JPS60153299A - Diaphragm for electroacoustic transducer - Google Patents

Abstract

PURPOSE:To increase Young's modulus and to enhance accuracy of a shape and dimensions in a diaphragm by heating and molding a mixture of a whisker and a material consisting of a mineral adsorbed a curing agent between layers, thermosetting resin and carbon fiber. CONSTITUTION:The diaphragm is mainly made of a composite material consisting of a laminated mineral adsorbed a curring agent or a hardening accelerator between layers, thermosetting resin monomer and a carbon fiber, and a whisker, and these mixtures are heated and molded. Thus a montmorillonite-epoxy composite material is scattered so that it will occupy a space between the carbon fiber and the whisker, and a blend polymer in which an epoxy polymer and montmorillonite are strongly bonded is formed, and systematized into three-dimensional network structure. Moreover, whiskers are scattered and arranged between carbon fibers, and Young's modulus can be larger.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in a diaphragm for an electroacoustic transducer, and particularly to a diaphragm made of a material that has high rigidity and is extremely easy to mold.

In recent years, diaphragms for electroacoustic transducers using carbon fiber as a component of the diaphragm have been considered and put into practical use primarily for the purpose of increasing rigidity.

Examples of this type of diaphragm are: (1) A diaphragm made by mixing carbon fiber and valve fiber and then shaping it using phenol resin, etc. (2) A sheet made by mixing carbon fiber with a thermoplastic resin such as polypropylene resin. A diaphragm made by molding and vacuum forming the same, or a diaphragm made by injection molding by mixing the above materials. Vibration plates and the like have been put into practical use.

However, 'the above conventional swing! Jl boards have various drawbacks.

For example, in (1), the high elasticity characteristic of carbon fiber is not fully utilized, and even if the amount of δθ sit% carbon fiber is mixed, the Young's modulus is at most 5×1. This is because a peak value occurs and there is a limit to the mixing ratio of carbon fiber.

In addition, in (2), the amount of carbon fiber mixed is limited by the fluidity of the mixture during sheet molding and the dimensions of the discharge nozzle.

For example, in a sheet with a thickness of 0.3 to 0.5 mm, the amount of carbon fiber mixed is at most 20 wt%.

Further, the above mixing amount is also limited by the vacuum forming process.

On the other hand, in injection molding, the mixing amount is at most 15 wt%.

Therefore, the rigidity of the diaphragm cannot be sufficiently increased.

Furthermore, in (3), a highly rigid diaphragm can be obtained when compared to the above two examples, but carbon fiber is required to form a flat cloth into a cone or dome shape once organized as a woven cloth. Because it cannot be expected to expand or contract itself, it must be shaped using the 1-m-th misalignment, so shaping is possible through a number of processes such as preforming! ! The manufacturing cost was extremely high, and it was difficult to mold diaphragms with complex shapes such as shapes with large apex angles or integrally molded corrugation ribs.

This invention is a diaphragm for an electroacoustic transducer obtained by mixing whiskers into a composite material of layered minerals, thermosetting resins, and carbon fibers on which a curing agent or curing accelerator is interlayer-adsorbed, and then heating and molding the mixture.

Examples of the layered mineral in which a curing agent or curing accelerator is adsorbed between the layers used in the diaphragm of the present invention include montmorillonite (A t2o
3-4 S i20- n H2O, also known as bentonite), and the montmorillonite is deposited (60° C., several hours) in a solution of a hardener or hardening accelerator in a suitable solvent.

As a result, the curing agent or curing accelerator is adsorbed between the silicate layers of montmorillonite.

After solution washing, this is dried to obtain a composite with a curing agent or curing accelerator.

Next, an example of the diaphragm of the present invention using the composite will be described.

[Example] Composite (diaminodiphenylmethane adsorption as curing agent) 10 parts epoxy resin monomer (trade name Araldite 6071)
30 parts hardening agent (diaminodiphenyl sulfone) 4.4 parts mold release agent (zinc stearate) 1 part carbon fiber (polyacnylonitrile carbon fiber)
Average length: 0.35 mm) 45 parts of the above mixture under heating (
The mixture was mixed uniformly by stirring at 85° C.), then cooled and pulverized to obtain a powdered composite material.

Silicon carbide whiskers (m!t
ttIO, 2~0, 5 H, m) The lo part was mixed uniformly and molded into a mold of a predetermined shape at a temperature of 160°C with a press 5.
A cone-shaped diaphragm was obtained by press molding at 85 kg/em for 10 minutes.

Conventional diaphragm using the diaphragm obtained in the above embodiment and carbon fiber [Conventional Example 1] A diaphragm made of kraft valve δOut%, carbon fiber 35vt%, and phenolic resin 15wt%.

[Conventional Example 2] A diaphragm made by injection molding a mixture of polypropylene resin and 15 νt% carbon fiber.

As is clear from the table of measured physical properties (density ρ, Young's modulus E), the diaphragm according to the present invention has an extremely high E/ρ.

The reason why the Young's modulus of the diaphragm of the invention of B rises significantly is that the montmorillonite-epoxy composite is dispersed to fill the spaces between the carbon fibers and whiskers, and the epoxy polymer and montmorillonite that have entered between the montmorillonite layers become strong. A bonded blended polymer is formed, and the blended polymer is organized into a three-dimensional network structure so as to entangle the carbon fibers and whiskers, and the gaps between the carbon fibers with a large diameter are filled with the whiskers with a small diameter. This seems to be because they are distributed in a distributed manner.

In addition, in the diaphragm of this invention, the epoxy resin once melts in the press mold and becomes low in viscosity and flows, but up to a certain temperature (150°C), the curing agent or curing accelerator adsorbed between the layers of montmorillonite does not dissolve. The conventional epoxy resin and curing agent mixture maintains a low viscosity fluid state because it does not ooze out, making it possible to fill every corner of a mold with a complex shape and obtain a diaphragm with high shape and dimension accuracy. When molding, curing starts immediately, so molding can only be carried out for a short time, and it is difficult to fill every corner of the mold, making injection molding impossible. Accordingly, these drawbacks can be overcome and the diaphragm can be formed by injection molding.

In the above embodiment, a silicon carbide whisker was used as the whisker, but other whiskers that can be used in the present invention include one or more of potassium titanate whiskers, silicon nitride whiskers, and alumina whiskers. Can be used together.

In addition, as a hardening accelerator to be adsorbed to layered minerals,
For example, ethylmethylimidazole can be used in combination with phthalic anhydride (hardening agent).

As explained above, the present invention uses whiskers and a composite material consisting of a layered mineral, a thermosetting resin monomer, and carbon fiber to which a curing agent or curing accelerator is adsorbed between the eyebrows as main materials, and a mixture of the above materials. This diaphragm for an electroacoustic transducer is characterized by being formed by heat molding, and since the diaphragm can be made highly rigid or lightweight, it is possible to provide a speaker with good frequency characteristics. Although the invention has been described in the case where it is applied to a cone-shaped diaphragm, it can of course be applied to a dome-shaped diaphragm or even a center dome radiator.

Patent applicant: Ongyo Co., Ltd.

Claims (1)

[Scope of Claims] 1. A mixture of whiskers and a composite material whose main materials are layered minerals, thermosetting resin monomers, and carbon fibers with a curing agent or curing accelerator adsorbed between the layers, is formed by heating. A diaphragm for electroacoustic transducers featuring: 2. The diaphragm for an electroacoustic transducer according to claim 1, wherein the thermosetting resin monomer is an epoxy resin monomer. 3. The diaphragm for an electroacoustic transducer according to claim 1, wherein the N-type mineral is montmorillonite. 4. The whisker is one or more selected from silicon carbide whiskers, potassium titanate whiskers, silicon nitride whiskers, and alumina whiskers.
The diaphragm for an electroacoustic transducer according to claim 1, characterized in that the diaphragm is a combination of H and H.