Method for manufacturing conductive sheet and resin molded product

Abstract

To provide a conductive sheet with good appearance design.SOLUTION: A conductive sheet (1) includes a base material sheet (2) and a conductive wire (3) embedded in the upper surface of the base material sheet. The base material sheet includes a wire holding portion (4) formed so as to rise from the upper surface along edges (31, 32) of the conductive wire, and the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion is 1: (1.5 to 4.0).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 and a method for manufacturing a resin molded product using the same.

Background Art

[0002] Japanese Unexamined Patent Application Publication No. 2019-169417 (Patent Document 1) discloses a conductive sheet in which a wire is embedded on the upper surface of a base sheet.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The conductive sheet of Patent Document 1 is formed by embedding a wire at a place where the base sheet is ultrasonically welded. However, no consideration is given to the appearance designability at this time. For example, there are problems such as the base sheet being twisted or the base sheet becoming white due to excessive embedding of the wire.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a conductive sheet capable of improving the appearance designability.

Means for Solving the Problems

[0006] The conductive sheet according to one aspect of the present invention includes a base sheet and a conductive wire embedded in the upper surface of the base sheet. The base sheet includes a wire holding portion formed so as to bulge upward from the upper surface along the edge of the conductive wire. The width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion = 1:(1.5 to 4.0).

[0007] Preferably, the height position Y2 of the wire holding portion is lower than the height position Y1 of the conductive wire.

[0008] Preferably, 40 to 75% of the height dimension H1 of the conductive wire is embedded in the base sheet with reference to the upper surface of the base sheet.

[0009] Preferably, the tensile strength of the conductive wire is 200 to 600 N / mm 2 is.

[0010] A method for manufacturing a resin molded product according to one aspect of the present invention includes a step of preparing a conductive sheet in which a conductive wire is embedded such that a wire holding portion rising along the edge of the conductive wire is formed from the upper surface of the base sheet and the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion = 1: (1.5 to 4.0), a step of preparing an injection molding die having a fixed die and a movable die that forms a cavity between the fixed die, a step of disposing the conductive sheet on any cavity surface of the die, a step of clamping the injection molding die, a step of injecting molten resin into the cavity to mold a resin molded body and simultaneously fixing the conductive sheet to the surface of the resin molded body, and a step of opening the injection molding die and taking out the resin molded body to which the conductive sheet is fixed.

[0011] A method for manufacturing a resin molded product according to another aspect of the present invention includes a step of preparing a conductive sheet in which a conductive wire is embedded such that a wire holding portion rising along the edge of the conductive wire is formed from the upper surface of the base sheet and the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion = 1: (1.5 to 4.0), a step of preparing a resin molded body having a shape corresponding to the shape of the conductive sheet, and a step of fixing the resin molded body to the upper surface and / or the lower surface of the conductive sheet.

Advantages of the Invention

[0012] According to the conductive sheet of the present invention, by appropriately embedding the wire in the upper surface of the base sheet, it is possible to prevent twisting of the upper surface of the base sheet and dropping of the wire, and improve the appearance design.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Modes for Carrying Out the Invention

[0014] 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.

[0015] (Regarding the configuration) Referring to FIG. 1, the conductive sheet 1 according to an embodiment of the present invention will be described. The conductive sheet 1 includes a base material sheet 2 having a rectangular shape in a plan view, a conductive wire 3 embedded in the upper surface of the base material sheet 2, and a wire holding portion 4 formed so as to bulge along the edge of the conductive wire 3. FIG. 1 is an explanatory drawing showing a cross-sectional view including the conductive wire 3 of the conductive sheet 1 in a front view. Also, the direction of arrow A1 shown in FIGS. 1 and 2 is referred to as the width direction of the wire.

[0016] The base sheet 2 is formed of a thermoplastic resin, for example, polycarbonate, polyethylene terephthalate, polyethylene naphthalate, polypropylene, PC-ABS, polyvinyl chloride, acrylic resin, etc. The base sheet 2 preferably has a heat shrinkage rate of 2.5% or less and has stretchability suitable as a conductive film for injection molding. Thereby, not only can the moldability during injection molding be improved, but also warpage deformation during the formation of the conductive sheet 1 can be prevented.

[0017] The base sheet 2 includes an upper surface 2a and a lower surface 2b, and the conductive wire 3 is embedded in the upper surface 2a. An arbitrary functional layer, such as an adhesive layer or a decorative layer, may be laminated on the lower surface 2b.

[0018] From the viewpoint of good moldability, the thickness dimension H3 of the base sheet 2 is preferably 0.2 mm to 0.8 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 float white on the back surface 2b of the sheet, and the appearance design may deteriorate during the molding process. If it is thicker than 0.8 mm, there is a possibility that the molding process becomes difficult.

[0019] The conductive wire 3 forms an arbitrary pattern on the upper surface 2a of the base sheet. The pattern is, for example, a meander shape, a spiral shape, a diagonal line shape, etc. In the present embodiment, the pattern is formed by one wire, but two or more wires may be provided. Both ends of the conductive wire 3 are connected to a terminal portion (not shown).

[0020] The conductive wire 3 can be appropriately selected from conductive materials made of, for example, copper, silver, lead, aluminum, nickel, beryllium, zirconium, etc., according to the use and purpose of the molded product. That is, only one type of conductive material may be used, or it may be an alloy containing two or more types of metals. The conductive wire 3 of the present embodiment preferably uses a material with a hardness and resistance value considering deformation prevention during embedding and easy exertion of the heater function. For example, a silver-containing copper alloy is used.

[0021] The diameter of the conductive wire 3 is preferably 0.05 mm to 0.3 mm, more preferably 0.1 mm to 0.2 mm. If it is thinner than 0.05 mm, in addition to being prone to wire breakage, the resistance value becomes too high, resulting in a reduction in the heater function. If it is thicker than 0.3 mm, the formed conductive sheet is prone to warping, and the handling during the forming process becomes complicated.

[0022] The conductive wire 3 is embedded by ultrasonic welding while applying pressure and tensile force to the base material sheet 2. Specifically, a wire embedding device (not shown) feeds out the conductive wire 3 while melting the upper surface 2a of the base material sheet with ultrasonic waves, and embeds the wire while applying pressure to the upper surface 2a of the base material sheet 2. In a plan view, both side portions in the extending direction of the conductive wire 3 embedded in the base material sheet 2 are referred to as the edge portions 31, 32 of the wire.

[0023] The cross-sectional shape of the conductive wire 3 is slightly deformed by the pressure and heat during embedding. Specifically, referring to the photos in FIGS. 4 and 5, the upper surface of the wire is deformed flat. Therefore, the description of the "diameter of the conductive wire" intends the diameter before embedding. After embedding, the maximum dimensions in the height direction and width direction in the cross-sectional view are denoted as the "height dimension H1 of the conductive wire" and the "width dimension W1 of the conductive wire".

[0024] From the viewpoint of preventing deformation during embedding, the tensile strength of the conductive wire 3 is preferably 200 to 600 N / mm 2 and more preferably 300 to 500 N / mm from the viewpoints of the difficulty of wire deformation and the stability of the wire embedding process. 2 When the tensile strength is 600 N / mm 2 or more, due to the force (elastic force) with which the conductive wire 3 tries to return to its original shape like a return spring, the conductive wire 3 is likely to be peeled off from the base material sheet 2. By using the conductive wire 3 with a predetermined tensile strength, the conductive sheet 1 of the present embodiment can prevent the wire from being broken during wire embedding or the base material sheet 2 from being twisted due to excessive deformation of the wire.

[0025] Note that the conductive wire 3 is preferably coated with a coating film (not shown) around it from the viewpoints of preventing corrosion of the wire and strengthening the adhesion to the base sheet 2. The coating film is a resin such as polyurethane, and plays a role of maintaining insulation in the non-current-carrying region of the conductive wire 3. In this case, the "diameter of the wire" is the diameter of only the conductive wire, but the "height dimension of the conductive wire" and the "width dimension of the conductive wire" are the height dimension and the width dimension of the conductive wire including the coating film.

[0026] The wire holding portion 4 includes a first wire holding portion 41 along one side in the extending direction of the conductive wire 3 and a second wire holding portion 42 along the other side in the extending direction of the conductive wire 3. The wire holding portion 4 is formed such that the base sheet 2 bulges upward from the edge portions 31, 32 of the wire when the wire is embedded, and is formed by bending so as to draw an arc after extending in the height direction. Here, as can also be seen in the photos of FIGS. 4 and 5, the wire holding portion bends so as to form an air layer 43 inside thereof. Since the base sheet 2 turns white when it contains air, the appearance is significantly impaired when used together with a molded product having a black design. Therefore, it is preferable that the wire holding portion 4 be accommodated in as small an area as possible.

[0027] The height dimension H2 of the wire holding portion is the height dimension H2 from the wire edge portion to the top end portion in the height direction of the wire holding portion. Also, the width dimension W2 of the wire holding portion is the width dimension including from the widthwise end portion of the first wire holding portion 41 to the widthwise end portion of the second wire holding portion 42. Note that since the wire holding portion 4 extends outward or inward of the wire so as to draw an arc upward, the height dimension H2 and the width dimension W2 of the wire holding portion are not necessarily the end faces of the wire holding portion.

[0028] The height position Y1 of the conductive wire is the height position Y1 at the top end of the conductive wire 3 in the height direction. The height position Y2 of the wire holding part is the height position Y2 at the top end of the wire holding part in the height direction. Due to the relationship with a wire embedding device (not shown) provided above the conductive wire 3, the height position Y1 of the wire becomes the upper limit value, and (the height position Y1 of the wire) ≥ (the height position Y2 of the wire holding part) for the wire holding part 4 in the present embodiment.

[0029] (Regarding the dimensional ratio) The conductive sheet 1 of the present embodiment is formed such that the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding part = 1:(1.5 to 4.0). If W2 / W1 exceeds 4.0, the wire holding part will spread too much in the width direction, significantly damaging the appearance of the conductive sheet. If W2 / W1 is less than 1.5, the wire cannot be firmly held, and the wire is likely to peel off. From the perspective of design, W1:W2 = 1:(1.5 to 3.5) is more preferable, and from the perspective of combining design and preventing the wire from peeling off, W1:W2 = 1:(1.7 to 3.0) is even more preferable.

[0030] The height position Y2 of the wire holding part is preferably lower than the height position Y1 of the conductive wire and occupies 50% or more of the height position Y1 of the conductive wire (0.5Y1 ≤ Y2 < Y1). Thereby, while the wire holding performance is good, the wire holding part 4 does not spread along the wire embedding device, so good design can be ensured.

[0031] The conductive sheet 1 of the present embodiment has a height dimension H1 of the conductive wire: a thickness dimension H3 of the base sheet = 1:(1.7 to 3.5). Since the base sheet 2 of the conductive sheet 1 of the present embodiment has an appropriate thickness in the present embodiment, it is not easily warped, and unevenness of the wire embedded in the back surface 2b of the base sheet is not formed. Therefore, the design of the conductive sheet 1 can be improved.

[0032] In the conductive wire 3 of the present embodiment, 40 to 75% of the height dimension H1 of the conductive wire is embedded in the base material sheet 2 with reference to the upper surface 2a of the base material sheet 2. Further, from the viewpoint of the design property of the conductive sheet, a wire embedding rate of 40 to 65% is more preferable, and from the viewpoint of surely preventing the wire from peeling off, a wire embedding rate of 50 to 65% is even more preferable.

[0033] The wire holding portion 4 of the present embodiment is formed to rise from the wire edge portion so as to scrape the upper surface 2a of the base material sheet when the conductive wire 3 is embedded. Here, if it is lower than 40%, the wire may peel off from the upper surface 2a of the base material sheet, which may impair the design property. If the wire is larger than 75%, when the conductive sheet is processed by injection molding, the wire holding portion 4 may be turned up and the conductive wire 3 may be buried, which may impair the design property. On the other hand, in the conductive sheet according to the present embodiment, the volume of the wire holding portion 4 formed at the time of wire embedding can be released outward from the wire edge portion. Thereby, the conductive sheet 1 with good conductivity and design property can be obtained.

[0034] (Regarding Examples) Next, with reference to FIGS. 3 to 5, Examples 1 to 9 and Comparative Examples 1 to 3 of the conductive sheet 1 according to the present embodiment will be described as examples. FIG. 3 is an explanatory diagram regarding an example of the conductive sheet according to the present embodiment. FIG. 4 is a table showing various evaluation cross-sections of the conductive sheets according to Examples 1 to 9. FIG. 5 is a table showing various evaluations of the conductive sheets according to Comparative Examples 1 to 3.

[0035] As the base material sheet, a polycarbonate sheet Makrofol (registered trademark) DE1-4 manufactured by Covestro was used, and as the conductive wire, a silver-containing copper wire (wire diameter 0.11 mm; coating layer 0.01 mm; total diameter 0.12 mm) was used. The conductive wire was embedded using a wire embedding device WCE150 manufactured by Ruhlamat.

[0036] Figure 3 shows the positions when the meander shape is patterned with the wires according to Examples 1 to 9 and Comparative Examples 1 to 3. Positions i and iv are at the center of the straight region, positions ii and iii are at the ends of the straight region, and positions v and vi are at the ends of the curved region.

[0037] Figures 4 and 5 show various evaluation results based on the cross-sectional photographs of the conductive wires patterned under the above conditions. The details of each evaluation item are as follows. Position: Indicates the position corresponding to Figure 3. W2 / W1: Represents the value of the width dimension W2 of the wire holding part / the width dimension W1 of the conductive wire. Magnitude relationship between Y1 and Y2: Indicates the magnitude relationship between the height position Y2 of the wire holding part and the height position Y1 of the conductive wire. Embedding rate: Indicates the embedding rate of the conductive wire based on the upper surface of the base sheet. Evaluation: It is represented by ◎〇× for the appearance shape of the conductive sheet of each example. Photograph: It is an SEM image of the cross-section taken corresponding to each example and comparative example.

[0038] Note that the dimensions of the width dimension W2 of the wire holding part, the width dimension W1 of the conductive wire, the height position Y1 of the wire holding part, and the height position Y2 of the conductive wire were measured by observing the cross-sectional samples created with a mitochondrion.

[0039] Referring to Figure 4, the conductive sheets of Examples 1 to 9 had an embedding rate of 52.3 to 73.2% and a W2 / W1 of 2.4 to 3.2. From these results, it was found that the conductive wires of Examples 1 to 9 had good wire holding force while having good appearance design. Also, the conductive sheets of Examples 7 to 9 had a W2 / W1 of 3.2, and an expansion of the wire holding part was observed compared to Examples 1 to 6. Therefore, the conductive sheets of Examples 7 to 9 were evaluated as ○ as having an appearance design within the allowable range, and the conductive sheets of Examples 1 to 6, which are the most preferable forms, were evaluated as ◎.

[0040] Referring to Fig. 5, in Comparative Examples 1 to 3, the embedding rate was 78.3 to 90.9%, and W2 / W1 was 4 or more. From these results, it was found that the conductive wires in Comparative Examples 1 to 3 were embedded deeper than in the Examples, the wire holding portion spread wider than the predetermined width, and the appearance design was impaired. Therefore, the appearance shape of the conductive sheets in Comparative Examples 1 to 3 was evaluated as × because it was in an unfavorable form.

[0041] The Examples and Comparative Examples were evaluated by taking out the portions corresponding to the positions shown in Fig. 3 from the conductive wires patterned under predetermined conditions. Usually, the wire embedding device moves fast in the central portions i, iv of the straight region and slowly in the end portions ii, iii, v, vi of the curved region. However, according to this Example, the wire can be embedded uniformly regardless of the patterning position, and a conductive sheet with good appearance design can be provided.

[0042] (Example 10) Next, referring to Figs. 6 and 7, Example 10 of the conductive sheet of the present embodiment will be described. Fig. 6 is a table showing the relationship between the ratio of W2 / W1 and the wire embedding rate.

[0043] As the base sheet, a polycarbonate sheet Makrofol DE1-4 manufactured by Covestro was used, and as the conductive wire, a silver-containing copper wire (total diameter 0.19 mm) manufactured by Electrisola was used. The conductive wire was embedded using a wire embedding device WCE150 manufactured by Ruhlamat.

[0044] The table shown in Fig. 6 is compiled based on the data obtained as a result of operating the wire embedding device under various conditions when embedding the conductive wire in the above-described base sheet, and for which no peeling off of the wire was observed. The wire embedding rate is defined such that the region below 50% is a "shallow" region, the region of 50 to 65% is a "medium" region, and the region above 65% is a "deep" region.

[0045] As shown in Fig. 6, the region indicated by arrow A is the region with a "deep" wire embedding rate, and W2 / W1 = (3.0 - 4.0). The region indicated by arrow B is the "intermediate" region of the wire embedding rate, and W2 / W1 = (1.7 - 3.5). The region indicated by arrow C is the "shallow" region of the wire embedding rate, and W2 / W1 = (1.5 - 2.0).

[0046] Fig. 7 shows a photograph taken in a plan view of one of the conductive wires in the region of each wire embedding rate. (a) is the deep region, and a state where the wire holding part spreads greatly in the lateral direction was observed. (b) is the intermediate region, and (c) is the shallow region. Compared with the deep region, the spread of the wire holding part in the lateral direction could be kept within an acceptable range. In particular, when using a black base sheet, since the wire holding part becomes white, it was found that if the lateral dimension of the wire holding part is large, the appearance design will be greatly damaged.

[0047] The conductive sheet 1 of the present embodiment can embed linear wires without the conductive sheet being twisted. As a result, since the wires stay at the desired positions, good radio wave transmissivity can be maintained. In addition, since it is possible to prevent the wires from being buried by the wire holding parts, the conductivity and the appearance design can be improved.

[0048] (Regarding the manufacturing method) Next, the manufacturing method of the resin molded product according to the present embodiment will be described. The resin molded product according to the present embodiment is manufactured by setting a conductive sheet in which wires are embedded in a mold and performing injection molding.

[0049] First, a wire holding portion that rises along the edge of the conductive wire from the upper surface of the base sheet is formed, and a conductive sheet in which the conductive wire is embedded is prepared such that the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion = 1:(1.5 to 4.0) (conductive sheet preparation step). Next, an injection mold having a fixed mold and a movable mold that forms a cavity between the fixed mold is prepared (mold preparation step). Next, the conductive sheet is disposed on any cavity surface of the mold (disposal step). Next, the injection mold is clamped (clamping step). Next, molten resin is injected into the cavity to form a resin molded body, and at the same time, the conductive sheet is fixed to the surface of the resin molded body (fixing step). Next, the injection mold is opened, and the resin molded body to which the conductive sheet is fixed is taken out (taking-out step). Thereby, a resin molded product can be manufactured.

[0050] The conductive sheet can fix the resin molded body to its upper surface and / or lower surface. The conductive wire 3 of the present embodiment may be further embedded in the fixing step. At this time, since the entire conductive sheet 1 is heated during injection molding and the pressure inside the mold is high, no further wire holding portion is formed.

[0051] Also, a method for manufacturing a resin molded product according to another embodiment will be described. The resin molded product according to the present embodiment is manufactured by bonding a conductive sheet in which a wire is embedded and a resin molded body formed by, for example, injection molding.

[0052] First, a wire holding portion that rises along the edge of the conductive wire from the upper surface of the base sheet is formed, and a conductive sheet in which the conductive wire is embedded is prepared such that the width dimension W1 of the conductive wire: the width dimension W2 of the wire holding portion = 1:(1.5 to 4.0) (conductive sheet preparation step). Next, a resin molded body having a shape corresponding to the shape of the conductive sheet is prepared (resin molded body preparation step). The resin molded body is fixed to the upper surface and / or lower surface of the conductive sheet (fixing step). Thereby, a resin molded product can be manufactured.

[0053] In addition, in the wire holding portion 4 of the present embodiment, by performing injection molding on the upper surface 2a of the conductive sheet, the air layer 43 formed inside the wire holding portion 4 may be filled with resin and become invisible.

Explanation of reference numerals

[0054] 1 Conductive sheet, 2 Base material sheet, 3 Conductive wire, 4 Wire holding portion, 31, 32 Wire edge portions, 41, 42 Wire holding portions, 43 Air layer, W1 Width dimension of the conductive wire, W2 Width dimension of the wire holding portion, H1 Height dimension of the conductive wire, H2 Height dimension of the wire holding portion, H3 Thickness dimension of the base material sheet, Y1 Height position of the conductive wire, Y2 Height position of the wire holding portion.

Claims

1. A base sheet, and a conductive wire embedded in the upper surface of the base sheet, wherein the base sheet includes a wire holding portion formed to rise from the upper surface along the edge of the conductive wire, and a conductive sheet, wherein a width dimension W1 of the conductive wire: a width dimension W2 of the wire holding portion = 1: (1.5 to 4.0).

2. The conductive sheet according to claim 1, wherein a height position Y2 of the wire holding portion is lower than a height position Y1 of the conductive wire.

3. The conductive sheet according to claim 1, wherein 40 to 75% of a height dimension H1 of the conductive wire is embedded in the base sheet with reference to the upper surface of the base sheet.

4. The tensile strength of the conductive wire is 200 to 600 N / mm ２ The conductive sheet according to claim 1, which is such.

5. A step of preparing a conductive sheet in which a wire holding portion rising from the upper surface of the base sheet along the edge of the conductive wire is formed, and the conductive wire is embedded so that a width dimension W1 of the conductive wire: a width dimension W2 of the wire holding portion = 1: (1.5 to 4.0); 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 on any cavity surface of the mold; a step of clamping the injection mold; a step of injecting a molten resin into the cavity to form a 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. A method for manufacturing a resin molded product.

6. A step of preparing a conductive sheet in which a wire holding portion rising from the upper surface of the base sheet along the edge of the conductive wire is formed, and the conductive wire is embedded so that a width dimension W1 of the conductive wire: a width dimension W2 of the wire holding portion = 1: (1.5 to 4.0); a step of preparing a resin molded body having a shape corresponding to the shape of the conductive sheet; and a step of fixing the resin molded body to the upper surface and / or the lower surface of the conductive sheet. A method for manufacturing a resin molded product.

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