JP3387012B2 - Electret condenser microphone and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electret condenser microphone and a method for manufacturing the same.

[0002]

2. Description of the Related Art Electret condenser microphones, which form a condenser portion with a diaphragm, an electrode plate and an electret material, are roughly classified into a back electret method and a wheel electret method according to the positional relationship between the diaphragm and the electret material. The so-called method has also been developed by the applicant. Of these, schematic structures of a back electret condenser microphone and a front electret condenser microphone are shown in FIGS. 6 and 7.

As shown in FIG. 6, a back electret type condenser microphone includes a printed circuit board 2, a holder 3, a back electrode plate 4, an electret layer 5, a spacer 6 and a vibration in a capsule 1 from the rear surface side to the front surface side. The plate 7 and the ring 8 are arranged in order, and the IC element 9 is arranged inside the holding body 3.

Here, the electret layer 5 is located on the rear surface side of the diaphragm 7 with a space formed by the spacer 6 interposed therebetween. For this reason, this method is called a back electret method. And the electret layer 5
Was welded to the surface of the back electrode plate 4 as an electrode plate.
It is formed of a polymer film (usually FEP) having a thickness of about 5 to 25 μm. The width of the back electrode plate 4 is 365.
It is manufactured by welding the above-mentioned polymer film to a brass plate having a length of 1200 mm and a length of 1200 mm, and then cutting a 26 mm wide strip.

The IC element 9 is an FE for impedance conversion.
The input terminal 9a is connected to the back electrode plate 4 on the front surface side, and the output terminal 9b is connected to the printed circuit board 2 on the rear surface side. 1a is a sound hole formed in the front surface of the capsule 1 and 1'is a front cloth attached to the surface of the front surface.

On the other hand, in the front electret type condenser microphone, as shown in FIG. 7, the printed board 2, the holder 3, the diaphragm 7, the spacer 6 and the electret layer 5 are provided in the capsule 1 from the rear side to the front side. The IC elements 9 are arranged in order, and the IC element 9 is arranged inside the holder 3.

The electret layer 5 is a diaphragm 7 in this case.
This method is called a front electret method in that it is covered on the back surface of the capsule front surface portion serving as an electrode plate located on the front surface side of the plate and the electret layer 5 is arranged on the front surface side of the diaphragm 7. . The electret layer 5 has a thickness of 12.5 to 12.5 welded to the back surface of the capsule front surface portion 11 as in the case of the back electret method.
It is formed of a polymer film (usually FEP) of about 25 μm.

In any of the methods, the spacer 6 for forming a space between the electret layer 5 and the diaphragm 7 has a thickness of 3 mm formed by punching in a frame shape.
A polymer film having a thickness of about 0 μm (usually PET) is used.

In the foil electret type condenser microphone, the diaphragm itself provided on the front side of the back electrode plate is formed of a polymer film having an electret effect, and the electret layer is not separated from the diaphragm. In this respect, the back electret type and the front electret type are distinguished.

[0010]

However, the above-mentioned conventional electret condenser microphone has the following problems. That is, since the electret layer is formed of a polymer film having a thickness of about 12.5 to 25 μm, which is welded and pressed on the surface of a back electrode plate as an electrode plate, the lot-to-lot quality of the polymer film. However, there were individual differences in the performance of electret condenser microphones due to variations in thickness and burrs of the polymer film that occur when the back plate is pressed. This is a front electret type,
Similar problems have arisen with the pressing of capsules.

The distance between the diaphragm and the back plate is
Since the thickness of the spacer, which is a polymer film, is included, it is substantially too large, which causes a problem in performance.
That is, since the spacer has a thickness of 30 μm and the electret layer has a thickness of 12.5 to 25 μm, the spacing is 42.5 to 55 μm. This also applies to the front electret type.

Further, in the conventional back electret system, a polymer film is welded to form a back electrode plate, a metal plate on which the polymer film is welded is cut, and press working is performed.
A process is required, and in the front electret system,
Instead of pressing, drawing was performed, which also required a total of 3 steps. In particular, equipment for press working and drawing is operated by a skilled operator, which is disadvantageous in terms of productivity and cost.

The present invention has been made in view of the above circumstances, and does not cause individual differences in performance due to variations in the thickness of the electret layer in the electret condenser microphone as in the prior art, and has higher performance. so,
An object of the present invention is to provide an electret condenser microphone that can be an easily manufactured electret condenser microphone and a method for manufacturing the same.

[0014]

An electret condenser microphone according to the present invention is formed on a diaphragm, a back electrode plate as an electrode plate arranged on the rear surface side, and a surface of the back electrode plate on the diaphragm side. A back electret-type electret condenser microphone that forms a condenser part with an electret layer, wherein the back electrode plate is sprayed with a spray liquid in which fine particles of FEP are dispersed on the surface of the material to be the back electrode plate, and then fired. And make it an electret layer,
And it is processed into the desired shape , and the spray
In the liquid, fine particles of FEP are dispersed and a thickener or
Is a mixture of surfactant and diluted with pure water.
And has a viscosity of 30 c. p. , The temperature is below 25 ℃
It is what

Another electret condenser microphone according to the present invention comprises a diaphragm, a front surface of the capsule arranged on the front surface of the diaphragm, and an electret layer formed on the back surface of the front surface of the condenser portion. Which is a front electret-type electret condenser microphone, wherein the capsule is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the surface of a material to be a capsule and then firing the electret layer. in it is obtained by machining the desired capsule, prior to
The spray liquid has fine particles of FEP dispersed therein.
Is mixed with a thickener or surfactant, and diluted with pure water
Having a viscosity of 30 c. p. , Temperature is 25
It is below ℃.

Further, another electret condenser microphone according to the present invention comprises a diaphragm, an electrode plate attached to a capsule arranged on the front surface of the diaphragm, and an electret layer formed on the back surface of the electrode plate. In the electret condenser microphone of the front electret system that constitutes the condenser section, the electret layer is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the back surface of a material to be an electrode plate, and then firing the electret layer. The spray liquid is
Fine particles of FEP are dispersed, and thickener or interface
It was mixed with an activator and diluted with pure water.
And has a viscosity of 30 c. p. , The temperature is below 25 ℃
It is something.

On the other hand, the electret condenser according to the present invention
The manufacturing method of the microphone is the diaphragm and the rear side.
Back plate as an electrode plate arranged on the back and a vibration plate of the back plate
Capacitor with electret layer formed on the side surface
Back electret type electret forming part
In the method of manufacturing a condenser microphone,
The surface of the material that becomes the back electrode plate in the process of forming the tret layer
A process of spraying a spray liquid in which fine particles of FEP are dispersed.
The material is fired to form an electret layer on the surface.
And a step of processing the material into a desired shape
The spray liquid contains fine particles of FEP.
When it is dispersed, a thickener or a surfactant is mixed,
It was diluted with pure water and had a viscosity of 30 c.
p. The temperature is 25 ° C. or lower.

Further, another electret connector according to the present invention
The method of manufacturing the condenser microphone is the diaphragm and the vibration
The front part of the capsule placed on the front of the moving plate and this front
Capacitor with the electret layer formed on the back surface of the part
Front electret type electret
A method of manufacturing a condenser microphone, which comprises:
The process of forming the ctret layer
Spray a spray liquid in which fine particles of FEP are dispersed on the back surface.
The process of firing the material and firing the material on the back side of the material
Step of forming a coating layer and the front part of the material with a drawing die
Add to the capsule with the electret layer on the back side of the
And a spraying process, wherein the spray liquid is FEP.
Fine particles are dispersed, and a thickener or surfactant
Is mixed with pure water and has a viscosity of
Is 30c. p. , The temperature is below 25 ℃
is there.

Furthermore, another electret according to the present invention
The manufacturing method of the condenser microphone is
The electricity attached to the capsule placed in front of the diaphragm
Electrode plate and electret formed on the back surface of this electrode plate
Front electret that forms a capacitor part with layers
Method of manufacturing electret condenser microphone
A method of forming the electret layer,
Fine particles of FEP are dispersed on the back surface of the material that will become the electrode plate.
The process of spraying the spray liquid and the back side after firing this material
The step of forming the electret layer on the desired material
And the step of processing into the shape of
Are fine particles of FEP dispersed and a thickener or
It contains a surfactant and is diluted with pure water.
Has a viscosity of 30 c. p. , The temperature is below 25 ℃
There is something.

Furthermore, in another method for manufacturing an electret condenser microphone according to the present invention, a step of spraying a spray liquid in which fine particles of FEP are dispersed on the surface of the material, and firing the material to form an electret layer on the surface. The step of forming is repeated a plurality of times.

[0021]

1 is a schematic explanatory view showing each step of a method for manufacturing an electret condenser microphone according to an embodiment of the present invention, and FIG. 2 is a schematic diagram of a front electret type electret condenser microphone according to the present invention. 3 is a schematic cross-sectional view of a portion, FIG. 3 is a graph showing the stability of the electret potential of an electret layer in the case of a method for manufacturing an electret condenser microphone according to another embodiment of the present invention, and FIG. FIG. 5 is a schematic explanatory view showing one step of the method for manufacturing the electret condenser microphone according to the embodiment, and FIG. 5 is a schematic explanatory view showing one step of the method for manufacturing the electret condenser microphone according to the embodiment of the present invention. In addition,
Parts and the like that are substantially the same as the conventional ones will be described with the same reference numerals.

The construction of the back electret type electret condenser microphone according to the first embodiment of the present invention is the same as that of the conventional back electret type electret condenser microphone except for the method of forming the electret layer 5 and the thickness thereof. Since it is the same as that of FIG.

The electret condenser microphone according to the first embodiment of the present invention includes a diaphragm 7, a back electrode plate 4 as an electrode plate arranged on the rear surface side, and a back electrode plate 4.
Is a back electret-type electret condenser microphone that forms a condenser portion with the electret layer 5 formed on the surface of the diaphragm 7 side, and the back electrode plate 4 is a brass plate 200 that is a material to be a back electrode plate. FE
After spraying the spray liquid 100 in which the fine particles of P are dispersed, it is fired to form the electret layer 5 and processed into a desired shape.

The electret layer 5 is formed by directly depositing FEP or the like on the surface of the back electrode plate 4, and is a thin film having a thickness of about 5.00 μm. On the surface of the peripheral portion of the electret layer 5, a spacer 6 for forming a space between it and the diaphragm arranged on the front side is formed by screen printing to a thickness of about 30 μm.

Such a back electrode plate 4 and an electret layer 5
By using the integrated member of the spacer 6 and the spacer 6,
A back electret type electret condenser microphone as shown in FIG.

The back electrode plate 4 and the electret layer 5 are formed by the following steps. First, an electret layer forming step of directly forming the electret layer 5 which is a thin film with fine particles having a diameter of the polymer FEP of about 0.1 μm to 0.25 μm on the surface of the back electrode plate 4 made of a brass plate excellent in heat conduction. And a brass plate 2 on which the electret layer 5 is formed
00 is pressed.

First, the brass plate 200 has a width of 26 mm.
The length is about 500 to 1000 m, and is supplied in a rolled state.

More specifically, in the electret layer forming step, the spray liquid 10 in which fine particles of polymer FEP are dispersed is used.
0 is sprayed on the brass plate 200, and the brass plate 200 sprayed with the spray liquid 100 in which the fine particles of the polymer FEP are dispersed is heated to fire the electret layer 5 and polarize it. .

As the fine particles of the polymer FEP, for example, fine particles of tetrafluoroethylene-hexafluoropropylene copolymer are used. As the spray liquid 100 in which the fine particles of the polymer FEP are dispersed, for example, ND-1 which is NEOFLON (trademark) FEP dispersion manufactured by Daikin Industries, Ltd. is suitable. This ND-1 has a viscosity of 1
0-30c. p. The temperature is 25 ° C., and it is suitable for spraying on the brass plate 200 which becomes the back electrode plate 4.

As a method for spraying the brass plate 200 with the spray liquid 100 in which the fine particles of the polymer FEP are dispersed, as shown in FIG. 1 (A), the brass plate 200 wound in a roll shape is sequentially. There is a method of performing the spray spray 300 while pulling out in the direction of arrow A. By doing this, as shown in FIG.
The spray liquid 100 is applied with a film thickness of about 0 μm.

Next, as shown in FIG. 1C, the brass plate 200 sprayed with the spray liquid 100 is heated to remove the organic solvent 110 contained in the spray liquid 100 to form a base for the electret layer 5. Forming a thin film 50 on which fine particles of polymer FEP are deposited. Here, it is heated in an electric furnace at an ambient temperature of about 300 ° C. for about 20 minutes.
By this heating, only the organic solvent 110 is removed, and the thin film 50 on which the fine particles of the polymer FEP are deposited is formed on the brass plate 200.

In this way, the polymer FE is attached to the brass plate 200.
After the thin film 50 in which the P particles are deposited is formed, the thin film 50 is subjected to general polarization treatment such as heating, cooling, plasma discharge, and corona discharge, and then the electret layer 5 is formed.
Is obtained (see FIG. 1D).

The electret layer 5 thus obtained was formed to a thickness of about 5.0 μm, and its surface resistance was 2.0 μm and was 1 × 10 ¹³ Ω. Here, as in the conventional case, the FEP film is attached to the back electrode plate 4
If it is welded to the surface of, the thickness of 12.5 μm was 2 × 10 ¹³ Ω. That is, it is possible to form the extremely thin electret layer 5 with the same resistance value by the manufacturing method according to the present embodiment.

Next, as shown in FIG. 1 (E), the brass plate 200 having the electret layer 5 polarized in the above step is sequentially supplied to the press machine 400, whereby the back electrode plate 4 is formed. Is formed. Since the brass plate 200 is roll-shaped, it can be automatically supplied to the press machine 400, and the back electrode plate 4 can be automatically and continuously formed.

As shown in FIG. 6, an electret condenser microphone using the back electrode plate 4 on which the electret layer 5 is formed is held in the capsule 1 from the rear side to the front side by holding the printed circuit board 2. The body 3, the back electrode plate 4 on which the electret layer 5 is formed, the spacer 6, the diaphragm 7, and the ring 8 are sequentially arranged, and the IC element 9 is arranged inside the holding body 3.

In the above-mentioned embodiment, ND-1 which is NEOFLON (trademark) FEP dispersion manufactured by Daikin Industries, Ltd. was used as the spray liquid 100. However, DS-101 ( Unidyne), EV-1300 (Unicef), Polystar OM
(Manufactured by NOF Corporation) thickeners such as, by mixing a surfactant, viscosity
30-90 c. p. Use the one whose temperature is 25 ℃.
May be used.

For example, this spray liquid 100 is diluted with pure water to have a viscosity of 30 c. p. When the diluted spray liquid whose temperature is 25 ° C. is used, the residual rate of the electret potential of the electret layer 5 is improved.

For example, when a diluted spray liquid prepared by mixing the spray liquid 100 and pure water at a ratio of 1: 4 is used,
As indicated by the white circles in FIG. 3, the remaining electret potential is improved. That is, the electret potential of the electret layer 5 is stable even when the back electrode 4 is exposed to the atmosphere of 150 ° C. for a long time.

The reason why the residual rate of the electret potential is improved is that the electret layer 5 having a small surface roughness is formed by reducing the viscosity, although the unclear part remains for the detailed reason. It is believed that there is.

It was also confirmed that if the completed back electrode 4 is re-fired, the electret potential remaining rate is further improved. For example, when firing was performed at 330 ° C. for 10 minutes, as shown by a black circle in FIG. 3, the residual rate of the electret potential was improved as compared with the case where the diluted spray liquid diluted with pure water was used. It could be confirmed.

The reason for this may be that the crystallinity and crystallinity of FEP have become higher.

Further, the step of firing after spraying the spray liquid 100 is repeated to obtain the following. For example, Polystar O as a thickener for the ND-1
M (manufactured by Nippon Oil & Fats Co., Ltd.) and has a viscosity of 35 to 40 c.
p. After spraying the spray liquid 100 having a temperature of 25 ° C. at 20 ° C., baking at 330 ° C. for 20 minutes, and then spray liquid 1 again.
When 00 is sprayed and fired under the same conditions as described above, a more stable electret layer 5 can be obtained.

The reason for this is considered as follows. In the first formation of the electret layer 5, there is a problem in the flatness of the electret layer 5 due to variations in the thickness of the electret layer 5 or pinholes. That is, the electret layer 5 having a uniform film thickness with improved flatness without pinholes is obtained.

It can also be considered that the first-time electret layer 5 plays a role as an adhesive between the back electrode plate 4 and the second-time electret layer 5.

On the other hand, in the front electret type electret condenser microphone, unlike the back electret type microphone, the front part 1 of the capsule 1 is
The electret layer 5 is formed on the back surface 11 </ b> A of No. 1.

The structure of the front electret-type electret condenser microphone according to the second embodiment of the present invention is the same as that of the conventional front electret-type electret condenser microphone except for the method of forming the electret layer 5 and the thickness thereof. Since it is the same as that of FIG.

That is, this front electret type electret condenser microphone is, as shown in FIG. 7, a vibrating plate 7, a front face part 11 of the capsule 1 arranged on the front face of the vibrating plate 7, and this front face part 11. Is a front electret-type electret condenser microphone that constitutes a condenser portion with the electret layer 5 formed on the back surface 11A of the electret layer 5, wherein the electret layer 5 is a spray liquid 100 in which fine particles of FEP are dispersed in a material to be the capsule 1. Is sprayed and then fired to form an electret layer 5 and processed into a desired capsule 1 by a drawing die.

Capsule 1 constituting this front electret type electret condenser microphone
Is an electret for directly forming a thin film electret layer 5 of fine particles of polymer FEP having a diameter of about 0.1 μm to 0.25 μm on the surface of an aluminum plate 600 excellent in heat conduction as a material constituting the capsule 1. It includes a layer forming step and a step of drawing the aluminum plate 600 on which the electret layer is formed.

First, the aluminum plate 600 has a width dimension of 26 mm and a length dimension of about 500 to 1000 m, and is supplied in a rolled state.

More specifically, in the electret layer forming step, the spray liquid 10 in which fine particles of polymer FEP are dispersed is used.
0 is sprayed onto the aluminum plate 600, and the aluminum plate 600 sprayed with the spray liquid 100 in which fine particles of polymer FEP are dispersed is heated to electret layer 5
And a step of firing. That is, the difference from the back electret type electret condenser microphone is that the back electret type has the electret layer 5 formed on the back electrode plate 4, whereas the front electret type has the capsule 1
That is, the electret layer 5 is formed on the back surface 11A of the front surface portion 11 of FIG.

As the fine particles of the polymer FEP, for example, fine particles of tetrafluoroethylene-hexafluoropropylene copolymer are used. As the spray liquid 100 in which the fine particles of the polymer FEP are dispersed, for example, ND-1 which is NEOFLON (trademark) FEP dispersion manufactured by Daikin Industries, Ltd. is suitable. This ND-1 has a viscosity of 1
0-30c. p. The temperature is 25 ° C. , and it is suitable for application to the aluminum plate 600 which will be the capsule 1.

As a method of spraying the aluminum plate 600 with the spray liquid 100 in which the fine particles of the polymer FEP are dispersed, as shown in FIG. 1 (A), the aluminum plate 600 wound in a roll shape is drawn out. Meanwhile, there is a method of performing the spray spray 300. By doing so, as shown in FIG. 1 (B), 1.0 to 5.0 μm
The spray liquid 100 is applied with a film thickness of.

When applying the spray liquid 100, as shown in FIG.
As shown in, a mask (not shown) is applied to the aluminum plate 600 so that the spray liquid 100 is applied only to the portion exposed from the opening of the mask. The opening of this mask is set so that the spray liquid 100 is applied only to the bottom surface of the capsule 1, that is, the back surface 11A of the front surface 11 of the capsule 1, for example.

Reference numeral 610 in FIGS. 4 and 5 denotes a feed hole formed in the aluminum plate 600.
A part corresponding to the feeding hole 610 is also formed in the brass plate 200 in FIG.

The mask may be formed by applying the spray liquid 100 in a strip shape as shown in FIGS. 5 (A) and 5 (B). As shown by the diagonal lines in FIG. 5 (A), when the spray liquid 100 is applied in a strip shape along the longitudinal direction of the aluminum plate 600, the spray liquid 100 can be sprayed only on the bottom surface of the capsule 1 and waste can be saved. effective. In addition, as shown by the diagonal lines in FIG. 5B, the capsule 1 is also applied when the spray liquid 100 is applied to the aluminum plate 600 in a diagonal strip shape.
It can be sprayed only on the bottom surface, which has the effect of eliminating waste.

Next, as shown in FIG. 1C, the aluminum plate 600 sprayed with the spray liquid 100 is heated to remove the organic solvent 110 contained in the spray liquid 100 to form a base for the electret layer 5. Polymer FE
A thin film 50 on which P particles are deposited is formed. Here, it is heated in an electric furnace at an ambient temperature of about 300 ° C. for about 20 minutes. By this heating, only the organic solvent 110 is removed, and the thin film 50 in which the fine particles of the polymer FEP are deposited is formed on the aluminum plate 600.

When the thin film 50 in which the fine particles of the polymer FEP are deposited on the aluminum plate 600 in this manner, the thin film 50 is generally polarized by heating, cooling, plasma discharge, corona discharge, or the like. Then, the electret layer 5 is obtained (see FIG. 1D).

The electret layer 5 thus obtained was formed to a thickness of about 5.0 μm, and its surface resistance was 2.0 μm and was 1 × 10 ¹³ Ω. Here, as in the conventional case, if the FEP film is welded to the back surface 11A of the front surface portion 11 of the capsule 1,
The thickness of 12.5 μm was 2 × 10 ¹³ Ω.
That is, it is better to manufacture by the manufacturing method according to the present embodiment,
It is possible to form an extremely thin electret layer 5 having the same resistance value.

After the electret layer 5 is formed on the aluminum plate 600 in this way, the electret layer 5 is subjected to general polarization treatment such as heating, cooling, plasma discharge, and corona discharge.

Next, as shown in FIG. 1 (E), a capsule 1 is formed on the aluminum plate 600 on which the electret layer 5 is formed by using a drawing die (not shown) instead of the press 400. . Needless to say, the capsule 1 is formed according to the size and size of the electret condenser microphone.

As shown in FIG. 4C, the electret layer 5 is formed only on the back surface 11A of the front surface portion 11 of the capsule 1.

As shown in FIG. 6, the electret condenser microphone using the capsule 1 having the electret layer 5 formed in this manner has the printed circuit board 2 and the holder 3 in the capsule 1 from the rear side to the front side. The diaphragm 7 and the spacer 6 are sequentially arranged, and the IC element 9 is arranged inside the holding body 3. Therefore, the electret layer 5 formed on the back surface 11A of the front surface portion 11 of the capsule 1
Together with the diaphragm 7 form a capacitor section.

Although the back electrode plate 4 is formed of the brass plate 200 in the above-described embodiment of the back electret type electret condenser microphone, it may be formed of a stainless plate, a titanium plate or the like.

In the electret condenser microphone of the front electret type, the spray liquid 100 is formed by using a mask that forms the electret layer 5 only on the back surface 11A of the front surface portion 11 of the capsule 1.
However, as shown in FIG. 4D, a mask that forms the electret layer 5 not only on the back surface 11A of the front surface portion 11 of the capsule 1 but also on the side surfaces thereof may be used.

In the above-described embodiment of the electret condenser microphone of the front electret type, the electret layer 5 is formed on the back surface 11A of the front surface portion 11 of the capsule 1. However, as shown in FIG. Alternatively, the electret layer 5 may be formed and the electrode plate 10 may be attached to the front surface portion 11 of the capsule 1. The electrode plate 10 has a sound hole 101.

The electrode plate 10 is attached to the front surface portion 11 of the capsule 1 by closing the opening 11B provided in the front surface portion 11 of the capsule 1, as shown in FIG. In this case, in order to prevent the electrode plate 10 from coming off, it is desirable that the opening 11B has a two-step diameter structure in which the outer diameter of the capsule 1 is small and the inner diameter is large. In this case, the outer peripheral portion of the electrode plate 10 is formed so as to match this two-step diameter structure.

Also, in this case, the capsule 1 of the electrode plate 10
In terms of strength and the like, it is most preferable to use adhesive and press-fit together, but it is needless to say that an appropriate method can be adopted. Further, a spacer 6 is interposed to provide a space between the diaphragm 7 and the electret layer 5.

The front part 1 of the capsule 1 of the electrode plate 10
The attachment to 1 may be as shown in FIG. That is, the opening 11B is not provided in the front surface portion 11 of the capsule 1, the recess portion 11C is formed in the back surface side 11A of the front surface portion 11, and the electrode plate 10 is attached to the recess portion 11C. Also in this case, it is desirable that the recess 11C has a two-step diameter structure. In this case, the outer peripheral portion of the electrode plate 10 is formed so as to match this two-step diameter structure.
The electrode plate 10 has a sound hole 101.

In this case, the capsule 1 of the electrode plate 10
In terms of strength and the like, it is most preferable to use adhesive and press-fit together, but it is needless to say that an appropriate method can be adopted. Further, a spacer 6 is interposed to provide a space between the diaphragm 7 and the electret layer 5.

Also, in the above method for manufacturing the electret condenser microphone of the front electret system, the spray liquid contains fine particles of FEP dispersed therein, a thickener or a surfactant mixed therein, and diluted with pure water. Having a viscosity of 30 c. p. At temperature
Is less than or equal to 25 ° C., it is possible to obtain the same effect as that of the method for manufacturing the back electret type electret condenser microphone described above.

That is, for example, this spray liquid 100
Is diluted with pure water to give a viscosity of 30 c. p. When the diluted spray liquid whose temperature is 25 ° C. is used, the residual rate of the electret potential of the electret layer 5 is improved.

For example, when a diluted spray liquid prepared by mixing the spray liquid 100 and pure water at a ratio of 1: 4 is used,
As indicated by the white circles in FIG. 3, the remaining electret potential is improved. That is, the electret potential of the electret layer 5 is stable even when the back electrode 4 is exposed to the atmosphere of 150 ° C. for a long time.

It was also confirmed that when the completed back electrode 4 was re-fired, the electret potential remaining rate was further improved. For example, when firing was performed at 330 ° C. for 10 minutes, as shown by a black circle in FIG. 3, the residual rate of the electret potential was improved as compared with the case where the diluted spray liquid diluted with pure water was used. It could be confirmed.

Further, the same effect can be obtained by forming the electret layer 5 twice. this is,
As described above, it is considered that the reason is to improve the homogenization by forming the second electret layer 5 on the first electret layer 5 having a problem in homogenization.

Although the electret layer 5 is formed twice, it goes without saying that it may be formed three times or more.

[0076]

The electret condenser microphone according to the present invention includes a diaphragm, a back electrode plate as an electrode plate disposed on the rear surface side, and an electret layer formed on the surface of the back electrode plate on the diaphragm side. Is a back electret-type electret condenser microphone for forming a condenser part, wherein the back electrode plate is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the surface of a material to be the back electrode plate, and then firing the electret layer. And processed into a desired shape , and the spray liquid is FEP
While the fine particles are dispersed, the thickener or surfactant
Being mixed and diluted with pure water, the viscosity is
30c. p. And the temperature is below 25 ° C
is there.

By forming the back electrode plate in this way, there is no variation in the quality and thickness of the electret layer unlike the conventional electret condenser microphone in which the FEP film is welded to the back electrode plate. Can be achieved. Further, since it is not necessary to press the polymer FEP film on the back electrode plate after welding, there is no problem of film burr which causes deterioration of performance as in the conventional case. In particular, when the material in which the fine particles of FEP are dispersed is applied to the material by spraying, it becomes possible to form an electret layer which is superior in mass productivity and cost to the spin-on coating method and the dipping method. In addition,
As the FEP fine particles are dispersed as a pre-solution,
Is mixed with a thickener or surfactant, and diluted with pure water
Having a viscosity of 30 c. p. And the temperature is 2
If the temperature is below 5 ° C, the viscosity will decrease.
As a result, the electret layer with less surface roughness is formed.
It is thought that the electret potential of
The survival rate is improved.

Further, in the electret condenser microphone according to the present invention, the diaphragm, the front surface of the capsule arranged on the front surface of the diaphragm, and the electret layer formed on the back surface of the front surface constitute the condenser portion. A front electret-type electret condenser microphone, wherein the capsule is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the surface of a material to be a capsule, and then firing the electret layer to obtain a desired electret mold. and which has been processed into capsules, the scan
As the FEP fine particles are dispersed in the play liquid,
Sticky agent or surfactant was mixed and diluted with pure water
Having a viscosity of 30 c. p. And the temperature is 25 ° C or higher
It is the one below.

Therefore, this electret condenser microphone is also uniform in quality because there is no variation in the quality and thickness of the electret layer unlike the conventional electret condenser microphone in which the FEP film is welded to the back electrode plate. Further, since it is not necessary to press the polymer FEP film on the back electrode plate after welding, there is no problem of film burr which causes deterioration of performance as in the conventional case. In particular, when the material in which the fine particles of FEP are dispersed is applied to the material by spraying, it becomes possible to form an electret layer which is superior in mass productivity and cost to the spin-on coating method and the dipping method.
Furthermore, fine particles of FEP are dispersed as a spray liquid.
In addition, a thickener or surfactant is mixed and
Diluted with water, having a viscosity of 30 c. p. so,
If you use the one whose temperature is below 25 ℃,
The electret with less surface roughness
It is thought that the
The residual rate of the electrical potential is improved.

Further, the electret condenser microphone according to the present invention comprises a diaphragm, an electrode plate attached to the capsule arranged on the front surface of the diaphragm, and an electret layer formed on the back surface of the electrode plate. A front electret-type electret condenser microphone constituting a part, wherein the electret layer is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the back surface of a material to be an electrode plate, and then firing the electret layer. And the spray liquid is FE
Fine particles of P are dispersed and thickener or surface active
The agent is mixed and diluted with pure water.
The degree is 30c. p. And the temperature is below 25 ℃
Of.

In addition to the effects of the above-mentioned electret condenser microphone, this electret condenser microphone does not have a risk of the electret layer peeling off during the molding of the capsule, so that the electret condenser microphone can be made to have higher production efficiency. Have an effect.

On the other hand, in the method of manufacturing the electret condenser microphone according to the present invention, the diaphragm, the back electrode plate as the electrode plate disposed on the rear surface side, and the surface of the back electrode plate on the diaphragm side are formed. A method for manufacturing a back electret-type electret condenser microphone in which a condenser portion is formed with an electret layer, wherein the step of forming the electret layer is a spray liquid in which fine particles of FEP are dispersed on the surface of a material serving as a back electrode plate. It comprises a step of spraying, a step of firing the material to form an electret layer on the surface, and a step of processing the material into a desired shape. The spray liquid contains fine particles of FEP.
When it is dispersed, a thickener or a surfactant is mixed,
It was diluted with pure water and had a viscosity of 30 c.
p. The temperature is 25 ° C or lower.

The electret layer thus formed can be formed to be much thinner than the conventional electret layer. As a result, the distance between the diaphragm and the back electrode plate was extremely small, such as 55 μm to 35 μm, as compared with the conventional one. Therefore, the sensitivity as a microphone can be improved. For example, in the case of the conventional product in which the distance between the diaphragm and the back plate is 55 μm and the product of the present invention in which the distance is 35 μm, the sensitivity of the present product is improved by at least 5 dB. Confirmed by experiment.
Moreover, when the electret layer is formed by spraying, it becomes possible to form an electret layer which is more excellent in mass productivity and cost than the spin-on coat method or the dip method. Also, as spray liquid, fine particles of FEP
Thickeners or surfactants are mixed in while the particles are dispersed
And is diluted with pure water and has a viscosity of 30.
c. p. Use a temperature below 25 ℃
Then, the surface roughness is low due to the reduced viscosity.
It is thought that an electret layer is formed, and as a result,
The remaining rate of electret potential is improved.

Another method of manufacturing an electret condenser microphone according to the present invention is a diaphragm, a front surface of the capsule arranged on the front surface of the diaphragm, and an electret layer formed on the back surface of the front surface. In the method for manufacturing the electret condenser microphone of the front electret system, which comprises the condenser part, the step of forming the electret layer is a step of spraying a spray liquid in which fine particles of FEP are dispersed on the back surface of the material to be the capsule, And a step of forming an electret layer on the back surface of the material by firing, and a step of processing the material into a capsule in which the electret layer is arranged on the back surface side of the front part with a drawing die, and the spray liquid is , FEP
Fine particles are dispersed, and a thickener or surfactant
Is mixed with pure water and has a viscosity of
Is 30c. p. And the temperature is below 25 ℃
Is.

Therefore, the electret layer can be formed much thinner than the conventional electret layer. Thereby, the distance between the diaphragm and the back plate is
It was much smaller than the conventional one, such as 55 μm to 35 μm. Therefore, the sensitivity as a microphone can be improved. For example, the conventional product having a gap of 55 μm between the diaphragm and the back plate, and the gap of 35 μm.
With this product, the sensitivity of this product is at least 5
It has been confirmed by experiments that the dB is improved. Moreover, when the electret layer is formed by spraying, it becomes possible to form an electret layer which is more excellent in mass productivity and cost than the spin-on coat method or the dip method. In addition, fine particles of FEP are dispersed as the spray liquid.
Is mixed with a thickener or a surfactant, and
It is diluted with pure water and has a viscosity of 30 c. p.
And if you use the one whose temperature is below 25 ℃,
Elect with low surface roughness due to reduced viscosity
It is thought that the lett layer is formed, and as a result, the elect
The residual rate of the let potential is improved.

[0086]

[0087]

Further, when the spray liquid in which the fine particles of FEP are dispersed and the thickener or the surfactant is mixed is used, the electret is used as compared with the case where the thickener or the like is not mixed. The potential remaining rate is improved.

Further, as the spray liquid, fine particles of FEP are dispersed, a thickener or a surfactant is mixed and diluted with pure water, and the viscosity is 30 c. p. , 25 ° C. or less, it is considered that the electret layer having a small surface roughness is formed by decreasing the viscosity, and as a result, the residual rate of the electret potential is improved.

When the firing process is performed again after the firing process for forming the electret layer, the FEP crystallinity,
It was confirmed that the crystallinity became higher, and as a result, the residual rate of the electret potential was further improved.

Furthermore, when the step of spraying a spray liquid in which fine particles of FEP are dispersed on the surface of the material and the step of firing the material to form an electret layer on the surface are repeated a plurality of times, the first time In the formation of the electret layer, there is a problem in the flatness of the electret layer due to variations in the thickness of the electret layer or pinholes, but the formation of the second electret layer causes
It becomes an electret layer in which the pinholes are eliminated and the flatness is improved and the film thickness is made uniform, so that a more stable electret layer can be obtained.

Furthermore, when a brass plate, a stainless plate, a titanium plate, or an aluminum plate wound in a roll is used as the material, the back electrode plate and the capsule can be manufactured automatically and continuously. It can contribute to cost reduction. Particularly, in the case of a back electret type electret condenser microphone, a brass plate, a stainless plate or a titanium plate is used, but in the case of the front electret type, it is desirable to use an aluminum plate in consideration of processing into a capsule.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing each step of a method for manufacturing an electret condenser microphone according to an embodiment of the present invention.

FIG. 2 is a schematic sectional view of a main part of a front electret type electret condenser microphone according to the present invention.

FIG. 3 is a graph showing the stability of the electret potential of the electret layer when the method for manufacturing an electret condenser microphone according to another embodiment of the present invention is used.

FIG. 4 is a schematic explanatory view showing one step of a method for manufacturing the electret condenser microphone according to the embodiment of the present invention.

FIG. 5 is a schematic explanatory view showing one step of a method for manufacturing the electret condenser microphone according to the embodiment of the present invention.

FIG. 6 is a schematic vertical sectional view of a conventional electret condenser microphone (back electret type).

FIG. 7 is a schematic vertical sectional view of a conventional electret condenser microphone (front electret type).

[Explanation of symbols]

1 capsule 4 back plate 5 Electret layer 100 spray liquid

Front page continuation (72) Inventor Fumihiko Jinbe, 1-3-4 Kitakuhoji, Yao-shi, Osaka, Hosiden Co., Ltd. (56) Reference JP-A-8-107599 (JP, A) JP-A-59-101998 (JP, A) JP-A-53-52543 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H04R 19/04 H04R 31/00

Claims (9)

(57) [Claims] 1. A back electret system in which a capacitor is formed by a diaphragm, a back electrode plate as an electrode plate arranged on the rear surface side, and an electret layer formed on the surface of the back electrode plate on the diaphragm side. In the electret condenser microphone, the back electrode plate is formed by spraying a spray liquid in which fine particles of FEP are dispersed on the surface of a material to be the back electrode plate, and then firing the electret layer to obtain a desired shape. And the spray liquid is a small amount of FEP.
While the particles are dispersed, thickener or surfactant is mixed.
It was put in and diluted with pure water and had a viscosity of 3
0c. p. , The temperature is below 25 ° C
An electret condenser microphone characterized in that 2. A front electret-type electret condenser microphone in which a diaphragm, a front surface of a capsule arranged on the front surface of the diaphragm, and an electret layer formed on the back surface of the front surface constitute a condenser portion. , the capsule, after spraying a spray liquid in which fine particles of FEP is distributed on the surface of the material to be encapsulated, and the electret layer by firing, and is obtained by machining the desired capsule diaphragm molds, said spray
In the liquid, fine particles of FEP are dispersed and a thickener or
Is a mixture of surfactant and diluted with pure water.
And has a viscosity of 30 c. p. , The temperature is below 25 ℃
Electret condenser microphone, which is characterized by being 3. A front electret type electret which comprises a diaphragm, an electrode plate attached to a capsule arranged on the front surface of this diaphragm, and an electret layer formed on the back surface of this electrode plate. In the condenser microphone, the electret layer is obtained by spraying a spray liquid in which fine particles of FEP are dispersed on the back surface of a material to be an electrode plate, and then firing the electret layer , and the spray liquid is fine particles of FEP.
Thickeners or surfactants are mixed in while the particles are dispersed
And is diluted with pure water and has a viscosity of 30.
c. p. , The temperature is below 25 ℃
And electret condenser microphones. 4. A vibrating plate and an electrode arranged on the rear surface side thereof.
It is formed on the back plate as a plate and on the surface of the back plate on the diaphragm side.
And the electret layer that forms the capacitor section.
Quelectret type electret condenser
Electret layer is formed in the method of manufacturing kurohon
The FEP particles on the surface of the back electrode plate
And the process of spraying the spray liquid in which
Before the step of firing to form an electret layer on the surface,
It is equipped with a step of processing the material into a desired shape,
In the spray liquid, fine particles of FEP are dispersed.
Is mixed with a thickener or surfactant, and diluted with pure water
Having a viscosity of 30 c. p. , Temperature is 25
Electrics characterized by being below ℃
Tret condenser microphone manufacturing method. 5. A diaphragm and a front surface of the diaphragm.
Formed on the front of the capsule and on the back of this front
Front that constitutes the capacitor section with the electret layer
Electret type electret condenser microphone
The electret layer is formed in the production method of rohon.
The FEP particles on the back surface of the material that becomes the capsule
And the process of spraying the spray liquid in which
Process of firing to form the electret layer on the back surface of the material
Then, the material is drawn on the back side of the front part with a drawing die.
And a step of processing into a capsule in which the jet layer is arranged.
In the spray liquid, fine particles of FEP are dispersed.
In addition, a thickener or surfactant is mixed and
Diluted with water, having a viscosity of 30 c. p. , Warm
Characterized in that the temperature is below 25 ° C
Electret condenser microphone manufacturing method. 6. A diaphragm and a front surface of the diaphragm.
The electrode plate attached to the capsule and the back of this electrode plate
The capacitor part is constructed with the electret layer formed on the surface.
Front electret type electret
In the method of manufacturing a microphone for a microphone,
The back of the material that will become the electrode plate in the process of forming the tret layer
A process of spraying a spray liquid in which fine particles of FEP are dispersed.
The material is fired to form an electret layer on the back surface.
And a step of processing the material into a desired shape
The spray liquid contains fine particles of FEP.
It is dispersed and mixed with thickener or surfactant.
And has a viscosity of 30
c. p. , This temperature is what has become a 25 ℃ below
And a method for manufacturing an electret condenser microphone, which is characterized by : 7. A step of firing for forming an electret layer
The firing is performed again after the above step.
5. The method for manufacturing the electret condenser microphone according to 5 or 6 . 8. The fine particles of the FEP to the surface of the previous SL material dispersion
The process of spraying the spray liquid and the firing of this material
Process to form an electret layer on the surface and repeat multiple times.
8. The method according to claim 4, 5, 6 or 7, characterized in that
Manufacturing method of the above electret condenser microphone. 9. The material is an aluminum plate, a brass plate,
A stainless steel plate or titanium plate wound in a roll
9. The method according to claim 4, 5, 6, 7 or 8, wherein
Manufacturing method of electret condenser microphone of.