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The present invention relates to a diaphragm having a high Young's modulus used for a speaker.
BACKGROUND ART In general, performance required of a speaker diaphragm is lightweight, has
high Young's modulus, low density, and appropriate internal loss so that the output sound
pressure frequency characteristics of the speaker and the like can be favorably obtained. It is that
bending rigidity is large. That is, the higher the Young's modulus and the lower the density, the
higher the resonant frequency of the diaphragm and the wider the piston movement area, the
wider the frequency range of the speaker, and the larger the internal loss, the smaller the split
resonance of the diaphragm. The frequency characteristic is flattened. Furthermore, when the
diaphragm is soft or when high frequency vibration is applied to the diaphragm, partial vibration
occurs and the frequency characteristics deteriorate, so the bending rigidity must also be large.
As a diaphragm that satisfies the above-described required performance, a diaphragm made of a
substrate made of a conventionally beaten natural fiber, a chemical fiber, or a fiber material
obtained by mixing these is widely manufactured. However, such a diaphragm has a limit in the
improvement of Young's modulus and is weak to moisture, and absorption of moisture occurs in
the air due to the rise of humidity or water droplets in the air, and the performance is degraded
due to swelling or the like. For this reason, recently, for example, a diaphragm made of paper
making of inorganic fibers having high rigidity, such as ceramic fibers and carbon fibers, has
been developed. However, in the diaphragm, since physical bonding between fibers such as
entanglement of fibers as in natural fibers is not performed, it is only an overlap between fibers
and the rigidity of the diaphragm itself can not be increased. The Therefore, as the blending
amount of these inorganic fibers is increased, an undesirable result such as a decrease in Young's
modulus is obtained. Furthermore, with regard to adhesion of ceramic, there is also a method of
adhering a resin to a base material after paper forming to sinter the ceramic, but the process is
complicated and the physical properties are unstable compared to the diaphragm of natural fiber.
It was difficult to manufacture. Therefore, an object of the present invention is to provide a
speaker diaphragm having a waterproof property which is more sufficient while maintaining the
physical properties preferable as a diaphragm such as high Young's modulus, low density,
sufficient internal loss and high bending rigidity. To provide. The diaphragm for a speaker
according to the present invention comprises a base material made of paper stock obtained by
adding a paper strengthening agent to a main raw material consisting of natural fibers and
ceramic fibers, and a thermosetting material formed on the main surface of the base material It is
characterized by comprising a resin film. EXAMPLES Hereinafter, examples of the present
invention will be described based on the attached drawings. As a first embodiment, a diaphragm
is manufactured in the following process.
First, as a raw material, for example, a ceramic having 47.3% of alumina Al 2 O 3, 52.3% of silica
SiO 2, and 0.4% of other inorganic components has an average fiber diameter of 2.8 μm and an
average fiber length of 2 mm 5 mm Prepare ceramic fibers formed in the shape of mei.
Furthermore, natural fibers such as NtJKP (non-soft-leaved kraft pulp) are prepared. The watersoluble polymer as a paper strength agent is corn starch, PVA (polyvinyl alcohol), CMC
(carboxymethyl cellulose) and the like, but corn starch is used in this embodiment. Furthermore,
as the thermosetting resin, for example, using an epoxy resin mixed at a ratio of 50% of an epoxy
resin main agent (polyglycidyl ether) and 50% of an epoxy resin curing agent (phthalic
anhydride), the active resin component concentration is 30 wt. A solution obtained by dissolving
it in a suitable organic solvent such as MEK (methyl ethyl ketone) so as to be about 10% is used
as an epoxy resin solution. The ceramic fibers and the natural fibers described above are mixed
in a ratio of 25% by weight: 75% by weight of ceramic fibers H: natural fibers and dispersed in
water of a paper making tank. After that, corn starch is added as an aqueous solution so as to be
about 10 wt% of the mixed fiber material to adjust the stock. Next, a desired diaphragm shape,
for example, a paper shape with a cone shape, is made into a sheet, and the obtained product is
dried under a pressure of about 5.0 kQ / Cm2 with a cone shape mold at a temperature of about
200 ° C. To form a substrate. Next, the obtained cone-shaped substrate is immersed in the
above-mentioned epoxy resin solution prepared as a thermosetting resin to impregnate and
adhere the resin solution between the fibers forming the substrate. Here, a resin solution film
remains on the substrate surface. Thereafter, the solvent is volatilized and dried by hot air at a
temperature of about 100 ° C. in a dryer, and the epoxy resin is semi-cured (semi-cured).
Further, the epoxy resin is completely cured by heating and pressing at a temperature of about
200 ° C. and a pressure of about 6.0 kQ / cm 2 for about 30 seconds with a mold having the
same shape as the base material. The base material having undergone these steps is cut into a
predetermined shape to obtain the speaker diaphragm of the first embodiment. Next, as a second
embodiment, a diaphragm is manufactured in the same process as the first embodiment. The
above-mentioned ceramic and natural fibers are mixed at a ratio of 5Q wt%: 50 wt% and
dispersed in a paper making tank. Thereafter, the diaphragm of the second embodiment is
obtained by the same process as that of the first embodiment.
FIG. 1 is a cross-sectional view of the speaker diaphragm of the present embodiment obtained by
the above-described manufacturing method, and shows a cone-shaped one. FIG. 2 is a partially
enlarged cross-sectional view shown by a circle A in FIG. 1, in which a base material 4 is formed
of ceramic 1 and natural fibers 2 and an epoxy resin portion 3 (coating) is formed inside from its
main surface Indicates that each fiber is covered. Thus, the water repellent effect on water
droplets and the like can be obtained. In the speaker diaphragm of the present embodiment
obtained in this manner, the blended ceramic imparts rigidity and mechanical strength to the
diaphragm. A substrate containing ceramic fibers is suitable for heat and pressure molding
because of its excellent heat resistance. Moreover, there is no restriction | limiting in particular
about the component of the ceramic fiber mixed with natural am in a present Example. However,
the longer the average fiber length, the higher the rigidity, but the entanglement with natural
fibers becomes worse and the dispersibility also becomes worse. However, in the present
invention, it was found that the best results can be obtained by setting the average fiber length of
the ceramic fibers to about 2.5 mm. In the present invention, the covering property and the
cross-linking cohesivity of the valve fiber can be improved by forming a strong fiber-to-fiber
bond at the time of paper making, and adding a water-soluble polymer as a paper strength agent.
By causing the ceramic to increase the strength of the substrate, a ceramic which does not
physically bond is incorporated into the substrate. If the amount of the thermosetting resin
applied to the surface of the substrate is too large, the weight will increase and the efficiency will
decrease accordingly, but in this example it will be about 20 wt% of the diaphragm obtained. It
came to obtain the diaphragm which had the value which becomes favorable in physical property
in adhesion. Table 1 shows physical property values of the diaphragm of this embodiment and a
diaphragm made only of paper making using natural fibers, and the comparison of the two in
Table 1 shows the increase of the density of the diaphragm of this embodiment. It is minutely
suppressed to increase both the Young's modulus and the internal loss, and sufficiently exerts the
excellent performance of the diaphragm made of fibrous paper. In addition, even if the
compounding ratio of ceramic is increased, the Young's modulus does not extremely decrease
because the natural fibers at the time of papermaking have strength, and it is possible to change
the compounding ratio of the ceramic according to the purpose. It becomes. However, when the
compounding amount is too large, the dispersibility of the ceramic is deteriorated, but in the
present invention, the best result is obtained when the compounding ratio is about 25 to 50%. In
the above-mentioned embodiment, although the ceramic fiber and the natural fiber and mixed
papermaking were explained, the same effect can be obtained in the papermaking of other
inorganic fibers having high rigidity consisting of alumina, carbon etc. instead of the ceramic
fiber and natural fiber. A diaphragm is obtained.
In addition, as a paper strengthening agent, other water-soluble polymers such as PVA and CMC
may be used. The waterproofness can be further improved by adding an inner size material such
as urea formaldehyde resin or styrene resin to the mixed stock in the papermaking process to the
beating valve. Furthermore, by changing the type of natural fiber, the degree of beating, the
amount of addition of the paper strength enhancing agent, etc., it is possible to obtain a speaker
diaphragm of performance according to the purpose. Further, the present invention exhibits the
same effects as those of the above-described embodiment not only with the diaphragm but also
with other speaker members such as a center cap obtained by paper forming. Effects of the
Invention According to the present invention as described above, the flexural rigidity of the
diaphragm is further maintained while maintaining the preferable physical properties of the
diaphragm such as high Young's modulus, low density and appropriate internal loss without
using complicated processes. An improved loudspeaker diaphragm is obtained. In addition, a
speaker diaphragm having waterproofness can be obtained which is further sufficient while
maintaining these preferable physical properties.
Brief description of the drawings
FIG. 1 is a cross-sectional view of the speaker diaphragm of the present invention, and FIG. 2 is a
partially enlarged cross-sectional view shown by a circle A in FIG.
Explanation of the symbols of the main part 1 ........ Ceramic fiber 2.
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