JP2023007546A - Push-button switch - Google Patents

Abstract

To provide a push-button switch that has both high sensitivity to change in capacitance and high durability of a rubber key.SOLUTION: The present invention relates to a push-button switch that has a circuit board 15, a key sheet 20 and a key top 10 arranged in order, and the push-button switch 1 which comprises a conductive film 30 electrically connecting a detection part for capacitance located between a dome part 22 and key top 10 to a signal transmission part 45 is characterized in that: the key sheet 20 comprises the dome part 22 and a first electrode 24; the circuit board 15 comprises a second electrode 16 which can come into contact with the first electrode 24 through the deformation of the dome part 22 as the key top 10 is pressed down toward the circuit board 15; the key top 10 is arranged on a tip side of the dome part 22; and the circuit board 15 comprises the signal transmission part 45 which is located outside the key top 10 in plan view and transmits change in capacitance to wiring of the circuit board 15.SELECTED DRAWING: Figure 2C

Description

The present invention relates to pushbutton switches.

Conventionally, a push button has both the function of a push-down switch that enables the switch to be turned on or off by pressing it, and the function of a non-contact switch that enables the switch to be turned on or off by the proximity or contact of an operating part such as a finger. A switch is known (see, for example, Patent Document 1). The function of a push-down switch is realized, for example, by the elastic action of a dome-shaped rubber key, and the electrical contact and disconnection between the electrode protruding toward the circuit board inside the dome and the electrode on the circuit board. . Also, the function of the non-contact switch is realized by detecting a change in capacitance caused by, for example, an operation part represented by a human finger coming close to or touching the key top.

The known input device having both a press type and a capacitance type disclosed in Patent Document 1 can eliminate the risk of erroneous determination of capacitance detection, simplify the circuit configuration and control, and moreover, It is an excellent device capable of exerting a unique effect of being able to appropriately output a signal even if the operation is continued with the operating body.

On the other hand, there is also known a capacitive switch device in which the rubber key itself is made of conductive rubber (see, for example, Patent Document 2).

JP 2016-091803 A JP 2007-335374 A

However, the known input device disclosed in Patent Document 1 is required to have further improved performance. The performance is an improvement in capacitance detection sensitivity. Also, the known switch device disclosed in Patent Document 2 is a capacitive switch device that uses rubber keys made of conductive rubber as electrodes. Therefore, there is a problem that the durability of the rubber key is low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a push button switch having both high sensitivity to changes in capacitance and high durability of a rubber key. .

(1) A push button switch according to an embodiment for achieving the above object,
a circuit board;
a key sheet having one or more openings opening in one direction of thickness;
a key top;
is arranged in order,
The key sheet includes a dome portion provided on the side opposite to the opening side of the opening portion and expanding in diameter toward the circuit board, and a first electrode provided at a portion inside the dome portion facing the circuit board side. and
The circuit board includes a second electrode inside the opening, which can come into contact with the first electrode by deformation of the dome portion caused by pressing the key top toward the circuit board,
The key top is arranged on the tip side of the dome portion,
The circuit board includes a signal transmission section, which is a portion provided outside the key top in plan view and transmits a change in capacitance to wiring of the circuit board,
A conductive film is provided for electrically connecting a capacitance detection portion located between the dome portion and the key top and the signal transmission portion.
(2) In the push button switch according to another embodiment, preferably, the key sheet further includes a head portion on the tip side of the dome portion, and the conductive film extends from between the head portion and the key top. You may make it extend to the said signal transmission part.
(3) In the push button switch according to another embodiment, preferably, a groove is formed in a path from the outer edge of the enlarged diameter portion of the dome portion to the signal transmission portion, and the conductive film extends along the groove. It may be arranged.
(4) A push button switch according to another embodiment preferably further comprises a conductor electrically connected to the signal transmission section and exposed on a surface of the key sheet opposite to the circuit board, The conductive film may be electrically connected to the signal transmission section through the conductor.
(5) In the push button switch according to another embodiment, preferably, the conductive film is a laminated film of a conductive layer and an insulating layer, and the conductive layer may face the signal transmission section.
(6) In the push button switch according to another embodiment, preferably, the conductive film has a three-layer structure including the insulating layer, and a first conductive layer and a second conductive layer sandwiching the insulating layer as the conductive layers. and
The insulating layer has a hole in the middle of its length direction that penetrates in the thickness direction of the insulating layer, and the first conductive layer and the second conductive layer are connected through the hole,
The key top has a conductive member on the side in contact with the conductive film side,
The conductive film can conduct electricity from the conductive member to the first conductive layer, from the first conductive layer to the second conductive layer through the hole, and further from the second conductive layer to the signal transmission section. good.
(7) In the push button switch according to another embodiment, preferably, the conductive film includes an elastic layer that can be elastically deformed by a load and release of pressure from the key top, and a conductive film that It may have a structure sandwiched between layers.
(8) In the push button switch according to another embodiment, preferably, the conductive film may be formed with a narrower width between the dome portion side and the signal transmission portion side than on both sides thereof. .
(9) In the push button switch according to another embodiment, preferably, the dome side of the conductive film may be translucent in the thickness direction of the film.
(10) In the push button switch according to another embodiment, preferably, the key sheet includes two or more of the dome portions, and the conductive films are provided between the dome portions and the key tops respectively. A ground electrode may be provided between the above conductive films.
(11) In a push button switch according to another embodiment, preferably the two or more conductive films and the ground electrode are formed on an insulating film.
(12) In the push button switch according to another embodiment, the key sheet preferably includes an inwardly recessed recess on the tip side of the dome portion,
The conductive film has a convex portion that can be fitted into the concave portion at one end in its length direction,
The conductive film may be fixed to the key sheet by fitting the convex portion into the concave portion.

According to the present invention, it is possible to provide a push button switch having both high sensitivity to changes in capacitance and high durability of a rubber key.

FIG. 1 shows a plan view of a push button switch according to an embodiment of the present invention. FIG. 2A shows a cross-sectional view of the push button switch of FIG. 1 taken along the line AA. FIG. 2B shows a cross-sectional view of the push button switch of FIG. 1 taken along line BB. FIG. 2C shows a cross-sectional view of the push button switch of FIG. 1 taken along line CC. FIG. 3A shows a plan view of the key sheet of FIG. 2A. FIG. 3B shows a DD cross-sectional view of the key sheet of FIG. 3A. FIG. 4A shows a plan view of a modification of the key sheet of FIG. 3A. FIG. 4B shows a cross-sectional view of the key sheet of FIG. 4A taken along line EE. FIG. 5 shows top and side views of a variation of the conductive film of FIG. 2C. FIG. 6 shows plan views of each of three variations of the conductive film of FIG. 2C. FIG. 7 shows a plan view of a modification of the conductive film of FIG. FIG. 8A shows a plan view of a variation of the conductor of FIG. 2C. FIG. 8B shows a cross-sectional view of the conductor of FIG. 8A taken along line FF. FIG. 9 shows a plan view of a modification of the circuit board of FIG. 2A and an enlarged view of the second electrode. FIG. 10 shows a state a in which a human finger approaches one of the key tops of the push button switch, a state b in which the finger is brought into contact with the key top, and a switch input by pushing the key top with the finger to deform the dome portion. A cross-sectional view similar to FIG. 2A shows the state c over time. FIG. 11A shows a cross-sectional view of a modification of the configuration in which the conductive film is connected to the signal transmission section on the circuit board. FIG. 11B shows a cross-sectional view of another modification different from the modification shown in FIG. 11A. FIG. 12 shows a cross-sectional view of the push button switch in which the key top of FIG. 2C is changed, as seen in FIG. 2C. 13 shows a plan view and a side view of a conductive film that can be suitably used for the push button switch of FIG. 12. FIG. FIG. 14A shows a plan view of a variation of the conductive film. 14B shows a cross-sectional view of the push button switch with the conductive film of FIG. 14A, which is the same view as FIG. 2A. FIG. 15A shows a plan view and a cross-sectional view along line GG of a modification of the conductive film. FIG. 15B shows a plan view and a cross-sectional view taken along the line HH of the conductive film of FIG. 15A folded in two. FIG. 16A shows side and bottom views of a variation of the conductive film. FIG. 16B shows a cross-sectional view of how the conductive film of FIG. 16A is fixed to the key sheet.

Next, embodiments of the present invention will be described with reference to the drawings. In addition, the embodiments described below do not limit the invention according to the claims, and all of the elements described in the embodiments and their combinations are essential to the solution of the present invention. not necessarily.

FIG. 1 shows a plan view of a push button switch according to an embodiment of the present invention. FIG. 2A shows a cross-sectional view of the push button switch of FIG. 1 taken along the line AA. FIG. 2B shows a cross-sectional view of the push button switch of FIG. 1 taken along line BB. FIG. 2C shows a cross-sectional view of the push button switch of FIG. 1 taken along line CC. Note that the cross-sectional view taken along the line CC is shown with the key top facing upward.

In the present application, “conductivity” or “conductivity” refers to the property that the volume resistivity at 20° C. exceeds 0 (Ohm cm) and is 1.0×10 ⁶ (Ohm cm) or less, more preferably 1.0 A property of ×10 ³ (Ohm·cm) or less. The volumetric efficiency is measured according to the standard ASTM D 991 of the constant current application method. In addition, “insulating” or “insulating” means that the volume resistivity at 20° C. is greater than 1.0×10 ⁶ (Ohm·cm), more preferably greater than 1.0×10 ¹² (Ohm·cm). Say. The volumetric efficiency is measured according to the standard ASTM D 257 of the constant voltage application method.

A push button switch 1 according to this embodiment includes a circuit board 15 and a key sheet 20 in a space formed by overlapping a first cover 2 and a second cover 3 . The first cover 2 and the second cover 3 are preferably fixed by fastening members 4 such as screws at four corner positions in a plan view of the push button switch 1 . The push button switch 1 has three keys. However, the number of keys is not limited to three, and may be one, two, or four or more. Each push button switch 1 exposes one key top 10 from a through hole 5 extending through the first cover 2 . The key top 10 has a flange portion larger in diameter than the through hole 5 on the surface on the second cover side so that the key top 10 does not come off from the through hole 5 in the outward direction. In this embodiment, the through-holes 5 are formed in a straight line in the first cover 2 in plan view. However, the through holes 5 may be formed in a positional relationship other than on a straight line.

The push button switch 1 has a structure in which a circuit board 15 , a key sheet 20 and a key top 10 are arranged in order from the second cover 3 toward the first cover 2 . The key sheet 20 has one or more openings 25 opening in one of its thickness directions. The key sheet 20 has an outer peripheral portion 21 positioned on the outer periphery of the opening 25, and a dome portion 22 which is provided on the side opposite to the opening side of the opening 25 and which expands toward the circuit board 15 in plan view. and a first electrode 24 provided at a portion facing the circuit board 15 inside the dome portion 22 . In this embodiment, the key sheet 20 has a pusher portion protruding toward the circuit board 15 from the inner top surface of the dome portion 22, and the first electrode 24 at the tip of the pusher portion. However, the pusher portion is not an essential component of the key sheet 20 and the first electrode 24 may be provided on the inner top surface of the dome portion 22 . Further, in this embodiment, the key sheet 20 preferably further includes a head portion 23 protruding toward the key top 10 on the tip side of the dome portion 22 , that is, on the key top 10 side. One end of a conductive film 30 to be described later is sandwiched between the key top 10 and the head portion 23 . The one end is a detection portion that is located between the dome portion 20 and the keytop 10 and detects capacitance between an operation portion (human finger or the like) for operating the keytop 10 . However, the head portion 23 is not an essential component for the key sheet 20 . In that case, the conductive film 30 may be sandwiched between the outer top surface of the dome portion 22 and the key top 10 .

The circuit board 15 includes a second electrode 16 inside the opening 25 that can come into contact with the first electrode 24 by deformation of the dome part 22 caused by pressing the keytop 10 toward the circuit board 15 . The second electrode 16 consists in this embodiment of two electrodes separated from each other. The contact of the first electrode 24 with the two second electrodes 16 makes it possible to conduct electricity between the two second electrodes 16 . However, by using the second electrode 16 as one electrode and contacting the first electrode 24 , it is possible to conduct electricity between the first electrode 24 and the second electrode 16 .

The circuit board 15 is an electrode provided on the outside of the keytop 10 in a plan view, and detects the capacitance located between the operation part (for example, a human finger) and the dome part 22 and the keytop 10 . A signal transmission unit 45 that transmits a change in capacitance between the circuit board 15 and the wiring of the circuit board 15 (see FIGS. 2B and 2C). A signal related to the change in capacitance is transmitted to, for example, a CPU (not shown) through the wiring. In this embodiment, the circuit board 15 is provided with the same number of the signal transmission units 45 as the number of the key tops 10, that is, three. Further, the signal transmission part 45 is fixed on the circuit board 15 at a position away from the second electrode 16 . The key sheet 20 has an opening 25 covered with the dome portion 22, and also has another through hole 26, which will be described later. The through hole 26 is formed at a position facing the signal transmission portion 45 of the circuit board 15 . A conductor 40 is fixed in the through hole 26 . The conductor 40 is an electrode that is electrically connected to the signal transmission portion 45 and exposed on the surface of the key sheet 20 opposite to the circuit board 15 . The circuit board 15 includes a microcomputer (not shown), and is configured to accept input based on connection between the first electrode 24 and the second electrode 16 and input based on detection of capacitance.

The push button switch 1 includes a conductive film 30 that electrically connects the signal transmission section 45 from between the dome section 22 and the key top 10 . More specifically, the conductive film 30 has one end (portion for detecting capacitance) sandwiched between the head portion 23 and the key top 10 and the other end extending to the signal transmission portion 45 . are placed in Also, the conductive film 30 is electrically connected to the signal transmission section 45 via the conductor 40 . That is, the conductive film 30 is not directly connected to the signal transmission section 45 , but is electrically connected to the signal transmission section 45 by being connected to the conductor 40 .

The conductive film 30 connects both ends of the head portion 23 of the key sheet 20 and the conductor 40 located closer to the circuit board 15 than the head portion 23 with a height difference L (see FIG. 2C). The conductive film 30 is a thin member having both end surfaces parallel to the head portion 23 and the outer peripheral portion 21 of the key sheet 20 and inclined surfaces connecting the both end surfaces. In this embodiment, the conductive film 30 is a member that can be deformed into a substantially S-shape. A "conductive film" may also be referred to as a "conductive layer." The conductive film 30 is elastically deformable as the dome portion 22 is deformed. Other conductive films, which will be described later, are also preferably elastically deformable.

The material of the key sheet 20 is not particularly limited as long as the dome portion 22 is elastically deformable, but is preferably made of a rubber-like elastic body. Examples of rubber-like elastic bodies include thermosetting elastomers such as silicone rubber, urethane rubber, isoprene rubber, ethylene propylene rubber, natural rubber, ethylene propylene diene rubber, nitrile rubber (NBR), and styrene butadiene rubber (SBR); thermoplastic elastomers such as elastomers, esters, styrenes, olefins, butadiene, and fluorine, or composites thereof. The key sheet 20 may be made of synthetic resin or natural resin such as thermoplastic resin and thermosetting resin. The key sheet 20 is not a member capable of detecting capacitance with an operation portion such as a human finger. The key sheet 20 preferably does not contain conductive filler such as carbon or metal.

The conductive film 30 positioned closer to the keytop 10 than the dome portion 22 has the function of detecting the capacitance with an operation portion such as a human finger. Therefore, when an operation site such as a finger of a person approaches the key top 10, the change in capacitance can be detected with higher sensitivity than in the past. The conductive film 30 is preferably made of highly conductive metal (gold, silver, copper, aluminum, tungsten, SUS, iron) or carbon. The conductive film 30 may be composed of a conductive polymer typified by PEDOT-PSS, or an indium tin oxide (ITO). Also, the conductive film 30 may contain a material other than the above metals or carbon. The thickness of the conductive film (including the conductive film described later) is not particularly limited as long as it is smaller than the height difference L between the head portion 23 and the conductor 40, but is preferably 5 to 2000 μm, more preferably 25 to 1000 μm, and further More preferably, it is 25 to 100 μm.

The material of the keytop 10 is not particularly limited, but is preferably made of thermoplastic resin, thermosetting resin, rubber, ceramics, wood, or a composite thereof. Further, the keytop 10 may contain metal as described later. However, at least the top surface of the key top 10 is preferably made of a material other than metal, which is lower in hardness than metal (for example, resin, rubber, or wood), in order to improve the feeling of contact.

FIG. 3A shows a plan view of the key sheet of FIG. 2A. FIG. 3B shows a DD cross-sectional view of the key sheet of FIG. 3A.

The key sheet 20 includes a dome portion 22 and a head portion 23 directly below each of the three key tops 10 in its thickness direction. The inside of the dome portion 22 has a space in which the first electrode 24 can be connected and separated from the second electrode 16 . The key sheet 20 has a through hole 26 outside the outer edge of the dome portion 22 in plan view. In this embodiment, the through hole 26 is formed at a position away from the dome portion 22 toward one side of the key sheet 20 when the key sheet 20 is viewed from above. The through-hole 26 is a hole that penetrates the key sheet 20 in the thickness direction and is closed by inserting the conductor 40 as described above. By inserting the conductor 40 into the through-hole 26, the push button switch 1 can reduce the risk of water entering the circuit board 15 side, thereby becoming a highly waterproof switch.

FIG. 4A shows a plan view of a modification of the key sheet of FIG. 3A. FIG. 4B shows a cross-sectional view of the key sheet of FIG. 4A taken along line EE.

The key sheet 20a is a modification of the key sheet 20 described above, and has a groove 27 recessed inward in the thickness direction of the key sheet 20a between the dome portion 22 and the through hole 26 in a plan view. More specifically, a groove 27 is formed along the path from the outer edge portion of the enlarged diameter portion of the dome portion 22 to the signal transmission portion 45 . At least a portion of the conductive film 30 from the head portion 23 to the through hole 26 is arranged along the groove 27 .

FIG. 5 shows top and side views of a variation of the conductive film of FIG. 2C.

Unlike the conductive film 30 described above, the conductive film 30a according to this modification has a two-layer structure in which two layers are laminated. Specifically, the conductive film 30 a is a laminated film of a conductive layer 31 and an insulating layer 32 . In the push button switch 1 , the conductive film 30 a is arranged with the conductive layer 31 facing the signal transmission section 45 . The conductive layer 31 can be made of the same materials as the candidate materials for the conductive film 30 described above. The insulating layer 32 can be made of the same material as suitable material candidates for the key sheet 20 . The conductive layer 31 can be formed by plating, printing, or the like, for example. Also, the conductive layer 31 is a plate-like member, and may be adhered to the insulating layer 32 via an adhesive, or may be adhered without an intervening layer such as an adhesive. A portion of the conductive layer 31 in contact with the head portion 23 may have an area larger than that of the head portion 23 in plan view.

FIG. 6 shows plan views of each of three variations of the conductive film of FIG. 2C.

The conductive film 30b according to the modified example includes a detection portion 33 that detects a capacitance corresponding to a distance from an operation portion such as a human finger, and an extraction electrode connected to a signal transmission portion 45 on the circuit board 15. 34 is connected by a wiring portion 35. FIG. The wiring portion 35 is formed narrower than the detection portion 33 and the extraction electrode portion 34 in plan view. That is, the conductive film 30b is a member having a dumbbell shape in plan view. Forming the wiring portion 35 narrowly makes it difficult to detect a change in the capacitance even when the operating portion is brought close to the wiring portion 35, and erroneous detection can be prevented. Also, by forming the wiring portion 35 narrow, it is possible to suppress the adverse effect on the click feeling caused by the deformation of the dome portion 22 when the key top 10 is pushed toward the circuit board 15 . The shape of the detection unit 33 in plan view may be a triangle, a quadrangle, a polygon with four or more sides, or an annular shape, in addition to the circle. The conductive film 30b can be preferably formed by, for example, attaching a copper vapor-deposited film or a copper foil laminated film on a PET film, and then cutting the film into a dumbbell shape.

A conductive film (also referred to as a conductive layer) 30c according to another modification is a film in which a dumbbell-shaped conductive layer is formed on one side of an insulating film (also referred to as an insulating layer) 36 . The conductive layer has the same shape as the conductive film 30b described above. The conductive layer is preferably made of a conductive material such as metal or carbon. The conductive layer can be preferably formed by, for example, patterning conductive ink containing carbon or the like on a PET film, which is an example of the insulating film 36, by screen printing. It should be noted that the insulating film 36 can be made of the same material as the suitable material candidates for the key sheet 20 .

A conductive film 30d according to another modification has the same form as the above-described conductive film 30c, but the detection portion 33 is changed to a detection portion 33a. The detection part 33a is a transparent electrode that transmits light in the thickness direction. A conductive polymer and ITO can be mentioned as a constituent material of the detection part 33a. When the conductive film 30d is used, the head portion 23 is provided with a through hole penetrating from the circuit board 15 side to the key top 10 side, a light source is provided at a position directly below the through hole of the circuit board 15, and the key top 10 is arranged in the thickness direction. By using a material that can transmit light, it is possible to form an illuminated push button switch 1 .

FIG. 7 shows a plan view of a modification of the conductive film of FIG.

The conductive film 30e according to the modification has a form in which three sheets of the conductive films 30c described above are prepared, and the adjacent conductive films 30c are joined together by the connecting portion 37 into one sheet. The connecting portion 37 is connected to the insulating film 36 regardless of whether it is separate from the insulating film 36 or integral with the insulating film 36 . Thus, even if a film is formed by integrating the three conductive films 30c, the same effect as the conductive film 30c can be obtained. The conductive layer corresponding to the conductive film 30b can be preferably formed by, for example, patterning conductive ink containing carbon or the like on the insulating film 36 portion of the PET film by screen printing. It should be noted that the lead-out electrode portions 34 may be concentrated in one place.

FIG. 8A shows a plan view of a variation of the conductor of FIG. 2C. FIG. 8B shows a cross-sectional view of the conductor of FIG. 8A taken along line FF.

The conductor 40a according to the modification is not made of a single material such as a metal like the conductor 40, but is a so-called "zebra rubber" in which a conductive rubber 47 and an insulating rubber 46 are laminated between two insulating rubbers 46. connector. In the case of pressure contact connection, it is preferable that the connection partner with the conductive film 30 is a zebra connector using rubber.

FIG. 9 shows a plan view of a modification of the circuit board of FIG. 2A and an enlarged view of the second electrode.

The circuit board 15 a according to the modification includes one second electrode 48 directly below each keytop 10 and one signal transmission section 45 at a position away from the second electrode 48 . The second electrode 48 is an electrode pair in which the electrodes 16a and 16a are separated from each other. More specifically, the second electrode 48 is an electrode pair in which the T-shaped electrode 16a and the U-shaped electrode 16a are arranged close to each other. When the first electrode 24 comes into contact with the electrodes 16a, 16a, electricity is applied between the electrodes 16a, 16a. The second electrode 48 may be a comb-shaped electrode.

FIG. 10 shows a state a in which a human finger approaches one of the key tops of the push button switch, a state b in which the finger is brought into contact with the key top, and a switch input by pushing the key top with the finger to deform the dome portion. A cross-sectional view similar to FIG. 2A shows the state c over time.

State a is a state in which the human finger SF is brought close to the position of the distance T1 from the sensing portion of the conductive film 30, and an input is performed by a change in capacitance. In state b, progressing from state a, the human finger SF is brought into contact with the key top 10, and the finger SF and the sensing portion of the conductive film 30 are brought closer to the position of the distance T2 (<T1), and the capacitance is increased. It is a state in which another input is performed by another change. State c is a state in which another input is performed by pressing the keytop 10 with the finger SF to bring the first electrode 24 and the second electrode 16 into contact with each other. By setting the capacitance at distance T1 and the capacitance at distance T2 as thresholds, respectively, a total of three types of input are possible: two types of capacitive input and one type of push type input. is. If the threshold value of the capacitance is set for either the distance T1 or the distance T2, a total of two types of input are possible: one type of capacitance type input and one type of push type input. be. By setting the threshold value of the capacitance of the distance T1, it is possible to input the finger SF to the key top 10 in a non-contact state.

FIG. 11A shows a cross-sectional view of a modification of the configuration in which the conductive film is connected to the signal transmission section on the circuit board. FIG. 11B shows a cross-sectional view of another modification different from the modification shown in FIG. 11A.

As shown in FIG. 11A , a through hole 49 may be provided in the key sheet 20 , and the conductive film 30 may be connected from the head portion 23 through the through hole 49 to the signal transmission portion 45 on the circuit board 15 . The through hole 49 is a hole penetrating through the key sheet 20 in the thickness direction, and is formed midway between the dome portion 22 and the signal transmission portion 45 . In this case, since the conductor 40 and the through hole 26 described above are not required, the number of constituent members can be reduced. In addition, part of the conductive film 30 extending from the head portion 23 to the signal transmission portion 45 is hidden behind the key sheet 20 (on the side of the circuit board 15). It is possible to reduce false detection of input accompanying.

As shown in FIG. 11B, a ZIF connector 50 may be provided on the circuit board 15 instead of the signal transmission section 45, and the end of the conductive film 30 may be connected to the ZIF connector 50. FIG. The ZIF connector 50 is a type of connector that requires almost no force for insertion, and is an example of a signal transmission section that transmits changes in capacitance to the wiring of the circuit board 15, like the signal transmission section 45 described above. Using the ZIF connector 50 eliminates the through hole 26 .

FIG. 12 shows a cross-sectional view of the push button switch in which the key top of FIG. 2C is changed, as seen in FIG. 2C. 13 shows a plan view and a side view of a conductive film that can be suitably used for the push button switch of FIG. 12. FIG.

The push button switch 1 of FIG. 12 has a two-layered key top 10 having a conductive member 10a on the head portion 23 side and an insulating member 10b outside the conductive member 10a. As shown in FIG. 13, the conductive film 30f has a three-layer structure including an insulating layer 32 and, as the conductive layer 31, a first conductive layer 31a and a second conductive layer 31b with the insulating layer 32 sandwiched therebetween. The insulating layer 32 has a hole 39 penetrating in the thickness direction of the insulating layer 32 in the middle of its length direction. The first conductive layer 31 a and the second conductive layer 31 b are connected through holes 39 . Such a conductive film 30f can be called a through-hole connection type conductive film. The conductive film 30f can conduct electricity from the conductive member 10a to the first conductive layer 31a, from the first conductive layer 31a to the second conductive layer 31b through the hole 39, and further from the second conductive layer 31b to the signal transmission section 45. The first conductive layer 31a and the second conductive layer 31b can be suitably formed by patterning a conductive ink containing carbon or the like on a PET film, which is an example of the insulating layer 32, by screen printing.

In this manner, when the conductive member 10a is formed on the head portion 23 side of the keytop 10 and the conductive member 10a is connected to the first conductive layer 31a of the conductive film 30f, when an operation portion such as a finger approaches the keytop 10, It is possible to further increase the input sensitivity corresponding to changes in the capacitance of .

FIG. 14A shows a plan view of a variation of the conductive film. 14B shows a cross-sectional view of the push button switch with the conductive film of FIG. 14A, which is the same view as FIG. 2A.

A conductive film 30g according to a modification shown in FIG. 14A is a modification of the conductive film 30e in FIG. In the conductive film 30g, an insulating film 36a of the same type as the insulating film 36 is arranged between the insulating films 36 provided with the dumbbell-shaped conductive film 30b. A connecting portion 37 connects between the insulating films 36 and 36a. The conductive film 30g has a form in which a total of five insulating films 36, 36a, 36, 36a, 36 are connected at intermediate positions in the longitudinal direction by connecting portions 37. As shown in FIG. The insulating film 36a also has a ground electrode 60 on at least one side thereof. The ground electrode 60 extends not only from the insulating film 36 a but also to a part of the connection portion 37 . However, the ground electrode 60 is not connected to the dumbbell-shaped conductive film 30b. Whatever form the ground electrode 60 takes, in this embodiment it is formed of a conductive metal mesh. The conductive layer corresponding to the conductive film 30b can be preferably formed by, for example, patterning conductive ink containing carbon or the like on the insulating film 36 portion of the PET film by screen printing.

As shown in FIG. 14B, the conductive film 30g is deformed into a corrugated shape in a cross-sectional view and provided inside the push button switch 1. As shown in FIG. In this embodiment, the key sheet 20 has three (two or more) dome portions 22 . The conductive film 30b is provided between the dome portion 22 and the key top 21, respectively. Also, the conductive film 30g has a ground electrode 60 between three (two or more) conductive films 30b. Three conductive films 30b and a ground electrode 60 are formed on the insulating films 36, 36a. A laminate of the insulating film 36 a and the ground electrode 60 is sandwiched between the first cover 2 and the key sheet 20 . A laminate of insulating film 36 and dumbbell-shaped conductive film 30 b is sandwiched between key top 10 and head portion 23 . By providing the conductive film 30 g, the push button switch 1 can reduce erroneous detection caused by the ground electrode 60 at positions other than the position of the key top 10 . The connecting portion 37 is connected to the insulating films 36, 36a regardless of whether it is separate from or integrated with the insulating films 36, 36a. Similar to the conductive film 30e, the lead-out electrode portions 34 may be concentrated in one place.

FIG. 15A shows a plan view and a cross-sectional view along line GG of a modification of the conductive film. FIG. 15B shows a plan view and a cross-sectional view taken along the line HH of the conductive film of FIG. 15A folded in two.

The conductive film 62 according to the modification includes a thin rectangular plane insulating layer 63 and a similarly thin rectangular plane insulating layer 64 that can be folded. In this embodiment, insulating layer 64 is smaller than insulating layer 63 . Insulating layer 64 has a portion of conductive layer 66 therein. The insulating layer 63 includes therein a conductive layer 65 and another portion of the conductive layer 66 other than the above-mentioned part, in a non-contact state. The conductive layer 65 is composed of a thin, substantially circular conductive film 30h capable of detecting a change in capacitance when an operation site such as a finger approaches the keytop 10, and an elongated conductive film having a width smaller than the diameter of the conductive film 30h. 30g. The conductive layer 66 comprises a ground electrode 30i (an example of a conductive film) and an elongated conductive film 30j having a width smaller than the diameter of the ground electrode 30i. A portion of conductive layer 66 includes ground electrode 30i and a portion of conductive film 30j extending from ground electrode 30i.

The conductive film 30 h corresponds to a detection section capable of detecting a change in capacitance when an operation site such as a finger is brought close to the key top 10 . The ground electrode 30i is provided on the insulating layer 64 so as to face the conductive film 30h when the insulating layers 63 and 64 are folded. In this embodiment, the conductive film 30h and the ground electrode 30i are formed in circular shapes of the same size in plan view. When the insulating layer 63 and the insulating layer 64 are folded, the conductive film 30h and the ground electrode 30i almost completely overlap in plan view.

Materials for the insulating layers 63 and 64 are preferably selected from the same options as for the key sheet 20 . More preferably, the material of the insulating layers 63 and 64 is rubber (including foamed rubber, sponge, etc.) that is highly elastically deformable, and more preferably silicone rubber. When the insulating layers 63 and 64 of the conductive film 62 are folded, the insulating layers 63 and 64 overlap between the conductive film 30h and the ground electrode 30i to form an elastic layer having a thickness t. The elastic layer having the thickness t is compressed to reduce the thickness t when an operation portion such as a finger is pushed from the top surface of the key top 10 toward the conductive film 62 . Such a change in thickness of the elastic layers 63, 64 causes a change in capacitance, allowing another input. Note that the ground electrode 30i may be a detection unit capable of detecting a change in capacitance due to an operation portion such as a finger coming closer to the keytop 10, as with the conductive film 30h. Also, the ground electrode 30i and the conductive film 30h may be turned upside down in FIG. 15B. The conductive layers 65 and 66 can be preferably formed by, for example, patterning conductive ink containing carbon or the like on a PET film, which is an example of the insulating layers 63 and 64, by screen printing.

As described above, the conductive film 62 becomes a laminated film in which the elastic layers of the insulating layers 63 and 64 are sandwiched between the conductive layers 65 and 66 by folding. The conductive film 62 faces the conductive layer 65 toward the signal transmission section 45 . As described above, the conductive film 62 is arranged so that both sides of the elastic layers (insulating layers 63 and 64) that can be elastically deformed by the load and release of the pressing from the keytop 10 are pressed against the conductive layer 66 (more specifically, the ground). It has a structure sandwiched between an electrode 30i) and a conductive layer 65 (more specifically, a conductive film 30h). Therefore, it is possible to change the capacitance by changing the thickness of the elastic layer and execute new input.

FIG. 16A shows side and bottom views of a variation of the conductive film. FIG. 16B shows a cross-sectional view of how the conductive film of FIG. 16A is fixed to the key sheet.

A conductive film 30k according to this modification is a modification of the above-described conductive film 30a (see FIG. 5). The key sheet 20 has an inward recessed portion 71 at the tip of the dome portion 22 (the head portion 23 in this embodiment). The conductive film 30k has an insulating projection 70 that can be fitted into the recess 71 at one end in the length direction. The convex portion 70 is preferably formed on the conductive layer 31 side. The conductive film 30k is fixed to the key sheet 20 by fitting the protrusions 70 into the recesses 71. As shown in FIG. As a result, the conductive film 30k can be attached to the key sheet 20 easily. Furthermore, both 30k and 20 become difficult to separate. Note that the convex portion 70 may be a member having conductivity (for example, conductive rubber) instead of insulation.

(Other embodiments)
As described above, preferred embodiments and modifications of the present invention have been described, but the present invention is not limited to these and can be implemented in various modifications.

For example, the key sheet 20 is an integrated sheet in which an outer peripheral portion 21, a dome portion 22, and a head portion 23 are connected. However, the key sheet 20 may be a sheet in which the outer peripheral portion 21, the dome portion 22, and the head portion 23 are separated and connected to each other. In that case, only the dome portion 22 may be made of an elastically deformable member (for example, rubber), and the outer peripheral portion 21 and the head portion 23 may be made of a material other than rubber.

Although there are three sets of key tops 10 and dome portions 22 in the above embodiment, only one, two, four or more may be provided. Moreover, in the above embodiment, the number of the conductive films 30 and the like is equal to the number of the sets or only one common to the sets. That is, when the number of sets is three, the number of conductive films 30 and the like is either three or one. However, when the number of sets is three, the number of conductive films 30 and the like may be two. In this manner, the conductive film 30 and the like may be provided in common for the plurality of sets, and may be provided for each set. Also, the number of signaling units may not be the same as the number of sets, but may be at least as many as the number of sets.

In the above-described embodiment, the through-hole type conductive film 30f is arranged in the push button switch 1 having the key top 10 having the conductive member 10a on the side in contact with the conductive film 30f side. However, the conductive film 30f may be disposed on the push button switch 1 having the key top 10 without the conductive member 10a.

In addition, the modifications described above are freely combinable, except in cases where they cannot be combined with each other. For example, ZIF connector 50 may be used with other variations.

INDUSTRIAL APPLICABILITY A push button switch according to the present invention can be used as a switch having a capacitance sensing switch function.

DESCRIPTION OF SYMBOLS 1 Pushbutton switch 10 Key top 10a Conductive member 15, 15a Circuit board 16 Second electrode 20, 20a Key sheet 22 Dome portion 23 Head portion 24 First electrode 25 Opening 26 Through hole 27 Groove 30, 30a, 30b, 30c, 30d, 30e , 30f, 30g, 30h, 30j, 30k Conductive film 30i Ground electrode (an example of a conductive film) 31 Conductive layer 31a First conductive layer (an example of a conductive layer) , 31b... second conductive layer (an example of conductive layer), 32... insulating layer, 33, 33a... detector, 36, 36a... insulating film, 39... hole, 40, 40a ... conductor, 45 ... signal transmission part, 48 ... second electrode, 50 ... ZIF connector (an example of signal transmission part), 60 ... ground electrode, 62 ... conductive film, 63, 64... Elastic layer, 65, 66... Conductive layer, 70... Convex part, 71... Concave part.

Claims (12)

a circuit board;
a key sheet having one or more openings opening in one direction of thickness;
a key top;
is arranged in order,
The key sheet includes a dome portion provided on the side opposite to the opening side of the opening portion and expanding in diameter toward the circuit board, and a first electrode provided at a portion inside the dome portion facing the circuit board side. and
The circuit board includes a second electrode inside the opening, which can come into contact with the first electrode by deformation of the dome portion caused by pressing the key top toward the circuit board,
The key top is arranged on the tip side of the dome portion,
The circuit board includes a signal transmission section, which is a portion provided outside the key top in plan view and transmits a change in capacitance to wiring of the circuit board,
A push button switch, comprising: a conductive film electrically connecting a capacitance detection portion positioned between the dome portion and the key top and the signal transmission portion. The key sheet further includes a head portion on the tip side of the dome portion,
2. The push button switch according to claim 1, wherein said conductive film extends from between said head portion and said key top to said signal transmission portion. 3. The method according to claim 1, wherein a groove is formed in a path from an outer edge portion of the enlarged diameter portion of the dome portion to the signal transmission portion, and the conductive film is arranged along the groove. push button switch. further comprising a conductor electrically connected to the signal transmission part and exposed on a surface of the key sheet opposite to the circuit board;
4. The push button switch according to claim 1, wherein the conductive film is electrically connected to the signal transmission section through the conductor. 5. The push button switch according to claim 1, wherein the conductive film is a laminated film of a conductive layer and an insulating layer, and the conductive layer faces the signal transmission section. . The conductive film has a three-layer structure including the insulating layer, and a first conductive layer and a second conductive layer sandwiching the insulating layer as the conductive layers,
The insulating layer has a hole extending through the insulating layer in a thickness direction in the middle of the length direction, and the first conductive layer and the second conductive layer are connected through the hole,
The key top has a conductive member on the side in contact with the conductive film side,
The conductive film can conduct electricity from the conductive member to the first conductive layer, from the first conductive layer to the second conductive layer through the hole, and further from the second conductive layer to the signal transmission section. The push button switch according to claim 5, characterized by: 6. The structure according to claim 5, wherein the conductive film has an elastic layer that can be elastically deformed by the load and release of pressure from the key top, and a structure in which both sides of the elastic layer in the pressing direction are sandwiched between the conductive layers. A push button switch as described. 8. The conductive film according to any one of claims 1 to 7, wherein the conductive film is formed to have a narrower width between the dome portion side and the signal transmission portion side than on both sides thereof. push button switch. 9. The push button switch according to claim 1, wherein the dome side of the conductive film is translucent in the thickness direction of the film. The key sheet has two or more dome portions,
The conductive film is provided between the dome portion and the key top,
10. The push button switch according to any one of claims 1 to 9, further comprising a ground electrode between two or more of said conductive films. 11. The push button switch according to claim 10, wherein said two or more conductive films and said ground electrode are formed on an insulating film. The key sheet has an inward recessed portion on the tip side of the dome portion,
The conductive film has a convex portion that can be fitted into the concave portion at one end in its length direction,
The push button switch according to any one of claims 1 to 11, wherein the conductive film is fixed to the key sheet by fitting the convex portion into the concave portion.

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