Heater and image forming apparatus

Abstract

To provide a heater that can prevent generation of warpage in the heater and can prevent an increase in the heat capacity of the heater, and an image forming apparatus.SOLUTION: A heater according to an embodiment is provided with: a substrate that includes metal and extends in one direction; an insulating part that is provided on one surface of the substrate; a heating element that is provided on the insulating part and extends in a longitudinal direction of the substrate; and a protection part that is provided on the insulating part and covers the heating element. The coefficient of linear expansion of material of the insulating part is smaller than the coefficient of linear expansion of material of the substrate, and the coefficient of linear expansion of material of the protection part is larger than the coefficient of linear expansion of the material of the insulating part. The coefficient of linear expansion of the material of the insulating part is larger than the coefficient of linear expansion of the material of the substrate, and the coefficient of linear expansion of the material of the protection part is smaller than the coefficient of linear expansion of the material of the insulating part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Embodiments of the present invention relate to a heater and an image forming apparatus.

Background Art

[0002] For example, heaters are provided in image forming apparatuses such as copiers, printers, and rewritable card readers / writers. Generally, such a heater includes a long substrate, an insulating portion provided on one surface of the substrate, a heating element provided on the insulating portion and extending in the longitudinal direction of the substrate, and a protective portion covering the insulating portion and the heating element.

[0003] The substrate is formed of a material having heat resistance and high thermal conductivity. For example, the substrate is formed of metal. If the material of the substrate is metal, improvement in the rigidity of the substrate and reduction in manufacturing cost can be achieved. The insulating portion and the protective portion are formed of a material having heat resistance and insulation properties and high thermal conductivity. For example, the insulating portion and the protective portion are formed of glass.

[0004] Here, when the materials of the substrate, the insulating portion, and the protective portion are thus configured, thermal stress is generated due to the difference in the linear expansion coefficients of the materials. Therefore, large thermal stress may be generated during use of the heater or during manufacture of the heater (for example, during firing of the insulating portion and the protective portion), and a large warp may occur in the heater.

[0005] Therefore, a technique has been proposed in which a layer formed of an inorganic material is provided on the surface of the substrate opposite to the side where the insulating portion and the protective portion are provided. If such a layer is provided, the thermal stress generated on the side of the substrate where the insulating portion and the protective portion are provided can be offset by the thermal stress generated on the opposite side of the substrate. Therefore, it is possible to suppress the occurrence of warping in the heater during use of the heater or during manufacture of the heater.

[0006] However, providing a layer formed of an inorganic material increases the heat capacity of the heater. When the heat capacity of the heater increases, it takes time for the temperature of the heater to rise and it also takes time for the heater to cool down. Therefore, there has been a demand for the development of a technology that can suppress warping of the heater and can also suppress an increase in the heat capacity of the heater.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] The problem to be solved by the present invention is to provide a heater and an image forming apparatus that can suppress warping of the heater and can also suppress an increase in the heat capacity of the heater.

Means for Solving the Problems

[0009] The heater according to the embodiment includes a substrate containing a metal and extending in one direction; an insulating portion provided on one surface of the substrate; a heating element provided on the insulating portion and extending in the longitudinal direction of the substrate; and a protective portion provided on the insulating portion and covering the heating element. The linear expansion coefficient of the material of the insulating portion is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is larger than the linear expansion coefficient of the material of the insulating portion. Or, the linear expansion coefficient of the material of the insulating portion is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is smaller than the linear expansion coefficient of the material of the insulating portion.

Effects of the Invention

[0010] According to an embodiment of the present invention, it is possible to provide a heater and an image forming apparatus that can suppress warping of the heater and suppress an increase in the heat capacity of the heater.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0012] Hereinafter, embodiments will be exemplified with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and detailed descriptions thereof are appropriately omitted. In addition, the arrows X, Y, and Z in each drawing represent three mutually orthogonal directions. For example, the longitudinal direction of the substrate is the X direction, the short-side direction (width direction) of the substrate is the Y direction, and the direction perpendicular to the plane of the substrate (thickness direction) is the Z direction.

[0013] (Heater) FIG. 1 is a schematic front view for exemplifying the heater 1 according to the present embodiment. Note that FIG. 1 is a view of the heater 1 seen from the side where the heat generating portion 30 is provided. FIG. 2 is a schematic rear view for exemplifying the heater 1. Note that FIG. 2 is a view of the heater 1 seen from the side opposite to the side where the heat generating portion 30 is provided. FIG. 3 is a schematic cross-sectional view of the heater 1 in the A-A line direction in FIG. 1. As shown in FIGS. 1 to 3, the heater 1 has, for example, a substrate 10, an insulating portion 20, a heating portion 30, a wiring portion 40, and a protection portion 50.

[0014] The substrate 10 is plate-shaped and has a surface 10a and a surface 10b facing the surface 10a. The substrate 10 extends in the X direction. The shape of the substrate 10 as viewed from the Z direction is, for example, a long rectangle. The thickness of the substrate 10 is, for example, about 0.5 mm to 1.0 mm. The dimensions of the substrate 10 in the X direction and the dimensions of the substrate 10 in the Y direction can be appropriately changed according to the size of the object to be heated (for example, paper).

[0015] The substrate 10 has heat resistance and is formed of a material with high thermal conductivity. The substrate 10 is formed of, for example, a metal such as stainless steel or an aluminum alloy. If the substrate 10 is formed of a metal, the rigidity of the substrate 10 can be improved and the manufacturing cost can be reduced.

[0016] The insulating portion 20 is provided on one surface 10a of the substrate 10. The insulating portion 20 covers, for example, the region of the surface 10a of the substrate 10 where the heating portion 30 is provided. The insulating portion 20 can also cover the entire region of the surface 10a of the substrate 10. The insulating portion 20 is formed of a material having heat resistance and insulation properties. The insulating portion 20 can be formed of, for example, an inorganic material. The material of the insulating portion 20 and the linear expansion coefficient of the material of the insulating portion 20 will be described later.

[0017] The heating portion 30 converts the applied electric power into heat (Joule heat). The heating portion 30 is provided on the insulating portion 20. The heating portion 30 and the substrate 10 are insulated by the insulating portion 20. The heating portion 30 has, for example, a heating element 31 and a heating element 32. As an example, the case where the heating element 31 and the heating element 32 are provided is illustrated, but the number and size of the heating elements can be appropriately changed according to the size of the substrate 10 and the size of the object to be heated. Also, a plurality of types of heating elements having different lengths, widths, shapes, materials, etc. can be provided. That is, at least one heating element may be provided.

[0018] The heating elements 31 and 32 can be arranged side by side with a predetermined interval in, for example, the Y direction (the short side direction of the substrate 10). The heating elements 31 and 32 extend, for example, in the X direction (the long side direction of the substrate 10).

[0019] The dimensions (length dimensions) of the heating elements 31 and 32 in the X direction can be, for example, the same or different. In this case, it is preferable that the centers of the heating elements 31 and 32 are located on the straight line 1a. That is, each of the heating elements 31 and 32 preferably has a shape that is line-symmetric with the straight line 1a as the axis of symmetry.

[0020] When attaching the heater 1 to the image forming apparatus 100, for example, the straight line 1a is made to overlap with the center line of the conveyance path of the object to be heated. By doing so, even when the dimension of the object to be heated in the direction orthogonal to the conveyance direction changes, the object to be heated can be heated substantially uniformly.

[0021] The electric resistance values of the heating elements 31 and 32 can be the same or different. For example, by making the dimensions (length dimensions) in the X direction, the dimensions (width dimensions) in the Y direction, and the dimensions (thickness dimensions) in the Z direction of the heating elements 31 and 32 the same, the electric resistance values of the heating elements 31 and 32 can be made the same. Also, by changing at least any of these dimensions, the electric resistance values of the heating elements 31 and 32 can be made different. Also, by changing the material, the electric resistance values of the heating elements 31 and 32 can be made different.

[0022] Also, the electric resistance per unit length of the heating element 31 can be made uniform in the X direction. For example, the dimensions (width dimensions) in the Y direction and the dimensions (thickness dimensions) in the Z direction of the heating element 31 can be made constant. The shape of the heating element 31 as viewed from the Z direction can be, for example, a rectangle extending in the X direction.

[0023] Also, the electrical resistance value per unit length of the heating element 32 can be made uniform in the X direction. For example, the dimensions (width dimension) in the Y direction and the dimensions (thickness dimension) in the Z direction of the heating element 32 can be made constant. The shape of the heating element 32 as viewed from the Z direction can be, for example, a rectangle extending in the X direction.

[0024] The heating element 31 and the heating element 32 are formed using, for example, ruthenium oxide (RuO2), a silver - palladium (Ag - Pd) alloy, or the like. The heating element 31 and the heating element 32 can be formed, for example, by applying a paste - like material onto the insulating portion 20 using a screen printing method or the like and curing it using a firing method or the like.

[0025] The wiring portion 40 is provided on the insulating portion 20. The wiring portion 40 has, for example, terminals 41, 42, wiring 43, wiring 44, and wiring 45.

[0026] The terminals 41 and 42 are provided, for example, in the vicinity of one end of the substrate 10 in the X direction. The terminals 41 and 42 are provided side - by - side in the X direction. The terminals 41 and 42 are electrically connected to, for example, a controller 210 of an image forming apparatus 100 to be described later via a connector, wiring, or the like.

[0027] The wiring 43 is provided, for example, on the side of the substrate 10 where the terminal 41 is provided in the X direction. The wiring 43 extends in the X direction. The wiring 43 is electrically connected to the terminal 41 and the end portion of the heating element 31 on the terminal 41 side.

[0028] The wiring 44 is provided, for example, in the vicinity of the end of the substrate 10 on the side opposite to the side where the terminals 41 and 42 are provided in the X direction. The end portion of the heating element 31 on the side opposite to the wiring 43 side and the end portion of the heating element 32 on the side opposite to the wiring 45 side are electrically connected to the wiring 44. That is, the heating element 31 and the heating element 32 are connected in series.

[0029] The wiring 45 is provided, for example, in the X direction on the side of the substrate 10 where the terminals 42 are provided. The wiring 45 extends in the X direction. The wiring 45 is electrically connected to the terminal 42 and the end portion of the heating element 32 on the side of the terminal 42.

[0030] The wiring portion 40 (terminals 41, 42, and wirings 43 to 45) is formed, for example, using a material containing silver, copper, or the like. For example, the terminals 41, 42, and wirings 43 to 45 can be formed by applying a paste-like material onto the insulating portion 20 using a screen printing method or the like and curing it using a firing method or the like.

[0031] The protection portion 50 is provided on the insulating portion 20 and covers the heating portion 30 (heating elements 31 and 32) and a part of the wiring portion 40 (wirings 43, 44, and 45). In this case, the terminals 41 and 42 of the wiring portion 40 are exposed from the protection portion 50.

[0032] The protection portion 50 extends in the X direction. The protection portion 50 has, for example, a function of insulating a part of the heating portion 30 and the wiring portion 40, a function of transferring the heat generated in the heating portion 30 to the outside, and a function of protecting a part of the heating portion 30 and the wiring portion 40 from external force, corrosive gas, or the like. The protection portion 50 has heat resistance and insulation properties and is formed from a material having high chemical stability and thermal conductivity. The protection portion 50 is formed, for example, from an inorganic material.

[0033] Also, the heater 1 can further be provided with a detection portion for detecting the temperature of the heating portion 30 or the temperature of the substrate 10. The detection portion is, for example, a thermistor or the like. The detection portion can be provided on at least either the side of the substrate 10 where the heating portion 30 is provided or the side of the substrate 10 opposite to the side where the heating portion 30 is provided. For example, the detection portion and the wiring and terminals electrically connected to the detection portion can be provided on the insulating portion 20. In this case, the detection portion and the wiring can be covered by the protection portion 50. The terminals electrically connected to the detection portion can be exposed from the protection portion 50.

[0034] Here, as described above, the substrate 10 is formed of a metal such as stainless steel or an aluminum alloy. On the other hand, the insulating portion 20 and the protective portion 50 are formed of an inorganic material. Therefore, the linear expansion coefficient of the material of the substrate 10 is different from the linear expansion coefficients of the materials of the insulating portion 20 and the protective portion 50. Further, when the heating portion 30 is caused to generate heat during the use of the heater 1, the substrate 10, the insulating portion 20, and the protective portion 50 are heated. When the insulating portion 20, the heating portion 30, the wiring portion 40, and the protective portion 50 are fired during the manufacture of the heater 1, the substrate 10, the insulating portion 20, and the protective portion 50 are heated. Therefore, thermal stress is generated due to the difference in the linear expansion coefficients of the materials during the use or manufacture of the heater 1. When thermal stress is generated on one surface 10a side of the substrate 10, the heater 1 is likely to warp.

[0035] In addition, when the length of the substrate 10 in the short side direction (width direction: for example, the Y direction) is short, or the length of the substrate 10 in the long side direction (for example, the X direction) is long, or the thickness of the substrate 10 is thin, the heater 1 is more likely to warp. When the heater 1 warps, the distance between the heater 1 and the object to be heated varies, and there is a possibility that heating unevenness may occur in the object to be heated.

[0036] In this case, if a layer formed of an inorganic material is provided on the other surface 10b of the substrate 10, the thermal stress generated on one surface 10a side of the substrate 10 can be offset by the thermal stress generated on the other surface 10b side of the substrate 10. Therefore, it is possible to suppress the occurrence of warping in the heater 1 during the use or manufacture of the heater 1.

[0037] In this case, in order to offset the thermal stress, it is preferable to provide a layer having a volume equivalent to the volumes of the insulating portion 20 and the protective portion 50 on the surface 10b of the substrate 10. However, when a layer having such a volume is provided on the surface 10b of the substrate 10, the heat capacity of the heater 1 increases. When the heat capacity of the heater 1 increases, new problems occur such that it takes time for the heater 1 to increase in temperature or for the heater 1 to cool down.

[0038] Therefore, in the heater 1 according to the present embodiment, the thermal stress generated between the substrate 10 and the insulating portion 20 is offset by the thermal stress generated between the insulating portion 20 and the protective portion 50. In this case, the magnitude of the thermal stress is affected by the difference in the linear expansion coefficients of the materials of the insulating portion 20 and the protective portion 50 and the thicknesses of the insulating portion 20 and the protective portion 50.

[0039] For example, the linear expansion coefficient of the material of the insulating portion 20 can be made smaller than the linear expansion coefficient of the material of the substrate 10. Also, the linear expansion coefficient of the material of the protective portion 50 can be made larger than the linear expansion coefficient of the material of the insulating portion 20.

[0040] For example, the linear expansion coefficient of stainless steel is about 10.4×10 -6 / K.

[0041] Here, there are some ceramics whose linear expansion coefficients are smaller than those of metals such as stainless steel. For example, the linear expansion coefficient of aluminum oxide is about 7.2×10 -6 / K, the linear expansion coefficient of silicon nitride is about 2.6×10 -6 / K, and the linear expansion coefficient of silicon carbide is about 4.4×10 -6 / K.

[0042] Also, there are some glasses whose linear expansion coefficients are smaller than those of metals. For example, the linear expansion coefficient of soda-lime glass is about 9×10 -6 / K, the linear expansion coefficient of borosilicate glass is about 3×10 -6 / K, and the linear expansion coefficient of fused silica is about 0.6×10 -6 / K.

[0043] As described above, there are some ceramics and glasses whose linear expansion coefficients are smaller than those of metals. Therefore, for example, the insulating portion 20 may be formed of a ceramic or a glass having a small linear expansion rate, and the protective portion 50 may be formed of a ceramic or a glass having a large linear expansion rate.

[0044] For example, the material of the substrate 10 may be stainless steel, the material of the insulating portion 20 may be quartz glass, borosilicate glass, silicon nitride, silicon carbide, etc., and the material of the protective portion 50 may be aluminum oxide, soda-lime glass, etc.

[0045] In this way, for example, when the insulating portion 20 is formed on the surface 10a of the substrate 10, a thermal stress is generated between the substrate 10 and the insulating portion 20 such that the surface 10a of the substrate 10 warps toward the insulating portion 20 side. Further, when the protective portion 50 is formed on the insulating portion 20, a thermal stress is generated between the insulating portion 20 and the protective portion 50 such that the surface 10a of the substrate 10 warps toward the side opposite to the insulating portion 20 side. Therefore, the thermal stress generated between the substrate 10 and the insulating portion 20 can be offset by the thermal stress generated between the insulating portion 20 and the protective portion 50.

[0046] Further, for example, the linear expansion coefficient of the material of the insulating portion 20 can be made larger than the linear expansion coefficient of the material of the substrate 10. Also, the linear expansion coefficient of the material of the protective portion 50 can be made smaller than the linear expansion coefficient of the material of the insulating portion 20.

[0047] For example, the material of the substrate 10 may be stainless steel, and the insulating portion 20 may be formed using a glass having a linear expansion coefficient larger than that of stainless steel. For example, the linear expansion coefficient of a glass containing BaO·SiO2·ZnO as a main component is about 11.9 -6 / K. The linear expansion coefficient of a glass containing SiO2·TiO2·R2O as a main component is about 11.3 -6 / K. The linear expansion coefficient of a glass containing La2O3·B2O3·ZnO as a main component is about 11.3 -6 / K. Also, the material of the protective portion 50 may be quartz glass, borosilicate glass, silicon nitride, silicon carbide, aluminum oxide, soda-lime glass, etc.

[0048] In this way, for example, when the insulating portion 20 is formed on the surface 10a of the substrate 10, a thermal stress is generated between the substrate 10 and the insulating portion 20 such that the surface 10a of the substrate 10 warps to the side opposite to the insulating portion 20 side. Further, when the protective portion 50 is formed on the insulating portion 20, a thermal stress is generated between the insulating portion 20 and the protective portion 50 such that the surface 10a of the substrate 10 warps to the insulating portion 20 side. Therefore, the thermal stress generated between the substrate 10 and the insulating portion 20 can be offset by the thermal stress generated between the insulating portion 20 and the protective portion 50.

[0049] By doing as described above, during the use or manufacture of the heater 1, the warping generated in the heater 1 can be reduced. In addition, since it is not necessary to provide a large-volume layer for offsetting the thermal stress on the surface 10b of the substrate 10, an increase in the heat capacity of the heater 1 can be suppressed. Therefore, the time required for the temperature rise and cooling of the heater 1 can be shortened. That is, the responsiveness of the heater 1 can be improved.

[0050] Further, as described above, the generated thermal stress can be adjusted by the thicknesses of the insulating portion 20 and the protective portion 50. According to the findings obtained by the present inventors, when the linear expansion coefficient of the material of the substrate 10 is x ( / K), the linear expansion coefficient of the material of the protective portion 50 is α ( / K), the thickness of the protective portion 50 is TA (mm), the linear expansion coefficient of the material of the insulating portion 20 is β ( / K), and the thickness of the insulating portion 20 is TB (mm), if it is set such that "0.9 ≦ (TA × (α - x)) / (TB × (x - β)) ≦ 1.1", the generation of warping can be more effectively suppressed.

[0051] FIG. 4 is a schematic cross-sectional view of a heater 11 according to another embodiment. Note that FIG. 4 is a figure corresponding to FIG. 3. In the case of FIG. 3 described above, the insulating portion 20 is integrally formed using the same material. Such an insulating portion 20 is formed, for example, by applying a paste-like material to the surface 10a of the substrate 10 and curing this using a firing method or the like. Further, the insulating portion 20 can also be formed on the surface 10a of the substrate 10 by thermal spraying or the like.

[0052] However, if done in these ways, holes such as pinholes may occur in the formed insulating portion 20. If there are holes such as pinholes, the reliability of the insulation between the heating elements 31 and 32 and the substrate 10 will decrease.

[0053] Also, in the case of FIG. 3 described above, the protection portion 50 is integrally formed using the same material. Such a protection portion 50 is formed, for example, by applying a paste-like material onto the insulating portion 20 and curing it using a firing method or the like. Also, the protection portion 50 can be formed on the insulating portion 20 by thermal spraying or the like.

[0054] However, if done in these ways, holes such as pinholes may occur in the formed protection portion 50. If there are holes such as pinholes, the reliability of the insulation between the heating elements 31 and 32 and the elements of the image forming apparatus 100 in the vicinity of the heater 11 will decrease.

[0055] Therefore, as shown in FIG. 4, the insulating portion 21 is provided with a layer 21a (corresponding to an example of the first layer) and a layer 21b (corresponding to an example of the second layer). The layer 21a is provided on the surface 10a of the substrate 10. The layer 21b is provided on the layer 21a. For example, the layer 21a and the layer 21b can be alternately laminated. Note that the number (number of laminations) of the layer 21a and the layer 21b is not limited to the example shown, and at least one of the layer 21a and the layer 21b may be provided.

[0056] The material of the layer 21a can be, for example, the same as the material of the insulating portion 20 described above. The material of the layer 21b can be, for example, the same as the material of the protection portion 50 described above. The respective thicknesses of the layer 21a and the layer 21b can be made thinner than the thickness of the insulating portion 20.

[0057] Also, as shown in FIG. 4, the protection part 51 is provided with a layer 51a (corresponding to an example of the third layer) and a layer 51b (corresponding to an example of the fourth layer). The layer 51b is provided on the layer 21a of the insulating part 20. The layer 51a is provided on the layer 51b. For example, the layer 51b and the layer 51a can be alternately laminated. Note that the number (number of laminations) of the layer 51b and the layer 51a is not limited to the exemplified ones, and at least one layer 51b and one layer 51a may be provided.

[0058] The material of the layer 51b can be the same as the material of the protection part 50 described above, for example. The material of the layer 51a can be the same as the material of the insulating part 20 described above, for example. The respective thicknesses of the layer 51a and the layer 51b can be made thinner than the thickness of the protection part 50.

[0059] Since the uppermost layer of the insulating part 21 exemplified in FIG. 4 is the layer 21a, the lowermost layer of the protection part 51 is the layer 51b. However, when the uppermost layer of the insulating part 21 is the layer 21b, the lowermost layer of the protection part 51 can be the layer 51b. For example, a layer containing the same material as the insulating part 20 and a layer containing the same material as the protection part 50 may be alternately laminated to form the insulating part 21 and the protection part 51. In this case, the insulating part 21 may be provided below the layer provided with the heating elements 31 and 32, and the protection part 51 may be provided above the layer provided with the heating elements 31 and 32.

[0060] The formation methods of layer 21a and layer 21b can be the same as the formation method of the insulation part 20 described above. The formation methods of layer 51a and layer 51b can be the same as the formation method of the protection part 50 described above. In this case, in each of layer 21a, layer 21b, layer 51a, and layer 51b, holes such as pinholes may occur. However, since these layers are sequentially formed in the stacking direction, it is almost impossible for the holes in the upper layer and the holes in the lower layer to communicate with each other. Therefore, the reliability of insulation between the heating elements 31 and 32 and the substrate 10, and the reliability of insulation between the heating elements 31 and 32 and the elements of the image forming apparatus 100 near the heater 11 can be improved.

[0061] Also, even if the insulation part 20 is composed of a plurality of layers of the same material stacked, or the protection part 50 is composed of a plurality of layers of the same material stacked, the reliability of insulation can be improved. However, if the insulation part 21 is composed of a plurality of layers of different materials (different linear expansion coefficients) stacked, and the protection part 51 is composed of a plurality of layers of different materials (different linear expansion coefficients) stacked, it becomes easier to cancel out the thermal stress. Therefore, when the heater 11 is in use or during the manufacture of the heater 11, the warping generated in the heater 11 can be further reduced.

[0062] Also, the generated thermal stress can be adjusted by the thicknesses of layer 21a, layer 21b, layer 51a, and layer 51b. According to the findings obtained by the present inventors, when the linear expansion coefficient of the material of the substrate 10 is x ( / K), the linear expansion coefficient of the materials of layer 21b and layer 51b is α ( / K), the total thickness of layer 21b and layer 51b is TAa (mm), the linear expansion coefficient of the materials of layer 21a and layer 51a is β ( / K), and the total thickness of layer 21a and layer 51a is TBa (mm), if "0.9 ≦ (TAa × (α - x)) / (TBa × (x - β)) ≦ 1.1", the occurrence of warping can be more effectively suppressed.

[0063] Note that the above is the case where the linear expansion coefficients of the materials of layer 21b and layer 51b are the same, and the linear expansion coefficients of the materials of layer 21a and layer 51a are the same. However, the linear expansion coefficients and thicknesses of the materials of each layer may be different from each other.

[0064] In such a case, it is sufficient to satisfy the following formula.

[0065]

Equation

[0066] (Image forming apparatus) In one embodiment of the present invention, an image forming apparatus 100 including a heater 1 can be provided. The above description regarding the heater 1 and the modified examples of the heater 1 (for example, the heater 11 and those obtained by appropriately adding, deleting, or modifying components by those skilled in the art and having the features of the present invention) can all be applied to the image forming apparatus 100.

[0067] Also, hereinafter, as an example, the case where the image forming apparatus 100 is a copying machine will be described. However, the image forming apparatus 100 is not limited to a copying machine, and any apparatus provided with a heater may be used. For example, the image forming apparatus 100 may be a printer, a rewritable card reader / writer, or the like.

[0068] FIG. 5 is a schematic diagram for exemplifying the image forming apparatus 100 according to the present embodiment. FIG. 6 is a schematic diagram for exemplifying the fixing unit 200. As shown in FIG. 5, the image forming apparatus 100 includes, for example, a frame 110, an illumination unit 120, an imaging element 130, a photosensitive drum 140, a charging unit 150, a discharging unit 151, a developing unit 160, a cleaner 170, a storage unit 180, a conveyance unit 190, a fixing unit 200, and a controller 210.

[0069] Frame 110 is box-shaped and houses, inside thereof, an illumination unit 120, an imaging element 130, a photosensitive drum 140, a charging unit 150, a developing unit 160, a cleaner 170, a part of a storage unit 180, a conveying unit 190, a fixing unit 200, and a controller 210. On the upper surface of frame 110, a window 111 made of a light-transmitting material such as glass can be provided. On window 111, an original document 500 to be copied is placed. Also, a moving unit for moving the position of original document 500 can be provided.

[0070] The illumination unit 120 is provided near window 111. The illumination unit 120 has, for example, a light source 121 such as a lamp, and a reflecting mirror 122. The imaging element 130 is provided near window 111. The photosensitive drum 140 is provided below the illumination unit 120 and the imaging element 130. The photosensitive drum 140 is rotatably provided. On the surface of the photosensitive drum 140, for example, a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer is provided. The charging unit 150, the discharging unit 151, the developing unit 160, and the cleaner 170 are provided around the photosensitive drum 140.

[0071] The storage unit 180 has, for example, a cassette 181 and a tray 182. The cassette 181 is detachably attached to one side portion of the frame 110. The tray 182 is provided on the side portion of the frame 110 opposite to the side where the cassette 181 is attached. In the cassette 181, paper 510 (for example, blank paper) before copying is stored. In the tray 182, paper 511 on which a copied image 511a is fixed is stored.

[0072] The conveying unit 190 is provided below the photosensitive drum 140. The conveying unit 190 conveys the paper 510 between the cassette 181 and the tray 182. The conveying unit 190 has, for example, a guide 191 for supporting the conveyed paper 510, and conveying rollers 192 to 194 for conveying the paper 510. Also, a motor for rotating the conveying rollers 192 to 194 can be provided in the conveying unit 190.

[0073] The fixing unit 200 is provided on the downstream side (the side of the tray 182) of the photosensitive drum 140. As shown in FIG. 6, the fixing unit 200 has, for example, a heater 1, a stay 201, a film belt 202, and a pressure roller 203. The heater 1 is attached to the stay 201 on the conveyance line side of the paper 510. The heater 1 can be embedded in the stay 201. In this case, the side of the heater 1 where the protection part 50 is provided is exposed from the stay 201.

[0074] The film belt 202 covers the stay 201 provided with the heater 1. The film belt 202 can contain, for example, a resin having heat resistance such as polyimide.

[0075] The pressure roller 203 is provided so as to face the stay 201. The pressure roller 203 has, for example, a core metal 203a, a drive shaft 203b, and an elastic part 203c. The drive shaft 203b protrudes from the end of the core metal 203a and is connected to a drive device such as a motor. The elastic part 203c is provided on the outer surface of the core metal 203a. The elastic part 203c is formed of an elastic material having heat resistance. The elastic part 203c can contain, for example, a silicone resin or the like.

[0076] The controller 210 is provided inside the frame 110. The controller 210 has, for example, an arithmetic unit such as a CPU (Central Processing Unit), and a storage unit in which a control program is stored. The arithmetic unit controls the operations of the respective elements provided in the image forming apparatus 100 based on the control program stored in the storage unit. Further, the controller 210 can also include an operation unit for the user to input copy conditions and the like, a display unit for displaying the operation state, an abnormality display, and the like. Note that since known techniques can be applied to the control of the respective elements provided in the image forming apparatus 100, detailed description thereof is omitted.

[0077] As described above, several embodiments of the present invention have been illustrated. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalent scope thereof. In addition, the above-described embodiments can be implemented in combination with each other.

[0078] Hereinafter, appendices related to the above-described embodiments are shown.

[0079] (Appendix 1) A substrate containing a metal and extending in one direction; An insulating portion provided on one surface of the substrate; A heating element provided on the insulating portion and extending in the longitudinal direction of the substrate; A protective portion provided on the insulating portion and covering the heating element; Comprising: The linear expansion coefficient of the material of the insulating portion is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is larger than the linear expansion coefficient of the material of the insulating portion, Or A heater in which the linear expansion coefficient of the material of the insulating portion is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is smaller than the linear expansion coefficient of the material of the insulating portion.

[0080] (Appendix 2) When the linear expansion coefficient of the material of the substrate is x ( / K), the linear expansion coefficient of the material of the protective portion is α ( / K), the thickness of the protective portion is TA (mm), the linear expansion coefficient of the material of the insulating portion is β ( / K), and the thickness of the insulating portion is TB (mm), the heater according to Appendix 1 that further satisfies the following formula. 0.9 ≦ (TA × (α - x)) / (TB × (x - β) ≦ 1.1

[0081] (Appendix 3) A substrate containing a metal and extending in one direction; An insulating portion provided on one surface of the substrate, having a first layer and a second layer laminated on the first layer; A heating element provided on the insulating portion and extending in the longitudinal direction of the substrate; A protection portion provided on the insulating portion, covering the heating element, having a third layer and a fourth layer laminated on the third layer; Comprising: The linear expansion coefficient of the material of the first layer is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the second layer is larger than the linear expansion coefficient of the material of the first layer. The linear expansion coefficient of the material of the third layer is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the fourth layer is larger than the linear expansion coefficient of the material of the third layer. Or, The linear expansion coefficient of the material of the first layer is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the second layer is smaller than the linear expansion coefficient of the material of the first layer. The linear expansion coefficient of the material of the third layer is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the fourth layer is smaller than the linear expansion coefficient of the material of the third layer. A heater.

[0082] (Appendix 4) When the linear expansion coefficient of the material of the substrate is x ( / K), the linear expansion coefficient of the material of the first layer and the third layer is α ( / K), the total thickness of the first layer and the third layer is TAa (mm), the linear expansion coefficient of the material of the second layer and the fourth layer is β ( / K), and the total thickness of the second layer and the fourth layer is TBa (mm), the heater according to Appendix 3 further satisfying the following formula. 0.9 ≦ (TAa × (α - x)) / (TBa × (x - β) ≦ 1.1

[0083] (Appendix 5) An image forming apparatus including the heater according to any one of Appendices 1 to 4.

Explanation of Reference Numerals

[0084] 1 heater, 10 substrate, 10a surface, 11 heater, 20 insulating part, 21 insulating part, 21a layer, 21b layer, 30 heating part, 31 heating element, 32 heating element, 50 protection part, 51 protection part, 51a layer, 51b layer, 100 image forming apparatus, 200 fixing part

Claims

Claim 1 A substrate containing a metal and extending in one direction; An insulating portion provided on one surface of the substrate; A heating element provided on the insulating portion and extending in the longitudinal direction of the substrate; A protective portion provided on the insulating portion and covering the heating element; Comprising: The linear expansion coefficient of the material of the insulating portion is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is larger than the linear expansion coefficient of the material of the insulating portion, Or A heater in which the linear expansion coefficient of the material of the insulating portion is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the protective portion is smaller than the linear expansion coefficient of the material of the insulating portion. Claim 2 When the linear expansion coefficient of the material of the substrate is x ( / K), the linear expansion coefficient of the material of the protective portion is α ( / K), the thickness of the protective portion is TA (mm), the linear expansion coefficient of the material of the insulating portion is β ( / K), and the thickness of the insulating portion is TB (mm), the heater according to Claim 1, which further satisfies the following formula. 0.9 ≤ (TA × (α - x)) / (TB × (x - β)) ≤ 1.1 Claim 3 A substrate containing a metal and extending in one direction; An insulating portion provided on one surface of the substrate, having a first layer and a second layer laminated on the first layer; A heating element provided on the insulating portion and extending in the longitudinal direction of the substrate; A protective portion provided on the insulating portion, covering the heating element, and having a third layer and a fourth layer laminated on the third layer; Comprising: The linear expansion coefficient of the material of the first layer is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the second layer is larger than the linear expansion coefficient of the material of the first layer, The linear expansion coefficient of the material of the third layer is smaller than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the fourth layer is larger than the linear expansion coefficient of the material of the third layer, Or The linear expansion coefficient of the material of the first layer is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the second layer is smaller than the linear expansion coefficient of the material of the first layer, A heater in which the linear expansion coefficient of the material of the third layer is larger than the linear expansion coefficient of the material of the substrate, and the linear expansion coefficient of the material of the fourth layer is smaller than the linear expansion coefficient of the material of the third layer. Claim 4 When the linear expansion coefficient of the material of the substrate is x ( / K), the linear expansion coefficient of the materials of the first layer and the third layer is α ( / K), the total thickness of the first layer and the third layer is TAa (mm), the linear expansion coefficient of the materials of the second layer and the fourth layer is β ( / K), and the total thickness of the second layer and the fourth layer is TBa (mm), the heater according to claim 3, which further satisfies the following formula. 0.9 ≤ (TAa × (α - x)) / (TBa × (x - β)) ≤ 1.1

5. An image forming apparatus including the heater according to claim 1.

Images