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JP2008205974

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2008205974
When a thermoplastic material is used as a speaker diaphragm, balance with heat resistance can
be obtained without significantly changing formability, and moreover, necessary internal loss and
smooth frequency characteristics can be obtained. A speaker diaphragm of the present invention
has a three-layer resin structure of a resin speaker diaphragm made of a thermoplastic polymer
material. That is, a polyethylene terephthalate (PET) layer 22 was used as a polyester film as a
polyester film having a three-layer structure, and polyimide (PI) layers 21 and 23 were used as
polyimide resins for the surface and back layers having a three-layer structure. [Selected figure]
Figure 2
Speaker diaphragm
[0001]
The present invention relates to a diaphragm for a speaker (hereinafter referred to as a speaker
diaphragm) capable of reproducing an audio signal.
[0002]
Heretofore, there has been a tweeter speaker diaphragm which has a high frequency band, which
first uses an acoustic diaphragm material having a large elastic modulus for the purpose of
improving frequency characteristics.
Thus, the divided vibration start frequency can be shifted as high as possible using the large
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elastic modulus of the acoustic diaphragm material itself having a large elastic modulus.
[0003]
For this reason, ceramic materials such as silicon carbide (SiC), carbon graphite, and titanium
oxide are used as the acoustic diaphragm material of the speaker diaphragm. In addition, metal
materials such as aluminum and titanium are used.
[0004]
Second, there is one using an acoustic diaphragm material having a small elastic modulus by
devising the shape and structure of the speaker diaphragm. Thereby, even if the acoustic
diaphragm material having a small elastic modulus is used, the elastic modulus can be secured by
devising the shape and the structure of the speaker diaphragm. Therefore, the divided vibration
start frequency can be shifted as high as possible. The above means are adopted.
[0005]
In addition, a technique for forming a speaker diaphragm using a polyimide foam has been
proposed. In this technique, a polyimide foam, which is an object to be molded, formed in a block
shape of a predetermined thickness is heated and pressurized using a mold (see Patent
Document 1). According to this, it is possible to obtain a speaker diaphragm which is light in
weight (low density), excellent in environmental resistance, high in internal loss, and easily
formed and having a high degree of freedom in shape design. Unexamined-Japanese-Patent No.
2002-374593
[0006]
Here, there is an internal loss in the operating characteristic of the speaker diaphragm. The
internal loss is a value indicating the degree of absorbing sound energy. A speaker diaphragm
made of a ceramic material or a metal material has a very small internal loss of 0.01 or less.
11-05-2019
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[0007]
For this reason, in the sound pressure characteristics in the frequency band in which the divided
vibration occurs, the generation bands of peaks and dips become sharp due to the influence of
the divided vibration. Moreover, there is a disadvantage that the occurrence values of the peak
and the dip become large.
[0008]
Also, by using a material having a relatively large internal loss, it is possible to suppress the
occurrence of peaks and dips. In addition to this, there is adopted a method capable of
reproducing an acoustic signal up to a high frequency by reviewing the shape of the speaker
diaphragm.
[0009]
In this method, it is important to be able to form and hold the diaphragm material in a
predetermined shape in order to exhibit acoustic performance. A polymer material is often used
as a material having a relatively large internal loss. However, among polymer materials,
particularly with thermoplastic materials, there is a disadvantage that ease of molding and heat
resistance are contradictory results.
[0010]
Here, the glass transition point is a characteristic property of the thermoplastic material. The
glass transition point is a value indicating a boundary point of temperature at which the property
of the material changes in hardness. When it exceeds the glass transition point, the material
softens and becomes liquid.
[0011]
It is conceivable to use, for example, polyethylene terephthalate (hereinafter referred to as PET)
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having a relatively low glass transition point as a speaker diaphragm material. When using PET,
good acoustic characteristics can be obtained during initial operation. However, when the
operation is performed for a long time, the heat generated from the bobbin coil is transferred to
the PET. As a result, the shape of the initial PET can not be maintained, and predetermined
acoustic characteristics can not be obtained. Therefore, the input resistance is limited.
[0012]
Moreover, the method of using a material with a comparatively high glass transition point is also
considered. For example, when polyimide is used, it is necessary to set the molding temperature
to the glass transition point or higher. For this reason, since temperature rising and cooling time
take at the time of shaping | molding, productivity is inferior. As a result, the cost of the
diaphragm increases. Also, the film itself is more expensive than PET and the like. Furthermore,
the internal loss is lower than that of the PET material, and approaching the characteristics of the
metal material brings about the disadvantage that the occurrence of peaks and dips becomes
large.
[0013]
In addition, when a single polyimide is used as the material of the speaker diaphragm as in the
technique described in Patent Document 1 described above, the molding temperature is as high
as 300 ° C., which complicates the manufacturing process. In addition, since the internal loss is
low, the required operating characteristics can not be obtained. Furthermore, there is a
disadvantage that it is difficult to form a uniform polyimide foam.
[0014]
Therefore, in the present invention, when a thermoplastic material is used as the speaker
diaphragm, the speaker diaphragm can achieve balance between heat resistance without
significantly changing formability, and can obtain necessary internal loss and smooth frequency
characteristics. It is intended to be provided.
[0015]
In order to achieve the above object according to the present invention, according to the present
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invention, a polyester diaphragm is used as a substrate of a three-layer structure in which the
resin of the resin speaker diaphragm made of a thermoplastic polymer material has a three-layer
structure. The polyimide resin is used for the surface layer and back layer of 3 layer structure
used.
In the present invention, since a material obtained by coating polyimide having good heat
resistance with a polyester film having good formability is used, the frequency characteristics are
smoothed while heat resistance is improved.
[0016]
At this time, the setting of the thickness of the base of the three-layer structure, the surface layer
of the three-layer structure, and the thickness of the back layer is set based on the manufacturing
process and molding temperature at the time of molding of the three-layer speaker diaphragm.
Further, it is set based on the internal loss at the time of operation of the speaker diaphragm and
the frequency characteristic. In addition, it is set based on the elastic modulus at the time of
temperature rise of the speaker diaphragm.
[0017]
Moreover, the polyimide-type resin used for the surface layer and back layer of 3 layer structure
is a polyimide or a polyether imide, and a polyester film applies a polyethylene terephthalate or a
polybutylene terephthalate.
[0018]
According to the experiments, the optimum values for the thickness of the three-layer substrate,
the surface and back layers of the three-layer structure are the thickness of the polyester film of
the three-layer substrate when the total thickness of the three-layer structure is 50 microns. Is
38 microns, and the thickness of the polyimide resin of the surface layer and the back layer of
the three-layer structure is 6 microns.
[0019]
As explained above, the speaker using the diaphragm of the present invention uses a polyester
film as the base of the three-layer structure, and uses a polyimide resin as the surface layer and
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the back layer of the three-layer structure.
As a result, the heat resistance can be improved, so that the moldability can be improved
simultaneously with the improvement of the input resistance.
[0020]
Therefore, the shape of the speaker diaphragm can be maintained when the temperature rises.
For this reason, the internal loss required at the time of operation | movement of a speaker
diaphragm is obtained, and the effect that it becomes smooth and favorable also about a
frequency characteristic is acquired.
[0021]
Hereinafter, an embodiment of the present invention will be described in detail with reference to
FIGS. FIG. 1 is an explanatory view of a speaker vibration portion of the speaker device. As shown
in FIG. 1, the speaker vibration part is provided to constitute a speaker unit.
[0022]
In FIG. 1, the cone to be the speaker diaphragm 1 needs to be thin, light and strong in order to
facilitate movement. Furthermore, in order to reduce peaks and valleys of the frequency
characteristic and transient characteristics, it should be such as to give a moderate loss called
internal loss.
[0023]
That is, this internal loss indicates the degree of absorption of the energy of the sound produced
from the speaker diaphragm 1. As an operation characteristic of the speaker diaphragm 1, a
constant internal loss is required.
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[0024]
The magnetic circuit of the speaker device includes a doughnut-shaped magnet 5, first and
second magnetic yokes made of a magnetic material such as iron, and a magnetic gap. The first
magnetic yoke comprises a cylindrical center pole 4 and a disk-shaped flange 5 orthogonal to the
center pole 4.
[0025]
The second magnetic yoke is called a plate 9. The plate 9 has a donut shape whose inner
diameter is larger than the outer diameter of the center pole 4 by the amount of the magnetic
gap. Then, the center pole 4 is inserted into the inner peripheral hollow portion of the magnet 6
and the inner peripheral hollow portion of the plate 9.
[0026]
In this state, the magnet 6 is sandwiched and attached by the upper surface of the flange 5 and
the lower surface of the plate 9. The upper surface of the flange 5 and the lower surface of the
plate 9 and the contact portion between the magnet 6 are bonded by an adhesive.
[0027]
The speaker diaphragm 1 is composed of a dome portion 2 and an edge portion 3. That is, the
dome portion 2 is located at the central portion, and its cross-sectional shape is substantially arcshaped. Further, the edge portion 3 is located on the outer peripheral side of the dome portion 2
through the connecting portion. The dome portion 2 and the edge portion 3 are integrally
formed.
[0028]
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Then, the upper end portion of the cylindrical voice coil bobbin 8 made of a non-conductive
material is adhered and fixed to the inner peripheral edge portion of the dome portion 2 of the
speaker diaphragm 1 with an adhesive. At the same time, the voice coil 7 wound at a
predetermined position of the voice coil bobbin 8 is disposed to be inserted into the magnetic
gap between the plate 9 and the center pole 4. Further, the outer peripheral end of the edge
portion 2 of the speaker diaphragm 1 is bonded and fixed to the speaker frame 10 by an
adhesive.
[0029]
In the speaker device as shown in FIG. 1, by supplying an acoustic signal to the voice coil 7, a
current flows in the voice coil 7. Therefore, due to the electromagnetic induction interaction
between the current flowing through the voice coil 7 and the magnetic flux of the magnetic gap,
the speaker diaphragm 1 vibrates and emits sound.
[0030]
FIG. 2 is a cross-sectional view of the speaker diaphragm. FIG. 2 shows a partially enlarged crosssectional view of the speaker diaphragm 1 shown in FIG. In FIG. 2, the resin configuration of the
resin speaker diaphragm made of a thermoplastic polymer material has a three-layer structure.
Specifically, a polyester film of a polyethylene terephthalate (PET) layer 22 is used as the base of
the three-layer structure.
[0031]
And the coating film of polyimide (PI) layers 21 and 23 is used for the surface layer and back
layer of 3 layer structure. That is, on both sides of the polyester film of the polyethylene
terephthalate (PET) layer 22 as the base material, the coating films of the polyimide (PI) layers
21 and 23 are coated in a thin film shape.
[0032]
As described above, the polyester film of the polyethylene terephthalate (PET) layer 22 is used as
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the substrate because the moldability of the polyethylene terephthalate (PET) in the
manufacturing process is good. Moreover, the coating film of polyimide (PI) layers 21 and 23 is
used for surface layer and a back layer because the heat resistance of polyimide (PI) at the time
of temperature rise is favorable.
[0033]
Thus, the material which coated the coating film of the polyimide (PI) layers 21 and 23 on the
polyester film of the polyethylene terephthalate (PET) layer 22 was used for the speaker
diaphragm. For this reason, the characteristic of the internal loss of polyethylene terephthalate
(PET) can be approximated while heat resistance is improved. In addition, frequency
characteristics can be smoothed.
[0034]
At this time, the base of the three-layer structure, the surface layer of the three-layer structure,
and the process of manufacturing the speaker diaphragm of the three-layer structure are the
same as the manufacturing process of the speaker diaphragm of the single polyester film. The
thickness of the back layer is set.
[0035]
In addition, the base material of the three-layer structure, the surface layer of the three-layer
structure, and the back so that the molding temperature at the time of molding of the three-layer
speaker diaphragm becomes the same temperature as the molding temperature of the polyester
diaphragm single-piece speaker diaphragm. The thickness of the layer is set.
[0036]
In addition, the base material of the three-layer structure, the three-layer structure, so that the
internal loss at the time of operation of the three-layer speaker diaphragm has characteristics
near the characteristics of the internal loss of the polyester film single speaker diaphragm. The
thicknesses of the surface layer and the back layer are set.
[0037]
Also, the base material of the three-layer structure is such that the frequency characteristics at
the time of operation of the speaker diaphragm of the three-layer structure have a characteristic
that the peak and dip are lower than the frequency characteristics of the speaker diaphragm of a
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single polyester film The thicknesses of the surface layer and the back layer of the layer structure
are set.
[0038]
In addition, the elastic modulus of the three-layer speaker diaphragm at the time of temperature
rise has a characteristic of maintaining the elastic modulus at the temperature increase when the
elastic modulus of the polyester diaphragm of the single speaker film decreases. The thicknesses
of the base material, the surface layer and the back layer of the three-layer structure are set.
[0039]
Moreover, the coating film used for the surface layer and back layer of 3 layer structure should
just be a polyimide-type resin.
For example, polyimide (PI) or polyetherimide (PEI) is applied as a coating film.
In addition, polyethylene terephthalate (PET) or polybutylene terephthalate (PBT) is applied as
the polyester film.
[0040]
Hereinafter, embodiments of the present invention will be described based on specific
experimental results.
The speaker device was assembled so as to have the configuration shown in FIG. 1 described
above.
The speaker diaphragm was molded to have a fixed shape.
As a method of forming the speaker diaphragm, press forming, pressure air forming, etc. may be
mentioned. In any of the molding methods, a mold heated at a molding temperature is used, and
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cooling is gradually performed while maintaining the shape. Thereby, the shape of the speaker
diaphragm can be obtained. This shape indicates a shape that conforms to a predetermined
specification.
[0041]
FIG. 3 is a view showing the optimum thickness of the cone of the speaker diaphragm. In FIG. 3,
the value of the optimum thickness 32 of the member 31 of the three-layer structure was found
by experiments. This is an optimum value when using a polyethylene terephthalate (PET) layer
34 as a substrate and using a polyimide (PI) layer 35 as a coating film of the surface layer and
the back layer having a three-layer structure.
[0042]
That is, the case where the total thickness of the three-layered cone whole 33 was 50 μm was
optimum. At this time, it was optimal that the thickness of the polyethylene terephthalate (PET)
layer 34 of the three-layer base material was 38 μm. In addition, the thickness of the polyimide
(PI) layer 35 of the surface layer and the back layer of the three-layer structure was 6 μm,
respectively.
[0043]
The characteristics of the speaker diaphragm having such an optimum thickness will be
described below. FIG. 4 is a view showing the characteristics of polyethylene terephthalate (PET)
coated with polyimide (PI). In FIG. 4, the properties of polyethylene terephthalate (PET) with a
polyimide (PI) coat include the properties at the time of molding 42, the properties at the time of
operation 45, and the properties at the time of temperature deformation.
[0044]
First, the characteristics at the time of molding 42 include the molding temperature 43 and the
manufacturing process 44. Here, the molding temperature 43 is the same temperature as
polyethylene terephthalate (PET). Also, the manufacturing process 44 is the same manufacturing
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process as polyethylene terephthalate (PET).
[0045]
Next, the characteristics during operation 45 include an internal loss 46 and a frequency
characteristic 47. Here, the internal loss 46 is a characteristic closer to the characteristic of
polyethylene terephthalate (PET). The characteristics that are close to each other indicate that
the internal loss 46 can be obtained to the required extent. Also, the frequency characteristic 47
is a characteristic in which the peak and the dip are lower than that of polyethylene
terephthalate (PET).
[0046]
And, the characteristics during temperature deformation 48 include shape maintenance 49 and
heat resistance 50. Here, the shape maintenance 49 is a characteristic that can maintain the
shape at a constant temperature for 100 hours. Further, the heat resistance 50 has a
characteristic that the degree of softening after softening is difficult to soften.
[0047]
FIG. 5 is a diagram showing the temperatures of molding, operation and thermal deformation. In
FIG. 5, for example, in the molding area 51 at the time of molding, the temperature is a molding
temperature range 54 shown by T3 which is a glass transition point to T4 which is a relatively
high temperature. The molding temperature range 54 is a temperature range that facilitates
molding. Therefore, a member and thickness adapted to the temperature in the molding
temperature range 54 are required.
[0048]
Further, in the normal operable region 52, the temperature is in the operable temperature range
55 indicated by the relatively low temperature T1 to the glass transition point T3. This operable
temperature range 55 is a temperature range in which the required operating characteristics can
be obtained. Therefore, a member and thickness adapted to the temperature in the operable
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temperature range 55 are required.
[0049]
Then, in the thermally deformed region 53, the temperature becomes a thermally deformed
temperature range 56 indicated by T3 which is a glass transition point to T4 which is a relatively
high temperature. The heat deformation temperature range 56 is a temperature range in which
heat resistance can be obtained by maintaining the shape even when the temperature rises.
Therefore, a member and thickness adapted to the temperature are required in this heat
distortion temperature range 56.
[0050]
The evaluation of the operation characteristics was performed below using two film members
(thicknesses) as the material of the speaker diaphragm. The first film member is a polyethylene
terephthalate (PET) film (50 μm thick) alone. Hereinafter, the first film member is referred to as
a PET film.
[0051]
The second film member is a polyethylene terephthalate (PET) film (50 μm thick) coated with
polyimide (PI). Hereinafter, the second film member is referred to as a PI-coated PET film.
[0052]
The relationship between the internal loss and the frequency of the PET film and the PI-coated
PET film is shown below in comparison. First, the relationship between the internal loss of the
PET film and the frequency is shown. FIG. 6 is a view showing the relationship between the
internal loss of the PET film and the frequency. In FIG. 6, the internal loss is shown as a relative
value.
[0053]
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In FIG. 6, at point 61, the internal loss is 0.02 at a frequency of 170 Hz. At point 62, the internal
loss is 0.025 at a frequency of 1000 Hz. At point 63, the internal loss is 0.03 at a frequency of
3000 Hz. At point 64, the internal loss is 0.035 at a frequency of 5600 Hz.
[0054]
At point 65, the internal loss is 0.04 at a frequency of 9500 Hz. At point 66, the internal loss is
0.043 at a frequency of 15000 Hz. At point 67, the internal loss is 0.043 at a frequency of
20000 Hz. At point 68, the internal loss is 0.06 at a frequency of 26000 Hz. The internal loss
characteristics of this PET film provide the internal loss necessary for the operation of the
speaker diaphragm.
[0055]
FIG. 7 is a diagram showing frequency characteristics of a speaker device using a speaker
diaphragm of PET film. FIG. 7 shows the characteristics at normal temperature (20 to 25 ° C.).
In FIG. 7, a dip 71 is generated at a frequency of 2 k [Hz]. The dip 72 is also generated at a
frequency of 5 k [Hz]. A peak 73 occurs at a frequency of 6 k [Hz]. Furthermore, a peak 74
occurs at a frequency of 25 k [Hz]. The dip 75 is generated at the frequency of 30 k [Hz]. In the
frequency characteristic of this PET film, the smooth frequency characteristic necessary for the
operation of the speaker diaphragm is not obtained.
[0056]
FIG. 8 is a diagram showing the relationship between internal loss and frequency of PI-coated
PET film. Also in FIG. 8, the internal loss is shown as a relative value. In FIG. 8, at point 81, the
internal loss is 0.02 at a frequency of 170 Hz. The point 81 corresponds to the point 61 shown
in FIG. 6, and the necessary internal loss is obtained.
[0057]
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At point 82, the internal loss is 0.019 at a frequency of 900 Hz. Point 82 corresponds to point 62
shown in FIG. 6, and the required internal loss is not obtained. However, an internal loss close to
point 62 is obtained. At point 83, the internal loss is 0.022 at a frequency of 2600 Hz. Point 83
corresponds to point 63 shown in FIG. 6, and the required internal loss is not obtained. However,
an internal loss close to point 63 is obtained.
[0058]
At point 84, the internal loss is 0.025 at a frequency of 5000 Hz. Point 84 corresponds to point
64 shown in FIG. 6, and the required internal loss is not obtained. However, an internal loss close
to point 64 is obtained. Also, at point 85, the internal loss is 0.026 at a frequency of 9000 Hz.
Point 85 corresponds to point 65 shown in FIG. 6, and the required internal loss is not obtained.
However, an internal loss close to point 65 is obtained.
[0059]
At point 86, the internal loss is 0.03 at a frequency of 14000 Hz. Point 86 corresponds to point
66 shown in FIG. 6, and the required internal loss is not obtained. However, an internal loss close
to point 66 is obtained. At point 87, the internal loss is 0.032 at a frequency of 18000 Hz. Point
87 corresponds to point 67 shown in FIG. 6, and the required internal loss is not obtained.
However, an internal loss close to point 67 is obtained.
[0060]
At point 88, the internal loss is 0.026 at a frequency of 25000 Hz. Point 84 corresponds to point
64 shown in FIG. 6, and the required internal loss is not obtained. At point 89, the internal loss is
0.046 at a frequency of 30000 Hz. At point 90, the internal loss is 0.048 at a frequency of
38000 Hz. At point 91, the internal loss is 0.042 at a frequency of 56000 Hz. At point 92, the
internal loss is 0.03 at a frequency of 66000 Hz. In the characteristic of the internal loss of the
PI-coated PET film, the internal loss necessary for the operation of the speaker diaphragm is
obtained in the high frequency band.
[0061]
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FIG. 9 is a diagram showing frequency characteristics of a speaker apparatus using a speaker
diaphragm of PI-coated PET film. FIG. 9 shows the characteristics at normal temperature (20 to
25 ° C.). In FIG. 9, the dip 93 is smoothly eliminated when the frequency is 2 k [Hz]. The dip 93
corresponds to the dip 71 shown in FIG.
[0062]
When the frequency is 5 k [Hz], the dip 94 is lowered. The dip 94 corresponds to the dip 72
shown in FIG. At frequency 6 k [Hz], a peak 95 is generated. The peak 95 corresponds to the
peak 73 shown in FIG.
[0063]
Furthermore, at the frequency of 25 k [Hz], the peak 96 is eliminated smoothly. The peak 96
corresponds to the peak 74 shown in FIG. At the frequency of 30 k [Hz], the dip 97 is eliminated
smoothly. The dip 97 corresponds to the dip 75 shown in FIG. In the frequency characteristic of
this PET film, the smooth frequency characteristic necessary for the operation of the speaker
diaphragm is obtained.
[0064]
As described above, the PI-coated PET film shown in FIG. 8 has a slightly lower value of internal
loss than the PET film shown in FIG. However, it can be seen that the value of internal loss by the
PI-coated PET film is close to the value of internal loss by the PET film. Therefore, the two films
are assembled as a speaker apparatus using the speaker diaphragm, and what kind of influence is
produced at the time of actual sound emission is confirmed by the frequency characteristics of
FIG. 7 and FIG.
[0065]
From this, it can be seen that in the PI-coated PET film shown in FIG. 9, the peaks and dips on the
frequency characteristics are smaller than the peaks and dips of the PET film shown in FIG.
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Accordingly, it can be seen that the frequency characteristics of the PI-coated PET film are
smoother than those of the PET film.
[0066]
The speaker diaphragm used in the examination of the above-described experimental example is
a balance dome type diaphragm having an outer diameter of 25 mm and a thickness of 0.05 mm
as shown in FIG. As shown in FIG. 1, it was made into a predetermined shape by press molding.
The voice coil uses φ13, a polyimide bobbin, the voice coil wire uses φ0.07, and the number of
turns is adjusted so that the impedance is 6Ω. The film used for the diaphragm was a PI-coated
PET film coated on both sides with polyimide.
[0067]
The frequency was measured using a speaker diaphragm using a PI-coated PET film pressmolded in this manner. As a result, in the speaker diaphragm using the PI coated PET film, the
value and the width of the peak and the dip are reduced as compared with the single PET film
product of the comparative product. The number of peaks and dips also decreases. This indicates
that the effect of the present embodiment is occurring.
[0068]
FIG. 10 is a view showing the relationship between storage elastic modulus and voice coil
temperature of a speaker diaphragm of a PET film and a speaker diaphragm of a PI-coated PET
film. In FIG. 10, dynamic viscoelasticity is measured for a speaker diaphragm of a PET film and a
speaker diaphragm of a PI-coated PET film, and the temperature dependency of the storage
elastic modulus is measured. That is, when a certain vibration is applied to one end of the
diaphragm, the degree of elastic response transmitted to the other end is measured for each
temperature change.
[0069]
In FIG. 10, the temperature range up to 140 ° C. is the normal use range. In this range, a storage
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modulus of at least a certain value is required. Here, for example, a storage elastic modulus of
about 700 to 800 [Mpa] is required. However, in consideration of further temperature rise, it is
desirable to secure the above-mentioned storage elastic modulus even in the temperature range
of 140 ° C. to 175 ° C.
[0070]
When the speaker diaphragm of the PET film 101 is used, a storage elastic modulus of about 700
to 800 [Mpa] can be obtained in the temperature range up to 140 ° C. However, in the
temperature range of 150 ° C. to 175 ° C., only a storage elastic modulus of about 600 to 450
[Mpa] can be obtained.
[0071]
Then, when the speaker diaphragm of PI coated PET film 102 is used, a storage elastic modulus
of about 700 to 800 [Mpa] which is lower than that of PET film 101 can be obtained in the
temperature range of 100 ° C. to 140 ° C. . Furthermore, in the temperature range of 150 ° C.
to 175 ° C., it is possible to raise the decreasing property of the PET film 101 to a storage
elastic modulus of about 700 to 650 [Mpa].
[0072]
As a result, in the temperature range of 100 ° C. to 140 ° C., the PI-coated PET film 102 is
softer, but after 150 ° C., the decrease in elastic modulus is smaller than that of the PET film
101. Thereby, it turns out that the effect of the heat resistant improvement by polyimide coating
is appearing.
[0073]
Furthermore, a durability test was conducted using a speaker diaphragm of PI-coated PET film
102. The test conditions are as follows. Input: 130 W (6 Ω conversion), time: 100 h, signal: DIN
2 noise (random noise signal) conditions.
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[0074]
The voice coil temperature under this test condition is a maximum of 140 ° C. After the test, the
speaker diaphragm of PI coated PET film 102 kept its initial shape and there was no problem,
but with the normal PET film 101, which is a comparative product, the initial shape could not be
maintained and it was flat It was deformed. Together with the results of dynamic viscoelasticity,
it was found that the effect of improving the heat resistance was more effective than in the past
by the effect of improving the heat resistance.
[0075]
In addition, another embodiment will be described below. FIG. 11 is a cross-sectional view of
another speaker diaphragm. FIG. 11 shows a partially enlarged cross-sectional view of the
speaker diaphragm 1 shown in FIG. In FIG. 11, the resin configuration of the resin speaker
diaphragm made of a thermoplastic polymer material has a three-layer structure. Specifically, a
polyester film of polybutylene terephthalate (PBT) layer 112 is used as the base material of the
three-layer structure.
[0076]
And the coating film of the polyether imide (PEI) layers 111 and 113 is used for the surface layer
and back layer of 3 layer structure. That is, on both sides of the polyester film of the
polybutylene terephthalate (PBT) layer 112 as the base material, the coating films of the
polyetherimide (PEI) layers 111 and 113 are coated in a thin film.
[0077]
Thus, using the polyester film of the polybutylene terephthalate (PBT) layer 112 for a base
material is because the moldability of the polybutylene terephthalate (PBT) in a manufacturing
process is favorable. Moreover, the coating film of the polyether imide (PEI) layers 111 and 113
is used for surface layer and a back layer because the heat resistance of the polyether imide (PEI)
at the time of temperature rise is favorable.
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[0078]
As described above, a material obtained by coating the coating film of the polyetherimide (PEI)
layers 111 and 113 on the polyester film of the polybutylene terephthalate (PBT) layer 112 was
used for the speaker diaphragm. For this reason, it is possible to approximate the characteristics
of the internal loss of polybutylene terephthalate (PBT) while improving the heat resistance. In
addition, frequency characteristics can be smoothed.
[0079]
FIG. 12 is a view showing the optimum thickness of the cone of another speaker diaphragm. In
FIG. 12, the value of the optimum thickness 122 of the member 121 of the three-layer structure
was found by experiments. This is the optimum value when using a polybutylene terephthalate
(PBT) layer 124 as a substrate and using a polyetherimide (PEI) layer 125 as a coating film for
the surface and back layers of the three-layer structure.
[0080]
That is, the case where the total thickness of the whole three-layer cone 123 was 50 μm was
optimum. At this time, the case where the thickness of the polybutylene terephthalate (PBT) layer
124 of the three-layer base material is 38 μm was optimum. The optimum thickness was 6 μm
for each of the three-layered polyetherimide (PEI) layer 125 of the surface layer and the back
layer. Even when the other speaker diaphragms shown in FIGS. 11 and 12 are used, the same
operation characteristics as those of the above-described embodiment can be obtained.
[0081]
Needless to say, the present invention is not limited to the above-described embodiment, and
may be modified as appropriate without departing from the scope of the present invention
described in the claims.
[0082]
11-05-2019
20
It is explanatory drawing of the speaker vibration part of the speaker apparatus by one
embodiment of this invention.
It is a sectional view of a speaker diaphragm. It is a figure which shows the optimal thickness of
the cone of a speaker diaphragm. It is a figure which shows the characteristic of the polyethylene
terephthalate (PET) by a polyimide (PI) coat | court. FIG. 5 illustrates the temperatures of
molding, operational and thermal deformation. It is a figure which shows the relationship
between the internal loss of a PET film, and a frequency. It is a figure which shows the frequency
characteristic of the speaker apparatus using the speaker diaphragm of a PET film. It is a figure
which shows the relationship between the internal loss of PI coating PET film, and a frequency. It
is a figure which shows the frequency characteristic of the speaker apparatus using the speaker
diaphragm of PI coat PET film. It is a figure which shows the relationship of the storage elastic
modulus and voice coil temperature of the speaker diaphragm of PET film and the speaker
diaphragm of PI coat PET film. It is sectional drawing of another speaker diaphragm. It is a figure
which shows the optimal thickness of the cone of other speaker diaphragms.
Explanation of sign
[0083]
DESCRIPTION OF SYMBOLS 1 ... Speaker diaphragm, 2 ... dome part, 3 ... edge part, 4 ... center
pole, 5 ... flange, 6 ... magnet, 7 ... voice coil, 8 ... bobbin, 9 ... plate, 10 ... frame, 21, 23, ...
Polyimide (PI) layer, 22: polyethylene terephthalate (PET) layer, 31: member, 32: optimum
thickness, 33: whole cone, 34: polyethylene terephthalate (PET) layer, 35: polyimide (PI) layer,
41: PI coat Characteristics of PET film, 42: molding, 43: molding temperature, 44: manufacturing
process, 45: operation, 46: internal loss, 47: frequency characteristic, 48: temperature
deformation, 49: shape retention, 50: heat resistance
11-05-2019
21
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