JP2943114B2 - Conductive composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a conductive composition used for a developing roll of an electrophotographic copying machine, a printer or the like.

[Conventional technology]

There are a wet method and a dry method as a developing method in an electrophotographic copying machine. In recent years, the dry method has become the mainstream from the viewpoints of image handling and safety. In addition, the dry method is distinguished into a magnetic two-component development method in which toner and a carrier are separated according to a difference in a developer, and a magnetic one-component development method in which a toner contains a carrier.
Recently, attention has been paid to the magnetic one-component developing method from the viewpoint of easy maintenance and miniaturization of the apparatus. As such a magnetic one-component developing method, there is a developing method as shown in FIG. In this method, development is performed as follows. That is, first, as shown in FIG. 6, the outer peripheral surface of the photosensitive drum 1 provided with the photoconductor surface layer is uniformly charged, and then the outer peripheral surface of the photosensitive drum 1 is transferred via the image to be copied (not shown). To form an electrostatic latent image on the outer peripheral surface. Next, toner is supplied from the toner supply device 4 to the outer peripheral surface of the developing roll 3 containing the cylindrical magnet 2,
The toner is triboelectrically charged by the layer forming blade 5, uniformly formed into a thin layer, and adhered to the outer peripheral surface of the developing roll 3. Thereafter, the toner is caused to fly on the photosensitive drum 1 and the electrostatic latent image to form a toner image on the electrostatic latent image, which is transferred to the copying machine 6 and then fixed. In the figure, 7 is a magnetic pole.

FIG. 7 shows an example of the structure of the developing roll 3 used in the magnetic one-component developing method as described above. That is, in the developing roll 3, magnetic poles 7 of SNSN... Are formed alternately in the circumferential direction on the outer peripheral surface inside a cylindrical sleeve 8 made of a non-magnetic material (stainless steel, aluminum, synthetic resin, or the like). The center axis 9 which passes through the center of the cylindrical magnet 2 is extended to the left and right, and end caps 11 are provided at both left and right ends via pairings 10, and the left and right ends of the sleeve 8 are provided by the end caps 11. The opening is closed. In such a developing roll 3, the electric resistance of the semiconductive region is maintained from the viewpoint of improving the image quality and leak resistance. In order to satisfy both of the above and to improve the safety of toner transportability (roughening of the outer peripheral surface of the sleeve 8 and improvement of requirements for durability safety, etc.), a cylindrical body made of synthetic resin is often used for the sleeve 8 body. ing. Usually, as such a synthetic resin cylindrical article, a synthetic resin extruded product in which particles of carbon black are blended for imparting conductivity is used.

[Problems to be solved by the invention]

However, in the developing roll 3 using the sleeve 8 made of the synthetic resin, it is very difficult to control the electric resistance.
However, there is a drawback that the uniformity of the image is lacking due to a remarkable decrease in rigidity as compared with the above. Further, due to the above, as shown in FIG. 8, the sleeve 8 of the developing roll 3 bends as indicated by a dashed line due to the pressing of the layer forming blade 5 (in the direction of the arrow P). There is a problem in quality such as occurrence of ping (development in which the density of an image becomes like a film along the rotation direction of a roll). To solve such a problem, the sleeve 8
It has been attempted to fill the glass fiber reinforcing material into the synthetic resin for the purpose of improving the rigidity of the resin. However, when the filling amount of the glass fiber is increased, the surface roughness of the outer peripheral surface of the sleeve 8 is significantly increased by use. And the durability is deteriorated. That is, depending on the frequency of use, the surface of the sleeve 8 is worn to expose the glass fiber, and the surface roughness becomes too large. As a result, the toner transport amount increases and the durability also deteriorates.

The present invention has been made in view of such circumstances,
It is an object of the present invention to provide a conductive composition capable of forming an excellent conductive layer which is controlled to an appropriate electric resistance and can always maintain a predetermined surface roughness even when the outer peripheral surface is worn.

[Means for solving the problem]

In order to achieve the above object, the conductive composition of the present invention includes the following components (A) to (C), and the component (B) is 40 to 100 parts by weight of the following component (A). 80 parts by weight,
(C) A conductive composition in which the component is blended in a proportion of 100 parts by weight or more and 140 parts by weight or less, and the electric resistance of a cured product of the conductive composition is set to 10 ⁶ to 10 ⁹ Ω · cm. Take the configuration that.

(A) phenolic resin.

(B) Carbon black particles (X) having an average particle size of 0.05 μm or more and 0.5 μm or less, and graphite particles (Y) having an average particle size of 1 to 5 μm, and the mixing ratio X / Y of both is 1/4 to
Conductive material set to be 4/1.

(C) Reinforcement comprising glass fibers having a diameter of 15 μm or less and ceramic whiskers having a diameter of about 1 μm, wherein the amount of the glass fibers is set to 50 parts by weight or less with respect to 100 parts by weight of the component (A). Filling material.

[Action]

That is, the present inventors have repeated a series of studies to obtain a conductive composition that can achieve the intended purpose. As a result,
The carbon black particles and the guasphite particles each having a predetermined particle size are used in a specific mixing ratio as a conductive material, and the glass fibers and the ceramic whiskers each having a specific value in diameter are used as a reinforcing filler in a specific ratio. And the reinforcing filler, satisfying all three requirements of being blended at a specific blending ratio with respect to the resin component, respectively, and further setting the cured body to have a specific range of electric resistance. The inventors have found that a conductive composition can be obtained, and have reached the present invention.

 Next, the present invention will be described in detail.

The conductive composition of the present invention is obtained using a phenolic resin (component A), which is a matrix component, a conductive material (component B), and a reinforcing filler (component C).

The phenol resin (A component) is not particularly limited, and a conventionally known phenol resin is used.

As the conductivity (component B), carbon black particles, graphite particles, carbon fibers, conductive metal oxides, and the like have been conventionally used from the viewpoint of controlling electric resistance and the like. However, there is a problem in terms of fibers having a rough surface. In addition, the conductive metal oxide must be incorporated in a large amount in order to set a target electric resistance value. As a result, the amount of the reinforcing filler (component C) is adversely affected. Therefore, in the conductive composition of the present invention, carbon black particles and graphite particles which do not cause the above-mentioned problems are used as the conductive material (component B), and these are used in combination. As the carbon black particles, the average particle size is 0.05 μm or more.
Those of 5 μm or less, and as graphite particles,
It is necessary to use one having an average particle size in the range of 1 to 5 μm.
That is, the average particle size as carbon black particles is 0.05
If the diameter is less than μm, the obtained cylindrical sleeve has too large variation in electric resistance. In addition, if the average particle size of the graphite particles is less than 1 μm, the electric resistance becomes too large. On the contrary, if the average particle size is 5 μm, the electric resistance of the sleeve is controlled in an appropriate range. Because it will have to be done. The mixing ratio of the carbon black particles (X) and the graphite particles () is expressed as a weight ratio of X / Y = 1/4 to
It must be set to be in the range of 4/1. That is,
In the mixing ratio of both, when the mixing ratio of the carbon black particles falls below the above range, the surface roughness of the obtained cylindrical sleeve becomes extremely large due to the use, and conversely, when the mixing ratio exceeds the above range, the variation in electric resistance becomes large. Because it becomes too much. Further, the mixing ratio of the conductive material composed of a mixture of such specific carbon black particles and graphite particles is 40 to 80 parts with respect to 100 parts by weight (hereinafter abbreviated as “parts”) of the phenol resin (component A). Must be set in the range. That is, if the amount of conductive material is below 40 parts, exceeds the upper limit (10 ⁹ Ω · cm) of the later proper electrical resistance, greater than 80 parts would proper electric resistance value lower limit (10 [Omega · cm).

As the reinforcing filler (C component), glass fiber,
Ceramic whiskers finer than glass fibers are formed using the conductive composition and are used to improve the rigidity of the sleeve and maintain the surface roughness. It is necessary to use a glass fiber having a diameter of 15 μm or less and a ceramic whisker having a diameter of 1 μm or less. That is, when the diameters of the glass fibers and the ceramic whiskers exceed the above values, the surface roughness of the cylindrical sleeve becomes extremely large after a short period of use. The compounding ratio of such a reinforcing filler composed of a mixture of glass fibers and ceramic whiskers is 100 parts or more and 140 parts or less for 100 parts of the phenolic resin (component (A)). Should be set to 450 parts or less with respect to 100 parts of phenol resin. In other words, if the amount of the reinforcing filler is less than 100 parts, the rigidity of the cylindrical sleeve decreases, and if the amount of the glass fiber exceeds 50 parts, the surface roughness of the cylindrical sleeve increases with use. This is because durability decreases.

The conductive composition of the present invention can be obtained by, for example, mixing and stirring each component using the above-described components at a desired mixing ratio using a kneader or the like.

The conductive composition rice thus obtained becomes a cylindrical sleeve through the following steps, for example. That is, the conductive composition is kneaded in a continuous roll and formed into a sheet. Next, the sheet is formed into a pellet by a pulverizer, and extruded by a plunger type extruder 18 as shown in FIG. 4 to form a cylindrical body 16a. Next, this is cut into a predetermined length to form a conductive layer of a conductive roll having a structure as shown in FIG.
16 (cylindrical sleeve). In the drawing, the other configuration is the same as that of the roll 3 in FIG. 7, and the same portions are denoted by the same reference numerals. The electrical resistance of the cylindrical sleeve thus obtained must be set in the range of 10 ⁶ to 10 ⁹ Ω · cm. That is, when the electric resistance is 10 ⁶ Ω · cm or less, the copy density becomes too high, and when the electric resistance is 10 ⁹ Ω · cm or more, the copy density becomes thin.

The above 16 conductive layers are formed by a special conductive composition containing dispersed conductive material (carbon black particles + graphite particles) and reinforcing filler (glass fibers + ceramic whiskers) in phenolic resin. 2, the glass fibers 31 and the graphite particles 32 dispersedly contained in a binder resin (phenolic resin) 30 form a mat-like unevenness on the surface.
Is a carbon black particle, and 34 is a ceramic whisker. Then, the conductive roll on which the conductive layer is formed,
When incorporated and used as a developing roll 3 of an electrophotographic copying machine as shown in FIG. 6, as the binder resin 30 is worn, the glass fibers 31 are sequentially left as shown in FIG. Since the particles 32 fall off, the traces of the falling off become the concave portions Q. Therefore, even if the use is continued, the surface of the cylindrical sleeve 16 and moderate unevenness are always maintained. Therefore, even after long-term use, the toner can be stably supplied without changing the amount of the toner that enters the concave portion Q and is conveyed. In addition, since the reinforcing filler is contained, rigidity is improved, and occurrence of strobing can be prevented.

〔The invention's effect〕

As described above, in the conductive composition of the present invention, the reinforcing filler (glass fiber + ceramic whisker) of the conductive material (carbon black particles + graphite particles) is dispersed and contained in the phenol resin at a specific ratio. Therefore, when the conductive layer is formed, the surface thereof always becomes a suitable uneven rough surface even when the use is continued, and the toner can be transported in a stable state. Therefore, for example, even if a conductive roll is formed using the conductive composition of the present invention and incorporated into an electrophotographic copying machine, the occurrence of strobing can be prevented, and the durability is improved. That is, when a conductive roll obtained by using the conductive composition of the present invention is incorporated in an electrophotographic copying machine and used for a long period of time, the density of a copied image hardly decreases due to an increase in the number of copies. This has the advantage that no strobing occurs. Such a conductive composition is widely used not only for forming a conductive roll for an electrophotographic copying machine but also for forming a conductive layer such as various kinds of conductive rolls such as a facsimile and a printer.

 Next, examples will be described together with comparative examples.

[Examples 1 to 9] Novolak type phenolic resin (PR, manufactured by Sumitomo Yules Co., Ltd.)
-50072) For each 100 parts, the components shown in Table 1 below were blended at the ratio shown in the table, and the resulting mixture was rolled at a roll temperature of 110 ° C.
Are mixed and kneaded by a kneading machine of (1) to form a sheet. Then, this sheet-like material is pelletized with a crusher,
With a plunger type extruder 18 as shown in FIG. 4, at an extrusion pressure of 50 kg / cm ^2, it is extruded into a cylindrical body 16a having an outer diameter of 30 mm and an inner diameter of 25 mm, then cut into predetermined dimensions, polished, and the surface is sandpapered. The surface was roughened by vertical polishing or shot blasting to produce a cylindrical sleeve. Then, a conductive roll as shown in FIG. 1 was produced using the cylindrical sleeve.

[Comparative Examples 1 to 11] The raw materials shown in Table 1 below were blended in the proportions shown in the same table,
After kneading according to the kneading description, the same treatment as in the above example was performed.

[Comparative Example 12] A cylindrical sleeve was produced by a screw extruder 20 shown in Fig. 5 using polypropylene (Sumitomo Chemical Co., Ltd., Sumitomo Noprene W531) instead of the phenol resin.
Then, a conductive roll was produced in the same manner as in the above example.

The average electric resistance, variation of electric resistance, copy image, uniformity of density (presence or absence of image density), leak resistance, strobing resistance and durability of each of the conductive rolls thus obtained are described below. Was measured and evaluated. The results are shown in Table 2 below.

<< Average Electric Resistance and Variation in Electric Resistance >> The average electric resistance is measured by a measurement system shown in FIG. 9B by forming 20 electrodes 21 having the shape shown in FIG. 9A on the roll surface. did. In the figure, 20 is a roll, 21a is a main electrode, and 21b is a guard electrode. And the average value of each measured value was calculated. In addition, the variation of the electric resistance was determined by measuring the electric resistance at 20 points of each conductive roll in the same manner as the measurement of the average electric resistance, and determining the difference between the maximum value and the minimum value of the measured values.

<< Uniformity of copied image >> A conductive roll was used as a developing roll, incorporated in a copying machine, and an image was displayed to check for image unevenness. Then, those in which image unevenness occurred were evaluated as x, and those in which image unevenness did not occur were evaluated as o, and the results are shown in Table 2 below.

<< Density of Copied Image >> An image was produced in the same manner as described above. In this image production, a solid black copy was taken at the maximum density, and the density was measured with a reflection densitometer manufactured by Macbeth. And the measured value is 1.
One or more were evaluated as ○, and those with a measured value of less than 1.1 were evaluated as ×, and are shown in Table 2 below.

<< Leak Resistance >> Images were printed (black copy) under high-temperature and high-humidity conditions (30 ° C. × 90% RH), and those without white spots were evaluated as 発 生, and those generated were evaluated as ×. The results are shown in Table 2.

《Strobing resistance》 Leave the layer forming blade in pressure contact (50 ℃ × 90% RH)
× 14 days), and an image was displayed (black copy). Then, the case where no stripe-like shading occurred was evaluated as ○, and the case where the shading occurred was evaluated as ×, and the results are shown in Table 2 below.

"Durability" initial image digital toner conveyance amount M _o mg / cm ² of the toner conveyance amount of the number of copies t th image digital and M _t mg / cm ^2, holding the following relationship The number of copies is shown. The results are shown in Table 2 below.

From the results shown in Table 2 above, it can be seen that the comparative example product has a problem in either the electrical characteristics or the copied image characteristics, while the example product is generally good in any of the characteristics and can be an excellent developing roll. Wakata.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of the conductive roll of the present invention, FIGS. 2 and 3 are explanatory views of the change with time of the conductive layer surface of the conductive roll of the present invention, and FIG. FIG. 5 is a longitudinal sectional view of a plunger type extruder used for production, FIG. 5 is a longitudinal sectional view of a screw type extruder used for production of a cylindrical sleeve, FIG. FIG. 7 is a longitudinal sectional view of a conventional conductive roll, FIG. 8 is an explanatory view showing a problem when using the conventional conductive roll, and FIG. 9 (A) examines electrical characteristics of an example product and a comparative example product. FIG. 9B is a plan view showing a configuration and a shape of an electrode for measurement, and FIG. 9B is a configuration diagram showing a measurement system when measuring the electric resistance of the conductive roll using the electrode. 15 Conductive roll, 16 Cylindrical sleeve, 30 Phenolic resin, 31 Glass fiber, 32 Graphite particles, 33 Black carbon particles, 34 Ceramic whiskers

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tetsuya Ito Komaki City, Aichi Prefecture, Kokugaiyama, Gezu 3600 Tokai Rubber Industries Co., Ltd. Tokai Rubber Industry Co., Ltd. (72) Inventor Mitsutoshi Tomita Komaki City, Aichi Prefecture, Oita Kita-gaiyama, Gezu 3600 Tokai Rubber Industry Co., Ltd. (56) References JP-A-2-33166 (JP, A) JP JP-A-2-34665 (JP, A) JP-A-2-33167 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G03G 15/08 C08K 7/02 C08L 101/00

Claims (1)

(57) [Claims] (1) It contains the following components (A) to (C), and the component (B) is 40 to 80 parts by weight and the component (C) is 100 parts by weight based on 100 parts by weight of the following component (A). Parts by weight or more and 140 parts by weight or less, wherein the cured product of the conductive composition has an electric resistance set to 10 ⁶ to 10 ⁹ Ωcm. Conductive composition. (A) phenolic resin. (B) Carbon black particles (X) having an average particle size of 0.05 μm or more and 0.5 μm or less, and graphite particles (Y) having an average particle size of 1 to 5 μm, and the mixing ratio X / Y of both is 1/4 to
Conductive material set to be 4/1. (C) Reinforcement comprising glass fibers having a diameter of 15 μm or less and ceramic whiskers having a diameter of 1 μm or less, wherein the amount of the glass fibers is set to 50 parts by weight or less based on 100 parts by weight of the component (A). Filling material.