JPH028474Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a speaker diaphragm with particular consideration to moisture resistance and water resistance.

Conventionally, diaphragms for speakers have mainly been made of pulp fibers, but as is well known, pulp fibers are highly hygroscopic and have the disadvantage that their acoustic properties deteriorate due to the humidity of the surrounding environment, and their water resistance performance is even worse. could not be achieved at all.

Therefore, diaphragms are being considered in which various moisture-resistant or water-resistant substances are mixed into the pulp fibers, but the addition of such substances may cause an increase in the weight of the diaphragm or a deterioration of the physical properties of the diaphragm. many.

Also, diaphragms made of synthetic resin sheets, which have superior moisture and water resistance properties compared to pulp fibers, have been considered, but they are not always satisfactory when considered from the standpoint of acoustic properties.

For example, a diaphragm made of polyethylene terephthalate resin sheet, which is most commonly used, has a small internal loss (tan δ) (0.009; 20°C), which causes peaks and dips in frequency characteristics in the divided vibration region, and increases distortion.

In addition, diaphragms made of polycarbonate resin sheets have low internal loss (0.005; 20°C), and have the same drawbacks as the polyethylene terephthalate resin diaphragms mentioned above, but are also easily dissolved in organic solvents, and are often used when assembling speakers. It has the disadvantage that only a limited number of adhesives can be used because rubber adhesives using organic solvents cannot be used.

Furthermore, polyolefin resins, especially polypropylene (tan δ = 0.097;
20℃) and polyethylene (tan δ = 0.18; 20℃) are used as diaphragms for speakers, and have achieved somewhat satisfactory acoustic properties, but moisture resistance and
The water resistance properties were still unsatisfactory.

Therefore, this invention maintains the good acoustic properties of the polyolefin resin, while also providing moisture resistance and
The water resistance properties are improved, and examples will be explained in more detail below.

FIG. 1 shows a dome-shaped speaker according to an embodiment of this invention, and has a structure in which a polyolefin resin 1 such as polypropylene or polyethylene is used as a base, and vinylidene chloride resin 2 is layered on both sides of the base.

To obtain the diaphragm, for example, after activating both sides of a polyolefin resin sheet by corona discharge treatment, the vinylidene chloride resin solution is layered on both sides by passing it through a vinylidene chloride resin solution, and this is coated with a coat knife to a certain thickness. After that, dry it.

Then, the sheet obtained in the above steps is formed into a dome shape by vacuum forming.

In order to confirm the moisture resistance and water resistance characteristics of the diaphragm obtained in this way, we measured the moisture permeability and water content of diaphragms using polypropylene and polyethylene as the base, and the results shown in Figures 2 and 3 were obtained. Obtained.

In addition, in Figures 2 and 3, a is 50 μm thick.
diaphragm made of polypropylene, b is the thickness
Vibration plate made of 50 μm polyethylene, c is the thickness
The diaphragm of the present invention is made of a 30 μm thick polypropylene base and 10 μm of vinylidene chloride resin is layered on each side, and d is the present invention that has a 40 μm thick polyethylene base and 5 μm of vinylidene chloride resin is layered on each side. These are the characteristics of each diaphragm in practice.

As is clear from this figure, according to this idea,
Compared to conventional diaphragms made of polyolefin resin alone, the moisture permeability and moisture content can be reduced to approximately 1/2.

The vinylidene chloride resin layer of the present invention not only contributes to the improvement of moisture resistance and water resistance as described above, but also has the following advantages.

In other words, as is well known, polyolefin resin has extremely poor adhesion and has problems when assembled into speakers, but according to this invention, the vinylidene chloride resin layer becomes the outermost skin layer involved in adhesion, so it can be used instead of epoxy, which is commonly used in the past. Adhesion could be achieved using a reactive adhesive such as a resin-based adhesive or a solvent-volatile adhesive such as a chloroprene rubber-based adhesive.

As explained above, this invention is a speaker diaphragm that has a polyolefin resin as its base and vinylidene chloride resin layers on both sides.
This is an extremely practical idea that can provide a speaker diaphragm with excellent moisture and water resistance properties, and also improves adhesiveness during speaker assembly.

[Brief explanation of drawings]

FIG. 1 is a sectional view of the diaphragm of this invention, and FIGS. 2 and 3 are diagrams showing moisture permeability and moisture content, respectively.

Claims (1)

[Claims for Utility Model Registration] 1. A diaphragm for a speaker, characterized in that it has an olefin resin as a base, and that vinylidene chloride resin is layered on both sides of the base without using an adhesive. 2. The speaker diaphragm according to claim 1, wherein the olefin resin is polypropylene. 3. The speaker diaphragm according to claim 1, wherein the olefin resin is polyethylene.