KR100774303B1 - Electret for high temperature, process for preparing the same, and microphone comprising the electret - Google Patents

Abstract

An electret for high temperature, a fusion method thereof, and a microphone having the electret are provided to be used in an SMD(Surface Mount Device) condition by obtaining a high-temperature charge characteristic and improving the environment resistance of the electret. An electret(20) for high temperature is composed of a metal plate and an electret film formed by compressing and molding the mixture containing heat-resistant fluorine resin powder and ceramic dielectric powder, and plasticizing the molded material. The metal plate and the electret film are bonded by applying heat-resistant fluorine primer between the metal plate and the electret film. The heat-resistant fluorine resin powder is one selected from a group comprising PTFE(Polytetrafluoreethylene), PFA(Perfluorealkoxy), FEP(Fluorinated Ethylene Prophylene resin), and PVDF(Polyvinylidene Fluoride). The ceramic dielectric powder is one selected from a group comprising SiO2(Silicon Dioxide), Si3N4(Silicon Nitride), TiO2(Titanium Trioxide), BaTiO3(Barium Titanate), PBZO3(Lead), and BN(Boron Nitride). The heat-resistant fluorine primer is one selected from a group comprising PTFE, PFA, FEP, and PVDF. The electret film contains the ceramic dielectric powder of 5wt.% to the total weight of solid matter. A plasticizing process is executed at 350 - 380 degrees centigrade for 2 hours per 1cm of the compressed material.

Description

Electret for high temperature, process for preparing the same, and microphone comprising the electret

1 shows a schematic diagram of a microphone according to the invention.

<Description of the code used in the main part of the drawing>

11: diaphragm 12: spacer

13: first support 14: second support

15: PCT substrate 16: field effect transistor

17: bipolar plate 18: housing

19: Polaring 20: Electret

21: sound hole

The present invention relates to a high temperature electret, a fusion method thereof, and a microphone having the same, and more particularly, to a high temperature electret useful for manufacturing a high quality microphone by improving high temperature charge characteristics, a fusion method thereof, and a microphone having the same. will be.

In general, the microphone vibrates a carbon type using the electrical resistance characteristics of the carbon particles, a crystal type using the piezoelectric effect of the Rossel salt, and a diaphragm equipped with a coil in a magnetic field according to a method of converting mechanical vibration into an electrical signal to induce an induced current. It can be classified into a movable coil type to be generated, a velocity type using an induced current generated when a metal film disposed in a magnetic field is vibrated by sound waves, and a condenser type using capacitance changed by vibration of the film by sound waves.

Such condenser microphones typically consist of a voltage bias component (typically an electret), a diaphragm / double plate pair to form a capacitance that changes in response to sound pressure, and a field effect transistor to buffer the output signal. to be. Among the most widely used electret condenser microphones, electrets are formed in either the diaphragm or the bipolar plate, and the electret formed in the diaphragm is called the front electret, and the one formed on the bipolar plate is called the back electret. . Such electrets are typically formed by forcibly injecting charge into an organic film.

Looking at the operation of the microphone of the electret condenser described above, when the sound pressure introduced through the sound hole located at the end of the microphone is applied to the diaphragm, the diaphragm vibrates and the distance from the bipolar plate is changed. In this way, when the distance between the diaphragm and the bipolar plate is changed by sound pressure, the capacitance formed between the diaphragm and the bipolar plate is changed, so that a change in the electrical signal (voltage) according to sound waves can be obtained, and this signal is provided in the circuit part. Passed through the amplifier to the outside.

In addition, the conventional electret condenser microphone is not only a material resistant to high temperatures, but also a material having a high temperature resistant component such as a bipolar plate that forms an electret. Therefore, this causes a problem that the sensitivity is lowered and it is difficult to apply a surface mount device (SMD) to the electret condenser microphone. That is, as the manufacturing technology of electronic products is developed, the trend is to miniaturize products, and surface mount technology (SMT) is widely used for manufacturing such small products. However, since the electret condenser microphone is formed by forcibly injecting electrons into the organic film fused on the metal plate, when the humidity is high or the temperature is high, the charged electrons are easily released and the performance of the electret is deteriorated.

In particular, the conventional manufacturing method is a dispersion for forming an organic film, for example, fluoro ethylene propylene (FEP: FluoroEthylene Propylene), poly tetrafluoro ethylene (PEFE; Poly TetraFluoro Ethylene), polyethylene terephthalate (PET: Poly Ethylene terephthalate) The dispersion is coated on a metal plate using a thickness of 1 to 50 μm or continuously laminated by fusion of a metal heating roll and a rubber roll to be punched out, and then mounted on a microphone and charged with a general soldering microphone electret, and then 30 to 80 ° C. to 110 ° C. Aging is done in less than a minute. In this case, the charge loss occurs around 15%, and the remaining charge is used as a capacitor electret to convert the voice signal of the microphone into an electrical signal. The charge-charge capacity of the electrets here affects the signal transfer performance. The amount of charge charged in the electret greatly affects the quality of the condenser microphone, and as much as possible, the charge is charged, and when the amount of charge is not reduced in the aging process, it is possible to manufacture a microphone of high quality. However, conventional fluorine-based resins such as FEP or PET are difficult to charge a large amount of charge, there is a problem that can not maintain the charge charged at a high temperature of SMD conditions. This is because the crystallinity of the material forming the electret is low or the heat resistance is low.

As a method of fusion of the high temperature electret as described above, for example, there is a method of first bonding the FEP film to the metal plate and then fusion bonding the PTFE film, but the heat resistance of the FEP itself, that is, the melting point is low, at 250 ° C. A large amount of the charged charges is lost and the practicality is lowered. In addition, PTFE is a non-adhesive resin, which has a very high melting point of 325 ° C to 335 ° C and a high melting point. Therefore, in order to fuse it alone with a metal plate, it is melted by hot press using a hot press and then melted. The fusion process is carried out by pressure cooling to prevent the shrinkage of the metal plate and the PTFE film, but the crystals are formed largely by the slow cooling process, so that the space for accommodating the electric charge is reduced, and the protective film used for hot press fusion is fused. The problem is that the charge charged by roughening the PTFE surface is easily attenuated at high temperatures.

In addition, since the protective film used in the above process must endure at a temperature of 330 to 380 ° C., a polyimide film, a copper foil or an aluminum foil is used, and thus the polyimide film has a high price and is limited in its use. Aluminum foil is used, which is in contact with the PTFE surface has a problem that the release is difficult. Therefore, in the case of using copper foil or aluminum foil, a protective film such as PE adhesive is attached to the back of the metal plate and then etched to remove copper foil or aluminum foil, and a complex process of removing the protective film must be performed.

In addition, as the material of the high-temperature electret, ceramic-based SiO ₂ , Si ₃ N ₄ , TiO ₂ , BaTiO ₃ , PBZO _3, etc. have been developed. It is difficult to charge with an electret, and even when charged, since it is charged from the surface, it easily disappears when humidity or other foreign substances come into contact with the surface, and there is a problem that it is very weak to humidity or the surrounding environment.

The technical problem to be achieved by the present invention is to provide an electret suitable for high temperature.

Another object of the present invention is to provide a method for producing the high temperature electret.

Another object of the present invention is to provide a method for continuously welding the electret.

Another object of the present invention is to provide a microphone having the electret.

The present invention to achieve the above technical problem,

A high temperature electret comprising a heat resistant fluororesin material or a heat resistant fluororesin and ceramic dielectric material is provided.

According to one embodiment of the present invention, the heat resistant fluororesin-based material is preferably polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), fluorinated ethylenepropylene resin (FEP), Polyvinylidene fluoroide (PVDF), or the like.

According to one embodiment of the present invention, in order to attach a non-tacky fluorine-based PTFE

By heat-resistant fluorine-based primers (PTFE, PFA-based) or a heat-resistant conductive adhesive, the metal is first fused.

The present invention to achieve the above other technical problem,

Compression molding a mixture comprising a heat resistant fluororesin powder or a heat resistant fluororesin and ceramic dielectric powder; And

It provides a method for producing an electret film comprising the step of firing the compression molding.

The present invention to achieve the above another technical problem,

Applying a fluorine-based primer or a conductive adhesive onto the metal plate and then performing dry firing; And

It provides a method of fusion of the high temperature electret comprising the step of placing and fusion welding the electret film on a metal plate formed with a fluorine-based primer or a heat-resistant adhesive.

According to one embodiment of the present invention, the fluorine-based heat-resistant primer is preferably polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), fluorinated ethylenepropylene resin (FEP), Polyvinylidene fluoroide (PVDF), as a heat-resistant conductive adhesive at 250 degrees 20 minutes It is desirable to endure.

According to one embodiment of the present invention, as the fusion step of the electret film, a double roll press treatment or a double belt press treatment is preferable.

According to one embodiment of the present invention, the double roll press treatment comprises: heating rolls / rubber rolls of the electret film on a metal plate coated with a fluorine-based primer; And a fusion process using two pairs of symmetric top and bottom rolls composed of a rubber roll / cooling roll.

According to one embodiment of the present invention, the double belt press treatment is a metal plate and the electret film coated with a heat-resistant fluorine-based primer or a heat-resistant conductive adhesive between two rotating belts in which a heating roll and a cooling roll are inserted therein. The process of fusing these by heating, pressurization, and cooling is shown.

According to one embodiment of the invention, the belt used in the double belt press treatment is coated with a polyimide film, or preferably to form a protective film on the electret film in contact with the belt.

The present invention to achieve the above another technical problem

Bipolar plate;

A high temperature electret formed on the bipolar plate and including a heat resistant fluororesin-based material and a ceramic dielectric material;

Diaphragm; And

It provides a microphone having a field effect transistor.

Hereinafter, the present invention will be described in more detail.

The present invention provides an electret capable of SMD having a structure resistant to high temperature while improving high temperature charge characteristics. The electret according to the present invention comprises a ceramic dielectric material having high temperature dielectric properties in addition to a heat resistant fluororesin material having a very high melting point.

The heat resistant fluororesin-based material forming the electret according to the present invention means a material having a high melting point and capable of maintaining charged charge at high temperature, which is an SMD condition. For example, polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), and fluorinated ethylenepropylene. Resin (FEP), Polyvinylidenefluoroide (PVDF), etc. are preferable. In particular, the PTFE is a non-adhesive resin having a very high melting temperature of about 325 to 335 ° C, which is suitable for use in the present invention. As such PTFE, a modified PTFE or a low molecular weight PTFE may be used.

The ceramic dielectric material forming the electret according to the present invention preferably has its own ultra-high temperature properties, for example, SiO ₂ , Si ₃ N ₄ , TiO ₂ , BaTiO ₃ , PBZO ₃ , or BN may be used. However, it is not limited to these. Such a ceramic dielectric material may be included in an amount of less than about 5% by weight based on the total solids forming the electret. When the content of the ceramic dielectric material exceeds 5% by weight, high-temperature charge characteristics may be reduced, which is not preferable. .

This ceramic dielectric material not only improves the high temperature charge properties of PTFE, but also acts as a polymer crystal seed to generate large amounts of crystals in the PTFE layer, forming an interface where large amounts of charge can be trapped, and provide a dense and uniform surface. After being applied to the phase it serves to trap the charge between the crystals by rapid firing and cooling. Such ceramic dielectric materials are not significantly affected by the surrounding environment such as humidity or temperature, thereby enhancing the environmental resistance of the electret.

When the electret according to the present invention is configured in the form of a film, it is preferable to have a thickness of 10 to 50 μm. When the thickness is less than 10 μm, the particle size of the PTFE raw material is too small to trap the charge. There is, there is a problem that the economy is lowered because the effect due to the excess thickness is less than 50㎛.

The electret according to the present invention as described above can be manufactured as follows.

It is possible to prepare an electret film according to the present invention by first compression molding a mixture comprising a heat resistant fluororesin powder and a ceramic dielectric powder, and then firing the obtained compact.

The heat resistant fluororesin-based powder and ceramic dielectric powder may be the same as described above, and the heat-resistant fluororesin-based powder may have a particle size of about 100 μm or less, and an average particle diameter of 30 to 50 μm. In the case of the ceramic dielectric powder, it is preferable to use a particle diameter of 10 mu m or less.

Their content ratio may be less than 5% by weight of the ceramic dielectric powder with respect to the total solid content of the film, the heat-resistant non-resin-based powder may be more than 95% by weight.

As the compression molding step of the mixture, for example, a mixture uniformly mixed using a high speed mixer is put into a die for compression molding of PEPE, and molded into a film at a molding pressure of 100 to 600 kg / cm ² , and then 350 to 380. It bakes at the temperature of ° C. It is preferable to maintain the firing time within about 2 hours per 1 cm thickness of the molded article. The obtained PIPE fired product can be scraped off with a skiving machine to have a thickness of about 20 to 50 μm to produce an electret film according to the present invention.

The electret film obtained by the process as described above can be continuously fused on a metal plate, the specific method is as follows.

After applying the fluorine-based primer on the metal plate, and drying and firing it, the hot electret is fused on the metal plate by continuously placing the electret film obtained according to the above process on the metal plate on which the fluorine-based primer is formed and fusing it continuously.

Generally, the compression molded electret film as described above is non-adhesive and does not fuse with metal. In the present invention, a high temperature fluororesin primer such as Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), Fluorinated ethylenepropylene resin (FEP), Polyvinylidenefluoroide (PVDF), or the like is previously formed on a metal plate, and then the electret film is fused. .

The high temperature fluororesin primer is continuously applied to the metal plate with a thickness of 1 to 30 μm using a spray method or a gravure coating method and dried and fired at a temperature between 200 and 380 ° C. for 5 to 30 minutes to form one side of the metal plate. The electret film is fused on the thus formed primer.

The metal plate on which the high temperature fluororesin primer is formed is not particularly limited as long as it is used in the art, but for example, brass, bronze, phosphor bronze, nickel silver, sus etc. having a thickness of 0.1 to 0.5 mm may be used. At this time, the metal plate may be nickel plated by corrosion prevention, but the plating thickness is 0.5 to 4 μm.

As a method of fusion | melting the said electret film on the metal plate in which the primer was formed, the double roll press process or the double belt press process which can continuously process is preferable.

The double roll press treatment comprises: heating rolls / rubber rolls of the electret film on a metal plate on which a heat resistant fluorine-based primer or a heat conductive adhesive is formed; And a process of fusing using two pairs of symmetric top and bottom rolls composed of a rubber roll / cooling roll. That is, the metal plate on which the primer is formed and the electret film are passed between the rotating first upper and lower rolls (heating roll / rubber roll) to be fused by heating and pressure, and the second upper and lower rolls (rubber roll / cooling roll) which rotates again. Passed through, cooled and pressurized to continuously fuse.

The heating roll used in the first upper and lower rolls is preferably an induction heating roll, and the cooling roll used in the second upper and lower rolls is preferably water-cooled, in which a cooling water flows inside. The rubber rolls used in the first and second may be suitable for high temperature.

The first upper and lower rolls and the second upper and lower rolls preferably have a structure that is symmetrical with each other. For this purpose, when the upper roll is the heating roll in the first upper and lower rolls, and the lower roll is the rubber roll, the upper roll in the second upper and lower rolls is It is a rubber roll, the lower roll is a cooling roll, it is preferable that the electret film is cooled immediately after fusion to the metal plate to which the primer is applied.

At this time, the temperature of the heating roll is preferably 300 to 500 ℃, the temperature of the cooling roll is preferably maintained at less than 30 ℃. If the temperature of the heating furnace is less than 300 ℃ can not be obtained sufficient fusion, if it exceeds 500 ℃ there is little benefit due to the excess temperature there is a possibility that the economic efficiency may be lowered is not preferable. When the temperature of the said cooling roll exceeds 30 degreeC, since sufficient cooling cannot be obtained, it is not preferable.

In addition, the rubber rolls in contact with the heating rolls are preferably cooled to allow the cooling water to flow therein or to be uniformly cooled so as not to cause deterioration or deformation even at a high temperature by a contact cooling method.

In the continuous welding process employing the double roll press method, the welding speed is preferably 0.3 to 5 m / min. If the welding speed is less than 0.3 m / min, the electret film may be fused to the roller. If the amount exceeds minutes, there is a possibility that sufficient fusion is not achieved, which is not preferable. In the fusion process, the line pressure between the roll and the roll is preferably used in the range of 5 to 200 kg / cm, and when the line pressure is less than 5 kg / cm, sufficient fusion between the metal plate and the electret film cannot be formed, and 200 kg If it exceeds / cm, the electret film may be damaged, which is not preferable.

In the fusion process of the above method, the metal plate is supplied by a heating roll, the electret film is supplied in the rubber roll direction is fused by heat compression, and quenched in the second upper and lower rolls, thereby preventing shrinkage deformation, thereby preventing adhesion It can improve the shape of the tissue by quenching, thereby forming a large amount of space in which charge is trapped.

In addition to the double roll press treatment, a double belt press treatment may also be used as a step of fusing the metal plate coated with the primer and the electret film.

The double belt press process refers to a process in which a metal plate coated with a fluorine-based primer and the electret film are inserted between two rotating belts in which a heating roll and a cooling roll are inserted therein to heat, pressurize and cool them, and fuse them. That is, the heating roll and the cooling roll are put in the upper belt, and the heating roll and the cooling roll are put in the lower belt, and a pair of rolls are rotated so that the belt is also rotated, and a metal plate and an electret film coated with a primer are coated between the two rotating belts. Means that the primer and the primer are inserted adjacent to each other and fused by heating and pressurization, and then cooled.

The belt usable in the double belt press method may be used without limitation as long as it is used in the corresponding field, but a SUS belt or the like may be used. However, when the SUS belt is used, the fused electret film may be released from the metal plate and adhered to the SUS belt. To prevent this, the SUS belt itself may be coated with a polyimide film or the like, or may be in contact with the belt. It is preferable to further form a protective film on the electret film. The protective films usable here include polyimide films, copper foils, aluminum foils, and the like, which can be removed by etching or directly peeling off after completion of the fusion process.

In the continuous welding process employing the double belt press method, the welding speed is preferably 0.3 to 5 m / min, if the welding speed is less than 0.3 m / min, the economical deterioration due to the decrease in the welding speed is concerned, 5 m / min When exceeding, since there exists a possibility that sufficient fusion may not be performed, it is unpreferable. In the fusion process, the line pressure between the belt and the belt is preferably used in the range of 5 to 200 kg / cm. When the line pressure is less than 5 kg / cm, sufficient fusion between the metal plate and the electret film cannot be formed, and 200 kg If it exceeds / cm, the electret film may be damaged, which is not preferable.

In the continuous fusion process employing the double belt press method, the temperature of the heating roll mounted inside the belt is preferably 300 to 500 ℃, the temperature of the cooling roll is preferably maintained below 30 ℃. If the temperature of the heating furnace is less than 300 ℃ can not be obtained sufficient fusion, if it exceeds 500 ℃ there is little benefit due to the excess temperature there is a possibility that the economic efficiency may be lowered is not preferable. When the temperature of the said cooling roll exceeds 30 degreeC, since sufficient cooling cannot be obtained, it is not preferable.

In such a double belt press method of fusion, it is possible to fuse the electret film for microphone with more uniform and excellent adhesion to the metal plate more easily.

In the present invention, it is possible to continuously fusion the electret film according to the present invention on the metal plate through the fusion process as described above.

In order to achieve the above another technical problem, the present invention provides a microphone having an electret according to the present invention, the schematic diagram of which is shown in FIG.

As shown in FIG. 1, the microphone according to the present invention is divided into an acoustic unit and a PCB circuit unit, and is mounted in one housing 18, and the acoustic unit includes a diaphragm 11 and a bipolar plate with a spacer 12 interposed therebetween. (back plate: 17) is faced, the diaphragm 11 is supported in the housing 18, the sound hole 21 is formed through the polar ring 19, the bipolar plate 17 is the first support 13 which is an insulator And the second support 14 which is a conductor are supported on the PCB substrate 15. The field effect transistor 16 is mounted on the PCB substrate 15. Here, the electrode plate 11 is formed with an electret 20 comprising a PTFE-based material and a ceramic dielectric material as described above according to the present invention.

In the driving mechanism of the microphone according to the present invention, first, when the sound pressure introduced through the sound hole 21 is applied to the diaphragm 11, the diaphragm 11 vibrates and the distance from the bipolar plate 20 changes. When the interval is changed by the sound pressure, the capacitance formed by the diaphragm 11 and the bipolar plate 20 is changed to obtain a change in the electrical signal according to the sound wave, and the signal is transmitted through the field effect transistor 16. It is amplified and passed out.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Electret film manufacturing

97% by weight of a PTFE molding powder (manufactured by DuPont) having a size of 100 µm or less and an average particle diameter of 30 µm and 1% by weight of SiO ₂ powder having a particle diameter of 10 µm or less were uniformly mixed using a high speed mixer. . The obtained mixed powder was put into a PIPE compression molding die, and molded at a molding pressure of 300 kg / cm ² , and then fired at 340 ° C. for 2 hours of holding time per cm of PIPE molded article thickness. The fired PIPE fired product was scraped off to a thickness of 30 μm using the skiving method to obtain an electret film as a target.

Example 1

PTFE-based primer (manufactured by DuPont), a high-temperature fluororesin primer, was applied on a 0.2 mm thick brass plate 150 mm wide and 500 mm long using a spray method, and then dried at a temperature of 250 ° C. for 10 minutes. One surface of the metal plate was formed under the condition that it was fused.

Subsequently, the metal plate on which the primer is formed is heated between a double roll press provided with a first upper and lower roll in which an upper roll is a heating roll, a lower roll is a rubber roll, and a second upper and lower roll in which an upper roll is a rubber roll and a lower roll is a cooling roll. The electret film was supplied along the rubber rolls of the first upper and lower rolls so as to contact the primers, and the fusion process was performed to fuse the electret film to the metal plate.

In this case, the temperature of the heating roll was maintained at 350 ℃, the temperature of the cooling roll was cooled to 25 ℃ by cooling water-cooled, in the case of rubber roll cooling uniformly so as not to deteriorate or deform even at high temperature by flowing the cooling water inside I was.

In the fusion process, the fusion rate was maintained at 1 m / min, the fusion line pressure between the roll and the roll was maintained at 100 kg / cm.

Example 2

PTFE-based primer (manufactured by DuPont), a high-temperature fluororesin primer, was applied on a 0.2 mm thick brass plate 150 mm wide and 500 mm long using a spray method, and then dried at a temperature of 250 ° C. for 10 minutes. One surface of the metal plate was formed under the condition that it was fused.

Subsequently, in a double belt press having an upper SUS belt and a lower SUS belt each having a heating roll and a rubber roll therein, the upper SUS belt and the lower SUS belt are rotated while rotating the roll, and the primer is between the belts. The electret film was fused to the metal plate by supplying the metal plate coated with the above, and the electret film in contact with the primer to be fused and cooled by heating and pressing. Here, a polyimide film was coated on the surface of the belt in contact with the metal plate or the electret film, the temperature of the heating roll was maintained at 350 ° C., and the temperature of the cooling roll was cooled by water cooling to 25 ° C., and the rubber roll In this case, the cooling water flowed inside to cool uniformly so as not to deteriorate or deform even at high temperatures. In the fusion process, the fusion rate was maintained at 1 m / min, the fusion pressure between the belt and the belt was maintained at 100 kg / cm.

Comparative Example 1

First, a PTFE molding powder (manufactured by DuPont) having a size of 100 µm or less and having an average particle diameter of 40 µm was introduced into a PIPE compression molding mold, molded at a molding pressure of 300 kg / cm ² , and then the thickness of the PIPE molded article at 340 ° C. Firing was carried out with a holding time of 2 hours per cm. The fired PIPE fired product was scraped to a thickness of 50 μm using the skiving method to obtain a PTFE film. The PTFE film was deposited on a width of 150 mm and a length of 500 mm on a brass plate having a thickness of 0.2 mm, and 16 μm of aluminum foil was deposited as a protective film, and then 40 kg / cm ² at a temperature of 340 ° C. using both press plates of a hot press. After pressurizing for 50 minutes by pressure, it was cooled. Subsequently, the aluminum foil was removed with a naphthalene-based etching solution to prepare an electret having a thickness of 50 μm.

Experimental Example 1: High Temperature Charge Characteristic Test

Classification Example 1 Example 2 Comparative Example 1   Metal Plate (Nickel Plating) Brass 0.2mm Brass 0.2mm Brass 0.2mm Primer thickness 5um 5um - PTFE dielectric film thickness 45um 45um 50um Fusion method Roll press Belt press Hot press Adhesion (g / cm) 417 521 273 High temperature charge characteristics Initial charge charge (v) 440 470 400 After 260 degrees Celsius ten minutes Ageing (v) 392 409 308 Charge retention (%) 89 87 77

Charge charging condition: Room temperature, -6kv, Speed 30m / min

The high temperature electret according to the present invention has excellent high temperature charge characteristics, improved environmental resistance, can be used under SMD conditions, can be fused onto a metal plate by a continuous process, and is obtained by the process according to the present invention. The let film may be particularly useful for microphones and sensors.

Claims (12)

plate; And An electret film obtained by compression molding a mixture comprising a heat resistant fluororesin-based powder and a ceramic dielectric powder, and then firing the mixture; Bonding them between the metal plate and the electret film by interposing a heat-resistant fluorine-based primer, The heat resistant fluororesin powder is one selected from the group consisting of Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), Fluorinated ethylenepropylene resin (FEP), and Polyvinylidene fluoroide (PVDF). The ceramic dielectric powder is one selected from the group consisting of SiO ₂ , Si ₃ N ₄ , TiO ₂ , BaTiO ₃ , PBZO ₃ and BN, The heat resistant fluorine-based primer is one selected from the group consisting of Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), Fluorinated ethylenepropylene resin (FEP), and Polyvinylidene fluoroide (PVDF), The content of the ceramic dielectric material is 5% by weight or less based on the total weight of solids of the electret film, High temperature electret, characterized in that the firing process is carried out at a temperature of 350 to 380 ℃, a firing time of 2 hours per 1 cm of the thickness of the compression molding. delete delete delete delete Applying a heat resistant fluorine-based primer on the metal plate and then drying and baking; Compressing the mixture including the heat resistant fluororesin-based powder and the ceramic dielectric powder and then firing to form an electret film; Simultaneously supplying the electret film on a metal plate to which the heat resistant fluorine-based primer is applied and fusing them, The heat resistant fluororesin powder is one selected from the group consisting of Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), Fluorinated ethylenepropylene resin (FEP), and Polyvinylidene fluoroide (PVDF). The ceramic dielectric powder is one selected from the group consisting of SiO ₂ , Si ₃ N ₄ , TiO ₂ , BaTiO ₃ , PBZO ₃ and BN, The heat resistant fluorine-based primer is one selected from the group consisting of Polytetrafluoroethylene (PTFE), Perfluoroalkoxy (PFA), Fluorinated ethylenepropylene resin (FEP), and Polyvinylidene fluoroide (PVDF), The content of the ceramic dielectric material is 5% by weight or less based on the total weight of solids of the electret film, The firing process is carried out at a temperature of 350 to 380 ℃, a firing time of 2 hours per 1 cm thickness of the compression molding, The drying firing process is a method for producing a high temperature electret, characterized in that performed for 5 to 30 minutes at a temperature of 200 to 380 ℃. delete The fusion method of the high temperature electret according to claim 6, wherein the fusion step of the electret film is a double roll press step or a double belt press step. The method according to claim 8, wherein the double roll press step comprises: the electret film on a metal plate coated with the fluorine primer, a heating roll and a rubber roll; And a step of continuously feeding between two pairs of symmetric top and bottom rolls composed of a rubber roll and a cooling roll to fusion them. The method of claim 8, wherein the double belt press process continuously supplies the metal plate and the electret film coated with a fluorine-based primer or a heat-resistant conductive adhesive between two rotating belts in which a heating roll and a cooling roll are inserted therein. And fusing them under heating and pressurization, and then cooling them. 12. The method of claim 10, wherein the belt used in the double belt press process is coated with a polyimide film, or a protective film is further formed on the electret film in contact with the belt. . A high temperature electret according to claim 1; Diaphragm; And And a field effect transistor.

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