JP2002258584A - Electrifying roller, manufacture of the same, process cartridge and electrophotographic device equipped with the electrifying roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrifying roller constituted so that the occurrence of uneven electrification in a circumferential direction may be suppressed to a minimum, to provide a method for manufacturing the electrifying roller, and to provide a process cartridge and an electrophotographic device equipped with the electrifying roller. SOLUTION: As for the electrifying roller with a core bar, a foam elastic layer formed on the outer periphery of the core bar and a functional double- layered film seamless tube on the outer periphery of the foam elastic layer, in the case of the seamless tube having the outside diameter of 8 to 22 mm, a difference between the width Xa of the end part of a sample cut by a length of 28 cm and the maximum distance Xb from a line orthogonal to the cut surface of the end part to the other cut end surface, that is, Xb-Xa is <=2.1 mm/10 pieces average, the ratio of the maximum current Imax to the minimum current Imin in the roller circumferential direction ( unevenness in circumferential direction) of the electrifying roller formed by covering with the seamless tube, that is, Imax/Imin is <=1.7 times.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

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

[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 roller 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 lowered. 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 roller is not only a method of applying only DC (DC application method), but also a charging start voltage of the member to be charged when a DC voltage is applied to the contact charging roller.
A method of forming an oscillating electric field (an electric field whose voltage value changes periodically with time) having a peak-to-peak voltage of twice or more between the contact charging roller and the object to be charged, and charging the surface of the object to be charged (AC application method) ), Which enables more uniform charging.

Further, the contact charging device is a roller type charging device using a roller-shaped member (charging roller) as a charging member (Japanese Patent Application Laid-Open No. 63-7 / 1988).
Nos. 380 and 56-91253), a blade-type charger (such as Japanese Patent Laid-Open Nos. 64-24264 and 56-194349) as a blade-like member (charging blade), and a brush-like member (charging brush) Brush type chargers (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.

Further, the elastic layer usually has a thickness of 10 ⁴ to 10 ⁹ Ω.
Since it is required to have a volume specific resistance of cm and a function of ensuring uniform contact with the member to be charged by being elastically deformed, usually, a rubber hardness (J
IS A) A vulcanized rubber having a flexibility of 70 degrees or less 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. Conventionally, this surface layer has been formed by applying a conductive paint or covering a seamless tube.

[0010]

In a seamless tube manufacturing apparatus, the seamless tube is extruded by an extruding means, and the seamless tube is manufactured by using an air cooling means, a water cooling sizing means and a tube taking-off means in this order. If the gap between the seamless tube and the sizing wall is not proper when using the water-cooled sizing means, there is a problem that the tube is warped because the tube is not taken straight in the extrusion direction.

[0011] The charging roller may have uneven charging in the circumferential direction due to the shape of the roller. This problem is caused by the fact that the shape of the seamless tube affects the soft foamed elastic material layer because the shape of the seamless tube is not straight but is warped. It is considered that this occurred because stress was applied by the seamless tube.

An object of the present invention is to provide a charging roller in which the shape of a seamless tube covered with a soft foamed elastic material layer is almost straight, and the occurrence of unevenness in charging in the circumferential direction is suppressed as much as possible. It is to provide.

Another object of the present invention is to provide a process cartridge having the charging roller mounted thereon and an electrophotographic apparatus incorporating the process cartridge.

[0014]

According to the present invention, there is provided a charging roller having a cored bar, a foamed elastic layer on the outer periphery of the cored bar, and a functional multi-layer seamless tube on the outer periphery of the foamed elastic layer. In the case where the seamless tube has an outer diameter of 8 to 22 mm, the width Xa of the end of the sample cut to a length of 28 cm
And the maximum distance Xb from a line perpendicular to the cut surface at the end to the cut surface at the other end is Xb−Xa within 2.1 mm / 10
The ratio between the maximum current Imax and the minimum current Imin in the roller circumferential direction of the charging roller formed by covering the seamless tube (circumferential unevenness) Imax / Imin is 1.7 times or less. Charging roller.

Further, the present invention relates to a method for manufacturing a charging roller comprising a cored bar, a foamed elastic layer on the outer periphery of the cored bar, and a seamless tube of a functional multilayer film on the outer periphery of the foamed elastic layer. When the distance between the seamless tube and the sizing wall is 0.1 to 0.3 mm, the amount of cooling water is 30 to
60 m ³ / h and the pressure in the vacuum water tank is -6 to-
A method for manufacturing a charging roller, comprising a step of performing water cooling sizing at 10 MPa.

According to the present invention, there is provided a process cartridge which integrally supports an electrophotographic photosensitive member and at least a charging roller and is detachable from an electrophotographic apparatus main body. A process roller for charging the electrophotographic photosensitive member by applying a voltage having an AC component, wherein the charging roller is the charging roller according to claim 1.

Further, the present invention relates to an electrophotographic apparatus having an electrophotographic photosensitive member, a charging roller, an exposing means, a developing means, and a transferring means, wherein the charging roller is arranged in contact with the member to be charged and has at least an AC component. An electrophotographic apparatus comprising: a charging roller configured to charge the electrophotographic photosensitive member when a voltage is applied, wherein the charging roller is the charging roller according to claim 1.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

FIG. 1 shows an example of the charging roller 1 'of the present invention, which is used as a charger of an electrophotographic apparatus. This charging roller is provided with a foamed elastic layer 2 made of a conductive elastic material on the outer periphery of a cored bar 1 made of a good conductive material such as stainless steel, plated iron, brass and conductive plastic. The outer periphery of the elastic layer 2 is coated with a tubular functional multilayer film 3. At present, those having an outer diameter of 8 to 18 mm are on the market, but the technology of the present invention is not limited to this. The present invention has been studied up to 22 mm in view of speeding up and large format.

Here, 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.

In this case, the rubber component constituting the foamed conductive rubber composition is not particularly limited.
Foam of ethylene-propylene-diene rubber (EPDM) and chloroprene rubber, chlorosulfonated polyethylene mixed with conductive material, foam of copolymer rubber of epichlorohydrin and ethylene oxide, and copolymerization of epichlorohydrin and ethylene oxide A foam obtained by mixing a conductive material with rubber can be suitably used.

Examples of the conductive material to be incorporated in these rubber compositions include conductive powders such as carbon black, graphite, metals and various conductive metal oxides (such as tin oxide and titanium oxide), carbon fibers and metal oxides. 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 mass of all rubber components.
00 parts by mass, particularly preferably 5 to 50 parts by mass, whereby the volume resistance of the foamed elastic layer is 10 ¹ to 10 ⁹ Ω · c.
It is preferable to adjust to about m. The foamed elastic material layer 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, a functional multilayer film 3 is coated on the foamed elastic layer 2 in the form of a tube. In this case, the thermoplastic resin constituting the functional multilayer film 3 may be any thermoplastic resin which can be extruded, and specifically, ethylene propylene rubber (E
PDM), polyamide such as ethylene vinyl acetate, 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, 1,2
-Ordinary rubbers such as polybutadiene, isoprene rubber and polynorbornene rubber, and styrene-butadiene-
Thermoplastic rubbers such as styrene (SBS) and styrene-butadiene-styrene water additive (SEBS) can be used, and are 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-based resins such as acrylonitrile-acrylic rubber-styrene resin (AAS); acrylic resins; vinyl chloride resins; vinylidene chloride resins; and other resin and copolymer combinations.

As the core metal (metal layer) in the present invention,
For example, good conductors such as aluminum, copper, iron, and alloys containing these are 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, the functional multilayer film used in the present invention will be described. The functional multilayer film in the present invention is a polymer previously formed in the form of a seamless tube, and is externally fitted on the foamed elastic material layer on the outer periphery of the core metal (metal layer), and is tightly covered.

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 composed of two or more kinds of polymers selected from the above rubbers, thermoplastic elastomers and thermoplastic resins can also be used.

The tube of the functional multilayer film of the present invention is obtained by extrusion molding, injection molding and blow molding of the above polymer, a conductive polymer composition comprising the following conductive material 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 above various molding methods, the extrusion molding method is particularly preferable.

Furthermore, in order to obtain a uniform thickness of each thin film layer of the tube to be formed and a more uniform dispersibility such as a conductive material, a vertical tube extruder (FIG. 2) is used. I do.

As the conductive material, known materials can be used, for example, fine carbon particles such as carbon black and graphite; fine metal 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 Conductive whiskers such as conductive potassium titanate whiskers whose surfaces are made conductive with metal oxides or carbon; and conductive polymer fine particles such as polyaniline and polypyrrole.

The tube of the functional multilayer film 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 are 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.

Next, a method of forming a tube will be described.

The multi-layer tube 3 composed 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. 2, 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 by extruders 8 and 9. Extruded from a die 4 having a slit-like shape into a central through-hole 5, and water-cooled sizing 1
By cooling at 0, a seamless tube can be manufactured continuously. In FIG. 2, 3 (3 (i) and 3 (o)) are seamless tubes, 6 and 7 are push-out channels, 11 is a tube pulling timing pulley, and 12 is a pulling belt.

The shape of the warp of the seamless tube in the extrusion direction is determined to some extent by the uneven thickness of the tube. The tube warps in the direction in which the film thickness decreases in the tube. This can be solved by adjusting the position of the mold and keeping the thickness of the tube within a certain range.

However, in the manufacturing method of the present invention, the shape of the seamless tube tends to be determined by the distance between the water-cooled sizing wall and the seamless tube shown in FIG. 2 even when there is no uneven thickness. As shown in FIG. 5B, when the distance between the wall of the water cooling sizing 10 and the seamless tube 3 is not uniform (for example, the relationship between the gap Ga and the opposed gap Gb is Ga> Gb), the cooling water Therefore, there is a difference in the amount of water and the flow velocity, uneven cooling occurs, and the sizing and the tube come into contact with each other, so that it is impossible to obtain a seamless tube that is straight and has no warpage in the extrusion direction. For this reason, the roller after coating in the next step may cause uneven resistance, and an abnormal image may be generated. Therefore, as shown in FIG. 5A, the distance between the sizing wall and the seamless tube is uniform (the distance Ga is equal to the distance Ga in all directions).
The horizontal position of the sizing is adjusted so that the relationship between this and the opposing interval Gb is close to Ga = Gb).

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

FIG. 3 shows a schematic configuration of an electrophotographic apparatus incorporating a roller-shaped charging roller 1 'having a multilayer film formed as described above.

In FIG. 3, reference numeral 13 denotes a drum-shaped electrophotographic photosensitive member (hereinafter, referred to as a photosensitive drum), which is driven to rotate at a predetermined peripheral speed in the direction of an arrow. The photosensitive drum 13
In the rotation process, the peripheral surface thereof is uniformly charged with a predetermined positive or negative potential by the charging roller 1 ', and then receives an image exposure 15 from an exposure unit (not shown) such as a slit exposure or a laser beam scanning exposure. Thus, the photosensitive drum 1
An electrostatic latent image is sequentially formed on the peripheral surface of No. 3. Reference numeral 14 denotes a power supply for the charging roller 1 '.

The formed electrostatic latent image is then developed
6, and the developed toner image is transferred from a paper supply unit (not shown) to the transfer material 21 fed between the photosensitive drum 13 and the transfer unit 18 in synchronization with the rotation of the photosensitive drum 13. Are sequentially transferred by the transfer means 18.

The transfer material 21 having undergone the image transfer is separated from the surface of the photoreceptor, introduced into a fixing means, and subjected to image fixing to be printed out of the apparatus as a copy.

The surface of the photosensitive drum 13 after the transfer of the image is cleaned and cleaned to remove the untransferred toner, and is used repeatedly for image formation.

The above-described photosensitive drum 13, charging roller 1 ',
Of the components such as the developing means 16 and the cleaning means 17, a plurality of components are integrally connected as a process cartridge, and this process cartridge is detachable from an electrophotographic apparatus body such as a copying machine or a laser beam printer. May be configured. For example, as shown in FIG. 4, the developing means 16 and the cleaning means 17 are integrally supported together with the photosensitive drum 13 and the charging roller 1 'to form a cartridge, and are attached to and detached from the apparatus main body by using guide means 20 such as rails of the apparatus main body. Flexible process cartridge 23
It can be. Reference numeral 22 denotes a fixing unit.

When the electrophotographic apparatus is a copying machine or a printer, the image exposure 15 reads the reflected light or transmitted light from the original, or reads the original with a sensor and converts it into a signal.
Laser beam scanning performed according to this signal, LE
Light emitted by driving the D array, driving the liquid crystal shutter array, and the like.

The above-described apparatus is used for evaluation and the like as a process cartridge incorporating a charging roller coated with a tube formed by the apparatus of the present invention, and an electrophotographic apparatus incorporating the same.

(Method of measuring warp of seamless tube)
The width Xa of the end of the seamless tube and the maximum distance Xb from a line perpendicular to the cut surface of the end to the other cut surface (FIG. 6)
) Is measured using measuring instruments such as a laser length measuring instrument capable of measuring the length.

Warpage ΔX in the state of a seamless tube
Is ΔX = Xb−Xa.

(Method of Measuring Circumferential Irregularity of Charging Roller) As shown in FIG. 7, a load of 9.8 N is applied to a φ30 mirror-finished metal roll (SUS or the like) 24 rotating the charging roller 1 ′ at 0.5 s ^−1.
(1 kgf) (end load 4.8 N (0.5 kgf) x
2) contact, AC500Vpp (300Hz), D
C-200V is applied. At this time, the maximum current Imax and the minimum current Imin of the third rotation of the charging roller flowing through the metal roll were measured, and the circumferential unevenness of the current (Imax / Im) was measured.
in). Since the voltage is constant, the circumferential unevenness of the current matches the circumferential unevenness of the resistance of the charging roller.

[0050]

The present invention will be described below with reference to examples. In the examples, "parts" indicates parts by mass.

(Core Metal) A core metal was prepared by extruding an iron material into a bar having a diameter of about 5 mm by extrusion, cutting the bar to a length of 260 mm, and applying a chemical plating to the bar at a thickness of about 3 μm.

(Formation of Foamed Elastic Material Layer)
A hose-shaped foamed elastic body layer having an outer diameter of 11.5 mm [Ethylene-propylene-diene rubber (EPDM) is compounded with a vulcanizing agent and a foaming agent, and the mixture is formed into a hose shape by an extruder. Foamed in a vulcanizing can] with a length of 2
Cut into 25mm, the center hole, the above-mentioned diameter 5mm,
A core bar having a length of 260 mm was inserted.

(Formation of Tube of Functional Multilayer Film) As a material for the outer layer of the functional multilayer film, a styrene resin (styrene-ethylene / butylene-olefin copolymer resin, trade name Dinalon, manufactured by Nippon Synthetic Rubber Co., Ltd.) ), 20 parts of polyethylene and 15 parts of carbon black (trade name Ketjen Black EC, manufactured by Lion Akzo Co., Ltd.) were mixed in a V-type blender for several minutes. This was further 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.

As a material for the inner layer, 100 parts of a polyurethane elastomer, 15 parts of carbon black (Ketjen Black EC), 10 parts of magnesium oxide and 1 part of calcium stearate were pelletized in the same process as the material of the outer layer.

Using a vertical extruder (custom-made product from Plagiken Co., Ltd., see FIG. 2), these are combined into a double layer with one crosshead, and cooled at an appropriate temperature (4 to 16 ° C.).
Extrude into 10 and adjust the horizontal position of the sizing so that the spacing between the tube and the cooling sizing wall is close to uniform,
It was further cooled and taken off. In this way, the outer diameter is about 12m
m was obtained. The tube of this functional multilayer film is placed on the foamed elastic layer into which the core metal is inserted, for 23 hours.
The piece cut to a length of 0 mm was fitted around the outer periphery of the foamed elastic body layer by a tube covering device (not shown) and brought into pressure contact.

(Example 1) After adjusting the horizontal position of the sizing so that the distance between the tube and the sizing wall was close to uniform, the sample had an average ΔX of 2.1 mm or less in 10 sampling tubes. After confirming that this is the case, tubes having the following values were used as examples.

Example 1-1 ΔX = 0.60 mm Example 1-2 ΔX = 2.07 mm

Next, these seamless tubes were coated on a foamed elastic material layer by a tube coating device to prepare a charging roller. The circumferential unevenness of the resistance of these charging rollers was 1.7 times or less.

An image was formed by using the charging roller as a primary charger of an LBP (laser beam printer: Laser Jet 2-P manufactured by Hewlett-Packard Co.) to obtain a good image.

Next, this 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 halftone images in an environment of 50 ° C. and 50% RH and visually evaluating the image quality of the output image, no abnormality was recognized.

Comparative Example 1 A charging roller was prepared and evaluated in the same manner as in Example 1 except that a tube of ΔX = 4.58 mm was used.

Table 1 summarizes the results of Example 1 and Comparative Example 1.

[0063]

[Table 1]

As is clear from the above results, in order to output a good halftone image on a roller in which a tube is covered with a foamed elastic material layer, the warp ΔX = Xb− in the state of the seamless tube before covering. Xa is 2.1m
It has been found that in a charging roller in which a seamless tube having a thickness of m or less is covered with a foamed elastic material layer, the unevenness in the circumferential direction is required to be 1.7 times or less. Also, in other samples, by setting ΔX close to 0, the circumferential unevenness of the charging roller was reduced.

(Embodiment 2) The outline of the specific device configuration and the configuration of the charging roller are the same as those in Embodiment 1. In particular, the spacing between the seamless tube and the cooling sizing wall, the amount of cooling water, and the pressure in the vacuum water tank will be described because there are technical points in the manufacturing method.

Under the conditions for manufacturing the seamless tube,
Examples and comparative examples were prepared under the conditions shown in Tables 2 and 3 below.

[0067]

[Table 2]

[0068]

[Table 3]

Tables 4 and 5 show the results of the stability of tube molding, the presence or absence of uneven cooling, and the presence or absence of water marks on the tube surface for each example.

[0070]

[Table 4]

[0071]

[Table 5]

When the distance between the seamless tube and the sizing wall is less than 0.1 mm, if the tube flaps even a little, it comes into contact with the sizing, so that the tube cannot be stably pulled out and cannot be drawn in the extrusion direction. A shape without warpage cannot be obtained. On the other hand, when the thickness exceeds 0.3 mm, the cooling water does not uniformly hit the tube, resulting in uneven cooling.

This cooling unevenness can be eliminated by increasing the amount of cooling water. However, when the amount of cooling water exceeds 60 m ³ / h, the tube is affected by the flow of water and flutters when it is taken off. Occurs and cannot be stably picked up. In addition, cooling water adheres to the obtained tube, leaving a trace of water. When the amount of the cooling water is less than 30 m ³ / h, the cooling of the tube becomes insufficient, and the distance between the tube and the sizing wall cannot be maintained uniformly.
The tube contacts the sizing and warps.

The downward flowing water is sucked by the pressure (negative pressure) in the vacuum water tank, and the dripping of water under the apparatus is suppressed. That is, when the amount of cooling water is large, the pressure (negative pressure) is increased, and when the amount is small, the pressure is decreased. However, when the pressure in the vacuum water tank exceeds -10 MPa, flapping occurs when the tube is pulled, and the tube comes into contact with the sizing, and warpage occurs. If the pressure is less than -6 MPa, cooling water adheres to the obtained tube, leaving a trace of water.

[0075]

As described above, according to the charging roller of the present invention, "when the seamless tube has an outer diameter of 8 to 22 mm, the width Xa of the end of the sample cut to a length of 28 cm,
The difference Xb-Xa between the line perpendicular to the cut surface at the end and the maximum distance Xb from the cut surface at the other end is within 2.1 mm / 10 average, and the charge roller formed by covering the seamless tube is The ratio (maximum in the circumferential direction) Imax / Imin of the maximum current Imax and the minimum current Imin in the roller circumferential direction is 1.
By not more than seven times, "it is possible to minimize the occurrence of circumferential unevenness in resistance.

Further, according to the method of manufacturing the charging roller of the present invention, "when the distance between the seamless tube and the sizing wall is 0.1 to 0.3 mm, the amount of cooling water is 30 to 60.
m ³ / h and the pressure in the vacuum water tank is -6 to -10
By performing water-cooling sizing as MPa ", it is possible to make the shape of the tube coated on the foamed elastic material layer small, and to suppress the occurrence of circumferential unevenness in resistance as much as possible.

Further, it becomes possible to provide a charging member capable of obtaining a good image with uniform charging 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 vertical sectional front view of an example of a charging member of the present invention.

FIG. 2 is a schematic longitudinal sectional front view of a vertical extruder corresponding to various types of multilayers of the functional multi-layer seamless tube of the present invention.

FIG. 3 is a schematic view 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 sizing diagram of a water cooling means of a seamless tube used in the present invention, and a shape diagram and a relationship diagram of the seamless tube.

FIG. 6 is a shape diagram of a seamless tube used in the present invention.

FIG. 7 shows a charging roller resistance measuring device used in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core metal (metal layer) 1 'Charging roller 2 Foam elastic layer 3 Functional multilayer film (seamless tube) 4 Die 5 Central through hole 6 Extrusion channel 7 Extrusion channel 8 First extruder 9 Second extruder 10 Water-cooling sizing 11 Timing pulley (tube take-up unit) 12 Take-up belt (tube take-up unit) 13 Charged body (photosensitive drum) 14 Power supply 15 Exposure 16 Developing device 17 Cleaning device 18 Transfer device 20 Rail 21 Transfer material 22 Fixing device 23 Process cartridge 24 Metal roll 25 High voltage power supply 26 Pulse oscillator 27 Low pass FNF circuit 28 DMM (digital multimeter) 29 Personal computer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 105: 04 B29K 105: 04 B29L 23:00 B29L 23:00 (72) Inventor Ayumu Sato Ibaraki 1888-2 Kusazaki, Kusazaki-cho, Inashiki-gun F-term (reference) 2H200 HA02 HA28 HB12 HB22 HB43 HB45 HB46 HB47 HB48 LA01 LA12 LC03 MA03 MA08 MB10 MC20 NA03 3J103 AA02 AA15 AA51 BA41 FA15 FA18 GA52 HA03 HA04 HA12 HA12 HA12 HA12 HA53 4F207 AA09 AB02 AB03 AG08 AG20 AH04 KA01 KA17 KK54 KK76

Claims (4)

[Claims] 1. A charging roller having a cored bar, a foamed elastic layer on the periphery of the cored bar, and a seamless tube of a functional multilayer film on the periphery of the foamed elastic layer, wherein the seamless tube has an outer diameter. In the case of 8 to 22 mm, the difference Xb between the width Xa of the end of the sample cut to a length of 28 cm and the maximum distance Xb from a line perpendicular to the cut surface of the end to the cut surface of the other end.
−Xa is within 2.1 mm / 10 average, and the ratio (maximum in the circumferential direction) Imax / Imin of the maximum current Imax and the minimum current Imin in the roller circumferential direction of the charging roller formed by covering the seamless tube is 1. A charging roller, wherein the ratio is not more than 7 times. 2. A method for manufacturing a charging roller comprising a cored bar, a foamed elastic layer on the periphery of the cored bar, and a seamless tube of a functional multilayer film on the periphery of the foamed elastic layer. And the spacing between the sizing walls is 0.1 ~
In the case of 0.3 mm, the amount of cooling water is 30 to 60 m ³ /
h, and the pressure in the vacuum water tank is -6 to -10 MPa
A method for manufacturing a charging roller, comprising a step of performing water-cooling sizing. 3. A process cartridge which integrally supports an electrophotographic photosensitive member and at least a charging roller and is detachable from an electrophotographic apparatus main body, wherein the charging roller is disposed in contact with a member to be charged and has at least an AC component. A process roller for charging the electrophotographic photosensitive member by applying a voltage, wherein the charging roller is the charging roller according to claim 1. 4. An electrophotographic apparatus having an electrophotographic photosensitive member, a charging roller, an exposure unit, a developing unit, and a transfer unit, wherein the charging roller is disposed in contact with a member to be charged, and a voltage having at least an AC component is applied. An electrophotographic apparatus comprising: a charging roller for charging the electrophotographic photosensitive member, wherein the charging roller is the charging roller according to claim 1.