer in Japanese Patent Publication 43-014517; a method of successively 
overlaying an adhesive layer and an insulating layer on a photoconductive 
layer in Japanese Patent Publication 43-027591; and methods of laminating 
an amorphous silicon (a-Si) layer, a-Si:N:H layer or a-Si:O:H layer on a 
photoconductive layer by the plasma CVD or the photo CVD in Japanese 
Laid-Open Patent Applications 57-179859 and 59-058437. 
However, when the above-mentioned protective layers have a resistivity of 
10.sup.14 .OMEGA..multidot.cm or more, which is considered to be too high 
in electrophotography, the residual potential of the photoconductor 
increases while in use, and the residual electric charges are gradually 
accumulated during the repetition of copying operation, which will hinder 
the practical operation of the photoconductor. 
In order to cover the above-mentioned shortcoming of the protective layer, 
there is proposed in Japanese Patent Publication 52-024414 a method of 
optimizing the resistivity of a protective layer by adjusting the 
composition of a resin contained in the protective layer. Furthermore, 
methods of forming a photoconductive protective layer on a photoconductive 
layer are proposed, as disclosed in Japanese Patent Publications 
48-038427, 43-016198 and 49-010258, and U.S. Pat. No. 2,901,348. In 
addition, there are disclosed a method of adding to a protective layer 
sensitizers such as dyes and charge transporting agents represented by 
Lewis acids, as in Japanese Patent Publication 44-000834 and Japanese 
Laid-Open Patent Application 53-133444; and a method of controlling the 
resistivity of a protective layer by adding finely-divided particles of 
metals or metallic oxides, as in Japanese Laid-Open Patent Application 
53-003338. 
When the particles of metals or metallic oxides are added to the protective 
layer, projected light for image formation is partially absorbed in the 
protective layer while passing therethrough. As a result, the amount of 
the light which reaches the photoconductive layer is decreased and 
accordingly the photosensitivity of the photoconductor is 
disadvantageously decreased. 
To eliminate the above-mentioned disadvantage, there is further proposed in 
Japanese Laid-Open Patent Application 57-030546 a method of making a 
protective layer which is substantially transparent to visible light by 
dispersing in a protective layer metallic oxide particles having an 
average particle diameter of 0.3 .mu.m or less, which serve as a 
resistivity-controlling agent. 
In the photoconductor provided with the above-mentioned protective layer, 
the reduction in the photosensitivity can be minimized, and the mechanical 
strength of the protective layer can be increased so that the resistance 
to wear can be remarkably improved. 
However, it is found that the above-mentioned photoconductor has a problem 
that image flow occurs. Namely, blurred images are formed when the 
photoconductor is used repeatedly in a copying machine for an extended 
period of time under the conditions of high humidities or in the 
atmosphere where the ambient humidity drastically increases. The cause of 
such a phenomenon has not yet been clarified, but it is supposed that a 
resin contained in the protective layer is oxidized and deteriorated by 
ozone or various ions which are generated by corona charges applied to the 
photoconductor while it is repeatedly used. As a result, the resin is 
fractured or some radicals are formed. In addition to the above, the ozone 
and ions generated by the corona discharging of the photoconductor react 
with water and impurities such as a carbon dioxide gas in the air, so that 
nitrogen compounds and hydrophilic compounds containing carboxyl groups 
and aldehyde groups are formed. Those compounds are chemically adsorbed by 
deteriorated portions at the surface of the protective layer. When the 
photoconductor is operated under the conditions of high humidities or 
drastically increasing humidities, the protective layer of the 
photoconductor adsorbs a large amount of moisture, and the resistivity of 
the surface of the photoconductor is so much decreased that the image flow 
problem will occur in the photoconductor. 
Furthermore, positively chargeable electrophotographic photoconductors 
comprising a charge transport layer, a charge generation layer and a 
protective layer, which are successively overlaid on a support, containing 
a particular anti-oxidizing agent either in the charge generation layer or 
in the protective layer are proposed as described in Japanese Laid-Open 
Patent Applications 63-44662, 63-50848 to 63-50851, 63-52146 and 63-52150, 
which are capable of preventing the deterioration of the electric 
chargeability of the photoconductors resulting from the generation of 
ozone by the anti-oxidizing agent. 
In these electrophotographic photoconductors, however, the anti-oxidizing 
effect of the anti-oxidizing agent does not last for an extended period of 
time while in use. 
SUMMARY OF THE INVENTION 
It is therefore a first object of the present invention to provide an 
electrophotographic photoconductor which has high environmental resistance 
and is not deteriorated by ozone and various ions generated by corona 
discharging while used repeatedly in electrophotographic copying 
apparatus, and capable of yielding high quality images for a long period 
of time. 
A second object of the present invention is to provide an 
electrophotographic recording process by using the above-mentioned 
electrophotographic photoconductor. 
A third object of the present invention is to provide an 
electrophotographic copying apparatus using the above electrophotographic 
recording process. 
The first object of the present invention can be achieved by an 
electrophotographic photoconductor comprising an electroconductive 
support, a photoconductive layer comprising a selenium alloy formed on the 
support, and a protective layer, formed on the photoconductive layer, 
which comprises a binder resin component and an anti-oxidizing agent, and 
preferably can be abraded at a predetermined rate by friction or hard 
rubbing. 
The second object of the present invention can be achieved by an 
electrophotographic process comprising the steps of uniformly charging the 
electrophotographic photoconductor in the dark, exposing the uniformly 
charged electrophotographic photoconductor to a light image to form an 
electrostatic latent image corresponding to the light image thereon, 
developing the latent electrostatic image with a toner to a visible toner 
image, transferring the visible toner image to a transfer sheet, cleaning 
the surface of the electrophotographic photoconductor to eliminate a 
residual toner from the surface thereof, if any, abrading and renewing the 
surface of the protective layer with a predetermined rate so as to expose 
the anti-oxidizing agent contained in the protective layer, and quenching 
residual electric charges on the surface of the photoconductor. 
The third object of the present invention can be achieved by an 
electrophotographic copying apparatus comprising the above-mentioned 
electrophographic photoconductor, a charge application means for charging 
the surface of the photoconductor uniformly to a predetermined polarity in 
the dark, an exposure means for exposing the uniformly charged 
photoconductor to a light image to form a latent electrostatic image 
corresponding to the light image thereon, a development means for 
developing the latent electrostatic image with a toner to a visible toner 
image, an image transfer means for transferring the visible toner image to 
a transfer sheet, a cleaning means for cleaning the surface of the 
electrophotographic photoconductor to remove a residual toner therefrom, 
and an abrasion means for abrading and renewing the protective layer of 
the electrophotographic photoconductor with a predetermined rate during 
the operation of the electrophotographic copying apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As the materials for the electroconductive support of the 
electrophotographic photoconductor according to the present invention, 
electroconductive materials, and insulating materials which are treated so 
as to be electroconductive can be employed. Examples of such materials are 
metals of Al, Ni, Fe, Cu and Au, and alloys thereof; insulating materials 
such as polyester, polycarbonate, polyimide and glass which are coated by 
a thin film of a metal such as Al, Ag and Au or an electroconductive 
material such as In.sub.2 O.sub.3 and SnO.sub.2 ; and a sheet of paper 
treated so as to be electroconductive. 
There is no limitation to the shape of the electroconductive support. It 
can be shaped in a plate, a drum or a belt in accordance with the 
application thereof. 
On the electroconductive support, a single-layered type photoconductive 
layer or a multi-layered type photoconductive layer comprising Se, or a 
selenium alloy such as Se-Te, As.sub.2 Se.sub.3 or Se-As, is overlaid. 
For preventing the mechanical wear of the above-mentioned photoconductive 
layer and the deposition of toner particles in the form of a film on the 
surface of a photoconductor (the so-called toner-filming phenomenon), a 
protective layer is provided on the photoconductive layer. 
The protective layer for use in the present invention comprises as the main 
component a resin component. For example, protective layers consisting of 
a resin such as polystyrene, polyamide, polyester or polycarbonate, as 
disclosed in Japanese Patent Publications 38-015446 and 38-020697, are 
applicable to the present invention. In addition to this, a protective 
layer comprising a resin such as urethane resin, with the resistivity 
thereof lowered by modifying the composition thereof, as proposed in 
Japanese Patent Publication 52-024414, can be employed in the present 
invention. Furthermore, as disclosed in Japanese Laid-Open Patent 
Applications 57-128344, 54-121044 and 59-223442, protective layers 
comprising a resin such as polyurethane in which electroconductive 
particles such as antimony-doped tin oxide particles are dispersed to 
lower the resistivity thereof can be employed in the present invention. 
Furthermore, polyarylate resin, epoxy resin, acrylic resin, vinyl chloride 
- vinyl acetate copolymer, silicone resin, alkyd resin, vinyl chloride 
resin and fluoroplastic may be used as the binder resin component in the 
protective layer. 
The protective layer further comprises an anti-oxidizing agent in the 
present invention. Examples of the anti-oxidizing agent are phenolic 
compounds, sulfur compounds and phosphorus compounds. Specific examples of 
the anti-oxidizing agent for use in the present invention are listed 
below. The anti-oxidizing agents for use in the present invention are 
necessarily not limited to the following examples. 
(I) Phenolic compounds 
2,6-di-t-butyl-p-cresol (BHT), 2,6-di-t-butylphenol, 
2,4-di-methyl-6-t-butylphenol, butyl hydroxyanisole, 
2,2'-methylenebis(4-methyl-6-t-butylphenol), 
4,4'-thiobis(3-methyl-6-t-butylphenol), bisphenol A, 
DL-.alpha.-tocopherol, styrenated phenol, styrenated cresol, 
3,5-di-t-butyl hydroxybenzaldehyde, 2,6-di-t-butyl-4-hydroxymethylphenol, 
2,6-di-s-butylphenol, 2,4-di-t-butylphenol, 3,5-di-t-butylphenol, 
o-n-butoxyphenol, o-t-butylphenol, m-t-butylphenol, p-t-butylphenol, 
o-isobutoxyphenol, o-n-propoxyphenol, o-cresol, 
4,6-di-t-butyl-3-methylphenol, 2,6-dimethylphenol, 
2,3,5,6-tetramethylphenol, 3-(3',5'-di-t-butyl-4'-hydroxyphenyl)stearyl 
propionate, 2,4,6-tri-t-butylphenol, 2,4,6-trimethylphenol, 
2,4,6-tris(3',5'-di-t-butyl-4'-hydroxybenzyl)mesitylene, 
1,6-hexanediol-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 
2,2-thio-diethylenebis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], 
2,2-thiobis(4-methyl-6-t-butylphenol), 
3,5-di-t-butyl-4-hydroxy-benzylphophatediethyl ester, 
1,3,5-trimethyl-2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, 
##STR1## 
n-octadecyl-3-(3',5'-di-t-butyl-4-hydroxyphenyl)propionate, 
2-t-butyl-6(3'-t-butyl-5'-methyl-2-hydroxybenzyl)-4-methylphenylacrylate, 
4,4'-butylidene-bis(3-methyl-6-t-butylphenol), hydroquinone, 
2,5-di-t-butyl hydroquinone, and tetramethyl hydroquinone. 
These phenolic compounds can be used alone or in combination as the 
anti-oxidizing agents in the protective layer of the electrophotographic 
photoconductor according to the present invention. 
(II) Sulfur compounds 
di-n-dodecyl 3,3'-thiodipropionate, di-myristyl 3,3'-thiodipropionate, 
di-n-octadecyl 3,3'-thiodipropionate, 2-mercaptobenzimidazole, 
pentaerythritoltetrakis-(.beta.-lauryl thiopropionate), di-tridecyl 
3,3'-thiodipropionate, dimethyl 3,3'-thiodipropionate, octadecyl 
thioglycollate, phenothiazine, .beta.,.beta.'-thiodipropionic acid, 
n-butyl thioglycollate, ethyl thioglycollate, 2-ethylhexyl thioglycollate, 
iso-octyl thioglycollate, n-octyl thioglycollate, di-t-dodecyl-disulfide, 
n-butyl sulfide, di-n-amyl disulfide, n-dodecyl sulfide, n-octadecyl 
sulfide, p-thiocresol, 
##STR2## 
wherein R represents an alkyl group having 12 to 14 carbon atoms, and 
##STR3## 
These sulfur compounds can be used alone or in combination as the 
anti-oxidizing agent in the protective layer of the electrophotographic 
photoconductor according to the present invention. 
(III) Phosphorus compounds 
Aromatic phosphites, such as tris(nonylphenyl)phosphite, 
tris(2,4-di-t-butylphenyl)phosphite, diphenyl mono(tridecyl)phosphite, 
tetraphenyl dipropylene glycol diphosphite, tetraphenyl 
tetra(tridecyl)pentaerythritol tetraphosphite, 
4,4'-butylidene-bis(3-methyl-6-t-butylphenyl-di-tridecyl)phosphite, 
tetrakis(2,4-di-t-butylphenyl)-4,4'-biphenylene phosphite, triphenyl 
phosphite and tetra(tridecyl)-4,4'-isopropylidene diphenyl diphosphite; 
aliphatic phosphites such as trimethyl phosphite, triethyl phosphite, 
tri-n-butyl phosphite, trioctyl phosphite, triisodecyl phosphite, 
tridodecyl phosphite, tristridecyl phosphite, trioleyl phosphite and 
tris(2-bromoethyl)phosphite; triphenyl phosphine; trilauryl thiophosphite; 
tris(2-chloro-ethyl)phosphite; and distearyl pentaerythritol diphosphite. 
These phosphorus compounds can be used alone or in combination as the 
anti-oxidizing agent in the protective layer of the electrophotographic 
photoconductor according to the present invention. 
It is preferable that the ratio of the amount of the anti-oxidizing agent 
to the total amount of the resin components in the protective layer be in 
the range of 0.001 wt. % to 10 wt. %. If the amount of the anti-oxidizing 
agent in the protective layer is too small, it will not work sufficiently, 
but when the amount is excessive, the anti-oxidizing agent may be 
separated from the resin component in the protective layer if the 
compatibility of the anti-oxidizing agent with the resin component is 
poor. 
In the present invention, the protective layer may further comprise a 
resistivity-controlling agent to obtain an electrophotographic 
photoconductor with an appropriate resistivity for use in practice. For 
example, finely-divided particles of tin oxide can be used as the 
resistivity-controlling agent. 
In the protective layer, other additive components, such as a curing agent 
and a lubricant, may be further added when necessary. The curing agent is 
contained in the protective layer for crosslinking the resin component, 
and a polyisocyanate-type curing agent, for example, acrylpolyol resin is 
preferably employed. 
It is preferable that the thickness of the protective layer for use in the 
present invention be in the range of 0.2 .mu.m to 20 .mu.m, more 
preferably in the range of 0.5 .mu.m to 5 .mu.m. 
In electrophotographic photoconductors according to the present invention, 
a protective layer 4 is provided in such a fashion as shown in FIGS. 1 and 
2. 
In an electrophotographic photoconductor as shown in FIG. 1, a 
photoconductive layer 2 and a protective layer 4 are successively overlaid 
on an electroconductive support 1 in this order. Furthermore, as shown in 
FIG. 2, at least one intermediate layer 3 may be interposed between a 
photoconductive layer 2 and a protective layer 4 to increase the adhesive 
strength therebetween and prevent charge injection therebetween, thereby 
minimizing the charged potential of the photoconductor layer 2. 
Examples of the materials for the above-mentioned intermediate layer 3 
include a variety of polymeric organic compounds such as epoxy resin, 
polyester resin, polyamide resin, polystyrene resin, polyvinylidene 
chloride resin, polyvinyl acetate, polyvinyl chloride, acrylic resin, 
silicone resin and fluoroplastics; and polymeric materials prepared from 
(1) silane coupling agents such as trimethyl 8monomethoxy silane, 
.gamma.-glycidoxy propyltrimethoxy silane and .gamma.-methacryloxy 
propyltrimethoxy silane, and (2) at least one metal alkoxide or metal 
acetylacetone, for example, metal alkoxides such as titanium 
tetrabutoxide, aluminum tripropoxide and zirconium tetrabutoxide; and 
metal acetylacetone complexes such as titanium acetylacetonate and 
zirconium acetylacetonate. The above polymeric materials can be used alone 
or in combination. 
It is preferable that the thickness of the intermediate layer for use in 
the electrophotographic photoconductor according to the present invention 
be 1 .mu.m or less, more preferably 0.5 .mu.m or less. 
The electrophotographic copying process according to the present invention 
comprises the steps of uniformly charging the electrophotographic 
photoconductor in the dark, exposing the uniformly charged 
electrophotographic photoconductor to a light image to form a latent 
electrostatic image thereon corresponding to the light image, developing 
the latent electrostatic image with a toner to a visible toner image, 
transferring the visible toner image to a transfer sheet, cleaning the 
surface of the electrophotographic photoconductor to eliminate a residual 
toner from the surface thereof, if any, abrading the surface of the 
protective layer with a predetermined rate so as to expose the 
anti-oxidizing agent contained in the protective layer, and quenching 
residual electric charges on the surface of the photoconductor. 
In the above electrophotographic process, the cleaning step and the 
abrading step can be performed simultaneously by a cleaning means which 
can serve as an abrading means as well. 
The electrophotographic photoconductor according to the present invention, 
available in the form of a belt or a drum, is incorporated in an 
electrophotographic copying apparatus, in which there are disposed around 
the electrophotographic photoconductor (1) a charge application means for 
charging the surface of the photoconductor uniformly to a predetermined 
polarity in the dark, (2) an exposure means for exposing the uniformly 
charged photoconductor to a light image to form a latent electrostatic 
image corresponding to the light image thereon, (3) a development means 
for developing the latent electrostatic image to a visible image, (4) an 
image transfer means for transferring the developed visible image to a 
transfer sheet, (5) a cleaning means for cleaning the surface of the 
electrophotographic photoconductor to remove a residual developer or toner 
therefrom, (6) an abrasion means for abrading the protective layer of the 
electrophotographic photoconductor with a predetermined rate during the 
operation of the electrophotographic copying apparatus, and (7) a charge 
quenching means for quenching residual charges on the surface of the 
photoconductor. The cleaning means may serve as the abrasion means as 
well. 
The key feature of the electrophotographic photoconductor according to the 
present invention is that the protective layer of the photoconductor 
contains an anti-oxidizing agent and that the anti-oxidizing agent is 
always present on its surface as the protective layer is abraded in the 
course of repeated use of the photoconductor. Thus the electrophotographic 
photoconductor has high environmental resistance and is not deteriorated 
by ozone and various ions generated by corona charging thereof while in 
use in an electrophotographic copying apparatus for an extened period of 
time. 
The above-mentioned effect of the electrophotographic photoconductor 
according to the present invention is remarkable when it is repeatedly 
used in the electrophotographic copying apparatus. 
By contrast, in the case of a conventional electrophotographic 
photoconductor with a protective layer in which an anti-oxidizing agent is 
contained, it has been found that the anti-oxidant action of the 
anti-oxidizing agent is deteriorated as the electrophotographic 
photoconductor is repeatedly used. For example, it was found that after 
the completion of making about 10,000 copies, there was substantially no 
anti-oxidant action in the anti-oxidizing agent. This is because the 
protective layer in the conventional electrophotographic photoconductor is 
not appropriately abraded while in use in such a manner that the 
anti-oxidizing agent is always present at the surface thereof. 
In the present invention, the anti-oxidant effect of the anti-oxidizing 
agent contained in the protective layer can be sufficiently maintained by 
providing an abrasion means by which the surface of the protective layer 
is abraded at a predetermined ratio and constantly renewed while in 
operation of the electrophotographic copying apparatus. 
A specific example of the abrasion means for use in the electrophotographic 
copying apparatus according to the present invention is shown in FIG. 4. 
As shown in the figure, brush members 19a and 19b, which are provided in 
vicinity of a photoconductor drum 15, perform the function of cleaning 
residual toner particles deposited on the surface of the photoconductor 
and abrading the surface of a protective layer 16 thereof as the 
photoconductor drum 15 and the brush members 19a and 19b are rotated. The 
brush members 19a and 19b are rotated in an opposite direction to the 
rotating direction of the photoconductor drum 15 at the contact point 
thereof and scrape the residual toner particles off the surface of the 
photoconductor drum 15 and abrading the surface of the protective layer 
16. The toner particles are scraped off the surface of the photoconductor 
drum 15 by the brush members 19a and 19b, transferred thereto and then 
scraped off by cleaning members 20a and 20b. A blade cleaning member 18 is 
also provided near the photoconductor drum 1, by which residual toner 
particles on the photoconductor drum 15 are completely removed therefrom. 
Reference numeral 17 indicates a quenching lamp by which the residual 
electric charges on the surface of the photoconductor drum 15 are 
completely quenched. 
The abrasion amount of the protective layer 16 of the photoconductor drum 
15 can be controlled by changing the contact pressure between the brush 
members 19a and 19b and the protective layer 16 of the photoconductor drum 
15, the rotating speed of the brush members 19a and 19b relative to that 
of the photoconductor drum 15, and the number of the brush members 19a and 
19b. It is preferable that the abrasion rate of the protective layer 16 of 
the photoconductor drum 15 be 0.01 to 4 .mu.m, more preferably 0.05 to 2 
.mu.m, in thickness per 10,000 revolutions of the photoconductor drum 15. 
In the example shown in FIG. 4, the brush members 19a and 19b not only 
abrade the surface of the protective layer 16 but also clean the residual 
toner particles off the photoconductor drum 15. These two functions may be 
separated by using independent members. 
Other features of this invention will become apparent in the course of the 
following description of exemplary embodiments, which are given for 
illustration of the invention and are not intended to be limiting thereof. 
EXAMPLE 1 
Formation of Photoconductive Layer 
A cylindrical electroconductive support 1 made of an aluminum alloy having 
an outer diameter of 80 mm and a length of 340 mm was washed and mounted 
on a rotatable mandrel 7 of a vacuum-deposition apparatus as shown in FIG. 
3. 
The vacuum-deposition apparatus shown in FIG. 3 is constructed in such a 
manner that the rotatable mandrel 7 is equipped with a heater 8 for 
heating the electroconductive support 1 and an evaporating source 9 which 
holds a photoconductive material 10 (in this case, an As.sub.2 Se.sub.3 
alloy) for forming a photoconductive layer on the electroconductive 
support 1 is incorporated in a vacuum chamber 11. The mandrel 7 is driven 
in rotation by a motor 13 which is disposed outside the chamber 11, and 
the evaporating source 9 is heated by a power source 12 for the 
evaporating source 9, which is also disposed outside the chamber 11. The 
chamber 11, provided with a vacuum gauge 14, is evacuated with a vacuum 
pump 15. 
With the chamber 11 evacuated to -5 Torr or less, the evaporating source 9 
was heated as the temperature of the electroconductive support 1 was 
maintained at 210.degree. C., and the As.sub.2 Se.sub.3 alloy in the 
evaporating source 9 was deposited on the electroconductive support 1. 
Thus, a photoconductive layer of the As.sub.2 Se.sub.3 alloy with a 
thickness of 60 .mu.m was formed on the electroconductive support 1. 
Formation of Intermediate Layer 
On the above-prepared photoconductive layer, a ligroin solution of a 
commercially available silicone resin, "Toray Silicone AY42-441" 
[Trademark), made by Toray Silicone Co., Ltd., was coated in a deposition 
of 0.2 .mu.m on a dry basis, so that an intermediate layer was formed on 
the photoconductive layer. 
Formation of Protective Layer 
A mixture of the following components was dispersed, with addition of an 
appropriate amount of a solvent thereto, in a ball mill for 100 hours. 
______________________________________ 
Parts by Weight 
______________________________________ 
Acryl polyol (styrene- 
15 
methylmethacrylate-2- 
hydroxyethyl methacrylate 
copolymer) 
Finely-divided particles 
30 
of tin oxide 
2,6-di-t-butyl-p-cresol 
0.2 
______________________________________ 
To this mixture, 5 parts by weight of a polyisocyanate type curing agent 
was added, so that a protective layer coating liquid was obtained. 
The thus obtained protective layer coating liquid was coated on the 
above-prepared intermediate layer, and then dried at 120.degree. C. for 1 
hour, whereby a protective layer having a thickness of about 5 .mu.m was 
formed on the intermediate layer. Thus, an electrophotographic 
photoconductor No. 1 according to the present invention was obtained. 
COMATIVE EXAMPLE 1 
The procedure for preparation of the electrophotographic photoconductor No. 
1 in Example 1 was repeated except that 2,6-di-t-butyl-p-cresol employed 
in Example 1 was eliminated from the composition of the protective layer 
coating liquid in Example 1, whereby a comparative electrophotographic 
photoconductor No. 1 was obtained. 
For the evaluation of the thus obtained electrophotographic photoconductor 
No. 1 according to the present invention and comparative 
electrophotographic photoconductor No. 1, they were incorporated in a 
commercially available plain paper electrophotographic copying apparatus, 
"Ricopy FT6550" (Trademark), made by Ricoh Company Ltd., and subjected to 
a copying test by using a 5 lines/mm resolution chart. 
These electrophotographic photoconductors were evaluated by visually 
inspecting the resolution of the obtained images. 
The results are shown in Table 1. 
TABLE 1 
__________________________________________________________________________ 
No. of Copies 
At Initial Stage 
After 10,000 Copies 
After 50,000 Copies 
Environmental Conditions 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
Example No. 
50% RH 
90% RH 
50% RH 
90% RH 
50% RH 
90% RH 
__________________________________________________________________________ 
Example 1 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.smallcircle. 
Comparative 
.circleincircle. 
.circleincircle. 
.smallcircle. 
x .DELTA. 
x 
Example 1 
__________________________________________________________________________ 
.circleincircle.: resolution of 5.6 lines/mm 
.smallcircle.: resolution of 4.5 to 5.0 lines/mm 
.DELTA.: resolution of 3.0 to 4.0 lines/mm 
x: resolution of 2.8 lines/mm or less 
As apparent from the results shown in Table 1, both photoconductors were 
capable of producing copied images with excellent resolution at the 
initial stage, regardless of the environmental conditions such as the 
temperature and humidity. After repetition of the copying operation, 
however, the comparative electrophotographic photoconductor No. 1 produced 
an image flow problem under the conditions of high humidity and the image 
quality was therefore considerably degraded. On the other hand, the 
electrophotographic photoconductor No. 1 according to the present 
invention yielded clear images without image flow even after 50,000 copies 
were made. 
EXAMPLE 2 
The procedure for preparation of the electrophotographic photoconductor No. 
1 in Example 1 was repeated except that the composition of the protective 
layer coating liquid employed in Example 1 was replaced as follows, 
whereby an electrophotographic photoconductor No. 2 according to the 
present invention was obtained: 
______________________________________ 
Parts by Weight 
______________________________________ 
Acryl polyol (styrene- 
15 
methylmethacrylate- 
2-hydroxyethyl methacrylate 
copolymer) 
Finely-divided particles 
30 
of tin oxide 
3,3'-thiodipropionic acid-di- 
0.2 
m-dodecyl 
______________________________________ 
COMATIVE EXAMPLE 2 
The procedure for preparation of the electrophotographic photoconductor No. 
2 in Example 2 was repeated except that 3,3'-thiodipropionic 
acid-di-m-dodecyl employed in Example 2 was eliminated from the 
composition of the protective layer coating liquid in Example 2, whereby a 
comparative electrophotographic photoconductor No. 2 was obtained. 
The thus obtained electrophotographic photoconductor No. 2 according to the 
present invention and comparative electrophotographic photoconductor No. 2 
were evaluated in the same manner as in Example 1 by using a 5 lines/mm 
resolution chart. 
The results are shown in Table 2. 
TABLE 2 
__________________________________________________________________________ 
No. of Copies 
At Initial Stage 
After 10,000 Copies 
After 50,000 Copies 
Environmental Conditions 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
Example No. 
50% RH 
90% RH 
50% RH 
90% RH 
50% RH 
90% RH 
__________________________________________________________________________ 
Example 2 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.smallcircle. 
Comparative 
.circleincircle. 
.circleincircle. 
.smallcircle. 
x .DELTA. 
x 
Example 1 
__________________________________________________________________________ 
.circleincircle.: resolution of 5.6 lines/mm 
.smallcircle.: resolution of 4.5 to 5.0 lines/mm 
.DELTA.: resolution of 3.0 to 4.0 lines/mm 
x: resolution of 2.8 lines/mm or less 
As apparent from the results shown in Table 2, both photoconductors were 
capable of producing copied images with excellent resolution at the 
initial stage, regardless of the environmental conditions such as the 
temperature and humidity. After repetition of the copying operation, 
however, the comparative electrophotographic photoconductor No. 2 produced 
an image flow problem under the conditions of high humidity and the image 
quality was therefore considerably degraded. On the other hand, the 
electrophotographic photoconductor No. 2 according to the present 
invention yielded clear images without image flow even after 50,000 copies 
were made. 
EXAMPLE 3 
The procedure for preparation of the electrophotographic photoconductor No. 
1 in Example 1 was repeated except that the composition of the protective 
layer coating liquid employed in Example 1 was replaced as follows, 
whereby an electrophotographic photoconductor No. 3 according to the 
present invention was obtained: 
______________________________________ 
Parts by Weight 
______________________________________ 
Acryl polyol (styrene- 
15 
methylmethacrylate- 
2-hydroxyethyl methacrylate 
copolymer) 
Finely-divided particles 
30 
of tin oxide 
Tris(2,4-di-t-butylphenyl) 
0.2 
phosphite 
______________________________________ 
COMATIVE EXAMPLE 3 
The procedure for preparation of the electrophotographic photoconductor No. 
3 in Example 3 was repeated except that 
tris(2,4-di-t-butylphenyl)phosphite employed in Example 3 was eliminated 
from the composition of the protective layer coating liquid in Example 3, 
whereby a comparative electrophotographic photoconductor No. 3 was 
obtained. 
The thus obtained electrophotographic photoconductor No. 3 according to the 
present invention and comparative electrophotographic photoconductor No. 3 
were evaluated in the same manner as in Example 1. 
The results are shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
No. of Copies 
At Initial Stage 
After 10,000 Copies 
After 50,000 Copies 
Environmental Conditions 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
Example No. 
50% RH 
90% RH 
50% RH 
90% RH 
50% RH 
90% RH 
__________________________________________________________________________ 
Example 3 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.smallcircle. 
Comparative 
.circleincircle. 
.circleincircle. 
.smallcircle. 
x .DELTA. 
x 
Example 3 
__________________________________________________________________________ 
.circleincircle.: resolution of 5.6 lines/mm 
.smallcircle.: resolution of 4.5 to 5.0 lines/mm 
.DELTA.: resolution of 3.0 to 4.0 lines/mm 
x: resolution of 2.8 lines/mm or less 
As apparent from the results shown in Table 3, both photoconductors were 
capable of producing copied images with excellent resolution at the 
initial stage, regardless of the environmental conditions such as the 
temperature and humidity. After repetition of the copying operation, 
however, the comparative electrophotographic photoconductor No. 3 produced 
an image flow problem under the conditions of high humidity and the image 
quality was therefore considerably degraded. On the other hand, the 
electrophotographic photoconductor No. 3 according to the present 
invention yielded clear images without image flow even after 50,000 copies 
were made. 
EXAMPLE 4 
The procedure for preparation of the electrophotographic photoconductor No. 
1 in Example 1 was repeated except that the composition of the protective 
layer coating liquid employed in Example 1 was replaced as follows, 
whereby an electrophotographic photoconductor No. 4 according to the 
present invention was obtained: 
______________________________________ 
Parts by Weight 
______________________________________ 
Acryl polyol (styrene- 
15 
methylmethacrylate- 
2-hydroxyethyl methacrylate 
copolymer) 
Finely-divided particles 
30 
of tin oxide 
2,6-di-t-butylphenyl 
0.2 
______________________________________ 
COMATIVE EXAMPLE 4 
The procedure for preparation of the electrophotographic photoconductor No. 
4 in Example 4 was repeated except that 2,6-di-t-butylphenyl employed in 
Example 4 was eliminated from the composition of the protective layer 
coating liquid in Example 4, whereby a comparative electrophotographic 
photoconductor No. 4 was obtained. 
The thus obtained electrophotographic photoconductor No. 4 according to the 
present invention and comparative electrophotographic photoconductor No. 4 
were evaluated in the same manner as in Example 1. 
The results are shown in Table 4. 
TABLE 4 
__________________________________________________________________________ 
No. of Copies 
At Initial Stage 
After 50,000 Copies 
After 100,000 Copies 
Environmental Conditions 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
20.degree.C. 
30.degree.C. 
Example No. 
50% RH 
90% RH 
50% RH 
90% RH 
50% RH 
90% RH 
__________________________________________________________________________ 
Example 4 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.circleincircle. 
.smallcircle. 
Comparative 
.circleincircle. 
.circleincircle. 
.DELTA. 
x .DELTA. 
x 
Example 4 
__________________________________________________________________________ 
.circleincircle.: resolution of 5.6 lines/mm 
.smallcircle.: resolution of 4.5 to 5.0 lines/mm 
.DELTA.: resolution of 3.0 to 4.0 lines/mm 
x: resolution of 2.8 lines/mm or less 
As apparent from the results shown in Table 4, both photoconductors were 
capable of producing copied images with excellent resolution at the 
initial stage, regardless of the environmental conditions such as the 
temperature and humidity. After repetition of the copying operation, 
however, the comparative electrophotographic photoconductor No. 4 produced 
an image flow problem under the conditions of high humidity and the image 
quality was therefore considerably degraded. On the other hand, the 
electrophotographic photoconductor No. 4 according to the present 
invention yielded clear images without image flow even after 100,000 
copies were made. 
Thus, the electrophotographic photoconductors according to the present 
invention are not deteriorated by ozone and ions generated by the corona 
charging of the photoconductors even when used repeatedly for an extended 
period of time and capable of producing high quality images, without being 
affected by the environmental conditions.