JPH07304117A - Charge roll and production thereof - Google Patents

Abstract

PURPOSE:To reduce the electric etching action on a photosensitive drum and the shaving quantity of a sensitive material by forming a protective layer on a roll main body so that the protective layer is made thinnest at the axial central part of the roll main body and becomes gradually thick toward both end parts thereof to form the whole of a roll into a hand drum-shape. CONSTITUTION:A charge roll is constituted so that a conductive elastic material layer 2 is formed on the outer peripheral surface of a core body 1 and a semiconductor resistance adjusting layer 3 is formed on the outer peripheral surface thereof and a protective layer 4 is further formed on the outer peripheral surface thereof so as to be made thinnest at the axial central part of the roll and to become gradually thick toward both end parts thereof and formed into a hand drum-shape as a whole. By this constitution, since the resistance of both end parts of the charge roll is higher than that of the central part thereof when the charge roll is used in contact with a photosensitive drum, AC voltage is reduced and a current value becomes low and the shaving quantity of a sensitive material at both end parts of the roll is reduced. Since a change of a resistance value is provided in the axial direction of the protective layer 4 by the film thickness difference of the same material, the central part and both end parts of the charge roll have the same environmental dependence.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charging roll for charging the surface of a photosensitive drum of an electrophotographic copying machine or the like and a method for producing the charging roll.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic copying machine, an outer peripheral surface of a photosensitive drum is uniformly charged, and then the outer peripheral surface is exposed through a copied image of a copying object. In general, an electrostatic latent image is formed on a sheet, a toner is attached to the electrostatic latent image to form a toner image, and the toner image is transferred to a copy paper or the like to perform copying. And
In order to charge the outer peripheral surface of the photosensitive drum, a charging roll is brought into direct contact with the surface of the photosensitive drum to charge it.

In the charging roll, as shown in FIG. 5, a conductive elastic material layer 2 is usually formed on the outer peripheral surface of a core body 1, and a semiconductive resistance adjusting layer 3 is formed on the outer peripheral surface thereof. A protective layer 4 is formed on the outer peripheral surface of the resistance adjusting layer 3 for the purpose of preventing contamination of the photosensitive drum and toner adhesion.
The charging roll is attached to the photosensitive drum in a state where both ends of the core body 1 are pressed, and since the roll itself has a slight bend or a dent on the surface, the charging roll is exposed at the central portion in the axial direction of the roll. A gap is generated between the drum surface and the surface of the drum, and image defects due to poor charging are likely to occur. Therefore, in order to prevent a gap from being formed between the charging roll and the photosensitive drum in the central portion in the roll axial direction, the thickness of the resistance adjusting layer 3 is set to be thickest in the central portion in the axial direction of the roll as shown in FIG. A drum-shaped charging roll, which is gradually thinned, has been proposed and used for a prize (JP-A-6-39948). The thickness adjustment is performed as follows, for example. That is, as shown in FIG. 7, the coating roll 6 is brought into contact with the outer peripheral surface of the roll main body 5 on which the conductive elastic material layer 2 is formed while supplying the coating liquid for forming the resistance adjusting layer, and And rotating the coating roll 6 in the circumferential direction,
In the roll coating method in which the coating roll 6 is moved relative to the roll body 6 in the vertical direction to apply the coating liquid to form the resistance adjusting layer 3, the coating roll 6 is moved up and down relative to the roll body 5. The speed is gradually reduced when the coating roll 6 moves toward the center of the roll body 5 in the axial direction, and conversely when the coating roll 6 moves from the center of the roll body 5 toward the end. Is controlled to gradually increase so that the coating thickness of the coating liquid is thickest in the central portion of the roll body 5 in the axial direction and gradually decreases toward both end portions. In this way, the drum-shaped charging roll shown in FIG. 5 can be obtained. In addition, in FIG.
Is a coating liquid supply pipe, 8 is a coating liquid regulating plate, and 9 is a coating liquid recovery container.

[0004]

However, if the drum-shaped charging roll is rotated in contact with the photosensitive drum and a DC voltage and an AC voltage of high frequency are applied between the drum and the drum, the photosensitive drum is used for a long time. When the photosensitive material (organic photosensitive material) is etched and its abrasion becomes large, the aluminum material, which is the base material of the photosensitive drum, is exposed, and the surface potential of the photosensitive material leaks, resulting in image defects and damage to the charging roll. Was found to be likely to occur. This is considered to be due to the following reasons. That is, in a photosensitive drum, generally, a base material which is vertically stood is immersed in a dip solution for forming a photosensitive material layer and then pulled up to form a coating of the photosensitive material layer on the outer peripheral surface of the base material. During the drying process, the dip liquid drips downward, and the coating film tends to be thicker toward the lower end side of the shaft and thinner toward the upper end side. Therefore, as shown in FIG. 6, the end portion of the photosensitive drum 10 where the film thickness of the photosensitive material 11 is thin (the end portion which is on the upper side at the time of dipping) and the film thickness of the resistance adjustment layer 3 are formed. The contact width (nip width) of the portion contacting with the charging roll that is thinner than the center is smaller than that of the center portion, and the charging roll resistance is low, so that the AC voltage is high and the electric etching action on the photosensitive drum 10 is caused. It is thought that this will increase the amount of abrasion of the sensitive material.

The present invention has been made in view of the above circumstances, and provides a charging roll which has a small electric etching effect on the photosensitive drum and a small amount of scraping of the photosensitive material, and can be used satisfactorily for a long period of time. The purpose is to provide.

[0006]

In order to achieve the above object, the present invention has a resistance adjusting layer and a protective layer integrally formed in this order on the outer peripheral surface of a cylindrical roll body made of a conductive elastic body. In the charging roll, the protective layer is thinnest in the axial center part of the roll main body and gradually thickens toward both ends, and the entire roll is in a zigzag shape. The charging roll formed in 1 is the first gist, and the semi-finished product roll in which the resistance adjusting layer is formed on the outer peripheral surface of the cylindrical roll body made of a conductive elastic body is arranged so that the axial direction is vertical. Together with the cylindrical coating roll, the axial direction is arranged horizontally, the semi-finished product roll and the coating roll are respectively rotated in the circumferential direction, and the coating liquid for forming the protective layer is supplied to the coating roll. Protecting the outer peripheral surface of the semi-finished product roll by repeatedly moving the application roll in the vertical direction relative to the semi-finished product roll in a state where the coating surface of the application roll is in contact with the outer peripheral surface of the semi-finished product roll. A method of manufacturing a charging roll, wherein a coating liquid for forming a layer is applied to form a protective layer, wherein the coating roll is a semi-finished product when the semi-finished product roll moves from the axial end to the center. The relative moving speed of the coating roll with respect to the roll is gradually increased, and when the coating roll moves from the axial center of the semi-finished product roll toward the end, the moving speed is set to be gradually reduced, The coating thickness of the coating liquid for forming a protective layer formed on the outer peripheral surface of the semi-finished product roll is thinnest in the central portion in the axial direction of the semi-finished product roll, and gradually decreases toward both ends. The method of charging roll was set to be thicker and second aspect.

[0007]

In other words, the present inventors intend to increase the resistance of the end portion of the charging roll facing the thin end portion of the photosensitive drum photosensitive material layer in order to suppress the etching action of the charging roll on the photosensitive drum. A series of studies were repeated. As a result, the charging roller, which was conventionally formed in the shape of a drum, maintains the diameter of the central portion so that the central portion does not create a gap between the photosensitive drum and the charging roller, and the diameter increases toward both ends. From the idea that if it is formed in a staggered shape, the resistance increases toward both ends and the etching action decreases, so the thickness of the protective layer provided on the outer peripheral surface of the resistance adjusting layer is the thinnest in the central part and The present invention has been found out that a staggered charging roll can be easily obtained by forming the charging roll so that the thickness gradually increases.

Next, the present invention will be described in detail.

In the charging roll of the present invention, for example, as shown in FIG. 1, a conductive elastic material layer 2 is formed on the outer peripheral surface of a core body 1, and a semiconductive resistance adjusting layer 3 is formed on the outer peripheral surface thereof. ,
Further, the protective layer 4 is formed on the outer peripheral surface thereof. The protective layer 4 is formed so as to be the thinnest in the central portion in the axial direction of the roll and gradually thicker toward both end portions, and is formed in a zigzag shape as a whole.

The core body 1 is not particularly limited, but a core metal made of a solid metal body, a hollow metal pipe, or the like may be used.

The conductive elastic material layer 2 may be formed of any material used in the conductive elastic material layer of the conventional charging roll. For example, ethylene-propylene-as a matrix component
Examples include diene rubber (EPDM), polynorbornene rubber, styrene-butadiene rubber (SBR), chloroprene rubber (CR), epichlorohydrin rubber (CHC), silicon rubber, and the like, and a composition in which conductive powder such as carbon black is mixed. Is used. Among them, styrene-butadiene rubber is used as the matrix component,
It is preferable to add carbon black to this.
Then, in order to improve the contact property with the photosensitive drum, the hardness (H
s) is adjusted to about 20 to 30 ° and the electric resistance is 10 ⁴ Ω
-It is preferable to set it to be equal to or less than cm.

Further, the resistance adjusting layer 3 may be formed of any material used in the resistance adjusting layer of the conventional charging roll. For example, as the matrix component, epichlorohydrin-ethylene oxide copolymer rubber, hydrogenated acrylonitrile-
Examples thereof include butadiene rubber, hydrogenated butadiene rubber, acrylic resin and the like, and a composition in which carbon black, a conductive powder such as a metal oxide, and an ionic conductivity control agent are mixed is used. Among them, it is preferable to use epichlorohydrin-ethylene oxide copolymer rubber or hydrogenated acrylonitrile-butadiene rubber as a matrix component, and to add carbon black thereto. The electric resistance is preferably set within the range of the semiconductive region (10 ⁵ to 10 ⁸ Ω · cm).

Further, the protective layer 4 formed on the outer periphery of the resistance adjusting layer 3 may be formed of any conventionally used one. For example, N-methoxymethylated nylon (8-nylon) with a conductive agent such as tin oxide added if necessary is used. The electric resistance is preferably set to 10 ⁵ to 10 ⁸ Ω · cm.

In the charging roll of the present invention, as shown in FIG. 1, the core body 1 does not necessarily have to penetrate the center of the conductive elastic material layer 2, and for example, the conductive elastic material formed into a cylindrical shape can be used. You may make it fit the plug body in which the shaft part for attachment holding was formed in the opening of both ends of the material layer 2.

The most characteristic feature of the present invention is that the protective layer 4 is formed so as to be thinnest in the central portion in the axial direction and gradually thicker toward both end portions. In order to do so, a roll applied when the thickness of the resistance adjusting layer 3 is changed in the axial direction with respect to the semi-finished product roll on which the conductive elastic material layer 2 and the resistance adjusting layer 3 are formed in the same manner as in the conventional case. It is preferable to form the protective layer 4 according to a coating method (see FIG. 7). That is, the semi-finished product roll (corresponding to the roll main body 5 in FIG. 7) is placed upright so that the axial direction is vertical, and a cylindrical coating roll 6 is provided on the side thereof so that the axial direction is horizontal. Deploy. Then, while supplying the coating liquid for forming the protective layer from the coating liquid supply pipe 7 to the coating roll 6, the semi-finished product roll and the coating roll 6 are each rotated in the circumferential direction, and the coating surface of the coating roll 6 is Contact the outer peripheral surface of the semi-finished product roll. Then, in this state, the coating roll 6 is repeatedly moved in the vertical direction relative to the semi-finished product roll to coat the outer peripheral surface of the roll body 5 with the coating liquid to adjust the protective layer 4 (resistance adjustment in FIG. 7). Corresponding to layer 3). At this time, the conventional resistance adjusting layer 3
In the method of forming the above, as shown by the broken line P in FIG. 2, when the relative vertical movement speed of the coating roll 6 with respect to the roll body 5 is moved toward the center of the roll body 5 in the axial direction, The coating thickness of the coating liquid is controlled to gradually increase when the coating roll 6 moves from the axial center of the roll body 5 toward the end portion. The thickness is thickest at the central portion in the axial direction and gradually becomes thinner toward both end portions, but in the case of forming the protective layer 4 in the present invention, it is reversed. That is, as indicated by the solid line Q in FIG. 2, the speed is gradually increased when the coating roll 6 moves toward the center of the semi-finished product roll in the axial direction, and conversely, the coating roll 6 is the semi-finished product roll. When moving from the center to the end in the axial direction, it is controlled so that it gradually becomes slower, and the coating thickness of the coating liquid is the thinnest in the center of the semi-finished product roll in the axial direction and gradually increases toward both ends. Make it thick. In this way, it is possible to obtain a charging roll as a whole as shown in FIG.

In the above-mentioned manufacturing method, the greater the difference between the relative moving speed of the coating roll 6 at the central portion in the axial direction and the relative moving speed at the both end portions in the axial direction, the larger the protective layer 4 at the central portion and the both end portions. The difference in the film thickness can be increased. However, if the central portion is too recessed, the central portion of the charging roll is less likely to come into contact with the surface of the photosensitive drum when the resulting charging roll is used in contact with the photosensitive drum, so that The difference in thickness between the central part and both ends is 20 μm or less, especially 10 to 10 μm.
It is preferable to set it to 15 μm.

In the charging roll thus obtained, an example of a change in the thickness of the protective layer 4 in the axial direction is shown in FIG.
Shown in. As described above, in the charging roll of the present invention, the thickness of the protective layer 4 is gradually increased toward the end portion in the axial direction, and the protective layer 4 is formed in a zigzag shape as a whole.
When the charging roller is actually used by contacting it, as shown in FIG. 4, both ends of the charging roll have higher resistance than the central part, so that the AC voltage is reduced and the current value is low. I understand. Therefore, using the product of the present invention,
Since the amount of scraping of the photosensitive material is reduced at both ends, the photosensitive material surface potential does not leak on the surface of the photosensitive drum as in the conventional case, resulting in an image defect or damage to the charging roll. It can be used well. Further, in the present invention, since the resistance value changes in the axial direction due to the film thickness difference of the same material as the protective layer 4, unlike the case where layers of different materials are added, the center and the end are the same. It has the advantage that it does not cause image defects such as fog at the central portion or the end portion even if it is subject to temperature changes and humidity changes.

Next, examples will be described together with comparative examples.

[0019]

Example 1 A conductive elastic material layer 2 was formed on the outer periphery of a core 1 having a diameter of 6 mm by using the following composition according to a usual method.
(Thickness 3 mm) was formed. The conductive elastic material layer 2 has a hardness (Hs) of 25 ° and an electric resistance of 10 ² Ω · cm.

[Composition of Conductive Elastic Material Layer 2] Styrene-butadiene rubber 100 parts by weight Carbon black 20 〃

Next, on the outer peripheral surface of the roll main body 5 on which the conductive elastic material layer 2 is formed, the thickness of the central portion in the axial direction is increased and the both ends are thickened by a roll coating method similar to the conventional one (see FIG. 7). The resistance adjusting layer 3 was formed so that the thickness thereof becomes thinner as it goes (the thickness of the central portion is 160 μm).
m, and the film thickness at both ends is 150 μm). The composition of the resistance adjusting layer 3 is as follows. The electric resistance of the resistance adjusting layer 3 is 10 ⁶ Ω · cm.

[Composition of Resistance Adjustment Layer 3] Hydrogenated acrylonitrile-butadiene rubber 100 parts by weight Carbon black 45 〃 Quaternary ammonium salt 0.5 〃

Further, the outer peripheral surface of the resistance adjusting layer 3 is
The roll coating method described in (see FIG. 7) was used.
Then, the protective layer 4 is formed to obtain the target charging roll.
It was The composition of the protective layer 4 is as follows. This
The electric resistance of the protective layer 4 is 10 ⁶Ω · cm. However
Then, as described above, the relative moving speed of the coating roll 6 is controlled.
As a result, the film thickness is 15 μ at both ends in the axial direction.
m and 10 μm in the central part.

[Composition of protective layer 4] N-methoxymethylated nylon 100 parts by weight Tin oxide 50 〃

[0025]

Examples 2, 3 and Comparative Example As shown in Table 1 below, the thickness of the protective layer 4 was changed. Except for this, the target charging roll was obtained in the same manner as in Example 1 above. Then, with respect to these Example products and Comparative Example products, electric resistance values were obtained at the central portion and the end portion in the axial direction, and the difference between them was calculated. The results are also shown in Table 1 below. In addition, each charging roll is actually attached to the photosensitive drum to make a copy, and whether or not the photosensitive material is scraped off at the end of the photosensitive drum is observed, and whether a trouble occurs in the copied image. It was observed. The results are shown in Table 2 below.

[0026]

[Table 1]

[0027]

[Table 2]

From the above results, all of the products of Examples have resistance differences between both ends and the center, and when used for a photosensitive drum in which the film thickness of the photosensitive material on one end side is thin, It can be seen that since the resistance value of the end portion of the charging roll that abuts the portion where the film thickness is thin is increased, the amount of abrasion of the photosensitive material in this portion is reduced and image defects are less likely to occur.

[0029]

As described above, the charging roll of the present invention is
Since the thickness of the protective layer is gradually increased from the central portion in the axial direction toward the end portion and is formed in a zigzag shape as a whole, the resistance value at both end portions is high. Therefore, when the photosensitive material is actually used by being brought into contact with the photosensitive drum, the resistance value of the end portion of the charging roll, which is in contact with the photosensitive drum end portion where the film thickness of the photosensitive material is thin, is high. Is reduced. Therefore, unlike the conventional case, the photosensitive material surface potential does not leak on the surface of the photosensitive drum to cause an image defect or damage to the charging roll, and it can be used satisfactorily for a long time. Further, in the present invention, since the resistance value changes in the axial direction due to the film thickness difference of the same material as the protective layer, unlike the case where layers of different materials are added, the center and the end are the same. It has the advantage of being environmentally dependent and not causing image defects such as fog at the center or at the edges even when subjected to temperature changes and humidity changes.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an example of a charging roll of the present invention.

FIG. 2 is a diagram illustrating a method of manufacturing the charging roll of the present invention.

FIG. 3 is a diagram illustrating the shape of a charging roll of the present invention.

FIG. 4 is a diagram illustrating characteristics of the charging roll of the present invention.

FIG. 5 is a sectional view showing an example of a conventional charging roll.

FIG. 6 is a diagram illustrating a problem of a conventional charging roll.

FIG. 7 is an explanatory diagram of a conventional method for producing a charging roll.

[Explanation of symbols]

 1 core 2 conductive elastic material layer 3 resistance adjusting layer 4 protective layer

Claims (2)

[Claims] 1. A charging roll in which a resistance adjusting layer and a protective layer are integrally laminated in this order on the outer peripheral surface of a cylindrical roll body made of a conductive elastic body, wherein the protective layer is A charging roll, characterized in that it is formed so as to be thinnest in a central portion in the axial direction of the roll main body and gradually thicker toward both end portions, and the entire roll is formed in a zigzag shape. 2. A semi-finished product roll in which a resistance adjusting layer is formed on the outer peripheral surface of a cylindrical roll body made of a conductive elastic body is arranged so that the axial direction is vertical, and a cylindrical coating roll is provided in the axial direction. Are arranged so as to be horizontal, the semi-finished product roll and the coating roll are respectively rotated in the circumferential direction, and the coating surface of the coating roll is provided on the outer periphery of the semi-finished product roll while supplying the coating liquid for forming a protective layer to the coating roll. By repeatedly moving the coating roll in the vertical direction relative to the semi-finished product roll in a state of being in contact with the surface, a coating liquid for forming a protective layer is applied to the outer peripheral surface of the semi-finished product roll to form a protective layer. In the method for producing the charging roll, the coating roll is applied to the semi-finished product roll when the coating roll moves from the axial end of the semi-finished product roll toward the center. The relative moving speed of the rolls is gradually increased, and when the coating roll is moved from the axial center of the semi-finished product roll toward the end, the moving speed is set to be gradually reduced. The coating thickness of the coating liquid for forming a protective layer formed on the outer peripheral surface of the roll is the thinnest in the central portion in the axial direction of the semi-finished product roll, and is gradually thickened toward both end portions. How to make rolls.