JPS61148476A - Roller for heat fixing and fixing device having said roller - Google Patents

Abstract

PURPOSE:To make possible the provision of electrodes in the state of having no cracks by providing a heating layer which has a positive resistance temp. characteristic (PTC) after calcination and on which the electrodes are formed in the axial direction of a roller. CONSTITUTION:The electrodes 5A, 5B are formed to a mixture composed of raw material and binder prior to the calcination to obtain the PTC characteristic. The mixture is calcined at a high temp. in succession to such formation by which the electrodes and the mixture are united. The heating layer 4 is the PTC ceramic layer provided as an upper layer of an inside surface layer 7 and constitutes the layer of the resistance lower than the resistance of the ceramics of the layer 7. Conductors 5A, 5B are alternately and successively printed at approximately specified intervals on the inside of the layer 4. The conductors 5A, 5B form the line-shape pattern relative to the longitudinal direction over the entire part of the longitudinal direction of the layer 4. The dimensional deformation and cracks are thus obviated and the excellent temp. distribution is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field to which the invention pertains) The present invention relates to a heat fixing roller of a fixing device applied to a recording device such as an electrophotographic copying machine, a printing machine, a printer, or a facsimile.

The present invention relates to a heat fixing roller and a fixing device as a heating means used for fixing an unfixed image.

(Prior Art) A heat fixing roller that has been put into practical use in the past has a temperature sensor on one surface, and its temperature is controlled by switching a halogen heater provided at the center of the roller into a energized state or a non-energized state.

Since this temperature control is quite complex, a positive resistance temperature that has a self-temperature control function, that is, PositiveTemp, is used.
erature co-efficient of
It has been proposed to use ceramics with high resistance (hereinafter abbreviated as PTC).

U.S. Pat. No. 4.28El, 155 discloses that PTC
A heated fusing roller using a semiconductor ceramic having properties in the form of a rod is shown. However, since this rod-shaped PTC ceramic is thick, it must be provided at a large distance from the inner peripheral surface of the roller.

In particular, the PTC ceramic disclosed in this U.S. patent
Since it is a rod-shaped ceramic after firing, there is a problem when providing an electrode for applying voltage to the PTC ceramic.

When an electrode is provided on the surface of a ceramic with PTC characteristics, the ceramic is locally heated to 500°C when setting the electrode.
Cracks occur in ceramics due to the high temperature up to ~1000°C. Conventionally, ceramics used in the fixing field have been made by mixing powder with a binder, but the ceramics have been so crumbly that they cannot maintain their shape, and they must be fired to obtain the shape. Therefore, the present inventor believed that there was a need for a ceramic material that could easily change the shape of the conventional ceramic material before firing. Conventional ceramics before firing have a binder content of less than a few percent based on the powder raw material and cannot be deformed.

Furthermore, conventional PTC ceramics sometimes have poor heat conversion efficiency for power supply, and no clear explanation has been given regarding this problem.

(Object of the Invention) In view of the above-mentioned problems, an object of the present invention is to provide a heating fixing roller in which electrodes can be provided on a heat generating layer having PTC characteristics without generating cracks. .

The present invention aims to provide a fixing device having the above-mentioned heating fixing roller, and other objects are achieved as described below. (Structure of the Invention) In order to achieve the above-mentioned object, the present invention Positive Temperature Characteristic
reCo-eHicient of resistiv
A step of forming an unfired annular substrate by mixing a raw material capable of obtaining ity properties) and a binder for holding this raw material, and an electrode to which an applied voltage for heat generation is supplied during the forming step. The heating layer is formed through a step of firing an unfired annular substrate on which the electrode is formed after a step of providing it on the mixture, the heating layer having a positive resistance-temperature characteristic after firing and a surface The present invention relates to a heat-fixing roller having a heat-generating layer on which the electrode is formed extending in the axial direction of the roller, and a fixing device having the same.

(Embodiments and Overview of the Invention) Embodiments and application examples thereof that meet each object of the present invention will become clear from the description of FIG. 1.

In FIG. 1, numeral 36 indicates a block of image forming means, and the built-in structure shows that various image forming means such as a general facsimile, laser printer, printing machine, etc. are gold-colored.

For convenience, means A to H for forming a visual image by electrophotography are shown as an example of the image forming means 36.

B shows a photosensitive drum having a photosensitive layer as an example of an image carrier. The photosensitive drum B receives the copy signal, rotates in the direction of the arrow by the driving force of a drive source (not shown), and is pre-discharged by a pre-discharge charger (not shown). Next, the photosensitive drum B is charged by a fuse charger E, and then subjected to secondary charge removal by a secondary charger H. On the other hand, at the same time, origin
Optical device A in which the al image includes an optical member and an optical member moving means
The photosensitive drum B is image-exposed by being scanned by. Then, an electrostatic latent image is formed on the drum B by the next whole surface exposure (not shown). This latent image is developed by developer C.
It is developed into a visible image, which rotates together with the drum B, and reaches the transfer charger F.

On the other hand, recording materials s and si of different width sizes are stored in a cassette 30.
．． 31, the sheets are fed one by one by conveyance rollers 32 and 33, moved along a guide member 34, and conveyed close to the drum B at a timed timing by a registration roller G in order to receive the developed image. At this time, the recording materials s and si are charged by the transfer charger F from the back side thereof to a polarity opposite to that of the visible image, so that the visible image is transferred onto the recording materials S and SL. After this, the surface of the optical drum B is cleaned by the cleaning means in preparation for the next copying.

On the other hand, the recording material S reliably carries the visible image T.

Sl is separated from the photosensitive drum B and sent to the fixing device 37.

The heat fixing roller l has a configuration described later, and the pressure roller 2
The recording materials S and SL are sandwiched and conveyed between the two. At this time, the thermoplastic powder developer (hereinafter referred to as toner) of the developed image in contact with the fixing roller 1 is melted and pressurized, and is heated and fixed onto the recording material.

The pressure roller 2 has a thick coating 43 made of an offset-preventing elastic material such as silicone rubber on the circumferential surface of a rigid metal roll 44 . The fixing roller 1 and the pressure roller 2 are in pressure contact with each other, and the elastic coating 43 is elastically deformed, so that the recording material S
, and forms a nip portion for fixing the SL. These rollers 1 and 2 are driven by a motor (not shown) on the main body side of the electrophotographic recording apparatus 3, which rotates the roller 1 in the direction of the arrow, and the roller 2 is rotated by the rotation of the roller 1 due to frictional force. Further, a web 51 for cleaning the surface of the fixing roller l is pressed against the circumferential surface of the fixing roller l by a pressing roller 38. After cleaning the surface of the fixing roller, the web wound around the shaft 40 is moved to the rotating shaft 39 by the driving force, and is wound around the shaft 39. Zero or more rollers 1, 2, 38 and the shaft 39, 40 have a width is recording material S
, 51 or more, and is rotatably supported by the fuser box body 52. 41 is a separation claw that comes into contact with the fixing roller and separates the recording material from the roller surface; 42 is a separation claw that comes into contact with the fixing roller;
This is the information board near the. Reference numerals 46 and 47 designate discharge rollers that discharge the recording material conveyed between the separating claw 41 and the guide plate 42 onto the tray 48.

It is removable.

The aforementioned heat fixing roller l will be described in detail.

As seen in FIGS. 1 to 4, the roller 1 has a multilayer structure. 50 is a hollow metal cylindrical roller, which forms the base of the roller l. 49 is a metal cylindrical roller 5
The electrically insulating layer provided on the roller 50 electrically insulates the upper PTC ceramic heating layer 4 and the PTC ceramic inner layer 7 from the base body of the roller 50. This insulating layer 49 is provided to increase the heat generation efficiency of the upper PTC ceramic layer.

The inner layer 7 is a cylindrical PTC ceramic layer as seen in FIG. 2, and has a joint 6 to form a cylinder. The inner layer 7 has a conductor 8 printed on the entire circumference of both ends.
There are electrodes A and 8B, which constitute electrodes that receive the applied voltage from the device 3.

The heat generating layer 4 is a cylindrical PTC ceramic layer provided as an upper layer of the inner layer 7, and has a resistance higher than that of the ceramic of the inner layer 7. Conductors 5A are arranged inside this layer 4 at approximately regular intervals.

5B are printed in alternating order. These conductors 5A and 5B form a linear pattern extending longitudinally over the entire length of the heat generating layer 4, with a conductor 5B between the two conductors 5A and a conductor 5B between the two conductors 5B.
A are provided so as to be adjacent to each other in the circumferential direction.

The distance between adjacent conductors 5A and 5B is constant, and
The distances between the conductors 5A and 5B are also constant. It is preferable that such line-shaped conductors 5A and 5B with a constant interval be provided at least in an area beyond the passage area of the recording materials S and SL.The reason for this is that when the conductor interval is constant, the distance between the conductors This is because the sandwiched PTC ceramic can generate heat uniformly in the longitudinal direction of the roller.

The conductors 5A and 5B each form an electrode, but the conductor 5A and the conductor 5B have different polarities, so that the collective conductor 5A' is connected to the conductor 5A.
A concentrated conductor 5E3' gathers the conductors 5B. These concentrated conductors 5C' and 5B' are provided on the left and right sides of both ends of the heat generating layer 4 over the entire inner peripheral surface thereof (
(See Figure 2). Only these concentrated conductors 5Δ/, S# are joined to the conductors 8A, 8B on the inner surface layer, forming a power feeding mechanism for the roller l.

The joint part 6 of the heat generating layer 4 is opposed to the joint part 6 of the inner surface layer 7 with a difference of 180@ so that the joint part 6 and the joint part 6 of the inner surface layer 7 are not at the same position with respect to the circumference. Not overlapping the joint portions 6 has the effect of increasing the strength of the heat fixing roller. The heat fixing roller coats the surface of the heat generating layer 4 with a release layer 9, for example PFA, to prevent the toner from the image T from fusing.
It has a layer made of a polymer material such as resin, FEP resin, or PTFE resin.

35 is a voltage application device that applies a voltage between all the conductors 5A and 5B to flow current, and includes a power supply brush 35A to both poles;
35B (or power supply filament 35A' as shown in Figure 3)
, 35B'). In Figure 2, conductors 8A, 8
Brush 35A for each B.

35B is in contact with it.

As mentioned above, the width LO of the recording material S and the width L l of the recording material S1
On the roller surface corresponding to (L o > L l), conductors 5A and 5B of different electrodes are provided in order in the circumferential direction, so that heat generation in the heat generating layer can be performed in the circumferential direction. As a result, when the roller surface temperature in an area corresponding to the width of the recording material decreases, only the area where the temperature has decreased is heated due to the reduced resistance of the PTC ceramic in that area. Therefore, unnecessary temperature rise on the roller surface is prevented, and the roller surface temperature distribution can be made uniform in the axial direction of the roller. Also, conductors 5A, 5
Making the interval B substantially constant produces more preferable temperature uniformity, and by alternately arranging the conductors 5A and 5B, uniform temperature distribution in the circumferential direction of the roller can be achieved.

In FIG. 2, the surface layer 9, the insulating layer 49, and the base roller 50 are not shown (however, the configuration shown in this figure with the surface release layer 9 provided is also an example of the roller configuration of the present invention).
, a longitudinal section through the roller 1 can be seen in FIG. In addition, in FIG. 3, the power supply filament 3 explained in FIG.
5A' and 35B', a heat-insulating electric insulating flange 52 is provided on one end surface of the roller, and an annular shape is provided on the outer surface of the flange 52 so as to draw a double concentric circle around the axis 54 of the roller l. It has collecting conductor rails 5A'' and 5B''. Conductors 5A and 5B are electrically connected to the rails 5A'' and 5B'', respectively. Further, in FIG. 3, the shaft 54 is fixed to a substrate 56 of the device, and a bearing 53 is provided on the flange 52 to enable the roller 1 to rotate relative to the shaft 54. filament 3
5 A'.

, 35B are connected to the voltage applying device 35 and are brought into contact with the rails 5A'', 5B'' by pressure springs 57, respectively. The tips of filaments 35A' and 35B' are
Since the width is smaller than the width of the rails 5A'' and 5B'', it makes stable contact with the rails. Reference numeral 55 denotes a shaft support that accommodates a filament and a pressure spring, and is fixed to the device through a minute gap with respect to the flange 52.

Next, the manufacturing flowchart shown in FIG. 6 will be explained while also explaining FIG. 4.

By firing, a solvent 11. Add dispersant 12,
The ceramic raw material 10 to be subjected to the mixing/pulverizing step 13 is P
Raw materials for BaTiO3-based ceramics with TC characteristics 10
Additive elements (for example, La, Ce, etc.) are added to BaCO3 and TiO2 to make them semiconductor.

Oxides such as Nb, Ta, Ei, Sb, W, etc.) are added, and components that increase the positive temperature coefficient of resistance (Mn, Fe, etc.) are added.
, Cu, Cr, etc.) and components that promote semiconductor formation and adjust grain size (see A, 03).

5i02, TiO□).

In this example, the raw materials are mixed to have a composition ratio of 9 parts (or less) of lead titanate to 16 parts of barium titanate, and a heat generating layer with a curie temperature of 100°C to 250°C is created. I'm trying to get it.

Here, as the solvent 11, trichlene, alcohol, ethyl acetate, toluene, acetone, MEK.

Using water etc., as the dispersant 12, fish oil, octylamine, glyceryl monooleate (GlycerylIIon)
ooleate), glyceryl triolate (Glyc
eryltrioleate) etc. are used.

Further, a plasticizer 15 and a binder 16 are added, and the mixture is thoroughly mixed again, pulverized 14, molded and dried 17 to produce a green sheet 18. Here, the green sheet contains 10 to 20% of the binder and is flexible. This plasticizer 15 is polyethylene glycol.

Using DBP (dibutyl phthalate), DOP (dioctyl phthalate), 5AIB (inbutyral stearate), glycerin, etc., as the binder 16, cellulose acetate, polyacrylate, PVA (polyvinyl alcohol), PVB (polyvinyl butyral).
, EVA (ethyl vinyl acetate), PVA (polyvinyl acetate), etc. are used. After producing a green sheet 18 with a thickness of 0.5 to 2II11 in this manner, a conductive paste for high temperature sintering, preferably a tungsten powder paste, is applied onto this sheet by a screen printing method to form the conductors 5A, 5B, 5A', 5E3
' is printed 19 in a comb tooth shape as shown. In the printed state, it is in the form of a sheet as shown by the broken line in FIG. 4, and during printing, it is heated at a much lower temperature of 200°C or less, unlike the high temperature of 500°C to 1500°C, which is the firing temperature of ceramics.

If a green sheet with a conductor pattern printed in this way is placed so that the conductor is on the inner side, it will become the heat generating layer 4 shown in Figure 1, and if the conductor is placed on the front side, it will be the heat generating layer 4' shown in Figure 4. becomes. In any case, the sheet is formed into a cylindrical shape 2
It will be 0.

Next, this sheet is formed into a cylindrical shape 20.

Since this cylindrical molded product does not require any means for applying pressure from the outside, the molded product is free from the influence of residual stress, strain, etc. inside the molded product.

The binder 16 remaining inside the cylindrical molded product thus formed is heated to be removed (21).

This heating is followed by sintering 22 at about 1300-1400° C. in a reducing atmosphere for 2 hours with a temperature increase of 200-400° C. per hour.

Under this high temperature and reducing atmosphere condition, the ceramic contracts and acquires PTC properties. At this time, the patterned conductors 5A, 5B, 5A', and 5B' are also exposed to high temperature at the same time, so the conductors that were unstable due to being printed on the ceramic are tightly fixed to the ceramic during this firing. . This fired product is heated at 100°C to 2°C per hour.
If the roller is cooled at 00''C, a roller as shown in FIG. 4 will be produced.

In FIG. 1, since it has an inner layer 7, to supplement this manufacturing method, a ceramic green sheet is prepared 18 for the inner layer 7 in the same manner as the eruption layer 4, and a conductor 8A as a pattern electrode is used for the inner layer 7.
8B is printed 19 in a line shape on both ends of one side of the sheet.
The conductors 8A and 8B of the sheet of the inner layer 7 are prepared as a sheet with B etc. printed on them, and the conductors 5A' and 513 are
A pair of overlapping sheets are formed into a cylindrical shape 20 so that the sheets on which the conductors 8A and 8B are printed are on the inside so that their seams do not overlap. Thereafter, the heating 21° sintering 22 described above is performed, whereby the heat generating layer 4 and the inner surface layer 7 are formed into a conductive roller shape.

Generally, ceramics shrink depending on the firing cycle, and this local unevenness in shrinkage causes crankiness, quality unevenness, and even dimensional unevenness. This uneven local shrinkage is caused by uneven mixing of raw materials, residual stress and strain due to pressure during molding.

Conventionally, cracks and qualitative unevenness occurred during firing, but with this method, there is no influence of external pressure during molding, and as a result, there is no residual stress or strain within the molded product, so cracks are eliminated. The roller can be manufactured without causing any unevenness or quality unevenness.

In this way, a PTC ceramic roller having PTC characteristics is manufactured. The electrodes of this roller are baked at the same time as the sintering process, and there is no need to add electrodes afterwards, so this electrode material can be prevented from cracking or dimensional deformation due to thermal shock.

FIG. 2 is a perspective view of another embodiment that can be used as the heat fixing roller of the present invention, and in this case, in this method,
It is possible to manufacture products with a wall thickness of 0.51 to 4'ms (thickness of two sheets 4.7 pasted together) of about 30φ. Further, the dimensions after firing are approximately 10 φ rollers with an accuracy of about ±0.3 to 0.5%.

The examples shown in Figures 1 and 2 have electrodes (5A,
5A', 5B, 58') are not exposed, and has the following advantages: 1. There is no unevenness in the electrode portion; 1. There is no diffusion of heat into the air due to heat generation from the surface.

The PTC characteristics of roller 1 created by this method are
This figure shows the temperature change of the resistance according to this example.
It is standardized based on the resistance at 5°C. The data in Figure 5 is based on the case where Ba atoms are replaced with 25% by weight of Pb, but in this case, the amount of Pb replaced increases and non-uniformity during firing is likely to occur due to evaporation of Pb. , the smaller the amount of Pb substitution, the better.

By creating PTC ceramic in this way,
Not only is it possible to make a roller with a thin wall, but
Rollers with good dimensional accuracy and low distortion can be made by baking electrodes at the same time. This PTC ceramic roller whose surface is coated with a fluororesin is used as a toner image heating and melting member in electrophotography with a bearing at the end. Surface PTFE coat both 2
5±5μ thickness). As a result, as shown in Table 1, good rise characteristics and temperature distribution were obtained.

In the conventional method, which simply uses a rod-shaped PTC ceramic to heat a roller that is a good heat conductor, the PTC ceramic itself has a temperature of 20%.
Although the temperature can be raised to 180°C in ~30 seconds, it takes 90 to 100 seconds for the surface of the fixing roller to reach approximately 180°, and the temperature distribution on the surface is quite uneven, which is difficult to achieve with the present invention. A big difference was seen.

As explained above, by forming the PTC ceramic raw material into a sheet shape, printing electrodes on its surface, forming it into a cylinder and sintering it to make a PTC ceramic roller, ■ 3. There are no defects that impair dimensional accuracy, and there are no cracks. It is now possible to manufacture PTC rollers without causing qualitative unevenness, and PTC ceramic rollers with good heat generation efficiency can be manufactured. 2. By forming the electrodes at the same time as the ceramic roller is fired, the polarity can be improved over time. In addition to preventing dimensional deformation and cracking due to thermal shock, it is possible to provide a low-cost roller. 3. By using it as a heating roller in an electrophotographic fixing device, it has good start-up characteristics and short heating time to reach the specified temperature. It has the above effects of providing a melting device that can be started quickly.

Further, as described above, when different electrodes are formed in sequence on the circumferential surface (on either the inner surface or the outer surface) of the roller, a large amount of heat can be generated.

This is defined as the distance 1lIId between each electrode conductor 5A and 5B, the number n of conductors, and the parallel length of conductors 5A and 5B, and assuming that the resistivity of unit length is Os, the resistance of the layer is R= OS
-T-X n, and in order to obtain the total calorific value in lKW, l = 30
0mm, applied voltage 1OO(v),! −R=l
OQ TofZru. In other words, when the above calorific value is obtained by the pattern electrode, d (s
*) Since d and n need only be set so that X n = 300 (■l), there are advantages in that the design is easy and the practical range can be expanded. Conversely, if the unit resistance, distance #d, and number of conductors n are changed, a larger amount of heat generation can be obtained. Therefore, good fixing performance can be expected when an unfixed toner image is fixed.

Even if separate electrodes are provided on the surface and inner surface of this heat generating layer 4 to generate heat, the resistance is R= h l b/a (a is the inner diameter of the inner electrode, b is the outer diameter of the outer electrode, and ρ is the unit (specific resistance of length), so the limited voltage 100 (V)
When trying to obtain IKW by multiplying , the resistance is 30
If 0i + shoe, ρ = 10Ω/chopeng, and R = 10Ω,
ln b/a = 200 → b/a = e200, which makes it impossible to realize, and 10 (V) and 1
(V) Apply chisel pressure and go as follows: j/a = e2. b/a
= eO.02 Iso 1.02, which is impossible or requires an extremely large transformer, which is a big disadvantage in practice.

In the above embodiment, (dXn) is preferably 18<(dXn)≦42 based on the above formula, and P
The resistance of the TC ceramic is suitably 6Ω to 50Ω, preferably 14Ω or less considering the heat generation of 1.5KW or less and the heat generation at a rise of 700W or more.

When both the inner surface layer 7 and the heat generating layer yfj4 are PTC heat generating layers as in the example in FIG. This has the advantage of shortening the time and preventing heat loss during continuous fixing. Further, by disposing a plurality of PTC heat generating layers, there is an effect that the temperature distribution on the surface of the fixing roller can be made more uniform.

It is preferable to provide a releasable layer on the surface of the heat fixing roller, and the layers 49, 59, and 9, which are other components in FIG. An electrically insulating layer made of ceramics that provides sufficient strength may also be used.

The heat-fixing roller in the present invention includes a fixing roller that comes into contact with an unfixed toner image, a roller that pinches and conveys a recording material between the fixing roller, a roller that heats the fixing roller, and the like.

Further, the present invention is novel and sufficiently effective not only for a heat-fixing roller, but also for a fixing device including a pressure roller used together with the heat-fixing roller. be.

The voltage applying means 35 may be a device for substantially flowing current, but may be either an alternating current (including a voltage wave meter such as a sine wave, a rectangular wave, a pulse wave, a triangular wave, etc.) or a direct current. In this case, the conductor alternately changes into a positive electrode and a negative electrode, and the expressions in the claims include these.

The above electrode pair is shown as being parallel to the axial direction of the roller, but it may also be spiral-shaped on the inner and outer peripheral surfaces of the roller, or slightly inclined with respect to the axial direction of the roller. Preferably, the spiral electrode pair has a narrowing gap in a direction fairly close to the circumferential direction.

(Effects of the present invention) In the present invention, an electrode part is formed in a mixture of raw materials and a binder before firing to obtain PTC characteristics, and then the electrode part is integrated by high-temperature firing, so there is no dimensional deformation and no cracks. Provides excellent temperature distribution without any turbulence. Therefore, the fixing effect is significantly improved compared to the conventional method.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of the overall configuration of an embodiment of the present invention, FIG. 2 is a perspective view of an embodiment of the heat fixing roller of FIG. 1, and FIG.
4 is a perspective view of another embodiment of the heat fixing roller, and FIG. 5 is a graph showing a resistance change curve of the heat generating layer of the heat fixing roller of the present invention. FIG. 6 is a detailed explanatory flowchart of the present invention. 1 is a heat fixing roller, 2 is a pressure roller, 4 is a heat generating layer (P
TC ceramic), 7 is the inner layer (PTC ceramic),
5A, 5B, 8A, 8B are conductors. 9 is a surface release layer, 35 is a voltage application device, 49 is an insulating layer,
50 is a metal cylindrical roller. pigeon 6 torture

Claims (20)

[Claims] (1) Positive resistance temperature characteristics (Positive) due to firing
eTemperature Co-efficient
of resistivity property) and a binder for holding this raw material to form an unfired annular substrate, and an electrode to which an applied voltage for heat generation is supplied. A heat generating layer formed through a step of firing an unfired annular substrate on which the electrode is formed after a step of providing the mixture inside the mixture, and having a positive resistance temperature characteristic after firing. A heating fixing roller having a heat generating layer on the surface of which the electrode is formed extending in the axial direction of the roller. (2) The heat fixing roller according to claim 1, wherein the heat fixing roller has an offset prevention layer on its surface. (3) The heat fixing roller according to claim 2, wherein the heat fixing roller conveys the recording material in order to fix the unfixed toner image on the recording material between the heat fixing roller and another roller provided opposite to each other. roller. (4) The heat fixing roller according to claim 1, wherein the electrode is provided on the surface of the sheet after forming the mixture of the raw material and the binder onto the sheet. (5) The electrode has conductors that are longer than the width of the largest recording material arranged in sequence and spaced apart from each other in the circumferential direction of the heat-fixing roller, and these conductors extend in the longitudinal direction of the roller. The heating fixing roller according to item 4. (6) The above-mentioned conductor forms an electrode with a different polarity from the adjacent conductor, and the portion of the firing layer with positive resistance-temperature characteristics between the pair of electrodes with different polarity along the longitudinal direction of the roller is located at a position relative to the longitudinal direction of the roller. 5. The heat fixing roller according to claim 4, which generates heat uniformly without being affected by heat. (7) The heat fixing roller according to claim 6, wherein the distance between the electrode pairs of different polarities is a constant interval in the circumferential direction. (8) The heating fixing roller according to claim 6, wherein the electrode is provided on the inner circumferential surface of the heat generating layer. (9) The heat fixing roller according to claim 6, wherein the heat generating layer has a resistance of 6Ω or more and 50Ω or less. (10) The heat-fixing roller according to claim 9, wherein the heat generating layer has a resistance of 14Ω or less. (11) Positive resistance temperature characteristics (Positi
veTemperature Co-efficient
A process of forming an unfired annular substrate by mixing a raw material capable of obtaining a high resistance property (of resistance property) and a binder for holding this raw material, and forming an electrode to which an applied voltage for heat generation is supplied. A heat-generating layer formed through a step of firing an unfired annular substrate on which the electrode is formed after a step of providing the mixture during the process, and having a positive resistance temperature characteristic after firing. A fixing device comprising: a heat fixing roller having a heat generating layer on the surface of which the electrode is formed extending in the axial direction of the roller. (12) The fixing device according to claim 11, wherein the heat fixing roller has an offset prevention layer on its surface. (13) The fixing device according to claim 12, wherein the heat fixing roller conveys the recording material in order to fix the unfixed toner image on the recording material between the heat fixing roller and another roller provided opposite to each other. . (14) The fixing device according to claim 11, wherein the electrode is provided on the surface of the sheet after forming the mixture of the raw material and the binder onto the sheet. (15) The electrode has conductors that are longer than the width of the largest recording material arranged in sequence and spaced apart from each other in the circumferential direction of the heat-fixing roller, and these conductors extend in the longitudinal direction of the roller. The fixing device according to item 14. (16) The above-mentioned conductor forms an electrode with a different polarity from the adjacent conductor, and the portion of the fired heat generating layer having a positive resistance temperature characteristic between the pair of electrodes with different polarity along the longitudinal direction of the roller is located at a position in the longitudinal direction of the roller. 15. The fixing device according to claim 14, which generates uniform heat regardless of the (17) The fixing device according to claim 16, wherein the spacing between the electrode pairs of different polarities is a constant spacing in the circumferential direction. (18) The fixing device according to claim 16, wherein the electrode is provided on the inner circumferential surface of the provided heat generating layer. (19) The fixing device according to claim 16, wherein the heat generating layer has a resistance of 6Ω or more and 50Ω or less. (20) The fixing device according to claim 19, wherein the resistance of the heat generating layer is 14Ω or less.