WO2013157505A1 - エレクトレット構体及びその製造方法並びに静電誘導型変換素子 - Google Patents
エレクトレット構体及びその製造方法並びに静電誘導型変換素子 Download PDFInfo
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- WO2013157505A1 WO2013157505A1 PCT/JP2013/061130 JP2013061130W WO2013157505A1 WO 2013157505 A1 WO2013157505 A1 WO 2013157505A1 JP 2013061130 W JP2013061130 W JP 2013061130W WO 2013157505 A1 WO2013157505 A1 WO 2013157505A1
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- WIPO (PCT)
- Prior art keywords
- silica
- fluororesin film
- island
- electret
- electret structure
- Prior art date
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Images
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
- H01G7/02—Electrets, i.e. having a permanently-polarised dielectric
- H01G7/028—Electrets, i.e. having a permanently-polarised dielectric having a heterogeneous dielectric
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
- H01G7/02—Electrets, i.e. having a permanently-polarised dielectric
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02N—ELECTRIC MACHINES NOT OTHERWISE PROVIDED FOR
- H02N1/00—Electrostatic generators or motors using a solid moving electrostatic charge carrier
- H02N1/06—Influence generators
- H02N1/08—Influence generators with conductive charge carrier, i.e. capacitor machines
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/08—Mouthpieces; Microphones; Attachments therefor
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
- H04R19/00—Electrostatic transducers
- H04R19/01—Electrostatic transducers characterised by the use of electrets
- H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
- H01G7/02—Electrets, i.e. having a permanently-polarised dielectric
- H01G7/021—Electrets, i.e. having a permanently-polarised dielectric having an organic dielectric
- H01G7/023—Electrets, i.e. having a permanently-polarised dielectric having an organic dielectric of macromolecular compounds
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01G—CAPACITORS; CAPACITORS, RECTIFIERS, DETECTORS, SWITCHING DEVICES, LIGHT-SENSITIVE OR TEMPERATURE-SENSITIVE DEVICES OF THE ELECTROLYTIC TYPE
- H01G7/00—Capacitors in which the capacitance is varied by non-mechanical means; Processes of their manufacture
- H01G7/02—Electrets, i.e. having a permanently-polarised dielectric
- H01G7/025—Electrets, i.e. having a permanently-polarised dielectric having an inorganic dielectric
-
- 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
- Y10T29/49—Method of mechanical manufacture
- Y10T29/49002—Electrical device making
- Y10T29/49226—Electret making
Definitions
- the present invention uses an electret structure having heat resistance and pressure resistance, which can maintain a high charge retention even when exposed to high temperatures or strongly contacted with an insulating layer, a manufacturing method thereof, and the electret structure.
- the present invention relates to an electrostatic induction conversion element such as an electret condenser microphone (ECM).
- ECM electret condenser microphone
- FIG. 24 shows an example of the structure of the ECM.
- the ECM includes a vibrating electrode 10 that vibrates with sound pressure, an electret film 11 that faces the vibrating electrode 10 through a gap held by a spacer ring 14, a back electrode 12 that is fixed to the back of the electret film 11, An FET 13 that amplifies a signal output from the back electrode 12 and a metal case 15 that is electrically connected to the vibration electrode 10 are provided.
- electrot structure the structure of the electret film 11 as shown in FIG. 24 and the back electrode 12 integrated therewith and a similar structure are referred to as “electret structure”.
- the electret film 11 and the back electrode 12 are provided with holes 16a and 16b leading to the gap space so as not to suppress the vibration of the vibration electrode 10.
- the metal case 15 is grounded, and a DC power source E for driving the FET 13 is externally attached together with a resistor R.
- the gate electrode of the FET 13 is connected to the back electrode 12, the source electrode is grounded through the metal case 15, and the drain electrode that outputs the amplified audio signal is connected to an external device via the coupling capacitor C.
- a fluororesin film having high charge retention characteristics is widely used.
- Typical electret materials include fluorine such as polytetrafluoroethylene (PTFE), perfluoroalkoxyethylene copolymer (PFA), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and polychlorotrifluoroethylene (PCTFE). Resin.
- PTFE polytetrafluoroethylene
- PFA perfluoroalkoxyethylene copolymer
- FEP tetrafluoroethylene-hexafluoropropylene copolymer
- PCTFE polychlorotrifluoroethylene
- FIG. 25 shows an example of a reflow temperature profile used when a component is mounted on a substrate such as a cellular phone.
- reflow using Pb-free solder has been performed from the viewpoint of removing toxic substances.
- the mounted component is held at 217 to 260 ° C. for about 30 to 60 seconds in the reflow process, and 5 ° C. at 260 ° C. It is heated for about 10 seconds.
- the fluororesin film is thus exposed to a high temperature exceeding 250 ° C., the trapped negative charge cannot be retained, and much of it is lost.
- the fluororesin is modified by irradiation with radiation (see Patent Document 1), or inorganic fine particles are included in the fluororesin (see Patent Document 2). ) An attempt is being made.
- an ECM using a silicon oxide film having good charging stability even at a high temperature as an electret material instead of a fluororesin has been proposed (see Patent Document 3).
- the inventor of the present invention first bonded an electret insulating layer to the upper surface of an electret layer having a back electrode on the lower surface, and provided a vibrating electrode insulating film on the lower surface of the vibrating electrode, and the electret insulating layer and the vibrating electrode insulating film.
- the charge retention rate of the electret film 11 decreases at the high temperature due to the following reasons. As shown in FIG. 26, the negative charge a trapped on the electret film 11 constituting the electret structure 1 p is partially passed through the defect level of the electret film 11 at a high temperature, and a part of the negative charge a is in the surface direction of the electret film 11. And the charge retention rate decreases. The other part of the trapped negative charge a diffuses in the thickness direction of the electret film 11 via the defect level of the electret film 11 at a high temperature.
- the positive charge b induced in the back electrode 12 is injected into the electret film 11 from the interface defect between the back electrode 12 and the electret film 11 (or the electric field concentration portion due to the surface roughness of the back electrode 12). Spread in the vertical direction. When the diffused negative charge and positive charge are combined, the negative charge disappears and the charge retention rate decreases.
- Patent Document 3 describes that the conventional silicon oxide film electret has a significantly reduced moisture resistance and cannot withstand practical use. This is influenced by the property of silica having high hydrophilicity. Moisture in the air is adsorbed by the highly hydrophilic silicon oxide film, and the positive charge of the electrode diffuses through the adsorbed water through the surface of the silicon oxide film, and combines with the negative charge to disappear. To do.
- the present invention was devised in view of such circumstances, and a new electret structure capable of maintaining a high charge retention rate even at a high temperature, a manufacturing method of the electret structure, and an electrostatic induction conversion using the electret structure
- the object is to provide an element.
- the gist of the present invention is an electret structure having a layer.
- the silica layer of the electret structure according to the first aspect of the present invention is composed of a plurality of island-like silica regions covering the fluororesin film in a state of being isolated from each other, and negative charges are attached to the island-like silica regions.
- the “electrode” of the electret structure according to the first aspect is, for example, when the electret structure of the present invention is applied to an electret condenser microphone (ECM), “back electrode” or “vibration electrode” of the ECM.
- ECM electret condenser microphone
- the electrode on the side constituting the electret structure corresponds to any one of the above.
- the negative charge injected into the island-like silica region by corona discharge or plasma discharge is fixed at a deep trap level in the island-like silica region, so that the negative charge does not diffuse into the fluororesin film even at the reflow processing temperature. .
- the negative charge shown in FIG. 26 does not diffuse in the surface and thickness direction. Therefore, the disappearance of the negative charge held in the island-like silica region is merely disappearance due to the combination with the positive charge (hole) diffusing from the electrode, and the charge retention characteristics at high temperature are improved.
- the island-like silica regions are isolated from each other on the fluororesin film having a high surface resistance, almost no diffusion of the negative charge in the surface direction shown in FIG. 26 occurs at room temperature. The diffusion of positive charges from the electrode is blocked by the fluororesin film. Therefore, even under high humidity, the moisture resistance characteristics do not deteriorate due to the adsorbed water in the island-like silica region.
- the fluororesin film described in the first aspect an electrode formed on one surface of the fluororesin film, and a silica layer formed on the other surface of the fluororesin film are provided.
- the present invention relates to a method for manufacturing an electret assembly.
- a plurality of island-like silica regions are isolated from each other by spraying a silica sol in which fine particles of amorphous silica are dispersed in a solvent onto the other surface of the fluororesin film.
- the present invention is summarized as a method for producing an electret assembly, which includes forming a silica layer with a plurality of island-like silica regions on the other surface and attaching negative charges to the island-like silica regions.
- the fluororesin film described in the first aspect an electrode formed on one surface of the fluororesin film, and a silica layer formed on the other surface of the fluororesin film are provided.
- the present invention relates to a manufacturing method of a method of manufacturing an electret structure.
- the method of manufacturing an electret structure according to the third aspect includes a plurality of island-like silica regions made of a thin film of amorphous silica or polycrystalline silica by physical vapor deposition (PVD) or chemical vapor deposition (CVD).
- a method for producing an electret structure comprising forming a silica layer on a second surface of a fluororesin film in an isolated state, forming a silica layer with a plurality of island-like silica regions, and attaching negative charges to the island-like silica regions. This is the gist.
- the fluororesin film described in the first aspect a silica layer formed on one side of the fluororesin film, and an electrode formed on the other side of the fluororesin film.
- the present invention relates to a manufacturing method of a method of manufacturing an electret structure.
- a plurality of island-like silica regions constituting a silica layer are formed in an isolated state on one surface of the fluororesin film, and then the other surface of the fluororesin film.
- the gist of the present invention is a method for producing an electret structure, which includes simultaneously applying a negative charge to the island-like silica region when forming the electrode by welding.
- a fluororesin film a back electrode formed on one side of the fluororesin film, a silica layer formed on the other side of the fluororesin film, and the other side of the fluororesin film.
- the gist of the invention is an electrostatic induction conversion element including a vibrating electrode disposed opposite to a silica layer on a surface and an insulating layer provided on a surface of the vibrating electrode facing the silica layer.
- the silica layer of the electrostatic induction conversion element according to the fifth aspect is composed of a plurality of island-like silica regions covering the fluororesin film in an isolated state, and negative charges are attached to the island-like silica regions.
- the electrostatic induction conversion device According to the fifth aspect, even when the vibrating electrode vibrates due to the sound pressure and the insulating layer on the vibrating electrode side contacts the island-like silica region, the deep trap level of the island-like silica region is reached. The attached negative charges do not diffuse into the insulating layer, and ECM deterioration can be avoided. Therefore, the maximum allowable sound pressure of ECM can be significantly improved.
- the sixth aspect of the present invention includes a fluororesin film, a back electrode formed on one side of the fluororesin film, a silica layer formed on the other side of the fluororesin film, and the other side of the fluororesin film.
- a gist of the invention is an electrostatic induction conversion element including a vibrating electrode disposed opposite to a silica layer on a surface.
- the silica layer of the electrostatic induction conversion element according to the sixth aspect is composed of a plurality of island-like silica regions covering the fluororesin film in a state of being isolated from each other, and on the fluororesin film of the plurality of island-like silica regions
- the distribution density is high in a region facing the periphery of the vibration electrode and low in a region facing the center of the vibration electrode.
- the arrangement of the island-like silica regions in the electrostatic induction conversion element according to the sixth aspect can be arbitrarily set by ink jet printing or screen printing.
- the present invention it is possible to provide a new electret structure capable of maintaining a high charge retention rate even at a high temperature, a manufacturing method of the electret structure, and an electrostatic induction conversion element using the electret structure.
- ECM electrostatic induction type conversion element
- FIG. 1 It is typical sectional drawing which shows the electrostatic induction type conversion element (ECM) which concerns on the 1st Embodiment of this invention. It is a top view which shows the sample for a measurement test of the electret structure used for the electrostatic induction type conversion element which concerns on 1st Embodiment. It is sectional drawing which shows typically the electret structure which concerns on 1st Embodiment. It is typical sectional drawing which shows the formation method of the silica aggregate by the spray method as a manufacturing method of the electret structure which concerns on 1st Embodiment. It is a figure which shows the moisture-proof test result of the electret structure which concerns on 1st Embodiment.
- ECM electrostatic induction type conversion element
- FIG. 9 is a diagram showing the relationship between the retention time and the charge retention rate of the electret assembly according to the first embodiment, obtained as a result of performing a heating test using the temperature profile of temperature increase / decrease in FIG.
- FIG. 15A is a schematic cross-sectional view showing an electret structure according to a modification (first modification) of the first embodiment of the present invention in which an island-like silica region drop prevention coating is provided.
- FIG. 15B is a schematic cross-sectional view showing an electret structure according to a second modification of the first embodiment. It is typical sectional drawing which shows the electrostatic induction type conversion element (ECM) which concerns on the modification (3rd modification) of the 1st Embodiment of this invention. It is typical sectional drawing which shows the electrostatic induction type conversion element (ECM) which concerns on the 2nd Embodiment of this invention. It is typical sectional drawing which shows the electrostatic induction type conversion element (ECM) which concerns on the 3rd Embodiment of this invention. It is typical sectional drawing which shows the electrostatic induction type conversion element which concerns on the 4th Embodiment of this invention.
- FIG. 20A is a schematic cross-sectional view showing the position of the first fold line for folding the flexible electrostatic induction conversion element according to the fourth embodiment in FIG. 20B.
- FIG. 20 is a side view showing the position of a second fold line for further folding the electrostatic induction conversion element folded in half in FIG. 20 (a)
- FIG. 20 (c) is a side view of FIG. 20 (b).
- FIG. 10 is a side view showing a completed view of the conversion element according to the fourth embodiment in which an extraction electrode is attached to the electrostatic induction conversion element that is folded in half and finally folded in four.
- first to fifth embodiments of the present invention will be described with reference to the drawings.
- the same or similar parts are denoted by the same or similar reference numerals.
- the drawings are schematic, and the relationship between the thickness and the planar dimensions, the ratio of the thickness of each layer, and the like are different from the actual ones. Therefore, specific thicknesses and dimensions should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.
- the following first to fifth embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention is the material of component parts. The shape, structure, arrangement, etc. are not specified as follows. The technical idea of the present invention can be variously modified within the technical scope defined by the claims described in the claims.
- an electrostatic induction conversion element includes a vibrating electrode (vibrator) 10 made of a conductor having a flat vibrating surface, and a vibrating electrode 10.
- a fluororesin film 21 defined by a flat first main surface that opposes the vibration surface and a second main surface that opposes the first main surface in parallel, and an upper surface (first main surface) of the fluororesin film 21.
- a microphone capsule comprising electrostatic induction charge measuring means (13, R, C, E) for measuring the charge.
- the silica layer 20 is composed of a plurality of island-like silica regions 201 that are adhered to the fluororesin film 21 in a state of being isolated from each other, but from the back electrode 22 as shown in FIGS. 3 (a) and 3 (b).
- the polarization directions in the fluororesin film 21 toward the lower surfaces of the plurality of island-like silica regions 201 are aligned.
- the fluororesin film 21 shown in FIG. 1, the back electrode 22 formed on the bottom surface of the fluororesin film, and the top surface of the fluororesin film 21 ( The entire laminated structure including the silica layer 20 formed on the first main surface is referred to as an “electret structure”.
- the electrode formed on one surface of the fluororesin film 21 constituting the “electret structure” may be the vibrating electrode 10. That is, the “electrode formed on one surface of the fluororesin film” forming a part of the structure defining the “electret structure” of the present invention may be a vibrating electrode or a back electrode.
- the fluororesin film 21 and the back electrode 22 are provided with holes 16 a and 16 b leading to a “gap space” defined between the fluororesin film 21 and the vibration electrode 10 so as not to suppress vibration of the vibration electrode 10. ing.
- the electret assembly 1 and the vibrating electrode 10 according to the first embodiment are housed in a conductive (metal) metal case 15, but the metal case 15 is grounded. When no load is applied, the first main surface (upper surface) of the fluororesin film 21 faces the vibration surface of the vibration electrode 10 in parallel.
- the electrostatic induction charge measuring means 13, R, C, E is connected to the back electrode 22.
- An amplifier (FET) 13 housed inside the metal case 15 and an output circuit (R, C, E) connected to the FET 13 are provided.
- the output circuit (R, C, E) is externally attached to the outside of the metal case 15, one terminal is grounded, and the DC power source E that drives the FET 13 is connected between the DC power source E and the FET 13.
- An output resistor R and a coupling capacitor C having one electrode connected to a connection node between the output resistor R and the FET 13 and having the other electrode as an output terminal are provided.
- the gate electrode of the FET 13 is connected to the back electrode 22, the source electrode is grounded through the metal case 15, and the drain electrode that outputs the amplified audio signal is connected to the external circuit (external device not shown) via the coupling capacitor C. ) Is connected. That is, an external circuit is connected to the output terminal of the coupling capacitor C, which is the output terminal of the electrostatic induction charge measuring means (13, R, C, E), and the communication device or recording device is connected to the microphone by the external circuit. The signal processing necessary for this is performed.
- the electrostatic induction charge measuring means (13, R, C, E) of the ECM according to the first embodiment amplifies the potential between the back electrode 22 and the vibrating electrode 10 constituting the electret structure 1 by the FET 13, The electrostatic induction charge that is electrostatically induced in the silica layer 20 in accordance with the displacement of the vibration surface of the vibration electrode 10 is measured.
- the vibrating electrode 10, the fluororesin film 21, and the back electrode 22 of the microphone capsule shown in FIG. 1 each have a disk shape with a radius of 3 to 40 mm.
- an insulating spacer ring 14 is sandwiched between the disc-shaped fluororesin film 21 and the vibration electrode 10.
- a peripheral portion of the disc-shaped vibrating electrode 10 is connected to the upper end surface of the spacer ring 14. For this reason, the electret structure 1, the spacer ring 14, and the vibration electrode 10 are housed in a metal case 15 to form a microphone capsule.
- the spacer ring 14 defines the distance between the vibrating electrode 10 and the fluororesin film 21 that face each other in parallel.
- the thickness of the fluororesin film 21 can be selected from about 10 to 400 ⁇ m
- the thickness of the back electrode 22 can be selected from about 10 to 500 ⁇ m
- the thickness of the vibration electrode 10 can be selected from about 1 to 100 ⁇ m. Specific thicknesses and radii of the fluororesin film 21 and the back electrode 22 are determined according to required performance and specifications.
- the electret structure 1 may be sandwiched between an insulating spacer ring 14 and a holder.
- the holder may be made of an insulator so that the outer periphery is in contact with the inner wall of the metal case 15 and has a substantially cylindrical shape similar to the spacer ring 14.
- the FET 13 is electrically connected to the back electrode 22 through solder fused in the vicinity of the center of the back electrode 22.
- the back electrode 22 and the fluororesin film 21 are provided with holes 16 a and 16 b penetrating the back electrode 22 and the fluororesin film 21.
- the holes 16 a and 16 b are formed between the fluororesin film 21 and the vibration electrode 10.
- a high-insulating gas (insulating gas) may be enclosed in the space (if necessary) and sealed using the holes 16a, 16b and the like. Nitrogen, sulfur hexafluoride, etc. can be used as the insulating gas.
- the dielectric breakdown strength is increased and the discharge is less likely to occur.
- the amount of charge on the surface of the fluororesin film 21 attached by discharge can be reduced, and the sensitivity is improved.
- the sensitivity can be improved even when the gap space between the fluororesin film 21 and the vibrating electrode 10 is in a vacuum state instead of filling the insulating gas or the insulating fluid.
- the vibrating electrode 10 and the electret assembly 1 do not have to be in the shape of a disk, and may have other geometric shapes such as an ellipse or a rectangle. In this case, other members such as the metal case 15 may be used as the vibrating electrode 10. Of course, it is designed to be adapted to the geometric shape of the electret structure 1.
- the fluororesin film 21 has a surface resistance of 10 16 ⁇ / sq. Although it is above, heat resistance, insulation, excellent water repellency are required, polytetrafluoroethylene (PTFE), perfluoroalkoxyethylene copolymer (PFA) generally used as electret, Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), polychlorotrifluoroethylene (PCTFE) or the like satisfies the conditions. These resins have a surface resistance of 10 16 ⁇ / sq.
- the back electrode 22 is required to be conductive and to withstand the reflow temperature.
- Al alloy, stainless steel, Ti alloy, Ni alloy, Cr alloy, Cu alloy and the like can be used.
- FIG. 2A shows a sample N obtained by vacuum-welding a fluororesin film 21 made of PFA having a thickness of 12.5 ⁇ m to which silica agglomerate has not been applied to one side of an Al plate having a thickness of 0.1 mm, and sample N
- a silica sol (colloidal silica, 20 wt%, primary particle size 40-50 nm, Snowtex 20L, manufactured by Nissan Chemical Industries, Ltd.) is sprayed on the entire surface of the fluororesin film 21 made of PFA to form a silica aggregate on the entire surface of the fluororesin film.
- a sample U 0 is shown
- FIGS. 2B and 2C are plan views of the island-like silica region 201 disposed on the fluororesin film 21.
- an Al punch plate mask 31 as shown in FIG. 4B is placed on the fluororesin film 21 made of the same PFA as used for the sample N, and colloidal silica is made of fluororesin film.
- colloidal silica is applied onto a fluororesin film at a discharge amount of 360 pl (picoliter) by an ink jet printing apparatus (LabJet, manufactured by MicroJet), and an isolated silica aggregate is 100 ⁇ m.
- Sample I formed in a square lattice of pitch is shown.
- colloidal silica atomized by an ultrasonic nebulizer is sprayed, but FIGS. 2 (b) and 2 (c) are formed for experiments.
- the arrangement and shape of the island-like silica region 201 of the electret structure used in the actual ECM are not limited to this.
- FIG. 3A schematically illustrates details of the cross-sectional structure of the electret structure 1 according to the first embodiment.
- the island-like silica region 201, the fluororesin film 21, and the back electrode as viewed from the cross-section. 22 is shown.
- the island-like silica region 201 is composed of an aggregate of amorphous silica fine particles.
- Amorphous silica fine particles are fine particles having an average primary particle diameter of 4 to 450 nm, but are dispersed in the solution as aggregates of several hundred nm to several ⁇ m. If the solution in which the aggregates are dispersed is applied onto the fluororesin film 21, island-like silica regions 201 made of aggregates of amorphous silica fine particles can be formed.
- the aggregate of amorphous silica has a large surface area, a large amount of water molecules are adsorbed on the surface, and the apparent dielectric constant of the aggregate increases due to the influence.
- the electric field concentrates on the aggregate of amorphous silica, and negative charges can be selectively attached to the island-like silica region 201.
- the island-like silica region 201 of the electret structure 1 according to the first embodiment is not limited to an aggregate of amorphous silica.
- the island-like silica region 201 is shown in FIG. Alternatively, it may be formed of a thin film of amorphous silica or polycrystalline silica.
- the thin film of amorphous silica or polycrystalline silica shown in FIG. 3B can be formed by vacuum evaporation, sputtering, chemical vapor deposition (CVD), physical vapor deposition (PVD), or the like. .
- CVD chemical vapor deposition
- PVD physical vapor deposition
- island-like silica regions can be selectively formed on the fluororesin film 21.
- FIG. 4A shows an example in which a water-soluble silica sol is applied on a fluororesin film by adjusting the spray amount from the spray nozzle 30 without using a mask.
- 2B and 2C in the formation of the samples U 1 , U 2 and I, as shown in FIG. 4B, the shape of the island-like silica region 201 on the fluororesin film 21 A mask 31 for defining the position is disposed, and a mist 201r of a droplet of silica sol aqueous solution is sprayed from the spray nozzle 30 through the mask 31 onto the fluororesin film 21 to form an island-like silica region 201.
- the mist 201r of the silica sol aqueous solution that has reached the fluororesin film 21 adheres to the fluororesin film 21 as water droplets having a shape close to a sphere.
- the size of the silica aggregate is determined by the size of water droplets formed on the fluororesin and the silica concentration (10 to 50 wt%) of the silica sol.
- the size of the water droplets is not limited to the size of the silica sol droplets (1 ⁇ m to 1 mm) sprayed by the spray nozzle 30, and the mist (mist) 201 r of the silica sol aqueous solution adhering to the fluororesin film is different from each other. The fact that the mist 201r repeatedly adheres and coalesces is also affected.
- island-like silica regions 201 made of isolated silica aggregates are formed.
- the electret structure in which the island-like silica region 201 is formed is subjected to electret processing in which a negative charge is charged by corona discharge or plasma discharge.
- the electretization process itself has been widely performed conventionally, and although not described in detail here, by performing the electretization process, as shown in FIG. Negative charge adheres. This is because a large amount of water molecules contained in the air are chemically adsorbed on the surface of the silica aggregate having a large surface area, and the apparent dielectric constant of the island-like silica region 201 is increased.
- the electric field concentrates on the island-like silica region 201, negative charges are attracted to the island-like silica region 201, and most of the negative charges adhere to the island-like silica region 201.
- the reflow treatment temperature of Pb-free solder is also shown in FIG.
- the diffusion of negative charges in the surface direction and the diffusion in the thickness direction of the fluororesin film 21 hardly occur. Therefore, the negative charge held in the island-like silica region 201 disappears only when combined with the positive charge (holes) diffusing from the back electrode 22.
- the fluororesin film 21 there are defective portions that are inferior in insulation at a certain rate, and holes (positive charges) are likely to diffuse from the back electrode 22 through the defective portions. Therefore, when the island-like silica region 201 exists on the defective portion of the fluororesin film 21, the negative charge attached to the island-like silica region 201 is likely to be lost at a high temperature.
- the probability that the island-like silica region 201 exists on the defect portion of the fluororesin film 21 depends on the area of each island-like silica region 201, and the probability increases when the area is large, and the probability when the area is small. Lower.
- the ECM incorporating the electret assembly 1 according to the first embodiment can perform reflow processing of Pb-free solder when mounted on the substrate.
- silica sol is sprayed onto the fluororesin film 21 to form isolated silica aggregates.
- the silica sol is formed on the fluororesin film 21 by inkjet printing or screen printing. It can also be applied to form an isolated silica aggregate.
- Sample U 1 (diameter of aggregate: 1.5 mm) and sample U 2 (diameter of aggregate: 0.5 mm), and colloidal as shown in FIG.
- Sample I was prepared by applying silica on a fluororesin film at a discharge rate of 360 pl (picoliter) at a single point using an inkjet printing device (LabJet), and forming isolated silica aggregates in a square grid of 100 ⁇ m pitch did.
- inkjet printing device LabJet
- colloidal silica atomized by an ultrasonic nebulizer is sprayed.
- Sample I and Sample U 2 even when compared with the sample N (silica aggregates without), no change in the charge retention characteristics, lowering of moisture resistance by the silica aggregates is eliminated.
- Sample U 1 had a slightly lower charge retention than sample N, but no further decrease in charge retention was observed after about 10 days.
- Sample U 0 (silica aggregate entire surface application) has a monotonous decrease in charge retention, indicating that the moisture resistance is greatly deteriorated by the silica aggregate.
- Table 1 shows the measurement results of samples U 0 , U 1 , U 2 and I after 110 days.
- the ratio of the charge retention amount of the samples U 0 , U 1 , U 2 and I and the charge retention amount of the sample N is shown as the charge retention rate.
- Ds is the diameter of the aggregate
- the relationship between the covering area As and the covering ratio Rs will be considered.
- the surface area of the fluororesin film is Af
- the number of defects per unit area on the surface of the fluororesin film is Pd
- the number of aggregates per unit area is Ns
- FIG. 6 shows the relationship between the product Rs ⁇ As and the charge retention rate r obtained from the measurement results in Table 1.
- the charge retention ratio r is 10 even when silica aggregate is applied to the fluororesin film as compared with the fluororesin film not applied thereto. It can be seen that it can be suppressed at a rate of decrease of less than%.
- the fluororesin film 21 there are defective portions that are inferior in insulation at a certain rate, and holes (positive charges) are easily diffused from the electrodes through the defective portions. Therefore, when the island-like silica region 201 is on the defective portion of the fluororesin film 21, the negative charge attached to the island-like silica region 201 is lost at a high temperature, and the charge retention rate is lowered.
- the charge retention ratio r is proportional to the product of the covering ratio Rs of all the island-like silica regions 201 and the covering area As per island-like silica region, and this product Rs ⁇ As is 0.5 mm. If it is 2 or less, a decrease in the charge retention ratio r at high temperatures can be suppressed.
- the heat resistance characteristics of the electret structure 1 according to the first embodiment were measured by the following method. Samples having the same conditions as Sample N and Sample I were prepared, and electretized so that the surface potential was ⁇ 1 kV by corona discharge. Each sample was gently heated to 300 ° C. on a hot plate at a rate of 4 ° C./min, and during that time, the surface potential of the sample was measured every 5 minutes to examine the charge retention characteristics.
- FIG. 7B shows the temperature rise characteristics during the measurement. The measurement result is shown in FIG.
- the charge retention rate r of a sample under the same conditions as the sample N is indicated by a circle
- the charge retention rate r of a sample under the same conditions as the sample I is indicated by a ⁇ .
- the rate of temperature increase in this experiment is significantly slower than the actual reflow process, and it takes 650 seconds to increase the temperature to 217-260 ° C.
- a temperature range of 217 to 260 ° C. is about 60 seconds. Since the charge retention rate depends on the power of the heating time, the charge retention rate r when the retention time at 217 to 260 ° C. is 60 seconds is calculated from the result of FIG. It is found that the heat resistance is greatly improved, with the sample having the same conditions as the sample I being 92%, which is 59%.
- FIG. 8 shows a temperature profile of temperature rise / fall at this time. At this time, the peak temperature was 262 ° C., and the retention time of 217 ° C. or higher was 151 seconds.
- FIG. 9 is a plot of the relationship between the retention time of 217 ° C. or more and the charge retention ratio r from the results of FIG. 7 and the results of FIG. Further, the curve in FIG. 9 shows the relationship between the charge retention rate r and the retention time predicted from the results in FIG. 7, assuming that the charge retention rate r depends on the power of the heating time. It can be seen from FIG. 9 that the charge retention rate r depends on the power of the retention time for the sample having the same condition as the sample I indicated by a circle.
- the charge retention rate r during the reflow test is significantly lower than the value predicted from the power law of the retention time.
- the cause of this is unknown, but it is presumed that hopping conduction during heating of the negative charge trapped in the trap level is related.
- the negative charge trapped in the trap level repeats hopping conduction to other trap levels during heating, finally reaches the conduction band, and diffuses inside the film.
- the rate of temperature rise is slow, there is a possibility that negative charges are trapped in deeper trap levels by hopping at a low temperature and stabilized. Therefore, it is considered that the sample having the same condition as the sample N has a result as shown in FIG. 9 because the negative charge was easily stabilized when heated by a hot plate having a slow temperature increase rate.
- an ECM according to the first embodiment as shown in FIG. 1 having an outer diameter of 10 mm was manufactured.
- Table 2 shows the results of measuring the average sensitivity of 100 Hz to 10 kHz at that time.
- the sensitivity reduction is suppressed to 3 dB.
- the ECM is required to have a sensitivity decrease within 3 dB after two reflow treatments.
- PTFE having a thickness of 25 ⁇ m is used for the electret.
- the holding time of 217 ° C. or more is 151 seconds, which exceeds the total holding time of the two reflow processes. Therefore, it can be seen that by forming a silica aggregate on the fluororesin film 21, it is possible to manufacture an electret assembly 1 that can withstand a reflow process even with a half thickness of 12.5 ⁇ m using PFA cheaper than PTFE. .
- FIG. 10 shows the result of measuring the relationship between the coating ratio Rs and the charge retention rate r.
- a plurality of samples having different coating ratios Rs are prepared by changing the application interval of the silica aggregate by ink jet printing, and these samples are heated to 250 ° C. according to the temperature rise characteristics of FIG.
- the charge retention rate r at 0 ° C. was measured.
- the horizontal axis represents the coating ratio Rs
- the vertical axis represents the charge retention rate r at 250 ° C.
- the peak temperature of the reflow process needs to be expected to be at least 250 ° C.
- the rate r is required.
- FIG. 10 shows that the above condition is satisfied when the covering ratio Rs is 5% or more. If the covering ratio Rs of the covering area by all of the island-like silica regions 201 does not exist 5% or more, it is not possible to improve the charge retention characteristics at high temperatures. As shown in FIG. 10, even when the coating ratio Rs is 5%, the charge retention characteristics at high temperatures are greatly improved. As described above, a large amount of water molecules are chemically formed on the surface of the silica aggregate. This is because the dielectric constant increases due to adsorption, and most negative charges adhere to the silica aggregate during the electretization process.
- the covering ratio Rs exceeds 90%, the surface resistance drops by an order of magnitude, and the leakage of charges in the surface direction shown in FIG. 26 cannot be ignored.
- the surface resistance needs to be 10 16 or more. Therefore, the covering ratio Rs needs to be set in the range of 5 to 90%. As is apparent from FIG. 10, the desirable range of the coating ratio Rs is 6 to 25%.
- the interval between the silica aggregates the shortest distance along the fluorine film from the silica aggregate to another silica aggregate
- the interval between the silica aggregates needs to be 100 nm or more, and preferably 1 ⁇ m or more.
- the electret structure 1 in which the silica aggregate is formed on the fluororesin film 21 can maintain a large surface potential and has a high electric field compared to the conventional electret structure only of the fluororesin film 21 having no silica aggregate. Can be released.
- a negative charge is adhered as much as possible within a range in which the PFA film does not cause dielectric breakdown. The surface potential reached -1.76 kV.
- the surface potential gradually decreased when left as it was, and decreased to ⁇ 1.26 kV when left as it was for 1 hour.
- the surface potential was It reached -1.98 kV.
- the size of the surface potential is finally improved by about 50% or more by forming the silica aggregate on the fluororesin film 21. .
- the thickness of the fluororesin film 21 required to obtain a constant surface potential is 34% by forming a silica aggregate on the fluororesin film 21 in the electret structure 1 according to the first embodiment. That means it can be reduced. Therefore, the thickness of the fluororesin film 21 can be further reduced.
- the reduction in the thickness of the fluororesin film 21 leads to an increase in the capacitance of the ECM, and as a result, noise can be reduced or further miniaturization can be achieved.
- the thickness of the PFA film used for the fluororesin film 21 is reduced to 7 ⁇ m, the electret structure (sample N (7 ⁇ m)) welded to the Al electrode, and the silica aggregate on the 7 ⁇ m thick PFA film under the same conditions as the sample I
- FIG. 11 shows the behavior of the charge retention ratio r when the electret structure (sample I (7 ⁇ m)) formed in 1 is left at room temperature with a surface potential of ⁇ 1.4 kV by corona discharge.
- the surface potential deterioration is significantly suppressed by applying the silica aggregate on the fluororesin film 21.
- the fluororesin film 21 can be thinned by the silica aggregate according to the electret structure 1 according to the first embodiment.
- the electret structure 1 according to the first embodiment can further improve the charge retention characteristics at high temperatures by performing the following processing: a.
- a silica aggregate When a silica aggregate is applied on the fluororesin film 21 using silica sol, excessive moisture may be retained in a capillary tube or the like inside the silica aggregate. This tendency is particularly remarkable in ink jet printing and screen printing.
- the charge retention rate r at high temperature is improved by heating the electret structure 1 and removing excess water adsorbed on the silica aggregate before the electretization treatment.
- FIG. 7A a sample in which silica aggregates are formed on the fluororesin film 21 by inkjet printing to form the silica layer 20 is heated to 250 ° C. (preheating) to remove excess moisture, The characteristics when charged are shown by squares.
- the preheating temperature may be 100 ° C. or higher as long as unnecessary water other than chemically adsorbed water can be removed. However, a higher temperature is preferable in order to shorten the water removal time. Conversely, even if the fluororesin film 21 is melted by heating to 300 ° C.
- the silica aggregate does not sink into the fluororesin film 21 because there is no significant difference between the density of the fluororesin and silica. Therefore, it is possible to heat to 400 ° C. at which the fluororesin film 21 starts to decompose.
- FIG. 12 shows the measurement of the charge retention rate r when the electret structure 1 in which the silica aggregate is coated on the fluororesin film 21 by inkjet printing is subjected to a heating test up to 300 ° C. after electretizing once.
- the value ( ⁇ ) and the measured value (square) of the charge retention rate r when the sample is electretized again and the heating test up to 300 ° C. is performed again are shown.
- the charge retention characteristics of the electret assembly 1 according to the first embodiment are improved by performing the heat treatment and re-electretization. If the heating temperature after this charging is set to 180 ° C. or higher at which the charge retention rate r starts to decrease in FIG. 12 and is set to 300 ° C. or lower, the charge holding characteristics at high temperatures are improved. In practice, it is desirable to perform heat treatment at a reflow treatment temperature of 250 to 260 ° C.
- the charge retention characteristics of the electret assembly 1 according to the first embodiment at a high temperature are improved. This is because the negative charge is trapped in the deep trap level of the silica aggregate and the negative charge is difficult to diffuse by the electretization treatment at a high temperature.
- FIG. 12 the heat test result of the electret structure 1 which performed electretization by corona discharge at 250 degreeC is shown by (circle). As is clear from FIG. 12, the charge retention characteristics are improved by performing electretization at 250.degree. The normal fluororesin film 21 not coated with the silica aggregate cannot be charged at 250 ° C.
- the silica aggregate when the silica aggregate is coated on the fluororesin film 21, the silica aggregate is negatively charged even at a temperature of 250 ° C. In fact, an electret having a surface potential of ⁇ 1 kV has been obtained.
- the electret structure 1 according to the first exemplary embodiment it was possible to charge up to ⁇ 0.7 kV even at 300 ° C. just below the melting point 310 ° C. of the PFA film used as the fluororesin film 21. If the heating temperature during this charging is set to 180 ° C. or higher at which the charge retention rate r starts to decrease in FIG. 12 and is set to 300 ° C. or lower, the charge holding characteristics at high temperatures are improved. In practice, it is desirable to set the reflow treatment temperature at 250 to 260 ° C.
- the charge retention characteristics at high temperature of the electret assembly 1 according to the first embodiment can be improved.
- the charge retention characteristics at high temperature of the electret assembly 1 according to the first embodiment can be improved.
- the back electrode 22 By providing island-like silica regions 201 that are isolated from each other on the fluororesin film 21, leakage of negative charges in the surface direction shown in FIG. 26 can be prevented, but injection of holes from the back electrode 22 can be prevented. Can not. Therefore, it is important to prevent injection of holes from the back electrode 22 in order to improve charge retention characteristics at high temperatures.
- FIG. 13 About the adhesiveness of the fluororesin film 21 and the back electrode 22, the change of the charge retention rate r by a heating test as shown in FIG. 13 is shown.
- FIG. 13 with respect to an electret structure in which a PFA film having a thickness of 12.5 ⁇ m as a fluororesin film 21 is welded to an Al electrode as the back electrode 22, the welding temperature of the fluororesin film 21 is lowered to intentionally cause poor welding.
- the change in the charge retention ratio r is shown for the sample with ⁇ ( ⁇ mark) and the normal sample with good welding indicated by the ⁇ mark.
- a heating test was performed with the same temperature rise characteristics as shown in FIG.
- the decrease in the charge retention rate r starts from 200 ° C. or lower, and the adhesion at the joint between the back electrode 22 and the fluororesin film 21 is important in improving the charge retention characteristics. I understand that. In the following, three methods (d-1, d-2, d-3) for improving the charge retention characteristics at high temperatures will be described.
- d-1 Smoothing the back electrode (reducing electric field concentration): (1) After the back electrode 22 is polished to reduce the surface roughness, the fluororesin film 21 is welded. (2) Coating the conductive material (metal such as Al, Ti, Cr, Ni, Ag, or carbon) by vapor deposition, physical vapor deposition (PVD), or sputtering on the fluororesin film 21 to form a smooth back electrode 22 Form. (3) A conductive coating (conductive fluorine resin, carbon, metal such as Al, Ti, Cr, Ni, Ag) is applied to the back electrode 22 by vapor deposition, PVD, sputtering and smoothing treatment is performed. Weld.
- the electret assembly 1 it is desirable to smooth the surface of the back electrode 22 formed on one surface of the fluororesin film 21.
- the surface of the back electrode 22 constituting the electret structure 1 is rough, the adhesion at the interface between the back electrode 22 and the fluororesin film 21 is lowered, and local electric field concentration occurs.
- this local electric field concentration holes are easily injected from the back electrode 22 into the fluororesin film 21, and the charge retention rate of the electret structure is lowered.
- Insulating coating (reduction of defective layers): An insulating material having high heat resistance is coated on the back electrode 22 in advance, and an insulating layer having good adhesion to the back electrode 22 is formed.
- the following methods are conceivable for forming the insulating layer: (1) A PTFE dispersion or polyimide varnish is applied to the back electrode 22 by spin coating or dipping and heated to form an insulating layer. (2) An oxide (alumina, chromium oxide, titania, zirconia, etc.) is coated on the back electrode 22 by vapor deposition, PVD, chemical vapor deposition (CVD), or sputtering. And the silica layer 20 is apply
- the surface of the back electrode 22 formed in one surface of the fluororesin film 21 is coat
- an insulating layer having good adhesion interface defects between the back electrode 22 and the fluororesin film 21 can be reduced, and the fluororesin can be removed from the back electrode 22 due to the interface defects. Injection of holes into the film 21 can be suppressed.
- the back electrode 22 formed on the bottom surface of the fluororesin film 21, and the insulation provided between the back electrode 22 and the fluororesin film 21 of course, the electret structure according to the first embodiment is defined by the layer and the silica layer 20 formed on the upper surface of the fluororesin film 21.
- d-3 Charge when welding: Before the back electrode 22 is welded to the fluororesin film 21, a silica aggregate is applied to the fluororesin film 21, and then the fluororesin film 21 is welded to the back electrode 22, and simultaneously charged by corona discharge during this welding. , Negative charge adhesion. By doing so, a negative charge can be attached to the deep trap level of the silica aggregate coated on the fluororesin film 21 having no defect or electric field concentration portion. It should be noted that the same effect can be obtained even if the welding is performed after the corona discharge is charged before the back electrode 22 is welded to the fluororesin film 21, but the effect is greater when charging is performed at the time of welding.
- silica sol droplets or mist 201r are attached to the fluororesin to form water droplets having a nearly spherical shape, and when dried, an isolated silica aggregate is formed.
- silica sol can be sprayed by using various types of nozzles such as a watering nozzle for gardening, a nozzle for spraying paint, and a nozzle for generating mist, which are selected according to the particle diameter.
- atomization by ultrasonic waves used in an ultrasonic nebulizer is also an effective method.
- a spray gun having a nozzle diameter of 0.3 mm and colloidal silica (Nissan Chemical Industries, 20L) is applied to an electret structure in which PTFE having a thickness of 25 ⁇ m as the fluororesin film 21 is baked on a stainless steel electrode as the back electrode 22.
- An electret structure 1 coated with a silica aggregate as shown in FIG. 2 (b) was produced by the method shown in FIG. 4 (a). Then, the behavior of the charge retention ratio r when the surface potential was set to ⁇ 0.4 kV by corona discharge and the reflow test similar to the temperature rise / fall characteristics of FIG. 8 was repeated was examined. The result is shown in FIG.
- the charge retention ratio r was less than 80% after three reflow tests.
- the electret structure 1 in which the silica aggregate shown by ⁇ and coated with a spray gun to form the silica layer 20 has a charge retention ratio r exceeding 90% even after three reflow tests. From this result, even with a simple technique such as a spray gun, according to the electret structure 1 according to the first embodiment, the charge retention rate is obtained by forming the silica layer 20 on the fluororesin film 21 with the silica aggregate. It can be seen that the improvement of r is effective.
- the primary particle diameter of the silica sol can be selected in the range of 4 to 450 nm in order to maintain the state as a colloidal solution.
- the smaller the primary particle size the easier it is for negative charges to collect in the silica aggregates when charging by corona discharge, so the coating area ratio can be reduced, but it is difficult to remove excess moisture inside the aggregates, so that excess moisture can be removed. This heat treatment or charging during heating is required.
- the height of the silica aggregate needs to be smaller than the gap width of the ECM according to the first embodiment. Generally, the gap width of ECM is 25 ⁇ m or less.
- the height of the silica aggregate is 50 ⁇ m or more, it is easy to drop off from the fluororesin film 21 (usually, the silica aggregate is electretized, and the fluororesin is generated by electrostatic force. Strongly attached on top).
- the primary particle diameter of the silica sol is 4 nm or more, the height cannot be lower than this.
- the silica fine particles have already started to aggregate in the colloidal solution, and the size is considered to be several hundred nm to several ⁇ m. Therefore, the height of the aggregate is 4 nm to 50 ⁇ m, and preferably 1 ⁇ m to 25 ⁇ m.
- a silica sol using an organic solvent as a dispersant can also be used.
- the organic solvent include ethanol, methanol, acetone, isopropanol, ethylene glycol, and the like.
- ESD Electrospray deposition
- the spray nozzle 30 or the spray liquid mist 201r is set to a negative potential (negative with respect to the back electrode 22 attached to the fluororesin film 21 to be applied),
- a negative potential negative with respect to the back electrode 22 attached to the fluororesin film 21 to be applied
- both the coating amount of the island-like silica region 201 made of silica aggregate on the fluororesin film 21 and the surface potential of the electret can be controlled.
- the potential of the spray nozzle 30 with respect to the back electrode 22 is set to -1 to -50 kV, and the potential of the mask 31 with respect to the back electrode 22 is set to -0.1 to -5 kV).
- the size of the droplets of the mist 201r is determined by the flow rate of the solution sprayed from the spray nozzle 30, the dielectric constant of the solution, the temperature, and the like, so the size of the mist 201r is several nm to several mm. It can be controlled on the order.
- the silica sol sprayed from the spray nozzle 30 may be either water-soluble or organic solvent-dispersible.
- the repellency of the fluororesin film 21 is not improved. Due to the aqueous property, the silica sol becomes a water droplet mist 201r having a shape close to a sphere and adheres to the fluororesin film 21. In this case, the size of the silica layer 20 is not uniform because it depends on the size of the attached mist 201r. However, the surface potential of the fluororesin film 21 is proportional to the product of the applied amount of the applied mist 201r and the potential of the spray nozzle 30 with respect to the back electrode 22. Therefore, even without the mask 31, the surface potential can be easily controlled by the application amount of the mist 201r and the potential of the spray nozzle 30. By using this technique, nano-level aggregates can be applied, and therefore the aggregate height can be 1 ⁇ m or less.
- silica sol by inkjet printing and screen printing: If the inkjet printing technique and the screen printing technique are used, it is possible to draw the silica layer 20 composed of silica sol droplets at an arbitrary location on the fluororesin film 21. When this method is used, a silica layer 20 made of a uniform silica aggregate can be obtained. At this time, the silica sol may be either water-soluble or organic solvent-dispersible.
- thin-film island-like silica region 201 by vacuum deposition, PVD, CVD, sputtering: It is also possible to form the thin-film island-like silica region 201 using the silica coating technique used for the gas barrier film.
- a thin island silica region 201 may be formed on the fluororesin film 21 masked by vacuum deposition, PVD, CVD, or sputtering.
- FIG. 3B schematically shows the relationship among the thin-film island-like silica region 201, the fluororesin film 21, and the back electrode 22 formed by this method.
- the height of the thin-film island-like silica region 201 needs to be 1 nm or more because it is necessary to form a silica band gap structure. In addition, it is not practical to form a thin island-like silica region 201 having a thickness exceeding 10 ⁇ m by vacuum deposition, PVD, CVD, or sputtering because it takes a very long time. Accordingly, the height is 1 nm to 10 ⁇ m, and preferably 1 nm to 1 ⁇ m. Also in this case, it is necessary to apply the thin film island-like silica region 201 so that the covering ratio Rs ⁇ the covering area As is 0.5 mm 2 or less.
- the thin-film island-like silica region 201 is a porous film. Since the porous film has a large surface area, a large amount of water molecules are adsorbed on the surface and the apparent dielectric constant increases. As a result, when electretization is performed by corona discharge or plasma discharge, the electric field concentrates on the thin island-like silica region 201 made of a porous film, and negative charges are selectively attached to the island-like silica region 201. it can.
- the electret structure 1 of the electrostatic induction conversion device As described above, according to the electret structure 1 of the electrostatic induction conversion device according to the first embodiment, a high charge retention ratio r can be maintained even when exposed to the reflow processing temperature of Pb-free solder. Therefore, the electrostatic induction conversion element according to the first embodiment having the electret assembly 1 can be mounted on the substrate by reflow using Pb-free solder. In the electret structure 1 according to the first embodiment, since the negative charge is trapped in the deep level of the island-like silica region 201, the charge does not diffuse into the fluororesin film 21, and a high charge retention rate r is maintained. it can. Therefore, the maximum allowable displacement of the electrostatic induction conversion element having this electret structure 1 is improved.
- a strong electrostatic force acts between the back electrode 22 through the fluororesin film 21 due to adhesion of negative charges.
- the thickness of the fluororesin film 21 is 12.5 ⁇ m
- the relative dielectric constant is 2.2
- the surface potential is ⁇ 1 kV
- an electrostatic force of 124 kPa or more acts on the island-like silica region 201 (the electrostatic force is the dielectric constant and Expressed as the product of the square of the field strength).
- the island-like silica region 201 Since it is adsorbed by such a strong electrostatic force, the island-like silica region 201 does not fall off due to vibration or a drop impact in daily life. If there is still an impact that may cause the island-like silica region 201 to drop off, as shown in FIG. 15A, a coating film made of a fluororesin is formed on the island-like silica region 201 made of a silica aggregate. Dropping can be prevented by stacking 301.
- the surface of the fluororesin film 21 on which the silica layer 20 composed of island-like silica regions 201 is formed If a covering film 301 is provided, and this covering film 301 is applied to the upper surface of the island-like silica region 201 and the upper surface (front surface) of the fluororesin film 21 between the island-like silica regions 201, In this electret structure 1a, a strong electrostatic force acts between the island-like silica region 201 to which negative charges are attached and the back electrode 22 via the fluororesin film 21, so that in an everyday life vibration or drop impact There is no possibility that the island-like silica region 201 falls off the fluororesin film 21.
- the island-like silica region 201 can be prevented by laminating a coating film 301 such as a fluororesin on the fluororesin film 21 on which the silica layer 20 is formed. it can.
- the fluororesin film 21, the back electrode 22 formed on the bottom surface of the fluororesin film, and the top surface of the fluororesin film 21 are formed.
- the electret structure 1a is defined by the island-like silica region 201 constituting the silica layer 20 and the coating film 301 covering the island-like silica region 201.
- the covering film 301 to be laminated on the island-like silica region 201 may be simply laminated on the fluororesin film 21 as a base material, and the covering film 301 and the fluororesin film 21 may be in dry contact with each other. Then, the covering film 301 and the fluororesin film 21 may be welded. In addition, when electretization is performed, an island-like silica region 201 made of silica aggregate is applied on the fluororesin film 21 as a base material, and then charged by corona discharge to attach a negative charge to the island-like silica region 201.
- the covering film 301 may be laminated, or after the covering film 301 is laminated, charging is performed, and a negative charge is deposited on the laminated covering film 301, and then the negative charge is applied by heating at 150 ° C. to 300 ° C. You may make it diffuse and adhere to the island-like silica area
- FIG. 1
- the negative charge diffuses into the island-like silica region 201 and is neutralized by the holes (positive charge) remaining on the fluororesin surface. Therefore, when holes are diffused by heating, only the negative charges diffused in the island-like silica region 201 remain.
- the negative charge can be diffused into the island-like silica region 201 made of the silica aggregate by charging with corona discharge while heating at 150 ° C. to 300 ° C.
- the covering film 301 made of a fluororesin may be laminated by the method described above. Also in the modified example (second modified example) of the first embodiment of the present invention shown in FIG. 15 (b), as in the first modified example of FIG.
- the electret structure 1b is composed of a back electrode 22 formed on the lower surface, an island-like silica region 201 constituting the silica layer 20 formed on the upper surface of the fluororesin film 21, and a covering film 301 covering the island-like silica region 201. Is defined. Further, in the electret structure 1b according to the second modification of the first embodiment, after the island-like silica region 201 is formed, PTFE dispersion (AD911L, Asahi Glass, etc.) is applied by spin coating, dipping, spray coating, etc. The coating film 301 made of a PTFE film may be formed by heating.
- FIG. 1 shows the case where the electrode of the electret assembly 1 is the back electrode 22, the electrode of the electret assembly 1c may be the vibration electrode 10 as shown in FIG.
- the fluororesin film 21, the vibrating electrode 10 formed on the top surface of the fluororesin film 21, and the fluororesin film 21 The electret structure 1c is defined by the silica layer 20 formed on the lower surface.
- the silica layer 20 formed on the lower surface of the fluororesin film 21 is attached to the fluororesin film 21 in a state of being isolated from each other. An island-like silica region 201 is formed.
- Electrodes formed on one surface of the fluororesin film defining a part of the configuration of the “electret structure” of the present invention. May be a vibrating electrode or a back electrode.
- the electrostatic induction conversion element (ECM) As shown in FIG. 17, the electrostatic induction conversion element (ECM) according to the second embodiment of the present invention includes a vibrating electrode (vibrator) 10 made of a conductor having a flat vibrating surface, and a vibrating electrode 10.
- An insulating layer 40 provided on the lower surface of the substrate, a flat first main surface facing the insulating layer 40, a fluororesin film 21 defined by a second main surface facing the first main surface in parallel, and a fluororesin
- the silica layer 20 formed on the upper surface (first main surface) of the film 21 and having the same polarization direction, the back electrode 22 bonded to the lower surface (second main surface) of the fluororesin film 21, and the vibration of the vibration electrode 10
- the microphone capsule includes electrostatic induction charge measuring means (13, R, C, E) for measuring charges induced between the vibrating electrode 10 and the back electrode 22 in accordance with the displacement of the surface.
- the silica layer 20 is composed of a plurality of island-like silica regions 201 made of silica aggregates that are attached to the fluororesin film 21 in a state of being isolated from each other.
- the polarization directions in the fluororesin film 21 toward the respective lower surfaces are aligned.
- the fluororesin film 21 shown in FIG. 17 is defined by the whole laminated structure including the silica layer 20 formed on the upper surface of the vibration electrode 21, but compared with the structure of the ECM according to the first embodiment shown in FIG. The only difference is that the insulating layer 40 is formed on the side facing the ten island-like silica regions 201.
- the fluororesin film 21 and the back electrode 22 are provided with holes 16 a and 16 b that lead to a gap space defined between the fluororesin film 21 and the vibration electrode 10 so as not to suppress vibration of the vibration electrode 10.
- the other features such as the electret assembly 1 and the vibrating electrode 10 being housed in the metal case 15 are the same as those of the ECM according to the first embodiment, and thus redundant description is omitted.
- the negative charges are attached to the deep trap levels of the silica aggregate constituting the island-like silica region 201.
- the fluororesin film 21 does not diffuse negative charges.
- the ECM according to the second embodiment a microphone capsule having an improved maximum allowable sound pressure can be produced.
- the ECM is deteriorated by contact of the vibrating electrode 10 with the fluororesin film 21 that is an electret by sound pressure and leakage of negative charges. Therefore, the maximum allowable sound pressure of the ECM is a sound pressure at which such contact does not occur.
- the ECM according to the second embodiment shown in FIG. 17 even if the insulating layer 40 provided on the lower surface of the vibrating electrode 10 contacts the island-like silica region 201, the negative electrode attached to the island-like silica region 201 is lost. Since the electric charge does not diffuse into the insulating layer 40, the ECM does not deteriorate. Therefore, according to the ECM according to the second embodiment, the maximum allowable sound pressure can be significantly improved.
- the ECM insulating layer 40 according to the second embodiment needs to be made of a material having high heat resistance that can withstand the reflow temperature.
- the following method may be considered: (1) The vibrating electrode 10 is formed by vapor deposition, PVD, sputtering on a film of fluorine resin, PPS (polyphenylene sulfide), PEN (polyethylene naphthalate), and the film is used as the insulating layer 40. (2) welding the fluororesin film 21 to the vibrating electrode 10; (3) A PTFE dispersion or a polyimide varnish is applied to the vibrating electrode 10 by spin coating or dipping and heated to form the insulating layer 40. (4) Oxide (alumina, chromium oxide, titania, zirconia, etc.) is coated on the vibrating electrode 10 by vapor deposition, PVD, CVD, sputtering.
- a high charge retention ratio r can be maintained even when exposed to a reflow processing temperature of Pb-free solder. Therefore, the electrostatic induction conversion element according to the second embodiment having the electret assembly 1 can be mounted on the substrate by reflow using Pb-free solder.
- the electret structure 1 according to the second embodiment since the negative charge is trapped in the deep level of the island-like silica region 201, the insulating layer 40 on the vibrating electrode 10 side is in strong contact with the island-like silica region 201. However, negative charges do not diffuse into the insulating layer 40, and a high charge retention ratio r can be maintained.
- the electrostatic induction conversion element having the electret structure 1 can cope with a large displacement such that the insulating layer 40 on the vibration electrode 10 side contacts the island-like silica region 201.
- the maximum permissible displacement is improved by using the electret structure 1 according to the second embodiment.
- the electrostatic induction conversion element (ECM) includes a vibrating electrode (vibrator) 10 made of a conductor having a flat vibrating surface, and a vibrating electrode 10.
- a fluororesin film 21 defined by a flat upper surface facing the vibration surface and a lower surface facing parallel to the upper surface, a plurality of island-like silica regions 201 formed on the upper surface of the fluororesin film 21, and a fluororesin film
- a back electrode 22 bonded to the lower surface of the vibration electrode 21 and electrostatic induction charge measuring means (13, R, C) for measuring charges induced between the vibration electrode 10 and the back electrode 22 as the vibration surface of the vibration electrode 10 is displaced.
- a plurality of island-like silica regions 201 deposited on the fluororesin film 21 in a state of being isolated from each other constitute a silica layer, and the fluorine resin directed from the back electrode 22 to the lower surface of each of the plurality of island-like silica regions 201 The polarization direction in the film 21 is aligned.
- the fluororesin film 21 shown in FIG. 18 and the back electrode 22 formed on the lower surface of the fluororesin film is defined by the whole laminated structure including the plurality of island-like silica regions 201 formed on the upper surface of the fluororesin film 21, the structure of the ECM according to the first and second embodiments is defined. The difference is that the distribution density of the island-like silica regions 201 made of silica aggregates on the fluororesin film 21 is not uniform, but the electret assembly 1 and the vibrating electrode 10 are accommodated in the metal case 15. Other features such as the above are the same as those of the ECM according to the first embodiment shown in FIG.
- the central portion of the vibrating electrode 10 is greatly bent and the gap width is narrowed. Only the central part is an effective area as an ECM.
- the surface density of the island-like silica region 201 made of the silica aggregate in the peripheral portion is increased, so the electric field in the peripheral portion is higher than that in the central portion.
- the bending of the peripheral portion of the vibration electrode 10 increases.
- the ECM electret assembly 1 according to the third embodiment can control the potential distribution of the electret assembly 1 by controlling the formation pattern of the silica aggregates constituting the plurality of island-like silica regions 201. It is.
- the electrostatic induction conversion element according to the third embodiment having this electret structure ((201, 21, 22) can be mounted on the substrate by reflow using Pb-free solder.
- the electret structure 1 according to the third embodiment since the negative charge is trapped in the deep level of the island-like silica region 201, the charge is not diffused into the fluororesin film 21, and a high charge retention rate r can be maintained. Therefore, the maximum allowable displacement of the electrostatic induction conversion element having this electret structure 1 is improved.
- an electrostatic induction conversion device (ECM) according to a fourth embodiment of the present invention includes a vibrating electrode (vibrator) 10 made of a conductor having a flat vibrating surface, and a vibrating electrode 10. Formed on the upper surface of the fluororesin film 21, the fluororesin film 21 defined by the insulating layer 40 provided on the lower surface, the flat upper surface facing the insulating layer 40 and the lower surface facing the upper surface in parallel. And the back electrode 22 bonded to the lower surface of the fluororesin film 21.
- a plurality of island-like silica regions 201 made of silica aggregates are applied to the fluororesin film 21 in a state of being isolated from each other to form a silica layer on the fluororesin film 21.
- the polarization directions in the fluororesin film 21 toward the lower surfaces of the island-like silica regions 201 are aligned.
- electrostatic induction charge measuring means such as an FET is provided for measuring the charge induced between the vibration electrode 10 and the back electrode 22 in accordance with the displacement of the vibration surface of the vibration electrode 10.
- the fluororesin film 21 shown in FIG. 19 the back electrode 22 formed on the lower surface of the fluororesin film
- An “electret structure” is defined by the entire laminated structure including a silica layer composed of a plurality of island-like silica regions 201 formed on the upper surface of the fluororesin film 21.
- the ECM according to the fourth embodiment is similar in structure to the ECM according to the second embodiment shown in FIG.
- the insulating layer 40 is provided on the lower surface of the vibration electrode 10, but the fluororesin
- the point that the island-like silica region 201 formed on the film 21 is also used as a spacer for keeping the distance between the insulating layer 40 on the vibrating electrode 10 side and the fluororesin film 21 is the ECM according to the second embodiment. Is different.
- the negative charge attached to the deep trap level of the island-like silica region 201 does not diffuse into the insulating layer 40 even if the island-like silica region 201 contacts the insulating layer 40. Absent. Therefore, the ECM according to the fourth embodiment can be configured to have an extremely narrow gap (microgap) between the vibrating electrode 10 and the back electrode 22 and has an excellent breakdown voltage. For this reason, the electrostatic induction conversion element according to the fourth embodiment can be applied to a detection device that detects ultrasonic waves in addition to the ECM, and can cope with a wide band.
- the manufacture of the ECM according to the fourth embodiment is performed as follows.
- An insulating layer 40 made of a fluororesin film or the like is formed on the gap space side of the vibrating electrode 10.
- the fluororesin film 21 is welded to the back electrode 22, the island-like silica region 201 is formed on the fluororesin film 21, and charging is performed by corona discharge.
- the vibrating electrode 10 on which the insulating layer 40 is formed is stacked, and an ECM is assembled. Note that the island-like silica region 201 may be formed on the insulating layer 40 on the vibration electrode 10 side.
- a high-performance, thin and flexible acceleration sensor can be manufactured by producing and folding the entire ECM structure according to the fourth embodiment shown in FIG. 19 from a fluororesin film.
- a specific example of manufacturing a flexible acceleration sensor is shown below.
- the vibration electrode 10 and the back electrode 22 were both 10 ⁇ m thick Al films, and the insulating layer 40 and the fluororesin film 21 were 12.5 ⁇ m thick PFA films.
- the insulating layer 40 made of PFA film was welded to the vibrating electrode 10 made of Al film, and the fluororesin film 21 made of PFA film was welded to the back electrode 22 made of Al film.
- the island-like silica region 201 made of the silica aggregate was applied to the fluororesin film 21 by ink jet printing under the same procedure and conditions as in Sample I of FIG.
- this flexible structure includes a vibrating electrode (vibrator) 10, an insulating layer 40 provided on the lower surface of the vibrating electrode 10, a fluororesin film 21 facing the insulating layer 40, A plurality of island-like silica regions 201 formed on the upper surface of the fluororesin film 21 and a back electrode 22 bonded to the lower surface of the fluororesin film 21 are provided.
- the first folding is performed so that the back electrode 22 side is folded as shown in FIG.
- the sensor having the size of 40 ⁇ 40 mm is folded in two using the double-sided tape 52 and bonded through the line II, the size becomes 40 ⁇ 20 mm as shown in FIG.
- the sensor having a size of 40 ⁇ 20 mm is folded in two using the double-sided tape 53 and bonded through the second fold line II-II. Folded into four, and miniaturized to a size of 20 ⁇ 20 mm as shown in FIG.
- the vibrating electrode side lead electrode 54 is provided on the vibrating electrode 10 using copper tape, and a PP tape having a thickness of 40 ⁇ m is bonded to the surface for surface protection, whereby the conversion element 64 according to the fourth embodiment is manufactured. did.
- a conversion element 64 according to the fourth embodiment and a commercially available acceleration sensor 63 (Fuji Ceramics, S2SG) 63 are attached to an aluminum plate 61 having a thickness of 2 mm and 300 ⁇ 400 mm so as to be in a control position from the vibration generation point 62. .
- the outputs of the conversion element 64 and the commercially available acceleration sensor 63 according to the fourth embodiment are connected to an oscilloscope 66 via a charge amplifier 65.
- the vibration generation point 62 of the aluminum plate 61 is tapped by hand, a rubber ball or an iron ball is dropped on the vibration generation point 62 of the aluminum plate 61, and the vibration generation point 62 of the aluminum plate 61 is vibrated by a piezoelectric actuator. Then, vibration from 1 Hz to 100 kHz was generated at the vibration generating point 62 of the aluminum plate 61, and the acceleration on the surface of the aluminum plate 61 at that time was measured.
- FIG. 22 shows the frequency characteristic of the output ratio of the conversion element 64 according to the fourth embodiment manufactured with respect to the commercially available acceleration sensor 63.
- the fourth embodiment is more effective than the commercially available acceleration sensor 63 at 1 Hz to 10 kHz. It turned out that the sensitivity of the conversion element 64 which concerns on this is high, The average output ratio was 10 dB.
- the volume of commercial acceleration sensor 63, with respect to 123 mm 3, the volume of the conversion element 64 according to the fourth embodiment produced is 200 mm 3, slightly larger but is sufficiently miniaturized. Further, since the thickness of the conversion element 64 according to the fourth embodiment is 0.5 mm, it can be easily deformed, and the conversion element 64 according to the fourth embodiment can be attached to a curved surface or the like.
- the commercially available acceleration sensor 63 requires a fixing tool such as a screw for attachment, but the conversion element 64 according to the fourth embodiment can be firmly attached with a double-sided tape.
- a high charge retention ratio r can be maintained even when exposed to the reflow processing temperature of Pb-free solder. Therefore, the electrostatic induction conversion element according to the fourth embodiment having the electret structure 1 can be mounted on the substrate by reflow using Pb-free solder. Further, in the electret structure 1 according to the fourth embodiment, since the negative charges are trapped in the deep level of the island-like silica region 201, the insulating layer 40 on the vibrating electrode 10 side is in strong contact with the island-like silica region 201. However, negative charges do not diffuse into the insulating layer 40, and a high charge retention ratio r can be maintained.
- the electrostatic induction conversion element having the electret structure 1 according to the fourth embodiment can cope with such a large displacement that the insulating layer 40 on the vibration electrode 10 side contacts the island-like silica region 201.
- the maximum allowable displacement of the electrostatic induction conversion element is improved by using the electret assembly 1 according to the fourth embodiment.
- the conversion element 64 according to the fourth embodiment can be manufactured at a cost equivalent to that of a commercially available ECM, the conversion element 64 according to the fourth embodiment can significantly reduce the cost compared to the commercially available acceleration sensor 63.
- a high-performance and inexpensive acceleration sensor can be manufactured.
- the electrostatic induction conversion element vibrates due to an electrostatic force, and can be used as a speaker.
- the electrostatic induction conversion element since the high electric field is applied to the gap portion by the electret assembly 1, an electrostatic force significantly larger than that of the electrostatic speaker that does not use the electret assembly 1 is obtained. be able to.
- an electrostatic induction conversion element includes a vibrating electrode (vibrator) 10 made of a conductor having a flat vibrating surface, and a vibrating electrode 10. Formed on the upper surface of the fluororesin film 21, the fluororesin film 21 defined by the insulating layer 40 provided on the lower surface, the flat upper surface facing the insulating layer 40 and the lower surface facing the upper surface in parallel. And the back electrode 221 bonded to the lower surface of the fluororesin film 21.
- a plurality of island-like silica regions 201 made of silica aggregates are applied to the fluororesin film 21 in a state of being isolated from each other to form a silica layer on the fluororesin film 21.
- the polarization directions in the fluororesin film 21 toward the lower surfaces of the island-like silica regions 201 are aligned.
- electrostatic induction charge measuring means such as an FET is provided for measuring the charge induced between the vibration electrode 10 and the back electrode 221 in accordance with the displacement of the vibration surface.
- electrostatic induction charge measuring means such as an FET is provided for measuring the charge induced between the vibration electrode 10 and the back electrode 221 in accordance with the displacement of the vibration surface.
- FET electrostatic induction charge measuring means
- the fluororesin film 21 shown in FIG. 23, the back electrode 221 formed on the lower surface of the fluororesin film Similar to the ECM according to the first to fourth embodiments, also in the ECM according to the fifth embodiment, the fluororesin film 21 shown in FIG. 23, the back electrode 221 formed on the lower surface of the fluororesin film,
- the “electret structure 1d” is defined by the entire laminated structure including the silica layer formed of the plurality of island-like silica regions 201 formed on the upper surface of the fluororesin film 21.
- the ECM according to the fifth embodiment has a substantially similar structure to the ECM according to the fourth embodiment shown in FIG. 19, but is different from the ECM according to the fourth embodiment shown in FIG.
- the thickness of the back electrode 221 is set to the same thickness as that of the vibrating electrode 10 to constitute a flexible ECM.
- a spacer layer 41f made of a fluororesin film provided with a cavity 411 for dividing a gap space defined between the fluororesin film 21 and the insulating layer 40 into a plurality of spaces is provided between the insulating layer 40 and the fluorine layer.
- An island-like silica region 201 made of a silica aggregate that also serves as a spacer is arranged at the position of the cavity 411 of the spacer layer 41f.
- the spacer layer 41f made of the fluororesin film is provided for the purpose of preventing a large shift between the vibrating electrode 10 and the back electrode 221 when the ECM is bent. Yes.
- the spacer layer 41f and the insulating layer 40, and the spacer layer 41f and the fluororesin film 21 may be bonded.
- the manufacture of the ECM according to the fifth embodiment is performed as follows.
- An insulating layer 40 made of a fluororesin film is formed on the gap space side of the vibrating electrode 10.
- the fluororesin film 21 is welded to the back electrode 22, and the fluororesin film 21 is laminated and integrated with a spacer layer 41f made of a fluororesin film provided with a cavity 411.
- an island-like silica region 201 is formed on the fluororesin film 21 at the position of the cavity 411 and charged by corona discharge.
- the vibrating electrode 10 is overlaid thereon, and a spacer layer 41f made of a fluororesin film is heated and welded to bond the vibrating electrode 10 and the back electrode 22 together to prevent displacement due to deformation.
- the spacer layer 41f is heated by pressing a metal plate or metal protrusion having a hole in contact with only the spacer layer 41f against the spacer layer 41f to heat the metal plate or protrusion.
- the insulating layer 40 of the vibrating electrode 10 is pressed against the spacer layer 41f melted by this treatment, and the insulating layer 40 is welded to the spacer layer 41f.
- the peripheral portion of the spacer layer 41f may reach a temperature close to 300 ° C.
- the charge retention characteristics at high temperatures are improved, and thus a flexible ECM that can withstand such welding can be manufactured.
- a perforated metal plate or metal protrusion is pressed against the part of the fluororesin film 21 where the island-like silica region 201 is not formed, and is heated and melted.
- the insulating layer 40 of the vibration electrode 10 may be pressed to weld the insulating layer 40 to the fluororesin film 21.
- the ECM according to the fifth embodiment can be manufactured very thinly.
- a PFA film having a thickness of 12.5 ⁇ m is used for the fluororesin film 21 and the insulating layer 40
- the height of the island-like silica region 201 is 25 ⁇ m
- the vibrating electrode 10 and the back electrode 221 are aluminum deposition layers
- a film-like sensor having a thickness of about 50 ⁇ m is obtained. Since this is a thickness that can be easily folded, a large-area film-like sensor can be folded and downsized in the same manner as shown in FIG. In this case, the capacitance of the sensor can be dramatically increased, so that the influence of the circuit parasitic capacitance can be ignored. Therefore, it is possible to install the amplifier (FET) 13 shown in FIG. 16 and the like away from the film-like sensor according to the fifth embodiment, or to obtain an electrical signal directly without using the amplifier (FET) 13. .
- the patent document 4 since the patent document 4 previously proposed by the present inventor has an extremely narrow gap defined by the particle size of the insulating fine particles, it is a mechanoelectric transducer that can be used as an ultrasonic probe. Is described.
- the fine particles of the insulator disposed in the gap space defined between the electret layer and the insulating layer function as a spacer in the gap space.
- This is different from the ECM according to the fifth embodiment. That is, a technique such as the ECM according to the fifth embodiment in which negative charges are selectively attached to the insulating fine particles and the insulating fine particles holding the negative charges are used as a part of the electret structure. This idea is neither disclosed nor suggested in the invention described in Patent Document 4.
- the ECM according to the fifth embodiment can be applied to an ultrasonic probe other than the microphone. That is, since the ECM according to the fifth embodiment also has a very narrow gap space defined by the spacer layer 41f and the island-like silica region 201, it can be used as an ultrasonic probe.
- An electrostatic induction conversion element (ECM) is an electromechanical device described in Patent Document 4 in that an island-like silica region 201 that also serves as a gap space spacer is electretized. Although it is completely different from the conversion element, it is similar in that it has a narrow gap space, and can be used as an ultrasonic probe as well as the electromechanical conversion element described in Patent Document 4. Since the electrostatic induction conversion element (ECM) according to the fifth embodiment has negative charges attached to the deep trap level of the island-like silica region 201, the charge retention property at high temperature is excellent, and reflow is performed. An ultrasonic probe that can withstand the treatment can be manufactured.
- a high charge retention ratio r can be maintained even when exposed to the reflow processing temperature of Pb-free solder. Therefore, the electrostatic induction conversion element according to the fifth embodiment having the electret structure 1d according to the fifth embodiment can be mounted on the substrate by reflow using Pb-free solder.
- the electret structure 1d according to the fifth embodiment since the negative charges are trapped in the deep level of the island-like silica region 201, the insulating layer 40 on the vibrating electrode 10 side is in strong contact with the island-like silica region 201. However, negative charges do not diffuse into the insulating layer 40, and a high charge retention ratio r can be maintained.
- the electrostatic induction conversion element having the electret structure 1d according to the fifth embodiment can cope with such a large displacement that the insulating layer 40 on the vibration electrode 10 side contacts the island-like silica region 201.
- the maximum allowable displacement of the electrostatic induction conversion element is improved by using the electret structure 1d according to the fifth embodiment.
- the electrostatic induction conversion element according to the fifth embodiment is excellent in pressure resistance, if the thickness of the vibration electrode 10 is increased, the inertial force of the vibration electrode 10 due to vibration is converted into an electric signal. It can also be used as an acceleration sensor. Since the acceleration sensor according to the fifth embodiment can be bent, it can be easily attached to a complicated shape surface such as a curved surface that is difficult to install with a conventional acceleration sensor. Further, it is easy to manufacture a large area with the structure as shown in FIG. 23. For example, it can be used as an inexpensive flat speaker.
- the electrostatic induction conversion element according to the fifth embodiment is easy to carry because it is folded in four or the like, and can also be used as a poster if the surface protective layer is a printing surface.
- the electrostatic induction conversion element according to the fifth embodiment has both high directivity, which is a feature of a flat speaker, high design that allows printing on the surface, and high portability that can be easily folded and pasted. It can also be used as a flexible speaker.
- the structure of the first modified example of the first embodiment shown in FIG. 15A or the second modified example of the first embodiment shown in FIG. 15B is shown in FIG.
- a covering film is provided to cover the surface of the fluororesin film 21 on which the island-like silica regions 201 are formed.
- the island-like silica region 201 to which negative charges are attached and the vibration are obtained by being attached to the upper surface of the silica region 201 and the surface of the fluororesin film 21 between the island-like silica regions 201.
- the smoothing process of the surface of the back electrode 22 of the electret assembly 1 according to the first embodiment described above is applied to the electret assembly 1c according to the third modification of the first embodiment shown in FIG. Also good.
- the surface of the vibrating electrode 10 formed on one surface of the fluororesin film 21 may be smoothed. If the surface of the vibrating electrode 10 is rough, the adhesion at the interface between the vibrating electrode 10 and the fluororesin film 21 is lowered, and local electric field concentration occurs. Due to this local electric field concentration, holes are easily injected from the vibrating electrode 10 into the fluororesin film 21, and the charge retention rate of the electret structure is lowered. By smoothing the surface of the vibrating electrode 10, local Injecting holes from the vibrating electrode 10 into the fluororesin film 21 due to a strong electric field concentration can be suppressed.
- the process of coating the insulating layer on the surface of the back electrode 22 of the electret assembly 1 according to the first embodiment described above is applied to the electret assembly 1c according to the third modification of the first embodiment shown in FIG. May be.
- the surface of the vibrating electrode 10 formed on one surface of the fluororesin film 21 is an insulating layer having high heat resistance and good adhesion. It may be covered with.
- the electret structure of the present invention can be reflowed with Pb-free solder, and can be used in technical fields such as an ECM in which the electret structure is incorporated, an ultrasonic sensor, an acceleration sensor, a seismometer, a power generation element, a speaker, and an earphone.
- the manufacturing process in these technical fields can be greatly improved.
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Abstract
Description
又、以下に示す第1~第5の実施形態は、本発明の技術的思想を具体化するための装置や方法を例示するものであって、本発明の技術的思想は、構成部品の材質、形状、構造、配置等を下記のものに特定するものでない。本発明の技術的思想は、特許請求の範囲に記載された請求項が規定する技術的範囲内において、種々の変更を加えることができる。
図1に示すように、本発明の第1の実施形態に係る静電誘導型変換素子(ECM)は、平坦な振動面を有する導電体からなる振動電極(振動子)10と、振動電極10の振動面に対向した平坦な第1主面及びこの第1主面に平行に対向する第2主面で定義されたフッ素樹脂フィルム21と、フッ素樹脂フィルム21の上面(第1主面)に形成されたシリカ層20と、フッ素樹脂フィルム21の下面(第2主面)に接合された背面電極22と、振動電極10の振動面の変位に伴い振動電極10と背面電極22間に誘導される電荷を測定する静電誘導電荷測定手段(13,R,C,E)とを備えるマイクロフォンカプセルである。シリカ層20は、互いに孤立した状態でフッ素樹脂フィルム21に被着された複数の島状シリカ領域201で構成されているが、図3(a)及び(b)に示すように背面電極22から複数の島状シリカ領域201のそれぞれの下面に向かうフッ素樹脂フィルム21中の分極方向が揃っている。
平面図や鳥瞰図の図示を省略しているが、図1に示すマイクロフォンカプセルの振動電極10、フッ素樹脂フィルム21及び背面電極22はそれぞれ半径3~40mmの円板形状である。図1に示すように、円板状のフッ素樹脂フィルム21と振動電極10の間には絶縁体のスペーサリング14が挟み込まれている。スペーサリング14の上端面には、円板状の振動電極10の周辺部が接続されている。このため、エレクトレット構体1、スペーサリング14及び振動電極10が金属ケース15に収納されてマイクロフォンカプセルを構成している。
(耐湿特性)
親水性が高いシリカを含むことで懸念されるエレクトレット構体の耐湿特性について測定した。ここでは、図2(a)に示すように、シリカ凝集体を塗付していない厚さ12.5μmのPFAフィルムを厚さ0.1mmのAl板の片面に真空溶着したサンプルNと、サンプルNのPFAフィルムの全面にシリカゾル(コロイダルシリカ、20wt%、一次粒子径40~50nm、スノーテックス20L、日産化学社製)を吹き付けてフッ素樹脂フィルム上の全面にシリカ凝集体を形成したサンプルU0と、図2(b)に示すように、サンプルNのPFAフィルムの上にAlパンチ板のマスクを置き、コロイダルシリカをフッ素樹脂フィルム上に吹き付けて、孤立したシリカ凝集体を三角格子状に形成したサンプルU1(凝集体の径:1.5mm)及びサンプルU2(凝集体の径:0.5mm)と、図2(c)に示すように、コロイダルシリカをインクジェットプリンティング装置(LabJet)により1点360pl(ピコリットル)の吐出量でフッ素樹脂フィルム上に塗付して、孤立したシリカ凝集体を100μmピッチの正方格子状に形成したサンプルIとを用意した。なお、サンプルU0,U1,U2の形成に当たり、超音波ネブライザーによって霧化されたコロイダルシリカを吹き付けている。
前述するように、シリカ凝集体1個当たりの被覆面積Asが大きくなると、フッ素樹脂フィルム21の欠陥部の上に位置する確率が高まり、電荷保持率が低下する。表1において、サンプルU1の電荷保持率がサンプルU2やサンプルIの値より低下しているのは、そのためである。そうかと言って、シリカ凝集体1個当たりの被覆面積Asを小さくし、その結果、すべてのシリカ凝集体の被覆面積Asの合計面積がフッ素樹脂フィルム21の表面積に占める割合(被覆比率)Rsが極めて小さくなると、シリカ凝集体を設ける効果が薄れるのは明らかである。
r=1-Ns・As・Pd(As/Af)fs
=1-Rs・As・Pd・fs ………(1)
よって、電荷保持率rは、被覆比率Rsと被覆面積Asの積Rs・Asに比例する。図6は、表1の測定結果から求めた、積Rs・Asと、電荷保持率rとの関係を示している。
第1の実施形態に係るエレクトレット構体1の耐熱特性を次の方法で測定した。サンプルN及びサンプルIと同じ条件のサンプルを用意し、コロナ放電により表面電位が-1kVになるようにエレクトレット化した。そして、各サンプルをホットプレート上で4℃/minの昇温速度で緩やかに300℃まで加熱し、その間、5分置きにサンプルの表面電位を測定して電荷保持特性を調べた。図7(b)には、測定時の昇温特性を示している。この測定結果を図7(a)に示している。サンプルNと同じ条件のサンプルの電荷保持率rを○印、サンプルIと同じ条件のサンプルの電荷保持率rを△印で示している。
フッ素樹脂フィルム21上にシリカ凝集体を形成したエレクトレット構体1は、シリカ凝集体を有しないフッ素樹脂フィルム21のみの従来のエレクトレット構体に比べて、大きい表面電位を維持することができ、高い電界を放出することができる。比較のために、Al電極に厚さ12.5μmのPFAフィルムを溶着したエレクトレット構体に対し、コロナ放電により、PFAフィルムが絶縁破壊を生じない範囲で、負電荷を可能な限り付着させたところ、表面電位は-1.76kVに達した。
第1の実施形態に係るエレクトレット構体1は、次のような処理を施すことで高温時の電荷保持特性のさらに向上が可能である:
a.シリカゾルを用いてフッ素樹脂フィルム21上にシリカ凝集体を塗付した場合、シリカ凝集体内部の毛細管などに過剰な水分が保持されたままになっている場合がある。特にインクジェットプリンティングやスクリーン印刷においては、その傾向が顕著である。このようにフッ素樹脂フィルム21上のシリカ凝集体に物理的に吸着した余分な水分が存在すると、余分な水分を介してシリカ凝集体からフッ素樹脂フィルム21表面に一部の負電荷が拡散するため、耐熱特性が低下する。そのため、エレクトレット化処理の前にエレクトレット構体1を加熱してシリカ凝集体に吸着した余分な水分を除去することで高温時の電荷保持率rが向上する。
(1)背面電極22を研磨して表面粗さを低減した後にフッ素樹脂フィルム21を溶着する。
(2)フッ素樹脂フィルム21に蒸着、物理的気相堆積(PVD),スパッタリングにより導電性材料(Al、Ti、Cr、Ni、Agなどの金属やカーボン)をコートして平滑な背面電極22を形成する。
(3)背面電極22に蒸着、PVD、スパッタリングにより導電性コーティング(導電性フッ素樹脂、カーボン、Al、Ti、Cr、Ni、Agなどの金属)を施して平滑化処理した後にフッ素樹脂フィルム21を溶着する。
あらかじめ背面電極22に耐熱性の高い絶縁材料をコーティングし、背面電極22と密着性が良好な絶縁層を形成する。絶縁層形成のために、以下の方法が考えられる:
(1)PTFEディスパージョンやポリイミドワニスをスピンコーティングやディッピングで背面電極22に塗付し加熱して絶縁層を形成する、
(2)酸化物(アルミナ、酸化クロム、チタニア、ジルコニアなど)を蒸着、PVD、化学的気相堆積(CVD)、スパッタリングで背面電極22にコーティングする。そして、その上にフッ素樹脂フィルム21をさらに溶着した後にシリカ層20を塗布する。PTFEコーティングの場合、その上に直接シリカ層20を塗布してもよい。
フッ素樹脂フィルム21に背面電極22を溶着する前に、フッ素樹脂フィルム21にシリカ凝集体を塗付し、それからフッ素樹脂フィルム21を背面電極22に溶着し、この溶着時に同時にコロナ放電によるチャージを行い、負電荷の付着を行う。こうすることで、欠陥や電界集中部のないフッ素樹脂フィルム21上に塗布されたシリカ凝集体の深いトラップ準位に負電荷を付着させることができる。なお、フッ素樹脂フィルム21に背面電極22を溶着する前にコロナ放電によるチャージをしてから溶着を行っても、同様の効果が得られるが、溶着時にチャージした方が効果は大きい。
(1)スプレーを用いたシリカゾルの塗付
フッ素樹脂フィルム21上にスプレーで水溶性のシリカゾルを塗布する例は、先に説明した(図4(b))。そのとき、マスク31を用いてシリカ凝集体の形状や形成位置を規制したが、図4(a)に示すように、スプレーからの噴霧量を調節して、マスクを用いずに孤立状態のシリカ凝集体をフッ素樹脂フィルム21上に形成することも可能である。フッ素樹脂は撥水性が高いので、シリカゾルの液滴又は霧201rは、フッ素樹脂に付着して球形に近い形状の水滴になり、乾燥すると孤立したシリカ凝集体が形成される。又、シリカゾルの散布には、園芸用の散水ノズル、塗料の吹付け用のノズル、ミスト生成用のノズルなど様々なものを用いることができ、粒子径に応じて選択する。又、超音波ネブライザーに用いられるような超音波による霧化も有効な手法である。
図4(b)に示すように、スプレーノズル30とフッ素樹脂フィルム21との間にマスク31を置く場合、スプレーノズル30をフッ素樹脂フィルム21に設置された電極より負の電位にすることで、負電荷を有する液滴を複数の島状シリカ領域201としてフッ素樹脂フィルム21に付着させることができる。これは、エレクトロスプレーデポジションと呼ばれる手法であるが、これによりナノレベルの径の複数の島状シリカ領域201を散布できるので、シリカ凝集体の塗付パターンの精度が向上することが期待できる。さらに、負電荷を有する液滴からなる複数の島状シリカ領域201がフッ素樹脂フィルム21上に付着するため、エレクトレット化を同時に行うことが可能である。なお、エレクトロスプレーデポジション(ESD)は、静電噴霧法、静電塗付法とも呼ばれる。
インクジェットプリンティング技術及びスクリーン印刷技術を用いれば、フッ素樹脂フィルム21上の任意の場所にシリカゾル液滴からなるシリカ層20を描画することが可能になる。この手法を用いると均一なシリカ凝集体からなるシリカ層20を得ることができる。このとき、シリカゾルは水溶性及び有機溶媒分散性のいずれでも構わない。
ガスバリアフィルムに使用されるシリカコーティング技術を用いて薄膜状の島状シリカ領域201を形成することも可能である。真空蒸着、PVD、CVD、スパッタリングによりマスキングされたフッ素樹脂フィルム21上に薄膜状の島状シリカ領域201を形成すればよい。図3(b)には、この方法で形成した薄膜状の島状シリカ領域201とフッ素樹脂フィルム21と背面電極22との関係を模式的に示している。ただし、この場合、シリカ凝集体と比較すると吸着水が少ないため、チャージ時に負電荷をシリカ層20のみに選択的に付着させることはできない。そのため、被覆比率Rsは高くする必要があり、Rs=80~90%が望ましい。なお、シリカの多孔質膜が形成できれば、シリカ層20への吸着水が増加し、負電荷のシリカ層20への選択的な付着が可能になる。
図17に示すように、本発明の第2の実施形態に係る静電誘導型変換素子(ECM)は、平坦な振動面を有する導電体からなる振動電極(振動子)10と、振動電極10の下面に設けられた絶縁層40と、絶縁層40に対向した平坦な第1主面及びこの第1主面に平行に対向する第2主面で定義されたフッ素樹脂フィルム21と、フッ素樹脂フィルム21の上面(第1主面)に形成され、分極方向を揃えたシリカ層20と、フッ素樹脂フィルム21の下面(第2主面)に接合された背面電極22と、振動電極10の振動面の変位に伴い振動電極10と背面電極22間に誘導される電荷を測定する静電誘導電荷測定手段(13,R,C,E)とを備えるマイクロフォンカプセルである。シリカ層20は、互いに孤立した状態でフッ素樹脂フィルム21に被着されたシリカ凝集体からなる複数の島状シリカ領域201で構成されているが、背面電極22から複数の島状シリカ領域201のそれぞれの下面に向かうフッ素樹脂フィルム21中の分極方向が揃っている。
(1)フッ素樹脂、PPS(ポリフェニレンスルファイド)、 PEN(ポリエチレンナフタレート)などのフィルムに振動電極10を蒸着、PVD,スパッタリングで形成し、フィルムを絶縁層40とする、
(2)フッ素樹脂フィルム21を振動電極10に溶着する、
(3)PTFEディスパージョンやポリイミドワニスをスピンコーティングやディッピングで振動電極10に塗付し加熱して絶縁層40を形成する、
(4)酸化物(アルミナ、酸化クロム、チタニア、ジルコニアなど)を蒸着、PVD、CVD、スパッタリングで振動電極10にコーティングする。
図18に示すように、本発明の第3の実施形態に係る静電誘導型変換素子(ECM)は、平坦な振動面を有する導電体からなる振動電極(振動子)10と、振動電極10の振動面に対向した平坦な上面及びこの上面に平行に対向する下面で定義されたフッ素樹脂フィルム21と、フッ素樹脂フィルム21の上面に形成され、複数の島状シリカ領域201と、フッ素樹脂フィルム21の下面に接合された背面電極22と、振動電極10の振動面の変位に伴い振動電極10と背面電極22間に誘導される電荷を測定する静電誘導電荷測定手段(13,R,C,E)とを備えるマイクロフォンカプセルである。互いに孤立した状態でフッ素樹脂フィルム21に被着された複数の島状シリカ領域201がシリカ層を構成しているが、背面電極22から複数の島状シリカ領域201のそれぞれの下面に向かうフッ素樹脂フィルム21中の分極方向が揃っている。
図19に示すように、本発明の第4の実施形態に係る静電誘導型変換素子(ECM)は、平坦な振動面を有する導電体からなる振動電極(振動子)10と、振動電極10の下面に設けられた絶縁層40と、絶縁層40に対向した平坦な上面及びこの上面に平行に対向する下面で定義されたフッ素樹脂フィルム21と、フッ素樹脂フィルム21の上面に形成され、複数の島状シリカ領域201と、フッ素樹脂フィルム21の下面に接合された背面電極22とを備える。互いに孤立した状態でフッ素樹脂フィルム21に被着され、それぞれがシリカ凝集体からなる複数の島状シリカ領域201で、フッ素樹脂フィルム21上にシリカ層を構成しているが、背面電極22から複数の島状シリカ領域201のそれぞれの下面に向かうフッ素樹脂フィルム21中の分極方向が揃っている。図示を省略しているが、振動電極10の振動面の変位に伴い振動電極10と背面電極22間に誘導される電荷を測定するFET等の静電誘導電荷測定手段が設けられている。
図23に示すように、本発明の第5の実施形態に係る静電誘導型変換素子(ECM)は、平坦な振動面を有する導電体からなる振動電極(振動子)10と、振動電極10の下面に設けられた絶縁層40と、絶縁層40に対向した平坦な上面及びこの上面に平行に対向する下面で定義されたフッ素樹脂フィルム21と、フッ素樹脂フィルム21の上面に形成され、複数の島状シリカ領域201と、フッ素樹脂フィルム21の下面に接合された背面電極221とを備える。互いに孤立した状態でフッ素樹脂フィルム21に被着され、それぞれがシリカ凝集体からなる複数の島状シリカ領域201で、フッ素樹脂フィルム21上にシリカ層を構成しているが、背面電極22から複数の島状シリカ領域201のそれぞれの下面に向かうフッ素樹脂フィルム21中の分極方向が揃っている。
上記のように、本発明は第1~第5の実施形態によって記載したが、この開示の一部をなす論述及び図面は本発明を限定するものであると理解すべきではない。この開示から当業者には様々な代替実施の形態、実施例及び運用技術が明らかとなろう。
10…振動電極
11…エレクトレットフィルム
12…背面電極
13…FET
14…スペーサリング
15…金属ケース
16a,16b…孔
20…シリカ層
21…フッ素樹脂フィルム
22…背面電極
30…スプレーノズル
31…マスク
40…絶縁層
41f…スペーサ層
51…背面電極側引出電極
52,53…両面テープ
54…振動電極側引出電極
61…アルミニウム板
62…振動発生点
63…加速度センサ
64…変換素子
66…オシロスコープ
201…島状シリカ領域
201r…霧
221…背面電極
301…被覆フィルム
411…空洞部
63…加速度センサ
Claims (25)
- フッ素樹脂フィルムと、
前記フッ素樹脂フィルムの一方の面に形成された電極と、
前記フッ素樹脂フィルムの他方の面に形成されたシリカ層と、
を有し、前記シリカ層が、互いに孤立した状態で前記フッ素樹脂フィルムを被覆する複数の島状シリカ領域からなり、前記島状シリカ領域に負電荷が付着されていることを特徴とするエレクトレット構体。 - 請求項1に記載のエレクトレット構体であって、前記フッ素樹脂フィルムが、ポリテトラフルオロエチレン(PTFE)、パーフルオロアルコキシエチレン共重合体(PFA)、テトラフルオロエチレン‐ヘキサフルオロプロピレン共重合体(FEP)又はポリクロロトリフルオロエチレン(PCTFE)の少なくとも1を含むことを特徴とするエレクトレット構体。
- 請求項2に記載のエレクトレット構体であって、前記島状シリカ領域のすべてによって被覆される被覆面積の前記フッ素樹脂フィルムの表面積に対する被覆比率が、5%以上、90%以下であり、
1つの前記島状シリカ領域によって被覆される被覆面積と前記被覆比率との積が0.5mm2以下であることを特徴とするエレクトレット構体。 - 請求項3に記載のエレクトレット構体であって、前記島状シリカ領域の相互間の間隔が100nm以上であることを特徴とするエレクトレット構体。
- 請求項4に記載のエレクトレット構体であって、前記島状シリカ領域が非晶質シリカ微粒子のシリカ凝集体からなることを特徴とするエレクトレット構体。
- 請求項4に記載のエレクトレット構体であって、前記島状シリカ領域が非晶質シリカ又は多結晶シリカの薄膜からなることを特徴とするエレクトレット構体。
- 請求項6に記載のエレクトレット構体であって、前記薄膜が多孔質膜であることを特徴とするエレクトレット構体。
- 請求項1に記載のエレクトレット構体であって、前記シリカ層が形成された前記フッ素樹脂フィルムの面を覆う被覆フィルムを有し、該被覆フィルムが、前記島状シリカ領域の上面、及び、前記島状シリカ領域の間の前記フッ素樹脂フィルムの上面に被着されていることを特徴とするエレクトレット構体。
- 請求項1に記載のエレクトレット構体であって、前記フッ素樹脂フィルムの一方の面に形成される前記電極の表面が、平滑化処理されていることを特徴とするエレクトレット構体。
- 請求項1に記載のエレクトレット構体であって、前記フッ素樹脂フィルムの一方の面に形成される前記電極の表面が、絶縁層で被覆されていることを特徴とするエレクトレット構体。
- フッ素樹脂フィルムと、前記フッ素樹脂フィルムの一方の面に形成された電極と、前記フッ素樹脂フィルムの他方の面に形成されたシリカ層とを有するエレクトレット構体の製造方法であって、
非晶質シリカの微粒子が溶媒に分散してなるシリカゾルを前記フッ素樹脂フィルムの前記他方の面に吹き付けて、複数の島状シリカ領域を互いに孤立した状態で前記他方の面上に形成し、前記複数の島状シリカ領域によって前記シリカ層を形成し、
前記島状シリカ領域に負電荷が付着させること、
を含むことを特徴とするエレクトレット構体の製造方法。 - 請求項11に記載のエレクトレット構体の製造方法であって、前記フッ素樹脂フィルムの上方に前記島状シリカ領域の形状を規定するマスクを配置し、該マスクを通して前記シリカゾルを前記フッ素樹脂フィルムに吹き付けることを特徴とするエレクトレット構体の製造方法。
- 請求項12に記載のエレクトレット構体の製造方法であって、前記シリカゾルを吹き付けるスプレーノズル、及び、金属で形成した前記マスクを負電位に設定し、前記フッ素樹脂フィルムの一方の面に形成した電極を正電位に設定して、前記シリカゾルを前記フッ素樹脂フィルムに吹き付けることを特徴とするエレクトレット構体の製造方法。
- 請求項1に記載のエレクトレット構体の製造方法であって、非晶質シリカの微粒子が溶媒に分散してなるシリカゾルをインクジェットプリンティングで前記フッ素樹脂フィルムに塗布し、前記島状シリカ領域を形成することを特徴とするエレクトレット構体の製造方法。
- 請求項1に記載のエレクトレット構体の製造方法であって、非晶質シリカの微粒子が溶媒に分散してなるシリカゾルをスクリーン印刷で前記フッ素樹脂フィルムに塗布し、前記島状シリカ領域を形成することを特徴とするエレクトレット構体の製造方法。
- 請求項11、14又は15に記載のエレクトレット構体の製造方法であって、前記フッ素樹脂フィルム上に前記島状シリカ領域が形成された前記エレクトレット構体を加熱することを特徴とするエレクトレット構体の製造方法。
- 請求項16に記載のエレクトレット構体の製造方法であって、前記島状シリカ領域に負電荷が付着される前の前記エレクトレット構体を100℃以上に加熱して、前記島状シリカ領域から余剰な水分を除去することを特徴とするエレクトレット構体の製造方法。
- 請求項16に記載のエレクトレット構体の製造方法であって、前記島状シリカ領域に負電荷が付着された後の前記エレクトレット構体を180℃以上、300℃以下に加熱し、その後に、前記島状シリカ領域への負電荷の付着を再び行うことを特徴とするエレクトレット構体の製造方法。
- 請求項16に記載のエレクトレット構体の製造方法であって、前記島状シリカ領域に負電荷を付着する際に、前記エレクトレット構体を180℃以上、300℃以下に加熱しながら前記負電荷の付着を行うことを特徴とするエレクトレット構体の製造方法。
- フッ素樹脂フィルムと、前記フッ素樹脂フィルムの一方の面に形成された電極と、前記フッ素樹脂フィルムの他方の面に形成されたシリカ層とを有するエレクトレット構体の製造方法であって、
PVD又はCVDにより非晶質シリカ又は多結晶シリカの薄膜からなる複数の島状シリカ領域を前記フッ素樹脂フィルムの前記他方の面上に互いに孤立した状態で形成し、前記複数の島状シリカ領域によって前記シリカ層を形成し、
前記島状シリカ領域に負電荷が付着させること
を含むことを特徴とするエレクトレット構体の製造方法。 - フッ素樹脂フィルムと、前記フッ素樹脂フィルムの一方の面に形成されたシリカ層と、前記フッ素樹脂フィルムの他方の面に形成された電極とを有するエレクトレット構体の製造方法であって、
前記フッ素樹脂フィルムの一方の面に前記シリカ層を構成する複数の島状シリカ領域を互いに孤立した状態で形成し、
その後、前記フッ素樹脂フィルムの他方の面に前記電極を溶着で形成するときに、同時に、前記島状シリカ領域への負電荷の付与を行うこと
を含むことを特徴とするエレクトレット構体の製造方法。 - フッ素樹脂フィルムと、
前記フッ素樹脂フィルムの一方の面に形成された背面電極と、
前記フッ素樹脂フィルムの他方の面に形成されたシリカ層と、
前記フッ素樹脂フィルムの他方の面上の前記シリカ層に対向して配置された振動電極と、
該振動電極の前記シリカ層への対向面に設けられた絶縁層と、
を備え、前記シリカ層が、互いに孤立した状態で前記フッ素樹脂フィルムを被覆する複数の島状シリカ領域からなり、前記島状シリカ領域に負電荷が付着されていることを特徴とする静電誘導型変換素子。 - 請求項22に記載の静電誘導型変換素子であって、前記島状シリカ領域が、前記絶縁層と前記フッ素樹脂フィルムとの間隔を保つスペーサを兼ねていることを特徴とする静電誘導型変換素子。
- 請求項23に記載の静電誘導型変換素子であって、前記背面電極が折曲可能な厚さを有し、全体が柔軟性を有することを特徴とする静電誘導型変換素子。
- フッ素樹脂フィルムと、
前記フッ素樹脂フィルムの一方の面に形成された背面電極と、
前記フッ素樹脂フィルムの他方の面に形成されたシリカ層と、
前記フッ素樹脂フィルムの他方の面上の前記シリカ層に対向して配置された振動電極と、
を備え、前記シリカ層が、互いに孤立した状態で前記フッ素樹脂フィルムを被覆する複数の島状シリカ領域からなり、
該複数の島状シリカ領域の前記フッ素樹脂フィルム上での分布密度が、前記振動電極の周辺部に対向する領域で高く、前記振動電極の中央部に対向する領域で低いことを特徴とする静電誘導型変換素子。
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JP2021012911A (ja) * | 2019-07-04 | 2021-02-04 | 東邦化成株式会社 | 環境発電用耐熱エレクトレット素子及びそれを用いた振動発電素子 |
JP7311330B2 (ja) | 2019-07-04 | 2023-07-19 | 東邦化成株式会社 | 環境発電用耐熱エレクトレット素子及びそれを用いた振動発電素子 |
JP7475189B2 (ja) | 2019-11-14 | 2024-04-26 | アネスト岩田株式会社 | マスキング治具 |
Also Published As
Publication number | Publication date |
---|---|
JP6214054B2 (ja) | 2017-10-18 |
EP2840581B1 (en) | 2017-01-11 |
KR101618141B1 (ko) | 2016-05-04 |
EP2840581A4 (en) | 2015-12-16 |
JPWO2013157505A1 (ja) | 2015-12-21 |
KR20140139006A (ko) | 2014-12-04 |
US20150061458A1 (en) | 2015-03-05 |
EP2840581A1 (en) | 2015-02-25 |
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