JPH11109657A - Electrophotographic equipment - Google Patents

Abstract

(57) [Summary] In an electrophotographic apparatus, a positive charge is considerably injected into a photosensitive layer after transfer, and the positive charge accumulated in the photosensitive layer causes an influence on the main charge in the next electrophotographic process. This makes it impossible to stably charge the photosensitive member to the negative side. An electrophotographic apparatus includes a conductive charging member disposed in contact with an electrophotographic photoreceptor, and charges the surface of the photoreceptor by injecting charge from the charging member into the photoreceptor. The dark decay rate (defined by the formula 1) of the charge having the polarity of the voltage applied when transferring the transferred developer is set to 30% or less. (However, the surface potential of the photoconductor immediately after charging is from -500 V to-
It is assumed that the voltage is set in the range of 1000 or +500 V to +1000 V. )

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus, and more particularly, to charging an electrophotographic photosensitive member by directly injecting charge from a charging member in contact with the electrophotographic photosensitive member onto the surface of the photosensitive member. The present invention relates to an electrophotographic apparatus.

[0002]

2. Description of the Related Art In an electrophotographic method, electrophotographic photosensitive members such as selenium, cadmium sulfide, zinc oxide, amorphous silicon and organic photoconductors are subjected to basic operations such as charging, exposure, development, transfer, fixing and cleaning. When an image is obtained by performing the process, the charging process is performed by applying a higher voltage (DC 5 to 8 kV) to the metal wire than before.
Is applied, and charging is performed by the generated corona. However, if allowed to proceed is not image blurring or deterioration alter the surface of the photoreceptor by corona products such as ozone and NO _x during corona generating in this way, contamination of the wire affects the image quality, the image white spots and black streaks There were problems such as occurrence.
In particular, the electrophotographic photoreceptor in which the photosensitive layer is mainly composed of an organic photoconductor has lower chemical stability than other selenium photoreceptors and amorphous silicon photoreceptors, and when exposed to a corona product, a chemical reaction ( (Mainly an oxidation reaction), which tends to cause deterioration. Therefore, when the toner is repeatedly used under corona charging, the image is blurred or the sensitivity is lowered due to the above-mentioned deterioration, and the copy density is reduced due to the increase in the residual potential, and the life of printing (copying) is apt to be shortened.

Further, in the corona charging, only 5% to 30% of the electric current directed toward the photosensitive member in terms of electric power, most of the current flows to the shield plate, and the charging means is inefficient.

Further, the ozone concentration increases by repeating the electrophotographic process by corona charging,
This has been a problem in providing a comfortable use environment.

In order to make up for such a problem, Japanese Patent Application Laid-Open No. 57-178267 discloses a method without using a corona discharger.
JP-A-56-104351, JP-A-58-405
No. 66, Japanese Patent Application Laid-Open No. 58-139156, Japanese Patent Application Laid-Open No. 58-150975, and the like, a method of contact charging has been studied.

More specifically, the surface of the photoconductor is charged to a predetermined potential by contacting the surface of the photoconductor with a charging member such as a conductive elastic roller to which a DC voltage of about 1 to 2 kV is externally applied. .

[0007] However, the direct charging system is disadvantageous in comparison with the corona charging system in terms of non-uniform charging and occurrence of discharge breakdown of the photoreceptor by applying a direct voltage. Due to the non-uniform charging, streak-like charging unevenness having a length of about 2 to 200 mm and a width of about 0.5 mm or less occurs in a direction perpendicular to the moving direction of the charged surface. In this case, image defects such as white streaks (a phenomenon in which white streaks appear in a solid black or halftone image) or black streaks that occur in the case of the reversal development method occur.

In order to solve such problems and improve the uniformity of charging, there has been proposed a method in which an AC voltage is superimposed on a DC voltage and applied to a charging member (Japanese Patent Application Laid-Open No. Sho 63-163).
149668). This charging method uses a DC voltage (V
_The pulsating voltage is applied by superimposing an _AC voltage (V _AC ) on the _DC voltage to perform uniform charging.

In this case, while maintaining the uniformity of charging, white dots in the normal development system, black dots in the reversal development system,
In order to prevent image defects such as fogging, it is necessary that the AC voltage to be superimposed has a peak-to-peak potential difference (V _PP ) that is at least twice the DC voltage.

However, when the superimposed AC voltage is increased in order to prevent image defects, discharge breakdown occurs at a small defective portion inside the photosensitive member due to the maximum applied voltage of the pulsating voltage. In particular, when the photoconductor is an organic photoconductor having a low withstand voltage, this dielectric breakdown is remarkable.
In this case, in the normal development system, the image becomes blank in the longitudinal direction of the contact portion, and in the reversal development system, black stripes occur. Further, when there is a pinhole, there is a problem that a portion there serves as a conduction path, current leaks, and the voltage applied to the charging member drops. Furthermore, since the discharge is caused in the minute gap, there is a problem that the damage to the photoconductor is large, the shaving amount of the photoconductor is large, and the durability is poor.

As an attempt to eliminate the deterioration of the organic photoreceptor due to the charging as described above, a semiconductive film is provided on the surface of the organic photoreceptor, and a charging member is brought into contact with the semiconductive film, and a charge is applied from the charging member to which a voltage is applied. A charging method of directly injecting the surface of the photoconductor has been proposed.

[0012]

However, in this case, in the case where the structure of the organic photoconductor is a photoconductor in which semiconductivity is provided on the positive charge transport layer, if the surface of the semiconductive film is positively charged, A phenomenon is observed in which positive charges are injected from the semiconductive film into the lower positive charge transport layer.
In particular, in a so-called reversal developing type electrophotographic apparatus in which the polarity of the main charge of the photoreceptor is negative and the voltage applied when transferring the developed toner to the surface of the photoreceptor is positive, the positive charge is exposed after the transfer. Due to the positive charge accumulated in the photosensitive layer, it was not possible to stably charge the photoconductor to the negative side during the next main charge in the electrophotographic process. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a charge-injection process for charging a photoreceptor by injecting electric charge from the contact charging member into the photoreceptor with less damage to the photoreceptor due to discharge during charging, and a stable reversal development process Accordingly, it is an object of the present invention to provide an electrophotographic apparatus capable of maintaining uniform charging during a continuous copying process.

[0014]

Means for Solving the Problems The inventors of the present invention have studied the above problem, and as a result, it has been found that an electrophotographic photosensitive member having a surface provided with a semiconductive film has a positive effect when the surface is positively charged. In a photoreceptor having a dark decay rate of 30% / min or less, it has been found that even if the electrophotographic photoreceptor receives a history of positive charge, the surface can be stably and uniformly charged by subsequent negative charge. .

The electrophotographic photosensitive member of the present invention has an electrophotographic photosensitive member and a conductive charging member arranged in contact with the photosensitive member,
In an electrophotographic apparatus for charging the surface of the photoreceptor by injecting charge from the charging member to the photoreceptor, a charge having a polarity of a voltage applied when transferring a developed developer onto the surface of the photoreceptor is used. An electrophotographic photoreceptor having a dark decay rate (defined by Equation 1) of 30% or less is used.

[0016] (However, the surface potential of the photoconductor immediately after charging is from -500 V to-
It is assumed that the voltage is set in the range of 1000 or +500 V to +1000 V. That is, in the present invention, the charge is injected from the charging member in contact with the semiconductive film-coated photoreceptor that suppresses the dark decay of the positive charge, thereby charging the photoreceptor, and the polarity of the voltage applied for toner transfer. The electrophotographic apparatus is characterized in that the surface of the photoreceptor can be stably charged even if the value is positive.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the direct charging method in which a charging member is brought into contact with an electrophotographic photosensitive member to perform charging, the direct charging method is performed by discharging in a minute space near a contact portion between the photosensitive member and the charging member as compared with the case where a conventional photosensitive member is used. Will be

Therefore, also in the direct charging method, charging is performed by ionizing molecules in the air and flowing the ions to the surface of the photoreceptor, and direct charge injection from the charging member to the surface of the photoreceptor is not performed. Of course, the charging in such a charging mechanism largely depends on the surface shapes of the charging member and the photosensitive member, and unevenness of each surface causes uneven charging.

Further, since the discharge is caused in the minute gap,
The movement of ions in a strong electric field causes significant damage to the photoreceptor, increases the amount of shaving, and reduces durability.

[0021] Compared to yet corona charging, but orders of magnitude less, still image blurring occurs ozone, due to the occurrence of such NO _x.

On the other hand, in the electrophotographic apparatus of the present invention, the surface layer of the photoreceptor is made of a layer in which conductive particles are dispersed in a resin, and the charge of the ordinary photoreceptor is improved by improving the charging member. Injection became possible, thereby eliminating the charging unevenness observed in the discharge, reducing the damage to the photoreceptor, and improving the durability.

Further, ozone, NO _{x and the} like are hardly generated, and image blur is not generated, so that the problem is greatly improved.

FIG. 1 shows a basic configuration of an electrophotographic apparatus according to the present invention. The charging member 2 is arranged in contact with the electrophotographic photosensitive member 1 and charges the photosensitive member 1 with a voltage applied from an external power supply connected thereto. 1a is a semiconductive layer (injection layer), 1b is a photosensitive layer, and 1c is a conductive support.

The shape of the charging member 2 used in the present invention may be any shape such as a fur brush as shown in FIG. 1 or a magnetic brush. Can be selected.

The material of the fur brush is as follows:
Carbon, copper sulfide, a metal, and a polymer subjected to a conductive treatment with a metal oxide or the like are used. The material of the polymer is rayon, acrylic, polypropylene, PET,
Polyethylene or the like is used.

These electrically treated furs are wound or stuck on a metal or other conductively treated core to form a charger.

The resistance of the fur brush was measured from the value of a current flowing when a voltage of 100 V was applied by contacting an aluminum cylinder instead of the photosensitive member under the same conditions as those actually used.

Further, the magnetic brush uses various ferrite particles such as Zn-Cu ferrite as a charging member, and is constituted by a non-magnetic conductive sleeve for supporting the ferrite particles and a magnet roll contained therein.

The photosensitive layer of the present invention has a single layer or a laminated structure. In the case of a single-layer structure, generation and movement of photocarriers are performed in the same layer. In the case of a stacked structure, a charge generation layer that generates photocarriers and a charge transport layer in which carriers move are stacked.

The thickness of the single-layer photoreceptor is 5 to 1
00 μm is preferable, and 10 to 60 μm is more preferable.
The content of the charge generation material and the charge transport material is preferably from 20 to 80% by weight, more preferably from 30 to 70% by weight. In the laminated photoreceptor, the thickness of the charge generation layer is preferably 5 μm or less, more preferably in the range of 0.01 to 1 μm. The content of the charge generating material is preferably from 10 to 100% by weight,
0-100% by weight is more preferred. The thickness of the charge transport layer is preferably from 5 to 100 μm, more preferably from 5 to 60 μm. The content of the charge transporting material is preferably from 20 to 80% by weight, more preferably from 30 to 70% by weight.

The electrophotographic photosensitive member shown in FIG.
4, a charge generation layer 13 and a charge transport layer 12 are provided, and an injection layer 11 is further provided on the outermost surface.

As shown in FIGS. 3 and 4, a binder layer 15 and an undercoat layer 16 for preventing interference fringes may be provided between the conductive support and the charge generation layer. Good.

As the conductive support 14, a support having conductivity itself, for example, aluminum, aluminum alloy, stainless steel, etc. can be used. In addition, aluminum, aluminum alloy, indium oxide-tin oxide alloy, etc. can be used in vacuum. The conductive support or plastic having a layer formed by vapor deposition, conductive fine particles (for example, carbon black, tin oxide, titanium oxide,
A support in which silver or the like is impregnated in a plastic or paper together with a suitable binder, a plastic having a conductive binder, or the like can be used.

An undercoat layer (adhesive layer) having a barrier function and an adhesive function can be provided between the conductive support and the photosensitive layer.

The undercoat layer is used for improving the adhesiveness of the photosensitive layer, improving the coating property, protecting the support, covering defects of the support, improving the charge injection property from the support, and protecting the photosensitive layer against electrical breakdown. Formed for The undercoat layer can be formed of casein, polyvinyl alcohol, ethyl cellulose, ethylene-acrylic acid copolymer, polyamide, modified polyamide, polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is preferably 5 μm or less, and 0.2 to 3 μm.
μm is more preferred. The undercoat layer preferably has a resistivity of 10 ⁸ Ω · cm or more in order to exhibit its function.

Examples of the charge generating substance used in the present invention include phthalocyanine pigments, azo pigments, indigo pigments, polycyclic quinone pigments, perylene pigments, quinacridone pigments, azurenium salt pigments, pyrylium dyes, thiopyrylium dyes, squarylium dyes, cyanine dyes, Examples include xanthene dyes, quinone imine dyes, triphenylmethane dyes, styryl dyes, selenium, selenium-tellurium, amorphous silicon, cadmium sulfide, and zinc oxide.

The solvent used for the coating for the charge generating layer is selected from the solubility and dispersion stability of the resin and the charge generating material used. Examples of the organic solvent include alcohols, sulfoxides, ketones, ethers and esters. And aliphatic halogenated hydrocarbons or aromatic compounds.

As the charge transport material, hydrazone compounds, pyrazoline compounds, styryl compounds, oxazole compounds, thiazole compounds, triarylmethane compounds, polyarylalkane compounds, and the like can be used.

The charge generation layer 3 is prepared by adding the above-mentioned charge generation substance to a binder resin and a solvent in an amount of 0.3 to 4 times the amount of a homogenizer, an ultrasonic wave, a ball mill, a vibration ball mill, a sand mill, an attritor, a roll mill, or the like. It is formed by well dispersing, applying and drying by a method. Its thickness is 5μ
m or less, particularly preferably in the range of 0.01 to 1 μm.

The charge transport layer 2 is generally formed by dissolving the charge transport material and the binder resin in a solvent and applying the resulting solution.
The mixing ratio of the charge transport material and the binder resin is 2: 1 to 1:
About 2. Examples of the solvent include ketones such as acetone and methyl ethyl ketone, esters such as methyl acetate and ethyl acetate, aromatic hydrocarbons such as toluene and xylene, and chlorinated hydrocarbons such as chlorobenzene, chloroform and carbon tetrachloride. . When applying this solution, for example, a coating method such as a dip coating method, a spray coating method, or a spinner coating method can be used, and drying is performed at 10 ° C to 200 ° C.
Preferably at a temperature in the range of 20C to 150C for 5 minutes to 5 minutes.
The drying can be carried out for a period of time, preferably 10 minutes to 2 hours, under blast drying or still drying.

Examples of the binder resin used to form the charge transport layer 2 include an acrylic resin, a styrene resin, a polyester, a polycarbonate resin, a polyarylate,
A resin selected from polysulfone, polyphenylene oxide, epoxy resin, polyurethane resin, alkyd resin, unsaturated resin and the like is preferable. Particularly preferred resins include polymethyl methacrylate, polystyrene,
Examples include a styrene-acrylonitrile copolymer, a polycarbonate resin, and a diallyl phthalate resin.

The charge generation layer or the charge transport layer may contain various additives such as an antioxidant, an ultraviolet absorber and a lubricant.

Next, in the present invention, on these photosensitive layers,
An injection layer in which conductive fine particles are dispersed is provided.

The conductive particles used in the injection layer include:
Ultrafine particles such as zinc oxide, titanium oxide, tin oxide, antimony oxide, indium oxide, bismuth oxide, tin-doped indium oxide, antimony and tantalum-doped tin oxide, and zirconium oxide can be used. These metal oxides are used alone or in combination of two or more. When two or more kinds are mixed, they may be in the form of solid solution or fusion. Further, as the resin for the surface layer, commercially available polyester, polycarbonate, polyurethane, acrylic, epoxy, silicone, alkyd, vinyl chloride-vinyl acetate copolymer and the like can also be used. Investigations were made to further improve the intensity distribution and dispersibility. As a result, the conductive particles were dispersed in a photocurable acrylic monomer having two or more acryloyl groups in one molecule, and this was used as a photosensitive material. By using a surface layer formed by coating and photocuring on the layer, both the film strength and the dispersibility of the conductive particles can be dramatically improved.

As a method for suppressing the dark decay of the transfer charge applied to the photoreceptor, the drying temperature of the hot air when forming the charge injection layer is set to 120 ° C. or less, and the binder resin of the charge injection layer is cured by photocuring. When a hydrophilic resin is used, a self-cleavable compound such as benzyl methyl ketal or 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1 is used as a photopolymerization initiator. In the case of (1), a material having an oxidation potential of 0.6 V or more is used as the positive charge transporting agent in the charge transporting layer.

FIG. 1 shows a specific example of an electrophotographic apparatus using the electrophotographic photosensitive member of the present invention. In this apparatus, a cleaner 5 having a fur brush charging member 2, an image exposing unit 3, a developing unit 4, a transfer roller 8, and a blade 6 is arranged on a peripheral surface of an electrophotographic photosensitive member 1. The fur brush charging member 2 is provided with a power supply for sending electric charges thereto.

In the image forming method, first, a voltage is applied to the charging member 2 which is arranged in contact with the electrophotographic photosensitive member 1,
The surface of the photoreceptor 1 is charged by injection of electric charges, and the image exposure unit 3
An image corresponding to the document is exposed on the surface of the photoreceptor 1 to form an electrostatic latent image. Next, the electrostatic latent image on the photoconductor 1 is developed (visualized) by attaching the toner in the developing device 4 to the photoconductor 1. Further, the transfer roller 8 transfers the toner image formed on the photoconductor 1 onto a transfer material 7 such as a supplied paper, and the residual toner remaining on the photoconductor 1 without being transferred to the transfer material by the cleaner 5. Collect.

In this image forming apparatus, the image exposing means 3
, A halogen light, a fluorescent lamp, a laser light, or the like can be used. Other auxiliary processes may be added as needed.

Further, in the present invention, it is possible to omit the cleaning step and to adopt a process of collecting the residual toner using a charger or a developing device.

[0051]

【Example】

(Example 1) A 30φ357 mm Al cylinder was used as a support, and a coating composed of the following materials was applied to the support by a dipping method and thermally cured at 140 ° C. for 30 minutes to obtain 1
A 5 μm conductive layer was formed.

Conductive pigment: SnO ₂ coated barium sulfate 10 parts Resistance adjusting pigment: titanium oxide 2 parts Binder resin: phenol resin 6 parts Leveling material: silicone oil 0.001 parts Solvent: methanol, methoxypropanol 0.2 / 0.8 20 parts Next, 3 parts of N-methoxymethylated nylon and 3 parts of copolymerized nylon were added thereto with 65 parts of methanol and 3 parts of n-butanol.
The solution dissolved in 0 parts of the mixed solvent was applied by dipping.
An intermediate layer of 5 μm was formed.

Next, the diffraction angle 2θ ± 0.
2 ° is 9.0 °, 14.2 °, 23.9 °, and 2 °
10.5 parts of oxytitanium phthalocyanine crystal having a strong peak at 7.1 ° and the following structure

[0054]

Embedded image Was added to a solution prepared by dissolving 1.5 parts of an azoxy pigment in 10 parts of a polyvinyl butyral resin (trade name: Eslek BX-1, manufactured by Sekisui Chemical) and 250 parts of cyclohexanone.
A hindered phenol compound having the following structure is dispersed in a sand mill using glass beads of mφ.

[0055]

Embedded image Was added and dissolved, and ethyl acetate was added to dilute the solution. The solution was coated on the undercoat layer, and then dried at 80 ° C. for 10 minutes to form a charge generation layer having a thickness of 0.25 μm. .

Next, the following structural formula

[0057]

Embedded image 10 parts of a charge transport agent (oxidation potential: 0.81 eV) and Bizphenol Z-type polycarbonate (trade name: Z-80)
0, Mitsubishi Chemical) 10 parts by weight of monochlorobenzene 100
Dissolves in the part. This solution is applied on the charge generation layer,
The resultant was dried with hot air at 100 ° C. for 1 hour to form a charge transporting layer having a thickness of 15 μm.

Next, dipentaerythritol hexaacrylate (trade name: Kayarad DPHA, Nippon Kayaku) 60
Parts, ultrafine tin oxide particles having an average particle size before dispersion of 0.04 μm, 60 parts of polytetrafluoroethylene fine particles (average particle size of 0.18 μm), 50 minutes, benzyl methyl ketal (trade name: Irgacure) as a photopolymerization initiator (651, Ciba-Geigy) and 400 parts of methanol were dispersed in a sand mill for 66 hours.

Using this mixture, a film was formed by coating the above charge transport layer, and the film was formed using a high pressure mercury lamp at 150 W / cm ^2.
Light curing at a light intensity of 60 seconds, followed by hot air drying at 120 ° C. for 1 hour to provide an injection layer. The thickness of the injection layer obtained at this time was 3 μm.

(Example 2) In Example 1, the following compound (oxidation potential: 0.63 eV) was used as the charge transporting agent.

[0061]

Embedded image A photoconductor was prepared in the same manner as in the example, except that the photoconductor was replaced with the photoconductor.

(Example 3) In Example 1, the photopolymerization initiator was changed to 2-methyl-1 [4- (methylthio) phenyl].
A photoreceptor was obtained in the same manner as in Example 1, except that -2-morpholinopropane-1 (trade name: Irgacure 907, Ciba Geigy) was used.

Example 4 In Example 2, the photopolymerization initiator was changed to 2-methyl-1 [4- (methylthio) phenyl].
A photoreceptor was obtained in the same manner as in Example 2, except that -2-morpholinopropane-1 (trade name: Irgacure 907, Ciba Geigy) was used.

Example 5 Example 1 was repeated except that the photopolymerization initiator was changed to 2,4-diethylthioxanthone (trade name: Kayacure DETX, Nippon Kayaku).
A photosensitive member was obtained in the same manner as described above.

Comparative Example 1 Example 2 was repeated except that the photopolymerization initiator was changed to 2,4-diethylthioxanthone (trade name: Kayacure DETX, Nippon Kayaku).
A photosensitive member was obtained in the same manner as described above.

(Comparative Example 2) In Example 1, the charge transporting agent was changed to the following compound (oxidation potential: 0.57 eV), the light irradiation time for curing the surface layer was 20 seconds, and the hot air drying was performed at 140 ° C. for 2 seconds. A photoreceptor was obtained in the same manner as in Example 1 except that the operation was performed for a long time.

[0067]

Embedded image (Comparative Example 3) The light irradiation time in Example 2 was set to 20 seconds,
A photoconductor was obtained in the same manner as in Example 2, except that the subsequent hot-air drying was performed at 140 ° C. for 2 hours.

<< Measurement of Dark Decay Rate >>
A drum tester SYNTHIA90 manufactured by Gentec was used. As a charging member used for charging the photoreceptor, a fur brush made of conductive rayon fiber REC-C manufactured by Unitika Ltd. was used.

The voltage applied to the charger was +700 V, the process speed was 94 mm / sec, and the photosensitive member surface potential was measured at a position 180 ° from the charging member.

If the surface potential V0 immediately after charging and the surface potential V60 60 seconds after charging are defined, the dark decay rate is defined as Rvdd = (V0−V60) × 100 / V0.

Table 1 shows the results.

[0072]

[Table 1] << Evaluation of Actual Machine >> The potential stability of the photoreceptors prepared in Examples 1 to 5 and Comparative Examples 1 to 3 was confirmed by a modified Canon reversal developing digital copying machine GP-55II shown in FIG. Here, in the figure, reference numeral 21 is a magnetic brush charger. Reference numeral 9 denotes a transfer blade made of conductive rubber, which applies a transfer potential to the photoconductor via a transfer belt 10 made of carbon-dispersed polyimide. 1, 3 and 4 are the same as in FIG.

As a charging member of this magnetic brush charger, zinc-copper ferrite particles having an average particle size of 25 μm and an average particle size of 1
0 μm zinc-copper ferrite particles in a weight ratio of 1: 0.05
And magnetic particles coated with a medium-resistance resin layer of ferrite particles having an average particle size of 25 μm having a peak at each average particle size position.

The contact charging member comprises the surface-coated magnetic particles prepared as described above, a non-magnetic conductive sleeve for supporting the magnetic particles, and a magnet roll contained therein. To form a charging nip having a width of about 5 mm between the photosensitive member and the photosensitive member. The gap between the magnetic particle holding sleeve and the photoconductor was about 500 μm. In addition, the magnet roll is fixed and rotated so that the surface of the sleeve rubs in the opposite direction at twice the speed of the peripheral speed of the surface of the photoreceptor,
The photoreceptor and the magnetic brush were uniformly contacted. At this time, the resistance per 1 cm of the length of the charging member is 5 × 10 ⁵ /
Ω.

The potential was measured by removing the developing unit and attaching a potential measuring sensor. The charging condition of the photoconductor is as follows: DC: -700 V, AC: 1000 V
pp, the applied voltage was set to 1 kHz. Further, 50 sheets of paper were continuously passed without irradiation for image exposure, and the potentials of the first and 50th sheets were measured. In order to see the effect of the transfer charge, the transfer current was set to 0 μA and 30 μA, and the potential was measured to compare the charge stability. Table 2 shows the results.

[0076]

[Table 2]

[0077]

As can be seen from the comparison between the embodiment and the comparative example,
According to the present invention, in an electrophotographic apparatus in which an injection layer is provided on the surface of a photoreceptor and a charging member is brought into contact with the injection layer to inject and charge a charge, the photoreceptor is stably affected without being affected by transfer charge. It is possible to provide a device that can be charged.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view showing a basic configuration of an electrophotographic apparatus of the present invention.

FIG. 2 is a partial longitudinal sectional view showing a layer structure of an electrophotographic photosensitive member used in the electrophotographic apparatus of the present invention.

FIG. 3 is a partial longitudinal sectional view showing a layer configuration of another electrophotographic photosensitive member used in the electrophotographic apparatus of the present invention.

FIG. 4 is a partial longitudinal sectional view showing a layer structure of still another electrophotographic photosensitive member used in the electrophotographic apparatus of the present invention.

FIG. 5 is a schematic longitudinal sectional view showing a basic configuration of an electrophotographic apparatus used in an embodiment of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 electrophotographic photoreceptor 1 a semiconductive layer (injection layer) 1 b photosensitive layer 1 c conductive support 2 charging member 3 image exposure means 4 developing device 5 cleaner 6 blade 7 transfer material 8 transfer roller 9 transfer blade 10 transfer belt 11 injection Layer 12 charge transport layer 13 charge generation layer 14 conductive support 15 binding layer 16 undercoat layer 21 magnetic brush charger

Claims (6)

[Claims] 1. An electrophotographic apparatus comprising: an electrophotographic photoreceptor; and a conductive charging member disposed in contact with the photoreceptor, and charging the surface of the photoreceptor by injecting charge from the charging member into the photoreceptor. In the apparatus, an electrophotographic photoreceptor having a dark decay rate (defined by Equation 1) of a charge having a polarity of a voltage applied when transferring the developed developer onto the surface of the photoreceptor is 30% or less. An electrophotographic apparatus, characterized in that: (However, the surface potential of the photoconductor immediately after charging is from -500 V to-
It is assumed that the voltage is set in the range of 1000 or +500 V to +1000 V. ) 2. The polarity of a voltage applied when charging the photosensitive member surface with the charging member and a polarity of a voltage applied when transferring a developed developer onto the photosensitive member surface are opposite to each other. The electrophotographic apparatus according to claim 1. 3. The electrophotographic apparatus according to claim 1, wherein the surface layer of the electrophotographic photosensitive member is an electrophotographic photosensitive member that is a semiconductive film in which conductive fine particles are dispersed. 4. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has a layer structure in which at least a semiconductive layer, a charge transport layer, and a charge generation layer are formed in this order from the surface.
The electrophotographic apparatus according to any one of the above. 5. The electrophotographic photoreceptor according to claim 1, wherein the electrophotographic photoreceptor has a layer structure in which at least a semiconductive layer, a charge generation layer, and a charge transport layer are formed in this order from the surface.
The electrophotographic apparatus according to any one of the above. 6. An electrophotographic photoreceptor having a layer structure in which at least a semiconductive layer, a charge transport material, and a single-layer photosensitive layer containing both charge generation materials are formed in this order from the surface. The electrophotographic apparatus according to claim 1, wherein: