JP2022165833A - Heater film for on-vehicle component and manufacturing method of insert molded product - Google Patents

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 The present disclosure relates to a method of manufacturing an in-vehicle component heater film and an insert-molded product, and more specifically, an in-vehicle component heater film including a substrate layer, a heater circuit, and a protective circuit layer, and the in-vehicle component heater film. It relates to a method for manufacturing an insert molded product using

A heater film for vehicle-mounted parts is a heater that can be attached to the curved outer surface of a part of an automobile or the like while being bent or stretched, and is used as a snow melting heater, for example. Such a heater film is obtained by laminating a heater circuit formed using copper foil or the like on a base material layer, and by coating the heater circuit with a thermoplastic resin or the like, a module is produced. Used. This module is usually manufactured by insert molding, in which thermoplastic resin is injected onto the heater circuit side of the heater film.In insert molding, high-temperature and high-pressure resin is injected directly onto the heater circuit. Therefore, depending on the molding conditions such as the shape of the mold, the temperature and pressure of the thermoplastic resin to be injected, etc., the wire of the heater circuit may be bent, torn, or the circuit may be exposed, causing the heater circuit to fail. It could have been destroyed.

A method of forming a surface protective layer is conceivable as a method of suppressing breakage that occurs in such insert molding. Patent Document 1 relates to a decorative sheet having a low-gloss picture ink layer and a surface protective layer covering it, wherein the surface protective layer contains an ionizing radiation curable resin and a thermoplastic resin at a ratio of 75:25 to 25:75. The resin composition contained in the ratio (mass ratio) is crosslinked and cured, and the polystyrene conversion weight average molecular weight measured by gel permeation chromatography (GPC) of this thermoplastic resin is in the range of 90,000 to 120,000, It is disclosed that the surface protective layer has a thickness of 1 to 1000 μm.

JP 2009-132145 A

However, in the production of the module of the heater film for automotive parts, the strength of the heater circuit is smaller, and the temperature and pressure of the resin to be injected are higher. Therefore, the breakage of the heater circuit could not be suppressed, and the injection molding resistance of the heater film could not be improved.

An object of the present disclosure is to provide a heater film for automotive components that has excellent injection molding resistance, and a method for manufacturing an insert-molded product using the same.

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

A method for manufacturing an insert-molded product according to an aspect of the present disclosure includes the steps of: placing the automotive component heater film in a mold; injecting a molten resin into the mold; and solidifying the resin. Prepare.

Advantageous Effects of Invention According to the present disclosure, it is possible to provide a heater film for automotive parts that is excellent in injection molding resistance, and a method for manufacturing an insert-molded product using the same.

FIG. 1A is a schematic cross-sectional view of an automotive component heater film according to an embodiment of the present disclosure. FIG. 1B is a schematic cross-sectional view of an automotive component heater film according to another embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of an insert molded article according to one embodiment of the present disclosure; 3A and 3B are schematic diagrams showing a method for measuring interfacial adhesion strength in a die shear test between a substrate layer and a circuit protection layer. FIG. 4 is a schematic diagram showing a method for evaluating injection molding resistance of a heater film for vehicle-mounted parts.

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

The inventors performed insert molding by injecting a high-temperature and high-pressure resin from a heater film for automotive parts, which includes a heater circuit and a circuit protection layer laid so as to surround the heater circuit. It has been found that the injection molding resistance of the heater film and the heat resistance and tensile modulus of the circuit protective layer have the following relationship when a module is produced by the method. That is, by setting the 5% weight loss temperature of the circuit protective layer to 300° C. or higher, decomposition of the circuit protective layer due to high-temperature molten resin in injection molding is suppressed. Further, by setting the tensile elastic modulus of the circuit protective layer to 1 GPa or more and 300 GPa or less at 25° C., the stress applied to the heater circuit 12 in the circuit protective layer 13 can be further reduced, thereby reducing the stress during injection molding. Destruction of the heater circuit 12 is suppressed. Further, by setting the tensile elastic modulus of the circuit protective layer 13 at 300° C. to 10 MPa or more, deformation of the circuit protective layer 13 and exposure of the heater circuit 12 due to the high-temperature molten resin are suppressed. As a result, breakage of the heater circuit 12 and the circuit protection layer 13 can be suppressed even when high-temperature and high-pressure resin is injected during insert molding, and the injection molding resistance of the heater film can be improved. It is possible.

2. Details <Heater film for in-vehicle parts>
A heater film for vehicle-mounted parts according to the present embodiment (hereinafter also simply referred to as a heater film) is a planar heater used for warming or heating vehicle-mounted parts. The heater film is suitably used as a snow-melting heater mounted on vehicles such as automobiles. The heater film is preferably flexible so that it can be attached to a curved outer surface of an in-vehicle component or the like.

The heater film according to this embodiment includes a substrate layer, a heater circuit, and a circuit protection layer. When the heater circuit is made of a metal foil such as copper foil, the base layer of the heater film preferably has an adhesive portion 21 that adheres to the metal foil.

The heater film 1 of FIG. 1A includes a substrate layer 11 , a heater circuit 12 and a circuit protection layer 13 . The heater film 1 of FIG. 1B includes a substrate layer 11, a heater circuit 12, and a circuit protection layer 13, and the substrate layer 11 has an adhesive portion 21. As shown in FIG. In FIGS. 1A and 1B, the heater circuit 12 is illustrated as having only two parts in the cross-sectional view, but actually the cross-sectional shape of the heater circuit 12 is not particularly limited.
Each configuration will be described below.

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

The shape of the base material layer 11 is, for example, film-like, sheet-like, or plate-like.

The dimensions of the base material layer 11 in plan view are not particularly limited. The thickness of the base material layer 11 is appropriately selected depending on the intended flexibility of the heater film 1 and the like, but 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 material 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.

The material of the base material layer 11 is, for example, a resin, preferably a thermoplastic resin. If the base material layer 11 is made of a thermoplastic resin, it can be heat-sealed to an object such as a vehicle body. Examples of thermoplastic resins include polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefins such as polyethylene and polypropylene; Ether ketone, polyphenylene ether, polyphenylene sulfide, polyarylate, polysulfone, liquid crystal polymer and the like. Among these, polycarbonate is preferred from the viewpoint of crack resistance and transparency. The base material layer 11 may contain materials other than resin, such as inorganic fillers.

As the material of the base material layer 11, it is preferable to use the same kind of resin as the resin injected in insert molding, which will be described later. In this case, the strength of the manufactured module can be further improved.

(Adhesion part)
As shown in FIG. 1B, the bonding portion 21 is a part of the base layer 11, and is a portion that can be bonded to the metal foil when the heater circuit 12 is formed of a metal foil such as copper foil. be. In the heater film 1, since the base layer 11 has the adhesive portion 21, even when the heater circuit 12 is formed of a metal foil, peeling of the heater circuit 12 from the base layer 11 can be prevented. can be suppressed, and thereby the injection molding resistance of the heater film 1 can be further improved.

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 preferable, and an adhesive that is used by mixing a main agent and a curing agent. 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, at least one of polyester-based adhesives and acrylic-based adhesives is preferable, and polyester-based adhesives are more preferable, from the viewpoint of superior adhesion to metals.

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

The dimension of the bonding portion 21 in plan view is generally equal to or less than the dimension in plan view of the substrate forming the bonding portion 21, and preferably the same dimension as the substrate. The thickness of the adhesive portion 21 is, for example, 0.1 μm or more and 100 μm or less, preferably 1 μm or more and 60 μm or less, and more preferably 3 μm or more and 20 μm or less.

[Heater circuit]
As shown in FIGS. 1A and 1B, the heater circuit 12 is laminated on the substrate layer 11 . The planar view shape of the heater circuit 12 is not particularly limited, and examples thereof include arbitrary wiring pattern shapes such as lattice, mesh, fan, spiral, and meandering.

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

Methods of forming the heater circuit 12 include a method of forming by etching a metal foil, a method of forming by vapor deposition of metal, a method of forming by plating of metal, and the like. When the heater circuit 12 is formed by etching, the heater circuit 12 is formed by, for example, laminating a metal foil such as copper foil on an adhesive film applied to a base material, and then curing the adhesive. A substrate layer with a metal foil is obtained, and unnecessary portions of the metal foil are removed from the substrate layer with the metal foil by photoetching or the like to form an arbitrary wiring pattern.

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.

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

In the heater film 1 according to this embodiment, the 5% weight loss temperature of the circuit protective layer 13 in thermogravimetric differential thermal analysis (TG-DTA) is 300° C. or higher. The 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 more, the decomposition of the circuit protective layer 13 by the high-temperature molten resin in injection molding can be further suppressed, thereby further improving the injection molding resistance of the heater film 1. can be done. Although the upper limit of the 5% weight loss temperature is not particularly limited, it is, for example, less than 500°C, preferably 400°C or less. The “5% weight loss temperature” is the temperature at which the weight loss of the circuit protective layer material is 5% by mass, measured under the conditions of a temperature increase rate of 10° C./min in an air atmosphere using a TG-DTA device. .

In the heater film 1 according to this embodiment, the tensile elastic modulus of the circuit protection layer 13 is 1 GPa or more and 300 GPa or less at 25°C. Moreover, the tensile elastic modulus of the circuit protective layer 13 is 10 MPa or more at 300°C.

The tensile modulus of the circuit protective layer 13 at 25° C. is preferably 1.1 GPa or more, more preferably 1.2 GPa or more, further preferably 1.3 GPa or more, and 1.4 GPa or more. It is particularly preferred to have The tensile modulus 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 elasticity at 25° C. within the above range, the stress applied to the heater circuit 12 in the circuit protective layer 13 can be further reduced, thereby further improving the injection molding resistance of the heater film 1 . can.

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

As a material for forming the circuit protective layer 13, any material can be used as long as the formed circuit protective layer 13 has a 5% weight loss temperature and a tensile elastic modulus at 25° C. and 300° C. within the above ranges. Various thermosetting resins can be used, and those containing an epoxy resin as a main component are preferred. That is, the circuit protection layer 13 preferably contains a cured product of a composition containing an epoxy resin as a main component (hereinafter also referred to as composition (X)). A "main component" refers to a component having the largest mass ratio, for example, 50% by mass or more, preferably 70% by mass or more. By using the 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 the tensile modulus at 25°C and 300°C can be adjusted to more appropriate values. The injection molding resistance of the heater film 1 can be further improved.

An epoxy resin is a compound 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, and cresol novolak. type epoxy resin, triphenylmethane type epoxy resin, aliphatic epoxy resin, triglycidyl isocyanurate, glycidyl group-containing silicone resin, glycidylamine type epoxy resin, and the like.

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 preferably 65% by mass or more and 90% by mass or less. more preferred.

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

Curing accelerators include imidazoles such as 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole, 2-ethyl-4-methylimidazole; 1,8-diazabicyclo[5.4.0]undecene-7 , 1,5-diazabicyclo[4.3.0]nonene-5,5,6-dibutylamino-1,8-diazabicyclo[5.4.0]undecene-7; cycloamidines such as 2-(dimer tertiary amines such as aminomethyl)phenol, triethylenediamine, benzyldimethylamine, triethanolamine, dimethylaminoethanol, tris(dimethylaminomethyl)phenol; tributylphosphine, methyldiphenylphosphine, triphenylphosphine, tris(4- organic phosphines such as methylphenyl)phosphine, diphenylphosphine, adducts of triphenylphosphine and parabenzoquinone, and phenylphosphine; tetraphenylphosphonium/tetraphenylborate, tetraphenylphosphonium/ethyltriphenylborate, tetrabutylphosphonium/tetrabutyl Tetra-substituted phosphonium such as borate, tetra-substituted borate; quaternary phosphonium salt having a counter anion other than borate; etc. 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.

Examples of commercially available products of the composition (X) include CV5340E manufactured by Panasonic Corporation and TB2082C manufactured by ThreeBond.

The dimensions of the circuit protective 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 protective layer 13 is, for example, 1.1 times or more, preferably 1.2 times or more, the thickness of the heater circuit 12 . The thickness of the circuit protective layer 13 is, for example, 5 μm or more, preferably 10 μm or more, larger than the thickness of the heater circuit 12 . The thickness of the circuit protective 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.

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

The interfacial adhesion strength between the substrate 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 higher 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, further preferably 1.2 MPa or more. Although the upper limit of the interfacial adhesion strength at 120° C. is not particularly limited, 3 MPa is sufficient.

A method for measuring the interfacial adhesion strength in the 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 substrate layer 11 has the adhesive portion 21 , the interface adhesion strength between the substrate layer 11 and the circuit protection layer 13 means the interface adhesion strength between the adhesion portion 21 and the circuit protection layer 13 .

Both the substrate layer 11 and the circuit protective layer 13 in the heater film 1 preferably have transparency. In this case, the heater circuit 12 in the heater film 1 can be visually recognized.

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

<Insert molded product>
An insert-molded product according to the present embodiment includes the above-described on-vehicle component heater film, and a resin formed by insert molding and adhered to the on-vehicle component heater film. Since the insert-molded product according to the present embodiment is produced using the heater film 1 having excellent injection molding resistance, breakage of the heater circuit in the insert-molded product is suppressed and the shape is maintained. Therefore, the insert-molded product according to this embodiment can exhibit excellent heater performance.

FIG. 2 shows a cross-sectional view of an example of the insert-molded product of this embodiment. The insert-molded product 2 includes the heater film 1 and resin 31 shown in FIG. 1B. The resin 31 is formed by insert molding and adhered to the heater film 1 .

The shape of the insert-molded product 2 is, for example, film-like, sheet-like, or plate-like.

The dimensions of the insert-molded product 2 in plan view are not particularly limited. The thickness of the insert-molded product 2 is, for example, 10 μm or more and 100 mm or less, preferably 100 μm or more and 10 mm or less, and more preferably 1 mm or more and 5 mm or less. By setting it as such a thickness, the flexibility etc. of the insert-molded product 2 can be improved more.

All of the substrate layer 11, the circuit protection layer 13 and the resin 31 in the insert-molded product 2 preferably have transparency. In this case, it becomes possible to visually recognize the heater circuit 12 in the insert-molded product 2 .

<Manufacturing method of insert molded product>
The insert-molded product 2 can be manufactured by a known method. For example, the insert-molded product 2 is produced by 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). ) can be easily and reliably manufactured by a manufacturing method including the above.

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 in a mold with the surface of the substrate layer 11 opposite to the heater circuit 12 .

In step 2, molten resin is injected into the mold. A thermoplastic resin is usually used as the resin. As the resin, it is preferable to use the same material as that of the base material 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 resistance to cracking and transparency. The mold temperature in step 2 is, for example, 80° C. or higher and 150° C. or lower, preferably 100° C. or higher and 140° C. or lower. The temperature of the molten resin is, for example, 200° C. or higher and 400° C. or lower, preferably 250° C. or higher and 350° C. or lower. The holding pressure in step 2 is, for example, 10 Pa or more and 100 Pa or less, 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, preferably 50 mm/s or more and 150 mm/s.

In step 3, the melted resin is solidified. Step 3 is performed, for example, by gradually lowering the mold temperature. Thereby, an insert-molded article 2 including the heater film 1 can be obtained.

EXAMPLES The present disclosure will be described in more detail below with reference to Examples, but the present disclosure is not limited to these Examples.

<Production of heater film>
[Preparation of substrate with circuit]
A transparent polycarbonate film with a thickness of 300 μm was used as the substrate.
The solvent-based adhesive to be applied to the surface of the base material is composed of the main agent "Dynareo VA-3020" (manufactured by Toyo Ink Mfg. Co., Ltd.) and the curing agent "Dynareo HD-701" (manufactured by Toyo Ink Mfg. Co., Ltd.). , were prepared by mixing so that the main agent/curing agent (mass ratio) = 100/7. Then, this solvent-based adhesive was applied to the surface of the substrate in an amount of 3 g/m ² and dried at 120° C. for 1 minute to form a transparent adhesive film with a thickness of 12 μm.
Next, a copper foil is attached to the surface of the formed adhesive film, and then heated at 40 ° C. for 48 hours and at 60 ° C. for 96 hours to cure the adhesive, thereby forming a base material with copper foil. got a layer. A copper foil having a thickness of 35 μm was used as the copper foil.
A substrate layer with a heater circuit was produced by removing unnecessary portions of the copper foil from the substrate layer with the copper foil by photoetching and providing an arbitrary wiring pattern on the substrate layer.

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

Two pieces of heat-resistant polyimide tape (7413D manufactured by 3M) were superimposed on the part where the circuit was not formed on the fabricated substrate layer with circuit for heater, and it was pasted on the end of the substrate layer with circuit for heater. , to form a frame with a thickness of 135 μm. Subsequently, various circuit protective layer materials were placed on the substrate layer with a heater circuit, and an aluminum rod with a diameter of 3 mm was attached to the polyimide tape, and the aluminum rod was placed on the surface of the polyimide tape. The material for the circuit protective layer was spread over the circuit-attached substrate layer for the heater by moving along the .

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

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

[Interfacial adhesion strength]
As shown in FIG. 3A, from a copper foil-attached substrate having a size of 15×15 mm, the copper foil is etched to form an adhesive-attached substrate 42, and various circuit protective layers are applied to the adhesive-attached substrate 42. After forming the film 43 using the material, the aluminum rivets 44 are attached and cured for a predetermined time, so that the aluminum rivets 44 are attached to the surface of the substrate 42 with the adhesive via the circuit protection layer material 43 . A test piece 41 was produced. Using the prepared test piece 41, as shown in FIG. 3B, a die shear test was performed with a bond tester (4000 type manufactured by Dega) to determine the interfacial adhesion strength between the adhesive portion (base material layer) and the circuit protective layer. was measured. The bottom surface of the aluminum rivet 44 is circular with a diameter of 6 mm. The width of the tool A used for the measurement was 9 mm, the height of the tool A (the distance between the base material 42 with adhesive and the lower end of the tool A) was 100 μm, and the speed of the tool A was 100 μm/sec. The stage on which 41 was installed was heated to 120° C. and the measurement was carried out.

[Injection molding resistance]
First, a heater film having a circuit protective layer was produced using an injection molding machine (Si-80 manufactured by Toyo Machinery & Metal Co., Ltd.). The heater film having the circuit protective layer thus produced was cut into a size of 30 mm×30 mm and attached to a position directly below the gate of the mold. The conditions for preparing a test piece for injection molding resistance evaluation are as follows: resin used: Polycarbonate (Mitsubishi Engineering-Plastics Iupilon S-3000), resin temperature 320°C, mold temperature 80°C, injection speed 80mm/s, holding pressure The pressure was 40 Pa and the gate width was 7 mm. In this way, as shown in FIG. 4, a flat test piece 51 of 100 mm square and 2 mm thick including a heater film 52 having a circuit protective layer was produced.
Regarding the obtained test piece 51, the area of the portion B where the circuit protective layer was destroyed by the resin injected from the gate adjacent to the portion 53 corresponding to the gate was superimposed on the test piece with a 1 mm grid. Calculated.

Injection molding resistance was evaluated according to the following criteria based on the area of portion B where the circuit protective layer was destroyed.
◎: 10 mm ² or less ○: 88 mm ² or less ×: more than 88 mm ²

From the results in Table 1, the heater films of the examples have excellent injection molding resistance because the 5% weight loss temperature of the circuit protective layer and the tensile elastic modulus at 25°C and 300°C are within specific ranges. It has been shown. It was also shown that the heater film of the comparative example had poor injection molding resistance because at least one of the 5% weight loss temperature of the circuit protective layer and the tensile modulus at 25°C and 300°C was outside the specified range. .

Reference Signs List 1 Heater film for in-vehicle parts 2 Insert molded product 11 Base material layer 12 Heater circuit 13 Circuit protection layer 21 Adhesion part

Claims (5)

a substrate layer;
a heater circuit laminated on the base material layer;
a circuit protection layer laid so as to surround the heater circuit,
The circuit protective layer has a 5% weight loss temperature of 300° C. or higher in thermogravimetric differential thermal analysis, a tensile elastic modulus of 1 GPa or more and 300 GPa or less at 25° C., and 10 MPa or more at 300° C. Heater film for automotive parts. 2. The heater film for automotive parts according to claim 1, wherein said 5% weight loss temperature is less than 500[deg.]C. 3. The heater film for in-vehicle parts according to claim 1 or 2, wherein the circuit protective layer contains a cured product of a composition containing an epoxy resin as a main component. 4. The heater film for in-vehicle parts according to claim 1, wherein an interfacial adhesion strength between the substrate layer and the circuit protective layer in a die shear test is 1 MPa or more at 120[deg.]C. a step of placing the heater film for automotive parts according to any one of claims 1 to 4 in a mold;
injecting molten resin into the mold;
A method of manufacturing an insert-molded product, comprising the step of solidifying the molten resin.

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