JPH056095A - Conductive roll - Google Patents

Abstract

PURPOSE:To obtain the conductive roll having uniform electric resistance and excellent electrostatic chargeability by constituting a conductive layer by dispersing at least either of a titanium black and magnetic iron oxide into a phenolic resin used as a matrix component. CONSTITUTION:A metallic sleeve 12 formed coaxially with the conductive layer 15 in the state of having a gap on the outer periphery of a magnet shaft 42 and further, end caps 41 are fitted to both right and left ends thereof, by which the conductive roll is produced. The phenolic resin (more particularly preferably resol type phenolic resin) is used as the matrix component of the conductive material forming the conductive layer 15. In addition, either or both of the titanium black and magnetic iron oxide are used as the conductive material to be compounded with the phenolic resin matrix component. The conductive material is thereby uniformly dispersed into the matrix component in the conductive layer.

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 of an electrophotographic copying machine.

[0002]

2. Description of the Related Art Generally, an electrophotographic copying machine is constructed as shown in FIG. 3 and performs copying 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 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. A developing roll 4 adheres toner to the electrostatic latent image to form a toner image. 6
Is 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 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 developing toner, and further is irradiated with light from the entire surface by an eraser lamp 10 to be brought to a zero potential to prepare for the next charging. In such an electrophotographic copying machine, the developing roll 4 is usually 1
It is required to have conductivity of 0 ⁵ to 10 ¹⁰ Ω · cm, particularly about 10 ⁶ Ω · cm. When the developer (toner) has magnetism, such a developing roll 4 has a metal sleeve 40, end caps 41 at both ends thereof, and a magnet shaft 42 in the metal sleeve 40, as shown in FIG. And a conductive layer 43 on the outer circumference of the metal sleeve 40. In the figure, 44
Is a bearing.

In recent years, from the viewpoint of cost reduction and the like, the conductive layer 43 is formed of a molded body obtained by molding a conductive material obtained by mixing a conductive material such as carbon powder into a synthetic resin matrix into a cylindrical shape. The molded body is replaced with the metal sleeve 40 described above.
The developing roll 4 can be obtained by externally fitting the outer peripheral surface of the developing roll 4.

[0004]

However, it is impossible to ensure the uniformity of the copied image by controlling the electric resistance by the developing roll 4 having the conductive layer 43 made of the above conductive material. Even if it is possible, the phenomenon that the density of the image itself becomes thin occurs. Such a phenomenon is
This is due to the low chargeability of the developer (toner) with respect to the developing roll 4. Therefore, in addition to the control of the electric resistance, the developing roll 4 having excellent chargeability with respect to the developer (toner) is required. There is.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a conductive roll having a uniform electric resistance and excellent chargeability.

[0006]

In order to achieve the above object, in the conductive roll of the present invention, a cylindrical sleeve is coaxially arranged with a gap provided on the outer circumference of a permanent magnet roller. In a conductive roll having a conductive layer formed on the outer circumference of a sleeve, the conductive layer is formed by using a phenol resin as a matrix component and at least one of titanium black and magnetic iron oxide dispersed in the matrix component. Take the configuration.

[0007]

In other words, the present inventors have found that the electric resistance is uniform,
Moreover, in order to obtain a conductive roll having an excellent charging property, a series of studies have been conducted focusing on the conductive material forming the conductive layer of this conductive roll. As a result, a phenol resin was used as the matrix component of the conductive material, and as the conductive material to be blended with this phenol resin matrix component, one or both of titanium black and magnetic iron oxide was used instead of the carbon powder conventionally used. With,
The present inventors have found that the above conductive material is uniformly dispersed in the matrix component in the conductive layer of the conductive roll to make the electric resistance uniform, and further, the charging property is improved, 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 permanent magnet roller, a cylindrical sleeve provided with a gap on the outer circumference of the permanent magnet roller, and a conductive layer formed on the outer circumference of the cylindrical sleeve. It consists of and.

As the above-mentioned permanent magnet roller, those usually used can be cited.

The cylindrical sleeve provided on the outer circumference of the permanent magnet roller is not particularly limited, and may be a commonly used one, for example, a metallic one.

The conductive layer formed on the outer circumference of the cylindrical sleeve is made of a synthetic resin matrix, and a special conductive material is dispersed in the matrix. And the thickness is generally set to 30 to 300 μm,
It is preferably set to 50 to 200 μm.

A phenol resin is used as the synthetic resin for the matrix, and a resole-type phenol resin is particularly preferable.

The special conductive material dispersed in the synthetic resin matrix has excellent dispersibility, and one or both of titanium black and magnetic iron oxide is used.

The titanium black is a titanium oxide type compound and exhibits a black color. This titanium black is obtained by removing some oxygen from titanium dioxide,
It has a small particle size, does not have magnetism, and has excellent dispersibility in an aqueous or organic system. The titanium black is, for example, titanium black 13R manufactured by Mitsubishi Metals.

The magnetic iron oxide is Fe ₃ O.
_The powdery material represented by ₄ is used, and examples thereof include magnetite powder manufactured by Mitsubishi Metals.

In addition to the above raw materials, a filler or the like may be added to the conductive material, if necessary.

Examples of the filler include glass powder and silica. As described above, the use of the above-mentioned filler can further improve the charging property.

The conductive roll of the present invention can be manufactured using the above-mentioned raw materials, for example, as follows.
That is, one or both of the titanium black and the magnetic iron oxide, which are the conductive materials, and a filler, if necessary, are mixed with the phenol resin as a matrix component, and the filler is mixed and stirred using a ball mill or the like. Dissolve in a suitable solvent (methanol, etc.) to make a mixed resin solution of conductive material. Next, the mixed resin solution is coated on the outer peripheral surface of the metal sleeve by dipping or the like, dried, and cured by heating to form a conductive layer. More specifically, the mixed resin liquid is stored as a drip liquid in a tank 13 as shown in FIG. Next, the metal sleeve 12 is erected vertically and repeatedly immersed in the mixed resin liquid to form a conductive layer on the outer peripheral surface of the metal sleeve 12. The mixing ratio of the special conductive material is
100 parts by weight of the above-mentioned phenol resin (hereinafter abbreviated as "part")
It is preferable to mix it in a ratio of 50 to 150 parts. Further, the conditions such as the viscosity of the dispersion liquid, the ascending / descending speed, and the number of ascending / descending at this time are such that the liquid film of the mixed resin liquid is 50 to 200.
It is preferable to set the conditions such that the thickness falls within the range of μm. The thus formed liquid film was dried at a temperature of 50 ° C. for 2 hours to remove the solvent, and then 150
The phenol resin is cured by heating at a temperature of ℃ for 1 hour to form a conductive layer. Then, as shown in FIG.
A metal sleeve 12 in which the conductive layer 15 is coaxially formed with a gap provided on the outer periphery of the magnet shaft 42.
And the end caps 4 on the left and right ends.
A conductive roll is obtained by inserting 1. In the figure, 44 is a bearing.

In the conductive roll thus obtained, the conductive layer 15 is made of the above conductive material. The special conductive material is uniformly dispersed in the phenol resin which is a matrix component of the conductive material.

[0021]

As described above, in the electroconductive roll of the present invention, the cylindrical sleeve is coaxially arranged with a gap provided on the outer circumference of the permanent magnet roller, and the outer circumference of the cylindrical sleeve is circumferentially arranged. Along with the above, since the conductive layer is formed by using the conductive material in which the special conductive material is dispersed in the phenol resin which is the matrix component, the conductive material in the conductive layer is uniformly dispersed. , The electrical resistance is uniform throughout. Moreover, since the phenol resin is used, it has excellent chargeability. Therefore, it is most suitable as a developing roll of an electrophotographic copying machine, and when this conductive roll is used as a developing roll, image unevenness does not occur, a uniform and good copied image is obtained, and a sufficient image density is obtained. Be done.

Next, examples will be described together with comparative examples.

[0023]

[Examples 1 to 5 and Comparative Examples 1 and 2] The raw materials shown in Table 1 below were blended in the proportions shown in the same table (electrical resistance of 10 ⁶ Ω · cm). Then, this mixture was mixed and stirred by a ball mill to prepare a conductive material. Next, the conductive material was dissolved in a solvent of methanol and the viscosity was adjusted to 300 cps to prepare a dip solution. A metal sleeve having an outer diameter of 25 mm was immersed in this solution for coating, then pulled up and dried, and then heated to form a conductive roll having a conductive layer of 50 μm in thickness. And
As shown in FIG. 1, on the outer periphery of the magnet shaft 42,
A conductive roller was manufactured by arranging the metal sleeve 12 on which the conductive layer 15 was formed coaxially in the state where a gap was provided, and further inserting the end caps 41 on both left and right ends thereof.

[0024]

[Table 1]

With respect to each of the conductive rolls thus obtained, the average electric resistance, the dispersion of the electric resistance, the chargeability of the developer (toner), the uniformity of the image (the presence or absence of image unevenness)
And the confirmation of the concentration reproducibility was measured and evaluated by the following method. The results are shown in Table 2 below.

[Average electric resistance] The electrode 2 having the shape shown in FIG.
1 was formed on the roll surface at 20 locations, and the measurement was performed using the measurement system shown in FIG. And the average value of each measured value was calculated | required. In the figure, 20 is a roll, 21a is a main electrode, 21
b is a guard electrode.

[Dispersion of Electric Resistance] In the same manner as the above-mentioned measurement of the average electric resistance, the electric resistance at 20 points of each conductive roll was measured and determined by the difference between the maximum value and the minimum value of the measured values.

[Chargeability of Developer] As shown in FIG. 7, a layer of developer (toner) 22 is formed on the surface of the conductive roll 20, the developer 22 is sucked by a suction pump 23, and measured by a Faraday cage 24. (Faraday cage method).
In the figure, 25 is a filter, 26 is an insulator pipe,
27 is an electrometer. Then, the index when the chargeability of the conductive roll of Comparative Example 1 was taken as 100 and the chargeability was taken as a reference was shown.

[Image Uniformity] A conductive roll was used as a developing roll, incorporated into a copying machine, and an image was output to examine whether or not there was image unevenness. Then, the case where the image unevenness was generated was evaluated as x, and the case where the image unevenness was not generated was evaluated as o.

[Density Reproducibility] An image was printed out in the same manner as described above. In this imaged, a solid black copy was taken at the maximum density, and the density of the copy was measured by a Macbeth reflection densitometer. When the measured value was 1.1 or more, the density reproduction was good, and when the measured value was less than 1.1, the density was light. Then, the sample with good density reproduction was evaluated as ◯, and the sample with light density was evaluated as x, and the results are shown in Table 2 below.

[0031]

[Table 2]

From the results shown in Table 2 above, the product of Example has less variation in electric resistance than the product of Comparative Example, and is excellent in the charging property of the developer. Moreover, the obtained copied image was free from unevenness and had good density reproducibility. From this, it can be seen that the product of Example can be a developing roll excellent in both electric characteristics and chargeability.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a conductive roll of the present invention.

FIG. 2 is an explanatory view showing an example of a method for producing a conductive roll of the present invention.

FIG. 3 is a configuration diagram of an electrophotographic copying machine incorporating a conductive roll.

FIG. 4 is a vertical sectional view of a conductive roll of a conventional example.

FIG. 5 is a plan view showing the configuration and shape of electrodes.

FIG. 6 is a configuration diagram showing a measurement system for measuring the electric resistance of a conductive roll.

FIG. 7 is a configuration diagram showing a measurement state by a Faraday cage method used when evaluating chargeability.

[Explanation of symbols]

 12 Metal Sleeve 15 Conductive Layer 41 End Cap 42 Magnet Shaft 44 Bearing

Claims (1)

Claim: What is claimed is: 1. A conductive roller having a cylindrical sleeve coaxially arranged in the outer circumference of a permanent magnet roller with a gap provided, and a conductive layer formed on the outer circumference of the cylindrical sleeve. 2. The conductive roll, wherein the conductive layer comprises a matrix resin as a matrix component, and at least one of titanium black and magnetic iron oxide is dispersed in the matrix component.