JP2011197596A - Conductive composition for electrophotographic apparatus and member for electrophotographic apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive composition for an electrophotographic apparatus capable of advantageously obtaining a cured material having excellent properties such as resistance to settling and small conductive variations.SOLUTION: The conductive composition for the electrophotographic apparatus is obtained in such a manner that a fine carbon fiber in which the average diameter of a single body is 50 nm or less and a carbon black whose nitrogen adsorption specific surface area is 300 m/g or less and pH is 4.5 or less are blended in a polymer component, the fine carbon fiber is dispersed in such a state that the single body and an aggregate body are mixed, wherein the average axial length of the single body is 5.0 μm or less and the maximum diameter of the aggregate body is 1.0 μm or less, and the carbon black is dispersed in such a state that the maximum diameter is 400 nm or less.

Description

  The present invention relates to a conductive composition for an electrophotographic apparatus and a member for an electrophotographic apparatus using the same, and in particular, a developing roll or an intermediate transfer belt used for a copying machine or a printer using an electrophotographic method. The present invention relates to a conductive composition for electrophotographic equipment that can be suitably used in the process.

  2. Description of the Related Art Conventionally, image forming apparatuses (hereinafter referred to as electrophotographic equipment) such as copying machines, printers, and facsimiles using an electrophotographic system have conductive rolls and endless belts having various configurations according to their respective uses. Widely used. For example, an endless belt (see FIG. 1) in which an elastic body layer made of a rubber layer is provided on the surface of a base layer that is a resin layer, a toner image formed on a photoconductor (photosensitive drum) is primarily transferred to the belt surface. It is used in electrophotographic equipment as an intermediate transfer belt that performs a function of transferring and then secondarily transferring a toner image on the belt surface to a printing material (paper). Moreover, in the conductive roll (refer FIG. 2) by which the elastic body layer which is a rubber layer is provided on the outer peripheral surface of a metal shaft body, and the resin layer is provided on the surface of the elastic body layer, see FIG. In an electrophotographic apparatus adopting a contact developing method, in a state where a toner layer is formed on a roll surface by a toner regulating member, the image bearing member (photosensitive drum) on which an electrostatic latent image is formed is contacted, It is employed as a developing roll that performs the function of developing an electrostatic latent image by rotating relative to the image carrier.

  By the way, when forming a rubber layer or a resin layer in an endless belt or a conductive roll as described above, generally a composition (conductive composition) in which various additives such as a conductive agent are blended with a rubber material or a resin material. ) Is used. In preparing such a conductive composition, carbon black and conductive metal oxides, and more recently, fine carbon fibers such as carbon nanotubes are used as a conductive agent.

  Among such conductive agents, conductive metal oxides generally have low conductivity. For example, when forming a rubber layer or a resin layer that can express desired conductivity using the conductive metal oxide, In addition, it is necessary to add a large amount to the conductive composition, but it is known that physical properties such as sag resistance in the resulting rubber layer deteriorate due to the addition of a large amount. On the other hand, fine carbon fibers and high-conductivity carbon black, which can develop excellent conductivity, can develop the desired conductivity by using a small amount, but the conductivity changes greatly only by changing the amount used. It is known that there is a risk that the conductivity may be different depending on different parts of the obtained rubber layer or resin layer (conductivity varies).

  Further, in recent years, demands for higher durability and higher image quality for electrophotographic equipment are increasing more than ever, and for the above-mentioned members for electrophotographic equipment such as intermediate transfer belts and developing rolls, characteristics more than conventional. Is required.

  Under such circumstances, conventionally, various compositions obtained by blending a plurality of types of conductive agents and various members for electrophotographic equipment constituted using the same have been proposed (see Patent Documents 1 and 2). reference).

  However, in the conventional conductive compositions for electrophotographic equipment including those proposed in Patent Documents 1 and 2, the rubber layer and the resin layer obtained using them have excellent anti-sag resistance. However, it is difficult to say that there is little variation in conductivity while having such physical properties, and there is still room for improvement in this respect.

JP 2005-275249 A JP 2009-102630 A

  Here, the present invention has been made in the background of such circumstances, and the problem to be solved is a curing that has excellent characteristics such as anti-sagging and has little variation in conductivity. An object of the present invention is to provide a conductive composition for an electrophotographic apparatus that can advantageously obtain a product.

In order to advantageously solve such a problem, the present invention provides the polymer component with fine carbon fibers having an average diameter of 50 nm or less, a nitrogen adsorption specific surface area of 300 m ² / g or less, and a pH. Is a conductive composition comprising a carbon black having a carbon content of 4.5 or less, the fine carbon fibers are dispersed in a state where a simple substance and an aggregate are mixed, and the average axial length of the simple substance is The maximum diameter of the aggregate is 5.0 μm or less, and the carbon black is dispersed in a state where the maximum diameter is 400 nm or less. The gist of the present invention is a conductive composition.

  One preferred embodiment of the present invention is an endless belt for electrophotographic equipment having a functional layer formed using the electroconductive composition for electrophotographic equipment as described above, and 100 parts by weight of the polymer component. On the other hand, an endless belt for an electrophotographic apparatus, wherein the fine carbon fiber is blended in a proportion of 0.4 to 5.0 parts by weight and the carbon black is blended in a proportion of 3 to 30 parts by weight. is there. In such an embodiment, advantageously, the polymer component is a polyamideimide resin.

  Another desirable embodiment of the present invention is a conductive roll for an electrophotographic apparatus having a functional layer formed using the electroconductive apparatus composition for electrophotography as described above. For electrophotographic equipment, wherein the fine carbon fiber is blended at a ratio of 0.1 to 5.0 parts by weight and the carbon black is blended at a ratio of 5 to 30 parts by weight with respect to parts by weight. It is a conductive roll. In such an embodiment, advantageously, the polymer component is a urethane-based resin.

  Thus, in the conductive composition for electrophotographic equipment according to the present invention, the polymer component is blended with a predetermined fine carbon fiber and a predetermined carbon black, and the fine carbon fiber is a simple substance and Aggregates are dispersed in a mixed state, the average axial length of such simple substance is 5.0 μm or less, the maximum diameter of the aggregate is 1.0 μm or less, and carbon black has a maximum diameter of 400 nm. It is dispersed in the following state. Thus, by defining the dispersion state of the predetermined fine carbon fibers and carbon black, the conductive composition of the present invention has low hardness and excellent anti-sag and flex resistance (toughness). Accordingly, a cured product having the above-described characteristics and less conductive variation is advantageously obtained.

  In particular, when forming one functional layer in an endless belt for electrophotographic equipment composed of one or more functional layers using the electroconductive composition for electrophotographic equipment of the present invention, 100 parts by weight of the polymer component In contrast, in the functional layer obtained by blending fine carbon fibers in a proportion of 0.4 to 5.0 parts by weight and carbon black in a proportion of 3 to 30 parts by weight, the above-described excellent You can enjoy the effect.

  In addition, using the electroconductive composition for electrophotographic equipment of the present invention, one functional layer in the electroconductive roll for electrophotographic equipment, in which one or more functional layers are provided on the outer peripheral surface of the shaft body, is formed. At the time of the caulking, the fine carbon fiber is blended at a ratio of 0.1 to 5.0 parts by weight and the carbon black is blended at a ratio of 5 to 30 parts by weight with respect to 100 parts by weight of the polymer component. Thus, the above-described excellent effect can be enjoyed in the obtained functional layer.

It is sectional explanatory drawing and a partial cross-sectional explanatory drawing which show an example of the endless belt for electrophotographic apparatuses produced using the electroconductive composition for electrophotographic apparatuses according to this invention. It is an axis perpendicular cross-section explanatory drawing which shows an example of the electroconductive roll for electrophotographic apparatuses produced using the electroconductive composition for electrophotographic apparatuses according to this invention.

  By the way, the electroconductive composition for electrophotographic equipment according to the present invention (hereinafter also referred to as electroconductive composition) is obtained by blending predetermined fine carbon fibers and carbon black with a polymer component. First, as the polymer component used in the present invention, any of those conventionally used in conductive compositions can be used. Specifically, acrylic resins, urethane resins, fluorine resins, polyamide resins, polyimide resins, polyamideimide resins, epoxy resins, urea resins, polyester resins, polyether resins, polycarbonate resins , Synthetic resin materials such as thermoplastic elastomers, natural rubber (NR), butadiene rubber (BR), acrylonitrile-butadiene rubber (NBR), hydrogenated NBR (H-NBR), styrene butadiene rubber (SBR), isoprene rubber ( IR), urethane rubber, chloroprene rubber (CR), epichlorohydrin rubber (ECO), ethylene-propylene-diene polymer (EPDM), acrylic rubber (ACM), chlorosulfonated polyethylene (CSM), polysulfide rubber, fluoro rubber Explain rubber materials such as Can. In the present invention, one type or two or more types are appropriately selected and used depending on the intended use of an electrophotographic apparatus member (hereinafter also referred to as a member).

  In the conductive composition according to the present invention, fine carbon fibers having a single average diameter of 50 nm or less, preferably 1 to 20 nm, are blended with the polymer component as described above. The reason why the average diameter of the simple substance exceeds 50 nm is that even if it is used in combination with a predetermined carbon black described later, there is a possibility that the resulting cured product may have conductive variation. The average diameter of the fine carbon fiber is measured according to an electron microscope method.

Carbon black blended in the polymer component together with such fine carbon fibers has a nitrogen adsorption specific surface area of 300 m ² / g or less, preferably 40 to 200 m ² / g, and a pH of 4.5 or less. Preferably it is 2.0-3.5. Carbon black having a nitrogen adsorption specific surface area exceeding 300 m ² / g and carbon black having a pH exceeding 4.5 are electrically conductive in the resulting cured product even when used in combination with fine carbon fibers having a single average diameter of 50 nm or less. This is because there is a risk of sexual variation. The pH of carbon black is measured in accordance with ASTM D1512.

  And in the electrophotographic equipment conductive composition according to the present invention, the above-mentioned fine carbon fibers and carbon black are dispersed in a state where 1) the fine carbon fibers are mixed with simple substances and aggregates. The average axial length of such a single body is 5.0 μm or less, preferably 0.1 to 2.0 μm, and the maximum diameter of the aggregate is 1.0 μm or less, preferably 0.3 to 0.8 μm, 2) Carbon black has a great feature in that it is dispersed in a state where the maximum diameter is 400 nm or less, preferably 50 to 250 nm. That is, by controlling the dispersion state of the fine carbon fibers and carbon black, the conductive composition of the present invention has low hardness, excellent settling resistance, bending resistance (toughness) and the like. Thus, a cured product having characteristics and less conductive variation is advantageously obtained.

  Here, the average axial length in the simple substance of a fine carbon fiber means what is measured and calculated according to the following procedures. First, the conductive composition is cooled and solidified with liquid nitrogen, and a thin section having a size of about 100 nm is cut out from the solidified product using a microtome to obtain a sample. About this sample, the cross-sectional enlarged observation about the area | region of length: 3micrometer x width: 4micrometer is performed about three places in a sample with a transmission scanning electron microscope (STEM), and all the fine carbon fibers confirmed in the observation are confirmed. The axial length is measured, and the average value is taken as the average axial length. The maximum diameter of the fine carbon fiber aggregates means the maximum diameter of the aggregates observed in the observation of the cross-section enlarged by the STEM at three locations in the sample. Furthermore, the maximum diameter of carbon black means the maximum diameter of the carbon black aggregates observed in the cross-sectional enlarged observation by the STEM described above.

  As described above, in the conductive composition for electrophotographic equipment according to the present invention, predetermined fine carbon fibers and carbon black are advantageously dispersed in the polymer component. Specifically, since the conductive composition is in a state in which carbon black with low conductivity enters between conductive paths of fine carbon fibers having high conductivity, it is obtained from the conductive composition. The cured product thus obtained has a small variation in conductivity. In addition, since highly conductive fine carbon fibers are used, it is possible to develop desired conductivity with a small amount of blending, so that the properties of the resulting cured product, such as hardness, It is possible to effectively suppress deterioration of physical properties such as property and bending resistance (toughness).

  In preparing the conductive composition of the present invention, generally, a predetermined fine carbon fiber and carbon black are blended with a polymer component in a proportion corresponding to the characteristics of the target member for electrophotographic equipment. It is prepared by dispersing the blend so that the average axial length of the fine carbon fiber alone, the maximum diameter of the fine carbon fiber aggregates, and the maximum diameter of the carbon black are not more than predetermined values.

  In addition, if the disperser, the dispersion | distribution method, etc. which are used when preparing the electrically conductive composition of this invention are conventionally well-known, all can be used. Specifically, three rolls, a ball mill, a jet mill, a bead mill, an ultrasonic disperser and the like can be exemplified, and these can be used alone, and two or more kinds can be used in combination. is there. Various conditions for dispersion are appropriately set according to the type of fine carbon fiber used, the characteristics of the target member for electrophotographic equipment, and the like. Further, a known dispersant can be used.

  Further, the electroconductive composition for electrophotographic equipment according to the present invention includes a cross-linking agent, a cross-linking accelerator, a catalyst, an anti-aging agent, a fluorine-based or silicone-based leveling agent, ionic conductivity, as long as the object of the present invention is not impaired. Various conventionally known additives such as an agent, a thickener, and a coupling agent can be blended. Furthermore, as described later, it is also possible to prepare a liquid using a predetermined organic solvent.

  An electrophotographic apparatus member having a functional layer formed using the above-described electrophotographic apparatus conductive composition will be described below.

  First, FIG. 1 shows a cross section of an endless belt 10 for an electrophotographic apparatus that is advantageously used as an intermediate transfer belt or the like. The endless belt 10 shown there is composed of only a single functional layer 12, and the functional layer 12 is formed of the above-described conductive composition for electrophotographic equipment.

  Here, in the endless belt having various structures including the endless belt 10 shown in FIG. 1, when the functional layer constituting the endless belt is formed of the electroconductive composition for electrophotographic equipment of the present invention, such an electroconductive composition is used. As a product, it is preferable that fine carbon fibers are blended at a ratio of 0.4 to 5.0 parts by weight and carbon black at a ratio of 3 to 30 parts by weight with respect to 100 parts by weight of the polymer component. Is preferred. By adopting such a blending ratio, the resulting functional layer (12), and thus the endless belt (10), has less electrical conductivity variation, so that the occurrence of leakage voltage is suppressed and the durability is excellent. And can be suitably used as an intermediate transfer belt in an electrophotographic apparatus. The polymer component is preferably a polyamideimide resin from the viewpoint of durability and the like.

  The endless belt 10 can be manufactured according to various conventionally known methods. For example, an appropriate amount of an organic solvent is added to the electrophotographic apparatus conductive composition of the present invention to form a liquid material, and this liquid material is formed on the surface of a cylindrical substrate as a mold according to the technique described in Japanese Patent No. 3855896. After coating in a helical shape and applying heat treatment, air is blown between the coating layer (functional layer) provided by the coating and the cylindrical substrate, and the cylindrical substrate is pulled out. The endless belt 10 consisting only of the functional layer formed using the composition is obtained.

  Further, FIG. 2 shows a conductive roll 14 suitably used as a developing roll or the like in a cross-sectional view cut along a cross section perpendicular to the axis. Here, an elastic body layer 18 as a base layer is provided on the outer peripheral surface of the metal shaft body 16. And the surface layer 20 as a protective layer is provided in the surface of this elastic body layer 18 using the electroconductive composition for electrophotographic apparatuses according to this invention.

  Here, in the conductive roll of various structures including the conductive roll shown in FIG. 2, when forming the functional layer constituting this with the conductive composition of the present invention, as the conductive composition, The fine carbon fibers are blended at a ratio of 0.1 to 5.0 parts by weight and carbon black at a ratio of 5 to 30 parts by weight with respect to 100 parts by weight of the polymer component. Is preferred. By adopting such a blending ratio, the resulting functional layer (20), and hence the conductive roll (14), has less electrical conductivity variation, so that the occurrence of leakage voltage is suppressed and excellent durability. Furthermore, since the hardness can be kept low, the occurrence of toner filming can be advantageously suppressed, and particularly, it can be suitably used as a developing roll. The polymer component is preferably a urethane resin from the viewpoints of durability and low hardness.

  In addition, the electroconductive roll 14 can be manufactured according to conventionally well-known various methods. For example, while an appropriate amount of an organic solvent is added to the electrophotographic apparatus conductive composition of the present invention to prepare a liquid material, an elastic body layer made of a rubber material or the like is formed on the outer peripheral surface of a metal shaft body by injection molding or the like. Form. Thereafter, the surface of the elastic layer is coated with a separately prepared liquid material according to a conventionally known coating method, and is dried and heated as necessary, whereby a conductive roll 14 having a two-layer structure as shown in FIG. Is obtained.

  Some examples of the present invention will be shown below to clarify the present invention more specifically. However, the present invention is not limited by the description of such examples. Needless to say. In addition to the following examples, the present invention includes various changes and modifications based on the knowledge of those skilled in the art without departing from the spirit of the present invention other than the specific description described above. It should be understood that improvements can be made.

In addition, as a dispersion method when preparing the conductive composition, any of the following methods was employed.
Dispersion method I: Circulating dispersion was performed using a bead mill (zirconia beads: 1 mm was used) and an ultrasonic disperser.
Dispersion method II: Dispersion was carried out using a bead mill (using zirconia beads: 1 mm).
-Dispersion method III: First, the particles were dispersed using a bead mill (using zirconia beads: 1 mm), and further dispersed using an ultrasonic disperser.
-Dispersion method IV: Dispersion was carried out using a jet mill.
-Dispersion method V: Dispersion was performed using a bead mill (zirconia beads: 1 mm and 2 mm in combination).

First, the following were prepared as each component for preparing a conductive composition. In the following, “specific surface area” means a nitrogen adsorption specific surface area.
-Fine carbon fiber A: Nanocyl 7000 (trade name, average diameter: 9.5 nm), manufactured by Nanocyl-Fine carbon fiber B: Ctube 100 (trade name, average diameter: 10 nm), manufactured by CNT-Fine carbon fiber C: VGCF (trade name, average diameter: 150 nm), manufactured by Showa Denko KK ・ Carbon black a: Color Black FW18 (trade name, specific surface area: 260 m ² / g,
pH: 4.5), manufactured by Evonik Degussa Japan Co., Ltd. Carbon black b: Special Black 250 (trade name, specific surface area: 40 m ² / g,
pH: 3.1), manufactured by Evonik Degussa Japan Co., Ltd. • Carbon Black c: Black Pearls 2000 (trade name, specific surface area: 1475 m ² / g, pH: 9.7), manufactured by Evonik Degussa Japan Co., Ltd. • Carbon Black d : # 2350 (trade name, specific surface area: 320m ² /g,pH:2.5), Mitsubishi Chemical Co., Ltd. carbon black e: Toka black # 4300 (trade name, specific surface area: 33m ² / g,
pH: 5.0), manufactured by Tokai Carbon Co., Ltd. Carbon black f: Color Black FW200 (trade name, specific surface area: 460 m ² / g,
pH: 2.5), manufactured by Evonik Degussa Japan Co., Ltd. ・ Carbon black g: Talker black # 7400 (trade name, specific surface area: 85 m ² / g,
pH: 7.0), manufactured by Tokai Carbon Co., Ltd. ・ Conductive zinc oxide: Pasette CK (trade name), Hakusuitec Co., Ltd. ・ Urethane resin: Nipponran 5193 (trade name), manufactured by Nippon Polyurethane Industry Co., Ltd. ・ Polyol: PTMG1000 ( Product name), manufactured by Mitsubishi Chemical Corporation ・ Isocyanate curing agent: Coronate L (trade name), manufactured by Nippon Polyurethane Industry Co., Ltd. ・ Polyamideimide resin: Viromax HR16NN (trade name), manufactured by Toyobo Co., Ltd.

A. Production and evaluation of endless belt Fine carbon fiber, carbon black and polyamideimide resin are added to N-methylpyrrolidone (NMP) in a quantitative ratio such that the solid content ratio is the ratio shown in Table 1 and Table 2 below. 11 types of liquid conductive compositions were prepared by dispersing by the dispersion method shown in Table 1 and Table 2 below. The obtained liquid conductive composition was coated on a PET film with a bar coater, and the coated PET film was heated in an oven from room temperature to 300 ° C. over 2 hours, and then at 300 ° C. for 1 hour. By performing the heat treatment, a film having a thickness of 90 μm made of each conductive composition was obtained. About the obtained film, the surface resistivity was measured according to the method described below. The results are shown in Table 1 and Table 2 below. In addition, the average axial length of the fine carbon fibers alone in the liquid conductive composition, the maximum diameter of the fine carbon fiber aggregates, and the maximum diameter of the carbon black were measured and calculated, and these are also shown in Tables 1 and 2 below. Also shown.

-Measurement of surface resistivity-
Using a Hiresta UP (trade name, probe: ring probe (URS)) manufactured by Mitsubishi Chemical Corporation, the surface resistivity (Ω / □) is measured at any five points on the sample, and the average value is used as the surface resistance. Rate.

  Eleven types of liquid conductive compositions were spray-coated on the surface of a separately prepared cylindrical substrate according to the technique described in Japanese Patent No. 3855896. Then, after heating up from room temperature to 300 degreeC with a cylindrical base | substrate over 2 hours, heat processing were performed at 300 degreeC for 1 hour. And 11 types of endless belts (belts No. 1 to 11) having the structure as shown in FIG. 1 are blown out by blowing air between the coating layer provided by coating and the cylindrical substrate. Got. The obtained belt was subjected to the following tests and evaluations. The results are shown in Table 1 and Table 2 below.

-Bending test-
Using the obtained belt cut out to a predetermined size as a sample, according to JIS-P8115, using Folding Endurancetester MIT-D (trade name) manufactured by Toyo Seiki Seisakusho, load: 9.8 N Under the conditions, the number of MITs (flexibility) was measured.

−Measurement of leakage voltage−
In a state where the endless belt is in contact with a metal roll (outer diameter: 30 mm), it is rotated at a speed of 100 mm / s, a direct current is applied on the step, and a voltage at which discharge breakdown occurs is defined as a leakage voltage. .

-Image evaluation (presence / absence of vitiligo image)-
The endless belt was incorporated as an intermediate transfer belt in an actual machine (product name: IMAGIO MPC2500, manufactured by Ricoh Co., Ltd.), a solid image (black) was printed, and the presence or absence of a white spot image in the solid image portion was visually observed. The case where no white spot image was recognized was evaluated as “◯”, and the case where it was recognized was evaluated as “×”.

-Evaluation of durability-
Two metal rolls having a diameter of 13 mm were prepared, and one metal roll was fixed on the table in a state where an endless belt was stretched between the two metal rolls. Next, the other metal roll not fixed to the table is placed at the end of the table, and a weight of 2 kg is suspended from both ends of this metal roll (total load: 4 kg), and the laboratory environment (25 ° C. × 40 % RH), the endless belt was driven to rotate. And the accumulated rotation speed until a crack was confirmed in an endless belt was measured. Those with a cumulative rotational speed of 300000 revolutions or more were evaluated as ◯, and those with a cumulative rotational speed of less than 300000 revolutions were evaluated as ×.

  As is clear from the results in Tables 1 and 2, the endless belts (belt Nos. 1 to 4) produced using the conductive composition according to the present invention have a high leakage voltage and a medium. Since a good solid image was obtained when used as a transfer belt, it was recognized that there was little variation in conductivity, and it was also recognized that the durability was excellent.

B. Production and Evaluation of Conductive Roll First, a predetermined amount of fine carbon fiber, carbon black or conductive zinc oxide, and urethane resin is added to methyl ethyl ketone (MEK), and dispersed by the dispersion method shown in Table 3 and Table 4 below. By doing so, 18 types of dispersion liquids were prepared. Using the obtained dispersion, polyol, and isocyanate curing agent, 18 types of liquid conductive compositions were prepared so that the solid content ratio of each component was the ratio shown in Tables 3 and 4. The obtained liquid conductive composition was coated on a PET film with a bar coater, and the coated PET film was heated to obtain a film having a thickness of 40 μm made of each conductive composition. About the obtained film, surface resistivity, Martens hardness, and creep rate were measured. The results are also shown in Tables 3 and 4 below. In addition, the average axial length of the fine carbon fibers alone in the liquid conductive composition, the maximum diameter of the fine carbon fiber aggregates, and the maximum diameter of the carbon black were measured and calculated, and these are also shown in Tables 3 and 4 below. Also shown.

-Measurement of Martens hardness-
In accordance with ISO 14577, the Martens hardness (N / mm ² ) when compressed by 1 mN was measured using a micro hardness meter (manufactured by Fischer Instruments Co., Ltd., trade name: H100).

-Creep rate-
According to ISO 14577, the above-mentioned microhardness meter was used to measure the elastic part of the indentation work at the time of 1 mN compression: [ηIT], and the creep rate was calculated from the following formula.
Creep rate (%) = 100− [ηIT]

  In producing a conductive roll, first, a silicone rubber (manufactured by Shin-Etsu Chemical Co., Ltd., manufactured by adding carbon black into an injection mold having a shaft body (core metal, diameter: 10 mm) made of SUS304. Name: KE1350AB) was cast, heated under the conditions of 150 ° C. × 45 minutes, and then demolded to prepare a base roll having an elastic layer provided on the outer peripheral surface of the shaft. Next, a liquid conductive composition is applied to the surface of the elastic body layer according to a roll coating method and dried to form a surface layer, thereby forming 18 conductive rolls having a two-layer structure (see FIG. 2). Kind and produced (Roll No. 1-18). In each conductive roll, the thickness of the elastic layer was 3 mm, and the thickness of the surface layer was 10 μm. About the obtained electroconductive roll, the following tests and evaluation were performed. The results are also shown in Tables 3 and 4 below.

−Measurement of leakage voltage−
The conductive roll is brought into contact with a metal roll (outer diameter: 30 mm) and rotated at 20 rpm with a load of 0.5 kg applied to both ends of the conductive roll. In this state, a direct current was applied on the step, and a voltage at which discharge breakdown occurred was defined as a leakage voltage.

-Evaluation of light and shade unevenness-
A conductive roll is incorporated into a color laser printer (product name: LBP-2510, manufactured by Canon Inc.) as a developing roll, and a halftone solid image is output in an environment of 10 ° C. × 10% RH. The presence or absence of unevenness and white spots was evaluated. A case where no image unevenness or white spot omission was observed was evaluated as ◯, a case where image unevenness or the like was observed was within an allowable range, and a case where remarkable image unevenness was observed was evaluated as ×.

-Evaluation of toner filming resistance-
A conductive roll was incorporated in the color laser printer as a developing roll, and 20000 sheets (A4 size) of images were passed under an environment of 32.5 ° C. × 85% RH. Thereafter, the developing roll was taken out from the printer, the toner not fixed on the roll surface was removed by air blow, and the thickness of the toner layer fixed on the roll surface was measured. The thickness of the toner layer was measured by cutting the roll in the thickness direction and observing the cut surface with an electron microscope (manufactured by Keyence Corporation, trade name: VK-9510). When the measured toner layer thickness was 0.5 μm or less, the evaluation was “◯”, “Δ” exceeding 0.5 μm and 1.0 μm or less, and “X” when exceeding 1.0 μm. The evaluation results for the respective conductive rolls are shown in Tables 3 and 4 below as “toner filming resistance”.

−Evaluation of presence / absence of set lines−
A conductive roll was incorporated into the color laser printer as a developing roll, and was allowed to stand for 1 month in an environment of 10 ° C. × 10% RH, and then imaged. About the obtained image, the presence or absence of the stripe corresponding to the axial direction of an electroconductive roll (development roll) was observed visually. The case where a streak was not recognized was evaluated as ○, and the case where a streak was recognized was evaluated as ×. The evaluation results for each conductive roll are shown in the following Tables 3 and 4 as “presence / absence of set streaks”.

  As is apparent from the results of Tables 3 and 4, among the conductive rolls produced using the conductive composition according to the present invention, the blending ratio of carbon black is particularly 3 to 30 parts by weight ( In rolls No. 1-6, 8, 9), the leakage voltage is high, and since there is no significant shading unevenness in the image obtained when used as a developing roll, there are variations in conductivity. It was found that there were few. Also, the conductive rolls (roll Nos. 1-6, 8, 9) have sufficiently low surface hardness, excellent toner filming resistance, and no set streaks. It was confirmed that it was excellent in durability.

DESCRIPTION OF SYMBOLS 10 Endless belt for electrophotographic equipment 12 Functional layer 14 Conductive roll for electrophotographic equipment 16 Shaft body 18 Elastic body layer 20 Surface layer

Claims (5)

A conductive composition comprising a polymer component and fine carbon fibers having an average diameter of 50 nm or less and carbon black having a nitrogen adsorption specific surface area of 300 m ² / g or less and a pH of 4.5 or less. Stuff
The fine carbon fibers are dispersed in a state where a simple substance and an aggregate are mixed, the average axial length of the simple substance is 5.0 μm or less, and the maximum diameter of the aggregate is 1.0 μm or less. The conductive composition for electrophotographic equipment, wherein the carbon black is dispersed in a state where the maximum diameter is 400 nm or less.   An endless belt for an electrophotographic apparatus having a functional layer formed using the electroconductive composition for an electrophotographic apparatus according to claim 1, wherein the fine carbon fiber is 0 with respect to 100 parts by weight of the polymer component. An endless belt for an electrophotographic apparatus, wherein the carbon black is blended at a ratio of 4 to 5.0 parts by weight at a ratio of 3 to 30 parts by weight.   The endless belt for an electrophotographic apparatus according to claim 2, wherein the polymer component is a polyamide-imide resin.   The electroconductive roll for electrophotographic equipment having a functional layer formed using the electroconductive composition for electrophotographic equipment according to claim 1, wherein the fine carbon fiber is contained in 100 parts by weight of the polymer component. A conductive roll for electrophotographic equipment, wherein the carbon black is blended at a ratio of 0.1 to 5.0 parts by weight at a ratio of 5 to 30 parts by weight. The electroconductive roll for electrophotographic equipment according to claim 4, wherein the polymer component is a urethane resin.

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