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JPH05300588

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DESCRIPTION JPH05300588
[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 appropriate internal loss and rigidity, and is
extracted from the coat of the sea squirt, It is a diaphragm for electroacoustic transducers which
consists of cellulosic fiber which graft-polymerized polyvinyl alcohol, and cellulosic fiber
obtained from wood pulp.
[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.
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Next, in order to remove protein, the slurry pulverized in the above step is heated in, for example,
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]
Polyvinyl alcohol is graft-polymerized to the asty cellulose fiber thus obtained.
[0013]
That is, a cerium salt is used as an oxidizing agent to desorb hydrogen atoms in cellulose to
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generate radicals to polymerize polyvinyl alcohol.
Next, cellulose fibers obtained from wood pulp are mixed, stirred, and formed into a cone shape.
[0014]
Since the cellulose fine fibers extracted from the coat of the sea squirt used in the present
invention are beaten to the microfibrillar state, the surface is activated.
As a result, hydrogen bonding between cellulosic fibers obtained from wood pulp is promoted,
bonding between fibers becomes strong, and a diaphragm with high rigidity is obtained.
In addition, since a polyvinyl alcohol having a large internal loss is graft-polymerized to the
cellulose fine fiber obtained from the ascidian, the internal loss of the diaphragm can be
improved, and the generation of a peak dip harmful to frequency characteristics can be
suppressed.
[0015]
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.
[0016]
Hereinafter, the present invention will be described based on examples.
[0017]
Example 1 The outer sheath of the chabo is cut with a cutter or the like to a size of about 5 to 20
mm.
The cut pieces are ground using a homogenizer for 10 minutes.
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Next, it was treated in a 0.25 N NaOH solution at 100 ° C. for 6 hours by a reflux apparatus to
remove proteins.
[0018]
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.
[0019]
The thus obtained cellulose fiber is subjected to polyvinyl alcohol polymerization. That is, a
cerium salt is used as an oxidizing agent to the ascidian cellulosic fiber, and these polyvinyl
alcohols are mixed. Then, it forms a complex with the alcohol, which is decomposed to generate a
radical in the alcohol. As a result, the hemicellulose of the molecular terminal of cellulose and the
above-mentioned alcohol undergo graft polymerization to obtain a copolymer. The obtained graft
copolymer has a property in which the properties of both cellulose and polyvinyl fulcor overlap
to some extent, but both components are not separated but chemically bonded even by
reprecipitation.
[0020]
The weight of the graft-polymerized ascidian cellulose fiber was mixed with the cellulose fiber
obtained from the wood pulp in a weight ratio of 3: 7, and the mixture was formed into a cone
shape by a conventional corn paper sheet forming apparatus.
[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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Test pieces were cut out from the cone-shaped diaphragms of the example and the comparative
example, and the density, Young's modulus, propagation velocity and internal loss (tan δ) were
measured, respectively, and the results of Table 1 were obtained.
[0023]
【Effect of the invention】
[0024]
As shown in Table 1, according to the present invention, an increase in density (ρ) is observed,
but the improvement of Young's modulus (E) significantly improves the specific elastic modulus
(E / ρ) compared to the increase rate We were able to.
Also the propagation speed could be improved.
[0025]
Furthermore, the internal loss (tan δ) could also be raised.
[0026]
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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