JPS586118A - Electret element and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electret element suitable for use in a compact, lightweight, and highly sensitive electret condenser f-microphone, etc. The present invention relates to a reliable and easy manufacturing method.

Conventionally, the method for manufacturing electret elements is (
1) Thermal electret method, (2) Electron beam irradiation electret method, etc. are known, but the thermal electret method maintains the temperature at a high temperature above the glass transition point and below the melting point, and applies a high voltage under a constant pressure. However, the method of cooling to room temperature has the disadvantage that it takes more than 1 hour to work. Also,
The electron beam irradiation electret method is a method of producing electrets by irradiating them with low-energy electrons, and this method has the disadvantage that the equipment required for this method is not suitable for mass production and is expensive. The electret elements based on the two conventionally known electret methods described above have a polymer film with a power of 1 to 2 Kv/
aII2 high v! I vertical O surface charge is charged, but this is an electret capacitor! In order to put it into practical use as a confectionery, K must be placed in a stable habitat so that it has a stable surface potential with little change over time. Generally, a value of about 1000 of the initial surface potential is the most temporarily stable and is called the nine surface potential, and is treated at a high temperature of 70° C. to 80° C. to attenuate and stabilize the initial surface potential. However, it takes a long time from SOO to SOa to reduce the K to about 1/10 of the initial surface potential, which is a bottleneck in mass production.

In addition, electret elements that use surface potential have poor moisture resistance and are not reliable, so they must be protected against humidity.
I need a friend.

Therefore, an object of the present invention is to solve the above-described drawbacks of the conventional electret element and method of manufacturing the same, and to provide a stable electret element and method of manufacturing the same in a short time and with little change over time.

This invention Kl! The electret material is made of fluorine-based resin, and when it is immersed in water, alcohol, or steam and then heated at a temperature below the glass transition point of the fluorine-based resin, the amount of charge becomes substantially lower. It has surface potential characteristics such that it is moldy.

According to the present invention, the method for manufacturing a nine-element totlet element comprises:
℃ or higher, polarized and charged by a corona discharge method in a good state, and immersed the nine-fluorine resin film in water, Flucor, or steam to remove the unstable charge of the scissors-charged film. It consists of heat treatment at a temperature below the glass transition point of the base resin.

The fluororesin films used in the electret element and the method for using the same according to the present invention are fluoroethylene, ethylene hexafluoropropylene polymer (FMP), boroph, vinylidene chloride (PVF'1), polytetrafluoropropylene, Fluorinated ethylene (TFE)
and other fluororesin films. Polyethylene terephthalate) (P112T) film can also be used, but the fluororesin film with low water absorption is preferred because it is stable over time.
4lum is polarized and charged by a corona discharge method at a temperature of 80° C. or higher.

A schematic diagram of a polarization device using a corona discharge method is shown in FIG. ), cover it with a fuvpH4 resin film 2 to be converted into an electret,
Part 1: Approximately 1O-C) Cut 1 ton of WrK tungsten wire. W pole I [4 uses aluminum (enoki, iron plate, copper plate, etc.),
Directly connected to the ground side of the high voltage power supply 7, and
) It also carries the X-element and also plays the role of keeping the distance under the tungsten wire constant. This outfit f! Fluorine resin film A to be converted into electret by placing it in a constant temperature bath at a predetermined temperature or by hot spraying it under the electrode plate 4.
2 to a predetermined temperature. In Figure 1, 6
indicates a moving vehicle, and 7 indicates a high-voltage power source that causes corona discharge. The moving vehicle 6 # has the role of controlling the time for the electret element to pass under the tungsten wire, that is, the corona discharge time, by moving a certain distance in a certain time.

Polarization conditions are related to temperature, applied voltage, and time. Samples were prepared using FIF as the fluororesin film, with a polarization time of 20 seconds, and by varying the applied voltage and temperature as shown in #11 below.

Beast 1 Next, each sample was immersed in ethyl alcohol for a few seconds to bring the surface potential of the film to zero volts, and then heated in a constant temperature bath at 80°C for 3 seconds.
After processing for 0 minutes, the surface potential becomes low.

Measured value of surface potential of each sample after treatment (V) As can be seen from the results shown in the graph, the surface potential recovers when the polarization temperature is 80°C or higher, but polarization occurs below 60°C. No recovery phenomenon was observed for the animals. Also, ・O℃
As stated above, the higher the applied voltage, the greater the recovered surface potential.

Furthermore, almost similar results were obtained when a polyvinyl vinylidene (PVP2) film was tested in place of the %FiilP film.

Even when polarization is performed at a temperature of 80° C. and an applied voltage of 6 KV, the longer the application time, the higher the recovered surface potential of the electret element. Incidentally, even if the polarization temperature is 80° C. and the applied voltage is less than t4 KV, it is possible to obtain a practical L/t tag as long as the application is applied for a long time. 9, 12
A recovery phenomenon of the element surface potential is observed even during polarization and travel time at temperatures exceeding 0°C. However, as long as the temperature is below the melting point of the fluororesin used, polarization can be achieved in a shorter time at a higher temperature.

In addition, in the above-mentioned stabilization treatment, even when treated at high temperature (70 ° C., 100 °C) etc. in methyl alcohol, water, steam, etc. instead of ethyl allol, the results obtained in the case of ethyl alcohol are the same. In the case of PIP film, if the treatment time is kept constant and the travel heat treatment temperature is increased, the value of the recovered surface potential will gradually increase. Once it reaches that level, it suddenly becomes lower.

This is because the change in this phenomenon is often caused by exceeding the glass transition point of the fluororesin used. Therefore, O heat treatment at a temperature exceeding the glass transition point is not preferable.Of course, when the heat treatment temperature is low, is charged 1 to a predetermined surface potential.
It took a long time to recover! ! So, for example, Fl
In the case of iF film, the temperature range close to the glass transition point is 80
℃~·SC can be said to be the optimum condition for the heat treatment temperature.

Electret elements manufactured using commonly used thermal electret elements have an operating temperature range (-sO to 60°C).
The amount of charge shows a tendency to attenuate over time, and there is also a problem in terms of reliability. On the other hand, in the electret element according to the present invention, the amount of charge tends to increase over time within the operating temperature range, and therefore it can be said that it is reliable and stable.

More than a margin below! Tomorrow, Mototaka 1! According to the method, polarization is performed using 711-element-based tree-maro twillum at 0°C or higher by the discharge method (if the applied voltage is low, it is necessary to polarize for a long time), Next, by removing unstable surface charges on the 74 lum with alcohol, water, steam, etc., and further heating at a temperature below the glass transition point of the fluororesin, an electret element with high Confucian properties can be easily produced. It is possible to prepare jin in the same way. The charge amount (II
Temperature and humidity nital test (70℃X?
@%R,H,Xt5H~-5ec×tlH). The results are shown in Figure S (Datura:).

The test conditions are high temperature 7 as shown in No. 111i (b).
・CX?・%R, H, Xt 1 hour ~ Low temperature - Black O℃ x t1
The test was carried out by continuously turning the edges at a time of O nital and a day of S nite (It cycle/time).

FIG. The surface potential has already begun to drop by more than 5% at 5t ital density, about 10% at 10 nite, and about 2s0% at SO nite. Extreme deterioration is seen.Therefore, if these X and Y elements are used in a microphone/phone, a problem will occur over time in terms of KII performance.

On the other hand, in the case of electret devices using 1mK zero-fire, in SO Nital S*, the surface potential tends to increase by about 5% at most, indicating an improvement in performance. The rate of change up to Nycle is also within ±5%), and has extremely stable time running performance compared to the secondary example. By the way, 50 Nykles in the 1 temperature/humidity Nykles test, when converted to normal time, will rise from about S to 10 years, and 1
In the 00 cycle, it is expected to vary from about 1 s to 20 years.

Therefore, the electret element of the present invention can practically provide sufficiently stable characteristics for about 15 years.

It is clear from this result that the nine-element totlet element manufactured by the manufacturing method of the present invention has high reliability.

Furthermore, the electret element having the recovery phenomenon shown in No. 211 is immersed in ethyl alcohol again, and the W potential is set to zero volts, and then heat treatment is performed again for SO sorting in a constant temperature bath at 80°C. Recognizing that the surface potential in particular decreases, the measured values of the surface potential of each sample after this treatment are shown in the 4th EK.

This clearly shows that low-voltage charges are trapped within the heptadium-based resin film.

That’s 11ijl! As described above, according to the present invention, a highly reliable electret element can be manufactured easily and in a short time, and can be suitably used as an electret element for an electret; ndenna miter.

Figure 2 is a schematic explanatory diagram showing an example of a device for polarizing and charging a fluororesin film (by a corona discharge method) in accordance with Hon'ei Meikan Ori. Write the polarization under some conditions,
Next, the surface potential of the film was brought to zero volts by immersion in ethyl alcohol, and after that, it was heat-treated at 10°C for 50 minutes to show the recovered surface potential. 51I (bl) is a graph showing the results of a humidity and temperature nital test showing the change over time in the amount of charge (surface potential) of an electret element made of FIP74 lume manufactured by FIP74), and No. 51I (bl) is a temperature and humidity Nycl diagram showing the test conditions. For a reason.

The 41st meter is the main departure @Kl! The electret element made of nine FIP films was immersed in ethyl alcohol again to bring the potential of the film surface to zero volts, and the electret element was heated at 41a after death.
This is a graph showing the recovered surface potential when exposed to heat for SO minutes at 0°C.

In Figure 1, 1 is a tundsten wire, 2 is a 7-silicon resin film to be converted into an electret, black is an insulating film, 4 is an electrical appliance, the bottom line is a hot play), 4a is a moving vehicle, and A is a high-voltage power source. .

patent applicant Iwasaki Sushinki Co., Ltd. patent application agent Patent attorney Aoki Ami Patent Attorney Painter Kazuyuki Tate Benri Doseki 1) Kei Patent attorney Sarayuki Yamaguchi

Claims (1)

[Scope of Claims] 1. Am potential characteristics such that the amount of charge is substantially maintained when heated at a temperature below the glass transition point of the 7V resin after being immersed in water, alcohol or steam. Possessing 1*Electret element made of moldy fluororesin film. L Heated to a temperature of 80°C or higher and polarized and charged by a corona discharge method in good condition to form a fluorine-based resin filter Aj water,
Production of an electret element characterized by removing the unstable charge of the scissor-charged film by immersing it in alcohol or water vapor, and then heating it at a temperature below the glass transition point of silicon-based resin 7. Method.