JPH06264919A - Conductive roll - Google Patents

Abstract

PURPOSE:To provide a conductive roll whereby a proper initial resistance value can be obtained and, in addition, a proper electric resistance can be maintained even if it is used for a long period and an excellent image can be obtained. CONSTITUTION:A conductive elastic body layer 27 is formed on the outer periphery of a core metal 26, a softening agent moving prevention layer 28 formed mainly of N-methoxymethyl nylon is formed on the outer periphery of the conductive elastic body layer 27, and a resistance adjusting layer 29 is formed on the outer periphery of the softening agent moving prevention layer 28. Also a protective layer 30 formed mainly of N-methoxymethyl nylon is formed as the outermost layer on the outer periphery of the resistance adjusting layer 29, and the resistance adjusting layer 29 is formed of a composition mainly of (A) to (C) components as described below.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll used in electrophotographic copying machines and the like.

[0002]

2. Description of the Related Art In an electrophotographic copying machine, an original image is formed as an electrostatic latent image on a surface of a photosensitive drum, toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to a copy paper. Is to be copied. In this case, in order to form an electrostatic latent image on the surface of the photosensitive drum, the surface of the photosensitive drum is charged in advance, the original image is projected onto the charged portion through the optical system, and the light-transmitted portion is projected. It is practiced to create an electrostatic latent image by removing the charge.
As a method of charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, there has conventionally been a corona discharge method or a contact charging method. The corona discharge method is a method in which the surface of the photosensitive drum is subjected to a corona discharge from a corona discharger to be charged. Since this method generally uses a high voltage power supply of 5 to 10 kV, it is necessary to take thorough safety measures, and there is a drawback in that harmful ozone is generated with discharge. Therefore, recently, a contact charging method in which a conductive roll is brought into sliding contact with the surface of the photosensitive drum to charge the surface of the photosensitive drum has attracted attention. An electrophotographic copying machine to which such a contact charging system is applied is constructed as shown in FIG. 4, and copying is performed as follows. That is, the charging roller 2 made of a conductive roller is rotated around the outer peripheral surface of the photosensitive drum 1 rotating around the shaft 1a in the direction of the arrow, and a voltage is applied to the charging roller 2 to apply the voltage to the photosensitive drum 1. The outer peripheral surface of is charged. Reference numeral 3 denotes an exposure mechanism section through which slit exposure 8 of the original light image reaches the surface of the photosensitive drum 1 and an electrostatic latent image corresponding to the original image is formed on the surface of the photosensitive drum 1. A developing device 4 forms toner images by attaching toner to the electrostatic latent image. Reference numeral 6 denotes a paper feed mechanism roll that supplies copy paper 11 to the surface of the photosensitive drum 1 and transfers a toner image onto the copy paper 11 via the transfer device 5. Reference numeral 7 denotes a fixing roll for passing and fixing the copy paper 11 on which the toner image is formed. In this way, a copy is obtained. The surface of the photosensitive drum 1 is cleaned by a cleaner 9 to remove transfer residual images and residual toner.
Further, the entire surface is irradiated with light by the eraser lamp 10 to have a zero potential, and the next charging is prepared. In the figure, 12 is a power source for applying a voltage of about 1 to 3 kV to the charging roll 2.

For an electrophotographic copying machine, a charging roll and a developing roller are used.
Many conductive materials such as rolls, transfer rolls and cleaning rolls
Sex rolls are used. With such conductive roll
Then 10¹-10¹²Has conductivity of about Ω · cm
Is usually required, as shown in FIG.
Shaft (core metal) 21 and conductivity formed on its outer peripheral surface
The elastic layer 22 is generally made of synthetic rubber such as silicone rubber.
Conductive powder (carbon black, metal powder, etc.) and conductivity
Formed by a composition containing fibers (carbon fiber, etc.)
Has been done. Of this kind of conductive roll, charging roll
About 10 ^Five-10⁹Ω ・ cm semi-conductive area
It is required to have a resistance. However, above
Conductive roll having a conductive elastic layer 22 such as
If the conductive particles mixed in the synthetic rubber are in contact with each other,
Since it gives conductivity, it is not always uniform
I haven't got any touch. This is especially noticeable in the semiconductive region.
And therefore has an electrical resistance above the semiconducting region (10
^Five-10⁹Ω · cm) is difficult to fit
It As a result, it is difficult to obtain a good copy image.
Occurs.

In order to solve such a problem, conductive ammunition is used.
As shown in FIG. 6, the resistance adjusting layer 2 is formed on the outer periphery of the body layer 22.
A conductive roll provided with 3 has been proposed. But Naga
, Ordinary synthetic resin (polyethylene, polyester,
Epoxy resin) and synthetic rubber (ethylene-propylene rubber)
Rubber, styrene-butadiene rubber, chlorinated polyethylene rubber
Has an electric resistance of 10¹²Ω · cm or more insulator
The resistance adjusting layer 23 is made of synthetic resin or synthetic rubber.
10 is required for the charging roll.^Five-10 ⁹Ω ・
When it is tried to satisfy the electric resistance of cm, the resistance adjusting layer 2
It is necessary to set the thickness of 3 to 1 μm or less. However, this
Such a thin resistance adjusting layer 23 has no practical durability.
Become

As described above, the conventional conductive rolls, especially the charging rolls, have problems such as non-uniform resistance and lack of practicality, and in reality, satisfactory ones have not yet been obtained.

[0006]

In order to solve such a problem, the present inventors have found that an excellent effect can be obtained if the resistance adjusting layer is made of epichlorohydrin-ethylene oxide copolymer (CHC). Has filed a patent application (JP-A-1-142569). That is, in this way, the electric resistance is uniform throughout, and the thickness of the resistance adjusting layer can be arbitrarily adjusted to withstand practical use. However, when such a conductive roll, particularly a charging roll, is put into practical use, the electrical resistance increases when a DC voltage is continuously applied to the roll for a long period of time, the current value flowing in the roll decreases, and an image due to a charging failure occurs. There is a problem that a defect (whitening etc.) occurs. Further, depending on the type of material for forming the resistance adjustment layer, the initial resistance value may be higher than the required initial resistance value. In this way, the actual situation is that a satisfactory charging roll has not yet been obtained.

The present invention has been made in view of the above circumstances, and is a conductive material that can obtain a proper initial resistance value, maintain proper electrical resistance even after long-term use, and can obtain a good image. The purpose is to provide rolls.

[0008]

In order to achieve the above object, the conductive roll of the present invention has a conductive elastic body layer formed on the outer circumference of a shaft body, and a resistance is formed on the outer circumference of the conductive elastic body layer. A conductive roll having an adjustment layer formed, wherein the resistance adjustment layer is formed of a composition mainly containing the following components (A) to (C). (A) Epichlorohydrin-ethylene oxide copolymer. (B) At least one selected from the group consisting of acrylonitrile-butadiene rubber, epichlorohydrin rubber and acrylic rubber. (C) Ion conductive agent.

[0009]

That is, the present inventors mainly set the material for forming the resistance adjusting layer for the purpose of setting an appropriate electric resistance (initial value) and suppressing the increase in the electric resistance of the resistance adjusting layer. Repeated research. In the course of that research, it was found that the use of a specific rubber component (B component) and ionic conductive agent (C component) can suppress an increase in electric resistance due to long-term voltage application. As a result of further research, in addition to the above ion conductive agent and a specific rubber component, CHC (A component)
It has been found that the addition of the above formula makes it possible to set a desired electric resistance (initial value) together with the effect of suppressing an increase in electric resistance due to voltage application, and a good copy image can be obtained.

Next, the present invention will be described in detail.

The conductive roll of the present invention comprises a shaft body, a conductive elastic layer formed on the outer periphery thereof, and a resistance adjusting layer formed on the outer periphery thereof.

The shaft body is not particularly limited, and for example, a cored bar made of a metal columnar body or a metal cylindrical body having a hollow hollow inside is used.

The conductive elastic layer formed along the circumference on the outer periphery of the shaft is not particularly limited, and polynorbornene rubber, ethylene-propylene-diene rubber (EPDM), styrene-butadiene rubber, etc. The synthetic rubbers mentioned above can be used alone or in combination. Such a conductive elastic layer usually has a conductivity of 10 ¹ to 1
It is set to about 0 ⁴ Ω · cm. And its thickness is
Usually, it is set to about 1 to 10 mm, preferably about 2 to 4 mm.

In particular, the hardness of the conductive elastic layer (JIS
When (A) is set to 25 (Hs) or less, when a conductive roll, especially a charging roll is used by incorporating it in the apparatus as shown in FIG. 4, it is caused by a slight vibration between the photoconductor and the conductive roll, which rarely occurs. The occurrence of image quality defects (horizontal unevenness) and fogging phenomenon can be prevented. Thus, in order to set the hardness of the conductive elastic layer itself to a desired value, a softening agent such as oil is added. As the softening agent, naphthenic oil or the like is preferably used. Further, carbon black such as Ketjen black is used as a conductive agent, if necessary.

The resistance adjusting layer formed on the outer periphery of the conductive elastic layer is composed of CHC (component A) and acrylonitrile-
Using a composition mainly composed of at least one rubber (component B) selected from the group consisting of butadiene rubber (NBR), epichlorohydrin rubber (CHR) and acrylic rubber (ACM), and an ion conductive agent (component C) It is what is formed. And the thickness is usually 10 to 30.
It is set to 0 μm, and a suitable range is 80 to 2
It is 00 μm. The epichlorohydrin rubber is a homopolymer or copolymer containing no ethylene oxide as a copolymerization component. The term “main body” in the present invention is intended to include a case where the whole body is composed of only the main body.

As described above, the present inventors have found that the combination of the components A to C is preferable as the material for forming the resistance adjusting layer, and the electric resistance value of the material for forming the resistance adjusting layer is as follows. A material having a range of 10 ⁸ to 10 ¹¹ Ω · cm is used.

The compounding ratio of the above CHC (component A) (X) and the rubber material (component B) (Y) consisting of three types of rubber is in the range of X / Y = 80/20 to 20/80. It is preferable to set to. That is, CHC is less than 20 (B
This is because when the component exceeds 80), the initial electric resistance tends to be high, and when CHC exceeds 80 (the B component is less than 20), the degree of increase in the electric resistance after applying the DC voltage tends to increase.

Examples of the ionic conductive agent (component C) include quaternary ammonium salts, which may be used alone or in combination. Here, the quaternary ammonium salt is meant to include not only a pure salt but also a quaternary ammonium salt in which a perchlorate is ionically bonded.

The blending amount of the above-mentioned ion conductive agent (component C) is
It is preferable to set it to 0.5 to 5 parts with respect to 100 parts by weight (hereinafter, abbreviated as "part") of the total amount of the above components A and B. That is, if the compounding amount of the ionic conductive agent is less than 0.5 part, the electrical resistance does not decrease, and if it exceeds 5 parts, the electrical resistance increases, or the ionic conductive agent tends to bloom (exude) on the surface. is there.

The materials for forming the resistance adjusting layer include A to
In addition to the C component, a vulcanizing agent, a filler and the like are appropriately blended.
The above-mentioned vulcanizing agent is not particularly limited, and conventionally known ones such as thiourea, triazine and sulfur can be used. Examples of the filler include insulating fillers such as silica, talc, clay and titanium oxide, which may be used alone or in combination. Since a conductive filler such as carbon black is apt to cause dielectric breakdown when used under a high voltage, it should be used in an amount of 10% by volume or less based on the rubber component.

In the conductive roll of the present invention, a softener migration preventing layer mainly composed of N-methoxymethylated nylon is formed between the conductive elastic layer and the resistance adjusting layer, and the resistance is further increased. It is particularly preferable that the outermost layer of the adjustment layer has a protective layer mainly composed of N-methoxymethylated nylon.

The softener migration preventing layer composed mainly of N-methoxymethylated nylon formed between the conductive elastic layer and the resistance adjusting layer is formed of the oil or the like contained in the conductive elastic layer. It is formed to prevent the exudation of such a softening agent. The thickness of the softener migration prevention layer is generally 3
˜20 μm, preferably 4 to 10 μm. The electric resistance of the softening agent migration prevention layer is 1
It is set to about 0 ³ Ω · cm.

The N-methoxymethylated nylon (8-
Nylon) is not particularly limited, and conventionally known ones are used. Further, the softening agent migration prevention layer contains carbon black such as Ketjen black as a conductive agent.

The protective layer formed as the outermost layer on the outer periphery of the resistance adjusting layer is mainly composed of N-methoxymethylated nylon described above. As the N-methoxymethylated nylon, as described above, the conventionally known one can be used as it is. Then, when a conductive agent such as carbon black is mixed and dispersed in this protective layer, the conductivity becomes good at low temperature and low humidity, and good performance is exhibited even in a low temperature and low humidity environment. Such a protective layer is
Usually, it is preferable to set the thickness to 5 to 30 μm,
A particularly suitable range is 7 to 23 μm. The electric resistance value of this protective layer is set to 10 ⁸ to 10 ⁹ Ω · cm. The conductive agent is not limited to carbon black, and a conventionally known conductive agent can be used in place of the carbon black.

The conductive roll of the present invention, particularly the charging roll, can be manufactured, for example, as follows. That is, an adhesive is applied to the outer peripheral surface of the cored bar, and the conductive elastic body layer is formed using the rubber composition described above and utilizing mold vulcanization. Next, a mixed resin liquid in which N-methoxymethylated nylon and a conductive agent are mixed in advance is prepared, and the surface of the conductive elastic layer is polished as necessary, and then coated by spraying, dipping, or the like. Then, it is dried, and if necessary, it is heat treated to be crosslinked to form a softener migration-preventing layer. Then, the resistance adjusting layer is formed on the conductive agent-containing softener migration preventing layer thus formed.
The resistance adjusting layer is formed by adding a reinforcing agent to the components A to C,
A processing aid, a vulcanizing agent, a filler, and the like are kneaded by an ordinary rubber processing method (Banbury mixer, roll, etc.) to form an unvulcanized rubber composition, and the unvulcanized rubber composition is mixed with an appropriate solvent (for example, It can be formed by dissolving it in methyl ethyl ketone, methyl isobutyl ketone, etc.), coating it on the outer peripheral surface of the conductive elastic layer, drying it, and then heating and vulcanizing it. A dip method is suitable for the above coating. More specifically, the solution containing the composition containing the component A as a main component is contained as a dip solution in a tank 24 as shown in FIG. Next, the roll 25 on which the conductive elastic body layer is formed is erected vertically and repeatedly immersed in the solution to form a rubber film mainly composed of the component A on the outer peripheral surface of the conductive elastic body layer. . At this time, the conditions such as the viscosity of the dip solution, the ascending / descending speed, the number of ascending / descending, and the drying time are 1
It is preferable to set the conditions such that the range is 0 to 200 μm. The thus formed liquid film is dried at a temperature of 25 to 80 ° C. for 0.5 to 4 hours to remove the solvent, and then at a temperature of 150 to 200 ° C. for 10 minutes to 2
By heating for a time, the rubber film mainly composed of the component A is vulcanized to form a resistance adjusting layer. Next, after forming the resistance adjusting layer as described above, a resin solution made of N-methoxymethylated nylon, or a resin solution in which a conductive agent or the like is mixed, is coated thereon by spraying, dipping or the like. It is dried and, if necessary, heat-treated to be crosslinked to form a protective layer. In this way, a conductive roll having a layer structure as shown in FIGS. 2 and 3 is obtained. In the figure, 26 is a core metal, 27 is a conductive elastic layer, 28 is a softener migration preventing layer, 29 is a resistance adjusting layer, and 30 is a protective layer.

The conductive roll thus obtained is
The electric resistance of the entire roll can be set to about 10 ⁶ to 10 ⁹ Ω · cm.

[0027]

As described above, the conductive roll of the present invention uses the composition containing mainly the above-mentioned components A to C on the outer circumference of the conductive elastic layer formed along the outer circumference of the shaft body. The resistance adjusting layer is formed. Therefore, the electric resistance is uniform throughout, and the increase in the electric resistance is suppressed even after long-term use. As a result, problems such as a fog phenomenon in the copied image do not occur. Further, it becomes possible to widely control the electric resistance (initial value), and it is possible to set an appropriate electric resistance (10 ⁵ to 10 ⁹ Ω · cm for the charging roll).

Next, examples will be described together with comparative examples.

[0029]

[Examples 1 to 12, Comparative Examples 1 to 3]

[Preparation of Conductive Elastic Body Layer Forming Material] As a conductive elastic body layer forming material, a rubber composition was prepared using the following components.

Polynorbornene rubber 100 parts Ketjen black 50 parts Naphthene-based oil 400 parts

[Preparation of Softening Agent Migration Prevention Layer Forming Material] As a softening agent migration preventing layer forming material, a carbon black dispersion resin liquid was prepared using the following components.

N-methoxymethylated nylon 100 parts Carbon black 15 parts

[Preparation of Resistance Adjustment Layer Forming Material] As the resistance adjustment layer forming material, the respective components shown in Tables 1 to 3 below were blended in the proportions shown in the same table to prepare an unvulcanized rubber composition. The electric resistance values of the unvulcanized rubber compositions are also shown in the table.

[Preparation of Material for Forming Protective Layer] As a material for forming a protective layer, a resin solution was prepared using the following components.

N-methoxymethylated nylon 100 parts Carbon black 8 parts

Next, an adhesive is applied to the outer periphery of a cored bar made of a metal shaft having a diameter of 8 mm, and the outer periphery of the core is vulcanized with the rubber composition of the conductive elastic layer forming material. The conductive elastic body layer was formed so that the entire outer diameter was 15 mm. Then, the outer periphery of the conductive elastic layer was spray-coated with the carbon black dispersion resin liquid for the material for forming a softening agent migration preventing layer, and then dried to form a softening agent migration preventing layer having a thickness of 6 to 10 μm. on the other hand,
After roll-kneading the rubber composition for forming the resistance adjusting layer, methyl ethyl ketone / methyl isobutyl ketone = 3
It was dissolved in a solvent (1/1 by weight) and the viscosity was adjusted to 500 centipoise to prepare a dip solution. A cored bar on which the softening agent migration prevention layer was formed as described above was dipped in this solution for coating, then pulled up and dried, and then heat treated for crosslinking. Then, a resin solution for forming a protective layer was spray-coated on the surface and dried to form a protective layer. As a result, the intended conductive roll was obtained.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

[Table 3]

For each conductive roll thus obtained, 10 mm of silver paste was applied on the outer surface of the conductive roll.
The electrodes on four sides were drawn (with guard electrodes), and the electrical resistance (initial value) between the metal shaft and the electrodes was measured. Further, the electrical resistance after applying a DC voltage (-550V) to this conductive roll was also measured. Further, the above conductive roll was incorporated as a charging roll into the apparatus shown in FIG. 4, and it was incorporated into a copy, and the state immediately (initial state) and the copy image after taking 60,000 copies were visually observed and evaluated. Then, those in which no image defect such as fogging phenomenon occurred were displayed as ◯, and those in which image defect occurred were displayed as x. The results are shown in Tables 4 to 8 below.

[0042]

[Table 4]

[0043]

[Table 5]

[0044]

[Table 6]

[0045]

[Table 7]

[0046]

[Table 8]

From the results of Tables 4 to 8 above, in all the comparative examples, the degree of increase in electric resistance was as high as one digit or more, and defects occurred in the copied image. On the other hand, it can be seen that the example products have a low degree of increase in electric resistance, and the increase in electric resistance is suppressed even after application of the DC voltage. Furthermore, no image defects occurred.

[Brief description of drawings]

FIG. 1 is an explanatory view showing an example of a method for producing a conductive roll of the present invention.

FIG. 2 is an explanatory view showing a constitution of a conductive roll of the present invention.

FIG. 3 is a vertical sectional view of a conductive roll of the present invention.

FIG. 4 is a configuration diagram of an electrophotographic copying machine in which a conductive roll is incorporated.

FIG. 5 is a vertical cross-sectional view of a conventional conductive roll.

FIG. 6 is a vertical cross-sectional view of a conventional conductive roll.

[Explanation of symbols]

 26 Core Metal 27 Conductive Elastic Layer 28 Softening Agent Migration Prevention Layer 29 Resistance Adjustment Layer 30 Protective Layer

Claims (3)

[Claims] 1. A conductive roll having a conductive elastic body layer formed on the outer circumference of a shaft body, and a resistance adjusting layer formed on the outer circumference of the conductive elastic body layer, wherein the resistance adjusting layer comprises: 1. A conductive roll formed of a composition mainly containing the components (A) to (C). (A) Epichlorohydrin-ethylene oxide copolymer. (B) At least one selected from the group consisting of acrylonitrile-butadiene rubber, epichlorohydrin rubber and acrylic rubber. (C) Ion conductive agent. 2. Between the conductive elastic body layer and the resistance adjusting layer,
2. A softener migration preventing layer mainly composed of N-methoxymethylated nylon is formed, and a protective layer mainly composed of N-methoxymethylated nylon is formed as an outermost layer on the outer periphery of the resistance adjusting layer. The conductive roll described. 3. The conductive roll according to claim 1, wherein the ionic conductive agent as the component (C) is a quaternary ammonium salt.