JP2001042681A - Fixing roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing roller, capable of dealing with speed up of copying having superior release property and wear resistance and full-coloring of images. SOLUTION: This fixing roller has a reformed fluororesin layer formed by having a fluororesin irradiated with ionizable radiation in the range of 1 kGy to 10 MGy in irradiation dose, in a state where the fluororesin is heated to its melting point or higher under an inert gas atmosphere of 100 Torr or lower in oxygen concentration directly or via another layer on the outer periphery of a metallic core shaft.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing roller used for heat fixing of a toner image in an electronic copying machine, a laser beam printer, a laser facsimile or the like.

[0002]

2. Description of the Related Art In an image forming apparatus such as an electrophotographic copying machine, generally, a charging step of uniformly and uniformly charging a photosensitive drum, an exposure step of forming an electrostatic latent image on the photosensitive drum by exposure, and a toner Developing the electrostatic latent image into a visible image, transferring the toner image on the photosensitive drum to the transfer material, fixing the toner image on the transfer material, and applying the toner image to the photosensitive drum after the transfer process. The image is formed through a cleaning process for cleaning the remaining toner.

In the fixing step, a toner image is fixed on a transfer material by using various methods such as heating, pressurizing, and solvent vapor. Usually, a fixing roller having a built-in heat source and a pressing roller are used. The transfer material is passed through the gap, and the toner on the transfer material is heated and melted and fixed. As the fixing roller, a roller having a structure in which a fluororesin layer is formed directly or via a rubber layer on the outer surface of a roller-shaped substrate to prevent offset is used. As the fluororesin, a tetrafluoroethylene-based polymer, a tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer, a tetrafluoroethylene-hexafluoropropylene-based copolymer, or the like is used. A fixing roller having a fluororesin layer formed on its surface generally has good releasability and abrasion resistance, prevents contamination of the roller surface, and has excellent fixability.

[0004]

However, in recent years, with the increase in copying speed and the full color image, it is required to lower the melting point of toner, and a fixing roller having a fluororesin layer formed by changing the toner component. In this case, the offset phenomenon frequently occurs, and the wear resistance is insufficient, so that a problem occurs in durability. That is, when the melting point of the toner is lowered, the toner tends to adhere to the surface of the fixing roller, and the offset phenomenon is likely to occur.In addition, due to the high speed of copying, the load on the fixing roller increases, and the fluororesin layer is worn. It becomes easier. In particular, the fixing roller has a high temperature (100 to 150).
° C), a material which softens easily at that temperature further wears, and the releasability becomes insufficient, so that the offset phenomenon frequently occurs. As described above, the fixing roller provided with the fluororesin layer is required to be improved in terms of wear and thermal stability.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing roller having excellent releasability and abrasion resistance, which can cope with high-speed copying and full-color images.

[0006]

According to the present invention, in order to achieve the above object, a fluororesin is applied to an outer periphery of a metal core shaft directly or through another layer under an inert gas atmosphere having an oxygen concentration of 100 torr or less. An object of the present invention is to provide a fixing roller having a modified fluororesin layer formed by irradiating an ionizing radiation in a range of 1 kGy to 10 MGy in a state of being heated to a melting point of the fluororesin or higher.

As the material of the metal core shaft, metals such as aluminum and stainless steel, ceramics and the like are generally used. The modified fluororesin layer is formed directly on the outer periphery of the metal core shaft or via an intermediate layer such as a rubber layer. The rubber layer may be a single layer, or may be formed in two or more layers as desired. The thickness is 0.1 to 1 mm, preferably 0.15 to 0.5.
mm. Examples of the material for forming the rubber layer include various silicone rubbers and various fluorine rubbers.

The fluororesin used in the present invention includes:
PTFE, tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymer (hereinafter, referred to as “PFA”), or tetrafluoroethylene-hexafluoropropylene-based copolymer (hereinafter, referred to as “FEP”).

[0009] Among the above PTFE, perfluoro (alkyl vinyl ether), hexafluoropropylene,
Also included are those containing 1 mol% or less of polymerized units based on copolymerizable monomers such as (perfluoroalkyl) ethylene or chlorotrifluoroethylene. In the case of the copolymer type fluororesin, a small amount of the third component may be included in the molecular structure.

In the modified fluororesin of the present invention, an irradiation dose of 1 kGy of ionizing radiation is applied to the fluororesin in an inert gas atmosphere having an oxygen concentration of 100 torr or less, preferably 10 torr or less and heated to a temperature higher than its melting point. It is obtained by irradiating in the range of 10 MGy. In the present invention, γ-rays, electron beams, X-rays, neutron rays, high-energy ions, or the like are used as ionizing radiation.

When irradiating with ionizing radiation, it is necessary to heat the fluororesin above its crystalline melting point. For example, when PTFE is used as the fluororesin, it is necessary to irradiate ionizing radiation while heating the fluororesin to a temperature higher than the crystal melting point of 327 ° C. of this material, and use PFA or FEP. In this case, the former is heated to a temperature higher than the melting point specified at 310 ° C. and the latter at 275 ° C. for irradiation. Heating the fluororesin above its melting point activates the molecular motion of the main chain constituting the fluororesin, and as a result, it is possible to efficiently promote the cross-linking reaction between molecules.
However, excessive heating will cause the main chain of the molecule to be broken and decomposed. Therefore, from the viewpoint of suppressing the occurrence of such a depolymerization phenomenon, the heating temperature should be one point lower than the melting point of the fluororesin.
It should be kept within the range of 0-30 ° C. higher.

As a method of manufacturing the fixing roller of the present invention, a method of applying a modified fluororesin powder to the outer periphery of a metal core shaft directly or through another layer and baking it, or a method of unmodified fluororesin tube May be provided directly or via another layer on the outer periphery of the metal core shaft, and then irradiated with ionizing radiation under predetermined conditions, but the method is not limited thereto. The thickness of the modified fluororesin layer is
A range of 5 to 200 μm is preferred.

In the present invention, the fluororesin layer may be formed solely of the modified fluororesin, or the fluororesin layer may be formed of a mixture containing the modified fluororesin and an unmodified fluororesin. Examples of unmodified fluororesins include tetrafluoroethylene-based polymers, tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymers, tetrafluoroethylene-hexafluoropropylene-based copolymers, and ethylene-tetrafluoroethylene-based copolymers. Examples include a polymer, an ethylene-chlorotrifluoroethylene-based copolymer, a propylene-tetrafluoroethylene-based copolymer, and a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based copolymer. The mixing ratio of the modified fluororesin and the unmodified fluororesin can be appropriately selected from the ratio of the modified fluororesin of 99 to 1% by weight and the unmodified fluororesin of 1 to 99% by weight.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [Example 1] PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 40 μm), oxygen concentration 0.2 torr, nitrogen concentration 7
The reforming treatment was performed by irradiating 100 kGy of an electron beam at a heating temperature of 340 ° C. in an atmosphere of 55 torr. This modified P
TFE was pulverized with a jet mill until the average particle size was about 10 μm. 20% by weight of the modified PTFE powder and 80% by weight of a fluororesin powder mixed at a ratio of 80% by weight of a commercially available unmodified PFA powder (MP102, manufactured by DuPont, average particle size 25 μm) were mixed. This mixed powder is subjected to electrostatic coating at a voltage of 35 kV on a degreased aluminum alloy core shaft (a cylindrical shape having a diameter of 39 mm, a length of 330 mm, and a thickness of 3 mm), and is heated at 350 ° C. for 30 minutes in an electric furnace. Bake,
After cooling outside the furnace, the coating layer is polished to 0.4S and the thickness is 30 μm.
A modified fluororesin layer was formed.

Example 2 A commercially available PTFE tube (thickness: 40 μm) was coated on a degreased aluminum alloy core shaft (a cylindrical shape having a diameter of 39 mm, a length of 330 mm, and a thickness of 3 mm) and an oxygen concentration of 0.2 torr. In a nitrogen atmosphere of 755 torr, a reforming treatment was performed by irradiating 100 kGy of an electron beam while rotating the roller at a heating temperature of 340 ° C. After cooling, the coating layer was polished to 0.4 S to form a modified fluororesin layer having a thickness of 30 μm.

Comparative Example 1 A core shaft (39 mm in diameter, 330 mm in length, 3 mm in thickness) made of a degreased PFA powder (MP102, manufactured by DuPont, average particle size 20 μm) was degreased.
Is cylindrically coated with a voltage of 35 kV, baked in an electric furnace at a temperature of 350 ° C. for 30 minutes, allowed to cool outside the furnace, and polished the coating layer to 0.4 S to a thickness of 30 μm. A fluororesin layer was formed.

Comparative Example 2 PTFE molding powder (trade name: G-163, manufactured by Asahi Glass Co., Ltd., average particle size: 10 μm)
m) An aluminum alloy core shaft (39 mm in diameter, length 330) obtained by degreased a mixture of 20% by weight and 80% by weight of a powder mixture of PFA powder (MP102, manufactured by DuPont, average particle size 20 μm).
mm, cylindrical shape with a thickness of 3 mm), apply an electrostatic coating at a voltage of 35 kV, bake it in an electric furnace at a temperature of 350 ° C. for 30 minutes, cool it outside the furnace and polish the coating layer to 0.4 S. 30 thick
A μm fluororesin layer was formed.

Comparative Example 3 A commercially available PTFE tube (thickness: 40 μm) was coated on a degreased aluminum alloy core shaft (a cylindrical shape having a diameter of 39 mm, a length of 330 mm, and a thickness of 3 mm) and polished to 0.4 S. Thus, a fluororesin layer having a thickness of 30 μm was formed.

For the fixing rollers obtained in the examples and comparative examples, A4 paper (Canon recycled paper EW-
500), a wear test was carried out after 500,000 copies of a 2 mm wide paper having a 1 cm square grid pattern drawn thereon. Further, it was examined whether or not the toner adhered to the surface of the fixing roller on 500,000 sheets to cause an offset on the fixed image or whether the toner adhered to the roller surface and became dirty, and the releasability was evaluated in the following three steps. Table 1 shows the measurement results of the wear thickness and the evaluation results of the releasability.

A: No offset, no contamination of the roller.

B: No offset, dirt on the roller.

C: Offset, roller dirt.

[0023]

[Table 1]

[0024]

According to the present invention described above, as is clear from the comparison between the embodiment and the comparative example, it is possible to realize a fixing roller having excellent releasability and abrasion resistance. It is possible to cope with high speed and full color image.

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Claims (2)

[Claims] The fluororesin is ionized in an inert gas atmosphere having an oxygen concentration of 100 torr or less and directly above the melting point of the fluororesin, directly or through another layer on the outer periphery of the metal core shaft. A fixing roller having a modified fluororesin layer formed by irradiating radiation at an irradiation dose of 1 kGy to 10 MGy. 2. The fluororesin is at least one selected from tetrafluoroethylene-based polymers, tetrafluoroethylene-perfluoro (alkyl vinyl ether) -based copolymers and tetrafluoroethylene-hexafluoropropylene-based copolymers. The fixing roller according to claim 1.