JP6439250B2 - Laminate - Google Patents

Description

  The present invention relates to a laminate.

Conventionally, various organic dielectric films and inorganic dielectric films have been known as piezoelectric films or films.
Among these, the polarized vinylidene fluoride / tetrafluoroethylene copolymer film has the advantage of having transparency and flexibility unlike the inorganic dielectric film, so that it can be applied to various applications. Is possible.
For example, Patent Document 1 discloses a polarized vinylidene fluoride / tetrafluoroethylene copolymer film for a touch panel or a touch pressure detection as a piezoelectric film.

JP 2011-222679 A

Before using the piezoelectric film for touch panel or touch pressure detection, the piezoelectric film may be transported in the state of a laminate in which a protective film is disposed adjacent to at least one main surface of the piezoelectric film. In this case, the protective film can suppress the generation of wrinkles, scratches and dirt on the piezoelectric film.
However, the inventors have found that when the peel strength between the protective film and the piezoelectric film is too high, the piezoelectric film is broken or wrinkled when the protective film is peeled off.
Therefore, the present invention can suppress the generation of wrinkles, scratches, dirt, etc. on the piezoelectric film, and can easily protect the piezoelectric film without tearing or wrinkling when only the piezoelectric film is stored. An object is to provide a laminate that can be peeled off.

As a result of intensive studies, the present inventors have
A laminate having a protective film and a piezoelectric film,
The protective film is arranged on at least one main surface of the piezoelectric film directly or adjacently via another layer,
The integrated average peel strength I _IA (mN / cm) and the maximum point peel strength I _MP (mN / cm) between the protective film and the piezoelectric film measured by the measurement method described later are the following (1) and (2):
(1) 1 ≦ I _IA ≦ 100
(2) _IMP- I _IA ≦ 40
A laminate, characterized by satisfying
<Peel strength measurement method>
T-peel measurement: The peel strength when the laminate having a width of 20 mm is peeled off while maintaining the T-shape at 300 mm / min under a temperature condition of 25 ° C.,
As a result, the inventors have found that the above problems can be solved, and as a result of further studies, the present invention has been completed.

  The present invention includes the following aspects.

Item 1.
A laminate having a protective film and a piezoelectric film,
The protective film is arranged on at least one main surface of the piezoelectric film directly or adjacently via another layer,
The integrated average peel strength I _IA (mN / cm) and the maximum point peel strength I _MP (mN / cm) between the protective film and the piezoelectric film measured by the measurement method described later are the following (1) and (2):
(1) 1 ≦ I _IA ≦ 100
(2) _IMP- I _IA ≦ 40
The laminated body characterized by satisfy | filling.
<Peel strength measurement method>
T-peel measurement: The peel strength when the laminate having a width of 20 mm is peeled off while maintaining the T-shape at 300 mm / min under a temperature condition of 25 ° C. is measured.
Item 2.
Item 2. The laminate according to Item 1, wherein the rate of change in electromechanical coupling coefficient when the piezoelectric film is heated at 85 ° C for 10 hours is 10% or less.
Item 3.
Item 3. The laminate according to Item 1 or 2, wherein the resin constituting the protective film is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polypropylene, and polyethylene.
Item 4.
Item 4. The laminate according to any one of Items 1 to 3, which is for producing a piezoelectric panel.

  In the laminate of the present invention, since the protective film and the piezoelectric film are arranged with a specific peel strength, the piezoelectric film can be prevented from being wrinkled, scratched or soiled, and only the piezoelectric film is stacked. When it is desired to store the protective film, the protective film can be easily peeled without tearing, wrinkling or scratching.

Meaning of Terms In this specification, “detection” of “touch position” means determination of touch position, while “detection” of “touch pressure” means presence / absence of pressure, speed, magnitude (strength), Or the change of these, or the determination of these combination is meant.
As used herein, the term “touch” includes touching, touching, pushing, pushing, and touching.
In this specification, the term “polarization” means that a surface is charged. That is, the polarizing film can be an electret.

The laminate of the present invention is
A laminate having a protective film and a piezoelectric film,
The protective film is arranged on at least one main surface of the piezoelectric film directly or adjacently via another layer,
The integrated average peel strength I _IA (mN / cm) and the maximum point peel strength I _MP (mN / cm) between the protective film and the piezoelectric film measured by the measurement method described later are the following (1) and (2):
(1) 1 ≦ I _IA ≦ 100
(2) _IMP- I _IA ≦ 40
The laminated body characterized by satisfy | filling.
<Peel strength measurement method>
T-peel measurement: The peel strength when the laminate having a width of 20 mm is peeled off while maintaining the T-shape at 300 mm / min under a temperature condition of 25 ° C. is measured.
Hereinafter, the laminate of the present invention will be described in detail.

Laminate The laminate of the present invention is a laminate having a protective film and a piezoelectric film,
The protective film is disposed on at least one main surface of the piezoelectric film directly or adjacently via another layer. For this reason, it is possible to prevent the piezoelectric film from being scratched or soiled in the process after the heat treatment (for example, at the time of transportation or storage).
The laminated body of this invention should just be comprised from 2 layers or more of a protective film and a piezoelectric film. That is, the laminate of the present invention has the following (a) to (f) and the like:
(a) a laminate composed of two layers of a protective film and a piezoelectric film in order from the bottom;
(b) a laminate composed of three layers of a protective film, another layer and a piezoelectric film in order from the bottom;
(c) a laminate composed of three layers of a protective film, a piezoelectric film and a protective film in order from the bottom; (d) a laminate composed of four layers of a protective film, another layer, a piezoelectric film and a protective film in order from the bottom;
(e) a laminate comprising four layers of a protective film, a piezoelectric film, another layer and a protective film in order from the bottom;
(f) In order from the bottom, any laminate such as a laminate comprising a protective film, another layer, a piezoelectric film, another layer, and a protective film having 5 layers is included. In the above embodiments (a) and (c), the protective film is disposed directly adjacent to at least one main surface of the piezoelectric film. In the above-described aspects (b) and (f), the protective film is disposed on at least one main surface of the piezoelectric film adjacent to each other via another layer. In the above aspects (d) and (e), the first protective film is disposed directly adjacent to at least one main surface of the piezoelectric film, and the second protective film is at least one of the piezoelectric films. Are arranged adjacent to each other via another layer on the main surface.

When the integrated average peel strength (integrated average unit load) between the protective film and the piezoelectric film in the laminate of the present invention is I _IA (mN / cm), the following formula (1) is satisfied: 1 ≦ I _IA ≦ 100 . That is, the integrated average peel strength is 1 to 100 mN / cm. When the integrated average peel strength is less than 1 mN / cm, the protective film is peeled off except when necessary, and the function as a protective film (function to suppress scratches, dirt, etc.) may not occur. . If the integrated average peel strength exceeds 100 mN / cm, it is difficult to peel off the protective film, and the piezoelectric film may be broken or damaged when the protective film is peeled off. The upper limit of the integrated average peel strength is 100 mN / cm or less, preferably 70 mN / cm or less, and more preferably 30 mN / cm or less. The lower limit of the integrated average peel strength is preferably 3 mN / cm or more, more preferably 5 mN / cm or more, and still more preferably 10 mN / cm or more.
Also, when the maximum point peel strength between the protective film and the piezoelectric film in the laminate of the present invention (maximum point load per unit) was _{I MP (mN / cm),} (2) formula: _I MP _{-I IA} ≦ 40 is satisfied. That is, the difference between the maximum point peel strength and the integrated average peel strength is 40 mN / cm or less. When the difference between the maximum point peel strength and the integrated average peel strength exceeds 40 mN / cm, it is difficult to peel off the protective film, and the piezoelectric film may be broken or damaged when the protective film is peeled off. The _IMP- I _IA is preferably 30 mN / cm or less, more preferably 20 mN / cm or less ( _IMP- I _IA ≦ 30 is preferable, and _IMP- I _IA ≦ 20 is more preferable).

In the present invention, the integral average peel strength and the maximum point peel strength are both values measured by the following T-shaped peel measurement method. Specifically, the integrated average peel strength and the maximum point peel strength were measured when the laminate of the present invention having a width of 20 mm was peeled off while maintaining the T-shape at a temperature of 25 ° C. at 300 mm / min, This is the value obtained.
Both the integrated average peel strength and the maximum point peel strength in the present invention can be appropriately set by adjusting the heating temperature, heating time, etc. in the heat treatment step (step C) described later. In addition, the integrated average peel strength and the maximum point peel strength can be appropriately set depending on the selection of the resin constituting the protective film, the presence or absence of other layers, the selection of the resin constituting the other layers, and the like. it can.

Protective film The protective film in this invention is used in order to protect a piezoelectric film.
Examples of the resin constituting the protective film include PET (polyethylene terephthalate), PEN (polyethylene naphthalate), PP (polypropylene), and PE (polyethylene). In addition, the protective film in this invention includes the extended | stretched protective film.
The thickness of the protective film is usually in the range of 10 to 200 μm, preferably in the range of 30 to 50 μm.

Other layers In the laminate of the present invention, other layers may be provided between the protective film and the piezoelectric film. Examples of the other layers include an adhesive layer and an electrode layer. The other layer includes one layer or two or more layers.
When the adhesive layer is provided in the laminated body of this invention, the piezoelectric film is laminated | stacked on the protective film which has an adhesive layer. On the other hand, when an electrode layer is provided in the laminate of the present invention, a protective film is laminated on the piezoelectric film having the electrode layer.
Examples of the adhesive layer include EVA (ethylene-vinyl acetate copolymer), acrylic resin, silicone resin, polyolefin resin, and the like.
Examples of the electrode layer include ITO (indium tin oxide) and tin oxide.
The thickness of the other layer is not particularly limited as long as the laminate of the present invention satisfies the above expressions (1) and (2).

Piezoelectric Film The piezoelectric film in the present invention (the piezoelectric film of the present invention) is preferably an organic piezoelectric film. The “organic piezoelectric film” is a film (polymer film) formed from a polymer that is an organic substance. Examples of the “organic piezoelectric film” include a polarized vinylidene fluoride polymer film, an odd-chain nylon piezoelectric film, 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, a film in which an inorganic substance is dispersed in the polymer, a film containing the polymer and a component other than the polymer, and the like.
The content of the polymer in the piezoelectric film in the present invention is preferably 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by 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 polymer.
The piezoelectric film in the present invention is preferably composed of a polarized vinylidene fluoride polymer film.
In this specification, examples of the “vinylidene fluoride polymer film” include a vinylidene fluoride / tetrafluoroethylene copolymer film, a vinylidene fluoride / trifluoroethylene copolymer film, and a polyvinylidene fluoride film. Can be mentioned.
The vinylidene fluoride 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 polymer film” is a film composed of a vinylidene fluoride polymer and contains a vinylidene fluoride polymer.

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

Examples of “monomer copolymerizable with this” in “(1) copolymer of vinylidene fluoride and one or more monomers copolymerizable therewith” include trifluoroethylene, tetrafluoroethylene , Hexafluoropropylene, chlorotrifluoroethylene, and vinyl fluoride.
The “one or more monomers copolymerizable therewith” or one of them is preferably tetrafluoroethylene.
Preferable examples of the “vinylidene fluoride polymer” include a 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 relating to the present invention are not significantly impaired.
The “(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 (a repeating unit derived from tetrafluoroethylene) / (a repeating unit derived from vinylidene fluoride) in the “vinylidene fluoride / tetrafluoroethylene copolymer” is preferably 5/95 to 36/64. Within the range, more preferably within the range of 15/85 to 25/75, still more preferably within the range of 18/82 to 22/78.

The “vinylidene fluoride / tetrafluoroethylene copolymer” may contain a repeating unit derived from a monomer other than vinylidene fluoride and tetrafluoroethylene as long as the properties of 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 is copolymerizable with a vinylidene fluoride monomer or a tetrafluoroethylene monomer.
(1) Fluoromonomer (eg, vinyl fluoride (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), perfluoroacrylate, 2, 2,2-trifluoroethyl acrylate, 2- (2) hydrocarbon monomers (eg, ethylene, propylene, maleic anhydride, vinyl ether, vinyl ester, allyl glycidyl ether, acrylic acid monomers, methacrylic acid monomers, vinyl acetate) It is done.

  A polymer is mentioned as an example of components other than the said polymer. Among polymers other than the polymer, acrylic / methacrylic polymers, cellulose derivative polymers, polyester polymers, polycarbonate polymers, and the like are preferable. In particular, when a cellulose derivative polymer is used in combination with a vinylidene fluoride polymer, it is more preferable because the thixotropy of the paint is also improved when cast coating is performed. Preferred examples of the cellulose derivative-based polymer include carboxybutyl cellulose, carboxypropyl cellulose, carboxyethyl cellulose and the like.

  Preferable examples of the “inorganic substance” include inorganic oxide particles. By containing the “inorganic oxide particles”, it is possible to adjust electrical properties, mechanical properties, and the like.

  The piezoelectric film in the present invention may contain other components such as an affinity improver as necessary.

  The “affinity improver” increases the affinity between the “inorganic oxide particles” and the “polymer”, uniformly disperses the “inorganic oxide particles” in the “polymer”, The “inorganic oxide particles” and the “polymer” can be firmly bonded in the film, the generation of voids can be suppressed, and the relative dielectric constant can be increased.

  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, organic aluminum compounds, and organic phosphorus compounds.

  Examples of the “organic titanium compound” include coupling agents such as alkoxytitanium, titanium chelate, and titanium acylate. Among these, alkoxy titanium and titanium chelate are preferable examples from the viewpoint of good affinity with the “inorganic oxide particles”.

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

  The “organosilane compound” may be a polymer type or a low molecular type, and examples thereof include monoalkoxysilanes, dialkoxysilanes, trialkoxysilanes, and tetraalkoxysilanes. Can be mentioned. In addition, vinyl silane, epoxy silane, amino silane, methacryloxy silane, mercapto silane, and the like can be suitably used.

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

  The “surfactant” as the affinity improver may be a polymer type or a low molecular type, and examples thereof include a nonionic surfactant, an anionic surfactant, and A cationic surfactant is mentioned. Among these, a high molecular weight surfactant is preferable from the viewpoint of good thermal stability.

  Examples of the “nonionic surfactant” include a polyether derivative, a polyvinylpyrrolidone derivative, and an alcohol derivative, and in particular, from the viewpoint of good affinity with the “inorganic oxide particles”. Ether derivatives are preferred.

  Examples of the “anionic surfactant” include polymers containing sulfonic acid, carboxylic acid, and salts thereof. Among them, preferred examples of the affinity with the “polymer” include acrylic acid derivative polymer (poly (acrylic acid) derivative) and methacrylic acid derivative polymer (poly (methacrylic acid) derivative). Is mentioned.

  Examples of the “cationic surfactant” include amine compounds, compounds having a nitrogen-containing complex ring such as imidazoline, and halogenated salts 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 from the viewpoint of particularly good affinity with the “polymer”.

  As a preferable example of the “epoxy group-containing compound”, the compound having the formula:

  (In the formula, R represents a hydrogen atom, a methyl group, an oxygen atom or a nitrogen atom which may have an intervening C 2-10 hydrocarbon group or an optionally substituted aromatic ring group. L is 0. Or m represents 0 or 1, and n represents an integer of 0 to 10).

  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 the range in which the effect of the present invention is not lost. The amount is preferably 0.01 to 30 parts by mass, more preferably 0.1 to 25 parts by mass, and still more preferably 1 to 20 parts by mass with respect to parts.

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

  The piezoelectric film in the present invention preferably has a total light transmittance of 85% or more. The total light transmittance of the piezoelectric film in the present invention is more preferably 90% or more, still more preferably 92% or more, and still more preferably 95% or more. The upper limit of the total light transmittance is not limited, but the total light transmittance of the piezoelectric film in the present invention is usually 99% or less. In the present specification, “total light transmittance” is obtained by a light transmission test using Hazeguard II (product name, Toyo Seiki Seisakusho) or an equivalent thereof based on ASTM D1003.

The total haze value of the piezoelectric film in the present invention is preferably 4.0% or less, more preferably 3.0% or less, still more preferably 2.0% or less, still more preferably 1.5% or less, most preferably Preferably it is 1.0% or less. The lower the total haze value, the better. The lower limit is not limited, but the total haze value of the piezoelectric film in the present invention is usually 0.2% or more.
In this specification, “total haze” is based on ASTM D1003, and is determined by haze (HAZE, turbidity) test using haze guard II (product name) (Toyo Seiki Seisakusho) or its equivalent. can get.

The internal haze value of the piezoelectric film in the present invention is preferably 2.0% or less, more preferably 1.5% or less, still more preferably 1.2% or less, and still more preferably 1.0% or less. The lower the internal haze value, the better. The lower limit is not limited, but the internal haze value of the piezoelectric film in the present invention is usually 0.1% or more.
In the present specification, “inner haze” means that in the method for measuring the total haze value, water is put into a glass cell, a film is inserted therein, and the haze value is measured. Is obtained.

The external haze value of the piezoelectric film in the present invention is preferably 2.0% or less, more preferably 1.5% or less, and still more preferably 1% or less. The lower the external haze value, the better. The lower limit is not limited, but the external haze value of the piezoelectric film in the present invention is usually 0.1% or more.
In the present specification, the “outer haze value” (outer haze) is calculated by subtracting the internal haze value from the total haze value of the film.

The electromechanical coupling coefficient of the piezoelectric film in the present invention is usually in the range of 0.1 to 0.01, preferably in the range of 0.09 to 0.02, more preferably in the range of 0.08 to 0.03. It is.
The rate of change of the electromechanical coupling coefficient of the piezoelectric film in the present invention is preferably 10% or less, more preferably 8% or less, and still more preferably 6% or less.
In this specification, the electromechanical coupling coefficient may be abbreviated as kt.

  In the present invention, the “electromechanical coupling coefficient” (kt) of the piezoelectric film is determined by forming an Al vapor-deposited electrode on both sides of the piezoelectric film, cutting out a 13 mm disk at a predetermined position of the piezoelectric film, 4194A) or an equivalent thereof, and calculated by the method described in H. Ohigashi et al., “The application of ferroelectric polymer, Ultrasonic transducers in the megahertz range”.

In this specification, “rate of change of electromechanical coupling coefficient” is the rate of change of electromechanical coupling coefficient when heated at 85 ° C. for 10 hours unless otherwise specified.
The "rate of change of electromechanical coupling coefficient" is
(1) measuring the electromechanical coupling coefficient (kt before heating) of the piezoelectric film;
(2) heating the piezoelectric film in air at 85 ° C. for 10 hours;
(3) Allowing the piezoelectric film to stand at room temperature and cooling to room temperature, and (4) Measuring the electromechanical coupling coefficient (kt after heating) of the piezoelectric film after the heating and cooling. “Kt before heating” and “kt after heating” are determined by calculating into the following equation.
Change in electromechanical coupling coefficient (%) =
((Kt after heating−kt before heating) / kt before heating) × 100
Change rate of electromechanical coupling coefficient (%) = | Change amount of electromechanical coupling coefficient (%) |
In this specification, “room temperature” is a temperature within a range of 15 to 35 ° C.

  The thickness of the piezoelectric film in the present invention is, for example, in the range of 0.5 to 100 μm, in the range of 0.8 to 50 μm, in the range of 0.8 to 40 μm, in the range of 3 to 100 μm, or in the range of 3 to 50 μm. Within the range, within the range of 6-50 μm, within the range of 9-40 μm, within the range of 10-40 μm, or within the range of 10-30 μm. The preferred thickness can vary depending on the application of the piezoelectric film in the present invention. For example, when the piezoelectric film in the present invention is used for a piezoelectric panel such as a touch panel, the thickness of the piezoelectric film in the present invention is preferably in the range of 10 to 40 μm, more preferably in the range of 10 to 30 μm. When the piezoelectric film in the present invention is used for an electrowetting device, the thickness of the piezoelectric film in the present invention is preferably in the range of 0.5 to 5 μm, more preferably in the range of 0.8 to 2 μm. When the piezoelectric film in the present invention is used for a film capacitor, the thickness of the piezoelectric film in the present invention is preferably in the range of 1.5 to 12 μm.

Manufacturing method of laminate The laminate of the present invention is, for example,
A step A for polarizing a non-polarized polymer film (eg, non-polarized vinylidene fluoride polymer film);
A protective film is disposed directly adjacent to at least one main surface of a polarized polymer film (eg, polarized vinylidene fluoride polymer film), or at least one of the polarized polymer films A step B of disposing a protective film adjacent to each other via another layer on the main surface; and a step of heat-treating the subsequent polarized polymer film (eg, polarized vinylidene fluoride polymer film) and the protective film C
It can manufacture by the manufacturing method containing.

Process A (polarization process)
In step A, the non-polarized polymer film is polarized.

  The “non-polarized polymer film” used in step A can be produced by a known method such as a casting method, a hot press method, or a melt extrusion method. The “non-polarized polymer film” used in step A is preferably a film produced by a casting method.

The production method of “non-polarized polymer film” by the casting method is, for example,
(1) A liquid composition is prepared by dissolving or dispersing a polymer (eg, vinylidene fluoride polymer) and desired components (eg, inorganic oxide particles and affinity improver) in a solvent. Process;
(2) A process comprising casting (applying) the liquid composition on a substrate; and (3) vaporizing the solvent to form a film.

The dissolution temperature in the preparation of the liquid composition is not particularly limited, but a higher dissolution temperature is preferable because dissolution can be promoted. However, if the melting temperature is too high, the resulting film tends to be colored, so the melting temperature is preferably from room temperature to 80 ° C.
From the viewpoint of preventing such coloring, preferred examples of the solvent include ketone solvents (eg, methyl ethyl ketone (MEK), methyl isobutyl ketone (MIBK), acetone, diethyl ketone, dipropyl ketone), ester solvents ( Examples include ethyl acetate, methyl acetate, propyl acetate, butyl acetate, ethyl lactate), ether solvents (eg, tetrahydrofuran, methyltetrahydrofuran, dioxane), and amide solvents (eg, dimethylformamide (DMF), dimethylacetamide). It is done. These solvents may be used alone or in combination of two or more. As the solvent, an amide solvent which is a solvent widely used for dissolving polyvinylidene fluoride (PVDF) may be used, but the content of the amide solvent in the solvent is desirably 50% or less.

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

The solvent can be vaporized by a conventional drying method such as heating.
Although the drying temperature in the vaporization of the solvent can be appropriately determined according to the type of the solvent and the like, it is usually in the range of 20 ° C to 200 ° C, preferably in the range of 40 ° C to 170 ° C.
The drying temperature may be a constant temperature or may be changed. By changing the drying temperature from a low temperature (eg, 40 to 100 ° C.) to a high temperature (eg, 120 to 200 ° C.), the haze value of the resulting film can be lowered. This can be achieved, for example, by dividing the drying zone into several zones and the film (or cast solution before film formation) enters the cold zone and moves to the hot zone.
Specifically, for example, the drying zone may be divided into four zones of 50 ° C., 80 ° C., 120 ° C., and 150 ° C., and the film may be continuously moved from the zone of 50 ° C. to the zone of 150 ° C.
The drying time in the vaporization of the solvent is usually in the range of 1 to 600 seconds, preferably in the range of 10 to 300 seconds.

The “non-polarized vinylidene fluoride polymer film” (hereinafter sometimes simply referred to as “non-polarized film”) used in Step A is preferably not stretched. Also preferably, in the production method of the present invention, the non-polarized film is not stretched. That is, the piezoelectric film of the present invention is preferably an unstretched piezoelectric film.
The piezoelectric film of the present invention thus obtained has a high thickness uniformity. Specifically, preferably, in the piezoelectric film of the present invention, the variation coefficient of the thickness measured at 10 points per 1 cm square over the whole film is ± 20% or less of the average film thickness.

  The non-polarized film used in step A may be heat-treated after film formation.

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

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

The polarization treatment in step A is preferably performed by corona discharge.
For the corona discharge, either a negative corona or a positive corona may be used, but it is desirable to use a negative corona from the viewpoint of easy polarization of the non-polarized resin film.

  The corona discharge treatment is not particularly limited. For example, as described in JP 2011-181748 A, a non-polarized film is applied using a linear electrode; or the non-polarized film is a needle. The application can be performed by using the electrode. In addition, a corona discharge process is normally performed in the state in which the protective film is not affixed.

The conditions for the corona discharge treatment may be appropriately set based on common sense in the technical field to which the present invention belongs. If the corona discharge treatment conditions are too weak, the piezoelectricity of the resulting piezoelectric film may be insufficient. On the other hand, if the corona discharge treatment conditions are too strong, the resulting piezoelectric film may have point defects. is there.
For example, when continuous application is performed roll-to-roll using a linear electrode, it varies depending on the distance between the linear electrode and the non-polarized film, the film thickness, etc., for example, -15 to -25 kV DC electric field. The processing speed is, for example, 10 to 500 cm / min.
Alternatively, the polarization treatment may be performed by, for example, sandwiching and applying the flat electrode from both sides of the non-polarized film in addition to the corona discharge. Specifically, for example, when the application is performed 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 second to 60 minutes. The conditions for the application time can be adopted.

Process B (Process to arrange protective film)
Step B is performed after Step A. In step B, a protective film is applied directly or on another layer on at least one main surface of the polarized polymer film obtained by the polarization treatment in step A (hereinafter sometimes simply referred to as a polarized film). To be adjacent to each other. Here, “arranging so as to be adjacent” means that the polarized film and the protective film are arranged so that the polarized film and the protective film adhere after the heat treatment step of Step C described later. .

Process C (heat treatment process)
Step C is performed after Step B or simultaneously with Step B. That is, in the step C, the protective film is disposed on at least one main surface of the polarizing film so as to be adjacent directly or via another layer, or is protected on at least one main surface of the polarizing film. The polarizing film obtained by the polarization treatment in step A and the protective film are heat-treated while disposing the films so as to be adjacent to each other directly or via other layers. By this step, the adhesive force (peel strength) between the protective film and the piezoelectric film can be increased.
The heat treatment in Step C can be performed on the polarizing film or the portion where the polarization has been completed in Step A. That is, while performing the polarization process of the process A, the heat treatment of the process C may be performed on the portion where the polarization process has been completed.

The method for heat treatment is not particularly limited. Here, when the laminate of the present invention is a laminate comprising a polarizing film and a protective film, for example, as a heat treatment method, for example, 1) sandwiching the polarizing film and the protective film between two metal plates, Heating the metal plate; 2) heating the roll of the polarizing film and the protective film in a thermostatic bath; 3) passing the polarizing film and the protective film through a roll-to-roll through a heated furnace. 4) In the production of a polarized film in a roll-to-roll system, heating a metal roller, and contacting the polarized film and the protective film with the heated metal roller . In addition, when the method of heat treatment is the above 4) contact with the metal roller, the polarizing film and the protective film are heated so that the protective film and the metal roller are in contact (the heat from the metal roller is polarized through the protective film). It is preferable to heat the polarizing film and the protective film so as to be transmitted to
The temperature of the heat treatment may vary depending on the kind of the polarized film to be heat-treated, and is preferably in the range of (melting point of the polarizing film to be heat-treated) -100 ° C. to (melting point of the polarized film to be heat-treated + 40) ° C. Is within.
Specifically, the temperature of the heat treatment is preferably 80 ° C. or higher, more preferably 85 ° C. or higher, and still more preferably 90 ° C. or higher.
The temperature of the heat treatment is preferably 170 ° C. or lower, more preferably 160 ° C. or lower, and still more preferably 140 ° C. or lower.
The time for the heat treatment is usually 10 seconds or longer, preferably 0.5 minutes or longer, more preferably 1 minute or longer, and further preferably 2 minutes or longer.
Moreover, although the upper limit of the said heat processing time is not limited, Usually, the time of the said heat processing is 60 minutes or less.
The conditions for the heat treatment are preferably 90 ° C. or more and 1 minute or more.
In the present specification, the melting point of a film is a maximum value in a heat of fusion curve obtained when the temperature is raised at a rate of 10 ° C./min using a differential scanning calorimetry (DSC) apparatus.

After the heat treatment, the polarized polymer 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. The rapid cooling can be performed by means such as air blowing.
Laminate Roll The laminate of the present invention can preferably be stored and shipped as a roll.
The elastic modulus of the piezoelectric film of the present invention is preferably 500 MPa or more from the viewpoint of suppressing the generation of wrinkles when it is in the form of such a roll. The elastic modulus can be adjusted by selecting the material of the piezoelectric film.
In this invention, it may consist only of the piezoelectric film in this invention which peeled the protective film from the laminated body, and may comprise the core of this invention wound around the cores, such as a paper tube.
The roll of the laminate 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 laminated body of the present invention can be prepared, for example, by winding the laminated body of the present invention using a winding roller and a winding roller.
Here, from the viewpoint of suppressing the deflection of the laminate (or film), it is preferable that the unwinding roller and the take-up roller be parallel to each other, as is usually done.
Moreover, from the viewpoint of suppressing the deflection of the laminate (or film), a film having an elastic modulus of 500 MPa or more may be used among the piezoelectric films in the present invention.
As the roller, in order to improve the slipperiness of the laminate of the present invention, a slippery roller, specifically, a roller coated with a fluororesin, a plated roller, or a roller coated with a release agent is used. It is preferable.
Here, when the thickness of the laminated body (or film) is not uniform, so-called roll earing (high edge; the end portion becomes thicker than the center portion in the axial direction of the roll; both end portions are the center portions. When the film thickness is lower, both ends are dented than the center; or when the thickness changes from one end to the other, the end on the side where the film thickness is thinner Unevenness of the roll thickness occurs, such as dents), which can cause wrinkles. In addition, this may cause a deflection of the laminate (or film) (curvature in a state where no tension other than the tension due to gravity is applied) when the laminate is rolled out.
Generally, for the purpose of preventing the roll from standing, the end of the roll film is slitted (slit), but the non-uniform thickness of the laminate (or film) is wide from the end of the film. In this case, it is difficult to prevent the roll from standing and dents with only the ears.
In general, as the width of the laminated body is wider (eg, a width of 100 mm or more) and the length of the laminated body is longer (eg, 50 m or more), the ear standing, the dent, and the deflection are more likely to occur.
However, since the laminated body of the present invention (and the piezoelectric film in the present invention) has high thickness uniformity, the laminated body can be obtained as it is or by simply slitting the film end that becomes the end of the roll. Even when the width of the laminate is wide (eg, a width of 100 mm or more) and the length of the laminate is long (eg, 50 m or more), the roll with the ear standing, the dent, and the deflection suppressed can be obtained.
The ear (film end) removed by the slit can be collected and recycled as a raw material for the piezoelectric film in the present invention.
The roll of the laminate of the present invention has high thickness uniformity, and preferably the ratio of the thickness of the thicker end to the thickness of the central portion in the axial direction of the roll is in the range of 70 to 130%. Is within. Thereby, as for the roll of the laminated body of this invention, the bending of the laminated body (or film) unwound from this is suppressed.

The surface roughness Ra of the roller used for manufacturing the piezoelectric film and its roll in the present invention is preferably 1 μm or less. In this specification, “surface roughness Ra” is “arithmetic average height” defined in JIS B0601: 2001.
Moreover, it is preferable that the roller used for manufacture of the piezoelectric film and its roll in the present invention is made of polytetrafluoroethylene (PTFE), chrome plating, or stainless steel (SUS).
By these things, the wrinkle of a laminated body (or film) can be suppressed.

Apply
Piezoelectric panel After the protective film is peeled off, the laminate of the present invention can use the piezoelectric film (piezoelectric film in the present invention) as a piezoelectric panel (eg, a touch panel (preferably, a touch panel capable of detecting touch pressure)).
The touch panel having a piezoelectric film in the present invention can detect both the touch position and the touch pressure, and even when exposed to an extremely high temperature, the touch pressure detection performance is not easily lowered, and the transparency is high.
The piezoelectric film in the present invention can be used for touch panels of all types such as a resistive film type and a capacitance type.
When the piezoelectric film in the present invention is used for a touch panel, it does not necessarily need to be used for detection of both the touch position and the touch pressure, and the piezoelectric film in the present invention has either a touch position or a touch pressure. It may also be used for detection.
The piezoelectric panel having the piezoelectric film in the present invention has the piezoelectric film and the electrode in the present invention, preferably,
A first electrode (preferably a transparent electrode);
A piezoelectric film in the present invention (preferably a transparent piezoelectric film);
A second electrode (preferably a transparent electrode);
In this order.
The first electrode is directly or indirectly disposed on one main surface of the piezoelectric film, and the second electrode is directly or indirectly disposed on the other main surface of the piezoelectric film.
Examples of the electrode include an ITO (indium tin oxide) electrode and a tin oxide electrode.

  When a piezoelectric panel having a piezoelectric film according to the present invention (eg, a touch panel (preferably, a touch panel capable of detecting touch pressure)) is pressed with a finger or the like, an electrical signal corresponding to a temporal change in strain of the piezoelectric film according to the present invention is obtained. Therefore, if the piezoelectric panel is used, the presence / absence of pressure, speed, size (strength), or a change thereof, or a combination thereof can be determined. Here, the magnitude of the pressure (that is, the static pressure) can be determined using the integrated value of the electric signal.

In the piezoelectric panel having the piezoelectric film of the present invention, one or two or more (preferably two) piezoelectric films can be used in the present invention.
When using two or more (preferably two) piezoelectric films in the present invention, the two or more piezoelectric films in the present invention may be bonded to each other by an adhesive sheet. The pressure-sensitive adhesive sheet is not particularly limited as long as the piezoelectric films in the present invention can be bonded to each other, and can be composed of one or more layers. That is, when the said adhesive sheet consists of one layer, the said adhesive sheet consists of an adhesive layer, and when the said adhesive sheet consists of two or more layers, the both outer layers are adhesive layers. When the said adhesive sheet consists of 3 or more layers, the said adhesive sheet may have a base material layer as an inner layer.
The pressure-sensitive adhesive layer in the pressure-sensitive adhesive sheet can be a layer containing an acrylic pressure-sensitive adhesive as a pressure-sensitive adhesive.
The base material layer in the pressure-sensitive adhesive sheet may be a transparent film, and may preferably be a film of polyimide, polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyparaphenylene sulfide, or polyamideimide, for example.

For example, the piezoelectric panel (eg, touch panel (preferably a touch panel capable of detecting touch pressure)) having the piezoelectric film in the present invention is preferably,
A first electrode;
A piezoelectric film according to the first invention;
An adhesive sheet;
A piezoelectric film according to the second invention;
A second electrode;
In this order.
The first electrode is disposed on the outer surface of the piezoelectric film in the first aspect of the present invention, and the second electrode is disposed on the outer surface of the piezoelectric film in the second aspect of the present invention.
Although the piezoelectric film in the present invention may have pyroelectricity, in the piezoelectric panel (eg, touch panel (preferably a touch panel capable of detecting touch pressure)), the piezoelectric film in the first invention and the second book The piezoelectric film in the invention is arranged so that the surfaces where charges of the same polarity (for example, positive charges and positive charges) are generated on the outside due to a temperature rise, and the potential difference between the two surfaces is set to the first electrode. When the electrical signal is obtained with the second electrode, the electrical signal due to pyroelectricity is reduced, and the electrical signal due to piezoelectricity can be selectively obtained.

  The touch panel having a piezoelectric film in the present invention can be used for an input device and a touch sensor device. The input device having the touch panel (that is, the input device having the piezoelectric film in the present invention) is input based on the touch position, the touch pressure, or both (eg, input based on the magnitude (strength) of pressure such as writing pressure) Is possible. The input device having the touch panel and the touch sensor device can include a position detection unit and a pressure detection unit.

The input device is an electronic device (eg, mobile phone (eg, smart phone), personal digital assistant (PDA), tablet PC, ATM, automatic ticket vending machine, digitizer, touch pad, car navigation system, FA (factory automation) device. It can be used for a touch panel display (touch panel monitor). An electronic device having the input device has an operation and an operation based on the touch position, the touch pressure, or both (for example, an operation such as changing the thickness of a line displayed on the screen according to the writing pressure in paint software). Is possible.
The touch sensor device can be used for electronic devices (eg, collision sensors, robot cleaners).
The electronic device may include the touch input device of the present invention or the touch sensor device of the present invention, or may include the touch input device of the present invention or the touch sensor device of the present invention.

  Since the piezoelectric film in the present invention has flexibility, it can be suitably used for various applications.

The present invention will be specifically described below with reference to examples and comparative examples. However, the present invention is not limited to the examples.
Hereinafter, the molar ratio of the repeating unit derived from tetrafluoroethylene / the repeating unit derived from vinylidene fluoride in the vinylidene fluoride / tetrafluoroethylene copolymer may be represented by “TFE / VDF”.

Example 1
(1) A paint having a solid content of 25 wt% was prepared by dissolving vinylidene fluoride / tetrafluoroethylene copolymer (TFE / VDF = 20/80) in methyl ethyl ketone (MEK). Thereafter, the paint was filtered through a filter, and the filtrate was applied to a PET film with a die coater. By further drying, a vinylidene fluoride / tetrafluoroethylene copolymer film (copolymer film thickness: 30 μm) was produced on the PET film. At this time, the drying was performed at a peripheral speed of 8 m / min in a drying furnace in which the drying temperatures of the four zones (2 m per zone) were set to 50 ° C./80° C./120° C./150° C., respectively.
(2) Next, the copolymer film is peeled from the PET film, the copolymer film is sandwiched from above and below using a metal electrode, and a DC voltage is applied at room temperature for 5 minutes under the condition of 300 kV / cm, The copolymer film was polarized. As a result, a polarizing film (polarized film thickness: 30 μm, polarized film width: 500 mm) was obtained.
(3) A self-adhesive stretched polypropylene (OPP) protective film having a thickness (film thickness) of 30 μm and a width of 500 mm was prepared.
(4) The protective film is placed on the polarizing film and arranged so that one side of the protective film is in contact with a heating roll (dielectric heating heating roll having a diameter of 300 mm and a width of 700 mm). The polarizing film was heated for 10 minutes at 95 ° C. by two heating rolls while continuously feeding the protective film and the polarizing film at a peripheral speed of min.
(5) Thereby, the laminated body which has a protective film and a piezoelectric film was obtained.
Examples 2-3 and Comparative Example 1
A laminate having a protective film and a piezoelectric film in the same manner as in Example 1 except that the type of protective film, other layers (adhesive layer), the temperature and time of heat treatment, and the like are appropriately changed as shown in Table 1 below. Got.
The results of peeling the protective film and the piezoelectric film are shown in Table 1 below.

Claims (4)

A laminate having a protective film and a piezoelectric film,
The protective film is disposed in contact directly Settonari on at least one major surface of said piezoelectric film,
The integrated average peel strength I _IA (mN / cm) and the maximum point peel strength I _MP (mN / cm) between the protective film and the piezoelectric film measured by the measurement method described later are the following (1) and (2):
(1) 1 ≦ I _IA ≦ 100
(2) _IMP- I _IA ≦ 40
The laminated body characterized by satisfy | filling.
<Peel strength measurement method>
T-peel measurement: The peel strength when the laminate having a width of 20 mm is peeled off while maintaining the T-shape at 300 mm / min under a temperature condition of 25 ° C. is measured.   The laminate according to claim 1, wherein a rate of change of an electromechanical coupling coefficient when the piezoelectric film is heated at 85 ° C for 10 hours is 10% or less.   The laminate according to claim 1 or 2, wherein the resin constituting the protective film is at least one selected from the group consisting of polyethylene terephthalate, polyethylene naphthalate, polypropylene, and polyethylene.   The laminate according to any one of claims 1 to 3, which is used for manufacturing a piezoelectric panel.