JPS59215197A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To obtain a diaphragm having flat high frequency characteristic, having wide reproducing frequency band and excellent weather-proof and water- proof by using an olefin polymer material as a base member and a titania coated by aluminum oxide as a reinforcing member. CONSTITUTION:Polypropylene is used as the base member and titania having grain size of 5mum immersed in an 10% of an aluminum hydrooxide aqueous and sintered at 1,400 deg.C in an electric furnace is used as the reinforcing member. After 70wt% of the base member and 30wt% of the reinforcing member are mixed well in a Brabender, a master pellet is formed once by a two-axis screw extruder, then this master pellet is used, a composite film having a thickness of 300mum is drawn by a T-die film extruder. Then, this film is heated for about 15sec in pot at 250 deg.C and after the composite film is softened, the vacuum forming is conducted to obtain the diaphragm having a diameter of 12cm. The frequency characteristic of the speaker by using this diaphgram is flat and the wide reproducing band is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention has a flat frequency characteristic and a wide reproduction frequency band.
This invention relates to a thermoformable speaker diaphragm that is water-based and has excellent weather resistance.

Conventional structure and its problems Paper cones have traditionally been used as a material for speaker diaphragms, but this is because paper has a low density, moderate elastic modulus, internal loss, and high bending rigidity. be. These physical properties are efficient in terms of acoustic characteristics.

It is largely related to the reproduction frequency band, the flatness of the f characteristic, and the input resistance. However, since paper cannot be thermoformed, it is necessary to form each sheet into a cone shape, which makes the process complicated. Therefore, the quality at the time of manufacture is unstable, and the water resistance and moisture resistance are also poor.

In recent years, metal materials such as aluminum and berylum, and polymeric materials such as polypropylene, polyethylene, and polyester have been used as materials to replace paper. However, while metal materials have a high specific modulus, they have the disadvantage of extremely low internal loss, and their f-characteristics exhibit sharp peaks in the high range.

- In the case of the real polymer material t1, although it has a high internal loss and is excellent in moldability, water resistance, and weather resistance, it has the disadvantage of a low specific modulus of elasticity 2 and low bending rigidity.

OBJECTS OF THE INVENTION The present invention improves the specific elastic modulus and low rigidity, which are disadvantages of diaphragms made of polymeric materials, and enables a wider band and higher input resistance.

DESCRIPTION OF THE INVENTION The present invention is a speaker diaphragm that is based on an olefinic polymer, which has the lowest density among polymers, and has titania coated with aluminum oxide as a reinforcing layer.

Olefinic polymers refer to polyethylene, polypropylene, 4-methylpentene polymers, etc., which have the advantage of excellent moldability and large internal loss.

On the other hand, it has low elastic modulus, low heat resistance, and poor adhesion. Heat resistance and adhesion are improved by incorporating titania, but titania alone tends to form an agglomerated structure, has poor dispersibility, and has a high elastic modulus that does not increase.

It has been found that the above drawbacks can be overcome by forming an aluminum oxide film on the titania surface.

This means that the elastic modulus of aluminum oxide is 4.3×1o12d
)'n/cnf is high, and it also has good compatibility with the resin base material, making it difficult to form an agglomerated structure.

Since the diaphragm of the present invention has high internal loss, high elastic modulus, and low density, it has flat high frequency characteristics and excellent water resistance and weather resistance over a wide reproduction frequency band. In addition, since thermoplastic resin is the base material, thermoforming is possible, and the quality between lots is stable.0 Description of Examples Examples of the present invention will be described below.0 [Example 1] Polypropylene ( Mitsui Petrochemical F301
), 1 titania (rutile) with a particle size of 6 μm was used as a reinforcement material.
The material used was immersed in a 0% aluminum hydroxide aqueous solution and then sintered at 1400° C. in an electric kiln. Base material 70wt
% and 30 wt % of the reinforcing material were well mixed in a plastic bender, a master pellet was made using a twin screw extruder, and then a composite film with a thickness of 300/Im was made using a T-die film extruder using this master pellet. I pulled it.

Next, this film was heated in a pot at 250° C. for about 15 seconds to soften the composite film, and then vacuum-formed to obtain a diaphragm with a diameter of 12 cm. The drawing shows the f-characteristics of a speaker using the same diaphragm, which is flatter and has a wider reproduction band than the f-characteristics of a speaker using a conventional polyester film diaphragm. Furthermore, it is far superior to conventional paper cones in terms of water resistance and weather resistance. Titania alone has poor compatibility with the base material, forming aggregates and having a low elastic modulus, but the reinforcing material in this example forms a sintered layer of aluminum oxide on the surface of the titania, making it compatible with the base material. was well and uniformly dispersed, and the elastic modulus was approximately doubled.

[Example 2] 90 wt% 4-methylpentene polymer (TPXDX-845 manufactured by Mitsui Petrochemicals) as a base material 10 wt% titania coated with aluminum oxide of Example 1 as a reinforcing material
A composite film with a thickness of 5C and 50μm was heated with far infrared rays for about 30 seconds, and when it softened, it was vacuum formed to obtain a woofer diaphragm with a diameter of 20cm. This woofer characteristic also had a wide band with few peaks and dips in the high range.

As described above, the diaphragm of the present invention has high internal loss, high elastic modulus,
Because of its low density, it has flat high frequency characteristics and has excellent water resistance and weather resistance over a wide reproduction frequency band.

[Brief explanation of the drawing]

The figure is a diagram comparing the frequency characteristics of a speaker using a diaphragm according to an embodiment of the present invention and a conventional speaker using a polyester diaphragm.

Claims (1)

[Claims] A speaker diaphragm characterized by having an olefinic polymer material as a base material and titania coated with aluminum oxide as a reinforcing material.