JP2006033024A - Speaker diaphragm and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight speaker diaphragm exhibiting excellent internal loss, heat resistance, strength, stability in quality, and moldability, and to provide its convenient and inexpensive manufacturing process. <P>SOLUTION: The speaker diaphragm is molded of a resin composition containing an alloy which contains polyphenylene ether resin and polystyrene resin at a weight ratio of 90/10-70/30, and an inorganic filler. Preferably, the resin composition contains 5-30 pts.wt. of inorganic filler for 100 pts.wt. of alloy. Preferably, the inorganic filler is at least one selected from a group of graphite, talc, mica, molybdenum disulfide and glass fiber. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a speaker diaphragm and a manufacturing method thereof. More specifically, the present invention relates to a speaker diaphragm that is lightweight and has excellent internal loss, heat resistance, strength, quality stability, and moldability, and a simple and inexpensive manufacturing method thereof.

  As a material for the speaker diaphragm, various materials are employed depending on applications. For example, as a diaphragm for a micro speaker used for a personal computer, a mobile phone, a portable game device, or the like, typically, a metal foil, a coating cloth, or a polymer film is used. However, each of these materials has problems. Although the metal foil has high rigidity, since the internal loss is small, a unique sound peculiar to metal is likely to be generated, resulting in a poor S / N ratio. The coated fabric is typically a fabric in which a woven fabric (for example, cotton or synthetic fiber) is impregnated with a thermosetting resin (for example, a phenol resin) and the surface thereof is coated with an acrylic resin or a urethane resin. . Such a coated fabric is excellent in both rigidity and internal loss, but it is necessary to apply multiple layers of coating to prevent the ventilation of the diaphragm, so that the weight increases and the sound pressure decreases. .

  As the polymer film, an engineering plastic film is increasingly used. This is because engineering plastics have higher rigidity than general-purpose plastics and are lighter than metal foils and coated fabrics. Engineering plastic (eg, polyetheretherketone (PEEK), thermoplastic polyimide (PI), polyetherimide (PEI)) films have excellent rigidity and heat resistance, but have low internal loss. As a result, the S / N ratio becomes poor, and only a diaphragm having many distortion characteristics can be obtained. Furthermore, engineer plastics generally have a higher specific gravity, which causes a problem that sound pressure is reduced.

  As a means for improving the internal loss of a diaphragm obtained from an engineering plastic film, a technique for coating a paint containing a polyester resin or an acrylic resin as a binder on at least one surface of the film has been proposed. This technique is intended to cause internal friction during vibration by the coating. However, according to this technique, there is a problem that not only the weight is further increased and the problem of sound pressure reduction is increased, but the quality is not stabilized due to variations in the thickness of the coating.

  On the other hand, in Patent Document 1, as a diaphragm having excellent characteristics, a mixture of a polyphenylene ether resin and a styrene resin, or a graft polymer of a polyphenylene ether resin and a styrene resin, an alloy of a crystalline polyamide resin, and a rubber-like substance are disclosed. A large-diameter speaker diaphragm molded from a resin composition containing an inorganic filler and a compatibilizing agent has been proposed. According to Patent Document 1, it is described that a large-diameter speaker diaphragm that is excellent in sound speed, adhesiveness, heat resistance, and internal loss and is inexpensive can be obtained.

Japanese Patent No. 3317052

  However, the resin composition described in Patent Document 1 has insufficient fluidity when melted. As a result, a large-diameter and simple-shaped diaphragm (for example, a cone-shaped diaphragm) can be molded without any problem, but a small-diameter diaphragm having a complicated shape and requiring thin-wall molding (for example, 1 and 2 is virtually impossible to form. Actually, according to the technique of Patent Document 1, only a diaphragm having a thickness of millimeter order can be formed.

  As described above, there is a strong demand for a speaker diaphragm that is lightweight and has excellent internal loss, quality stability, and moldability, and a simple and inexpensive manufacturing method thereof.

  The present invention has been made in order to solve the above-described conventional problems, and an object of the present invention is to make a speaker vibration that is lightweight and has excellent internal loss, heat resistance, strength, quality stability, and moldability. It is to provide a plate and a simple and inexpensive manufacturing method thereof.

  According to one aspect of the present invention, a speaker diaphragm is provided. This diaphragm is formed from a resin composition containing an alloy containing polyphenylene ether resin and polystyrene resin in a weight ratio of 90/10 to 70/30 and an inorganic filler.

  In preferable embodiment, the said resin composition contains the said inorganic filler in the ratio of 5-30 weight part with respect to 100 weight part of said alloys.

  In a preferred embodiment, the inorganic filler is at least one selected from the group consisting of graphite, talc, mica, molybdenum disulfide, and glass fiber. In a more preferred embodiment, the inorganic filler is molybdenum disulfide.

  According to another aspect of the present invention, a speaker is provided. The speaker includes the speaker diaphragm.

  According to still another aspect of the present invention, a method for manufacturing a speaker diaphragm is provided. This manufacturing method includes a step of melt-kneading a polyphenylene ether resin and a polystyrene resin at a ratio of 90/10 to 70/30 by weight to prepare an alloy; and melt-kneading the alloy and an inorganic filler to obtain a resin. A step of preparing a composition; a step of extruding the resin composition at 260 ° C. to 300 ° C. to form a film; and a step of hot press forming the film using a mold having a predetermined shape .

  In another embodiment, the method of the present invention comprises a step of preparing a resin composition by melt-kneading a polyphenylene ether resin and a polystyrene resin in a weight ratio of 90/10 to 70/30 and an inorganic filler. And a step of extruding the resin composition at 260 ° C. to 300 ° C. to form a film; and a step of hot press-molding the film using a mold having a predetermined shape.

  As described above, according to the present invention, excellent strength and heat resistance can be obtained by molding a diaphragm from a resin composition containing an inorganic filler and an alloy containing polyphenylene ether resin and polystyrene resin at a specific ratio. The thin-walled molding of a small speaker having a characteristic and a complicated shape (which was practically impossible in the past) becomes possible. More specifically, by containing the polyphenylene ether resin and the polystyrene resin in a specific ratio, the fluidity (for example, melt flow rate: MFR) is obtained without reducing the inherent strength and heat resistance of the polyphenylene ether resin. Can be effectively improved. As a result, a speaker diaphragm having excellent strength and heat resistance and improved formability when forming a complicated shape and / or a very thin shape is obtained. Furthermore, the speaker diaphragm of the present invention has excellent internal loss due to friction during vibration of the polyphenylene ether resin molecule and the polystyrene resin molecule. And since the resin composition used for this invention does not require a compatibilizing agent, the outstanding fluidity | liquidity is maintained.

  In a preferred embodiment, strength and heat resistance can be improved without substantially reducing the fluidity (for example, MFR) of the resin composition by using molybdenum disulfide as the inorganic filler. As a result, a speaker diaphragm having further excellent strength and heat resistance can be obtained. In addition, the internal loss can be further improved by friction between the inorganic filler and the resin molecules.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

  The speaker diaphragm of the present invention is formed from a resin composition containing an alloy containing polyphenylene ether resin and polystyrene resin in a weight ratio of 90/10 to 70/30, and an inorganic filler. Preferably, the alloy contains polyphenylene ether resin and polystyrene resin in a weight ratio of 85/15 to 75/25. If the proportion of the polyphenylene ether resin in the alloy is too large, the fluidity of the resin composition becomes insufficient, and a thin diaphragm having a complicated shape cannot often be molded. If the proportion of the polyphenylene ether resin in the alloy is too small, the resulting diaphragm often has insufficient heat resistance. By alloying the polyphenylene ether resin and the polystyrene resin at such a specific ratio, it is possible to achieve both the fluidity and dimensional stability of the resin composition, heat resistance and strength, which have been difficult in the past. As a result, thin molding of a small speaker having excellent strength and heat resistance and having a complicated shape (which was practically impossible in the past) is possible.

ここで、ｎは、好ましくは４２〜８４００、さらに好ましくは８４〜４２００、最も好ましくは２５０〜２５００である（このようなｎに対応する数平均分子量は、好ましくは５０００〜１００００００、さらに好ましくは１００００〜５０００００、最も好ましくは３００００〜３０００００である）。ｎ（すなわち、重合度または分子量）が小さすぎると、所望の耐熱性および強度が得られない場合が多い。ｎが大きすぎると、流動性が不十分となり、複雑な形状を有する薄肉の振動板が成形できない場合がある。ポリフェニレンエーテル樹脂は、数多く市販されている。ポリフェニレンエーテル樹脂とアロイ化されるポリスチレン樹脂は、好ましくは４００〜５０００００、さらに好ましくは７０００〜１０００００、最も好ましくは１００００〜３００００の数平均分子量を有する。ポリスチレン樹脂がこのような範囲の分子量を有することにより、ポリフェニレンエーテル樹脂本来の耐熱性や強度を低下させることなく、流動性および寸法安定性を効果的に改善することができる。 The polyphenylene ether resin is generally represented by the following chemical formula:

Here, n is preferably 42 to 8400, more preferably 84 to 4200, and most preferably 250 to 2500 (the number average molecular weight corresponding to n is preferably 5,000 to 1,000,000, more preferably 10,000. ~ 500,000, most preferably 30000-300000). If n (that is, degree of polymerization or molecular weight) is too small, desired heat resistance and strength are often not obtained. If n is too large, fluidity may be insufficient and a thin diaphragm having a complicated shape may not be formed. Many polyphenylene ether resins are commercially available. The polystyrene resin to be alloyed with the polyphenylene ether resin preferably has a number average molecular weight of 400 to 500,000, more preferably 7000 to 100,000, and most preferably 10,000 to 30,000. When the polystyrene resin has a molecular weight in such a range, fluidity and dimensional stability can be effectively improved without reducing the inherent heat resistance and strength of the polyphenylene ether resin.

  Any appropriate inorganic filler can be adopted as the inorganic filler as long as the effects of the present invention can be obtained. Representative examples of such inorganic fillers include graphite, talc, mica, molybdenum disulfide, and glass fibers. These inorganic fillers can be used alone or in appropriate combination depending on the purpose. A particularly preferred inorganic filler is molybdenum disulfide. Molybdenum disulfide has a lower degree of lowering the fluidity (for example, melt flow rate) of the resin composition than other fillers, so that heat resistance can be reduced without reducing moldability when molding complex shapes. Property and strength can be improved. The inorganic filler is contained in an amount of preferably 5 to 30 parts by weight, more preferably 10 to 20 parts by weight, based on 100 parts by weight of the alloy. When the inorganic filler is less than 5 parts by weight, the effect of improving strength and heat resistance may be insufficient. When the inorganic filler exceeds 30 parts by weight, the fluidity is lowered, and a thin diaphragm having a complicated shape may not be formed.

  The melt flow rate (MFR: index of fluidity) of the resin composition can vary depending on the type and amount of the inorganic filler. MFR is measured according to JIS K-6760. The MFR of the resin composition when 20 parts by weight of the inorganic filler is added is preferably 17 g / 10 minutes or more, more preferably 22 g / 10 minutes or more, and most preferably 30 g / 10 minutes or more. The realizable upper limit of MFR is 42 g / 10 minutes. When the MFR of the resin composition has such a value, the thickness can be precisely controlled when a thin film is formed. As a result, it is possible to form a thin diaphragm having a complicated shape.

  The resin composition may further contain any appropriate additive (for example, a surface modifier such as hydrogenated styrene-ethylene-butylene-styrene block copolymer (SEBS)). The kind and amount of the additive can be appropriately adjusted according to the purpose.

  Next, a preferable example of the method for manufacturing the speaker diaphragm of the present invention will be described. First, an alloy is prepared by melt-kneading a polyphenylene ether resin and a polystyrene resin at a weight ratio of 90/10 to 70/30, preferably 85/15 to 75/25. Next, the alloy and the inorganic filler are melt-kneaded to prepare a resin composition. Alternatively, a resin composition may be prepared by melting and kneading a polyphenylene ether resin, a polystyrene resin, and an inorganic filler all at once. The melt-kneading is performed using any appropriate means (for example, a Henschel mixer or a universal mixer). The melt kneading temperature can vary depending on the composition of the intended resin composition, but is typically 240 to 290 ° C.

  Next, the resin composition is extruded at 260 to 300 ° C., preferably 275 to 285 ° C., to form a film. Extrusion is typically performed using a T die (thus the temperature during extrusion is typically the temperature of the T die). If the temperature at the time of extrusion is less than 260 ° C., the fluidity of the resin composition becomes insufficient, and it may be difficult to form a film. As a result, a thin diaphragm having a complicated shape may not be formed. When the temperature at the time of extrusion exceeds 300 ° C., the resin in the composition is decomposed, and a diaphragm having desired characteristics may not be obtained. The discharge rate in extrusion molding is preferably 25 to 35 kg / hour. The screw speed is preferably 50 to 70 rpm. By controlling the discharge amount and the screw speed in such a range, precise film forming becomes possible. As a result, it is possible to form a thin diaphragm having a complicated shape. The thickness of the film obtained by extrusion may vary depending on the purpose, but is typically 25 to 75 μm. For example, when used for a mobile phone speaker, the film thickness is preferably 25 to 50 μm. For example, when used for a tweeter, the film thickness is preferably 50 to 75 μm. One of the features of the present invention is that such a thin speaker diaphragm film can be formed using polyphenylene ether resin.

Finally, the film is hot press molded using a mold having a predetermined shape to obtain a speaker diaphragm. Any appropriate shape (including a complicated shape) may be adopted as the shape of the mold depending on the purpose. Preferably, the mold temperature during hot pressing is 180 to 200 ° C., the pressing pressure is 300 to 400 kg / cm ² , and the molding time is 5 to 15 seconds. By performing hot press molding under such conditions, it is possible to form a diaphragm having a complicated shape using a thin film.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight.

An alloy was prepared by melt-kneading polyphenylene ether resin and polystyrene resin at a weight ratio of 80/20 at 260 ° C. using a Henschel mixer. The alloy was subjected to film forming without adding an inorganic filler. The film forming conditions were a T die temperature of 280 ° C., a discharge rate of 30 kg / hour, and a screw speed of 60 rpm. The thickness of the obtained film was 55 μm. Next, using a mold having a shape as shown in FIG. 2, heat press molding was performed at a mold temperature of 200 ° C., a press pressure of 350 kg / cm ² , and a molding time of 10 seconds to obtain a speaker diaphragm. The density, elastic modulus, and internal loss (tan δ) of the obtained diaphragm were measured by ordinary methods. The obtained results are shown in Table 1 below together with the results of Examples 2-3 and Comparative Examples 1-2 described later.

  A speaker diaphragm was obtained in the same manner as in Example 1 except that 20 parts of talc powder was added to 100 parts of alloy. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

  A speaker diaphragm was obtained in the same manner as in Example 1 except that 10 parts of molybdenum disulfide powder was added to 100 parts of alloy. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Comparative Example 1)
A speaker diaphragm was obtained in the same manner as in Example 1, except that a film (thickness 55 μm) of polyetherimide resin (manufactured by Mitsubishi Resin Co., Ltd., Superior UT) was used. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Comparative Example 2)
A speaker diaphragm was obtained in the same manner as in Comparative Example 1 except that one surface of the polyetherimide resin film was coated with 5 μm of a powder paint using a polyester resin as a binder. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown in Table 1.

(Melt flow rate of resin composition)
The melt flow rate (MFR) of the resin composition used for the speaker diaphragm of the present invention was measured at 220 ° C. according to JIS K-6760. The measurement results are shown in Table 2. All of these were capable of forming a good film with a thickness on the order of micrometers. On the other hand, a composition in which polyphenylene ether resin and polystyrene resin are mixed at 95/5 (weight ratio) has an MFR of only about 15 g / 10 minutes even when the die temperature is higher than 300 ° C., and the polyphenylene ether resin is decomposed. Therefore, it was difficult to form a good film.

  As is clear from Table 1, the speaker diaphragm of the example of the present invention has a low density (that is, light weight) and an excellent elastic modulus and internal loss. Furthermore, as is clear from Table 2, the resin composition used for the speaker diaphragm of the present invention is excellent in fluidity. As a result, it is possible to form a thin diaphragm (thickness on the order of micrometers) having a complicated shape. Judging from such fluidity evaluation, regarding the polystyrene content in the alloy, it is considered that there is a critical point as to whether or not film formation with a thickness of micrometer order is possible somewhere between 5% and 10%. It is done. The critical MFR corresponding to such critical polystyrene content is believed to be around 15 g / 10 min. In addition, when the prescription of the said patent document 1 is used, the thickness which can be shape | molded is 0.7 mm-5 mm typically.

  The speaker diaphragm of the present invention can be used for any appropriate speaker, and can be particularly preferably used for a micro speaker and a tweeter.

It is a schematic sectional drawing for demonstrating the shape of a speaker diaphragm. It is a schematic sectional drawing for demonstrating the shape of a speaker diaphragm.

Claims (7)

  A speaker diaphragm formed by molding a resin composition containing an alloy containing a polyphenylene ether resin and a polystyrene resin in a ratio of 90/10 to 70/30 by weight and an inorganic filler.   The speaker diaphragm according to claim 1, wherein the resin composition includes the inorganic filler in a ratio of 5 to 30 parts by weight with respect to 100 parts by weight of the alloy.   The speaker diaphragm according to claim 1 or 2, wherein the inorganic filler is at least one selected from the group consisting of graphite, talc, mica, molybdenum disulfide, and glass fiber.   The speaker diaphragm according to any one of claims 1 to 3, wherein the inorganic filler is molybdenum disulfide. A step of preparing an alloy by melt-kneading a polyphenylene ether resin and a polystyrene resin in a weight ratio of 90/10 to 70/30;
A step of melt-kneading the alloy and the inorganic filler to prepare a resin composition;
Extruding the resin composition at 260 ° C. to 300 ° C. to form a film;
And a step of hot press-molding the film using a mold having a predetermined shape. A step of melt-kneading a polyphenylene ether resin and polystyrene resin in a ratio of 90/10 to 70/30 by weight ratio and an inorganic filler to prepare a resin composition;
Extruding the resin composition at 260 ° C. to 300 ° C. to form a film;
And a step of hot press-molding the film using a mold having a predetermined shape. A speaker comprising the speaker diaphragm according to claim 1.

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