JPH05265311A - Conductive roll - Google Patents

Abstract

PURPOSE:To obtain an image density which is uniform and sufficient and has excellent fogging resistance by setting the volumetric resistance and surface resistance of the conductive roll itself so as to satisfy a specific relation, thereby facilitating the escape of the residual charges of a toner from the roll surface into the air. CONSTITUTION:This conductive roll is produced by using a conductive coating material compsn. Namely, the conductive coating material compsn. is applied by dipping, etc., on the outer peripheral surface of a metallic sleeve 12 and is dried, by which conductive layers 13a, 13b, 13c are formed. The conductive layers 13a, 13b, 13c formed on the outer periphery of this shaft body are formed by using a binder resin and the conductive coating material compsn. formed by dispersing the conductive powder in this resin. The conductive layers 13a, 13b, 13c are formed into multilayered structures of at least two layers rather than a single layer system. The volumetric resistance(Rv) and surface resistance(Rs) of the roll itself are so set as to satisfy the relation (Rv/5)>Rs.

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 as a developing roll for electrophotographic copying machines, printers and the like.

[0002]

2. Description of the Related Art Generally, an electrophotographic copying machine is constructed as shown in FIG. 5, and copying is performed as follows. That is, the corotron 2 uniformly charges the photosensitive drum 1 which rotates in the direction of the arrow around the shaft 1a. Reference numeral 3 denotes an exposure mechanism section, through which slit exposure 8 of the light image of the original 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 roll built in the case 4a, which is frictionally charged by the sliding contact of the layer forming member 12 and adheres the toner in the case 4a. Then, the toner flies toward the electrostatic latent image on the surface of the photosensitive drum 1, and a toner image is formed on the surface of the photosensitive drum 1. The toner image is transferred by the paper feed roller 6 as shown by the arrow, transferred onto the copy paper 11 via the transfer device 5, and fixed onto the copy paper 11 by the fixing roll 7. Copying is performed in this manner. In the figure, 9 is a cleaner for removing transfer residual images and residual toner on the surface of the photosensitive drum 1, and 10 is an eraser lamp for zeroizing the photosensitive drum 1 to prepare for the next charging.

When the toner is non-magnetic, the developing roller 4 of this type is generally constituted by a metal shaft (core metal) 41a and a conductive layer 42a on the outer periphery thereof, as shown in FIG. In the case of having it, as shown in FIG. 7, it is constituted by a metal sleeve (core metal) 41b, end caps 41c at both ends thereof, a magnet shaft 41d in the metal sleeve 41b, and a conductive layer 42b on the outer periphery of the metal sleeve 41b. ing. In the figure, 4
3 is a bearing.

[0004]

The conductive layers 42a and 42b of the developing roll 4 are formed from the viewpoint of cost reduction and the like.
Recently, a coating material is used in which a conductive material such as carbon black or a conductive metal oxide is dispersed in a synthetic matrix (binder), and the surface of the metal sleeve is coated with the coating material. However, in the conductive roll formed by such a coating, by controlling the electric resistance of the coating layer, it is possible to secure a copy image without density unevenness, but the toner charge caused by the thin coating layer is generated. It is difficult to escape (due to the increased electrostatic capacity), so that there is a problem that a decrease in image density and a fog phenomenon occur.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a conductive roll capable of obtaining a uniform and sufficient copy image density and having excellent fog resistance.

[0006]

In order to achieve the above object, the conductive roll of the present invention is a conductive roll having a conductive layer formed on the outer periphery of a shaft body. The conductive roll itself has a volume resistance (Rv) and a surface. Resistance (Rs) is (Rv / 5)> R
It is configured to satisfy the relationship of s.

[0007]

That is, the inventors of the present invention have conducted a series of studies to obtain a developing roll capable of obtaining a uniform and sufficient copy image density and having excellent fog resistance. As a result, if the volume resistance (Rv) and the surface resistance (Rs) of the roll itself are set to satisfy the relationship of (Rv / 5)> Rs, the residual charge of the toner easily escapes. Therefore, the inventors have found that the flight of the toner from the roll can be easily controlled, a uniform and sufficient image density can be obtained, and further excellent fog resistance can be obtained, and the present invention has been reached.

Next, the present invention will be described in detail.

The conductive roll of the present invention comprises a shaft and a conductive layer formed on the outer periphery of the shaft.

The shaft body is not particularly limited,
A metal core made of a solid metal body or a metal cylindrical body hollowed out inside is used.

The conductive layer formed on the outer periphery of the shaft body is formed by using a binder resin and a conductive coating composition containing conductive powder dispersed therein. The conductive layer is preferably formed in a multilayer structure of at least two layers rather than a single layer system. In the case of a multi-layer structure, the thickness of the conductive layer is preferably set to 10 to 200 μm for each layer, and more preferably set to 50 to 300 μm in total thickness.

The binder resin is not particularly limited, and conventionally known binder resins can be used. Examples thereof include acrylic resin, melamine resin, phenol resin, and epoxy resin. These may be used alone or in combination.

As the above-mentioned conductive powder, c-TiO ₂ ,
Conductive metal oxide such as c-ZnO, carbon black,
Examples include graphite. These may be used alone or in combination. The above "c-" means having conductivity.

The conductive coating composition may contain other additives other than the above components, if necessary. Examples of other additives include titanium oxide, calcium carbonate, talc, clay and the like.

The conductive coating composition, which is the material for forming the conductive polymer layer formed on the outer periphery of the conductive roll of the present invention, is obtained as follows, for example. That is, the binder resin, the conductive powder and other additives are appropriately mixed,
It can be obtained by mixing and stirring using a ball mill or the like, and dissolving this mixture in a suitable solvent (xylene, methanol, etc.).

The conductive roll of the present invention can be manufactured using the above conductive coating composition, for example, as follows. That is, the conductive coating composition is applied to the outer peripheral surface of the metal sleeve by dipping or the like and dried to form a conductive layer. More specifically, the conductive coating composition is used as a dipping solution and the tank 17 as shown in FIG.
To house. Next, the metal sleeve 12 is erected vertically and repeatedly immersed in the conductive coating composition to form a conductive layer on the outer peripheral surface of the metal sleeve 12.
At this time, the conditions such as the viscosity of the conductive coating composition, the ascending / descending speed, and the number of times of ascending / descending are preferably set so that the liquid film of the conductive coating composition is in the range of 50 to 300 μm. The liquid film thus formed is dried at a temperature of about 60 ° C. for 1 hour to remove the solvent, and then 150 ° C.
A conductive layer is formed by heating at the temperature of 30 minutes.
When the conductive layer has a multi-layer structure, the coating and drying steps are repeated a desired number of times to form a multi-layer conductive layer. In this way, a conductive roll having a multi-layer structure (three-layer structure) as shown in FIG. 1 can be manufactured. In the figure, 12 is a metal sleeve, and 13a, 13b and 13c are conductive layers.

In the electroconductive roll thus obtained, it is necessary to set the volume resistance (Rv) and the surface resistance (Rs) of the electroconductive roll itself so as to satisfy the relationship of (Rv / 5)> Rs. That is, by setting the above relationship, a uniform and sufficient copy image density can be obtained, and a conductive roll excellent in fogging resistance can also be obtained.

Further, in this conductive roll, when a conductive layer having a multilayer structure composed of n layers (n ≧ 2) is formed, the outermost layer (nth layer) has a volume resistance (Rvn) and a surface resistance (Rsn). However, it is preferable to set each of them to satisfy the following inequalities.

[0019]

[Equation 1]

The above inequality is satisfied, that is, the volume resistance (Rvn) and the surface resistance (Rsn) of the outermost layer are
The volume resistance (Rv) and the surface resistance (Rs) of the conductive roll itself, which are the electrical resistances of the conductive rolls, are set by setting the total volume resistance and the surface resistance of the conductive layers inside the outermost layer to be smaller than the total. Is (Rv /
This is because it becomes easy to satisfy the relationship of 5)> Rs.

FIG. 2 shows another embodiment of the conductive roll of the present invention. Reference numeral 14 denotes a metal cylindrical body.
On the outer peripheral surface of the three-layered conductive layers 13a, 13b and 1
3c are sequentially formed. Reference numeral 15 is an end cap.

FIG. 3 shows still another embodiment of the conductive roll of the present invention. Reference numeral 41d denotes a magnet shaft. The magnet shaft 41d is coaxial with the conductive layers 13a, 13b and 1 having a three-layer structure with a gap provided on the outer periphery thereof.
A metal sleeve 16 formed with 3c is arranged.
Then, the end caps 41c are fitted in the left and right ends thereof. In the figure, 43 is a bearing.

[0023]

As described above, the conductive roll of the present invention is set so that the volume resistance (Rv) and the surface resistance (Rs) of the conductive roll itself satisfy the relationship of (Rv / 5)> Rs. . For this reason, the residual charge of the toner can be easily released from the roll surface into the air, a sufficient image density can be obtained, and a copy image with good fog resistance can be obtained. Therefore, the conductive roll of the present invention is optimal as a developing roll for electrophotographic copying machines, printers and the like.

Next, examples will be described together with comparative examples.

[0025]

Examples 1 to 5 and Comparative Examples 1 to 4 and Tables 1 to 1 below.
The components shown in Table 5 were blended in the proportions shown in the same table, mixed and stirred using a ball mill, and the mixture was mixed with methanol 10
A conductive coating composition was prepared by dissolving it in 0 parts by weight (hereinafter abbreviated as “part”). Then, a conductive coating composition was applied to the outer peripheral surface of the metal sleeve as the core metal by a dipping method and dried to form a conductive layer. Then, by repeating the coating and drying steps, a conductive roll having a conductive layer having a multilayer structure was obtained.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

[0030]

[Table 5]

The volume resistance and surface resistance in the single layer and all layers of the example product and the comparative example product thus obtained,
The image density and fogging index of the conductive roll were measured.
The results are shown in Tables 6 to 10 below. The image density was obtained by incorporating a conductive roll into an electrophotographic copying machine to produce an image. In this image production, a solid black copy was taken at the maximum density and the copy density was measured by a reflection densitometer manufactured by Macbeth. Further, the fogging index is shown as an index when the target fogging amount is set to 100 by measuring the fogging amount at 10 arbitrary positions (10 mm × 10 mm) in the solid white image portion. Further, the volume resistance and surface resistance of the single layer and all layers are the same as those of the electrode 2 having the shape shown in FIG.
1 was formed on the roll surface at 20 locations, and the value was measured by the measurement system shown in FIG.

Volume resistance Rv = ρv / σ Surface resistance Rs = 20ρs [where ρv is the measured value in the solid line circuit of FIG. 8B, ρ
s is a value measured by the broken line circuit in FIG. 8B, and σ is a layer thickness (cm). ]. In FIG. 8, 20 is a roll,
21a is a main electrode and 21b is a guard electrode. And
The electric resistance value in the examples and comparative examples is the average value of the measured values at 20 points.

[0033]

[Table 6]

[0034]

[Table 7]

[0035]

[Table 8]

[0036]

[Table 9]

[0037]

[Table 10]

From the results shown in Tables 6 to 10, the conductive rolls of the examples were higher in image density and lower in fogging index than the comparative examples. From this, it can be seen that the product of Example can obtain a sufficient image density and is excellent in fogging resistance.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a conductive roll of the present invention.

FIG. 2 is a cross-sectional view showing another embodiment of the conductive roll of the present invention.

FIG. 3 is a sectional view showing still another embodiment of the conductive roll of the present invention.

FIG. 4 is an explanatory view showing a method of manufacturing a conductive roll of the present invention.

FIG. 5 is a configuration diagram showing a copying mechanism of an electrophotographic copying machine.

FIG. 6 is a cross-sectional view showing a conventional developing roll.

FIG. 7 is a cross-sectional view showing another conventional developing roll.

FIG. 8A is an explanatory diagram showing the shape of an electrode formed on the surface of a conductive roll when measuring the electric resistance of the conductive roll;
(B) is an explanatory view showing a measuring system of the electric resistance value (volume resistance, surface resistance) of the conductive roll using the same.

[Explanation of symbols]

 12 Metal sleeves 13a, 13b, 13c Conductive layer

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akihiko Kaji 3600 Gyokutsu, Kotomaki, Aichi Prefecture Tohoku Rubber Industrial Co., Ltd.

Claims (2)

[Claims] 1. A conductive roll having a conductive layer formed on the outer periphery of a shaft body, wherein the volume resistance (Rv) and the surface resistance (Rs) of the conductive roll itself satisfy a relationship of (Rv / 5)> Rs. Characteristic conductive roll. 2. In a conductive layer having a multilayer structure composed of n layers (n ≧ 2), the volume resistance (Rvn) and the surface resistance (Rsn) of the outermost layer (nth layer) are higher than those of the outermost layer. The conductive roll according to claim 1, wherein the conductive roll is set to be smaller than the total volume resistance and the total surface resistance of the layers.