JP2006336142A - Flat electrically conductive fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide electrically conductive yarn affording uniform and clear printed images by the use as electrically conductive yarn for the brush of image formation equipment, and to provide a method for producing the electrically conductive yarn. <P>SOLUTION: The electrically conductive fiber (in the form of yarn) is composed of one or more polymers containing an electrically conductive substance and is crimped. The fiber is flat with flat cross section ≤0.47 in the ratio b/a, wherein (a) is the maximum length (major axis) for the cross section and b is the maximum length (minor axis) of the axis rectangular to the major axis. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a flat conductive fiber and a method for producing the same. More specifically, a brush used in an image forming apparatus such as a laser printer, for example, a static elimination brush for neutralizing the photosensitive drum surface after image transfer, a charging brush for charging the photosensitive drum surface, and residual toner on the photosensitive member. The present invention relates to a flat conductive fiber that can be suitably used as a cleaning brush for removal, and a method for producing the same.

  As fibers for brushes used in electrophotographic recording type dry copying machines, facsimiles, printers, etc., vinylon conductive yarns, nylon conductive yarns or polyester conductive yarns containing cellulosic fibers or conductive carbon are used (for example, Patent Documents 1 to 4).

  Conventionally, the conductive yarn remains as a straight filament yarn, and is used as a raised fiber of a cut pile knitted fabric or a raised fabric raised by tuft or raising, and further used as a conductive brush. Most of them.

  However, when the conductive brush is brought into contact with a photosensitive drum or the like, it becomes a point contact, so that there are discharge spots, charged spots and cleaning spots, and there is a problem that a uniform and clear printed image cannot be obtained. For this reason, a method of increasing the napping density of a pile knitted fabric or the like is conceivable, but this method also has a limit.

JP-A-9-491117 JP 2000-355823 A JP 2000-160427 A JP 2003-66669 A

  The present invention has been made in view of the above-described background art, and an object thereof is to provide a conductive yarn that can be used as a conductive yarn for a brush of an image forming apparatus to obtain a uniform and clear printed image, and a method for manufacturing the conductive yarn. .

  As a result of repeated studies to solve the above problems, the present inventor imparts crimps to the conductive fibers used in the brush, so that the tips of the conductive fibers are bent or curved, and the photosensitive drum or the like. It was considered that the above problem can be solved by the effect that the contact area becomes larger and the action area of static elimination, charging and cleaning becomes larger. Moreover, when false twisting was applied to the fibers in order to impart crimps, it was found that the above effect was further increased when the specific fibers were processed. Furthermore, there have been problems that the quality of the conductive fiber is lowered or the yarn is broken during processing. However, these problems have been solved and the present invention has been achieved.

  Thus, according to the present invention, a fiber made of one or more polymers containing a conductive substance, the fiber is crimped, and the fiber has a maximum length in its cross section. When the axis shown is the major axis and the axis orthogonal to the minor axis is the minor axis, the ratio b / a between the maximum length a and the maximum length b of the minor axis is 0.47 or less. A flat conductive fiber is provided.

  Further, according to the present invention, a synthetic fiber comprising one or more polymers containing a conductive substance and having an elongation of 120% or more is stretched at a draw ratio of 1.4 times or more at a temperature lower than the melting point of the polymer. There is provided a method for producing a flat conductive fiber, characterized by subjecting a drawing false twisting to a twist coefficient of 0.93 or more.

  According to the flat conductive fiber of the present invention, a uniform and clear printed image can be obtained by using it as a conductive thread for a brush of an image forming apparatus. Moreover, according to the manufacturing method of this invention, the conductive fiber which has a high quality crimp can be manufactured stably.

  The flat conductive fiber of the present invention may be a fiber made of one or more polymers containing a conductive substance. This will be specifically described below with reference to FIG. FIG. 1 schematically shows a flat cross section of the conductive fiber of the present invention. The flat cross section includes a polygonal shape as shown in FIG.

  The conductive fiber of the present invention may be a fiber made of a single polymer containing a conductive material as shown in FIG. Moreover, it may be a composite fiber in which a polymer containing a conductive substance and a polymer not containing a conductive substance are combined as shown in (b) to (h), and conductive like (f) to (h). The core-sheath composite fiber is preferably a core-sheath composite fiber with a polymer containing a conductive substance as a core and a polymer containing no conductive substance as a sheath, and the core is close to the surface of the core-sheath composite fiber as in (h) A core-sheath composite fiber having 6 or more protrusions is particularly preferred.

  When the composite fiber is composed of a polymer containing a conductive substance and a polymer not containing a conductive substance as in (b) to (h), the following are preferred as the respective polymers and conductive substances: I can give you.

  That is, examples of the polymer containing a conductive substance in the present invention include polyolefins such as polyethylene, polypropylene, polystyrene, and polybutadiene, polyamides such as nylon-6 and nylon 6,6, and copolymer polyamides and polyethylenes containing these as main components. Examples thereof include polyesters such as terephthalate and polybutylene terephthalate, and copolymerized polyesters containing these as the main components. Among them, polyolefin, particularly polyethylene is preferable. Two or more of these may be used in combination.

  As the conductive material, conductive carbon black, a conductive metal compound, or the like can be used. Examples of the carbon black include acetylene black, oil furnace black, thermal black, channel black, and ketjen black. On the other hand, as the conductive metal compound, a conductive metal oxide is mainly used, and stannic oxide and zinc oxide having excellent whiteness are particularly preferable. As used herein, stannic oxide includes stannic oxide containing a small amount of antimony compound, and a conductive metal composite obtained by coating the surface of titanium oxide particles with stannic oxide containing a small amount of antimony compound. It is. Zinc oxide also includes conductive zinc oxide in which a small amount of aluminum oxide, lithium oxide, indium oxide and the like are dissolved. These can be used by being dispersed in a polymer constituting the core as a fine powder.

  On the other hand, examples of the polymer that does not contain a conductive substance include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon-6 and nylon-6,6, etc. It may be a polymerized copolymer. Of these, polyethylene terephthalate having an intrinsic viscosity of 0.50 to 0.70 is preferable from the standpoint of yarn production. Moreover, you may make the said polymer contain arbitrary additives, for example, a matting agent, a coloring agent, antioxidant, a dyeability improving agent, an antistatic agent etc. as needed.

  In addition, when it is set as the fiber cross section which consists of a single polymer like (a), what was illustrated to the polymer containing the said electrically conductive substance as this polymer can be mentioned preferably, Especially, a polyethylene terephthalate Is preferred.

  In the present invention, crimping is imparted to the conductive fiber, and the maximum length (major axis) a and the length (minor axis) at which the fiber is the largest in an axis perpendicular thereto are shown in the cross section. It is important to have a flat cross section in which the ratio b / a to b is 0.47 or less. Here, a and b specifically refer to the lengths shown in FIG.

  That is, since the conductive fiber has a bent or curved shape due to crimping as described above, when this is used as a conductive brush of an image forming apparatus, the fiber is compared with a conventional straight conductive thread. The contact area between the front end and the photosensitive drum and the like is increased, and the area of charge removal, charging, and cleaning is increased. As a result, a more uniform and clear printed image can be obtained.

  As the conductive fiber, the smaller the fiber diameter, the denser the charge removal, charging and cleaning, but the hardness is also required for scraping off toner. On the other hand, the conductive fiber of the present invention has a flat cross section with the flatness as described above, and the flat surface is easily oriented horizontally with respect to the photosensitive drum, etc. While maintaining the hardness, it has the effect of increasing the fiber density.

  The conductive fiber described above can be manufactured by the following method. That is, a fiber composed of one or more polymers containing the above-described conductive substance, and a synthetic fiber having an elongation of 120% or more is twisted by 1.4 times or more at a temperature lower than the melting point of the polymer. It can be manufactured by drawing false twisting with a coefficient of 0.93 or more.

  That is, as a polymer containing a conductive substance, in particular, when a composite fiber is used, in order to improve the dispersibility of the conductive substance, generally a low melting point or low viscosity polymer is preferably used, which is higher than the melting point of the polymer. Performing false twisting at a temperature is not preferable because the fiber melts, in the case of a composite fiber, peels between components, and in the case of a core-sheath composite fiber, the sheath portion is damaged.

  In addition, by setting the elongation of the composite fiber before drawing false twisting to 120% or more and making the fiber thin while drawing this at a draw ratio of 1.4 times or more, the twist coefficient is set to 0.93 or more. By tightening with a large force in the fiber cross-section direction, the composite fiber having a round cross section can be deformed to produce a conductive fiber having a flat cross section having the above-described flatness. According to this method, crimping and fiber flattening can be performed simultaneously.

  However, if the elongation of the above-mentioned composite fiber is too large, the orientation of the conductive fibers becomes too low, and it becomes easy for fusion to occur during false twisting or the strength is lowered. The following is preferable. Further, if the twisting factor becomes too large, a double twisted structure is generated by false twisting, or the yarn is easily cut off. Therefore, the twisting factor is preferably 1 or less.

  Even if the crimp ratio of the conductive fiber is too high, the orientation and arrangement of the nappings are likely to be disturbed when the napped fabric for a brush is used. For example, the problem that the toner to be cleaned accumulates inside the brush tends to occur. On the other hand, even if the crimp rate is too low, the above-described effects due to crimping cannot be sufficiently exhibited. Accordingly, the crimp rate is preferably 2 to 8%.

Moreover, the cross-sectional electrical resistance value of the conductive fiber is preferably 10 ² to 10 ¹¹ Ω / cm. Although it varies depending on the type of image forming apparatus, it is easy to obtain uniform charging, static elimination, and cleaning effects by setting the cross-sectional electric resistance value within the range.

  In order to make a conductive brush using the above-mentioned conductive fibers, for example, a napped fabric using at least the napped portions of the conductive fibers is used, and this is affixed to a flat surface, or is wound spirally around a support (shaft). And brush shape. Thereafter, napping treatment and shearing treatment are performed to obtain a conductive brush for an image forming apparatus.

Hereinafter, the present invention will be described in more detail with reference to examples. The evaluation method is as follows.
(1) Intrinsic viscosity of polyester Measured at 25 ° C. using orthochlorophenol.
(2) Print image quality A test chart issued by the Electrophotographic Society was copied, and sensory evaluation was performed by five people on the uniformity and clearness of the print image quality with one printing.

[Example 1]
Conductive polymer chips (melting point 130 ° C.) obtained by adding 30 parts by weight of furnace-based conductive carbon black to 70 parts by weight of polyethylene (Sumitomo Chemical Sumikasen G-807) and melting and mixing, inherently 56 dtex 4 having a viscosity of 0.64 and a melting point of 256 ° C. and a polyethylene terephthalate chip (manufactured by Teijin Fibers Ltd.) using a composite spinneret at a spinning temperature of 290 ° C. and a take-up speed of 2400 m / min. A core-sheath composite fiber having a cross section of the filament in FIG.

  Next, 6 composite fibers were combined, and using a false twisting machine equipped with a spindle type twisting device, a processing temperature of 130 ° C., a draw ratio of 1.7 times, and a false twist number of 2327 T / m (twist coefficient) 0.95), a drawing false twisting process was performed at a processing speed of 120 m / min to obtain flat conductive fibers having a crimp rate of 6% and an average flatness of 0.42.

Further, a twisted yarn of 100 T / m is applied to the crimped yarn, a napped fabric is prepared using a pile loom, this is slit into a 20 mm wide tape and wound around a metal shaft in a spiral shape. A conductive brush was prepared by cutting and making the height constant.
When this conductive yarn brush was used in an image forming apparatus, the printed image was excellent in both uniformity and sharpness.

[Comparative Example 1]
Spinning was performed at a spinning temperature of 290 ° C. and a take-up speed of 1200 m / min using the same conductive polymer tip as in Example 1 and a polyethylene terephthalate tip, and an undrawn yarn was obtained. This undrawn yarn is heat-drawn at a preheating of 100 ° C., a heat setting temperature of 180 ° C. and a draw ratio of 3.1 times, an elongation of 40%, and a core sheath having a cross section of FIG. A composite fiber elongation yarn was obtained.

Next, eight drawn yarns were combined and processed using a false twisting machine equipped with a spindle-type twisting device at a processing temperature of 130 ° C., a false twist number of 1741 T / m (a false twisting factor of 0.83), False twisting was performed at a speed of 100 m / min to obtain a conductive fiber having a crimp rate of 6% and an average flatness of 0.85. Further, a conductive brush was prepared in the same manner as in Example 1 using the crimped fiber.
When this conductive yarn brush was used in an image forming apparatus, the printed image was inferior to the printed image of Example 1 in both uniformity and sharpness.

[Comparative Example 2]
A conductive brush was prepared and used in an image forming apparatus in the same manner as in Comparative Example 1 except that the combined drawn yarn was not subjected to false twisting. The obtained printed image was inferior to the printed image of Comparative Example 1 both in uniformity and sharpness.

  According to the conductive fiber of the present invention, a uniform and clear printed image can be obtained using the conductive fiber for a brush of an image forming apparatus. Moreover, according to the manufacturing method of this invention, the conductive fiber which has a high quality crimp can be manufactured stably. For this reason, both the conductive fiber and the manufacturing method of the present invention have extremely high industrial utility value.

It is a schematic diagram which shows the example of the cross-sectional shape of the composite fiber which comprises the flat conductive yarn of this invention. The figure explaining the maximum length (major axis) a in the cross section and the maximum length (minor axis) b in the axis orthogonal to a in the cross section of the composite fiber constituting the flat conductive yarn of the present invention. It is.

Explanation of symbols

a Maximum length in fiber cross section (major axis)
b Length that is maximum on the axis orthogonal to a (short axis)
1 core 2 sheath

Claims (8)

  A fiber made of one or more polymers containing a conductive substance, the fiber being crimped, and the fiber being orthogonal to the maximum length (major axis) a in its cross section A flat conductive fiber having a flat cross section in which a ratio b / a to a maximum length (short axis) b of the shaft is 0.47 or less.   The flat conductive fiber according to claim 1, wherein the flat conductive fiber is a fiber made of a single polymer containing a conductive substance.   2. The flat conductive fiber according to claim 1, wherein the flat conductive fiber is a composite fiber obtained by combining a polymer containing a conductive substance and a polymer not containing a conductive substance.   The flat conductive fiber according to claim 3, wherein the flat conductive fiber is a core-sheath composite fiber having a core containing a polymer containing a conductive substance and a sheath containing a polymer containing no conductive substance.   The flat conductive fiber according to claim 4, wherein six or more projecting portions that approach the surface of the core-sheath composite fiber are provided in the core portion.   The flat conductive fiber in any one of Claims 1-5 whose crimp rate is 2-6.   A synthetic fiber made of one or more polymers containing a conductive substance and having an elongation of 120% or more, at a temperature lower than the melting point of the polymer, a draw ratio of 1.4 times or more, and a twist coefficient of 0.93 or more A method for producing a flat conductive fiber, characterized by subjecting to stretching false twisting.   The electroconductive brush which uses the flat conductive fiber in any one of Claims 1-6 for at least one part.

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