Electrostatic transducer and diaphragm

Abstract

To provide an improved electrostatic transducer with more excellent performance and greater reliability and a method for manufacturing a diaphragm for an electrostatic transducer.SOLUTION: In a method for manufacturing a composite laminate diaphragm, a composite laminate diaphragm 2 is manufactured by providing a first insulating layer 4, providing a conductive layer 6 on a surface of the first insulating layer, and bonding a second insulating layer 10 to the conductive layer 6 via an adhesive layer 8 such that the second insulating layer extends over the conductive layer. The first insulating layer 4 and the second insulating layer 10 each include a sheet of an uncharged insulating material. The thickness of the composite laminate diaphragm is less than 20 μm. A method for manufacturing an electrostatic converter includes overlapping a first insulating spacer between a first conductive stator and a diaphragm to provide a spacing of less than 1 mm between the first conductive stator and the diaphragm and fixing the first conductive stator, the first insulating spacer, and the diaphragm.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to electrostatic transducers and diaphragms for electrostatic transducers, and more particularly to electrostatic transducers and diaphragms for automotive applications, such as for use inside an automobile.

Background Art

[0002] Conventional electrostatic loudspeakers include a conductive diaphragm disposed between two perforated conductive stators to form a capacitor. A DC bias is applied to the diaphragm, and an AC drive signal voltage is applied to the two stators. Voltages of several hundred or several thousand volts may be required. This signal applies an electrostatic force to the diaphragm, and the diaphragm moves to drive the air on both sides thereof. As a modification of such a transducer, a single-ended configuration can be used. This configuration includes a single stator and a diaphragm, and both a DC bias voltage and an AC drive voltage are applied to the diaphragm to drive the movement of the diaphragm.

[0003] Other transducers operating on a slightly different principle, such as planar electric transducers and electret transducers operating based on a magnetic field, can employ a similar diaphragm, and in those, a diaphragm having a permanent charge, i.e., an electrostatic field, is manufactured.

[0004] All of the above types of transducers typically require a conductive surface on the diaphragm film, although the specific requirements vary depending on the type of transducer. Among those described above, the electrostatic type can be the most difficult in diaphragm design as a result of the very high voltage (e.g., hundreds or thousands of volts) that is constantly applied to the diaphragm mainly to form charges. The high voltage poses a risk of arc discharge or corona discharge as the diaphragm moves towards the stator during normal operation, which can damage the diaphragm. Certain conditions such as high humidity can significantly increase this risk. Even when not operating, the diaphragm may exhibit a leakage current sufficient to reduce the charging voltage and change the performance characteristics of the transducer. A large displacement, i.e., when the diaphragm deflects by a distance long enough to approach the stator, can further exacerbate the problem.

[0005] Existing solutions to mitigate the possibilities of arc discharge, corona discharge, and excessive leakage current have been limited to either providing a large gap between the diaphragm and the stator or applying a special high-voltage electrical insulation coating to either the conductive surface (either the diaphragm or the stator).

[0006] However, these solutions create further problems. As the gap between the stator and the diaphragm increases, the electric field strength decreases, and the transducer sensitivity and / or the transducer maximum output (quantified, for example, in sound pressure level (SPL)) decrease. When the insulation coating is applied to the diaphragm, this increases the mass of the diaphragm, decreases the SPL output, and reduces the high-frequency extension of the transducer's frequency range. When the insulation coating is applied to the conductive surface of the stator, this can reduce the size of the holes in the stator, resulting in a decrease in the available aperture area for air to pass through and an increase in the acoustic impedance of the stator. This can reduce the output level and affect the audio fidelity. In addition, the application of high-voltage insulation coatings is generally very difficult and expensive technically, typically resulting in a non-uniform coating and making mass production unrealistic.

[0007] As a result of issues related to the insulating coating, most electrostatic transducers rely on increasing the gap from the stator to the diaphragm, and do not have an insulating coating on the conductive surface of the diaphragm or stator. As a result, such electrostatic transducers suffer from lower output (SPL), and are particularly prone to performance changes, reliability issues, and early failures associated with long-term, wide-ranging use and variations in temperature and humidity during use.

[0008] In addition to the above problems, conventional electrostatic transducers have the limitation of not being suitable for specific applications. In particular, electrostatic transducers are not robust enough to withstand the environmental conditions that the transducer experiences inside a vehicle, for example, during normal use of the vehicle or while the vehicle is parked and not in use. Therefore, they are not suitable for automotive applications such as being used or installed inside a vehicle. For example, a vehicle is typically or at least sometimes left parked in the external environment when not in use. Therefore, they are exposed to the specific conditions of this environment (e.g., weather / season / climate conditions). This can include extreme high temperatures (e.g., when parked in direct sunlight in a hot climate in summer) or extreme low temperatures (e.g., when parked overnight in a cold climate in winter). As a further example, a vehicle user can drive with the interior of the vehicle open to the external environment, for example, through an open window, open sunroof, or retracted roof. At typical driving speeds of a vehicle, this can result in buffeting, i.e., pressure waves of air striking the transducer. Also, the transducer can be subject to air pressure waves caused by the vehicle door being slammed shut. For the transducer to be suitably used in automotive applications, the transducer must be able to withstand these and other harsh conditions. Currently, electrostatic transducers do not have sufficient robustness to meet these stringent requirements. As a result, the advantages of electrostatic transducers are not available for automotive applications. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0009] Accordingly, there is a need for an improved electrostatic transducer with better performance and higher reliability, and in particular, an improved transducer suitable for use in automotive applications installed within a vehicle is needed.

Means for Solving the Problem

[0010] In a first aspect, the present invention provides a method for manufacturing an electrostatic transducer suitable for use in an automobile, the method including a step of manufacturing a composite laminated diaphragm and a step of assembling the electrostatic transducer. Here, the step of manufacturing the composite laminated diaphragm includes a step of providing a first insulating layer including a sheet of non-charged insulating material, a step of providing a conductive layer on the surface of the first insulating layer, a step of providing a second insulating layer including a sheet of non-charged insulating material, a step of joining the second insulating layer to the conductive layer such that the second insulating layer extends over the conductive layer and wherein the thickness of the composite laminated diaphragm is less than 20 μm, the step of assembling the electrostatic transducer includes a step of providing a first conductive stator and a first insulating spacer, a step of stacking the first insulating spacer between the first conductive stator and the diaphragm to provide a spacing of less than 1 mm between the first conductive stator and the diaphragm, and fixing the first conductive stator, the first insulating spacer, and the diaphragm and

[0011] The present invention also relates to an electrostatic transducer suitable for use in an automobile, the electrostatic transducer including a first conductive stator, a composite laminated diaphragm and a first insulating spacer disposed between the first conductive stator and the diaphragm to provide a spacing of less than 1 mm between the first conductive stator and the diaphragm and wherein the composite laminated diaphragm ​ A first insulating layer formed from a sheet of non-charged insulating material, A conductive layer on the surface of the first insulating layer, A second insulating layer extending over and joined to the conductive layer and formed from a sheet of non-charged insulating material having, wherein the thickness of the composite laminated diaphragm is less than 20 μm.

[0012] The present invention can provide an electrostatic transducer capable of generating a high electric field strength between the diaphragm and the stator by providing a small gap of less than 1 mm between the stator and the diaphragm. Thus, the present invention can provide improved transducer sensitivity and / or maximum output (SPL) compared to prior art transducers having a large gap and thus a lower electric field strength.

[0013] From the teachings of the present application, it will be understood that the use of a diaphragm having the characteristics defined above opens up the possibility of a gap of less than 1 mm. Specifically, according to the present invention, a sheet of non-charged insulating material is used such that the second insulating layer is provided over the conductive layer of the diaphragm. This is in contrast to prior art transducer diaphragms which typically use a single insulating layer with a metal layer laminated thereon and optionally an insulating coating laminated on this metal layer. The applicant has recognized that by providing a second insulating layer formed from a sheet of non-charged insulating material rather than a deposited coating, the insulating layer can be provided over the conductive layer (i.e., insulating the conductive layer from an adjacent stator) without introducing the drawbacks of the prior art described above.

[0014] Thus, it should be understood that in this specification, a distinction is drawn between a coating (e.g., deposited as a liquid, gel, or vapor onto or applied to a conductive layer to build a layer on a conductive surface when a coating material is deposited) and an insulating layer formed from an independent sheet-like material as compared thereto (e.g., formed as an individual layered piece laid over and joined to a conductive layer).

[0015] The applicant has recognized that by using a sheet-like material, the second insulating layer can be made extremely uniform while being very thin. In contrast, coatings are generally less uniform, and in particular, when only thin layers are deposited, the possibility of an actually thin coating is excluded. The thin layer is advantageous because it enables the conductive layer to be covered with an insulating layer without significantly increasing the mass of the diaphragm. As described above, increasing the mass of the diaphragm is undesirable because it can reduce the SPL output and the high-frequency extension of the transducer. The areal weight of the diaphragm is less than 50 g / m 2 less, preferably less than 30 g / m 2 less, more preferably less than 20 g / m 2 less, for example less than 10 g / m 2 and may be less.

[0016] The thin insulating layer is also advantageous because it enables the overall thickness of the diaphragm to be reduced (i.e., less than 20 μm), which can advantageously provide the diaphragm with a desirable acoustic response (e.g., linear acoustic performance at frequencies above 15 kHz, including frequencies above 50 kHz). The diaphragm can have a thickness of less than 15 μm, or less than 10 μm. This can further enhance the acoustic performance and / or frequency response. The electrostatic transducer can have, for example, an output frequency range from 10 Hz to 65 kHz.

[0017] Furthermore, a diaphragm with high flexibility can be manufactured by the second insulating layer formed from a sheet of insulating material. The mechanical compliance of this diaphragm can be made similar to that of a conventional thin-film diaphragm consisting of an insulating layer with a metal deposition layer, which advantageously enables the realization of a low fundamental resonance of this diaphragm. and advantageously enables the realization of a low fundamental resonance of this diaphragm.

[0018] Also, by providing the second insulating layer, the risks of arc discharge and corona discharge can be advantageously reduced, and any current leakage that could impair the performance of the transducer can also be reduced. For example, the first and second insulating layers can "encapsulate" the conductive layer completely.

[0019] Accordingly, according to the present invention, a lightweight, thin, and highly compliant diaphragm can be provided, which provides improved acoustic performance and frequency response (e.g., frequency range and output SPL), while also having an insulating layer that mitigates the risks of arc discharge, corona discharge, and current leakage. Thus, a small gap between the stator and the diaphragm can be enabled, which can improve the output level and audio fidelity.

[0020] Such a diaphragm is novel and inventive in itself. Thus, when viewed from a second aspect, the present invention provides a method for manufacturing a composite laminated diaphragm for an electrostatic transducer that is preferably used in an automobile. This method includes: providing a first insulating layer including a sheet of non-charged insulating material; providing a conductive layer on the surface of the first insulating layer; providing a second insulating layer including a sheet of non-charged insulating material; joining the insulating layers to the conductive layer such that the second insulating layer extends over the conductive layer; including wherein the thickness of the composite laminated diaphragm is less than 20 μm.

[0021] This aspect of the present invention relates to a composite laminated diaphragm for an electrostatic transducer suitable for use in an automobile, for example according to the first aspect of the present invention, and this composite laminated diaphragm includes: a first insulating layer formed from a sheet of non-charged insulating material; a conductive layer on the surface of the first insulating layer; a second insulating layer extending over and joined to the conductive layer and formed from a sheet of non-charged insulating material having wherein the thickness of the composite laminated diaphragm is less than 20 μm.

[0022] When it is said that the first and second insulating layers are formed from a sheet of uncharged insulating material, this is understood to mean that the sheet is not provided with permanent charges such as stable uncompensated surface charges or permanent dipole moments in the dielectric material (e.g., generating a permanent external electric field).

[0023] Also, when it is said that there is a conductive layer on the surface of the first insulating layer, it is understood to mean that the conductive layer is deposited or applied on the surface of the first insulating layer so as to be bonded thereto.

[0024] The electrostatic transducer can have a single-ended configuration. For example, the electrostatic transducer can include a single stator with a single spacer and a composite laminated diaphragm. In such a configuration, the electrostatic transducer can be configured to apply only an attractive electrostatic force between the stator and the diaphragm, as opposed to the so-called "push-pull" configuration. For example, a signal including a high-voltage DC bias and an additional variable drive signal voltage can be applied to the diaphragm to operate the diaphragm to generate a desired acoustic output.

[0025] However, the present invention is not limited to this possibility, and in a series of embodiments , the method further includes providing a second conductive stator and a second insulating spacer, superposing the second insulating spacer between the second conductive stator and the diaphragm to provide a spacing of less than 1 mm between the second conductive stator and the diaphragm, and fixing the second conductive stator and the second insulating spacer. The method further includes the steps of

[0026] Similarly, in a series of embodiments, the electrostatic transducer includes a second conductive stator, a second insulating spacer disposed between the second conductive stator and the diaphragm to provide a spacing of less than 1 mm between the second conductive stator and the diaphragm and the electrostatic transducer further includes the second insulating spacer.

[0027] Such an electrostatic transducer of an embodiment can be called a five-layer transducer or a "push-pull" transducer, that is, the transducer can be configured such that the diaphragm is simultaneously pulled toward one stator and pushed away from the other stator by a varying drive signal applied to the stator. For example, while a varying voltage corresponding to a desired audio signal is applied to the stator (the signal applied to one stator is inverted with respect to the signal applied to the other stator), a high-voltage DC bias can be applied to the diaphragm.

[0028] In a series of embodiments, the second insulating layer is adhered to the conductive layer by applying an adhesive layer to the conductive layer and overlaying the second insulating layer on the adhesive layer, or by applying the adhesive layer to the second insulating layer and overlaying the second insulating layer on the conductive layer. However, this is not essential, and the second insulating layer may be joined to the conductive layer using other methods, such as ultrasonic welding.

[0029] The adhesive may be a sheet (different from the coating as described above), for example, a thin film sheet overlaid on the conductive layer. Alternatively, the adhesive may be applied as a coating, for example, as a liquid or a gel. The adhesive layer may be cured or set by self-curing, pressure curing, UV curing, heat curing, chemical curing, or another method. The type, thickness, and composition of the adhesive may vary depending on the specific application of the electrostatic transducer.

[0030] In a preferred series of embodiments, the adhesive layer includes an acrylic adhesive. However, this is not essential, and other adhesives may be selected to provide properties that have been confirmed to be advantageous by the applicant. For example, the adhesive is selected to be compliant, that is, it does not become hard during setting / curing and make the diaphragm more rigid. It is possible. Once the diaphragm is manufactured, for example, by laminating and compressing layers, the adhesive may be selected such that the diaphragm is airtight and moisture-tight, that is, the adhesive prevents air or liquid from penetrating or moving through the film. The adhesive may be selected so that it can be cured or set without significantly changing its properties later.

[0031] In embodiments where the adhesive layer is not provided as a sheet-like material (for example, in embodiments where the adhesive layer is applied as a coating, such as sprayed in a liquid form, etc.), the adhesive may be selected such that once applied, the adhesive layer provides a uniform coating. The adhesive may be selected, for example, to provide internal damping of the diaphragm, particularly to attenuate resonance behavior at low frequencies (for example, in relation to the selection of the thickness of the adhesive layer as discussed below).

[0032] As a non-limiting example, suitable adhesives that can be used include two-component adhesives using resins and curing agents (for example, thermosetting polymers), epoxies, acrylates, and polyurethanes (solvents may be used); hot melt adhesives; PVA (polyvinyl acetate), EVA (ethylene-vinyl acetate), and polyurethane thermoplastic resins (which can be applied in the form of sheets); and pressure-sensitive adhesives. However, other suitable adhesives known to those skilled in the art and having the desired properties described above may also be used in embodiments of the present invention. As a non-limiting example, suitable adhesives that can be used include two-component adhesives using resins and curing agents (for example, thermosetting polymers), epoxies, acrylates, and polyurethanes (solvents may be used); hot melt adhesives; PVA (polyvinyl acetate), EVA (ethylene-vinyl acetate), and polyurethane thermoplastic resins (which can be applied in the form of sheets); and pressure-sensitive adhesives. However, other suitable adhesives known to those skilled in the art and having the desired properties described above may also be used in embodiments of the present invention.

[0033] The adhesive can be selected such that, as part of the curing reaction, it does not generate any gas, such as any volatile organic compound (VOC). This avoids the formation of bubbles in the final film that could affect the performance of the diaphragm. The adhesive should be selected to have an appropriate adhesive strength, for example, to provide sufficient adhesive strength such that when exposed to the conditions present in automotive applications as described above (e.g., when exposed to a temperature range from -40°C to +120°C), the layers of the film remain adhered to each other. In this regard, epoxy-based adhesives are suitable for use. However, other adhesives are known that do not cause any "gas evolution" and have an appropriate high bonding strength and can be used.

[0034] In a series of embodiments, the adhesive layer has a thickness of from 1 μm to 10 μm, preferably from 3 μm to 5 μm, more preferably from 3 μm to 4 μm. The Applicant has recognized that by selecting an appropriate thickness, the internal damping characteristics of the diaphragm can be enhanced using the adhesive layer. The Applicant has found that a thickness in the range of 3 μm to 5 μm is particularly advantageous for many applications that allow for damping of resonance behavior.

[0035] The conductive layer can distribute and hold charges (e.g., from a DC bias voltage), and / or the conductive layer can conduct a drive signal (e.g., an AC voltage). The thickness of the conductive layer is selected to provide a sufficient thickness for manufacturability and durability and sufficient conductivity for a particular application, while avoiding an excessive thickness that could unnecessarily add to the mass of the diaphragm (which affects its acoustic performance) and / or use more material than necessary in manufacturing the diaphragm. In a series of embodiments, the conductive layer has a thickness of less than 1% of the thickness of the composite laminated diaphragm, preferably less than 0.5%, more preferably less than 0.1%. The conductive layer can have a thickness of from 5 nm to 50 nm, preferably from 8 nm to 30 nm, although the thickness can be outside these ranges, e.g., less than 5 nm, e.g., from 1 nm to 2 nm.

[0036] The conductivity of the required conductive layer may depend on a specific application, for example, the configuration of the transducer in which the diaphragm is used. For example, in an embodiment where an alternating voltage is applied to the diaphragm, such as the single-ended configuration described above, the conductivity may need to be higher than in an embodiment where only a biased DC voltage is applied to the diaphragm, such as a push / pull configuration. In the former case, the conductive layer needs to conduct the alternating signal, and thus, a thicker conductive layer and / or a more conductive material can be used as the conductive layer. For example, 30 nm of aluminum can be used. In the latter case, the conductive layer only needs to hold the electrostatic charge, and thus, a thinner conductive layer and / or a less conductive material can be used. For example, 8 nm of gold can be used for the conductive layer.

[0037] The conductive layer may be conductive by including a conductive material. The conductive material may be a metal, such as gold or aluminum. The conductive layer may be a metal layer deposited on the first insulating layer, for example, by evaporation. However, a conductive non-metal, such as graphite or other forms of carbon, may also be used. The conductive layer may be conductive by including a semiconductor material.

[0038] The conductive layer may be uniform or masked in a specific pattern, such as a signal trace path or a coil. The conductive layer can be attached to the first insulating layer by any suitable technique, such as evaporation, sputtering, or photochemical masking. etc.

[0039] In a series of embodiments, the first insulating layer has a thickness of from 5 μm to 15 μm, preferably from 6 μm to 8 μm, more preferably about 7 μm. In a series of embodiments, the second insulating layer has a thickness of from 5 μm to 15 μm, preferably from 6 μm to 8 μm, more preferably about 7 μm. The thicknesses of the first and second insulating layers are, as a result, selected so as to meet the requirement that the thickness of the composite laminated diaphragm is less than 20 μm while providing the desired low mass and high compliance characteristics to achieve the desired linear acoustic performance as described above.

[0040] In a series of embodiments, the composite laminated diaphragm has a length and / or width greater than 1 cm, preferably greater than 5 cm. Thus, the composite laminated diaphragm according to the present invention can be regarded as a "thin film" diaphragm, that is, the diaphragm can be made thin in view of the overall length scale of the diaphragm and the electrostatic transducer. This is understood to be different from miniature systems, such as microelectromechanical systems (MEMS), in which the entire transducer and diaphragm are provided on a small length scale, such as a transducer and diaphragm having a length / width of, for example, micrometers or a few millimeters.

[0041] In a series of embodiments, the first insulating layer and / or the second insulating layer is formed from a polymer material. The applicant has found that such materials can be effective not only in reducing arc discharge and corona discharge but also in reducing leakage current. The first insulating layer and / or the second insulating layer can be formed from a material having a breakdown strength greater than 500 V / μm, preferably greater than 550 V / μm. The first insulating layer and / or the second insulating layer may be formed from a material having a breakdown strength in the range of 300 V / μm to 600 V / μm. The applicant has found that selecting a material having this property, such as a polymer material, is particularly effective in reducing the risk of arc discharge and corona discharge. However, materials having a lower breakdown strength can be used, for example, by providing a thicker layer (for example, compared to an equivalent layer made of a material having a higher breakdown strength). The breakdown strength is 150 It may be greater than V / μm or may be greater than 200 V / μm. It is not essential that the first and / or second insulating layer be formed from a polymer material. For example, a ceramic material, such as an alkali-free glass, can be used. When values or ranges of dielectric breakdown strength are given, it should be understood that these can be applied over all temperatures preferably in the range from -40 °C to +120 °C under the conditions of use in automotive applications. The dielectric breakdown strength can be measured according to the standard test ASTM D149 or IEC 60243-1.

[0042] The first insulating layer and / or the second insulating layer can be formed from a material having a dielectric constant less than 2.5, preferably less than 2.3. The applicant has found that selecting a material having these properties, such as a polymer material, is particularly effective in reducing leakage current.

[0043] In a series of embodiments, the first insulating layer and / or the second insulating layer is formed from a capacitor film, such as a dielectric film suitable for use in a capacitor.

[0044] In a series of embodiments, the first insulating layer and / or the second insulating layer has a thickness of up to 20 nm and has a compliance equal to that of a layer formed from biaxially oriented polypropylene (BOPP), or polyaryl ether ether ketone (PEEK®), or polytetrafluoroethylene (PTFE, such as TEFLON®).

[0045] In a series of embodiments, the first insulating layer and / or the second insulating layer is selected from the group consisting of materials formed from the following. Biaxially oriented polypropylene (BOPP); Polyaryl ether ether ketone (PEEK®); Polytetrafluoroethylene (PTFE, such as TEFLON®); Biaxially oriented polyethylene terephthalate (BOPET); Polyphenylene sulfide (PPS); Polyetherimide (PEI); Polyethylene naphthalate (PEN); Polyimide (PI); Polyethylene terephthalate (PET); Polycarbonate (PC); Polyethersulfone (PESU); Polyphenylsulfone (PPSU); Polysulfone (PSU); Ethylene tetrafluoroethylene (ETFE); Perfluoroalkoxy (PFA); Polyvinylidene fluoride (PVDF); Poly(vinylidene fluoride-trifluoroethylene) copolymer (PVDF-TrFE); And poly(vinylidene fluoride-trifluoroethylene) copolymer (PVDF-TrFE-CFE) incorporating chlorotrifluoroethylene.

[0046] However, other materials other than those listed above can be used, and within the scope of expertise of those skilled in the art who understand the advantages taught by this application, other materials having the above dielectric breakdown strength and permittivity characteristics that can be used by the present invention can be selected.

[0047] The transducer is preferably a loudspeaker, but this is not essential. In some embodiments, the transducer is a microphone.

[0048] As described above, this electrostatic transducer is preferably suitable for use in an automobile. In this context, "inside" is not limited to meaning the inside (e.g., interior) of an automobile, and it should be understood to include being suitable for use inside or on an automobile. For example, this can be used inside or on a road vehicle such as a passenger car, a lorry, a bus, a motorcycle or a coach. The present invention is particularly used in a passenger car.

[0049] The present invention extends to the use of the electrostatic transducer described herein in an automobile.

[0050] This electrostatic transducer may be suitable for installation within an automobile. For example, the electrostatic transducer may be shaped for installation within an automobile, for example, having a shape that conforms to a part of the interior of the automobile. The electrostatic transducer may include a housing shaped for installation within an automobile, for example, the housing may be shaped to conform to a part of the interior of the automobile.

[0051] This method may include installing the electrostatic transducer within an automobile.

[0052] The present invention extends to an automobile comprising the electrostatic transducer described herein.

[0053] As described above, the transducer within an automobile may be exposed to extreme temperatures, including rapid temperature changes (e.g., in the range of -40°C to +120°C), and harsh conditions such as buffeting by air pressure waves caused by, for example, an open window or a sudden closing door (e.g., during use of the automobile or while the vehicle is parked and not in use). Other examples include moisture, salt spray, dust, and / or chemicals such as fuel, oil, and cleaning agents, vibration, and the presence of mechanical, thermal, and acoustic shocks. Conventional electrostatic transducers cannot withstand these conditions. For example, high temperatures can cause breakdown of the insulating material within the transducer and may lead to dielectric breakdown.

[0054] Furthermore, a transducer for use in an automobile not only needs to maintain structural and functional integrity under such conditions, but may also have to achieve robustness while meeting performance requirements (e.g., specified acoustic performance requirements) that can result in competing objectives. For example, it is possible to manufacture a more robust diaphragm by manufacturing a thicker diaphragm or from certain materials that provide higher robustness. However, increasing the thickness of the diaphragm reduces the SPL output and the high-frequency extension of the transducer's frequency range, thus degrading performance. Additionally, materials that improve robustness typically have greater stiffness, which is detrimental to the low-frequency performance of the diaphragm. Other considerations for meeting the required performance may include maintaining charge confinement, providing a diaphragm with high compliance, and achieving a wide frequency range.

[0055] The Applicant has recognized that certain materials, in particular certain combinations of materials, when used in the manufacture of a composite laminated diaphragm for an electrostatic transducer according to the present invention, are not only robust enough to withstand the difficult environmental conditions present in automotive applications, but also effectively result in diaphragms and electrostatic transducers that meet high performance requirements in terms of, for example, SPL, frequency response, and low distortion levels.

[0056] The desired characteristics of the manufactured diaphragm can be readily determined or specified, for example, based on the measured environmental conditions and the selected or specified performance requirements. However, it should be understood that it is not easy to determine which specific materials and material properties (and in particular, which combinations thereof) will necessarily result in those desired characteristics when used in the manufacture of a composite diaphragm. As described above, in automotive applications, multiple robustness criteria as well as performance criteria may be defined, where these criteria are not necessarily independent of each other, and the diaphragm ideally must meet all of these criteria. Therefore, it may not be straightforward to identify the materials and material properties (or combinations thereof) that simultaneously meet all of these criteria.

[0057] As will be described later, the composite laminated diaphragm may be manufactured from a composite material or a film, where the composite material or film includes a first and a second insulating layer and a conductive layer. References to layers (or constituent layers) of the composite material or film are to be understood to mean one or more (e.g., all) of the layers used in the formation of the composite material or film (and thus the composite laminated diaphragm), e.g., the first and / or second insulating layer and / or conductive layer and / or adhesive layer.

[0058] For use in the manufacture of diaphragms for automotive applications, the Applicant has identified some of the main criteria for the composite materials described herein. These include, but are not limited to, the glass transition temperature (Tg), the coefficient of thermal expansion (CTE) (both in the machine direction and transverse / diectional direction), and the surface energy (e.g., polar surface energy) of the composite material or film. The surface energy (e.g., polar surface energy) can at least partially determine the bond strength between layers (and other related properties, e.g., interlaminar shear strength). The main criteria may also include the degree of match of certain parameters between the constituent layers of the composite material or film and / or between the composite material or film and other components within the transducer (e.g., spacers and / or stators). The main criteria may also include the isotropy of the composite material or film.

[0059] The Applicant has confirmed that one of the problems with existing composite materials for use in the manufacture of diaphragms is the lack of uniformity in these mechanical properties and / or other performance characteristics when measured in the machine direction and the transverse direction, i.e., such prior art materials tend to be anisotropic when measured in these two directions. This is particularly problematic when attempting to use the diaphragm in automotive applications.

[0060] In a series of embodiments, the composite material or film for use in manufacturing a diaphragm according to the present invention is substantially isotropic during manufacturing and retains this property even when exposed to any of the environmental conditions described herein, such as temperature and / or pressure, under the intended use conditions. "Isotropic" means that the material has substantially the same properties in all directions, and when used in this context, being substantially the same means that the difference in the properties of the material in different directions is 50% or less, preferably 20% or less, more preferably 10% or less, more preferably 5% or less, and even more preferably 1% or less. In one embodiment, in all directions the properties of the material "match" as described herein.

[0061] For example, in a series of embodiments, the Young's modulus of the composite material is substantially the same when measured in the machine direction and the transverse direction. Alternatively, or in addition, the CTE of the composite material is substantially the same when measured in the machine direction and the transverse direction. Alternatively, or in addition, the yield strength and / or tensile strength of the composite material is substantially the same when measured in the machine direction and the transverse direction. As used in this context, "substantially the same" means that the measured values of the properties differ by more than 50%, preferably more than 20%, more preferably more than 10%, more preferably more than 5%, for example more than 1%, and are intended to mean that they are different. As is well understood, such properties must be substantially the same not only for the composite material "as manufactured" but, importantly, also under its intended use conditions.

[0062] In a series of embodiments, the ratio Emin / Emax of the Young's modulus of the composite material and / or the constituent layer, measured in the machine direction and the transverse direction, is greater than 0.7, preferably greater than 0.8, for example greater than 0.9 where Emin is the lower of the Young's modulus values in the machine direction and the transverse direction, and Emax is the higher of the Young's modulus values in the machine direction and the transverse direction.

[0063] In a series of embodiments, the yield strength of the composite material and / or the constituent layers measured in the machine direction and the transverse direction is greater than 0.7, preferably greater than 0.8, for example greater than 0.9 and has a ratio σmin / σmax greater than, where σmin is the lower of the yield strength values in the machine direction and the transverse direction, and σmax is the higher of the yield strength values in the machine direction and the transverse direction.

[0064] In a series of embodiments, the coefficient of thermal expansion of the composite material and / or the constituent material measured in the machine direction and the transverse direction is greater than 0.5, preferably greater than 0.7, for example greater than 0.9 and has a ratio CTEmin / CTEmax greater than, where CTEmin is the lower of the CTE values in the machine direction and the transverse direction, and CTEmax is the higher of the CTE values in the machine direction and the transverse direction.

[0065] In a series of embodiments, the composite material or film for use as a diaphragm according to the present invention has at least one parameter whose respective measured values match between two or more layers of the composite material or film (e.g., at least a first and a second insulating layer), where the at least one parameter is preferably selected from the group consisting of the coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength.

[0066] In a series of embodiments, the composite material or film for use as a diaphragm according to the present invention has the following properties. i) A glass transition temperature of at least 120°C. ii) At least one parameter whose respective measured values match between two or more layers of the composite material or film. Here, the at least one parameter is selected from the group consisting of the coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength. iii) A surface energy in the range of 30 to 60 dynes / cm and / or a polar surface energy exceeding 12 dynes / cm

[0067] ​Preferably, this parameter has respective measurement values that match between all layers of the composite material or film. Preferably, this parameter has respective measurement values that match between some or all layers both when the parameter is measured in the machine direction and when the parameter is measured in the transverse direction. In this context, "matching" can mean that the values of the parameters are close enough to each other such that none of the composite material or film or its constituent layers expands or contracts beyond its yield point due to any expansion and / or contraction of the composite material or film or its constituent layers caused by exposure to high or low temperatures. In this context, high and low temperatures can refer to the extreme temperatures to which the transducer is exposed during use in automotive applications (e.g., temperatures up to +120 °C and / or down to -40 °C). In this context, "matching" can mean "substantially the same" within the meaning defined above herein. For example, "matching" can mean that the parameter values do not differ by more than 10%, preferably more than 5%, for example more than 1% can be.

[0068] The glass transition temperature (Tg) of the composite material and / or the constituent layer can be in the range of at least 120 °C, for example, at least 140 °C, preferably from 120 °C to 260 °C, more preferably from 140 °C to 220 °C. The composite film and / or the constituent layer can have a continuous use temperature of at least 150 °C.

[0069] The glass transition temperature can be measured according to the standard test ASTM D3418. The continuous use temperature can be measured according to the standard test ISO 11357.

[0070] The CTE of the composite material needs to be such that it does not expand or contract beyond its yield point both "as manufactured" and under the intended use conditions, for example, when exposed to typical conditions during use in automotive applications, such as temperatures up to +120 °C and / or down to -40 °C.

[0071] For the composite material and / or the constituent layer, when measured in the machine direction (MD), the Young's modulus can be in the range of, for example, 2 GPa to 8 GPa, preferably 2 GPa to 3 GPa. When measured in the transverse direction (or cross-sectional direction CD), the Young's modulus can be in the range of, for example, 2 GPa to 8 GPa, preferably 2 GPa to 3 GPa. The average of the Young's modulus of the composite material measured in the machine direction and the transverse direction can be in the range of 2 GPa to 8 GPa, preferably 2 GPa to 3 GPa.

[0072] For the composite material and / or the constituent layer, when measured in the machine direction (MD), the yield strength can be, for example, greater than 80 MPa, preferably greater than 100 MPa, for example, at least 120 MPa. When measured in the transverse direction (or cross-sectional direction CD), the yield strength can be, for example, greater than 80 MPa, preferably greater than 100 MPa, for example, at least 120 MPa. The lower of the yield strength of the composite material measured in the machine direction and the yield strength of the composite material measured in the transverse direction can be greater than 80 MPa, preferably greater than 100 MPa, for example, at least 120 MPa. The value of Young's modulus Or when ranges are given, it should be understood that these can be applicable over all temperatures preferably in the range of -40 °C to +120 °C under the service conditions for automotive applications. The Young's modulus and / or the yield strength can be measured according to standard test ISO 527 or ASTM D638 can be measured in accordance with.

[0073] For the composite material and / or the constituent layer, the coefficient of thermal expansion when measured in the machine direction (MD) is, for example, less than 80×10 -5 / °C, preferably less than 80×10 -6 / °C. When measured in the transverse direction (or cross-sectional direction, CD), the coefficient of thermal expansion is, for example, less than 80×10 -5 / °C, preferably less than 80×10 -6It can be less than / ℃. When the value or range of the coefficient of thermal expansion is given, it should be understood that these can be applicable over all temperatures preferably in the range from -40°C to +120°C under the use conditions for automotive applications. The coefficient of thermal expansion can be measured according to Standard Test ASTM E831, ASTM D696 or ISO 11359 in accordance with -2.

[0074] The surface energy of the composite material can be, for example, in the range from 35 to 55 dynes / cm, preferably from 35 to 45 dynes / cm. The polar surface energy of the composite material can be, for example, greater than 15 dynes / cm and, for example, greater than 20 dynes / cm. When the value or range of the surface energy and / or polar surface energy is given, it should be understood that these can be applicable over all temperatures preferably in the range from -40°C to +120°C under the use conditions for automotive applications. The surface energy and / or polar surface energy can be measured according to Standard Test ASTM-D7334-08.

[0075] The surface energy and / or polar surface energy can refer to the value obtained before the application of any process or treatment (for example, plasma treatment, flame treatment).

[0076] In a series of embodiments where the transducer comprises a diaphragm formed from a composite material or film according to the above description, at least one parameter measured for the composite material or film has one or more values that match one or more corresponding values of the same parameter measured for at least one structural component of the transducer, such as the first stator, the first spacer, the second stator (if provided), and the second spacer (if provided). This at least one parameter can include one or more parameters selected from the group consisting of the coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength. Preferably, this at least one parameter matches in both the machine direction and the transverse direction of the composite material or film. The at least one structural component can include the first stator and the first spacer. The at least one structural component can include the first and second stators and the first and second spacers. Additionally, or alternatively, the diaphragm can be mounted within the transducer by an intervening material or structure having sufficient flexibility or compliance to allow the diaphragm and the structural components of the transducer (such as spacers and stators) to expand or contract by different amounts without damaging the diaphragm (e.g., by bending, compressing, or expanding to compensate for differences in expansion or contraction).

[0077] The Applicant has identified several polymeric materials that can be used in the manufacture of composite materials that meet the desired primary criteria defined herein.

[0078] The first insulating layer and / or the second insulating layer can be formed from a thermoplastic polymer having a glass transition temperature (Tg) in the range of at least 120°C, preferably in the range of 120 to 260°C, such as in the range of 140 to 220°C.

[0079] In a series of embodiments, the first insulating layer and / or the second insulating layer has the properties defined herein and, in particular, is formed from a material having the defined glass transition temperature, CTE, surface energy, and polar surface energy.

[0080] The applicant has found that polymer materials selected from the group consisting of polyaryl ether ether ketone (PEEK), polyetherimide (PEI), and polyethylene naphthalate (PEN) are particularly suitable for use in forming the first and / or second insulating layers. Accordingly, the first insulating layer and / or the second insulating layer of the composite material may include a polymer selected from polyaryl ether ether ketone (PEEK), polyetherimide (PEI), and polyethylene naphthalate (PEN). In a series of embodiments, one or both of the first and second insulating layers may consist essentially of such a polymer.

[0081] In a series of embodiments, the composite material for use as a diaphragm according to the present invention A first insulating layer formed from a sheet of insulating material comprising polyaryl ether ether ketone, polyetherimide, or polyethylene naphthalate, A conductive layer on the surface of the first insulating layer and A second insulating layer extending over and joined to the conductive layer and formed from a sheet of insulating material comprising polyaryl ether ether ketone, polyetherimide, or polyethylene naphthalate including.

[0082] The polymer materials used to form the first and second insulating layers of the composite material may be the same or different. In a series of embodiments, these may be selected from the same class of polymers. For example, they may both be PEEK polymers, both be PEI polymers, or both be PEN polymers. In other sets of embodiments, the polymer materials forming the insulating layers will be the same.

[0083] In a series of embodiments, both the first and second insulating layers are formed from a material that includes or consists essentially of polyaryl ether ether ketone (PEEK). Suitable PEEK polymers can be readily identified by one of ordinary skill in the art considering the primary criteria described herein. Such polymers can include, but are not limited to, VICTREX® PEEK381G, Sciengy® PEEK-GRN20G, and KetaSpire® KT850. Suitable film materials containing such polymers can include, but are not limited to, APTIV 1000, APTIV 1100, and APTIV 2000. Such products are available from Victrex PLC, Shanong Sciengy New Materials, and Solvay Specialty Polymers.

[0084] In a series of embodiments, both the first and second insulating layers are formed from a material that includes or consists essentially of polyetherimide (PEI). Suitable PEI polymers can be readily identified by one of ordinary skill in the art considering the primary criteria described herein. Such polymers can include, but are not limited to, ULTEM Resin 1000, ULTEM Resin 1010, ULTEM Resin 1100, and Duratron U1000. Suitable film materials containing such polymers can include, but are not limited to, SABIC ULTEM UTF120, SABIC ULTEM 1000B, Norton Kemid Film, and Tempalux Film. Such products are available from SABIC, Mitsubishi Advanced Chemicals, and Westlake Plastics Company Saint Gobain.

[0085] In a series of embodiments, both the first and second insulating layers are formed from a material that includes or consists essentially of polyethylene naphthalate (PEN). Suitable PEN polymers can be readily identified by one of ordinary skill in the art considering the primary criteria described herein. Such polymers can include, but are not limited to, NOPLA® KE901. Suitable film materials containing such polymers include, but are not limited to, Teonex and Kaladex. Such products are available from KOLON Plastics Inc. and DuPont.

[0086] The Applicant has found that the diaphragm according to the second aspect of the present invention can be particularly effectively used in an electrostatic transducer having a stator-diaphragm spacing of less than 1 mm, for example, an electrostatic transducer according to the first aspect of the present invention. However, this diaphragm can also be effectively used in other applications. This diaphragm can be used in an electrostatic transducer similar to that defined above according to the first aspect of the present invention, except that the spacing between the first stator and the diaphragm (and, if provided, the second stator and the diaphragm) is not necessarily less than 1 mm. Further, this diaphragm can also be used in a planar electrodynamic transducer. A modification of the diaphragm of the second aspect can be used in an electret transducer by manufacturing the diaphragm using a sheet of insulating material that is charged instead of being uncharged. Thus, viewed from a third aspect, the present invention provides a method of manufacturing a composite laminated diaphragm for a transducer, the method comprising: providing a first insulating layer including a sheet of insulating material; providing a conductive layer on a surface of the first insulating layer; providing a second insulating layer including a sheet of insulating material; joining the second insulating layer to the conductive layer such that the second insulating layer extends over the conductive layer; comprising, wherein the thickness of the composite laminated diaphragm is less than 20 μm.

[0087] This aspect of the present invention A first insulating layer formed from a sheet of insulating material, A conductive layer on the surface of the first insulating layer, Extending over the conductive layer and joined to the conductive layer, including a second insulating layer formed from a sheet of insulating material, wherein the thickness of the composite laminated diaphragm is less than 20 μm, and extends to a composite laminated diaphragm for a transducer.

[0088] In an embodiment according to a third aspect, the first insulating layer and / or the second insulating layer may be formed from a sheet of charged insulating material. The sheet of charged insulating material may have a permanent charge, for example, a stable uncompensated surface charge or a permanent dipole moment. The sheet of charged insulating material may be a dielectric material.

[0089] Any feature or combination of features of the first and second aspects (including any feature related to the transducer, diaphragm, composite material or film, and / or the constituent layers of the composite diaphragm or film) may, where applicable, be features of the third aspect of the present invention.

[0090] Hereinafter, with reference to the accompanying drawings, some preferred embodiments will be described by way of example only.

Brief Description of the Drawings

[0091]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0092] Figure 1 shows a cross-sectional view of a composite laminated diaphragm 2 according to a first embodiment of the present invention. The diaphragm 2 includes a first insulating layer 4 that functions as a substrate. The first insulating layer 4 is made of biaxially oriented polypropylene (BOPP) and has a thickness of 7 μm.

[0093] The conductive layer 6 is deposited on the surface of the first insulating layer 4. The conductive layer 6 is a layer of gold with a thickness of 8 nm. In this embodiment, the conductive layer 6 is deposited on the first insulating layer 4 by vapor deposition, but any other suitable method known to those skilled in the art may also be used.

[0094] An adhesive layer 8 is overlaid on the conductive layer 6. In this example, the adhesive layer is applied as a coating to the second insulating layer 10. Then, the second insulating layer is overlaid on the conductive layer 6 and pressure is applied so that these layers adhere to each other. However, any other suitable method known to those skilled in the art may be used. For example, the adhesive layer 8 may be applied to the conductive layer 6 as a coating (e.g., in the form of a liquid by spraying), and then the second insulating layer 10 may be overlaid on the adhesive. The second insulating layer 10 also has a thickness of 7 μm and is made of biaxially oriented polypropylene (BOPP).

[0095] After overlaying the second insulating layer 10 on the adhesive, the adhesive is cured to fix it. The layers may be pressed together during the curing process, depending on the specific adhesive used (e.g.). In this example, the adhesive is a viscoelastic acrylic adhesive. The thickness of the adhesive layer is 5 μm.

[0096] It should be understood that the layer thicknesses in Figure 1 are not shown to scale because there is a difference in the order of magnitude between the thickness of the gold conductive layer 6 and the thicknesses of the insulating and adhesive layers 4, 8, 10.

[0097] The electrical and mechanical properties of the layers 4, 6, 8, 10 are shown in Tables 1 and 2 below. The properties shown include the Young's modulus, which affects the rigidity of the diaphragm and thus its acoustic properties. The dissipation factor affects the energy dissipation of the diaphragm and, as a result, the Q (quality) factor of its mode.

[0098] [Table 1]

[0099] [Table 2]

[0100] Tables 3 and 4 show electrical and mechanical properties of some exemplary materials that may be used for the first and / or second insulating layers. Table 3 shows exemplary layer thickness ranges that may be used for each material.

[0101] [Table 3]

[0102] [Table 4]

[0103] Table 5 lists the environmental characteristics of some materials that can be used for the first and / or second insulating layers. Indicates gender.

[0104] [Table 5]

[0105] As will be described below with reference to Figure 3, when the diaphragm is placed into a push-pull electrostatic transducer, a DC bias voltage is applied to the gold conductive layer 6 and a varying drive signal voltage is applied to the stator of the electrostatic transducer, causing the diaphragm 2 to flex in response to the drive signal. Small areas of the adhesion layer 8 and second insulating layer 10 may be removed during manufacture (or subsequently removed) to expose portions of the conductive layers for the purpose of making electrical contacts (not shown).

[0106] Figure 2 shows the composite laminated diaphragm 12 according to the second embodiment of the present invention. The diaphragm 12 includes a first insulating layer 14 that functions as a substrate. The thickness of the first insulating layer 14 is 7 μm and it is made of biaxially oriented polypropylene (BOPP). Similar to the embodiment of FIG. 1, the conductive layer 16 is deposited on one surface of the first insulating layer 14. The conductive layer 16 is a layer of gold with a thickness of 8 nm deposited by vapor deposition.

[0107] In contrast to the embodiment of FIG. 1, in this embodiment, no adhesive layer is provided. Instead, a second insulating layer 18 is laid on top of the conductive layer 16, and the layers 16, 18 are joined to each other using ultrasonic welding. The thickness of the second insulating layer 18 is also 7 μm and it is made of biaxially oriented polypropylene (BOPP). Electrical contacts (not shown) are provided in the same way as described above with reference to FIG. 1.

[0108] As described above, in embodiments having an adhesive layer, the additional mass due to the adhesive can provide internal damping that attenuates resonance behavior, for example, at lower frequencies. Thus, in embodiments without an adhesive layer, the internal damping can be less. However, the mass of the diaphragm is smaller compared to an equivalent diaphragm having an adhesive layer. This relatively small mass raises the frequency of the resonance phenomenon, in which case, they can be sufficiently attenuated by the insulating layer, or they can be high enough in frequency such that they exceed, for example, 20 kHz (20 kHz is a typical upper limit of human hearing) in the audio range of interest for audio applications.

[0109] As described above, in embodiments having an adhesive layer, the adhesive can be selected such that the adhesive layer is airtight and moisture-tight. In embodiments without an adhesive, this airtightness and moisture-tightness can be provided instead by joining the insulating layer with the conductive layer in a way that is airtight and moisture-tight over the entire diaphragm (for example, by ensuring that the joint is airtight and moisture-tight over the entire circumference of the diaphragm).

[0110] In the above two embodiments, specific materials and thicknesses are given, but it will be understood that in other embodiments, different thicknesses and / or different materials can be used. Further, other variations (such as deposition methods) may be used. It should be understood that each manufacturing step (for example, deposition / coating of the conductive layer, coating of the adhesive layer, superposition of the second insulating layer, etc.) can be carried out according to manufacturing techniques that are known per se in the art.

[0111] FIG. 3 shows an exploded view of an electrostatic transducer 20 according to an embodiment of the present invention. The electrostatic transducer 20 includes a composite laminated diaphragm 2 having the structure described above with reference to FIG. 1, and the electrostatic transducer 20 further includes a first stator 24 and a second stator 26. Each stator 24, 26 includes a planar conductive plate having an array of holes provided therein.

[0112] The electrostatic transducer 20 also includes a first spacer 28 disposed between the first stator 24 and the diaphragm 2. A second spacer 30 is disposed between the second stator 26 and the diaphragm 2. Each spacer 28, 30 is provided with a large opening 32. The electrostatic transducer also includes a first support frame 34 and a second support frame 36 each having a large opening 38 corresponding to and aligned with the opening 32 of the spacer.

[0113] When the electrostatic transducer is assembled, the diaphragm 2, the spacers 28, 30 and the stators 24, 26 are superposed on each other and fixed together by the frames 34, 36, and these are held together using screws 40. The spacers 28, 30 hold the stators 24, 26 in a spaced relationship from the diaphragm 2 therebetween. The thickness of each spacer 28, 30 is 0.8 mm, whereby the distance between the diaphragm 2 and each stator 24, 26 is 0.8 mm.

[0114] In use, a DC bias of 1800 V is applied to the conductive layer of the diaphragm 2. As described above, the electrical contact is provided on the conductive layer by removing or omitting a part of the second insulating layer and the adhesive layer from the region selected for providing the contact. The electrical contact and the voltage source of the transducer are omitted from FIG. 3 for clarity.

[0115] To drive the movement of the diaphragm 2, a variable drive signal voltage corresponding to a desired audio signal is applied to the first stator 24, and a corresponding inverted signal is applied to the second stator 26. The DC bias supplied to the diaphragm 2 generates an electrostatic field between the diaphragm and the stator, and the variable voltage applied to the stator generates a force on the diaphragm, thereby vibrating the diaphragm and generating a sound wave corresponding to the drive signal voltage applied to the stator. Thereby, a desired audio signal is reproduced. As described above, the electrical contact is provided on the conductive layer by removing or omitting a part of the second insulating layer and the adhesive layer from the region selected for providing the contact. The electrical contact and the voltage source of the transducer are omitted from FIG. 3 for clarity.

[0116] FIG. 4 shows a cross-sectional view of a composite laminated diaphragm 42 according to a fourth embodiment of the present invention. The diaphragm 42 includes a first insulating layer 44 that functions as a substrate. The first insulating layer 44 is made of ULTEM (registered trademark) UTF120. In this example, the thickness of the first insulating layer 44 is 5 μm, but other thicknesses, such as 7 μm, 10 μm, or other thicknesses, may be taken according to the acoustic performance requirements.

[0117] The conductive layer 46 is deposited on the surface of the first insulating layer 44. The conductive layer 46 is a layer of aluminum with a thickness of 25 nm deposited on the first insulating layer 44 by sputtering or metal evaporation.

[0118] Following the plasma treatment of the conductive layer 46, an epoxy-based adhesive layer 48 applied as a coating to the conductive layer 46 is overlaid on the conductive layer 46. Next, the second insulating layer 50 is extended with a roller over the adhesive layer 48, further plasma-treated, and pressure is applied with a heating roller to bond the layers to each other. The adhesive is cured at a temperature of 130°C. The thickness of the second insulating layer 50 is also 5 μm and is made of ULTEM (registered trademark) UTF120 (however, similar to the first insulating layer 44, other thicknesses, for example, 7 μm, 10 μm, or other thicknesses, are possible depending on the acoustic performance requirements). The thickness of the adhesive layer is 4 μm.

[0119] It will be understood that the thicknesses of the layers in FIG. 4 are not shown to scale.

[0120] Although only four embodiments of the present invention have been described above, it should be understood that other embodiments and variations of the above embodiments are possible within the scope of the present invention.

Claims

1. 1. A method for manufacturing an electrostatic converter suitable for use in an automobile, comprising the steps of manufacturing a composite laminate diaphragm and assembling an electrostatic converter, The step of manufacturing the composite laminate diaphragm comprises: providing a first insulating layer comprising a sheet of electrically uncharged insulating material; providing a conductive layer on a surface of the first insulating layer; providing a second insulating layer comprising a sheet of uncharged insulating material; and bonding the second insulating layer to the conductive layer such that the second insulating layer extends over the conductive layer. Including, The thickness of the composite laminate diaphragm is less than 20 μm; The step of assembling the electrostatic converter comprises: providing a first conductive stator and a first insulating spacer; overlapping the first insulating spacer between the first conductive stator and the diaphragm to provide a gap of less than 1 mm between the first conductive stator and the diaphragm, and securing the first conductive stator, the first insulating spacer, and the diaphragm. A method for manufacturing an electrostatic converter comprising:

2. The method of claim 1 further comprising installing or using the electrostatic converter in a vehicle.

3. providing a second conductive stator and a second insulating spacer; and overlapping the second insulating spacer between the second conductive stator and the diaphragm to provide a gap of less than 1 mm between the second conductive stator and the diaphragm, and securing the second conductive stator and the second insulating spacer. The method of claim 1 or 2, further comprising:

4. 1. A method of manufacturing a composite laminate diaphragm for an electrostatic transducer suitable for use in an automobile, comprising the steps of: providing a first insulating layer comprising a sheet of electrically uncharged insulating material; providing a conductive layer on a surface of the first insulating layer; providing a second insulating layer comprising a sheet of uncharged insulating material; and bonding the second insulating layer to the conductive layer such that the second insulating layer extends over the conductive layer. Including, Here, the method for manufacturing a composite laminated diaphragm, wherein the thickness of the composite laminated diaphragm is less than 20 μm.

5. 5. The method of claim 1, wherein the step of bonding the second insulating layer to the conductive layer comprises applying an adhesive layer to the conductive layer and overlapping the second insulating layer to the adhesive layer, or applying an adhesive layer to the second insulating layer and overlapping the second insulating layer to the conductive layer.

6. The method of claim 1 , wherein the adhesive layer comprises an acrylic adhesive.

7. 7. The method according to any of the preceding claims, wherein the adhesive layer has a thickness of from 1 μm to 10 μm, preferably from 3 μm to 5 μm, more preferably from 3 μm to 4 μm.

8. 8. The method of claim 1, wherein the conductive layer has a thickness of less than 1%, preferably less than 0.5%, more preferably less than 0.1% of the thickness of the composite laminate diaphragm.

9. The method according to any of the preceding claims, wherein the conductive layer has a thickness of 5 nm to 50 nm, preferably 8 nm to 30 nm.

10. 10. A method according to any preceding claim, wherein the first insulating layer has a thickness of from 5 to 15 μm, preferably from 6 to 8 μm, more preferably about 7 μm.

11. A method according to any preceding claim, wherein the second insulating layer has a thickness of from 5 μm to 15 μm, preferably from 6 μm to 8 μm, more preferably about 7 μm.

12. The method according to any of the preceding claims, wherein the composite laminate diaphragm has a length and / or width greater than 1 cm, preferably greater than 5 cm.

13. The method of claim 1 , wherein the first insulating layer and / or the second insulating layer are formed from a polymeric material.

14. 14. The method according to any of the preceding claims, wherein the first insulating layer and / or the second insulating layer are formed from a material having a dielectric breakdown strength of more than 500 V / μm, preferably more than 550 V / μm.

15. 15. The method according to any of the preceding claims, wherein the first insulating layer and / or the second insulating layer are formed from a material having a dielectric constant less than 2.5, preferably less than 2.

3.

16. 16. The method of claim 1, wherein the first insulating layer and / or the second insulating layer are formed from a capacitor film.

17. 17. The method of claim 1, wherein the first insulating layer and / or the second insulating layer are formed from a material selected from the group consisting of: Biaxially oriented polypropylene; Polyaryletheretherketone; Polytetrafluoroethylene; Biaxially oriented polyethylene terephthalate; Polyphenylene sulfide; Polyetherimide; Polyethylene naphthalate; Polyimide; Polyethylene terephthalate; Polycarbonate; Polyethersulfone; Polyphenylsulfone; Polysulfone; Ethylene tetrafluoroethylene; Perfluoroalkoxy; Polyvinylidene fluoride; Poly(vinylidene fluoride-trifluoroethylene) copolymer; and Poly(vinylidene fluoride-trifluoroethylene) copolymer incorporating chlorotrifluoroethylene.

18. further comprising manufacturing the diaphragm from a composite material or film including the first and second insulating layers and the conductive layer; 18. The method of any of claims 1 to 17, wherein the composite material or film is preferably substantially isotropic with respect to at least one of the following: Young's modulus of the composite material or film, the coefficient of thermal expansion of the composite material or film, and the yield strength or tensile strength of the composite material or film.

19. further comprising manufacturing the diaphragm from a composite material or film including the first and second insulating layers and the conductive layer; the composite material or film has at least one parameter whose respective measurements match between two or more layers of the composite material or film; 19. The method of any of claims 1 to 18, wherein the at least one parameter is selected from the group consisting of coefficient of thermal expansion, Young's modulus, yield strength and tensile strength.

20. further comprising manufacturing the diaphragm from a composite material or film including the first and second insulating layers and the conductive layer; at least one parameter measured for the composite or film has one or more values ​​that match a corresponding value or values ​​of the same parameter measured for at least one of the first stator and the first spacer; 20. The method of any of claims 1 to 3, or any of claims 5 to 19 when directly or indirectly dependent on claim 1, wherein the at least one parameter comprises one or more parameters selected from the group consisting of thermal expansion coefficient, Young's modulus, yield strength and tensile strength.

21. 21. The method of claim 1, further comprising the step of fabricating the diaphragm from a composite material or film comprising the first and second insulating layers and the conductive layer, the composite material or film having the following properties: i) a glass transition temperature of at least 120°C; ii) at least one parameter whose respective measurements match between two or more layers of said composite or film, wherein said at least one parameter is selected from the group consisting of coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength; and iii) a surface energy in the range of 30 to 60 dynes / cm and / or 12 dynes / cm Polar surface energy exceeding

22. 22. The method of any of claims 1 to 21, wherein both the first and second insulating layers are formed from a material that includes or consists essentially of polyaryletheretherketone (PEEK), or polyetherimide (PEI), or polyethylenenaphthalate (PEN).

23. An electrostatic converter suitable for use in an automobile, comprising: A first conductive stator; Composite Laminated Diaphragm and a first insulating spacer disposed between the first conductive stator and the diaphragm to provide a spacing between the first conductive stator and the diaphragm of less than 1 mm; Equipped with The composite laminate diaphragm comprises: a first insulating layer formed from a sheet of electrically uncharged insulating material; a conductive layer on a surface of the first insulating layer; a second insulating layer extending over and bonded to the conductive layer and formed from a sheet of uncharged insulating material; having An electrostatic transducer, wherein the composite laminate diaphragm has a thickness of less than 20 μm.

24. Second conductive stator and a second insulating spacer disposed between the second conductive stator and the diaphragm to provide a spacing between the second conductive stator and the diaphragm of less than 1 mm; 24. The electrostatic converter of claim 23 further comprising:

25. 25. An electrostatic transducer as claimed in claim 23 or 24, wherein the second insulating layer is joined to the conductive layer by an adhesive layer between the conductive layer and the second insulating layer.

26. 26. The electrostatic transducer of claim 23, 24 or 25, wherein the adhesive layer comprises an acrylic adhesive.

27. 27. An electrostatic converter according to any of claims 23 to 26, wherein the adhesion layer has a thickness of from 1 μm to 10 μm, preferably from 3 μm to 5 μm, more preferably from 3 μm to 4 μm.

28. 28. An electrostatic transducer according to any one of claims 23 to 27, wherein the conductive layer has a thickness of less than 1%, preferably less than 0.5%, more preferably less than 0.1% of the thickness of the composite laminate diaphragm.

29. 29. An electrostatic converter according to any of claims 23 to 28, wherein the conductive layer has a thickness of 5 nm to 50 nm, preferably 8 nm to 30 nm.

30. 30. An electrostatic converter according to any of claims 23 to 29, wherein the first insulating layer has a thickness of from 5 to 15 μm, preferably from 6 to 8 μm, more preferably about 7 μm.

31. 31. An electrostatic converter according to any of claims 23 to 30, wherein the second insulating layer has a thickness of from 5 μm to 15 μm, preferably from 6 μm to 8 μm, more preferably about 7 μm.

32. 32. An electrostatic transducer according to any of claims 23 to 31, wherein the composite laminate diaphragm has a length and / or a width greater than 1 cm, preferably greater than 5 cm.

33. 33. An electrostatic transducer as claimed in any one of claims 23 to 32, wherein the first insulating layer and / or the second insulating layer are formed from a polymer material.

34. 34. An electrostatic converter according to any of claims 23 to 33, wherein the first insulating layer and / or the second insulating layer are formed from a material having a dielectric breakdown strength of more than 500 V / μm, preferably more than 550 V / μm.

35. 35. An electrostatic transducer according to any of claims 23 to 34, wherein the first insulating layer and / or the second insulating layer are formed from a material having a dielectric constant less than 2.5, preferably less than 2.

3.

36. the first insulating layer and / or the second insulating layer are formed from a capacitor film. Item 36. An electrostatic converter according to any one of items 23 to 35.

37. 27. An electrostatic transducer as claimed in any one of claims 23 to 26, wherein the first insulating layer and / or the second insulating layer are formed from a material selected from the group consisting of: Biaxially oriented polypropylene; Polyaryletheretherketone; Polytetrafluoroethylene; Biaxially oriented polyethylene terephthalate; Polyphenylene sulfide; Polyetherimide; Polyethylene naphthalate; Polyimide; Polyethylene terephthalate; Polycarbonate; Polyethersulfone; Polyphenylsulfone; Polysulfone; Ethylene tetrafluoroethylene; Perfluoroalkoxy; Polyvinylidene fluoride; Poly(vinylidene fluoride-trifluoroethylene) copolymer; and Poly(vinylidene fluoride-trifluoroethylene) copolymer incorporating chlorotrifluoroethylene.

38. the diaphragm is manufactured from a composite material or film including the first and second insulating layers and the conductive layer; 38. An electrostatic transducer according to any of claims 23 to 37, wherein the composite material or film is preferably substantially isotropic with respect to at least one of the following: Young's modulus of the composite material or film, the coefficient of thermal expansion of the composite material or film, and the yield strength or tensile strength of the composite material or film.

39. the diaphragm is manufactured from a composite material or film including the first and second insulating layers and the conductive layer; the composite material or film has at least one parameter whose respective measurements match between two or more layers of the composite material or film; 39. An electrostatic converter as claimed in any of claims 23 to 38, wherein the at least one parameter is selected from the group consisting of coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength.

40. the diaphragm is manufactured from a composite material or film including the first and second insulating layers and the conductive layer; at least one parameter measured for the composite or film has one or more values ​​that match a corresponding value or values ​​of the same parameter measured for at least one of the first stator and the first spacer; 40. An electrostatic converter as claimed in any of claims 23 to 39, wherein the at least one parameter comprises one or more parameters selected from the group consisting of coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength.

41. 23. The diaphragm is made of a composite material or film including the first and second insulating layers and the conductive layer, the composite material or film having the following properties:

41. An electrostatic converter according to any one of claims 1 to 40. i) a glass transition temperature of at least 120°C; ii) at least one parameter whose respective measurements match between two or more layers of said composite or film, wherein said at least one parameter is selected from the group consisting of coefficient of thermal expansion, Young's modulus, yield strength, and tensile strength; and iii) a surface energy in the range of 30 to 60 dynes / cm and / or 12 dynes / cm Polar surface energy exceeding

42. 42. An electrostatic converter as claimed in any one of claims 23 to 41, wherein both the first and second insulating layers are formed from a material comprising or consisting essentially of polyaryletheretherketone (PEEK), or polyetherimide (PEI), or polyethylenenaphthalate (PEN).

43. Use of an electrostatic converter according to any one of claims 23 to 42 in a motor vehicle.

44. A motor vehicle comprising an electrostatic converter according to any one of claims 23 to 42.

45. 1. A composite laminate diaphragm for an electrostatic transducer suitable for use in an automotive vehicle, comprising: a first insulating layer formed from a sheet of electrically uncharged insulating material; a conductive layer on a surface of the first insulating layer; a second insulating layer extending over and bonded to the conductive layer and formed from a sheet of uncharged insulating material; having A composite laminate diaphragm, wherein the thickness of the composite laminate diaphragm is less than 20 μm.

46. 46. ​​A composite laminate diaphragm according to claim 45, having the features according to any of claims 25 to 42.

47. 1. A method of manufacturing a composite laminate diaphragm for an electrostatic transducer, comprising: providing a first insulating layer comprising a sheet of electrically uncharged insulating material; providing a conductive layer on a surface of the first insulating layer; providing a second insulating layer comprising a sheet of uncharged insulating material; bonding the second insulating layer to the conductive layer such that the second insulating layer extends over the conductive layer. Including, A method for manufacturing a composite laminate diaphragm, wherein the thickness of the composite laminate diaphragm is less than 20 μm.

48. A first insulating layer formed from a sheet of insulating material. a conductive layer on a surface of the first insulating layer; a second insulating layer extending over and bonded to the conductive layer and formed from a sheet of insulating material; having A composite laminate diaphragm for an electrical transducer, wherein the thickness of the composite laminate diaphragm is less than 20 μm.

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