JPS5881400

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DESCRIPTION JPS5881400
[0001]
The present invention relates to a speaker diaphragm having high efficiency, flat and wide
frequency band, and excellent mass productivity. In general, as a diaphragm material for a
speaker, one having a low density and high elastic modulus and a high internal loss is desirable.
The density is related to the sound pressure, the elastic modulus is related to the upper limit fH,
and the internal loss is related to the flatness of the frequency characteristic. Conventionally,
paper has often been used as a speaker diaphragm material. This is because paper has the abovementioned physical properties in a well-balanced manner. However, in the case of paper, since
there is almost no elongation, there is a problem in the processability to the diaphragm shape,
there are many processes and man-hours, and the variation in physical properties and
characteristics is also large. In addition, metals such as aluminum and titanium have low internal
loss and high resonance, so they are used only for tweeters. In recent years, diaphragms based
on polypropylene have been made. Although this diaphragm has high internal loss compared to
paper, it is considerably large in terms of density, and weighs several times the weight of the
paper with respect to the same-aperture speaker, and a drop in efficiency is not unacceptable.
The present invention solves such conventional drawbacks, and is based on a copolymer
consisting mainly of 4-methylpentene-1 polymer or 4-methylpentene-1 polymer, and has a high
elastic modulus. And a composite in which at least one of inorganic fibers is mixed as a
reinforcing material. The 4-methylpentene-1 polymer as a base material is obtained by
trimerizing heptapolymerization of propylene, and is the lightest of glasstic. As a reinforcing
material, at least one of organic U & fiber such as polyester fiber and aramid fiber having high
elastic modulus, and inorganic such as boron fiber, SiC fiber, carbon fiber, and crow fiber can be
used. Here, the high elastic modulus means one having an elastic modulus of 10 ° K9 / ml Ld.
The speaker diaphragm having such a configuration has low density, high internal loss, and high
elastic modulus physical properties, and has cylindrical efficiency and wide band and flat
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frequency characteristics as acoustic characteristics. In addition, since a copolymer mainly
composed of 4-methylpentene-1 polymer or 4-methylpentene-1 polymer as a base material is a
thermoplastic resin, it is formed into a film, heated and softened to be pressed. It is possible and
is excellent in mass productivity. Furthermore, since the melting point is 240 ° C., the heat
resistance is better than conventional olefin based diaphragms. Hereinafter, the embodiment V +
of the present invention will be described.
Example 14-Main body 1) 90 wt% of a mer and 10 wt% of an aramid fiber (fiber length 2 mm,
trade name: Kevlar-49) were kneaded, and the dough was drawn into a film of 100 μm
thickness. Using this film, the film was softened with a far-infrared heater as a molding method,
and then press molding was performed to make a diaphragm for a micro speaker of 4.5 cIrL in
diameter. The frequency characteristic of this diaphragm is shown in the curve of FIG. Those with
reinforcements have higher high frequency limits than those without reinforcement (see curve B
in 5g1) and flatter frequency characteristics than paper cones (see curve C in FIG. 1) Met.
EXAMPLE 4 85 ft% of methylpentene-1 polymer and 15 wt% of glass fiber (fiber length 3 mm,
fiber diameter 10 μm) were kneaded, and this was drawn into a film of 100 μm thickness. This
film was formed into a diaphragm shape in the same manner as in Example 1. The high
frequency limit of the frequency characteristic is higher than that of the diaphragm not mixed
with the reinforcing material. Example 3 10% by weight of carbon fiber and 10% by weight of
aramid fiber were kneaded with sowt% of 3-methylpentene-1 polymer, and this was ground in a
300 μm thick film. This film was used to make a diaphragm having a diameter of 2.degree. In
the same manner as in Example 1. The frequency characteristic of this speaker diaphragm is
shown by the curve in FIG. The efficiency is higher than that of a diaphragm made of
polyglobylene film of the same thickness (see curve B in FIG. 2), and the castle is extended.
Example 4 4-methylpentene-1 polymer is spun, fibrillated and subjected to hydrophilic treatment
to make synthetic pulp (80 Wt 9 o) as a base material, and carbon fiber (fiber diameter 101-1 m,
fiber length 6 a + m) as a reinforcing material 1) 1.0 wt% of 10 wt% boron fiber (fiber diameter
50 μm, fiber length 6 city) was mixed. In the composite method, a sheet was made into a film by
applying heat to the sheet once made using a sheet forming process. Dense fffdo4y / cI of film
made. Areal density 1201 / rT '+! , Modulus of elasticity 2.6 x 102 Ky / wtp. The internal loss
was also paper level. A speaker diaphragm having a diameter of 10α was produced in the same
manner as in this film example 1. The frequency characteristics of this speaker diaphragm are
shown in the system of FIG. The acoustic characteristics of this speaker diaphragm were high
efficiency, wide band and low distortion, and had a great advantage over the paper cone (see
curve B in FIG. 3). EXAMPLE 6 A random copolymer of methylpe / ten-1 and ethylene and
containing 80% by weight of a polymer having an ethylene content of 10% and 20% by weight of
carbon fiber (fiber diameter 10 μm, fiber length 1 mm) as a reinforcing material The mixture
was kneaded to make a composite bellet once, and this was used to make a 3 oO μm thick film
of a film forming machine.
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This film was molded in the same manner as in Example 1 to obtain a speaker diaphragm having
a diameter of 2 °. The use of the copolymer lowers the elastic modulus but increases the
internal loss. Also, it has an advantage that the melting point has a temperature range and the
thermoforming becomes easy. As acoustic characteristics, as shown by curve C in FIG. 2, the
sound pressure is 100 Hz, 20 oflz, 5 o as compared with the conventional olefin speaker. It has
improved within 1.2 dB on average in Hz. The speaker diaphragm of the present invention is
mainly composed of 4-methylpentene-1 polymer or 4-methylpentene-1 polymer, which has the
lowest density among polymers, as in the case of two or more in which the high frequency band
H is also extended. The copolymer of the present invention is used as a base material, and the
composite of the base material and the high elastic modulus fiber has good acoustical physical
property values, and has high efficiency, wide band and flat circumferential V-number
characteristics.
[0002]
Brief description of the drawings
[0003]
1, 2, and 3 are comparative characteristic diagrams showing the conditions of the speaker
diaphragm of the present invention and the conventional speaker diaphragm.
Name of Agent Attorney Nakao Toshio and 1 other person Fig. 1 @ II number LH 2 Fig. 2 Wave
number (h)
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