JP3233349B2 - Fixing device and fixing endless belt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device used in an image forming apparatus utilizing an electrophotographic method, such as a copying machine, a printer, a facsimile, etc., and more particularly to a fixing device having a roll and an endless belt. So,
The present invention relates to a fixing device capable of coping with high speed and / or miniaturization and an endless fixing belt used for the fixing device.

[0002]

2. Description of the Related Art Conventionally, as a fixing device of this type, typically, as shown in FIG. 5, for example, a pair of fixing rolls 1 and pressure rolls 2 which can be heated are pressed into contact with each other. A recording sheet 3 carrying an unfixed toner image 4 is introduced into a nip area formed between the fixing roll 1 and the pressure roll 2, and the recording sheet 3 is heated and pressed when passing through the nip area. A so-called heating / pressing roll type fixing device (hereinafter sometimes referred to as a roll-roll type fixing device) for fixing the unfixed toner image 4 to the recording sheet 3 is used. In such a heat and pressure roll type fixing device, the fixing roll 1 generally includes a metallic hollow roll 1a having a high thermal conductivity such as aluminum, an elastic layer 1b sequentially laminated thereon, and an oil-resistant / separating layer. Mold layer 1
and a heating source 1 such as a halogen lamp therein.
e, and the pressure roll 2 is composed of a metal core roll 2a having a high thermal conductivity and a release layer 2d of polytetrafluoroethylene or the like laminated thereon,
A heating source 2e such as a halogen lamp is provided inside. Reference numeral 5 in FIG. 5 denotes an oil supply device for supplying oil such as silicone oil for preventing so-called offset, in which a part of the unfixed toner image 4 is transferred to the fixing roll 1 during fixing. Reference numeral 7 denotes a peeling claw that peels off the recording sheet 3 wound around the fixing roll 1 and the pressing roll 2, and reference numeral 8 denotes a temperature sensor that detects the temperature of the fixing roll 1 and the pressing roll 2.

In order to increase the speed of such a fixing device, the fixing is performed when the unfixed toner image 4 passes through the nip area between the fixing roll 1 and the pressure roll 2. Since it is generated by the action of the pressure and thermal energy supplied from the pressure roll 1 and the pressure roll 2, it is necessary to increase the width of the nip area, that is, the nip width according to the speed. Therefore, in the above-described roll-roll type fixing device, as a method for increasing the nip width, a method of increasing a load between the rolls of the fixing roll 1 and the pressure roll 2 and a method of increasing an elastic layer of the fixing roll 1 are described. A method of increasing the layer thickness and a method of increasing the roll diameter of the fixing roll 1 and the pressure roll 2 are considered. However, in the method of increasing the load between rolls or the method of increasing the thickness of the elastic layer, the shape of the nip width in the nip region becomes uneven in the roll axis direction due to the bending of the roll, or the fixing unevenness. And the recording sheet wrinkles,
There is a problem that the load between the rolls and the thickness of the elastic layer 1b are naturally limited, and it is not possible to cope with a desired high speed.
In the method of increasing the diameter of the roll, the size of the apparatus is inevitably increased, and the time required for raising the temperature of the fixing roll 1 and the pressure roll 2 from room temperature to a temperature at which fixing can be performed (warm-up time). There is a problem that becomes longer.

As another method for securing a large nip width in the nip area, a pressure roller side is replaced with an endless belt, and a fixing roll provided with a heating source and a polytetrafluoroethylene which rotates while being pressed against the fixing roll. Ethylene (see JP-A-2-73279), silicon rubber (see JP-A-4-115279), or a mixture of a porous material and an elastomer (see JP-A-6-2144)
There is known a so-called roll-belt type fixing device including a fixing endless belt described in Japanese Patent Application Laid-Open No. 79-79). However, when using an endless belt coated with polytetrafluoroethylene,
The phenomenon that the toner once offset to the fixing roll side is transferred to the endless belt side and contaminates the recording sheet is small, but the friction coefficient on the belt surface is small and slippage occurs between the recording sheet and the fixing roller rotation speed. And the rotation speed of this endless belt occurs,
When an unfixed toner image is fixed on a recording sheet, a so-called image shift problem occurs in which a fixed image shifts.
In order to prevent this, both the fixing roll and the belt must be driven at a constant speed, which makes the driving device large. When an endless belt coated with silicon rubber is used, such a problem of image shift does not occur because the friction coefficient of the belt surface is large, but the endless belt is swollen by the anti-offset liquid and the rubber hardness is reduced. There is a problem that the recording sheet is deteriorated and deteriorated, and is worn due to contact with the recording sheet, and the recording sheet is wrinkled. Furthermore, in these roll-belt type fixing devices, if the diameter of the supporting roll or the fixing roll on which the endless belt is stretched is reduced to reduce the size, the endless belt is bent or extended with a large curvature. As a result, there is a problem that the belt surface is easily cracked and the life is short. When an endless belt coated with a mixture of a porous material and an elastomer is used, the above-mentioned problem of image misalignment does not occur because the friction coefficient of the belt surface is large, but the double-sided copied recording sheet is fixed. At this time, the fixed toner image on the first surface (the surface that comes into contact with the belt), which has already been fixed, is re-melted and offset on the belt surface, causing a problem that the recording sheet is wound without being peeled off.

[0005]

Accordingly, the present inventor has achieved the simplification of the driving device without the problems of image misalignment, peeling failure at the time of double-sided copying / fixing, and a short life, and has achieved high speed and small size. As a result of intensive studies on the development of fixing devices capable of individually or simultaneously responding to the development, the present invention has been completed. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device which does not have the problems of image misalignment, peeling failure at the time of double-sided copying / fixing, and a short life, and can cope with high speed and / or downsizing. Another object of the present invention is suitable for use in a fixing device which does not have the problems of image misalignment, peeling failure at the time of double-sided copying / fixing, and a short life, and which can cope with high speed and / or miniaturization. To provide a fixing endless belt.

[0006]

That is, the present invention provides a fixing roll, and an endless belt that forms a predetermined nip area on the fixing roll and presses against the fixing roll. In a fixing device capable of fixing both sides of an unfixed toner image on a recording sheet in the nip region when passing between the roll and the endless belt, the toner image on the already fixed surface is brought into contact.
When the endless belt is pressed against the base film and the fixing roll thereon, distortion occurs such that the recording sheet does not wind around the base film.
Characterized in that it is an endless belt provided with a heat-resistant elastic layer and a surface layer thereon.

In the present invention, the base film constituting the endless belt may be any film having a strength suitable for winding a support roll or a pressure roll for stretching the endless belt. , A metal film, a ceramic film, a glass fiber film, or a composite film obtained by compounding any two or more of them. Examples of the polymer film include polyesters such as polyethylene terephthalate, polycarbonates, polyimides, fluoropolymers such as polyvinyl fluoride and polytetrafluoroethylene, polyamides such as nylon, polystyrene and polyacryls, and polyethylene. And polypropylenes, cellulose-modified products such as polyacetate cellulose, polysulfones, polyxylylenes, polyacetals and other sheet-like or cloth-like molded products, and the like. And a polymer composite obtained by laminating a heat-resistant resin layer such as a system or a crosslinkable polymer. Further, such a polymer film may be composited with a heat-resistant layer formed of metal, ceramics, or the like, and may have a granular, acicular, or fibrous carbon black,
Add a thermal conductivity improver such as graphite, alumina, silicon, carbide, boron nitride, etc.
Additives such as a magnetic substance, a release agent and a reinforcing agent may be added or applied. Further, in addition to the above-described polymer film, for example, paper such as condenser paper and glassine paper, a ceramic film, a glass fiber film formed into a cross shape with glass fiber, a stainless film, and a metal such as a nickel film. Film can be used.

[0008] At least a heat-resistant elastic layer is formed on such a base film. As the heat-resistant elastic layer, a room temperature curing type (RTV: Room Temper) is used.
attraction vulcanization and low temperature curing type (LTV: Low Temperature Vul)
can be used, and specific examples thereof include RTV silicone rubber, LTV silicone rubber, fluorine rubber, and fluorosilicone rubber. The elastic layer is important for enabling peeling during double-sided copying / fixing due to the effect of distortion. In addition, an inorganic powder such as carbon black, alumina, or silica may be added to the elastic layer in order to improve performance such as thermal conductivity. An oil- and wear-resistant elastic surface layer can be provided on the surface of the heat-resistant elastic layer. This oil resistant
The wear-resistant elastic layer does not swell in the oil supplied from the oil supply device, and is important in providing a high friction coefficient. As a particularly preferred oil-resistant and wear-resistant elastic layer, specifically,
Fluorine rubber, fluorosilicone rubber and the like can be mentioned.

The endless belt used in the present invention is:
The belt thickness is usually 350 μm or less, preferably 150 μm.
It is preferably a film having a thickness of μm or less, and it may be thin as long as the strength enough to withstand use is secured, but if it is too thin, the desired strength cannot be achieved, and elasticity and high frictional properties are imparted. It is usually at least 15 μm, since it becomes difficult to give the desired performance to the coating layer important above.
About a belt thickness is required. This belt thickness is 350μ
If it exceeds m, it is not possible to increase the curvature when the belt is stretched, which is not preferable for miniaturizing the apparatus while securing the durability of the endless belt. Also,
The film thickness of the base film constituting such an endless belt is usually 15 to 200 μm, preferably 50 to 75 μm, and the layer thickness of the coating layer laminated on the base film is usually 50 to 25 μm.
0 μm, preferably 100 to 170 μm. If the thickness of the coating layer is too thin, distortion cannot be obtained uniformly, and if it is too thick, the distortion obtained with respect to the load applied by the pressure roll becomes small, and in any case, it is difficult to peel at the time of double-sided copying and fixing. To FIG. 4 shows the relationship between the thickness of the coating layer and the releasability during duplex copying / fixing. The experiment was performed using the fixing device of Example 2 of the present invention described later under the same conditions as in the continuous fixing test described later. However, S-paper manufactured by Fuji Xerox Co., Ltd. was used as the recording paper, and the oil supply amount was 4 mg.
The surface temperature of the fixing roll was measured and the peelable temperature range during double-sided copying and fixing was measured. In FIG. 4, a shaded portion indicates a peelable temperature range. That is, 12
0 ° C. or more is the peelable temperature range. The friction coefficient between the endless belt and the recording sheet on the belt surface, for example, paper, is usually 0.15 to 1.0,
Preferably, it is in the range of 0.2 to 0.8. If the friction coefficient of the belt surface is smaller than 0.15, a slip may occur between the fixing roll and the endless belt. When the friction coefficient is 1.0 or more, the adhesion between the paper and the belt becomes too large, and the paper is hard to peel off from the belt, and further, unmelted matter such as paper dust and dust easily adheres to the belt surface. Also, cleaning becomes difficult. further,
In general, since the lower limit of the toner melting temperature is about 100 ° C., for the endless belt used in the present invention,
The film is preferably formed so as to have a heat resistance of 100 ° C. or more, preferably 150 ° C. or more. This enables fixing not only under pressure but also under heat and pressure.

[0010] The endless belt formed in this manner is a roll comprising a fixing roll and a fixing endless belt that rotates while being pressed against the fixing roll.
Any type of belt-type fixing device can be used as an endless belt for any type of fixing device.However, in order to increase the speed of fixing and reduce the size of the device, preferably, a plurality of endless belts are used. It is preferable that the fixing device is stretched by the supporting roll and has a wide nip width in the nip region and is configured to be pressed against the fixing roll by the pressure roll.

[0011]

According to the present invention, since the endless belt to be used has at least the heat-resistant elastic layer formed on the base material, good peeling at the time of double-sided copying and fixing is possible due to the effect of distortion. Further, when an oil-resistant and abrasion-resistant layer is provided as a surface layer, excellent swelling resistance and a high coefficient of friction can be achieved by the surface layer. Excellent in properties and durability. In addition, a wide nip width can be obtained in the nip region, which can cope with a high speed. In addition, a roll diameter of a support roll or the like for supporting the endless belt can be designed to be small, so that it is possible to cope with miniaturization. Further, in the driving method, one of the fixing roll and the endless belt can be driven and the other can be driven, so that the driving device can be simplified.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on examples and comparative examples.

FIG . 1 shows a fixing device of a roll-belt type employed in an embodiment of the present invention. Members corresponding to those of the fixing device shown in FIG. 5 are denoted by the same reference numerals. This fixing device is composed of an aluminum hollow roll 1a having an outer diameter of 47 mm, an inner diameter of 40 mm, and a length of 330 mm, and a 2 mm thick high-temperature-curable silicone rubber (HTV silicone rubber, rubber hardness of 45 degrees) laminated thereon. A fixing roll 1 having a heating source 1e composed of a halogen lamp, which is composed of an elastic layer 1b made of) and an oil-resistant layer 1c having a thickness of 30 μm and a dip-coated fluorocarbon rubber on the surface;
An endless belt 10 in the form of a film having a size of 00 mm × a peripheral length of 189 mm × a thickness of 230 μm is provided. The endless belt 10 is stretched between two support rolls 11 having a diameter of 18 mm and a pressure roll 12 having a diameter of 23 mm. The endless belt 10 is pressed against the surface of the fixing roll 1 by the pressure roll 12 and is widened by a sponge roll 13. The configuration is such that a nip region having a nip width is formed. The fixing roll 1 and the endless belt 10
Is driven by driving the fixing roller 1 and the endless belt 1
No. 0 was performed so as to follow the fixing roll 1.
In FIG. 1, reference numeral 5 denotes an oil supply device, and reference numeral 6 denotes an oil supply device.
Reference numeral 8 denotes a temperature sensor, and reference numeral 9 denotes a chute for guiding the discharge of the sheet 3.

As shown in FIG. 2, the endless belt 10 has a thickness of 5 μm on a surface of a base film 10 a made of a polyimide film having a thickness of 75 μm.
It is formed of an elastic surface layer 10d dip-coated with a 150 [mu] m-thick fluoro rubber through an adhesive layer 10b of m.

Here, the endless belt 10 weighs 10 kg.
The pressure roll 12 is urged toward the center of the fixing roll 1 by a compression coil spring (not shown) at a pressure of 20 kg. Is 45 °, and the nip width in this nip area is 19.6 mm.

Using the roll-belt type fixing device constructed as described above, the rotation speed of the fixing roll 1 and the endless belt 10 is 200 mm / sec, the surface temperature of the fixing roll is 150 ° C., and the copy speed is A4 size paper. 10
A continuous fixing test was carried out under the conditions of sheet / minute, recording paper P (manufactured by Fuji Xerox Co., Ltd.), toner composition 95% by weight of polyester resin, pigment 4% by weight and charge controlling agent 1% by weight. As a result, even after the fixing of 50,000 sheets, no swelling phenomenon due to silicone oil was observed in the endless belt 10, no crack was generated on the surface, the releasability, the paper peeling property including duplex copying / fixing, and the stability. The toner was fixed well in terms of color development and color development. In addition, there was no problem of poor rotation of the fixing roll 1 due to slippage in the nip region or image misalignment due to this.

Embodiment As shown in FIG. 3, the endless belt 10 has a thickness of 75 mm.
μm base film 10a made of polyimide film
Intermediate dip coated with 120 μm-thick silicone rubber on the surface of the substrate through an adhesive layer 10 b having a thickness of 5 μm
A layer fluororubber having a thickness of 30 μm was dip-coated with an adhesive layer 10 b having a thickness of 5 μm and an adhesive layer 10 c.
It is formed by laminating the elastic surface layer 10d . Using the obtained endless belt, a continuous fixing test was performed in the same manner as in Example 1. As a result, even after the fixing of 20,000 sheets, the phenomenon of swelling of the endless belt 10 due to the silicone oil was not observed.
The surface was free from cracks and the like, and the image was fixed satisfactorily in terms of releasability, paper releasability including double-sided copying and fixing, stability, and color development. In addition, there was no problem of poor rotation of the fixing roll 1 due to slippage in the nip region or image misalignment due to this.

Comparative Example 1 Polytetrafluoroethylene as a release layer was 25 μm thick on the surface of the same base film used in each of the above Examples.
To form an endless belt. The endless belt was mounted on the fixing device of Example 1 and a continuous fixing test was performed in the same manner as in Example 1. As a result, no mechanical damage was observed on the endless belt itself, but at the time of double-sided copying / fixing of the recording paper, uneven gloss was generated on the first fixed image formed on the surface of the recording paper. When the unfixed toner image exists, there is a problem that the toner image is wrapped around the endless belt. Further, when the silicone oil was sufficiently supplied to the fixing roll side, a rotation failure of the fixing roll occurred, and a problem of image shift occurred.

Comparative Example 2 RTV silicone rubber was laminated as a release layer to a thickness of 150 μm as a release layer on the surface of the same base film used in each of the above-mentioned examples, to produce an endless belt. This endless belt was mounted on the fixing device of the first embodiment, and
A continuous fixing test was performed in the same manner as described above. As a result, during the double-sided copying / fixing of the recording paper, the fixed image initially formed on the surface of the recording paper did not have uneven gloss and wrapping around in a large amount of unfixed toner images. The phenomenon of swelling due to silicone oil occurred, a level difference occurred between the paper passing area and the non-paper passing area, wrinkles occurred on the recording paper, and peeling of the release layer occurred partially.

Comparative Example 3 An expanded porous PTFE having a porosity of 90% was formed as a coating layer on the surface of the same base film used in each of the above Examples.
(Trade name: Gore-Tex manufactured by JGI) was impregnated with RTV silicone rubber and laminated to a thickness of 20 μm to form an endless belt. The endless belt was mounted on the fixing device of Example 1 and a continuous fixing test was performed in the same manner as in Example 1. As a result, no mechanical damage was found on the endless belt itself and no image misalignment due to improper rotation of the fixing roll was found. Uneven gloss due to poor peeling from the endless belt occurred in the fixed image formed first on the paper surface.

[0021]

According to the present invention, an endless belt having at least a heat-resistant elastic layer formed on a base film is employed as an endless belt used in a roll-belt type fixing device. Good peeling is possible. Further, when an oil-resistant and abrasion-resistant layer is provided as a surface layer, excellent swelling resistance and a high coefficient of friction can be achieved by the surface layer. Excellent in properties and durability. In addition, a wide nip width can be obtained in the nip region, and high speed can be accommodated. In addition, the diameter of a roll such as a support roll for supporting the endless belt can be reduced by a thin endless belt, and the apparatus can be downsized.
For this reason, according to the present invention, it is possible to simultaneously achieve particularly high speed and downsizing of the fixing device, and it is extremely useful as a fixing device used in an image recording apparatus such as a copying machine, a printer, and a facsimile. is there.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a fixing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a cross section of an endless belt used in the fixing device of FIG.

FIG. 3 is an explanatory view showing a cross section of another embodiment of the endless belt.

FIG. 4 is an experimental result showing the relationship between the thickness of the coating layer and the releasability during duplex copying / fixing.

FIG. 5 is an explanatory diagram showing a conventional roll-roll type fixing device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fixing roll, 1a ... Hollow roll, 1b ... Elastic body layer,
1c: oil-resistant release layer, 1e: heating source, 2: pressure roll,
2a: Core roll, 2d: Release layer, 2e: Heat source, 3 ...
Sheet, 4: unfixed toner image, 5: oil supply device, 6
... cleaning device, 7 ... peeling claw, 8 ... temperature sensor,
9 Chute, 10 Endless belt, 10a Base film, 10b Adhesive layer, 10c Heat resistant elastic layer,
10d: oil and wear resistant layer, 11: support roll, 12: pressure roll, 13: sponge roll

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-27620 (JP, A) JP-A-5-27621 (JP, A) JP-A-7-210019 (JP, A) 214479 (JP, A) JP-A-7-219380 (JP, A) JP-A-7-104598 (JP, A) JP-A-4-67661 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G03G 13/20 G03G 15/20

Claims (1)

(57) [Claims] 1. A fixing roll, comprising an endless belt that forms a predetermined nip area on the fixing roll and presses against the fixing roll, wherein a recording sheet carrying an unfixed toner image passes between the fixing roll and the endless belt. In the fixing device, the unfixed toner image can be fixed on both sides of the recording sheet in the nip area when the image is already fixed.
The endless belt in contact with the toner image on the bottom surface is provided with a base film and a heat-resistant elastic layer of 20 to 220 μm in which the recording sheet is distorted so that the recording sheet is not wound by being pressed against the fixing roll. An endless belt provided with a surface layer thereon.