JP2614282B2 - Contact charging device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a contact charging device provided with an electrophotographic photosensitive member and a charging conductive member.

[Conventional technology]

Conventionally, inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide have been known as photoconductive materials used in electrophotographic photoreceptors. While these photoconductive materials have many advantages, such as being able to be charged to an appropriate potential in a dark place and dissipating the charge in a dark place, they have various drawbacks. For example, selenium-based photoconductors easily crystallize due to factors such as temperature, humidity, dust, and pressure. Particularly when the ambient temperature exceeds 40 ° C., crystallization becomes remarkable, causing a decrease in chargeability and white spots on images. There is a drawback that occurs. Cadmium sulfide photoreceptors do not provide stable sensitivity in a humid environment, and zinc oxide photoreceptors require a sensitizing effect of a sensitizing dye represented by rose bengal. The photosensitive dye has a disadvantage that a stable image cannot be provided for a long period of time because charge deterioration due to corona charging and light fading due to exposure light occur.

On the other hand, various organic photoconductive polymers such as polyvinyl carbazole have been proposed, but these polymers are superior to the above-mentioned inorganic photoconductive materials in terms of film formability, lightness, and the like. Nevertheless, it has been difficult to put it to practical use until now because inorganic photoconductive materials have not yet been obtained with sufficient film-forming properties and are sensitive, durable, and stable due to environmental changes. It was because it was inferior. In addition, low molecular organic photoconductors have also been proposed. Such a low-molecular organic photoconductor can solve the problem of the film forming property which has been a problem in the field of the organic photoconductive polymer by appropriately selecting a binder to be used. It is not enough in terms of sensitivity.

For these reasons, a laminated structure in which a photosensitive layer is separated into a charge generation layer and a charge transport layer in function has recently been known. The electrophotographic photoreceptor having this laminated structure as a photosensitive layer can be improved in sensitivity to visible light, charge retention, surface strength, and the like. Such an electrophotographic photosensitive member is disclosed in, for example, U.S. Pat. Nos. 3,837,851 and 3,871,882.

The charging process in an electrophotographic process using an electrophotographic photosensitive member in which a photosensitive layer containing such an organic photoconductor is provided on a conductive support is higher than a conventional method in that a high voltage (about 5 to 8 KV DC) is applied to a metal wire. Is applied, and charging is performed by the generated corona. However, in this method, a large amount of corona products such as ozone and NOx are generated when corona is generated, and this corona product alters the surface of the photoreceptor and causes image blurring to progress. And there are problems such as white spots on the image and black stripes. A photoreceptor containing an organic photoconductor has a disadvantage that deterioration and deterioration due to corona products are more likely to occur than other photoreceptors. That is, the organic photoreceptor is another inorganic photoreceptor, such as amorphous silicon or
The chemical stability is lower than that of Se photoreceptors, and when exposed to corona products, they tend to undergo a chemical reaction (mainly an oxidation reaction) and deteriorate easily. This causes image blur, image deletion, and a decrease in sensitivity.

In addition, the corona products such as ozone and NOx adhere not only to the photoreceptor but also to the shield plate of the charger.These deposits are volatilized and released not only during the copying operation but also during a pause such as at night, and adhere to the photoreceptor. It is known that in a later copy, the image is blurred in the portion opposite to the charger at rest.

On the other hand, as a charging method that does not use corona discharge,
JP-A-56-104351, JP-A-57-178267, JP-A-58-178267
-40566, JP-A-58-139156, JP-A-58-1
A direct charging method as proposed in Japanese Patent Publication No. 50975 has been studied.

Specifically, a charge is directly injected into the surface of the photoreceptor by bringing a charging member such as a conductive elastic roller capable of externally applying a DC voltage of about 1 to 2 KV to the surface of the photoreceptor so that the surface of the photoreceptor has a predetermined shape. It is charged to a potential.

When using a photoreceptor having a photosensitive layer containing an organic photoconductor, direct charging with high charging efficiency and extremely low generation of corona products suppresses the occurrence of image defects such as image blur, It is also very effective in extending the printing life of the photoreceptor.

[Problems to be solved by the invention]

However, such a direct charging method has no market record despite many proposals. This is due to the non-uniformity of charging and the possibility of image defects such as white spots due to discharge breakdown of the photoconductor due to direct application of voltage.

That is, an object of the present invention is to provide a contact charging device which does not cause discharge breakdown of a photosensitive member due to contact charging.

Another object of the present invention is to provide a contact charging device capable of obtaining an excellent image without image defects.

[Means for solving the problem]

The present inventor has conducted studies on these points, and as a result, by controlling the maximum particle diameter of the particles contained in the photosensitive member of the electrophotographic photosensitive member arranged in contact with the charging conductive member to a certain value or less. The present inventors have found that the above-mentioned problems can be solved, and have achieved the present invention.

That is, the present invention relates to an electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor on a conductive support, wherein the maximum particle diameter of the particles contained in the photosensitive member is 1 μm or less. A contact charging device comprising: a photosensitive member; and a charging conductive member disposed in contact with the electrophotographic photosensitive member.

 Hereinafter, the present invention will be described in detail.

According to the knowledge of the present inventors, the discharge breakdown of the photoreceptor due to contact charging is caused when the maximum particle size contained in the photoreceptor is 1%.
μm particles, that is, aggregates of charge generation materials such as azo pigments and phthalocyanine pigments dispersed in the photosensitive layer, or solid lubricants such as ethylene tetrafluoride resin powder and vinylidene fluoride resin powder. Aggregates, solid impurities, and solid impurities such as cuttings from the cutting of the support in the intermediate layer such as the undercoat layer are formed as nuclei.

In the present invention, particles exceeding 1 μm that cause discharge breakdown in direct charging are not contained in the photoreceptor, and the particle diameter contained in the film constituting each layer is suppressed to a maximum of 1 μm. This can prevent dielectric breakdown, which has been a problem with direct charging. As a method of controlling the particle size in this way, the coating liquid for forming a layer such as a photosensitive layer is filtered, centrifugation or the like is used to remove aggregates and impurities, or an organic solvent of the coating liquid is appropriately selected. And preventing agglomeration in the drying process.

The maximum particle size in the present invention is the length of the particle in the major axis direction, and can be observed with a microscope.

FIG. 1 is a schematic sectional view of a contact charging device of the present invention, in which a charging conductive member 1 is arranged in contact with a photoreceptor 2,
The voltage from the power source 3 is applied to the charging conductive member 1, and is charged directly on the photoconductor 2 from the charging conductive member 1.

In the present invention, the electrophotographic photosensitive member containing the organic photoconductor is configured as follows.

The photosensitive layer is provided on a conductive support. As the conductive support, a substrate having conductivity itself, for example, aluminum, an aluminum alloy, stainless steel, or the like can be used. In addition, aluminum, an aluminum alloy, indium oxide, tin oxide, or the like is formed into a film by a vacuum evaporation method. Using a plastic having a coated layer, a support in which conductive particles are coated on the support plastic together with a suitable binder, a support in which conductive particles are impregnated in a plastic or paper, or a plastic having a conductive polymer. Can be.

An undercoat layer having a barrier function and an adhesive function may be provided between the conductive support and the photosensitive layer. The undercoat layer can be formed of casein, polyvinyl alcohol, nitrocellulose, polyamide, polyurethane, gelatin, aluminum oxide, or the like. The thickness of the undercoat layer is 5 μm or less, preferably 0.5 to 3 μm. The barrier layer preferably has a resistivity of 10 ⁷ Ωcm or more in order to exhibit its function.

The photosensitive layer containing an organic conductor according to the present invention includes a single-layer type photosensitive body in which a charge generation material and a charge transport material whose functions are separated are mixed, or a charge generation layer containing a charge generation material and a charge transport material. It takes the form of a laminated photoreceptor having a charge transport layer laminated thereon.

Organic photoconductors such as azo pigments, phthalocyanine pigments, quinone pigments, quinocyanine pigments, perylene pigments, indigo pigments, bisbenzimidazole pigments, and quinacridone pigments are used as the charge generation material.

Organic photoconductors such as pyrazoline-based, hydrazone-based, stilbene-based, triphenylamine-based, benzidine-based, oxazole-based, indole-based, and carbazole-based compounds are used as the charge transport material.

In the case of a single-layer type photoreceptor, the above-described charge generation material and charge transport material are dissolved or dispersed in an appropriate binder resin, and a layer is formed on a conductive support by coating.

On the other hand, as the lamination type, there is a type in which 1) a charge generation layer and a charge transport layer are laminated in this order on a conductive support, or 2) a type in which a charge transport layer and a charge generation layer are laminated in this order. In the case of 1), as a method for forming the charge generation layer, there are a method of dispersing and applying a charge generation material in a binder resin and a solvent, and a method such as vapor deposition and sputtering. The film thickness is 5 μm or less, especially 0.01
３3 μm is preferred.

The charge transport layer is formed by dissolving the above-described charge transport material in a binder resin having a film forming property and laminating it on the charge generation layer. The film thickness is 5
40 μm, particularly preferably 8-35 μm.

On the other hand, in the case of 2) in which the charge generation layer is laminated on the charge transport layer, both layers can be formed by applying the above-mentioned organic photoconductor together with a binder resin. At this time, it is preferable to include a charge transport material also in the charge generation layer.

Examples of the above-mentioned binder resin include phenoxy resin, polyacrylamide, polyvinyl butyral, polyarylate, polysulfone, polyamide, acrylic resin, acrylonitrile resin, methacryl resin, vinyl chloride resin, vinyl acetate resin, phenol resin, epoxy resin, polyester Alkyd resins, polycarbonates, polyurethanes, and copolymers containing two or more of the repeating units of these resins.

The photosensitive layer may contain additives such as solid lubricants such as ethylene tetrafluoride resin powder, vinylidene fluoride resin powder, and carbon fluoride powder, and antioxidants and ultraviolet absorbers. .

Further, a protective layer having a thickness of 0.05 to 20 μm may be provided on the photosensitive layer as needed. The above-mentioned additives may be contained in this protective layer.

The charging conductive member of the present invention is disposed in contact with the surface of the photoreceptor, applies an external voltage directly and uniformly to the photoreceptor, and charges the surface of the photoreceptor to a predetermined potential. As such a charging conductive member, conductive particles such as metals such as aluminum, iron and copper, conductive polymer materials such as polyacetylene, polypyrrole and polythiophene, carbon black and metal are used for insulating such as polycarbonate, polyvinyl and polyethylene. Rubber or artificial fiber dispersed in a resin and subjected to a conductive treatment, or an insulating resin whose surface is coated with a conductive substance can be used. Also,
These shapes may be any shape such as a roller, a brush (including a magnetic brush), a blade, and a belt.

Resistance of the charging conductive member in terms of preventing good and uniform charging and breakdown, preferably 10 ⁰ to 10 ¹² [Omega] cm, in particular 10 ² -
A range of 10 ¹⁰ Ωcm is good.

The method of installing the charging conductive member is not limited to a specific method, and a fixed type or a movable type such as rotating in the same direction as the photoconductor or in the opposite direction can be used. Further, the charging conductive member can also have a toner cleaning function on the photoconductor.

As the voltage applied to the charging conductive member, either DC or AC can be used, and DC + AC can also be applied. The method of applying the voltage depends on the use of each electrophotographic apparatus.However, a method of instantaneously applying a voltage, a method of gradually increasing the applied voltage for the purpose of protecting a photoreceptor, etc., DC → AC or AC → A method of applying a voltage in the order of DC can be used.

FIG. 2 shows a specific example for arranging such a charging conductive member in contact with a photoreceptor.

FIG. 2 is a schematic view showing a specific example of a charging conductive member unit. A supporting member 5 for supporting the charging conductive member 1 from both sides is provided on a support 4. The member 1 can be pressed against the photoconductor by a pressure spring 7 via a fulcrum 6. The charging conductive member 1 is supplied with a voltage via a metal core 9 by a power supply brush 8.

By using such a unit, the pressing force against the photoconductor can be appropriately adjusted.

 Hereinafter, the present invention will be described with reference to examples.

Examples 1 and 2 and Comparative Examples 1 to 3 Preparation of Photoreceptor No. 1 A methanol solution (4% by weight) of polyamide (alkoxymethylated nylon) was filtered on an aluminum cylinder for a copying machine NP-3525 made by Canon through a membrane filter. After that, dip coating was performed, followed by drying to form an undercoat layer having a coating amount of 1.0 g / m ² .

Next, the following structural formula Of bisazo pigment (parts by weight, hereinafter the same), 8 parts of polyvinyl butyral resin (trade name: Esrec BXL, manufactured by Sekisui Chemical Co., Ltd.) and 60 parts of cyclohexanone are dispersed in a sand mill using 1φ glass beads for 20 hours. did. To this dispersion, 70 to 120 parts (as appropriate) of methyl ethyl ketone was added, and the mixture was centrifuged at 10,000 RPM for 30 minutes to remove aggregates and applied to the undercoat layer. The thickness was 0.12 μm.

Next, the following structural formula 7 parts of hydrazone compound, polystyrene resin (trade name:
10 parts of Dialect HF-55, manufactured by Mitsubishi Monsanto Kasei) were dissolved in 50 parts of monochlorobenzene. This solution was filtered through a membrane filter and then applied on the charge generation layer. The film thickness after drying was 17 μm.

In addition, in this photoreceptor forming step, after visualization of each layer, 10 visual fields were observed with a microscope. As a result, no aggregates or solid impurities having a particle diameter exceeding 1 μm were present in any of the layers, and the maximum particle diameter of the particles was 0.8 μm of the aggregate of the charge generation material in the charge generation layer.

Preparation of photoconductor No.2 Instead of bisazo pigment of photoconductor No.1, the following structural formula Polycarbonate resin (weight average molecular weight 5,000) instead of polyvinyl butyral resin
A photoconductor was prepared in the same manner as photoconductor No. 1 except that No. was used.

In this photoreceptor forming step, when 10 fields of view were observed with a microscope after each layer was formed, the maximum particle size of the particles was 0.9 μm of the aggregate of the charge generation material in the charge generation layer.
Met.

Preparation of Photoreceptor No. 3 Photoreceptor No. 3 was prepared using the same material as photoreceptor No. 1, except that the steps of filtration and centrifugation by a membrane filter were omitted.

After microscopic observation after formation of each layer, solid impurities having a maximum particle size of 1.1 μm were observed in the charge generation layer.

Preparation of Photoconductor No. 4 Photoconductor No. 4 was prepared in the same manner as in Comparative Example 1 using the same material as photoconductor No. 2. After microscopic observation after forming each layer, aggregates of the charge generating material having a maximum particle size of 1.3 μm were observed in the charge generating layer.

The above photoreceptor is used in a copier (modified NP-
3525: Canon). In this configuration, a charging conductive member 1, an image exposure 10, a developing device 1
1, transfer paper feed roller and paper feed guide 12, transfer charger B,
Conveyor unit 1 that sends transfer paper to separation charger 14, fixing unit (not shown)
5, a cleaner 16 and a pre-exposure light source 17 are arranged. In particular, the cleaner 16 is a blade cleaning using a silicon rubber blade, the blade pressure is 20 g / cm, and the contact angle is 25.
゜, blade penetration amount is 1.0mm.

The voltage applied to the charging conductive member is DC-700V + AC
With a peak difference of 1,500 V (1,000 Hz), the conductive member for charging is a roller with a diameter of 30 mm, coated with urethane rubber (resistance value 10 ⁶ Ω · cm) of carbon dispersion around the center iron core diameter of 5 mm. It has become.

Using the above copier, printing durability was performed in an environment of 35 ° C. and 90% humidity, and image blur / flow, sensitivity reduction, and dielectric breakdown were evaluated. The results are shown in Table 1. Further, as Comparative Example 3, the evaluation result when the photoconductor No. 1 is used and corona charging by a corona charger is used instead of direct charging by the charging conductive member is also shown.

From the above results, those containing particles having a maximum particle diameter of more than 1 μm have caused dielectric breakdown by direct charging.
On the other hand, those having a maximum particle diameter of 1 μm or less have no dielectric breakdown at any one place. In addition, direct charging reduces the ozone concentration as compared with corona charging, and prevents image blur / flow and reduction in sensitivity.

Examples 3 and 4 and Comparative Examples 4 and 5 The above-described roller-shaped charging conductivity was changed to a plate-like blade having a resistance of 10 ⁸ Ωcm by dispersing carbon in urethane rubber, and rotating the photosensitive member. Was set in the above-described copying machine so as to contact the printer in the forward direction, and printing durability was performed in the same manner as in Example 1. Table 2 shows the results.

As is evident from Table 2, any one containing particles having a maximum particle diameter of more than 1 μm has caused dielectric breakdown, but one having a maximum particle diameter of 1 μm or less does not cause any dielectric breakdown,
Good images were obtained even with 10,000 copies.

Example 5 A brush iron core as shown in FIG. 4 as a charging conductive member
Around 18 was changed to a brush (resistance: 10 ⁶ Ω · cm) coated with polyester dispersed with carbon.

Further, a photoreceptor was prepared by the following method and evaluated in the same manner as in Example 1. Aqueous ammonia solution of casein (casein 11.2%, ammonia water) on aluminum cylinder for NP3525
(1 g, 222 ml of water) was filtered through a membrane filter, applied by dip coating so that the film thickness after drying was 1.0 μm, and dried.

Then the following structural formula 5 g of stilbene type compound and 5 g of polymethyl methacrylate resin (number average molecular weight 100,000) are dissolved in 70 ml of benzene, filtered through a membrane filter, and then dip-coated on the undercoat layer so that the film thickness after drying is 20 μm. It was applied by a process and dried to form a charge transport layer.

Next, the following structural formula Was added to a solution prepared by dissolving 2 g of polymethyl methacrylate resin in 95 ml of ethanol, and dispersed by a sand mill for 2 hours. This dispersion liquid was centrifuged at 500 rpm, applied on the previously formed charge transport layer by dip coating so that the film thickness after drying was 5 μm, and dried to form a charge generation layer.
o.5.

Observation with a microscope after formation of each layer revealed that the maximum particle size of the particles contained in the photoreceptor was 0.6 μm of the aggregate of the charge generation material in the charge generation layer. As a result of printing durability, no blurring or running of the image was observed after continuous copying of 10,000 sheets, and a satisfactory image was obtained without problems such as a decrease in image density due to a decrease in sensitivity.
No dielectric breakdown was observed.

〔The invention's effect〕

As described above, the photosensitive layer containing the organic photoconductor that is easily affected by ozone, NOx, ion products, and the like due to charging can be prevented from being blurred or blurred, and from having a reduced sensitivity by being directly charged. By setting the maximum particle size of the particles in the electrophotographic photoreceptor to 1 μm or less, dielectric breakdown, which has been a problem in direct charging, can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a contact charging device, FIG. 2 is a schematic diagram of a conductive member unit for charging, FIG. 3 is a cross-sectional view of a copying machine used in the embodiment, and FIG. FIG.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroyuki Omori 3-30-2 Shimomaruko, Ota-ku, Tokyo Inside Canon Inc. (72) Inventor Yuichi Hashimoto 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (56) References JP-A-63-208877 (JP, A) JP-A-61-179464 (JP, A)

Claims (1)

(57) [Claims] 1. An electrophotographic photosensitive member having a photosensitive layer containing an organic photoconductor on a conductive support, wherein the maximum particle diameter of particles contained in the photosensitive member is 1 μm or less. A contact charging device comprising: a photosensitive member; and a charging conductive member disposed in contact with the electrophotographic photosensitive member.