WO2015080109A1 - Piezoelectric sensor and portable terminal - Google Patents

Piezoelectric sensor and portable terminal Download PDF

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Publication number
WO2015080109A1
WO2015080109A1 PCT/JP2014/081140 JP2014081140W WO2015080109A1 WO 2015080109 A1 WO2015080109 A1 WO 2015080109A1 JP 2014081140 W JP2014081140 W JP 2014081140W WO 2015080109 A1 WO2015080109 A1 WO 2015080109A1
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WIPO (PCT)
Prior art keywords
piezoelectric
piezoelectric film
glass plate
piezoelectric sensor
plate
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PCT/JP2014/081140
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French (fr)
Japanese (ja)
Inventor
斉藤誠人
遠藤潤
河村秀樹
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株式会社村田製作所
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Publication of WO2015080109A1 publication Critical patent/WO2015080109A1/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01L—MEASURING FORCE, STRESS, TORQUE, WORK, MECHANICAL POWER, MECHANICAL EFFICIENCY, OR FLUID PRESSURE
    • G01L1/00—Measuring force or stress, in general
    • G01L1/16—Measuring force or stress, in general using properties of piezoelectric devices
    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06F—ELECTRIC DIGITAL DATA PROCESSING
    • G06F3/00—Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
    • G06F3/01—Input arrangements or combined input and output arrangements for interaction between user and computer
    • G06F3/03—Arrangements for converting the position or the displacement of a member into a coded form
    • G06F3/041—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
    • G06F3/0414—Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means using force sensing means to determine a position
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H10N30/302—Sensors
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/80—Constructional details
    • H10N30/85—Piezoelectric or electrostrictive active materials
    • H10N30/857—Macromolecular compositions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/07—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base
    • H10N30/072—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies
    • H10N30/073—Forming of piezoelectric or electrostrictive parts or bodies on an electrical element or another base by laminating or bonding of piezoelectric or electrostrictive bodies by fusion of metals or by adhesives
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H10N30/304—Beam type
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/30—Piezoelectric or electrostrictive devices with mechanical input and electrical output, e.g. functioning as generators or sensors
    • H10N30/308—Membrane type

Definitions

  • the present invention relates to a piezoelectric sensor that detects pressure and a portable terminal including the piezoelectric sensor.
  • the piezoelectric sensor is mounted on a multifunctional mobile terminal, for example, and is used to detect a press on the touch panel.
  • a conventional piezoelectric sensor for example, there is a transparent piezoelectric sheet described in Patent Document 1.
  • This transparent piezoelectric sheet includes a piezoelectric film, an adhesive layer, and a flat plate electrode.
  • the flat plate electrode is disposed on the main surface of the piezoelectric film via an adhesive layer.
  • the transparent piezoelectric sheet described in Patent Document 1 since the pressure is relaxed by the adhesive layer, the pressure may not be sufficiently transmitted to the piezoelectric film. In this case, a sufficient voltage is not generated in the piezoelectric film. Moreover, there exists a possibility that the elasticity modulus of an adhesive bond layer may change a lot with use temperature. In this case, the pressure transmitted to the piezoelectric film and the voltage generated in the piezoelectric film vary depending on the operating temperature. As a result, the transparent piezoelectric sheet may not be able to detect the press with high accuracy.
  • An object of the present invention is to provide a piezoelectric sensor capable of accurately detecting a pressure regardless of a change in operating temperature.
  • the piezoelectric sensor of the present invention includes a plate member, a piezoelectric film, and a sticking layer.
  • the plate member is distorted by pressing.
  • the piezoelectric film is attached to the plate member.
  • the sticking layer is disposed between the plate member and the piezoelectric film.
  • the plate member, piezoelectric film, and adhesive layer are arranged in layers.
  • the adhesive layer has an elastic modulus that is less temperature dependent within the use temperature range than outside the use temperature range.
  • the elastic modulus of the adhesive layer affects the sensor output.
  • the temperature dependence of the elastic modulus is small within the operating temperature range, fluctuations in the sensor output due to the operating temperature are suppressed. For this reason, it is possible to detect the press with high accuracy regardless of the change in the use temperature.
  • the elastic modulus is 0.9 MPa to 1.1 MPa at ⁇ 30 ° C. to 60 ° C.
  • the adhesive layer has a substantially constant elastic modulus with a predetermined size in the operating temperature range. For this reason, the distortion of the plate member can be reliably transmitted to the piezoelectric film. Moreover, the fluctuation
  • the adhesive layer is made of rubber, silicone or polyethylene adhesive.
  • the elastic modulus of the adhesive layer can be made almost constant at a predetermined size in the operating temperature range.
  • the piezoelectric sensor of the present invention includes first and second flat plate electrodes.
  • the first flat plate electrode is disposed between the plate member and the piezoelectric film.
  • the second flat plate electrode faces the first flat plate electrode through the piezoelectric film.
  • the attaching layer attaches the piezoelectric film and the first flat plate electrode.
  • the plate member is a glass plate or a stainless plate.
  • the piezoelectric film is formed from a chiral polymer.
  • the chiral polymer is polylactic acid.
  • the polylactic acid is L-type polylactic acid.
  • PVDF polyvinylidene fluoride
  • a change in operating temperature may affect the piezoelectric characteristics of the piezoelectric film.
  • polylactic acid does not have pyroelectricity, it is possible to accurately detect pressing by the piezoelectric film.
  • the portable terminal of the present invention includes the piezoelectric sensor of the present invention.
  • FIG. 1 is a cross-sectional view of the piezoelectric sensor according to the first embodiment, taken along the line AA.
  • 2 is a cross-sectional view of the sensor unit 13 along AA. It is sectional drawing explaining the press detection by the piezoelectric sensor which concerns on 1st Embodiment. It is a graph which shows the output charge amount with respect to the elasticity modulus of the sticking layers 22, 23, and 28. It is a top view of the piezoelectric sensor which concerns on 2nd Embodiment. It is a BB sectional view of a piezoelectric sensor concerning a 2nd embodiment.
  • FIG. 1 is a plan view of the piezoelectric sensor 10.
  • FIG. 2 is a cross-sectional view of the piezoelectric sensor 10 taken along the line AA.
  • the piezoelectric sensor 10 includes a box-like back side housing part 11, a rectangular flat plate-like glass plate 12, a stripe-like sensor part 13, and a circuit part (not shown).
  • casing part 11 is comprised from the frame-shaped side surface and the rectangular bottom face, and has a rectangular-shaped opening part.
  • a rectangular parallelepiped casing 14 having a hollow portion is configured.
  • the sensor unit 13 is attached to the glass plate 12 with an adhesive so as to be disposed inside the housing 14.
  • the sensor unit 13 is disposed at the end of the glass plate 12 in the longitudinal direction in plan view.
  • the longitudinal direction of the sensor unit 13 is parallel to the lateral direction of the glass plate 12.
  • the circuit unit is disposed inside the housing 14 and is electrically connected to the sensor unit 13.
  • the longitudinal direction of the main surface of the housing 14 is referred to as the X direction
  • the short direction of the main surface of the housing 14 is referred to as the Y direction
  • the direction perpendicular to the main surface of the housing 14 is referred to as the Z direction.
  • FIG. 3 is a cross-sectional view of the sensor unit 13 taken along the line AA.
  • the sensor unit 13 includes a piezoelectric film 21, adhesive layers 22 and 23, flat plate electrodes 24 and 25, and base material layers 26 and 27.
  • a plate electrode 24 is disposed on one main surface of the piezoelectric film 21 with a sticking layer 22 interposed therebetween.
  • the adhesive layer 22 has a flat plate electrode 24 attached to one main surface of the piezoelectric film 21.
  • a plate electrode 25 is disposed on the other main surface of the piezoelectric film 21 with a sticking layer 23 interposed therebetween.
  • the affixing layer 23 affixes the plate electrode 25 to the other main surface of the piezoelectric film 21.
  • the plate electrodes 24 and 25 are electrically connected to a circuit unit (not shown).
  • a base material layer 26 is disposed on the main surface of the plate electrode 24 opposite to the piezoelectric film 21 side.
  • a base material layer 27 is disposed on the main surface of the plate electrode 25 opposite to the piezoelectric film 21 side.
  • the sensor unit 13 is disposed on the main surface of the glass plate 12 via the adhesive layer 28 so that the base material layer 26 side faces the glass plate 12. That is, the adhesive layers 22 and 28 are disposed between the glass plate 12 and the piezoelectric film 21. The sticking layer 28 sticks the sensor unit 13 to the glass plate 12.
  • the piezoelectric film 21, the adhesive layers 22 and 23, the flat plate electrodes 24 and 25, the base material layers 26 and 27, and the glass plate 12 are arranged in layers.
  • the glass plate 12 corresponds to the plate member of the present invention.
  • the adhesive layers 22 and 28 correspond to the “adhesive layer” of the present invention.
  • the plate electrode 24 corresponds to the first plate electrode of the present invention.
  • the plate electrode 25 corresponds to the second plate electrode of the present invention.
  • the piezoelectric film 21 is formed from PLLA (L-type polylactic acid).
  • PLLA is a chiral polymer, and the main chain has a helical structure.
  • PLLA is uniaxially stretched and has piezoelectricity when the molecules are oriented.
  • the piezoelectric constant of uniaxially stretched PLLA belongs to a very high class among polymers.
  • PLLA generates piezoelectricity by molecular orientation processing such as stretching, and there is no need to perform poling processing like other polymers such as PVDF and piezoelectric ceramics. That is, the piezoelectricity of PLLA that does not belong to ferroelectrics is not expressed by the polarization of ions like ferroelectrics such as PVDF and PZT, but is derived from a helical structure that is a characteristic structure of molecules. is there. For this reason, the pyroelectricity generated in other ferroelectric piezoelectric materials does not occur in PLLA.
  • the temperature of the piezoelectric film of the piezoelectric sensor is likely to change due to the temperature of the operator's finger or the heat generated by the battery.
  • stable pressure detection can be realized by using PLLA for the piezoelectric film of the piezoelectric sensor.
  • PVDF or the like shows a change in piezoelectric constant over time, and in some cases, the piezoelectric constant may be significantly reduced, but the piezoelectric constant of PLLA is extremely stable over time.
  • the PLLA Stretching direction of PLLA to take three axes, taking uniaxially and biaxially in a direction perpendicular to the three axial directions, the PLLA there is the piezoelectric constant of d 14 (piezoelectric constant shear).
  • the striped piezoelectric film 21 is cut so that the uniaxial direction is the thickness direction and the direction that forms an angle of 45 ° with respect to the triaxial direction (stretching direction) is the longitudinal direction. Thereby, when the piezoelectric film 21 expands and contracts in the longitudinal direction, the piezoelectric film 21 is polarized in the thickness direction.
  • the material of the adhesive layers 22, 23, 28 is an adhesive other than the acrylic adhesive.
  • the material of the adhesive layers 22, 23, 28 is preferably rubber, silicone or polyethylene adhesive.
  • the characteristic of the pressure-sensitive adhesive is that, while the adhesive is changed from a liquid to a solid at the time of bonding, the wet state is always kept stable.
  • the sensor part of this invention may be a type without the adhesive layers 22 and 23 and the base materials 26 and 27. That is, the sensor unit may have a structure in which a plate electrode (a resist may be laminated as a protective layer) is formed on a piezoelectric film without using an adhesive. In that case, the sticking layer 28 should just satisfy
  • the mobile terminal can be thinned.
  • the interval with the peripheral component becomes wide, unnecessary coupling with the peripheral component can be reduced.
  • the plate electrodes 24 and 25 are made of a metal film such as copper foil. By using a hard metal material for the flat plate electrode 24 disposed between the piezoelectric film 21 and the glass plate 12, the strain of the glass plate 12 due to pressing is easily transmitted to the piezoelectric film 21.
  • the material of the base material layers 26 and 27 is a resin such as polyimide.
  • FIG. 4 is a cross-sectional view for explaining detection of pressing (pushing) by the piezoelectric sensor 10.
  • the end portion of the glass plate 12 is fixed to the back side housing portion 11, so that the glass plate 12 bends so as to be convex in the pushed-in direction.
  • the sensor unit 13 attached to the main surface extends in the longitudinal direction (Y direction). Since the piezoelectric film 21 (see FIG. 3) constituting the sensor unit 13 extends in the longitudinal direction, the piezoelectric film 21 is polarized in the thickness direction by the piezoelectric effect as described above.
  • Electric charges are induced in the plate electrodes 24 and 25 by the electric charges generated on both main surfaces of the piezoelectric film 21.
  • the charges induced in the plate electrodes 24 and 25 are absorbed by the circuit unit (not shown).
  • the circuit unit converts this flow of electric current (current) into a voltage. In this way, the pressure applied to the glass plate 12 can be detected as a voltage.
  • FIG. 5 is a graph showing the amount of output charge with respect to the elastic modulus of the adhesive layers 22, 23, and 28.
  • the output charge amount is the amount of charge that flows from the sensor unit 13 to the circuit unit when a predetermined pressure is applied to the piezoelectric sensor 10.
  • the output charge amount when the elastic modulus of the adhesive layer is 10 9 Pa is 100%.
  • the output charge amount is almost constant, and the value is close to 0%.
  • the elastic modulus of the adhesive layer is changed from 10 5 Pa to 10 8 Pa, the output charge amount increases.
  • the elastic modulus of the adhesive layer is changed from 10 6 Pa to 10 7 Pa, the output charge amount changes greatly.
  • the elastic modulus of the adhesive layer is 10 8 Pa to 10 9 Pa, the output charge amount is almost constant, and the value is close to 100%.
  • the lower surface of the glass plate 12 (the side on which the sensor unit 13 is attached) extends and the upper surfaces of the adhesive layers 22 and 28 (the glass plate 12 side) extend.
  • the lower surface (the piezoelectric film 21 side) of the adhesive layers 22 and 28 does not extend much. That is, when the elastic modulus of the adhesive layers 22 and 28 is small, the adhesive layers 22 and 28 relieve the strain on the lower surface of the glass plate 12 (the vertical strain in the Y direction). For this reason, even if the lower surface of the glass plate 12 extends, the piezoelectric film 21 hardly extends.
  • the strain on the lower surface of the glass plate 12 is not sufficiently transmitted to the piezoelectric film 21.
  • the elastic modulus of the adhesive layers 22 and 28 is small, the output charge amount is small.
  • the elastic modulus of the adhesive layers 22 and 28 is large, the distortion of the lower surface of the glass plate 12 is not relieved by the adhesive layers 22 and 28, so that the distortion of the lower surface of the glass plate 12 is transmitted to the piezoelectric film 21 with certainty.
  • the elastic modulus of the adhesive layers 22 and 28 is large, the output charge amount becomes large. That is, the elastic modulus of the adhesive layers 22 and 28 disposed between the glass plate 12 and the piezoelectric film 21 affects the output charge amount and further the sensor output (voltage).
  • the adhesive layers 22, 23, 28 are designed, for example, such that the elastic modulus is greater than 10 5 Pa in the operating temperature range.
  • the operating temperature range is set to, for example, ⁇ 30 ° C. to 60 ° C.
  • the temperature dependence of the elastic modulus is smaller in the use temperature range than in the use temperature range.
  • the adhesive layers 22, 23, 28 are designed such that the change in elastic modulus with respect to the change in use temperature is within ⁇ 10% of the average value of the elastic modulus in the use temperature range. Thereby, the fluctuation
  • the adhesive layers 22, 23, 28 are preferably designed so that the elastic modulus is 0.9 MPa to 1.1 MPa at ⁇ 30 ° C. to 60 ° C.
  • a pressure sensitive adhesive other than an acrylic pressure sensitive adhesive such as rubber, silicone or polyethylene pressure sensitive adhesive is selected as the material of the adhesive layers 22, 23 and 28 satisfying such conditions. It is particularly effective to use such an adhesive for the material of the adhesive layers 22 and 28 disposed between the glass plate 12 and the piezoelectric film 21.
  • the adhesive layers 22, 23, 28 have a predetermined size and a substantially constant elastic modulus in the operating temperature range. Thereby, the distortion of the glass plate 12 due to pressing is reliably transmitted to the piezoelectric film 21 as described above. Moreover, the fluctuation
  • the sensor unit 13 is provided on a part of the glass plate 12, but the present invention is not limited to this form.
  • a plurality of sensor units may be arranged in the X direction, or the sensor units may have substantially the same area as the glass plate in plan view.
  • FIG. 6 is a plan view of the piezoelectric sensor 30.
  • FIG. 7 is a cross-sectional view of the piezoelectric sensor 30 taken along the line BB.
  • the piezoelectric sensor 30 includes a back housing 11, a glass plate 12, a sensor unit 13, spacers 35 a and 35 b, a striped SUS (stainless steel) plate 36, a columnar pusher 37, and a circuit unit (not shown).
  • the SUS plate 36 corresponds to the plate member of the present invention.
  • a housing 14 is composed of the back housing portion 11 and the glass plate 12.
  • the spacers 35 a and 35 b are disposed inside the housing 14.
  • the spacer 35 a is disposed in the vicinity of the first side surface parallel to the X direction among the side surfaces of the housing 14.
  • the spacer 35b is disposed in the vicinity of the second side surface (side surface facing the first side surface) of the housing 14.
  • the spacers 35a and 35b are disposed at a substantially central portion of the housing 14 in the X direction.
  • the SUS plate 36 is disposed inside the housing 14 so that its main surface is parallel to the main surface of the glass plate 12.
  • the SUS plate 36 is disposed at a substantially central portion in the X direction of the housing 14.
  • the longitudinal direction of the SUS plate 36 is parallel to the Y direction. Both ends in the longitudinal direction of the SUS plate 36 are supported by spacers 35a and 35b, respectively. Spaces are formed between the SUS plate 36 and the glass plate 12 and between the SUS plate 36 and the bottom surface of the back-side housing unit 11.
  • the sensor unit 13 is affixed to the main surface of the SUS plate 36 on the glass plate 12 side with an adhesive so that the longitudinal direction is the Y direction.
  • the circuit unit is disposed inside the housing 14 and is electrically connected to the sensor unit 13.
  • the pusher 37 is disposed between the glass plate 12 and the sensor unit 13 and is in contact with the glass plate 12 and the sensor unit 13.
  • the pusher 37 is shorter than the sensor unit 13 in the Y direction.
  • the pusher 37 is disposed at a substantially central portion of the SUS plate 36 in the Y direction.
  • the SUS plate 36 When the glass plate 12 is pushed in, the SUS plate 36 is pushed in via the pusher 37. The SUS plate 36 bends so as to be convex in the pushed-in direction. Since the main surface on the glass plate 12 side of the main surface of the SUS plate 36 contracts, the piezoelectric film 21 (see FIG. 3) attached to the main surface contracts. The charges induced in the plate electrodes 24 and 25 by the piezoelectric effect are absorbed by the circuit unit (not shown). The circuit unit converts this flow of electric current (current) into a voltage. In this way, the pressure applied to the glass plate 12 can be detected as a voltage.
  • the adhesive layers 22, 23, and 28 have a predetermined size and a substantially constant elastic modulus in the operating temperature range. Thereby, the distortion of the SUS plate 36 due to pressing is reliably transmitted to the piezoelectric film 21. Moreover, the fluctuation
  • the piezoelectric sensor of this invention is not limited to this.
  • a panel in which a glass plate, a touch panel and a liquid crystal panel are stacked in layers may be used.
  • the piezoelectric sensor of the present invention can be used for small electronic devices such as smartphones, tablet terminals, and displays for personal computers.

Abstract

This piezoelectric sensor is provided with a glass plate (12), a piezoelectric film (21) and a bonding layer (22). The glass plate (12) warps when pressed down. The piezoelectric film (21) is bonded to the glass plate (12). The bonding layer (22) is arranged between the glass plate (12) and the piezoelectric film (21). The glass plate (12), the piezoelectric film (21) and the bonding layer (22) are arranged in layers. The bonding layer (22) has an elastic modulus that has a lower temperature dependence within the service temperature range than outside the service temperature range.

Description

圧電センサおよび携帯端末Piezoelectric sensor and portable terminal
　本発明は、押圧を検出する圧電センサおよびそれを備える携帯端末に関する。 The present invention relates to a piezoelectric sensor that detects pressure and a portable terminal including the piezoelectric sensor.
　圧電センサは、例えば、多機能携帯端末に搭載され、タッチパネルに対する押圧を検出するために使用される。従来の圧電センサとして、例えば、特許文献１に記載の透明圧電シートがある。この透明圧電シートは、圧電膜、接着剤層および平板電極を備える。平板電極は接着剤層を介して圧電膜の主面に配置されている。この透明圧電シートに押圧をかけると、圧電膜に、押圧に応じた電圧が生じる。平板電極によりこの電圧を検出回路に伝達することで、押圧を検出することができる。 The piezoelectric sensor is mounted on a multifunctional mobile terminal, for example, and is used to detect a press on the touch panel. As a conventional piezoelectric sensor, for example, there is a transparent piezoelectric sheet described in Patent Document 1. This transparent piezoelectric sheet includes a piezoelectric film, an adhesive layer, and a flat plate electrode. The flat plate electrode is disposed on the main surface of the piezoelectric film via an adhesive layer. When the transparent piezoelectric sheet is pressed, a voltage corresponding to the pressure is generated in the piezoelectric film. The pressure can be detected by transmitting this voltage to the detection circuit by the plate electrode.
特開２０１１－２２２６７９号公報JP 2011-222679 A
　特許文献１に記載の透明圧電シートでは、接着剤層で押圧が緩和されるため、押圧が圧電膜に十分に伝わらないおそれがある。この場合、圧電膜に十分な電圧が生じない。また、接着剤層の弾性率が使用温度により大きく変化するおそれがある。この場合、圧電膜に伝わる押圧、さらに、圧電膜に生じる電圧が使用温度により変化する。これらの結果、この透明圧電シートでは、押圧を精度良く検出することができないおそれがある。 In the transparent piezoelectric sheet described in Patent Document 1, since the pressure is relaxed by the adhesive layer, the pressure may not be sufficiently transmitted to the piezoelectric film. In this case, a sufficient voltage is not generated in the piezoelectric film. Moreover, there exists a possibility that the elasticity modulus of an adhesive bond layer may change a lot with use temperature. In this case, the pressure transmitted to the piezoelectric film and the voltage generated in the piezoelectric film vary depending on the operating temperature. As a result, the transparent piezoelectric sheet may not be able to detect the press with high accuracy.
　本発明の目的は、使用温度の変化にかかわらず、押圧を精度良く検出することができる圧電センサを提供することにある。 An object of the present invention is to provide a piezoelectric sensor capable of accurately detecting a pressure regardless of a change in operating temperature.
（１）本発明の圧電センサは、板部材、圧電フィルムおよび貼付層を備える。板部材は押し込みによって歪む。圧電フィルムは板部材に貼付される。貼付層は、板部材と圧電フィルムとの間に配置される。板部材、圧電フィルムおよび貼付層は層状に配置される。貼付層は、使用温度域外より使用温度域内での温度依存性が小さい弾性率を有する。 (1) The piezoelectric sensor of the present invention includes a plate member, a piezoelectric film, and a sticking layer. The plate member is distorted by pressing. The piezoelectric film is attached to the plate member. The sticking layer is disposed between the plate member and the piezoelectric film. The plate member, piezoelectric film, and adhesive layer are arranged in layers. The adhesive layer has an elastic modulus that is less temperature dependent within the use temperature range than outside the use temperature range.
　板部材のひずみは貼付層を介して圧電フィルムに伝わるため、貼付層の弾性率はセンサ出力に影響を与える。この構成では、使用温度域内で弾性率の温度依存性が小さいので、使用温度によるセンサ出力の変動が抑制される。このため、使用温度の変化にかかわらず、押圧を精度良く検出することができる。 Since the strain of the plate member is transmitted to the piezoelectric film through the adhesive layer, the elastic modulus of the adhesive layer affects the sensor output. In this configuration, since the temperature dependence of the elastic modulus is small within the operating temperature range, fluctuations in the sensor output due to the operating temperature are suppressed. For this reason, it is possible to detect the press with high accuracy regardless of the change in the use temperature.
（２）前記弾性率は、－３０℃～６０℃において、０．９ＭＰａ～１．１ＭＰａである。 (2) The elastic modulus is 0.9 MPa to 1.1 MPa at −30 ° C. to 60 ° C.
　この構成では、貼付層は、使用温度域において所定の大きさでほぼ一定の弾性率を有する。このため、板部材のひずみを圧電フィルムに確実に伝えることができる。また、使用温度によるセンサ出力の変動を抑制することができる。 In this configuration, the adhesive layer has a substantially constant elastic modulus with a predetermined size in the operating temperature range. For this reason, the distortion of the plate member can be reliably transmitted to the piezoelectric film. Moreover, the fluctuation | variation of the sensor output by use temperature can be suppressed.
（３）貼付層は、ゴム、シリコーンまたはポリエチレン系粘着剤を材料とする。 (3) The adhesive layer is made of rubber, silicone or polyethylene adhesive.
　この構成では、貼付層の弾性率を、使用温度域において所定の大きさでほぼ一定にすることができる。 In this configuration, the elastic modulus of the adhesive layer can be made almost constant at a predetermined size in the operating temperature range.
（４）本発明の圧電センサは第１および第２の平板電極を備える。第１の平板電極は板部材と圧電フィルムとの間に配置される。第２の平板電極は圧電フィルムを介して第１の平板電極と対向する。貼付層は圧電フィルムと第１の平板電極とを貼付する。 (4) The piezoelectric sensor of the present invention includes first and second flat plate electrodes. The first flat plate electrode is disposed between the plate member and the piezoelectric film. The second flat plate electrode faces the first flat plate electrode through the piezoelectric film. The attaching layer attaches the piezoelectric film and the first flat plate electrode.
　この構成では、圧電センサの具体的態様が示されている。 In this configuration, a specific mode of the piezoelectric sensor is shown.
（５）板部材はガラス板またはステンレス板である。 (5) The plate member is a glass plate or a stainless plate.
　この構成では、板部材の具体的態様が示されている。 In this configuration, a specific aspect of the plate member is shown.
（６）圧電フィルムはキラル高分子から形成される。 (6) The piezoelectric film is formed from a chiral polymer.
（７）キラル高分子はポリ乳酸である。 (7) The chiral polymer is polylactic acid.
（８）ポリ乳酸はＬ型ポリ乳酸である。 (8) The polylactic acid is L-type polylactic acid.
　例えば、圧電フィルムにＰＶＤＦ（ポリフッ化ビニリデン）を用いた場合、使用温度の変化が圧電フィルムの圧電特性に影響を及ぼすおそれがある。しかし、この構成では、ポリ乳酸には焦電性がないので、圧電フィルムによる押圧の検出を精度良く行うことができる。 For example, when PVDF (polyvinylidene fluoride) is used for the piezoelectric film, a change in operating temperature may affect the piezoelectric characteristics of the piezoelectric film. However, in this configuration, since polylactic acid does not have pyroelectricity, it is possible to accurately detect pressing by the piezoelectric film.
（９）本発明の携帯端末は本発明の圧電センサを備える。 (9) The portable terminal of the present invention includes the piezoelectric sensor of the present invention.
　本発明によれば、使用温度の変化にかかわらず、押圧を精度良く検出することができる。 According to the present invention, it is possible to detect a press with high accuracy regardless of a change in operating temperature.
第１の実施形態に係る圧電センサの平面図である。It is a top view of the piezoelectric sensor which concerns on 1st Embodiment. 第１の実施形態に係る圧電センサのＡ－Ａ断面図である。1 is a cross-sectional view of the piezoelectric sensor according to the first embodiment, taken along the line AA. センサ部１３のＡ－Ａ断面図である。2 is a cross-sectional view of the sensor unit 13 along AA. 第１の実施形態に係る圧電センサによる押圧検知を説明する断面図である。It is sectional drawing explaining the press detection by the piezoelectric sensor which concerns on 1st Embodiment. 貼付層２２，２３，２８の弾性率に対する出力電荷量を示すグラフである。It is a graph which shows the output charge amount with respect to the elasticity modulus of the sticking layers 22, 23, and 28. 第２の実施形態に係る圧電センサの平面図である。It is a top view of the piezoelectric sensor which concerns on 2nd Embodiment. 第２の実施形態に係る圧電センサのＢ－Ｂ断面図である。It is a BB sectional view of a piezoelectric sensor concerning a 2nd embodiment.
　《第１の実施形態》
　本発明の第１の実施形態に係る圧電センサ１０について説明する。圧電センサ１０は、例えば、多機能携帯端末で利用される。図１は圧電センサ１０の平面図である。図２は圧電センサ１０のＡ－Ａ断面図である。圧電センサ１０は、箱状の裏側筐体部１１、矩形平板状のガラス板１２、ストライプ状のセンサ部１３および回路部（図示せず）を備える。裏側筐体部１１は、枠状の側面および矩形状の底面から構成され、矩形状の開口部を有する。裏側筐体部１１の開口部を塞ぐようにガラス板１２が裏側筐体部１１に当接することにより、中空部を有する直方体状の筐体１４が構成される。センサ部１３は、筐体１４の内部に配置されるように、ガラス板１２に粘着剤で貼付されている。センサ部１３は、平面視して、ガラス板１２の長手方向の端部に配置されている。センサ部１３の長手方向はガラス板１２の短手方向に平行になっている。回路部は、筐体１４の内部に配置され、センサ部１３に電気的に接続されている。以下では、筐体１４の主面の長手方向をＸ方向と称し、筐体１４の主面の短手方向をＹ方向と称し、筐体１４の主面に垂直な方向をＺ方向と称することがある。 << First Embodiment >>
The piezoelectric sensor 10 according to the first embodiment of the present invention will be described. The piezoelectric sensor 10 is used in, for example, a multifunctional portable terminal. FIG. 1 is a plan view of the piezoelectric sensor 10. FIG. 2 is a cross-sectional view of the piezoelectric sensor 10 taken along the line AA. The piezoelectric sensor 10 includes a box-like back side housing part 11, a rectangular flat plate-like glass plate 12, a stripe-like sensor part 13, and a circuit part (not shown). The back side housing | casing part 11 is comprised from the frame-shaped side surface and the rectangular bottom face, and has a rectangular-shaped opening part. When the glass plate 12 abuts on the back-side casing 11 so as to close the opening of the back-side casing 11, a rectangular parallelepiped casing 14 having a hollow portion is configured. The sensor unit 13 is attached to the glass plate 12 with an adhesive so as to be disposed inside the housing 14. The sensor unit 13 is disposed at the end of the glass plate 12 in the longitudinal direction in plan view. The longitudinal direction of the sensor unit 13 is parallel to the lateral direction of the glass plate 12. The circuit unit is disposed inside the housing 14 and is electrically connected to the sensor unit 13. Hereinafter, the longitudinal direction of the main surface of the housing 14 is referred to as the X direction, the short direction of the main surface of the housing 14 is referred to as the Y direction, and the direction perpendicular to the main surface of the housing 14 is referred to as the Z direction. There is.
　図３はセンサ部１３のＡ－Ａ断面図である。センサ部１３は、圧電フィルム２１、貼付層２２，２３、平板電極２４，２５および基材層２６，２７を備える。圧電フィルム２１の一方の主面には平板電極２４が貼付層２２を介して配置されている。貼付層２２は平板電極２４を圧電フィルム２１の一方の主面に貼付している。圧電フィルム２１の他方の主面には平板電極２５が貼付層２３を介して配置されている。貼付層２３は平板電極２５を圧電フィルム２１の他方の主面に貼付している。平板電極２４，２５は回路部（図示せず）に電気的に接続されている。平板電極２４の主面のうち圧電フィルム２１側と反対側の主面には、基材層２６が配置されている。平板電極２５の主面のうち圧電フィルム２１側と反対側の主面には、基材層２７が配置されている。センサ部１３は、基材層２６側がガラス板１２に向くように、貼付層２８を介してガラス板１２の主面に配置されている。すなわち、貼付層２２，２８はガラス板１２と圧電フィルム２１との間に配置されている。貼付層２８はセンサ部１３をガラス板１２に貼付している。圧電フィルム２１、貼付層２２，２３、平板電極２４，２５、基材層２６，２７およびガラス板１２は層状に配置されている。 FIG. 3 is a cross-sectional view of the sensor unit 13 taken along the line AA. The sensor unit 13 includes a piezoelectric film 21, adhesive layers 22 and 23, flat plate electrodes 24 and 25, and base material layers 26 and 27. A plate electrode 24 is disposed on one main surface of the piezoelectric film 21 with a sticking layer 22 interposed therebetween. The adhesive layer 22 has a flat plate electrode 24 attached to one main surface of the piezoelectric film 21. A plate electrode 25 is disposed on the other main surface of the piezoelectric film 21 with a sticking layer 23 interposed therebetween. The affixing layer 23 affixes the plate electrode 25 to the other main surface of the piezoelectric film 21. The plate electrodes 24 and 25 are electrically connected to a circuit unit (not shown). A base material layer 26 is disposed on the main surface of the plate electrode 24 opposite to the piezoelectric film 21 side. A base material layer 27 is disposed on the main surface of the plate electrode 25 opposite to the piezoelectric film 21 side. The sensor unit 13 is disposed on the main surface of the glass plate 12 via the adhesive layer 28 so that the base material layer 26 side faces the glass plate 12. That is, the adhesive layers 22 and 28 are disposed between the glass plate 12 and the piezoelectric film 21. The sticking layer 28 sticks the sensor unit 13 to the glass plate 12. The piezoelectric film 21, the adhesive layers 22 and 23, the flat plate electrodes 24 and 25, the base material layers 26 and 27, and the glass plate 12 are arranged in layers.
　ガラス板１２は本発明の板部材に相当する。貼付層２２，２８は本発明の「貼付層」に相当する。平板電極２４は本発明の第１の平板電極に相当する。平板電極２５は本発明の第２の平板電極に相当する。 The glass plate 12 corresponds to the plate member of the present invention. The adhesive layers 22 and 28 correspond to the “adhesive layer” of the present invention. The plate electrode 24 corresponds to the first plate electrode of the present invention. The plate electrode 25 corresponds to the second plate electrode of the present invention.
　圧電フィルム２１はＰＬＬＡ（Ｌ型ポリ乳酸）から形成される。ＰＬＬＡは、キラル高分子であり、主鎖が螺旋構造を有する。ＰＬＬＡは、一軸延伸され、分子が配向すると、圧電性を有する。一軸延伸されたＰＬＬＡの圧電定数は、高分子中で非常に高い部類に属する。 The piezoelectric film 21 is formed from PLLA (L-type polylactic acid). PLLA is a chiral polymer, and the main chain has a helical structure. PLLA is uniaxially stretched and has piezoelectricity when the molecules are oriented. The piezoelectric constant of uniaxially stretched PLLA belongs to a very high class among polymers.
　また、ＰＬＬＡは、延伸等による分子の配向処理で圧電性を生じ、ＰＶＤＦ等の他のポリマーや圧電セラミックスのように、ポーリング処理を行う必要がない。すなわち、強誘電体に属さないＰＬＬＡの圧電性は、ＰＶＤＦやＰＺＴ等の強誘電体のようにイオンの分極によって発現するものではなく、分子の特徴的な構造である螺旋構造に由来するものである。このため、ＰＬＬＡには、他の強誘電性の圧電体で生じる焦電性が生じない。例えばスマートフォンなどの小型携帯端末に圧電センサを用いる場合、操作者の指の温度やバッテリーの発熱などによって圧電センサの圧電フィルムの温度が変化しやすい。この場合でも、圧電センサの圧電フィルムにＰＬＬＡを用いることで安定した押圧検知を実現できる。さらに、ＰＶＤＦ等は経時的に圧電定数の変動が見られ、場合によっては圧電定数が著しく低下する場合があるが、ＰＬＬＡの圧電定数は経時的に極めて安定している。 In addition, PLLA generates piezoelectricity by molecular orientation processing such as stretching, and there is no need to perform poling processing like other polymers such as PVDF and piezoelectric ceramics. That is, the piezoelectricity of PLLA that does not belong to ferroelectrics is not expressed by the polarization of ions like ferroelectrics such as PVDF and PZT, but is derived from a helical structure that is a characteristic structure of molecules. is there. For this reason, the pyroelectricity generated in other ferroelectric piezoelectric materials does not occur in PLLA. For example, when a piezoelectric sensor is used in a small portable terminal such as a smartphone, the temperature of the piezoelectric film of the piezoelectric sensor is likely to change due to the temperature of the operator's finger or the heat generated by the battery. Even in this case, stable pressure detection can be realized by using PLLA for the piezoelectric film of the piezoelectric sensor. Further, PVDF or the like shows a change in piezoelectric constant over time, and in some cases, the piezoelectric constant may be significantly reduced, but the piezoelectric constant of PLLA is extremely stable over time.
　ＰＬＬＡの延伸方向に３軸をとり、３軸方向に垂直な方向に１軸および２軸をとると、ＰＬＬＡにはｄ１４の圧電定数（ずりの圧電定数）が存在する。１軸方向が厚み方向となり、３軸方向（延伸方向）に対して４５°の角度をなす方向が長手方向となるように、ストライプ状の圧電フィルム２１が切り出される。これにより、圧電フィルム２１が長手方向に伸縮すると、圧電フィルム２１は厚み方向に分極する。 Stretching direction of PLLA to take three axes, taking uniaxially and biaxially in a direction perpendicular to the three axial directions, the PLLA there is the piezoelectric constant of d 14 (piezoelectric constant shear). The striped piezoelectric film 21 is cut so that the uniaxial direction is the thickness direction and the direction that forms an angle of 45 ° with respect to the triaxial direction (stretching direction) is the longitudinal direction. Thereby, when the piezoelectric film 21 expands and contracts in the longitudinal direction, the piezoelectric film 21 is polarized in the thickness direction.
　貼付層２２，２３，２８の材料はアクリル系粘着剤以外の粘着剤である。特に、貼付層２２，２３，２８の材料は、ゴム、シリコーンまたはポリエチレン系粘着剤であることが好ましい。粘着剤の特徴は、接着剤が接着時に液体から固体になるのに対して、常に濡れた状態を安定して保っていることである。貼付層２２，２３，２８の材料に粘着剤を用いることにより、接着剤に比べて粘着剤の厚みを容易に制御することができる。貼付層２２，２３，２８の詳細については後述する。 The material of the adhesive layers 22, 23, 28 is an adhesive other than the acrylic adhesive. In particular, the material of the adhesive layers 22, 23, 28 is preferably rubber, silicone or polyethylene adhesive. The characteristic of the pressure-sensitive adhesive is that, while the adhesive is changed from a liquid to a solid at the time of bonding, the wet state is always kept stable. By using a pressure-sensitive adhesive as the material of the adhesive layers 22, 23, 28, the thickness of the pressure-sensitive adhesive can be easily controlled as compared with the adhesive. Details of the adhesive layers 22, 23, 28 will be described later.
　なお、本発明のセンサ部は貼付層２２，２３や基材２６，２７が無いタイプでもよい。すなわち、センサ部は、粘着剤を使用することなく圧電フィルム上に平板電極（保護層としてレジストが積層されても良い）を形成した構造でもよい。その場合、貼付層２８が後述の条件を満たしていれば良い。この構造を用いることによって携帯端末の薄型化が可能になる。また周辺部品との間隔が広くなるので、周辺部品との不要結合軽減が可能になる。 In addition, the sensor part of this invention may be a type without the adhesive layers 22 and 23 and the base materials 26 and 27. That is, the sensor unit may have a structure in which a plate electrode (a resist may be laminated as a protective layer) is formed on a piezoelectric film without using an adhesive. In that case, the sticking layer 28 should just satisfy | fill the conditions mentioned later. By using this structure, the mobile terminal can be thinned. In addition, since the interval with the peripheral component becomes wide, unnecessary coupling with the peripheral component can be reduced.
　平板電極２４，２５は銅箔等の金属膜からなる。圧電フィルム２１とガラス板１２との間に配置された平板電極２４に硬い金属材料を用いることにより、押圧によるガラス板１２のひずみが圧電フィルム２１に伝わりやすくなる。基材層２６，２７の材料はポリイミド等の樹脂である。 The plate electrodes 24 and 25 are made of a metal film such as copper foil. By using a hard metal material for the flat plate electrode 24 disposed between the piezoelectric film 21 and the glass plate 12, the strain of the glass plate 12 due to pressing is easily transmitted to the piezoelectric film 21. The material of the base material layers 26 and 27 is a resin such as polyimide.
　図４は、圧電センサ１０による押圧（押し込み）検知を説明する断面図である。ガラス板１２が押し込まれると、ガラス板１２の端部が裏側筐体部１１に固定されているため、ガラス板１２は、押し込まれた方向に凸となるように撓む。ガラス板１２の主面のうち筐体１４の内部側の主面が伸びる（歪む）ため、その主面に貼付されているセンサ部１３は長手方向（Ｙ方向）に伸びる。センサ部１３を構成する圧電フィルム２１（図３参照）が長手方向に伸びるため、上述のように、圧電効果により圧電フィルム２１は厚み方向に分極する。圧電フィルム２１の両主面に発生した電荷により、平板電極２４，２５に電荷が誘起される。平板電極２４，２５に誘起された電荷は、回路部（図示せず）に吸収される。回路部はこの電荷の流れ（電流）を電圧に変換する。このようにして、ガラス板１２にかかる押圧を電圧として検出することができる。 FIG. 4 is a cross-sectional view for explaining detection of pressing (pushing) by the piezoelectric sensor 10. When the glass plate 12 is pushed in, the end portion of the glass plate 12 is fixed to the back side housing portion 11, so that the glass plate 12 bends so as to be convex in the pushed-in direction. Since the main surface on the inner side of the housing 14 of the main surface of the glass plate 12 extends (distorts), the sensor unit 13 attached to the main surface extends in the longitudinal direction (Y direction). Since the piezoelectric film 21 (see FIG. 3) constituting the sensor unit 13 extends in the longitudinal direction, the piezoelectric film 21 is polarized in the thickness direction by the piezoelectric effect as described above. Electric charges are induced in the plate electrodes 24 and 25 by the electric charges generated on both main surfaces of the piezoelectric film 21. The charges induced in the plate electrodes 24 and 25 are absorbed by the circuit unit (not shown). The circuit unit converts this flow of electric current (current) into a voltage. In this way, the pressure applied to the glass plate 12 can be detected as a voltage.
　図５は、貼付層２２，２３，２８の弾性率に対する出力電荷量を示すグラフである。出力電荷量は、圧電センサ１０に所定の押圧をかけたとき、センサ部１３から回路部に流れる電荷量である。図５では、貼付層の弾性率が１０９Ｐａである場合の出力電荷量を１００％としている。 FIG. 5 is a graph showing the amount of output charge with respect to the elastic modulus of the adhesive layers 22, 23, and 28. The output charge amount is the amount of charge that flows from the sensor unit 13 to the circuit unit when a predetermined pressure is applied to the piezoelectric sensor 10. In FIG. 5, the output charge amount when the elastic modulus of the adhesive layer is 10 9 Pa is 100%.
　貼付層の弾性率が１０４Ｐａ～１０５Ｐａである場合、出力電荷量はほぼ一定であり、その値は０％に近い。貼付層の弾性率を１０５Ｐａから１０８Ｐａに変化させると、出力電荷量は増加する。特に、貼付層の弾性率を１０６Ｐａから１０７Ｐａに変化させるとき、出力電荷量は大きく変化している。貼付層の弾性率が１０８Ｐａ～１０９Ｐａである場合、出力電荷量はほぼ一定であり、その値は１００％に近い。 When the elastic modulus of the adhesive layer is 10 4 Pa to 10 5 Pa, the output charge amount is almost constant, and the value is close to 0%. When the elastic modulus of the adhesive layer is changed from 10 5 Pa to 10 8 Pa, the output charge amount increases. In particular, when the elastic modulus of the adhesive layer is changed from 10 6 Pa to 10 7 Pa, the output charge amount changes greatly. When the elastic modulus of the adhesive layer is 10 8 Pa to 10 9 Pa, the output charge amount is almost constant, and the value is close to 100%.
　ガラス板１２（図３参照）が押し込まれると、ガラス板１２の下面（センサ部１３が貼付されている側）が伸びるとともに、貼付層２２，２８の上面（ガラス板１２側）が伸びる。しかし、貼付層２２，２８の弾性率が小さい場合、貼付層２２，２８の下面（圧電フィルム２１側）はあまり伸びない。すなわち、貼付層２２，２８の弾性率が小さい場合、貼付層２２，２８でガラス板１２の下面のひずみ（Ｙ方向の垂直ひずみ）が緩和される。このため、ガラス板１２の下面が伸びても、圧電フィルム２１はほとんど伸びない。すなわち、ガラス板１２の下面のひずみは圧電フィルム２１に十分に伝わらない。この結果、貼付層２２，２８の弾性率が小さい場合、出力電荷量が小さくなる。一方、貼付層２２，２８の弾性率が大きい場合、 貼付層２２，２８でガラス板１２の下面のひずみが緩和されないため、ガラス板１２の下面のひずみは圧電フィルム２１に確実に伝わる。このため、貼付層２２，２８の弾性率が大きい場合、出力電荷量が大きくなる。すなわち、ガラス板１２と圧電フィルム２１との間に配置された貼付層２２，２８の弾性率は、出力電荷量さらにセンサ出力（電圧）に影響を与える。 When the glass plate 12 (see FIG. 3) is pushed in, the lower surface of the glass plate 12 (the side on which the sensor unit 13 is attached) extends and the upper surfaces of the adhesive layers 22 and 28 (the glass plate 12 side) extend. However, when the elastic modulus of the adhesive layers 22 and 28 is small, the lower surface (the piezoelectric film 21 side) of the adhesive layers 22 and 28 does not extend much. That is, when the elastic modulus of the adhesive layers 22 and 28 is small, the adhesive layers 22 and 28 relieve the strain on the lower surface of the glass plate 12 (the vertical strain in the Y direction). For this reason, even if the lower surface of the glass plate 12 extends, the piezoelectric film 21 hardly extends. That is, the strain on the lower surface of the glass plate 12 is not sufficiently transmitted to the piezoelectric film 21. As a result, when the elastic modulus of the adhesive layers 22 and 28 is small, the output charge amount is small. On the other hand, when the elastic modulus of the adhesive layers 22 and 28 is large, the distortion of the lower surface of the glass plate 12 is not relieved by the adhesive layers 22 and 28, so that the distortion of the lower surface of the glass plate 12 is transmitted to the piezoelectric film 21 with certainty. For this reason, when the elastic modulus of the adhesive layers 22 and 28 is large, the output charge amount becomes large. That is, the elastic modulus of the adhesive layers 22 and 28 disposed between the glass plate 12 and the piezoelectric film 21 affects the output charge amount and further the sensor output (voltage).
　図５に示した結果から、貼付層２２，２３，２８は、例えば、その弾性率が使用温度域で１０５Ｐａより大きくなるように設計される。使用温度域は、例えば、－３０℃～６０℃に設定される。これにより、押圧によるガラス板１２のひずみが圧電フィルム２１に確実に伝わる。また、貼付層２２，２３，２８では、使用温度域外より使用温度域内で弾性率の温度依存性が小さい。貼付層２２，２３，２８は、例えば、使用温度の変化に対する弾性率の変化が使用温度域における弾性率の平均値の±１０％以内となるように設計される。これにより、使用温度によるセンサ出力の変動を抑制することができる。貼付層２２，２３，２８は、その弾性率が－３０℃～６０℃において０．９ＭＰａ～１．１ＭＰａとなるように設計されることが好ましい。 From the results shown in FIG. 5, the adhesive layers 22, 23, 28 are designed, for example, such that the elastic modulus is greater than 10 5 Pa in the operating temperature range. The operating temperature range is set to, for example, −30 ° C. to 60 ° C. Thereby, the distortion of the glass plate 12 due to pressing is reliably transmitted to the piezoelectric film 21. Further, in the adhesive layers 22, 23, 28, the temperature dependence of the elastic modulus is smaller in the use temperature range than in the use temperature range. For example, the adhesive layers 22, 23, 28 are designed such that the change in elastic modulus with respect to the change in use temperature is within ± 10% of the average value of the elastic modulus in the use temperature range. Thereby, the fluctuation | variation of the sensor output by use temperature can be suppressed. The adhesive layers 22, 23, 28 are preferably designed so that the elastic modulus is 0.9 MPa to 1.1 MPa at −30 ° C. to 60 ° C.
　このような条件を満たす貼付層２２，２３，２８の材料として、上述のように、ゴム、シリコーンまたはポリエチレン系粘着剤等のアクリル系粘着剤以外の粘着剤が選択される。ガラス板１２と圧電フィルム２１との間に配置された貼付層２２，２８の材料に、このような粘着剤を用いることは特に有効である。 As described above, a pressure sensitive adhesive other than an acrylic pressure sensitive adhesive such as rubber, silicone or polyethylene pressure sensitive adhesive is selected as the material of the adhesive layers 22, 23 and 28 satisfying such conditions. It is particularly effective to use such an adhesive for the material of the adhesive layers 22 and 28 disposed between the glass plate 12 and the piezoelectric film 21.
　第１の実施形態では、貼付層２２，２３，２８は、使用温度域において所定の大きさでほぼ一定の弾性率を有する。これにより、上述のように、押圧によるガラス板１２のひずみが、圧電フィルム２１に確実に伝わる。また、使用温度によるセンサ出力の変動が抑制される。このため、圧電センサ１０において、使用温度の変化にかかわらず、押圧を精度良く検出することができる。 In the first embodiment, the adhesive layers 22, 23, 28 have a predetermined size and a substantially constant elastic modulus in the operating temperature range. Thereby, the distortion of the glass plate 12 due to pressing is reliably transmitted to the piezoelectric film 21 as described above. Moreover, the fluctuation | variation of the sensor output by use temperature is suppressed. For this reason, in the piezoelectric sensor 10, a press can be detected with high precision irrespective of a change in operating temperature.
　なお、第１の実施形態ではガラス板１２の一部にセンサ部１３が設けられるような形になっているが、本発明はこの形態に限るものではない。例えばセンサ部がＸ方向に複数配置されても良いし、また平面視でセンサ部がガラス板とほぼ同じ面積を有しても良い。これらの構造を用いることによって、押圧位置による感度ばらつきを軽減することができる。 In the first embodiment, the sensor unit 13 is provided on a part of the glass plate 12, but the present invention is not limited to this form. For example, a plurality of sensor units may be arranged in the X direction, or the sensor units may have substantially the same area as the glass plate in plan view. By using these structures, it is possible to reduce the sensitivity variation due to the pressed position.
《第２の実施形態》
　本発明の第２の実施形態に係る圧電センサ３０について説明する。図６は圧電センサ３０の平面図である。図７は圧電センサ３０のＢ－Ｂ断面図である。圧電センサ３０は、裏側筐体部１１、ガラス板１２、センサ部１３、スペーサ３５ａ，３５ｂ、ストライプ状のＳＵＳ（ステンレス）板３６、柱状の押し子３７および回路部（図示せず）を備える。ＳＵＳ板３６は本発明の板部材に相当する。 << Second Embodiment >>
A piezoelectric sensor 30 according to a second embodiment of the present invention will be described. FIG. 6 is a plan view of the piezoelectric sensor 30. FIG. 7 is a cross-sectional view of the piezoelectric sensor 30 taken along the line BB. The piezoelectric sensor 30 includes a back housing 11, a glass plate 12, a sensor unit 13, spacers 35 a and 35 b, a striped SUS (stainless steel) plate 36, a columnar pusher 37, and a circuit unit (not shown). The SUS plate 36 corresponds to the plate member of the present invention.
　第１の実施形態と同様に、裏側筐体部１１およびガラス板１２から筐体１４が構成されている。スペーサ３５ａ，３５ｂは筐体１４の内部に配置されている。スペーサ３５ａは筐体１４の側面のうちＸ方向と平行な第１の側面付近に配置されている。スペーサ３５ｂは筐体１４の第２の側面（第１の側面に対向する側面）付近に配置されている。スペーサ３５ａ，３５ｂは筐体１４のＸ方向の略中央部に配置されている。 As in the first embodiment, a housing 14 is composed of the back housing portion 11 and the glass plate 12. The spacers 35 a and 35 b are disposed inside the housing 14. The spacer 35 a is disposed in the vicinity of the first side surface parallel to the X direction among the side surfaces of the housing 14. The spacer 35b is disposed in the vicinity of the second side surface (side surface facing the first side surface) of the housing 14. The spacers 35a and 35b are disposed at a substantially central portion of the housing 14 in the X direction.
　ＳＵＳ板３６は、その主面がガラス板１２の主面と平行になるように、筐体１４の内部に配置されている。ＳＵＳ板３６は筐体１４のＸ方向の略中央部に配置されている。ＳＵＳ板３６の長手方向はＹ方向に平行になっている。ＳＵＳ板３６の長手方向の両端は、それぞれ、スペーサ３５ａ，３５ｂで支持されている。ＳＵＳ板３６とガラス板１２との間およびＳＵＳ板３６と裏側筐体部１１の底面との間にはスペースが形成されている。 The SUS plate 36 is disposed inside the housing 14 so that its main surface is parallel to the main surface of the glass plate 12. The SUS plate 36 is disposed at a substantially central portion in the X direction of the housing 14. The longitudinal direction of the SUS plate 36 is parallel to the Y direction. Both ends in the longitudinal direction of the SUS plate 36 are supported by spacers 35a and 35b, respectively. Spaces are formed between the SUS plate 36 and the glass plate 12 and between the SUS plate 36 and the bottom surface of the back-side housing unit 11.
　センサ部１３は、長手方向がＹ方向になるように、ＳＵＳ板３６の主面のうちガラス板１２側の主面に粘着剤で貼付されている。回路部は、筐体１４の内部に配置され、センサ部１３に電気的に接続されている。 The sensor unit 13 is affixed to the main surface of the SUS plate 36 on the glass plate 12 side with an adhesive so that the longitudinal direction is the Y direction. The circuit unit is disposed inside the housing 14 and is electrically connected to the sensor unit 13.
　押し子３７は、ガラス板１２とセンサ部１３との間に配置され、ガラス板１２およびセンサ部１３に当接している。押し子３７は、Ｙ方向においてセンサ部１３に比べて短くなっている。押し子３７は、Ｙ方向においてＳＵＳ板３６の略中央部に配置されている。 The pusher 37 is disposed between the glass plate 12 and the sensor unit 13 and is in contact with the glass plate 12 and the sensor unit 13. The pusher 37 is shorter than the sensor unit 13 in the Y direction. The pusher 37 is disposed at a substantially central portion of the SUS plate 36 in the Y direction.
　その他の構成は第１の実施形態と同様である。 Other configurations are the same as those in the first embodiment.
　ガラス板１２が押し込まれると、押し子３７を介して、ＳＵＳ板３６が押し込まれる。ＳＵＳ板３６は押し込まれた方向に凸となるように撓む。ＳＵＳ板３６の主面のうちガラス板１２側の主面が縮むため、その主面に貼付されている圧電フィルム２１（図３参照）は縮む。圧電効果により平板電極２４，２５に誘起された電荷は、回路部（図示せず）に吸収される。回路部はこの電荷の流れ（電流）を電圧に変換する。このようにして、ガラス板１２にかかる押圧を電圧として検出することができる。 When the glass plate 12 is pushed in, the SUS plate 36 is pushed in via the pusher 37. The SUS plate 36 bends so as to be convex in the pushed-in direction. Since the main surface on the glass plate 12 side of the main surface of the SUS plate 36 contracts, the piezoelectric film 21 (see FIG. 3) attached to the main surface contracts. The charges induced in the plate electrodes 24 and 25 by the piezoelectric effect are absorbed by the circuit unit (not shown). The circuit unit converts this flow of electric current (current) into a voltage. In this way, the pressure applied to the glass plate 12 can be detected as a voltage.
　第２の実施形態では、第１の実施形態と同様に、貼付層２２，２３，２８は、使用温度域において所定の大きさでほぼ一定の弾性率を有する。これにより、押圧によるＳＵＳ板３６のひずみが、圧電フィルム２１に確実に伝わる。また、使用温度によるセンサ出力の変動が抑制される。このため、圧電センサ３０において、使用温度の変化にかかわらず、押圧を精度良く検出することができる。 In the second embodiment, as in the first embodiment, the adhesive layers 22, 23, and 28 have a predetermined size and a substantially constant elastic modulus in the operating temperature range. Thereby, the distortion of the SUS plate 36 due to pressing is reliably transmitted to the piezoelectric film 21. Moreover, the fluctuation | variation of the sensor output by use temperature is suppressed. For this reason, in the piezoelectric sensor 30, it is possible to accurately detect the press regardless of the change in the use temperature.
　なお、上述の実施形態ではガラス板が押し込まれていたが、本発明の圧電センサはこれに限定されない。ガラス板の代わりに、ガラス板、タッチパネルおよび液晶パネルが層状に重なったパネルを用いてもよい。 In addition, although the glass plate was pushed in in the above-mentioned embodiment, the piezoelectric sensor of this invention is not limited to this. Instead of the glass plate, a panel in which a glass plate, a touch panel and a liquid crystal panel are stacked in layers may be used.
　また、本発明の圧電センサは、スマートフォンやタブレット端末、またパソコン用ディスプレイなどの小型電子機器に用いることができる。 Moreover, the piezoelectric sensor of the present invention can be used for small electronic devices such as smartphones, tablet terminals, and displays for personal computers.
１０，３０…圧電センサ
１１…裏側筐体部
１２…ガラス板（板部材）
１３…センサ部
１４…筐体
２１…圧電フィルム
２２，２３，２８…貼付層
２４…平板電極（第１の平板電極）
２５…平板電極（第２の平板電極）
２６，２７…基材層
３５ａ，３５ｂ…スペーサ
３６…ＳＵＳ板（板部材）
３７…押し子 DESCRIPTION OF SYMBOLS 10, 30 ... Piezoelectric sensor 11 ... Back side housing | casing part 12 ... Glass plate (plate member)
DESCRIPTION OF SYMBOLS 13 ... Sensor part 14 ... Housing | casing 21 ... Piezoelectric film 22,23,28 ... Adhesion layer 24 ... Flat plate electrode (1st flat plate electrode)
25 ... Flat plate electrode (second flat plate electrode)
26, 27 ... base material layers 35a, 35b ... spacer 36 ... SUS plate (plate member)
37 ... Pusher

Claims (9)

  1. 　押し込みによって歪む板部材と、
    　前記板部材に貼付される圧電フィルムと、
    　前記板部材と前記圧電フィルムとの間に配置される貼付層と、を備え、
    　前記板部材、前記圧電フィルムおよび前記貼付層は層状に配置され、
    　前記貼付層は、使用温度域外より使用温度域内での温度依存性が小さい弾性率を有する、圧電センサ。     A plate member that is distorted by pressing, and
    A piezoelectric film attached to the plate member;
    A sticking layer disposed between the plate member and the piezoelectric film,
    The plate member, the piezoelectric film and the adhesive layer are arranged in layers,
    The adhesive layer is a piezoelectric sensor having an elastic modulus that is less temperature-dependent within the use temperature range than outside the use temperature range.
  2. 　前記弾性率は、－３０℃～６０℃において、０．９ＭＰａ～１．１ＭＰａである、請求項１に記載の圧電センサ。 2. The piezoelectric sensor according to claim 1, wherein the elastic modulus is 0.9 MPa to 1.1 MPa at −30 ° C. to 60 ° C.
  3. 　前記貼付層は、ゴム、シリコーンまたはポリエチレン系粘着剤を材料とする、請求項１または２に記載の圧電センサ。 The piezoelectric sensor according to claim 1 or 2, wherein the adhesive layer is made of rubber, silicone or polyethylene adhesive.
  4. 　前記板部材と前記圧電フィルムとの間に配置される第１の平板電極と、
    　前記圧電フィルムを介して前記第１の平板電極と対向する第２の平板電極と、を備え、
    　前記貼付層は、前記圧電フィルムと前記第１の平板電極とを貼付する、請求項１ないし３のいずれか１項に記載の圧電センサ。     A first flat plate electrode disposed between the plate member and the piezoelectric film;
    A second flat plate electrode facing the first flat plate electrode through the piezoelectric film,
    4. The piezoelectric sensor according to claim 1, wherein the adhesive layer attaches the piezoelectric film and the first flat plate electrode. 5.
  5. 　前記板部材はガラス板またはステンレス板である、請求項１ないし４のいずれか１項に記載の圧電センサ。 The piezoelectric sensor according to any one of claims 1 to 4, wherein the plate member is a glass plate or a stainless steel plate.
  6. 　前記圧電フィルムはキラル高分子から形成される、請求項１ないし５のいずれか１項に記載の圧電センサ。 The piezoelectric sensor according to any one of claims 1 to 5, wherein the piezoelectric film is formed of a chiral polymer.
  7. 　前記キラル高分子はポリ乳酸である、請求項６に記載の圧電センサ。 The piezoelectric sensor according to claim 6, wherein the chiral polymer is polylactic acid.
  8. 　前記ポリ乳酸はＬ型ポリ乳酸である、請求項７に記載の圧電センサ。 The piezoelectric sensor according to claim 7, wherein the polylactic acid is L-type polylactic acid.
  9. 　請求項１に記載の圧電センサを備える、携帯端末。 A portable terminal comprising the piezoelectric sensor according to claim 1.
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