Electrophotographic photosensitive member, and electrophotographic apparatus, device unit, and facsimile machine employing the same

An electrophotographic photosensitive member has an electroconductive support, and a photosensitive layer formed thereon. The photosensitive layer contains a compound represented by the formula (1).

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an electrophotographic photosensitive 
member, particularly to an electrophotographic photosensitive member 
having a photosensitive layer which does not cause image deterioration on 
repeated image formation and exhibits excellent durability. 
The present invention relates also to an electrophotographic apparatus, a 
device unit, and a facsimile machine employing the above 
electrophotographic photosensitive member. 
2. Related Background Art 
Many kinds of electrophotographic photosensitive members employing an 
organic compound as the photoconducting substance have been developed and 
practically used so far. 
Such electrophotographic photosensitive members employing an organic 
photoconductive substance are expected to be further improved in 
electrophotographic properties such as sensitivity and photoresponsiveness 
because of the flexibility in material design thereof, and are 
advantageous in ease of film formation, high productivity, and relatively 
low cost. 
However, such types of photosensitive members generally have serious 
disadvantages of low durability. The durability includes 
electrophotographic durability such as of sensitivity, residual potential, 
chargeability, blurring of images, etc. and mechanical durability such as 
resistance to abrasion and scratching of the surface of the photosensitive 
member by rubbing. It is already known that the lowering of the durability 
of the electrophotographic properties results mainly from the 
deterioration of the organic photoconductive substance in the 
photosensitive layer caused by ozone, NOx, or the like generated by a 
corona charger. 
The deterioration of the organic photoconductive substance leads to crushed 
images and undecipherable images, namely blurring of images. The 
deterioration was found to be more remarkable with organic photoconductive 
substances having a lower oxidation potential since the deterioration 
results from a kind of oxidation. 
From the viewpoint of the electrophotographic properties, polishing of the 
surface of the photosensitive member to constantly provide a fresh surface 
is effective for obtaining high-quality images. On the other hand, from 
the viewpoint of the mechanical durability, less abrasion is desired and 
therefore a slipping agent is dispersed on the surface of the 
photosensitive member, which retards the rapid removal of the deteriorated 
charge-transporting substance and tends to cause blurring of images. 
To solve such problems, for example, Japanese Patent Application Laid-Open 
No. Sho-63-30850 discloses use of a compound having an oxidation potential 
of not less than 0.6 V as the charge-transporting substance contained in 
the surface layer of the photosensitive member. 
Recently, as the result of prolongation of the life of the photosensitive 
member, the problem has surfaced that, when the photosensitive member is 
left standing in a copying machine for a long time after continuous use, 
the chargeability of a photosensitive member becomes apparently lowered at 
the portion of the photosensitive member kept in proximity to the 
corona-discharging charger. This cause a so-called dormant memory 
phenomenon, giving blank areas in stripes (white bands in positive 
development, and black bands in reversal development) in the image. 
This dormant memory phenomenon is especially remarkable when the employed 
charge-transporting substance has an oxidation potential of 0.6 V or 
higher. The occurrence of the aforementioned blurring of images is caused 
by ozone or NOx generated by corona discharge. In the case where the 
employed charge-transporting substance has an oxidation potential of less 
than 0.6 V, the charge-transporting substance itself is oxidized by the 
ozone or NOx at the surface of the photosensitive member which causes 
lower resistance, and is liable to cause blurring of images. On the other 
hand, in the case where the employed charge-transporting substance has an 
oxidation potential of not less than 0.6 V, the charge-transporting 
substance is relatively resistant to oxidation, and therefore the ozone or 
NOx is considered to penetrate deeply into the photosensitive layer to 
oxidize the charge-generating substance and lower the resistance thereof, 
whereby hole injection from the support is promoted, resulting in lower 
apparent potential and causing a dormant memory phenomenon. Although this 
reduction in the apparent potential is considered to occur during the use 
of the photosensitive member, the reduction occurs uniformly throughout 
the surface of the photosensitive member, so that the blanking of images 
caused by local potential drop is not observed. When the photosensitive 
member is left standing after continuous operation, local potential drop 
occurs in the vicinity of the charger where the concentrations of ozone 
and NOx are extremely high, resulting in blanking of images to a 
remarkable extent. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide an electrophotographic 
photosensitive member which is capable of giving images of high quality 
without blurring nor blanking of images. 
Another object of the present invention is to provide an 
electrophotographic photosensitive member which is capable of giving 
stably high-quality images without accumulation of the residual potential 
even after repeated use. 
A further object of the present invention is to provide an 
electrophotographic apparatus, a device unit, and a facsimile machine 
employing the photosensitive member. 
The present invention provides an electrophotographic photosensitive member 
comprising an electroconductive support and a photosensitive layer formed 
thereon, the photosensitive layer containing a compound represented by the 
formula (1) below: 
##STR1## 
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are 
respectively a hydrogen atom, a hydroxy group, a carboxyl group, a 
substituted or unsubstituted alkyl group, a substituted or unsubstituted 
alkenyl group, a substituted or unsubstituted alkoxy group, a substituted 
or unsubstituted aryl group, or substituted or unsubstituted heterocyclic 
group; the groups of R.sub.1 to R.sub.6 may be the same or different; and 
R.sub.1 and R.sub.2, R.sub.3 and R.sub.4, R.sub.4 and R.sub.5, and R.sub.5 
and R.sub.6 may link together to form a ring. 
The present invention further provides an electrophotographic apparatus, a 
device unit, and a facsimile machine employing the photosensitive member 
defined above.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The electrophotographic photosensitive member of the present invention 
comprises a photosensitive layer containing the compound represented by 
the formula (1) below 
##STR2## 
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5, and R.sub.6 are 
respectively a hydrogen atom, a hydroxy group, a carboxyl group, a 
substituted or unsubstituted alkyl group, a substituted or unsubstituted 
alkenyl group, a substituted or unsubstituted alkoxy group, a substituted 
or unsubstituted aryl group, or substituted or unsubstituted heterocyclic 
group; the groups of R.sub.1 to R.sub.6 may be the same or different; and 
R.sub.1 and R.sub.2, R.sub.3 and R.sub.4, R.sub.4 and R.sub.5, and R.sub.5 
and R.sub.6 may link together to form a ring. 
In the formula (1), the alkyl group includes methyl, ethyl, propyl, etc.; 
the alkenyl group includes vinyl, propenyl, allyl, etc.; the alkoxy group 
includes methoxy, ethoxy, propoxy, etc.; the aryl group includes phenyl, 
naphthyl, etc.; and the heterocyclic group includes pyridyl, pyrimidyl, 
thiazolyl, etc. 
The substituent which may substitute the above groups includes halogen 
atoms; the alkyl groups, the alkenyl groups, the alkoxyl groups, the aryl 
groups and the heterocyclic groups mentioned above. 
The compound of the formula (1) is exemplified below specifically without 
limiting the invention. 
##STR3## 
In these exemplified compounds, the exemplified compounds No. 2 and No. 7 
are preferably employed. 
The amount to be added of the compound of the formula (1) in the present 
invention is preferably in the range of from 0.2 to 30%, more preferably 
from 0.4 to 15% by weight, based on the weight of the layer to which the 
compound is added. With the amount of addition of less than 0.2% by 
weight, the prevention of the deterioration may be insufficient, while 
with the amount of the addition of more than 30% by weight, the 
sensitivity or the residual potential is liable to be adversely affected. 
The compound of the formula (1) may be used individually or in combination 
of two or more thereof, and further may be used in combination with an 
additive such as an antioxidant, a UV absorber, and a plasticizer. 
The photosensitive layer employed in the electrophotographic photosensitive 
member of the present invention may be of a monolayer type which contains 
a charge-generating substance and a charge-transporting substance one and 
the same layer, or may be of a lamination type which comprises a 
charge-generating layer containing a charge-generating substance and a 
charge-transporting layer containing a charge-transporting substance. 
The charge-generating substance may be any substance which has 
charge-generating ability, including the substances below: 
(1) Azo type pigments including monoazo, bisazo, and trisazo type pigments, 
(2) Phthalocyanine pigments including metal phthalocyanine and non-metal 
phthalocyanine, 
(3) Indigo type pigments including indigo and thioindigo, 
(4) Perylene type pigments including perylenic anhydride and perylenimide, 
(5) Polycyclic quinones type pigments including anthraquinone and pyrene 
quinone, 
(6) Squarilium dyes, 
(7) Pyrylium salts and thiopyrylium salts, 
(8) Triphenylmethane dyes, 
(9) Inorganic substances such as selenium and amorphous silicon. 
These charge-generating substances may be used individually or in 
combination of two or more thereof. 
The charge-transporting substance is selected from hydrazone type 
compounds, stilbene type compounds, carbazole type compounds, pyrazoline 
type compounds, oxazole type compounds, thiazole type compounds, 
triarylmethane type compounds, polyarylalkanes, and the like. These may be 
used individually or in combination of two or more thereof. The higher the 
oxidation potential of the charge-transporting substance, the higher is 
the durability thereof. The improvement of the durability is more 
remarkable with the substances having the oxidation potential of 0.6 V or 
higher, particularly 0.7 V or higher. 
In a lamination type of photosensitive layer, the charge-generating layer 
may be formed by dispersing the aforementioned charge-generating substance 
together with a suitable solvent in a binder resin and applying the 
dispersion on an electroconductive support and drying, or otherwise may be 
formed by depositing the substance in a thin film on an electroconductive 
support according to a dry process such as sputtering, and CVD. 
The aforementioned binder resins include polycarbonates, polyesters, 
polyarylates, butyral resins, polystyrenes, polyvinylacetals, diallyl 
phthalate resins, acrylic resins, methacrylic resins, vinyl acetate 
resins, phenol resins, silicone resins, polysulfones, styrene-butadiene 
copolymers, alkyd resins, epoxy resins, urea resins, and vinyl 
chloridevinyl acetate copolymers, but is not limited thereto. These resins 
may be used individually or in combination of two or more thereof. The 
resin contained in the charge-generating layer is in an amount of not more 
than 80% by weight, more preferably not more than 40% by weight based on 
the total weight of the charge-generating layer. 
The charge-generating layer has a film thickness preferably not more than 5 
.mu.m, more preferably in the range of from 0.01 to 2 .mu.m. 
The charge-generating layer may further contain a sensitizer. 
The charge-transporting layer may be formed by dissolving the 
aforementioned charge-transporting substance in a suitable binder resin 
with the aid of a suitable solvent, and applying to a charge-generating 
layer and drying the resulting solution. 
The binder resin includes the resins mentioned above for the 
charge-generating resin and additionally includes photoelectric polymers 
such as polyvinylcarbazole and polyvinylanthracene. The blending ratio of 
the charge-transporting substance to the binder resin is preferably in the 
range of from 10 to 500 parts by weight of the charge-transporting 
substance to 100 parts by weight of the binder resin. 
The charge-transporting layer has a thickness preferably in the range of 
from 5 to 40 .mu.m, more preferably from 10 to 30 .mu.m. 
In the present invention, a compound represented by the formula (1) may be 
contained in any layers of a charge-generating layer, a 
charge-transporting layer, and a protecting layer as mentioned below as 
well as a single type of a photosensitive layer. When the photosensitive 
layer on which the charge-transporting layer is laminated, the compound 
represented by the formula (1) may be contained preferably in at least one 
of the charge-transporting layer or the protecting layer, more preferably 
in the charge-transporting layer. 
The charge-transporting layer may be laminated on the charge-generating 
layer, or conversely the charge-generating layer may be laminated on the 
charge-transporting layer, in the present invention. 
In the case where the photosensitive layer is of a monolayer type, it may 
be formed by dispersing and dissolving the charge-generating substance and 
the charge-transporting substance in the aforementioned binder resin and 
applying and drying the resulting liquid. The film thickness is preferably 
in the range of from 5 to 40 .mu.m, more preferably from 10 to 30 .mu.m. 
The present invention is particularly suitably employed in the cases where 
the durability of the photosensitive member is improved by use of a 
charge-transporting substance having a relatively high oxidation potential 
(e.g., 0.6 V or higher), or where the durability is improved by applying a 
lubricant, or additionally a dispersing agent for dispersing the lubricant 
uniformly on the surface layer to reduce the abrasion of the 
photosensitive member. 
The lubricant suitably used in the present invention includes powdery 
fluoro-resins, powdery polyolefin resins, powdery silicone resins, powdery 
fluorinated carbon, and the like. Powdery fluoro-resins are preferred in 
view of lubricity and releasability. The powdery fluoro-resins include 
tetrafluoroethylene resins, chlorotrifluoroethylene resins, 
tetrafluoroethylene-hexafluoropropylene resins, vinyl fluoride resins, 
vinylidene fluoride resins, difluorochloroethylene resins and copolymers 
comprising polymer components of these resins. The powdery polyolefins 
includes polyethylenes, polypropylenes, and copolymers comprising 
components of these polymers. The amount of addition of such a lubricant 
is preferably in the range of from 1 to 100%, more preferably from 1.5 to 
30% by weight based on the binder resin in the layer to which the 
lubricant is added. 
A subbing layer, which has a barrier function and an adhesion function, may 
be provided between the electroconductive support and the photosensitive 
layer in the present invention. The material for the subbing layer 
includes polyvinyl alcohol, polyethylene oxide, ethylcellulose, 
methylcellulose, casein, polyamides, glue and gelatin. The material is 
dissolved in a suitable solvent and applied on the electroconductive 
support. The thickness of the resulting layer is preferably not more than 
5 .mu.m, more preferably in the range of from 0.2 to 3.0 .mu.m. 
Further, a protecting layer, which is made of a simple resin layer or a 
resin layer containing an electroconductive substance dispersed therein, 
may be provided on the photosensitive layer in the present invention for 
the purpose of protecting the photosensitive layer from various external 
mechanical and electrical forces. The protecting layer is included in the 
photosensitive layer in the present invention. 
The above-described layers are formed on the electroconductive support by 
use of a suitable organic solvent according to a coating method such as 
immersion coating, spray coating, spinner coating, roller coating, Meyer 
bar coating, and blade coating. 
The electroconductive support in the present invention may be in such a 
structure as shown below: 
(1) A metal such as aluminum, aluminum alloys, stainless steel, and copper, 
(2) A non-electroconductive support such as glass, a resin, or paper, or an 
electroconductive support mentioned in the above item (1) on which a film 
of a metal such as aluminum, palladium, rhodium, gold, and platinum is 
formed by dispersion, vapor-deposition, or lamination, and 
(3) A non-electroconductive support such as glass, a resin, or paper, or an 
electroconductive support mentioned in the above item (1) on which a layer 
of an electroconductive polymer, a layer of electroconductive compound 
such as tin oxide, and indium oxide, or a layer of a resin containing such 
electroconductive compound dispersed therein is formed by 
vapor-deposition, or coating. 
The electroconductive support may be in a shape of a drum, a sheet, or a 
belt, but is not limited thereto. 
The electrophotographic photosensitive member of the present invention is 
not only applicable to electrophotographic copying machines but also 
applicable widely in electrophotographic fields including laser printers, 
CRT printers, facsimile machines, electrophotographic engraving systems, 
and the like. 
FIG. 1 illustrates roughly an example of the constitution of an 
electrophotographic apparatus employing the photosensitive member of the 
present invention. 
In FIG. 1, a drum type photosensitive member 1 serves as an image carrier, 
being driven to rotate around the axis 1a in the arrow direction at a 
predetermined peripheral speed. The photosensitive member 1 is charged 
positively or negatively at the peripheral face uniformly during the 
rotation by an electrostatic charging means 2, and then exposed to 
image-exposure light L (e.g. slit exposure, laser beam-scanning exposure, 
etc.) at the exposure portion 3 with an image-exposure means (not shown in 
the drawing), whereby electrostatic latent images are sequentially formed 
on the peripheral surface of the photosensitive member in accordance with 
the exposed image. 
Thus formed electrostatic latent image is developed with a toner by a 
developing means 4. The toner-developed images are sequentially 
transferred by a transfer means 5 onto a surface of a transfer-receiving 
material P which is fed between the photosensitive member 1 and the 
transfer means 5 synchronously with the rotation of the photosensitive 
member 1 from a transfer-receiving material feeder not shown in the 
drawing. 
The transfer-receiving material P having received the transferred image is 
separated from the photosensitive member surface, and introduced to an 
image fixing means 8 for fixiation of the image and sent out of the 
copying machine as a duplicate copy. 
The surface of the photosensitive member 1, after the image transfer, is 
cleaned with a cleaning means 6 to remove any remaining un-transferred 
toner, and is treated for charge elimination with a pre-exposure means 7 
for repeated use for image formation. 
The generally employed charging means 2 for uniformly charging the 
photosensitive member 1 is a corona charging apparatus. The generally 
employed transfer means 5 is also a corona charging means. In the 
electrophotographic apparatus, two or more of the constitutional elements 
of the above described photosensitive member, the developing means, the 
cleaning means, etc. may be integrated into one device unit, which may be 
made demountable from the main body of the apparatus. For example, at 
least one of the charging means, the developing means, and the cleaning 
means is combined with the photosensitive member 1 into one device unit 
which is demountable from the main body of the apparatus by aid of a 
guiding means such as a rail in the main body of the apparatus. An 
electrostatic charging means and/or a developing means may be combined 
with the aforementioned device unit. 
When the electrophotographic apparatus is used as a copying machine or a 
printer, the light L for optical image exposure may be projected onto the 
photosensitive member as reflected light or transmitted light from an 
original copy, or otherwise the information read out by a sensor from an 
original is signalized, and according to the signalized information light 
is projected onto a photosensitive member, by scanning with a laser beam, 
driving an LED array, or driving a liquid crystal shutter array. 
When the electrophotographic apparatus is used as a printer of a facsimile 
machine, the optical image exposure light L is for printing the received 
data. FIG. 2 is a block diagram of an example of this case. 
A controller 11 controls the image-reading part 10 and a printer 19. The 
entire of the controller 11 is controlled by a CPU 17. Readout data from 
the image reading part 10 is transmitted through a transmitting circuit 13 
to the other communication station. Data received from the other 
communication station is transmitted through a receiving circuit 12 to a 
printer 19. The image data is stored in image memory 16. A printer 
controller 18 controls a printer 19. The numeral 14 denotes a telephone 
set. 
The image received through a circuit 15, namely image information from a 
remote terminal connected through the circuit, is demodulated by the 
receiving circuit 12, treated for decoding of the image information in CPU 
17, and successively stored in the image memory 16. When at least one page 
of image information has been stored in the image memory 16, the images 
are recorded in such a manner that the CPU 17 reads out the one page of 
image information, and sends out the decoded one page of information to 
the printer controller 18, which controls the printer 19 on receiving the 
one page of information from CPU 17 to record the image information. 
During recording by the printer 19, the CPU 17 receives the subsequent page 
of information. 
Images are received and recorded in the manner as described above. 
The present invention is described in more detail by reference to Examples. 
In Examples, the oxidation potential was shown by the peak position of the 
current-potential curve which was obtained by sweeping the potential of 
the working electrode by means of a potential sweeper by use of a 
saturated calomel electrode as the reference electrode, and 0.1N 
(n-Bu).sub.4 N.sup.+ ClO.sub.4 in acetonitrile as the electrolyte 
solution. More specifically, the sample was dissolved in the 0.1N 
(n-Bu).sub.4 N.sup.+ ClO.sub.4 in acetonitrile as the electrolyte at a 
concentration of form 5 to 10 mmol %. Then a potential was applied to this 
sample solution and the potential was raised linearly from a low 
potential. The change of the current was measured to obtain a 
current-potential curve. The potential value at the first inflection point 
in the current-potential curve was taken as the oxidation potential of the 
present invention. 
The unit "part" is based on weight hereinafter. 
EXAMPLE 1 
An aluminum cylinder of 80 mm diameter and 360 mm long was employed as the 
electroconductive support. Onto this support, 5% solution of a polyamide 
resin (Amylan CM-8000, made by Toray Industries, Inc.) in methanol was 
applied by immersion coating to form a subbing layer of 0.5 .mu.m thick. 
Subsequently, 10 parts of the trisazo pigment represented by the formula 
below: 
##STR4## 
6 parts of a polyvinylbutyral resin (Eslec BL-S, made by Sekisui Chemical 
Co., Ltd.), and 50 parts of cyclohexanone were dispersed by means of a 
sand mill employing glass beads. This liquid dispersion was diluted with 
100 parts of methyl ethyl ketone, and the resulting liquid was applied on 
the above subbing layer by immersion coating to form a charge-generating 
layer of 0.2 .mu.m thick. 
Then, 10 parts of the stilbene compound (oxidation potential: 0.81 V) 
represented by the formula below: 
##STR5## 
and 10 parts of a Polycarbonate resin (Panlite L-1250, made by Teijin 
Kasei K.K.) were dissolved in a mixture of 50 parts of dichloromethane and 
10 parts of monochlorobenzene. To this solution, the liquid dispersion was 
added which had been separately prepared by dispersing 1 part of a 
tetrafluoroethylene resin (Lubron L-2, made by Daikin Industries, Ltd.) 
and 0.1 part of a dispersing agent (Arron GF-300, made by Toagosei 
Chemical Industry Co., Ltd.) in 10 parts of monochlorobenzene. Further 
thereto, 0.1 part of quinoxaline (Exemplified Compound No. 1) was added. 
This solution was applied onto the above charge-generating layer by 
immersion coating to form a charge-transporting layer of 19 .mu.m thick. 
The resulting electrophotographic photosensitive member was set in an 
electrophotographic copying machine (NP-3825, made by Canon K.K.), and the 
properties of the electrophotographic photosensitive member were measured 
as below. 
Firstly, the conditions for latent image formation were determined to 
achieve the dark area potential (V.sub.D) of -650 V and the light area 
potential (V.sub.L) of -150 V. The quantity of image exposure therefor was 
defined as the initial sensitivity. After 5000 sheets of copying was 
practiced continuously, the values of V.sub.D and V.sub.L were measured, 
and the fall of V.sub.D and the rise of V.sub.L were determined. 
Thereafter, the photosensitive member was left standing in the copying 
machine. The portion of the photosensitive member left standing directly 
below the corona charger is marked. After standing for 10 hours, the 
photosensitive member was subjected to measurement of the surface 
potentials at the portion of the member which had been left directly below 
the corona charger and at the portion which was not directly below the 
corona charger, and the difference of the two potentials (.DELTA.V.sub.D) 
was derived. The quality of the image after 5000 sheets of copying was 
evaluated visually. 
The results are shown in Table 1. 
EXAMPLE 2 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 1 except that the amount of the quinoxaline was changed to 0.5 
part. 
The results are shown in Table 1. 
Comparative Example 1 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 1 except that the quinoxaline was not used. 
The results are shown in Table 1. 
Comparative Example 2 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 1 except that 2,6-di-p-tolylpyridine was used instead of the 
quinoxaline. 
The results are shown in Table 1. 
EXAMPLE 3 
A subbing layer was provided on an electroconductive support in the same 
manner as in Example 1. 
10 Parts of a disazo pigment represented by the formula below as the 
charge-generating substance: 
##STR6## 
6 parts of a polyvinylbutyral resin (Eslec BX-1, made by Sekisui. Chemical 
Co., Ltd.), and 50 parts of cyclohexanone were dispersed by means of a 
sand mill employing glass beads. This dispersion was diluted with 100 
parts of tetrahydrofuran. The diluted dispersion was applied on the above 
subbing layer to form a charge-generating layer of 0.2 .mu.m thick. 
Separately, a solution for the charge-transporting layer was prepared in 
the same manner as in Example 1 except that 2,3-dimethylquinoxaline 
(Exemplified Compound No. 2) was used instead of the quinoxaline. This 
solution was applied on the above charge-generating layer by immersion 
coating to form a charge-transporting layer of 19 .mu.m thick. 
The resulting photosensitive member was evaluated in the same manner as in 
Example 1. 
The results are shown in Table 2. 
EXAMPLE 4 
A photosensitive member was prepared in the same manner as in Example 3 
except that the amount of the 2,3-dimethylquinoxaline was changed to 0.5 
part. 
The results are shown in Table 2. 
Comparative Example 3 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 3 except that the 2,3-dimethylquinoxaline was not used. 
The results are shown in Table 2. 
Comparative Example 4 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 4 except that 4,4'-dipyridyl was used instead of the 
2,3-dimethylquinoxaline. 
The results are shown in Table 2. 
EXAMPLE 5 
A subbing layer was provided on an electroconductive support in the same 
manner as in Example 1. 
10 Parts of a disazo pigment represented by the formula below as the 
charge-generating substance: 
##STR7## 
6 parts of a polyvinylbutyral resin (Eslec BX-1, made by Sekisui Chemical 
Co., Ltd.), and 50 parts of cyclohexanone were dispersed by means of a 
sand mill employing glass beads. This liquid dispersion was diluted by 100 
parts of tetrahydrofuran. The diluted dispersion was applied on the above 
subbing layer to form a charge-generating layer of 0.2 .mu.m thick. 
Separately, 8 parts of a benzocarbazole compound (oxidation potential: 0.83 
V) represented by the formula below: 
##STR8## 
and 10 parts of a styrene-acryl copolymer resin (Estyrene MS-200, made by 
Nippon Steel Chemical Co., Ltd.) were dissolved in a mixture of 15 parts 
of dichloromethane and 45 parts of monochlorobenzene. One part of a 
tetrafluoroethylene resin (Lubron L-2, made by Daikin Industries, Ltd.) 
which had been dispersed, and 0.1 part of a dispersing agent (Modiper 
F-110, made by Nippon Oil and Fats Co., Ltd.) were added to the above 
solution. Further thereto, 0.1 part of 3-methyl-2-quinoxalinol 
(Exemplified Compound No. 3) was added. The resulting liquid mixture was 
applied onto the above charge-generating layer by immersion coating to 
form a charge-transporting layer of 19 .mu.m thick. 
The resulting photosensitive member was evaluated in the same manner as in 
Example 1. 
The results are shown in Table 3. 
EXAMPLE 6 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 5 except that the amount of the 3-methyl-2-quinoxalinol was 
changed to 0.5 parts. 
The results are shown in Table 3. Comparative Example 5 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 5 except that the 3-methyl-2-quinoxalinol was not used. 
The results are shown in Table 3. 
Comparative Example 6 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 5 except that phenanthroline was used instead of the 
3-methyl-2-quinoxalinol. 
The results are shown in Table 3. 
EXAMPLE 7 
A subbing layer was provided on an electroconductive support in the same 
manner as in Example 1. 
10 Parts of a disazo pigment represented by the formula below as the 
charge-generating substance: 
##STR9## 
6 parts of a polyvinylbutyral resin (Eslec BX-1, made by Sekisui Chemical 
Co., Ltd.), and 50 parts of cyclohexanone were dispersed by means of a 
sand mill employing glass beads. This dispersion was diluted by 100 parts 
of tetrahydrofuran. The diluted dispersion was applied on the above 
subbing layer to form a charge-generating layer of 0.2 .mu.m thick. 
Separately, 8 parts of a compound (oxidation potential: 0.62 V) represented 
by the formula below as the charge-transporting substance: 
##STR10## 
and 10 parts of a styrene-acryl copolymer resin (Estyrene MS-200, made by 
Nippon Steel Chemical Co., Ltd.) were dissolved in a mixture of 15 parts 
of dichloromethane and 45 parts of monochlorobenzene. One part of a 
tetrafluoroethylene resin (Lubron L-2, made by Daikin Industries, Ltd.) 
which had been dispersed and 0.1 part of a dispersing agent (Modiper 
F-110, made by Nippon Oil and Fats Co., Ltd.) were added to the above 
solution. Further thereto 0.1 part of 2-quinoxalinecarbonyl chloride 
(Exemplified Compound No. 6) was added. The resulting liquid mixture was 
applied onto the above charge-generating layer by immersion coating to 
form a charge-transporting layer of 19 .mu.m thick. 
The resulting photosensitive member was evaluated in the same manner as in 
Example 1. 
The results are shown in Table 4. 
EXAMPLE 8 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 7 except that the amount of the 2-quinoxalinecarbonyl chloride was 
changed to 0.5 parts. 
The results are shown in Table 4. 
Comparative Example 7 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 7 except that the 2-quinoxalinecarbonyl chloride was not used. 
The results are shown in Table 4. 
Comparative Example 8 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 7 except that dithio-bis-nitropyridine was used instead of 
2-quinoxalinecarbonyl chloride. 
The results are shown in Table 4. 
EXAMPLE 9 
A photosensitive member was prepared in the same manner as in Example 7 
except that the compound (oxidation potential: 0.54 V) represented by the 
formula below was used as the charge-transporting substance: 
##STR11## 
The results are shown in Table 5. 
Comparative Example 9 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 9 except that 2-quinoxalinecarbonyl chloride was not used. 
The results are shown in Table 5. 
Comparative Example 10 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 9 except that diphenylpyridine was used instead of 
2-quinoxalinecarbonyl chloride. 
The results are shown in Table 5. 
EXAMPLE 10 
A subbing layer was provided on an electroconductive support in the same 
manner as in Example 1. 
Then, 15 parts of the stilbene compound (oxidation potential: 0.81 V) 
represented by the formula below: 
##STR12## 
and 10 parts of a polycarbonate resin (trade name: Panlite L-1250, made by 
Teijin Kasei K.K.) were dissolved in a mixture of 50 parts of 
dichloromethane and 10 parts of monochlorobenzene. This solution was 
applied on the above subbing layer to form a charge-transporting layer of 
15 .mu.m thick. 
4 Parts of the disazo pigment represented by the formula below: 
##STR13## 
10 parts of a polyvinylbutyral resin (Eslec BL-S, made by Sekisui Chemical 
Co., Ltd.), and 0.63 part of phenazine (Exemplified compound No. 8) were 
dispersed and dissolved in a mixture of 150 parts of cyclohexane and 50 
parts of tetrahydrofuran. The resulting coating liquid was applied on the 
above charge-transporting layer by spray coating to form a 
charge-generating layer of 5 .mu.m thick. 
Further, 1 part of a lubricant (Lubron L-2, made by Daikin Industries, 
Ltd.), 9 parts of the aforementioned polycarbonate, and 0.1 part of a 
dispersing agent (Modiper F-210, made by Nippon Oil and Fats Co., Ltd.) 
were dispersed and dissolved in 90 parts of monochlorobenzene. The 
solution was applied on the above charge-generating layer by spray coating 
to form a protecting layer of 3 .mu.m thick. 
The resulting photosensitive member was evaluated in the same manner as in 
Example 1 except that the charging polarity was positive, and V.sub.D was 
650 V and V.sub.L was 150 V. 
The results are shown in Table 6. 
Comparative Example 11 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 10 except that phenazine was not used. 
The results are shown in Table 6. 
Comparative Example 12 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 10 except that 2,2'-dipyridyl was used instead of the phenazine. 
The results are shown in Table 6. 
EXAMPLE 11 
A subbing layer was provided on an electroconductive support in the same 
manner as in Example 1. 
5 Parts of the disazo pigment represented by the formula below: 
##STR14## 
10 parts of the stilbene compound (oxidation potential: 0.81 V) 
represented by the formula below: 
##STR15## 
and 15 parts of a polycarbonate resin (Z-200, made by Mitsubishi Gas 
Chemical Co., Inc. ) were dispersed and dissolve in 170 parts of 
monochlorobenzene by means of a sand mill. Further thereto, 1 part of 
6,7-dimethyl-2,3-dipyridylquinoxaline (Exemplified compound No. 9) was 
added. This solution was applied on the above subbing layer by immersion 
coating to form a photosensitive layer of 20 .mu.m thick. 
The resulting photosensitive member was evaluated in the same manner as in 
Example 1. 
The results are shown in Table 7. 
Comparative Example 13 
A photosensitive member was prepared and evaluated in the same manner as in 
Example 11 except that 6,7-dimethyl-2,3-dipyridylquinoxaline was not used. 
The results are shown in Table 7. 
As described above, the present invention provides an electrophotographic 
photosensitive member which gives images of high quality stably even after 
repeated use without blurring or blanking of the images. 
TABLE 1 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive (parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 1 No. 1 0.1 2.5 20 15 25 Good 
Example 2 No. 1 0.5 2.6 10 20 10 Good 
Comparative Example 1 
-- -- 2.5 60 10 90 White blank 
Comparative Example 2 
2,6-di-p-tolylpyridine 
0.1 2.5 55 20 90 White blank 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive 
(parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 3 No. 2 0.1 2.1 15 15 20 Good 
Example 4 No. 2 0.5 2.1 10 15 20 Good 
Comparative Example 3 
-- -- 2.1 70 10 80 White blank 
Comparative Example 4 
4,4'-dipyridyl 
0.5 2.3 20 55 20 Fogging 
__________________________________________________________________________ 
TABLE 3 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive 
(parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 5 No. 3 0.1 2.5 25 15 20 Good 
Example 6 No. 3 0.5 2.6 15 15 10 Good 
Comparative Example 5 
-- -- 2.5 70 15 85 White blank 
Comparative Example 6 
Phenanthroline 
0.1 3.8 45 25 40 Fogging 
__________________________________________________________________________ 
TABLE 4 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive (parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 7 No. 6 0.1 3.0 25 15 20 Good 
Example 8 No. 6 0.5 3.1 15 15 15 Good 
Comparative Example 7 
-- -- 3.0 75 20 70 White blank 
Comparative Example 8 
Dithio-bis-nitropyridine 
0.1 3.0 65 25 60 White blank 
__________________________________________________________________________ 
TABLE 5 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive (parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 9 No. 6 0.1 2.8 15 15 25 Good 
Comparative Example 9 
-- -- 2.8 35 15 50 Blurring 
Comparative Example 10 
Diphenylpyridine 
0.1 3.0 30 25 45 Blurring 
__________________________________________________________________________ 
TABLE 6 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive 
(parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 10 No. 8 0.63 4.2 20 15 20 Good 
Comparative Example 11 
-- -- 4.0 100 15 100 
White blank 
Comparative Example 12 
2,2'-dipyridyl 
0.63 4.2 30 60 25 Blurring 
__________________________________________________________________________ 
TABLE 7 
__________________________________________________________________________ 
Initial 
Amount of 
sensi- 
Fall 
Rise 
additive 
tivity 
of V.sub.D 
of V.sub.L 
.DELTA.V.sub.D 
Image 
Additive 
(parts) 
(lux.sec) 
(V) (V) (V) 
quality 
__________________________________________________________________________ 
Example 11 No. 9 
1 4.1 30 30 25 Good 
Comparative Example 13 
-- -- 4.0 100 50 70 White blank 
__________________________________________________________________________