JP7746129B2 - Heater, heating device and image forming apparatus - Google Patents

Description

The present invention relates to a heating device, such as a fixing device installed in an image forming apparatus such as a copying machine or printer that uses an electrophotographic or electrostatic recording method, or a gloss imparting device that improves the glossiness of a toner image by reheating a fixed toner image on a recording material. It also relates to an image forming apparatus equipped with such a heating device, and a heater used in the heating device.

Some heating devices installed in electrophotographic printers and copiers have a heater with a heating element on a ceramic substrate, a film that moves while in contact with the heater, and a pressure roller that forms a nip with the heater via the film. A recording material carrying an unfixed toner image is heated while being sandwiched and transported through the nip, thereby thermally fixing the toner image to the recording material.

Power savings have long been a requirement for heating devices like those described above. Patent Document 1 discloses a configuration in which the film unit is offset upstream of the nip in the conveyance direction compared to conventional configurations in order to fix a toner image to a recording material with a low amount of heat. In this configuration, the toner is heated from upstream to downstream of the nip in the conveyance direction of the recording material, softened, and then strongly pressurized downstream of the nip in the conveyance direction, thereby efficiently fixing the toner to the recording material, improving fixing performance and reducing power consumption.

Japanese Patent Application Laid-Open No. 2005-49839

However, in a configuration in which the film unit is offset upstream in the transport direction, if the nip width decreases due to variations in the pressure roller hardness, pressure, etc., the heater's heat-generating portion is biased toward the upstream side in the transport direction, which can easily lead to a deterioration in fixing performance. In other words, with the above configuration, there is a risk that fixing performance will fluctuate if the nip width changes.

The present invention was made in consideration of the above-mentioned problems, and aims to suppress fluctuations in fixing performance.

In order to achieve the above object, the heater of the present invention comprises:
A plurality of heating elements;
A coating layer;
an elongated substrate on which the heating element and the coating layer are provided;
Equipped with
Among the plurality of heat generating elements, a first heat generating element extending in the longitudinal direction of the substrate is provided at a position different from a second heat generating element in a lateral direction of the substrate perpendicular to the longitudinal direction,
a heat generation amount of the first heat generating element is greater than a heat generation amount of the second heat generating element,
When the coating layer is viewed from a surface opposite to a surface in contact with the substrate in a thickness direction of the substrate perpendicular to the longitudinal direction and the lateral direction, the coating layer has a first region overlapping with the first heating element and a second region overlapping with the second heating element,
The height from the substrate to the first region is greater than the height from the substrate to the second region.

According to the present invention, fluctuations in fixing performance can be suppressed.

1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. FIG. 2 is a cross-sectional view of the fixing device according to the first embodiment. FIG. 2 is an exploded perspective view of a film unit of the fixing device according to the first embodiment. FIG. 2 is a front view of the fixing device according to the first embodiment. FIG. 10 is a cross-sectional view of a heater according to a comparative example having a conventional configuration. FIG. 10 is a perspective view of a heater according to a comparative example having a conventional configuration. FIG. 2 is a cross-sectional view of the heater according to the first embodiment. FIG. 10 is a cross-sectional view of a heater according to a second embodiment. FIG. 10 is a cross-sectional view of a heater according to a third embodiment. FIG. 10 is a cross-sectional view of a heater according to a fourth embodiment.

The following describes in detail exemplary embodiments of the present invention, with reference to the drawings. However, the dimensions, materials, shapes, and relative positions of the components described in the embodiments should be modified as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not intended to be limited to the following embodiments. Image forming devices to which the present invention can be applied include printers and copiers that use electrophotographic or electrostatic recording methods, and the following description focuses on the application to a laser printer.

<Embodiment 1>
(1) Image Forming Apparatus: As a general image forming apparatus 100 in this embodiment, the operation of a laser printer using electrophotographic recording technology will be briefly described with reference to Fig. 1. Fig. 1 is a cross-sectional view of the general image forming apparatus 100 in this embodiment.

The image forming operation in the image forming section of image forming apparatus 100 will be described. When image forming apparatus 100 receives a print command from an external device, scanner unit 3 emits laser light L corresponding to the image information toward photoconductor 1. Photoconductor 1, charged to a predetermined polarity by charging roller 2, is scanned by laser light L, and an electrostatic latent image corresponding to the image information is formed on the surface of photoconductor 1. Developer 4 then supplies toner to photoconductor 1, and a toner image corresponding to the image information is formed on photoconductor 1. The toner image on photoconductor 1 moves to the transfer position formed by photoconductor 1 and transfer roller 5 as photoconductor 1 rotates in the direction of arrow R, and is transferred to recording material P fed from cassette 6 by pickup roller 7. After passing the transfer position, cleaner 8 cleans the surface of photoconductor 1.

The recording material P onto which the toner image has been transferred is fixed using heat and pressure in a fixing device 9, which serves as a fixing section. The recording material P is then discharged onto a paper discharge tray 11 by paper discharge rollers 10.

(2) Fixing Device Next, the configuration and operation of the fixing device 9 will be described. In this embodiment, a tensionless film heating type fixing device 9 is used as an example of a heating device. The fixing device 9 of this embodiment uses an endless belt-shaped (or cylindrical) heat-resistant film, and at least a portion of the circumferential length of the film is always tension-free (in a state where no tension is applied).
This is a device in which the film is rotated by the rotational driving force of the pressure member.

The configuration of the fixing device 9 will be described with reference to Figure 2. Figure 2 is a schematic cross-sectional view of the fixing device 9 of this embodiment. The fixing device 9 of this embodiment includes a rotatable cylindrical film 23 as a first rotating body, a heater 22 that heats the film 23 within the internal space of the film 23, and a heater holder 21 made of heat-resistant resin that supports the heater 22 and guides the rotation of the film 23. The fixing device 9 also includes a reinforcing member 24 that reinforces the heater holder 21, and a pressure roller 30 as a second rotating body that forms a nip portion N with the film 23. The film unit 20 of this embodiment is composed of members such as the film 23, heater 22, heater holder 21, and reinforcing member 24. Here, the heater 22, film 23, heater holder 21, and pressure roller 30 are all members that extend elongated in the direction of the rotation axis of the pressure roller 30. The axial direction of the cylindrical shape of the film 23 (the direction of the arrow in Figure 3 in which the fixing film is inserted), which is parallel to the rotational axis of the pressure roller 30, will hereinafter be referred to as the longitudinal direction. In addition, in this embodiment, the conveyance direction of the recording material P within the nip N is perpendicular to the longitudinal direction.

When the pressure roller 30 receives power from the motor and rotates in the direction of arrow b, the film 23 is driven and rotates in the direction of arrow a. As the recording material P is sandwiched and transported in the nip portion N, the toner image T on the recording material P is heated and fixed to the recording material P. The pressure position of the pressure roller 30 is approximately the same as the center of the heater 22 in the transport direction of the recording material P. In other words, as with the conventional configuration, the fixing device 9 of this embodiment has the centers of the heater 22 and pressure roller 30 overlap in the transport direction.

Next, the components that make up the fixing device 9 will be described in detail using Figure 3. Figure 3 is an exploded perspective view of the film unit 20 used in the fixing device 9.

The heater 22 has a long, thin, plate-shaped substrate made primarily of ceramic or metal alloy, a heating element that generates heat when electricity is applied, and a coating layer that protects the substrate and heating element. Details of the heater 22 will be described later.

When the film 23 is a single-layer film, it is preferable to use materials such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), and PPS as the film base layer. When it is a composite layer film, it is preferable to use materials such as PI (polyimide), PAI (polyamide imide), PEEK (polyether ether ketone), and PES (polyether sulfone) as the film base layer. It is also preferable to form a composite layer film by further coating the surface with PTFE, PFA, FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether), etc. as a film release layer. It is also preferable to use a pure metal or alloy with high thermal conductivity, such as SUS, Al, Ni, Cu, or Zn, as the base layer, and then apply the aforementioned coating process or cover the release layer with a fluororesin tube. The thickness of the film 23 is preferably approximately 20 μm or more and 100 μm or less to ensure good thermal conductivity.

In this embodiment, the film base layer is made of 60 μm thick PI, and the film release layer is coated with 12 μm thick PFA, taking into consideration both wear of the film release layer due to paper passing and thermal conductivity.

The heater holder 21 is a longitudinally elongated member with a roughly trough-shaped cross section. Because the heater holder 21 requires heat resistance and rigidity, it is preferable to use a material such as liquid crystal polymer resin, which has high heat resistance and excellent strength. Heat-resistant resin molded products such as PPS (polyphenylene sulfite) and LCP (liquid crystal polymer) are particularly suitable for the heater holder 21.

The reinforcing member 24 is made of a metal such as iron, and presses the heater 22 toward the pressure roller 30 via the heater holder 21 under the force of a pressure spring (described below). Furthermore, the reinforcing member 24 also serves to maintain the strength of the heater holder 21 so that it does not deform significantly even under the pressure that forms the nip portion N.

A reinforcing member 24 fits inside the tub-shaped heater holder 21. A heater receiving groove is provided on the side of the heater holder 21 facing the pressure roller 30, and the heater 22 fits into this heater receiving groove and is fitted in the desired position. The film 23 fits around the outside of the heater holder 21, on which the above-mentioned parts are assembled, with some leeway in the circumferential length.

The pressure roller 30, which serves as a pressure rotating body, has a core made of a material such as iron or aluminum, an elastic layer made of a material such as silicone rubber, and a release layer made of a material such as PFA.

The thermistor 25 is a temperature detection component and is in contact with the heater 22 on the side opposite the surface that contacts the film 23. The power supply to the heater 22 is controlled according to the temperature detected by the thermistor 25.

Flanges 26 are provided on both longitudinal ends of the reinforcing member 24 and restrict the longitudinal movement of the film 23 as it rotates. A power supply terminal for the heater 22 also protrudes from one end of the film 23, and a power supply connector 27 is fitted into it. The power supply connector 27 contacts the electrode portion of the heater 22 with abutment pressure, forming a power supply path. At the other end opposite the end where the power supply connector 27 is provided, a heater clip 28 formed from a metal plate bent into a U-shape holds the end of the heater 22 to the heater holder 21 with its springiness. The protruding portions of the reinforcing member 24 protrude from both longitudinal ends of the film 23, and a flange 26 is fitted to each end, assembling the entire unit as the film unit 20.

Next, the pressure mechanism of the heating device will be explained using Figure 4. Figure 4 is a front view of the fixing device 9 as seen from the recording material transport direction, with part of the film 23 not shown to show the inside of the film unit 20.

The film unit 20 is positioned opposite the pressure roller 30 and is supported on the top panel housing 41 of the fixing device so that movement in the longitudinal direction (left-right direction in Figure 4) is restricted but movement in the pressure direction (up-down direction in Figure 4) is free. A pressure spring 45 is attached in a compressed state to the top panel housing 41 of the fixing device. The pressure force of the pressure spring 45 is received by the protruding portion of the reinforcing member 24, which presses the reinforcing member 24 toward the pressure roller 30, thereby pressing the film unit 20 toward the pressure roller 30. The bearing member 31 is positioned to support the core metal of the pressure roller 30 and receives the pressure force from the film unit 20 via the pressure roller 30. In order to rotatably support the core metal of the pressure roller, which becomes relatively hot, the bearing member 31 is made of a material that is heat-resistant and has excellent sliding properties. The bearing member 31 is attached to the bottom panel housing 43 of the fixing device. A pressure roller drive gear 33 is attached to one end of the core of the pressure roller 30, and receives a rotational driving force from a driving means (not shown), causing the pressure roller 30 to rotate.

(3) Heater Before describing the heater of this embodiment, a heater 52 having a conventional configuration will be described as a comparative example with reference to Figures 5 and 6. Figure 5 is a cross-sectional view of the heater 52 according to the comparative example having a conventional configuration, and Figure 6 is a perspective view.

A typical heater 52 in a conventional configuration includes a long, narrow plate-shaped substrate 521, a band-shaped heating element 522 that generates heat when current is applied, and a coating layer 523 that serves as a protective layer to protect the substrate 521 and the heating element 522. The heater 52 further includes a power supply electrode 524 provided for the purpose of supplying power to the heating element 522, and a conductive pattern 525, and the conductive pattern 525 is also covered with the coating layer 523. The heater 52 is provided in the fixing device so that the coating layer 523 abuts against the inner circumferential surface of the film 23.

The substrate 521 must be made of a heat-resistant material, taking into account the actual operating temperatures; ceramic or metal is typically used. If metal is used for the substrate 521, an insulating layer must be provided between the substrate 521 and the heating element 522. The thickness of the substrate 521 can be determined taking into account strength, heat capacity, and heat dissipation performance. A thin substrate 521 has a low heat capacity, which is advantageous for quick start-up; however, if it is too thin, problems such as distortion are more likely to occur when the heating element 522 is heat-molded. Conversely, a thick substrate 521 is advantageous in terms of distortion when the heating element 522 is heat-molded, but if it is too thick, the large heat capacity makes it disadvantageous for quick start-up. The preferred thickness of the substrate 521 is 0.3 mm to 2.0 mm, taking into account the balance of mass productivity, cost, and performance.

Heating element 522 is formed by applying a heating element paste containing a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binder component to substrate 521 and then firing the paste. When the heating element paste is fired, the organic binder component (C) is burned away, leaving components (A) and (B), resulting in heating element 522 containing the conductive component and the glass component. Here, the conductive component (A) is preferably silver-palladium (Ag-Pd), ruthenium oxide (RuO ₂ ), or the like, used alone or in combination, and preferably has a sheet resistance of 0.1 Ω/□ to 100 kΩ/□. Furthermore, it is acceptable to include other materials in addition to the above (A) to (C) in trace amounts that do not impair the characteristics of the present invention.

The power supply electrode 524 and conductive pattern 525 are primarily made of silver (Ag), platinum (Pt), gold (Au), a silver-platinum (Ag-Pt) alloy, or a silver-palladium (Ag-Pd) alloy. Similar to the heating element paste, the power supply electrode 524 and conductive pattern 525 are formed by applying a paste containing a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binder component to the substrate 521 and then firing it. The resistance of the power supply electrode 524 and conductive pattern 525 is set sufficiently low relative to the heating element 522 for the purpose of supplying power to the heating element 522. The heating element paste, power supply electrode paste, and conductive pattern paste must be made of materials that soften and melt at a temperature lower than the melting point of the substrate 521, and must be heat-resistant in consideration of the actual operating temperatures.

While the material for the coating layer 523 is not particularly limited, a heat-resistant material must be selected taking into account the actual operating temperature. Glass and PI (polyimide) are preferred materials from the perspective of heat resistance. In the case of glass, the specific powder material may be selected appropriately as long as it does not impair the characteristics of the present invention. If necessary, a thermally conductive filler with insulating properties may be mixed in. When forming an insulating layer of glass or PI (polyimide) on the substrate 521, the linear expansion coefficients of the substrate 521 and the coating layer 523 must be appropriately adjusted to prevent cracking or peeling in the coating layer 523 due to differences in the linear expansion coefficients between the materials. The molding method for the heating element 522, power supply electrode 524, conductive pattern 525, and coating layer 523 is not particularly limited. For example, screen printing can be used to achieve a smooth molding. When using a metal for the substrate 521, forming the coating layer 523 on both sides of the substrate 521 can prevent warping of the substrate 521 during manufacturing.

Next, we will explain the detailed configuration and manufacturing method of heater 52, which has a conventional configuration. Heater 52 is the heater used in comparative examples 1, 2, and 3 in the evaluation tests described below.

An alumina substrate measuring 11 mm in width, 270 mm in length, and 1 mm in thickness was used for the substrate 521. In addition, a heating element paste containing silver-palladium (Ag-Pd) as a conductive component, a glass component, and an organic binder component, and a power supply electrode paste and a conductive pattern paste containing silver (Ag) as a conductive component, a glass component, and an organic binder component were prepared.

After the heating element paste, power supply electrode paste, and conductive pattern paste are applied to the substrate 521 by screen printing, the substrate is dried at 180°C and fired at 850°C to form two heating elements 522, a power supply electrode 524, and a conductive pattern 525. After firing, the two heating elements 522 have a width of 2.5 mm, a length of 230 mm, and a thickness of 15 μm. The two heating elements 522 are connected by the conductive pattern 525 at one longitudinal end of the heater 52, forming a folded heating pattern.

Next, glass paste is prepared and applied to the substrate 521, heating element 522, and conductive pattern 525 by screen printing. After drying at 180°C and firing at 850°C, a smooth coating layer 523 is formed. After firing, the coating layer 523 has a width of 10.5 mm, a length of 260 mm, and a height above the substrate 521 of 60 μm. In this way, the heater 52 is completed.

Next, the configuration of the heater 22 according to embodiment 1 will be described using Figure 7. Figure 7 is a cross-sectional view of the heater 22 according to embodiment 1. The heater of this embodiment differs from the comparative example with a conventional configuration in that the heat generation amounts of the two heating elements are not the same, and the area downstream in the conveying direction of the surface that abuts the inner circumferential surface of the film protrudes more toward the pressure roller than the area upstream in the conveying direction.

The heater 22 in this embodiment has a long, thin, plate-shaped substrate 221, two heating elements 222 that generate heat when current is applied, and a coating layer 223 that serves as a protective layer to protect the substrate 221 and heating elements 222. The heater 22 also has a power supply electrode and a conductive pattern that are provided for the purpose of supplying power to the heating elements 222, and the conductive pattern is also covered by the coating layer 223. The heater 22 is provided in the fixing device so that the coating layer 223 abuts against the inner surface of the film 23. In this embodiment, the width direction of the heater 22, which is perpendicular to the length direction, is parallel to the direction in which the recording material is transported.

The substrate 221 in this embodiment is an alumina substrate with a width of 11 mm, a length of 270 mm, and a thickness of 1 mm, similar to the comparative example described above. Furthermore, the heating element paste, power supply electrode paste, and conductive pattern paste used are also similar to those used in the comparative example. The configuration and method of forming the power supply electrode and conductive pattern are similar to those in the comparative example, so a detailed description will be omitted. Below, the configuration of the heating element 222 and coating layer 223, which are characteristic of the present invention, will be described in detail. In this embodiment, the thickness direction of the substrate 221 is parallel to the pressure direction in the nip portion N.

After the heating element paste is applied to the substrate 221 by screen printing, it is dried at 180°C and fired at 850°C to form two heating elements 222. Of the two heating elements 222 after firing, the first heating element 222a, located downstream in the conveyance direction of the recording material P, is 2.2 mm wide, 230 mm long, and 15 μm thick so that it generates more heat than the second heating element 222b, located upstream in the conveyance direction. Meanwhile, the second heating element 222b is 3.0 mm wide, 230 mm long, and 15 μm thick, and a folded heating pattern is formed by connecting the two heating elements 222a and 222b at one longitudinal end of the heater 22 with a conductive pattern. In other words, the heater 22 of this embodiment is configured so that two heating elements with different heat generation values are provided on the substrate in the conveyance direction.

Next, glass paste is applied to the substrate 221, the heating elements 222a and 222b, and the conductive pattern by screen printing, followed by drying at 180°C and firing at 850°C. Furthermore, glass paste is again applied to the first heating element 222a by screen printing, followed by drying at 180°C and firing at 850°C, forming a convex coating layer 223. That is, the coating layer 223 on the first heating element 222a is thicker than the coating layer 223 on the second heating element 222b. Here, in order to maintain the relationship between the set temperature, power consumption, and heat generation of the fixing device 9 equivalent to that of the comparative example and to uniformize the heat transfer unevenness caused by the convex shape of the coating layer 223, the width of each heating element 222 was adjusted to adjust the resistance value and resistance ratio of the heating pattern.

In addition, a glass paste with a lower softening temperature than the glass paste applied first can be selected for the second application, and the firing temperature for firing the second application of glass paste can be set lower than the softening temperature of the glass paste applied first. This makes it even easier to form a coating layer 223 with a convex shape.

The heater 22 has, on the surface of the coating layer 223 that abuts the inner surface of the film 23, a first region 223a that overlaps with the first heating element 222a when viewed in the thickness direction of the substrate 221, and a second region 223b that overlaps with the second heating element 222b. Inside the fixing device 9, the first region 223a is positioned so that it protrudes further toward the pressure roller 30 than the second region 223b in the thickness direction of the substrate 221. Both the first region 223a and the second region 223b extend across the entire longitudinal area of the heater 22. The first region does not necessarily need to extend across the entire heater, as long as it is long enough to cover the entire width of the recording material being transported.

After baking, the coating layer 223 had a width of 10.5 mm and a length of 260 mm. Furthermore, for the evaluation tests described below, three different examples were created with different thicknesses of the coating layer 223. In Examples 1-1, 1-2, and 1-3, the height Ha from the substrate 221 to the surface of the coating layer 223 in the first region 223a was 75 μm, 80 μm, and 85 μm, respectively. Furthermore, the height Hb from the substrate 221 to the surface of the coating layer 223 in the second region 223a was 65 μm, 60 μm, and 55 μm, respectively. The amount by which the surface of the first region 223a of the coating layer 223 protrudes toward the pressure roller 30 relative to the surface of the second region 223b in the thickness direction of the substrate 221 is defined as the protrusion amount Pt = Ha - Hb. Here, the protrusion amounts Pt for Examples 1-1, 1-2, and 1-3 were 10 μm, 20 μm, and 30 μm, respectively.

<Embodiment 2>
Next, the configuration of the heater 62 according to the second embodiment will be described with reference to Fig. 8. Fig. 8 is a cross-sectional view of the heater 62 according to the second embodiment. Of the configuration of the second embodiment, the same configuration as that of the first embodiment will be assigned the same reference numerals and description thereof will be omitted.

The heater 62 of this embodiment has a long, thin plate-shaped substrate 621, four heating elements 622 that generate heat when current is applied, and a coating layer 623 that serves as a protective layer to protect the substrate 621 and heating elements 622. The heater 62 also has a power supply electrode and a conductive pattern that are provided for the purpose of supplying power to the heating elements 622, and the conductive pattern is also covered by the coating layer 623. The heater 62 is installed in the fixing device so that the coating layer 623 abuts against the inner surface of the film 23.

The substrate 621 in this embodiment is an alumina substrate with a width of 11 mm, a length of 270 mm, and a thickness of 1 mm, similar to the comparative example described above. Furthermore, the heating element paste, power supply electrode paste, and conductive pattern paste used were also similar to those used in the comparative example. The configuration and method of forming the power supply electrode and conductive pattern are the same as those in the comparative example, so a detailed explanation will be omitted. Below, we will explain in detail the configuration of the heating element 622 and coating layer 623, which are characteristic of the present invention.

After the heating element paste is applied to the substrate 621 by screen printing, it is dried at 180°C and baked at 850°C to form four heating elements 622. Of the four heating elements 222 after baking, the first heating element 622a, which is located at the most downstream position in the conveyance direction of the recording material P, has a width of 0.9 mm, a length of 230 mm, and a thickness of 15 μm so that it generates more heat than the other three heating elements 622b. On the other hand, the other three heating elements 622b have a width of 1.4 mm, a length of 230 mm, and a thickness of 15 μm, and the four heating elements 622 are connected at the longitudinal end of the heater 62 with a conductive pattern to form a three-fold heating pattern. That is, in the heater 62 of this embodiment, four heating elements are provided on the substrate in the conveyance direction, and the heating element located at the most downstream position in the conveyance direction generates the largest amount of heat among the multiple heating elements.

Next, using the same glass paste as in the comparative example and embodiment 1, the glass paste is applied by screen printing to the substrate 621, heating elements 622a and 622b, and conductive pattern, followed by drying at 180°C and firing at 850°C. Furthermore, glass paste is again applied by screen printing to the first heating element 622a, followed by drying at 180°C and firing at 850°C to form a convex coating layer 623. In other words, the coating layer 623 on the first heating element 622a is thicker than the coating layer 623 on the second heating element 622b. Here, to maintain the relationship between the set temperature, power consumption, and heat generation of the fixing device 9 equivalent to that of the comparative example, and to even out uneven heat transfer due to the convex shape of the coating layer 223, the width of each heating element 222 was adjusted to adjust the resistance value and resistance ratio of the heating pattern.

The heater 62 has, on the surface of the coating layer 623 that abuts against the inner circumferential surface of the film 23, a first region 623a that overlaps with the first heating element 622a when viewed in the thickness direction of the substrate 621, and a second region 623b that overlaps with the other three heating elements 622b. In this case, within the fixing device 9, the first region 623a is positioned so that it protrudes further toward the pressure roller 30 than the second region 623b in the thickness direction of the substrate 621.

After firing, the coating layer 623 had a width of 10.5 mm and a length of 260 mm. Furthermore, for the evaluation tests described below, three different examples were created with different thicknesses of the coating layer 623. In Examples 2-1, 2-2, and 2-3, the height Ha from the substrate 621 to the surface of the coating layer 623 in the first region 623a was 75 μm, 80 μm, and 85 μm, respectively. Furthermore, the height Hb from the substrate 621 to the surface of the coating layer 623 in the second region 623b was 65 μm, 60 μm, and 55 μm, respectively. In other words, the protrusion amounts Pt for Examples 2-1, 2-2, and 2-3 were 10 μm, 20 μm, and 30 μm, respectively.

<Embodiment 3>
Next, the configuration of a heater 72 according to embodiment 3 will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the heater 72 according to embodiment 3. Of the configuration of embodiment 3, the same configurations as those of embodiment 1 are denoted by the same reference numerals and description thereof will be omitted.

The heater 72 of this embodiment includes a thin, plate-shaped metal substrate 721, two heating elements 722 that generate heat when energized, a coating layer 723 that serves as a protective layer to protect the heating elements 722, and an insulating layer 724 that insulates the heating elements 722 from the substrate 721. The heater 72 also includes a coating layer 725 on the surface of the substrate 721 opposite the surface on which the heating elements 722 and insulating layer 724 are provided, to prevent warping of the substrate 721. The heater 72 further includes a power supply electrode and a conductive pattern that are provided to supply power to the heating elements 722, and the conductive pattern is also covered by the coating layer 723. The heater 72 is installed in the fixing device so that the coating layer 723 abuts against the inner circumferential surface of the film 23. The configuration and method of forming the power supply electrode and conductive pattern are similar to those in the comparative example, and therefore will not be described here. The configuration of the heating elements 722 and coating layer 723, which are characteristic of the present invention, are described in detail below.

The substrate 721 of this embodiment is a ferritic stainless steel substrate (SUS430: 18Cr stainless steel) having a width of 11 mm, a length of 270 mm, and a thickness of 0.5 mm. Suitable metallic materials for the substrate 721 include stainless steel, nickel, copper, aluminum, and alloys containing these materials as the primary material. Of these, stainless steel is most preferred in terms of strength, heat resistance, and corrosion resistance. The type of stainless steel is not particularly limited, and may be selected based on the required mechanical strength, a linear expansion coefficient suitable for forming the insulating layer 724 and the heating element 722, and the availability of the plate material in the market. For example, martensitic and ferritic chromium-based stainless steel (400 series) has a relatively low linear expansion coefficient among stainless steels, making it suitable for forming the insulating layer 724 and the heating element 722.

The insulating layer 724 is formed using an insulating glass paste to insulate the substrate 721 from the heating element 722. The insulating glass paste is applied to the substrate 721 by screen printing, then dried at 180°C and baked at 850°C to form the insulating layer 724. After baking, the insulating layer 724 has a width of 10.5 mm, a length of 260 mm, and a height of 50 μm. Regarding the thickness of the insulating layer 724, it is generally preferable for heaters used in image forming devices to have a dielectric strength of approximately 1.5 kV. Therefore, to achieve a dielectric strength of 1.5 kV between the heating element 722 and the substrate 721, the film thickness of the insulating layer 724 can be determined according to the material.

Next, a heating element paste is applied onto the insulating layer 724 by screen printing, then dried at 180°C and baked at 850°C to form two heating elements 722. Of the two heating elements 722 after baking, the first heating element 722a, located downstream in the conveyance direction of the recording material P, is designed to have a width of 2.2 mm, a length of 230 mm, and a thickness of 15 μm so that it generates more heat than the second heating element 722b, located upstream in the conveyance direction. Meanwhile, the second heating element 722b is designed to have a width of 3.0 mm, a length of 230 mm, and a thickness of 15 μm, and a folded heating pattern is formed by connecting the two heating elements 722a and 722b at one longitudinal end of the heater 72 with a conductive pattern. In other words, the heater 72 of this embodiment is configured so that two heating elements with different heat generation values are arranged in the conveyance direction on an insulating layer.

Next, using the same glass paste as in the comparative example and the above-described embodiment, the glass paste is applied by screen printing onto the insulating layer 724, heating element 722, and conductive pattern. Furthermore, to prevent warping of the substrate 721 during firing, the glass paste is also applied by screen printing to the side of the substrate 721 opposite the side on which the insulating layer 724 is formed, followed by drying at 180°C and firing at 850°C, forming a coating layer on both sides of the substrate 721. Furthermore, the glass paste is again applied by screen printing onto the first heating element 722a, followed by drying at 180°C and firing at 850°C, forming a coating layer 723 having a convex shape.

The heater 72 has, on the surface of the coating layer 723 that abuts against the inner circumferential surface of the film 23, a first region 723a that overlaps with the first heating element 722a when viewed in the thickness direction of the substrate 721, and a second region 723b that overlaps with the second heating element 722b. In this case, within the fixing device 9, the first region 723a is positioned so that it protrudes further toward the pressure roller 30 than the second region 723b in the thickness direction of the substrate 721.

The coating layer 723, which covers the heating element 722 and abuts the inner peripheral surface of the film 23, had a width of 10.5 mm and a length of 260 mm. The coating layer 725, which was provided on the surface of the substrate 721 opposite the coating layer 723, had a width of 10.5 mm, a length of 260 mm, and a thickness of 110 μm. Furthermore, for the evaluation tests described below, three examples were created in which the thickness of the coating layer 723 was varied. In Examples 3-1, 3-2, and 3-3, the height Ha from the substrate 721 to the surface of the coating layer 723 in the first region 723a was 75 μm, 80 μm, and 85 μm, respectively. Furthermore, the height Hb from the substrate 721 to the surface of the coating layer 723 in the second region 723b was 65 μm, 60 μm, and 55 μm, respectively. That is, the protrusion amounts Pt for Examples 3-1, 3-2, and 3-3 are 10 μm, 20 μm, and 30 μm, respectively.

<Effects of Embodiments 1, 2, and 3>
To confirm the effects of the present invention, a fixing performance evaluation test was conducted using fixing devices equipped with heaters of the above-mentioned examples and comparative example. Examples 1-1, 1-2, and 1-3 were equipped with heater 22 (see FIG. 7), Examples 2-1, 2-2, and 2-3 were equipped with heater 62 (see FIG. 8), Examples 3-1, 3-2, and 3-3 were equipped with heater 72 (see FIG. 9), and the comparative example was equipped with heater 52 (see FIG. 5). The results of the evaluation test and the effects of reduced power consumption and stabilization of fixing performance due to improved fixing performance are described below.

As mentioned above, Comparative Examples 1, 2, and 3 all use heaters with the same configuration, but the positional relationship between the film unit 20 and the pressure roller 30 is changed in each case. In Comparative Example 1, as with the conventional configuration and each example, the center of the heater 52 is located at the same position as the center of the pressure roller 30 in the recording material transport direction. On the other hand, in Comparative Examples 2 and 3, the film unit 20 is offset so that the center of the heater 52 is located upstream of the center of the pressure roller 30 in the recording material transport direction. The offset amount is 1 mm in Comparative Example 2 and 2 mm in Comparative Example 3.

For the fixing performance evaluation test, a solid black pattern printed entirely with toner was used as the evaluation image pattern. The environment was a room temperature and humidity environment with a temperature of 23°C and a humidity of 50% RH. The paper feed conditions were a cold state, with three sheets of evaluation image pattern fed continuously. The test was conducted multiple times by changing the set temperature of the fixing device 9, and the fixing temperature for each configuration was measured, with the lowest set temperature at which no defects in the image pattern were observed being defined as the fixing temperature. In addition, to evaluate the stability of the fixing performance, tests were conducted by varying the nip width between 10 mm, 8 mm, and 6 mm by varying the rubber hardness of the pressure roller 30 and the spring constant of the pressure spring 45.

The test results for each example and comparative example are summarized in Table 1. The fixing temperature when the nip width of Comparative Example 1 was 10 mm was used as the reference value, and the difference from this reference value is shown in the table as the evaluation result. In other words, the smaller the fixing temperature value shown in the table (larger in the negative direction), the lower the temperature at which fixing can be performed and the lower the power consumption of the fixing device. The difference between the maximum and minimum fixing temperatures when the nip width is changed in a fixing device with the same configuration is also shown in the table as fixing temperature variation.

In Comparative Example 1, the fixing temperature at a nip width of 8 mm was equivalent to the reference nip width of 10 mm, and the fixing temperature at a nip width of 6 mm was 5°C higher than the reference. In other words, in Comparative Example 1, the fixing temperature variation within the nip width range of 6 mm to 10 mm was 5°C. Below, we will use this result as the reference to explain the results for other configurations.

In Comparative Example 2, the fixing temperature was -10°C below the reference when the nip width was 10 mm and 8 mm, and +0°C above the reference when the nip width was 6 mm. Comparing the results for the same nip width as Comparative Example 1, Comparative Example 2 had a lower fixing temperature than Comparative Example 1 under all conditions, demonstrating the effect of offsetting the film unit upstream in the conveyance direction to improve fixing performance. Meanwhile, the fusing temperature variation in Comparative Example 2 within the nip width range of 6 mm to 10 mm was 10°C, resulting in a less stable fixing performance than Comparative Example 1. That is, by offsetting the film unit upstream in the conveyance direction relative to the pressure roller, stronger pressure is applied downstream of the nip N in the conveyance direction than upstream, improving fixing performance. However, the offset film unit configuration makes it easier for the heating element and heater to protrude outside the nip N, which reduces the stability of fixing performance relative to changes in nip width.

In Comparative Example 3, the fixing temperature was -15°C below the reference temperature when the nip width was 10 mm and 8 mm, and +5°C above the reference temperature when the nip width was 6 mm. Comparing the results for the same nip width, Comparative Example 3 had a lower fixing temperature than Comparative Examples 1 and 2 when the nip width was 10 mm and 8 mm, demonstrating further improvements in fixing performance. Meanwhile, the fixing temperature variation in Comparative Example 3 within the nip width range of 6 mm to 10 mm was 15°C, resulting in even worse fixing performance stability than Comparative Examples 1 and 2. In other words, offsetting the film unit upstream in the transport direction reduces the fixing temperature and improves fixing performance, but at the same time worsens the stability of fixing performance in response to changes in nip width.

In Example 1-1 of Embodiment 1, the fixing temperature was 0°C above the reference when the nip width was 10 mm and 8 mm, and 5°C above the reference when the nip width was 6 mm. The fixing temperature and the variation in fixing temperature were similar to those in Comparative Example 1.

In Example 1-2 of Embodiment 1, the fixing temperature was -15°C when the nip width was 10 mm and 8 mm, and -10°C when the nip width was 6 mm. Comparing the results for the same nip width, Example 1-2 had a lower fixing temperature than Comparative Example 1 under all conditions, demonstrating the improved fixing performance achieved by changing the heater shape, applying stronger pressure to the downstream side of the nip in the conveying direction, and applying stronger heat. Furthermore, the variation in fixing temperature in Example 1-2 within the nip width range of 6 mm to 10 mm was 5°C, the same as Comparative Example 1. In other words, the configuration of Example 1-2 allows for a lower fixing temperature than the conventional configuration without sacrificing the stability of fixing performance.

In Example 1-3 of Embodiment 1, the fixing temperature was -15°C when the nip width was 10 mm and 8 mm, and -10°C when the nip width was 6 mm, which were similar results to those in Example 1-2. In other words, the larger the protrusion amount Pt, the lower the fixing temperature; it is sufficient that the protrusion amount Pt is greater than a certain amount that improves fixing performance. In Embodiment 1, by setting the protrusion amount Pt of the heater 22 to 20 μm or more, it is possible to stably heat the recording material at a low fixing temperature with less power consumption than conventional configurations.

When comparing embodiment 2 with embodiment 1 using the same protrusion amount Pt, the results were similar to those of embodiment 1. That is, even in a configuration with three or more heating elements, by having the downstream side of the heater in the conveying direction protrude toward the pressure roller, the fixing temperature can be reduced compared to the conventional configuration without sacrificing the stability of fixing performance.

When comparing embodiment 3 with embodiment 1 using the same protrusion amount Pt, the results were similar to those of embodiment 1. In other words, even in a configuration in which an insulating layer is provided on a metal substrate, by having the downstream side of the heater in the conveying direction protrude toward the pressure roller, the fixing temperature can be reduced compared to the conventional configuration without sacrificing the stability of fixing performance.

As explained above, by increasing the heat generation amount of the heater downstream of the film conveyance direction relative to the upstream side and by having the heater's contact surface with the film protrude toward the pressure roller (the second rotating body side), it is possible to lower the fixing temperature without sacrificing the stability of the fixing performance. In other words, by configuring the film unit to be heated more strongly downstream of the nip portion of the film conveyance direction relative to the upstream side and to apply strong pressure without offsetting the film unit relative to the pressure roller, it is possible to heat the film stably with low power consumption. However, the present invention can also be preferably applied even if the film unit is offset from the pressure roller, as long as the offset amount is sufficient to form a stable nip width.

In the above-described embodiments, the first and second regions are formed flat, and the contact surface between the heater and the inner circumferential surface of the film is formed in a stepped shape, but the configuration of the present invention is not limited to this. Possible variations include, for example, a configuration in which there is a third region between the first and second regions that is lower than the first region and higher than the second region, or a configuration in which the first region is formed as a curved surface rather than a flat surface. Other possible variations include a configuration in which the coating layer is not stepped, but gradually slopes toward the pressure roller as it moves downstream in the conveying direction.

Furthermore, in each of the above-described embodiments, the heat generation amount of each heating element is differentiated by changing the width of the heating element, but the method of differentiating the heat generation amount of each heating element is not limited to this, and a configuration in which the power supply to the heating elements is individually controlled may also be used.

In addition, in embodiments 1, 2, and 3, by setting the protrusion amount Pt to 20 μm or more, it was possible to achieve both a reduction in the fixing temperature and stable fixing performance, but the above numerical value may vary depending on the configuration and material of each component. If the protrusion amount Pt is too small, the effect of reducing the fixing temperature will not be obtained, and if it is too large, there is a concern that the recording material may become bent, so it is important to select an appropriate value under each set of conditions.

<Fourth Embodiment>
Next, the configuration of a heater 82 according to embodiment 4 will be described with reference to Fig. 10. Fig. 10 is a cross-sectional view of the heater 82 according to embodiment 4. Of the configuration of embodiment 4, the same configurations as those of embodiment 1 are denoted by the same reference numerals and description thereof will be omitted.

The heater 82 of this embodiment includes a thin, plate-shaped metal substrate 821, two heating elements 822 that generate heat when energized, a coating layer 823 that serves as a protective layer to protect the heating elements 822, and an insulating layer 824 that insulates the heating elements 822 from the substrate 821. The heater 82 also includes a coating layer 825 on the surface of the substrate 821 opposite the surface on which the heating elements 822 and insulating layer 824 are provided, in order to prevent warping of the substrate 821. Note that in this embodiment, the surface of the substrate 821 on which the heating elements 822 and insulating layer 824 are provided is the opposite side from the previously described embodiments, and faces the heater holder 21 rather than the inner surface of the film 23. The substrate 821 of this embodiment is a ferritic stainless steel substrate (SUS430:18Cr stainless steel) with a width of 11 mm, a length of 270 mm, and a thickness of 0.5 mm, as in embodiment 3.

The heater 82 further has a power supply electrode and a conductive pattern provided for the purpose of supplying power to the heating element 822, and the conductive pattern is also covered with a coating layer 823. The heater 82 is provided in the fixing device so that the coating layer 823 abuts the inner surface of the film 23. The configuration and formation method of the power supply electrode and conductive pattern are the same as those in the comparative example, so a description thereof will be omitted. Below, a detailed description is given of the configuration of the heating element 822 and coating layer 823, which are characteristic of the present invention.

The insulating layer 824 is formed using insulating glass paste to insulate the substrate 821 from the heating element 822. The insulating layer 824 is formed by screen-printing the insulating glass paste onto the substrate 821, drying at 180°C, and firing at 850°C. After firing, the insulating layer 824 has a width of 10.5 mm, a length of 260 mm, and a height of 50 μm. As mentioned above, in the heater 82 of this embodiment, the insulating layer 824 is formed on the surface of the substrate 821 opposite the surface facing the film 23.

Next, a heating element paste is applied onto the insulating layer 824 by screen printing, and then dried at 180°C and baked at 850°C to form two heating elements 822. Of the two heating elements 822 after baking, the first heating element 822a, located downstream in the conveyance direction of the recording material P, is designed to have a width of 2.2 mm, a length of 230 mm, and a thickness of 15 μm so that it generates more heat than the second heating element 822b, located upstream in the conveyance direction. Meanwhile, the second heating element 822b is designed to have a width of 3.0 mm, a length of 230 mm, and a thickness of 15 μm, and a folded heating pattern is formed by connecting the two heating elements 822a and 822b at one longitudinal end of the heater 82 with a conductive pattern. That is, the heater 82 of this embodiment is configured such that two heating elements with different heat generation values are provided on the insulating layer in the conveyance direction, and each heating element is provided on the surface opposite to the surface facing the film of the substrate.

Next, using the same glass paste as in the comparative example and the above-mentioned examples, the glass paste is applied by screen printing onto the insulating layer 824, heating element 822, and conductive pattern. Furthermore, to prevent warping of the substrate 821 during firing, the glass paste is also applied by screen printing to the side of the substrate 821 opposite the side on which the insulating layer 824 is formed, followed by drying at 180°C and firing at 850°C, forming a coating layer on both sides of the substrate 821. Furthermore, the glass paste is again applied by screen printing onto the first heating element 822a, followed by drying at 180°C and firing at 850°C, forming a coating layer 823 having a convex shape.

The heater 82 has, on the surface of the coating layer 823 that abuts against the inner circumferential surface of the film 23, a first region 823a that overlaps with the first heating element 822a when viewed in the thickness direction of the substrate 821, and a second region 823b that overlaps with the second heating element 822b. In this case, within the fixing device 9, the first region 823a is positioned so that it protrudes more toward the pressure roller 30 than the second region 823b in the thickness direction of the substrate 821.

The coating layer 823 in contact with the film 23 had a width of 10.5 mm and a length of 260 mm, while the coating layer 825 covering the heating element 822 had a width of 10.5 mm, a length of 260 mm, and a thickness of 60 μm. Furthermore, for the evaluation tests described below, three examples were created in which the thickness of the coating layer 823 was varied. In Examples 4-1, 4-2, and 4-3, the height Ha from the substrate 821 to the surface of the coating layer 823 in the first region 823a was 75 μm, 80 μm, and 85 μm, respectively. Furthermore, the height Hb from the substrate 821 to the surface of the coating layer 823 in the second region 823b was 65 μm, 60 μm, and 55 μm, respectively. In other words, the protrusion amounts Pt for Examples 4-1, 4-2, and 4-3 were 10 μm, 20 μm, and 30 μm, respectively.

<Effects of the Fourth Embodiment>
To confirm the effects of the present invention, a fixing performance evaluation test was conducted using a fixing device equipped with the heater of this embodiment. Examples 4-1, 4-2, and 4-3 were equipped with heater 82 (see FIG. 10). The results of the evaluation test and the effects of reduced power consumption and stabilization of fixing performance due to improved fixing performance are described below.

The fixing performance evaluation test was conducted under the same conditions as described above. That is, a solid black pattern in which toner was printed across the entire surface was used as the evaluation image pattern, and the environment was a room temperature and humidity environment with a temperature of 23°C and a humidity of 50% RH. The paper feed conditions were a cold state, with three sheets of evaluation image pattern fed consecutively. The test was conducted multiple times by changing the set temperature of the fixing device 9, and the fixing temperature for each configuration was measured using the lowest set temperature at which no defects in the image pattern were observed. Additionally, to evaluate the stability of the fixing performance, the nip width was varied between 10 mm, 8 mm, and 6 mm by varying the rubber hardness of the pressure roller 30 and the spring constant of the pressure spring 45.

The test results for each example and the comparative example described above for comparison are summarized in Table 2. The fixing temperature when the nip width of Comparative Example 1 was 10 mm was used as the reference value, and the difference from the reference value was shown in the table as the evaluation result. The difference between the maximum and minimum fixing temperatures when the nip width was changed in a fixing device with the same configuration was also shown in the table as the fixing temperature variation.

In Example 4-1 of Embodiment 4, the fixing temperature was +5°C above the reference when the nip width was 10 mm and 8 mm, and +8°C above the reference when the nip width was 6 mm. At both nip widths, the fixing temperature was higher than in Comparative Example 1. This is thought to be because the small protrusion amount Pt prevented a sufficient effect of lowering the fixing temperature, and because the heating element was located farther from the inner circumferential surface of the film, it became difficult for the heat from the heating element to be quickly transferred to the film. Meanwhile, the variation in fixing temperature in Example 4-1 within the nip width range of 6 mm to 10 mm was 3°C, which was smaller than that of Comparative Example 1 and the aforementioned Examples 1-1, 2-1, and 3-1.

In Example 4-2 of Embodiment 4, the fixing temperature was -10°C when the nip width was 10 mm and 8 mm, and -7°C when the nip width was 6 mm. Comparing the results for the same nip width with Comparative Example 1, Example 4-2 had a lower fixing temperature under all conditions, demonstrating improved fixing performance by changing the heater shape and applying stronger pressure and heat on the downstream side of the nip in the conveyance direction. Furthermore, the variation in fixing temperature in Example 4-2 within the nip width range of 6 mm to 10 mm was 3°C, smaller than Comparative Example 1. In other words, the configuration of Example 4-2 improves the stability of fixing performance and reduces the fixing temperature compared to the conventional configuration.

On the other hand, when Example 4-2 was compared with Examples 1-2, 2-2, and 3-2 using the same nip width, Example 4-2 had a higher fixing temperature under all conditions. However, the fixing temperature variation in Example 4-2 within the nip width range of 6 mm to 10 mm was 3°C, which was smaller than that of Examples 1-2, 2-2, and 3-2. This difference is due to the fact that Example 4-2 is configured with the heating element further away from the inner surface of the film than Examples 1-2, 2-2, and 3-2, which increases the time it takes for the heat from the heating element to be transmitted to the inner surface of the film.

In Example 4-3 of the fourth embodiment, the fixing temperature when the nip width was 10 mm and 8 mm was the reference temperature of -10°C, and when the nip width was 6 mm, the fixing temperature was the reference temperature of -7°C, which were the same results as in Example 4-2.

As explained above, even in a configuration in which the heating element and insulating layer are provided on the surface of the substrate opposite the surface facing the inner circumferential surface of the film, the present invention makes it possible to lower the fixing temperature without sacrificing the stability of fixing performance in response to changes in the nip portion. Furthermore, which side of the substrate the heating element is provided on can be selected appropriately depending on whether priority is given to reducing the fixing temperature or improving the stability of fixing performance.

9...fixing device (heating device), 22...heater, 221...heating element, 223a...first region, 223b...second region, 23...film (first rotating body), 30...pressure roller (second rotating body)

Claims (14)

A plurality of heating elements;
A coating layer;
an elongated substrate on which the heating element and the coating layer are provided;
Equipped with
Among the plurality of heat generating elements, a first heat generating element extending in the longitudinal direction of the substrate is provided at a position different from a second heat generating element in a lateral direction of the substrate perpendicular to the longitudinal direction,
a heat generation amount of the first heat generating element is greater than a heat generation amount of the second heat generating element,
When the coating layer is viewed from a surface opposite to a surface in contact with the substrate in a thickness direction of the substrate perpendicular to the longitudinal direction and the lateral direction, the coating layer has a first region overlapping with the first heating element and a second region overlapping with the second heating element,
A heater, wherein a height from the substrate to the first region is greater than a height from the substrate to the second region. the plurality of heating elements are provided on the same surface of the substrate on which the coating layer is provided,
2. The heater according to claim 1, wherein the coating layer covers the plurality of heating elements. The heater described in claim 1, characterized in that the multiple heating elements are provided on the surface of the substrate opposite to the surface on which the coating layer is provided. the substrate is made of metal;
4. The heater according to claim 1, further comprising an insulating layer provided between the substrate and the plurality of heating elements. a first rotating body;
the heater according to any one of claims 1 to 4, which is provided in the internal space of the first rotating body;
a second rotating body that forms a nip portion with the heater via the first rotating body;
Equipped with
a heating device that nip-conveys the recording material while heating it in the nip portion; 6. The heating device according to claim 5, wherein the first heat generating element is provided downstream of the second heat generating element in the conveying direction of the recording material. a conductive pattern provided on the substrate for supplying power to the heating element;
7. The heating device according to claim 6, wherein the first region and the second region extend in the longitudinal direction so as to cover the conductive pattern . A heating device as described in claim 6 or 7, wherein the first area and the second area are planes parallel to the surface of the recording material. A heating device as described in any one of claims 6 to 8, characterized in that the first region is located 20 μm or more closer to the second rotor than the second region in the thickness direction. The heating device described in any one of claims 6 to 9, characterized in that the width of the first heating element in the conveying direction is smaller than the width of the second heating element in the conveying direction. A heating device described in any one of claims 6 to 10, characterized in that the thickness of the coating layer in the first region is greater than the thickness of the coating layer in the second region. the heater includes three or more heating elements,
12. The heating device according to claim 6, wherein the first heating element is located at the most downstream position in the transport direction among the heating elements and has the largest amount of heat generated. the first rotating body is a cylindrical film,
13. The heating device according to claim 5, wherein the second rotating body is a roller. an image forming section for forming an image on a recording material;
a heating device according to any one of claims 5 to 13, which fixes an image formed on a recording material to the recording material;
An image forming apparatus having the same.