JP2019163568A - Conductive fiber and brush - Google Patents

Abstract

To provide conductive fibers including a fiber section having an optimum balance between torsional readiness and bendability and being suitable for a conductive brush to be incorporated into a printer, a copy machine, a fax machine, etc. with an electrophotographic recording method.SOLUTION: Conductive fibers of this invention can be achieved when a secondary moment ratio (I) of a fiber section satisfies the inequality (1): 1.5≤I≤30.0 (1), where I=I/I; I=I/I(I: maximum sectional secondary moment; I: minimum sectional secondary moment); and I=I/I(I: sectional secondary moment of the same fineness round section).SELECTED DRAWING: None

Description

  The present invention relates to conductive fibers used in electrophotographic recording printers, copiers, fax machines, and the like, and in particular, contributes to improving the quality of printed images and preventing image quality deterioration during long-term use. The present invention also relates to a charging brush and a cleaning brush that are incorporated in a printer, a copier, a fax machine, or the like, using the fiber.

  For electrophotographic printers, copiers, fax machines, etc., lubricant application brushes that apply lubricant to the photoreceptor, charging brushes that charge the photoreceptor, toner supply brushes that supply toner to the photoreceptor, and remaining on the photoreceptor Various brushes such as a cleaning brush for removing toner are used.

The electrostatic force is important for charging the photosensitive member, supplying the toner, removing the residual toner, and the like, and a conductive yarn having a specific resistance of 10 ² to 10 ¹² Ω · cm is used for the brush. . As such a conductive yarn, a multifilament containing conductive carbon fine particles is generally used, and various modes of fibers have been proposed for improving brush performance.

  Patent Document 1 proposes a conductive fiber having a multi-leaf cross-sectional shape using only a thermoplastic resin containing conductive fine particles, and increases the number of contact points with a photoconductor as compared with a normal round cross-section. This makes it possible to make the charge of the photoreceptor uniform and to improve the removal efficiency of residual toner.

  In Patent Documents 2 and 3, fibers having moderate elasticity are proposed by setting the cross-sectional second moment of the conductive fiber within a certain range, thereby improving the quality of the printed image and preventing the deterioration of the image quality during long-term use. It is possible.

JP 2005-264399 A JP 2004-183180 A JP 2005-256207 A

  However, the multi-leaf cross section described in Patent Document 1 can increase the number of contact points with the photoconductor as compared with the round cross section, and can make the charging uniform and improve the removal efficiency of the residual toner. It was inadequate for conversion. Further, since the cross-sectional shape is complicated, the brush density is reduced when the brush is used, and when the device such as a printer is downsized, the performance cannot be sufficiently exhibited. In Patent Documents 2 and 3 as well, the fiber tension alone is insufficient for improving the quality of printed images in recent years.

  Therefore, in the present invention, when providing a conductive fiber having a fiber cross-sectional shape having an optimal balance between twistability and bendability, and a conductive brush incorporated in an electrophotographic recording printer, copier, fax machine, etc., It is an object of the present invention to provide a conductive brush that is excellent in improving the quality of printed images and preventing deterioration of image quality during long-term use.

In order to solve the above problems, the present invention takes the following forms.
(1) A conductive fiber characterized in that the ratio (I _r ) of the second moment of the fiber cross section satisfies the formula (I).
1.5 ≦ I _r ≦ 30.0 Formula (I)
I _r = I ₁ / I ₂
I ₁ = I _max / I _min (I _max : secondary moment of the maximum fiber section, I _min : secondary moment of the minimum fiber section)
I ₂ = I _min / I ₀ (I ₀ : secondary moment of a round cross section of the same fineness)
(2) The conductive fiber according to (1), wherein the conductive fiber has a side substantially parallel to the horizontal plane in the direction of the minimum moment of inertia in the cross section of the fiber.
(3) A brush used in an electrophotographic recording apparatus manufactured using the conductive fiber according to (1) or (2).

  Provided is a conductive brush having a fiber cross section having an optimal balance between twistability and bendability, and suitable for an electrophotographic recording apparatus.

(A) is a model figure of a rectangular section, (b) is a model figure of the round section of the same fineness as the said rectangular section. It is a model figure of cross-sectional secondary moment calculation of the axial direction of a H-shaped section. It is a model figure of cross-sectional secondary moment calculation of the orthogonal | vertical direction to the axis | shaft of an H-shaped cross section.

The conductive fiber of the present invention needs to satisfy the range of the secondary moment ratio (I _r ) of the fiber cross section of the following formula (I).
1.5 ≦ I _r ≦ 30.0 Formula (I)
I _r = I ₁ / I ₂
I ₁ = I _max / I _min (I _max : secondary moment of the maximum fiber section, I _min : secondary moment of the minimum fiber section)
I ₂ = I _min / I ₀ (I ₀ : Sectional moment of the circular section of the same fineness)
The second moment ratio (I _r ) of the fiber cross-section here is expressed by the ratio of I ₁ and I ₂ and serves as an index indicating the ease of twisting and bending of the fiber. I ₁ is the ratio of I _max to I _min , I _max is the second moment of the maximum fiber cross section in the fiber cross section, and I _min is the second moment of the minimum fiber cross section in the fiber cross section. Here, FIG. 1 (b) is a model diagram of a round cross section having the same fineness as the rectangular cross section of FIG. 1 (a). I _max of the rectangular cross section 1 (a) is a cross-sectional second moment of the b-axis direction of the rectangular cross-section, I _min is the rectangular cross section of the a-axis direction of the second moment of Figure 1 (a). That is, I ₁ is an index representing the ease of twisting of the fiber, and the larger the I ₁ value, the easier the fiber is twisted. I ₂ is the ratio of I _min to I ₀ , and I ₀ is the cross-sectional second moment of the round cross section of FIG. That is, I ₂ is an index representing the ease of bending of a fiber when compared with a round cross-section fiber having the same fineness, and the smaller the I ₂ value, the easier the fiber is bent.

  The fiber cross-sectional shape of the conductive fiber of the present invention is not limited as long as it satisfies the above-mentioned second moment ratio (Ir) of the fiber cross-section, but a flat shape such as a rectangle, an ellipse, an H shape, and a saddle shape is preferable.

  The cross-sectional secondary moment as used in the field of this invention refers to the cross-sectional secondary moment for every single yarn which comprises a multifilament. Usually, the section moment of inertia is an index of ease of bending when a bending stress is applied parallel to a certain linear axis passing through the center of gravity of the section, but in the present invention, in addition to bendability, an index of ease of twisting. The meaning as is also included. For example, when used as a brush for an electrophotographic recording apparatus, when a bending stress is applied to the fiber when the brush comes into contact with the rotating photoconductor, the fiber comes into contact with the photoconductor in the direction in which the second moment of section is minimized. Twisted in the direction and its surface is in contact with the photoreceptor.

  As a specific example, a rectangular cross section having substantially parallel sides will be described. The minimum cross-sectional moment in the rectangular cross section is perpendicular to the long side of the cross section, and the maximum cross-sectional moment is parallel to the long side. The larger these ratios, the easier the fibers are twisted, and the fibers are twisted so that the surface in the direction of the minimum moment of inertia is in contact with the photoreceptor. That is, twisting occurs so that the long side of the rectangle comes into contact with the photoreceptor. Moreover, it shows that a fiber is easy to bend, so that the ratio of the cross-section secondary moment of a round cross section of the same fineness as the elliptic cross section and the minimum cross-section second moment of an elliptic cross section is small.

  When the conductive fiber of the present invention is piled and used as a brush for an electrophotographic recording apparatus, it is necessary that the brush be twisted and bent appropriately.

The I ₁ values by the appropriate range, when the bending stress is applied to the fibers in contact with the photoreceptor brush is rotated, it can be brought into contact with any surface on the fiber cross section the photosensitive member, the printed image High image quality can be achieved. The larger I ₁ is, the more easily the fibers are twisted, and the arbitrary surface can be brought into contact with the photoreceptor more. However, if it is too large, the brush is liable to fall down and the image quality deteriorates during long-term use. Further, the smaller I ₁ is, the more difficult the fibers are twisted. If it is too small, any surface cannot be brought into contact with the photoreceptor.

I ₂ is that the appropriate range, repeating the brush is less likely to fall down hair by using, keep it in contact with the photoreceptor soft, also possible to maintain the printing quality in long-term use. More fibers bend easily I ₂ is small, too small repetition becomes brush is liable to fall down hair by the use, the contact pressure to the photosensitive member gradually decreases, the printing quality tends to decrease. As I ₂ is larger, the fiber is less likely to bend, and when it is too large, the brush gradually damages the photoreceptor due to repeated use, and spots and streaks are generated during printing, and the print image quality is likely to deteriorate.

This balance of twist Yasu Is the pliability, i.e., for I ₂ which is an index of I ₁ and pliability is indicative of torsional ease, the results of the examination inventors have intensively, the geometrical moment of inertia ratio (I _r ) Is controlled within the range of 1.5 to 30.0, and the conclusion has been reached that it has extremely excellent printed images and printing durability during long-term use. If I _r is less than 1.7, the fiber is hardly twisted, can not contact any surface in the photosensitive member, more brushes may damage gradually photoreceptor by repeated use, spots and streaks occur when printed However, the print image quality is degraded. In the case where I _r exceeds 30.0, the brush tends to fall hair by repeated use, the contact pressure to the photosensitive member gradually decreases, the printing quality tends to decrease. Preferably it is 2.0-15.0, More preferably, it is 3.0-8.0.

The cross-sectional shape of the conductive fiber of the present invention is not limited as long as the cross-sectional second moment ratio (I _r ) described above is satisfied, but a flat shape such as a rectangle, an ellipse, an H shape, and a saddle shape is preferable. More preferably, a flat shape such as a rectangle or an H shape having a side substantially parallel to the horizontal plane in the direction of the minimum moment of inertia in the fiber cross section is preferable. By having a side substantially parallel to the horizontal plane, the brush and the photoconductor are in close contact with each other on the surface, and the contact area with the photoconductor on which the brush rotates can be further increased. Charging and cleaning can be performed. As a result, the quality of the printed image can be improved. Here, “substantially parallel” means that an angle formed by two line segments is 0 ° or more and 3 ° or less, and an angle formed by an arbitrary side of the fiber cross section and a horizontal plane, and more preferably 0 ° or more and 1 ° or less. It is.

  When the cross-sectional shape is a rectangle, the aspect ratio (ratio of long side to short side) is preferably 1.2 to 3.1. By setting such a range, an appropriate ratio of the moment of inertia of the cross section can be obtained. In addition to appropriate twisting and bending of the fiber, the brush and the photoconductor are in contact with each other, and the brush using this fiber is used. By using, it is possible to achieve higher image quality of printed images and prevention of image quality deterioration during long-term use.

  On the other hand, in the case of the H-shaped cross section, when the H-shaped axis has the minimum secondary moment of inertia in the direction perpendicular to the H-shaped axis, the target cross-sectional secondary moment ratio can be obtained. If there is a moment, the target cross-sectional second moment ratio cannot be obtained. For this reason, the cross-section design is important for the H type.

The conductive fiber of the present invention is a fiber containing conductive particles such as carbon black, metal oxide, and carbon nanotube and having a specific resistance of about 10 ² to 10 ¹⁰ Ω · cm. In addition, as a form, a form in which conductive particles are uniformly dispersed throughout the fiber or a form in which a polymer containing conductive particles is disposed in the sheath part of the core-sheath composite is preferable. When the polymer containing conductive particles is placed in the core of the core-sheath composite or the polymer containing conductive particles is only partially exposed in the sheath of the core-sheath composite, the specific resistance of the fiber surface It tends to vary and the print image quality is not stable.

  As the polymer containing the conductive particles, any thermoplastic resin such as nylon or polyester may be used, but nylon is preferable because it has moderate flexibility and is superior in hair fallability. Furthermore, when used as a brush, the device can be used in various environments such as low-temperature and low-humidity environments and high-temperature and high-humidity environments. Of these, nylon having a low moisture absorption rate is more preferable. Illustrative examples are nylon 610 and nylon 12.

The specific resistance of the conductive fiber of the present invention is 10 ² to 10 ¹⁰ Ω · cm (temperature 20 ° C., humidity 30% RH condition). When the specific resistance is less than 10 ² Ω · cm, when a voltage is applied as a brush, electrons move to adjacent single yarns, and printing cannot be performed. On the other hand, if the specific resistance exceeds 10 ¹⁰ Ω · cm, there is a problem that even if voltage is applied, printing cannot be performed because electrons cannot move through the single yarn. In other words, an image can be printed within this range. The specific resistance of the conductive fiber can be controlled by the content of the conductive particles, the spinning temperature in the spinning process, the spinning speed, or the draw ratio or drawing temperature in the drawing process.

  As the conductive particles to be contained in the conductive fiber, carbon black, metal oxide, carbon nanotube, etc. can be used as described above, but carbon black is preferable from the viewpoint of price and ease of processing, and its content rate Is preferably 10 to 40% by weight, more preferably 15 to 35% by weight, and still more preferably 20 to 30% by weight. When the content of carbon black is less than 10% by weight, the specific resistance of the fiber becomes too high, causing a problem that printing cannot be performed. On the other hand, if the carbon black content exceeds 40% by weight, the strength of the fiber is lowered and lacks practicality, and yarn breakage increases during spinning, resulting in poor productivity. That is, by setting it as this range, it is possible to obtain a fiber having a specific resistance suitable for image printing with high productivity.

  The fineness of the conductive fiber of the present invention is not particularly limited, but is preferably about 60 to 400 dtex. The single yarn fineness of the conductive fiber of the present invention is preferably 1.5 to 10.0 dtex. In recent years, color is mainly used for electrophotographic copying machines and the like, and the improvement in image quality has been greatly advanced. As the image quality increases, the toner particles become smaller and the demand for higher density of the conductive brush is increasing. For these reasons, 2.0 to 8.0 dtex is more preferable from the standpoint that an excellent printed image can be obtained even in the case of toner particle size reduction accompanying high image quality.

  The strength of the conductive fiber of the present invention is preferably 1.3 cN / dtex or more. By setting it as such a range, when processing into a brush, favorable process passability is obtained without thread breakage. More preferably, it is 1.5 cN / dtex or more.

  The hot water shrinkage of the conductive fiber of the present invention is preferably 12% or less. By setting it as such a range, the shrinkage | contraction variation of the electrically conductive fiber in a heat processing process in brush processing becomes small, and a specific resistance variation becomes small. Therefore, when the brush is used, the variation in the resistance value of the brush is reduced, and the image quality is improved. More preferably, it is 10% or less, More preferably, it is 8% or less.

  The conductive fiber of the present invention contains conductive particles by blending thermoplastic resin pellets and conductive particles and melt spinning, blending thermoplastic pellets with high concentration conductive pellets. And a method of melt spinning, a method of adding conductive particles to a molten thermoplastic resin, and kneading. Moreover, the conductive fiber of this invention may also contain additives, such as a light-resistant agent, a flame retardant, a lubricant, and antioxidant, in the range which does not impair the effect of this invention.

  The conductive fiber of the present invention can be obtained by a known melt spinning method. For example, the raw material is melted with an extruder, the fiber is extruded from a spinning pack, the fiber is cooled with cooling air, and the spinning oil is supplied. A general method is to wind and unwind the wound undrawn yarn with a drawing machine and heat set.

  The electroconductive brush used in the electrophotographic recording system is a printing brush that contacts and charges the photoreceptor in place of non-contact corona discharge, a cleaning brush that removes charge and toner remaining on the photoreceptor, and toner in the toner cartridge. This is a toner supply brush that gives electric charge to the toner, a transfer brush for transferring the toner adhered to the photosensitive member to the printing paper, etc., which is incorporated in a printer, copier, facsimile, etc., and is woven as a pile of conductive fibers Thereafter, the pile tape, which is backed with a conductive backing agent and cut to a width of 10 to 30 mm, is wound around a cylindrical metal rod with a bias, or simply a pile woven fabric is attached to a plate to make it into a brush shape.

  The fiber used as the base fabric when making the pile fabric may be conductive or insulating, but polyester spun yarn is preferably used in view of cost. The obtained pile fabric is dried and heated at about 120 to 200 ° C. in order to prevent shrinkage over time.

  The pile fabric subjected to the above drying and heating treatment is subjected to a backing treatment from the viewpoint of stabilizing the brush resistance value when the conductive brush is made and preventing the conductive fibers from coming off and falling off. The backing treatment is performed by applying a conductive backing agent to the fabric on the opposite side where the pile-like conductive fibers stand up and drying at a temperature of about 50 to 100 ° C. after the application.

  The conductive backing agent is a solution in which a binder and a conductive substance are dissolved in a solvent, and the polymer used as the binder is not particularly limited. For example, a copolymer of an aromatic vinyl monomer and a conjugated diene monomer is used. A polymer, a copolymer of a nitrile group-containing vinyl polymer and a conjugated diene monomer, an acrylate copolymer, an ethylene oxide-propylene oxide copolymer, or the like can be used. Among them, it is preferable to use a copolymer of an aromatic vinyl monomer and a conjugated diene monomer, and specific examples thereof include a copolymer of styrene and butadiene. There are no particular limitations on the monomer composition ratio and molecular weight of the copolymer, and these can be produced by known methods.

  As the conductive substance, carbon black, graphite carbon, carbon fiber, metal powder, or the like can be used. Among these, carbon black is preferably used from the viewpoints of availability, ease of handling, and the like.

  Next, the pile fabric for conductive brushes obtained by the above method is cut with scissors or the like to obtain a ribbon-like pile fabric having a width of 20 mm and a length of 400 mm, for example. Then, it is partially affixed to a conductive shaft, for example, a stainless steel shaft having an outer diameter of 8 mm and a length of 250 mm with a double-sided tape. Electricity will not flow to. This double-sided tape may be insulative or conductive. In addition, the cut pile fabric is attached to the shaft with a double-sided tape in a spiral manner by inclining the stainless steel shaft.

  Finally, the brush tip is brought into contact with a hot plate of about 120 to 200 ° C. while rotating the shaft, and the conductive tip is set in the same direction. At this time, it may be set while applying steam.

  Hereinafter, the present invention will be described in detail by way of examples. In addition, the measuring method in an Example is as follows.

(1) Sectional secondary moment ratio (Ir)
Using a KEYENCE digital microscope (VHX-2000), the cross section of the conductive conjugate fiber was magnified 100 to 300 times and a cross-sectional photograph was taken. Select from a cross-sectional photograph of the single yarn in five randomly second moment I ₀ of each single yarn, I _max, were calculated I _min, was calculated I _r from the average value of single yarn 5 duty. In addition, the calculation formula of the cross-sectional secondary moment ratio of the Example of this invention and a comparative example is as follows. It should be noted that there is no problem if other cross-sectional shapes are calculated by a general calculation formula.
[circular]
I = (π × R ⁴ ) / 4 (R: radius)
[ellipse]
I _max = (π × a × b ³ ) / 64 (a: minor axis, b: major axis)
I _min = (π × b × a ³ ) / 64 (a: minor axis, b: major axis)
[Rectangle]
I _max = (a × b ³ ) / 12 (a: short side, b: long side)
I _min = (b × a ³ ) / 12 (a: short side, b: long side)
[triangle]
I _max = (l _min × h _max ³ ) / 36 (l _min : shortest side, h _max : longest height)
I _min = (l _max × h _min ³ ) / 36 (l _max : longest side, h _min : shortest height)
[H type]
The calculation formula for the H-shaped cross section is shown below based on FIGS. FIG. 2 was used for calculating the axial secondary moment (I ₁ ) of the H-shaped section, and FIG. 3 was used for calculating the sectional secondary moment (I ₂ ) perpendicular to the axis of the H-shaped section.
I ₁ and I ₂ are calculated, a large numerical value is set as I _max , and a small numerical value is set as I _min .
I ₁ = (B × H ³ −b × h ³ ) / 12 (secondary moment in section in the arrow direction in FIG. 2)
I ₂ = (B ′ × H ′ ³ + b ′ × h ′ ³ ) / 12 (second moment of section in the arrow direction in FIG. 3).

(2) Image quality The brush is incorporated into an electrophotographic printer as a charging brush and a cleaner brush. The temperature is 20 ° C., the humidity is 30% RH, the temperature is 30 ° C., the humidity is 90% RH, the temperature is 10 ° C. A test chart issued by the Imaging Society of Japan was printed under conditions of a humidity of 10% RH, and 10 were evaluated as being the most excellent, with a score of 7 or higher being a passing level.

(3) Changes in image quality during long-term use Test charts issued by the Imaging Society of Japan are compared between the first and 20,000 times printed, and sensory evaluation is performed by 10 people, and points are assigned according to the following criteria: The total score for 10 people was classified according to the following criteria. In addition, it was set as the pass above (triangle | delta).
No difference: 2 points are slightly different: 1 point is observed: 0 points The above score is 18-20 points: ◎
15-17 points: ○
10-14 points: △
0-9 points: x.

(4) Specific resistance Using a super insulation meter (TERAOHMMETER R-503, manufactured by Kawaguchi Electric Manufacturing Co., Ltd.), a voltage of 1000 V was applied to a sample with a test length of 10 cm, and the electrical resistance value under the conditions of temperature 20 ° C. and humidity 30% RH was obtained. The specific resistance (Ω · cm) was calculated (measurement was performed twice and the average value was calculated). Tables 1 and 2 show logarithmic values of specific resistance.

(5) Fineness Calculated according to JIS L 1013 (2010) 8.3.1 A method.

(6) Strength and elongation Tensile strength and elongation were measured according to JIS L 1013 (2010).

(7) Hot water shrinkage rate Measured according to JIS L 1013 (2010) 8.18.1.

[Example 1]
Carbon black as conductive particles was kneaded into nylon 610 so as to have an addition amount of 25% by weight to obtain pellets. Subsequently, the pellet was melted at 285 ° C., and 30 holes each having two slits having a slit width of 0.1 mm and a slit length of 0.1 mm radially arranged at both ends of the slit having a slit width of 0.1 mm and a slit length of 0.3 mm were formed. After discharging from the individual die and cooling, the spinning oil was supplied, and the undrawn yarn was wound up at 800 m / min. Next, the obtained undrawn yarn was drawn with a drawing machine at a draw ratio of 2.6 times and a hot plate temperature of 160 ° C. so that the single yarn had a rectangular cross section with an aspect ratio of 1.5, and the conductivity of 170 dtex 30 filaments. Fiber was obtained. The obtained conductive fibers were used to weave the piles so that the pile density was 1000 pieces / inch and the pile length was 7 mm, followed by hot water treatment at 90 ° C. and drying. Next, the back of the pile was backed with a backing agent to form a tape having a width of 15 mm, and then wound around a metal rod having a diameter of 6 mm in a spiral shape to produce a brush. The produced brush was incorporated into an electrophotographic printer and evaluated for changes in image quality and image quality during long-term use. The results are shown in Table 1.

[Example 2]
Except for using a base designed so that the conductive fiber has a rectangular cross section with an aspect ratio of 1.2, a conductive fiber is obtained by the same method as in Example 1, and further a brush is produced by the same method as in Example 1. Image quality was evaluated. The results are shown in Table 1.

[Example 3]
A conductive fiber is obtained by the same method as in Example 1 except that a base designed so that the conductive fiber becomes a rectangle having an aspect ratio of 1.4 is obtained. Further, a brush is produced by the same method as in Example 1, and an image is obtained. The quality was evaluated. The results are shown in Table 1.

[Example 4]
Except for using a base designed so that the conductive fiber has a rectangular cross section with an aspect ratio of 2.5, a conductive fiber is obtained by the same method as in Example 1, and further a brush is produced by the same method as in Example 1. Image quality was evaluated. The results are shown in Table 1.

[Example 5]
Except for using a base designed so that the conductive fiber has a rectangular cross section with an aspect ratio of 3.1, a conductive fiber is obtained by the same method as in Example 1, and further a brush is produced by the same method as in Example 1. Image quality was evaluated. The results are shown in Table 1.

[Example 6]
A conductive fiber was obtained in the same manner as in Example 1 except that a base having a slit width of 0.1 mm and a slit length of 0.2 mm was used so that the conductive fiber had an elliptical cross section with a major axis / minor axis ratio of 1.5. Further, a brush was produced by the same method as in Example 1, and the image quality was evaluated. The results are shown in Table 1.

[Example 7]
Except for using a base having 30 H-shaped holes joined by a slit having a slit width of 0.1 mm and a slit length of 0.3 mm between parallel slits having a slit width of 0.08 mm and a slit length of 0.24 mm Conductive fibers having an H-shaped cross section were obtained in the same manner as in Example 1, and brushes were produced in the same manner as in Example 1 to evaluate the image quality. The results are shown in Table 1.

[Example 8]
A conductive fiber is obtained by the same method as in Example 1 except that the thermoplastic resin containing carbon black, which is conductive particles, is nylon 6, and a brush is produced by the same method as in Example 1. Was evaluated. The results are shown in Table 2.

[Example 9]
A conductive fiber is obtained by the same method as in Example 1 except that the thermoplastic resin containing carbon black, which is conductive particles, is nylon 12, and a brush is produced by the same method as in Example 1. Was evaluated. The results are shown in Table 2.

[Example 10]
Except that the thermoplastic resin containing conductive carbon black is polyethylene terephthalate, a conductive fiber is obtained by the same method as in Example 1, and a brush is produced by the same method as in Example 1 to obtain image quality. Was evaluated. The results are shown in Table 2.

[Example 11]
Except for containing 30% by weight of carbon black as conductive particles, conductive fibers were obtained by the same method as in Example 1, and further brushes were produced by the same method as in Example 1 to evaluate the image quality. . The results are shown in Table 2.

[Example 12]
Except for containing 20% by weight of carbon black as conductive particles, conductive fibers were obtained by the same method as in Example 1, and further brushes were produced by the same method as in Example 1 to evaluate the image quality. . The results are shown in Table 2.

[Example 13]
A conductive fiber of 170 dtex 68 filament was obtained by the same method as in Example 1 except that the number of base holes was 68, and a brush was produced by the same method as in Example 1 to evaluate the image quality. The results are shown in Table 2.

[Example 14]
A conductive fiber of 170 dtex 18 filament was obtained by the same method as in Example 1 except that the number of holes in the die was set to 18, and a brush was produced by the same method as in Example 1 to evaluate the image quality. The results are shown in Table 2.

[Comparative Example 1]
Except for using a base having 30 circular holes with a diameter of 0.1 mm, a conductive fiber having a round cross-section was obtained by the same method as in Example 1, and a brush was produced by the same method as in Example 1 to obtain image quality. Was evaluated. The results are shown in Table 3.

[Comparative Example 2]
Except for using a base designed so that the conductive fiber has a rectangular cross section with an aspect ratio of 1.1, a conductive fiber is obtained by the same method as in Example 1, and further a brush is produced by the same method as in Example 1. Image quality was evaluated. The results are shown in Table 3.

[Comparative Example 3]
A conductive fiber having a triangular cross section is obtained in the same manner as in Example 1 except that a base having 30 Y-shaped holes in which three slits having a slit width of 0.1 mm and a slit length of 0.4 mm are radially arranged is used. Further, a brush was produced by the same method as in Example 1, and the image quality was evaluated. The results are shown in Table 3.

[Comparative Example 4]
Except for using a base having 30 H-shaped holes joined by a slit having a slit width of 0.1 mm and a slit length of 0.1 mm between parallel slits having a slit width of 0.08 mm and a slit length of 0.4 mm. Conductive fibers having an H-shaped cross section were obtained in the same manner as in Example 1, and brushes were produced in the same manner as in Example 1 to evaluate the image quality.

[Comparative Example 5]
Except for using a base designed so that the conductive fiber has a rectangular cross section with an aspect ratio of 3.2, a conductive fiber is obtained by the same method as in Example 1, and further a brush is produced by the same method as in Example 1. Image quality was evaluated. The results are shown in Table 3.

[Comparative Example 6]
Except for using a base designed so that the conductive fibers are regular hexagons, conductive fibers are obtained by the same method as in Example 1, and further, a brush is produced by the same method as in Example 1, and the image quality is evaluated. It was. The results are shown in Table 3.

  As is apparent from the results of Tables 1 and 2, the conductive fibers of the present invention and the brushes produced using the conductive fibers are electrophotographic recording printers that can print printed images in any environment from low temperature and low humidity to high temperature and high humidity. It can be seen that high image quality can be achieved and that it has a remarkable effect in preventing image quality deterioration during long-term use.

a: short side of rectangular section b: long side of rectangular section h: shaft length H: H-type width b: height-shaft width B: H-type height h ': shaft width H': H-type Height b ': shaft length B': width of both shafts of H type x 2

Claims (3)

A conductive fiber, wherein the second moment ratio (Ir) of the fiber cross section satisfies the formula (I).
・ 5 ≦ Ir ≦ 30.0 ... Formula (I
・)
Ir = I ₁ / I ₂
I ₁ = I _max / I _min (I _max : maximum cross-section secondary moment, I _min : minimum cross-section secondary moment)
I ₂ = I _min / I ₀ (I ₀ : Sectional secondary moment of the same fineness round section)   2. The conductive fiber according to claim 1, wherein the conductive fiber has a side substantially parallel to a horizontal plane in a direction of a minimum moment of inertia in a cross section of the fiber.   A brush used for an electrophotographic recording apparatus manufactured using the conductive fiber according to claim 1.