JPH0748450B2 - Electret material - Google Patents

Description

TECHNICAL FIELD The present invention relates to an electret material used for an electret condenser microphone or the like.

2. Description of the Related Art Conventionally, an electret material of this type is coated with a dispersion liquid 2 such as Teflon-based material on the surface of a metal plate 1 and baked as shown in a partially enlarged sectional view of FIG. The polymer film 3 of a system or the like is formed by heat fusion with a roller or the like. (JP-A-51-87798
Next, a detailed manufacturing process of the above conventional example will be described. FIG. 4 is a process drawing. First, in order to remove oils and fats, stains and the like on the surface of the metal plate 1, after cleaning with trichlene or alkali degreasing, the surface is dried with warm air or the like. Next, a dispersion liquid 2 of Teflon type or the like is applied on the surface of the metal plate 1 in an amount of about 2 to 4 μm, and moisture etc. is removed by a high temperature furnace at about 300 to 350 ° C., which is above the melting point of the dispersion liquid 2. It is removed and fired in order to fuse it to the surface of the metal plate 1. Then on this surface 10
The Teflon-based polymer film 3 having a thickness of about 20 μm is thermally fused to the dispersion layer 2 by applying a high temperature of about 300 ° C. near the melting point with a roller or the like.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, although the electret material of the above-mentioned conventional example has a sufficient fusion bonding strength between the polymer film 3 and the dispersion layer 2, the fusion bonding strength with the metal plate 1 is weak and peeling or the like occurs. It is generated and is insufficient as an electret material.

The cause of this is that the degreasing of the surface of the metal plate 1 in the cleaning step is incomplete, or the cleaning liquid remains, so that an oxide film or the like is generated on the surface when high temperature is applied and the fusion strength is deteriorated. Is considered to be. As a countermeasure against this, it is conceivable that the surface of the metal plate 1 is plated with a metal such as Ni, and although some improvement effects can be expected, it can be said that there is no plating that can withstand high temperatures at a low price. Several common metal plating experiments were performed with similar results.

The present invention solves such a conventional problem, and an object of the present invention is to provide an electret material of high quality having sufficient fusion strength and being resistant to peeling of the polymer film 3. Is.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention forms a heat-resistant primer layer on the surface of a metal plate, coats the dispersion liquid on the surface, and bake it, and also on this surface. The polymer film is formed by heat fusion.

Action The present invention has the following effects due to the above-mentioned configuration.
That is, since the heat-resistant primer layer is formed on the surface of the metal plate, high-temperature oxidation or the like is less likely to occur, and the Teflon-based substance is less likely to be fused to the metal surface, but the primer layer and the dispersion liquid serve as a surfactant. Since it adheres strongly to the metal surface, it is possible to obtain a high quality electret material in which peeling or the like does not easily occur.

Embodiment FIG. 1 is a partially enlarged sectional view showing an embodiment of the present invention. In the figure, 4 is a heat-resistant primer such as a polyamide-imide type, which is applied on the surface of the metal plate 1 and is in close contact therewith, and the dispersion liquid 2 is applied on this surface and baked, and at the same time, on the surface. The polymer film 3 is formed by heat fusion or the like.

Next, a detailed manufacturing process of the above embodiment will be described. FIG. 2 is this process drawing. First, oil and fat, dirt and the like on the surface of the metal plate 1 are removed by washing with trichlene, alkali degreasing and the like, and dried with warm air or the like. Next, heat-resistant primer 4 such as polyamide-imide type 2
Apply about 4 μm. This heat-resistant primer 4 is made of 70% organic solvent such as dimethyl and MEK so that it can be easily applied in advance.
It has a degree. After coating, the primer layer 4 is formed at a temperature of about 80 ° C. Unlike the Teflon type, this primer gives strong adhesion to the metal surface.

A plurality of small irregularities are formed on the surface of the primer layer 4. Next, a dispersion liquid 2 of Teflon or the like is applied on the surface layer to a thickness of 2 to 4 μm, and the temperature is around the melting point or higher.
Baking is performed in a high temperature furnace at 300 to 350 ° C. In this case, the water content of the dispersion liquid 2 is removed and the primer layer 4 is removed.
Since it melts into the unevenness of, strong fusion is obtained at this interface. The combined thickness of the primer layer 4 and the dispersion layer 2 is about 3 to 6 μm, which is about the same as the conventional thickness.

Further, since the primer layer is formed on the metal surface during firing, high temperature oxidation or the like is unlikely to occur.

Then, a polymer film 3 of Teflon type or the like having a thickness of about 10 to 20 μm is heat-sealed to the dispersion layer 2 on this surface by applying a high temperature of about 300 ° C. near the melting point by a roller or the like. Therefore, since strong adhesion is obtained between the layers, peeling is unlikely to occur.

In the case of the present invention, it seems that the number of steps is increased and the cost is increased. However, since the heat-resistant primer layer 4 has a strong adhesion strength to the metal plate 1 in practice, it is very difficult to wash the metal plate 1 as in the conventional case. Since there is no need to perform any special process and only degreasing of trichlene is required, a high quality electret material that is difficult to peel off can be obtained at the same overall cost.

EFFECTS OF THE INVENTION The present invention forms a heat-resistant primer layer on the surface of a metal plate as is clear from the above-mentioned examples, and therefore, when fusing a polymer film such as Teflon-based, there is little influence such as high temperature oxidation, and By baking at a high temperature after applying the dispersion liquid, the water content of this liquid is removed, the primer layer is strongly adhered, and strong fusion is obtained, so that it is possible to obtain a high-quality electret material that is unlikely to cause peeling or the like. Has the effect that can.

[Brief description of drawings]

FIG. 1 is a partially enlarged sectional view of an electret material in one embodiment of the present invention, FIG. 2 is a manufacturing process diagram of the same, FIG. 3 is a partially enlarged sectional view of a conventional example, and FIG. FIG. 1 ... Metal plate, 2 ... Teflon-based dispersion layer,
3 ... Teflon-based polymer film, 4 ... Polyamideimide-based heat-resistant primer layer, etc.

Claims (1)

[Claims] 1. A heat-resistant primer layer such as a polyimide-based material is formed on the surface of a metal plate, a dispersion liquid is applied onto the surface of the heat-resistant primer layer and baked, and a polymer such as Teflon-based polymer is applied on the baked surface. Electret material formed by heat-sealing a film.