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JPS58221595

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DESCRIPTION JPS58221595
[0001]
The present invention relates to a diaphragm for a speaker, and more particularly, it is an object
of the present invention to provide a diaphragm for a speaker which can be matured and formed
with flat frequency characteristics, high efficiency, and excellent water resistance in a wide
frequency band. Conventionally, a paper cone has often been used as a diaphragm material for a
speaker, because the paper has a low density and an appropriate elastic modulus and internal
loss. These physical properties are greatly related to the efficiency as the acoustic characteristic
and the flatness of the band 1 frequency characteristic. However, in the case of paper cones,
there are two methods: either one can not be thermoformed one at a time into sheet shape into a
cone shape one by one, or it can be molded with a hot mold in a state where water drainage once
laminated into a conical shape is sufficiently absorbed. It is taken. Many methods rely on
craftsmanship, and both methods have the disadvantage of large variation among lots. On the
other hand, metal materials such as aluminum and beryllium and polymer materials such as
polypropylene and polyethylene have been used as materials to replace paper, but in the case of
metal materials, the specific modulus is high, but internal loss is extremely low. It produces a
sharp resonance peak. Therefore, it is mainly used for tweeters. Moreover, in the case of a
polymer material, while the specific modulus of elasticity and the flexural rigidity are low, the
internal loss is high and the formability is excellent, so it is mainly used for the woofer. The
present invention provides a film diaphragm using a lightest 4-methylpentene polymer among
polymers as a substrate and having a high internal loss and a high specific modulus and a high
flexural rigidity. 4-Methylpentene alone has the disadvantage of low melt viscosity and poor film
formability and formability, and the glass transition temperature is near room temperature (29 to
60 ° C), so the elastic modulus and internal loss change significantly depending on temperature.
Causes sound quality change. By blending other olefin polymers with 4-methylpentene, the film
formability and the formability are improved, and a rapid change in elastic modulus and internal
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loss at the glass transition temperature can be suppressed. However, the addition of a
reinforcement to this system further increases the modulus of elasticity and the rapid change in
physical properties at the glass transition temperature. The other olefin polymers referred to in
the present invention refer to polyethylene, polypropylene and polybutylene. The 4methylpentene polymer is an olefin polymer and is nonpolar, and it is effective to use a polymer
with a polar polymer. As for the mixing ratio, it is required that the characteristics (low density,
high melting point, etc.) of 4-methylpentene are not impaired and it is required to compensate
for the above-mentioned drawbacks. The volume ratio is preferably h or more.
As reinforcing materials, scale-like substances, hollow particles, inorganic fillers, whiskers,
inorganic fibers and wood flour are effective to suppress changes in physical properties at the
glass transition temperature and to increase the elastic modulus. Scale-like substances are scalelike graphite, mica glass flakes, fish scale, etc. Hollow particles are glass balloon, shirasu balloon,
carbon balloon etc. Inorganic fillers are talc, calcium carbonate, titanium dioxide, bengara, carbon
Powders etc., whiskers are metal whiskers such as copper and iron, silicon carbide, inorganic
whiskers such as alumina and graphite, polymer whiskers such as polyoxymethyleph, etc.
Inorganic fibers are carbon fibers, glass fibers, ceramics Fibers, metal fibers, etc., wood flour
means wood flour, rice husk flour, etc. Film forming property 2 elastic modulus as composite
amount of reinforcing material. From the point of bending rigidity, 20 vo1% or less is desirable.
As described above, low density, high internal loss, high rigidity physical properties are obtained
by using a blend of 4-methylpentene and other olefin polymers, and the frequency characteristics
are flat and highly efficient as acoustic characteristics. A wide frequency band can be realized.
Also, while conventional corn paper has problems with water resistance, moisture resistance and
processability, the film diaphragm of the present invention does not have these problems at all.
Furthermore, since 4-methylpentene polymer is soluble in carbon tetrachloride and slightly
swells in toluene, there is no exacerbation of extreme adhesion as with other olefin polymers, and
the melting point is as high as 246 ° C. and the heat resistance is also excellent. ing. Examples
of the present invention will be described below. (Example 1) 80% of 4-methylpentene polymer
(made by Mitsui Petrochemicals Co., Ltd. TPX) 80% and polypropylene (made by Chisso®) 20%
by 1% using a twin-screw extruder to make blend remastered pellets, and then this pellet is made
A 400 μm thick sheet was produced by using an extruder. The physical properties of this sheet
are shown in Table 1. While the density is increased and the elastic modulus is decreased by
compounding with polypropylene, the internal loss, the film forming property and the formability
are greatly improved, and vacuum forming can be easily performed. It became so. When the
volume fraction of polypropylene is e es vol% or more, the adhesion is extremely deteriorated,
and the flexural rigidity is too low. The frequency characteristics are shown in Fig. 1 (see Fig. 1),
but they are more efficient than polypropylene single sheet (see Fig. 1 b). It became broadband.
(Example 2) 4-methylpentene polymer (Mitsui Petrochemicals ■ T P X) 60 vo 1% and
polypropylene (Chisso ■) 30 vo 1% Mica sieved with 326 mesh as a reinforcing material 10 voA
'% The mixture was mixed using a twin-screw extruder to make -H master pellet, and then this
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master bellet was used to obtain a 400 μm thick composite sheet by an extruder.
This sheet was heated by far infrared rays for about 1 minute, and when the sheet was slackened,
center molding was performed to a speaker diaphragm shape with a diameter of 16 em. The
physical properties of this sheet are shown in Table 1, but it has high specific modulus and high
flexural rigidity as compared with the sheet of polypropylene alone and the sheet not containing
a reinforcing material as in Example 1, to achieve wide band and low strain. it can. The filmforming property of the sheet of Example 1 was superior. Changes in physical properties when
the mixing ratio of 4J-methylpentene polymer and polypropylene is changed while keeping the
amount of mica constant at 10%, are shown in FIG. 2 to FIG. 4 as the content of polypropylene
increases The sharp peak of internal loss at the glass transition temperature disappears, its
absolute value increases, and the formability also improves. On the other hand, the modulus of
elasticity decreases and the adhesion also deteriorates. It is desirable that the volume of 4methylpentene polymer / polypropylene be greater than fear. The same was true for the blends
with polyethylene and polyethylene. Changes in physical properties when the content ratio of
mica is successively changed while keeping the volume ratio of 4-methylpentene polymer /
polypropylene constant at% are shown in FIG. 5 and FIG. The modulus of elasticity also increases
with the increase of The flexural rigidity peaks at around 20 vo 1%, and the internal loss
decreases. In addition, when the content of the film forming property and the formability mica
was 20 vo /% or more, it was extremely deteriorated. Also in the case of other reinforcements,
when the content is 2 Qvo 1% or more, problems such as breakage in film formability and
formability occur. (Example 3) 4-methylpentene polymer (TPX) 50vod, high density polyethylene
(made by Mitsui Petrochemicals) 30voA, glass balloon (particle diameter 4oμm, bulk density 0,
25) 20vo, j? % Were blended in the same manner as in Example 2 to obtain a sheet 400 μm
thick. The physical properties of this sheet are shown in Table 1. However, since the specific
gravity of the sheet is low, the bending rigidity is large, and-low strain can be realized. (Example
4) 4-methylpentene polymer (TPX) 86voJ, 10vo1% polybutyl lev, 5VO1% talc (sieved at 40 °
mesh) are mixed in the same manner as in Example 2 and thick A sheet of 400 μm was
obtained. The physical properties of this sheet are shown in Table 1. The internal loss was high,
and it was effective in improving the adhesion. Example 6 4-methylpentene polymer (TPX) 30
vol, polypropylene 60vo /%, polyoxymethylene whisker (fiber length 200 μm) 10vo /% are
mixed in the same manner as in Example 2 and a sheet having a thickness of 400 μm I got
The physical properties of this sheet are shown in Table 1, but high internal loss and high
specific elastic modulus were obtained, and the film forming property was also excellent. The
sharp peak of internal loss at the glass transition temperature was also eliminated. Example 6 4Methylpentene Polymer (TPX) 90voA! %。 Polypropylene 5 vo 7 +%, carbon fiber (east, 2% of
tore force fiber length) s VOA! % Were mixed in the same manner as in Example 2 to obtain a
400 μm thick sheet. The physical properties of this sheet are shown in Table 1, but the specific
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modulus 1 bending stiffness was improved and the adhesion was also improved. Example 7 4Methylpentene Polymer (TP X ') 70vo /%. Polyethylene 20vo 1%, Momigara powder (sieved with
300 mesh) 10voA! % Were mixed in the same manner as in Example 2 to obtain a 400 μm thick
sheet. The physical properties of this sheet are shown in Table 1, but the density decreased and
the bending rigidity increased. Also the adhesion was improved. By mixing other olefin polymers
with lupentene polymer, the film formability and formability of the sheet are significantly
improved, and by incorporating the reinforcing material, the elastic modulus is improved and the
adhesiveness is also improved. . As described above, the speaker diaphragm of the present
invention has a large internal loss (the internal loss of paper is 0.035), a low density, and a high
elastic modulus. Therefore, it has flat frequency characteristics, high efficiency, excellent water
resistance in a wide frequency band, and has an advantage of being able to be thermoformed.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a comparison diagram of sound pressure frequency characteristics of the speaker
diaphragm of the present invention and a conventional polypropylene diaphragm, and FIG. 2 is
an elastic modulus 1 internal loss to the mixing ratio of 4-methylpentene polymer and
polypropylene in the diaphragm. 3 is the change curve of the peeling strength to the same
mixing ratio, FIG. 4 is the temperature-internal loss characteristic graph at the same mixing ratio,
and FIG. 5 is the elastic modulus to the mica content in the same diaphragm, FIG. 6 is a change
curve diagram of bending rigidity with respect to the mica content in the same diaphragm.
Name of agent Attorney Nakao Toshio et al. Fig. 1 Side rotation number 04t) Fig. 2 IIF type 4ratio (Nφ) Fig. 3 Fig. 4; IL freeze ('t)
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