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JP2005348045

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DESCRIPTION JP2005348045
PROBLEM TO BE SOLVED: To provide a speaker diaphragm excellent in balance between rigidity
and internal loss and excellent in formability. SOLUTION: The speaker diaphragm of the present
invention has a substrate including a woven fabric of polytrimethylene terephthalate fibers, and a
thermosetting resin impregnated and cured on the substrate. Preferably, the 1,3-propanediol that
constitutes the polytrimethylene terephthalate fiber is derived from corn. Preferably, the
thermosetting resin is an unsaturated polyester resin, and at least a portion of the
polytrimethylene terephthalate fibers are coated with the second thermosetting resin. [Selected
figure] None
Speaker diaphragm
[0001]
The present invention relates to a speaker diaphragm. More particularly, the present invention
relates to a speaker diaphragm having an excellent balance between rigidity and internal loss and
excellent formability.
[0002]
Generally, the characteristics required for the speaker diaphragm include high Young's modulus
(elastic modulus, rigidity) and having a proper internal loss (tan δ). As a means to improve
Young's modulus, typically, a diaphragm using FRP made of a combination of carbon fiber and
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epoxy resin is mentioned. As a means for improving the internal loss, typically, a diaphragm
using a synthetic resin such as polypropylene can be mentioned.
[0003]
Each of the above-mentioned diaphragms has a problem. Specifically, although the FRP
diaphragm has a high Young's modulus, the internal loss of the epoxy resin which is a matrix
resin is small, and as a result, the internal loss of the whole diaphragm is reduced. Therefore,
such a diaphragm is likely to generate resonance, have frequency characteristics with many peak
dips, and it is difficult to prevent the generation of the sound unique to the material. Synthetic
resin diaphragms often have good frequency characteristics due to large internal loss, but they
have insufficient rigidity and heat resistance.
[0004]
In order to improve the rigidity, a diaphragm formed by impregnating and curing a
thermosetting resin in a woven fabric of high elastic modulus fibers (for example, aramid fibers)
has been proposed (for example, see Patent Document 1).
[0005]
JP-A-1-270490
[0006]
However, according to the technique described in Patent Document 1, a very large problem
occurs particularly in the formation of a large diameter cone diaphragm.
Specifically, the woven fabric is misaligned during molding, and often only a diaphragm having a
poor appearance can be obtained.
If the fibers are plugged so as not to cause eye slippage, distortion will remain at the time of
molding, and the diaphragm will often be deformed very largely along the thread.
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[0007]
As described above, there is a strong demand for a speaker diaphragm that is excellent in balance
between rigidity and internal loss and is excellent in formability.
[0008]
The present invention has been made to solve the above-described conventional problems, and
an object of the present invention is to provide a speaker diaphragm excellent in balance
between rigidity and internal loss and excellent in formability. is there.
[0009]
The speaker diaphragm of the present invention has a substrate comprising a woven fabric of
polytrimethylene terephthalate fibers, and a thermosetting resin impregnated and cured in the
substrate.
[0010]
In a preferred embodiment, the thermosetting resin is an unsaturated polyester resin.
[0011]
In a preferred embodiment, the polytrimethylene terephthalate fiber is a non-twisted fiber.
[0012]
In a preferred embodiment, at least a portion of the polytrimethylene terephthalate fiber is
coated with a second thermosetting resin.
[0013]
In a preferred embodiment, the second thermosetting resin is an epoxy resin or a melamine resin.
[0014]
In a preferred embodiment, the 1,3-propanediol constituting the polytrimethylene terephthalate
fiber is derived from corn.
[0015]
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In another aspect of the present invention, a speaker provided with the above-described speaker
diaphragm is provided.
[0016]
According to the present invention, by using the woven fabric as the base material, the fibers are
easily displaced at the time of vibration, so the vibration energy is converted to heat energy and
the internal loss is increased.
Furthermore, since the polytrimethylene terephthalate (PTT) woven fabric used in the present
invention has a very high weave density, in the formed diaphragm, the thermosetting resin as a
binder is a small amount between the fibers constituting the woven fabric. Only exists.
As a result, a laminated structure substantially having a woven layer and a resin layer is formed
on the substrate, and such a structure contributes to further improvement of the internal loss.
In addition, the very high weave density of PTT woven fabric also maintains excellent Young's
modulus.
Therefore, coexistence with Young's modulus and internal loss which were difficult in the prior
art is achieved.
Moreover, since PTT has very excellent flexibility (elongation), it is possible to perform good deep
drawing, and as a result, a large-diameter cone diaphragm having very excellent properties can
be obtained.
[0017]
The speaker diaphragm of the present invention has a substrate and a thermosetting resin
impregnated and cured in the substrate.
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The thermosetting resin is preferably unsaturated polyester resin or melamine resin, although
any appropriate thermosetting resin may be employed.
The unsaturated polyester resin is easy to manufacture because of its high curing speed and low
curing temperature, and a speaker diaphragm having excellent internal loss can be obtained.
Melamine resin greatly contributes to the improvement of strength.
[0018]
The substrate comprises a woven fabric of polytrimethylene terephthalate (PTT) fibers.
PTT is very flexible and stretchable, which allows good deep-drawing. As a result, a largeaperture cone-shaped diaphragm having very excellent characteristics can be obtained.
Preferably, the breaking elongation of PTT is 42 to 48%. By having the breaking elongation in
this range, very good deep drawing can be performed. Furthermore, since PTT fibers are
excellent in texture, a diaphragm having an excellent appearance can be obtained. In addition,
since the PTT fiber is very excellent in light resistance, a speaker diaphragm which hardly
changes in appearance can be obtained even when used in an environment (for example,
outdoors) where the ultraviolet light is directly received.
[0019]
As is well known, PTT is obtained from 1,3-propanediol and polyethylene terephthalate.
Preferably, the 1, 3-propanediol is not of petroleum origin but is of corn origin. Specifically, 1,3propanediol is obtained by fermenting corn. More specifically, sugar obtained from corn is
converted to glycerin and further converted to 1,3-propanediol. Such a series of reactions is
performed by a single genetically modified microorganism. By using such a process, mass
production of 1,3-propanediol is possible. Moreover, since this process proceeds by spontaneous
fermentation, there is no need to introduce a large amount of energy from the outside, and the
environmental load is extremely low. Therefore, using such corn-derived materials is extremely
preferable from the viewpoint of solving environmental problems. In addition, since the obtained
PTT itself is biodegradable, there is little adverse effect on the environment when the diaphragm
is discarded.
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[0020]
As a weave structure of this PTT woven fabric, any suitable structure (for example, plain weave,
twill weave, satin weave, a combination thereof) can be adopted, but preferably it is plain weave.
This is because the vertical / horizontal strength is strong and it is easy to perform deep drawing.
Therefore, it is particularly preferable in large aperture cone diaphragm applications. The weave
density (grain weight) in the case of plain weave is preferably 150 to 190 g / m <2>, more
preferably 160 to 180 g / m <2>. This range of weave density is significantly larger than that of
ordinary woven fabrics, so the effect of increasing the strength is large. Furthermore, it is
because it is excellent in moldability.
[0021]
Preferably, PTT fibers constituting the woven fabric are non-twisted fibers (untwisted fibers). By
using non-twisted fibers, the thickness per layer can be extremely reduced, and as a result, it is
possible to obtain a diaphragm that is lightweight and has very excellent strength. For example,
plain thermoplastic resin fibers are twisted and the thickness of the woven fabric is about 1 mm
when the basis weight is about 170 g / m <2>, while plain weave non-twisted PTT fibers are The
thickness of the same basis weight is about 0.18 mm, which is less than one-fifth. Furthermore, if
such a woven fabric is used, the amount of impregnated resin can be significantly reduced (as the
fiber / resin ratio of the diaphragm can be significantly increased), the internal loss is
significantly improved ( Details of the resin ratio will be described later). The thickness of the
PTT fiber is preferably 800 to 1200 denier although fibers of any appropriate thickness may be
adopted depending on the purpose. When the thickness of the fiber is less than 800 denier, the
basis weight often decreases and the strength is often insufficient. When the thickness of the
fiber exceeds 1200 denier, the weight increases and as a result, the sound pressure often
decreases. Preferably, the PTT fibers are monofilaments. By using a monofilament, diffuse
reflection occurs on the inner surface of the fiber, so that a speaker diaphragm having an
excellent appearance (specifically, a glossy fiber pattern) can be obtained.
[0022]
Preferably, at least a portion of the PTT fiber is coated with a second thermosetting resin. As the
second thermosetting resin, any appropriate thermosetting resin other than the above-mentioned
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impregnated thermosetting resin may be employed. For example, if the thermosetting resin to be
impregnated is an unsaturated polyester resin, the preferred second thermosetting resin is an
epoxy resin or a melamine resin. By coating with an epoxy resin or a melamine resin, the
wettability of the PTT fiber surface to the unsaturated polyester resin is improved, so the degree
of fiber reinforcement of the unsaturated polyester resin with PTT fibers becomes very large. As
a result, a speaker diaphragm having a very good Young's modulus can be obtained. On the other
hand, since the coated PTT fiber and the unsaturated polyester resin are appropriately displaced
during vibration, an appropriate internal loss is maintained. Such coating is carried out by a
conventional impregnation operation. The amount of coating is adjusted by changing the amount
of resin to be impregnated. As an example of the suitable coating amount, the resin amount is 3
to 7 parts by weight, preferably about 5 parts by weight, with respect to 100 parts of the
substrate.
[0023]
The fiber / resin ratio of the diaphragm of the present invention is preferably in the range of
60/40 to 80/20, more preferably in the range of 70/30 to 80/20. The high fiber / resin ratio
results in a loudspeaker diaphragm with very good internal loss without reducing the Young's
modulus. Here, the fiber / resin ratio is the ratio of the weight of the woven fabric before
impregnation to the weight of the impregnated resin. As described above, such a very high fiber /
resin ratio is achieved by making the fibers (PTT fibers) constituting the substrate non-twisting
fibers.
[0024]
The substrate may be the PTT fiber woven fabric alone or may be a laminate containing the PTT
fiber woven fabric. Preferably, the substrate is a laminate. This is because it is possible to prevent
the generation of the inherent sound that is likely to occur in the case of the PTT woven fabric
alone (single material), and it is possible to obtain a speaker diaphragm having a frequency
characteristic without peak dip. When a base material is used as a laminated body, it is preferable
to make a PTT woven fabric into the outermost layer (the side which radiates an acoustic wave).
It is because the speaker diaphragm which has the appearance of a glossy fiber pattern excellent
in the designability is obtained. In the laminate, each layer other than PTT woven fabric may be
in any form of woven fabric, non-woven fabric or film. Each layer other than the PTT woven
fabric may be appropriately selected depending on the purpose. Representative examples of such
layers include cotton woven fabrics, liquid crystal polymer nonwoven fabrics, thermoplastic resin
woven fabrics, nonwoven fabrics or films, or thermoplastic elastomer woven fabrics, nonwoven
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fabrics or films. When the base material is a laminate, two layers (for example, PTT woven fabric
/ cotton woven fabric, PTT woven fabric / liquid crystal polymer nonwoven fabric, PTT woven
fabric / thermoplastic resin film) are representative, but three layers are typical. It goes without
saying that the above may be applied.
[0025]
EXAMPLES Hereinafter, the present invention will be specifically described by way of examples,
but the present invention is not limited to these examples. In the Examples and Comparative
Examples, parts and percentages are by weight unless otherwise indicated.
[0026]
A thermosetting resin composition having the following composition was prepared: 100 parts of
unsaturated polyester resin (manufactured by Nippon Shokubai Co., Ltd., N 350 L) 5 parts of a
low-shrinkage agent (Nippon Yushi Co., Ltd., Modipar S 501) curing agent 1.3 parts (Nippon
Yushi Co., Ltd. product, Perocta O)
[0027]
Plain weave woven fabric of untwisted polytrimethylene terephthalate (PTT) fibers (Asahi Kasei
Corporation / Teijin Limited, yarn count: 1100 × 1100 (dtex), density: 17 × 17 (book / inch),
fabric weight: 166 g / m <2>) 100 parts of melamine resin was impregnated with 30 parts of
melamine resin to coat PTT fibers.
The PTT woven fabric was used as the front side, and the PTT woven fabric and the cotton woven
fabric (cotton count: 20 count, the number of threads: 40 longitudinal × 40 lateral, basis weight:
110 g / m <2>) were laminated. The laminate was cut into about 15 cm × 15 cm to give a
substrate.
[0028]
Two jigs having a hole of about 13 cm in diameter were prepared in the central part of a
stainless steel plate of about 16 cm × 16 cm, and the base was sandwiched between the two jigs.
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The above unsaturated polyester resin composition (about 5 g) was then dropped near the center
of the clamped substrate. Then, it was molded at a pressure of 90 to 140 kg / cm <2> at 130 °
C. for 30 seconds using a matched die mold of a predetermined shape. After the mold was cooled,
the mold was opened and the molded article was taken out. Thus, a speaker diaphragm having a
diameter of 12 cm, a thickness of 0.29 mm, a voice coil diameter of 2.5 cm, and a height of 3.0
cm was obtained.
[0029]
The density, weight, Young's modulus and internal loss (tan δ) of the obtained diaphragm were
measured by a conventional method. The obtained results are shown in Table 1 below together
with the results of Comparative Examples 1 and 2 described later. Furthermore, the frequency
characteristic of the speaker using the obtained diaphragm was measured. The results are shown
in FIG. In addition, the moisture resistance of the obtained diaphragm was measured according to
the following procedure: The obtained diaphragm was left to stand in an environment of 40 ° C.,
90% RH for 96 hours and in a normal temperature / normal humidity environment for 24 hours.
Later, changes in height were measured. The height was measured four times each at an interval
of 30 degrees at the height of the inner diameter portion of the cone. The results are shown in
FIG.
[0030]
[0031]
(Comparative example 1) An example except that two layers of cotton woven fabric (cotton
count: 20 #, number of threads: 40 vertical × 40 horizontal, basis weight: 110 g / m <2>) were
laminated to form a substrate In the same manner as in 1, a loudspeaker diaphragm having a
diameter of 12 cm and a thickness of 0.29 mm was obtained.
The obtained speaker diaphragm was subjected to the same evaluation as in Example 1. The
results are shown in Table 1 above. Furthermore, the frequency characteristic of the speaker
using the obtained diaphragm was measured. The results are shown in FIG.
[0032]
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(Comparative Example 2) Plain weave woven fabric (trade name: Kevlar) instead of PTT woven
fabric (made by Toray DuPont Co., Ltd., yarn count: 1100 × 1100 (dtex), density: 17 × 17 (book
/ A speaker diaphragm having a diameter of 12 cm and a thickness of 0.29 mm was obtained in
the same manner as in Example 1 except for using an inch) and a basis weight: 166 g / m <2>).
The obtained speaker diaphragm was subjected to the same evaluation as in Example 1. The
results are shown in Table 1 above.
[0033]
Comparative Example 3 Plain weave woven fabric of polyethylene naphthalate fiber (made by
Teijin Ltd., yarn count: 1100 × 1100 (dtex), density: 17 × 17 (book / inch), fabric weight: 166 g
instead of PTT woven fabric A speaker diaphragm having a diameter of 12 cm and a thickness of
0.29 mm was obtained in the same manner as in Example 1 except that / m <2> was used. The
moisture resistance of the obtained speaker diaphragm was evaluated in the same manner as in
Example 1. The results are shown in FIG.
[0034]
As apparent from Table 1, it can be seen that the speaker diaphragm of Example 1 has a low
density (that is, is lightweight), and is excellent in the balance between the rigidity (Young's
modulus) and the internal loss. Further, as apparent from comparison between FIG. 1 and FIG. 3,
in the speaker of Example 1, distortion is reduced due to the excellent internal loss, and
improvement in sound quality is recognized. Furthermore, as apparent from comparison between
FIG. 2 and FIG. 4, the diaphragm of Example 1 is smaller in deformation after the moisture
resistance test than in Comparative Example 3. In addition, with regard to the eye shift of the
woven fabric, in the diaphragm of Comparative Example 3, the eye shift in visual observation is
remarkable, while in the diaphragm of Example 1, the eye shift can not be confirmed visually.
[0035]
(Deep Drawing Characteristics) The same material as in Example 1 was used to perform deep
drawing with an outer diameter of 200 mm and a depth of 50 mm to obtain a diaphragm. On the
other hand, deep drawing with an outer diameter of 200 mm and a depth of 50 mm was
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performed using the same material as in Comparative Example 2 to obtain a diaphragm. In the
diaphragm using the material of Example 1, no eye displacement occurred even in deep drawing,
and there was no problem in appearance. On the other hand, the diaphragm using the material of
Comparative Example 2 had severe eye misalignment, and the appearance was significantly
different in the vertical, horizontal and 45 degree directions. Furthermore, when a moisture
resistance test (40 ° C., 95% RH, 96 hours) was performed for each of the diaphragms, no
deformation was found in the diaphragm using the material of Example 1 after the moisture
resistance test. On the other hand, in the diaphragm using the material of Comparative Example
2, since distortion at the time of molding was left, the shrinkage deformation occurred in the
longitudinal, transverse and 45 degree directions along with the water absorption of the base
cotton fabric. .
[0036]
The speaker diaphragm of the present invention can be suitably used for a speaker for any
application (that is, regardless of small or large diameter), and can be particularly suitably used
for a large diameter cone-shaped speaker.
[0037]
It is a graph which shows the frequency characteristic of the speaker using the diaphragm of the
Example of this invention.
It is a graph which shows the moisture resistance of the diaphragm of the Example of this
invention. It is a graph which shows the frequency characteristic of the speaker using the
diaphragm of the comparative example 1. FIG. 15 is a graph showing the moisture resistance of
the diaphragm of Comparative Example 3;
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