JPH0792703A - Electrophotographic photoreceptor, process cartridge having the photoreceptor and electrophotographic device - Google Patents

Abstract

PURPOSE:To provide an electrophotographic photoreceptor in which uneven charge does not exist, and potemtial variation and transfered memory are reduced by applying d.c.voltage to a charged member coming into contact with a sensitive layer having a charge generating layer containing a polycarbonate resin and a charge transport layer. CONSTITUTION:A photosensitive layer 11 provided on a conductive supporting body 10 has a charge generating layer 13 to dispersedly contain a charge generating substance 12 such as pyrylium-based dye in binding resin and a charge transport layer 14 containing a charge transport substance. The charge generating layer 13 is formed by sufficiently dispersing the charge generating substance 12 together with 0.5 to 4 multiplied quantity of polycarbonate resin and solvent by a homogenizer, applying an obtained dispersed liquid and drying it, and the thikness of an applied film is desirable to be 5mum or less. In addition, the weight average molecular weight of the polycarbonate resin is desirably to be 10000 to 1000000. Thus, the electrophotographic photoreceptor in which the spot-shaped or stripe-shaped unevenness of charge is difficult to occur, and potential variation is small, and moreover a transfered memory is few, can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic photosensitive member, and more particularly to an electrophotographic photosensitive member containing a specific resin which is directly charged by a charging means. The present invention also relates to a process cartridge and an electrophotographic apparatus having the above charging means and electrophotographic photosensitive member.

[0002]

2. Description of the Related Art When an image is obtained by performing basic processes such as charging, exposure, development, transfer, fixing and cleaning on an electrophotographic photosensitive member, most charging processes have hitherto been applied with a high voltage (DC5 to DC5) on a metal wire. It was a so-called corona charging method in which 8 kV) was applied and charging was performed by the generated corona. However, in this method, corona products such as ozone and NOx adhere to the surface of the photoconductor, image deletion or image blurring occurs due to alteration of the photosensitive layer itself, and image white spots due to wire stains occur. There was a problem that black streaks may occur. In particular, photoreceptors whose photosensitive layer contains an organic photoconductor have lower chemical stability than other photoreceptors that use inorganic photoconductors such as selenium and amorphous silicon and are chemically stable when exposed to corona products. A reaction (mainly an oxidation reaction) occurs and tends to deteriorate.

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

As a method of solving such a problem,
JP-A-57-178267 and JP-A-56-104
351, JP-A-58-40566, JP-A-58-139156, and JP-A-58-150975.
A so-called direct charging method has been proposed in Japanese Patent Application Laid-Open No. 2005-242242, etc., in which a photoreceptor is charged by applying a voltage to a charging member that is in contact with the surface of the photoreceptor without using a corona discharger. Specifically, a charging member such as a conductive elastic roller is brought into contact with the surface of the photoconductor, and a DC voltage of about 1 to 2 kV is externally applied to the charging member to charge the surface of the photoconductor to a predetermined potential. It is a thing.

However, the direct charging method has a problem that the charging tends to be nonuniform. The non-uniformity of charging is caused by uneven charging on each part of the surface of the photoconductor, or a length of 2 to 200 mm in the longitudinal direction of the photoconductor,
It causes streaky uneven charging with a width of about 0.5 mm or less. White spots and white streaks (a phenomenon in which white spots and streaks appear on a solid black image) that occur in the case of the positive development method, or the reverse development method. Image defects such as black spots and black lines (a phenomenon in which black spots and lines appear in a solid white image) occur in some cases.

Therefore, in order to improve the uniformity of charging,
DC voltage (V _DC) to an alternating voltage (V _AC) method of applying a pulsating voltage obtained by superimposing the charging member has been proposed (JP 63-149668 discloses the like). In this case, in order to maintain the uniformity of charging and prevent image defects such as white spots, white streaks, black spots, and black streaks, the superimposed AC voltage has a peak-to-peak potential difference (V _{PP) that is at} least twice the DC voltage. ) Is necessary.

[0007]

However, in order to prevent image defects, the maximum applied voltage of the pulsating current voltage increases as the superposed AC voltage is increased, so that even in a slight defect portion inside the photoconductor. Discharge insulation breakdown is more likely to occur. Particularly when the photoconductor is a photoconductor using an organic photoconductor having a low withstand voltage, dielectric breakdown is very likely to occur. In this case, in the normal development method, the image is blank in the longitudinal direction of the contact portion, and in the reverse development method, a black band occurs.

Further, since the superposition of V _AC means that the charging member to which high frequency is applied is brought into contact with the electrophotographic photosensitive member, noise may be generated during charging. Further, since an alternating current flows excessively through the electrophotographic photosensitive member, electrical deterioration such as increase in residual potential occurs, or the surface of the photosensitive member is partially damaged, and toner or the like adheres to the part. So-called fusion may occur.

For this reason, the method of applying only V _DC without superimposing V _AC has been reviewed, but the problem of nonuniform charging as described above still remains.

Further, with the recent increase in image quality, there has been a problem of so-called transfer memory in which the capacity inside the photosensitive member changes due to transfer charging, and the sensitivity changes between where the transfer charging is performed and where it is not. There is.

An object of the present invention is to provide an electrophotographic photosensitive member that does not cause spotted or streaky charging unevenness and has a small potential fluctuation.

Another object of the present invention is to provide an electrophotographic photosensitive member with less transfer memory.

A further object of the present invention is to provide a process cartridge and an electrophotographic apparatus having the above electrophotographic photosensitive member and charging means.

That is, the present invention provides an electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer having a charge generating layer containing a polycarbonate resin, and a charge transporting layer. An electrophotographic photosensitive member characterized by being charged by applying a DC voltage to a charging member in contact with the surface of the body.

The present invention also provides a process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member and the charging means as described above.

FIG. 1 shows an example of the arrangement of the electrophotographic photosensitive member of the present invention and the charging means. As shown in the figure, the charging member 1 is in contact with the electrophotographic photosensitive member 2 and is connected to the external power source 3
A DC voltage is applied to the photoconductor 2 to charge it.

The charging member used in the present invention may be any known charging member, and examples thereof include a blade, a brush and a belt in addition to the roller as shown in FIG. When the charging member is a roller or a blade, a conductive resin such as a metal or an alloy is molded around the conductive core metal, or a resin subjected to a conductive treatment such as dispersing carbon black, metal or metal oxide, or the like. It can be prepared by drying after coating. Further, as the brush, there are a magnetic brush using magnetic particles, a fur brush using a brush of the above-mentioned resin having conductivity or a resin subjected to a conductive treatment, and the like.

FIG. 2 shows a specific example of a charging unit for pressing the charging member against the photosensitive member. The roller-shaped charging member 1 can be pressed against the photosensitive member by the action of the spring 5 via the fulcrum 4, and the core metal 6 at the center of the charging member 1 is supplied with voltage by the contacting power supply brush 7. It Reference numeral 8 is a power receiving connector from the main body, and 9 is a support body that supports the charging member 1 for mounting on the main body along the main body side guide rail.

FIG. 3 shows an example of the constitution of the electrophotographic photosensitive member of the present invention. In the figure, the photosensitive layer 1 is formed on the conductive support 10.
1 is provided, and the photosensitive layer 11 has a charge generating layer 13 containing a charge generating substance 12 dispersed in a binder resin, and a charge transporting layer 14 containing a charge transporting substance (not shown). In the present invention, the charge transport layer 14 may be laminated on or below the charge generation layer 13, but may be laminated on the charge generation layer 13 in view of mechanical durability and the like. Is preferred.

Examples of the charge generating substance used in the present invention include pyrylium dyes, thiopyrylium dyes, phthalocyanine pigments, anthanthrone pigments, dibenzpyrenequinone pigments, pyratron pigments, azo pigments, indigo pigments, Examples include quinacridone pigments and quinocyanine dyes. The charge generation layer is obtained by thoroughly dispersing the charge generation substance together with 0.5 to 4 times the amount of the polycarbonate resin and the solvent by a method such as homogenizer, ultrasonic wave, ball mill, vibrating ball mill, sand mill, attritor and roll mill. It is formed by applying the above dispersion and drying. The film thickness is preferably 5 μm or less, and particularly preferably 0.01 to 1 μm.

Specific preferred examples of the polycarbonate resin used in the present invention are shown below, but the present invention is not limited thereto. In the examples, n and m indicate the degree of polymerization (molar ratio).

[0022]

[Outer 1]

[0023]

[Outside 2]

The weight average molecular weight of the polycarbonate resin used in the present invention is 10,000 to 1,000,000.
It is preferably 0, particularly 20,000 to 50
It is preferably 10,000.

Examples of the charge transport material used in the present invention include hydrazone compounds, pyrazoline compounds, styryl compounds, oxazole compounds, thiazole compounds, triarylmethane compounds and polyarylalkane compounds.

The charge transport layer 14 is generally formed by applying a solution prepared by dissolving the above charge transport material and a binder resin in a solvent and drying the solution. The mixing ratio of the charge transport material and the binder resin is about 2: 1 to 1: 2. The thickness of the charge transport layer is preferably 5 to 30 μm, particularly preferably 10 to 25 μm.

The binder resin used to form the charge transport layer 14 includes acrylic resin, styrene resin, polyester, polycarbonate resin, polyacrylate, polysulfone, polyphenylene oxide, epoxy resin, polyurethane resin, alkyd resin and non-bonded resin. Examples of the resin include a saturated resin, but in the present invention, a resin having the same monomer unit as the polycarbonate resin used for the charge generation layer is particularly preferable. The weight average molecular weight of the binder resin is preferably 10,000 to 1,000,000, and particularly preferably 15,000 to 100,000.

Further, an antioxidant, an ultraviolet absorber, a plasticizer or a known charge transporting substance may be added to the charge transporting layer as required.

Examples of the conductive support used in the present invention include the following.

(1) Aluminum, aluminum alloys,
Metals and alloys such as stainless steel and copper.

(2) Aluminum on the non-conductive support such as glass, resin and paper or the conductive support of (1) above,
A thin film formed by vapor deposition or lamination of metals or alloys such as aluminum alloys, palladium, rhodium, gold and platinum.

(3) On a non-conductive support such as glass, resin and paper or the conductive support of (1) or (2) above,
Those formed by depositing a conductive substance such as a conductive polymer, tin oxide and indium oxide, or those formed by applying and drying a solution in which these conductive substances are dispersed in a suitable binder resin.

The conductive support has a drum shape,
Examples thereof include a sheet shape and a belt shape, but it is preferable that the shape is most suitable for the electrophotographic apparatus to which it is applied.

In the present invention, an undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. The subbing layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide (nylon 6, nylon 66, nylon 610, copolymerized nylon, alkoxymethylated nylon, etc.), polyurethane, aluminum oxide and the like. The thickness of the undercoat layer is 5μ
It is preferably m or less, and particularly preferably 0.1 to 3 μm.

Further, in the present invention, in order to protect the photosensitive layer from external mechanical and chemical adverse effects, a resin layer as a protective layer, a resin layer containing conductive particles or a charge transport substance, and the like are exposed. It can also be provided on a layer.

As a coating method for forming the above-mentioned various layers by coating, a dip coating method, a spray coating method, a spinner coating method, a roller coating method, a Mayer bar coating method, a blade coating method and the like can be mentioned.

The electrophotographic photosensitive member of the present invention can be used not only in an electrophotographic copying machine but also in a laser beam printer,
It can be widely used in electrophotographic application fields such as CRT printers, LED printers, facsimiles and electrophotographic plate making systems.

Next, the electrophotographic apparatus of the present invention will be specifically described.

An example of the structure of the electrophotographic apparatus of the present invention is shown in FIG. This apparatus comprises a roller-shaped charging member 1, an image exposure means 15, a developing means 16, a paper feed roller and a paper feed guide 17, a transfer belt means 18, a cleaning means 19 and a pre-exposure means on the peripheral surface of the electrophotographic photoreceptor 2. 20 are arranged.
In the image forming method, first, a DC voltage is applied to the charging member 1 which is arranged in contact with the electrophotographic photosensitive member 2, and the photosensitive member 2
The surface of is charged, and an image corresponding to the document is image-exposed on the photoconductor 2 by the image exposure means 15 to form an electrostatic latent image. Next, the electrostatic latent image on the photoconductor 2 is developed (visualized) by adhering toner to the photoconductor 2 by the developing means 16.
To do. Further, the toner image formed on the photoconductor 2 is transferred onto the transfer material such as paper supplied through the paper feed roller and the paper feed guide 17 by the transfer charger 18, and is not transferred onto the transfer material by the cleaning means 19. Then, the residual toner remaining on the photoconductor 2 is collected. If residual charges remain inside the photoconductor, it is better to remove light by applying light to the photoconductor 2 by the pre-exposure means 20. On the other hand, the transfer material on which the toner image is formed is sent to a fixing device (not shown) by a conveying unit (not shown), and the toner image is fixed. In this electrophotographic apparatus, a halogen light, a fluorescent lamp, a laser light, or the like can be used as the light source of the image exposure unit 15. Also, other auxiliary processes may be added if necessary.

In the present invention, the electrophotographic photoreceptor 2, the charging member 1, the developing means 16 and the cleaning means 1 described above are used.
A plurality of components such as 9 may be integrally combined as a process cartridge, and the process cartridge may be detachably attached to an image forming apparatus body such as a copying machine or a laser beam printer. . For example, at least one of the charging member 1, the developing means 16 and the cleaning means 19 is integrally supported together with the photoconductor into a cartridge, and a process cartridge which can be attached to and detached from the apparatus body by using a guide means such as a rail of the apparatus body. Good.

Hereinafter, the present invention will be described in more detail with reference to Examples.

[0042]

【Example】

Example 1 A 5% methanol solution of a polyamide resin (trade name: Amilan CM8000, manufactured by Toray) was applied onto an aluminum cylinder of φ30 mm × 350 mm by a dipping method to give 0.3 μm.
An m-thick undercoat layer was provided.

Next, the following equation

[0044]

[Outside 3] 2 parts by weight of a bisazo pigment represented by 10 parts by weight (the same applies hereinafter), 10 parts of a polycarbonate resin (Exemplified Compound No. 1, weight average molecular weight of 28,000) and 60 parts of cyclohexane in a sand mill apparatus using 1φ glass beads.
Dispersed for 0 hours. Methyl etiketone 100 is added to this dispersion.
The charge-generating layer was formed by coating the above-mentioned subbing layer with the solution added with the above parts and drying. The film thickness is 0.12 μm
Met.

Next, the following equation

[0046]

[Outside 4] 7 parts of a triarylamine compound represented by

[0047]

[Outside 5] Polycarbonate resin (Exemplary Compound No. 1, weight average molecular weight 28,000)
It was dissolved in 10 parts and 60 parts of monochlorobenzene. This solution was applied onto the charge generation layer and dried to form a charge transport layer. The film thickness after drying was 25 μm.

The obtained electrophotographic photosensitive member was manufactured by Canon NP.
It was attached to -6030. First, DC-700V was applied to the charging roller from the outside, and a halftone original having a reflection density of 0.45 was placed on a platen with a Macbeth reflection densitometer (manufactured by Macbeth Co.) to print an image. Visually observing the obtained image, streaks due to non-uniform charging on the image were 5 or more in the image area for one rotation of the drum ×, 4 to 1 in Δ, and not streak. And

In this state, the original is replaced (printing rate 3%).
Character pattern) About 10,000 continuous images are output, and the light potential at the start and at the end (hereinafter abbreviated as V _L )
Were measured, | the end of the V _L | - | was V _L the amount of change with | V _L at the start.

Furthermore, V _L when development and transfer are not performed
And the absolute value of the difference in V _L when only development was not performed was taken as the transfer memory amount.

The results are shown in Table 2.

Examples 2 to 12 An electrophotographic photosensitive member was prepared in the same manner as in Example 1 except that the binder resin for the charge generation layer and the binder resin for the charge transport layer of Example 1 were replaced with those shown in Table 1. Was created and evaluated.

In Table 1, Mw represents a weight average molecular weight.

[0054]

[Table 1]

Examples 13 to 15 Instead of the azo pigment of Example 1, CuKα has an X-ray diffraction angle of 2θ ± 0.2 ° of 9.0 °, 14.2 ° and 2 °.
Electrophotographic photoreceptors were prepared and evaluated in the same manner as in Examples 1 to 3 except that oxytitanium phthalocyanine having strong peaks at 3.9 ° and 27.1 ° was used. However,
A laser jet III-Si (manufactured by Hewlett Packard) is used as an electrophotographic apparatus, a black and white repeating halftone original for each dot is used as a halftone original, and 1 dot black and 100 is used as an original for continuous image output. A manuscript with repeated white horizontal lines of dots was used.

The results are shown in Table 2.

Example 16 An undercoat layer was formed on an aluminum cylinder in the same manner as in Example 1 except that the layer order of the charge generation layer and the charge transport layer was reversed.
The charge transport layer and the charge generation layer were formed in this order. However,
The thickness of the charge generation layer was 0.5 μm.

Further, the following formula

[0059]

[Outside 6] A solution obtained by mixing 25 parts of an acrylic curable monomer represented by 2), 2.0 parts of 2-methylthioxanthone and 300 parts of toluene is spray-coated on the charge generation layer, dried, and then dried with a high-pressure mercury lamp at 800 mW / cm ² . 20 in light intensity
A protective layer was formed by irradiating ultraviolet rays for 2 seconds. The film thickness was 2.0 μm.

The obtained electrophotographic photosensitive member was evaluated in the same manner as in Example 1. However, the charging polarity was positive.

The results are shown in Table 2.

Comparative Examples 1 to 4 Polyvinyl butyral (weight average molecular weight: 100,000, butyralization degree: 65%), polymethylmethacrylate (instead of the polycarbonate resin as the binder resin of the charge generation layer of Example 1) Weight average molecular weight 47,000),
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 1 except that a phenoxy resin (weight average molecular weight 30,000) and a cellulose resin (weight average molecular weight 60,000) were used.

Comparative Example 5 An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Example 13 except that the binder resin in the charge generation layer of Example 13 was changed to that of Comparative Example 1.

The results are shown in Table 2.

Comparative Examples 6 and 7 Example 1 was repeated except that the charging member was superposed with an AC voltage having a peak-to-peak potential difference of 1.8 kV and a frequency of 400 Hz in addition to the DC voltage.
An electrophotographic photosensitive member was prepared and evaluated in the same manner as in Nos. 13 and 13.

The results are shown in Table 2. It should be noted that although no streaks due to non-uniform charging were observed in the images after continuous image formation, image defects due to toner fusion occurred.

[0067]

[Table 2]

[0068]

As described above, according to the present invention, the electrophotographic photosensitive member is less likely to cause spotted or streaky charging unevenness, has a small potential fluctuation, and has a small transfer memory.
A process cartridge and an electrophotographic apparatus having the electrophotographic photosensitive member can be provided.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of arrangement of an electrophotographic photosensitive member of the present invention and a charging unit.

FIG. 2 is a diagram showing an example of a charging unit for pressing a charging member against an electrophotographic photosensitive member.

FIG. 3 is a diagram showing an example of a configuration of an electrophotographic photosensitive member of the present invention.

FIG. 4 is a diagram showing an example of a configuration of an electrophotographic apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging member 2 Electrophotographic photoreceptor 3 External power supply 4 Support point 5 Spring 6 Core metal 7 Power supply brush 8 Power receiving connector 9 Support 10 Conductive support 11 Photosensitive layer 12 Charge generation substance 13 Charge generation layer 14 Charge transport layer 15 Image exposure Means 16 Developing means 17 Paper feed roller and paper feed guide 18 Transfer charging means 19 Cleaning means 20 Pre-exposure means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yama ▲ Saki ▼ To 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Hidetoshi Hirano 3-30-2 Shimomaruko, Ota-ku, Tokyo No. Canon Inc. (72) Mayumi Kimura Inventor Mayumi Kimura 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (6)

[Claims] 1. An electrophotographic photosensitive member having a photosensitive layer on a conductive support, the photosensitive layer having a charge generating layer containing a polycarbonate resin, and a charge transporting layer, the surface of the electrophotographic photosensitive member. An electrophotographic photosensitive member characterized by being charged by applying a DC voltage to a charging member in contact therewith. 2. The electrophotographic photosensitive member according to claim 1, wherein the electrophotographic photosensitive member has a charge generating layer on a conductive support and a charge transporting layer on the charge generating layer. 3. An electrophotographic photoreceptor having a photosensitive layer on a conductive support, wherein the photosensitive layer has a charge generating layer containing a polycarbonate resin, and a charge transporting layer. An electrophotographic photosensitive member that is charged by applying a DC voltage to a charging member that is in contact with the surface, and at least one unit selected from the group consisting of a charging unit having a charging member, a developing unit, and a cleaning unit are integrated. A process cartridge, which is supported and detachable from the main body of the electrophotographic apparatus. 4. The process cartridge according to claim 3, wherein the electrophotographic photosensitive member has a charge generation layer on a conductive support, and has a charge transport layer on the charge generation layer. 5. An electrophotographic apparatus having an electrophotographic photoreceptor, a charging means having a charging member, an image exposing means, a developing means and a transferring means, wherein the electrophotographic photoreceptor has a photosensitive layer on a conductive support. A photographic photoreceptor, wherein the photosensitive layer has a charge generation layer containing a polycarbonate resin, and a charge transport layer, and the charging member is in contact with the surface of the electrophotographic photoreceptor, and a direct current is applied. The electrophotographic apparatus is characterized in that the electrophotographic photosensitive member is charged thereby. 6. The electrophotographic apparatus according to claim 5, wherein the electrophotographic photosensitive member has a charge generating layer on a conductive support, and has a charge transporting layer on the charge generating layer.