JPH01134458A - electrophotographic photoreceptor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

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 a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transports carriers are made of different materials. By selecting materials according to function in this way, we can not only provide an excellent photoreceptor with highly sensitive electrophotographic properties, but also improve mechanical strength, thermal stability, printing durability,
You can consider the optimal combination from a wide range of materials in terms of environmental resistance, manufacturing cost, and other aspects.

Typical examples of such material combinations using organic materials include methyl squarate and triarylpyrazoline, diampurus and oxadiazole, perylene pigment and oxadiazole, bisazo pigment and methylanthrazoline. Sen et al.

Further, as an example of using an inorganic material as a photoconductive layer, amorphous selenium and polyvinyl carbazole, JP-A-54-1436
No. 45 discloses a functionally separated photoreceptor using an amorphous silicon-based photoconductive layer and an organic semiconductor material as a charge transport layer, and JP-A-56-24355 discloses a photoreceptor using an inorganic semiconductor material as a charge transport layer. A functionally separated photoreceptor using layers has been proposed.

Among such materials, JP-A-55-90954 and JP-A-60-59353 disclose that pps <poly P-phenylene sulfide) has high hole mobility or , has been proposed as an excellent material that can be manufactured at low cost by being used as a charge transport layer in the form of a film.

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, greater mobility and carrier life, and a higher charge generation are required. A combination of capable photoconductive layers is desirable. However, even if the respective requirements are satisfied, carrier injection between the two must be carried out efficiently. 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 that has excellent heat resistance, mechanical processing precision, and high electrical resistance, and is used as a plastic molding material and a sealing material.

On the other hand, the comparison with conductive materials is also attracting attention, and it is well known that conductivity can be significantly improved by adding a charge-accepting material, similar to other polymeric materials (poly-acrylonitrile, etc.). There is. At this time, carrier mobility was also improved, and application to charge transport layers of electrophotographic photoreceptors was expected.
Since the electrical resistance decreased due to the increase in carrier concentration, it did not have the required charge-accepting ability, and improvements were desired.

JP-A No. 60-59353 describes forming PPS as a charge transport layer by thinning it and improving its charge transport ability by vacuum evaporation, but generally in this state the charge transport ability is small and the sensitivity is low. , residual potential is not sufficient.

In addition, in Japanese Patent Application Laid-open No. 55-90954, PP
It has been proposed to use S film as a charge transport layer. However, since the charge transport ability is not sufficient, the photosensitivity has not reached the practical level of today's electrophotographic photoreceptors.

In order to overcome the above drawbacks, we conducted various studies and found that P.
Heat-treating a polymer layer whose main component is a linear compound polymer layer containing P-phenylene and a chalcogen element at the para position, typified by PS, in an atmosphere containing oxygen atoms. We have found that the charge transport ability can be dramatically improved.

Further, if an atmosphere containing ionized atoms such as ozone is used as the atmosphere in L, the charge transport ability can be improved without performing heat treatment. However, the charge transporting layer in this state has a problem in that the charge transporting ability is significantly reduced when the photoconductive layer is formed while being held in a vacuum and heated.

Further, there was a problem in that the hardness of films such as PPS is small (3B or less in terms of pencil hardness) and printing durability is not sufficient.

Means for solving the problem A functionally separated electrophotographic photoreceptor consisting of a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transfers the carriers has P-phenylene and a chalcogen element at the para position. The photoconductive layer is composed of a charge transport layer and a photoconductive layer, the hardness of which is made to have a Vickers hardness of 10 to 80 by heat treatment.

Effect In a polymer with a structure such as PPS, which has P-phenylene in the main chain direction and a chalcogen element in the para position, the charge transport ability is significantly improved by heat treatment in an oxygen-containing atmosphere. This has not been sufficiently analyzed at present. However, at this point, we can think of the following.

Generally, carrier movement in polymers occurs through hopping conduction in front of electron orbits along the main chain direction of the polymer, but the carrier mobility increases as the overlap between adjacent orbits increases. ,To increase. When the chalcogen element at the para position of P-phenylene is in a neutral state, the π electron orbits of adjacent P-phenylenes are in a spatially orthogonal coordination state, and the mobility is small. However, when the chalcogen element is positively charged and ionized by the added 0 atom, the spatial twist of P-phenylene is resolved and the π electron orbitals are arranged in the same plane, resulting in an increase in hopping probability and an improvement in mobility. It is thought that this will be achieved.

Furthermore, if an atmosphere containing ionized atoms such as ozone is used as the above atmosphere, the charge transport ability can be improved without heat treatment, but such films lack heat resistance and cannot be heated by heating in a vacuum. It is thought that it easily returns to its original state with low charge transport ability.

In other words, films such as PPS, which have low hardness (3B or less on pencil hardness), do not have sufficient binding energy in the ionized state, so bonded ions can be easily removed by treatments such as heating in a vacuum. It is thought that the substance is released and returns to a neutral state.

On the other hand, in those heat-treated in an atmosphere containing ozone or simply in an oxygen atmosphere, no decrease in charge transport ability is observed even when heated at 200° C. or higher in vacuum.

This is thought to be because heat treatment improves the crystallinity of the polymer layer and at the same time causes thermal hardening, allowing stable maintenance of a state with high charge transport ability.

Furthermore, since the hardness increases through curing, printing durability also improves.

The embodiment diagram schematically shows a cross section of one embodiment of the most basic electrophotographic photoreceptor of the present invention.

The electrophotographic photoreceptor shown in the figure includes a polymer layer having a structure having P-phenylene at least in the main chain direction and a chalcogen element at the para position on a support l as an electrophotographic photoreceptor, and a polymer layer containing oxygen. It has a charge transport layer 2 made of a polymer layer heat-treated in an atmosphere and a photoconductive layer 3, and the photoconductive layer 3 has a free surface 4 on one side.

In the present invention, the photoconductive layer is an amorphous layer containing silicon such as a-5i (:II:X),
a-5it-yCy (:H:XX0y<1), a-5
it-, 0, (:H:X) (0<y<1), a-5i
+ -vN, (:H:X) (0<y<1), a-5+
+-zGez(:H:X)(0<z<1), a-(S
it-zGez)+-vNs+(:H:XXO<y,z
<1), a-(Sit-zGez)+-vO,,(:
It:X) (0<y, z<1), or a-(Sit
-zGet)+-yC+(':H:XXO<y, z<1
) or a stacked layer of these can be used. It can also be used when y is changed continuously.

A4J2Se is used as a photoconductive layer containing a chalcogen element.
An amorphous layer such as 3.5e (containing Tc) or GeSe may also be used. In addition to this, CdS, CdSe,
A layer may be formed by binding CdTe crystal powder with a resin.

At this time, the thickness of the charge transport layer is 5 to 50 μm, preferably 1 μm.
0~25μ, and the film thickness of the photoconductive layer is 0.11-1O7
z The preferred range is 0.2 to 5 μm.

In the present invention, in order to further improve the electrophotographic properties, a barrier layer is provided between the support 1 and the charge transport layer 2 in the figure to effectively prevent carriers from being injected from the support 1 into the charge transport layer 2. may be provided.

Materials for forming the barrier layer include A I 203, Ba
O1Ba02, Beos B i 203, CaO5C
e02, Ce20z, La2O3, Dy2O3, Lu2
O3, C'203, CuO1CLI20, Fed, P
bO1M80.5rO1Ta20a, ThO2, ZrO
2, HfO2, Ti02, Ti05Si02, Ge
Metal oxides such as O2,5iO1GeO or TiN,
Metal nitrides such as AlN, SnN, NbN, Tag, GaN, or metal carbides such as WC, SrC%TiC, or SiC, SiN, GeC, GeN, BC
, ON and other insulators, polyethylene, polycarbonate,
Organic compounds such as polyurethane and polyparaxylene are used.

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. Materials suitable for the surface coating layer include S+xO+-S+xC+-5iXN
I-1% Ge+cOs-xs GexCt-X
ll GexN+-xb BxN+-x, 88C+
-x-AIJ+-x (0<X<1), and inorganic materials such as layers containing hydrogen or halogen, or polyethylene terephthalate, polycarbonate, polypropylene, polyvinyl chloride, polyvinyl alcohol,
Synthetic resins such as polystyrene, polyamide, polyethylene tetrafluoride, polyethylene chloride trifluoride, polyvinylidene fluoride, and polyurethane can be mentioned.

Furthermore, in the present invention, the above a-5i(:H:X)
, a-5! +-, c, (If:xXo<y<t), a
-5i1-. 0. (:H:X) (0<y<1), a-5
By adding impurities to i+-, Nv (:H:XXO<y<1), or Ge-added films, conductivity can be controlled and desired electrophotographic characteristics can be obtained. The p-type impurity that gives p-type conductivity is 8% A I -G a, In, which belongs to Group Ⅰ of the periodic table.
B%Al, Ga are preferably used, and as n-type impurities that provide n-type conductivity, N, P-As%Sb, etc. belonging to V*b of the periodic table are preferably used. P, A
s is used.

In addition, as a method of adding these impurities, in the case of p-type impurities ~B2116-BaH+s%B689% 8
51111SB8812, BaH+4, BF3
, BCh, BBr2, AlCl3, (
CH3)3A1, (C2Hs)3Al, (icJs)a
Al, (CH3)3Ga, (C2H6)3M, I
When nCH3, (C2Hs)31n is an n-type impurity,
N2, NH3, N01N20, NO2, pH3, P2H
4, PHal, PF3, PFs, PCl3, PCl5,
PBr3. Pars, PI3, ASH3, ASF3,
AsC13, AsBr3, SbH3, SbF3.5BF
s, 5bCIi, 5bCls, etc., or these gases in 12. In the plasma CV and D methods, a gas diluted with He or Ar may be mixed with the above-mentioned source gas such as Si atoms to be used during film formation, or in the reactive sputtering method, Ar may be used. It is used by mixing with other sputtering gases.

In addition, the following organic semiconductors can be used as the photoconductive layer: (1) Phthalocyanine pigments (referred to as PC), such as metal-free Pc, XPc, CX=Cu, Ni, Co,
Ti01Mg, Si(OH)2, etc.), Al
ClPcC1, Ti0CIPcC1, InClPcC1
, 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 (10
) Eutectic complexes formed from biryllium salt dyes and polycarbonate resins (11) Azulenium salt compounds, etc.

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

The polymer layer, which is the charge transport layer, uses a film oriented by biaxial stretching, and as described below, it is heated in an oxygen-containing atmosphere on a quartz glass substrate or on a conductive support of an electrophotographic photoreceptor. They were fused and formed, and further heat-treated in oxygen if necessary.

On the other hand, in order to determine the hardness of the polymer layer after film formation, a quartz glass substrate was used, and a film with a thickness of 10 μm or more was formed on the substrate and evaluated.

The hardness was measured using a micro-Vickers hardness meter, with the load applied to the diamond indenter being 10 g.

Furthermore, since the hardness of a film with low hardness such as an untreated PPS film is inaccurate with a micro-Vickers hardness meter, evaluation was performed using pencil hardness as described above.

Examples will be described below.

Example 1 A PPS film with a film thickness of 12, 10,000, or 50 μm was layered on a quartz glass substrate, and in order to further improve the uniformity,
A stainless steel substrate coated with Teflon as a mold release agent was placed on top of the substrate as a weight, and PPS was fused by carrying out a one-hour immersion treatment at 280° C. in oxygen. When the hardness of this film was measured using a micro Vickers hardness meter, it was found to be 12
For a film thickness of μm, it is 25 ± 5. For a film thickness of 25 μm, it is 15 ± 5.
．． At a film thickness of 50 μm, it was 7±2.

Under these conditions, PPS was also fused onto the aluminum substrate to form a charge transport layer.
E was formed to a thickness of about 0.8 μm by vacuum evaporation to obtain an electrophotographic photoreceptor.

At this time, the electrophotographic photoreceptor with a charge transport layer made of PPS with a film thickness of 12 μm was charged to a surface potential of +600 V.
Exposure was performed with 500 nm light. However, in terms of illuminance, the half-potential exposure amount was 1.51 ux-sec, which showed very high sensitivity. Further, the residual potential was 50 V or less, which showed excellent characteristics.

In addition, when an electrophotographic photoreceptor with a charge transport layer made of PPS with a film thickness of 2571 m was evaluated under the same conditions as above, the half-potential exposure was as high as l and 21 ux-sec, but the residual potential was a little toov. There were many results.

However, an electrophotographic photoreceptor using PPS with a film thickness of 50 μm has an extremely high residual potential of 300 to 350 V or more.
It did not reach a practical level.

Example 2 Next, a PPS film with a thickness of 15 μm was soaked in ozone for 1 hour.
After the treatment, aluminum was vapor-deposited as an electrode, and As25es was deposited on the opposite side as a photoconductive layer to a thickness of 1.2 μm in vacuum, at a substrate heating temperature of 100°C.
Vapor deposition was performed using

On the other hand, a heat fusion process was performed on the aluminum substrate at 285°C in air, and further a 9-hour leap process was performed at 280°C in oxygen.

The former film was adhered onto a quartz substrate and its hardness was measured to be 5±2. On the other hand, when the hardness of the latter PPS was measured, it was 60±5.

When the surfaces of both electrophotographic photoreceptors were charged to a potential of 600 V and exposed to white light, the former had a residual potential of 250 V, which was so large that it could not be put to practical use. However, the residual potential of the latter is as low as 80V, and the sensitivity is also 0.
It showed extremely high sensitivity of 71ux-3eC.

Example 3 Next, similarly to Example 2, a 15 μm film was placed on an aluminum substrate.
PPS with a thickness of m was fused and further treated in oxygen at 280° C. for 12 hours, while at 320° C. for 6 hours.

The hardness of the PPS film under the former condition was 75±5. However, cracks occurred in some parts of the latter film, and the hardness was 85±5 when measured.

The former substrate was placed on the anode side of a parallel plate type capacitively coupled plasma CVD apparatus having a 6-inch discharge electrode, and after evacuating the inside of the reaction vessel to 5X to Torr or less, the substrate was heated at 150 to 200°C. heated to. 1 SiH4
0 to 40 scaw, 10 ppm+ of Ihh introduced, pressure 0.2 to 1°0 Torr, high frequency power 20 to 100 W
A-5i: 8 layers were formed as photoconductive layers with a thickness of 0.2 to 1 μm. Furthermore, SiH4 is added to 10 to 30 SCCIl, C
Introduce 20-40 SCC 1l of 2H4 and pressurize 2-1.
S at 0 Torr and high frequency power of 50 to 150 W! +-xc
x: 0.08 with H (0<x<1) as the surface coating layer
An electrophotographic photoreceptor was prepared by forming a thickness of 0.3 μm.

The former sample also has improved resistance to plasma, and when exposed to white light after being charged to a surface potential of 500μ, it showed a high sensitivity of 0.71ux-sec and a residual potential of 1
00V, a photoreceptor with a practical level was obtained.

On the other hand, in the latter sample, cracks further increased and some film peeling occurred.

Example 4 Cylindrical P with a film thickness of 15 μm was formed by the inflation method.
Create PS film. At this time, the stretching magnification is 20 to 30 times on the cylinder axis, and 10 times in the direction perpendicular to the cylinder axis.
-15 times. The diameter of the cylindrical film was 92φ.

A mirror-polished 88φ aluminum drum was inserted into the above cylindrical PPS film, heated to 200° C., and PPS was laminated on the aluminum drum by heat shrinkage. On the other hand, a sample fused onto a quartz substrate for hardness measurement was placed in a heat treatment device in oxygen at the same time as the drum above, and
Processed the time leap.

When Vickers hardness was measured using a sample for hardness measurement, it showed a hardness of 55±4.

Further, the drum was placed in a cylindrical rotary type vacuum evaporation apparatus, and after evacuating the inside of the apparatus to 5X fO-'Torr or less, the substrate was heated at 25 to 40°C as a photoconductive layer, and a metal-free Pc was applied at 0.5 to 100°C.
The film was deposited to a thickness of 2 to 0.37 tm. Metal-free Pc was washed with hot water twice and Tetrahythm'0 flange washed once before vapor deposition.
After repeated purification, vapor deposition was performed.

The photosensitive drum thus obtained had a surface potential of 600 V.
After being subjected to charging treatment, exposure to white light was performed, and a photosensitive drum was obtained which exhibited high sensitivity with a half-potential exposure amount of 1.31 υx"sec and a sufficiently small residual potential of 60 V or less.

Example 5 Similarly to Example 4, when laminating a PPS film as a charge transport layer on an aluminum drum substrate by heat shrinkage, T CN Q (
The heat treatment was performed in an atmosphere to which 7,7,8,8,-tetracyanoquinodimethane) was added.

Furthermore, it was placed in a heat treatment apparatus in oxygen and was treated at 265° C. for 6 hours.

Similarly, a film was simultaneously treated as a sample for hardness measurement, and the hardness was measured by adhering it onto a quartz substrate.

The film hardness at this time was 25±4.

In addition, the drum was immersed in a solution containing 100:20 parts by weight of CdS photoconductive powder and a binder resin (the binder resin was a polyurethane resin), dried at 170°C for 30 minutes, and exposed to 5 μm light. A conductive layer was formed.

The photosensitive drum thus obtained had a surface potential of 600
After performing the charging process on V, exposure to white light was performed, and a photosensitive drum was obtained that exhibited high sensitivity with a half-potential exposure amount of 2.31 ux-sec and a sufficiently small residual potential of 90 V or less.

Here, TCNQ was used as an electron acceptor, but SO
3. The same thing can be done using A S F s or the like.

In addition, although a film containing PPS as the main component was used as the charge transport layer, similar effects can be obtained with polymers having a structure that has P-phenylene in the main chain direction and other chalcogen elements in the para position. It will be done.

Example 6 Contrary to the drawings, an example in which a photoconductive layer is disposed on a substrate will be described.

A mirror-polished 15 cm square aluminum substrate was placed in a parallel plate type capacitively coupled plasma CVD device with a 6 inch discharge electrode, and the interior of the reaction vessel was set at 5X 10-'T.
After evacuation to below orr, the substrate was heated to 250°C or higher, preferably 280 to 320°C. Next, 5iHa from 10 to
40 sec was introduced, and C2H2 was mixed as a carbon source so that C atoms were mixed with Si atoms in an amount of 1 to 25 atmX.
Gas diluted to 5% or less with hydrogen gas at a pressure of 0.2 to 1 liters, 0 Torr, and high frequency power of 20 to 100
W with a-5it-, C,: 0.5 as photoconductive layer with 8 layers
~5 μm was formed.

Further, the PPS polymer film of 25III is adhered tightly and the edges are fixed, and heated in air at a temperature of 280 to 290°C for 1 to 5 hours in a saccharide atmosphere to fuse and form a charge transfer layer. An electrophotographic photoreceptor was prepared.

The hardness of PPS at this time was 50±4.

When this photoreceptor was charged to -500V and exposed to white light, the potential exposure amount was halved! “,01ux*se
Sensitivity was significantly improved to below c. Also, the residual potential is 18
It was possible to obtain excellent characteristics of 0V or less.

Also, at this time, between the a-S++-xcxrH layer and the substrate,
As a charge injection blocking layer, 0.1 μm a-5it-xN
By inserting x:8 layers, the charge retention ability was improved and an image with high contrast was obtained.

Effects of the Invention In a function-separated electrophotographic photoreceptor consisting of a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transfers the carriers, a straight-chain soft material containing P-phenylene and a chalcogen element at the para position is used. By forming the charge transport layer, which has a compound polymer layer as its main component, by heat treatment so that the Vickers hardness is ■θ~80, electrophotographic sensitization with high sensitivity and low residual potential can be achieved. It is something that gives you a body. Furthermore, since the charge transport layer can be manufactured by polymer fusing, an inexpensive electrophotographic photoreceptor can be provided.

In addition, such a photoreceptor has excellent printing durability, has a long life, and maintains stable characteristics even when subjected to heat treatment.

Furthermore, the improved hardness also improves resistance to plasma, making it possible to deposit films without damage caused by plasma in the process of forming a photoconductive layer using plasma such as amorphous silicon.

[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... Photoconductive layer, 4... Free surface.

Claims (8)

[Claims] (1) A functionally separated electrophotographic photoreceptor in which a photoconductive layer that generates carriers by photoexcitation and a charge transport layer that transfers the carriers are laminated on at least a conductive support, wherein the charge transport layer An electrophotographic photoreceptor, the main component of which is a linear compound polymer layer having P-phenylene and a chalcogen element at the para position, and having a hardness of 10 to 80 on the Vickers scale. (2) The electrophotographic photoreceptor according to claim 1, characterized in that the charge transport layer contains O atoms. (3) The electrophotographic photoreceptor according to claim 1 or 2, wherein an electron acceptor is added to the charge transport layer. (4) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer is a non-single crystal layer containing a modifier that reduces spin density. (5) The electrophotographic photoreceptor according to claim 4, wherein the photoconductive layer contains at least either hydrogen or a halogen element. (6) The electrophotographic photoreceptor according to claim 1, wherein the photoconductive layer has a non-single crystal layer containing at least chalcogen atoms. (7) The electrophotographic photoreceptor according to claim 4, wherein the photoconductive layer contains an element of Group III B or Group V of the periodic table. (8) The electrophotographic photoreceptor according to claim 1, wherein a surface coating layer is formed on the free surface.