JP2004274661

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DESCRIPTION JP2004274661
An object of the present invention is to improve rigidity in the radial direction, thereby improving
the speed of sound, improve the frequency characteristics of middle to high frequency, and make
the sound quality better and appearance as compared with the case of adding scaly mica to
polyolefin resin The present invention provides a diaphragm for an electroacoustic transducer
which is also preferable. The diaphragm is formed of a composite material in which a synthetic
resin is reinforced with basic magnesium sulfate having a needle-like particle shape. As this basic
magnesium sulfate, whiskers having an average fiber diameter of 0.5 to 1 μm and an average
fiber length of 5 to 20 μm are used, which are 5 to 50% of synthetic resin, or other
reinforcements, preferably phosphorus It is made to contain 5 to 50% in the synthetic resin in
the flake-like filler or the inorganic fiber and the organic fiber combined use system. [Selected
figure] Figure 2
Electroacoustic transducer diaphragm
TECHNICAL FIELD The present invention uses a basic magnesium sulfate as a reinforcing
material for synthetic resin, and is a speaker which is lightweight, has high rigidity, high internal
loss, and is excellent in formability, dimensional stability, and heat resistance. And a diaphragm
for an electroacoustic transducer used for a microphone or the like. [0002] A synthetic resin and
a synthetic resin composite material are used as a molding material of a diaphragm for an
electroacoustic transducer, but in particular, a material in which a synthetic resin is reinforced
with a plate-like filler such as mica is used. The molded products are widely used because they
can obtain balanced physical properties at relatively low cost. As shown in Japanese Patent
Publication No. 2-53999 and Japanese Patent Publication No. 2-41960, scale-like mica is mixed
with polyolefin resin as a reinforcing material for good formability and excellent acoustic
characteristics. A diaphragm with the material is shown. In these prior examples, the addition of
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scaly mica improves the rigidity, reduces the distortion and improves the sound quality, but the
orientation of the scaly mica is improved. Because of the randomness, the rigidity in the radial
direction of the diaphragm, which is particularly effective for improving the sound quality, can
not be further enhanced, so there is a problem that dips occur in the middle to high frequency
characteristics and desired sound quality can not be obtained. . The present invention has been
proposed in view of the above, and its purpose is to improve the rigidity in the radial direction
and thus the speed of sound, as compared with the case of adding scaly mica to a polyolefin resin
It is an object of the present invention to provide a diaphragm for an electroacoustic transducer
which improves the frequency characteristics of the middle to high frequency, makes the sound
quality better, and is also appearanceally good. SUMMARY OF THE INVENTION The present
invention achieves the above object by molding a diaphragm with a composite material in which
a synthetic resin is reinforced with basic magnesium sulfate. In this case, the basic magnesium
sulfate is whisker-like with an average fiber diameter of 0.5 to 1 μm and an average fiber length
of 5 to 20 μm, which is 5 to 50% of synthetic resin, or other reinforcement Preferably, it is
characterized by containing 5 to 50% in a synthetic resin in a scale-like filler or an inorganic fiber
/ organic fiber combined use system. Further, as the synthetic resin, at least one of polyethylene,
polypropylene, polymethylpentene, methacrylic resin, polyamide, and liquid crystal polymer as a
main component, as a compatibilizer, styrene-based saturated thermoplastic elastomer, ethylene ·
It is characterized in that at least one of an ethyl acrylate / maleic anhydride copolymer, an
ethylene-based modified α-olefin copolymer, and a modified polyolefin is used.
BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a diaphragm for an
electroacoustic transducer is formed of a composite material in which a synthetic resin is
reinforced with basic magnesium sulfate. Basic magnesium sulfate (MgSO 4 · 5 Mg (OH) 2 · 3 H 2
O) is produced by using magnesium hydroxide and sulfuric acid as raw materials, and is
manufactured by Ube Materials Co., Ltd. under the trade name of MOS · HIGE. Using. The basic
magnesium sulfate has a needle-like particle shape, is easily complexed with the resin, has good
moldability, has good surface smoothness, and exhibits white granular appearance. As the
synthetic resin, at least one of polyethylene, polypropylene, polymethylpentene, methacrylic
resin, polyamide, and liquid crystal polymer as a main component, and as a compatibilizer,
styrene-based saturated thermoplastic elastomer, ethylene ethyl At least one of an acrylate /
maleic anhydride copolymer, an ethylene-based modified α-olefin copolymer, and a modified
polyolefin is used. EXAMPLES The following synthetic resin, basic magnesium sulfate, was
kneaded in a twin-screw kneader. Polypropylene Product Name J-136 Sumitomo Mitsui
Polyolefin Co., Ltd. Modified Polypropylene Product Name OREVAC CA100 ATOFINA Basic
Magnesium Sulfate Product Name Moss Heidi (A) Ube Materials Co., Ltd. [0013] The basic
magnesium sulfate has an average fiber diameter of 0.5 to 0.5. A whisker-like one with an
average fiber length of 5 to 20 μm was used. This is contained in the synthetic resin in an
amount of 5 to 50%, or in the above synthetic resin in combination with another reinforcing
material, preferably a scale-like filler or an inorganic fiber, and an organic fiber. At the time of
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kneading, in order to uniformly disperse basic magnesium sulfate as a reinforcing material in the
resin, the resin is sufficiently kneaded by a twin-screw kneader. As shown in FIG. 1 (a), a molding
material prepared by kneading is injected into a cavity of a mold (3) consisting of a movable
mold (1) and a fixed mold (2). The nozzle (4) is placed on the gate in the center, and as shown in
(b), the molding material (5) is filled inside and injection molded. You can take out the FIG. 2
schematically shows the orientation of the reinforcing inorganic filler in the conical diaphragm 6
produced. That is, the dashed line 6a shown radially in the drawing is the orientation direction of
the inorganic filler.
The inorganic fillers are radially oriented in this manner because the basic magnesium sulfate
has a needle-like shape and is excellent in the composite property with the resin and the
moldability. As this vibrating plate 6, a single J-136, and one in which 15%, 30%, and 50% of
basic magnesium sulfate were added thereto were manufactured. Further, in comparison with
this, a diaphragm was prepared by adding 15% and 30% of mica (trade name: clarite mica 300W,
Kuraray Co., Ltd.) to the above-mentioned synthetic resin and kneading. Test pieces are cut out
from these diaphragms, and the physical property values measured by the vibration reed method
are as follows. The values in parentheses are physical property values in the direction
perpendicular to the radiation direction. <Img class = "EMIRef" id = "198343701-000003" />
From the above table, the mica powder-kneaded composite material has a scale-like shape of
mica, so the difference in Young's modulus in the direction perpendicular to the flow direction is
Although it is hard to notice, it can be understood that the basic magnesium sulfate in the
present invention is needle-like and has good formability, so that the Young's modulus in the flow
direction is extremely high and extremely oriented. FIG. 3 compares the frequency characteristics
of the product of the present invention to which 15% of basic magnesium sulfate is added and
the conventional product to which 15% of scaly mica is added. According to the product of the
present invention, the Young's modulus in the radial direction is improved, the speed of sound is
improved, the dip in the vicinity of 2 to 5 KHz is improved, and the frequency characteristics in
the middle and high frequencies become good. The shape of the diaphragm 6 is not limited to a
cone, and may be a flat or other shape. As described above, according to the present invention,
Young's modulus in the radial direction of the diaphragm is improved, the speed of sound is
improved, and dips in the middle and high regions are improved, and good sound quality can be
obtained . Also, although the diaphragm to which mica is added has a slightly dark appearance,
the basic magnesium sulfate used in the present invention has an advantage that the appearance
is also good because it is a white type. BRIEF DESCRIPTION OF THE DRAWINGS [FIG. 1] (a), (b)
show an explanatory view of the manufacturing process of the diaphragm of the present
invention. FIG. 2 shows an explanatory view of the manufactured diaphragm of the present
invention. FIG. 3 shows a comparative explanatory view of frequency characteristics of the
present invention and a conventional product. [Explanation of the code] 1 movable side mold 2
fixed side mold 3 mold 4 nozzle of injection molding machine 5 molding material 6 diaphragm
6a orientation direction of inorganic filler
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