WO2016129400A1 - 高分子圧電フィルム及びその製造方法 - Google Patents
高分子圧電フィルム及びその製造方法 Download PDFInfo
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- H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/80—Constructional details
- H10N30/85—Piezoelectric or electrostrictive active materials
- H10N30/857—Macromolecular compositions
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
- C08K5/00—Use of organic ingredients
- C08K5/16—Nitrogen-containing compounds
- C08K5/29—Compounds containing one or more carbon-to-nitrogen double bonds
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
- C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
- C08L67/04—Polyesters derived from hydroxycarboxylic acids, e.g. lactones
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- H—ELECTRICITY
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- H10N30/00—Piezoelectric or electrostrictive devices
- H10N30/01—Manufacture or treatment
- H10N30/09—Forming piezoelectric or electrostrictive materials
- H10N30/098—Forming organic materials
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F2500/00—Characteristics or properties of obtained polyolefins; Use thereof
- C08F2500/01—High molecular weight, e.g. >800,000 Da.
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N25/00—Investigating or analyzing materials by the use of thermal means
- G01N25/20—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity
- G01N25/48—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation
- G01N25/4846—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation for a motionless, e.g. solid sample
- G01N25/4866—Investigating or analyzing materials by the use of thermal means by investigating the development of heat, i.e. calorimetry, e.g. by measuring specific heat, by measuring thermal conductivity on solution, sorption, or a chemical reaction not involving combustion or catalytic oxidation for a motionless, e.g. solid sample by using a differential method
Definitions
- the present invention relates to a polymer piezoelectric film and a method for producing the same.
- PZT PbZrO 3 —PbTiO 3 -based solid solution
- PZT contains lead
- a polymer piezoelectric material polymer piezoelectric film
- Currently known polymer piezoelectric materials are nylon 11, polyvinyl fluoride, polyvinyl chloride, polyurea, polyvinylidene fluoride ( ⁇ -type) (PVDF), vinylidene fluoride-trifluoroethylene copolymer (P (VDF -TrFE)) (Pauling type polymer represented by 75/25).
- polylactic acid polymers exhibit piezoelectricity only by mechanical stretching operation.
- polylactic acid has a small volume fraction of side chains with respect to the main chain and a large ratio of permanent dipoles per volume, and can be said to be an ideal polymer among the polymers having helical chirality.
- polylactic acid that exhibits piezoelectricity only by stretching treatment does not require poling treatment and the piezoelectricity does not decrease over several years.
- Patent Document 1 Japanese Patent Application Laid-Open No. 5-152638
- Patent Document 2 Japanese Patent Application Laid-Open No. 2005-213376
- Patent Document 3 Japanese Patent Application Laid-Open No. 2014-086703
- the longitudinal and lateral magnifications may be increased and the longitudinal and lateral magnifications may be stretched to the same extent.
- the orientation of the molecular chain is lowered, and the piezoelectricity of the polymer piezoelectric film is lowered.
- An object of the present invention is to provide a polymer piezoelectric film with reduced phase difference stripes and excellent longitudinal crack strength while maintaining piezoelectricity, and a method for producing the same.
- Microwave transmission molecule comprising a helical chiral polymer (A) having an optical activity with a weight average molecular weight of 50,000 to 1,000,000, crystallinity obtained by DSC method of 20% to 80%
- A helical chiral polymer having an optical activity with a weight average molecular weight of 50,000 to 1,000,000, crystallinity obtained by DSC method of 20% to 80%
- the standard thickness measured with an orientation meter is 50 ⁇ m
- the normalized molecular orientation MORc is 3.5 to 15.0
- the direction parallel to the phase difference stripe is the direction X
- the direction X is perpendicular to the film.
- evaluation method A When the direction Y is defined as a direction parallel to the principal surface of the film and the phase difference streak is evaluated by the following evaluation method A, the number of phase difference streaks having an evaluation value of 60 or more per 0 mm length in the direction Y is zero.
- Evaluation method A (A) In-plane retardation data of the film is obtained at intervals of 0.143 mm in the direction Y to obtain an in-plane retardation profile. (B) Fast Fourier transform is performed on the obtained in-plane phase difference profile, and after removing low frequency components with a cutoff frequency of 0.273 / mm, inverse Fourier transform is performed.
- ⁇ 2> When evaluated by the evaluation method A, there are zero phase difference lines having an evaluation value of 40 or more per 1000 mm length in the direction Y, and the total sum of evaluation values of the phase difference lines having an evaluation value of 20 or more is 200.
- the polymer piezoelectric film according to ⁇ 1> which is the following.
- ⁇ 3> When evaluated by the evaluation method A, there are 0 phase difference lines having an evaluation value of 20 or more per 1000 mm length in the direction Y, and the sum of evaluation values of the phase difference lines having an evaluation value of 20 or more is 0.
- ⁇ 4> internal haze to visible light is 50% or less, and the stress at 25 ° C.
- - piezoelectric constant d 14 measured by the charge method is 1 pC / N or more, any one of ⁇ 1> to ⁇ 3> The polymer piezoelectric film as described in 1.
- ⁇ 7> The polymeric piezoelectric film according to any one of ⁇ 1> to ⁇ 6>, wherein the content of the helical chiral polymer (A) is 80% by mass or more.
- ⁇ 8> The polymer piezoelectric film according to any one of ⁇ 1> to ⁇ 7>, wherein a product of the normalized molecular orientation MORc and the crystallinity is 75 to 700.
- ⁇ 9> The polymer piezoelectric film according to any one of ⁇ 1> to ⁇ 8>, wherein an internal haze with respect to visible light is 1.0% or less.
- a stabilizer (B) having at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group and having a weight average molecular weight of 200 to 60,000 is used as the helical chiral polymer (A).
- a method for producing a polymeric piezoelectric film comprising: a step of extruding from a T-die having a diameter of 0.001 mm to 0.100 mm under an extrusion temperature of 200 ° C. to 230 ° C. to form a film; and a step of stretching the formed film .
- a numerical range expressed using “to” means a range including numerical values described before and after “to” as a lower limit value and an upper limit value.
- film is a concept including not only what is generally called “film” but also what is generally called “sheet”.
- the film surface means the main surface of the film.
- the “main surface” means the surface having the largest area among the surfaces of the polymer piezoelectric film.
- the polymer piezoelectric film of the present invention may have two or more main surfaces.
- the polymer piezoelectric film has two surfaces A each having a 10 mm ⁇ 0.3 mm square surface A, a 3 mm ⁇ 0.3 mm square surface B, and a 10 mm ⁇ 3 mm square surface C
- the polymer piezoelectric film The main surface of the film is surface C, which has two main surfaces.
- the “MD direction” is a direction in which the film flows (Machine Direction)
- the “TD direction” is a direction perpendicular to the MD direction and parallel to the main surface of the film (Transverse Direction). ).
- the piezoelectric polymer film according to an embodiment of the present invention includes a helical chiral polymer (A) having an optical activity having a weight average molecular weight of 50,000 to 1,000,000, and has a crystallinity of 20% obtained by a DSC method.
- A helical chiral polymer having an optical activity having a weight average molecular weight of 50,000 to 1,000,000, and has a crystallinity of 20% obtained by a DSC method.
- the normalized molecular orientation MORc is 3.5 to 15.0 when the reference thickness measured by a microwave transmission type molecular orientation meter is 50 ⁇ m, and the direction parallel to the phase difference streak is When the direction X is perpendicular to the direction X and the direction parallel to the main surface of the film is the direction Y, and the retardation streak is evaluated by the following evaluation method A, the evaluation value is 60 or more per 1000 mm in the length of the direction Y
- the polymer piezoelectric film has zero retardation lines and the sum of evaluation values of retardation lines having an evaluation value of 20 or more is 1000 or less.
- Evaluation method A (A) In-plane retardation data of the film is obtained at intervals of 0.143 mm in the direction Y to obtain an in-plane retardation profile. (B) Fast Fourier transform is performed on the obtained in-plane phase difference profile, and after removing low frequency components with a cutoff frequency of 0.273 / mm, inverse Fourier transform is performed. (C) The inclination of two adjacent points is calculated for the in-plane phase difference profile after performing the inverse Fourier transform, and converted into an inclination profile. (D) The height from the bottom of the valley of the obtained inclination profile to the peak of the mountain adjacent to the valley is used as the evaluation value of the phase difference streak.
- the phase difference streak is reduced, and the longitudinal crack strength is excellent while maintaining the piezoelectricity. More specifically, when the phase difference streak is evaluated by the evaluation method A, there are 0 phase difference streaks with an evaluation value of 60 or more per 1000 mm length in the direction Y, and the evaluation value of the phase difference streak with an evaluation value of 20 or more. Therefore, the phase difference streaks of the polymer piezoelectric film is reduced, and as a result, a polymer piezoelectric film having excellent longitudinal tear strength while maintaining piezoelectricity can be provided.
- a decrease in tear strength in a specific direction is sometimes referred to as “longitudinal tear strength decreases”, and a state in which the tear strength in a specific direction is low is referred to as “longitudinal tear strength is low”.
- the phenomenon in which the tear strength in a specific direction is suppressed is sometimes referred to as “longitudinal tear strength is improved”, and the phenomenon in which the tear strength in a specific direction is decreased.
- the suppressed state may be referred to as “high longitudinal crack strength” or “excellent longitudinal crack strength”.
- the polymer piezoelectric film includes a helical chiral polymer (A) having a weight average molecular weight (Mw) of 50,000 to 1,000,000.
- Mw weight average molecular weight
- the weight average molecular weight of the helical chiral polymer (A) is 50,000 or more, the mechanical strength when the helical chiral polymer (A) is formed into a molded body is improved.
- the weight average molecular weight of the helical chiral polymer (A) is 1,000,000 or less, the moldability when a polymer piezoelectric film is obtained by molding (for example, extrusion molding) is improved.
- the polymer piezoelectric film has a crystallinity of 20% to 80% obtained by the DSC method. For this reason, the polymer piezoelectric film has a good balance of piezoelectricity, transparency, and longitudinal crack strength, and when the polymer piezoelectric film is stretched, it is difficult to whiten or break and is easy to manufacture. More specifically, when the crystallinity is 20% or more, the piezoelectricity of the polymer piezoelectric film is maintained high, and when the crystallinity is 80% or less, the longitudinal crack strength and It can suppress that transparency falls.
- the polymer piezoelectric film has a normalized molecular orientation MORc of 3.5 to 15.0.
- the normalized molecular orientation MORc is 3.5 or more, there are many molecular chains (for example, polylactic acid molecular chains) of the helical chiral polymer (A) having optical activity arranged in the stretching direction. The rate of generation increases, and the polymer piezoelectric film can exhibit high piezoelectricity.
- the normalized molecular orientation MORc is 15.0 or less, the longitudinal crack strength of the polymer piezoelectric film is improved.
- the polymer piezoelectric film according to the present embodiment has 0 phase difference streak having an evaluation value of 60 or more per 1000 mm length in the direction Y, and an evaluation value of 20 or more.
- the total sum of the evaluation values of the phase difference stripes is 1000 or less. Therefore, the polymer piezoelectric film has reduced streaks, and as a result, it has excellent longitudinal crack strength while maintaining piezoelectricity.
- the evaluation method A which is a method for evaluating the retardation stripes of the polymer piezoelectric film according to the present embodiment, will be described. Evaluation method A is performed according to the following procedures (a) to (d).
- In-plane retardation data of the film is obtained at intervals of 0.143 mm in the direction Y to obtain an in-plane retardation profile.
- B Fast Fourier transform is performed on the obtained in-plane phase difference profile, and after removing low frequency components with a cutoff frequency of 0.273 / mm, inverse Fourier transform is performed.
- C The inclination of two adjacent points is calculated for the in-plane phase difference profile after performing the inverse Fourier transform, and converted into an inclination profile.
- D The height from the bottom of the valley of the obtained inclination profile to the peak of the mountain adjacent to the valley is used as the evaluation value of the phase difference streak.
- the in-plane retardation data (phase difference amount) of the film is obtained at intervals of 0.143 mm in the direction parallel to the main surface of the film (direction Y, for example, TD direction) to obtain an in-plane retardation profile.
- the in-plane retardation data of the film can be obtained by using, for example, a wide-range birefringence evaluation system “WPA-100” manufactured by Photonic Lattice.
- WPA-100 wide-range birefringence evaluation system manufactured by Photonic Lattice.
- the in-plane retardation data (phase difference amount) of the film is a product of the birefringence and the thickness, and assuming that the birefringence is constant, the phase difference is proportional to the thickness.
- the inclination of two adjacent points is calculated for the in-plane phase difference profile after the inverse Fourier transform is performed, and converted into an inclination profile.
- the height from the bottom of the valley of the obtained slope profile to the top of the mountain adjacent to the valley is obtained, and that height is used as the evaluation value of the phase difference streak.
- the evaluation value of the phase difference line corresponds to the intensity of the phase difference line, and the higher the value, the more remarkable the phase difference line is generated. Therefore, the value is preferably low.
- the sum total of the evaluation values of the retardation lines per 1000 mm in length in the direction Y corresponds to the influence of the retardation lines on the surface of the film, and the higher the numerical value, the more widely the retardation lines are generated. Alternatively, it is preferable that the numerical value is low because many significant phase difference lines are generated.
- the polymer piezoelectric film according to the present embodiment has 0 phase difference streak having an evaluation value of 40 or more per 1000 mm length in the direction Y, and the evaluation value is 20 or more.
- the total sum of the evaluation values of the phase difference lines is preferably 200 or less, the number of the phase difference lines having the evaluation value of 20 or more is 0, and the sum of the evaluation values of the phase difference lines having the evaluation value of 20 or more is 0. Is more preferable.
- the phase difference streak is further reduced in the polymer piezoelectric film, and as a result, the longitudinal crack strength is more excellent while maintaining the piezoelectricity more suitably.
- the sum of the phase difference lines and the phase difference lines when converted per 1000 mm in the direction Y is the object of evaluation, and the length in the direction Y is less than 1000 mm or the length in the direction Y.
- the sum of the number of retardation lines having an evaluation value of 60 or more and the evaluation value of retardation lines having an evaluation value of 20 or more is converted into a value per 1000 mm in length in the direction Y. evaluate.
- the number of retardation lines having a calculated evaluation value of 60 or more and the sum of evaluation values of retardation lines having an evaluation value of 20 or more are each doubled. It is converted into a value per 1000 mm length in the direction Y.
- the helical chiral polymer (A) having optical activity (hereinafter also referred to as “helical chiral polymer (A)”) has molecular optical activity in which the molecular structure is a helical structure, and has a weight average molecular weight of 50,000 to A polymer that is 1 million.
- Examples of the helical chiral polymer (A) include polypeptides, cellulose, cellulose derivatives, polylactic acid polymers, polypropylene oxide, poly ( ⁇ -hydroxybutyric acid), and the like.
- the polypeptide include poly (glutarate ⁇ -benzyl), poly (glutarate ⁇ -methyl) and the like.
- the cellulose derivative include cellulose acetate and cyanoethyl cellulose.
- the helical chiral polymer (A) preferably has an optical purity of 95.00% ee or more, more preferably 97.00% ee or more. It is more preferably 99.00% ee or more, and particularly preferably 99.99% ee or more. Desirably, it is 100.00% ee.
- the optical purity of the helical chiral polymer (A) is a value calculated by the following formula.
- Optical purity (% ee) 100 ⁇
- the amount of L-form [mass%] of the helical chiral polymer (A) and the amount of D-form [mass%] of the helical chiral polymer (A) can be obtained by a method using high performance liquid chromatography (HPLC). Use the value. Details of the specific measurement will be described later.
- a polymer having a main chain containing a repeating unit represented by the following formula (1) is preferable from the viewpoint of increasing optical purity and improving piezoelectricity.
- Examples of the compound having a repeating unit represented by the formula (1) as a main chain include polylactic acid polymers. Among them, polylactic acid is preferable, and L-lactic acid homopolymer (PLLA) or D-lactic acid homopolymer (PDLA) is most preferable.
- polylactic acid is preferable, and L-lactic acid homopolymer (PLLA) or D-lactic acid homopolymer (PDLA) is most preferable.
- PLLA L-lactic acid homopolymer
- PDLA D-lactic acid homopolymer
- the polylactic acid polymer refers to “polylactic acid”, “copolymer of L-lactic acid or D-lactic acid and a copolymerizable polyfunctional compound”, or a mixture of both.
- the above-mentioned “polylactic acid” is a polymer in which lactic acid is polymerized by an ester bond and is connected for a long time, a lactide method via lactide, and a direct polymerization method in which lactic acid is heated in a solvent under reduced pressure and polymerized while removing water. It is known that it can be manufactured by, for example.
- the “polylactic acid” includes L-lactic acid homopolymer, D-lactic acid homopolymer, block copolymer including at least one polymer of L-lactic acid and D-lactic acid, and at least one of L-lactic acid and D-lactic acid.
- the graft copolymer containing the polymer of these is mentioned.
- Examples of the “copolymerizable polyfunctional compound” include glycolic acid, dimethyl glycolic acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxypropanoic acid, 3-hydroxypropanoic acid, 2-hydroxyvaleric acid, 3 -Hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 2-hydroxycaproic acid, 3-hydroxycaproic acid, 4-hydroxycaproic acid, 5-hydroxycaproic acid, 6-hydroxycaproic acid, 6-hydroxy Hydroxycarboxylic acids such as methylcaproic acid and mandelic acid, glycolides, cyclic esters such as ⁇ -methyl- ⁇ -valerolactone, ⁇ -valerolactone and ⁇ -caprolactone, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid , Pimelic acid, azelaic acid, sebacic acid, undecanedioic acid, Polyvalent carboxylic acids such as decaned
- Examples of the “copolymerizable polyfunctional compound” include the compounds described in paragraph 0028 of International Publication No. 2013/054918.
- the “copolymer of L-lactic acid or D-lactic acid and a copolymerizable polyfunctional compound” includes a block copolymer or a graft copolymer having a polylactic acid sequence capable of forming a helical crystal.
- the concentration of the structure derived from the copolymer component in the helical chiral polymer (A) is preferably 20 mol% or less.
- the helical chiral polymer (A) is a polylactic acid polymer, a structure derived from lactic acid in the polylactic acid polymer and a structure derived from a compound copolymerizable with lactic acid (copolymer component)
- the copolymer component is preferably 20 mol% or less based on the total number of moles.
- the helical chiral polymer (A) (for example, polylactic acid polymer) is obtained, for example, by directly dehydrating and condensing lactic acid described in JP-A-59-096123 and JP-A-7-033861. Alternatively, it can be produced by a ring-opening polymerization method using lactide which is a cyclic dimer of lactic acid described in US Pat. Nos. 2,668,182 and 4,057,357. Furthermore, the helical chiral polymer (A) (for example, polylactic acid polymer) obtained by each of the production methods described above is prepared by, for example, converting polylactic acid by the lactide method so that the optical purity is 95.00% ee or more. When manufacturing, it is preferable to polymerize lactide whose optical purity is improved to 95.00% ee or higher by crystallization operation.
- the helical chiral polymer (A) used in this embodiment has a weight average molecular weight (Mw) of 50,000 to 1,000,000.
- Mw weight average molecular weight
- the weight average molecular weight of the helical chiral polymer (A) is preferably 100,000 or more, and more preferably 150,000 or more, from the viewpoint of further improving the mechanical strength when formed into a molded body.
- the weight average molecular weight of the helical chiral polymer (A) is 1,000,000 or less, the moldability when a polymer piezoelectric film is obtained by molding (for example, extrusion molding) is improved.
- the weight average molecular weight of the helical chiral polymer (A) is preferably 800,000 or less, and more preferably 300,000 or less, from the viewpoint of further improving the moldability when obtaining a polymer piezoelectric film.
- the molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) is preferably 1.1 to 5 and more preferably 1.2 to 4 from the viewpoint of the strength of the polymer piezoelectric film. preferable. Further, it is preferably 1.4 to 3.
- the weight average molecular weight Mw and the molecular weight distribution (Mw / Mn) of the helical chiral polymer (A) are measured by the following GPC measurement method using gel permeation chromatography (GPC). Measured.
- -GPC measuring device Waters GPC-100 -column- Made by Showa Denko KK, Shodex LF-804 -Sample preparation-
- the helical chiral polymer (A) is dissolved in a solvent (for example, chloroform) at 40 ° C. to prepare a sample solution having a concentration of 1 mg / mL.
- a solvent for example, chloroform
- -Measurement condition- 0.1 mL of the sample solution is introduced into the column at a solvent [chloroform], a temperature of 40 ° C., and a flow rate of 1 mL / min.
- polylactic acid may be used as the polylactic acid polymer that is an example of the helical chiral polymer (A).
- polylactic acid for example, PURAC Co. PURASORB (PD, PL), manufactured by Mitsui Chemicals, Inc. of LACEA (H-100, H- 400), NatureWorks LLC Corp. Ingeo TM Biopolymer, and the like.
- the helical chiral polymer can be obtained by the lactide method or the direct polymerization method. It is preferable to produce the molecule (A).
- the polymer piezoelectric film according to this embodiment may contain only one kind of the above-described helical chiral polymer (A), or may contain two or more kinds.
- the content of the helical chiral polymer (A) (the total content when there are two or more kinds; the same shall apply hereinafter) is not particularly limited, but the polymer piezoelectric film It is preferable that it is 80 mass% or more with respect to the total mass. When the content is 80% by mass or more, the piezoelectric constant tends to be larger.
- the polymeric piezoelectric film of the present embodiment is a compound having a weight average molecular weight of 200 to 60,000 having at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group as a stabilizer (B). It may contain. Thereby, the heat-and-moisture resistance of a polymeric piezoelectric film improves more. Furthermore, the polymeric piezoelectric film preferably has at least one functional group selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule as the stabilizer (B). As the stabilizer (B), “stabilizer (B)” described in paragraphs 0039 to 0055 of International Publication No. 2013/054918 can be used.
- Examples of the compound containing a carbodiimide group (carbodiimide compound) that can be used as the stabilizer (B) include a monocarbodiimide compound, a polycarbodiimide compound, and a cyclic carbodiimide compound.
- a monocarbodiimide compound dicyclohexylcarbodiimide, bis-2,6-diisopropylphenylcarbodiimide, and the like are preferable.
- As a polycarbodiimide compound what was manufactured by the various method can be used. Conventional methods for producing polycarbodiimides (for example, U.S. Pat. No.
- the cyclic carbodiimide compound can be synthesized based on the method described in JP2011-256337A.
- the carbodiimide compound commercially available products may be used.
- B2756 (trade name) manufactured by Tokyo Chemical Industry Co., Ltd.
- Carbodilite LA-1 manufactured by Nisshinbo Chemical Co., Ltd.
- Stabaxol P Stabaxol P400
- Stabaxol I any Product name
- Examples of the compound (isocyanate compound) containing an isocyanate group in one molecule that can be used as the stabilizer (B) include 3- (triethoxysilyl) propyl isocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate.
- Compounds (epoxy compounds) containing an epoxy group in one molecule that can be used as the stabilizer (B) include phenyl glycidyl ether, diethylene glycol diglycidyl ether, bisphenol A-diglycidyl ether, hydrogenated bisphenol A-diglycidyl ether. Phenol novolac type epoxy resin, cresol novolac type epoxy resin, epoxidized polybutadiene and the like.
- the weight average molecular weight of the stabilizer (B) is 200 to 60000, more preferably 200 to 30000, and still more preferably 300 to 18000.
- the weight average molecular weight of the stabilizer (B) is particularly preferably 200 to 900.
- the weight average molecular weight of 200 to 900 is almost the same as the number average molecular weight of 200 to 900.
- the molecular weight distribution may be 1.0. In this case, “weight average molecular weight 200 to 900” can be simply referred to as “molecular weight 200 to 900”. .
- the polymer piezoelectric film may contain only one kind of stabilizer (B) or two or more kinds.
- the content of the stabilizer (B) (when there are two or more kinds, the total content; the same shall apply hereinafter).
- the content is 0.01 parts by mass or more, the heat and humidity resistance is further improved. Moreover, the transparency fall is suppressed more as the said content is 10 mass parts or less.
- a preferred embodiment of the stabilizer (B) is a stabilizer having one or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group, and having a number average molecular weight of 200 to 900.
- S1 and S2 a stabilizer having two or more functional groups selected from the group consisting of a carbodiimide group, an epoxy group, and an isocyanate group in one molecule and having a weight average molecular weight of 1,000 to 60,000 ( S2) is used in combination.
- the weight average molecular weight of the stabilizer (S1) having a number average molecular weight of 200 to 900 is about 200 to 900, and the number average molecular weight and the weight average molecular weight of the stabilizer (S1) are almost the same value. .
- the stabilizer (S1) and the stabilizer (S2) are used in combination as the stabilizer (B), it is preferable to contain a large amount of the stabilizer (S1) from the viewpoint of improving the transparency.
- the stabilizer (S2) is preferably in the range of 10 to 150 parts by mass with respect to 100 parts by mass of the stabilizer (S1), from the viewpoint of achieving both transparency and wet heat resistance. The range of 30 to 100 parts by mass is more preferable, and the range of 50 to 100 parts by mass is particularly preferable.
- Stabilizer SS-1 The compound name is bis-2,6-diisopropylphenylcarbodiimide.
- the weight average molecular weight (in this example, simply equal to “molecular weight”) is 363.
- Commercially available products include “Stabaxol I” manufactured by Rhein Chemie and “B2756” manufactured by Tokyo Chemical Industry.
- Stabilizer SS-2 The compound name is poly (4,4′-dicyclohexylmethanecarbodiimide).
- “Carbodilite LA-1” manufactured by Nisshinbo Chemical Co., Ltd., having a weight average molecular weight of about 2000 can be mentioned.
- Stabilizer SS-3 The compound name is poly (1,3,5-triisopropylphenylene-2,4-carbodiimide).
- “Stabaxol P” manufactured by Rhein Chemie Co., Ltd. can be mentioned as having a weight average molecular weight of about 3000.
- “Stabaxol P400” manufactured by Rhein Chemie is listed as having a weight average molecular weight of 20,000.
- the polymer piezoelectric film according to the present embodiment may contain an antioxidant.
- the antioxidant is preferably at least one compound selected from the group consisting of hindered phenol compounds, hindered amine compounds, phosphite compounds, and thioether compounds. Moreover, it is more preferable to use a hindered phenol compound or a hindered amine compound as the antioxidant.
- the polymeric piezoelectric film which is excellent also in heat-and-moisture resistance and transparency can be provided.
- the polymer piezoelectric film according to the present embodiment is a known resin typified by polyvinylidene fluoride, polyethylene resin and polystyrene resin, inorganic fillers such as silica, hydroxyapatite, and montmorillonite, as long as the effects of the present invention are not impaired. It may contain other components such as a known crystal nucleating agent such as phthalocyanine.
- the polymer piezoelectric film contains components other than the helical chiral polymer (A), the content of components other than the helical chiral polymer (A) is 20% by mass or less based on the total mass of the polymer piezoelectric film. It is preferable that it is 10 mass% or less.
- the polymer piezoelectric film of the present embodiment has the above-described helical chiral polymer (A) (that is, an optical activity having a weight average molecular weight (Mw) of 50,000 to 1,000,000) as long as the effects of the present invention are not impaired.
- a helical chiral polymer having optical activity other than the helical chiral polymer (A)) may be included.
- a polymeric piezoelectric film does not contain components other than the helical chiral polymer (A) which has optical activity from a transparent viewpoint.
- the crystallinity of the polymer piezoelectric film is determined by the DSC method.
- the crystallinity of the polymer piezoelectric film is 20% to 80%, preferably 30% to 70%, more preferably 35% to 60%. If the crystallinity is within the above range, the piezoelectricity, transparency, and longitudinal tear strength of the polymer piezoelectric film are well balanced, and when the polymer piezoelectric film is stretched, whitening and breakage are unlikely to occur and it is easy to manufacture.
- the degree of crystallinity is 20% or more, the piezoelectricity of the polymer piezoelectric film is maintained high. Moreover, it can suppress that longitudinal crack strength and transparency fall because a crystallinity degree is 80% or less.
- the crystallinity of the polymer piezoelectric film can be adjusted in the range of 20% to 80% by adjusting the crystallization and stretching conditions when producing the polymer piezoelectric film.
- the normalized molecular orientation MORc of the polymer piezoelectric film is 3.5 to 15.0.
- the normalized molecular orientation MORc is a value determined based on the “molecular orientation degree MOR” which is an index indicating the degree of orientation of the helical chiral polymer (A). If the normalized molecular orientation MORc is 3.5 or more, there are many molecular chains (for example, polylactic acid molecular chains) of the helical chiral polymer (A) arranged in the stretching direction, and as a result, the rate of formation of oriented crystals is high. Thus, the polymer piezoelectric film can exhibit higher piezoelectricity. If the normalized molecular orientation MORc is 15.0 or less, the longitudinal tear strength of the polymer piezoelectric film is further improved.
- the molecular orientation degree MOR (Molecular Orientation Ratio) is measured by the following microwave measurement method. That is, the surface of the polymer piezoelectric film in the microwave traveling direction in the microwave resonant waveguide of a known microwave transmission type molecular orientation meter (also referred to as a microwave molecular orientation degree measuring device). Arrange so that (film surface) is vertical. The polymer piezoelectric film is rotated 0-360 ° in a plane perpendicular to the microwave traveling direction while continuously irradiating the sample with microwaves whose vibration direction is biased in one direction, and transmitted through the sample. The degree of molecular orientation MOR is obtained by measuring the measured microwave intensity.
- the normalized molecular orientation MORc can be measured with a known molecular orientation meter such as a microwave molecular orientation meter MOA-2012A or MOA-6000 manufactured by Oji Scientific Instruments Co., Ltd. at a resonance frequency near 4 GHz or 12 GHz.
- the polymer piezoelectric film has a normalized molecular orientation MORc of 3.5 to 15.0, preferably 4.0 to 15.0, more preferably 4.0 to 10.0. More preferably, it is 0.0 to 8.0. Moreover, from the viewpoint of further improving the adhesion between the polymer piezoelectric film and the intermediate layer, the normalized molecular orientation MORc is preferably 7.0 or less.
- the normalized molecular orientation MORc can be controlled by heat treatment conditions (heating temperature and heating time) before stretching, stretching conditions (stretching temperature and stretching speed), and the like. .
- the normalized molecular orientation MORc can be converted into a birefringence ⁇ n obtained by dividing the retardation amount (retardation) by the thickness of the film. Specifically, retardation can be measured using RETS100 manufactured by Otsuka Electronics Co., Ltd. MORc and ⁇ n are approximately in a linear proportional relationship, and when ⁇ n is 0, MORc is 1. For example, when the helical chiral polymer (A) is a polylactic acid polymer and the birefringence ⁇ n of the polymer piezoelectric film is measured at a measurement wavelength of 550 nm, the normalized molecular orientation MORc is 2.0. The birefringence ⁇ n 0.005 can be converted, and if the normalized molecular orientation MORc is 4.0, the birefringence ⁇ n 0.01 can be converted.
- the product of the crystallinity of the polymer piezoelectric film and the normalized molecular orientation MORc is preferably 75 to 700.
- the product of the normalized molecular orientation MORc and the crystallinity of the polymer piezoelectric film is more preferably 75 to 600, still more preferably 100 to 500, particularly preferably 125 to 400, and particularly preferably 150 to 300.
- the above product can be adjusted to the above range by adjusting the crystallization and stretching conditions in producing the polymer piezoelectric film.
- the normalized molecular orientation MORc can be controlled by crystallization conditions (for example, heating temperature and heating time) and stretching conditions (for example, stretching temperature and stretching speed) when the polymer piezoelectric film is produced.
- Piezoelectricity of polymeric piezoelectric film for example, can be assessed by measuring the piezoelectric constant d 14 of the piezoelectric polymer film.
- the stress - describing an example of a method for measuring a piezoelectric constant d 14 due to charge method is described.
- the polymer piezoelectric film is cut to 150 mm in a direction formed by 45 ° with respect to the stretching direction (MD direction) and 50 mm in a direction orthogonal to the direction formed by 45 ° to produce a rectangular test piece.
- Al aluminum
- vapor deposition is similarly performed on the other side of the test piece, and Al is coated on both sides of the test piece to form an Al conductive layer.
- a test piece of 150 mm x 50 mm with an Al conductive layer formed on both sides is 120 mm in a direction of 45 ° with respect to the stretching direction (MD direction) of the polymer piezoelectric film, and 10 mm in a direction perpendicular to the direction of 45 °. Cut and cut out a rectangular film of 120 mm ⁇ 10 mm. This is a piezoelectric constant measurement sample.
- the obtained sample is set so as not to be loosened in a tensile tester (manufactured by AND, TENSILON RTG-1250) with a chuck distance of 70 mm.
- the force is periodically applied so that the applied force reciprocates between 4N and 9N at a crosshead speed of 5 mm / min.
- a capacitor having a capacitance Qm (F) is connected in parallel to the sample, and the voltage V between the terminals of the capacitor Cm (95 nF) is converted into a buffer amplifier. Measure through.
- the above measurement is performed under a temperature condition of 25 ° C.
- the generated charge amount Q (C) is calculated as the product of the capacitor capacitance Cm and the terminal voltage Vm.
- the stress at 25 ° C. - piezoelectric constant d 14 measured by the charge method is preferably at least 1 pC / N, more preferably at least 3pC / N, 5pC / N or more Is more preferable, and 6 pC / N or more is particularly preferable.
- the upper limit of the piezoelectric constant d 14 is not particularly limited, from the viewpoint of the balance, such as transparency, preferably less 50pc / N is a polymer piezoelectric film using a helical chiral polymer, more preferably at most 30 pC / N. From the viewpoint of the balance with similarly transparency is preferably a piezoelectric constant d 14 measured by a resonance method is not more than 15pC / N.
- the transparency of the polymer piezoelectric film according to this embodiment can be evaluated by, for example, visual observation or haze measurement.
- the polymer piezoelectric film preferably has an internal haze with respect to visible light (hereinafter also simply referred to as “internal haze”) of 50% or less, more preferably 20% or less, and further preferably 13% or less. Preferably, it is more preferably 5% or less, particularly preferably 2.0% or less, and most preferably 1.0% or less. The lower the internal haze of the polymer piezoelectric film of the present embodiment, the better.
- the piezoelectric constant and the like it is preferably 0.01% to 15%, preferably 0.01% to 10%. % Is more preferable, 0.1% to 5% is further preferable, and 0.1% to 1.0% is particularly preferable.
- internal haze refers to haze excluding haze due to the shape of the outer surface of the polymer piezoelectric film. Further, the “internal haze” here is a value measured on a polymer piezoelectric film at 25 ° C. in accordance with JIS-K7105.
- the internal haze refers to a value measured as follows. Specifically, first, a haze in the optical path length direction (hereinafter also referred to as “haze H2”) was measured for a cell having an optical path length of 10 mm filled with silicon oil. Next, the polymer piezoelectric film of this embodiment is immersed in the silicon oil of the cell so that the optical path length direction of the cell and the normal direction of the film are parallel, and the optical path of the cell in which the polymer piezoelectric film is immersed The haze in the long direction (hereinafter also referred to as “haze H3”) is measured.
- haze H3 a haze in the optical path length direction
- the measurement of haze H2 and haze H3 can be performed using, for example, a haze measuring machine [TC-HIII DPK, manufactured by Tokyo Denshoku Co., Ltd.].
- a haze measuring machine [TC-HIII DPK, manufactured by Tokyo Denshoku Co., Ltd.].
- silicone oil for example, “Shin-Etsu Silicone (trademark), model number KF-96-100CS” manufactured by Shin-Etsu Chemical Co., Ltd. can be used.
- the tear strength (longitudinal tear strength) of the polymer piezoelectric film of the present embodiment conforms to the test method “Right-angle tear method” described in “Tear strength of plastic film and sheet” of JIS K 7128-3. Is evaluated based on the measured tear strength.
- T represents the tear strength (N / mm)
- F represents the maximum tear load
- d represents the thickness (mm) of the test piece.
- the thickness of the polymer piezoelectric film of the present embodiment is not particularly limited, but is preferably 10 ⁇ m to 400 ⁇ m, more preferably 20 ⁇ m to 200 ⁇ m, still more preferably 20 ⁇ m to 100 ⁇ m, and particularly preferably 20 ⁇ m to 80 ⁇ m.
- the crystallinity can be adjusted to 20% to 80%, and the normalized molecular orientation MORc can be adjusted to 3.5 to 15.0.
- the number of retardation lines having an evaluation value of 60 or more can be adjusted to 0 per 1000 mm in the length of the direction Y, and the total sum of evaluation values of the retardation lines having an evaluation value of 20 or more is 1000 or less.
- the method is not particularly limited as long as it can be adjusted.
- this method for example, it can be suitably produced by a method comprising a step of forming a composition containing the helical chiral polymer (A) into a film and a step of stretching the formed film.
- a method comprising a step of forming a composition containing the helical chiral polymer (A) into a film and a step of stretching the formed film.
- a composition containing the helical chiral polymer (A) and, if necessary, other components such as a stabilizer (B), is added to a melting point Tm (° C.) or higher of the helical chiral polymer (A). It is a process of heating to temperature and forming into a film shape. By this forming step, a film containing the helical chiral polymer (A) and other components such as a stabilizer (B) as required is obtained.
- the melting point Tm (° C.) of the helical chiral polymer (A) and the glass transition temperature (Tg) of the helical chiral polymer (A) are respectively a differential scanning calorimeter (DSC). Is a value obtained from a melting endothermic curve when the temperature of the helical chiral polymer (A) is raised at a temperature rising rate of 10 ° C./min.
- the melting point (Tm) is a value obtained as a peak value of the endothermic reaction.
- the glass transition temperature (Tg) is a value obtained as the inflection point of the melting endothermic curve.
- the said composition can be manufactured by mixing helical chiral polymer (A) and other components, such as a stabilizer (B) as needed.
- each of the helical chiral polymer (A), the stabilizer (B), and other components may be used alone or in combination of two or more.
- the mixing may be melt kneading.
- the composition comprises a helical chiral polymer (A) and other components such as a stabilizer (B) if necessary, a melt kneader [for example, Labo Plast Mill manufactured by Toyo Seiki Seisakusho.
- the melt kneading conditions include, for example, conditions such as a mixer rotational speed of 30 rpm to 70 rpm, a temperature of 180 ° C. to 250 ° C., and a kneading time of 5 minutes to 20 minutes.
- a melt extrusion molding As a method of molding the composition into a film, a melt extrusion molding, a press molding, an injection molding, a calendar molding, or a molding method using a casting method is used. Further, it may be formed into a film by a T-die extrusion method or the like.
- the evaluation value and the retardation of the retardation film of the polymer piezoelectric film of the present embodiment are adjusted by adjusting the extrusion temperature and the lip tip edge radius of the T-die. It is possible to adjust the total sum of streak evaluation values.
- the extrusion temperature is preferably adjusted to 200 ° C. to 230 ° C., more preferably 210 ° C. to 225 ° C.
- the lip tip edge radius of the T die is preferably 0.001 mm or more and 0.100 mm or less, more preferably 0. It is preferable to adjust to 0.001 mm or more and 0.050 mm or less.
- the composition may be heated to the above temperature to form a film, and the resulting film may be quenched.
- the crystallinity of the film obtained in this step can be adjusted by rapid cooling.
- rapid cooling means cooling immediately after extrusion to at least the glass transition temperature Tg of the helical chiral polymer (A). In the present embodiment, it is preferable that no other treatment is included between the forming into a film and the rapid cooling.
- the method of rapid cooling is a method of immersing the film in a coolant such as water, ice water, ethanol, ethanol or dry ice, methanol, or liquid nitrogen; spraying a liquid spray with low vapor pressure on the film and cooling the film by latent heat of vaporization Method; and the like.
- a coolant such as water, ice water, ethanol, ethanol or dry ice, methanol, or liquid nitrogen
- the metal roll and film controlled to the temperature below the glass transition temperature Tg of helical chiral polymer (A) contact.
- count of cooling may be only once or may be 2 times or more.
- the film obtained in the molding step may be an amorphous film or a pre-crystallized film (hereinafter referred to as “pre-crystallized film”).
- pre-crystallized film refers to a film having a crystallinity of less than 3%.
- pre-crystallized film refers to a film having a crystallinity of 3% or more (preferably 3% to 70%).
- the crystallinity indicates a value measured by the same method as the crystallinity of the polymer piezoelectric film.
- the thickness of the film (amorphous film or pre-crystallized film) obtained in the molding step is mainly determined by the thickness of the polymer piezoelectric film finally obtained and the draw ratio, but preferably from 50 ⁇ m to It is 1000 ⁇ m, more preferably about 100 ⁇ m to 800 ⁇ m.
- the pre-crystallized film is obtained by heat-treating an amorphous film containing the helical chiral polymer (A) and other components such as a stabilizer (B) as necessary, and crystallizing it. Can do.
- the heating temperature T for pre-crystallization of the amorphous film is not particularly limited, but the glass transition temperature of the helical chiral polymer (A) is enhanced in terms of enhancing the piezoelectricity and transparency of the produced polymer piezoelectric film. It is preferable that the relationship between Tg and the following formula is satisfied, and the crystallinity is set to 3% to 70%.
- the heating time for pre-crystallization of the amorphous film can be appropriately set in consideration of the normalized molecular orientation MORc and crystallinity of the finally obtained polymer piezoelectric film.
- the heating time is preferably 5 seconds to 60 minutes, and more preferably 1 minute to 30 minutes from the viewpoint of stabilizing the production conditions.
- the normalized molecular orientation MORc increases and the crystallinity tends to increase.
- it is 20 ° C. to 170 ° C. for 5 seconds to 60 minutes (preferably 1 minute to 30 minutes). ) Heating is preferred.
- a cast roll adjusted to the above temperature range can be used.
- the polymer piezoelectric film is brought into close contact with the cast roll for preliminary crystallization to perform preliminary crystallization, and the thickness peak can be adjusted.
- the peak of thickness can be adjusted by adjusting the position of the electrode, the material, the applied voltage, and the like.
- the stretching step is a step of stretching a film (for example, a pre-crystallized film) obtained in the forming step mainly in a uniaxial direction.
- a polymer piezoelectric film having a large principal surface area can be obtained as a stretched film.
- the area of a main surface is large means that the area of the main surface of a polymeric piezoelectric film is 5 mm ⁇ 2 > or more.
- the area of a main surface is 10 mm ⁇ 2 > or more.
- the molecular chains of the helical chiral polymer (A) contained in the film can be aligned in one direction and aligned at a high density, and higher piezoelectricity can be obtained. Presumed to be obtained.
- a method of stretching in a uniaxial direction in a continuous process even in the case of longitudinal stretching in which the process flow direction (MD direction) matches the stretching direction, the direction perpendicular to the process flow direction (TD direction) matches the stretching direction. Lateral stretching may be used.
- the stretching temperature of the film is about 10 ° C. to 20 ° C. from the glass transition temperature of the film (or the helical chiral polymer (A) in the film) when the film is stretched only by tensile force as in the uniaxial direction.
- a high temperature range is preferred.
- the draw ratio (main draw ratio) in the stretching treatment is preferably 2 to 10 times, more preferably 3 to 5 times, and even more preferably 3 to 4 times. Thereby, a polymer piezoelectric film having higher piezoelectricity and transparency can be obtained.
- a film for example, a pre-crystallized film
- secondary stretching refers to a stretching method in which stretching is performed in a uniaxial direction and then stretching in a direction intersecting with the stretching direction.
- the stretching ratio of the secondary stretching is preferably 1 to 3 times, more preferably 1.1 to 2.5 times, and 1.2 to 2.0 times. Double is more preferred. Thereby, the phase difference streaks generated in the polymer piezoelectric film can be further reduced, and the tear strength can be further increased.
- preheating when the pre-crystallized film is stretched, preheating may be performed to facilitate stretching the film immediately before stretching.
- This preheating is generally performed in order to soften the film before stretching and make it easy to stretch. Therefore, the preheating is performed under the condition that the film before stretching is not crystallized and hardened. It is normal.
- the pre-heating since pre-crystallization may be performed before stretching, the pre-heating may be performed together with pre-crystallization.
- preheating and precrystallization can be performed by performing preheating at a temperature higher or longer than the normal temperature in accordance with the heating temperature and heat treatment time in the precrystallization step.
- the manufacturing method of this embodiment may have an annealing process as needed.
- the annealing step is a step of annealing (heat treatment) the film stretched in the stretching step (hereinafter also referred to as “stretched film”).
- annealing step crystallization of the stretched film can be further advanced, and a polymer piezoelectric film having higher piezoelectricity can be obtained.
- the preliminary crystallization operation in the above-described forming step may be omitted.
- a film in an amorphous state can be selected as a film obtained in the molding process (that is, a film used in the stretching process).
- the annealing temperature is preferably 80 ° C. to 160 ° C., more preferably 100 ° C. to 155 ° C.
- the method of annealing is not particularly limited, but a method in which a stretched film is directly contacted with a heating roll or heated using a hot air heater or an infrared heater; a stretched film is heated to a liquid (silicon oil). Etc.) and a method of heating by immersing in, etc .;
- the annealing is preferably performed while applying a certain tensile stress (for example, 0.01 MPa to 100 MPa) to the stretched film so that the stretched film does not sag.
- a certain tensile stress for example, 0.01 MPa to 100 MPa
- the annealing time is preferably 1 second to 5 minutes, more preferably 5 seconds to 3 minutes, and further preferably 10 seconds to 2 minutes.
- the productivity is excellent.
- the annealing time is 1 second or longer, the crystallinity of the film can be further improved.
- the annealed stretched film (that is, the polymer piezoelectric film) is preferably rapidly cooled after annealing.
- the “rapid cooling” that may be performed in the annealing process is the same as the “rapid cooling” that may be performed in the above-described forming process.
- the number of times of cooling may be only once, or may be two or more. Furthermore, annealing and cooling can be alternately repeated.
- Polymer piezoelectric film is a speaker, headphones, touch panel, remote controller, microphone, underwater microphone, ultrasonic transducer, ultrasonic applied measuring instrument, piezoelectric vibrator, mechanical filter, piezoelectric transformer, delay device, sensor, acceleration sensor, impact Sensors, vibration sensors, pressure sensors, tactile sensors, electric field sensors, sound pressure sensors, displays, fans, pumps, variable focus mirrors, sound insulation materials, sound insulation materials, keyboards, acoustic equipment, information processing equipment, measurement equipment, medical equipment, etc.
- the polymer piezoelectric film can also be used as a touch panel combined with a display device.
- a display device for example, a liquid crystal panel, an organic EL panel, or the like can be used.
- the polymer piezoelectric film can also be used as a pressure-sensitive sensor in combination with another type of touch panel (position detection member). Examples of the detection method of the position detection member include an anti-film method, a capacitance method, a surface acoustic wave method, an infrared method, and an optical method.
- the polymer piezoelectric film preferably has at least two surfaces, and is used as a piezoelectric element having electrodes on the surfaces.
- the electrode may be provided on at least two surfaces of the polymer piezoelectric film.
- limit especially as said electrode For example, ITO, ZnO, IZO (trademark), IGZO, a conductive polymer, silver nanowire, a metal mesh etc. are used.
- a polymer piezoelectric film and an electrode can be repeatedly stacked to be used as a laminated piezoelectric element.
- the unit having two repetitions is a laminated piezoelectric element in which electrodes, a polymer piezoelectric film, an electrode, a polymer piezoelectric film, and electrodes are stacked in this order.
- one of the polymer piezoelectric films used for the laminated piezoelectric element may be a polymer piezoelectric film, and the other layers may not be polymer piezoelectric films.
- the laminated piezoelectric element includes a plurality of polymer piezoelectric films, if the helical chiral polymer (A) contained in one layer of the polymer piezoelectric film has an L-form optical activity, the other layer of the polymer The helical chiral polymer (A) contained in the piezoelectric film may be L-form or D-form.
- the arrangement of the polymer piezoelectric film can be appropriately adjusted according to the use of the piezoelectric element.
- the first layer of the polymer piezoelectric film containing the L-form helical chiral polymer (A) as the main component contains the second high-density polymer containing the L-form helical chiral polymer (A) as the main component via the electrode.
- the uniaxial stretching direction (main stretching direction) of the first polymer piezoelectric film intersects, preferably orthogonal, with the uniaxial stretching direction (main stretching direction) of the second polymer piezoelectric film. This is preferable because the direction of displacement between the first polymer piezoelectric film and the second polymer piezoelectric film can be made uniform, and the piezoelectricity of the entire laminated piezoelectric element is enhanced.
- the first layer of the piezoelectric polymer film containing the L-form helical chiral polymer (A) as the main component contains the second high-density polymer containing the D-form helical chiral polymer (A) as the main component via the electrode.
- the uniaxial stretching direction (main stretching direction) of the first polymeric piezoelectric film is substantially parallel to the uniaxial stretching direction (main stretching direction) of the second polymeric piezoelectric film. It is preferable that the first polymer piezoelectric film and the second polymer piezoelectric film can be arranged in the same direction, and the piezoelectricity of the entire laminated piezoelectric element is enhanced.
- the transparency of the electrode specifically means that the internal haze is 40% or less (total light transmittance is 60% or more).
- the piezoelectric element using a polymer piezoelectric film can be applied to the above-described various piezoelectric devices such as speakers and touch panels.
- a piezoelectric element provided with a transparent electrode is suitable for application to a speaker, a touch panel, an actuator, and the like.
- the polymer piezoelectric film of the present invention will be described more specifically by way of examples.
- the present embodiment is not limited to the following examples unless it exceeds the gist thereof.
- Example 1 As helical chiral polymer (A), NatureWorks LLC Corp. polylactic acid (product name: Ingeo TM Biopolymer, brand: 4032D) was prepared, to this polylactic acid 100 parts by weight, the following additives X (stabilizer (B )) was added in an amount of 1.0 part by mass and dry blended to prepare a raw material.
- the prepared raw material is put into an extrusion molding machine hopper, extruded from a T-die having a width of 2000 mm (lip tip edge radius is 0.030 mm) while being heated to 230 ° C., and brought into contact with a cast roll at 50 ° C. for 0.5 minutes.
- a pre-crystallized film having a thickness of 150 ⁇ m was formed (molding step).
- the obtained pre-crystallized film was brought into contact with a roll heated to 70 ° C. and heated while being roll-to-roll, started to be drawn at a drawing speed of 1650 mm / min, and uniaxially drawn in the MD direction up to 3.5 times.
- a stretched film was obtained (stretching step). Thereafter, the uniaxially stretched film is annealed by roll-to-roll for 78 seconds on a roll heated to 130 ° C., and then rapidly cooled with a roll set at 50 ° C., and both ends in the film width direction are slit evenly. After cutting, the film was cut off to obtain a film having a width of 1000 mm, and further wound into a roll to obtain a polymer piezoelectric film (annealing step).
- Stabaxol P400 poly (1,3,5-triisopropylphenylene-2,4-carbodiimide) (weight average molecular weight: 20000) Stabaxol I ...
- Example 2 A polymer piezoelectric film was obtained in the same manner as in Example 1 except that the extrusion temperature from the T die was changed to 230 ° C. to 220 ° C.
- Example 3 A polymer piezoelectric film was obtained in the same manner as in Example 1 except that the T die having a lip tip edge radius of 0.030 mm was changed to a T die having a lip tip edge radius of 0.003 mm.
- Example 1 A polymer piezoelectric film was obtained in the same manner as in Example 1 except that the T die having a lip tip edge radius of 0.030 mm was changed to a T die having a lip tip edge radius of 0.300 mm.
- the sample solution was cooled to room temperature, neutralized by adding 20 mL of 1.0 mol / L hydrochloric acid solution, and the Erlenmeyer flask was sealed and mixed well.
- 1.0 mL of the sample solution was placed in a 25 mL volumetric flask, and HPLC sample solution 1 was prepared with 25 mL of mobile phase.
- 5 ⁇ L of the HPLC sample solution 1 was injected into the HPLC apparatus, the D / L body peak area of polylactic acid was determined under the following HPLC conditions, and the amount of L body and the amount of D body were calculated.
- -HPLC measurement conditions - ⁇ Column Optical resolution column, SUMICHIRAL OA5000 manufactured by Sumika Chemical Analysis Co., Ltd.
- Measurement conditions 0.1 mL of the sample solution was introduced into the column at a solvent (chloroform), a temperature of 40 ° C. and a flow rate of 1 mL / min, and the sample concentration in the sample solution separated by the column was measured with a differential refractometer.
- a solvent chloroform
- Mw weight average molecular weight
- the “internal haze” in the present application refers to the internal haze of the polymer piezoelectric film of the present invention, and is measured by the following method. Specifically, the internal haze (hereinafter also referred to as internal haze (H1)) of each polymer piezoelectric film of Examples 1 to 3 and Comparative Example 1 was measured by measuring light transmittance in the thickness direction. did. More specifically, haze (H2) is measured by sandwiching only silicon oil (Shin-Etsu Silicone (trademark) manufactured by Shin-Etsu Chemical Co., Ltd., model number: KF-96-100CS) between two glass plates in advance.
- Si oil Shin-Etsu Silicone (trademark) manufactured by Shin-Etsu Chemical Co., Ltd., model number: KF-96-100CS
- the haze (H2) and haze (H3) in the above formula were measured by measuring the light transmittance in the thickness direction using the following apparatus under the following measurement conditions.
- Measuring apparatus Tokyo Denshoku Co., Ltd., HAZE METER TC-HIII DPK Sample size: 30mm width x 30mm length
- Measurement conditions Conforms to JIS-K7105 Measurement temperature: Room temperature (25 ° C)
- piezoelectric constant d 14 stress-charge method
- the piezoelectric constant of the crystallized polymer film was measured according to the above-described “Example of Method for Measuring Piezoelectric Constant d 14 by Stress-Charge Method”.
- each of the polymer piezoelectric films of Examples 1 to 3 and Comparative Example 1 is obtained by making light incident from a direction perpendicular to the main surface of the film and projecting the emitted light on a screen to observe the brightness of the light.
- the degree of evaluation was evaluated. Specifically, the appearance was evaluated according to the following criteria. A: Light and darkness of streak-like light can hardly be recognized. B: Several light and dark streaks can be observed. C: Light and darkness of streaky light can be observed on the entire surface.
- FIG. 1 is a graph showing the in-plane retardation profile of the polymer piezoelectric film of Comparative Example 1 (from the end to the position of 55 mm).
- FIG. 2 is a graph showing the in-plane retardation profile of the polymer piezoelectric film of Comparative Example 1 after performing inverse Fourier transform (after removing low-frequency components).
- C The slope of two adjacent points was calculated for the in-plane phase difference profile after the inverse Fourier transform, and converted into a slope profile.
- FIG. 3 is a graph showing an inclination profile for the polymer piezoelectric film of Comparative Example 1.
- Non-contact 3D surface roughness The non-contact three-dimensional surface roughness Sa of each of the polymer piezoelectric films of Examples 1 to 3 and Comparative Example 1 was measured by the following method. First, platinum was sputtered onto the measurement surface of the polymer piezoelectric film using a sputtering apparatus (J-1000 manufactured by ULVAC), and then 645 ⁇ m using a confocal laser microscope (LEXT OLS4000 manufactured by Olympus, objective lens ⁇ 20). From the result of image analysis within an area of ⁇ 644 ⁇ m, non-contact three-dimensional surface roughness Sa was calculated in accordance with ISO25178. Specifically, this measurement was performed at three points in the film measurement plane, and the average value was defined as the non-contact three-dimensional surface roughness Sa.
- the thickness peak per 1000 mm in the direction Y was determined as follows. The thickness peak was determined using an in-line film thickness meter. When the thickness of the polymer piezoelectric film was measured, a waveform indicating the relationship between the position in the width direction of the film and the thickness of the film was detected by an in-line film thickness meter.
- the distance between the position in the width direction of the film corresponding to the apex of the convex part (or the concave part) and the position in the width direction of the film corresponding to the apex of the concave part (or the convex part) is measured, and the distance between peaks is calculated. Calculated. Then, the peak slope is calculated by the following formula, and the peak slope is expressed as an absolute value. [Formula]:
- (Peak height) / (Distance between peaks) Peaks A and B were determined according to the obtained peak height and peak slope, and the number of peaks A and B in each of the polymer piezoelectric films of Examples 1 to 3 and Comparative Example 1 was determined.
- the peak A represents a peak having a peak height of 1.5 ⁇ m or more and a peak slope below (that is, a value obtained by dividing the peak height by the distance between peaks) of 0.000035 or more.
- Peak B represents a peak having a peak height of 1.5 ⁇ m or more and a peak slope of 0.00008 or more.
- the number of phase difference lines having an evaluation value of 60 or more is 0 per 1000 mm in the length in the direction Y, and the sum of the evaluation values of phase difference lines having an evaluation value of 20 or more is 1000 or less.
- the appearance was excellent, the tear strength in the MD direction was large, and the decrease in longitudinal crack strength was suppressed. That is, it was confirmed that the tearability was improved by reducing the phase difference streak.
- the values of the piezoelectric constant d 14 , 45 ° elastic modulus and 45 ° breaking elongation can be made larger than those of Comparative Example 1, and d 14 ⁇ 45 ° elastic modulus which is a sensor sensitivity parameter. The value of can be maintained larger than that of Comparative Example 1.
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Abstract
Description
現在知られている高分子圧電材料は、ナイロン11、ポリフッ化ビニル、ポリ塩化ビニル、ポリ尿素、ポリフッ化ビニリデン(β型)(PVDF)、フッ化ビニリデン-トリフルオロエチレン共重合体(P(VDF-TrFE))(75/25)などに代表されるポーリング型高分子である。
光学活性を有する高分子の中でも、ポリ乳酸のような高分子結晶の圧電性は、螺旋軸方向に存在するC=O結合の永久双極子に起因する。特にポリ乳酸は、主鎖に対する側鎖の体積分率が小さく、体積あたりの永久双極子の割合が大きく、ヘリカルキラリティをもつ高分子の中でも理想的な高分子といえる。延伸処理のみで圧電性を発現するポリ乳酸は、ポーリング処理が不要で、圧電率は数年にわたり減少しないことが知られている。
特許文献1 特開平5-152638号公報
特許文献2 特開2005-213376号公報
特許文献3 特開2014-086703号公報
さらに、特許文献3に記載されているような一軸延伸フィルムとした場合、延伸方向と平行な方向に裂けやすく、特定方向についての引裂強さが低いという問題がある。以下、特定方向についての引裂強さを、「縦裂強度」ともいう。
本発明の目的は、位相差スジが低減され、かつ、圧電性を維持しつつ縦裂強度に優れる高分子圧電フィルム及びその製造方法を提供することである。
<1> 重量平均分子量が5万~100万である光学活性を有するヘリカルキラル高分子(A)を含み、DSC法で得られる結晶化度が20%~80%であり、マイクロ波透過型分子配向計で測定される基準厚さを50μmとしたときの規格化分子配向MORcが3.5~15.0であり、位相差スジに平行な方向を方向X、前記方向Xに直交し、フィルムの主面と平行な方向を方向Yとし、前記位相差スジを下記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が1000以下である、高分子圧電フィルム。
評価法A:
(a)方向Yについてフィルムの面内位相差データを0.143mm間隔で取得して面内位相差プロファイルを得る。
(b)得られた面内位相差プロファイルについて高速フーリエ変換を行ない、0.273/mmを遮断周波数として低周波成分を除去した後、逆フーリエ変換を行なう。
(c)逆フーリエ変換を行なった後の面内位相差プロファイルについて隣り合う2点の傾きを計算し、傾きプロファイルに変換する。
(d)得られた傾きプロファイルの谷の底点から前記谷に隣接する山の頂点までの高さを位相差スジの評価値とする。
<3> 前記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値20以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が0である、<1>又は<2>に記載の高分子圧電フィルム。
<4> 可視光線に対する内部ヘイズが50%以下であり、かつ25℃において応力-電荷法で測定した圧電定数d14が1pC/N以上である、<1>~<3>のいずれか1つに記載の高分子圧電フィルム。
<5> 可視光線に対する内部ヘイズが13%以下である、<1>~<4>のいずれか1つに記載の高分子圧電フィルム。
<6> 前記ヘリカルキラル高分子(A)が、下記式(1)で表される繰り返し単位を含む主鎖を有するポリ乳酸系高分子である、<1>~<5>のいずれか1つに記載の高分子圧電フィルム。
<8> 前記規格化分子配向MORcと前記結晶化度との積が75~700である、<1>~<7>のいずれか1つに記載の高分子圧電フィルム。
<9> 可視光線に対する内部ヘイズが1.0%以下である、<1>~<8>のいずれか1つに記載の高分子圧電フィルム。
<10> カルボジイミド基、エポキシ基、及びイソシアネート基からなる群から選ばれる1種類以上の官能基を有する重量平均分子量が200~60000の安定化剤(B)を、前記ヘリカルキラル高分子(A)100質量部に対して0.01質量部~10質量部含む、<1>~<9>のいずれか1つに記載の高分子圧電フィルム。
本明細書において、「~」を用いて表される数値範囲は、「~」の前後に記載される数値を下限値及び上限値として含む範囲を意味する。
また、本明細書において、「フィルム」は、一般的に「フィルム」と呼ばれているものだけでなく、一般的に「シート」と呼ばれているものをも包含する概念である。
本発明の一実施形態に係る高分子圧電フィルムは、重量平均分子量が5万~100万である光学活性を有するヘリカルキラル高分子(A)を含み、DSC法で得られる結晶化度が20%~80%であり、マイクロ波透過型分子配向計で測定される基準厚さを50μmとしたときの規格化分子配向MORcが3.5~15.0であり、位相差スジに平行な方向を方向X、前記方向Xに直交し、フィルムの主面と平行な方向を方向Yとし、前記位相差スジを下記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が1000以下である、高分子圧電フィルム。
評価法A:
(a)方向Yについてフィルムの面内位相差データを0.143mm間隔で取得して面内位相差プロファイルを得る。
(b)得られた面内位相差プロファイルについて高速フーリエ変換を行ない、0.273/mmを遮断周波数として低周波成分を除去した後、逆フーリエ変換を行なう。
(c)逆フーリエ変換を行なった後の面内位相差プロファイルについて隣り合う2点の傾きを計算し、傾きプロファイルに変換する。
(d)得られた傾きプロファイルの谷の底点から前記谷に隣接する山の頂点までの高さを位相差スジの評価値とする。
より詳細には、位相差スジを評価法Aで評価した際、方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が1000以下であることから、高分子圧電フィルムの位相差スジが低減されており、その結果、圧電性を維持しつつ縦裂強度に優れる高分子圧電フィルムが提供できる。
また、本明細書中では、特定方向についての引裂強さが低下する現象が抑制されることを「縦裂強度が向上する」ということがあり、特定方向についての引裂強さが低下する現象が抑制された状態を「縦裂強度が高い」又は「縦裂強度に優れる」ということがある。
より詳細には、結晶化度が20%以上であることにより、高分子圧電フィルムの圧電性が高く維持され、結晶化度が80%以下であることにより、高分子圧電フィルムの縦裂強度及び透明性が低下することを抑制できる。
規格化分子配向MORcが3.5以上であることにより、延伸方向に配列する光学活性を有するヘリカルキラル高分子(A)の分子鎖(例えばポリ乳酸分子鎖)が多く、その結果、配向結晶の生成する率が高くなり、高分子圧電フィルムは、高い圧電性を発現することが可能となる。
規格化分子配向MORcが15.0以下であることにより、高分子圧電フィルムの縦裂強度が向上する。
本実施形態に係る高分子圧電フィルムは、評価法Aにて位相差スジを評価したとき、方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が1000以下である。そのため、高分子圧電フィルムは、スジが低減されており、その結果、圧電性を維持しつつ縦裂強度に優れる。
以下、本実施形態に係る高分子圧電フィルムの位相差スジを評価する方法である評価法Aについて説明する。評価法Aは、以下の(a)~(d)の手順で行なわれる。
(a)方向Yについてフィルムの面内位相差データを0.143mm間隔で取得して面内位相差プロファイルを得る。
(b)得られた面内位相差プロファイルについて高速フーリエ変換を行ない、0.273/mmを遮断周波数として低周波成分を除去した後、逆フーリエ変換を行なう。
(c)逆フーリエ変換を行なった後の面内位相差プロファイルについて隣り合う2点の傾きを計算し、傾きプロファイルに変換する。
(d)得られた傾きプロファイルの谷の底点から前記谷に隣接する山の頂点までの高さを位相差スジの評価値とする。
光学活性を有するヘリカルキラル高分子(A)(以下、「ヘリカルキラル高分子(A)」ともいう)とは、分子構造が螺旋構造である分子光学活性を有し、重量平均分子量が5万~100万である高分子をいう。
ヘリカルキラル高分子(A)としては、例えば、ポリペプチド、セルロース、セルロース誘導体、ポリ乳酸系高分子、ポリプロピレンオキシド、ポリ(β―ヒドロキシ酪酸)等を挙げることができる。前記ポリペプチドとしては、例えば、ポリ(グルタル酸γ-ベンジル)、ポリ(グルタル酸γ-メチル)等が挙げられる。前記セルロース誘導体としては、例えば、酢酸セルロース、シアノエチルセルロース等が挙げられる。
光学純度(%ee)=100×|L体量-D体量|/(L体量+D体量)
すなわち、『「ヘリカルキラル高分子(A)のL体の量〔質量%〕とヘリカルキラル高分子(A)のD体の量〔質量%〕との量差(絶対値)」を「ヘリカルキラル高分子(A)のL体の量〔質量%〕とヘリカルキラル高分子(A)のD体の量〔質量%〕との合計量」で割った(除した)数値』に、『100』をかけた(乗じた)値を、光学純度とする。
さらに、前記の各製造方法により得られたヘリカルキラル高分子(A)(例えばポリ乳酸系高分子)は、光学純度を95.00%ee以上とするために、例えば、ポリ乳酸をラクチド法で製造する場合、晶析操作により光学純度を95.00%ee以上の光学純度に向上させたラクチドを、重合することが好ましい。
本実施形態で用いるヘリカルキラル高分子(A)は、重量平均分子量(Mw)が、5万~100万である。
ヘリカルキラル高分子(A)の重量平均分子量が、5万以上であることにより、ヘリカルキラル高分子(A)を成形体としたときの機械的強度が向上する。ヘリカルキラル高分子(A)の重量平均分子量は、成形体としたときの機械的強度をより向上させる観点から、10万以上であることが好ましく、15万以上であることがさらに好ましい。
一方、ヘリカルキラル高分子(A)の重量平均分子量が、100万以下であることにより、成形(例えば押出成形)によって高分子圧電フィルムを得る際の成形性が向上する。ヘリカルキラル高分子(A)の重量平均分子量は、高分子圧電フィルムを得る際の成形性をより向上させる観点から、80万以下であることが好ましく、30万以下であることがさらに好ましい。
Waters社製GPC-100
-カラム-
昭和電工社製、Shodex LF-804
-サンプルの調製-
ヘリカルキラル高分子(A)を40℃で溶媒(例えば、クロロホルム)へ溶解させ、濃度1mg/mLのサンプル溶液を準備する。
-測定条件-
サンプル溶液0.1mLを溶媒〔クロロホルム〕、温度40℃、1mL/分の流速でカラムに導入する。
本実施形態に係る高分子圧電フィルムについて、ヘリカルキラル高分子(A)の含有量(2種以上である場合には総含有量。以下同じ。)には特に制限はないが、高分子圧電フィルム全質量に対して、80質量%以上であることが好ましい。
上記含有量が80質量%以上であることにより、圧電定数がより大きくなる傾向がある。
本実施形態の高分子圧電フィルムは、安定化剤(B)として、カルボジイミド基、エポキシ基、及びイソシアネート基からなる群より選ばれる少なくとも1種の官能基を有する重量平均分子量が200~60000の化合物を含有してもよい。これにより、高分子圧電フィルムの耐湿熱性がより向上する。
更に、高分子圧電フィルムは、安定化剤(B)として、カルボジイミド基、エポキシ基、及びイソシアネート基からなる群から選ばれる少なくとも1種の官能基を1分子内に1つ有することが好ましい。
安定化剤(B)としては、国際公開第2013/054918号の段落0039~0055に記載された「安定化剤(B)」を用いることができる。
モノカルボジイミド化合物としては、ジシクロヘキシルカルボジイミド、ビス-2,6-ジイソプロピルフェニルカルボジイミド、等が好適である。
また、ポリカルボジイミド化合物としては、種々の方法で製造したものを使用することができる。従来のポリカルボジイミドの製造方法(例えば、米国特許第2941956号明細書、特公昭47-33279号公報、J.0rg.Chem.28,2069-2075(1963)、Chemical Review 1981,Vol.81 No.4、p619-621)により、製造されたものを用いることができる。具体的には特許4084953号公報に記載のカルボジイミド化合物を用いることもできる。
ポリカルボジイミド化合物としては、ポリ(4,4’-ジシクロヘキシルメタンカルボジイミド)、ポリ(N,N’-ジ-2,6-ジイソプロピルフェニルカルボジイミド)、ポリ(1,3,5-トリイソプロピルフェニレン-2,4-カルボジイミド、等が挙げられる。
環状カルボジイミド化合物は、特開2011-256337号公報に記載の方法などに基づいて合成することができる。
カルボジイミド化合物としては、市販品を用いてもよく、例えば、東京化成社製、B2756(商品名)、日清紡ケミカル社製、カルボジライトLA-1、ラインケミー社製、Stabaxol P、Stabaxol P400、Stabaxol I(いずれも商品名)等が挙げられる。
安定化剤(B)の重量平均分子量が上記範囲内であると、安定化剤がより移動しやすくなり、耐湿熱性改良効果がより効果的に奏される。
安定化剤(B)の重量平均分子量は、200~900であることが特に好ましい。なお、重量平均分子量200~900は、数平均分子量200~900とほぼ一致する。また、重量平均分子量200~900の場合、分子量分布が1.0である場合があり、この場合には、「重量平均分子量200~900」を、単に「分子量200~900」と言い換えることもできる。
高分子圧電フィルムがヘリカルキラル高分子(A)及び安定化剤(B)を含む場合、安定化剤(B)の含有量(2種以上である場合には総含有量。以下同じ。)は、ヘリカルキラル高分子(A)100質量部に対し、0.01質量部~10質量部であることが好ましく、0.01質量部~5質量部であることがより好ましく、0.1質量部~3質量部であることがさらに好ましく、0.5質量部~2質量部であることが特に好ましい。
上記含有量が0.01質量部以上であると、耐湿熱性がより向上する。
また、上記含有量が10質量部以下であると、透明性の低下がより抑制される。
安定化剤(B)として安定化剤(S1)と安定化剤(S2)とを併用する場合、安定化剤(S1)を多く含むことが透明性向上の観点から好ましい。
具体的には、安定化剤(S1)100質量部に対して、安定化剤(S2)が10質量部~150質量部の範囲であることが、透明性と耐湿熱性の両立という観点から好ましく、30質量部~100質量部の範囲であることがより好ましく、50質量部~100質量部の範囲であることが特に好ましい。
・安定化剤SS-1 … 化合物名は、ビス-2,6-ジイソプロピルフェニルカルボジイミドである。重量平均分子量(この例では、単なる「分子量」に等しい)は、363である。市販品としては、ラインケミー社製「Stabaxol I」、東京化成社製「B2756」が挙げられる。
・安定化剤SS-2 … 化合物名は、ポリ(4,4’-ジシクロヘキシルメタンカルボジイミド)である。市販品としては、重量平均分子量約2000のものとして、日清紡ケミカル社製「カルボジライトLA-1」が挙げられる。
・安定化剤SS-3 … 化合物名は、ポリ(1,3,5-トリイソプロピルフェニレン-2,4-カルボジイミド)である。市販品としては、重量平均分子量約3000のものとして、ラインケミー社製「Stabaxol P」が挙げられる。また、重量平均分子量20000のものとして、ラインケミー社製「Stabaxol P400」が挙げられる。
また、本実施形態に係る高分子圧電フィルムは、酸化防止剤を含有してもよい。酸化防止剤は、ヒンダードフェノール系化合物、ヒンダードアミン系化合物、ホスファイト系化合物及びチオエーテル系化合物からなる群より選ばれる少なくとも1種の化合物であることが好ましい。
また、酸化防止剤として、ヒンダードフェノール系化合物又はヒンダードアミン系化合物を用いることがより好ましい。これにより、耐湿熱性及び透明性にも優れる高分子圧電フィルムを提供することができる。
本実施形態に係る高分子圧電フィルムは、本発明の効果を損なわない限度において、ポリフッ化ビニリデン、ポリエチレン樹脂やポリスチレン樹脂に代表される公知の樹脂や、シリカ、ヒドロキシアパタイト、モンモリロナイト等の無機フィラー、フタロシアニン等の公知の結晶核剤等、その他の成分を含有していてもよい。
なお、高分子圧電フィルムがヘリカルキラル高分子(A)以外の成分を含む場合、ヘリカルキラル高分子(A)以外の成分の含有量は、高分子圧電フィルム全質量に対して、20質量%以下であることが好ましく、10質量%以下であることがより好ましい。
高分子圧電フィルムの結晶化度は、DSC法によって求められるものである。高分子圧電フィルムの結晶化度は20%~80%であり、30%~70%が好ましく、35%~60%がより好ましい。前記範囲に結晶化度があれば、高分子圧電フィルムの圧電性、透明性、縦裂強度のバランスがよく、また高分子圧電フィルムを延伸するときに、白化や破断がおきにくく製造しやすい。
結晶化度が20%以上であることにより、高分子圧電フィルムの圧電性が高く維持される。
また、結晶化度が80%以下であることにより、縦裂強度及び透明性が低下することを抑制できる。
高分子圧電フィルムの規格化分子配向MORcは、3.5~15.0である。規格化分子配向MORcは、ヘリカルキラル高分子(A)の配向の度合いを示す指標である「分子配向度MOR」に基づいて定められる値である。規格化分子配向MORcが3.5以上であれば、延伸方向に配列するヘリカルキラル高分子(A)の分子鎖(例えばポリ乳酸分子鎖)が多く、その結果、配向結晶の生成する率が高くなり、高分子圧電フィルムはより高い圧電性を発現することが可能となる。規格化分子配向MORcが15.0以下であれば、高分子圧電フィルムの縦裂強度が更に向上する。
MORc=(tc/t)×(MOR-1)+1
(tc:補正したい基準厚さ、t:高分子圧電フィルムの厚さ)
規格化分子配向MORcは、公知の分子配向計、例えば王子計測機器株式会社製マイクロ波方式分子配向計MOA-2012AやMOA-6000等により、4GHzもしくは12GHz近傍の共振周波数で測定することができる。
また、高分子圧電フィルムと中間層との密着性をより向上させる観点からは、規格化分子配向MORcは、7.0以下であることが好ましい。
例えば、ヘリカルキラル高分子(A)がポリ乳酸系高分子であり、かつ、高分子圧電フィルムの複屈折率Δnを測定波長550nmで測定した場合、規格化分子配向MORcが2.0であれば、複屈折率Δn 0.005に変換でき、規格化分子配向MORcが4.0であれば、複屈折率Δn 0.01に変換できる。
本実施形態において、高分子圧電フィルムの結晶化度と規格化分子配向MORcとの積は75~700であることが好ましい。この範囲に調整することで、高分子圧電フィルムの圧電性と透明性とのバランスが良好であり、かつ寸法安定性も高く、縦裂強度(即ち、特定方向についての引裂強さ)の低下が抑制される。
高分子圧電フィルムの規格化分子配向MORcと結晶化度との積は、より好ましくは75~600、さらに好ましくは100~500、特に好ましくは125~400、特に好ましくは150~300である。
高分子圧電フィルムの圧電性は、例えば、高分子圧電フィルムの圧電定数d14を測定することによって評価することができる。
以下、応力-電荷法による圧電定数d14の測定方法の一例について説明する。
d14=(2×t)/L×Cm・ΔVm/ΔF
t:サンプル厚(m)
L:チャック間距離(m)
Cm:並列接続コンデンサー容量(F)
ΔVm/ΔF:力の変化量に対する、コンデンサー端子間の電圧変化量比
具体的には、本実施形態における高分子圧電フィルムにおいて、25℃における応力-電荷法で測定した圧電定数d14は、1pC/N以上が好ましく、3pC/N以上がより好ましく、5pC/N以上がさらに好ましく、6pC/N以上が特に好ましい。また圧電定数d14の上限は特に限定されないが、透明性などのバランスの観点からは、ヘリカルキラル高分子を用いた高分子圧電フィルムでは50pC/N以下が好ましく、30pC/N以下がより好ましい。
また、同様に透明性とのバランスの観点からは共振法で測定した圧電定数d14が15pC/N以下であることが好ましい。
本実施形態に係る高分子圧電フィルムの透明性は、例えば、目視観察やヘイズ測定により評価することができる。
高分子圧電フィルムは、可視光線に対する内部ヘイズ(以下、単に「内部ヘイズ」ともいう)が50%以下であることが好ましく、20%以下であることがより好ましく、13%以下であることがさらに好ましく、5%以下であることがさらに好ましく、2.0%以下であることが特に好ましく、1.0%以下であることがもっとも好ましい。
本実施形態の高分子圧電フィルムの内部ヘイズは、低ければ低いほどよいが、圧電定数などとのバランスの観点からは、0.01%~15%であることが好ましく、0.01%~10%であることがより好ましく、0.1%~5%であることがさらに好ましく、0.1%~1.0%であることが特に好ましい。
また、ここでいう「内部ヘイズ」は、高分子圧電フィルムに対して、JIS-K7105に準拠して、25℃で測定したときの値である。
即ち、まず、シリコンオイルで満たした光路長10mmのセルについて、光路長方向のヘイズ(以下、「ヘイズH2」ともいう)を測定した。次いで、このセルのシリコンオイルに本実施形態の高分子圧電フィルムを、セルの光路長方向とフィルムの法線方向とが平行となるように浸漬させ、高分子圧電フィルムが浸漬されたセルの光路長方向のヘイズ(以下、「ヘイズH3」ともいう)を測定する。ヘイズH2及びヘイズH3は、いずれもJIS-K7105に準拠して25℃で測定する。
測定されたヘイズH2及びヘイズH3に基づき、下記式に従って内部ヘイズH1を求める。
内部ヘイズ(H1)=ヘイズ(H3)-ヘイズ(H2)
また、シリコンオイルとしては、例えば、信越化学工業(株)製の「信越シリコーン(商標)、型番KF-96-100CS」を用いることができる。
本実施形態の高分子圧電フィルムの引裂強さ(縦裂強度)は、JIS K 7128-3の「プラスチックーフィルム及びシートの引裂強さ」に記載の試験方法「直角形引裂法」に準拠して測定された引裂強さに基づいて評価される。
ここで、引張試験機のクロスヘッド速度は毎分200mmとし、引裂強さは下式より算出する。
T=F/d
上記式において、Tは引裂強さ(N/mm)、Fは最大引裂荷重、dは試験片の厚さ(mm)を表す。
本実施形態の高分子圧電フィルムを製造する方法としては、結晶化度を20%~80%に調整でき、かつ、規格化分子配向MORcを3.5~15.0に調整でき、位相差スジを下記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個に調整でき、評価値20以上の位相差スジの評価値の総和が1000以下に調整できる方法であれば特に制限されない。
この方法として、例えば、ヘリカルキラル高分子(A)を含む組成物をフィルム状に成形する工程と、成形されたフィルムを延伸する工程と、を含む方法によって好適に製造することができる。例えば、国際公開第2013/054918号の段落0065~0099に記載の製造方法が挙げられる。
成形工程は、ヘリカルキラル高分子(A)と、必要に応じ安定化剤(B)等のその他の成分と、を含む組成物を、ヘリカルキラル高分子(A)の融点Tm(℃)以上の温度に加熱してフィルム形状に成形する工程である。この成形工程により、ヘリカルキラル高分子(A)と、必要に応じ安定化剤(B)等のその他の成分と、を含むフィルムが得られる。
ここで、ヘリカルキラル高分子(A)、安定化剤(B)、及びその他の成分は、それぞれ、1種のみ用いてもよいし、2種以上用いてもよい。
上記混合は、溶融混練であってもよい。
具体的には、上記組成物は、ヘリカルキラル高分子(A)と、必要に応じ安定化剤(B)等のその他の成分と、を溶融混練機〔例えば、東洋精機製作所製のラボプラストミル〕に投入し、ヘリカルキラル高分子(A)の融点以上の温度に加熱して溶融混練することにより製造してもよい。この場合、本工程では、ヘリカルキラル高分子(A)の融点以上の温度に加熱して溶融混練することによって製造された組成物を、ヘリカルキラル高分子(A)の融点以上の温度に維持した状態でフィルム形状に成形する。
溶融混練の条件としては、例えば、ミキサー回転数30rpm~70rpm、温度180℃~250℃、混練時間5分間~20分間、といった条件が挙げられる。
ここで、「急冷」とは、押出した直後に少なくともヘリカルキラル高分子(A)のガラス転移温度Tg以下に冷やすことをいう。
本実施形態では、フィルムへの成形と急冷との間に他の処理が含まれないことが好ましい。
また、冷却の回数は、1回のみであっても、2回以上であってもよい。
ここで、非晶状態のフィルムとは、結晶化度が3%未満であるフィルムをいう。
また、予備結晶化フィルムとは、結晶化度が3%以上(好ましくは3%~70%)であるフィルムを指す。
ここで、結晶化度は、高分子圧電フィルムの結晶化度と同様の方法によって測定される値を指す。
非晶状態のフィルムを予備結晶化するための加熱温度Tは特に限定されないが、製造される高分子圧電フィルムの圧電性や透明性など高める点で、ヘリカルキラル高分子(A)のガラス転移温度Tgと以下の式の関係を満たし、結晶化度が3%~70%になるように設定されることが好ましい。
Tg-40℃≦T≦Tg+40℃
(Tgは、ヘリカルキラル高分子(A)のガラス転移温度を表す)
上記加熱時間は、5秒~60分が好ましく、製造条件の安定化という観点からは、1分~30分がより好ましい。加熱時間が長くなるに従い、上記規格化分子配向MORcが高くなり、上記結晶化度が高くなる傾向となる。
例えば、ヘリカルキラル高分子(A)としてポリ乳酸系高分子を含む非晶状態のフィルムを予備結晶化する場合は、20℃~170℃で、5秒~60分(好ましくは1分~30分)加熱することが好ましい。
延伸工程は、成形工程において得られたフィルム(例えば予備結晶化フィルム)を主として一軸方向に延伸する工程である。本工程により、延伸フィルムとして、主面の面積が大きな高分子圧電フィルムを得ることができる。
なお、主面の面積が大きいとは、高分子圧電フィルムの主面の面積が5mm2以上であることをいう。また、主面の面積が10mm2以上であることが好ましい。
なお、ここで言う「逐次的な延伸」とは、まず一軸方向に延伸した後に、前記延伸の方向と交差する方向に延伸する延伸方法をいう。
延伸工程にて副次的延伸を行なう場合、副次的延伸の延伸倍率は、1倍~3倍が好ましく、1.1倍~2.5倍がより好ましく、1.2倍~2.0倍がさらに好ましい。これにより、高分子圧電フィルムに発生する位相差スジをより低減することができ、引裂強さをより高めることができる。
本実施形態の製造方法は、必要に応じ、アニール工程を有していてもよい。
アニール工程は、上記延伸工程において延伸されたフィルム(以下、「延伸フィルム」ともいう)を、アニール(熱処理)する工程である。アニール工程により、延伸フィルムの結晶化をより進行させることができ、より圧電性が高い高分子圧電フィルムを得ることができる。
また、主に、アニールによって延伸フィルムが結晶化する場合は、前述の成形工程における、予備結晶化の操作を省略できる場合がある。この場合、成形工程で得られるフィルム(即ち、延伸工程に供されるフィルム)として、非晶状態のフィルムを選択できる。
冷却の回数は、1回のみであっても、2回以上であってもよく、さらには、アニールと冷却とを交互に繰り返し行なうことも可能である。
高分子圧電フィルムは、スピーカー、ヘッドホン、タッチパネル、リモートコントローラー、マイクロホン、水中マイクロホン、超音波トランスデューサ、超音波応用計測器、圧電振動子、機械的フィルター、圧電トランス、遅延装置、センサ、加速度センサ、衝撃センサ、振動センサ、感圧センサ、触覚センサ、電界センサ、音圧センサ、ディスプレイ、ファン、ポンプ、可変焦点ミラー、遮音材料、防音材料、キーボード、音響機器、情報処理機、計測機器、医用機器などの種々の分野で利用することができ、デバイスに用いた際のセンサ感度を高く維持することができる点から、特に各種センサの分野で高分子圧電フィルムを利用することが好ましい。
また、高分子圧電フィルムは、表示装置と組み合わせたタッチパネルとして用いることもできる。表示装置としては、例えば、液晶パネル、有機ELパネルなどを用いることもできる。
また、高分子圧電フィルムは、感圧センサとして、他方式のタッチパネル(位置検出部材)と組み合わせて用いることもできる。位置検出部材の検出方式としては抗膜方式、静電容量方式、表面弾性波方式、赤外線方式、光学方式等が挙げられる。
また、積層圧電素子に複数の高分子圧電フィルムが含まれる場合は、ある層の高分子圧電フィルムに含まれるヘリカルキラル高分子(A)の光学活性がL体ならば、他の層の高分子圧電フィルムに含まれるヘリカルキラル高分子(A)はL体であってもD体であってもよい。高分子圧電フィルムの配置は圧電素子の用途に応じて適宜調整することができる。
ヘリカルキラル高分子(A)として、NatureWorks LLC社製ポリ乳酸(品名:IngeoTM biopolymer、銘柄:4032D)を用意し、このポリ乳酸100質量部に対して、下記添加剤X(安定化剤(B))を1.0質量部添加してドライブレンドし原料を調製した。
調製した原料を押出成形機ホッパーに入れて、230℃に加熱しながら幅2000mmのTダイ(リップ先端エッジ半径が0.030mm)から押出し、50℃のキャストロールに0.5分間接触させ、厚さ150μmの予備結晶化フィルムを製膜した(成形工程)。
得られた予備結晶化フィルムを70℃に加熱したロールに接触させて加熱しながらロールツーロールで、延伸速度1650mm/分で延伸を開始し、3.5倍までMD方向に一軸延伸し、一軸延伸フィルムを得た(延伸工程)。
その後、一軸延伸フィルムを、ロールツーロールで、130℃に加熱したロール上に78秒間接触させアニール処理した後、50℃に設定したロールで急冷し、フィルム幅方向の両端部を、均等にスリットを入れた後切り落とし、幅1000mmのフィルムとし、さらにロール状に巻き取ることで、高分子圧電フィルムを得た(アニール工程)。
実施例1では、添加剤Xとして、ラインケミー社製Stabaxol P400(10質量部)、ラインケミー社製Stabaxol I(80質量部)、及び日清紡ケミカル社製カルボジライトLA-1(10質量部)の混合物を用いた。
上記混合物における各成分の詳細は以下のとおりである。
Stabaxol P400 … ポリ(1,3,5-トリイソプロピルフェニレン-2,4-カルボジイミド)(重量平均分子量:20000)
Stabaxol I … ビス-2,6-ジイソプロピルフェニルカルボジイミド(分子量(=重量平均分子量):363)
カルボジライトLA-1 … ポリ(4,4’-ジシクロヘキシルメタンカルボジイミド)(重量平均分子量:約2000)
Tダイからの押出温度230℃を220℃に変更したこと以外は実施例1と同様にして高分子圧電フィルムを得た。
リップ先端エッジ半径が0.030mmであるTダイをリップ先端エッジ半径が0.003mmであるTダイに変更したこと以外は実施例1と同様にして高分子圧電フィルムを得た。
リップ先端エッジ半径が0.030mmであるTダイをリップ先端エッジ半径が0.300mmであるTダイに変更したこと以外は実施例1と同様にして高分子圧電フィルムを得た。
50mLの三角フラスコに1.0gのサンプル(高分子圧電フィルム)を秤り込み、IPA(イソプロピルアルコール)2.5mLと、5.0mol/L水酸化ナトリウム溶液5mLとを加えた。次に、サンプル溶液が入った前記三角フラスコを、温度40℃の水浴に入れ、ポリ乳酸が完全に加水分解するまで、約5時間攪拌した。
-HPLC測定条件-
・カラム
光学分割カラム、(株)住化分析センター製 SUMICHIRAL OA5000
・測定装置
日本分光社製 液体クロマトグラフィ
・カラム温度
25℃
・移動相
1.0mM-硫酸銅(II)緩衝液/IPA=98/2(V/V)
硫酸銅(II)/IPA/水=156.4mg/20mL/980mL
・移動相流量
1.0mL/分
・検出器
紫外線検出器(UV254nm)
ゲル浸透クロマトグラフ(GPC)を用い、下記GPC測定方法により、実施例1~3及び比較例1の各高分子圧電フィルムの製造に使用したポリ乳酸の分子量分布(Mw/Mn)を測定した。
-GPC測定方法-
・測定装置
Waters社製GPC-100
・カラム
昭和電工社製、Shodex LF-804
・サンプルの調製
実施例1~3及び比較例1の各高分子圧電フィルムを、それぞれ40℃で溶媒〔クロロホルム〕へ溶解させ、濃度1mg/mLのサンプル溶液を準備した。
・測定条件
サンプル溶液0.1mLを溶媒(クロロホルム)、温度40℃、1mL/分の流速でカラムに導入し、カラムで分離されたサンプル溶液中のサンプル濃度を示差屈折計で測定した。ポリ乳酸の分子量は、ポリスチレン標準試料にてユニバーサル検量線を作成し、ポリ乳酸の重量平均分子量(Mw)を算出した。
以上のようにして得られた実施例1~3及び比較例1の高分子圧電フィルムについて、外観及び後述の評価法Aにより位相差スジを評価し、ピークA及びピークBの個数、非接触三次元表面粗度、引裂強さ、圧電定数(d14)、45°方向の弾性率(45°弾性率)、45°方向の破断伸度(45°破断伸度)、結晶化度、MORcならびに内部ヘイズを測定した。評価結果及び測定結果を表2に示す。
本願でいう「内部ヘイズ」とは本発明の高分子圧電フィルムの内部ヘイズのことをいい、以下の方法で測定される。
具体的には、実施例1~3及び比較例1の各高分子圧電フィルムの内部ヘイズ(以下、内部ヘイズ(H1)ともいう)は、厚さ方向の光透過性を測定することにより、測定した。より詳細には、予めガラス板2枚の間に、シリコンオイル(信越化学工業社製信越シリコーン(商標)、型番:KF-96-100CS)のみを挟んでヘイズ(H2)を測定し、次にシリコンオイルで表面を均一に塗らしたフィルム(高分子圧電フィルム)を、ガラス板2枚で挟んでヘイズ(H3)を測定し、下記式のようにこれらの差をとることで、実施例1~3及び比較例1の各高分子圧電フィルムの内部ヘイズ(H1)を得た。
内部ヘイズ(H1)=ヘイズ(H3)-ヘイズ(H2)
測定装置:東京電色社製、HAZE METER TC-HIII DPK
試料サイズ:幅30mm×長さ30mm
測定条件:JIS-K7105に準拠
測定温度:室温(25℃)
前述した「応力-電荷法による圧電定数d14の測定方法の一例」に従い、結晶化高分子フィルムの圧電定数(詳細には、圧電定数d14(応力-電荷法))を測定した。
実施例1~3及び比較例1の各高分子圧電フィルムについて、規格化分子配向MORcを、王子計測機器株式会社製マイクロ波方式分子配向計MOA-6000により測定した。基準厚さtcは、50μmに設定した。
実施例1~3及び比較例1の各高分子圧電フィルムを10mg正確に秤量し、示差走査型熱量計(パーキンエルマー社製DSC-1)を用い、昇温速度10℃/分の条件で測定し、融解吸熱曲線を得た。得られた融解吸熱曲線から結晶化度を得た。
実施例1~3及び比較例1の各高分子圧電フィルムについて、JIS K 7128-3の「プラスチックーフィルム及びシートの引裂強さ」に記載の試験方法「直角形引裂法」に準拠し、MD方向の引裂強さ(縦裂強度)を測定した。
これらの例では、MD方向の引裂強さが大きいことが、縦裂強度の低下が抑制されていることを意味している。
引裂強さの測定において、引張試験機のクロスヘッド速度は毎分200mmとした。
引裂強さ(T)は下式より算出した。
T=F/d
上記式において、Tは引裂強さ(N/mm)、Fは最大引裂荷重、dは試験片の厚さ(mm)を表す。
実施例1~3及び比較例1の各高分子圧電フィルムを延伸方向(MD方向)に対して45°なす方向に180mm、45°なす方向に直交する方向に10mmにカットして得た矩形の試験片について、東洋精機製作所製引張試験機 ストログラフVD1Eを用いてJIS-K-7127に準拠し、45°方向の弾性率及び破断伸度を測定した。
実施例1~3及び比較例1の各高分子圧電フィルムの外観を、フィルムの主面に対して垂直方向から光を入射させ、その出射光をスクリーンに投影して観察した際の光の明暗の程度により評価した。具体的には、外観を以下の基準で評価した。
A:スジ状の光の明暗がほとんど認識できない
B:スジ状の光の明暗が数本観察できる
C:スジ状の光の明暗が全面に観察できる
実施例1~3及び比較例1の各高分子圧電フィルム(厚さ50μm)について、フォトニックラティス社製のワイドレンジ複屈折評価システム「WPA-100」を用い、以下の評価法Aにて位相差スジを評価した。評価法Aは、以下の(a)~(d)の手順で行なった。
(a)方向Yについてフィルムの面内位相差データを0.143mm間隔で取得して面内位相差プロファイルを得た。図1は、比較例1の高分子圧電フィルムについて取得したフィルムの面内位相差プロファイルを示すグラフである(端部から位置55mmまで)。
(b)得られた面内位相差プロファイルについて高速フーリエ変換を行ない、0.273/mmを遮断周波数として低周波成分を除去した後、逆フーリエ変換を行なった。図2は、比較例1の高分子圧電フィルムについて逆フーリエ変換を行なった後(低周波成分除去後)のフィルムの面内位相差プロファイルを示すグラフである。
(c)逆フーリエ変換を行なった後の面内位相差プロファイルについて隣り合う2点の傾きを計算し、傾きプロファイルに変換した。図3は、比較例1の高分子圧電フィルムについて傾きプロファイルを示すグラフである。
(d)得られた傾きプロファイルの谷の底点から前記谷に隣接する山の頂点までの高さを位相差スジの評価値とした。
また、図4、5は、実施例2及び比較例1の高分子圧電フィルムについて、位相差スジの評価値を示すグラフである。図4、5のグラフからも分かるように、比較例1では多くの位相差スジが観察される一方、実施例2では位相差スジが大幅に低減されており、位相差スジがほとんど観察されなかった。
以下の方法により、実施例1~3及び比較例1の各高分子圧電フィルムの非接触三次元表面粗度Saを測定した。
まず、高分子圧電フィルムの測定面にスパッタリング装置(アルバック社製J-1000)を用いて白金をスパッタした後、共焦点型レーザー顕微鏡(オリンパス社製LEXT OLS4000、対物レンズ×20)を用いて645μm×644μmの面積内の画像解析の結果から、ISO25178に準拠して非接触三次元表面粗度Saを算出した。具体的には、この測定をフィルム測定面内で3点実施し、平均した値を非接触三次元表面粗度Saとした。
次に、実施例1~3及び比較例1の各高分子圧電フィルムのうねり(厚さムラ)確認のため、以下のようにして、方向Y1000mm当たりの厚みのピークを求めた。
厚みのピークは、インライン膜厚計を用いて求めた。
高分子圧電フィルムの厚みを計測した際に、インライン膜厚計により、フィルムの幅方向の位置とフィルムの厚みとの関係を示す波形が検出された。
この波形のうち、凸部の頂点に該当するフィルムの幅方向の位置と、この凸部の頂点を境に減少する凹部の頂点に該当するフィルムの幅方向の位置との間(又は、凹部の頂点に該当するフィルムの幅方向の位置と、この凹部の頂点を境に増加する凸部の頂点に該当するフィルムの幅方向の位置との間)を一つのピーク単位とした。
そして、凸部(又は凹部)の頂点に該当する厚さと、凹部(又は凸部)の頂点に該当する厚さとの差を計測して、ピーク高さを算出した。
また、凸部(又は凹部)の頂点に該当するフィルムの幅方向の位置と、凹部(又は凸部)の頂点に該当するフィルムの幅方向の位置との距離を計測して、ピーク間距離を算出した。そして、ピーク傾きを次式により算出し、ピーク傾きを絶対値で表す。
[式]:|ピーク傾き|=(ピーク高さ)/(ピーク間距離)
求めたピークの高さ及びピーク傾きに応じてピークA及びピークBを定め、実施例1~3及び比較例1の各高分子圧電フィルムにおけるピークA及びピークBの個数を求めた。
ピークAとは、ピーク高さが1.5μm以上、かつ、以下のピーク傾き(すなわち、ピーク高さをピーク間距離で除した値)が0.000035以上であるピークを表す。ピークBとは、ピーク高さが1.5μm以上、かつピーク傾きが0.00008以上であるピークを表す。
本明細書に記載された全ての文献、特許出願、及び技術規格は、個々の文献、特許出願、及び技術規格が参照により取り込まれることが具体的かつ個々に記された場合と同程度に、本明細書中に参照により取り込まれる。
Claims (11)
- 重量平均分子量が5万~100万である光学活性を有するヘリカルキラル高分子(A)を含み、
DSC法で得られる結晶化度が20%~80%であり、
マイクロ波透過型分子配向計で測定される基準厚さを50μmとしたときの規格化分子配向MORcが3.5~15.0であり、
位相差スジに平行な方向を方向X、前記方向Xに直交し、フィルムの主面と平行な方向を方向Yとし、前記位相差スジを下記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値60以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が1000以下である、高分子圧電フィルム。
評価法A:
(a)方向Yについてフィルムの面内位相差データを0.143mm間隔で取得して面内位相差プロファイルを得る。
(b)得られた面内位相差プロファイルについて高速フーリエ変換を行ない、0.273/mmを遮断周波数として低周波成分を除去した後、逆フーリエ変換を行なう。
(c)逆フーリエ変換を行なった後の面内位相差プロファイルについて隣り合う2点の傾きを計算し、傾きプロファイルに変換する。
(d)得られた傾きプロファイルの谷の底点から前記谷に隣接する山の頂点までの高さを位相差スジの評価値とする。 - 前記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値40以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が200以下である、請求項1に記載の高分子圧電フィルム。
- 前記評価法Aで評価したとき、前記方向Yの長さ1000mm当たり、評価値20以上の位相差スジが0個であり、評価値20以上の位相差スジの評価値の総和が0である、請求項1又は請求項2に記載の高分子圧電フィルム。
- 可視光線に対する内部ヘイズが50%以下であり、かつ25℃において応力-電荷法で測定した圧電定数d14が1pC/N以上である、請求項1~請求項3のいずれか1項に記載の高分子圧電フィルム。
- 可視光線に対する内部ヘイズが13%以下である、請求項1~請求項4のいずれか1項に記載の高分子圧電フィルム。
- 前記ヘリカルキラル高分子(A)の含有量が80質量%以上である、請求項1~請求項6のいずれか1項に記載の高分子圧電フィルム。
- 前記規格化分子配向MORcと前記結晶化度との積が75~700である、請求項1~請求項7のいずれか1項に記載の高分子圧電フィルム。
- 可視光線に対する内部ヘイズが1.0%以下である、請求項1~請求項8のいずれか1項に記載の高分子圧電フィルム。
- カルボジイミド基、エポキシ基、及びイソシアネート基からなる群から選ばれる1種類以上の官能基を有する重量平均分子量が200~60000の安定化剤(B)を、前記ヘリカルキラル高分子(A)100質量部に対して0.01質量部~10質量部含む、請求項1~請求項9のいずれか1項に記載の高分子圧電フィルム。
- 請求項1~請求項10のいずれか1項に記載の高分子圧電フィルムを製造する方法であって、
前記ヘリカルキラル高分子(A)を含む組成物を、リップ先端エッジ半径が0.001mm~0.100mmであるTダイから押出温度200℃~230℃の条件で押出してフィルム状に成形する工程と、
成形されたフィルムを延伸する工程と、を含む高分子圧電フィルムの製造方法。
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