Conductive sheet, resin molded article and production method therefor

Abstract

[Problem] To provide a conductive sheet, a resin molded article and a production method therefor, which make it possible to prevent disconnection during injection molding and to obtain good moldability and functionality. [Solution] A conductive sheet (1) comprises: a base material sheet (2) that includes a functional region (A1) and an extended region (A2); a conductive pattern (3) that is formed in the functional region; a lead wire (4) that is formed in the extended region and that is provided in contact with or in proximity to at least a portion of the conductive pattern; and a conductive material (5) that electrically connects the conductive pattern and the lead wire. The resistance value of the lead wire is lower than the resistance value of the conductive pattern.

Description

Conductive sheet, resin molded product, and manufacturing method thereof

[0001] The present invention relates to a conductive sheet, and more particularly to a conductive sheet used in a vehicle heater.

[0002] Japanese Patent Application Laid-Open No. 2019-169417 (Patent Document 1) discloses a film heater having a conductive pattern formed on a sheet using copper wire or the like.

[0003] Japanese Patent Application Laid-Open No. 2019-169417

[0004] The film heater of Patent Document 1 has copper wires with low extensibility embedded in the entire sheet, which has the problem that the copper wires break during injection molding.

[0005] The present invention has been made to solve the above-mentioned problems, and its object is to provide a conductive sheet and a resin molded product that have good formability and functionality, and a method for manufacturing the same.

[0006] A conductive sheet according to one embodiment of the present invention comprises a base sheet including a functional region and an extension region, a conductive pattern formed in the functional region, a routing wiring formed in the extension region and arranged in contact with or in close proximity to at least a portion of the conductive pattern, and a conductive material that electrically connects the conductive pattern and the routing wiring, wherein the resistance value of the routing wiring is lower than the resistance value of the conductive pattern.

[0007] Preferably, the base sheet has a three-dimensional shape having a bent portion where the lead wiring is bent at a predetermined angle.

[0008] Preferably, the conductive pattern has an overlapping portion that overlaps with the routing wiring, and the conductive material is disposed in the overlapping portion.

[0009] Preferably, the conductive material has a lower resistance than the conductive pattern.

[0010] A resin molded product according to another aspect of the present invention comprises a preform body in which the routing wiring of the conductive sheet according to one aspect of the present invention is bent, and a resin molded body laminated on the front and / or back surface of the preform body.

[0011] A method for manufacturing a conductive sheet according to another aspect of the present invention includes the steps of preparing a base sheet including a functional region and an extension region, forming a routing wiring in the extension region on the base sheet, forming a conductive pattern in the functional region on the base sheet, the conductive pattern having a resistance value higher than the resistance value of the routing wiring, and providing a conductive material that electrically connects the conductive pattern and the routing wiring.

[0012] Preferably, the method further includes a step of bending the lead-out wiring of the base sheet.

[0013] A method for manufacturing a resin molded product according to another aspect of the present invention includes the steps of preparing an injection molding die having a fixed die and a movable die that forms a cavity between the fixed die and the movable die, placing a conductive sheet according to one aspect of the present invention on one of the cavity surfaces of the die, clamping the injection molding die, injecting molten resin into the cavity to form a resin molded body while simultaneously adhering a conductive sheet to the surface of the resin molded body, and opening the injection molding die and removing the resin molded body with the adhering conductive sheet.

[0014] A method for manufacturing a resin molded product according to another aspect of the present invention includes the steps of preparing a preform body in which the routing wiring of the conductive sheet according to one aspect of the present invention is bent, preparing a resin molded body having a shape corresponding to the shape of the preform body, and adhering the resin molded body to the front and / or back surface of the preform body.

[0015] The conductive sheet of the present invention can prevent wire breakage during injection molding and can provide good moldability and functionality.

[0016] 1A to 1C are diagrams schematically illustrating a conductive sheet according to the present embodiment; FIG. 1A is a schematic cross-sectional view showing a state before molding of the conductive sheet according to the present embodiment; FIG. 1B is a schematic cross-sectional view showing a preform of the conductive sheet; and FIG. 1C is a schematic cross-sectional view showing a resin molded product obtained by laminating a resin molded product on the preform. FIG. 1A is a plan view showing a first modified conductive material; and FIG. 1B is a schematic cross-sectional view showing a second modified conductive material. FIG. 1C is a flowchart showing a method for manufacturing a conductive sheet according to the present embodiment; FIG. 1D is a flowchart showing a method for manufacturing a resin molded product according to another embodiment; FIG. 1D is a flowchart showing a method for manufacturing a resin molded product according to the present embodiment; and FIG. 1E is a schematic cross-sectional view showing a method for manufacturing a resin molded product according to another embodiment.

[0017] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described in detail with reference to the accompanying drawings, in which like reference numerals denote like or corresponding parts and will not be described repeatedly.

[0018] <Conductive Sheet> A conductive sheet 1 according to one embodiment of the present invention will be described with reference to Fig. 1. The conductive sheet 1 includes a rectangular base sheet 2, a conductive pattern 3 patterned in a meandering shape, routing wiring 4 routed around the conductive pattern 3, and a conductive material 5 connecting the conductive pattern 3 and the routing wiring 4.

[0019] The base sheet 2 has a rectangular shape in a plan view and includes a functional region A1 and an extension region A2 on the same plane. The functional region A1 is typically a region having a heater function, and can have various functions such as a sensing function, a light transmission function, an antenna function, etc. depending on the application of the conductive sheet 1. The extension region A2 is a region that can be folded during injection molding of the conductive sheet 1.

[0020] The base sheet 2 is formed of a thermoplastic resin, such as polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polypropylene, PC-ABS, polyvinyl chloride, or acrylic resin. The base sheet 2 preferably has a heat shrinkage rate of 2.5% or less and has suitable stretchability for a conductive film used in injection molding. This not only improves moldability during injection molding, but also prevents warpage during molding of the conductive sheet 1.

[0021] From the viewpoint of good formability, the thickness of the base sheet 2 is preferably 0.2 mm to 0.5 mm. If the thickness is thinner than 0.2 mm, when the conductive pattern 3 is embedded in the base sheet 2, the shape of the conductive pattern 3 may stand out on the back surface of the sheet, which may impair the appearance design of the resin molded product described below. If the thickness is thicker than 0.5 mm, it may be difficult to form a preform body described below.

[0022] Referring to Figure 2, the base sheet 2 can be formed into a three-dimensional shape 10 (also referred to as a "preform" of the conductive sheet 1) having a bent portion 21 where the routing wiring 3 is bent at a predetermined angle. From the viewpoint of good formability, the thickness of the base sheet 2 after preforming is preferably 150 µm or more. The "predetermined angle" is an angle appropriately set by the user, and the interior angle can preferably be set to an obtuse angle, i.e., 90 to 179 degrees.

[0023] The preform 10 has one or more bent portions 21 and can be molded into a desired shape. In the conductive sheet 1 of this embodiment, highly extensible wiring 4 is arranged in the extension region A2. This makes the wire less likely to break compared to conventional embedded wires that are bent by injection molding, and allows for the formation of dynamic shapes.

[0024] The conductive pattern 3 can be patterned in various ways depending on the function of the functional area A1. For example, referring to FIG. 1 , the conductive pattern 3 may be arranged at equal intervals in the short direction. That is, the conductive pattern 3 of this embodiment is a meander-shaped pattern formed in one stroke using a single wire. The conductive pattern 3 is formed using a single copper wire 3, and both ends of the conductive pattern 3 are gathered at one location on the routing wiring 4.

[0025] The conductive pattern 3 is provided in the functional region A1. The conductive pattern 3 is typically a copper wire, and is formed from various conductive materials such as copper, etched copper, indium tin oxide (ITO), polyethylenedioxythiophene (PEDOT), silver nanowire (AgNW), and copper mesh. The conductive material may be a single type or an alloy containing two or more types of metals. The conductive pattern 3 of this embodiment has a higher resistance value than the routing wiring 4. This makes the conductive pattern 3 more likely to generate heat than the routing wiring 4, allowing it to efficiently perform its heater function.

[0026] When the conductive pattern 3 is a copper wire 3, its diameter is preferably 0.05 mm to 0.5 mm, and more preferably 0.2 mm to 0.5 mm. If it is thinner than 0.05 mm, it becomes prone to breakage and the resistance becomes too high, resulting in a decrease in heater function. If it is thicker than 0.5 mm, the visible light and radio wave transmittance of the functional area becomes poor.

[0027] Although the conductive pattern 3 in this embodiment is composed of one wire, the conductive pattern 3 may be composed of two or more wires. Even in this case, each of the plurality of wires is appropriately connected to the routing wiring 4 so as to be electrically conductive.

[0028] Furthermore, although the conductive pattern 3 in this embodiment is a meander-shaped pattern, the conductive pattern 3 can take various patterns, such as a shape arranged to surround the functional area A1, a spiral shape, or a diagonal line shape.

[0029] The routing wiring 4 connects the conductive pattern 3 to a terminal portion (not shown) that is connected to an external member. The routing wiring 4 is provided in contact with or close to both ends of one copper wire 3, and is formed in the extension region A2. The term "in contact with or close to" here means that the routing wiring 4 and the conductive pattern 3 may be arranged to overlap each other, or may be arranged about 5 mm apart.

[0030] The routing wiring 4 is typically silver wiring, and is formed from, for example, silver nanowires, carbon paste, or the like. It is formed from a conductive material that is more extensible than the conductive pattern 3. This allows for a greater depth during injection molding than conventional methods, allowing for more flexible design. Furthermore, the thickness and width of the routing wiring 4 of this embodiment are designed so that its resistance is lower than that of the conductive pattern 3, thereby suppressing heat generation. This makes it possible to prevent problems caused by heat generation outside the functional area.

[0031] The thickness and width of the routing wiring 4 are designed appropriately depending on the resistance value of the conductive pattern 3 used and the resistance value and length of the routing wiring 4. For example, when the routing wiring 4 is a silver wiring, the thickness is preferably 2 to 30 μm, more preferably 10 to 20 μm. The width is preferably 5 to 30 mm, more preferably 10 to 20 mm.

[0032] The conductive material 5 is typically a conductive paste, and electrically connects the conductive pattern 3 and the routing wiring 4, which are provided in contact with or adjacent to each other. The conductive material 5 is, for example, copper, aluminum, phosphor bronze, nickel, iron, carbon, polyethylenedioxythiophene (PEDOT), etc. The form of the conductive material 5 is not particularly limited, and may be a paste, plate, tape, or the like, but it is preferable to use a paste-like material from the viewpoint of preventing peeling during injection molding.

[0033] The conductive material 5 in this embodiment is designed to have a lower resistance value than the conductive pattern 3. To lower the resistance value, for example, a conductive plate material or the like may be additionally fixed. This prevents the conductive material 5 from generating heat and melting. The conductive material 5 may be provided in either the functional region A1 or the extension region A2 on the conductive sheet 2, and is provided appropriately depending on the application of the conductive sheet 1. For example, the conductive material 5 may be provided in the functional region A1 from the viewpoint of preventing the conductive pattern 3 from peeling off during injection molding, or may be provided in the extension region A2 from the viewpoint of increasing the visibility of the functional region A1. In other words, the region where the conductive material 5 is provided can be the "connection region" between the conductive pattern 3 and the routing wiring 4.

[0034] (Modifications) Next, modifications of the conductive material 5 will be described with reference to Fig. 3. Fig. 3(a) is a plan view showing a first modification of the conductive material 5A, and Fig. 3(b) is a schematic cross-sectional view showing a second modification of the conductive material 5B.

[0035] 3( a), the conductive pattern 3A may have an overlapping portion 31 that overlaps with the routing wiring 4. In this embodiment, a conductive material 5A (shown by a dotted line) is provided so as to cover the overlapping portion 31. This ensures that two different wirings, i.e., the conductive pattern 3A and the routing wiring 4, are electrically connected.

[0036] 3(b), the conductive pattern 3B may be provided so as to be spaced apart from the routing wiring 4. In this case, the conductive material 5B is provided so as to be embedded in the base sheet 2B located between the conductive pattern 3B and the routing wiring 4, and conducts electricity between the conductive pattern 3B and the routing wiring 4. This can reduce irregularities that occur on the surface of the conductive sheet 1B (the surface on which the conductive pattern 3B and the routing wiring 4 are provided), and can result in a conductive sheet 1B with good formability.

[0037] (Resistance Difference) Here, the conductive sheet 1 of the present embodiment includes two wirings with different resistance values. Generally, the heat generation amount P can be calculated by the following formula: P=I ２ ×R=V ２×R P: heat generation amount (W) I: current (A) R: resistance (Ω) V: voltage (V) From the above formula, the higher the resistance value R, the larger the heat generation amount P. Therefore, in the conductive sheet 1 of the present embodiment, the wiring with the higher resistance value, i.e., the conductive pattern 3, can generate heat preferentially. From the viewpoint of suppressing heat generation in the routing wiring 4, the resistance value of the routing wiring 4 extended by preforming is preferably 1 / 10 or less, and more preferably 1 / 20 or less, of the resistance value of the conductive pattern 3.

[0038] (Effects) Conventional conductive sheets have copper wires embedded throughout. Copper wires generally have low extensibility, making them prone to breakage during injection molding, and it has been difficult to form molded products with depths greater than the allowable depth. In contrast, the conductive sheet 1 according to this embodiment uses highly extensible silver wiring in the areas that are bent during injection molding. This makes it possible to apply more dynamic uneven shapes than before, enabling the sheet to accommodate a wide range of user-desired designs.

[0039] Another conventional conductive sheet had silver wiring provided over the entire sheet. Although silver wiring has good extensibility, in order to obtain the required amount of heat in the required area (functional area), the entire sheet had to be heated uniformly, resulting in poor heat generation efficiency (energy loss). In contrast, the conductive sheet 1 according to the present embodiment uses two wirings with different resistance values, which allows heat to be generated only in the required area (functional area) with a small amount of energy, thereby improving the heat generation efficiency of the conductive sheet.

[0040] <Conductive Sheet Manufacturing Method> Next, a conductive sheet manufacturing method S10 according to this embodiment will be described with reference to Fig. 4. Fig. 4 is a flowchart showing the conductive sheet manufacturing method according to this embodiment.

[0041] First, a base sheet including a functional region and an extension region is prepared (base sheet preparation step; step S11). The base sheet is rolled up to improve operability. Next, routing wiring is formed on the base sheet in the extension region (routing wiring formation step; step S12). The routing wiring is drawn by, for example, screen printing using silver paste, and a base sheet is formed on which a desired pattern is repeatedly printed. The base sheet on which the routing wiring has been formed is wound into a roll, similar to step S1.

[0042] Next, a conductive pattern is formed in the functional region on the base sheet (conductive pattern forming step; step S13). The conductive pattern is formed from a material with a higher resistance than the routing wiring, and is bonded by, for example, embedding copper wire using ultrasonic welding. Next, a conductive material is provided to electrically connect the conductive pattern and the routing wiring (conductive material attachment step; step S14). The conductive material is provided so as to fill the gap between the conductive pattern and the routing wiring or to cover the ends of each wiring. This allows two wirings made of different materials to be firmly connected electrically.

[0043] The conductive sheet according to this embodiment may be a preform 10 that has been folded into a desired shape in advance (folding step; step S15). In this case, the folding step is not limited to injection molding, and the sheet can be folded by a known method such as vacuum forming. The folded conductive sheet is fixed to a resin molded article, which will be described later, and incorporated into the resin molded product.

[0044] <Regarding the Resin Molded Product> As shown in FIG. 2( c), a resin molded product 12 according to another aspect of the present invention includes a preform 10 in which the routing wiring of the conductive sheet according to one aspect of the present invention is bent, and a resin molded product 11 laminated on the front and / or back surface of the preform 10.

[0045] The resin molded body 11 is made of a material having properties suitable for the intended use of the resin molded product 12, such as polycarbonate, acrylonitrile butadiene styrene, or PC-ABS alloy.

[0046] The resin molded body 11 is fixed to the preform body 10 with an adhesive or by thermocompression bonding during injection molding. When fixing by thermocompression bonding, the resin molded body 11 is preferably formed from the same type of thermoplastic resin as the base sheet 2, from the viewpoint of facilitating fixing to the base sheet 2.

[0047] The conductive sheet 1 of this embodiment has highly extensible wiring 4 provided in an area that is bent during injection molding. This makes it possible to prevent the wiring 4 from breaking or peeling off when manufacturing the resin molded product 12 of this embodiment. In other words, the resin molded product 12 of this embodiment has good moldability and functionality.

[0048] The resin molded article 12 may include a laminated body including not only the preform body 10 and the resin molded body 11 but also a decorative layer, a transfer layer, an adhesive layer, and other functional layers.

[0049] Furthermore, the conductive sheet 1 according to this embodiment has better light transmittance than conventional vehicle heaters that have silver wiring in their functional areas. Therefore, it can be suitably used in resin molded products that require high visible light transmittance without impairing the external design, such as heaters for vehicle headlights. In this case, the functional area of ​​the conductive sheet can be considered a "light-transmitting area."

[0050] Furthermore, the conductive sheet 1 according to this embodiment transmits microwaves and laser light emitted from RADAR (Radio Detecting and Ranging) and LiDAR (Light Detection and Ranging), while using its heater function to remove snow and other obstacles that may obstruct the sensor. This prevents malfunctions of vehicle sensors that may be caused by weather. In this case, the functional area of ​​the conductive sheet can be considered a "sensing functional area."

[0051] <Regarding the manufacturing method of a resin molded product> (Embodiment 1) A manufacturing method S20 of a resin molded product according to this embodiment will be described with reference to Fig. 5 and Fig. 7. Fig. 5 is a flowchart showing the manufacturing method of a resin molded product according to this embodiment. Fig. 7 is a schematic cross-sectional view showing the manufacturing method of a resin molded product according to this embodiment.

[0052] 7(a), first, an injection molding die 6 is prepared, which includes a fixed die 61 and a movable die 62 that forms a cavity 63 between the fixed die 61 and the fixed die 61 (die preparation step; step S21). Next, a conductive sheet 1 according to one aspect of the present invention is placed on one of the cavity surfaces 64 of the die 6 (sheet placement step; step S22). In this embodiment, the conductive sheet 1 is placed so as to conform to the cavity surface of the movable die 62. Note that the conductive sheet 1 is placed so that the extension region of the conductive sheet 1 is placed in the curved region of the die 6, and the functional region of the conductive sheet 1 is placed in the smooth region of the die 6. Here, "smooth" includes not only a planar shape but also a slightly uneven shape that the copper wire can withstand.

[0053] 7(b), the injection mold 6 is clamped (clamping step; step S23). Clamping is performed by moving the movable mold 62. The fixed mold 61 has a resin inlet 65 for pouring molten resin 65a into the cavity 63, and the molten resin is injected into the cavity 63 formed by clamping. Here, a conductive sheet 1 is provided on the cavity surface 64 on the movable mold 62 side. That is, by injecting the molten resin 65a into the cavity 63, the resin molded body 11 is molded, and at the same time, the conductive sheet 1 (preform body 10) is fixed to the surface of the resin molded body 11 (injection and fixing step; step S24).

[0054] 7(c), the injection molding die 6 is opened to remove the resin molded product 12 to which the conductive sheet 1 (preform 10) and the resin molded body 11 are fixed (mold opening step; step S25). The mold opening is performed by moving the movable die 62.

[0055] According to the manufacturing method S20 for a resin molded product of this embodiment, the conductive sheet 1 can be bent to a greater depth than conventional methods. This allows the resin molded product of this embodiment to accommodate a wide range of designs desired by users. Furthermore, since "injection molding" and "bonding of the conductive sheet to the resin molded product" are performed simultaneously, production efficiency can be improved.

[0056] 6 and 8, a method S30 for manufacturing a resin molded product according to the second embodiment will be described. Fig. 6 is a flowchart showing the method for manufacturing a resin molded product according to the second embodiment. Fig. 8 is a schematic cross-sectional view showing the method for manufacturing a resin molded product according to the second embodiment.

[0057] 8(a), a preform 10 is prepared by bending the routing wiring 21 of the conductive sheet 1 according to one embodiment of the present invention at the bending portion 21 (preform preparation step; step S31). At the same time, a resin molded body 11 having a shape corresponding to the shape of the preform 10 is prepared (resin molded body preparation step; step S32). Note that the "shape corresponding to the shape of the preform" mentioned here does not necessarily mean that the resin molded body 11 and the preform 10 have the same shape. Specifically, it is intended to include a design that is completed by combining different corresponding shapes.

[0058] 8(b), a resin molded body 11 is fixed to the front and / or rear surface of the preform body 10 (fixing step; step S33), whereby a resin molded product 12 is formed.

[0059] Although the resin molded article 12 of this embodiment includes the conductive sheet 1 and the resin molded body 11, it goes without saying that various layers can be provided depending on the desired design and function. For example, an embossed surface layer may be provided on the upper surface of the resin molded body 11, or an adhesive layer may be provided between the preform 10 and the resin molded body 11.

[0060] REFERENCE SIGNS LIST 1 Conductive sheet, 2 Base sheet, 3 Conductive pattern, 4 Routed wiring, 5 Conductive material, 6 Mold, 10 Preform, 11 Resin molded body, 12 Resin molded product, 21 Bent portion, 31 Overlap portion, A1 Functional region, A2 Extension region.

Claims

1. A conductive sheet comprising: a base sheet including a functional region and an extension region; a conductive pattern formed in the functional region; a routing wiring formed in the extension region and arranged in contact with or adjacent to at least a portion of the conductive pattern; and a conductive material electrically connecting the conductive pattern and the routing wiring, wherein the resistance value of the routing wiring is lower than the resistance value of the conductive pattern.

2. The conductive sheet according to claim 1, wherein the base sheet has a three-dimensional shape having a bent portion where the lead-out wiring is bent at a predetermined angle.

3. The conductive sheet according to claim 1, wherein the conductive pattern has an overlapping portion that overlaps with the routing wiring, and the conductive material is disposed in the overlapping portion.

4. The conductive sheet according to claim 1, wherein the conductive material has a lower resistance than the conductive pattern.

5. A resin molded product comprising: a preform in which the lead-out wiring is bent in the conductive sheet according to claim 2; and a resin molded body laminated on the front and / or back surface of the preform.

6. A method for manufacturing a conductive sheet, comprising the steps of: preparing a base sheet including a functional region and an extension region; forming a wiring pattern in the extension region on the base sheet; forming a conductive pattern in the functional region on the base sheet, the conductive pattern having a resistance value higher than that of the wiring pattern; and providing a conductive material that electrically connects the conductive pattern and the wiring pattern.

7. The method for producing a conductive sheet according to claim 6, further comprising a step of bending the lead-out wiring of the base sheet.

8. A method for manufacturing a resin molded product, comprising the steps of: preparing an injection molding die having a fixed die and a movable die that forms a cavity between the fixed die and the movable die; placing the conductive sheet described in claim 1 on any of the cavity surfaces of the die; clamping the injection molding die; injecting molten resin into the cavity to form a resin molded product while simultaneously fixing the conductive sheet to a surface of the resin molded product; and opening the injection molding die and removing the resin molded product with the conductive sheet fixed thereto.

9. A method for manufacturing a resin molded product, comprising the steps of: preparing a preform in which the routing wiring of the conductive sheet described in claim 1 is folded; preparing a resin molded body having a shape corresponding to the shape of the preform; and adhering the resin molded body to the front and / or back surface of the preform.

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