JPH0472438B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an acoustic vibrating body based on Mg or an Mg alloy, such as a diaphragm for a speaker, a diaphragm for a microphone, a cantilever for a pick-up cartridge, etc., and in particular, a method for putting the Mg or Mg alloy acoustic vibrating body into practical use. This invention relates to improvements in the structure of anti-rust coatings. Conventional horn type speaker, dome type speaker,
Metal materials such as aluminum (Al), titanium (Ti), and duralumin are often used for the diaphragms of microphones and the pickups of cartridges, but these metals have a large density compared to Young's modulus, so their specific elasticity EI value (E: Young's modulus, I: bending moment), which has a small modulus and is a measure of rigidity.
In addition, it has the disadvantage of small internal loss. Especially when applied to a speaker diaphragm, the low internal loss tends to generate self-resonance in a specific relatively high frequency band, which inhibits the flattening of the frequency characteristics of the speaker and This causes deterioration of the fidelity of output characteristics. Similar drawbacks also exist in other acoustic vibrating bodies such as microphone diaphragms and cartridge cantilevers. Therefore, in recent years, magnesium (Mg) or an Mg alloy has been used for the acoustic vibrator because of its low density and significantly larger internal loss than conventional metals. However, as is well known, Mg or Mg alloys are extremely chemically active, and therefore require some kind of anti-rust treatment when used in air containing oxygen, moisture, and corrosive gases. Products in other fields using Mg or Mg alloys,
For example, for bag frames, tire wheels, camera bodies, etc., JISH8651 or MIL-M-
Apply a base treatment of chemical conversion treatment or anodization as specified in 3171C, etc., apply a primer coating of vinyl chloride, epoxy resin, etc., then coat with acrylic, vinyl alkyd, epoxy, polyurethane resin, etc., and bake harden. A rust-preventive coating was formed. It has been found that when such anti-corrosion treatment is applied to an extremely light acoustic vibrator, the following various drawbacks occur. That is, the weight of the coating resulting from the treatment is relatively large, and when applied to the product whose main body is relatively heavy, the weight increase due to the treatment coating is almost negligible.
Or for diaphragms etc. made of Mg alloy foil,
Since the weight of the diaphragm base is small, the increase in weight due to the treated coating cannot be ignored, leading to deterioration of conversion efficiency. Also, it is molded into a predetermined shape, such as a dome shape.
After chemical conversion treatment or anodic oxidation of the Mg or Mg alloy diaphragm substrate, in order to form the above-mentioned organic synthetic resin coating, the resin must have a viscosity such that it can be dissolved in an organic solvent and applied to the diaphragm substrate subjected to the above-mentioned treatment. Adjust to
It is applied by dipping or spraying, and dried at room temperature or by heating to volatilize the solvent and form the organic synthetic resin film. It flows, making it difficult to form a film with a uniform thickness across the front surface of the diaphragm, and the rust prevention ability is limited at the thinnest part of the film, so other parts are simply It will only cause weight increase. In addition, as mentioned above, if the thickness of the coating is uneven, the physical characteristics of each part of the diaphragm will differ, resulting in
This may cause distortion or rolling of the diaphragm. Furthermore, in this type of treatment, pinholes may be generated where the solvent molecules volatilize and are released into the air, and air bubbles that are mixed in when the organic synthetic resin is dissolved in the organic solvent may cause damage to the coating layer. It is difficult to completely isolate the rust from the air, making it difficult to obtain the desired rust prevention effect. Although this can be prevented to some extent by forming a thick coating, this treatment is not desirable for acoustic vibrators that are desirably lightweight. Therefore, the purpose of this invention is to minimize the increase in the weight of the acoustic vibrator and obtain the maximum rust prevention effect.
This is an acoustic vibrator in which a vapor-deposited coating of xylylene resin is formed on a Mg alloy vibrating body substrate via a silane coupling agent layer, and will be described below along with its processing steps using a speaker diaphragm as an example. [Example 1] 45μm Mg alloy (Al: 6wt%, Zn: 1wt%,
Mg: remainder) foil was formed into a dome shape with a top height of 6.5 mm and a diameter of 25 mm (hereinafter referred to as the diaphragm substrate), and the diaphragm substrate was immersed in a NaOH (200 g/) solution maintained at 60°C for 60 seconds. , clean the surface of the diaphragm base, and then rinse with water. The diaphragm base is subjected to a chemical conversion treatment. In other words, sodium hydroxide (NaOH) 10g / potassium stannate (K ₂ ShO ₃・3H ₂ O) 50g / sodium acetate (Na ₂ C ₂ H ₃ O ₂・3H ₂ O) 10g / sodium phosphate (Na ₄ P ₂ A stannate treatment solution containing 50 g of O ₇ ) is maintained at 80 to 85° C., and the diaphragm substrate is immersed for 5 to 6 minutes while air stirring is performed. After that, wash with cold water and dry with hot air at 50° to 60°C for 7 to 10 minutes. The chemically treated diaphragm substrate is referred to as Material (1). Next, the material (1) was stored in a first vacuum container at 0.1 Torr, and trimethacryloxypropyltrimethoxysilane was heated to 140° to 150° C. as a silane coupling agent in the container to evaporate it, Trimethacryloxypropyltrimethoxysilane is vapor-deposited as a silane coupling agent layer to a thickness of 350 Å to 400 Å on the surface of the material (1). Meanwhile, in a separate second vacuum container, G-paraxylylene resin (trade name: Parylene, United States UNION
CARBIDE) was evaporated at approximately 1 Torr and a temperature of 150° to 170°C, and then introduced into a third vacuum container maintained at an atmosphere of approximately 0.5 Torr and 650° to 680°C, and G-paraxylylene resin was It is thermally decomposed to produce paraxylylene. Then, the para-xylylene generated in the third vacuum container is transferred to the first container at about 0.1 Torr, 20°~
After setting the atmosphere to 25°C, the atmosphere is introduced to vapor-deposit paraxylylene on the surface of the silane coupling agent layer. At this time, paraxylylene undergoes a polymerization reaction to form a polyparaxylylene film. That is, a reaction expressed by the following chemical formula occurs. In addition, this polyparaxylylene coating has a processing time of
The thickness was 3 μm after 100 minutes and 4 μm after 140 minutes. The following is a material of a 3μm polyparaxylylene diaphragm.
(2), a 4 μm thick diaphragm is used as material (3). [Example 2] The chemically treated material (1) was immersed in a trimethacryloxypropyltrimethoxysilane solution,
After draining the liquid, it was dried with hot air at about 55°C for 30 minutes to form a 3 μm thick silane coupling agent layer.
A 3μm thick film was produced. This is referred to as material (4). [Comparative Example 1] The chemical conversion treated material (1) was immersed in a 45wt% solution of vinyl acetate-acrylic copolymer resin, dried at room temperature for 30 minutes, then dried with hot air at 50° to 60°C for 30 minutes, and then immersed in acrylic resin. After being immersed in a 50 wt% solution of , it was dried at room temperature for 30 minutes, and then dried with hot air at 50° to 60°C for 30 minutes. This is referred to as material (5). [Comparative Example 2] Same as Comparative Example 1, but with 60wt of acrylic resin
% solution was used. This is material (6). [Comparative Example 3] Same as Comparative Example 1, but with 65wt of acrylic resin
% solution was used. This is material (7). [Comparative Example 4] Same as Comparative Example 1, but with 70wt of acrylic resin
% solution was used. This is material (8). Next, in order to measure the rust prevention effect of each material (2), (3), (4), (5), (6), (7), (8), each material was heated at 40℃ and 95%
As a result of an accelerated test in which the diaphragm was left in a constant temperature, constant humidity, and corrosive gas with RH and formaldehyde of 5.5 ppm for 96 hours, materials (5) and (6) showed that the Mg alloy of the diaphragm base was corroded and magnesium hydroxide was removed. [Mg(OH) ₂ ] white rust occurred. Materials (2), (3), (4), (7), and (8) were found to have sufficient rust prevention effects without any change in appearance. That is, in the accelerated test described above, the diaphragm of the example of the present invention obtained a sufficient rust prevention effect, and Comparative Examples 3 and 4 also obtained similar results. Next, the materials that passed the accelerated test (2), (3),
When we measured the weights of materials (4), (7) and material (1) with only chemical conversion treatment, we obtained the results shown in the following table.

[Table] As is clear from the above table, it can be seen that according to the present invention, the weight increase in obtaining the rust prevention effect is small compared to the comparative example. In particular, a diaphragm with a layer of silane coupling agent and polyparaxylene vapor-deposited (Reference (2) and
Although the effect is most remarkable in (3)), the object of the present invention can also be fully achieved in the diaphragm obtained in Example 2 (Reference (4)). That is, according to the present invention, since the polyparaxylene resin in the outermost layer is a film obtained by a polymerization reaction of paraxylylene during vapor deposition, it is a dense film without pinballs, etc., and even if the film thickness is thin. This is due to the fact that a sufficient air barrier effect can be achieved. In addition, the silane coupling agent layer is interposed between the chemical conversion coating and the polyparaxylylene coating, and through chemical reaction bonding at the interface between the two, it increases the bonding strength between the chemical conversion coating and the polyparaxylylene coating, and prevents their peeling. It is intended to prevent As explained above, the present invention provides Mg or Mg
This is an acoustic vibrator that uses an alloy as a base and has a xylylene resin coating formed on the chemical conversion coating formed on its surface via a silane coupling agent. It can significantly suppress Mg or
This makes it possible to put an acoustic vibrator made of Mg alloy into practical use. In the embodiment, a diaphragm for a speaker has been described, but the present invention can also be applied to other acoustic vibrators such as a diaphragm for a microphone and a cantilever for a pickup cartridge.

Claims (1)

[Claims] 1. A substrate made of Mg or an Mg alloy, and a vapor-deposited coating of polyparaxylylene resin is formed on the chemical conversion coating formed on the surface of the substrate via a silane coupling agent layer. acoustic vibrator. 2. The acoustic vibrator according to claim 1, wherein the silane coupling agent is trimethacryloxypropyltrimethoxysilane resin. 3. The acoustic vibrator according to claim 1, wherein the silane coupling layer is a vapor-deposited coating of trimethacryloxypropyltrimethoxysilane resin.