JP2012173529A - Manufacturing method for conductive elastic roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method for eliminating electric resistivity unevenness that results from a weld line, in a manufacturing device using a crosshead of a conductive elastic roller.SOLUTION: A manufacturing method for a conductive elastic roller that includes a conductive shaft core body and a conductive rubber layer for covering a periphery of the shaft core body includes: a step for supplying the shaft core body to a through-hole of a crosshead and supplying an unvulcanized rubber mixture containing a hollow particle and an electronically conductive filler to the crosshead from an extruder connected to the crosshead, and then forming a layer of the rubber mixture around the shaft core body; a step for repeatedly applying pressurization and depressurization processing to a surface of the layer of the rubber mixture; and a step for vulcanizing the layer of the rubber mixture after the step for applying pressurization and depressurization processing to a surface of the layer of the rubber mixture, and then forming a layer of conductive rubber.

Description

  The present invention relates to a method for manufacturing a conductive elastic roller used in an electrophotographic apparatus.

  As a method for producing a conductive elastic roller used in an electrophotographic apparatus, a method is known in which a peripheral surface of a conductive shaft core is coated with a conductive rubber composition by coating extrusion using a crosshead.

  In this method, as shown in FIG. 5, the conductive rubber composition 341 introduced into the annular flow path 317 is divided into two directions in the annular flow path 317 and merges at a position on the opposite side of about 180 °. To fill the annular flow path. Therefore, a weld line 204 as shown in FIG. 2 is formed at a position corresponding to the joining point of the conductive rubber composition 340 in the obtained conductive rubber cylindrical body 203. Since the weld line 204 is often different in electric resistance from other regions, the conductive elastic roller 201 formed using the conductive rubber cylinder 203 having such a weld line is used. Will have a region where the electrical resistance value differs from the surroundings in the direction along the axis. When such a conductive elastic roller is used as, for example, a charging roller, uneven charging may occur on the photoreceptor, and streaky image defects due to the uneven charging may occur on the electrophotographic image.

  In view of the above-mentioned problems caused by the weld line, in Patent Document 1, the conductive rubber composition is stirred by the impeller installed in the annular flow path in the annular flow path of the crosshead to diffuse the weld line. A method is disclosed.

JP 2003-311811 A

However, the method according to Patent Document 1 complicates the configuration of the extrusion molding apparatus. Further, the weld line portion is dispersed in the conductive rubber composition, and there is a possibility that the electric resistance is uneven in the circumferential direction of the conductive rubber cylindrical body.
Therefore, an object of the present invention is to provide a method for manufacturing a conductive elastic roller with little unevenness in electric resistance value.

  That is, according to one aspect of the present invention, there is provided a method for manufacturing a conductive elastic roller having a conductive shaft core and a conductive rubber layer covering a peripheral surface of the shaft core, the method comprising: (1) cross The shaft core is supplied to the through-hole of the head, and an unvulcanized rubber mixture containing hollow particles and an electronically conductive filler is supplied to the crosshead from an extruder connected to the crosshead. A step of forming a layer of the rubber mixture around the core, (2) a step of repeatedly applying pressure and pressure to the surface of the layer of the rubber mixture, and (3) the step through the step (2). And a step of vulcanizing a rubber mixture layer to form a conductive rubber layer. A method for producing a conductive elastic roller is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the electroconductive elastic roller which reduced and suppressed the nonuniformity of the electrical resistance value of the circumferential direction of an electroconductive elastic roller can be manufactured.

It is the schematic of an extrusion process provided with (a) single layer crosshead and (b) two-layer crosshead which form an elastic body layer on a conductive shaft core. It is a schematic diagram which shows a conductive elastic roller. It is a cross-sectional schematic diagram of one embodiment of a crosshead extrusion molding apparatus. It is (a) plane schematic diagram and (b) cross-sectional schematic diagram of one embodiment of an apparatus which repeats pressurization and depressurization of the present invention. It is a cross-sectional schematic diagram which shows the flow of the conductive rubber composition in a crosshead. It is a schematic diagram of the apparatus which measures the nonuniformity of the electrical resistance value of the circumferential direction of a conductive elastic roller. It is the schematic block diagram which showed an example of the electrophotographic apparatus using the electroconductive elastic roller of this invention.

The method for producing a conductive elastic roller of the present invention is a method for producing a conductive elastic roller having a conductive shaft core and a conductive rubber layer covering the peripheral surface of the shaft core.
The shaft core is supplied to the through hole of the crosshead, and an unvulcanized rubber mixture containing hollow particles and an electronically conductive filler is supplied to the crosshead from an extruder connected to the crosshead. A step of forming an unvulcanized rubber mixture layer comprising a rubber mixture around the shaft core, a step of repeatedly applying and depressurizing the surface of the rubber mixture layer, and a surface of the rubber mixture layer. And the step of repeatedly vulcanizing and depressurizing the rubber mixture layer to form a conductive rubber layer.

  As a result of intensive studies by the present inventors, the reason why the weld line generated by extrusion molding with a crosshead has a different electric resistance value in the conductive rubber cylindrical body compared with the non-weld line region is estimated as follows. ing.

As shown in FIG. 3 and FIG. 5, the conductive rubber composition 341 is discharged from the extruder 300, passes through the mesh 303, passes through the adapter 304 and the inlet 311 of the crosshead 310, The flow is diverted in an annular flow path 317 constituted by the outer peripheral surface of the inner die 312 and the inner peripheral surface of the outer die 315. Thereafter, the conductive rubber cylinders 203 are formed while joining again to form a weld line. At this time, the conductive rubber composition constituting the weld line is a conductive rubber composition that passes through the wall surface of the flow path and the vicinity of the wall surface of the flow path in the inlet 304 of the adapter 304 or the crosshead 310.
The conductive rubber composition flowing through the flow path such as the inlet of the adapter or the crosshead flows toward the base 318 while generating friction with the wall surface of the flow path. In the conductive rubber composition in contact with the flow path wall surface, the dispersion state of substances such as a conductive agent and a filler in the conductive rubber composition changes due to friction generated between the flow path wall surface and the conductive rubber composition. To do. For this reason, the conductive rubber composition in the part in contact with the flow path wall surface is different from the conductive rubber composition not in contact with the flow path wall surface in the dispersion state of substances such as a conductive agent and a filler. . In the conductive rubber composition, when the dispersion state of a substance such as a conductive agent or a filler changes, the electrical resistance value of the conductive rubber composition changes.
For the above reason, in the conductive rubber cylindrical body, it is considered that the weld line has a different electric resistance value compared with the non-weld line region.

In the present invention, as a method for reducing the unevenness of the electrical resistance value caused by the weld line, the surface of the unvulcanized rubber mixture layer containing hollow particles and the electronically conductive filler is pressed around the shaft core body. It was found that the process of repeatedly depressurizing was effective. By vulcanizing the rubber mixture layer that has undergone this step to form a conductive rubber layer, it is possible to obtain a conductive elastic roller with reduced electrical resistance unevenness.
For example, when a pressing member is used, the shape of the hollow particles contained in the unvulcanized rubber mixture layer is deformed through a process of repeatedly pressing and depressurizing the unvulcanized rubber mixture layer. And the restoration will be repeated. The deformation and restoration of the shape of the hollow particles makes it easy for the polymer and the electronic conductive filler around the hollow particles to be displaced, and the uneven distribution of the electronic conductive filler around the hollow particles and the agglomeration collapse Can be encouraged. As a result, it is possible to reduce the unevenness of the electric resistance value caused by the weld line. In the step of repeatedly performing pressurization and depressurization by the pressing member, depending on the thickness of the unvulcanized rubber mixture layer, the polymer material contained in the layer, the hollow particles, the type and amount of the electronically conductive filler, Parameters such as pressing load, construction time, and heating temperature are appropriately selected and set. It is preferable to set so that pressurization and depressurization are repeated so that the shape of the hollow particles contained in the layer of the unvulcanized rubber mixture is repeatedly deformed and restored.

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

[Step of forming a layer of the unvulcanized rubber mixture around the shaft core]
An unvulcanized rubber mixture is produced by blending and kneading additives such as rubber, hollow particles and electronic conductive filler. The obtained unvulcanized rubber mixture is extruded simultaneously with an unvulcanized rubber mixture and a conductive shaft core using an extrusion device to form an elastic roller preform. 1A and 1B are schematic views of the extrusion process. As shown in FIG. 1A, the extruder 101 includes a single layer crosshead 102. The conductive shaft core body 202 is supplied to the through hole of the single layer crosshead 102 by the feed roll 103 to the single layer crosshead 102, and the conductive shaft core body 202 and the unvulcanized rubber mixture are extruded simultaneously. Thus, a single-layer elastic roller preform 104 in which the periphery of the conductive shaft core is covered with the unvulcanized rubber mixture is obtained. Also, as shown in FIG. 1B, by using two extruders 101 and a two-layer crosshead 105, a two-layer elastic roller preform 106 made of two types of unvulcanized rubber mixture is obtained. You can also.

[Step of repeatedly applying pressure and pressure to the surface of the rubber mixture layer]
Next, a description will be given of the process of repeatedly applying pressure and pressure to the surface of the unvulcanized rubber mixture layer of the elastic roller preform. 4 (a) and 4 (b) are schematic views of a process of repeatedly applying pressure and pressure release to the surface of the rubber mixture layer. The pressing member 401 is held in a rotatable state by a pressing member holder 408 and is connected to a motor 403 by a coupling 402 and is driven to rotate. The pressing member holder 408 is fixed to the pressing member mounting base 410. The pressing member mounting base 410 is installed so as to be slidable in the horizontal direction with respect to the apparatus base 411. The pressing member 401 is provided with a pressure applying jig 407, which is a mechanism that can apply a load to the pressing member 401 by the pressing spring 405 and the eccentric cam 404. The eccentric cam 404 is rotatably held by an eccentric cam holder 406 and is connected to a motor 414 by a coupling 413 and is driven to rotate.
The elastic roller preform 412 is held by the shaft center holder 409 in a state where the conductive shaft center body can be rotated.
In the present invention, it is possible to appropriately select and set parameters such as pressing load, working time, and heating temperature in the step of repeatedly applying and releasing pressure to the surface of the rubber mixture layer.

  In the step of repeatedly pressing and depressurizing the surface of the rubber mixture layer, the elastic roller preform molded body of the elastic roller preform is rotated by the pressing member while rotating the conductive shaft body in the apparatus having the above-described configuration. Press the surface of the layer. Furthermore, it is possible to change the pressure applied to the surface of the rubber mixture layer by the action of the eccentric cam and the pressure spring. As a result, the rubber mixture layer is repeatedly pressurized and depressurized.

  Here, the shape of the pressing surface of the pressing member may be linear or curved, and a shape that is less likely to cause a gap with the rubber mixture layer of the elastic roller preform when pressed is preferable. When a gap occurs in the pressing surface of the pressing member and the rubber mixture layer of the elastic roller preform, the gap is not pressed. For this reason, the dispersion state of the electronic conductive filler is different between the gap portion and the region other than the gap portion, and as a result, the electric resistivity may be different, and a phenomenon such as an image defect may occur. .

  4A and 4B, the pressing surface length of the pressing member 401 is set longer than the axial length of the rubber mixture layer of the elastic roller preform 412. However, in the present invention, the length of the pressing surface of the pressing member 401 can be set arbitrarily. For example, when the pressing surface length of the pressing member is shorter than the axial length of the rubber mixture layer, the pressing surface is appropriately changed while moving the pressing member in the axial direction of the elastic roller preform, and the elastic roller preliminary Pressurization and depressurization can be repeatedly performed on the rubber mixture layer of the molded body.

  As the material of the pressing member, a material having a strength capable of withstanding a desired pressing load or heating temperature can be used, but metals are preferable from the viewpoint of good thermal conductivity and strength. The pressing surface may be subjected to a surface treatment such as chrome plating, nitriding treatment, or coating with Teflon (registered trademark). Furthermore, a surface treatment for roughening the surface or providing irregularities may be performed.

[Pressing method]
When the pressing surface length of the pressing member is shorter than the axial length of the rubber mixture layer of the elastic roller preform, pressurization is performed at an arbitrary number of times on the outer peripheral surface of the elastic roller preform. Depressurization can be repeated.

  For example, a method of repeatedly pressing and depressurizing the rubber mixture layer of the elastic roller preform while moving the pressing surface in the axial direction or a plurality of times at the same position on the outer peripheral surface of the rubber mixture of the elastic roller preform. A method in which pressurization and depressurization are repeatedly performed is allowed.

  In the example of FIG. 4, one pressing member 401 is used, but a plurality of pressing members may be used. For example, a plurality of pressing members are fixedly arranged in the circumferential direction so as not to contact the periphery of the elastic roller preform, and the parameters such as the pressing load, the operating time, or the heating temperature are changed, whereby the rubber mixture layer You may implement the process of repeatedly performing pressurization and depressurization to the surface.

[Electric resistivity of conductive elastic roller]
The electrical resistivity of the conductive elastic roller is not particularly limited and is appropriately set according to desired characteristics. For example, when used as a charging roller, the electrical resistivity in the axial direction when contacting the photosensitive drum is 1 ×. It is desirable to be about 10 ³ Ω · cm to about 1 × 10 ¹⁰ Ω · cm. Further, the electrical resistivity in the circumferential direction of the conductive elastic roller is preferably set so that the ratio of the maximum value to the minimum value is 1.0 to 5.0 times. More preferably, it is about 1.0 to 3.0 times.

[Pressing load]
In the process of repeatedly performing the above pressurization and depressurization, the pressing load by the pressing member depends on the thickness of the unvulcanized rubber mixture layer and the type and amount of the polymer material, hollow particles, and electronic conductive filler contained in the layer. It is set accordingly. It is preferable to set so that a pressure load that repeats pressurization and depressurization is applied to such an extent that the shape of the hollow particles contained in the layer of the unvulcanized rubber mixture repeats deformation and restoration.
The shape of the hollow particles contained in the layer of the unvulcanized rubber mixture is repeatedly deformed and restored by the repeated action of pressurization and depressurization by the pressing member. The deformation and restoration of the shape of the hollow particles are likely to cause displacement of the polymer and the electronic conductive filler around the hollow particles, and the uneven distribution of the electronic conductive filler existing around the hollow particles and the collapse of the aggregates Can be urged.

For example, when the thickness of the unvulcanized rubber mixture layer is in the range of about 1 mm to 4 mm, it is preferable to apply a pressure of about 0.2 kg to 4 kg on the pressing surface, and the higher the pressure, the more the hollow particles are deformed. It is more preferable because it can be made. When the pressure load is too low, the shape of the hollow particles is not sufficiently deformed, so that the effect of the present invention may be weakened. When the pressure load is too high, the hollow particles are deformed by pressurization, and when the pressure is removed, the shape of the hollow particles may not be recovered, and the effect of the present invention may be weakened.
The step of repeatedly applying and depressurizing is a step of giving an amplitude to the pressurization of the unvulcanized rubber mixture layer by the pressing member and changing the pressing position of the pressing member against the unvulcanized rubber mixture layer. It is preferable that The amplitude of pressurization by the pressing member is always positive pressure during the process, and does not become negative pressure at the time of depressurization, and the amplitude does not become negative pressure at the time of depressurization with respect to the weight of the press member It is necessary to. That is, the load by the pressing member> the amplitude of pressurization. As a mechanism for giving the pressure amplitude by the pressing member, for example, an eccentric cam can be used as shown in FIG. The mechanism shown in FIG. 4 can generate an amplitude in the weight generated by the pressure spring by the displacement amplitude of the eccentric cam, and the amplitude weight is transmitted to the pressing member through the pressure applying jig. As a result, the preformed elastic roller in contact with the pressing member is repeatedly pressurized and depressurized to the unvulcanized rubber mixture layer. Further, the method for giving the pressure amplitude is not limited to the above method, and a mechanism for bringing a member such as a known vibrator into contact with the pressing member may be used.

  For the above reasons, in the step of repeatedly performing the pressurization and depressurization, the pressing load by the pressing member and the amplitude of the pressurization are the thickness of the unvulcanized rubber mixture layer and the polymer material contained in the layer, It is necessary to set appropriately according to the kind and amount of the hollow particles and the electronic conductive filler.

[Enforcement time]
The time required to repeat the pressurization and depressurization steps can be to ease the uneven distribution of the electronically conductive filler existing around the hollow particles and the collapse of the agglomerates under the set pressure load conditions. It is appropriately set so that sufficient pressurization and depressurization are repeated. In the present invention, it is necessary to repeat the pressurization and depressurization by the pressing member at least once over the entire peripheral surface of the elastic roller preformed unvulcanized rubber mixture layer.
Since the elastic roller preform is held in a rotatable state by the shaft center holder, the elastic roller preform is driven and rotated by the contact of the rotating pressing member. It is preferable that f1> f2 when the rotational speed of the elastic roller preform is f2 [Hz] and the period of the amplitude of pressurizing and depressurizing by the pressing member is f1 [Hz]. That is, pressurization and depressurization of the pressing member are repeated while the outer peripheral surface of the layer of the unvulcanized rubber mixture of the elastic roller preform is contacted with the pressing member over the entire circumference. By increasing the period f1 of the amplitude of pressurization and depressurization by the pressing member, the pressurization and depressurization are performed a plurality of times while the outer peripheral surface of the unvulcanized rubber mixture layer of the elastic roller preform is processed once. Can be repeated. The amplitude of pressure and pressure release on the rubber mixture layer by the pressing member may be a periodically weighted amplitude such as a sine wave or a weighted amplitude such as a triangular wave or a rectangular wave. Moreover, it is preferable that the ratio of f1 / f2 does not become an integral multiple. Under the conditions where the ratio is an integral multiple, the repetition timing of pressurization and depressurization coincides with the circumferential position of the rubber mixture layer, and a constantly pressurized portion and a constantly depressurized portion are generated. It is because it ends up.

[Heating method and heating temperature]
In addition to the process of repeatedly pressing and depressurizing the surface of the rubber mixture layer in a desired atmosphere such as in an electric furnace, the elastic roller is preliminarily provided with a heater in the pressing member. A method of blowing warm air to a part of the outer peripheral surface of the molded body can be used.
The heating temperature in the step of repeating the pressurization and depressurization by the pressing member is preferably performed at a temperature lower than the vulcanization temperature. Specifically, it is desirable to carry out at a temperature that is higher than the glass transition temperature of the polymer material and lower by 20 ° C. than the vulcanization temperature.

[Step of forming a conductive rubber layer by vulcanizing a rubber mixture layer]
Regarding the method of heating and vulcanizing the elastic roller preform thus obtained, conventionally known methods such as a hot air furnace, a vulcanizing can, a hot platen, a far / near infrared heating furnace, a UHF furnace, induction heating, etc. Either method may be used. It is preferable to vulcanize the elastic roller preform by heating at a temperature in the range of 140 ° C. or more and 220 ° C. or less for a time of 10 minutes to 120 minutes. In this way, an end uncut elastic roller is obtained. Further, depending on the material, vulcanization can also be performed by irradiating active energy rays, and in this case, vulcanization can be performed in a short time. Moreover, you may make it raise | generate a vulcanization density by irradiating an active energy ray after vulcanization heating.

[Step of cutting both ends of elastic layer]
Next, the obtained end uncut elastic roller cuts the end using a cutting device. The cutting device holds the end uncut elastic roller by the elastic roller holding means and rotates it at a predetermined rotation speed. This is cut by pressing a cutting blade. The interval between the two cutting round blades corresponds to the length of the elastic layer of the elastic roller. When the cut pieces are removed, the elastic roller can be obtained after the end cutting.

[Process of polishing the elastic layer]
Next, in order to obtain a predetermined outer diameter, the outer peripheral surface of the elastic layer is polished by a cylindrical polishing machine and finished. In general, an elastic roller uniformly contacts an end of a conductive shaft core with another member by a spring. Therefore, in consideration of bending due to the contact of the elastic roller, the outer diameter of the central portion, generally called a crown shape, is ended. Finish in a shape that is thicker than the outer diameter of the part. Since it is difficult to remove such a shape with a cylindrical mold, it is preferable to finish with a polishing machine. As the cylindrical polishing machine, a traverse NC polishing machine or a plunge cut NC cylindrical polishing machine can be used. The plunge cut type NC polishing machine uses a grinding wheel that is wider than that of the traverse type, and can polish the entire length of the elastic layer in the longitudinal direction at the same time.

[Step of providing surface layer on elastic layer]
The elastic roller of the present invention can also form a surface layer on the elastic layer. The surface layer is formed for the purpose of further enhancing the functionality and durability of the elastic roller. For example, by making the surface layer function as a resistance adjusting layer, charging uniformity and leakage resistance can be improved when used as a charging roller.
The step of forming the surface layer on the elastic layer can be performed by a coating method such as electrostatic spray coating or dipping coating. Or it can form by adhere | attaching or coat | covering the sheet-shaped or tube-shaped layer previously formed into the predetermined film thickness. Alternatively, a method of curing and molding the material into a predetermined shape in the mold can also be used. Among these, it is preferable to apply a paint by a coating method to form a surface layer.
When the surface layer is formed by a coating method, the solvent used in the coating solution may be any solvent that can dissolve the binder resin. Specifically, alcohols such as methanol, ethanol and isopropanol, ketones such as acetone, methyl ethyl ketone and cyclohexanone, amides such as N, N-dimethylformamide and N, N-dimethylacetamide, and dimethyl sulfoxide Sulfoxides, tetrahydrofuran, dioxane, ethers such as ethylene glycol monomethyl ether, esters such as methyl acetate and ethyl acetate, and aromatic compounds such as xylene, ligroin, chlorobenzene and dichlorobenzene. These solvents are appropriately selected according to the binder resin used.
As a method for dispersing a substance such as a binder resin or particles in the coating solution, known solution dispersing means such as a ball mill, a sand mill, a paint shaker, a dyno mill, and a pearl mill can be used.

Examples of the step of forming the surface layer on the elastic layer include a method of modifying the rubber surface by irradiation with a known energy beam such as an ultraviolet ray or an electron beam.
For example, a light source such as a high-pressure mercury lamp, a metal halide lamp, a low-pressure mercury lamp, or an excimer UV lamp can be used for the irradiation of ultraviolet rays. Among these, ultraviolet rays containing abundant light having an ultraviolet wavelength of 150 nm to 480 nm. A source is preferably used.

The integrated light quantity of ultraviolet rays is defined as follows.
UV integrated light quantity [mJ / cm ² ] = UV intensity [mW / cm ² ] × irradiation time [s]

The adjustment of the integrated amount of ultraviolet light can be performed by parameters such as irradiation time, lamp output, and distance between the lamp and the irradiated object. Moreover, you may give a gradient to integrated light quantity within irradiation time.
In the case of using a low-pressure mercury lamp, the integrated light amount of ultraviolet rays can be measured using an ultraviolet integrated light amount meter UIT-150-A or UVD-S254 manufactured by USHIO INC. When an excimer UV lamp is used, the integrated light quantity of ultraviolet rays can be measured using an ultraviolet integrated light quantity meter UIT-150-A or VUV-S172 manufactured by USHIO INC.
For example, an electron beam irradiation apparatus irradiates an electron beam onto the surface of an elastic layer while rotating an elastic roller, and includes an electron beam generation unit, an irradiation chamber, and an irradiation port.
The electron beam generator includes a terminal that generates an electron beam and an acceleration tube that accelerates the electron beam generated at the terminal in a vacuum space (acceleration space). The inside of the electron beam generator is kept at a vacuum of about 10 ⁻³ [Pa] to 10 ⁻⁴ [Pa] by a device such as a vacuum pump in order to prevent electrons from colliding with gas molecules and losing energy. I'm leaning.
When a filament is heated by a power source through a current, the filament emits thermoelectrons, and only those thermoelectrons that have passed through the terminal are effectively extracted as electron beams. Then, the electron beam is accelerated in the acceleration space in the accelerating tube by the acceleration voltage, then penetrates the irradiation port foil, and is irradiated to the elastic roller conveyed in the irradiation chamber below the irradiation port.
When the elastic roller is irradiated with an electron beam, the inside of the irradiation chamber is a nitrogen atmosphere or an air atmosphere. Further, the elastic roller is rotated by a roller rotating member and can be moved and passed by the conveying means in the irradiation chamber. In addition, the surroundings of the electron beam generator and the irradiation chamber are shielded from lead so that X-rays that are secondarily generated during electron beam irradiation do not leak to the outside.
The irradiation port foil is made of a metal foil, and partitions the vacuum atmosphere in the electron beam generator and the air atmosphere in the irradiation chamber, and takes out the electron beam into the irradiation chamber through the irradiation port foil. When an electron beam is applied to the irradiation of the elastic roller, the inside of the irradiation chamber where the elastic roller is irradiated with the electron beam is a nitrogen atmosphere or an air atmosphere. Therefore, the irradiation port foil provided at the boundary between the electron beam generating part and the irradiation chamber has no pinhole, has a mechanical strength that can sufficiently maintain the vacuum atmosphere in the electron beam generating part, and easily transmits the electron beam. Thus, a metal having a small specific gravity and a small thickness is desirable. For example, Ti having a thickness of about 5 μm to 15 μm is often used as a metal used for the irradiation port foil.
For example, an electron beam irradiation device (manufactured by Iwasaki Electric Co., Ltd.) having a maximum acceleration voltage of 150 kV and a maximum electron current of 40 mA is used. Further, the irradiation is performed in a nitrogen atmosphere or an air atmosphere, but irradiation in a nitrogen atmosphere is preferable, and an environment having an oxygen concentration of 500 ppm or less is preferable.

The electron beam dose is defined below.
Dose (kGy) = [equipment constant K × electron current (mA)] / processing speed (m / min)

Here, the device constant K is a constant representing the efficiency of each device, and serves as an index of device performance. For example, in an electron beam irradiation apparatus, it is originally necessary to set K = 18 or more. Therefore, for a certain electron current and processing speed, the acceleration voltage is changed, the dose is measured, and the acceleration voltage is determined by obtaining the acceleration voltage so that the device constant K obtained from this is a predetermined value or more. Is obtained.
What is necessary is just to select suitably about the dose of an electron beam according to the effect of surface treatment. The adjustment can be performed using either the electronic current or the processing speed, and may be determined so as to obtain a desired dose.

  The material used for the manufacturing method of the electroconductive elastic roller of this invention is demonstrated.

[Conductive shaft core]
The conductive shaft core used in the conductive elastic roller of the present invention has conductivity and has a function of supporting an elastic layer provided thereon. Examples of the material include metals such as iron, copper, stainless steel, aluminum, and nickel, and alloys thereof.

[Elastic layer]
(Elastic layer material)
The elastic body layer is manufactured using, for example, a rubber mixture in which hollow particles and a conductive agent are dispersed in rubber. Examples of the rubber include the following. Examples include synthetic rubbers such as epichlorohydrin rubber, acrylonitrile-butadiene rubber, chloroprene rubber, urethane rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber, isoprene rubber, and butyl rubber. Alternatively, thermoplastic elastomers such as styrene / butadiene / styrene block copolymers and styrene / ethylene / butylene / styrene block copolymers may be used. Moreover, these rubber | gum can be used individually or in combination of 2 or more types.

(Hollow particles)
The elastic body layer of the conductive elastic roller used in the present invention contains hollow particles. As the hollow particles, particles in which the inside of the particles are bubbles may be used, or the so-called thermal expansibility that includes the inclusion substance inside the particle and expands the inclusion substance by applying heat to become a hollow particle. Microcapsules may be used. When the thermally expandable microcapsule is used in the present invention, a microcapsule that has been previously expanded by heating the thermally expanded microcapsule in advance can be used. In the step of repeatedly applying pressure and pressure to the elastic layer, the pressure and pressure may be repeatedly applied while the elastic layer is heated to expand the thermoplastic resin serving as the shell. Depending on the temperature conditions at the time of molding, the capsule can be molded while maintaining the shell structure without melting or rupturing.
Examples of the thermoplastic resin used for the shell of the hollow particles include known thermoplastic resins. Examples thereof include acrylonitrile resin, vinyl chloride resin, vinylidene chloride resin, methacrylic acid resin, styrene resin, urethane resin, amide resin, methacrylonitrile resin, acrylic acid resin, acrylic ester resin, and methacrylic ester resin. Among these, it is preferable to use a thermoplastic resin composed of at least one selected from acrylonitrile resin, vinylidene chloride resin, and methacrylonitrile resin having low gas permeability and high resilience. These thermoplastic resins can be used alone or in combination of two or more. Furthermore, these thermoplastic resin monomers may be copolymerized and used as a copolymer.
When using a thermally expandable microcapsule, the substance encapsulated in the capsule is one that expands as a gas at a temperature below the softening point of the shell of the hollow particles. For example, propane, propylene, butene, normal butane, isobutane, normal Low boiling liquids such as pentane and isopentane, and high boiling liquids such as normal hexane, isohexane, normal heptane, normal octane, isoheptane, isooctane, normal decane and isodecane are often used.

These thermally expandable microcapsules can be produced by a known production method such as a suspension polymerization method, an interfacial polymerization method, an interfacial precipitation method, or a submerged drying method.
Although there is no limitation in particular about the volume average particle diameter of a hollow particle, Preferably they are 5 micrometers-1000 micrometers, Especially preferably, they are 10 micrometers-500 micrometers.

  Examples of the hollow particles include thermally expandable microcapsules in which pentane and hexane are encapsulated in a capsule and vinylidene chloride resin or acrylonitrile resin having low gas permeability is used as a shell. In the present invention, as described above, the shape of the hollow particles contained in the elastic layer needs to be repeatedly deformed and restored by the process of repeatedly applying and removing pressure. For these reasons, in order to expand the gas contained in the elastic layer, it is preferable to use a thermally expandable microcapsule that is effective for producing an elastic layer containing single bubbles.

(Conductive agent)
By appropriately using a conductive agent, the conductivity of the elastic roller can be set to a predetermined value. The electric resistance value of the elastic roller can be adjusted by appropriately selecting the type and amount of the electronic conductive filler as the conductive agent.
Examples include graphite such as natural graphite and artificial graphite, metal oxide conductive particles such as titanium oxide, tin oxide and zinc oxide, and metal conductive particles such as aluminum, iron, copper and silver. it can. These electronic conductive fillers can be used alone or in combination of two or more.

  Further, a conductive substance such as a conductive polymer or an ionic conductive agent may be used in combination with the electronic conductive filler to impart conductivity to the elastic roller.

(Additive)
Further, an additive such as an inorganic or organic filler or a crosslinking agent may be added to the rubber mixture.

[Surface layer]
(Surface layer material)
As the binder resin used for the surface layer, a known binder can be employed. Examples thereof include resins, natural rubber, vulcanized products thereof, and rubbers such as synthetic rubber.
As the resin, a resin such as a thermosetting resin or a thermoplastic resin can be used. Among these, fluorine resin, polyamide resin, acrylic resin, polyurethane resin, silicone resin, and butyral resin are more preferable.
Synthetic rubbers include ethylene-propylene-diene copolymer (EPDM), styrene-butadiene copolymer rubber (SBR), silicone rubber, urethane rubber, isoprene rubber (IR), butyl rubber, acrylonitrile-butadiene copolymer rubber (NBR). Chloroprene rubber (CR), acrylic rubber and epichlorohydrin rubber can be used.
When the surface layer needs to be conductive, it can be adjusted by adding a conductive agent such as an ionic conductive agent or an electronic conductive filler in the same manner as the elastic layer.

[Electrophotographic equipment]
FIG. 7 shows a schematic configuration diagram of an example of an electrophotographic apparatus provided with a conductive elastic roller manufactured according to the present invention as a charging roller.
An electrophotographic apparatus collects a photosensitive member, a charging device that charges the photosensitive member, a latent image forming device that performs exposure, a developing device that develops a toner image, a transfer device that transfers to a transfer material, and a transfer toner on the photosensitive member. The apparatus includes a cleaning device and a fixing device for fixing a toner image.
The electrophotographic photosensitive member (photosensitive member) 701 is a rotary drum type having a photosensitive layer on a conductive shaft core. The photoreceptor is driven to rotate in the direction of the arrow at a predetermined peripheral speed (process speed).
The charging device includes a contact-type charging roller 702 that is placed in contact with the photosensitive member 701 by contacting the photoreceptor 701 with a predetermined pressing force. The charging roller 702 is driven rotation that rotates in accordance with the rotation of the photosensitive member, and charges the photosensitive member to a predetermined potential by applying a predetermined voltage from a charging power source 712. As the latent image forming apparatus 708 that forms an electrostatic latent image on the photoreceptor 701, an exposure apparatus such as a laser beam scanner is used. An electrostatic latent image is formed by performing exposure corresponding to image information on a uniformly charged photoconductor.
The developing device has a developing roller 703 disposed close to or in contact with the photoreceptor 701. The toner electrostatically processed to the same polarity as the photosensitive member charge polarity is developed by reversal development to visualize and develop the electrostatic latent image into a toner image.
The transfer device has a contact-type transfer roller 705. The toner image is transferred from the photoconductor to a print medium 704 such as plain paper (the print medium is conveyed by a paper feed system having a conveyance member).
The cleaning device has a blade-type cleaning member 707 and a recovery container, and after transferring, mechanically scrapes and recovers transfer residual toner remaining on the photosensitive member.
Here, it is possible to omit the cleaning device by adopting a development simultaneous cleaning system in which the transfer device collects the transfer residual toner.
The fixing device 706 is configured by a member such as a heated roller, and fixes the transferred toner image on the print medium 704 and discharges it outside the apparatus.

  The manufacturing method of the conductive elastic roller of the present invention described above will be described in further detail with reference to specific examples and comparative examples, but these do not limit the technical scope of the present invention. .

  Below, the manufacturing method of the electroconductive elastic roller of this invention demonstrated above is demonstrated concretely.

<Production Examples 1-4>
Hollow particles 1 to 4 according to the present invention were prepared as follows.

<Production Example 1> [Preparation of hollow particles 1]
To the polymerization reaction vessel, 8000 parts by mass of ion-exchanged water, 9 parts by mass of colloidal silica and 0.3 parts by mass of polyvinylpyrrolidone as a dispersion stabilizer were added to prepare a water-soluble dispersion medium.
Next, from 200 parts by mass of acrylonitrile resin as a raw material monomer, 25 parts by mass of normal hexane as an inclusion substance, 1.5 parts by mass of dicumyl peroxide as a polymerization initiator, and 1.0 part by mass of methyl methacrylate as a crosslinking substance The resulting oily mixture was added to a water-soluble dispersion medium, and 0.8 parts by mass of sodium hydroxide was further added to prepare a dispersion.
The obtained dispersion was stirred and mixed using a homogenizer, charged into a nitrogen-substituted polymerization reaction vessel, pressurized, and reacted at 60 ° C. for 20 hours to prepare a reaction product. The obtained reaction product was repeatedly filtered and washed, and then dried to obtain hollow particles 1 as thermally expandable microcapsules of Production Example 1. The volume average particle diameter of the obtained hollow particles 1 was set to 12 μm by classification.

<Production Example 2> [Preparation of hollow particles 2]
In Production Example 1, hollow particles 2 were produced in the same manner as in Production Example 1 except that the raw material monomer was methacrylonitrile resin. The volume average particle diameter of the obtained hollow particles 2 was set to 15 μm by classification.

<Production Example 3> [Preparation of hollow particles 3]
In Production Example 1, hollow particles 3 were produced in the same manner as in Production Example 1 except that the raw material monomer was vinylidene chloride resin. The volume average particle diameter of the obtained hollow particles 3 was set to 18 μm by classification.

<Production Example 4> [Preparation of hollow particles 4]
In Production Example 1, hot hollow particles 4 were produced in the same manner as in Production Example 1 except that the raw material monomer was styrene resin. The volume average particle size of the obtained hollow particles 4 was set to 20 μm by classification.

<Production Examples 5 to 35>
Conductive rollers 5 to 35 were manufactured as follows.

<Production Example 5> [Production of Conductive Elastic Roller 5]
(Production of elastic layer)
The components shown below were kneaded for 15 minutes in a closed mixer adjusted to 80 ° C.
NBR 100 parts by mass
(Bound acrylonitrile content 35% Mooney viscosity 32)
5 parts by mass of zinc oxide
1 part by weight of zinc stearate
25 parts by weight of calcium carbonate
Sebacic acid polyester 10 parts by mass
40 parts by mass of carbon black 1
(Average particle size: 28nm, DBP oil absorption of 87cm ^3/100 g)
The components shown below were kneaded with a two-roll mill cooled to 25 ° C. for 20 minutes to obtain an unvulcanized rubber mixture.
1.2 parts by weight of sulfur powder
Dibenzothiazyl disulfide (DM) 1 part by mass
Tetramethylthiuram monosulfide (TS) 1 part by mass
Hollow particles 1 (Production Example 1) 12 parts by mass
A thermosetting adhesive (trade name: “Metaloc U-20”, manufactured by Toyo Chemical Laboratories) was applied to a stainless steel rod having a diameter of 6 mm and a length of 258 mm in advance to the area excluding both ends 12 mm, and the temperature was adjusted to 180 ° C. It left still for 30 minutes in the adjusted hot stove, and obtained the electroconductive shaft core.
Subsequently, an extrusion molding apparatus including the crosshead shown in FIGS. 1 (a) and 3 was used. A general-purpose rubber extruder (trade name: “extruder with vent”, manufactured by Mitsuba Seisakusho; screw diameter: 45 mm, L / D = 20 extruder, L: screw length, D: screw diameter) was used. The flight shape of the screw was a full flight shape except for the vent zone. The temperature control during extrusion was 90 ° C. for the head temperature, 90 ° C. for the cylinder 301, and 90 ° C. for the screw 302.
As for the shape of the circular flow path of the cross head, the cross section perpendicular to the extrusion flow direction was circular. As shown in FIG. 3, the annular flow path has an inner diameter A of 68 mm and an outer diameter a of 102 mm on the inlet side on the extruder side, and an inner diameter B of 18 mm and an outer diameter b of 50 mm on the base side. The taper type has a reduced cross-sectional area of the ring. The length of the annular channel was 130 mm.
A feed roll 321 for continuously supplying the conductive shaft core 202 was installed at one end of the through hole 314 of the inner die 312. The feed roll is connected to a motor (not shown) and is given a rotational force.
A base 318 having an inner diameter of 9.8 mm was attached to the tip of the crosshead. The screw speed of the extruder is set so that the discharge speed (the amount of extrusion per unit time) of the unvulcanized rubber composition by the extruder 101 (FIG. 1 (a)) becomes the outer diameter of a predetermined elastic roller preform. 10.5 rpm.
A cylindrical rubber mixture was coaxially coated with the conductive shaft core as the central axis to obtain an elastic roller preform with an outer diameter of the rubber mixture layer of φ9.4 mm.
Using the pressurizing apparatus shown in FIG. 4, the process of repeating pressurization and depressurization on the elastic roller preform was performed. At this time, the applied pressure was 4.9 N, and the amplitude was 2.9 N.

  This elastic roller preform was heated in a hot air oven adjusted to 160 ° C. for 60 minutes and vulcanized to obtain an end-uncut elastic roller.

  In this example, both ends of the elastic body layer of this end uncut elastic roller were cut, and an unpolished elastic roller was obtained after the end was cut. The length of the elastic layer was 228 mm. A cylindrical polishing machine was used to polish the outer peripheral surface of the unpolished elastic roller after end cutting and adjust the outer diameter to 8.5 mm.

(Crown amount measurement method)
As the outer diameter measuring device, (trade names: “LS-7500 (controller)” and “LS-7030M (measurement unit)”, manufactured by Keyence Corporation) were used. Three outer diameters were measured: a central part (114 mm) in the longitudinal direction of the elastic body layer and 90 mm parts (24 mm, 204 mm) in both end directions from the central part. The outer diameter of the central part was D2, the outer diameters of each 90 mm part in both end directions were D1 and D3, respectively, and the crown amount D was calculated as D = (D2− (D1 + D3) / 2). As a result, the crown amount was 100 μm.

(Preparation of surface layer)
The surface layer 1 which is a surface layer was produced as follows.
Methyl isobutyl ketone was added to the caprolactone-modified acrylic polyol solution to adjust the solid content to 18% by mass.
The following components were added to 555.6 parts by mass of this solution (100 parts by mass of acrylic polyol solid content) to prepare a mixed solution of urethane resin.
20 parts by mass of carbon black
(Primary particle diameter 22nm, DBP oil absorption 100ml / g)
Titanium oxide particles 20 parts by mass
Modified dimethyl silicone oil (* 1) 0.08 parts by mass
Block isocyanate mixture (* 2) 80.14 parts by mass
At this time, the blocked isocyanate mixture was such that the amount of isocyanate was “NCO / OH = 1.0”.
(* 1) Modified dimethyl silicone oil “SH28PA” (trade name, manufactured by Toray Dow Corning Silicone Co., Ltd.)
(* 2) 7: 3 mixture of each butanone oxime block of hexamethylene diisocyanate (HDI) and isophorone diisocyanate (IPDI)
200 g of the above mixed solution was placed in a glass bottle having an inner volume of 450 mL together with 200 g of glass beads having an average particle diameter of 0.8 mm as a medium, and dispersed for 12 hours using a paint shaker disperser.
After the dispersion, the glass beads were removed to obtain a surface layer coating solution.
Using the above surface layer coating solution, dipping coating was performed once on the elastic roller using a coating apparatus (not shown). Here, the dipping coating is as follows. The immersion time was 9 seconds, the dipping coating lifting speed was an initial speed of 20 mm / s and a final speed of 2 mm / s, and the speed was changed linearly with respect to the time. After coating, the film was air-dried at room temperature for 30 minutes or more, and dried with a hot air circulating drier at 80 ° C. for 1 hour and further at 160 ° C. for 1 hour to obtain a conductive elastic roller 5 having a surface layer formed on the elastic layer.

<Production Examples 6-15> [Production of Conductive Elastic Rollers 6-15]
Conductive elastic rollers 6 to 15 were produced in the same manner as in Production Example 5 except that the treatment conditions for pressurization and pressure removal were as shown in Table 1.

<Production Examples 16 to 30> [Production of Conductive Elastic Rollers 16 to 30]
In Production Example 5, conductive elastic rollers 16 to 30 were obtained in the same manner as in Production Example 5 except that the treatment conditions for pressurization and depressurization were as shown in Table 1 and the rubber composition shown in Table 2 was used. It was.
In Table 2, the following materials were used.
Epichlorohydrin rubber (hydrin) (trade name: Epion ON301, manufactured by Daiso Corporation)
EPDM (trade name: Espren EPDM505A, manufactured by Sumitomo Chemical Co., Ltd.)
SBR (trade name: SBR1500, manufactured by JSR)
Hollow particles 2 (Production Example 2)
Hollow particles 3 (Production Example 3)
Hollow particles 4 (Production Example 4)
Carbon black 2 (trade name: Seast S, manufactured by Tokai Carbon Co., Ltd.)
Carbon black 3 (trade name: Seast GSO, manufactured by Tokai Carbon Co., Ltd.)
Quaternary ammonium salt (trade name: Adeka Sizer LV70, manufactured by Asahi Denka Kogyo Co., Ltd.)

<Production Example 31> [Production of Conductive Elastic Roller 31]
In Production Example 5, a conductive elastic roller 31 was produced in the same manner as in Production Example 5 except that the surface layer 1 was changed to the following surface layer 2.
The surface layer 2 was produced as follows.
An ultraviolet lamp having a wavelength of about 250 nm is installed in parallel with the elastic roller axial direction, and the elastic roller is rotated in the circumferential direction, and irradiation is performed for 2 minutes so that the cumulative amount of ultraviolet light having a wavelength of 254 nm is 9000 mJ / cm ^2. Thus, an ultraviolet treatment layer was formed on the surface. In this way, a conductive elastic roller 31 was obtained. A low pressure mercury lamp (trade name: “QLC500”, manufactured by Harrison Toshiba Lighting Co., Ltd.) was used for ultraviolet irradiation.

<Production Example 32> [Production of Conductive Elastic Roller 32]
In Production Example 5, a conductive elastic roller 32 was produced in the same manner as in Production Example 5 except that the surface layer 1 was changed to the following surface layer 3.
The surface layer 3 was produced as follows.
An irradiation body of an electron beam irradiation apparatus (manufactured by Iwasaki Electric Co., Ltd.) having a maximum acceleration voltage of 150 kV and a maximum electron current of 40 mA is installed in parallel with the elastic roller axial direction, and the elastic body is rotated while rotating the elastic roller in the circumferential direction. An electron beam was directly irradiated on the layer to form an electron beam treatment layer on the surface. In this way, a conductive elastic roller 32 was obtained. The electron beam irradiation conditions were an acceleration voltage of 150 KV, an electron current of 15 mA, and an irradiation time of 1 sec. The irradiation was performed in a nitrogen atmosphere (oxygen concentration of about 300 ppm). While the elastic roller was rotated at a rotation speed of 500 rpm, it was conveyed so as to have the irradiation time and irradiated with an electron beam.

<Production Example 33> [Production of Conductive Elastic Roller 33]
A conductive elastic roller having an elastic layer provided with an upper layer on the surface of the elastic layer was manufactured as follows.
As a rubber composition to be an elastic layer, a rubber composition was obtained in the same manner as in Production Example 5 using the components shown below.
100 parts by weight of hydrin rubber
(Epichlorohydrin: ethylene oxide: allyl glycidyl ether = 23 mol%: 73 mol%: 4 mol% Mooney viscosity 60)
5 parts by mass of zinc oxide
1 part by weight of zinc stearate
45 parts by weight of calcium carbonate
Sebacic acid polyester 10 parts by mass
Quaternary ammonium salt 2 parts by mass
(Tetrabutylammonium perchlorate)
1.2 parts by weight of sulfur powder
Dibenzothiazyl disulfide (DM) 1 part by mass
Tetramethylthiuram monosulfide (TS) 1 part by mass
Hollow particles 1 (Production Example 1) 12 parts by mass
As an upper layer rubber composition, a rubber composition was obtained in the same manner as in Production Example 5 using the components shown below.
NBR (bound acrylonitrile content 35% Mooney viscosity 32) 100 parts by weight
5 parts by mass of zinc oxide
1 part by weight of zinc stearate
25 parts by weight of calcium carbonate
Sebacic acid polyester 10 parts by mass
48 parts by mass of carbon black 1
(Average particle size: 28nm, DBP oil absorption of 87cm ^3/100 g)
Powdered sulfur 0.8 parts by mass
Dibenzothiazyl disulfide (DM) 1 part by mass
Tetramethylthiuram monosulfide (TS) 1 part by mass
A conductive shaft core was obtained in the same manner as in Production Example 5.
Subsequently, by using a two-layer extrusion molding apparatus having a two-layer crosshead shown in FIG. 1B, a cylindrical rubber composition is coated coaxially with a conductive shaft core as a central axis, An elastic roller preform with an outer diameter of the rubber composition layer of φ10.0 mm was obtained.
This was heated in a hot air oven adjusted to 160 ° C. for 60 minutes, foamed and vulcanized to obtain an end uncut elastic roller having an outer diameter of φ13.0 mm. In the same manner as in Production Example 5, the outer peripheral surface of the unpolished elastic roller after end cutting was polished using a cylindrical grinder to adjust the outer diameter to 12.0 mm. The thickness of the upper layer was 0.5 mm.
Thereafter, in the same manner as in Production Example 5, a conductive elastic roller 33 was obtained.

<Production Example 34> [Production of Conductive Elastic Roller 34]
As shown in Table 1, the same procedure as in Production Example 5 was conducted except that the hollow particle 1 was changed to 4 parts by mass of OBSH (4,4′-oxybisbenzenesulfonylhydrazide) as the blowing agent 1 in Production Example 5. A conductive elastic roller 34 was obtained.

<Production Example 35> [Production of Conductive Elastic Roller 35]
In Production Example 33, the conductive elastic roller 35 was changed in the same manner as in Production Example 33 except that the hollow particles 1 were changed to 4 parts by mass of OBSH (4,4′-oxybisbenzenesulfonylhydrazide) as the foaming agent 1. Obtained.

[Example 1]
The following evaluation was performed using the conductive elastic roller 5 manufactured in Manufacturing Example 5 as a charging roller.

[Evaluation of unevenness of electrical resistance value in the circumferential direction]
The unevenness of the electric resistance value in the circumferential direction of the conductive elastic roller 5 was calculated by the following method. That is, as shown in FIG. 6, both ends of the conductive shaft core 202 are brought into contact with a cylindrical metal 601 having the same curvature as that of the photosensitive member by a bearing 602 under load so as to be parallel to each other. In this state, the cylindrical metal 601 is rotated in the direction of the arrow by a motor (not shown), and a DC voltage of −200 V is applied from the stabilized power supply 603 while the conductive elastic roller 201 that is in contact with the driven elastic roller 201 is rotated. The current flowing at this time was measured with an ammeter 604. The ratio (maximum value / minimum value) was obtained from the maximum value and the minimum value of the current values measured by the ammeter 604, and was regarded as unevenness in the circumferential direction of the electrical resistance value. Each load was 4.9 N, the diameter of the cylindrical metal was 30 mm, and the rotation of the cylindrical metal was a peripheral speed of 45 mm / sec.
The unevenness in the circumferential direction of the electric resistance value of the conductive elastic roller 5 was 2.21.

[Image evaluation test]
A color laser printer (trade name: HP Color LaserJet 4700dn, manufactured by Hewlett-Packard Company) which is an electrophotographic apparatus having the configuration shown in FIG. 7 was used. The printer was used by modifying it so that it could output recording media at 200 mm / sec (A4 vertical output). The primary charging output is a DC voltage (Vdc) of −1100V. The resolution of the image is 600 dpi. As the photoreceptor 701, an organic photoreceptor drum having a total film thickness including the photosensitive layer of 40 μm was used. The charging roller was removed from the electrophotographic apparatus, and the produced conductive elastic roller 5 was set. The conductive elastic roller 5 was brought into contact with the photosensitive member by a pressing force of a spring of 4.9 N at one end and a total of 9.8 N at both ends. This electrophotographic apparatus was placed in a high-temperature and high-humidity environment at 30 ° C. and 80% RH for 6 hours, and then paper passing durability evaluation was performed. The evaluation method is to output one halftone image (an image in which a straight line having a width of 1 dot and a spacing of 2 dots is drawn in the rotation direction and the longitudinal direction of the photosensitive member) after passing through 50,000 sheets, and the output image has a streak-like shape. Images were evaluated. Here, the evaluation criteria are as follows.
Rank A: No streak-like image is generated.
Rank B: A very slight streak-like image is recognized.
Rank C: Some streaky images can be confirmed by the pitch of the charging roller, but the image quality has no practical problem.
Rank D: A streak-like image is conspicuous and a deterioration in image quality is recognized.
As a result of the image evaluation test, no streak-like image was generated for the conductive elastic roller 5 of this example, and a good image was obtained. The image rank was rank A.

[Examples 2, 4 to 29]
Evaluation was performed in the same manner as in Example 1 using the conductive elastic roller manufactured in Manufacturing Examples 6 and 8-33 as a charging roller. The results are shown in Table 3. In Examples 2, 4 to 29, the unevenness in the circumferential direction was similar to that in Example 1, and even in the image evaluation test, a streak-like image was not generated and a good image was obtained. The image rank was rank A.

Example 3
Evaluation was performed in the same manner as in Example 1 using the conductive elastic roller manufactured in Manufacturing Example 7 as a charging roller. The results are shown in Table 3. In Example 3, the unevenness in the circumferential direction was slightly larger than that in Example 1, and in the image evaluation test, a very slight streak-like image was slightly observed in a part of the halftone. It is an image with no problem. The image rank was rank B.

[Comparative Examples 1 and 2]
Evaluation was performed in the same manner as in Example 1 using the conductive elastic roller manufactured in Manufacturing Examples 34 and 35 as a charging roller. The results are shown in Table 3. In Comparative Examples 1 and 2, the unevenness in the circumferential direction was considerably larger than that in Example 1, and even in the image evaluation test, streaky images were conspicuous on the halftone image, and the image quality was found to be deteriorated. . The image rank was rank D.

DESCRIPTION OF SYMBOLS 101 ... Extruder 102 ... Single layer cross head 103 ... Feed roll 104 ... Single layer elastic roller preform 105 ... Double layer cross head 106 ... Double layer elastic roller preform 201 ... Conductivity Elastic roller 202 ... Conductive shaft core 203 ... Conductive rubber cylinder 204 ... Weld line 300 ... Extruder 301 ... Cylinder 302 ... Screw 303 ... Mesh 304 ... Adapter 310 ... Cross Head 311 ... Introduction port 312 ... Inside die 314 ... Through hole 315 ... Outside die 317 ... Annular channel 318 ... Base 321 ... Feed roll 341 ... Conductive rubber composition 401 ... Pressing member 402 Coupling 403 Motor 404 Eccentric cam 405 Pressure spring 406 Eccentric cam holder 407 Pressure application jig 408 Press member holder 409 ... Shaft core holder 410 ... Press member mounting base 411 ... Equipment base 412 ... Elastic roller preform 413 ... Coupling 414 ... Motor 601 ... Columnar metal 602 ... Bearing 603 ... Stabilized power supply 604 ... Ammeter 701 ... Electrophotographic photosensitive member 702 ... Charge roller 703 ... Development roller 704 ... Print media 705 ... Transfer roller 706 ... Fixing device 707 ... Cleaning member 708 ... Latent image forming device 712 ... Power supply

Claims (3)

A method for producing a conductive elastic roller having a conductive shaft core and a conductive rubber layer covering a peripheral surface of the shaft core,
(1) The shaft core is supplied to the through hole of the crosshead, and an unvulcanized rubber mixture containing hollow particles and an electronically conductive filler is supplied to the crosshead from an extruder connected to the crosshead. Forming a layer of the rubber mixture around the shaft core;
(2) repeatedly applying pressure and pressure to the surface of the rubber mixture layer;
(3) A method for producing a conductive elastic roller, comprising the step of vulcanizing the layer of the rubber mixture that has undergone the step (2) to form a layer of conductive rubber.   The method of manufacturing a conductive elastic roller according to claim 1, wherein the step (2) is a step in which the shape of the hollow particles contained in the rubber mixture layer is repeatedly deformed and restored.   The method of manufacturing a conductive elastic roller according to claim 1 or 2, wherein the step (2) is a step of changing the pressing position of the pressing member while giving an amplitude to the pressing by the pressing member.

Images