JP2006343717A - Electroconductive rubber roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electroconductive rubber roller which is not accompanied by problems such as deterioration of electrical conductivity and rise of hardness and has uniform electrical properties, low hardness and excellent compression set properties. <P>SOLUTION: The electroconductive rubber roller is constituted of an electroconductive metal core and an electroconductive crosslinked rubber layer including an epichlorohydrin-based rubber stacked on the electroconductive metal core, wherein the epichlorohydrin-based rubber is at least one copolymer selected from the group consisting of an epichlorohydrin-ethylene oxide copolymer and an epichlorohydrin-ethylene oxide-allyl glycidyl ether ternary copolymer. The ethylene oxide constitutional unit in the epichlorohydrin-based rubber is in a content of 40-90 mol%, and, the electroconductive crosslinked rubber layer has a heat quantity (enthalpy: ΔH) of ≤5 mJ/mg as measured by a differential scanning calorimetry (DSC) and indicated by a peak appearing within a range of -20 to 150°C. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a conductive rubber roller such as a charging roller, a developing roller, and a transfer roller used in an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus typified by a copying machine, a printer, and a facsimile machine.

  2. Description of the Related Art Conventionally, electrophotographic image forming apparatuses such as copying machines and printers employ a method in which toner is attached to an electrostatic latent image and the toner image is transferred to a recording medium such as transfer paper for printing. That is, first, the surface of the photosensitive member is uniformly charged, an image is projected onto the photosensitive member from the optical system, and the latent image is formed by erasing the charged portion of the exposed portion. Next, a method of printing is performed by forming (developing) a toner image by toner adhesion and transferring the toner image onto a recording medium such as transfer paper.

  As a means for uniformly charging the surface of the photoconductor, a charging member to which a voltage (for example, 1 to 2 kV) is applied is brought into contact with the photoconductor with a predetermined pressing force to charge the photoconductor to a predetermined potential. A charging method is known. The charging roller is an important point for uniform charging by the contact charging method. Since the two rotating cylinders make uniform contact with the photosensitive member, other contact charging methods such as brush charging and blade charging. It is easier to implement and is adopted.

  The charging roller is required to have a large and uniform contact area (nip width) between the charging roller and the photosensitive member in order to contact the photosensitive member and impart uniform and good charging properties. Therefore, the charging roller is required to have an appropriate hardness (low hardness). Further, the charging roller is deformed by contact, but needs to have sufficient recoverability with respect to the compression force. On the other hand, in order to apply a necessary bias voltage to the charging roller, the charging roller needs to have a low volume resistance and be adjusted to a desired current value. In addition, when the charging roller is electrically non-uniform, charging density unevenness reflecting this electric non-uniformity occurs on the photosensitive member. Therefore, the charging roller is required to have a predetermined resistance and be electrically uniform. In this way, the charging roller that is in direct contact with the photosensitive member is required to have many physical properties.

Further, the volume resistivity of the rubber roller used for the charging member needs a predetermined semiconductive region of 1 × 10 ⁵ to 1 × 10 ¹⁰ Ω · cm. In order to achieve the desired conductivity, conventional charging member manufacturing methods employ a method in which a conductive filler such as carbon black is added and dispersed, or a method in which a rubber having conductivity is selected. It was. In the method of adding and dispersing the conductive filler, the electrical characteristics are affected by the slight difference in the blending amount of the filler, the dispersion state and the orientation. For this reason, variation occurs in each kneading batch, and further, variation in each roller easily occurs in the same batch. Furthermore, the dependence on the applied voltage is large, and it is difficult to obtain a stable volume resistivity. However, the method of using a rubber material having electrical conductivity hardly causes such variations, so that it can be easily adjusted to have a predetermined electrical conductivity and can be obtained stably. Therefore, in recent years, the production of rollers using conductive rubber has been increasing with the improvement in performance of products.

  Examples of the conductive rubber generally include acrylonitrile butadiene rubber, epichlorohydrin rubber, and acrylic rubber. Among these, epichlorohydrin rubber is known to be a low resistance polymer among various rubbers.

  An epichlorohydrin homopolymer is known as an epichlorohydrin rubber. Further, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer, and epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer are known. These epichlorohydrin rubbers are characterized in that the resistance value can be controlled by variously changing the copolymerization ratio of ethylene oxide constituting the rubber, and the volume resistance increases as the copolymerization ratio increases. Is generally known to be low.

  However, for example, when an epichlorohydrin rubber having a high copolymerization ratio of ethylene oxide is used to produce a conductive rubber roller that requires a low volume resistance, a conductive rubber roller that satisfies the desired performance can be stably obtained. It was very difficult. This is because when a roller is manufactured using the above-mentioned epichlorohydrin rubber, there is a large variation in roller performance from lot to lot, a sufficient decrease in volume resistance is not observed, and the rubber hardness after vulcanization is poor. In some cases, the current value was abnormally small. When the current value is small, it is difficult to satisfy the required charging ability, and a good image cannot be obtained even when incorporated in an electrophotographic forming apparatus. Further, when the hardness is increased, a sufficient nip width cannot be secured even if the hardness is brought into contact with the photosensitive member, and not only good chargeability can be obtained, but also the photosensitive member itself may be damaged. Therefore, it is a fatal defect in exerting the performance of the conductive rubber roller.

As an example of overcoming the above-mentioned problem, there is a material disclosed in Patent Document 1. That is, this material has a volume resistivity of 1 × 10 ⁵ Ωcm to 2 × 10 ⁷ Ωcm at 23 ° C. and 50% RH as a semiconductive material for a low resistance conductive rubber roller, and It is a vulcanizable material having an ether copolymer having an environmental dependency of 2.5 or less.

  However, although the conductive rubber roller obtained from such a material is certainly obtained within the range of the resistance value shown above, there is a large variation in conductivity from lot to lot, and the conductivity for the image forming apparatus is large. As a functional rubber roller, it was poor in practicality.

Further, as a means for obtaining a conductive rubber roller having an appropriate hardness, a method of adding a plasticizer to epichlorohydrin rubber is usually employed. However, when a plasticizer used in general epichlorohydrin rubber is used, the plasticizer that has exuded from the conductive roller due to contact with the photoconductor for a long period of time partially alters the photoconductor (photosensitivity). Body contamination) and may affect the image. Therefore, there has been a problem that the types and blending amounts of plasticizers that can be used are limited.
JP 2000-063656 A

  The present invention has been made in view of the above-described problems, and has a uniform electrical characteristic without causing problems such as deterioration in conductivity and increase in hardness, and has a low hardness and excellent compression set. It is an object to provide a rubber roller.

  The conductive rubber roller according to the present invention is a conductive rubber roller comprising a conductive metal core and a conductive cross-linked rubber layer having an epichlorohydrin rubber laminated on the conductive metal core. The chlorohydrin rubber is at least one copolymer selected from the group consisting of an epichlorohydrin-ethylene oxide copolymer and an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, The ethylene oxide structural unit of the epichlorohydrin rubber is 40 mol% or more and 90 mol% or less with respect to the epichlorohydrin rubber, and the differential scanning calorimetry ( The calorific value (enthalpy: ΔH) of the peak appearing at −20 ° C. or more and 150 ° C. or less obtained by DSC) is 5 mJ / mg or less. Characterized in that there.

  According to the present invention, it is possible to provide a conductive rubber roller having a low resistance and an excellent compression set property while maintaining desired electrical characteristics without impairing conductivity and hardness characteristics. .

  Hereinafter, the present invention will be described in detail.

  The conductive rubber roller of the present invention is a conductive rubber roller comprising a conductive metal core and a conductive cross-linked rubber layer having an epichlorohydrin rubber laminated on the conductive metal core. The chlorohydrin rubber is at least one copolymer selected from the group consisting of an epichlorohydrin-ethylene oxide copolymer and an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, The ethylene oxide structural unit of the epichlorohydrin rubber is 40 mol% or more and 90 mol% or less with respect to the epichlorohydrin rubber, and the differential scanning calorimetry ( The calorific value (enthalpy: ΔH) of the peak appearing at −20 ° C. or more and 150 ° C. or less obtained by DSC) is 5 mJ / mg or less. It is characterized in. With such a configuration, it is possible to provide a conductive rubber roller having a low volume resistance, a desired current value, and an appropriate rubber elasticity. Further, a conductive rubber roller having a conductive cross-linked rubber layer in which no peak in the range of −20 ° C. or higher and 150 ° C. or lower by the differential scanning calorimetry (DSC) is observed is most preferable. The DSC characteristic of the conductive crosslinked rubber layer depends on the DSC characteristic of the epichlorohydrin rubber itself that is the raw material of the rubber layer. The amount of heat (enthalpy: ΔH) when the crosslinked rubber layer is measured is actually 0 mJ / mg or more and 5 mJ / mg or less due to variations in the production batches of the epichlorohydrin rubber. Conversely, if it exceeds 5 mJ / mg, the crystallinity derived from the ethylene oxide chain constituting the epichlorohydrin rubber is considered to affect the physical properties of the crosslinked rubber layer, and the hardness becomes abnormally high. Further, since the degree of freedom of the molecular chain is limited by crystallinity, the volume resistance is increased, leading to problems such as deterioration of compression set.

  In the present invention, the epichlorohydrin rubber was measured by differential scanning calorimetry (DSC), and the calorie (enthalpy: ΔH) indicated by a peak appearing at 0 ° C. or higher and 70 ° C. or lower was 15 mJ. / Mg or less is preferable. By having the epichlorohydrin rubber in the above range, it is possible to provide a conductive rubber roller having a low volume resistance, a desired current value, and an appropriate rubber elasticity. Further, it is more preferable to select a material having the above calorie of 12 mJ / mg or less because it is possible to stably obtain the desired volume resistance and rubber elasticity. When it exceeds 15 mJ / mg, it is presumed that crystallization derived from the ethylene oxide chain constituting the epichlorohydrin-based rubber occurs and affects the characteristics of the conductive rubber roller, and as a result, the volume resistance increases, and Since the hardness is increased, it is not preferable for practical use.

  In order to obtain a conductive crosslinked rubber layer in which the above calorific value (enthalpy: ΔH) is 15 mJ / mg or less using an epichlorohydrin rubber having an ethylene oxide constitutional unit of 40 mol% or more and 90 mol% or less, The synthesis temperature of epichlorohydrin rubber is appropriately adjusted. The amount of heat tends to increase as the synthesis temperature increases. The reason is presumably because the polymer chain becomes longer in the polymerization process, and the randomness of the units constituting the polymer chain is poor, and the ethylene oxide portion is likely to be blocked (partially crystallized). Therefore, since the mobility of the ethylene oxide site that affects the electrical characteristics of the epichlorohydrin rubber is restricted, the conductivity is lowered and the hardness is increased. On the contrary, since the polymerization reaction proceeds slowly when the synthesis temperature is low, it is considered that the polymer chain length and randomness are in an appropriate state, and it is difficult to cause blocking as described above, and it has excellent conductivity and hardness. It will be a thing.

  The conductive crosslinked rubber layer constituting the conductive rubber roller according to the present invention has epichlorohydrin rubber. Further, the epichlorohydrin-based rubber has at least one copolymer selected from the group consisting of epichlorohydrin-ethylene oxide copolymer and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer. Have coalescence. As this epichlorohydrin rubber, an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer is particularly preferable in that it is suitable for adjusting the volume resistance. In addition to the above, the conductive crosslinked rubber layer may have a known epichlorohydrin compound. Examples of this include the following compounds.

Epichlorohydrin homopolymer Epichlorohydrin-ethylene oxide copolymer Epichlorohydrin-allyl glycidyl ether copolymer Epichlorohydrin-ethylene oxide-allyl glycidyl ether copolymer

  Especially, what has ethylene oxide as a structural unit of a polymer can obtain a thing with comparatively low resistance easily, and is easy to adjust to a desired resistance value by blending with another polymer, etc. However, when blended and used, it is preferable to mainly have epichlorohydrin rubber as long as it does not impair the volume resistance characteristics of epichlorohydrin rubber. Moreover, it is preferable to have allyl glycidyl ether as a structural unit of the epichlorohydrin type rubber contained in the conductive crosslinked rubber layer. The reason is that allyl glycidyl ether has an unsaturated bond and can be vulcanized with a sulfur-based vulcanizing agent (sulfur or sulfur donor), thereby reducing restrictions on the vulcanization method and production conditions. is there. Furthermore, the point that heat-softening deterioration property and ozone resistance can be improved is mentioned.

  There are many types of epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymers depending on the copolymerization ratio, but in the present invention, the ethylene oxide constituent unit of the epichlorohydrin rubber is 40 mol. % Or more and 90 mol% or less. When the structural unit of ethylene oxide is less than 40 mol%, it is difficult to adjust to a desired volume resistance. On the other hand, when it exceeds 90 mol%, volume resistance increases due to crystallization of ethylene oxide and hardness increases, and in either case, it is not practically preferable. The constitutional unit of ethylene oxide is preferably 65 mol% or more and 85 mol%. If it is less than 65 mol%, the low resistance value, which is the object of the present invention, may be difficult to achieve sufficiently. Although it may not be obtained stably, it can be realized by adjusting the material prescription surface and the like.

  In the conductive rubber roller according to the present invention, the structural unit of epichlorohydrin constituting the epichlorohydrin-based rubber is not particularly limited as long as it does not cause a problem in volume resistance, hardness, workability, or the like. In particular, it is preferably 8 mol% or more and 58 mol% or less, and more preferably 13 mol% or more and 33 mol% or less. When there are few structural units of epichlorohydrin, crystallization of an ethylene oxide chain cannot be inhibited. Moreover, when there are many this structural unit, epichlorohydrin itself crystallizes easily, and all become a factor which becomes high in volume resistance and hardness.

  In the conductive rubber roller according to the present invention, the structural unit of allyl glycidyl ether constituting the epichlorohydrin rubber is not particularly limited as long as it does not cause problems in volume resistance, hardness, workability and the like. In particular, it is preferably 2 mol% or more and 12 mol% or less. If it is less than 2 mol%, vulcanization with a sulfur-based vulcanizing agent (sulfur or sulfur donor) becomes difficult. On the other hand, if the amount is more than 12 mol%, it causes a problem of curing due to heat, losing rubber elasticity and becoming brittle.

  In the conductive rubber roller according to the present invention, the conductive cross-linked rubber layer may have various rubber materials or polymer materials in addition to the epichlorohydrin rubber described above. The rubber material is not particularly limited as long as it contains at least the epichlorohydrin rubber as a main component. For example, the epichlorohydrin rubber alone may be used, or one or more other polymers may be blended and used. Examples thereof include ethylene propylene diene rubber, urethane rubber, acrylonitrile butadiene rubber, silicone rubber, chloroprene rubber, butadiene rubber, styrene butadiene rubber, isoprene rubber, natural rubber, butyl rubber, and acrylic rubber.

In the conductive rubber roller according to the present invention, the conductive cross-linked rubber layer can be appropriately mixed with various compounding agents in addition to the above components in the rubber composition used for the conductive roller. Examples of the compounding agent include ionic conductive agents, vulcanizing agents, vulcanization accelerators, reinforcing agents such as carbon black, fillers, anti-aging agents, processing aids, and the like. The ion conductive agent is not particularly limited, and various salts can be used. For example, metal salts such as Li ⁺ and Na ⁺ such as LiClO ₄ , LiCF ₃ , LiSO ₃ , LiBF ₄ , LiN (CF ₃ SO ₃ ) ₂ , and NaClO ₄ can be used. Moreover, the following quaternary ammonium salts are mentioned.

Tetraethylammonium perchlorate tetrabutylammonium perchlorate tetramethylammonium chloride tetraethylammonium chloride tetrabutylammonium chloride tetramethylammonium bromide tetrapropylammonium bromide tetramethylammonium iodide

  These ionic conductive agents may be used alone or in combination of two or more.

  The vulcanizing agent can be used without any particular limitation as long as it does not have a harmful effect on the manufacturing process and as a member used in the image forming apparatus. Examples of the vulcanizing agent used for the epichlorohydrin rubber include sulfur, organic peroxide crosslinking, triazine thiol vulcanization, and 2,3-dimethylquinoxaline vulcanization. The rubber roller produced by any vulcanization method can exert the effect of the present invention, but the production process is limited because organic peroxide crosslinking is difficult to use in the presence of oxygen. In triazine thiol vulcanization and 2,3-dimethylquinoxaline, an acid acceptor is added to the rubber composition to prevent vulcanization inhibition by hydrogen chloride generated during vulcanization. There are concerns about the impact on In addition, these vulcanizing agents generally have a high scorch and inferior storage stability, and thus cause problems in the production process. Sulfur vulcanization is the most common rubber vulcanization method, and can be preferably used in terms of cost and production.

  Moreover, you may use a vulcanization accelerator. As this vulcanization accelerator, various vulcanization accelerators known for rubber can be used. Examples thereof include benzothiazoles such as 2-mercaptobenzothiazole and dibenzothiazyl disulfide. In addition, sulfenamides such as N-cyclohexyl-2-benzothiazolylsulfenamide and N-tert-butyl-2-benzothiazolylsulfenamide may be mentioned. Further examples include thiurams such as tetraethylthiuram disulfide, tetramethylthiuram monosulfide and dipentamethylenethiuram tetrasulfide, and dithiocarbamates. You may use these individually or in combination of 2 or more types.

  When using a reinforcing agent, various carbon blacks can be used. Various carbons for rubber such as SAF, ISAF, HAF, MAF, FEF, GPF, SRF, FT, MT, etc. Black. In addition to these, conductive carbon blacks such as ketjen black and acetylene black may be used, and these may be used alone or in combination of two or more.

  Examples of the filler include heavy calcium carbonate, light calcium carbonate, silica, magnesium carbonate, clay and the like, and these may be used alone or in combination of two or more.

  The method for producing the conductive rubber roller includes a method of using a mold, a method of vulcanizing a rubber composition extruded in a tube shape, and press-fitting into a core metal, and a vulcanization after coating an unvulcanized rubber on a core metal. And the like. The manufacturing method of these conductive rubber rollers may be arbitrarily selected from manufacturing methods suitable for satisfying processability, cost, dimensional accuracy, physical and electrical characteristics required as a member for an image forming apparatus. In recent years, it is suitable for downsizing and continuation of the production line. In comparison with the method using a mold or the method of press-fitting a vulcanized tube into a core metal, the core metal is coated with unvulcanized rubber and then vulcanized. Is preferred.

  The means for laminating the conductive crosslinked rubber layer on the core metal is not particularly limited. Especially, the method of manufacturing by the following processes from a viewpoint of suppressing the continuation of a manufacturing line or manufacturing cost is preferable. In other words, the unvulcanized rubber composition is extruded using an extruder, and at the same time, the core metal is continuously passed through the crosshead die of the extruder to place the rubber composition on the circumference of the core metal. A method manufactured in the step of forming a roller shape is preferable. It is also possible to separately extrude a raw rubber composition that has not been vulcanized into a tube shape and push a cored bar coated with an adhesive into a piece cut into a predetermined length.

  With respect to the vulcanization method, conventionally known methods such as far-infrared vulcanization and steam vulcanization may be used in addition to hot-air oven vulcanization. Also effective is a method in which unvulcanized rubber is placed on the circumference of the core metal and then directly injected into the mold cavity for vulcanization. Furthermore, even if the vulcanization conditions such as time and temperature are arbitrarily changed, the effect of preventing the corrosion of the metal core and the adhesive force are not affected at all, so that the process can be designed freely.

  Furthermore, it is preferable that a polyurethane layer obtained by polyisocyanate crosslinking at least a polyol is formed on the outer periphery of the conductive rubber roller. Even when a small amount of the above-described blending component oozes out from the rubber layer, it can be prevented from oozing out from the urethane layer formed by crosslinking with the polyisocyanate when the polyol and polyisocyanate are cross-linked on the outer periphery of the rubber layer.

  As described above, since the conductive roller obtained in the present invention can be uniformly reduced in resistance and has low hardness, it can be particularly suitably used for a charging roller that has to uniformly charge the photosensitive member. .

  EXAMPLES Next, although an Example demonstrates this invention in detail, this invention is not limited at all by these examples. In addition, "part" shows a mass part.

<Preparation of epichlorohydrin rubber>
The epichlorohydrin rubber was prepared by a general solution polymerization method using ethylene oxide, epichlorohydrin and allyl glycidyl ether with the monomer composition shown in Table 1, and the desired composition ratio. Got stuff. Further, rubbers having different crystallinities were produced by using a heat temperature reaction vessel provided in an apparatus (autoclave) provided in the polymerization reaction vessel, and controlling the progress of the polymerization reaction.

<Preparation of rubber composition>
The following components were kneaded using a closed kneader and an open roll machine to obtain an unvulcanized rubber composition.

Epichlorohydrin rubber (A to G) obtained by the above method 100 parts Zinc oxide 5 parts [Product name: Zinc oxide 2 types, manufactured by Hakusuitec Co., Ltd.]
1 part of stearic acid [Product name: Stearic acid S manufactured by Kao Corporation]
Carbon black 5 parts [Product name: Asahi # 15 Asahi Carbon Co., Ltd.]
40 parts of calcium carbonate [Product name: Silver W Shiraishi Kogyo Co., Ltd.]
Plasticizer 5 parts [Sebacic acid polyester, trade name: Polycizer P-202, Dainippon Ink Co., Ltd.]
2 parts of ionic conductive agent [Quaternary ammonium salt, trade name: KS-555, manufactured by Kao Corporation]
Dibenzothiazyl disulfide 1 part [Product name: Noxeller DM Ouchi Shinsei Chemical Co., Ltd.]
Tetramethylthiuram monosulfide 1 part [Product name: Noxeller TS manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Sulfur 1 part [Brand name: Sulfax 200S Tsurumi Chemical Co., Ltd.]

<Production of conductive rubber roller (single layer roller)>
Extruding the unvulcanized rubber composition using an extruder and simultaneously applying an adhesive with an outer diameter of 6 mm and a length of 250 mm passed through the crosshead die continuously on the core metal. Sulfur rubber was coated. Then, the unpolished rubber roller which has a crosslinked rubber layer was created by heating at 180 degreeC for 1 hour with a hot-air oven. Further, a cutter blade was inserted at a position 10 mm from both ends, and the rubber layers at both ends were peeled off. After that, it is set in a polishing machine equipped with a polishing grindstone GC80 and polished so that the outer diameter is 9 mm at a rotational speed of 2000 rpm and a feed speed of 500 m / min as polishing conditions, and a conductive rubber roller (1) (see FIG. 1). .)created.

<Production of conductive roller (two-layer charging roller with surface urethane layer)>
A mixed solution having the following components was dispersed by passing it through a horizontal sand mill three times using zirconia beads (average particle size 0.5 mm) as a dispersion medium.

ε-Caprolactone-modified acrylic polyol solution 100 parts (Diluent: MEK (methyl ethyl ketone), solid content 20% by mass, hydroxyl value 50)
20 parts of conductive tin oxide

  The beads were filtered and separated from this dispersion, and hexamethylene diisocyanate (HDI) was added so that OH / NCO = 1.0 to prepare a surface coating composition.

  Next, the surface layer coating material was dip-coated on the surface of the conductive elastic layer of the conductive rubber roller (1), and then dried at 150 ° C. for 1 hour in a hot air circulating dryer. The thickness of the surface layer (urethane layer) after drying was 30 μm. The conductive roller thus obtained was used as a conductive roller (2) (a two-layer charging roller with a surface urethane layer; see FIG. 2).

<Measurement / Evaluation>
About each measured physical property and evaluation, it carried out by the method shown below.

[Differential scanning calorimetry (DSC) of epichlorohydrin rubber and conductive crosslinked rubber layer]
Using a differential scanning calorimeter DSC6200 (manufactured by SII Nano Technology Co., Ltd.), the amount of heat related to the epichlorohydrin rubber and the conductive crosslinked rubber layer was determined from the peak area obtained by raising the temperature under the following conditions. Calculated.

Temperature range: -20 ° C to 150 ° C Temperature increase rate: 10 ° C / min

[Mooney viscosity of unvulcanized rubber composition]
The Mooney viscosity [ML1 + 4/100 ° C.] was measured at 100 ° C. using an L-shaped rotor in accordance with JIS K6300-1995.

[hardness]
Hardness was measured in accordance with JIS K-6253.

[Compression set rate]
The compression set was measured using a large test piece (diameter 29 mm, thickness 12.5 mm) of JIS K-6262, and the compression set after standing for 22 hours at 70 ° C. and 25% compression.

[Electric resistance of conductive rubber roller (1)]
The roller resistance was measured as follows. First, the conductive rubber roller (1) was conditioned in an environment of 23 ° C. × 53% RH for 12 hours or more. Thereafter, measurement was performed by applying a voltage of 200 V between the shaft body and the aluminum drum in a state where the roller body was pressure-bonded to an aluminum drum having an outer diameter of 30 mm so that a load of 1 kg was applied to the shaft body.

[Image evaluation]
The conductive rubber roller (2) obtained by the above method was mounted as a charging roller of a process cartridge (coaxially contacted with a photosensitive member having a diameter of 30 mm at both ends of the roller at a load of 5 N). This was incorporated into an electrophotographic apparatus (Laser Shot LBP-470 (manufactured by Canon Inc.)), printed, and image evaluation was performed visually. An excellent image was obtained as ◎, a slight unevenness was observed, but a practical level was indicated as ○, and an image defect was indicated as ×.

  Examples 1-4 are the result about the conductive rubber roller which has the following epichlorohydrin-type rubber | gum, a conductive crosslinked rubber layer, etc. As shown in FIG.

Epichlorohydrin rubber: Epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer Ethylene oxide unit: 65 mol% or more and 85 mol% or less Calorific value of epichlorohydrin rubber: 15 mJ / mg or less (differential Peak obtained by scanning calorimetry in the range of 0 ° C to 70 ° C)
Amount of heat related to the crosslinked rubber layer of the conductive rubber roller: 5 mJ / mg or less (peak amount of heat obtained in the range of −20 ° C. to 150 ° C. by differential scanning calorimetry)

  In Examples 1 to 3, both hardness and electric characteristics were excellent as a conductive rubber roller, and the obtained images were satisfactory without any problems. Compared with Examples 1 to 3, Example 4 had a higher hardness and lower electrical characteristics, so the obtained image was somewhat affected, but at a sufficiently practical level.

  Example 5 is a result about a conductive rubber roller having an epichlorohydrin rubber and a conductive cross-linked rubber layer as described below.

Epichlorohydrin rubber: Epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer Ethylene oxide unit: 46 mol%
Calorific value related to epichlorohydrin rubber: 15 mJ / mg or less (peak obtained in the range of 0 ° C. or more and 70 ° C. or less by differential scanning calorimetry)
Amount of heat related to the crosslinked rubber layer of the conductive rubber roller: 5 mJ / mg or less (peak amount of heat obtained in the range of −20 ° C. to 150 ° C. by differential scanning calorimetry)

  In Example 5, since the number of ethylene oxide units was small, the roller current value was the smallest among Examples 1 to 5, but the hardness was the lowest and the compression set was good. Therefore, it is considered that the image forming apparatus to be assembled is sufficiently practical if it satisfies the required electrical characteristics in the process.

  Comparative Examples 1 and 2 are the results for a conductive rubber roller having an epichlorohydrin rubber and a conductive crosslinked rubber layer as described below.

Epichlorohydrin-based rubber: Epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer Heat amount related to epichlorohydrin-based rubber: Value exceeding 15 mJ / mg (0 to 70 ° C. in differential scanning calorimetry Peak obtained in the range of
Amount of heat related to the crosslinked rubber layer of the conductive rubber roller: a value exceeding 5 mJ / mg (a peak amount of heat obtained in the range of −20 ° C. to 150 ° C. by differential scanning calorimetry)

  In both cases of Comparative Examples 1 and 2, an increase in hardness and a decrease in electrical characteristics appeared remarkably. Even if an image was printed by assembling it in the process cartridge, a good image could not be obtained, and the practicality was poor.

The schematic showing the cross section of one Embodiment of the conductive rubber roller of this invention is shown. The schematic showing the cross section of one Embodiment of the conductive rubber roller of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Conductive rubber roller 1a Conductive core 1b Conductive elastic body layer (hydrin rubber layer)
2 Conductive Roller 2a Conductive Core 2b Conductive Elastic Layer (Hydrin Rubber Layer)
2c Surface layer (urethane layer)

Claims (5)

A conductive rubber roller comprising a conductive core and a conductive cross-linked rubber layer having epichlorohydrin rubber laminated on the conductive core,
The epichlorohydrin rubber is at least one copolymer selected from the group consisting of epichlorohydrin-ethylene oxide copolymer and epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer. Yes,
The ethylene oxide constituent unit of the epichlorohydrin rubber is 40 mol% or more and 90 mol% or less with respect to the epichlorohydrin rubber,
About this electroconductive crosslinked rubber layer, the calorie | heat amount (enthalpy: (DELTA) H) which the peak which appears in -20 degreeC or more and 150 degrees C or less obtained by differential scanning calorimetry (DSC) is 5 mJ / mg or less. Conductive rubber roller characterized by   About the epichlorohydrin rubber, the calorie (enthalpy: ΔH) indicated by the peak appearing at 0 ° C. or higher and 70 ° C. or lower, obtained by measuring by differential scanning calorimetry (DSC), is 15 mJ / mg or less. The conductive rubber roller according to claim 1.   The conductive rubber roller according to claim 2, wherein the heat quantity of the epichlorohydrin rubber is 12 mJ / mg or less. The epichlorohydrin rubber is an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer,
The conductive rubber roller according to any one of claims 1 to 3, wherein a constituent unit of the ethylene oxide is 65 mol% or more and 85 mol% or less.   The conductive rubber roller according to any one of claims 1 to 4, wherein the conductive rubber roller is a charging roller.

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