JPH10123856A - Electrophotographic device and image forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrophotographic device capable of executing a high speed processing without requiring the no-load rotation of an electrophotographic photoreceptor and further, suppressing the generation of the ghost in an initial stage of an image forming process. SOLUTION: This device is provided with a main electrifying means, an image exposure means, a developing means and a transfer means which are for attaining main electrification, image exposure, reversal development and a transfer respectively, with respect to the rotary elecrophotographic photoreceptor having a charge generating layer incorporating a phthalocyanine compound and a charge transfer layer, on a conductive substrate. At this time, a pretransfer exposure means for exposing the electrophotographic photoreceptor before the transfer is performed by the transfer means is further provided. Electrification potential in an unexposed part on the electrophotographic photoreceptor after being mainly electrified by the main electrifying means is made on-third of that before exposure by the pretransfer exposure means by this exposure, even if the potential is high.

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 an image forming method for reversal development using a laminated electrophotographic photosensitive member containing a phthalocyanine compound, and more particularly, to idling of the laminated electrophotographic photosensitive member. The present invention relates to an electrophotographic apparatus for reversal development and an image forming method capable of quickly and easily obtaining a high-quality image by suppressing the occurrence of a negative ghost, a positive ghost or the like in an early stage of an image forming process. .

[0002]

2. Description of the Related Art F. The electrophotography process according to Carlson's invention is widely used in various printers and facsimile machines in recent years, not only in the field of copiers but also in the field of printers and facsimile machines, because of its ability to obtain images with immediacy, high quality and high storage stability Is showing. Basically, this electrophotographic process is performed by uniformly charging the surface of a photoconductor, forming an electrostatic latent image by image exposure corresponding to a document, developing the latent image with toner, and transferring the toner image to paper (intermediate). And a fixing process, and an initialization process for removing the toner and charge remaining on the surface of the photoconductor, which is performed to repeatedly use the photoconductor.

As for the photoreceptor which is the core of the electrophotographic process, conventional photoconductive materials such as selenium,
Recently, photosensitive materials using inorganic photoconductors, such as arsenic-selenium alloys, cadmium sulfide, and zinc oxide, using organic photoconductive materials, which have the advantages of being easily polluted, easy to form films, and easy to manufacture, have been developed. The body is being developed. Among these, the so-called laminated type photoreceptor in which the charge generation layer and the charge transport layer are laminated, a photoreceptor with higher sensitivity can be obtained, a photoreceptor with a wide selection of materials and a highly safe photoreceptor can be obtained, Due to its high productivity and relatively low cost, photoconductors are now the mainstream and are produced in large quantities.

On the other hand, in recent years, digitization for image formation has been rapidly progressing in order to obtain higher quality images and to store and freely edit input images. Until now, digital image formation was limited to laser printers, LED printers and some color laser copiers, which are output devices of word processors and personal computers, but analog image formation has been the mainstream in the past. Digitization is also rapidly progressing in the field of ordinary copying machines.

When digitally forming an image, when computer information is used directly, the electrical signal is converted into an optical signal. When information is input from a document, the document information is read as optical information. Thereafter, the signal is once converted into a digital electric signal, converted into an optical signal again, and then input to the respective photoconductors. In any case, an optical signal is input to the photoconductor, but laser light or LED light is mainly used for the optical input of such a digital signal. Currently, the most frequently used oscillation wavelength of input light is near-infrared light of 780 nm or 660 nm or long-wavelength light close thereto. For a photoreceptor used for image formation digitally, the first required property is to have sensitivity to these long-wavelength lights. ing. Among them, phthalocyanine compounds have been widely studied and put to practical use because many of them are relatively easy to synthesize and exhibit sensitivity to long-wavelength light.

For example, Japanese Patent Publication No. 5-55860 discloses a photoreceptor using titanyl phthalocyanine.
JP-A-155851 discloses a photoreceptor using β-type indium phthalocyanine, JP-A-2-23369 discloses a photoreceptor using a χ-type metal-free phthalocyanine, and JP-A-61-28557 discloses a vanadyloxy group. Photoreceptors using phthalocyanine are disclosed.

On the other hand, in the case of digitally forming an image, a so-called reversal developing method of forming an image by adhering toner to a portion irradiated with light is used for the purpose of effectively utilizing light or increasing resolution. There are many. In the reversal developing method, a dark potential portion becomes a white background, and a bright potential portion becomes a black background portion (image portion). As described above, the photoreceptor after the completion of the image is subjected to an initialization process for forming the next image, or a method of removing electricity in the photoreceptor.
A method using corona discharge, a method using light, and the like are known. Among them, a photo-static discharge method which can be performed by a simple apparatus and does not involve generation of harmful gas such as ozone as in the case of AC corona discharge is often used.

[0008] However, when the present inventors formed an image using a laminated electrophotographic photosensitive member containing a phthalocyanine compound in the charge generating layer in such a copying process by reversal development, the laminated electrophotographic photosensitive member was first used. It has been found that electrons after holes have been injected into the photographic photosensitive layer are likely to remain in the charge generation layer, and as a kind of memory, there is a drawback that potential fluctuation is apt to occur.

In principle, it is presumed that electrons remaining in the charge generation layer proceed to the interface between the charge generation layer and the charge transport layer for some reason, and lower the barrier property of hole injection near the interface. . Actually, in the case of using a laminated electrophotographic photosensitive member containing a phthalocyanine compound in the charge generation layer, the exposed portion potential in the previous cycle exposure portion in the next cycle exposure region in the next cycle exposure region due to the difference in the presence or absence of exposure in the previous cycle. It rises higher than the surroundings, and a so-called negative ghost phenomenon occurs. Alternatively, the sensitivity at the place where light was irradiated during the previous cycle is apparently faster, and when a uniform image is taken over the entire surface at the next cycle, the so-called positive ghost phenomenon, in which the previous cycle portion appears black, is remarkably observed.

The use of a layered electrophotographic photosensitive member containing a phthalocyanine compound in the charge generation layer in a reversal developing electrophotographic process potentially involves the problems described in detail above. Therefore, conventionally, the process of the first rotation of the photosensitive member in which the charged voltage is reduced is not used for image formation (so-called idle rotation), and is used for image formation from the second rotation onward when the charged voltage is stable. The current situation is to avoid such problems. In a reversal developing system printer or the like having a relatively low copy speed (for example, A4 paper 10 sheets / min or less) as in the past, such development is remarkably exhibited because the charging control capability of the charger can be provided with a margin. There was no particular problem in the process of making the first rotation idle because there is no data transfer and it takes time to transfer data from a computer, etc. In the case of directly copying an original such as a copier, there is a problem that if the first rotation is idling, a high speed operation is greatly hindered. There has been a demand for the development of an electrophotographic apparatus and an image forming method capable of forming an image from the first rotation of a laminated electrophotographic photosensitive member.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to achieve the following objects in response to such a demand. That is, according to the present invention, high-speed processing is possible without the need for idling of the laminated electrophotographic photosensitive member, and the occurrence of negative ghosts, positive ghosts, and the like in the early stage of the image forming process is suppressed, and high-quality images can be produced quickly and simply. It is another object of the present invention to provide an electrophotographic apparatus for reversal development and an image forming method which can be obtained as described above.

[0012]

In view of such circumstances, the present inventors of the present invention have proposed a case where a laminated photoreceptor using a phthalocyanine compound for a charge generation layer is used in an electrophotographic copying method of a reversal development system. Various investigations have been made on means for eliminating such useless idle rotation, and it has been found that in order to solve these problems, the method of starting the image forming process at the beginning is important. That is, in the image forming process, exposure is performed prior to performing transfer to the laminated electrophotographic photosensitive member, and the exposure causes the potential of a non-exposed portion of the electrophotographic photosensitive member after main charging to be changed before the exposure. It has been found that by reducing to 1/3, idling inside the laminated electrophotographic photosensitive member can be made unnecessary, and the occurrence of ghost in the early stage of the image forming process can be effectively suppressed. The present invention is based on the above findings by the inventors of the present invention.

The means for solving the above problems are as follows. (1) A charge generating layer containing a phthalocyanine compound and a charge transport layer are provided on a conductive support, and a main charging means for main charging the rotating electrophotographic photosensitive member, and an image for image exposure. An electrophotographic apparatus having an exposure unit, a developing unit for performing reversal development, and a transfer unit for performing transfer, further comprising a pre-transfer exposure unit for exposing the electrophotographic photosensitive member before performing transfer by the transfer unit. And exposing the non-exposed portion of the electrophotographic photosensitive member after the main charging by the main charging unit to at most 1/3 of the charging potential before the exposure by the exposure by the pre-transfer exposure unit. Is an electrophotographic apparatus.

(2) The electrophotographic apparatus according to (1), wherein a charging potential of a non-exposed portion of the electrophotographic photosensitive member after main charging by the main charging unit is at least -700 V.

(3) The electrophotographic apparatus according to (1) or (2), wherein at least one of the main charging unit and the transfer unit is a contact charger.

(4) The phthalocyanine compound is at least one selected from gallium phthalocyanine halide, tin phthalocyanine halide, hydroxygallium phthalocyanine, oxytitanyl phthalocyanine, indium phthalocyanine halide, vanadyl phthalocyanine and metal-free phthalocyanine. The electrophotographic apparatus according to any one of (1) to (3).

(5) The electrophotographic apparatus according to any one of (1) to (4), wherein the pre-transfer exposure means operates only during the first rotation of the electrophotographic photosensitive member.

(6) An image forming method, wherein an image is formed using the electrophotographic apparatus according to any one of (1) to (5).

(7) A charge generating layer and a charge transporting layer containing a phthalocyanine compound are provided on a conductive support.
In an image forming method including performing reversal development and transfer, exposing the electrophotographic photoreceptor before performing the transfer, and exposing the electrophotographic photoreceptor to non-exposure after the main charging. The image forming method is characterized in that the potential of the portion is at most １ ／ of that before the exposure.

(8) The image forming method according to (7), wherein the exposure is performed only in the first rotation of the electrophotographic photosensitive member.

In the electrophotographic apparatus described in the above (1) to (5) and the image forming method described in the above (6) to (8), the electrophotographic photosensitive member is transferred to the electrophotographic photosensitive member before the transfer. To expose the non-exposed portion of the electrophotographic photoreceptor after the main charging to 1% before the exposure.
/ 3. That is, in the early stage of the image forming process, the exposure is performed on the laminated electrophotographic photosensitive member before the transfer, and the potential of the non-exposed portion of the electrophotographic photosensitive member after the main charging is significantly reduced as compared with before the exposure. The transfer is performed after the state. As a result, the occurrence of ghost in the early stage of the image forming process is effectively suppressed.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrophotographic photoreceptor used in the present invention comprises a photoconductive layer provided on a conductive support.
The electrophotographic photoconductor may be a single-layer electrophotographic photoconductor,
In the present invention, a function-separated type electrophotographic photosensitive member is preferable. Examples of the conductive support include mainly metal materials such as aluminum, aluminum alloy, stainless steel, copper, and nickel, polyester films on which aluminum is deposited, and paper.

A known barrier layer, which is generally used, may be provided between the conductive support and the photoconductive layer.
For example, aluminum anodized film, aluminum oxide, inorganic layers such as aluminum hydroxide, polyvinyl alcohol, casein, polyvinylpyrrolidone, polyacrylic acid, celluloses, organic layers such as resins such as gelatin, starch, polyurethane, polyimide, polyamide, Alternatively, a silane coupling agent, an organic metal compound such as an organic zirconium, or a mixture thereof may be used. Further, these barrier layers may include conductive or semiconductive fine particles such as metals such as aluminum, steel, tin, zinc, and titanium, or metal oxides.

As the photoconductive layer, in the case of the laminated electrophotographic photoreceptor, at least a charge generating layer containing a charge generating substance and a charge transporting layer containing a charge transporting substance are exemplified.

Examples of the charge generating material include metal-free phthalocyanine, copper indium chloride, gallium chloride,
Metals such as tin, oxytitanium, zinc, and vanadium, or phthalocyanines to which oxides and chlorides thereof are coordinated are exemplified. Among these, in terms of light sensitivity, electrical property stability, image quality, metal-free phthalocyanine, halogenated gallium phthalocyanine such as chlorogallium, halogenated tin phthalocyanine such as dichlorotin, hydroxygallium phthalocyanine, oxytitanyl phthalocyanine, chloroindium and the like At least one selected from indium phthalocyanine halide and vanadyl phthalocyanine is preferred. Note that a plurality of these central metals may be used in the form of a mixed crystal, or a plurality of these may be mixed as a single product.

The charge generation layer may contain a charge generation material other than phthalocyanine in order to change the spectral sensitivity and to improve the electrical characteristics such as chargeability and residual potential. Such charge generating materials include, for example, selenium and its alloys, arsenic-selenium, cadmium sulfide, zinc oxide,
Other inorganic photoconductive substances, azo dyes, quinacridone, polycyclic quinones, pyrylium salts, thiapyrylium salts, indigo, thioindigo, anthantrone, pyranthrone,
Cyanine and the like.

The average particle size of the above-mentioned charge generating substance is as follows:
It is preferably 1 μm or less, more preferably 0.5 μm or less, and particularly preferably 0.3 μm or less.

Examples of the binder used in the charge generation layer include polyvinyl acetate, polyacrylate, polymethacrylate, polyester, polycarbonate, polyvinyl acetoacetal, and the like.
Examples include polyvinyl propional, polyvinyl butyral, phenoxy resin, epoxy resin, urethane resin, cellulose ester, cellulose ether and the like.

The content of the charge generating substance in the charge generating layer is usually 30 to 500 parts by weight based on 100 parts by weight of the binder. The thickness of the charge generation layer is usually 0.1 to 2 μm,
0.8 μm is preferred. If necessary, various additives such as a leveling agent, an antioxidant, and a sensitizer may be added to the charge generation layer.
The charge generating layer may be a layer formed by binding the fine particles of the charge generating substance in a state of being dispersed in the binder, or may be a deposition film of the charge generating substance.

As the charge transport material, for example,
4,7-trinitrofluorenone, electron-withdrawing substances such as tetracyanoquinodimethane, carbazole, indole, imidazole, oxazole, pyrazole, oxadiazole, pyrazoline, thiadiazole, and other heterocyclic compounds, aniline derivatives, hydrazone compounds, An electron donating substance such as an aromatic amine derivative, a stilbene derivative, or a polymer having a group consisting of these compounds in a main chain or a side chain is exemplified. The charge transport layer is formed in a state where these charge transport substances are bound to a binder.

Examples of the binder used in the charge transport layer include vinyl polymers such as polymethyl methacrylate, polystyrene, and polyvinyl chloride, and copolymers thereof, polycarbonate, polyester, polyester carbonate, polysulfone, polyimide, and phenoxy. , Epoxy, silicone resin and the like, and partially crosslinked and cured products thereof.

The content of the charge transporting material in the charge transporting layer is usually 30 to 200 parts by weight, preferably 40 to 150 parts by weight, based on 100 parts by weight of the binder. The thickness of the charge transport layer is usually 5
To 50 μm, preferably 10 to 45 μm. To the charge transport layer, known plasticizers, antioxidants, ultraviolet absorbers, leveling agents, and other additives may be added as necessary to improve film formability, flexibility, coatability, and the like. Can be.

The electrophotographic photoreceptor may have an outermost surface layer provided on the photoconductive layer. Such an outermost surface layer is mainly composed of, for example, a conventionally known thermoplastic or thermosetting polymer. Overcoat layer. In the present invention, the charge transport layer or the overcoat layer is obtained by curing a polymer type charge transport material or a reactive low-molecular charge transport material having a charge transport function and polymerizing the same. You may. In the case of forming each of the layers, a known method such as sequentially applying and drying a coating solution obtained by dissolving or dispersing a substance to be contained in the layer in a solvent can be applied. The above electrophotographic photosensitive member is suitably used in the following electrophotographic apparatus and image forming method of the present invention.

In the image forming method of the present invention, the electrophotographic photoreceptor is subjected to main charging, image exposure, reversal development and transfer, and exposure before the transfer (hereinafter sometimes referred to as "pre-transfer exposure"). Including performing. The image forming method of the present invention can be carried out according to a usual method, but can be suitably carried out using the electrophotographic apparatus of the present invention described below. The electrophotographic apparatus of the present invention includes a main charging unit for performing main charging, an image exposing unit for performing image exposure, a developing unit for performing reversal development, a transfer unit for performing transfer, and an operation for performing these operations. A control means for controlling; and a pre-transfer exposure means for exposing the electrophotographic photosensitive member before transferring by the transfer means.

The main charging includes, for example, contact charging using a conductive or semiconductive roller, brush, film, rubber blade, etc., scorotron charging using corona discharge, corotron charging and the like. The main charging can be performed using a known main charger or the like, but can be suitably performed by a main charging unit in the electrophotographic apparatus of the present invention described below. The main charging unit is not particularly limited, and includes, for example, a contact type charger using a conductive or semiconductive roller, a brush, a film, a rubber blade, a scorotron charger using a corona discharge, and a corotron charger. And other known main chargers. Among these, a contact-type charger is preferable because of its excellent charge compensation ability. The main charging unit is provided for the electrophotographic photosensitive member.
Normally, a DC current is applied, but an AC current may be further superimposed and applied. For example, the electrophotographic photoreceptor is usually −300 to −1000 by such a main charging unit.
V, preferably at least -700 V, more preferably-
It is charged to a potential in the range of 700 to -1000V. If the potential is less than -700 V, in other words, -700 V
When charged to a negative polarity with a lower potential than that, ghosts may easily occur.

The image exposure can be performed by using an image exposure device using a known light source such as an LED light, a liquid crystal shutter light or the like in addition to the semiconductor laser light. Can be suitably performed by the image exposure means in the above. The image exposure unit is not particularly limited, and includes, for example, an optical device capable of exposing a light source such as a semiconductor laser light, an LED light, and a liquid crystal shutter light to the surface of the electrophotographic photosensitive member in a desired image. Can be

The reversal development can be performed, for example, by using a general developing device which develops by contacting or non-contacting a magnetic or non-magnetic one-component developer or a two-component developer. This can be suitably performed by the developing means in the electrophotographic apparatus of the present invention described below. The developing unit is not particularly limited, and includes, for example, a developing device having a function of attaching the one-component developer or the two-component developer to the electrophotographic photosensitive member using a brush, a roller, or the like. .

The transfer includes, for example, transfer by corona discharge, contact transfer using a transfer belt, a transfer roller and the like. The transfer can be performed using a known transfer charger or the like, but can be suitably performed by a transfer unit in the electrophotographic apparatus of the present invention described below. The transfer unit is not particularly limited, and includes, for example, a transfer belt, a contact-type transfer charger using a transfer roller, and a transfer charge known per se such as a scorotron transfer charger and a corotron transfer charger using corona discharge. Vessels. Among these, a contact-type transfer charger is preferable because of its excellent transfer charge compensation ability. In the present invention, it is preferable that at least one of the main charging unit and the transfer unit is a contact-type charger (including a contact-type transfer charger) in terms of charge compensation ability.

The pre-transfer exposure can be performed using a pre-transfer exposure device using a known light source such as LED light, tungsten lamp light, halogen lamp light, etc.
It can be suitably performed by the following pre-transfer exposure means in the electrophotographic apparatus of the present invention. The light quality of the light source may be white or red as long as it is included in the spectral region where the electrophotographic photosensitive member has photosensitivity, and can be appropriately selected according to the purpose. In the present invention, among these, red LED light is preferable in terms of availability, cost, and the like. The pre-transfer exposure means is not particularly limited, and includes, for example, an optical device capable of exposing a light source such as an LED light, a tungsten lamp light, a halogen lamp light, or the like to the electrophotographic photosensitive member surface in a desired image. No. In the present invention, among these,
An optical system device capable of imagewise exposing the red LED light in terms of availability, cost, and the like is preferable.

The exposure amount in the pre-transfer exposure is as follows.
By the pre-transfer exposure, the potential of the non-exposed portion of the electrophotographic photoreceptor after the main charging is at most 1/3 before the pre-transfer exposure, that is, 1/3 or less of the pre-transfer exposure. It is set in a suitable range. Specifically, the exposure amount of the pre-transfer exposure by the pre-transfer exposure means is adjusted so as to achieve such an exposure amount. If the exposure amount in the pre-transfer exposure is larger than １ ／ of that before the transfer exposure, ghosts in the early stage of the image forming process cannot be effectively suppressed, and a high-quality image cannot be obtained.

In the present invention, the pre-transfer exposure may be performed at least in the first rotation of the electrophotographic photosensitive member, and the pre-transfer exposure may be performed subsequent to the second rotation or later. Although only the rotation may be performed, the latter is more advantageous in terms of operating costs and the like. The reason why the pre-transfer exposure is performed at least in the first rotation of the electrophotographic photosensitive member is that ghost is remarkably generated at the beginning of the image forming process, that is, at the first copy, so This is to effectively suppress the occurrence of ghost in the initial stage.

In the image forming method according to the present invention, the main charger,
The image exposure device, the developing device, and the pre-transfer exposure device are operated in this order, and the pre-transfer exposure by the pre-transfer exposure device increases the potential of the non-exposed portion of the electrophotographic photosensitive member after the main charging at most. 1/3 before the pre-transfer exposure, that is, 1/3 or less before the transfer exposure, but such an operation may be performed using a known controller such as a computer,
It can also be suitably performed using the control means in the electrophotographic apparatus of the present invention. The control means operates the main charging means, the image exposing means, the developing means, and the pre-transfer exposure means in this order, and the pre-transfer exposure by the pre-transfer exposure means causes the electrophotographic photosensitive member after the main charging. , The potential of the non-exposed portion at most is 1 /
3, that is, a function of controlling the operation of each means so as to reduce the amount to 1/3 or less of that before the transfer exposure. In the present invention, it is preferable that the control unit has a function of operating the pre-transfer exposure unit only for at least the first rotation of the electrophotographic photosensitive member. When the control means has such a function, it is advantageous in that a high-quality image free from ghost can be efficiently formed at low cost.

As an example of the electrophotographic apparatus of the present invention, as shown in FIG. 1, for example, a main charger 2, an image exposing unit 3, a developing unit 4, a pre-transfer exposing unit 7, a transfer charger 5, a cleaning unit A copying apparatus is provided in which the blade 6 and the blade 6 are arranged in this order with respect to the rotational direction of the stacked electrophotographic photosensitive member 1 and includes a controller (not shown) for controlling the operation of these devices and the like.

[0044]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Examples 1 to 3 and Comparative Examples 1 to 5) <Preparation of Electrophotographic Photoreceptor>-Preparation of Conductive Support-First, as described in JP-A-2-87154, aluminum The wet honing of the pipe was performed as follows. An 84 mmφ × 340 mm mirror-finished aluminum pipe was prepared, and 10 kg of an abrasive (Green Desic GC 400, manufactured by Showa Denko KK) was suspended in 40 liters of water using a liquid honing device. The liquid is sent to the gun at a flow rate of liter / min, the spraying speed is 60 mm / min, and the air pressure is 0.85 kgf / cm ²
Then, the aluminum pipe was moved in the axial direction while rotating at 120 rpm to perform wet honing. At this time, the center line average roughness Ra was 0.16 μm. The obtained material was used as a conductive support of an electrophotographic photosensitive member.

-Formation of Undercoat Layer- n-butyl alcohol 1 in which 4 parts of polyvinyl butyral resin (S-lec BM-S, manufactured by Sekisui Chemical Co., Ltd.) is dissolved
70 parts, an organic zirconium compound (acetylacetone zirconium butyrate) 30 parts and an organic silane compound mixture (γ-aminopropyltrimethoxysilane) 3 parts were additionally mixed and stirred to obtain a coating liquid for forming an undercoat layer. 84 m of this coating solution was roughened by a honing process.
After coating on a mφ aluminum conductive support and air-drying at room temperature for 5 minutes, the conductive support was heated at 50 ° C. for 10 minutes, and then heated to 50 ° C. and 85% RH (dew point 47 ° C.).
C.) and a humidifying and curing acceleration treatment for 20 minutes, followed by drying in a hot air dryer at 170 ° C. for 10 minutes to form an undercoat layer on the conductive support. .

-Formation of charge generation layer- As a charge generation substance, gallium chloride phthalocyanine 15
Parts, vinyl chloride-vinyl acetate copolymer resin (VMCH,
A mixture comprising 10 parts of Nippon Unicar Co., Ltd.) and 300 parts of n-butyl alcohol was dispersed in a sand mill for 4 hours. The resulting dispersion is dip-coated on the undercoat layer,
After drying, a charge generation layer having a thickness of 0.2 μm was formed.

-Formation of charge transport layer- Next, N, N'-diphenyl-N, N'-bis (3-methylphenyl)-[1,1'-biphenyl] -4,4 '
4 parts of a diamine and 6 parts of a bisphenol Z polycarbonate resin (molecular weight: 40,000)
0 parts were added and dissolved to prepare a solution. The obtained solution was applied and dried on the charge generation layer to form a charge transport layer having a thickness of 20 μm. Thus, a laminated electrophotographic photosensitive member having three layers was produced.

The electrophotographic photosensitive member of Comparative Example 4 was manufactured as follows. The electrophotographic photoreceptor of Comparative Example 4 was the same as the electrophotographic photoreceptor, except that only the charge generation layer was formed and formed under the following conditions. Butyral resin [XY
HL (UCC)] 5 parts by weight of cyclohexanone 150
The trisazo pigment 10 dissolved in parts by weight
A part by weight was added and dispersed by a ball mill for 48 hours. Further, 210 parts by weight of cyclohexanone was added and dispersed for 3 hours. This is adjusted so that the solid concentration becomes 1.8% by weight.
Dilute with cyclohexanone with stirring. The thus-obtained charge generation layer coating solution was applied on the intermediate layer,
After drying at 0 ° C. for 20 minutes, a charge generation layer having a thickness of 0.2 μm was formed.

[0050]

Embedded image

The image quality was evaluated using these electrophotographic photosensitive members. The apparatus used for the image quality evaluation is as follows.

Able 33 manufactured by Fuji Xerox Co., Ltd.
The 00 digital copier was modified and used. As shown in FIG. 1, this copying machine includes a charger 2, an image exposure unit 3, a development unit 4, a pre-transfer exposure unit 7, a transfer charger 5, and a cleaning blade 6, and A controller (not shown) is arranged in this order with respect to the rotation direction and controls the operation of these devices and the like. As a modification point of this copier, the process speed (peripheral speed) is 26
The speed was increased to 0 mm / sec. A pre-transfer exposure device 7 (made by Tottori Sanyo Electric Co., Ltd .: capable of exposing green LED light (wavelength: 570 nm, 64 chips, rated 24 V)) was installed. The value of the exposure light amount of the pre-transfer exposure device 7 is set by adjusting the applied voltage of the green LED light, and the light amount corresponding to the potential ( _VL ) of the non-exposed portion of the electrophotographic photosensitive member after the main charging. It was decided to grasp how many times the number of hits. The main charger 2 is a scorotron charger and has a photoconductor surface potential of -700 V
Set to. The potential _VL was set to be -200V.

In Example 3 and Comparative Example 3,
Able3321 digital copier manufactured by Fuji Xerox Co., Ltd. was modified and used. In addition, the diameter of the drum of the electrophotographic photosensitive member 1 is 30 mm, the surface potential of the photosensitive member by the main charger is -500V, and the potential _VL is -160V.
It was set to become. In the copying machines of Example 3 and Comparative Example 3, the main charger 2 and the transfer charger 5 are contact roller chargers. Except for these points, it is the same as the first embodiment. In Example 2 and Comparative Example 2, the pre-transfer exposure device 7 was replaced with the first drum of the electrophotographic photosensitive member 1.
The operation was performed in the same manner as in Example 1 except that only the rotation was started and the operation was stopped after the second rotation. Comparative Example 4 was the same as Example 1 except that the charge generation layer was changed as described above, and Comparative Example 5 was the same as Example 1 except that the pre-transfer exposure was not performed. went.

The image quality was evaluated in an environment of 10 ° C. and 20% RH in the following manner. The first half of the copy is 5m
m, 25 mm square English letters, 30 mm square solid black part arranged side by side, sampling in the latter part with a half-tone uniform test chart of halftone dot density of 1 dot on 1 off did. Ghosts were visually inspected for halftones in the second half of the copy, and those that were not visible were ranked 0, those that clearly showed ghosts from the density difference were ranked 5, those that were slightly visible were rank 3, and so on. A standard grade sample was prepared in advance, including the ranking between, and used for evaluation. The negative ghost was distinguished from N and the positive ghost was distinguished from P. The evaluation level is a level that is practically no problem as long as it is equal to or less than N1 and P1. These results are shown in Table 1.

The evaluation procedure is as follows.
Image copy was performed by copying 0 sheets, and thereafter, image quality was repeated continuously for 10,000 sheets, and thereafter, after stopping overnight (about 16 hours), ghost evaluation was performed again for 10 sheets. Table 1 shows the evaluation results.

[0056]

[Table 1]

From the results shown in Table 1, when the electrophotographic apparatus of the present invention is used, that is, when the image forming method of the present invention is used, idling is unnecessary and high-speed processing can be performed. It is clear that the occurrence of ghosts can be suppressed, and the occurrence of ghost in the early stage of the electrophotographic process can be effectively suppressed, and a high-quality image can be obtained quickly and easily (Examples 1 to 3). In Examples 1 to 3, in Table 1, the potential of the non-exposed portion of the electrophotographic photoreceptor after the main charging was 1/100 of that before the pre-transfer exposure.
3 or less, that is, the ratio of the charging potential is a small number of 0.33 or less. On the other hand, in the case of an image forming method using a conventional image forming apparatus (Comparative Examples 1 to 5)
Clearly shows that a negative ghost occurs in the early stage of the image forming process, and a good image cannot be obtained.
In addition, in the case of Comparative Example 4, although the generation of the negative ghost is slightly smaller than Comparative Examples 1 to 3 and 5,
Since a phthalocyanine compound is not used as a charge generating substance, the photosensitivity is low (a large exposure amount is required), which is clearly disadvantageous compared to the present invention.

[0058]

According to the present invention, the above-mentioned conventional problems can be solved. Further, according to the present invention, high-speed processing is possible without the need for idle rotation of the laminated electrophotographic photosensitive member, and the occurrence of negative ghosts, positive ghosts, and the like in the early stage of the image forming process is suppressed, and high-quality images can be produced quickly and quickly. An electrophotographic apparatus for reversal development and an image forming method which can be obtained easily can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view for explaining an example of an electrophotographic apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 laminated electrophotographic photosensitive member 2 main charger 3 image exposure device 4 developing device 5 transfer charger 6 cleaning blade 7 exposure device before transfer

Claims (8)

[Claims] 1. An electrophotographic photosensitive member comprising: a charge generating layer containing a phthalocyanine compound and a charge transporting layer provided on a conductive support; An electrophotographic apparatus having an exposure unit, a development unit for performing reversal development, and a transfer unit for performing transfer, further comprising a pre-transfer exposure unit for exposing the electrophotographic photosensitive member before performing transfer by the transfer unit. And exposing the non-exposed portion of the electrophotographic photosensitive member after the main charging by the main charging unit to at most 1/3 of the charging potential before the exposure by the exposure by the pre-transfer exposure unit. Electrophotographic apparatus. 2. The electrophotographic apparatus according to claim 1, wherein a charging potential of a non-exposed portion of the electrophotographic photosensitive member after the main charging by the main charging unit is at least -700 V. 3. The electrophotographic apparatus according to claim 1, wherein at least one of the main charging unit and the transfer unit is a contact charger. 4. The phthalocyanine compound is at least one selected from gallium phthalocyanine halide, tin phthalocyanine halide, hydroxygallium phthalocyanine, oxytitanyl phthalocyanine, indium phthalocyanine halide, vanadyl phthalocyanine and metal-free phthalocyanine. Items 1 to 3
The electrophotographic apparatus according to any one of the above. 5. The electrophotographic apparatus according to claim 1, wherein said pre-transfer exposure means operates only in the first rotation of said electrophotographic photosensitive member. 6. An image forming method, wherein an image is formed using the electrophotographic apparatus according to claim 1. 7. A charge generating layer and a charge transport layer containing a phthalocyanine compound are provided on a conductive support, and a rotating electrophotographic photosensitive member is subjected to main charging, image exposure, reversal development, and transfer. In the image forming method, the electrophotographic photoconductor is exposed before the transfer, and the exposure causes the potential of a non-exposed part of the electrophotographic photoconductor after the main charging to be at most. 1 before the exposure
/ 3, the image forming method. 8. The image forming method according to claim 7, wherein the exposure is performed only in the first rotation of the electrophotographic photosensitive member.