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
  • H10N30/80—Constructional details
  • H10N30/85—Piezoelectric or electrostrictive active materials
  • H10N30/857—Macromolecular compositions
• • 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
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T29/00—Metal working
  • Y10T29/42—Piezoelectric device making

Definitions

• Piezoelectric polymer film element in particular polymer film, and method for its production
• the present invention relates to a piezoelectric polymer film element, in particular a polymer film, comprising a polymer matrix, wherein in the polymer matrix cavity articles are arranged.
• the invention further relates to a process for producing such polymer film elements.
• ferroelectrets are made of polymeric materials with a cavity structure that can store electrical charges over long periods of time. Some known ferroelectrets have a cellular cavity structure and are formed either as foamed polymer films or as multilayer systems of polymer films or polymer fabrics. If electrical charges are distributed on the different surfaces of the cavities according to their polarity, each charged cavity represents an electric dipole. If the cavities are now deformed, this causes a change in the dipole size and leads to a flow of current between external electrodes. The ferroelectrets can exhibit a piezoelectric activity comparable to that of other piezoelectrics.
• No. 4,654,546 describes a process for producing polypropylene foam films as a precursor to a ferroelectret film.
• the polymer films are mixed with filler particles.
• the filler used is, for example, titanium dioxide.
• the polypropylene films are biaxially stretched after extrusion so that small voids are formed in the film around the filler particles. This method has since been applied to other polymers. For example, in M. Wegener, M. Paajanen, O. Voronina, R. Schulze, W. Wirges, and R.
• Another method for producing foamed ferroelectret polymer films is the direct physical foaming of a homogenous film with supercritical fluids, for example with carbon dioxide.
• Advanced Functional Materials 17, 324-329 (2007), Werner Weges, Michael Wegener, Olena Voronina, Larissa Zirkel, and Reimund Gerhard-Multhaupt Optimized preparation of elastically soft, highly piezoelectric, cellular ferroelectrets from nonvoided poly (ethylene terephthalate) films "and in Applied Physics Letters 90, 192908 (2007), P. Fang, M. Wegener, W. Wirges, and R. Gerhard L.
• T129 pp 274-277, 2007 describes the structuring of the polymer layers by pressing a metal lattice onto a polymer layer stack comprising at least three FEP and PTFE layers superimposed in alternating succession.
• a polymer layer stack comprising at least three FEP and PTFE layers superimposed in alternating succession.
• the polymer layers are interconnected according to the grid structure such that dome-shaped or bubble-shaped cavities with a rectangular base area form between the bars.
• this method leads to ferroelectrets of different quality, since the formation of uniform cavities is difficult to control, especially with increasing number of layers.
• Another method for producing vesicular cavities using a grid is by RAC Altafim, HC Basso, RAP Altafim, Lima L., CV De Aquino, L. Gonalves Neto and R. Gerhard-Multhaupt, in "Piezoelectrets from thermo-formed bubble structures of fluoropolymer-electret films", IEEE Transactions on dielectrics and Electrical Insulation, Vol. 13, No.5, pp. 979-985, 2006.
• two superimposed Teflon-FEP films between a metal grid and an upper cylindrical metal part are arranged. This structure is pressed with the metal grid on a lower cylindrical metal part, which has openings for applying a vacuum.
• the FEP films are heated by the upper metal part and by a vacuum applied to the lower metal part the lower film is pulled into the openings of the grid and corresponding cavities are formed.
• the described methods using a lattice to form voids in the polymer multilayer composites are expensive and difficult to scale-up.
• Piezoelectric materials continue to be of increasing interest for commercial applications such as sensor, actuator and generator systems. For economy, an applicability of a manufacturing process on an industrial scale is essential.
• the invention is therefore based on the object to provide new alternative Piezoelektret materials and alternative methods for producing such Piezoelektret materials with which defined Piezoelektret cavity structures can be produced and which can be carried out easily and inexpensively on a large scale and industrial scale.
• a piezoelectric polymer film element in particular a polymer film, which comprises a polymer matrix, wherein hollow space particles are arranged in the polymer matrix.
• a film of polymer material is provided which contains hollow space particles as fillers.
• a "cavity article” may, in particular, be understood as meaning a particle which has a defined shape and a defined void volume enclosed therein before being introduced into the polymer matrix
• the cavity structure in particular the shape and size of the cavities themselves, can be precisely predetermined
• the cavity volume in the polymer film elements according to the invention, in particular polymer films can advantageously be precisely determined by the size and density of the cavity articles
• the number of cavity articles per unit area of a polymer film can be determined the average (maximum) distance of the cavity article to each other, can be suitably selected according to the desired properties of the polymer film elements.
• the cavity articles may be in the form of hollow balls, and / or hollow strands (tubes).
• the hollow space articles preferably have the smallest possible size distribution.
• the cavity articles may not only have substantially the same height, but also a substantially equal diameter of the cavities.
• the height of the cavity articles is understood to be the (outer) height in the direction of the thickness of the polymer film.
• "essentially the same height” and "a substantially equal diameter” can be understood to mean that the cavity articles have the same height and / or within the production tolerance, for example less than 5%, in particular less than 1% have the same diameter.
• the further conditions and properties for the piezoelectric polymer film element such as, for example, a poling process or the adjustment of the resonant frequency can advantageously be optimized particularly well.
• the size, in particular the height and / or the diameter, of the hollow space particles is preferably adjusted in relation to the thickness of the polymer matrix in such a way that the polymer matrix completely surrounds the hollow space particles.
• the polymer matrix formed as a polymer film can have continuous planar surfaces.
• volume fraction of the cavity particles can according to the invention in relation to the polymer matrix
• volume fractions of the cavity articles in relation to the polymer matrix for example> 50% by volume, or even> 60% by volume, of the cavity articles are possible.
• the volume fractions of the cavity articles and the polymer matrix complement each according to the invention to 100 vol .-%
• the size, in particular the height and / or the diameter, of the cavity articles may preferably be selected such that after completion of the piezoelectric polymer film element according to the invention, the resulting total void volume is as large as possible.
• the cavities may have a height of> 1 ⁇ to ⁇ 800 ⁇ , in particular of> 2 ⁇ to ⁇ 300 ⁇ , in particular of> 5 ⁇ to ⁇ 100 ⁇ and / or a diameter of
• the cavity articles are formed of a substantially electrically non-conductive and / or electrically non-polarizable material.
• the cavity articles can be arranged both homogeneously and heterogeneously distributed in the polymer matrix.
• the hollow space articles can be arranged homogeneously distributed.
• the hollow space articles disposed in the polymer matrix may be formed in the same or different shapes.
• a plurality of cavity articles formed in a first mold and a plurality of cavity articles formed in a second mold, and optionally a plurality of spacer elements, et cetera, formed in a third mold may be arranged in the polymer matrix.
• the hollow space articles formed in different shapes can in turn be distributed homogeneously or heterogeneously.
• the electromechanical, in particular piezoelectric, properties of the piezoelectric polymer film element provided according to the invention can be adapted by selecting the hollow article shape, hollow particle arrangement and / or hollow space particle distribution.
• the cavity articles can be formed, optionally independently of one another, of any material which is suitable for enabling a poling process in the cavities and for separating and storing the charges formed after the charging process.
• the cavity articles may be formed from glass or a polymer or even a substantially electrically non-conductive, non-electrically polarizable ceramic material.
• the hollow space articles may be formed of mineral glass, in particular silica glass or quartz glass.
• Polymers for the formation of hollow article according to the invention can be chosen almost arbitrarily.
• polymeric materials are selected for the cavity articles which are good charge storage devices and have good electret properties.
• polymeric materials are polycarbonates, perfluorinated or partially fluorinated polymers and copolymers such as PTFE, fluorinated ethylene propylene (FEP), perfluoroalkoxyethylenes (PFA), polyesters such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), cyclo-olefin polymers, cyclo-olefin -Copolymers, polyimides, in particular polyetherimide, polyethers, polymethylmethacrylate and polypropylene or polymer blends thereof mentioned. With these materials, good to very good piezo activities can be achieved.
• the invention wide Material selection can advantageously also allow adaptation to specific applications.
• the hollow space articles may be in the form of glass spheres and / or polymer spheres and / or glass strands and / or polymer strands and / or ceramic spheres and / or strands.
• the polymer matrix can consist of an electrically non-conductive polymer or electrically non-conductive polymer mixture, in particular of an elastomer, non-conductive according to the invention meaning that the polymer has a sufficiently high electrical resistance to produce a suitable polymer To enable poling process.
• the polymer matrix in a preferred embodiment can consist of a polyurethane elastomer, silicone elastomer, acrylate elastomer, or rubber or a mixture thereof.
• Particularly high piezoelectric constants of the polymer film element according to the invention can be achieved with these comparatively soft materials.
• the stiffness of the polymer matrix can be advantageously adapted according to the invention to specific requirements and / or applications.
• the polymer matrix can be formed from any material which is suitable for enabling a poling process and for separating and storing the charge layers formed in the cavities after the charging process.
• the polymer matrix may be selected from the group consisting of preferably elastomeric rubber derivatives, polyester resins, unsaturated polyesters, alkyd resins, phenolic resins, amino resins, amido resins, ketone resins, xylene-formaldehyde resins, epoxy resins, phenoxy resins, polyolefins, polyvinyl chloride, polyvinyl esters, polyvinyl alcohols, polyvinyl acetals , Polyvinyl ethers, polyacrylates, polymethacrylates, polystyrenes, polycarbonates, polyesters, copolyesters, polyamides, silicone resins, polyurethanes, in particular one- or two-component polyurethane resins or silicone resins, and mixtures of said polymers, in particular as
• the polymer matrix of the piezoelectric polymer film element according to the invention in particular a polymer film, a thickness (D) of> 5 ⁇ to ⁇ 1000 ⁇ , preferably from> 10 ⁇ to ⁇ 500 ⁇ , for example, from> 20 ⁇ to ⁇ 250 ⁇ have ,
• the invention further relates to a method for producing a piezoelectric polymer element, comprising the steps:
• Suitable polymeric cavity articles can be produced, for example, by surrounding a propellant, for example isobutane or isopropane, with a selected polymer material and then controlled heating.
• a propellant for example isobutane or isopropane
• pore formers for the formation of cavities in the particles, which can be removed without residue, for example in a sintering process.
• suitable hollow space articles for example glass hollow spheres from 3M, are commercially available.
• the glass bubbles 3M TM Glass Bubbles Kl, 3M TM Glass Bubbles Kl 5, 3M TM Glass Bubbles S38, or 3M TM Glass Bubbles S60 are suitable in the present invention.
• the introduction of the hollow space particles into the polymer matrix can be effected, for example, by mixing into the polymer material, for example into a granulate of a thermoplastic material which is subsequently melted, or already melted polymer material from which the polymer matrix is formed. Subsequently, the polymeric material for the polymer matrix with the hollow space particles distributed therein can then be solidified, for example dried and / or crosslinked and / or solidified. This can be done, for example, thermally, by irradiation with ultraviolet light, by irradiation with infrared light and / or by drying.
• the intended cavities can be mixed with a first component of a two-component silicone resin and to this mixture, the second component of the silicone resin can subsequently be added and mixed again.
• the polymer material mixture with the mixed-in cavity particles can then be shaping, for example, processed into a polymer film.
• the polymer material can also be provided, for example, in dissolved form or mixed with solvent, so that the hollow space particles are introduced into a polymer material solution or solvent material sufficiently softened by solvent. Subsequently, by drying, so removing the solvent, the solidification of the polymer material with the introduced Hohlraumpumblen done.
• the drying can be carried out, for example, by evaporation at room temperature. However, it can also be thermally and / or assisted with the aid of an air flow and accelerated.
• step C) of the process to produce the polymer film element according to the invention, the polymer matrix can be formed and / or shaped from a polymer material as polymer film.
• the product resulting from the process ie the polymer film element, may be a polymer film which contains hollow space particles as fillers.
• the formation and / or shaping of the polymer film element from the polymer material with the introduced cavity articles can be effected by extrusion or by resin injection molding.
• Thermoplastic polymer materials may also be other well-known thermoplastic processing techniques, such as injection molding, for shaping the polymer material into the polymer film.
• the formation of the polymer element, in particular a polymer film according to the invention by film-forming processes as they are also known from the paint application, for example, to a substrate and optionally subsequent detachment of the polymer film from the substrate, take place.
• film-forming processes are doctoring, spin coating, dipcoating, spray coating, curtain coating, slot dye coating, and / or roller application methods, for example with roller application units for hot melt adhesives from Hardo Maschinenbau GmbH (Bad Salzuflen, Germany).
• the invention likewise encompasses the fact that the polymer matrix is applied directly to an electrode, for example by a film-forming method mentioned above, for example by spin-coating, so that advantageously a subsequent detachment of the resulting polymer film can be dispensed with.
• the electrode may be, for example, a metal plate.
• the polymer material for forming the polymer matrix is at least one polymer, preferably an elastomeric polymer material selected from the group consisting of rubber, rubber derivatives, unsaturated polyesters, alkyd resins, phenolic resins, amino resins, amido resins, ketone resins, xylene-formaldehyde resins, epoxy resins , Phenoxy resins, polyolefins, polyvinyl chloride, polyvinyl esters, polyvinyl alcohols, polyvinyl acetals, polyvinyl ethers, polyacrylates, polymethacrylates, polystyrenes, polycarbonates, polyesters, copolyesters, polyamides, silicone resins, polyurethanes, and mixtures of these polymers.
• one- or two-component silicone resins or one- or two-component polyurethanes can be used as polymer material for the polymer matrix.
• step D) the charging of the polymer film element can take place with opposite electrical charges.
• dipoles are produced in the cavities of the particles.
• step E) the application of electrodes to the surfaces of the polymer film element, in particular a polymer film, may be included as step E).
• process step D) and then process step E) and also process step E) and then process step D) can be carried out.
• the charging in step D) can be carried out, for example, by direct charging, that is to say applying a high electric field, applying an electrical voltage to the electrodes or by corona discharge.
• the charging can be done by a two-electrode corona arrangement.
• the needle voltage may be at least> 10 kV, for example at least> 25 kV, in particular at least> 30 kV.
• the charging time may be at least> 20 s, for example at least> 30 s, in particular at least> 1 min.
• the electrodes can be applied to the polymer film element in step E) by methods known to those skilled in the art. These include, for example, methods such as physical vapor deposition (PVD), sputtering, and / or vapor deposition, chemical vapor deposition (CVD), printing, knife coating, spin coating in question.
• PVD physical vapor deposition
• CVD chemical vapor deposition
• the electrodes can also be glued in prefabricated form.
• the electrode materials may be conductive materials known to those skilled in the art.
• metals, metal alloys, semiconductors, conductive oligo- or polymers such as polythiophenes, polyanilines, polypyrroles, conductive oxides or mixed oxides, such as indium tin oxide (ITO), or polymers filled with conductive fillers come into question.
• Suitable fillers for polymers filled with conductive fillers are, for example, metals such as silver, aluminum and / or copper, conductive carbon-based materials, for example carbon black, carbon nanotubes (CNTs), graphenes or conductive oligo- or polymers.
• the filler content of the polymers is preferably above the percolation threshold, which is characterized in that the conductive fillers form continuous electrically conductive paths.
• the electrodes may also be structured in the context of the present invention.
• the electrodes may be structured so that the piezoelectric polymer element active and passive areas.
• the electrodes can be structured in such a way that, in particular in the sensor mode, the signals are detected spatially resolved and / or, in particular in the actuator mode, the active regions can be specifically controlled. This can be achieved, for example, by providing the active regions with electrodes, whereas the passive regions have no electrodes.
• the invention further relates to an electromechanical transducer comprising at least a first polymer film, which comprises hollow particles as fillers.
• an electromechanical transducer comprises at least one piezoelectric polymer film according to the invention. Furthermore, it may comprise at least two electrodes, in particular electrode layers, one electrode contacting the first surface of the polymer film and the other electrode contacting the second surface of the polymer film.
• Another object of the present invention is the use of a piezoelectric polymer film element or electromechanical transducer according to the invention as a sensor, generator and / or actuator, for example in the electro-mechanical and / or electroacoustic field, especially in the field of energy from mechanical vibrations (energy harvesting), the acoustics , ultrasound, medical diagnostics, acoustic microscopy, mechanical sensors, in particular pressure force and / or strain sensors, robotics and / or communication technology, in particular in loudspeakers, vibration transducers, light deflectors, membranes, modulators for fiber optics, pyroelectric detectors , Capacitors and control systems.
• FIG. 1 shows a schematic cross section through a first embodiment of a polymer film element according to the invention.
• FIG. 2 shows a schematic cross section through another embodiment of a polymer film element according to the invention after polarity.
• FIG. 1 shows a schematic cross section through a first embodiment of a piezoelectric polymer film element 1 according to the invention, which comprises a polymer matrix 2 and cavity articles 3 with cavities 4 enclosed therein.
• a piezoelectric polymer film element 1 which comprises a polymer matrix 2 and cavity articles 3 with cavities 4 enclosed therein.
• the cavity articles 3 may also be randomly distributed, arranged in multiple layers, offset from each other and / or one above the other in the polymer matrix 2.
• the cavity articles 3 are configured as hollow balls and have substantially the same height and substantially the same diameter.
• the polymer matrix 2 may be formed of an elastomeric polymer material non-conductive and non-polarizable material, such as glass, a polymeric material or a ceramic material, and may be blended into a polymeric film prior to final shaping of the polymer matrix, for example, by extrusion of the selected polymer material into the polymeric material.
• FIG. 2 shows a schematic cross section through a further embodiment of the polymer film element 1 according to the invention from FIG.
• the application of the electrodes 5, 5 ' can take place, for example, by physical vapor deposition, sputtering, and / or vapor deposition, chemical vapor deposition, printing, knife coating, spin coating, or by bonding on prefabricated electrodes.
• the polymer film element 1 is already poled in this embodiment, that is to say the cavities 4 of the cavity articles 3 are charged with opposite electrical charges.
• the polarity can be done for example by a corona discharge.
• all process steps of the manufacturing process according to the invention are at least partially automated. By the following example, the invention will be further explained without being limited to this.
• the polymer matrix material used was the Wacker Elastosil RV 625.
• the Wacker Elastosil material is a two-component silicone resin system.
• Glass hollow spheres namely 3M TM glass bubbles Kl from 3M, were used as cavity articles.
• the ratio of Wacker Elastosil polymer matrix to glass hollow spheres was 83% by volume to 17% by volume, with the proportions by volume of polymer matrix material and glass hollow spheres always adding up to 100% by volume.
• the glass bubbles were mixed with the component A of Elastosil in a SpeedMixer at a rotation of 2700 per minute. Then the component B of the Elastosil was added to it and mixed again for one minute in the SpeedMixer at a rotation of 2700 per minute.
• the material mixture of polymer matrix material and glass bubbles was spun onto bronze substrates. Rotation speeds in spinning were set between 600 and 1000 revolutions per minute for 30 to 120 seconds.
• the samples were annealed for 24 hours at 80 ° C in an oven. The sample was poled with a -15 kV corona without grid voltage. Then, the polymer film was peeled from the substrate and the piezoelectric coefficient was measured by the dynamic method at a frequency of 2 Hz. The piezo coefficient was directly after the poling at 45 pC / N.
• the following three main components are required for the measuring device: Force generator, force measuring device and charge measuring device.
• a power generator an electric shaker type 4810 from Brüel & Kjaer was chosen.
• the vibration exciter makes it possible to exert a defined force as a function of the input voltage.
• This vibrator was mounted on a movable platform, its position in the vertical direction manually is adjustable. The height adjustment of the vibration exciter is necessary for clamping the samples. In addition, it can be used to set the static pre-pressure required for the measurement.
• a DS 345 function generator from Stanford Research Systems was used in conjunction with a Brüel & Kjaer Type 2718 power amplifier.
• the force gauge used was a force sensor Type 8435 from Burster.
• the force sensor is designed for both pressure and tension measurements in the range of 0 to 200 N. However, the force may only be vertical, so that no lateral force components or torques act on the sensor. To ensure this, the force sensor was provided with a cylindrical pressure guide rail with a stainless steel bolt sliding almost smoothly therein. At the free end of the bolt was a two-centimeter-wide polished plate, which served as a support surface for the samples. The signals from the force sensor are detected by a Burster type 9243 module amplifier and passed on to a G.99 4094 oscilloscope.
• the charge meter used was a charge amplifier Type 2635 from Brüel & Kjaer.
• the charge amplifier makes it possible to detect charges up to 0, 1 pC.
• the two sides of the sample must be electrically connected to the charge amplifier.
• the electrical contact to the lower side of the sample is made possible by the support surface, which in turn is connected to the entire structure.
• the upper side of the sample was connected to the charge amplifier through the brass pressure-applying punch.
• the stamp is electrically insulated from the rest of the structure by an attachment made of Plexiglas on the oscillator and connected by a cable to the charge amplifier.
• the cable should be as thin and soft as possible in order to avoid mechanical stress and thus distortion of the measurement results.
• the measured signal is finally passed from the charge amplifier to the oscilloscope.
• a pre-pressure of 3 N (static) was set and measured with an amplitude of 1 N (dynamic).

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• 2009
  • 2009-12-04 EP EP09015050A patent/EP2330648A1/de not_active Withdrawn
• 2010
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  • 2010-11-29 US US13/512,361 patent/US20130026411A1/en not_active Abandoned
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