JPS58154996A - Diaphragm for speaker - Google Patents

Abstract

PURPOSE:To attain a diaphragm incorporated with an edge having larger internal loss, by providing an ultraviolet-ray curing resin layer containing a reinforced member for both sides of a diaphragm of a thermoplastic resin foaming sheet for the three-layered construction. CONSTITUTION:A polypropylene foamed sheet, 1mm. thick and 15 times foaming is heated for ten and several seconds by using a far-infrared ray heater, press forming is executed when the sheet is softened sufficiently to obtain a diaphragm 3 incorporated with a diaphragm section 1 and an edge section 2. The press metal die has a clearance of about 0.3mm. at the diaphragm and the metal die without gap is used for the edge section. The ultraviolet curing resin (Three Bond Co., 3022) composed with mica (Kurare Co., 325S) by 5wt% is coated on both sides of the diaphragm section 1 of the obtained diaphragm 3 in the rate of 20g/m<2>, the ultraviolet ray curing resin including mica is cured by irradiating ultraviolet-rays, to obtain the three-layered construction having ultraviolet-ray cured resin layers 5, 6 including mica on front and back side of a foamed sheet 4 for the diaphragm section 1 as shown in Fig. 2.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a speaker diaphragm in which an edge portion is integrally formed on the outer periphery of a diaphragm portion, and its purpose is to provide a diaphragm portion with high bending rigidity and a large internal loss. An object of the present invention is to provide a diaphragm for a speaker in which an edge portion and an edge portion can be formed simultaneously using the same material.

Generally, paper is often used as a material for speaker diaphragms. This is because paper has physical properties such as low density, excessive specific modulus of elasticity of 5, bending stiffness, and internal loss.These physical properties include acoustic properties such as efficiency, reproduction frequency band, input resistance, and distortion of 1. It is largely related to the flatness of frequency characteristics.

However, paper cannot be thermoformed, so there are two ways to do this: either paper is made into a cone shape one by one, or the paper is pasted together into a cone shape and then molded with a hot mold after absorbing enough water. Both methods relied heavily on craftsmanship and had the drawback of large variations in density between lofts. Therefore, recently, metal materials such as aluminum and beryllium, and polymer materials such as polypropylene and polyethylene have come to be used as materials to replace paper.

However, materials for speaker diaphragms must be lightweight and highly rigid, and it is difficult to meet these requirements with a single material. Materials are being developed. On the other hand, the edge material is required to have high internal loss, but the characteristics required of the diaphragm material and the edge material, high rigidity and high internal loss, are contradictory. Therefore, it is extremely difficult to simultaneously mold the diaphragm portion and the edge portion while satisfying these physical properties.

The present invention solves these conventional problems,
It has a three-layer structure in which UV-curable resin layers containing reinforcing materials are provided on both sides of the diaphragm portion of a thermoplastic resin foam sheet. According to this configuration, the three-layered diaphragm portion and the outer peripheral edge portion of the diaphragm portion can be thermoformed at the same time. In addition, by coating both sides of the diaphragm section of the thermoplastic resin foam sheet with an ultraviolet curable resin compounded with a reinforcing material and curing it to create a three-layer structure, it is possible to obtain a diaphragm section with high rigidity. At the same time, the edges can be made into a state with high internal loss, ranging from a foamed state to a melted film state, depending on the thermoplastic resin foam sheet used, making it possible to obtain edge parts with high internal loss8. Hereinafter, the diaphragm for speakers of the present invention will be specifically explained with reference to Examples.

<Example 1> A polypropylene foam sheet 1 mm thick and 16 times foamed was heated for several seconds using a far-infrared heater, and when it had sufficiently softened, it was press-molded to form a diaphragm as shown in Figure 1. A diaphragm 3 integrally provided with a portion 1 and an edge portion 2 was obtained. The press mold at this time had a gap of about 0.3 mm in the diaphragm part, and a mold with a large gap in the edge part was used. Mica on both sides (
20 g/r' of ultraviolet curing resin (3022 manufactured by Three Bond), which is a composite of 5% by weight (3253 manufactured by Kuraray)
r1'', and then irradiated with ultraviolet rays for about 2 minutes to cure the mica-containing ultraviolet curing resin, and as shown in FIG. It has a three-layer structure with resin layers 5 and 6.The physical properties of the diaphragm portion and the edge portion of the diaphragm thus obtained are shown in Table 1. Table 1 shows the physical properties of the diaphragm portion and edge portion of the diaphragm when a cured resin is used and when paper is used.

Table 1 Also, FIG. 3 shows the frequency characteristics when each of the above-mentioned diaphragms is incorporated into a speaker. In Figure 3, the solid line a is the sound pressure frequency characteristic of a diaphragm made of paper, the dashed line is the sound pressure frequency characteristic of a diaphragm made of a foam sheet with an unreinforced ultraviolet curable resin layer, and the dashed line C is the sound pressure frequency characteristic of the diaphragm used in this implementation. This is the sound pressure frequency characteristic of an example diaphragm. As is clear from FIG. 3, the diaphragm reinforced with mica as a reinforcing material in this example had a large specific modulus of elasticity, so high frequency reproduction was good. or,
Due to its high bending rigidity, there was little distortion.

<Example 2> Reinforcement of the physical properties of the diaphragm portion of a diaphragm obtained in the same manner as in Example 1 except that 3% by weight carbon fiber and 3% by weight aramid fiber were used as reinforcing materials. The effect of the reinforcing material shown in Table 2 is proportional to the amount added, and the larger the amount added, the greater the effect.However, the larger the amount added, the more the UV transmission becomes This will prevent the resin from curing.

In the case of this example, when carbon fiber or aramid fiber was added in a weight ratio of 6% or more, curing of the resin was significantly inhibited.

Therefore, the amount of carbon fibers and aramid fibers added as reinforcing materials is considered to be within a practically usable range in terms of weight ratio of 5 inches or less.

In Examples 1 and 2, the thermoplastic resin foam was thermoformed into a diaphragm that integrally included a diaphragm portion and a portion of the edge, and then an ultraviolet curable resin was applied and cured. It goes without saying that by selecting an appropriate material, it is also possible to cure the ultraviolet curable resin on both sides of the foam sheet and then thermoform it into a diaphragm in the same manner as in the embodiments.As detailed above, according to the present invention, For example, by coating both sides of the diaphragm part of a thermoplastic resin foam sheet with ultraviolet curable resin reinforced with a reinforcing material and curing it, a three-layer structure is created. It is possible to obtain a diaphragm that integrally includes an edge portion with a large internal loss.

Furthermore, since the material of the diaphragm is a thermoplastic resin foam sheet, it has the advantage that the diaphragm portion and the edge portion can be thermoformed at the same time.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the speaker diaphragm of the present invention, Fig. 2 is an enlarged sectional view of the main part of the diaphragm, and Fig. 3 is the sound pressure frequency of the diaphragm and a conventional diaphragm. It is a comparison curve diagram of characteristics. 1... diaphragm part, 2... edge part, 3
... Vibration plate, 4 ... Thermoplastic resin foam sheet, 6, 6 ... Ultraviolet curing resin layer containing reinforcing material. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3

Claims (1)

[Claims] A speaker diaphragm integrally comprising 177 parts. (2) The speaker diaphragm according to claim 1, characterized in that mica, carbon fiber, or aramid fiber is used as a reinforcing material for the ultraviolet curable resin.