JP2000035032A - Conductive roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive roller excellent in vibration sound preventive effect, conductivity, and an uncontaminable property, and easy in working and forming. SOLUTION: In a conductive roller composed of structure providing a core metal on a column, and rubber layers concentrically laminated in the periphery of the code metal and having conductivity; the rubber layers are composed of at least two layers, and the outer rubber layer out of the rubber layers is composed of epichlorohydrin copolymer obtained by copolymerizing at least the epichlorohydrin and an ethylene oxide, and liquid NBR rubber having the low molecular weight of a combined acrylonitrile content of 20-50%.

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. When the photoreceptor is operated, the outer peripheral surface of the photoreceptor is uniformly charged.
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.

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, it is difficult to control the dispersion. 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 using an epichlorohydrin-based copolymer 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, if the vulcanized rubber is used for a roller and applied to a use method in which the vulcanized rubber comes into direct contact with another member, there is a problem that a counterpart agent is contaminated. One of the causes of the contamination is that a low molecular weight component, particularly an oily component or a plasticizer, blended in the rubber bleeds out to the surface and migrates to other members in contact.

As a method for solving this problem, first, an oil component or a plasticizer is not used. However, such a composition restricts processing and molding,
There is a problem that the hardness of the completed roll increases. Second, a method of using a low molecular weight liquid rubber in place of an oil component or a plasticizer is disclosed in JP-A-59-46664. As the liquid rubber, liquid butadiene rubber,
A method using a liquid styrene-butadiene rubber, a liquid nitrile rubber, and a liquid chloroprene rubber is disclosed. However, when such a liquid rubber is blended with an epichlorohydrin-based copolymer, the desired plasticizing and low-hardening effects are not sufficiently exhibited if the affinity for the epichlorohydrin-based copolymer is low, As in the case of ordinary oily components and plasticizers, there is a problem that bleed-out and transfer to other members in contact are caused.

A third method is to coat the surface with a non-contaminating material (urethane resin, acrylic resin, etc.), or to add a reactive material to the vulcanized rubber to form a cured film of the non-contaminating substance near the surface. Methods of forming have been proposed. However, there is a problem that when the surface of the formed and vulcanized roll is coated, the cost is high due to the provision of the coating layer, and it is difficult to control the film thickness in the formation of the cured film, so that uniform quality cannot be obtained. There is a possibility that the intended performance cannot be obtained due to changes in the surface condition.

[0009]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a conductive roller which is excellent in vibration noise prevention effect, has excellent conductivity and non-staining properties, and is easy to process and form. It is.

[0010]

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 is composed of at least two layers, and among the rubber layers, the outer rubber layer has an epichlorohydrin-based copolymer obtained by copolymerizing at least epichlorohydrin and ethylene oxide, and a bound acrylonitrile content. A conductive roller comprising a liquid NBR rubber having a low molecular weight of 20 to 50%. Hereinafter, the present invention will be described in detail.

[0011] The conductive roller of the present invention has a structure in which a conductive rubber layer laminated concentrically around a cylindrical cored bar is provided. The core metal is not particularly limited, and examples thereof include those generally used as a core metal for rollers such as a hollow cylindrical or solid iron core metal and a steel core metal.

The rubber layer comprises at least two layers. Among the rubber layers, the components constituting the outer rubber layer include an epichlorohydrin-based copolymer obtained by copolymerizing at least epichlorohydrin and ethylene oxide, and a bound acrylonitrile content of 20 to 5.
It contains 0% low molecular weight liquid NBR rubber. The outer layer is preferably a non-foamed rubber layer.
Further, the outer rubber layer may be composed of a plurality of layers.

Since the outer rubber layer contains the epichlorohydrin copolymer and the liquid NBR rubber, it can be easily processed and formed, and the roll surface layer can be easily reduced in hardness. . Furthermore, contamination due to bleed-out of the formulation can be prevented.

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 epichlorohydrin copolymer may be a copolymer of two compounds of epichlorohydrin and ethylene oxide, or a copolymer of three or more compounds containing compounds other than the two compounds. But it is good.

The above liquid NBR rubber is acrylonitrile butadiene rubber which is liquid at normal temperature. The liquid NBR rubber has a low molecular weight. Here, "low molecular weight"
Mw means 1000-20,000. Preferably, it is 3000-10000.

The liquid acrylonitrile rubber has a bound acrylonitrile content of 20 to 50%. If the bound acrylonitrile content is less than 20%, the affinity with the epichlorohydrin copolymer is poor, and bleed out may occur. As a result, sufficient plasticizing curing cannot be obtained. Preferably, it is 30 to 45%.

The compounding amount of the NBR rubber is not particularly limited. Since the compatibility between the NBR rubber and the epichlorohydrin copolymer is good, the compounding amount depends on the roll hardness design, processing method, moldability and the like. Can be set. Preferably, it is 5 to 30 phr with respect to 100 parts by weight of the rubber forming the outer rubber layer, more preferably,
10-20 phr. If the amount is less than 5 phr, a desired plasticizing effect or low hardness may not be obtained. If the amount is more than 30 phr, mechanical properties may be reduced, or semi-conductive properties inherent to the epichlorohydrin copolymer may be obtained. May be impaired.

Of the above rubber layers, the component constituting the inner rubber layer is preferably a foamed rubber in that a low hardness can be achieved. Further, the inner rubber layer may be composed of a plurality of layers.

The composition of the foamed rubber is not particularly limited, and examples thereof include a copolymer of ethylene, propylene and ethylidene norbornene. The foamed rubber can be produced, for example, by adding a foaming agent such as azodicarbonamide and a foaming aid such as Celton NP (manufactured by Sankyo Chemical Co., Ltd.) to the rubber composition.

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

[0024] The method of manufacturing the conductive roller described above is characterized in that an unvulcanized rubber layer composed of at least two layers of an inner layer and an outer layer is concentrically laminated around a cylindrical cored bar. And then a step of vulcanizing the unvulcanized rubber layer in a mold and foaming 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 cored bar. 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 the 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 configuration, 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.

[0028]

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 to 7 Using Formulations 1 to 7 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. 14 in a 90% humidity environment
The vulcanizate sheet was then removed, and the photoreceptor surface was visually observed. The results are shown in Table 3. As shown in Table 3, Formulations 1, 2, 3, and 4 showed no staining, while Formulations 5, 6, and 7 showed surface fogging. As a result of observing the photoconductor surface in detail with a metallographic microscope,
In Formulations 1, 2, 3, and 4, the surface of the photoreceptor was smooth, but in Formulation 5, the surface was not smooth, and irregularities were observed on the surface. In Formulation 6, viscous deposits were observed on the photoreceptor surface. In Formulation 7, it was confirmed that a liquid which seemed to be an oily component adhered remarkably.

When the electric resistance was measured, Table 3
As shown in Table 2, Formulations 1, 2 and 3 showed the electric resistance value in the semiconductive region, and Formulation 4 had a higher electric resistance value. Further, when the hardness was measured, it was found that the composition 1
Showed a high value.

[0031]

[Table 1]

[0032]

[Table 2]

[0033]

[Table 3]

[0034]Evaluation method  1. Volume resistivity The resistance value at an applied voltage of 250 V was measured. 2. Hardness Type A durometer based on JIS K 6253
It measured using. 3. Visual observation Visually observe the photoconductor contact surface of the vulcanized sheet, and
The evaluation criteria were as follows. ＝= The surface of the photoreceptor is smooth and no clouding is observed. × = The photoreceptor surface is not smooth and cloudiness is remarkably observed.
You. XX = clouding of the photoreceptor surface is remarkable. 4. Observation with a metallographic microscope
Evaluation was made using the same criteria as the evaluation criteria for observation.

In Tables 1 and 2, each component is as follows. Polymer 1): epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer (ethylene oxide 25 mol%, allyl glycidyl ether 4 mol)
%) Polymer 2): Epichlorohydrin-ethylene oxide copolymer (ethylene oxide 25 mol%) Polymer 3): Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer (ethylene oxide 60 mol%, allyl glycidyl ether 4 mol)
%) Polymer 4): Ethylene-propylene-ethylidene norbornene copolymer

Liquid NBR1): Bound nitrile amount 32% Liquid NBR2): Bound nitrile amount 18% Plasticizer: Dioctyl adipate Acid acceptor: Hydrotalside compound Vulcanizing agent 1): Oil sulfur Vulcanizing agent 2): 6 -Methylquinoxaline-2,3-dithiocarbamate Vulcanization accelerator 1): Tellurium diethyldithiocarbamate Vulcanization accelerator 2): N-cyclohexyl-2-benzothiazole-sulfenamide Carbon black: SRF carbon Softener: Paraffin-based process Oil Foaming agent: Azodicarbonamide Foaming aid: Celton NP (manufactured by Sankyo Chemical)

Example 1 A conductive rubber roller was produced using the combinations shown in Table 4 as the compounds used for the inner layer and the outer layer. The obtained roller was brought into contact with the photoconductor at 40 ° C. and 90% humidity.
Of the photoreceptor when left in the environment for 14 days was good. 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 procedure of Example 1 was repeated, except that a conductive rubber roller was prepared in place of the combination shown in Table 5. As a result, contamination by clouding was observed on the surface of the photoreceptor. When this roller was applied to an electrophotographic apparatus, no image disturbance due to background fogging or abnormal discharge was observed, but a good image was not obtained because there were portions where no image was formed.

Comparative Example 2 The procedure of Example 1 was repeated, except that a conductive rubber roller was prepared in place of the combination of the compounds shown in Table 5. As a result, the photoreceptor contamination was good. When this roller was applied to an electrophotographic apparatus, background fogging, black spot contamination,
Although a good image without disturbance of the image due to abnormal discharge or the like was obtained, the sound generated when the electrophotographic apparatus was driven was measured. As a result, the vibration sound generated from the conductive rubber roller was a little annoying.

[0040]

[Table 4]

[0041]

Since the conductive roller of the present invention has the above-described structure, it is possible to provide a conductive roller which is excellent in vibration noise prevention effect, excellent in conductivity and non-contamination, and can be easily processed and formed.

[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

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) G03G 15/16 103 G03G 15/16 103 F term (reference) 2H003 BB11 BB16 CC05 2H032 AA05 2H077 AD06 FA00 FA13 FA22 FA25 3J103 AA02 AA14 AA23 BA41 EA02 EA20 FA04 FA15 FA30 GA02 GA32 GA52 GA57 GA58 GA60 GA74 HA03 HA12 HA18 HA20 HA53 4J002 AC072 CH041 FD022 FD140 FD150

Claims (3)

[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. Layer, the rubber layer of the outer layer among the rubber layers,
Epichlorohydrin copolymer obtained by copolymerizing at least epichlorohydrin and ethylene oxide,
And a conductive roller comprising a low molecular weight liquid NBR rubber having a bound acrylonitrile content of 20 to 50%. 2. The conductive roller according to claim 1, wherein the epichlorohydrin copolymer has a copolymerization ratio of ethylene oxide of 5 to 40 mol%. 3. A method for producing a conductive roller according to claim 1, wherein at least two unvulcanized conductive rubber layers are formed concentrically around a core metal on a cylinder. ,
The inner rubber layer is a foamed rubber layer, and the outer rubber layer is a non-foamed rubber layer composed of an epichlorohydrin copolymer and a low molecular weight liquid NBR rubber having a bound acrylonitrile content of 20 to 50%. Step of creating a conductive roller preform by laminating, and then,
A method for producing a conductive roller, comprising a step of vulcanizing and foaming the conductive roller preform in a molding die.