JP2001062849A - Rubber roller and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foam rubber roller which can be manufacture with high reproducibility using a molding die and has less surface roughness and high shape accuracy as well as a method for manufacturing the foam rubber roller. SOLUTION: This rubber roller has a double layer structure of a cylindrical elastic material layer consisting of a foamed rubber layer 11 formed close to the outer periphery of a core 10 and a non-foamed rubber layer 12 formed outside the layer 11. The vuncanization rate of an unvulcanized nonfoamed raw material composition which is a raw material for the non-formed rubber layer 12 is set to be lower than the vulcanization rate of an unvulcanized unfoamed raw material composition which is a raw material for the foamed rubber layer 11. Further, the Mooney viscosity of the unvulcanized non-foamed raw material composition is set to be lower than the Mooney viscosity of the unvulcanized unfoamed raw material composition. Thus the compositions are made to foam and vulcanized in a molding die to obtain the cylindrical elastic material layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber roller in which an elastic body composed of two layers, a foamed rubber layer and a non-foamed rubber layer, is formed on an outer peripheral surface of a cored bar, and a method of manufacturing the same. More specifically, for example, various rubber rollers used in an image forming apparatus using an electrophotographic process, that is, suitable for a charging / transfer roller, a developing roller, or a transport roller, an image fixing roller, an intermediate transfer member, and the like. The present invention relates to a rubber roller that can be used and a method for manufacturing the same.

[0002]

2. Description of the Related Art In an electrophotographic process, in a charging / transfer process, a non-contact type corona discharge has been conventionally used for charging a photosensitive member surface. It has been found that ozone and the like are generated during the corona discharge, and that the generated ozone and the like are factors that cause deterioration of the photoconductor surface. Furthermore, if dirt adheres to the wire used for corona discharge, the surface of the photoreceptor may become non-uniformly charged, thereby affecting image quality, for example, causing white spots and black streaks on the image. are doing.

Conventionally, as a method of charging the photoreceptor surface instead of the corona discharge, a method of contact charging / transfer has been studied by many researchers. FIG. 1 is a cross-sectional view schematically showing an example of the configuration of an electrophotographic apparatus using a contact charging / transfer member proposed by these studies. In this device configuration, the member to be charged is an image bearing member. Specifically, the member to be charged is composed of a conductive base layer using aluminum or the like and a photoconductive layer formed of amorphous silicon or the like on the outer peripheral surface thereof. Drum-type photoconductor 1. A roller-shaped charging member 2 is provided so as to be in contact with the photoconductor 1, and uniformly charges the surface of the photoconductor 1 to a predetermined potential.

The charging member 2 in the form of a roller, that is, a charging roller, is composed of a central metal core and a layer of conductive elastic material formed on the outer periphery thereof. The charging roller 2 is pressed against the photoreceptor 1 with a predetermined pressing force by a pressing means using a spring or the like, and accordingly, the photoreceptor 1 is driven to rotate. On the other hand, a DC or DC + AC bias is applied to the metal core of the charging roller 2 to contact-charge the photoconductor 1 to a predetermined potential. At this time, in order to obtain a good copy image, the surface of the photoconductor 1 needs to be charged to a uniform potential, that is, a uniform contact state of the charging roller 2 and
Conductivity uniformity is required. The charged surface of the photoconductor 1 is exposed to image information using an exposure unit 3 using a laser, an LED, or the like as a light source, thereby forming an electrostatic latent image corresponding to the target image information.

Then, toner is applied to the electrostatic latent image by the developing means 4 to visualize the electrostatic latent image as a toner image. The toner image formed on the surface of the photoconductor 1 is charged from the back surface of the transfer material 5 (copy paper or the like) by a transfer member 6 (transfer roller) with a polarity opposite to that of the toner, so that the transfer material 5 Transfer to the surface. After transferring the toner image,
The transfer material 5 is separated from the surface of the photoreceptor 1, and an image is fixed by heat and pressure in a fixing member 7 (fixing roller) installed earlier. On the other hand, after the image transfer, the surface of the photoreceptor 1 is removed by a cleaning unit 8 in a series of transfer steps to remove attached matter such as residual toner remaining on the surface.
It is restored to a clean surface again. By repeating this, the electrophotographic process can be performed continuously.

In this type of apparatus, as shown in FIG. 1, for example, rollers are used for the charging member 2, the transfer member 6, the fixing member 7, and the like. For example, a charging roller or the like is composed of a core metal rotatably supported at both ends, and a conductive elastic layer provided in a columnar shape on the outer periphery of the core metal. Thus, for example, the conductive elastic body used for the charging roller, when applying the AC component as described above, suppresses the charging noise caused by the AC component, and furthermore, is always in pressure contact. In order to prevent the surface of the photoconductor from being damaged, a material having a low surface hardness and a controlled resistance is used. Specifically, desired conductivity and hardness are often achieved by dispersing conductive particles in a foam having low hardness.

The surface of the foam itself generally has a tendency to have a rough surface. If the contact with the photoreceptor becomes nonuniform, the discharge tends to become nonuniform. If the contact pressure is increased to increase the contact, the surface of the photoreceptor is likely to be unevenly worn or scraped during repeated use, and there is also a problem of shortening the service life. To eliminate the drawbacks caused by the properties of the foam itself, apply a conductive paint to the surface of the conductive elastic body using the foam, or cover the surface with a conductive tube with a smooth surface. A method of forming a coating layer has also been applied.
With this coating layer, the surface roughness is improved and the roller resistance is adjusted.

A method of manufacturing a roller using a foam as a conductive elastic body includes a method in which a polymer material of a foam, a foaming agent, and various additives are blended, and a kneaded material composition is extruded into a cylindrical shape. After vulcanization / foaming, a core metal is pressed into the center of the cylindrical shape, and the outer periphery is polished so as to have a desired outer diameter and trimmed, or the core metal is positioned in advance in the center. Using the arranged molding die, put the raw material composition together with the core metal inside the mold, heating the molding die,
A method of forming a cylindrical foamed elastic body having a predetermined outer diameter around a core metal by vulcanization and foaming is known.

[0009] The foam roller manufactured by these methods is:
For the purpose of eliminating surface defects and the like and improving the surface roughness as described above, for example, coating of a coating layer is performed.
If the surface is rough, it is necessary to increase the thickness of the coating layer, and as a result, problems such as an increase in roller hardness may occur.

[0010] As a method of forming a coating layer having an appropriate thickness, when the surface roughness of the foam is not sufficiently small, a foamed material to be a foam and a non-foamed material to be a coating layer are separately extruded. A method is also known in which a roller having a structure in which a non-foamed layer covering an internal foamed layer is provided by simultaneously forming a concentric cylindrical shape using a machine and then vulcanizing the same.

If there is no external non-foaming layer, the raw material composition of the foam, that is, the foaming material, starts the foaming reaction, and at the same time, the gap between the cell forming the foamed structure and the cell adjacent thereto is formed. A depression is formed, and the surface expands while leaving the fine irregularities on the surface, and is pressed against the inner wall of the mold. When the roller surface is formed by this pressing, most of the surface irregularities are crushed, but a small amount of unevenness and wrinkles often remain due to insufficient local pressing. Also, the cell may be exposed on the surface by chance, and the trace of the cell may form a pinhole. On the other hand, if there is a non-foamed layer on the outside, even if there is a gap in the adjacent cell, it will be supported by the outer non-foamed layer, and when pressed against the inner wall of the mold, fine irregularities and wrinkles will remain and generate Therefore, a roller having low surface roughness can be obtained, which is a useful method.

However, if the thickness of the layer, the Mooney viscosity, and the vulcanization rate are unbalanced between the inner foamed layer and the outer non-foamed layer, the foamed material serving as the inner foamed layer is not sufficiently foamed. In such a case, the accuracy of the outer diameter is reduced, or the deflection of the shaft is increased. Also, if the expansion ratio is not sufficiently increased, the hardness will increase.On the other hand, if the support by the non-foamed layer is insufficient, the gas due to the foam will penetrate the non-foamed layer and generate a pinhole on the surface. The problem is inherent, such as causing the surface to be roughened.

As means for preventing the generation of pinholes on the surface, as described in JP-A-10-156917, the scorch time of the non-foamed layer is reduced in order to cope with the phenomenon that air bubbles escape to the outside during foaming. However, under such conditions, if the thickness of the non-foamed layer is too large, there is a possibility that the foaming ratio may not be sufficiently increased.

[0014]

Conventionally, attempts have been made to improve surface roughness and form accuracy while maintaining appropriate roller hardness, but there is still room for improvement. . For example, there is still a need for a method of manufacturing an elastic roller capable of improving surface roughness while maintaining good roller hardness with good reproducibility.

The present invention solves the above problems,
An object of the present invention is to provide a foamed rubber roller that can be produced with good reproducibility, has a small surface roughness, and has a high shape accuracy by using a molding die, and a method of manufacturing the same. More specifically, the purpose of the present invention is, for example,
A foam rubber roller having a small surface roughness and a high shape accuracy while maintaining a roller hardness suitable for a rubber roller used in an electrophotographic apparatus or the like, and the foam rubber roller is manufactured with good reproducibility using a molding die. An object of the present invention is to provide a manufacturing method that enables the above. Furthermore, the present invention provides a foamed rubber roller satisfying the above characteristics, and a method of manufacturing the same, in a rubber roller used for an electrophotographic apparatus or the like, particularly a rubber roller for a charging member used for charging an electrophotographic photosensitive member. It is in.

[0016]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors changed the properties, vulcanization and foaming conditions of a raw material composition used for producing a foamed rubber roller in various ways, and obtained Research was conducted to compare and examine the characteristics. As a result, when a cylindrical elastic body layer having a two-layer structure having a foamed layer on the inner side and a non-foamed layer on the outer side is formed around the core using a molding die, the raw material of the foamed layer is not used. The vulcanized unfoamed raw material composition and the unvulcanized non-foamed raw material composition that is the raw material of the non-foamed layer are obtained by the vulcanization rate of the unvulcanized unfoamed raw material composition. If it is slower and the Mooney viscosity of the unvulcanized non-foamed raw material composition is lower than the Mooney viscosity of the unvulcanized unfoamed raw material composition, the surface roughness of the formed roller becomes sufficiently small, The inventors have found that shape accuracy such as diameter accuracy and runout is high, and that an appropriate roller hardness can be obtained with good reproducibility, and based on such knowledge, the present invention has been completed.

That is, the rubber roller of the present invention is a rubber roller in which a concentric cylindrical elastic body having a foamed rubber layer on the inner side and a non-foamed rubber layer on the outer side is formed on the outer periphery of the cored bar. The foamed rubber layer is a foamed rubber obtained by mixing and kneading an unvulcanized unfoamed raw material composition obtained by blending a polymer raw material of a foam, a foaming agent, and various additives to be added as necessary, and kneading the mixture. The non-foamed rubber layer is made of a non-foamed rubber obtained by vulcanizing an unvulcanized non-foamed raw material composition obtained by compounding a polymer raw material and various additives to be added as necessary. The vulcanization rate of the unvulcanized non-foamed raw material composition is lower than the vulcanization rate of the unvulcanized non-foamed raw material composition, and the Mooney viscosity of the unvulcanized non-foamed raw material composition is Unvulcanized unfoamed raw material composition Knead viscosity, the unvulcanized non-foamed raw material composition is formed as a concentric cylindrical laminate integrally and simultaneously extruded on the outer periphery of the unvulcanized unfoamed raw material composition, and the concentric cylinder The core metal is disposed in the shape of the laminated body so that the axial center thereof is coincident, has a predetermined cylindrical inner peripheral surface larger than the outer periphery of the concentric cylindrical laminated body, and the core metal is Using a cylindrical molding die having a lid at both ends for holding on a concentric axis of the cylindrical inner peripheral surface, the laminated body integrally disposed with the core metal, in the molding die After being subjected to vulcanization and foaming treatment, the outer peripheral surface of the laminate is pressed against the inner peripheral surface of the molding die along with the foaming, and a foamed rubber layer is formed on the inside formed by molding, and a non-foamed rubber layer is formed on the outside thereof. A rubber roller having a concentric cylindrical elastic rubber layer having a foamed rubber layer. .

Further, the method for producing a rubber roller according to the present invention comprises:
A method of manufacturing a rubber roller in which a concentric cylindrical elastic body having a foamed rubber layer on the inner side and a non-foamed rubber layer on the outer side is formed on the outer periphery of the core metal, wherein the raw material of the foamed rubber layer is
When vulcanized and foamed, an unvulcanized unfoamed raw material composition obtained by blending and kneading a polymer raw material of a foam, a foaming agent, and various additives to be added as necessary to obtain a desired foamed rubber material And the raw material of the non-foamed rubber layer is
When vulcanized, a polymer material and various additives to be added as necessary are blended and kneaded to obtain a desired non-foamed rubber material to obtain a desired non-foamed rubber material. Vulcanization rate of the product, slower than the vulcanization rate of the unvulcanized unfoamed raw material composition, and, the Mooney viscosity of the unvulcanized non-foamed raw material composition, the unvulcanized unfoamed raw material composition A Mooney viscosity smaller than that of the unvulcanized non-foamed raw material composition, and a concentric cylindrical laminate formed simultaneously and integrally on the outer periphery of the unvulcanized unfoamed raw material composition; The core metal is arranged in the shape of the laminated body, the axial center thereof is aligned, larger than the outer periphery of the concentric cylindrical laminated body, has a predetermined cylindrical inner peripheral surface, and the core metal is Has lids at both ends for holding on the concentric axis of the cylindrical inner peripheral surface Using a cylindrical molding die, the laminate formed integrally with the cored bar is placed in the molding die, subjected to vulcanization and foaming treatment, and with the foaming, the laminate is formed. The outer peripheral surface is pressed against the inner peripheral surface of the molding die, a foamed rubber layer is formed on the inner side formed by molding, and a concentric cylindrical elastic rubber layer having a non-foamed rubber layer is formed on the outer side. This is a method of manufacturing a rubber roller.

In the rubber roller of the present invention, the thickness of the non-foamed rubber layer is preferably 50% or more of the cell diameter of the foamed rubber layer in the foamed rubber layer. Further, in the rubber roller of the present invention, both the foamed rubber layer and the non-foamed rubber layer may have conductivity. In addition, the rubber roller of the present invention may have a structure in which one or more conductive coating thin film layers are provided on the outer peripheral surface of the elastic rubber layer.

In the above rubber roller of the present invention, if the cylindrical elastic body formed on the outer periphery of the cored bar has conductivity, for example, it is disposed in contact with the surface of an electrophotographic photoreceptor, It can be suitably used for a charging roller used for charging a body.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION In the rubber roller of the present invention, an elastic layer, which is a main component of the roll portion, is formed integrally with a foamed rubber layer, which mainly provides elasticity, on the outside of the roll portion. The non-foamed rubber layer that governs the shape has a concentric cylindrical two-layer structure. The outer surface shape, when performing the foaming process, in order to make the unvulcanized unfoamed raw material composition into a foamed rubber layer, a predetermined shape and size, as well as using a molding die formed on a smooth inner surface. , Formed by pressing with foaming. That is,
The outline of the outer shape of the rubber roller of the present invention is originally defined by the inner surface shape of the molding die.

Accordingly, the rubber roller according to the present invention has a configuration in which an example is shown in FIG. 2 when a cross section of the roll portion is schematically shown. When the surface of the elastic layer molded using the mold is further provided with one or two or more coating thin film layers, the cross section has, for example, the shape schematically shown in FIG. Become. In FIGS. 2 and 3, metal is often used for the core metal 10, but a material having conductivity such as a conductive resin can be used, for example.
A foamed rubber layer 11 and a non-foamed rubber layer 12 are formed concentrically on the outer periphery of the cored bar 10 as elastic layers having a two-layer structure. In FIG. 3, one or more coating thin film layers 13 are provided on the outer peripheral surface of the elastic layer. Normally, the thickness of the non-foamed rubber layer 12 is
The thickness of the cover thin film layer 13 is selected to be significantly smaller than the thickness of the foamed rubber layer 11.

That is, for example, the coating thin film layer 13
The charging roller used for charging the photoreceptor, which is arranged in contact with the surface of the electrophotographic photoreceptor, is formed by a coating film coated with a conductive paint or a coating with a conductive tube formed of a conductive thin film. I do. In the charging roller, in order to make the potential on the roller surface uniform, a coating thin film layer made of the above-mentioned conductive material is provided to further increase the conductivity on the roller surface. Further, in the electrophotographic apparatus, when used as a transfer member, similarly to the charging roller, in order to make the potential on the roller surface uniform, a coating thin film layer made of the above-described conductive material is provided. It is configured to further increase the conductivity. Alternatively, in a roller used as a fixing member that applies heat and pressure to fix a transferred toner image, a coating or the like that increases durability against heat or the like may be provided as the coating thin film layer 13. As described above, the coating thin film layer 13 is formed according to the purpose of use.
It is preferable to appropriately select a thin film layer having desired characteristics.

In the configuration shown in FIG. 3, a coating thin film layer 13 is provided on the outermost surface of the roller, and the surface shape, surface roughness, etc., of the non-foamed rubber layer 1 before the coating thin film layer 13 is formed.
A slight improvement is seen from the surface shape and surface roughness of No. 2.
However, the film thickness of the coating thin film layer 13 is formed so as to be uniform within the roller surface, and in many cases, the surface shape and surface roughness of the non-foamed rubber layer 12 are different from those of the outermost surface of the roller. It is thin enough to be reflected on the surface roughness.

The rubber roller of the present invention can be manufactured, for example, by the following procedure.

First, a non-vulcanized non-foamed raw material composition for a non-foamed rubber layer is extruded simultaneously and integrally on the outer periphery of the unvulcanized unfoamed raw material composition for a foamed rubber layer. Without a laminate, a core metal in the concentric cylindrical laminate,
The one in which the axial centers are aligned is produced. The formation of the concentric cylindrical laminate is performed using an apparatus capable of simultaneously extruding two types of raw material compositions from a single extrusion head as shown in FIG. The apparatus shown in FIG. 4 includes an extruder 14 for a foamed rubber layer, an extruder 15 for a non-foamed rubber layer, and an extrusion head 16 disposed at the center thereof. The inside of the extrusion head 16 has, for example, a configuration shown in FIG. Concentrically, a flow path 20 for the unvulcanized unfoamed raw material composition and a flow path 19 for the unvulcanized non-foamed raw material composition are provided around the flow path, and the extruder 14 for the foamed rubber layer and the non-foamed From the extruder 15 for the rubber layer, the raw material composition is extruded at a desired supply amount. At the center of the extrusion head 16, a nipple 17 corresponding to the hole diameter of the cylindrical laminate and a die 18 for defining the outer diameter of the cylindrical laminate are set. Immediately before the die 18, the raw material composition supplied from the flow path 20 of the unvulcanized unfoamed raw material composition and the flow path 19 of the unvulcanized non-foamed raw material composition around the die 18 has a predetermined film thickness ratio. Laminated. That is, the discharge speed (rotation speed) from the extruder 14 for the foamed rubber layer and the extruder 15 for the non-foamed rubber layer is adjusted to a predetermined film thickness ratio.

The cylindrical laminate extruded from the die 18 is provided with a cored bar aligned with the axis of the center hole thereof,
Integrate. The length dimension depends on the final roll length,
Cut to the specified length. Next, the cylindrical laminated body integrated with the core metal is subjected to foaming and vulcanization treatment in a molding die shown in FIG. 6, for example, to be an elastic body, and at the same time, its outer shape is molded.

An example of a molding die shown in FIG. 6 comprises a concentric cylindrical die body 21 and lids 22 at both ends. The cover 22 has a hole for holding a metal core, and has a function of a metal core holding member for arranging the metal core on the central axis of the concentric cylindrical mold body 21. Further, the lid 22 is provided with a gas vent hole 23 for letting out gas expelled from the inside of the mold due to volume expansion caused by foaming and vulcanization.
The inner surface of the molding die has a smooth surface, and the inner diameter is set in accordance with the outer diameter of the rubber roller to be produced.

At the time of foaming and vulcanization, the cylindrical laminate is
The molding die is heated so as to have a uniform temperature. For example, the heating is performed by mounting a molding die in a heating plate whose shape is schematically shown in FIG. The heating board shown in FIG. 7 is composed of a heat storage block (heating board) 26 divided into two parts, and a hole 25 for inserting a molding die is formed in the center. The heating plate is preheated to a predetermined temperature in advance, and a molding die holding a laminated body integrated with the core is inserted and heated.

When heating causes foaming and vulcanization to proceed, and when the foamed inner rubber layer reaches a desired expansion ratio by foaming, the upper non-foamed rubber layer is pressed against the inner surface of the molding die and defined. Molded into shape. When the vulcanization of the non-foamed rubber layer has progressed, heating is terminated, and after cooling, the non-foamed rubber layer is removed from the mold, thereby completing a series of rubber roller manufacturing steps. In addition, when a coating thin film layer is further provided on the surface of the obtained elastic body layer, coating of a coating material is performed as a post-process to obtain a finished rubber roller.

In the production method of the present invention, the vulcanization rate of the unvulcanized non-foamed raw material composition used for the raw material of the non-foamed rubber layer is determined by the vulcanization rate of the unvulcanized unfoamed raw material composition used for the raw material of the foamed rubber layer. The vulcanization rate is made slower, and the Mooney viscosity of the unvulcanized non-foamed raw material composition used for the raw material of the non-foamed rubber layer is made smaller than the Mooney viscosity of the unvulcanized unfoamed raw material composition used for the raw material of the foamed rubber layer. ing. Therefore, when heating is started, first, foaming of the unvulcanized unfoamed raw material composition starts to advance, and vulcanization also starts. At this time, since the vulcanization rate of the unvulcanized non-foamed raw material composition is made slower, the rise in viscosity and the curing along with the cross-linking proceed more slowly. In addition, since the Mooney viscosity of the unvulcanized non-foamed raw material composition is made smaller, when the inner unvulcanized unfoamed raw material composition expands and the occupied volume expands, it does not hinder the expansion at all. . That is, the fluidity of the unvulcanized non-foamed raw material composition is
At this stage, since the flowability of the unvulcanized unfoamed raw material composition is higher than that of the unvulcanized unfoamed raw material composition, the unvulcanized unfoamed raw material composition can be deformed more rapidly in accordance with the expansion caused by foaming. The foaming proceeds to an extent comparable to the case where the foaming raw material composition is not present.

If the unvulcanized non-foamed raw material composition is not present in the upper layer, the cell formed by the very surface layer of the unvulcanized unfoamed raw material composition sometimes breaks through the surface thereof, There is a phenomenon that air bubbles escape to the outside. In the present invention, although the viscosity is smaller, since the layer of the unvulcanized non-foamed raw material composition is present in the upper layer, the cell formed by the very surface layer breaks through the surface. Has the effect of suppressing. In addition, even if air bubbles escaped from the surface of the unvulcanized unfoamed raw material composition, air bubbles were released because the upper unvulcanized non-foamed raw material composition layer had higher fluidity. The remaining holes can be filled more quickly and easily without leaving pinhole-shaped marks.

When the above-mentioned air bubbles escape to the outside, a dome-shaped bulge is formed on the surface due to the internal pressure of the cell.
The surface of the cell is maintained only by the viscosity. When the dome-shaped bulge grows beyond the middle of the diameter of the cell, it is pushed out at the bottom of the cell by an external force that has been applied so as to oppose the internal pressure of the cell, so that the bubbles rapidly escape to the outside. Therefore, when the unvulcanized non-foamed raw material composition layer has a thickness of 50% or more of the average cell diameter as the upper layer, the surface (interface) of the unvulcanized unfoamed raw material composition has a mid-cell diameter. As described above, it functions to suppress the escape of bubbles to the outside until it rises in a dome shape. On the other hand, more than half of the diameter of the cell, bulging in a dome shape, when a hole is formed in the surface layer of the unvulcanized non-foamed raw material composition, since the unvulcanized non-foamed raw material composition layer has a smaller viscosity, promptly, The air bubbles may escape from the surface (interface) of the unvulcanized unfoamed raw material composition, pass through the unvulcanized non-foamed raw material composition layer, and escape to the outside. At this time, the pores occupied by the bubbles remain in the unvulcanized non-foamed raw material composition layer, but since the fluidity is higher, the pores are quickly filled and eliminated. Therefore, it is more preferable that the thickness of the unvulcanized non-foamed raw material composition layer, that is, the film thickness of the non-foamed rubber layer is 50% or more of the average cell diameter in the foamed rubber layer. Even if the thickness of the non-foamed rubber layer is less than 50% of the average cell diameter, the above effect is maintained in a considerable range, but the effect decreases as the film thickness becomes smaller.

When the expansion of the unvulcanized unfoamed raw material composition proceeds and is pressed against the inner surface of the molding die, further expansion in the radial direction is suppressed. In addition, the unvulcanized unfoamed raw material composition itself, although the foaming agent contained therein is kneaded so as to be uniformly dispersed, the foaming reaction itself is a reaction which is started by a possibly accidental trigger, Is accompanied by density. The densely foamed portion reaches the inner surface of the molding die first, the radial expansion is suppressed, and the sparse portion reaches the inner surface of the molding die later. Meanwhile, in the dense portion, the axial expansion is still progressing, and sometimes, on the surface (interface) of the unvulcanized unfoamed raw material composition, fine wrinkles are formed at the boundary between the dense portion and the sparse portion. May be done. Further, as described above, extremely fine irregularities also exist with the dome-shaped bulge due to the cells reaching the surface (interface) of the unvulcanized unfoamed raw material composition. Since the unvulcanized non-foamed raw material composition is more fluid, it fills fine dents and wrinkles generated on the surface (interface) of these unvulcanized unfoamed raw material compositions, and is easily flattened. You. These fine dents and wrinkles are usually only about 50% of the cell average diameter in the foamed rubber layer at most, and the thickness of the unvulcanized non-foamed raw material composition layer, that is, the film of the non-foamed rubber layer When the thickness is 50% or more of the average cell diameter in the foamed rubber layer, flattening becomes more reliable. In many cases, the pressing also has an embedding effect by the unvulcanized unfoamed raw material composition itself that still retains fluidity, and the fine irregularities and wrinkles are reduced to 50% of the average cell diameter in the foamed rubber layer. Since there is only less than the variation, even when the thickness of the unvulcanized non-foamed raw material composition layer, that is, the thickness of the non-foamed rubber layer is less than 50% of the average cell diameter in the foamed rubber layer, Planarization is achieved to a considerable extent. At the time when this surface flattening is achieved, even in an unvulcanized non-foamed raw material composition having a lower vulcanization rate, vulcanization proceeds, loses fluidity, and the surface shape of the elastic layer is smooth. It matches the inner surface of the mold.

As described above, in the present invention, since the vulcanization rate is lower and the unvulcanized non-foamed raw material composition having a lower Mooney viscosity is provided in the upper layer, the molding is carried out by pressing against a molding die. The surface of the elastic layer does not have pinhole-like surface defects,
Further, the rubber roller has extremely small surface roughness and does not vary in outer diameter. The effect of using the unvulcanized non-foamed raw material composition having a lower Mooney viscosity as the upper layer is lower than the vulcanization rate, and the thickness of the unvulcanized non-foamed raw material composition layer, Even if the thickness of the rubber layer becomes thicker, it is not essentially impaired. However, since the non-foamed rubber layer has no cell structure inside,
Usually, it does not show the elasticity of the foamed rubber layer, and the hardness of the resin is relatively high. If the hardness of the resin is high, the overall hardness of the roller increases as the thickness of the non-foamed rubber layer increases. In consideration of this point, it is more preferable that the thickness of the non-foamed rubber layer be in a range where the thickness of the non-foamed rubber layer does not become significantly larger than the value of 50% of the average cell diameter in the foamed rubber layer, unless otherwise specified. Therefore, it is generally more preferable that the thickness of the non-foamed rubber layer is selected to be not more than 10 times the average cell diameter in the foamed rubber layer, or about several times, for example, not exceeding 2 to 3 times. .

In the rubber roller of the present invention, the thickness of the non-foamed rubber layer used as the upper layer can be reduced, so that a roller having low hardness can be obtained. For example, when the elastic layer is made of a conductive material, resistance unevenness and the like in the circumference can be reduced. It is more suitable for a charging member (charging roller) or a transfer member (transfer roller) used for transferring a toner image onto copy paper.

The unvulcanized unfoamed raw material composition used as the raw material for the foamed rubber layer and the raw material polymer used for the unvulcanized non-foamed raw material composition used as the raw material for the non-foamed rubber layer are intended for the intended use of the roller. For example, natural rubber, butadiene rubber, styrene butadiene rubber (S
BR), nitrile rubber (acrylonitrile-butadiene rubber), ethylene-propylene rubber (EPDM: ethylene-propylene-diene terpolymer), ethylene-propylene rubber (EPM), chloroprene rubber (CR), nitrile butadiene rubber (NBR) ), Epichlorohydrin rubber, butyl rubber, silicon rubber, urethane rubber, fluorine rubber, chlorine rubber, and other commonly used polymers. Specifically, the unvulcanized unfoamed raw material composition, as well as the unvulcanized non-foamed raw material composition, so that the vulcanization rate and Mooney viscosity respectively satisfy the above conditions,
It is good to select from the above various polymers or to combine them.

A foaming agent is added to the unvulcanized unfoamed raw material composition used as the raw material for the foamed rubber layer, and a desired expansion ratio is determined according to the type of the raw material polymer, vulcanization conditions, crosslinking temperature and the like. Is selected, and the type of the foaming agent is selected. For example, as an organic foaming agent, ADCA (azodicarbonamide), DPT (dinitrosopentamethylenetetraamine), TSH (p-toluenesulfonylhydrazide)
And OBSH (oxybisbenzenesulfenyl hydrazide). When the above-mentioned organic foaming agent is used, the amount of the foaming agent is usually selected in the range of 2 to 30 parts by weight based on 100 parts by weight of the raw material polymer. In addition, depending on the case, an inorganic foaming agent can be used, and examples thereof include sodium bicarbonate and ammonium carbonate. Further, in addition to the foaming agent, a foaming aid may be appropriately added.

The unvulcanized unfoamed raw material composition and the unvulcanized non-foamed raw material composition may be sulfur or a non-sulfur vulcanizing agent as a vulcanizing agent, depending on the type of raw material polymer used. In order to obtain a desired vulcanization rate from a metal oxide, an organic peroxide, or the like, an appropriate one is added. Further, according to the amount of the vulcanizing agent, a suitable one is selected from known vulcanization accelerators, and the amount is appropriately selected and added so as to obtain a desired crosslinking density. Further, various vulcanization accelerators may be added.

When making the foamed rubber layer and the non-foamed rubber layer conductive, a conductive powder is dispersed in the raw material polymer in the raw material composition. For example, conductive powders that are frequently used include carbons such as carbon black and conductive carbon; graphite; conductive metal oxides such as TiO ₂ , SnO ₂ and ZnO; solid solutions of SnO ₂ and Sb ₂ O ₃ ;
And a composite oxide of the metal oxide such as a solid solution of Al ₂ O ₃ , a metal powder such as Cu and Ag, and a conductive fiber. Depending on the desired conductivity and the specific gravity of the conductive powder material to be used, the amount of the conductive powder to be added is selected in the range of 5 to 200 parts by weight and is appropriately added to 100 parts by weight of the raw material polymer.

In addition, an inorganic filler such as carbon black, talc, or clay may be added to the raw material composition. The raw material composition may be used for kneading the raw material composition and forming a cylindrical shape by extrusion. For example, a process oil, a softening agent, and the like, as needed, are appropriately added as necessary.

In the production method of the present invention, the unvulcanized non-foamed raw material composition and the unvulcanized unfoamed raw material composition obtained by adding and kneading each of the above components are mixed with the unvulcanized non-foamed raw material composition. The vulcanization rate is made lower than the vulcanization rate of the unvulcanized unfoamed raw material composition, and the Mooney viscosity of the unvulcanized non-foamed raw material composition is made smaller than the Mooney viscosity of the unvulcanized unfoamed raw material composition. The type of the raw material polymer and other additional components are selected and the content is adjusted so as to satisfy the above conditions. The vulcanization rate should be measured in advance at the actual vulcanization conditions and temperatures, and the values should be compared.
In general, a representative value may be determined based on a vulcanization test specified in JIS or the like, and the representative value may satisfy the above condition. Even if there is a slight difference in the conditions, the magnitude relation of the vulcanization rates is generally preserved, so that there is no problem as long as there is a significant difference in the magnitude relation of the vulcanization rates. Similarly, regarding the Mooney viscosity, a representative value may be determined based on the Mooney viscosity test specified in JIS or the like, and the representative value may satisfy the above condition.

For example, as a representative value of the vulcanization rate, JIS
Based on K 6300, the vulcanization test of Method A
C. and a deflection angle of 1 degree (JSR Curastometer III type), and the value of t30 calculated from the measurement results can be used. Further, for example, as a representative value of the Mooney viscosity, a Mooney viscosity test is similarly performed based on JIS K 6300, and a value of ML (1 + 4) 100 ° C. is obtained.
A value of L (1 + 4) 100 ° C. can be used.

In the present invention, for example, the vulcanization rate of the unvulcanized unfoamed raw material composition is set to 1.
When selected in the range of 5 to 8, the vulcanization rate of the unvulcanized non-foamed raw material composition is selected in the range of 2 to 12 in the value of t30, and the unvulcanized non-foamed raw material composition is selected. The vulcanization rate of the uncured unfoamed raw material composition is about 1.
If it is selected to be 2-3 times, more preferable results are obtained. At the same time, for example, when the Mooney viscosity of the unvulcanized unfoamed raw material composition is selected in the range of 28 to 36 at the value of ML (1 + 4) 100 ° C., ML (1 + 4)
４０40, wherein the Mooney viscosity of the unvulcanized non-foamed raw material composition is selected to be 0.8 to 0.3 times the Mooney viscosity of the unvulcanized unfoamed raw material composition. Then
More favorable results are obtained.

In the rubber roller of the present invention, a coating thin film layer can be provided on the outer peripheral surface of the elastic layer. For example,
When forming a conductive film as the coating thin film layer,
As the material of the coating, for example, N-methylmethoxylated nylon, polyvinyl butyral, polyethylene, polyvinyl acetate, polystyrene, polybutadiene, polyamide,
Polyimide, polyurethane, polyester, silicone resin, and the like, as well as epichlorohydrin, urethane, chloroprene, and acrylonitrile-butadiene rubber can be used. In order to adjust the conductivity to a desired value, a coating material selected from these, a conductive pigment,
For example, an appropriate amount of carbon black, carbon graphite, titanium oxide, zinc oxide, or the like may be added. For example, by coating the conductive coating material, when forming a coating, these coating components are dissolved or dispersed in a solvent or the like to form a paint, depending on the coating thickness, dipping,
It is preferable that a suitable means is selected from a means such as a spray coat and a roll coat, and the outer periphery of the roller is uniformly coated.

The thickness of the coating thin film layer should be appropriately selected according to the purpose of coating.
It is generally preferred to select a smaller thickness as long as the desired function is maintained. That is, generally, when the coating thin film layer is provided, as the film thickness increases, the roller hardness tends to increase, and in order to prevent unnecessary high hardness, a thinner film is used as long as the purpose of coating is not impaired. It is generally preferred to choose a thickness.

[0047]

EXAMPLES The rubber roller of the present invention and the method of manufacturing the same will now be described in more detail with reference to specific examples. In the specific examples described below, an example is described in which the present invention is applied to a rubber roller having a conductive roller portion, which is mainly disposed in contact with an electrophotographic photosensitive member and is suitable for a charging roller used for charging the surface of the photosensitive member. The present invention is not limited by these specific examples.

Example 1 This example is an example of manufacturing a charging roller used for charging the surface of a photoreceptor, and the formed charging roller has a sufficiently small surface roughness of a formed roller. In addition, at the same time, it is an example of verifying that the outer diameter accuracy and the shape accuracy such as runout are high, and that an appropriate roller hardness is obtained with good reproducibility.

In the present embodiment, the unvulcanized non-foamed raw material composition for the non-foamed rubber layer is an ethylene-propylene-diene terpolymer (product model number: EPT404) as a raw material polymer.
5) Ketjen Black (product model number: Ketjen Black EC manufactured by Mitsubishi Chemical Corporation) or SRF carbon black (product model number: Asahi # 35 Asahi) as a conductive agent (conductive powder) Carbon Co., Ltd.), a softening agent, paraffin oil, a crosslinking agent (vulcanizing agent), sulfur, and a vulcanization accelerator, mercaptobenzothiazole (M) and cyclohexylbenzothiazolesulfenamide (CBS). Lead oxide and stearic acid were used as vulcanization accelerators, and the content (parts by weight) of each component was set to the value shown in Table 1. For the kneading, an open roll was used to obtain a uniform composition.

The unvulcanized unfoamed raw material composition for the foamed rubber layer is obtained by using an ethylene-propylene-diene terpolymer (product number: EPT8075E manufactured by Mitsui Petrochemical Co., Ltd.) as a raw material polymer. As an agent (conductive powder), Ketjen Black (product number: Ketjen Black EC manufactured by Mitsubishi Chemical Corporation) or SRF carbon black (product number: Asahi # 35 manufactured by Asahi Carbon Co., Ltd.) is used. As a crosslinking agent (vulcanizing agent),
As a vulcanization accelerator, mercaptobenzothiazole (M), zinc dibutyldithiocarbamate (ZnBD
C), tetramethylthiuram disulfide (TMT
D), cyclohexylbenzothiazolesulfenamide (CBS), lead oxide and stearic acid as vulcanization accelerators, ADCA and OB as blowing agents.
Using SH, the content of each component (parts by weight)
The values shown in Table 1 were used. For the kneading, an open roll was used to obtain a uniform composition.

Regarding the unvulcanized non-foamed raw material composition for the non-foamed rubber layer and the unvulcanized unfoamed raw material composition for the foamed rubber layer, JIS K
Based on 6300, a vulcanization test of Method A was conducted under the conditions of 160 ° C. and a deflection angle of 1 degree (JSR Curastometer III type), and the value of t30 calculated from the measurement results was used as a representative value. Also, as an index value of Mooney viscosity, JI
A Mooney viscosity test was performed based on SK 6300,
The value of ML (1 + 4) at 100 ° C. was used as a representative value. Representative values of the vulcanization rate and Mooney viscosity are also shown in Table 1. As can be seen from the comparison of the representative values, the vulcanization rate of the unvulcanized non-foamed raw material composition used in this example is significantly lower than the vulcanization rate of the unvulcanized unfoamed raw material composition, and It is confirmed that the Mooney viscosity of the vulcanized non-foamed raw material composition is significantly lower than the Mooney viscosity of the unvulcanized unfoamed raw material composition.

Using the above-mentioned unvulcanized non-foamed raw material composition for a non-foamed rubber layer and the unvulcanized unfoamed raw material composition for a foamed rubber layer, an extruder shown in FIG. 4 and an extrusion head shown in FIG. Using a die with an inner diameter of φ7.75mm and an outer diameter of φ5.0m
The nipple of m was set on the head and extruded simultaneously and integrally to form a cylindrical laminate. The length of the cylindrical laminated body was cut into approximately the same length so as to fit in the inside of the cavity of the molding die so as to have a length of 224 mm.

In the extruder shown in FIG. 4, the unvulcanized unfoamed raw material composition for the foamed rubber layer was extruded by extruding the unvulcanized unfoamed raw material composition for the foamed rubber layer. Is extruded by using extruders each having a screw diameter of φ75 mm, and by setting the rotation ratio of the two extruders to φ50: φ75 = 1: 3, the thickness of the raw material composition of the foamed rubber layer and the non-foamed rubber layer Was adjusted.

The core is coated in advance with a conductive adhesive on its surface and inserted into the center hole of the obtained cylindrical laminate to assemble the core with the cylindrical laminate. Was. Then, as schematically shown in FIG. 6, the ends of the core metal were fixed to lids provided at both ends of the molding die so that their axes were aligned, and the laminate was placed inside the die. This molding die was inserted into the heating plate of FIG.
The mixture was heated for a minute to perform a vulcanization / foaming treatment. As a result, an elastic layer having outer dimensions of 224 mm in length and 12 mm in diameter and corresponding to the inner dimensions of the mold used and 12.3 mm in diameter was formed on the surface of the core metal having a diameter of 6 mm. The average thickness of the non-foamed rubber layer on the surface was 100 μm, and the average cell diameter of the internal foamed rubber layer was 153 μm. Therefore, the thickness of the non-foamed rubber layer is about 65% of the cell diameter of the foamed rubber layer.

The average cell diameter is determined by observing the cross-section of the foamed rubber layer with a microscope or the like. Is selected, and the measured value of the cell diameter is averaged. When the cell cross-sectional shape was greatly distorted from a perfect circle and became elliptical, the simple average of the major axis and the minor axis was used as the measured value of the cell diameter.

FIG. 6 schematically shows the shape and configuration of the molding die used in this embodiment. The mold body 21 has a cylindrical shape with an outer diameter of 26 mm and an inner surface of 12.3 mm in inner diameter, and a lid (core metal holding member) 22 having holes for inserting and holding the core of the roller at both ends. Be attached. With the lid 22 attached, the length of the inner surface is slightly longer than 224 mm as described above. The lid 22 is provided with a gas vent hole 23 which serves as a passage for gas inside. The cylindrical laminated body 24 serving as the elastic layer of the roller is formed by attaching the central core metal to the lid 22.
By holding by, the inner surface of the mold and the axis are aligned,
Be placed. On the other hand, the heating plate is composed of a heat storage block divided into two, as schematically shown in FIG. 7, and has a hole 2 corresponding to the outer dimensions of the molding die on the divided surface.
5 are formed. When the molding die is inserted, uniform heating is performed from the outer periphery.

The outer diameter accuracy and the surface roughness of the rubber roller produced by the above procedure were evaluated. The average value was calculated for N = 10 pieces in consideration of the variation of the cylindrical laminate itself produced by the extruder. Regarding the outer diameter, a non-contact type laser length measuring machine was used to measure the outer diameter in a range excluding the portion 5 mm at both ends of the rubber roller, and the difference between the maximum value and the minimum value was defined as the outer diameter accuracy. In the case of the charging roller having the outer diameter of this embodiment, if the outer diameter accuracy is 0.1 mm or less, the charging roller is considered to be good.

Further, a conductive coating layer was applied on the surface of the rubber roller manufactured by the above procedure to prepare a charging roller used in an electrophotographic apparatus. For the coating of the conductive coating layer, the pH is adjusted to 5 to 6 with respect to the polyurethane liquid in which the polyurethane is dispersed in water, and the conductive oxidation in which the powdery tin oxide is dispersed by the electric repulsion at the interface. As the tin slurry, a conductive tin oxide-added polyurethane paint obtained by dispersing tin oxide equivalent to 30% in solid content ratio was used. On the roller surface whose surface has been treated with a silane coupling agent, the above-mentioned paint is applied, and heated at 120 ° C. for 30 minutes in a hot air oven.
A drying treatment was performed to coat a conductive thin film having a thickness of 40 μm. Finally, the resistance of the roller itself becomes 10 × 10 ⁶
Ω charging roller.

The coated roller was coated with the above-mentioned conductive thin film, and the surface roughness was measured. The surface roughness was Rz = 0.89 μm, and the surface of the elastic layer before coating was measured. It reflected roughness.

In addition, the resistance distribution of the roller was measured in the circumferential direction by using an evaluation apparatus schematically shown in FIG. 8 in order to examine the uniformity of the resistance of the produced charging roller in the circumference. In the evaluation device shown in FIG. 8, the core metal 2 is pressed so that the charging roller 27 is pressed against the drum 29 made of aluminum.
A pressing force f = 500 g is applied to eight ends. In this pressed state, the charging roller 27 is driven to rotate by the drum 29. From the power supply 30 via the cored bar 28, the drum 2
9, a voltage of 100 V DC was applied to rotate the charging roller 27, and the resistance of the roller was measured. For the circumferential direction, based on the measured value of the roller resistance, for the circumferential direction,
The ratio between the maximum value Rmax and the minimum value Rmin was determined. The ratio Rmax / Rmin was 1.3.

The charging roller provided with the conductive thin film coating prepared in this example was used in an electrophotographic apparatus (model: LBP-320).
When the actual image was output in an environment of 15 ° C. and 10 RH, it was reported that the outer diameter of the charging roller was non-uniform (insufficient outer diameter accuracy) or a defect on the surface was reported to be caused by surface defects. No outbreaks were found.

Comparative Example 1 manufactured by a conventional method described later.
3 and the charging roller manufactured in Comparative Example 4. First, the outer diameter accuracy of the elastic layer before the coating of the conductive thin film is also shown in Table 2. As in the present embodiment, the roller of the present embodiment has an outer diameter accuracy smaller than the rollers prepared in Comparative Examples 1 to 3, in which the elastic layer has a two-layer structure of a foamed rubber layer and a non-foamed rubber layer. Significantly improved,
It is a good level of 0.1 mm or less.

[0063]

[Table 1]

[0064]

[Table 2] (Embodiment 2) In this embodiment, unlike Embodiment 1 described above,
In the unvulcanized unfoamed raw material composition for the foamed rubber layer, the raw material polymer was replaced with ethylene-propylene-diene terpolymer (product number: EPT8075E manufactured by Mitsui Petrochemical Co., Ltd.). A diene terpolymer (product model number: EPT4045 manufactured by Mitsui Petrochemical Co., Ltd.) was used, and the content of paraffin oil added as a softener was adjusted accordingly. On the other hand, the unvulcanized non-foamed raw material composition for the non-foamed rubber layer had the same composition as that used in Example 1. Table 1 also shows the component compositions (parts by weight) of the unvulcanized unfoamed raw material composition for the foamed rubber layer and the unvulcanized non-foamed raw material composition for the non-foamed rubber layer.

The vulcanization rate and Mooney viscosity of each raw material composition were evaluated in accordance with the method described in Example 1. The results are also shown in Table 1. As can be seen from the comparison of the representative values, also in this example, the vulcanization rate of the unvulcanized non-foamed raw material composition used is significantly lower than the vulcanization rate of the unvulcanized unfoamed raw material composition, and It is confirmed that the Mooney viscosity of the unvulcanized non-foamed raw material composition is significantly lower than the Mooney viscosity of the unvulcanized unfoamed raw material composition. However, Example 1
In comparison, the difference in Mooney viscosity is smaller.

According to the procedure of Example 1, a cylindrical laminate was produced using an extruder shown in FIG. The extrusion of the unvulcanized non-foamed raw material composition for the non-foamed rubber layer is performed by an extruder having a screw diameter of φ50 mm, and the extrusion of the unvulcanized unfoamed raw material composition for the foamed rubber layer is performed by an extruder having a screw diameter of φ75 mm. And the thickness ratio of the raw material composition of the foamed rubber layer and the non-foamed rubber layer was adjusted by setting the rotation ratio of the two extruders to φ50: φ75 = 1: 3. Then, according to the procedure of Example 1, integration of the cylindrical laminate and the core metal,
A vulcanization / foaming treatment was performed to form an elastic layer. The dimensions of the cylindrical laminate and the molding die used were the same as in Example 1.
The same design dimensions were used. The outer dimensions of the obtained elastic layer are essentially the same as those in Example 1, and the average cell diameter in the foamed rubber layer and the average size of the non-foamed rubber layer are obtained by the method described in Example 1. The film thickness was measured. In this example, the average thickness of the non-foamed rubber layer on the surface was 100 μm, and the average cell diameter of the internal foamed rubber layer was 151 μm. Therefore, the film thickness of the non-foamed rubber layer is about 66% of the cell diameter of the foamed rubber layer.

The outer diameter accuracy of the produced elastic layer was also measured by the evaluation method of Example 1. The outer diameter accuracy of the evaluated elastic layer is also shown in Table 2. The result of the roller of the present embodiment was slightly inferior to the accuracy of the outer diameter of the roller of the first embodiment. In spite of this slight difference, the roller of the present embodiment is different from the rollers prepared in Comparative Examples 1 to 3 in that the elastic layer has a two-layer structure of a foamed rubber layer and a non-foamed rubber layer. As in the case of the roller No. 1, the accuracy of the outer diameter is significantly improved, which is a good level of 0.1 mm or less.

Further, a conductive thin film was coated in the same procedure and under the same conditions as in Example 1, and finally, a charging roller having a resistance of about 10 × 10 ⁶ Ω was obtained. According to the evaluation method described in Example 1, the resistance of the charging roller manufactured in this example was evaluated for uniformity in the circumference, and the ratio Rmax / Rmin was 1.3. Correspondingly, the charging roller provided with the conductive thin film coating prepared in this example was transferred to an electrophotographic apparatus (model: LBP-32).
0, manufactured by Canon Inc., and output an actual image under an environment of 15 ° C. and 10 RH. As in the case of the charging roller of Example 1, the outer diameter of the charging roller is non-uniform (insufficient outer diameter) and surface defects. No image defect was found due to the above.

Example 3 In this example, the unvulcanized unfoamed raw material composition for the foamed rubber layer and the unvulcanized non-foamed raw material composition for the non-foamed rubber layer were used in Example 1. The composition was the same as the one that was used.

According to the procedure of Example 1, a cylindrical laminate was produced using an extruder shown in FIG. For extruding the unvulcanized non-foamed raw material composition for the non-foamed rubber layer, an extruder with a screw diameter of φ50 mm is used.For extruding the unvulcanized unfoamed raw material composition for the foamed rubber layer, an extruder with a screw diameter of φ75 mm is used. The thickness of the raw material composition of the non-foamed rubber layer was adjusted to be smaller than that of Example 1 by setting the rotation ratio of the two extruders to φ50: φ75 = 1: 4. Then, according to the procedure of Example 1, the cylindrical laminate and the cored bar were integrated, vulcanized and foamed, and an elastic layer was formed. The dimensions of the cylindrical laminate and the molding die used were the same design dimensions as in Example 1. The outer dimensions of the obtained elastic layer are essentially the same as those in Example 1, and the average cell diameter in the foamed rubber layer and the average size of the non-foamed rubber layer are obtained by the method described in Example 1. The film thickness was measured.
In this example, as designed, the average thickness of the non-foamed rubber layer on the surface was 60 μm, and the average cell diameter of the internal foamed rubber layer was 159 μm. Therefore, the thickness of the non-foamed rubber layer is about 38% of the cell diameter of the foamed rubber layer.

When the surface of the elastic layer was observed, the surface of the roller of Example 2 was found to have a very small surface roughness at a considerable frequency. Specifically, on the surface of the non-foamed rubber layer, there were portions where fine wrinkles were observed, and further, in the lower foamed rubber layer, the occurrence of pinhole-shaped depressions corresponding to the crushed cells was also observed. . Due to these fine surface roughnesses, the surface roughness was larger than the surface of the roller elastic layer of Example 1.

The accuracy of the outer diameter of the produced elastic layer was also measured by the evaluation method of Example 1. The outer diameter accuracy of the evaluated elastic layer is also shown in Table 2. The outer diameter accuracy of the roller of this embodiment is slightly smaller than the outer diameter accuracy of the roller of the first embodiment, but the result is significantly inferior. This difference in the outer diameter accuracy reflects local fluctuations in the outer diameter corresponding to the fine wrinkles and the pinhole-shaped depressions. However, Comparative Example 1 in which the elastic layer has a two-layer structure of a foamed rubber layer and a non-foamed rubber layer
In comparison with the rollers prepared in Nos. 1 to 3, it was determined that the roller of the present example also had significantly improved outer diameter accuracy,
Therefore, a good level of 0.1 mm or less is maintained.

Further, a conductive thin film was coated under the same procedure and conditions as in Example 1, and finally, a charging roller having a resistance of about 10 × 10 ⁶ Ω was obtained. As a result of the formation of the coating thin film layer, the coating material filled the fine wrinkles and the pinhole-shaped depressions, and the coating was smoothed.
At the stage of the charging roller, both the surface roughness and the outer diameter accuracy were comparable to those of the charging roller manufactured in Example 1.

According to the evaluation method described in Example 1,
As for the resistance of the charging roller manufactured in this example, when the uniformity in the circumference was evaluated, the ratio Rmax / Rmin was calculated as follows:
1.4. The charging roller provided with the conductive thin film coating prepared in this embodiment is connected to an electrophotographic apparatus (model: LBP-
When the actual image was output in an environment of 15 ° C. and 10 RH, the outer diameter of the charging roller was non-uniform as in the case of the charging roller of Example 1 (insufficient outer diameter).
And occurrence of image defects due to surface defects was not found.

(Comparative Examples 1 to 3) The unvulcanized unfoamed raw material composition for the foamed rubber layer and the unvulcanized non-foamed raw material composition for the non-foamed rubber layer used in Comparative Examples 1 to 3 The composition (parts by weight) is also shown in Table 1 for comparison. In addition, the vulcanization rate and Mooney viscosity of each raw material composition were evaluated according to the method described in Example 1, and the results are also shown in Table 1. In Comparative Examples 1 to 3, except for Comparative Example 2, the vulcanization rate of the unvulcanized and non-foamed raw material composition used was faster than the vulcanization rate of the unvulcanized and unfoamed raw material composition.
Except for the above, it is confirmed that the Mooney viscosity of the unvulcanized non-foamed raw material composition is higher than the Mooney viscosity of the unvulcanized unfoamed raw material composition.

According to the procedure of Example 1, a cylindrical laminate was produced using an extruder shown in FIG. For extruding the unvulcanized non-foamed raw material composition for the non-foamed rubber layer, an extruder with a screw diameter of φ50 mm is used.For extruding the unvulcanized unfoamed raw material composition for the foamed rubber layer, an extruder with a screw diameter of φ75 mm is used. The thickness of each raw material composition was adjusted by setting the rotation ratio of the two extruders to φ50: φ75 = 1: 3. Then, according to the procedure of Example 1, the cylindrical laminate and the cored bar were integrated, vulcanized and foamed, and an elastic layer was formed. The dimensions of the cylindrical laminate and the molding die used were the same design dimensions as in Example 1.

The external dimensions of the obtained elastic body layer were as described in Example 1.
Was almost the same. Further, the average cell diameter in the foamed rubber layer and the average thickness of the non-foamed rubber layer were measured by the method described in Example 1. In this comparative example, as designed, the average thickness of the non-foamed rubber layer on the surface is 100 μm, while, depending on the composition of the unvulcanized unfoamed raw material composition in each comparative example, the internal foamed rubber The average cell diameter of the layer is 120
It was distributed in the range of 150150 μm.

The outer diameter accuracy of the produced elastic layer was also measured by the evaluation method of Example 1. The outer diameter accuracy of the evaluated elastic layer is also shown in Table 2. Comparative Examples 1-3
The outer diameter precision of each roller significantly exceeded 0.1 mm, and was not at a satisfactory level.

Further, when the surface of the elastic layer was observed, the rollers of Comparative Examples 1 to 3 were found to have a clear surface roughness with high frequency. Specifically, on the surface of the non-foamed rubber layer, fine wrinkles and irregularities were observed in some parts. Alternatively, a large number of pinhole-shaped depressions that propagated from the lower foamed rubber layer and hit the crushed cells on the surface were observed. The factor of the low outer diameter accuracy described above reflects local fluctuations in the outer diameter corresponding to uneven wrinkles and pinhole-shaped depressions generated on the surface.

That is, these surface roughnesses are the result of the local unevenness of foaming in the foamed rubber layer and the unevenness caused by abnormal foaming or insufficient foaming affecting the upper non-foamed rubber layer. Was.

Further, a conductive thin film was coated in the same procedure and under the same conditions as in Example 1, and finally, the charging roller had a resistance of about 10 × 10 ⁶ Ω. The charging roller with the conductive thin film coating is incorporated in an electrophotographic apparatus (model: LBP-320 manufactured by Canon), and the temperature is set to 15 ° C. and 10 RH.
When an actual image was output under the above environment, a number of rollers having image defects due to surface defects reflecting abnormal foaming and the like were found.

(Comparative Example 4) Using the same unvulcanized unfoamed raw material composition for a foamed rubber layer used in Example 2 above, a rubber roller was prepared without an upper non-foamed rubber layer. did. That is, although a series of procedures described in Example 2 was followed, the raw material composition to be the upper non-foamed rubber layer was not charged into the extruder.

The outer diameter accuracy of the produced elastic layer was evaluated in accordance with the method described in Example 1, and the results are shown in Table 2 for comparison.

Further, in the same manner as in Example 2, the conductive thin film was coated, and finally, the resistance of the roller itself was reduced to about 10
A charging roller of × 10 ⁶ Ω was used. Even after forming the coating layer, the surface roughness of the roller surface is Rz = 4.1 μm
Met. When the uniformity in the circumference of the resistance of the produced charging roller was evaluated, the ratio Rmax / Rmin was calculated as follows:
It had reached 1.8. This charging roller is incorporated in an electrophotographic apparatus (model: LBP-320 made by Canon),
When an actual image was output in an environment of 0 RH, occurrence of image defects determined to be caused by resistance unevenness in the periphery of the charging roller was observed at a frequency of 2 out of 10 images.

[0085]

The rubber roller according to the present invention comprises a foamed rubber layer as an elastic layer and a non-foamed rubber layer having a small thickness on the foamed rubber layer in a concentric cylindrical shape. Using a foamed raw material composition and a non-vulcanized non-foamed raw material composition for a non-foamed rubber layer, a laminate that is integrally extruded and heated at the same time is subjected to vulcanization and foaming treatment, so that it is manufactured. In this case, abnormal foaming or insufficient foaming hardly occurs, and as a result, surface defects and surface roughness due to abnormal foaming or insufficient foaming can be extremely reduced. Therefore, a rubber roller having sufficiently small surface roughness, high accuracy in outer diameter, and proper roller hardness itself can be obtained. In particular, according to the manufacturing method of the present invention, the rubber roller having such high quality is
Since it can be manufactured by a single heat treatment using a laminate that is integrally extruded and formed at the same time, there is an advantage that its productivity is high and it can be manufactured with good reproducibility. In addition, in the rubber roller of the present invention, as described above, the surface of the elastic layer, as it is, has a high outer diameter accuracy, has no surface roughness, and has a sufficiently small surface roughness. It is not necessary to provide a coating film layer on the surface for the purpose of improving the roughness. For example, when providing a coating thin film layer on a surface for the purpose of, for example, improving the abrasion resistance of the surface, or further uniforming the conductivity of the surface, it is possible to minimize the thickness of the coating thin film layer. It becomes possible. For example, when applied to a charging roller, it is possible to suppress an increase in roller hardness caused by the coating thin film layer, while keeping the hardness low, uniformity in conductivity is achieved, and a charging roller with less resistance unevenness.
It can be manufactured with good reproducibility.

[Brief description of the drawings]

FIG. 1 shows a configuration of an electrophotographic apparatus in which a rubber roller of the present invention can be used as a contact charging member, a transfer member, and the like;
It is a figure which shows the role of each rubber roller typically.

FIG. 2 is a diagram illustrating an example of a rubber roller of the present invention, and is a schematic diagram illustrating a configuration of an elastic layer.

FIG. 3 is a schematic diagram illustrating a configuration of an example of a rubber roller of the present invention having a coating thin film layer on a surface.

FIG. 4 is a view schematically showing a configuration of an extruder used for forming a cylindrical laminate.

FIG. 5 is a cross-sectional view schematically showing a configuration of an extrusion head used for forming a cylindrical laminate.

FIG. 6 is a cross-sectional view schematically showing a state in which a molding die used for manufacturing a rubber roller and a core metal integrated with a cylindrical laminated body are held.

FIG. 7 is a view schematically showing an example of a heating plate used for heating a molding die.

FIG. 8 is a diagram schematically showing a configuration of a resistance roller resistance measuring device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 photoconductor (image carrier) 2 charging member (charging roller) 3 exposing means 4 developing member 5 transfer member (transfer roller) 6 transfer material 7 fixing member 8 cleaning member 9 toner 10 core metal 11 foam rubber layer 12 non-foamed rubber Layer 13 Coated thin film layer 14 Extruder (for foamed rubber layer) 15 Extruder (for non-foamed rubber layer) 16 Extrusion head 17 Nipple 18 Dice 19 Flow path of unvulcanized non-foamed raw material composition 20 Unvulcanized unfoamed raw material Composition flow path 21 Mold main body 22 Lid (core metal holding member) 23 Gas vent hole 24 Cylindrical laminated body 25 Void portion (for inserting molding die) 26 Hot plate (heat storage block) 27 Charging roller (Conductive rubber roller) 28 Metal core 29 Aluminum drum 30 Power supply

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08K 3/04 C08K 3/04 4F074 3/22 3/22 4F203 C08L 101/00 C08L 101/00 4J002 G03G 15 / 02 101 G03G 15/02 101 4J038 15/08 501 15/08 501D 15/16 103 15/16 103 15/20 103 15/20 103 // C09D 5/24 C09D 5/24 201/00 201/00 B29K 21:00 105: 04 105: 22 105: 24 B29L 31:32 F term (reference) 2H003 BB11 BB13 BB16 CC05 2H032 AA05 BA09 2H033 BB02 BB05 BB06 BB29 BB30 BB31 2H077 AD06 FA01 FA13 FA16 FA22 FA25 4F006 AA04AA18A14A31 AA42 AB05 AB13 AB16 AB20 AB32 AB35 AB37 AB38 AB39 AB72 AB74 BA07 CA00 DA00 DA04 4F074 AA05 AA06 AA12 AA13 AA14 AA25 AA26 AA29 AA38 AA76 AA78 AB00 AB05 A C02 AC05 AC17 AG08 BA03 BA04 BA13 BA16 BA17 BA19 BB02 BB05 BB09 CA23 CC04Y CC05Z CC06Y CC22X CC24X DA59 4F203 AA09 AA42 AA45 AB02 AB03 AB13 AB16 AB18 AD03 AD15 AH04 DA11 DB01 DB18 DC01 DD02 DF05 AC1 BE1 AC03 BE011 CH041 CK021 CL001 CM041 CP031 DA026 DA036 DE106 DE136 FD116 GH00 HA05 HA08 4J038 CA021 CA071 CA081 CB021 CC021 CE071 CF021 DD001 DG001 DH001 DJ021 DL031 HA026 HA036 HA216 KA12 KA20 NA20 PB06 PC07

Claims (5)

[Claims] 1. A rubber roller in which a concentric cylindrical elastic body having a foamed rubber layer on the inner side and a non-foamed rubber layer on the outer side is formed on the outer periphery of a cored bar. The foamed rubber obtained by compounding the polymer raw material of the body, the foaming agent, and various additives to be added as necessary and vulcanizing and foaming the unvulcanized unfoamed raw material composition is used as the material. The foamed rubber layer is made of a non-foamed rubber obtained by vulcanizing an unvulcanized non-foamed raw material composition obtained by mixing and kneading a polymer raw material and various additives to be added as necessary. The vulcanization rate of the foamed raw material composition is lower than the vulcanization rate of the unvulcanized unfoamed raw material composition, and the Mooney viscosity of the unvulcanized non-foamed raw material composition is the unvulcanized unfoamed raw material. Less than the Mooney viscosity of the composition, The vulcanized non-foamed raw material composition is formed into a concentric cylindrical laminate integrally and extruded on the outer periphery of the unvulcanized unfoamed raw material composition, and the concentric cylindrical laminate is formed in the concentric cylindrical laminate. The core has a predetermined cylindrical inner peripheral surface that is larger than the outer periphery of the concentric cylindrical laminated body, and the core has the concentric axis of the cylindrical inner peripheral surface. Using a cylindrical molding die having lids at both ends for holding on top, the laminated body integrally disposed with the cored bar is arranged in the molding die, and vulcanized and foamed. Applying the process, with the foaming, pressing the outer peripheral surface of the laminate to the inner peripheral surface of the molding die, a foamed rubber layer on the inside formed by molding,
A rubber roller having a concentric cylindrical elastic rubber layer having a non-foamed rubber layer on the outside thereof. 2. The rubber roller according to claim 1, wherein the thickness of the non-foamed rubber layer is at least 50% of the cell diameter with respect to the foamed cell diameter in the foamed rubber layer. 3. The rubber roller according to claim 1, wherein both the foamed rubber layer and the non-foamed rubber layer have conductivity. 4. The method according to claim 1, wherein one or more conductive coating thin film layers are provided on the outer peripheral surface of the elastic rubber layer by coating. Rubber roller. 5. The elastic rubber layer has conductivity, and the core metal is also formed of a conductive material. The rubber roller according to any one of claims 1 to 4, wherein the rubber roller is selected to have a value suitable for a charging roller used for charging a body surface.