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JPH05300586

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DESCRIPTION JPH05300586
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
improvement of a diaphragm used in an electroacoustic transducer such as an electrodynamic
speaker or a microphone.
[0002]
2. Description of the Related Art Conventionally, as a diaphragm for an electroacoustic
transducer such as a speaker, a cellulose fiber obtained from wood pulp which is a natural fiber
is often used. Also, polymer materials, metal materials, and ceramic materials are also used as
diaphragm materials.
[0003]
As physical properties required for diaphragm materials, the density (と し て) is small in order
to improve conversion efficiency, and the specific elastic modulus (E / た め に) is in order to
expand the regeneration zone. Large) and having a moderate internal loss in order to suppress
the occurrence of harmful peak dips in frequency characteristics. Polymeric materials, metallic
materials and ceramic materials have large rigidity due to the large Young's modulus of the
material itself compared to the cellulose fibers obtained from wood pulp, and have an effect in
expanding the frequency band, but the homogeneity and internal loss of the material There is a
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problem that a harmful peak dip occurs on the frequency characteristic in the inherent
resonance frequency band due to the small.
[0004]
On the other hand, diaphragms using cellulosic fibers obtained from wood pulp can not have
high rigidity because the Young's modulus of the material itself is small, and beaks and dips that
are harmful in frequency characteristics due to split vibration in the high frequency band Had a
problem to occur.
[0005]
In addition, although a diaphragm in which a fibrous material having a high Young's modulus
such as alamid fiber or carbon fiber is mixed with the cellulose fiber is employed, in order to
obtain rigidity as the diaphragm, the fiber itself has a high Young's modulus and a fiber The
cohesion between them is a factor, and since this kind of aramid fiber and carbon fiber do not
have self cohesion, it has not come to obtain the expected effect.
[0006]
SUMMARY OF THE INVENTION The present invention solves the above problems and provides a
diaphragm of low density while maintaining adequate internal loss and rigidity, and cellulose
extracted from the coat of the sea squirt It is a diaphragm made of quality fiber and fibrous or
finely powdered inorganic material.
[0007]
EXAMPLE The outer coat of the squirt is cut with a cutter or the like to a size of about 5 to 20
mm.
The cut pieces are pulverized using a pulverizing apparatus such as a homogenizer or a mixer.
The treatment time is about several minutes, and as a result of pulverization, a fibrous slurry is
obtained.
Next, in order to remove protein, the slurry pulverized in the above step is heated in, for example,
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about 0.25 N NaOH solution, and treated in a reflux apparatus for about 2 to 8 hours.
[0008]
After removing the protein, it is neutralized with an acid such as hydrochloric acid or sulfuric
acid and washed with distilled water. Next, in order to remove fat, for example, it is heated in a
mixed solution of ether and ethanol (volume ratio 1: 1) and treated for about 4 hours using a
Soxhlet extractor or the like. Next, microfibrillation is carried out using a high-pressure
homogenizer, disc finer, Jordan, beater or the like.
[0009]
The selection of the model may be made on the basis that fine fibers having a desired degree of
beating can be obtained. Among the above devices, the high-pressure homogenizer is particularly
excellent in the refinement of the material because a high shear force can be obtained.
[0010]
The obtained cellulose fine fiber forms a stable water suspension and exhibits a value of 2000 cp
according to a measurement using a normal B-type viscometer at a 2% solids suspension station.
Dilution to solids does not form a water separation layer.
[0011]
Most of the cellulose fine fibers in this state were fine fibers having a diameter of 0.1 μm or less.
[0012]
A diaphragm is obtained by mixing and forming the fibers thus obtained and the fibrous or finely
powdered inorganic material.
[0013]
Since the cellulose fine fibers extracted from the coat of the sea squirt used in the present
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invention are beaten to the microfibrillar state, the surface is activated.
Therefore, the cellulose fibers are bonded by strong hydrogen bonds in the form of wrapping the
inorganic material, and the properties of both of them are synergistically obtained to obtain a
diaphragm with high rigidity.
[0014]
There are more than 100 types of sea squirts, but since maboyas are currently cultivated, it is
desirable to use this in light of the material supply circumstances.
[0015]
Hereinafter, the present invention will be described based on examples.
(Example 1) The outer coat of the sea squirt is cut with a cutter or the like to make it about 5 to
20 mm in size.
The cut pieces are ground using a homogenizer for 10 minutes.
Next, it was treated in a 0.25 N NaOH solution at 100 ° C. for 6 hours by a reflux apparatus to
remove proteins.
[0016]
Thereafter, it was neutralized with 0.25 N HCl and then washed with distilled water. The mixture
was heated at 70 ° C. for 2 hours in a mixed solution of ether and ethanol (volume ratio 1: 1)
using a Soxhlet extractor. The mixture was further subjected to fibrillation treatment 30 times at
a pressure of 500 Kgf / cm 2 by a high pressure homogenizer. The obtained cellulose fiber was
beaten to a microfibrillar state, and the fiber diameter was 0.1 μm and the fiber length was 800
μm.
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[0017]
To the cellulose fiber thus obtained, 80% by weight of mica fine powder having a particle size of
60 to 70 μm is added, and the mica fine powder is dispersed by dissociation for 1 to 2 hours at
a concentration of 3%.
[0018]
The dispersion was formed into paper by a conventional cone paper sheet forming apparatus to
obtain a cone-shaped diaphragm.
(Example 2) The cellulose fiber obtained in the same manner as in Example 1 had a fiber
diameter of 12.1 μm, a specific gravity of 1.5, a strength of 290 kg / mm, an elastic modulus of
13 t / mm 2 and a fiber length of 0.5-0. Aramid fibers are dispersed by mixing 50% by weight of
8 mm aramid fiber chopped fibers and disaggregating at a concentration of 3% for 1 to 2 hours.
[0019]
The dispersion was formed into paper by a conventional cone paper sheet forming apparatus to
obtain a cone-shaped diaphragm. EXAMPLE 3 A cellulose fiber obtained in the same manner as
in Example 1 has a fiber diameter of 7.5 μm, a specific gravity of 1.7, a strength of 290 kg /
mm, an elastic modulus of 23 t / mm 2 and a carbon fiber length of 3 to 5 mm. The chopped
fibers are mixed at a weight ratio of 50% and disintegrated at a concentration of 3% for 1 to 2
hours to disperse the alamid fibers.
[0020]
The dispersion was formed into paper by a conventional cone paper sheet forming apparatus to
obtain a cone-shaped diaphragm.
[0021]
As a comparative example, a cellulose fiber obtained from wood pulp was formed into paper by a
conventional corn paper sheet making apparatus to obtain a corn diaphragm.
[0022]
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The test pieces were cut out from the cone-shaped diaphragms of Examples and Comparative
Examples, and the density, Young's modulus, and propagation velocity were measured,
respectively, to obtain the results shown in Table 1.
[0024]
As shown in Table 1, according to the present invention, an increase in density (ρ) is observed,
but the improvement in Young's modulus (E) is remarkably improved as compared with the
increase ratio. / で き) could be improved.
Also the propagation speed could be improved.
[0025]
Therefore, the electroacoustic transducer using the diaphragm of the present invention can
obtain flat frequency characteristics that can be highly efficient and in a wide band.
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