JP2001142333A - Fixing device and surface processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smooth unevenness in a fold part, and to remove a crease in the fold part of an image and soiling of a roll of a fluorinated resin tube with the unevenness in the fold part by utilizing a simple method. SOLUTION: In the device, the unevenness in the fold part is made smooth by pressing a heated surface smoothing member to a surface of the fluorinated resin tube with the unevenness in the fold part.

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 for an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, and a recording machine, and a fixing member used for the fixing device. The present invention relates to a method for processing the surface of a fluororesin tube, which covers the surface of a pressure member. More specifically, using a toner composed of a heat-fusible resin or the like by an appropriate image forming process means such as electrophotography, electrostatic recording, and magnetic recording,
Recording material (paper, printing paper, transfer material sheet, electrofax sheet, electrostatic recording sheet, OHT sheet, glossy paper,
A non-fixed toner image corresponding to the target image information is formed and carried on the surface of a glossy film or the like by a direct transfer method or an indirect transfer method, and the unfixed toner image is permanently put on the recording material surface carrying the image. The present invention relates to a fixing device that performs a heat fixing process as a fixed image, and a surface processing method for a fluororesin tube that covers the surface of a fixing member or a pressure member used in the fixing device.

[0002] The present invention particularly relates to a fixing device provided with a fixing member or a pressure member coated with a fluororesin tube which has been subjected to a surface treatment for smoothing unevenness of a fold portion on the surface,
Further, the present invention relates to a surface processing method for smoothing surface irregularities of a fold portion of a fluororesin tube by a simple method.

[0003]

2. Description of the Related Art Conventionally, the surface of a fixing member or a pressing member used in a fixing device of an image forming apparatus has been used after being coated with a fluororesin. However, in the case of a fixing member or a pressure member having a surface coated with a fluororesin, the coating is baked at a high temperature equal to or higher than the melting point of the fluororesin. In the pressure member, since the firing temperature is much higher than the heat resistance temperature of the elastic layer, there is a problem of thermal deterioration of the elastic layer. In addition, there are problems such as foreign matter and agglomeration on the surface, and the surface is undulated and rough, so it is necessary to polish the surface after firing to obtain the surface property required as a fixing or pressing member. . For this reason, a fixing member or a pressing member having a surface covered with a fluororesin tube is often used.

FIG. 4 shows an example of such a conventional fixing device. The fixing roller 1 in the conventional example has an outer diameter of about φ40.
mm, and a roller having a roller length of about 240 mm, and a heater 2 (490 W /
127H rated halogen heater).
A16063, a primer layer (not shown), an elastic layer 5, a primer layer (not shown) on a core metal 3 having a thickness of 2.5 mm,
It is composed of a surface release layer 6 '. As the elastic layer 5,
The test piece hardness is about 11 ° (measured by an Asker-C hardness tester manufactured by Kobunshi Keiki) and the thermal conductivity is about 0.8 × 10 ⁻³ ca1 / cms.
ecK low hardness silicone rubber is used. As the surface release layer 6 ′, in this apparatus, a 50 μm-thick perfluoroalkoxy (copolymer of perfluoroalkylvinylether and tetrafluoroethylene: hereinafter referred to as “PF
A), and a heat-shrinkable tube that shrinks in the radial direction so as not to cause wrinkles on the product roller surface. The inner surface of the tube is etched by a liquid ammonium method to ensure adhesive strength to the elastic layer 5 and heat resistance. By using such a low-hardness silicone rubber, the product hardness of the fixing roller of this apparatus is about 61 ° (measured value with a total weight of 1 kgf using an Asker-C hardness meter).

As the pressure roller 7, a roller having an outer diameter of φ40 mm and a roller length of about 230 mm is used similarly to the fixing roller, and a heater 8 (490 W / 1
Using a halogen heater rated at 27 V)
It comprises a primer layer (not shown), an elastic layer 11, a primer layer (not shown), and a surface release layer 12 'on an A16063, 2.7 mm thick cored bar 9.

The elastic layer 11 is made of the same silicone rubber as the elastic layer of the fixing roller, and has a thickness of 1.9 mm, which is different from that of the fixing roller. For the surface release layer, a PFA tube having a thickness of about 50 μm, which is the same as the fixing roller, is used. The product hardness of the pressure roller is about 65 ° (using an Asker-C hardness tester.
(Measured value at a total weight of 1 kgf).

The fixing roller and the pressure roller are pressed by a pressure spring (not shown), and a fixing nip width of about 9.5 mm is obtained at a total pressure of 40 kgf. Thermistors 13 and 14 as temperature detectors are brought into contact with the respective surfaces of the fixing roller 1 and the pressure roller 7. Based on the detected roller surface temperature, the roller surface temperature is determined by a heater driving circuit (not shown). The temperature is controlled so as to reach the target temperature (the print temperature is about 180 ° C. in this apparatus).
In addition, thermoswitches 15 and 16 as safety elements are arranged close to the surfaces of the fixing roller 1 and the pressure roller 7, and a non-contact type thermoswitch is used to prevent the roller surface from being damaged. I have.

In an example of an image forming apparatus using such a fixing device of this embodiment, the process speed is about 120 mm.
/ Sec, a throughput of 4 ppm of full color A4 and 16 ppm of monocolor A4 per minute is obtained.

[0009]

However, the conventional fixing member or pressure member coated with a fluororesin tube has the following problems.

In the conventional fluororesin tube, the surface of the fold for being pinched by a pinch roller or wound up in a roll during the processing of the fluororesin tube has irregularities. The fold unevenness was also left on the surface of the fixing member or the pressing member coated with the uneven fluorine resin tube. Such fold unevenness was generally about 4 to 10 μm, which was larger than the surface roughness required for the surface properties of the fixing member or the pressing member.

For this reason, 1) In a fixing device using a fixing member in which a fixing member is covered with a fluororesin tube having folds and projections, marks of the folds and projections appear on an image after fixing, thereby deteriorating image quality. Was.

In particular, in the case of a color image or a color OHT, the creases significantly reduce the image quality. Even in a fixing device using a pressure member coated with a fluororesin tube with fold irregularities, when printing on both sides, fold marks may appear on the image after fixing, or pressure may be applied to a color OHT having a coating layer on both sides. In some cases, unevenness of the fold portion is formed on the roller side, and a mark may appear on the projected image.

2) In a fixing device using a pressing member and a fixing member coated with a fluororesin tube having unevenness at the fold portion, particularly, an on-demand fixing device in which the surface temperature of the pressing member is low, a heater inside the pressing member, etc. In the case of a fixing device of a high-speed printing device that does not have a heat source, toner and paper dust adhere from the unevenness of the fold of the pressing member, and surface contamination of the fixing member and the pressing member occurs earlier than the life of the fixing device. Resulting in.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has been made by using a fixing member and a pressing member using a fluororesin tube in which unevenness of a fold is previously smoothed. Another object of the present invention is to provide a fixing device that has no fold marks on an image after fixing, and has less surface contamination of the fixing member and the pressing member. Further, the present invention provides a surface processing method for smoothing the uneven surface of the fold portion of the fluororesin tube by a simple method.

That is, the present invention is a fixing device provided with a fixing member or a pressing member for fixing a toner image to a recording material, wherein the fixing member or the pressing member is a member having a heated surface smooth member. By pressing, the unevenness of the fold on the surface is smoothed in advance by the fluororesin tube,
The fixing device is characterized by being coated.

The fixing member or the pressing member used in the fixing device is not particularly limited, but is preferably a roller or an endless belt. Further, the fluororesin tube is not particularly limited, but PFA resin, PTFE (polytetrafluoroethylene, hereinafter referred to as “PTFE”) resin, FEP (copolymer of tetrafluoroethylene and hexafluoropropylene, A tube formed of one or more resins selected from the group consisting of resins (hereinafter referred to as “FEP”) is preferable. Further, the fluororesin tube is
It is preferable that the surface is smoothed by pressing a surface smooth member heated within a range of ± 20 ° C. of the melting point temperature.

Further, the present invention is a surface processing method for smoothing the unevenness of the fold by pressing a heated surface smooth member against the surface of the fluororesin tube having the unevenness of the fold. Although this surface processing method is not particularly limited, a dummy roller having substantially the same diameter is inserted into the fluororesin tube having the rugged portion, and the surface of the fluororesin tube covering the dummy roller is Preferably, the method is to smooth the unevenness of the fold by rotating the heated surface smooth member while pressing it. Further, the heating temperature of the surface smoothing member is preferably within a range of ± 20 ° C. of the melting point temperature of the fluororesin tube.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. <1> Surface treatment method of the present invention As the fluororesin used for the fluororesin tube of the present invention, perfluoroalkoxy resin (PFA resin), polytetrafluoroethylene resin (hereinafter referred to as “PTFE resin”), perfluoroethylene propylene resin (Hereinafter, referred to as “FEP resin”), a copolymer of ethylene and tetrafluoroethylene (hereinafter, referred to as “ETFE resin”), and among these, selected from the group consisting of PFA resin, PTFE resin, and FEP resin. Preferably, the resin is selected from one or more types of resins, and more preferably, a resin capable of molding a heat-shrinkable tube that shrinks not only in the radial direction but also in the longitudinal direction.

The fluororesin tube molded from the above-described resin is folded at the tube itself by being pinched by a pinch roller in the heat shrinkage treatment process or the inner surface etching treatment process of the tube at the time of manufacturing the tube. Of 20 μm to 10 μm
In a tube having a thickness of 0 μm, the unevenness is about 4 to 10 μm.

A heated surface smooth member is pressed against the surface of the fluororesin tube having such fold irregularities to smooth the fold irregularities. That is, by pressing the heated member, the surface of the fluororesin tube is softened or dissolved, and by transferring the surface smoothness by pressing the member having a smooth surface in this state, the unevenness of the fold portion can be easily smoothed. Become

The material of the surface smooth member is preferably a hard metal such as steel. The surface may be mirror-finished to make it smooth, and the roller surface may be plated with hard chrome. The shape of the surface smooth member is not particularly limited as long as the unevenness of the fold of the fluororesin tube can be smoothed by pressing, but a roller-shaped member is preferably used.

The heating temperature of the smooth surface member depends on the material of the fluororesin tube used for the surface coating, but is preferably near the melting point of the fluororesin tube. If the temperature is lower than the melting point, the resin does not soften much and takes a long time. If the temperature is higher than the melting point, the melted surface sticks to the surface smooth member and the tube surface is not smooth. Therefore, the heating temperature of the smooth surface member is preferably within the range of ± 20 ° C. of the melting point temperature of the fluororesin tube.

A more specific method of the present invention can be carried out, for example, in the following manner in addition to the conditions described above. FIG. 3 illustrates an example of such a surface processing method. First, a dummy roller having substantially the same diameter is inserted into the fluororesin tube. The dummy roller is not particularly limited as long as it does not adversely affect the transfer of the flatness of the surface and has heat durability and the like, but it is preferable to use a hard metal such as steel as the material. Preferably, the roller surface is mirror-finished and smoothed.

Next, the roller, which is a heated smooth member, is
By rotating the fluoro-resin tube covering the dummy roller while pressing it with an appropriate pressure, the surface of the tube can be smoothed. Further, the heated roller having a smooth surface is pressed against the surface of the fluororesin tube covering the dummy roller with an appropriate pressure, and further, the dummy roller or the roller which is the smooth surface member is rotated, and the This object can also be achieved by making one of the rollers driven to rotate.

Usually, the above treatment may be performed for several seconds to one minute, depending on the heating temperature. By the method described above,
The unevenness of the fold at the surface of the fluororesin tube can be made 2 μm or less, preferably about 1 μm or less. The unevenness of the fold is measured using a contact-type surface roughness meter (produced by Kosaka Laboratory Co., Ltd., stylus-type surface roughness meter SE-3400).
It can be measured by the method of IS B0651.

<2> Fixing Device of the Present Invention The fixing device of the present invention develops an electrostatic latent image using toner, and transfers and fixes the obtained toner image to a recording member to form an image. Used for equipment,
The fixing device includes a fixing member or a pressing member for fixing a toner image. The fixing device of the present invention fixes the developed toner image on the recording member by heat and / or pressure. As the fixing means, a heat fixing treatment is preferable, and as a fixing method, for example, a heat roller method using a halogen lamp as a heat source, a film heating method using a ceramic heater, or a method of directly heating a fixing film by utilizing generation of an induced current Preferably, an electromagnetic induction heating method is used.

In the case of the heat roller system, for example, a fixing roller as a fixing member and a pressing roller as a pressing member are preferably used in combination. In the case of a film heating method or an electromagnetic induction heating method, an endless belt as a fixing member, for example, a fixing film and a pressure roll as a pressure member are used in combination.

The fixing member or the pressure member provided in the fixing device of the present invention is characterized in that it is covered with a fluororesin tube which has been smoothed in advance by the above-mentioned surface processing method. Here, the term “smoothing” means that the unevenness of the fold on the surface of the tube is 2 μm or less, preferably about 1 μm or less. The fold unevenness is measured using a contact-type surface roughness meter (produced by Kosaka Laboratory Co., Ltd., stylus-type surface roughness meter SE-3400) according to JIS B0651.
Can be measured by the following method.

The thickness of the fluororesin tube is
It is preferable to use one having a thickness of 20 μm to 100 μm.
Those having a thickness of 0 μm to 50 μm are more preferred. Further, the tube is preferably a heat-shrinkable tube that shrinks not only in the radial direction but also in the longitudinal direction.

The fixing member or the pressing member is not particularly limited, but preferably includes the above-described rollers, endless belts, etc., and is appropriately selected according to the fixing device to be used. I do. The coating of the fixing member or the pressing member with the fluororesin tube may be performed by appropriately selecting a coating method which is usually performed. The coating method referred to here includes not only a method of covering the formed member with the tube but also a method of forming the member in the tube and covering the member with the tube. As the latter method, for example, a core metal and a fluororesin tube are set in a mold, and injected there, and molded,
A vulcanization method may be used.

When an image is formed in an image forming apparatus including a fixing member provided with a fixing member or a pressing member covered with the fluororesin tube whose folds are smoothed as described above, an image after fixing is obtained. The device can be used for a long period of time without causing traces of the folds to appear as streaks during OHT projection and without deteriorating image quality.

Next, the toner used when forming an image using the fixing device of the present invention will be described. The toner used in the image forming apparatus including the fixing device of the present invention is not particularly limited as long as it is fixed on the recording paper by the thermal transfer type fixing as described above. It is preferred to use

As the toner, for example, a substantially spherical toner (hereinafter simply referred to as a polymerized toner) produced by a polymerization method, containing a low softening point substance at about 5 to 30% by weight, and having a shape factor SF-1 of 100 to 110 is used. It is preferable to use
The low softening point substance is a compound having a main maximum peak value of 40 to 90 ° C. measured according to ASTM D3418-8.

For the measurement of the temperature of the maximum peak value of the polymerized toner, for example, DSC-7 manufactured by PerkinElmer is used.
The temperature correction of the device detection unit uses the melting points of indium and zinc, and the correction of the calorific value uses the heat of fusion of indium. For the sample, an empty pan is set as a control using an aluminum pan, and the measurement is performed at a heating rate of 10 ° C./min. Specifically, paraffin wax, polyolefin, Fischer-Tropsch wax, amide wax, higher fatty acid, ester wax, derivatives thereof, or graft / block compounds thereof can be used. Preferably, the carbon number represented by the following general structural formula is 10
An ester wax having one or more long-chain ester moieties. The structural formulas of typical compounds of specific ester waxes are shown below as general structural formulas, and.

General structural formula of ester wax

[0036]

Embedded image [R1-COO- (CH ₂ ) n] aC-[(CH
₂ ) m-OCO-R2] b a, b: an integer of 0 to 4, a + b = 4 R1, R2: an organic group such as an alkyl group having an integer of 1 to 40 carbon atoms, and R1 and R2 The difference in carbon number is 10
that's all. n and m are integers from 0 to 15, and n and m do not become 0 at the same time.

General structural formula of ester wax

[0038]

Embedded image [R1-COO- (CH ₂ ) n] aC-[(CH
₂ ) m-OH] ba a, b: an integer of 0 to 4, a + b = 4 R1: an organic group such as an alkyl group having an integer of 1 to 40 carbon atoms n, m: an integer of 0 to 15 Yes, n and m do not become 0 at the same time.

General structural formula of ester wax

[0040]

Embedded image a, b: integers of 0 to 4; a + b ≦ 3 R1, R2: an organic group such as an alkyl group having an integer of 1 to 40 carbon atoms and a difference in carbon number between R1 and R2 of 10
that's all. R3: an organic group such as an alkyl group having 1 or more carbon atoms. n and m are integers from 0 to 15, and n and m do not become 0 at the same time.

The ester wax preferably used in the present invention has a hardness of 0.5 to 5.0. The hardness of the ester wax is 20 mm in diameter and 5 mm in thickness.
Is a value obtained by measuring the Vickers hardness using a dynamic microhardness tester (DUH-200) manufactured by Shimadzu Corporation after preparing the cylindrical sample of the above. The measurement condition is 10 μm under the condition that the load speed is 9.67 mm / sec with a load of 0.5 g.
After displacing, it is held for 15 seconds, and the resulting dent shape is measured to determine Vickers hardness.

Examples of specific compounds of the ester wax more preferably used in the present invention include the following chemical formula (4):
These are shown in (5), (6) and (7).

[0043]

Embedded image

[0044]

Embedded image

[0045]

Embedded image

[0046]

Embedded image

Note that the shape factor SF-1 here is
It is a numerical value indicating the degree of spherical roundness of a spherical substance, and the square of the maximum length MAXLNG of an elliptical figure formed by projecting a spherical substance on a two-dimensional plane is divided by a figure area AREA to obtain 1
It is represented by the value when multiplied by 00π / 4. That is, the shape factor SF-1 is given by

[0048]

SF-1 = {π (MAXLNG / 2) ² / AREA} × 100 = {(MAXLNG) ² / AREA} × (100π / 4), and the Hitachi FE-SEM ( S
−800), 100 toner images were sampled at random, the image information was introduced into an image analyzer (Luzex3) manufactured by Nicole via an interface, analyzed, and calculated by the above equation.

The other components of the image forming apparatus when forming an image using the fixing device of the present invention are not particularly limited, and may be appropriately selected to configure the image forming apparatus. I just need.

[0050]

EXAMPLES Hereinafter, Examples 1 to 3 will be described in more detail with respect to the case of using a fixing device of a heat roller system, a film heating system using a ceramic heater, and an electromagnetic induction heating system. It is not limited to these examples.

[0051]

Embodiment 1 <Heat Roller Type Fixing Device> A description will be given of a fluororesin tube which covers a fixing member and a pressing member of a heat roller type fixing device. This tube is a 50 μm-thick PFA tube. This tube is a heat-shrinkable tube that shrinks not only in the radial direction but also in the longitudinal direction, and the shrinkage in the longitudinal direction is about 4%.
The inner surface of the tube is etched by a liquid ammonium method, and has an adhesive strength with an elastic layer 4 described later,
Ensures heat resistance.

Here, before the surface processing method is carried out, the outer surface of the tube may be pinched by a pinch roller in a heat shrinkage treatment process or an inner surface etching process of the tube at the time of manufacturing the tube. The surface of the fold is provided on the tube itself by using a contact surface roughness meter (produced by Kosaka Laboratory Co., Ltd., stylus type surface roughness meter SE-3400).
When measured by the method of No. 1, there was about 4 μm unevenness.

Therefore, when the fluororesin tube in such a state is used, the surface irregularities appear as traces on the screen. Therefore, the tube was smoothed by the surface processing method of the present invention. First, a dummy roller having substantially the same diameter was first inserted into the fluororesin tube having the fold irregularities. This dummy roller is made of a hard metal such as steel, and its surface is mirror-finished and smoothed.

A metal roller was used as a smooth surface member.
In the present embodiment, the one having a diameter of about 50 mm was used. A hard metal such as steel was used for the metal roller, the surface was mirror-finished and smoothed, and the roller surface was subjected to hard chrome plating or the like. Then, the metal roller is heated to the melting point temperature (300 to 31) of the PFA tube as the fluororesin tube.
(0 ° C.), which is about 290 ° C. to 320 ° C. The metal roller, which is a surface smooth member heated in this manner, was rotated around the tube while pressing against the surface of the fluororesin tube covering the dummy roller. Then, after that, the metal roller was separated, and the surface-processed tube was removed.

By pressing a metal roller heated near the melting point temperature of the fluororesin tube, the surface of the fluororesin tube is softened, and furthermore, the metal roller having a mirror-finished surface is pressed against the surface of the metal roller. Was transferred to the surface-processed tube surface, and the surface of the surface-processed tube was smoothed. The surface unevenness of the fold portion of the treated fluororesin tube was measured by a method of JISB0651 using a contact type surface roughness meter (produced by Kosaka Laboratory Co., Ltd., stylus type surface roughness meter SE-3400). About 1μ
m.

Next, a description will be given of a heat roller type fixing device using the above tube. Example 1 of the present invention
FIG. 1 is a schematic configuration diagram of the fixing device.

The fixing roller 1 serving as a fixing member uses an A4 / LTR size roller having a roller diameter of about φ40 mm and a roller length of about 240 mm in this apparatus, and a heater 2 (in the present embodiment, as a heat source) as a heat source. 490W / 127V
Rated halogen heater) and A160
63, a core layer 3 having a thickness of 2.5 mm, a primer layer (not shown), an elastic layer 5, a primer layer (not shown), and a surface release layer 6.

As the elastic layer 5, a low hardness rubber is used. In this apparatus, the hardness of the test piece is about 11 ° (measured by an Asker-C hardness tester manufactured by Kobunshi Keiki) and the thermal conductivity is about 0.8. A low-hardness silicone rubber of × 10 ⁻³ cal1 / cmsecK is used. For the surface release layer 6, the above-mentioned smoothed fluororesin tube is used.

The product hardness of this fixing roller is about 61 ° (Asker-
C with a C hardness tester and a total weight of 1 kgf). The pressure roller 7 serving as a pressure member uses a roller having an outer diameter of φ40 mm and a roller length of about 230 mm similarly to the fixing roller, and has a heater 8 (490) inside similarly to the fixing roller.
W / 127 V rated product halogen heater), A16063, 2.7 mm thick cored bar 9, primer layer (not shown), elastic layer 11, primer layer (not shown), surface It is composed of a release layer 12.

As the elastic layer 11, the same silicone rubber as the elastic layer of the fixing roller is used, the thickness is set to 1.9 mm, which is different from that of the fixing roller, and the fixing and discharging direction is optimized. It is possible to separate the recording material without using it. The surface release layer 12 has the same surface roughness of about 50 μm as the fixing roller, which has been smoothed by the surface processing method described above.
An m-thick heat-shrinkable PFA tube is used. The product hardness of the pressure roller was about 65 ° (measured value using an Asker-C hardness meter at a total weight of 1 kgf).

The fixing roller and the pressure roller are pressed by a pressure spring (not shown), and a fixing nip width of about 9.5 mm is obtained at a total pressure of 40 kgf. Thermistors 13 and 14 as temperature detectors are brought into contact with the respective surfaces of the fixing roller 1 and the pressure roller 7. Based on the detected roller surface temperature, the roller surface temperature is determined by a heater driving circuit (not shown). The temperature control is controlled so as to be the temperature control target temperature (in the present embodiment, the print temperature is about 180 ° C.).
In addition, thermoswitches 15 and 16 as safety elements are arranged close to the surfaces of the fixing roller 1 and the pressure roller 7, and a non-contact type thermoswitch is used to prevent the roller surface from being damaged. I have.

FIG. 2 shows an example of a color image forming apparatus provided with the fixing device of the first embodiment of the present invention. This color image forming apparatus uses an intermediate transfer member. In FIG. 2, a rotating drum type electrophotographic photosensitive member (hereinafter, referred to as a “photosensitive drum”) 31 repeatedly used as a first image carrier has a predetermined peripheral speed (process speed) in a clockwise direction indicated by an arrow. Is driven to rotate.

The photosensitive drum 31 is uniformly charged to a predetermined polarity and potential by a primary charger (corona discharger) 32 in the course of rotation, and then is subjected to image exposure means (not shown) (color image of a color original image). By receiving the image exposure 33 by the separation optical system or the like, an electrostatic latent image corresponding to a first color component image (for example, a black component image) of a target color image is formed.

Next, the electrostatic latent image is developed by the first developing device (black developing device) 41 with black toner (colored charged particles) BK as the negative color. At this time, the second to fourth developing devices (magenta, cyan, and yellow developing devices) 42, 43, and 44 are turned off and do not act on the photosensitive drum 1, and the first color black toner image Is
It is not affected by the second to fourth developing devices 42 to 44.
An intermediate transfer drum 20 as an intermediate transfer member includes a pipe-shaped core metal 21 and a medium-resistance elastic layer 22 formed on an outer peripheral surface thereof.
Consists of The elastic layer 22 having a medium resistance has an electric resistance value (volume resistivity) of 10 ⁵ by mixing and dispersing a metal oxide such as carbon or zinc oxide in an elastic material such as silicon rubber, fluorine rubber, urethane rubber, or EPDM. It is a solid or foamed layer adjusted to have a medium resistance of 10 to 10 ¹¹ Ωcm.

The intermediate transfer drum 20 is a photosensitive drum 3
1 and is arranged in contact with the lower surface of the photosensitive drum 31 so as to rotate in the direction of the arrow at the same peripheral speed as the photosensitive drum 31. The intermediate transfer drum 20 is held in a state of being pressed against the photosensitive drum 31 with a predetermined pressing force.
A transfer nip portion N as a transfer portion is formed between.

In the process in which the black toner image of the first color formed and held on the surface of the photosensitive drum 1 passes through the transfer nip portion N, the first metal with respect to the intermediate transfer drum 20 is attached to the metal core 21 of the intermediate transfer drum 20. From the bias power supply 61, the polarity (plus) opposite to the toner charging polarity (minus in this embodiment)
Is applied, and an intermediate transfer is performed on the outer surface of the intermediate transfer drum 20 by the electric field formed in the transfer nip area. In this device, the applied voltage is between +2 KV and +5 KV.
It is. The surface of the photosensitive drum on which the transfer of the first color black toner image to the intermediate transfer drum 20 has been completed is cleaned by the cleaning device 34 (referred to as a series of steps using these black toners).

Similarly, charging of the rotating photosensitive drum 31 → image exposure 33 corresponding to a second color component (for example, a magenta component image) → development by magenta toner M of a second developing device (magenta developing device) 42 → formation. Transfer of the magenta toner image of the second color to the intermediate transfer drum 2O → cleaning of the surface of the photosensitive drum 31 by the cleaning device 34, charging of the rotating photosensitive drum 31 → corresponding to a third color component (for example, a cyan component image) Image exposure 33 → Development with cyan toner C of third developing device (cyan developing device) 43 →
Transfer of the formed cyan toner image of the second color to the intermediate transfer drum 20 → cleaning of the surface of the photosensitive drum 31 by the cleaning device 34, charging of the rotating photosensitive drum 31 → to a fourth color component (for example, a yellow component image) Corresponding image exposure 33 → development with yellow toner Y of fourth developing device (yellow developing device) 44 → transfer of formed yellow toner image as second color to intermediate transfer drum 20 → cleaning device for photosensitive drum 31 surface The four toner images (black, magenta, cyan, and yellow toner images) are formed on the outer surface of the rotating intermediate transfer drum 20 by sequentially performing the cleaning, the image formation, and the transfer cycle described above. Are sequentially superimposed and transferred to form a composite color toner (mirror image) corresponding to a target color image.

The transfer roller 25 is arranged in parallel with the intermediate transfer drum 20 and in contact with the lower surface of the intermediate transfer drum 20, and has the same peripheral speed as the intermediate transfer drum 20 or about 0.5 to 1 Rotate clockwise with arrows at peripheral speeds that differ by a percentage.

The transfer roller 25 includes a cored roller 26
And an elastic layer 27 formed on the outer periphery thereof.
In this embodiment, the elastic member 7 has a medium resistance.

In the process of sequentially transferring the first to fourth toner images from the photosensitive drum 31 to the intermediate transfer drum 20, the core metal 26 of the transfer roller 25 is supplied with toner from the second bias power supply 29 for the transfer roller 25. A bias voltage of the same polarity (minus) is applied. This bias voltage generates an electric field that repels the toner image from the transfer roller 25 to the intermediate transfer drum 20, and prevents transfer of the toner image on the transfer roller 25 or the intermediate transfer roller 20 side.

When the toner image on the photosensitive drum 31 is transferred to the intermediate transfer roller 20, the potential of the non-image portion is different from the potential of the toner image portion. Since the potential difference between the non-image portion 31 and the non-image portion is larger than the potential difference between the photosensitive drum 31 and the toner image portion, the transfer current flows more than the non-image portion.

This tendency is remarkable when the resistance value of the intermediate transfer roller 20 is low. For example, when the current value to the non-image portion is more than twice the current value to the toner image portion, the non-image The electric field of the portion affects the toner image.
That is, the low resistance body is not suitable for the intermediate transfer body. Conversely, in the case of a high-resistance body, the electric field that can be formed by the bias power supply 61 becomes too small, and the intermediate transfer itself is impaired. Therefore, a medium resistor in the range of 10 ⁵ to 10 ¹¹ Ωcm, preferably 10 ⁷ to 10 ¹⁰ Ωcm is suitable for the intermediate transfer member. Elastic body 22 having a volume resistance value in this range
By using +2 to +5 KV to the metal core 21, the above-described appropriate transfer current value can be set.

From the photosensitive drum 31 side, the intermediate transfer drum 20
The first to fourth toner images superimposed and transferred to the recording material 24 are transferred to the recording material 24 by the paper feed roller 36 from the paper feed cassette 35 side to the pressure nip n between the intermediate transfer roller 20 and the transfer roller 25. The recording material P separated and conveyed by a number of sheets is fed at a predetermined timing through a registration roller 37 and a transfer guide 38, and a bias power supply for the core metal 26 of the transfer roller 25 is changed from a second bias power supply 29 to a first bias power supply. , And a transfer bias of the polarity (+) opposite to that of the toner is applied to the metal core 26. This transfer bias has an absolute value larger than the bias of the polarity (+) opposite to that of the toner applied to the core metal 21 of the intermediate transfer drum 20 from the bias power supply 61, and the transfer bias causes the intermediate transfer. The toner image on the drum 20 side is transferred to the recording material P side fed to the pressure nip n between the intermediate transfer drum 20 and the transfer roller 25. The recording material P to which the toner image has been transferred is introduced into the fixing device 40 via the guide 39.

When the recording material P passes through the pressure nip n,
A bias power source for the core metal 21 of the intermediate transfer drum 20 and a bias power source for the core metal of the transfer roller 25 apply a bias having the same polarity (-) as the toner, respectively.
29. By this bias switching, the transfer residual toner on the surface of the intermediate transfer drum 20 is returned to the surface of the photosensitive drum 31 and collected by the cleaning device 34, so that the intermediate transfer drum 20 is cleaned. The toner adhered to the transfer roller 25 is also returned to the surface of the intermediate transfer drum 20 and further returned to the surface of the photosensitive drum 31 to be collected by the cleaning device 34, whereby the transfer roller 25 is also cleaned. As described above, since the elastic layer 22 has a medium resistance, the intermediate transfer drum 20 sufficiently transfers the transfer residual toner to the surface of the photosensitive drum 31 by applying a bias having the same polarity as the toner (cleaning bias), and enters a cleaning state. Therefore, there is no need to provide a special cleaning device, and the device configuration can be simplified.

An image was formed by using a fixing roller and a pressure roller using a fluororesin tube in which the surface unevenness of the fold was reduced in the fixing device of the image forming apparatus. In this image formation, a process speed of about 120
mm / sec, full color A4 4pp / min
m, Monocolor A4 16 ppm throughput was obtained. For evaluation of plain paper images, paper with high surface smoothness, for example, Futura La of CoatedPrinting Paper by Cosalidated
Using gser paper, a solid image was output on the entire surface, and the crease portion was evaluated. Such a post-fixing image could be improved to a level where the fold marks could not be recognized, and the image quality did not deteriorate. Further, in the OHP image, when a solid image of the entire surface of yellow was output so that the crease portion was conspicuous and projected and evaluated, the crease portion was not recognized as a black streak even when the color OHT was projected. .

The toner used for the image formation is as follows.
It was prepared as follows.

Here, the non-magnetic volume average particle diameter is about 10 μm.
m one-component toner, and the specific charge amount is about -2.
5 μC / g negative polarity toner is used. In particular,
Various toners were manufactured as follows.

First, a cyan toner was prepared as follows. In a 21-liter four-necked flask equipped with a high-speed stirring device, 710 parts by weight of ion-exchanged water and 0.1 mol /
L -Na ₃ was added P0 ₄ aqueous solution 450 parts by weight to adjust the rotational speed to 12,000 rpm and warmed to 65 ° C.. Here, 68 parts by weight of a 1.0 mol / l-CaCl ₂ aqueous solution was gradually added, and a minute hardly water-soluble dispersant Ca ₃ (P
A dispersion medium system containing O ₄ ) ₂ was prepared.

On the other hand, as the dispersoid, a mixture having the following composition was used.

Styrene monomer 165 parts by weight n-butyl acrylate monomer 35 parts by weight Pigment Blue 15:30 14 parts by weight Saturated polyester 10 parts by weight {terephthalic acid-propylene oxide modified bisphenol A acid value 15, peak molecular weight: 6000} salicylic acid metal compound 2 parts by weight Compound represented by the following general formula (8) (Maximum peak value 59.4 ° C) 60 parts by weight

[0081]

Embedded image

After the above mixture was dispersed for 3 hours using an attritor, a dispersion containing 10 parts by weight of 2,2′-azobis (2,4-dimethylvaleronitrile) as a polymerization initiator was added to a dispersion medium. 15 while maintaining the rotation speed
Granulated for minutes. Then, the stirring device was changed from a high-speed stirring device to a blade stirring blade, the internal temperature was raised to 80 ° C., and the polymerization was continued at 50 rotations for 10 hours. After completion of the polymerization, the slurry was cooled, and dilute hydrochloric acid was added to remove the dispersion medium. After further washing and drying, the weight average particle size of the cyan toner measured by a Coulter counter was 6.2 μm, the number variation coefficient was 27%, and SF-1 was 104.

Similarly, a yellow toner, a magenta toner, and a black toner with SF-1 of 104 were produced. In addition, as a coloring agent, C.I.
I. Pigment Yellow 17, Magenta Toner
C. I. Pigment Red 122 and black toner used carbon black.

[0084]

Embodiment 2 <Electromagnetic induction heating type fixing device> A description will be given of a fluororesin tube which covers a fixing member of an electromagnetic induction heating type fixing device. This tube was a PFA tube having a thickness of about 30 μm. When a smoothing treatment was performed by pressing a heated member under the same conditions as in Example 1, the unevenness of the fold became about 1 μm.

Next, a description will be given of a fixing device of the electromagnetic induction heating type using the above tube. In Example 2, unlike Example 1, an electromagnetic induction heating type fixing device using an endless belt for the fixing member was used. FIG. 5 is a cross-sectional side view of a main part of the fixing device. This fixing device is a device of an electromagnetic induction heating system in which a cylindrical electromagnetic induction heating film is used as an endless belt and a pressing roller as a pressing member is driven.

The magnetic field generating means is a magnetic core 217a or 217.
b.217c and the exciting coil 218. The magnetic cores 217a, 217b, and 217c are members having high magnetic permeability, and are preferably made of a material used for a transformer core such as ferrite or permalloy, and more preferably 100 kHz.
Even above, it is preferable to use ferrite having a small loss.

The excitation coil 218 is connected to an excitation circuit (not shown) at a power supply section. This excitation circuit is 20kHz
To 500 kHz can be generated by the switching power supply. The exciting coil 218 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the exciting circuit. The alternating magnetic flux generates an eddy current in the electromagnetic induction heating layer of the fixing film 210. This eddy current generates Joule heat due to the specific resistance of the electromagnetic induction heating layer.

Reference numerals 216a and 216b denote a film guide member having a trough-like shape with a substantially semi-circular cross section. Is loosely fitted. The film guide member 216a includes magnetic cores 217a, 217b, and 217c as magnetic field generating means.
And the exciting coil 218 are held inside. The film guide member 2116 serves to pressurize the fixing nip, support the exciting coil 218 and the magnetic core 217 as the magnetic field generating means 215, support the fixing film 210, and stabilize the conveyance of the film 210 during rotation. I do. The film guide member 216 is an insulating member that does not hinder the passage of magnetic flux, and is made of a material that can withstand a high load.

The film guide member 216a has
A good heat conducting member 240 extending in the direction perpendicular to the paper is provided on the side of the nip portion N facing the pressure roller 230, and the fixing film 210.
It is arranged inside.

In this apparatus, the good heat conductive member 24
Aluminum is used for 0. The good heat conducting member 24
0 means that the thermal conductivity k is k = 240 [W · m ⁻¹ · K ⁻¹ ];
The thickness is 1 [mm]. The good heat conducting member 240 includes an exciting coil 218 as a magnetic field generating means and a magnetic core 217a.
217b and 217c are disposed outside this magnetic field so as not to be affected by the magnetic field generated from the magnetic field.

More specifically, the good heat conducting member 240 is disposed at a position where the magnetic core 217c is separated from the exciting coil 218, and is positioned outside the magnetic path formed by the exciting coil 218 to form the good heat conducting member 240. Try not to affect. 2
Reference numeral 22 denotes a horizontally long pressing rigid stay which is disposed in contact with the inner surface flat portion of the film guide member 216b. Magnetic cores 217a, 217b, 217c and excitation coil 218
There is an insulating member 219 for insulation between the pressurizing rigid stay 222 and the pressurizing rigid stay 222.

The flange members 223a and 223b are detached from the left and right ends of the assembly of the film guide members 216a and 216b, and are rotatably mounted while fixing the left and right positions. As a result, the fixing film serves to regulate the shift of the fixing film along the length of the film guide member.

The pressure roller 230 as a pressure member is made of a heat-resistant and elastic material such as silicone rubber, fluoro rubber, fluoro resin, etc., which is formed by coating a core 230a and a roller concentrically and integrally around the core. A layer 230b is provided, and both ends of the core bar 230a are rotatably supported by bearings between sheet metal (not shown) of the apparatus.

By pressing compression springs between both ends of the rigid pressing stay 222 and the spring receiving member on the apparatus chassis side, a pressing force is applied to the pressing constituent stay 222. Thereby, the film guide member 216a
Of the fixing film 21 and the upper surface of the pressure roller 230
The fixing nip portion N having a predetermined width is formed by being pressed against each other with 0 therebetween.

The pressure roller 230 is driven by driving means M (not shown).
As a result, it is driven to rotate in the counterclockwise direction indicated by the arrow. Due to the rotational driving of the pressure roller 230, the fixing film 2 is formed by the frictional force between the pressure roller 230 and the outer surface of the fixing film 210.
10, a rotational force acts on the pressure roller 2 while the inner surface of the fixing film 210 slides in the fixing nip N in close contact with the lower surface of the good heat conducting member 240.
The outer circumferences of the film guide members 216a and 216b are rotated at a peripheral speed substantially corresponding to the peripheral speed of 30.

In this case, in order to reduce the mutual sliding friction between the lower surface of the good heat conducting member 240 in the fixing nip N and the inner surface of the fixing film 210, the lower surface of the good heat conducting member 240 in the fixing nip N is fixed. A lubricant such as heat-resistant grease may be interposed between the inner surface of the film 210 and the lower surface of the good heat conductive member 240 may be covered with a lubricating member. This is because when the surface sliding property is not good in material, such as when aluminum is used as the good heat conducting member 240, or when the finishing process is simplified, the sliding fixing film 210 is damaged. Fixing film 2
This is to prevent the durability of No. 10 from deteriorating.

The good heat conducting member 240 has the effect of making the temperature distribution in the longitudinal direction uniform. For example, when small size paper is passed, the amount of heat in the non-sheet passing portion of the fixing film 210 is reduced by the good heat conducting member. The heat is transferred to the small-size paper passing portion by the heat conduction to the small-size paper passing portion by the heat conduction in the longitudinal direction of the good heat conducting member 240. As a result, an effect of reducing power consumption when passing small-sized paper is also obtained.

Further, a convex rib is formed on the peripheral surface of the film guide member 216a at a predetermined interval along the length thereof so that the peripheral surface of the film guide member 216a slides in contact with the inner surface of the fixing film 210. The rotational load of the fixing film 210 is reduced by reducing the resistance. Such a convex rib portion can be similarly formed and provided on the film guide member 216b.

The temperature of the fixing nip N is controlled such that a predetermined temperature is maintained by controlling the current supply to the exciting coil 218 by a temperature control system including a temperature detecting means (not shown). This apparatus includes a temperature sensor 226 such as a thermistor for detecting the temperature of the fixing film 210, and in this example, controls the temperature of the fixing nip N based on the temperature information of the fixing film 210 measured by the temperature sensor 226. Like that. In this apparatus, the control temperature can be switched according to the transport speed by a CPU (not shown) of the image forming apparatus main body.

Thus, the fixing film 210 rotates, and the power is supplied from the excitation circuit 227 to the excitation coil 218 to generate the electromagnetic induction heat of the fixing film 210 as described above, so that the fixing nip N rises to a predetermined temperature. In the temperature-controlled state, the recording material P on which the unfixed toner image t conveyed from the image forming unit has been formed has an image surface facing upward between the fixing film 210 and the pressure roller 230 in the fixing nip N. That is, the fixing nip portion N is introduced so as to face the fixing film surface, and the image surface is brought into close contact with the outer surface of the fixing film 210 at the fixing nip portion N, and the fixing nip portion N is conveyed together with the fixing film 210. In the process in which the recording material P is sandwiched and conveyed in the fixing nib portion N together with the fixing film 210, the fixing film 210 is heated by electromagnetic induction heating, and the unfixed toner image t on the recording material P is heated and fixed. You. After passing through the fixing nip N, the recording material P is separated from the outer surface of the rotary fixing film 210 and is discharged and conveyed. After passing through the fixing nip, the heat-fixed toner image on the recording material is cooled and becomes a permanent fixed image.

In this apparatus, as shown in FIG. 5, a thermo switch 250, which is a temperature detecting element, is provided at a position of the fixing film 210 opposite to the heat generating area H in order to cut off power supply to the exciting coil 218 during runaway. are doing. Further, the thermoswitch 250 is disposed in a non-contact manner on the outer surface of the fixing film 210 so as to face the heat generating region H of the fixing film 210. The distance between the thermoswitch 250 and the fixing film 210 was about 2 m. This prevents the fixing film 210 from being damaged by the contact of the thermoswitch 250,
Deterioration of the fixed image due to durability can be prevented.

According to this device, when the fixing device goes out of control due to a device failure, unlike the configuration in which heat is generated in the nip portion N, the fixing device stops in a state where paper is pinched in the fixing nip N, and power is supplied to the exciting coil 218. Even when the fixing film 210 continues to generate heat, the paper is not directly heated because no heat is generated in the nip portion N where the paper is sandwiched. Further, in the heat generation region H where the heat generation amount is large, the thermo switch 250
Is installed, the thermo switch 250
Is detected, and when the thermo switch is turned off, the power supply to the exciting coil 218 is cut off by the relay switch.

According to this apparatus, the ignition temperature of paper is about 400
Since the temperature is around ° C., the heat generation of the fixing film can be stopped without firing the paper. A temperature fuse may be used as the temperature detection element in addition to the thermoswitch.

When a toner containing a low softening substance is used, it is preferable not to provide an oil application mechanism for preventing offset in the fixing device. However, when a toner containing no low softening substance is used, May be provided with an oil application mechanism. Also, when a toner containing a low softening substance is used, oil application or cooling separation may be performed.

As the exciting coil 218, a bundle (bundle) of a plurality of thin copper wires, each of which is insulated and coated, is used as a conducting wire (electric wire) constituting a coil (wire loop). It is wound to form an exciting coil. In this device, the exciting coil 218 is formed by winding 10 turns.

As the insulating coating, a coating having heat resistance is preferably used in consideration of heat conduction due to heat generation of the fixing film 210. For example, a coating of amide imide or polyimide may be used.

The density of the excitation coil 218 may be improved by applying pressure from the outside. The shape of the exciting coil 218 is set to follow the curved surface of the heat generating layer. In this apparatus, the distance between the heating layer of the fixing film and the exciting coil 218 was set to be about 2 m. Excitation coil holding member 2
As the material of No. 19, a material having excellent insulation properties and good heat resistance is preferable. For example, phenolic resin, fluorine resin, polyimide resin, polyamide resin, polyamideimide resin, PE
EK resin, PES resin, PPS resin, PFA resin, PT
It is preferable to select FE resin, FEP resin, LCP resin, or the like. The shorter the distance between the magnetic cores 217a, 217b, 217c and the exciting coil 218 and the heat generating layer of the fixing film is, the higher the efficiency of magnetic flux absorption is. However, when the distance exceeds 5m, the efficiency is reduced. It is preferable to keep the distance within 5 m, because it is significantly reduced. If the distance is within 5 m, the distance between the heating layer of the fixing film 210 and the exciting coil 218 does not need to be constant.

Excitation coil holding member 2 for excitation coil 218
With respect to the lead wires from, that is, 218a and 218b, the outside of the bundle is insulated from the exciting coil holding member 219 for insulation.

The fixing film 210 of this apparatus includes a heat generating layer made of a metal film or the like serving as a base layer of the electromagnetically induced heat generating fixing film 210, an elastic layer laminated on the outer surface thereof,
It has a composite structure of a release layer laminated on its outer surface. For adhesion between the heat generating layer and the elastic layer and between the elastic layer and the release layer, a primer layer (not shown) may be provided between each layer. In the substantially cylindrical fixing film 210, the heat generating layer is on the inner surface side, and the release layer is on the outer surface side. As described above, when the alternating magnetic flux acts on the heat generating layer, an eddy current is generated in the heat generating layer, and the heat generating layer generates heat. The heat heats the fixing film 210 via the elastic layer and the release layer, and heats the recording material P as the material to be passed through the fixing nip N to heat and fix the toner image.

The heat generating layer is preferably made of a ferromagnetic metal such as nickel, iron, ferromagnetic SUS, and nickel-cobalt alloy. A non-magnetic metal may be used, but a metal such as nickel, iron, magnetic stainless steel, or a cobalt-nickel alloy, which has good magnetic flux absorption, is more preferable.

It is preferable that the thickness is larger than the skin depth represented by the following formula and 200 μm or less. The skin depth σ [m] is determined by the frequency f [Hz] of the excitation circuit and the magnetic permeability μ.
And the specific resistance ρ [Ωm]

[0112]

Σ = 503 × (ρ / fμ) ^1/2

This indicates the depth of absorption of electromagnetic waves used in electromagnetic induction. At a depth deeper than this, the intensity of the electromagnetic waves is 1 / e or less. Absorbed in.

The thickness of the heat generating layer is preferably 1 to 100 μm.
Is good. If the thickness of the heat generating layer is smaller than 1 μm, most of the electromagnetic energy cannot be absorbed, so that the efficiency becomes poor. On the other hand, if the heat generating layer exceeds 100 μm, the rigidity becomes too high, and the flexibility deteriorates, which is not practical for use as a rotating body. Therefore, the thickness of the heat generating layer is 1 to 100.
μm is preferred.

The elastic layer is made of silicone rubber, fluorine rubber,
It is a material with good heat resistance and good thermal conductivity such as fluorosilicone rubber. The thickness of the elastic layer is preferably from 10 to 500 μm. This elastic layer has a thickness necessary to guarantee the quality of the fixed image.

When a color image is printed, a solid image is formed over a large area on the recording material P, especially for a photographic image. In this case, if the heating surface (release layer) cannot follow the unevenness of the recording material or the unevenness of the toner layer, uneven heating will occur, and uneven gloss will occur in the image in portions where the amount of heat transfer is large and small. The glossiness is high in a portion having a large amount of heat transfer, and low in a portion having a small amount of heat transfer. If the thickness of the elastic layer is 10 μm or less, the elastic layer cannot follow the irregularities of the recording material or the toner layer, resulting in uneven image gloss. On the other hand, when the thickness of the elastic layer is 1000 μm or more, the thermal resistance of the elastic layer becomes large, and it is difficult to realize a quick start. More preferably, the thickness of the elastic layer is 50 to 500 μm
Is good.

If the hardness of the elastic layer is too high, the elastic layer cannot follow the irregularities of the recording material or the toner layer, resulting in uneven image gloss. Therefore, the hardness of the elastic layer is 60
° (JIS-A) or less, more preferably 45 ° (JIS
-A) The following is preferred.

The thermal conductivity λ of the elastic layer is 6 × 10 ⁻⁴ to 2 ×
It is preferably 10 ⁻³ [ca1 / cm · sec · deg]. Thermal conductivity λ is 6 × 10 ^-4 [ca1 / cm · se
c · deg], the thermal resistance is large,
The temperature rise in the surface layer (release layer) of the fixing film becomes slow. Thermal conductivity λ is 2 × 10 ^-3 [ca1 / cm · sec]
[Deg], the hardness becomes too high or the compression set becomes worse. Therefore, the thermal conductivity λ is 6 × 10 ⁻⁴ to 2 × 10 ⁻³ [ca1 / cm · sec ·
deg] is preferred, and 8 × 10 ^{−4 to} 1.5 × 10 ⁻³ [c
a1 / cm · sec · deg] is more preferable.

The release layer has a smoothed thickness of about 3
A 0 μm PFA tube is formed.

In the configuration of the fixing film 210,
A heat insulating layer may be provided on the film guide surface side of the heat generating layer (the side opposite to the elastic layer of the heat generating layer). As the heat insulating layer, a fluororesin, a polyimide resin, a polyamide resin, a polyamideimide resin, a PEEK resin, a PES resin, a PPS resin,
A heat-resistant resin such as PFA resin, PTFE resin, and FEP resin is preferable. The thickness of the heat insulating layer is preferably from 10 to 100 μm. When the thickness of the heat insulating layer is smaller than 10 μm, the heat insulating effect cannot be obtained and the durability is insufficient. ―
On the other hand, if it exceeds 1000 μm, the magnetic cores 217a and 217
The distance from b.217c and the exciting coil 218 to the heating layer becomes large, and the magnetic flux is not sufficiently absorbed by the heating layer. Since the heat insulating layer can insulate heat generated in the heat generating layer from going to the inside of the fixing film, the efficiency of heat supply to the recording material P side is improved as compared with the case without the heat insulating layer.
Therefore, power consumption can be suppressed.

The nip width of the fixing device of the full-color image forming apparatus is preferably at least 7.0 m in order to sufficiently secure the fixability of a full-color image having a large amount of applied toner. If the temperature is less than this, it is not possible to apply a sufficient amount of heat to the unfixed toner and the recording material for fixing, so that a fixing defect occurs. Further, in order to sufficiently secure the transparency of the OHP full-color image, the surface pressure of the nip portion is preferably 0.8 kgf / cm ² or more. Below this range, the surface of the fixed toner layer cannot be made sufficiently smooth, so that irregularly reflected light increases and the amount of transmitted light in the 0HP image area decreases. In view of the above, in this fixing device, the pressure roller and the fixing film are pressed at 21 kgf, the nip width is set to about 8.0 m, and the surface pressure of the nip is set to 1.2 kgf / cm ² (longitudinal length of the nip) The length in the direction is 220 mm).

Since the fixing device described above can directly generate heat from the fixing film by utilizing the generation of the induced current, the fixing process is more efficient than the heat roller type fixing device using a halogen lamp as a heat source. And thermal responsiveness is also improved. Further, due to its structure, this fixing device can set the pressing force higher than that of a film heating type fixing device using a ceramic heater.

The above-described fixing device provided with an endless belt coated with a fluororesin tube having a reduced surface unevenness at the fold portion is used for the fixing device of the image forming device used in the first embodiment. As a result, the unevenness of the fold portion was smoothed in this way, so that the image of the fold portion did not appear as a streak when the image after fixing or the OHP projection was performed, and the image quality did not deteriorate. The same toner used in the evaluation of Example 1 was used as the toner, and the image forming conditions were evaluated in the same manner as in Example 1.

[0124]

Embodiment 3 <Film Heating Fixing Device Using Ceramic Heater> A fluororesin tube for covering a pressing member of a film heating fixing device using a ceramic heater will be described.

This tube is made of PFA having a thickness of about 50 μm.
When a smoothing treatment was performed by pressing a member which was a tube and heated under the same conditions as in Examples 1 and 2, the unevenness of the fold became about 1 μm. Next, a film heating type fixing device using a ceramic heater using the above tube will be described.

In the third embodiment of the present invention, an on-demand fixing device using a ceramic heater and using an endless belt as a fixing member is used.

FIG. 6 is a sectional view of the fixing device. The rotating body forming the nip N is a cylindrical fixing film 310.
It is. The fixing film 310 has a thickness of 100 to reduce the heat capacity and improve the quick start property.
μm or less, preferably 20 to 50 μm heat-resistant PTF
Single layer of E, PFA, FEP, or PI, PAI, P
It is preferable to use a composite layer film in which the outer peripheral surface of EEK, PES, PPS, or the like is coated with PTFE, PFA, FEP, or the like via a conductive primer layer. A film guide 316 having a semicircular trough-shaped section is provided inside the rotating body. A ceramic heater 305 is provided at a position extending along the longitudinal direction of the film guide nip. The ceramic heater 305 is formed by applying an electric resistance material such as Ag / Pd to the surface of a substrate 305a made of alumina or the like by about 10 μm.
A heating layer 305b applied by screen printing or the like is provided in a width of 1 to 5 m, and a protective layer 305c is coated thereon with glass, fluororesin, or the like. There is a pressure roller 330 as a pressure rotating body. Reference numeral 326 denotes a temperature detecting element using a thermistor, which is installed on the back surface of the ceramic heater 305. The temperature control is performed by controlling the power supplied to the ceramic heater 305 by controlling the phase and wave number of the AC voltage supplied to the ceramic heater 305 by the triac 306 based on information from the temperature detection element 326.

Ceramic heater 305 as heating element
And a pressure roller 330 as a pressure member, with a heat-resistant film 310 interposed therebetween to form a nip portion N, and an unfixed toner between the fixing film 310 of the nip portion N and the pressure roller 330. The recording material P on which the image T is formed and carried is introduced, and is nipped and conveyed together with the fixing film 310, so that the heat of the ceramic heater 305 is applied through the film 310 and the unfixed toner is pressed by the nip N. Statue T
Is fixed on the recording material surface P.

This fixing device includes a ceramic heater 305
An on-demand type apparatus can be configured by using a low heat capacity member for the fixing film 310, and only when performing image formation, the ceramic heater 305 serving as a heat source may be energized to generate heat to a predetermined fixing temperature. The waiting time from the power-on of the image forming apparatus to the image forming executable state is short (quick start property), the power consumption during standby is significantly small (power saving), and the thermal responsiveness is much better than the heat roller method. There are advantages such as. The surface of the pressure roller 330 is covered with a fluororesin tube whose surface has been smoothed for durability and the like described above.
It is covered with a μm PFA tube.

In such an on-demand fixing device, since only the amount of heat necessary for the toner and the recording material is efficiently added, the amount of heat applied to the pressure roller is small and the surface temperature of the pressure roller is lowered. I will. In addition, the fixing operation is started before the pressure roller is warmed due to the quick start property.

For this reason, toner, paper powder and paper filler (calcium carbonate, talc, kaolin, etc.) are placed on the surface of the pressure roller.
In addition, when these mist easily adhere as dirt, particularly when there are surface irregularities, the dirt on the roller may spread from the portion. The conventional pressure roller has a tube fold of about 4 μm and has a large amount of calcium carbonate in paper powder and filler. KYM LU made by Kymi Paper Mills (Finland)
When a sheet of paper such as X (Laser & InkJet) paper (A4, 80 g / m ² ) was passed, about 500 sheets were found to have stains on the uneven portion of the fold.

Then, when the fixing device including the pressure roller was used for the fixing device of the image forming device used in the first embodiment to form an image, about 3,000 KYM LUX sheets were passed. However, no particularly problematic roller contamination was observed, and the occurrence of roller contamination was reduced.
The same toner used in the evaluation of Example 1 was used as the toner, and the image forming conditions were evaluated in the same manner as in Example 1.

[0133]

According to the present invention, a heated member is pressed against the surface of a fluororesin tube having irregularities at the folds, thereby smoothing the surface irregularities at the folds of the fluororesin tube by a simple method. Can be processed. In addition, by covering the fixing member and the pressing member with such a surface smoothing-treated fluororesin tube, or by using the surface peeling layer of the fixing member and the pressing member, a fold mark is formed on an image after fixing, OHT, or the like. It is possible to prevent the image quality from deteriorating due to the appearance. Further, since the surface unevenness of the fold portion is smoothed, it is possible to reduce the generation of stains on the fixing member and the pressing member.

[0134]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram illustrating an example of a color image forming apparatus using the fixing device of the present invention.

FIG. 3 is a diagram showing an example of the surface processing method of the present invention.

FIG. 4 is a schematic configuration diagram of a conventional fixing device.

FIG. 5 is a sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 6 is a sectional view of a fixing device according to a third embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixing roller 2, 8 Heater 3, 9 Core metal 5, 11 Elastic layer 6, 12, 6 ', 12' Surface release layer (fluororesin tube) 7 Pressure roller 14 Thermistor 16 Thermoswitch 20 Intermediate transfer body 21 Core Gold 22 Elastic layer 25 Transfer roller 26 Core metal 27 Elastic layer 28, 29, 61, 62 Bias power supply 31 Photoconductor 32 Charger 33 Light beam 34 Cleaner 35 Paper feed cassette 36 Paper feed roller 37 Registration roller 39 Guide 40 Fixing device 41 42, 43, 44 Developing device 100 Discharge roller 101 Discharge roller t Toner P Recording material 200 Fixing device 210 Fixing film 215 Magnetic field generating means (not shown) 216a / 216b Film guide member 217a / 217b / 217c Magnetic core 218 Exciting coil 219 Excitation coil holding member 222 223a / 223b Flange member 226 Temperature sensor 227 Excitation circuit (not shown) 230 Pressure roller 230a Core bar 230b Heat resistant / elastic material layer 240 Heat conduction member 250 Thermoswitch 305 Ceramic heater 305a Substrate 305b Heat generation layer 305c Protective layer 306 Triac 310 Fixing film 316 Film guide 326 Temperature detecting element 330 Pressure roller

Claims (8)

[Claims] 1. A fixing device comprising a fixing member or a pressing member for fixing a toner image to a recording material, wherein the fixing member or the pressing member is formed by pressing a heated surface smooth member. A fixing device, wherein the unevenness of the fold portion on the surface is covered with a fluororesin tube whose smoothness has been previously smoothed. 2. The fixing device according to claim 1, wherein the fixing member or the pressing member is a roller. 3. The fixing device according to claim 1, wherein the fixing member or the pressing member is an endless belt. 4. The tube according to claim 1, wherein the fluororesin tube is a tube molded from one or more resins selected from the group consisting of PFA resin, PTFE resin, and FEP resin. The fixing device according to claim 1. 5. The fluororesin tube according to claim 1, wherein the fluororesin tube is smoothed by pressing a surface smooth member heated within a range of ± 20 ° C. of its melting point temperature. The fixing device according to claim 1. 6. A surface processing method in which a heated surface smooth member is pressed against the surface of a fluororesin tube having folds and projections to smooth the folds and projections. 7. A dummy roller having substantially the same diameter is inserted into the fluororesin tube having the creases and depressions, and the heated surface smooth member is pressed against the surface of the fluororesin tube covering the dummy roller. The surface processing method according to claim 6, wherein the unevenness of the fold portion is smoothed by rotating while applying. 8. The surface processing method according to claim 6, wherein a heating temperature of the surface smoothing member is within ± 20 ° C. of a melting point temperature of the fluororesin tube.