JPH09127809A - Heating body, fixing film, thermal fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an adverse effect caused by the offset of toner from occurring by substantially eliminating the offset of the toner caused by an electrostatic factor with respect to a fixing film in a film heating system thermal fixing device. SOLUTION: An electrical conductive layer 1e is provided on the contact surface with the fixing film 1 of the heating body 1 of the film heating system thermal fixing device. By connecting a rectifying device 8 to the layer 1e and grounding it or directly impressing a bias, the polarity of the surface potential of the film 2 is made to identical to the electrostatic charge polarity of the toner (developer) so that the turbulence of a toner image is not caused on a recording material. By also connecting the rectifying device to a pressure member 9 and impressing the bias on it in the same way as the heating body 1, the polarity of the surface potential of the pressure member 9 is made to reverse to the electrostatic charge polarity of the toner and set so that the transfer electric charge of the recording material is not lost from the pressure member side and the toner image is attracted to the recording material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a laser beam printer, a microfilm reader printer, an image display device and a recording machine.
The present invention relates to a film heating type heat fixing device as a heating device for heating and fixing (including hypothetical fixing processing) a developer image formed and carried on a recording material as a permanently fixed image. Further, the present invention relates to a heating body and a fixing film as constituent members of the apparatus. Furthermore, the present invention relates to an image forming apparatus including the device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus, a recording material such as a transfer material or a photosensitive paper is formed and carried by a transfer method or a direct method by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording and the like. Further, as a device for heating and fixing a developer image (toner image) of desired image information, a heat roller type device is often used. This is because the recording material to be image-fixed is nipped and conveyed by a heating roller (fixing roller) which is heated and maintained at a predetermined temperature and a pressure roller which has an elastic layer and is in pressure contact with the heating roller. To heat and fix the developer image on the recording material surface. Also, the hot plate method
Various methods and configurations such as belt heating method, flash heating method and oven heating method are also known.

Recently, a film heating type heating device has been put into practical use (Japanese Patent Laid-Open No. 63-313182).
JP-A-2-157878 and JP-A-4-44075
-44083, JP-A-4-20498-204
984, etc.).

FIG. 9 shows a schematic cross-sectional view of a main part of a film heating type heat fixing device. Reference numeral 1 denotes a horizontally long heater having a low heat capacity, which is fixedly supported by a heat-resistant / heat-insulating support member 3, and is, for example, a ceramic heater. Reference numeral 2 is a thin heat-resistant film (fixing film) such as polyimide. Reference numeral 9 is an elastic pressure roller as a pressure member. The heating body 1 and the pressure roller 9 are pressed against each other with a predetermined pressing force sandwiching the fixing film 2 to form a fixing nip portion (heating nip portion) N having a predetermined width. The fixing film 2 moves and passes through the fixing nip portion N while being brought into close contact with and sliding on the surface of the heating body 1 in the direction of the arrow by the rotational driving force of the pressure roller 9 or another driving member.

When the fixing film 2 is moved and driven, and the heating body 1 rises to a predetermined temperature and is temperature-controlled, a material to be heated is provided between the fixing film 2 and the pressure roller 9 in the fixing nip portion N. The recording material P carrying the toner image (developer image) T is introduced with the toner image carrying surface side being the fixing film 2 side, so that the recording material P is fixed to the fixing nip portion N.
In the above, the heating element 1 is brought into close contact with the fixing film 2 and moves through the fixing nip portion N together with the fixing film 2. In the moving and passing process, the heat of the heating element 1 is applied to the recording material P via the fixing film 2, and the toner image T is heated and fixed on the surface of the recording material P. The recording material P passing through the fixing nip portion N is separated from the surface of the fixing film 2 and conveyed.

In such a film heating type apparatus, a heating body having a low heat capacity and a fixing film having a thin film having a low heat capacity can be used as compared with other heating apparatuses such as a heat roller system. It is possible to save power and shorten the wait time (the time from when the device is turned on to when it is ready to print), and it has the advantages of quick start and suppressing the temperature rise inside the machine.

[0007]

In the heat fixing device of the film heating type as described above, a part of the unfixed toner image T on the recording material P is transferred to the surface of the fixing film,
A so-called toner offset phenomenon (hereinafter referred to as an offset) that adheres to the image thereafter occurs.

Generally, the occurrence of the offset can be roughly classified into a temperature factor and an electrostatic factor.

The offset due to the temperature factor includes a so-called low temperature offset in which the toner heating temperature of the apparatus is too low and the toner is not fixed, and a high temperature offset caused by the toner heating temperature being too high and the toner being melted in a liquid state. But
The high temperature offset can be prevented by appropriately setting the characteristics of the developer (toner) used, the recording material conveying speed, the pressing force, and the temperature control means.

On the other hand, the offset due to an electrostatic factor is an electrostatic transfer of the charged toner on the recording material to the fixing film. Since this phenomenon largely depends on the type of recording material, environment, material of pressure member, resistance, etc., its control is difficult, and adverse effects due to offset, for example, recording material stain due to retransfer of offset toner, offset toner Occasionally, the recording material is wrapped around the pressure member due to the toner being attached to the pressure member and soiling the toner.

SUMMARY OF THE INVENTION It is an object of the present invention to substantially eliminate the occurrence of toner offset due to electrostatic factors on a fixing film in a film heating type heat fixing device, and prevent the above-mentioned adverse effects of toner offset. To do.

[0012]

The present invention provides a heating element, a fixing film, a heat fixing device and an image forming apparatus, which are characterized by the following constitutions.

(1) An image-carrying recording material carrying a developer image between the fixing film and the pressing member in the fixing nip portion formed between the heating body and the pressing member with the fixing film interposed therebetween. The heat of the heating element is applied to the recording material through the fixing film by introducing the surface side to the fixing film side and adhering it to the heating element through the fixing film and moving and passing through the fixing nip part with the fixing film. A heating element used in a heat fixing device for heating and fixing the developer image on the surface of the recording material, wherein the heating element has a conductive layer on the contact surface with the fixing film.

(2) An image bearing recording material carrying a developer image between the fixing film and the pressing member in the fixing nip portion formed between the heating body and the pressing member with the fixing film interposed therebetween. The heat of the heating element is applied to the recording material through the fixing film by introducing the surface side to the fixing film side and adhering it to the heating element through the fixing film and moving and passing through the fixing nip part with the fixing film. A fixing film used in a heat fixing device for heating and fixing a developer image on the surface of a recording material, wherein the fixing film has a conductive layer on a contact surface with a heating body.

(3) A recording material carrying a developer image between the fixing film and the pressing member in the fixing nip portion formed between the heating member and the pressing member with the fixing film sandwiched therebetween. The heat of the heating element is applied to the recording material through the fixing film by introducing the surface side to the fixing film side and adhering it to the heating element through the fixing film and moving and passing through the fixing nip part with the fixing film. In the heat fixing device for heating and fixing the developer image on the recording material surface, the heating body has a conductive layer on the contact surface with the fixing film.

(4) The heat fixing device as described in (3) above, wherein the conductive layer of the heating element is grounded through a rectifying element.

(5) The heat fixing device as described in (3) above, wherein a bias having the same polarity as that of the developer is applied to the conductive layer of the heating element.

(6) The heat fixing device as described in any one of (3) to (5) above, wherein the fixing film has a conductive layer on the contact surface with the heating body.

(7) In the heat-fixing device according to any one of (3) to (6), the pressing member has a release layer having an insulating surface and a conductive inner elastic layer. A heat-fixing device characterized in that a core metal of the pressure member is grounded through a rectifying element.

(8) In the heat fixing device according to any one of (3) to (6), the pressing member has a release layer having an insulating surface and a conductive inner elastic layer. A heat fixing device characterized in that a bias having a polarity different from that of the developer is applied to the core metal of the pressure member.

(9) In the heat fixing device according to any one of (3) to (6), a conductive material is used for the pressure member, and the core metal of the pressure member is a rectifying element. A heating and fixing device characterized in that it is grounded through.

(10) Any one of the above (3) to (6)
The heat fixing device according to the third aspect is characterized in that a conductive member is used for the pressure member, and a bias having a polarity different from that of the developer is applied to the core metal of the pressure member.

(11) The heating and fixing device as described in any one of (3) to (10) above, wherein the fixing film is moved and driven by the rotational driving of the pressing member.

(12) In the heat fixing device described in any one of (3) to (10), the fixing film is moved and driven by a film driving member other than the pressure member. Heat fixing device.

(13) An image forming apparatus having an image forming means for forming and carrying a developer image on a recording material and a fixing means for heating and fixing the developer image on the recording material, wherein the fixing means is the above (3). An image forming apparatus, comprising the heat fixing device according to any one of (1) to (12).

<Operation> In order to achieve the above object, the present invention provides a conductive layer on the contact surface of the heating body of the film heating type heat fixing device with the fixing film, and connects the rectifying element to this conductive layer. The potential of the surface of the fixing film is made to have the same polarity as the charging polarity of the toner by grounding or directly applying a bias so that the toner image on the recording material is not disturbed.

Further, by connecting a rectifying element and applying a bias to the pressure member in the same manner as the heating element, the potential on the surface of the pressure member is made to have a polarity opposite to the charge polarity of the toner, and the pressure member is pressed. The toner image is set to be attracted onto the recording material without losing the transfer charge of the recording material from the side.

With the above-described structure, it is possible to output a good image without offset even under various recording materials and environments, and prevent the harmful effects caused by the offset.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION

<Embodiment 1> (FIGS. 1 to 4) (1) Example of image forming apparatus FIG. 1 is a schematic view of an example of an image forming apparatus. The image forming apparatus of this example is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 31 denotes an electrophotographic photosensitive drum (hereinafter abbreviated as drum) as an image bearing member, which has a predetermined process speed (peripheral speed, image forming speed) in a clockwise direction indicated by an arrow.
Is driven to rotate. This example has a process speed of 50 mm /
sec.

In the rotating process, the drum 31 is uniformly subjected to a primary charging process by a charging roller 32 as a charging means to have a predetermined polarity and potential. This example is negatively charged. S
Reference numeral 1 denotes a charging bias application power source for the charging roller 32.

Next, the primary charging surface is subjected to scanning exposure L by the laser light intensity-modulated corresponding to the time-series electric digital pixel signal of the target image information outputted from the laser scanner 32, thereby exposing the exposure light. The drum electric potential of the part is attenuated, and an electrostatic latent image corresponding to the target image information is formed on the drum peripheral surface.

Then, the electrostatic latent image is reversely developed as a toner image (toner is attached to the exposed bright portion on the drum surface) by a negative developer (negatively charged toner) by a reversal developing device 33 as a developing means. 33a is a developing roller (or a developing sleeve). S2 is a developing bias application power source for the developing roller 33a.

Next, the toner image is fed to the transfer portion 34a at a predetermined timing from a paper feeding portion (not shown) at the transfer portion 34a which is a pressure contact nip portion between the drum 31 and the transfer roller 34 as the transfer means. The images are sequentially transferred onto the surface of the recorded recording material (transfer material) P. S3 is the transfer roller 34
Is a transfer bias application power source. In this example, the back surface of the recording material P is positively charged by the transfer roller 34 to which a transfer bias is applied, which is a polarity opposite to the charging polarity (negative) of the toner, and thus the toner image of the negative polarity on the surface of the drum 31 is formed. Is transferred to the recording material P side by electrostatic force.

The recording material that has passed through the transfer portion 34a is a charge eliminating needle 35.
(Or a separation charger) removes the electric charge, and is separated from the surface of the drum 31 in cooperation with a separation unit (not shown), conveyed to the heat fixing device 37, and subjected to heat fixing processing of the toner image and output as a print. Alternatively, in the double-sided print mode or the multiple print mode, the transfer unit 34
Introduced into the refeed section to a.

After the recording material is separated, the surface of the drum 31 is subjected to removal of residual adhered substances such as transfer residual toner by a cleaning device 36, and is repeatedly used for image formation.

(2) Heat Fixing Device 37 FIG. 2 is an enlarged model diagram of the heat fixing device 37, and FIG. 3 is an enlarged model diagram of the fixing nip portion and a block diagram of the energization control system.

A) Overall configuration and operation of the apparatus The heating and fixing apparatus 37 of this example is disclosed in Japanese Patent Laid-Open No. 4-44075-44.
This is a so-called tensionless type film heating system device disclosed in, for example, JP-A-083, JP-A-4-204980-204984. That is, a cylindrical (endless) fixing film 2 is used, and at least a part of the peripheral length of the fixing film 2 is tension-free (a state in which no tension is applied), and the film 2 is pressed as a pressure rotator. It is configured to be rotationally driven by the rotational driving force of the roller 9 (pressing roller, backup roller).

Reference numeral 3 is a gutter-shaped heat-resistant and heat-insulating stay having a substantially semicircular cross section as a heating member supporting member and a film inner surface guiding member. This example is a plastic stay made of a heat-resistant molding material. The heating element 1 is fitted into a groove formed along the length of the stay at the substantially central portion of the lower surface of the stay 3 and fixedly supported by a heat resistant adhesive. The plastic stay 3 is backed up by a sheet metal stay 3a made of Fe or Al in order to suppress the pressure of the pressure roller 9 and the bending of the heating body 1.

The cylindrical fixing film 2 is loosely fitted onto the assembly consisting of the plastic stay 3, the heating body 1 and the sheet metal stay 3a.

The elastic pressure roller 9 has the shafts of both ends of the cored bar 9a rotatably supported by bearings. Then, the plastic stay 3 and the heating body 1 to which the fixing film 2 is fitted are attached.
The metal sheet stay 3a is placed on the pressure roller 9 with the heating element 1 facing downward.
Further, by pressing down force of a total pressure of 4 to 15 kg by an unillustrated urging means, the fixing member 2 is sandwiched between the heating body 1 and the pressure roller 9 to be pressed against the elasticity of the pressure roller. . N is a fixing nip portion formed between the heating body 1 and the pressure roller 9 with the fixing film 2 interposed therebetween.

The pressure roller 9 is rotationally driven in the counterclockwise direction indicated by the arrow by transmitting the rotational driving force by the driving means M through a power transmission system (not shown). When the pressure roller 9 is driven to rotate, a rotational force acts on the fixing film 9 due to a frictional force between the roller and the outer surface of the fixing film in the fixing nip portion N, and the film 9 is in close contact with the heating body 1 and slides in an arrow direction. Is driven to rotate around the outside of the stay 3 in the clockwise direction a. The stay 3 functions to facilitate the rotational movement of the fixing film 2. In order to reduce the sliding resistance between the heating body 1 and the fixing film 2 in the fixing nip portion N, it is preferable to add a lubricant such as heat resistant grease between them.

Recording based on a print start signal, or by pressing a copy button, or recording by a recording material detecting means disposed in the recording material conveying path upstream of the heat fixing device 37 in the recording material conveying direction. Based on the material detection signal, the rotation driving of the pressure roller 9 is started, and the heating of the heating body 1 is started.

Fixing film 2 by rotation of pressure roller 9
In a state in which the rotation peripheral speed of No. 1 has become steady and the temperature of the heating body 1 has risen to a predetermined value, the toner image T as a material to be heated is carried between the fixing film 2 and the pressure roller 9 in the fixing nip portion N. Since the recording material P is introduced with the toner image bearing surface side being the fixing film 2 side, the recording material P is in close contact with the heating body 1 via the fixing film 2 in the fixing nip portion N and the fixing nip portion N is fixed. It moves and passes with the film 2. In the moving and passing process, the heat of the heating element 1 is applied to the recording material P via the fixing film 2, and the toner image T is heated and fixed on the surface of the recording material P. The recording material P passing through the fixing nip portion N is separated from the surface of the fixing film 2 and conveyed.

In the tensionless type film heating type apparatus of this example, the fixing nip portion N, the stay outer surface portion upstream of the fixing nip portion in the rotating direction of the fixing film, and the fixing film are in the rotational driving state of the fixing film. Tension acts only on the fixing film part of the contact sliding part area,
No tension acts on most of the remaining film. Therefore, there are features such as a small fixing film driving torque and a small moving force of the fixing film 9 along the length of the stay.

B) Heating Body 1 The heating body 1 is a horizontally elongated linear heating body having a low heat capacity and having a longitudinal direction in a direction orthogonal to the recording material P conveying direction. This example is a ceramic heater. In the enlarged model view of the heating element 1 of FIG. 3, reference numeral 1a is a heater substrate having good thermal conductivity, insulation, high heat resistance, and low heat capacity, having a thickness of 1 mm, and having a length in a direction orthogonal to the conveyance direction of the recording material P. , A ceramic substrate such as alumina. 1b is one surface (front surface) of this heater substrate 1a
It is an electric heating element layer in which a strip-shaped pattern is formed by screen printing or the like along the length of the substrate at a substantially central portion in the width direction of the substrate, for example, silver-paradium. Reference numeral 1c is a withstand voltage glass layer (insulating protective layer) formed by covering the energization heating element layer 1b. 1e is a conductive layer (electrode layer) formed on the surface of the withstand voltage glass layer 1c. 1d is a heater substrate 1
It is a heating element temperature detecting element provided in contact with the other surface (back surface) side of a, for example, a thermistor.

The above-mentioned heating element 1 is exposed to the surface side, which is the side on which the electric heating element layer is formed, to the outside, and is fitted into a groove portion formed along the length of the stay in the substantially central portion of the lower surface of the stay 3 for heat resistance. It is fixed and supported by a transparent adhesive.

The conductive layer 1e formed on the surface of the withstand voltage glass layer 1c is in close contact with the inner surface of the fixing film 2 at the fixing nip portion N. The conductive layer 1e is grounded via a rectifying element (diode) 8 and a resistor 12.

Electric power is supplied to both ends of the energization heating element layer 1b by the A / C driver 7 so that the energization heating element layer 1b generates heat and the entire heating element 1 is rapidly heated. The temperature rise of the heating element 1 is detected by the temperature detecting element 1d on the back side of the heating element. The detected heating element temperature is A / D as an electric signal.
Sent to the converter 5 and the CPU 6 via the converter
Is input to The CPU 6 operates the AC based on this input signal.
The driver 7 is controlled, and the electric power supplied to the electric heating element layer 1b is controlled so that the temperature of the heating element is adjusted to a predetermined appropriate temperature.

C) Fixing film 2 In the case of this example, the fixing film 2 has a three-layer structure of a base film layer (base layer) 2a, a primer layer 2b and a release layer 2c as shown in the layer structure model in FIG. It is a film.

The base film layer 2a is made of a material having heat resistance and insulation such as polyimide, polyetherketone, polyethersulfone, polyetherimide, polyparabanic acid, etc., on which the thermal conductivity of metal boride powder or the like is added. 20 ~ 80 thick by mixing and dispersing high filler
It is formed into a cylindrical film of about μm.

The outer peripheral surface of the base film layer 2a is coated with the primer layer 2b so as to have a thickness of about 5 μm.
A release layer 2c made of a fluororesin such as FA / PTFE or a silicone resin and having a thickness of about 5 to 20 μm is formed.

When the adhesiveness between the base film layer 2a and the release layer 2c is good, the two-layer structure 2 and 2c without the primer layer 2b will not cause any problem. It is also possible to use the fixing film 2 composed of two or more layers by interposing a layer having another function between them, but in order to maintain the fixing property, the total thickness should be as small as possible. A layer structure that is thin and has good thermal conductivity is desirable.

D) Pressure Roller 9 The pressure roller 9 of this example has the same structure as the layer structure model of FIG.
Silicone rubber around the metal core 9a such as e.Al.
An elastic rubber layer 9b made of fluororubber or the like is provided, and an insulating release layer 9c is further provided on the outer periphery thereof.

The elastic rubber layer 9b of the pressure roller 9 of this example is
Low resistance (10 ⁸ Ωcm or less) by dispersing conductive filler such as carbon black or graphite in rubber material
Let me do it.

The insulating release layer 9c is made of PFA / PTFE /
Insulating fluororesin such as FEP / ETFE with a thickness of 20-
It is formed by coating or coating in a tube shape to a thickness of about 100 μm.

A sliding contact 10 such as a conductive brush or carbon chip is provided on the exposed portion of the core metal 9a.
Is grounded through a sliding contact 10, a rectifying element (diode) 11 and a resistor 13.

Regarding the actual use of the heating and fixing device 37 of this example, the heating and fixing device 37 is provided on the surface of the heating body 1 in terms of safety in the case where the heating body 1 is damaged or high frequency noise enters the power source of the heating body. In order to prevent the electrical noise from being grounded by the conductivity of the conductive layer 1e and the surface of the pressure roller and damaging the machine body, a resistor 12 having a resistance of 100 MΩ or more is provided on the ground side of the rectifying elements 8 and 11.・ 13 is inserted.

(3) Offset Prevention Mechanism A mechanism for preventing offset due to an electrostatic factor of toner on the fixing film 2 in the film heating type heating and fixing device 37 of the present embodiment is shown in FIG. Figure 4 shows the relationship with the beam printer.
It will be described based on.

The recording material P is given a positive charge Q _TR having a polarity opposite to the toner charging polarity (minus) Q _TO on the back surface of the transfer portion 34a, and the toner image T is electrostatically held on the surface of the recording material P. Is conveyed to the heat fixing device 37 in the state,
The toner image T is heated and fixed by being guided to the fixing nip portion N formed through the fixing film 2 by the heating body 1 and the pressure roller 9.

Normally, in an image forming apparatus having a transfer process, the recording material P is transferred from the image carrier 31 to the transfer charging means 34.
The unfixed toner image T transferred onto the recording material P is strongly and electrostatically held on the recording material P by the charge Q _{TO of the} unfixed toner and the transfer charge Q _TR of the opposite polarity to the unfixed toner injected on the back surface of the recording material. ing.

Therefore, if the fixing film 2 always maintains the potential V _TO of the same polarity (minus) as the toner with respect to the recording material P, the potential formed between the fixing film 2 and the recording material P is small. Therefore, the electrostatic force of the unfixed toner toward the fixing film 2 is reduced, and the offset can be prevented.

The pressure roller 9 holds a transfer charge Q _TR having a polarity opposite to that of the unfixed toner injected on the back surface of the recording material and a potential so as to attract the toner image T on the surface of the recording material P. It needs to be formed.

Such fixing film 2 and pressure roller 9
In order to achieve the potential configuration of No. 2, the diode 7 used as the rectifying element is connected to the conductive layer 1e provided on the surface of the heating body 1 so that the conductive layer 1e holds negative charges. .

On the pressure roller 9 side, a core metal 9a is connected to a diode 11 used as a rectifying element, which is connected in the direction opposite to the direction in which the fixing film 2 is connected to the pressure roller surface. A positive charge is induced.

In the experiments conducted by the present inventors, the image forming speed was 5
0mm / sec printer, on the surface of the fixing film-
It was confirmed that a potential of about 100 V and about +400 V on the surface of the pressure roller was induced.

By doing so, the charge Q _TR and the charge Q _{TO of the} toner carried by the recording material P from the transfer portion 34a do not leak in the fixing device 37, so that the unfixed toner image T is disturbed. It is possible to fix the recording material P on the recording material P without any need.

However, further experiments by the present inventors show that one of the offsets of the toner from the recording material P side to the fixing film 2 side due to electrostatic factors is to electrostatically retain the toner on the recording material P. In some cases, a transfer charge (plus) having a polarity opposite to the toner charging polarity (minus) given to the recording material P partially accumulates on the fixing film 2, and this charge adsorbs unfixed toner and causes toner offset. It turned out to be. In particular, this phenomenon is that the recording material P has a low moisture absorption and is easily charged on the surface. When an insulating material is used as the pressing member 9, the trailing end of the recording material P is separated from the fixing nip portion N. Sometimes noticeable.

When such a phenomenon occurs, the surface release layer 9c of the pressure roller 9 is made electrically conductive and is grounded via the rectifying element, so that the fixing film 2 is partially grounded. The charged electric charge can be dispersed on the surface of the pressing member.

With the above-mentioned structure, electrostatic fixing toner offset generated in the film heating type heat fixing device in various recording materials and environments can be prevented, and a good image is output. I was able to do it.

<Embodiment 2> (FIG. 5) In the heat fixing device 37 of Embodiment 1 described above, the transfer unit 3 is used.
Transfer charge Q transferred from 4a onto recording material P
_Although a self-bias method in which a potential is formed inside the fixing device by using _TR and toner charge Q _TO is used, in this example, the fixing device is positively used without using the charge on the recording material. It is configured to prevent offset by forming a potential inside.

FIG. 5 is a schematic configuration diagram of the heating and fixing device 37 of this example, which is almost the same as the device configuration used in the first embodiment, and is different in the rectifying elements 8 and 11 shown in FIG. Instead, the high voltage power supply 14 is used.

The high-voltage power supply 14 applies a bias of the same polarity (minus) as the toner to the conductive layer 1e set on the heating body 1, and the same polarity as the transfer charge on the pressure roller core metal 9a or the pressure roller surface. A (plus) bias is applied.

According to experiments by the present inventors, the magnitude of the bias applied to the fixing film 2 and the pressure roller 9 is
As described in the first embodiment, the surface of the fixing film is -10.
It was found that the toner offset was almost eliminated by setting the potential of about 0 V and about +500 V on the surface of the pressure roller. Also, the timing of bias application is
A predetermined bias must be applied at least before the recording material P reaches the fixing device 37, and
If the main body of the image forming apparatus is not recording,
Cut off for safety reasons such as leaks and electric shock.

Further, as described in the first embodiment, as a measure against the damage of the heating body 1 and the power source noise, the fixing film 2
A high-voltage power supply 14 that applies a bias to the pressure roller 9 is provided with resistors 15 of 100 MΩ or more so that they are not directly grounded.

The feature of this example is that by applying a bias to the fixing film 2 and the pressure roller 9, the charge on the recording material P is
Since the toner offset can be surely prevented without being influenced by the electric potential, the recording material (A3
When a sheet (size or more) is passed, the transfer applied to the recording material P by applying a bias to the separation charger / static elimination needle 35 aiming at the effect of separating the recording material P from the surface of the image carrier 1 at the time of transfer separation. When the charge Q _TR decreases, the effect is most exerted, and the transfer charge Q _TR, which decreases remarkably in a high humidity environment, is supplemented inside the fixing device.
It is possible to reliably prevent toner offset under any environment.

Further, by adopting this structure, the electrostatic offset which occurs when the low humidity recording material P is separated from the fixing nip portion N does not occur.

<Embodiment 3> (FIGS. 6 and 7) In this embodiment, in the heat fixing apparatus of Embodiment 1 or 2 described above, the fixing film 2 is formed by using the film 2 as in the layer structure model of FIG. Conductive layer 2d is formed on the inner surface (surface contacting the heating body) of the conductive layer 1 set on the surface of the heating body.
By contacting e with the fixing nip portion N, the potential of the fixing film can be surely controlled.

The operation of implementing this example will be described below. When the above-described first or second embodiment is used, in the fixing nip portion N, if the conductive layer 1e provided on the surface of the heating body 1 and the inner surface of the fixing film 2 are not surely brought into contact with each other, they are in contact with each other. The electric potential cannot be controlled in the non-existing part,
Toner offset may be caused partially (in the form of stripes in the sheet passing direction). In particular, in order to prevent abrasion of the conductive layer 1e and the base film layer 2a of the fixing film 2 due to friction between the inner surface of the fixing film and the heating element 1, heat-resistant insulating grease as a lubricant is interposed between the two. In some cases, the heat-resistant insulating grease partially deteriorates the contact between the inner surface of the film and the surface of the heating body, and the toner offset in the paper feeding direction streak described above may occur.

In order to reliably prevent this, in this example, the conductive layer 2d is provided on the inner surface of the fixing film 2. The fixing film 2 includes a resin layer 2a made of polyamide-imide or the like, PFA / PT, on the surface of a cylindrical metal film as the conductive layer 2d.
The releasable layer 2c made of a fluororesin such as FE is laminated, or the fixing film 2 used in the first and second embodiments described above.
It can be made by coating the inner surface of the with a conductive layer mainly composed of conductive particles such as Ketjen black.

The conductive layer 1e provided on the surface of the heating body 1 is set to have the same polarity (minus) potential as the toner by the rectifying element 8. The conductive layer 1e and the conductive layer 2d provided on the inner surface of the fixing film are brought into contact with each other at the fixing nip portion N, and the potential of the conductive layer 2d on the inner surface of the fixing film and the potential of the conductive layer 1e on the surface of the heating element are the same. is there. Therefore, the surface of the fixing film 2 can have a potential of the same polarity (minus) as the toner even in the portion other than the fixing nip portion N.

In the examination of this example, the conductive layer 1 is formed over the entire length of the surface of the heating body which is in contact with the inner surface of the fixing film 2.
In this region, a potential that does not cause toner offset can be formed if the conductive layer 2d on the inner surface of the fixing film 2 and the conductive layer 1e on the surface of the heating element are in contact with each other in this region. As shown in, it is possible to obtain the same effect only by partially providing the conductive layer 1f at the end portion of the fixing film without providing the conductive layer 1e over the entire length.

Further, the conductive layer 2d is formed on the inner surface of the fixing film 2.
In the case where the fixing film is used, a conductive layer may be provided on a part of the stay 3 or the like in addition to the surface of the heating body to form a contact with the inner surface of the fixing film, but in order to reliably contact the inner surface of the fixing film with the stay 3. Is most suitable for the fixing nip portion N where the fixing film 2 is pressed against the surface of the heating body 1.
In order to surely make contact with other portions, the driving torque of the fixing film increases, which causes a film drive failure that occurs during the first drive in the morning in a low temperature environment, which is not practical.

<Embodiment 4> (FIG. 8) FIGS. 8 (a) to 8 (d) are other structural examples of the film heating type heat fixing device.

In the case of (a), the endless belt-shaped fixing film 2 is suspended between three substantially parallel members of the heating body 1 held by the stay 3, the film driving roller 21, and the tension roller 22. The heating member 1 and the pressure roller 9 are stretched and pressed against each other with the fixing film 2 sandwiched therebetween to form a fixing nip portion N, and the fixing film 2 is rotationally driven by the drive roller 21. The pressure roller 9 is rotated by the rotation of the fixing film 2. M is a drive source of the film drive roller 21. A recording material P as a material to be heated is introduced into the fixing nip portion N to heat and fix the toner image.

In the case of (b), an endless belt-shaped fixing film 2 is suspended and stretched between two members of the heating body 1 held by the stay 3 and the film driving roller 21 which are substantially parallel to each other. The heating body 1 and the pressure roller 9 are pressed against each other with the fixing film 2 sandwiched therebetween to form a fixing nip portion N, and the fixing film 2 is rotationally driven by the driving roller 21. The pressure roller 9 is rotated by the rotation of the fixing film 2.

In (c), a long end film wound in a roll is used as the fixing film 2, and the end film is wound from the feeding shaft 23 through the lower surface of the heating body 1 held by the stay 3. The fixing film 2 is wound around the take-up shaft 24, and the heating body 1 and the pressure roller 9 are pressed against each other with the fixing film 2 sandwiched therebetween to form a fixing nip portion N, and the fixing film 2 is taken up.
It is wound up at 4 and traveled and moved at a predetermined speed.

Even in the apparatus having the above configuration,
The same effects can be obtained by making the heating element 1, the fixing film 2, the pressure roller 9 and the like have the same configurations as those of the first to third embodiments.

The heating element 1 is not limited to the ceramic heater of the above-described embodiment, but other appropriate heating element configuration such as an electromagnetic (magnetic) induction heating method can be adopted. (D) is an example of an electromagnetic induction heating system. Reference numeral 1g is a magnetic metal member which generates heat by electromagnetic induction, and 1h is an exciting coil as a magnetic field generating means. The high frequency magnetic field generated by energizing the exciting coil 1h causes the magnetic metal member 1g to generate electromagnetic induction heat as a heater, and the heat is introduced into the fixing nip portion N through the fixing film 2 at the pressure contact nip portion N. It is applied to the recording material P as a material. The fixing film 2 itself may be a member having an electromagnetic induction heat generation property.

[0090]

As described above, according to the present invention, in the heat fixing of the film heating system, the occurrence of the toner offset due to the electrostatic factor to the fixing film is substantially eliminated even under various recording materials and environments. Therefore, it is possible to prevent a harmful effect due to the toner offset.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an example of an image forming apparatus.

[Fig.2] Enlarged model view of heat fixing device

FIG. 3 is an enlarged model diagram of a fixing nip portion and a block diagram of an energization control system.

FIG. 4 is a conceptual diagram of a potential configuration for preventing toner offset.

FIG. 5 is an enlarged model diagram of a heat fixing device according to a second embodiment.

FIG. 6 is an enlarged model diagram of a fixing nip portion of the heat fixing device according to the third embodiment.

FIG. 7 is a vertical sectional model view of the device.

FIG. 8A to FIG. 8D are schematic diagrams of another example of the configuration of a film heating type heat fixing device.

FIG. 9 is a schematic view of a main part of a film heating type heat fixing device.

[Explanation of symbols]

1 ... Heating body (ceramic heater), 1a ... Heater substrate, 1b ... Electric heating layer, 1c ... Voltage withstanding glass layer (insulating protective layer), 1d ...
2 ・ ・ Fixing film, 2a ・ ・ Base film, 2b ・
.Primer layer, 2c ... Release layer, 2d ... Conductive layer, 3
..Plastic stays, 3a ... Sheet metal stays, 5 ...
A / D converter, 6 ... CPU, 7 ... A / C driver, 8, 11 ... Rectifying element (diode), 12, 1
3 ・ 15 ・ ・ Resistor, 9 ・ ・ Pressure roller, 10 ・ ・ Sliding contact, 14 ・ ・ High-voltage power supply, P ・ ・ Recording material, T ・ ・ Toner image, 31 ・ ・ Image carrier (photosensitive drum ), 32 ··· charging roller, 33 · · developing device, 34 · · transfer roller, 3
4a .. Transfer part, 35 .. Static elimination needle, 36 .. Cleaning device, 37 ..

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Koichi Okuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Ooba 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Incorporated (72) Inventor Michihito Yamazaki 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Kazuo Suzuki 1998-1 Yamada, Chichibu-shi, Saitama (72) Inventor Akinori Hara 728 Otani, Ogose Town, Iruma District, Saitama Prefecture

Claims (13)

[Claims] 1. A recording material carrying a developer image between a fixing film and a pressing member in a fixing nip portion formed between a heating member and a pressing member with a fixing film interposed therebetween. The side of the fixing film is introduced so that the fixing member is brought into close contact with the heating member through the fixing film, and the fixing nip portion is moved and passed together with the fixing film so that the heat of the heating member is applied to the recording material through the fixing film. A heating element used in a heat fixing device for heating and fixing a developer image on a recording material surface, wherein the heating element has a conductive layer on a contact surface with a fixing film. 2. A recording material carrying a developer image between a fixing film and a pressing member in a fixing nip portion formed between a heating body and a pressing member with a fixing film interposed therebetween. The side of the fixing film is introduced so that the fixing member is brought into close contact with the heating member through the fixing film, and the fixing nip portion is moved and passed together with the fixing film so that the heat of the heating member is applied to the recording material through the fixing film. A fixing film used in a heat fixing device for heating and fixing a developer image on a recording material surface, wherein the fixing film has a conductive layer on a contact surface with a heating body. 3. A recording material carrying a developer image between a fixing film and a pressing member in a fixing nip portion formed between a heating body and a pressing member with a fixing film interposed therebetween. The side of the fixing film is introduced so that the fixing member is brought into close contact with the heating member through the fixing film, and the fixing nip portion is moved and passed together with the fixing film so that the heat of the heating member is applied to the recording material through the fixing film. A heating and fixing device for heating and fixing a developer image on a recording material surface, wherein the heating body has a conductive layer on the contact surface with the fixing film. 4. The heating and fixing device according to claim 3, wherein the conductive layer of the heating element is grounded via a rectifying element. 5. The heat fixing device according to claim 3, wherein a bias having the same polarity as that of the developer is applied to the conductive layer of the heating body. 6. The heating and fixing device according to claim 3, wherein the fixing film has a conductive layer on a contact surface with a heating body. 7. The heating and fixing device according to claim 3, wherein the pressing member is a release layer having an insulating surface and a conductive inner elastic layer. Further, the heating and fixing device is characterized in that the core metal of the pressing member is grounded via a rectifying element. 8. The heating and fixing device according to claim 3, wherein the pressing member is a release layer having an insulating surface and a conductive elastic layer inside. A heating and fixing device characterized in that a bias having a polarity different from that of the developer is applied to the core metal of the pressing member. 9. The heating and fixing device according to claim 3, wherein the pressing member is electrically conductive, and the core metal of the pressing member is grounded via a rectifying element. The heat fixing device is characterized by being provided. 10. The heating and fixing device according to claim 3, wherein the pressing member is made of a conductive material, and the core metal of the pressing member has a polarity different from that of the developer. A heating and fixing device characterized in that a bias is applied. 11. The heating and fixing device according to claim 3, wherein the fixing film is moved and driven by rotational driving of a pressure member. 12. The heating and fixing device according to claim 3, wherein the fixing film is moved and driven by a film driving member other than the pressing member. 13. An image forming apparatus comprising: an image forming means for forming and carrying a developer image on a recording material; and a fixing means for heating and fixing the developer image on the recording material, wherein the fixing means is any one of claims 3 to 12. An image forming apparatus, wherein the image forming apparatus is the heat fixing apparatus described in any one of 1.