JPH09269629A - Semiconducting rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconducting rubber roll such as an electrification roll having a semiconducting rubber member which shows little dependence of the electric resistance on the environment and has stable semiconducting property and excellent wear resistance of a resin layer (which hardly peels), having little dependence on environment of electric resistance without causing contamination on a photoreceptor drum nor fog due to deposition of a toner. SOLUTION: This roll consists of a metal core 1, a rubber layer 2 which covers the outer surface of the core, and a resin layer which covers the outer surface of the rubber layer. The resin layer consists of an inner layer 3a and an outer layer 3b, and the inner layer consists of a resin having 10 to 60 deg.C glass transition temp., while the outer layer consists of a resin having 35 to 90 deg.C glass transition temp. The glass transition temp. of the resin for the outer layer is made higher than the glass transition temp. of the resin for the inner layer.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a semiconductive rubber roll used in an electrophotographic apparatus.

[0002]

2. Description of the Related Art An electrophotographic copying machine or electrophotographic printing machine forms an electrostatic latent image by uniformly charging the outer peripheral surface of a photosensitive drum and then exposing the outer peripheral surface of the photosensitive drum with a print pattern or a copy pattern. Then, a toner is attached to the electrostatic latent image to form (develop) a toner image, and the toner image is transferred to a copy sheet or a printing sheet to print or copy. In the above description, in order to uniformly charge the outer peripheral surface of the photoconductor drum, a charging rubber roll rotatably provided in direct contact with the photoconductor drum is used. As a charging rubber roll,
A core material and a rubber layer covering the core material are known. For charging rubber rolls used in electrophotographic devices,
In order to uniformly charge the photoconductor drum, it is necessary to adjust the electric resistance between the core material and the outer peripheral surface of the rubber layer. Further, in an electrophotographic apparatus that cleans the toner on the outer peripheral surface of the photoconductor at the same time as development, a so-called cleanerless electrophotographic apparatus does not include means for cleaning the toner before the photoconductor drum and the charging rubber roll contact each other. It is necessary to charge the outer peripheral surface of the photosensitive drum with the transfer residual toner attached to the outer peripheral surface of the photosensitive drum. In order to evenly charge the photoconductor drum and prevent the photoconductor drum from being contaminated, a charging rubber roll in which a rubber layer outer peripheral surface is coated with a resin is proposed. For example, polyurethane or silicone is used as a resin coating layer. One layer, nylon layer / rubber layer /
A device having a three-layer structure including a nylon layer has been proposed. However, the uniformity of charging was insufficient with a rubber roll whose outer peripheral surface was covered with a single layer of resin. In the cleanerless electrophotographic apparatus, transfer residual toner on the outer peripheral surface of the photoconductor may adhere to the charging roll, which causes a defective image. Further, since the resin layer coated on the rubber layer is in sliding contact with the toner and the photosensitive drum, it may be peeled off due to abrasion.

[0003]

DISCLOSURE OF THE INVENTION An object of the present invention is to have a stable semiconductivity with less environmental dependence of electric resistance.
Provided is a semi-conductive rubber roll such as a charging roll having a semi-conductive rubber member which does not cause contamination of the photosensitive drum, does not cause fogging due to adhesion of toner, and has excellent abrasion resistance of the resin layer (hard to peel off). The purpose is to

[0004]

According to the present invention, in order to solve the above-mentioned problems, a metal core material, a rubber layer coating the outer peripheral surface of the core material, and a rubber layer coating the outer peripheral surface of the rubber layer. A resin layer having a glass transition temperature of 10 to 60 ° C., an outer layer formed of a resin having a glass transition temperature of 35 to 90 ° C., and an inner layer formed of an inner layer and an outer layer. Provided is a semiconductive rubber roll characterized in that the glass transition temperature of a resin forming an outer layer is higher than the glass transition temperature of a resin to be formed. That is, the present inventors, in the electrophotographic apparatus semiconductive rubber roll having a resin layer formed on the outer peripheral surface of the rubber layer, the resin layer comprises an inner layer and an outer layer,
The inner layer is formed of a resin having a glass transition temperature of 10 to 60 ° C.,
The outer layer is formed of a resin having a glass transition temperature of 35 to 90 ° C.,
Further, they have found that the above problems can be solved by making the glass transition temperature of the resin forming the outer layer higher than the glass transition temperature of the resin forming the inner layer, and have reached the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be shown below to specifically describe the manufacturing method and constitution of the semiconductive rubber roll of the present invention. In the semiconductive rubber roll of the present invention, first, an adhesive is applied to the outer peripheral surface of a metal core material, a rubber layer is laminated thereon to adhere the core material and the rubber layer, and then the rubber layer is coated on the rubber layer. An inner layer and an outer layer, the inner layer is formed of a resin having a glass transition temperature of 10 to 60 ° C., the outer layer is formed of a resin having a glass transition temperature of 35 to 90 ° C., and the outer layer is higher than the glass transition temperature of the resin forming the inner layer. It is manufactured by forming a resin layer having a high glass transition temperature of the resin forming the. In order to coat the surface of the metal core material with the rubber layer, a roll-shaped base material such as a metal rotating shaft is used as a core metal, and an adhesive such as a phenol resin, an epoxy resin, or an acrylic resin is attached to the outer peripheral surface of the core metal. An adhesive having at least one resin selected from the group consisting of resin and polyurethane resin as an adhesive component is applied,
An adhesive layer having a layer thickness of 2 to 50 μm is formed. When the layer thickness of the adhesive layer is as thin as less than 2 μm, peeling is easy, and when the layer thickness of the adhesive layer exceeds 50 μm, volume control becomes difficult. When the volume resistivity of the adhesive layer is reduced, the adhesive force is reduced and the durability of the rubber roll is deteriorated. On the other hand, when the volume resistivity increases, the volume resistivity of the entire rubber roll varies, so
It is preferably in the range of 10 ³ Ω · cm to ^{10 10} Ω · cm. The core metal having the adhesive layer formed as described above is put into a roll mold, the rubber composition containing a vulcanizing agent and the like is put therein, and the rubber is formed into a roll shape around the core metal. The layers may be formed and then heated to vulcanize. The layer thickness of the rubber layer is not particularly limited, but is usually 1 to 10 mm. Vulcanization conditions such as vulcanization temperature and vulcanization time can be appropriately determined according to the type of rubber component used. For example, when the rubber component is an epihalohydrin copolymer rubber or a blend rubber containing the epihalohydrin copolymer rubber, usually,
It may be heated at 100 to 250 ° C. for about 10 to 60 minutes. As the vulcanizing agent, a sulfur-based vulcanizing agent or peroxide is usually used. Metal oxides can be used, but they are not preferable because they may contaminate the photosensitive drum. The vulcanizing agent is usually 0.1 to 100 parts by weight of the rubber composition.
It is used in an amount of 5 parts by weight, preferably 0.2 to 3 parts by weight. The volume resistivity of the rubber layer is preferably in the range of 10 ⁷ to 10 ¹¹ Ω · cm in order to give the semiconductive roll having a volume resistance of 10 ⁷ to 10 ¹¹ Ω · cm. . The volume resistivity of the rubber layer can be adjusted by selecting the material of the rubber layer and / or adding a conductive filler such as conductive carbon. The layer thickness of the rubber layer is not particularly limited, but is usually 1 to 10 mm.

Examples of the material for the rubber layer include various rubbers and rubber compositions (blends of two or more rubbers). The rubber or rubber composition forming the rubber layer has a glass transition temperature (Tg) of usually -80 to 10 ° C, but preferably -80 to -10 ° C in order to improve strain recovery at low temperatures. Specific examples of such rubber include epihalohydrin rubber, urethane rubber, silicone rubber, polybutadiene, NBR (acrylonitrile-butadiene rubber), H-NBR (hydrogenated acrylonitrile-butadiene rubber), styrene-butadiene copolymer rubber, Examples thereof include propylene oxide rubber. Among these, the one using a rubber composition containing an epihalohydrin rubber and an acrylonitrile-butadiene copolymer rubber is preferable because the electric resistance can be easily adjusted and the pressing force of the roll tends to be uniform. More specifically, preferable rubber components include (A) epihalohydrin copolymer rubber 40 to 90% by weight, (B) unsaturated rubber 5 to 40% by weight, and (C) liquid unsaturated rubber 5 to 40% by weight. The rubber composition contained can be mentioned. That is, when a rubber layer is formed using a rubber composition in which an epihalohydrin copolymer rubber, an unsaturated rubber that is solid at room temperature, and a liquid unsaturated rubber that is liquid at room temperature are blended in a specific ratio, the conductive layer contains that much conductive filler. Even if it is not carried out, a roll having a reasonably low electric resistance, being excellent in environmental stability of the electric resistance, having a reasonably low hardness, and having a small dynamic friction coefficient is preferable. In the rubber composition, the proportion of the unsaturated rubber as the component (B) is 5 to 40% by weight, preferably 5 to 35% by weight, more preferably 5 to 30% by weight. If the proportion of the component (B) is too large, it becomes difficult to obtain an appropriately low electric resistance, and if it is too small, the workability is lowered and the hardness and the coefficient of dynamic friction are increased. In the rubber composition,
The proportion of the liquid unsaturated rubber as the component (C) is 5 to 40% by weight, preferably 5 to 35% by weight, more preferably 5 to 3%.
0% by weight. If the proportion of component (C) is too high, the coefficient of dynamic friction will be high, and the adhesion of toner to the charging roll will occur. If it is too low, the hardness will be high and the contact with the photosensitive drum will be insufficient, resulting in uneven charging. become.

After vulcanization and molding, the obtained rubber roll is preferably subjected to a polishing treatment before forming the resin layer in order to improve the dimensional accuracy and to improve the smoothness of the surface. As the polishing method, a method of mechanically polishing with an abrasive is usually employed. Surface roughness is JIS
0.5 at 10 point average roughness described in B-0601
The thickness is set to 10 μm, preferably 1 to 8 μm. At this stage, if the surface roughness of the rubber layer exceeds 10 μm, even if the resin is coated, the surface roughness of the coated surface cannot be sufficiently reduced, and the coefficient of dynamic friction becomes large. As a result, the OPC photoreceptor Contamination becomes remarkable, and moreover, the toner remaining on the photosensitive drum adheres to the rubber roll, causing fog on the printing paper. In addition, the dynamic friction coefficient of the rubber layer is set to 1 by polishing.
It is preferable to adjust it within the range of 3 to 3. After performing the polishing treatment as needed, the resin layer is sequentially formed on the surface of the rubber layer, including the inner layer and the outer layer. Each of the inner layer and the outer layer is formed by coating and drying the resin solution or dispersion liquid constituting each layer by brush coating, spray coating, dipping, or the like. Examples of the method for drying the resin layer include methods such as natural drying and heating. Among them, heating drying is preferable in order to increase the uniformity of the film thickness of the coating layer. Further, it is preferable to further irradiate ultraviolet rays to harden the surface to reduce the frictional resistance, if necessary.
Examples of the resin forming the resin layer include polyurethane resin, silicone resin, polyamide resin, polyester resin, polyimide resin, and the like, but polyurethane resin is preferable. The coating of the polyurethane resin is preferably performed using a self-emulsifying type or forced emulsifying type polyurethane resin aqueous dispersion. Conventionally, a charging roll having a structure in which a surface of a rubber roll is coated with a polyurethane resin is known, but as a coating method, a method of immersing the rubber roll in an organic solvent solution of the polyurethane resin has been adopted. However, the method using the polyurethane resin solution is
In addition to the problem of environmental pollution due to volatilization of the organic solvent, it is difficult to reduce the surface roughness of the polyurethane resin coating layer due to the high evaporation rate of the organic solvent. It is easy to cause inconveniences such as extracting the compounding agent from. As the self-emulsifying type or forced emulsifying type polyurethane resin aqueous dispersion, commercially available products can be used. The polyurethane resin may contain a functional group or a reactive group. Regarding the film forming conditions of the aqueous dispersion, there are various types such as drying, heat curing, and ultraviolet curing.

The polyurethane resin which can be preferably used in the present invention is a reaction product of a polyfunctional isocyanate compound and a polyether polyol or a polyester polyol. This polyurethane resin may have a hydrophilic functional group in the molecular chain. As the functional group, a hydroxyl group,
A carboxyl group etc. can be illustrated. Polyfunctional isocyanate compound (ie, 2 isocyanate groups
Examples of aromatic compounds such as triphenylmethane triisocyanate, 4,4-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, tolylene diisocyanate, tetramethylxylene diisocyanate and xylene diisocyanate; and dicyclohexane diisocyanate, dicyclohexyl. Aliphatic isocyanates such as methane diisocyanate, hexamethylene diisocyanate and isophorone diisocyanate; and the like.

Examples of the polyether polyol include polyoxytetramethylene glycol, polyethylene glycol, polypropylene glycol and the like. Examples of the polyester polyol include those having a hydroxyl group at the molecular end obtained by reacting a polyvalent carboxylic acid with a polyol (including a polyether polyol), and also include a polycarbonate diol and the like. Examples of the polycarboxylic acid include adipic acid, phthalic acid, sebacic acid, and dimer acid. Examples of the polyol include ethylene glycol, diethylene glycol, propylene glycol, butylene glycol, 1,3-butanediol, hexanetriol, trimethylolpropane, glycerin, pentaerythritol, sorbitol, and glycol dicarboxylate. Polyurethane resin
Those having a molecular weight of usually 100,000 to 500,000, preferably 200,000 to 300,000 are used.

Examples of the silicone resin which can be used as the coating resin include those having a methyl group or a phenyl group in the side chain, and those modified with an acryl group, an epoxy group, an ester group or the like.

The glass transition temperature (Tg
i) is 10 to 60 ° C, preferably 15 to 40 ° C. By setting Tgi in this range, the adhesion with the outer layer and the rubber layer is improved. The layer thickness of the inner layer is 5 to 60 μm in order to improve the adhesion with the rubber layer and the outer layer.
The range of m is preferable, and its volume resistivity is 10 ⁶ in order to reduce the variation of the volume resistivity of the entire rubber roll.
-10 ¹² Ω · cm is preferable. The glass transition temperature (Tgo) of the resin of the outer layer is 35 to 90 ° C., preferably 40.
８０80 ° C. When a resin having a glass transition temperature (Tgo) of less than 35 ° C. is used, adhesion of toner occurs, and when a resin having a glass transition temperature (Tgo) of more than 90 ° C. is used, cracks are formed in the coating and it cannot be put to practical use. . Also,
The thickness of the outer layer, is less than 5μm lowered durability against wear, and because easily cracked in exceeds 40μm coating, preferably in the range of 5 to 40 m, as well as its volume resistivity inner layer 10 ⁶ -10 ¹² Ω · cm is preferable. Further, the total layer thickness of the inner layer and the outer layer is 10 to
It is 100 μm, preferably 10 to 85 μm. If the total layer thickness is less than 10 μm, charging failure tends to occur, and
If it exceeds 00 μm, the production efficiency of the rubber roll decreases.
Further, if the glass transition temperatures of the resins constituting the inner layer and the outer layer are not separated by 10 ° C. or more, it becomes difficult to balance the durability and the adhesiveness of the toner. Therefore, Tgi + 10
It is preferable that the relationship of ° C <Tgo is satisfied. In the present invention, a differential thermal analyzer (DSC) was used as the method for measuring the glass transition temperature.

The core metal used in the present invention comprises a core rod and a core material made of a conductive rigid body. Examples of the conductive rigid body include metals such as stainless steel and copper. The core material may be a solid body or a hollow body. The shape of the core material may be, for example, a columnar shape. As shown in FIG. 1, the shape in which the outer diameter of the central portion in the axial direction is the largest and the outer diameter of both end portions is small is By doing so, it is possible to reduce the bending of the core metal and prevent the pressing force at the central portion in the axial direction from decreasing. The one shown in FIG. 1 has a cylindrical shape at the center and the both ends have a tapered diameter, and the one shown in FIG. 2 has a straight cored bar. In the core material of FIG. 1, the outer diameter of the central part of the core material is usually 4 to 40 mm. The outer diameter of both ends of the core material can be appropriately selected depending on the elasticity of the coating layer from the core material to the outer peripheral surface of the charging roll, but is usually 3 to 30 mm. The length of the core material is usually 150 to 300 mm. The range of diameter reduction at both ends is usually 5 to 100 mm. It is preferable that the outer peripheral surface of the core material has a large surface roughness by polishing or the like in order to improve the bonding with the above-mentioned coating layer that covers the outer peripheral surface.

The core rod is formed by extending from both ends of the core material coaxially with the core material. The shaft rod usually has an outer diameter equal to or smaller than the outer diameter of the both ends of the core metal body. The shaft rod usually has a columnar shape, and may be provided with a groove in the circumferential direction, if necessary, for easy installation on the bearing. The cored bar may be a structure in which the shaft rod and the cored bar main body are integrated, or may be a structure in which the shaft bar and the cored bar main body are separate structures and assembled from each other.

The outer diameter of the above-mentioned central portion in the axial direction is the largest,
When the above-mentioned coating layer is formed on the outer peripheral surface of the core material in which the outer diameters of both ends are small, the coating layer from the outer peripheral surface of the core material to the outer peripheral surface of the charging roll is thick at both ends, It is thinly laminated in the central part. By increasing the thickness of both ends, the distance between the cored bar made of a rigid body and other roll surfaces, etc. is increased, and since a thick elastic body is interposed between them,
The pressing force applied to the other roll surface or the like is absorbed by the elastic body, and wear can be reduced. The thickness of the central portion of the coating layer is usually 0.5.
It is preferable that the thickness of both ends corresponds to the diameter reduction of the core metal body, and the outer diameter of the entire rubber roll is equal from both ends to the central part.

[0015]

EXAMPLES Examples 1 and 2 were carried out by using the rubber component and the polyurethane component shown in Tables 1 and 2 below and forming the inner and outer layers of polyurethane with the thicknesses shown in the same table, and the results are shown below. It shows in Table 3. As shown in Tables 1 and 2 below, Comparative Examples 1 to 3 were carried out by forming a single layer of polyurethane or an inner layer and an outer layer of polyurethane which do not satisfy the glass transition temperature requirement of the resin of the present invention. (Durability) Using a rubber roll as a charging roll, continuous printing was performed, 10,000 sheets, 20,000 sheets, 30,
The state of adhesion between the resin layer and the rubber layer on 00 sheets was observed. (Toner adhesion) Using a rubber roll as a charging roll, 1
The toner adhesion state was observed after continuous printing of 10,000 sheets.

[0016]

[Table 1] * 1 NBR: Acrylonitrile-butadiene copolymer containing 33% by weight of acrylonitrile * 2 Liquid NBR: Liquid acrylonitrile-butadiene copolymer containing 33% by weight of acrylonitrile * 3 TMTD: Tetramethylthiuram disulfide

[0017]

[Table 2]

[0018]

[Table 3] The T of the polyurethane resin used in the above Examples and Comparative Examples
The g and the source are as follows. Tg = 72 ° C .: Daiichi Kogyo Seiyaku Co., Ltd. Super Flex 1
26 (trade name) Tg = 40 ° C .: Daiichi Kogyo Seiyaku Co., Ltd. Super Flex 1
50 (brand name) Tg = 37 ° C .: Daiichi Kogyo Seiyaku Co., Ltd. Super Flex 1
60 (trade name) Tg = 20 ° C .: Asahi Denka Kogyo ADEKA BON TITER Hu
x232 (trade name)

[0019]

According to the present invention, the environmental dependence of the electric resistance is small, the electric resistance is stable, the hardness is low, the dynamic friction coefficient is small, and the photosensitive drum is not contaminated.
Provided is a semi-conductive rubber roll that is free from contamination due to toner adhesion. INDUSTRIAL APPLICABILITY The semiconductive rubber roll of the present invention is a non-magnetic one-component contact developing system and is suitable for a cleanerless system image forming apparatus which does not require a device for cleaning the photosensitive drum. In the semiconductive rubber roll of the present invention, toner is less attached to the roll surface and the contact portion with the photoconductor is uniform, so that the photoconductor drum is also uniformly charged. As a result, the toner is likely to adhere uniformly, and uneven printing, blurring, and fog do not occur. Further, according to the present invention, an image forming apparatus provided with a semi-conductive rubber roll such as a charging roll having such excellent characteristics is provided.

[Brief description of drawings]

FIG. 1 is an axial sectional view of an example of a rubber roll according to the present invention.

FIG. 2 is an axial sectional view of another example of the rubber roll according to the present invention.

[Explanation of symbols]

 1 core metal 2 resistance adjusting layer (rubber layer) 3a polyurethane coating layer (inner layer) 3b polyurethane coating layer (outer layer)

Claims (2)

[Claims] 1. A metal core material, a rubber layer covering the outer peripheral surface of the core material, and a resin layer covering the outer peripheral surface of the rubber layer, the resin layer comprising an inner layer and an outer layer, The inner layer is formed of a resin having a glass transition temperature of 10 to 60 ° C, the outer layer is formed of a resin having a glass transition temperature of 35 to 90 ° C, and the glass transition temperature of a resin forming an outer layer is higher than the glass transition temperature of a resin forming the inner layer. Highly conductive semi-conductive rubber roll. 2. The semiconductive rubber roll according to claim 1, wherein the resin layer satisfies the following requirements. (I) Inner layer (1) Glass transition temperature (Tgi) = 10 to 60 ° C. (2) Layer thickness = 5 to 60 μm (3) Volume resistivity = 10 ⁶ to 10 ¹² Ω · cm (II) Outer layer (1) Glass Transition temperature (Tgo) = 35 to 90 ° C. (2) Layer thickness = 5 to 40 μm (3) Volume resistivity = 10 ⁶ to 10 ¹² Ω · cm (III) Total layer thickness of inner layer and outer layer = 10 to 100 μm (IV ) Glass transition temperature (Tgo)> glass transition temperature (T
gi) + 10 ° C