JP7520910B2 - Film Heater - Google Patents

Description

The present invention relates to a film heater, and in particular to a film heater having a conductive pattern on the film that can be electrically connected to an external power source.

Conventionally, there have been known film-like sheet heating elements with conductive patterns for heating, which are attached to the adherend to be heated, for the purposes of preventing ice and snow from adhering, melting snow, preventing fogging, and maintaining heat.

For example, Patent Document 1 discloses a sheet heating element in which bare nichrome wire processed into an arbitrary shape is disposed inside two multilayer composite films via an adhesive layer made of an insulating material, and describes that this sheet heating element is attached to an object to be heated by double-sided adhesive tape, double-sided adhesive film, or the like.
Patent Document 2 discloses a semi-cured sheet for manufacturing a hard planar heating element, which has a flexible planar heating part and a semi-cured resin coating layer in a semi-cured state formed to enclose the heating part. It is described that the semi-cured resin coating layer enclosing the heating part is in a semi-cured state (B stage) and has flexibility and plasticity, and its surface is adhesive, so that it can be attached to any shape of an adherend.

Patent document 3 discloses a planar heater for signal lights, characterized in that it has metal wire resistors formed in a predetermined pattern on the surface or inside of a circular sheet-like flexible transparent substrate having sector-shaped cutouts with a central angle of 90 degrees or less, and describes how by bringing the straight line portions of the sector-shaped cutouts into contact or close to each other and transforming the flexible transparent substrate from a circular sheet into a conical sheet shape, it is easy to achieve close contact even if the display window of the signal light is dome-shaped.

JP 2003-257597 A JP 2006-278138 A JP 2017-004918 A

The invention disclosed in Patent Document 1 has a complex structure in which a bare nichrome wire is disposed between two sheets of multi-layer composite film using an adhesive layer for fixing the wiring, and the peripheral portions of the multi-layer composite film are heat-sealed.
The invention disclosed in Patent Document 2 requires the use of a special resin coating, and requires special equipment for completely curing the semi-cured resin coating layer by a photocuring method, which tends to make the application method complicated.
The invention disclosed in Patent Document 3 is effective when the display window of the signal lamp is dome-shaped, but is difficult to use in other cases.

The present invention aims to provide a film heater that is easy to manufacture, does not impair the design of the adherend, and can be easily attached to adherends with uneven shapes.

The present invention is a film heater characterized in that a conductive pattern consisting of conductive wires is provided on one surface of a support sheet made of a transparent thermoplastic resin sheet, and the conductive pattern has a connection terminal portion, a lead wire extending from the connection terminal portion, and a heater portion continuing from the lead wire, which are provided as a continuous linear pattern consisting of a single conductive wire.
In the present invention, the connection terminal portion may be configured in a pattern in which the conductive wire is bent at a plurality of points, for example, in a meandering shape in which the conductive wire is bent at a plurality of points and meanders.

In the present invention, a film heater can be provided in which an exterior sheet made of a transparent thermoplastic resin sheet separate from the support sheet is provided on the surface of the support sheet on which the conductive pattern is provided, so as to cover the conductive pattern, and the exterior sheet is provided with a through hole that exposes at least a portion of the connection terminal portion to the outside.
In the present invention, a metal plate can be further provided on the connection terminal portion.
In the present invention, the conductive wires constituting the conductive pattern may be covered with a self-adhesive insulating coating, except for the connection terminal portion.In the present invention, the support sheet may be configured such that an adhesive layer is provided on the side opposite to the side on which the conductive pattern is provided.

The film heater according to the present invention is a transparent film heater overall, and can be attached to various adherends without impairing the design of the adherend to be heated. In addition, by using thermoplastic resin sheets for the support sheet and, if present, the exterior sheet, it can be easily attached to adherends with uneven shapes, and in particular, when the adherend is a resin molded body, in-mold transfer is possible, which allows the film heater to be formed on the surface of the resin molded body at the same time as the resin is molded. In addition, since the conductive pattern is made of a single conductive wire, the conductive pattern can be continuously formed with a single conductive wire, making production easier, and the conductive pattern can be protected by covering the entire surface of the support sheet on which the conductive pattern is formed with the exterior sheet.

The present invention is a film heater that has good formability, high mechanical strength, and excellent adhesion to substrates, and can be used for a variety of purposes, such as preventing ice and snow from adhering, melting snow, preventing fogging, and keeping warm. For example, it can be used in automobile headlights, motorcycle grips and seats, outdoor lights, traffic lights, etc.

1A is a plan view showing an example of a film heater according to the present invention, and FIG. 1B is a cross-sectional view thereof. FIG. 1A is a plan view showing an example of an exterior sheet that can be used in the present invention, and FIG. FIG. 1A is a plan view showing an example of a film heater of the present invention using an exterior sheet, and FIG.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
Fig. 1(a) is a plan view and Fig. 1(b) is a cross-sectional view showing an example of the film heater of the present invention.
1, a conductive pattern 2 made of conductive wires is provided on one surface of a support sheet 1 made of a transparent thermoplastic resin sheet. The conductive pattern 2 is provided as a continuous linear pattern made of a single conductive wire, including a pair of left and right connection terminals 21a, 21b, lead wires 22a, 22b extending from the connection terminals 21a, 21b, respectively, and a heater portion 23 continuing from the lead wires 22a, 22b. As in this embodiment, the heater portion may be non-linear as a whole.

The support sheet used in the film heater of the present invention is made of a transparent thermoplastic resin sheet. This makes it possible to suitably manufacture a film heater that is transparent as a whole. The film heater that is transparent as a whole can be attached to various adherends without impairing the design of the adherend to be heated.
Furthermore, by using a thermoplastic resin sheet, it can be easily attached to an adherend having an uneven shape. In particular, when the adherend is a resin molded body, a film heater can be formed on the surface of the resin molded body by a molding method such as vacuum molding, hot press molding, lamination molding, in-mold molding, or insert molding.

The thermoplastic resin sheet may be made of ethylene-based resin, propylene-based resin, polyolefin-based resin, thermoplastic polyester-based resin, polyamide-based resin, polyvinyl chloride, polycarbonate, ABS resin, etc., or may contain two or more of these. In particular, it is preferable to use a polypropylene-based resin, which has excellent moldability, mechanical strength, flexibility, and weather resistance.
To the thermoplastic resin sheet, inorganic fine powder or organic filler, dispersant, antioxidant, compatibilizer, ultraviolet stabilizer, antiblocking agent, antistatic agent, etc. may be appropriately added.
The thickness of the thermoplastic resin sheet is preferably 0.030 mm to 1.000 mm, and more preferably 0.100 mm to 0.700 mm.

The conductive pattern can also be formed by printing with a conductive ink such as silver paste or by etching a metal foil such as copper foil. When forming the conductive pattern, it is preferable to form a circular conductive wire having a certain diameter in a predetermined pattern, since this makes it easy to form the heater portion, the lead portion, and the connection terminal portion as one continuous line.
When the conductive pattern is made of a conductive wire, the conductive wire is preferably made of at least a metal wire, and more preferably, the metal wire is coated with a self-adhesive insulating coating. As the metal wire, for example, a metal wire such as copper, iron, gold, copper-nickel, nickel-chrome, iron-nickel-chrome, etc. can be used, but other materials can also be used as long as they are conductive. From the viewpoints of electrical resistance, durability, and cost, it is preferable to use copper or a copper alloy in which copper is combined with zinc, lead, tin, silver, aluminum, nickel, beryllium, zirconium, etc. alone or in combination.

The insulating coating that covers the metal wire is an insulating resin coating, and the conductive wire covered with the insulating coating can be a commercially available enameled wire. Specific examples of the insulating resin coating include polyester, polyethylene, polyurethane, polyvinyl chloride, polyamide, polyimide, polyesterimide, polyamideimide, and fluororesin. The insulating coating is typically black, but may be colored in any color to match the color of the adherend to be heated.
The diameter of the conductive wire constituting the conductive pattern is, for example, 0.03 mm to 0.20 mm. Although it may not be easy to form a thin conductive wire, it is better for the conductive wire to be as thin as possible in order not to impair the design of the adherend to be heated, and the diameter of the conductive wire is preferably 0.05 mm to 0.15 mm. The length of the conductive wire can be determined according to the pattern form of the conductive pattern, etc.

The conductive pattern can typically be formed by drawing conductive lines on a support sheet to form a predetermined pattern, and then fixing the conductive lines by embedding them into at least the surface of the support sheet.
As a method for embedding the conductive wire in the surface of the support sheet, for example, it is desirable to embed the conductive wire in the surface of the support sheet by utilizing the principle of ultrasonic fusion. When performing ultrasonic fusion, a wiring drawing device can be used that can melt the surface of the support sheet made of thermoplastic resin while feeding out the conductive wire, and embed the conductive wire in the surface of the support sheet. The ultrasonic head of such a wiring drawing device can embed the conductive wire in the surface of the support sheet by vibration and pressure while feeding out the conductive wire onto the surface of the support sheet.
Embedding the conductive wires in the surface of the support sheet allows the conductive pattern to be positioned on the support sheet, and can prevent the conductive wires from being displaced due to external impact, etc. Furthermore, embedding the conductive wires in the surface of the support sheet can reduce the degree of unevenness of the surface of the support sheet caused by arranging the conductive wires on the surface of the support sheet.

Next, an embodiment of the conductive pattern of the film heater of the present invention will be described.
Referring to FIG. 1, the conductive pattern 2 is provided as a continuous linear pattern consisting of a single conductive wire, which includes a pair of left and right connection terminal portions 21a, 21b, lead wires 22a, 22b extending from the connection terminal portions 21a, 21b, respectively, and a heater portion 23 continuing from the lead wires 22a, 22b and having a non-linear shape as a whole.
By forming the connection terminal portion, the lead wire, and the heater portion from a single continuous conductive wire, the manufacturing process can be simplified, making it possible to manufacture a low-cost film heater.
In Fig. 1, the connection terminals 21a and 21b are formed in a meandering shape in which the conductive wire is bent and meandered at multiple points. In this case, it is preferable that the number of turns of the turn-back parts of the connection terminals 21a and 21b that are bent and meandered at multiple points is increased within a specified plane area to densely pack the turn-back lines. In the case of the embodiment shown in Fig. 1, the meandering shape is preferably such that relatively short bent parts and relatively long straight parts are repeated, and the number of these straight parts is 2 or more per mm.

If necessary, a conductive piece made of a metal plate can be provided on the connection terminal portion to improve the efficiency of connection with an external electrode. The metal plate can be made of, for example, copper, a copper alloy, iron, or an alloy of iron and nickel.
If the conductive wire is covered with an insulating coating, the insulating coating covering the conductive wire in the connection terminal is removed to expose the internal metal wire. This can be done by cutting with a milling device or the like, but the insulating coating can also be melted and removed by the heat generated when soldering to a metal plate or external electrode.

The heater section 23 is formed by drawing out lead wires 22a, 22b extending from a pair of left and right connection terminals 21a, 21b, respectively. In Fig. 1, the heater section 23 has a non-linear linear pattern as a whole, in which relatively short bent portions and relatively long straight portions are repeated, and the heater section 23 bends and meanders at multiple points. The pattern of the heater section can be any pattern taking into consideration the shape of the adherend, the heating area, and the heating efficiency, and may be a repeated curved shape not including straight portions, or a spiral shape.
In FIG. 1 , the conductive pattern consists of a pair of left and right connection terminal portions 21a, 21b and a pair of left and right lead portions 22a, 22b centered around the heater portion 23, with a meander-shaped connection portion 21a formed with a conductive wire starting from an end of one connection terminal portion 21a, a lead wire 22a extending from the other end of this connection terminal portion 21a, and the heater portion 23 being formed with a conductive wire drawn from this lead wire 22a, and the other lead wire 22b extending from this heater portion 23 to the other connection terminal portion 21b, the heater portion 23, lead portion 22 and connection terminal portion 21 being formed with a single conductive wire that continues to the other connection terminal portion 21b.

In another embodiment of the present invention, a film heater can be formed by providing an exterior sheet made of another transparent thermoplastic resin sheet covering the conductive pattern on the surface of the support sheet on which the conductive pattern is provided, and providing the exterior sheet with a through hole that exposes at least a portion of the connection terminal portion to the outside.

Fig. 2(a) is a plan view and Fig. 2(b) are cross-sectional views each showing an example of an exterior sheet that can be used in the present invention.
In FIG. 2, an exterior sheet 3 having substantially the same shape as the support sheet of the film heater is provided with a through hole 31 for exposing at least a part of the connection terminal of the film heater to the outside.

The exterior sheet can be a thermoplastic resin sheet similar to that of the support sheet, and the exterior sheet can be laminated by subjecting the surface of the support sheet on which the conductive pattern is formed to a heat treatment and/or press treatment. For lamination, an adhesive layer, a pressure-sensitive adhesive layer, a heat seal layer, or the like may be interposed between the support sheet and the exterior sheet as necessary. The exterior sheet is provided with a through hole that exposes at least a part of the connection terminal to the outside. For forming the through hole in the exterior sheet to expose the connection terminal, cutting means such as punching with a die or a laser device can be used, and specifically, a Vic blade, a cutting blade, a laser cutter, a milling device, or the like can be used.

Fig. 3(a) is a plan view and Fig. 3(b) are cross-sectional views showing an example of the film heater of the present invention using an exterior sheet.
3, the entire surface of the support sheet 1 on which the conductive pattern is formed is covered with the exterior sheet 3 except for the through holes 31, so that the connection terminal portion 21 can be reliably electrically connected to an external power source even in a configuration in which the conductive pattern made of conductive wires is sandwiched between the support sheet 1 made of a transparent thermoplastic resin sheet as a whole and the exterior sheet 3. In addition, it becomes possible to protect the heater portion and the lead portion on the surface of the support sheet by covering them with the exterior sheet.
If necessary, an antifouling layer, an antifogging layer, an antistatic layer, a hard coat layer, etc. may be formed on the surface of the exterior sheet.

In the present invention, if necessary, an adhesive layer may be provided on the surface of the support sheet opposite to the surface on which the conductive pattern is provided. By using the adhesive layer, it is possible to easily attach the support sheet to an adherend having an uneven shape. For example, an acrylic, urethane, epoxy, rubber, polyester, cellulose, emulsion, or other adhesive may be used as the adhesive layer. In addition, if necessary, a filler, a tackifier, a curing agent, or the like may be appropriately used as an additive for improving the properties of the adhesive.
The thickness of the adhesive layer is not particularly limited as long as it has sufficient adhesive strength, and is usually 20 μm to 200 μm, and preferably about 25 μm to 75 μm. When forming the adhesive layer, the adhesive can be formed using a coating method such as gravure coating, gravure reverse coating, comma coating, knife coating, and die coating.

Example 1
A thermoplastic resin sheet (polycarbonate sheet DPI-AO manufactured by Mitsubishi Plastics, Inc., thickness 0.075 mm) serving as a support sheet was prepared, and a conductive wire (self-adhesive coated conductor wire AB15 φ0.10 mm manufactured by ELEKTRISOLA) was embedded on the surface of the support sheet using a wiring drawing device equipped with an ultrasonic head (WCE150 manufactured by Ruhlamat, setting conditions: USP1200, speed 40%) to form a conductive pattern as shown in FIG. 1.
The conductive pattern had a lead length (length of the straight line portion from the terminal portion to the first folded position) of 130 mm, a heater portion with a straight line portion of 90 mm, a folded portion (pitch) of 10 mm, and a number of folds (number of lines in the straight line portion) of 8, and a connection terminal portion with a straight line portion of 17 mm, a folded portion (pitch) of 0.3 mm, and a number of folds (number of lines in the straight line portion) of 12. Finally, it was cut to a length of 170 mm x width of 120 mm to produce a film heater.

Example 2
A thermoplastic resin sheet (polycarbonate sheet DPI-AO manufactured by Mitsubishi Plastics, Inc., thickness 0.075 mm) was prepared as an exterior sheet, and a through hole of 10 mm x 10 mm was formed at a position corresponding to the connection terminal. The exterior sheet was attached to the surface of the support sheet on which the conductive pattern of Example 1 was wired, and hot pressed with a vacuum laminator (MVLP-500 manufactured by Meiki Seisakusho, temperature 180°C, pressure 0.5 MPa) to sufficiently adhere to the support sheet. Finally, the sheet was cut to a length of 170 mm x width of 120 mm to prepare a film heater.

REFERENCE SIGNS LIST 1 Support sheet 2 Conductive patterns 21a, 21b Connection terminals 22a, 22b Leads 23 Heater section 3 Exterior sheet 31 Through hole

Claims (4)

A method for manufacturing a film heater, comprising: a step of providing a conductive pattern made of conductive wires on one surface of a support sheet made of a transparent thermoplastic resin sheet; the conductive pattern has a connection terminal portion, a lead wire extending from the connection terminal portion, and a heater portion continuing from the lead wire; and the step of providing the conductive pattern comprises a step of feeding the conductive wires onto a surface of the support sheet with an ultrasonic head, and embedding the conductive wires in the surface of the support sheet by vibration and pressure,
moreover,
A step of providing an adhesive layer by a coating method on the surface of the support sheet opposite to the surface on which the conductive pattern is provided ; and
A step of further providing a metal plate on the connection terminal portion.
Including,
A method for manufacturing a film heater, wherein the connection terminal portion is configured in a pattern in which the conductive wire is bent at multiple points. The method for manufacturing a film heater according to claim 1, wherein the conductive pattern is formed from a single continuous conductive line. The method for manufacturing a film heater according to claim 1 or 2 further includes the steps of providing an exterior sheet made of a transparent thermoplastic resin sheet separate from the support sheet on the surface of the support sheet on which the conductive pattern is provided so as to cover the conductive pattern, and providing a through hole in the exterior sheet to expose at least a portion of the connection terminal portion to the outside. 4. The method for producing a film heater according to claim 1, wherein the conductive wires constituting the conductive pattern are covered with a self-adhesive insulating coating except for the connection terminal portions.

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