JPS5838700Y2 - Diaphragm for electroacoustic transducer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an improvement of a diaphragm for an electroacoustic transducer such as a speaker.

Regarding diaphragms for electroacoustic transducers such as speakers, for example, when talking about diaphragms for speakers, conventional diaphragms of this type have been made of natural materials such as wood pulp or synthetic fibers such as carbon fibers, polyester, polypropylene, polycarbonate, etc. Synthetic resin film molded products, and products having a composite structure in which metal is layered on the surface of the synthetic resin film are often used.

Products using the above-mentioned fibers have the drawbacks that the manufacturing process is complicated and that it is difficult to obtain the necessary rigidity.

On the other hand, diaphragms made of synthetic resin films have extremely good moldability and are suitable for mass production; however, the rigidity of the diaphragm is determined by the quality of the material itself, and the material itself does not have a sufficient Young's modulus. Therefore, it was not possible to obtain the necessary rigidity for the diaphragm with this alone.

As a means to solve this problem, a synthetic resin film is used as a base material, and a metal with a high elastic modulus such as beryllium, aluminum, titanium, or boron is layered on one or both sides of the film by means of vacuum deposition, etc., and the rigidity is increased by the metal layer. At the same time, a composite diaphragm has been devised in which a moderate amount of energy loss is imparted through the internal loss of a synthetic resin film.

However, in the composite diaphragm having the above structure, the bonding force between the synthetic resin film serving as the base and the metal layer layered on the surface thereof poses a problem.

That is, since the surface of the synthetic resin film is extremely smooth, its bonding force with the metal layer is small, and accidents often occur in which the two separate due to sudden vibrations of the diaphragm.

As a means to solve this problem, the surface of the synthetic resin film is roughened by sandblasting or chemical etching, or the surface is oxidized to increase the adsorption power of metals, but the former creates a fine rough surface. Therefore, it is not possible to obtain a contact area large enough to obtain sufficient bonding force.

In the latter case, if impurities adhere to the film surface, the non-uniformity of the bonding force will be impaired due to non-uniform oxidation.

Taking into consideration the above-mentioned drawbacks of the conventional diaphragm, this invention is a diaphragm having a microporous polypropylene film having a number of fine pores as a base, and metal layered on one or both sides of the diaphragm, and will be explained in more detail below.

Microporous polypropylene film is made of PP propylene as a base material, and has a thickness of 20 to 8 mm and has fine pores with a diameter of 100 to 1000 A with a porosity of 35 to 50%.
It is a film with a thickness of 0 μ and an apparent specific gravity of 0°49 to 0.5.
It is a film-like material with an extremely low density of 6 g and 7 cm3.

The above microporous polypropylene film is then heated and pressed in a diaphragm-shaped (eg, dome-shaped) mold to form it into a diaphragm shape.

At this time, in order to prevent the micropores from being destroyed, the temperature (130 to 1
This is done in a mold at 40°C.

Then, a microporous polypropylene film formed in the shape of a diaphragm is used as a base, and a metal such as aluminum, titanium, beryllium, boron, etc. is layered on both sides using a surface treatment technique such as vacuum deposition.

In this vapor deposition process, the metal is not only deposited and layered on the surface of the film, but also manually vapor deposited inside the micropores.

Therefore, as shown in FIGS. 1A and 1B, the film base 1a
Metal layers 1b and lb are formed on both sides of the diaphragm 1, and the diaphragm 1 is formed in which the micropores 1C are filled with metal.

The diaphragm having such a configuration has the following effects.

(1) Metal layers 1b and lb layered on the front and back surfaces have micropores 1C
Since it is structured so as to sandwich the base 1a by being connected by the metal filled in the base 1a, the bonding strength with the base is significantly increased compared to the conventional structure in which the base 1a is layered only on the surface.

(2) Since the metal is filled not only on the surface of the base 1a but also inside the base 1a, the rigidity can be significantly increased compared to conventional composite structures.

(3) Since the internal loss of the polypropylene that forms the base 1a is extremely close to the value required for the diaphragm (tan δ = about 0.1), the vibration absorption property is good.

As a result of the above effects, a speaker equipped with the diaphragm of this invention can expand the piston vibration range, raise the treble reproduction limit frequency, improve input resistance characteristics, and suppress disturbances in frequency characteristics due to steep resonance, compared to conventional diaphragms. It has excellent effects that are difficult to obtain.

In the above embodiments, the structure in which both metals of the substrate are layered is described, but of course, even when the metals are layered on one side, the bond strength with the substrate is increased by the metal filling some of the micropores. There is no difference in what will happen.

[Brief explanation of the drawing]

FIGS. 1A and 1B are cross-sectional views of the diaphragm of each invention. 1C is a micropore, 1a is a polypropylene film, and 1b is a metal layer.

Claims (1)

[Scope of utility model registration request] A microporous polypropylene film 1a having micropores 1C with a diameter of 100 to 1000 A is used as a base, a metal layer 1b is layered on both sides or one side thereof, and all or a part of the micropores 1C are filled with the metal. A diaphragm for electroacoustic transducers with special features.