JP3194340B2 - Conductive roll - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll suitably used as a charging roll, a developing roll and the like in a copying machine, a printer or the like utilizing an electrophotographic system.

[0002]

2. Description of the Related Art Conventionally, conductive rolls such as charging rolls and developing rolls used in copying machines and printers utilizing electrophotography have been required to have low hardness or flexibility and conductivity. And, as one of those which can satisfy those requirements, a predetermined conductive elastic layer is provided with a predetermined thickness on the outer peripheral surface of the shaft body, and on the outer peripheral surface of the conductive elastic layer, A structure in which a thin resistance adjusting layer is coated is known. In the conductive roll having such a structure, the conductive elastic layer is formed of a low-resistance conductive elastic body containing a large amount of a softener or a low-resistance conductive foam having a sponge structure. Therefore, low hardness or flexibility and conductivity can be provided, and the resistance adjusting layer provided on the outer peripheral surface of the conductive elastic layer has a medium resistance. The electrical resistance can be controlled by
Thus, the leak resistance can be advantageously improved.

In such a conductive roll, a predetermined conductive filler is mixed with a material for forming the conductive elastic layer and the resistance adjusting layer, so that the volume resistivity of each of the layers is in a desired range. Are generally adjusted so as to satisfy the following values. Generally, an electronic conductive agent and an ionic conductive agent are used as such a conductive filler. Also, as is well known, when the two types of conductive fillers are individually and separately compared with each other, when those materials having the same volume resistivity are ionic conductive materials, In the case where the agent is blended, a material having more excellent leak resistance can be obtained than in the case where the electronic conductive agent is blended.

For this reason, in a conventional conductive roll, as a material for forming the resistance adjusting layer, a predetermined rubber material is mixed with an ionic conductive agent, and the volume resistivity is usually 10 ⁷ Ωcm.
A rubber composition adjusted to a certain degree is used, so that the leak resistance can be more effectively improved.

However, the resistance adjusting layer containing an ionic conductive agent has a drawback that the resistance decreases as the temperature and humidity increase, and conversely, the resistance increases as the temperature and humidity decrease. In a conductive roll provided with such a resistance adjusting layer, the environmental resistance of the electric resistance increases, and when the temperature and the temperature are high, a leak phenomenon is caused, and an image is adversely affected. Also, when the temperature becomes low and low humidity,
There is an inherent problem that the roll performance significantly changes with changes in temperature and humidity, such as insufficient charging and fogging.

In order to solve such a problem, it is conceivable to form a conductive roll by forming a resistance adjusting layer using an electronic conductive agent instead of the ionic conductive agent. As described above, a general electronic conductive agent, for example, carbon black or the like blended in a material for forming a conductive elastic layer, is used in such a manner that the volume resistivity of such a resistance adjustment layer is equivalent to that of a conventional resistance adjustment layer. When it is blended with the forming material of the above, it is difficult to obtain sufficient leak resistance, and if the amount of such an electronic conductive agent is reduced to satisfy the leak resistance, the current value on the roll surface is reduced. In particular, the DC current value becomes insufficient, and in any case, the desired conductive roll cannot sufficiently exhibit satisfactory roll performance.

[0007]

Here, the present invention has been made in view of the above-mentioned circumstances, and a problem to be solved is to provide a sufficient current value and excellent leak resistance on the roll surface. It is an object of the present invention to provide a conductive roll capable of improving the environment dependency of electric resistance while ensuring stable roll performance irrespective of environmental changes.

[0008]

SOLUTION: In order to solve such a problem,
The present inventors, earnestly, as a result of repeated research, a specific rubber material, while blending a predetermined ratio of carbon black having a dibutyl phthalate oil absorption of a predetermined value or less, a small amount of an ionic conductive agent. By forming a resistance adjusting layer by using a rubber composition, and by providing this on the outer peripheral surface of a predetermined conductive elastic layer, the required characteristics of the roll can be sufficiently satisfied, and the electric resistance It has been found that a conductive roll whose environment dependency can be advantageously improved can be obtained.

That is, the present invention has been completed on the basis of such findings, and is characterized in that a predetermined conductive elastic layer is provided on the outer peripheral surface of a shaft body.
Further, in a conductive roll having a resistance adjusting layer provided on the outer peripheral surface of the conductive elastic body layer, the resistance adjusting layer may have at least a conductive filler based on 100 parts by weight of hydrogenated nitrile rubber or nitrile rubber. As the agent, a rubber composition prepared by compounding carbon black having a dibutyl phthalate oil absorption of 50 ml / 100 g or less at a ratio of 40 to 90 parts by weight and an ion conductive agent at a ratio not exceeding 1 part by weight is used. In the formed conductive roll.

According to the preferred embodiment of the conductive roll according to the present invention as described above, the ionic conductive agent may be a fourth conductive roll.
Consisting of grade ammonium salts.

According to one preferred embodiment of the present invention, a softener migration preventing layer is provided between the conductive elastic layer and the resistance adjusting layer, and furthermore, an outer peripheral surface of the resistance adjusting layer. A protective layer will be provided thereon.

[0012]

In short, in the conductive roll according to the present invention, carbon black having a smaller structure than that generally used as a conductive filler in a specific rubber material does not impair the leak resistance. A rubber composition that is compounded in an amount within the range and that the ionic conductive agent is compounded in a small amount within a range that compensates for the shortage of current value that cannot be satisfied only by such carbon black compounding. The resistance adjusting layer is formed using a material, whereby a decrease in leak resistance due to the use of carbon black as an electronic conductive agent can be advantageously avoided, and excellent leak resistance can be effectively achieved. A sufficient current value can be effectively ensured by the combined use of the carbon black and the ionic conductive agent. And, since the compounding amount of the ionic conductive agent is suppressed to a small amount, the change of the electric resistance due to the change of the environment can be made extremely small.

Therefore, in the conductive roll according to the present invention as described above, while the required characteristics of the roll such as securing a sufficient current value and excellent leak resistance are sufficiently satisfied, the environment dependence of the electric resistance is reduced. It can be effectively improved, so that good roll performance can be exhibited extremely stably regardless of changes in the environment. Then, by using such a conductive roll, the adverse effect on the image due to a change in the environment can be extremely effectively reduced.

And in such a conductive roll,
As described above, since the amount of the ionic conductive agent contained in the resistance adjusting layer is extremely small, the ionic conductive agent dissolves in the moisture absorbed in the resistance adjusting layer, and Transfer to the surface can be advantageously suppressed, and so-called blooming can be effectively prevented or suppressed.

In the present invention, a softener migration preventing layer is provided between the conductive elastic layer and the resistance adjusting layer, and a protective layer is provided on an outer peripheral surface of the resistance adjusting layer. In such a case, the softener migration preventing layer can advantageously prevent bleeding of a softener such as oil from the conductive elastic layer, and the protective layer effectively prevents the roll from sticking to the photoconductor. Can be done.

Further, in the present invention, since carbon black having a relatively small structure is used as the carbon black to be contained in the resistance adjusting layer, the content of carbon black in the resistance adjusting layer increases when the structure has a large structure. As compared with the case of using a material, it can be advantageously increased, so that the softener migration preventing layer and the protective layer are provided inside and outside the resistance adjusting layer, respectively, as described above. In this case, the adhesion between the resistance adjusting layer and the softener migration preventing layer and the protective layer can be effectively increased without excessively lowering the electric resistance. In such an environment, the occurrence of peeling or the like between the respective layers can be effectively avoided or suppressed.

[0017]

FIG. 1 shows an example of a conductive roll according to the present invention. As is clear from this figure, the conductive roll 10 is provided with a conductive elastic layer 14 having a predetermined thickness on the outer peripheral surface of a metal shaft 12 (core bar). On the outer peripheral surface of the conductive elastic layer 14, a thin resistance adjusting layer 16 is formed by lamination.

More specifically, the conductive elastic layer 14
In the same manner as the conventional one, a conductive elastic material obtained by mixing a conductive filler into a predetermined elastic material is used. And, as the elastic material constituting such a conductive elastic material, rubber materials such as ethylene propylene diene terpolymer, styrene butadiene rubber, natural rubber, and polynorbornene rubber are each independently used. Or various combinations thereof. In addition, as the conductive filler, an electronic conductive agent such as metal powder or carbon black is used. The conductive elastic material is used in a state where the volume resistivity of the conductive elastic layer 14 is preferably adjusted to 10 ¹ to 10 ⁴ Ωcm.

In such a conductive elastic material, conventionally known various compounding agents and additives such as vulcanizing agents, vulcanizing aids, fillers and the like may be used, if necessary, in a usual manner. They are added and mixed at the mixing ratio. Particularly, in order to reduce the hardness of the intended conductive roll 10, various known softeners such as process oil and liquid polymer are blended at a predetermined blending ratio with the conductive elastic material. May be. Further, in addition to these, a predetermined foaming agent may be compounded at a predetermined compounding ratio, whereby the conductive elastic layer 14 can be formed as a foam layer, and its weight reduction is effective. The conductive elastic layer 1 can be formed without depending on the blending of the softener.
4. As a result, the hardness of the conductive roll 10 itself can be advantageously reduced, so that the occurrence of bleed is effectively suppressed.
The contact property of the photosensitive material can be effectively improved, and more excellent roll performance can be obtained.

On the other hand, the resistance adjusting layer 16 is formed using a hydrogenated nitrile rubber or a rubber composition in which carbon black and an ionic conductive agent are blended as a conductive filler in a nitrile rubber.

Here, the hydrogenated nitrile rubber or nitrile rubber has an electric resistance lower than that of epichlorohydrin rubber or epichlorohydrin-ethylene oxide copolymer rubber which is generally used as a rubber material for providing a resistance adjusting layer of a conventional conductive roll. Therefore, even if carbon black is blended as a conductive filler, an excessive decrease in electric resistance can be avoided. Therefore, in the conductive roll 10 according to the present invention, either the hydrogenated nitrile rubber or the nitrile rubber is used as the raw material rubber which is the main component of the rubber composition that provides the resistance adjusting layer 16, An excessive decrease in the electric resistance of the resistance adjusting layer 16 due to the compounding of the carbon black, and thus a decrease in the leak resistance can be advantageously prevented.

As the carbon black to be blended with such a specific rubber material, one having a dibutyl phthalate oil absorption of 50 ml / 100 g or less is used. However, when carbon black having a dibutyl phthalate oil absorption exceeding the above range is used, the degree of decrease in the electrical resistance of the rubber composition with respect to the amount of the carbon black added to the rubber material becomes sharp, so that The volume resistivity of the resistance adjusting layer 16 formed of such a rubber composition has a large variation, and as a result, it is possible to stably secure excellent leak resistance in the conductive roll 10. This is because it becomes difficult. In other words, the use of a carbon black having such a small value of dibutyl phthalate oil absorption, that is, a carbon black having a small structure makes it possible to obtain, for the first time, the desired conductive roll 10 having excellent leak resistance. It becomes. Examples of such carbon black include those having a product type (grade) of FT or MT, and color carbon black used for coloring. On the other hand, as the ionic conductive agent, any of various conventionally known ones can be used. Among them, quaternary ammonium salts such as trimethyloctadecyl ammonium perchlorate and benzyltrimethyl ammonium chloride are particularly preferable. Used.

In such a rubber composition, 40 to 100 parts by weight of the hydrogenated nitrile rubber or the nitrile rubber contains such a characteristic carbon black in an amount of 40 to 40 parts by weight.
90 parts by weight, and the ionic conductive agent does not exceed 1 part by weight. This is because if such a carbon black is blended in a proportion of less than 40 parts by weight, the current value on the roll surface, especially the DC current value, becomes insufficient, and it is 90 parts by weight. This is because, if it exceeds, the leak resistance will be significantly reduced. Furthermore, if the ionic conductive agent is added in a proportion exceeding 1 part by weight, the electric resistance also greatly changes with the change of the environment. in short,
In the rubber composition that provides the resistance adjusting layer 16, when the specific carbon black and the ionic conductive agent described above are blended as electronic conductive agents at a different blending ratio from the above, the purpose is as follows. In the conductive roll, not only the roll required characteristics cannot be satisfied, but also the improvement of the environmental dependency of the electric resistance cannot be expected at all. In that sense, carbon black is 45 to 75
It is desirable that the ionic conductive agent is blended in the rubber composition at a ratio of 0.1 to 0.5 part by weight, respectively.

In such a rubber composition,
The volume resistivity of the resistance adjusting layer 16 is usually 10 ⁸ to 10 ¹¹
It will be adjusted to be about Ωcm. It goes without saying that, in the rubber composition for providing the resistance adjusting layer 16, similarly to the material for forming the conductive elastic layer 14, various commonly used compounding agents and the like can be appropriately compounded.

As described above, in the conductive roll 10, the resistance adjusting layer 16 provided on the outer peripheral surface of the conductive elastic layer 14 has a specific rubber material and a specific carbon black and an ionic conductive agent. Is formed by using a rubber composition compounded in the range as described above, whereby roll required characteristics such as securing a sufficient current value and excellent leak resistance on the roll surface are advantageous. In addition, the environmental dependency of the electrical resistance can be effectively improved, and as a result, the above-described excellent operation and effect of the present invention can be extremely well exhibited.

Meanwhile, the conductive roll 10 as shown in FIG. 1 is advantageously produced as follows.

That is, using the conductive elastic material and the rubber composition, first, the conductive elastic layer 14 is formed on the outer peripheral surface of the shaft body 12 by a known molding technique such as die molding.
Then, the resistance adjusting layer 16 is formed on the outer peripheral surface of the conductive elastic layer 14 by a known coating technique such as dipping. When using a conductive elastic material mixed with a predetermined foaming agent, the vulcanization and the foaming operation of the elastic material are simultaneously performed by heating at the time of molding. The conductive elastic layer 14 is formed as a foam. Thus, the intended conductive roll 10 is obtained.

The conductive roll 10 thus obtained is
The thickness of each layer is appropriately determined depending on its use and the like, but usually, the conductive elastic layer 14 is 1 to 10
mm, desirably about 2 to 4 mm, and the resistance adjusting layer 16 is 10 to 300 μm, preferably 80 to 2 μm.
It is formed with a thickness of about 00 μm.

Next, FIG. 2 shows the conductive roll 10 of FIG.
Shows a specific example in which a softener migration preventing layer 18 is provided between the conductive elastic layer 14 and the resistance adjustment layer 16 and a protective layer 20 is provided on the outer peripheral surface of the resistance adjustment layer 16. I have. The softener transfer prevention layer 18 and the protective layer 20 provided on the conductive roll 22 shown in FIG. 2 are formed by using the same material as that of the related art. That is, as a material for providing the two layers 18 and 20, for example, a material in which an electronic conductive agent such as carbon black or metal powder is blended with a nylon-based material such as N-methoxymethylated nylon is used. is there. And, in such a material, the volume resistivity is 10 ³
The material adjusted to about Ωcm is used as a material for forming the softener transfer prevention layer 18, and the material whose value is adjusted to about 10 ⁸ to 10 ¹⁰ Ωcm is used as a material to form the protective layer 20.
Each is used.

The conductive roll 22 having such a configuration
In addition to the above, the excellent action and effect as described above can be extremely satisfactorily enjoyed. Of course, the presence of the softener migration preventing layer 18 causes the bleeding of the softener such as oil from the conductive elastic layer 14. It can be advantageously prevented and the protective layer 2
By the presence of 0, sticking to the photoreceptor can be effectively prevented.

In the conductive roll 22, the carbon black contained in the resistance adjusting layer 18 is smaller than that of a commonly used carbon black contained in the resistance adjusting layer 18. The black content is increased compared to the conventional one, whereby the resistance adjusting layer 1
6, the adhesion between the softener transfer preventing layer 18 and the protective layer 20 can be effectively increased, and as a result, for example, even in a high temperature and high humidity environment, the resistance adjusting layer 16 and the softener transfer preventing layer 18
And between the resistance adjusting layer 16 and the protective layer 20 can be effectively avoided or suppressed.

When producing the conductive roll 22 shown in FIG. 2, for example, first, a conductive elastic layer is formed on the outer peripheral surface of the shaft 12 in the same manner as the conductive roll 10 of FIG. 14, and thereafter, using the rubber composition for providing the resistance adjusting layer 16 and the material for forming the softener migration preventing layer 18 and the protective layer 20 described above, respectively, using a known coating technique such as dipping, and conducting elasticity. On the outer peripheral surface of the body layer 14, a softener transfer prevention layer 18, a resistance adjustment layer 16, and a protective layer 20 are provided from inside to outside in the roll radial direction,
The conductive rolls 22 are formed sequentially, thereby obtaining the desired conductive roll 22.

The conductive roll 22 thus obtained
The thickness of each layer is also determined as appropriate depending on its use or the like, but usually, the conductive elastic layer 14 and the resistance adjusting layer 16 are formed with the same thickness as the conductive roll 20 in FIG. . And the softener transfer prevention layer 18 is 3 to 20 μm.
m, preferably about 4 to 10 μm, and the protective layer 20 has a thickness of 5 to 30 μm, preferably 7 to 23 μm.
It will be formed with a thickness of about.

[0034]

EXAMPLES Hereinafter, some examples of the present invention will be described to clarify the present invention more specifically. However, the present invention imposes some restrictions by the description of such examples. It goes without saying that you don't receive anything. In addition, the present invention, in addition to the following examples, and in addition to the above-described specific description, various modifications based on the knowledge of those skilled in the art, unless departing from the spirit of the present invention,
It should be understood that modifications, improvements and the like can be made.

First, 50 parts by weight of Ketjen black and 400 parts by weight of a naphthenic oil were blended with 100 parts by weight of polynorbornene rubber to prepare a conductive elastic layer forming material. Then, using the conductive elastic layer forming material thus obtained and a core metal (diameter: 6 mm),
Die molding was performed to produce seven base rolls each having a conductive elastic layer provided on the outer peripheral surface of a cored bar. In addition,
The thickness of the conductive elastic layer of each base roll is 3
mm.

Next, a material for forming a softener migration preventing layer and a material for forming a protective layer were prepared according to the following composition. That is, the softener transfer preventing layer forming material is obtained by mixing 15 parts by weight of carbon black with respect to 100 parts by weight of N-methoxymethylated nylon, and the protective layer forming material is formed of N-methoxymethylated nylon. Of 10
Each was prepared by mixing 8 parts by weight of carbon black with 0 parts by weight. The material for forming a softener transfer prevention layer and the material for forming a protective layer thus obtained were dissolved in methanol to prepare coating solutions having predetermined viscosities.

Subsequently, in order to prepare a material for forming a resistance adjusting layer, a hydrogenated nitrile rubber, dibutyl phthalate oil absorption of 28 ml / 100 g and an average particle size of 80 μm were used.
m and a predetermined amount of carbon black, respectively, and a predetermined amount of trimethyloctadecyl ammonium perchlorate as a quaternary ammonium salt. Then, according to the composition shown in Table 1 and Table 2 below, they are blended to prepare seven types of resistance adjustment layer forming materials (A to G) having different composition, and they are dissolved in methyl ethyl ketone. Each was prepared into a coating liquid having a predetermined viscosity.

[0038]

[Table 1]

[0039]

[Table 2]

Thereafter, using each of the coating liquids thus obtained and the seven base rolls obtained above, a softening agent was applied on the outer peripheral surface of each base roll from the inside in the roll radial direction to the outside by a dipping technique. The migration preventing layer, the resistance adjusting layer, and the protective layer are formed by lamination, respectively, and
Various kinds of conductive rolls were obtained. Then, among the seven types of conductive rolls, those having a resistance adjustment layer formed using the resistance adjustment layer forming materials A to D having the compounding composition defined in the present invention were prepared in Examples 1 to 3, respectively. 4 and Comparative Examples 1 to 3 in which the resistance adjusting layers were formed using the resistance adjusting layer forming materials E to G having a compounding composition outside the specified range of the present invention. The thickness of each layer is
8 μm for the softener transfer prevention layer, 160 μm for the resistance adjusting layer,
The protective layer had a thickness of 10 μm.

Using the seven conductive rolls thus obtained (Examples 1 to 4 and Comparative Examples 1 to 3), various performance evaluations were performed as described below. The results are shown in Tables 3 and 4 below.

In a temperature / humidity environment of a current value of 10 ° C. × 10%, a voltage of 500 Vp-p, 750 Hz, 200 V was applied to each roll, and a metal mirror-finished roll having a diameter of 30 mm was pressed at both ends (500 g at one end).
), And the AC current value and the DC current value under rotation (17 rpm) were measured.

Environment-dependent For each roll, (a) 10 ° C. ×
10%, (b) 25 ° C x 60%, (c) 30 ° C x 85%
The AC current value under each temperature and humidity environment was measured, and the value of log [(current value of a) / (current value of c)] was calculated based on the obtained measured value.

In a temperature / humidity environment of 10 ° C. × 10% leak voltage , each roll was brought into contact with a smooth metal roll under a predetermined pressure, and a DC voltage was applied in this state. In the roll, the PP voltage at the time when the breakdown occurred was measured.

Evaluation Rolling Out Each roll was applied to a laser printer [Laser Jet 40].
4E: manufactured by Canon Inc.], and under each of the above-mentioned environments (a), (b), and (c), image output was performed. Was observed. Under all circumstances, when no image unevenness or white spots were observed, it was evaluated as ○, when they were partially observed, as △, and when they were clearly observed, as ×, evaluated.

[0046]

[Table 3]

[0047]

[Table 4]

As is clear from the results in Tables 3 and 4, Examples 1 to 4 in which the resistance adjusting layers were formed using the resistance adjusting layer forming materials A to D having the composition specified in the present invention. In No. 4, in the current value, both the AC component and the DC component show high values, the value showing the magnitude of the environment dependence is small, the leak voltage is high, and the environment is low. It can be seen that even if it changes, no image unevenness or white dropout occurs at all. On the other hand, in Comparative Examples 1 to 3, in which the resistance adjustment layer was formed using the resistance adjustment layer forming material E in which only the ionic conductive agent was incorporated in a large amount as the conductive filler, , The value representing the environmental dependency is significantly larger than the other ones, and as the conductive filler, carbon black is blended in the blending ratio specified in the present invention, but the ionic conductivity In Comparative Example 2 in which the resistance adjusting layer was formed using the resistance adjusting layer forming material F containing no agent, the DC current value was extremely small. Further, as the conductive filler, only the carbon black was used, and the resistance adjustment layer was formed using the resistance adjustment layer G in which the carbon black was blended at a ratio outside the range specified in the present invention. Comparative Example 3 shows that the leak voltage has a small value and that image defects such as image unevenness and white spots occur.

That is, from the facts described above, by adopting the present invention, for the first time, a sufficient current value and excellent leak resistance on the roll surface can be effectively ensured, and the environment dependency of the electric resistance is advantageous. It is clearly recognized that excellent effects not obtained with conventional conductive rolls, such as good images can be obtained irrespective of environmental changes such as temperature and humidity, can be achieved. It can be done.

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory view showing an example of a conductive roll according to the present invention.

FIG. 2 shows another example of a charging roll according to the present invention.
FIG.

[Explanation of symbols]

 10, 22 Conductive roll 12 Shaft 14 Conductive elastic layer 16 Resistance adjustment layer 18 Softener migration prevention layer 20 Protective layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C08K 5/17 C08K 5/17 G03G 15/02 101 G03G 15/02 101 15/08 501 15/08 501D // H01B 5/16 H01B 5/16 (72) Inventor Tetsuya Ito 3600, Gezu, Kitai-gaiyama, Komaki-shi, Aichi Prefecture Inside Tokai Rubber Industries Co., Ltd. (56) References JP-A-7-1134472 (JP, A) 143456 (JP, A) JP-A-7-295332 (JP, A) JP-A-6-73235 (JP, A) JP-A-7-332350 (JP, A) JP-A-7-295331 (JP, A) JP-A-7-140760 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 9/02 B32B 1/08 B32B 25/08 B32B 25/14 C08K 3/04 C08K 5 / 17 G03G 15/02 G03G 15/08 H01B 5/16

Claims (3)

(57) [Claims] 1. A conductive roll comprising: a predetermined conductive elastic layer provided on an outer peripheral surface of a shaft body; and a resistance adjusting layer provided on an outer peripheral surface of the conductive elastic layer. The adjusting layer has a dibutyl phthalate oil absorption of 50 ml / 100 g as a conductive filler based on 100 parts by weight of the hydrogenated nitrile rubber or nitrile rubber.
The following carbon black in a ratio of 40 to 90 parts by weight,
Also, a conductive roll formed by using a rubber composition obtained by blending an ionic conductive agent in a ratio not exceeding 1 part by weight. 2. The conductive roll according to claim 1, wherein the ionic conductive agent is a quaternary ammonium salt. 3. A softener migration preventing layer is provided between the conductive elastic layer and the resistance adjusting layer, and a protective layer is provided on an outer peripheral surface of the resistance adjusting layer. The conductive roll according to claim 1 or 2.