Conductive sheet, resin molded article, and method for producing same

Abstract

The purpose of the present invention is to provide a conductive sheet, a resin molded article, and a method for manufacturing the same, wherein peeling and breaking of an electric wire caused by forming the conductive sheet into a three-dimensional shape are prevented. A film heater (10), which is a conductive sheet, is provided with: a base sheet (11) having a rectangular shape in plan view; a conductive pattern (13) formed from a conductive wire (12) fixed to the base sheet (11); and a protective sheet (21) formed on the base sheet (11) so as to cover the conductive pattern (13) thereof. The membrane heater (10), for example, is incorporated into a logo, bumper of an automobile for melting snow. The end of the base sheet (11) has a curved region (A) extending in a strip shape in the short-side direction of the base sheet (11). The conductive pattern (13) is a meandering pattern formed by repeating U-shaped turns arranged at a certain width left and right in the short side direction of the base sheet (11), and is formed at equal intervals in the long side direction. The pattern constitutes the heater part (14).

Description

Technical Field

[0001] There is a membrane heater in which a conductive sheet has a conductive pattern of conductive wires formed on one side of a substrate sheet. The conductive wires are ultrasonically welded into the surface of the substrate sheet along their entire length (see, for example, Patent Document 1). Background Technology

[0002] Previously, conductive sheets with conductive patterns on a substrate sheet were proposed.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-169417 Summary of the Invention

[0004] The technical problem that the invention aims to solve

[0005] When the conventional conductive sheet described above is formed into a three-dimensional shape, since the elongation rate of the film is different from that of the wire, the wire may sometimes peel off from the substrate sheet or break at the bending point.

[0006] The present invention was made to solve the aforementioned technical problems, and its object is to provide a conductive sheet, a resin molded article, and a method for manufacturing the same, which prevent wire stripping and breakage caused by forming a three-dimensional shape.

[0007] Solutions for solving technical problems

[0008] To achieve the above objectives, the first invention comprises: a substrate having a curved region; a conductive pattern formed by conductive wires fixed to the substrate; and a protective sheet formed on the substrate to cover the conductive pattern. A portion of the wire traverses the curved region, and when the curved region is bent, the linear expansion of the outer sheet of the substrate and the protective sheet is set to be greater than the linear expansion of the inner sheet.

[0009] When configured in this way, the difference in expansion and contraction between the outer and inner sides of the conductive sheet when it is bent is absorbed. Even when the conductive sheet is bent, the protective sheet remains fixed to the base sheet, thereby suppressing wire stripping.

[0010] The second invention is to set the length of the outer surface of the inner sheet of the conductive sheet to be equal to the length of the inner surface of the outer sheet when the conductive sheet is bent in the bending region.

[0011] When configured in this way, it is not easy to apply stress to the contact surface between the protective sheet and the substrate sheet due to their respective expansion differences, thus maintaining stability and preventing wire stripping.

[0012] The third invention is that, in the structure of the first invention, the linear expansion of the base sheet is set as A1, the linear expansion of the protective sheet is set as A2, the thickness of the conductive sheet is set as d, when the conductive sheet is bent in the bending region, the bent portion of the base sheet is regarded as an arc and its radius is set as R, the forming temperature when the conductive sheet is bent in the bending region is set as T1, and the room temperature at this time is set as T2, then it is set to have the relationship of the following formula (1) or (2).

[0013] (1) When A1 < A2

[0014] [Formula 1]

[0015]

[0016] (2) When A1 > A2

[0017] [Formula 2]

[0018]

[0019] When structured like this, when the conductive sheet is bent, when there is an expansion difference between the base sheet and the protective sheet, the conductive sheet will warp towards the side of the sheet with a smaller linear expansion, so this warping can be used to assist the conductive sheet to be formed into a three-dimensional shape.

[0020] The fourth invention is that, in the structure of the first invention, the conductive pattern is composed of 1 continuous wire and includes a heater part and a connection terminal part.

[0021] When structured like this, the wire is protected by the protective sheet and adheres closely to the base sheet, so even when the conductive sheet is bent, the wire will not peel off.

[0022] The fifth invention is a resin molded product, comprising: a preform obtained by bending the conductive sheet of the first invention in a bending region; and a resin molded body laminated on the surface, back surface or both surfaces of the preform.

[0023] When structured like this, the preform with the wire not peeled off is laminated on the resin molded body, so it becomes a resin molded product with the wire not peeled off.

[0024] The sixth invention is a method for manufacturing a resin molded product, comprising the following steps: a step of arranging the conductive sheet of the first invention on any cavity surface of an injection molding die, the injection molding die having a fixed die and a movable die, and the movable die forms a cavity between the movable die and the fixed die by clamping; a step of clamping the injection molding die; a step of injecting molten resin into the cavity to form a resin molded body and fixing the conductive sheet to the surface of the resin molded body at the same time; and a step of opening the injection molding die and taking out the resin molded body.

[0025] When configured in this way, the wire is protected by the protective sheet and adheres tightly to the substrate sheet when the conductive sheet is bent, thus enabling the injection molding of a resin molded product in which the wire is not detached.

[0026] The seventh invention is a method for manufacturing resin molded articles according to the sixth invention, which is a preform formed by bending the conductive sheet of the first invention in the bending region.

[0027] When configured in this way, the preform with the wires intact is embedded in the injection molding mold, thus obtaining a resin molded product with the wires intact.

[0028] The eighth invention is a method for manufacturing a resin molded article, comprising the following steps: a step of preparing a preform by bending the conductive sheet of the first invention in a bending region; and a step of fixing a resin molded article having a surface shape corresponding to the shape of the surface, back or both sides of the preform.

[0029] When configured in this way, a preform with an unbroken wire is stacked on a resin molded body, thus obtaining a resin molded product with an unbroken wire.

[0030] The effects of the invention

[0031] According to the present invention, it is possible to prevent the conductive wires attached to the conductive sheet from peeling or breaking when the conductive sheet is formed into a three-dimensional shape. Attached Figure Description

[0032] Figure 1 This is a schematic top view illustrating the membrane heater according to the first and second embodiments of the present invention.

[0033] Figure 2 yes Figure 1 The schematic cross-sectional view of line II-II is shown.

[0034] Figure 3 (1) is to make the first embodiment of the present invention Figure 1 The diagram shown is a schematic cross-sectional view of line II-II when the membrane heater is bent in the bending region. Figure 3 (2) is to make the second embodiment of the present invention Figure 1 The diagram shows a schematic cross-sectional view of line II-II when the membrane heater is bent in the bending region.

[0035] Figure 4 This is a diagram showing the process of manufacturing a membrane heater molded product.

[0036] Figure 5 This diagram illustrates other steps in the manufacturing of the membrane heater molded product. Detailed Implementation

[0037] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0038] Reference Figure 1 A membrane heater 10 based on a conductive sheet according to a first embodiment of the present invention includes: a substrate 11 having a rectangular shape when viewed from above; a conductive pattern 13 formed by conductive wires 12 fixed on the substrate 11; and a protective sheet 21 formed on the substrate 11 to cover the conductive pattern 13. The membrane heater 10 is assembled, for example, into a car emblem or bumper for snow melting. At the end of the substrate 11, there is a curved region A extending in a strip-like manner along the short side of the substrate 11. The conductive pattern 13 is a meandering pattern formed in a single stroke with U-shaped turns arranged at a certain width on both sides along the short side of the substrate 11 and at equal intervals along the long side. This pattern constitutes a heater portion 14. A portion of the wire 12 traverses the curved region A, and the two ends of the wire 12 converge at one point in the pattern, with the two wires extending parallel at a certain interval from the outer edge of the corner of the substrate 11 to the outside. This portion constitutes a connecting terminal portion 15. Decorative layers, transfer layers, adhesive layers, and other functional layers can also be laminated on the surface and back of the film heater 10, depending on the applicable product. The substrate sheet 11 can be rectangular, or it can be an irregular shape or other shapes that conform to the shape of the final product.

[0039] Reference Figure 2 The wire 12 is fixed to the substrate 11 by embedding a portion of its cross-section therein. A protective sheet 21 is overlapped on the substrate 11 to cover the wire 12. The substrate 11 and the protective sheet 21 sandwich the wire 12. As a method of embedding the wire 12 into the substrate 11, it is ideal, for example, to flexibly apply the principle of ultrasonic welding to embed the wire 12 into the substrate 11. During ultrasonic welding, a wiring drawing device can be used that melts the surface of the substrate 11, which is made of thermoplastic resin, while releasing the wire 12, thereby embedding the wire 12 into the substrate 11. By embedding the wire 12 into the substrate 11, a conductive pattern 13 can be positioned on the substrate 11.

[0040] Figure 3 (1) is a schematic cross-sectional view along line II-II with the protective sheet 21 as the upper surface, so that the membrane heater 10 based on the first embodiment of the present invention is bent downward in the bending region A. Due to the bending, the substrate sheet 11 elongates, and the length of the outer surface 30 of the bent substrate sheet 11 becomes longer than the length of the outer surface 30 of the substrate sheet 11 before bending.

[0041] When the membrane heater 10 according to the first embodiment of the present invention is heated and bent in the bending region A, it can be configured such that the length of the outer surface 30 of the substrate sheet 11 located on the inner side is equal to the length of the inner surface 41 of the protective sheet 21 located on the outer side. Specifically, expansion occurs due to thermal expansion between room temperature and the glass transition point, and this difference in expansion is used to make the lengths equal. Furthermore, by applying a temperature exceeding the glass transition point, the molecular arrangement is changed, thereby maintaining the shape.

[0042] When configured in this way, it is not easy to apply stress to the contact surface between the protective sheet 21 and the substrate sheet 11 due to their respective expansion differences, thus maintaining stability and preventing the wire 12 from peeling off.

[0043] The linear expansion of the substrate sheet 11 according to the first embodiment of the present invention is defined as A1, the linear expansion of the protective sheet 21 is defined as A2, the thickness of the film heater 10 is defined as d, and the bending portion of the substrate sheet 11 when the film heater 10 is bent is regarded as an arc and its radius is defined as R (refer to...). Figure 3 (1)), if the forming temperature when bending in the bending area is set to T1 and the room temperature at this time is set to T2, then it can be configured to have the following relationship (1). (1)

[0045] [Mathematical Expression 1]

[0046]

[0047] By setting it in this way, when the film heater 10 is bent, warping occurs on the side of the substrate 11 with small linear expansion due to the expansion difference between the substrate 11 and the protective sheet 21. Therefore, this warping can be used to help the conductive sheet be formed into a three-dimensional shape.

[0048] The substrate sheet 11 is made of thermoplastic resin such as polycarbonate, acrylic resin, or ABS resin. For example, if a thermoplastic resin sheet of the same type as that used in the resin molded body 17 is used, it is easy to fix the substrate sheet 11 to the resin molded body 17. In particular, it is preferable to use a thermoplastic resin sheet with excellent formability, mechanical strength, flexibility, and weather resistance.

[0049] The thickness of the substrate 11 is preferably 3 to 4 times the diameter of the wire 12. If it is thinner than 3 times the diameter of the wire 12, the shape of the wire 12 will be visible on the opposite side of the substrate 11, which may cause cracking of the decorative layer laminated on the opposite side, or result in a poor appearance when the opposite side becomes the appearance of the molded product. If it is thicker than 4 times the diameter of the wire 12, it will be difficult to mold the film heater 10 into a three-dimensional shape. For example, when the diameter of the wire 12 is 0.2 mm, the thickness of the substrate 11 is preferably 0.6 mm to 0.8 mm.

[0050] The protective sheet 21 is made of thermoplastic resin such as polyethylene terephthalate, polyethylene, or polypropylene. For example, if a thermoplastic resin sheet of the same type as that used in the resin molded body 17 is used, it is easier to fix the protective sheet 21 to the resin molded body 17. In particular, it is preferable to use a thermoplastic resin sheet with excellent moldability, mechanical strength, flexibility, and weather resistance.

[0051] The thickness of the protective sheet 21 is preferably 1 to 2 times the diameter of the wire 12. If it is thinner than 1 times the diameter of the wire 12, the shape of the wire 12 will be visible when covering the wire 12 fixed to the substrate sheet 11, which may cause cracking of the decorative layer stacked on the protective sheet 21 or deteriorate the appearance of the protective sheet 21 when it becomes a molded product. If it is thicker than 2 times the diameter of the wire 12, it will be difficult to mold the film heater 10 into a three-dimensional shape. For example, when the diameter of the wire 12 is 0.2 mm, the thickness of the protective sheet 21 is preferably 0.2 mm to 0.4 mm.

[0052] For wire 12, various conductive metal materials can be selected according to the intended use and purpose of the manufactured product. For example, pure copper, or copper alloys in which silver, lead, tin, aluminum, nickel, beryllium, zirconium, etc., are incorporated into copper, either individually or in combination, are examples. In particular, pure copper with low resistivity and alloys with excellent mechanical strength are preferred.

[0053] The diameter of the wire 12 is preferably 0.05 mm to 0.2 mm, and more preferably 0.15 mm to 0.2 mm. If it is thinner than 0.05 mm, the resistance value becomes higher, thereby reducing the performance of the heater, or the wire may break when the film heater 10 is formed into a three-dimensional shape. If it is thicker than 0.2 mm, it is difficult to form the film heater 10 into a three-dimensional shape. The length of the wire 12 can correspond to the pattern shape of the conductive pattern 13, etc.

[0054] The embedment amount of the wire 12 into the substrate 11 is set to 1 / 3 of the thickness of the substrate 11 and approximately 2 / 5 to 4 / 5 of the diameter of the wire 12, preferably 1 / 2 to 3 / 4.

[0055] The resin molded body 17 uses a material with properties suitable for the intended use and purpose of the molded article being manufactured. Examples include polycarbonate, acrylonitrile-butadiene-styrene, and PC-ABS alloys.

[0056] When the membrane heater 10 based on the first embodiment of the present invention is used for a car logo or bumper, the substrate sheet 11 is suitable to be made of polycarbonate, the protective sheet 21 is suitable to be made of polyethylene terephthalate, the wire 12 is suitable to be made of silver-copper alloy, the resin molded body 17 is suitable to be made of polycarbonate when it is a component that needs to transmit light, and is suitable to be made of PC-ABS when it is a component that needs to be strong.

[0057] Next, the second embodiment of the present invention will be described with reference to the accompanying drawings, focusing on the differences from the previous embodiment.

[0058] The membrane heater 10 based on the conductive sheet of the second embodiment of the present invention is the same as the membrane heater 10 based on the first embodiment, except that the linear expansion relationship between the substrate sheet 11 and the protective sheet 21 and the material of the protective sheet 21 are different.

[0059] Figure 3 (2) is a schematic cross-sectional view along line II-II with the substrate sheet 11 as the upper surface, so that the membrane heater 10 based on the second embodiment of the present invention is bent downward in the bending region A. Due to the bending, the substrate sheet 11 elongates, and the length of the outer surface of the bent substrate sheet 11 becomes longer than the length of the outer surface of the substrate sheet 11 before bending.

[0060] When the membrane heater 10 based on the second embodiment of the present invention is bent in the bending region A, it can be configured such that the length of the outer surface of the inner protective sheet 21 is equal to the length of the inner surface of the outer substrate sheet 11.

[0061] When configured in this way, it is not easy to apply stress to the contact surface between the protective sheet 21 and the substrate sheet 11 due to their respective expansion differences, thus maintaining stability and preventing the wire 12 from peeling off.

[0062] The linear expansion of the substrate 11 according to the second embodiment of the present invention is defined as A1, the linear expansion of the protective sheet 21 is defined as A2, the thickness of the film heater 10 is defined as d, and the bending portion of the substrate 11 when the film heater 10 is bent is regarded as an arc and its radius is defined as R (refer to...). Figure 3 (2)), the forming temperature when bending in the bending area is set to T1, and the room temperature at this time is set to T2, which can be configured to have the following relationship (2). (2)

[0064] [Mathematical Expression 2]

[0065]

[0066] By setting it in this way, when the film heater 10 is bent, due to the expansion difference between the substrate sheet 11 and the protective sheet 21, warping will occur on the side of the protective sheet 21 with smaller linear expansion. Therefore, this warping can be used to help the conductive sheet be formed into a three-dimensional shape.

[0067] The protective sheet 21 uses an inorganic resin sheet such as a filler with negative thermal expansion. In particular, it is preferable to use an inorganic resin sheet with excellent moldability, mechanical strength, flexibility, and weather resistance.

[0068] The thickness of the protective sheet 21 is preferably 1 to 2 times the diameter of the wire 12. If it is thinner than 1 times the diameter of the wire 12, the shape of the wire 12 will be visible when covering the wire 12 fixed to the substrate sheet 11, which may cause cracking of the decorative layer stacked on the protective sheet 21 or deteriorate the appearance of the protective sheet 21 when it becomes a molded product. If it is thicker than 2 times the diameter of the wire 12, it will be difficult to mold the film heater 10 into a three-dimensional shape. For example, when the diameter of the wire 12 is 0.2 mm, the thickness of the protective sheet 21 is preferably 0.2 mm to 0.4 mm.

[0069] Next, the process of manufacturing the film heater molded article 18 as a resin molded article will be described.

[0070] Reference Figure 4 (1) The injection molding mold 22 includes a movable mold 23 and a fixed mold 24. In this embodiment, the mold on the left side of the injection molding mold 22 is designated as the movable mold 23, and the mold on the right side is designated as the fixed mold 24. The movable mold 23 is positioned by means of a horizontal ( Figure 4 The movable mold 23 moves in the left-right direction (1) to approach or separate from the fixed mold 24. The movable mold 23 has a cavity surface 26, which corresponds to the shape of the preform 16 that bends the film heater 10 in the bending region A. The fixed mold 24 has a resin flow path 25 for injecting molten resin 28. With the injection molding mold 22 open to the left and right, the preform 16 is placed on the cavity surface 26 of the movable mold 23.

[0071] Next, refer to Figure 4 (2) The fixed mold 24 and the movable mold 23 are closed to form a cavity 27 between them. While molten resin 28 is injected from the resin flow path 25 of the fixed mold 24 into the cavity 27 to form the resin molded body 17, the film heater molded article 18 is also formed. The molded film heater molded article 18 is cooled and solidified while the mold is closed as is.

[0072] Next, refer to Figure 4(3) Open the injection molding mold 22 and remove the membrane heater molded article 18. In this way, the membrane heater molded article 18 is formed simultaneously with the preform 16 and the resin molded article 17 through injection molding.

[0073] Reference Figure 5 A resin molded body 17, corresponding to the shape of the outer sheet surface of the preform 16, is laminated onto the curved outer sheet surface of the preform 16. For the lamination, an adhesive layer may be used between the preform 16 and the resin molded body 17 for fixation, as needed. The adhesive layer may use adhesives such as acrylic, polyurethane, epoxy, rubber, polyester, cellulose, or emulsion adhesives. In this way, a membrane heater molded article 18 is manufactured.

[0074] In summary, in the membrane heater 10 configured as described above, when the membrane heater 10 is formed into a three-dimensional shape, the wires 12 are in close contact with the substrate sheet 11, thus preventing the wires 12 from peeling or breaking due to bending. Furthermore, in the manufacturing method of the membrane heater molded article 18 using the membrane heater 10 configured as described above, it is possible to manufacture the membrane heater molded article 18 with unbroken wires 12.

[0075] It should be noted that in the first and second embodiments of the present invention, the wire 12 is directly embedded in the substrate 11, but other layers such as an adhesive layer can also be formed on the substrate 11 and the wire 12 can be fixed to the layer.

[0076] In addition, in the first and second embodiments of the present invention, the protective sheet 21 is directly fixed to the substrate sheet 11, but other layers such as an adhesive layer may also be formed on the substrate sheet 11 and the protective sheet 21 may be fixed to the layer.

[0077] Furthermore, in the first and second embodiments of the present invention, a conductive pattern 13 is provided on the substrate 11 by a wire 12. However, as long as the wire 12 is configured to cross the curved area, the number of wires and the number and shape of the pattern are not limited to the above embodiments.

[0078] Furthermore, in the first and second embodiments of the present invention, a bending region is provided at the end of the membrane heater 10, but as long as a portion of the wire 12 crosses the bending region, a bending region may also be provided at other locations on the substrate sheet 11.

[0079] Furthermore, in the first and second embodiments of the present invention, in other steps of manufacturing the membrane heater molded article 18, a resin molded body 17 is stacked on the sheet surface of the curved outer side of the preform 16, but the resin molded body 17 can be stacked on the surface, back or both sides of the preform 16.

[0080] Explanation of reference numerals in the attached figures

[0081] 10. Membrane heater

[0082] 11 Matrix sheet

[0083] 12 electrical wires

[0084] 13 Conductive Patterns

[0085] 14. Heater Section

[0086] 15 Connecting terminal section

[0087] 16 Preforms

[0088] 17 Resin Molded Body

[0089] 18. Membrane heater molded products

[0090] 21 Protective Film

[0091] 22 Injection molding mold

[0092] 23 Movable Models

[0093] 24 Fixed mold

[0094] Type 26 cavity surface

[0095] 27-type cavity

[0096] 30, 40 outer surface

[0097] 31, 41 Inner surface

[0098] A. Curved area.

Claims

1. A conductive sheet, comprising: A base sheet having a bending region; A conductive pattern formed by a conductive wire fixed on the base sheet; and A protective sheet formed on the base sheet so as to cover the conductive pattern, A part of the wire crosses the bending region, and is set such that when the base sheet is bent in the bending region, the linear expansion ratio of the outer sheet between the base sheet and the protective sheet is greater than that of the inner sheet.

2. The conductive sheet according to claim 1, wherein It is set such that when the conductive sheet according to claim 1 is bent in the bending region, the length of the outer surface of the inner sheet is equal to the length of the inner surface of the outer sheet.

3. The conductive sheet according to claim 1, wherein Let the linear expansion of the base sheet be A1, the linear expansion of the protective sheet be A2, the thickness of the conductive sheet according to claim 1 be d, when the bending part of the base sheet when the conductive sheet is bent in the bending region is regarded as an arc and the radius of the arc is set as R, the molding temperature when the conductive sheet is bent in the bending region is set as T1, and the room temperature at this time is set as T2, then it is set to have the relationship of the following formula (1) or (2), (1) When A1 < A2: (2) When A1 > A2: 。 4. The conductive sheet according to claim 1, wherein The conductive pattern is composed of a continuous single wire and includes a heater part and a connection terminal part.

5. A resin molded product, comprising: A preform formed by bending the conductive sheet according to claim 1 in the bending region; and A resin molded product laminated on the surface, back surface or both surfaces of the preform.

6. A method for manufacturing a resin molded product, comprising the following steps: A step of arranging the conductive sheet according to claim 1 on any cavity surface of an injection molding die, the injection molding die having a fixed die and a movable die, and the movable die forms a cavity between the movable die and the fixed die by clamping; A step of clamping the injection molding die; A step of fixing the conductive sheet to the surface of the resin molded product while injecting molten resin into the cavity to form a resin molded product; and A step of opening the injection molding die and taking out the resin molded product.

7. The method for manufacturing a resin molded product according to claim 6, wherein The conductive sheet is a preform bent in the bending region.

8. A method for manufacturing a resin molded product, comprising the following steps: A step of preparing a preform formed by bending the conductive sheet according to claim 1 in the bending region; and A step of fixing a resin molded product having a surface shape corresponding to the surface, back surface or both surfaces on the surface, back surface or both surfaces of the preform.

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