JPH09186009A - Resistance adjusting method of conductive silicon rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resistance adjusting method for obtaining a conductive silicon rubber roll whose resistance changes little over aging in a practical use. SOLUTION: A conductive silicon rubber roll formed by covering a conductive central object with a conductive elastic member layer composed of conductive silicon rubber composite is brought into forcible contact with a roll electrode. A voltage is applied across the conductive central object of the conductive silicon rubber roll and the roll electrode, in the state that the rubber roll and the roll electrode are made to face each other and rotated. Thereby a specified amount of surface oxide material is electrically formed on the conductive silicon rubber roll, and resistance of the conductive silicon rubber roll is adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resistance value adjusting method for obtaining a conductive silicone rubber roll whose resistance value changes little with time during actual use.

[0002]

2. Description of the Related Art Electrostatic transfer type copying machines, laser beam printers, etc., such as a charging section, a developing section, and a transfer section, usually have a conductive center material made of a metal such as iron, aluminum or stainless steel. A conductive roll having a structure in which a conductive elastic body layer made of a conductive rubber composition is formed by coating is used in a state where a voltage of about 0.5 kv to 4.0 kv is applied. Examples of the conductive rubber composition forming the conductive elastic layer include, as main components, various synthetic rubbers such as ethylene-propylene rubber, silicone rubber, and urethane rubber, and carbon black particles as a conductivity imparting agent, A mixture of conductive particles such as graphite particles in a predetermined ratio is used.

[0003]

Among these, the conductive rolls using conductive ethylene-propylene rubber or conductive urethane rubber have a temperature and humidity higher than those using conductive silicone rubber. Although it has an advantage that the resistance value changes little with time and is excellent in resistance value stability, it has a drawback in that the resistance value stability in an environment from low temperature and low humidity to high temperature and high humidity is poor. Further, recently, since improvement in durability at high temperature and correspondence to fire resistance in various standards such as UL and CSA are required, when considering the correspondence to these future technological trends, A conductive roll using a conductive silicone rubber is suitable. However, in the conductive silicone rubber roll,
Si generated and deposited from low-molecular siloxane contained in silicone rubber, which easily volatilizes, and from the base polydimethylsiloxane itself due to the effect of corona discharge when voltage is applied.
There is a drawback that the resistance value increases with time due to O ₂ , SiC and the like.

The present invention has been made on the basis of such a point, and an object thereof is to provide a resistance value adjusting method for obtaining a conductive silicone rubber roll whose resistance value hardly changes with time in actual use. To do.

[0005]

Means for Solving the Problems As a result of various studies to achieve the above-mentioned object, the present inventor found that if the increase in the resistance value over time is collectively expressed in advance, the resistance in actual use will be reduced. The inventors have found that a conductive silicone rubber roll whose value does not change with time can be obtained, and completed the present invention. That is, the method for adjusting the resistance value of the conductive silicone rubber roll according to the present invention is a conductive silicone rubber roll obtained by coating a conductive elastic material layer made of a conductive silicone rubber composition on a conductive center material, to form a roll electrode. A surface oxide is electrically placed on the conductive silicone rubber roll by applying a voltage between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode in a state of being pressed against each other and rotated while facing each other. It is characterized in that the resistance value of the conductive silicone rubber roll is adjusted by quantitative formation.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION A conductive silicone rubber roll to which the present invention can be applied has a conductive elastic material made of a conductive silicone rubber composition on a conductive center material made of metal such as iron, aluminum and stainless steel. Any body layer may be used as long as it is formed by coating. A solid conductive elastic material layer or a sponge-shaped conductive elastic material layer (foamed conductive elastic material layer) coated on a conductive center material has been conventionally known. Can be applied.

The roll-shaped electrode used in the present invention may be any one that has electrical conductivity and strength against pressure contact. Examples of the constituent material include metals such as iron, aluminum, and stainless steel as in the conductive center material of the conductive silicone rubber roll.

In the present invention, first, the conductive silicone rubber roll is pressed against the roll-shaped electrode with a predetermined force.
The pressing force is not particularly limited because it varies depending on the hardness of the conductive silicone rubber roll used, but preferably, the nip width when the conductive silicone rubber roll is pressed against the roll-shaped electrode is 5 times the outer diameter of the conductive silicone rubber roll. It is set to be in the range of ˜50%.

Then, the conductive silicone rubber roll and the roll-shaped electrode are rotated so as to face each other, and in that state, a voltage is applied between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode to form the conductive silicone rubber roll. A predetermined amount of surface oxide is electrically formed to adjust the resistance value. According to the present invention, the resistance value of the conductive silicone rubber roll is thus collectively raised to a desired resistance value in advance, thereby preventing the resistance value from changing with time during actual use. In other words, a voltage is applied in advance before actual use, whereby the low-molecular-weight siloxane or polydimethylsiloxane contained in the silicone rubber is forcibly decomposed and deposited to form a predetermined amount of surface oxide, and the resistance value is collectively measured. And raise it.

It is preferable that the applied voltage is 2.5 kV or more for efficient resistance value adjustment. If it is less than 2.5 kv, the surface oxide cannot be sufficiently formed, and it becomes difficult to efficiently adjust the resistance value. The upper limit value of the applied voltage is not particularly limited as long as the conductive silicone rubber composition does not deteriorate or causes dielectric breakdown. If the applied voltage is set higher than 2.5 kv, the amount of surface oxide formed by the decomposition and deposition of the above-mentioned components also increases, so that the resistance value is higher than that when 2.5 kv is applied. That is, by appropriately setting the applied voltage in the range of 2.5 kv or more, the resistance value of the conductive silicone rubber roll can be efficiently adjusted to a higher desired resistance value.

The application time is also not particularly limited. The resistance value is appropriately set in consideration of the original resistance value of the conductive silicone rubber roll used, the thickness and length of the conductive elastic layer, the applied voltage, the desired resistance value, and the like.

[0012]

EXAMPLES The present invention will be described in more detail below with reference to examples.

In the following examples, as a conductive silicone rubber roll, a conductive silicone rubber composition having a thickness of 4.0 mm and a length of 215 mm was formed on a conductive center material made of stainless steel having an outer diameter of 6 mm and a length of 260 mm. A foamed conductive elastic layer made of
An Asker C hardness of 40 ° and an initial resistance value of 10 ⁷ to 10 ⁸ Ω were used. Moreover, as a roll-shaped electrode, an outer diameter of 25
An iron columnar body having a length of mm and a length of 300 mm and having a motor mounted on one end was used. In the following examples, when a voltage was applied, the conductive center material of the conductive silicone rubber roll was set to the high voltage side and the roll-shaped electrode was set to the ground side, but the same result can be obtained by applying the voltage in reverse. . In addition, the resistance value is measured by applying a load of 500 g to both ends of the roll, pressing the roll against the aluminum plate, and then calculating the current value flowing when a DC voltage of 500 V is applied between the conductive center material and the aluminum plate. I decided to do it. Roll 9
It was decided to rotate at 0 degree and to show the average value at 4 points.

Example 1 First, a conductive silicone rubber roll (initial resistance value: 3.
A load of 1 kg each was applied to both ends of (8 × 10 ⁷ Ω), and the roll-shaped electrodes were pressed against each other, and both were opposed and rotated at a rotation speed of 30 rpm. Then, in that state, between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode, 0.
The DC voltage was applied up to 3.0 kv by stepping up from 5 kv to 0.5 kv. The application time was 90 seconds, and the resistance value was measured after each voltage application. The results are shown in Table 1.

Example 2 First, a conductive silicone rubber roll (initial resistance value: 8.
A load of 1 kg was applied to both ends of (7 × 10 ⁷ Ω), and the roll-shaped electrodes were pressed against each other, and both were rotated opposite to each other at a rotation speed of 30 rpm. Then, in that state, between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode, 3.
A direct current voltage of 0 kv was applied for 120 seconds and the resistance value was measured. Then, on the assumption of actual use, put 5 on both ends of the roll.
Apply a load of 00g each and press it into contact with the roll electrode,
Both of them were rotated opposite to each other at a rotation speed of rpm, and in that state, a DC voltage of 1.5 kv was continuously applied for 20 minutes. The resistance value was measured every 5 minutes. The results are shown in Table 2.

Example 3 First, a conductive silicone rubber roll (initial resistance value: 3.
A load of 1 kg was applied to both ends of (1 × 10 ⁷ Ω), and the roll-shaped electrodes were pressed against each other, and both were rotated at 30 rpm. Then, in that state, between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode, 2.
A DC voltage of 5 kv was applied for 120 seconds and the resistance value was measured. After that, 1 for both ends of the roll, assuming actual use.
Apply a load of kg each and press it into contact with the roll electrode for 30r
Both of them were rotated opposite to each other at a rotation speed of pm, and in this state, a DC voltage was applied up to 2.5 kv from 0.5 kv and 4.0 kv. The application time was 120 seconds, and the resistance value was measured after each voltage application. The results are shown in Table 3.

Comparative Example Conductive Silicone Rubber Roll (Initial Resistance Value: 8.9 × 1
(0 ⁷ Ω), a load of 500 g is applied to each end of the roll-shaped electrode, and the roll-shaped electrodes are pressed against each other. . The resistance value was measured every 5 minutes. Table 4 shows the results
It was shown to.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

According to the measurement result of Example 1, 2.5 kv
When the above DC voltage is applied, the difference from the initial resistance value (increase in resistance value) becomes large. Therefore, in the present invention, a DC voltage of 2.5 kv or more is applied in advance before actual use. It can be understood that the adjustment to the desired resistance value can be efficiently performed by performing such resistance value adjustment.

According to the measurement results of Example 2 and Comparative Example, in Example 2, the change with time from the resistance value after applying 3.0 kv, 120 seconds to the resistance value after 20 minutes of actual use was 0.09 order. In contrast, the comparative example is actually used from the initial resistance value 2
Since the change with time to the resistance value after 0 minutes is 0.47 order, it can be understood that the resistance value change according to the present invention can reduce the change with time in the actual resistance value.

According to the measurement result of Example 3, by appropriately setting the applied voltage in the range of 2.5 kv or more,
It is understood that the resistance value of the conductive silicone rubber roll can be efficiently adjusted to a higher desired resistance value.

[0025]

As described in detail above, according to the resistance value adjusting method of the present invention, it is possible to obtain a conductive silicone rubber roll whose resistance value is less likely to change with time during actual use.
Therefore, it becomes possible to actually make use of the excellent flame retardancy inherent in silicone rubber and resistance value stability against environmental changes, etc., and it is possible to secure various OA equipment such as electrostatic transfer copying machines and laser beam printers. This greatly contributes to improved productivity and cost reduction.

Claims (1)

[Claims] 1. A conductive silicone rubber roll having a conductive center material coated with a conductive elastic layer made of a conductive silicone rubber composition is pressed against a roll-shaped electrode and rotated in a state of being opposed to each other. A predetermined amount of surface oxide is electrically formed on the conductive silicone rubber roll by applying a voltage between the conductive center material of the conductive silicone rubber roll and the roll-shaped electrode. The method for adjusting the resistance value of a conductive silicone rubber roll is characterized in that the resistance value is adjusted.