JP2000275114A - Sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make flexible a sensitive surface and to achieve improved sensitivity and response by lifting a piezoelectric element where a piezoelectric crystal thin film is formed on one surface or both the surfaces of a flexible substrate by a specific thickness for retention with a supporting member on a reverse side. SOLUTION: In a sensor 1 for sensing the contact pressure or the like of an object, a piezoelectric lamination body 2 where both the surfaces of a piezoelectric element are covered with an electrode film and further an area on it is laminated by a protection film is lifted by a specific thickness ranging from 0.1 to 20 mm on the ground base by a support spacer 3 or a specific elastic body being provided on a reverse side. In the piezoelectric element, a piezoelectric crystal thin film made of a compound oxide containing lead or the like in Perovskite structure is preferably formed by hydrothermal synthesis on a flexible substrate surface that is made of a metal thin film or the like containing a titanium constituent, for example, on the uppermost surface. The piezoelectric element preferably has a piezoelectric constant of 0.1-20 pC/N and a bending stiffness of 0.1×102-0.1×103 N.mm to obtain improved sensor performance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a sensor capable of sensing pressure and strain.

[0002]

2. Description of the Related Art In recent years, the development of pressure sensors and force sensors has progressed, and they are used for various purposes such as consumer electronic devices, home and home electronic devices, security devices, health appliances, automation factories, automobiles, office equipment, and the like. It has been considered and partially used.

For example, a sensor that senses the contact pressure of an object is a robot capable of performing force control such as deburring, grinding work, and assembling work, and a bed slippage phenomenon caused by contact between a body surface of a sick person and bedding. It is used in the design of mats and air mats for prevention and devices for measuring the contact pressure, and in the design of automobile seats and sports shoes. Sensors for detecting fluid / gas pressures are used in flow meters, combustion sensors of automobiles, pressure sensors for controlling the degree of vacuum of a vacuum cleaner, and the like.

As described above, a pressure sensor, a force sensor, and a load sensor that sense subtle pressure, displacement, distortion, and the like are:
Piezoelectric sensors using sintered PZT (lead zirconate titanate), strain gauge sensors, pressure-sensitive conductive rubber sensors,
Examples include a piezoelectric sensor using a piezoelectric element in which a piezoelectric thin film is laminated on a substrate by a hydrothermal synthesis method, a sputtering method, or the like.

[0005]

However, in the above piezoelectric sensor (using sintered PZT), sintered PZT is brittle,
There is a problem that the thickness of a thin film is limited to 50 μm, and it is difficult to form a thinner film. In addition, there is a problem that the manufacturing process is complicated and it takes two weeks to manufacture, which is expensive and not economical. In addition, the above-mentioned strain gauge type sensor has a small output, and therefore has an amplifier, particularly 1000 to 1000.
There is a problem that an amplifier of 0 times must be used, which is also expensive. In addition, the pressure-sensitive conductive rubber sensor
There is a problem that the sensor performance changes due to repeated use. In addition, a piezoelectric sensor using a piezoelectric element obtained by a hydrothermal synthesis method or a sputtering method has a structure in which the thin film piezo is held in a cantilever manner so that the displacement of the thin film piezo is as large as possible under pressure. and has, but the output when the load on the tip portion in a cantilever state such, or a problem that the output was absolutely stable because it does not displace in a given direction can not be obtained, the charge by the impact from different directions to the pressure to be detected originally There is a problem of doing it.

The present invention has been made in view of such circumstances, and has an output level of 10 mV or more which does not require an amplifier even with a low load, has a flexible sensing surface, and has excellent sensitivity and responsiveness to pressure changes. It is another object of the present invention to provide a sensor that is inexpensive and economical, such as a pressure sensor or a force sensor, while maintaining a compact and thin shape.

[0007]

In order to achieve the above object, a sensor according to the present invention comprises a piezoelectric substrate having a piezoelectric crystal thin film formed on one or both surfaces of a flexible substrate, and an electrode attached to the piezoelectric crystal thin film. The element is lifted and held by a thickness of 0.1 to 20 mm by a support member provided on the back surface side of the piezoelectric element.

That is, the sensor according to the present invention uses a piezoelectric element in which a piezoelectric crystal thin film is formed on a flexible substrate, and the back surface on which the piezoelectric element is mounted is 0.1 to 0.1 mm by a support member. Because it is designed to be lifted and held by the thickness of 20 mm, the sensing surface is flexible,
It does not damage the surface of the target article and exhibits excellent sensitivity and responsiveness to pressure changes. Then, the obtained output voltage peak value is stable. It also has the advantage of being thin and bulky, inexpensive and economical.

In the present invention, "the output voltage peak value is stable" means that the output voltage peak value is measured ten times and the standard deviation of the measured value is 0.3 or less. .

In the present invention, the piezoelectric element has a piezoelectric constant of 0.1 to 20 pC / N and a flexural rigidity of 1.0.
A sensor using a material exhibiting a characteristic of × 10 ^{−2 to} 1.0 × 10 ³ N · mm has particularly excellent output performance.

In the present invention, the support member may be
A sensor composed of a base material and a support spacer provided on the base material and partially supporting the back surface of the piezoelectric element has particularly excellent pressure-sensitive response. The support spacer is provided to support the peripheral portion of the back surface of the piezoelectric element at a plurality of locations separated by a predetermined distance, and the support spacer is provided to support the entire peripheral portion of the back surface of the piezoelectric element in an annular shape. Are provided with excellent performance.

Further, in the present invention, the above-mentioned supporting spacer is not used, and instead, an elastic body is stuck on the entire back surface of the piezoelectric element and held up to a predetermined thickness. As in the case of the above, it has excellent performance. Among them, when the elastic body has a storage elastic modulus of 1.0 × 10 ^{5 to} 1.0 × 10 ¹⁰ dyn / cm ² , it is particularly excellent. It has excellent performance.

In the present invention, the sensor using the lead-containing composite oxide thin film as the piezoelectric crystal thin film, and the sensor in which the piezoelectric crystal thin film is formed by hydrothermal synthesis also have particularly excellent performance. I have.

[0014]

Next, an embodiment of the present invention will be described.

FIG. 1 shows an embodiment of the present invention. That is, the sensor 1 has a piezoelectric laminate 2 (see FIG. 1) in which a piezoelectric element is covered on both sides with an electrode film, and further laminated thereon with a protective film.
In this embodiment, the laminated structure and the terminals extending sideways are omitted), and the supporting spacers 3 provided at the four corners on the back surface thereof lift and hold the base material 4 by a predetermined thickness.

The piezoelectric element used in the piezoelectric laminate 2 may be obtained by any method. In particular, the piezoelectric element is formed by forming a piezoelectric crystal thin film on the surface of a flexible substrate by hydrothermal synthesis. Are preferred.

The flexible substrate has flexibility,
Those that can withstand the heating and pressurizing conditions during hydrothermal synthesis are suitable, and usually, metal thin plates, foils, films and the like are used. Examples of the above metals include metals such as stainless steel, iron, aluminum, titanium, and lead, and alloys containing these metals. However, in order to strongly bond the piezoelectric crystal thin film formed on the flexible substrate to the substrate, it is preferable that the outermost surface of the flexible substrate contains a titanium component. Therefore, it is preferable to use a titanium substrate as the flexible substrate or, if the substrate is not made of titanium, to take measures such as depositing or coating a titanium component on the surface.

The thickness of the flexible substrate is 2 to 20.
It is preferable to set the thickness to 0 μm, especially 5 to 150 μm. That is, if the thickness is less than 2 μm, the flexible substrate may be deformed during hydrothermal synthesis when obtaining a piezoelectric crystal thin film by hydrothermal synthesis. Conversely, if the thickness exceeds 200 μm, the surface of the sensor may be deformed. This is because flexibility may be poor, and a large output from the sensor may not be obtained.

The composition of the piezoelectric crystal thin film may be any composition as long as it has piezoelectric characteristics, but it is preferable to set the composition to a composition suitable for obtaining by the above-mentioned hydrothermal synthesis. It is. As such a composition,
A composite oxide having a perovskite (ABO ₃ ) structure is exemplified. And, as the above-mentioned site A, usually, Pb, B
a, Ca, Sr, La and Bi at least one element selected from the group consisting of T
i alone or Zr, Zn, Ni, Mg, Co, W, Nb,
A composite of Ti with at least one element selected from Sb, Ta and Fe can be used. Examples of such a composite oxide include Pb (Zr, Ti) O ₃ , PbTi
O ₃ , BaTiO ₃ , SrTiO ₃ , (Pb, La)
(Zr, Ti) O _{3 and the} like.

In the hydrothermal synthesis, usually, an aqueous solution prepared by adjusting an aqueous solution of a metal salt containing a metal element capable of constituting the above composition to alkaline, and a flexible substrate are charged into an autoclave and heated under pressure. It is done by doing. Thereby, a piezoelectric crystal thin film is formed on the front and back surfaces of the flexible substrate (bimorph type). In order to obtain a unimorph type, one side of the flexible substrate is coated with a heat-resistant and alkali-resistant resist material and hydrothermally synthesized, or a piezoelectric crystal thin film formed on the front and back surfaces of the flexible substrate is used. And scrape off one side.

The thickness of the piezoelectric crystal thin film thus obtained is usually set to 0.5 to 100 μm, preferably 1 to 30 μm. That is, the thickness is 0.5μ
m, it is difficult to obtain a sufficient sensor output.
If the thickness exceeds 0 μm, the flexibility of the sensor surface may be poor even though the flexible substrate is used.

The above-mentioned hydrothermal synthesis is disclosed in Japanese Patent Application Laid-Open No. 4-342.
As disclosed in Japanese Patent Application Laid-Open No. 489/1989, it may be performed in two stages of crystal nucleus generation and crystal growth, or disclosed in JP-A-9-217178 and JP-A-9-27.
As disclosed in Japanese Patent No. 8436, synthesis may be performed in only one step. Further, as disclosed in JP-A-9-278436, the above-mentioned autoclave is
It may be performed while vibrating in the vertical direction. In this case, for example, as shown in FIG. 2, a heating means (not shown)
And heat-resistant container (oil bath or the like) 12 provided with stirring means 11
Inside, the autoclave 10 is vertically movably supported by supporting means 13 and 14, and is 1 Hz or more in the vertical direction, particularly 3 Hz.
It is preferable to perform the hydrothermal synthesis while applying vibration of 50 Hz.

Further, the surface of the flexible substrate-piezoelectric crystal thin film laminate obtained by the above hydrothermal synthesis may be subjected to a sealing treatment (Japanese Patent Application No. 8-277826). The sealing process,
(A) a method of filling a porous portion and a pinhole of a piezoelectric crystal thin film with an insulating material using an insulating material such as a resin or ceramic; and (b) placing the laminate in a high-temperature oxidizing atmosphere and coating with a thin film. A method of forming an insulating oxide film on pinholes that are not covered or have insufficient coating,
Can be performed by any of the methods described above. By this sealing treatment, the performance of the obtained piezoelectric element can be improved.

The insulating material or its precursor used for the above-mentioned sealing treatment may be either organic or inorganic. Examples of the organic material include polyvinyl chloride, polyethylene, polypropylene, polyester, polycarbonate, polyamide, polyimide, epoxy resin, phenol resin, urea resin, acrylic resin, polyacetal, polysulfone, liquid crystal polymer, and PEEK (polyetheretherketone). Is raised. Examples of the inorganic material include a ceramic coating material based on a material such as alumina, zirconia, silica, and titania, and a ceramic precursor such as a metal alkoxide and polysilazane.

After the piezoelectric crystal thin film is formed on both sides (or one side) of the flexible substrate in this manner, for example, as shown in FIG.
Is formed, the piezoelectric element 21 can be obtained. Reference numeral 15 denotes a flexible substrate, and reference numeral 16 denotes a piezoelectric crystal thin film.

The electrode layer 20 is formed of Al, Ni, P
This is performed by depositing or coating a conductive material such as t, Au, Ag, or Cu on the surface of the piezoelectric crystal thin film 16. The method is not particularly limited, and for example, application of a conductive paste, electroless plating, sputtering, chemical vapor deposition, or the like can be used. The thickness of the electrode layer 20 is usually preferably set to 1 μm or less, particularly preferably 0.1 μm or less.

The piezoelectric element 21 thus obtained is
For example, as shown in FIG. 4, a protective film (insulating film) 2 is placed from above and below with an electrode film 22 having an arbitrary pattern formed of a metal material such as copper foil sandwiched therebetween.
3 and the piezoelectric laminate 2 used in the present invention.
(See FIG. 1). It is not necessary to prepare the electrode film 22 separately from the protective film 23, and the electrode pattern may be directly formed on the protective film 23 by a screen printing method, a sputtering method, or the like. In FIG. 4, reference numeral 22a denotes a terminal.
Reference numeral 4 denotes an adhesive layer (or an adhesive layer) for fixing the piezoelectric element 21, the electrode film 22, and the protective film 23.

In the present invention, a support spacer 3 for supporting the piezoelectric laminate 2 and a base material 4 (return to FIG. 1)
May be any material having a certain level of strength, such as resin, thermoplastic elastomer (TPE), rubber, metal, and inorganic material. As the molding method, not only a method of simply adhering the base substrate 4 and the support spacer 3 but also an appropriate method according to the material can be adopted.

For example, when a resin, TPE, or rubber is used, the support spacer 3 and the base substrate 4 can be integrally formed by press molding, transfer molding, injection molding, or the like.

Further, the support spacer 3 can be formed by applying a resist to a portion of the base substrate 4 where the support spacer 3 is to be formed and curing the resist. Alternatively, a laminate in which the base material 4 and the copper foil are laminated is prepared,
By removing unnecessary portions of the copper foil by etching with a solvent or the like, the remaining copper foil can be used as the support spacer 3.

In general, the support member composed of the support spacer 3 and the base material 4 is integrated with the piezoelectric laminate 2 by bonding the upper surface of the support spacer 3 and the lower surface of the piezoelectric laminate 2 with an adhesive. It is performed by joining.

The thickness of the support spacer 3, that is, the height (indicated by T in FIG. 1) at which the piezoelectric laminate 2 is lifted from the base substrate 4 and held must be set to 0.1 to 20 mm. . That is, when T is smaller than 0.1 mm, the effect of lifting and holding the piezoelectric laminate 2 is small,
This is because the pressure measurement range becomes small, and conversely, if T is larger than 20 mm, the shape does not become thin and is not practical.

In the sensor 1 thus obtained, the piezoelectric element 21 is composed of the flexible substrate 15, the piezoelectric crystal thin film 16 formed by hydrothermal synthesis, and the electrode layer 20 (see FIG. 3). Moreover, the piezoelectric laminate 2 including the piezoelectric element 21
However, since it is lifted and held by the thickness of 0.1 to 20 mm by the supporting spacer 3, the sensing surface is flexible and does not damage the surface of the target article, and also exhibits excellent sensitivity and responsiveness to pressure changes. I do. In addition, it has the advantage that the overall shape is very thin, not bulky, and simple and inexpensive and economical.

In the above example, the front and back surfaces of the piezoelectric element 21 are laminated in the order of the electrode film 22 and the protective film 23. However, when the piezoelectric element 21 is repeatedly subjected to stress, the flexible substrate 15 And the piezoelectric crystal thin film 16 may be separated. However,
In the sensor 1 of the present invention, it is not always necessary to perform the lamination with the protective film 23 as described above. Therefore, in the present invention, "providing the support member on the back surface side of the piezoelectric element" means that both the case where the support member is directly joined to the back surface of the piezoelectric element and the case where the support member is joined via the protective film or the like It is used for the purpose including.

Further, in the above example, the piezoelectric element 21 is constituted by a bimorph type, but is not limited thereto, and may be a unimorph type.

The method for forming the piezoelectric element 21 is as follows.
The method is not limited to the hydrothermal synthesis method, and any method may be used. However, in order to form a uniform piezoelectric crystal film of 1 μm or more, Japanese Patent Application Laid-Open Nos. It is optimal to use a hydrothermal synthesis method as disclosed in JP-A-278436. And
Above all, at the time of hydrothermal synthesis, a vertical vibration to the autoclave 10 is applied within a range of 3 to 50 Hz, and a mixed aqueous solution of a metal salt (lead nitrate, zirconium oxychloride, titanium tetrachloride) and an alkali (potassium hydroxide) is used. By setting the respective concentrations in the following manner, a piezoelectric constant of 0.1 to 20 pC / N and a bending rigidity of 1.0 × 10 ^-2 to 1.
It is preferable to obtain the piezoelectric element 21 having a characteristic of 0 × 10 ³ N · mm in order to obtain excellent sensor performance.

[Preferred Concentrations of Metal Salt and Alkali at Hydrothermal Synthesis] Lead nitrate 0.1 to 1.0 mol / l Zirconium oxychloride 0.05 to 2.0 mol / l Titanium tetrachloride 0 to 0.5 mol / l Potassium hydroxide 2.5 to 8.0 mol / l

The above-mentioned piezoelectric constant is determined as follows. That is, first, FIG.
As shown in FIGS. 14A and 14B and FIG.
The piezoelectric element 21 on which 0 'is formed is supported by the fixture 40, and a load is applied to the center (indicated by P) of the cantilevered tip as shown by the arrow in FIG. Then, the displacement of the measurement point Q 1.5 mm inside from the point P is measured by the laser displacement meter, and the output voltage from the piezoelectric crystal thin film on one side is measured by the A / D converter. The measured values (= the ratio between the output voltage peak value and the displacement amount, measured 10 times and calculated by the least squares method) obtained in this manner, and FIG.
It can be calculated by the following equation (1) using the structural factors shown in (b).

[0039]

[Number 1] piezoelectric constant ^{_{(d 31) = 4L 3 CV}} / _{^{[3btEd (L 2 2 -L 1 2}} ) ] ... (1) V: output voltage d: displacement C: The impedance * impedance analyzer, one side of the piezoelectric The impedance of the crystal thin film portion at a frequency of 100 Hz was measured. E: Young's modulus * Calculated from the gradient of stress-strain in the elastic region after measurement according to JIS Z2241. L, b, t, L ₁ , L ₂ : shown in FIGS. 13 (a) and 13 (b).

The bending stiffness can be obtained by the following equation (2) using the measured values and the like.

[0041]

## EQU2 ## Flexural rigidity (D) = Et ³ / [12 (1-υ ² )] (2) E, t: Same as in equation (1)）: Poisson's ratio (= 0.3)

On the other hand, the form of the supporting member for lifting and holding the piezoelectric laminate 2 is not limited to the form shown in FIG. 1, but may be set to various forms. For example, instead of supporting the back surface of the piezoelectric laminate 2 at the four corners with the support spacers 3, two left and right strip-shaped support spacers 3 a are provided on the base material 4 as shown in FIG. The left and right ends of the laminate 2 may be supported.

As shown in FIG. 7, a support spacer 3c may be provided annularly on the entire periphery of the base substrate 4 to support the entire periphery of the piezoelectric laminate 2.

The piezoelectric laminate 2 can be formed into an appropriate shape according to the target articles having various shapes and the sensor installation space, and the shape of the support member can be appropriately changed according to the shape. . For example, as shown in FIG. 8, with respect to the triangular piezoelectric laminate 2 ', the three corners are supported by the support spacer 3d, and the shape of the base material 4 is also triangular. can do. Of course, as shown in FIG. 9, the entire peripheral portion can be supported by the annular spacer 3e.

As shown in FIG. 10, the circular piezoelectric laminate 2 ″ can be supported by an annular spacer 3f.

Further, instead of using the above-described series of support spacers 3 and the like, as shown in FIG.
May be entirely supported by an elastic body 30 made of an elastic material such as rubber, TPE, gel, or foam. In that case, the base material 4 may or may not be present. And
The elastic body 30 preferably follows the deformation of the piezoelectric laminate 2 as much as possible, and for that purpose, the storage elastic modulus (measured by a dynamic viscoelasticity measurement method) is 1.0 × 10 5
It is preferable to use an elastic body of ^{6 to} 1.0 × 10 ¹⁰ dyn / cm ² . However, the thickness must be set to 0.1 to 20 mm, more preferably 0.5 to 20 mm, as in the above-described series of support spacers 3 and the like.

In the present invention, in order to further stabilize the output of the sensor, a convex cover 32 having a convex portion 31 formed in the center of the lower surface as shown in FIG. Can be integrated. In this manner, the sensor 1 (see FIG. 1 and the like) having a structure in which the center portion is formed as a gap by the support spacer 3 or the like or a sensor having a structure in which the whole is supported by the flexible elastic body 30 (see FIG. 11) On the other hand, when a load is applied from above, as shown in FIG. 18, the piezoelectric laminate 2 can be intensively pressed by the protrusions 31, so that the piezoelectric laminate 2 is larger and is not biased. Is displaced.

In the convex cover 32, the convex portion 31
It suffices to contact or adhere to the piezoelectric laminate 2, and the shape may be any shape such as a sphere, a hemisphere, or a rectangular parallelepiped. Also, the dimensions may be any size as long as the piezoelectric laminate 2 can be pressed smoothly when pressed. The convex cover 32 can be manufactured in the same manner as the method of manufacturing a support member including the base material 4 and the support spacer 3.

The above-mentioned convex cover 32 can be used in combination with sensors of various types of support according to the present invention.

Next, examples will be described together with comparative examples.

[0051]

Examples 1 to 10 120 mmol of lead nitrate, 58.3 mmol of zirconium oxychloride and potassium hydroxide 1
360 ml of a solution of 642 mmol in water was placed in a Teflon-lined autoclave vessel. Further, the titanium foil was cut into a predetermined shape, washed and dried, then charged into the above-mentioned autoclave and sealed. Then, by applying a vibration of 30 Hz in the vertical direction at about 150 ° C. for about 48 hours under pressure in an oil bath and performing hydrothermal synthesis treatment, lead zirconate titanate having a predetermined thickness is formed on both surfaces of the titanium foil. A (PZT) crystal layer was formed. Then, by forming a platinum electrode layer having a thickness of 10 nm on the surface of the PZT layer by RF sputtering,
A piezoelectric element was obtained.

Then, the piezoelectric element was sandwiched from above and below by a protective film having an electrode pattern formed of a copper foil, thereby producing a piezoelectric laminate. The thickness of the copper foil is 18 μm, the material of the protective film is polyethylene terephthalate resin (PET), and the thickness is 25 μm. The pressure-sensitive adhesive layer (adhesive layer) formed on the back surface of the protective film is formed of an acrylic polymer, and has a thickness of 5 μm.

On the other hand, the support member shown in FIG. 5 was manufactured as follows. That is, using a polycarbonate resin (PC) as a material, the support member was integrally molded by injection molding. However, the thickness of the support spacer,
The contact area with the piezoelectric laminate and the spacer interval are as shown in Tables 1 and 2 below. And it joined with the said piezoelectric laminated body, and manufactured ten types of sensors of the structure shown in FIG.

[0054]

Comparative Examples 1 and 2 Two types of piezoelectric laminates were produced in accordance with the production methods of Examples 1 to 10 described above. 12
As shown in (1), the end was clamped from above and below by a fixture 40 and fixed to a cantilever. 41 is a piezoelectric laminated body.

[0055]

Comparative Examples 3 and 4 Further, a piezoelectric laminate was obtained in the same manner as in Example 7, except that the thickness of the supporting spacer was set as shown in Table 3 below to provide a sensor having a configuration deviating from the present invention. 2
Kinds were made.

FIG. 1 shows a comparison between these examples and comparative examples.
As shown in FIG. 5, an impact load was applied by dropping a hard sphere 50 having a diameter of 10.0 mm from above by 5 cm toward the center thereof, and the output voltage was measured by an A / D converter (measured value was 10 times). Average). Regarding the sensor characteristics, a sensor having a peak output voltage of 10 mV or more and exhibiting a regular waveform was determined to be good. Further, other criteria (whether or not thinning was achieved, etc.) were also determined, and only when both of them were ○, the overall judgment was ○. The results are shown in Tables 1 to 3 below. The output voltage waveform of the product of Example 7 is shown in FIG.

[0057]

[Table 1]

[0058]

[Table 2]

[0059]

[Table 3]

[0060]

Examples 11 to 20 A support member having the structure shown in FIG. 6 was manufactured and joined to the piezoelectric laminate obtained in the same manner as in Examples 1 to 10. However, the thickness of the support spacer, the contact area with the piezoelectric laminate, and the spacer interval are shown in Tables 4 and 5 below.
As shown in FIG. Then, the output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. The results are shown in Tables 4 and 5 below. The output voltage waveform of the product of Example 17 is shown in FIG.

[0061]

[Table 4]

[0062]

[Table 5]

[0063]

Examples 21 to 26 A support member having the structure shown in FIG. 7 was manufactured and joined to the piezoelectric laminate obtained in the same manner as in Examples 1 to 10. However, the thickness of the support spacer and the contact area with the piezoelectric laminate are as shown in Tables 6 and 7 below. Then, the output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. The results are shown in Tables 6 and 7 below. The output voltage waveform of the product of Example 26 is shown in FIG.

[0064]

[Table 6]

[0065]

[Table 7]

[0066]

Embodiments 27 to 32 A support member having the structure shown in FIG. 8 is produced and joined to a piezoelectric laminate obtained in the same manner as in Embodiments 1 to 10 except that the planar shape is a right isosceles triangle. did. However, the thickness of the support spacer, the contact area with the piezoelectric laminate, and the spacer interval are as shown in Tables 8 and 9 below. Then, the output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. The results are shown in Tables 8 and 9 below. Example 32
The output voltage waveform of the product is shown in FIG.

[0067]

[Table 8]

[0068]

[Table 9]

[0069]

Embodiments 33 to 36 A support member having the structure shown in FIG. 9 was manufactured and joined to the piezoelectric laminate obtained in the same manner as in Embodiments 27 to 32 (Examples 33 and 34). Further, a support member having a configuration shown in FIG. 10 was formed and joined to a piezoelectric laminate having a circular planar shape (Examples 35 and 36). However, the thickness of the support spacer and the contact area with the piezoelectric laminate are as shown in Table 10 below. Then, the output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. The results are shown in Table 10 below. The output voltage waveform of the product of Example 33 is shown in FIG.
FIG. 16E shows the output voltage waveform of the product of Example 35 in FIG.
(F).

[0070]

[Table 10]

[0071]

Embodiments 37 to 40 A support member having the structure shown in FIG. 11 was manufactured and joined to a piezoelectric laminate obtained in the same manner as in Embodiments 1 to 10. However, the material, Young's modulus, and thickness of the support member are as shown in Table 11 below. Then, the output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. These results are shown in Table 11 below.
Are shown together. The output voltage waveform of the product of Example 39 was
As shown in FIG.

[0072]

[Table 11]

[0073]

Embodiments 41 to 43 Piezoelectric laminates were obtained in the same manner as in Embodiments 1 to 10, but the thickness constitutions were different as shown in Table 12 below.
It became a kind of piezoelectric element. Using these, three types of sensors having the same configuration as that of the seventh embodiment were obtained. The output voltage was measured in the same manner as above, and the sensor characteristics and the like were evaluated. The results are shown in Table 12 below. For reference, Examples 6 and 7 are also shown, including the values of the piezoelectric constant and the bending rigidity.

[0074]

[Table 12]

[0075]

Embodiments 44 to 46 As shown in Table 13 below, three types of sensors were manufactured in the same manner as in the above embodiments, and each was fitted with a convex cover 32 shown in FIG. The output voltage was measured in the same manner as described above, and the sensor characteristics and the like were evaluated. The results are shown in Table 13 below. The output voltage waveform of the working example 44 is shown in FIG.

[0076]

[Table 13]

[0077]

As described above, in the sensor of the present invention, the piezoelectric element is composed of a flexible substrate and a piezoelectric crystal thin film, and the piezoelectric element is formed by a special support member for 0.5 to 20 m.
As the sensing surface is lifted and held by the thickness of m, the sensing surface is not only flexible and does not damage the surface of the target article, but also exhibits excellent sensitivity and responsiveness to pressure changes, and a stable output voltage peak of 10 mV or more. The value is obtained. In addition, since the overall shape is very thin, not bulky, and has a simple configuration, it has the advantage of being inexpensive and economical.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method for manufacturing a piezoelectric element used in the above embodiment.

FIG. 3 is an explanatory diagram of a piezoelectric element used in the embodiment.

FIG. 4 is an explanatory diagram of a configuration of a piezoelectric laminate used in the above embodiment.

FIG. 5 is an explanatory diagram of a support member used in the embodiment.

FIG. 6 is an explanatory view of a modification of the support member.

FIG. 7 is an explanatory view of a modified example of the support member.

FIG. 8 is an explanatory view of a modification of the support member.

FIG. 9 is an explanatory view of a modification of the support member.

FIG. 10 is an explanatory view of a modification of the support member.

FIG. 11 is an explanatory view of a modification of the support member.

FIG. 12 is an explanatory view of a support structure of a comparative example.

FIGS. 13A and 13B are explanatory diagrams of a method of measuring an output voltage of a piezoelectric element.

FIG. 14 is an explanatory diagram of a method of measuring an output voltage of a piezoelectric element.

FIG. 15 is an explanatory diagram of a sensor output voltage measuring method.

FIGS. 16A to 16G are diagrams illustrating output voltage waveforms according to the embodiment.

FIG. 17 is an explanatory diagram of a convex cover used in the present invention.

FIG. 18 is an explanatory view showing a state where the convex cover is attached.

FIG. 19 is a diagram showing an output voltage waveform of the embodiment in which the convex cover is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sensor 2 Piezoelectric laminated body 3 Support spacer 4 Base material

Claims (9)

[Claims] 1. A piezoelectric element having a piezoelectric crystal thin film formed on one or both sides of a flexible substrate, and a piezoelectric element having an electrode attached to the piezoelectric crystal thin film is supported by a support member provided on the back side of the piezoelectric element. A sensor lifted and held by a thickness of 1 to 20 mm. 2. The method according to claim 1, wherein the piezoelectric element has a piezoelectric constant of 0.1 to 20.
pC / N, flexural rigidity 1.0 × 10 ^{-2 to} 1.0 × 10 ³ N
The sensor according to claim 1, wherein the sensor has a characteristic of mm. 3. The sensor according to claim 1, wherein the support member includes a base substrate and a support spacer provided on the base substrate and partially supporting a back surface of the piezoelectric element. 4. The sensor according to claim 3, wherein the support spacer is provided to support a peripheral portion of the back surface of the piezoelectric element at a plurality of locations separated by a predetermined interval. 5. The sensor according to claim 3, wherein the support spacer is provided so as to annularly support the entire periphery of the back surface of the piezoelectric element. 6. The piezoelectric device according to claim 1, wherein the support member is formed of an elastic body attached to the entire back surface of the piezoelectric element.
A sensor according to claim 1. 7. The elastic body has a storage elastic modulus of 1.0 × 10.
7. The sensor according to claim 6, wherein the sensor has a density of ^{5 to} 1.0 × 10 ¹⁰ dyn / cm ² . 8. The sensor according to claim 1, wherein the piezoelectric crystal thin film is a composite oxide thin film containing lead. 9. The sensor according to claim 1, wherein the piezoelectric crystal thin film is formed by hydrothermal synthesis.