Manufacturing method of heater film for in-vehicle parts and insert molding

Abstract

To provide a heater film for an on-vehicle component which is excellent in injection molding resistance.SOLUTION: A heater film 1 for an on-vehicle component includes a base material layer 11, a heater circuit 12 laminated on the base material layer 11, and a circuit protective layer 13 laid so as to surround the heater circuit 12. A 5% weight loss temperature of the circuit protective layer 13 in a thermogravimetric differential thermal analysis is 300°C or higher. A tensile modulus of the circuit protective layer 13 is 1 GPa or more and 300 GPa or less at 25°C and 10 MPa or more at 300°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a heater film for an in-vehicle part and a manufacturing method for an insert molded product, and more particularly to a heater film for an in-vehicle part including a base material layer, a heater circuit, and a protective circuit layer, and a manufacturing method for an insert molded product using this heater film for an in-vehicle part. [Background technology]

[0002] A heater film for on-vehicle parts is a heater that can be attached to the curved outer surface of a part in an automobile or the like while being folded or stretched, and is used, for example, as a snow melting heater. Such a heater film is formed by laminating a heater circuit formed using copper foil or the like on a base layer, and this heater circuit is covered with a thermoplastic resin or the like to prepare a module for use. This module is usually prepared by insert molding in which a thermoplastic resin is injected onto the heater circuit side of the heater film. In insert molding, however, since high-temperature and high-pressure resin is directly injected onto the heater circuit, depending on molding conditions such as the shape of the mold, the temperature and pressure of the injected thermoplastic resin, the wires of the heater circuit may be bent, torn, or the circuit may be exposed, resulting in the destruction of the heater circuit.

[0003] A method of forming a surface protective layer is considered as a method of suppressing the destruction that occurs in such insert molding. Patent Document 1 discloses a decorative sheet having a low gloss pattern ink layer and a surface protective layer covering it, in which the surface protective layer is crosslinked and cured from a resin composition containing an ionizing radiation curable resin and a thermoplastic resin in a ratio (mass ratio) of 75:25 to 25:75, the polystyrene-equivalent weight average molecular weight of the thermoplastic resin measured by gel permeation chromatography (GPC) is in the range of 90,000 to 120,000, and the thickness of the surface protective layer is 1 to 1000 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-132145 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the production of heater film modules for automotive components, the strength of the heater circuit is weaker and the temperature and pressure of the injected resin are higher, so using the conventional surface protection layer materials described above does not prevent damage to the heater circuit and does not improve the injection molding resistance of the heater film.

[0006] An object of the present disclosure is to provide a heater film for in-vehicle parts having excellent injection molding resistance, and a method for producing an insert molded product using the same. [Means for solving the problem]

[0007] A heater film for an in-vehicle component according to one embodiment of the present disclosure includes a base layer, a heater circuit, and a circuit protection layer. The heater circuit is laminated on the base layer. The circuit protection layer is laid so as to surround the periphery of the heater circuit. The circuit protection layer has a 5% weight loss temperature of 300°C or higher in a thermogravimetric differential thermal analysis. The circuit protection layer has a tensile modulus of elasticity of 1 GPa or more and 300 GPa or less at 25°C and 10 MPa or more at 300°C.

[0008] A manufacturing method for an insert molded product according to one aspect of the present disclosure includes the steps of placing the heater film for automotive components in a mold, injecting molten resin into the mold, and solidifying the resin. Effect of the Invention

[0009] According to the present disclosure, it is possible to provide a heater film for in-vehicle parts having excellent injection molding resistance, and a manufacturing method for an insert molded product using the same. [Brief description of the drawings]

[0010] [Figure 1] Fig. 1A is a schematic cross-sectional view of a heater film for an in-vehicle part according to one embodiment of the present disclosure, and Fig. 1B is a schematic cross-sectional view of a heater film for an in-vehicle part according to another embodiment of the present disclosure. [Diagram 2] FIG. 2 is a schematic cross-sectional view of an insert molding according to one embodiment of the present disclosure. [Diagram 3] 3A and 3B are schematic diagrams showing a method for measuring the interfacial adhesion strength between a base layer and a circuit protection layer in a die shear test. [Figure 4] FIG. 4 is a schematic diagram showing a method for evaluating the injection molding resistance of a heater film for in-vehicle parts. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 1. Overview The heater film for an in-vehicle component according to the present embodiment includes a base layer, a heater circuit, and a circuit protection layer. The heater circuit is laminated on the base layer. The circuit protection layer is laid so as to surround the periphery of the heater circuit. The 5% weight loss temperature of the circuit protection layer in a thermogravimetric differential thermal analysis is 300°C or higher. The tensile elastic modulus of the circuit protection layer is 1 GPa or higher and 300 GPa or lower at 25°C, and 10 MPa or higher at 300°C.

[0012] The inventors have found that, when a module is produced by insert molding a heater film for vehicle-mounted components, which includes a heater circuit and a circuit protection layer laid so as to surround the heater circuit, by injecting a high-temperature and high-pressure resin, there is a relationship between the injection molding resistance of the heater film and the heat resistance and tensile modulus of the circuit protection layer, as shown below. That is, by setting the 5% weight loss temperature of the circuit protection layer to 300°C or higher, decomposition of the circuit protection layer due to high-temperature molten resin during injection molding is suppressed. In addition, by setting the tensile modulus of the circuit protection layer at 25°C to 1 GPa or more and 300 GPa or less, the stress applied to the heater circuit 12 in the circuit protection layer 13 can be reduced, thereby suppressing destruction of the heater circuit 12 during injection molding. Furthermore, by setting the tensile modulus of the circuit protection layer 13 at 300°C to 10 MPa or more, deformation of the circuit protection layer 13 due to high-temperature molten resin and exposure of the heater circuit 12 are suppressed. As a result, it is possible to suppress damage to the heater circuit 12 and the circuit protection layer 13 even when high-temperature and high-pressure resin is injected during insert molding, and it is believed that this makes it possible to provide the heater film with excellent injection molding resistance.

[0013] 2.Details <Heater film for automotive parts> The heater film for on-vehicle parts according to this embodiment (hereinafter, simply referred to as the heater film) is a planar heater used to warm or heat on-vehicle parts. The heater film is preferably used as a snow melting heater mounted on a vehicle such as an automobile. The heater film is preferably flexible so that it can be attached to a curved outer surface of the on-vehicle part.

[0014] The heater film according to the present embodiment includes a base layer, a heater circuit, and a circuit protection layer. When the heater circuit is formed of a metal foil such as a copper foil, the base layer of the heater film preferably has an adhesive part 21 that adheres to the metal foil.

[0015] The heater film 1 in Fig. 1A comprises a base material layer 11, a heater circuit 12, and a circuit protection layer 13. The heater film 1 in Fig. 1B comprises a base material layer 11, a heater circuit 12, and a circuit protection layer 13, and the base material layer 11 has an adhesive part 21. In Fig. 1A and Fig. 1B, the heater circuit 12 is shown to have only two parts in the cross-sectional view, but in reality, the cross-sectional shape of the heater circuit 12 is not particularly limited. Each component will be described below.

[0016] [Base material layer] As shown in FIGS. 1A and 1B, the base layer 11 is a member for laminating the heater circuit 12 in the heater film 1.

[0017] The base layer 11 may be in the form of, for example, a film, a sheet, or a plate.

[0018] The dimensions of the base layer 11 in plan view are not particularly limited. The thickness of the base layer 11 is appropriately selected depending on the desired flexibility of the heater film 1, and is preferably 1 μm or more and 5000 μm or less. In this case, the flexibility of the heater film 1 can be further improved. The thickness of the base layer 11 is more preferably 10 μm or more and 1000 μm or less, further preferably 50 μm or more and 800 μm or less, and particularly preferably 100 μm or more and 500 μm or less.

[0019] The material of the base layer 11 is, for example, a resin, and preferably a thermoplastic resin. When the base layer 11 is made of a thermoplastic resin, it can be heat-sealed to an object such as a car body. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; polycarbonate, polyamide, polyimide, polyamideimide, polyetherimide, polyethersulfide, polyethersulfone, polyetherketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polysulfone, and liquid crystal polymers. Among these, polycarbonate is preferable from the viewpoint of crack resistance and transparency. The base layer 11 may contain materials other than resin, such as inorganic fillers.

[0020] It is preferable to use the same type of resin as the resin injected in the insert molding described below as the material for the base layer 11. In this case, the strength of the manufactured module can be further improved.

[0021] (Adhesive part) 1B, the adhesive portion 21 is a part of the base layer 11, and is a portion that can be adhered to the metal foil when the heater circuit 12 is formed from a metal foil such as a copper foil. Since the base layer 11 of the heater film 1 has the adhesive portion 21, even when the heater circuit 12 is formed from a metal foil, peeling of the heater circuit 12 from the base layer 11 can be further suppressed, and thus the injection molding resistance of the heater film 1 can be further improved.

[0022] A known adhesive can be used to form the adhesive portion 21, and from the viewpoint of ease of application to the substrate, a solvent-based adhesive is preferred, and an adhesive in which a base agent and a curing agent are mixed is preferred. Examples of adhesives include polyester-based adhesives, acrylic-based adhesives, polyamide-based adhesives, polyurethane-based adhesives, olefin-based adhesives, and EVA (ethylene-vinyl acetate copolymer)-based adhesives. Among these, from the viewpoint of superior adhesion to metal, at least one of polyester-based adhesives and acrylic-based adhesives is preferred, and polyester-based adhesives are more preferred.

[0023] The adhesive portion 21 is formed, for example, by first mixing the main agent and the curing agent of a solvent-based adhesive, applying the mixture on the surface of the substrate, and drying to form a coating of the adhesive. The drying temperature is, for example, 50°C or higher and 200°C or lower, and preferably 100°C or higher and 140°C or lower. The drying time is, for example, 5 seconds or higher and 1 hour or lower, and preferably 10 seconds or higher and 3 minutes or lower. Next, a metal foil such as a copper foil is attached to the coating of the adhesive, and then the adhesive is heated and cured. The heating temperature is, for example, 30°C or higher and 100°C or lower, and preferably 40°C or higher and 60°C or lower. The heating time is, for example, 1 hour or higher and 1000 hours or lower, and preferably 50 hours or higher and 300 hours or lower. The heating may be performed at one temperature, or may be performed by increasing the temperature stepwise at two or more temperatures. The adhesive portion 21 to which the metal foil as the heater circuit 12 is bonded is formed by heating and curing.

[0024] The dimensions of the adhesive portion 21 in a plan view are usually equal to or smaller than the dimensions of the base material forming the adhesive portion 21 in a plan view, and preferably the same dimensions as the base material. The thickness of the adhesive portion 21 is, for example, 0.1 μm to 100 μm, preferably 1 μm to 60 μm, and more preferably 3 μm to 20 μm.

[0025] [Heater circuit] 1A and 1B, the heater circuit 12 is laminated on a base material layer 11. The shape of the heater circuit 12 in a plan view is not particularly limited, and examples thereof include any wiring pattern shape such as a lattice shape, a mesh shape, a fan shape, a spiral shape, and a meandering shape.

[0026] The material of the heater circuit 12 is not particularly limited as long as it is conductive, but examples thereof include metals such as gold, silver, copper, stainless steel, nickel, aluminum, and alloys of two or more of these metals. Among these, copper is preferred.

[0027] Methods for forming the heater circuit 12 include a method of forming by etching a metal foil, a method of forming by vapor deposition of a metal, a method of forming by plating of a metal, etc. When forming the heater circuit 12 by etching, the heater circuit 12 is formed, for example, by laminating a metal foil such as a copper foil onto a film of adhesive applied to a substrate, curing the adhesive to obtain a substrate layer with a metal foil, and removing unnecessary parts of the metal foil from this substrate layer with a metal foil by a photoetching method or the like to form an arbitrary wiring pattern.

[0028] When the heater circuit 12 has a planar shape, the thickness of the heater circuit 12 is usually 1 μm or more and 100 μm or less, preferably 5 μm or more and 70 μm or less, and more preferably 10 μm or more and 50 μm or less.

[0029] [Circuit protection layer] As shown in FIGS. 1A and 1B, the circuit protection layer 13 is laid so as to surround the periphery of the heater circuit 12.

[0030] In the heater film 1 according to the present embodiment, the 5% weight loss temperature of the circuit protection layer 13 in thermogravimetric differential thermal analysis (TG-DTA) is 300°C or higher. This 5% weight loss temperature is preferably 320°C or higher, more preferably 350°C or higher, and even more preferably 370°C or higher. By setting the 5% weight loss temperature to the above value or higher, it is possible to further suppress the decomposition of the circuit protection layer 13 caused by the high-temperature molten resin in injection molding, and thus it is possible to further improve the injection molding resistance of the heater film 1. The upper limit of this 5% weight loss temperature is not particularly limited, but is preferably less than 500°C and 400°C or lower, for example. The "5% weight loss temperature" is the temperature at which the weight loss of the circuit protection layer material becomes 5% by mass, as measured by a TG-DTA device under conditions of an air atmosphere and a heating rate of 10°C / min.

[0031] In the heater film 1 according to this embodiment, the tensile modulus of elasticity of the circuit protection layer 13 is 1 GPa or more and 300 GPa or less at 25° C. In addition, the tensile modulus of elasticity of the circuit protection layer 13 is 10 MPa or more at 300° C.

[0032] The tensile modulus of the circuit protection layer 13 at 25° C. is preferably 1.1 GPa or more, more preferably 1.2 GPa or more, even more preferably 1.3 GPa or more, and particularly preferably 1.4 GPa or more. The tensile modulus of the circuit protection layer 13 at 25° C. is preferably 100 GPa or less, more preferably 30 GPa or less, even more preferably 10 GPa or less, and particularly preferably 2 GPa or less. By setting the tensile modulus of the circuit protection layer 13 at 25° C. within the above range, the stress applied to the heater circuit 12 in the circuit protection layer 13 can be further reduced, and thus the injection molding resistance of the heater film 1 can be further improved.

[0033] The tensile modulus of the circuit protection layer 13 at 300°C is preferably 11 MPa or more, more preferably 12 MPa or more, even more preferably 20 MPa or more, and particularly preferably 30 MPa or more. By making the tensile modulus of elasticity at 300°C equal to or more than the above value, deformation of the circuit protection layer 13 and exposure of the heater circuit 12 due to high-temperature molten resin can be further suppressed, and thus the injection molding resistance of the heater film 1 can be further improved. The upper limit of the tensile modulus of elasticity at 300°C is not particularly limited, but 100 MPa is sufficient.

[0034] The material for forming the circuit protection layer 13 may be any material that allows the 5% weight loss temperature and tensile modulus at 25°C and 300°C of the formed circuit protection layer 13 to fall within the above ranges, and examples of such materials include various thermosetting resins, and preferably includes a material containing an epoxy resin as a main component. That is, the circuit protection layer 13 preferably includes a cured product of a composition (hereinafter also referred to as composition (X)) containing an epoxy resin as a main component. The "main component" refers to a component with the largest mass ratio, for example, 50 mass% or more, preferably 70 mass% or more. By using composition (X) containing an epoxy resin as a main component as the material for forming the circuit protection layer 13, the 5% weight loss temperature and tensile modulus at 25°C and 300°C can be adjusted to more appropriate values, and the injection molding resistance of the heater film 1 can be further improved.

[0035] Epoxy resins are compounds having two or more epoxy groups in one molecule. Examples of epoxy resins include bisphenol-type epoxy resins, hydrogenated bisphenol-type epoxy resins, biphenyl-type epoxy resins, naphthalene ring-containing epoxy resins, alicyclic epoxy resins, dicyclopentadiene-type epoxy resins, phenol novolac-type epoxy resins, cresol novolac-type epoxy resins, triphenylmethane-type epoxy resins, aliphatic epoxy resins, triglycidyl isocyanurate, glycidyl group-containing silicone resins, and glycidylamine-type epoxy resins.

[0036] The proportion of the epoxy resin in the composition (X) is, for example, 50% by mass or more and 100% by mass or less, preferably 60% by mass or more and 95% by mass or less, and more preferably 65% ​​by mass or more and 90% by mass or less.

[0037] The composition (X) usually contains a curing agent for the epoxy resin, a curing accelerator, and the like. Examples of the curing agent include phenolic curing agents, acid anhydrides, amines, imidazoles, hydrazides, polymercaptans, Lewis acid-amine complexes, and the like. The equivalent of the curing agent relative to 1 equivalent of the epoxy resin is, for example, 0.6 to 1.4. The ratio of the curing agent to the composition (X) is, for example, 1% by mass to 50% by mass, preferably 5% by mass to 40% by mass, and more preferably 10% by mass to 35% by mass.

[0038] Examples of the curing accelerator include imidazoles such as 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, and 2-ethyl-4-methylimidazole; cycloamidines such as 1,8-diazabicyclo[5.4.0]undecene-7, 1,5-diazabicyclo[4.3.0]nonene-5, and 5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7; tertiary amines such as 2-(dimethylaminomethyl)phenol, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, and tris(dimethylaminomethyl)phenol; tributylphosphine, methyldiphenylphosphine, and the like. Organic phosphines such as phenylphosphine, triphenylphosphine, tris(4-methylphenyl)phosphine, diphenylphosphine, an addition product of triphenylphosphine and parabenzoquinone, and phenylphosphine; tetra-substituted phosphonium and tetra-substituted borates such as tetraphenylphosphonium tetraphenylborate, tetraphenylphosphonium ethyltriphenylborate, and tetrabutylphosphonium tetrabutylborate; quaternary phosphonium salts having a counter anion other than borate; and tetraphenylboron salts such as 2-ethyl-4-methylimidazole tetraphenylborate and N-methylmorpholine tetraphenylborate. The ratio of the curing accelerator to the composition (X) is, for example, 0.1% by mass or more and 2% by mass or less.

[0039] Examples of commercially available products of composition (X) include CV5340E manufactured by Panasonic Corporation and TB2082C manufactured by Three Bond Co., Ltd.

[0040] The dimensions of the circuit protection layer 13 in a plan view are not particularly limited as long as they are large enough to surround the heater circuit 12. The thickness of the circuit protection layer 13 is not particularly limited as long as it is larger than the thickness of the heater circuit 12. The thickness of the circuit protection layer 13 is, for example, 1.1 times or more, and preferably 1.2 times or more, the thickness of the heater circuit 12. The thickness of the circuit protection layer 13 is, for example, 5 μm or more larger, and preferably 10 μm or more larger than the thickness of the heater circuit 12. The thickness of the circuit protection layer 13 is, for example, 10 μm or more and 1000 μm or less, preferably 50 μm or more and 500 μm or less, and more preferably 100 μm or more and 200 μm or less.

[0041] The interfacial adhesion strength between the base layer 11 and the circuit protection layer 13 in a die shear test is preferably 1 MPa or more at the mold temperature in the insert molding. In this case, the injection molding resistance in the insert molding can be further improved. The mold temperature in the insert molding is usually 80°C or more and 150°C or less.

[0042] The interfacial adhesion strength between the base material layer 11 and the circuit protection layer 13 in a die shear test is preferably 1 MPa or more at 120°C. When the interfacial adhesion strength at 120°C, which is a typical mold temperature in insert molding, is equal to or more than the above value, the injection molding resistance of the heater film 1 can be further improved. The interfacial adhesion strength at 120°C is more preferably 1.1 MPa or more, and even more preferably 1.2 MPa or more. The upper limit of the interfacial adhesion strength at 120°C is not particularly limited, but 3 MPa is sufficient.

[0043] A method for measuring the interfacial adhesion strength in a die shear test between the base material layer 11 and the circuit protection layer 13 will be described in the Examples section below. When the base material layer 11 has an adhesive part 21, the interfacial adhesion strength between the base material layer 11 and the circuit protection layer 13 means the interfacial adhesion strength between the adhesive part 21 and the circuit protection layer 13.

[0044] It is preferable that both the base layer 11 and the circuit protection layer 13 in the heater film 1 have transparency. In this case, the heater circuit 12 in the heater film 1 can be visually confirmed.

[0045] The circuit protection layer 13 can be formed, for example, by applying a material for forming the circuit protection layer 13 onto the base material layer 11 on which the heater circuit 12 is laminated, and then curing the material.

[0046] <Insert molding> The insert molded product according to this embodiment includes the above-mentioned heater film for vehicle-mounted parts and a resin formed by insert molding and bonded to the heater film for vehicle-mounted parts. Since the insert molded product according to this embodiment is produced using the above-mentioned heater film 1 having excellent injection molding resistance, the heater circuit in the insert molded product is prevented from being broken and maintains its shape. Therefore, the insert molded product according to this embodiment can exhibit excellent heater performance.

[0047] A cross-sectional view of an example of the insert molded product of this embodiment is shown in Fig. 2. The insert molded product 2 includes the heater film 1 shown in Fig. 1B and a resin 31. The resin 31 is formed by insert molding and is bonded to the heater film 1.

[0048] The insert molded product 2 may be in the form of, for example, a film, a sheet, or a plate.

[0049] The dimensions of the insert molded product 2 in a plan view are not particularly limited. The thickness of the insert molded product 2 is, for example, 10 μm to 100 mm, preferably 100 μm to 10 mm, and more preferably 1 mm to 5 mm. By setting the thickness in this range, the flexibility of the insert molded product 2 can be further improved.

[0050] It is preferable that the base layer 11, the circuit protection layer 13, and the resin 31 in the insert molding 2 all have transparency. In this case, the heater circuit 12 in the insert molding 2 can be visually confirmed.

[0051] <Manufacturing method of insert molding> The insert molded article 2 can be manufactured by a known method. For example, the insert molded article 2 can be simply and reliably manufactured by a manufacturing method including a step of placing the heater film 1 in a mold (step 1), a step of injecting molten resin into the mold (step 2), and a step of solidifying the molten resin (step 3).

[0052] In step 1, the heater film 1 is placed in a mold. In step 1, the heater film 1 is placed, for example, on one wall inside the mold, with the surface of the base layer 11 opposite to the heater circuit 12 attached thereto.

[0053] In step 2, the molten resin is injected into the mold. As the resin, a thermoplastic resin is usually used. As the resin, it is preferable to use the same material as the material of the base layer 11. In this case, the strength of the insert molded product 2 can be further improved. As the resin, polycarbonate is preferable from the viewpoint of crack resistance and transparency. The mold temperature in step 2 is, for example, 80°C or more and 150°C or less, and preferably 100°C or more and 140°C or less. The temperature of the molten resin is, for example, 200°C or more and 400°C or less, and preferably 250°C or more and 350°C or less. The holding pressure in step 2 is, for example, 10 Pa or more and 100 Pa or less, and preferably 20 Pa or more and 60 Pa or less. The injection speed in step 2 is, for example, 10 mm / s or more and 200 mm / s or less, and preferably 50 mm / s or more and 150 mm / s.

[0054] In step 3, the molten resin is solidified. Step 3 is performed, for example, by gradually lowering the mold temperature. In this way, the insert molded product 2 including the heater film 1 can be obtained. EXAMPLES

[0055] The present disclosure will be described in more detail below with reference to examples, but the present disclosure is not limited to these examples in any way.

[0056] <Preparation of heater film> [Preparation of circuit-equipped substrate] A transparent polycarbonate film having a thickness of 300 μm was used as the substrate. The solvent-based adhesive to be applied to the surface of the substrate was prepared by mixing the base material "Dynaleo VA-3020" (manufactured by Toyo Ink Mfg. Co., Ltd.) and the hardener "Dynaleo HD-701" (manufactured by Toyo Ink Mfg. Co., Ltd.) in a base material / hardener (mass ratio) of 100 / 7. This solvent-based adhesive was then applied at a rate of 3 g / m 2 and dried at 120° C. for 1 minute to provide a transparent adhesive film having a thickness of 12 μm. Next, copper foil was attached to the surface of the formed adhesive film, and then the adhesive was cured by heating at 40°C for 48 hours and at 60°C for 96 hours to obtain a base layer with copper foil. Copper foil with a thickness of 35 μm was used as the copper foil. An unnecessary portion of the copper foil was removed from the base layer with the copper foil by photoetching, and an arbitrary wiring pattern was provided on the base layer, thereby producing a base layer with a heater circuit.

[0057] [Formation of circuit protection layer] The following materials were used for the circuit protection layer. Example 1: Panasonic CV5340E Example 2: TB2082C manufactured by ThreeBond Co., Ltd. Comparative Example 1: ThreeBond TB3732 Comparative Example 2: LQM014 manufactured by Henkel Comparative Example 3: Stretchable film manufactured by Panasonic Comparative Example 4: Panasonic CV5390

[0058] Two sheets of heat-resistant polyimide tape (7413D manufactured by 3M) were placed on the part of the substrate layer with the heater circuit where no circuit was formed, and attached to the edge of the substrate layer with the heater circuit to form a frame with a thickness of 135 μm. Next, various circuit protection layer materials were placed on the substrate layer with the heater circuit, and an aluminum rod with a diameter of 3 mm was placed so that both ends of the rod were hanging on the polyimide tape to which it was attached, and the aluminum rod was moved along the surface of the polyimide tape to spread the circuit protection layer material on the substrate layer with the heater circuit, and a heater film with a circuit protection layer was formed by passing it through the specified curing conditions.

[0059] <Evaluation> [5% weight loss temperature] The circuit protection layer material was applied onto a release film, cured under specified conditions, and then the release film was peeled off to obtain a bulk film of the circuit protection layer material. A specified weight was cut out from the bulk film of the circuit protection layer material, and the temperature at which the weight loss of the circuit protection layer material was 5% was measured using a TG / DTA6300 manufactured by Seiko Instruments Inc. The measurement was performed under the conditions of an air atmosphere (flow rate 200 mL / min) and a heating rate of 10°C / min.

[0060] [Tensile modulus] The circuit protection layer material was applied onto a release film, cured under specified conditions, and then the release film was peeled off to obtain a bulk film of the circuit protection layer material. The obtained bulk film of the circuit protection layer material was cut into pieces with a width of 5 mm, and the tensile modulus was measured at 25°C and 300°C using a dynamic viscoelasticity measuring device (DMS6100 manufactured by Seiko Instruments Inc.). At this time, the measurement was performed in tension mode, with a frequency of 10 Hz and a temperature increase rate of 10°C / min, from room temperature to 300°C.

[0061] [Interface adhesion strength] As shown in FIG. 3A, a copper foil-attached substrate having a size of 15×15 mm was etched to form an adhesive-attached substrate 42, and a film 43 using various circuit protection layer materials was formed on the adhesive-attached substrate 42. An aluminum rivet 44 was then attached and cured for a predetermined time to produce a test piece 41 in which the aluminum rivet 44 was attached to the surface of the adhesive-attached substrate 42 via the circuit protection layer material 43. Using the prepared test piece 41, a die shear test was performed using a bond tester (4000 model manufactured by Dega Co., Ltd.) as shown in FIG. 3B to measure the interfacial adhesion strength between the adhesive portion (substrate layer) and the circuit protection layer. The bottom surface of the aluminum rivet 44 is a circle with a diameter of 6 mm. The width of the tool A used in the measurement was 9 mm, the height of the tool A (the distance between the adhesive-attached substrate 42 and the bottom end of the tool A) was 100 μm, and the speed of the tool A was 100 μm / sec. The stage on which the test piece 41 was placed was heated to 120° C. to perform the measurement.

[0062] [Injection molding resistance] First, a heater film having a circuit protection layer was produced by an injection molding machine (Si-80 manufactured by Toyo Machinery & Metals Co., Ltd.). The heater film having the produced circuit protection layer was cut into a size of 30 mm x 30 mm and attached to a position directly under the gate of a mold. The conditions for producing a test piece for evaluating the resistance to injection molding were as follows: resin used: polycarbonate (Iupilon S-3000 manufactured by Mitsubishi Engineering Plastics Corporation), resin temperature 320°C, mold temperature 80°C, injection speed 80 mm / s, holding pressure 40 Pa, and gate width 7 mm. In this way, as shown in FIG. 4, a flat test piece 51 having a 100 mm square and a thickness of 2 mm including a heater film 52 having a circuit protection layer was produced. For the obtained test piece 51, the area of ​​portion B adjacent to portion 53 corresponding to the gate and where the circuit protection layer was destroyed by the resin injected from the gate was calculated by overlaying a grid of 1 mm squares on the test piece.

[0063] The injection molding resistance was evaluated according to the following criteria based on the area of ​​portion B where the circuit protection layer was destroyed. ◎: 10mm 2 below 〇:88mm 2 below ×:88mm 2 Super

[0064] [Table 1]

[0065] The results in Table 1 show that the heater films of the Examples have excellent injection molding resistance because the 5% weight loss temperature and the tensile modulus at 25° C. and 300° C. of the circuit protection layer are within the specific ranges. The heater films of the Comparative Examples also show poor injection molding resistance because at least one of the 5% weight loss temperature and the tensile modulus at 25° C. and 300° C. of the circuit protection layer is outside the specific range. [Explanation of symbols]

[0066] 1. Heater film for automotive parts 2 Insert molding 11 Base material layer 12 Heater circuit 13 Circuit protection layer 21 Adhesive part

Claims

1. A heater film for vehicle-mounted parts used in the manufacture of insert molded products by injection molding, comprising: A base layer; A heater circuit laminated on the base layer; a circuit protection layer disposed so as to surround the heater circuit; Equipped with the circuit protection layer is in direct contact with the heater circuit, The heater film for in-vehicle parts, wherein the 5% weight loss temperature in a thermogravimetric differential thermal analysis of the circuit protection layer is 300°C or more and less than 500°C, and the tensile modulus of the circuit protection layer is 1 GPa or more and 300 GPa or less at 25°C and 10 MPa or more and 100 MPa or less at 300°C.

2. A heater film for automotive components as described in claim 1, wherein the circuit protection layer includes a cured product of a composition containing an epoxy resin as a main component.

3. A heater film for automotive parts as described in claim 1 or 2, wherein the interfacial adhesion strength between the base material layer and the circuit protection layer in a die shear test is 1 MPa or more at 120°C.

4. A step of placing a heater film for an automotive part according to any one of claims 1 to 3 in a mold; injecting molten resin into the mold; solidifying the molten resin; A method for manufacturing an insert molding comprising:

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