JPH06125593A - Vibration plate for electro-acoustic transducer - Google Patents

Abstract

(57) [Summary] [Purpose] In a diaphragm using microbial cellulose,
As a characteristic of the diaphragm, it has high elasticity and high internal loss,
It is also intended to have high strength and durability. [Structure] Liquid crystalline polymer fibers such as aromatic polyamide fibers were mixed with microbial cellulose composed of ribbon-shaped microfibrils produced by microorganisms, and the mixture was made into paper, followed by heat-press molding or heat-drying.

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 using microbial cellulose composed of ribbon-shaped microfibrils produced by microorganisms.

[0002]

2. Description of the Related Art The physical properties required for a diaphragm for an electroacoustic transducer are that the density is small, the elasticity is high, the internal loss is appropriate, the mechanical fatigue is not caused, and the weather resistance is good. Various polymer materials, ceramics, and the like have been proposed and used to satisfy the above physical properties, but they are expensive due to problems in physical property control and manufacturing. On the other hand, paper diaphragms, synthetic resin films, metal diaphragms and the like are often used at present because of the control of physical properties and the ease of manufacturing. The mechanical properties of the paper diaphragm are determined by the physical properties of the single fibers used, the interfiber bonding strength, the bonding area, and the treating agent for resin processing.

However, since the paper diaphragm using plant fibers such as wood pulp is a natural fiber, the physical properties of the single fiber are limited. Single fibers are beaten with a beater for the purpose of increasing the bond strength between fibers and the bonding area.However, as the beating process proceeds, the physical properties of the single fibers deteriorate and the density as a vibration plate increases. The internal loss becomes small.

In order to improve these physical properties, a method of improving the physical properties of the vibration plate by mixing aromatic polyamide fibers having good single fiber properties with pulp and natural fibers is disclosed in Japanese Examined Patent Publication No. 53.
-46088 and is used. in this case,
Pulp and paper-made natural fibers have a weak interfiber bond strength with aromatic polyamide fibers. Therefore, if aromatic polyamide fibers are added in an amount of 10% or more, the elastic modulus decreases, and there is a drawback that a sufficient composite effect cannot be obtained. It was

When a diaphragm is manufactured by molding a synthetic resin film, the manufacturing method is easy, but
There is a drawback that the thickness of the diaphragm becomes uneven.

Further, as the metal diaphragm, a metal plate made of titanium, aluminum or the like is used as a diaphragm having a large elastic modulus. However, since these metal plates have a small internal loss, they vibrate with a large amplitude. The method of using the plate is complicated.

[0007]

For the purpose of improving the above-mentioned physical properties, a method for obtaining a diaphragm for acoustics having a high elasticity and a large internal loss by using microbial cellulose has been proposed (Japanese Patent Laid-Open Publication No. 6-58242).
No. 1-281800) and used. In this prior example, a sheet made of microbial cellulose has a Young's modulus of 15 to 35 (G
Pa), the internal loss is 0.04, and the material has suitable properties as a diaphragm material. However, compared with the paper diaphragm and the synthetic resin film, there are drawbacks that internal loss is small and tear strength is small. Therefore, there is a problem that it cannot be used for a diaphragm that requires a large amplitude.

The present invention was proposed in order to improve the above-mentioned drawbacks of a diaphragm using microbial cellulose, and its purpose is to provide a vibration having high elasticity, high internal loss, and high strength and durability. It is to provide the board at low cost.

[0009]

[Means for Solving the Problems] To achieve this object, liquid crystalline polymer fibers such as aromatic polyamide fibers are mixed with microbial cellulose consisting of ribbon-shaped microfibrils produced by microorganisms, and after papermaking, heat and pressure molding Alternatively, it is formed by heating and drying. In addition, after mixing liquid crystalline polymer fibers such as aromatic polyamide fibers into microbial cellulose consisting of ribbon-shaped microfibrils produced by microorganisms, and adding an organic substance or an inorganic substance alone or in a mixture, papermaking,
It is configured by heat-press molding or heat-drying.

[0010]

According to the present invention, the vibrating plate containing microbial cellulose as a main component has low elasticity, high internal strength and low internal loss as compared with a vibrating plate made of paper or a synthetic resin film. Corrected with lossy liquid crystalline polymer fibers, organic substances, inorganic substances, etc., the diaphragm is lightweight, has high elasticity, has high internal loss, and has high strength. Further, when an inorganic substance such as colored mica is used, the color appears in the appearance of the diaphragm, and the diaphragm can have gloss to improve the appearance.

[0011]

Example 1 In the first example of the present invention, liquid crystalline polymer fibers such as aromatic polyamide fibers are mixed with microbial cellulose composed of ribbon-shaped microfibrils produced by microorganisms, paper-making, and then heat-press molding. There is. Further, it is possible to use as a so-called flat plate vibration plate by punching into a predetermined shape a sheet-shaped product obtained by heat-drying after papermaking without heat-press molding, by attaching an edge to the outer peripheral portion. In this case, among the above-mentioned cellulosic substances, for example, acetic acid bacterium Acetobacter aceti subspice xylinum (Ac
In the gel-like membrane in the culture using etobacter aceti subsp. xylinumAJ 12368), straight stretched fibrils of about 20 to 50 nm run randomly and form a network structure. The fibril length is 10 μm or more. Fibrils can be independent or branched.

This gel film contains 99% or more of water. Then, when this gel film is dried, it contracts to become a hard cellulose sheet. Table 1 shows a comparison value with a polyester film which is widely used with this sheet-like substance as an acoustic diaphragm. As is clear from Table-1, microbial cellulose is harder and more brittle than polyester films. In the present invention, this weakness is improved by incorporating liquid crystal polymer fibers or the like.

In the present invention, the following method was used to produce microbial cellulose. The medium composition was 50 g of sucrose, 5 g of yeast extract (Difco), ammonium sulfate ((NH ₄ ) ₂
SO ₄ ) 5 g, potassium hydrogen phosphate (KH ₂ PO ₄ ) 3
g, magnesium sulfate _{(MgSO 4 · 7H 2 O)} 0.5
g, distilled water 1 liter, pH 5.0 was used.
Static culture is performed using this medium, and the produced gel-like membrane is purified by combining washing with running water and boiling washing with a 2% sodium hydroxide solution to purify cells contained in the gel-like membrane and adsorbed. It was prepared by removing various medium components.

(Example 1) Next, a method for producing the diaphragm of the present invention using the gelled microbial cellulose will be described. First, 2 to 3 times as much tap water is added to a gel film substance containing 99% or more of water to prepare a solution in which the gel film is disaggregated with a mixer. Incorporate fibers.

As the liquid crystalline polymer, there are a thermotropic liquid crystal and a lyotropic liquid crystal, and Kevlar 49 is used in this embodiment. The Kevlar 49 is made by spinning liquid crystal of paraphenylene terephthalamide in the form of a filament having a diameter of about 12 μm. The physical properties of Kevlar 49 are 1.45 for specific gravity and 300 for tensile strength.
kg / mm ² , tensile elastic modulus 11.100 kg / mm ² ,
The breaking elongation is 2.4%.

Then, in the solution obtained by disaggregating the gel film,
The Kevlar 49 long fibers cut to a length of 3 mm were added at 10% and stirred until uniform, and paper was made as the main raw material of the vibration plate.

Then, after the papermaking, a predetermined die is used to heat and pressurize to produce, for example, a cone-shaped diaphragm. At this time, the mold temperature is 120 ° C. and the pressure is 4 kg / cm ² .

A diaphragm made in this way and a diaphragm made of paper made in the same shape have a diameter of 10c.
m speakers were produced and their frequency characteristics were measured. Fig. 1 shows the sound pressure-frequency characteristics, and Fig. 2 shows the distortion-
The frequency characteristic is shown.

As is clear from these characteristic diagrams, according to the diaphragm of the present invention, since it has high elasticity and high internal loss, the dip from the middle range to the high range is reduced, and the treble part A frequency characteristic with a significantly improved band and less distortion was obtained. In addition, various durability tests were conducted, but because microbial cellulose is reinforced with Kevlar,
Its durability was more than twice as high as that of the diaphragm made of microbial cellulose alone. After the papermaking, a sheet-shaped material may be punched out into a predetermined shape if necessary, and an edge may be attached to the outer periphery by using, for example, an adhesive, and this may be used as a vibration plate. was gotten.

(Second Embodiment) Next, a second embodiment of the present invention will be described. That is, in this second embodiment,
Microbial cellulose consisting of ribbon-shaped microfibrils produced by microorganisms, mixed with liquid crystalline polymer fibers such as aromatic polyamide fibers, is added to an organic substance or an inorganic substance alone or in a mixture, and then paper is heated and pressure molded. Alternatively, it is characterized by being dried by heating.

In the production, first, 2-3 times as much tap water is added to the gel film substance containing 99% or more of water, and the gel film is disaggregated by a mixer. Next, for example, aluminum is vapor-deposited on the surface of mica as an inorganic substance, and finely colored mica ME-100 which exhibits a silver-based color.
(Nihon Koken Kogyo Co., Ltd.) 1 against microbial cellulose
0% was added and stirred until uniform.

A long fiber of Kevlar 49 similar to that used in the above example, which was cut into a length of 3 mm, was added to the above stirring solution in an amount of 10% with respect to microbial cellulose, and the mixture was stirred until it became uniform. The paper was made. At this time, the organic sizing agent is an alkyl ken dimer (Accorpel 1
2. Dick Hercules Co., Ltd. was used.

After the papermaking, the vibrating plate was made into a cone shape, for example, by applying heat and pressure using a predetermined mold. At this time, the mold temperature is 120 ° C. and the pressure is 4 kg / cm ² .

Speakers each having a diameter of 10 cm were prepared using the diaphragm thus manufactured and the paper diaphragm manufactured in the same shape, and the frequency characteristics thereof were measured. Similar properties were obtained. A similar effect was obtained when a sheet-shaped diaphragm was used instead of a cone-shaped diaphragm for use in a flat speaker.

In the first embodiment, the Kevlar 49 is simply used.
However, the color of Kevlar 49 appears in the appearance of the diaphragm, and it has a slightly yellowish white color.
In the examples, since the colored mica is mixed, it has a pearly color with a gloss, has an extremely good appearance, and has an advantage of improving the product value. In addition, although the diaphragm for the speaker is described in each of the above-described embodiments, a thin diaphragm having a thickness of 100 μm or less can be easily manufactured.
It is most suitable for diaphragms for electroacoustic transducers such as microphones. Further, as the shape of the diaphragm, it is possible to select a cone shape, a dome shape, or the like as appropriate, and in addition to the diaphragm body, it is possible to use the center cap or the edge alone.

[0026]

As described above, according to the present invention as set forth in claim 1, since the liquid crystalline polymer fiber is mixed in the microbial cellulose, it is lightweight and compared with a paper diaphragm or a synthetic resin film. Thus, a diaphragm having high elasticity, high internal loss and high strength can be obtained. Further, according to claim 2, since an organic substance and an inorganic substance are further added in addition to the liquid crystalline polymer fiber, insufficient internal loss and tear strength of the microbial cellulose alone are further improved, and light weight and high elasticity, It is possible to obtain a diaphragm having high internal loss, high strength, and good appearance.

[Brief description of drawings]

FIG. 1 is a sound pressure when the present invention is compared with a paper diaphragm.
Frequency characteristic chart.

FIG. 2 shows distortion when the present invention is compared with a paper diaphragm.
Frequency characteristic chart.

[Explanation of symbols]

 a Invention b Conventional paper diaphragm

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Eiichiro Suzuki 512, Miyazawa-cho, Akishima-shi, Tokyo Foster Electric Co., Ltd.

Claims (2)

[Claims] 1. A method in which liquid crystalline polymer fibers such as aromatic polyamide fibers are mixed into microbial cellulose composed of ribbon-shaped microfibrils produced by microorganisms, paper-making, and then heat-press molding or heat-drying is performed. A diaphragm for an electro-acoustic transducer. 2. After papermaking by mixing liquid crystalline polymer fibers such as aromatic polyamide fibers into microbial cellulose composed of ribbon-shaped microfibrils produced by microorganisms, and adding an organic substance or an inorganic substance alone or as a mixture, A diaphragm for an electroacoustic transducer, characterized by being formed by heat-press molding or heat-drying.