Conductive sheet, resin molded product, and manufacturing method thereof

Abstract

To provide a conductive sheet, a resin molded product, and a manufacturing method thereof, which are capable of preventing breakage during injection molding and achieving good moldability and functionality.SOLUTION: A conductive sheet (1) includes a base sheet (2) including a functional region (A1) and an extension region (A2), a conductive pattern (3) formed in the functional region, a wiring (4) provided in contact with or adjacent to at least a portion of the conductive pattern and formed in the extension region, and a conductive material (5) electrically connecting the conductive pattern and the wiring. The resistance value of the wiring is lower than the resistance value of the conductive pattern.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2019-169417 (Patent Document 1) discloses a film heater including a conductive pattern formed of a copper wire or the like on a sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the film heater of Patent Document 1, since a copper wire with low stretchability is embedded in the entire sheet, there is a problem that the copper wire is disconnected during injection molding.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a conductive sheet, a resin molded product, and a method for manufacturing the same, which have good moldability and functionality.

Means for Solving the Problems

[0006] The conductive sheet according to one aspect of the present invention includes a base sheet including a functional region and a stretching region, a conductive pattern formed in the functional region, a lead wiring formed in the stretching region provided in contact with or close to at least a part of the conductive pattern, and a conductive material electrically connecting the conductive pattern and the lead wiring, and a resistance value of the lead wiring is lower than a resistance value of the conductive pattern.

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

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

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

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

[0011] The method for manufacturing a conductive sheet according to another aspect of the present invention includes a step of preparing a base sheet including a functional region and a stretching region, a step of forming a lead wire in the stretching region on the base sheet, a step of forming a conductive pattern having a higher resistance value than the resistance value of the lead wire in the functional region on the base sheet, and a step of providing a conductive material for electrically connecting the conductive pattern and the lead wire.

[0012] Preferably, the base sheet further includes a step of bending the lead wire.

[0013] The method for manufacturing a resin molded product according to another aspect of the present invention includes a step of preparing an injection mold having a fixed mold and a movable mold that forms a cavity between the fixed mold, a step of disposing the conductive sheet according to one aspect of the present invention on any cavity surface of the mold, a step of clamping the injection mold, a step of injecting molten resin into the cavity to mold the resin molded body, and simultaneously fixing the conductive sheet to the surface of the resin molded body, and a step of opening the injection mold and taking out the resin molded body to which the conductive sheet is fixed.

[0014] The method for manufacturing a resin molded product according to another aspect of the present invention includes a step of preparing a preform body in which a lead wire is bent among the conductive sheets according to one aspect of the present invention, a step of preparing a resin molded body having a shape corresponding to the shape of the preform body, and a step of fixing the resin molded body to the front surface and / or the back surface of the preform body.

Advantages of the Invention

[0015] According to the conductive sheet of the present invention, disconnection during injection molding can be prevented, and good moldability and functionality can be obtained.

Brief Description of the Drawings

[0016]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Embodiments for Carrying Out the Invention

[0017] Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their description will not be repeated.

[0018] 〈Regarding the conductive sheet〉 With reference to FIG. 1, a conductive sheet 1 according to an embodiment of the present invention will be described. The conductive sheet 1 includes a rectangular base sheet 2, a conductive pattern 3 patterned in a meander shape, a routing wire 4 routed around the conductive pattern 3, and a conductive material 5 connecting the conductive pattern 3 and the routing wire 4.

[0019] The base sheet 2 is rectangular in 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, and an antenna function according to the use of the conductive sheet 1. The extension region A2 is a region that can be bent during injection molding of the conductive sheet 1.

[0020] The base sheet 2 is formed of a thermoplastic resin, for example, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polypropylene, PC-ABS, polyvinyl chloride, acrylic resin, or the like. The base sheet 2 preferably has a thermal shrinkage rate of 2.5% or less and has suitable stretchability as a conductive film for use in injection molding. Thereby, not only can the moldability during injection molding be improved, but also warpage deformation during molding of the conductive sheet 1 can be prevented.

[0021] From the viewpoint of good moldability, the thickness of the base sheet 2 is preferably 0.2 mm to 0.5 mm. If it 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 protrude from the back surface of the sheet, which may deteriorate the appearance design of the resin molded product described later. If it is thicker than 0.5 mm, it may be difficult to form the preform body described later.

[0022] Referring to FIG. 2, the base sheet 2 can form a three-dimensional shape (also referred to as the "preform body" of the conductive sheet 1) 10 having a bent portion 21 where the lead 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 preferably, the inner angle can be set to an obtuse angle, that is, 90 to 179 degrees.

[0023] The preform body 10 has one or more bent portions 21 and can be formed into a desired shape. In the conductive sheet 1 of the present embodiment, a highly stretchable lead wiring 4 is arranged in the stretching region A2. As a result, it is less likely to break compared to the case of bending an embedded wire by injection molding in the prior art, and a dynamic shape can be formed.

[0024] The wiring patterning of the conductive pattern 3 can adopt various patterns according to the function of the functional region A1. For example, referring to FIG. 1, a form arranged at equal intervals in the short side direction can be mentioned. That is, the conductive pattern 3 of the present embodiment is a meander-shaped pattern formed by a single wire in one stroke. The conductive pattern 3 is formed of a single copper wire 3, and both ends thereof are concentrated at one location of the lead 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 of various conductive materials such as copper, etched copper, indium tin oxide (ITO), polyethylenedioxythiophene (PEDOT), silver nanowire (AgNW), and copper mesh. Note that only one type of conductive material may be used, or it may be an alloy containing two or more types of metals. The conductive pattern 3 of the present embodiment has a higher resistance value than the lead wiring 4. As a result, the conductive pattern 3 is more likely to generate heat than the lead wiring 4, and the heater function can be efficiently exhibited.

[0026] When the conductive pattern 3 is a copper wire 3, its diameter is preferably from 0.05 mm to 0.5 mm, more preferably from 0.2 mm to 0.5 mm. If it is thinner than 0.05 mm, in addition to being prone to disconnection, the resistance value becomes too high, resulting in a reduction in the heater function. If it is thicker than 0.5 mm, the visible light and radio wave transmissivity of the functional area deteriorates.

[0027] Note that although the conductive pattern 3 in the present embodiment is composed of a single 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 wire 4 so as to be energizable.

[0028] Also, although the conductive pattern 3 in the present embodiment is a meander-shaped pattern, the conductive pattern 3 can adopt various patterns such as a shape arranged to surround the periphery of the functional area A1, a spiral shape, a diagonal line shape, etc.

[0029] The routing wire 4 connects the conductive pattern 3 and a terminal portion (not shown) connected to an external member. The routing wire 4 is provided in contact with or close to both ends of a single copper wire 3 and is formed in the extension area A2. The "contact or proximity" mentioned here is a description intended to mean that the routing wire 4 and the conductive pattern 3 may be arranged so as to overlap each other, or may be arranged at a distance of about 5 mm.

[0030] The routing wire 4 is typically a silver wiring and is formed of, for example, silver nanowires, carbon paste, etc. It is formed of a conductive material having higher stretchability than the conductive pattern 3. Thereby, the allowable depth during injection molding is larger than before, and the design can be flexibly adapted. Also, the routing wire 4 in the present embodiment is designed in terms of thickness and width dimension so that its resistance value is lower than that of the conductive pattern 3, and heat generation can be suppressed. Thereby, problems caused by heat generation outside the functional area can be prevented.

[0031] The thickness dimension and width dimension of the lead-back wiring 4 are appropriately designed according to the resistance value of the conductive pattern 3 to be used, the resistance value of the lead-back wiring 4, and the length. For example, when the lead-back wiring 4 is a silver wiring, its thickness dimension is preferably 2 to 30 μm, more preferably 10 to 20 μm. Also, the width dimension 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 provided in contact or proximity and the lead-back wiring 4. 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, such as paste form, plate form, tape form, etc., but from the viewpoint of not peeling off during injection molding, it is preferable to use the paste form.

[0033] The conductive material 5 of the present embodiment is designed to have a lower resistance value than the conductive pattern 3. In addition, in order to lower the resistance value, for example, a conductive plate material or the like may be additionally fixed. Thereby, it is possible to prevent 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 appropriately provided according to the use of the conductive sheet 1. For example, from the viewpoint of preventing the conductive pattern 3 from peeling off during injection molding, it may be provided in the functional region A1, or from the viewpoint of enhancing the visibility of the functional region A1, it may be provided in the extension region A2. In other words, the region where the conductive material 5 is provided can be the "connection region" between the conductive pattern 3 and the lead-back wiring 4.

[0034] (Modification example) Next, with reference to FIG. 3, a modification example of the conductive material 5 will be described. FIG. 3(a) is a plan view showing a modification example 1 of the conductive material 5A, and FIG. 3(b) is a schematic cross-sectional view showing a modification example 2 of the conductive material 5B.

[0035] Referring to FIG. 3(a), the conductive pattern 3A may have an overlapping portion 31 that overlaps with the routing wire 4. The conductive material 5A (illustrated by a dotted line) of the present embodiment is provided so as to cover the overlapping portion 31. Thereby, two different wirings, that is, the conductive pattern 3A and the routing wire 4, can be surely energized.

[0036] Referring to FIG. 3(b), the conductive pattern 3B may be provided so as to be separated from the routing wire 4. In this case, the conductive material 5B is provided so as to be embedded in the base material sheet 2B located between the conductive pattern 3B and the routing wire 4, and the conductive pattern 3B and the routing wire 4 are energized. Thereby, unevenness generated on the surface of the conductive sheet 1B (the surface on which the conductive pattern 3B and the routing wire 4 are provided) can be reduced, and the conductive sheet 1B with good moldability can be obtained.

[0037] (Regarding the resistance value difference) Here, the conductive sheet 1 of the present embodiment includes two wirings having different resistance values. Generally, the calorific value P can be calculated from the following formula. P = I 2 ×R = V 2 ×R P: Calorific value (W) I: Current (A) R: Resistance (Ω) V: Voltage (V) From the above formula, the higher the resistance value R, the larger the calorific value P. Therefore, in the conductive sheet 1 of the present embodiment, the wiring with the higher resistance value, that is, the conductive pattern 3, can preferentially generate heat. From the viewpoint of suppressing the heat generation of the routing wire 4, the resistance value of the routing wire 4 stretched by preforming is preferably 1 / 10 or less of the resistance value of the conductive pattern 3, and more preferably 1 / 20 or less.

[0038] (Effect) In the conventional conductive sheet, copper wires were embedded throughout. Since copper wires generally have low ductility, they are prone to breakage during injection molding, making it difficult to form molded products with a depth greater than the allowable depth. In contrast, in the conductive sheet 1 according to the present embodiment, silver wiring with high ductility is used in the region that is bent during injection molding. As a result, it becomes possible to apply it to a more dynamic uneven shape than before, and it can widely correspond to the designs desired by users.

[0039] Also, in another conventional conductive sheet, silver wiring was provided throughout. Although silver wiring has good ductility, in order to obtain the required amount of heat generation in the necessary region (functional region), it is necessary to uniformly raise the temperature of the entire sheet, and there was a problem that the heat generation efficiency of the conductive sheet was poor (energy loss). In contrast, the conductive sheet 1 according to the present embodiment can generate heat in only the necessary region (functional region) with a small amount of energy by using two wirings with different resistance values, and the heat generation efficiency of the conductive sheet can be improved.

[0040] 〈Regarding the manufacturing method of the conductive sheet〉 Next, with reference to FIG. 4, the manufacturing method S10 of the conductive sheet according to the present embodiment will be described. FIG. 4 is a flowchart showing the manufacturing method of the conductive sheet according to the present embodiment.

[0041] First, a base sheet including a functional region and a stretching region is prepared (base sheet preparation step; step S11). The base sheet is rolled up for improved operability. Next, on the base sheet, a lead-back wiring is formed in the stretching region (lead-back wiring formation step; step S12). The lead-back wiring is drawn, for example, by screen printing using silver paste, and a base sheet on which the desired pattern is repeatedly printed is formed. The base sheet on which the lead-back wiring is formed is wound up in a roll shape in the same manner as in step S1.

[0042] Next, on the base sheet, a conductive pattern is formed in the functional region (conductive pattern forming step; step S13). The conductive pattern is formed of a material having a higher resistance value than the routing wiring, and is bonded, for example, by embedding a copper wire by ultrasonic melting. Next, a conductive material for electrically connecting the conductive pattern and the routing wiring is provided (conductive material mounting step; step S14). The conductive material is provided so as to fill the space between the conductive pattern and the routing wiring or to cover the ends of the respective wirings. Thereby, two wirings formed of different materials can be electrically and firmly connected.

[0043] Note that the conductive sheet according to the present embodiment may be a preform body 10 bent in a desired shape in advance (bending step; step S15). In this case, the bending step is not limited to injection molding, and can be bent by a known method such as vacuum molding. The bent conductive sheet is fixed to a resin molded body described later and incorporated into a 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 body 10 in which the routing wiring of the conductive sheet according to one aspect of the present invention is bent, and a resin molded body 11 laminated on the front surface and / or the back surface of the preform body 10.

[0045] The resin molded body 11 is formed of a material having characteristics suitable for the purpose of use of the resin molded product 12, such as polycarbonate, acrylonitrile-butadiene-styrene, PC-ABS alloy, and the like.

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

[0047] The conductive sheet 1 of the present embodiment is provided with a highly stretchable wiring 4 in a region that is bent during injection molding. Thereby, when manufacturing the resin molded product 12 according to the present embodiment, it is possible to prevent the wiring 4 from being disconnected or peeled off. That is, the resin molded product 12 according to the present embodiment has good moldability and functionality.

[0048] In addition, as the laminate that the resin molded product 12 may include, in addition to the preform 10 and the resin molded body 11, a decorative layer, a transfer layer, an adhesive layer, and other functional layers may be laminated.

[0049] Further, the conductive sheet 1 according to the present embodiment has good translucency compared to a conventional vehicle heater in which a silver wiring is provided in a functional region. Therefore, for example, it can be suitably used for a resin molded product that requires high translucency of visible light without impairing the appearance design, such as a heater for a vehicle headlight. At this time, the functional region of the conductive sheet can be regarded as a "translucent region".

[0050] Further, the conductive sheet 1 according to the present embodiment transmits microwave and laser light emitted from RADAR (Radio detecting and ranging), LiDAR (Light Detection and Ranging), etc., and removes snow etc. that becomes a barrier to the sensor by the heater function. Thereby, it is possible to prevent problems of vehicle sensors that may occur due to the weather. At this time, the functional region of the conductive sheet can be regarded as a "sensing functional region".

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

[0052] Referring to FIG. 7(a), first, an injection mold 6 having a fixed mold 61 and a movable mold 62 that forms a cavity 63 between the fixed mold 61 is prepared (mold preparation step; step S21). Next, a conductive sheet 1 according to one aspect of the present invention is disposed on any cavity surface 64 of the mold 6 (sheet disposition step; step S22). In the present embodiment, the conductive sheet 1 is disposed along the cavity surface of the movable mold 62. Note that the stretching region of the conductive sheet 1 is disposed in the refracted region of the shape of the mold 6, and the functional region of the conductive sheet 1 is disposed in the smooth region of the shape of the mold 6. Here, the term "smooth" includes not only a planar shape but also some uneven shapes that a copper wire can withstand.

[0053] Referring to FIG. 7(b), the injection mold 6 is clamped (clamping step; step S23). The clamping is performed by moving the movable mold 62. The fixed mold 61 has a resin inlet 65 for flowing the molten resin 65a into the cavity 63, and the molten resin is injected into the cavity 63 formed by the clamping. Here, the 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 fixing step; step S24).

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

[0055] According to the method S20 for manufacturing a resin molded product according to the present embodiment, the conductive sheet 1 can be bent while having a depth greater than before. Thereby, the resin molded product according to the present embodiment can correspond to a wide range of designs desired by the user. In addition, since "injection molding" and "fixing of the conductive sheet to the resin molded body" are performed simultaneously, the production efficiency can be improved.

[0056] (Embodiment 2) Referring to FIGS. 6 and 8, the manufacturing method S30 of the resin molded product according to Embodiment 2 will be described. FIG. 6 is a flowchart showing the manufacturing method of the resin molded product according to Embodiment 2. FIG. 8 is a schematic cross-sectional view showing the manufacturing method of the resin molded product according to Embodiment 2.

[0057] Referring to FIG. 8(a), a preform body 10 in which the lead wiring 21 of the conductive sheet 1 according to an aspect of the present invention is bent at the bent portion 21 is prepared (preform body preparation step; step S31). At the same time, a resin molded body 11 having a shape corresponding to the shape of the preform body 10 is prepared (resin molded body preparation step; step S32). Here, the "shape corresponding to the shape of the preform body" is not limited to making the resin molded body 11 and the preform body 10 have the same shape. Specifically, it is intended that designs completed by combining different corresponding shapes are also included.

[0058] Referring to FIG. 8(b), the resin molded body 11 is fixed to the front surface and / or the back surface of the preform body 10 (fixing step; step S33). Thereby, the resin molded product 12 is molded.

[0059] In addition, although the resin molded product 12 of the present embodiment includes the conductive sheet 1 and the resin molded body 11, it goes without saying that various layers can be provided according to a desired design and function. For example, a surface layer with embossing may be provided on the upper surface of the resin molded body 11, or an adhesive layer may be provided between the preform body 10 and the resin molded body 11.

Description of Reference Numerals

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

Claims

1. A base material sheet including a functional region and an extension region; A conductive pattern formed in the functional region; A routing wire provided in contact with or in proximity to at least a part of the conductive pattern and formed in the extension region; And a conductive material for electrically connecting the conductive pattern and the routing wire, A conductive sheet in which the resistance value of the routing wire is lower than the resistance value of the conductive pattern.

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

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

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

5. In the conductive sheet according to claim 2, a preform body in which the routing wire is bent, And a resin molded body laminated on the front surface and / or the back surface of the preform body.

6. A step of preparing a base material sheet including a functional region and an extension region; A step of forming a routing wire in the extension region on the base material sheet; A step of forming a conductive pattern having a resistance value higher than that of the routing wire in the functional region on the base material sheet; And a step of providing a conductive material for electrically connecting the conductive pattern and the routing wire.

7. The method for manufacturing a conductive sheet according to claim 6, further comprising a step of bending the routing wire in the base material sheet.

8. A step of preparing an injection mold having a fixed mold and a movable mold that forms a cavity between the fixed mold; A step of disposing the conductive sheet according to claim 1 on any cavity surface of the mold; A step of clamping the injection mold; A step of injecting molten resin into the cavity to form a resin molded body, and at the same time, fixing the conductive sheet to the surface of the resin molded body; A method for manufacturing a resin molded product, comprising a step of opening the injection mold and taking out the resin molded body to which the conductive sheet is fixed.

9. A step of preparing a preform body in which the lead wiring of the conductive sheet according to claim 1 is bent; A step of preparing a resin molded body having a shape corresponding to the shape of the preform body; A method for manufacturing a resin molded product, comprising a step of fixing the resin molded body to the front surface and / or the back surface of the preform body.

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