JP6993555B2 - Organic piezoelectric film - Google Patents

Description

The present invention relates to an organic piezoelectric film.

Conventionally, various organic piezoelectric films and inorganic dielectric films are known as films or films having piezoelectricity.
Among them, the organic piezoelectric film has an advantage of having flexibility unlike the inorganic dielectric film, and therefore can be applied to various applications.
For example, Patent Document 1 discloses a polarized vinylidene fluoride / tetrafluoroethylene copolymer film for a touch panel or for touch pressure detection as a piezoelectric film.

In recent years, due to the advantage of excellent operability, an increasing number of electronic devices are equipped with a touch panel instead of a mechanical button as an input member. However, in the case of a mechanical button, the user can obtain an operation feeling by moving the button, whereas the touch panel has a disadvantage that such an operation feeling cannot be obtained.
In order to eliminate such a disadvantage, a touch panel provided with a flexible piezo actuator that feeds back the tactile sensation to the user who operates the touch panel has been proposed (for example, Patent Document 2). A device using such a technique of feeding back a tactile sensation to a user who operates a touch panel is generally called a haptic device.

On the other hand, mobile electronic devices such as smartphones and tablets are equipped with a secondary battery because they are carried by the user. In order to reduce the frequency of charging, a vibration power generation device using a piezoelectric element that can be used in such electronic devices has been proposed (Patent Document 3).

The piezoelectric film is a piezoelectric element that has good workability and is easy to thin in a large area, and it is possible to manufacture a dynamic pressure sensor having a large area and high voltage sensitivity as compared with a conventional ceramic piezoelectric element. For example, it is used as a pressure sensor that detects the load applied to an elastic support such as a bed, mat, or sheet, and determines the presence or absence of a person, animal, object, or the like.

In recent years, research on flexible displays using flexible substrates such as plastic has been advanced.
As a substrate for such a flexible display, for example, Patent Document 4 discloses a flexible display substrate in which a gas barrier layer and a transparent conductive layer are laminated on a transparent plastic film.
The flexible display has advantages in lightness, thinness, flexibility, and the like as compared with a display using a conventional glass substrate, and therefore can be installed on a curved surface such as a cylinder. Furthermore, since it can be rolled up and stored, it does not impair portability even on a large screen. Due to these advantages, flexible displays are attracting attention in applications such as posting advertisements and display devices such as PDAs (Personal Digital Assistants).
When such a flexible display is used as an image display device and a sound generator that reproduces sound together with an image, such as a television receiver, a speaker that is an acoustic device for generating sound is required.
Here, as the conventional speaker shape, a funnel-shaped so-called cone shape, a spherical dome shape, or the like is generally used. However, if these speakers are built in the above-mentioned flexible display, the lightness and flexibility which are the advantages of the flexible display may be impaired. On the other hand, if the speaker is externally attached, there is a risk that it will not be easy to carry, it will be difficult to install it on a curved wall, and the aesthetic appearance will be impaired.
Against this background, for example, Patent Document 5 discloses that a sheet-like flexible piezoelectric film is used as a speaker that can be integrated into a flexible display without impairing lightness and flexibility. Has been done.

Japanese Unexamined Patent Publication No. 2011-22679 Japanese Patent Application Laid-Open No. 2003-288158 Japanese Unexamined Patent Publication No. 2011-97661. Japanese Unexamined Patent Publication No. 2000-338901 Japanese Unexamined Patent Publication No. 2008-294493

In recent years, there is a demand for a touch panel having a larger screen. Therefore, in a touch panel capable of detecting touch pressure, it is desirable that the piezoelectric film used for detecting touch pressure also has a large screen.
However, when the conventional piezoelectric film is used for such a large-screen touch panel, the small in-plane variation in piezoelectricity is not sufficient.
Specifically, if the in-plane variation in the piezoelectricity of the organic piezoelectric film used for a touch panel capable of detecting touch pressure (particularly a touch panel with a large screen) is not sufficient, the touch position may be the same even if the pressure is the same. Since the electric signal generated by the device fluctuates, there is a problem that the device determines that the pressing is different and causes a malfunction.

Further, when the conventional piezoelectric film is used for a haptic device, the small in-plane variation of the piezoelectricity is not sufficient.
Specifically, if the in-plane variation in the piezoelectricity of the organic piezoelectric film used for the haptic device is not sufficient, the tactile sensation to be fed back varies, a stable operation feeling cannot be obtained, and an operation error occurs. And there is a problem of causing malfunction of the device.

Further, when the conventional piezoelectric film is used for a vibration power generation device, the small in-plane variation in piezoelectricity is not sufficient.
Specifically, if the in-plane variation in the piezoelectricity of the organic piezoelectric film used for the vibration power generation device is not sufficient, a constant and stable power generation amount cannot be obtained even if the vibration amount is the same. There's a problem.

Further, if the in-plane variation in the piezoelectricity of the organic piezoelectric film used for the pressure sensor (particularly a large area pressure sensor) is not sufficient, the electric signal generated depending on the position where the pressure is applied even if the pressure is the same. There is a problem that the sensing becomes unstable because the voltage fluctuates.

In addition, if the in-plane variation in the piezoelectricity of the organic piezoelectric film used for flat speakers (particularly large-area flat speakers) is not sufficient, the sound generated varies depending on the location in the plane, resulting in poor sound quality. There is a problem of doing.

Therefore, it is an object of the present invention to provide an organic piezoelectric film having particularly small in-plane variation in piezoelectricity.

As a result of diligent studies, the present inventors have conducted diligent studies.
We have found that the above problems can be solved by an organic piezoelectric film having a coefficient of variation of the piezoelectric constant d ₃₃ of 50% or less, and have completed the present invention.

The present invention includes the following aspects.

Item 1.
An organic piezoelectric film having a coefficient of variation of the piezoelectric constant d ₃₃ of 2.0 or less.
Item 2.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 0.5 to 30 pC / N.
Item 3.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 0.5 to 2.0 pC / N.
Item 4.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 2.0 to less than 4.0 pC / N, and the coefficient of variation thereof is 1.0 or less.
Item 5.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 4.0 to less than 6.0 pC / N, and the coefficient of variation thereof is 0.6 or less.
Item 6.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 6.0 to less than 10.0 pC / N, and the coefficient of variation thereof is 0.4 or less.
Item 7.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 10.0 to 14.0 pC / N or less, and the coefficient of variation thereof is 0.3 or less.
Item 8.
Item 2. The organic piezoelectric film according to Item 1, wherein the piezoelectric constant d ₃₃ is in the range of 14.0 to 30.0 pC / N, and the coefficient of variation thereof is 0.15 or less.
Item 9.
Item 6. The organic piezoelectric film according to any one of Items 1 to 8, wherein the tensile elastic modulus is in the range of 0.4 to 5 GPa.
Item 10.
Item 6. The organic piezoelectric film according to any one of Items 1 to 9, wherein the retardation is in the range of 200 to 10000 nm.
Item 11.
Item 6. The organic piezoelectric film according to any one of Items 1 to 9, wherein the retardation is in the range of 0.5 to 200 nm.
Item 12.
Item 6. The organic piezoelectric film according to any one of Items 1 to 11, which comprises a polarized fluorovinylidene polymer film.
Item 13.
Item 6. The organic piezoelectric film according to any one of Items 1 to 12, wherein the internal haze value is in the range of 0.05 to 80%.
Item 14.
Item 6. The organic piezoelectric film according to any one of Items 1 to 12, wherein the internal haze value is in the range of 5 to 90%.
Item 15.
A piezoelectric panel having the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1 to 13).
Item 16.
A pressure sensor having the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1 to 12 and 14).
Item 17.
A haptic device having the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14).
Item 18.
A vibration power generation device having the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14).
Item 19.
A flat speaker having the organic piezoelectric film according to any one of Items 1 to 14 (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14).

According to the present invention, there is provided an organic piezoelectric film having a small in-plane variation in piezoelectricity.
The organic piezoelectric film of the present invention is excellent in that, for example, when it is used for a touch panel capable of detecting touch pressure (particularly, even when it is used for a touch panel capable of detecting a large area of touch pressure), malfunction is unlikely to occur. ..
Further, the organic piezoelectric film of the present invention is excellent in that stable sensing can be realized, for example, when it is used for a pressure sensor (particularly, even when it is used for a pressure sensor having a large area).
Further, the organic piezoelectric film of the present invention is excellent in that, when used for a haptic device, for example, operation errors and malfunction of the device are unlikely to occur.
Further, the organic piezoelectric film of the present invention is excellent in that, for example, when it is used in a vibration power generation device, a constant and stable power generation amount can be obtained.
Further, the organic piezoelectric film of the present invention is excellent in that high sound quality can be obtained, for example, when it is used for a flat speaker (particularly, even when it is used for a large area flat speaker).

It is a schematic diagram which shows the outline of the manufacturing apparatus used for manufacturing the organic piezoelectric film of Example 3.

Terms Symbols and abbreviations herein are in the context of the present specification and are to be understood as commonly used in the art to which the present invention belongs, unless otherwise noted.
In the present specification, the phrase "contains" is used with the intention of including the phrase "consisting of" and the phrase "consisting of".
In the present specification, "detection" of "touch position" means determination of touch position, while "detection" of "touch pressure" means determination of presence / absence of pressing, speed, magnitude or a combination thereof. means.
As used herein, the term "touch" includes touching, being touched, being pushed, being pushed, and being in contact.
As used herein, the term "polarization" means that the surface is charged. That is, the polarized film can be an electret.
As used herein, the term "haptic device" means a device having the ability to feed back tactile sensation to the user.
Unless otherwise stated, the symbols and abbreviations herein are in the context of the present specification and are understood to have the meaning commonly used in the art to which the present invention belongs.
As used herein, the "variable value" is the ratio of standard deviation / arithmetic mean.

Organic Piezoelectric Film The organic piezoelectric film of the present invention is an organic piezoelectric film having a coefficient of variation of the piezoelectric constant d ₃₃ of 2.0 or less.
Hereinafter, the organic piezoelectric film of the present invention will be described in detail.

The organic piezoelectric film of the present invention is a film (polymer film) formed from a polymer which is an organic substance. Examples of the "organic piezoelectric film" include polarized fluorovinylidene-based polymer films, odd-chain nylon piezoelectric films, and polylactic acid. The "organic piezoelectric film" may contain components other than the polymer. The "organic piezoelectric film" includes a film made of the polymer and a film in which an inorganic substance is dispersed in the polymer.
The content of the polymer (that is, the polymer forming the organic piezoelectric film of the present invention) in the organic piezoelectric film of the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, still more preferably 90. It is mass%. The upper limit of the content is not particularly limited, and may be, for example, 100% by mass or 99% by mass.
The polymer is preferably a vinylidene fluoride-based polymer.
The organic piezoelectric film of the present invention preferably comprises a polarized vinylidene fluoride-based polymer film.
In the present specification, examples of the "vinylidene fluoride-based polymer film" include vinylidene fluoride / tetrafluoroethylene copolymer film, vinylidene fluoride / trifluoroethylene copolymer film, and polyvinylidene fluoride film. Can be mentioned.
The vinylidene fluoride-based polymer film is preferably a vinylidene fluoride / tetrafluoroethylene copolymer film.
The "vinylidene fluoride polymer film" may contain an additive usually used for a resin film.

The "vinylidene fluoride-based polymer film" is a film composed of a vinylidene fluoride-based polymer and contains a vinylidene fluoride-based polymer.

As an example of the "vinylidene fluoride polymer",
Examples thereof include (1) a copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith; and (2) polyvinylidene fluoride.

Examples of the "monomer capable of copolymerizing with this" in the "(1) copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith" include trifluoroethylene and tetrafluoroethylene. , Hexafluoropropylene, chlorotrifluoroethylene, and vinyl fluoride.
The "one or more monomers copolymerizable with this" or one of them is preferably tetrafluoroethylene.
Preferred examples of the "vinylidene fluoride-based polymer" include vinylidene fluoride / tetrafluoroethylene copolymer.
The "vinylidene fluoride / tetrafluoroethylene copolymer" may contain repeating units derived from monomers other than vinylidene fluoride and tetrafluoroethylene, as long as the properties according to the present invention are not significantly impaired.
The above-mentioned "(1) copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith" contains 50 mol% or more (preferably 60 mol% or more) of repeating units derived from vinylidene fluoride. )contains.
The molar ratio of (repeating unit derived from tetrafluoroethylene) / (repeating unit derived from vinylidene fluoride) in the "vinylidene fluoride / tetrafluoroethylene copolymer" is preferably 5/95 to 36/64. It is within the range, more preferably within the range of 15/85 to 25/75, and even more preferably within the range of 18/82 to 22/78.

The "vinylidene fluoride / tetrafluoroethylene copolymer" may contain repeating units derived from monomers other than vinylidene fluoride and tetrafluoroethylene, as long as the properties according to the present invention are not significantly impaired. Usually, the content of such repeating units is 10 mol% or less. Such a monomer is not limited as long as it can be copolymerized with a vinylidene fluoride monomer and a tetrafluoroethylene monomer, but examples thereof include.
(1) Fluoromonomer (eg, vinylfluoride (VF), trifluoroethylene (TrFE), hexafluoropropene (HFP), 1-chloro-1-fluoro-ethylene (1,1-CFE), 1-chloro- 2-Fluoro-Ethylene (1,2-CFE), 1-Chloro-2,2-Difluoroethylene (CDFE), Chlorotrifluoroethylene (CTFE), Trifluorovinyl Monomer, 1,1,2-Trifluorobutene- 4-Bromo-1-butene, 1,1,2-trifluorobutene-4-silane-1-butene, perfluoroalkyl vinyl ether, perfluoromethyl vinyl ether (PMVE), perfluoropropyl vinyl ether (PPVE), perfluoroacryllate, 2, 2,2-Trifluoroethyl acrylate, 2- (perfluorohexyl) ethyl acrylate); and (2) Hydrocarbon monomers (eg, ethylene, propylene, maleic anhydride, vinyl ether, vinyl ester, allyl glycidyl ether, acrylic). Examples thereof include acid-based monomers, methacrylic acid-based monomers, and vinyl acetate.

Preferable examples of the "inorganic substance" include inorganic oxide particles. By containing the "inorganic oxide particles", the highly dielectric film of the present invention can have a high dielectric constant. Further, this makes it possible to significantly improve the volume resistivity while maintaining a high dielectric constant.

Preferable examples of the "inorganic substance" include inorganic oxide particles. By containing the "inorganic oxide particles", the organic piezoelectric film of the present invention can have a high dielectric constant. In addition, the volume resistivity can be significantly improved while maintaining a high dielectric constant. In addition, the electrical insulation can be improved.

The "inorganic oxide particles" are preferably at least one selected from the group consisting of the following inorganic oxide particles (B1) to (B3).

[Inorganic Oxide Particles (B1)] Particles of inorganic oxides of metal elements of Group 2, 3, 4, 12, or 13 in the periodic table, or composite particles of these inorganic oxides. Examples thereof include Be, Mg, Ca, Sr, Ba, Y, Ti, Zr, Zn, and Al. Of these, oxides of Al, Mg, Y, and Zn are preferable because they are general-purpose, inexpensive, and have a high volume resistivity.
Among them, specifically, particles of at least one metal oxide selected from the group consisting of Al ₂ O ₃ , MgO, ZrO ₂ , Y ₂ O ₃ , BeO, and MgO · Al ₂ O ₃ have a volume. It is preferable because of its high resistance.
Among them, Al ₂ O ₃ having a γ-type crystal structure has a large specific surface area and is dispersed in the above-mentioned “polymer” such as a vinylidene fluoride-based polymer, particularly a vinylidene fluoride / tetrafluoroethylene copolymer. It is preferable because of its good properties.

[Inorganic Oxide Particles (B2)] Formula: M ¹ _a1 M ² _b1 O _c1 (In the formula, M ¹ is a Group 2 metal element; M ² is a Group 4 metal element; a1 is 0.9 to 1.1. B1 is 0.9 to 1.1; c1 is 2.8 to 3.2; M ¹ and M ² can be one or more metal elements, respectively). Represented Inorganic Composite Oxide Particles As the "Group 4 metal element", for example, Ti and Zr are preferable.
As the "Group 2 metal element", for example, Mg, Ca, Sr, and Ba are preferable.
Among the "particles of the inorganic composite oxide", specifically, at least one selected from the group consisting of BaTIO ₃ , SrTIO ₃ , CaTIO ₃ , MgTIO ₃ , BaZrO ₃ , SrZrO ₃ , CaZrO ₃ , and MgZrO ₃ . Particles of the seed inorganic oxide are preferred because of their high volumetric resistance.

[Inorganic Oxide Particles (B3)] Oxides of metal elements of Group 2, Group 3, Group 4, Group 12, or Group 13 of the Periodic Table, and Inorganic Oxide Composite Particles of Silicon Oxide. "B3)" is a composite particle of the "inorganic oxide" of the "inorganic oxide particles (B1)" and silicon oxide.
Specifically, the "inorganic oxide particles (B3)" is specifically selected from the group consisting of, for example, 3A1 ₂ O _{3.2SiO 2} , 2MgO · SiO ₂ , ZrO ₂ · SiO ₂ , and MgO · SiO ₂ . Examples include particles of seed inorganic oxides.

The "inorganic oxide particles" do not necessarily have to be highly dielectric, and can be appropriately selected depending on the use of the organic piezoelectric film of the present invention. For example, by using one kind of general-purpose and inexpensive metal oxide particles (B1) (particularly, Al ₂ O ₃ particles and Mg O particles), the volume resistivity can be improved. The relative permittivity (1 kHz, 25 ° C.) of the particles (B1) of one of these metal oxides is usually less than 100, preferably 10 or less.

The "inorganic oxide particles" include ferroelectric oxide particles (for example, inorganic oxide particles (B2)) having a ferroelectricity (relative permittivity (1 kHz, 25 ° C.) of 100 or more) for the purpose of improving the dielectric constant. (B3)) may be used. Examples of the inorganic material constituting the ferroelectric inorganic oxide particles (B2) and (B3) include composite metal oxides, composites thereof, solid solutions, sol-gel bodies and the like, but are limited to these. is not it.

The organic piezoelectric film of the present invention can contain the "inorganic oxide particles" in an amount of preferably 0.01 to 300 parts by mass, more preferably 0.1 to 100 parts by mass, based on 100 parts by mass of the "polymer". .. If the content of the "inorganic oxide particles" is too large, it may be difficult to uniformly disperse the "inorganic oxide particles" in the "polymer", and electrical insulation (withstand voltage). ) May decrease. Further, when the content is 300 parts by mass or more, the film may become brittle and the tensile strength may decrease. From this point of view, the upper limit of the content is preferably 200 parts by mass, more preferably 150 parts by mass. If the content is too small, it is difficult to obtain the effect of improving the electrical insulation. From this point of view, the lower limit of the content is preferably 0.1 part by mass, more preferably 0.5 part by mass, and further preferably 1 part by mass. On the other hand, when the organic piezoelectric film of the present invention is required to have a high total light transmittance and a low total haze value, the content is preferably smaller, and more particularly to the organic piezoelectric film of the present invention. When a high total light transmittance and a low total haze value are required, the organic piezoelectric film of the present invention can preferably not contain the "inorganic oxide particles". As described above, when the organic piezoelectric film of the present invention is required to have a high total light transmittance and a low total haze value, specifically, the organic piezoelectric film of the present invention may be used for a piezoelectric panel such as a touch panel. Can be mentioned.

The average primary particle diameter of the "inorganic oxide particles" is preferably small, and so-called nanoparticles having an average primary particle diameter of 1 μm or less are particularly preferable. By uniformly dispersing such inorganic oxide nanoparticles, the electrical insulating property of the film can be significantly improved with a small amount of compounding. The average primary particle size is preferably 800 nm or less, more preferably 500 nm or less, still more preferably 300 nm or less. The lower limit of the average primary particle size is not particularly limited, but the average primary particle size is preferably 10 nm or more, more preferably 20 nm or more, still more preferably 20 nm or more, from the viewpoint of manufacturing difficulty, uniform dispersion difficulty, and price. It is 50 nm or more. Here, when the organic piezoelectric film of the present invention is required to have a high total light transmittance and a low total haze value, the average primary particle size is preferably smaller. The average primary particle diameter of the "inorganic oxide particles" is calculated using a laser diffraction / scattering type particle size distribution measuring device LA-920 (trade name) (HORIBA, Ltd.) or an equivalent product thereof.

The relative permittivity (25 ° C., 1 kHz) of the "inorganic oxide particles" is preferably 10 or more. From the viewpoint of increasing the dielectric constant of the piezoelectric film, the relative dielectric constant is preferably 100 or more, more preferably 300 or more. The upper limit of the relative permittivity is not particularly limited, but is usually about 3000. The relative permittivity (ε) (25 ° C., 1 kHz) of the "inorganic oxide particles" is measured by measuring the capacitance (C) using an LCR meter, and the capacitance, the electrode area (S), and the thickness of the sintered body ( It is a value calculated from d) by the formula C = εε ₀ × S / d (ε ₀ vacuum permittivity).

The organic piezoelectric film of the present invention may contain other components such as an affinity improver, if necessary.

The "affinity improver" is contained in the organic piezoelectric film of the present invention when the organic piezoelectric film of the present invention contains the "inorganic oxide particles".
The "affinity improver" enhances the affinity between the "inorganic oxide particles" and the "polymer", and the "inorganic oxide particles" are uniformly dispersed in the "polymer". The "inorganic oxide particles" and the "polymer" can be firmly bonded in the film to suppress the generation of voids and increase the relative permittivity.

As the "affinity improver", a coupling agent, a surfactant, or an epoxy group-containing compound is effective.

Examples of the "coupling agent" include organic titanium compounds, organic silane compounds, organic zirconium compounds, organoaluminum compounds, and organophosphorus compounds.

Examples of the "organic titanium compound" include coupling agents such as alkoxytitanium, titanium chelate, and titanium acylate. Among them, alkoxytitanium and titanium chelate are mentioned as preferable examples from the viewpoint of good affinity with the above-mentioned "inorganic oxide particles".

Specific examples thereof include tetraisopropyl titanate, titanium isopropoxyoctylene glycolate, diisopropoxybis (acetylacetonato) titanium, diisopropoxytitanium diisostearate, tetraisopropylbis (dioctylphosphite) titanate, and Examples thereof include isopropyltri (n-aminoethyl-aminoethyl) titanate and tetra (2,2-diallyloxymethyl-1-butyl) bis (di-tridecyl) phosphite titanate.

The "organic silane compound" may be of a high molecular weight type or a low molecular weight type, and examples thereof include alkoxysilanes such as monoalkoxysilane, dialkoxysilane, trialkoxysilane, and tetraalkoxysilane. Can be mentioned. Further, vinylsilane, epoxysilane, aminosilane, metachloroxysilane, mercaptosilane and the like can also be preferably used.

When alkoxysilane is used, hydrolysis can further improve the volume resistivity (improvement of electrical insulation), which is the effect of surface treatment.

Examples of the "organic zirconium compound" include alkoxyzirconium and zirconium chelate.

Examples of the "organoaluminum compound" include alkoxyaluminum and aluminum chelate.

Examples of the "organophosphorus compound" include phosphite ester, phosphoric acid ester, and phosphoric acid chelate.

The "surfactant" as an affinity improver may be of a high molecular weight type or a low molecular weight type, and examples thereof include a nonionic surfactant, an anionic surfactant, and an anionic surfactant. Examples include cationic surfactants. Of these, polymer-type surfactants are preferable because of their good thermal stability.

Examples of the "nonionic surfactant" include a polyether derivative, a polyvinylpyrrolidone derivative, and an alcohol derivative. Among them, poly has a good affinity with the "inorganic oxide particles". Ether derivatives are preferred.

Examples of the "anionic surfactant" include polymers containing sulfonic acids, carboxylic acids, and salts thereof. Among them, a preferable example is a poly (acrylic acid) derivative and a poly (methacrylic acid) derivative from the viewpoint of good affinity with the above-mentioned "polymer". Can be mentioned.

Examples of the "cationic surfactant" include an amine compound, a compound having a nitrogen-containing heterocyclic ring such as imidazoline, and a halogenated salt thereof.

The "epoxy group-containing compound" as the "affinity improver" may be a low molecular weight compound or a high molecular weight compound, and examples thereof include an epoxy compound and a glycidyl compound. Among them, a low molecular weight compound having one epoxy group is preferable because it has a particularly good affinity with the "polymer".

A preferred example of the "epoxy group-containing compound" is the formula:

(In the formula, R represents a hydrocarbon group having 2 to 10 carbon atoms which may intervene a hydrogen atom, a methyl group, an oxygen atom or a nitrogen atom, or an aromatic ring group which may be substituted. L represents 0. Alternatively, a compound represented by 1), m represents 0 or 1, and n represents an integer of 0 to 10) can be mentioned.

等の、ケトン基、又はエステル基を有する化合物が挙げられる。 As a specific example,

Examples thereof include compounds having a ketone group or an ester group.

The "affinity improver" can be used in an amount within a range in which the effect of the present invention is not lost, but specifically, from the viewpoint of uniform dispersion and high relative permittivity of the obtained film. The amount thereof is preferably in the range of 0.01 to 30 parts by mass, more preferably in the range of 0.1 to 25 parts by mass, and further preferably in the range of 1 to 20 parts with respect to 100 parts by mass of the "inorganic oxide particles". It is within the range of parts by mass.

Further, the organic piezoelectric film of the present invention may contain additives other than these as long as the effects of the present invention are not lost.

In the present specification, the "piezoelectric constant d ₃₃ " of the organic piezoelectric film is a value determined according to the following measuring method.

Piezoelectric constant and its coefficient of variation

<Method of determining the piezoelectric constant d ₃₃ >
The measurement of the piezoelectric constant d ₃₃ is performed using the piezometer system PM300 manufactured by PIEZOTEST (a pin having a tip of 1.5 mmφ is attached as a sample fixing jig) or an equivalent product thereof. Here, the piezoelectric constant d ₃₃ is measured at 10 points on the film selected excluding arbitrariness, and the arithmetic mean value thereof is defined as the piezoelectric constant d ₃₃ . In the present invention, selecting 10 points on the film excluding arbitrariness can be performed, for example, by selecting 10 points at intervals of 50 mm on a straight line. Here, the arbitrariness means that the coefficient of variation, which will be described later, is intended to be small.
The measured value of the piezoelectric constant d ₃₃ may be a positive value or a negative value depending on the front and back of the film to be measured, but in the present specification, the absolute value is described as the value of the piezoelectric constant d ₃₃ . ..

The coefficient of variation of the "piezoelectric constant d ₃₃ " of the organic piezoelectric film is the ratio of the standard deviation of the "piezoelectric constant d ₃₃ " to the arithmetic mean.

The coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention is 2.0 or less.
As a result, the organic piezoelectric film of the present invention has a small in-plane variation in piezoelectricity, and specifically, it has the following advantages, for example.
When the organic piezoelectric film of the present invention is used, for example, in a touch panel capable of detecting touch pressure (particularly, even when used in a touch panel capable of detecting a large area of touch pressure), malfunction is unlikely to occur.
Further, the organic piezoelectric film of the present invention can realize stable sensing, for example, when used for a pressure sensor (particularly, even when used for a pressure sensor having a large area).
Further, when the organic piezoelectric film of the present invention is used for a haptic device, for example, an operation error and a malfunction of the device are unlikely to occur.
Further, when the organic piezoelectric film of the present invention is used in a vibration power generation device, for example, a constant and stable power generation amount can be obtained.
Further, the organic piezoelectric film of the present invention is excellent in that high sound quality can be obtained, for example, when it is used for a flat speaker (particularly, even when it is used for a large area flat speaker).

From this point of view, the coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention is preferably smaller, and therefore the upper limit of the coefficient of variation is preferably 1.0, more preferably 0.6. It can be even more preferably 0.4, even more preferably 0.3, and particularly preferably 0.15.

On the other hand, in the use or mode of use of the organic piezoelectric film of the present invention, it may not be necessary to have a very small coefficient of variation. In this case, a larger coefficient of variation may be advantageous in terms of manufacturing cost and the like.
Therefore, the lower limit of the coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention can be, for example, 0.0001, 0.001, 0.01, or 0.02.

The coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film is, for example, in the range of 0.01 to 1.0, in the range of 0.01 to 0.6, in the range of 0.01 to 0.5, and 0. It can be in the range of 01 to 0.4, or in the range of 0.01 to 0.3.

The preferred piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention may differ depending on its use, mode of use, and the like.
The upper limit of the preferable piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention can be, for example, 30 pC / N, 28 pC / N, 26 pC / N, or 20 pC / N.
The lower limit of the preferable piezoelectric constant d ₃₃ of the organic piezoelectric film of the present invention can be, for example, 0.5 pC / N, 3 pC / N, 5 pC / N, 7 pC / N, or 9 pC / N.
The piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 0.5 to 30 pC / N, in the range of 0.5 to 28 pC / N, in the range of 0.5 to 26 pC / N, and 0.5 to 20 pC / N. It can be in the range of 3 to 30 pC / N, in the range of 5 to 30 pC / N, in the range of 7 to 30 pC / N, or in the range of 9 to 30 pC / N.

The organic piezoelectric film of one preferred aspect of the present invention (the aspect of item 3 above) has a piezoelectric constant d ₃₃ in the range of 0.5 to 2.0 pC / N. The coefficient of variation of the piezoelectric constant d ₃₃ of the organic piezoelectric film of this embodiment is preferably 1.0 or less, more preferably 0.8 or less, and even more preferably 0.5 or less. The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel or a pressure sensor.

In another preferred embodiment of the present invention (the aspect of item 4 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 2.0 to 4.0 pC / N and has a coefficient of variation of 1. It is 0 or less (preferably 0.8 or less, more preferably 0.5 or less, still more preferably 0.3 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel or a pressure sensor.

In another preferred embodiment of the present invention (the aspect of item 5 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 4.0 to 6.0 pC / N or a coefficient of variation of 0. 6 or less (preferably 0.5 or less, more preferably 0.4 or less, still more preferably 0.3 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generator, or a flat speaker.

In another preferred embodiment of the present invention (the aspect of item 6 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 6.0 to less than 10.0 pC / N, and has a coefficient of variation of 0. 4 or less (preferably 0.3 or less, more preferably 0.25 or less, still more preferably 0.2 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generator, or a flat speaker.

In another preferred embodiment of the present invention (the aspect of item 7 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 10.0 to 14.0 pC / N or a coefficient of variation of 0. 3 or less (preferably 0.25 or less, more preferably 0.2 or less, still more preferably 0.15 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generator, or a flat speaker.

In another preferred embodiment of the present invention (the aspect of item 8 above), the organic piezoelectric film has a piezoelectric constant d ₃₃ in the range of 14.0 to 30.0 pC / N and a coefficient of variation of 0.15. The following (preferably 0.1 or less, more preferably 0.08 or less, still more preferably 0.07 or less). The organic piezoelectric film of this embodiment can be suitably used for, for example, a piezoelectric panel, a pressure sensor, a haptic device, a piezoelectric vibration power generator, or a flat speaker.

Total light transmittance

<Method of determining total light transmittance>
In the present specification, "total light transmittance" is obtained by a light transmittance test using a haze meter NDH-7000 SP (product name, Nippon Denshoku Kogyo) or an equivalent product based on JIS K-7361.

The preferred total light transmittance of the organic piezoelectric film of the present invention may vary depending on its use, mode of use, and the like.
In applications or usage modes where high transparency is required, higher total light transmittance is required. On the other hand, in applications or usage modes where high total light transmittance is not required, an organic piezoelectric film having a relatively low total light transmittance may be advantageous in terms of manufacturing cost and the like.
The upper limit of the total light transmittance of the organic piezoelectric film of the present invention can be, for example, 97%, 96%, or 94%.
The lower limit of the total light transmittance of the organic piezoelectric film of the present invention can be, for example, 70%, 80%, or 90%.
The total light transmittance of the organic piezoelectric film of the present invention can be, for example, in the range of 70 to 97%, in the range of 80 to 96%, or in the range of 80 to 94%.

Haze value

<Method of determining haze value>
In this specification, the "total haze value" is based on JIS K-7136, and the haze meter NDH-7000 SP (product name, Nippon Denshoku Kogyo) or its equivalent is used for haze (HAZE,). Turbidity) Obtained by the test.
In the present specification, "inner haze" refers to measuring the haze value by putting water in a glass cell, inserting a film into the glass cell, and measuring the haze value in the method for measuring the total haze value. Is obtained.
In the present specification, the "outer haze" is calculated by subtracting the internal haze value from the total haze value of the film.

The preferred total haze value of the organic piezoelectric film of the present invention may vary depending on its use, mode of use, and the like.
In applications or modes of use where high transparency is required, a lower haze value is required. On the other hand, in applications or usage modes in which a low total haze value is not required, an organic piezoelectric film having a relatively high total haze value may be more advantageous in terms of manufacturing cost and the like.
The upper limit of the total haze value of the organic piezoelectric film of the present invention can be, for example, 90%, 80%, 70%, or 60%.
The lower limit of the total haze value of the organic piezoelectric film of the present invention can be, for example, 0.3%, 0.4%, 0.5%, 5%, 20%, or 40%.
The total haze value of the organic piezoelectric film of the present invention is, for example, in the range of 0.3 to 80%, in the range of 0.4 to 70%, in the range of 0.5 to 70%, and in the range of 0.5 to 60%. It can be within the range of, or within the range of 0.5 to 50%.

The preferable internal haze value of the organic piezoelectric film of the present invention may differ depending on its use, mode of use, and the like.
In applications or modes of use where high transparency is required, a lower internal haze value is required. On the other hand, in applications or usage modes in which a low total haze value is not required, an organic piezoelectric film having a relatively high internal haze value may be more advantageous in terms of manufacturing cost and the like.
The upper limit of the internal haze value of the organic piezoelectric film of the present invention can be, for example, 90%, 80%, 70%, 60%, 50%, or 40%.
The lower limit of the internal haze value of the organic piezoelectric film of the present invention can be, for example, 0.01%, 0.05%, 0.1%, 0.15%, 5%, 10%, or 20%. ..
The internal haze value of the organic piezoelectric film of the present invention is, for example, in the range of 0.05 to 80%, in the range of 0.1 to 70%, or in the range of 0.15 to 60%, and in the range of 5 to 90%. Within the range, it can be within the range of 10-80%, or within the range of 20-70%.

The preferred external haze value of the organic piezoelectric film of the present invention may vary depending on its use, mode of use, and the like.
In applications or modes of use where high transparency is required, a lower external haze value is required. On the other hand, in applications or usage modes in which a low total haze value is not required, an organic piezoelectric film having a relatively high external haze value may be more advantageous in terms of manufacturing cost and the like.
Since the external haze value is calculated by subtracting the internal haze value from the total haze value of the film, examples of the external haze value of the organic piezoelectric film of the present invention are the above-mentioned example of the total haze value and the above-mentioned internal haze value. It is understood from the example of haze.

thickness

<How to determine the thickness>
In the present specification, the arithmetic mean value of each thickness measured at 10 points on the film selected excluding arbitrariness is defined as the film thickness.

The lower limit of the thickness of the organic piezoelectric film of the present invention can be, for example, 0.1 μm, 0.5 μm, 0.8 μm, 1 μm, 3 μm, 6 μm, 9 μm, or 10 μm.
The upper limit of the thickness of the organic piezoelectric film of the present invention can be, for example, 200 μm, 100 μm, 50 μm, 40 μm, or 30 μm.
The thickness of the organic piezoelectric film of the present invention is, for example, in the range of 0.1 to 200 μm, in the range of 1 to 100 μm, in the range of 0.5 to 100 μm, in the range of 0.8 to 50 μm, and 0.8. Within ~ 40 μm, within 3-100 μm, within 3-50 μm, within 6-50 μm, within 9-40 μm, within 10-50 μm, within 10-40 μm, or 10 It can be in the range of ~ 30 μm. The preferred thickness can vary depending on the application of the organic piezoelectric film of the present invention.

The organic piezoelectric film of the present invention can be a stretched or unstretched piezoelectric film.
The organic piezoelectric film of the present invention is preferably a non-stretched piezoelectric film.
In this regard, the organic piezoelectric film of the present invention has high thickness uniformity. Specifically, the organic piezoelectric film of the present invention has a thickness variation coefficient of 10% or less. Here, the coefficient of variation of the thickness is the ratio of the standard deviation of the thickness of the film, which is the arithmetic mean value, to the arithmetic mean.
Further, in relation to this, the organic piezoelectric film of the present invention has high shape uniformity and visual uniformity (that is, wrinkles and deflection (in a state where tension other than tension due to gravity is not applied). There is little curvature).
Further, in relation to this, the organic piezoelectric film of the present invention has high uniformity of polarizability.

The organic piezoelectric film of the present invention is preferably a non-stretched piezoelectric film.
In this regard, the organic piezoelectric film of the present invention has high thickness uniformity. Specifically, the organic piezoelectric film of the present invention has a thickness variation coefficient of 10% or less. Here, here, the thickness is measured at 5 mm intervals (that is, at the grid points of a 5 mm × 5 mm square grid) over the entire plane of the film, and the arithmetic mean value thereof is used for the organic piezoelectric film of the present invention. The thickness. The coefficient of variation of the thickness of the organic piezoelectric film is the ratio of the standard deviation of the thickness to the arithmetic mean.
Further, in relation to this, the organic piezoelectric film of the present invention has high shape uniformity and visual uniformity (that is, wrinkles and deflection (in a state where tension other than tension due to gravity is not applied). There is little curvature).
Further, in relation to this, the organic piezoelectric film of the present invention has high uniformity of polarizability.

Tension modulus

<Method of determining tensile elastic modulus>
In the present specification, the tensile elastic modulus is based on JIS K 7127 by cutting a film sample into a width of 20 mm and a length of 100 mm, using an autograph (Shimadzu Corporation), and under the conditions of a chuck distance of 50 mm and a speed of 50 mm / min. Determined by measurement.

The lower limit of the tensile elastic modulus of the organic piezoelectric film of the present invention can be, for example, 0.4 GPa, 0.5 GPa, or 0.6%.
The upper limit of the tensile elastic modulus of the organic piezoelectric film of the present invention can be, for example, 5 GPa, 4 GPa, or 3 GPa.
The tensile elastic modulus of the organic piezoelectric film of the present invention can be, for example, in the range of 0.5 to 10000 nm, in the range of 0.5 to 7000 nm, or in the range of 0.5 to 4000 nm.

Ritaration

<How to determine retardation>
In the present specification, the retardation measures by cutting a film sample into a size of 2 cm × 2 cm or more and using a retardation film / optical material inspection device RETS-100 (product name, Otsuka Electronics) or an equivalent product thereof. Is determined by. In the present specification, a value of 550 nm is adopted as the value of retardation.

The lower limit of the retardation of the organic piezoelectric film of the present invention is not particularly limited, but can be, for example, 0.5 nm.
The upper limit of the retardation of the organic piezoelectric film of the present invention can be, for example, 10,000 nm, 7,000 nm, or 4000 nm.
The retardation of the organic piezoelectric film of the present invention can be preferably in the range of 0.5 to 10000 nm, more preferably in the range of 0.5 to 7000 nm, and even more preferably in the range of 0.5 to 4000 nm. ..
A preferred embodiment of the organic piezoelectric film of the present invention is a stretched film and has a retardation in the range of 200-10000 nm.
Another preferred embodiment of the organic piezoelectric film of the present invention is a non-stretched film and has a retardation in the range of 0.5-200 nm.

Manufacturing Method The organic piezoelectric film of the present invention is, for example,
Step A to prepare a non-stretched and non-polarized polymer film (eg, non-polarized vinylidene fluoride polymer film) by a casting method;
Step B to polarize the unstretched and non-polarized polymer film; and step C to heat-treat the unstretched polymer film at any time point with respect to step B.
It can be manufactured by a manufacturing method including.

Step A (film preparation step)

The method for producing the "non-stretched and non-polarized film" by the casting method is, for example,
(1) In the solvent, the polymer (that is, the polymer forming the organic piezoelectric film of the present invention) (eg, vinylidene fluoride-based polymer), and the desired component (eg, inorganic oxide particles, and A step of preparing a liquid composition by dissolving or dispersing the affinity improver) in a solvent to dissolve the liquid composition;
(2) A production method including a step of casting (coating) the liquid composition on a substrate; and (3) a step of vaporizing the solvent by heating and drying to form a film.

The dissolution temperature in the preparation of the liquid composition is not particularly limited, but it is preferable to raise the dissolution temperature because the dissolution can be promoted. However, if the melting temperature is too high, the obtained film tends to be colored. Therefore, the melting temperature is preferably room temperature or higher and 80 ° C. or lower.
Further, from the viewpoint of preventing such coloring, preferred examples of the solvent include a ketone solvent (eg, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone, cyclohexanone), and an ester solvent. Solvents (eg, ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate), ether solvents (eg, tetrahydrofuran, methyl tetrahydrofuran, dioxane), and amide solvents (eg, dimethylformamide (DMF), dimethylacetamide). Can be mentioned. These solvents may be used alone or in combination of two or more. As the solvent, an amide-based solvent which is a general-purpose solvent for dissolving polyvinylidene fluoride (PVDF) may be used, but the content of the amide-based solvent in the solvent is preferably 50% by weight or less.

The spreading (coating) of the liquid composition on the substrate is a knife coating method, a cast coating method, a roll coating method, a gravure coating method, etc. It may be performed based on a conventional method such as a blade coating method, a rod coating method, an air doctor coating method, or a slot die method. Of these, the gravure coating method or the slot die method is preferable because it is easy to operate, there is little variation in the obtained film thickness, and it is excellent in productivity. As the base material, for example, a polyethylene terephthalate (PET) film can be used.

The vaporization of the solvent by heating and drying may be carried out according to a usual method of heating and drying for film formation. The heat drying can be preferably carried out, for example, by passing the liquid composition coated on the substrate through a drying oven in a roll-to-roll manner. Alternatively, the film may be formed by heating and drying in a batch manner.
The drying temperature varies depending on the type of polymer constituting the organic piezoelectric film of the present invention, but specifically, for example, when the polymer is a vinylidene fluoride / tetrafluoroethylene copolymer, it is preferably 20 ° C. It is in the range of about 200 ° C., more preferably in the range of 60 ° C. to 190 ° C., and even more preferably in the range of 80 ° C. to 190 ° C.

The thickness of the non-polarized film prepared in step A may be set according to the piezoelectric film to be obtained.

Step B (polarization treatment step)
In step B, the non-polarized film is polarized.

The non-polarized copolymer film (hereinafter, may be simply referred to as “non-polarized film”) used in step B is preferably unpolarized. Further, preferably, even in the method for producing an organic piezoelectric film of the present invention, the non-polarized film is not stretched.
The organic piezoelectric film thus obtained has high piezoelectricity even after being exposed to a high temperature. Further, the organic piezoelectric film thus obtained has a small variation in thickness.

The polarization treatment in step B can be performed by a conventional method such as a corona discharge treatment.

The polarization treatment of step B is preferably performed by corona discharge.
Either a negative corona or a positive corona may be used for the corona discharge, but it is desirable to use the negative corona from the viewpoint of the ease of polarization of the non-polarizing resin film.

The corona discharge treatment is not particularly limited, but for example; application is performed to the non-polarized film using a linear electrode as described in JP-A-2011-181748; needle-like to the non-polarized film. It can be carried out by performing the application using electrodes; or by performing the application using grid electrodes on the non-polarized film.
The conditions for the corona discharge treatment may be appropriately set based on the common sense in the technical field to which the present invention belongs. If the conditions of the corona discharge treatment are too weak, the piezoelectricity of the obtained piezoelectric film may be insufficient, while if the conditions of the corona discharge treatment are too strong, the obtained piezoelectric film may have punctate defects. be.
Here, in order to suppress the in-plane variation of the piezoelectric constant d ₃₃ of the obtained polarization film, the distance between each needle-shaped electrode and / or the linear electrode and the film is constant, that is, the electrode and the film. There is no in-plane variation (or extremely small) in the distance between the films (specifically, the difference between the longest distance and the shortest distance is preferably within 6 mm, more preferably within 4 mm, still more preferably within 3 mm. Is desirable).
Further, in order to suppress the in-plane variation of the piezoelectric constant d ₃₃ of the obtained polarized film, for example, when continuous application is performed roll-to-roll, a constant tension is applied to the film so that the film is subjected to constant tension. It is desirable that the film is appropriately and uniformly adhered to the roll.
For example, when continuous application is performed roll-to-roll using a linear electrode, the distance between the linear electrode and the non-polarized film, the film thickness, etc., may vary, but for example, -15 to -25 kV. It is a DC electric field. The processing speed is, for example, 10 to 500 cm / min.
Alternatively, the polarization treatment may be carried out by, for example, sandwiching the non-polarization film from both sides with a flat plate electrode and applying the treatment, in addition to the corona discharge. Specifically, for example, when the application is carried out by sandwiching the non-polarized film from both sides with a flat plate electrode, a DC electric field of 0 to 400 MV / m (preferably 50 to 400 MV / m) and 0.1 seconds to 60 minutes. The condition of the application time of can be adopted.

Process C (heat treatment process)
Step C is performed at any time point with respect to step B. That is, the step C can be carried out before the step B, at the same time as the step B, or after the step B. When the step C is performed after the step B, the heat treatment of the step C can be performed on the polarized film obtained in the step B or the portion where the polarization is completed in the step B. That is, while carrying out the polarization treatment in step B, the heat treatment in step C may be carried out on the portion where the polarization treatment has been completed.
The method of heat treatment is not particularly limited, but for example, the unstretched polymer film (hereinafter, may be simply referred to as the film) is sandwiched between two metal plates to heat the metal plate; the film. The roll is heated in a constant temperature bath; or in the production of the film in a roll-to-roll manner, the metal roll is heated and the film is brought into contact with the heated metal roll; or the film is brought into contact with the heated metal roll. This can be done by rolling-to-roll through a heated furnace. Here, when step C is performed after step B, the polarized film may be heat-treated by itself, or may be laminated on another type of film or metal foil to form a laminated film, which may be heat-treated. .. In particular, in the case of heat treatment at a high temperature, the latter method is preferable because the polarized film is less likely to wrinkle.
The temperature of the heat treatment may vary depending on the type of the polarized film to be heat-treated, and is preferably in the range of (melting point of the polarized film to be heat-treated -100) ° C. to (melting point of the polarized film to be heat-treated +40) ° C. Inside.
Specifically, the temperature of the heat treatment is preferably 80 ° C. or higher, more preferably 85 ° C. or higher, and further preferably 90 ° C. or higher.
The temperature of the heat treatment is preferably 170 ° C. or lower, more preferably 160 ° C. or lower, still more preferably 140 ° C. or lower.
The heat treatment time is usually 10 seconds or longer, preferably 0.5 minutes or longer, more preferably 1 minute or longer, still more preferably 2 minutes or longer.
Further, although the upper limit of the heat treatment time is not limited, the heat treatment time is usually 60 minutes or less.
The conditions of the heat treatment are preferably 90 ° C. or higher for 1 minute or longer.

After the heat treatment, the film is cooled to a predetermined temperature. The temperature is preferably in the range of 0 ° C to 60 ° C and can be room temperature. The cooling rate may be slow cooling or rapid cooling, and rapid cooling is preferable from the viewpoint of productivity. Quenching can be performed by means such as blowing air. In the present specification, the heat treatment of such a film may be referred to as an annealing treatment.

Rolls of Organic Piezoelectric Films The organic piezoelectric films of the invention can preferably be stored and shipped as rolls.
The organic piezoelectric film of the present invention preferably has an elastic modulus of 500 MPa or more from the viewpoint of suppressing the generation of wrinkles when it is formed into such a roll form. The elastic modulus can be adjusted by selecting the material of the film or the like.
The roll of the organic piezoelectric film of the present invention may be made of only the organic piezoelectric film of the present invention, or may be wound by laminating a protective film or the like on the organic piezoelectric film of the present invention, a core of a paper tube or the like, and a roll. The organic piezoelectric film of the present invention wound around the core may be provided.
The roll of the organic piezoelectric film of the present invention preferably has a width of 50 mm or more and a length of 20 m or more.
The roll of the organic piezoelectric film of the present invention can be prepared, for example, by winding the organic piezoelectric film of the present invention using a winding roller and a winding roller.
Here, from the viewpoint of suppressing the deflection of the film, it is preferable to make the unwinding roller and the winding roller parallel as is usually performed.
Further, from the viewpoint of suppressing the deflection of the film, among the organic piezoelectric films of the present invention, a film having an elastic modulus of 500 MPa or more may be used.
As the roller, in order to improve the slipperiness of the film of the present invention, a roller having good slipperiness, specifically, a roller coated with a fluororesin, a plated roller, or a roller coated with a mold release agent is used. Is preferable.
Here, if the film thickness is non-uniform, the so-called roll ears (high edge; the edges are thicker than the axial center of the roll; the film thickness is lower at both ends than the center. In some cases, both ends are dented compared to the center; or the end on the thinner side is dented when the thickness changes in an inclined manner from one end to the other), etc. Roll thickness non-uniformity occurs, which can cause wrinkles. Further, this may cause the film to bend (curve in a state where no tension other than the tension due to gravity is applied) when the film is unwound.
Generally, for the purpose of preventing the roll from standing on the ears, the end of the film, which is the end of the roll, is slit into the slitter, but if the non-uniform thickness of the film extends over a wide range from the edge of the film, the ears are removed. It is difficult to prevent the roll from standing and denting by itself.
In general, the wider the film (eg, width 100 mm or more) and the longer the film length (eg, 50 m or more), the more likely the ears, the dents, and the deflections are to occur.
However, since the organic piezoelectric film of the present invention has high thickness uniformity, the width of the film can be widened (eg, width) as it is or by simply slitting the end of the film, which is the end of the roll, into the slitter ear. Even when the length of the film is long (eg, 50 m or more) and the length of the film is 100 mm or more, the roll can be made into a roll in which the ears, the dents, and the deflection are suppressed.
The ears (film edges) removed by the slits can be collected and recycled as a raw material for the organic piezoelectric film of the present invention.
The roll of the organic piezoelectric film of the present invention has high thickness uniformity, and preferably, the ratio of the thickness of the thicker end portion to the thickness of the axial center portion of the roll is 70 to 130%. It is within the range.
As a result, the roll of the organic piezoelectric film of the present invention suppresses the deflection of the film unwound from the roll.

The surface roughness Ra of the roller used in the production of the organic piezoelectric film of the present invention and its roll is preferably 1 μm or less. In the present specification, the "surface roughness Ra" is the "arithmetic mean height" defined in JIS B0601: 2001.
Further, it is preferable that at least the surface material of the roller used for producing the organic piezoelectric film of the present invention and its roll is polytetrafluoroethylene (PTFE), chromium plating, or stainless steel (SUS).
By these things, wrinkles of a film can be suppressed.

Application Since the organic piezoelectric film of the present invention has high piezoelectricity even after being exposed to high temperature, it can be suitably used for various applications in which high piezoelectricity is required and there is a possibility of being exposed to high temperature. ..
Further, since the organic piezoelectric film of the present invention has flexibility, it can be suitably used for various purposes.

Piezoelectric Panel The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of Items 1 to 13 above) can be used for a piezoelectric panel (eg, a touch panel capable of detecting touch pressure) or the like.
The touch panel having the organic piezoelectric film of the present invention can detect both the touch position and the touch pressure, and the touch pressure detection performance is unlikely to deteriorate even after being exposed to a high temperature.
The organic piezoelectric film of the present invention can be used for any type of touch panel such as a resistance film type and a capacitance type.
When the organic piezo film of the present invention is used for a touch panel, it does not necessarily have to be used for detecting both the touch position and the touch pressure, and the organic piezo film of the present invention has a touch position or a touch pressure. It may also be used for either detection.
The piezoelectric panel having the organic piezoelectric film of the present invention is preferably preferred.
With the first electrode
With the organic piezoelectric film of the present invention
2nd electrode) and
In this order.
The first electrode is placed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is directly or indirectly placed on the other main surface of the organic piezoelectric film of the present invention. Be placed.
Here, the number of organic piezoelectric films included in the piezoelectric panel can be one or more. Here, in order to remove the pyroelectric noise of the piezoelectric panel, the two organic piezoelectric films have a bimorph structure (eg, a bimorph structure as shown in FIG. 18 of the International Publication No. 2015/053343 pamphlet). It may be formed. At this time, the two organic piezoelectric films may be bonded with a transparent adhesive or a transparent adhesive. Here, the thickness of the transparent pressure-sensitive adhesive or the transparent adhesive layer is preferably thicker when its tensile elastic modulus is larger than that of the organic piezoelectric film, and thinner when it is smaller. Further, regarding the thickness of the two organic piezoelectric films, it is preferable that the film on the side to which pressure is applied is thicker.
Examples of the electrode include an ITO (indium tin oxide) electrode, a tin oxide electrode, metal nanowires, metal nanoparticles, an organic conductive resin, and the like.

Pressure sensor The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of the above items 1 to 12 and 14) can be used for the pressure sensor.
The pressure sensor having the organic piezoelectric film of the present invention is preferably preferred.
With the first electrode
With the organic piezoelectric film of the present invention
2nd electrode) and
In this order.
The first electrode is placed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is directly or indirectly placed on the other main surface of the organic piezoelectric film of the present invention. Be placed.
Examples of the electrode include an ITO (indium tin oxide) electrode, a tin oxide electrode, metal nanowires, metal nanoparticles, an organic conductive resin, and the like.

Haptic device The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14) can be suitably used for a haptic device.
The haptic device having the organic piezoelectric film of the present invention is preferably
First electrode,
The organic piezoelectric film of the present invention and the second electrode are provided in this order.
The first electrode is placed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is directly or indirectly placed on the other main surface of the organic piezoelectric film of the present invention. Be placed.
In the haptic device, the organic piezoelectric film of the present invention can convert the electrical energy received through the first electrode and the second electrode into mechanical energy. As a result, the organic piezoelectric film of the present invention is deformed and vibrates, and the tactile sensation can be fed back to the user.

Piezoelectric Vibration Power Generation Device The organic piezoelectric film of the present invention (preferably the organic piezoelectric film according to any one of Items 1, 2, 5 to 12, and 14 above) is suitably used for a piezoelectric vibration power generation device. can.
The piezoelectric vibration power generator having the organic piezoelectric film of the present invention is preferably used.
Preferably,
First electrode,
The organic piezoelectric film of the present invention and the second electrode are provided in this order.
The first electrode is placed directly or indirectly on one main surface of the organic piezoelectric film of the present invention, and the second electrode is directly or indirectly placed on the other main surface of the organic piezoelectric film of the present invention. Be placed.
The organic piezoelectric film of the present invention can convert the mechanical energy of the vibration received by the piezoelectric vibration power generator into electrical energy. The electric energy is sent to a secondary battery or the like via the first electrode and the second electrode.

Flat speaker The organic piezoelectric film of the present invention can be suitably used for a flat speaker.
The flat speaker having the organic piezoelectric film of the present invention is preferably preferred.
Preferably,
First electrode,
The organic piezoelectric film of the present invention and the second electrode are provided in this order.
In the flat speaker, the organic piezoelectric film of the present invention can convert electrical energy received through the first electrode and the second electrode into mechanical energy. As a result, the organic piezoelectric film of the present invention can be deformed, vibrated, and generate sound.

The touch panel having the organic piezoelectric film of the present invention can be used for an input device (that is, an input device having the organic piezoelectric film of the present invention). The input device having the touch panel can input based on the touch position, the touch pressure, or both. The input device having the touch panel can have a position detection unit and a pressure detection unit.

The input device can be used for electronic devices (eg, mobile phones (eg, smartphones), personal digital assistants (PDAs), tablet PCs, ATMs, automatic teller machines, and car navigation systems). The electronic device having the input device can be operated and operated based on the touch position, the touch pressure, or both.

Bimorph type piezoelectric film When the organic piezoelectric film of the present invention is used for a pressure sensor or a haptic device, the organic piezoelectric film of the present invention constitutes a so-called bimorph structure in which two organic piezoelectric films are bonded to each other. May be. That is, the present invention also provides the bimorph type piezoelectric film. When such a bimorph type piezoelectric film is used as a pressure sensor, particularly from the viewpoint of removing pyroelectric noise, the bimorph type piezoelectric film has two organic piezoelectric films so that the polarization directions are opposite to each other. It is preferable to have a bonded bimorph structure. As a result, the surfaces that generate charges of the same polarity due to the temperature rise are arranged so as to be on the outside, so that a part or all of the pyroelectric signals (pyroelectric noise) generated from each pyroelectric film are canceled out. be able to. The bimorph type piezoelectric film can usually have a rectangular (eg, rectangular, square) shape or a circular (eg, elliptical, perfect circular) shape in a plan view. Detection electrodes can be provided on both sides of the bimorph type piezoelectric film (piezoelectric element) (that is, two organic piezoelectric films of the present invention).
The two organic piezoelectric films of the present invention may be bonded to each other with an adhesive sheet or an adhesive layer, may be in direct contact with each other, may be heat-sealed with each other, or may be thermally fused to each other. They may be thermocompression bonded to each other.
The pressure-sensitive adhesive sheet is not particularly limited as long as two organic piezoelectric films of the present invention can be bonded to each other, and may be composed of one or two or more layers. That is, when the pressure-sensitive adhesive sheet is composed of one layer, the pressure-sensitive adhesive sheet is composed of a pressure-sensitive adhesive layer, and when the pressure-sensitive adhesive sheet is composed of two or more layers, both outer layers are pressure-sensitive adhesive layers. When the pressure-sensitive adhesive sheet is composed of three or more layers, the pressure-sensitive adhesive sheet may have a base material layer as an inner layer.
The base material layer in the pressure-sensitive adhesive sheet may be a transparent film, and preferably, for example, a film of polyimide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyparaphenylene sulfide, or polyamide-imide.
The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet can be, for example, a layer containing an acrylic pressure-sensitive adhesive as a pressure-sensitive adhesive.
The adhesive forming the adhesive layer can be, for example, an acrylic adhesive.

Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited thereto.

In the examples and comparative examples described later, the following electrodes were used.
<Electrode used>
(1) Needles for electrodes (needle-shaped electrodes) (R = 0.06 mm; manufactured by Morita Needle Co., Ltd.) arranged in a row on the center line of a 20 mm wide (10 mm thick, 500 mm long) brass rod at 10 mm intervals. Needle-shaped electrode rods (3) with a diameter of 0.1 mm in which electrode needles (R = 0.06 mm; manufactured by Morita Needle Co., Ltd.) are arranged in a row at intervals of 15 mm, similar to the shaped electrode rods (2) and (1). Gold-plated tungsten linear electrode (500 mm long)

In the examples and comparative examples described later, the total light transmittance, the total haze value, and the piezoelectric constant d33 were measured by the following methods.
<Total light transmittance>
The measurement was performed using a haze meter NDH-7000SP (product name, Nippon Denshoku Kogyo) based on the method described in JIS K-7361.
<All haze values>
The measurement was performed using a haze meter NDH-7000SP (product name, Nippon Denshoku Kogyo) based on the method described in JIS K-7136.
<Internal haze value>
Water was put into a quartz cell, a film was inserted into it, and NDH-7000SP (product name, Nippon Denshoku Kogyo) was used for measurement in accordance with JIS K-7136.
<Piezoelectric constant d33 measurement>
The piezoelectric constant d ₃₃ was measured using the piezometer system PM300 manufactured by PIEZOTEST. In this measurement, the sample was clipped at 1N, and the generated charge when a force of 0.25N and 110Hz was applied was read.
<Tension modulus>
The tensile elastic modulus is determined by cutting a film sample into a width of 20 mm and a length of 100 mm and measuring it using an autograph (Shimadzu Corporation) under the conditions of a chuck distance of 50 mm and a speed of 50 mm / min based on JIS K 7127. did.
<Ritaration>
The retardation is determined by cutting a film sample into a size of 2 cm × 2 cm or more and measuring using a retardation film / optical material inspection device RETS-100 (product name, Otsuka Electronics Co., Ltd.). In the present specification, a value of 550 nm is adopted as the value of retardation.

Production Example 1 (Production of non-polarized film)
A vinylidene fluoride / tetrafluoroethylene copolymer film (molar ratio 80:20) having a thickness of 40 μm was produced by the following production method.
A dimethylacetamide (DMAc) solution or a methyl ethyl ketone (MEK) solution of vinylidene fluoride-tetrafluoroethylene copolymer (molar ratio 80:20) is cast on a PET (polyethylene terephthalate) substrate, and the solvent is applied at 180 ° C. It was vaporized to form a film having a thickness of 40 μm.

Example 1
In an ISO class 7 clean room (humidity 60%), as outlined in FIG. 1, a hugging angle of 200 is placed on a ground electrode made of SUS, which is a grounded roller 1 (diameter 200 mm, width 800 mm). Vinylidene fluoride / tetrafluoroethylene copolymer film 2 having a width of 550 mm, a length of 200 m, and each film thickness (20 to 40 μm) shown in Table 1 so as to move along the roller 1 at ° (hereinafter referred to as hereafter). It may be simply referred to as film 2). As the first electrode E1, the needle-shaped electrode is arranged so that the arrangement of the needle-shaped electrodes is perpendicular to the surface of the roller 1 (that is, in the radial direction of the roller 1), and the needle-shaped electrode is formed from the film 2 (first). It was installed so that the tip of the electrode E1) was located 10 mm above the sky. The first high voltage power supply V1 is connected to the first electrode E1. Further, at a position 100 mm away from the needle-shaped electrode (first electrode E1) in terms of the length of the film 2 and a position 150 mm away from the film 2, gold-plated tungsten having a diameter of 0.1 mm is used as the second electrode E2, respectively. One linear electrode (550 mm long) made of the same material was installed so as to be 20 mm above the film 2 at a position away from the film 2. A second high voltage power supply V2 is connected to each of the second electrodes E2.
After applying a voltage of -10 kV to the needle-shaped electrode (first electrode E1) and a voltage of -10 to -15 kV to the linear electrode (second electrode E2), the film 2 is applied at a speed of 96 cm / min. Move in the direction of the arrow in FIG. 3 to pass under the corona discharge generated from the tip of the needle-shaped electrode (first electrode) and the subsequent linear electrode (second electrode), and further, a grounded metal roll. The film 2 was statically eliminated by contacting with 3 (diameter 70 mm). Then, using a slitter, both ends of the film 2 were removed by 0.5 cm in width, and the obtained polarized film was wound around a cylindrical core having a diameter of 6 inches while sandwiching the PET film.
Here, the distance between the needle-shaped electrode (first electrode E1) and the film 2 and the distance between the linear electrode (second electrode E2) and the film 2 are both constant (the longest distance and the shortest distance between the electrode and the film). Eight samples were produced by preparing so that the difference in distance was 0 mm) (sample numbers 1 to 8).
In addition to this, the following two samples (sample numbers 9 and 10)
Unlike the above-mentioned sample numbers 1 to 8, the distance between the needle-shaped electrode (first electrode E1) and the film 2 was adjusted to be constant, while the linear electrode (second electrode E2) and the film 2 were prepared. Since it was omitted to prepare so that the distance from the film was constant, the linear electrode was tilted and fixed, and the right end was 25 mm above the film 2 and the left end was 15 mm above the film 2 in the traveling direction. One sample (thickness 40 μm) was manufactured (sample number 9) in a state of being fixed at a position distant from each other.
Unlike the above-mentioned sample numbers 1 to 8, the distance between the linear electrode (second electrode E2) and the film 2 was adjusted to be constant, while the needle-shaped electrode (first electrode E1) and the film 2 were prepared. Since it was omitted to prepare so that the distance from the film was constant, the linear electrode was tilted and fixed, and the right end was 20 mm above the film 2 and the left end was 10 mm above the film in the traveling direction. One sample (thickness 20 μm) was manufactured (sample number 10) in a state of being fixed at a distant position.

Test Example 1
For the measurement of piezoelectricity, a d33 meter PM300 manufactured by Piezo Test (a pin with a tip of 1.5 mmφ was attached to this as a sample fixing jig) was used. In the meter, set the conditions of Rng / Mode: VLO / d33, Frequency: 110 Hz, and Dyn Force: 0.25 N, put a weight of 102 g on the detection part, and St.F of the meter becomes 1.0 N. After confirming that, the measurement was performed by the following procedure at the tip of the sample fixing jig.
(1) The film was cut to a size of 50 mm [flow direction] / 500 mm [width direction].
(2) The film was placed on a flat and clean table so that the piezoelectric film would not have creases or wrinkles.
(3) Marked 10 places with an oil-based pen at intervals of 50 mm in the width direction.
(4) Set the film on the detection part so that there are no wrinkles or creases, turn the trigger clockwise, lower the force head until St.F: 1.0 N, and at each place marked above, 30 After a second, the value of d33 was read.
Table 1 shows the measurement results.

Claims (18)

This is a manufacturing method for manufacturing an organic piezoelectric film having a piezoelectric constant d ₃₃ with a fluctuation coefficient of 2.0 or less by a roll-to-roll method, in which the distance between a non-stretched and non-polarized polymer film and an electrode is set. A production method comprising a step B of carrying out a constant polarization treatment of the polymer film. The production method according to claim 1 , wherein the difference between the longest distance and the shortest distance between the non-stretched and non-polarized polymer film and the electrode is within 6 mm. The production method according to claim 1 or 2 , further comprising step C of heat-treating the unstretched polymer film at any time point with respect to step B. The production method according to claim 3 , wherein step C is a step of heating the unstretched polymer film and then cooling the film. The production method according to any one of claims 1 to 4 , further comprising a step A of preparing a non-stretched and non-polarized polymer film by a casting method. The manufacturing method according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 0.5 to 30 pC / N. The manufacturing method according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 0.5 to 2.0 pC / N or less. The production according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 2.0 to less than 4.0 pC / N and the coefficient of variation thereof is 1.0 or less. Method. The production according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 4.0 to 6.0 pC / N or less, and the coefficient of variation thereof is 0.6 or less. Method. The production according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 6.0 to less than 10.0 pC / N and the coefficient of variation thereof is 0.4 or less. Method. The production according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 10.0 to 14.0 pC / N or less, and the coefficient of variation thereof is 0.3 or less. Method. The manufacturing method according to any one of claims 1 to 5 , wherein the piezoelectric constant d ₃₃ of the organic piezoelectric film is in the range of 14.0 to 30.0 pC / N, and the coefficient of variation thereof is 0.15 or less. .. The production method according to any one of claims 1 to 12 , wherein the tensile elastic modulus of the organic piezoelectric film is in the range of 0.4 to 5 GPa. The production method according to any one of claims 1 to 13 , wherein the retardation of the organic piezoelectric film is in the range of 200 to 10000 nm. The production method according to any one of claims 1 to 13 , wherein the retardation of the organic piezoelectric film is in the range of 0.5 to 200 nm. The production method according to any one of claims 1 to 15 , wherein the organic piezoelectric film is made of a polarized vinylidene fluoride-based polymer film. The production method according to any one of claims 1 to 16 , wherein the internal haze value of the organic piezoelectric film is in the range of 0.05 to 80%. The manufacturing method according to any one of claims 1 to 16 , wherein the internal haze value of the organic piezoelectric film is in the range of 5 to 90%.

Images