Polymeric piezoelectric material, and process for producing the same

Patent metadata

Field	Value
Publication number	US-9905750-B2
Application number	US-201615263862-A
Country	US
Kind code	B2
Filing date	Sep 13, 2016
Priority date	Dec 13, 2011
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

Provided is a process for producing a polymeric piezoelectric material including a first step of heating a sheet in an amorphous state containing the helical chiral polymer to obtain a pre-crystallized sheet, and a second step of stretching the pre-crystallized sheet in biaxial directions, wherein the polymeric piezoelectric material includes a helical chiral polymer having a weight-average molecular weight of from 50,000 to 1,000,000 and having optical activity, wherein a crystallinity of the material measured by a DSC method is from 20% to 80%, and a product of a standardized molecular orientation MORc measured by a microwave transmission type molecular orientation meter based on a reference thickness of 50 μm and the crystallinity is from 25 to 250.

First claim

The invention claimed is:

1. A process for producing a polymeric piezoelectric material comprising a first step of heating a sheet in an amorphous state containing a helical chiral polymer to obtain a pre-crystallized sheet, and a second step of stretching the pre-crystallized sheet in biaxial directions, wherein
the polymeric piezoelectric material comprises a helical chiral polymer having a weight-average molecular weight of from 50,000 to 1,000,000 and having optical activity,
wherein a crystallinity of the material measured by a DSC method is from 20% to 80%, and a product of a standardized molecular orientation MORc measured by a microwave transmission type molecular orientation meter based on a reference thickness of 50 μm and the crystallinity is from 25 to 250.

2. The process for producing a polymeric piezoelectric material according to claim 1 , wherein, in the first step for obtaining the pre-crystallized sheet, the sheet in an amorphous state is heated at a temperature T satisfying the following formula until the crystallinity becomes between 1% and 70%:
Tg −40° C.≦ T≦Tg +40° C.

wherein Tg represents a glass transition temperature of the helical chiral polymer.

3. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the sheet in an amorphous state contains polylactic acid as the helical chiral polymer, and wherein the sheet is heated at from 20 ° C. to 170 ° C. for from 5 sec to 60 min in the first step.

4. The process for producing a polymeric piezoelectric material according to claim 1 , wherein an annealing treatment is conducted after the second step.

5. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the crystallinity of the polymeric piezoelectric material is from 20% to 40.8%.

6. The process for producing a polymeric piezoelectric material according to claim 1 , wherein an internal haze of the polymeric piezoelectric material with respect to visible light is 40% or less.

7. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the standardized molecular orientation MORc of the polymeric piezoelectric material is from 4.0 to 10.0.

8. The process for producing a polymeric piezoelectric material according to claim 1 , wherein a piezoelectric constant d 14 measured by a displacement method at 25° C. of the polymeric piezoelectric material is 1 pm/V or higher.

9. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the helical chiral polymer is a polylactic acid-type polymer having a main chain comprising a repeating unit represented by the following formula (1):

10. The process for producing a polymeric piezoelectric material according to claim 1 , wherein an optical purity of the helical chiral polymer is 95.00% ee or higher.

11. The process for producing a polymeric piezoelectric material according to claim 1 , wherein a piezoelectric constant d 14 measured by a displacement method at 25° C. of the polymeric piezoelectric material is from 3 pm/V to 6.4 pm/V.

12. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the crystallinity of the polymeric piezoelectric material is from 36.3% to 40.8%, and the product of the standardized molecular orientation MORc and the crystallinity is from 113 to 185.

13. The process for producing a polymeric piezoelectric material according to claim 1 , wherein the crystallinity of the polymeric piezoelectric material is from 20% to 39.3%.

Assignees

• Mitsui Chemicals Inc

Inventors

• Yoshida Mitsunobu
• Nishikawa Shigeo
• Shimizu Masaki
• Fukuda Hiroshi

Classifications

• B29K2995/0039

  Amorphous · CPC title

• B29K2995/0003

  having particular electrical or magnetic properties, e.g. piezoelectric · CPC title

• B29C55/005

  characterised by the choice of materials · CPC title

• C08G63/08

  Lactones or lactides · CPC title

• H01L41/193

  Electricity · mapped topic