JP2694734B2 - Fixing device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device in an image forming apparatus such as a copying machine, a laser beam printer, a facsimile, a microfilm reader printer, an image display (display) device, and a recorder. .

More specifically, a recording material (electrofax sheet, electrostatic recording sheet, transfer material sheet, transfer material sheet, etc.) is formed by using a toner made of a heat-meltable resin by an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. A recording material having an unfixed toner image corresponding to the target image information formed and carried by a direct method or an indirect (transfer) method on the surface of a printing paper or the like, and carrying the unfixed toner image. The present invention relates to a fixing device in an image forming apparatus of a type in which heat fixing processing is performed on a surface as a permanently fixed image.

(Prior Art) Conventionally, a fixing device used in this type of image forming apparatus includes a heating roller that is maintained at a predetermined temperature, and a pressure roller that has an elastic layer and is in pressure contact with the heating roller. Accordingly, a roller fixing method is adopted in which a recording material on which an unfixed toner image is formed is held and conveyed while being heated.

A belt fixing system as disclosed in U.S. Pat. No. 3,578,797 is also known. this is . Contacting the toner image with the heating web and heating it to its melting point to melt; After fusing, the toner is cooled to a relatively high viscosity; This is a method in which the toner is fixed without causing offset by passing through a process of peeling the toner from the heating element web in a state where the tendency of the toner to adhere is weakened.

(Problems to be Solved by the Invention) However, the conventional hot roll fixing method as described above,
The belt fixing method has the following problems.

Heat roll fixing method. It takes a long time to rise to the predetermined temperature,
During that time, the image forming operation is prohibited. That is, there is a so-called wait time.

. Large electric power is required because heat capacity is required.

. A high heat-resistant roller bearing requires a heat-resistant special bearing.

. The configuration is such that the roller touches the roller directly, which is dangerous and requires a protective member.

. The recording material is wrapped around the roller due to the constant temperature and the curvature of the roller, so that a jam problem of the recording material is easily observed.

Belt fixing method This method also has the same problems as those of the above-described heat roller fixing method, such as the wait time and large power consumption.

The present invention solves the problems that the above-described conventional device has, and makes it possible to reduce the heat capacity of the heating element without causing fixing failure or offset, and as a result, standby time or power consumption, and further It is an object of the present invention to provide a fixing device which has a small temperature rise in the machine and has other remarkable features.

(Means for Solving the Problems) The present invention has a heating body, and a film in which one surface slides with the heating body and the other surface comes in contact with a recording material carrying an unfixed toner image and moves together. In a fixing device that heats and fixes an unfixed toner image on a recording material by heat from the heating body through the film, the film is provided on a base material layer made of a heat-resistant resin, and the base material layer is provided on the base material layer. And a release layer in contact with the toner image, the thickness of the film is 50 μm or less, and the thickness of the base material layer is greater than or equal to the thickness of the release layer. .

(Working) (1) The recording material to be image-fixed, which is introduced between the fixing film and the pressing member, which is running and driven at the same speed as the conveying direction of the recording material, is not fixed on the surface of the fixing film. While the surface on the toner image bearing side is in close contact with the fixing film and overlapped with the fixing film, the mutual pressure contact portion (fixing nip portion) between the heating member and the pressure member receives a pressing force and causes a surface deviation due to a speed difference between them. Without overlapping or wrinkling, they will pass over each other in close contact with each other.

. Heating process In the process of passing through the mutual pressure contact portion, the unfixed toner image on the surface of the recording material is heated and softened and melted by the heating element via the fixing film, and particularly the surface layer portion thereof greatly exceeds the melting point of the toner and is completely softened and melted. In this case, the heating element, fixing film, toner image,
The recording material is satisfactorily pressed and adhered by the pressing member, and heat is effectively transferred, so that the toner is sufficiently softened and melted by heating for a short time, and good fixing properties are obtained. On the other hand, the temperature rise of the recording material itself is extremely small in practice, and the waste of heat energy is small. In other words, the recording material itself is not heated substantially, and only the toner is heated and softened and melted effectively, and the heat fixing of the toner image can be satisfactorily executed with low power.

Here, note the softening and melting of the toner described in the present invention. The temperature, which is conveniently expressed as the "melting point" of the toner, means the minimum temperature required for the toner to be fixed. In some cases. Therefore, even when the term “melting” is used for the sake of convenience for fixing, the viscosity may actually decrease such as softening. The present invention includes such a case. Similarly, when the expression that the toner is cooled and fixed is used for convenience, depending on the toner, it may be more appropriate to increase the viscosity rather than to solidify. The present invention includes such a case.

. Cooling process The toner image which has passed through the mutual pressure contact part of the heating element and the pressure member in close contact with the fixing film surface and the heated softened and melted recording material part remains in close contact with the fixing film surface even after passing through the pressure contact part Is continued for a while, and during this time, a cooling step is performed, and the heat of the toner softened and melted in the heating step is radiated to cool and fix the toner. By this cooling and solidification, the cohesive force of the toner becomes very large, and the toner behaves as a group. In addition, while the adhesive / fixing force on the recording material side increases, that on the fixing film side extremely decreases. When the toner is heated and softened and melted in the heating step, the toner is pressed by the pressing member, so that at least a part of the toner image permeates into the recording material surface layer, and the permeated portion is cooled and solidified. The adhesive effect of the solidified toner on the recording material side increases due to the anchor effect of the toner.

. Separation (separation) step After the toner image is cooled and solidified by the above-mentioned cooling step, the recording material is sequentially separated from the fixing film surface.
At the time of separation, the toner image has a sufficiently large adhesive / adhesive force to the recording material due to cooling and solidification, and has a very small state with respect to the fixing film, so that the image-fixed recording material portion causes toner offset with respect to the fixing film. It is easily separated one after another.

The recording material to be image-fixed is brought into close contact with the fixing film at the same speed so that the unfixed toner image carrying surface faces the fixing film surface running in this way, and the toner image is heated and melted by a heating element through the fixing film. Since the recording material and the fixing film are separated from each other after the toner image is cooled and fixed, no toner offset occurs with respect to the fixing film, and a heating element having a small heat capacity is used, and power is supplied to the heating element. This method can be performed with a simple configuration, and by maintaining a heating element at a temperature sufficiently high with respect to the temperature (melting point or softening point) at which the toner is to be heated for fixing, the toner image can be efficiently produced. Heating can be performed, and a sufficiently good fixing without a fixing failure can be achieved with a small amount of energy. As a result,
This has the effect of obtaining an image forming apparatus with a small standby time during use of the apparatus, low power consumption, and a small rise in temperature inside the apparatus.

If the toner is sufficiently melted at a high temperature among the three steps of heating, cooling, and separation, the recording material is separated from the fixing film surface immediately after the toner is sufficiently melted at a high temperature in the heating step. The cooling process after the process may be abolished, and it belongs to the scope of the present invention.

(2) If the thickness of the fixing film used is too large, the following problems will occur.

. The thermal resistance between the heating element and the toner increases. Therefore, the thicker the fixing film, the more power for softening and melting the toner. As a result, the power supply, and hence the entire device, becomes large.

. The toner does not soften unless the peak temperature of the heating element is raised. In general, the heating element has a shorter life as the operating temperature is higher. Therefore, the thicker the fixing film, the shorter the life of the heating element. When the temperature of the heating element is increased, the temperature of the surface of the fixing film, particularly on the heating element side, also increases. Then, the durability of the fixing film becomes a problem.

. It takes time to transfer heat to the toner. Therefore, it takes a long time after the toner has passed through the position of the heating element and after the toner has been softened and melted until the viscosity becomes high again. Then, the fixing film and the toner may be separated while the toner is softening and melting. In order to prevent this, if a member that conveys the recording material having the fixing film and the toner image in close contact is provided until the toner is completely cooled and solidified, the apparatus becomes complicated.

. The recording material generally has unevenness, and the toner image is unevenly distributed on the surface with unevenness. When the fixing film is thin, the fixing film deforms following the unevenness of the toner image in the pressure contact portion formed by the heating body and the pressure roller. Then, the toner image is uniformly heated regardless of the unevenness of the toner image,
Fixing failure does not occur. However, if the fixing film is thick, the fixing film does not follow the unevenness of the toner image, and the fixing film does not adhere well to the toner image. Therefore, heating to the toner becomes non-uniform, and fixing failure or toner offset may occur.

As will be described in Examples below, the inventors of the present invention have found from the results of various experiments that if the thickness of the fixing film is set to 50 μm or less, the fixing method of the present invention will not occur without causing the above problems (1) to (3). It has been found that it is possible to stably carry out a good toner fixing process by making full use of the features described in the item (1). The thickness of the fixing film may theoretically be any thickness as long as durability is satisfied. However, in practice, there is a practical lower limit due to durability and handling, and according to experiments, for example, a 2.3 μm PTFE (tetrafluoroethylene resin) coating layer was applied to a polyimide film with a thickness of 6.3 μm (a thickness of 4 μm). Instability was found in the running drive of the film, and it seems that this level of thickness is the lower limit of practical use.

Further, in an apparatus that transfers the heat from the heating element to the unfixed toner image through the film, it is preferable to make the film thin as described above in order to improve the heat transfer in the film. There is a problem that the film may drop and the film may be deformed. In order to solve the problem, the present invention provides a film having a base layer made of a heat-resistant resin and a release layer in contact with the toner image provided on the base layer, and the film has a thickness of 50 μm. And the thickness of the base material layer is equal to or more than the thickness of the release layer.

Accordingly, the present invention can suppress the deformation of the film, particularly the deformation of the release layer in contact with the toner image, with the base material layer made of the heat-resistant resin without impairing the heat transfer from the heating body,
Good fixing can be performed.

(Embodiment) The present embodiment is an electrophotographic copying apparatus of a reciprocating type, a rotating drum type and a transfer type on a document table.

(1) Overall Schematic Configuration of the Apparatus (FIG. 1) In FIG. 1, reference numeral 100 denotes an apparatus housing, and 1 denotes a reciprocating motion made of a transparent plate member such as a glass plate disposed on an upper plate 100a of the apparatus housing. It is a document mounting table of a mold, and is driven to reciprocate at a predetermined speed to the right side a and the left side a 'on the machine housing upper surface plate 100a in the drawing.

G is an original, which is placed on the upper surface of the original placing table 1 with the image side to be copied facing downward according to a predetermined placing reference;
The original is set by placing the original cover 1a on top of the cover.

Reference numeral 100b denotes a slit opening serving as a document illuminating unit which is opened on a surface of the machine housing upper plate 100a with a direction perpendicular to the reciprocating movement direction of the document placing table 1 (direction perpendicular to the paper surface) as a longitudinal direction. The downward image surface of the document G placed and set on the document placing table 1 sequentially passes through the position of the slit opening 100b from the right side to the left side in the process of reciprocating to the right a of the document placing table 1. , Slit L the light L of the lamp in the process of passing through it
100b, it is illuminated and scanned by being received through the transparent document table 1. The reflected light of the illumination scanning light on the document surface is image-formed and exposed on the surface of the photosensitive drum 3 by the short-focus small-diameter imaging element array 2.

The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and is driven to rotate clockwise as indicated by an arrow b at a predetermined peripheral speed around a center support shaft 3a. The charger 4 was subjected to a uniform charging process of positive or negative polarity, and the uniformly charged surface was subjected to the image forming exposure (slit exposure) of the original image to form an image on the surface of the photosensitive drum 3. An electrostatic latent image corresponding to a document image is sequentially formed.

The electrostatic latent image is sequentially visualized by a toner made of a resin or the like which is softened and melted by heating by the developing device 5, and the developed toner image is transferred to a portion where the transfer discharger 8 as a transfer portion is provided. I will do it.

S denotes a cassette in which transfer material sheets P as recording materials are stacked and stored, and the sheets in the cassette are fed one by one by the rotation of the feed roller 6, and then the toner on the drum 3 is moved by the registration roller 9. When the leading end of the image forming section reaches the transfer discharger 8, the leading end of the transfer material sheet P also reaches the position between the transfer discharger 8 and the photosensitive drum 3, and the timing is synchronized so that they coincide with each other. Will be fed. Then, the transfer discharger 8 is applied to the surface of the sheet.
As a result, the toner image on the photosensitive drum 3 side is sequentially transferred.

The sheet that has received the toner image transfer at the transfer portion is sequentially separated from the surface of the photosensitive drum 3 by separation means (not shown), and is conveyed as a conveyance guide.
The unfixed toner image carried by the fixing device 11 described below is heated and fixed by 10 and is subjected to a heat fixing process, and is discharged onto a paper output tray 12 outside the apparatus as an image formed product (copy).

On the other hand, the surface of the photosensitive drum 3 after the transfer of the toner image is repeatedly used for image formation by receiving the removal of adhered contaminants such as untransferred toner by the cleaning device 13.

(2) Fixing device (FIGS. 1 and 2) 24 is an endless belt-shaped fixing film, and includes a left driving roller 25, a right driven roller 26, and a driving roller.
25 between the separating roller 27 arranged below the driving roller 25 and the driven roller 26, and between the four members 25, 26, 27, 20 parallel to each other of the low heating capacity linear heating body 20 as a heating body arranged below It is suspended around.

The driven roller 26 is an endless belt-shaped fixing film 24.
The fixing film is also used as the tension roller.
Reference numeral 24 denotes a transfer material sheet P carrying an unfixed toner image Ta conveyed from the image forming unit 8 on the upper surface at a predetermined peripheral speed in the clockwise direction accompanying the clockwise rotation of the drive roller 25.
Is rotated at wrinkles, meanders, and speed delays at the same peripheral speed as the transport speed of.

Reference numeral 28 denotes a pressure roller having a rubber elastic layer having good release properties such as silicon rubber as a pressure member, and the endless belt-shaped fixing film 24 sandwiching the descending side film portion of the heating member 20 so as to sandwich the same. The transfer material sheet P is rotated counterclockwise in the forward direction in the transport direction of the transfer material sheet P by being pressed against the lower surface by a biasing means (not shown) with a contact pressure of, for example, a total pressure of 4 to 7 kg.

Endless belt-shaped fixing film 24 driven to rotate
Since it is repeatedly used for heat-fixing toner images, it should be thin and have excellent heat resistance, releasability and durability, and a thickness of 50 μm or less. For example, polyimide, polyetherimide,
A 20 μm thick film of a heat-resistant resin such as PEA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer resin), a release coating in which a conductive material is added to PTFE (tetrafluoroethylene resin) at least on the image contact surface side. For example, the layer is applied to a thickness of 10 μm.

A low heat capacity linear heating element as a heating element has, for example, a thickness of 1.
Along the length, an electrical resistance material such as Ta ₂ N is formed along the length of the lower surface of the alumina substrate 21 having a width of 0 mm, a width of 10 mm, and a length of 240 mm.
It is provided with a linear or band-shaped heating element 22 coated on 1.0 mm. In the case of this example, the linear or belt-shaped heating element 22 is energized from both longitudinal ends thereof to generate heat over the entire length. Energization is DC100V cycle
With a pulsed waveform of 20 msec, the temperature is controlled by the temperature sensing element 23, and a pulse corresponding to the amount of energy released is provided in the energization control circuit configuration, and the pulse width is approximately 0.5 to 5 msec. The heating element 22 is controlled within a range, and the temperature of the heating element 22 instantly rises to around 200 to 300 ° C. each time a pulse is input. In this embodiment, a sensor for detecting the leading and trailing edges of the sheet (not shown) is provided closer to the fixing device on the upstream side of the fixing device 11 in the transfer material sheet conveyance direction, and the sensor supplies a current to the heating element 22 according to a sheet detection signal. The period is controlled only for the necessary period during which the sheet P passes through the fixing device 11.

The fixing film 24 is not limited to the endless belt shape.
As shown in the example, the end-fixed film 24 wound in a roll around the feed shaft 30 is locked to the take-up shaft 31 between the heating body 20 and the pressure roller 28, under the separation roller 27, and the like. The transfer material sheet P may travel from the delivery shaft 30 to the take-up shaft 31 at the same speed as the transfer speed of the transfer material sheet P.

(3) Fixing operation The leading end of the transfer material sheet P carrying the unfixed toner image Ta on the upper surface, which has been conveyed from the transfer unit 8 to the fixing device 11 by the image forming operation of the apparatus in response to the image forming start signal, is fixed to the fixing device. The rotation (or running) of the fixing film 24 is started when it is detected by the above-mentioned sensor (not shown) disposed closer to it,
The transfer material sheet P is guided by the guide 29 and enters between the fixing sheet 24 and the pressure roller 22 at the pressure contact portion N between the heating body 20 and the pressure roller 28, and the unfixed toner image surface is the sheet P. Fixing film 24 that moves in the same direction as the transport speed in the same direction
The heating member 20 and the pressure roller 28 pass while being pressed against each other in a state of being overlapped together with the fixing film 24 without causing surface deviation or wrinkling by being in close contact with the lower surface of the fixing member 24.

The toner image is heated and softened and melted as described in the item (1)-of the above-mentioned (action) as a heating step in the process of passing through the mutual pressing portion. As described above, in the heating step in this embodiment, a linear heating element 22 is provided on the heating element 20, and the heating element 22 having a low heat capacity formed integrally with the heating element 21 is energized in a pulse shape to repeat heat generation. This is performed by the heating body 21 configured as described above. In other words, the toner image Ta on the sheet P conveyed at the predetermined conveying speed, together with the fixing film 24 on which the sheet P is conveyed, is a linear heating unit which is sequentially determined according to the width of the heating element 22 of the heating element 20. After being fed into the effective width W and receiving heat, it becomes a softened / melted image Tb.

The sheet portion that has passed through the mutual press-contact portion N between the heating member 20 and the pressure roller 28 is extended between the heating member 20 and the separation roller 27 until it reaches the position of the separation roller 27, and the fixing portion is traveling forward. It is conveyed while keeping it in close contact with the film part.

This transporting process is defined as a cooling process (1) of the above (action).
As described in section-, the heat of the softened / molten toner Tb is radiated to cool and solidify the toner Tc.

When the fixing film 24 reaches the position of the separation roller pair 27, the traveling direction of the fixing film 24 is turned in a direction away from the sheet P along the surface of the separation roller 27 having a large curvature, and the fixing film 24 and the sheet P are separated from each other ( Then, the sheet P is discharged to the discharge tray 11. By the time of the separation, the toner is sufficiently cooled and solidified, and the above (action) (1)-
As described in the section, the adhesion / fixing force of the toner to the sheet P is sufficiently large and the adhesion to the fixing film 24 is extremely small. Therefore, the separation between the fixing film 24 and the sheet P substantially reduces the toner offset with respect to the fixing film 24. It is easily done sequentially without any random occurrence.

In this embodiment, the linear heating element 22 of the heating element 22 instantly heats up to a sufficiently high temperature with respect to the melting point (or fixing temperature) of the toner when energized, so that preheating of the heating element is unnecessary. The heat transfer to the pressure roller 28 during non-fixing is small. Also during fixing, the fixing film, toner image,
Since the sheet is interposed between the heating body 20 and the pressure roller 28 and a short heat generation time causes a rapid temperature gradient, the pressure roller 28 is unlikely to rise in temperature and is continuous as much as practically required. The temperature is maintained below the melting point of the toner even when the image formation is performed. In the apparatus of this embodiment having such a configuration, the toner image formed of the heat-fusible toner on the sheet P is first heated and melted by the heating body 20 via the fixing film 24, and particularly, the surface portion thereof is completely removed. Softens and melts. At this time, the heating member, the fixing film, the toner image, and the sheet are satisfactorily adhered by the pressure roller 28, and the heat is efficiently transferred. Thereby, the heating of the sheet P itself can be suppressed as much as possible, and the toner image can be efficiently heated and melted. In particular, the energy saving can be achieved by limiting the heating time.

Since the heating body is small enough, the heat capacity is small, and it is not necessary to raise the temperature of the heating body in advance. Therefore, the power consumption during non-image formation can be reduced, and the temperature rise in the apparatus can be prevented. .

In the present embodiment, since the temperature of the pressure roller 28 is maintained lower than the melting point of the toner as described above, it is possible to promote the heat radiation of the toner image in the cooling step following the toner image heating step. . Therefore, the time required for cooling can be reduced, and the size of the apparatus can be reduced.

(4) Thickness of Fixing Film 24 FIG. 4 is a cross-sectional model view of the fixing film 24. Reference numeral 24a is a base layer, which in this example is a heat-resistant film layer made of polyimide having a thickness of 9 μm. Reference numeral 24b is a release layer made of PTFE having a thickness of 3.5 μm coated on the outer surface of the base layer film 24a. Therefore, the total thickness of the film 24 is 12.5 μm, which is the total thickness of the layers 24a and 24b. And the release layer 24 of the film 24
The toner image bearing surface of the transfer material sheet P contacts the free surface side of a, and the heating element 20 contacts the free surface of the base layer film 24a.

Using such a fixing film, a PPC paper (64 g / m) was used as the transfer material sheet, and a polyethylene magnetic toner with a melting point of 150 ° C was used as the toner. No problem occurred and there was no heat damage to the fixing film.

Table 1 shows the results when the fixing operation was performed while changing the thickness of the fixing film 24. The fixing film 24 is a multi-layer film as shown in FIG. 4, the heat-resistant layer 24a is polyimide, and the release layer 24b is PTFE.

The thickness of the release layer 24b is 10% of the thickness of the heat-resistant layer 24a.
Various attempts up to 150%. Table 1 shows the best results. If the thickness of the release layer 24b exceeds the thickness of the heat-resistant layer 24a, the strength of the fixing film 24 will be deteriorated, and curling will easily occur, which makes the manufacturing and assembling difficult. Therefore, it is preferable that the thickness of the release layer 24b be equal to or less than the thickness of the heat resistant layer 24a.

In Table 1, the fixing power ratio is the power required to completely fix the solid toner image on the transfer material when each film is used, standardized by the value when the film thickness is 25 μm. Is. The increase in the fixing power means that the temperature of the heating element rises, and the temperature of the fixing film near the heating element also rises. As shown in Table 1, when the thickness of the fixing film exceeds 50 μm, the fixing film is wrinkled due to heating, but it is practically acceptable.

Further, when a toner image having many irregularities such as a line image is fixed, a difference in fixability depending on the location (fixing unevenness) is seen from the film thickness of 25 μm, and when it exceeds 50 μm, it becomes a practically problematic level.

That is, the toner in the concave portion did not come into contact with the fixing film, the thermoelectric power to the toner was deteriorated, and the fixing was defective. When the fixing power was increased in order to prevent this, the temperature of the fixing film rose, and the damage due to heating of the fixing film deteriorated to the extent of practical problems.

The reason why the fixing film thickness exceeds 12.5 μm causes some fixing unevenness, and when the fixing film thickness exceeds 50 μm, the fixing unevenness worsens to a practically unacceptable level can be explained as follows.

That is, the particle diameter of the toner is about 10 μm, and the diameter of the pulp that causes the unevenness of the transfer material sheet is 10 μm to 40 μm. Therefore, in order for the fixing film to follow the unevenness of the toner image due to the toner and transfer material factors, the thickness of the fixing film is also about 10 μm.
About m is preferable.

Further, when forming a linear toner image in a pixel photograph, the pitch is about 10 Line / mm, and if the line width L ₁ and the line interval L ₂ are as shown in the model diagram of FIG. 5,
L ₁ = 100 μm · L ₂ = 100 μm. As shown in FIG. 5, the fixing film 24 is formed on the line-shaped toner image T.
For good adhesion, the film thickness must be 100/2 = 50 μm or less.

When the fixing film 24 becomes thicker, heat transfer from the heating element 22 to the toner is delayed, and the time until the toner is cooled and solidified (viscosity increased) after the toner thickens and melts. Therefore, after the toner is heated, the fixing film other than the pressure roller 28
If there is no means to bring the toner image into close contact with 24, the toner may be separated from the fixing film before the viscosity is sufficiently increased.
According to the experiments conducted by the present inventors, when the fixing film has a thickness of 50 μm or more, some early peeling occurred, and the offset toner adhered to the fixing film, but the amount was very small, and there was no problem in practical use.

The upper limit of the thickness of the fixing film has been described above,
As for the lower limit, any thickness may be used as long as the durability of the fixing film is satisfied. However, according to the experiments by the present inventors, when the thickness is 6.3 μm (polyimide 4 μm coated with PTFE 2.3 μm), the driving of the fixing film is not stable, which is considered to be the lower limit of practical use.

(5) Others As shown in FIG. 3 described above, when a fixed film is used as the fixing film 24, if the fixing film on the sending shaft side is almost completely wound on the winding shaft side and used, a new roll-wound film is used. It can be replaced (rewinding replacement type).

In the case of such a winding exchange type, the thickness can be reduced regardless of the durability of the fixing film, and the power consumption can be reduced. For example, an inexpensive base material such as a PET (polyester) film or the like may be used as the fixing film, and a heat-treated thin film having a thickness of about 12.5 μm or less may be used.

Or, since the toner offset to the fixing film surface does not substantially occur as described above, if the thermal deformation or deterioration accompanying the use of the fixing film is small, the used sheet wound on the take-up shaft side can be removed in a timely manner. And rewinding control to the shaft side,
Alternatively, it can be used a plurality of times by reversing the winding shaft side and the sending shaft side, etc. (rewinding repetitive use type).

In the rewinding repeated use type, as the fixing film, for example, a 25 μm thick polyimide resin film is used as a base material having excellent heat resistance, mechanical strength, etc., and a release layer made of a highly releasable fluororesin or the like on its surface. It is preferable to automatically control the pressure release mechanism during reverse rewinding to keep the contact between the heating element and the pressure roller in the released state.

In the case of multiple use such as a rewinding repetitive use type or an endless belt type, a felt pad is provided for cleaning the film surface, and a slight release agent, for example, silicon oil is impregnated to contact the pad with the film surface. For example, the film surface may be cleaned and the releasability may be further improved. In the case where the fixing film is an insulating fluororesin-treated product, static electricity that disturbs the toner image is likely to be generated on the film. Therefore, in order to cope with this, it is preferable to remove the static electricity with a grounded removing brush. A bias voltage may be applied to the brush without grounding to charge the film within a range that does not disturb the toner image. Further, it is one measure to add conductive powder fibers, for example, carbon black or the like, to the fluororesin to prevent the above-mentioned image disturbance due to static electricity. In addition, the charge roller can be de-charged and made conductive by the same means. Further, an antistatic agent or the like may be applied or added.

Fixing film is endless belt type, rewindable type,
Regardless of the type of rewinding and repetitive use, the replacement of the fixing film and the like can be facilitated by making the cartridge structure detachable at a predetermined portion of the fixing device 11.

The configuration of the heating element 20 and the control of energization to the heating element 22 are not limited to those in the embodiment. The heating element 20 may be a heat roller type, and the heating element 22 has a thick-film resistor or PTC characteristic. A ceramic chip array or the like may be used, and the energization control may not be performed in a pulsed manner but may be an ordinary energization.

The cooling and solidification of the toner heated and melted in the heating step may be performed by natural heat radiation, or may be performed by forced cooling by arranging a blowing means, a heat radiation fin, or the like.

If the toner is sufficiently melted at a high temperature, if the toner is melted at a sufficiently high temperature in the heating step (fixing nip portion) as shown in FIG. 6, the recording material (transfer material) is immediately transferred without a cooling step after the heating step. The sheet P may be separated from the surface of the fixing film 24.

The above-described apparatus is a transfer-type electronic copying apparatus.
The image forming process and means are electrofax paper,
An image is formed on a recording material with a heat-fusible toner by a direct type in which a toner image is formed and held directly on an electrostatic recording paper or the like, a magnetic recording image forming type, or any other appropriate image forming process or means, and heated. The present invention can be effectively applied to various image forming apparatuses such as copiers, laser beam printers, facsimile machines, microfilm reader printers, display devices, and recording machines of a fixing system.

As described above, according to the present invention, in the toner image heating and fixing device, it is possible to reduce the heat capacity of the heating member which is the heating means without causing the fixing failure or the offset, and the thickness of the fixing film. The thickness is set to be 50 μm or less, and the film is a base material layer made of a heat-resistant resin,
In addition to having a release layer in contact with the toner image provided on the base material layer, and the thickness of the base material layer being equal to or greater than the thickness of the release layer, standby time, power consumption, and It is possible to realize an image forming apparatus capable of constantly and stably outputting an image formed article having a good fixed image quality with a small temperature rise. Further, the fixing film can be repeatedly used for a long period of time without any problem without generation of wrinkles without any problem.

[Brief description of the drawings]

FIG. 1 is a vertical sectional front view showing a schematic configuration of an apparatus of one embodiment, FIG. 2 is an enlarged view of a fixing device portion, FIG. 3 is a schematic view of another configuration example of the fixing device, and FIG. 4 is a fixing film. FIG. 5 is a schematic diagram of an example of the layer configuration, FIG. 5 is a schematic diagram of the adhesion of the fixing film to the linear toner image surface, and FIG. 6 is a schematic diagram of another configuration example of the fixing device. Reference numeral 3 denotes a drum-type rotating photoconductor, 11 denotes a fixing device, 24 denotes a fixing film, 20 denotes a heating member, 28 denotes a pressure roller, and P denotes a transfer material sheet.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Hosoi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Hiroyuki Adachi 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Within the corporation (56) Reference JP 59-68766 (JP, A) JP 61-252190 (JP, A) JP 61-162074 (JP, A) JP 63-56662 (JP, A) JP-A-61-122667 (JP, A) JP-A-61-149966 (JP, A)

Claims (1)

(57) [Claims] 1. A heating body comprising: a heating body; and a film, one side of which slides on the heating body, and the other side of which is in contact with a recording material carrying an unfixed toner image and moves together. In a fixing device that heats and fixes an unfixed toner image on a recording material by heat from, the film is a base material layer made of a heat-resistant resin, and a release layer in contact with the toner image provided on the base material layer, And a thickness of the film is 50 μm or less, and a thickness of the base material layer is not less than a thickness of the release layer.