JPS60226300A - Diaphragm member for electroacoustic transducer - Google Patents

Abstract

PURPOSE:To obtain an electroacoustic transducer diaphragm member having a high elastic characteristic and a high regidity by heating and forming a laminated mineral where a curing agent or a hardening accelerator is adsorbed between layers and a composite material obtained by mixing a thermosetting resin and inorganic single crystal fiber. CONSTITUTION:For a laminated mineral where a curing agent or a hardening acclerator is adsorbed between layers, for instance, montmorillonite, one of hydrated aluminum silicates, is used after it has been immersed in a solution for a few hours, where the curing agent or the hardening accelerator is dissolved. After cleaning the montmorillonite with solution, a composite material with the curing agent or the hardening accelerator can be obtained by drying. The composite material is blended by an epoxy resin monomer, the curing agent, a mold release agent and an SiC whisker at a certain rate, and mixed while it is heated, for instance, at 85 deg.C. Then it is cooled, and a powder-like composite material can be obtained. Said material is put into a mold in the prescribed shape, and press-molded at about 160 deg.C under a pressure of about 50kg/cm<2> for a molding period of about 10min, thereby obtaining a diaphragm.

Description

[Detailed Description of the Invention] "Object of the Invention" [Industrial Application Field] This invention relates to improvements in vibration members for electroacoustic transducers such as speaker diaphragms, dust caps, center dome radiators, microphone diaphragms, etc. In particular, the present invention relates to a vibrating member for an electroacoustic transducer made of a material that has high rigidity and is extremely easy to mold.

[Prior Art] In recent years, the use of carbon fiber as a component of a diaphragm component has been considered and put to practical use in vibrating members for electroacoustic transducers, such as diaphragms for speakers, mainly for the purpose of increasing rigidity. There is.

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.

[Problems to be Solved by the Invention] However, the conventional diaphragm described above has various drawbacks.

For example, in (1), the high elasticity characteristic of carbon fibers is not fully utilized, and the Young's modulus is at most 5×Q 10 dyn/cm even if the amount of carbon fibers is 50 wt %.

This is because a peak value occurs in Young's modulus with respect to the mixing ratio of carbon fibers and valve fibers, and there is a limit to the mixing ratio of carbon fibers.

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

For example, in a sheet having 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 diaphragm with higher rigidity can be obtained compared to the above two examples, but in order to form a flat cloth into a cone or dome shape once organized as a woven cloth, the carbon fiber itself must be formed. Since expansion and contraction cannot be expected, it is necessary to take advantage of the weave misalignment to form the product, so the manufacturing cost is extremely high as it is possible to form the product through a number of processes such as preforming. It was difficult to mold diaphragms with complex shapes such as integral molding of ribs.

"Structure of the Invention" This invention provides a vibrating member for an electroacoustic transducer which is made of a composite material obtained by mixing a layered mineral with a curing agent or a curing accelerator adsorbed between the eyebrows, a thermosetting resin, and an inorganic single crystal fiber. It is.

Examples of layered minerals to which curing agents or curing accelerators are adsorbed between the eyebrows used in the present invention include montmorillonite (A1203.4 S 1
02.n H2O, also known as bentonite), and the montmorillonite is placed in a solution containing a curing agent or curing accelerator in a suitable solvent (60° C., several hours).

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 a 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)
35 parts Curing agent (diaminodiphenylsulfone) 4.4 parts Mold release agent (zinc stearate) 1 part SiC whiskers (fiber diameter 0.1-1.0 μm fiber length 5
0 to 200 μm) 50 parts The above blend was stirred under heating (85° C.) to mix uniformly, then cooled and ground to obtain a powdered composite material.

Next, this composite material is molded into a mold with a predetermined shape at a temperature of 160°C.
A diaphragm was obtained by press molding at a press pressure of 50 kg/cm2 and a molding time of 10 minutes.

"Effects of the Invention" A conventional diaphragm using the diaphragm obtained in the above embodiment and carbon fiber [Conventional Example 1] Consisting of kraft valve 50 wt%, carbon fiber 35 wt%, and phenol resin 1δwt% Diaphragm [Conventional Example 2] A diaphragm made by injection molding a mixture of 15 wt % carbon fiber in polypropylene resin and a comparative example [Comparative Example] In place of the SiC whiskers in the above embodiment, short carbon fibers (polyacrylonitrile-based, Fiber length 3
The table below shows the results of measuring the physical properties (density, Young's modulus) of a diaphragm obtained by mixing 50 parts of 60 μm) and undergoing the same soil process as in the above example.

11 n/cm, specific modulus of elasticity:

The reason for the remarkable increase in the Young's modulus of the diaphragm of this invention is that the montmorillonite-composite is dispersed to fill the spaces of the SiC whiskers, and the epoxy polymer and montmorillonite are firmly bonded to each other in the space between the eyebrows of the montmorillonite. This is believed to be because a shaped polymer is formed and the blended polymer is organized into a three-dimensional network structure so as to entangle the SiC whiskers.

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 the curing agent adsorbed between the eyebrows of montmorillonite does not leach out until a certain temperature (150°C). As a result of maintaining the viscosity in a fluid state, it was possible to obtain a diaphragm that was filled to every corner and had high shape and size accuracy even in a mold with a complicated shape.

When molding conventional epoxy and curing agent mixtures, curing starts immediately, so molding can only be done for a short time, and it is difficult to fill every corner of the mold, and furthermore, injection molding is impossible. However, according to this invention,
By solving these drawbacks, it becomes possible to mold the imaging plate by injection molding.

Furthermore, although the comparative example has a higher specific elasticity than the conventional diaphragm, the diaphragm of the present invention was able to further increase the specific elastic modulus compared to this.

The reason for this is thought to be that when comparing SiC whiskers and carbon fibers, first, SiC whiskers have a higher elastic modulus, and second, they have a higher aspect ratio.

Furthermore, compared to the comparative example, the diaphragm of the present invention has a smaller fiber length and thus has better fluidity during molding, making it possible to mold a diaphragm with a more complex shape.

For example, 5g of each material is placed in a flat mold at a temperature of 17.
When we investigated how much the material spreads when press-formed at 0°C and a press pressure of 10 tons, we found that the material of the diaphragm of this invention was formed into a disk shape with a diameter of about 190 mm, while the comparative example had a diameter of about 120 mm. The diameter of the lid was fixed.

Although this invention has been described using SiC whiskers as an example of the inorganic single crystal fiber, it goes without saying that various other inorganic single crystal fibers can be applied.

Patent applicant: Onkyo Corporation

Claims (1)

[Claims] 1. A composite material whose main materials are a layered mineral with a curing agent or curing accelerator adsorbed between the layers, a thermosetting resin monomer, and an inorganic single crystal fiber, and a composite material in which the above materials are uniformly mixed is heated. A vibrating member for an electroacoustic transducer characterized by being formed by molding. 2. The vibration member for an electroacoustic transducer according to claim 1, wherein the thermosetting resin monomer is an epoxy resin monomer. 3. The vibrating member for an electroacoustic transducer according to claim 1, wherein the layered mineral is montmorillonite. 4. The vibration member for an electroacoustic transducer according to claim 1, wherein the single crystal fiber is a SiC whisker.