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JPH0787592

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DESCRIPTION JPH0787592
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker cone made of a novel material and a method of manufacturing the same.
[0002]
2. Description of the Related Art As materials for conventional speaker cones, films made of
natural wood pulp, synthetic fibers or synthetic pulps made of synthetic resins, natural fibers,
synthetic fibers, carbon fibers, glass fibers or synthetic resins (for example, polypropylene) There
are various materials, etc., and speaker cones that make use of the characteristics of each
material are manufactured.
[0003]
Loudspeaker corn made from natural wood pulp is prepared by adding various additives such as
fine powder of carbon, resin and the like to the pulp subjected to disaggregation and beating, if
necessary, to prepare a raw material for papermaking, It is manufactured by putting what was
paper-made into the shape of a speaker cone with the formwork for papermaking in the metal
mold | die for shaping | molding further, and heating and pressurizing.
[0004]
In this production method, the process up to the preparation of the raw material is long and
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complicated, and various additives such as carbon fine powder, resin and the like are usually
added. There is.
In addition, waste water and waste containing these additives cause environmental pollution.
Further, as described above, since the speaker cone is first made by the paper making frame,
thickness unevenness is likely to occur in the speaker cone obtained by molding, and the weight
of the speaker cone varies among products. It is easy to do and has become a quality control
problem. Although how to reduce such thickness unevenness and weight variation is an
important point in the speaker cone papermaking process, it has not been sufficiently improved
at present.
[0005]
As one of the methods to solve this problem, a method is considered in which the material for
speaker cone is made into paper and processed in advance into a sheet, and this sheet is used to
mold it into a speaker cone by heating and pressing using a mold. Be In this method, a stretching
force acts on the sheet because the speaker cone is three-dimensional, but the sheet obtained by
papermaking can not sufficiently cope with this stretching force, and the sheet is partially cut or
stretched. Be beaten.
[0006]
In order to give the sheet a strength corresponding to the drawing force, it is preferable to use
long fibers, but the fiber length which can be used when producing the sheet by the papermaking
method is 1 to 5 mm, 5 mm or more, particularly 10 mm. It has been very difficult to produce
uniform sheets from the above long fibers by the papermaking method. Therefore, it is extremely
difficult to form a speaker cone by a method of heating and pressing using a mold as described
above with a sheet obtained by papermaking.
[0007]
Furthermore, in the case of using a synthetic resin, for example, polypropylene as a raw material,
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a pellet of the raw material resin is formed into a film and then vacuum formed, and then plasma
treatment or flame is performed to improve the adhesion between the speaker cone main body
and the edge portion. It is manufactured through processes such as treatment and primer
application. As described above, when using synthetic resin such as polypropylene as the raw
material, the work up to the paper making process is somewhat simplified compared to the case
where natural wood pulp or synthetic pulp is used as the raw material, but plasma treatment is
performed after speaker cone formation. And complicated processes such as flame treatment and
primer coating are required.
[0008]
Loudspeaker cones, which conventionally use pulp made of synthetic fibers as a raw material, are
made of cone paper made of synthetic pulp whose raw material is acrylic synthetic fibers having
many elongated voids along the length direction inside the fibers. A speaker cone is disclosed in
Japanese Patent Laid-Open No. 3-154600, and a speaker made of a vibrating plate prepared by
mixing wood pulp and porous acrylic fiber and refining it, and making this mixed pulp into paper
is disclosed in Japanese Patent Laid-Open No. 57-196694. Is disclosed in Japanese.
[0009]
When speaker cones are produced from the synthetic pulp described in JP-A-3-154600, the
number of wrinkles generated when forming into speaker cones is smaller than that of natural
pulp, but this synthetic pulp is used in the paper making process. Since the dispersibility in water
is poor, the generation of fiber lumps can not be avoided, and the thickness unevenness and
weight variation of the obtained product are very large.
Furthermore, the papermaking speed is slower than that of natural pulp and the productivity is
extremely low.
[0010]
On the other hand, in the case of producing a speaker cone from a mixture of porous acrylic fiber
pulp and wood pulp described in JP-A-57-196694, it is the same as the case of producing a
speaker cone from natural wood pulp described above. Have problems. In these conventional
speaker cones, internal loss (tan δ), which is one of the acoustic characteristics, is greatly
affected by post-processing such as changing the manufacturing conditions, resin processing of
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the speaker cone, and laminating processing of bonding metal foil to the speaker cone. As a
result, there is a drawback that a large change occurs in acoustic characteristics. In addition,
when changing the acoustic property by mixing high strength and high modulus fibers such as
carbon fiber, inorganic fiber or aromatic polyamide fiber, the internal loss is largely changed, so
that it has an ideal acoustic property. I could not get a speaker cone.
[0011]
SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems in
the prior art, simplifies the manufacturing process of the speaker cone, improves the working
environment, and further reduces the generation of waste, and A speaker cone with less variation
in thickness, less variation in weight among products, stable speaker cones, and no change in
internal loss that occurs when improving acoustic characteristics due to post-processing and
mixing of other fibers, and a method for manufacturing the same. It is intended to be provided.
[0012]
SUMMARY OF THE INVENTION The speaker cone of the present invention is composed of an
acrylic synthetic fiber which internally has a number of elongated gaps extending along the
length direction, and the cross-sectional shape of the gaps is not specified. A sheet in which at
least a portion of the fibers present on the surface of the sheet is divided into fine fibers, and the
undivided acrylic synthetic fibers are mostly present in the inside of the sheet; Is characterized in
that a laminate of a sheet A (hereinafter referred to as a sheet A) in which the fibers of the
present invention are integrated by interlacing each other and a sheet B (hereinafter referred to
as a sheet B) composed of carbon fibers is formed in a cone shape. Speaker cone.
[0013]
The method of manufacturing the speaker cone according to the present invention is
characterized in that the laminate of the sheet A and the sheet B is formed in a cone shape at a
temperature of 100 to 250 ° C. and a pressure of 0.5 to 30 kg / cm 2. It is a manufacturing
method of a speaker cone.
At least a portion of the acrylic synthetic fiber present on the surface of the sheet A (meaning the
front side and / or the back side of the sheet A) is divided into a large number of finer fine fibers
along the entire length of the fiber Although necessary, partially divided fibers may be present in
the lengthwise direction, and furthermore undivided fibers may be present.
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However, it is preferable that most of the acrylic synthetic fibers present on the surface of the
sheet A be split, and it is more preferable that all the fibers be split. If a large number of
undivided fibers are present on the surface of the sheet A, the entanglement between fibers
becomes insufficient, and the tensile strength and tear strength of the sheet A decrease.
[0014]
The fibers present on the surface of the sheet A are intertwined with each other to form a fiber
layer on the surface of the sheet A. In addition, although acrylic synthetic fibers present in the
interior sandwiched by the fiber layer on the surface of the sheet A are mostly undivided fibers,
partially divided fibers may be present, and they were further divided. Although fibers may be
present, it is preferred that all the fibers be undivided, these fibers being intertwined with one
another to form the middle fiber layer of sheet A. Further, the fibers present in the fiber layer on
the surface and the fiber layer in the middle are respectively entangled and integrated to form a
sheet A.
[0015]
An intermediate fiber layer composed of undivided acrylic synthetic fibers present in the inside
of the sheet A affects the internal loss which is one of the acoustic characteristics of the speaker
cone, and the unique fiber structure of this fiber causes the speaker cone to The characteristic
effect of significantly reducing the change of the internal loss due to the change of the
manufacturing conditions or the post-processing of the speaker cone is exhibited.
[0016]
The electron micrograph (4,000 times) of the cross section of the said undivided acrylic synthetic
fiber is shown in FIG. 1, and the electron micrograph (4,000 times) of a longitudinal cross section
is shown in FIG.
In FIG. 1, a black portion a is a cross section of the air gap, and the shape thereof is various, such
as an approximately circular shape, a flat shape, an edge repeatedly repeating bending, and a
large cross section. It can be seen that a large number of elongated voids with irregular crosssections, which are small, not constant, are randomly present in the fibers.
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[0017]
Also in FIG. 2, it can be seen that the black portions b are the voids, and the voids extend
generally parallel along the length of the fiber. The acrylic synthetic fiber having the above
special fiber structure has a unique property of being divided into a large number of finer fine
fibers along the longitudinal direction of the fiber by applying an external force to the fiber. In
order to facilitate this division, the length of the aforementioned elongated gap is preferably 60
μm or more.
[0018]
Further, adjacent ones of the elongated gaps may be partially connected by holes. Furthermore, it
is preferable that the number of the elongated voids in one cross section of the fiber be 100 or
more in order to easily divide into fine fibers by the above-mentioned external force. This acrylic
synthetic fiber is produced from an acrylic polymer as follows.
[0019]
An acrylic polymer is abbreviated to an acrylonitrile unit (following, "AN" 50 mass% (Hereafter,
"%" shows "weight%" unless otherwise stated)). ), Polymers of AN and other monomers
copolymerizable with AN, or mixed polymers of these polymers. If the AN is less than 50%, the
thermal property that the acrylic polymer inherently has the non-melting property and
thermoplasticity is lost, and the laminate of the sheet A and the sheet B is put in a mold, heated
and When pressurized and formed into a cone, it becomes difficult to maintain the cone shape.
There is no upper limit to the content of AN, and it may be a 100% polymer of AN. In addition,
even when the acrylic polymer is a mixture, the content of AN needs to be 50% or more based on
the weight of the mixed polymer.
[0020]
Monomers copolymerizable with AN are, for example, acrylic acid, methacrylic acid and esters
thereof (methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate etc.), vinyl
acetate, vinyl chloride, etc. There are vinylidene chloride, acrylamide, methacrylamide,
methacrylonitrile, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, vinylpyridine, N,
N-dimethylaminoethyl methacrylate and the like.
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[0021]
The above-mentioned acrylic polymer and polyalkylene glycol are solvents of acrylic polymers
conventionally known, for example, dimethylformamide, dimethylacetamide, dimethylsulfoxide,
aqueous solution of rhodan salt, aqueous solution of concentrated zinc chloride, aqueous solution
of nitric acid and the like To prepare a stock solution for spinning.
The optimum concentration of the acrylic polymer in the stock solution for spinning varies
depending on the solvent, but it is preferably about 10 to 30%.
[0022]
The addition of this polyalkylene glycol is an important requirement for forming the abovementioned elongated voids in the synthetic acrylic fiber. The polyalkylene glycol is a random
copolymer or a block copolymer obtained by copolymerizing ethylene oxide and propylene oxide
in a weight ratio of 80:20 to 20:80, and the number average molecular weight thereof Is 5,000 to
50,000, preferably 6,000 to 20,000.
[0023]
When the number average molecular weight is less than 5,000, elongated voids extending
continuously in the longitudinal direction of the fiber are not formed, and a porous fiber having
very fine, substantially spherical voids is obtained. On the other hand, when the number average
molecular weight exceeds 50,000, it becomes a fiber having a huge streak-like cavity, and also
becomes a fiber having at most several tens of cavities in the cross section of the fiber. Such
fibers are difficult to divide into fine fibers by external force, and are not suitable for the speaker
cone fiber of the present invention. In order to obtain a fiber having an elongated void which
extends along the longitudinal direction of the fiber and whose cross-sectional shape in cross
section is an indefinite shape, one having a number average molecular weight of 10,000 to
20,000 Particularly preferred.
[0024]
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Further, the spinning stock solution prepared by dissolving the above polyalkylene glycol is then
aged for at least 4 hours. Aging of the spinning solution is a necessary condition to obtain an
acrylic synthetic fiber having a large number of continuous elongated voids along the
longitudinal direction of the fiber. Here, ripening refers to, for example, leaving the solution as it
is or gently sending it, without vigorously stirring or vibrating the spinning stock solution
prepared by dissolving the above acrylic polymer and polyalkylene glycol. It is.
[0025]
By aging the stock solution to which the polyalkylene glycol has been added in this way, it is not
clear why the above-mentioned elongated voids are formed for what reason, but it is presumed
as follows. That is, aging of the stock spinning solution causes aggregation of the polyalkylene
glycol, and shear force acts on the stock spinning solution when the stock spinning solution is
spun from the pores of the spinneret into the coagulation medium through the tube. Fine streaks
of polyalkylene glycol are formed. Then, it is considered that due to the difference between the
two solidifying properties that the acrylic polymer solidifies and the polyalkylene glycol does not
solidify, voids having a complicated shape as described above are generated due to phase
separation of the two polymers. The ripening time may be longer than 4 hours, but is preferably
4 to 10 hours.
[0026]
The amount of polyalkylene glycol added is 5 to 20%, preferably 10 to 15%, based on the acrylic
polymer. If the amount added is less than 5%, the above-mentioned elongated voids become
small, and if it exceeds 20%, the amount becomes too large, and the fibers can be divided into
finer fine fibers in the fiber production process, and stable spinning can be performed. It causes
problems such as disappearance. When the addition amount is 10 to 15%, the number of the
elongated voids, the stability of spinning and the like are most balanced, which is preferable.
[0027]
The spinning solution is extruded through a spinneret into a coagulating medium of the spinning
solution to form a coagulated yarn, and the coagulated yarn is subjected to various treatments
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such as washing with water, stretching, drying, heat treatment, etc. to extend along the length
direction An acrylic synthetic fiber having a large number of elongated voids therein is produced.
The polyalkylene glycol added to the stock solution for spinning may be eluted by any method
such as wet spinning, dry spinning, or dry / wet spinning, from the coagulated yarn in the fiber
production process such as coagulation, water washing, and drawing. After spinning, in order to
elute the polyalkylene glycol from the coagulated yarn, stretching and washing in an aqueous
medium are preferred.
[0028]
The above-mentioned acrylic synthetic fiber is easily divided into a number of finer fine fibers
along its length direction by the action of external force. Therefore, utilizing this property, the
sheet A for speaker cone can be obtained, for example, by forming an acrylic synthetic fiber web
into a non-woven fabric by a columnar flow punching process using high pressure water, which
is conventionally known. By this treatment, at least a part, preferably a large part, of the acrylic
synthetic fibers present on the surface of the non-woven fabric is divided into a large number of
finer fine fibers along its length direction. At this time, in some cases, fibers obtained by partially
dividing acrylic synthetic fibers may be present on the surface of the non-woven fabric, and
further, undivided fibers may be present, but all the fibers present on the non-woven surface are
split. It is preferable that it is a fine fiber. These fibers are dispersed and spread randomly in one
part, bunched up in another part, and these fibers are entangled with one another.
[0029]
On the other hand, most of the fibers present inside the non-woven fabric are undivided acrylic
synthetic fibers, and in some cases partially divided fibers and further divided fine fibers may be
present. However, it is preferable that the fibers present inside the non-woven fabric be fibers in
which all fibers are undivided. By the columnar flow punching treatment of the high pressure
water, the division of the fibers present in the vicinity of the non-woven fabric surface and the
entanglement of the divided fine fibers simultaneously proceed, and the fiber layer of the surface
of the sheet A is formed. In addition, the internal fibers sandwiched by the fiber layers on the
surface are simultaneously entangled to form an internal fiber layer, and the fibers forming the
surface fiber layer and the internal fiber layer are entangled and integrated with each other. The
inventive speaker cone sheet A is formed.
[0030]
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The degree of division of the above-mentioned acrylic synthetic fiber can be adjusted by
changing the magnitude of the external force applied to this fiber, and the dispersion state of the
obtained fine fibers and the degree of interlacing of the fibers are also possible. It can be adjusted
by the size. The length of the fibers constituting the sheet A is not particularly limited, and both
long fibers and short fibers can be used, but fibers of 20 to 150 mm in length are preferable and
30 to 60 mm in view of shape retention of the speaker cone. Fiber is more preferred.
[0031]
Although the weight per unit area of the non-woven fabric varies depending on the intended use
environment of the speaker cone, acoustic characteristics and the like, it is usually 50 to 500 g /
m <2>, preferably 100 to 300 g / m <2>. The nozzle diameter used for column flow punching of
high pressure water is usually 0.05 to 1 mm, preferably 0.1 to 0.5 mm, and the pressure of high
pressure water column flow is 20 to 100 kg / cm 2, preferably 40 -80 kg / cm2.
[0032]
The speaker cone consisting of the sheet A of the present invention can be obtained by putting
the sheet A consisting of the above-mentioned acrylic synthetic fiber into a mold of a
predetermined shape and molding it under a predetermined temperature and pressure. The
temperature at this time is 100 to 250 ° C., preferably 150 to 200 ° C., the pressure is 0.5 to
30 kg / cm 2, preferably 1 to 10 kg / cm 2, and the molding time is 1 to 60 seconds, preferably 2
~ 10 seconds.
[0033]
By molding under the above conditions, the fibers forming the fiber layer on at least one surface
of the speaker cone are pressed against each other by heat and pressure and firmly fixed. At this
time, by raising both the temperature and the pressure within the above range, a speaker cone in
which a part of the fibers on the surface of the fiber layer is fused can be obtained. When the
molding temperature exceeds 250 ° C, denaturation and decomposition of the acrylic synthetic
fiber occur and molding becomes difficult. When the pressure exceeds 30 kg / cm 2, fusion of
the fibers on each side of the sheet A becomes severe and molding is difficult. It becomes. If the
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molding temperature is less than 100 DEG C. and the pressure is less than 0.5 kg / cm @ 2, the
shape retention of the speaker cone is deteriorated, and no fused part of the fibers is formed on
the surface of the sheet A.
[0034]
By appropriately adjusting these conditions within the above range, a speaker cone having
various characteristics can be manufactured. Further, this mold can be appropriately designed
and changed in accordance with the shape and the like of the intended speaker cone. The carbon
fibers forming the sheet B are fibers produced from acrylic synthetic fibers, cellulosic fibers,
petroleum-based or coal-based pitch fibers, and the length thereof is not particularly limited, and
both long fibers and short fibers are used. can do.
[0035]
The sheet B is preferably a non-woven fabric from the easiness of production of the sheet B and
the production of a laminate of the sheet B and the sheet A, easiness of molding of the speaker
cone, uniformity thereof and the like. Although the weight per unit area of the sheet B varies
depending on the purpose of improvement of shape retention characteristics, acoustic
characteristics and the like, it is usually 10 to 300 g / cm 2, preferably 20 to 100 g / cm 2.
Further, the proportion of the sheet B in the speaker cone is 5% to 50%, preferably 10 to 30% by
weight.
[0036]
The carbon fiber sheet can accelerate the sound velocity with almost no change in the internal
loss of the speaker cone, and can improve the Young's modulus. For this reason, the speaker
cone of the present invention in which the carbon fiber sheets are laminated is an ideal speaker
cone having a more natural sound quality with a more transparent feeling. The laminate of the
sheet A and the sheet B is a laminate of two or more layers in which the sheets A and B are
alternately laminated. The laminate is not particularly limited as long as it has two or more
layers, but a three-layer laminate in which both sides of the sheet B are sandwiched by the sheet
A is preferable.
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[0037]
The speaker cone can be manufactured by placing the laminate in a mold of a predetermined
shape and forming it into a cone shape at a predetermined temperature and pressure. An
undivided acrylic synthetic fiber is present inside in the thickness direction of the sheet A that
has become a speaker cone. The undivided fibers are intertwined with each other to form an
intermediate fiber layer, and at the same time, they are also entangled with the divided fine fibers
forming the fiber layer on the surface, and all the fibers are integrally bonded.
[0038]
The undivided acrylic synthetic fiber present in the inside of the sheet A is an acrylic synthetic
fiber having a structure that is almost the same as before being molded into a speaker cone. The
undivided fibers and the divided fine fibers present inside the thickness direction are in close
contact with each other and merely strongly crimped. Furthermore, there are many spaces
between the fibers.
[0039]
When manufacturing the nonwoven fabric which consists of the above-mentioned acrylic
synthetic fiber as sheet A for speaker cones in the present invention, other fibers such as natural
wood pulp, carbon fibers, aromatic polyamide fibers or mineral fibers are used as speaker cones.
It can be mixed in amounts of up to 10% depending on the properties required. It is also possible
to add additives such as carbon powder, resin powder, coloring agent and ceramic. Furthermore,
the molded speaker cone can be processed by resin impregnation or coating, metal deposition,
coloring, etc., to impart various characteristics to the speaker cone characteristics and design.
[0040]
[Regarding Shape Retaining Property] The sheet A of the present invention has a special fiber
structure of acrylic synthetic fiber, this sheet itself has a special structure, and the fiber length
does not depend on the paper making method. It is characterized in that physical properties such
as tensile strength of the sheet A are significantly improved due to factors such as being a
uniform sheet using long fibers.
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[0041]
A combination of the structural and physical factors of the sheet A and the thermal properties
that the acrylic synthetic fiber originally has, that is, the acrylic synthetic fiber is non-melting but
is thermoplastic, the sheet When forming A into a speaker cone with a mold, the sheet A can
sufficiently correspond to the stretching force acting on the sheet A.
Therefore, when the sheet A is formed into a speaker cone having a three-dimensional shape, the
sheet A can be formed into a uniform speaker cone without breakage or distortion.
[0042]
In the speaker cone made of the sheet A, the fused part of the fibers present on the surface of the
sheet A is present on at least one surface, and an undivided acrylic synthetic fiber is present in
the inside thereof. There is. The fused portion greatly contributes to the shape retention of the
speaker cone, and undivided acrylic synthetic fibers are present in the inside of the sheet A
which is formed in a cone shape, and many spaces are contained between the fibers. In spite of
that, it is a big factor to keep the shape of the speaker cone firmly.
[0043]
In addition, also in the speaker cone having high strength or high modulus fiber such as carbon
fiber inside, the fused part existing on the surface is a major factor to maintain its shape in the
same manner as described above. The fusion-bonded portion of the synthetic acrylic fiber is
formed by forming a laminate of sheet A and sheet B into a speaker cone at a temperature of 100
to 250 ° C. and a pressure of 0.5 to 30 kg / cm 2 to form at least one surface thereof. Can be
formed. [Sound Characteristics] The speaker cone of the present invention is formed of a
laminate of a sheet A and a sheet B made of special acrylic synthetic fibers, and this sheet A is
molded into a speaker cone as described above. Even after being made, it contains an acrylic
synthetic fiber having a structure (having a large number of elongated voids extending in the
longitudinal direction) which is almost the same as that before being molded, inside the thickness
direction.
[0044]
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Further, on the surface of the speaker cone, fine fibers obtained by dividing the acrylic synthetic
fiber are dispersed and spread in a certain portion, and present in a bundle in another portion.
The synergetic effect of these and the inherent thermal properties of the acrylic synthetic fiber is
responsible for the following effects on the properties required of the speaker cone, in particular
the internal loss .
[0045]
That is, the internal loss of a speaker cone using natural pulp changes depending on its molding
temperature and pressure, and also changes depending on resin processing and metal laminates
such as aluminum, and also changes depending on fibers mixed with natural pulp. The inventive
speaker cone has an equivalent value to the internal loss of natural pulp which is supposed to be
ideal, and the internal loss is hardly changed by these processes.
[0046]
The size and dispersion state of the space present inside the speaker cone of the present
invention can be adjusted by appropriately changing the pressure and temperature at the time of
molding.
From this, in the speaker cone of the present invention, the sound velocity, which is another
characteristic of the speaker cone, can be freely changed by changing processing conditions such
as molding pressure, temperature or metal laminate.
[0047]
In the carbon fiber sheet B, the sound velocity can be increased with almost no change in the
internal loss of the speaker cone, and the Young's modulus can be improved. For this reason, the
speaker cone of the present invention in which the carbon fiber sheets are laminated is an ideal
speaker cone having a more natural sound quality with a more transparent feeling. Furthermore,
speaker cones with different timbres can be easily manufactured.
[0048]
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The present invention will be described in more detail by way of the following examples. First, an
acrylic synthetic fiber forming sheet A for a speaker cone was manufactured as follows.
Dimethylformamide, a copolymer having a composition of 95.0% AN, 4.5% methyl acrylate, and
0.5% sodium methallyl sulfonate, and a block type polyether of polyethylene oxide-polypropylene
oxide-polyethylene oxide ( A spinning stock solution containing 23% of a copolymer and 2.3% of
a block-type polyether was prepared by dissolving a number average molecular weight of 10,000
and a polymerization ratio of polyethylene oxide: polyethylene oxide = 70: 30). .
[0049]
After this spinning stock solution is allowed to stand for 6 hours, it is coagulated by extruding
into a water-based coagulation bath containing 75% of dimethylformamide and 25% of water
through a spinneret having a diameter of 0.08 mm and a temperature of 35 ° C. Yarn was
manufactured. Then, the coagulated yarn was washed with water, drawn 10 times in boiling
water, dried in hot air at 80 ° C., crimped, and cut into 76 mm to produce an acrylic synthetic
fiber.
[0050]
The single denier of this fiber was 2 d, the tensile strength was 3.2 g / d, and the tensile
elongation was 32%. The electron micrograph which shows the state of the cross section and
longitudinal cross section of this fiber is shown in FIG.1 and FIG.2 (4,000 times). As can be seen
from these figures, this fiber had a very large number of elongated voids extending along its
length.
[0051]
The fibers were formed into three webs with a basis weight of 100, 120 and 200 g / m @ 2 using
a spinning carder. These webs were placed on a wire mesh moving at a speed of 4 m / min, and a
high pressure of 60 kg / cm2 was achieved by a columnar flow processing device in which
nozzles having pores with a diameter of 0.1 mm were arranged in a row at 0.8 mm intervals.
Treated with water. After repeating this process ten times alternately on the front and back of the
web, the obtained nonwoven fabric (sheet A) was dried in hot air at 80 ° C.
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[0052]
In the sheet produced by the above method, almost all of the fibers present on the front and back
of the sheet are divided into a large number of finer fine fibers, and the fine fibers are dispersed
and spread in one portion and in a bundle in another portion. While being assembled, undivided
acrylic synthetic fibers are present between the front and back of the sheet, and these fibers are
mutually entangled to form sheet A by entanglement of the fibers as a whole. The fibers were
integrated.
[0053]
The three types of sheets A thus obtained were used to form various speaker cones.
[0054]
EXAMPLE 1 A three-layered laminate in which a 50 g / m 2 non-woven fabric consisting of
carbon fibers is sandwiched between sheets of 100 g / m 2 above is put in a mold for
manufacturing a speaker cone, and the temperature is 180 ° C. A number of speaker cones
were manufactured by molding for 5 seconds at a pressure of 2 kg / cm2.
[0055]
The undivided acrylic synthetic fibers exist inside in the thickness direction of the speaker cone,
and these undivided acrylic synthetic fibers are intertwined with each other and also with the
divided fine filaments.
The undivided acrylic synthetic fibers present inside the thickness direction and the divided fine
fibers are in close contact with one another.
That is, even after being formed into a speaker cone, there is an acrylic synthetic fiber having a
large number of elongated voids extending in the lengthwise direction, which has almost the
same structure as before being formed in the thickness direction. .
In addition, the carbon fiber is firmly fixed by being sandwiched by the above-mentioned acrylic
synthetic fiber sheet.
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[0056]
Furthermore, no abnormality such as deformation or breakage of the laminate was observed
during molding, and the moldability was extremely good. The variation in weight among the
speaker cones was within ± 4%. Table 1 shows the characteristics of the speaker cones (Nos. 1
to 3). As can be seen from Table 1, this speaker cone is greatly improved in sound speed with
little change in internal loss.
[0057]
[Example 2] After applying 100H clear (trade name, manufactured by Ron Chemical Co., Ltd.) as
a modified silica resin solution containing 20% by weight of solid content on the entire surface of
the speaker cone No. 1 manufactured in Example 1 The slurry was naturally dried to produce a
ceramic-containing speaker cone. The variation in weight among the speaker cones was within ±
4%.
[0058]
Table 2 shows the characteristics of each speaker cone (No. 4 to 6). As can be seen from Table 2,
the speaker cone is greatly improved in sound velocity and Young's modulus by resin processing,
but the internal loss hardly changes and is similar to a speaker cone made of natural pulp.
[0059]
EXAMPLE 3 A large number of speaker cones were manufactured by laminating an aluminum
foil having a thickness of 50 μm to the No. 1 speaker cone manufactured in Example 1 with an
adhesive. The variation in weight among the obtained speaker cones was within ± 4%. Table 3
shows the characteristics of each of the speaker cones (Nos. 7 to 9).
[0060]
As can be seen from Table 3, the speaker cone has the sound velocity and Young's modulus
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greatly improved by laminating the aluminum foil, but the internal loss is hardly changed by this
processing and is the same as the speaker cone made of natural pulp. It is.
[0061]
Comparative Example 1 A speaker cone was produced from natural pulp as follows.
After swelling treatment of the raw material pulp, the raw material is prepared through the steps
of dissociation, beating etc. To this raw material, "Perosa WS" (rosin-based resin) manufactured
by Modern Chemical Industry Co., Ltd. is added to adjust the pH and concentration Then, paper
was made into a speaker cone shape by wire mesh, dewatered and pressed, and a sloped portion
of the speaker cone was formed. After cutting this sloped part, it was finished and manufactured
a large number of speaker cones. The variation in weight of each speaker cone was ± 10%.
[0062]
Table 4 shows the characteristics of an example (No. 10) of these speaker cones.
[0067]
As described above, according to the speaker cone of the present invention, the laminate of the
sheet A of the special structure and the carbon fiber sheet, which is formed of the acrylic
synthetic fiber of the special structure, has a specific temperature and temperature. It is molded
by pressure and has the following characteristics. 1. The shape retention is very good as
compared with those formed by the sheet obtained by the papermaking method.
[0068] 2. The speaker cone can be manufactured without performing the paper making
process, and the working environment at the speaker cone manufacturing site can be
significantly improved, and the generation of waste can be suppressed. 3. Since the
unevenness in thickness of the speaker cone and the variation in weight among products can be
reduced, it is possible to provide a speaker cone with stable quality.
[0069] 4. When a synthetic resin film is used as a raw material in the prior art, complicated
processes such as plasma treatment, flame treatment, primer coating and the like are required
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after molding, but the speaker cone of the present invention requires such a process. And not.
5. Among the acoustic characteristics, the internal loss hardly changes due to the change of
the manufacturing condition, the resin processing, the laminating process of the metal foil, etc.
Therefore, the other characteristics such as the sound speed can be widely changed by changing
the manufacturing condition or the processing condition. Can be changed in a well-balanced
manner.
[0070] 6. Since the carbon fiber sheets are laminated, the sound velocity can be increased with
almost no change in the internal loss of the speaker cone, and the Young's modulus can be
improved. 7. For this reason, the speaker cone of the present invention in which the carbon
fiber sheets are laminated is an ideal speaker cone having a more natural sound quality with a
more transparent feeling.
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