JPH087447B2 - Electrophotographic photoreceptor - Google Patents

Description

The present invention relates to an electrophotographic photoreceptor.

2. Description of the Related Art Conventionally, as an electrophotographic photosensitive member, an electrophotographic photosensitive member provided with a photosensitive layer made of various organic and inorganic materials on a support has been proposed.
A so-called function-separated electrophotographic photosensitive member having a layer structure in which at least a charge-generating layer that generates a charge upon exposure and a charge-transporting layer that transports a charge is separated is predominant.

In the electrophotographic photosensitive member having the photosensitive layer thus functionally separated, a positive charging type and a negative charging type electrophotographic photosensitive member can be obtained by changing the stacking order of the charge generation layer and the charge transport layer. However, at present, as the charge-transporting material constituting the charge-transporting layer, the hole-transporting (P-type) material is mainly used, and the electron-transporting material is very few, and it has not been put into practical use. Therefore, in order to obtain a positive charging type laminated electrophotographic photosensitive member, it is usual to stack a charge generation layer on the charge transport layer.

However, since the charge generation layer usually needs to be used with a film thickness of about several microns, it has a drawback that the mechanical strength during repeated use is weak. In order to eliminate this drawback, it has been proposed to provide a low-resistance surface protective layer on the uppermost layer, and for the purpose of improving the charging property, a charge injection blocking auxiliary layer is provided at the interface between the low-resistance surface protective layer and the charge generation layer. It is also proposed to provide.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the electrophotographic photoreceptor having such a structure needs to further include a charge injection blocking auxiliary layer and a low resistance surface protective layer on the charge generation layer, and these layers are required. Depending on the type of solvent used when applying the dip coating method, the charge generation layer may be dissolved or deteriorated, and as a result, the resulting electrophotographic photoreceptor may be unusable. Further, even if it can be used, it has a drawback that the residual potential is high, and the uneven image density is caused by the uneven charging.

The present invention has been made in view of the above-mentioned drawbacks in the prior art, and an object of the present invention is to provide a positive charging type electrophotographic photoreceptor having a low residual potential. Another object of the present invention is to provide a positive charging type electrophotographic photosensitive member which forms an image without density unevenness due to uneven charging.
Still another object of the present invention is to provide a positive charging type electrophotographic photosensitive member having high photosensitivity.

Means for Solving the Problems As a result of the study, the inventors of the present invention have found that the above-mentioned drawbacks of the conventional art
The inventors have found that this can be achieved by using a polyvinyl butyral resin as a binder resin which is a constituent component of the charge generation layer and curing it with a curing agent to make it insoluble in a solvent, and completed the present invention.

Therefore, the electrophotographic photosensitive member of the present invention comprises a conductive support, a charge transport layer and a charge generating layer laminated in this order, and further, in the electrophotographic photosensitive member having a surface layer on the charge generating layer, the surface layer is , A charge injection prevention auxiliary layer and a low resistance surface protective layer provided thereon are respectively applied by a dip coating method, and the charge generation layer uses polyvinyl butyral as a binder resin and a solvent as a curing agent. It is characterized by being formed by insolubilizing it.

Next, each layer constituting the electrophotographic photosensitive member of the present invention will be described.

The conductive support in the electrophotographic photoreceptor of the present invention, aluminum, copper, iron, zinc, a drum or sheet of a metal such as nickel, and paper, plastic or glass on aluminum, copper, gold, silver, platinum, palladium,
Titanium, nickel-chrome, stainless steel, copper-
Metal such as indium is vapor-deposited, conductive metal compound (eg, In ₂ O ₃ , SnO ₂ ) is vapor-deposited, metal foil is laminated, or carbon black, conductive metal compound (eg, In ₂ O 3 _{3, Sb 2 O 3 -SnO 2} , SnO 2, TiO X) powder, metal powder or the like dispersed in a binder resin coating conductive treated drum-shaped by a sheet, those of the plate-like, etc. are used It

The charge transport layer in the electrophotographic photoreceptor of the present invention is composed of a charge transport material and a binder resin. As the charge transport material, pyrene, N-ethylcarbazole, N-isopropylcarbazole, 2,5-bis (p-diethylaminophenyl) -1,3,4-oxadiazole, 1-phenyl-
3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, 1- [pyridyl-
(2)]-3- (p-Diethylaminostyryl) -5-
(P-Diethylaminophenyl) pyrazoline, 1- [quinolyl- (2)]-3- (p-diethylaminostyryl) -5- (p-diethylaminophenyl) pyrazoline, triphenylamine, N, N'-diphenyl-N, N'-
Bis (3-methylphenyl)-[1,1'-biphenyl]
-4,4'-diamine, 4-diethylaminobenzaldehyde-1,1-diphenylhydrazone, 4,4'-benzylidene-bis (N, N'-diethyl-m-toluidine, poly-
Examples thereof include N-vinylcarbazole, halogenated poly-N-vinylcarbazole, polyvinylpyrene, polyvinylanthracene, polyvinylacridine, poly-9-vinylphenylanthracene, pyrene-formaldehyde resin and ethylcarbazole-formaldehyde resin. These charge transport materials can be used alone or in combination of two or more. The charge transport material is not limited to those described herein.

Examples of the binder resin used in the charge transport layer include acrylic resins, methacrylic resins, polystyrene, polyester, polyarylate, polysalifone, general-purpose resins such as polycarbonate, and hole-transporting polymers such as poly-N-vinylcarbazole. Can be used.

In the present invention, the charge generation layer contains, for example, 5% by weight in polyvinyl butyral in which the charge generation material is a binder resin.
To 90% by weight, preferably 20% to 50% by weight. The particle size of the charge generating material is 0.02 μm to 3 μm, preferably 0.05 μm to 1
μm is suitable.

As the charge generating material, known materials such as a phthalocyanine pigment and an azo pigment can be used, but it is particularly preferable to use a squaric acid derivative. This is because the square phosphoric acid derivative has extremely good dispersibility, particularly when an alcohol solvent is used.

In the present invention, the charge generation layer needs to be insolubilized in the solvent contained in the coating solution for applying the coating solution for forming the surface layer.

Therefore, in the present invention, a curing agent is used to cure and insolubilize polyvinyl butyral. Examples of curing agents for curing such polyvinyl butyral include isocyanates, blocked isocyanates, phenol resins, melamine resins, and epoxy resins.

Among these, it is practically advantageous to use blocked isocyanates. This is because the blocked isocyanates do not react with the aliphatic alcohol at room temperature, so that the aliphatic alcohol can be used as a solvent for the coating solution and the layer can be formed by dip coating.

The charge generation layer is formed by applying a coating solution containing a charge generation material, polyvinyl butyral and a curing agent onto the charge transport layer,
Then, it is formed by a conventional method or under heating, for example, by curing at a temperature of 130 to 160 ° C.

The surface layer of the electrophotographic photosensitive member of the present invention comprises a charge injection blocking auxiliary layer and a low resistance surface protective layer provided thereon.

A layer of a reaction product composed of a silane coupling agent and an organic zirconium compound is used as the charge injection blocking auxiliary layer.

The low resistance surface protective layer is a layer in which fine particles of a conductive metal oxide are dispersed in an insulating resin.The conductive metal oxide has an electric resistance of 10 ⁹ Ωcm or less and is white, gray or blue. Fine particles having a white average particle size of 0.3 μm or less, preferably 0.1 μm or less are suitable, and examples thereof include antimony oxide, tin oxide, titanium oxide, indium oxide,
Examples include simple substances such as a solid solution of tin oxide and antimony or antimony oxide, a mixture thereof, a mixture of these metal oxides in a single particle, or a coated product. Among them, tin oxide and antimony or a solid solution of antimony oxide, or tin oxide is preferably used because it can lower the electric resistance and can make the protective layer substantially transparent (Japanese Patent Application Laid-Open Publication No. S60-18753).
57-30847, JP-A-57-128344).

The low resistance surface protective layer has an electric resistance of 10 ⁹ to 10 ¹⁴ Ω · cm.
It is desirable to configure so that Electrical resistance 10 ¹⁴ Ω
・ If it is more than cm, the residual potential rises, resulting in a copy with a lot of fog, and if it is less than 10 ⁹ Ω ・ cm, the image becomes blurred and the resolution is lowered. Further, the low resistance surface protective layer must be constructed so as not to substantially prevent passage of light used for image exposure. If the particle size of the conductive metal oxide used is too large, the low-resistance surface protective layer becomes opaque, resulting in desensitization and reduction in image density. It is desirable to use particles having a particle size of not more than the wavelength of light used for image exposure (0.42 to 0.8 μm), preferably not more than half thereof, that is, 0.3 μm, preferably not more than 0.1 μm.
As the insulating resin, it is desirable to use an electrically insulating transparent resin whose electric resistance does not easily change due to changes in humidity or temperature. As the insulating resin, polyamide, polyurethane, polyester, epoxy resin,
Examples thereof include condensation resins such as polyketone and polycarbonate, and vinyl polymers such as polyvinyl ketone, polystyrene and polyacrylamide. Among them, polyurethane is preferably used in terms of film strength and chemical stability. The fine particles of the conductive metal oxide are preferably dispersed in the insulating resin in an amount of 20% by weight to 60% by weight. 20
If it is less than 10% by weight, the electric resistance will be 10 ¹⁴ Ω · cm or more, and if it is more than 60% by weight, the film strength of the low resistance surface protective layer will be remarkably reduced. Therefore, the dispersion is preferably performed in the range of 30% by weight to 50% by weight.

The thickness of each layer in the electrophotographic photosensitive member of the present invention is 5 to 40 μm, preferably 8 to 30 μm for the charge transport layer.
Is suitable, 5 μm or less for the charge generation layer, preferably 0.1 to 3 μm, and 3 for the charge injection blocking auxiliary layer.
It is suitable to be not more than μm, preferably 0.5 to 1 μm, and for the low resistance surface protective layer, 0.5 to 20 μm, preferably 1 to 10 μm.

Action In the present invention, since the charge generation layer is formed by using polyvinyl butyral as the binder resin and curing with a curing agent, the charge generation layer is a solvent,
Has resistance. Therefore, even when the surface layer is formed on the charge generation layer by dip coating, layer disorder does not occur in the charge generation layer and the surface layer.

Examples Hereinafter, the present invention will be described with reference to Examples.

Example 1 A charge transport layer, a charge generation layer, a charge injection element blocking auxiliary layer and a low resistance surface protective layer were sequentially laminated by dip coating on an aluminum drum by using a coating solution having the following composition, and electrophotographic exposure was performed. The body was made.

Charge transport layer (film thickness 25 μm) Polycarbonate resin 50 parts by weight (Teijin KK: Panlite C-1400) N, N′-diphenyl NN′-bis 50 parts by weight (3-methylphenyl)-[1 , 1'-Biphenyl] -4,
4'-diamine Coating solvent: Methylene chloride Appropriate amount Charge generation layer (film thickness 0.5 µm) Compound of structural formula (I) 50 parts by weight Polyvinyl butyral resin 45 parts by weight (BM-1 from Sekisui Chemical Co., Ltd.) Block isocyanate 5 parts by weight Nippon Polyurethane, Coronate 2507) Coating solvent: Ethanol / n-butanol = 1: 1 Appropriate amount After dip coating a coating solution containing the above components, 13 layers generated
It was heated to 0 to 160 ° C. and cured.

Charge injection blocking auxiliary layer (film thickness 0.1 μm) Silane coupling agent 20 parts by weight (Shin-Etsu Chemical KBN 503) Organozirconium compound 80 parts by weight (Matsumoto Pharmaceutical ZA 60) Coating solvent: ethanol / n-butanol / amyl alcohol = 4: 2: 1 Proper amount Low-resistance surface protective layer (film thickness 2 μm) Tin oxide powder 40 parts by weight Polyurethane resin 60 parts by weight Coating solvent: n-butanol / amyl alcohol = 1: 1 Appropriate amount Commercially available electrophotographic photoreceptor Electrostatic copying paper tester (Kawaguchi Denki: Electrostatic Paper Analyzer SP-428) was used to positively charge by corona discharge of + 6kV, and the surface potential VDDP after left in the dark for 1 second.
Immediately after that, tungsten light of 5 lux was irradiated for 3 seconds, and the light amount E1 / 2 required for VDDP to be reduced by half was determined. After that, the surface potential was further attenuated by irradiating 200 lux light for 0.5 seconds, and the residual potential RP was obtained. The measurement results are shown below.

VDDP: 900V E1 / 2: 3 lux ・ sec RP: 90V After that, repeat the 10K cycle measurement, surface potential VDD
P and residual potential RP were determined. The results were as follows.

VDDP: 860V RP: 110V From the above results, it was confirmed that the electrophotographic photosensitive member of this example had little potential fluctuation, and that it showed good image quality characteristics even after 10 K cycles.

Furthermore, as a result of observing a cross section of this electrophotographic photosensitive member with a transmission electron microscope, it was confirmed that the layer structure had high integrity, and the surface property was also good with Rmax of 1 μm or less. I understood.

Comparative Example No blocked isocyanate was used for the charge generation layer in Examples, and the charge injection auxiliary blocking layer was
An electrophotographic photosensitive member was produced in the same manner as in the above-described examples except that the production was performed by spray coating, and the measurement was performed in the same manner as in the examples. The measurement results are shown below.

VDDP: 850V E1 / 2: 3 lux ・ sec RP: 110V After that, repeat the 10K cycle measurement, surface potential VDD
P and residual potential RP were determined. The results were as follows.

VDDP: 700V RP: 150V As is clear from the above results, the electrophotographic photosensitive member of Comparative Example had a slightly high residual potential and a decrease in cycle characteristics. Regarding this image quality, after 1K cycles, it was a copy image with high fog due to poor cleaning.

Observation of the cross section of this electrophotographic photosensitive member revealed that the charge generation layer was disturbed by the coating of the charge injection blocking auxiliary layer, which is considered to be dissolved. It was also found that the surface resistance of the low-resistance surface protective layer was not uniform, corresponding to the disturbance of the lower layer, and Rmax was 3 μm.

EFFECTS OF THE INVENTION Since the electrophotographic photoreceptor of the present invention has the above-mentioned constitution, even if a dip coating method is used for forming the layer, the charge generation layer, the charge injection blocking auxiliary layer and the low resistance surface formed thereon are formed. The protective layer is a positively charged type having uniform surface characteristics without disturbance of the layer. Therefore, the electrophotographic photosensitive member of the present invention has high photosensitivity, shows a low residual potential, and forms an image without density unevenness due to uneven charging. Furthermore, the electrical characteristics are stable during repeated use.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyokazu Shimowa 1600 Takematsu, Minamiashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Plant (72) Inventor Noriaki Takahashi 1600 Takematsu, Minami Ashigara City, Kanagawa Prefecture Fuji Xerox Co., Ltd. Takematsu Business In-house (56) References JP 61-34548 (JP, A) JP 50-96230 (JP, A) JP 60-232553 (JP, A) JP 57-128344 (JP, A)

Claims (1)

[Claims] 1. An electrophotographic photosensitive member comprising a conductive support, a charge transport layer and a charge generating layer which are sequentially laminated, and a surface layer on the charge generating layer, wherein the surface layer is a charge injection blocking auxiliary layer. And a low-resistance surface protective layer provided thereon by a dip coating method, and the charge generation layer is formed by using polyvinyl butyral as a binder resin and insolubilizing it in a solvent with a curing agent. An electrophotographic photosensitive member characterized by being obtained.