JPS6211343B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a roller used in an electrophotographic copying machine.

An electrophotographic copying machine has a charging roller, a developing roller,
Rollers are used everywhere, such as transfer rollers and cleaning rollers. Conventionally, these rollers include (1) a conductive elastic material made by mixing silicone rubber with conductive powder such as carbon powder or metal powder (Cu, Al, etc.), and (2) a conductive elastic material on the outer periphery of the conductive elastic material. Furthermore, those provided with an insulating coating for resistance adjustment are known.

However, in these rollers, the conductive powder is simply dispersed uniformly in the rubber, and conductivity is imparted by the contact between the particles of the conductive powder, so it is not always possible to achieve uniform contact between the particles. The resistance is not uniform over the details. Furthermore, since the contact between particles of the conductive powder changes depending on unevenness in external pressure, unevenness tends to occur in the roller itself, and this tendency is remarkable when the rubber hardness is low or when the roller is made of foam. Furthermore, the way this interparticle contact changes depending on changes in temperature and by passing an electric current through it. Due to such changes or non-uniformity of resistance, there is a drawback that when charging, development, transfer, and cleaning are performed using conventional rollers, unevenness occurs in each of them.

SUMMARY OF THE INVENTION An object of the present invention is to provide a roller that eliminates the above-mentioned drawbacks and can be used for a variety of purposes in electrophotographic copying machines. Another object of the present invention is to provide a roller for an electronic copying machine that is elastic and has considerable electrical conductivity.

That is, the present invention relates to a charging, developing, transferring, or cleaning roller in an electrophotographic copying machine, and the roller has a specific amount of carbon fiber and metal powder coated with rubber around a metal shaft connected to a power source. It is characterized by a rubber layer mixed into an elastic body.

The present invention will be explained in more detail below with reference to the accompanying drawings. FIG. 1 is a schematic diagram showing the main parts of a typical electrophotographic copying machine, in which 1 is a drum-shaped photoreceptor, 2 is a charging roller, 3 is an optical system, 4 is a developing roller, 5 is a transfer roller, 6 7 is a cleaning roller, 7 is a toner, 8 is an image receiving paper, and 9, 9',
9'', 9 is a power source. Note that the photoreceptor 1 is coated with a photoconductive material (for example, selenium, polyurethane, etc.) on a metal drum.
N-vinylcarbazole, etc.) is vapor-deposited or coated, and each roller 2, 4, 5
and 6 are axes 21, 41, 51 or 6 respectively
1 at the center, and a rubber layer with carbon fiber and metal powder dispersed in a rubber elastic body is attached around this axis to have a circular cross section.

As is clear from the above description, the rollers according to the present invention include a charging roller 2, a developing roller 4,
This is applied to both the transfer roller 5 and the cleaning roller 6. The roller of the present invention has a rubber elastic body mixed with carbon fiber in an amount of 1 to 50% by weight, preferably 1 to 35% by weight, and further contains carbon powder and metal powder such as Al, Cu, or Ag.
It is mixed in a range of 0.1 to 50% by weight. however,
The total amount of carbon fiber and carbon powder or metal powder must be about 50% by weight or less. The need for this total amount to be approximately 50% by weight or less is a value obtained experimentally. In other words, if the filler such as the carbon fibers blended into the rubber elastic body is up to about 50% by weight, the rubber will sufficiently cover them, and as long as this is the case, the function as a rubber elastic body will be maintained. However, if the rubber elastic body contains more filler than about 50% by weight, the roller no longer functions as an elastic body.

Materials for the rubber elastic body used here include nitrile rubber, acrylic rubber, neoprene rubber, natural rubber, SBR, silicone rubber, fluorine rubber, urethane rubber, etc., and the rubber hardness is JIS
A size between A5 and 90° is suitable. Carbon fiber has a carbon content of about 90 to 98%, and is a cellulose fiber.
Preheating acrylic fibers and polyvinyl alcohol fibers in inert gas (temperature 200-500℃ or less)
It is made by firing it at a temperature of 800 to 1,200°C, and is easily available as a commercial product.

When carbon fibers are mixed in the rubber elastic body, the carbon fibers themselves are conductive, so even a small amount of carbon fibers will make the roller conductive. However, if the amount of carbon fiber mixed is less than 1% by weight, the strength of the roller will not be sufficient, and if it exceeds 50% by weight, it cannot be practically formed into a roller with good surface properties.

Although it is not necessarily necessary to mix conductive powder (carbon powder, metal powder, etc.) into the roller of the present invention, a roller made only of rubber elastic body and carbon fiber has a rough texture. It is desirable that appropriate amounts of conductive powder and general fillers such as silica, inorganic powder, etc. are mixed.

FIG. 2 shows a rubber elastic body 101 and a carbon fiber 1
02 and conductive powder 103 are mixed. In this way, carbon fiber 10
When the conductive powder 103 and the conductive powder 103 are intertwined with each other, even more uniformity of electrical resistance can be obtained. The average particle size of the conductive powder 103 is about 0.5 μm, and the carbon fiber 102 is a collection of several thousand filaments of about 0.5 to 100 μm.

In order to actually make the roller according to the present invention, carbon fiber is added while kneading rubber dissolved in an appropriate solvent using three rolls, or rubber and conductive powder dissolved in an appropriate solvent are kneaded using three rolls. Carbon fibers may be added to the mixture while kneading it, and the kneaded product may be applied around a metal shaft or covered and fixed by other known means. In this case, if the carbon fiber is subjected to a surface treatment such as silane coupling in advance, adhesion with the conductive powder will be improved. However, an increase in the amount of carbon fiber mixed in increases the hardness of the roller;
It is necessary to adjust the amount of mixture within a range that does not exceed 100 degrees.

Furthermore, if glass fiber is further mixed in an amount of 30% by weight or less, the reinforcing effect will be increased, and it will be mechanically strong and will not cause distortion, which is advantageous.

The roller of the present invention can be used even if the rubber elastic body mixed with carbon fiber is not directly provided on the metal shaft. (C) Contrary to (B) above, the amount of carbon fiber decreases as it approaches the shaft. Variations may be envisaged, such as by constructing it in one layer or in multiple layers.

The thus obtained roller of the present invention is used as a charging roller, a transfer roller, etc. that constitute a part of an electrophotographic copying machine, but when this roller is used as a charging roller, the surface of the photoreceptor is The electric charge will be charged like this. Furthermore, when used as a developing roller, since the resistance value of the roller surface is uniform, toner adheres uniformly and development is uniformly performed, particularly in solid areas. When used as a transfer roller, uneven transfer can be prevented, similar to when used for charging.
Furthermore, when used as a cleaning roller, residual toner adheres uniformly, resulting in an extremely clean surface of the photoreceptor.

These excellent effects of the roller of the present invention are as follows:
This is thought to be because this roller is less susceptible to changes in temperature, current, etc. In addition, it is thought that in rollers containing conductive powder, not only the uniformity of interparticle contact is improved, but also the presence of carbon fibers prevents deterioration of interparticle contact even under high pressure.

It goes without saying that the amount of carbon fiber, conductive powder, etc. mixed into the roller of the present invention may be changed depending on the application. Next, examples will be shown.

Example 1 Conductive silicone rubber (8603U, Shin-Etsu Chemical KK
When we gradually mixed carbon fiber (Torayaki Yoppudo Fiber T007, Toray KK) into JIS A50°, the conductivity was always good, but the amount of carbon fiber mixed exceeded 30% by weight. It was observed that the elasticity of the roller deteriorated.

Therefore, by overcoating this roller with silicone rubber to a thickness of 5 .mu.m to 0.5 mm, preferably 10 .mu.m to 300 .mu.m, as reinforcement, a roller which could be put to practical use as a transfer roller for an electrophotographic copying machine was obtained. Carbon fibers can also be incorporated into the overcoat agent, but the amount should be 30% by weight or less, preferably
It was confirmed that the amount was 20% by weight or less.

Example 2 When KE530U (JIS A27°, manufactured by Shin-Etsu Chemical KK) was used in place of 3603U, the transfer roller did not lose its elasticity even when carbon fiber was mixed in an amount of 30 to 50% by weight.

Example 3 KE12 (silicone RTV rubber, manufactured by Shin-Etsu Chemical KK)
A roller was made by mixing 1% by weight of carbon fiber into the material. This roller was used as a charging roller with an applied voltage of 1 KV. On the other hand, when this was further overcoated with KE12 to a thickness of approximately 50 μm to form a charging roller, the applied voltage was increased by 1000 V, but the uniformity was even better.

Here, whether or not the charge was uniform was determined by whether or not the toner was evenly applied to the photoreceptor by a magnetic brush development method after being charged. Also,
Regarding development, the same one that had been used as a charging roller was used as a developing roller, and judgment was made by whether or not the toner uniformly adhered to the photoreceptor after corona charging. Regarding the transfer, the charging roller was used as the developing roller in the same manner as described above, and judgment was made based on whether or not the transfer was missed, for example, ordinary fine print was uniformly adhered to the transfer paper (image receiving paper) side. Furthermore, regarding cleaning, as in the case above, a charging roller was first used and then a cleaning roller was used, and judgment was made based on how much of the residual toner on the photoreceptor after transfer was transferred to the cleaning roller side. .

As a result, the obtained roller satisfied all of the above criteria. Moreover, the rollers in Example 1 and Example 2 showed similar results.

Example 4 KE34 (silicone RTV rubber, manufactured by Shin-Etsu Chemical KK) -
A developing roller was prepared by mixing 5% by weight of carbon fiber into JIS A50° and a volume resistivity of 10 ⁴ to ^{10 5} Ωcm.
The obtained roller was stable with little resistance change. Incidentally, a product having this composition could also be used as an endless belt.

Further, another roller was made by coating this developing roller with KE34 mixed with 3% by weight of carbon fiber to a thickness of 50 μm, and this roller was also stable with little resistance change.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing the main parts of an electrophotographic copying machine;
FIG. 2 is a diagram showing a state in which carbon fibers and conductive powder are mixed into the rubber elastic body. DESCRIPTION OF SYMBOLS 1...Photoreceptor, 2...Charging roller, 3...Optical system, 4...Developing roller, 5...Transfer roller, 6...
...Cleaning roller, 8...Receiving paper, 101...
...Rubber elastic body, 102...Carbon fiber, 103
...Conductive powder.

Claims (1)

[Claims] 1. In the charging roller, developing roller, transfer roller, or cleaning roller used in an electrophotographic copying machine, the roller contains carbon fiber in a rubber elastic body in a range of 1 to 50% by weight and metal powder in a range of 0.1 to 50% by weight. An electrophotographic copying apparatus characterized in that a rubber layer having a circular cross section and containing a total of about 50% by weight of carbon fiber and metal powder is attached around a metal shaft connected to a power source. Machine roller.