JPH01109356A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To prevent deterioration in sensitivity due to the increase of residual potential by incorporating a charge transfer material into a surface protecting layer on a charge transfer layer. CONSTITUTION:An electrophotographic sensitive body is formed on an electroconductive base body by laminating a charge generating layer (A), a charge transfer layer (B), and a surface protecting layer (C) in the order, and a charge transfer material, pref. a hydrazone compd. (a compd. expressed by the formula ) is incorporated into the layer (C). The photosensitive body is formed by coating the layer (A) after dispersing a phthalocyanine dye in a binder resin, or by vapor deposition, then coating the layer (B), (C) after dispersing the compd. expressed by the formula in a binder resin. By this constitution, a photosensitive body causing no elevation of residual potential nor deterioration in sensitivity even after it is used repeatedly is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to electrophotographic photoreceptors containing organic photoconductive materials.

Conventional technology Photoreceptors made of inorganic photoconductive substances such as selenium, selenium-tellurium alloy, cadmium sulfide, and zinc oxide have been widely used as electrophotographic photoreceptors in the past, but in recent years, it has become easier to synthesize and semiconductors have been used. With the advancement of laser technology, research is progressing on organic photoconductive materials that have characteristics such as the ability to select compounds that exhibit photoconductivity in an appropriate wavelength range.

An electrophotographic photoreceptor using an organic photoconductive substance in the photosensitive layer is
Film formation is easy. Although they have advantages such as being highly flexible and having a large degree of freedom in design, being inexpensive and non-polluting, they have been inferior in sensitivity and photoreceptor life compared to inorganic photoconductive materials. In order to improve these problems, a laminated electrophotographic photoreceptor in which a photosensitive layer is formed by separating the functions of a charge generation layer and a charge transport layer has been proposed and put into practical use.

On the other hand, these electrophotographic photoreceptors are usually electrically charged.

It is repeatedly subjected to the processes of exposure, development, transfer, cleaning, and static elimination, but in this series of processes,
Since the surface of the photoreceptor is exposed to an oxidizing atmosphere such as ozone generated during corona charging, changes in the surface condition such as ozone oxidation and adsorption of oxides occur, resulting in changes in electrophotographic properties such as a decrease in charging potential and an increase in residual potential. Deterioration occurs. In addition, abrasion, scratches, and damage to the surface of the photoreceptor occur due to rubbing by a cleaning blade during cleaning of residual toner, entry of transfer paper, and contact, etc., resulting in deterioration of electrophotographic characteristics.

Therefore, for example, it has been proposed that a surface protective layer such as polyvinyl butyral, maleic acid resin, or ketone resin be installed to prevent ozone oxidation, or that a surface protective layer of amorphous silicon carbide or amorphous silicon nitride be installed to improve mechanical strength. Proposals have been made to improve this (for example, Japanese Patent Laid-Open No. 56-128950, Japanese Patent Laid-Open No. 58-54347, etc.).

Problems to be Solved by the Invention However, even with the photoreceptor having the above-mentioned protective layer, the protective layer made of thermoplastic resin such as polyvinyl butyral does not have sufficient durability when it is a thin film, and it also dissolves the photosensitive layer during coating and can cause electronic damage. It deteriorates the characteristics as a photographic photoreceptor. Furthermore, since the surface protective layer has high insulating properties, it has problems such as extremely poor charge transfer and an increase in residual potential. Also,
Inorganic protective layers such as amorphous silicon carbide are not easy to form, and not only do they lose their advantages as organic photoreceptors, but they also make it difficult to form a film for transferring charge as described above. Become something. Therefore, it is desired to develop an electrophotographic photoreceptor that has a longer life span and satisfies the characteristics required for an electrophotographic photoreceptor by taking advantage of the advantages of organic photoconductive materials.

Means for Solving the Problems In order to solve the above problems, the electrophotographic photoreceptor of the present invention is provided by laminating a charge generation layer and a charge transport layer in this order on a conductive support, and on the charge transport layer. This electrophotographic photoreceptor has a surface protective layer laminated thereon, contains a charge transporting material in the surface protective layer, prevents surface deterioration due to an oxidizing atmosphere, and satisfies electrophotographic characteristics with excellent durability.

Function The present invention aims to strengthen the protection 1 of the photosensitive layer.If the purpose is simply to increase the strength, it is sufficient to laminate a high molecular weight polymer or an inorganic hard material. By containing a charge transporting material to move charges, charges accumulated at the interface between the photosensitive layer and the surface protective layer are moved to the surface, preventing deterioration of sensitivity due to increase in residual potential and improving repeatability stability. . In particular, this effect is enhanced by incorporating the charge transport material used in the charge transport layer into the surface protective layer.

EXAMPLE An example of the electrophotographic photoreceptor of the present invention will be described in detail below.

The conductive support used in the present invention may be a conventionally known conductive support, such as a metal plate such as aluminum, a plate made of a metal oxide such as tin oxide, or a metal plate made of such a metal and metal oxide. Various plastic films attached by vapor deposition, lamination, etc. and treated to be conductive.
Paper, etc.

The charge generation layer of the electrophotographic photoreceptor of the present invention is prepared by dispersing a phthalocyanine photoconductive pigment in a suitable binder resin.
It can be obtained by coating this on a conductive support or by forming a vapor deposited film on the conductive support using a vacuum deposition apparatus. Specifically, the phthalocyanine-based photoconductive pigment has ε
Type steel phthalocyanine, α-type copper phthalocyanine, β-type copper phthalocyanine, other metal phthalocyanines, metal-free phthalocyanines, etc. can be used. Furthermore, the binder resin used when forming the charge generation layer can be used as necessary for the purposes of improving adhesion with other layers, improving the uniformity of the coating film, and adjusting fluidity during coating. can.

Specifically, polyvinyl butyral, polyvinyl acetate,
PVC.

Polycarbonate, polyester, polysulfone.

Acrylic resin, methacrylic resin, epoxy resin.

Examples include urethane resins, phenoxy resins, and copolymers thereof. The amount of binder resin used is preferably 50% by weight or less based on the weight of the charge generation layer.The solvent for dissolving these resins is determined depending on the type of resin, the dispersibility of the phthalocyanine photoconductive pigment, and other factors in the case of accumulation. It can be selected depending on the relationship with the resin, specifically methanol and ethanol.

Alcohols such as isopropyl alcohol and butanol, ethers such as tetrahydrofuran, dioxane, and ethylene glycol monomethyl ether, acetone,
Ketones such as methyl ethyl ketone and cyclohexanone, esters such as methyl acetate and ethyl acetate, N, N-
Amides such as dimethylformamide, aromatics such as toluene and chlorobenzene, chloroform and methylene chloride.

Halogenated hydrocarbons such as ethylene dichloride can be used. A coating solution prepared in a dispersion manner as described above is applied by a normal coating method and dried by heating to form a charge generation layer with a thickness of several micrometers. From the viewpoint of reliability, it is preferable to form the film to a thickness of 0.2 to 2 μm.

The charge transport layer of the electrophotographic photoreceptor of the present invention can be obtained by applying a coating liquid in which a hydrazone compound and a binder resin are dissolved onto the charge generation layer. Specific examples of the hydrazone compound which is a charge transport substance include those having the structural formula shown below, but are not limited to these compounds (and it is also possible to combine two or more types).

C, H.

Since this hydrazone compound does not have film-forming properties by itself, a binder resin must be used when forming the charge transport layer, but a well-known binder resin can be used like that used for the charge generation layer. .

The amount of binder resin used is 50% of the weight of the charge transport layer.
The solvent used for dissolving the hydrazone compound and the binder resin and preparing the coating liquid is preferably the one used for the charge generation layer, depending on the composition of the charge generation layer, the hydrazone metal, and the binder resin. Similarly, well-known ones can be selected and used. In this case, depending on the layer to be laminated, a coating solution prepared with a composition of 0 or more is applied using a normal coating method, with the condition that it does not erode the layer, and charge transport is carried out in a film thickness of several μm to several tens of μm. Although a layer can be formed, it is preferably 5 to 25 in terms of chargeability etc.
μm is good.

The surface protective layer of the electrophotographic photoreceptor of the present invention is formed by adding a charge transporting material to a suitable binder resin, and is obtained by coating this on the photoreceptor.

The binder resin used to form the surface protective layer can be the same as that used for the charge transport layer described above, but in order to prevent the charge transport layer from being attacked by solvents, alcohol-soluble resins are preferred. In this preferred embodiment, an alcohol-soluble silicone resin (5R-120 manufactured by Toshi Co., Ltd.) was used. Further, the charge transporting material added to the surface protective layer can be the materials listed in (1) to (8) above, but is not limited to these compounds, and two or more kinds may be combined. Possible 0 The hydrazone compound used in this example is one shown in (5) above, and a coating solution prepared as above is applied by a conventional coating method to form a surface protective layer. In addition, the film thickness structure of the layers, etc. are shown in the table. However, the table shows the amount added relative to 20 parts by weight of solid resin.

The electrophotographic photoreceptor of the present invention is thus formed by laminating the charge generation layer, the charge transport layer 9 and the surface protection layer on a conductive support.

A specific embodiment of the present invention will be described below.
The present invention is not limited to the combinations shown in the following examples.

(Example 1) The charge generation layer was prepared by dispersing 3 parts by weight of butyral resin (Slenc BH-3, a product of Sekisui Chemical Co., Ltd.) and 4 parts by weight of τ-type metal-free phthalocyanine in 80 parts by weight of tetrahydrofuran. It was dip-coated onto a plate and dried at 80° C. for 1 hour to form a charge generation layer with a thickness of 0.3 μm.

Next, the charge transport layer to be formed on the charge generation layer is a coating liquid prepared by dissolving 1 part by weight of the hydrazone compound and 1 part by weight of polycarbonate (product name: TUVALEX 7030A manufactured by Mitsubishi Chemical Corporation) in 9 parts by weight of methylene chloride. was applied onto the charge generation layer by dip coating and dried at 80° C. for 1 hour to form a charge transport layer with a thickness of 16 μm. Further, for the surface protective layer, a hydrazone compound similar to that used in the charge transport layer as a charge transport material is dissolved in a silicone resin (5R-120 manufactured by Toshi Co., Ltd.) in the weight percentage shown in the table. This solution was applied onto the charge transport layer by dip coating and dried at 100° C. for 20 minutes to form a surface protective layer having a thickness of 0.6 μm and 1.2 μm, respectively.

The thus obtained laminated electrophotographic photoreceptor was tested using an electrostatic copying paper tester (EPA-810 manufactured by Kawaguchi Electric Seisakusho Co., Ltd.).
0), the initial surface potential V0 is set by a constant current high voltage power supply.
Adjust so that (volt) is charged around 700v,
Surface potential vi (volts) after 1 second of dark decay, 800 nm
When exposed to monochromatic light with a wavelength of 2.1 μW/-, the surface potential is 1/2 V.

The half-decrease exposure amount E'4 (μJ/d) as the exposure energy required to attenuate to (volt) and the residual potential vR2 (volt) at 2 seconds after exposure were measured, respectively.

Figure 1 shows the potential v after 1 second of dark decay after charging when the above-mentioned charging, dark decay, and exposure are repeated 300 times.
1. It shows how the residual potential vR2 changes 2 seconds after exposure, and similarly, FIG. 2 shows an example of how the half-reduced exposure amount EH changes. In Figure 1, the * mark indicates that the thickness of the surface protective layer is 1.2 μm and 0.05% by weight of the charge transport material is added, and the O mark indicates that the surface protective layer has a thickness of 1.2 μm and that the charge transport material is not added. Those without a surface protective layer and those marked with * indicate the variation in vi of those without a surface protective layer. Ten marks, x marks.

The marks ◇ indicate the variations in ■2□ of each of the above-mentioned surface protective layers. In addition, in FIG. 2, fluctuations in E are similarly indicated by marks, 0 marks, and ○ marks.

From Figure 1, it can be seen that the variation in vl does not change much depending on the presence or absence of a protective layer on the surface or the presence or absence of additives, but the variation in VR2 does not change significantly when no charge transport material is included in the surface protective layer. It shows the increase. This is considered to be because the charges that have moved through the charge transport layer are accumulated at the interface between the charge transport layer and the surface protective layer.

On the other hand, in the case of the case containing the additive, the increase in vR□ was the same as in the case without the surface protective layer, indicating that charge transfer was carried out smoothly. From Figure 2, half-reduced exposure amount E
〃 is also the same result as above.

Although the surface protective layer does not contain a charge transporting material, the deterioration in sensitivity is expected to occur because, as described above, the charges accumulated at the interface impede the movement of charges due to repetition.

Figure 3 shows the results when the above-mentioned repeated experiment was carried out by changing the thickness of the surface protective layer and the amount added.
The horizontal axis is the amount of hydrazone compound added, and the vertical axis is the residual potential VR1.
0 in the figure showing the amount of change ΔV of 1 indicates that the film thickness is 0
．． 6 μm, the cross indicates the case of 1.2 μm, and the Δ mark indicates the amount of change without the surface protective layer.As is clear from Figure 0, the amount of the hydrazone compound added is 0.01 to 0.
The increase in residual potential v,2 is suppressed within the range of 0.07% by weight,
Repeated stability as an electrophotographic photoreceptor can be obtained.

This is because when the thickness of the surface protective layer is 0.6 to 1.2 μm, the charge does not reach the surface only through the charge transport material, but through so-called tunneling, which passes through the silicone binder resin that forms the surface protective layer. It is also thought that it reaches the surface. This is thought to cause the amount of charge transport material added to vary to some extent.

As described above, a charge generation layer is formed on a conductive support.

When stacking charge transport layers and forming a surface protective layer containing a small amount of charge transport material on this bridge transport layer, by selecting the same material as the charge transport material contained in the charge transport layer as the charge transport material, it is possible to repeatedly An electrophotographic photoreceptor with good stability and long printing durability can be obtained.

Effects of the Invention As described above, the present invention includes laminating a charge generation layer and a charge transporting layer in this order, laminating a surface protective layer on the charge transporting layer, and including a charge transporting material in the surface protective layer. A stable electrophotographic photoreceptor with no increase in residual potential or deterioration of sensitivity can be obtained even after repeated use, and by using a silicone resin surface protective layer on the surface, an electrophotographic photoreceptor with high printing durability and excellent ozone resistance can be obtained. A photoreceptor can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are explanatory diagrams showing the relationship between the number of repetitions and electrophotographic characteristics (surface potential v1, residual potential VR, sensitivity E%) of the electrophotographic photoreceptor in an example of the present invention, and FIG. FIG. 3 is an explanatory diagram showing the relationship between the amount of charge transport material added and the amount of change in residual potential vR2.

Claims (4)

[Claims] (1) A charge generating layer and a charge transporting layer are laminated in this order on a conductive support, a surface protective layer is laminated on the charge transporting layer, and the surface protective layer contains a charge transporting material. Electrophotographic photoreceptor. (2) The electrophotographic photoreceptor according to claim (1), wherein the charge generation layer is a phthalocyanine pigment. (3) The electrophotographic photoreceptor according to claim (2), wherein the charge transport layer is a hydrazone compound. (4) The electrophotographic photoreceptor according to claim (3), wherein the charge transport material is a hydrazone compound.