JP2002169394A - Fixing belt and fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing belt and a fixing device in which triboelectrification of the belt is effectively prevented, offset development is hardly caused and excellent durability of the belt is obtained. SOLUTION: The fixing belt is to be used by spreading at least a heating roller and a release roller having a smaller diameter than the heating roller. The belt has a heat-resistant resin layer 1 having 101 to 1014 Ω/unit square surface resistivity, a silicone rubber elastic layer 2 applied on the outer surface of the layer 1, and a heat-resistant release layer 4 as the outermost layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device that can be used in an image forming apparatus such as an electrophotographic copying machine, a printer (such as a laser printer), and a facsimile, and a fixing belt used in the fixing device.

[0002]

2. Description of the Related Art In a copying machine or the like, a method most frequently used at present to fix a toner image formed on a recording sheet is a heat roller. In this fixing method, a toner image is fixed on a recording sheet by passing a recording sheet on which a toner image is formed with a fixed nip width between rollers which are pressed against each other and heating the roller from one or both rollers. This fixing method has many advantages such as high thermal efficiency and easy high-speed operation.

[0003] As the fixing roller, a roller in which the surface of a metal roller is coated with a silicone rubber or a fluororesin in order to release the fixed toner and prevent the offset has been used. Further, recently, a material in which a fluororesin is applied and baked on an elastic layer made of silicone rubber has been proposed.

On the other hand, from the viewpoint of improving the nip length and shortening the waiting time, various fixing methods using a fixing belt have been proposed. As the fixing belt, a polyimide resin excellent in heat resistance and mechanical strength has been proposed. A single-layer tubular body consisting of
Alternatively, a composite tubular body comprising an inner layer made of a polyimide resin and an outer layer made of a fluororesin (JP-A-3-130149)
Also, a composite tubular body in which an outer layer made of silicone rubber or fluorine rubber is provided on the outer peripheral surface of an inner layer made of a polyimide resin (JP-A-5-154963) has been proposed. But,
In this composite tubular body, since the entire belt is insulative, when a recording sheet with toner is fed between the fixing belt and the pressure roller, the friction tends to generate an electrostatic charge, and as a result, the electrostatic charge is fixed. There is a problem that the toner image is likely to be disturbed by affecting the toner image (so-called peeling offset).

Japanese Patent Application Laid-Open No. 10-305500 proposes a composite tubular body in which a conductive substance is added to both a tubular inner layer made of polyimide resin and a tubular outer layer made of silicone rubber or fluorine rubber. However, in this composite tubular body, although the triboelectric charging of the belt is unlikely to occur, the outer layer contains a conductive substance such as carbon black, so that the toner is applied to the fixing belt due to the influence of the surface shape and the adhesion of the toner. It has been found that an offset phenomenon (normal offset) in which the toner remains and is fixed on different portions is likely to occur.

On the other hand, JP-A-10-3224 discloses that
An endless belt was stretched between the heating roller and the peeling roller having a smaller diameter than this, and a pressure roller for pressing the heating roller from below was provided through the belt, thereby forming a nip portion between the belt and the pressure roller. A fixing device that, after fixing an unfixed toner image formed on a recording sheet at a nip portion, facilitates releasing of the recording sheet by using a releasing layer on a belt surface and a radius of curvature of a peeling roller. Is disclosed. In this device, the recording sheet is peeled off from the belt after the heated and melted toner is cooled to some extent, so the offset resistance is superior to the heat roller fixing method and the curvature at the time of peeling is smaller than the general belt fixing method. Since the radius can be reduced, the offset resistance is also advantageous from this point.

[0007]

However, it has been found that when a conventional endless belt is used in the above-mentioned fixing device, a so-called peeling offset occurs and the above-mentioned decrease in offset resistance occurs. Also,
Since the peeling roller has a small diameter, internal stress is easily generated as compared with a general belt fixing method, and the durability of the belt tends to be a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a fixing belt and a fixing device which can effectively prevent frictional electrification of the belt while making it difficult to cause an offset phenomenon and have excellent belt durability. .

[0009]

Means for Solving the Problems The present inventors have conducted intensive studies in order to achieve the above object, and surprisingly found that the surface resistivity of the inner layer can be surpassed by a specific range even when a conductive material is not added to the outer layer. It has been found that by setting to, triboelectric charging of the belt can be effectively prevented, and the present invention has been completed.

That is, the fixing belt of the present invention comprises a heat-resistant resin layer having a surface resistivity of 10 ¹ to 10 ¹⁴ Ω / □, an elastic layer made of silicone rubber provided on the outer surface side, and an outermost layer. And a heat-resistant release layer provided.

In the above, it is preferable that the outer surface of the elastic layer is subjected to a primer treatment, and the surface is coated with a heat-resistant release layer made of a fluororesin having a thickness of 1 to 50 μm.

The fluororesin is a tetrafluoroethylene resin (hereinafter abbreviated as PTFE), a tetrafluoroethylene-perfluoroalkoxyethylene copolymer (hereinafter abbreviated as PFA), and a tetrafluoroethylene-hexafluoropropylene copolymer (Abbreviated as FEP) is preferably one or more selected from the group consisting of:

On the other hand, in the fixing device of the present invention, an endless belt is stretched between at least a heating roller and a peeling roller having a smaller diameter, and a pressure roller for pressing the heating roller via the endless belt is provided. In a fixing device in which a nip portion is formed between the endless belt and the pressure roller, any one of the fixing belts described above is used as the endless belt.

According to the fixing belt of the present invention, by setting the surface resistivity of the heat-resistant resin layer in the above range, static electricity generated in the outermost layer and the like can be eliminated by the heat-resistant resin layer. Therefore, the addition of a conductive substance to the outermost layer or the like can be unnecessary or minimized. Therefore, the outermost layer and the like of the fixing belt are smooth and the toner hardly adheres thereto, and the triboelectric charging hardly occurs, so that the offset phenomenon hardly occurs. In addition, the durability of the belt is high.

When the outer surface of the elastic layer is treated with a primer and the surface is coated with a heat-resistant release layer made of a fluororesin having a thickness of 1 to 50 μm, the adhesion between the silicone rubber and the fluororesin is performed by the primer treatment. The releasability is improved, and the fluororesin having an appropriate thickness can improve the releasability after fixing the toner and the flexibility when fixing the toner.

Further, the fluororesin is PTFE, PF
When it is at least one selected from the group consisting of A and FEP, heat resistance, durability, manufacturability, and the like are improved.

On the other hand, according to the fixing device of the present invention, any one of the above fixing belts is used as the endless belt of the fixing device as described above. And the offset phenomenon is less likely to occur, and the durability of the belt becomes excellent.

[0018]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing an example of the fixing belt of the present invention.

In this figure, the fixing belt of the present invention has a heat-resistant resin layer 1 as a cylindrical base material, an elastic layer 2 made of silicone rubber provided on the outer surface thereof, and a primer treatment on the outer surface. This is exemplified as an endless belt having a primer layer 3 formed of a heat-resistant release layer 4 provided on the outermost layer.

As the heat-resistant resin layer 1, a resin such as polyimide, polyamide imide, or polybenzimidazole is used because of its high heat resistance, high strength, high elastic modulus, flexibility, and dimensional stability. Among them, aromatic polyimides are particularly preferred. An endless belt containing such a resin as a resin component can be formed by a known method using the resin or a raw material thereof.

In the present invention, in order to prevent peeling offset,
The surface resistivity of the heat-resistant resin layer 1 is 10 ¹ -10¹⁴In Ω / □
Need to be^Two -10¹³Ω / □ is preferred
No. To obtain the surface resistivity, metal, carbon, metal
A method of dispersing a conductive filler represented by an oxide is
Effective, but not limiting. Surface resistance
The rate depends on the type, amount, particle size, etc. of the conductive filler.
Can be adjusted.

If the surface resistivity exceeds 10 ¹⁴ Ω / □, triboelectric charging cannot be effectively prevented, and there is no effect in preventing peeling offset. On the other hand, if it is less than 10 ¹ Ω / □, the amount of the conductive filler is increased, so that the filler is brittle, high strength cannot be obtained, and durability is reduced.

The thickness of the heat-resistant resin layer 1 in the present invention is preferably 1 to 50 μm. In addition, heat-resistant resin layer 1
May contain a silicone-based or fluorine-based organic compound, a coupling agent, a lubricant, an antioxidant, and other additives to the extent that the physical properties are not impaired, in addition to the above essential components. The resin may be copolymerized or blended with another polymer component to such an extent that its physical properties are not impaired.

The elastic layer 2 is formed by using silicone rubber as a main component. As the silicone rubber, a general-purpose silicone rubber having a rubber hardness of about 20 to 50 degrees can be used. For example, methyl silicone rubber, vinyl methyl silicone Rubber and fluorosilicone rubber can be used alone or in combination of two or more. However, since it is necessary to withstand the sintering temperature for forming the heat-resistant release layer 4 such as a fluororesin, a material having high heat resistance is preferable. In particular, it is suitable because it is reinforced by the blending of fillers such as silica and titanium oxide and the blending of pigments and the like, and heat resistance is improved. The thickness of the elastic layer 2 is preferably from 5 to 500 μm, more preferably from 10 to 400 μm, in order to exhibit appropriate elasticity and fix the toner appropriately.

The elastic layer 2 is formed by applying a silicone rubber solution or the like to a predetermined thickness by spray coating, dipping, or the like, and then allowing the solution to cure at a temperature of 20 to 200 ° C. for 0.1 to 24 hours. be able to. When the elastic layer 2 is formed, in order to improve the adhesive strength, a known adhesive treatment such as an alkali treatment, a primer treatment, an ultrasonic treatment, and an etching treatment is applied to the surface of the heat-resistant resin layer 1. A dry treatment such as a corona treatment, a plasma treatment, an ultraviolet (UV) irradiation treatment, an electron beam irradiation treatment, and a laser treatment may be performed.

As the heat-resistant release layer 4, a fluororesin having excellent non-adhesiveness is preferable, and a fluororesin such as PTFE, PFA and FEP is preferable. The thickness of the heat-resistant release layer 4 is 1 to
50 μm is preferable, and 5 to 40 μm is more preferable.

The primer layer 3 is formed to bond the silicone rubber and the fluororesin layer, and is interposed between the layers. For example, the silicone rubber and the fluororesin can be firmly bonded by a fluorinated silicone primer such as PRM-027-3 manufactured by Du Pont-Mitsui Fluorochemicals.

Next, the fixing device of the present invention will be described. In the fixing device of the present invention, as shown in FIG. 2, an endless belt 10 is stretched between at least a heating roller 11 and a peeling roller 12 having a smaller diameter than the heating roller 11, and the heating roller 11 is A pressure roller 13 for pressing is provided, and the endless belt 10 and the pressure roller 1 are provided.
A nip portion is formed between the three. The present invention is characterized in that the fixing belt of the present invention is used as the endless belt 10.

In this fixing device, the unfixed toner image formed on the recording sheet 14 is fixed by heating and pressing at the nip n, and thereafter, the heat-resistant release layer 4 of the endless belt 10 and the peeling roller With the curvature radius of 12, release of the recording sheet 14 and prevention of offset are suitably performed.

Since the fixing belt of the present invention has a relatively small total thickness, the heat capacity can be set small, and the unfixed toner formed on the recording sheet 14 can be efficiently transmitted from the heating roller 11 via the fixing belt 10. The toner heated and melted in the nip n is sufficiently cooled and solidified before moving to the peeling roller 12. The fixed toner image 15 can be easily separated from the fixing belt 10 by the peeling roller 12 having a small radius of curvature (for example, a diameter of 10 to 30 mm).

The heating roller 11 is constituted by, for example, providing a 3 mm thick heat-resistant elastic coating layer made of silicone rubber on a core metal of an alloy mainly composed of aluminum having a diameter of 40 mm. The temperature of the heating roller 11 is appropriately set according to the type of the toner.

The peeling roller 12 is, for example, 15 mm in diameter.
200mm thick aluminum alloy core metal
It is composed of a roller in which a μm PFA tube is shrink-coated.

The pressure roller 13 has a diameter of, for example, 40 mm.
3mm thick on the core of an alloy containing aluminum as the main component
mm of silicone rubber. The heating roller 11 is set so as to press the heating roller 11 from below through the endless belt 10 at a pressure of, for example, 2 kgf / cm ² . The nip width of the nip n is set to about 10 mm. The nip width of the nip portion n can be adjusted by the hardness of the silicone rubber and the pressing of the pressure roller.

It is also possible to provide a pressing member having a slidable layer on the surface of the elastic body instead of the pressing roller 13, so that the nip n
Can be formed. The fixing belt of the present invention can also be used for the fixing device.

The linear velocity of the fixing belt 10 of the fixing device is about 100 to 300 mm / sec. For example, when the heating roller 11 is driven, the other rollers and the fixing belt 1 are driven.
0 is driven at the same speed. It is also possible to drive other rollers.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below.

Production Example 1 (Manufacture of a polyimide belt) NMP was 10 wt% based on the solid content of the polyamic acid solution.
3,3 ', 4,4'-biphenyltetracarboxylic dianhydride in an NMP solution added with carbon (Ketjen Black, manufactured by Lion Corporation) and dispersed in a ball mill for 12 hours, Approximately equimolar p-phenylenediamine was added (monomer concentration 20% by weight), and the temperature was 20 ° C.
For 5 hours to obtain a polyamic acid solution of 2600 poise. After supplying the polyamic acid solution to the inner surface of the cylindrical mold, the bullet-shaped traveling body was dropped by its own weight, and defoaming was performed to remove bubbles in the coating film to obtain a uniform coating surface. Next, the mold is heated stepwise from 150 ° C. to 370 ° C. to remove the solvent, remove the ring-closed water, and perform a complete reaction of imide conversion,
A polyimide belt having an inner diameter of 60 mm, a length of 380 mm, and a thickness of 75 μm was manufactured.

Example 1 A methylsilicon rubber (DX, manufactured by Dow Corning Toray Co., Ltd.) was coated on the outer peripheral surface of a 75 μm-thick polyimide belt containing 10 wt% of carbon (Ketjen Black) obtained in Production Example 1. 35-2083) was applied by spraying, and heated and cured in a hot air circulating furnace at 180 ° C. for 30 minutes to form an elastic layer having a uniform thickness of 150 μm. Next, a primer (PRM-027-3, manufactured by DuPont-Mitsui Fluorochemicals Co., Ltd.) is spray-coated on the elastic layer,
It was dried by heating in a hot air circulating furnace at 120 ° C. for 10 minutes to form a primer layer having a thickness of 5 μm. Further, a FEP dispersion paint (manufactured by DuPont Mitsui Fluorochemicals, EN
A-020-45) is spray-coated, and dried by heating in a hot air circulating furnace at 320 ° C. for 30 minutes to form a fluorine release layer having a thickness of 20 μm. A fixing belt having a total thickness of 250 μm was obtained. The surface resistivity of the polyimide belt was 2.3 × 10 ⁵ Ω / □.

Example 2 A 75 μm thick polyimide belt containing 15 wt% of carbon (Ketjen Black) obtained in the same manner as in Production Example 1 was used, and a PFA aqueous paint (Daikin Industries Co., Ltd., AW-5000), and dried by heating in a hot air circulating furnace at 320 ° C. for 30 minutes to form a fluorine release layer having a thickness of 20 μm. A fixing belt having a total thickness of 250 μm was obtained. The surface resistance was 4.6 × 10 ³ Ω / □.

Example 3 The same procedure as in Example 1 was carried out except that a 75 μm-thick polyimide belt containing 25 wt% of carbon (Ketjen Black) was obtained in the same manner as in Production Example 1. A fixing belt having a total thickness of 250 μm was obtained. The surface resistance was 1.1 × 10 ¹ Ω / □.

Example 4 Carbon (Kettsch) obtained in the same manner as in Production Example 1
Polyimide with a thickness of 75 μm containing 3 wt%
Except that a midbelt was used, the procedure was the same as in the example. Total thickness
As a result, a fixing belt of 250 μm was obtained. Also surface resistance
Is 5.6 × 10 ¹⁴Ω / □.

Comparative Example 1 The same procedure as in Example 1 was carried out except that a 75 μm-thick polyimide belt containing 30 wt% of carbon (Ketjen Black) was obtained in the same manner as in Production Example 1. Although a fixing belt having a total thickness of 250 μm was obtained, the belt was a film having no flexibility. The surface resistance was 0.8 × 10 ¹ Ω / □.

Comparative Example 2 Carbon (Kettsch) obtained in the same manner as in Production Example 1
75μm thick poly (1 wt%)
Except that a midbelt was used, the procedure was the same as in the example. Total thickness
As a result, a fixing belt of 250 μm was obtained. Also surface resistance
Is 1.5 × 10 ¹⁵Ω / □.

Test Example In the fixing device shown in FIG.
A 3 mm thick heat-resistant elastic body coating layer made of silicone rubber is provided on a core metal of an alloy containing aluminum as a main component of 0 mm, and a peeling roller 12 is formed on a core metal of an alloy containing aluminum as a main component having a diameter of 15 mm. 200 μm thick PFA
The tube consisted of a roller with shrink coating. Further, the pressure roller 13 is constituted by providing a heat-resistant elastic body coating layer of silicone rubber having a thickness of 3 mm on a core metal of an alloy containing aluminum as a main component and having a diameter of 40 mm, and a pressing force of 2 kgf / c.
m ² and the nip width was set to about 10 mm.

The fixing belt obtained in Examples and the like is mounted on this fixing device, and the fixing property of the toner, the releasability, the occurrence of offset, the presence / absence of occurrence of peeling offset, and the prevention and durability are checked. Therefore, evaluation was performed under the following conditions. That is, an A4 sheet was used as a recording sheet using color toner. Heating roller temperature 170 ° C,
The linear velocity of the fixing belt was 120 mm / sec, the pressure of the pressure roller was 2 kgf / cm ^2, and abnormalities in the surface state and offset of the fixing belt after copying 50,000 sheets were observed. The results are shown in Tables 1 and 2.

[0046]

[Table 1]

[Table 2] As shown in the results of Tables 1 and 2, the fixing belt of the present invention was excellent in all of fixing property, anti-offset property and durability. On the other hand, in Comparative Example 1 where the surface resistivity of the heat-resistant resin layer was too small, the durability was poor, and in Comparative Example 2 where the surface resistivity of the heat-resistant resin layer was too large, peeling offset occurred.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an example of a fixing belt of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an example of a fixing device of the present invention.

[Description of Signs] 1 heat-resistant resin layer 2 elastic layer 3 primer layer 4 heat-resistant release layer 10 fixing belt (endless belt) 11 heating roller 12 peeling roller 13 pressure roller

Claims (4)

[Claims] 1. A surface resistivity of 10 ¹ ~10 ¹⁴ Ω / □ heat-resistant resin layer of the, its outer surface to the silicone rubber elastic layer provided, heat peeling type provided in the outermost layer And a fixing belt. 2. The fixing belt according to claim 1, wherein an outer surface of the elastic layer is subjected to a primer treatment, and a surface of the elastic layer is coated with a heat-resistant release layer made of a fluororesin having a thickness of 1 to 50 μm. 3. The method according to claim 1, wherein the fluororesin is a tetrafluoroethylene resin, a tetrafluoroethylene-perfluoroalkoxyethylene copolymer, and a tetrafluoroethylene-
3. The fixing belt according to claim 2, wherein the fixing belt is at least one member selected from the group consisting of a hexafluoropropylene copolymer. 4. An endless belt is stretched between at least a heating roller and a peeling roller having a smaller diameter than the heating roller, and a pressure roller for pressing the heating roller via the endless belt is provided. A fixing device having a nip portion formed between pressure rollers, wherein the fixing belt according to claim 1 is used as the endless belt.