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JPH02158298

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DESCRIPTION JPH02158298
[0001]
[Industrial field of application] The present invention relates to a so-called soft dome diaphragm
obtained by forming a diaphragm base fabric made of a woven fabric of natural fibers or
synthetic fibers into a predetermined shape. [Background Art] As a dome diaphragm of an
electroacoustic transducer, a so-called soft dome diaphragm is known which is formed by
forming a diaphragm base fabric made of a woven fabric of natural fibers or synthetic fibers into
a predetermined dome shape. This type of diaphragm is flexible enough to maintain its shape
against vibration and has a large vibration loss rate to suppress resonance (--generally, one with
a + haδ of about 0.06 or more is often used Materials are used. Also, it is used for high
frequency range as well as hard dome diaphragm made of metal such as aluminum and titanium,
and voice coil bobbin and magnetic coil due to inclination or abnormal resonance of voice coil
bobbin due to deformation of dome and edge of diaphragm. Since a plate portion forming a gap
is in contact and an abnormal sound is easily generated, it is required that the deformation due to
humidity, heat or the like is small. In response to these requirements, a diaphragm base fabric
conventionally made of a woven fabric of natural fibers such as cotton and silk is impregnated
with a shape-imparting material such as a phenol resin, an epoxy resin, or a melamine resin to
form a dome A film of vibration loss material resin such as acrylic resin and urethane resin is
formed on the surface of diaphragm base fabric made of woven fabric of thermoplastic polymer
fiber such as polyester or nylon, then it is heated and pressed to form dome shape The ones of
the molded structure are known. However, since the former uses natural fibers, the hygroscopic
deformation is large, and the latter is superior in hygroscopic resistance to the former but is not
sufficient yet, and the thermal deformation is large. is there. And, even in the case of the latter
structure using an acrylic resin as the vibration loss material resin, it is insufficient in terms of
moisture resistance, heat resistance, oil resistance, etc., particularly in applications such as
automotive and musical instruments. In the latter case, the heat and pressure molding conditions
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are high temperature (about 195 to 205 ° C.), and the vibration loss material resin (acrylic
resin) adheres to the molding die, so this molding die is a fluorocarbon resin, A release agent
such as silicone resin must be applied for each molding, and there is a problem in mass
productivity, and transfer transfer of the release agent to the surface of the vibration loss
material resin occurs, as shown in FIG. The electrodynamic speaker having the structure as
shown has problems such as adhesion failure of the lead portion 6a of the voice coil 6 and the
like. Therefore, in recent years, as shown in FIG. 8 for the purpose of improving the moisture
resistance, heat resistance and oil resistance, in JP-A-59-6558, JP-A-61-225998 and JP-A61267499. A structure in which the fluorine resin film 4 is formed on the surface of the base
fabric 1 via the acrylic resin layer 3 or a structure in which the fluorine resin film is directly
formed on the surface of the base fabric without the acrylic resin layer Has been proposed.
[Problems to be Solved by the Invention] However, although the above-mentioned fluorocarbon
resin film is heat resistant, has good mold releasability and has an advantage in production, it is
relatively inactive chemically. There is almost no adhesion to other members. Therefore, in an
actual electroacoustic transducer, for example, an electrodynamic speaker, there are the
following problems. As shown in FIG. 8, the lead portion 6 of the voice coil 6 wound around the
voice coil bobbin 5! Must be led to the outside through the edge portion 7 of the diaphragm, but
the fluorocarbon resin film 4 is formed on the surface of the edge portion 7, so the lead portion 6
of the voice coil 6! Has a problem that it can not adhere. Therefore, in order to enable adhesion
between the edge portion 7 and the lead portion 6a of the voice coil 6, the surface of the
fluorocarbon resin film 4 is activated by performing low temperature oxygen plasma treatment
to the extent that the diaphragm does not thermally deform. Adhesiveness must be imparted,
which is not practical and causes cost increase. Further, in the structure in which the fluorine
resin film is formed on both the front and back sides of the diaphragm, there is a problem that
the voice coil bobbin 5 can not be adhered, and the same process as described above must be
performed. And in the case of the structure in which the fluorine resin film 4 is formed on the
surface of the base fabric 1 through the acrylic resin layer 3 through the acrylic resin layer 3, the
weight of the diaphragm increases and the sound pressure radioactivity ratio is low (not
practical. , And the fluorine resin film 4 is made as thin as possible. Therefore, moisture
permeates the thin fluorocarbon resin film 4 on the surface, and is moisture-permeable to the
acrylic resin layer 3 and the base cloth 1 inside, resulting in deformation of the diaphragm and
softening of the acrylic resin layer 3. This causes abnormal resonance of the diaphragm at the
time of large input, and also has the problem that the initial stiffness changes with time and the
initial characteristics of the speaker can not be maintained. Also, in the latter structure in which a
fluorine resin film is directly formed on the surface of the base fabric, the vibration loss ratio tan
δ is as small as about 0.035 to 0.045, which is an unnecessary vibration characteristic of the
soft dome diaphragm. There is a problem that the suppression of [Means for Solving the
Problems] In the present invention, a mixed composition layer of a vibration loss material resin
and a fluorine resin is formed on the surface of a diaphragm base fabric directly or through a
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vibration loss material resin layer, {Circle over (1)} An inorganic powder is mixed in the mixed
composition layer of the vibration loss material resin and the fluorine resin. [Operation] The first
invention {circle over (1)} is a mixture composition layer formed of an acrylic resin and a
fluorocarbon resin formed on the surface of the diaphragm base cloth, even under high
temperature and humidity in the acrylic resin composition which functions as a vibration loss
material. The change in stiffness of the diaphragm is small even under high temperature and
humidity due to the presence of a fluorine resin composition with a small change in stiffness, and
the speaker incorporating the diaphragm of the present invention is near the fO and high
frequency limit frequency of the vibration system. There is almost no change in the
characteristics of the above, and deformation of the diaphragm becomes small even under high
temperature and humidity.
In the second invention {circle over (2)}, since the inorganic powder is mixed in the vibration loss
material resin and the fluorocarbon resin and the mixed composition layer, as shown in FIG.
Since the surface becomes uneven and the contact area with the mold surface becomes small,
mold releasability becomes good, and it is not necessary to apply a mold release agent to the
mold every time as in the prior art, and continuous automatic forming Since the mold
releasability is good and uniform, when the formed diaphragm is removed from the mold,
deformation of the diaphragm is eliminated, and the stiffness of the diaphragm can be further
increased. it can. [Examples] Hereinafter, representative examples of the present invention will be
described. First, in order to facilitate comparison between the present example and the
conventional example, the following AlB and C liquids were prepared as vibration loss material
resin compositions. Liquid A (acrylic resin composition): 85 parts of an acrylic acid ester
copolymer emulsion (resin concentration 35 wt%) obtained by mixing 30 parts of methyl acrylate
and 70 parts of butyl acrylate, and 3 parts of trimethylol melamine as a crosslinking accelerator
Add and mix to prepare an emulsion. Then, ammonia water is added to the solution A, and the
mixture is stirred and thickened to prepare a solution for coating A having a viscosity of about
7000 CPS. Liquid B (mixed composition of acrylic resin and fluorocarbon resin): 12 parts of a
fluorocarbon resin liquid (resin concentration 25 W 1%) having a skeleton of 07F17 was added
to liquid A and mixed to prepare an emulsion liquid. Liquid C (fluorinated resin composition):
Liquid of fluorinated resin (resin concentration 25 w!) In liquid of 3 parts of isopropyl alcohol
and 87 parts of water. %) Were mixed to prepare a coating solution C in which the fluororesin
was suspended. Next, a base fabric is prepared by plain-weaving polyester fibers of 100 g / l 81
g / l "and 52 g / rti. (Example 1) (FIG. 1) After coating solution B (acrylic resin and fluorine resin
and mixed composition) on base fabric J- by doctor knife coating method, in a hot air drier at
about 130 ° C. for 5 minutes The film was dried and formed into a film, and a diaphragm base
fabric having a mixed composition layer 2 of an acrylic resin and a fluorine resin formed on the
surface was produced. The weight of this diaphragm base fabric was 68.2 g / nf. Next, this
diaphragm base cloth is heated and pressed under molding conditions of a mold temperature of
195 to 205 ° C., a pressing pressure of 200 kg / ci, and a clamping time of 12 seconds to form
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a dome shape, diameter 25 barrel, depth 6 . A 5 mm diaphragm was completed. (Example 2) (Fig.
2) After coating solution A (acrylic resin composition) on the base fabric 1 in the same manner as
in (Example 1), it is dried and formed under the same conditions to form an acrylic resin
composition. Layer 3 was formed and a base fabric with a weight of 63.3 g / rrr was produced.
Furthermore, after coating B liquid (mixture composition of acrylic resin and fluorine resin) on
the surface of this acrylic resin composition layer 3 in the same manner as in (Example 1), drying
and film formation under the same conditions are carried out. The diaphragm base fabric in
which the mixed composition layer 2 of resin and fluorine resin was formed was manufactured.
In addition, the coating amount of A liquid and B liquid was each 1/2 in weight ratio (Example 1).
The weight of this diaphragm base fabric was 68.9 g / rrf. Next, this diaphragm base cloth was
heated and pressurized under the same conditions as in (Example 1) to form a dome shape, and a
diaphragm of 25 mm in diameter and 6.5 mm in depth was completed. The following was
manufactured as a comparative example of this example. (Comparative Example 1) (FIG. 3) After
coating solution A (acrylic resin composition) on the base fabric 1 in the same manner as in
(Example 1), it is dried and formed into a film under the same conditions to form an acrylic resin
on the surface. The diaphragm base fabric in which the composition layer 3 was formed was
manufactured. The weight of this diaphragm base fabric was 68.3 g / + d. Next, this diaphragm
base cloth was heated and pressurized under the same conditions as (Example 1) to form a dome
shape, and a diaphragm with a diameter of 25 M and a depth of 6.51 was completed.
Comparative Example 2 (FIG. 4) (Comparative Example 1) After spraying solution C (fluororesin
composition) on the surface of the acrylic resin composition layer 3 by a spray method,
approximately 130 ° C. The diaphragm base cloth which formed the fluorine resin composition
layer 4 on the surface through the acrylic resin composition layer 3 was produced by drying and
forming a film in a hot air drying mold for -3 minutes. The weight of this diaphragm base cloth is
68.9 g / rr? であった。 Next, this diaphragm base cloth was heated and pressurized under the
same conditions as in Example 1 to form a dome shape, and a diaphragm with a diameter of 25
taps and a depth of 6.5 was completed. Next, in each of these Examples and Comparative
Examples, a high temperature multi-temperature test was conducted, and the stiffness at the top
of the dome portion was allowed to stand under the conditions of 25 ° C.-humidity 60% RH for
96 hours 73 ° C. -It measured on the conditions of leaving-to-stand for 96 hours on the
conditions of-humidity 92% R) l, and calculated | required each change rate. In the method of
measuring the stiffness, as shown in FIG. 5, the diaphragm was placed on a jig, the top was
pressed, and the force required to displace 2 mm was measured. The measurement results are as
follows. According to the above measurement results, the change rate of the stiffness in Example
1 is as low as 5.6%, which is about / 3 as compared with the other comparative examples, and
the change rate in (Example 2) is It is 9.9% and it can confirm that it is about 1 / 1.5-1.8
compared with another comparative example. This is because, in the mixed composition layer 2
of the acrylic resin and the fluorine resin formed on the surface of the base fabric 1, the change
in the stiffness of the acrylic resin composition which functions as a vibration loss material is
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small even under high temperature and humidity. This is because the composition is mixed.
In addition, (Example) and (Comparative Example 2) were incorporated into a speaker of the
same specification, and sound pressure frequency characteristics before and after the high
temperature multi-temperature test and admittance characteristics showing fO of a vibration
system were measured. According to the measurement results, as shown by the solid line in FIG.
6 in (Example 1), there is almost no characteristic change near the fO and high frequency limit
frequency of the vibration system, while in (Comparative example 2), the solid line in FIG. As
shown in, the fO of the vibration system decreases by about 25 Hx, and the high frequency limit
frequency is about 700 H in the high frequency region! The sound pressure was also reduced by
about 2 dB. (Example 3) (FIG. 9) 130 parts of an emulsion of an acrylic acid ester copolymer
(resin concentration 35 v 1%) prepared by mixing 30 parts of methyl acrylate 11 and 0 parts of
butyl acrylate-door, fluorocarbon resin ( A resin concentration of 25 w (%) and 12 parts are
mixed and stirred, and to this, 50 parts of 32 w] titanium oxide powder suspension as an
inorganic powder is added and mixed to prepare a coating solution. After coating this D solution
on the base fabric 1 in the same manner as in Example 1 (Example 1), the solution D is dried and
formed into a film under the same conditions to form an acrylic resin and fluorine resin liquid
composition layer 2 on the surface. A diaphragm base fabric was produced in which a vibration
loss material layer was formed in which titanium oxide powder 8 was mixed. That is, in Example
1, the powder 8 of titanium oxide is mixed in the mixed composition layer 2 of an acrylic resin
and a fluorine resin. Next, this diaphragm base cloth was heated and pressurized under the same
conditions as (Example 1) to complete a dome-shaped C-shaped diaphragm. (Example 4) (Fig. 10)
(Example 2), after coating solution D with the same method as (Example 3) on the surface of the
acrylic resin composition layer 3 of the base fabric 1, it is dried under the same conditions Then,
a diaphragm base cloth was produced by forming a film, and forming a vibration loss material
layer in which powder 8 of titanium oxide is mixed in the mixed composition layer 2 of acrylic
resin and fluorine resin on the surface. That is, in Example 2, the powder 8 of titanium oxide is
mixed in the mixed composition layer 2 with the acrylic resin and the fluorocarbon resin. Next,
this diaphragm base cloth was heated and pressurized under the same conditions as (Example 1)
to form a dome shape to complete a diaphragm. In addition, if the acrylic resin solution is mixed
after mixing the titanium oxide powder solution and the fluorine resin solution at the time of
preparation of the solution D, the fluorine resin concentration on the surface of the titanium
oxide powder becomes higher than other parts, and the hygroscopicity preventing effect It will
be further improved. (Example 5) (FIG. 11) (Example 2) E for coating E was prepared by adding
and mixing a 32 vt% titanium oxide powder solution as an inorganic powder to solution A (acrylic
resin composition) on the surface of the base fabric 1 The solution is coated in the same manner
as in Example 1 and then dried and formed under the same conditions to form an acrylic resin
composition layer 3 in which titanium oxide powder 8 is mixed on the surface, and further, this
acrylic resin After coating the surface of the composition layer 3 with the same method as
(Example 1) and coating D liquid (a mixed composition of acrylic resin and fluorine resin mixed
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with powder 8 of titanium oxide), it is dried under the same conditions to form a film Then, a
mixed composition layer 2 of an acrylic resin and a fluorocarbon resin in which titanium oxide
powder 8 is mixed is formed to form a diaphragm base cloth, which is heated and pressurized
under the same conditions as in Example 1 to form a dome shape. Then, the diaphragm was
completed.
Next, in each of these examples, a high-temperature multi-humidity test is conducted, and the
stiffness at the top of the dome portion is as follows: ■ normal temperature and normal humidity
(before the test) ■ left under conditions of temperature 43 ° C-humidity 92% RH for 96 hours
The rate of change was determined. The method of measuring the stiffness is the same as
(Example 1) and (Example 2). The measurement results are as follows. According to the above
measurement results, the stiffness of the diaphragm is increased by about 25% as compared with
Comparative Example 1 in Example 3 and Example 5, and the change in stiffness due to humidity
is 12.1% and 8%, respectively. 9%, which is lower than 18.3% of Comparative Example 1. The
increase in the stiffness is because titanium oxide powder is mixed in the mixed composition
layer of the vibration loss material resin and the fluorine resin or the vibration loss material resin
layer. In addition, when the mold releasability at the time of molding is examined for each of the
above-mentioned Examples and Comparative Examples, (Comparative Example 1), since it fuses
to the mold, it is necessary to apply a mold release agent to the mold there were. Comparative
Example 2 The mold releasability was good, and the application of the release agent was
unnecessary. (Examples 1 and 2) Although the application of the release agent was unnecessary,
it was necessary to adjust the release force so that the diaphragm was not deformed at the time
of release. Examples 3.4 and 5 The mold releasability was good, and the application of the
release agent was unnecessary. Thus, particularly in (Examples 3.4 and 5), the coating surface of
the diaphragm base cloth becomes uneven as shown in FIG. 9 due to the mixture of the inorganic
powder, and the contact area with the mold surface The mold releasability is good, and there is
no need to apply a mold release agent to the mold every time it is molded as in the prior art,
continuous automatic molding becomes possible, and the mold releasability is good. And since it
becomes uniform, deformation of the diaphragm is eliminated when the formed diaphragm is
removed from the mold. Moreover, in (Example 3)-(Example 5), even if it uses silicon oxide
powder instead of a titanium oxide powder as an inorganic powder, it is equivalent. Effect of the
Invention "■ 1st invention: The diaphragm formed by forming the mixed composition layer of
the vibration loss material resin and the fluorine resin directly or through the vibration loss
material resin layer on the surface of the diaphragm base cloth Since the vibration loss material
resin layer is mixed with a fluorine resin having a small change in stiffness with temperature and
humidity, the change in stiffness of the diaphragm is small even under high temperature and
humidity, and the speaker incorporating the diaphragm of the present invention vibrates It is
possible to provide a stable speaker with a small quality with the passage of time, with little
characteristic change near the fO1 upper limit frequency of the system.
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In addition, since the change in stiffness of the diaphragm is small even under high temperature
and humidity, the inclination of the voice coil bobbin due to the deformation of the diaphragm
and the generation of abnormal noise due to abnormal resonance can be suppressed, and
furthermore, the fluorocarbon resin is mixed in the surface layer. As it is excellent in sexuality, it
is particularly suitable for applications such as car door mount speakers with a high degree of
adhesion of water droplets and oil and speakers for musical instruments for outdoor use. 2nd
invention: In addition to the effect of 1st invention, in addition to the effect of 1st invention, in
addition to the effect of 1st invention, in the diaphragm characterized by mixing inorganic
powder in the mixed composition layer of said vibration loss material resin and a fluorine resin,
Since the stiffness can be increased, abnormal resonance of the diaphragm hardly occurs at the
time of large input, the input resistance is improved, and the high frequency limit frequency is
expanded, and furthermore, the mixture of the vibration loss material resin and the fluorine resin
Since the inorganic powder is mixed in the composition layer, the coating surface of the
diaphragm base cloth becomes uneven, the contact area with the mold surface becomes small,
and the mold releasability between the mold and the molded diaphragm There is no need to
apply a mold release agent to the mold every time as in the prior art, continuous automatic
molding becomes possible, not only mass productivity improves, but also molding processing
cost can be reduced. Because mold releasability is good and uniform, When the formed
diaphragm is removed from the mold, the diaphragm is not deformed (it becomes the design as
designed, so that abnormal resonance due to deformation during molding or abnormal shape can
be eliminated, which is ideal) The vibration mode can be realized, abnormal resonance at large
input can be suppressed, and input resistance can be improved.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a view showing the structure of a representative embodiment (first embodiment) of the
diaphragm for an electroacoustic transducer according to the first invention of the present
invention, and FIG. 2 is a view showing the second embodiment. FIG. 3 shows the structure, FIG.
3 and FIG. 4 show the structures of the first and second comparative examples, FIG. 5 is a
schematic view showing the method of measuring stiffness, and FIG. Fig. 7 shows sound pressure
frequency characteristics and admittance characteristics of a speaker incorporating the
embodiment of Fig. 7, Fig. 7 shows sound pressure frequency characteristics and admittance
characteristics of a speaker incorporating the second comparative example before and after the
star degree test, FIG. 8 is a view showing the structure of a conventional diaphragm for
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electroacoustic transducer (corresponding to the second comparative example), and FIG. 9 is a
representative of the diaphragm for electroacoustic transducer of the second invention according
to the present invention. The figure which shows the structure of an Example (3rd Example), FIG.
10, FIG. 11 is the same, and the 4th, 5th Example. It is a diagram illustrating a structure.
Patent Assignee Onkiyo Co., Ltd. 巳 244 巳 6 責 Yaa 肯 5 ア 82tcr 図
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