JPH0145280B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vibrating body for an acoustic transducer such as a diaphragm of a speaker, a microphone, a cantilever of a pickup cartridge, etc., and particularly relates to an improvement of the vibrating body based on Mg or an Mg alloy.

This type of vibrating body will be explained below using a speaker diaphragm as an example. Conventionally, metal materials such as Al and Ti are used as diaphragm materials for speakers, but they have high density and internal loss ( The material was not necessarily satisfactory as a diaphragm for speakers due to its small value (tan δ).

Therefore, as a metal with low density and large internal loss,
Mg or an alloy containing Mg as a main component (hereinafter simply referred to as Mg alloy) is considered as a diaphragm material.

However, as is well known, Mg or Mg alloys are extremely chemically active and are easily corroded by oxygen, moisture, and other corrosive gases in the air, making them unsuitable for practical use.

Therefore, it is necessary to form a corrosion-resistant coating on the surface of Mg or Mg alloy to isolate Mg or Mg alloy, which is the base of the diaphragm, from the air.

Methods for forming such a film include coating with synthetic resin, chemical plating, vacuum plating to form a corrosion-resistant film, or sputtering or ion plating of oxides or other compounds with excellent corrosion resistance. A method of forming a film on a substrate using a method has been considered.

However, in the method of coating the synthetic resin described above, in the process of applying and drying the synthetic resin solution dissolved in a solvent, the synthetic resin solution flows due to gravity, causing uneven thickness of the coating. Moreover, since the thickness of the coating is relatively large, it affects the characteristics of the diaphragm and causes a decrease in conversion efficiency due to an increase in weight.

In addition, when using chemical plating, harmful processing waste liquid causes construction damage, and a large amount of cost is required for processing equipment.

Furthermore, coatings obtained by vacuum plating, sputtering, and ion plating have pinholes and minute cracks, and cannot completely isolate the substrate from air, and the coatings obtained by the above methods are metal coatings. This has drawbacks such as increased weight of the diaphragm and decreased conversion efficiency.

Therefore, in the present invention, a phenolic resin having a relatively low density is used for the coating, and high frequency sputtering is used to coat the resin to form an extremely thin coating layer.Examples will be described in more detail below.

In an Ar gas atmosphere with a vacuum degree of 10 ^-2 to 10 ^-3 Torr, place the phenol resin on the target electrode, and place the Mg substrate previously formed in a desired shape, for example a dome shape, on the other electrode where the substrate should be placed. Then, high-frequency power (approximately 200W) with a frequency of 13.56MHz with a DC voltage superimposed between both electrodes is supplied.

Then, the Ar gas becomes ionized Ar ⁺ and collides elastically or inelastically with the surface of the target phenolic resin, and this collision destroys the phenolic resin on the target surface, causing the particles ejected in a molecular or radical state to vibrate. Deposits on the surface of the plate substrate.

The deposited particles are then polymerized again through a polymerization reaction.

Since the phenolic resin coating thus obtained has been polymerized again as described above, it is extremely dense and shows no pinholes or minute cracks.

Furthermore, since the coating can be formed as thin as 0.1 μm in thickness, the increase in the weight of the diaphragm due to the coating is negligible and does not substantially affect the conversion efficiency.

In this way, according to the present invention, as explained in detail in the above embodiments, the surface of the vibrating body is coated with an extremely thin and dense phenolic resin film formed by high-frequency sputtering, so that it can be coated with an extremely thin and dense phenol resin film that is formed by high-frequency sputtering. It has the advantage that it can completely block air and completely prevent corrosion of the substrate, and that the increase in weight due to the coating is negligibly small, and that a reduction in conversion efficiency can be substantially prevented.

Although the above description has been made regarding a diaphragm for a speaker, it can also be applied to a diaphragm for a microphone, a cantilever for a pickup cartridge, and the like.

Claims (1)

[Claims] 1. A vibrating body for acoustic conversion, characterized in that it has a Mg or Mg alloy base and a phenol resin coating is formed on its surface by high-frequency sputtering.