Patent Publication Number: US-2022229388-A1

Title: Heater and Image Forming Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2021-005295, filed on Jan. 15, 2021; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate to a heater and an image forming apparatus. 
     BACKGROUND 
     An image forming apparatus such as a copier or a printer is provided with a heater for fixing a toner. In general, such a heater is provided with a long substrate, a heating element provided on one surface of the substrate, and a wiring electrically connected to the heating element. 
     Further, there is a proposed heater having a pair of wirings extending along a long side of a substrate and a plurality of heating elements provided between the pair of wirings and arranged along the pair of wirings. One end of the plurality of heating elements is electrically connected to one of the wires. The other end of the plurality of heating elements is electrically connected to the other wiring. Further, the plurality of heating elements is inclined with respect to a direction in which the wirings extend. When such heating elements are provided, it is possible to suppress an occurrence of temperature distribution in the heater (substrate). 
     However, when the heating elements merely inclined with respect to the direction in which the wirings extend are provided, dielectric breakdown (electric field destruction) may occur at a connecting part between the heating elements and the wirings, and at least one of the heating elements and the wirings may be damaged. 
     Therefore, it is desired to develop a technology capable of suppressing dielectric breakdown at the connecting part between the heating elements and the wirings even when the heating elements inclined with respect to the direction in which the wirings extend are provided. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic plan view of a heater according to the present embodiment as viewed from a side where a heat generating portion is provided. 
         FIG. 2  is a schematic cross-sectional view of the heater of  FIG. 1  in an A-A line direction. 
         FIG. 3  is a schematic plan view for illustrating planar shapes of heating elements according to a comparative example. 
         FIG. 4  is a schematic plan view for illustrating planar shapes of heating elements according to the present embodiment. 
         FIG. 5  is a schematic plan view for illustrating planar shapes of heating elements according to another embodiment. 
         FIG. 6  is a schematic diagram for illustrating an image forming apparatus according to the present embodiment. 
         FIG. 7  is a schematic diagram for illustrating a fixing portion. 
     
    
    
     DETAILED DESCRIPTION 
     A heater according to an embodiment includes a substrate having a plate shape and extending in a first direction, a first wiring provided on one surface of the substrate to extend in the first direction, a second wiring provided on the one surface of the substrate and separated from the first wiring in a second direction orthogonal to the first direction, the second wiring extending in the first direction, and a plurality of first heating elements provided between the first wiring and the second wiring and arranged in the first direction. Each of the plurality of first heating elements includes an inclined portion, a first connecting portion provided on a first wiring side of the inclined portion and electrically connected to the first wiring, and a second connecting portion provided on a second wiring side of the inclined portion and electrically connected to the second wiring. When viewed from a direction perpendicular to the one surface of the substrate, the inclined portion is provided between the first wiring and the second wiring and inclined with respect to the first direction. An angle between a side of the first connecting portion and a side of the first wiring on an inclined portion side is larger than an angle between the side of the first wiring on the inclined portion side and a side of the inclined portion on one side of the first direction where an angle between the side of the inclined portion and a side of the first wiring on the inclined portion side is 90° or less. An angle between a side of the second connecting portion and a side of the second wiring on an inclined portion side is larger than an angle between the side of the second wiring on the inclined portion side and a side of the inclined portion on the other side of the first direction where an angle between the side of the inclined portion and a side of the second wiring on the inclined portion side is 90° or less. 
     Hereinafter, embodiments will be illustrated with reference to the drawings. Note that in each drawing, similar components are designated by the same reference symbols and detailed description thereof will be omitted as appropriate. 
     In addition, arrows X, Y, and Z in each drawing represent three directions orthogonal to one another. For example, a longitudinal direction of a substrate is set to an X direction (corresponding to an example of a first direction), a short direction (width direction) of the substrate is set to a Y direction (corresponding to an example of a second direction), and a direction perpendicular to a surface of the substrate (thickness direction) is set to a Z direction. 
     First, a heater  1  according to the present embodiment will be described. 
     (Heater) 
       FIG. 1  is a schematic plan view of the heater  1  according to the present embodiment as viewed from a side where a heat generating portion  20  is provided. 
       FIG. 2  is a schematic cross-sectional view of the heater  1  of  FIG. 1  in an A-A line direction. 
     As illustrated in  FIGS. 1 and 2 , for example, the heater  1  includes a substrate  10 , the heat generating portion  20 , a wiring portion  31 , a wiring portion  32 , and a protective film  40 . 
     The substrate  10  has a plate shape and has a shape extending in one direction (for example, the X direction). A planar shape of the substrate  10  can be, for example, a long rectangular shape. A thickness of the substrate  10  can be, for example, about 0.5 mm to 1.0 mm. The plane dimensions of the substrate  10  can be appropriately changed depending on the size of an object to be heated (for example, paper), etc. 
     The substrate  10  is formed from a material having a heat-resisting property and an insulation property. The substrate  10  can be formed from, for example, ceramics such as aluminum oxide or aluminum nitride, crystallized glass (glass ceramics), and a metal plate whose surface is coated with an insulating material. 
     The heat generating portion  20  converts applied electric power into heat (Joule heat). The heat generating portion  20  is provided on one surface of the substrate  10 . 
     The heat generating portion  20  has, for example, a plurality of heating elements  21  and a plurality of heating elements  22 . The plurality of heating elements  21  is arranged in the X direction, for example. The plurality of heating elements  22  is arranged in the X direction, for example. Rows of the plurality of heating elements  21  and rows of the plurality of heating elements  22  are arranged in the Y direction. 
     Note that as an example, the plurality of heating elements  21  arranged in a row and the plurality of heating elements  22  arranged in a row were illustrated. However, any of the plurality of heating elements  21  and the plurality of heating elements  22  may be provided. Further, a plurality of heating elements provided side by side in the X direction may be provided in three or more rows in the Y direction. The number, plane dimensions, thickness, arrangement, etc. of the heating elements can be appropriately changed according to the size of the object to be heated, etc. Further, it is possible to provide heating elements having different plane dimensions and thicknesses, and it is possible to provide heating elements having at least one of the same plane dimensions and the same thickness. 
     Note that details regarding planar shapes of the heating elements  21  and the heating elements  22  will be described later. 
     For example, the plurality of heating elements  21  and the plurality of heating elements  22  have a film shape and can be formed by using ruthenium oxide (RuO 2 ), a silver-palladium (Ag—Pd) alloy, graphite, etc. For example, the plurality of heating elements  21  and the plurality of heating elements  22  may be formed by applying a paste-like material to the surface of the substrate  10  using a screen printing method, etc., and curing the paste-like material using a firing method, etc. 
     The wiring portion  31  and the wiring portion  32  are provided on the surface of the substrate  10  on which the heat generating portion  20  is provided. 
     The wiring portion  31  has, for example, a wiring  31   a  (corresponding to an example of a first wiring), a wiring  31   b  (corresponding to an example of the first wiring), and a terminal  31   c.  The wiring  31   a,  the wiring  31   b,  and the terminal  31   c  can be integrally formed. 
     In the Y direction, the wiring  31   a  is provided near one peripheral edge of the substrate  10 . The wiring  31   a  extends in the X direction along one peripheral edge of the substrate  10 . 
     In the Y direction, the wiring  31   b  is provided near the other peripheral edge of the substrate  10 . The wiring  31   b  extends in the X direction along the other peripheral edge of the substrate  10 . 
     The terminal  31   c  is provided near one end of the substrate  10  in the X direction. One end of each of the wiring  31   a  and the wiring  31   b  is electrically connected to the terminal  31   c.    
     In the Y direction, the wiring portion  32  is provided in a central region of the substrate  10 . The wiring portion  32  has, for example, a wiring  32   a  (corresponding to an example of a second wiring) and a terminal  32   b.  The wiring  32   a  and the terminal  32   b  can be integrally formed. 
     In the Y direction, the wiring  32   a  is provided between the wiring  31   a  and the wiring  31   b  of the wiring portion  31 . That is, the wiring  32   a  is separated from the wirings  31   a  and  31   b  in the Y direction orthogonal to the X direction. The wiring  32   a  extends in the X direction along the peripheral edge of the substrate  10 . 
     The terminal  32   b  is provided near the other end of the substrate  10  in the X direction. One end of the wiring  32   a  is electrically connected to the terminal  32   b.    
     One end of the plurality of heating elements  21  is electrically connected to the wiring  31   a  of the wiring portion  31 . The other end of the plurality of heating elements  21  is electrically connected to the wiring  32   a  of the wiring portion  32 . That is, the plurality of heating elements  21  is connected in parallel. 
     One end of the plurality of heating elements  22  is electrically connected to the wiring  31   b  of the wiring portion  31 . The other end of the plurality of heating elements  22  is electrically connected to the wiring  32   a  of the wiring portion  32 . That is, the plurality of heating elements  22  is connected in parallel. 
     The wiring portion  31  and the wiring portion  32  may be formed by using a material containing, for example, silver or copper. In this case, for example, the wiring portion  31  and the wiring portion  32  may be formed by applying a paste-like material to the surface of the substrate  10  on which the heat generating portion  20  is provided by using the screen printing method, etc., and curing the paste-like material using the firing method, etc. 
     The protective film  40  covers the heating element  21 , the heating element  22 , the wiring portion  31 , and the wiring portion  32 . In this case, the terminal  31   c  of the wiring portion  31  and the terminal  32   b  of the wiring portion  32  can be exposed from the protective film  40  for electrical connection with a power-supply, etc. 
     For example, the protective film  40  has a function to insulate the heating element  21 , the heating element  22 , the wiring portion  31 , and the wiring portion  32 , a function to transfer heat generated in the heating element  21  and the heating element  22  to the outside, and a function of protecting the heating element  21 , the heating element  22 , the wiring portion  31 , and the wiring portion  32  from external force, corrosive gas, etc. 
     The protective film  40  is preferably formed from a material having a heat-resisting property and an insulation property and having high chemical stability. For example, the protective film  40  can be formed using ceramics, glass, etc. In this case, when glass to which a filler containing a material having high thermal conductivity such as aluminum oxide is added is used, the protective film  40  can be easily formed. For example, the thermal conductivity of the glass to which the filler is added can be set to 2 [W/(m·K)] or more. For example, the protective film  40  can be formed by applying the paste-like material onto the substrate  10 , the heat generating portion  20 , the wiring portion  31 , and the wiring portion  32  using the screen printing method, etc., and curing the paste-like material using the firing method, etc. 
     Further, a temperature sensor and a wiring electrically connected to the temperature sensor may be provided on the surface of the substrate  10  opposite to the side on which the heat generating portion  20  is provided. The temperature sensor can be, for example, a film-like thermistor. The film-like thermistor can be formed by, for example, applying a paste-like material to the surface of the substrate  10  by using a screen printing method, etc., and curing the paste-like material by using a firing method, etc. For example, the film-like thermistor can be formed by using a material containing barium titanate, a material containing an oxide, etc. The oxide can be, for example, an oxide of nickel, manganese, cobalt, iron, copper, etc. 
     The wiring electrically connected to the temperature sensor can be formed by using, for example, a screen printing method, a firing method, etc., similarly to the wiring portions  31  and  32  described above. In addition, it is possible to provide a protective film that covers the temperature sensor and the wiring. The protective film can be, for example, similar to the protective film  40  described above. 
     Next, a description will be given of planar shapes of the heating element  21  and the heating element  22 . 
     First, a description will be given of planar shapes of heating elements  221  and  222  according to a comparative example. 
       FIG. 3  is a schematic plan view for illustrating the planar shapes of the heating elements  221  and  222  according to the comparative example. 
     As illustrated in  FIG. 3 , the planar shape of each of the heating elements  221  and  222  is a parallelogram. 
     The heating element  221  is electrically connected to the wiring  31   a  and the wiring  32   a.  The heating element  221  is inclined with respect to a direction (X direction) in which the wiring  31   a  and the wiring  32   a  extend. 
     As illustrated in  FIG. 3 , an angle θ 1  between one side of the heating element  221  intersecting the wiring  31   a  and the wiring  31   a  is smaller than 45°. An angle θ 2  between the other side of the heating element  221  intersecting the wiring  31   a  and the wiring  31   a  is larger than 135°. An angle θ 3  between one side of the heating element  221  intersecting the wiring  32   a  and the wiring  32   a  is larger than 135°. An angle θ 4  between the other side of the heating element  221  intersecting the wiring  32   a  and the wiring  32   a  is smaller than 45°. 
     The heating element  222  is electrically connected to the wiring  31   b  and the wiring  32   a.  The heating element  222  is inclined with respect to the wiring  31   b  and the wiring  32   a.    
     As illustrated in  FIG. 3 , an angle θ 5  between one side of the heating element  222  intersecting the wiring  31   b  and the wiring  31   b  is smaller than 45° . An angle θ 6  between the other side of the heating element  222  intersecting the wiring  31   b  and the wiring  31   b  is larger than 135°. An angle θ 7  between one side of the heating element  222  intersecting the wiring  32   a  and the wiring  32   a  is larger than 135°. An angle θ 8  between the other side of the heating element  222  intersecting the wiring  32   a  and the wiring  32   a  is smaller than 45°. Here, when an angle between the heating element and the wiring is smaller than 45° (acute angle), electric field concentration is likely to occur in the vicinity of a connecting part between the heating element and the wiring. For example, electric field concentration is likely to occur at portions of angles θ 1 , θ 4 , θ 5 , and θ 8 . In this case, as the angle between the heating element and the wiring decreases, the strength of the electric field increases. When the strength of the electric field increases, dielectric breakdown occurs in the vicinity of the connecting part between the heating element and the wiring, and a large current may flow. For example, when an inrush current or a surge current flows through the heater  1 , dielectric breakdown is more likely to occur. When dielectric breakdown occurs and a large current flows, there is concern that at least one of the heating element and the wiring may be damaged. 
       FIG. 4  is a schematic plan view for illustrating planar shapes of the heating elements  21  and  22  according to the present embodiment. 
     As illustrated in  FIG. 4 , the heating element  21  has an inclined portion  21   a,  a connecting portion  21   b  (corresponding to an example of a first connecting portion), and a connecting portion  21   c  (corresponding to an example of a second connecting portion). The inclined portion  21   a,  the connecting portion  21   b,  and the connecting portion  21   c  are integrally formed. 
     The inclined portion  21   a  is provided between the wiring  31   a  and the wiring  32   a  when viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  21  is provided. Further, the inclined portion  21   a  is inclined with respect to the direction (X direction) in which the wiring  31   a  and the wiring  32   a  extend. In this case, as illustrated in  FIG. 1 , when a plurality of inclined portions  21   a  inclined with respect to the longitudinal direction of the substrate  10  is provided side by side in the longitudinal direction of the substrate  10 , it is possible to suppress occurrence of temperature distribution in the heater  1  (substrate  10 ). 
     The connecting portion  21   b  is provided on the wiring  31   a  side of the inclined portion  21   a.  The connecting portion  21   b  is electrically connected to the wiring  31   a.  The inclined portion  21   a  side of the connecting portion  21   b  is exposed from the wiring  31   a.    
     Angles θa and θb between a side of the connecting portion  21   b  and a side of the wiring  31   a  on the inclined portion  21   a  side when viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  21  is provided are 45° or more. In the case of the heating element  21  illustrated in  FIG. 4 , the angles θa and θb are set to 90°. The planar shape of the connecting portion  21   b  can be, for example, a rectangle or a square. The connecting portion  21   c  is provided on the wiring  32   a  side of the inclined portion  21   a.  The connecting portion  21   c  is electrically connected to the wiring  32   a.  The inclined portion  21   a  side of the connecting portion  21   c  is exposed from the wiring  32   a.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  21  is provided, angles θc and θd between the side of the connecting portion  21   c  and the side of the wiring  32   a  on the inclined portion  21   a  side are 45° or more. In the case of the heating element  21  illustrated in  FIG. 4 , the angles θc and θd are set to 90°. 
     The planar shape of the connecting portion  21   c  can be, for example, a rectangle or a square. 
     As illustrated in  FIG. 4 , the heating element  22  has an inclined portion  22   a,  a connecting portion  22   b  (corresponding to an example of the first connecting portion), and a connecting portion  22   c  (corresponding to an example of the second connecting portion). The inclined portion  22   a,  the connecting portion  22   b,  and the connecting portion  22   c  are integrally formed. 
     The inclined portion  22   a  is provided between the wiring  31   b  and the wiring  32   a  when viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  22  is provided. Further, the inclined portion  22   a  is inclined with respect to the direction (X direction) in which the wiring  31   b  and the wiring  32   a  extend. In this case, as illustrated in  FIG. 1 , when a plurality of inclined portions  22   a  inclined with respect to the longitudinal direction of the substrate  10  is provided side by side in the longitudinal direction of the substrate  10 , it is possible to suppress occurrence of temperature distribution in the heater  1  (substrate  10 ). 
     The connecting portion  22   b  is provided on the wiring  31   b  side of the inclined portion  22   a.  The connecting portion  22   b  is electrically connected to the wiring  31   b.  The inclined portion  22   a  side of the connecting portion  22   b  is exposed from the wiring  31   b.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  22  is provided, angles θe and θf between the side of the connecting portion  22   b  and the side of the wiring  31   b  on the inclined portion  22   a  side are 45° or more. In the case of the heating element  22  illustrated in  FIG. 4 , the angles θe and θf are set to 90°. 
     The planar shape of the connecting portion  22   b  can be, for example, a rectangle or a square. 
     The connecting portion  22   c  is provided on the wiring  32   a  side of the inclined portion  22   a.  The connecting portion  22   c  is electrically connected to the wiring  32   a.  The inclined portion  22   a  side of the connecting portion  22   c  is exposed from the wiring  32   a.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  22  is provided, angles θg and θh between the side of the connecting portion  22   c  and the side of the wiring  32   a  on the inclined portion  22   a  side are 45° or more. In the case of the heating element  22  illustrated in  FIG. 4 , the angles θg and θh are set to 90°. 
     The planar shape of the connecting portion  22   c  can be, for example, a rectangle or a square. 
     When the angle between the heating element and the wiring is 45° or more, it is possible to suppress the occurrence of electric field concentration in the vicinity of the connecting part between the heating element and the wiring. In addition, the strength of the generated electric field can be reduced. Therefore, for example, even when an inrush current or a surge current flows through the heater  1 , it is possible to suppress dielectric breakdown at the connecting part between the heating elements  21  and  22  and the wirings  31   a,    31   b,  and  32   a.  As a result, damage to the heating elements  21  and  22  and the wirings  31   a,    31   b,  and  32   a  can be suppressed.  FIG. 5  is a schematic plan view for illustrating planar shapes of heating elements  23  and  24  according to another embodiment. 
     As illustrated in  FIG. 5 , the heating element  23  has an inclined portion  21   a,  a connecting portion  23   b  (corresponding to an example of the first connecting portion), and a connecting portion  23   c  (corresponding to an example of the second connecting portion). The inclined portion  21   a,  the connecting portion  23   b,  and the connecting portion  23   c  are integrally formed. The connecting portion  23   b  is provided on the wiring  31   a  side of the inclined portion  21   a.  The connecting portion  23   b  is electrically connected to the wiring  31   a.  The inclined portion  21   a  side of the connecting portion  23   b  is exposed from the wiring  31   a.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  23  is provided, angles θa and θb 1  between the side of the connecting portion  23   b  and the side of the wiring  31   a  on the inclined portion  21   a  side are 45° or more. In the case of the heating element  23  illustrated in  FIG. 5 , the angle θa is set to 90°, and the angle θb 1  is set to be larger than 90°. 
     The planar shape of the connecting portion  23   b  can be, for example, a trapezoid. 
     The connecting portion  23   c  is provided on the wiring  32   a  side of the inclined portion  23   a.  The connecting portion  23   c  is electrically connected to the wiring  32   a.  The inclined portion  23   a  side of the connecting portion  23   c  is exposed from the wiring  32   a.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  23  is provided, angles θc 1  and θd between the side of the connecting portion  23   c  and the side of the wiring  32   a  on the inclined portion  23   a  side are 45° or more. In the case of the heating element  23  illustrated in  FIG. 5 , the angle θc 1  is set to be larger than 90°, and the angle θd is set to 90°. 
     The planar shape of the connecting portion  23   c  can be, for example, a trapezoid. 
     As illustrated in  FIG. 5 , the heating element  24  has an inclined portion  22   a,  a connecting portion  24   b  (corresponding to an example of the first connecting portion), and a connecting portion  24   c  (corresponding to an example of the second connecting portion). The inclined portion  22   a,  the connecting portion  24   b,  and the connecting portion  24   c  are integrally formed. 
     The connecting portion  24   b  is provided on the wiring  31   b  side of the inclined portion  22   a.  The connecting portion  24   b  is electrically connected to the wiring  31   b.  The inclined portion  22   a  side of the connecting portion  24   b  is exposed from the wiring  31   b.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  24  is provided, angles θe and θf 1  between the side of the connecting portion  24   b  and the side of the wiring  31   b  on the inclined portion  22   a  side are 45° or more. In the case of the heating element  24  illustrated in  FIG. 5 , the angle θe is set to 90°, and the angle θf 1  is set to be larger than 90°. 
     The planar shape of the connecting portion  24   b  can be, for example, a trapezoid. 
     The connecting portion  24   c  is provided on the wiring  32   a  side of the inclined portion  22   a.  The connecting portion  24   c  is electrically connected to the wiring  32   a.  The inclined portion  22   a  side of the connecting portion  24   c  is exposed from the wiring  32   a.    
     When viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element  24  is provided, angles θg 1  and θh between the side of the connecting portion  24   c  and the side of the wiring  32   a  on the inclined portion  22   a  side is 90° or more. In the case of the heating element  24  illustrated in  FIG. 5 , the angle θg 1  is set to be larger than 90° and the angle θh is set to 90°. 
     The planar shape of the connecting portion  24   c  can be, for example, a trapezoid. 
     Even the heating elements  23  and  24  having the above-mentioned planar shape can have the same actions and effects as those of the heating elements  21  and  22  described above. 
     That is, when viewed from the direction (Z direction) perpendicular to the surface of the substrate  10  on which the heating element is provided, as long as the angle between the connecting portion of the heating element and the wiring is 90° or more, the planar shape of the connecting portion can be changed as appropriate. 
     As described with reference to  FIG. 4 , the angle between the side of the connecting portion  21   b  ( 22   b ) and the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side is larger than the angle between the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side and the side of the inclined portion  21   a  ( 22   a ) on one side in the X direction where the angle between the side of the inclined portion  21   a  ( 22   a ) and the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side is 90° or less. 
     The angle between the side of the connecting portion  21   c  ( 22   c ) and the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side is larger than the angle between the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side and the side of the inclined portion  21   a  ( 22   a ) on the other side in the X direction where the angle between the side of the inclined portion  21   a  ( 22   a ) and the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side is 90° or less. 
     As described with reference to  FIG. 5 , the angle between the side of the connecting portion  23   b  ( 24   b ) and the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side is larger than the angle between the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side and the side of the inclined portion  21   a  ( 22   a ) on one side in the X direction where the angle between the side of the inclined portion  21   a  ( 22   a ) and the side of the wiring  31   a  ( 31   b ) on the inclined portion  21   a  ( 22   a ) side is 90° or less. 
     The angle between the side of the connecting portion  23   c  ( 24   c ) and the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side is larger than the angle between the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side and the side of the inclined portion  21   a  ( 22   a ) on the other side in the X direction where the angle between the side of the inclined portion  21   a  ( 22   a ) and the side of the wiring  32   a  on the inclined portion  21   a  ( 22   a ) side is 90° or less. 
     Next, a description will be given of an image forming apparatus  100  according to the present embodiment. 
     (Image Forming Apparatus) 
     In the following, as an example, a case where the image forming apparatus  100  is a copier will be described. However, the image forming apparatus  100  is not limited to the copier, and may be any one provided with a heater for fixing the toner. For example, the image forming apparatus  100  may be a printer, etc. 
       FIG. 6  is a schematic diagram for illustrating the image forming apparatus  100  according to the present embodiment. 
       FIG. 7  is a schematic diagram for illustrating a fixing portion  200 . 
     As illustrated in  FIG. 6 , in the image forming apparatus  100 , it is possible to provide a frame  110 , an illumination portion  120 , an imaging element  130 , a photosensitive drum  140 , a charging portion  150 , a discharging portion  151 , a developing portion  160 , a cleaner  170 , a storage portion  180 , a transport portion  190 , a fixing portion  200 , and a controller  210 . 
     The frame  110  has a box shape, and can store the illumination portion  120 , the imaging element  130 , the photosensitive drum  140 , the charging portion  150 , the developing portion  160 , the cleaner  170 , a part of the storage portion  180 , the transport portion  190 , the fixing portion  200 , and the controller  210  therein. 
     A window  111  made of a translucent material such as glass can be provided on an upper surface of the frame  110 . An original document  500  to be copied can be placed on the window  111 . In addition, a moving portion for moving a position of the original document  500  can be provided. 
     The illumination portion  120  can be provided in the vicinity of the window  111 . The illumination portion  120  can include a light source  121  such as a lamp and a reflector  122 . 
     The imaging element  130  can be provided in the vicinity of the window  111 . 
     The photosensitive drum  140  can be provided below the illumination portion  120  and the imaging element  130 . The photosensitive drum  140  can be provided so as to be rotatable. For example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer can be provided on a surface of the photosensitive drum  140 . 
     The charging portion  150 , the discharging portion  151 , the developing portion  160 , and the cleaner  170  can be provided around the photosensitive drum  140 . 
     The storage portion  180  has a cassette  181  and a tray  182 . The cassette  181  can be detachably attached to one side of the frame  110 . The tray  182  can be provided in a side portion of the frame  110  on the opposite side from a side where the cassette  181  is mounted. The cassette  181  stores paper  510  (for example, blank paper) before copying is performed. The tray  182  stores the paper  511  on which a copy image  511   a  is fixed. 
     The transport portion  190  can be provided below the photosensitive drum  140 . The transport portion  190  transports the paper  510  between the cassette  181  and the tray  182 . The transport portion  190  includes a guide  191  that supports the paper  510  to be transported, and transport rollers  192  to  194  that transport the paper  510 . Further, the transport portion  190  may be provided with a motor for rotating the transport rollers  192  to  194 . 
     The fixing portion  200  can be provided on a downstream side (tray  182  side) of the photosensitive drum  140 . 
     As illustrated in  FIG. 7 , the fixing portion  200  includes, for example, a heater  1 , a stay  201 , a film belt  202 , and a pressure roller  203 . 
     The heater  1  can be attached to a transport line side of the paper  510  of the stay  201 . The heater  1  can be embedded in the stay  201 . A side of the heater  1  provided with the protective film  40  can be exposed from the stay  201 . The film belt  202  covers the stay  201  provided with the heater  1 . The film belt  202  can contain, for example, a resin having a heat-resisting property such as polyimide. 
     The pressure roller  203  can be provided so as to face the stay  201 . The pressure roller  203  has a core metal  203   a,  a drive shaft  203   b,  and an elastic portion  203   c.  The drive shaft  203   b  protrudes from an end of the core metal  203   a  and is connected to a drive device such as a motor. The elastic portion  203   c  can be provided on an outer surface of the core metal  203   a.  The elastic portion  203   c  is formed of an elastic material having a heat-resisting property. The elastic portion  203   c  contains, for example, a silicone resin, etc. 
     The controller  210  is provided inside the frame  110 . The controller  210  has, for example, a calculation unit such as a central processing unit (CPU) and a storage unit in which a control program is stored. The calculation unit controls an operation of each element provided in the image forming apparatus  100  based on a control program stored in the storage unit. Further, the controller  210  may include an operation unit for inputting copying conditions, etc. by a user, a display unit for displaying an operating state, an abnormality display, etc. 
     Note that since a known technology can be applied to control the operation of each element provided in the image forming apparatus  100 , detailed description thereof will be omitted. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions. Moreover, above-mentioned embodiments can be combined mutually and can be carried out.