JPH06335086A - Diaphragm for electric/acoustic converter - Google Patents

Abstract

PURPOSE:To lower density and to easily manufacture the diaphragm with desired thickness by mixing the prescribed amount of any specified foaming agent into biological cellulose composed of microfibril produced by microbes and foaming it. CONSTITUTION:The foaming agent is mixed into the bilogical cellulose composed of the microfibril produced by microbes and foamed 3. This foaming agent is composed of a thermal expansive microcapsule, and the amount to be added is almost 0.1-50wt.% to the biological cellulose. Since the cellulose fiber with strong inter-fiber coupling strentgh and large coupling area is used, a light and high-rigidity diaphragm 1 with enough thickness can be provided. In this case, since the cellulose is made into the microfibril, the catahcing ability of the foaming agent is satisfactory. Corresponding to the foaming agent to be used, foaming is enabled simultaneously with drying in a mold (press) process after manufacture, and the diaphragm can be presented at low cost. Further, since the thickness of the diaphragm 1 can be easily adjusted by the clearance of a mold metal die or the amount of the foaming agent, acoustic characteristics can be easily controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroacoustic transducer diaphragm using microbial cellulose composed of microfibrils produced by microorganisms.

[0002]

2. Description of the Related Art The physical properties required for diaphragms for electroacoustic transducers such as speakers and microphones (especially those used for the mid / low range and wide band) have low density and high elasticity (that is, lightweight and high rigidity). ) Has an appropriate internal loss, has no mechanical fatigue, and has good weather resistance. Various polymer materials, ceramics, etc. have been proposed and used to satisfy the above physical properties, but they are expensive due to problems in controlling the physical properties and manufacturing. On the other hand, synthetic resin films, metal diaphragms, paper diaphragms, etc. are often used at present because of the control of physical properties and the ease of manufacturing.

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.

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, the diaphragm having a large amplitude is used. As a result, the method of use becomes complicated.

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, the treating agent for resin processing, etc. A desired diaphragm can be obtained.

However, the material of this diaphragm is made of wood pulp, and the cutting of wood has become a problem in recent years due to global environmental problems, and paper resources have been reviewed. In other words, the issue of forest conservation is a major theme imposed on us as well as prevention of global warming and desertification. In order to use this forest resource with care and to reduce the amount used, it is desired to study a forest substitute resource, that is, a wood substitute.

[0007] Recently, however, in addition to cellulose mainly composed of wood pulp, microorganisms are cultured as one means of wood substitutes, and the cellulose produced by the microorganisms is used for high elasticity and acoustic loss with large internal loss. A method for obtaining a diaphragm has been proposed and used (Japanese Patent Laid-Open No. 61-281800). In this prior example, the sheet made of microbial cellulose has a Young's modulus of 15 to 35 (GPa) and an internal loss of 0.04 when the density is 1.2 to 1.4.
It has suitable physical properties as a diaphragm material.

[0008]

However, the diaphragm using microbial cellulose is preferable from the viewpoint of resources, and compared with a simple paper diaphragm, a synthetic resin diaphragm, and a metal diaphragm.
Although it is an excellent diaphragm that balances elastic modulus and internal loss at a high level, it is the only one with a high density as shown in Fig. 2, so the thickness is not sufficient, and light weight and high rigidity are required.・ There was a problem that it was unsuitable for diaphragms that require large amplitude for the low range and wide band.

The present invention has been proposed in order to improve the above-mentioned drawbacks of a diaphragm using microbial cellulose. The object of the present invention is to provide a diaphragm having a reduced density and a desired thickness. To provide.

[0010]

The present invention achieves the above object by mixing a foaming agent with microbial cellulose composed of microfibrils produced by microorganisms and foaming the mixture.
The foaming agent is composed of heat-expandable microcapsules, and the addition amount of the heat-expandable microcapsules is set to about 0.1 to 50% by weight based on the microbial cellulose composed of microfibrils produced by microorganisms. Has achieved.

[0011]

In the present invention, a microbial cellulose fiber composed of microfibrils produced by microorganisms having a high interfiber bond strength and a large bonding area is mixed with a foaming agent, paper-formed, and then dried and foamed to obtain the foamed amount, It is possible to obtain a lightweight, highly rigid diaphragm with sufficient thickness. In this case, since the cellulose is microfibrillated, the ability to capture the foaming agent is good. In other words, if it is not microfibrillated, the fiber diameter of the monofilament is large, the length is long, and the density is low, so the capturing property of the foaming agent is poor, and even when foaming, the foam only enters the space between the fibers. However, the thickness of the diaphragm does not increase, but this does not occur in the present invention. Further, depending on the foaming agent, in the molding (pressing) step after papermaking, it is possible to foam at the same time as drying, and it is possible to provide at low cost. Further, since the thickness of the diaphragm can be easily adjusted by the clearance of the molding (pressing) die, the amount of the foaming agent, etc., there is an advantage that the acoustic characteristics can be easily controlled.

[0012]

Example 1 Microexpanded microbial cellulose produced by microorganisms was mixed with heat-expandable microcapsules, which was heated after papermaking to obtain a foamed and dried diaphragm. Specifically, it was created by the following procedure. 1. 2 to 3 times as much tap water was added to the gel film material of microbial cellulose, and after disaggregation with a mixer, 5% by weight of Expansel DU manufactured by Nippon Philite Co., Ltd., which is a heat-expandable microcapsule, was added, After stirring well, add retention aid 7
A solution (slurry) was prepared by adding it in a weight percentage. 2. The solution (slurry) obtained in the above 1 was made into a predetermined shape (cone, flat plate, dome, etc.) on a wire net, etc., and adjusted to an appropriate water content in the dehydration process (this time, the water content was 80 %). 3. The paper product obtained in the above 2 was heated and foam-molded using a mold having an appropriate clearance. Also in this embodiment, similar to the above embodiment,
It is possible to reduce the density and obtain a diaphragm having a desired thickness.

In the above examples, the amount of the heat-expandable microcapsules added to the microbial cellulose is preferably in the range of approximately 0.1 to 50% by weight, and the amount of foaming can be adjusted according to the amount added. it can.

By this method, a cone type, a flat plate,
A diaphragm of any shape such as a dome shape can be manufactured, and the diaphragm can be used as another member such as a dust cap. In addition, the base material does not have to be 100% microbial cellulose, and can be made of carbon fibers, ceramic fibers, liquid crystalline polymer fibers, synthetic pulp (polyethylene, polypropylene, etc.), organic substances such as mica, and inorganic physical properties. It may be a mixture of.

[0015]

As described above, according to the present invention, it is possible to protect forest resources by using microbially produced cellulose.
Since the microbial cellulose was mixed with the foaming agent and foamed, a diaphragm having a desired thickness can be obtained. Further, since the microbial cellulose is microfibrillated cellulose, the foaming agent can be easily captured, and as the foaming agent, heat-expandable microcapsules having good foamability are used, and therefore, the production is easy. . Further, the addition amount of the heat-expandable microcapsules is approximately 0.1 to 50% by weight,
A diaphragm having desired thickness and characteristics can be obtained according to the added amount.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional view of a diaphragm according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view of a diaphragm using microbial cellulose composed of microfibrils produced by microorganisms.

[Explanation of symbols]

 1 Vibration plate 2 Molded product 3 Foaming

Claims (2)

[Claims] 1. A vibrating plate for an electroacoustic transducer, characterized in that microbial cellulose composed of microfibrils produced by microorganisms is mixed with a foaming agent for foaming. 2. The foaming agent is composed of heat-expandable microcapsules, and the addition amount of the heat-expandable microcapsules is about 0.1 to 50 relative to the microfibrillated cellulose.
The vibrating plate for an electroacoustic transducer according to claim 1, wherein the vibrating plate is in weight%.