Organic piezoelectric thin films, piezoelectric bodies, and methods for manufacturing organic piezoelectric thin films.

Abstract

The subject of this invention is to provide an organic piezoelectric thin film with high piezoelectricity and high transparency. The organic piezoelectric thin film of this invention has a total light transmittance of 90% or more, an internal haze value of 0.2% / μm or less per unit film thickness, or an internal haze value of 4% or less, and a piezoelectric constant d33 of 10 pC / N or more after heating at 110°C for 10 minutes.

Description

Technical Field

[0001] This invention relates to an organic piezoelectric thin film. Prior Technology

[0002] Organic piezoelectric films are formed from polymers of organic materials and possess piezoelectric properties (the property of converting applied force into voltage, or the property of converting applied voltage into force). Organic piezoelectric films are used in various applications utilizing piezoelectricity [e.g., detectors, actuators, touch panels, haptic devices (devices that provide tactile feedback to the user), vibration-generating devices, loudspeakers, microphones]. In applications where visibility is critical (e.g., windows, panels), in order to avoid compromising visibility, in addition to high transparency, low hysteresis (phase difference) is also required. For example, when an organic piezoelectric film is placed on a panel, sufficient light transmittance is required. Furthermore, to avoid interference with components constituting the panel (e.g., polarizing plates, phase difference plates), low hysteresis is required.

[0003] As an organic piezoelectric film, polyvinyl fluoride (PVDF) film is typically used. In order to impart good piezoelectricity to the PVDF film, the PVDF film must be uniaxially stretched and subjected to polarization treatment (e.g., Patent Document 1). [Previous Technical Documents] [Patent Literature]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2008-171935 Summary of the Invention

[0005] [The problem this invention aims to solve] However, uniaxially stretched PVDF films exhibit greater in-plane non-uniformity in film thickness and piezoelectricity, as well as higher hysteresis. Furthermore, due to the trade-off between piezoelectricity and transparency, obtaining a film that achieves both high piezoelectricity and high transparency is difficult, especially when the film has a thickness suitable for use as a self-supporting film, making this balance even more challenging. Moreover, heating the film reduces both piezoelectricity and transparency, further complicating the process of achieving this balance.

[0006] The purpose of this invention is to provide an organic piezoelectric thin film with high voltage and high transparency. [Methods for solving problems]

[0007] The present invention includes the following types. Item 1. An organic piezoelectric thin film, characterized in that, The total light transmittance is over 90%. The internal haze value per unit film thickness is below 0.2% / μm. The piezoelectric constant d33 after heating at 110℃ for 10 minutes is above 10 pC / N. Item 2. The organic piezoelectric film of item 1 contains a fluorinated vinylidene copolymer film. Item 3. As in the organic piezoelectric film of item 2, the aforementioned fluorinated vinylidene copolymer is selected from at least one group consisting of fluorinated vinylidene / tetrafluoroethylene copolymer and fluorinated vinylidene / trifluoroethylene copolymer. Item 4. For example, in the organic piezoelectric film of item 2 or 3, the composition ratio of fluorinated vinylidene in the aforementioned fluorinated vinylidene copolymer is in the range of 60 to 85 mol%. Item 5. Organic piezoelectric thin films, such as those in any of items 1 to 4, wherein the film thickness is 10 nm to 1000 μm. Item 6. Organic piezoelectric thin films, such as those in any of items 1 to 5, wherein the hysteresis is less than 500 nm. Item 7. Organic piezoelectric thin films, such as those in any of items 1 to 6, wherein the YI value is 4 or less. Item 8. Organic piezoelectric thin films, such as those in any of items 1 to 7, wherein the residual polarization is 40 mC / m² or higher. Item 9. For any of the organic piezoelectric thin films in items 1 to 8, where the thin film sample is directly loaded into a sample holder with an opening, and the diffraction angle 2θ covers the range of 10 to 40°, the X-ray diffraction pattern obtained during X-ray diffraction measurement is as follows: The base line is set by connecting the diffraction intensity at a diffraction angle of 10° and 2θ at a diffraction angle of 25°. The region enclosed by the baseline and the diffraction intensity curve is separated into two symmetrical peaks by profile fitting. Among them, the peak with the larger diffraction angle 2θ is identified as the crystalline peak, and the peak with the smaller diffraction angle 2θ is identified as the amorphous halo peak. A crystallinity of 40% or higher is expressed as 100 × (area of ​​crystalline peaks) / (sum of the area of ​​crystalline peaks and the area of ​​amorphous halo peaks). Item 10. An organic piezoelectric thin film, characterized in that, The film contains a fluorinated vinylidene copolymer, and the fluorinated vinylidene copolymer contains needle-like crystals. The maximum crystal length is below 800 nm. The piezoelectric constant d33 after heating at 110℃ for 10 minutes is above 10 pC / N. Item 11. For example, the organic piezoelectric thin film in item 10 has an average crystal length of less than 450 nm. Item 12. As in item 10 or 11, the organic piezoelectric thin film, wherein, When a thin film sample is directly loaded into a sample holder with an opening, and the diffraction angle 2θ ranges from 10° to 40°, the resulting X-ray diffraction pattern is as follows: The base line is set by connecting the diffraction intensity at a diffraction angle of 10° and 2θ at a diffraction angle of 25°. The region enclosed by the baseline and the diffraction intensity curve is separated into two symmetrical peaks by profile fitting. Among them, the peak with the larger diffraction angle 2θ is identified as the crystalline peak, and the peak with the smaller diffraction angle 2θ is identified as the amorphous halo peak. A crystallinity of 40% or higher is expressed as 100 × (area of ​​crystalline peaks) / (sum of the area of ​​crystalline peaks and the area of ​​amorphous halo peaks). Item 13. The organic piezoelectric film of any one of items 1 to 12 is used in one or more of the group selected from the group consisting of detectors, actuators, touch panels, tactile devices, vibration power generation devices, loudspeakers and microphones. Item 14. A piezoelectric material, which is a laminate, and possesses: Organic piezoelectric thin films such as any of items 1 to 12, and An electrode disposed on the surface of at least one of the aforementioned organic piezoelectric films. Item 15. A method for manufacturing an organic piezoelectric thin film, comprising steps A to C. Step A involves fabricating non-stretched and non-polar fluorinated vinylidene polymer films using a casting method. Step B of polarizing the aforementioned non-stretched and non-polarized vinylidene fluoride-based polymer film; and At any point in time, step C of heat-treating the non-stretched vinylidene fluoride-based polymer film in step B, Step A includes step A3 of heating within the range of (T - 10)°C to (T + 5)°C when the melting point of the vinylidene fluoride-based polymer is set to T°C. [Advantages of the Invention]

[0008] By the present invention, it is possible to provide an organic piezoelectric film having high piezoelectricity and high transparency. Furthermore, an organic piezoelectric film having high piezoelectricity and high transparency even after heating (for example, heating at 110°C for 10 minutes) is provided. Brief Explanation of the Drawings

[0009] [FIG. 1] is a schematic diagram showing an overview of a manufacturing apparatus used in the manufacture of the piezoelectric film of the embodiment. [FIG. 2] is a diagram showing scanning electron microscope images of Example 1 and Comparative Example 3. Embodiment

[0010] All journals, patents, and patent applications cited in this specification are directly incorporated herein by reference.

[0011] Terms The symbols and abbreviations in this specification, unless otherwise specified, can be construed in accordance with the context of this specification to mean the meanings commonly used in the technical field to which the present invention pertains.

[0012] The phrase "comprising" in this specification includes the meanings of the phrases "consisting essentially of" and "having".

[0013] The steps, processes, or operations described in this specification, unless otherwise specified, can be carried out at room temperature.

[0014] In this specification, room temperature can mean a temperature within the range of 10 to 40°C.

[0015] In this specification, the notation "C n-m" (where n and m are each integers and n < m), as is generally understood by those skilled in the art, means having a carbon number of n or more and m or less.

[0016] Organic piezoelectric film The organic piezoelectric film of this invention contains a piezoelectric polymer of organic matter. Examples of piezoelectric polymers include, but are not limited to, fluorinated vinylidene polymers, cyanide vinylidene polymers, odd-chain nylon, and polylactic acid. The piezoelectric polymer can also be a single type or a combination of two or more types. Fluorinated vinylidene polymers are preferred as piezoelectric polymers. Fluorinated vinylidene polymers are preferably polarized fluorinated vinylidene polymers. In this specification, the term "polarized" means imparting a charge to the surface. That is, the polarized fluorinated vinylidene polymer can be a dielectric, a piezoelectric, or a strongly inductive material.

[0017] A fluorinated vinylidene polymer is a polymer in which at least vinylidene (VDF) is used as a polymerizing component (monomer). A fluorinated vinylidene polymer can be a polymer of vinylidene alone (polyfluorinated vinylidene), or a copolymer of vinylidene with one or more monomers capable of copolymerizing with vinylidene (fluorinated vinylidene copolymer). The one or more monomers capable of copolymerizing with vinylidene can be one or more halogenated monomers, one or more non-halogenated monomers, or combinations thereof.

[0018] Examples of halogenated monomers include fluorinated vinyl (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropylene (HFP), 1-chloro-1-fluoroethylene (1,1-CFE), 1-chloro-2-fluoroethylene (1,2-CFE), 1-chloro-2,2-difluoroethylene (CDFE), chlorotrifluoroethylene (CTFE), trifluorovinyl monomers, 1,1,2-trifluorobutene-4-bromo-1-butene, 1,1,2-trifluorobutene-4-silane-1-butene, perfluoropropyl vinyl ether (PPVE), perfluoroacrylates, 2,2,2-trifluoroethyl acrylate, and 2-(perfluorohexyl)ethyl acrylate.

[0019] Examples of non-halogenated monomers include α-olefins (e.g., ethylene, propylene); unsaturated dicarboxylic acids or their derivatives (e.g., maleic acid, water maleic anhydride); vinyl ethers (e.g., ethyl vinyl ether); propylene ethers (e.g., propylene-based glycidyl ether); vinyl esters (e.g., vinyl acetate); acrylic acid or its esters; methacrylic acid or its ethers, etc.

[0020] The fluorinated vinylidene polymer is preferably a copolymer of vinylidene and one or more monomers capable of copolymerizing with vinylidene (fluorinated vinylidene copolymer). In this copolymer, the lower limit of the vinylidene composition ratio [the molar ratio of repeating units (-CH₂-CF₂-) from vinylidene relative to the total repeating unit] is preferably 65 mol%, 66 mol%, 67 mol%, 68 mol%, 69 mol%, 70 mol%, 71 mol%, 72 mol%, or 73 mol]. The upper limit of the vinylidene composition ratio in this copolymer is preferably 85 mol%, 84 mol%, 83 mol%, or 82 mol.

[0021] The copolymer is preferably selected from at least one of the groups consisting of vinylidene / trifluoroethylene copolymer and vinylidene / tetrafluoroethylene copolymer.

[0022] In the vinylene fluoride / trifluoroethylene copolymer, the lower limit of the composition ratio of vinylene fluoride to trifluoroethylene [the molar ratio of repeating units from vinylene fluoride (-CH₂-CF₂-) to repeating units from trifluoroethylene (-CF₂-CHF-)] is preferably 65 / 35, more preferably 70 / 30, and even more preferably 73 / 27. The upper limit of this composition ratio is preferably 85 / 15, and even more preferably 82 / 18. This composition ratio is preferably in the range of 65 / 35 to 85 / 15, more preferably in the range of 70 / 30 to 85 / 15, and even more preferably in the range of 73 / 27 to 82 / 18.

[0023] The vinylene fluoride / trifluoroethylene copolymer can also be a copolymer in which only vinylene fluoride and trifluoroethylene are polymerizable components, or it can be a copolymer in which vinylene fluoride, trifluoroethylene, and one or more other monomers are polymerizable components (e.g., ternary copolymers, quaternary copolymers). The one or more other monomers can be selected from, for example, the monomers exemplified as "one or more monomers capable of copolymerizing with vinylene fluoride" (but excluding trifluoroethylene). The lower limit of the composition ratio of the one or more other monomers is, for example, 0.01 mol%, 0.05 mol%, or 0.1 mol%. The upper limit of the composition ratio of the one or more other monomers is, for example, 10 mol%, 5 mol%, or 1 mol.

[0024] In the vinylene fluoride / tetrafluoroethylene copolymer, the lower limit of the composition ratio of vinylene fluoride to tetrafluoroethylene [the molar ratio of repeating units (-CH₂-CF₂-) from vinylene fluoride to repeating units (-CF₂-CF₂-) from tetrafluoroethylene] is preferably 65 / 35, further preferably 66 / 34, and even more preferably 67 / 33. The upper limit of this composition ratio is preferably 85 / 15, further preferably 82 / 18, and even more preferably 80 / 20. This composition ratio is preferably in the range of 65 / 35 to 85 / 15, further preferably in the range of 66 / 34 to 82 / 18, and even more preferably in the range of 67 / 33 to 80 / 20.

[0025] The vinylene fluoride / tetrafluoroethylene copolymer can also be a copolymer in which only vinylene fluoride and tetrafluoroethylene are polymerizable components, or it can be a copolymer in which vinylene fluoride, tetrafluoroethylene, and one or more other monomers are polymerizable components (e.g., ternary copolymers, quaternary copolymers). The one or more other monomers can be selected from, for example, the monomers exemplified as "one or more monomers capable of copolymerizing with vinylene fluoride" (but excluding tetrafluoroethylene). The lower limit of the composition ratio of the one or more other monomers is, for example, 0.01 mol%, 0.05 mol%, or 0.1 mol%. The upper limit of the composition ratio of the one or more other monomers is, for example, 10 mol%, 5 mol%, or 1 mol.

[0026] The weight-average molecular weight (Mw) of the aforementioned piezoelectric polymer is preferably between 50,000 and 2,000,000. By setting it within the above range, it is preferable to have both excellent processability and superior piezoelectricity. In particular, a weight-average molecular weight of 100,000 to 2,000,000 is preferred. Furthermore, a lower limit of 200,000 is even better, 300,000 is even better, and 600,000 is ideal. An upper limit of 1,900,000 is even better, 1,800,000 is even better, and 1,100,000 is ideal. Furthermore, the weight-average molecular weight (Mw) can be determined using, for example, a gel permeation chromatography (GPC) instrument. Specifically, the molecular weight can be calculated based on the results obtained by GPC under the following conditions, using standard polystyrene as a benchmark. (condition) GPC equipment: TOSOH AS-8010, CO-8020 and SIMADZURID-10A Tubing string: GMHHR-H 3 tubes Solvent: Dimethylformamide [DMF] Sample concentration: 0.05% by mass

[0027] The melting point of a piezoelectric polymer is not particularly limited to any temperature that does not deteriorate the substrate. It can be, for example, above 100°C, above 105°C, above 110°C, or above 115°C, or below 200°C, below 190°C, below 180°C, below 170°C, or below 160°C. The melting point is determined, for example, by using differential scanning calorimetry (DSC) according to the method for determining the transfer temperature of plastics (JIS K7121), and taking the maximum value from the heat of melting curve obtained when the temperature is increased at a rate of 10°C / minute.

[0028] In the organic piezoelectric thin film of the present invention, the lower limit of the piezoelectric polymer content is, for example, 10%, 20%, 30%, 40%, 50%, 60%, or 70% by mass, preferably 80% by mass, even more preferably 85% by mass, and even more preferably 90% by mass. The upper limit of this content is not particularly limited, for example, 100% by mass or 99% by mass.

[0029] The organic piezoelectric film of the present invention can further contain polymers other than piezoelectric polymers. Examples of polymers other than piezoelectric polymers include polycarbonate, polyesters (e.g., polyethylene terephthalate, polyethylene naphthalate), polyamide, silicone resins, polyethers, polyvinyl acetate, acrylic resins, methacrylic resins, and polyolefins (e.g., polyethylene, polypropylene). The content of polymers other than piezoelectric polymers is not particularly limited, but relative to 100 parts by weight of the piezoelectric polymer, it is, for example, 100 parts by weight or less, 80 parts by weight or less, 60 parts by weight or less, 40 parts by weight or less, 20 parts by weight or less, 10 parts by weight or less, 5 parts by weight or less, or 1 part by weight or less.

[0030] The organic piezoelectric film of the present invention may also be a film containing a piezoelectric polymer (or a piezoelectric polymer and a polymer other than a piezoelectric polymer), or a film containing a piezoelectric polymer and additives. A specific example of the latter film is a film in which the piezoelectric polymer contains dispersed inorganic matter.

[0031] Specific examples of additives include one or more of the following: fillers (e.g., inorganic oxide particles), affinity enhancers, heat stabilizers, ultraviolet absorbers, pigments, etc. More suitable examples include inorganic oxide particles and combinations of inorganic oxide particles and affinity enhancers.

[0032] Suitable examples of inorganic oxide particles include at least one selected from the group of inorganic oxide particles (B1) to (B3).

[0033] [Inorganic oxide particles (B1)] (B1) refers to particles of oxides of metallic elements belonging to Groups 2, 3, 4, 12, or 13 of the periodic table, or inorganic oxide composite particles thereof. Examples of the aforementioned metallic elements include Be, Mg, Ca, Sr, Ba, Y, Ti, Zr, Zn, and Al. (B1) is more suitable for particles containing oxides of Be, Al, Mg, Y and Zr. The aforementioned particles are more widely used and cheaper, and are also preferred for their higher volume resistivity. A more suitable example of (B1) includes particles of at least one inorganic oxide selected from the group consisting of Al₂O₃, MgO, ZrO₂, Y₂O₃, BeO, and MgO·Al₂O₃. The aforementioned particles are preferred for their higher volume resistivity. A more suitable example of (B1) is Al₂O₃ with a γ-type crystalline structure. The aforementioned particles are preferred for their large specific surface area and good dispersibility with piezoelectric polymers.

[0034] [Inorganic oxide particles (B2)] (B2) is the formula: M 1 a1M 2 b1O c1 (In the formula, M1 is a group 2 metallic element; M2 is a group 4 metallic element; a1 is in the range of 0.9 to 1.1; b1 is in the range of 0.9 to 1.1; c1 is in the range of 2.8 to 3.2; M1 and M2 can each be one or more metallic elements) Inorganic composite oxide particles are represented. Suitable examples of the aforementioned group 2 metal elements include Mg, Ca, Sr and Ba. Suitable examples of the aforementioned four groups of metallic elements include Ti and Zr. (B2) A more suitable example includes particles of at least one inorganic oxide selected from the group consisting of BaTiO3, SrTiO3, CaTiO3, MgTiO3, BaZrO3, SrZrO3, CaZrO3 and MgZrO3. The aforementioned particles are preferred to have a higher volume resistivity.

[0035] [Inorganic oxide particles (B3)] (B3) refers to oxides of metallic elements in groups 2, 3, 4, 12, or 13 of the periodic table, as well as inorganic oxide composite particles of silicon oxide. Examples of the aforementioned metallic elements include Be, Mg, Ca, Sr, Ba, Y, Ti, Zr, Zn, and Al. (B3) is a specific example of at least one inorganic oxide particle in the group consisting of 3Al2O3･2SiO2, 2MgO･SiO2, ZrO2･SiO2 and MgO･SiO2.

[0036] Inorganic oxide particles do not necessarily need to have high electrophoretic properties and can be appropriately selected according to the application of the organic piezoelectric thin film. For example, if widely used and inexpensive inorganic oxide particles [e.g., (B1), especially Al2O3 particles and MgO particles] are used, it is possible to try to increase the volume resistivity. The specific electrophoretic properties (1 kHz, 25 °C) of such inorganic oxide particles (B1) are usually less than 100, preferably in the range of 10 or less.

[0037] As inorganic oxide particles, to enhance the electrophoretic activity, inorganic oxide particles with strong electrophoretic activity [e.g., specific electrophoretic activity (1 kHz, 25 °C) of 100 or higher] [e.g., (B2) and (B3)] may also be used. Inorganic materials constituting strongly electrophoretic inorganic oxide particles include, but are not limited to, composite metal oxides, their composites, solid solutions, and sol-gels.

[0038] The specific electrophoresis of inorganic oxide particles (25°C, 1kHz) is preferably in the range of 10 or higher. From the viewpoint of improving the electrophoresis of organic piezoelectric thin films, the aforementioned specific electrophoresis is preferably in the range of 100 or higher, and even more preferably in the range of 300 or higher. There is no particular upper limit to the aforementioned specific electrophoresis, but it is usually around 3000. The specific electrophoresis (ε) of inorganic oxide particles (25℃, 1kHz) is determined by measuring the capacity (C) using an LCR meter, and calculated from the capacity, electrode area (S), and sintered body thickness (d) using the formula C=εε0×S / d (ε0: electrophoresis of vacuum).

[0039] The inorganic oxide particles preferably have a small average primary particle size, especially nanoparticles with an average primary particle size of less than 1 μm. By uniformly dispersing such inorganic oxide nanoparticles, the electrical insulation of the organic piezoelectric film can be significantly improved with only a small amount of mixing. The aforementioned average primary particle size is preferably less than 800 nm, more preferably less than 500 nm, and even more preferably less than 300 nm. Considering the difficulty of manufacturing, the difficulty of uniform dispersion, and the cost, the aforementioned average primary particle size is preferably greater than 10 nm, more preferably greater than 20 nm, and even more preferably greater than 50 nm. The average primary particle size of inorganic oxide particles was calculated using a laser diffraction and scattering particle size distribution measuring device LA-920 (trade name) (Horiba Seisakusho) or an equivalent.

[0040] Organic piezoelectric films are preferably transparent and free of inorganic oxide particles. However, without compromising transparency, they contain inorganic oxide particles in a range of 0.01 to 300 parts by mass relative to 100 parts by mass of the piezoelectric polymer, and more preferably in a range of 0.1 to 100 parts by mass. The lower limit of the aforementioned content for improving electrical insulation is preferably 0.1 parts by mass, more preferably 0.5 parts by mass, and even more preferably 1 part by mass. The aforementioned upper limit of the content, in order to ensure that the inorganic oxide particles are uniformly dispersed in the piezoelectric polymer and to prevent the reduction of electrical insulation (voltage resistance) and tensile strength, is preferably 200 parts by mass, more preferably 150 parts by mass, and even more preferably 100 parts by mass.

[0041] When organic piezoelectric films contain inorganic oxide particles, they can further contain affinity enhancers. Affinity enhancers can improve the affinity between inorganic oxide particles and piezoelectric polymers, enabling the inorganic oxide particles to be uniformly dispersed in the piezoelectric polymer, allowing the inorganic oxide particles to fully combine with the piezoelectric polymer, suppressing the formation of pores and improving the specific electrophoresis.

[0042] Specific examples of affinity enhancers include coupling agents, surfactants, and epoxy-containing compounds.

[0043] Examples of coupling agents include organotitanium compounds, organosilicon compounds, organozirconium compounds, organoaluminum compounds, and organophosphorus compounds.

[0044] Examples of organotitanium compounds include organotitanium coupling agents (e.g., alkoxytitanium, titanium chelates, titanium acetylates), and specific examples include tetraisopropyl titanate, titanium isopropoxy octyl glycolate, diisopropoxy bis(acetylacetonate) titanium, diisopropoxy titanium diisostearate, tetraisopropyl bis(dioctyl phosphite) titanate, and isopropyl tris(n-aminoethyl-aminoethyl) titanate, tetra(2,2-diallyloxymethyl-1-butyl)bis(di-tridecyl) phosphite titanate. Suitable examples of organotitanium compounds, in terms of their good affinity for inorganic oxide particles, include alkoxytitanium and titanium chelates.

[0045] Organosilane compounds can be either high-molecular-weight or low-molecular-weight, including alkoxysilanes (e.g., monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, tetraalkoxysilanes), ethylene silanes, epoxy silanes, amino silanes, methacryloxysilanes, and hydrothiosilanes. When using alkoxysilanes, hydrolysis can be used to further improve the volume resistivity (enhancement of electrical insulation) of the surface treatment.

[0046] Examples of organozirconium compounds include alkoxyzirconium and zirconium chelates.

[0047] Examples of organoaluminum compounds include aluminum alkoxy and aluminum chelates.

[0048] Examples of organophosphorus compounds include phosphites, phosphates, and phosphate chelates.

[0049] Surfactants used as affinity enhancers can be either high molecular weight or low molecular weight, but high molecular weight surfactants are preferred in terms of thermal stability. Examples of surfactants include nonionic surfactants, anionic surfactants, and cationic surfactants.

[0050] Examples of nonionic surfactants include polyether derivatives, polyvinylpyrrolidone derivatives, and alcohol derivatives, and suitable examples of these include polyether derivatives due to their good affinity for inorganic oxide particles.

[0051] Examples of anionic surfactants include sulfonic acids and carboxylic acids and polymers containing such salts, and suitable examples, for their good affinity with piezoelectric polymers, include acrylic acid derivative polymers and methacrylic acid derivative polymers.

[0052] Examples of cationic surfactants include amine compounds, compounds having nitrogen-containing heterocycles (e.g., imidazolines), and their halide salts.

[0053] The epoxy-containing compound used as an affinity enhancer can be a low molecular weight compound or a high molecular weight compound. Specific examples include epoxy compounds and glycidyl compounds, and more suitable examples, based on the affinity with piezoelectric polymers, include low molecular weight compounds having one epoxy group.

[0054] More suitable examples of compounds containing epoxy groups include those with the following formula: (In the formula, R represents a hydrogen atom, a methyl group, an oxygen atom, or a hydrocarbon group with 2 to 10 carbon atoms separated by a nitrogen atom, or an aromatic cyclic group that may be substituted. l represents 0 or 1, m represents 0 or 1, and n represents an integer from 0 to 10.) represents a compound.

[0055] Examples of compounds represented by the aforementioned formulas include compounds having a ketone or ester group, and more specifically, compounds represented by the following formulas:

[0056] The content of the affinity enhancer, relative to 100 parts by mass of inorganic oxide particles, is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 25 parts by mass, and even more preferably 1 to 20 parts by mass, so as to achieve uniform dispersion and high specific electrophoresis of the resulting organic piezoelectric film.

[0057] Organic piezoelectric films are preferably non-stretched films. Organic piezoelectric films are preferably cast films. By constructing organic piezoelectric films using casting, the uniformity of thickness can be improved. For example, as described later, the coefficient of variation of film thickness can be set to less than 10%.

[0058] physical properties Organic piezoelectric films are preferably characterized by the following physical properties. Furthermore, in this specification, unless otherwise specified, various physical properties refer to properties measured without requiring pretreatment before measurement. When noted "after heating at 110°C for 10 minutes," it means that the property is measured after heating at 110°C for 10 minutes as a pretreatment. Moreover, the object heated at 110°C for 10 minutes can be the manufactured organic piezoelectric film. For example, when manufacturing an organic piezoelectric film using a method including steps A through C described later, the organic piezoelectric film after step C is considered the object. In one embodiment, the organic piezoelectric film preferably has at least the following total light transmittance, internal haze value per unit film thickness, and piezoelectric constant d33 after heating at 110°C for 10 minutes. In other embodiments, the organic piezoelectric film preferably has at least the following crystal size (especially the average crystal length), and piezoelectric constant d33 after heating at 110°C for 10 minutes. Furthermore, in other embodiments, the organic piezoelectric film preferably has at least the following rate of change of internal haze value per unit film thickness, and the following rate of change of piezoelectric constant d33. In these embodiments, the organic piezoelectric thin film further exhibits at least one preferred physical property selected from the group consisting of the following film thickness, the following hysteresis, the following YI value, the following remanent polarization, and the following crystallinity. The organic piezoelectric thin film further exhibits at least one preferred physical property selected from the group consisting of the following piezoelectric constant d33 variation coefficient, the following film thickness variation coefficient, and the following area.

[0059] Total light transmittance <Methods for determining total light transmittance> In this manual, "total light transmittance" can be measured according to JIS K-7361 using a haze meter NDH-7000SP (product name, Nippon Denshoku Kogyo Co., Ltd.) or equivalent.

[0060] The lower limit of total light transmittance, relative to transparency, is preferably 90%, even better at 91%, still better at 92%, and particularly better at 93%. The lower limit of total light transmittance after heating at 110°C for 10 minutes can also be set to the same value. There is no particular upper limit to the total light transmittance, but it can be, for example, 99.99%, 99.9%, or 99%. The upper limit of the total light transmittance after heating at 110°C for 10 minutes can also be set to the same value. The total light transmittance is preferably 90% or higher (e.g., within the range of 90% to 99.99%), even more preferably 91% or higher (e.g., within the range of 91% to 99.99%), and still more preferably 92% or higher (e.g., within the range of 92% to 99.99%). The range of total light transmittance after heating at 110°C for 10 minutes can also be set to the same range.

[0061] Internal haze value <Methods for Determining Internal Haze Value> In this manual, the "inner haze value" is based on JIS K-7361 and is obtained by adding water to a glass cell and inserting a thin film into it during a haze test using a haze meter NDH-7000SP (product name, Nippon Denshoku Kogyo Co., Ltd.) or its equivalent, and measuring the haze value.

[0062] The upper limit of the internal haze value, based on the transparency, is preferably 6%, more preferably 5.5%, and even more preferably 5%. Furthermore, the upper limit of the internal haze value can be further set to a lower value, such as 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, or 1%. The upper limit of the internal haze value after heating at 110°C for 10 minutes, in terms of transparency, is preferably 7%, more preferably 6.5%, and even more preferably 6%. Furthermore, the upper limit of the internal haze value after heating at 110°C for 10 minutes can be further set to a lower value, such as 5.5%, 5%, 4.5%, 4%, 3.5%, 3%, 2.5%, 2%, 1.5%, or 1%. There is no particular limitation on the lower limit of the internal haze value, but it can be, for example, 0.01%, 0.05%, or 0.1%. The lower limit of the internal haze value after heating at 110°C for 10 minutes can also be set to the same value. The internal haze value is preferably below 6% (e.g., in the range of 0.01 to 6%), more preferably below 5.5% (e.g., in the range of 0.01 to 5.5%), and even more preferably below 5% (e.g., in the range of 0.01 to 5%). The internal haze value after heating at 110°C for 10 minutes is preferably below 7% (e.g., within the range of 0.01 to 7%), more preferably below 6.5% (e.g., within the range of 0.01 to 6.5%), and even more preferably below 6% (e.g., within the range of 0.01 to 6%). Even within such a range of internal haze values, high voltage electrical properties can still be maintained.

[0063] Rate of change in internal haze value [%) In this manual, "rate of change of internal haze value" refers to the absolute value of the value obtained by the formula: ((internal haze value after heating at 110°C for 10 minutes) - (internal haze value)) / (internal haze value) × 100. The upper limit of the rate of change of internal haze value, based on thermal stability, is preferably 140%, more preferably 120%, even more preferably 100%, and even more preferably 90%. Furthermore, the upper limit of the rate of change of internal haze value can be further set to a lower value, such as 80%, 70%, 60%, or 50%. There is no particular limit to the lower limit of the rate of change of internal haze values, but it may be, for example, 1%, 2%, 3%, 4%, or 5%. The rate of change of internal haze value is preferably below 140% (e.g., within the range of 1 to 140%), more preferably below 120% (e.g., within the range of 1 to 120%), and even more preferably below 100% (e.g., within the range of 1 to 100%).

[0064] Ratio of internal haze value [%] to film thickness [μm] The upper limit of the ratio of internal haze value [%] to film thickness [μm] is preferably 0.2, more preferably 0.15, even more preferably 0.1, and particularly preferably 0.05, depending on the transparency. The upper limit of the ratio of internal haze value [%] to film thickness [μm] after heating at 110°C for 10 minutes can also be set to the same value. There is no particular limitation on the lower limit of the ratio of internal haze value [%] to film thickness [μm], but it can be, for example, 0.0001, 0.0005, 0.001, or 0.005. The lower limit of the ratio of internal haze value [%] to film thickness [μm] after heating at 110°C for 10 minutes can also be set to the same value. The ratio of internal haze value [%] to film thickness [μm] is preferably 0.2 or less (e.g., within the range of 0.0001 to 0.2), more preferably 0.15 or less (e.g., within the range of 0.0001 to 0.15), and even more preferably 0.1 or less (e.g., within the range of 0.0001 to 0.1). The range of the ratio of internal haze value [%] to film thickness [μm] after heating at 110°C for 10 minutes can also be set to the same range. Even within such a range, this ratio can still exhibit high voltage electrical properties.

[0065] Rate of change of the ratio of internal haze value [%] to film thickness [μm] In this specification, "the rate of change of the ratio of internal haze value [%] / film thickness [μm]" means the absolute value of the value obtained by the formula: ((r value after heating at 110°C for 10 minutes) - (r value)) / (r value) × 100 when the ratio is set as r. The upper limit of the rate of change of the r-value, based on the point of thermal stability, is preferably 140%, more preferably 120%, even more preferably 100%, and even more preferably 90%. Furthermore, the upper limit of the rate of change of the r-value can be further set to a lower value, such as 80%, 70%, 60%, or 50%. There is no particular limitation on the lower limit of the rate of change of the r value, but it can be, for example, 1%, 2%, 3%, 4%, or 5%. The rate of change of the r-value is preferably below 140% (e.g., within the range of 1 to 140%), even more preferably below 120% (e.g., within the range of 1 to 120%), and even more preferably below 100% (e.g., within the range of 1 to 100%).

[0066] piezoelectric constant d 33 <Method for determining the piezoelectric constant d33> In this specification, "piezoelectric constant d33" refers to the piezoelectric constant measured using a PIEZOTEST PM300 pressure gauge system or an equivalent, with a force of 1.0 N and 110 Hz applied. The piezoelectric constant d33 is measured at 10 points on a thin film selected excluding arbitrary measurements, and their arithmetic mean is taken as the piezoelectric constant d33. The 10 points on the thin film can be selected, for example, at 50 mm intervals along a straight line. Here, "arbitrary" means attempting to minimize the coefficient of variation described later. The measured value of the piezoelectric constant d33 may be positive or negative depending on whether the film being measured is inside or outside the film; however, in this specification, the value of the piezoelectric constant d33 is stated as its absolute value.

[0067] The lower limit of the piezoelectric constant d33 is preferably 13 pC / N, more preferably 14 pC / N, even more preferably 15 pC / N, and even more preferably 16 pC / N. The lower limit of the piezoelectric constant d33 can be further set to a higher value, such as 17 pC / N. The lower limit of the piezoelectric constant d33 after heating at 110°C for 10 minutes is preferably 10 pC / N, more preferably 11 pC / N, even more preferably 12 pC / N, and even more preferably 13 pC / N. There is no particular upper limit to the piezoelectric constant d33, but it can be, for example, 100 pC / N, 50 pC / N, 35 pC / N, or 30 pC / N. The upper limit of the piezoelectric constant d33 after heating at 110°C for 10 minutes can also be set to the same value. The piezoelectric constant d33 is preferably 13 pC / N or more (e.g., in the range of 13 to 100 pC / N), more preferably 14 pC / N or more (e.g., in the range of 14 to 100 pC / N), and even more preferably 15 pC / N or more (e.g., in the range of 15 to 100 pC / N). The piezoelectric constant d33 after heating at 110°C for 10 minutes is preferably 10 pC / N or more (e.g., in the range of 10 to 100 pC / N), more preferably 11 pC / N or more (e.g., in the range of 11 to 100 pC / N), and even more preferably 12 pC / N or more (e.g., in the range of 12 to 100 pC / N). Even within such a range, the piezoelectric constant d33 exhibits high transparency.

[0068] Rate of change of piezoelectric constant d33 [%) In this specification, "the rate of change of the piezoelectric constant d33" refers to the absolute value of the value obtained by the formula: ((d33 after heating at 110°C for 10 minutes) - (d33)) / (d33) × 100. The upper limit of the rate of change of the piezoelectric constant d33, based on thermal stability, is preferably 50%, more preferably 45%, and even more preferably 40%. Furthermore, the upper limit of the rate of change of the piezoelectric constant d33 can be further set to a lower value, such as 35%, 30%, 25%, 20%, or 15%. There is no particular limitation on the lower limit of the rate of change of the piezoelectric constant d33, but it is, for example, 0.5% or 1%. The rate of change of the piezoelectric constant d33 is preferably below 50% (e.g., in the range of 0.5 to 50%), more preferably below 45% (e.g., in the range of 0.5 to 45%), and even more preferably below 40% (e.g., in the range of 0.5 to 40%).

[0069] The variation coefficient of piezoelectric constant d33 The coefficient of variation of the piezoelectric constant d33 is the ratio of the standard deviation of the arithmetic mean of the piezoelectric constant d33.

[0070] The upper limit of the variation coefficient of the piezoelectric constant d33 is preferably 2, even more preferably 1.5, and even more preferably 1, depending on the point of in-plane uniformity. The lower limit of the variation coefficient of the piezoelectric constant d33, based on manufacturing cost, is preferably 0.01. The variation coefficient of the piezoelectric constant d33 is preferably less than 2 (e.g., in the range of 0.01 to 2), more preferably less than 1.5 (e.g., in the range of 0.01 to 1.5), and even more preferably less than 1 (e.g., in the range of 0.01 to 1).

[0071] Hysteresis <Methods for Determining Hysteresis> In this specification, "hysteresis" is determined by cutting a thin film sample into pieces of 2cm x 2cm or larger and measuring it using the RETS-100 phase difference thin film and optical material inspection device (product name: Otsuka Electronics) or an equivalent. In this specification, the value for hysteresis is 550nm.

[0072] The upper limit of the hysteresis, based on optical characteristics, is preferably 9000 nm, more preferably 8500 nm, and even more preferably 8000 nm. The upper limit of the hysteresis can be further set to a lower value, such as 7000 nm, 6000 nm, 5000 nm, 4000 nm, 3000 nm, 2000 nm, 1000 nm, 500 nm, 100 nm, 50 nm, or 30 nm. There is no particular limitation on the lower limit of the hysteresis, but it can be, for example, 0.1 nm, 0.5 nm, or 1 nm. The hysteresis is preferably in the range of 0.1~100nm, more preferably in the range of 0.5~50nm, and even more preferably in the range of 1~30nm.

[0073] The ratio of hysteresis [nm] to film thickness [μm] The upper limit of the ratio of hysteresis [nm] to film thickness [μm] is preferably 10, even more preferably 5, even more preferably 1, and even more preferably 0.5, depending on the optical properties. The lower limit of the ratio of hysteresis [nm] to film thickness [μm] is not particularly limited, but can be, for example, 0.01, 0.02, 0.03, 0.04, 0.05 or 0.1. The ratio of hysteresis [nm] to film thickness [μm] is preferably in the range of 0.01 to 10, more preferably in the range of 0.01 to 1, and even more preferably in the range of 0.01 to 0.5.

[0074] Degree of crystallinity <Methods for Determining the Degree of Crystallinity> When a thin film sample is directly loaded into a sample holder with an opening, and the diffraction angle 2θ ranges from 10° to 40°, the resulting X-ray diffraction pattern is as follows: The base line is set by connecting the diffraction intensity at a diffraction angle of 10° and 2θ at a diffraction angle of 25°. The region enclosed by the baseline and the diffraction intensity curve is separated into two symmetrical peaks by profile fitting. Among them, the peak with the larger diffraction angle 2θ is identified as the crystalline peak, and the peak with the smaller diffraction angle 2θ is identified as the amorphous halo peak. The value expressed as 100 × (area of ​​crystalline peak) / (sum of area of ​​crystalline peak and area of ​​amorphous halo peak) is taken as the degree of crystallinity.

[0075] The lower limit of crystallinity, in terms of piezoelectricity, is preferably 40%, more preferably 45%, even more preferably 50%, even more preferably 55%, particularly preferably 60%, and even more preferably 65%. The lower limit of crystallinity after heating at 110°C for 10 minutes can also be set to the same value. The upper limit of crystallinity can be, for example, 99%, 95%, or 90%. The upper limit of crystallinity after heating at 110°C for 10 minutes can also be set to the same value. The degree of crystallinity is preferably 40% or higher (e.g., within the range of 40-99%), more preferably 50% or higher (e.g., within the range of 50-99%), and even more preferably 60% or higher (e.g., within the range of 60-99%). The range of crystallinity after heating at 110°C for 10 minutes can also be set to the same range. Even within this range of crystallinity, it can still exhibit high transparency.

[0076] YI value In this specification, the YI value refers to the yellowness measured according to JIS K7105. The YI value is determined by cutting a film sample into pieces larger than 2cm × 2cm and measuring its transmittance using a spectrophotometer (CM-5, Konica Minolta) or an equivalent. The upper limit of the YI value is preferably 4, even better is 3, and still better is 2. The upper limit of the YI value after heating at 110°C for 10 minutes can also be set to the same value. There is no particular limitation on the lower limit of the YI value, but it can be, for example, 0.1 or 0.2. The lower limit of the YI value after heating at 110°C for 10 minutes can also be set to the same value. The YI value is preferably below 4 (e.g., within the range of 0.1 to 4), even more preferably below 3 (e.g., within the range of 0.1 to 3), and even more preferably below 2 (e.g., within the range of 0.1 to 2). The range of YI values ​​after heating at 110°C for 10 minutes can also be set to the same range.

[0077] Rate of change of YI value [%] In this specification, "rate of change of YI value" refers to the absolute value of the value obtained by the formula: ((YI value after heating at 110°C for 10 minutes) - (YI value)) / (YI value) × 100. The upper limit of the rate of change of the YI value, based on the point of thermal stability, is preferably 150%, even better is 100%, even better is 90%, even better is 80%, and particularly better is 70%. There is no specific limit to the lower limit of the rate of change of the YI value, but it may be, for example, 1% or 5%. The rate of change of the YI value is preferably below 150% (e.g., within the range of 1 to 150%), even more preferably below 100% (e.g., within the range of 1 to 100%), and even more preferably below 80% (e.g., within the range of 1 to 80%).

[0078] Residual polarization [mC / m²] <Methods for determining remanent polarization> The sample film was prepared by vacuum-depositing an aluminum electrode (planar electrode) into the central 5mm x 5mm portion of a 20mm x 20mm film. Insulating tape was then applied to this planar electrode, and two reinforcing aluminum foil electrodes (3mm x 80mm) were attached to it using conductive double-sided tape. This sample film, a function generator, a high-voltage amplifier, and an oscilloscope were mounted in a Sawyer-Tower circuit. A triangular wave (maximum ±10kV) was applied to the sample film, and the response of the sample film was measured using an oscilloscope to obtain the residual polarization of 80MV / m at the applied electrical interface.

[0079] The lower limit of the residual polarization is preferably 30 mC / m², 35 mC / m², 40 mC / m², 45 mC / m², or 50 mC / m². There is no particular upper limit to the residual polarization, but it can be, for example, 200 mC / m², 150 mC / m², 100 mC / m², 90 mC / m², 80 mC / m², or 70 mC / m². The residual polarization is preferably 30 mC / m² or more (e.g., 30~200 mC / m², or 30~100 mC / m²), more preferably 40 mC / m² or more (e.g., 40~90 mC / m²), and even more preferably 50 mC / m² or more (e.g., 50~80 mC / m²).

[0080] Crystal size There is no particular limitation on crystal size. Organic piezoelectric films are preferably composed of needle-like or fibrous crystals, and are preferably characterized by the following average crystal length, average crystal width and / or maximum crystal length. <Methods for determining average crystal length, average crystal width, and maximum crystal length> Observe the surface of the thin film sample using a scanning electron microscope (SEM). Depending on the size of the needle-like crystals, observe the electron microscope image at a magnification range of 10,000 to 100,000. However, the sample, observation conditions, and magnification are adjusted to meet the following conditions (1) and (2). (1) Draw a straight line X at any point in the image and intersect this line X with more than 20 needle-like crystals. (2) In the same observation image, draw a straight line Y that is perpendicular to and intersects the straight line X, and there are more than 20 needle-like crystals intersecting the straight line Y. From the obtained electron microscope images, read at least 20 (i.e., at least 40 in total) crystal lengths (major axis) and widths (minor axis) for each of the needle-like crystals intersecting line X and line Y. Observe at least 3 sets of such electron microscope images and read at least 40 × 3 sets (i.e., at least 120) crystal lengths and widths. Average the crystal lengths and widths read in this way to calculate the average crystal length and average crystal width, and take the longest crystal length read as the maximum crystal length.

[0081] The upper limit of the average crystal length is preferably 450 nm, further preferably 400 nm, even more preferably 350 nm, even more preferably 300 nm, particularly preferably 250 nm, and even more preferably 200 nm. There is no particular limitation on the lower limit of the average crystal length, but it can be, for example, 1 nm, 5 nm, 10 nm, 120 nm, 30 nm, 40 nm, or 50 nm. The average crystal length is preferably below 450 nm (e.g., in the range of 1 to 450 nm), more preferably below 300 nm (e.g., in the range of 1 to 300 nm), and even more preferably below 200 nm (e.g., in the range of 1 to 200 nm).

[0082] The upper limit of the maximum crystal length is preferably 800 nm, further preferably 700 nm, even more preferably 600 nm, even more preferably 500 nm, and particularly preferably 400 nm. The upper limit of the maximum crystal length, based on the point of transparency, is preferably the minimum wavelength of visible light (380 nm), even more preferably 350 nm, and even more preferably 300 nm. There is no particular limitation on the lower limit of the maximum crystal length, but it is, for example, 10 nm. The maximum crystal length is preferably below 800 nm (e.g., in the range of 10 to 800 nm), more preferably below 600 nm (e.g., in the range of 10 to 600 nm), and even more preferably below 380 nm (e.g., in the range of 10 to 380 nm).

[0083] The upper limit of the average crystal width is preferably 100 nm, more preferably 80 nm, even more preferably 60 nm, and even more preferably 50 nm. The upper limit of the average crystal width can be further set to a lower value, such as 40 nm, 35 nm, or 30 nm. There is no particular limitation on the lower limit of the average crystal width, but it is, for example, 1 nm. The average crystal width is preferably less than 100 nm (e.g., in the range of 1 to 100 nm), more preferably less than 80 nm (e.g., in the range of 1 to 80 nm), and even more preferably less than 60 nm (e.g., in the range of 1 to 60 nm).

[0084] If the average crystal length and average crystal width are within the ranges mentioned above, then both piezoelectricity and transparency are good.

[0085] Film thickness <Methods for determining film thickness> In this specification, the thickness of the entire planar direction of the film is measured at every 10 points in a 1cm square using a photoelectric digital length measuring system (Digimicro MH-15M, Nikon) or an equivalent, and the average value is taken as the film thickness.

[0086] From the viewpoint of being able to use it as a self-supporting membrane, the lower limit of the film thickness is preferably 1 μm, more preferably 5 μm, even more preferably 10 μm, even more preferably 15 μm, and particularly preferably 20 μm. When the film thickness is formed on a support such as glass or PET film, there is no particular limitation, but to obtain a defect-free smooth surface, the lower limit of the film thickness is preferably 10 nm, even more preferably 30 nm, and even more preferably 50 nm. There is no particular upper limit to the film thickness, but from the point of view of obtaining flexibility, it is preferable to be, for example, 1000 μm, 900 μm, or 800 μm. From the viewpoint of enabling its use as a self-supporting membrane, the film thickness is preferably 1 μm or more (e.g., in the range of 1 to 1000 μm), more preferably 5 μm or more (e.g., in the range of 5 to 1000 μm), and even more preferably 10 μm or more (e.g., in the range of 10 to 1000 μm). When formed on a support such as glass or PET film, the thickness is preferably 10 nm or more (e.g., in the range of 10 nm to 1000 μm), more preferably 30 nm or more (e.g., in the range of 30 nm to 1000 μm), and even more preferably 50 nm or more (e.g., in the range of 50 nm to 1000 μm).

[0087] Coefficient of variation of film thickness <Method for determining the coefficient of variation of film thickness> In this specification, the coefficient of variation of the film thickness is the value measured at every 10 points in a 1cm square grid, covering the entire planar direction of the film.

[0088] The upper limit of the coefficient of variation of film thickness, based on the point of in-plane uniformity, is preferably 10%, and more preferably 5%. There is no particular limitation on the lower limit of the coefficient of variation of film thickness, but it can be, for example, 0.01%, 0.05%, or 0.1%. The coefficient of variation of film thickness is preferably less than 10% (e.g., in the range of 0.01 to 10%), and more preferably 5% (e.g., in the range of 0.01 to 5%).

[0089] area There is no particular limitation on the lower limit of the area, but for industrial production purposes, 9 cm² is preferred, and more preferably 10 cm². The lower limit of the area can be further set to higher values, such as 50 cm², 100 cm², 200 cm², 300 cm², 400 cm², or 500 cm². When printing or coating on fine areas, the lower limit of the area can be, for example, 0.1 μm², 1 μm², 10 μm², 50 μm², or 100 μm². There is no particular limit to the upper limit of the area, but it can be, for example, 4000m², 3000m², 2000m², 1000m², or 500m². When printing or coating on fine areas, the upper limit of the area can be, for example, 10mm², 5mm², or 1mm². The area is preferably 9 cm² or more (e.g., within the range of 9 cm² to 4000 m²), and more preferably 10 cm² or more (e.g., within the range of 10 cm² to 4000 m²). This range corresponds to the area range manufactured by the roll-to-roll process.

[0090] For example, organic piezoelectric films are preferably those that satisfy any of the following (a) to (w). (a) The total light transmittance is above 90%, the internal haze value per unit film thickness is below 0.2% / μm, and the piezoelectric constant d33 after heating at 110°C for 10 minutes is above 10 pC / N; (b) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, and the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more; (c) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the internal haze value per unit film thickness is 0.2% / μm or less, and the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more; (d) The total light transmittance is above 90%, the internal haze value per unit film thickness is below 0.2% / μm, the piezoelectric constant d33 after heating at 110℃ for 10 minutes is above 10pC / N, the hysteresis per unit film thickness is in the range of 0.01~10nm / μm, and the film thickness is in the range of 1~1000μm; (e) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, the hysteresis is 100 nm or less, and the film thickness is in the range of 1 to 1000 μm; (f) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the internal haze value per unit film thickness is 0.2% / μm or less, the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, the hysteresis is 100 nm or less, the hysteresis per unit film thickness is in the range of 0.01~10 nm / μm, and the film thickness is in the range of 1~1000 μm; (g) Total light transmittance is above 90%, internal haze value per unit film thickness is below 0.2% / μm, piezoelectric constant d33 after heating at 110℃ for 10 minutes is above 10pC / N, and YI value is below 4; (h) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, and the YI value is 4 or less; (i) Total light transmittance is 90% or more, internal haze value per unit film thickness is 0.2% / μm or less, piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, and residual polarization is 40 mC / m2 or more; (j) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, and the residual polarization is 40 mC / m2 or more; (k) Total light transmittance is above 90%, internal haze value per unit film thickness is below 0.2% / μm, piezoelectric constant d33 after heating at 110°C for 10 minutes is above 10 pC / N, and crystallinity is above 40%; (l) The total light transmittance is 90% or more, the internal haze value (or the internal haze value after heating at 110°C for 10 minutes) is 6% or less, the piezoelectric constant d33 after heating at 110°C for 10 minutes is 10 pC / N or more, and the degree of crystallinity is 40% or more; (m) The maximum crystal length is less than 800 nm, and the piezoelectric constant d33 after heating at 110 °C for 10 minutes is greater than 10 pC / N; (n) The average crystal length is less than 450 nm, the maximum crystal length is less than 800 nm, and the piezoelectric constant d33 after heating at 110 °C for 10 minutes is greater than 10 pC / N; (o) The maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, and the piezoelectric constant d33 after heating at 110 °C for 10 minutes is greater than 10 pC / N; (p) The average crystal length is less than 200 nm, the maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, and the piezoelectric constant d33 after heating at 110 °C for 10 minutes is greater than 10 pC / N; (q) The maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, the piezoelectric constant d33 after heating at 110 °C for 10 minutes is greater than 10 pC / N, and the degree of crystallinity is greater than 40%; (r) The average crystal length is less than 200 nm, the maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, the piezoelectric constant d33 after heating at 110 °C for 10 minutes is more than 10 pC / N, and the degree of crystallinity is more than 40%; (s) The rate of change of internal haze value per unit film thickness is less than 100%, the internal haze value per unit film thickness after heating at 110°C for 10 minutes is less than 0.2% / μm, the rate of change of piezoelectric constant d33 is less than 40%, and the... The piezoelectric constant d33 after heating at 110℃ for 10 minutes is above 10 pC / N; (t) The maximum crystal length is below 800 nm, and the degree of crystallinity is above 40%; (u) The average crystal length is less than 450 nm, the maximum crystal length is less than 800 nm, and the degree of crystallinity is more than 40%; (v) The maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, and the degree of crystallinity is more than 40%; (w) The average crystal length is less than 450 nm, the maximum crystal length is less than 800 nm, the average crystal width is less than 100 nm, and the degree of crystallinity is more than 40%.

[0091] use The organic piezoelectric film of this invention is applicable to a variety of uses. Specific examples of uses include detectors (e.g., contact detectors, vibration detectors, bio-detectors, tire detectors (detectors disposed on the inner surface of tires)), actuators, touch panels, tactile devices (devices with the function of providing tactile feedback to users), vibration power generation devices (e.g., vibration power generation beds, vibration power generation tires), loudspeakers, and microphones.

[0092] Manufacturing method The organic piezoelectric thin film of the present invention can be manufactured by, for example, a manufacturing method including at least one of steps A to C, preferably a manufacturing method including steps A to C. Step A involves fabricating a non-polar thin film (e.g., a non-stretched, non-polar thin film) containing a piezoelectric polymer using a casting method. Step B involves performing a polarization process on a non-polarized thin film (e.g., a non-stretched and non-polarized thin film); and The non-polarized thin film (e.g., a non-stretched and non-polarized thin film) is subjected to heat treatment, or step C is performed on the thin film at any time point in step B.

[0093] Step A (Thin Film Modulation Step) The manufacturing method of non-polar thin films by casting is, for example, a manufacturing method including (A1) to (A4). (A1) The step of dissolving or dispersing a piezoelectric polymer (e.g., a fluorinated vinylidene polymer) and the aforementioned desired components (e.g., inorganic oxide particles and affinity enhancers) in a solvent to dissolve the liquid composition and prepare the liquid composition; (A2) The step of applying (casting or coating) the aforementioned liquid composition onto a substrate; (A3) The step of heating and drying the substrate to which the aforementioned liquid composition is applied at a first temperature; and (A4) The step of heating the substrate heated at the first temperature to a second temperature that is higher than the first temperature. These steps are better implemented using a coil-and-roll process at an industrial production point. Steps (A3) and (A4) can also be implemented by sequentially transferring the material to a block exposed to a first temperature and a block exposed to a second temperature that is higher than the first temperature.

[0094] In step (A1), the dissolution temperature during the preparation of the liquid composition can be appropriately selected according to the type of solvent used, and there is no particular limitation. However, for the purpose of promoting dissolution and preventing film coloring, it is preferable to be above room temperature, the vaporization temperature of the solvent, or below 80°C.

[0095] To prevent staining, suitable examples of the aforementioned solvents include ketone solvents (e.g., methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone, cyclohexanone), ester solvents (e.g., ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate), ether solvents (e.g., tetrahydrofuran, methyltetrahydrofuran, dioxane), and acetylamine solvents (e.g., dimethylformamide (DMF), dimethylacetylamine). These solvents can be used alone or in combination of two or more. Furthermore, it is preferable that the content of acetylamine solvents in the aforementioned solvents is 50% by mass or less.

[0096] In step (A2), the casting (or coating) of the liquid composition onto the substrate can be performed using any conventional method (e.g., blade coating, casting coating, roller coating, gravure coating, bar coating, air-blade coating, or slot coating). Among these, gravure coating or slot coating is preferred due to its ease of operation, less unevenness in film thickness, and superior productivity.

[0097] As the aforementioned substrate, plastic films such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), acrylic resins, cyclic olefin polymers, and polyimide (PI), or metal films such as aluminum (Al), stainless steel (SUS), and copper (Cu) can be used. Among these, polyethylene terephthalate (PET) is preferred due to its wide applicability and excellent cost and manufacturability. Furthermore, a smooth surface finish is also desirable. This not only improves the peelability of the cast-coated film but also results in a smoother surface.

[0098] In step (A3), the heating and drying of the substrate to which the liquid composition is applied can be performed using methods generally employed for heating and drying to form thin films. Preferably, this heating and drying is carried out, for example, in a roll-to-roll process, by applying the aforementioned liquid composition to the substrate in a high-temperature furnace (or drying oven). Alternatively, the heating and drying can be performed in batches to form the thin film.

[0099] The lower limit of the first temperature (heating and drying temperature) can be appropriately selected by the type of solvent used (or its vaporization temperature), for example, 20°C, preferably 30°C, even more preferably 40°C, even more preferably 50°C, even more preferably 60°C, particularly preferably 70°C, and even more preferably 80°C. The upper limit of the heating and drying temperature is, for example, 200°C, 190°C, 180°C, 170°C, 160°C. 150℃, 140℃, 130℃, or 120℃. The heating and drying temperature may be, for example, within the range of 50~140℃, 60~130℃, 70~120℃, or 80~130℃. The heating and drying temperature may be constant or variable. It may also be varied, for example, from a low temperature (e.g., 40~100℃) to a high temperature (e.g., 120~200℃). There are no particular limitations on the method of varying the heating and drying temperature, but it can also be achieved, for example, by moving multiple drying blocks set to different temperatures, thus varying the heating and drying temperature. The lower limit of the heating time at the first temperature (heating and drying time) is, for example, 1 second, preferably 10 seconds, and more preferably 30 seconds. The upper limit of the heating and drying time is, for example, 60 minutes, preferably 30 minutes, and more preferably 10 minutes. The heating and drying time is, for example, within the range of 10 seconds to 60 minutes, preferably within the range of 30 seconds to 10 minutes, and more preferably within the range of 30 seconds to 10 minutes.

[0100] In step (A4), the second temperature is preferably the melting point or a temperature near it. In this specification, the melting point or a temperature near it can be above (melting point -12°C) or below (melting point +12°C). More preferably, the second temperature is above (melting point -11°C), above (melting point -10°C), above (melting point -9°C), above (melting point -8°C), above (melting point -7°C), above (melting point -6°C), or above (melting point -5°C). Furthermore, more preferably, the second temperature is below (melting point +11°C), below (melting point +10°C), below (melting point +9°C), below (melting point +8°C), below (melting point +7°C), below (melting point +6°C), or below (melting point +5°C). The second temperature is preferably in the range of (melting point -12℃) to (melting point +12℃), even more preferably in the range of (melting point -10℃) to (melting point +10℃), and even more preferably in the range of (melting point -10℃) to (melting point +5℃), or in the range of (melting point -5℃) to (melting point +5℃). The second temperature will vary depending on the type of piezoelectric polymer, but is preferably [temperature value missing]. The temperature is preferably above 110℃, more preferably above 115℃, even more preferably above 120℃, and even more preferably above 125℃. Furthermore, the second temperature is preferably below 150℃, even more preferably below 145℃, even more preferably below 140℃, and even more preferably below 135℃. The second temperature is preferably in the range of 110~150℃, even more preferably in the range of 120~140℃, and even more preferably in the range of 125~135℃. The heating time at the second temperature is, for example, more than 1 minute, preferably more than 5 minutes, and more preferably more than 10 minutes. Furthermore, the heating time at the second temperature is, for example, less than 60 minutes, preferably less than 30 minutes. The heating time at the second temperature is, for example, in the range of 1 to 60 minutes, preferably in the range of 5 to 60 minutes, and more preferably in the range of 10 to 60 minutes. By heating at a second temperature, even if the crystals of the piezoelectric polymer are miniaturized, a high degree of crystallinity can be maintained. In this way, organic piezoelectric films can achieve both high transparency and piezoelectricity.

[0101] The aforementioned method for manufacturing non-polar thin films may further include (A5) the step of heating the substrate heated at the aforementioned second temperature at a third temperature. The third temperature is preferably the crystallization temperature or a temperature near it. In this specification, the crystallization temperature or a temperature near it can be (crystallization temperature -12°C) or higher, or (crystallization temperature +12°C) or lower. The third temperature is more preferably (crystallization temperature -11°C) or higher, (crystallization temperature -10°C) or higher, (crystallization temperature -9°C) or higher, (crystallization temperature -8°C) or higher, (crystallization temperature -7°C) or higher, (crystallization temperature -6°C) or higher, (crystallization temperature -5°C) or higher, (crystallization temperature -4°C) or higher, or (crystallization temperature -3°C) or higher. Furthermore, the third temperature is preferably below (crystallization temperature +11°C), below (crystallization temperature +10°C), below (crystallization temperature +9°C), below (crystallization temperature +8°C), below (crystallization temperature +7°C), below (crystallization temperature +6°C), below (crystallization temperature +5°C), below (crystallization temperature +4°C), or below (crystallization temperature +3°C). The third temperature is preferably in the range of (crystallization temperature -10°C) to (crystallization temperature +10°C), more preferably in the range of (crystallization temperature -5°C) to (crystallization temperature +5°C), and even more preferably in the range of (crystallization temperature -3°C) to (crystallization temperature +3°C). The third temperature may vary depending on the type of piezoelectric polymer, but is preferably above 108°C, more preferably above 110°C, even more preferably above 113°C, and particularly preferably above 115°C. Furthermore, the third temperature is preferably below 128°C, even more preferably below 125°C, even more preferably below 123°C, and particularly preferably below 121°C. The third temperature is preferably in the range of 108~128°C, even more preferably in the range of 113~123°C, and even more preferably in the range of 115~121°C. The heating time at the third temperature is, for example, 1 minute or more, preferably 3 minutes or more, and more preferably 5 minutes or more. Furthermore, the heating time at the third temperature is, for example, 10 minutes or less. The heating time at the third temperature is, for example, in the range of 1 to 10 minutes, preferably in the range of 3 to 10 minutes. Heating at a third temperature to promote crystal growth, suppress changes in heating properties, and obtain thin films with higher piezoelectric constants are preferred. On the other hand, heating at a third temperature can also be omitted from the perspective of industrial productivity, depending on the resulting thin film.

[0102] The thickness of the non-polar thin film modulated in step A can be set according to the resulting thin film.

[0103] Step B (polarization processing step) The polarization process can be carried out using conventional methods, but it is preferable to use corona discharge treatment.

[0104] The conditions for corona discharge treatment can be appropriately set based on common knowledge in the field. Corona discharge can use either negative or positive corona discharge, but from the viewpoint of easily separating non-polarized thin films, the use of negative corona discharge is more desirable.

[0105] There are no particular limitations on the corona discharge process, but it can be implemented by means of, for example, as described in Japanese Patent Application Publication Nos. 2011-181748 and 2016-219804, such as using a linear electrode to print on a non-polar thin film; using a needle electrode to print on a non-polar thin film; or using a gate electrode to print on a non-polar thin film.

[0106] In order to suppress the in-plane non-uniformity of the piezoelectric constant d33 of the obtained electrode thin film, the distance between each needle electrode and / or wire electrode and the thin film is fixed, that is, the distance between the electrode and the thin film is not in-plane non-uniform (or is very small) (specifically, the difference between the longest distance and the shortest distance is preferably within 15 mm, and even more preferably within 10 mm).

[0107] Furthermore, for example, when performing continuous printing using a roll-to-roll process, the film is appropriately and evenly adhered to the roll, giving the film a more desirable fixed tension.

[0108] For example, when using a linear electrode and performing continuous printing using a roll-to-roll process, the voltage range will vary depending on the distance between the linear electrode and the non-polarized film, the film thickness, etc., but the DC voltage range is, for example, -10 to -25 kV. The processing speed is, for example, 10 to 1200 cm / min.

[0109] As another method, in addition to corona discharge, polarization processing can also be implemented by, for example, sandwiching flat electrodes between the two sides of the non-polarized thin film for printing. Specifically, when printing is performed by sandwiching flat electrodes between the two sides of the non-polarized thin film, the DC current range of 0~400MV / m (preferably 50~400MV / m) and the printing time range of 0.1 seconds to 60 minutes can be used.

[0110] Step C (Heat Treatment Step) Step C is preferably performed at any point in time in relation to Step B, as necessary. That is, Step C can be performed before, simultaneously with, or after Step B. When Step C is performed after Step B, the heat treatment of Step C can be performed on the polarized film obtained in Step B or on the portion where polarization is completed in Step B. In other words, the heat treatment of Step C can be performed on the portion where polarization is completed while performing the polarization treatment of Step B.

[0111] The heat treatment is not particularly limited, but includes, for example, sandwiching the aforementioned film between two metal plates and heating the metal plates; heating the aforementioned film roll in a constant temperature bath; or, in the production of the aforementioned film using a roll-to-roll process, heating the metal roll and bringing the aforementioned film into contact with the heated metal roll; or preferably, passing the aforementioned film through a roll-to-roll process in a furnace that is heating the film. Alternatively, when step C is performed after step B, the polarized film can also be heat-treated individually, or it can be laminated onto another film or metal foil to create a multilayer film, which is then heat-treated. That is, when heat-treated at high temperatures, the latter method is less likely to cause wrinkles in the polarized film, and is therefore preferred.

[0112] The heat treatment temperature may vary depending on the type of heat-treated polarized film, and is preferably within the range of (melting point of the heat-treated polarized film - 100)℃ to (melting point of the heat-treated polarized film + 40)℃. Specifically, the heat treatment temperature is preferably above 80°C, even more preferably above 85°C, and even more preferably above 90°C. Furthermore, the heat treatment temperature is preferably below 170°C, even more preferably below 160°C, and even more preferably below 140°C.

[0113] The heat treatment time is usually more than 10 seconds, preferably more than 0.5 minutes, even more preferably more than 1 minute, and even more preferably more than 2 minutes. Furthermore, there is no upper limit to the heat treatment time, but the heat treatment time is usually less than 60 minutes.

[0114] The optimal conditions for heat treatment are above 90°C and for at least 1 minute.

[0115] Rolls of organic piezoelectric thin films Organic piezoelectric films are preferably stored and shipped as rolls.

[0116] The roll of one embodiment of the present invention may contain only the aforementioned film, or it may be rolled up by stacking a protective film or the like on the aforementioned film, or it may have a core such as a paper tube and the aforementioned film wound around the core.

[0117] The aforementioned film roll is preferably 50 mm or more in width and 20 m or more in length.

[0118] The aforementioned film can be wound up and modulated, for example, using take-up rollers and take-up rollers.

[0119] From the perspective of suppressing film, it is preferable to set the roll-out roller and the roll-in roller to be parallel, as is the general practice.

[0120] In order to ensure good lubrication of the film, rollers with better lubrication are preferred. Specifically, rollers coated with fluoropolymer, plated rollers, or rollers coated with release agent are preferred.

[0121] Therefore, when the film thickness is uneven, uneven roll thickness, such as the so-called roll protrusion (higher edge; thicker end compared to the center of the roll axis; thinner film at both ends compared to the center when the film thickness at both ends is lower than at the center; or thinner end concave when the thickness changes from one end to the other), will occur, which is the cause of wrinkles. Furthermore, when the film is rolled out, this will cause film deflection (bending under tension other than applied gravity).

[0122] Generally, to prevent the roll from bulging out, the film end of the roll is cut off (cut open). However, when the unevenness of the film thickness is widespread from the film end, removal alone is not enough to prevent the roll from bulging or denting.

[0123] Furthermore, generally speaking, films with a wider width (e.g., 100mm or more) and a longer length (e.g., 50m or more) are more prone to the aforementioned protrusions, depressions, and deflections.

[0124] However, since the aforementioned piezoelectric film has a high uniformity in thickness, it can be cut and removed directly or only at the end of the film that will become the end of the roll. Even if the film is wide (e.g., 100 mm or more) and long (e.g., 50 m or more), it can still become a roll that suppresses the aforementioned protrusions, depressions and deflections.

[0125] The portion removed by cutting (the film end) will be recycled and reused as raw material for the aforementioned film.

[0126] The aforementioned film roll has high uniformity in thickness, preferably with the ratio of the thickness of the thicker end relative to the center of the roll in the axial direction being in the range of 70% to 130%. This allows the aforementioned film roll to suppress deflection of the film as it is rolled out.

[0127] Furthermore, among the rollers used in the manufacture of the aforementioned films and their rolls, it is preferable that their surface material is at least polytetrafluoroethylene (PTFE), chromium-plated, or stainless steel (SUS).

[0128] In this way, wrinkles in the film can be suppressed.

[0129] piezoelectric The piezoelectric body in one embodiment of the present invention may also be a multilayer material, or may have an organic piezoelectric thin film and an electrode disposed on at least one side of the organic piezoelectric thin film.

[0130] Specific examples of the aforementioned electrodes include ITO (indium tin oxide) electrodes, tin oxide electrodes, aluminum electrodes, metal nanowires, metal nanoparticles (e.g., silver nanoparticles), and organic conductive resins.

[0131] The aforementioned piezoelectric material may be a laminate comprising an organic piezoelectric thin film, a positive electrode layer (or upper electrode layer) disposed on one side of the organic piezoelectric thin film, and a negative electrode layer (or lower electrode layer) disposed on the other side of the organic piezoelectric thin film.

[0132] The aforementioned piezoelectric material may also have an insulating layer on the surface of an organic piezoelectric thin film without a multilayer electrode layer. Furthermore, the aforementioned piezoelectric material may also have a covering layer (e.g., an electromagnetic shielding layer) on the surface (or outermost surface) of an organic piezoelectric thin film without a multilayer electrode layer.

[0133] Methods for manufacturing piezoelectric materials include, for example: The steps for preparing the aforementioned organic piezoelectric thin film; and The step of setting an electrode on at least one side of the aforementioned organic piezoelectric thin film.

[0134] In the steps of setting the aforementioned electrodes, the method of forming the electrodes typically includes heat treatment, and specific examples include methods of forming electrode materials into films using physical vapor phase growth methods (e.g., vacuum evaporation, ion plating, vacuum sputtering) or chemical vapor phase growth methods (e.g., plasma CVD), and methods of coating electrode materials onto a substrate.

[0135] The lower limit of the aforementioned heat treatment temperature is, for example, 25°C, more preferably 40°C, and even more preferably 50°C. The upper limit of the aforementioned heat treatment temperature (the melting point of the heat-treated polarized thin film -3°C) is, for example, 220°C, preferably 180°C, even more preferably 150°C, and even more preferably 130°C. The temperature of the aforementioned heat treatment can be, for example, in the range of 25~220°C, preferably in the range of 40~130°C.

[0136] The aforementioned heat treatment time is typically 10 seconds or more, preferably 1 minute or more, even more preferably 10 minutes or more, and even more preferably 15 minutes or more. [Example]

[0137] The following embodiments will illustrate one embodiment of the present invention in more detail, but the present invention is not limited thereto.

[0138] In the examples described later, the weight-average molecular weight (Mw) of the vinylene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer was calculated using a gel permeation chromatography (GPC) under the following conditions, with standard polystyrene as a reference. (condition) GPC equipment: TOSOH AS-8010, CO-8020 and SIMADZURID-10A Tubing string: GMHHR-H 3 tubes Solvent: Dimethylformamide [DMF] Sample concentration: 0.05% by mass

[0139] In the embodiments described later, the melting point of the fluorinated vinylidene (VDF) / tetrafluoroethylene (TFE) copolymer was determined by differential scanning calorimetry (DSC) using the method for measuring the transfer temperature of plastics (JIS K7121), as the maximum value in the heat of melting curve obtained when the temperature is increased at a rate of 10°C / min.

[0140] In the following embodiments, the following electrodes are used. <Electrodes Used> (1) On the center line of a brass rod with a width of 20 mm (a thickness of 10 mm and a length of 500 mm), needle electrodes for electrodes (needle-shaped electrodes) (R = 0.06 mm) are arranged in a row at intervals of 10 mm to form a needle-shaped electrode rod (2) Similarly to (1), a needle-shaped electrode rod in which needle electrodes for electrodes (R = 0.06 mm) are arranged in a row at intervals of 15 mm (3) A tungsten wire electrode with a diameter of 0.1 mm (a length of 500 mm)

[0141] In the following organic piezoelectric thin films, the total light transmittance, internal haze value, piezoelectric constant d33, hysteresis amount, and film thickness are measured by the following methods. <Total Light Transmittance> Measured using a haze meter NDH-7000SP (product name, Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7361. <Internal Haze Value> Water is placed in a quartz cell, and the thin film is inserted therein. Measured using NDH-7000SP (product name, Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K-7136. <Piezoelectric Constant d33> The measurement of the piezoelectric constant d33 is carried out using a piezometer system PM300 of PIEZOTEST Company. In this measurement, the sample is clamped with 1 N, and the charge generated when a force of 1.0 N and 110 Hz is applied is read. ​​​​​​​​​​​​A 5mm x 5mm aluminum electrode (planar electrode) was patterned in the center of a 20mm x 20mm sample film using vacuum deposition. Insulating tape was attached to the planar electrode, and two reinforcing aluminum foil electrodes (3mm x 80mm) were attached to the planar electrode using conductive double-sided tape. This sample film, a function generator, a high-voltage amplifier, and an oscilloscope were mounted in a Sawyer-Tower circuit, and a triangular wave (maximum ±10kV) was printed onto the sample film. The response of the sample film was measured using an oscilloscope to determine the residual polarization at the printed electrical interface of 80MV / m. Hysteresis The hysteresis was determined by cutting the thin film sample into pieces of 2cm x 2cm or larger and measuring it using the RETS-100 phase retardation thin film and optical material inspection device (product name, Otsuka Electronics). The value of 550nm was used as the hysteresis value. <Film thickness> The film thickness was measured at 10 points in a 1cm square along the entire planar direction of the thin film using a photoelectric digital length measurement system (Digimicro MH-15M, Nikon). The average film thickness was then calculated. <Average crystal length and maximum crystal length> Observe the surface of the thin film sample using a scanning electron microscope (SEM). Depending on the size of the needle-like crystals, observe the electron microscope image at a magnification range of 1,000 to 100,000 times. However, the sample, observation conditions, and magnification are adjusted to meet the following conditions (1) and (2). (1) Draw a straight line X at any point in the image. Intersect this straight line X with more than 20 needle-like crystals. (2) In the same observation image, draw a straight line Y that intersects the straight line X perpendicularly. There are more than 20 needle-like crystals intersecting the straight line Y. For the obtained electron microscope images, for individual needle-like crystals intersecting line X and line Y, read at least 20 (i.e., a total of at least 40) crystal lengths (major axis of the needle-like crystal). Observe at least 3 sets of such electron microscope images, reading at least 40 × 3 sets (i.e., at least 120) crystal lengths. Average the crystal lengths read in this way, calculate the average crystal length, and take the longest crystal length as the maximum crystal length. <Average crystal width> The average crystal width is determined by analyzing the electron microscope images used to measure the average crystal length. Specifically, for each individual needle-like crystal intersecting line X and line Y, at least 20 (i.e., a total of at least 40) crystal widths (minor axis of the needle-like crystal) are read from the aforementioned electron microscope images. At least three sets of such electron microscope images are observed, and at least 40 × 3 sets (i.e., at least 120) crystal widths are read. The average crystal width is then calculated by averaging these read crystal widths.

[0142] [Examples 1-6 and Comparative Examples 1-3] A vinylidene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer [VDF / TFE = 75 / 25 (molar ratio), weight average molecular weight (Mw) = 1.05 million, melting point = 131.6℃] was dissolved in methyl ethyl ketone (MEK) to prepare a coating with a solid content of 20 wt%. Then, using a rod coating method, the aforementioned coating was cast onto a PET film and dried at 80℃ for 10 minutes to form a copolymer film, which was then treated at the second temperature shown in Table 1 for 0.5 hours. After the copolymer film is peeled off from the PET film, the film thickness is as shown in Table 1. The following polarization treatment is performed on this copolymer film. Polarization Processing In an ISO Class 7 cleanroom (humidity 20-30%), as shown in Figure 1, a SUS-made grounding electrode on a grounding stand 1 (320mm long and 220mm wide) is maintained at 25°C. A non-polarized copolymer film 2 cut to 50mm x 50mm is placed on this grounding electrode. Above it, a 340mm x 240mm PET film 3 is placed, covering the central portion of the non-polarized copolymer film 2. A needle-shaped electrode (electrode E1) and a wire electrode (electrode E2) containing a tungsten wire (r=0.1mm) are placed parallel to the grounding electrode, positioned 10mm above the copolymer film and spaced 10mm apart. The DC voltage applied to the needle-shaped electrode and the wire electrode is set from 0kV to 11kV and 15kV respectively (Trek 610D high-voltage power supply). The non-polarized copolymer film 2, placed on the stand 1, is passed through the needle electrode E1 and the wire electrode E2 at a moving speed of 3000 mm / min to perform polarization treatment. The resulting polarized copolymer film is then placed in a drying oven maintained at 80°C for heat treatment to obtain an organic piezoelectric film. Furthermore, the scanning electron microscope images of Example 1 and Comparative Example 3 are shown in Figure 2.

[0143] [Examples 7-9] Except that after heating at the second temperature, the organic piezoelectric film was obtained in the same order as in Example 1, and then heated at the third temperature shown in Table 1 for 10 minutes.

[0144] [Example 10 and Comparative Example 4] A vinylidene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer [VDF / TFE = 80 / 20 (molar ratio), weight average molecular weight (Mw) = 230,000, melting point = 124.9°C] was dissolved in methyl ethyl ketone (MEK) to prepare a coating with a solid content of 20 wt%. Then, following the same procedure as in Example 1, an organic piezoelectric film was obtained.

[0145] [Examples 11 and 15] A vinylidene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer [VDF / TFE = 67 / 33 (molar ratio), weight average molecular weight (Mw) = 670,000, melting point = 146.8°C] was dissolved in methyl ethyl ketone (MEK) to prepare a coating with a solid content of 20 wt%. Then, following the same sequence as in Examples 1-6, an organic piezoelectric film was obtained.

[0146] [Examples 12-14] A vinylidene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer [VDF / TFE = 74 / 26 (molar ratio), weight average molecular weight (Mw) = 730,000, melting point = 133.4℃] was dissolved in methyl ethyl ketone (MEK) to prepare a coating with a solid content of 14 wt%. The coating was then filtered, and the filtrate was applied onto a PET film using a die-coating technique. A copolymer film was then formed on the PET film by drying. The drying was carried out in drying ovens with four sections (each 2 m in size) set at drying temperatures of 80℃ / 100℃ / 129℃ / 129℃. After the copolymer film was peeled off from the PET film, the film thickness was as shown in Table 1. For this copolymer film, a linear electrode was used, and continuous printing was performed using a roll-to-roll process, followed by electrode separation. Then, an organic piezoelectric film was obtained in the same order as in Example 1.

[0147] [Comparative Example 5] A vinylidene fluoride (VDF) / tetrafluoroethylene (TFE) copolymer [VDF / TFE = 80 / 20 (molar ratio), weight average molecular weight (Mw) = 230,000, melting point = 124.9°C] was dissolved in methyl ethyl ketone (MEK) to prepare a coating with a solid content of 20 wt%. Organic piezoelectric films were then obtained in the same order as in Example 7.

[0148] The evaluation results of the organic piezoelectric films prepared according to the examples and comparative examples are shown in Table 1 below.

Claims

1. An organic piezoelectric film, characterized in that it contains a fluorinated vinylidene copolymer film, and has a total light transmittance of 90% or more, an internal haze value of 0.2% / μm or less per unit film thickness, and a piezoelectric constant d33 of 10 pC / N or more after heating at 110°C for 10 minutes, wherein the aforementioned fluorinated vinylidene copolymer is selected from at least one group consisting of fluorinated vinylidene / tetrafluoroethylene copolymer and fluorinated vinylidene / trifluoroethylene copolymer.

2. The organic piezoelectric thin film as claimed in claim 1, wherein, In the aforementioned fluorinated vinylidene copolymers, the composition ratio of fluorinated vinylidene is in the range of 60-85 mol%.

3. The organic piezoelectric thin film as claimed in claim 1, wherein, The film thickness ranges from 10 nm to 1000 μm.

4. The organic piezoelectric thin film as claimed in claim 1, wherein, The hysteresis is below 500 nm.

5. The organic piezoelectric thin film as claimed in claim 1, wherein, The YI value is below 4.

6. The organic piezoelectric thin film as claimed in claim 1, wherein, The residual polarization is above 40 mC / m2.

7. The organic piezoelectric thin film as claimed in claim 1, wherein, When a thin film sample is directly loaded into a sample holder with an opening, and the diffraction angle 2θ covers the range of 10~40°, the X-ray diffraction pattern obtained during X-ray diffraction measurement is set as a base line by connecting the diffraction intensity at a diffraction angle 2θ of 10° and the diffraction intensity at a diffraction angle 2θ of 25°. The area enclosed by the base line and the diffraction intensity curve is separated into two symmetrical peaks by profile fitting. The peak with the larger diffraction angle 2θ is identified as the crystalline peak, and the peak with the smaller diffraction angle 2θ is identified as the amorphous halo peak. The degree of crystallinity expressed as 100×(area of ​​crystalline peak) / (sum of the area of ​​crystalline peak and the area of ​​amorphous halo peak) is 40% or more.

8. An organic piezoelectric film, characterized in that it contains a fluorinated vinylene copolymer film, wherein the fluorinated vinylene copolymer film contains needle-like crystals with a maximum crystal length of less than 800 nm, and the piezoelectric constant d33 after heating at 110°C for 10 minutes is greater than 10 pC / N, wherein the aforementioned fluorinated vinylene copolymer is selected from at least one group consisting of fluorinated vinylene / tetrafluoroethylene copolymers and fluorinated vinylene / trifluoroethylene copolymers.

9. The organic piezoelectric thin film as claimed in claim 8, wherein, The average crystal length is below 450 nm.

10. For the organic piezoelectric thin film as described in claim 8, when the thin film sample is directly loaded into a sample holder with an opening, and the diffraction angle 2θ covers the range of 10~40°, in the X-ray diffraction pattern obtained during X-ray diffraction measurement, the straight line connecting the diffraction intensity at a diffraction angle 2θ of 10° and the diffraction intensity at a diffraction angle 2θ of 25° is set as the base line, and the area enclosed by the base line and the diffraction intensity curve is separated into two symmetrical peaks by profile fitting. When the peak with the larger diffraction angle 2θ is identified as the crystalline peak and the peak with the smaller diffraction angle 2θ is identified as the amorphous halo peak, the degree of crystallinity expressed as 100×(area of ​​crystalline peak) / (sum of area of ​​crystalline peak and area of ​​amorphous halo peak) is 40% or higher.

11. The organic piezoelectric film of any one of claims 1 to 10 is used in one or more of the group selected from detectors, actuators, touch panels, tactile devices, vibration power generation devices, loudspeakers and microphones.

12. A piezoelectric material, which is a laminate, and having an organic piezoelectric thin film as claimed in any one of claims 1 to 10, and an electrode disposed on the surface of at least one of the aforementioned organic piezoelectric thin films.

13. A method for manufacturing an organic piezoelectric thin film as claimed in any one of claims 1 to 10, comprising steps A, B and C, wherein step A is to prepare a non-stretched and non-polarized fluorinated vinylidene polymer film by casting; step B is to perform polarization treatment on the aforementioned non-stretched and non-polarized fluorinated vinylidene polymer film; and step C is to perform heat treatment on the non-stretched fluorinated vinylidene polymer film in step B at any time point, wherein step A includes step A3 of heating within the range of (T-10)℃ to (T+5)℃ when the melting point of the fluorinated vinylidene polymer is set to T℃.

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