JPS6057280B2 - Manufacturing method of diaphragm for audio equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves kneading synthetic resin and carbon powder and then molding them.
The present invention relates to a manufacturing method that allows the molded product to be gradually prefired and then carbonized to easily and efficiently manufacture a diaphragm for audio equipment that has low density and high elasticity.

In general, thin plates used as diaphragms for audio equipment, especially speakers, are lightweight, have high rigidity, and have a high Young's modulus E and density ρ in order to reproduce efficiently and faithfully over a wide frequency band. A large ratio E/ρ is required.

Conventionally, wood pulp, synthetic resin, aluminum, titanium, etc. have been used from these points of view, but it is difficult to say that any of them have sufficient properties.

In addition, an example of using a carbon-based material is a composite material of carbon fiber and synthetic resin, but due to the lubricity of the surface of the carbon fiber itself, the bonding of the carbon fibers by the synthetic resin is not sufficient. Also, due to the large anisotropy of carbon fiber, it is not possible to obtain large rigidity as a surface like a diaphragm. Therefore, the inventor focused on carbon as a material that is lightweight, has high rigidity, and has a large ratio E/ρ between Young's modulus E and density p, and previously proposed a diaphragm made of carbonized or graphitized synthetic resin. During the carbonization and graphitization processes of synthetic resins, it has been confirmed that the material undergoes significant shrinkage and deformation, causing cracks and other problems.

In view of these points, the object of the present invention is to provide a diaphragm for audio equipment made of carbonized or graphitized synthetic resin, which is lightweight, has high rigidity, and has a large Young's modulus to density ratio E/ρ. The object of the present invention is to provide a method that can prevent the deformation of a material that occurs during the carbonization or graphitization process without impairing the properties required for a diaphragm for an audio device. Examples of the present invention will be described in detail below.

As the carbon powder and synthetic resin, graphite powder and vinyl chloride resin with a particle size of 5 to 100 μm were used, respectively.
H), solvent (M.E.K) and 5 parts (both by weight) are thoroughly kneaded and molded into the desired shape of a speaker diaphragm (eg, dome shape, cone shape, etc.) using a mold. To prevent this molded product from softening and deforming, it was placed in a heating furnace while being held in a mold, and the temperature was gradually raised from room temperature to 300°C for about 8 hours in an atmospheric atmosphere to oxidize it, and then oxidize it with argon, nitrogen, etc. Calcinate at 1000° C. for about 1 hour in a non-oxidizing atmosphere to carbonize. Note that oxidation here refers to the phenomenon in which hydrogen in the resin separates, and due to the release of hydrogen, the surface of the resin changes in composition.
That is, the carbon content increases, and as a result, carbon chains come together to form a three-dimensional network structure of carbon, that is, a graphite structure. In an inert atmosphere, the carbon chains of the synthetic resin are insufficiently condensed, and in an oxidizing atmosphere, a one-carbon precursor of a benzene nucleus structure with a series of conjugated double bonds is formed. Therefore, it is necessary to carry out the process in an oxidizing atmosphere.

After this oxidation, it becomes possible to rapidly raise the temperature to the carbonization and graphitization temperature. The diaphragm obtained in this way has extremely small deformation during carbonization compared to a carbonized synthetic resin that does not contain graphite powder, and its density is 1.54y/
It has the characteristic of All Young's modulus of 1600k9/i, and has a higher reproduction frequency band than conventional diaphragm materials. It also reduces distortion across that band, making excellent playback possible.

Furthermore, this diaphragm was held in a graphite mold so that it would not deform, and was heated at 240°C for 5 minutes in an inert atmosphere.
When graphitized, the density was 1.8y/C! 11 Young's modulus increased to 1800 kg/Wllt, resulting in a diaphragm with excellent characteristics. In the present invention, the synthetic resin may be any resin that does not sublimate at temperatures below the oxidation temperature of 20's to 30's, but regardless of whether it is a thermoplastic resin or a thermosetting resin, the synthetic resin may It is desirable to use a resin with a high resin content, and in addition to vinyl chloride shown in the examples, polystyrene, silicone, acrylic, phenol, furan, urea,
It is possible to use other synthetic resins such as polyester alone or in combination of several kinds, and carbon black is another example of carbon powder.

In addition, various appropriate plasticizers, solvents, etc. are selected and used for the resin, and the heat treatment conditions for carbonization or graphitization can be adjusted as appropriate depending on the mixed system of the resin, plasticizer, and solvent. As explained above, according to the manufacturing method of the present invention,
Before carbonization or graphitization, the temperature is gradually raised to approximately 300°C and preliminarily fired, and as in the case where the temperature is rapidly raised to the carbonization or graphitization temperature, changes occur in the molded product and the desired dimensions are achieved. There is no possibility that you will not be able to obtain the desired shape.

Claims (1)

[Claims] 1. Carbon powder such as graphite or carbon black and thermoplastic or thermosetting synthetic resin are kneaded and molded into a desired shape, and the molded product is heated in an air atmosphere at a temperature below the sublimation temperature of the synthetic resin. An acoustic device characterized by preliminary firing while gradually raising the temperature to 300°C, then raising the temperature to the firing temperature in a non-oxidizing atmosphere, and then firing at that temperature for a predetermined period of time to carbonize or graphitize. Method of manufacturing a diaphragm for use.