Method for manufacturing film heater

Abstract

Provided is a method for manufacturing a novel film heater which is required to be thin, lightweight, and space-saving, is suitable for use in heating a site in contact with the human body, and can be manufactured at low cost. A method for manufacturing a film heater in which a heating element is manufactured by separating a film, which includes a base film, a conductive layer formed on the upper surface of the base film, and a coating layer formed on the upper surface of the conductive layer, into a predetermined shape. It is preferable that the conductive layer and the coating layer are formed by a sputtering method, the conductive layer has a resistivity of 10 [mu] [omega] cm or less and is mainly composed of any one of Al, Cu and Ag, and the coating layer is a non-magnetic alloy film mainly composed of any one of Ti, Cr, Mo and Ni.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a film heater. Background Art

[0002] In recent years, from the viewpoint of environmental protection, electrification has been gradually promoted for automobiles, motorcycles, etc. that are powered by internal combustion engines. In automobiles, a heater including a heat exchanger and a fan is provided in the interior using the heat generated by the engine, and warm air is blown into the interior space for heating. Therefore, there is a drawback that the effect of the heater cannot be obtained before the engine warms up. Furthermore, for electric vehicles, there is the following problem: if an electric heater is used to heat the space, the battery is consumed and the driving distance becomes shorter. Therefore, a method of directly heating by providing a heater on the steering wheel or seat that people often touch has been adopted.

[0003] For these heaters, the following methods are used: a method of forming a heating wire by spirally winding a linear or foil-shaped strip of metal as a heating element around a filamentous insulating wire having heat resistance and strength, and incorporating it into a cloth in the form of a high-density wiring pattern (Patent Document 1); or a method of photoetching a copper plate into a shape of a thin and long-path wiring and embedding it in a resin of a required shape to form a heater (Patent Document 2).

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-157824

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 10-22065 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The heater is an excellent technology with sufficient heat generation performance and shape followability, etc. On the other hand, there are problems of complex manufacturing processes and high costs. Therefore, it is limited to being applied to some expensive vehicles or vehicles of customers who accept the price increase.

[0010] Therefore, an object of the present invention is to provide a novel thin heater, i.e., a film heater, that can be manufactured at low cost.

[0011] Technical Means for Solving the Problems

[0012] In view of the above problems, the inventor of the present invention has made intensive studies on a thin heat-generating body that can be manufactured at low cost. As a result, it has been found that by forming a thin film on a film and separating it into a specified size, a film heater having a resistance value as a heat-generating body can be obtained at low cost, and thus the present invention has been completed.

[0013] That is, the present invention is a method for manufacturing a film heater, characterized in that a film comprising a base film, a conductive layer formed on the upper surface of the base film, and a coating layer formed on the upper surface of the conductive layer is separated into a specified shape to form a heat-generating body.

[0014] In addition, preferably, the base film is an insulating resin.

[0015] In addition, preferably, the thickness of the conductive layer is 1000 nm or less, and the thickness of the coating layer is 10 nm to 200 nm.

[0016] In addition, preferably, the conductive layer and the coating layer are formed by sputtering. Preferably, the resistivity of the conductive layer is 10 μΩcm or less, and any one of Al, Cu, and Ag is used as the main component.

[0017] In addition, preferably, the coating layer contains a non-magnetic alloy film having any one of Ti, Cr, Mo, and Ni as the main component.

[0018] In addition, preferably, the coating layer is an alloy having Mo as the main component and containing 60 at% or less of Ni and Ti in total.

[0019] In addition, preferably, the coating layer is an alloy having Ni as the main component and containing 60 at% or less of Cu, Mn, and Mo in total.

[0020] Effect of the Invention

[0021] By the present invention, it is possible to provide a thin, lightweight, and low-cost film heater to replace an expensive heater manufactured by processing a copper wire or a copper foil. Description of the Drawings

[0022] Figure 1 is an example of a cross-sectional schematic view of the film heater of the present invention.

[0023] Figure 2 is a photograph of the appearance of the film heater of the present invention example. Detailed Description of the Invention

[0024] ​​One of the important features of the film heater of the present invention lies in a method for manufacturing a film heater: after forming a conductive layer on a film and a coating layer covering the conductive layer, it is separated into a specified size, thereby manufacturing a heater having a specified resistance value. Hereinafter, the film heater of the present invention will be described in detail. The film heater of the present invention can be applied to, for example, the following uses: uses for heating parts in contact with the human body, such as a steering wheel heater of an automobile or a handlebar heater of a motorcycle, which are required to be thin, lightweight, and space-saving; or uses for winding pipes that are required to be flexible, moisture-resistant and not corroded due to surface heating and condensation, etc., and that promote the gasification of liquefied fuel or heat low-temperature gaseous fuel. In addition, the film heater obtained by the manufacturing method of the present invention includes a base film, a conductive layer formed on the upper surface of the base film, and a coating layer formed on the upper surface of the conductive layer.

[0025] Copper is a conductor with a low resistance value. In order to make a heating element, it is necessary to make a thin wire with a small cross-sectional area and extend its path to increase the resistance value. Therefore, as described above, the following methods are used: a method of insulating a copper wire processed into a thin wire so that it does not short-circuit even when densely arranged, and fixing it in a fiber in a specified shape with a longer path to make a heater; or a method of making a copper foil into a thin specified shape through a photo-etching process and embedding it in resin to make a heater. The photo-etching process requires processing using an expensive exposure machine, photoresist, or chemical solution, and then cleaning with an organic solvent or a large amount of pure water, etc., resulting in high costs.

[0026] In addition, the diameter of the thin wire that can usually be obtained required in the above method is about several hundred micrometers, and even the copper foil obtained by further thinning the copper plate has a thickness of about several tens of micrometers. For thin wires or thin foils of this level or above, due to further special processing, they are expensive and difficult to handle.

[0027] In contrast, the present invention can inexpensively manufacture a film heater as a film-like heating element by adjusting the thickness of the thin conductive layer formed on the base film and cutting it together with the base film to make a heating element having a specified resistance value. For example, it can also contribute to reducing the environmental load caused by the increase in power consumption of automobiles or motorcycles.

[0028] In addition, the film formed with the thin conductive layer of the present invention can be cut into stripes to make a film heater, or can also be cut into a ladder shape or a spiral shape with a resistance value required for heating a broad area. In addition, the separation method can be cutting with a tool such as scissors or a cutting knife, or a method of irradiating a laser to burn it into a complex shape.

[0029] The base film of the film heater of the present invention is preferably made of an insulating resin. This is to prevent electrical short circuits caused by contact between the conductive layer and other metals, etc. For example, it can be an inexpensive polyethylene terephthalate (PET) film, or a polyimide film with higher heat resistance, as long as it is selected according to the temperature range of heat generation. Regarding its thickness, as long as it has the strength required for processing the film heater and the flexibility for easy operation, the thinner it is, the better, and it is easier to cut into a film heater. Furthermore, it is preferably formed by laminating an insulating film having a shape conforming to the shape of the conductive layer formed surface of the film heater after cutting. In addition, in order to improve the adhesion, a film having the same composition as the coating layer can also be formed as a base layer between the base film and the conductive layer. In addition, when forming the base layer, the thickness can be set to 10 nm to 200 nm. Moreover, the lower limit of the thickness of the preferred base layer can be set to 20 nm, and the upper limit of the thickness of the preferred base layer can be set to 100 nm.

[0030] For the formation of the conductive layer or the coating layer in the film heater of the present invention, sputtering is preferably used. Among the methods for forming the conductive layer, there are plating methods as one of the wet methods or several physical vapor deposition methods formed in a vacuum as the dry method. However, in order to suppress the deterioration or shrinkage of the resin film due to heat and to form the conductive layer stably over a large area, sputtering is most suitable.

[0031] Regarding the conductive layer of the film heater of the present invention, even if it is thin, conductivity is required. In terms of resistivity, it is suitable to easily obtain an alloy having any one of Al, Cu, and Ag as the main component (including 80 at% or more) or a pure metal with a purity of 98% or more. In addition, it is ideal to use Al or Cu, which is cheaper than expensive Ag. Furthermore, considering the long-term reliability such as heating at high temperatures or electromigration, it is more suitable to use Cu with a melting point higher than Al as the main component.

[0032] The coating layer used in the film heater of the present invention protects the conductive layer from the influence of the external environment. Moreover, in order to improve the environmental resistance for suppressing the corrosion of the conductive layer or the adhesion to the film substrate (base film) when forming a film having the same composition as the coating layer as the base layer, a non-magnetic alloy film mainly composed of Ti, Cr, Mo, or Ni is ideal. The reason for using non-magnetic is that in the case of using a magnetron sputtering method with a high film formation rate, if it is a magnetic material, in order to obtain a film formation rate, a target with a very thin thickness needs to be used, resulting in a reduction in the life of the target and a decrease in productivity.

[0033] In addition, the so-called "environmental resistance" means that it can suppress surface deterioration under high-temperature and high-humidity environments and heating in the atmosphere, which can be confirmed by color change, and can be quantitatively evaluated by reflectance, for example.

[0034] Cr or Ti is a metal with high corrosion resistance. However, when formed by sputtering, Cr has high internal stress and the film sometimes warps. Ti and Ni sometimes thermally diffuse into Cu at high temperatures, increasing the resistance. Mo is an element that can easily suppress film warping, has low stress, and is not prone to thermal diffusion into Al, Ag, or Cu as conductive films. However, it has the following drawbacks: low tolerance to high temperature and high humidity, and since it is a high melting point metal, it is prone to embrittlement and cracks are likely to appear inside the film when the film is bent.

[0035] Therefore, in order to improve moisture resistance and form an amorphous structure that is not prone to cracks, it is preferably a Mo alloy added with Ni or Ti. The total content of Ni and Ti is preferably 60 at% or less, and more preferably contains 20 at% - 40 at% of Ni and 5 at% - 30 at% of Ti.

[0036] In addition, in order to improve moisture resistance and enhance the electrical connectivity during soldering for welding bonding with a control substrate or Cu-coated wiring, the coating layer is preferably a Ni alloy added with Cu, Mn, and Mo. The total content of Cu, Mn, and Mo is preferably 60 at% or less, and more preferably contains 10 at% - 40 at% of Cu, 7 at% - 25 at% of Mn, and 5 at% - 30 at% of Mo.

[0037] If the thickness of the conductive layer of the film heater of the present invention is thick, the resistance value decreases and it is not easy to generate heat. Therefore, it is preferably thin, and there is a tendency to be set to 1000 nm or less. On the other hand, if it becomes too thin, it is prone to wire breakage due to electromigration or the stress generated by the curvature when bending the film. Therefore, it is considered preferably 100 nm or more. The upper limit of the thickness of the more preferred conductive layer is 800 nm, and the upper limit of the thickness of the further preferred conductive layer is 600 nm or less. Regarding the thickness of the coating layer, in order to suppress the deterioration of the conductive layer caused by moisture on the film surface or permeating through the film, it is preferably at least 10 nm or more. If it is less than 10 nm, there is a tendency for the film continuity to decrease and the protection function to become insufficient. In addition, if it becomes thick, it takes time to form and the productivity decreases. Therefore, the upper limit of the thickness of the coating layer is preferably set to 200 nm or less. The lower limit of the thickness of the more preferred coating layer is 30 nm, and the upper limit of the thickness of the more preferred coating layer is 100 nm.

[0038] In addition, a composite film with both wiring and a magnetic shield can also be made by forming a magnetic film with soft magnetic properties such as permalloy on the lower surface or upper surface of the coating layer.

[0039] Examples

[0040] (Example 1)

[0041] As a base film for manufacturing a film heater, a PET film with a thickness of 100 μm was cut into 200 mm × 100 mm. To form a conductive layer and a coating layer, a sputtering device with the model number: SME-200E manufactured by ULVAC, Inc. was used. The diameter of the target material installed on the sputtering device is 100 mm and the thickness is 5 mm. For the use in conductive films, it is processed from an oxygen-free copper plate with a purity of 4N. For the use in coating layers, powders of Mo, Ni-Mo alloy, and Ti are sintered to form Mo-30Ni-20Ti (atomic %). After brazing these target materials to a copper backplane, they are installed on the sputtering device. The cut PET film is fixed on the substrate holder of the sputtering device, and the vacuum is pumped to 5×10 -5 Pa, then Ar as a sputtering gas is introduced. In an atmosphere of 0.5 Pa, a 30-nm Mo-Ni-Ti alloy as a base layer is formed at a power of 300 W. Then, a 500-nm Cu as a conductive layer is formed at 500 W. After that, a 30-nm Mo-Ni-Ti alloy as a coating layer is formed under the same conditions as the base layer. The cross-section of the layer structure is shown in Figure 1 . In addition, for comparison purposes, only a 500-nm Cu film as a conductive layer was formed on the PET film. The resistivity of the Cu film is 2.1 μΩcm.

[0042] The PET film with a Cu conductive layer and a Mo-Ni-Ti coating layer and the PET film with only a Cu conductive layer were cut into 25 mm × 50 mm and placed in a high-temperature and high-humidity chamber set at a relative humidity of 85% and a temperature of 85°C for 300 hours. As a result, when the Mo-Ni-Ti coating layer was formed, it hardly changed color and had a metallic luster, but when only the Cu conductive layer was formed, it changed color to brownish-yellow. It was confirmed that the moisture resistance was significantly improved by forming the Mo-Ni-Ti coating layer.

[0043] The PET film with a coating layer and a conductive layer was cut into a length of 200 mm and a width of 3 mm using a rotary cutter (manufactured by LION OFFICE PRODUCTS: model RC-B4). A potential of 5 V was applied from both ends, and the temperature of the upper surface of the film was measured. As a result, it was confirmed that the temperature of the heater rose from about 20°C before application to about 45°C, making it feel warm.

[0044] (Example 2)

[0045] As a base film for making a film heater, a polyimide film with a thickness of 50 μm was cut into 280 mm × 100 mm. In order to form a conductive layer and a coating layer, a sputtering device of model number: CS-200 manufactured by ULVAC Co., Ltd. was used. The target material installed on the sputtering device has a diameter of 100 mm and a thickness of 5 mm. For the conductive film use, it is processed from an oxygen-free copper plate with a purity of 4N. The Ni-30Cu-15Mo-10Mn (atomic %) used for the coating layer is made by weighing the electrolytic Ni, oxygen-free copper block, block-shaped Mn and Mo raw materials according to the specified amount, and then making an ingot by the melting casting method in a vacuum melting furnace, and then machining. These target materials are brazed to a copper backing plate and then installed in the sputtering device. The cut polyimide film is fixed on the substrate holder of the sputtering device and evacuated to 7×10 -5 After the sputtering gas Ar was introduced at 0.5 Pa, a Cu conductive layer of 500 nm was formed at 500 W, and then a Ni-Cu-Mo-Mn alloy was formed at 300 W as a coating layer of 20 nm. The cross-section of the layer structure is shown in FIG. Figure 1 (However, the base layer 2 was not formed.) In addition, in the comparative application, only a Cu film as a conductive layer was formed on the polyimide film to a thickness of 500 nm.

[0046] A polyimide film having a Cu conductive layer and a Ni-Cu-Mo-Mn coating layer and a polyimide film having only a Cu conductive layer were compared. Regarding the warping of the film, when the coating layer was formed, it was less and flat, and it was confirmed that the warping could be reduced. The film was cut into 25 mm × 50 mm and placed in a high temperature and high humidity tank set to 85% relative humidity and 85°C for 300 hours. As a result, when the Ni-Cu-Mo-Mn coating layer was formed, it had almost no color change and had a metallic luster, but when only the Cu conductive layer was formed, it changed color to brown. It was confirmed that the moisture resistance can be greatly improved by forming a Ni-Cu-Mo-Mn coating layer.

[0047] Using a rotary cutter (manufactured by LION OFFICE PRODUCTS: model RC - B4), a polyimide film having only a Cu conductive layer and a polyimide film having a coating layer and a conductive layer were cut into stripes with a width of 5 mm and a length of 100 mm. The wire part of the copper - coated wiring with Sn - based solder attached to its end was brought into close contact with a soldering iron heated to about 280°C, melted, and pressed for soldering. Confirmation was carried out using a tester, and conduction was confirmed as a result. In the film having only a Cu conductive layer, the soldering joint was charred and discolored, and when the copper - coated wiring was pulled, it was easily peeled off from the soldering joint. In contrast, in the film having a coating layer and a conductive layer, the discoloration of the soldering joint was less and it did not peel off even when the copper - coated wiring was pulled. It was confirmed that by forming a Ni - Cu - Mo - Mn coating layer on the Cu conductive layer, the oxidation resistance and the soldering joint strength can be improved.

[0048] Furthermore, using scissors and a cutter, a 50 - μm - thick polyimide film having a coating layer and a conductive layer was cut into a crank shape as Figure 2 shown, with a width of about 5 mm, a folded - back length of about 70 mm, and a height of about 80 mm, and wound around a steering wheel with a grip diameter of φ30 mm wound with synthetic leather and an outer diameter of 360 mm. A voltage of 12 V was applied from both ends, and the temperature of the upper surface of the film was measured. As a result, it was confirmed that the temperature was about 20°C before application but rose to about 50°C, and it became a heater.

[0049] (Example 3)

[0050] As the base film for manufacturing the film heater, a 50 - μm - thick polyimide film was cut into 290 mm × 100 mm in the same manner as in Example 2. To form a conductive layer and a coating layer, a sputtering device with the model number CS - 200 manufactured by ULVAC, Inc. was used. In the application of the coating layer, a target material of Mo - 20Ni - 30Ti (atomic %) including a sintering method was used. In the application of the conductive layer, an Al target with a purity of 4N manufactured by Sumitomo Chemical was used, and in the same method as in Example 2, after forming 500 - nm - thick Al as the conductive layer at 500 W, a 50 - nm - thick Mo - Ni - Ti alloy as the coating layer was formed at a power of 300 W. In addition, a comparative example in which only a 500 - nm - thick Al conductive layer was formed on the polyimide film was also prepared. When scratched on the surface with a 2B - hardness pencil, it was confirmed that the Al film was soft and easily left scratches, but the laminated film with a Mo - Ni - Ti coating layer hardly left scratches.

[0051] Using a rotary cutter (manufactured by LION OFFICE PRODUCTS: model RC-B4), a polyimide film formed with a coating layer and a conductive layer was cut into a length of 290 mm and a width of 5 mm. A potential of 5 V was applied from both ends, and the temperature on the upper surface of the film was measured. As a result, it was confirmed that a heater was obtained, where the temperature before application was about 20 °C but rose to about 50 °C, making it feel warm. From the above results, it was confirmed that, similar to the Cu film, even the Al film can be used as a film heater.

[0052] Explanation of reference numerals in the drawings

[0053] 1: Base film

[0054] 2: Base layer

[0055] 3: Conductive layer

[0056] 4: Coating layer

Claims

1. A manufacturing method of a membrane heater, characterized in that The film including a base film, a conductive layer formed on the upper surface of the base film, and a coating layer formed on the upper surface of the conductive layer is separated into a specified shape to fabricate a heating element.

2. The manufacturing method of the film heater according to claim 1, characterized in that, The base film is an insulating resin.

3. The manufacturing method of the film heater according to claim 1, characterized in that, The conductive layer and the coating layer are formed by a sputtering method.

4. The manufacturing method of the film heater according to claim 1, characterized in that, The thickness of the conductive layer is 1000 nm or less, and the thickness of the coating layer is 10 nm to 200 nm.

5. The manufacturing method of the film heater according to claim 1, characterized in that, The resistivity of the conductive layer is 10 μΩcm or less, and any one of Al, Cu, and Ag is used as the main component.

6. The manufacturing method of the membrane heater according to claim 1, characterized in that, The coating layer includes a non-magnetic alloy film having any one of Ti, Cr, Mo, and Ni as the main component.

7. The manufacturing method of the film heater according to claim 6, characterized in that, The coating layer is an alloy having Mo as the main component and containing 60 at% or less of Ni and Ti in total.

8. The manufacturing method of the film heater according to claim 6, characterized in that, The coating layer is an alloy having Ni as the main component and containing 60 at% or less of Cu, Mn, and Mo in total.

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