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The present invention relates to a thermoformable speaker diaphragm having flat frequency
characteristics, low distortion, and excellent water resistance in a wide reproduction frequency
band. The configuration of the prior art and its problems Conventionally, paper cones have been
used extensively as the imaging plate material for speakers, but this is because the paper has a
low density, an appropriate elastic modulus, an internal loss, and a large bending stiffness. It is.
These physical properties are greatly related to the efficiency, the reproduction band, the flatness
of the frequency characteristics, and the pressure resistance in the acoustic characteristics.
However, in the case of paper cones, it is not possible to carry out ripe forming, and it is
necessary to make them into a cone shape one by one, for example, the processing process
becomes complicated, and therefore there is a disadvantage that the quality at the time of
manufacture is not stable. It is also inferior in the moisture resistance. Although attempts have
been made to use diaphragms made of metal materials such as aluminum and beryllium, and
polymer materials such as polypropylene and polyethylene as materials to replace paper, in the
case of metal materials, although the specific modulus is high, internal loss is extremely high. It
has a low defect and produces a sharp peak in the high region on the frequency characteristics.
Therefore, it is mainly used for tweeters. On the other hand, in the case of the cylindrical
molecular material, the internal loss is high and the moldability, the water resistance and the
moisture resistance are excellent, but the specific elastic modulus 2 has a low bending rigidity.
OBJECTS OF THE INVENTION The object of the present invention is to improve the specific
modulus and low stiffness, which are the disadvantages of diaphragms made of polymeric
materials, and to broaden the bandwidth. An object of the present invention is to provide a
speaker diaphragm capable of achieving high human resistance. The speaker diaphragm of the
present invention has a high specific elastic modulus without reducing internal loss by using a
thermoplastic resin such as polypropylene as a base material and mica or flake graphite as a
reinforcing material. , Takaoka j1 sexualization has been achieved. When mica alone is mixed as a
reinforcing material, the specific gravity of mica is as large as 2.7, which is disadvantageous in
terms of bending rigidity, and has a disadvantage of being susceptible to repeated fatigue. On the
other hand, when scaly graphite alone is mixed, the elastic modulus does not become very high,
and when the content is increased, it becomes conductive and has a defect that it can not be used
for an indirect lead type diaphragm. However, by mixing a small amount of mica in flaky
graphite, the elastic modulus is greatly improved and the bending rigidity is also increased. This
is considered to be because mica promotes hardness of scaly graphite during kneading, since
scaly graphite has a hardness of approximately 1 and mica has a large hardness of 3 and thus is
hard. The elastic modulus in the case of using a scaly material as a reinforcing material has
already been studied in detail by Halpin-Tsai and n1elser et al. It is well known that the elastic
modulus of a composite is represented by the following equation.
El 1-RV2A = 2 W / The subscripts 1 and 2 respectively indicate the reinforcement of the base
material 2, E is elastic modulus, ? is volume fraction, W is diameter of flakes, t is thickness. is
there. As the opening progresses, t becomes smaller and A becomes larger. FIG. 1 shows the
relationship between the value of A and E. It can be seen that as the value of A increases, E also
increases. On the other hand, the internal loss was affected by both of the polymer resin itself
and the contribution of the loss between the layers of the scaly material, and the decrease was
not observed even in the state where the hexopen was advanced. The physical property values of
various sheets are shown in Table 1, but in the composite system of scale-like graphite and My 5
иии tsuka using olefin resin as a base material, the elastic modulus and the specific elastic modulus
2 bending rigidity are considerably large, As a base material, it is understood that an olefin resin
is effective in terms of density and internal loss. Description of Examples Example 1 75 wt% of
polypropylene (manufactured by Ube Industries, Ltd.) was used as a base material, and 22 wt% of
scaly graphite (average diameter 10 ?m) and 3 wt% of mica (average diameter 4011 m2) were
added as reinforcements. After kneading well using a twin-screw screen extruder to make a
master bellet, and then predrying this bellet at 110 ░ C. for 1 o hour, using an axial screw
extruder, thickness 1607 zm from T-die I grabbed a composite sheet. Next, this sheet was heated
for about 7 to 8 seconds with far infrared rays, and was vacuum molded when it was softened.
The physical properties of the sheet are shown in Table 1. The sheet was superior in the elastic
modulus and the specific elastic modulus in bending rigidity to the composite of graphite and
mica alone. The frequency characteristics of the 12cIn speaker diaphragm using these sheets are
shown in FIG. 2. It is observed that the distortion is smaller than that of the graphite and mica
single ones, and the reproduction band is also expanded. In FIG. 2, A1. ??? A3 shows sound
pressure frequency characteristics in the case of this example, mica alone, graphite alone, B1.
??? B3 also shows distortion characteristics. Example 2 Based on methyl pentene polymer
(Mitsui Petrochemical Co., Ltd. 'rpx') ? wt% as a base, 16 wt% of scaly graphite (average
diameter 10 Jim) and 4 wt% mica (average diameter 40 ?m) A 150 ?m thick sheet was
prepared in the same manner as in Example 1 by adding it as a reinforcing material. Fig. 3 shows
the change in elastic modulus when the mixing ratio of graphite and mica in the reinforcing
material is changed, but as the compounding ratio of mica, 10 to 3 wt% should be effective for
flaky graphite I understand. Further, as a substrate, an olefin resin is advantageous in terms of
internal loss, density, and bending rigidity as compared to other resins, and it is understood that
high efficiency and low strain can be achieved in frequency characteristics.
The following margin 7--]] Figure 4 the frequency of the diaphragm for 10cm speaker which is
made from the sheet which uses polyester (sowt%) as a base material and 16'wt% of scale-like
graphite and 4wt% of mica as reinforcement Although the characteristics are compared, the wide
band and low distortion are obtained in this example, and it is understood that an olefin resin is
effective as a base material. In FIG. 4, 01. C2 indicates the sound pressure frequency
characteristic in the case of the present embodiment in the prior art, and D1 and D2 similarly
indicate distortion characteristics. Effects of the Invention As described in detail above, according
to the present invention, since it is a diaphragm for a speaker comprising a sheet having a
thermoplastic resin (in particular, an olefinic resin) as a substrate and mica having scaly graphite
as a reinforcing material, The frequency characteristics are: "Bear, wide frequency band, low
distortion, excellent in water resistance, can be thermoformed by vacuum forming, cold press,
etc., and has excellent advantages in terms of productivity and quality .
Brief description of the drawings
FIG. 1 is a characteristic diagram showing the relationship between the volume fraction and the
elastic modulus of a scale-like material as a reinforcing material, and FIG. 2 is a speaker
diaphragm showing one embodiment of the present invention and a conventional speaker 9.
Figure 3 is a characteristic chart showing the relationship between the content of mica and scalelike graphite in the speaker diaphragm showing another embodiment of the present invention,
and FIG. It is a comparison characteristic view of the frequency characteristic of a board and the
conventional diaphragm for speakers.
Name of the agent Attorney Nakao Toshio and others 1 person Figure 1 5 year old man, #Kai
book storage car (О / l;)-Figure 4 is -1 lead 2? 15 f? ? ?) y / 6 10 / 62? ? y! , Lead, cars
with snail name (u / l-, ? ? ? ? / (/ /
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