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Description 1, title of the invention
Vibrating plate and method of manufacturing the same
3. Detailed Description of the Invention The present invention relates to a diaphragm used for an
acoustic transducer such as a speaker and a microphone, and a method of manufacturing the
same. 'Speakers, microphones and other diaphragms are materials that have high elasticity and
low density as much as possible, that is, materials with high sound velocity (high sound velocity),
and two-dimensional strength, etc. In order to improve its properties, it is desirable that it be
possible to easily use boron as a thin film, such as boron, IJIJ, EndPage: 1 film, etc. However,
these materials are not easy to form into a thin film to form a diaphragm. Therefore, recently,
diaphragms made of laminated mica in which fine mica pieces having a relatively high aspect
ratio (area equivalent to the area of the scale pieces / diameter of the scale pieces) are bonded
with a resin or the like are commercially available. This is because the mica has relatively high
elasticity and low density, and by orienting the mica flakes parallel to the plane of the diaphragm
to improve two-dimensional rigidity, etc. Have. However, as the diaphragm of the acoustic
transducer, it is the fact that materials having higher sound velocity and higher rigidity are low.
The present invention has been made with a focus on aluminum boride flakes having a modulus
of elasticity much higher than that of mica flakes for the purpose of solving the above-mentioned
conventional problems. As aluminum borides, diboride monoaluminum (AlB2) and 12 boride
monoaluminum (AIB + 2) are known. Among them, scale-like microcrystals are easily obtained
AlB2. This tendency is a natural consequence of the atomic structure of AlB2 having a layered
structure. The scaly aluminum borides used in the present invention are found to be mostly
composed of AIB 2 from X-ray diffraction measurement and the like. At this time, although some
AIB + z diffraction lines may appear, there is no influence of the plugging corrosion of the
diaphragm made from this scale. The present invention is a diaphragm of an acoustic transducer
comprising a scaly aluminum halide and having high elasticity and low density, ie, twodimensional rigidity at high sound velocity (sound velocity E is elastic modulus, ρ is density). It
provides a manufacturing method. Boron and beryllium are limit materials considered to be
physical properties having high sound velocity and high rigidity. However, due to toxicity and
manufacturing problems, these have not been widely used. The present invention has been made
focusing on elastic modulus comparable to boron at high sound velocities (~ 12 oooms / s) of
aluminum boride, especially AlB2.
Furthermore, by using scaly aluminum borohydride crystallites and orienting it parallel to the
plane of the diaphragm, the velocity of sound and rigidity in the plane direction were further
raised to the same level. A relatively high sound velocity, low density aluminum, magne / lam, or
an alloy of these metals is used as a bonding material for bonding and integrating scale-like
brazing and aluminum crystallites. Incidentally, the speed of sound of the organic resin used as a
bonding material is about 2000 m / s, but the speed of sound of aluminum, magnesium or their
alloys is': 5000 m / g. The effect of the present invention exists even if the average aspect ratio of
the scaly aluminum fluoride microcrystals constituting the diaphragm is about 10. Still, since the
average aspect ratio is about 60, the diaphragm characteristics are significantly improved, and
the diaphragm characteristics are saturated when the average aspect ratio is about 700. In
addition, when the average aspect ratio is too large, the workability at the time of molding is
deteriorated. The characteristics of the diaphragm according to the present invention are a
density of 2.3 to 3.0 sheets, a porosity of 6 to 70%, a sound velocity of 7,000 to 11,000 m / a,
and it can be seen that the density is low and the sound velocity is high. As a method of realizing
the diaphragm, a method of vapor-depositing aluminum, magnesium or an alloy thereof on
aluminum flake flakes, or thermal spraying followed by heating and pressing to obtain a sintered
body Attempts have also been made and desired results have been obtained, but most preferably
using conventional powder metallurgy techniques. That is, flake-like aluminum borohydride
crystallites and aluminum powder, and additives such as a suitable lubricant and a caking agent
are further added and mixed. At this time, it is necessary to pay attention to the change in the
aspect ratio of the scaly aluminum borohydride crystal before and after the mixing operation.
Next, this is poured into a mold of a predetermined shape and two dimensions, heated and
pressurized to evaporate and evaporate the additive, and at the same time dissolve the aluminum,
or scaly aluminum microcrystals by solid-solid reaction. Wrap, connect and integrate. Thereby, a
diaphragm made of scale-like aluminum fine crystals and aluminum is obtained. Since the
sintered body obtained here is a binary solid solution composite material and has pores of fine to
small diameters, the internal EndPage: 2 part loss is large and has an effective damping effect. In
the above, even if magnesium or an alloy of magnesium and aluminum is used instead of
aluminum, the same effect can be obtained. Hereinafter, the present invention will be described
in detail by way of examples. EXAMPLE First, pure & 99.9% aluminum and 99.0% pure boron to
aluminum hydride L ラ are synthesized.
As a result of X-ray diffraction, the obtained aluminum boride scaly crystal is AlB2 except for
some AlB12, and the thickness of microcrystal is 0.5 to 1 μm, and the length is 100 μm-%-500
μm. The average aspect ratio was about 300. Heat treated with 100 parts by weight of the
aluminum foil piece and a vacuum degree of 3 × 105 torr at a temperature of 450 ° C. for 1
hour to remove the oxide layer on the particle surface 99.5% purity aluminum powder with an
average particle diameter of 1.0 μm , 30 parts are put into a ball mill in which the inside of the
vessel is kept at a degree of vacuum of 1 × 10'torr; and the rotation speed is considerably lower
than usual and mixed. Then, 50 parts by weight of paraffin having a melting point of 16 ° C. and
a purity of 99% are further added, and ball mill mixing is performed under the same conditions
as above. Next, the mixed powder obtained as described above has a predetermined shape. Place
in a mold of dimensions, raise the degree of vacuum 3 × 1 σ 2 torr, pressure 400Kp / c4
temperature to 500 ° C, pressurize. Hold for 2 minutes under heat to obtain the product. The
product has a density of 2.7. The porosity was 40%, the speed of sound was 9600 m / s, and the
diaphragm was excellent. The polished cross section of the product was observed by SEM
(scanning electron microscope), and as a result, the aspect ratio of scaly aluminum borohydride
crystallites was about 200. Although the above example described the example which used
aluminum as a jointing material of scaly aluminum borohydride crystallite, it was a similar result,
even if it used magnesium and an alloy of aluminum and magnesium. As apparent from the
above description, according to the present invention, a diaphragm having a good characteristic
which surpasses the characteristic of a commercially available diaphragm can be obtained, and
the industrial value is large. Name of Agent Attorney Nakao and 1 other EndPage: 3
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