JPH02151869A - Electrophotographic sensitive body and its production - Google Patents

Abstract

PURPOSE:To obtain an electrophotographic sensitive body having high sensitivity and low residual potential, and improved charge receiving capacity, wear resistance, and resistance to environmental changes by incorporating a specified p-phenylene compd. into a charge transfer layer. CONSTITUTION:The electrophotographic sensitive body is constituted of a charge transfer layer consisting of a layer of a high molecular linear compd. contg. p-phenylene residues and a group IIb element in the p-position of the p-phenylene compd. Suitable group IIb element is at least one among S, Se, Te, having >=280 deg.C m.p. Thus, an electrophotographic sensitive body having high sensitivity and low residual potential is obtd. Moreover, the film of the charge transfer layer is attained by the melt-sticking, coating, or vapor-deposition of the polymer, so an inexpensive electrophotographic sensitive body having high stability and high printing resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application 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.

In this way, by selecting the monthly yield according to the function, an excellent photoreceptor with high sensitivity electrophotographic properties is provided. 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 triarylpyrazoline, Diane blue and oxadiazole, perylene pigment and oxadiazole,
Examples include bisazo pigments and styria anthracene.

Also, as a method using an amorphous layer, JP-A-54-143
No. 845 proposes a functionally separated photoreceptor using an organic semiconductor material, and JP-A-58-24355 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 a layer mainly composed of amorphous carbon, and the charge generation layer is made of amorphous cricon.

Among such materials, PP5 (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. 1
(No. id-59353) However, PPS usually has a high resistance, and it is necessary to find some way to improve its mobility. We have obtained an electrophotographic photoreceptor with improved hole mobility and good characteristics by heat-treating PPS in an oxygen atmosphere.

Problems to be Solved by the Invention In order to achieve higher sensitivity in a function-separated electrophotographic photoreceptor, it is necessary to create a charge transport layer with a smaller dielectric constant and greater mobility, and a charge transport layer with a higher charge generation ability. A combination of generation layers is desirable.

However, even if the required collapsing conditions are satisfied, carrier injection between the two must be performed efficiently.

In addition, the charge acceptance ability required in the electrophotographic process,
It must have sufficient 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-59353 describes thinning and forming a transport layer by a pps vacuum deposition method, but in this state, mobility is generally 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.

As a method to solve these problems, we proposed heat treatment of PPS in an oxygen atmosphere. However, when heating at a constant processing temperature, the electrophotographic properties tend to be saturated with respect to the processing time, and it is necessary to take measures to improve the properties.

Means for Solving the Problems The present invention has been made in view of the above problems, and the invention according to claim 1 comprises a photoconductive layer that generates carriers by photoexcitation, and a charge transport layer that transports the carriers. In the functionally separated electrophotographic photoreceptor, the charge transport layer is P-
consisting of a linear compound polymer layer containing phenylene and having a group IIb element at the para position, containing at least one of Sr's'el'r and el as the group IIb'element; The invention according to claim 5, characterized in that the melting point is 280° C. or higher, is the method for producing an electrophotographic photoreceptor according to claim 2, wherein the charge transport layer is formed in an atmosphere containing oxygen in the step □ of forming the charge transport layer.・Includes one or more heat treatment steps, and the treatment temperature is increased over time in each treatment step□
It is characterized by the fact that the processing temperature in the latter stage is higher than that in the former stage.

Carrier movement in active polymers is carried out by hopping conduction between electron orbits along the main chain direction of the polymer, and the carrier mobility increases as the hopping probability □ increases as the overlap between adjacent orbitals increases. increase 'help'; P in the main chain direction
- In a polymer with a structure containing phenylene and a Group IIb element at the para position, the □benzene ring □゛, which is “neighboring” according to its crystal structure analysis, is in a coordination state in which the π electron orbitals are spatially perpendicular to each other. , □Mobility is small. Therefore, it is considered that carriers tend to move in the direction perpendicular to the polymer axis. Therefore, in the crystalline part where the polymer coordination is uniform, carrier movement is good, reducing the amorphous region with poor orientation and creating a structure that facilitates carrier transfer from the amorphous part to the crystalline part. is important.

It has been found that the expansion of the first crystal region can be solved by heat treatment, and the second structural change can be solved by introducing oxygen molecules into the film. It is thought that oxygen molecules taken into the film by heating in an oxygen atmosphere exist in the amorphous region within the film and weakly bond with the polymer, thereby improving intermolecular hobbing of carriers in this region. The heat treatment method for increasing the amount of weakly bonded oxygen in the film is preferably performed by increasing the heating temperature stepwise or continuously. An increase in weakly bound oxygen results in an increase in the melting point of the polymer. It is thought that the effective bonding of oxygen progresses only after heating to a high temperature above the melting point. However, if each molecule is heated to a high enough temperature that its position changes significantly, a strong bond with oxygen, or a chemical change, occurs. Therefore, by gradually increasing the heating temperature as the melting point increases, a polymer having a crystalline melting point can be obtained.

Tables 1 to 4 show changes in melting points of polymers due to heat treatment in the presence of oxygen. Tables 1 to 4 show changes in melting point when PPS films are heat treated in oxygen and vacuum. In Table 1, at a heating temperature of 285℃ in oxygen, 12
After an hour it increases by about 25°C to 300'C. On the other hand, heat treatment in vacuum does not increase the melting point (it can be seen that the melting point increases only with the presence of oxygen.Table 2 shows that the melting point changes reversibly by heat treatment in oxygen and vacuum, and it correlates with the reversible increase and decrease of oxygen in the film. Table 3 shows changes in melting point depending on heat treatment temperature in oxygen, and Table 4 shows changes in melting point depending on heat treatment temperature in vacuum. Oxygen-mediated heat treatment increases the temperature when the treatment temperature is near the melting point or below, and increases when the temperature exceeds the melting point. Therefore, there is a large change in the vicinity of 285 to 290'C.

Embodiment FIG. 1 schematically shows a cross section of an embodiment of a basic electrophotographic photoreceptor according to the present invention. The electrophotographic photoreceptor shown in FIG. On the body 1 there is provided a charge transport layer 2 consisting of a polymer layer according to the invention and a charge generation layer 3, said charge generation layer 3 having a free surface 4 on one side.

At this time, the thickness of the charge transport layer is 5 to 50 μm, preferably 1 μm.
0~25μm1 The film thickness of the photoconductive layer is 0.2~10μm1.
[mu]m is preferably 0.5 to 5 [mu]m.

FIG. 2 shows the heating temperature profile in the oxygen atmosphere heat treatment method of the present invention.

Figure 2 (a) shows the case in which the treatment temperature is increased stepwise in three steps with a constant temperature during each treatment, and Figure 2 (b) shows the case in which the heat treatment temperature is increased in one treatment with a constant temperature increase rate. Indicate the case.

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

Examples of materials forming the barrier layer include Al□03,
BaO1Ba02, Be01Bj20a, CaO1Ce
02, Ce2O3, La2O3, Dy2O3, Lu2O
3, Cr2O3, CuO1Cu20, Fe01P bO
.

MgO1SrO1Ta203, Th02, ZrO2, H
fO2, TiO2, Ti0l-5j02, GeO2, S
10. Metal oxides such as GeO or TiN.

Metal nitrides such as AlN15nN, NbN, TaN1GaN, or metal carbides such as WC, SnC, TiCl, or SiC, 5IN1G eClG eN
Insulators such as 1BC18N and heat-resistant organic compounds such as polyimide, polyamideimide, and polyacrylonitrile are used.

In addition, in order to improve cleaning performance, abrasion resistance, or corona resistance, in Figures 1 and 2,
A surface coating layer is formed on the free surface 4. Examples of suitable materials for the surface coating layer include S+xO+-x, S
L, CI-x, 5IxN+-1G"x O+ -X
N Ge, CI-x, GexN+-xs
BXNI-XN BXCI-X, A1. N+-
-(Oxx1), carbon, and inorganic substances 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 by vacuum evaporation from powder, ion cluster beam method, etc., or it can be formed into a film by extrusion from 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. Further, as shown in FIG. 3, the oxygen heat treatment and the addition of electron acceptors by vapor phase doping may be performed alternately.

Examples of the charge acceptor to be added include I2, Br2,
C12, ■C1, lBr1(NO2)BF4, (NO2
) P Flll, (NO2) S b Fs, HC10
a, H2SO4, HN O'a, H3O4-1A
gCl0n, Fe(ClO2), BF3, FeCl
3, FeBr3, AlCl3, InCl3, InI3,
ZrCl4, HfCl4, TeCl4, TeBr4, T
eI4, SnC14, S n I4N S e C1
4, T i C1a, T i I4, F e CI 4
-1A ICl 4-1A s FE, SbF6, N
bC1G, NbFe, TaC16, Ta I6, MOC
15, ReFe, ■ rC16, Eng nF6, UF6.08
=11- Fe, XeF6, TeFe, SF6, SeF6
, WF6, WCl, Re F7, etc. As an organic charge acceptor, for example, TCNQl TCN
There are also El DDQ etc. As the organic semiconductor of the charge generation layer, (a) phthalocyanine pigment (referred to as Pc), for example, metal-free PC1XPC (X=Cu1 Nis Co1 T
10, M gz S 1 (OH) 2, etc.), AI
CIPcCL Ti0CIPcC1, InClPcC
111nCIPc1 InBrPcBr, etc. Furthermore, (b) azo dyes such as monoazo dyes and disazo dyes, (c) penylene pigments such as penylene acid anhydride and penylene acid imide, (d) indigoid dyes, (e)
Quinacridone pigments, (f) polycyclic quinones such as anthraquinones and pyrenequinones, (g) cyanine dyes,
(l) xanthine dyes, (l) charge transfer complexes such as PVK/TNF, (l) eutectic complexes formed from vinyl salt dyes and polycarbonate resins, and (r) 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.

As a charge generation layer and a non-single crystal layer, S eX 's eTe1As2Se having a chalcogen element as a component is used.
The amorphous layer, such as 3+ Cd S+, has at least one of silicon, germanium, and carbon as a main component and contains a modification (eg, hydrogen, halogen) that reduces the density of 9 localized groups.

Plasma CVD using plasma is used to form these films.
method, ECR method, ordinary sputtering method, vacuum evaporation method, etc. are used.

Next, the present invention will be explained by giving more specific examples.

Example 1 A film-shaped PPS (poly p-phenylene sulfide) containing sulfur as the group (■) was pasted on a mirror-polished aluminum substrate, a fluororesin sheet was wrapped from above the film, and the film was heated in a heat treatment furnace. 'P
A PS film was fused onto an aluminum substrate. The heating temperature is 290°C, which is higher than the melting temperature of PPS, 285°C.
°C, and the heating atmosphere was air. After taking out the substrate from the heat treatment furnace, the fluororesin sheet was removed and placed in the heat treatment furnace again, and heat treatment was performed in an oxygen atmosphere. The heat treatment was performed by the method shown in FIG. 2(a), and the heat treatment time for each step was constant for 3 hours. Table 5 summarizes the processing temperatures for each step studied. Process 1 in the table is a one-time step, process 2 is a two-time step, and processes 31, 32, and 33 are a three-time step. The thickness of the PPS film after treatment is
The thickness was 10 to 25 μm.

These layers are used as a charge transport layer, and a phthalocyanine compound Ti0Pc is coated with 0.05% by coating method as a charge generation layer.
The layers were laminated to a thickness of ~5.0 μm. Table 6 shows the electrophotographic characteristics of the photoreceptors manufactured in each process, when the surface potential was set at 800 V and the exposure amount was halved (E+721x, '5ec
) and the residual potential (VreS'''V).

Example 2 After a PPS film was fused onto a □ aluminum substrate in the same manner as in Example 4, heat treatment in oxygen was performed by the method shown in FIG. 2(b). Heating start temperature 280°C, final temperature 295°
0 to 5 (°C/hour) so that C2=1.7
(°C/hour) and C3''1.1 ('C/hour). Thereafter, a phthalo7-anine compound A]ClPcCl was formed as a charge generation layer by vacuum evaporation. As a result of evaluating the electrophotographic characteristics similar to Example 1,
The C2 process photoreceptor has a half-life exposure of 0.7 lx, 5
ec1 Good characteristics were obtained with a residual potential of 50 V or less.

Example 3 When forming a charge transport layer, T'CNQ (7,7,8,8,-tetracyanoquinodimethane) was added as an electron acceptor after the fusion treatment. The addition method was a vapor phase doping method in which TCNQ gas was directly exposed to the fused PPS film and diffused into the film from the upper surface of the film.

The heat treatment in oxygen and the vapor phase doping were performed alternately as shown in FIG. 3, and the temperature profile of the heat treatment with oxygen was set to increase so that the TCNQ was effectively incorporated into the film and the melting point increased. In Figure 3 (a, ), T + =270°C1T
2 = 275°C1T3 = 280°C, Figure 3 (b
), the heating rate was kept constant at 1.7 ('C/hour).

An azulenium salt compound was used for the charge generation layer. 1
．． 4-dimethyl-7-itsuprobyl azulene and P dimethylaminocinnamaldehyde were dissolved in tetrahydrofuran, and acid (HXl X=Cl0.l, BFa, BrtI
) was reacted while cooling to below 10'C, and this solution was dried at e o'c to form a zeathrenium salt compound 1-
'(P-dimethylaminannaylidene) 5-isopropyl-3,8-dimethylazulenium salt was obtained. This was mixed with butyral resin and dispersed in butyl acetate, and then coated on the charge transport layer to a thickness of 0.1 to 5.0 μm.
Dry at 0°C.

Azulenium salts have excellent photoconductivity in the wavelength range of 400 to 900 nm, and have a peak sensitivity at long wavelengths of 700 nm or more, making them suitable for printers using semiconductor lasers as light sources. Among the four types of azulenium salts described in Section 2, the one containing ■ (iodine) as an acid showed good sensitivity of 0.821 x sec to white light and 0.551 x sec to red light of 800 nm.

Effects of the Invention According to the present invention, it is possible to obtain an electrophotographic photoreceptor with high sensitivity and low residual potential, and furthermore, the charge transport layer can be formed by polymer fusing, coating, or vapor deposition, and is an inexpensive electronic photoreceptor. We can provide photographic photoreceptors. Furthermore, since the charge transport layer is made of a heat-resistant thermosetting polymer, it has excellent stability and printing durability.

Table 1 Table 4 Table 3 Table 2 Table 5 Set temperature for multi-stage oxygen heat treatment process (°C) Table 5 (continued) Table 6 Table 6 (continued)

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of an electrophotographic photoreceptor in an example of the present invention, FIG. 2 is a diagram showing a time profile of the heating temperature of the heat treatment in oxygen in Example 1.2 of the present invention, and FIG. The figure shows the case of alternating oxygen heating and charge acceptor addition (Example 3)
It is a figure showing the time profile of the heating temperature. 1. Fist-support, 2. Fist-charge transport layer, 3. Charge generation layer, 4. Free surface. Name of agent: Patent attorney Shigetaka Awano and one other person Fig. 1 beat-3 Fig. (αn H H H processing waiting b) 6 hours

Claims (6)

[Claims] (1) A photoconductive layer that generates carriers by photoexcitation;
In a functionally separated electrophotographic photoreceptor comprising a charge transport layer for transporting carriers, the charge transport layer comprises a linear compound polymer layer having P-phenylene and a group IIb element at the para position, The group IIb elements include S, Se
, Te, and has a melting point of 280° C. or higher. (2) The electrophotographic photoreceptor according to claim 1, wherein the charge transport layer contains oxygen atoms. (3) The electrophotographic photoreceptor according to claim 2, wherein the atomic ratio of oxygen atoms to carbon 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) The step of forming the charge transport layer includes one or more heat treatment steps in an oxygen-containing atmosphere, and the treatment temperature is increased over time in each treatment step, or the treatment temperature of the latter step is higher than that of the earlier step. The method for producing an electrophotographic photoreceptor according to claim 2, wherein the electrophotographic photoreceptor is relatively expensive. (6) The method for producing 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 260 to 300°C.