JPWO2015064327A1 - the film - Google Patents

Abstract

An object of this invention is to provide the film which shows high insulation and was excellent in withstand voltage property. The present invention provides a polarized vinylidene fluoride polymer film, wherein the film is produced using a vinylidene fluoride polymer that satisfies the following conditions (1) to (3): 1) Surfactant content is 100 ppm or less; (2) Methylcellulose content is 6000 ppm or less; (3) The sum of metal content and ion content is 200 ppm or less.

Description

  The present invention relates to a film.

Conventionally, various organic dielectric films and inorganic dielectric films are known as films or films used for piezoelectric films, electrowetting applications, and film capacitor applications.
Among these, the polarized vinylidene fluoride polymer film has the advantage of having transparency and being flexible unlike the inorganic dielectric thin film, and thus can be applied to various uses. .
For example, Patent Document 1 and Patent Document 2 disclose a technique for providing a touch panel with a function of detecting a touch pressure using a polarized vinylidene fluoride / tetrafluoroethylene copolymer film.

JP 2010-26938 A JP 2011-222679 A

However, the polarized vinylidene fluoride / tetrafluoroethylene copolymer films described in Patent Documents 1 and 2 have not been sufficiently studied on the characteristics of the copolymer used in the production. When the copolymer used at the time of manufacture is a polymer obtained by emulsion polymerization, a surfactant, metal, and ions are contained in the copolymer. Moreover, when it is polymerized by suspension polymerization, methylcellulose, metal and ions are contained in the copolymer.
Since the surfactant, methylcellulose, metal, and ions contained in such a film lower the insulating properties of the film, there is a problem of lowering the voltage resistance of the film. The polarized vinylidene fluoride / tetrafluoroethylene copolymer films described in Patent Documents 1 and 2 have room for improvement in insulation and voltage resistance.
Accordingly, an object of the present invention is to provide a film that exhibits high insulation properties and excellent voltage resistance.

As a result of intensive studies, the present inventors have
A polarized vinylidene fluoride polymer film;
The film is manufactured using a vinylidene fluoride polymer that satisfies the following conditions (1) to (3):
(1) The surfactant content is 100 ppm or less;
(2) The content of methylcellulose is 6000 ppm or less;
(3) The total of the metal content and the ion content is 200 ppm or less.
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 polarized vinylidene fluoride polymer film;
The film is manufactured using a vinylidene fluoride polymer that satisfies the following conditions (1) to (3):
(1) The surfactant content is 100 ppm or less;
(2) The content of methylcellulose is 6000 ppm or less;
(3) The total of the metal content and the ion content is 200 ppm or less.
Item 2.
Item 2. The film according to Item 1, wherein the polarized vinylidene fluoride polymer film is a polarized vinylidene fluoride / tetrafluoroethylene copolymer film.
Item 3.
Item 3. The film according to Item 1 or 2, which is a piezoelectric film.
Item 4.
Item 4. The film according to any one of Items 1 to 3, wherein the curl generated by heating at 100 ° C. for 60 minutes is within ± 10 mm.
Item 5.
Item 5. A piezoelectric panel, film capacitor, or electrowetting device comprising the film according to any one of Items 1 to 4.
Item 6.
Item 5. An input device having the film according to any one of Items 1 to 4.
Item 7.
Item 7. An electronic apparatus having the input device according to Item 6.

The film of the present invention is a polarized vinylidene fluoride copolymer film;
The following conditions (1) to (3)
(1) The surfactant content is 100 ppm or less;
(2) The content of methylcellulose is 6000 ppm or less;
(3) The sum of the metal content and the ion content is 200 ppm or less;
Since it is manufactured using a vinylidene fluoride-based polymer that satisfies the requirements, the content of the surfactant, methylcellulose, and metal and ions in the obtained film is suppressed, and thus shows high insulation and is excellent Shows withstand voltage.

In this specification, “detection” of “touch position” means determination of touch position, while “detection” of “touch pressure” means presence / absence of pressure, speed, magnitude, or a combination thereof. Means the decision.
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.
In the present specification, the “ether group” means an alkyl group in which one or more —O— is inserted into a carbon-carbon bond. The “ether group” includes “polyether group”. The “ether group” is preferably an ether group having 2 to 50 carbon atoms.
In the present specification, the “polyether group” means an alkyl group in which two or more —O— is inserted in a carbon-carbon bond. The “polyether group” is preferably an ether group having 8 to 30 carbon atoms.

Film The film of the present invention is
A polarized vinylidene fluoride polymer film;
The film is produced using a vinylidene fluoride polymer that satisfies the following conditions (1) to (3):
(1) The surfactant content is 100 ppm or less;
(2) The content of methylcellulose is 6000 ppm or less;
(3) The total of the metal content and the ion content is 200 ppm or less.
For this reason, since the content of surfactant, methylcellulose, and metal and ions is suppressed, the film of the present invention can exhibit high insulation properties and excellent voltage resistance.

In (1) above, the surfactant is a polymer obtained by emulsion polymerization of a vinylidene fluoride polymer (hereinafter also simply referred to as “polymer”) used in the production of the film of the present invention. Furthermore, it can be contained in a film by producing a film using a copolymer in which a surfactant remains.
The content of the surfactant is 100 ppm or less. The content of the surfactant is preferably 50 ppm or less. The lower limit of the surfactant content is not particularly limited, but is usually 0 ppm when the polymer is polymerized by suspension polymerization.
The content of the surfactant in the film of the present invention was determined by measuring the water from which the surfactant was extracted by suspending the polymer in water and treating with ultrasonic waves for 10 minutes or longer with a DX500 measuring instrument manufactured by Dionex. Can be detected.

Examples of the surfactant contained in the polymer include a surfactant used in emulsion polymerization of the polymer and a surfactant added after polymerization for stabilizing the dispersion.
As the surfactant used in the emulsion polymerization of the polymer, the following formula Rf ¹ -X
(In the formula, Rf ¹ represents an alkyl group having 2 or more carbon atoms substituted with one or more fluorine atoms, the upper limit is 50 or less, preferably 30 or less, and X is a sulfo group, a carboxyl group, or a group thereof. Indicates salt.)
A sulfonic acid having a fluoroalkyl group, or a carboxylic acid, or a salt thereof;
The following formula ^Rf 2 -X
(In the formula, Rf ² represents an ether group having 2 or more carbon atoms substituted with one or more fluorine atoms, the upper limit is 50 or less, preferably 30 or less, and X is a sulfo group, a carboxyl group, or a group thereof. Indicates salt.)
A sulfonic acid having a fluoroether group, a carboxylic acid, or a salt thereof;
Is mentioned.
As the surfactant used in the emulsion polymerization, the following formula R ¹ -X
(Wherein R ¹ represents an alkyl group having 2 or more (preferably 8 or more) carbon atoms, an upper limit of 50 or less, preferably 30 or less, and X represents a sulfo group, a carboxyl group, or a salt thereof. )
A non-fluorine-containing sulfonic acid, a non-fluorine-containing carboxylic acid, or a salt thereof;
The following formula ^R 2 -X
(In the formula, R ² represents an ether group having 2 or more carbon atoms and an upper limit of 50 or less, preferably 30 or less, and X represents a sulfo group, a carboxyl group, or a salt thereof.)
A non-fluorine-containing sulfonic acid or a non-fluorine-containing carboxylic acid, or a salt thereof;
Is mentioned. In the above formula, R ² is preferably a polyether group having 8 or more carbon atoms, and R ² can contain, for example, an oxyethylene group and / or an oxypropylene group.
As the surfactant used in the emulsion polymerization, a polymer surfactant may be used. Examples of such a polymer surfactant include polyacryl / methacrylate and polyvinyl sulfonate.
Examples of the surfactant used in the emulsion polymerization include polysiloxane surfactants.
As the surfactant used in the emulsion polymerization, a monomer that can be copolymerized with vinylidene fluoride, which includes a sulfo group, a carboxyl group, or a salt thereof in the side chain can be used. Is used as a self-emulsifier. Examples of such surfactants include acrylic acid, methacrylic acid, vinyl sulfonic acid, carboxylic acid having a vinyl ether chain, sulfonic acid, and salts thereof.

As the surfactant to be added after the polymerization for stabilizing the dispersion, the same surfactants as those used in the above emulsion polymerization can be used. Among these, as a surfactant to be added after polymerization for stabilizing the dispersion, the following formula R ¹ -X
(Wherein R ¹ represents an alkyl group having 2 or more (preferably 8 or more) carbon atoms, an upper limit of 50 or less, preferably 30 or less, and X represents a sulfo group, a carboxyl group, or a salt thereof. )
A non-fluorinated sulfonic acid, a non-fluorinated carboxylic acid, or a salt thereof represented by:
The following formula ^R 2 -X
(In the formula, R ² represents an ether group having 2 or more carbon atoms and an upper limit of 50 or less, preferably 30 or less, not containing fluorine, and X represents a sulfo group, a carboxyl group, or a salt thereof.)
A fluorine-free sulfonic acid, a fluorine-free carboxylic acid, or a salt thereof represented by:
Are preferably used. In the above formula, R ² is preferably a polyether group having 8 or more carbon atoms and an upper limit of 50 or less, preferably 30 or less. R ² is, for example, an oxyethylene group and / or an oxypropylene group. Etc. can be contained.
Examples of the surfactant added after polymerization for stabilizing the dispersion include polymer surfactants, and among them, polyacryl / methacrylate, polyvinyl sulfonate and the like are preferable.
Examples of the surfactant added after polymerization for stabilizing the dispersion include polysiloxane surfactants.
The surfactant used in the technical field to which the present invention belongs is usually the surfactant described herein. Therefore, in the present specification, it can be estimated that the “surfactant content” is usually the total content of the respective surfactants described herein. “Surfactant content” can be determined, for example, by determining the amount of each surfactant by a known method according to its structure and / or properties, and calculating the total amount thereof.

In the above (2), methylcellulose is a fluoropolymer in which methylcellulose used in the polymerization remains when the vinylidene fluoride polymer used in the production of the film of the present invention is polymerized by suspension polymerization. It can be contained in a film by producing a film using a vinylidene chloride polymer.
The methyl cellulose content is 6000 ppm or less. The methylcellulose content is preferably 5000 ppm or less. Further, the lower limit of the content of methylcellulose is not particularly limited, but is usually 0 ppm when the polymer is polymerized by emulsion polymerization, and usually about 3000 ppm when the polymer is polymerized by suspension polymerization.
The content of methylcellulose in the film of the present invention is detected by measuring the water from which methylcellulose is extracted by suspending the polymer in water and then treating with ultrasound for 10 minutes or more with a DX500 measuring instrument manufactured by Dionex. Can do.

In the above (3), the metal and ions can be contained in any of the vinylidene fluoride polymers polymerized by any of emulsion polymerization and suspension polymerization, and the present invention is made using the vinylidene fluoride polymer. Can be included in the film.
The total of the metal content and the ion content is 200 ppm or less. The total content is preferably 100 ppm or less. Further, the lower limit of the total of the metal content and the ion content is not particularly limited. However, when the polymer is polymerized by emulsion polymerization, it is usually about 30 ppm, and the polymer is polymerized by suspension polymerization. In some cases, it is usually about 10 ppm.
Although it does not specifically limit as said metal, For example, Fe, Cr, etc. are mentioned.
As the ion is not particularly limited, for _example, ^SO 4 _2-, Cl ^-, and the like.
The metal content in the film of the present invention is measured by extracting the metal with 0.1 wt% dilute hydrochloric acid after measuring the film with a SPS3000 measuring instrument manufactured by Seiko Instruments Inc. Can be detected.
In addition, the ion content in the film of the present invention is such that the film is cut into a state close to a powder, immersed in water and subjected to ultrasonic treatment for 1 hr or more, and the extracted water is extracted from a DX500 measuring instrument manufactured by Dionex. It can measure by analyzing by.

The film of the present invention is preferably a piezoelectric film, and more preferably an organic piezoelectric film. The “organic piezoelectric film” is a film (polymer film) formed from a vinylidene fluoride polymer that is an organic substance. The “organic piezoelectric film” may contain components other than the vinylidene fluoride polymer. The “organic piezoelectric film” includes a film made of the vinylidene fluoride polymer and a film in which an inorganic substance is dispersed in the polymer.
The content of the polymer in the film of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, still more preferably 85% by mass or more, and particularly 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.
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, More preferably, it exists in the range of 15 / 85-25 / 75, More preferably, it is in the range of 18 / 82-22 / 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) Examples of fluoromonomers, 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 monomers, methacrylic monomers, vinyl acetate) Can be mentioned.

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

When the film of the present invention is used for optical applications such as a piezoelectric film for touch panel or an electrowetting film, the total light transmittance is preferably 85% or more. The total light transmittance of the film of the present invention is more preferably 90% or more, still more preferably 92% or more, and most preferably 95% or more. Although the upper limit of the total light transmittance is not limited, the total light transmittance of the film of 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 film of the present invention is preferably 4.0% or less. The total haze value of the film of the present invention is more preferably 3.0% or less, still more preferably 2.0% or less, particularly preferably 1.5% or less, and most preferably 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 film of 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 film of 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 film of 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 film of the present invention is preferably 2.0% or less, more preferably 1.5% or less, still more preferably 1.0% or less, particularly preferably 0.9% or less, and most preferably 0.00. 7% or less. The lower the external haze value is, the better. The lower limit is not limited, but the external haze value of the film of 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 film of 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. is there.
The rate of change of the electromechanical coupling coefficient of the film of the present invention is preferably 10% or less, more preferably 8% or less, and even 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 film is obtained by forming an Al vapor-deposited electrode on both sides of the film, cutting out a 13 mm disk at a predetermined portion of the film, and impedance analyzer (Hewlett Packard, 4194A). Alternatively, it is measured using an equivalent product 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 film;
(2) heating the film in air at 85 ° C. for 10 hours;
(3) The film was allowed to stand at room temperature and cooled to room temperature, and (4) the heating and the electromechanical coupling coefficient (kt after heating) of the film after cooling were measured and measured. It is determined by adding “kt before heating” and “kt after heating” to 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 film of 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. In the range of 6-50 μm, in the range of 9-40 μm, in the range of 10-40 μm, or in the range of 10-30 μm. The preferred thickness can vary depending on the application of the film of the present invention. For example, when the film of the present invention is used for a piezoelectric panel such as a touch panel, the thickness of the film of 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 inventive film is used in an electrowetting device, the thickness of the inventive film is preferably in the range of 0.5-5 μm, more preferably 0.8-2 μm, and the inventive film is When used for a film capacitor, the thickness of the film of the present invention is preferably in the range of 1.5 to 12 μm.

The film of the present invention preferably has a curl of ± 10 mm or less caused by heating at 100 ° C. for 60 minutes. By setting the degree of curling to the above-described range, the film of the present invention can be made into a film suitable for use in applications that require accuracy such as a piezoelectric film.
The curl is a caliper that lifts from the metal plate at both ends after a film cut to a width of 100 mm and a length of 100 mm is attached to the metal plate with a tape along the center line and heated at 100 ° C. for 60 minutes. It is measured by the method of measuring in
Examples of the method of setting the curl of the film of the present invention within ± 10 mm include, for example, in the film production method of the present invention described later, the peel strength between the substrate and the vinylidene fluoride polymer film is 0.1 N / cm or less. And a drying temperature for vaporizing the solvent of 200 ° C. or less, and a vinylidene fluoride polymer in a liquid composition prepared by dissolving or dispersing a vinylidene fluoride polymer and a desired component in the solvent. The method of making solid content concentration of 5 mass% or more is mentioned.

Production method The film of the present invention is, for example,
Step A for polarizing a non-polarized vinylidene fluoride polymer film; and Step B for subsequent heat treatment of the polarized vinylidene fluoride polymer film
It can manufacture by the manufacturing method containing.

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

The vinylidene fluoride polymer can be polymerized by solution polymerization, suspension polymerization in water, and emulsion polymerization in water. From the viewpoint of productivity and cost, suspension polymerization or emulsion polymerization in water is preferable.
In the case of emulsion polymerization, impurities that may be contained in the polymer at the end of the coagulation step after polymerization include surfactants, ionic components derived from initiators, metals derived from coagulants, and ionic components. It is desirable to remove in the washing step after coagulation. In the washing step, washing with water is desirable for production, but when impurities cannot be removed, washing with water mixed with an organic solvent such as warm water or ethanol can be carried out in order to increase washing efficiency.
In the case of suspension polymerization, impurities that may be contained in the polymer after polymerization include ionic content derived from the initiator, metal content derived from the apparatus, methylcellulose used during suspension polymerization, etc. It is desirable to perform the removal. In the washing step, washing with water is desirable for production, but when impurities cannot be removed, washing with water mixed with an organic solvent such as warm water or ethanol can be carried out in order to increase washing efficiency.
The “non-polarized vinylidene fluoride polymer film” used in step A is, for example, a known method such as a casting method, a hot press method, or a melt extrusion method using the above-mentioned vinylidene fluoride polymer. Can be manufactured. The “non-polarized vinylidene fluoride polymer film” used in Step A is preferably a film produced by a casting method.

The production method of the “non-polarized vinylidene fluoride polymer film” by the casting method is, for example,
(1) A step of preparing a liquid composition by dissolving or dispersing a vinylidene fluoride polymer and desired components (eg, inorganic oxide particles and affinity improver) in a solvent;
(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 substrate, for example, a polyethylene terephthalate (PET) film, a PET film subjected to a release treatment, or a steel belt 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 10 to 600 seconds, preferably in the range of 30 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 film of the present invention is preferably an unstretched film.
The film of the present invention thus obtained has a high thickness uniformity. Specifically, preferably, in the film of the present invention, the variation coefficient of the thickness measured at 10 points per 1 cm square over the entire 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 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, the corona discharge treatment is performed by sandwiching the non-polarized film from both sides with flat electrodes; as described in JP 2011-181748 A (the above-mentioned Patent Document 2). Can be applied using a linear electrode; or can be applied to a non-polarized film using a needle electrode.

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 conditions for corona discharge treatment are too weak, the piezoelectricity of the resulting film may be insufficient. On the other hand, if the conditions for corona discharge treatment are too strong, the resulting film may have point defects.
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 (heat treatment process)
Step B is performed after Step A. In Step B, the polarized vinylidene fluoride polymer film obtained by the polarization treatment in Step A (hereinafter sometimes simply referred to as a polarized film) is heat-treated.
The heat treatment in step B can be performed on the polarized film or the portion where polarization has been completed in step A. That is, while performing the polarization process of the process A, the heat treatment of the process B may be performed on the portion where the polarization process has been completed.
The method of the heat treatment is not particularly limited. For example, the polarizing film is sandwiched between two metal plates and the metal plate is heated; the polarizing film roll is heated in a thermostatic bath; -In the production of a polarized film in a roll mode, the metal roller is heated and the polarized film is brought into contact with the heated metal roller; or in a furnace in which the polarized film is heated in a roll-to-roll manner This can be done by passing it through. At this time, the polarized film may be heat-treated alone, or may be laminated on another type of film or metal foil to form a laminated film, which may be heat-treated. In particular, when the heat treatment is performed at a high temperature, the latter method is preferable because the polarizing film is less likely to wrinkle.
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 non-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.

Film Roll The film of the present invention can preferably be stored and shipped as a roll.
The 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 in the form of such a roll. The elastic modulus can be adjusted by selecting the material of the film.
The roll of the film of the present invention may consist only of the film of the present invention, or may be formed by laminating a protective film or the like on the film of the present invention, wound around a core such as a paper tube, and the core. You may provide the film of this invention.
The roll of the 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 film of the present invention can be prepared, for example, by winding the 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 that the unwinding roller and the take-up roller be parallel to each other, as is usually done.
Moreover, you may use the film whose elasticity modulus is 500 Mpa or more among the films of this invention from a viewpoint of suppressing the bending of a film.
As a roller, in order to improve the slipperiness of the film of the present invention, a roller having a good slipperiness, specifically a roller coated with a fluororesin, a plated roller, or a roller coated with a release agent is used. Is preferred.
Here, when the film thickness is non-uniform, so-called roll earing (high edge; the end portion becomes thicker than the central portion in the axial direction of the roll; both end portions are thinner than the central portion. In some cases, both ends are recessed compared to the center; or when the thickness changes from one end to the other in an inclined manner, the end on the side where the film thickness is thinner is recessed) Unevenness of the roll thickness occurs, which may cause wrinkles. In addition, this may cause the film to bend (bend in a state in which no tension other than that due to gravity is applied) when the film is rolled out.
Generally, for the purpose of preventing the roll from standing, the end of the film that is the end of the roll is slitted (slit). However, if the film thickness varies widely from the end of the film, the end of the roll It is difficult to prevent the roll from standing and dents with only the roller.
In general, the larger the width of the film (for example, 100 mm or more) and the longer the length of the film (for example, 50 m or more), the more likely the ear standing, the dent and the deflection are generated. However, since the thickness of the film of the present invention is high, the width of the film is wide (eg, a width of 100 mm or more, as it is or just by slitting the end of the film as the end of the roll). ) And a long film (e.g., 50 m or longer), it is possible to obtain a roll in which the ear standing, the dent and the deflection are suppressed.
The ear (film end) removed by the slit can be collected and recycled as a raw material for the film of the present invention.
The roll of the film 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%. It is. Thereby, as for the roll of the film of this invention, the deflection | deviation of the film unwound from this is suppressed.

The surface roughness Ra of the roller used for producing the film of the present invention and its roll 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 film of the present invention and its roll has at least a surface material of polytetrafluoroethylene (PTFE), chrome plating, or stainless steel (SUS). By these things, the wrinkle of a film can be suppressed.

Apply
Piezoelectric panel The film of the present invention can be used for a piezoelectric panel (eg, a touch panel capable of detecting a touch pressure).
The touch panel having the film of 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 hardly deteriorated and has high transparency.
The film of the present invention can be used for touch panels of all types such as a resistive film type and a capacitance type.
When the film of 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 film of the present invention detects either the touch position or the touch pressure. May also be used.
The piezoelectric panel having the film of the present invention is preferably
A first electrode (preferably a transparent electrode);
A film of the present invention (preferably a transparent piezoelectric film);
A second electrode (preferably a transparent electrode);
In this order.
The first electrode is disposed directly or indirectly on one major surface of the film of the present invention, and the second electrode is disposed directly or indirectly on the other major surface of the film of the present invention.
Examples of the electrodes include ITO (indium tin oxide) electrodes, tin oxide electrodes, metal nanowires, metal nanoparticles, and organic conductive resins.

  The touch panel having the film of the present invention can be used for an input device. An input device having the touch panel can perform input based on a touch position, a touch pressure, or both. An input device having the touch panel can include a position detection unit and a pressure detection unit.

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

Electrowetting Device The film of the present invention has electrowetting properties and can be used in an electrowetting device. Here, the “electrowetting” means that the wettability (wetability) of the film surface is changed from hydrophobic (water repellent) to hydrophilic using an electric field. The “electrowetting device” means a device using the “electrowetting”.
The film of the present invention includes an optical element, a display device (display), a variable focus lens, a light modulation device, an optical pickup device, an optical recording / reproducing device, a developing device, a droplet manipulation device, and an analytical instrument (eg, for analyzing a sample). It can be suitably used for an electrowetting device in chemical, biochemical, and biological analytical instruments) that needs to move a minute conductive liquid.
The film of the present invention can have a high dielectric constant and a low dielectric loss tangent. Thereby, a conductive liquid can be driven with a low voltage.

Film Capacitor Since the film of the present invention can have a high relative dielectric constant and a low dielectric loss tangent, it can be suitably used as a film for a film capacitor. Further, it is advantageous as a film for a film capacitor in that the high dielectric property characteristic of the vinylidene fluoride / tetrafluoroethylene copolymer is not impaired even when a voltage is applied for a long time.

Transparent cover film The film of the present invention can be used as a transparent cover film because it is made of a vinylidene resin excellent in weather resistance and has very high transparency. In this case, for example, by laminating a polycarbonate or PET film on the film of the present invention, weather resistance can be imparted to these films.

  Since the film of this invention has flexibility, it can be used suitably for various uses.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to this.
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 as a piezoelectric film)
Examples 1-7, Comparative Examples 1-3
(Preparation of non-polarized film)
A vinylidene fluoride / tetrafluoroethylene copolymer (TFE / VDF = 20/80) was dissolved in methyl ethyl ketone (MEK) to prepare a paint having a solid content of 25 wt%. Table 1 shows the surfactant amount, metal content, ion content, and methylcellulose content of the vinylidene fluoride / tetrafluoroethylene copolymer used.
In addition, the measurement of the metal content of the vinylidene fluoride / tetrafluoroethylene copolymer was performed with an ICP (Emission Analyzer). Specifically, after burning the vinylidene fluoride / tetrafluoroethylene copolymer, the ash was dissolved in 0.1% hydrochloric acid, the metal was extracted, and measurement was performed by ICP. As the ICP, SPS3000 manufactured by Seiko Instruments Inc. was used.
The analysis of the amount of surfactant, the content of ions, and the amount of methylcellulose in the vinylidene fluoride / tetrafluoroethylene copolymer was performed by ion chromatography. Specifically, after vinylidene fluoride / tetrafluoroethylene copolymer is placed in water and treated with ultrasonic waves for about 2 hours, the vinylidene fluoride / tetrafluoroethylene copolymer is filtered and the water is subjected to ion chromatography. Measured with For ion chromatography, Dionex Corporation DX500 was used.

The obtained paint is filtered through a depth bleach type filter having a pore size of 3 μm, and the filtered paint is cast on a PET film using a die coater, followed by drying to obtain a polymer film having a thickness of 25 μm. Prepared.
At this time, the drying is divided into 4 zones with the drying device as 1m 2m, and the drying temperature is set to 50 ° C, 80 ° C, 120 ° C and 150 ° C from the entrance side, and the passing speed of each zone is set. It was carried out by setting the peripheral speed to 8 / min and passing the film (or cast paint).

(Polarization treatment)
Thereafter, the polymer film is peeled off from the PET film, the polymer film is sandwiched from above and below with a metal electrode, and a DC voltage is applied to the polymer film having a thickness of 25 μm under a condition of 300 kV / cm at room temperature for 5 minutes. Application was polarized to obtain a polarized film.
(Heat treatment)
Thereafter, the polarized film was heated in a hot air dryer at 90 ° C. for 5 minutes, and then allowed to stand at room temperature to cool to room temperature, thereby obtaining a piezoelectric film.

About the piezoelectric film after the said heat processing, the number of defects of the piezoelectric film at the time of polarization was measured with the following method.
Relative number of defects above piezoelectric film of 1 m ² per during polarization was 1 m ² defects per (short broken number portion) (number / m ²⁾ measured as follows (calculated). Specifically, the measurement was performed according to the following procedures (1) to (3).
(1) Each film of 20 cm × 10 cm is subjected to polarization treatment by the method of the above example.
(2) After (1), the number of destruction is counted visually.
(3) The above operation was performed on five films, and the number of defects was converted to the number of m ² .
Total haze value The total haze value was measured by a light transmission test using Hazeguard II (product name) (Toyo Seiki Seisakusho) based on ASTM D1003.
The results are shown in Table 1.

  From the results in Table 1, it was found that as the content of impurities such as surfactants increased, the haze value deteriorated and the number of defects during polarization also increased.

(Example as film capacitor)
Examples 8-14
(Preparation of film)
A vinylidene fluoride / tetrafluoroethylene copolymer (TFE / VDF = 7/93) and carboxybutyl cellulose were mixed at a weight ratio of 90/10. This was dissolved in a solvent in which NMP / MEK was mixed at a weight ratio of 30/70 to prepare a paint having a solid content of 20 wt%. Table 2 shows the amount of surfactant, metal content, ion content, and methylcellulose content of the vinylidene fluoride / tetrafluoroethylene copolymer used.

In addition, the measurement of the metal content of the vinylidene fluoride / tetrafluoroethylene copolymer was performed with an ICP (Emission Analyzer). Specifically, after burning the vinylidene fluoride / tetrafluoroethylene copolymer, the ash was dissolved in 0.1% hydrochloric acid, the metal was extracted, and measurement was performed by ICP. As the ICP, SPS3000 manufactured by Seiko Instruments Inc. was used.
The analysis of the amount of surfactant, the content of ions, and the amount of methylcellulose in the vinylidene fluoride / tetrafluoroethylene copolymer was performed by ion chromatography. Specifically, after vinylidene fluoride / tetrafluoroethylene copolymer is placed in water and treated with ultrasonic waves for about 2 hours, the vinylidene fluoride / tetrafluoroethylene copolymer is filtered and the water is subjected to ion chromatography. Measured with For ion chromatography, Dionex Corporation DX500 was used.

The obtained paint is filtered through a depth bleach type filter having a pore diameter of 3 μm, and the filtered paint is cast on a PET film using a die coater, followed by drying to obtain a polymer film having a thickness of 3 μm. Prepared.
At this time, the drying is divided into 4 zones with the drying device as 1m 2m, the respective drying temperatures are set to 170 ° C, 140 ° C, 140 ° C and 120 ° C from the entrance side, and the passing speed of each zone is set. It was carried out by setting the peripheral speed to 8 / min and passing the film (or cast paint).

Aluminum was vapor-deposited so that it might become 4 ohms on one side of the obtained film. A film on which aluminum was vapor-deposited was cut into a width of 30 mm and a length of 80 mm, and four sheets were laminated and sandwiched between glass plates, and leads were taken out from both end faces to prepare stamp-type film capacitors.
A voltage was applied to the obtained film capacitor while increasing the voltage at a speed of 100 V per minute to measure a withstand voltage until short-circuiting, and a 99% withstand voltage based on reliability evaluation by Weibull distribution was measured.

Comparative Examples 4-6
A film capacitor was prepared by the same method as in Examples 8 to 14 except that the filter was not filtered, and the 99% withstand voltage was measured based on the withstand voltage and reliability evaluation by Weibull distribution.

  The results are shown in Table 2.

  From the results shown in Table 2, when the content of impurities such as surfactants increases, the 99% withstand voltage based on the reliability evaluation by the Weibull distribution of the film decreases, and as a result, the withstand voltage when used as a capacitor also decreases. I understood.

  The film of the present invention can be used for a touch panel or the like.

Claims (7)

A polarized vinylidene fluoride polymer film;
The film is manufactured using a vinylidene fluoride polymer that satisfies the following conditions (1) to (3):
(1) The surfactant content is 100 ppm or less;
(2) The content of methylcellulose is 6000 ppm or less;
(3) The total of the metal content and the ion content is 200 ppm or less. The film according to claim 1, wherein the polarized vinylidene fluoride polymer film is a polarized vinylidene fluoride / tetrafluoroethylene copolymer film. The film according to claim 1 or 2, which is a piezoelectric film. The film according to any one of claims 1 to 3, wherein a curl generated by heating at 100 ° C for 60 minutes is within ± 10 mm. A piezoelectric panel, a film capacitor, or an electrowetting device comprising the film according to claim 1. The input device which has a film in any one of Claims 1-4. An electronic apparatus comprising the input device according to claim 6.