JPH01134461A - Electrophotographic sensitive body and manufacture of same - Google Patents

Abstract

PURPOSE:To obtain a superior electrophotographic sensitive body having electrophotographic characteristics of high sensitivity by forming an electric charge transfer layer made of a straight chain polymer and regulating its kinetic viscoelasticity to a specified value or less at a temperature of its glass transition point or lower. CONSTITUTION:The charge transfer layer 2 formed on a substrate 1 is made of the straight chain polymer having p-phenylene units substituted by at least one of atoms. of S, Se, and Te of group VIb at the para position, and having a kinetic viscoelasticity of <=1.0X10<1theta>dyne/cm<2> at a temperature of 200 deg.C of the glass transition point of said polymer or lower, and a photoconductive layer 3 having a free surface 4, and formed on the layer 2 contains an organic semiconductor, thus permitting 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 material combinations include amorphous selenium and polyvinylcarbazole, methyl squarate and triaryl (Labrin 1
．． Examples include Diane blue and oxadiazole, perylene pigment and oxadiazole, bisazo pigment and methylanthracene, etc.

Also, as a device that utilizes an amorphous layer, JP-A-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 these flat materials, PPS (poly P-phenylene sulfide) has been proposed as a material that exhibits high hole mobility and excellent thermal properties for the charge transport layer. (Unexamined Japanese Patent Publication No. 6
(No. 0-59353) However, the general V P P S,
Since it has high resistance, 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. A sheathing of the charge generating layer is desirable.

However, even if the respective requirements are satisfied, carrier injection between the two must be performed efficiently.

In addition, the charge acceptance ability required in the electrophotographic process,
It must be more than satisfactory in terms of wear resistance, environmental resistance, etc.

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 comprises P-phenylene. , composed of a linear compound polymer layer having a VIb group element at the para position, and S, S e-T as the VIb group element.
The dynamic viscoelasticity at 200° C., which is higher than the glass transition temperature, is 1.
OX 1011ildyne/cm2 or less.

The mechanism of carrier mobility or lifetime improvement in working polymers is thought to be as follows.

Carrier movement in polymers is carried out by hopping conduction of electron orbits along the main chain direction of the polymer, and the carrier mobility increases as the overlap between adjacent orbitals increases, and the probability of hopping increases. do. In a polymer with a structure having P-phenylene in the main chain direction and a group VIb element in the para position.

In the VIb group element state, when adjacent P-phenylenes are in a coordination state in which the π electron orbits are perpendicular to each other in space, the mobility is small. However, when the VIb group element is positively charged and ionized, the spatial twist of P-phenylene is resolved, and the π electron orbits are arranged in the same plane, increasing the hopping probability and improving the mobility. it is conceivable that.

By the way, the carrier electromotive force between the main chains is greatly affected by the spatial coordination of the main chains of the polymer. The degree to which the unprecedented coordination of the main chain is determined depends on the crystallinity when viewed microscopically.
and the ratio of crystalline and non-crystalline parts when viewed macroscopically differs greatly. In any case, improvement in crystallinity is linked to improvement in mobility.

Conversely, bridges are a factor that prevents crystalline coordination in the front of the main chain. The bridging points act as fixed points for the coordination relaxation of the main chain and act as deep traps during carrier electrolysis, reducing mobility.

Here, the crystallinity, which improves mobility, and the degree of crosslinking, which conversely reduces it, both affect the elastic modulus. The value of the elastic modulus above the glass transition temperature (in the present invention, a typical temperature of 200° C.) increases both with an increase in crystallinity and an increase in the degree of crosslinking. In the polymer of the present invention having a structure having a group VIb element at the para position, the crosslinking reaction via the group VIb element is likely to proceed and the degree of crosslinking is greatly influenced. Therefore, it is considered that the lower the elastic modulus of the bridge, which indicates the lower the elasticity, the higher the mobility.

Various electron-accepting additives that ionize Group VIb elements at the para position are known, but when the amount added is increased to increase the mobility, the mobility increases beyond a certain - quantitative level. begins to decrease. 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. Naturally, a significant increase in the elastic modulus is seen. Therefore, without destroying the main chain structure of PPS, V at the para position can be
It is necessary to ionize the Ib group elements.

This has become possible with zero atoms. Furthermore, by superimposing a small amount of other electron acceptors in this state, the effect of improving mobility can be enhanced without causing a significant increase in carrier concentration.

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 is a support as an electrophotographic photoreceptor! It has a charge transport layer 2 made of a polymer layer and a photoconductive layer 3 containing an organic semiconductor layer thereon, and the photoconductive layer Fj3
has a free surface 4 on the one hand.

At this time, the thickness of the charge transport layer is 5 to 5071 m, preferably 10 to 2571 m, and the thickness of the photoconductive layer is 0.2 to 10 m.
71 m is preferably 0.5 to 5 It m.

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 properties, in FIG. 1, between the support l and the charge transport layer 2,
A barrier layer may be provided to effectively prevent carriers from being injected into the charge transport layer 2 from the support l.

Materials for forming the barrier layer include Al2O3 and BaO3.
"a02, Be01Ri2(h, CaO1Ce02, C
e2O3, La2O3, 0y201, Lu2Q3, Cr
+03, CuO1Cu 20, FeO1PbO1M80
, SrO, Ta2O3, Th02, z"02.1lf0
2, T i 02, Ti05Si02, GeO2, S+
0- Metal oxides such as GeO or TiN, AIN,
Metal nitrides such as SnN, NbN, TaN%GaN, etc., metal carbides such as VC, SnC, TiC1, etc., or insulators such as SiC, SiN, Gi, GeN% BC, BN, polyimide, polyamideimide, polyacrylonitrile, etc. Organic compounds are used that have a heat resistance of .

Furthermore, in order to improve cleaning properties, abrasion resistance, or corona resistance, a surface coating layer is formed on the free surface 4 in the figure. Suitable materials for the surface coating layer include 5lxO+-xs 5IXCI-X, S+xN+
-x, Gex O+-X, GexC+-x, GexN+
-x-BxN+ -x, nfCI-1AlxN+-x(
0<x<1), carbon atoms, and inorganic materials such as 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. It may also be a method of wearing.

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

The charge acceptors to be added are I2, Br2, Ct2,
ICI, rBr, (NO2) B F4, (N O
2) PFs, (N02) S b Fe, HCI O
a, H2S 04, HNO3, H5Oa-1A g C
l 04, Fe(ClO2), RF3, FeCl3, F
eBr3, AlCl3, InCl3, I n Ii, Z
rCIa, HfCl a, Tec14, TeBr4,
TeTa, 5nC14, SnI4.5eC14, TiC
l4, TiF4, FeCl4-1AIC14-1AsF
s, 5l) Fs, NbCIs, N b Fs, TaCl
5, TaTs, MoCl5, ReFe, IrC15, I
nFe, UF6.0sFe, XeF6, TeFs, SF
Examples include 6.5eFe, W F s, WCl5, and ReFy.

As the organic semiconductor of the charge generation layer, (1) Phthalocyanine pigment (referred to as Pc), for example, metal-free Pc, XPc
(X=Cu, Ni, Co, TiO, Mg, Si
(OH)p, etc.), AlClPcC1, Ti0clPc
cl, InClPcCl, InClPc, InBrPc
Br et al. 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) anthraquinones,
Polycyclic quinones such as pyrenequinones (7) Cyanine dyes (
8) Xanthine dyes (9) Charge transfer complexes such as PVK/TNF (10) Eutectic complexes formed from biryllium salt dyes and polycarbonate resins (11) Azulenium salt compounds.

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.

The charge generation layer and the non-single crystal layer include Se, 5eTe, AS2Se3. CdS
, etc., the amorphous layer has at least one of silicon, germanium, and carbon as a main component and contains a modification (for example, hydrogen, halogen) that reduces the two-localized position density.

For forming these films, a plasma CvD method using plasma, an ECR method, an ordinary sputtering method, a vacuum evaporation method, etc. are used.

Example 1 A film-shaped PPS (poly p-phenylene
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 closing time during the heat treatment was kept constant for 3 hours. After this process,
The thickness of the PPS film was 10 to 25 μm.

At this point, the elastic loss of the film was determined by dynamic viscoelasticity measurements. As the heating temperature was increased under a constant closed condition during heat treatment, the vitrification temperature shifted to lower temperatures and the dynamic viscoelastic modulus decreased. 1 at 285°C. IX 10”dy
n/cnr', 0.9X 10"dyn/ at 300℃
cII+2゜0.63X 10I8dyn/at 320℃
0.20X 10'” dynl at co12.350℃
cII+2, and it was expected that at 285°C, there would be a considerable number of bridging points remaining.

These layers were made into a charge transport layer and a charge generation layer using a phthalocyanine compound of 0.05 to 5.0 μm by vacuum deposition.
II+ laminated. Ti0Pc, MgPc by coating method as phthalocyanine compounds, Cu by vacuum evaporation method
Pc, , AIC, lPcC1 was performed.

6. These electrophotographic photoreceptors. When charged with corona at OkV, the dynamic viscoelasticity of the charge transport layer was 0.63X 10
'gdyn/c+++2, it is possible to obtain a surface potential of +1500V, and when exposed to white light, the residual potential is less than +50V, and the half-exposure layer is less than 1.01x-s, showing very excellent electrophotographic properties. Ta. However, as the value of dynamic viscoelasticity increases, both the residual potential and the half-exposure layer tend to deteriorate, and the residual potential was as high as 200 V after heat treatment at 285°C. Further, the difference in the charge generation layer at this time was secondary, and all of the above four types showed good characteristics. A compositional analysis of this electrophotographic photoreceptor revealed that the composition ratio of O atoms to C atoms contained in the charge transport layer heat-treated at 300° C. was 12 atm %.

Example 2 When forming the 8 charge generating layers, T CN Q (7,7,8,8,-tetracyanoquinodimethane) was added as an electron acceptor simultaneously with the fusing process. PPS, the raw material
The film was added in an amount of 5% by weight to a thickness of 25 μm, and heat-treated in an oxygen atmosphere under the same conditions as in Example 1 to obtain a charge transport layer. The dynamic viscoelasticity of the film at this time is
Although it increases slightly with the addition of TCNQ, 1. OX 10' was below 8dyn/cn+2. An azulenium salt compound was used for the charge generation layer. 1. 4-Dimethyl-7-itubrobyl azulene and P-dimethylaminocinnamaldehyde were dissolved in tetrahydrofuran, and acid (HX, X” CI Oa, BF
a, B'', l) are reacted while cooling to below 10°C, and this solution is dried at 60°C to form an azulenium salt compound.
1-(P-Dimethylaminocinnamylidene>-5-isopropyl-3,8-dimethylazurenium salt was obtained. This was mixed with butyral resin and dispersed in butyl acetate, and then O01~! was applied on the charge transport layer. After coating 5.0 layers, it was dried at 70°C.

Azulenium salt has excellent photoconductivity in a wavelength range of 400 to 9000 m, has a sensitivity peak in a long wavelength of 700 nm or more, and is suitable for printers using semiconductor lasers as light sources. Among the above four types of azulenium salts, those containing I (iodine) as an acid have a resistance of 0 to white light.
．． 71xs 0.41 for 800nm red light
It showed a good sensitivity of xs.

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 rose position. It is a linear compound polymer layer having S, Se, Te, as group VIb elements.
contains at least one of the following, and has a dynamic viscoelasticity of 1 at 200°C, which is higher than its glass transition temperature, OX
By setting it to 10'θdyne/cm2 or less, an electrophotographic photoreceptor with high sensitivity and low residual potential can be obtained. Furthermore, the charge transport 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. 1...Support, 2...Charge transport layer, 3...
Charge generation layer, 4...free surface.

Claims (6)

[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, The group VIb elements include S, Se, and T.
e, and has a dynamic viscoelasticity of 1.0 at 200°C, which is higher than its glass transition temperature
An electrophotographic photoreceptor characterized in that it is not more than ×10^1^θdyne/cm^2. (2) The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer contains O atoms. (3) The electrophotographic photoreceptor according to claim 2, wherein the atomic ratio of O atoms to C atoms in the charge transport layer is 1 to 35 atm %. (4) The electrophotographic photoreceptor according to claim 2, wherein an electron acceptor is added to the charge transport layer. (5) a photoconductive layer that generates carriers by photoexcitation;
A functionally separated electrophotographic photoreceptor comprising a charge transport layer for transporting carriers, the charge transport layer comprising a linear compound polymer layer containing P-phenylene and a group VIb element at the para position. Yes, and the group VIb elements include S, Se, and T.
e, and has a dynamic viscoelasticity of 1.0 at 200°C, which is higher than its glass transition temperature
×10^1^θdyne/cm^2 or less, the method for manufacturing an electrophotographic photoreceptor, characterized in that the step of forming the charge transport layer includes heat treatment in an atmosphere containing oxygen. Method of manufacturing a photoreceptor. (6) The method for manufacturing an electrophotographic photoreceptor according to claim 5, wherein the heating temperature of the heat treatment in an oxygen-containing atmosphere is in the range of 200 to 350°C.