Heater, heating device and image forming apparatus

Abstract

To prevent a variation in fixing performance.SOLUTION: A heater comprises a plurality of heating elements, a coat layer 223, and a slender substrate 221 provided with the heating elements and the coat layer 223. Of the plurality of heating elements, a first heating element 222a extending in the longitudinal direction of the substrate is provided at a position different from that of a second heating element 222b in the short direction orthogonal to the longitudinal direction of the substrate 221, and the quantity of heat generated by the first heating element 222a is larger than the quantity of heat generated by the second heating element 222b. When the coat layer 223 is seen from a surface on the opposite side of a surface in contact with the substrate 221 in the thickness direction of the substrate 221 orthogonal to the longitudinal direction and short direction, the coat layer 223 has a first area 223a overlapping the first heating element 222a and a second area 223b overlapping the second heating element 222b. The height from the substrate 221 to the first area 223a is larger than the height from the substrate 221 to the second area 223b.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a heating device such as a fixing device mounted in an image forming apparatus such as a copying machine or printer using an electrophotographic or electrostatic recording system, or a gloss imparting device that improves the glossiness of a toner image by reheating a fixed toner image on a recording material, and also to an image forming apparatus equipped with such a heating device and a heater used in the heating device. [Background technology]

[0002] Some heating devices installed in electrophotographic printers and copiers include a heater having 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 in the nip, and the toner image is thermally fixed to the recording material.

[0003] In the heating device described above, there has long been a demand for power saving. Patent Document 1 discloses a configuration in which a film unit is offset upstream of the nip portion 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 the upstream to downstream of the nip portion in the conveyance direction of the recording material and softened, and then strongly pressurized downstream of the nip portion in the conveyance direction to efficiently fix the toner to the recording material, improving fixing performance and reducing power consumption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-49839 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in a configuration in which the film unit is offset upstream in the transport direction, if the nip width is reduced due to variations in the hardness of the pressure roller, the pressure applied, etc., the heating portion of the heater is biased toward the upstream side in the transport direction, which can easily deteriorate the fixing performance. In other words, with the above configuration, there is a possibility that the fixing performance will fluctuate when the nip width changes.

[0006] The present invention has been made in view of the above-mentioned problems, and has an object to suppress fluctuations in fixing performance. [Means for solving the problem]

[0007] 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, The heat generation amount of the first heat generating element is greater than the 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. It is characterized by being larger than [Effects of the Invention]

[0008] According to the present invention, fluctuations in fixing performance can be suppressed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic configuration diagram of an image forming apparatus according to a first embodiment. [Figure 2]1 is a cross-sectional view of a fixing device according to a first embodiment. [Figure 3] FIG. 2 is an exploded perspective view of a film unit of the fixing device according to the first embodiment. [Figure 4] FIG. 2 is a front view of the fixing device according to the first embodiment. [Figure 5] FIG. 10 is a cross-sectional view of a heater according to a comparative example having a conventional configuration. [Figure 6] FIG. 10 is a perspective view of a heater according to a comparative example having a conventional configuration. [Figure 7] 1 is a cross-sectional view of a heater according to a first embodiment. [Figure 8] FIG. 10 is a cross-sectional view of a heater according to a second embodiment. [Figure 9] FIG. 10 is a cross-sectional view of a heater according to a third embodiment. [Figure 10] FIG. 10 is a cross-sectional view of a heater according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] 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 may be changed as appropriate depending on the configuration of the device to which the invention is applied and various conditions. 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 will be given of the application to a laser printer.

[0011] <Embodiment 1> (1) Image forming device 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 Figure 1. Figure 1 is a cross-sectional view of the general image forming apparatus 100 in this embodiment.

[0012] The image forming operation in the image forming section of the image forming apparatus 100 will be described. When the image forming apparatus 100 receives a print command from an external device, the scanner unit 3 emits a laser beam L corresponding to the image information toward the photoconductor 1. The photoconductor 1, which has been charged to a predetermined polarity by the charging roller 2, is scanned by the laser beam L, and an electrostatic latent image corresponding to the image information is formed on the surface of the photoconductor 1. The developer 4 then supplies toner to the photoconductor 1, and a toner image corresponding to the image information is formed on the photoconductor 1. The toner image on the photoconductor 1 moves to a transfer position formed by the photoconductor 1 and transfer roller 5 as the photoconductor 1 rotates in the direction of arrow R, and is transferred to a recording material P fed from a cassette 6 by a pickup roller 7. The surface of the photoconductor 1 that has passed the transfer position is cleaned by a cleaner 8.

[0013] The recording material P onto which the toner image has been transferred is subjected to a fixing process using heat and pressure in a fixing device 9 serving as a fixing unit. Thereafter, the recording material P is discharged onto a paper discharge tray 11 by a paper discharge roller 10.

[0014] (2) Fixing device Next, the configuration and operation of the fixing device 9 will be described. In this embodiment, a fixing device 9 of a tensionless film heating type 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 part of the circumference 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.

[0015] The configuration of the fixing device 9 will be described with reference to FIG. 2. FIG. 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 serving as a first rotating body, a heater 22 that heats the film 23 in 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 serving as a second rotating body that forms a nip portion N between the film 23 and the pressure roller 30. The film unit 20 of this embodiment is composed of members such as the film 23, the heater 22, the heater holder 21, and the reinforcing member 24. Here, the heater 22, the film 23, the heater holder 21, and the pressure roller 30 are all members that extend long 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 FIG. 3 in which the fixing film is inserted) which is parallel to the rotational axis direction of the pressure roller 30 will hereinafter be referred to as the longitudinal direction. In addition, in this embodiment, the conveying direction of the recording material P within the nip portion N is perpendicular to the longitudinal direction.

[0016] 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 conveyed at 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 conveyance direction of the recording material P. That is, in the fixing device 9 of this embodiment, as in the conventional configuration, the centers of the heater 22 and the pressure roller 30 overlap in the conveyance direction.

[0017] Next, the components that make up the fixing device 9 will be described in detail with reference to Fig. 3. Fig. 3 is an exploded perspective view of the film unit 20 used in the fixing device 9.

[0018] The heater 22 includes a long, thin plate-shaped substrate made primarily of ceramic or metal alloy, a heating element that generates heat when energized, and a coating layer that protects the substrate and the heating element. The heater 22 will be described in detail later.

[0019] When the film 23 is a single-layer film, the base layer is preferably made of a material such as PTFE (polytetrafluoroethylene), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether), or PPS. When a composite film is used, the base layer is preferably made of a material such as PI (polyimide), PAI (polyamide imide), PEEK (polyether ether ketone), or PES (polyether sulfone). It is also preferable to coat the surface with a film release layer such as PTFE, PFA, or FEP (tetrafluoroethylene-perfluoroalkyl vinyl ether). 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 coat the release layer with the aforementioned coating or a fluororesin tube. The thickness of the film 23 is preferably between 20 μm and 100 μm to ensure good thermal conductivity.

[0020] In this embodiment, the film base layer is made of PI with a thickness of 60 μm, and the film release layer is coated with PFA with a thickness of 12 μm, taking into consideration both the wear of the film release layer due to paper passing and thermal conductivity.

[0021] The heater holder 21 is a member that is elongated in the longitudinal direction and has a generally trough-shaped cross section. Because the heater holder 21 requires heat resistance and rigidity, it is preferable to use a material such as a liquid crystal polymer resin that has high heat resistance and excellent strength. Molded products of heat-resistant resins such as PPS (polyphenylene sulfite) and LCP (liquid crystal polymer) are particularly suitable for the heater holder 21.

[0022] The reinforcing member 24 is made of a metal such as iron, and receives the force of a pressure spring (described later) to press the heater 22 toward the pressure roller 30 via the heater holder 21. Furthermore, the reinforcing member 24 is also a member for maintaining strength so that the heater holder 21 does not deform significantly even under the pressure that forms the nip portion N.

[0023] 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 the heater receiving groove to be fitted at the desired position. A film 23 is fitted around the outside of the heater holder 21 with the above-mentioned parts assembled thereon, leaving some leeway in the circumferential length.

[0024] The pressure roller 30 as a pressure rotating body has a core metal made of iron, aluminum or the like, an elastic layer made of silicone rubber or the like, and a release layer made of PFA or the like.

[0025] The thermistor 25 is a temperature detecting member, and is in contact with the heater 22 on the side opposite to the surface that is in contact with the film 23. The power supply to the heater 22 is controlled in accordance with the temperature detected by the thermistor 25.

[0026] Flanges 26 are provided on both longitudinal ends of reinforcing member 24 and restrict longitudinal movement of film 23 as it rotates and travels. A power supply terminal of heater 22 also protrudes from one end of film 23, and power supply connector 27 is fitted into it. Power supply connector 27 comes into contact with the electrode portion of heater 22 with abutment pressure to form a power supply path. At the other end opposite the end where power supply connector 27 is provided, heater clip 28, formed from a metal plate bent into a U-shape, uses its spring properties to hold the end of heater 22 to heater holder 21. Protruding portions of reinforcing member 24 protrude from both longitudinal ends of film 23, and flanges 26 are fitted into each end, and the entire assembly is assembled into film unit 20.

[0027] Next, the pressure mechanism of the heating device will be described with reference to Figure 4. Figure 4 is a front view of the fixing device 9 as seen from the recording material conveyance direction, and part of the film 23 is not shown to show the inside of the film unit 20.

[0028] The film unit 20 is disposed opposite the pressure roller 30 and is supported by a top-side housing 41 of the fixing device so that its movement in the longitudinal direction (left-right direction in FIG. 4) is restricted but its movement in the pressure direction (up-down direction in FIG. 4) is free. A pressure spring 45 is attached in a compressed state to the top-side housing 41 of the fixing device. The pressure 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 provided to pivotally support the core metal of the pressure roller 30 and receives the pressure 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 a bottom-side housing 43 of the fixing device. A pressure roller drive gear 33 is attached to one end of the core metal of the pressure roller 30, and receives a rotational driving force from a driving means (not shown), thereby rotating the pressure roller 30.

[0029] (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 heater 52 according to the comparative example having a conventional configuration, and Figure 6 is a perspective view.

[0030] A typical heater 52 in a conventional configuration includes a long, thin plate-shaped substrate 521, a strip-shaped heating element 522 that generates heat when energized, and a coating layer 523 that serves as a protective layer for protecting the substrate 521 and the heating element 522. The heater 52 further includes a protective layer 523 that is provided for the purpose of supplying power to the heating element 522. The heater 52 has a power supply electrode 524 and a conductive pattern 525, and the conductive pattern 525 is also covered with a 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 .

[0031] The substrate 521 must be made of a heat-resistant material, taking into account the actual operating temperature. Ceramics and metals are typically used. When using metal 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 its strength, heat capacity, and heat dissipation performance. A thin substrate 521 is advantageous for quick start-up due to its small heat capacity, but if it is too thin, problems such as distortion may occur during the heat-forming of the heating element 522. Conversely, a thick substrate 521 is advantageous in terms of preventing distortion during the heat-forming of the heating element 522, but if it is too thick, its large heat capacity is 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 between mass productivity, cost, and performance.

[0032] Heating element 522 is formed by applying a heating element paste, which is a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binder component, onto 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), thereby forming heating element 522 containing the conductive component and the glass component. Here, the conductive component (A) is preferably silver-palladium (Ag-Pd), ruthenium oxide (RuO2), or the like, used alone or in combination, and 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.

[0033] Power supply electrode 524 and conductive pattern 525 are mainly made of silver (Ag), platinum (Pt), gold (Au), a silver-platinum (Ag-Pt) alloy, a silver-palladium (Ag-Pd) alloy, or the like. Power supply electrode 524 and conductive pattern 525 are formed by applying a paste, similar to the heating element paste, containing a mixture of (A) a conductive component, (B) a glass component, and (C) an organic binder component onto substrate 521 and then firing the paste. The resistance of power supply electrode 524 and conductive pattern 525 is set sufficiently low relative to heating element 522 in order to supply power to heating element 522. Here, for the heating element paste, power supply electrode paste, and conductive pattern paste, materials that soften and melt at a temperature lower than the melting point of substrate 521 and that are heat-resistant in consideration of the temperatures in actual use must be selected.

[0034] The material of the coating layer 523 is not particularly limited, but 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. 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, a screen printing method can be used to achieve a smooth molding. When a metal is used as the material of the substrate 521, forming the coating layer 523 on both sides of the substrate 521 can prevent warping of the substrate 521 during manufacturing.

[0035] Next, a detailed description will be given of the configuration and manufacturing method of the conventional heater 52. The heater 52 is a heater used in comparative examples 1, 2, and 3 in evaluation tests to be described later.

[0036] An alumina substrate having a width of 11 mm, a length of 270 mm, and a thickness of 1 mm was used as the substrate 521. Silver and palladium (Ag and Pd) were used as conductive components, and other components such as glass components and organic binder components were also used. A heating element paste containing the above, a power supply electrode paste containing silver (Ag) as a conductive component, a glass component, and an organic binder component, and a conductive pattern paste were prepared.

[0037] Heating element paste, power supply electrode paste, and conductive pattern paste are applied onto substrate 521 by screen printing, and then the substrate is dried at 180°C and fired at 850°C to form two heating elements 522, power supply electrodes 524, and conductive patterns 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, and the two heating elements 522 are connected by conductive pattern 525 at one longitudinal end of heater 52 to form a folded heating pattern.

[0038] Next, a glass paste is prepared and applied to the substrate 521, the heating element 522, and the conductive pattern 525 by screen printing, and then dried at 180°C and fired at 850°C to form a smooth coating layer 523. After firing, the coating layer 523 has a width of 10.5 mm, a length of 260 mm, and a height of 60 μm above the substrate 521. In this way, the heater 52 is completed.

[0039] Next, the configuration of heater 22 according to embodiment 1 will be described with reference to Fig. 7. Fig. 7 is a cross-sectional view of heater 22 according to embodiment 1. The heater of this embodiment differs from the comparative example having a conventional configuration in that the heat generation amounts of the two heating elements are not the same and the region on the downstream side in the conveying direction of the surface that abuts against the inner circumferential surface of the film protrudes more toward the pressure roller than the region on the upstream side in the conveying direction.

[0040] The heater 22 of this embodiment has a long, thin plate-shaped substrate 221, two heating elements 222 that generate heat when energized, and a coating layer 223 that serves as a protective layer to protect the substrate 221 and the heating elements 222. The heater 22 further 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 with the coating layer 223. The heater 22 is provided in the fixing device so that the coating layer 223 abuts against the inner circumferential 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 conveyance direction of the recording material.

[0041] The substrate 221 of this embodiment was 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 similar to those of the comparative example. The configuration and formation method of the power supply electrode and conductive pattern are similar to those of the comparative example, so a detailed description will be omitted. The configurations of the heating element 222 and coating layer 223, which are characteristic of the present invention, will be described below. In this embodiment, the thickness direction of the substrate 221 is parallel to the pressure direction in the nip portion N.

[0042] After the heating element paste is applied to the substrate 221 by screen printing, it is dried at 180°C and baked at 850°C to form two heating elements 222. Of the two heating elements 222 after baking, the first heating element 222a, located downstream in the conveyance direction of the recording material P, has 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 222b, located upstream in the conveyance direction. On the other hand, the second heating element 222b has a width of 3.0 mm, a length of 230 mm, and a thickness of 15 μm, and the two heating elements 222a and 222b are connected by a conductive pattern at one end of the heater 22 in the longitudinal direction, forming a folded heating pattern. In other words, the heater 22 of this embodiment is configured such that two heating elements with different heat generation amounts are provided on the substrate in the conveyance direction.

[0043] Next, glass paste is applied onto 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 onto the first heating element 222a by screen printing, followed by drying at 180° C. and firing at 850° C., forming a coating layer 223 having a convex shape. That is, the coating layer 223 on the first heating element 222a is formed 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 amount of the fixing device 9 at the same level as in the comparative example, and to even out uneven heat transfer 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.

[0044] In addition, a glass paste having a lower softening temperature than the glass paste applied first can be selected as the glass paste applied second, and the firing temperature for firing the glass paste applied second can be set lower than the softening temperature of the glass paste applied first. By doing so, it is possible to form the coating layer 223 having a convex shape more easily.

[0045] The heater 22 has, in the surface of the coating layer 223 that abuts against the inner circumferential surface of the film 23, a first region 223a that overlaps with the first heating element 222a and a second region 223b that overlaps with the second heating element 222b when viewed in the thickness direction of the substrate 221. In this case, within the fixing device 9, the first region 223a is positioned so that it protrudes more toward the pressure roller 30 than the second region 223b in the thickness direction of the substrate 221. Furthermore, both the first region 223a and the second region 223b extend over the entire area of ​​the heater 22 in the longitudinal direction. Note that the first region does not necessarily need to extend over the entire area of ​​the heater, as long as it is long enough to cover the entire width of the recording material being conveyed.

[0046] The fired coating layer 223 had a width of 10.5 mm and a length of 260 mm. 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. 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 of protrusion Pt = Ha - Hb, in the thickness direction of the substrate 221, of the surface of the first region 223a of the coating layer 223 toward the pressure roller 30 relative to the surface of the second region 223b. The protrusion amounts Pt for Examples 1-1, 1-2, and 1-3 were 10 μm, 20 μm, and 30 μm, respectively.

[0047] <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 configurations as those of the first embodiment will be assigned the same reference numerals and the description thereof will be omitted.

[0048] The heater 62 of this embodiment has a long, thin plate-shaped substrate 621, four heating elements 622 that generate heat when energized, and a coating layer 623 that serves as a protective layer to protect the substrate 621 and the heating elements 622. The heater 62 further 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 with the coating layer 623. The heater 62 is provided in the fixing device so that the coating layer 623 abuts against the inner circumferential surface of the film 23.

[0049] The substrate 621 of this embodiment was 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 were also similar to those of the comparative example. The configuration and formation method of the power supply electrode and conductive pattern are the same as those of the comparative example, so a detailed description will be omitted. The configurations of the heating element 622 and coating layer 623, which are characteristic of the present invention, will be described below in detail.

[0050] 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 side in the conveying direction of the recording material P, is the other three heating elements. The width of the heater 622 is 0.9 mm, the length is 230 mm, and the thickness is 15 μm so that the heat generation amount is larger than that of the heater 622b. On the other hand, the other three heater elements 622b are 1.4 mm in width, 230 mm in length, and 15 μm in thickness, and a three-fold heat generation pattern is formed by connecting the four heater elements 622 with a conductive pattern at the longitudinal end of the heater 62. That is, the heater 62 of this embodiment is configured so that four heater elements are provided on the substrate in the transport direction, and the heater located at the most downstream in the transport direction has the largest heat generation amount among the multiple heater elements.

[0051] Next, using the same glass paste as in the comparative example and embodiment 1, the glass paste is applied by screen printing onto substrate 621, heating elements 622a and 622b, and the conductive pattern, followed by drying at 180°C and firing at 850°C. Furthermore, glass paste is again applied by screen printing onto first heating element 622a, followed by drying at 180°C and firing at 850°C, forming coating layer 623 having a convex shape. That is, coating layer 623 on first heating element 622a is thicker than coating layer 623 on second heating element 622b. Here, in order to maintain the relationship between the set temperature, power consumption, and heat generation of fixing device 9 equivalent to that of the comparative example and to uniformize the heat transfer unevenness due to the convex shape of coating layer 223, the width of each heating element 222 is adjusted to adjust the resistance value and resistance ratio of the heating pattern.

[0052] The heater 62 has, in 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, in the fixing device 9, the first region 623a is positioned so as to protrude more toward the pressure roller 30 than the second region 623b in the thickness direction of the substrate 621.

[0053] The fired 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 heights Ha from the substrate 621 to the surface of the coating layer 623 in the first region 623a were 75 μm, 80 μm, and 85 μm, respectively. The heights Hb from the substrate 621 to the surface of the coating layer 623 in the second region 623b were 65 μm, 60 μm, and 55 μm, respectively. That is, the protrusion amounts Pt of Examples 2-1, 2-2, and 2-3 were 10 μm, 20 μm, and 30 μm, respectively.

[0054] <Embodiment 3> Next, the configuration of the heater 72 according to the third embodiment will be described with reference to Fig. 9. Fig. 9 is a cross-sectional view of the heater 72 according to the third embodiment. Of the configuration of the third embodiment, the same configurations as those of the first embodiment will be assigned the same reference numerals and the description thereof will be omitted.

[0055] 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 as a protective layer to protect the heating elements 722, and an insulating layer 724 to insulate 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 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 configurations and methods of forming the power supply electrodes and conductive patterns are similar to those in the comparative example, and therefore will not be described here. The configurations of the heating elements 722 and coating layer 723, which are characteristic of the present invention, are described in detail below.

[0056] 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. Metal materials used for the substrate 721 include stainless steel, nickel, copper, aluminum, and alloys containing these as the main materials. Gold is preferably used. Of these, stainless steel is most preferable in terms of strength, heat resistance, and corrosion. The type of stainless steel is not particularly limited, and may be selected appropriately taking into consideration the required mechanical strength, the linear expansion coefficient suited to the formation of the insulating layer 724 and the heating element 722, the ease of obtaining the plate material on the market, and the like. As an example, martensitic and ferritic chromium-based stainless steel (400 series) has a relatively low linear expansion coefficient among stainless steels, and is preferably used because it is easy to form the insulating layer 724 and the heating element 722.

[0057] The insulating layer 724 is formed using an insulating glass paste to insulate the substrate 721 from the heating element 722. The insulating layer 724 is formed by applying the insulating glass paste to the substrate 721 by screen printing, drying at 180°C, and firing at 850°C. The fired 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 a heater used in an image forming apparatus to have a dielectric strength of approximately 1.5 kV. Therefore, in order to obtain a dielectric strength of 1.5 kV between the heating element 722 and the substrate 721, the thickness of the insulating layer 724 can be determined depending on the material.

[0058] 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, has 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 has a width of 3.0 mm, a length of 230 mm, and a thickness of 15 μm. The two heating elements 722a and 722b are connected by a conductive pattern at one longitudinal end of the heater 72, forming a folded heating pattern. In other words, the heater 72 of this embodiment has a configuration in which two heating elements with different heat generation amounts are provided on an insulating layer in the conveyance direction.

[0059] 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, the heating element 722, and the conductive pattern. Furthermore, in order 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 to the side on which the insulating layer 724 is provided, and then the substrate is dried at 180°C and fired at 850°C, thereby forming coating layers on both sides of the substrate 721. Furthermore, the glass paste is again applied by screen printing onto the first heating element 722a, and then the substrate is dried at 180°C and fired at 850°C, thereby forming a coating layer 723 having a convex shape.

[0060] The heater 72 has, in 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, in the fixing device 9, the first region 723a is positioned so as to protrude more toward the pressure roller 30 than the second region 723b in the thickness direction of the substrate 721.

[0061] 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 prepared in which the thickness of the coating layer 723 was varied. In Examples 3-1, 3-2, and 3-3, the heights Ha from the substrate 721 to the surface of the coating layer 723 in the first region 723a were 75 μm, 80 μm, and 85 μm, respectively. The heights Hb from the substrate 721 to the surface of the coating layer 723 in the second region 723b were 65 μm, 60 μm, and 55 μm, respectively. That is, the protrusion amounts Pt of Examples 3-1, 3-2, and 3-3 are 10 μm, 20 μm, and 30 μm, respectively.

[0062] <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.

[0063] As mentioned above, Comparative Examples 1, 2, and 3 all use heaters of 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 conveyance 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 conveyance direction. The offset amount is 1 mm in Comparative Example 2 and 2 mm in Comparative Example 3.

[0064] 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 lowest set temperature at which no defects in the image pattern were observed was set as the fixing temperature for each configuration, and the fixing temperature for each configuration was measured. To evaluate the stability of the fixing performance, the test was also conducted by varying the rubber hardness of the pressure roller 30 and the spring constant of the pressure spring 45 to change the nip width to 10 mm, 8 mm, and 6 mm.

[0065] 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 the reference value was 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 was changed in a fixing device with the same configuration was also shown in the table as the fixing temperature variation.

[0066] [Table 1]

[0067] 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 the reference + 5°C. That is, in Comparative Example 1, the variation in fixing temperature within the nip width range of 6 mm to 10 mm was 5°C. Below, we will explain the results of other configurations based on this result.

[0068] In Comparative Example 2, the fixing temperature was -10°C when the nip width was 10mm and 8mm, and the fixing temperature was +0°C when the nip width was 6mm. 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 improving fixing performance by offsetting the film unit upstream in the transport direction. On the other hand, the variation in fixing temperature in Comparative Example 2 within the nip width range of 6mm to 10mm was 10°C, resulting in a result inferior to Comparative Example 1 in stability of fixing performance. In other words, the film unit By offsetting the film unit upstream in the conveying direction relative to the pressure roller, stronger pressure is applied downstream of the nip N in the conveying direction than upstream, improving fixing performance. However, with an offset film unit configuration, the heating element and heater tend to protrude outside the nip N, which reduces the stability of fixing performance relative to changes in the nip width.

[0069] 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 a further improvement in fixing performance. On the other hand, the fixing temperature variation in Comparative Example 3 within the nip width range of 6 mm to 10 mm was 15°C, resulting in a further deterioration in the stability of fixing performance compared to 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, it also worsens the stability of fixing performance relative to changes in nip width.

[0070] In Example 1-1 of Embodiment 1, the fixing temperature when the nip width was 10 mm and 8 mm was the reference +0°C, and the fixing temperature when the nip width was 6 mm was the reference +5°C, and both the fixing temperature and the fixing temperature variation were similar to those of Comparative Example 1.

[0071] In Example 1-2 of Embodiment 1, the fixing temperature was -15°C (reference temperature) when the nip width was 10 mm and 8 mm, and -10°C (reference temperature) 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 effect of improving fixing performance 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.

[0072] 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 be greater than or equal to a certain amount that improves fixing performance. In Embodiment 1, by setting the protrusion amount Pt of 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.

[0073] In the second embodiment, when compared with the first embodiment with the same protrusion amount Pt, the results were similar to those of the first embodiment. That is, even in a configuration with three or more heat generating 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 the fixing performance.

[0074] In the third embodiment, when compared with the first embodiment with the same protrusion amount Pt, the results were similar to those of the first embodiment. That is, even in a configuration in which an insulating layer is provided on a metal substrate, by making the downstream side of the heater in the transport direction protrude toward the pressure roller, it is possible to lower the fixing temperature compared to the conventional configuration without sacrificing the stability of the fixing performance.

[0075] As explained above, by increasing the amount of heat generated by the heater downstream of the feed direction compared to the upstream side and by having the heater's contact surface with the film protrude toward the pressure roller (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 than upstream of the feed direction and to apply strong pressure without offsetting the film unit relative to the pressure roller, it is possible to heat stably with low power consumption. However, it is necessary to set the nip portion width to a level where it can be formed stably. As long as it is the offset amount, the present invention can be preferably applied even to a configuration in which the film unit is offset with respect to the pressure roller.

[0076] In the above-described embodiments, the first and second regions are formed flat, and the contact surface between the heater and the inner peripheral 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 a third region is provided 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 conveyance direction.

[0077] Furthermore, in each of the above-described embodiments, the heat generation amount of each heating element was differentiated by changing the width of the heating element, but the method of differentiating the heat generation amount of the heating elements is not limited to this, and a configuration in which the power supply to the heating elements is individually controlled may also be used.

[0078] Furthermore, in the first, second, and third embodiments, 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 member, etc. If the protrusion amount Pt is too small, the effect of reducing the fixing temperature cannot 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.

[0079] <Embodiment 4> 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.

[0080] 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 as a protective layer for protecting the heating elements 822, and an insulating layer 824 for insulating 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 to the surface on which the heating elements 822 and insulating layer 824 are provided, for the purpose of preventing warping of the substrate 821. 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 surface of the substrate 821 in the previously described embodiments, and is the surface facing the heater holder 21 rather than the inner circumferential surface of the film 23. The substrate 821 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, as in the third embodiment.

[0081] 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 against the inner circumferential surface of the film 23. The configurations and formation methods of the power supply electrode and the conductive pattern are the same as those in the comparative example, so a description thereof will be omitted. Below, a detailed description will be given of the configurations of the heating element 822 and the coating layer 823, which are characteristic of the present invention.

[0082] The insulating layer 824 is provided using an insulating glass paste to insulate the substrate 821 from the heating element 822. The insulating layer 824 is formed by applying the insulating glass paste onto the substrate 821 by screen printing, drying at 180°C, and firing at 850°C. The fired insulating layer 824 has a width of 10.5 mm, a length of 260 mm, and a height of 50 μm. As described above, in the heater 82 of this embodiment, the insulating layer 824 is provided on the surface of the substrate 821 opposite to the surface facing the film 23.

[0083] Next, the 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 heating elements 822, the first heating element 822a, which is located downstream in the conveyance direction of the recording material P, has 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, which is located upstream in the conveyance direction. Meanwhile, the second heating element 822b has 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 with a conductive pattern at one longitudinal end of the heater 82. That is, the heater 82 of this embodiment has a configuration in which two heating elements with different heat generation amounts are provided on an insulating layer in the conveyance direction, and each heating element is provided on the surface of the substrate opposite to the surface facing the film.

[0084] 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 insulating layer 824, heating element 822, and conductive pattern. Furthermore, in order to prevent warping of substrate 821 during firing, the glass paste is also applied by screen printing to the side of substrate 821 opposite to the side on which insulating layer 824 is provided, and then the substrate is dried at 180°C and fired at 850°C, and coating layers are formed on both sides of substrate 821. Furthermore, the glass paste is again applied by screen printing onto first heating element 822a, and then the substrate is dried at 180°C and fired at 850°C, and coating layer 823 having a convex shape is formed.

[0085] The heater 82 has, in 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, in the fixing device 9, the first region 823a is positioned so as to protrude more toward the pressure roller 30 than the second region 823b in the thickness direction of the substrate 821.

[0086] The coating layer 823 in contact with the film 23 had a width of 10.5 mm and a length of 260 mm, and 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 prepared 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. 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. That is, the protrusion amounts Pt of Examples 4-1, 4-2, and 4-3 were 10 μm, 20 μm, and 30 μm, respectively.

[0087] <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.

[0088] The fixing performance evaluation test was conducted under the same conditions as described above. Specifically, a solid black pattern printed entirely with toner was used as the evaluation image pattern, and the environment was a room temperature and humidity environment with a temperature of 23°C and 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. The lowest set temperature at which no defects in the image pattern were observed was set as the fixing temperature for each configuration, and the fixing temperature for each configuration was measured. 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.

[0089] The test results of each example and the comparative example mentioned 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. In addition, when the nip width was changed in a fixing device with the same configuration, The difference between the maximum and minimum values ​​of the fixing temperature at each time point is shown in the table as the fluctuation in fixing temperature.

[0090] [Table 2]

[0091] 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. For 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.

[0092] In Example 4-2 of Embodiment 4, the fixing temperature was -10°C below the reference temperature when the nip width was 10 mm and 8 mm, and -7°C below the reference temperature when the nip width was 6 mm. Comparing the results for the same nip width as Comparative Example 1, Example 4-2 had a lower fixing temperature under all conditions, demonstrating the effect of improving fixing performance 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 4-2 within the nip width range of 6 mm to 10 mm was 3°C, which was smaller than that of Comparative Example 1. In other words, the configuration of Example 4-2 can improve the stability of fixing performance and lower the fixing temperature compared to the conventional configuration.

[0093] 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 was due to the fact that Example 4-2 was configured with the heating element farther from the inner circumferential surface of the film than Examples 1-2, 2-2, and 3-2, and therefore took longer for the heat from the heating element to reach the inner circumferential surface of the film.

[0094] In Example 4-3 of the fourth embodiment, the fixing temperature is −10° C. when the nip width is 10 mm and 8 mm, and the fixing temperature is −7° C. when the nip width is 6 mm. The results were similar.

[0095] As explained above, even in a configuration in which the heating element and insulating layer are provided on the surface of the substrate opposite to the surface facing the inner circumferential surface of the film, the present invention can reduce the fixing temperature without sacrificing the stability of fixing performance against changes in the nip portion. Moreover, which side of the substrate the heating element is provided on can be appropriately selected depending on whether priority is given to the effect of reducing the fixing temperature or the effect of improving the stability of fixing performance. [Explanation of symbols]

[0096] 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

1. 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.

2. 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.

3. 2. The heater according to claim 1, wherein the plurality of heating elements are provided on a surface of the substrate opposite to the surface on which the coating layer is provided.

4. 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.

5. 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. 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.

7. The heat generating element further includes a conductive pattern provided on the substrate for supplying power to the heat generating 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.

8. 8. The heating device according to claim 6, wherein the first area and the second area are flat surfaces parallel to the surface of the recording material.

9. The heating device according to any one of claims 6 to 8, characterized in that the first region is located 20 μm or more closer to the second rotating body than the second region in the thickness direction.

10. 10. The heating device according to claim 6, wherein the width of the first heat generating element in the transport direction is smaller than the width of the second heat generating element in the transport direction.

11. 11. The heating device according to claim 6, wherein the thickness of the coating layer in the first region is greater than the thickness of the coating layer in the second region.

12. 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.

13. the first rotating body is a cylindrical film, 13. The heating device according to claim 5, wherein the second rotating body is a roller.

14. 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.

Images