JPH0514480B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to an acoustic diaphragm for microphones, headphones, speakers, etc., and a method for manufacturing the same. Background Art and Its Problems Acoustic diaphragms for microphones, headphones, speakers, etc. must have flexibility at the edges and high rigidity at other parts. In the resin coating method, which is one of the known manufacturing methods for such an acoustic diaphragm, a thermosetting resin is applied only to the vibration surface of the diaphragm and hardened to increase rigidity. In addition, the present applicant proposed in Japanese Patent Application No. 198804/1983 a method for manufacturing an acoustic diaphragm that can obtain an acoustic diaphragm with good characteristics and sensitivity, and is suitable for mass production. In this manufacturing method, a small amount of additives (polymerization terminator,
A sensitizer) is mixed and applied to the entire surface of a base film, which is then molded into the shape of a diaphragm, and then only the vibrating surface of the diaphragm is irradiated with radiation or ultraviolet rays to cure it. However, in any of these methods, heat, radiation, and ultraviolet curable resins are sticky and fluid in an uncured state, so they may stick when the base film coated with the resin is wound up. Further, there was a problem in that the resin flowed during molding and the coating became non-uniform. Therefore,
These resins were mixed with another resin to prevent sticking, but when this anti-sticking resin was mixed, the hardness after curing was reduced and the strength of the coating film was also reduced. Therefore,
The type and amount of resin to be mixed must be controlled to suppress stickiness and fluidity while maintaining the desired strength, which limits the manufacturing conditions and range of application. OBJECTS OF THE INVENTION In view of the above-mentioned problems, it is an object of the present invention to provide an acoustic diaphragm with excellent characteristics and sensitivity, and a manufacturing method suitable for mass production of the acoustic diaphragm. Summary of the Invention The acoustic diaphragm according to the present invention is composed of a base film and a coating layer formed on the base film, and the coating layer is made of a radiation-curable, ultraviolet-curable or thermosetting resin, and a micro-acoustic diaphragm. Containing a filler consisting of at least one of a balloon and particulate silicon carbide, and a reinforcing material, the vibrating surface is hardened by irradiation or heating with radiation or ultraviolet rays, and has a higher hardness than the edge portion. It is characterized by: Further, the method for manufacturing an acoustic diaphragm according to the present invention includes radiation curable,
A base film having a substantially uniform coating layer containing an ultraviolet curable or thermosetting resin, a filler made of at least one of micro balloons and microparticulate silicon carbide, and a reinforcing material is shaped into a diaphragm shape. After molding, the vibrating surface is cured by irradiating with radiation or ultraviolet rays or by heating. In the acoustic diaphragm of this invention, the filler contained in the coating layer improves the uniformity of the coating film and further increases the rigidity by increasing the clay content of the coating layer and suppressing stickiness and fluidity. Preferably. Further, it is more preferable to use a filler having a relatively low specific gravity because the coating film becomes lighter and the sensitivity of the diaphragm can be increased. In this invention, at least one of microballoons and particulate silicon carbide is used as such a filler. The microballoon may be made of silicon carbide, carbon, silicon dioxide, alumina, iron oxide, etc., and preferably has an average particle size of about 10 to 50 μm. The fine particle silicon carbide preferably has an average particle size of about 0.1 μm. The above-mentioned filler is used in combination with a resin, and the amount of the filler mixed is preferably 25% by weight or less. This is because too much filler causes problems such as a decrease in the strength of the coating film. These fillers can be used alone or in combination depending on the purpose of use. In this invention, the material that can be used as the base film is not particularly limited as long as it has been conventionally used for acoustic diaphragms, but polyethylene terephthalate is particularly preferred. The resin that can be used in this invention may be any resin that can be cured when irradiated with radiation and/or ultraviolet rays or cured by heat to impart desired rigidity to the vibrating surface. The present invention is not limited to the following resins.
As such a resin, it is preferable to use, for example, a monomer or oligomer having an acrylic or methacrylic double bond. Among such monomers, those having an acrylate double bond include, for example, vinylpyrrolidone, 2-ethylhexyl acrylate, lauryl acrylate, hydroxyethyl acrylate, ethoxyethoxy acrylate, tetrahydrofurfuryl acrylate, Fronix M-5700 (trade name), etc. monofunctional monomers, diethylene glycol diacrylate, tetraethylene glycol diacrylate,
Bifunctional monomers such as neopentyl glycol diacrylate and Aronix M-6100 (trade name),
Examples include polyfunctional monomers such as trimethylolpropane triacrylate, tetramethylolmethanetetraacrylate, dipentaerythritol hexaacrylate, and dipentaerythritol pentaacrylate. Examples of such monomers having a methacrylic double bond include those in which the acrylic double bond of the above-mentioned monomer is replaced by a methacrylic double bond. In addition, the resin species that form the skeleton having such double bonds include:
Examples include alkyd resins, polyesters, acrylic resins, polyurethanes, and epoxy resins. When an oligomer is used as the resin, it may be converted into an oligomer using a conventional method using the monomers described above. It is preferable to use the above-mentioned resin together with a photomultiplier, and upon irradiation with light, the sensitizer decomposes to generate radicals, which polymerize and crosslink through the radicals. Such sensitizers include, for example,
Examples include benzoin compounds and benzophenone-amine mixtures. Examples of benzoin compounds include benzoin alkyl ethers, and examples of the alkyl group include methyl, isopropyl, n-butyl, and t-butyl. Examples of amine compounds used in the benzophenone-amine mixture include methyldiethanolamine, triethanolamine, N-methylmorpholine, triethylamine, dibutylamine, N,N-dimethylbenzylamine, N,N-
Examples include dimethylaniline. Further, in the present invention, as the reinforcing agent contained in the coating layer, graphite, polyoxymethylene whiskers, etc., which are suitable for increasing the strength of the vibration surface by increasing the strength of the curable resin, can be used. The amount of the reinforcing material can be appropriately determined in consideration of conditions such as curing speed and press moldability. Next, a method for manufacturing an acoustic diaphragm according to the present invention will be described with reference to the drawings in the case where a radiation or ultraviolet curable resin is used. First, as shown in FIG.
Next, a coating layer 2 containing a resin, a filler, and a reinforcing material that is cured by radiation, ultraviolet rays, etc. is molded by an appropriate method. Next, as shown in FIG. 2, this base film 1 is molded into a well-known predetermined diaphragm shape using a molding machine, and a ring 3 is glued to a portion corresponding to the outer periphery of the edge portion of the acoustic diaphragm. let Next, as shown in FIG. 3A, the base film is cut and separated into a large number of diaphragms, and a mask 4 is formed on the edge portion of a suitable material, such as aluminum or steel, so that this portion is Prevents curing due to irradiation with radiation, ultraviolet rays, etc. The molded body 10 in which the mask has been formed is irradiated with radiation, ultraviolet rays, etc. by an appropriate means to harden the portion corresponding to the vibration surface to an appropriate hardness, and the mask 4 is removed. As a result, a hardened coating layer 5 is formed on the molded body 10, as shown in FIG. 3B. FIG. 4 shows an example of a method of irradiating main lines or ultraviolet rays. In FIG. 4, a large number of molded bodies 10 forming masks are arranged on a plate 11, and this plate 11 is placed on a belt conveyor 12 moving at a predetermined speed. These molded bodies 10 are irradiated with radiation or ultraviolet rays when passing under the radiation or ultraviolet ray irradiation device 13 . In the above-mentioned method, electron beams, gamma rays, etc. are used as the radiation. In addition, the amount of radiation, ultraviolet rays, etc. is not particularly limited;
It may be selected appropriately taking into consideration the type of resin, curing speed, etc. Even when a thermosetting resin is used instead of a radiation or ultraviolet curable resin, the acoustic diaphragm can be manufactured in the same manner as described above. In this case, a heat insulating material is used as the mask, and the resin may be cured by heating with a heating device instead of a radiation or ultraviolet irradiation device. In the acoustic diaphragm manufactured by the method described above, a coating layer of cured resin is formed on the vibrating surface, while the resin remains uncured on the edge portions where the mask is formed. . This uncured resin may be removed by suitable means, such as a solvent, and in this way, as shown in FIG. 3C,
A hardened coating layer 5 is formed only on the vibrating surface of the molded body 10. Preferred solvents for removing the resin in this case include methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. In the method for manufacturing the acoustic diaphragm described above, any of the conventional methods can be used to form a coating layer almost uniformly on the base film, including spraying, brush coating, gravure roll, and doctor-coating.
An example is the blade method. Also,
The base film on which the coating layer has been formed almost uniformly is molded into a well-known predetermined diaphragm shape using a molding machine as described above, but this molding method is not specific to the specific method. It is not limited,
For example, a pressure forming method may be used. Further, these steps can be carried out either continuously or batchwise. Example 1 A polyfunctional acrylate monomer (trade name "DPHA", manufactured by Nippon Kayaku Kogyo Co., Ltd.) was mixed with 20% silicon carbide in the form of fine particles (trade name "Aerosil", manufactured by Nippon Aerosil Co., Ltd.) as a filler. A mixture of 3% polyoxymethylene whiskers as a reinforcing material, which was further diluted with methyl ethyl ketone, was applied almost uniformly to a 40μ thick film on a 9μ thick polyethylene terephthalate film using a doctor blade method. Next, this film was pressure-molded to form a dome-shaped diaphragm for a dynamic microphone. Subsequently, the edge portion of this diaphragm was masked with aluminum, and the dome portion was cured by irradiating ultraviolet rays at a distance of 20 cm, an intensity of 80 W/cm, and a feed rate of 10 cm/min. After curing, this diaphragm was immersed in methyl ethyl ketone to remove the resin at the edges, and when dried, the dome portions were cured and a desired diaphragm with integrated edge molding could be obtained. The results of measuring the output frequency characteristics of a dynamic microphone using this diaphragm are shown in broken lines in FIG. Also, as a comparative example,
The output frequency characteristic measured in the same manner for a dynamic microphone using a diaphragm containing no filler or reinforcing material is shown by a solid line in FIG. In Fig. 5, the dynamic type microphone of Example 1 has a frequency of 8KHz, which was observed in the case of the comparative example.
The nearby dip has disappeared, and the stability of the high range has increased. Also, the results of the listening tests showed that the sound had a wider range and more depth. Example 2 Polyfunctional acrylate monomer (trade name "DPHA", manufactured by Nippon Kayaku Kogyo Co., Ltd.) was mixed with 10% silicon dioxide microballoons as a filler and 5% polyoxymethylene whiskers as a reinforcing material.
%, and this mixture was applied almost uniformly to a 40μ thick polyethylene terephthalate film with a thickness of 9μ using a doctor blade method. Next, this film was pressure-molded to form a dome-shaped diaphragm of a dynamic microphone. Next, the edge of this diaphragm was masked with aluminum, and the distance was 20cm, and the intensity was 80W/
The dome portion was cured by irradiation with ultraviolet rays at a feed rate of 10 cm/min. After curing, this diaphragm was immersed in methyl ethyl ketone to remove the resin at the edges, and then dried to obtain a desired diaphragm with a hardened edge molding mold. The results of measuring the output frequency characteristics of a dynamic microphone using this diaphragm are shown in broken lines in FIG. Further, the output frequency characteristic of the dynamic microphone using the diaphragm of the comparative example described above is shown by a solid line in FIG. In FIG. 6, the dynamic type microphone of Example 2 has increased overall sensitivity and increased stability in high frequencies compared to the comparative example. In addition, the results of the trial listening showed that the volume became louder, and as in Example 1, the sound became wider and thicker. Example 3 In Example 1, the mixed amount of Aerosil was 5%.
A dome-shaped diaphragm for a dynamic microphone was formed in the same manner as in Example 1, except for the following. In this case, the coating thickness when the coating layer was formed on the base film was 49μ±3μ. During molding, the coating thickness was 49μ±4μ, with almost no change in the uniformity of the coating thickness. On the other hand, in the case of a diaphragm that did not contain Aerosil, which was formed as a comparative example, the film thickness during molding varied to 49μ±15μ, making it non-uniform. Furthermore, Example 1 was added to the molded diaphragm.
In the same manner as above, ultraviolet rays were irradiated to remove the resin at the edge portions to obtain a desired diaphragm with a hardened dome portion. The output frequency characteristics measured by incorporating the obtained diaphragm into a microphone unit are shown by broken lines in FIG. Further, the output frequency characteristics of the microphone using the diaphragm of the comparative example described above are shown by a solid line in FIG. The data shown in Figure 7 is
This was obtained using a different unit from that shown in FIGS. 5 and 6. From Figure 7, the comparative example has a large dip due to unstable movement of the diaphragm in the high range.
In Example 3, the dip in the high range was small and the shoulder characteristics in the low range were also good. In addition, the directivity characteristics of Example 3 were also better than those of the comparative example, and the sound was clear and lively in the listening results. Further, the physical properties of the diaphragms obtained in Example 3 and Comparative Example are shown in the table below. In the table, Reference Example 1 uses an acrylate monomer (trade name "Aronix", manufactured by Toagosei Kagaku Kogyo Co., Ltd.) as the resin.
Reference Example 2 shows the physical properties of a diaphragm made only of a base film of polyethylene terephthalate.

[Table] As shown in the table, the diaphragm of Example 3 was
It can be seen that the sound velocity is the highest and the Q value is the lowest, making it an ideal diaphragm. Effects of the Invention The present inventor first achieved a method of achieving adhesiveness and fluidity by mixing a resin that has adhesiveness and fluidity but is hard when cured, and a resin that has neither adhesiveness nor fluidity but is soft. The idea was to form a coating layer with little hardness and a certain degree of hardness, and a trial production experiment was conducted, but there was a limit to the hardness of this coating layer. However, in the acoustic diaphragm of the present invention, a filler consisting of at least one of microballoons and particulate silicon carbide is added to the curable resin, so even if the soft resin is hardly mixed, tackiness and fluidity can be reduced. Since it has become possible to suppress the adhesiveness, it has become possible to obtain an even harder coating layer. Therefore,
When winding up resin-coated film during the manufacturing process, the film no longer sticks, making the work easier and making it possible to further increase mass production. Further, even when the molding temperature was raised when molding the film into the shape of a diaphragm, the applied resin did not flow and become non-uniform, and a uniform coating layer was obtained. As a result, the acoustic diaphragm moves smoothly when used in microphones and speakers. Furthermore, in the acoustic diaphragm of the present invention, since a reinforcing material is added to the curable resin, the strength of the curable resin can be increased, and as a result, the strength of the vibration surface can be increased. Further, according to the method for manufacturing an acoustic diaphragm according to the present invention, the base film having a substantially uniform coating layer is formed into the shape of a diaphragm, and then the vibration surface is hardened. It does not require the time-consuming and complicated process of applying resin only to the vibrating surface, and can be efficiently mass-produced on a production line. As described above, the present invention has made it possible to provide an acoustic diaphragm with excellent sensitivity and various characteristics and good sound quality, and a manufacturing method that allows mass production of such an acoustic diaphragm.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the structure of the material of the acoustic diaphragm used in this invention, Fig. 2 is a sectional view showing the molded state, Fig. 3A is a sectional view showing the state with a mask on, and Fig. 3B is 3C is a cross-sectional view showing the state after the resin has been cured; FIG. 3C is a cross-sectional view showing the state after removing the uncured portion of the resin; FIG. 6 and 7 are curve diagrams showing the output frequency characteristics of a dynamic microphone using an acoustic diaphragm according to the present invention. In addition, in the symbols used in the drawings, 1...
...Base film, 2... Coating layer, 4... Mask, 5... Cured coating layer, 10... Molded object, 1
3...Irradiation device.

Claims (1)

[Scope of Claims] 1 Consisting of a base film and a coating layer formed on the base film, the coating layer comprising a radiation-curable, ultraviolet-curable or thermosetting resin, micro balloons and fine particulate carbonized resin. a filler consisting of at least one side of silicon;
and a reinforcing material, the vibration surface of which is hardened by irradiation or heating with radiation or ultraviolet rays, and has a higher hardness than the edge portions. 2. A base film in which a coating layer is almost uniformly formed, each containing a radiation-curable, ultraviolet-curable or thermosetting resin, a filler consisting of at least one of microballoons and microparticulate silicon carbide, and a reinforcing material. 1. A method for manufacturing an acoustic diaphragm, which comprises: forming a diaphragm into a diaphragm shape, and then curing the vibrating surface by irradiating the vibrating surface with radiation or ultraviolet rays or by heating.