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JP2004193716

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
complete, reliable or fit for specific purposes. Critical decisions, such as commercially relevant or
financial decisions, should not be based on machine-translation output.
DESCRIPTION JP2004193716
To provide a speaker diaphragm having excellent Young's modulus and internal loss. A speaker
diaphragm of the present invention is formed by impregnating a substrate containing a woven
fabric of polyethylene naphthalate fibers with a thermosetting resin. Preferably, the
thermosetting resin is an unsaturated polyester resin. Preferably, the polyethylene naphthalate
fibers are non-twisted fibers, at least a portion of which is coated with a second thermosetting
resin. Preferably, the second thermosetting resin is an epoxy resin or a melamine resin.
Furthermore, the substrate may be a laminate further comprising a cotton woven or liquid
crystalline polymer nonwoven. [Selected figure] None
Speaker diaphragm
TECHNICAL FIELD The present invention relates to a speaker diaphragm. More particularly, the
present invention relates to a speaker diaphragm excellent in the balance between Young's
modulus and internal loss. 2. Description of the Related Art Generally, characteristics required of
a 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 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. Each of the above-described 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, has 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. As a means for improving the rigidity
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(Young's modulus) and the internal loss in a well-balanced manner, a diaphragm using a
polyethylene naphthalate film has been proposed (see, for example, Patent Documents 1 and 2).
Patent Document 1: Japanese Patent Application Laid-Open No. 1-67099 Patent Document 2:
Japanese Patent Application Laid-Open No. 6-181598 The technology described in the above
patent documents is limited to small diameter speakers (so-called microspeakers) It is
Specifically, according to the technology described in the above-mentioned patent documents,
although a diaphragm sufficient for both rigidity and internal loss can be obtained in the micro
speaker application, the internal loss is extremely insufficient in the large aperture speaker
application Therefore, a diaphragm that can withstand practical use can not be obtained. As
described above, a speaker diaphragm having excellent Young's modulus and internal loss in any
application is strongly desired. SUMMARY OF THE INVENTION The present invention has been
made to solve the above-mentioned conventional problems, and the object of the present
invention is to provide excellent Young's modulus and internal loss in any application. To provide
a speaker diaphragm having
A speaker diaphragm according to the present invention is formed by impregnating a base
material containing a woven fabric of polyethylene naphthalate fibers with a thermosetting resin.
In a preferred embodiment, the thermosetting resin is an unsaturated polyester resin. In a
preferred embodiment, the polyethylene naphthalate fiber is a non-twisted fiber. In a preferred
embodiment, at least a portion of the polyethylene naphthalate fiber is coated with a second
thermosetting resin. In a preferred embodiment, the second thermosetting resin is an epoxy resin
or a melamine resin. In a preferred embodiment, the substrate further comprises a cotton woven
or liquid crystal polymer non-woven fabric. In a preferred embodiment, the fiber / resin ratio of
the substrate is in the range of 60/40 to 80/20. BEST MODE FOR CARRYING OUT THE
INVENTION The speaker diaphragm of the present invention is formed by impregnating a base
material with a thermosetting resin. The thermosetting resin is preferably an unsaturated
polyester resin, although any appropriate thermosetting resin may be employed. This is because
a speaker diaphragm having a high curing rate and a low curing temperature is easy to
manufacture and has an excellent internal loss. The substrate comprises a woven fabric of
polyethylene naphthalate (PEN) fibers. As a weave structure of this PEN 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.
Preferably, the PEN 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.
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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>, but plain weave woven fabric of nontwisted PEN fibers is 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 the impregnated resin (fiber
/ resin ratio of the base material) can be significantly reduced, so the internal loss is significantly
improved (the details of the resin ratio will be described later). . The thickness of the PEN fibers
is preferably 800 to 1200 denier although fibers of any appropriate thickness may be employed
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, at least a portion of the PEN fiber is coated with a second thermosetting resin. As the
second thermosetting resin, any appropriate thermosetting resin other than the above-mentioned
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 PEN fiber surface to the unsaturated polyester resin is improved, so the degree
of fiber reinforcement of the unsaturated polyester resin with PEN fibers becomes very large. As
a result, a speaker diaphragm having a very good Young's modulus can be obtained. On the other
hand, proper internal loss is maintained because the coated PEN fibers and the unsaturated
polyester resin are properly displaced during vibration. 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. The substrate may be the above-mentioned PEN woven fabric alone or may be a
laminate containing PEN 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 a
single material, and it is possible to obtain a speaker diaphragm having frequency characteristics
without peak dip. In the case where the substrate is a laminate, it is preferable that the PEN
woven fabric be the outermost layer (the side emitting the sound wave).
It is because the speaker diaphragm which has the appearance of a glossy fiber pattern excellent
in the designability is obtained. Each layer other than the PEN woven layer in the laminate may
be a woven or non-woven fabric. Representative examples of such layers include cotton woven
fabrics and liquid crystal polymer nonwoven fabrics. Representative examples of liquid crystal
polymers include wholly aromatic polyesters and wholly aromatic polyamides. The wholly
aromatic polyester is commercially available, for example, from Shin Nippon Petrochemical Co.,
Ltd. under the trade name Zyder and from Kuraray Co., Ltd. as the trade name Vectran. Fully
aromatic polyamides are commercially available, for example, from Toray DuPont Co., Ltd. under
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the trade name Kevlar, and from Teijin Ltd. under the trade name Technora. The weave density of
the woven fabric, the weave structure, the method of forming the non-woven fabric, and the like
may be appropriately selected depending on the purpose. The base material is typically a twolayer structure such as PEN woven fabric / cotton woven fabric, PEN woven fabric / liquid crystal
polymer non-woven fabric, but it may be a laminate of three or more layers. Absent. The fiber /
resin ratio of the substrate is preferably in the range of 60/40 to 80/20, more preferably in the
range of 70/30 to 80/20. By using a substrate having a high fiber / resin ratio, it is possible to
obtain a speaker diaphragm having an extremely excellent internal loss without reducing the
Young's modulus. Here, the fiber / resin ratio is the ratio of the weight of the base material
before impregnation to the weight of the impregnated resin. As described above, such an
extremely high fiber / resin ratio is achieved by making the fibers (PEN fibers) constituting the
substrate non-twisting fibers. Hereinafter, the operation of the present invention will be
described. According to the present invention, a speaker having very excellent Young's modulus
and internal loss by impregnating a base material containing polyethylene naphthalate (PEN)
fiber woven fabric with a thermosetting resin to form a speaker diaphragm A diaphragm can be
obtained. Specifically, by using a woven fabric as the base material, the fibers are easily displaced
at the time of vibration, so that vibration energy is converted into heat energy and the internal
loss becomes large. Moreover, since the PEN woven fabric used in the present invention has a
very high weave density, in the formed diaphragm, the thermosetting resin as a binder is present
only in a small amount between the fibers constituting the woven fabric. As a result, a laminated
structure having a fabric layer and a resin layer is substantially formed, and such a structure
contributes to further improvement of internal loss.
In addition, the very high weave density of PEN 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. In a preferred embodiment, the PEN fibers 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. Furthermore, if such a woven fabric is used, the amount of the impregnated resin (fiber
/ resin ratio of the base material) can be greatly reduced, so that the internal loss can be
remarkably improved. In the present invention, a fiber / resin ratio of 60/40 to 80/20 can be
achieved, and a speaker diaphragm having a very small amount of resin can be obtained. As a
result, due to the displacement between the PEN fibers at the time of vibration, it is possible to
achieve an internal loss superior to that of the film diaphragm. In fact, the speaker diaphragm of
the present invention has an internal loss of more than 10 times that of the PEN film diaphragm
(0.038 in the above-mentioned Patent Document 2) (0.45 in Example 1 described later) ).
EXAMPLES The present invention will be specifically described by way of the following 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. Example 1 An
unsaturated polyester solution having the following composition was prepared: Unsaturated
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polyester resin (manufactured by Nippon Shokubai Co., Ltd .; N 350 L): 100 (parts) Low
shrinkage agent (Nippon Yushi Co., Ltd.) Made; Modipar S501): 5 Per Octa O (manufactured by
NOF Corp.): 1.3 Cotton woven fabric (cotton count: 20th, number of punches in: 40 vertical × 40
horizontal, basis weight: 110 g / m) <2> was cut into a size of 15 cm x 15 cm. Place a plain
weave woven fabric of PEN fibers (manufactured by Teijin Ltd., yarn count: 1100 tex, density: 17
× 17 (book / inch), fabric weight: 166 g / m <2>) on which PEN fiber cut into 15 cm × 15 cm
did. This two-layer laminate was used as a substrate. Two jigs having a hole of about 13 cm in
diameter were prepared in the center of a stainless plate of about 16 cm × 16 cm, and the
laminate was sandwiched between the two jigs. About 5 g of the above unsaturated polyester
solution was dropped from above (from the side of the PEN woven fabric) near the center of the
substrate fixed with the jig.
Then, it was molded at 130 ° C. for 30 seconds using a matched die mold of a predetermined
shape to obtain a speaker diaphragm having a diameter of 12 cm and a thickness of 0.25 mm.
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 Examples 2 to 3 and Comparative Example 1 described later. Furthermore, the
frequency characteristic of the speaker using the obtained diaphragm was measured. The results
are shown in FIG. The fiber / resin ratio of Example 1 was 78/22. In addition, with respect to the
obtained diaphragm, a contact angle measurement device (CA-, manufactured by Kyowa Interface
Science Co., Ltd.). The contact angle was measured using Q1). The results are shown in Table 2
below together with the results of Example 3 described later. <Example 2> <Example 2> Liquid
crystalline polymer non-woven fabric (manufactured by Kuraray Co., Ltd., Vectran) instead of
cotton woven fabric. A speaker diaphragm was produced in the same manner as in Example 1
except that the fiber thickness: 1,600 denier, and the basis weight: 60 g / m <2> were used. The
obtained 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. Example 3 A speaker vibration is carried
out in the same manner as in Example 1 except that 5 parts of melamine resin is impregnated
and dried with respect to 100 parts of plain weave woven fabric of PEN fiber, and then laminated
with cotton woven fabric. A board was made. The obtained 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. Furthermore, the contact angle was measured in the same manner as in Example 1. The
results are shown in Table 2 above. Comparative Example 1 A speaker diaphragm was produced
in the same manner as in Example 1 except that two cotton woven fabrics in Example 1 were
stacked to form a laminate base. The fiber / resin ratio of this diaphragm was 46/54. The
obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown
in Table 1 above.
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Furthermore, the frequency characteristic of the speaker using the obtained diaphragm was
measured. The results are shown in FIG. In addition, a schematic cross sectional view from a
micrograph of a cross section of the diaphragm is shown in FIG. 5 together with the schematic
cross sectional view of the diaphragm of the third embodiment. As apparent from Table 1, the
speaker diaphragm of the present invention has excellent Young's modulus and internal loss. In
particular, in the diaphragm of Example 3 coated with the second thermosetting resin (melamine
resin), the Young's modulus and the internal loss are both approximately doubled as compared
with Comparative Example 1. Further, as is clear from Table 2, it can be seen that the diaphragm
of Example 3 coated with the melamine resin is significantly improved in wettability as compared
to the diaphragm of Example 1. It should be noted that the characteristics of the diaphragm of
Example 1 are also significantly superior to those of the prior art. As apparent from FIG. 5, the
diaphragm of the present invention substantially forms a three-layer structure of resin layer /
PEN woven layer / cotton woven fabric and resin layer. On the other hand, in the diaphragm of
the comparative example, the binder resin penetrates between the fibers of the woven fabric. The
diaphragm of the present invention has an excellent internal loss due to the laminated structure,
as well as due to the very high weave density of PEN fibers and the presence of an adequate
amount of binder resin around the fibers. It is considered to have excellent Young's modulus. As
described above, according to the present invention, a speaker diaphragm excellent in both
Young's modulus and internal loss can be obtained by impregnating a polyethylene naphthalate
woven fabric with a thermosetting resin. can get. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1
is a graph showing frequency characteristics of a speaker using a diaphragm according to an
embodiment of the present invention. FIG. 2 is a graph showing frequency characteristics of a
loudspeaker using a diaphragm according to another embodiment of the present invention. FIG.
3 is a graph showing frequency characteristics of a loudspeaker using a diaphragm according to
yet another embodiment of the present invention. FIG. 4 is a graph showing frequency
characteristics of a speaker using a diaphragm of a comparative example. FIG. 5 is a schematic
cross-sectional view for explaining the difference in the internal structure of a diaphragm
according to an embodiment of the present invention and a diaphragm of a comparative example.
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