JP2013104140A - Conductive fiber, charging member using the same and electrophotographic image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive fiber superior in yarn-making properties and conductivity.SOLUTION: The conductive fiber comprises: a core part containing a polyester resin; a sheath part that covers the core part and contains a polyester resin and a carbon nanotube; and an outermost layer that covers the sheath part and contains a thermoplastic resin. The sheath part further contains an aromatic amide compound represented by the following formula (1). (where, X is the following chemical formula (2) or (3), and R1 and R2 are the same or different and are each a 5-12C cycloalkyl group.)

Description

  The present invention relates to a conductive fiber, a charging member using the same, and an electrophotographic image forming apparatus.

There are two known charging mechanisms for contact charging in an electrophotographic image forming apparatus: (1) discharge charging and (2) direct injection charging.
In the direct injection charging, the surface of the charged body is charged by directly injecting the charge from the contact charging member to the charged body. A charging device related to direct injection charging using a charging brush as a contact charging member is simple in terms of mechanism, and is less expensive than a charging device related to discharge charging using a charging roller.

In order to perform direct injection charging on the member to be charged with the charging brush, it is necessary to bring the brush bristles of the charging brush into uniform contact with the surface of the member to be charged. Therefore, as the bristle, for example, conductive fibers in which a conductive filler such as carbon is dispersed in a base resin such as nylon-6, nylon-66, nylon-12, polyethylene terephthalate, polyethylene, and polypropylene are used. . Such conductive fibers are prepared by, for example, kneading and melting a resin compound pellet in which a base resin and a conductive filler are adjusted to a desired composition, for example, using an extruder, extruding from a spinneret, and performing cooling and stretching. It is manufactured by.
By the way, when using the single fiber containing base resin and conductive agents, such as carbon, as this conductive fiber, in order to improve electroconductivity, it is necessary to mix | blend a lot of conductive agents. However, a thermoplastic resin containing a large amount of carbon or the like has a problem of poor melt spinnability. Even if melt spinning can be performed, yarn breakage is likely to occur during the subsequent stretching process or when creating a ribbon-shaped pile fabric. Therefore, it is practically difficult to use a single fiber as the conductive fiber for the charging brush.
Therefore, in Patent Document 1, a core-sheath structure in which the core part is made of polyester mainly composed of ethylene terephthalate, and the sheath part covering the core part is made of a mixture of copolymerized polyester containing ethylene terephthalate and carbon black. A conductive fiber is disclosed. It is described that the conductive fibers have good yarn-making properties and are excellent in conductivity and durability.

JP 2008-156810 A

However, according to the study by the present inventors, it was difficult to satisfactorily disperse carbon black in polyester. Therefore, in order to impart high conductivity to the conductive fiber according to Patent Document 1, an attempt was made to contain a large amount of carbon black in the sheath portion, and the melt viscosity of the resin for forming the sheath portion significantly increased. Therefore, when a conductive fiber having a core-sheath structure is to be produced by melt spinning, the difference in melt viscosity between the resin that forms the core and the resin mixture that forms the sheath becomes very large. It was difficult to produce a conductive fiber having a uniform core-sheath structure in which the sheath part is concentric. Thus, since the fiber whose core part and sheath part are not concentric is easily cut in the subsequent drawing process, it is difficult to stably produce a small-diameter conductive fiber.
Accordingly, an object of the present invention is to provide a conductive fiber having good yarn-making properties and excellent conductivity.
Another object of the present invention is to provide a charging member that exhibits high charge injection efficiency.
Furthermore, another object of the present invention is to provide an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image.

The conductive fiber according to the present invention includes a core containing a polyester resin,
A sheath containing a polyester resin and carbon nanotubes covering the core;
In the conductive fiber comprising the outermost layer that covers the sheath and contains a thermoplastic resin,
The sheath part further includes an aromatic amide compound represented by the following general formula (1).

  (In formula (1), X is the following chemical formula (2) or (3), and R1 and R2 are the same or different cycloalkyl groups having 5 to 12 carbon atoms.)

The charging member according to the present invention is a charging member having a conductive substrate and a conductive fiber having one end bonded to the substrate, the conductive fiber including a core containing a polyester resin. A sheath portion including a carbon nanotube that is intertwined with a polyester resin and an aromatic amide compound represented by the structural formula (1), and covers the sheath portion and includes a thermoplastic resin. An outermost layer, and the conductive fiber has a carbon nanotube contained in the sheath portion exposed on the surface of the conductive fiber at a tip portion on the side not bonded to the substrate. It is characterized by being.
Furthermore, an electrophotographic image forming apparatus according to the present invention includes the above-described charging member, and an electrophotographic photosensitive member disposed so as to be in contact with the leading end portion of the conductive fiber in the charging member. Features.

According to the present invention, even when the sheath portion contains a large amount of carbon nanotubes, the melt viscosity of the sheath portion hardly increases during melt spinning. Therefore, the difference in melt viscosity between the resin for forming the core part and the resin mixture for forming the sheath part is difficult to increase. As a result, a conductive fiber having a concentric and uniform core-sheath structure can be obtained.
Further, such conductive fibers are less likely to cause yarn breakage at the time of drawing treatment after melt spinning and at the time of producing a ribbon-like pile fabric, and are excellent in yarn production.
Furthermore, according to the present invention, a charging member having high charge injection efficiency can be obtained.
Furthermore, according to the present invention, an electrophotographic image forming apparatus capable of forming a high-quality electrophotographic image can be obtained.

It is the schematic of the charging member which concerns on this invention. 3 is a graph showing melt viscosity characteristics of a polyester resin compound pellet A and a polyester resin compound pellet B containing carbon nanotubes according to Production Example 1. FIG. FIG. 4 is a schematic view showing a dispersion state of carbon nanotubes existing in the sheath portion of the conductive fiber according to the present invention, (a) before the outermost layer removal and (b) after the outermost layer removal. 1 is a schematic view of an image forming apparatus according to the present invention. It is a schematic sectional drawing of the ribbon-shaped pile fabric used for the charging member which concerns on this invention. It is the schematic of a core-sheath type composite nozzle in this invention. 1 is a schematic view of a scanning probe microscope according to the present invention.

Below, the electroconductive fiber which concerns on this invention, and the charging member using the same are demonstrated in detail.
(Conductive fiber)
The conductive fiber according to the present invention includes a core portion containing a polyester resin, a sheath portion covering the core portion and containing a polyester resin and a carbon nanotube, and an outermost layer covering the sheath portion and containing a thermoplastic resin Is a conductive fiber consisting of The sheath part further includes an aromatic amide compound represented by the following general formula (1).

(In formula (1), X is the following chemical formula (2) or (3), and R1 and R2 are the same or different cycloalkyl groups having 5 to 12 carbon atoms.)

When producing conductive fibers having a core-sheath structure by melt spinning, the sheath part contains an aromatic amide compound, so that the sheath part melts during melt spinning even if the sheath part contains a large amount of carbon nanotubes. Viscosity decreases. Thereby, it is possible to produce a conductive fiber having a uniform core-sheath structure in which the core and the sheath are concentric.
The aromatic amide compound represented by the formula (1) has one or more aromatic rings between two amide bonds. When this aromatic amide compound is mixed with a polyester resin, it is presumed that the aromatic ring of the aromatic amide compound and the polyester structure are regularly arranged. Furthermore, when carbon nanotubes are mixed with a polyester resin containing an aromatic amide compound, it is presumed that the carbon nanotubes are more uniformly dispersed. As a result of the carbon nanotubes being more uniformly dispersed in the polyester resin, it is presumed that the melt viscosity of the polyester resin containing the carbon nanotubes is lowered.

  Specific examples of the aromatic amide compound include N, N′-dicyclopentyl-2,6-naphthalene dicarboxyamide, N, N′-dicyclohexyl-2,6-naphthalene dicarboxyamide, N, N′-di. Cyclooctyl-2,6-naphthalenedicarboxamide, N, N′-dicyclododecyl-2,6-naphthalenedicarboxamide, N, N′-dicyclohexyl-2,7-naphthalenedicarboxyamide, N, N ′ -Dicyclopentyl-4,4'-biphenyldicarboxamide, N, N'-dicyclohexyl-4,4'-biphenyldicarboxamide, N, N'-dicyclooctyl-4,4'-biphenyldicarboxamide, N, N′-dicyclododecyl-4,4′-biphenyldicarboxamide, N, N′-dicyclohexyl-2,2 '-Biphenyldicarboxamide and the like can be mentioned.

  What is necessary is just to select suitably content of the aromatic amide compound represented by said Formula (1) so that it may become the amount of the carbon nanotube in a polyester resin, and a melt viscosity suitable for a spinning method and spinning conditions. As one guideline, for example, 5 to 10 parts by mass of carbon nanotubes having a preferable length L and a preferable aspect ratio L / D described later are included with respect to 100 parts by mass of the polyester resin, and by a melt spinning method. In the case of yarn production, the content of the aromatic amide compound represented by the formula (1) is preferably 0.05 parts by mass or more and 0.25 parts by mass or less.

(carbon nanotube)
The carbon nanotube used in the present invention preferably has a length L of 5 μm or less and an aspect ratio L / D which is a ratio of the length L to the diameter D of 400 or less. By setting the length L and the aspect ratio L / D within the above ranges, even when conductive fibers are formed by the melt spinning method, the carbon nanotubes are suppressed from being oriented in the fiber spinning direction. An intertwined sheath can be easily obtained.
Examples of the carbon nanotube used in the present invention include single-walled carbon nanotubes that are cylindrical tubes made of a single graphene. Further, multi-walled carbon nanotubes in which two or more cylindrical tubes made of graphene having different diameters are stacked.

The conductive fiber according to the present invention is prepared by preparing a polyester resin pellet for each of the core part and the sheath part and using the melt-spinning method using the core-sheath type composite nozzle 4 shown in FIGS. 6 (a) and 6 (b). Can be manufactured.
The polyester resin compound pellets used for the sheath can be manufactured using, for example, a biaxial extruder. Specifically, the polyester resin pellet, the aromatic amide compound represented by the formula (1), and the carbon nanotube can be directly pelletized by kneading and melting. The polyester resin pellets are freeze-pulverized, the base resin fine powder having a desired particle size distribution and the aromatic amide compound powder represented by the formula (1) are uniformly mixed with a powder mixer, and the carbon nanotubes are directly kneaded, Thereafter, it is preferably pelletized by melting. This is because the carbon nanotubes are uniformly dispersed in the polyester resin.

The core-sheath type composite nozzle 4 includes a base plate 401 having 36 round holes narrowed, and a distribution plate which is disposed on the top surface of the base plate and narrows the distribution holes corresponding to the round holes of the base plate. It has a structure in which plates 402 are bonded together. The pipe 403 through which the core resin 404 circulates is inserted into the distribution hole, and the resin 405 containing the carbon nanotubes in the sheath circulates outside the pipe. It is pushed out from a round spinneret 406.
After being extruded from the spinneret, a core portion made of a thermoplastic resin in a cooling process, a sheath portion covering the core portion and containing carbon nanotubes in the thermoplastic resin, and further covering the sheath portion, a thermoplastic resin A conductive fiber having a three-layer structure composed of the outermost layer including the slag is formed.
The formation of the outermost layer 23 made of a thermoplastic resin will be described below. When the molten resin flows through the inner surface of the core-sheath composite nozzle having a plurality of round hole caps, the molten resin tip is sprayed from the center of the cross section of the base to the inner surface of the surrounding base. To flow. This is called fountain flow. At this time, the molten resin in contact with the inner surface of the die is rapidly cooled on the inner surface of the die to form a skin layer. In the case where a filler containing carbon nanotubes is contained in the molten resin, the skin layer does not contain fillers containing carbon nanotubes, and is formed only from the resin.
The conductive fiber having a three-layer structure extruded from the core-sheath type composite nozzle in a molten state is cooled, and after having attached a water-containing or non-water-containing treatment agent, preferably 100 m / min or more and 10,000 m / min. Hereinafter, the film is particularly preferably wound at a winding speed of 300 m / min to 2000 m / min. Here, the fiber extruded from the core-sheath type composite nozzle is preferably a multifilament composed of a bundle of a plurality of fibers rather than one monofilament, and the number of the bundle of fibers is preferably 20 to 200.
The conductive fiber having the core-sheath structure according to the present invention can be obtained by stretching the unstretched conductive fiber having the core-sheath structure produced by the melt spinning method while heating with a heating type stretching device. .

(Charging member)
The charging member according to the present invention is a charging member using the above-described conductive fiber, and the carbon nanotube is exposed at the tip of the conductive fiber that comes into contact with the electrophotographic photosensitive member that is the object to be charged. ing.
FIG. 1 schematically shows a cross section of a charging member according to an embodiment of the present invention, in which conductive fibers 11 are attached to the surface of a base 13 via a conductive adhesive layer 12. As shown in FIG. 3 (a), the conductive fiber 11 is composed of a core portion 21 made of a polyester resin and a polyester resin that covers the core portion and contains an aromatic amide compound represented by the formula (1). And a three-layer core-sheath structure that includes a sheath portion 22 and an outermost layer 23 that covers the sheath portion and is made of a thermoplastic resin.

Furthermore, as shown in FIG. 3 (b), in order to expose the sheath portion containing a plurality of entangled carbon nanotubes on the fiber surface at the tip of the conductive fiber that is in contact with the member to be charged, A method of removing the outermost layer containing the thermoplastic resin covering the sheath part by oxygen plasma treatment or alkali treatment is preferably used.
In the oxygen plasma treatment, oxygen gas is introduced into a vacuum vessel and kept under reduced pressure, oxygen plasma is induced between the vacuum vessel and the porous metal cylindrical electrode installed in the vacuum vessel, The surface of the installed charging member is treated. By installing a charging member in the porous metal cylindrical electrode, it is possible to remove the outermost layer on the surface of the conductive fiber by oxygen atom radicals by controlling ions and electrons in the plasma. . The plasma generation conditions are preferably selected depending on the apparatus configuration and the size of the processed object, but the high frequency power is preferably 30 W or more and 500 W or less. Further, the oxygen gas flow rate is preferably 30 sccm or more and 200 sccm or less.

The oxygen plasma treatment time is preferably 2 minutes or more and 60 minutes or less. By setting it in the above range, sufficient oxygen plasma treatment can be performed. When oxygen plasma treatment is performed for 10 minutes or more, it is preferable to interrupt the plasma treatment for several minutes every 10 minutes to lower the temperature of the charging member surface.
The alkali treatment is preferably held for several tens of minutes to several hundreds of minutes in a several percent sodium hydroxide solution or potassium hydroxide solution held at a temperature of 50 ° C. or more and 100 ° C. or less, particularly preferably. The temperature is within a range of 100 minutes to 300 minutes in a sodium hydroxide solution at a temperature of 60C to 70C and 3% to 5%.

By the way, in injection charging, in order to ensure the convergence of the potential, the time required for the electrophotographic photosensitive member to pass through the nip in contact with the charging member is the resistance of the conductive fibers on the outer peripheral surface of the charging member and the static of the photosensitive member. It is desirable that the time constant is 5 times or more of the electric capacity. For example, it may be used at a peripheral speed of 200 mm / sec or more, as in the case of using an amorphous silicon photoconductor having a higher dielectric constant than that of an organic photoconductor (OPC). In this case, that is, when the time constant is 2 msec or less, the contact portion between the photosensitive member and the tip of the conductive fiber in the charging member, the so-called penetration amount is several hundreds μm or more, preferably in the range of 300 μm to 1500 μm. In addition, it is preferable that the width of the nip in contact with the electrophotographic photosensitive member in the direction of rotation of the photosensitive member is some.
Therefore, in the tip portion of the conductive fiber according to the present invention, the range in which the sheath portion is exposed is preferably at least 400 μm or more from the tip portion of the conductive fiber.

The resistance value per conductive fiber used in the present invention is preferably 1 × 10 ³ Ω or more in order to prevent destruction of the photoreceptor due to current concentration on a part of the photoreceptor. In order to stabilize the charging potential even under injection charging conditions where the time constant is 2 msec or less, it is preferable to set the resistance value per conductive fiber to 1 × ^{10 10} Ω or less as necessary.

(Substrate)
As the base of the charging member according to the present invention, a conductive material such as a metal or an alloy is preferably used. However, a base obtained by coating an insulator or a semiconductor with a conductive metal may be used. Specifically, stainless steel (SUS), Al or Al alloy, Fe or Fe alloy, Cu or Cu alloy, Ni or Ni alloy, or the like can be used. Alternatively, a conductive rubber layer may be provided on the surface of the metal or alloy.

(Method for manufacturing charging member)
Specific examples of the charging brush according to the present invention include those manufactured by the following two methods.
1) A woven brush produced by spirally winding a strip-shaped base fabric in which a bundle of a plurality of conductive fibers produced by a melt spinning method is woven, around a conductive metal core shaft.
2) A conductive fiber produced by melt spinning is cut to a length of 0.5 mm or more and 3 mm or less, then flying using static electricity, and planted on a substrate coated with a conductive adhesive layer in advance. An electrostatic flocking brush manufactured by the electric flocking method.

The manufacturing method of the woven brush is as follows. The conductive fabric manufactured by the melt spinning method is woven with, for example, a bristle weave to stand, thereby obtaining a base fabric having conductive fibers having a length of 0.5 mm or more and 5 mm or less. Next, the surface of the substrate is coated with a conductive adhesive by a spray method, for example, to a thickness of 20 μm to 100 μm. Thereafter, the surface of the base fabric on which the conductive fibers are not erected is spirally wound and bonded to the surface coated with the conductive adhesive, and then several hours in a dryer at a temperature of 60 ° C. or higher and 100 ° C. or lower. dry.
Next, in order to remove the outermost layer containing the thermoplastic resin at the tip of the conductive fiber, oxygen plasma treatment or alkali treatment is performed. Thereafter, a process for inclining the conductive fibers of the charging member uniformly along one rotation direction, that is, an oblique hair process is performed to obtain a charging member woven brush.

The manufacturing method of the electrostatic flocking brush is as follows. The conductive fiber manufactured by the melt spinning method is cut to a length of 0.5 mm to 3 mm to obtain a cut pile. Next, the surface of the substrate is coated with a conductive adhesive by a spray method, for example, to a thickness of 20 μm to 100 μm. Next, the electrode plate is disposed below the substrate coated with the conductive adhesive layer while rotating around the axis. Next, the cut pile is placed on the electrode plate, and the electrode plate and the substrate are connected to a high voltage power source, so that the cut pile flies and is implanted in the conductive adhesive layer on the substrate.
The conductive adhesive layer formed on the surface of the metal core that is the substrate has a thickness of 50 to 200 μm by spraying a conductive adhesive in which a conductive blower is dispersed in an acrylic, epoxy, or urethane resin adhesive. It is formed by coating and then thermosetting.
The resistivity value of the conductive adhesive layer used in the present invention is preferably in the range of 1.0 × 10 ² Ωcm to 1.0 × 10 ⁸ Ωcm.

(Image forming device)
As shown in FIG. 4, the electrophotographic image forming apparatus according to the present invention includes the above-described charging member 3 and a drum-shaped electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) that is charged thereby to form a latent image. 201). The photosensitive drum 201 is disposed so that the surface of the conductive fiber of the charging member 3 is in contact.
As the photosensitive drum 201, for example, a negatively chargeable a-Si photosensitive drum having a diameter (φ) of 80 mm is used, and the rotational speed of the photosensitive member is 300 mm / sec. As the pre-exposure lamp 202, an LED having a wavelength of 660 nm is used, and the surface of the photosensitive drum is exposed to uniformly reduce the surface potential of the photosensitive drum immediately before charging. Scanning exposure is performed by laser light emitted from the exposure device 203, and an electrostatic latent image is formed on the photosensitive drum.
The developer 204 is coated with a developer on four-color developing sleeves (M, Y, C, K) including a magnet roller, and a developing bias is applied using a developing device power supply (not shown). Toner is developed on the photosensitive drum. As the developer, for example, a negatively chargeable toner having a particle size of about 7 μm and a developing magnetic particle of about 35 μm are used. The developing sleeve rotates in the same direction as the photosensitive drum, and its peripheral speed is, for example, about 450 mm / sec. Further, the magnetic pole of the magnet roller facing the photosensitive drum 201 is, for example, 90 mT, and the gap between the developing sleeve and the photosensitive drum 201 is, for example, 350 μm.
The transfer device includes a conductive sponge roller 205 having a diameter (φ) of 16 mm, for example, and a DC power source 206. The transfer member 209 is sandwiched between the photosensitive drum 201 and a voltage having a polarity opposite to the charging polarity of the toner. Is applied to move the toner onto the member to be transferred.
As the cleaner 207, for example, a urethane cleaning blade having a thickness of 2 mm is used, and cleaning is performed by scraping off transfer residual toner from the photosensitive drum with the cleaning blade.
The charging member (charging brush) 3 mounted on the charging device according to the present invention has an outer diameter of, for example, 20 mm including the tip of the conductive fiber according to the present invention, and the rotation shaft with respect to the photosensitive drum 201. Arrange them so that they are parallel.
The so-called penetration amount, which is a value obtained by subtracting the distance between the respective rotation axes from the value obtained by adding the radius of the charging member 3 and the radius of the photosensitive member, is 750 μm, for example. The rotation direction of the charging member 3 is the same as that of the photoconductor, so that the contact area between the photoconductor and the charging member 3 moves in opposite directions, and the rotation speed is, for example, 450 mm / sec or more and 550 mm / sec or less. And
For example, a DC voltage of −700 V is applied from the power supply 208 as a bias for charging. In this embodiment, only a direct voltage (DC) is applied, but an alternating voltage (AC) may be applied in a superimposed manner.
As described above, by performing an image forming operation using the image forming apparatus on which the charging member 3 is mounted, it is possible to perform satisfactory image output.

Examples of the present invention will be described below.
[Production Example 1]
(Preparation of pellet O)
A polyethylene terephthalate (PET) pellet O having an intrinsic viscosity (hereinafter referred to as IV value) of 0.95 was prepared.
(Preparation of pellet A)
After pellet O was frozen and pulverized, fine powder having a particle size of 20 μm or less was obtained by classification. This fine powder and carbon nanotubes having a length of 5 μm or less, an average length of 3 μm, and an aspect ratio of 400 or less were dry blended so that the mass ratio of the carbon nanotubes was 8 wt%, and then these were biaxially expanded. It knead | mixed and melted using the ruder. The obtained melt-kneaded product was pulverized to produce pellet A.

(Preparation of pellet B)
After freeze-pulverizing the pellet O, fine powder having a particle size of 20 μm or less was obtained by classification. To 100 parts by mass of this fine powder, 0.25 part of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide powder (trade name: NJ Star NU100, manufactured by Shin Nippon Rika Co., Ltd.) is mixed. Thus, a mixed powder was obtained. This mixed powder was dry blended with carbon nanotubes having a length of 5 μm or less, an average length of 3 μm, and an aspect ratio of 400 or less so that the mass ratio of the carbon nanotubes was 8 wt%. Then, it knead | mixed and fuse | melted with the biaxial extruder. The obtained melt-kneaded material was pulverized to produce pellets B.

(Evaluation of pellets A and B)
For pellets A and B, the melt viscosity was measured using a capillary rheometer (trade name: Twin Bore Capillary Rheometer, manufactured by CEAST). The result is shown in FIG. From FIG. 2, it was confirmed that the melt viscosity was lowered by containing N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide.
In addition, each of the pellets A and B was embedded in an epoxy resin and then buffed, and the cross section of each pellet was observed using a scanning electron microscope (SEM). As a result, it was confirmed that the pellet B was more uniform in dispersibility of the carbon nanotubes than the pellet A.

Furthermore, in order to confirm the content of N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide for the pellet B, quantitative analysis of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide was performed as follows. I went by the procedure.
Pellet B was frozen and ground, and 1 g of the sample was dissolved in 30 ml of hexafluoroisopropanol. Next, the solution was added to 150 ml of methanol, and then the polyethylene terephthalate resin component was stirred and precipitated and filtered to separate the insoluble component in the solution, that is, the polyethylene terephthalate resin component. Next, after concentrating and drying the components soluble in the solution, the sample is subjected to quantitative analysis of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide using a hydrogen nuclear magnetic resonance apparatus. It was. As a result of quantitative analysis, N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide obtained 0.24 parts with respect to 100 parts of polyethylene terephthalate resin.

[Production Example 2]
(Preparation of pellet C)
A pellet C was produced in the same manner as the pellet A, except that the amount of carbon nanotube added was 6% by mass.
(Preparation of pellet D)
Pellet in the same manner as pellet B, except that the amount of carbon nanotube added was 6% by mass and the amount of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide powder was 0.4% by mass. D was produced.

(Evaluation of pellets C and D)
For pellets C and D, the melt viscosity was measured in the same manner as for pellets A and B. As a result, compared with the pellet C, the melt viscosity of the pellet D was low. Thereby, it has confirmed that addition of N, N'-dicyclohexyl-2,6-naphthalenedicarboxamide reduced melt viscosity.
Further, each of the pellets C and D was embedded in an epoxy resin, subjected to plasma treatment, and the cross sections of the pellets C and D were observed with a scanning electron microscope. As a result, it was confirmed that the carbon nanotubes were more uniformly dispersed in the pellet D of the resin compound than in the pellet C.

[Production Example 3]
(Preparation of pellet E)
Pellet E was prepared in the same manner as pellet B, except that the amount of carbon nanotube added was 8% by mass and the amount of N, N′-dicyclohexyl-2,6-naphthalenedicarboxyamide powder was 0.05% by mass. Produced.

  Table 1 shows the content of carbon nanotubes and the content of N, N′-dicyclohexyl-2,6-naphthalenedicarboxamide according to the present invention for pellets A to E.

[Example 1]
(Preparation of conductive fiber)
Conductive fibers having a core-sheath structure were prepared using pellet O as a core-forming material and pellet B as a sheath-forming material.
That is, first, the pellet O and the pellet B were dried at a temperature of 140 ° C. for 4 hours. Next, the pellet O and the pellet B are respectively introduced into two biaxial extruders, and at a spinning temperature of 290 ° C., a core-sheath type composite nozzle having a mouthpiece of a round hole with a diameter of 0.3 mm and a number of holes of 36 ( From FIG. 6, the pellet O and B melts were discharged and spun so that the area ratio of the core portion to the sheath portion was 6: 4.
The spun yarn with the core-sheath structure obtained was cooled and solidified with a cooling device having a cooling length of 1 m (uniflow type) with a cooling air with an air temperature of 25 ° C. and a wind speed of 0.5 m / sec. Was wound to prepare an unstretched multifilament yarn having a fiber diameter of 42 μm. In the course of cooling and solidification, an oil agent (effective component 10 mass% concentration) was adhered.
The obtained unstretched multifilament yarn was heat-drawn at a temperature of 150 ° C. so that the draw ratio was doubled to obtain a multifilament yarn composed of 36 conductive fibers having a core-sheath structure with a diameter of 30 μm. Produced.

(Production of pile fabric)
Next, using this multifilament yarn, a ribbon-like pile fabric having a width of 15 mm was produced as shown in FIG. A ribbon-shaped pile fabric was wound around an aluminum pipe, and was installed in a state where only both ends of the aluminum pipe were supported in a porous metal cylindrical electrode in a vacuum vessel, and an oxygen plasma treatment was performed.
One conductive fiber was extracted from the ribbon-shaped pile fabric after the oxygen plasma treatment, and SEM observation was performed on the surface and cross-section of the tip of the conductive fiber on the plasma treatment side. As a result, as shown in FIG. 3B, it was found that the carbon nanotubes formed an intertwined network structure in the sheath portion of the conductive fiber. In addition, entangled carbon nanotubes were exposed on the surface of the conductive fiber.
Further, the surface of the pile fabric base side (the side in contact with the aluminum pipe) on the side opposite to the plasma-treated side of the conductive fiber was observed with an SEM. As a result, no exposure of carbon nanotubes was observed. This means that the outermost layer is present on the surface of the conductive fiber not subjected to plasma treatment.

(Example 2)
A multifilament yarn was produced in the same manner as in Example 1 except that the sheath forming material was changed to pellet E. Then, using this multifilament yarn, a ribbon-shaped pile fabric having a width of 15 mm was produced in the same manner as in Example 1 and then subjected to oxygen plasma treatment.
One conductive fiber was extracted from the obtained ribbon-like pile fabric, and the tip of the conductive fiber on the plasma processing side was observed with an SEM. As a result, it was found that the carbon nanotubes formed an intertwined network structure in the sheath portion of the conductive fiber. In addition, entangled carbon nanotubes were exposed on the surface of the conductive fiber. The resistance value of this conductive fiber was 5 × 10 ⁷ Ω.
Moreover, the discharge property of the surface of the part which performed the oxygen plasma process of the front-end | tip part of this conductive fiber was evaluated with the following method. That is, using the scanning probe microscope shown in FIG. 7, a bias voltage of 10 V is applied to the probe 304, and the probe 304 is brought into contact with the surface of the conductive fiber 305 placed on the conductive sheet 303, 5 μm × 5 μm. While scanning this area, the value of the current flowing through the probe was measured over the entire scanning range. As a result, it was found that a conductive path was formed between the electrode and the electrode in a region of about 74% based on the total surface area of the measurement portion of the oxygen plasma processing unit.

(Example 3)
A multifilament yarn was produced in the same manner as in Example 1. Further, using this multifilament yarn, a ribbon-like pile fabric was produced in the same manner as in Example 1.
The ribbon-shaped pile fabric was wound around a SUS substrate, and then installed in a state where only both ends of the substrate were supported in a porous metal cylindrical electrode in a vacuum vessel, and oxygen plasma treatment was performed. After the plasma treatment, a final finishing process was performed on the surface to produce a charging brush having an outer diameter of 20 mm. The conductive fiber density on the surface of this charging brush was 200 kF / inch ² .
One conductive fiber was extracted from the charging brush, and the surface and cross section of the plasma treatment side tip of the conductive fiber were observed with an SEM. As a result, as shown in FIG. 3B, it was confirmed that the carbon nanotubes formed an intertwined network structure in the sheath portion of the conductive fiber. In addition, entangled carbon nanotubes were exposed on the surface of the conductive fiber. The resistance value of this conductive fiber was 2 × 10 ⁷ Ω.
Furthermore, the discharge property of the surface of the conductive fiber was evaluated by the following method. That is, the current value on the surface of the conductive fiber was measured over the entire scanning range using a scanning probe microscope in the same manner as in Example 2. As a result, it was found that a conductive path was formed between the electrode and the electrode in an area of about 79% based on the total surface area of the measurement part of the oxygen plasma processing part.
Next, this charging brush was mounted on the copying machine shown in FIG. 4, and the penetration amount of the charging member into the photosensitive member was set to 1 mm. An electrophotographic image was formed by setting the rotation speed of the charging member to 500 mm / sec and applying a DC voltage of −700 V to the charging member. As a result, the mesh size of the halftone part was uniform and a good image was obtained. From this, it was confirmed that the photoreceptor could be charged uniformly and satisfactorily.

(Comparative Example 1)
An unstretched multifilament was produced by melt spinning in the same manner as in Example 1 except that the pellet A was used as the sheath forming material. As a result of SEM observation of the fiber cross section of 36 multifilament yarns immediately after melt spinning, many filaments in which the core portion and the sheath portion were not concentric but eccentric were observed.
Next, the unstretched multifilament was subjected to a stretching treatment in the same manner as in Example 1. As a result, yarn breakage occurred frequently, and the multifilament could not be produced stably.

(Comparative Example 2)
A multifilament yarn composed of 36 conductive fibers was produced in the same manner as in Example 3, and then a ribbon-like pile fabric having a width of 15 mm was produced.
Next, this ribbon-like pile fabric was wound around a SUS substrate, and then the surface was subjected to final finishing to produce a charging member having an outer diameter of 20 mm. The conductive fiber density on the surface of the charging member was 200 kF / inch ² .
One conductive fiber was extracted from the charging member, and SEM observation of the surface and cross section of the conductive fiber was performed. As a result, as shown in the schematic diagram of FIG. 3 (a), the outermost layer made of a thermoplastic resin covers the sheath constituting the network structure in which the carbon nanotubes are intertwined in the polyester resin. It was confirmed. The resistance value of this conductive fiber was 7 × ^{10 10} Ω.
Moreover, the discharge property of the surface of this conductive fiber was evaluated by the following method. That is, the current value on the surface of the conductive fiber was measured over the entire scanning range using a scanning probe microscope in the same manner as in Example 2. As a result, it was found that a conductive path was formed between the electrode and the electrode in a region of about 35% based on the total surface area of the measurement portion of the oxygen plasma processing unit. Next, this charging member was mounted on the copying machine shown in FIG. 4 in the same manner as in Example 3, and the amount of the conductive fibers entering the photosensitive member in the charging member was set to 1 mm. As a result of applying a DC voltage of −700 V to the charging member at a rotation speed of the charging member of 500 mm / sec, an image in which the toner was covered in a streak along the paper traveling direction on the white background portion was output. In addition, the halftone mesh size was disordered, resulting in a rough image.

  The present invention is applicable to an image forming apparatus using an electrophotographic method. More specifically, an image is formed by charging a photoreceptor having a charge injection layer on its surface as an image carrier by contact charging, forming a latent image and a developer image, and transferring and fixing the image on a transfer material. In the forming apparatus, a uniform charging potential can be obtained without using discharge.

3 Charging Member 11 Conductive Fiber 12 Conductive Adhesive Layer 13 Base 21 Core 22 Sheath 23 Outermost Layer 201 Photosensitive Drum 202 Pre-exposure Lamp 203 Exposure Device 204 Developer 205 Conductive Sponge Roller 206 DC Power Supply 207 Cleaner 208 Power Supply 209 Covered Transfer member 4 Core-sheath type composite nozzle 401 Cap plate 402 Distribution plate 403 Pipe 404 Core resin 405 Sheath carbon nanotube-containing resin 406 Spinning port 301 Current detection circuit 302 Sample stage (made of aluminum)
303 Conductive sheet 304 STM probe 305 Conductive fiber

Claims (4)

A core containing polyester resin;
A sheath containing a polyester resin and carbon nanotubes covering the core;
In the conductive fiber comprising the outermost layer that covers the sheath and contains a thermoplastic resin,
The sheath part further contains an aromatic amide compound represented by the following general formula (1):
(In formula (1), X is the following chemical formula (2) or (3), and R1 and R2 are the same or different cycloalkyl groups having 5 to 12 carbon atoms, respectively):
.   2. The conductive fiber according to claim 1, wherein the sheath includes the aromatic amide compound in a proportion of 0.05% by mass or more and 0.25% by mass or less with respect to the polyester resin in the sheath. A charging member having a conductive substrate and conductive fibers having one end bonded to the substrate;
The conductive fiber includes a core portion including a polyester resin;
A sheath that covers the core and includes carbon nanotubes intertwined with a polyester resin and an aromatic amide compound represented by the following structural formula (1);
An outermost layer that covers the sheath and contains a thermoplastic resin, and a conductive fiber comprising:
The charging member, wherein the conductive fiber has a carbon nanotube contained in the sheath portion exposed on a surface of the conductive fiber at a tip portion on the side not bonded to the base body:
(In formula (1), X is the following chemical formula (2) or (3), and R1 and R2 are the same or different cycloalkyl groups having 5 to 12 carbon atoms, respectively):
. The charging member according to claim 3,
An electrophotographic image forming apparatus comprising: an electrophotographic photosensitive member disposed so as to be in contact with a leading end portion of a conductive fiber in the charging member.