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Polymeric piezoelectric material, and process for producing the same

Inactive Publication Date: 2014-02-20
MITSUI CHEM INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a polymeric piezoelectric material that has a high piezoelectric constant, is transparent, and has suppressed deterioration of its longitudinal tear strength. Furthermore, a process for producing this material is also provided.

Problems solved by technology

However, polymeric piezoelectric materials are inferior to PZT in terms of piezoelectricity, and therefore improvement of the piezoelectricity has been demanded.
However, there has been a problem in view of practical use that the orientation of permanent dipoles achieved by a poling treatment tends to relax, because an opposite electric charge of water or an ion in the air can easily attach to a polarized film surface in the direction of canceling the orientation, and the piezoelectricity declines remarkably with time.

Method used

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  • Polymeric piezoelectric material, and process for producing the same
  • Polymeric piezoelectric material, and process for producing the same
  • Polymeric piezoelectric material, and process for producing the same

Examples

Experimental program
Comparison scheme
Effect test

first embodiment

[0136]The first embodiment of a process for producing a polymeric piezoelectric material according to the present invention includes, for example, a first step of heating a sheet in an amorphous state containing the optically active polymer (namely, a helical chiral polymer with the weight-average molecular weight from 50,000 to 1,000,000 having optical activity) to obtain a pre-crystallized sheet, and a second step of stretching the pre-crystallized sheet in biaxial directions (for example, while stretching mainly in a uniaxial direction, simultaneously or successively stretched in a direction different from said stretching direction).

[0137]Generally, by intensifying a force applied to a film during stretching, there appears tendency that the orientation of optically active polymers is promoted, and the piezoelectric constant is enhanced, meanwhile, crystallization is progressed to increase the crystal size, and consequently the internal haze also increases. Further, as the result ...

second embodiment

[0189]The second embodiment of a process for producing a polymeric piezoelectric material according to the present invention includes a step of stretching a sheet containing the optically active polymer (preferably a sheet in an amorphous state) mainly in a uniaxial direction and a step of an annealing treatment, in the order mentioned.

[0190]In the second embodiment the step of stretching mainly in a uniaxial direction is a step of conducting at least the principal stretching (according to need secondary stretching is further carried out).

[0191]The respective conditions for the step of stretching mainly in a uniaxial direction and the step of an annealing treatment in the second embodiment are regulated appropriately so that the crystallinity of a polymeric piezoelectric material to be produced becomes from 20% to 80% and that the product of the standardized molecular orientation MORc and the crystallinity becomes from 25 to 250.

[0192]Moreover, preferable conditions for the step of ...

example 1

[0204]A polylactic acid-type resin (Registered trade mark LACEA, H-400; weight-average molecular weight Mw: 200,000; made by Mitsui Chemicals, Inc.) was charged into an extruder hopper, heated to 220° C. to 230° C., extruded through a T-die, and contacted with a cast roll at 50° C. for 0.3 min to form a 230 μm-thick pre-crystallized sheet (pre-crystallization step). The crystallinity of the pre-crystallized sheet was measured to find 4%.

[0205]The obtained pre-crystallized sheet was stretched biaxially simultaneously with heating at 80° C. to 3.0-fold in the TD direction by a tenter method (principal stretching) and to 2.0-fold in the MD direction by a roll-to-roll method (secondary stretching) to obtain a film (stretching step).

[0206]The film after the stretching step was contacted with rolls heated to 145° C. by a roll-to-roll method to perform an annealing treatment, and quenched to produce a polymeric piezoelectric material (annealing treatment step). In this regard, the quenchin...

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Abstract

The invention provides a polymeric piezoelectric material including 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.

Description

TECHNICAL FIELD[0001]The present invention relates to a polymeric piezoelectric material and a process for producing the same.BACKGROUND ART[0002]As a piezoelectric material a ceramic material of PZT (PBZrO3-PbTiO3 type solid solution) has been heretofore broadly used. However, since PZT contains lead, a polymeric piezoelectric material, which imposes less environmental burden and has higher flexibility, has been currently coming into use as a piezoelectric material.[0003]Currently known polymeric piezoelectric materials can be classified roughly into 2 types. Namely, into 2 types of poled polymers, as represented by nylon 11, polyvinyl fluoride, polyvinyl chloride, polyurea, etc. and ferroelectric polymers, as represented by (β-type) polyvinylidene fluoride (PVDF), a vinylidene fluoride-trifluoroethylene copolymer (P(VDF-TrFE)) (75 / 25), etc.[0004]However, polymeric piezoelectric materials are inferior to PZT in terms of piezoelectricity, and therefore improvement of the piezoelectr...

Claims

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Application Information

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IPC IPC(8): H01L41/193H01L41/45
CPCH01L41/45H01L41/193H10N30/857H10N30/098H10N30/00H10N30/20B29C35/02B29C55/005B29C55/16B29C71/02B29C2071/022B29K2067/046B29K2995/0003B29K2995/0039B29K2995/004C08G63/08
Inventor YOSHIDA, MITSUNOBUNISHIKAWA, SHIGEOSHIMIZU, MASAKIFUKUDA, HIROSHI
Owner MITSUI CHEM INC
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