JPH01134460A - Electrophotographic sensitive body and manufacture of same - Google Patents

Abstract

PURPOSE:To enhance sensitivity and to lower residual potential by forming an electric charge transfer layer made of a straight chain polymer having p- phenylene units substituted by at least one of S, Se, and Te as the atom. of group VIb, further, combined with O atom., and a charge generating layer containing an organic semiconductor. CONSTITUTION:The charge transfer layer 2 formed on a substrate 1 is made of the straight chain polymer arranged in the main chain direction having the p-phenylene units substituted by at least one of atoms. of S, Se, and Te of group VIb at the para position, further combined with the O atom. and a charge generating layer 3 having a free surface 4, and formed on the layer 2 contains an organic semiconductor, thus permitting probability of hopping to be increased and mobility to be enhanced by adding the O atom., the charge generating layer 3 to be less damaged at the time of forming a film, and the film to be made at low cost by using the organic semiconductor, and consequently, electrophotographic characteristics to be improved, that is, sensitivity to be enhanced and residual potential to be lowered.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor used in electrophotographic copying machines, optical printers, and the like.

2. Description of the Related Art Among electrophotographic photoreceptors, functionally separated electrophotographic photoreceptors are widely used in which carrier generation by photoexcitation and carrier transport are made of different materials.

By selecting materials according to their functions in this way, we can provide excellent photoreceptors with highly sensitive electrophotographic properties. In addition, the optimal combination of materials has been studied from a wide variety of aspects, including mechanical strength, thermal stability, printing durability, environmental resistance, and manufacturing cost. Typical examples of such combinations of materials include amorphous selenium and polyvinylcarbazole, methyl squarate and triarylpyrazoline,
Examples include Diane blue and oxadiazole, perylene pigment and oxadiazole, bisazo pigment and methylanthracene, etc.

In addition, as a method using an amorphous layer, Japanese Patent Application Laid-Open No. 54-14
No. 3645 proposes a functionally separated photoreceptor using an organic semiconductor material, and Japanese Patent Application Laid-open No. 56-24355 proposes a functionally separated photoreceptor using an inorganic semiconductor material. Furthermore, we have proposed a functionally separated photoreceptor in which the charge transport layer is made of amorphous carbon and the charge generation layer is made of amorphous silicon.

Among such materials, PPS (poly P-phenylene sulfide) has been proposed as a material with high hole mobility and excellent heat resistance for the charge transport layer. (Unexamined Japanese Patent Publication No. 6
(Publication No. 1-59353) However, PPS usually has a high resistance, and it is necessary to find some way to improve its mobility.

Problems to be Solved by the Invention In order to achieve higher sensitivity in a function-separated electrophotographic photoreceptor, a charge transport layer with a smaller dielectric constant and greater mobility and a high charge generation ability are required. Combinations of charge generating layers are desirable.

However, even if the required conditions are satisfied.

Carrier injection must be carried out efficiently in both the injectors. It must also fully satisfy the charge-accepting ability, abrasion resistance, environmental resistance, etc. required in the electrophotographic process.

PPS is known as an insulator with excellent heat resistance, mechanical strength, and high electrical resistance, and is used as a plastic agent and a sealing material. On the other hand, the use of conductive materials is also attracting attention, and it is well known that conductivity can be significantly improved by adding electron-accepting materials. At this time, the mobility also improved and it was expected that it could be applied to the charge transport layer of electrophotographic photoreceptors, but as the electrical resistance decreased due to the increase in carrier concentration, it did not have the required charge-accepting ability and was not improved. was desired.

JP-A No. 60-59353 describes the thinning and formation of a transport layer by the vacuum evaporation method of PPS.
Generally, in this state, mobility is low, and both sensitivity and residual potential are poor.

In addition to having a high charge generation ability as a charge generation layer, it must also have good carrier injection efficiency into the charge transport layer. Furthermore, it is desirable that the method for forming it be inexpensive.

Means for Solving the Problems In a functionally separated electrophotographic photoreceptor comprising a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports the carriers, the charge transport layer contains P-phenylene. , a linear soft compound polymer layer having a group VIb element at the para position, and the group VIb elements include S, Se,
The charge generation layer contains at least one of Te and further contains 0 atoms, and the charge generation layer contains an organic semiconductor.

Effect A polymer layer mainly composed of a linear compound containing P-phenylene and a chalcogen element at the para position, such as PPS, is heated in an atmosphere containing oxygen atoms to generate electric charges. The significant improvement in transportation capacity has not been sufficiently analyzed at present. However, at this point, we can think of the following.

Carrier movement in polymers occurs through hopping conduction between electron orbits along the main chain direction of the polymer, and the carrier mobility increases as the overlap between adjacent orbitals increases, increasing the probability of hopping. do. When the VIb group element is in a neutral state in a polymer having a structure of P-phenylene in the main chain direction and a VIb group element in the para position, the adjacent P-phenylene spatially has a π electron orbital. , are in orthogonal coordination states and have low mobility. However, when the VIb group element is positively charged by the added O atoms and ionized, the spatial twist of P-phenylene is resolved, and the π electron orbitals are arranged in the same plane, increasing the hopping probability and improving the mobility. It is thought that this will be achieved.

On the other hand, various electron-accepting additives are known, but when the amount added is increased to increase mobility, the mobility begins to decrease after a certain amount. This phenomenon occurs because the main chain structure of PPS is destroyed by the oxidation effect of the added electron acceptor, and the number of new crosslinked structures having a structure that acts as a carrier trap increases significantly. At this time, the electrical resistance also decreases due to the increase in carrier concentration, and the charge retention ability deteriorates. Therefore, it is necessary to ionize the VIb group element at the para position without destroying the main chain structure of PPS. This has become possible with zero atoms. Furthermore, by incorporating a small amount of other electron acceptors in this state, the effect of improving mobility can be increased without causing a significant increase in carrier concentration.

By using an organic semiconductor for the charge generation layer, there is a vacuum evaporation method that causes less damage to the interface during film formation, and a dip method that allows lamination without any increase in thickness, and each method is inexpensive. I can do it. In these methods, interface traps, which are the biggest hindrance to carrier injection at the interface, are less likely to be induced, and both sensitivity and residual potential in electrophotographic characteristics are improved.

The embodiment diagram schematically shows a cross section of an embodiment of a basic electrophotographic photoreceptor according to the present invention.

The electrophotographic photoreceptor shown in the figure has a charge transfer layer 2 made of a polymer layer and a photoconductive layer 3 containing an organic semiconductor layer on a support i as an electrophotographic photoreceptor, and the photoconductive layer 3 has a free surface 4 on the one hand.

At this time, the thickness of the charge transfer layer is 5 to 50 μm, preferably 1 μm.
0 to 25 μm, and the thickness of the photoconductive layer is 0.2 to IO μm
The intestine size is preferably 0.5 to 5 μm.

In the present invention, the conductive support may be made of a metal material, such as aluminum, or may be coated with a metal material.

In the present invention, in order to further improve the electrophotographic characteristics, in FIG. 1, between the support l and the charge transfer layer 2,
A barrier layer may be provided to effectively prevent carriers from being injected from the support 1 into the charge transfer layer 2.

Materials for forming the barrier layer include A I 203, Ba
OlRam2, Be0%R12(h, CaO1Ce02
, Ce2O3, La2O3, Dy20a, Lu2O3
, Cr20q, Cub, Cu2O, Fed, pb
oNMgO.

5rO1Ta203, Th02, ZrO2, )lf02
, TiO2, Ti01Si02, GeO2,5iO1G
Metal oxides such as eO or TiN, AIN, SnN
, NbN, TaN, GaN, or other metal nitrides, or WC, SnC, TiC, or other metal carbides, or SiC.
, SiN, GK, GeN, BC, and ON, and heat-resistant organic compounds such as polyimide, polyamideimide, and polyacrylonitrile are used.

Further, in order to improve cleaning properties, abrasion resistance, or corona resistance, a surface coating layer is formed on the free surface 4-A in the figure. Suitable materials for the surface coating layer include S+xO+-t, SiA-C1-S! xN+
-xx GexO+-x%GexC+-xx Ge
xNl-xs BxN+-x-B-C+--1^IX
Examples include inorganic materials such as NI-X (0<X<1), carhorn, and layers containing hydrogen or halogen.

PPS, which is the main raw material for the charge transport layer, can be formed directly on the substrate surface using a vacuum evaporation method, ion cluster beam method, etc. from powder, or it can be formed into a film by extruding the powder and then melted onto the substrate surface. You may also use the printing method.

At this time, a predetermined amount of an electron-accepting additive may be mixed in advance.

The charge acceptors to be added are: ■2, Br2, C12,
ICL IBr, (N 02) B F4, (NO
2) PFs, (NO2) S b Fs, HCI O
n, H2S Oa, HNO3, H5Oa-1A g C
I Os, Fe (ClO2), BFi, FeCl:+
, FeBr3, AlCl3, InCl3, InI3, Z
rCl4, HfCIa, Tecla, TeBrn, Te
ra, 5nCIJ, Sit■4, 5eC1a, TiC
l4, TiI4, FeCl4-1A ICl a-
1ASF5, S b Fs, NbCl5, N t)
Fs, TaCl5, Tal5, MoCl5, R
eF6, IrC15, InFe, UFe, 0sFe
, XeF6, T e Fe, SFs, S e F
s, WF6, WCle, ReF7, etc.

As the organic semiconductor of the charge generation layer, (1) phthalocyanine pigment (referred to as Pc) such as metal-free Pc, XPc (
X=Cu, Ni, Co, TiO, Mg% 5i(OH)
2, etc.), AlClPcC1, Ti0clPccl, T
nCIPcCl, InClPc, InBrPcBr
etc. Furthermore, (2) azo dyes such as monoazo dyes and disazo dyes, (3) penylene pigments such as penylene acid anhydride and penylene acid imide, (4) indigoid dyes (5)
) Quinacridone pigments (6) Polycyclic quinones such as anthraquinones and pyrenequinones (7) Cyanine dyes (8) Xanthine dyes (9) Charge transfer complexes such as PVK/TNF (1)
0) Eutectic complex formed from biryllium salt dye and polycarbonate resin (11) Azulenium salt compound, etc.

A vacuum evaporation method, a dip method, an ion cluster beam method, an electrodeposition method, etc. are used to form films of these organic semiconductors.

Example 1 A film of swollen PPS (poly p-phenylene) having S as the
sulfide), wrap the fluororesin sheet from the top of the film, heat it in a heat treatment furnace, and then
The film was fused onto an aluminum substrate. The heating temperature is higher than the melting temperature of PPS, 285°C.
The temperature was 0° C., and the heating atmosphere was air. After taking out the substrate from the heat treatment furnace, the fluororesin sheet was removed, placed in the heat treatment furnace again, and heat treated in an oxygen atmosphere. The heating temperature was controlled within the range of 285°C to 350°C, and the heating treatment time was kept constant at 3 o'clock. After this process,
The thickness of the PPS film was 10 to 25 μm. This layer was used as a charge transport layer, and as a charge generation layer, a phthalocyanine compound was laminated to a thickness of 0.05 to 5.0 μm by vacuum evaporation. T by coating method as a phthalocyanine compound
i0Pc.

MgPc, CuPc by vacuum evaporation method, AlClPcC
I did l.

When these electrophotographic photoreceptors were corona charged at 6.0 kV, a surface potential of +1500 V could be obtained with a charge transport layer having a thickness of 2011111, and when exposed to white light, the residual potential was +50 V or less, The half-reduced exposure amount is 1
．． It showed very excellent electrophotographic properties with a value of 0 Ix-s or less. A compositional analysis of this electrophotographic photoreceptor revealed that the composition ratio of O atoms to C atoms contained in the charge transport layer was 12 atm %.

For comparison, heat treatment after fusion of PPS film was performed at 0-
This was carried out under a reduced pressure of I Torr or less to obtain a charge transport layer in which the number of O atoms was 1 ata+% or less relative to C atoms, and a phthalocyanine compound was formed as a charge generation layer in the same manner as described above. The characteristics of this electrophotographic photoreceptor are that the residual potential is +400v.
As mentioned above, the half-reduced exposure amount was 1501x-s or more, which was poor. Furthermore, when the number of O atoms in the film was changed to 50 atm% during heat treatment in an oxygen atmosphere, it was 1 to 35 atm%.
Up to +%, the residual potential was +50 V or less, which showed electrophotographic properties with no practical problems.

Example 2 When forming a charge generation layer, T CN Q (7,7,8,8,-tetracyanoquinodimethane) was added as an electron acceptor at the same time as the fusion treatment. A charge transport layer was prepared by adding 5% by weight to the raw material PPS film, making the film thickness 25 μm, and subjecting it to heat treatment in an oxygen atmosphere under the same conditions as in Example 1. An azulenium salt compound was used for the charge generation layer.

1. Dissolve 4-dimethyl-7-itubrobyl azulene and P-dimethylaminocinnamaldehyde in tetrahydrofuranic acid (HX, X = CI Oa, BF4
, Br, [) are reacted while cooling to 10°C or less,
This solution was dried at 60°C to form an azulenium salt compound 1.
-(P-dimethylaminocinnamylidene)-5-isopropyl-3,8-dimethylazulenium salt was obtained. This was mixed with a butyral resin and dispersed in butyl acetate, and then coated on the charge transport layer in an amount of O91-5.0/j'll and dried at 70°C.

Azulenium salt has excellent photoconductivity in the wavelength range of 400 to 900 rv+, has a sensitivity peak in a long wavelength of 700 r+m or more, and can be applied to a printer using a semiconductor laser as a light source. Among the above four types of azulenium salts, those containing I (iodine) as an acid are
It showed good sensitivity as L41xs.

Effects of the Invention In a functionally separated electrophotographic photoreceptor consisting of a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transfers the carriers, the charge transport layer has P-phenylene and a group VIb element at the para position. It is a linear compound polymer layer having S, Se, Te, as group VIb elements.
By containing at least one of the following, further containing 0 atoms, and using an organic semiconductor in the charge generation layer, an electrophotographic photoreceptor with high sensitivity and low residual potential can be obtained.

Furthermore, both the charge transport layer and the charge generation layer can be formed by polymer fusing, coating, or vapor deposition, making it possible to provide an inexpensive electrophotographic photoreceptor. Furthermore, since the charge transport layer is made of a heat-resistant thermosetting polymer, it has excellent stability and printing durability.

[Brief explanation of the drawing]

The figure is a sectional view of an electrophotographic photoreceptor in an example of the present invention. l...Support, 2...Charge transport layer, 3...
Charge generation layer, 4...free surface.

Claims (1)

[Claims] (1) A photoconductive layer that generates carriers by photoexcitation;
In a functionally separated electrophotographic photoreceptor comprising a charge transport layer that transports carriers, the charge transport layer is a linear compound polymer layer containing P-phenylene and a group VIb element at the para position, Group VIb elements include S, Se, Te,
An electrophotographic photoreceptor comprising at least one of the following, further comprising an O atom, and the charge generation layer comprising an organic semiconductor. (2) The electrophotographic photoreceptor (3) charge transport layer according to claim 1, wherein the ratio of O atoms to C atoms in the charge transport layer is 1 to 35 atm%. 3. The electrophotographic photoreceptor according to claim 2, further comprising an electron acceptor. (4) a photoconductive layer that generates carriers by photoexcitation;
A functionally separated type consisting of a charge transport layer that transports carriers, the charge transport layer having P-phenylene,
A linear compound polymer layer having a group VIb element at the para position, containing at least one of S, Se, Te, as a group VIb element, and further containing an O atom,
A method for producing an electrophotographic photoreceptor in which the charge generation layer contains an organic semiconductor, wherein the step of forming the charge transport layer includes heat treatment in an atmosphere containing oxygen. Method. (5) The method for manufacturing an electrophotographic photoreceptor according to claim 4, wherein the heating temperature of the heat treatment in an oxygen-containing atmosphere is in the range of 200 to 350°C.