JP2001016682

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DESCRIPTION JP2001016682
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for a speaker. More particularly, the present invention relates to a speaker diaphragm
excellent in water resistance and internal loss and inexpensive.
[0002]
2. Description of the Related Art Generally, a speaker of a mobile phone or a portable small toy is
required to be lightweight and thin. Therefore, a dynamic type or piezoelectric type speaker is
typically used, and among them, a dynamic type speaker having a shallow cone type diaphragm
is typically used in consideration of sound quality. In portable applications, since the device is
often used outdoors, the diaphragm used for the speaker is required to be water resistant. From
the viewpoint of water resistance, PET (polyethylene terephthalate) resin is typically used for
such a diaphragm.
[0003]
However, PET has poor internal quality due to its high elastic modulus, so that it has poor sound
quality (for example, in mobile phones, there is a serious problem that the conversation is
difficult to hear).
[0004]
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As described above, there is a strong demand for a speaker diaphragm that is excellent in water
resistance and internal loss.
[0005]
SUMMARY OF THE INVENTION The present invention has been made to solve the abovementioned conventional problems, and the object of the present invention is to provide an
inexpensive speaker which is excellent in water resistance and internal loss. It is in providing the
diaphragm for.
[0006]
SUMMARY OF THE INVENTION As a result of intensive studies on the material of the speaker
diaphragm, the present inventors have obtained poly (trimethylene terephthalate) at a low cost,
and used this material. As a result, it has been found that a speaker diaphragm having excellent
water resistance and internal loss can be obtained, and the present invention has been
completed.
[0007]
The speaker diaphragm of the present invention is formed of a thermoplastic resin composition
containing poly (trimethylene terephthalate) as a main component.
[0008]
In a preferred embodiment, the thermoplastic resin composition further contains fine powder
mica.
[0009]
In a further preferred embodiment, the thermoplastic resin composition contains 5 to 20 parts
by weight of the fine powder mica with respect to 100 parts by weight of the poly (trimethylene
terephthalate).
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION The speaker diaphragm of the present
invention is formed of a thermoplastic resin composition containing poly (trimethylene
terephthalate) (PTT) as a main component.
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[0011]
PTT is represented by the following chemical formula.
[0012]
[Chem. 1]
[0013]
The weight average molecular weight of PTT is preferably 1 × 10 4 to 5 × 10 4, more
preferably 2 × 10 4 to 3 × 10 4.
PTT is obtained by condensation polymerization of aliphatic propanediol (trimethylene diol) and
terephthalic acid.
[0014]
The thermoplastic resin composition used in the present invention contains PTT as a main
component.
As used herein, main component
weight or more in the composition.
means a component contained in an amount of 50% by
Therefore, in the present specification, the term "thermoplastic resin composition" includes not
only a composition containing 50% by weight or more of PTT but also PTT itself.
[0015]
Preferably, the thermoplastic resin composition may further contain fine powder mica.
By containing fine powder mica, Young's modulus, specific modulus and internal loss can be
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further improved.
The finely divided mica preferably has a particle size of 3 to 5 μm.
The fine powder mica can be contained in the thermoplastic resin composition in a proportion of
preferably 5 to 20 parts by weight, more preferably 10 to 15 parts by weight with respect to 100
parts by weight of PTT.
If the content is less than 5 parts by weight, the improvement effect may be insufficient.
If it exceeds 20 parts by weight, the density becomes too large compared to the improvement
effect.
[0016]
Furthermore, the thermoplastic resin composition may contain any suitable additive (eg, colorant,
antioxidant, mold release agent, antiaging agent, light stabilizer) depending on the purpose.
[0017]
The speaker diaphragm of the present invention may be used for any suitable speaker, but in
particular, it may be suitably used for a speaker of a portable device.
[0018]
The diaphragm for a speaker of the present invention can be obtained by molding the above
thermoplastic resin composition by any appropriate method (for example, after film forming the
above thermoplastic resin composition by T-die extrusion) , Obtained by hot press molding).
T-die extrusion and hot pressing may be performed under any suitable conditions.
[0019]
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The operation of the present invention will be described below.
According to the present invention, by using a thermoplastic resin composition containing PTT as
a main component, a speaker diaphragm having excellent water resistance and internal loss can
be obtained.
PTT is similar to PET in chemical structure and has similar water resistance to PET.
In addition, the glass transition temperature of PTT is 45 ° C., which is lower than that of PET
(80 ° C.). As a result, PTT has the following advantages. In general, since the internal loss of a
polymer material is maximum near the glass transition temperature, PTT having a glass
transition temperature near normal temperature has a significantly larger internal loss near
normal temperature than PET. Therefore, PTT is very good as a diaphragm material. In a
preferred embodiment, the thermoplastic resin composition further contains fine powder mica.
Young's modulus and internal loss are significantly improved by using PTT and fine powder mica
in combination. Furthermore, PTT can improve Young's modulus simply and inexpensively
because the improvement of Young's modulus by the addition of mica is remarkable as compared
with PET.
[0020]
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.
[0021]
Example 1 A 50 μm thick film was produced by extrusion molding with a T-die using a PTT
resin composition (CORTERRA (Natural) manufactured by Shell Chemical Co., Ltd.). The obtained
film was heat-pressed for about 30 seconds with a matched die mold (dome shape, mold
temperature 160 ° C.) to obtain a dome-shaped diaphragm (φ 25). The Young's modulus, the
density, the specific elastic modulus and the internal loss of the obtained diaphragm were
measured by a conventional method. The results are shown in Table 1 below together with the
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results of Examples 2 to 4 and Comparative Examples 1 to 2 described below.
[0022]
[Table 1]
[0023]
Example 2 The same procedure as in Example 1 was performed except that 5 parts by weight of
fine mica powder (manufactured by Coop Chemical Co .; micro mica MK100DS (average particle
diameter 4 μm)) was added to 100 parts by weight of PTT resin. Thus, a dome-shaped
diaphragm (φ25) was obtained.
The obtained diaphragm was subjected to the same evaluation as in Example 1. The results are
shown in Table 1 above.
[0024]
EXAMPLE 3 A dome-shaped diaphragm (φ 25) was obtained in the same manner as in Example
1 except that 10 parts by weight of mica fine powder was added to 100 parts by weight of PTT
resin. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results
are shown in Table 1 above.
[0025]
EXAMPLE 4 A dome-shaped diaphragm (φ25) was obtained in the same manner as in Example 1
except that 20 parts by weight of mica fine powder was added to 100 parts by weight of PTT
resin. The obtained diaphragm was subjected to the same evaluation as in Example 1. The results
are shown in Table 1 above.
[0026]
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Comparative Example 1 A dome-shaped diaphragm (φ 25) was obtained in the same manner as
in Example 1 except that a PET resin was used instead of the PTT resin composition. The
obtained diaphragm was subjected to the same evaluation as in Example 1. The results are shown
in Table 1 above.
[0027]
Comparative Example 2 A dome-shaped diaphragm (φ25) was obtained in the same manner as
in Comparative Example 1 except that 20 parts by weight of mica fine powder was added to 100
parts by weight of PET resin. The obtained diaphragm was subjected to the same evaluation as in
Example 1. The results are shown in Table 1 above.
[0028]
Referring to Table 1, it can be seen that the diaphragm of the present invention has an internal
loss close to twice that in the case of using PET, and is very excellent as a diaphragm.
Furthermore, since the diaphragm of the present invention significantly improves Young's
modulus when mica is added, it is possible to obtain a diaphragm excellent in both internal loss
and Young's modulus by using PTT and mica in combination. Recognize.
[0029]
As described above, according to the present invention, by using PTT, a speaker diaphragm can
be obtained inexpensively and excellent in water resistance and internal loss.
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