JPH11125953A - Electrifying member, production of the electrifying member, and process cartridge and electrophotographic device having the electrifying member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrifying member with a small electrification noise and uniform electrification with which a good image can be obtd. in any environment for a long time. SOLUTION: This electrifying member has a crown form and consists of a core metal 4, a foamed elastic layer 2 around the core metal, and a seamless tube 3 comprising plural layers around the foamed elastic layer. Before the seamless tube 3 of plural layers is applied, the foamed elastic layer 2 forms a straight cylinder. After applying the tube, the outer diameter on both ends of the layer 2 is made smaller than the outer diameter of the center part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging member which is arranged in contact with a member to be charged and charges the member to be charged by applying a voltage, and a method of manufacturing the same.

[0002] The present invention also relates to a process cartridge and an electrophotographic apparatus having the charging member.

[0003]

2. Description of the Related Art In recent years, as a charging means used in an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, a charging means of a contact charging system has been adopted. Contact charging is
By applying a voltage to a charging member that is placed in contact with the object to be charged, the object to be charged is charged to a predetermined polarity and potential, and the voltage of the power supply can be reduced. There are advantages that generation can be reduced and that the structure can be simplified and the cost can be reduced.

The voltage applied to the charging member is not only a method of applying a direct current (DC application method), but also a peak-to-peak voltage which is at least twice the charging start voltage of the member to be charged when a direct voltage is applied to the contact charging member. There is a method of forming an oscillating electric field having a voltage (an electric field whose voltage value changes periodically with time) between a contact charging member and a charged body to charge the surface of the charged body (AC application method). Can be more uniformly charged.

Further, the contact charging device is a roller type charging device using a charging member in the form of a roller (charging roller) (Japanese Patent Application Laid-Open No.
Nos. 7380 and 56-91253, and a blade-type charger as a blade-shaped member (charging blade) (Japanese Patent Laid-Open Nos. 64-24264 and 56-194349).
JP-A-64-24264, and the like, and a brush-type charger using a brush-like member (charging brush) (JP-A-64-24264, etc.).

[0006] The charging roller is rotatably supported by a bearing, is pressed against the member to be charged at a predetermined pressure, and rotates following the movement of the member.

The above-mentioned charging roller usually has a multilayer structure having a core provided as a base, a conductive elastic layer provided in a roller shape on the outer periphery of the core, and a surface layer provided on the outer periphery. Body.

[0008] Of the above layers, the core metal (metal layer) is a rigid body for maintaining the shape of the roller and also has a role as a power supply electrode.

The elastic layer usually has a thickness of 10 ⁴ to 10 ^9.
Since it is required to have a volume specific resistance of Ω · cm and a function of ensuring uniform contact with the member to be charged by being elastically deformed, a rubber hardness (JIS A) to which conductivity is imparted is usually 70. A vulcanized rubber having a flexibility of not more than a degree is used. Conventional charging rollers include a foam type using a rubber foam (or sponge-like rubber) as an elastic layer and a solid type using no rubber foam. Further, the surface layer improves the charging uniformity of the member to be charged, prevents the occurrence of leaks due to pinholes and the like on the surface of the member to be charged, and has a function of preventing sticking of toner particles and paper powder. Has a function of preventing bleeding of a softening agent such as an oil or a plasticizer used for lowering the hardness of the elastic layer. The volume resistivity of the surface layer is usually 10 ⁵ to 10 ¹³ Ω · cm, and conventionally, it has been formed by applying a conductive paint or covering a seamless tube.

As a method for manufacturing the tube-coated roller, there are a method using a heat-shrinkable tube and a method using a non-heat-shrinkable tube. When using a heat-shrinkable tube, insert a metal core or an elastic roller with an elastic body formed on the metal core into a heat-shrinkable tube with a primer applied on the inner surface, and heat the entire tube to shrink the tube to make the roller Cover the outer circumference. When a non-heat-shrinkable tube is used, the non-heat-shrinkable tube is placed on the inner wall of the cylindrical mold while being pulled in the longitudinal direction, and the pressure between the tube and the inner wall of the cylindrical mold is reduced to form the inner wall of the tube. Then, after inserting an elastic roller having an elastic body formed on the outer periphery of the cored bar, the tube was coated on the outer periphery of the roller by heat fusion.

However, when using a heat-shrinkable tube,
Although the manufacturing process is simple, it is difficult to manufacture the heat-shrinkable tube, and uneven wall thickness is inevitable and expensive. Also,
Adjustment of shrinkage is also difficult, and there are problems such as wrinkles.

On the other hand, when the above-mentioned multilayer portion is formed of a tube, problems such as pinholes can be avoided and the control of the film thickness is relatively easy. In this case, a plurality of resistance layers are sequentially superposed to obtain a roller having a desired resistance value.

As a device utilizing this, there is known a contact charging device that contacts a member to be charged with a conductive member to charge the member. For example, the applicant of the present invention has proposed a bias voltage in which a DC voltage and an AC voltage are superimposed. Is applied to a conductive member, and the conductive member is brought into contact with a member to be charged to charge the member to be charged (JP-A-3-174).
562 gazette).

As shown in FIG. 3, the charging roller 1 rotates while contacting the photosensitive drum 5, which is an image carrier of an image forming apparatus such as a copying machine, and charges the charging roller 1. A charging start voltage (refers to a voltage at which a member to be charged can be charged by contact charging; approximately 550 at room temperature and normal pressure)
The power supply 6 applies a bias voltage obtained by superimposing a constant DC voltage and an AC voltage having a peak-to-peak voltage V _pp that is twice or more of the volts.

[0015]

However, when the charging roller 1 is brought into contact with the photosensitive drum 5 and the contact charging of the photosensitive drum 5 is started, the AC component of the bias voltage applied to the metal core 4 causes There is a disadvantage that the charging roller 1 vibrates and generates a vibration sound called charging noise.

SUMMARY OF THE INVENTION An object of the present invention is to provide a charging member capable of producing a good image with low charging noise and uniform charging for a long period of time in all environments, a method of manufacturing the charging member, a process cartridge having the charging member, and an electronic device. A photographic device is provided.

[0017]

That is, the present invention comprises a core, a foamed elastic layer on the outer periphery of the core, and a plurality of seamless tubes on the outer periphery of the foamed elastic layer. In the charging member having a shape, the foamed elastic material layer has a straight shape before the covering of the plurality of seamless tubes, and the outer diameter of both ends of the charging member is smaller than the outer diameter of the central portion after the covering. It is a charging member.

In the present invention, it is preferable that the outer diameter De at both ends and the outer diameter Dc at the center be in a relationship of De / Dc = 0.97 to 0.99, or Dc-De = 20 to 350 μm. Is the charging member having a relationship of 20 to 150 μm.

Further, the present invention provides a method for manufacturing a crown-shaped charging member having a cored bar, a foamed elastic layer on the outer periphery of the cored bar, and a plurality of seamless tubes on the outer periphery of the foamed elastic layer. In the method, one end of the seamless tube is plugged and the seamless tube is expanded by adjusting the pressure in a coating device, and then the outer periphery of the straight foamed elastic layer is coated to form a first layer, and then the core is formed. After reversing the gold position, the expanded seamless tube is coated on the first layer to form a second layer once or twice.
This is a method for manufacturing a charging member, characterized in that the outer diameter of both ends of the charging member is made smaller than the outer diameter of the central portion by repeating at least twice.

Further, according to the present invention, in a process cartridge which integrally supports an electrophotographic photosensitive member and at least a charging member and is detachable from an electrophotographic apparatus main body, the charging member is supplied with a voltage having at least an AC component. A charging member for charging the electrophotographic photosensitive member by bringing the charging member into contact with the electrophotographic photosensitive member, wherein the charging member is the charging member.

Further, according to the present invention, there is provided an electrophotographic apparatus having an electrophotographic photosensitive member, a charging member, an exposing means, a developing means and a transferring means, wherein the charging member comprises a charging member to which a voltage having at least an AC component is applied. An electrophotographic apparatus, wherein the charging member charges the electrophotographic photosensitive member by being brought into contact with the electrophotographic photosensitive member, and the charging member is the charging member.

[0022]

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

The charging member (hereinafter also referred to as a charging roller)
The pressing spring is pressed against the photosensitive drum. More specifically, the urging force of a pressure spring is applied to both ends of the core bar exposed at both ends of the foamed elastic body layer to press the foamed elastic body layer of the charging roller against the photosensitive drum.

As described above, since the charging roller is urged at both ends, the pressing force of the charging roller against the photosensitive drum is strong near both ends of the charging roller and becomes weaker toward the center. For this reason, the width of the contact portion (referred to as “nip”) between the charging roller and the photosensitive drum is not uniform in the longitudinal direction, and becomes narrow near the center.

Therefore, in order to obtain a uniform charging effect by making the nip width uniform, the shape of the charging roller is formed into a so-called crown shape in which the outer diameter gradually increases from both ends toward the center. In the case where the film is processed into a crown shape in advance or the coating layer is a coating film, a method of changing the coating speed to form a coating film at the center portion thicker than both end portions is performed. The amount of the crown provided on the charging member depends on the length, hardness and pressing force of the charging member, but is approximately several hundred μm.
It is as follows. Here, the crown amount is a value obtained by subtracting the outer diameter at the end from the outer diameter at the center of the charging member.

Next, the charging operation of the charging roller of the present invention will be described.

FIG. 3 is a schematic diagram showing an electrophotographic apparatus to which the charging roller 1 is applied.

The charging roller 1 is in contact with a photosensitive drum 5 as a member to be charged in a state where a power source 6 is connected.
A developing device 8 and a cleaner 9 are arranged on both sides of the photosensitive drum 5, and a transfer unit 10 is arranged below the photosensitive drum 5.

In this electrophotographic apparatus, after the photosensitive drum 5 is neutralized, the photosensitive drum 5 is charged by the charging roller 1.

At this time, since the charging roller 1 has a crown shape, the nip width between the charging roller 1 and the photosensitive drum 5 is uniform in the longitudinal direction of the charging roller 1. Therefore, the charging of the photosensitive drum 5 by the charging roller 1 is performed uniformly.

In this charged state, an electrostatic latent image is formed by receiving image exposure light 7 from exposure means (not shown), and the latent image is developed by the developing device 8. Then, by the transfer device 10,
The developed image is transferred to the receiving paper P. Finally, the developer remaining on the photosensitive drum 5 is cleaned by the cleaner 9. When the electrophotographic apparatus is a copying machine or a printer, the image exposure light 7 is reflected light or transmitted light from the original, or the original is read by a sensor and converted into a signal. Scan, LED
Light emitted by driving the array, driving the liquid crystal shutter array, and the like.

In this electrophotographic apparatus, a DC voltage V _DC = −700 V, an AC voltage V _AC = 2 kV _PP ,
A paper passing test was performed by applying a bias at an AC frequency of f = 500 Hz to perform charging.

FIGS. 1 and 2 show an example of the charging roller of the present invention. This charging roller 1 is provided with a foamed elastic layer 2 made of a conductive elastic material on the outer periphery of a core 4 made of a good conductive material such as stainless steel, plated iron, brass, and conductive plastic. This foam elastic layer 2
Is covered with an even number of multi-layer tubes 3.

As the conductive elastic material constituting the foamed elastic layer 2, a foamed conductive rubber composition containing a conductive material or a conductive polyurethane foam can be used.

The rubber component constituting the foamed conductive rubber composition is not particularly limited, but a foam obtained by blending a conductive material with ethylene propylene rubber (EPDM), chloroprene, chlorosulfonated polyethylene, and epichlorohydrin A foam of a copolymer rubber of ethylene oxide and ethylene oxide or a foam of a copolymer rubber of epichlorohydrin and ethylene oxide mixed with a conductive material can be suitably used.

Examples of the conductive material to be incorporated into these rubber compositions include conductive powders such as carbon black, graphite, metal and various conductive metal oxides (such as tin oxide and titanium oxide), carbon fiber and metal oxide. Various conductive fibers such as short fibers of the product can be used. The compounding amount is preferably 3 to 1 with respect to 100 parts by weight of all rubber components.
00 parts by weight, particularly preferably 5 to 50 parts by weight, so that the volume resistance of the foamed elastic layer 2 is 10 ¹ to 10 ⁹ Ω.
-It is preferable to adjust to about cm. The foamed elastic layer 2 can be formed by a known vulcanization molding method, and its thickness is appropriately set according to the use of the charging roller and the like, but is usually preferably 1 to 20 mm.

In the present invention, an even number of multi-layer tubes 3 are coated on the foamed elastic layer 2. In this case, the thermoplastic resin constituting the even-numbered multi-layer tubes may be any thermoplastic resin which can be extruded, and specifically, ethylene propylene rubber (EPDM), ethylene acetic acid Polyamides such as vinyl, ethylene ethyl acrylate, ethylene methyl acrylate, styrene butadiene rubber, polyester, polyurethane, nylon 6, nylon 66, nylon 11, nylon 12, and other copolymerized nylon, styrene ethylene butyl, ethylene butyl, nitrile butadiene rubber , Chlorosulfonated polyethylene, polysulfide rubber, chlorinated polyethylene, chloroprene rubber, butadiene rubber,
Conventional rubbers such as 1,2-polybutadiene, isoprene rubber and polynorbornene rubber, and styrene-butadiene-styrene (SBS) and styrene-butadiene-
A thermoplastic rubber such as a water additive of styrene (SEBS) can be used, and is not particularly limited.

Alternatively, elastomers such as the above-mentioned resins and copolymers and modified elastomers, and polyethylene, polypropylene, polyethylene terephthalate (PET) and polybutylene terephthalate (PB)
T) and other saturated polyesters, polyethers, polyamides, polycarbonates, polyacetals, acrylonitrile butadiene styrene, polystyrene, high impact polystyrene (HIPS), polyurethane, polyphenylene oxide, polyvinyl acetate, polyvinylidene fluoride, polytetrafluoroethylene, acrylonitrile-butadiene -Styrene resin (ABS), acrylonitrile-ethylene / propylene rubber-styrene resin (AE
S) and styrene resins and acrylic resins such as acrylonitrile-acrylic rubber-styrene resin (AAS);
A combination of each resin such as a vinyl chloride resin and a vinylidene chloride resin and a material composed of a copolymer is preferable.

As the core metal (metal layer) in the present invention,
For example, a good conductor such as aluminum, copper, iron, or an alloy containing these is preferably used. The metal core used in the present invention may be a metal tube having a thickness of about 0.1 to 1.5 mm or a rod.

Next, an even number of multi-layer tubes used in the present invention will be described. The even number of multi-layer tubes in the present invention is a polymer formed in advance in the form of a seamless tube, and is fitted over the foamed elastic material layer on the outer periphery of the metal core (metal layer), and is tightly covered. I do.

The resin, elastomer, copolymer and the like used in this case are as described above, and a tube structure having desired characteristics can be obtained by appropriately blending a conductive material described later.

Further, a polymer alloy or a polymer blend comprising two or more kinds of polymers selected from the above rubbers, thermoplastic elastomers and thermoplastic resins can also be used.

The even number of multi-layer tubes of the present invention are prepared by extrusion molding, injection molding, and blow molding of the above-mentioned various polymers and a conductive polymer composition comprising the following conductive materials and, if necessary, other additives. It can be obtained by forming a film into a tube by a molding method or the like. Among the various molding methods described above, the extrusion molding method is particularly preferable.

Further, in order to obtain a uniform thickness of each thin film layer of the formed tube and a more uniform dispersibility of the conductive material and the like, a vertical tube extruder (FIG. 5) is used. I do.

As the conductive material, known materials can be used, for example, carbon fine particles such as carbon black and graphite; metal fine particles such as nickel, silver, aluminum and copper; tin oxide, zinc oxide, titanium oxide, and the like.
Conductive metal oxide fine particles containing aluminum oxide and silica as main components and doped with impurity ions having different valences; conductive fibers such as carbon fibers; metal fibers such as stainless steel fibers; carbon whiskers and potassium titanate whiskers A conductive whisker such as a conductive potassium titanate whisker whose surface is made conductive with a metal oxide or carbon; and a conductive polymer fine particle such as polyaniline and polypyrrole.

The even number of multi-layer tubes used in the present invention can be used simply by being formed by the above-mentioned various molding methods. For example, in order to obtain more excellent durability and environmental resistance, the above-mentioned various tubes can be used. The seamless tube obtained by the molding method can be further crosslinked to obtain a conductive crosslinked polymer. As a method of cross-linking a conductive polymer formed in a tube shape, a cross-linking agent such as sulfur, an organic peroxide and an amine is added in advance depending on the type of the polymer, and the cross-linking is performed at a high temperature. Is effective, and a radiation cross-linking method of cross-linking by irradiating radiation such as an electron beam or γ-ray is effective. Among the above various crosslinking methods, the electron beam crosslinking method is preferred in that there is no risk of contamination of the member to be charged due to transfer of a crosslinking agent or a decomposition product thereof, and further, there is no need for high-temperature treatment and safety.

The charging roller is pressed against the photosensitive drum by the pressure spring as described above. Specifically, a biasing force of a pressing spring is applied to both ends of the core bar exposed on both sides of the elastic layer to press the elastic layer of the charging roller against the photosensitive drum.

As described above, since the charging roller is urged at both ends, the pressing force of the charging roller against the photosensitive drum is strong near both ends of the charging roller and becomes weaker toward the center. For this reason, the width of the contact portion between the charging roller and the photosensitive drum is not uniform in the longitudinal direction, becomes narrow near the center, and uneven charging occurs. Since the charging is performed by applying an AC electric field, the direction of the electric field is applied alternately. When the nip width is uneven, the force applied to the nip portion is also uneven, so that the vibration of the electric field applied alternately becomes uneven and is recognized as sound.

Therefore, in order to obtain a uniform charging effect by making the nip width uniform, the shape of the charging roller is formed in a so-called crown shape in which the outer diameter gradually increases from both ends toward the center.

As a method for manufacturing such a charging roller having a crown shape, a method of forming the material using a mold having a crown shape material storage portion can be considered. Because it is difficult to process into a shape, first use a mold in which the shape of the material storage part is constant in the longitudinal direction, store the core metal and the elastic material in the material storage part, heat it, and then cool it. A method of forming a charging roller having a straight outer diameter and then polishing the outer periphery of the elastic body into a crown shape has been adopted.

On the other hand, in the present invention, a charging roller is manufactured by providing a foamed elastic material layer on the outer periphery of a core metal (metal layer) and covering the tube with a foamed elastic material layer. That is, a desired crown shape can be obtained only by covering the tube with the straight foamed elastic body.

Next, a method of forming a tube will be described. In the present invention, an even number of tubes whose functions are properly separated are covered.

The multilayer tube 3 consisting of an even number can be formed by various methods, but the extrusion molding method is preferable as described above. That is, as shown in FIG. 5, a compound in which a polymer, a conductive material, and, if necessary, a crosslinking agent, a stabilizer and other additives are mixed is prepared, and the compound is formed into a ring-shaped slit by an extruder 16. Is extruded from the die 14 having the
By cooling at 7, a seamless tube can be manufactured continuously. In FIG. 5, 3 (i) is a middle layer tube of the first layer, 18 is a timing pulley of the tube feeder, and 19 is a feed belt.

The seamless tube used in the present invention may be either non-heat-shrinkable or heat-shrinkable. In the embodiment, a non-heat-shrinkable tube is used.

In the case of a non-heat-shrinkable tube, it is necessary that the inner diameter of the tube be equal to or less than the outer diameter of the foamed elastic layer in order to secure the adhesion to the foamed elastic layer. When the tube diameter is enlarged by blowing compressed air, the tube is inserted into the foamed elastic body layer having the metal core and the air pressure is released to complete the external fitting process.

In the present invention, in the above outer fitting process (or coating process), after the tube of the first layer is coated, the vertical relationship of the cored bar is reversed, and the tube is reset in the coating device.
Coat layer of tube. The coating is done by first plugging one side of the tube, depressurizing the inside of the device, and blowing air inside the tube (or blowing air inside the tube while depressurizing the outside of the tube). The swelling method differs between the side with the stopper and the side without the stopper. That is, the bulge is limited at the end with the stopper,
Since the air is pushed in from the side without the stopper, the compressed air works from the center of the tube to the vicinity of the stopper expands more greatly by the action of the compressed air. On the other hand, since the air flows out on the side without the stopper, the expanding force is not applied to the end of the tube on the side without the stopper.

For this reason, if the tube is covered in the next step, the method of fastening the foamed elastic body after covering is different, probably because of the hysteresis effect, and the shape after covering the tube of the first layer is approximately tapered. Shape. Next, when the core bar is turned upside down and then covered with the tube of the second layer, the tube is tightened so as to have a reverse taper, so that the entire tube has a roughly crown shape. The length of the tube is slightly longer than the length of the foamed elastic body so that the tube end slightly covers the end side surface of the foamed elastic body. As described above, the influence of the tube coating on the end of the tube does not affect the vicinity of the central portion, and the process from expansion to contraction occurs promptly, and the portion protruding from the foamed elastic layer at the end of the tube. In this case, since the foamed elastic body does not have a repulsive force and merely contracts, the end portion has a further compressed shape. Therefore, it is considered that the vicinity of the center portion forms a roughly crown shape bulging from the end portion.

The charging roller was applied to the electrophotographic apparatus schematically shown in FIG. 3 to evaluate the sample of the example and the sample of the comparative example.

[0059]

The present invention will be described in more detail with reference to the following examples.

For forming the tube, a resin whose material itself has an appropriate resistance value may be used, or a resin whose resistance value is adjusted by mixing a conductive powder such as carbon and a conductive metal oxide may be used. . In the present invention, the tube was formed using a vertical extrusion device. In a horizontal extrusion device, the flow direction of the extruded tube is orthogonal to the gravity, so the effect of gravity acts in the circumferential direction of the tube, especially in the hot state immediately after extrusion. Therefore, it was considered that the electrophotographic use of the present invention lacked in definition.

Example 1 (Molding of Surface Tube) A styrene resin (styrene-ethylene / butylene-olefin copolymer resin, trade name: Dinalon, manufactured by Nippon Synthetic Rubber Co., Ltd.) was used as a material for the surface layer.
0 parts by weight, 18 parts by weight of polyethylene and carbon black (Ketjen Black EC, manufactured by Lion Akzo) 1
6 parts by weight were mixed in a V-blender for several minutes. Next, the mixture was melt-kneaded at 190 ° C. for 10 minutes using a pressure kneader. Furthermore, after cooling, it was pulverized by a pulverizer and pelletized by a single screw extruder.

A tube was extruded from the above pellets using a vertical extruder (a custom-made product manufactured by Plagiken Co., Ltd., see FIG. 5).
It was extruded into hot water (40 ° C. to 90 ° C.) 10 at an appropriate temperature, and further cooled and taken out (18, 19). Thus, a surface tube having an outer diameter of about 11 mm and a thickness of 250 μm was obtained.

(Molding of Middle Layer Tube) As the material for the middle layer, 100 parts by weight of polyethylene elastomer, 17 parts by weight of carbon black (Ketjen Black EC), 10 parts by weight of magnesium oxide and 1 part by weight of calcium stearate
The parts by weight were pelletized in the same process as the surface layer material.

A tube was extruded from the above pellets using a vertical extruder (a custom-made product manufactured by Plagiken Co., Ltd., see FIG. 5).
It was extruded into hot water (40 ° C. to 90 ° C.) 10 at an appropriate temperature, and further cooled and taken out (18, 19). Thus, a middle-layer tube having an outer diameter of about 11 mm and a thickness of 400 μm was obtained.

(Formation of Foamed Elastic Material Layer)
A hose-shaped foamed elastic body with an outer diameter of 11.5 mm (a compound obtained by blending a vulcanizing agent and a foaming agent with EPDM rubber, forming the mixture into a hose shape using an extruder, and foaming in a vulcanizing can. Cut into 225mm length, diameter 5mm, length 26
A 0-mm core (metal layer) was inserted.

In addition, the above-mentioned middle-layer tube has a length of 228.
The material cut into mm was coated with a tube coating device, and was pressure-adhered to the foamed elastic material layer.

Next, the above-mentioned surface layer tube was cut into a length of 230 mm on the one coated with the middle layer tube. A roller was made. At this time, the outer diameter of the central portion of the charging roller is 11.90 to 12.00 m.
m, and the outer diameter between the ends was in the range of 11.55 to 11.98 mm from a point 90 mm away from the center.

As a result of forming an image by using this charging roller as a primary charger of an LBP (laser beam printer, Laser Jet 2-P manufactured by Hewlett-Packard Company), a result was obtained between the middle tube and the surface tube, and between the middle tube and the middle tube. The adhesiveness between the foamed elastic layers was good, and a good image was obtained.

The electric resistance of the charging roller was measured by the following method. That is, as shown in FIG.
An aluminum foil (or copper thin plate) 21 having a width of 10 mm is wound thereon, and a direct current 2 is supplied from a power source 20 between the core 4 and the aluminum foil.
50 V was applied, and the current flowing at that time was measured, and the resistance between the core metal and the aluminum foil was calculated. Then, by moving the position of the aluminum foil or the like, the local fluctuation of the resistance value in the longitudinal direction of the charging roller was measured. The local resistance value of the charging roller measured in this way is 0.6 to
0.9 MΩ, and the uniformity was extremely high.

Further, as a result of visually observing the surface of the charging roller, no inconvenience such as streaks, unevenness and wrinkles was found.

Next, the charging roller is mounted on a cartridge (trade name EP-L, manufactured by Canon Inc.), and the cartridge is mounted on a laser beam printer (trade name Laser S).
hot A404, manufactured by Canon Inc.)
As a result of outputting 3,500 images in an environment of 50% RH and visually evaluating the image quality of the output image, no abnormality was recognized at all.

(Comparative Example 1) This corresponds to Example 1.

In Example 1, up to the foamed elastic material layer was formed in the same manner. Next, a layer corresponding to the surface layer and the middle layer of Example 1 was formed by a dip coating method using a material obtained by coating. These materials were subjected to viscosity adjustment and the like so as to be suitable for coating. However, the compositions and amounts of the materials after application were adjusted to be substantially the same as those in Example 1.

Next, at the center in the longitudinal direction of the foamed elastic material layer, the application speed is adjusted so that the application speed becomes the fastest, and in order to further reduce the influence of dripping, the intermediate layer and the surface layer are coated. The application direction was reversed to produce a crown-shaped charging member.

However, in the obtained coating film, the film thickness at the end portion becomes thicker than the other portions due to liquid dripping, and the outer diameter at the center portion is 11.1 mm.
90 to 12.00mm, about 12.00m at the dripping part
m, near the center, with a slight dent, about 11.8
It was 0 mm. When the local resistance value of the charging roller was measured in the same manner as in Example 1, it was found to be more non-uniform than in Example 1.

Using the obtained charging member, the image was evaluated in the same manner as in Example 1. The result was that the initial image was equivalent to that of Example 1, but under the high-temperature high-humidity environment or the low-temperature low-humidity environment,
It became inferior as the number of displayed images increased.

The charging sound of Example 1 was slightly superior to that of Comparative Example, but the comparative example had a convex portion at the end of the coating film. Occurred.

In the present invention, among the above-mentioned components such as the electrophotographic photosensitive member 5, the charging member 1, the developing means 8 and the cleaning means 9, a plurality of components are integrally supported as a process cartridge. The process cartridge may be configured to be detachable from a main body of an electrophotographic apparatus such as a copying machine or a laser beam printer. For example, the developing unit 8 and the cleaning unit 9 are integrally supported together with the photoconductor 5 and the charging member 1 to form a cartridge,
A process cartridge (FIG. 4) that can be attached to and detached from the apparatus main body using guide means such as rails of the apparatus main body can be provided. In FIG. 4, reference numeral 11 denotes a photoconductor shutter, and reference numeral 12 denotes a developer (toner).

The charging members of Example 1 and Comparative Example 1 were mounted on the above-described process cartridge, and were assembled into an electrophotographic apparatus to evaluate an image. As a result, the images were the same in Example 1 and Comparative Example 1. However, with respect to the charging noise, Example 1 was slightly superior as described above.

[0080]

As described above, according to the present invention, in order to form a rough crown shape, the elastic layer is previously processed into a crown or a film is formed on the elastic layer by a coating method. As in the case described above, there is no need to perform precise coating speed control or to reverse the upper and lower sides in order to reduce the effect of liquid dripping in the coating process, so that the approximate crown shape can be formed by a simple method. Therefore, the manufacturing cost is low. Also,
In the coating method, the thickness of the end portion of the coating film is increased. To eliminate this, another step such as polishing is required, but is not required in the present invention. ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture a charging roller having no surface irregularities such as pinholes and a stable surface potential without charging unevenness at low cost.

Further, it becomes possible to provide a charging member which has a small charging noise, uniform charging and can obtain a good image for a long period of time in all environments, and a process cartridge and an electrophotographic apparatus having the charging member.

[Brief description of the drawings]

FIG. 1 is a schematic view of a crown-shaped charging roller of the present invention.

FIGS. 2A and 2B are schematic diagrams showing a stepwise tube coating process for forming a crown shape, wherein FIG. 2A shows a state after coating a first layer, and FIG. 2B shows a state after coating a second layer.

FIG. 3 is a schematic diagram of an electrophotographic apparatus having the charging roller of the present invention.

FIG. 4 is a schematic view of a process cartridge on which the charging roller of the present invention is mounted.

FIG. 5 is a schematic view of a vertical extrusion device for forming a tube used in the present invention.

FIG. 6 is a schematic diagram of an apparatus for measuring local resistance of a charging roller used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Charging member (charging roller) 2 Elastic foam layer 3 Even number of multilayer tubes 3 (i) Middle layer 4 Core metal (metal layer) 5 Charged body (photosensitive drum) 6 Power supply 7 Exposure 8 Developing device 9 Cleaning device REFERENCE SIGNS LIST 10 transfer device 11 photoconductor shutter 12 developer (toner) 14 dice 15 central through hole 16 extruder 17 water cooling ring 18 timing pulley (tube feeding device) 19 feed belt (tube feeding device) 20 power supply for evaluation device 21 electrode for evaluation device Board

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tsutomu Ninomiya 1888-2 Kusazaki, Kusazaki-cho, Inashiki-gun, Ibaraki Pref. (72) Inventor Hiroshi Inoue 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A crown-shaped charging member having a cored bar, a foamed elastic layer on the outer periphery of the cored bar, and a plurality of seamless tubes on the outer periphery of the foamed elastic layer. A charging member characterized in that the foamed elastic layer has a straight shape before the seamless tube is coated, and the outer diameter of both ends of the charging member is smaller than the outer diameter of the central portion after the coating. 2. An outer diameter De at both ends and an outer diameter D at the center.
2. The charging member according to claim 1, wherein c has a relationship of De / Dc = 0.97 to 0.99. 3. An outer diameter De of the both ends and an outer diameter D of the central part.
2. The charging member according to claim 1, wherein c has a relationship of Dc-De = 20 to 350 [mu] m. 4. An outer diameter De of said both ends and an outer diameter D of said central part.
2. The charging member according to claim 1, wherein c is in a relationship of Dc-De = 20 to 150 [mu] m. 5. A method for producing a charging member having a crown shape, comprising a cored bar, a foamed elastic layer on the outer periphery of the cored bar, and a plurality of seamless tubes on the outer periphery of the foamed elastic layer. After plugging one end of the tube and adjusting the pressure in the coating device to expand the seamless tube, the outer periphery of the straight foamed elastic layer is coated to form a first layer, and then the core metal is moved up and down. After inversion, the expanded seamless tube is coated on the first layer to form a second
A method for manufacturing a charging member, wherein the outer diameter of both ends of the charging member is made smaller than the outer diameter of the central portion by repeating a two-layer forming step of forming a layer once or twice or more. 6. A process cartridge which integrally supports an electrophotographic photosensitive member and at least a charging member and is detachable from an electrophotographic apparatus main body, wherein the charging member is a charging member to which a voltage having at least an AC component is applied. A process for charging the electrophotographic photosensitive member by contacting the electrophotographic photosensitive member, wherein the charging member is the charging member according to any one of claims 1 to 4. cartridge. 7. An electrophotographic photosensitive member, a charging member, an exposure unit,
In an electrophotographic apparatus having a developing unit and a transfer unit,
The charging member is a charging member that charges the electrophotographic photosensitive member by bringing the charging member to which a voltage having at least an AC component is applied into contact with the electrophotographic photosensitive member,
An electrophotographic apparatus, wherein the charging member is the charging member according to any one of claims 1 to 4.