JP4939122B2 - Method for manufacturing conductive elastic roller - Google Patents

Description

  The present invention relates to a conductive elastic roller used in, for example, a copying machine, a printing machine, a laser beam printer, a photographic developing machine, and the like, and more particularly to a conductive elastic roller used in an image forming apparatus using an electrophotographic process. . The present invention also relates to a conductive elastic body extrusion molding apparatus that can be used to manufacture such a conductive elastic body roller, and a crosshead coating die for conductive elastic body extrusion molding used in this apparatus.

  Image formation of electrophotographic printers, copiers, electrostatic recording devices, and the like is composed of charging, exposure, development, transfer, and fixing processes. As shown schematically in FIG. 1, in the image forming apparatus, the conductive roller is a charging roller 92 for charging the surface of the photosensitive drum 91, a developing roller 93 for developing the electrostatic latent image on the surface of the photosensitive drum into a toner image, and a surface on the surface of the photosensitive drum. Used as a transfer roller 94 for transferring the toner image. In addition, these conductive rollers are often used by being pressed against the photosensitive drum. In order to obtain a uniform nip between the photosensitive drum and the conductive roller, and to uniformly charge the photosensitive drum, the conductive roller has a uniform electric resistance value. It is required that the photosensitive drum is less contaminated. In the figure, P is a material to be transferred such as paper.

  The conductive roller has a structure having at least a support shaft located inside and a conductive layer on the outer peripheral surface thereof, but has a low hardness in order to obtain a uniform nip between the photosensitive drum and the conductive roller. Is needed. Therefore, a conductive elastic roller is used in which the conductive layer material on the outer peripheral surface of the conductive roller is made of a rubber-like elastic body.

  For making the electrical resistance value of the conductive elastic roller uniform, a manufacturing method using extrusion molding is widely adopted in order to make the electrical resistance value in the longitudinal direction of the conductive elastic roller uniform.

  As a method for producing a conductive elastic roller using extrusion molding, the following method is known. That is, after forming a conductive elastic body composition into a hollow cylindrical shape by an extrusion molding apparatus, the conductive elastic body composition is solidified by heating or cooling according to the properties of the composition, thereby forming a hollow conductive elastic composition. A cylinder is obtained. A support shaft made of metal or resin is inserted into the internal through-hole of the obtained conductive elastic cylindrical body, and a conductive elastic roller is obtained through secondary processes such as polishing and surface treatment.

In addition, in order to manufacture a conductive elastic roller at a low cost, the conductivity using cover extrusion molding with a crosshead coating die is omitted in order to omit the step of inserting the conductive support shaft into the through hole of the conductive elastic tube. A method for manufacturing an elastic roller is known (Patent Document 1).
JP 2001-353766 A

  A method of manufacturing a conductive elastic roller using coating extrusion molding with a crosshead coating die will be described with reference to FIGS. FIG. 3 is a schematic view of a coating extrusion molding apparatus using a crosshead coating die. The coating extrusion molding apparatus includes an extruder 10, a crosshead coating die 30 having an annular flow path 37 constituted by an inner die 33 and an outer die 35, and a circular die lip 38. First, the conductive elastic composition 11 charged into the inlet 12 of the extruder 10 is plasticized and kneaded in the cylinder 13 by the shearing force received from the cylinder 13 and the screw 14 and conveyed to the extruder cylinder outlet 15. Is done. Subsequently, it passes through the breaker plate 16 and is conveyed to the material introduction port of the crosshead coating die 30. The conductive elastic body composition 11 introduced into the crosshead-covering die 30 is divided by the inner die 33 and then merged again to form a cylindrical shape in an annular channel 37 composed of the inner die 33 and the outer die 35 ( The cross section is formed in an annular shape to form a conductive elastic cylinder. The conductive elastic cylindrical body is previously coated on the support shaft 3 installed in the through hole inside the inner die 33 and is adjusted to a desired outer diameter by a circular die lip 38. In this way, the conductive elastic cylindrical covering 1 having the conductive elastic cylindrical body 2 on the outer periphery of the support shaft 3 as shown in FIG. 2 is obtained. When the conductive elastic cylindrical body is rubber, the conductive elastic cylindrical covering obtained in this way is subjected to a crosslinking step, and when the conductive elastic body composition is a thermoplastic elastomer, a conductive elastic roller is obtained through a cooling step. The cylinder 13 is provided with a deaeration port 17 between the charging port 12 and the extruder cylinder outlet 15.

  By the way, the joint of the conductive elastic composition 11 called a weld line is generated at the point where the conductive elastic composition 11 is divided by the inner die 33 in the annular flow path 37 of the crosshead coating die 30 and joined again. To do. As a result, a weld line 4 may occur in the conductive elastic cylindrical covering 1. Since the weld line 4 is continuously present from the inner peripheral surface to the outer peripheral surface of the conductive elastic cylindrical body 2 of the conductive elastic cylindrical cover 1, the secondary process such as polishing is applied to the conductive elastic cylindrical cover. The weld line 4 also remains on the conductive elastic roller obtained in this way. In the conductive elastic composition, the weld line 4 portion has a different composition from that of the region other than the weld line, so that the electric resistance value is different. For this reason, variation occurs in the electric resistance value in the circumferential direction of the conductive elastic roller. For example, when the conductive elastic roller is a charging roller, the photosensitive drum cannot be uniformly charged, resulting in poor image quality. May occur.

  Therefore, it is desired to reduce the weld line 4 of the conductive elastic cylindrical covering 1. For this purpose, a crosshead covering die (inner spiral die type crosshead covering die) having an annular flow path constituted by an inner die outer peripheral surface having a winding groove on the outer peripheral surface and a smooth outer die inner peripheral surface is provided. The coated extrusion used can be employed.

  In this molding, as shown in FIG. 6, the conductive elastic material composition introduced into the crosshead coating die 30 from the conductive elastic material inlet 32 is diverted by the inner die 33. After that, the conductive elastic body composition is joined again and formed into a cylindrical shape in the annular flow path 37 constituted by the inner die 33 and the outer die 35 to become a conductive elastic cylindrical body. FIG. 6 is a cross-sectional view in a plane perpendicular to the extrusion direction of the crosshead-coated die, and the flow of the conductive elastic composition is indicated by arrows. At this time, a flow (hereinafter referred to as a “circular flow”) that is guided to the winding groove on the outer peripheral surface of the inner die and circulates in the inner die circumferential direction occurs. As a result, a leakage flow that flows in the direction of the extrusion axis is generated in the gap between the winding groove on the outer peripheral surface of the inner die and the inner peripheral surface of the outer die, thereby reducing the weld line generated in the conductive elastic cylinder.

  However, even in the case of cross head covering extrusion using an inner spiral die type cross head covering die, depending on the behavior of the conductive elastic body composition 11 to be extruded through the annular flow path 37, the following phenomenon is caused. May occur. That is, when the conductive elastic composition exhibits a large elastic behavior such as rubber or thermoplastic elastomer in addition to the viscous behavior shown by the thermoplastic resin, the flow around the inner die circumferential direction is It may not occur sufficiently. In this case, the leakage flow generated in the gap between the winding groove on the outer peripheral surface of the inner die and the inner peripheral surface of the outer die is insufficient.

  Furthermore, the behavior of the conductive elastic body composition 11 to be extruded through the annular flow path 37 is elastic like that of rubber and thermoplastic elastomer, in addition to the behavior of viscosity as shown by thermoplastic resins. In the case where a large value is exhibited (when the elastic behavior is large), there is also the following concern. That is, unless the width of the gap between the inner die and the outer die (hereinafter referred to as the annular channel width) is increased, there is a possibility that the conductive elastic body cannot flow in the annular channel and extrusion molding cannot be performed. is there. For this reason, a crosshead coating die for extruding a conductive elastic composition in which the flow behavior in the annular channel exhibits a large elastic behavior needs to increase the annular channel width of the crosshead coating die. is there. However, when the annular channel width is increased, the conductive elastic composition 11 exhibits a large elastic behavior, so that the circulation flow received from the winding groove on the outer peripheral surface of the inner die in the vicinity of the outer die of the annular channel. Power may be insufficient. As a result, the conductive elastic body composition in the vicinity of the outer die of the annular channel cannot sufficiently generate a circular flow, and the leakage flow may be insufficient. For this reason, when an inner spiral die type cross head is used for a conductive elastic composition that exhibits a large elastic behavior, the weld line may not be sufficiently reduced. For this reason, the weld line 4 of the conductive elastic cylindrical body 2 cannot be sufficiently reduced, and the weld line 4 may be generated in the conductive elastic cylindrical covering 1. For this reason, the weld line may remain on the conductive elastic roller obtained by processing the conductive elastic cylindrical covering 1 in the next step, and the circumferential electric resistance value of the roller may vary. In addition, the conductive elastic composition 11 may contain carbon black, carbon fiber, metal powder, metal oxide powder, etc. for imparting conductivity and improving mechanical strength. Since these are likely to be unevenly distributed in the weld line, the variation in the electric resistance value other than the weld line and the weld line is further increased, and the variation in the electric resistance value due to the weld line of the conductive elastic roller may be increased.

The purpose of the present invention, the variation in circumferential electrical resistance of the conductive resilient roller is reduced, the manufacturing method capable of reducing conductive elastic roller an image defect when used in electrophotographic image forming apparatus Is to provide.

According to the present invention,
An extruder for extruding the conductive elastic composition, and a crosshead coating die,
The crosshead coating die is
Has an inner die and an outer die,
The outer peripheral surface of the inner die and the inner peripheral surface of the outer die have an annular flow path that forms the conductive elastic composition extruded from the extruder into a cylindrical shape;
The inner die has a through hole in which the support shaft is mounted in the same direction as the central axis of the annular flow path,
The annular channel has an outlet facing the through hole, and
An apparatus for producing a conductive roller, in which a helically wound groove is formed on the outer peripheral surface of the inner die and the inner peripheral surface of the outer die with the extrusion direction of the conductive elastic composition as a central axis. A method for producing a conductive elastic roller having a support shaft and a conductive elastic body covering the support shaft,
Attaching a support shaft to the through hole of the crosshead covering die;
A conductive elastic body composition containing rubber and carbon black is supplied from the extruder to the crosshead coating die, and the support shaft attached to the through hole is formed in a cylindrical shape in the annular flow path. And a step of coating with the conductive elastic body composition .

According to the present invention, there is provided a method for manufacturing a conductive elastic roller that can reduce variations in the circumferential electric resistance value of the conductive elastic roller and reduce image defects when used in an electrophotographic image forming apparatus. .

  The crosshead coated die for extrusion molding of the conductive elastic body of the present invention includes an inner die having an inner winding groove on the outer peripheral surface of the inner die and a central direction of the extrusion direction on the inner peripheral surface of the outer die. It comprises an annular channel composed of an outer die having an outer vine winding groove as an axis. The conductive elastic material extrusion molding apparatus of the present invention includes this crosshead coating die and a circular die lip. The helical winding shape indicates a state in which the position in the extrusion axis direction is different when it makes a round in the circumferential direction on the inner die outer peripheral surface or the outer die inner peripheral surface, and the direction of the extrusion axis changes in the extrusion axis direction at that time. Define distance as lead. FIG. 7 shows a vine winding, a lead, a lead angle, and the like.

  The conductive elastic roller of the present invention is formed using the conductive elastic body extrusion molding apparatus. Examples of the material for forming the conductive elastic body constituting the conductive elastic roller include natural rubber, butadiene rubber, styrene butadiene rubber (SBR), nitrile rubber, ethylene propylene rubber (EPDM), chloroprene rubber (CR), and nitrile butadiene. Examples thereof include rubber (NBR), epichlorohydrin rubber, butyl rubber, silicone rubber, urethane rubber, fluorine rubber, rubber containing chlorine rubber and thermoplastic elastomer.

  In the extrusion molding apparatus according to the present invention, in a crosshead-coated die having an annular flow path composed of an inner die and an outer die, a winding shape is formed on each of the inner die outer peripheral surface and the outer die inner peripheral surface. Has a groove.

  For this reason, the behavior of the extruded elastic elastomer composition when it flows through the annular flow path greatly increases the behavior of elasticity like rubber and thermoplastic elastomer, in addition to the viscous behavior shown by thermoplastic resins. Even in the case shown, the weld line can be suppressed as follows. That is, when the conductive elastic composition is formed in a cylindrical shape in the crosshead-coated die annular flow path, the winding groove on the inner die outer peripheral surface of the annular flow path and the spiral winding shape on the outer peripheral surface of the outer die are formed. Leakage flows in the direction of the extrusion axis are generated from both grooves. Accordingly, the leakage flow rate in the direction of the extrusion axis in the annular channel increases, the uniformity of the composition of the conductive elastic body composition is improved, and the weld line of the conductive elastic body cylindrical body is reduced. Therefore, the conductive elastic roller obtained from the conductive elastic cylindrical body manufactured by using this extrusion molding apparatus has a small variation in the circumferential electric resistance value of the roller, and electrophotography using this conductive elastic roller. The occurrence of image quality defects in the apparatus can be suppressed.

[Groove quantity]
The number of vine windings existing between one vine winding lead is defined as the number of grooves. The number of grooves on the inner die outer peripheral surface and the outer die inner peripheral surface can be arbitrarily provided, but is preferably in the range of 1 to 36, more preferably 4 to 20. From the viewpoint of suppressing an increase in the flow resistance of the conductive elastic composition in the vine winding groove by setting the number of grooves to 36 or less, the number of grooves is preferably 36, and 20 or less. Is more preferable.

  From the viewpoint of uniformizing the amount of extrusion in the circumferential direction at the annular channel outlet, the number of grooves is preferably four or more.

[Groove shape]
As for the shape of the vine winding groove, the shape when the groove shape is projected onto a surface whose normal is the tangent of the vine winding (hereinafter referred to as the projected groove shape) is, for example, a semicircular shape or a semi-elliptical shape. , Polygonal shapes (eg, triangles, rectangles, trapezoids, etc.), etc. Among these, from the viewpoint of preventing the retention of the conductive elastic composition, a streamline shape having no corner portion in the projected groove shape such as a semicircular shape and a semi-elliptical shape is desirable. The size and shape of the projected groove shape may change along the coiled groove.

[Lead angle of helical winding groove]
The angle formed by the vine winding groove and a plane perpendicular to the axis of the extrusion direction passing through one point on the vine winding groove is projected onto a plane perpendicular to the radial line of the inner die or outer die passing through the point. The angle is defined as the lead angle (see FIG. 7).

  The lead angle of the coiled groove on the outer peripheral surface of the inner die and the lead angle of the coiled groove on the inner peripheral surface of the outer die can be set arbitrarily. The lead angle of the vine winding groove allows the lead angle to be changed at any position on the vine winding groove.

[Groove arrangement]
The arrangement of the winding groove on the outer peripheral surface of the inner die and the arrangement of the winding groove on the inner peripheral surface of the outer die can be arbitrarily set, but they are arranged so that the circumferential extrusion amount at the annular channel outlet is uniform. It is desirable.

[Annular channel]
Further, the extrusion molding apparatus according to the present invention is not limited to an apparatus for forming a single-layer conductive elastic roller. A winding groove is formed on the outer peripheral surface of the outer die, and a second outer die having an inner peripheral surface having a winding groove extending on the outer periphery is provided to provide a second annular channel. Thus, a two-layered conductive elastic cylinder can be provided on the support shaft. Such an apparatus can be applied to the production of a two-layered conductive elastic roller. Further, by using a third or more outer die and laminating a plurality of annular flow paths in the same manner as described above, a multilayer (three layers or more) conductive elastic body roller can be obtained.

  Further, it is preferable that the winding direction of each of the winding-shaped grooves on the outer circumferential surface of the inner die and the inner winding surface of the outer die is the same.

  In this case, when the behavior of the extruded elastic elastomer composition flowing through the annular flow channel shows a large elastic behavior, such as rubber or thermoplastic elastomer, in addition to the viscous behavior shown by thermoplastic resins The following effects can be obtained. That is, when the conductive elastic body composition is formed into a cylindrical shape in the annular flow path to obtain a conductive elastic cylindrical body, the winding groove on the outer peripheral surface of the inner die and the winding shape of the inner peripheral surface of the outer die Leakage flow is generated from the groove. And since the winding direction of the coiled groove on the inner die outer peripheral surface and the coiled groove on the outer die outer peripheral surface are the same, the circumferential flow of the conductive elastic composition in the annular channel is growing. Therefore, the leakage flow in the direction of the extrusion axis generated from the helical winding groove on the inner die outer peripheral surface and the helical winding groove on the outer die inner peripheral surface increases. As a result, the uniformity of the composition of the conductive elastic body composition is improved and the weld line of the conductive elastic cylinder can be further reduced, and the weld line of the conductive elastic roller obtained from the conductive elastic cylinder is obtained. Can be further reduced. Accordingly, the variation in the circumferential electric resistance value in the conductive elastic roller is further reduced.

  Conductive elasticity produced using an extrusion molding machine having a crosshead coated die for extrusion molding of a conductive elastic body in which the winding direction of the winding grooves on the inner peripheral surface and inner peripheral surface of the opposing die is the same direction. The body roller has a smaller variation in the circumferential electrical resistance value of the roller. As a result, it is possible to further reduce the occurrence of image quality defects in an electrophotographic apparatus using the conductive elastic roller.

  The extrusion molding apparatus of the present invention is an extrusion molding apparatus that includes a crosshead covering die having an annular flow path constituted by an inner die outer peripheral surface and an outer die inner peripheral surface, and a circular die lip. This device has an annular flow path having an inner spiral groove on the inner die outer peripheral surface and an outer spiral groove on the outer die inner surface while having an outer spiral groove on the outer die inner peripheral surface. It has the crosshead coating die | dye which comprises these. Hereinafter, a preferred embodiment of the present invention will be described with reference to FIG.

  FIG. 4 shows an example of an extrusion molding apparatus according to the present invention. This apparatus has an extruder 10 and an annular coating die 30 having an annular flow path 37. The extruder 10 has a loading port 12 for charging the conductive elastic composition 11 and a cylinder 13 and a screw 14 for conveying the conductive elastic composition 11 while plasticizing and kneading. Further, it has a discharge port (extruder cylinder outlet) 15 and a breaker plate 16 for discharging the plasticized and kneaded conductive elastic composition. The cylinder 13 has a deaeration port 17 between the input port 12 and the discharge port 15, and a vacuum pump (not shown) is connected to the deaeration port 17. In addition, the shape of the conductive elastic composition to be charged into the charging port 12 is preferably a shape capable of continuously supplying the conductive elastic composition to the extruder, and specifically, a strip shape, a string shape, a granular shape, or the like. The shape is suitable. The breaker plate 16 is allowed to be provided with a metal mesh for the purpose of removing foreign substances in the conductive elastic composition or increasing the pressure in the cylinder.

  In this example, a screw type extruder was shown as an apparatus for supplying the conductive elastic composition to the crosshead coating die. However, as the conductive elastic body composition supply device, a gear pump type extruder or a combination device of a screw extruder and a gear pump can be used in addition to the screw type extruder.

  The discharge port 15 of the extruder 10 is connected to the conductive elastic composition introduction port of the outer die 35 constituting the crosshead coating die 30. The crosshead covering die 30 includes an annular flow path 37 constituted by the outer peripheral surface of the inner die 33 and the inner peripheral surface of the outer die 35. While the inner die 33 is fitted and fixed to a part of the inner peripheral surface of the outer die 35, the inner die 33 becomes a wall surface on the inner peripheral side of the annular flow path 37 and constitutes an inner peripheral surface of the outer die 35 and the annular flow path. The inner peripheral surface of the outer die 35 is a wall surface on the outer peripheral side of the annular flow path 37. The inner die 33 has a through hole in the same direction as the central axis of the annular flow path 37, and the support shaft 3 can be attached to the through hole. A circular die lip 38 is attached to the end of the crosshead covering die 30 in the extrusion direction, and a part of the support shaft 3 (part of the support shaft 3) is formed by a conductive elastic cylindrical body (the cross section is circular) as shown in FIG. The conductive elastic cylindrical covering 1 covered with) is discharged. The discharged conductive elastic cylindrical covering 1 is heated and crosslinked or cooled and solidified to obtain a conductive elastic roller.

  The support shaft 3 is installed in the inner die through hole in a state where it can freely reciprocate. The material of the support shaft is not particularly limited, and for example, metal or resin is used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by this.

[Example 1]
An extrusion molding apparatus having the structure shown in FIG. 4 was used. Specifically, an extruder with a deaeration port having a cylinder diameter of 50 mm and L / D (cylinder length / diameter ratio) of 22 was used. As shown in FIG. 4, as a crosshead covering die, a crosshead covering die having an annular flow path composed of an inner die having a winding groove on the outer peripheral surface and an outer die having a winding groove on the inner peripheral surface. It was used. The shape of the vine winding groove installed on the inner die outer peripheral surface is 12 vine winding groove grooves, the lead angle of the vine winding groove is 60 °, and the arrangement of the vine winding groove is on the inner die outer peripheral surface. Arranged at equal intervals. In addition, when the vine winding groove is projected onto a plane perpendicular to the lead angle, the projection shape of the vine winding groove (projection groove shape) is a semi-elliptical shape, and the winding direction of the vine winding is the right-handed screw direction. It was. On the other hand, the shape of the vine winding grooves on the inner peripheral surface of the outer die is 6 vine winding grooves, the lead angle of the vine winding is 45 °, and the arrangement of the vine winding groove is equally spaced on the inner peripheral surface of the outer die. Arranged. Further, the shape of the projected groove was semicircular, and the winding direction of the spiral winding was the left-handed screw direction.

In addition, as the conductive elastic composition,
-NBR (trade name "Nipol DN219": manufactured by Nippon Zeon Co., Ltd.) 100 parts by mass,
Carbon black 1 (conductive particles) (trade name “Asahi HS-500”: manufactured by Asahi Carbon) 14 parts by mass,
Carbon black 2 (conductive particles) (trade name “Ketjen Black EC600JD”: manufactured by Lion) 6 parts by mass,
-1 part by weight of zinc stearate,
-5 parts by mass of zinc oxide,
-10 parts by mass of liquid epoxidized polybutadiene (trade name "Adekaizer BF-1000": manufactured by Asahi Denka Kogyo Co., Ltd.)
・ 30 parts by weight of calcium carbonate (trade name “Nanox # 30”: manufactured by Maruo Calcium Co., Ltd.) ・ Bridged NBR particles containing 5% by weight of calcium carbonate (trade name “Baymod N PV KA 8641”: manufactured by Bayer Co., Ltd.) 50 parts by mass,
-1 part by weight of dibenzothiazolyl disulfide (trade name “Noxeller DM-P” manufactured by Ouchi Shinsei Chemical Co., Ltd.)
A rubber obtained by kneading 3 parts by mass of tetrabenzylthiuram disulfide (trade name “Perkasit TBzTD”: manufactured by Flexis Co., Ltd.) and 1.2 parts by mass of sulfur (vulcanizing agent) with an open roll was used.

  A round bar-shaped steel support shaft having an outer diameter of 6 mm and a length of 251 mm was mounted in advance on the inner die inner through-hole constituting the crosshead coating die.

  Using an extrusion molding apparatus having the structure shown in FIG. 4, the cylinder, screw, crosshead coating die, and die lip are molded at a temperature of 100 ° C., on a steel support shaft having an outer diameter of 6 mm at a screw rotation speed of 10 revolutions. A conductive elastic cylindrical covering was obtained by coating the elastic composition.

  The obtained conductive elastic cylindrical covering was crosslinked in a hot air oven at 160 ° C. for 1 hour to obtain a conductive elastic roller. Further, the end of the conductive elastic body (the hardened conductive elastic cylindrical body) is cut so that the length of the conductive elastic body of the conductive elastic roller becomes 230 mm, and this conductive elastic body portion is polished with a rotating grindstone. The conductive elastic body portion was formed into a crown shape having an end diameter of 8.3 mm and a central portion of 8.5 mm. Furthermore, an ultraviolet lamp having a wavelength of around 250 nm was installed in parallel with the axial direction of the obtained roller, and the roller was irradiated with ultraviolet rays for 2 minutes while rotating in the circumferential direction to form a highly crosslinked layer on the surface, and then charged. A roller.

[Example 2]
Winding groove shape of the inner die outer peripheral surface, 12 grooves, lead angle 60 °, groove arrangement at equal intervals on the inner die outer peripheral surface, projected groove shape is semi-circular, winding direction of the winding Is the right-hand screw direction. In addition, the winding groove shape of the outer peripheral surface of the outer die is 12 grooves, the lead angle is 60 °, the groove arrangement is equally spaced on the inner peripheral surface of the outer die, and the projected groove shape is trapezoidal. The wire winding direction was the left-handed screw direction. Other than that was carried out similarly to Example 1, and obtained the charging roller.

[Example 3]
Winding groove shape on the outer peripheral surface of the inner die, 12 grooves, lead angle 60 °, groove arrangement at equal intervals on the outer peripheral surface of the inner die, semi-circular projection groove shape, helical winding winding The direction was the right-handed screw direction. In addition, the winding-like groove form of the outer peripheral surface of the outer die is 12 grooves, the lead angle is 60 °, the grooves are arranged at equal intervals on the outer peripheral surface of the outer die, and the projected groove shape is semicircular. The coil winding direction was the right-handed screw direction. Other than that was carried out similarly to Example 1, and obtained the charging roller.

[Comparative Example 1]
Winding groove shape of the inner die outer peripheral surface, 12 grooves, lead angle 60 °, groove arrangement at equal intervals on the inner die outer peripheral surface, projected groove shape is semi-circular, winding direction of the winding Is the right-hand screw direction. The inner surface of the outer die was a smooth surface. Other than that was carried out similarly to Example 1, and obtained the charging roller.

[Comparative Example 2]
A charging roller was obtained in the same manner as in Comparative Example 1 except that the lead angle of the winding groove on the outer peripheral surface of the inner die was 45 °.

  The conditions of the above examples and comparative examples are listed in Table 1.

  The charging rollers obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were measured for variation in electrical resistance value in the circumferential direction and image evaluation.

<Dispersion of electrical resistance value>
The variation in the electrical resistance value in the circumferential direction of the charging roller was measured using the electrical resistance measuring device for the electrophotographic conductive member shown in FIG. By pressing both ends of the support shaft 3 of the charging roller 5 with pressing means (not shown), the charging roller is brought into pressure contact with the cylindrical stainless steel drum 81 and is rotated following the rotational driving of the stainless steel drum 61. In this state, a DC voltage is applied to the supporting shaft 3 of the electrophotographic conductive member (charging roller) using an external power source 82, and the voltage applied to the reference resistor 83 connected in series to the stainless steel drum 81 is used to determine the charging roller. The electrical resistance was calculated.

  A small power source PL-650-0.1 (trade name, manufactured by Matsusada Precision Co., Ltd.) was used as the DC power source, and a digital multimeter Fluke 83 (trade name, manufactured by Fluke) was used as the voltmeter.

  The electrical resistance of the charging roller is as follows: at a temperature of 23 ° C. and a relative humidity of 50%, using the apparatus of FIG. 5 and applying a DC voltage of 200 V between the support shaft and the stainless drum every 0.1 seconds. Measured for 5 seconds. The maximum value / minimum value of the measured values was calculated as the variation of the electric resistance value.

<Image evaluation>
The electroconductive elastic roller for electrophotography obtained in Examples 1 to 3 and Comparative Examples 1 and 2 described above is charged to LBP5500 (trade name, manufactured by Canon Inc.) which is an electrophotographic apparatus having the configuration of FIG. A roller was attached together with a member to be charged (photosensitive drum). The object to be charged used here has a charge transport layer mainly composed of a polycarbonate resin. Then, a halftone image (an image in which a horizontal line having a width of 1 dot and an interval of 2 dots was drawn in a direction perpendicular to the rotation direction of the photosensitive drum) was output in an environment of a temperature of 15 ° C. and a relative humidity of 10%. At this time, strip-like or stripe-like “image density unevenness” due to variation in the circumferential electric resistance value of the charging roller was evaluated. Based on the density difference between the bright part and the dark part, the following criteria were used for evaluation. In practical use, there is no problem as long as the evaluation is Δ.
○: No difference in density.
Δ: Concentration difference is slight.
X: There is a clear density difference.

  Table 2 shows the variation in electric resistance values of the conductive charging rollers obtained in Examples 1 to 3 and Comparative Examples 1 and 2 and the results of image evaluation.

  As described above, according to the extrusion molding apparatus of the present invention, it is possible to obtain a conductive elastic roller having a small variation in circumferential electric resistance value by reducing the weld line during the coating extrusion molding.

It is a schematic diagram for demonstrating the image forming apparatus by an electrophotographic process. It is a schematic diagram for demonstrating the electroconductive elastic cylindrical covering obtained from an extrusion molding apparatus. It is a typical fragmentary sectional view for demonstrating the conventional coating extrusion apparatus which has a crosshead coating die. It is a typical fragmentary sectional view for demonstrating the extrusion molding apparatus using the crosshead coating die of this invention. It is a schematic diagram of a conductive elastic roller electrical resistance measuring device. It is typical sectional drawing for demonstrating the shunting and confluence | merging of the electroconductive elastic body composition by the inner side die in a crosshead coating die. It is a schematic diagram for demonstrating a vine winding, a lead, and a lead angle.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Conductive elastic cylindrical covering body 2 ... Conductive elastic cylindrical body 3 ... Support shaft 4 ... Weld line 5 ... Conductive elastic body roller 10 ... Extruder 11 ... Conductive elastic body composition 12 ... input port 13 ... cylinder 14 ... screw 15 ... discharge port 16 ... breaker plate 17 ... deaeration hole 30 ... crosshead coating die 32 .. Conductive elastic body composition inlet 33... Inner die 35... Outer die 37... Annular channel 38... Circular die lip 81. ..Reference resistance 91 ... photosensitive drum 92 ... charging roller 93 ... developing roller 94 ... transfer roller

Claims (1)

An extruder for extruding the conductive elastic composition, and a crosshead coating die,
The crosshead coating die is
Has an inner die and an outer die,
The outer peripheral surface of the inner die and the inner peripheral surface of the outer die have an annular flow path that forms the conductive elastic composition extruded from the extruder into a cylindrical shape;
The inner die has a through hole in which the support shaft is mounted in the same direction as the central axis of the annular flow path,
The annular channel has an outlet facing the through hole, and
An apparatus for producing a conductive roller, in which a helically wound groove is formed on the outer peripheral surface of the inner die and the inner peripheral surface of the outer die with the extrusion direction of the conductive elastic composition as a central axis. A method for producing a conductive elastic roller having a support shaft and a conductive elastic body covering the support shaft,
Attaching a support shaft to the through hole of the crosshead covering die;
Formed in the crosshead coating die from the extruder, supplying conductive elastic composition containing a rubber and carbon black, the support shaft attached to the through hole, the Oite cylindrically said annular channel And a step of coating with the conductive elastic body composition thus formed.

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