JP5414497B2 - Manufacturing method of rubber roller - Google Patents

Description

  The present invention relates to a method of manufacturing a conductive rubber roller used in an image forming apparatus using an electrophotographic process.

  As a problem of a conductive rubber roller having a conductive vulcanized rubber layer around a core metal used for a charging roller or the like in an image forming apparatus using an electrophotographic process, a harsh environment (40 ° C./90% RH) There is a so-called bleed in which low-molecular-weight components ooze out from the conductive vulcanized rubber layer when placed on the surface. When the low molecular weight component bleed on the surface of the rubber roller migrates to the surface of the photosensitive drum, it may interfere with uniform charging of the peripheral surface of the photosensitive drum and affect the formation of a high-quality electrophotographic image. In response to this problem, Patent Document 3 discloses a method of forming a solidified layer on the surface of a conductive vulcanized rubber layer by irradiating the peripheral surface of a rubber roller with an electron beam.

JP-A-8-292640 JP-A-8-283578 JP-A-9-160355 Japanese Patent Laid-Open No. 2002-3651

However, according to the study by the present inventors, the surface hardness of a rubber roller having a conductive vulcanized rubber layer formed by irradiating the surface with an electron beam to form a solidified layer sometimes increases. As a result, with the long-term use of the conductive rubber roller, a layer of fixed matter such as toner and external additives is formed on the surface, which may adversely affect the formation of high-quality electrophotographic images. It was.
Accordingly, an object of the present invention is to provide a conductive material capable of suppressing the seepage of the conductive rubber roller to the surface of the conductive rubber roller while suppressing an increase in the hardness of the conductive vulcanized rubber layer. It is in providing the manufacturing method of a roller.

The method for producing a conductive roller according to the present invention is a method for producing a conductive roller having a cored bar and a conductive vulcanized rubber layer having a pattern of regions having different hardness on the surface,
The conductive vulcanized rubber layer formed around the core metal is irradiated with an electron beam through a mask member in which portions having different electron beam transmittances are arranged in a pattern on the peripheral surface of the conductive vulcanized rubber layer. It has the process of forming the area | region where hardness differs derived from the difference of the irradiation intensity | strength of an electron beam on the surface of a rubber layer.

  According to the present invention, it is possible to manufacture a conductive roller that suppresses adhesion of toner or the like to the surface of the conductive roller and exudation of a low molecular weight compound or the like to the surface.

It is a schematic diagram of an extruder. It is a schematic diagram which shows an example of an electron beam irradiation apparatus. It is a schematic diagram which shows the outline of rotation of an electron beam irradiation apparatus and a conveyance mechanism. It is a schematic diagram which shows an example of an electron beam irradiation apparatus. It is a schematic diagram (slit shape) showing an example of a mask member. It is a schematic diagram (uneven shape) showing an example of a mask member. It is a schematic diagram (circular hole shape) showing an example of a mask member. It is a schematic diagram (mesh shape) showing an example of a mask member. It is a schematic diagram which shows the charged rubber roller cross section which concerns on this invention, and the hardness distribution of the surface. 1 is a configuration diagram illustrating an outline of an image forming apparatus.

  Hereinafter, embodiments of the conductive roller (charging roller) of the present invention will be described in detail. First, the conductive roller has a configuration in which a conductive elastic layer is provided on a cored bar. The method for forming the conductive roller is not particularly limited. For example, two cylindrical pieces concentrically holding a shaft core are assembled in a cylindrical mold, and heated after injecting a rubber material. Injection molding in which the material is cured to form a conductive roller. Also, for example, after extrusion of a rubber material into a tube shape, the core metal is covered with the tube-shaped rubber material, or the core metal and the rubber material are integrally extruded to form a cylindrical conductive roller. And press molding. In view of shortening the manufacturing time, extrusion molding in which a rubber material is extruded integrally with a core metal to form a conductive roller is preferable.

  Here, FIG. 1 shows a schematic diagram of an extruder. The extruder 1 includes a crosshead 2. The crosshead can insert the cored bar 4 fed by the cored bar feed roller 3 from behind, and can simultaneously extrude the cylindrical rubber material simultaneously with the cored bar. After the rubber material is formed into a cylindrical shape around the core metal, the end portion is cut and removed 5 to obtain the conductive roller 6. The material used as the metal core is preferably a stainless steel bar, a phosphor bronze bar, an aluminum bar, or a heat-resistant resin bar containing a steel material such as nickel-plated SUM.

  The rubber layer provided on the cored bar is a conductive elastic layer. Examples of the rubber material include natural rubber, butadiene rubber, hydrin rubber, styrene-butadiene rubber, nitrile rubber, ethylene-propylene rubber, butyl rubber, silicone rubber, urethane rubber, fluorine rubber, and chlorine rubber. Examples of the conductive powder dispersed in the rubber layer include carbon black and metal powder.

  As for the method of heating the conductive roller, any method such as a hot stove, vulcanizer, hot platen, far / near infrared ray, induction heating, etc. may be used, and further, it is pushed while rotating on a heated cylindrical or planar member. A hitting method may be used.

  Next, a schematic configuration diagram of an electron beam irradiation apparatus that can be used in the present invention will be described in detail with reference to FIG. FIG. 2 is a schematic configuration diagram of an example of an electron beam irradiation apparatus that can be used in the present invention. The apparatus shown in FIG. 2 has a mechanism for irradiating the surface of the roller with an electron beam while rotating the conductive roller. As shown in FIG. 2, the electron beam irradiation apparatus includes an electron beam generator 7, an electron beam irradiation chamber 8, and an electron beam irradiation port 9. An irradiation port foil 13 is provided at the electron beam irradiation port.

The electron beam generator includes a terminal 10 that generates an electron beam, and an acceleration tube 11 that accelerates the electron beam generated at the terminal in a vacuum space (acceleration space). Further, the inside of the electron beam generating part is kept at a vacuum of 10 ⁻⁶ to 10 ⁻⁷ Torr by a vacuum pump or the like in order to prevent electrons from colliding with gas molecules and losing energy.

  When the filament 12 is heated by a power source through current, the filament emits thermoelectrons, and only those thermoelectrons that have passed through the terminal are effectively taken out as electron beams. Then, after being accelerated in an accelerating space in the accelerating tube by an accelerating voltage of an electron beam, it penetrates the irradiation port foil 13 and is irradiated to a roller conveyed in an irradiation chamber below the irradiation port.

  When irradiating an electron beam to a roller, the internal atmosphere of the irradiation chamber is not particularly limited, but is generally a nitrogen atmosphere or an air atmosphere. In addition, the roller is moved from the left side to the right side in FIG. As a method for conveying the rollers, either forward feed or pitch feed may be used, but forward feed is preferable in consideration of continuous electron beam irradiation. The number of rotations of the roller is preferably 100 to 3000 rpm in consideration of the short irradiation time, although it depends on the irradiation time of the electron beam. Note that the periphery of the electron beam generator and the irradiation chamber is shielded by a material that does not leak X-rays that are secondarily generated during electron beam irradiation. Generally it is shielded with lead.

  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 roller, the inside of the irradiation chamber for irradiating the roller with the electron beam is a nitrogen atmosphere or an air atmosphere. Therefore, the irradiation opening 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, titanium having a thickness of about 5 to 15 μm is often used as a metal used for the irradiation port foil. In this example, 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 was used.

Here, the transmission depth of the electron beam will be described. The penetration depth of the electron beam is calculated from the acceleration voltage and the density of the irradiated material, and is defined below.
Permeation depth (μm) = 0.0667 × {acceleration voltage (kV)} ^5/3 / material density (g / cm ³ )

The penetration depth of the electron beam is one of the indexes of modification by the electron beam. The electron beam reaches the calculated penetration depth and the modification is performed. 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, K = 18 or more is inherently set. 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 by either the electronic current or the processing speed, and it may be determined so as to obtain a desired dose. In this embodiment, the dose at an electron current / processing speed is measured in advance using a dose film, the device constant K is calculated, and the dose of the electron beam is calculated based on the device constant K. In addition, when the surface of the conductive roller is directly irradiated with an electron beam, the dose is preferably 100 to 3000 kGy.

  Here, the electron beam irradiation method, which is a method for producing the conductive rubber roller of the present invention, will be described in more detail. The rubber material for the conductive vulcanized rubber layer is shown above, but considering the modification and curing of the rubber roller surface by electron beam irradiation, nitrile rubber, styrene-butadiene rubber, butadiene rubber, ethylene-propylene rubber Hydrin rubber is preferred. When these rubbers are irradiated with an electron beam, the bonds between the polymers are broken and the crosslinking proceeds, resulting in high crosslinking and high hardness. By carrying out high crosslinking, it is possible to reduce the seepage of low molecular weight compounds.

  The acceleration voltage of the electron beam is preferably 50 to 300 kV. By setting the acceleration voltage to 300 kV or less, the hardness of the surface of the conductive roller does not become too large. For this reason, the pressure between the surface of the conductive roller and the toner or the external additive attached to the toner does not become crushed and the conductive roller can be easily prevented from becoming dirty. Further, the electron beam irradiation apparatus can be downsized. Moreover, by setting the acceleration voltage to 50 kV or more, the penetration depth of the electron beam from the surface of the conductive roller can be increased, and the hardness can be sufficiently increased. Therefore, it is possible to easily prevent the low molecular weight compound or the like from seeping out from the conductive elastic layer, and it is possible to easily prevent the surface of the conductive roller and the surface of the photosensitive drum from being soiled.

  As the feeding and rotating mechanism of the conductive roller in the electron beam irradiation apparatus when the mask member is disposed, an apparatus schematically shown in FIG. 2, 3 or FIG. 4 can be used. FIG. 3 shows a plan view in which only the conveying portion of FIG. 2 is extracted.

  In FIG. 3, reference numeral 14 denotes a mask member having a cylindrical shape. The mask member 14 may be a member in which a member is formed in a cylindrical shape, or a member in which a sheet-like mask member is rounded into a cylindrical shape. The work holding member 15 can hold a work and can hold a cylindrical mask member coaxially. Further, by driving the sprocket 18 provided at one end with the chain 17, it is possible to rotate in synchronization with the workpiece. A plurality of workpiece holding jigs as described above are attached to the transfer chain 16 and can pass through the electron beam irradiation port 9 at a constant speed. Further, the rotation speed of the workpiece can be arbitrarily adjusted by the speed difference between the chains 16 and 17. The rotation speed of the workpiece is preferably 200 rpm or more and 1000 rpm or less, and the workpiece feeding speed is preferably adjustable to 0.1 m / min or more and 5 m / min or less.

  FIG. 4 shows an irradiation apparatus having another structure. In FIG. 4, the mask member 14 has a flat plate shape and is fixedly placed under the electron beam irradiation port. The rotation speed (peripheral speed) of the workpiece holding jig is set to be the same as the workpiece feed speed, and the workpiece is rotated in the direction opposite to the workpiece feed direction when the rotation direction is viewed from the electron beam irradiation port. The position of the surface of the roller has a one-to-one correspondence. That is, it is possible to perform the same operation as processing a roller with an electron beam having an irradiation intensity distribution to which a pattern of a mask member is almost transferred. In order to transfer the pattern in the workpiece rotation direction properly, it is preferable to set the rotation speed of the workpiece holding jig and the workpiece feeding speed to be the same. In order to prevent the pattern from being transferred twice, the width of the mask member is preferably the same as the outer circumference of the workpiece. Furthermore, it is preferable that a cover is provided so that an electron beam is not irradiated from a portion other than the mask member.

  The electron beam irradiation port is preferably rectangular, and the length of the electron beam irradiation port in the longitudinal direction is preferably equal to or longer than the length of the conductive vulcanized rubber layer in the longitudinal direction. Particularly preferably, the length is about 20 mm to 100 mm longer than the entire length of the roller. In other words, by setting the width of the electron beam irradiation port in the direction parallel to the rubber roller to be conveyed to be equal to or longer than the length of the conductive vulcanized rubber layer in the longitudinal direction, the conductive vulcanized rubber layer is irradiated with the electron beam once through the rubber roller. It can be performed. Moreover, it is preferable that the length of the electron beam irradiation port in the short direction is the same as the outer circumference of the conductive vulcanized rubber layer. This is to prevent the pattern from being transferred twice as described above.

  However, when using a mask member having a pattern having the same cross-sectional shape in the roller feed direction as shown in FIG. 5, the mask member pattern can be transferred without setting the work rotation speed and the work feed speed to be the same. Is possible.

  Further, the treatment may be performed using an apparatus that uniformly irradiates an electron beam from the circumferential direction of the roller without rotating the roller (for example, Eyring Beam manufactured by Iwasaki Electric Co., Ltd.). In that case, the pattern of the mask member can be transferred to the entire surface of the roller simply by disposing the cylindrical mask member around the roller and passing the cylindrical irradiation space.

  The mask member has a pattern in which holes and irregularities of the same shape are repeated at equal intervals in at least one direction, that is, a structural unit consisting of a constituent part and an opening part or a thin film part and a thick film part is repeated in at least one direction. Has a shape.

  Examples of the shape of the pattern include configuration examples shown in FIGS.

  For example, the mask member 19 shown in FIG. 5 is provided with an opening in a slit shape. Further, the structural units between the lines AA ′ have a pattern shape formed by repeatedly arranging them. By using the mask member shown in FIG. 5, the electron beam can be easily irradiated as described above. That is, for example, by arranging the mask member 19 at the electron beam irradiation port of the electron beam irradiation apparatus shown in FIG. 4, the conductive vulcanized rubber can be passed only by passing under the electron beam irradiation port while rotating the rubber roller. High hardness regions and low hardness regions can be formed in the layer. At this time, it is not necessary to adjust the conveyance speed or rotation speed of the rubber roller or to select the size of the electron beam irradiation port. Therefore, the mask member is preferably provided with a slit shape in the thin film portion or opening.

  For example, the mask member 20 shown in FIG. 6 has an uneven shape composed of a thin film portion and a thick film portion, and has a pattern shape in which the thick film portion is provided in a lattice shape. In addition, it has a pattern shape in which structural units surrounded by a line AA'BB 'are repeatedly arranged. The mask member 20 can also be recognized as a pattern shape in which rectangular thin film portions are repeatedly arranged at equal intervals.

  For example, the mask member 21 shown in FIG. 7 has circular openings provided at equal intervals. In addition, it has a pattern shape in which structural units surrounded by a line AA'BB 'are repeatedly arranged.

  For example, as for the mask member 22 shown in FIG. 8, a structure part is mesh shape and an opening part is square shape. In addition, it has a pattern shape in which structural units surrounded by a line AA'BB 'are repeatedly arranged. In addition, examples of the quadrangular shape include a square and a rectangle.

  As shown in FIGS. 5 to 8, the opening or the thin film portion can be formed in, for example, a slit shape, a circular shape (including an ellipse), or a rectangular shape. Moreover, a structure part can be made into mesh shape and a lattice shape, for example. The thick film portion can be formed in a lattice shape, for example.

  In the mask member, portions having different electron beam transmittances are arranged in a pattern. That is, the opening or thin film portion of the mask member has a higher electron beam transmittance than the constituent portion or thick film portion of the mask member. Therefore, an electron beam is more permeate | transmitted in the opening part or thin film part of a mask member, and a difference can be provided in the irradiation intensity | strength of the electron beam in a conductive vulcanized rubber layer surface. Therefore, since the difference in pattern derived from the difference in electron beam irradiation intensity can be provided depending on the difference in film thickness of the mask member or the shape of the opening, the high hardness of the pattern approximating the pattern of the opening or thin film in the mask member A region is formed on the roller surface. That is, a high hardness region can be formed at a position corresponding to the opening or thin film portion on the roller surface by irradiation with an electron beam. The portion corresponding to the thick film portion of the mask member is substantially the same as or slightly harder than the inside, but is referred to as a low hardness region in the present specification in the sense of comparison with the high hardness region.

  The mesh shape refers to a knitted wire, and examples of the knitting method include general plain weave, twill weave, flat tatami weave, ton cap weave, flat top weave, etc. It may be in shape.

  As the size of the pattern forming the hardness distribution, the repeating width of the pattern is preferably 20 μm or more and 500 μm or less, and particularly preferably 40 μm or more and 200 μm or less. By making the pattern repeat width 20 μm or more, it becomes easy to prevent the surface flexibility from being insufficient because the repeat width is too small and the hardness difference is not accurately transferred. Also, by setting the pattern repetition width to 500 μm or less, it becomes easy to prevent defects from appearing on the image because the repetition width is too large and the distribution of high hardness causes stain unevenness.

  Here, the repeated width of the pattern refers to the distance from the adjacent pattern when one minimum unit shape (opening, unevenness, etc.) of the repeated pattern is extracted. When the distance varies depending on the direction, the length with the smallest distance is set as the minimum repetition length. When repeated only in a certain direction, it is the repeat length in the repeated direction. If the pattern has a complicated shape, it can be derived by calculating the centroid position of the pattern and calculating the distance between the centroid positions. It is possible to combine multiple different patterns and arrange the combined patterns continuously. In this case, the repetition width is obtained by calculating the distance of the center of gravity of different combined patterns between adjacent patterns and averaging them. The value obtained can be used as a representative value.

  The distance between the mask member and the workpiece is preferably close in order to transfer the mask member pattern more accurately. However, since it may contact if it is too close, it is preferably 0.5 mm to 10 mm, more preferably 0.5 mm to 2 mm.

  By forming a fine hardness distribution in the vicinity of the surface with the mask member, the seepage of a low molecular weight compound or the like from the rubber roller is reduced in a high hardness portion, that is, a highly crosslinked portion. In addition, the presence of a portion having a low hardness compared to the high hardness portion, that is, a low cross-linking portion, suppresses excessively high hardness in the vicinity of the surface of the rubber roller, and externally attached to the toner and the toner. It is possible to prevent dirt on the surface of the rubber roller such as an agent.

  The reason why the hardness in the vicinity of the surface is suppressed is that the high hardness region does not behave as a film, but the low hardness region between the high hardness regions has flexibility and can be easily deformed. Therefore, although there are many high hardness regions when viewed microscopically, it is considered that the macroscopic behavior is low hardness and flexible.

  In addition, the surface hardness of the conductive roller obtained by the manufacturing method according to the present invention is smaller when the measurement terminal is large than when the entire surface is irradiated with an electron beam under the same irradiation conditions to increase the hardness.

  The above characteristics cannot be achieved by adjusting the conditions in the method of manufacturing by irradiating the entire surface with an electron beam once.

  In addition, when compared with a roller formed by blending a high hardness material and a low hardness material, the blended material has a portion with high hardness to the inside. As a result, the hardness will increase. Therefore, some rollers may not have enough flexibility. In addition, since there may be large variations among lots or within a single roller, the present invention can further optimize the hardness of the roller surface.

  There are no particular restrictions on the material of the mask member, but it has durability against electron beams and is easy to achieve processing accuracy in the direction of electron beam transmission. Titanium, stainless steel, aluminum, silver, ceramic, glass, polystyrene Etc. are preferred. In view of durability, titanium is more preferable.

  Since the intensity of the transmitted electron beam can be calculated from the specific gravity and the film thickness of these materials, the thickness of the film thickness portion and the thin film portion can be selected so that irradiation is performed with a desired intensity.

  Further, the electron beam may be irradiated through the mask member and then again without the mask member. Moreover, you may carry out some electron beam irradiation previously before irradiating through a mask member. Furthermore, you may combine with ultraviolet irradiation, plasma irradiation, etc.

  Different mask member patterns may be combined in the longitudinal direction, or regions of different patterns may be provided in part. Alternatively, a pattern in which random variations are intentionally shifted at the positions of regular repeating patterns may be used.

  In addition, when the mask member is flat, a mask having a rectangular shape may be arranged, or a parallelogram may be arranged so that the joint is not conspicuous.

  The conductive roller obtained by the conductive roller manufacturing method according to the embodiment of the present invention is used as an electrophotographic member of an image forming apparatus such as an LBP (Laser Beam Printer), a copying machine, or a facsimile. Here, FIG. 10 shows a usage pattern when used as a charging roller. The image forming apparatus is a rotating drum type / transfer type electrophotographic apparatus, and 26 is an electrophotographic photosensitive member (photosensitive drum) as an image carrier, which rotates clockwise with a predetermined peripheral speed (process speed). Driven. The photosensitive drum is uniformly charged to a predetermined polarity and potential (-500 V in this embodiment) by a charging roller 27 to which a charging bias is applied from a power source E1 as a charging means during the rotation process. Next, the exposure system 28 receives negative image exposure (analog exposure of the original image, digital scanning exposure) corresponding to the target image information, and an electrostatic latent image of the target image information is formed on the peripheral surface. Next, the electrostatic latent image is developed as a toner image by a toner developing roller 29 of a reverse developing method using minus toner. Then, a transfer material is fed at a predetermined timing from a sheet feeding means (not shown) to a transfer portion between the photosensitive drum and a transfer roller 30 as a transfer means, and a toner image that is reversely developed on the surface of the photosensitive drum is transferred to the transfer material. Are sequentially transferred. A transfer bias of about +2 to 3 KV is applied to the transfer roller from the power source E2. The transfer material that has received the transfer of the toner image is separated from the surface of the photosensitive drum and introduced into fixing means (not shown) to undergo image fixing processing. The surface of the photosensitive drum after the transfer of the toner image is subjected to a removal process of adhering contaminants such as transfer residual toner by the cleaning unit 31 to be cleaned and repeatedly used for image formation.

  The charging roller described in the embodiment of the present invention is a conductive roller having a cored bar and a conductive elastic layer formed on the cored bar. In the present invention, it is preferable to irradiate the surface of the conductive vulcanized rubber layer on the core metal with an electron beam through a mask member and an electron beam through the mask member within an acceleration voltage range of 50 to 300 kV. As a result, the hardness distribution near the surface of the charging roller is controlled to prevent contamination of the roller surface such as toner and external additives adhering to the toner, and also prevent the low molecular weight compound from exuding from the roller. Thus, it is possible to provide a charging roller that does not contaminate the photosensitive drum. In addition, the present invention can provide a charging roller only by irradiating the surface of the conductive elastic layer on the core metal with an electron beam, and thus is excellent in mass productivity. Furthermore, it is possible to obtain various conductive rollers from the same vulcanized rubber roller by changing irradiation conditions, mask members, etc., and it is possible to stably manufacture high-quality conductive rollers at low cost. is there.

  FIG. 9 is a conceptual diagram of the charging roller cross section and surface hardness distribution obtained in the present invention. Reference numeral 23 denotes a metal core, 25 denotes a conductive elastic layer, and 24 denotes a portion hardened by electron beam irradiation through a mask member. For example, when a mesh member having a mesh shape is used as the mask member, the hardness of the inside or the portion where the electron beam is not strongly irradiated is not increased, and it is considered that the hardness before irradiation is substantially maintained.

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

[Examples 1 to 6]
<Production of rubber roller>
The following raw materials were kneaded with a pressure kneader for 15 minutes.
・ NBR 100 parts by mass (trade name “Nipol DN219”: manufactured by Nippon Zeon Co., Ltd.)
・ 14 parts by mass of carbon black 1 (trade name “Asahi HS-500” manufactured by Asahi Carbon Co., Ltd.)
・ Carbon black 2 4 parts by mass (trade name “Ketjen Black EC600JD” manufactured by Lion)
-1 part by weight of zinc stearate-5 parts by weight of zinc oxide-30 parts by weight of calcium carbonate (trade name "Nanox # 30" manufactured by Maruo Calcium Co., Ltd.)

  Furthermore, 1 part by mass of a vulcanization accelerator (DM: di-2-benzothiazolyl disulfide), 3 parts by mass of a vulcanization accelerator (TBzTD: tetrabenzylthiuram disulfide) and 1.2 parts by mass of a vulcanization agent (sulfur) And kneaded with an open roll for 15 minutes to obtain an unvulcanized rubber composition. Subsequently, a stainless bar core bar having an outer diameter of 6 mm and a length of 252 mm was prepared. Next, the core metal and the unvulcanized rubber composition were integrally extruded using a crosshead extruder to form a rubber roller. Thereafter, heat vulcanization was performed at 160 ° C. for 1 hour, and further, dry polishing using a rotating grindstone and cutting / removal processing of the end portion were performed to obtain a rubber roller having a thickness of 1.25 mm and a length of 232 mm (rubber roller outer diameter φ8 .5 mm).

<Electron beam irradiation method>
The surface of the obtained vulcanized rubber roller was irradiated with an electron beam to obtain a charging roller. For the electron beam irradiation, 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 was used, and nitrogen gas purge (oxygen concentration was about 200 ppm) was performed during irradiation. As the electron beam irradiation conditions, the electron beam irradiation conditions (acceleration voltage / electron current) shown in Table 1 were used, and the feed rate was set to 1.5 m / min so that the electron beam was irradiated for about 1 sec. The rubber roller was conveyed while being rotated at a rotation speed of 500 rpm (however, only Example 2 was set at a feeding speed of 0.75 m / min).

  The electron beam irradiation was performed by using a device schematically shown in FIGS. 2 and 3 for rotation and conveyance of the roller and arranging a cylindrical mask member having a pattern shown in Table 1. The shape of the mask member is a mesh shape, and the wire diameter, mesh size, and material of the mesh are shown in Table 1. As the mesh shape is schematically shown in FIG. 8, the shapes having the same lengths 8a and 8b were used. The mesh is plain weave. The repetition length is the sum of the wire diameter 8c and the opening 8d. The cylindrical mask member had a diameter of 10 mm and a length of 240 mm, covered the entire surface without being in contact with the vulcanized rubber roller, and was arranged coaxially. The distance from the electron beam irradiation hole 9 was 30 mm. The electron beam irradiation hole 9 has an opening of 450 mm in the longitudinal direction of the vulcanized rubber roller and 30 mm in the feed direction.

<Durable image dirt evaluation>
The obtained charging roller is incorporated in the image forming apparatus shown in FIG. 10, and is pressed against each end of the photosensitive drum with a load of 500 g applied, and continuously 6000 by a halftone image in an environment of 23.5 ° C./60%. Durability image stain evaluation was performed through sheets (sometimes referred to as 6K). In this durable image stain evaluation, the following items were evaluated. The obtained results are shown in Table 5.

A continuous image of 6000 sheets was used as a durable image. The presence or absence of image defects in the form of dots or lines due to toner or external additives fixed to the charging roller, or image defects in the form of black or white horizontal stripes due to charging unevenness was visually observed and inspected. Based on the obtained inspection results, image evaluation was performed according to the following criteria.
A: No defective image due to adhesion of toner or external additive to the charging roller B: Very little image defect described above C: Some image defect described above D: The above-mentioned image defects clearly occurred

<Cset image evaluation>
Further, a charging roller different from the above is incorporated in the image forming apparatus shown in FIG. 10, and is pressed with a load of 500 g applied to both ends of the photosensitive drum, and left in an environment of 40 ° C./95% for 30 days. . After standing, Cset image evaluation was performed using 1 to 10 sheets of halftone images as an initial image in an environment of 23.5 ° C./60%. In this Cset image evaluation, the following items were evaluated. The obtained results are shown in Table 5.

The presence or absence of black or white pitch streak image defects due to charging roller pitch and photosensitive drum pitch charging unevenness due to seepage of low molecular weight compounds or the like from the conductive elastic layer of the charging roller was visually inspected and inspected. Based on the obtained inspection results, image evaluation was performed according to the following criteria.
A: No image defect due to seepage from the charging roller. B: Very little image defect. C: Some image defect. D: Image defect. What happened clearly

[Examples 7 to 9]
A vulcanized rubber roller was produced in the same procedure as in Example 1 except that the shape of the mask member was changed to the shape shown in Table 2, and an electron beam was irradiated to obtain a charging roller. The electron beam irradiation conditions are shown in Table 1. The shape of the mask member is a shape as schematically shown in FIG. 6, and square-shaped concave portions are arranged in a pattern as shown in the drawing. What was used this time is a concave portion having a square shape in which 6c and 6d are equal, and the thickness of the thick portion is A, and the thickness of the thin portion is B, which are also shown in Table 1. Note that the repetition length is the same for both 6a and 6b. A polystyrene sheet was used as the material. The outer size of the mask member, the arrangement in the apparatus, and the like are the same as in the embodiment. Further, using the above charging roller, durability image stain evaluation and Cset image evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

[Example 10]
Except that the shape of the mask member was changed to the shape shown in Table 3, a vulcanized rubber roller was prepared and irradiated with an electron beam in the same procedure as in Example 1 to obtain a charging roller. The electron beam irradiation conditions are shown in Table 1. The shape of the mask member is a shape as schematically shown in FIG. 7, in which circular holes are repeatedly arranged with a repetition length 7a (= 7b), and are shown in Table 1 together with the diameter 7c of the circular holes. . The outer size and arrangement of the mask member are the same as in the first embodiment. Further, using the above charging roller, durability image stain evaluation and Cset image evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

[Examples 11 to 12]
After producing a roller in the same procedure as in Example 1, electron beam irradiation was performed using an apparatus using a conveyance and rotation mechanism as schematically shown in FIG. 4 to obtain a charging roll. In FIG. 4, the mask member has a flat plate shape and is arranged at a height of 0.5 mm from the upper end of the roller. Since the roller had an outer diameter of φ8.5 mm, the feed speed was set to 1 m / min and the rotation speed was set to 37.45 rpm. The width of the mask member in the feed direction was set to 27 mm, which is about one circumference of the roller outer periphery. As for the shape of the mask member, in Example 11, meshes having the same shape as in Example 1 were arranged in a flat plate shape. In Example 12, as shown schematically in FIG. 5, a flat plate having a slit parallel to the roller feeding direction was used. As shown in Table 4, the slit-shaped dimensions are those in which a metal wire having a repetition width 5a and a wire diameter 5b is stretched. The flat mask member was arranged parallel to the electron beam irradiation hole at a position 30 mm away from the electron beam irradiation hole, and the vulcanized rubber roller was arranged 0.75 mm below the position and parallel to the electron beam irradiation hole. Further, using the above charging roller, durability image stain evaluation and Cset image evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

[Comparative Examples 1-2]
A charging roller was obtained in the same procedure as in Example 1 except that the electron beam was irradiated without using a mask member. The electron beam irradiation conditions were 80 KV and 35 mA for Comparative Example 1 and 150 KV and 35 mA for Comparative Example 2. Further, using the above charging roller, durability image stain evaluation and Cset image evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

[Comparative Example 3]
A vulcanized rubber roller was obtained in the same procedure as in Example 1. In the present comparative example, the obtained vulcanized rubber roller was not irradiated with an electron beam, but irradiated with ultraviolet rays under the following conditions. Ultraviolet irradiation was performed for 5 minutes by using a low-pressure mercury lamp (manufactured by Harrison Toshiba Lighting) and rotating the vulcanized rubber roller in parallel with the lamp. The distance from the ultraviolet lamp was about 30 mm, and the rotation speed was 30 rpm. Regarding the low-pressure mercury lamp, the ultraviolet ray mainly represented by a wavelength of 254 nm was used, and the ultraviolet ray integrated light quantity at this time was about 10,000 mJ / cm ² (the ultraviolet ray intensity was 35 mW / cm ² ). Thereafter, using the above-described charging roller, durability image stain evaluation and Cset image evaluation were performed in the same manner as in Example 1. The results are shown in Table 5.

DESCRIPTION OF SYMBOLS 1 Extruder 2 Extruder crosshead 3 Core metal feed roller 4 Core metal 5 Cutting / removal processing 6 Rubber roller

Claims (6)

A method for producing a conductive rubber roller having a cored bar and a conductive vulcanized rubber layer having a pattern of regions having different hardness on the surface,
The conductive vulcanized rubber layer formed around the core metal is irradiated with an electron beam through a mask member in which portions having different electron beam transmittances are arranged in a pattern on the peripheral surface of the conductive vulcanized rubber layer. A method for producing a conductive rubber roller, comprising a step of forming regions of different hardness derived from a difference in electron beam irradiation intensity on a surface of a rubber layer.   The method for manufacturing a conductive rubber roller according to claim 1, wherein the mask member is provided with an opening in a slit shape.   The method of manufacturing a conductive rubber roller according to claim 1, wherein the mask member includes a thin film portion and a thick film portion, and the thick film portion is provided in a lattice shape.   The method for producing a conductive rubber roller according to claim 1, wherein the mask member is provided with circular openings at equal intervals.   The method of manufacturing a conductive rubber roller according to claim 1, wherein the mask member has a mesh shape and has a quadrangular opening. The method for producing a conductive rubber roller according to any one of claims 1 to 5, wherein the conductive vulcanized rubber layer contains carbon black and nitrile rubber.

Images