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The present invention relates to a speaker vibrator, and by using aluminum or an aluminum alloy
of which at least the surface is mainly crystalline γ-alumina as a constituent material of the
speaker vibrator, the internal loss is large and the sound absorption is good and the distorted
sound is good. It is an object of the present invention to provide a speaker vibrating body which
is extremely easy to hear, has a high sound propagation speed, is excellent in following
capability, and is wide even in a piston vibration zone. Conventionally, as a speaker diaphragm,
one in which aluminum is anodized to form an oxide film on the aluminum surface has been
proposed. For example, a means such as vapor deposition on a speaker diaphragm formed by
shaping aluminum into a predetermined shape and anodizing the surface thereof (Japanese
Utility Model Publication No. 32-2216) or a base formed of a thin plate of aluminum in the shape
of the diaphragm Speaker diaphragm in which the above-mentioned base is oxidized by anodic
oxidation in the diaphragm in which the ratio of Young's modulus E and density ρ is large by the
formation of the coating layer of beryllium and poron (JP-B-55-15911, JP-B-65 No. 15912) and
the like have been proposed. However, although these conventional speaker diaphragms are
made of aluminum, since the surface oxide film is amorphous alumina, the strength as the
speaker diaphragm is not sufficient and the internal loss is small. Furthermore, since the sound
propagation speed is not so high, there is a disadvantage that sound absorption is not sufficient
and distortion sound occurs, and the followability is not good and the piston vibration band is
narrow. The present invention eliminates the above-mentioned drawbacks, and an embodiment
thereof will be described below. That is, in the speaker vibrator according to the present
invention, for example, the surface of aluminum or an aluminum alloy is formed of crystalline ralumina. For example, the following method may be used to manufacture a speaker vibrator
having such a surface made of crystalline r-alumina. First, a speaker diaphragm is formed into a
predetermined shape as a speaker diaphragm using, for example, aluminum or an aluminum
alloy having a thickness of about 30 to 60 μm. Next, an alumina layer is formed on the surface
of the aluminum or aluminum alloy by the conventional anodizing method using the abovementioned molded speaker diaphragm. Here, the common anodizing method is a so-called
sulfuric acid method developed by C, H, Tt, Gower and S, O, O'Br1en, for example, sulfuric acid
with an electrolyte composition of 10 to 20%, current density is +陽極 2 A / dm ', voltage is 10 to
20v, temperature is 20 to 30 ° C, treatment time is 10 to 30 minutes, or it is developed by
Sakurai or plantation, widely used as alumite method Popular oxalic acid, for example oxalic acid
with an electrolyte composition of 2 to 4%, current density of 0.5 to I A / dtr? , Oxalic acid with a
voltage of 25 to 30 V, a temperature of 20 to 29 ° C., a treatment time of 20 to 60 minutes, or
an electrolytic solution composition of 3 to 6%, a current density of 1 to 2 A / d, a voltage of 30
to It is anodizing treatment under the conditions of 35 v, a temperature of 36 ° C., and a
treatment time of 20 to 30 minutes.
That is, the speaker vibrator of aluminum or aluminum alloy is connected to the anode to form
an alumina layer on the surface of the speaker diaphragm by using such a conventional
anodizing treatment method. After the second anodizing treatment, the speaker diaphragm on
which the alumina layer is formed is, for example, a carbonate such as sodium carbonate, sodium
hydrogencarbonate, ammonium carbonate, ammonium carbonate, potassium carbonate, lithium
carbonate, cesium carbonate or the like, or boric acid to carbonate. , Inorganic acids such as
phosphoric acid, silicic acid and metabosic acid or organic acids such as malic acid, tartaric acid,
citric acid, yh conic acid, oxalic acid, oxalic acid, malonic acid, faucic acid or salts of these
inorganic acids and organic acids And the speaker diaphragm connected to the anode, at a
temperature of about 30-80 ° C., a voltage of about 70-200 V, for a few minutes, eg 6 Anodize
for a minute. In the electrolyte composition, the concentration of carbonate is about 0.5 to 3 mol
/ 11, and when inorganic acid, organic acid and salts thereof are also used, the amount of one of
these components is about 1 to 200 y / 1. . It is desirable to be in the range of Thus, when the
secondary anodizing treatment is carried out, the alumina formed by the secondary anodizing
treatment is almost completely transformed to crystalline r-alumina, and the surface is
remarkably porous and the interior is porous to the inside. It becomes a speaker diaphragm. The
metallographic structure of the speaker diaphragm configured as described above and the
conventional aluminum speaker diaphragm that has only been subjected to a conventional
anodizing treatment is recognized in the cross-sectional perspective photograph in FIGS. 1 and 2,
respectively. As compared with the prior art, the surface according to the present invention is
extremely porous and the inside is porous, whereas the conventional one is flat in the surface,
has a frost-pillared alumina in the cross section, and The internal loss (tan δ) of the speaker
diaphragm according to the invention is as large as about 0.03, while the conventional one is as
small as about 0.01. In addition, the internal loss of the conventional speaker diaphragm which
has not been subjected to the ordinary anodizing treatment is as small as about 0.002 to o and
oos. Further, since the loudspeaker diaphragm according to the present invention is a crystalline
r-alumina, the loudspeaker diaphragm is also stronger than an amorphous one. Furthermore, the
sound propagation velocity is measured to be about 5.4- / 8 in the case of aluminum 6, about 4.4
Km / s in the case of amorphous alumina, and about 4.4 in the case of the present invention. 9 k
/! Although the material of the speaker diaphragm according to the present invention is porous
as in l, the propagation speed of sound is large.
Therefore, the follow-up property of the sound is excellent, and as shown in FIG. 3, it is smooth
and flat. In FIG. 3, the solid line is that of the loudspeaker diaphragm according to the present
invention, and the dotted line is that of the loudspeaker diaphragm using a material on which
amorphous alumina is formed by ordinary anodic oxidation. As described above, the loudspeaker
diaphragm according to the present invention has high internal loss and sound propagation
speed, and thus is harmonized with high performance. As a method of obtaining crystalline γalumina, it is possible to heat crystalline aluminum hydroxide to about 900 to 960 ° C, or to
heat At203 · H2O or At203 · 3H20 to about 500 ° C, or Is obtained by heating aluminum to 500
° C. or higher, but all of these methods are by reaction in a high-temperature furnace, and in the
case of a thin film speaker diaphragm, it is preferable to carry out these methods. It is not
suitable, and it is desirable to use the anodizing method described in the above example. Then,
although the primary anodizing treatment is not performed only by the secondary anodizing
treatment described in the above embodiment, crystalline γ-alumina is formed, but the alumina
layer is formed by the primary anodizing treatment. As a result, a stable reaction does not occur
during secondary anodizing treatment, resulting in a stable reaction, so that a uniform crystalline
γ-alumina film is obtained, and the accuracy of the funnel thickness of 4 significantly increases. .
As described above, the speaker vibrator according to the present invention has an internal loss
and a sound propagation speed greater than that of amorphous aluminum--at least the surface is
mainly made of aluminum or an aluminum alloy of crystalline γ-alumina. Therefore, the sound
absorption is good and distortion sound is eliminated, the sound becomes extremely easy to hear,
and the followability of the sound is good, and the strength is also excellent, the good frequency
band is wide, and the high frequency characteristics are also excellent. It is characterized by its
ability to absorb resonance noise that tends to be present in metal and to be excellent in sound
Brief description of the drawings
Patent applicant Nippon Victor Corporation
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