JPH06314047A - Press roller - Google Patents

Abstract

PURPOSE:To prevent the offset of the press roller to be used for an electrophotographic copying machine and a fixing section of a laser printer. CONSTITUTION:This press roller 1 is formed by coating the outer periphery of a metallic arbor 2 thereof with a rubber layer 3 consisting of addition type silicone rubber added with <=5wt.% conductive carbon black. The volume resistivity of the addition type silicone rubber is specified to 10<10> to 10<13>OMEGA.cm. Then, the amt. of the conductive carbon black to be added to the addition type silicone rubber in such a manner that its volume resistivity attains 10<10> to 10<13>OMEGA.cm and, therefore, the rubber layer having no electrostatic chargeability is obtd. and the generation of the offset is obviated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure roller in a fixing section of an electronic copying machine or a laser beam printer (hereinafter abbreviated as LBP).

[0002]

2. Description of the Related Art Heretofore, as a pressure roller in a fixing portion of an electronic copying machine or an LBP, a roller having an outer periphery of a metal core coated with an addition type silicone rubber has been known in order to have good releasability from toner. Has been. In recent years, miniaturization of electronic copying machines and LBPs using a fixing roller has progressed, and the outer diameter of the heat roller and pressure roller used for this has become about 10 to 25 mm. Since it is a roller, the elastic layer covering the outer periphery of the metal core tends to have a low hardness in order to secure a nip width during fixing.
A rubber having a hardness of about 18 degrees is used.

[0003]

When a small-diameter roller, in which the above-mentioned metal core metal is coated with the addition type silicone rubber, is used in the fixing device, the silicone rubber layer is insulative, so that frictional electrification occurs during paper passing, Since the surface of the pressure roller is electrified by minus several thousand volts, an offset phenomenon in which the toner attached to the fixing roller is transferred to the paper again often occurs. Therefore, in order to eliminate the above-mentioned offset phenomenon, a fluorine-containing surfactant is contained in a silicone rubber layer as disclosed in JP-A 1-2136833 as a means for preventing static electricity of a pressure roller. A pressure roller was proposed.

The heating and pressure roller fixing device disclosed in the above-mentioned publication uses the pressure roller having a surface layer composed of a silicone rubber composition in which a fluorine-containing surfactant is added to the silicone rubber, and Since the silicone rubber layer has a medium resistance (10 ⁷ to 10 ⁹ Ω · cm), charging of the surface of the pressure roller can be suppressed, and the offset as described above can be greatly reduced.

However, when the above-mentioned fluorine-containing surfactant is added to the addition type silicone rubber composition,
Curing obstacles to the addition reaction occur, and even if the addition amount is reduced, problems such as a slow vulcanization rate and a reduction in compression set are induced. Further, when such a pressure roller is used for a long period of time, toner adhesion may occur on the surface of the pressure roller, and further, the cost of the pressure roller increases because the fluorine-based surfactant is expensive. There were also points. Therefore, an object of the present invention is to provide a pressure roller having no vulcanization failure, excellent compression set, and no offset.

[0006]

The pressure roller according to the present invention has been subjected to intensive research to solve the problems of the above-mentioned conventional apparatus, and as a result, the pressure roller is Characteristically, the additive type silicone rubber covering the outer circumference of the metal core of the roller contains 5% by weight or less of conductive carbon black and has a volume resistivity of 10 ¹⁰ to 10 ¹³ Ω · cm. Is.

[0007]

In the pressure roller according to the present invention, the volume resistivity of the silicone rubber is 10 when the amount of the conductive carbon black added to the addition type silicone rubber coated on the outer periphery of the metal core is 5% by weight or less. ^Since the amount of the conductive carbon black is regulated as described above so as to be ¹⁰ to 10 ¹³ Ω · cm, the rubber itself does not have conductivity and therefore the offset phenomenon does not occur.

[0008]

Embodiments of the present invention will be described with reference to the drawings.
Reference numeral 1 denotes a pressure roller, 2 denotes a metal cored bar of the pressure roller 1, and the outer periphery of the metal cored bar 2 is covered with a rubber layer 3 made of an addition type silicone rubber. The above-mentioned addition type silicone rubber contains 5% by weight or less of conductive carbon black.

The composition of the above-mentioned addition type silicone rubber is
Although not particularly limited, (A) vinyl group-containing diorganosiloxane, (B) organohydrosiloxane, (C) platinum-based catalyst and reaction control agent, (D) inorganic filler, (E) conductivity Water is used as an essential component, and if necessary, usually 8% by weight or less of a non-functional silicone oil is added to improve releasability of the toner.

In the present embodiment, the amount of conductive carbon black added is set to 5% by weight or less so that if the added amount exceeds 5%, the rubber itself may have conductivity depending on the type of conductive carbon. This is because In addition, when the conductive silicone rubber is used, the roller itself becomes energized, and the antistatic effect itself can be achieved.
Since electricity flows through the fixing device itself, it cannot be used because an image cannot be formed by the charged toner.

Therefore, in this embodiment, it is necessary to control the type and amount of the conductive carbon black so that the volume resistivity of the silicone rubber is 10 ¹⁰ to 10 ¹³ Ω · cm. That is, when the volume resistivity is 10 ¹⁴ Ω · cm or more, there is no antistatic effect. In addition, since ordinary silicone rubber is an insulator of 10 ¹⁴ Ω · cm or more, simply adding conductive carbon black causes 10 ⁶ to 10 ⁹ Ω.
・ The semiconductive area in the cm range cannot be controlled and is 10 ⁵ Ω.
・ Easy to have conductive area below cm.

The conductive carbon black used in this example is acetylene black Denka Black (trade name, manufactured by Denki Kagaku Kogyo Co., Ltd.), oil furnace black Toka Black (trade name, Tokai Carbon Co., Ltd.), Mitsubishi Conductive Carbon (trade name, manufactured by Mitsubishi Kasei Co., Ltd.), Vulcan (trade name, manufactured by Cabot), Printex (trade name, manufactured by Degussa), Ketjen Black (trade name, manufactured by Akzo), etc. Black is used timely. Further, a conductivity-imparting agent other than carbon black such as metal powder, metal oxide, and carbon fiber may be used together.

The rubber hardness of the addition type silicone rubber composition in this embodiment is not particularly limited, and it is not limited to JI.
The SA hardness tester can be arbitrarily selected within the range of 3 to 60 degrees,
In the case of a small-diameter roller, the range of 8 to 18 degrees is desirable also in this embodiment from the viewpoint of the balance between the hardness and the nip width. Further, the compounding formulation of the filler and the like is not particularly limited, and may be determined in consideration of the mechanical properties of the cured addition-type silicone composition layer, that is, physical strength, rubber strength, compression set, and the like. There are, for example, aerosil and fumed silica, wet silica such as high sill and nip sill, diatomaceous earth such as celite and radiolite, quartz powder such as minucil and crystallite, and these fillers are usually used. Used in combination with several types. Further, in order to impart characteristics such as thermal conductivity, in addition to the above-mentioned filler, aluminum oxide (alumina),
Titanium oxide, magnesium oxide, aluminum silicate,
Zinc oxide, iron oxide, calcium carbonate, etc. may be used in combination, and a heat-resistant agent such as cerium oxide and an acid acceptor such as magnesium oxide may be added in consideration of aging properties.

The metal cored bar 2 and the silicone rubber layer 3 may be bonded to each other by using a normal addition type silicone rubber primer. 101A & B (trade name, manufactured by Shin-Etsu Chemical Co., Ltd.) can be exemplified. In addition, after forming the silicone rubber layer 3 on the metal cored bar 2, the rubber layer may be polished to obtain the outer diameter dimension and accuracy, or may be molded by molding.

Using the composition according to this example, a total length of 24
After containing 5% by weight or less of conductive carbon black on the outer periphery of a metal core metal having a diameter of 3 mm and an outer diameter of 9 mm, and coating a silicone rubber layer having a volume specific resistance of 10 ¹⁰ to 10 ¹³ Ω · cm, Polished to have an outer diameter of 17 mm. next,
When this pressure roller 1 was attached to a copying machine Mini Copier FC-2 (trade name) manufactured by Canon Inc. and a durability test was conducted on an actual machine, there was no problem such as offset after a durability test of 30,000 sheets. It was found that it did not occur and had sufficient durability.

According to the present embodiment, the conductive carbon black added to the addition type silicone rubber coating the outer periphery of the metal core 2 is 5% by weight or less and the volume resistivity of the addition type silicone rubber is 10 ¹⁰ to ¹⁰ 10. ^{Since it is set to 13} Ω · cm, the rubber layer 3 coated on the outer circumference of the metal cored bar 2 of the pressure roller 1 does not have conductivity, and therefore the offset phenomenon does not occur. With the rubber layer 3 formed on the outer circumference of the pressure roller 1, it is possible to obtain a pressure roller excellent in compression set.

[0017]

EFFECT OF THE INVENTION In the pressure roller according to the present invention, 5% by weight or less of conductive carbon black is added to the addition type silicone rubber which coats the outer periphery of the metal core metal so that the volume resistivity of the silicone rubber is 10 ^10. Since it is set to -10 ¹³ Ω · cm, the addition type silicone rubber which is the rubber layer forming the outer periphery of the pressure roller has an antistatic effect, and therefore does not cause an offset phenomenon. In addition, a pressure roller excellent in compression set could be obtained by the rubber layer on the outer circumference.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view showing the structure of a pressure roller.

[Explanation of symbols]

 1 Pressure roller 2 Metal core 3 Rubber layer

Claims (1)

[Claims] 1. A pressure roller having an outer periphery of a metal core coated with an addition type silicone rubber, wherein the addition type silicone rubber contains 5% by weight or less of conductive carbon black and has a volume resistivity of 10 or less. ^A pressure roller having a resistance of ¹⁰ to 10 ¹³ Ω · cm.