JPH08101594A - Fixing heater, fixing device and image forming device - Google Patents

Abstract

PURPOSE: To prevent a recessed part forming on an over-coat layer and to increase the electric withstand voltage between conductors by interposing the heat resistant insulator provided with the high electric withstand voltage between the plural conductors, near to the insulator of the over-coat layer. CONSTITUTION: In the fixing heater 10, on the planar surface 11a of the oblong substrate 11 consisting of the heat resistive electrically insulated material for instance, the alumina ceramic, the resistive heater 12 of the oblong inversely U-shaped film shaped mainly consisting of for instance, the silver palladium alloy or the nickel-tin alloy or the like, along the length direction, is coaxially composed. Then, in the resistive heater 12, the electrically insulative glass 13 as the heat resistive electric insulator provided with the high electrically withstanding voltage is interposed in the mutually opposing gap g0 in between the parallel parts 12a and 12b in parallel to each other along the lengthwise direction, the height (film thickness) of the electrically insulative glass 13 is set to the almost same height (film thickness) of the resistive heater parallel parts 12a and 12b on the both side, and the respective top surface is formed almost in the flat surface state.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin fixing heater to be used by being attached to small equipment such as office automation equipment, household electric equipment and precision manufacturing equipment, and a copying machine and a laser printer in which the fixing heater is mounted. The present invention relates to a fixing device used for fixing a toner image such as a facsimile, and an image forming apparatus using the fixing device.

[0002]

2. Description of the Related Art Generally, in an electronic copying machine, a copy sheet on which a toner image is formed is passed between a fixing plate heater and a pressure roller while directly or indirectly with a heat-resistant sheet interposed therebetween. The toner on the copy paper is heated, melted and fixed by the heating of the heater.

As a conventional fixing heater of this kind, one having a structure as shown in FIGS. 5 and 6, for example, has been put into practical use. The fixing heater H is an elongated heat resistant / electrically insulating substrate 1 made of alumina (Al ₂ O ₃ ) ceramics or the like.
A paste prepared by kneading silver / palladium alloy (Ag / Pd) powder and the like with a glass powder (inorganic binder) and an organic binder is printed and applied on the surface 1a of the above, and baked. A resistance heating element 2 having a band-shaped thick film shape is formed by, for example, thick film printing, and silver or a silver / platinum (Ag / Pt) alloy or a silver / palladium alloy (Ag / Pd) is formed on both ends of the resistance heating element 2. ) Or the like to form a pair of power supply terminal portions 2a, 2b, and the outer surface of the resistance heating element 2 is covered with a vitreous overcoat layer 3 which is a heat resistant protective layer. As a result, mechanical strength such as abrasion resistance and impact resistance is improved, deterioration such as sulfidation and oxidation is prevented, and electrical insulation from equipment such as a pressure roller is achieved. On the upper surface of the overcoat layer 3, for example, the copy paper P on which the toner image T is formed slides from in to out as shown by the arrow in the figure and is heated to fix the toner image T to the copy paper P. It is designed to let you.

On the back surface 1b opposite to the front surface 1a of the substrate 1, silver (Ag), a silver-platinum (Ag.Pt) alloy,
A pair of wiring conductors 5a and 5b made of a film of a good conductor such as silver / palladium (Ag / Pd) alloy is formed, and the resistance heating element 2 is formed on one end of these wiring conductors 5a and 5b.
The chip-shaped thermistor 4 as the temperature detecting element is fixed.

The thermistor 4 detects the temperature of the resistance heating element 2 via the temperature sensor terminal portion 1c on the substrate surface 1a,
The detected temperature signal is fed back to a temperature control circuit (not shown) to control the electric power applied to the resistance heating element 2 to keep the resistance heating element 2 at a constant temperature. Alumina (Al ₂ O ₃ ) ceramics A temperature-sensitive portion 4b is formed by a thin film formed by depositing an oxide of manganese (Mn), cobalt (Co), nickel (Ni) or the like in the central portion on a flat plate-shaped substrate 4a made of. Electrode portions 4c and 4d made of a platinum (Pt) layer or the like formed so as to be connected to the temperature sensing portion 4b are formed on both ends of the temperature sensing portion 4b. The outer surface of the temperature sensitive portion 4b is covered with an overcoat layer 4e made of lead borosilicate glass. Although each film formed on the substrate 1 or the thermistor base 4a is a thin film as compared with the substrate 1 or the base 4a, it is exaggeratedly thick in FIG. 6 for convenience of description.

In such a thermistor 4, both electrode portions 4c and 4d are provided with the temperature sensing portion 4b facing the back surface 1b of the substrate 1.
Are adhered to the wiring conductors 5a and 5b, respectively, through a conductive adhesive 6 in which silver (Ag) or an alloy powder of silver-palladium (Ag-Pd) is mixed with an organic adhesive such as an epoxy-based adhesive. Reinforcement of this adhesive strength and thermistor 4
In order to improve the thermal conductivity of the above, the thermistor 4 is fixed to the back surface 1b of the substrate 1 by filling a polyimide adhesive 7 having heat resistance and electrical insulation.

[0007]

However, in such a conventional fixing heater H, since the resistance heating element 2 is formed in an elongated inverted U-shape, the resistance heating element 2 is parallel to each other. Between the parallel portions 2c and 2d, for example, about 0.
A minute gap g of about 5 mm is formed.

Accordingly, when the paste of the overcoat layer 3 is printed on the resistance heating element 2 having an inverted U-shape,
When the overcoat layer 3 is fired, air in the minute gap g is entrained, and a foaming phenomenon of fine bubbles a occurs.

For this reason, the electric breakdown voltage of the overcoat layer 3 is lowered, and the concave portion 3a of the overcoat layer 3 is formed with a minute gap g, and the sliding phenomenon of the overcoat layer 3 is caused by the foaming phenomenon. Unevenness is formed on the moving surface.

As a result, streaks and wrinkles are formed in the copying paper P and the fixed image sliding on the sliding surface of the overcoat layer 3 along the conveying direction, and uneven fixing due to uneven heating occurs. There is a risk.

Further, when the copy paper P slides on the sliding surface of the overcoat layer 3, the toner T is separated from the copy paper P in the recess 3a and accumulates on the recess 3a to cause fixing unevenness. May cause

Therefore, the present invention has been made in consideration of such circumstances, and an object thereof is to prevent formation of recesses on an overcoat layer between a plurality of conductors such as a resistance heating element, and It is an object of the present invention to provide a fixing heater, a fixing device, and an image forming apparatus capable of increasing the electric breakdown voltage between these conductors.

[0013]

The present invention is configured as follows in order to solve the above-mentioned problems.

The invention according to claim 1 of the present application (hereinafter, referred to as the first
Of the invention), a substrate made of a heat-resistant electric insulating material, a conductor integrally or separately forming juxtaposed portions juxtaposed on one surface of the substrate at a predetermined interval, and one surface of the substrate. In a fixing heater having an overcoat layer covering the upper surface of the conductor layer with an electrical insulator, a heat-resistant electrical insulation between the plurality of conductors having a higher electrical breakdown voltage than the electrical insulator of the overcoat layer. It is characterized by interposing the body.

The invention according to claim 2 of the present application (hereinafter referred to as the second invention) is characterized in that an electric insulator having a high electric breakdown voltage is interposed only between a plurality of conductors.

Furthermore, the invention of claim 3 of the present application (hereinafter referred to as the third invention) is characterized in that an electrical insulator having a high electrical breakdown voltage is interposed between at least a plurality of conductors.

Furthermore, in the invention according to claim 4 of the present application (hereinafter, referred to as a fourth invention), an electric insulator having a high electric breakdown voltage is locally printed with the paste only between a plurality of conductors. It is characterized by being fired after being fired.

In the invention according to claim 5 of the present application (hereinafter referred to as the fifth invention), the electric insulator having a high electric breakdown voltage is formed to have substantially the same film thickness as the conductors on both sides thereof. Is characterized by.

Further, in the invention according to claim 6 of the present application (hereinafter referred to as the sixth invention), the electric insulator having a high electric insulation withstand voltage and the conductors on both sides thereof are coated with glass having smoothness. Characterize.

Furthermore, the invention according to claim 7 of the present application (hereinafter referred to as the seventh invention) is characterized in that the plurality of conductors are resistance heating elements.

The invention according to claim 8 of the present application (hereinafter referred to as the eighth invention) is any one of claims 1 to 6.
The fixing heater and the pressure roller are disposed so as to face each other.

Furthermore, an invention according to claim 9 of the present application (hereinafter referred to as a ninth invention) is characterized by including the fixing device according to claim 6.

[0023]

[Action]

<First to Ninth Inventions> Heat resistance having a higher electric breakdown voltage than the electric insulator of the overcoat layer between a plurality of resistance heating elements or a plurality of conductors such as a juxtaposed portion of one resistance heating element. Since the electrical insulator is interposed, the withstand voltage between these conductors can be increased, and since the gap between the conductors is filled with the electrical insulator, the recess is formed in the overcoat layer formed between these conductors. Can be effectively prevented.

For this reason, it is possible to effectively prevent the generation of streaks and wrinkles on the copy sheet due to the concave portions of the overcoat layer, the uneven heating and the peeling of the toner, and the uneven fixing due to these.

[0025]

Embodiments of the present invention will be described below with reference to FIGS. 1 to 4, the same or corresponding parts are designated by the same reference numerals.

FIG. 1 is a plan view of an embodiment of a fixing heater according to the present invention, and FIG. 2 is a sectional view taken along the line II--II of FIG. 1. As shown in these drawings, the fixing heater 10 is heat resistant. On the planar surface 11a of the elongated substrate 11 having a length of about 300 mm, a width of about 8 mm, and a thickness of about 0.6 to about 1 mm, which is made of an electrically insulating material such as alumina (Al ₂ O ₃ ) ceramics. Along the longitudinal direction, for example, an elongated inverted U-shape mainly composed of a silver / palladium (Ag / Pd) alloy or a nickel / tin (Ni / Sn) alloy having a length of about 230 mm and a thickness of about 10 μm. The film-shaped resistance heating element 12 is formed concentrically.
For example, the pattern width of the resistance heating element is 1.0 mm, and the gap of the resistance heating element is 0.3 to 0.5 mm.

As shown in FIG. 2, the resistance heating element 12 has a facing gap g0 (0.3 to 0.5 mm) between the parallel portions 12a and 12b which are substantially parallel to each other along the longitudinal direction thereof. An electric insulating glass 13 which is a heat-resistant electric insulator having a high electric insulation withstanding voltage is interposed. As shown in FIG. 2, the height (film thickness) of the electric insulating glass 13 is set to the parallel portion of the resistance heating elements on both sides thereof. The heights (film thicknesses) of 12a and 12b are set to be substantially the same, and the upper surfaces thereof are formed to be substantially flat.

The electrically insulating glass 13 is a glass having a higher withstand voltage than the electrically insulating glass of the overcoat layer 15, which will be described later, by increasing the amount of crystal filler, and contains lead borosilicate glass as a main component. . In addition, since the paste is locally printed on the electrically insulating glass 13 only by the screen printing method or the like only in the gap g between the resistance heating element parallel portions 12a and 12b, the paste pushes out the air in the gap g during the printing. While the substrate surface 11a
Applied over. Therefore, air entrapment can be almost prevented, and thus the foaming phenomenon at the time of firing the paste of the electrically insulating glass 13 can be almost prevented.

The resistance heating element 12 has a wide silver (A) having a length of about 15 mm and a width of about 6 mm on both ends of the inverted U-shape.
g), platinum (Pt), gold (Au) and silver / platinum (Ag / P)
t) Terminal portions 14a, 1a for power supply, which are made of a good conductor film mainly composed of alloy, silver-palladium (Ag-Pd) alloy, etc.
4b are overlapped and formed.

Further, except for the power supply terminal portions 14a and 14b and a part of the substrate 11, a glass powder or the like is used to cover almost the entire surface 11a of the substrate 11 including the resistance heating element 12 and the electrically insulating glass 13. For example, the vitreous overcoat layer 15 having a smoothness with a layer thickness of 20 to 100 μm is formed.

The overcoat layer 15 is a resistance heating element 1.
The outer surface and the like of 2 are covered with surface glass to form a protective layer that protects electrically and mechanically. This surface glass is mainly composed of lead glass containing a large amount of lead oxide, and the amount of the crystal filler is smaller than that of the electrically insulating glass 13. Therefore, the electrical insulating property is slightly lower, but the viscosity is low, and thus the smoothness is excellent. .

The overcoat layer 15 is formed by printing and firing the surface glass paste on the substrate surface 11a in a required step after printing and firing the paste of the electrically insulating glass 13 by screen printing or the like. . That is, since the overcoat layer 15 and the electrically insulating glass 13 are separately fired, the amount of air entrained in the electrically insulating glass 13 can be reduced.

On the other hand, as shown in FIG. 2, the substrate 11 has silver (Ag), platinum (Pt), gold (A) on the back surface 11b side.
u), silver / platinum (Ag / Pt) alloy, silver / palladium (Ag / Pd) alloy, etc.
A pair of wiring conductors 16a and 16b of .mu.m are arranged side by side, and a terminal portion (not shown) is integrally connected to one end of these.

Each tip of the wiring conductors 16a and 16b terminates at a substantially central portion of the back surface 11b of the substrate (just behind the central portion of the resistance heating element 12 on the front surface 11a of the substrate). Are straddling. The thermistor 17 detects the temperature of the resistance heating element 12 via the temperature sensor terminal 11c on the substrate surface 11a, and feeds back the detected temperature signal to a temperature control circuit (not shown) to control the electric power applied to the resistance heating element 12. This keeps the temperature of the resistance heating element 12 constant, for example, a thickness of about 250 made of alumina (Al ₂ O ₃ ) ceramics.
A temperature-sensing portion formed of a thin film formed by mixing oxides (MnO ₂ , Co ₃ O ₄ , NiO) such as manganese, cobalt, and nickel on the central portion of the upper surface of the plate-shaped thermistor substrate 17a of μm in the figure. 17b is formed, and the temperature sensing portion 17b is formed.
Are connected to both ends of, for example, a platinum (Pt) layer or Au.
Thin film electrode portions 17c and 17d composed of layers are formed. The outer surface of the temperature-sensitive portion 17b has a layer thickness of, for example, 5 to ₂ made of lead borosilicate glass (SiO ₂ ) in order to prevent the characteristic deterioration of the film due to the temperature in the atmosphere or the impurity gas.
The entire surface is covered with a 0 μm overcoat layer 17e.

Although the above-mentioned films and layers are thin films in comparison with the substrate 11 and the thermistor base 17a, they are exaggeratedly thick in FIG. 2 for convenience of explanation, and may be proportional in size. Absent.

The chip-shaped thermistor 17 uses an electric resistor having a large negative temperature coefficient, and when the temperature rises, the resistance value greatly decreases, and the temperature is converted into a large or small resistance value. It is a sensor composed of a heat detection element.

In such a thermistor 17, the base 17a has a pair of wiring conductors 16a and 16b on the back surface 11b of the substrate 11.
An organic adhesive such as an epoxy resin containing silver (Ag) or an alloy powder of silver-palladium (At-Pd) or the like on both electrode portions 17c and 17d in a state where the upper surface in the figure faces the back surface 11b of the substrate 11 in between. The conductive adhesive 18 mixed with the wiring conductor 16a, 16
Bonded on top of b.

Then, a polyimide adhesive 19 which is a heat resistant adhesive is applied on the overcoat layer 17e on the thermistor temperature-sensitive portion 17b, and the thermistor 17 is attached to the back surface 1 of the substrate.
It is adhered and fixed to approximately the center of 1b.

Therefore, according to the present embodiment, only the gap g0 between the pair of parallel portions 12a and 12b of the elongated inverted U-shaped resistance heating element 12 is locally coated with the paste of the electrically insulating glass 13 by a screen printing method or the like. Since the printing is performed in a positive manner, the paste can be applied while pushing out the air in the gap g0 during the printing. Therefore, as compared with the case where the glass paste of the overcoat layer 3 is printed on almost the entire surface 1a of the substrate as in the conventional example, the amount of air entrapped can be significantly reduced. Therefore, the bubbling phenomenon during firing of the electrically insulating glass 13 after printing can be almost prevented, so that the parallel portions 12a, 12a of the resistance heating elements are formed.
The electric breakdown voltage between 2b can be increased.

Further, as shown in FIG. 2, the electrically insulating glass 1
The height (film thickness) of 3 is the resistance heating element parallel portion 12 on both sides thereof.
Since the heights (film thicknesses) of a and 12b are almost the same and the upper surfaces of these figures are substantially flush with each other, the upper surface of the overcoat layer 15 laminated on these upper surfaces should be formed substantially flat. Therefore, it is possible to effectively prevent the formation of the concave portion 3a as in the conventional example shown in FIG.

Therefore, it is possible to effectively prevent the generation of streaks and wrinkles on the copy sheet P due to the concave portions 3a of the conventional example, and also it is possible to effectively prevent uneven heating, and further, the concave portions 3a. Toner T from copy paper P by
Since the peeling can be effectively prevented, the fixing unevenness can be effectively prevented. Moreover, since the overcoat layer 15 is made of the surface glass having excellent smoothness, the slidability of the heat resistant sheet or the copy paper P sliding on the sliding upper surface of the overcoat layer 15 can be enhanced.

In the above embodiment, the case where the resistance heating element 12 has an inverted U-shape has been described, but the present invention is not limited to this. For example, a plurality of resistance heating elements 12 having a straight shape, or It is also possible to apply a conductor such as a lead connected to this, which is arranged in parallel on the substrate surface 11a.

The electrically insulating glass 13 is not limited to the gap g0 between the parallel portions 12a and 12b of the resistance heating element,
It may be formed on all or part of the parallel portions 12a, 12b of the resistance heating elements on both sides thereof. Further, in the above-described embodiment, the case where one ends of the resistance heating element parallel portions 12a and 12b are integrally connected has been described, but the present invention is not limited to this, and the resistance heating element parallel portions 12a and 12b are not limited thereto.
It may be configured as a separate body without connecting b to each other. For example, the present invention can be applied to a case where a linear resistance heating element and a conductor such as a lead are arranged in parallel on the substrate surface 11a. .

FIG. 3 is a vertical cross-sectional view of a fixing device 21 having the fixing heater 10 having the above-described structure. This is the outer surface of a cylindrical roller body 23 having rotary shafts 22 projecting from both axial end surfaces. A heat resistant elastic material, for example, a silicone rubber layer 24 is fitted to the pressure roller 25.

The pressure roller 25 has the fixing heater 10 arranged in parallel so as to face the rotary shaft 22 thereof.
0 is attached to a base not shown.

An annular endless heat resistant sheet 26 such as a polyimide resin is wound around the base including the fixing heater 10, and the upper surface of the overcoat layer 15 just above the resistance heating element 12 is shown in the figure. It is in elastic contact with the silicone rubber layer 24 of the pressure roller 25 via the heat resistant sheet 26.

The fixing heater 10 has a power supply terminal portion 13
Silicone rubber and the outer surface of the heat-resistant sheet 26 provided on the overcoat layer 15 of the resistance heating element 12 which is energized by being energized through a connector (not shown) made of a phosphor bronze plate or the like which is in contact with a and 13b By heating the copy sheet P on which the toner image T is formed with the layer 24 by the plate heater 10, the unfixed toner image T is melted and fixed on the copy sheet P.

That is, on the inlet side of the pressure roller 25 into the copy sheet P, the unfixed toner image T on the copy sheet P is first heated and melted by the fixing heater 10 via the heat resistant sheet 26, and at least the surface portion thereof is The melting point largely exceeds the melting point, and the softening and melting is completed, and the copy sheet P is discharged from the outlet side while being cooled.

FIG. 4 shows the fixing device 21 constructed as described above.
Electronic copying machine 31 which is a kind of image forming machine incorporating
This copying machine 31 scans an original 34 by reciprocally moving an original placing table 33 made of a transparent member such as transparent glass provided on the upper surface of a housing 32 in the direction of the arrow in the figure. There is.

A lamp 3 for irradiating light is provided in the upper part of the housing 32.
5 is provided, and the light rays reflected from the original 34 irradiated by the lamp 35 are arranged in the short-focus small-diameter imaging element array 3
6 exposes the photosensitive drum 37 with slits. The photosensitive drum 37 is coated with, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer, and rotates in the arrow direction.

The charging device 38 uniformly charges the photosensitive drum 37, and the photosensitive drum 37 charged by the charging device 38 is image-wise exposed by the imaging element array 36. An electrostatic image is formed. This electrostatic image is visualized using a toner made of a resin or the like that is softened and melted by heating by the developing device 39.

On the other hand, the copy sheet P stored in the cassette 40 is conveyed as a pair of sheets which are rotated in pressure contact with each other in the vertical direction at a timing synchronized with the image on the feeding roller 41 and the photosensitive drum 37. It is fed onto the photosensitive drum 37 by the roller 42. Then, the toner image T formed on the photosensitive drum 37 by the transfer discharger 43 is transferred onto the copy paper P.

Thereafter, the copy sheet P separated from the photosensitive drum 37 is conveyed by the conveyance guide 44 to the fixing device 2 described above.
1 and is heated and fixed there, and then the tray 45
Is discharged to. After transferring the toner image, the photosensitive drum 3
The residual toner on 7 is removed by the cleaner 46.

The fixing device 21 has an effective length in the direction orthogonal to the moving direction of the copy paper P, which corresponds to the width (length) of the maximum size paper that can be copied by the copying machine 31, that is, the width of the maximum size paper (length). The plate heater 10 having a resistance heating element 12 (see FIGS. 2 and 3) extending longer than the length is disposed, and the overcoat layer 15 of the fixing heater 10 and the pressure roller are interposed via the heat resistant sheet 26. The unfixed toner image T on the copy sheet P sent between the sheet 25 and the sheet 25 is melted by receiving heat from the resistance heating element 12, and a copy image such as characters, alphanumeric characters and drawings appears on the surface of the copy sheet P. Let out.

In such a copy image by the fixing device 21, the resistance heating element 12 is continuously formed in a slender shape over the length (width) of the maximum size sheet permitted by the copying machine 31, and its extending direction. A substantially uniform temperature distribution can be obtained, and clear high-quality copying with the same contrast can be obtained on the copy paper P without uneven transfer or the like over the entire surface.

The present invention is not limited to the above embodiment, and the material of the substrate 11 of the fixing heater 10 is not limited to alumina (Al ₂ O ₃ ) ceramics, but may be other materials such as ceramics, glass, and polyimide resin. It may be a synthetic resin member having high heat resistance.

Further, the formation of the overcoat layer 15 for covering the resistance heating element 12 and the substrate 11 is not essential, and even when this is formed, the glass material is not limited to that of the embodiment, and the heat generation is not required. It goes without saying that the temperature can be appropriately selected according to the temperature and the situation of use. Further, the shape of the surface 11a of the substrate is not limited to the above embodiment.

[0058]

As described above, according to the first to ninth inventions of the present application, the electric power of the overcoat layer is provided between a plurality of resistance heating elements or a plurality of conductors such as a juxtaposed portion of one resistance heating element. Since an electrical insulator having a higher electrical breakdown voltage than the insulator is interposed, the electrical breakdown voltage between these conductors can be increased and the gap between the conductors is filled with the electrical insulator, so It is possible to effectively prevent the formation of recesses in the overcoat layer laminated on.

For this reason, it is possible to effectively prevent the generation of streaks and wrinkles on the copy sheet due to the concave portions of the overcoat layer, the uneven heating and the peeling of the toner, and the uneven fixing due to these.

[Brief description of drawings]

FIG. 1 is a plan view of an embodiment of a fixing device according to the present invention.

FIG. 2 is an end view taken along line II-II of FIG.

FIG. 3 is a vertical sectional view of an embodiment of a fixing device including the fixing heater shown in FIGS.

4 is an overall configuration diagram of an embodiment of an electronic copying machine including the fixing device shown in FIG.

FIG. 5 is a plan view of a conventional fixing device.

6 is an end view taken along line VI-VI of FIG.

[Explanation of symbols]

 10 Fixing Heater 11 Substrate 11a Substrate 11b Substrate Backside 12 Resistive Heating Element 12a, 12b Pair of Resistance Heating Element Parallel Section 13 Electrical Insulating Glass 15 Overcoat Layer 16a, 16b Pair of Wiring Conductors 17 Thermistor 17a Thermistor Base 17b Thermistor Sense Warm part 17c, 17d Thermistor electrode part 17e Overcoat layer 18 Conductive adhesive 19 Heat-resistant polyimide adhesive 21 Fixing device 22 Rotating shaft 23 Roller body 25 Pressure roller 26 Annular endless heat-resistant sheet 31 Copy machine 35 Lamp 36 Imaging element Sub-array 37 Photosensitive drum P Copy paper T Toner image

Claims (9)

[Claims] 1. A substrate made of a heat-resistant electrically insulating material, a conductor integrally or separately forming juxtaposed portions arranged in parallel on one surface of the substrate at a predetermined interval, and on one surface of the substrate. And an overcoat layer for covering the upper surface of the conductor layer with an electric insulator, wherein an electric insulator having an electric breakdown voltage higher than that of the overcoat layer is interposed between the plurality of conductors. Fixing heater characterized by 2. The fixing heater according to claim 1, wherein an electric insulator having a high electric breakdown voltage is interposed only between the plurality of conductors. 3. The fixing heater according to claim 1, wherein an electric insulator having a high electric breakdown voltage is interposed between at least a plurality of conductors. 4. The electric insulator having a high electric breakdown voltage is formed by locally printing the paste only between a plurality of conductors and then firing the paste. The fixing heater described in 1. 5. The fixing heater according to claim 1, wherein the electric insulator having a high electric breakdown voltage is formed to have substantially the same film thickness as the conductors on both sides thereof. 6. The fixing heater according to claim 1, wherein an electric insulator having a high electric breakdown voltage and conductors on both sides of the electric insulator are coated with glass having smoothness. 7. The fixing device according to claim 1, wherein the plurality of conductors are resistance heating elements. 8. A fixing device, wherein the fixing heater according to claim 1 and a pressure roller are arranged so as to face each other. 9. An image forming apparatus comprising the fixing device according to claim 8.