Pressure-sensitive element

Abstract

To provide a pressure sensitive element which is excellent in mutual adhesion stability between an insulation base material and a movable electrode or the like forming a pressure sensitive surface in a capacitance type pressure sensitive element.SOLUTION: A pressure sensitive element comprises: an insulation base material; a movable electrode which is arranged on a pressure sensitive surface of the insulation base material; and a fixed electrode which is arranged on a surface on the side opposite to the pressure sensitive surface of the insulation base material. The fixed electrode is coated with a protection film. The movable electrode is formed of a conductive filler blending in a matrix material made of an insulation elastic material. The protection film is formed of a material in the same system as the matrix material. The movable electrode and the protection film are joined to each other via a junction hole provided in the insulation base material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a capacitive pressure-sensitive element. [Background technology]

[0002] 2. Description of the Related Art Pressure-sensitive elements are known that detect an external pressure based on a change in capacitance caused by the pressure. These pressure-sensitive elements can be used for switching functions and input devices when pressed, and by arranging multiple pressure-sensitive elements, they can be used for pressure distribution measurement functions, and are being considered in various fields. The present inventors have previously proposed a pressure-sensitive element (input device) that is easy to make thin and has excellent stability in detecting changes in capacitance (Patent Document 1). The present invention further improves manufacturability and stability of detection changes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4585615 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a capacitance-type pressure-sensitive element having excellent adhesion stability between an insulating substrate and a movable electrode and the like that form a pressure-sensitive surface. [Means for solving the problem]

[0005] The pressure-sensitive element of the present invention comprises an insulating substrate, a movable electrode arranged on the pressure-sensitive surface of the insulating substrate, and a fixed electrode arranged on the surface of the insulating substrate opposite the pressure-sensitive surface, the fixed electrode being covered with a protective film, the movable electrode being a matrix material made of an insulating elastic material containing a conductive filler, the protective film being formed from the same material family as the matrix material, and the movable electrode and the protective film being joined to each other via a joining hole provided in the insulating substrate.

[0006] The purpose of the insulating substrate is to provide insulation between the movable electrode arranged on the pressure-sensitive surface and the fixed electrode arranged on the opposite surface, and when the movable electrode is displaced by pressure, the electrostatic capacitance between it and the fixed electrode changes. In the present invention, the insulating substrate is preferably a thin film, examples of which include resin films such as PET (polyethylene terephthalate), polyethylene, polypropylene, and nylon. These resin films are flexible and can be arranged as pressure-sensitive elements even when they have various concave or convex shapes.

[0007] In the present invention, the movable electrode is preferably made of a conductive material having elasticity such that it is elastically deformed in response to a pressure applied thereto. A widely used material of this type is one in which a conductive filler such as black carbon or metal powder is mixed with silicone rubber. However, it is difficult to bond silicone rubber and resin film, and a strong bond cannot be achieved with adhesive unless the bonding surfaces are plasma-treated or treated with a special primer.

[0008] Therefore, in the present invention, an insulating material of the same type as the matrix material used for the elastic material of the movable electrode is used as the protective film covering the fixed electrode, and a bonding hole as a through hole is provided in the insulating base material, so that the matrix material of the movable electrode and the protective film are bonded via this bonding hole. As a result, for example, when a conductive silicone rubber is used for the movable electrode, by adopting an insulating silicone rubber that does not contain conductive filler as the protective film, the electrodes can be firmly bonded to each other using a silicone adhesive or silicone welding agent via a through hole provided in the insulating base material. In this state, the insulating substrate is laminated in a state where it is sandwiched between the movable electrode and the protective film, so that even if a load is repeatedly applied to the pressure-sensitive element in the bending direction, the movable electrode can be prevented from peeling off from the insulating substrate.

[0009] The matrix material, which is an elastic material forming the conductive movable electrode, and the protective film are of the same material type, meaning that the polymers constituting the materials are the same. For example, when a conductive filler is mixed into a silicone rubber matrix material, various auxiliary agents may be mixed in, so it is not necessary for the silicone rubber to be the same as long as it is of the same type. In addition to silicone rubber, other examples of matrix materials include EPDM (ethylene propylene diene rubber), NBR (acrylonitrile butadiene rubber), and CR (chloroprene rubber).

[0010] In the present invention, when the movable electrode has a tip portion in contact with the insulating substrate and a base portion having a truncated cone-shaped expansion as disclosed in Patent Document 1, the movable electrode has a fixed portion formed on the outer periphery side of the movable electrode and a transition portion formed on the central portion side, and the fixed portion and the transition portion may each be joined to the protective film via a joining hole provided in the insulating substrate. In this way, the tip of the transition portion is firmly fixed to the insulating base material, so that the initial capacitance can be stabilized.

[0011] In addition, instead of the above-mentioned truncated cone-shaped transition portion, a dielectric material may be provided between the transition portion of the movable electrode and the insulating substrate, the dielectric material being formed from the same material family as the matrix, and the dielectric material and the protective film may be bonded to each other via a bonding hole provided in the insulating substrate.

[0012] In the present invention, the movable electrode and the protective film may be larger than the outer shape of the insulating base material, and the movable electrode and the protective film may be joined to the outside of the insulating base material. In this way, the pressure-sensing part of the insulating substrate is enclosed by the upper and lower movable electrodes and the protective film, and the outer edge of the movable electrode is joined to the outer edge of the protective film, thereby preventing misalignment of the pressure-sensing part and ensuring water prevention and airtightness.

[0013] In the present invention, the movable electrode may not have a fixed portion to the insulating substrate, and in this case, the device comprises an insulating substrate, a pressure-sensitive surface material arranged on the pressure-sensitive surface of the insulating substrate, and a fixed electrode arranged on the surface of the insulating substrate opposite the pressure-sensitive surface, and has a dielectric material between the insulating substrate and the pressure-sensitive surface material, the fixed electrode being covered with a protective film, and the pressure-sensitive surface material being a matrix material made of an insulating elastic material into which a conductive filler is blended, and it is preferable that the dielectric material and the protective film are formed from the same material type as the matrix material, and are joined to each other via a joining hole provided in the insulating substrate.

[0014] In the present invention, a shielding material may be provided on the outer surface of the protective film, and the movable electrode or the pressure-sensitive surface material may be integrally formed with the shielding material. In this way, the fixed electrode side of the insulating base material can be electrically shielded, making it possible to suppress electrostatic noise. In addition, by integrally forming the shielding material arranged on the outer surface of the protective film with the movable electrode or pressure-sensitive surface material, the pressure-sensitive surface side and the shielding material are electrically connected, and a contact electrode for electrically wiring the movable electrode or pressure-sensitive surface material with a terminal for connecting to the outside can also be formed on the back surface side of the insulating substrate. In this case, the contact electrode and the fixed electrode can be formed on one surface (rear surface) of the insulating base material.

[0015] In the present invention, the movable electrode or the pressure-sensitive surface material and the shielding material may be bonded via a bonding hole provided in the insulating base material.

[0016] In the present invention, by arranging a movable electrode and a pressure-sensitive surface material on the pressure-sensitive surface side and arranging a shielding material on the outer surface of the protective film of the fixed electrode, this shielding material can also be extended to the vicinity of the terminal that connects to the outside. Furthermore, the pressure detection portion of the pressure-sensitive surface material may be provided with a stepped portion, pattern, figure or the like as a marker, and the pressure-sensitive surface material and the shielding material may be clamped with a clip member. In addition, when the contact electrodes are provided on the surface of the insulating substrate on the shielding material side, the electrical connection with the contact electrodes can be strengthened by providing connection holes on both sides of the contact electrodes and joining them to the pressure-sensitive surface side. Effect of the Invention

[0017] In the pressure-sensitive element of the present invention, a junction 3L (through hole) is formed in the insulating substrate, and a protective film is provided using a material of the same type as the matrix material of the conductive elastic material that forms the movable electrode or pressure-sensitive surface material. The insulating substrate is sandwiched between the movable electrode or pressure-sensitive surface material and the protective film, and the insulating substrate is laminated so that each is firmly bonded to the other, resulting in stable detection performance for capacitance changes. In particular, when a plurality of pressure-sensitive elements are disposed on a sheet material or the like and pressure distribution or the like is detected, a bending deformation load is applied to the pressure-sensitive elements, but even in this case, the detection accuracy is high. In addition, the process is shorter than with conventional bonding methods that involve plasma treatment or special primer treatment, improving productivity. [Brief description of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of a pressure-sensitive element according to a first embodiment of the present invention. [Diagram 2] FIG. 11 shows Example 2, where (a) is a cross-sectional view and (b) is a view seen from the fixed electrode side. [Diagram 3] 13 shows a cross-sectional view of Example 3. [Figure 4]FIG. 11 shows Example 4, where (a) is a cross-sectional view and (b) is a view seen from the fixed electrode side. [Diagram 5] FIG. 1 shows Example 5, where (a) is a cross-sectional view and (b) shows the integrated silicone rubber. [Figure 6] Example 6 is shown below. [Figure 7] FIG. 13 shows Example 7, where (a) is a cross-sectional view and (b) shows the integrated silicone rubber. [Figure 8] 8 shows a cross-sectional view of a pressure-sensitive element of a pressure-sensitive surface material type as an eighth embodiment. [Figure 9] Example 9 is shown. [Figure 10] FIG. 10 shows Example 10, where (a) is a cross-sectional view before bonding and (b) is a cross-sectional view after bonding. [Figure 11] 11 shows Example 11, where (a) shows the state before the shielding material is extended, and (b) shows the state after the shielding material is extended close to the terminal. [Figure 12] Example 12 shows an example in which a mark is provided on the pressure-sensitive portion of the pressure-sensitive surface material. [Figure 13] FIG. 13 shows Example 13, where (a) is a cross-sectional view and (b) is a view seen from the fixed electrode side. [Figure 14] Example 14 shows an example in which a bonding portion is provided on both sides of a contact electrode. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] An example of the structure of the pressure-sensitive element according to the present invention will be described below with reference to the drawings, but the present invention is not limited thereto.

[0020] Example 1 is shown in FIG. In this embodiment, a PET film is used as the insulating substrate 11, conductive silicone rubber is disposed as the movable electrode 12 on the pressure-sensitive surface side, and an Ag electrode is patterned by printing as the fixed electrode 13 on the back surface opposite the pressure-sensitive surface. FIG. 1 is a cross-sectional view, and the movable electrode 12 has a circular outer shape, with a fixed portion 12a formed on the periphery and a transition portion 12b formed on the central side. The tip of transition portion 12b is in contact with the surface of insulating base material 11, and the base side has an outer shape that becomes larger in a truncated cone shape. The fixed portion 12a is electrically connected to a contact electrode 16 formed on the surface of the insulating base material 11, and this contact electrode 16 is electrically connected to some of the multiple terminals 17 for external connection (not shown). The fixed electrode 13 is disposed opposite the transition portion, and in this embodiment is printed in a disk shape. A protective film 14 is disposed so as to cover the fixed electrode 13 and has an outer shape corresponding to that of the movable electrode 12 . In this embodiment, insulating silicone rubber is used as the protective film 14. The insulating silicone rubber is a conductive silicone rubber that does not contain the conductive filler of the conductive silicone rubber. Therefore, the protective film 14 is an elastic material made of the same type of silicone polymer as the matrix material that constitutes the conductive silicone rubber. A bonding hole 11a consisting of a plurality of through holes is formed around the fixed portion 12a of the insulating base material 11, and a silicone adhesive is applied to this bonding hole 11a to form a bonding portion 15 where the fixed portion 12a on the movable electrode 12 side and the protective film 14 are bonded. By providing the bonding holes 11a in the insulating base material 11 in this manner, the movable electrode 12 and the protective film 14, which are made of the same type of rubber, are adhesively bonded together, resulting in high adhesive strength.

[0021] FIG. 2 shows Example 2, which differs from Example 1 shown in FIG. 1 in that a bonding hole is also formed in the portion located between transition portion 12b of insulating substrate 11 and protective film 14, and a bonding portion 15a between this transition portion 12b and protective film 14 is added. In this way, the tip of the transition portion 12b is firmly in contact with the surface of the insulating base material 11, so that the initial capacitance is stable. The fixed electrode 13A is doughnut-shaped.

[0022] FIG. 3 shows Example 3. In this embodiment, instead of the truncated cone-shaped transition portion 12b in the second embodiment, a circular recess is formed on the movable electrode side, and insulating silicone rubber made of the same rubber type as the protective film 14 is disposed in this recess as a dielectric material 18. In this case as well, the dielectric material 18 and the protective film 14 are bonded to each other at a bonding portion 15a with the silicone adhesive through a bonding hole provided in the insulating base material 11.

[0023] FIG. 4 shows Example 4. This embodiment is an example in which the outer shapes of the movable electrode 12 and the protective film 14 in the second embodiment are made larger than the outer shape of the insulating base material 11. In this embodiment, the movable electrode 12A has a substantially rectangular outer shape, and the protective film 14 has a size and outer shape corresponding to this. As a result, the movable electrode 12A and the protective film are bonded not only through the bonding holes provided in the insulating base material 11, but also directly at the four corners, that is, between the outer edge of the movable electrode 12A and the corners of the protective film . This prevents the transition portion 12b from being misaligned. In addition, since the pressure-sensitive portion is enclosed, water intrusion is prevented and airtightness is improved.

[0024] FIG. 5 shows Example 5. This embodiment is an example in which a shield portion 12d is integrally formed on the end of a movable electrode portion 12B via a joint portion 12c. By using the integrated conductive silicone rubber shown in FIG. 5(b), a shielding material 12d made of conductive silicone rubber can be placed on the outer surface of the insulating protective film 14, as shown in FIG. 5(a). This makes it possible to suppress electrostatic noise.

[0025] FIG. 6 shows Example 6. In contrast to the third embodiment, this is an example in which a shielding material 12d is disposed on the outer side of the protective film 14, and the movable electrode 12C and the shielding material 12d are connected by a connecting portion 12c.

[0026] FIG. 7 shows Example 7. This embodiment is an example in which a movable electrode 12D and a shielding material 12d are extended toward the terminal 17 side in comparison with the fifth embodiment shown in FIG. In this way, a joint hole can be provided in the insulating base material 11 in the extended portion as well, and the movable electrode 12D side and the shield material 12d can be directly joined at the joint 15b. Furthermore, since the movable electrode 12D and the shielding material 12d are connected by the connecting portion 12c, the contact electrode 16 can also be disposed on the extending portion 12e side of the shielding material 12d. In this way, the fixed electrode 13A and the contact electrode 16 can be disposed on one surface (rear surface) of the insulating base material 11, and can be electrically connected to the terminal 17 on this surface, respectively.

[0027] FIG. 8 shows Example 8. In this embodiment, a conductive pressure-sensitive surface material 12E made of a sheet-like elastic material is used as the movable electrode. In this case, a dielectric material 18 is placed on the pressure-sensitive surface side of the film-like insulating substrate 11, and a pressure-sensitive surface material 12E is layered on top of it, and a shielding material 12d connected by a joint 12c at the end is layered on the outside of the protective film 14. In this case as well, similarly to the seventh embodiment shown in FIG. 7, the contact electrode 16 is provided on the shield material 12d side. FIG. 9 shows a ninth embodiment, in which the pressure-sensitive surface material 12F and the shielding material 12d have the same thickness.

[0028] FIG. 10 shows Example 10. In this embodiment, a protruding connection portion 12f is formed from the movable electrode 12G side toward the shielding material 12d side, and thus the movable electrode 12G and the shielding material 12d are directly joined through a joining hole in the insulating base material, as shown in Figure 10(b).

[0029] FIG. 11 shows Example 11. In this embodiment, compared to the embodiment 9 in FIG. 9, the pressure-sensitive surface material 12H and the extension portion 12e of the shielding material 12d are arranged up to the vicinity of the terminal 17 as shown in FIG. 11(b), thereby improving the shielding properties. In this case, as shown in Example 12 in FIG. 12, a mark portion 112b having a step shape or a mark may be formed so that the pressure-sensitive portion of the pressure-sensitive surface material 12I can be easily identified.

[0030] FIG. 13 shows Example 13. In this embodiment, the pressure-sensitive surface material and the shielding material 12d are formed from a single piece of conductive rubber, and the ends of the material are clamped and fixed by clips 19. The clip may be made of an insulating material such as resin, or may be made of metal.

[0031] FIG. 14 shows Example 14. This embodiment is an example in which a contact electrode 16a is arranged on an extension portion 12e of a shielding material 12d, and a joint portion 15b with a dielectric 18 is formed on both sides of the contact electrode 16a, thereby improving the electrical connectivity of the contact electrode 16a. [Explanation of symbols]

[0032] 11 Insulating substrate 11a Junction hole 12 Movable electrode 12a Fixed part 12b Transition part 12E Pressure-sensitive surface material 13 Fixed electrode 14 Protective film 15 Joint 18 Dielectric Materials

Claims

1. The pressure sensor comprises an insulating substrate, a movable electrode disposed on a pressure-sensitive surface of the insulating substrate, and a fixed electrode disposed on a surface of the insulating substrate opposite to the pressure-sensitive surface, The fixed electrode is covered with a protective film, The movable electrode is made of an insulating elastic matrix material containing a conductive filler. The protective film is formed of a material of the same type as the matrix material, A pressure-sensitive element, characterized in that the movable electrode and the protective film are joined to each other through a joining hole provided in the insulating base material.

2. the movable electrode has a fixed portion formed on an outer periphery side of the movable electrode and a transition portion formed on a central portion side of the movable electrode, 2. The pressure-sensitive element according to claim 1, wherein the fixed portion and the transition portion are bonded to the protective film through bonding holes provided in the insulating base material.

3. the movable electrode has a fixed portion formed on an outer periphery side of the movable electrode and a dielectric material provided on a central portion side of the movable electrode, The dielectric material is formed of the same material as the matrix material, 2. The pressure-sensitive element according to claim 1, wherein the dielectric material and the protective film are bonded to each other through a bonding hole provided in the insulating base material.

4. A pressure-sensitive element as described in any one of claims 1 to 3, characterized in that the movable electrode and protective film are larger than the outer dimensions of the insulating substrate, and the movable electrode and protective film are joined outside the insulating substrate.

5. The pressure-sensitive electrode comprises an insulating substrate, a pressure-sensitive surface material disposed on a pressure-sensitive surface of the insulating substrate, and a fixed electrode disposed on a surface of the insulating substrate opposite to the pressure-sensitive surface, A dielectric material is provided between the insulating substrate and the pressure-sensitive surface material, The fixed electrode is covered with a protective film, The pressure-sensitive surface material is made of an insulating elastic material and a conductive filler is mixed into the matrix material. A pressure-sensitive element characterized in that the dielectric material and the protective film are formed from the same material as the matrix material, and are joined to each other via bonding holes provided in the insulating substrate.

6. A shielding material is disposed on an outer surface of the protective film, 4. The pressure-sensitive element according to claim 1, wherein the movable electrode and the shielding material are integrally formed.

7. A shielding material is disposed on an outer surface of the protective film, 4. The pressure-sensitive element according to claim 1, wherein the movable electrode and the shielding material are bonded to each other through a bonding hole provided in the insulating base material.

8. A shielding material is disposed on an outer surface of the protective film, 6. The pressure-sensitive element according to claim 5, wherein the pressure-sensitive surface material and the shielding material are integrally formed.

9. A shielding material is disposed on an outer surface of the protective film, 6. The pressure-sensitive element according to claim 5, wherein the pressure-sensitive surface material and the shielding material are joined via a joining hole provided in the insulating base material.

Images