EP0000449B1 - Improvements in or relating to piezoelectric materials and to methods for producing such materials. - Google Patents

Improvements in or relating to piezoelectric materials and to methods for producing such materials. Download PDF

Info

Publication number
EP0000449B1
EP0000449B1 EP78300160A EP78300160A EP0000449B1 EP 0000449 B1 EP0000449 B1 EP 0000449B1 EP 78300160 A EP78300160 A EP 78300160A EP 78300160 A EP78300160 A EP 78300160A EP 0000449 B1 EP0000449 B1 EP 0000449B1
Authority
EP
European Patent Office
Prior art keywords
film
piezoelectric
materials
treatment
poling
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired
Application number
EP78300160A
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0000449A1 (en
Inventor
Philippos Pantelis
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Post Office
Original Assignee
Post Office
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Post Office filed Critical Post Office
Publication of EP0000449A1 publication Critical patent/EP0000449A1/en
Application granted granted Critical
Publication of EP0000449B1 publication Critical patent/EP0000449B1/en
Expired legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N30/00—Piezoelectric or electrostrictive devices
    • H10N30/01—Manufacture or treatment
    • H10N30/09—Forming piezoelectric or electrostrictive materials
    • H10N30/098—Forming organic materials
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S522/00—Synthetic resins or natural rubbers -- part of the class 520 series
    • Y10S522/911—Specified treatment involving megarad or less
    • Y10S522/912—Polymer derived from ethylenic monomers only

Definitions

  • This invention relates to piezoelectric materials and to methods for producing such materials.
  • the invention has particular reference to polymeric materials exhibiting piezoelectric properties and to the production of such materials for use in electro-acoustic transducer devices.
  • PVF 2 polyvinylidene fluoride
  • PVF 2 polyvinylidene fluoride
  • polarising involves the application to the material of a high electric field, usually at an elevated temperature.
  • the material usually in the form of a film, has electrodes applied to both faces, is placed in an oven and when at the required temperature a polarising voltage is applied across the electrodes.
  • a polarising voltage is applied across the electrodes.
  • temperatures in the range of from 100°C-120°C are used in conjunction with voltages in the order of one megavolt per centimetre of film thickness.
  • An example of such a treatment is given in French patent application No. 2 108 561 of Kureha Kagaku Kogyo Kabushiki Kaisha.
  • the enhanced level of piezoelectricity produced in the film is a function of the magnitude of both the treatment temperature and the applied electric field.
  • the extent to which the treatment temperature can be raised is limited by the melting point of the material, whilst the extent to which the applied electric field can be increased is limited by the dielectric strength of the film.
  • Defects in the film for example bubbles, pin holes, scratches and included foreign bodies constitute weak spots in the film and electrical breakdown of the film is liable to occur at such spots. When breakdown occurs, damage is caused to the film and to the electrodes and results sometimes in the rejection of a length of film which is thus wasted. Breakdowns are more frequent at higher applied electric fields and elevated temperatures.
  • French patent application No. 2 031 247 of Western Electric Company Incorporated refers to the possibility of obtaining an electret by electron bombardment of a dielectric.
  • a method of enhancing the piezoelectric properties of a polymeric material exhibiting such properties is characterised in that, before subjecting the material to a "poling" treatment in an electric field, the material is exposed whilst in an atmosphere inert with respect to the material and at substantially room temperature to a dose of gamma (y) radiation lying within the range of from about 1 Mrad to about 99 Mrads.
  • the invention also provides a method of enhancing the piezoelectric activity of polyvinylidene fluoride by exposing the latter whilst in an atmosphere inert with respect thereto and at substantially room temperature to a dose of y radiation lying within the range of from about 1 Mrad to about 99 Mrads after which the material is subjected to a poling treatment.
  • the improved enhancement of the piezoelectric properties of the material renders the material more useful in nearly all of its applications. For example, it improves the sensitivity of an electro-acoustic transducer fitted with a piezoelectric material according to the invention.
  • the polyvinylidene fluoride is in the physical form of a biaxially oriented film.
  • an atmosphere inert with respect to the material is intended to include irradiation in a vacuum in which the air pressure does not exceed 10- 3 mm Hg (0.13 N/m 2 ) as well as irradiation in an atmosphere that does not cause embrittlement of the material undergoing irradiation. It has been found that it is important to exclude oxygen from the atmosphere.
  • An example of an inert atmosphere is a nitrogen atmosphere and this can be obtained by flushing out with nitrogen the chamber in which irradiation is to be effected to remove all air.
  • the dose of y radiation to which the material is exposed preferably lies in the range of from 12 Mrad to 99 Mrads (both limits included).
  • the enhancement of the piezoelectric properties of the material is known to be particularly pronounced at these exposure levels.
  • the invention also provides a polymeric material exhibiting piezoelectric properties which have been enhanced by a method as defined above.
  • a strip of the film 1 having, for example, a thickness of 25 ⁇ m, a width of about 30 cm and a length of a few hundred metres, is then wound onto a reel 2 and placed in a dessicator 3, maintained at room temperature and exhausted to 10- 5 mm Hg (1.3 x 10- 3 N/m 2 ), oxygen being excluded.
  • the dessicator is in turn placed in a concrete bunker 5 and irradiated from a source of radiation 6, for example Cobalt 60.
  • the film 1 is exposed to a preselected dose of radiation lying within the range of from 1 to 99 Mrads and illustrated schematically by arrows 4 in Figure 1; the direction and intensity of radiation incident on the film depends on the position of the dessicator 3 in the bunker.
  • the dessicator 3 is removed from the bunker, the reel 2 is removed from the dessicator and the film is poled by application across the electrodes of an electric field while the film is at an elevated temperature.
  • the aluminium electrodes are formed on the film before irradiation but the formation of electrodes may be deferred until after irradiation if desired.
  • the sample was then placed in a vacuum chamber maintained at room temperature and exhausted to 10- 5 mm Hg (1.3 x 10- 3 N/m 2 ), oxygen being excluded.
  • the chamber was then removed to a source of y radiation, namely Cobalt 60. After irradiation, the sample was removed. Subsequently, the sample was "poled" by application across the electrodes of an electric field while the sample was at an elevated temperature.
  • the sample was subjected to tests to measure its piezoelectric activity.
  • the activity was measured by stressing the sample in a direction lying along the machine or roll direction of the film.
  • the following table shows the piezoelectric activity of the film.
  • the first column of the table sets out the irradiation treatment to which the portion of film was exposed, whilst the second column gives details of the "poling" treatment.
  • the first figure is the poling field
  • the second is the poling temperature
  • the third is the duration of the poling treatment.
  • the third column gives the measured value of the piezoelectric coefficient for stress applied along the machine direction.
  • a given level of piezoelectric activity may be produced by employing the irradiation treatment in conjunction with a poling treatment employing lower levels of polarising potential than would be necessary to produce that level of piezoelectric activity employed without irradiation. Such a combination will enable material which would previously have been rejected as defective to be utilised.
  • Polymeric materials other than polyvinylidene fluoride, which exhibit latent piezoelectricity may also be treated by processes embodying the invention. While not constituting a limitation in the scope of the invention, such other materials would importantly include copolymers of polyvinylidene fluoride, e.g. coplymer of ethylene and vinylidene fluoride, copolymer of vinylidene fluoride and tetrafluoroethylene, copolymer of vinylidene fluoride and vinyl fluoride, copolymer of vinylidene fluoride and trifluoromonochloroethylene, and the like. Also included are such halogen containing polymers as polyvinyl fluoride, polyvinyl chloride and the like.
  • the material be in film form or in the form of a biaxially orientated film.
  • the treated material is suitable for use in microphone transmitters, receivers and pressure transducers.

Landscapes

  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Treatments Of Macromolecular Shaped Articles (AREA)
  • Organic Insulating Materials (AREA)
  • Manufacture Of Macromolecular Shaped Articles (AREA)
EP78300160A 1977-07-19 1978-07-18 Improvements in or relating to piezoelectric materials and to methods for producing such materials. Expired EP0000449B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB3023777 1977-07-19
GB3023777 1977-07-19

Publications (2)

Publication Number Publication Date
EP0000449A1 EP0000449A1 (en) 1979-01-24
EP0000449B1 true EP0000449B1 (en) 1981-10-21

Family

ID=10304468

Family Applications (1)

Application Number Title Priority Date Filing Date
EP78300160A Expired EP0000449B1 (en) 1977-07-19 1978-07-18 Improvements in or relating to piezoelectric materials and to methods for producing such materials.

Country Status (4)

Country Link
US (1) US4239608A (enrdf_load_stackoverflow)
EP (1) EP0000449B1 (enrdf_load_stackoverflow)
JP (1) JPS5421597A (enrdf_load_stackoverflow)
DE (1) DE2861190D1 (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10104605A1 (de) * 2001-02-02 2002-08-14 Daimler Chrysler Ag Klebeverbindung von Bauteilen, Kleber sowie Verfahren zur Herstellung der Klebeverbindung

Families Citing this family (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5140297A (en) * 1981-04-02 1992-08-18 Raychem Corporation PTC conductive polymer compositions
US4951382A (en) * 1981-04-02 1990-08-28 Raychem Corporation Method of making a PTC conductive polymer electrical device
US4951384A (en) * 1981-04-02 1990-08-28 Raychem Corporation Method of making a PTC conductive polymer electrical device
US4845838A (en) * 1981-04-02 1989-07-11 Raychem Corporation Method of making a PTC conductive polymer electrical device
US5195013A (en) * 1981-04-02 1993-03-16 Raychem Corporation PTC conductive polymer compositions
US4955267A (en) * 1981-04-02 1990-09-11 Raychem Corporation Method of making a PTC conductive polymer electrical device
US5227946A (en) * 1981-04-02 1993-07-13 Raychem Corporation Electrical device comprising a PTC conductive polymer
US4393093A (en) * 1981-06-12 1983-07-12 Pennwalt Corporation Preparation of high gamma (α)phase poly(vinylidene fluoride) piezoelectric materials
FR2535113B1 (fr) * 1982-10-22 1986-05-16 Thomson Csf Procede de fabrication d'un materiau polymere piezo- ou pyroelectrique comportant une etape de reticulation
US4808352A (en) * 1985-10-03 1989-02-28 Minnesota Mining And Manufacturing Company Crystalline vinylidene fluoride
US5204013A (en) * 1986-07-03 1993-04-20 Rutgers, The State Unversity Of New Jersey Polarized products
JPH0796607B2 (ja) * 1987-09-07 1995-10-18 富山県 高分子圧電材及びその製造方法
JP2585018B2 (ja) * 1987-09-08 1997-02-26 富山県 圧電型感圧素子及びその製造方法
JP5392090B2 (ja) * 2007-11-21 2014-01-22 コニカミノルタ株式会社 超音波受信用振動子、その製造方法、超音波探触子及び超音波医用画像診断装置

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE544324A (enrdf_load_stackoverflow) * 1955-01-11
US3644605A (en) * 1969-02-11 1972-02-22 Bell Telephone Labor Inc Method for producing permanent electret charges in dielectric materials
JPS5040720B1 (enrdf_load_stackoverflow) * 1970-09-26 1975-12-26
JPS5146919B1 (enrdf_load_stackoverflow) * 1971-02-09 1976-12-11
JPS5146280B2 (enrdf_load_stackoverflow) * 1971-09-21 1976-12-08
JPS4855273A (enrdf_load_stackoverflow) * 1971-11-11 1973-08-03

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10104605A1 (de) * 2001-02-02 2002-08-14 Daimler Chrysler Ag Klebeverbindung von Bauteilen, Kleber sowie Verfahren zur Herstellung der Klebeverbindung

Also Published As

Publication number Publication date
JPS5421597A (en) 1979-02-17
EP0000449A1 (en) 1979-01-24
US4239608A (en) 1980-12-16
JPS624875B2 (enrdf_load_stackoverflow) 1987-02-02
DE2861190D1 (en) 1981-12-24

Similar Documents

Publication Publication Date Title
EP0000449B1 (en) Improvements in or relating to piezoelectric materials and to methods for producing such materials.
Xie et al. Changes in wettability with time of plasma-modified perfluorinated polymers
US5444103A (en) Modified polytetrafluoroethylene and process for its production by irradiation
US3924324A (en) Method of making electret
Altafim et al. Laminated tubular-channel ferroelectret systems from low-density polyethylene films and from fluoroethylene-propylene copolymer films-A comparison
JPS6217801B2 (enrdf_load_stackoverflow)
JP2002513514A (ja) 強誘電性のリラクサー・ポリマー
US3794986A (en) Pyroelectric element of polymer film
EP0239637B1 (en) Crystalline vinylidene fluoride
Chen et al. Influence of radiation environments on space charge formation in/spl gamma/-irradiated LDPE
CA1204077A (en) Reverse field stabilization of polarized polymer films
An et al. Significantly improved piezoelectric thermal stability of cellular polypropylene films by high pressure fluorination and post-treatments
US3711941A (en) Fabrication of electret transducer elements using low energy electron beam
DE2911856B2 (de) Verfahren zur Erhöhung der Durchschlagsfestigkeit an einem Film aus Polyvinylidenfluorid
CN102227790A (zh) 驻极体材料的制造方法
Chong et al. Space charge and charge trapping characteristics of cross-linked polyethylene subjected to ac electric stresses
Rychkov et al. Influence of charge density on the trap energy spectrum in fluoroethylenepropylene copolymer films with chemically modified surfaces
US4565615A (en) Glow discharge stabilization of piezoelectric polymer film
US4248808A (en) Technique for removing surface and volume charges from thin high polymer films
Yu et al. Contact charge accumulation and reversal on polystyrene and PTFE films upon repeated contacts with mercury
JP2023093582A (ja) 架橋フッ素樹脂の品質管理方法及び架橋フッ素樹脂
US2967240A (en) Method of detecting and eliminating flaws in solid material of high molecular order
JPH0254848B2 (enrdf_load_stackoverflow)
Kolbeck Failure modes in piezoelectric poly (vinylidene fluoride)
DeReggi et al. Radiation-induced polarization in polyvinyl chloride revisited

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): BE DE FR GB NL SE

17P Request for examination filed
GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): BE DE FR GB NL SE

REF Corresponds to:

Ref document number: 2861190

Country of ref document: DE

Date of ref document: 19811224

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19820610

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: SE

Payment date: 19820630

Year of fee payment: 5

Ref country code: BE

Payment date: 19820630

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 19820731

Year of fee payment: 5

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19820930

Year of fee payment: 5

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Effective date: 19830718

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Free format text: THE PATENT HAS BEEN ANNULLED BY A DECISION OF A NATIONAL AUTHORITY

Effective date: 19830730

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Effective date: 19840201

NLV4 Nl: lapsed or anulled due to non-payment of the annual fee
PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19840330

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19840403

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

REG Reference to a national code

Ref country code: GB

Ref legal event code: 732

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19940620

Year of fee payment: 17

EUG Se: european patent has lapsed

Ref document number: 78300160.5

Effective date: 19850610

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19950718

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19950718

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT