JPS63210848A - Electrophotographic sensitive body - Google Patents

Abstract

PURPOSE:To increase the sensitivity of the titled body, and to lessen the decrease of the electrification and the increase of the residual potential of the titled body in case of repeated use, by providing with an intermediate layer contg. an electron- movable pigment, thereby smoothing the transfer of electron to be flowed to a conductive substrate side in charge carrier generated in a photosensitive layer by exposing the titled body. CONSTITUTION:The intermediate layer 2 contg. the electron movable pigment is provided between a conductive substrate body 1 and the photosensitive layer in the negative charge titled body which is formed the photosensitive layer contg. a photoconductive substance on the conductive substrate body. The negative charge is formed on the surface of an electric charge transfer layer 4 by charging the titled body, and in case of projecting a photoimage to the titled body by exposing, an electron-hole pair generates in the electric charge generating layer 3, and the electron flows to the charge transfer layer 4, thereby neutralizing the negative charge existing on the surface of the charge transfer layer. While, the electron flows to the conductive substrate body 1 through the intermediate layer. As the intermediate layer 2 contains the electron movable pigment, even if the thickness of the intermediate layer 2 is large, the electron generated in the charge generating layer 3 easily passes through the intermediate layer 2, whereby the sensitivity of the titled body does not reduce.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electrophotographic photoreceptor, and more particularly to an electrophotographic photoreceptor having an intermediate layer between a conductive substrate and a photosensitive layer.

Prior Art Conventionally, inorganic photoconductive substances such as selenium, cadmium sulfide, and zinc oxide have been widely used in the photosensitive layer of electrophotographic photoreceptors. In recent years, research on the use of organic photoconductive substances in photosensitive layers has progressed, and some of them have been put into practical use. Organic photoconductive materials have advantages over inorganic materials, such as light weight, good film-forming properties, good manufacturability, and safety.

The form of electrophotographic photoreceptors using these organic photoconductive substances is a dispersed single layer in which the photoconductive substance is dispersed in a binder resin, with a dye as a sensitizer added and dispersed as needed. There are photoreceptors and functionally separated photoreceptors in which charge generation and transfer are performed by different substances. Zaraani function-separated photoreceptors include a single-layer photoreceptor obtained by adding a charge-generating substance and a charge-mobilizing substance to a binder resin, and a charge-generating layer mainly composed of a charge-generating substance. There is a laminated type photoreceptor which is formed by laminating a charge transport layer containing a charge transporting substance as a main component.

By the way, when a single-layer photoreceptor in which a photoconductive substance is dispersed in a binder resin is installed in an electrophotographic device and used repeatedly, it will become charged due to electrophotographic processes such as charging, exposure, and neutralization. It has the disadvantage of exhibiting fatigue phenomena such as a decrease in potential and fluctuations in photosensitivity. In order to prevent this, it is known to provide an intermediate layer as a barrier layer between the photosensitive layer and the conductive substrate. . By providing such an intermediate layer, the charging potential in the charging process is improved, but in the exposure process, the ability to attenuate the charging potential decreases, resulting in poor photosensitivity.Moreover, during repeated and continuous use, it may remain on the photoreceptor. There is a tendency for the potential to accumulate and the background smudge of the image to become severe.

On the other hand, in a laminated photoreceptor, the surface of the photoreceptor is charged by corona discharge during use, and electron-hole pairs are generated in the charge generation layer according to the light image by exposure, and these positive and negative charge carriers are Charge carriers of one polarity flow toward the conductive substrate, and charge carriers of the other polarity are injected into the charge transport layer, move to the surface, neutralize the charged charges, and become static. Forms an electrolatent image.

Even in this case, intermediate steps are taken to improve the adhesion between the substrate and the charge generation layer, to improve the coatability of the charge generation layer, to protect the substrate, to cover defects on the substrate, to protect the photosensitive layer from electrical breakdown, etc. It is effective to form layers. However, depending on the composition of the charge generation layer, charge carriers that should flow into the substrate may be prevented from moving, and may be recombined with charge carriers of the other polarity in the charge generation layer, or at the boundary between the intermediate layer and the charge generation layer. Because they accumulate and form a barrier due to space charges, repeated use may cause fatigue phenomena such as a decrease in charged potential and an increase in residual potential.

As a means to prevent these defects, it has been proposed to include an electron-donating substance in the intermediate layer. For example, Japanese Patent Publication No. 61-35551 discloses that a barrier layer containing a non-hydrophilic peptide polymer and an electron donating substance or an electron accepting substance is provided in Japanese Patent Publication No. 60-21865.
5 discloses that an undercoat layer containing an electron-donating substance is provided, and JP-A-61-80158M discloses that an undercoat layer containing a hydrazone compound (a type of electron-donating substance) is provided. , JP-A No. 61-204640 discloses an undercoat containing a charge transporting material (all electron-donating substances) such as imidazole, pyrazoline, thiazole, oxadiazole, oxazole, hydrazone, ketazine, azine, carbazole, and polyvinylcarbazole. It is described that a layer is provided.

On the other hand, on the contrary, Japanese Patent Publication No. 61-35551 and Japanese Unexamined Patent Application Publication No. 59/1988 disclose that the above problem can be solved by incorporating an electron-accepting substance in the intermediate layer to facilitate the passage of electrons. It is described in the publication No.-160147.

Problems to be Solved by the Invention However, when the intermediate layer contains an electron-donating substance as described above, it is difficult for the electrons generated in the photosensitive layer to pass through, and the electrons become a trap. This inevitably causes recombination with the pores, resulting in a decrease in sensitivity, and the intermediate layer is no longer able to function satisfactorily.

On the other hand, when the intermediate layer contains an electron-accepting substance,
Although it functions well as an intermediate layer,
Nitro derivatives of aromatic compounds, chloranyl, bromoanil, 2,4.
7-dolinitro 9-fluorenone, 2,4.5.7-
Tetranitro-9-fluorenone, tetracyanopyrene, dinitroanthraquinone, trinitroindenothiophene, trinitroindenoquinoxaline, tetracyanoethylene, tetracyanoquinodimethane, 2,3-dichloro-p-benzoquinone, 2,5-dichloro -p-benzoquinone, trichloro-p-benzoquinone, p-iodoanil, 2,6-dichloro-p-benzoquinone, etc. are soluble in solvents, so when forming a photosensitive layer on the intermediate layer by coating, electron-accepting The disadvantage was that the chemical substance seeped into the photosensitive layer. That is, it has the disadvantage that it is unsuitable when a photosensitive layer is formed by a dip coating method that requires a considerably long contact time with a solvent.

The present invention has been made in view of the above-mentioned problems in the conventional technology.

Therefore, an object of the present invention is to provide an electrophotographic photoreceptor having excellent electrophotographic properties and having an intermediate layer that is not disturbed during the formation of the photosensitive layer.

Means for Solving the Problems As a result of investigation, the present inventors have determined that, in place of a solvent-soluble electron-accepting substance, an electron-mobilizing substance is used in the intermediate layer provided between the photosensitive layer and the conductive substrate. The inventors have discovered that the above objects of the present invention can be achieved by using pigments, and have completed the present invention.

The present invention provides a negatively charged electrophotographic photoreceptor in which a photosensitive layer containing a photoconductive substance is formed on a conductive substrate.
It is characterized in that an intermediate layer containing an electron-transfer pigment is provided between the conductive substrate and the photosensitive layer.

The present invention will be explained in detail below.

In the electrophotographic photoreceptor of the present invention, the conductive substrate is not particularly limited as long as it has conductivity and can serve as a support member. Specific examples include sheet aluminum, copper, nickel, silver, palladium,
Indium, lead, gold, platinum, stainless steel, etc.; aluminum, copper, nickel, silver, palladium, etc. on insulating sheets
Substrates obtained by coating indium, lead, gold, platinum, etc.; metal pipes made of aluminum, stainless steel, nickel, etc., and the like.

An intermediate layer is formed on the conductive substrate, and the intermediate layer is
Composed of electron-transfer pigment and resin.

In the present invention, the electron transfer pigments preferably used include organic pigments such as perylene pigments, polycyclic quinone pigments, bisbenzimidazole pigments, indigo pigments, and quinacridone pigments described in JP-A-47-30330, and zinc oxide pigments. , titanium oxide, and other inorganic pigments. Among these pigments, perylene pigments and polycyclic quinone pigments are preferred because they have high electron mobility. These pigments also have a high ability to absorb light and generate charges, so if they are dispersed in the intermediate layer, the intermediate layer will function as a charge-generating layer, which can also be expected to improve sensitivity.

In addition, in this specification, the polycyclic quinone pigment refers to a quinone compound having three or more condensed aromatic rings, such as anthoanthrone as described in JP-A-47-18544. , pyranthrone, dibenzpyrenequinone, pyrenequinone, 3,4.9.10-dibenzpyrenequinone, brominated anthrone, brominated dibenzpyrenequinone, brominated pyranthrone, anthraquinone thiazole, flavanthrone, etc., as well as chlorinated Examples thereof include anthantrone, dimethoxyanthanthrone, violanthrone, isoviolanthrone, dianthraquinone, anthrapyrimidine, indanthrone, dichloroisoviolanthrone, benzanthrone, acridine, acridone caflevazole, and sinapthaloyl acridone.

In addition, many bisazo pigments and phthalocyanine pigments are hole-transferring and therefore are not suitable for use in the present invention, but electron-withdrawing substituents such as cyan groups, nitro groups, nitroso groups, and halogen atoms can be introduced. Some of these have electron mobility and can be used in the present invention.

To determine whether or not a pigment is electron-mobile, the pigment can be vapor-deposited or dispersed in a resin at a high concentration, applied to form a thin layer, charged positively or negatively, and then measured for chargeability. good. In this case, the electron-transfer pigment is preferably one that is only negatively charged and has low positive chargeability. Conversely, it is only positively charged,
Those with low negative chargeability have hole mobility, and those that can be charged both positively and negatively have low conductivity and high insulation properties, and are not preferred for the present invention. Furthermore, those with low positive and negative chargeability have too high conductivity, lack barrier properties, and cannot be used in the present invention.

On the other hand, as the resin, resins that are well known as those conventionally used for intermediate layers can be used. Specifically, polyvinyl alcohol, polyvinyl methyl ether, poly-N-vinylimidazole, polyethylene oxide, ethyl cellulose, methyl cellulose, ethylene-acrylic acid copolymer, polyamide, casein, gelatin, polyethylene, polyester, phenolic resin, vinyl chloride. Examples include vinyl acetate copolymer, epoxy resin, polyvinylpyrrolidone, polyvinylpyridine, polyurethane, polyglutamic acid, polyacrylic acid, and the like. The resistivity of the resin alone is 10 to 10 in the conventional intermediate layer.
Although about 14 Ω·cm was preferable, in the present invention, since an electron-transfer pigment is mixed into the resin, the resistance is about 1014 Ω·cm.
It can be used even if it is higher than 10~1016Ω・
About cm is preferable. In the present invention, the thickness of the intermediate layer is 0.3 to 0.3 to bring out the barrier function.
It is preferable to set it slightly thicker, about 6μ.

To form the intermediate layer, the electron-transfer pigment is dispersed in a solution of the resin, coated on the substrate, and dried. The weight ratio of the electron transfer pigment to the resin is set to about 0.01:1 to 2:1. If the amount of the electron-transferring pigment is small, the effect of allowing electrons to pass therethrough is small, and if it is too large, the film-forming properties of the intermediate layer and the coating properties of the layer formed thereon may be impaired. As the dispersion method, a conventional method using a ball mill, roll mill, sand mill, attritor, ultrasonic wave, etc. is applied.

A photosensitive layer is formed on the intermediate layer. The photosensitive layer may be of a single layer type or of a function-separated layered structure as long as it is negatively chargeable. An example of a single layer type is dye-sensitized Zn
Examples include an O photosensitive layer, a CdS photosensitive layer, and a photosensitive layer in which a charge-generating substance is dispersed in a charge-transporting substance. On the other hand, in the case of a functionally separated layered structure, a charge generation layer is formed first. The charge generation layer is formed by dispersing a charge generation substance in a binder resin as required.

Examples of charge generating substances include selenium and selenium alloys; CdS, CdSe, Cd5Se, ZnO and Z
Inorganic photoconductors such as nS; metal phthalocyanine and metal-free phthalocyanine pigments; azo pigments such as bisazo pigments and trisazo pigments; squareium compounds, azulenium compounds, perylene pigments; indigo pigments; quinacridone pigments, polycyclics as mentioned above Examples include bovine non-dianine dyes; xanthine dyes; charge transfer complexes consisting of poly-N-vinylcarbazole and trinitrofluorenone; and eutectic complexes consisting of pyrylium salt dyes and polycarbonate resins. The pigment may be the same as the pigment used in the intermediate layer, as long as it is an electron-transferable pigment.

As the binder resin, well-known ones such as polycarbonate, polystyrene, polyester, polyvinyl butyral, methacrylic acid ester polymer or copolymer, vinyl acetate polymer or copolymer, cellulose ester or ether, polybutadiene, polyurethane, epoxy Resin etc. are used.

A charge transport layer is formed on the charge generation layer.

The charge transport layer is made of a charge transport substance.

The charge transfer substance is not particularly limited as long as it is transparent to visible light and has charge transport ability, and specific examples include imidazole, pyrazoline, thiazole, oxadiazole, and oxazole. , hydrazone, ketazine, azine, carbazole, polygonylcarbazole, and derivatives thereof, triphenylamine derivatives, stilbene derivatives, benzidine derivatives, and the like. A binder resin is used in combination as necessary, but
Examples of the binder resin include polycarbonate, polyarylate, polyester, polystyrene, styrene acriminitrile copolymer, polysulfone, polymethacrylate, and styrene-methacrylate copolymer.

Among these, polycarbonate is preferred.

Function The function of the electrophotographic photoreceptor of the present invention will be explained with reference to FIG. FIG. 1 is a schematic diagram of the electrophotographic photoreceptor of the present invention having a function-separated layered structure, in which (a> shows the state when charged, and (b) shows the state when irradiated with light. In the figure, 1 is a conductive substrate, 2 is an intermediate layer, 3 is a charge generation layer, and 4 is a charge transport layer.

The electrophotographic photoreceptor of the present invention is used with negative charge. That is, due to the charging, negative charges are formed on the surface of the charge transport layer (FIG. 1(a)). Next, when a light image is irradiated by exposure, electron-hole pairs are generated in the charge generation layer, and the holes flow through the charge transport layer and neutralize the negative charges on the surface, while the electrons
It flows through the intermediate layer to the conductive substrate. (Figure 1(b)
). In the case of the present invention, since the intermediate layer contains an electron-transporting pigment, electrons generated in the charge generation layer can easily pass through the intermediate layer even if the intermediate layer is thick. , without causing a decrease in sensitivity.

Example Hereinafter, the present invention will be explained by examples.

Examples 1-5 The following pigment was prepared as an electron-transferable pigment.

1. Brominated anthrone (C, 1, Pigment Red 168) 2. Flavanthrone (C, 1, Pigment Yellow)
112> 3, Perylene (C, 1, Pigment Red 179> 4
, Perylene (C,1, Pigment Red 123)5.
2nO The electron mobility of these pigments was investigated as follows.

First, 1 part (by weight, same hereinafter) of the pigment was dispersed by ultrasonic waves into 2.5 parts of a 2% cyclohexanone solution of polyvinyl butyral resin (trade name: 8M2 manufactured by Sekisui Chemical ■). Spread this dispersion onto aluminum foil using a wire bar.
It was coated to a thickness of μ and allowed to dry. This was positively or negatively charged using an electrostatic tester rSP-428 model (manufactured by Kawaguchi Electric), and the charging properties were compared. All of the above five examples have a large negative chargeability.

Next, to form the middle layer, a copolymerized nylon resin (
10 parts (trade name: CH3000 manufactured by Toshi ■) were dissolved in 60 parts of methanol and 30 parts of 1-butanol. Five parts of each of the above pigments were well dispersed in this using a sand mill device. This dispersion was mixed with a ring mum of 64φ
33 Bam aluminum pipe (maximum surface roughness 0.
5μ) and dried at 100°C for 10 minutes to form an intermediate layer with a thickness of 2μ.

Next, 8 parts of the same brominated anthrone as above was mixed with 20 parts of a 5% cyclohexanone solution of the same polyvinyl butyral resin as above, and sand mill dispersion was performed. Further, 30 parts of cyclohexanone was added to the dispersion to form a coating, which was then placed in the dip coating apparatus shown in FIG. FIG. 2 is an explanatory diagram showing the general structure of the dip coating device, in which the pipe 5 is immersed in the coating liquid 6 in the coating groove 7 and pulled up.
Coating is done. 8 is a pump for paint circulation, and 9 is a filter. The coating operation involved dipping the pipe at a speed of 800 m/min, then pulling it up at a speed of 150 m/min,
The whole thing took about 5 minutes.

Drying was performed at 100° C. for 10 minutes to form a charge generation layer with a thickness of 2 μm.

A charge transport layer was formed on the formed charge generation layer.

That is, 5 parts of N,N-diphenyl-N,N-bis(3-methylphenyl)[1,1°-biphenyl]-4,4-diamine are used as a charge transport material, along with 6 parts of polycarbonate Z resin and 40 parts of monochlorobenzene. dissolved in
The resulting solution was coated using a dip coater at a pulling speed of 11 cm/min. Dry at 110℃ for 1 hour.2
A charge transport layer with a thickness of 0μ is formed, and an electrophotographic photoreceptor (NQI
- No. 5) was obtained.

These electrophotographic photoreceptors were charged with a -5.5 kV corotron charger A), and after 1 second 9, Oerg
The electric potential of each part was measured by the process of irradiating white light of s/7 to cause discharge (B), and after 3 seconds, irradiating 50 ergs/crA (D green light to eliminate static electricity (C)). (The higher the potential of A>, the higher the acceptance potential of the photoreceptor, so the contrast can be increased, and (B)
The lower the potential of (C) is, the higher the sensitivity is, and the lower the potential of (C) is, the less residual charge there is, and it can be said that the photoreceptor has less image memory and less fog. Table 1 shows the measurement results of electrophotographic photoreceptors using each pigment.

Furthermore, when these electrophotographic photoreceptors were placed in an electronic copying machine and a copying operation was performed, good images with no image quality defects could be obtained in all cases.

Comparative Examples 1 to 4 Electrophotographic photoreceptors were prepared in the same manner as in Examples 1 to 5, except for the following points, and measurements were performed in the same manner.

1. No intermediate layer was formed.

2. An intermediate layer (thickness 2 μm) formed without adding pigment.

3. An intermediate layer (thickness 0.5 μm) formed without adding pigment.

4. Prepared in the same manner except that β-type copper phthalocyanine, which has no electron mobility, was used as the pigment.

5. Created in the same manner except for using chloranil, an electron-accepting substance, in place of the pigment.

In Comparative Example 5, when the charge generation layer was coated on the intermediate layer by dip coating, chloranil was eluted into the charge generation layer coating solution and changed the physical properties of the coating solution, which was unsuitable. Table 2 shows the potential measurement results for Comparative Examples 1 to 4.

In Comparative Example 1 of Table 2, since there was no intermediate layer, the acceptance potential was lowered, and in order to achieve a voltage of about -800 V, which is similar to other electrophotographic photoreceptors, it was necessary to strengthen the charging conditions. Comparative example 2
In this case, the residual potential increased due to the resistance of the intermediate layer itself, and the sensitivity also decreased. In Comparative Example 4, it was even worse.

When copying images of these electrophotographic photoreceptors were evaluated, the image density was lower in Comparative Example 1, and in Comparative Examples 1 and 3, a pattern was formed on the photosensitive layer depending on the roughness of the surface of the aluminum pipe used as the substrate. This made it unsuitable for use as an electrophotographic photoreceptor.

In Comparative Examples 2 and 4, images with fog were formed, which were also unfavorable.

As described above, the electrophotographic photoreceptor according to the present invention having an intermediate layer containing an electron-transferring pigment had good potential characteristics and no defects in the copied images.

Effects of the Invention In the present invention, by providing an intermediate layer containing an electron-transferring pigment, among the charge carriers generated in the photosensitive layer by exposure, electrons that should flow toward the conductive substrate side can be smoothly moved. Since recombination of charge carriers within the photosensitive layer is reduced and charge carriers are not accumulated at the boundary between the conductive substrate and the photosensitive layer, there is no space charge barrier, resulting in high sensitivity and ease of repeated use. Copies with less decrease in charging, less increase in residual potential, and less background smudge can be obtained.

In general, since it can be formed thicker than conventional intermediate layers, the original purpose of the intermediate layer, such as preventing the injection of unnecessary carriers, protecting against discharge breakdown, and covering defects in the substrate, can be further enhanced, making it possible to achieve high performance electronics. A photographic photoreceptor can be provided.

Furthermore, in the electrophotographic photoreceptor of the present invention, since the electron-transferring pigment contained in the intermediate layer does not bleed into the photosensitive layer during manufacture, the effects of the intermediate layer are further exhibited.

[Brief explanation of the drawing]

FIG. 1 shows an example of the electrophotographic photoreceptor of the present invention, in which (a) is a schematic diagram showing the state when charged, (b) is a schematic diagram showing the state when irradiated with light, and FIG. 2 is a schematic diagram showing the electrophotographic photosensitive member of the present invention. FIG. 1 is an explanatory diagram showing a schematic configuration of a dip coating device used to form a photoreceptor. DESCRIPTION OF SYMBOLS 1... Conductive substrate, 2... Intermediate layer, 3... Charge generation layer, 4... Charge transport layer, 5... Pipe, 6...
Coating liquid, 7...5 coating tanks, 8...Pump, 9...
filter. Patent applicant Fuji Xerox Co., Ltd. Agent
Patent Attorney Tsuyoshi Horabe 2 Middle class
' is also shown in Figure 1.

Claims (5)

[Claims] (1) In a negatively charged electrophotographic photoreceptor in which a photosensitive layer containing a photoconductive substance is formed on a conductive substrate, an intermediate containing an electron-transfer pigment is provided between the conductive substrate and the photosensitive layer. An electrophotographic photoreceptor characterized by having a layer. (2) The electrophotographic photoreceptor according to claim 1, wherein the electron transfer pigment is a polycyclic quinone pigment. (3) The electrophotographic photoreceptor according to claim 2, wherein the polycyclic quinone pigment is brominated anthrone. (4) The electrophotographic photoreceptor according to claim 1, wherein the electron transfer pigment is a perylene pigment. (5) The electrophotographic photoreceptor according to claim 1, wherein the electron-transferring pigment is the same as the pigment contained in the charge generation layer.