JP3271218B2 - 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 used in an electrophotographic copying machine or 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 the surface of a photosensitive drum, toner is adhered to the image, and a toner image is formed, and the toner image is transferred to 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, and a document image is projected on the charged portion through an optical system, and the portion where light is transmitted is formed. It has been practiced to create an electrostatic latent image by eliminating charge.
As a method for charging the surface of the photosensitive drum prior to the formation of the electrostatic latent image, a corona discharge method or a contact charging method has conventionally been used. In the corona discharge method, a corona discharge is applied to the surface of a photosensitive drum from a corona discharger to perform a charging process. Since this system generally uses a high voltage power supply of 5 to 10 kV, it is necessary to take thorough safety measures, and there is a problem that harmful ozone is generated with the discharge. For this reason, a contact charging method of charging a photosensitive drum surface by sliding a conductive roll on the surface of the photosensitive drum has recently attracted attention. An electrophotographic copying machine to which such a contact charging system is applied is configured as shown in FIG. 3, and performs copying as follows. That is, a charging roll 2 made of a conductive roll is rotated around the photosensitive drum 1 around the outer periphery of the photosensitive drum 1 which rotates in the direction of the arrow about the axis 1a. Is charged on its outer peripheral surface. Reference numeral 3 denotes an exposure mechanism through which the 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. Reference numeral 4 denotes a developing device that forms a toner image by attaching toner to the electrostatic latent image. Reference numeral 6 denotes a paper feed mechanism roll, which supplies the copy paper 11 to the surface of the photosensitive drum 1 and transfers the toner image onto the copy paper 11 via the transfer device 5. Reference numeral 7 denotes a fixing roll that fixes the sheet by passing the copy paper 11 on which the toner image is formed. In this way,
A copy is obtained. In addition. The transfer drum and residual toner are removed from the surface of the photosensitive drum 1 by a cleaner 9, and the surface of the photosensitive drum 1 is irradiated with light by an eraser lamp 10 to be zero potential to prepare for the next charging. In the figure, 1
Reference numeral 2 denotes a power supply for applying a voltage of about 1 to 3 kV to the charging roll 2.

[0003] Many electroconductive rolls such as a charging roll, a developing roll, a transfer roll, and a cleaning roll are used in an electrophotographic copying machine and the like. Such a conductive roll is required to have a conductivity of about 10 ¹ to 10 ¹² Ω · cm, and usually, as shown in FIG. 4, a metal shaft (core bar) 21 and its outer peripheral surface. The conductive elastic layer 22 is generally made of synthetic rubber such as silicon rubber, and is provided with conductive powder (carbon black, metal powder, etc.) or conductive fiber (carbon fiber, etc.) in synthetic rubber. It is formed by the mixed composition. Of the conductive rolls of this type, 10 ⁵ to 10 ⁹
It is required to have an electrical resistance of a semiconductive region of Ω · cm. However, the conductive elastic layer 2 as described above
In the conductive roll provided with No. 2, since the conductivity is given by the contact between the conductive particles mixed in the synthetic rubber, uniform contact between the particles is not necessarily obtained. This is particularly remarkable in the semiconductive region, so that it is difficult to keep the electric resistance in the above semiconductive region (10 ⁵ to 10 ⁹ Ω · cm). As a result, there is a problem that a good copied image cannot be obtained.

In order to solve such a problem, as shown in FIG.
3 has been proposed. However, ordinary synthetic resins (polyethylene, polyester, epoxy resin, etc.) and synthetic rubbers (ethylene-propylene rubber, styrene-butadiene rubber, chlorinated polyethylene rubber, etc.) are insulators having an electrical resistance of 10 ¹² Ω · cm or more. In these synthetic resins and synthetic rubbers, the resistance adjusting layer 2 is used.
3 to form 10 ⁵ to 10 ⁹ Ω required for the charging roll
In order to satisfy the electric resistance of cm, the thickness of the resistance adjusting layer 23 needs to be 1 μm or less. However,
Such a thin-film resistance adjusting layer 23 has no practical durability. As described above, the conventional conductive rolls, particularly the charging rolls, have problems such as non-uniform resistance and lack of practicality, and the fact is that satisfactory products have not yet been obtained.

[Problems to be solved by the invention]

In order to solve such a problem, the present inventors have found that an excellent effect can be obtained when the resistance adjusting layer is made of epichlorohydrin-ethylene oxide copolymer rubber (CHC), and have filed a patent application. (JP-A-1-
No. 142569). That is, in this case, the electric resistance is uniform throughout, and the thickness of the resistance adjusting layer can be arbitrarily adjusted so that it can be practically used. However, when a DC voltage is continuously applied to the roll for a long period of time, the electric resistance increases, the current flowing through the roll decreases, and a problem such as image defects (white spots or the like) due to poor charging occurs. As described above, the fact is that a satisfactory charging roll has not yet been obtained.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a conductive roll capable of maintaining an appropriate electric resistance even after long-term use and obtaining a good image.

[0007]

In order to achieve the above object, the conductive roll of the present invention has a conductive elastic layer formed on the outer periphery of a shaft, and a resistive layer is formed on the outer periphery of the conductive elastic layer. A conductive roll having an adjusting layer formed thereon, wherein the resistance adjusting layer is formed of a composition mainly composed of a hydrogenated nitrile rubber and an ionic conductive agent.

[0008]

In other words, the inventors of the present invention have repeatedly conducted research on the material for forming the resistance adjusting layer with the aim of suppressing an increase in the electric resistance of the resistance adjusting layer. As a result, it has been found that when a specific rubber material and an ionic conductive agent are used as the material for forming the resistance adjusting layer, an increase in electric resistance can be suppressed even during long-term use, and a good copied image can be obtained. The invention has been reached.

Next, the present invention will be described in detail. The conductive roll of the present invention includes a shaft, a conductive elastic layer formed on the outer periphery thereof, and a resistance adjusting layer formed on the outer periphery thereof. The shaft is not particularly limited, and for example, a metal core made of a metal cylinder or a metal cylinder having a hollow inside is used.

The conductive elastic layer formed on the outer periphery of the shaft is not particularly limited, and includes polynorbornene rubber, ethylene-propylene diene rubber (EPDM),
Synthetic rubber such as styrene-butadiene rubber can be used, and used alone or in combination. The conductivity of such a conductive elastic layer is usually set to about 10 ¹ to 10 ⁴ Ω · cm. And the thickness is usually 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, particularly a charging roll, is used by being incorporated in an apparatus as shown in FIG. The occurrence of image quality defects (horizontal unevenness) and fogging can be prevented. Then, 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 as needed.

The resistance adjusting layer formed on the outer periphery of the conductive elastic layer is formed using a composition mainly composed of hydrogenated nitrile rubber (H-NBR) and an ionic conductive agent. And the thickness is usually set to 10 to 300 μm, and a preferable range is 80 to 200 μm.
It is.

As described above, the hydrogenated nitrile rubber and the ionic conductive agent have been found by the present inventors as preferable materials for forming the resistance adjusting layer, and the electric resistance of the resistance adjusting layer is 10 ^8. Those having a range of 10 to 10 ¹¹ Ω · cm are used.

Examples of the ionic conductive agent include quaternary ammonium salts and the like, and are used alone or in combination. The compounding amount of the ionic conductive agent is 100 parts by weight of a rubber component composed of hydrogenated nitrile rubber (hereinafter, abbreviated as "part").
Is preferably set to 0.5 to 5 parts. That is, when the amount of the ionic conductive agent is less than 0.5 part, the electric resistance does not decrease. When the amount exceeds 5 parts, the electric resistance tends to increase and the ionic conductive agent tends to bloom on the surface.

[0015] In addition to the hydrogenated nitrile rubber and the ionic conductive agent, a vulcanizing agent, a filler and the like are appropriately compounded in the material for forming the resistance adjusting layer. The vulcanizing agent is not particularly limited, and includes conventionally known ones such as thiourea, triazine, and sulfur. Examples of the filler include insulating fillers such as silica, talc, clay, and titanium oxide, and are used alone or in combination. In addition, since conductive fillers such as carbon black easily cause dielectric breakdown when used under high voltage,
The amount used should not exceed 10% by volume with respect to the rubber component.

In the conductive roll according to 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. It is particularly preferable that a protective layer mainly composed of N-methoxymethylated nylon is formed as the outermost layer on the outer periphery of the protective layer.

The softener transfer preventing layer mainly composed of N-methoxymethylated nylon formed between the conductive elastic layer and the resistance adjusting layer is formed of a material such as oil contained in the conductive elastic layer. It is formed to prevent the seeping out of the softener. The thickness of the softener transfer preventing layer is generally 3
２０20 μm, preferably 4-10 μm. The electric resistance of the softener migration preventing layer is 10
It is set to about ³ Ω · cm. The N-methoxymethylated nylon (8-nylon) is not particularly limited, and conventionally known ones are used. Further, the softener transfer preventing 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 the above-mentioned N-methoxymethylated nylon. As the N-methoxymethylated nylon, a conventionally known N-methoxymethylated nylon can be used as it is. When a conductive agent such as carbon black is mixed and dispersed in this protective layer, the conductivity at low temperature and low humidity is good, and good performance is exhibited even in a low temperature and low humidity environment. Such a protective layer,
Usually, the thickness is preferably set to 5 to 30 μm,
A particularly preferred range is from 7 to 23 .mu.m. The electric resistance of this protective layer is set to 10 ⁸ to 10 ¹⁰ 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 produced, for example, as follows. That is, an adhesive is applied to the outer peripheral surface of the cored bar, and the conductive elastic layer is formed by 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. It is dried and, if necessary, heat-treated to crosslink and form a softener transfer prevention layer. Then, a resistance adjusting layer is formed on the conductive agent-containing softener migration preventing layer thus formed.
This resistance adjusting layer is formed by kneading a reinforcing agent, a processing aid, a vulcanizing agent, a filler, and the like with a hydrogenated nitrile rubber and an ion conductive agent by a usual rubber processing method (Banbury mixer, roll, etc.). A vulcanized rubber composition is obtained, and this unvulcanized rubber composition is dissolved in a suitable solvent (eg, methyl ethyl ketone, methyl isobutyl ketone, etc.), applied to the outer peripheral surface of the conductive elastic layer, dried, and then heated. It can be formed by vulcanization. In the above coating, a dipping method is preferably used. More specifically, a solution containing a composition mainly composed of the above-mentioned hydrogenated nitrile rubber and an ion conductive agent is accommodated as a dip solution in a tank 24 as shown in FIG. Next, the roll 25 on which the conductive elastic material layer is formed is set upright, and is repeatedly dipped in the above solution, so that the outer peripheral surface of the conductive elastic material layer mainly contains the hydrogenated nitrile rubber and the ionic conductive agent. To form a rubber film. At this time, the conditions such as the viscosity of the dip solution, the elevating speed, the number of elevating times, and drying conditions are such that the liquid film of the solution mainly composed of the hydrogenated nitrile rubber and the ionic conductive agent is 10 to
It is preferable to set conditions so as to be in the range of 200 μm. 25 for the case where such a liquid film is formed
The solvent is removed by drying at a temperature of ~ 80 ° C for 0.5 to 4 hours, and subsequently heated at a temperature of 150 to 200 ° C for 10 minutes to 2 hours to mainly contain the hydrogenated nitrile rubber and the ionic conductive agent. The rubber film to be cured is vulcanized to form a resistance adjusting layer. Next, after forming the resistance adjusting layer as described above, N
A resin liquid composed of -methoxymethylated nylon, and in some cases, a resin liquid mixed with a conductive agent or the like, are coated by spraying, dipping or the like, dried and, if necessary, heat-treated to crosslink and form a protective layer. Thus, a conductive roll having a layer structure as shown in FIG. 2 is obtained. In the figure, 26 is a metal core, 27 is a conductive elastic layer, 28 is a softener migration preventing layer, 29 is a resistance adjusting layer, 30
Is a protective layer. The conductive roll thus obtained has an electric resistance of about 10 ⁶ to 10 ⁹ Ω · cm.

[0020]

As described above, the conductive roll according to the present invention is provided on the outer periphery of the conductive elastic layer formed on the outer periphery of the shaft.
A resistance adjusting layer is formed using a composition mainly composed of a hydrogenated nitrile rubber and an ion conductive agent. For this reason,
The electric resistance is uniform throughout, and the increase in electric resistance is suppressed even after long-term use. As a result, a defect of a copied image such as a fogging phenomenon does not occur. Further, since the ionic conductive agent is added, the electric resistance (initial value) can be selected in a wide range.

Next, examples will be described together with comparative examples. The measurement results of Examples 1 to 3 and Comparative Examples 1 to 3 are shown in the table.

【Example】

[Preparation of conductive elastic body forming material] As the conductive elastic body layer forming material, a rubber composition was prepared using the following components. Polynorbornene rubber 100 parts Ketjen black 50 parts Naphthenic oil 400 parts

[Preparation of Softener Transfer Prevention Layer-Forming Material] Carbon black-dispersed resin liquids were prepared using the following components as the softener transfer prevention layer-forming material. N-methoxymethylated nylon 100 parts Carbon black 15 parts

[Preparation of Resistance Adjusting Layer Forming Material] As the resistance adjusting layer forming material, the respective components shown in Table 1 below were blended in the proportions shown in the table to prepare unvulcanized rubber compositions. The electric resistance of the unvulcanized rubber composition is also shown in the table.

[Preparation of Protective Layer Forming Material] A resin solution was prepared using the following components as the protective layer forming material. N-methoxymethylated nylon 100 parts Carbon black 8 parts

Next, an adhesive is applied to the outer periphery of a metal core made of a metal shaft having a diameter of 8 mm, and the outer periphery thereof is subjected to mold vulcanization using the rubber composition of the conductive elastic layer forming material. A conductive elastic body layer was formed so that the entire outer diameter became 15 mm by utilizing. Next, the outer periphery of the conductive elastic layer was spray-coated with the carbon black dispersion resin liquid for the material for forming a softener transfer prevention layer, and then dried to form a softener transfer prevention layer having a thickness of 6 to 10 μm. on the other hand,
After the rubber composition for forming the resistance adjusting layer was roll-mixed, methyl ethyl ketone / methyl isobutyl ketone = 3
/ 1 (weight ratio), and the viscosity was adjusted to 500 centipoise to prepare a dipping solution. The core metal on which the softener migration preventing layer was formed was immersed in this solution, coated, dipped and dried, and then heat-treated to crosslink. Then, the surface was spray-coated with a resin liquid for forming a protective layer, and then dried to form a protective layer. As a result, a desired conductive roll was obtained.

[0026]

[Table 1]

Each of the conductive rolls thus obtained was coated on the outer surface of the conductive roll with a silver paste by 10 mm.
Four electrodes were drawn (with guard electrodes), and the electrical resistance (initial value) between the metal shaft and the electrodes was measured. Further, the electric resistance after applying a DC voltage (−550 V) to the conductive roll was also measured. Further, the above conductive roll was incorporated as a charging roll into the apparatus shown in FIG. 3, and the state immediately after being incorporated into the copy (initial state) and the copied image after 60,000 copies were taken were visually observed and evaluated. Then, an image having no problem such as a fogging phenomenon was indicated by Δ, and an image having a problem was indicated by X. The results are shown in Tables 2 and 3 below.

[0028]

[Table 2]

[0029]

[Table 3]

From the results in Tables 2 and 3 above, Comparative Examples 1 and 2
In Example 2, the degree of increase in electric resistance was as high as one digit or more, and a defect occurred in a copied image. In Comparative Example 3, the electric resistance was high, and a defect occurred in the copied image. On the other hand, it can be seen that the example product has a low degree of increase in electric resistance, and the increase in electric resistance is suppressed even after the application of the DC voltage. Further, no image defects occurred.

[Brief description of the 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 a longitudinal sectional view of the conductive roll of the present invention.

FIG. 3 is a configuration diagram of an electrophotographic copying machine in which a conductive roll is incorporated.

FIG. 4 is a longitudinal sectional view of a conventional conductive roll.

FIG. 5 is a longitudinal sectional view of a conventional conductive roll.

[Explanation of symbols]

26: Core metal 27: Conductive elastic layer 28: Softener migration prevention layer 29: Resistance adjustment layer 30: Protective layer

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-107874 (JP, A) JP-A-57-102395 (JP, A) JP-A-5-88509 (JP, A) JP-A-4-107 350551 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/02 101 F16C 13/00 G03G 15/08 501 G03G 15/16 103 G03G 21/10

Claims (3)

(57) [Claims] 1. A conductive roll in which a conductive elastic layer is formed on an outer periphery of a shaft body, and a resistance adjusting layer is formed on an outer periphery of the conductive elastic layer. A conductive roll formed of a composition mainly composed of nitrile rubber and an ion conductive agent. 2. The method according to claim 1, wherein the conductive elastic layer and the resistance adjusting layer are
2. The conductive material according to claim 1, wherein a softener transfer 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 around the resistance adjusting layer. roll. 3. The conductive roll according to claim 1, wherein the ionic conductive agent is a quaternary ammonium salt.