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The present invention relates to a speaker diaphragm used for small speakers such as a
microcassette speaker and a heddle speaker. The conventional diaphragm for this type of
speaker is composed of an organic film such as polyethylene terephthalate, but it is particularly
problematic for the low frequency range as a diaphragm for a microminiature speaker that is
particularly suitable for use in ho-no-phones etc. Sufficient bass reproduction was possible (it had
become one thing. For this reason, the film thickness is adjusted to about 6 to 8μ to adjust the
minimum resonance frequency of the speaker, but rolling during driving, that is, the distortion
factor is high, the sound pressure frequency characteristics deteriorate, and the formation as a
diaphragm is extremely difficult It was An object of the present invention is to eliminate the
above-mentioned conventional defects, and to provide a speaker diaphragm having good bass
reproduction characteristics and excellent formability. In order to achieve the above object, the
present invention is characterized by comprising a film in which polybutadiene terephthalate and
a polyester elastomer are blended. An embodiment of the present invention will be described
below with reference to FIGS. 1 to 3 of the drawings. A speaker diaphragm 1 has a fixing portion
2 to a frame or the like at its peripheral edge, an edge 3 at its inner side, a conical portion 4 at its
inner side, and a dust at the center of the conical portion 4 It has a shape having a dome portion
6 for a cap. The speaker diaphragm 1 is formed into a shape as described above by heating and
vacuum forming it using a film in which polybutadiene terephthalate and a polyester elastomer
are blended. The polyester elastomer is produced by reacting polytetramethylene terephthalate
and glycol, and is very flexible and has a high internal loss, but has problems with weatherability
and solvent resistance. On the other hand, polybutadiene terephthalate can compensate for the
disadvantages of polyester elastomers and has good weatherability and solvent resistance. The
polybutadiene terephthalate and the polyester elastomer are highly compatible with each other
and form a uniform material, which is effective as a material of a speaker diaphragm. The rigidity
is improved by increasing the blending ratio of polybutadiene terephthalate, and the rigidity of
the diaphragm for a speaker can be freely adjusted by changing the blending ratio of this
polybutadiene terephthalate. For example, although the internal loss of the polyester elastomer is
about 0.007 to 0.01, the internal loss arrow can be adjusted in the range of 0.01 to 0.21 by
blending polybutadiene terephthalate.
The tensile elastic modulus (h / tri) when the compounding ratio of this polybutadiene
terephthalate to the polyester elastomer is changed is shown in FIG. If the compounding ratio in
the range shown in FIG. 2 is made constant, a stable speaker diaphragm can be obtained. As the
polyvinyl terephthalate used here, one manufactured by Tohsi Co., Ltd. was used, and as the
polyester elastomer, one manufactured by Hytrel 4056 (manufactured by DuPont, USA) was
used. Next, a speaker is manufactured using a speaker diaphragm having a 20+ am aperture
formed of a film having a blend ratio of conventional polyethylene terephthalate, polybutadiene
terephthalate of the present invention, and polyester elastomer of 30 near 0, 20: 80. The results
of examining the characteristics of the outside of the material and the speaker are shown in the
table below. (↓ down! In addition, this speaker is used to construct an open-air type headphone,
and its sound pressure frequency characteristics are shown in FIG. In FIG. 3, & indicates the
characteristics of nodophone using a conventional polyethylene terephthalate diaphragm, b
indicates the characteristics of nodophone using a diaphragm containing 30% of the
polybutadiene terephthalate of the present invention, C indicates this The characteristic of the
headphone using the diaphragm in which 20% of the polybutadiene terephthalate of the
invention is blended is shown, and the diaphragm for the speaker of the present invention has an
excellent sound quality in which the low range is extended despite the thick film thickness Is
shown. As described above, since the speaker diaphragm of the present invention is configured,
physical properties such as rigidity can be arbitrarily selected, reproduction of a low frequency
range can be made excellent, and thickness can be increased, so that the rolling phenomenon is
also eliminated. The distortion factor can be reduced, the sound pressure frequency
characteristics can be stabilized, and the thickness can be further improved to be excellent in
moldability, and the industrial value is increased.
Brief description of the drawings
FIG. 1 is a cross-sectional view showing an embodiment of the speaker diaphragm according to
the present invention, and FIG. 2 is a graph showing the relationship between the compounding
ratio of ester elastomer of the diaphragm material and polybutadiene terephthalate and tensile
modulus. FIG. 3 is a characteristic diagram showing sound pressure frequency characteristics of
headphones in which the speaker diaphragms of the prior art and the present invention are used
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