JPH0728476B2 - Method for manufacturing acoustic diaphragm - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an acoustic diaphragm used for a speaker, and more particularly to a method for manufacturing a diaphragm based on a laminated mica multi-foam structure.

Generally, a diaphragm constituting a speaker is required to have various physical characteristics in order to obtain excellent reproduction frequency characteristics. For example, it is preferable to reduce the weight by using a material having the smallest possible density to improve the efficiency of the speaker and to improve the transient characteristics, and to improve the Young's modulus to widen the reproduction frequency band and reduce the distortion. . Further, it is necessary to appropriately increase the internal loss to reduce the resonance sharpness and to flatten the reproduction frequency characteristic.

In order to meet such a demand, it has been proposed to use a so-called mica multi-foam structure, which is a multi-foam structure by forming fine mica flakes with pulp fibers or polyvinyl alcohol fibers and heating them to form a vibrating plate. This laminated mica multi-foam structure has an apparent density of 0.05 to 0.10 g / cm ^{3 which} is extremely small, which makes it possible to reduce the weight of the diaphragm. Also,
The fine mica flakes mixed in the assembled mica multi-foam structure has a large area compared to its thickness, the so-called aspect ratio, so that the overlapping area of these mica pieces becomes large and the integrated mica multi-foam structure. The Young's modulus of the thing is enlarged.

However, in the diaphragm using the above-mentioned mica multi-foam structure, the internal loss is small, and as a result, the resonance sharpness is high, the response is increased at a specific frequency, and a flat reproduction frequency characteristic is obtained. I can no longer do it. Further, in the above-mentioned diaphragm, when the diaphragm vibrates, the mica scales rub against each other and a rustling sound is generated. Furthermore, the diaphragm is inferior in moisture resistance and is easily affected by environmental changes such as humidity.

Therefore, the present invention has been proposed in order to eliminate the drawbacks of the above-mentioned conventional technology, and it is possible to increase the internal loss and improve the moisture resistance without impairing the advantages of the above-mentioned laminated mica multi-foam structure. It is an object of the present invention to provide a method for manufacturing an acoustic diaphragm.

As a result of earnest research to achieve the above-mentioned objects, the present inventors have made it possible to easily reduce internal loss by impregnating a synthetic synthetic resin solution or synthetic resin emulsion into a laminated mica multi-foam structure and coating it with an extremely thin resin film. It has been found that the invention can be enhanced, and the present invention has been completed. A paper product comprising fine mica scales, pulp fibers and polyvinyl alcohol fibers is heated to obtain a diaphragm substrate having a multi-foam structure, and then the diaphragm. It is characterized in that the substrate is impregnated with a synthetic resin solution or a synthetic resin emulsion.

That is, in the manufacturing method of the present invention, first, fine mica flakes, pulp fibers, and polyvinyl alcohol fibers are mixed, uniformly dispersed in water, and papermaking is performed using a papermaking machine or the like.

As the fine mica flakes, those having a particle size of 8 to 400 mesh are preferably used. On the other hand, it is preferable that the pulp fibers and polyvinyl alcohol fibers each have a length of 3 to 10 mm. And, for 100 parts by weight of the fine mica scale, pulp fiber 5 to 5
It is preferable that 0 part by weight and 5 to 50 parts by weight of polyvinyl alcohol fiber are mixed and dispersed in water so that the concentration of the mixed base material becomes 0.03 to 0.2%, and the above papermaking is performed. However, it does not necessarily have to be in this range.

Next, the wet papermaking product obtained as described above is placed in a mold and first heated to 60 to 90 ° C. By this heating, heat is transferred from the surface of the papermaking product to the inside, and a temperature gradient occurs in the thickness direction. First, the polyvinyl alcohol fibers near the surface are solubilized and become liquid. Then, this liquid polyvinyl alcohol permeates into the entangled structure of the fine mica flakes and the pulp fibers and the undissolved polyvinyl alcohol fibers, and forms a skin that prevents the passage of water vapor on the surface of the paper product. In this state, unvaporized water exists inside.

Then it is heated to above 100 ° C. When the heating temperature is 100 ° C. or higher, the unvaporized water present inside the paper product is evaporated to form spherical closed cells. Cooling in this state, the liquid polyvinyl alcohol is cured to obtain an assembled mica multi-foam structure.

Further, the laminated mica multi-foam structure thus obtained is used as a diaphragm substrate, and the diaphragm substrate is impregnated with a synthetic resin liquid.

The impregnation treatment may be carried out by immersing the diaphragm substrate in a tank filled with the synthetic resin solution, or by applying the synthetic resin solution using a spray or the like to impregnate it. Good. As the synthetic resin material used in the synthetic resin liquid, any kind of synthetic resin material such as epoxy resin, silicone resin, polyester resin, acrylic resin, polyurethane resin, cellulose derivative, synthetic rubber, etc. can be used. Further, these copolymers may be used. Then, these synthetic resin materials are dissolved in an organic solvent and used as a synthetic resin solution,
Alternatively, it is dispersed in water and emulsified to be used as a synthetic resin emulsion.

The concentration of the synthetic resin material, which is the solid content in the synthetic resin solution or synthetic resin emulsion, is preferably 0.5 to 30% by weight, more preferably 0.5 to 10% by weight, and the optimum value is 3 to 5% by weight. is there. If the concentration exceeds 30% by weight, the viscosity of the synthetic resin solution or the synthetic resin emulsion becomes high and the liquid is not easily drained, and the resin is coated with an extremely thick resin film to increase the apparent density. On the other hand, if the above concentration is 0.5% by weight or less, the coating becomes too dilute and a satisfactory coating cannot be obtained, and the desired effect cannot be obtained.

Finally, the impregnated diaphragm substrate is dried to cure the impregnated synthetic resin material to obtain a diaphragm in which the laminated mica multi-foam structure is coated with a thin synthetic resin film. The drying may be heating drying or natural drying.

In the diaphragm thus obtained, fine mica scales and pulp fibers are wrapped with a resin coating formed by impregnation, and since the fine mica scales are firmly bound by the resin coating, internal loss is reduced. Becomes higher, the resonance sharpness can be suppressed, and the reproduction frequency characteristic can be flattened. In addition, the rigidity of the diaphragm is increased, and the generation of a rustling noise is prevented. Further, since the diaphragm is entirely covered with the resin film having high moisture resistance, the humidity resistance of the diaphragm can be extremely improved. Also, since the resin film to be coated is extremely thin, the apparent density increase of the diaphragm is very slight.

As described above, according to the present invention, the internal loss is increased without impairing the advantages of the laminated mica multi-foam structure, the resonance sharpness is lowered, and the flat reproduction frequency characteristic is provided, and the moisture resistance is extremely excellent. It is possible to easily manufacture a vibrating plate.

Hereinafter, specific examples of the present invention will be described. Needless to say, the present invention is not limited to these examples.

[Example 1] 100 g of fine mica scale of 8 to 150 mesh, pulp fiber 20
g and 30 g of polyvinyl alcohol fiber were put in 80 kg of water, and sufficiently mixed by stirring. 5600 g of this suspension was collected and
The paper was made into a size of 00 mm x 200 mm. After heating this paper product to 80 ℃, insert it between the molds with gaps prepared in advance, and
Heated at 0 ° C. for 30 minutes. As a result, thickness 4.2mm weight 9.6g,
An assembled mica foam structure having an areal density of 0.024 g / cm ³ and an apparent density of 0.057 g / cm ³ was obtained.

This laminated mica multi-foam structure was used as a diaphragm base, and the diaphragm base was immersed in a synthetic resin solution in which 3 parts by weight of butadiene-styrene rubber was dissolved in 97 parts by weight of toluene, and the synthetic resin solution was sufficiently immersed. I let it in.

Next, this diaphragm base was taken out and placed in an explosion-proof constant temperature oven heated to 80 ° C., and dried with hot air to obtain a diaphragm.

The physical properties of the obtained diaphragm are shown in Table 1 in comparison with those of the laminated mica multi-foam structure before the impregnation treatment. Also, a graph showing the reproduction frequency characteristics when the obtained diaphragm is used for a full-range speaker having a diameter of 8 cm is similarly shown in FIG. 1 in comparison with that before the impregnation treatment.

As is clear from Table 1 above, in the diaphragm of this embodiment, the resonance sharpness is lowered and the Young's modulus is increased. As a result, it is clear from FIG. 1 that the reproduction frequency characteristic is flatter.

Example 2 The same mica multi-foam structure obtained by changing the gap between the molds as in Example 1 was used as a diaphragm substrate, and 20 parts by weight of the epoxy resin was diluted with 80 parts by weight of methyl ethyl ketone. The vibrating plate substrate was dipped in the synthetic resin solution prepared above to sufficiently soak the synthetic resin solution. Next, this diaphragm base was taken out and heated and dried at 80 ° C. to obtain a diaphragm.

The obtained vibration plate was cut into a strip of 20 mm × 100 mm, and the physical constant was measured by the vibration lead method. The measurement results are shown in Table 2 in comparison with those before the impregnation treatment.

As is apparent from Table 2, the Young's modulus and the speed of sound were improved, and when the actually obtained diaphragm was used as a speaker for trial listening, a gritty rustling sound was reduced.

[Example 3] In a synthetic resin emulsion containing 5% by weight of ethylene-vinyl alcohol copolymer as a solid content, using the laminated mica multi-foam structure obtained in the same manner as in Example 1 above as a diaphragm substrate. The above-mentioned diaphragm base was dipped and impregnated with the above, and further heated and dried to obtain a diaphragm.

The obtained diaphragm has the same effects as those obtained in the first and second embodiments.

Example 4 The laminated mica multi-foam structure obtained in the same manner as in Example 1 above was used as a vibrating plate substrate, and the lacquer containing nitrocellulose as the main component was diluted 10 times to obtain 30% by weight of the solid content. % Dioctyl phthalate was added, and after soaking sufficiently, it was placed in a thermostat and dried with hot air at 80 ° C. to obtain a vibration plate.

The obtained diaphragm has the same effects as those obtained in the first and second embodiments.

[Brief description of drawings]

FIG. 1 is a graph showing reproduction frequency characteristics of the diaphragm obtained in Example 1.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Shirota Sonoda, 1965, Nakazai, Fukuoka, Naka, Japan 1 stock company, Okabe Mica Industrial Co., Ltd. (56) Reference JP-A-57-62695 (JP, A) JP-A-SHO 54-114232 (JP, A)

Claims (1)

[Claims] 1. A vibrating plate substrate having a multi-foam structure is obtained by heating a paper product composed of fine mica flakes, pulp fibers and polyvinyl alcohol fibers, and then a synthetic resin solution or synthetic resin emulsion is applied to the vibrating plate substrate. A method of manufacturing an acoustic diaphragm, which comprises impregnating.