JP2002099107A - Electrophotographic photoreceptor and electrophotographic device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic photoreceptor in which an electrostatic leak is suppressed by improving a base layer and then has excellent performance, and to provide an electrophotographic device using it. SOLUTION: This electrophotographic photoreceptor which has a base layer and a photosensitive layer on a conductive base is characterized by that the volume resistance value of the base layer at an arbitrary voltage in an electrostatic charging direction has nonlinear characteristics times as large as the volume resistance value in an electric field >=5 times as large as the electric field. The electrophotographic device is equipped with this electrophotographic photoreceptor and a contact electrostatic charging member which comes into contact with the electrophotographic photoreceptor to electrostatically charge the electrophotographic photoreceptor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laminated type and a single-layer type electrophotographic photosensitive member having a photosensitive layer containing an organic material, which is used in an electrophotographic apparatus such as an electrophotographic printer or a copying machine. , And also simply referred to as a "photoreceptor") and an electrophotographic apparatus using the same.

[0002]

2. Description of the Related Art A photoreceptor for electrophotography has a structure in which a photosensitive layer having photoconductivity is laminated on a conductive substrate, and a single photosensitive layer has both functions of generating and transporting charges. A photoreceptor and a function-separated laminated photoreceptor having a photosensitive layer that is functionally separated into a layer contributing to charge generation and a layer contributing to surface charge retention and charge transport are generally used.

Many conventional photoconductors use an inorganic material such as selenium or a selenium alloy. In recent years, a so-called organic photoconductor using an organic material has been developed due to advantages such as thermal stability and film forming property. Many have been put to practical use. Since it is difficult for these photoconductors to form a mechanically stable photosensitive layer only with a functional material that is responsible for charge generation and charge transport, the photoconductor is usually formed by forming a photosensitive layer together with a resin binder. Has been realized.

[0004] In recent years, a function-separated laminated type photoreceptor using a laminated structure of a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance has become the mainstream. An organic pigment as a charge generating substance is deposited or dispersed in a resin binder to form a layer formed as a charge generating layer, and an organic low-molecular compound having a charge transport function is dispersed in the resin binder as a charge transport substance. There have been proposed many negatively charged organic photoreceptors in which these layers are used as charge transport layers and these layers are sequentially laminated. Further, a positively-charged photosensitive member using a single photosensitive layer in which a charge generating substance and a charge transporting substance are dispersed in a resin binder has been proposed.

Generally, between the support of the photosensitive layer and the charge generation layer or the photosensitive layer, unnecessary charge injection from the support to the photoreceptor is prevented, the surface of the substrate is covered with defects, and the adhesion of the photosensitive layer is reduced. An undercoat layer is provided for the purpose of improving the quality of a printed image and the like.

In particular, when the electrophotographic photosensitive member is applied to an electrophotographic apparatus of the Carlson process, in order to suppress defects such as black spots and white spots on a printed image, the electrophotographic photoreceptor may be disposed under the charge generating layer or under the photosensitive layer. The structure which introduces the pulling layer is adopted. In this case, as a material of the undercoat layer, casein, polyamide resin, polyvinyl butyral resin, polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl formal resin,
Polyurethane resins, epoxy resins, phenoxy resins, polyester resins, melamine resins, silicone resins, and the like are known, but when these resins are used to form an undercoat layer, dot defects on a printed image are thereby reduced. Can be suppressed, but the sensitivity characteristic of the photoreceptor tends to be deteriorated. Therefore, it is necessary to form the photosensitive member with the minimum necessary film thickness capable of suppressing the printing defect.

[0007]

However, if the thickness of the undercoat layer is too small, charge leakage of the photoconductor occurs due to deterioration due to repeated use of charging, exposure, development, transfer and cleaning in the Carlson process, This may cause defects, particularly when a contact charging process is used. As a countermeasure, a method has been proposed in which an anodized film is formed on a supporting substrate instead of an undercoat layer to suppress charge leakage, but this method is sufficiently satisfactory in terms of cost, quality stability, and the like. Was not.

It is an object of the present invention to provide an electrophotographic photoreceptor having good performance in which the occurrence of charge leakage is suppressed by improving the undercoat layer, and an electrophotographic apparatus using the same. .

[0009]

In order to solve the above-mentioned problems, a photoconductor for electrophotography according to the present invention is a single-layer electrophotographic photoconductor having an undercoat layer and a photosensitive layer on a conductive substrate. Wherein the undercoat layer has a non-linear characteristic in which a volume resistance value in an arbitrary electric field in a charging direction is five times or more a volume resistance value in an electric field five times the electric field.

In the present invention, the undercoat layer preferably has a non-linear characteristic of volume resistivity in the range of 2 V / μm to 60 V / μm. It is also preferable that the volume resistance value at a voltage is 100 times or more the volume resistance value of the undercoat layer under the same electric field. Preferably, the thickness of the undercoat layer is 2 μm or more.

An electrophotographic apparatus according to the present invention is an electrophotographic apparatus comprising: an electrophotographic photosensitive member; and a contact charging member that contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member. The electrophotographic photoconductor is the electrophotographic photoconductor of the present invention.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a negatively-charged-function-separated multi-layered electronic device in which a photosensitive layer 6 formed by sequentially laminating a charge generation layer 3 and a charge transport layer 4 on a conductive substrate (supporting substrate) 1 via an undercoat layer 2 is shown. FIG. 2 shows a positively charged single-layer electrophotographic photoconductor in which a single-layer photosensitive layer 5 is formed on a conductive substrate 1 via an undercoat layer 2.

The photoreceptor of the present invention only needs to have an undercoat layer and a photosensitive layer on a conductive substrate, and includes both a single layer type and a laminated type. Hereinafter, the present invention is shown in FIG.
This will be described in detail with reference to the laminated photoconductor shown in FIG.

The conductive substrate 1 serves not only as an electrode of the photoreceptor but also as a support for the other layers, and may be any of a cylinder, a plate, and a film.
A metal, such as aluminum, stainless steel, nickel, or the like, or glass, resin, or the like that has been subjected to a conductive treatment may be used.

The undercoat layer 2 is provided for the purpose of preventing injection of unnecessary charges from the conductive substrate into the photosensitive layer, covering defects on the surface of the substrate, improving the adhesiveness of the photosensitive layer, and improving the quality of printed images.
In the present invention, the undercoat layer 2 has a non-linear characteristic in which the volume resistance value in an arbitrary electric field in the charging direction is 5 times or more, preferably 10 times or more, the volume resistance value in an electric field 5 times the electric field. It is important that this non-linear characteristic is satisfied in the range of 2 V / μm to 60 V / μm,
In particular, the volume resistance at an electric field of 10 V / μm is at least five times the volume resistance at 50 V / μm. Thereby, since the volume resistance at the time of a high electric field is small and the volume resistance at the time of a low electric field is large, even when a current flows through the undercoat layer, the voltage applied to the undercoat layer becomes low, As a result, dielectric breakdown can be suppressed,
In particular, even when charging is performed by a contact charging method, an effect is obtained that a leak hardly occurs.

As a method of adjusting the volume resistance value, for example,
Means such as changing the amount of the titanium oxide fine powder to be added to the undercoat layer, performing a surface treatment on the titanium oxide fine powder with aminosilane or polyaniline, or changing the treatment rate can be used. There is no particular limitation.
For example, the volume resistivity can be increased by increasing the processing rate of the aminosilane treatment.

As long as the above conditions are satisfied, the material and additives of the undercoat layer can be appropriately determined. For example, as a resin binder for forming an undercoat layer as a resin layer, casein, polyethylene, polypropylene, polystyrene, acrylic resin, vinyl chloride resin, vinyl acetate resin, polyvinyl formal resin, polyurethane resin, epoxy resin, phenoxy resin, Examples thereof include a polyester resin, a melamine resin, a silicon resin, a polybutyral resin, a polyamide resin and a copolymer thereof, and these can be used alone or in an appropriate combination. The metal oxide fine particles to be dispersed in the resin may be SiO ₂ , TiO ₂ , In ₂ O ₂ , ZrO ₂ , Al ₂ O ₃ , which have no conductivity.
Etc. can be used. In addition, these metal oxide fine particles can be fine particles subjected to a surface treatment with a silane coupling agent in order to improve dispersion stability and photosensitive characteristics. The thickness of the undercoat layer is preferably 2 μm or more,
More preferably, it is 5 μm or more.

The charge generation layer 3 is formed by vacuum-depositing an organic photoconductive substance or applying a coating liquid in which particles of the organic photoconductive substance are dispersed in a resin binder, and receives light. Generate electric charge. It is important for the charge generation layer 3 to have high charge generation efficiency and at the same time to have an ability to inject generated charges into the charge transport layer 4. Therefore, it is possible to use a charge generation material as a main component and a charge transport material or the like added thereto. As the charge generating material, metal-free phthalocyanine, phthalocyanine pigments such as titanyl phthalocyanine, tin phthalocyanine, azo pigments, anthantrone pigments, perylene pigments, perinone pigments, squarylium pigments, thiapyrylium pigments, quinacridone pigments, and the like can be used. These pigments may be used in combination.

As the resin binder for the charge generation layer,
Polycarbonate resin, polyester resin, polyamide resin, polyurethane resin, epoxy resin, polyvinyl butyral resin, polyvinyl acetal resin, vinyl chloride resin, phenoxy resin, silicone resin, methacrylate resin and copolymers thereof alone or Can be used in appropriate combination.

The charge transport layer 4 is formed by forming a coating solution obtained by dissolving a charge transport material and a resin binder in a solvent by a seal coating method, a dip method, or the like. As the charge transport material, hydrazone compounds, styryl compounds, pyrazoline compounds, pyrazolone compounds, oxadiazole compounds, arylamine compounds, benzidine compounds, stilbene compounds, butadiene compounds and charge transport polymers such as polyvinylcarbazole,
It is possible to use a copolymer of a binder and a charge transporting material. In addition, as the resin binder, a polycarbonate resin, a polyester resin, a polystyrene resin, a polymer and a copolymer of methacrylic acid ester, and the like can be used. Charge transport layer 4 so that chemical and electrical stability and adhesion are ensured.
Is preferably formed. In order to maintain a practically effective surface potential, the thickness of the charge transport layer 4 should be 10 to 50.
The range of μm is preferred.

In the case of a single-layer type photoreceptor, it is sufficient that an undercoat layer satisfying the above conditions according to the present invention is provided. It can be formed using a binder or the like, and there is no particular limitation.

In the present invention, the volume resistance of the charge transport layer 4 in the dark and the photosensitive layer 5 in the case of the single layer type is 100 times the volume resistance of the undercoat layer 2 under the same electric field. It is preferable that the above values be used.

Further, the laminated photosensitive layer 6 and the single-layer photosensitive layer 5 may contain an antioxidant or the like as appropriate for the purpose of improving stability against heat, ozone and the like. Compounds used for such purposes include chromanol derivatives such as tocopherol or etherified compounds or esterified compounds, polyarylalkane compounds, hydroquinone derivatives and monoetherified or dietherified compounds thereof, benzophenone derivatives, benzotriazole derivatives, Thioether compounds, phenylenediamine derivatives, phosphonic acid esters,
Phosphite, phenolic compound, hindered phenolic compound, linear amine compound, cyclic amine compound,
Hindered amine compounds and the like.

Further, the photosensitive layer may contain an electron-accepting substance, if necessary, for the purpose of improving the sensitivity, reducing the residual potential, or reducing the characteristic fluctuation upon repeated use. As the electron acceptor, succinic anhydride, maleic anhydride, dibromosuccinic anhydride, phthalic anhydride, 3-nitrophthalic anhydride, 4-nitrophthalic anhydride, pyromellitic anhydride, pyromellitic acid, trimellitic acid, Examples thereof include compounds having a high electron affinity such as trimellitic anhydride, phthalimide, 4-nitrophthalimide, tetracyanoethylene, tetracyanodimethane, chloranil, bromanyl, and o-nitrobenzoic acid.

Further, the electrophotographic apparatus of the present invention may be any apparatus provided with the electrophotographic photoreceptor of the present invention and a contact charging member which contacts and charges the photoreceptor. There are no particular restrictions on conditions such as the structure. Since the electrophotographic apparatus of the present invention is provided with the photoreceptor of the present invention, there is no occurrence of charge leakage even when charging using the contact charging method, and the electrophotographic apparatus has good performance.

[0026]

Hereinafter, the present invention will be described in more detail with reference to examples. Example 1 In a mixed solution of 5 parts by weight of a vinylphenol resin, 5 parts by weight of a melamine resin, 10 parts by weight of methanol and 2 parts by weight of n-butanol, 20 parts by weight of titanium oxide fine powder whose surface was treated with aminosilane was ball milled. Dispersed in
Further, an undercoat layer solution prepared by adding 1 part by weight of a low molecular weight copolymer solution of polyethylene oxide and polypropylene oxide was applied on an aluminum cylindrical substrate at a film thickness of 3 μm by dipping, and then heated at 140 ° C. After curing and drying for 30 minutes, an undercoat layer was formed.

Thereafter, the upper layer was coated with a coating liquid for the charge generation layer in which 4 parts by weight of X-type metal-free phthalocyanine and 6 parts by weight of a modified vinyl chloride resin binder were dispersed in 40 parts by weight of dichloroethane. Coating was performed at about 0.1 μm to form a charge generation layer. Further, 5 parts by weight of 1,1'-bis (p-diethylaminophenyl) -4,4-diphenyl-1,3-butadiene and 1- (p-diethylaminophenyl) -1,4,4-triphenyl-1 , 3
5 parts by weight of butadiene and 10 parts by weight of a polycarbonate Z resin having a viscosity-average molecular weight of 50,000 are dissolved in 90 parts by weight of a dichloromethane solvent, coated by a dipping method so as to have a film thickness of 10 μm, and then formed at 100 ° C. After drying for a minute, a charge transport layer was formed, and a photoconductor (photoconductor drum) for electrophotography was produced.

Example 2 In a mixed solution of 5 parts by weight of a vinylphenol resin, 5 parts by weight of a melamine resin, 8 parts by weight of methanol and 2 parts by weight of n-butanol, 20 parts by weight of fine titanium oxide powder whose surface was treated with aminosilane A subbing layer solution prepared by dispersing a part and 1 part by weight of titanium oxide fine powder whose surface was treated with polyaniline in a ball mill was applied on an aluminum cylindrical substrate with a thickness of 10 μm by dipping. The coating was cured and dried at 140 ° C. for 30 minutes to form an undercoat layer. Except for this, a charge generation layer and a charge transport layer were sequentially formed in the same manner as in Example 1 to prepare an electrophotographic photoreceptor.

COMPARATIVE EXAMPLE 1 As a resin solution for an undercoat layer, 5 parts by weight of a polyamide resin was mixed with 5 parts by weight of dichloromethane, 3 parts by weight of methanol, and n
An undercoat layer solution was prepared by dispersing only 5 parts by weight of aminosilane-treated titanium oxide fine particles by a ball mill in a solution prepared by dissolving in a mixed solvent of 2 parts by weight of butanol, and dipped on an aluminum cylindrical substrate. After coating with a film thickness of 3 μm by the method, it was cured and dried at 120 ° C. for 30 minutes to form an undercoat layer. Except for this, a charge generation layer and a charge transport layer were sequentially formed in the same manner as in Example 1 to prepare an electrophotographic photoreceptor.

Evaluation of Photoreceptor A gold electrode was sputter-deposited on the undercoat layer of each photoreceptor prepared in the above Examples and Comparative Examples, and the electrode side was set to the negative pole, which is the charging direction, and the substrate side was set to the positive pole. 10 V / μm and 5
The volume resistance value at each applied electric field of 0 V / μm was measured. The specific measuring method is as follows. First, a photoreceptor aluminum cylindrical substrate after the application of the undercoat layer is cut out into a square of about 2 cm, a mask having an opening of about 0.5 cm ² is attached, and a film thickness of about 40 nm is formed by an ion sputtering apparatus.
To form an electrode. An electric field was applied between the gold electrode of this sandwich cell and the aluminum substrate, and the current flowing at this time was measured. From this measured value, the volume resistance was obtained. Further, the produced photosensitive drum was mounted on an actual machine (electrophotographic apparatus) equipped with a contact charging process, and a printing durability test was performed on 1,000 sheets to evaluate whether or not charge leakage occurred. The results are shown in Table 1 below.

[0031]

[Table 1]

From the comparison between Examples 1 and 2 and Comparative Example 1, the volume resistivity of the undercoat layer in the charging direction at 10 V / μm was 5 times the electric field, that is, the volume resistivity at 50 V / μm. It was confirmed that in the photoreceptor of the example having 5 times or more, no charge leakage of the photoreceptor occurred and good performance was obtained.

[0033]

As described above, according to the electrophotographic photoreceptor of the present invention, by improving the undercoating layer, an organic electrophotographic photoreceptor having good performance without charge leakage is obtained. It is possible to provide a body.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a laminated electrophotographic photosensitive member according to an example of the invention.

FIG. 2 is a schematic cross-sectional view illustrating a single-layer type electrophotographic photoconductor of another example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 conductive substrate 2 undercoat layer 3 charge generation layer 4 charge transport layer 5 single photosensitive layer 6 laminated photosensitive layer

Claims (5)

[Claims] 1. An electrophotographic photoreceptor having an undercoat layer and a photosensitive layer on a conductive substrate, wherein the undercoat layer has a volume resistance of 5 to 5 in an arbitrary electric field in a charging direction.
An electrophotographic photoreceptor having non-linear characteristics that are at least five times the volume resistance value in a double electric field. 2. The non-linear characteristic of the volume resistance value of the undercoat layer is established in the range of 2 V / μm to 60 V / μm.
The photoconductor for electrophotography according to the above. 3. The volume resistance of the photosensitive layer at an arbitrary voltage in the charging direction in the dark is at least 100 times the volume resistance of the undercoat layer under the same electric field. Or the electrophotographic photosensitive member according to 2. 4. The electrophotographic photoconductor according to claim 1, wherein the undercoat layer has a thickness of 2 μm or more. 5. An electrophotographic apparatus comprising: an electrophotographic photosensitive member; and a contact charging member that contacts the electrophotographic photosensitive member and charges the electrophotographic photosensitive member. An electrophotographic apparatus according to any one of claims 1 to 4.