Multilayer piezoelectric material and method for manufacturing the same

Abstract

Disclosed is a multilayer piezoelectric body which comprises: a piezoelectric film that contains a fluorine-based resin as a main component; an antistatic layer that is disposed on at least one surface of the piezoelectric film and has a thickness of 10 nm to 250 nm (inclusive); and a hard coating layer that is disposed on the antistatic layer and has a maximum height Rz of the surface of 40 nm to 150 nm (inclusive). The surface resistivity of the multilayer piezoelectric body as measured on the hard coating layer is 1.0 × 106 Ω / sq. to 1.0 × 1012 Ω / sq. (inclusive); the total light transmittance of the multilayer piezoelectric body is 85% or more; and the piezoelectric constant d33 is 7 pC / N to 40 pC / N (inclusive).

Description

[Technical Field]

[0001] The present invention relates to a multilayer piezoelectric material and a method for manufacturing the same. [Background technology]

[0002] Touch panels are attached to the displays of electronic devices and are used to operate those devices. While there are various types of touch panels, capacitive touch panels are often used because they have a simple structure, are inexpensive to manufacture, and can be made relatively large. However, capacitive touch panels are prone to malfunctions due to the complexity of their signal processing.

[0003] Generally, touch panels detect the two-dimensional position (position coordinates) of the touch panel surface by touching the surface with a finger or pen. In touch panel input, it is desirable that selection and execution be separated to avoid misinterpretation of input. Specifically, it is desirable that the two-dimensional position of the touch surface be selected and the selection be executed by applying pressure to the touch surface. For this reason, applying a pressure sensor to the touch panel and further detecting the magnitude of the pressure applied is being considered to improve reliability (for example, Patent Document 1).

[0004] As a pressure sensor for touch panels, the application of piezoelectric films that generate voltage in response to pressure has been proposed. Piezoelectric films containing polymer materials such as polylactic acid and fluororesins are known.

[0005] While these piezoelectric films offer excellent transparency, they are prone to static electricity buildup due to friction and vibration. Static electricity can easily attract foreign matter to the piezoelectric film, potentially degrading its quality. Furthermore, scratches on the film surface during handling can reduce visibility when used in touch panels. Therefore, piezoelectric films with antistatic and scratch-resistant properties are in demand.

[0006] In contrast, Patent Document 2 discloses a laminated piezoelectric body including a piezoelectric film containing polylactic acid and a surface layer disposed thereon and containing a conductive material (A) and a polymer (B). In this document, since the surface layer is an antistatic hard coat layer, the laminated piezoelectric body is said to have good antistatic properties and scratch resistance.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] However, according to the study by the present inventors, the laminated piezoelectric body of Patent Document 2 has poor slipperiness on the surface of the hard coat layer. For example, when wound in a roll shape, the laminated piezoelectric bodies are likely to adhere to each other and cause blocking. Further, the piezoelectric film containing polylactic acid used in Patent Document 2 has a problem that it is difficult to obtain a sufficient piezoelectric effect because the piezoelectric constant d 14 is as low as 6.4 pC / N.

[0009] In contrast, when the present inventors formed an antistatic layer on a piezoelectric film containing a fluororesin having a high piezoelectric constant d 33 and having a sufficient piezoelectric effect, a new problem was found that coating spots occurred in the obtained laminated piezoelectric body and the visibility decreased.

[0010] Therefore, a laminated piezoelectric body that exhibits high piezoelectricity without reducing visibility and has antiblocking properties and antistatic properties is desired.

[0011] This invention has been made in view of the above circumstances, and aims to provide a laminated piezoelectric material and a method for manufacturing the same that have high piezoelectricity, antiblocking properties, and antistatic properties without reducing visibility. [Means for solving the problem]

[0012] [1] A laminated piezoelectric material comprising: a piezoelectric film mainly composed of a fluororesin; an antistatic layer disposed on at least one surface of the piezoelectric film, having a thickness of 10 nm to 250 nm; and a hard coat layer disposed on the antistatic layer, having a maximum surface height Rz of 40 nm to 150 nm, wherein the surface resistivity of the laminated piezoelectric material measured on the hard coat layer is 1.0 × 10 6 Ω / sq. or more 1.0×10 12 The impedance is Ω / sq. or less, the total light transmittance of the laminated piezoelectric material is 85% or more, and the piezoelectric constant d 33 A multilayer piezoelectric material having a density of 7 pC / N or more and 40 pC / N or less. [2] The laminated piezoelectric material according to [1], wherein the fluororesin is a polymer mainly composed of constituent units derived from vinylidene fluoride. [3] The laminated piezoelectric material according to [1] or [2], wherein the fluorine-based resin is a polyvinylidene fluoride homopolymer. [4] The antistatic layer comprises carbon nanotubes, as described in any of [1] to [3]. [5] The laminated piezoelectric material according to any one of [1] to [4], wherein the thickness of the hard coat layer is 300 nm or more and 3000 nm or less. [6] The hard coat layer comprises silica particles having an average particle diameter of 10 nm or more and 200 nm or less, as described in any of [1] to [5]. A method for manufacturing a laminated piezoelectric material according to any of [7][1] to [5], wherein the piezoelectric constant d is mainly composed of a fluororesin. 33A method for manufacturing a laminated piezoelectric body, comprising the steps of: preparing a piezoelectric film having a static charge of 7 pC / N or more and 40 pC / N or less; applying an antistatic material to at least one surface of the piezoelectric film to form an antistatic layer; and applying a curable composition onto the antistatic layer and then curing it to form a hard coat layer. [8] The method for manufacturing a laminated piezoelectric body according to [7], wherein in the step of preparing the piezoelectric film, a film containing a fluororesin as the main component is formed by extrusion molding. [9] A method for manufacturing a laminated piezoelectric material according to [7] or [8], wherein in the step of preparing the piezoelectric film, a film containing a fluororesin as the main component is stretched and then subjected to polarization treatment.

[10] A method for manufacturing a laminated piezoelectric body according to any one of [7] to [9], wherein in the step of forming the antistatic layer, the piezoelectric film coated with the antistatic material is heat-treated at 100°C or more and 150°C or less and dried. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a laminated piezoelectric material having high piezoelectricity, antiblocking properties, and antistatic properties without reducing visibility, as well as a method for manufacturing the same. [Modes for carrying out the invention]

[0014] As described above, it has been newly discovered that laminated piezoelectric materials having a piezoelectric film mainly composed of fluororesin can develop coating irregularities, which were not a problem in laminated piezoelectric materials having a piezoelectric film made of polylactic acid.

[0015] According to the inventors' investigation, the above-mentioned coating irregularities are due to uneven application of the antistatic layer. These uneven coatings are thought to be caused by picking up fine irregularities on the surface of the piezoelectric film. Surface irregularities of the piezoelectric film result in a high piezoelectric effect (piezoelectric constant d 33) is considered to be formed in the process of performing stretching treatment or polarization treatment on a film containing a fluororesin as a main component. Specifically, it is considered that wrinkles occur on the surface of the piezoelectric film containing the fluororesin due to the disorder of the crystal structure caused by the transition of the crystal of the fluororesin from the α-type to the β-type and the relaxation of the molecular chain accompanying the change in the crystal structure during the polarization treatment. On the other hand, in a piezoelectric film made of polylactic acid, since the crystallinity is low and no polarization treatment is performed, it is considered that few (or no) wrinkles occur on the surface of the piezoelectric film.

[0016] In contrast, in one embodiment of the present invention, the thickness of the antistatic layer disposed on the piezoelectric film containing a fluororesin is made to be not more than a predetermined value. When the antistatic layer is thickly applied, the thick antistatic layer is applied to the concave portions of the piezoelectric film, so that the coating unevenness of the antistatic layer in the laminated piezoelectric body becomes large. On the other hand, by thinly applying the antistatic layer, the thickness unevenness of the antistatic layer is reduced, and the variation itself caused by the unevenness of the surface of the piezoelectric film is also reduced, so that coating unevenness is less likely to occur. Therefore, the coating unevenness in the laminated piezoelectric body can be reduced, and the reduction in visibility can be suppressed.

[0017] Furthermore, by laminating the antistatic layer and the hard coat layer with the surface roughness (Rz) adjusted so that the surface resistivity is not more than a predetermined value, antiblocking properties and antistatic properties can be highly compatible.

[0018] Hereinafter, a laminated piezoelectric body and a method for manufacturing the same according to one embodiment of the present invention will be specifically described.

[0019] 1. Laminated piezoelectric body The laminated piezoelectric body according to the present embodiment includes a piezoelectric film, an antistatic layer, and a hard coat layer.

[0020] 1-1. Piezoelectric film The piezoelectric film is a film containing a fluororesin as a main component, and the piezoelectric constant d 33 is adjusted to be 7 pC / N or more and 40 pC / N or less. The piezoelectric constant d of the piezoelectric film 33When the piezoelectric constant d of a piezoelectric film is 7 pC / N or higher, the amount of charge generated by the piezoelectric effect is sufficient, making it easier to obtain high pressure sensitivity. 33 If the piezoelectric constant d of the piezoelectric film is 40 pC / N or less, surface irregularities caused by polarization treatment, for example, can be further reduced, thereby reducing appearance defects. From a similar viewpoint, the piezoelectric constant d of the piezoelectric film 33 It is more preferably 10 pC / N or more and 35 pC / N or less, even more preferably 10 pC / N or more and 27 pC / N or less, and particularly preferably 10 pC / N or more and 24 pC / N or less.

[0021] Piezoelectric constant d 33 d is one of the indicators that shows the polarization behavior when a constant pressure is applied. 33 The larger the value, the greater the degree of polarization generated when subjected to a certain pressure, and the higher the charge density. Therefore, the degree of charging of the piezoelectric film also increases.

[0022] Piezoelectric constant d of piezoelectric film 33 This is the direct quasi-static method (d 33 Piezoelectric constant d of piezoelectric ceramics by the Meter method, Berlin coat method 33 The test method conforms to ISO 19622:2018 and the piezoelectric constant d 33 This can be measured. Specifically, a piezoelectric constant measuring device (for example, the PM300 piezometer system from PIEZOTEST) is used to clip a piezoelectric film sample with a force of 1.0 N, and the generated charge is read when a force of 0.15 N and 110 Hz is applied.

[0023] Piezoelectric constant d of piezoelectric film 33 This can be adjusted mainly by the type of resin contained in the piezoelectric film and the manufacturing conditions (polarization treatment and stretching treatment conditions). For example, among fluororesins, the more constituent units derived from vinylidene fluoride a resin contains, the higher the piezoelectric constant d of the piezoelectric film. 33 It tends to become larger. Also, by strengthening the polarization treatment or stretching treatment, the piezoelectric constant d of the piezoelectric film can be increased. 33 It tends to grow large.

[0024] As described above, the piezoelectric film contains a fluororesin as its main component. Containing a fluororesin as its main component means that the content of resins with fluororesin as a constituent unit (including the fluororesin itself) in the total mass of the resin constituting the piezoelectric film is 50% by mass or more. The fluororesin content is preferably 60% by mass or more, and more preferably 80% by mass or more. The upper limit of the above content is not particularly limited; it may be 100% by mass or 90% by mass or less.

[0025] From the viewpoint of easily obtaining a high piezoelectric effect among fluororesins, it is preferable that the fluororesin is a polymer that mainly contains constituent units derived from vinylidene fluoride.

[0026] The content of constituent units derived from vinylidene fluoride, which are included as the main component in the above polymer, is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% or more, and particularly preferably 90% or more, relative to the total amount of constituent units of the polymer. The higher the content, the easier it is to obtain a higher piezoelectric effect. The upper limit of the above content is not particularly limited and may be 100% by mass or 90% by mass or less.

[0027] The polymer described above may further contain constituent units derived from monomers copolymerizable with vinylidene fluoride, to the extent that it does not impair the effects of the present invention. Examples of monomers copolymerizable with vinylidene fluoride include fluorine-containing monomers such as trifluoroethylene, tetrafluoroethylene, hexafluoropropylene, trifluoroethylene chloride, and vinyl fluoride. Two or more of these monomers may be included.

[0028] In particular, the piezoelectric constant d of piezoelectric film 33 From the viewpoint of easily increasing the size and improving the sensitivity of the pressure sensor to which the piezoelectric film is applied, a polyvinylidene fluoride homopolymer is preferred.

[0029] The thickness of the piezoelectric film is preferably, for example, 25 μm to 120 μm. When the piezoelectric film is 25 μm or thicker, the amount of charge generated by the piezoelectric effect increases, making it easier to obtain higher piezoelectricity. The thickness of the piezoelectric film is more preferably 30 μm or thicker, and even more preferably 35 μm or thicker. When the thickness of the piezoelectric film is 120 μm or less, the transparency of the piezoelectric film is less likely to be impaired, and is more preferably 100 μm or less, and even more preferably 80 μm or less. From a similar viewpoint, the thickness of the piezoelectric film is more preferably 35 μm to 80 μm.

[0030] 1-2. Antistatic layer The antistatic layer has the function of preventing static charge buildup in the laminated piezoelectric material. The antistatic layer is disposed on at least one surface of the piezoelectric film.

[0031] The surface resistivity of the antistatic layer is adjusted so that the surface resistivity measured on the hard coat layer falls within the range described later. Therefore, it is preferable that the surface resistivity of the antistatic layer is lower than the surface resistivity measured on the hard coat layer, specifically 1.0 × 10⁻⁶. 4 Ω / sq. or more 1.0×10 9 It is preferable that the ratio is Ω / sq. or less, and 1.0 × 10 5 Ω / sq. or more 1.0×10 8 It is more preferable that the surface resistivity of the antistatic layer be less than or equal to / sq. The surface resistivity of the antistatic layer is 1.0 × 10⁻⁶. 9 A value of Ω / sq. or less makes it easier to lower the surface resistivity measured on the hard coat layer and to adequately impart antistatic properties. Surface resistivity can be measured, for example, using a known resistivity meter in accordance with JIS K 6911.

[0032] Surface resistivity can be adjusted by the thickness of the antistatic layer and the type and amount of conductive material contained in the antistatic layer. For example, increasing the thickness of the antistatic layer will decrease the surface resistivity. Also, increasing the amount of conductive material will decrease the surface resistivity.

[0033] The antistatic layer includes a conductive material. In this embodiment, the antistatic layer may include a cured product of a curable composition comprising a conductive material, a polymerizable compound, and an optional curing agent.

[0034] The conductive material can be any material such that the surface resistivity of the antistatic layer falls within the above range, and may be an ion-conducting conductive material or an electron-conducting conductive material.

[0035] Examples of ion-conducting conductive materials include (a) cationic antistatic agents having cationic groups such as quaternary ammonium salts, pyridinium salts, and primary to tertiary amino groups; (b) anionic antistatic agents having anionic groups such as sulfonic acid bases, sulfate ester bases, phosphate ester bases, and phosphonic acid bases; (c) amphoteric antistatic agents such as amino acid-based and aminosulfate ester-based agents; and (d) nonionic antistatic agents such as amino alcohol-based, glycerin-based, and polyethylene glycol-based agents.

[0036] Examples of electron-conducting conductive materials include conductive polymers and other conductive materials. Examples of conductive polymers include polyacetylene or its derivatives, polythiophene or its derivatives, polypyrrole or its derivatives, polyaniline or its derivatives, etc. Among these, polythiophene or its derivatives are preferred from the viewpoint of high transparency and high conductivity. Examples of conductive materials other than conductive polymers include carbon nanotubes, graphene, etc.

[0037] Among these, it is preferable to include an electron-conducting conductive material, as this makes it easier to lower the surface resistivity of the laminated piezoelectric material and reduces the likelihood of bleed-out. Among electron-conducting conductive materials, carbon nanotubes are more preferable, as this further lowers the surface resistivity of the antistatic layer and thereby lowers the surface resistivity measured on the hard coat layer.

[0038] The polymerizable compound may be either a thermopolymerizable compound or a photopolymerizable compound. Examples include acrylic compounds, epoxy compounds, oxetane compounds, polyurethane compounds, polyimide resins, melamine resins, silicone compounds, and vinyl acetate. For example, the same polymerizable compounds used to form the hard coat layer described later may be used.

[0039] The thickness of the antistatic layer can be any amount that provides antistatic properties, for example, 10 nm to 250 nm. If the thickness of the antistatic layer is 10 nm or more, the surface resistivity of the antistatic layer can be made lower, so the surface resistivity measured on the hard coat layer can also be made lower, and high antistatic properties can be easily obtained. If the thickness of the antistatic layer is 250 nm or less, uneven coating caused by surface irregularities of the piezoelectric film can be made less likely, and coating streaks can be made even less likely. From a similar viewpoint, the thickness of the antistatic layer is more preferably 15 nm to 220 nm, even more preferably 20 nm to 190 nm, and particularly preferably 20 nm to 160 nm.

[0040] 1-3. Hard coat layer The hard coat layer enhances the scratch resistance of the laminated piezoelectric surface and also improves its slipperiness, thereby suppressing blocking.

[0041] The hard coat layer may be a single layer or multiple layers. Preferably, at least one hard coat layer is placed on the antistatic layer. Furthermore, preferably, at least one hard coat layer is placed on the outermost surface of the laminated piezoelectric body.

[0042] From the viewpoint of suppressing blocking, the hard coat layer preferably has a moderate surface roughness. Specifically, the maximum surface height Rz of the hard coat layer is adjusted to be between 40 nm and 150 nm. When the Rz of the hard coat layer surface is 40 nm or more, it has sufficient slipperiness, which can suppress blocking between the laminated piezoelectric elements. When the Rz of the hard coat layer surface is 150 nm or less, it can suppress the decrease in transparency due to increased haze. From a similar viewpoint, the Rz of the hard coat layer surface is more preferably between 40 nm and 100 nm, even more preferably between 40 nm and 80 nm, and particularly preferably between 40 nm and 60 nm.

[0043] The Rz of the hard coat layer surface can be measured using a surface roughness meter (e.g., "SURFCOM1500," manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with the method specified in JIS B 0601-2013. The Rz is measured at any 10 locations on the hard coat layer in the width direction (TD direction) of the laminated piezoelectric material, and the average value is calculated.

[0044] The Rz value of the hard coat layer surface can be adjusted by factors such as the average particle size of the particles contained in the hard coat layer. For example, increasing the average particle size of the particles contained in the hard coat layer tends to increase the Rz value.

[0045] The hard coat layer may be a resin layer containing particles. From the viewpoint of improving scratch resistance, it is preferable that the resin layer containing particles is obtained by curing a curable composition containing polymerizable compounds and particles.

[0046] (polymerizable compound) The polymerizable compound may be a monomer, oligomer, or polymer. The polymerizable compound may be a thermosetting compound or an ionizing radiation compound, but is preferably an ionizing radiation compound. The ionizing radiation may usually be ultraviolet (UV) or electron beam (EB).

[0047] Ionizing radiation compounds are compounds having ionizing radiation-curable functional groups. Examples of ionizing radiation-curable functional groups include ethylenically unsaturated bonding groups such as (meth)acryloyl groups, vinyl groups, and allyl groups, and ring-opening polymerizable groups such as epoxy groups and oxetanyl groups. Among these, compounds having ethylenically unsaturated bonding groups are preferred, compounds having two or more ethylenically unsaturated bonding groups are more preferred, and polyfunctional (meth)acrylate compounds are even more preferred.

[0048] Among polyfunctional (meth)acrylate compounds, examples of bifunctional (meth)acrylate monomers include ethylene glycol di(meth)acrylate, bisphenol A tetraethoxydiaacrylate, bisphenol A tetrapropoxydiaacrylate, and 1,6-hexanediol diacrylate. Examples of trifunctional or more (meth)acrylate monomers include trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, dipentaerythritol tetra(meth)acrylate, and isocyanuric acid-modified tri(meth)acrylate. Furthermore, the above (meth)acrylate monomers may have a modified molecular skeleton, and those modified with ethylene oxide, propylene oxide, caprolactone, isocyanuric acid, alkyl, cyclic alkyl, aromatic, bisphenol, etc., can also be used.

[0049] Furthermore, examples of polyfunctional (meth)acrylate oligomers include acrylate polymers such as urethane (meth)acrylate, epoxy (meth)acrylate, polyester (meth)acrylate, and polyether (meth)acrylate. Urethane (meth)acrylate can be obtained, for example, by the reaction of polyhydric alcohols and organic diisocyanates with hydroxy (meth)acrylate.

[0050] (Polymerization initiator) When the ionizing radiation-curable compound is an ultraviolet-curable compound, the curable composition preferably contains a photopolymerization initiator. Examples of photopolymerization initiators include one or more selected from acetophenone, benzophenone, α-hydroxyalkylphenone, Michler ketone, benzoin, benzyl methyl ketal, benzoyl benzoate, α-acyloxime ester, thioxanthones, etc.

[0051] (particle) The particles may be inorganic or organic.

[0052] Examples of inorganic particles include silica particles, titanium dioxide particles, zirconia particles, aluminum oxide particles, diamond powder, sapphire particles, boron carbide particles, silicon carbide particles, and antimony pentoxide particles. Examples of organic particles include resin particles such as acrylic resin, acrylic-styrene copolymer, and silicone resin. Among these, inorganic particles are preferred, and silica particles are more preferred, because they do not impair the transparency of the hard coat layer. The surface of the inorganic particles may be treated with a surface modifier such as a silane coupling agent.

[0053] The average primary particle size is preferably between 10 nm and 200 nm, and more preferably between 30 nm and 100 nm. By setting the average primary particle size within the above range, the Rz of the hard coat layer surface can be adjusted to within the above range.

[0054] The average primary particle size of particles in the hard coat layer can be measured by observing the surface of the hard coat layer at 10 points using a scanning electron microscope (SEM) at an acceleration voltage of 2.0 kV and a magnification of 50,000, and taking the average value of these observations. The diameter of any 10 individual particles can be determined by measuring the area of ​​each particle, calculating the diameter corresponding to the circle of that area, and then obtaining the arithmetic mean of the diameters of each particle as the average primary particle size.

[0055] The particle content in the hard coat layer is preferably 3% to 80% by mass relative to the curable composition, and more preferably 6% to 70% by mass. When the particle content is 3% by mass or more, the Rz of the surface of the hard coat layer tends to increase, making it easier to improve antiblocking properties. When the particle content is 80% by mass or less, the decrease in transparency due to increased haze can be further suppressed.

[0056] The thickness of the hard coat layer is preferably 300 nm or more and 3000 nm or less. A hard coat layer thickness of 300 nm or more makes it easier to improve the scratch resistance of the laminated piezoelectric material. A hard coat layer thickness of 3000 nm or less makes it easier to lower the surface resistivity of the laminated piezoelectric material, thus making it easier to obtain higher antistatic properties. From a similar viewpoint, the surface thickness of the hard coat layer is more preferably 500 nm or more and 1500 nm or less, and even more preferably 700 nm or more and 1200 nm or less.

[0057] Furthermore, from the viewpoint of making it easier to adjust the surface resistivity of the laminated piezoelectric material to the above range, the ratio (T2 / T1) of the thickness of the hard coat layer (T2) to the thickness of the antistatic layer (T1) can be, for example, 3 to 26, depending on the surface resistivity of the antistatic layer. The smaller the above ratio, the thinner the hard coat layer and the thicker the antistatic layer, so that the surface resistivity measured on the hard coat layer can be lowered.

[0058] The thickness of each layer constituting the multilayer piezoelectric material can be measured using a spectroscopic interferometric film thickness gauge (for example, Hamamatsu Photonics' "Optical NanoGauge C13027-11"). The refractive index of each layer can be measured by the method described in JIS K7142, for example, by setting the refractive index of the substrate to 1.42 and the refractive index of the coating film to 1.50. Then, the thickness of each layer can be measured at three or more points at 5 mm intervals within a range including the center of the surface of the multilayer piezoelectric material, and the arithmetic mean value of these measurements can be obtained as the thickness of each layer.

[0059] 1-4. Layer configuration The antistatic layer and hard coat layer in the laminated piezoelectric material may each consist of one or more layers. Furthermore, the laminated piezoelectric material may have other layers besides those mentioned above. However, from the viewpoint of easily obtaining high antistatic properties, it is preferable that the antistatic layer and the hard coat layer are in contact with each other.

[0060] For example, a multilayer piezoelectric material can have the following layer configuration. Piezoelectric film / Antistatic layer / Hard coat layer Hard coat layer / Piezoelectric film / Antistatic layer / Hard coat layer

[0061] 1-5. Physical Properties (Surface resistivity) The laminated piezoelectric material according to this embodiment includes an antistatic layer, thereby reducing its surface resistivity. Specifically, the surface resistivity measured on the hard coat layer of the laminated piezoelectric material is 1.0 × 10⁻⁶. 6 Ω / sq. or more 1.0×10 12 The surface resistivity of the laminated piezoelectric material is less than or equal to Ω / sq. 1.0 × 10⁻⁶ 12 If the surface resistivity is Ω / sq. or less, sufficient antistatic properties are easily obtained. The above surface resistivity of the multilayer piezoelectric material is 1.0 × 10⁻⁶. 6 A surface resistivity of Ω / sq. or higher makes it easier to suppress unintended electrostatic discharge. From a similar perspective, the above surface resistivity of a multilayer piezoelectric material is 1.0 × 10⁻⁶. 8 Ω / sq. or more 5.0×10 11 It is more preferable that the resistivity is Ω / sq. or less. The surface resistivity of the laminated piezoelectric material can be measured in the same way as the surface resistivity of the antistatic layer.

[0062] The surface resistivity of a multilayer piezoelectric material can be adjusted primarily by the surface resistivity of the antistatic layer and the thickness of the hard coat layer. Lowering the surface resistivity of the antistatic layer and reducing the thickness of the hard coat layer tends to lower the surface resistivity of the multilayer piezoelectric material.

[0063] (Total light transmittance) From the viewpoint of application to touch panels mounted on image display devices, it is preferable that the laminated piezoelectric material has high transparency. Specifically, the total light transmittance of the laminated piezoelectric material is preferably 85% or more, and more preferably 90% or more.

[0064] The total light transmittance of a multilayer piezoelectric material can be measured using a haze meter (e.g., NDH7000SP II, manufactured by Nippon Denshoku Industries Ltd.) in accordance with the method described in JIS K 7361-1.

[0065] The total light transmittance of a laminated piezoelectric material can be adjusted by the thickness of the antistatic layer and the average particle size of the particles contained in the hard coat layer. For example, reducing the thickness of the antistatic layer makes coating irregularities less likely and tends to increase the total light transmittance. Similarly, reducing the average particle size of the particles in the hard coat layer also tends to increase the total light transmittance.

[0066] (Piezoelectric constant of laminated piezoelectric material) Piezoelectric constant d of a multilayer piezoelectric material 33 The piezoelectric constant d of the multilayer piezoelectric material is adjusted to be between 7 pC / N and 40 pC / N. 33 When the piezoelectric constant d of a laminated piezoelectric material is 7 pC / N or higher, the amount of charge generated by the piezoelectric effect is sufficient, making it easier to obtain high pressure sensitivity. 33 If the piezoelectric constant d of a laminated piezoelectric material is 40 pC / N or less, surface irregularities on the film caused by polarization treatment, for example, can be further reduced, thereby reducing appearance defects. From a similar viewpoint, 33 It is more preferably 10 pC / N or more and 40 pC / N or less, even more preferably 10 pC / N or more and 27 pC / N or less, and particularly preferably 13 pC / N or more and 24 pC / N or less.

[0067] Piezoelectric constant d of a multilayer piezoelectric material 33 This is mainly due to the piezoelectric constant d of the piezoelectric film. 33 It can be adjusted by the piezoelectric constant d of the piezoelectric film. 33 When the value is high, the piezoelectric constant d of the laminated piezoelectric material 33 The price tends to be high as well.

[0068] 1-6.Effect The laminated piezoelectric material according to the above embodiment has a piezoelectric constant d 33 Because it contains a piezoelectric film in a predetermined quantity or more, it has high piezoelectric properties. Furthermore, the laminated piezoelectric material has a laminated structure consisting of an antistatic layer and a hard coat layer having a predetermined or higher Rz, and the surface resistivity of the hard coat layer of the laminated piezoelectric material is adjusted to be below a predetermined level. This makes it possible to achieve both static electricity resistance and antiblocking properties. Furthermore, the thickness of the antistatic layer is adjusted to below a predetermined level. This reduces unevenness in the application of the antistatic layer caused by surface irregularities of the piezoelectric film containing fluororesin, thereby suppressing coating blemishes. As a result, a decrease in visibility can be suppressed.

[0069] 2. Manufacturing method of multilayer piezoelectric material The laminated piezoelectric material according to this embodiment can be manufactured by (1) preparing a piezoelectric film containing a fluororesin, (2) applying an antistatic material to at least one surface of the prepared piezoelectric film and then drying it to form an antistatic layer, and (3) applying a curable resin composition onto the antistatic layer and then curing it to form a hard coat layer. The piezoelectric film, antistatic layer, and hard coat layer are the piezoelectric film, antistatic layer, and hard coat layer described above, respectively.

[0070] (1) Steps to prepare the piezoelectric film Piezoelectric films containing fluororesin may be commercially available or manufactured.

[0071] When manufacturing a piezoelectric film containing a fluororesin, the piezoelectric film can be obtained through a process of polarization treatment of the film containing the fluororesin. The film containing the fluororesin may be a stretched film or an unstretched film. In this embodiment, from the viewpoint of exhibiting a high piezoelectric effect, it is preferable to stretch the film containing the fluororesin and then perform the polarization treatment.

[0072] Films containing fluororesins can be manufactured by any method, such as melt extrusion (extrusion molding) or solution casting. Among these methods, it is preferable to manufacture films containing fluororesins by melt extrusion, as this makes it easier to obtain piezoelectric films of a certain thickness or greater. In melt extrusion, the fluororesin and any additives are heated and melted in the cylinder of an extruder, and then extruded from the die to obtain the film.

[0073] The resulting film has a structure in which α-type crystals (with a helical main chain) and β-type crystals (with a planar zigzag main chain) are mixed. The β-type crystals have a large polarization structure. By stretching the film, the α-type crystals can be converted into β-type crystals, and the stretching process is preferably performed as needed to convert the fluororesin into β-type crystals. The stretching direction may be the TD direction or the MD direction, with the MD direction being more preferable.

[0074] The stretching method is not particularly limited and can be carried out using known stretching methods such as the tenter method or the drum method.

[0075] The stretching ratio is, for example, between 3.0 and 6.0 times. A stretching ratio of 3.0 times or higher makes it easier to adjust the film thickness and polarity to a more appropriate range. A stretching ratio of 3.0 times or higher allows for sufficient dislocation reactions in the β-type crystals, resulting in higher piezoelectricity and improved transparency. A stretching ratio of 6.0 times or lower further suppresses breakage due to stretching.

[0076] The resulting stretched film is subjected to polarization treatment. Polarization treatment can be performed, for example, by applying a DC voltage between a ground electrode and a needle electrode. The voltage can be adjusted according to the thickness of the stretched film, but for example, it can be between 1kV and 50kV.

[0077] Thus, in this embodiment, a piezoelectric film can be obtained by polarization treatment of a stretched film.

[0078] (2) Step of forming an antistatic layer After applying a curable composition containing, for example, the conductive material described above, to the obtained piezoelectric film, it is dried and cured to form an antistatic layer.

[0079] The above antistatic material may further contain water or a solvent. Examples of solvents include alcohol-based solvents such as methanol, ethanol, and isopropyl alcohol.

[0080] The coating method is not particularly limited and may be any of the following: spin coating, gravure coating, die coating, bar coating, dip coating, etc.

[0081] The drying method involves heating the coated antistatic material. The heating temperature is preferably above a temperature that can remove the solvent and below the heat distortion temperature of the fluororesin constituting the piezoelectric film, for example, it can be between 100°C and 150°C. The heat distortion temperature can be measured, for example, in accordance with JIS K 7191-2:2015.

[0082] (3) Process of forming a hard coat layer After applying the coating solution containing the above-mentioned curable composition onto the obtained antistatic layer, it is dried and cured to form a hard coat layer.

[0083] The above coating solution may further contain a diluent solvent as needed. A diluent solvent with a polarity similar to that of the particles is preferred. Examples of diluent solvents include organic solvents such as alcohol-based solvents, ketone-based solvents, ester-based solvents, carbonate-based solvents, and aromatic solvents.

[0084] The coating solution can be applied using the same method as described above. The coating solution can also be dried using the same method as described above. The heating temperature can be any temperature that allows the solvent to volatilize and is below the heat distortion temperature of the fluororesin constituting the piezoelectric film, for example, 60°C to 100°C.

[0085] Curing may be performed by heat or by ionizing radiation. Curing by ionizing radiation can be carried out by irradiation with ultraviolet light or electron beams. Furthermore, curing by heat and curing by ionizing radiation may be used in combination.

[0086] 3.Applications The laminated piezoelectric material according to this embodiment can be used in a variety of applications. In particular, because the laminated piezoelectric material according to this embodiment exhibits high piezoelectricity while having high transparency and visibility, it can be preferably used as a pressure sensor for touch panels mounted on various electronic devices. [Examples]

[0087] The present invention will be further described below with reference to examples and comparative examples. The technical scope of the present invention is not limited thereto.

[0088] 1. Evaluation of physical properties (1) Layer thickness The thickness of each layer was measured using a spectroscopic interferometric film thickness gauge (Hamamatsu Photonics "Optical NanoGauge C13027-11"). The thickness of each layer was measured at 30 points at 5 mm intervals within a range including the center of the laminated piezoelectric surface, and the arithmetic mean was calculated. The refractive index of each layer was set according to the material of each layer: 1.42 for the piezoelectric film containing PVDF, 1.50 for the antistatic layer, and 1.50 for the hard coat layer.

[0089] (2) Particle size The surface of the hard coat layer of the multilayer piezoelectric material was observed using a scanning electron microscope ("SU3800," manufactured by Hitachi High-Tech Corporation) under conditions of an acceleration voltage of 2.0 kV and a magnification of 50,000x. Ten points were measured, and the average of these measurements was used as the particle size of the nano-inorganic particles.

[0090] (3) Piezoelectric constant (Piezoelectric constant d) 33 ) Direct quasi-static method (d 33Piezoelectric constant d of piezoelectric ceramics by the Meter method, Berlin coat method 33 The test method conforms to ISO 19622:2018 and the piezoelectric constant d 33 The piezoelectric constant d of the multilayer piezoelectric material was measured. Specifically, the piezoelectric constant d of the multilayer piezoelectric material was measured. 33 The piezoelectric constant d was measured using a piezoelectric constant measuring device ("Piezometer System PM300", manufactured by PIEZOTEST). The sample was clipped at 1N, and the generated charge was read when a force of 0.15N and 110Hz was applied. 33 The measured value is obtained at a measurement temperature of 25°C, and the value will be positive or negative depending on whether the front or back of the film being measured is the front or back side; however, in this specification, the absolute value is given.

[0091] (d 14 ) Al was deposited on both surfaces of the laminated piezoelectric material. The piezoelectric film was then cut into sections of 120 mm in a direction 45° to the stretching direction (MD direction) and 10 mm in a direction perpendicular to the 45° direction, resulting in a rectangular film measuring 120 mm x 10 mm. This was used as the sample for measurement. Next, the sample was set in a tensile testing machine with a chuck distance of 70 mm, ensuring it did not sag. Then, a periodic force was applied to the sample at a speed of 5 mm / min, alternating between 4 N and 9 N. To measure the amount of charge generated in the sample in response to the applied force, a capacitor with capacitance Qm (F) was connected in parallel to the sample, and the terminal voltage Vm of this capacitor Cm (95 nF) was measured via a buffer amplifier. The generated charge Q(C) was calculated as the product of the capacitor capacitance Cm and the terminal voltage Vm. Piezoelectric constant d 14 This was calculated using the following formula. d 14 =(2×t) / L×Cm·ΔVm / ΔF t: Sample thickness (m) L: Distance between chucks (m) Cm: Capacitance (F) of parallel connected capacitors ΔVm / ΔF: Ratio of the change in voltage across the capacitor terminals to the change in force.

[0092] 2. Fabrication and evaluation of multilayer piezoelectric materials [Example 1] (1) Fabrication of piezoelectric film A polyvinylidene fluoride film (manufactured by Kureha Corporation, a film containing 100% by mass of polyvinylidene fluoride homopolymer) was stretched to a ratio of 4.2 times in the MD direction. Polarization treatment was then performed by applying a DC voltage between the ground electrode and the needle electrode, increasing from 0kV to 11.0kV, to obtain a piezoelectric film with a thickness of 42μm. The piezoelectric constant d of the piezoelectric film was determined. 33 When measured using the method described above, the result was 15 pC / N.

[0093] (2) Formation of an antistatic layer A solution was applied to side A of the obtained piezoelectric film using a multicoater (Hirano Tecseed Co., Ltd.), which was a mixture of paint P-400MP-A (manufactured by Nagase ChemteX Corporation) containing PEDOT:PSS as a conductive polymer and paint P-400MP-B (manufactured by Nagase ChemteX Corporation) containing a crosslinking agent and a conductivity improver, in a 4:1 ratio. The mixture was then heat-treated at 130°C for 0.67 minutes to form an antistatic layer with a thickness of 50 nm on the piezoelectric film.

[0094] (3) Formation of the hard coat layer Next, a hard coat agent (BS-CH271, manufactured by Arakawa Chemical Industries, Ltd., with an average particle size of amorphous silica of 60 nm) was applied to the antistatic layer using a multi-coater, followed by heat treatment at 80°C for 2 minutes, and then subjected to an integrated light intensity of 200 mJ / cm². 2 A hard coat layer with a thickness of 700 nm was formed by photocuring with UV light. This resulted in a laminated piezoelectric material having a laminated structure of piezoelectric film / antistatic layer / hard coat layer.

[0095] [Example 2] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the thickness of the hard coat layer was changed to 2000 nm.

[0096] [Example 3] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the thickness of the antistatic layer was changed to 140 nm.

[0097] [Example 4] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the heat treatment conditions for forming the antistatic layer were changed to 120°C for 60 min.

[0098] [Example 5] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that a solution (C-169PF) was obtained by mixing paint C-169PF-A (manufactured by Nagase ChemteX Corporation), which contains single-walled carbon nanotubes, and paint C-169PF-B (manufactured by Nagase ChemteX Corporation), which contains a crosslinking agent, in a 3:2 ratio, onto side A of a piezoelectric film using a multicoater (manufactured by Hirano Tecseed Co., Ltd.), and then heat-treated at 130°C for 1 minute to form an antistatic layer.

[0099] [Example 6] A hard coat layer with a thickness of 700 nm was further formed on the B-side of the piezoelectric film of the laminated piezoelectric material prepared in Example 1, using the same method as in Example 1, to obtain a laminated piezoelectric material. This resulted in a laminated piezoelectric material having a laminated structure of hard coat layer / piezoelectric film / antistatic layer / hard coat layer.

[0100] [Example 7] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the hard coating agent was changed to TYAB-M101 (an amorphous silica with an average particle size of 80 nm) manufactured by Toyo Chem Co., Ltd.

[0101] [Comparative Example 1] Neither the antistatic layer nor the hard coat layer was formed, and the piezoelectric film from Example 1 was used as is.

[0102] [Comparative Example 2] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the hard coat agent containing amorphous silica was replaced with a hard coat agent that does not contain amorphous silica (BS-575, manufactured by Arakawa Chemical Co., Ltd.).

[0103] [Comparative Example 3] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the thickness of the antistatic layer was changed to 5 nm.

[0104] [Comparative Example 4] A laminated piezoelectric material was obtained in the same manner as in Example 1, except that the thickness of the antistatic layer was changed to 260 nm.

[0105] [Comparative Example 5] The antistatic layer was formed in the same manner as in Example 1, except that the heat treatment conditions for forming the antistatic layer were changed to 160°C for 60 minutes. However, the appearance of the laminated piezoelectric material was poor, and the hard coat layer could not be formed.

[0106] [Comparative Example 6] An attempt was made to form an antistatic layer in the same manner as in Example 1, except that the heat treatment conditions for forming the antistatic layer were changed to 80°C and 0.67 minutes. However, the hardening of the antistatic layer was insufficient, and the formation of the hard coat layer was not achieved.

[0107] [Comparative Example 7] An antistatic hard coat agent (MT-3 / manufactured by Arakawa Chemical Co., Ltd.) was applied to the piezoelectric film of Example 1 using a multi-coater, and after heat treatment at 80°C for 2 minutes, 400 mJ / cm² was applied using a UV irradiation device CSOT-40 (manufactured by GS Yuasa Corporation). 2 A laminated piezoelectric material was obtained by irradiating it with UV light using the accumulated light intensity. This resulted in a laminated piezoelectric material having a laminated structure of piezoelectric film / antistatic hard coat layer.

[0108] [Comparative Example 8] (1) Preparation of a piezoelectric film containing polylactic acid To 100 parts by mass of polylactic acid (product name: Ingeo™ biopolymer) manufactured by NatureWorks LLC, 1.0 part by mass of a stabilizer [a mixture of 10 parts by mass of Stabaxol P400 manufactured by Rhein Chemie, 70 parts by mass of Stabaxol I manufactured by Rhein Chemie, and 20 parts by mass of Carbodilite LA-1 manufactured by Nisshinbo Chemical] was added and the raw material was prepared by dry blending. Next, the raw material was placed in the hopper of an extrusion molding machine, extruded from the T-die while being heated to 210°C, and brought into contact with a cast roll at 50°C to produce a pre-crystallized film with a thickness of 150 μm. This pre-crystallized film was uniaxially stretched to 3.5 times its original size in the MD direction at 70°C using a roll-to-roll method to obtain a uniaxially oriented film. The thickness of the obtained uniaxially oriented film was 49.2 μm. The obtained uniaxially oriented film was then annealed by contacting it on a roll at 145°C for 15 seconds using a roll-to-roll method, followed by rapid cooling to produce a piezoelectric film containing polylactic acid. The piezoelectric constant d of the piezoelectric film was then determined. 14 When measured using the method described above, the result was 6 pC / N.

[0109] (2) Formation of an antistatic hard coat layer One side of the obtained piezoelectric film was coated with an antistatic hard coat paint (Shin-Etsu Polymer, Sepulzida® HC-A) using a multi-coater, dried at 60°C for 5 minutes, and then exposed to a metal halide lamp with an integrated light intensity of 1000 mJ / cm². 2 An antistatic hard coat layer was formed by irradiating it with ultraviolet light. As a result, a laminated piezoelectric material having a laminated structure of piezoelectric film / antistatic hard coat layer was obtained.

[0110] [evaluation] The surface resistivity, charge amount, blocking resistance, maximum surface height Rz, and total light transmittance of the obtained laminated piezoelectric material were evaluated by the following method.

[0111] (1)Surface resistivity A laminated piezoelectric material or piezoelectric film was cut to a size of 100 mm x 100 mm to obtain a sample. The surface resistivity on the hard coat layer of the sample was measured using a surface resistance meter F-109 (manufactured by HOZAN Corporation) in accordance with JIS 6911. The measurement conditions were an output of 100 W, and the value was read after 10 seconds.

[0112] (2) Charge The surface potential (kV) of a rolled film was measured using an electrostatic potential meter (Keyence SK-H050). The measurement was taken at a distance of 10 cm from the outer surface of the film on the roll.

[0113] (3) Blocking resistance Two test pieces measuring 10 cm in length and 10 cm in width were cut from a laminated piezoelectric material or piezoelectric film. The hard-coated surfaces of one test piece were placed on top of the other, and the degree of adhesion when the films were rubbed together was visually inspected and evaluated according to the following criteria. ○: No sticking ×: Sticking

[0114] (4) Maximum height Rz The maximum surface height Rz of the hard coat layer of the laminated piezoelectric material was measured using a surface roughness meter ("SURFCOM1500", manufactured by Tokyo Seimitsu Co., Ltd.) in accordance with the method compliant with JIS B 0601-2013. The maximum surface height Rz was measured at 10 arbitrary locations on the hard coat layer in the width direction (TD direction) of the laminated piezoelectric film, and the average value was calculated.

[0115] (5) Total light transmittance The total light transmittance of the laminated piezoelectric material was measured using a haze meter ("NDH7000SP II", manufactured by Nippon Denshoku Industries Ltd.) in accordance with the method described in JIS K 7361-1.

[0116] (6) Uneven color The color unevenness of the laminated piezoelectric material was evaluated according to the following criteria to determine whether it was visible to the naked eye along the MD direction. ○: No color unevenness is visible. ×: Color unevenness is visible.

[0117] (7) Piezoelectric constant of laminated piezoelectric material The piezoelectric constant d of the laminated piezoelectric material is determined in the same manner as described above. 33 or d 14 We measured it.

[0118] Table 1 shows the manufacturing conditions and layer configurations of the multilayer piezoelectric materials for Examples 1-7 and Comparative Examples 1-8. Table 2 shows the evaluation results of the multilayer piezoelectric materials for Examples 1-7 and Comparative Examples 2-4 and 7.

[0119] [Table 1]

[0120] [Table 2]

[0121] As shown in Table 2, the laminated piezoelectric materials of Comparative Examples 2 and 7, which have a hard coat layer with an Rz of less than 40 nm, exhibit poor blocking resistance. Furthermore, the piezoelectric film of Comparative Example 1, which lacks an antistatic layer, and the laminated piezoelectric material of Comparative Example 3, which has an antistatic layer thinner than 10 nm, have high surface resistivity and poor antistatic properties. In addition, the laminated piezoelectric material of Comparative Example 4, which has an antistatic layer thicker than 250 nm, exhibits sufficient antistatic properties, but color unevenness occurs. Finally, the piezoelectric constant of the laminated piezoelectric material of Comparative Example 8, which uses a piezoelectric film containing polylactic acid, is lower.

[0122] In contrast, the laminated piezoelectric materials of Examples 1 to 7 all exhibited high piezoelectric constants without color unevenness, demonstrating high blocking resistance and antistatic properties.

[0123] In particular, it is suggested that reducing the thickness of the hard coat layer further reduces the surface resistivity and improves antistatic properties (comparison between Examples 1 and 2).

[0124] Furthermore, it can be seen that the total light transmittance can be further increased by making the antistatic layer thinner (comparison between Examples 1 and 3).

[0125] This application claims priority under Japanese Patent Application No. 2023-48031, filed on 24 March 2023. All provisions of the said application are incorporated herein by reference. [Industrial applicability]

[0126] The laminated piezoelectric material of the present invention possesses high piezoelectricity, antiblocking properties, and antistatic properties without reducing visibility. Therefore, this laminated piezoelectric material can be suitably used as a pressure sensor for touch panels.

Claims

1. A laminated piezoelectric material, A piezoelectric film containing a fluororesin as its main component, An antistatic layer having a thickness of 10 nm to 250 nm is disposed on at least one surface of the piezoelectric film, The antistatic layer comprises a hard coat layer disposed on the aforementioned antistatic layer, the hard coat layer having a maximum surface height Rz of 40 nm or more and 150 nm or less. The surface resistivity of the laminated piezoelectric material, as measured on the hard coat layer, is 1.0 × 10⁻⁶. ６ Ω / sq. More than 1.0×10 １２ It is less than or equal to Ω / sq. The total light transmittance of the laminated piezoelectric material is 85% or more, and the piezoelectric constant d ３３ The value is between 7 pC / N and 40 pC / N. Multilayer piezoelectric material.

2. The aforementioned fluorine-based resin is a polymer that mainly contains constituent units derived from vinylidene fluoride. The laminated piezoelectric material according to claim 1.

3. The aforementioned fluorine-based resin is a polyvinylidene fluoride homopolymer. The laminated piezoelectric material according to claim 1.

4. The antistatic layer contains carbon nanotubes, The laminated piezoelectric material according to claim 1.

5. The thickness of the hard coat layer is 300 nm or more and 3000 nm or less. The laminated piezoelectric material according to claim 1.

6. The hard coat layer contains silica particles with an average particle diameter of 10 nm to 200 nm. The laminated piezoelectric material according to claim 1.

7. A method for manufacturing a laminated piezoelectric body according to claim 1, It contains a fluororesin as its main component, and has a piezoelectric constant d ３３ A step of preparing a piezoelectric film having a density of 7 pC / N or more and 40 pC / N or less, The steps include applying an antistatic material to at least one surface of the piezoelectric film to form an antistatic layer, The process includes applying a curable composition onto the antistatic layer and then curing it to form a hard coat layer. A method for manufacturing a multilayer piezoelectric material.

8. In the step of preparing the piezoelectric film, A film containing a fluororesin as the main component is formed by extrusion molding. A method for manufacturing a laminated piezoelectric body according to claim 7.

9. In the step of preparing the piezoelectric film, A film containing a fluororesin as the main component is stretched and then subjected to polarization treatment. A method for manufacturing a laminated piezoelectric body according to claim 7.

10. In the step of forming the antistatic layer, The piezoelectric film coated with the antistatic material is heat-treated at 100°C to 150°C and dried. A method for manufacturing a laminated piezoelectric body according to claim 7.

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