JPH08262941A - Electrophotographic photoreceptor and electrophotographic device - Google Patents

Abstract

PURPOSE: To prevent the defect of an image such as image flowing or blurring and to eliminate the linear faulty image caused by electrostatic charge in a reverse polarity at the time of transferring by simultaneously performing exposure and electrostatic charge. CONSTITUTION: The surface of a photoreceptor drum 1 is electrostatically charged to be negative by a primary charger 2. Next, light from a semiconductor laser reaches the surface so as to form an electrostatic latent image, and the latent image is developed and made visualizable by a developing rotating body 3. Transfer paper passing a paper carrying part from a cassette is electrostatically attracted on a transfer drum 5 rotating in synchronization with the drum 1, and the developed toner image is transferred on the transfer paper according to output from a transfer charger 6. Untransferred toner remaining on the drum is scraped from the surface by a cleaner part 7. Then, charge existing on the surface of the drum 1 is discharged by a secondary charger 8 and discharging light 9 whose short wavelength component is cut. By simultaneously performing the exposure and the electrostatic charge by using the secondary charger 8 in such a way, the electrostatic charge of the drum 1 is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member and an electrophotographic apparatus, and more particularly, to an electrophotographic apparatus having an electrophotographic photosensitive member having a surface protective layer and having excellent environment resistance and durability.

[0002]

2. Description of the Related Art Conventionally, organic photoconductors have been inferior to inorganic photoconductors in terms of sensitivity, durability, environmental characteristics, etc. However, the above drawbacks have been overcome by improving and optimizing photoconductor materials, and they have been widely used. Came to be. In particular, it has been attempted to provide a surface protective layer on the photosensitive layer in order to further improve durability. However, carriers are easily trapped at the photosensitive layer-protective layer interface generated by providing the protective layer. In particular,
It cannot be easily erased if a charge having the opposite polarity to the charge is accumulated. Generally, in a reversal developing system, transfer is performed with the opposite polarity to charging, so that fog is apt to occur at a portion of the photoconductor where transfer charging is performed, and electric charge is concentrated particularly on an edge portion of the transfer paper, which may cause a problem in the paper traveling direction. It may appear as a line in the vertical direction. As a solution to this problem, it is conceivable that after the transfer, charging with a polarity opposite to that of the transfer is performed. In this case, the opposite polarity of transfer charging is negative charging.

[0003]

However, since negative charging is generally unstable, a large amount of current is required to eliminate the defective image. As a result, charged products such as O ₃ and NO _x are also increased, and as a result, they are adsorbed on the surface of the surface protective layer or penetrate into the photosensitive layer to cause image defects such as image deletion and blurring. There is.

Therefore, an object of the present invention is to provide an electrophotographic photosensitive member and an electrophotographic apparatus in which a linear defective image due to reverse polarity charging is eliminated without causing image defects such as image deletion and blurring. It is in.

[0005]

That is, the present invention provides an electrophotographic apparatus which has an electrophotographic photoreceptor having a photosensitive layer and a surface protective layer, and which forms an image at least in the order of charging, exposure, development and transfer. An electrophotographic apparatus comprising a transfer unit and a charging unit, and means for erasing the charging of the photoconductor by simultaneously performing exposure and charging.

The present invention also provides an electrophotographic photosensitive member used in the above electrophotographic apparatus, wherein the surface protective layer of the photosensitive member is
An electrophotographic photosensitive member characterized by containing fluorine atom-containing resin fine particles and a charge transporting material.

In the present invention, image defects such as image deletion and blurring are not caused by simultaneously performing exposure and charging,
Moreover, the linear defective image caused by the opposite polarity charging at the time of transfer is eliminated. This is because the electric field generated by charging facilitates the movement of carriers generated in the photosensitive layer by exposure, cancels the carriers trapped at the interface between the photosensitive layer and the surface protective layer, and eliminates the problem of reverse polarity. In addition, the synergistic effect requires a small charging current.

As the lamp used for the exposure, halogen, LED, cold cathode fluorescent lamp, fluorescent lamp and the like can be mentioned. Considering the fatigue of the photoreceptor, it is preferable to cut the wavelength of 400 nm or less.

As a charging method, a corotron, a scorotron, a roller, a brush, a blade, etc. can be considered. The electrification is preferably direct current or alternating current containing a direct current component having the same polarity as the electrification.

The photosensitive layer of the electrophotographic photoreceptor of the present invention contains at least a charge generating material and a charge transporting material. Examples of the charge generating material include phthalocyanine pigment, polycyclic quinone pigment, trisazo pigment, disazo pigment, azo pigment, perylene pigment, indigo pigment, quinacridone pigment, azurenium salt dye, squalium dye, cyanine dye, pyrylium dye, thiopyrylium dye, Examples include xanthene dyes, quinoneimine dyes, triphenylmethane dyes and styryl dyes.

Examples of charge transport materials include pyrene compounds, N-alkylcarbazole compounds, hydrazone compounds, N, N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, Examples thereof include stilbene compounds, polynitro compounds, polycyano compounds, and pendant polymers obtained by immobilizing these compounds on a polymer.

In many cases, the above-mentioned charge generating material, charge transporting material and the like are dispersed and contained in a binder resin having film forming properties to form a photosensitive layer and the like. Examples of such binder resin include polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene,
Examples thereof include polyimide, phenol resin, acrylic resin, silicone resin, epoxy resin, urea resin, allyl resin, alkyd resin, polyamide-imide, nylon, polysulfone, polyallyl ether, polyacetal and butyral resin.

Next, the layer structure of the electrophotographic photosensitive member of the present invention will be described. Examples of the conductive support include metals and alloys such as iron, copper, gold, silver, aluminum, zinc, titanium, lead, nickel, tin, antimony and indium, or oxides of the above metals, carbon, conductive polymers and the like. It can be used. There are a drum shape such as a cylindrical shape and a cylindrical shape, and a belt shape and a sheet shape. The conductive material, when molded as it is, when used as a paint,
It may be vapor-deposited, or may be processed by etching or plasma treatment. In the case of paint, not only the above-mentioned metals and alloys but also paper, plastic and the like are used as the support.

The photosensitive layer in the photoreceptor of the present invention may have a single layer structure or a laminated structure. The film thickness is preferably 10 to 35 μm, more preferably 15 to 30 μm.

In the case of a laminated structure, it is composed of at least a charge generating layer and a charge transporting layer. The charge generating layer and the charge transporting layer are used depending on whether the charge generating layer is provided on the conductive support side or the charge transporting layer is provided. The polarity of toner is different. The thickness of the charge generation layer is preferably 0.001
˜6 μm, more preferably 0.01 to 2 μm. The content ratio of the charge generating material contained in the charge generating layer is
It is preferably 10 to 100% by weight, more preferably 50 to 100% by weight. The thickness of the charge transport layer is the thickness of the photosensitive layer minus the thickness of the charge generation layer. The content of the charge transport material contained in the charge transport layer is preferably 20 to 80% by weight, more preferably 30 to 70% by weight.

An undercoat layer may be provided between the conductive support and the photosensitive layer. The undercoat layer functions as a charge injection control at the interface and as an adhesive layer. The undercoat layer is mainly composed of a binder resin, but the metal or alloy, or an oxide or salt thereof,
It may contain a surfactant and the like. Specific examples of the binder resin forming the undercoat layer are polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, phenol resin, acrylic resin, silicone resin, epoxy resin, urea resin, Examples thereof include allyl resin, alkyd resin, polyamide-imide, nylon, polysulfone, polyallyl ether, polyacetal, butyral resin and the like. The thickness of the undercoat layer is preferably 0.05 to 7 μm, more preferably 0.1 μ to 2 μm.

Although a protective layer is provided in the present invention, the protective layer is always provided on the photosensitive layer. The protective layer is mainly made of resin, examples of which are polyester, polyurethane, polyarylate, polyethylene, polystyrene, polybutadiene, polycarbonate, polyamide, polypropylene, polyimide, phenol resin, acrylic resin, silicone resin, epoxy resin, urea resin, allyl. resin,
Examples thereof include alkyd resin, polyamide-imide, nylon, polysulfone, polyallyl ether, polyacetal and butyral resin. The thickness of the protective layer is preferably 0.05 to 15 μm, more preferably 1 to
It is 10 μm.

Further, the protective layer contains a charge transporting material for maintaining the charge transporting property, conductive fine particles for controlling the electric resistance of the layer, and fluorine atom-containing resin fine particles for reducing the frictional resistance of the surface. You may add. As a specific example, the charge transport material is a pyrene compound or N-, respectively.
Alkylcarbazole compound, hydrazone compound, N,
N-dialkylaniline compounds, diphenylamine compounds, triphenylamine compounds, triphenylmethane compounds, pyrazoline compounds, styryl compounds, stilbene compounds, polynitro compounds, polycyano compounds, and
Examples include pendant polymers in which these compounds are fixed on a polymer.

Next, as the conductive fine particles, SnO ₂ , I
TO etc. are mentioned.

Next, as the fluorine atom-containing resin fine particles, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinylidene fluoride, polydichlorodifluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexa Examples thereof include a fluoropropylene copolymer, a tetrafluoroethylene-ethylene copolymer, and a tetrafluoroethylene-hexafluoropropylene-perfluoroalkyl vinyl ether copolymer.

As a method for producing the electrophotographic photosensitive member of the present invention, methods such as vapor deposition and coating are used. The coating method can form a wide range of films from thin films to thick films, and can form films of various compositions. Specifically, it is applied by a bar coater, knife coater, dip coating, spray coating, beam coating, electrostatic coating, roll coater, attritor, powder coating or the like.

In the coating material used for applying the protective layer, it is preferable to disperse the fluorine atom-containing resin fine particles and conductive fine particles in a binder resin and a solvent. As the dispersion method, a ball mill, ultrasonic wave, paint shaker, red devil, sand mill, or the like is used. The same dispersion method can be used when the conductive fine particles, the pigment, and the charge generation material are pigments.

[0023]

The present invention will be described below with reference to examples. In the examples, “parts” indicates “parts by weight”. Example 1 50 parts of conductive titanium oxide powder coated with tin oxide containing 10% antimony oxide, 25 parts of phenol resin, 20 parts of methyl cellosolve, 5 parts of methanol and silicone oil (polydimethylsiloxane polyoxyalkylene). Copolymer, number average molecular weight 30,000)
0.002 parts were dispersed for 2 hours by a sand mill using φ1 mm glass beads to prepare a conductive layer coating material. The above coating material was dip-coated on an aluminum cylinder (φ80 × 360) and dried at 140 ° C. for 30 minutes to form a conductive layer having a film thickness of 20 μm.

Next, 30 parts of methoxymethylated nylon resin (number average molecular weight 32,000) and alcohol soluble copolymer nylon resin (number average molecular weight 29,000) 10
Part was dissolved in a mixed solvent of 260 parts of methanol and 40 parts of butanol to form a subbing layer having a film thickness after drying of 1 μm by dip coating on the conductive layer.

Next, the following structural formula [1]

[0026]

Embedded image Disperse 4 parts of the disazo pigment, 2 parts of benzal resin, and 40 parts of tetrahydrofuran in a sand mill using φ1 mm glass beads for 60 hours, and then cyclohexanone /
It was diluted with a tetrahydrofuran mixed solvent to obtain a charge generation layer coating material. This coating solution was dip-coated on the undercoat layer to form a charge generation layer having a thickness of 0.1 μm after drying.

Next, the following structural formula [2]

[0028]

Embedded image 10 parts of the charge transport material and 10 parts of a polycarbonate resin (number average molecular weight 25,000) are added to dichloromethane 2
It is dissolved in a mixed solvent of 0 part and 40 parts of monochlorobenzene, and this solution is dip-coated on the charge generation layer,
It was dried at 120 ° C. for 60 minutes to form a charge transport layer having a film thickness of 20 μm.

Next, 3 parts of polyfluoroethylene fine particles (Lubron L-5: manufactured by Daikin Industries, Ltd.), polycarbonate resin (bisphenol Z type number, average molecular weight 80,
000) 4.67 parts, charge transport material of structural formula [2] 2.
33 parts, 300 parts of monochlorobenzene and 200 parts of dichloromethane were dispersed in a sand mill to obtain a protective layer coating material. This paint was spray-coated and dried at 120 ° C. for 60 minutes to form a protective layer of 6.0 μm.

The above photoconductor was mounted on the electrophotographic apparatus shown in FIG. The apparatus shown in FIG. 1 will be briefly described. There is a photosensitive drum 1 which rotates in the arrow direction by a drive system (not shown). First, the drum surface is negatively charged by the primary charger 2. Next, the light of the semiconductor laser reaches the surface through an optical system such as a polygon mirror, an fθ lens, and a mirror to form an electrostatic latent image. Next, the latent image is developed and visualized by the negatively charged powder called toner in the developer in the developing device 4 which is rotated by the developing rotator 3 and faces the drum.

On the transfer drum 5 which rotates in synchronism with the photosensitive drum 1, the transfer paper which has passed through the paper carrying section from the cassette is electrostatically adsorbed, and the developed toner image is transferred onto the transfer paper by the output of the transfer charger 6. Transcribed.

The untransferred toner remaining on the drum is scraped from the surface by the cleaning blade of the cleaner section 7. Then, the electric charge remaining on the drum surface is eliminated by the secondary charger 8 and the neutralizing light 9 whose short wavelength is cut by the red filter. The charging method was corotron, and the charging current was -180 μA.

The above is the process for one color. After the above process is repeated four times, the transfer paper is discharged by the paper static eliminator 10 and the transfer paper is separated from the transfer drum 5 by the separation charger 11 to move the transfer section. After passing, the fixing device fixes the toner on the transfer paper.

Comparative Example 1 The photosensitive drum of Example 1 was mounted in the same electrophotographic apparatus as in Example 1 except that the secondary charger was not provided after cleaning.

[Comparative Example 2] The photosensitive drum of Example 1 was set in the same electrophotographic apparatus as in Example 1 except that the secondary charger after cleaning was held before cleaning.

In the electrophotographic apparatus of Example 1, Comparative Example 1 and Comparative Example 2, with the cleaning blade removed,
The drum was rotated 100,000 times without passing the paper under the following conditions. After that, a cleaning blade was attached and an image was output. Table 1 shows the results.

[0037] After paper ○: None ×: Yes

As shown in Table 1, in Comparative Examples 1 and 2, since there was no secondary charger for charging at the same time as exposure, the positive charge due to the influence of transfer charging was not erased, and "paper marks" were produced.

[Comparative Example 3] A similar test was conducted in Comparative Example 2 with the inflow current of the secondary charger set to -800 μA. As a result, "paper marks" were not generated, but charged products due to the influence of the inflow current up. An increase in the number of images caused image deletion.

[Embodiment 2] In Embodiment 1, the secondary charger after cleaning was replaced with a scorotron using a wire as a grid, and an inflow current was set to -300 μA.

When the same evaluation as in Example 1 was carried out, a clear image without image defects was obtained.

[Third Embodiment] In the first embodiment, the secondary charger and the discharging light are set as shown in FIG.

The secondary charging device is a charging roller and 2 kHz
Is applied with a voltage in which DC of −3 kV is superimposed on the AC, and the static elimination light 15 is further removed by the light introduction mirror 16 from the photosensitive drum 12.
And the contact portion of the charging roller 14 was irradiated. When the same evaluation as in Example 1 was performed, a clear image without image deletion was obtained.

Example 4 Alcohol-soluble polyamide resin (Amilan CM-
A solution prepared by dissolving 10 parts of 8000, manufactured by Toray Industries, Inc. and 30 parts of methoxymethylated 6 nylon resin (Toresin EF-30T, manufactured by Teikoku Kagaku Co., Ltd.) in a mixed solvent of 150 parts of methanol and 150 parts of butanol. Dip coating,
An undercoat layer having a film thickness of 1 μm was formed by drying at 90 ° C. for 10 minutes.

Next, the following formula

[0046]

Embedded image To 100 parts of tetrahydrofuran (THF) was added to a solution in which 4 parts of the disazo pigment represented by 4 parts, 2 parts of butyral resin (S-REC BL-S, manufactured by Sekisui Chemical Co., Ltd.) and 100 parts of cyclohexanone were dispersed in a sand mill for 48 hours. Thus, a dispersion liquid for the charge generation layer was obtained. This dispersion was dip-coated on the undercoat layer and dried at 80 ° C. for 15 minutes to form a charge generation layer having a thickness of 0.15 μm.

Next, the following formula

[0048]

[Chemical 4] A solution obtained by dissolving 10 parts of a triarylamine compound represented by the formula 10 and a polycarbonate resin (Upilon Z-200, manufactured by Mitsubishi Gas Chemical Co., Inc.) in a mixed solvent of 20 parts of dichloromethane and 50 parts of monochlorobenzene is charged as described above. A charge transport layer having a film thickness of 20 μm was formed by dip coating on the generation layer and drying at 120 ° C. for 60 minutes.

Next, a dispersion liquid for the protective layer was prepared by the following procedure.

The following formula as a binder resin

[0051]

Embedded image 25 parts of an acrylic curable monomer represented by the following formula, 2.0 parts of 2-methylthioxanthone as a photopolymerization initiator, and antimony-containing tin oxide fine particles (T having an average particle diameter of 0.02 μm) (T
-1, Mitsubishi Materials Corp.) 45 parts and toluene 3
In a dispersion liquid in which 00 parts were mixed and dispersed in a sand mill for 72 hours, 25 parts of polytetrafluoroethylene fine particles (Lubron L-2, manufactured by Daikin Industries, Ltd.) and a fluorinated silane coupling agent (C ₄ F ₉ CH ₂ CH ₂ Si (OC
20 parts of H ₃ ) ₃ ) were mixed and dispersed for 4 hours with a sand mill to obtain a dispersion liquid for a protective layer. This dispersion is spray-coated on the charge transport layer, dried,
A protective layer having a film thickness of 6 μm was formed by irradiating ultraviolet rays with a high pressure mercury lamp at a light intensity of 800 mW / cm ² for 20 seconds.

The produced photosensitive drum was mounted on the electrophotographic apparatus shown in FIG. The output of the secondary charger is ACV _PP 1.5
When the same test as in Example 1 was performed with kV and 1.5 kHz, "paper marks" did not occur.

Example 5 The amount of polytetrafluoroethylene fine particles in the dispersion liquid for the protective layer used in Example 1 was set to 45.
Part, and a fluorinated silane coupling agent (C ₄ F ₉
A photoconductor was prepared in the same manner as in Example 1 except that 35 parts of CH ₂ CH ₂ Si (OCH ₃ ) ₃ ) was added. The output of the secondary charger is set to DC-450 μA for the produced photosensitive drum.
Was mounted on the electrophotographic apparatus of Example 1. When tested in the same manner as in Example 1, "paper marks" did not occur.

[0054]

According to the present invention, there are provided an electrophotographic photosensitive member and an electrophotographic apparatus in which a linear defective image caused by reverse polarity charging is eliminated without causing image defects such as image deletion and blurring. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view of an example of an electrophotographic apparatus of the present invention.

FIG. 2 is a partial schematic cross-sectional view of an electrophotographic apparatus of the present invention in which the secondary charger has a roller shape.

[Explanation of symbols]

 1 Photosensitive Drum 2 Primary Charger 3 Developing Rotator 4 Developing Device 5 Transfer Drum 6 Transfer Charger 7 Cleaner Section 8 Secondary Charger 9 Electrification Light 10 Paper Eliminating Device 11 Separation Charger 12 Photosensitive Drum 13 Cleaning Blade 14 Charging Roller 15 Static elimination light 16 Light introduction mirror

Claims (5)

[Claims] 1. An electrophotographic apparatus comprising an electrophotographic photosensitive member having a photosensitive layer and a surface protective layer, wherein an image is formed at least in the order of charging, exposure, development and transfer, and exposure is performed between a transfer unit and a charging unit. An electrophotographic apparatus comprising means for erasing the charging of the photoconductor by simultaneously performing the charging and the charging. 2. The electrophotographic apparatus according to claim 1, wherein the charging performed at the same time as the exposure has a polarity opposite to that of the transfer. 3. The electrophotographic photosensitive member for use in the electrophotographic apparatus according to claim 1, wherein the surface protective layer of the photosensitive member contains fluorine atom-containing resin fine particles and a charge transporting material. body. 4. The content of fluorine atom-containing resin fine particles is
The total solid content of the surface protective layer is 5 to 70% by weight.
The electrophotographic photosensitive member described. 5. The electrophotographic photosensitive member used in the electrophotographic apparatus according to claim 1, wherein the surface protective layer of the photosensitive member contains conductive fine particles.