JPH06194911A - Electrophotographic receptor - Google Patents

Abstract

PURPOSE:To provide the electrophotographic receptor with which good image characteristics having less fogging and sufficient image density are obtainable by specifying the surface resistivity and volumetric resistivity in the dark constituting the electrophotographic sensitive body. CONSTITUTION:The surface resistivity in the dark of the electrophotographic receptor of a rear exposure and simultaneous development system formed by successively laminating a light transparent conductive layer 2 and a photoconductive layer 3 on a light transparent base 1 is specified to <=1X10<15>OMEGA and the volumetric resistivity thereof to 5X10<9> to 1X10<18>OMEGAcm. Cylindrical moldings of glass, light transparent resins, such as glass, polycarbonate, having a cylindrical shape or light transparent sheet-like films of polyethylene terephthalate, etc., are used for the light transparent base 1. The light transparent conductive layer 2 is superfine particles of indium titanium oxide, tin oxide, zinc oxide, etc,. and is formed by using a method, such as sputtering. A function separated lamination type photoconductive layer or single layer type photo- conductive layer is usable for the photoconductive layer 3.

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 suitable for a back exposure simultaneous development type electrophotographic apparatus.

[0002]

2. Description of the Related Art Conventionally, an electrophotographic system has a structure as shown in FIG. That is, in the dark place, the surface of the electrophotographic photoreceptor 11 is uniformly charged by the corona charger 12, and then the electrostatic latent image is formed on the photoreceptor by the exposure device 13. Then, the developing device 14 causes the developer 15 to adhere to the electrostatic latent image for development, and then the toner image on the surface of the electrophotographic photosensitive member 11 is transferred to the recording paper 17 by the corona transfer device 16. In general, such an electrophotographic photoreceptor has a function of combining an inorganic material such as selenium, amorphous silicon, zinc oxide, Cds or the like, a carrier generating material such as a bisazo pigment or a perylene pigment and a carrier transporting material such as hydrazone. Separable organic photoconductors are known. However, the above-mentioned electrophotographic system has an environmental problem due to the generation of ozone due to the use of a corona charger, and since various devices are required around the photoconductor, the copier itself should be miniaturized. There was a limit.

Therefore, in recent years, in order to improve the problems of the electrophotographic system, an electrophotographic system of a back exposure and simultaneous development system has been proposed as shown in JP-A-58-44445. This method has the advantage that there is no environmental problem due to ozone generation because no corona charger is used, and the apparatus is compact because the image exposure apparatus is provided inside the electrophotographic photoreceptor. Specifically, the configuration is as shown in FIGS. 3 and 4. That is, in FIG.
An exposing device including an LED (light emitting diode) or the like provided in the electrophotographic photosensitive member 21 by applying a developing bias voltage to the developer 22 brought into contact with the electrophotographic photosensitive member 21 to give an electric charge to the electrophotographic photosensitive member 21. The image area is exposed by 23, the electric charge in the exposed area is removed, and the latent image of the well potential is formed. At the same time, the developer 22 is reversely developed to the latent image of the well potential to be visualized. After that, the image on the surface of the electrophotographic photosensitive member 21 is transferred onto the recording paper 26 by the transfer roller 25. Further, in FIG. 4, the surface of the electrophotographic photosensitive member 21 is uniformly charged by the charging roller 27, and then the image portion is exposed by the exposure device 23 including an LED (light emitting diode) or the like provided in the electrophotographic photosensitive member 21, The charge of the exposed portion is removed to form an electrostatic latent image, and at the same time, the developer 22 develops the electrostatic latent image by the developing device 24 to make it visible. After that, the image on the surface of the electrophotographic photosensitive member 21 is recorded on the recording paper 26 by the transfer roller 25.
Is to be transferred to.

When the electrophotographic photosensitive member used in the conventional electrophotographic system is applied to such a backside exposure simultaneous developing system, the following problems occur. That is, the conventional electrophotographic photosensitive member is designed so that electric charges are not easily charged and attenuated on the surface of the electrophotographic photosensitive member, and has a characteristic that charge injection hardly occurs inside the electrophotographic photosensitive member. Further, generally, in the back-exposure simultaneous development system, a bias potential for preventing fog in the non-image area cannot be applied between the electrophotographic photosensitive member and the developing device. Therefore, when a conventional electrophotographic photosensitive member is applied to the back exposure simultaneous development method, the developer adheres to the electric charges existing in the non-image area on the surface of the electrophotographic photosensitive member and is transferred to the recording paper as it is, causing fog. Had the problem of doing.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrophotographic photosensitive member suitable for the backside exposure simultaneous development system shown in FIGS. 3 and 4 described above. An object of the present invention is to provide an electrophotographic photosensitive member which has excellent image characteristics with various image densities.

[0006]

DISCLOSURE OF THE INVENTION The present inventors have made a detailed study on the relationship between the electrophotographic photoreceptor by the backside exposure simultaneous development system and the electrophotographic characteristics and image characteristics, and as a result, constitute the electrophotographic photoreceptor. The inventors have found that surface resistivity and volume resistivity in the dark are important factors for various properties, and have completed the present invention. That is, the present invention is an electrophotographic photosensitive member for a back exposure simultaneous development system, which comprises a translucent conductive layer and a photoconductive layer sequentially laminated on a translucent support, and the electrophotographic photosensitive member is in the dark. Surface resistivity at 1 × 10 ¹⁵ Ω
And volume resistivity of 5 × 10 ⁹ to 1 × 10 ¹⁸ Ω.
The electrophotographic photosensitive member is characterized by having a size of cm.

The present invention will be described in detail below. FIG. 1 is a layer structure diagram of the electrophotographic photosensitive member of the present invention. In the figure, 1 is a transparent support, 2 is a transparent conductive layer, and 3 is a photoconductive layer.
As the translucent support 1, a cylindrical glass, a cylindrical molded product of a translucent resin such as polycarbonate, or a translucent sheet film such as polyethylene terephthalate (PET) is used. The transparent conductive layer 2 is made of indium titanium oxide (hereinafter referred to as ITO), tin oxide,
Ultra-fine particles of zinc oxide or the like, which has the above-mentioned translucent support 1
Vacuum deposition, sputtering, chemical vapor deposition (CV
It can be formed using a method such as D) or ion plating.

As the photoconductive layer 3, a function-separated laminated photoconductive layer or a single-layer photoconductive layer can be used. The function-separated laminated photoconductive layer is formed by laminating a carrier transport layer on a carrier generation layer.As the photoconductive material for the carrier generation layer, organic materials such as phthalocyanine pigments, azo pigments, Ring quinone pigment, perylene pigment,
Examples thereof include quinacridone pigments, pyrrol pigments, and antantron pigments. Inorganic materials such as zinc oxide, titanium oxide, cadmium sulfide, selenium, SeAs,
SeTe, silicon, amorphous silicon, etc. may be mentioned. On the other hand, examples of the carrier transport layer include hydrazone, butadiene derivatives, polyvinylcarbazole, pyrazoline, oxadiazole, oxazole, triphenylmethane, amine derivatives, fluorenone derivatives, and diphenoquinone derivatives. In the case of the carrier generation layer made of the inorganic material, it can be formed on the translucent conductive layer 2 by a method such as vacuum deposition, sputtering, chemical vapor deposition (CVD), or ion plating. Further, the carrier generation layer and the carrier transport layer made of the organic material are formed by dispersing the material in a binder resin by a method such as roll coating, dipping, spin coating, casting, spraying, blade coating, and wire bar coating. It can be formed by coating. In this case, as the binder resin, polycarbonate, polystyrene, polyvinyl chloride, polymethacrylate, polyvinyl acetate, silicone resin, vinyl chloride-vinyl acetate copolymer resin, epoxy resin, polyvinyl butyral, polyester resin, polyamide resin, etc. Can be used. Further, as an organic solvent for dissolving these binder resins, toluene,
Methyl ethyl ketone, dichloromethane, dichloroethane, ethyl chlorobenzene acetate, methyl alcohol, ethyl alcohol and the like can be used. When used as a carrier generation layer of a function-separated laminated system, the organic pigment may be formed by a method such as vacuum vapor deposition, sputtering, chemical vapor deposition (CVD) or ion plating, and the transparent conductive layer 2
It can also be formed on top. As the single-layer photoconductive layer, the resin-dispersed organic photoconductive material or a coating solution obtained by adding an appropriate amount of the material for the carrier transport layer described above to the roll coating, dipping, spin coating, casting, It is formed by applying by spray coating, blade coating, wire bar coating, or the like. The photoconductive layer 3 has a layer thickness of 0.5 to 3
It is about 0 μm, preferably 3 to 20 μm.

The electrophotographic photosensitive member of the present invention is formed by applying casein, polyvinyl alcohol, polyvinyl butyral, polyamide resin, polyester resin, cellulose derivative or the like between the translucent conductive layer 2 and the photoconductive layer 3. A barrier layer formed by vapor deposition or a barrier layer formed by vapor deposition of an inorganic oxide such as amorphous silicon or titanium oxide may be provided for the purpose of preventing charge injection. The layer thickness of the barrier layer is preferably 0.01 to 10 μm. Further, an overcoat layer in which a conductive substance or the like is dispersed in a binder resin may be provided on the photoconductive layer 3.

In the electrophotographic photosensitive member of the present invention composed of the above-mentioned materials and laminated structure, the surface resistivity is 1 × 10 ¹⁵ Ω or less and the volume resistivity is 5 × 10 ⁹ to 1 × 10 ¹⁸ Ω · c.
It must be m. That is, in the back-exposure simultaneous development method, as described above, if electric charges are present on the surface of the electrophotographic photosensitive member, fogging of the non-image area occurs. Therefore, the charge generated by the developing bias voltage of the developer needs to be injected into the electrophotographic photoreceptor. For that purpose, the surface resistivity of the electrophotographic photosensitive member in the dark must be 1 × 10 ¹⁵ Ω or less. Therefore, when the surface resistivity exceeds 1 × 10 ¹⁵ Ω, the charge generated by the developing bias voltage is not injected into the photoconductor, so that the charge is accumulated on the surface of the electrophotographic photoconductor. Further, when the surface resistivity is 1 × 10 ¹⁵ Ω or less, frictional electrification between the electrophotographic photosensitive member and the developer is prevented, and adhesion of the developer to the electrophotographic photosensitive member surface due to frictional electrification is prevented. Play.

On the other hand, the electric charges injected into the electrophotographic photosensitive member must be held near the surface of the electrophotographic photosensitive member in order to clarify the contrast between the image area and the non-image area. Therefore, in the present invention, the volume resistivity of the electrophotographic photosensitive member needs to be 5 × 10 ⁹ to 1 × 10 ¹⁸ Ω · cm. That is, the volume resistivity is 5 × 10 ⁹ Ω · c
If it is less than m, it is difficult to maintain the electric charge near the surface of the electrophotographic photosensitive member, and the potential of the surface of the electrophotographic photosensitive member becomes low. Therefore, the developer is developed in the non-image area by the applied developing bias. Occurs. Also, the volume resistivity is 1
When it exceeds × 10 ¹⁸ Ω · cm, the surface resistivity is 1 × 10 ¹⁵
Even under the condition of Ω or less, it becomes difficult to inject charges from the surface of the electrophotographic photosensitive member due to the developing bias voltage, and the charges are gradually accumulated on the surface of the electrophotographic photosensitive member. Surface resistivity is 1
× 10 ¹⁵ Ω or less and volume resistivity of 5 × 10 ⁹ to 1 × 10
^As a technical means for controlling the range of ¹⁸ Ω · cm, it can be carried out by selecting the amount of the photoconductive material and the kind of the binder resin, or by adding the conductive material.

Next, the method of measuring the surface resistivity and volume resistivity in the dark specified in the present invention is as follows. That is, as shown in FIG. 1, a translucent conductive layer 2 and a photoconductive layer 3 are sequentially laminated on a translucent support 1 to prepare an electrophotographic photosensitive member, and then the electrophotographic photosensitive member is in a sheet form. Or, in the case of a belt, cut it into an appropriate size, and use ADVANTEST's RESISTIVITY CHAMBER (R127
04). In addition, the electrophotographic photosensitive member can be used like a cylindrical drum in a REISTIVITY CHAMBE.
If it cannot be set to R, gold is vapor-deposited on the surface of the photoconductor to provide an electrode. ULTRA HIGH RESIS from the same company that also functions as a power supply and resistance measuring device
The surface resistivity and the volume resistivity in the dark are measured by using TANCE METER (R8340).
The measurement conditions are as follows. In the dark, the surface of the electrophotographic photosensitive member is grounded, discharged for 10 seconds, and then 10 V is applied,
The value of 1 minute after application is defined as the surface resistivity and volume resistivity of the photoreceptor of the present invention.

[0013]

EXAMPLES Next, the present invention will be described using examples and comparative examples. Example 1 ITO is sputtered on the surface of a translucent support made of cylindrical glass to form a translucent conductive layer, and casein is dried on the translucent conductive layer to have a thickness of 2 μm. Thus coated to form a barrier layer. On the other hand, a composition having the following composition was dispersed for 4 hours by a dispersion device using glass beads to prepare a coating liquid for a photoconductive layer. Next, the coating liquid is applied onto the barrier layer, dried at 60 ° C. for 10 minutes, and further vacuum dried at 50 ° C. for 3 hours to form a photoconductive layer having a thickness of 10 μm. Got the body X-type metal-free phthalocyanine pigment 2 parts by weight Polyester resin 6 parts by weight (Unitika Elitel UE-3200) Dichloroethane 92 parts by weight

Example 2 As in Example 1, a transparent conductive layer of ITO and a barrier layer of casein were provided on a glass cylindrical substrate, and the dispersion having the following composition was formed on the barrier layer using glass beads. Apply the coating liquid dispersed for 2 hours by the device and
After drying for 1 minute, vacuum dry at 50 ° C for 3 hours, thickness 0.5μ
m carrier generation layer was obtained. X-type metal-free phthalocyanine 2 parts by weight Polyvinyl butyral resin 1 part by weight (Denki Kagaku Kogyo # 4000-1) dichloroethane 93 parts by weight The following composition is mixed and dissolved on this carrier generation layer for 2 hours. Apply the coating liquid and dry it in the same manner to obtain a thickness of 1
A carrier transport layer having a thickness of 0 μm was formed to obtain the electrophotographic photosensitive member of the present invention. Hydrazone compound 10 parts by weight

[Chemical 1] Polyvinyl butyral resin 10 parts by weight (Denki Kagaku Kogyo # 4000-1) Dichloroethane 80 parts by weight

Example 3 An electrophotographic photosensitive member of the present invention was obtained in the same manner as in Example 1 except that the coating liquid having the following composition was used instead of the coating liquid for the photoconductive layer of Example 1. X type metal-free phthalocyanine 4 parts by weight Polyvinyl butyral resin 4 parts by weight (Denki Kagaku Kogyo # 4000-1) Dichloroethane 92 parts by weight

Example 4 An electrophotographic photoreceptor of the present invention was obtained in the same manner as in Example 1 except that the coating liquid having the following composition was used instead of the coating liquid for the photoconductive layer of Example 1. X-type metal-free phthalocyanine 4 parts by weight Polyester resin 4 parts by weight (Unitika Elitel UE-3200) Dichloroethane 92 parts by weight

Example 5 An electrophotographic photosensitive member of the present invention was obtained in the same manner as in Example 1 except that the coating liquid having the following composition was used instead of the coating liquid for the photoconductive layer of Example 1. 2 parts by weight of titanyl phthalocyanine 6 parts by weight of polyvinyl butyral resin (# 4000-1 manufactured by Denki Kagaku Kogyo Co., Ltd.) 92 parts by weight of dichloroethane

Comparative Example 1 An electrophotographic photosensitive member for comparison was obtained in the same manner as in Example 2 except that the coating liquid for the carrier transport layer in Example 2 was replaced with the coating liquid having the following composition. Hydrazone compound 10 parts by weight

[Chemical 2] Polycarbonate resin 10 parts by weight (Tanjin Chemical Co., Ltd. Panlite L1250) Dichloroethane 80 parts by weight

Comparative Example 2 An electrophotographic photosensitive member for comparison was obtained in the same manner as in Example 1 except that the coating liquid having the following composition was used instead of the coating liquid for the photoconductive layer of Example 1. X type metal-free phthalocyanine 2 parts by weight Polyamide resin 6 parts by weight (Toray Nylon CM-4000) Methyl alcohol 92 parts by weight

Comparative Example 3 A coating solution obtained by mixing and dissolving the following compositions for 1 hour was applied on the electrophotographic photosensitive member of Comparative Example 1 and dried in the same manner to form an overcoat layer of 1 μm for comparison. To obtain an electrophotographic photoreceptor. Carbon 0.5 parts by weight Polyester resin 4.5 parts by weight (Unitika Elitel UE-3200) Dichloroethane 95 parts by weight

The surface resistivity and volume resistivity of the photoconductive layers of the electrophotographic photoreceptors of Examples 1 to 5 and Comparative Examples 1 to 3 obtained by the above operation were measured. Further, the above-mentioned electrophotographic photosensitive member was set in an electrophotographic apparatus of the back exposure simultaneous development system as shown in FIG. 3 and image characteristics were evaluated. The results are shown in Table 1. In Table 1, the fog was developed by developing the developer on the electrophotographic photosensitive member, and then the non-image area on the photosensitive member was peeled off the tape. The difference in whiteness between the peeled tape and the tape itself was measured by Nippon Denshoku Co., Ltd. It was measured by a Hunter color difference meter. The developer used at this time has a toner resistance of 10 ⁶ Ω · c.
m conductive magnetic toner was used.

[0022]

[Table 1]

As is clear from the results shown in Table 1, the electrophotographic photosensitive member of the present invention had little fogging. Also,
After developing the developer on the electrophotographic photosensitive member, the solid image on the electrophotographic photosensitive member was peeled off with a tape, and the peeled tape was measured with a reflection type image densitometer RD-914 manufactured by Macbeth Co. The photographic photosensitive member had a sufficient image density of 1.1 to 1.3. On the other hand, the electrophotographic photosensitive member for comparison had a problem in practice due to fogging.

[0024]

INDUSTRIAL APPLICABILITY The electrophotographic photoreceptor of the present invention is suitable for an electrophotographic apparatus comprising a back exposure type image forming method,
When the electrophotographic photosensitive member of the present invention is used, it is possible to obtain good image characteristics with less fogging and sufficient image density.

[Brief description of drawings]

FIG. 1 is a diagram showing a layer structure of an electrophotographic photosensitive member of the present invention.

FIG. 2 is a schematic diagram illustrating a conventional electrophotographic method.

FIG. 3 is a schematic diagram illustrating a backside exposure method.

FIG. 4 is a schematic diagram illustrating another backside exposure method.

[Explanation of symbols]

 1 translucent support 2 translucent conductive layer 3 photoconductive layer

Claims (1)

[Claims] 1. An electrophotographic photosensitive member for a backside exposure simultaneous development system, comprising a translucent conductive layer and a photoconductive layer sequentially laminated on a translucent support, wherein the electrophotographic photosensitive member is in the dark. Has a surface resistivity of 1 × 10 ¹⁵ Ω or less and a volume resistivity of 5
An electrophotographic photosensitive member characterized by having a density of × 10 ⁹ to 1 × 10 ¹⁸ Ω · cm.