Molded body and capacitance sensor

Abstract

A capacitance sensor 1A comprises: a decorative layer 21 having a three-dimensional shape; and a wiring assembly 3 joined to the decorative layer 21. The wiring assembly 3 comprises: a molded base member 4 that has a three-dimensional shape and is joined to the decorative layer 21; and a wiring board 5 that has a circuit part 5a in which an electric circuit is formed, and that is stacked onto the molded base member 4 so as to face the inner surface 21b of the decorative layer 21. The circuit part 5a is not joined to the decorative layer 21.

Description

Molded body and capacitance sensor

[0001] The present invention relates to a molded body and a capacitance sensor provided with this molded body. For designated countries where incorporation by reference is permitted, the content described in Japanese Patent Application No. 2024-179202 filed in Japan on October 11, 2024 is incorporated herein by reference and made part of the description of this specification.

[0002] A capacitance sensor is known that includes a circuit pattern layer provided with a conductive circuit pattern for detecting a change in capacitance on at least one of the front and back surfaces of a film, and a decorative layer laminated on the surface of this circuit pattern layer (see, for example, Patent Document 1). This capacitance sensor is manufactured by adhering the decorative layer and the circuit pattern layer with an adhesive layer to form a laminated film, and three-dimensionally molding and injection molding this laminated film (see, for example, Patent Document 1 (paragraphs

[0025] and

[0026] )).

[0003] Japanese Patent Application Laid-Open No. 2010-244776

[0004] In the three-dimensional molding of the laminated film, since the amount of elongation of the portion where the electrodes of the circuit pattern layer are formed is different from the amount of elongation of the portion where the electrodes are not formed, a difference in thickness occurs between these portions, and due to this difference in thickness, there is a problem that unevenness may be transferred from the circuit pattern layer to the decorative layer.

[0005] The problem to be solved by the present invention is to provide a molded body and a capacitance sensor having a good appearance by preventing the transfer of unevenness from the circuit portion to the decorative layer.

[0006] [1] Aspect 1 of the present invention includes a decorative layer having a three-dimensional shape and a wiring assembly joined to the decorative layer. The wiring assembly has a three-dimensional shape and includes a molded base material joined to the decorative layer, a circuit portion in which an electric circuit is formed, and a wiring board overlapped on the molded base material so as to face the inner surface of the decorative layer. The circuit portion is a molded body not joined to the decorative layer.

[0007] [2] A second aspect of the present invention is a molded body of the first aspect, wherein the molded substrate has a non-overlapping portion that does not overlap with the wiring board, and the molded substrate is joined to the decorative layer at the non-overlapping portion.

[0008] [3] Embodiment 3 of the present invention is a molded body in which the non-overlapping portion is joined to the decorative layer by a screw member or a snap-fit ​​joint, in the molded body of Embodiment 2.

[0009] [4] Embodiment 4 of the present invention is a molded body according to any of embodiments 1 to 3 in which no adhesive or tack is interposed between the circuit portion and the decorative layer.

[0010] [5] Embodiment 5 of the present invention is a molded body of any of embodiments 1 to 4, further comprising a pressing member for pressing the wiring assembly toward the decorative layer.

[0011] [6] Embodiment 6 of the present invention is a molded body according to any of embodiments 1 to 5, further comprising a spacer interposed between the decorative layer and the wiring board to make the distance between the decorative layer and the wiring board substantially constant.

[0012] [7] Embodiment 7 of the present invention is a capacitance sensor comprising a molded body according to any one of embodiments 1 to 6, wherein the electrical circuit includes a sensor electrode that forms capacitance with an object to be detected, and the capacitance sensor further comprises a control board that applies a voltage to the sensor electrode and detects changes in capacitance.

[0013] In this invention, a molded substrate with stacked wiring boards is bonded to a decorative layer, but the circuit portion of the wiring board is not bonded to the decorative layer. This prevents the irregularities in the circuit portion from being transferred to the decorative layer. As a result, a good appearance can be obtained for the molded body and the capacitance sensor.

[0014] Figure 1 is a cross-sectional view showing a capacitance sensor in an embodiment of the present invention. Figure 2 is a plan view showing a wiring board and spacer in an embodiment of the present invention. Figure 3 is a cross-sectional view showing a modified example of the capacitance sensor in an embodiment of the present invention.

[0015] Embodiments of the present invention will be described below with reference to the drawings.

[0016] Figure 1 is a cross-sectional view showing the capacitance sensor 1A in this embodiment. Figure 2 is a plan view showing the wiring board 5 and spacer 7 in this embodiment.

[0017] As shown in Figure 1, the capacitance sensor 1A in this embodiment is a sensor that can detect the proximity and contact of an object to be detected 100 by detecting a change in the capacitance value caused by the object to be detected 100. The capacitance sensor 1A in this embodiment is not particularly limited, but can be used in electronic devices having a decorative layer. Although not particularly limited, for example, the capacitance sensor 1A can be applied to a switch part of an electronic device.

[0018] The object to be detected 100 is not particularly limited as long as it can form capacitance with the sensor electrode 521 (see Figure 2), which will be described later, but examples include the human body and a stylus. The potential of the object to be detected 100 is not particularly limited, but can be considered as ground.

[0019] The capacitance sensor 1A in this embodiment comprises a case member 2, a wiring assembly 3, a control board 6, a plurality of spacers 7, and a plurality of pressing members 8.

[0020] In this embodiment, the case member 2 is a highly rigid resin housing that houses the wiring assembly 3 inside. This case member 2 is composed of a decorative layer (top case) 21 and a bottom case 22. In this embodiment, the decorative layer 21 is an insulating resin member that constitutes the upper part of the case member 2. The decorative layer 21 has a three-dimensional shape with a substantially U-shaped cross-section. The assembly composed of the decorative layer 21 and the wiring assembly 3 corresponds to an example of a "molded body" in an embodiment of the present invention.

[0021] The decorative layer 21 is not particularly limited, but can be manufactured by a molding method such as injection molding. In this case, the resin material constituting the decorative layer 21 is not particularly limited, but examples include liquid crystal polymer (LCP), polyphenylene sulfide (PPS), polybutylene terephthalate (PBT), polyamide (PA), polycarbonate (PC), etc.

[0022] In this embodiment, the decorative layer 21 is molded into a three-dimensional shape having a roughly U-shaped cross-section, but it is not limited to this, and it may be molded into a three-dimensional shape appropriate for the application of the capacitance sensor 1A.

[0023] The decorative layer 21 comprises a main body portion 211 and a plurality of joining portions 212. The main body portion 211 includes an operating surface 21c on its outer surface 21a that contacts the object to be detected 100. A predetermined pattern (not shown) is formed on the outer surface 21a or inner surface 21b of the main body portion 211. Although not particularly limited, this pattern may be formed on the surface of the decorative layer 21 manufactured by injection molding by printing, transfer, plating, etc. Alternatively, for example, the pattern may be formed by trimming a pattern formed on the entire surface of the decorative layer 21 by printing, transfer, or plating with a laser or the like.

[0024] A joint portion 212 is erected on the lower end surface 21d of the main body portion 211. In this embodiment, the joint portion 212 is formed integrally with the main body portion 211. This joint portion 212 joins the wiring assembly 3 to the decorative layer 21 and also joins the bottom case 22 to the decorative layer 21.

[0025] In this embodiment, the joint 212 is a cantilever-type snap-fit ​​joint. However, the joint 212 is not limited to a cantilever-type snap-fit ​​joint; for example, it may be an annular snap-fit ​​joint or the like.

[0026] The joint portion 212 in this embodiment comprises a beam portion 213 and a hook portion 214. The beam portion 213 is a cantilever beam extending in the -Z direction from the lower end surface 21d of the main body portion 211. This beam portion 213 is inserted through the first through hole 221 of the bottom case 22, which will be described later, and the second through hole 421 of the molded base material 4. This beam portion 213 restricts the movement of the wiring assembly 3 and the bottom case 22 in the XY direction.

[0027] The hook portion 214 protrudes from the tip of the beam portion 213 toward the outside of the capacitance sensor 1A and is engaged with the bottom case 22 from below the first through hole 221. As a result, the wiring assembly 3 and the bottom case 22 are sandwiched between the hook portion 214 and the decorative layer 21. This restricts the movement of the wiring assembly 3 and the bottom case 22 in the Z direction.

[0028] As described above, the joint 212 joins the wiring assembly 3 and the bottom case 22 to the decorative layer 21 by restricting the movement of the wiring assembly 3 and the bottom case 22 in the XYZ directions.

[0029] The bottom case 22 is an insulating resin member that constitutes the lower part of the case member 2. In this embodiment, the bottom case 22 supports the molded substrate 4 from below, and the bottom case 22 and the decorative layer 21 sandwich the molded substrate 4. The bottom case 22 also supports the control board 6, which will be described later.

[0030] The wiring assembly 3 is housed in such a case member 2. The wiring assembly 3 comprises a molded base material 4 and a wiring board 5. The molded base material 4 is a film material used in molding processes such as deep drawing. This molded base material 4 is molded into a three-dimensional shape corresponding to the three-dimensional shape of the decorative layer 21, and in this embodiment, it has a three-dimensional shape with a substantially U-shaped cross-section.

[0031] The molded base material 4 in this embodiment is not particularly limited, but is made of a thermoplastic resin that softens at approximately 100°C to 200°C. Specific examples of thermoplastic resins constituting the molded base material 4 include polycarbonate (PC), acrylonitrile butadiene styrene (ABS) resin, acrylic resin, cyclic olefin resin, polyester (PEs), or polyarylate (PAR). This molded base material 4 is not particularly limited, but after being heated to the above-mentioned softening temperature, it is molded into a predetermined three-dimensional shape using a mold or the like, and then solidified while maintaining its three-dimensional shape by cooling.

[0032] The molded base material 4 includes an overlapping portion 41 and a non-overlapping portion 42. The overlapping portion 41 is the portion that overlaps with the wiring board 5. This overlapping portion 41 is not bonded to the decorative layer 21. On the other hand, in this embodiment, the upper surface of this overlapping portion 41 is bonded to the lower surface of the wiring board 5 by an adhesive or bonding agent (not shown). The overlapping portion 41 is not particularly limited, but it has a third through-hole 411. The wiring board 5 is inserted through this third through-hole 411 and connected to the control board 6.

[0033] The non-overlapping portion 42 is the part that does not overlap with the wiring board 5 and is not joined to the wiring board 5. On the other hand, the end of this non-overlapping portion 42 is positioned between the decorative layer 21 and the bottom case 22 and is joined to the lower end surface 21d of the decorative layer 21. Specifically, the non-overlapping portion 42 in this embodiment has a second through hole 421 at its end, and as described above, the joining portion 212 is inserted through this second through hole 421. At the same time, the hook portion 214 of the joining portion 212 locks into the bottom case 22, thereby joining the non-overlapping portion 42 to the decorative layer 21.

[0034] The wiring board 5 is a circuit board that functions as a sensor. The wiring board 5 is placed on the molded base material 4 so as to face the inner surface 21b of the decorative layer 21.

[0035] As shown in Figure 2, the wiring board 5 comprises a flexible substrate 51 and an electrical circuit 52. The flexible substrate 51 is a film member made of a flexible insulating resin. The resin material constituting the flexible substrate 51 is not particularly limited, but examples include polyimide (PI), polyethylene terephthalate (PET), and polyethylene naphthalate (PEN).

[0036] An electrical circuit 52 is formed on this flexible substrate 51. The electrical circuit 52 is made of a conductive metallic material. The metallic material is not particularly limited, but copper and aluminum are examples. The electrical circuit 52 is not particularly limited, but can be formed using methods such as the subtractive method or the semi-additive method.

[0037] The electrical circuit 52 may also be formed by printing a conductive paste onto a flexible substrate 51 and allowing it to solidify (harden). Examples of methods for printing the conductive paste include screen printing, gravure offset printing, flexographic printing, and inkjet printing. The conductive paste is composed of conductive particles and a binder resin mixed with water or a solvent and various additives.

[0038] Specific examples of conductive particles include silver, copper, nickel, tin, bismuth, zinc, indium, palladium, and their alloys, metal salts thereof, carbon, conductive polymers such as PEDOT / PSS, etc. Specific examples of binder resins include acrylic resin, polyester resin, epoxy resin, vinyl resin, urethane resin, phenolic resin, polyimide resin, silicone resin, fluororesin, etc. Furthermore, examples of solvents included in the conductive paste include α-terpineol, butyl carbitol acetate, butyl carbitol, 1-decanol, butyl cellsolve, diethylene glycol monoethyl ether acetate, tetradecane, etc. The binder resin may be omitted from the above conductive paste. Alternatively, a conductive ink may be used instead of the above conductive paste.

[0039] As shown in Figure 2, the electrical circuit 52 in this embodiment includes a plurality of sensor electrodes 521 and a plurality of lead wires 522. The plurality of sensor electrodes 521 in this embodiment are arranged with a gap between them along the Y direction. The sensor electrodes 521 also have a strip shape that extends along the X direction. Each of the sensor electrodes 521 is a self-capacitive type capacitive sensor and forms capacitance with the object to be detected 100 (see Figure 1).

[0040] The lead wire 522 is electrically connected to the sensor electrode 521. This lead wire 522 is electrically connected to a control board 6 (see Figure 1) capable of applying voltage to the sensor electrode 521, and the sensor electrode 521 receives voltage from the control board 6 via the lead wire 522. The lead wire 522 is not particularly limited, but it can be electrically connected to the electrical circuit of the control board 6 via a connector (not shown), anisotropic conductive paste, etc.

[0041] Furthermore, the shape and arrangement of the sensor electrodes 521 are not limited to those described above and can be changed according to the design of the capacitive sensor 1A. Also, each of the sensor electrodes 521 may be a mutual capacitance type capacitive sensor. Specifically, the sensor electrodes 521 may be a transmitting electrode (T ｘ ) and the receiving electrode (R) adjacent to the transmitting electrode with a gap between them. ｘ ) and may be composed of . In this mutual capacitance type capacitance sensor, a capacitance is formed between the object to be detected 100 and the transmitting electrode, causing a change in the capacitance between the transmitting electrode and the receiving electrode. The mutual capacitance type capacitance sensor detects contact or approach of the object to be detected 100 by detecting this change in capacitance.

[0042] Furthermore, in a mutual capacitance type capacitance sensor, the transmitting electrode may be formed on a different layer from the receiving electrode, and the two may intersect in a grid pattern in a transmitted planar view. For example, although not particularly limited, the transmitting electrode may be provided so as to extend in the X direction on the surface of the flexible substrate 51, and the receiving electrode may be provided so as to extend in the Y direction on the back surface of the flexible substrate 51.

[0043] As shown in FIGS. 1 and 2, the circuit portion 5a in which the electric circuit 52 of such a wiring board 5 is formed is not joined to the inner surface 21b of the decorative layer 21, and in this embodiment, it is arranged so as to be separated from the decorative layer 21. In this embodiment, "the circuit portion is not joined to the inner surface of the decorative layer" means that the circuit portion 5a is not directly joined to the inner surface 21b of the decorative layer 21 using a joining material such as an adhesive, an adhesive agent, a screw member, or a snap-fit joint, and is not directly joined by welding or the like that melts and adheres the decorative layer 21 and the flexible base material 51. Further, if the circuit portion 5a is not joined to the inner surface 21b of the decorative layer 21, it may be in contact with the inner surface 21b.

[0044] As shown in FIG. 1, the control board 6 is a board that controls the voltage applied to the sensor electrode 521 and detects a change in capacitance. As this control board, a general printed circuit board (PCB) can be used. This control board is electrically connected to a power source (not shown) and is supplied with power from the power source.

[0045] The spacer 7 is interposed between the wiring board 5 and the decorative layer 21. This spacer 7 defines the distance between the decorative layer 21 and the wiring board 5 to be substantially constant. As shown in FIG. 2, the spacer 7 in this embodiment does not overlap with the circuit portion 5a and is arranged around the circuit portion 5a. When the circuit portion 5a is illuminated by the light of a backlight such as an LED, the spacer 7 is arranged avoiding the circuit portion 5a.

[0046] Such a spacer 7 is not particularly limited. For example, it may be a resin printed on the flexible base material 51. Alternatively, the spacer 7 may be a tape member attached to the flexible base material 51. Alternatively, the spacer 7 may be a rib portion formed on the inner surface 21b of the decorative layer 21.

[0047] Since such a spacer 7 defines the distance between the decorative layer 21 and the wiring board 5 to be substantially constant, a wedge-shaped air layer is not formed between the decorative layer 21 and the wiring board 5. Thereby, the generation of Newton rings can be suppressed, and a good appearance of the capacitance sensor 1A can be obtained.

[0048] The pressing member 8 is interposed between the control board 6 and the molded base material 4, and presses the wiring assembly 3 in the +Z direction. The pressing member 8 is an elastic material and is not particularly limited, but may be a rubber material, a spring material, or the like.

[0049] The pressing member 8 can reduce the distance between the wiring board 5 and the decorative layer 21 by pressing the wiring assembly 3 toward the inner surface 21b of the decorative layer 21. As a result, the thickness of the air layer interposed between the sensor electrode 521 and the decorative layer 21 can be reduced, thereby improving the sensitivity of the capacitance sensor 1A.

[0050] In the capacitance sensor 1A of this embodiment as described above, the molded substrate 4 is bonded to the decorative layer 21, but the circuit portion 5a of the wiring board 5 is not bonded to the decorative layer 21. As a result, the irregularities caused by the electrical circuit 52 in the circuit portion 5a are not transferred to the decorative layer 21. This makes it possible to obtain a good appearance for the capacitance sensor 1A.

[0051] Furthermore, the capacitance sensor 1A in this embodiment can be manufactured by joining the decorative layer 21 and the wiring assembly 3 after manufacturing them in separate processes. If the decorative layer 21 and the wiring assembly 3 can be manufactured in separate processes in this way, the decorative layer 21 and the wiring assembly 3 can be judged for quality separately. Therefore, it becomes possible to join the decorative layer 21 and the wiring assembly 3 that have been judged to be good products, thereby improving the final yield.

[0052] The embodiments described above are provided to facilitate understanding of the present invention and are not intended to limit it. Therefore, each element disclosed in the above embodiments is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0053] For example, in the above embodiment, the wiring assembly 3 and the decorative layer 21 are joined by a joint 212 (snap-fit ​​joint) integrally formed with the decorative layer 21, but the invention is not limited to this. For example, as shown in the modified example below, instead of the joint 212, the non-overlapping portion 42 of the molded base material 4 may be joined to the decorative layer 21 by a screw member 9.

[0054] Figure 3 is a cross-sectional view showing a modified example of the capacitance sensor 1A in this embodiment. As shown in Figure 3, the capacitance sensor 1B in this modified example is equipped with a screw member 9 instead of a joint portion 212. Although not shown in Figure 3, the capacitance sensor 1B may also be equipped with a bottom case 22, a control board 6, a spacer 7, and a pressing member 8, similar to the capacitance sensor 1A shown in Figure 1.

[0055] In this modified example, the decorative layer 21 includes a screw hole 215 that opens at the lower end surface 21d. The screw member 9 is inserted through the screw hole 215 and a second through hole 421 formed in the non-overlapping portion 42 of the molded base material 4, thereby fastening the molded base material 4 and the decorative layer 21.

[0056] Even in this modified example of the capacitance sensor 1B, as in the embodiment described above, the irregularities caused by the electrical circuit 52 are not transferred to the decorative layer 21. This makes it possible to obtain a good appearance for the capacitance sensor 1A. Also, as in the embodiment described above, it is possible to improve the final yield in the manufacturing process of the capacitance sensor 1B.

[0057] In the above embodiment, the molded base material 4 and the decorative layer 21 may be joined together by an adhesive, tack, or welding.

[0058] 1A, 1B...Capacitance sensor 2...Case member 21...Decorative layer 211...Main body 212...Joint 213...Beam 214...Hook 215...Screw hole 22...Bottom case 221...First through hole 3...Wiring assembly 4...Molded base material 41...Overlapping part 411...Third through hole 42...Non-overlapping part 421...Second through hole 5...Wiring board 5a...Circuit part 51...Flexible base material 52...Electrical circuit 521...Sensor electrode 522...Output wiring 6...Control board 7...Spacer 8...Pressing member 9...Screw member 100...Detected object

Claims

1. A decorative layer having a three-dimensional shape, and a wiring assembly joined to the decorative layer, wherein the wiring assembly has a three-dimensional shape and comprises a molded base material joined to the decorative layer, and a wiring board having a circuit portion on which an electrical circuit is formed and superimposed on the molded base material so as to face the inner surface of the decorative layer, wherein the circuit portion is a molded body not joined to the decorative layer.

2. A molded body according to claim 1, wherein the molded base material has a non-overlapping portion that does not overlap with the wiring board, and the molded base material is joined to the decorative layer at the non-overlapping portion.

3. A molded body according to claim 2, wherein the non-overlapping portion is joined to the decorative layer by a screw member or a snap-fit ​​joint.

4. A molded body according to any one of claims 1 to 3, wherein no adhesive or tack is interposed between the circuit portion and the decorative layer.

5. A molded body according to any one of claims 1 to 4, wherein the molded body further comprises a pressing member for pressing the wiring assembly toward the decorative layer.

6. A molded body according to any one of claims 1 to 5, wherein the molded body further comprises a spacer interposed between the decorative layer and the wiring board to make the distance between the decorative layer and the wiring board substantially constant.

7. A capacitance sensor comprising a molded body according to any one of claims 1 to 6, wherein the electrical circuit includes a sensor electrode that forms a capacitance with an object to be detected, and the capacitance sensor further comprises a control board that applies a voltage to the sensor electrode and detects changes in the capacitance.

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