PIEZOELECTRIC POLYMER MATERIAL AND METHOD FOR PRODUCING SAME

• US 20120132846A1
• Filed: 02/09/2012
• Published: 05/31/2012
• Est. Priority Date: 08/25/2010
• Status: Active Grant

• Current Assignee: A School Corporation Kansai University, Mitsui Chemicals Incorporated (Mitsui Chemicals)
• Original Assignee: A School Corporation Kansai University, Mitsui Chemicals Incorporated (Mitsui Chemicals)
• Inventors: Nishimoto, Taizo, Goto, Kenichi, YOSHIDA, Mitsunobu, Fujii, Shunsuke, Onishi, Hitoshi, Tajitsu, Yoshiro, Tanimoto, Kazuhiro
• Granted Patent: US 8,829,121 B2
• Time in Patent Office: Days
• US Class Current: 252/62.9R
• CPC Class Codes: B29C 2071/022 Annealing
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29C 55/04 uniaxial, e.g. oblique
• CPC Class Codes: B29C 71/0009 using liquids, e.g. solvents, swelling agents spectacle cases, e.g. for cleaning contact lenses A45C11/04; disinfecting or sterilising contact lenses A61L12/00, using liquid substances A61L2/20; cleaning involving the use of liquid in general B08B3/00; for hydrating contact lenses B29D11/00067
• CPC Class Codes: B29C 71/02 Thermal after-treatment B29C71/0063 and B29C71/0072 take precedence
• CPC Class Codes: B29K 2067/046 PLA, i.e. polylactic acid or polylactide
• CPC Class Codes: B29K 2105/256 Sheets, plates, blanks or films
• CPC Class Codes: B29K 2995/0003 having particular electrical or magnetic properties, e.g. piezoelectric
• CPC Class Codes: B29K 2995/0026 Transparent
• CPC Class Codes: B29K 2995/004 Semi-crystalline
• CPC Class Codes: B29K 2995/0051 mono-axially
• CPC Class Codes: B29K 2995/0088 Molecular weight
• CPC Class Codes: B29L 2007/002 Panels; Plates; Sheets
• CPC Class Codes: B29L 2031/34 Electrical apparatus, e.g. sparking plugs or parts thereof
• CPC Class Codes: C08L 27/16 Homopolymers or copolymers or vinylidene fluoride
• CPC Class Codes: C08L 67/04 Polyesters derived from hydroxycarboxylic acids, e.g. lactones C08L67/06 takes precedence
• CPC Class Codes: H10N 30/098 Forming organic materials
• CPC Class Codes: H10N 30/852 Composite materials, e.g. having 1-3 or 2-2 type connectivity
• CPC Class Codes: H10N 30/857 Macromolecular compositions

Abstract

The invention provides a piezoelectric polymer material comprising a helical chiral polymer having a weight average molecular weight of from 50,000 to 1,000,000 and optical activity, the piezoelectric polymer material having: crystallinity as obtained by a DSC method of from 20% to 80%; a transmission haze with respect to visible light of 50% or less; and a product of the crystallinity and a standardized molecular orientation MORc, which is measured with a microwave transmission-type molecular orientation meter at a reference thickness of 50 μm, of from 40 to 700.

Claims

1. A piezoelectric polymer material comprising a helical chiral polymer having a weight average molecular weight of from 50,000 to 1,000,000 and optical activity, the piezoelectric polymer material having:

crystallinity as obtained by a DSC method of from 20% to 80%;

a transmission haze with respect to visible light of 50% or less; and

a product of the crystallinity and a standardized molecular orientation MORc, which is measured with a microwave transmission-type molecular orientation meter at a reference thickness of 50 μ

m, of from 40 to 700.

2. The piezoelectric polymer material according to claim 1, wherein the MORc is from 2.0 to 15.0.

3. The piezoelectric polymer material according to claim 1, wherein the transmission haze with respect to visible light is from 0.05% to 30%, and the MORc is from 6.0 to 10.0.

4. The piezoelectric polymer material according to claim 1, wherein a piezoelectric constant d₁₄ measured by a displacement method at 25°

C. is 1 pm/V or more.

5. The piezoelectric polymer material according to claim 1, wherein the helical chiral polymer is a polylactic acid-based polymer having a main chain containing a repeating unit represented by the following Formula (1):

6. The piezoelectric polymer material according to claim 1, wherein the helical chiral polymer has an optical purity of 95.00% ee or more.

7. The piezoelectric polymer material according to claim 5, further comprising polyvinylidene fluoride, wherein

a content of the polyvinylidene fluoride is from more than 0 mass % to 5 mass % with respect to the total mass of the polylactic acid-based polymer;

and

a piezoelectric constant d₁₄ measured by a resonance method at 25°

C. is 10 pC/N or more.

8. The piezoelectric polymer material according to claim 7, wherein the content of the polyvinylidene fluoride is from 0.01 mass % to 5 mass % with respect to the total mass of the polylactic acid-based polymer.

9. The piezoelectric polymer material according to claim 7, wherein a weight average molecular weight of the polyvinylidene fluoride is from 3,000 to 800,000.

10. The piezoelectric polymer material according to claim 1, comprising from 0.01 to 1.0 part by weight of a crystal nucleating agent with respect to 100 parts by weight of the helical chiral polymer contained in the piezoelectric polymer material.

11. The piezoelectric polymer material according to claim 10, wherein the crystal nucleating agent is at least one compound selected from the group consisting of zinc phenylsulfonate, melamine polyphosphate, melamine cyanurate, zinc phenylphosphonate, calcium phenylphosphonate, magnesium phenylphosphonate, talc and clay.

12. The piezoelectric polymer material according to claim 1, wherein an area of a principal plane is 5 mm² or more.

13. A method for producing the piezoelectric polymer material according to claim 1, the method comprising:

obtaining a preliminarily crystallized sheet by heating a sheet that is in an amorphous state and contains a helical chiral polymer; and

stretching the preliminarily crystallized sheet mainly in a uniaxial direction.

14. The method for producing the piezoelectric polymer material according to claim 13, wherein in the obtaining of the preliminarily crystallized sheet, the sheet in an amorphous state is heated to have a crystallinity of from 10% to 70% at a temperature T represented by the following expression:

Tg≦

T≦

Tg+40°

C.

wherein Tg represents the glass transformation temperature of the helical chiral polymer material.

15. The method for producing the piezoelectric polymer material according to claim 13, wherein in the obtaining of the preliminarily crystallized sheet, the sheet in an amorphous state comprises polylactic acid as the helical chiral polymer and is heated at from 60°

C. to 170°

C. for from 5 seconds to 60 minutes.

16. The method for producing the piezoelectric polymer material according to claim 13, wherein an annealing treatment is performed after the stretching.

17. A method for producing the piezoelectric polymer material according to claim 1, the method comprising:

stretching a sheet that contains a helical chiral polymer mainly in a uniaxial direction; and

performing a hydrolysis treatment after the stretching.

18. A piezoelectric polymer material comprising a polylactic acid-based polymer and polyvinylidene fluoride, wherein a content of the polyvinylidene fluoride is from more than 0 mass % to 5 mass % with respect to the total mass of the polylactic acid-based polymer, and wherein a piezoelectric constant d₁₄ measured by a resonance method at 25°

C. is 10 pC/N or more.

19. The piezoelectric polymer material according to claim 18, wherein the content of the polyvinylidene fluoride is from 0.01 mass % to 5 mass % with respect to the total mass of the polylactic acid-based polymer.