EP0089770A1
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Piezoelectric and pyroelectric film
Assignee: British Telecommunications PLC
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Filing: 1983-03-07
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Granted: —
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Expires: 2003-03-07
Abstract
Abstract Film (20) with piezoelectric and pyroelectric properties is obtained by extruding PVDF, stretching the extrudate and applying a corona discharge, preferably at the place where stretching occurs. The PVDF may be homopolymer, but copolymers of at least 50 mole % of vinylidene fluoride with tetrafluoroethylene and/or trifluoroethylene may be used.
Inventors
- 👤 Philippos Pantelis
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-31 00:16
CPC Classifications
H; H10; H10N; H10N30/00; H10N30/01; H10N30/09; H10N30/098; H10N15/00; H10N15/10; H10N30/04; H10N30/045
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
50 words
Film having piezoelectric properties said film (20) being formed of a polymer containing at reast 50 mole% of'vinylidene fluoride units, characterised in that said film has a thickness between 100 micrometres and 1000 micrometres, a length of at least 1m and a hydrostatic piezoelectric coefficient of at least 10 pC/N.
Claim 2
Dependent Claim
50 words
Film having piezoelectric properties said film (20) being formed of a polymer containing at reast 50 mole% of'vinylidene fluoride units, characterised in that said film has a thickness between 100 micrometres and 1000 micrometres, a length of at least 1m and a hydrostatic piezoelectric coefficient of at least 10 pC/N.
Claim 3
Dependent Claim
18 words
Film according to claim 1 characterised in that the hydrostatic piezoelectric coefficient is between 10 and 30 pC/N.
Claim 4
Dependent Claim
20 words
Film according to either claim 1 or claim 2 characterised by having a width of not more than 10 cm.
Claim 5
Dependent Claim
20 words
Film according to any one of claims 1, 2 or 3 characterised by being in the form of a tube.
Claim 6
Dependent Claim
20 words
Tube according to claim 4 characterised in that the tube has an outer diameter of not more than 3 cm.
Claim 7
Dependent Claim
22 words
Film according to any one of the preceding claims characterised by having electrodes in contact with one or both of its surfaces.
Claim 8
Independent Claim
65 words
A method of making film with piezoelectric and/or pyroelectric properties, characterised in that the method comprises extruding a polymer containing at least 50 mole% of vinylidene fluoride units to form film, stretching the extrudate and subjecting it to corona discharge treatment by applying a transverse electric field of at least 10 volts per micrometre of thickness up to the maximum field which it will withstand.
Claim 9
Independent Claim
65 words
A method of making film with piezoelectric and/or pyroelectric properties, characterised in that the method comprises extruding a polymer containing at least 50 mole% of vinylidene fluoride units to form film, stretching the extrudate and subjecting it to corona discharge treatment by applying a transverse electric field of at least 10 volts per micrometre of thickness up to the maximum field which it will withstand.
Claim 10
Dependent Claim
21 words
A method according to claim 7 characterised in that the field strength is 30 to 150 volts per micrometre of thickness.
Claim 11
Dependent Claim
20 words
A method according to either claim 7 or claim 8 characterised in that the applied voltage is 5kV to lOkV.
Claim 12
Independent Claim
27 words
A method according to any one of claims 7, 8 or 9 characterised in that the polymer is a copolymer of vinylidene fluoride with tetrafluoroethylene and/or trifluoroethylene.
Claim 13
Independent Claim
19 words
A method according to any of claims 7 to 9 characterised in that the polymer is homopolymer poly(vinylidene fluoride).
Claim 14
Independent Claim
55 words
A method according to any.one of claims 7 to 11 characterised in that the extrudate is stretched by passing through a slow haul-off and then a fast haul-off which runs three to six times faster than the slow haul-off, the extrudate being heated to a temperature not exceeding its crystalline melting point between the haul-offs.
Claim 15
Dependent Claim
22 words
A method according to claim 12 characterised in that the corona discharge treatment is applied to the heated portion of the extrudate.
Claim 16
Dependent Claim
19 words
A method according to claim 13 characterised in that the corona discharge treatement is applied to the neck-down region.
Claim 17
Independent Claim
24 words
A method according to any one of claims 7 to 14 characterised in that the film is extruded in the form of a tube.
Claim 18
Dependent Claim
32 words
Film made by a method according to any one of claims 7 to 15 characterised by having conductors suitable for acting as electrodes in contact with one or both of its surfaces.
Claim 19
Dependent Claim
70 words
Apparatus for performing a method according to any one of claims 7 to 15 which comprises an extruder (11) for producing poly(vinylidene fluoride) film (12), slow and fast haul-offs (14,16) for orienting the extruder in the machine direction; characterised in that the apparatus also includes poling means (15) for applying poling voltage to said extrudate, said poling means being situated between the slow haul-off (14) and the fast haul-off (16).
Claim 20
Dependent Claim
23 words
Apparatus according to claim 17 in which the extruder (11) is a cross-head extruder for producing film in the form of a tube.
References Cited (Backward Citations)
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