Multilayer electrophotographic photosensitive member

An electrophotographic photosensitive member comprising a photosensitive layer having a laminated structure of charge generation and charge transport layers on a conductive substrate is characterized in that the charge generation layer contains a copper phthalocyanine pigment and the charge transport layer contains a hydrazone compound and a binder. A process for forming electrostatic latent images comprises the steps of (1) giving electric charge to the face of an electrophotographic photosensitive member comprising a photosensitive layer having a laminated structure on a conductive substrate, said laminated structure consisting of a charge generation layer containing copper phthalocyanine and a charge transport layer containing a hydrazone compound and a binder and (2) scanning the charged face with a laser beam. An image-forming process comprises the steps of (1) giving electric charge to the face of an electrophotographic photosensitive member having a photosensitive layer of a laminated structure on a conductive substrate, said laminated structure consisting of a charge generation layer containing copper phthalocyanine and a charge transport layer containing a hydrazone compound and a binder, (2) scanning the charged face with a laser beam, and (3) developing the resulting electrostatic latent image with a developer. A process for preparing an electrophotographic photosensitive member, comprises the steps of (1) applying a dispersion of copper phthalocyanine in a resin solution onto an aluminum cylinder by dip coating to form a charge generation layer and (2) applying a hydrazone compound dissolved in a resin solution onto the previously formed charge generation layer by dip coating to form a charge transport layer thereupon.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to electrophotographic photosensitive members and 
more particularly to those suited for electrophotographic printers 
employing a semiconductor laser as light source. 
2. Description of the Prior Art 
It suffices for a photosensitive member to be spectrally sensitized to 
light wavelength of about 650 nm or shorter when the light source used for 
operating is a gas laser such as a helium-cadmium laser (emission 
wavelength 441.6 nm) or a helium-neon laser (emission wavelength 632.8 
nm). As examples of such a photosensitive member, there are known (1) 
those using a charge transfer complex of polyvinylcarbazole with 
trinitrofluorenone for a photosensitive layer, (2) those employing a 
selenium-sensitized tellurium vacuum deposition layer as a photosensitive 
member, (3) those comprising a conductive layer, a charge transport layer 
of selenium vacuum-deposited on the conductive layer, and a 
selenium-tellurium layer vacuum-deposited on the charge transport layer, 
(4) those using cadmium sulfide spectrally sensitized with a pigment 
sensitizer, for a photosensitive layer, and (5) those comprising two 
separately functioning photosensitive layers: a charge generation layer, 
which contains an organic pigment to extend the sensible wavelength range 
to the longer side, and a charge transport layer. 
Meanwhile, semiconductor laser transmitters of small size and of low cost 
have been developed in recent years which additionally can be directly 
modulated. However, these semiconductor lasers in many cases have emission 
wavelengths of 750 nm or longer and the above-mentioned photosensitive 
members are insensitive at all or almost completely to the light of 750 nm 
or longer in wavelength, so that it is difficult to use semiconductor 
lasers for electrophotographic printers. 
Although attempts have been made to extend the maximum sensible wavelength 
of photosensitive members to 750 nm or longer by sensitization, these have 
the following disadvantages: The layer structure of photosensitive layer 
becomes complicated and setting of operational conditions in the 
production of photosensitive members becomes more difficult; sensitizing 
pigments or dyes used fade out during repetitions of light exposure and 
electric charging, and eventually image recording with semiconductor 
lasers becomes infeasible; and said photosensitive members comprising 
separately functioning charge generation and charge transport layers, 
although sensitized to extend their sensible wavelength range to the 
longer side, cannot obtain adequate sensitivity and exhibit undesirable 
photomemory, thereby causing various troubles. 
SUMMARY OF THE INVENTION 
The present invention has been achieved to solve the above mentioned 
problems. 
The primary object of this invention is to provide electrophotographic 
photosensitive members suitable for electrophotographic printers employing 
a laser as light source which are free from the foregoing disadvantages. 
An object of this invention is to provide electrophotographic 
photosensitive members suitable for electrophotographic printers employing 
a laser light source emitting a beam of wavelength 650 nm or longer. 
Another object of this invention is to provide electrophotographic 
photosensitive members suitable for electrophotographic printers employing 
a laser light source emitting a beam of wavelength 750 nm or longer. 
A further object of this invention is to provide electrophotographic 
photosensitive members highly sensitive to light beams of 750 nm and 
longer in wavelength. 
An even further object of this invention is to provide electrophotographic 
photosensitive members improved in respect to photomemory. 
According to one aspect of the present invention, there is provided an 
electrophotographic photosensitive member comprising a photosensitive 
layer having a laminated structure of charge generation and charge 
transport layers on a conductive substrate, which is characterized in that 
the charge generation layer contains a copper phthalocyanine pigment and 
the charge transport layer contains a hydrazone compound and a binder. 
According to another aspect of the present invention, there is provided a 
process for forming electrostatic latent images which comprises the steps 
of (1) giving electric charge to the face of an electrophotographic 
photosensitive member comprising a photosensitive layer having a laminated 
structure on a conductive substrate, said laminated structure consisting 
of a charge generation layer containing copper phthalocyanine and a charge 
transport layer containing a hydrazone compound and a binder and (2) 
scanning the charged face with a laser beam. 
According to a further aspect of the present invention, there is provided 
an image-forming process comprising the steps of (1) giving electric 
charge to the face of an electrophotographic photosensitive member having 
a photosensitive layer of a laminated structure on a conductive substrate, 
said laminated structure consisting of a charge generation layer 
containing copper phthalocyanine and a charge transport layer containing a 
hydrazone compound and a binder, (2) scanning the charged face with a 
laser beam, and (3) developing the resulting electrostatic latent image 
with a developer. 
According to still another aspect of the present invention, there is 
provided a process for preparing an electrophotographic photosensitive 
member, which comprises the steps of (1) applying a dispersion of copper 
phthalocyanine in a resin solution onto an aluminum cylinder by dip 
coating to form a charge generation layer and (2) applying a hydrazone 
compound dissolved in a resin solution onto the previously formed charge 
generation layer by dip coating to form a charge transport layer thereupon 
.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Electrophotographic printers utilizing a laser as light source can 
reproduce a desired image as follows: Original image information is 
converted into digital signals, a laser beam is modulated with electric 
signals varying in response to the digital signals, and a photosensitive 
member surface is scanned with this modulated laser beam by means of a 
galvanomirror or the like to form an electrostatic latent image, which is 
developed with a toner and than transferred to recording paper or the 
like. The lasers commonly used are gas lasers such as helium-cadmium laser 
(emission wavelength 441.6 nm) and helium-neon laser (emission wavelength 
632.8 nm) and a gallium-aluminum-arsenic semiconductor laser (emission 
wavelength 780 nm). 
This invention is characterized in that first place by incorporation of a 
copper phthalocyanine pigment into the charge generation layer. 
Of the various types of copper phthalocyanine used in this invention, the 
type .epsilon. is particularly preferred. The copper phthalocyanine of 
.epsilon. type can be prepared by the process described in Japanese Patent 
Publication No. 2780/1965, that is, by condensation of phthalic anhydride, 
copper or a copper salt, and urea or by condensation of phthalodinitrile, 
copper or a copper salt, and urea, in the presence or absence of a 
catalyst, wherein the condensation is carried out by adding phthalic 
anhydride or phthalodinitrile in limited amounts to a melt containing a 
large excess of urea (3-15 times the weight of phthalic anhydride or 
phthalodinitrile) and the product is subjected to the salt milling 
process. 
As shown in FIG. 1, such copper phthalocyanine of type .epsilon. exhibits 
X-ray diffraction angles (2.theta.), as measured with CuK.alpha./Ni by use 
of a Geiger counter-equipped X-ray diffraction apparatus (power method), 
which correspond to interplanar spacings of 11.63, 9.72, 6.24, 5.10, 4.35, 
4.19, 3.87, 3.36, 3.28, 3.19, and 3.03 .ANG.. This X-ray diffraction 
spectrum is different from those of copper phthalocyanines of types 
.alpha., .beta., and .gamma., and also of type X disclosed in U.S. Pat. 
No. 3,816,118; these spectra (2.theta.) are also shown in FIG. 1. 
The charge generation layer in this invention can be formed by means of 
various film-forming methods by coating of a dispersion of said pigment in 
a binder solution, preferably by coating, either directly on the 
conductive substrate or on an intermediary layer (undercoat) laid 
thereupon. It is also possible to form the charge generation layer on a 
charge transport layer, which will be described later in detail. In this 
case, the charge generation layer may be coated with a protective layer 
comprising a high polymer, for example, polyethylene, poly(vinyl 
chloride), poly(vinyl acetate), polycarbonates, polyesters, or poly(vinyl 
butyral). 
When the charge generation layer is formed by coating a dispersion of 
copper phthalocyanine, this dispersion is free from or contains a binder, 
for example, poly(vinyl butyral), poly(vinyl acetal), polyesters, 
polycarbonates, polyamides, polyurethanes, or phenolic resins. It is 
desirable that the binder resin content in the charge generation layer be 
restricted relatively low. In general, the weight ratio of the binder to 
copper phthalocyanine, in the charge generation layer, is 1:1-1:3 , 
preferably 1:1.5-1:25. In particular, the weight ratio of 1:ca. 2 gives 
best results. 
For dispering copper phthalocyanine, known means such as ball mills and 
attritors are available, whereby particle sizes of the pigment is made 
desirably 5.mu. or less, preferably 0.5.mu. or less. The dispersion of the 
pigment thus prepared is coated by any of coating methods of blade 
coating, Meyer-bar coating, spray coating, dip coating, curtain coating, 
bead coating, etc. Suitable thickness of the charge generation layer is up 
to 5.mu., preferably 0.01-1.mu.. 
The coating liquid for forming the charge generation layer also contains an 
organic solvent, which can be selected from a number of organic solvents. 
Typical examples of the solvents are aromatic hydrocarbons such as 
benzene, naphthalene, toluene, xylene, mesitylene, chlorobenzene, and the 
like; ketones such as acetone, 2-butanone, and the like; halogenated 
aliphatic hydrocarbons such as methylene chloride, chloroform, ethylene 
chloride, and the like; cyclic or linear ethers such as tetrahydrofuran, 
ethyl ether, and the like; and mixtures of these solvents. 
While types .alpha., .beta., .gamma., and X are known, besides type 
.epsilon., as crystal forms of phthalocyanine pigment, charge generation 
layers formed from copper phthalocyanine pigments of the types other than 
type .epsilon. have proved to generate less charge carriers as compared 
with a charge generation layer formed from the pigment of type .epsilon., 
when they are exposed to a laser beam of 750 nm or longer in wavelength. 
On the contrary, an electrophotographic photosensitive member having a 
charge generation layer containing copper phthalocyane of type .epsilon. 
is capable of injecting effectively electric charges into its charge 
transport layer, which are generated on exposure to a laser beam of 750 nm 
or in wavelength, and therefore can exhibit a high sensitivity. For 
choosing a charge transporting material used in this case, a great number 
of experiments are repeated in practice though an approach has been 
proposed which utilizes the ionization potential of a material to be used 
for charge transport as a measure. In particular, electrophotographic 
characteristics of photosensitive members, for example, the photomemory 
property, other than the sensitivity are nonpredictable at all. 
Thus, this invention is characterized in the second place by using a 
hydrazone compound-containing specific charge transport layer which faces 
the copper phthalocyanine-containing charge generation layer. This 
photosensitive layer of laminated structure exhibits an extremely high 
sensitivity to rays of 650 nm and longer, particularly 750 nm and longer, 
in wavelength and at the same time has an improved antiphotomemory 
property as compared with conventional photosensitive members, so far 
known, for use in laser printers. 
The charge transport layer in this invention is preferably formed by 
coating a solution of a hydrazone compound together with a binder in a 
suitable solvent and drying it. Binders used for this purpose include 
polysulfone, acrylic resins, methacrylic resins, vinyl chloride resin, 
vinyl acetate resin, phenolic resins, epoxy resins, polyester resins, 
alkyd resins, polycarbonates, polyurethanes, and copolymers comprising two 
or more kinds of repeating units of these resins, of which polyester 
resins and polycarbonates are preferred. A photoconductive polymer having 
in itself a charge-transporting ability such as poly(N-vinylcarbazole) can 
also be used as the binder. Blending ratios of the binder to the 
charge-transporting compound are preferably in the range 100:10-100:500 by 
weight. Thickness of the charge transport layer is in the range 2-100.mu., 
preferably 5-30.mu.. Coating methods applicable to the formation of the 
charge transport layer may be usual ones including blade coating, 
Meyer-bar coating, spray coating, dip coating, bead coating, air-knife 
coating, curtain coating, etc. 
Solvents used in the formation of the charge transport layer of this 
invention include a number of organic solvents. Typical examples thereof 
are aromatic hydrocarbons such as benzene, naphthalene, toluene, xylene, 
mesitylene, chlorobenzene, and the like; ketones such as acetone, 
2-butanone, and the like; halogenated aliphatic hydrocarbons such as 
methylene chloride, chloroform, ethylene chloride, and the like; cyclic or 
linear ethers such as tetrahydrofuran, ethyl ether, and the like; and 
mixtures of these solvents. 
Various additives can be incorporated into the charge transport layer of 
this invention. Such additives include diphenyl, chlorinated diphenyls, 
o-terphenyl, p-terphenyl, dibutyl phthalate, dimethyl glycol phthalate, 
dioctyl phthalate, triphenyl phosphate, methylnaphthalene, benzophenone, 
chlorinated paraffin, dilauryl thiodipropionate, 3,5-dinitrosalicyclic 
acid, various kinds of fluorocarbons, silicone oils, silicone rubbers, and 
phenolic compounds such as dibutyl hydroxytoluene, 
2,2'-methylene-bis(6-t-butyl-4-methylphenol), .alpha.-tocopherol, 
2-t-octyl-5-chlorohydroquinone, 2,5-di-t-octylhydroquinone, and the like. 
Hydrazone compounds particularly preferred in this invention are those 
represented by the formula 
##STR1## 
wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, and n are as follows: R.sub.1 
represents aryl such as phenyl or heterocyclic residue such as carbazolyl, 
furyl, pyridyl, benzimidazolyl, benzoxazolyl, benzothiazolyl, and the 
like. 
This aryl or heterocyclic residue is allowed to be substituted by alkyl 
such as methyl, ethyl, propyl, butyl, amyl and the like; alkoxy such as 
methoxy, ethoxy, propoxy, butoxy, and the like; di-substituted amino such 
as dimethylamino, diethylamino, dipropylamino, dibutylamino, 
dibenzylamino, diphenylamino, ditolylamino, dixylylamino, and the like; 
halogen such as chlorine, bromine, and the like; hydroxyl; or carboxyl. 
R.sub.1 especially suitable is the phenyl having a dialkylamino 
substituent at the 4-position. 
R.sub.2 represents hydrogen, aryl (e.g. phenyl, naphthyl, and the like), or 
substituted aryl (e.g. 4-dimethylaminophenyl, 4-diethylaminophenyl, 
4-dipropylaminophenyl, 4-methoxyphenyl, 4-ethoxyphenyl, 2-methylphenyl, 
2,4-dimethoxyphenyl, and the like). 
R.sub.3 and R.sub.4 represent alkyl such as methyl, ethyl, propyl, butyl, 
amyl, and the like; aryl such as phenyl, naphthyl, and the like; or 
aralkyl such as benzyl, phenethyl, and the like. And n is 0 or 1. 
Typical examples of the hydrazone compound used in this invention are 
numerated below. The following compounds also include the compounds other 
than ones represented by the aforesaid formula (1). 
Hydrazone compound: 
##STR2## 
These compounds can be used singly or in combination two or more. 
The electrophotographic photosensitive member of this invention can be 
prepared by forming the charge generation layer containing the foregoing 
dispersed phthalocyanine pigment in dispersion on a suitable substrate and 
laminating the charge transport layer containing the foregoing hydrazone 
compound, on the charge generation layer. As already stated, an 
intermediary layer can be formed between the charge generation and the 
conductive substrate. This intermediary layer inhibits the injection of 
free charges from the conductive substrate into the photosensitve layer, 
when the photosensitive layer of laminated structure is charged, and acts 
as an adhesive to fasten the photosensitive layer to the conductive 
substrate. The intermediary layer can be formed from aluminum oxide, 
indium oxide, tin oxide, an indium oxide-tin oxide mixture, polyethylene, 
polypropylene, acrylic resins, methacrylic resins, polyamide resins, vinyl 
chloride resin, vinyl acetate resin, phenolic resins, epoxy resins, 
polyester resins, alkyd resins, polycarbonates, polyurethanes, polyimide 
resins, vinylidene chloride resin, vinyl chloride-vinyl acetate copolymer, 
poly(vinyl alcohol), water-soluble copolymer of ethylene and acrylic acid, 
nitrocellulose, casein, gelatin, and the like. This layer can also be 
formed from a dispersion of conductive particles, for example, carbon 
black, silver particles, or aluminum particles, in a resin. With carbon 
black, in particular, it becomes possible to prevent the generation of an 
interference fringe upon forming the image. This interference fringe seems 
to be formed conceivably by the following mechanism: Since the thickness 
of the charge generation layer is as small as 0.01-1.mu., the quantity of 
laser beam absorbed in this layer is limited and the laser beam 
transmitted by this layer is reflected from the interface between this 
layer and the substrate; thus interference is caused between this 
reflected beam and the beam reflected from the surface of the 
photoconductive layer. When nd=integer x .lambda./2, wherein n is the 
refractive index of the photoconductive layer comprising the charge 
generation layer, d the thickness of the photoconductive layer, and 
.lambda. the wavelength of the layer beam, the intensity of reflected beam 
is maximum, that is, the intensity of beam entered the photoconductive 
layer is minimum. When n.alpha.=odd number x .lambda./4, the intensity of 
said reflected beam is minimum, that is, the intensity of said beam 
entered the photoconductive layer is maximum. On the other hand, while it 
is difficult that a variation in the thickness d of the photoconductive 
layer is suppressed to 0.2.mu. or less in the preparation of the 
photoconductive layer, laser beams are coherent and highly monochromatic. 
Accordingly, the conditions of said interference varies with the variation 
in d, and the intensity of the beam absorbed in the photoconductive layer 
is locally nonuniform, thus an interference fringe-like nonuniformity in 
image density appearing throughout the recording surface. 
Thickness of the intermediary or bond layer is in the range 0.1-5.mu., 
preferably 0.5-3.mu.. 
In the preparation of the electrophotographic photosensitive member of this 
invention, the surface of the charge generation layer may be subjected to 
mirror finishing as required for uniforming the injection of carriers from 
the charge generation layer into the upper charge transport layer. For 
example, the method disclosed in Japanese Patent Laid-Open No. 155356/1980 
can be applied to the mirror finishing. 
For the substrate in the electrophotographic photosensitive member of this 
invention, any kind of material that is provided with conductivity may be 
used; any type of conventional conductive substrate can be used. As 
example of the substrate may be cited metals such as aluminum, copper, 
stainless steel, bras, and the like; plastics on which aluminum, indium 
oxide, tin oxide, and the like is vacuum-deposited or laminated; and of 
resins in which conductive particles such as carbon black, silver 
particles, aluminum particles, and the like are dispersed. The shape of 
the substrate may be sheet-like, cylindrical, or of other form. 
When the electrophotographic photosensitive member of this invention is 
used, negative charges are given to the surface of the member, which is 
then scanned with an imaging laser beam, thereby an electrostatic latent 
image being formed on the surface. As stated before, laser beams available 
in this invention are those of helium-neon, helium-cadmium, 
semiconductors, etc. including those of long wavelengths, as 650 nm or 
longer, especially 750 nm or longer. The latent image-forming process is 
operated, for example, in the following way: As shown in FIG. 2, a 
semiconductor laser 1 is modulated with driving signals DS varying in 
response to the externally supplied image formation in the form of digital 
signals; the charged surface of photosensitive member 4 is scanned in the 
direction X with the modulated laser beam through an optical system 2 
comprising light deflectors such as an imaging lens, a galvanomirror, and 
the like, to form an electrostatic latent image. In FIG. 2, reference 
numeral 5 represents a charging unit and reference numeral 6 a developing 
unit. The electrostatic latent image thus formed is developed by a 
developer with a positive toner to form a visible image. 
The electrophotographic photosensitive member of this invention can be 
applied to processed using a laser as light source, for instance, to 
electrophotographic printing and electrophotographic printing-plate making 
systems. 
According to this invention, there are provided electrophotographic 
photosensitive members having markedly higher sensitivity to the light of 
750 nm or longer in wavelength as compared with the prior art 
electrophotographic photosensitive members for laser beams, and 
additionally being improved in anti-photomemory property. 
This invention will be illustrated in more detail with reference to the 
following Examples: 
EXAMPLE 1 
A solution of casein in aqueous ammonia (casein 11.2 g, 28% aqueous ammonia 
1 g, water 222 ml) was applied onto an aluminum cylinder by dip coating 
and dried to form an intermediate layer of 1.0 g/m.sup.2 in coating 
weight. 
Copper phthalocyanine of type .epsilon. (one part by weight, Lionol Blue 
ES, mfd. by Toyo Ink Manufacturing Co., Ltd.), a vinyl butyral resin (one 
part by weight, E slec BM-2, mfd. by Sekisui Chemical Co., Ltd.) and 
isopropanol (30 parts by weight) were dispersed in a ball mill for 4 
hours. The resulting dispersion was applied onto the previously formed 
intermediary layer by dip coating and dried to form a charge generation 
layer 0.3.mu. thick. 
Hydrazone compound No. 5 cited above (one part by weight) and a polysulfone 
resin (one part by weight, P 1700, mfd. by Union Carbide Corporation) were 
dissolved in monochlorobenzene (6 parts by weight) with stirring. This 
solution was applied onto the charge generation layer by dip coating and 
dried to form a charge transport layer 12.mu. thick. 
The photosensitive member thus prepared was corona-charged at a voltage of 
-5 KV to measure the initial surface potential V.sub.o and the dark decay 
potential V.sub.5 (the surface potential after 5-second standing in the 
dark). The sensitivity was evaluated with the exposure quantity for 
halving V.sub.5 (E 1/2 microjoule/cm.sup.2). Gallium-Aluminum-arsenic 
semiconductor laser (emission wavelength 780 nm) was used as the light 
source in this case. The photomemory property (P.sub.M) was evaluated with 
the time necessary for the photosensitive member to recover its original 
charge bearing characteristics after exposure thereof at an intensity of 
600 lux for 3 minutes. Results thereof are shown in Table 1. 
TABLE 1 
______________________________________ 
V.sub.o -600 volt 
V.sub.5 -580 volt 
P.sub.M 2 minutes 
E1/2 0.6 microjoule/cm.sup.2 
______________________________________ 
After corona charging at -5 KV, the photosensitive member was scanned with 
an imaging beam of gallium-aluminum-arsenic semiconductor laser, and 
subjected to magnetic brush development with a developer containing iron 
powder and a positive-working toner prepared from an epoxy resin, carbon, 
and Nigrosine, while applying a developing bias. The toner image was 
corona-transferred at -4.5 KV onto plain paper and fixed in an oven 
heater, giving a copy having no stain in the ground, with high fidelity to 
the original image information. 
EXAMPLE 2 
A photosensitive member was prepared and measured for its photographic 
characteristics, in the same manner as in Example 1 except for using 
copper phthalocyanine of type .beta. (Lionol Blue NCB Toner, mfd. by Toyo 
Ink Manufacturing Co., Ltd.) in place of the copper phthalocyanine of type 
.epsilon.. Results thereof are shown in Table 2. 
TABLE 2 
______________________________________ 
V.sub.o -600 volt 
V.sub.5 -580 volt 
V.sub.M 10 minutes 
E1/2 8.2 microjoule/cm.sup.2 
______________________________________ 
EXAMPLES 3-14 
Photosensitive members were prepared and measured for photographic 
characteristics thereof, in the same manner as in Example 1 except for 
using the individual hydrazone compounds shown in Table 3 in place of the 
hydrazone compound used in Example 1. Results thereof are shown also in 
Table 3. 
TABLE 3 
______________________________________ 
Hydrazone E1/2 
Example 
compound V.sub.o V.sub.5 
P.sub.M 
(microjoule/ 
No. No. (volt) (volt) 
(min.) 
cm.sup.2) 
______________________________________ 
3 No. (4) -600 -570 2 0.3 
4 No. (6) -620 -600 2 0.8 
5 No. (7) -610 -580 2 0.6 
6 No. (8) -600 -580 2 0.4 
7 No. (9) -580 -560 2 1.5 
8 No. (10) -570 -550 3 0.6 
9 No. (11) -590 -570 3 0.4 
10 No. (13) -570 -550 5 1.1 
11 No. (15) -560 -550 4 0.6 
12 No. (16) -560 -540 5 0.7 
13 No. (17) -570 -550 5 0.7 
14 No. (18) -560 -540 4 1.3 
______________________________________ 
Comparative Examples 1-5 
Photosensitive members were prepared and measured for photographic 
characteristics thereof, in the same manner as in Example 1 except for 
using the known charge-transporting compounds shown in Table 4 in place of 
the hydrazone compound used in Example 1. Results thereof are shown in 
Table 5. 
TABLE 4 
______________________________________ 
Comparative 
Example No. 
Charge-transporting compound 
______________________________________ 
##STR3## 
2 
##STR4## 
3 
##STR5## 
4 
##STR6## 
5 
##STR7## 
______________________________________ 
TABLE 5 
______________________________________ 
Comparative 
V.sub.o V.sub.5 P.sub.M 
E1/2 
Example No. 
(volt) (volt) (min.) 
(microjoule/cm.sup.2) 
______________________________________ 
1 -350 -240 40 13.5 
2 -380 -260 40 5.0 
3 -320 -220 35 11.2 
4 -330 -210 40 9.8 
5 -390 -300 30 7.5 
______________________________________ 
As can be seen from the foregoing Example and Comparative Examples, the 
electrophotographic photosensitive member of this invention has a 
remarkably high sensitivity to the light of 750 nm or longer in 
wavelength, excellent charge bearing characteristics such as the initial 
potential, the dark decay and the like, and an improved anti-photomemory 
property. 
EXAMPLE 15 
A photosensitive member was prepared and used for image formation, as in 
Example 1 except for dispersing carbon black in the intermediary layer. As 
a result, no interference fringe-like pattern appeared. 
EXAMPLE 16 
A photosensitive member was prepared and measured for photographic 
characteristics, in the same manner as in Example 1 except that the vinyl 
butyral resin was used in a proportion of 2 parts by weight in stead of 
one part by weight in the dispersion to form the charge generation layer 
and the thickness of this layer was 0.1.mu. in stead of 0.3.mu.. Results 
thereof are shown in Table 6. 
TABLE 6 
______________________________________ 
V.sub.o -600 volt 
V.sub.5 -570 volt 
P.sub.M 3 minutes 
E1/2 0.5 microjoule/cm.sup.2 
______________________________________