JP2000029273A - Conductive roller - Google Patents

Abstract

(57) [Problem] To provide a conductive roller excellent in vibration noise prevention effect, conductivity and non-staining property. A conductive roller having a structure in which a core metal on a cylinder and a rubber layer having conductivity that is concentrically laminated around the core metal is provided, wherein the rubber layer has at least two layers. Consisting of, the rubber layer of the inner layer,
A conductive roller having a foaming ratio of 2.0 to 4.0 and a foamed layer having an open cell degree of 1.3 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roller, and more particularly to a conductive roller suitably used as a charging roller, a transfer roller, a developing roller and the like of an electrophotographic apparatus.

[0002]

2. Description of the Related Art An electrophotographic apparatus such as a copying machine, a facsimile, and a printer is provided with a photoreceptor having a photoconductor layer on a surface thereof. Then, an outer peripheral surface is exposed to a laser beam corresponding to the irradiation reflected light or the electronic signal to form an electrostatic latent image on the object to be copied, and a toner image is formed by attaching toner to the electrostatic latent image. The image is fixed on the image by transferring the image onto the image.

In such a process, as shown in FIG. 3, a charging roller 4 for uniformly charging the photoconductor 11, a toner conveying roller 8 for conveying toner, and toner adhering to the photoconductor 11 Various rollers such as a developing roller 9 for transferring the toner image and a transfer roller 10 for transferring the toner image from the photoreceptor 11 to a sheet are used.

[0004] Such a roller is generally composed of a columnar cored bar and a vulcanized rubber layer laminated concentrically around the cored bar. And its stability and environmental stability), non-staining properties, low hardness, and dimensional stability. In particular,
In the "charging roller" used for the contact charging method,
Low hardness is required to prevent vibration noise during AC superposition driving.

One of the means for achieving low hardness is as follows:
A method using foamed rubber for the conductive elastic layer has been proposed. Due to the low elastic modulus and shock absorbing ability of the foamed rubber, the roller vibration during the AC superposition driving is prevented, and the generation of vibration noise is reduced. However, when foamed rubber is compressed for a long period of time, its surface undergoes permanent deformation, and it cannot be uniformly contacted with a partner material such as a photoreceptor or the like, causing problems such as uneven charging and uneven development.

Conventionally, electric resistance has been controlled by kneading and dispersing a charge imparting agent (carbon black, metal fine particles, metal oxide fine particles, etc.) in rubber. However, control of dispersion is difficult. In addition, there is a problem that the dispersion state changes due to the rubber flow during molding and vulcanization, and the electric resistance varies.

As a method for solving this problem, there has been proposed a method in which an epichlorohydrin copolymer is used as a material in which the polymer itself has conductivity. It is known that by using this polymer, a desired electric resistance value can be obtained without a conductivity-imparting agent or by adding a small amount thereof, and the variation in electric resistance is reduced. However, depending on the selection of the vulcanization system and the composition ratio of the polymer, there is a possibility that the photoconductor is contaminated.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a conductive roller having an effect of preventing vibration noise, and having excellent conductivity and non-staining properties.

[0009]

SUMMARY OF THE INVENTION The present invention relates to a conductive roller having a structure in which a core metal on a cylinder and a rubber layer having conductivity which is concentrically laminated around the core metal are provided. The rubber layer comprises at least two layers, and among the rubber layers, the inner rubber layer has an expansion ratio of 2.0 to 4.0.
And a foamed layer having a degree of open cell of 1.3 or more is a conductive roller. Hereinafter, the present invention will be described in detail.

The conductive roller according to the present invention has a structure in which a conductive rubber layer laminated concentrically around a cylindrical cored bar is provided. Examples of the core metal include, for example, a hollow columnar or solid iron core metal, a steel core metal, and the like conventionally used as a roller core metal.

The rubber layer is composed of at least two layers. Among the rubber layers, a component constituting the inner rubber layer is preferably a foamed rubber from the viewpoint that a low hardness can be achieved. Further, the inner rubber layer may be composed of a plurality of layers.

The expansion ratio of the foamed rubber is 2.0 to 4.
0 is preferred. If it is less than 2.0, the hardness is insufficiently reduced, the vibration absorbing ability is reduced, and a sufficient antistatic effect may not be obtained. If it exceeds 4.0, the bubble diameter after foaming may be too small. Because the roller surface becomes too large, the unevenness of the roller surface hardness increases, or `` undulations '' occur on the roller surface after molding, and uniform contact with the photoconductor cannot be performed.
In some cases, a desired charge amount cannot be uniformly applied to the surface of the photoconductor. The expansion ratio indicates the ratio of the solid specific gravity before foaming to the foam specific gravity.

The open cell ratio of the foamed rubber is preferably 1.3 or more. If it is less than 1.3, the restoring ability of the foam rubber against compression becomes small, and the contact surface of the roller with other members is deformed during long-term storage. Such deformation occurs,
If the roller is not restored, the cross-sectional shape of the roller changes, making it impossible to make uniform contact with the surface of the photoreceptor, causing charging unevenness, and as a result, desired charging characteristics may not be obtained. The open cell ratio indicates the ratio of the specific gravity of water absorption of the foam to the specific gravity of the foam. In the present invention, the specific gravity of water absorption is 125 m at a position 50 mm below the water surface using the foam of 20 × 20 × about 5 mm as a test piece.
This is a specific gravity when the pressure is reduced to mHg, the temperature is maintained for 5 minutes, and then left at atmospheric pressure for 3 minutes.

The foamed rubber composition includes, for example,
Copolymers of ethylene, propylene and ethylidene norbornene can be mentioned. The foamed rubber is, for example, a foaming agent such as azodicarbonamide in the composition,
It can be produced by incorporating a foaming aid such as SELTON NP (manufactured by Sankyo Kasei) into the rubber composition.

Among the above rubber layers, the components constituting the outer rubber layer can reduce contamination to the photoreceptor.
It is preferable to include an epichlorohydrin-based copolymer obtained by copolymerizing epichlorohydrin and ethylene oxide. The outer layer is preferably a non-foamed rubber layer.

The epichlorohydrin copolymer preferably has a copolymerization ratio of ethylene oxide of 5 to 40 mol%. If the amount is less than 5 mol%, a desired electrical resistance of the semiconductive region may not be obtained, and if it exceeds 40 mol%, a partner member such as a photoconductor may be contaminated. More preferably, it is 10 to 30 mol%.

The mechanism by which ethylene oxide contributes to contamination is not clear, but if the copolymerization ratio of ethylene oxide is large, the number of flexible oxygen atoms due to the ether chain present in the molecule increases, and this increases the photoreceptor and the like. It is thought that this surface is altered upon contact. It is also conceivable that as the number of ether chains increases, the amount of water contained in the polymer increases, and this plays a role in dissolving the photoreceptor contaminants (both intrinsic and extrinsic) and attaching them to the photoreceptor surface.

The composition of the above epichlorohydrin copolymer may be a copolymer of two compounds of epichlorohydrin and ethylene oxide as long as ethylene oxide is within the above-mentioned copolymerization ratio, or may be a copolymer other than the two compounds. Alternatively, a copolymer of three or more compounds including, for example, allyl glycidyl ether may be used.

The rubber component constituting the inner layer and the outer layer includes:
Examples of the vulcanizing agent for forming the rubber include oil sulfur and 6-methylquinoxaline-2,3-dithiocarbamate.

The rubber component constituting the inner layer and the outer layer includes
Examples of the vulcanization accelerator for forming the rubber include tellurium diethyldithiocarbamate, N-cyclohexyl-2-benzothiazole-sulfenamide, diphenylguanidine, tetramethylthiuram disulfide and the like. The vulcanization accelerator may be used alone,
Two or more kinds may be used in combination.

Since the conductive roller of the present invention has the above-described configuration, a sufficient vibration sound preventing effect can be obtained by the low elastic modulus and the vibration absorbing ability of the foamed rubber layer as the inner layer. Furthermore, the rubber layer made of an epichlorohydrin copolymer as the outer layer has excellent conductivity and non-staining properties.

The method of manufacturing the above-mentioned conductive roller is as follows. An unvulcanized rubber layer comprising at least two inner and outer layers is laminated concentrically around a cylindrical cored bar, thereby preforming the conductive roller. A method of forming a body, and thereafter vulcanizing the unvulcanized rubber layer in a molding die to foam the inner layer.

In the above-mentioned manufacturing method, first, an inner layer made of an unvulcanized rubber layer and an outer layer made of an unvulcanized rubber layer are laminated concentrically around the columnar core metal to form a conductive layer. To form a preform of a flexible roller. As a method of laminating the unvulcanized rubber layer, for example, a method of simultaneous extrusion using a crosshead or the like can be exemplified.
The crosshead is a device generally used for coating a wire, and is used by being attached to a discharge portion of a cylinder of an extruder.

As a method of vulcanizing the unvulcanized rubber layer in a molding die, for example, as shown in FIG. 4, an unvulcanized rubber layer comprising an unvulcanized inner layer 13 and an unvulcanized outer layer 14 is used. The conductive roller preform having the laminated layers is
5 and a method of heating it by mounting it in a cylindrical mold 16 having 5. Further, the inner rubber layer can be foamed in the mold.

Since the conductive roller of the present invention has the above-described structure, it is suitably used as a conductive roller such as a charging roller, a developing roller, a transfer roller, and a cleaning roller of an electrophotographic apparatus such as a copying machine, a facsimile, and a printer. be able to.

[0026]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Evaluation of Formulations 1 and 2 Using Formulations 1 and 2 having the compositions shown in Table 1, a vulcanized sheet produced by press vulcanization was adhered to the surface of a commercially available organic photoreceptor. 1 in an environment of 90% humidity
After leaving for 4 days, the vulcanizate sheet was removed and the surface of the photoreceptor was visually observed. The results are shown in Table 3. As shown in Table 3, Formulation 1 showed no staining, while Formulation 2 showed clouding of the surface. As a result of observing the surface of the photoreceptor in detail with a metallographic microscope, the surface of the photoreceptor was smooth in Formulation 1, but the surface was not smooth in Formulation 2 and clouding was remarkably observed. In the measurement of electric resistance,
Formulations 1 and 2 both exhibited electrical resistance in the semiconductive region.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]Evaluation method  1. Volume resistivity The resistance value at an applied voltage of 250 V was measured. 2. Visual observation The contact surface of the roller with the photoreceptor was visually observed and evaluated as follows.
The evaluation was based on criteria. ○ = Smooth photoconductor surface, cloudy
Etc. are not observed. × = The photoreceptor surface is not smooth and cloudiness is remarkably observed.
You. 3. Metallographic observation Observe the contact surface of the roller with the photoreceptor under a microscope.
Evaluation was performed using the same criteria as the evaluation criteria.

Evaluation of Formulations 3 and 4 Regarding the physical properties of Formulations 3 and 4 having the compositions shown in Table 2, the true specific gravity, the foaming specific gravity, the foaming ratio, the water absorption specific gravity, the open cell degree,
C _s (compression set) (%) and was measured sponge hardness. The results are shown in Table 4.

[0032]Measuring method Foaming ratio  Calculate the ratio of solid specific gravity before foaming to foam specific gravity
did.Specific gravity of water absorption  Using the above foam of 20 × 20 × about 5 mm as a test piece,
Reduce the pressure to 125 mmHg at a position 50 mm below and hold for 5 minutes.
After holding, measure the specific gravity when left under atmospheric pressure for 3 minutes
did.Open cell  Calculate the ratio of the water absorption specific gravity of the foam to the foam specific gravity.
Was.C _s (%)  According to the method of measuring compression set of JIS K 6262
The measurement was performed in a standing environment at 40 ° C. for 22 hours.Sponge hardness  Using a type E durometer for the rubber layer of the roller molding
It was measured.

[0033]

[Table 3]

[0034]

[Table 4]

In Tables 1 and 2, each component is as follows. Polymer 1): epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer (ethylene oxide 20 mol%, allyl glycidyl ether 5 mol)
%) Polymer 2): epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer (ethylene oxide 50 mol%, allyl glycidyl ether 5 mol)
%)

Polymer 3): Ethylene-propylene-ethylidene norbornene copolymer

Vulcanizing Agent: Oil Sulfur Vulcanizing Accelerator 1): Tellurium Diethyldithiocarbamate Vulcanizing Accelerator 2): N-Cyclohexyl-2-benzothiazol-sulfenamide Carbon Black: SRF Carbon Softener: Paraffin Process Oil Foaming agent: azodicarbonamide Foaming aid: Celton NP (manufactured by Sankyo Chemical Co., Ltd.)

Example 1 A conductive rubber roller was prepared using the combinations shown in Table 5 as the compounds used for the inner layer and the outer layer. The obtained roller exhibited good photoreceptor contamination when left in an environment of 40 ° C. and 90% humidity for 14 days in contact with the photoreceptor. Also, as a result of observing the photosensitive member contact surface of the removed roller, no deformation of the roller due to compression was observed.
This roller was applied to the electrophotographic apparatus shown in FIG. 3 as a charging roller, and a copied image was formed by reversal development. As a result, a good image was obtained without disturbing the image due to background fogging, black spot contamination, abnormal discharge and the like. . Also, as a result of measuring the sound generated when the electrophotographic apparatus was driven, the vibration sound generated from the conductive rubber roller was small.

Comparative Example 1 The same procedure as in Example 1 was carried out except that a conductive rubber roller was produced in place of the combination of the compounds shown in Table 5. As a result, the photoreceptor contamination was good, but as a result of observing the photoreceptor contact surface of the removed roller, deformation of the roller due to compression was observed. When this roller was applied to an electrophotographic apparatus, no disturbance of the image due to background fogging or abnormal discharge was observed, but there was a portion where an image was not formed in a white line in some places, and a good image was not obtained. Further, as a sound generated when the electrophotographic apparatus was driven, a phenomenon in which the vibration sound generated from the conductive rubber roller periodically increased was felt.

Comparative Example 2 The same procedure as in Example 1 was carried out except that a conductive rubber roller was produced in place of the combinations shown in Table 5. As a result, clouding was observed on the surface of the photoreceptor. When this roller was applied to an electrophotographic apparatus, band-like black spot stains were observed in some places, and good images could not be obtained.

[0041]

[Table 5]

[0042]

Since the conductive roller of the present invention has the above-described structure, it has excellent conductivity, and when applied to an electrophotographic apparatus or the like, does not contaminate a partner member such as a photoreceptor. A good image can be formed. Furthermore, by using a foam for the inner layer, vibration noise can be reduced and permanent deformation due to compression can be prevented.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a conductive roller of the present invention.

FIG. 2 is a schematic longitudinal sectional view of the conductive roller of the present invention.

FIG. 3 is a schematic diagram illustrating a structure of an electrophotographic apparatus.

FIG. 4 is a schematic view for explaining a method for manufacturing a conductive roller of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Core metal 2 Inner layer 3 Outer layer 4 Charging roller 5 Toner regulating blade 6 Toner stirring propeller 7 Developing machine 8 Toner transport roller 9 Developing roller 10 Transfer roller 11 Photoconductor 12 Cleaning blade 13 Unvulcanized inner layer 14 Unvulcanized outer layer 15 Flange 16 Mold

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) G03G 15/16 103 G03G 15/16 103 F-term (Reference) 2H003 BB11 BB13 BB16 CC05 2H032 AA05 2H077 AD06 FA13 FA22 3J103 AA02 AA14 AA23 BA41 EA02 EA20 FA04 FA15 FA30 GA02 GA52 GA74 HA03 HA12 HA18 HA20 HA53 4J002 BB151 CH031 CH041 EQ016 FD010 FD140 FD150 FD326 GF00

Claims (4)

[Claims] 1. A conductive roller having a structure in which a core metal on a cylinder and a rubber layer having conductivity that is concentrically laminated around the core metal are provided, wherein the rubber layer has at least two rubber layers. Consisting of a layer, among the rubber layers, an inner rubber layer,
A conductive roller having a foaming ratio of 2.0 to 4.0 and a foamed layer having an open cell degree of 1.3 or more. 2. The rubber layer comprising at least two layers,
2. The conductive roller according to claim 1, wherein the outer rubber layer is made of an epichlorohydrin copolymer obtained by copolymerizing at least epichlorohydrin and ethylene oxide. 3. The conductive roller according to claim 2, wherein the epichlorohydrin copolymer has a copolymerization ratio of ethylene oxide of 5 to 40 mol%. 4. A method for producing a conductive roller according to claim 1, wherein the unvulcanized conductive rubber comprises at least two layers concentrically around a core metal on a cylinder. Layer, the rubber layer of the inner layer is a foamed rubber layer, the rubber layer of the outer layer is laminated to form a non-foamed rubber layer made of epichlorohydrin copolymer, a step of creating a conductive roller preform, and And thereafter vulcanizing and foaming the conductive roller preform in a molding die.