TW201543015A - Pressure detection apparatus - Google Patents

Abstract

To improve detection sensitivity of a pressure detection apparatus that has a bimorph, and a glass or other material member as a pressing surface. In a pressure detector (110), a supporting substrate (1) has an input surface (1a) to which pressure is applied, and a rear surface (1b) having end portions thereof supported. A first piezoelectric sheet (3a) is disposed at a center part of the rear surface (1b) of the supporting substrate (1). A second piezoelectric sheet (3b) is disposed to face the first piezoelectric sheet (3a), said second piezoelectric sheet being on the first piezoelectric sheet (3a) side that is the reverse side of the supporting substrate (1). A first detection electrode (4a) is disposed on the first piezoelectric sheet (3a) side that is the reverse side of the second piezoelectric sheet (3b). A second detection electrode (4b) is disposed on the second piezoelectric sheet (3b) side that is the reverse side of the first piezoelectric sheet (3a). An intermediate adhesion layer (8) is disposed between the first piezoelectric sheet (3a) and the second piezoelectric sheet (3b). The elastic modulus of the intermediate adhesive layer (8) is less than 10 MPa.

Description

Pressure detecting device

The present invention relates to a pressure detecting device, and more particularly to a pressure detecting device using a bimorph to which two piezoelectric sheets are adhered.

As a device for detecting the amount of pressing of the touch panel, a pressure sensor using a piezoelectric sheet is known (for example, refer to Patent Document 1). In the touch input device disclosed in Patent Document 1, the pressure sensitive sensors are overlapped in such a manner as to be in close contact with each other on a plane of the flexible touch panel.

Prior technical literature Patent literature

Patent Document 1 Japanese Patent Publication No. 05-61592

As the piezoelectric material used for the piezoelectric sheet, there are lead zirconate titanate (PZT), polyvinylidene fluoride (PVDF), and a polymer thereof. However, such representative piezoelectric materials are difficult to perform correct pressing force detection due to their pyroelectricity.

Therefore, in order to improve this problem, the inventors of the present invention have focused on the so-called use of bonding two piezoelectric sheets in opposite directions of polarization to each other. Bimorph construction. The bimorph structure mainly has a rectangular or circular bimorph composed of two upper and lower piezoelectric elements. Detection electrodes are provided on both sides of the piezoelectric element. The bimorph construction further has a frame-shaped support member mounted around the underside of the bimorph. Further, in order to increase the strength of the piezoelectric element (preventing scratches and preventing breakage), the bimorph structure may have glass or other members as a protective material on the upper surface of the bimorph.

Hereinafter, the mechanism of the pressing force detection by the bimorph structure will be described. When the upper and lower piezoelectric elements are bent by the pressing force acting on the central portion, the stress σ _u and the stress σ _{1 which} are proportional to the pressing force of the upper and lower piezoelectric elements are generated in the respective piezoelectric elements.

In the bimorph structure in which no glass is provided, the stress σ _u is a negative value because it is a compressive stress, and the stress σ ₁ is a positive value because it is a tensile stress. In this case, the potential difference occurring between the detecting electrodes is proportional to the difference between the stress σ _u and the stress σ ₁ .

On the other hand, in the bimorph structure in which the glass is mounted, both the stress σ _u and the stress σ ₁ become tensile stress. In this case, since the stress σ _{1 is} larger than the stress σ _u , a potential difference corresponding to the difference is generated.

The inventors of the present invention have focused on the difference in tensile stress σ _u and tensile stress σ ₁ to reduce the potential difference between the detecting electrodes in the bimorph structure in which the glass is provided as described above (ie, detecting The problem of low sensitivity) has invented a means for solving this problem.

An object of the present invention is to improve detection sensitivity in a pressure detecting device having a bimorph and a glass or other member as a pressing surface.

Hereinafter, a plurality of states will be described as means for solving the problem. This isomorphism can be arbitrarily combined as needed.

A pressure detecting device according to an aspect of the present invention is a pressure detecting device that detects a pressure based on a potential difference between two piezoelectric sheets generated by pressure applied from the outside. The pressure detecting device includes a sheet member, a first piezoelectric sheet, a second piezoelectric sheet, a first detecting electrode, a second detecting electrode, and an elastic body.

The sheet member has a first surface to which pressure is applied and a second surface to which the edge portion is supported.

The first piezoelectric sheet is disposed at a central portion of the second surface of the sheet member.

The second piezoelectric sheet is disposed on the opposite side of the first piezoelectric sheet from the sheet member, and is disposed to face the first piezoelectric sheet.

The first detecting electrode is disposed on the opposite side of the first piezoelectric piece from the second piezoelectric piece.

The second detecting electrode is disposed on the opposite side of the second piezoelectric piece from the first piezoelectric piece.

The elastic body is disposed between the first piezoelectric sheet and the second piezoelectric sheet. The elastic modulus of the elastomer is less than 10 MPa.

In this apparatus, when the central portion of the first surface of the sheet member is pressed, the sheet member is bent while being supported by the other members at the edge portion. As a result, the first piezoelectric piece and the second piezoelectric piece are also bent. At this time, since the elastic modulus of the elastic body disposed between the first piezoelectric sheet and the second piezoelectric sheet is less than 10 MPa, the tensile stress of the second piezoelectric sheet is smaller than the tensile stress of the first piezoelectric sheet. Thereby, in the first test The amount of charge generated by the electrode is larger than the amount of charge generated at the second detecting electrode, and the potential difference between the first detecting electrode and the second detecting electrode becomes sufficiently large. Therefore, the pressure detection sensitivity of the pressure detecting device becomes high.

The elastic modulus of the elastomer may also be 1 MPa or less.

In this device, since the elastic modulus of the elastic body is 1 MPa or less, the potential difference between the first detecting electrode and the second detecting electrode is sufficiently large.

The thickness of the elastomer may also be 5 μm or more.

In this device, since the thickness range is sufficiently wide, the potential difference between the first detecting electrode and the second detecting electrode becomes sufficiently large.

The thickness of the elastomer may also be 25 to 100 μm.

In this device, since the thickness of the elastic body is made large, the potential difference between the first detecting electrode and the second detecting electrode is further increased.

The elastic body may be an adhesive to which the first piezoelectric sheet and the second piezoelectric sheet are adhered.

In this device, the aforementioned effects can be obtained depending on the type of the adhesive.

The pressure detecting device may further include a second sheet member. The second sheet member is disposed on the opposite side of the second piezoelectric sheet from the sheet member, and has a modulus of elasticity of 10 GPa or more.

In this device, since a member having a high elastic modulus is applied as the second sheet member, the potential difference between the first detecting electrode and the second detecting electrode is further increased. As a result, the pressure detection sensitivity of the pressure detecting device is further improved.

The pressure detecting device may further have an adhesive layer. The adhesive layer is disposed between the sheet member and the first piezoelectric sheet and the second piezoelectric sheet. The adhesive layer has an elastic modulus of 10 times or more of the elastic modulus of the elastic body.

In this device, since the elastic modulus of the adhesive layer is made large, the potential difference between the first detecting electrode and the second detecting electrode is further increased. As a result, the pressure detection sensitivity of the pressure detecting device is further improved.

In the pressure detecting device of the present invention, since the elastic modulus of the elastic body disposed between the first piezoelectric sheet and the second piezoelectric sheet is less than 10 MPa, the tensile stress of the second piezoelectric sheet is smaller than that of the first piezoelectric sheet. Tensile stress. Thereby, the potential difference between the first detecting electrode and the second detecting electrode is increased. As a result, the pressure detection sensitivity of the pressure detecting device becomes high.

1‧‧‧Support substrate

1a‧‧‧ input face

1b‧‧‧back

2‧‧‧Adhesive layer

3‧‧‧ Piezo Pieces

3a‧‧‧1st piezoelectric piece

3b‧‧‧2nd piezoelectric piece

4‧‧‧Detection electrode

4a‧‧‧1st detection electrode

4b‧‧‧2nd detection electrode

5‧‧‧Display device

6‧‧‧Shell

6a‧‧‧ recess

6b‧‧‧Support Department

7‧‧‧ Space

8‧‧‧Intermediate adhesive layer

9‧‧‧Adhesive layer

11‧‧‧ resin film

12‧‧‧Adhesive layer

13‧‧‧ resin film

14‧‧‧Adhesive layer

100‧‧‧ Pressure detector

100A‧‧‧ Pressure Detector

100B‧‧‧ Pressure detector

110‧‧‧Electronic machines

110C‧‧‧ touch panel

Σu‧‧‧ tensile stress

Σ1‧‧‧ tensile stress

V ₁ ‧‧‧potential difference

V ₂ ‧‧‧potential difference

Figure 1 is a perspective view of an electronic machine.

Figure 2 is a cross-sectional view taken along line II-II of Figure 1.

Figure 3 is a cross-sectional view of the pressure detector.

Figure 4 is a cross-sectional view of the pressure detector.

Fig. 5 is a cross-sectional view showing a pressure detector (second embodiment).

Fig. 6 is a cross-sectional view showing a pressure detector (third embodiment).

Fig. 7 is a cross-sectional view of a touch panel (fourth embodiment).

Fig. 8 is a developed view of an electrode (fourth embodiment).

[Formation for carrying out the invention]

1. First embodiment

(1) Summary of pressure detector

A pressure detector 100 according to an embodiment of the present invention will be described with reference to Figs. 1 and 2 . Figure 1 is a perspective view of an electronic machine. Figure 2 is a cross-sectional view taken along line II-II of Figure 1.

The pressure detector 100 is a device for measuring the magnitude of the pressing force (load) when pressed by a finger or a pen. In the following description, the front side (upper side in FIG. 2) viewed from the user's direction at the time of use is referred to as the "input side" of the pressure detector 100, and the back side viewed from the user's direction (the lower side of FIG. 2) The side is referred to as the "inside side" of the pressure detector 100.

As shown in FIG. 1, the electronic machine 110 mainly has a housing 6 and a pressure detector 100. The casing 6 has a rectangular frame shape and is made of synthetic resin. The pressure detector 100 is housed in the housing 6.

More specifically, the casing 6 has a recess 6a that opens in a rectangular shape toward the input surface side. The concave portion 6a is formed to have a step, and this step portion becomes the support portion 6b. The support portion 6b is formed in a rectangular frame shape corresponding to the shape of the concave portion 6a. The support portion 6b corresponds to an edge portion of the back surface 1b of the support substrate 1 to be described later, and is a structure for supporting the pressure acting on the support substrate 1. In the recessed portion 6a, a support substrate 1 to be described later is housed in a first region on the input surface side of the support portion 6b, and a pressure detector 100 is housed in a second region on the back surface side.

In the recessed portion 6a, the side surface of the first region is in contact with the support substrate 1 with a slight gap therebetween, and the side surface of the second region is in contact with the pressure detector 100 with a slight gap therebetween. Further, a space portion 7 is provided between the bottom surface of the casing 6 and the pressure detector 100.

The pressure detector 100 mainly has a support substrate 1, a piezoelectric sheet 3, and a detection electrode 4. With regard to the basic operation of the pressure detector 100, when the support substrate 1 is pressed, the pressure detector 100 is bent, and tensile stress is applied to the piezoelectric sheet 3, and electric charges are generated. Then, by detecting the electric charge by the two detecting electrodes 4, the pressing force applied to the pressure detector 100 can be detected.

More specifically, the pressure detector 100 has the support substrate 1, the adhesive layer 2, the first detecting electrode 4a, the first piezoelectric piece 3a, the intermediate adhesive layer 8, and the second piezoelectric piece 3b from the input surface side toward the back side. The second detecting electrode 4b. Hereinafter, each configuration will be described. In addition, the cross-sectional view of Fig. 2 and the like is appropriately adjusted for the position and thickness of each layer for convenience of explanation.

(2) Support substrate

The support substrate 1 (an example of a sheet member) is a sheet member and is disposed in the support portion 6b of the casing 6. The input surface 1a (first surface) of the pressure detector 100 is provided. The support substrate 1 has a back surface 1b (second surface) on the side opposite to the input surface 1a. The edge portion of the back surface 1b of the support substrate 1 is fixed so as to be supported by the support portion 6b.

The support substrate 1 is preferably a protective sheet having transparency, scratch resistance, and antifouling properties. The material of the support substrate 1 may be, for example, a general-purpose resin such as polyethylene terephthalate or an acrylic resin, a general engineering resin such as a polyacetal resin or a polycarbonate resin, a polyfluorene-based resin or polyphenylene. Sulfide) super engineering resin such as resin, glass.

Further, the thickness of the support substrate 1 is, for example, 0.4 mm to 1.0 mm.

The rigidity of the support substrate 1 is higher than other members described later.

(3) Piezoelectric sheet

The piezoelectric sheet 3 is fixed to the back surface 1b of the support substrate 1 by the adhesive layer 2. Further, the piezoelectric sheet 3 is disposed at a central portion of the back surface 1b of the support substrate 1.

As the adhesive layer 2, for example, a transparent optical adhesive can be used. For example, there is a pressure sensitive adhesive (Pressure sensitive Adhesive, hereinafter referred to as "PSA"). The thickness of A of the adhesive layer 2 is 5 μm to 300 μm.

The modulus of elasticity of the adhesive layer 2 is not limited and may be about 10 MPa, preferably about 10 MPa or more and about 1 GPa. Further, the material of the adhesive layer 2 is, for example, an acrylic, polyoxyn, or epoxy adhesive. The adhesive layer 2 is preferably cured by UV hardening or thermal hardening after the adhesive is adhered.

When the piezoelectric sheet 3 is bent by the application of the pressing force, a sheet having a potential difference applied to the pressing surfaces of the both surfaces is generated. The piezoelectric sheet 3 is composed of a first piezoelectric sheet 3a and a second piezoelectric sheet 3b. The two pieces are the same shape and are opposite each other. The first piezoelectric sheet 3a is disposed on the back surface 1b side of the support substrate 1, and the second piezoelectric sheet 3b is disposed on the back surface side of the first piezoelectric sheet 3a (the opposite side of the first piezoelectric sheet 3a from the support substrate 1). The first piezoelectric sheet 3a and the second piezoelectric sheet 3b are adhered to each other by the intermediate adhesive layer 8 made of PSA. The intermediate adhesive layer 8 will be described later.

(4) Detection electrode

The detecting electrode 4 is composed of a first detecting electrode 4a and a second detecting electrode 4b. The first detecting electrode 4a is disposed between the support substrate 1 (specifically, the adhesive layer 2) and the first piezoelectric sheet 3a (that is, the first piezoelectric sheet) 3a is opposite to the second piezoelectric sheet 3b), and the second detecting electrode 4b is disposed on the back side of the first piezoelectric sheet 3a (that is, the opposite side of the second piezoelectric sheet 3b from the first piezoelectric sheet 3a) ).

Further, the first detecting electrode 4a and the second detecting electrode 4b are made of a material having conductivity. For the conductive material, a transparent conductive oxide such as Indium-Tin-Oxide (ITO), Tin-Zinc-Oxide (TZO), or polyethylene II can be used. A conductive polymer such as polyethylenedioxythiophene (PEDOT). In this embodiment, the detecting electrode 4 is formed directly on the surface of the piezoelectric sheet 3 by, for example, vapor deposition or screen printing.

Further, the thickness of the detecting electrode 4 may be set to, for example, 1 nm to 30,000 nm.

Further, as the material having conductivity, a conductive metal such as copper or silver may be used. In this case, the detection electrode may be formed on the piezoelectric sheet by vapor deposition, or may be formed using a metal paste such as a copper paste or a silver paste. Further, the detecting electrode made of metal may have a mesh structure in order to improve light transmittance.

In addition, the detection electrode may be formed by forming a surface such as a resin film by vapor deposition, screen printing, or the like, and is fixed to the support substrate or the piezoelectric sheet with an adhesive (for example, the third embodiment).

Further, as the conductive material, a conductive material such as a carbon nanotube, a metal particle or a metal nanofiber may be dispersed in the binder.

(5) detector

A detector (not shown) is a device that detects a pressing amount from a voltage signal detected by the detecting electrode. The detector is constituted by a charge amplifier or the like using an operational amplifier.

(6) Pressing means

In addition, the pressing means for applying the pressing force to the pressure detector 100 is not particularly limited as long as it can apply a pressing. Examples of the pressing means include a finger, a stylus pen, and the like.

(7) Detailed description of the piezoelectric piece

The material of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b can be formed by forming a ferroelectric material into a sheet shape and then polarizing it in the thickness direction. Examples of the ferroelectric material include PVDF, a copolymer of PVDF and TrFE or ETFE, and PZT. The first piezoelectric sheet 3a and the second piezoelectric sheet 3b are laminated such that the polarization directions of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b are opposite to each other.

The combination of the materials of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b is not particularly limited.

However, it is preferable to use two piezoelectric sheets to use materials having the same characteristics. This is because the output from the piezoelectric sheet which is generated by the thermal stress and the thermoelectric effect due to the temperature change can be eliminated.

Referring to Fig. 3, a mechanism for canceling the output due to the thermoelectric effect of the piezoelectric sheet will be described. Figure 3 is a cross-sectional view of the pressure detector.

When the first piezoelectric sheet 3a and the second piezoelectric sheet 3b are made of a ferroelectric material, the first piezoelectric sheet 3a and the second piezoelectric sheet 3b are reversed in the direction of polarization in the non-pressed state. The method is better constructed. When configured in the above manner, temperature change occurs in the pressure detector 100. In the case where the pyroelectric effect occurs in the piezoelectric sheet 3, as shown in FIG. 3, positive and negative charges are generated on the input surface side of the first piezoelectric sheet 3a and the back surface side of the second piezoelectric sheet 3b.

When the thickness of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b is extremely thin (for example, 5 μm to 50 μm) and is made of a material having the same characteristics, the surface on the back side of the first piezoelectric sheet 3a and the second surface The potentials of the piezoelectric sheet 3b on the input surface side are substantially equal to each other, and as a result, between the surface on the input surface side of the first piezoelectric sheet 3a and the surface on the back side of the second piezoelectric sheet 3b. The potentials are equal to each other.

Therefore, when the piezoelectric sheet 3 is subjected to the thermoelectric effect, the potential of the surface on the input surface side of the first piezoelectric sheet 3a due to the thermoelectric effect and the second piezoelectric piece 3b are formed. The potential on the back side will be approximately the same. Then, in the pressure detector 100, when the first piezoelectric piece 3a and the second piezoelectric piece 3b are affected by the pyroelectric effect, the potential difference generated by the piezoelectric sheet 3 detected by the detecting electrode 4 due to the pyroelectric effect is substantially It is "0". Therefore, even if the thermoelectric effect is generated in the first piezoelectric sheet 3a and the second piezoelectric sheet 3b, the potential difference due to the pyroelectric effect of the entire piezoelectric sheet 3 is hardly detected. In other words, when the piezoelectric sheet 3 (the first piezoelectric sheet 3a and the second piezoelectric sheet 3b) is made of a ferroelectric material, the piezoelectric sheet 3 and the detecting electrode 4 are configured as described above. Therefore, there is almost no malfunction caused by the temperature change (especially due to the thermoelectric effect).

(8) Intermediate adhesive layer

As described above, the intermediate adhesive layer 8 is disposed between the first piezoelectric sheet 3a and the second piezoelectric sheet 3b. The intermediate adhesive layer 8 is, for example, a PSA.

The intermediate adhesive layer 8 is made of a softer material than before, and has an elastic modulus of less than 10 MPa. The elastic modulus of the intermediate adhesive layer 8 is preferably 1 MPa or less. More specifically, the elastic modulus of the intermediate adhesive layer 8 is preferably in the range of 0.05 MPa to 1 MPa, and more preferably in the range of 0.1 MPa to 0.3 MPa. As described above, in the present embodiment, the intermediate adhesive layer 8 is provided between the first piezoelectric sheet 3a and the second piezoelectric sheet 3b, and functions as an elastic body having a low elastic modulus.

The intermediate adhesive layer 8 is not particularly limited as long as the above-described elastic modulus can be achieved. However, the intermediate adhesive layer 8 is composed of, for example, an acrylic adhesive or a polyoxygen adhesive. This is because any adhesive has a small molecular weight and a small crosslink density, so the modulus of elasticity is small.

The thickness of the intermediate adhesive layer 8 is 5 μm or more. Preferably, the thickness of the intermediate adhesive layer 8 is in the range of 25 to 100 μm.

Referring to Fig. 4, a charge generation mechanism when a pressure is applied to the pressure detector 100 will be described. Figure 4 is a cross-sectional view of the pressure detector.

As shown in FIG. 4, when the pressure is applied to the pressure detector 100, the support substrate 1 has a higher rigidity than the piezoelectric sheet 3 and the detecting electrode 4, so that it is on the piezoelectric sheet 3 (the first piezoelectric sheet 3a). And the second piezoelectric sheet 3b) generates tensile stress. At this time, the tensile stress σ _{u is} generated in the first piezoelectric sheet 3a, and the tensile stress σ _{1 is} generated in the second piezoelectric sheet 3b. As a result, electric charges corresponding to the tensile stress are generated on the surfaces on the input surface side and the back surface side of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b, respectively. A potential difference is generated between the input surface side and the back surface side of each of the first piezoelectric sheet 3a and the second piezoelectric sheet 3b by the generated electric charge. The potential difference V ₁ ' generated between the first piezoelectric sheets 3a is a difference between the potential on the input surface side of the first piezoelectric sheet 3a and the potential on the back surface side, and the potential difference V ₁ ' is proportional to the magnitude of the tensile stress σ _u . The potential difference V ₂ ' generated between the second piezoelectric sheets 3b is the difference between the potential on the input surface side of the second piezoelectric sheet 3b and the potential on the back surface side, and the potential difference V ₂ ' is proportional to the magnitude of the tensile stress σ ₁ .

In this embodiment, the tensile stress σ _{1 is} smaller than the tensile stress σ _u , whereby the absolute value of the potential difference V ₂ is smaller than the absolute value of the potential difference V ₁ . Therefore, the detection sensitivity of the pressure detector 100 becomes high. This effect can be obtained because the intermediate adhesive layer 8 having the aforementioned characteristics is newly provided.

In addition to the above configuration, in the case where the thickness of the intermediate adhesive layer 8 exceeds 5 μm, the aforementioned effects are further enhanced. Further, the thickness of the intermediate adhesive layer 8 is preferably about 25 μm.

In addition to the above configuration, in the case where the elastic modulus of the adhesive layer 2 is 10 times or more the elastic modulus of the intermediate adhesive layer 8, the above effect is further enhanced. Specifically, the elastic layer of the adhesive layer 2 has a modulus of elasticity of 10 MPa or more, preferably about 1 GPa. In this case, the elastic modulus of the adhesive layer 2 is preferably 10 times or more the elastic modulus of the intermediate adhesive layer.

In the first embodiment, the intermediate adhesive layer 8 is only disposed between the first piezoelectric sheet 3a and the second piezoelectric sheet 3b. However, the elastic body satisfying the above characteristics is not limited to the configuration having only the adhesive layer. For example, the elastomer may also be composed of a core sheet and a double-sided adhesive. Further, a sheet which realizes optical characteristics can also be used for a part of the elastomer.

Example 1

Hereinafter, simulation results performed to show the principle and effect of the first embodiment will be described. The simulation system assumes the same structure as the above-described embodiment, and a bimorph (corresponding to the piezoelectric sheet 3) is bonded to the glass (corresponding to the support substrate 1), and the four sides are used as a base (corresponding to the shell of the electronic device 110). Body 6) A pressure detector (corresponding to the pressure detector 100) fixed by a double-sided tape. In this pressure detector, a condition of applying a force of 1 N to the central portion of the glass was employed. The piezoelectric sheet is a copolymer of a film-like PVDF. The glass size is, for example, 120 mm × 60 mm, and the thickness is, for example, 0.55 mm. The simulation system uses FEM simulation software.

Table 1 shows a bimorph in which two piezoelectric sheets (corresponding to the first piezoelectric sheet 3a and the second piezoelectric sheet 3b) are adhered by an elastic body (corresponding to the intermediate adhesive layer 8). The simulation result when the adhesive (corresponding to the adhesive layer 2) was attached to the glass. The X direction and the Y direction are the long side direction and the short side direction of the top view, respectively, and the first piezoelectric piece (PIEZO U) applied to the upper side and the second piezoelectric piece (PIEZO L applied to the lower side) are calculated for the X and Y directions. The stress of the piezoelectric sheet formed.

Analog No. A3, A4, A5, A6, A7, A10, A11, A12, A13, and A14 are examples in which the minimum conditions of the present embodiment are satisfied, and the simulation No. A1, A2, A8, and A9 are not satisfied. A reference example of the minimum condition of the embodiment. Further, A1 to A7 are cases in which the elastic modulus of the elastic body between the glass and the piezoelectric piece is lowered (10 MPa), and A8 to A14 are cases in which the elastic modulus of the elastic body between the glass and the piezoelectric piece is increased (1 GPa).

When there is no elastomer as shown in Reference Example A1, that is, when an extremely thin and very hard adhesive is adhered, the tensile stress generated in the second piezoelectric sheet is larger than that generated in the first piezoelectric sheet. The tensile stress is, and the difference (σux-σ1x, σuy-σ1y) is not large. On the contrary, as shown in Example A4, the case where the soft elastomer (elastic coefficient: 1 MPa) is interposed is opposite to the case where the elastomer is not present, and the tensile stress generated in the second piezoelectric sheet is smaller than that at the first pressure. The tensile stress generated by the electric sheet, and the difference (σux - σ1x, σuy - σ1y) was larger than that of Reference Example A1.

Further, when the elastic body is softened or thickened, the difference between the tensile stress generated in the second piezoelectric sheet and the tensile stress generated in the first piezoelectric sheet (σux-σ1x, σuy-σ1y) gradually Become bigger. Elastic coefficient ratio example Examples of still small A4 are Examples A5, A6, and A7. An example in which the modulus of elasticity is the same as in Example A5 but the thickness is increased is Example A6. Better results can be obtained in either case.

The elastic coefficients of the elastomers of Example A3 and Example A4 were the same, but the thickness of Example A4 became large. As a result, the difference in tensile stress occurring in Example A4 was larger than that in Example A3. The relationship between the embodiment A5 and the embodiment A6, the relationship between the embodiment A10 and the embodiment A11, and the relationship between the embodiment A12 and the embodiment A13 are also the same.

From the above, it is known that by forming an elastic body between the piezoelectric sheets, it is made softer or thicker, and the pressure detection sensitivity of the pressure detector can be improved.

When the examples A3 to A7 (the adhesive layer between the glass and the piezoelectric sheet is soft) and the examples A10 to A14 (the adhesive layer between the glass and the piezoelectric sheet are hard) are respectively compared, the latter is known. A large difference in tensile stress can be obtained. From this, it is understood that when the adhesive to which the glass and the bimorph are adhered is hardened, the tensile stress generated in the second piezoelectric sheet becomes smaller than the tensile stress generated in the first piezoelectric sheet. The pressure detection sensitivity of the pressure detector can be improved.

2. Second embodiment

A pressure detector 100A according to the second embodiment will be described with reference to Fig. 5 .

The basic structure of the pressure detector 100A is the same as that of the pressure detector 100 of the first embodiment. Therefore, only the differences will be explained here.

The pressure detector 100A includes a display device 5 (an example of a second sheet member) in addition to the configuration of the first embodiment. The display device 5 is fixed to the back side of the second detecting electrode 4b by the adhesive layer 9. Further, the display device 5 is composed of an LCD or an organic EL. The rigidity of the display device 5 is higher than that of the piezoelectric sheet 3.

In this manner, the pressure detector 100A has the support substrate 1, the adhesive layer 2, the first detecting electrode 4a, the first piezoelectric piece 3a, the intermediate adhesive layer 8, the second piezoelectric piece 3b, and the first surface from the input surface side toward the back surface side. 2 detecting electrode 4b, adhesive layer 9, and display device 5.

Also in this embodiment, by lowering the modulus of elasticity of the intermediate adhesive layer 8, the tensile stress σ ₁ is smaller than the tensile stress σ _u , whereby the potential difference V ₁ is greater than the potential difference V ₂ . Therefore, the detection sensitivity of the pressure detector 100B becomes high.

Further, by providing the display device 5 on the back side of the piezoelectric sheet 3, the tensile stress generated in the second piezoelectric sheet is smaller than the tensile stress generated in the first piezoelectric sheet as compared with the first embodiment. It is smaller to increase the pressure detection sensitivity of the pressure detector.

Further, if the elastic body is further softened or increased in thickness under these conditions, the tensile stress generated in the second piezoelectric sheet 3b becomes negative (that is, compressive stress is generated). As a result, the pressure detection sensitivity of the pressure detector can be further improved.

Further, by providing the display device 5, the bending rigidity of the pressure detector 100A is also increased. In other words, it is a pressure detector that is less likely to be pressed and bent.

Further, it is also effective to additionally provide a hard material such as glass instead of the display device. However, in either case, it is preferable that the elastic modulus of the member adhered to the lowermost portion of the pressure detector is 10 GPa or more.

Example 2

Hereinafter, simulation results performed to show the principle and effect of the second embodiment will be described.

In Table 2, a bimorph in which two piezoelectric sheets (corresponding to the first piezoelectric sheet 3a and the second piezoelectric sheet 3b) are adhered by an elastic body (corresponding to the intermediate adhesive layer 8) is shown ( Corresponding to the piezoelectric sheet 3), the adhesive (corresponding to the adhesive layer 2) is bonded to the glass (corresponding to the support substrate 1), and the glass (corresponding to the display device 5) is placed on the back side of the piezoelectric sheet. Simulation results. The X direction and the Y direction are the long side direction and the short side direction of the top view, respectively, and the first piezoelectric piece (PIEZO U) applied to the upper side and the second piezoelectric piece (PIEZO applied to the lower side) are calculated for the X direction and the Y direction. L) The stress of the piezoelectric sheet formed.

The simulation No. B3 to B7 are examples in which the minimum conditions of the present embodiment are satisfied, and the simulation No. B1 to B2 are reference examples in which the minimum conditions of the present embodiment are not satisfied.

When Examples B3 to B7 were compared with Examples A3 to A7 of the first embodiment which are the same as the elastic modulus and thickness of the elastomer, the examples B3 to B7 were pulled in comparison with Examples A3 to A7. The difference in the tensile stresses becomes larger, respectively. From the above, it is known that when the highly rigid sheet is fixed to the back side of the piezoelectric sheet, the detection sensitivity of the pressure detector can be further improved.

3. Third embodiment

A pressure detector 100B as a third embodiment will be described with reference to Fig. 6 . Figure 6 is a cross-sectional view of the pressure detector.

The basic structure of the pressure detector 100B is the same as that of the first embodiment. Therefore, only the difference points will be explained here.

In this embodiment, the detection electrode is formed on the surface of the resin film by vapor deposition, screen printing, or the like. Specifically, the first detection power The pole 4a is formed on the back surface of the resin film 11. The resin film 11 is fixed to the piezoelectric sheet 3 by the adhesive layer 12. Further, the resin film 11 is fixed to the support substrate 1 by the adhesive layer 2. The second detecting electrode 4b is formed on the input side surface of the resin film 13. The resin film 13 is fixed to the back surface of the piezoelectric sheet 3 by the adhesive layer 14.

In this manner, the pressure detector 100B has the support substrate 1, the adhesive layer 2, the resin film 11 (including the first detecting electrode 4a), the adhesive layer 12, the first piezoelectric piece 3a, and the intermediate bonding from the input surface side toward the back surface side. The layer 8, the second piezoelectric sheet 3b, the adhesive layer 14, and the resin film 13 (including the second detecting electrode 4b).

Also in this embodiment, by lowering the modulus of elasticity of the intermediate adhesive layer 8, the tensile stress σ ₁ is smaller than the tensile stress σ _u , whereby the potential difference V ₁ is greater than the potential difference V ₂ . Therefore, the detection sensitivity of the pressure detector 100B becomes high.

Further, by increasing the thickness of the intermediate adhesive layer 8, the aforementioned effects can be further enhanced.

Further, when the elastic modulus of the adhesive layer 2, the adhesive layer 12, and the adhesive layer 14 of the adhesive layer other than the intermediate adhesive layer 8 is 10 times or more of the elastic modulus of the intermediate adhesive layer 8, the above effect is further enhanced. Specifically, the elastic layer of these adhesive layers has a modulus of elasticity of 10 MPa or more, preferably about 1 GPa.

Example 3

Hereinafter, simulation results performed to show the principle and effect of the third embodiment will be described.

Table 3 shows that two piezoelectric sheets (corresponding to the first piezoelectric sheet 3a and the second piezoelectric sheet 3b) are bonded to each other by an elastic body (corresponding to the intermediate adhesive layer 8) to form a bimorph (corresponding to pressure). The electric sheet 3) is formed with a resin film (corresponding to the resin film 11) of the first detecting electrode (corresponding to the first detecting electrode 4a) and a resin film on which the second detecting electrode (corresponding to the second detecting electrode 4b) is formed. (corresponding to the simulation results when the resin film 13 is fixed to the bimorph and further bonded to the glass (corresponding to the support substrate 1) with an adhesive (corresponding to the adhesive layer 2). The X direction and the Y direction are the long side direction and the short side direction of the top view, respectively, and the first piezoelectric piece (PIEZO U) applied to the upper side and the second piezoelectric piece (PIEZO applied to the lower side) are calculated for the X direction and the Y direction. L) The stress of the piezoelectric sheet formed.

The simulation No. C3 to C7 and C10 to C14 are examples in which the minimum conditions of the present embodiment are satisfied, and the simulation Nos. C1 to C2 and C8 to C9 are reference examples in which the minimum conditions of the present embodiment are not satisfied.

Examples C3 to C7 (the adhesive layer between the glass and the piezoelectric sheet, and the adhesive layer between the respective resin film and the piezoelectric sheet were soft) and Examples C10 to C14 (between the glass and the piezoelectric sheet) When the adhesive layer and the adhesive layer between the respective resin films and the piezoelectric sheets are hard), when they are separately compared, it is known that the latter can obtain a large difference in tensile stress. This shows that when the elastic modulus of the adhesive other than the elastomer is increased, the difference between the tensile stress generated in the second piezoelectric sheet and the tensile stress generated in the first piezoelectric sheet is further increased. The pressure detection sensitivity of the pressure detector can be improved.

Example 4

Next, referring to Table 4, the results of measurement of the output of the pressure detector actually obtained by the test are shown below. Pressure detection The layer configuration of the device is the same as that of the third embodiment. A PSAmid (corresponding to an intermediate adhesive layer) having a soft adhesive layer between the piezoelectric sheets (corresponding to the first piezoelectric sheets 3a and the second piezoelectric sheets 3b) of the bimorph (corresponding to the piezoelectric sheet 3) 8). Moreover, it has been attempted to attach the bimorph (corresponding to the piezoelectric sheet 3) to the ITO film (corresponding to the resin film 11 and the resin film 13) from both sides, and further attach it via PSA1 (corresponding to the adhesive layer 2). A pressure detector (corresponding to the pressure detector 100b) having a structure of glass (corresponding to the support substrate 1). The ITO film is attached to the bimorph via PSA2 (corresponding to the adhesive layer 12) and PSA3 (corresponding to the adhesive layer 14). Next, the electric power generated by the pressing is used as the electric charge, and is detected by a charge amplifier (not shown).

In the sensor 1 as a reference example, PSA1, PSA2, PSA3, and PSAmid (corresponding to the intermediate adhesive layer 8) are configured to be thin and hard. In this case, each of the PSAs was subjected to UV curing after bonding, and the modulus of elasticity after curing was about 3 GPa. In this case, a charge output of 0.52 nC was observed under a pressure of 500 g.

In the sensor 2 as an embodiment, PSA1, PSA2, and PSA3 are made of a thin and hard structure, and PSAmid (corresponding to the intermediate adhesive layer 8) is made of a soft general PSA. The general PSA of PSAmid has a modulus of elasticity of about 0.1 MPa. The charge of the opposite sign to the sensor 1 was detected, the amount of which was 1.55 nC three times that of the sensor 1, and the effect was seen.

4. Fourth embodiment

In the first to third embodiments, the bimorph of the pressure detector is fixed to the support substrate 1, but the present invention is not limited to the embodiments. The bimorph of the pressure detector can also be attached to the back of the touch panel. In this case, not only the pressing force but also the position of the pressing can be detected.

Examples of the touch panel include a capacitive type, a resistive film type, and an optical type. Hereinafter, the case of the capacitance type will be described.

Hereinafter, the touch panel 110C will be described with reference to FIGS. 7 and 8. 7 is a cross-sectional view of the touch panel. Figure 8 is a developed view of the electrode. The basic structure of the pressure detector 100C included in the touch panel 110C is the same as that of the first to third embodiments. Therefore, the description of the common portion is omitted. The pressure detector 100C has the display device 5 on the most rear side as shown in the second embodiment. In the pressure detector 100, as shown in the third embodiment, the first detecting electrode 4a and the second detecting electrode 4b are formed in the resin film 11 and the resin film 13, respectively.

As shown in FIG. 7 and FIG. 8 , the touch panel 110C has a touch sensor 51 in addition to the pressure detector 100C. The touch sensor 51 mainly has an upper electrode 53 and a lower electrode 55.

The upper electrode 53 is formed in plural numbers on the input side surface of the resin film 11. The plurality of upper electrodes 53 are arranged in parallel with each other so as to be arranged at a predetermined interval in the Y-axis direction. In the present embodiment, the upper electrode 53 is formed in a stripe shape (linear shape having a constant width). Further, the upper electrode 53 may be formed in, for example, a wave shape or a zigzag shape. Regardless of the shape, each of the upper electrodes 53 is formed to extend integrally along the X-axis direction.

Further, the upper electrode 53 is preferably made of a material having excellent transparency. Examples of materials satisfying such requirements include metal oxides such as tin oxide, indium oxide, antimony oxide, zinc oxide, cadmium oxide, and ITO (Indium Tin Oxide); silver nanowires, carbon nanotubes, and conductive polymerization. Things and so on. The upper electrode 53 is a transparent conductive film formed using these materials, and its thickness can be set, for example, to 5 nm to 5000 nm. In the present embodiment, the upper electrode 53 is formed of an ITO thin film. In this case, the upper electrode 53 is formed on the input side surface of the resin film 11 by vapor deposition, screen printing, or the like, and is fixed to the support substrate 1 by an adhesive layer. Further, the upper electrode may be directly formed on the back surface of the support substrate 1 by vapor deposition, screen printing or the like. Further, the thickness of the upper electrode 53 is, for example, 1 nm to 20 μm.

In the present embodiment, the lower electrode 55 is formed in plural numbers on the back side of the upper electrode 53. The plurality of lower electrodes 55 are arranged in parallel with each other so as to be arranged at a predetermined interval in the X-axis direction. In the present embodiment, the lower electrode 55 is formed in a stripe shape (a linear shape having a constant width). Further, the lower electrode 55 may be formed, for example, in a wave shape or a zigzag shape. Regardless of the shape, each of the lower electrodes 55 is formed to extend integrally along the Y-axis direction. Thereby, the upper electrode 53 and the lower electrode 55 are arranged to cross each other in plan view (in this example, orthogonal). The lower electrode 55 is preferably made of a material having excellent transparency similarly to the upper electrode 53. The material or thickness constituting the lower electrode 55 is the same as that of the upper electrode 53. Further, the method of forming the lower electrode 55 is also the same as that of the upper electrode 53.

In this embodiment, the lower electrode 55 is formed on the surface of the resin film 13 by vapor deposition, screen printing, or the like, and is fixed to the first piezoelectric sheet 3a by the adhesive layer 12.

Further, the upper electrode 53 and the lower electrode 55 may have a mesh structure made of a conductive metal such as silver or copper, similarly to the detecting electrode.

A plurality of upper electrodes 53 are connected to a detection circuit (not shown) via lead wires, respectively. Further, a plurality of lower electrodes 55 are also connected to the detection circuit via the lead wires. Further, the wiring is formed by using a metal such as gold, silver, copper, or nickel, or a conductive paste such as carbon.

In this embodiment, the lower electrode 55 also serves as the first detecting electrode 4a of the pressure detector 100C. Therefore, other layers for insulating the two electrodes are not required, and therefore, the device can be made lighter and thinner. Moreover, the electrode material can be reduced.

The touch panel 110C is provided with a control unit (not shown) including an arithmetic processing unit such as a CPU, and the control unit is configured to perform position detection calculation and pressure detection calculation. Specifically, when the user's finger or the like touches the touch panel 110C (input surface 1a), the electrostatic capacitance between the upper electrode 53 and the user's finger or the like, or the lower electrode 55 and the user's finger or the like The electrostatic capacitance between them will change. The control unit can determine the pressing position of the X-Y coordinate system of the input surface 1a based on the change in the electrostatic capacitance obtained by the detector. Further, when the user's finger or the like touches the touch panel 110C, as described above, the potential difference between the piezoelectric sheets 3 changes depending on the magnitude of the applied pressing force. The control unit can determine the magnitude of the pressing force applied in the direction (Z direction) orthogonal to the input surface 1a by detecting the change in the potential difference of the piezoelectric sheet 3.

In addition, when the pressure detector and the touch panel are used in combination, the electrodes may not necessarily be common.

Further, the layer configuration of the above device is an embodiment, and the present invention is not limited thereto.

5. Common matters of the implementation

The first to fifth embodiments described above have the following configurations and functions in common.

The pressure detecting means (for example, the pressure detectors 100, 100A, 100B, 100C) is a pressure detecting means for detecting a pressure based on a potential difference between two piezoelectric sheets generated by externally applied pressure. The pressure detecting device includes a sheet member, a first piezoelectric sheet, a second piezoelectric sheet, a first detecting electrode, a second detecting electrode, and an elastic body.

The sheet member (for example, the support substrate 1 and the touch panel) has a first surface (for example, the input surface 1a) for supporting pressure and a second surface (for example, the back surface 1b) to which the edge portion is supported.

The first piezoelectric piece (for example, the first piezoelectric piece 3a) is disposed at a central portion of the second surface of the sheet member.

The second piezoelectric piece (for example, the second piezoelectric piece 3b) is disposed on the opposite side of the first piezoelectric piece from the sheet member, and is disposed to face the first piezoelectric piece.

The first detecting electrode (for example, the first detecting electrode 4a) is disposed on the opposite side of the first piezoelectric piece from the second piezoelectric piece.

The second detecting electrode (for example, the second detecting electrode 4b) is disposed on the opposite side of the second piezoelectric piece from the first piezoelectric piece. The elastic body (for example, the intermediate adhesive layer 8) is disposed between the first piezoelectric sheet and the second piezoelectric sheet. The elastic modulus of the elastomer is less than 10 MPa.

In this apparatus, when the central portion of the first surface of the sheet member is pressed, the sheet member is supported while being supported by the support portion at one edge, and is curved (see FIG. 4). As a result, the first piezoelectric piece and the second piezoelectric piece are also bent. At this time, since the elastic modulus of the elastic body disposed between the first piezoelectric sheet and the second piezoelectric sheet is less than 10 MPa, the tensile stress (for example, σ ₁ ) of the second piezoelectric sheet is smaller than that of the first piezoelectric sheet. Tensile stress (for example, σ _u ). Thereby, the amount of electric charge generated in the first detecting electrode is larger than the amount of electric charge generated in the second detecting electrode, and the potential difference between the first detecting electrode and the second detecting electrode becomes sufficiently large. As a result, the pressure detection sensitivity of the pressure detecting device becomes high.

6. Other embodiments

The various embodiments of the present invention are described above, but the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the scope of the invention. In particular, the plurality of embodiments and modifications described in the present specification can be arbitrarily combined as needed.

[Industrial availability]

The present invention is widely applicable to a pressure detecting device, and more particularly to a pressure detecting device using a bimorph having two piezoelectric sheets attached thereto.

1‧‧‧Support substrate

1a‧‧‧ input face

1b‧‧‧back

2‧‧‧Adhesive layer

3‧‧‧ Piezo Pieces

3a‧‧‧1st piezoelectric piece

3b‧‧‧2nd piezoelectric piece

4‧‧‧Detection electrode

4a‧‧‧1st detection electrode

4b‧‧‧2nd detection electrode

8‧‧‧Intermediate adhesive layer

100‧‧‧ Pressure detector

Claims (7)

A pressure detecting device for detecting a pressure based on a potential difference between two piezoelectric sheets generated by externally applied pressure, comprising: a sheet member having a first surface for applying the pressure, And a second surface supported by the edge portion; the first piezoelectric sheet is disposed at a central portion of the second surface of the sheet member; and the second piezoelectric sheet is opposite to the sheet member of the first piezoelectric sheet And the first piezoelectric sheet is disposed opposite to each other; the first detecting electrode is disposed on a side opposite to the second piezoelectric sheet of the first piezoelectric sheet; and the second detecting electrode is disposed on the second piezoelectric layer The sheet is opposite to the first piezoelectric sheet; and the elastic body is disposed between the first piezoelectric sheet and the second piezoelectric sheet, and has an elastic modulus of less than 10 MPa. The pressure detecting device according to claim 1, wherein the elastic modulus of the elastic body is 1 MPa or less. The pressure detecting device according to claim 1 or 2, wherein the thickness of the elastomer is 5 μm or more. The pressure detecting device of claim 3, wherein the thickness of the elastomer is 25 to 100 μm. The pressure detecting device according to claim 1, wherein the elastic system adheres the adhesive between the first piezoelectric sheet and the second piezoelectric sheet. The pressure detecting device according to claim 1, further comprising a second sheet member disposed on a side opposite to the sheet member of the second piezoelectric sheet and having an elastic modulus of 10 GPa or more. The pressure detecting device according to claim 1, further comprising an adhesive layer disposed between the sheet member and the first piezoelectric sheet and the second piezoelectric sheet and having a modulus of elasticity of 10 or more times that of the elastic body Elastic coefficient.