JP2011006596A - Polymer composition and polymer piezoelectric film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer composition and a polymer piezoelectric film that have easy adhesion.SOLUTION: The polymer composition includes 20-90 pts.wt. polyvinylidene fluoride and 80-10 pts.wt. vinylidene fluoride copolymer, provided that the total of the polyvinylidene fluoride and the vinylidene fluoride copolymer is 100 pts.wt. The vinylidene fluoride copolymer is produced by copolymerizing 100 pts.wt. vinylidene fluoride monomer containing not less than 60 wt.% vinylidene fluoride and 0.1-3 pts.wt. monoester of an unsaturated dibasic acid.

Description

  The present invention relates to a polymer composition and a polymer piezoelectric film using the same. In particular, the present invention relates to a polymer composition containing polyvinylidene fluoride and a polymer piezoelectric film.

A piezoelectric element (piezo element) using a piezoelectric effect of a specific substance has an element in which a piezoelectric body is sandwiched between two electrodes as a basic structure. In addition, there are various structures of piezoelectric sensors.
A conventional piezoelectric sensor is a film in which a silver paste is applied to both surfaces of a piezoelectric film made of polyvinylidene fluoride (PVDF), the upper side is a positive electrode layer, and the lower side is a negative electrode layer (the other electrode layer). (For example, refer to Patent Document 1 and FIG. 4). In addition, two piezoelectric films made of polyvinylidene fluoride are bonded using an adhesive layer formed of a urethane-based resin having good compatibility with the polyvinylidene fluoride film, thereby providing a plurality of piezoelectric films. There is also a piezoelectric sensor with an increased output (see, for example, Patent Document 2, paragraph 0033, FIG. 2).

  As described above, the piezoelectric bodies are often used by being laminated. However, polyvinylidene fluoride, which is a fluorine-based resin, is excellent in chemical resistance, weather resistance, stain resistance, and the like, but has a feature of poor adhesion to other thermoplastic resins. Therefore, in order to form a laminate with another thermoplastic resin or the like, it is necessary to use a substance that can adhere to polyvinylidene fluoride as an adhesive layer or an adhesive. Furthermore, the types of substances that can be used as adhesive layers and adhesives have been quite limited.

Japanese Patent Laid-Open No. 10-332509 JP 2008-304558 A

  Accordingly, the present invention provides a polymer composition containing polyvinylidene fluoride with improved adhesion, and a polymer piezoelectric film with improved adhesion obtained from the polymer composition. For the purpose.

  In order to solve the above problems, a polymer composition according to the first aspect of the present invention includes 20 to 90 parts by weight of polyvinylidene fluoride and 80 to 10 parts by weight of a vinylidene fluoride copolymer, The total of vinylidene and vinylidene fluoride copolymer is 100 parts by weight. Further, the vinylidene fluoride copolymer is composed of 100 parts by weight of a vinylidene fluoride monomer containing 60% by weight or more of vinylidene fluoride, and 0.1 to 3% by weight of a monoester monomer of an unsaturated dibasic acid. Obtained by copolymerization with a part.

If comprised in this way, the polymer composition which has adhesiveness easily can be obtained from the mixture of the vinylidene fluoride-type copolymer which has adhesiveness, and a polyvinylidene fluoride.
Note that “having easy adhesion” means having adhesion improved by introduction of a carbonyl group.

  The polymer composition according to the second aspect of the present invention is the polymer composition according to the first aspect of the present invention, wherein the monoester monomer of unsaturated dibasic acid is 0.1 to 0. 8 parts by weight.

  If comprised in this way, the polymer composition which has easily adhesiveness can be obtained from the mixture of the vinylidene fluoride type copolymer which has the adhesiveness of extrusion molding easily, and polyvinylidene fluoride.

The polymer piezoelectric film according to the third aspect of the present invention is formed by subjecting the polymer composition according to the first aspect or the second aspect of the present invention to a non-stretched film shape, and then polarization treatment. Can be obtained.
In the present specification, “non-stretched” means that the process of “stretching” has not been performed, and “non-stretched film (non-stretched and formed into a film shape)” means “stretched” A film molded without going through.
“Stretching” refers to processing by stretching a film in a specific direction (for example, uniaxial direction or biaxial direction). That is, “uniaxially stretched film” refers to a film stretched several times in one direction (for example, the length direction), and “biaxially stretched film” refers to two directions (for example, the length and width directions), respectively. A film stretched several times.

  With this configuration, an unstretched polymer piezoelectric film having piezoelectricity and easy adhesion can be obtained. Since the film is unstretched, it is possible to produce a film that suppresses heat shrinkage and shrinkage with time, which occur in a stretched film.

  The polymer piezoelectric film according to the fourth aspect of the present invention is obtained by applying a quaternary ammonium salt or a quaternary ammonium salt to the polymer composition according to the first aspect or the second aspect of the present invention. It is obtained by adding the treated clay, forming it into a film without stretching and then subjecting it to a polarization treatment.

  If comprised in this way, the non-stretched polymeric piezoelectric film which has piezoelectricity and an easily-adhesive property can be obtained similarly to the polymeric piezoelectric film which concerns on the 3rd aspect of this invention. Since the film is unstretched, it is possible to produce a film that suppresses heat shrinkage and shrinkage with time, which occur in a stretched film.

  The polymer piezoelectric film according to the fifth aspect of the present invention is subjected to polarization treatment after uniaxial stretching after the polymer composition according to the first aspect or the second aspect of the present invention is formed into a film shape. Can be obtained.

  If comprised in this way, the polymeric piezoelectric material film which has piezoelectricity and an easily-adhesive property can be obtained by uniaxial stretching and polarization process.

  The polymer piezoelectric film according to the sixth aspect of the present invention is a polymer piezoelectric film according to the first aspect or the second aspect of the present invention, which is formed into a film shape and then simultaneously polarized while being uniaxially stretched. It is obtained by processing.

  With this configuration, since the uniaxial stretching and the polarization treatment are performed at the same time, a polymer piezoelectric film having improved piezoelectricity and easy adhesion as compared with the film subjected to the polarization treatment after uniaxial stretching is obtained. be able to.

  A polymer piezoelectric film according to a seventh aspect of the present invention is a biaxially stretched polarization treatment after the polymer composition according to the first aspect or the second aspect of the present invention is formed into a film shape. Can be obtained.

  If comprised in this way, the polymeric piezoelectric material film which has piezoelectricity and an easily-adhesive property can be obtained by biaxial stretching and a polarization process.

A multilayer film according to an eighth aspect of the present invention comprises a polymer piezoelectric film according to any one of the third to seventh aspects of the present invention, and a laminate of the polymer piezoelectric film. And another thermoplastic resin different from the polymer piezoelectric film.
The “other thermoplastic resin” refers to, for example, a polyamide resin, a polyester resin, an acrylic resin, a urethane resin, or the like.

  If comprised in this way, since a polymeric piezoelectric film has adhesiveness easily, compared with the film which consists of polyvinylidene fluoride, the polymeric piezoelectric film which improved the adhesiveness with other thermoplastic resins, and other A multilayer film made of a thermoplastic resin can be obtained.

  The multilayer film according to the ninth aspect of the present invention is the multilayer film according to the eighth aspect of the present invention, wherein the polymer piezoelectric film and the other thermoplastic resin are laminated by coextrusion.

  If comprised in this way, since a polymeric piezoelectric film has easy adhesiveness, compared with the film which consists of polyvinylidene fluoride, the multilayer film which comprised the lamination with another thermoplastic resin by coextrusion can be obtained easily. .

  In the present invention, a copolymer of a monomer such as vinylidene fluoride and a monoester monomer of an unsaturated dibasic acid is mixed with polyvinylidene fluoride to obtain a piezoelectric material having easy adhesion. A molecular composition can be obtained. Further, a polymer piezoelectric film having both easy adhesion and piezoelectricity can be obtained from this polymer composition. Therefore, a laminated structure with another thermoplastic resin or the like can be easily configured as compared with a film made of polyvinylidene fluoride.

It is a table | surface which shows the experimental data of a vinylidene fluoride type copolymer. It is a flowchart which shows the method of manufacturing a polymeric piezoelectric material film from a polymeric composition. (A) to (e) show <Method 1> to <Method 5>, respectively. FIG. 3A is a conceptual diagram of an apparatus 60 for uniaxially stretching and / or polarizing a film. FIG. 3B is a conceptual diagram of an apparatus 80 for polarizing a film. It is a table | surface which shows the actual value of an Example and a comparative example. (A) is the actual measurement value of the film manufactured by <Method 3>. (B) is the measured value of the film manufactured by <Method 1>. It is a table | surface which shows the evaluation result by the cross cut tape method of an Example and a comparative example. It is a table | surface which shows the actual value of the Example and comparative example of a film which were manufactured by <Method 1>-<Method 5>.

  Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding members are denoted by the same or similar reference numerals, and redundant description is omitted. Further, the present invention is not limited to the following embodiments.

In the polymer composition and the polymer piezoelectric film of the present invention, the following vinylidene fluoride monomer and unsaturated dibasic acid monoester are used for the purpose of “improving adhesion as compared with polyvinylidene fluoride alone”. This was realized by a configuration in which a copolymer with an ester monomer and polyvinylidene fluoride were mixed at a certain ratio.
The improvement in adhesiveness is considered to be due to the influence of the functional group (carbonyl group) of the monoester of unsaturated dibasic acid. Therefore, it is considered that the polymer composition and the polymer piezoelectric film of the present invention have improved adhesion to a substance having an affinity for this functional group. Hereinafter, this improved adhesion is referred to as “easy adhesion”. That is, the present invention realizes a polymer composition and a polymer piezoelectric film that can be a piezoelectric material having easy adhesion.

In general, polyvinylidene fluoride has a feature that it is difficult to mix with other substances. Moreover, when another substance is mixed with polyvinylidene fluoride, the polarization treatment becomes difficult. As a result, the piezoelectricity of films made from this mixture is significantly lower than films made from polyvinylidene fluoride alone. Therefore, when producing a piezoelectric film from polyvinylidene fluoride, it has been necessary to use polyvinylidene fluoride alone to ensure a sufficient piezoelectric effect.
On the other hand, a vinylidene fluoride copolymer comprising a relatively small amount of a specific monomer having a carbonyl group (monoester of unsaturated dibasic acid) and a monomer mainly composed of vinylidene fluoride is a metal It functions as an adhesive with significantly improved adhesion to a substrate such as JP-A-6-172452. This vinylidene fluoride copolymer is used in battery binders and paints in a state of being dissolved in a liquid. This vinylidene fluoride copolymer has a feature that it is difficult to mold because of its low thermal stability, and foaming, surface roughening, and vertical stripes are likely to occur when it is molded into a film. If there is foaming in the film, a short circuit is likely to occur during the polarization treatment, and thus it is not suitable for applications that require polarization treatment.
The present inventors have found that a polymer piezoelectric film having easy adhesion can be produced from a composition in which polyvinylidene fluoride and this vinylidene fluoride copolymer are mixed at a specific ratio. The piezoelectricity of the polymer piezoelectric film having easy adhesion was sufficiently industrially usable. Furthermore, the composition was excellent in thermal stability as compared with the vinylidene fluoride copolymer alone.

  First, the polymer composition according to the first embodiment of the present invention will be described. The polymer composition is a mixture of polyvinylidene fluoride and a vinylidene fluoride copolymer.

The vinylidene fluoride copolymer will be described.
The “vinylidene fluoride copolymer” is obtained by copolymerizing a vinylidene fluoride monomer and an unsaturated dibasic acid monoester monomer at a certain ratio.
“Vinylidene fluoride monomer” refers to vinylidene fluoride alone or a mixture of vinylidene fluoride and other monomers. The “other monomer” refers to a fluorine monomer copolymerizable with vinylidene fluoride or a hydrocarbon monomer such as ethylene and propylene. “Fluorine-based monomer copolymerizable with vinylidene fluoride” refers to vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, fluoroalkyl vinyl ether, and the like. The amount of “other monomer” contained in the polymer composition is preferably 40% by weight or less of the total amount of vinylidene fluoride and the other monomer. In particular, it is preferably 20% by weight or less.
The “monoester monomer of unsaturated dibasic acid” preferably has 5 to 8 carbon atoms. For example, maleic acid monomethyl ester, maleic acid monoethyl ester, citraconic acid monomethyl ester, citraconic acid monoethyl ester and the like are preferable. In particular, maleic acid monomethyl ester and citraconic acid monomethyl ester are preferred.

  A method for copolymerizing a vinylidene fluoride monomer and an unsaturated dibasic acid monoester monomer will be described. For the copolymerization, methods such as suspension polymerization, emulsion polymerization, and solution polymerization can be employed. However, aqueous suspension polymerization and emulsion polymerization are preferable from the viewpoint of ease of post-treatment, and aqueous suspension polymerization is particularly preferable.

  In suspension polymerization using water as a dispersion medium, a suspending agent such as methyl cellulose, methoxylated methyl cellulose, propoxylated methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, polyvinyl alcohol, polyethylene oxide, and gelatin is added to 0.005 with respect to water. It is used by adding in the range of -1.0% by weight, preferably 0.01-0.4% by weight.

  As polymerization initiators, diisopropyl peroxydicarbonate, dinormalpropyl peroxydicarbonate, dinormalheptafluoropropyl peroxydicarbonate, isobutyryl peroxide, di (chlorofluoroacyl) peroxide, di (perfluoroacyl) Peroxide, tertiary butyl peroxypivalate, etc. can be used. The amount used is 0.1 to 5% by weight, preferably 0. 0% to the total amount of monomers (total amount of vinylidene fluoride monomer and unsaturated dibasic acid monoester monomer). 5 to 2% by weight.

  Adding a chain transfer agent such as ethyl acetate, methyl acetate, acetone, ethanol, n-propanol, acetaldehyde, propyl aldehyde, ethyl propionate, carbon tetrachloride, diethyl carbonate, etc. to adjust the degree of polymerization of the resulting polymer Is also possible. The amount used is usually 0.1 to 5% by weight, preferably 0.5 to 3% by weight, based on the total amount of monomers.

  The total amount of monomers charged is 1: 1 to 1:10, preferably 1: 2 to 1: 5, in the weight ratio of total monomer: water. The polymerization is carried out at a temperature of 10 to 80 ° C. for 5 to 100 hours.

  By the above suspension polymerization, the vinylidene fluoride monomer and the monoester monomer of unsaturated dibasic acid can be easily copolymerized.

0.1 to 3 parts by weight, especially 0.1 to 0.8 parts by weight of monoester monomer of unsaturated dibasic acid is copolymerized with 100 parts by weight of vinylidene fluoride monomer It is preferable to make it. If it is less than 0.1 part by weight, the effect of improving adhesiveness is poor. On the other hand, when it exceeds 3 parts by weight, the chemical resistance of the resulting vinylidene fluoride copolymer is lowered. For the same reason, the obtained vinylidene fluoride copolymer preferably contains 8 × 10 ^{−7 to} 5 × 10 ⁻⁴ mol / g of carbonyl group.

  The vinylidene fluoride copolymer thus obtained has a solution viscosity (logarithmic viscosity at 30 ° C. of a solution in which 4 g of resin is dissolved in 1 liter of N, N dimethylformamide. The same applies hereinafter) as a measure of molecular weight. Is preferably a value within the range of 0.5 to 2.0 dl / g, particularly 0.8 to 1.5 dl / g.

  The pellets of vinylidene fluoride copolymer and the pellets of polyvinylidene fluoride obtained as described above are mixed at a temperature of 190 to 220 ° C. using an extruder, and the first embodiment or the second embodiment of the present invention. A polymer composition according to the form is obtained. In addition, the present inventors have found that piezoelectricity is manifested only with a vinylidene fluoride copolymer. In addition, the mixing ratio is 100 to 1 part by weight of the vinylidene fluoride copolymer and 0 to 99 parts by weight of the polyvinylidene fluoride so that the total of vinylidene fluoride copolymer and polyvinylidene fluoride is 100 parts by weight. It was confirmed that it was possible to make a part. However, in consideration of the thermal stability of the polymer composition (or vinylidene fluoride copolymer), the mixing ratio is 80 to 10 parts by weight of the vinylidene fluoride copolymer and 20 to 90 parts by weight of the polyvinylidene fluoride. Part. With this mixing ratio, it is easier to mold because the thermal stability increases while maintaining moderate easy adhesion.

  The vinylidene fluoride copolymer is a monoester monomer of an unsaturated dibasic acid in a very limited amount (unsaturated dibasic acid monoester with respect to 100 parts by weight of vinylidene fluoride monomer). The present inventors have found that sheet extrudability is greatly improved when copolymerized with 0.1 to 0.8 parts by weight of an ester monomer). For reference, the vinylidene fluoride copolymer having excellent sheet extrudability will be described below using experimental data.

<Experimental data 1>
An autoclave having an internal volume of 2 liters is charged with 1040 g of ion-exchanged water, 0.6 g of methyl cellulose, 3 g of ethyl acetate, 4 g of diisopropyl peroxydicarbonate, 398 g of vinylidene fluoride and 2 g of maleic acid monomethyl ester (vinylidene fluoride: maleic acid monomethyl ester) = 100: 0.50), suspension polymerization was carried out at 25 ° C for 42 hours. After the polymerization was completed, the polymer slurry was dehydrated, washed with water, and dried at 80 ° C. to obtain a powdery copolymer. The polymerization rate was 85%. The obtained polymer had a solution viscosity of 1.1 dl / g. The carbonyl group content was 0.6 × 10 ⁻⁴ mol / g.

<Experimental data 2>
In an autoclave with an internal volume of 2 liters, 1040 g of ion-exchanged water, 0.6 g of methyl cellulose, 3 g of ethyl acetate, 4 g of isopropyl peroxydicarbonate, 375.2 g of vinylidene fluoride, 24 g of chlorotrifluoroethylene, 0.8 g of maleic acid monomethyl ester Preparation (vinylidene fluoride + chlorotrifluoroethylene: maleic acid monomethyl ester = 100: 0.20) and suspension polymerization were carried out at 25 ° C. for 24 hours. After completion of the polymerization, similarly, dehydration, washing with water, and drying at 80 ° C. were performed to obtain a powdery copolymer. The polymerization rate was 85%. The obtained polymer had a solution viscosity of 1.0 dl / g. The carbonyl group content was 0.06 × 10 ⁻⁴ mol / g.

<Experiment Data 3>
An autoclave having an internal volume of 2 liters is charged with 1040 g of ion-exchanged water, 0.8 g of methyl cellulose, 2.5 g of ethyl acetate, 4 g of diisopropyl peroxydicarbonate, 396 g of vinylidene fluoride and 4 g of maleic acid monomethyl ester (vinylidene fluoride: maleic acid Monomethyl ester = 100: 1.01), suspension polymerization was carried out at 28 ° C. for 47 hours. After completion of the polymerization, similarly, dehydration, washing with water, and drying at 80 ° C. were performed to obtain a powdery copolymer. The polymerization rate was 90%. The obtained polymer had a solution viscosity of 1.1 dl / g. The carbonyl group content was 1.2 × 10 ⁻⁴ mol / g.

<Experimental data 4>
An autoclave having an internal volume of 2 liters was charged with 1040 g of ion-exchanged water, 0.4 g of methyl cellulose, 8 g of ethyl acetate, 2 g of n-propyl peroxydicarbonate, and 400 g of vinylidene fluoride (vinylidene fluoride: monomethyl ester of maleic acid = 100: 0 ) And suspension polymerization at 25 ° C. for 22 hours. After completion of the polymerization, similarly, dehydration, washing with water and drying at 80 ° C. were performed to obtain a powdery polymer. The polymerization rate was 85%. The obtained polymer had a solution viscosity of 1.1 dl / g.

  Each of the above-obtained polymers was individually pelletized using a same-direction rotating twin-screw extruder. In the extrusion, the temperature condition of the cylinder was adjusted so that the resin temperature at the die outlet was in the range of 220 to 250 ° C.

[Measurement method of carbonyl group content]
The carbonyl group content of the polymer obtained above was measured by the following method.
For sample mixing polyvinylidene fluoride resin and polymethyl methacrylate resin in a predetermined ratio, plotting the relationship between the specific and the carbonyl group content of the absorption of 1726 cm ^-1 for absorption of 881 ^-1 in IR spectrum to create a calibration curve.
After washing the sample polymer with hot water, unreacted monomers and homopolymer remaining in the polymer were removed by Soxhlet extraction using benzene (at 80 ° C. for 24 hours). Thereafter, the ratio of the absorption of the carbonyl group due to the monoesterified unsaturated dibasic acid in the IR spectrum to the absorption of 881 cm ⁻¹ is determined, and the carbonyl group content is determined from the previously prepared calibration curve. For reference, the absorption of carbonyl groups (including carbonyl groups in ester groups and carbonyl groups in carboxyl groups) due to monoesterified unsaturated dibasic acids is in the range of 1700-1850 cm ⁻¹ (eg maleic acid In the case of monomethyl ester, it is observed at 1747 cm ⁻¹ ). On the other hand, polyvinylidene fluoride or a copolymer of vinylidene fluoride and fluorine or a hydrocarbon monomer does not show significant absorption in the range of 1500 to 2500 cm ⁻¹ .

[Method for evaluating extrudability]
The extrudability of the polymer obtained above was evaluated by the following method.
Each pellet of experimental data 1 to 4 and another thermoplastic resin were coextruded using two single screw extruders and a multi-manifold multilayer T-die. A two-layer sheet having a thickness of 540 μm (a vinylidene fluoride-containing resin 180 μm, another thermoplastic resin 360 μm) was obtained.
In addition, the following polyamide resin was used for the other thermoplastic resin.
PA12: Commercially available polyamide 12 ("Daiamide X7293" manufactured by Daicel Degussa)
Adhesive PA12: Commercially improved adhesive polyamide 12 ("Daiamide X7297" manufactured by Daicel Degussa)
The appearance of the obtained two-layer sheet was visually observed and evaluated according to the following criteria.
A: Good extrudability (appearance of any layer of the two-layer sheet is good)
B: Good extrudability (slight vertical streaks appear on the surface of the vinylidene fluoride-containing resin of the two-layer sheet)
C: Continuous operation not possible (foaming, surface roughening, and significant vertical streaks occur in vinylidene fluoride-containing resin)

[Evaluation method of peel strength (adhesiveness)]
The peel strength of the polymer obtained above was evaluated by the following method.
In accordance with the measurement method of adhesive T peel strength specified in JIS K6854-3, the sample width of the multilayer sheet is set to 5 mm, and the peel strength between the vinylidene fluoride-containing resin and the polyamide layer is measured with a tensile tester (Orientec). (STA-1150) manufactured by the manufacturer). In addition, the case where the peel strength exceeds 15 N / cm and the adhesive state is good is defined as “no peel”.

  In FIG. 1, the evaluation result of extrudability and peel strength about Experimental data 1-4 is shown. According to the experimental data 1 and 2, with respect to 100 parts by weight of vinylidene fluoride monomer, an extremely small amount of monoester monomer of unsaturated dibasic acid (particularly 0.1 to 0 out of 0.1 to 3 parts by weight) (8 parts by weight) of the vinylidene fluoride copolymer is excellent in extrudability. Furthermore, even if the content of the monoester monomer of unsaturated dibasic acid is extremely small, it exhibits good adhesion when laminated by coextrusion with polyamide 12 (PA12) which does not have adhesiveness. I understand.

A method for producing a polymer piezoelectric film from the polymer composition according to the first embodiment of the present invention will be described. The methods are roughly as follows.
<Method 1> The polymer composition is made into a film by melt extrusion and then subjected to polarization treatment.
<Method 2> A quaternary ammonium salt is added to the polymer composition, formed into a film by melt extrusion, and then subjected to polarization treatment.
<Method 3> The polymer composition is formed into a film by melt extrusion, uniaxially stretched, and then subjected to polarization treatment.
<Method 4> After the polymer composition is formed into a film by melt extrusion, uniaxial stretching and polarization treatment are simultaneously performed.
<Method 5> The polymer composition is formed into a film by melt extrusion, biaxially stretched, and then subjected to polarization treatment.
FIG. 2 is a flowchart showing the methods 1 to 5 described above. Details of each method will be described later. The term “melt extrusion” refers to extrusion of a molten resin from a discharge port (lip) of an extrusion mold.

  An apparatus 60 shown in FIG. 3A will be described as an example of an apparatus for uniaxially stretching and / or polarizing a film obtained by melt-extruding the polymer composition according to the first embodiment of the present invention. The apparatus 60 includes a first roll 61 that sends the melt-extruded film 10, a second roll 62, and a third roll 63 that sends the film 10 from the second roll. The film 10 is stretched longitudinally on the second roll 62 due to the peripheral speed difference between the first roll 61, the second roll 62, and the third roll 63. That is, the second roll 62 becomes a stretching roll. The device 60 further includes a pointed electrode 71 arranged so as to cover the film 10 in contact with the second roll 62 in a non-contact manner. During the polarization process, the second roll 62 functions as a counter electrode of the tip electrode 71. That is, the second roll 62 is a polarization roll. The second roll 62 that functions as the counter electrode is hereinafter referred to as an electrode 72. Further, the tip electrode 71 and the electrode 72 are connected via a DC high voltage power source 73. The DC high-voltage power source 73 can reverse the polarity of the tip electrode 71 and the electrode 72.

  The tip electrode 71 polarizes the film 10 with a direct current electric field between the counter electrode (electrode 72) while holding the charge generated by the corona discharge generated at the tip on the surface of the film 10. The pointed electrode 71 preferably has a pointed tip in order to cause an effective corona discharge. As an example of the pointed electrode, in addition to a needle-like electrode (literally an electrode having a needle-like tip) such as stainless steel or tungsten, a wire-like electrode (that is, approximately the same length as the width of the film 10 in the width direction of the film 10). A wire-like electrode extending in this manner is also preferably used. It is also possible to perform polarization treatment with the electrode 72 using an electrode that directly contacts the film 10 instead of such a non-contact type electrode. However, in the case where there is a risk of dielectric breakdown of the film, such as when the film 10 to be treated is subjected to a stretching process at the same time, a non-contact electrode is preferable in order to avoid the power supply shutdown associated therewith.

In general, the distance between the tip of the pointed electrode 71 and the electrode 72 is preferably about 5 to 30 mm. If the interval is too small, the dielectric breakdown of the film 10 is liable to occur. If it is too large, corona discharge is suppressed and the polarization treatment effect is reduced. When the pointed electrode 71 is a wire-like electrode, it is preferably provided at a density of about 0.5 to 2 pieces / cm 2, and when the pointed electrode 71 is a needle-like electrode, it is preferably provided with a density of about 0.5 to 3 pieces / cm ² .

  When the uniaxial stretching or polarization treatment is performed, the second roll 62 (electrode 72) functions as a heater in order to set the temperature of the film 10 to an appropriate temperature. In order to avoid abrupt heating of the film 10, the first roll 61 may be a preheating roll having a temperature lower than that of the heater. Alternatively, preheating means such as an infrared heater may be provided upstream of the first roll 61.

By using the apparatus 60 described above, the melt-extruded film can be simultaneously subjected to uniaxial stretching and polarization treatment. It is also possible to perform only the stretching process without using the tip electrode 71 and the electrode 72 (that is, without performing the polarization process). Further, by making the film supply speeds of the first roll 61, the second roll 62, and the third roll 63 the same, only the polarization treatment can be performed without stretching the film (that is, non-stretching).
Uniaxial stretching may be performed by the tenter method in addition to the above-described roll stretching.

  When the film obtained by melt-extrusion of the polymer composition according to the first embodiment of the present invention is biaxially stretched, either biaxial stretching or simultaneous biaxial stretching can be used every time. That is, biaxially formed by a combination of stretching between rolls having a difference in peripheral speed (roll stretching) and a tenter method that grips both ends of a sheet stretched in one direction (for example, the length direction) and stretches in the width direction. Stretching or biaxial stretching by a tenter method may be used. It should be noted that biaxial stretching that gives a film with good orientation uniformity in the plane direction is preferable, and biaxial stretching in which the stretching ratio in the biaxial direction is almost equal is more preferable.

  An apparatus 80 shown in FIG. 3B will be described as an example of an apparatus for polarizing a film obtained by melt-extruding the polymer composition according to the first embodiment of the present invention. The apparatus 80 includes a flat metal plate 82 for fixing the film 10 cut to an appropriate size, and a non-contact needle electrode 81 (at least one) disposed above the film 10. During the polarization process, the metal plate 82 functions as a counter electrode of the needle electrode 81. Further, the needle electrode 81 and the metal plate 82 are connected via a DC high voltage power source 73.

  The corona polarization process, the uniaxial stretching process, and the biaxial stretching process may use existing polarization processing apparatuses, uniaxial stretching apparatuses, and biaxial stretching apparatuses as appropriate.

  Returning to FIG. 2, <Method 1> will be described with reference to FIG. In <Method 1>, the polymer composition according to the first embodiment of the present invention is melt-extruded (ST11), the film obtained by melt-extrusion is polarized (ST12), and the polymer has easy adhesion. A piezoelectric film is obtained.

本発明者等は、ポリフッ化ビニリデンＫＦ＃１０００（株式会社クレハ製）からＴダイを備えた口径４０ｍｍφの単軸押出機を用いて、幅２５０ｍｍ、厚さ４０μｍのフィルムを作製した。次にこのフィルムをコロナ分極処理により分極した後、実際に圧電応力定数を測定したところ、図４（ｂ）の比較例３に示すように、例えばｄ３１が１２．８ｐＣ／Ｎを示した。この値は、圧電性フィルムとして工業的に十分に利用可能であることを示す値である。 Generally, it is known that polyvinylidene fluoride has a nonpolar α-type crystal structure when cooled and crystallized from a molten state. The inventors of the present invention polarized the film made from the nonpolar α-type polyvinylidene fluoride without stretching, and selected the polarization method and the voltage value at the time of polarization, thereby changing the crystal structure to the polar α-type. It has been found that polyvinylidene fluoride having a high piezoelectricity.
The nonpolar α-type polyvinylidene fluoride is a type II crystal having a crystal structure portion of ^** 1/2 helix, which depends on the dipole moment of C—F ₂ and C—H ₂ bonds in the crystal. Although it is a polar molecule, it has a center of symmetry so that the dipole moments cancel each other and the crystal is a nonpolar crystal.
Polar α-type polyvinylidene fluoride is a type II crystal with a crystal structure part of ^** 1/2 helix, and the dipoles are aligned in the same direction by rotation. Say.

The present inventors produced a film having a width of 250 mm and a thickness of 40 μm from a polyvinylidene fluoride KF # 1000 (manufactured by Kureha Co., Ltd.) using a single screw extruder having a diameter of 40 mmφ equipped with a T die. Next, after this film was polarized by corona polarization treatment, the piezoelectric stress constant was actually measured. As shown in Comparative Example 3 in FIG. 4B, for example, d31 was 12.8 pC / N. This value is a value indicating that the piezoelectric film can be sufficiently used industrially.

  <Method 1> is based on the above-described invention. That is, when a polymer composition having easy adhesion is crystallized from a molten state, the crystalline structure portion of polyvinylidene fluoride contained in the composition becomes a nonpolar α-type crystal. When a film made from this polymer composition is polarized by corona polarization treatment, nonpolar α-type crystals are transferred to polar α-type crystals. In this way, an easily adhesive polymer piezoelectric film containing polar α-type polyvinylidene fluoride can be obtained.

ST11 in FIG. 2A will be described in more detail. In ST11, the polymer composition according to the embodiment of the present invention in a molten state (temperature of 200 to 280 ° C.) is extruded by an extruder equipped with a T die, formed into a film, and cooled to 40 to 140 ° C. . In addition, it is preferable that the thickness of the film extruded is 10-2000 micrometers. Moreover, you may shape | mold a film not by melt extrusion but by solution casting.
In addition, in this specification, the film obtained by each process of the method shown to Fig.2 (a)-(e) attaches | subjects the number of each process, and distinguishes. For example, the film obtained in ST11 is referred to as film 11, and the film obtained in ST12 is referred to as film 12 (hereinafter the same). Moreover, when it is not necessary to distinguish the state of a film for every process, it is set as the film 10 generically.

ST 12 in FIG. 2A will be described in more detail. The film 11 is supplied to the second roll 62 at a speed R using the apparatus 60 shown in FIG. The film 11 is polarized by the action of a direct current high electric field between the tip electrode 71 connected to the direct current high voltage power source 73 and the electrode 72 (counter electrode) in a region in contact with the electrode 72 (second roll 62). The The polarized film 12 leaves the second roll 62 at the same speed R as at the time of supply. That is, the film 11 is not stretched but polarized without being stretched to become a film 12. Further, after being subjected to post-treatment such as heat treatment for dimensional stabilization as required, it is wound on a winding roll (not shown).
The voltage applied to the tip electrode 67 is 100 kV at the maximum. The temperature of the second roll 62 functioning as a heater during the polarization treatment (substantially the same as the temperature of the film 11) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140 ° C., more preferably Is room temperature to 130 ° C.

  By the method described above, an unstretched polymer piezoelectric film having easy adhesion and containing polyvinylidene fluoride in which the main crystal structure portion of polyvinylidene fluoride is a polar α-type can be obtained. The “main crystal structure portion” means a main component of the crystal structure portion (that is, more than 50% of the crystal structure portion). For example, the main crystal structure portion of polyvinylidene fluoride being polar α-type means that more than 50% of the crystal structure portion of polyvinylidene fluoride, which is a semicrystalline polymer, is polar α-type.

  <Method 2> will be described with reference to FIG. In <Method 2>, a quaternary ammonium salt is added to the polymer composition according to the first embodiment of the present invention (ST21), and the polymer composition to which the quaternary ammonium salt is added is melt-extruded. (ST22) The film obtained by melt extrusion is subjected to polarization treatment (ST23) to obtain a polymer piezoelectric film having easy adhesion.

Polyvinylidene fluoride transitions from a non-polar α-type to β-type by adding a quaternary ammonium salt. The present inventors have found that when a non-stretched film made of polyvinylidene fluoride to which a certain amount of a quaternary ammonium salt is added is polarized, high piezoelectricity is exhibited.
A certain amount of clay may be added in place of the quaternary ammonium salt. In that case, it is preferable to add clay surface-treated with an onium salt. In particular, it is preferable to add clay surface-treated with a quaternary ammonium salt.
The β-type polyvinylidene fluoride is a type I crystal having a planar zigzag crystal structure: TT conformation, the molecular chain has a dipole moment in the vertical direction, and in the same direction in the crystal. Since it is suitable, the crystal is a polar crystal.
The inventors made 100 parts by weight of polyvinylidene fluoride KF # 1000 (manufactured by Kureha Co., Ltd.) and 0.1 parts by weight of tetrabutylammonium hydrogen sulfate using a single screw extruder having a diameter of 40 mm and having a diameter of 4 mm and a pellet. Turned into. Next, a film having a width of 250 mm and a thickness of 40 μm was produced from this pellet using a single screw extruder having a diameter of 40 mmφ equipped with a T die, and this film was subjected to a polarization treatment. When the piezoelectric stress constant of this film was actually measured, d33 was 13.0 pC / N. This value is a value indicating that the piezoelectric film can be sufficiently used industrially.
In addition, d33 at the time of adding the clay surface-treated with the quaternary ammonium salt was 7.7 pC / N. The added clay is Somasif MTE manufactured by Corp Chemical Co., Ltd. The amount added is 0.1 parts by weight with respect to 100 parts by weight of polyvinylidene fluoride.

  <Method 2> is based on the present invention. That is, when a quaternary ammonium salt (or clay surface-treated with a quaternary ammonium salt) was added to a polymer composition having easy adhesion and crystallized from a molten state, it was contained in the composition. The crystal structure portion of polyvinylidene fluoride is a β-type crystal. By polarizing a film made from this polymer composition by corona polarization treatment, a polymer piezoelectric film having easy adhesion and containing β-type polyvinylidene fluoride can be obtained.

  ST21 in FIG. 2B will be described in more detail. In ST21, a quaternary ammonium salt is added to the polymer composition according to the embodiment of the present invention, and pelletized using a co-rotating twin screw extruder.

The quaternary ammonium salt to be added is preferably an alkyl quaternary ammonium sulfate or sulfite.
The alkyl quaternary ammonium sulfate used in the present invention is a compound represented below.
[R ¹ R ² R ³ R ⁴ NR ⁵ SO ₄ ]
In the above formula, R ^{1 to} R ⁴ are the same or different alkyl groups, and R ⁵ is an alkyl group, a fluoroalkyl group, or a hydrogen atom.
The alkyl quaternary ammonium sulfite used in the present invention is a compound represented by the following.
[R ⁶ R ⁷ R ⁸ R ⁹ NR ¹⁰ SO ₃ ]
In the above formula, R ^{6 to} R ⁹ are the same or different alkyl groups, and R ¹⁰ is an alkyl group, a fluoroalkyl group, or a hydrogen atom.
Among these compounds, alkyl quaternary ammonium sulfate is preferable because of its excellent stability.

In the above compound, the total number of carbon atoms of the alkyl group in R ^{1 to} R ⁴ or R ^{6 to} R ⁹ is usually 4 or more, preferably 8 to 30, more preferably 12 to 24, and particularly preferably 15 to 20. Examples of the alkyl group include short chain alkyl groups such as a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, a pentyl group, and a hexyl group. When R ⁵ and R ¹⁰ are alkyl groups, a short chain alkyl group such as a methyl group or an ethyl group is representative. When R ⁵ and R ¹⁰ are fluoroalkyl groups, short-chain fluoroalkyl groups such as CF ₃ and C ₂ F ₅ are typical.

Specific examples of these compounds include (C ₂ H ₅ ) ₄ N ⁺ , (C ₃ H ₇ ) ₄ N ⁺ , (C ₄ H ₉ ) ₄ N ⁺ , (C ₅ H ₁₁ ) ₄ N ^{+ and the} like. And an anion containing sulfuric acid or sulfite such as CF ₃ SO ₄ ⁻ , CH ₃ SO ₄ ⁻ , HSO ₄ ⁻ , CF ₃ SO ₃ ⁻ , CH ₃ SO ₃ ⁻ and HSO ₃ ^−. Mention may be made of salts. These compounds may be salts in which two or more types of anions and cations are combined. Further, the four alkyl groups of quaternary ammonium may be the same or different. Among these, hydrogen sulfate of alkyl quaternary ammonium is preferable, and tetrabutylammonium hydrogen sulfate (TBAHS) [(C ₄ H ₉ ) ₄ NHSO ₄ ] is particularly preferable. These compounds can be used alone or in combination of two or more.

  The amount of the quaternary ammonium salt to be added is preferably 0.1 to 0.3 parts by weight with respect to 100 parts by weight of the polymer composition. (In addition, when using the clay surface-treated with the quaternary ammonium salt, 0.1 to 3.0 parts by weight is preferable with respect to 100 parts by weight of the polymer composition.)

  ST22 in FIG. 2B will be described in more detail. The obtained pellet 21 is made into a molten state (temperature 200-280 degreeC), it extrudes with the extruder provided with T-die, shape | molds in a film form, and cools to 40-140 degreeC. In addition, it is preferable that the thickness of the film 22 is 10-2000 micrometers. Moreover, you may shape | mold a film not by melt extrusion but by solution casting.

ST23 in FIG. 2B will be described in more detail. Using the apparatus 60 shown in FIG. 3A, the film 22 is polarized in the same manner as ST12 of <Method 1>. The polarized film 23 leaves the second roll 62 at the same speed as the supply speed. That is, the film 22 is subjected to a polarization treatment without stretching and becomes a film 23 without being stretched. Further, after being subjected to post-treatment such as heat treatment for dimensional stabilization as required, it is wound on a winding roll (not shown).
The voltage applied to the tip electrode 71 is 100 kV at the maximum. The temperature of the second roll 62 functioning as a heater during the polarization treatment (substantially the same as the temperature of the film 22) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140 ° C., more preferably Is room temperature to 130 ° C.

  By the above method, an unstretched polymer piezoelectric film having easy adhesion, in which the main crystal structure portion of polyvinylidene fluoride contains β-type polyvinylidene fluoride, can be obtained.

  <Method 3> will be described with reference to FIG. In <Method 3>, the polymer composition according to the first embodiment of the present invention is melt extruded (ST31), the film obtained by melt extrusion is uniaxially stretched (ST32), and the uniaxially stretched film is polarized. (ST33) to obtain a polymer piezoelectric film having easy adhesion.

  Polyvinylidene fluoride has a nonpolar α-type crystal structure when cooled and crystallized from a molten state. Furthermore, it is known that when this poly (vinylidene fluoride) is uniaxially stretched, the crystal structure portion is transferred from the nonpolar α type to the β type. When a film made of β-type polyvinylidene fluoride is subjected to polarization treatment, a piezoelectric film having high piezoelectricity and containing β-type polyvinylidene fluoride is obtained.

  <Method 3> is based on the above properties of polyvinylidene fluoride. That is, when a polymer composition having easy adhesion is crystallized from a molten state, the crystalline structure portion of polyvinylidene fluoride contained in the composition becomes a nonpolar α-type crystal. When a film made from this polymer composition is uniaxially stretched, the crystal structure portion of polyvinylidene fluoride contained in the composition is changed to β-type. A polymer piezoelectric film having easy adhesion can be obtained by subjecting a film containing β-type polyvinylidene fluoride to polarization treatment by corona discharge.

  ST31 in FIG. 2C will be described in more detail. In ST31, the polymer composition according to the embodiment of the present invention in a molten state (temperature: 200 to 280 ° C.) is extruded by an extruder equipped with a T die, formed into a film, and cooled to 40 to 140 ° C. . In addition, it is preferable that the thickness of the film 31 is 10-2000 micrometers. Moreover, you may shape | mold a film not by melt extrusion but by solution casting.

ST32 in FIG. 2C will be described in further detail. The film 31 is uniaxially stretched using an apparatus 60 shown in FIG. That is, without using the tip electrode 71 and the electrode 72, the film 31 is supplied from the first roll 61 to the second roll 62 at a speed R, and the film 31 is moved within a region where the film 31 is in contact with the second roll 62. Stretch. The stretched film 32 leaves the second roll 62 and is sent to the third roll 63 at a speed R ′ (> R). Then, it is wound up on a winding roll (not shown).
In order to effectively cause uniaxial stretching, the temperature of the second roll 62 functioning as a heater (substantially the same as the temperature of the film 31) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably It is 0-140 degreeC, More preferably, it is room temperature-130 degreeC. The film 31 is preferably stretched 3 to 6 times. If it is less than 3 times, stretching is not stable, and if it exceeds 6 times, the film may be broken.

ST33 in FIG. 2C will be described in more detail. The uniaxially stretched film 32 is further polarized using an apparatus 60 shown in FIG. At this time, by making the supply speeds of the films of the first roll 61, the second roll 62, and the third roll 63 the same, the film 32 that has already been uniaxially stretched becomes the film 33 without being stretched during the polarization treatment. . Then, after receiving post-processing such as heat treatment for dimensional stabilization as required, the film is wound on a winding roll (not shown).
The voltage applied to the tip electrode 71 is 100 kV at the maximum. The temperature of the second roll 62 (electrode 72) functioning as a heater during the polarization treatment (substantially the same as the temperature of the film 32) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140. ° C, more preferably room temperature to 130 ° C.

  By the above method, a polymer piezoelectric film having easy adhesion, in which the main crystal structure portion of polyvinylidene fluoride contains β-type polyvinylidene fluoride, can be obtained.

  <Method 4> will be described with reference to FIG. In <Method 4>, the polymer composition according to the first embodiment of the present invention is melt-extruded (ST41), uniaxial stretching and polarization treatment are simultaneously performed on the film obtained by melt-extrusion (ST42), A polymer piezoelectric film having easy adhesion is obtained.

  <Method 4> utilizes the same characteristics of polyvinylidene fluoride as <Method 3>. However, it is characterized in that uniaxial stretching and polarization treatment are performed simultaneously. That is, when a polymer composition having easy adhesion is crystallized from a molten state, the crystalline structure portion of polyvinylidene fluoride contained in the composition becomes a nonpolar α-type crystal. When a film made from this polymer composition is polarized by corona polarization treatment while being uniaxially stretched, a polymer piezoelectric film having β-type polyvinylidene fluoride and having easy adhesion can be obtained. In addition, the heat resistance of a film can be improved by performing uniaxial stretching and polarization treatment simultaneously.

  ST41 in FIG. 2 (d) will be described in further detail. In ST41, the polymer composition according to the embodiment of the present invention in a molten state (temperature: 200 to 280 ° C.) is extruded by an extruder equipped with a T die and molded into a film shape. In addition, it is preferable that the thickness of the film 41 is 10-2000 micrometers. Moreover, you may shape | mold a film not by melt extrusion but by solution casting.

ST42 in FIG. 2 (d) will be described in more detail. Using the apparatus 60 shown in FIG. 3A, the polarization treatment is simultaneously performed while the film 41 is uniaxially stretched. The film 41 is supplied to the second roll 62 at a speed R. While the film 41 is uniaxially stretched in a region where the second roll 62 comes into contact with the second roll 62, the polarization treatment is performed simultaneously by the action of a DC high electric field between the tip electrode 71 and the electrode 72 (second roll 62). The film 42 after uniaxial stretching and polarization treatment (substantially already corresponding to the polymer piezoelectric film of the present invention) leaves the second roll 62 at a speed R ′ (> R), and is dimensionally stabilized as necessary. After being subjected to post-treatment such as heat treatment for winding, it is wound on a winding roll (not shown).
The voltage applied to the tip electrode 71 is 100 kV at the maximum. The temperature of the second roll 62 functioning as a heater (substantially the same as the temperature of the film 41) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140 ° C., more preferably room temperature to 130 ° C. The film 41 is preferably stretched 3 to 6 times. If it is less than 3 times, the stretching is not stable, and if it exceeds 6 times, the film may be broken.

  By the above method, a polymer piezoelectric film having easy adhesion, in which the main crystal structure portion of polyvinylidene fluoride contains β-type polyvinylidene fluoride, can be obtained.

  <Method 5> will be described with reference to FIG. In <Method 5>, the polymer composition according to the first embodiment of the present invention is melt extruded (ST51), the film obtained by melt extrusion is biaxially stretched (ST52), and the biaxially stretched film is obtained. Polarization treatment (ST53) is performed to obtain a polymer piezoelectric film having easy adhesion.

  Polyvinylidene fluoride has a nonpolar α-type crystal structure when cooled and crystallized from a molten state. Furthermore, it is known that when this poly (vinylidene fluoride) is biaxially stretched, non-polar α-type crystals and β-type crystals are mixed in the crystal structure portion. That is, polyvinylidene fluoride can be obtained in which both the nonpolar α-type crystal and β-type crystal can be the “main” crystal structure portion. Further, when the biaxially stretched polyvinylidene fluoride is subjected to polarization treatment, the nonpolar α-type crystal is transferred to the polar α-type crystal.

  <Method 5> is based on the above properties of polyvinylidene fluoride. That is, when a polymer composition having easy adhesion is crystallized from a molten state, the crystalline structure portion of polyvinylidene fluoride contained in the composition becomes a nonpolar α-type crystal. When the film 51 made from this polymer composition is biaxially stretched, the non-polar α-type and β-type are mixed in the crystalline structure portion of polyvinylidene fluoride contained in the composition. A polymer piezoelectric film having easy adhesion can be obtained by polarizing a film containing polyvinylidene fluoride by corona polarization treatment.

  ST 51 in FIG. 2E will be described in more detail. In ST51, the polymer composition according to the embodiment of the present invention in a molten state (temperature: 200 to 280 ° C.) is extruded by an extruder equipped with a T-die method, molded into a film, and cooled to 40 to 140 ° C. To do. In addition, it is preferable that the thickness of the film 51 is 10-2000 micrometers. Moreover, you may shape | mold a film not by melt extrusion but by solution casting.

ST52 in FIG. 2 (e) will be described in more detail. The film 51 is biaxially stretched using a biaxial stretching machine (not shown). In addition, as for biaxial stretching, you may use either sequential biaxial stretching (the method of extending | stretching a longitudinal direction and a horizontal direction sequentially) and simultaneous biaxial stretching.
The temperature of the film 51 during biaxial stretching is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140 ° C, more preferably room temperature to 130 ° C. In the case of sequential biaxial stretching, the film 51 can be stretched to a longitudinal stretching ratio (length direction) of about 3 to 4.5 times and a lateral stretching ratio (width direction) of about 3 to 6 times. preferable. In the case of simultaneous biaxial stretching, it is preferable to stretch the longitudinal stretching ratio (length direction) and the lateral stretching ratio (width direction) to about 3 to 4.5 times.

ST53 in FIG. 2E will be further described. The biaxially stretched film is further polarized using an apparatus 60 shown in FIG. The polarized film 53 leaves the second roll 62 at the same speed as at the time of supply. That is, the film 52 that has already been biaxially stretched becomes the film 53 without being stretched during polarization. Further, after being subjected to post-treatment such as heat treatment for dimensional stabilization as required, it is wound on a winding roll (not shown).
The voltage applied to the tip electrode 71 is 100 kV at the maximum. The temperature of the second roll 62 functioning as a heater during the polarization treatment (substantially the same as the temperature of the film 52) is desirably a glass transition temperature (Tg) to a melting point (Tm), preferably 0 to 140 ° C., more preferably Is room temperature to 130 ° C. Instead of the device 60 shown in FIG. 3A, the polarization processing may be performed using the device 80 shown in FIG.

  By the above method, a polymer piezoelectric film having easy adhesion can be obtained.

The polymer piezoelectric films 12, 23, 33, 42, and 53 having easy adhesion obtained by the above <Method 1> to <Method 5> need post-treatment such as heat treatment for dimensional stabilization thereafter. Is taken up by a take-up roll.
Since the obtained polymer piezoelectric film has easy adhesion, it can improve the adhesive strength when an electrode (metal or conductive polymer) is applied. Furthermore, when a polymer piezoelectric film and other thermoplastic resins are welded to form a laminated structure, the number of other thermoplastic resins to be welded can be increased as compared with polyvinylidene fluoride alone. In addition, when a laminate is formed, even when an adhesive layer or an adhesive is provided, not only can the adhesive force between the polymer piezoelectric film and the adhesive layer or the adhesive itself be improved, but the laminate is used. The type of adhesive layer or adhesive can be increased. Furthermore, it can be easily co-extruded by a conventional co-extrusion method using a single-screw or twin-screw extruder according to the number of extruded resins including other thermoplastic resins and a multilayer T-die according to the number of layers. A laminated film can be manufactured.
The piezoelectric polymer film of the present invention showing this piezoelectricity naturally also shows pyroelectricity. Therefore, it can be used not only for piezoelectric sensors but also for pyroelectric sensors.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

[Polyvinylidene fluoride]
As the polyvinylidene fluoride, KF # 1000 manufactured by Kureha Corporation was used.
[Preparation of vinylidene fluoride copolymer]
A vinylidene fluoride copolymer A was prepared as follows.
An autoclave having an internal volume of 2 liters was charged with 1040 g of ion-exchanged water, 0.6 g of methyl cellulose, 3 g of ethyl acetate, 4 g of diisopropyl peroxydicarbonate, 396 g of vinylidene fluoride and 4 g of maleic acid monomethyl ester (in terms of parts by weight, vinylidene fluoride). : Maleic acid monomethyl ester = 100: 1.0) and suspension polymerization was carried out at 25 ° C. for 42 hours. After the polymerization was completed, the polymer slurry was dehydrated, washed with water, and dried at 80 ° C. to obtain a powdery copolymer.
By the same method as described above, vinylidene fluoride copolymer B having a minimum content of maleic acid monomethyl ester (ie, vinylidene fluoride: maleic acid monomethyl ester = 100: 0.1) and a maximum (ie, A vinylidene fluoride copolymer C of vinylidene fluoride: maleic acid monomethyl ester = 100: 3) was prepared.

Examples 1 to 6 and Comparative Examples 1 and 2 shown in FIG. 4A were prepared as follows using polyvinylidene fluoride and vinylidene fluoride copolymers A to C.
<Example 1>
90 parts by weight of polyvinylidene fluoride and 10 parts by weight of vinylidene fluoride copolymer A were pelletized using a co-rotating twin screw extruder to obtain a polymer composition.
A polymer piezoelectric film was obtained from the obtained pellet of the polymer composition by <Method 3>. That is, using a single-screw extruder having a diameter of 40 mmφ equipped with a T-die, a film was prepared so as to have a width of 250 mm and a thickness of 80 μm after melting at 230 ° C. and cooled to 95 ° C.
Next, the film was supplied from the 1st roll 61 of the apparatus 60 shown to Fig.3 (a) with the supply speed of 1 m / min. The speed at which the film was separated from the second roll 62 was adjusted to 4 m / min so that the film was stretched 4 times. The temperature of the 2nd roll 62 which functions as a heater at the time of uniaxial stretching was 100 degreeC.
Next, the DC voltage shown in FIG. 4A was applied to the pointed electrode 71 (needle-like electrode) at a film supply rate of 1 m / min using the device 60 in the same manner. The temperature of the 2nd roll 62 which functions as a heater at the time of polarization processing was 30 degreeC.
<Example 2>
The mixing ratio of the polymer composition was 80 parts by weight of polyvinylidene fluoride and 20 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 1>.
<Example 3>
The mixing ratio of the polymer composition was 70 parts by weight of polyvinylidene fluoride and 30 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 1>.
<Example 4>
The mixing ratio of the polymer composition was 50 parts by weight of polyvinylidene fluoride and 50 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 1>.
<Example 5>
The mixing ratio of the polymer composition was 90 parts by weight of polyvinylidene fluoride and 10 parts by weight of vinylidene fluoride copolymer B. Thereafter, the same as <Example 1>. That is, in Example 5, vinylidene fluoride copolymer B, which is a copolymer with a minimum amount of maleic acid monomethyl ester (0.1 part by weight), is the minimum amount (10 parts by weight) in the polymer composition. It is a polymer composition to contain.
<Example 6>
The mixing ratio of the polymer composition was 20 parts by weight of polyvinylidene fluoride and 80 parts by weight of vinylidene fluoride copolymer C. Thereafter, the same as <Example 1>. That is, Example 6 contains the maximum amount (80 parts by weight) of the vinylidene fluoride copolymer C, which is a copolymer with the maximum amount of maleic acid monomethyl ester (3 parts by weight), in the polymer composition. It is a polymer composition.
<Comparative Example 1>
The mixing ratio of the polymer composition was 100 parts by weight of polyvinylidene fluoride and 0 parts by weight of the vinylidene fluoride copolymer. Thereafter, the same as <Example 1>. However, the thickness of the film before stretching was about 160 μm.
<Comparative Example 2>
The mixing ratio of the polymer composition was 0 part by weight of polyvinylidene fluoride and 100 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 1>. However, the thickness of the film before stretching was about 160 μm.

Examples 7 to 10 and Comparative Examples 3 to 4 shown in FIG. 4B were prepared as follows using polyvinylidene fluoride and vinylidene fluoride copolymer A.
In addition, the Example of FIG. 4 (a) and FIG.4 (b) and a comparative example differ only in the method of manufacturing a polymeric piezoelectric material film. That is, <Method 3> is used in the example and comparative example of FIG. 4A, whereas <Method 1> is used in the example and comparative example of FIG. 4B.
<Example 7>
90 parts by weight of polyvinylidene fluoride and 10 parts by weight of vinylidene fluoride copolymer A were pelletized using a co-rotating twin screw extruder to obtain a polymer composition.
A polymer piezoelectric film was obtained from the obtained pellet of the polymer composition by <Method 1>. That is, using a single-screw extruder having a diameter of 40 mmφ equipped with a T die, a film was prepared so as to have a width of 250 mm and a thickness of 40 μm after being melted at 225 ° C. and cooled to 70 ° C.
Next, the DC voltage shown in FIG. 4B was applied to the pointed electrode 71 (needle electrode) at a film supply speed of 1 m / min using the apparatus 60 shown in FIG. The temperature of the 2nd roll 62 which functions as a heater at the time of a polarization process was 100 degreeC.
<Example 8>
The mixing ratio of the polymer composition was 80 parts by weight of polyvinylidene fluoride and 20 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 7>.
<Example 9>
The mixing ratio of the polymer composition was 70 parts by weight of polyvinylidene fluoride and 30 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 7>.
<Example 10>
The mixing ratio of the polymer composition was 50 parts by weight of polyvinylidene fluoride and 50 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 7>.
<Comparative Example 3>
The mixing ratio of the polymer composition was 100 parts by weight of polyvinylidene fluoride and 0 parts by weight of the vinylidene fluoride copolymer. Thereafter, the same as <Example 7>.
<Comparative example 4>
The mixing ratio of the polymer composition was 0 part by weight of polyvinylidene fluoride and 100 parts by weight of vinylidene fluoride copolymer A. Thereafter, the same as <Example 7>. However, the thickness of the film was 130 μm.

Examples 11 to 13 and Comparative Examples 5 to 7 shown in FIG. 6 were adjusted as follows using polyvinylidene fluoride and a vinylidene fluoride copolymer A.
<Example 11>
The mixing ratio of the polymer composition was 50 parts by weight of polyvinylidene fluoride and 50 parts by weight of vinylidene fluoride copolymer A, and a polymer piezoelectric film was obtained by <Method 2>. That is, 50 parts by weight of polyvinylidene fluoride and 50 parts by weight of a vinylidene fluoride copolymer, 0.1 parts by weight of tetrabutylammonium hydrogen sulfate is further added, and pelletized using a co-rotating twin screw extruder. A polymer composition was obtained.
The obtained polymer composition pellets were melted at 220 ° C. using a 40 mmφ single screw extruder equipped with a T die, and then a film was prepared to have a width of 250 mm and a thickness of 40 μm. Cooled to.
Next, the DC voltage shown in FIG. 6 was applied to the pointed electrode 71 (needle electrode) at a film supply speed of 1 m / min using the device 60 shown in FIG. The temperature of the 2nd roll 62 which functions as a heater at the time of polarization processing was 30 degreeC.
<Example 12>
A polymer composition was obtained by pelletizing 50 parts by weight of polyvinylidene fluoride and 50 parts by weight of a vinylidene fluoride copolymer A using a co-rotating twin screw extruder.
A polymer piezoelectric film was obtained from the obtained pellet of the polymer composition by <Method 4>. That is, using a single-screw extruder having a diameter of 40 mmφ equipped with a T die, a film was prepared so as to have a width of 250 mm and a thickness of 160 μm after being melted at 220 ° C., and cooled to 75 ° C.
Next, the film was supplied from the 1st roll 61 of the apparatus 60 shown to Fig.3 (a) with the supply speed of 1 m / min. The speed at which the film was separated from the second roll 62 was adjusted to 4 m / min so that the film was stretched 4 times. Simultaneously with the uniaxial stretching, a DC voltage shown in FIG. 6 was applied to the tip electrode 71 (needle electrode). The temperature of the 2nd roll 62 which functions as a heater was 120 degreeC.
<Example 13>
80 parts by weight of polyvinylidene fluoride and 20 parts by weight of vinylidene fluoride copolymer A were pelletized using a co-rotating twin screw extruder to obtain a polymer composition.
A polymer piezoelectric film was obtained from the obtained pellet of the polymer composition by <Method 5>. That is, using a single screw extruder having a diameter of 40 mmφ equipped with a T-die, a film was prepared so as to have a width of 250 mm and a thickness of 320 μm after being melted at 230 ° C. and cooled to 90 ° C.
Next, using a simultaneous biaxial stretching machine, the film was adjusted to be stretched 4 times in the length direction and 4 times in the width direction. The temperature of the film during biaxial stretching was 165 ° C.
Next, the biaxially stretched film is cut into a size of 10 cm × 10 cm, fixed on the metal plate 82 of the apparatus 80 shown in FIG. 3 (b), and the film (FIG. In b), a DC voltage shown in FIG. 6 was applied to the film 10). During the polarization treatment, the metal plate 82 was heated using a heater (not shown) so that the temperature of the metal plate 82 (that is, the film 10) was 110 ° C.
<Comparative Example 5>
The mixing ratio of the polymer composition was 100 parts by weight of polyvinylidene fluoride and 0 parts by weight of the vinylidene fluoride copolymer. Thereafter, the same as <Example 11>.
<Comparative Example 6>
The mixing ratio of the polymer composition was 100 parts by weight of polyvinylidene fluoride and 0 parts by weight of the vinylidene fluoride copolymer. Thereafter, the same as <Example 12>.
<Comparative Example 7>
The mixing ratio of the polymer composition was 100 parts by weight of polyvinylidene fluoride and 0 parts by weight of the vinylidene fluoride copolymer. Thereafter, the same as <Example 13>.

[Measurement method of piezoelectric stress constant]
The piezoelectric stress constant of the obtained polymer piezoelectric film was measured as follows.
d31 (relative to the stress in the length direction) was measured using Rheograph solid manufactured by Toyo Seiki Seisakusho.
d32 (relative to the stress in the width direction) was measured using a Rheograph solid manufactured by Toyo Seiki Seisakusho.
d33 (with respect to the stress in the longitudinal direction) was calculated by applying a stress in the thickness direction at a constant speed using a pneumatic press and measuring the generated charge with a charge amplifier.

[Measurement method of contact angle with water]
The contact angle between the obtained polymer piezoelectric film and water was measured using DM-500 manufactured by Kyowa Interface Chemical Co., Ltd. based on JISK6768.

[Cross-cut tape method]
The adhesiveness of the obtained polymer piezoelectric film was evaluated as follows based on the cross-cut tape method (former JISK5400 8.5.2).
First, an electrode film was applied to the surface of the obtained polymer piezoelectric film having easy adhesion and dried. Next, cuts reaching the polymer piezoelectric film with a cutter knife were made at 1 mm intervals to form a 10 × 10 grid. An adhesive tape was affixed on this grid and rubbed with an eraser to completely adhere it, and the adhesive tape was peeled off after 1 to 2 minutes. The adhesion state of the electrode film was visually observed. As the electrode film, silver (Ag) paste was used as the metal electrode, and polyethylene dioxythiophene (PEDOT, Baytron (US registered trademark) SV3 manufactured by Bayer) was used as the conductive polymer.

The items in each table shown in FIGS. 4A, 4B, and 6 are as follows.
The mixing ratio is a mixing ratio of polyvinylidene fluoride and a vinylidene fluoride copolymer.
The thickness is the thickness of the polymer piezoelectric film.
The voltage Vp is a voltage value applied to the tip electrode.
The estimated Ep is the electric field strength (calculated value) during the polarization process. In this embodiment, since corona polarization treatment is performed, the electric field strength is obtained by dividing the applied voltage by the thickness of the film, excluding the voltage drop of air. That is, the estimated Ep was obtained by the following equation. The voltage drop was set to about 1 μA = 7.5 kV from the result of monitoring the current during polarization. For example, the estimated Ep in Examples 1 to 4 is a value calculated with a voltage drop of 7.5 kV.
[Estimated Ep = (applied voltage−voltage drop) / film thickness]
d31 is a piezoelectric stress constant in the length direction of the polymer piezoelectric film.
d32 is a piezoelectric stress constant in the width direction of the polymer piezoelectric film.
d33 is a piezoelectric stress constant in the height direction of the polymer piezoelectric film.
The contact angle is a contact angle of the polymer piezoelectric film with water.

FIG. 4A shows various measured values of the film manufactured by <Method 3>.
In Examples 1 to 4 of FIG. 4 (a), the content of maleic acid monomethyl ester contained in the vinylidene fluoride copolymer is constant (in terms of parts by weight, vinylidene fluoride: maleic acid monomethyl ester = 100: 1). 0.0), a polymer piezoelectric film in which only the mixing ratio of the polymer composition (polyvinylidene fluoride: vinylidene fluoride copolymer) is changed. That is, as the amount of the vinylidene fluoride copolymer increases, the content of maleic acid monomethyl ester contained in the vinylidene fluoride copolymer simply increases.
Piezoelectric stress constants (d31 to d33) of Examples 1 to 4 indicate that the polymer piezoelectric film produced from a mixture (polymer composition) of polyvinylidene fluoride and a vinylidene fluoride copolymer has piezoelectricity. It is shown that. Furthermore, even when compared with the piezoelectric stress constant of Comparative Example 1 (polyvinylidene fluoride 100%), it can be seen that there is no significant difference in the numerical values, and the piezoelectricity is sufficiently industrially usable. In addition, the piezoelectric stress constants of Examples 1 to 4 did not increase or decrease due to increase or decrease in the amount of the vinylidene fluoride copolymer contained in the polymer composition. That is, the piezoelectricity of the polymer piezoelectric film did not deteriorate as the amount of the mixed substance (vinylidene fluoride copolymer) increased.
Therefore, in Comparative Example 2 (vinylidene fluoride copolymer 100%), when the piezoelectric stress constant was measured, the expression of piezoelectricity could be confirmed.

FIG. 4B shows various actual measurement values of the film manufactured by <Method 1>.
In Examples 7 to 10 of FIG. 4 (b), the polymer was obtained when the content of monomethyl maleate contained in the vinylidene fluoride copolymer was constant and only the mixing ratio of the polymer composition was changed. It is a piezoelectric film. The piezoelectric stress constants (d31 to d33) of Examples 7 to 10 indicate that the polymer piezoelectric film has piezoelectricity even when <Method 1> is used. The piezoelectric stress constant when <Method 1> is used is generally lower than the piezoelectric stress constant when <Method 3> is used (see FIG. 4A). It is possible enough. Further, even when compared with the piezoelectric stress constant of Comparative Example 3 (100% polyvinylidene fluoride), there is no significant difference in the numerical value, and the polymer piezoelectricity increases as the amount of the mixed material (vinylidene fluoride copolymer) increases. The piezoelectricity of the body film did not decline.

  FIG. 5 shows the results of evaluating the polymeric piezoelectric film of Example 4 using the cross cut tape method. The adhesion state of the electrode film was expressed in fractions. That is, the denominator indicates the number of 10 × 10 grids, and the numerator indicates the number of electrode films peeled off by the tape. When compared with a film of Comparative Example 1 (100% polyvinylidene fluoride) and a film of 100% polyvinylidene fluoride (KF # 1300 manufactured by Kureha Co., Ltd.) having a molecular weight different from that of Comparative Example 1, In Example 4, the number of peeled electrode films is reduced. That is, Example 4 shows that both the adhesiveness with the metal electrode (silver paste) and the adhesiveness with the conductive polymer (PEDOT) are improved. In particular, when the silver paste was applied and dried at 100 ° C. for 1 hour, the electrode film was not peeled off, and a remarkable improvement in adhesion was observed. As described above, when the polymer piezoelectric film of the present invention is used, the adhesion to a metal or non-metal polymer can be improved.

4A and 4B show the measurement results of the contact angle with water. The contact angle with water is a value obtained by measuring the angle at which the polymer piezoelectric film of the present invention and water (droplets) on the film contact. The higher the water repellency of the film, the larger the contact angle, and the higher the hydrophilicity, the smaller the contact angle (that is, water droplets spread more on the film). The increase in hydrophilicity indicates that hydrophilic groups were generated on the film surface (polarity increased). This polarity improves the adhesion of the film. That is, a smaller contact angle indicates an improvement in adhesion.
Comparing Examples 1 to 4 and Comparative Example 1 in FIG. 4A, it can be seen that Examples 1 to 4 have a smaller contact angle than Comparative Example 1 and have increased adhesion. That is, when a vinylidene fluoride-based copolymer is mixed with vinylidene fluoride, a film obtained from the mixture (polymer composition) has improved adhesiveness as compared with a 100% polyvinylidene fluoride film.
Moreover, the numerical value of each contact angle of Examples 1-4 decreased little by little as the quantity of the vinylidene fluoride type copolymer increased. Then, when the contact angle with the water of the comparative example 2 (vinylidene fluoride copolymer 100%) was measured, the numerical value of the contact angle of Examples 1-4 was the comparative example 1 (polyvinylidene fluoride 100%). It is between the numerical values of Comparative Example 2 and tends to approach the numerical values of Example 2 as the amount of the vinylidene fluoride copolymer increases. Therefore, as the amount of the vinylidene fluoride copolymer increases, the adhesiveness of the film is further improved, and it can be easily predicted that the adhesiveness of the vinylidene fluoride copolymer is approaching.
About the contact angle with the water of Examples 7-10 shown in FIG.4 (b), the tendency similar to the contact angle with the water of Examples 1-4 is seen.

In Example 5 of FIG. 4 (a), the amount of the vinylidene fluoride copolymer contained in the polymer piezoelectric film is the minimum (polyvinylidene fluoride: vinylidene fluoride copolymer = 90 parts by weight): 10) in which the content of monomethyl maleate contained in the vinylidene fluoride copolymer is minimum (vinylidene fluoride: maleic acid monomethyl ester = 100: 0.1 by weight). It is a molecular piezoelectric film. It can be seen that the piezoelectric stress constant of Example 5 is not significantly different from that of Comparative Example 1 (100% polyvinylidene fluoride), and has piezoelectricity. Moreover, it turns out that the adhesiveness of a film is improving compared with the comparative example 1 from the numerical value of the contact angle with water.
Example 6 was a case where the amount of the vinylidene fluoride copolymer contained in the polymer piezoelectric film was the maximum (polyvinylidene fluoride: vinylidene fluoride copolymer = 20: 80 by weight ratio). In addition, the polymer piezoelectric film has a maximum content of maleic acid monomethyl ester contained in the vinylidene fluoride copolymer (by weight ratio, vinylidene fluoride: monomethyl ester = 100: 3). It can be seen that the piezoelectric stress constant of Example 6 is not significantly different from that of Comparative Example 1 (100% polyvinylidene fluoride), and has piezoelectricity. Moreover, it turns out that it has adhesiveness compared with the comparative example 2 (vinylidene fluoride type copolymer 100%) from the numerical value of the contact angle with water.

  The table shown in FIG. 6 shows the piezoelectric stress constant and the contact angle with water in Examples in which the method for producing a polymer piezoelectric film from the polymer composition of the present invention is different. The piezoelectric stress constants of Examples 4 and 10 to 13 indicate that the polymer piezoelectric film has piezoelectricity regardless of which method is used. Moreover, when the contact angles with water of Examples 4 and 10 to 13 were compared with those of Comparative Examples 1 and 3 and 5 to 7 (polyvinylidene fluoride 100%), a polymer piezoelectric film was produced by any method. Even in this case, it can be seen that the adhesion is improved as compared with a 100% polyvinylidene fluoride film.

DESCRIPTION OF SYMBOLS 10 Film 60, 80 Apparatus 61 1st roll 62 2nd roll 63 3rd roll 71 Pointed electrode 72 Electrode 73 DC high voltage power supply 81 Needle electrode 82 Metal plate

Claims (9)

20 to 90 parts by weight of polyvinylidene fluoride;
80 to 10 parts by weight of a vinylidene fluoride copolymer;
The total of the polyvinylidene fluoride and the vinylidene fluoride copolymer is 100 parts by weight,
The vinylidene fluoride copolymer comprises 100 parts by weight of a vinylidene fluoride monomer containing 60% by weight or more of vinylidene fluoride, and 0.1 to 3 parts by weight of an unsaturated dibasic acid monoester monomer. Obtained by copolymerizing with
Polymer composition. The monoester monomer of the unsaturated dibasic acid is 0.1 to 0.8 parts by weight;
The polymer composition according to claim 1. The polymer composition according to claim 1 or 2 is formed into a film without stretching and then subjected to polarization treatment.
Polymer piezoelectric film. After adding either one of the quaternary ammonium salt or the clay surface-treated with the quaternary ammonium salt to the polymer composition according to claim 1 or 2, and molding it into a film without stretching. , Polarized treatment,
Polymer piezoelectric film. The polymer composition according to claim 1 or 2 is molded into a film, and then subjected to polarization treatment after uniaxial stretching.
Polymer piezoelectric film. After the polymer composition according to claim 1 or 2 is molded into a film shape, it is subjected to polarization treatment simultaneously with uniaxial stretching.
Polymer piezoelectric film. After the polymer composition according to claim 1 or 2 is molded into a film, it is subjected to polarization treatment after biaxial stretching.
Polymer piezoelectric film. A polymeric piezoelectric film according to any one of claims 3 to 7;
Comprising another thermoplastic resin different from the polymer piezoelectric film, which constitutes a laminate with the polymer piezoelectric film;
Multilayer film. The polymer piezoelectric film and the other thermoplastic resin constitute a laminate by coextrusion.
The multilayer film according to claim 8.

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