JPH11187482A - Manufacture of diaphragm for electroacoustic transducer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the most use of features of respective materials, to enhance an adhesive force between upper and lower layers, to allow the diaphragm to withstand mechanical fatigue and to make satisfactory the acoustic characteristics by placing a foamed material slurry onto a lower layer material slurry, separating the upper layer from the lower layer, making sheets and applying heating, pressing and drying to them in paper-making. SOLUTION: A paper-making die 1, a paper-making net 2, a foamed material slurry 3 that is an upper layer, and a conventional slurry that is a lower layer are prepared. The previously foamed material slurry 3 is placed on a conventional slurry 4 which is the lower layer, and the upper layer and the lower layer are separated by utilizing the difference in the specific gravities of both the materials to paper-make the slurry. Then the paper-made material into a prescribed shape is dehydrated, heated, pressed and dried to produce a diaphragm of a multilayered structure. The upper layer and the lower layer of the diaphragm is clearly distinguished and the diaphragm has an intermediate layer where the materials of the upper and lower layers are intermingled. Then the features of the respective materials are adequately utilized, and the ideal diaphragm is obtained with a high interlayer adhesive force via the intermediate layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm for an electroacoustic transducer such as a speaker or a microphone, which is a kind of audio equipment.

[0002]

2. Description of the Related Art The physical properties required of a diaphragm for an electroacoustic transducer such as a speaker are large in specific elastic modulus (E / ρ) and specific bending rigidity (E / ρ ³ ), and have an appropriate internal loss. It is resistant to mechanical fatigue and has good weather resistance.

[0003] In order to meet the above demand, various metals, ceramics, synthetic resins, synthetic fibers, natural fibers,
More recently, materials such as cellulose fibers using biotechnology have been proposed and used. Also, various methods for processing these materials have been proposed and implemented.

[0004] Among them, the diaphragm using the wet papermaking method can relatively freely combine the materials, and therefore, conventionally, mica, carbon fiber, and vegetable cellulose fiber have been mainly used.
Various materials such as aramid fiber, ceramic fiber, and synthetic pulp made of polyethylene or polypropylene have been mixed and used according to each application.

More recently, diaphragms using cellulose fibers obtained by using biotechnology and diaphragms made of 100% synthetic fibers have also been manufactured by this wet papermaking method.

Further, in this wet papermaking method, not only is it easy to combine various materials, but also various performances can be obtained depending on the difference in the production method. Therefore, various production methods have been proposed. It has been put to practical use.

[0007] Among them, a multi-layer diaphragm having a material change in the thickness direction obtained by a multi-layer making technique is different from the conventional one in which the respective materials are simply mixed together. , And excellent acoustic characteristics can be obtained.

There is also a method in which diaphragms of two different materials are prepared in advance, and laminated in a later step using an adhesive to obtain a diaphragm having a multilayer structure.

[0009]

As described above, a diaphragm having a multilayer structure obtained by wet-paper-making a multilayer structure is a diaphragm having excellent performance as described above. In the case of a multi-layered structure in which another material slurry is charged on top of the material, or a material in which another material slurry is charged in the middle of paper making, etc.), the adhesion between the layers is not sufficient, However, when the method is sufficient, there is a problem that each material is not properly divided into a multilayer structure, and the characteristics of each material, which is the reason for using this method, cannot be utilized.

The present invention has been proposed in view of the above, and it is an object of the present invention to provide a method for manufacturing a multi-layered diaphragm, in which an upper layer and a lower layer are reliably separated from each other, and the characteristics of each material are determined. It is an object of the present invention to provide a method for producing a diaphragm which can be sufficiently utilized, has good adhesive strength between upper and lower layers, is resistant to mechanical fatigue, and has good acoustic characteristics.

[0011]

According to the present invention, there is provided a method of manufacturing a multi-layer vibrating plate in which different materials are arranged in layers in the thickness direction using a wet-type paper forming method. The above-mentioned object is achieved by putting on a material slurry, separating an upper layer and a lower layer by utilizing a difference in specific gravity of the materials, making the slurry, heating, pressing, and drying to produce a multilayered diaphragm. Have achieved. In this case, foaming of the upper layer material slurry is performed by mechanical stirring, or foaming of the upper layer material slurry is performed.
The method is characterized in that a surfactant is added to the slurry and the slurry is mechanically stirred.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in a method of manufacturing a so-called multi-layered diaphragm in which different materials are arranged in layers in the thickness direction using a wet papermaking method, the difference in specific gravity between different material slurries is ensured. It is characterized in that it is divided into an upper layer and a lower layer to form a multilayer structure.

Thus, one of the different materials is made of a material slurry having a low specific gravity and foamed, and this is used as the upper layer.

That is, specifically, as one material, a material slurry composed of 100% of para-aramid fiber and a small amount of a binder is used.

Further, as another material having a specific gravity that can be foamed, a material slurry composed of bacterial cellulose produced by microorganisms is used.

Then, both are put into a papermaking system at a preferable mixing ratio, are formed into a multilayer structure, and are subjected to a heating / pressurizing / drying step to produce a diaphragm.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The above diaphragm is manufactured by the following manufacturing procedure.

1. Preparation of Material Slurry 1-1 Para-aramid fibers cut to 3 mm and para-aramid pulp were mixed at a ratio of 50:50, and a small amount of a cellulose-based binder was added by 10% to prepare a material slurry to be a lower layer. 1-2 About twice the mass of water was added to bacterial cellulose obtained from the microorganism, and the mixture was disintegrated with a mixer for 3 minutes to prepare a pulp slurry as an upper layer.

2. A surfactant was added at 200 PPM to the bacterial cellulose material slurry prepared in 1-2, and the mixture was stirred for about 5 seconds with a mixer to prepare a foamed bacterial cellulose slurry having a low apparent specific gravity. Various methods can be considered for the foaming method, but the usual method is to put a surfactant in a material slurry and mechanically stir the surfactant, which is the safest and most economical method. Further, in the case of a material slurry having a high viscosity, it is possible to foam only by mechanical stirring without adding a surfactant.

3. A papermaking mold and a papermaking net having a predetermined shape are set in a papermaking system. First, about 1.6 g of a dry slurry of the para-aramid fiber material slurry prepared in 1-1 above is put into the papermaking system. Then, about 0.4 g of the foamed bacterial cellulose material slurry produced in 2 and having a reduced apparent specific gravity was used as a dry mass.
The slurry was slowly put on the para-aramid fiber material slurry of 1-1 to make paper. The mixing ratio of para-aramid fiber to bacterial cellulose was 80% for para-aramid fiber and 20% for bacterial cellulose.

That is, FIG. 1 shows a state in which two different material slurries are put into a paper making system, wherein 1 is a paper making mold, 2 is a paper making net, 3 is an upper layer, and a foamed material slurry is shown. Reference numeral 4 denotes a lower layer ordinary material slurry, in which a previously foamed material slurry 3 is placed on a lower layer ordinary material slurry 4, and a slurry in which the upper layer and the lower layer are separated by utilizing the specific gravity difference is extracted. Lift up.

4. Next, the paper made in a predetermined shape was dehydrated, heated, and dried under pressure to produce a diaphragm 5 having a multilayer structure as shown in FIG. As shown in the figure, the diaphragm 5 has a structure having an intermediate layer a in which the upper layer 3a and the lower layer 4a are clearly separated from each other and the upper layer and the lower layer are mixed. Thus, an ideal diaphragm having a large interlayer adhesion force can be obtained through the intermediate layer a.

5. For comparison, the material slurry of para-aramid fiber prepared in 1-1 and the material slurry of bacterial cellulose prepared in 1-2 were simply mixed, and papermaking was performed using the same equipment as in 3, and Dehydration under conditions, heating,
A pressure-dried diaphragm was produced.

6. The obtained two types of diaphragms were cut into predetermined dimensions, and urethane foam edges were bonded together.
Was obtained.

The diaphragm 5A was assembled in a speaker having a diameter of 13 cm, and frequency-sound pressure characteristics and sound quality were compared. A is the result of the conventional manufacturing, B is the present invention, compared with the diaphragm which usually only mixes each material,
According to the present invention, the sound pressure is improved on the high frequency side, and good acoustic characteristics are obtained.

As the above-mentioned material slurry, a case where a material slurry composed of para-aramid fibers and a small amount of a binder and a material slurry of bacterial cellulose produced by microorganisms have been described.
In the present invention, since the upper and lower material slurries 3 and 4 can be produced only by giving a specific gravity difference to each other, any combination of materials can be produced as long as the materials are used in a normal wet papermaking method. is there.

In addition, a dust cap and a dome diaphragm can be manufactured by the same method.

[0028]

As described above, according to the present invention, since a material slurry having a specific gravity difference is used for the upper layer and the lower layer, a diaphragm having a multilayer structure can be produced without fail. The structure has an intermediate layer in which the upper and lower layers are mixed clearly, making full use of the characteristics of each material, and because the interlayer adhesion is large, it also reduces mechanical fatigue. It is possible to obtain a method for manufacturing a diaphragm that is strong and has good acoustic characteristics.

[Brief description of the drawings]

FIG. 1 illustrates a production method of the present invention, in which different material slurries are charged into a papermaking system.

FIG. 2 shows a partial cross-sectional view of a diaphragm manufactured according to the present invention.

FIG. 3 shows a half sectional view of a diaphragm manufactured according to the present invention.

FIG. 4 is a frequency-sound pressure characteristic diagram comparing the present invention with that according to a conventional manufacturing method.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 papermaking mold 2 papermaking net 3 upper layer material slurry 3a upper layer 4 lower layer material slurry 4a lower layer 5 diaphragm 5A molded diaphragm a middle layer

Claims (3)

[Claims] 1. A method for producing a multi-layered diaphragm in which different materials are arranged in layers in the thickness direction by using a wet-type sheeting method.
A material slurry which has been foamed in advance is placed on a material slurry serving as a lower layer, and the upper layer and the lower layer are separated by utilizing a difference in their specific gravities, and the slurry is formed, heated, pressed and dried to obtain a multilayer structure. A method for producing a diaphragm for an electroacoustic transducer for producing a diaphragm. 2. The method for producing a diaphragm for an electroacoustic transducer according to claim 1, wherein the foaming of the upper layer material slurry is performed by mechanical stirring. 3. The method for producing a diaphragm for an electroacoustic transducer according to claim 1, wherein the foaming of the upper layer material slurry is performed by adding a surfactant to the slurry and further mechanically stirring the slurry.