JPS5811157B2 - Speaker diaphragm and its manufacturing method - Google Patents

Description

Detailed Description of the Invention This invention is a synthetic resin paint (hereinafter referred to as photopolymerized paint) that is cured by ultraviolet light with a wavelength of 400 nm (nanometers) or less.
The present invention relates to a speaker diaphragm made of natural fibers or synthetic fibers, which is characterized in that the diaphragm is impregnated over the entire surface or partially of the diaphragm, and then the surface is cured, and a method for manufacturing the same.

In general, the physical properties required for a speaker diaphragm are low density, high Young's modulus (E), and internal loss (ta).
nδ) is appropriately large.

That is, when the specific Young's modulus (E/ρ) is large, the resonance frequency becomes high in the frequency characteristics, and the reproduction band extends to the high frequency range.

Further, it is a well-known fact that the larger the tan δ, the gentler the resonance peak, which tends to be preferable as a diaphragm for a speaker.

Therefore, in order to increase the height or tanδ of speaker diaphragms made of natural fibers or synthetic fibers, conventional methods have been used to completely or partially coat the diaphragm with an organic solvent such as ethyl acetate or methyl ethyl ketone at an appropriate concentration. The surface was impregnated with a treatment agent such as nitrocellulose lacquer, acrylic paint, or silicone oil diluted in water.

However, with paints that harden even at room temperature, such as nitrocellulose lacquers and acrylic paints, the entire impregnated paint is completely cured, resulting in a high E but a significant drop in tan δ.

On the other hand, with a processing agent that does not harden semi-permanently, such as silicone oil, the tan δ will be slightly higher, but the E will be considerably lower, and overall the effect will be small.

Furthermore, if a treatment agent that does not harden semi-permanently is applied, especially partially, there is a risk that it will bleed over time and have an adverse effect on the acoustics.

In addition to the above, the conventional method of diluting a paint or treatment agent in an organic solvent such as ethyl acetate or methyl ethyl ketone and impregnating it on the diaphragm takes a long time to dry and harden, and there are problems due to the volatilization of the organic solvent. Environmental hygiene in the workplace deteriorates.

The photopolymerized paint used as the diaphragm treatment agent used in this invention is a resin having an unsaturated radical polymerization-reactive functional group in its molecule, such as unsaturated polyester resin, acrylic resin, alkyd resin, modified epoxy resin, and modified urethane resin. Photosensitizers whose main component is a monomer or prepolymer such as a resin, and which generate active radicals by absorbing ultraviolet rays, such as carbonyl compounds, sulfur compounds, azo compounds, organic peroxides, inorganic ions, and metal complexes. It is a mixture of appropriate amounts.

In addition, sunlight, low-pressure mercury lamps, medium-pressure mercury lamps, high-pressure mercury lamps, carbon arc lamps, xenon lamps, metal halide lamps, etc. can be used as light sources for drying and curing photopolymerized paints. Resin monomers and prepolymers with functional groups are highly reactive, and upon attack by the active radicals of the photosensitizer that absorbs ultraviolet light and decomposes, they immediately begin polymerization and become polymers.

The reaction is completed within a few seconds to several minutes.

Further, the curing state of the paint can be changed by changing the distance between the coated surface and the light source, the irradiation time of ultraviolet rays, the wavelength distribution, etc.

In any case, according to the method of the present invention, since the photopolymerizable paint is impregnated and coated and irradiated with ultraviolet rays, only the surface layer of the diaphragm is cured, while the layer impregnated between the fibers remains uncured. It remains semi-permanently in the form of a prepolymer.

This makes it possible to increase E/ρ without lowering tan δ, which is a preferable state for a speaker diaphragm.

Furthermore, since it does not use any volatile organic solvents, it is an excellent method that does not degrade the working environment and can be dried and cured in a short time.

Next, embodiments of the invention will be described.

Photopolymerized paint formulation example Photocurable unsaturated polyester 100 parts Styrene monomer 15 parts Anthraquinone
0.5 parts of the photopolymerized paint blended as above, triple-poled pulp beaten to a freeness of 400 ml and unbleached softwood pulp NUSP beaten to a freeness of 700 ml in a ratio of 1:4. 16.5 kg when mixed in the ratio of 16.5 kg
/cm' of pressure to sufficiently impregnate the neck of a cone-shaped diaphragm molded, and after a 3-minute setting period, a high-pressure mercury lamp with an output of 2KW that mainly generates light with a wavelength of 365 parts m was applied. was irradiated for 30 seconds from a distance of 10 cm from the painted surface to harden the surface layer.

FIG. 1 shows the density ρ of the cone-shaped diaphragm manufactured according to this example, and E and tan δ determined by the vibration lead method.

For comparison, a cone-shaped diaphragm made of the same triode and NUSP as in the above example was impregnated with a solution of 100 parts of nitrocellulose lacquer dissolved in 100 parts of ethyl acetate, and another was coated with a solution of dimethyl acetate as a silicone oil. Measurement results for samples coated with polysiloxane alone are also shown.

Next, FIG. 2 shows the results of measuring the sound pressure frequency characteristics of the cone-shaped diaphragm manufactured in the above example.

In the figure, 1 is a diaphragm that is not treated at all, and 2 is a curve that shows the sound pressure frequency characteristics of a diaphragm that has been treated with a polyester photopolymerized paint, which is an example of the product of the present invention.

3 and 4 are sound pressure frequency curves of conventionally treated diaphragms that were measured for comparison, the former being treated with dimethylpolysiloxane and the latter being treated with nitrocellulose lacquer.

As shown in the embodiments above, according to the manufacturing method of the present invention, a speaker diaphragm with excellent acoustic characteristics can be provided.

[Brief explanation of drawings]

Figure 1 is a diagram showing a comparative example of specific Young's modulus and internal loss between a conventional speaker diaphragm and one according to the present invention, and Figure 2 is a diagram showing frequency characteristics between the conventional speaker diaphragm and the one according to the present invention. be.

Claims (1)

[Scope of Claims] 1. A diaphragm made of natural fibers or synthetic fibers, either singly or mixed, and heated and molded, contains a photosensitizer that absorbs light with a wavelength of 400 nm or less and decomposes to generate active radicals, and molecules. A speaker diaphragm characterized in that it is entirely or partially impregnated and coated with a photopolymerizable paint mixed with an organic monomer or prepolymer having an unsaturated radically polymerizable functional group therein. . 2. A high-pressure mercury lamp that emits ultraviolet rays with a wavelength of 400 nm or less after impregnating the entire surface or part of a heat-formed diaphragm with a photopolymerized paint and a photosensitizer using natural fibers or synthetic fibers alone or in a mixture. A method of manufacturing a speaker diaphragm in which the surface is hardened by irradiation with a metal halide lamp or metal halide lamp.