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The present invention relates to an acoustic diaphragm, and by forming an acoustic diaphragm
with an alumina ceramic fiber and a pigmented binder having a fiber structure, the propagation
velocity is large and the internal loss is also large. It becomes very desirable as an acoustic
diaphragm, and the binder used as a constituent material of the acoustic diaphragm can be easily
made into a desired color by, for example, dyeing it with a dye and coloring it, It is an object of
the present invention to provide an acoustic diaphragm that is of a desired color. For example, an
acoustic diaphragm formed by mixing and making alumina fibers and fibers such as natural pulp
has been proposed. However, although the acoustic diaphragm according to this proposal
contains 30% or more of organic fibers such as natural fibers as a binder and is excellent in
moldability, a portion without binder fibers, particularly a cross chain portion between ceramic
fibers In this case, the connection is almost completely made, so that not only a sufficiently
homogeneous strength can not be obtained, but a frictional noise is generated in the unbonded
portion, which is also a cause of an increase in distortion characteristics of the speaker. Also,
although alumina ceramic fibers are relatively easy to colorize with dyes etc. compared to carbon
fibers, for example, only white-based colors are currently realized, and the color of acoustic
diaphragms using alumina ceramic fibers Is not made of the desired color. The present invention
eliminates the above-mentioned drawbacks, and an embodiment thereof will be described below.
For example, 100 parts by weight of a ceramic fiber (fiber diameter 0.5 to 4 μm, (Jl fiber length
0.1 to 1′0 c IrL)) containing 55 to 95 parts of alumina is dispersed in water. And, in order to
form a sheet in water, a water-soluble organic substance having no fiber structure and a dyed
dye with a dye, for example, a water-soluble acrylamide resin in which 2 to 5 parts by weight of
direct dye restriction is added and mixed About 50 to 100 parts by weight, particularly
preferably about 80 parts by weight of an anionic resin and having a molecular weight of about
800,000 to 1,000,000, is added and sufficiently stirred. Next, a sulfuric acid band is added to the
above mixed solution to adjust to pH 4 to 6, about 1 to 10 parts by weight of a sizing agent is
added thereto and stirred, and thereafter, it is formed into a sheet with a desired diaphragm
shape. . Then, the wet ceramic fiber mat removed from the wire mesh is heat-pressed under the
conditions of a mold temperature of about 140 to 200 ° C. and a pressing time of about 3 to 15
minutes to constitute the acoustic diaphragm according to the present invention . Thus, an
acoustic diaphragm made of a material including an alumina ceramic fiber and, for example, a
binder colored with a dye and having no fiber structure is characterized in that the alumina
ceramic fiber has characteristics as a diaphragm. Because the propagation speed is high and the
one used as the binder does not have a fiber structure, it causes defects such as almost no
bonding in the cross-linked part of the aluminous ceramic fiber. As a whole, a sufficiently
homogeneous intensity can be obtained, and the distortion characteristic of the speaker can not
be increased.
For example, in the acoustic diaphragm of the above embodiment, the propagation speed of the
acoustic diaphragm using natural pulp is 1.0 to 2.0 Km / s, but 2.2 to 2.6 Km / s and so on.
Propagation speed is large, and while the internal loss of alumina bulk is 0.002 to 0.005, the
internal loss is sufficiently large such as 0.02, and further, the acoustic diaphragm of the above
embodiment As shown by the solid line in the figure, the frequency characteristic of Spy Jy using
the above is “high” or the limit frequency is 3.5 KHz, while the frequency characteristic of the
speaker using an acoustic diaphragm using natural pulp is indicated by an alternate long and
short dash line As shown, the upper limit frequency is 2.6 KI4 z, and the acoustic diaphragm of
this embodiment is excellent. In addition, second harmonic distortion and the like are reduced as
compared with the case where natural pulp such as wood pulp is used as a binder. Furthermore,
since the binder not having a fiber structure, for example, a water-soluble acrylic resin, is colored
using a dye instead of directly coloring the alumina-based ceramic fiber, it is more preferable
than the case where the alumina-based ceramic fiber is dyed It is also rich in color durability and
excellent in color. Further, this acoustic diaphragm is flame-retardant, can be manufactured by
various manufacturing processes as in the case of using passively, and is excellent in formability
and mass productivity. Similarly, in the above embodiment, as the essential components of the
acoustic diaphragm, an alumina ceramic fiber and a colored binder which does not have a fiber
structure are used, but a metal oxide or the like may be contained therein. For example, the
acoustic diaphragm obtained in the second example is immersed in alumina sol (30% aqueous
solution of alumina), impregnated with 30% by weight or less of alumina in the acoustic
diaphragm element 42, and thereafter, approximately 1 oO to 160 °. By drying at C, for
example, an acoustic diaphragm having a propagation speed of 2.5 to 3.0 Km / s and an internal
loss of 0.01 can be obtained. As described above, since the acoustic diaphragm according to the
present invention is made of a material including an alumina ceramic fiber and a colored binder
having no fiber structure, both the propagation speed and the internal loss are large, and the
alumina ceramic fiber is also Since the binder for bonding the fibers is not of fiber structure, little
bonding is likely to be made in the cross-linked portion of the aluminous ceramic fiber,
homogeneous strength is obtained, sufficient rigidity is obtained, and further, the enterprise is
small. Because the upper limit frequency is high and is colored with binders without fiber
structure, such as dyes, it is rich in color fire resistance and can be easily colored to any desired
color, It has special features such as the ability to make the acoustic diaphragm a preferred color.
Brief description of the drawings
The drawing is a graph of frequency characteristics of the speaker.
Patent Applicant Nippon Victor Co., Ltd. Atsushi Udaka
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