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JP2006222485

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complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
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DESCRIPTION JP2006222485
PROBLEM TO BE SOLVED: To provide a diaphragm for an electroacoustic transducer whose
sound quality is improved and whose appearance is good by using synthetic mica or the like in a
diaphragm for electroacoustic transducer containing mica as a reinforcing material. SOLUTION:
In the present invention, synthetic mica is replaced with natural mica and synthetic mica having
a high aspect ratio is added. Since this synthetic mica has a large Young's modulus and a high
sound velocity, the sound pressure in the high region is improved and the sound quality is
improved. In this case, in order to improve adhesion with synthetic mica, styrene-based saturated
thermoplastic elastomer, ethylene / ethyl acrylate / maleic anhydride copolymer, ethylene-based
α-olefin copolymer, maleic anhydride-modified polyolefin alone Or it was set as the structure
which adds these mixtures. [Selected figure] Figure 1
Electroacoustic transducer diaphragm
[0001]
The present invention relates to a diaphragm for an electroacoustic transducer such as a speaker
or a microphone, which is a type of acoustic equipment.
[0002]
Conventionally, molding materials for diaphragms for electroacoustic transducers have various
synthetic resins or various constituent resins as a matrix, and as reinforcing materials, high
elastic modulus inorganic fibers such as glass fibers and carbon fibers, aromatic polyamides,
poly-p- High modulus organic fibers such as phenylene benzo bis oxazole fibers are used.
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In addition, as a reinforcing material other than fibers, scaly mica naturally produced, scaly
graphite powder, talc and the like are used.
[0003]
However, if, for example, phlogopite [KMg3.AlSi3O10. (OH) 2], muscovite mica [KAl2.AlSi3O10.
(OH) 2] or the like is used as a reinforcing material as a naturally occurring flaky mica, the
Young's modulus, the speed of sound, as well as the compounding amount Increase, but the
effect is not sufficient.
[0004]
In addition, since the naturally-occurring flaky mica contains a large amount of impurities such
as iron, it has poor transparency. For example, the appearance of a diaphragm obtained by
injection molding a composite material using a polyolefin resin as a matrix material has uneven
distribution of black spots. The light-colored diaphragm is not preferable in appearance.
[0005]
In addition, because it is a natural product, the variation by mining area, location, etc. is also
large.
[0006]
The present invention has been proposed in view of the above, and the object of the present
invention is to improve the sound quality by using synthetic mica or the like in the diaphragm for
an electroacoustic transducer containing mica as a reinforcing material. It is an object of the
present invention to provide a diaphragm for an electroacoustic transducer which has a good
appearance.
[0007]
The invention according to claim 1 is that the synthetic mica is added to the synthetic resin, and
the styrene-based saturated thermoplastic elastomer, ethylene / ethyl acrylate / maleic anhydride
copolymer, ethylene-based α-olefin copolymer, maleic anhydride modified polyolefin A single
material or a composite material to which a mixture of these materials is added is formed into a
diaphragm for an electroacoustic transducer.
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2
The invention according to claim 2 is characterized in that in the diaphragm for an
electroacoustic transducer according to claim 1, the synthetic resin is made of polyolefin or
polypropylene, and the synthetic mica is made of fluorine phlogopite.
[0008]
As described above, according to the present invention, since the synthetic mica having a high
aspect ratio is used as a reinforcing material of the molding material, the Young's modulus and
the speed of sound are further increased, and the diaphragm using this has an improved high
frequency characteristic. Sound quality is good.
[0009]
In addition, synthetic mica obtained by melt synthesis has few impurities and is excellent in
whiteness and transparency. For example, with a diaphragm obtained by injection molding of a
composite material using a polyolefin resin as a matrix material, no problems can be identified
and white and light colored vibrations are obtained. It does not matter at all even if used for the
board.
[0010]
Since natural mica has an OH group in its molecular structure, it has a relatively good bond to
the matrix material, but since synthetic mica does not have an OH group, it lacks adhesion to the
matrix material as it is .
For this reason, since a styrene-based saturated thermoplastic elastomer, ethylene / ethyl
acrylate / maleic anhydride copolymer, ethylene-based α-olefin copolymer, maleic anhydride
modified polyolefin is added singly or a mixture thereof, it is possible to use a polyolefin resin
The compatibility between the matrix material and the synthetic mica increased, and the
adhesion was improved.
[0011]
[Example 1] Polypropylene J-108M (polyolefin resin) manufactured by Mitsui Chemicals, Inc. is
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used as a matrix material, and wet and dry pulverized products of natural mica and synthetic
mica are used as reinforcements, natural mica is 30 wt% and synthetic mica is 10 to 10%. Each
physical property of a composite material obtained by adding in a range of 30 wt%, kneading
with a screw diameter 40 mm single screw extruder, and injection molding according to a
standard method is shown in Table 1.
Physical property values were measured by the vibration lead method.
In addition, as a naturally occurring mica, a wet milled product 300W manufactured by Kuraray
Co., Ltd. was used, and as a synthetic mica, a wet milled product SMW 325 manufactured by
Repco, and a dry milled product SMD 325 were used.
[0012]
This synthetic mica is made of fluorine phlogopite (KMg 3 · AlSi 3 O 10 · F 2) and has a high
aspect ratio.
[0013]
[0014]
In the above Table 1, specifications 1 to 5 use the synthetic mica SMW 325 of wet grinding with
respect to the matrix material J-108 M, specification 6 uses the synthetic mica SMD 325 of dry
grinding, and specification 7 the matrix material J- The conventional example using 300 M of
naturally occurring mica for 108 M, specification 8 shows that of the matrix material J-108 M
alone.
[0015]
Compared with the specification 7 (conventional example) which added 30 wt% of wet ground
natural mica, the specification 5 which added 30 wt% of wet ground synthetic mica has about
15% larger Young's modulus, and the sound velocity is also large.
[0016]
In this invention, what added synthetic mica in 10 to 30% of range with respect to the matrix
material of polyolefin or polypropylene 90 to 70% was used.
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[0017]
Moreover, in order to improve the adhesion between the matrix material and the synthetic mica,
styrene-based saturated thermoplastic elastomer, ethylene / ethyl acrylate / maleic anhydride
copolymer, ethylene-based α-olefin copolymer, maleic anhydride modified polyolefin Was added
alone or a mixture of these.
[0018]
A composite material obtained by melt-synthesizing these components was injection molded to
form a diaphragm having a diameter of 13 cm.
[0019]
A voice coil was coupled to the diaphragm, and the voice coil was provided in the magnetic gap
of the magnetic circuit, and the diaphragm, the magnetic circuit, and the like were
accommodated in a frame to manufacture a speaker.
[0020]
The frequency characteristics of the product of the present invention and the conventional
example of specification 7 are shown in FIG.
The solid line A is the product of the present invention, and the broken line B is the conventional
product.
[0021]
In the frequency characteristics of Example 1 according to the present invention in which
synthetic mica is blended compared with the frequency characteristics of a conventional product
in which natural mica is blended, a characteristic that the sound pressure in the high frequency
band is large is observed, and the sound quality is also high. Area characteristics were improved
and excellent.
[0022]
In addition, although the appearance of the diaphragm incorporating the conventional natural
mica is seen as black dots as shown in FIG. 3, the diaphragm incorporating the synthetic mica of
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Example 1 is, as shown in FIG. No particulate matter such as flake mica was observed, and the
appearance was good.
[0023]
[Example 2] 30% by weight of dry ground product synthesized from Mitsui Chemical Co., Ltd.
polypropylene J-139 as a matrix material and 30% by weight as a reinforcing material, SMD 325
manufactured by Mycarepco, and molded by adding Honewell maleic anhydride modified
polyolefin AC 907 P I got the material.
The molding conditions and physical properties were measured in the same manner as in
Example 1.
[0024]
As a result, in the specification in which no maleic anhydride-modified poly-off lefin is added, the
Young's modulus is 7.0 GPa, whereas in the specification in which 3 parts of maleic anhydridemodified polyolefin is blended, the adhesion is increased. Young's modulus increased 15% to 8.3
GPa.
[0025]
In addition, the matrix material J-108M used in the above-mentioned Example has high rigidity
and high flow type, J-139 has high rigidity, heat resistance, and super high fluidity.
[0026]
The frequency characteristic figure which contrasted the diaphragm for electroacoustic
transducers concerning 1st Example of this invention, and a prior art example is shown.
The external view of the diaphragm for electroacoustic transducers concerning 1st Example of
this invention is shown.
The external view of the conventional product which used the scaly mica of a natural origin is
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shown.
Explanation of sign
[0027]
A Inventive product B Conventional product
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