Input device

An input device includes a thin film substrate on which a fixed electrode is formed, and a movable electrode formed of a conductive material, the fixed electrode including a capacitance detection electrode and a connection section, the movable electrode including a displacement section that is disposed to be opposite to the capacitance detection electrode and deformed by a pressing force, and a stationary section that is connected to the connection section, the input device detecting a change in capacitance that occurs when the displacement section has been pressed. The input device has a reduced thickness, and can be inexpensively produced by reducing the number of parts. Moreover, the input device can be easily incorporated in an electronic instrument.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an input device that is incorporated in an electronic instrument. More specifically, the invention relates to an input device that detects at least one of the pressing direction and the pressing force based on a change in capacitance when an arbitrary position of the input device has been pressed.

2. Description of Related Art

A capacitance force sensor that allows a two-axis or three-axis input operation has been known as an input device that is incorporated in an electronic instrument (see JP-A-2005-38623, for example).

Such a sensor includes a printed circuit board that includes a base (e.g., glass epoxy) and provided with fixed electrodes, a movable electrode that is formed of a conductive rubber and spaced apart from the fixed electrodes to be opposite to the fixed electrodes, and a metal or resin casing that secures the printed circuit board and the movable electrode.

The fixed electrodes include four fan-shaped electrodes that are disposed concentrically with respect to the center of the sensor. Two electrodes disposed along the X-axis are, used as direction Y input detection electrodes, and two electrodes disposed along the Y axis are used as direction Y input detection electrodes. A Z-axis direction input detection electrode is disposed on the inner circumferential side or the outer circumferential side of the four electrodes.

A change in capacitance that occurs when an arbitrary position of the movable electrode has been pressed can be detected using these electrodes.

However, since many parts are required to form the capacitance force sensor, the cost of the capacitance force sensor increases.

It is difficult to reduce the total thickness of the capacitance force sensor since a reduction in thickness of each part (material) is limited. This makes it difficult to incorporate the capacitance force sensor in a thin electronic instrument.

Moreover, the capacitance force sensor has a large two-dimensional area, and may interfere with other parts (e.g., switch). Therefore, the capacitance force sensor has not been widely incorporated in an electronic instrument.

An input device that includes a plurality of fan-shaped electrodes that are disposed concentrically, and detects a change in capacitance that occurs when the electrodes are traced with a finger or the like. (see JP-T-2007-503052, for example).

This device can detect whether the user has traced the detection section clockwise or counterclockwise when the user has circularly traced the detection section with a finger, and has been applied to a volume operation or a scroll operation of a portable audio instrument.

The above input device can detect a simple two-dimensional input operation (e.g., scroll operation), but cannot detect the pressing force due to the detection principle.

SUMMARY OF THE INVENTION

The present invention provides a capacitance change detection input device that has a reduced thickness, and can be inexpensively produced by reducing the number of parts.

The input device should be easily incorporated in an electronic instrument with an improved degree of freedom.

The invention implements a capacitance change detection input device that is inexpensive and has a reduced thickness by forming the input device mainly using a thin resin film substrate on which a fixed electrode is formed, and a movable electrode formed of a conductive material.

More specifically, the input device according to the invention includes a thin film substrate on which a fixed electrode is formed, and a movable electrode formed of a conductive material, the fixed electrode including a capacitance detection electrode and a connection section, the movable electrode including a displacement section that is disposed to be opposite to the capacitance detection electrode and deformed by a pressing force, and a stationary section that is connected to the connection section of the fixed electrode, the input device detecting a change in capacitance that occurs when the displacement section has been pressed.

If the capacitance detection section includes a pressing force detection capacitance detection electrode that is disposed concentrically with respect to the center of the capacitance detection section, the overlapping area of the movable electrode and the fixed electrode in the capacitance detection section changes depending on the pressing force, so that the input/output signal can be changed. The input device can thus be provided with the function of an analog input/output sensor.

A plurality of pressing force detection electrodes may be formed concentrically.

This improves the pressing force detection resolution.

If the capacitance detection section includes a plurality of capacitance detection electrodes for detecting X-axis and Y-axis pressing directions that are disposed in a circumferential direction with respect to the center of the capacitance detection section, a two-direction input/output function based on the crosswise pressing direction of an input button can be implemented, for example.

This means that the detection can be detected based on vector synthesis of two direction components (e.g., an X-axis and a Y-axis that perpendicularly intersects the X-axis), for example.

Therefore, the resolution is improved by increasing the number of electrodes arranged in the circumferential direction.

The features of the capacitance detection section disposed concentrically and circumferentially may be individually employed. An input device that can detect the pressing force and the pressing direction is obtained by combining both features.

The displacement section of the movable electrode may include a plurality of protrusion sections that protrude toward the capacitance detection electrode, the plurality of protrusion sections may have a concentric ring shape with respect in the center of the capacitance detection section, or may be divided in the circumferential direction to have a hemispherical or conical shape, the movable electrode may include a center stationary section, and the displacement section disposed around the center stationary section, and a distance between an end of a protrusion section among the plurality of protrusion sections and the capacitance detections electrode may sequentially increase toward a periphery of the input device.

According to this configuration, the operation feel and the capacitance detection sensitivity of the input device can be optimized.

The input device can be easily mounted on an electronic instrument board by providing a thin adhesive layer on the back surface of the input device. If a double-sided tape that is partially formed of a conductive material is used as the adhesive layer, electrical noise from the electronic instrument board can be blocked.

A hole may be formed at an arbitrary position of the input device in order to provide the input device with an input function that detects the pressing direction and the pressing force without impairing the function of a switch or the like mounted on the electronic instrument board.

The capacitance input device according to the invention can be significantly reduced in thickness, and can reduce the material/production cost.

The input device can be incorporated in an electronic instrument without impairing the production process by providing a thin adhesive layer on the back surface of the input device. This facilitates the mounting process, and reduces the cost of the entire product.

Moreover, the input device can be provided with an input function that detects the pressing direction and the pressing force without impairing the function of a functional component mounted on an electronic instrument board by forming a hole at an arbitrary position of the input device.

DETAILED DESCRIPTION OF THE INVENTION

Exemplary embodiments of the input device according to the invention are described in detail below with reference to the drawings.

Note that the surface of the thin rosin film substrate on which the movable electrode is secured is referred to as “front surface”, and the surface of the thin resin film substrate on which the movable electrode is not secured is referred to as “back surface”.

First Embodiment

FIGS. 1 and 2illustrate an input device100according to a first embodiment of the invention. The input device100includes a movable electrode1formed of a conductive material, a fixed electrode2, and a thin resin film substrate3, the movable electrode1and the fixed electrode2being disposed on the thin resin film substrate3.

The movable electrode1shown inFIGS. 1 and 2is formed using a conductive rubber.

The movable electrode1includes a center stationary section11, a displacement section12, and a peripheral stationary section13.

The center stationary section11and the peripheral stationary section13are bonded to the thin resin film substrate3using an adhesive that has almost no thickness after being cured.

Part of the peripheral stationary section13comes in contact with a connection section23that is part of the fixed electrode2formed on the thin resin film substrate3.

An adhesive must not adhere to the connection section23so that the movable electrode1and the connection section23are reliably connected electrically.

The displacement section12includes a capacitance detection protrusion section121-1and a capacitance detection protrusion section121-2. The displacement section12is easily deformed when an arbitrary position of the movable electrode1has been pressed.

The capacitance detection protrusion section121-1is disposed to face a capacitance detection electrode211, and the capacitance detection protrusion section121-2is disposed to face capacitance detection electrodes212-1to212-4.

The movable electrode1having the above configuration can be produced so that the center stationary section11having the maximum thickness has a thickness of about 0.3 to 1 mm.

The fixed electrode2includes a plurality of silver electrodes formed on the thin resin film base31by screen printing.

The fixed electrode2includes a capacitance detection section21, a lead wire section22, and the connection section23that is electrically connected to the movable electrode1.

A plurality of capacitance detection sections21are formed concentrically.

The capacitance detection electrodes212-1to212-4are disposed around the capacitance detection electrode211at a given interval in the circumferential direction. The capacitance detection electrodes212-1to212-4detect a pressing direction (X-axis direction, Y-axis direction, and synthesized vector).

The capacitance detection electrodes212-1to212-4are connected to electrodes of the lead wire section22.

The lead wire section22is electrically connected to a substrate mounted with the input device.

The capacitance detection sections212,212-1to212-4and the lead wire section22are formed and connected on the back surface of the thin resin film base31. The connection section23is formed on the front surface of the thin resin film base31that opposes the movable electrode1and is connected to the lead wire section22by embedding a conductive material in a hole formed in the thin resin film base31, for example.

The fixed electrode2may be formed using copper deposited by sputtering or the like, or may be formed by patterning an aluminum thin film.

The thin resin film base31functions as an insulating layer for the movable electrode1and the capacitance detection section21, and also functions as a base (support).

It is desirable that the thin resin film base31be as thin as possible in order to improve the detection sensitivity of the input device100. On the other hand, the thin resin filet substrate31must have such a strength that the thin resin film substrate31is maintained flat.

Therefore, the thickness of the thin resin film base31is preferably 25 to 100 μm.

The thin resin film base31is formed using polyimide, polyethylene terephthalate (PET), or the like.

The input device100that includes the movable electrode1, the fixed electrode2, and the thin resin film substrate3can be formed to a very small thickness (minimum thickness: about 0.325 mm).

FIG. 3shows the capacitance detection section21and the connection section23.

A capacitance Ca1is formed by the electrode211of the capacitance detection section21and the protrusion section121-1.

Capacitances Cb1to Cb4are respectively formed by the electrodes212-1to212-4and the protrusion section121-2.

The effects of the input device100having the above configuration are described below.

FIG. 4shows a state in which the input device100is not pressed.

A resin disk4is secured on (bonded to) the input device100.

The outer diameter of the disk4is set to be slightly smaller than the inner diameter of the peripheral stationary section13of the movable electrode1so that the displacement section12can be efficiently moved.

Note that the disk4imitates a button of an electronic instrument mounted with the input device100.

When an arbitrary position of the disk4has been pressed, the movable electrode1is deformed due to a force F (FIG. 5).

The displacement section12of the movable electrode1is crushed, so that the distance from each electrode of the capacitance detection section21and the electrode overlapping area (minimum electrode-to-electrode distance: thin resin film base31) change, and the capacitances Ca1and Cb1to Cb4change.

The capacitances Cb1to Cb4are used to detect the pressing direction, and the capacitance Ca1is used to detect the pressing force. Therefore, output signals representing the pressing direction and the pressing force are obtained from the changes in capacitance.

Since the protrusion sections121-1and121-2protrude toward the thin resin film substrate3, the protrusion sections121-1and121-2function as a cushion when the disk4has been pressed, so that a soft stroke is obtained.

When it is desired to obtain a softer stroke, and increase a change in capacitance, it is possible to use a movable electrode1athat includes protrusion sections121-2ashown inFIG. 6(i.e., the displacement section12is divided).

When using a thin stainless steel sheet as the conductive material for the movable electrode, it is preferable to use a movable electrode1bshown inFIG. 7.

The thickness of the thin stainless steel sheet is preferably about 50 to 150 μm in order to obtain a soft operation feel and excellent durability.

When forming a circuit shown inFIG. 8, and applying a voltage that changes periodically to the capacitances Ca1and Cb1to Cb4, signals Va1and Vb1to Vb4to are obtained depending on the capacitances.

When no load is applied, the signals Va1and Vb1to Vb4have an identical value.

When an arbitrary position of the disk4secured on the input device has been pressed, the capacitances Ca1and Cb1to Cb4change depending on the pressing direction and the pressing force, so that voltage change amounts dVa1and dVb1to dVb4with respect to a no load state are obtained.

The voltage change amounts dVa1and dVb1to dVb4are processed by a central processing unit (CPU), and the pressing direction and the pressing force applied to the input device100are output to the electronic instrument.

Second Embodiment

FIGS. 9 and 10illustrate an input device200according to a second embodiment of the invention. InFIGS. 9 and 10, sections that respectively correspond to the sections shown inFIGS. 1 and 2are indicated by identical symbols.

A plurality of capacitance detection sections21aof a fixed electrode2aare concentrically formed on the front surface of thin film substrate31which opposes a movable electrode1c.

A lead wire section22ais formed on the back surface of the thin resin film substrate31in the same manner as in the input device100.

Electrodes of the capacitance detection sections21aand wires of the lead wire section22aare connected via holes formed in the thin resin film base31.

Pressing direction detection electrodes213-1to213-8are disposed on the innermost side of the capacitance detection section21aat a given interval in the circumferential direction.

Pressing force detection electrodes214-1to214-3dud are disposed at a given interval in the diametrical direction are formed around the pressing direction detection electrodes213-1to213-8.

The input device200includes eight pressing direction detection electrodes, while the input device100includes four pressing direction detection electrodes. The pressing direction angular resolution can be improved by doubling the number of pressing direction detection electrodes.

The input device200includes three pressing force detection electrodes, while the input device100includes one pressing force detection electrode. The pressing force resolution can be improved by tripling the number of pressing force detection electrodes.

A resin tape5that includes a base and an adhesive layer is bonded to the capacitance detection section21aas an insulating layer between the capacitance detection section21aand the movable electrode1c.

The base of the resin tape5is formed of polyimide or PET, and preferably has a thickness of 25 to 50 μm.

The movable electrode1cis formed of a conductive rubber. A center stationary section11aand a peripheral stationary section13aare bonded to a thin resin film substrate3ausing an adhesive that has almost no thickness after being cured.

As shown inFIG. 9, a displacement section12aincludes protrusion sections122-1to122-4. The protrusion sections122-1to122-4are formed so that the distance between the end of the protrusion and the thin resin film substrate3aincreases from the center toward the periphery of the thin resin film substrate3a(i.e., from the protrusion section122-1toward the protrusion section122-4).

If a plurality of protrusion sections are formed in an identical plane, the structure becomes hard, so that the input device does not implement a soft operation feel. On the other hand, it is possible to implement a soft operation feel, and achieve a larger change in capacitance by forming the protrusion sections of the displacement section12aso that the distance from the thin resin film substrate3aincreases toward the periphery of the thin resin film substrate3a.

FIG. 11shows the capacitance detection section21aand the connection section23a.

Capacitances Cc1to Cc8are formed by the electrodes213-1to213-8and the protrusion section122-1.

When an arbitrary position of a disk4athat is smaller to some extent than the inner diameter of the peripheral stationary section13ahas been pressed, the movable electrode1cis deformed due to a force F (seeFIG. 12).

The displacement section12aof the movable electrode1ais crushed, so that the distance and the overlapping area of each electrode of the capacitance detection section21achange, and the capacitances Cc1to Cc8and Cd1to Cd3change.

The capacitances Cc1to Cc8are used to detect the pressing direction, and the capacitances Cd1to Cd3are used to detect the pressing force. Therefore, output signals representing the pressing direction and the pressing force are obtained from the changes in capacitance.

Each protrusion section of the displacement section12ais initially positioned away from the thin resin film substrate3a. Therefore, the protrusion section is softly deformed to come in contact with the thin rosin film substrate3a, so that the capacitances Cc1to Cc8and Cd1to Cd3change while being constrained by the electrode-to-electrode distance.

After each protrusion section of the displacement section12ahas come in contact with the thin resin film substrate3a, the capacitances Cc1to Cc5and Cd1to Cd3change while being constrained by the electrode overlapping area (minimum electrode-to-electrode distance: resin tape5).

In the input device200, the initial distance between the displacement section12aand the thin resin film substrate3acan be optimized based on the desired to detection sensitivity and the desired operation feel.

A softer operation feel is obtained after the movable electrode has come in contact with the thin resin film substrate3aby utilizing a movable electrode1dshown inFIG. 13that includes protrusion sections122a-1to122a-4.

When forming a circuit shown inFIG. 14, and applying a voltage that changes periodically to the capacitances Cc1to Cc8and Cd1to Cd3, signals Vc1to Vc8and Vd1to Vd3are obtained depending on the capacitances.

When no load is applied, the signals Vc1to Vc8have an identical value.

When an arbitrary position of the disk4asecured on the input device200has been pressed, the capacitances Cc1to Cc8and Cd1to Cd3change depending on the pressing direction and the pressing force, so that voltage change amounts dVc1to dVc8and dVd1to dVd3with respect to a no-load state are obtained.

The voltage change amounts dVc1to dVc8and dVd1to dVd3are processed by a CPU, and the pressing direction and the pressing force applied to the input device200are output to the electronic instrument.

Third Embodiment

FIGS. 15 and 16illustrate an input device300according to a Third embodiment of the invention. InFIGS. 11 and 16, sections that respectively correspond to the sections shown inFIGS. 1 and 2are indicated by identical symbols.

The input device300has a structure in which an insulating double-sided tape7is bonded to the back surface of the input device100(i.e., on the side of a substrate6of an electronic instrument on which the input device100is mounted).

InFIG. 16, the input device300is connected to the substrate6of the electronic instrument via a connector8. In this case, since it is unnecessary to perform a high-temperature process (e.g., soldering), the input devise300can be easily and inexpensively mounted on the substrate6.

As shown inFIG. 16, the insulating double-sided tape7used for the input device300includes an insulating base71and an insulating adhesive material72.

It is preferable that the insulating double-sided tape7be as thin as possible so that the input device300is not displaced relative to the substrate6during a pressing operation. The insulating double-sided tape7preferably has a thickness of 50 to 200 μm.

The insulating base71(insulating layer) must prevent a situation in which each electrode of the capacitance detection section21is electrically connected to the wire or electrode on the substrate6even if a high load is applied to the input device300.

Therefore, the thickness of the insulating base71is preferably 25 μm or more. The insulating base71is preferably formed of a material (e.g., PET film) that has been reliably used for electronic instrument applications. The insulating adhesive material72may be formed using a thermoplastic material in order to obtain high adhesion.

A shown inFIG. 15, the insulating double-sided tape7is normally bonded to the input device300over an area larger than the outer diameter of the connection section23.

Note that the above effects can be obtained by applying the third embodiment to the input device200.

Fourth Embodiment

FIGS. 17,18, and19illustrate an input device400according to a fourth embodiment of the invention. InFIGS. 17,18, and19, sections that respectively correspond to the sections shown inFIGS. 1 and 2are indicated by identical symbols.

The input device400has a structure in which a double-sided tape9including a conductive base is bonded to the back surface of the input device100(i.e., on the side of a substrate6of au electronic instrument on which the input device100is mounted).

This makes it unnecessary to perform a high-temperature process (e.g., soldering) when mounting the input device400on the substrate6. Moreover, electrical noise from the wires formed on the substrate6can be blocked by a conductive base94included in the double-sided tape9.

The double-sided tape9includes an insulating adhesive material91, the insulating base92, an adhesive material93, a conductive base94, and an adhesive material95in this order from the input device100.

At least one of the adhesive materials93and95must be a conductive adhesive material so that the conductive base94can be grounded.

As shown inFIG. 18, the adhesive material93is grounded when the adhesive material93is a conductive adhesive material.

In this case, the adhesive material95may be either an insulating adhesive material or a conductive adhesive material.

As shown inFIG. 19, the adhesive material95is connected to a ground electrode on the substrate6when the adhesive material95is a conductive adhesive material.

In this case, the adhesive material93may be either an insulating adhesive material or a conductive adhesive material.

Note that the above effects can be obtained by applying the fourth embodiment to the input device200.

Fifth Embodiment

FIGS. 20 and 21illustrate an input device500according to a fifth embodiment of the invention.

The input device500includes a movable electrode1e, a fixed electrode, and a thin rosin film substrate3b, the movable electrode1eand the fixed electrode being formed of a conductive material, and disposed on the thin resin film substrate3b. Holes50and51having an arbitrary size are formed in the thin resin film substrate3bat arbitrary positions at which a capacitance detection function is not affected.

Therefore, even if a functional component101(e.g., membrane switch) has been provided at an arbitrary position of a board10of an electronic instrument mounted with The input device500, the functions of the input device500can be easily added without affecting the function of the functional component101.

A center stationary section11band a peripheral stationary section13bof the movable electrode1care bonded to the thin resin film substrate3busing an adhesive that has almost no, thickness after being cured.

A hole having the same diameter as that of the hole50is formed in the center area of the thin resin film substrate3b. The hole51that does not interfere with the movable electrode1cis also formed in the thin resin film substrate3b.

The electrodes of the capacitance detection section21bare disposed to avoid the holes50and51and face protrusion sections12bof the movable electrode1e.

The thickness of a thin resin film base31aused for the thin rosin film substrate3bis preferably 25 to 100 μm.

The thin resin film base31ais formed using polyimide, PET, or the like.

The input device508has a structure in which a double-sided tape7ais bonded to the surface of the input device500on the side of the capacitance detection section21b(i.e., on the side of a substrate10of the electronic instrument on which the input device500is mounted) so that the input device500can be easily mounted on the substrate10.

The double-sided tape7amay be the insulating double-sided tape7, or may be the double-sided tape9including a conductive base. Holes having the same diameter as that of the holes50and51formed in the thin resin film substrate3bare formed in the double-sided tape7aat positions corresponding to the holes50and51, so that the operation of the functional component101is not affected.

Sixth Embodiment

FIGS. 22A,22B and22C show a configuration example of a single-axis input device.

A configuration in which both the pressing direction and the pressing force are detected has been described in connection with the first to fifth embodiments. The simplest configuration example according to the invention is described below.

Specifically, the capacitance detection electrode21that detects the pressing force is disposed on the back surface of the thin resin film base31, and the connection section23is disposed on the front surface of the thin resin film substrate31.

The movable electrode1that is formed of a conductive rubber is disposed on the front surface of the thin resin film base31in order to utilize the thin resin film substrate31as an insulating layer.

The movable electrode1includes a conically protruding displacement section12that gradually slopes away from the capacitance detection electrode21toward the periphery of the input device, and a stationary section13that is connected to the connection section (GNU).

According to this configuration, when a pressing force f has been applied to the input device (movable electrode1) using a fingertip or the like, the overlapping area of the displacement section of the movable electrode and the capacitance detection electrode21changes due to the pressing force (seeFIG. 22C). Therefore, the input device can be used as a single-axis analog input device.

As shown inFIGS. 23A and 23R, the simplest pressing direction input device is obtained by disposing pressing direction-detecting capacitance detection electrodes21X1and21X2in the X-axis direction, and disposing pressing direction-detecting capacitance detection electrodes21Y1and21Y2in the Y-axis direction on the back surface of the thin resin film base31, and disposing X-axis direction displacement sections12X1and12X2and Y-axis direction displacement sections12Y1and12Y2on the front surface of the thin resin film substrate31so as to be opposite to the fixed electrode.

A doughnut-shaped operation button4is disposed on the movable electrode1.

Seventh Embodiment

FIGS. 24A and 24Bshow a configuration example of an input device that is configured so that the pressing direction and the pressing force can be detected by a movable electrode that includes a center stationary section11, and one displacement section12that is formed wound the center stationary section11and a ring-shaped concentric protrusion section.

FIG. 24Ais a cross-sectional view showing the movable electrode formed of a conductive rubber, andFIG. 21Bis a plan view showing a fixed electrode disposed to be opposite to the movable electrode1.

The center stationary section11of the movable electrode1corresponds to the center of the capacitance detection section, and includes an approximately concentric gear-shaped electrode Z1, and X-axis direction electrodes X1and X2and Y-axis direction electrodes Y1and Y2that are disposed around the electrode Z1to be alternately positioned between the radial electrodes.

Note that X1a, X2a, Y1a, and Y2aindicate a wiring pattern example.

According to this configuration, a thin pressing direction-pressing force detection input device in which the area of the capacitance section is reduced without decreasing the sensitivity can be obtained.

INDUSTRIAL APPLICABILITY

The input device according to the invention may be applied to an electronic instrument that allows input of at least one of the pressing direction and the pressing force, and is required to have a small thickness.

Although only some embodiments of the invention have been described in detail above, those skilled in the art would readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of the invention. Accordingly, such modifications are intended to be included within the scope of the invention.