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JPH0787591

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DESCRIPTION JPH0787591
[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 formwork for paper
making, thickness unevenness is likely to occur in the speaker cone obtained by molding, and
weight dispersion is likely to occur between the speaker cones, It is a problem in quality control.
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 for solving this problem, a method is conceivable in which a material for a
speaker cone is made into paper and processed in advance into a sheet, and this sheet is heated
and pressed by a mold to be formed into a speaker cone. In this method, since the speaker cone
is three-dimensional, the drawing force acts on the sheet, but the sheet obtained by papermaking
can not cope with the drawing force sufficiently, and the sheet may be partially cut. I will be
stretched.
[0006]
In order to provide the sheet with a strength corresponding to the drawing force, it is necessary
to use a fiber having a long fiber length, but in the case of producing a sheet by a papermaking
method, the usable fiber length is 1 to 5 mm, It has been very difficult to produce uniform sheets
by a papermaking process from fibers having a fiber length of 5 mm or more, in particular 10
mm or more. 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 the paper making
method.
[0007]
Furthermore, in the case of using a synthetic resin, for example, polypropylene as a raw material,
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pellets of the raw material resin are formed into a film and then vacuum formed, and then plasma
treatment or flame is performed to improve the adhesion between the speaker cone body and the
edge portion. It is manufactured through processes such as treatment and primer application.
Thus, when using a synthetic resin such as polypropylene as a raw material, the work up to the
paper making process is somewhat simplified as compared to the case where natural wood pulp
or synthetic pulp is used as a raw material, but plasma after speaker cone molding It requires
complicated processes such as treatment, flame treatment and primer coating.
[0008]
The speaker cone which uses the pulp which consists of acrylic synthetic fiber as a raw material
beats the acrylic synthetic fiber which has many long and narrow voids in the inside of the fiber
along with the length direction, manufactures synthetic pulp, makes this papermaking Japanese
Patent Laid-Open No. 3-154600 discloses a speaker cone made of corn paper obtained by mixing
the wood pulp and the porous acrylic fiber, and beating it, and a speaker made of a vibrating
plate made of this mixed pulp. Is disclosed in Japanese Patent Application Laid-Open No. 57196694.
[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 speaker cone 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. Furthermore, speaker
cones manufactured from acrylic synthetic fibers are particularly susceptible to humidity when
used in high-temperature, high-humidity environments such as outdoors, in cars, etc., and the
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shape of the speaker cone is deformed, and the sound quality is significantly degraded. And there
is a problem that the quality is severely degraded.
[0011]
SUMMARY OF THE INVENTION According to the present invention, the process of
manufacturing the conventional speaker cone is simplified to improve the working environment,
and the generation of waste is further reduced. It is an object of the present invention to provide
a speaker cone having a small variation in weight and having a small shape change even in a
high temperature and high humidity environment, and a method of manufacturing the same.
[0012]
A first aspect of the present invention is composed of an acrylic synthetic fiber which internally
has a number of elongated voids extending along the length direction and the cross-sectional
shape of the voids is not specified. Sheet, and most of the fibers present on the surface of the
sheet are divided into fine fibers, and most of undivided acrylic synthetic fibers are present inside
the sheet, A laminate of a sheet (A) (hereinafter referred to as a sheet (A)) in which fibers are
integrated by entanglement with each other and a sheet (B) (hereinafter referred to as a sheet
(B)) composed of heat melting fibers is a cone. It is molded in the shape of a speaker cone
characterized in that:
[0013]
In the second aspect of the present invention, a laminate of the above sheet (A) and a sheet (B)
consisting of heat melting fibers is formed into a cone at a temperature of 100 to 250 ° C and a
pressure of 0.5 to 30 kg / cm2. It is a manufacturing method of the speaker cone characterized
by molding.
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, for the most part, specifically 70% by weight or more
(hereinafter,% is not specified) As much as% by weight), preferably more than 90% of the fibers
are divided into a large number of finer fine fibers along their entire length, partially divided in
their length direction, and even undivided. Fibers may also be present.
When many undivided fibers are present on the surface of the sheet (A), entanglement of the
fibers becomes insufficient, and when the laminate including the sheet (A) is formed into a
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speaker cone, breakage of the sheet (A) occurs. It will be.
[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, the acrylic synthetic fiber present inside the
fiber layer on the surface of the sheet (A) is composed mainly of undivided fibers, specifically
70% or more, preferably 90% or more. However, partially divided fibers may be present, and
further divided fibers may be present. These fibers are intertwined with each other to form an
intermediate fiber layer of the sheet (A). Furthermore, the fibers present in the fiber layer on the
surface and the fiber layer in the middle are mutually entangled and integrated to form a sheet
(A).
[0015]
The middle fiber layer consisting 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 this fiber has a unique fiber structure. This produces the characteristic effect of extremely
reducing the change in the manufacturing conditions of the speaker cone or the change in
internal loss due to the post-processing of the speaker cone.
[0016]
The electron micrograph (4,000 times) of the cross section of the undivided acrylic synthetic
fiber is shown in FIG. 1, and the electron micrograph (4,000 times) of the longitudinal 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.
[0017]
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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 above-mentioned acrylic synthetic fiber
having a special fiber structure has a unique property of being divided into many finer fine fibers
along the longitudinal direction of the fiber by applying an external force to this fiber However,
in order to facilitate this division, it is preferable that the length of the aforementioned elongated
gap be 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]
The acrylic polymer is a polymer of 50% or more of acrylonitrile units (hereinafter abbreviated as
"AN") and another monomer copolymerizable with AN, or a mixed polymer obtained by mixing
these polymers. is there. If the AN is less than 50%, the thermal characteristics that the acrylic
polymer inherently has the non-melting and thermoplastic properties are lost, and the laminate
of the sheet (A) and the sheet (B) is used as a mold. When it is put, heated and pressed to form a
cone, it becomes difficult to maintain its shape. There is no upper limit to the content of AN, and
it may be a 100% polymer of AN. 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. And vinylidene chloride, acrylamide, methacrylamide,
methacrylonitrile, allylsulfonic acid, methallylsulfonic acid, styrenesulfonic acid, vinylpyridine, N,
N-dimethylaminoethyl methacrylate and the like.
[0021]
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The above-mentioned acrylic polymers and polyalkylene glycols are conventionally known
solvents for acrylic polymers, such as dimethylformamide, dimethylacetamide, dimethylsulfoxide,
rhodanate concentrated aqueous solution, zinc chloride concentrated aqueous solution, nitric
acid aqueous solution, etc. It is dissolved in a solvent 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 huge streak-like cavities, and
moreover, it 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]
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
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longitudinal direction of the fiber. In this ripening, for example, the spinning stock solution
prepared by dissolving the acrylic polymer and the polyalkylene glycol is allowed to stand still or
sent gently without vibrating or vibrating vigorously. It is.
[0025]
As described above, it is not clear why the above-mentioned elongated voids are formed by aging
the stock solution to which the polyalkylene glycol is added, 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 addition amount is less than 5%, the above-mentioned elongated voids become
small, and if it exceeds 20%, this becomes too much, the fibers are divided into finer fine fibers in
the fiber production process, stable spinning It causes problems such as being unable to do it.
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
such as washing with water, stretching, drying, heat treatment, etc., along the length direction An
acrylic synthetic fiber is produced having a number of elongated voids extending therein. The
polyalkylene glycol added to the spinning solution may be eluted from the coagulated yarn in the
process of coagulation, water washing, drawing, etc. The spinning method may be any method
such as wet spinning, dry spinning or dry / wet spinning, and after spinning In order to elute the
polyalkylene glycol from the coagulated yarn, it is preferable to draw and wash in an aqueous
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medium.
[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 a speaker cone is obtained by forming the above-mentioned web of acrylic synthetic
fiber into a non-woven fabric by a columnar flow punching process using high-pressure water,
which is conventionally known. Be By this treatment, most of the acrylic synthetic fibers present
on the surface of the non-woven fabric, specifically 70% or more, preferably 90% or more, are
divided into a large number of finer fine fibers along the length direction. Be done. At this time, in
some cases, fibers obtained by partially dividing acrylic synthetic fibers or even undivided fibers
may be present on the surface of the non-woven fabric, but all fibers present on the surface of
the non-woven fabric may be present. It is preferable that it is a divided 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, specifically 70% or
more, preferably 90% or more, are undivided acrylic synthetic fibers, and in some cases, partially
divided fibers, and further, Divided fine fibers may be present. However, the fibers present inside
the non-woven fabric are preferably fibers in which all the fibers are undivided.
[0030]
By the columnar flow punching treatment of high-pressure water as described above, the division
of fibers present in the vicinity of the surface of the non-woven fabric and the entanglement of
the divided fine fibers simultaneously proceed to form a fiber layer on the surface of the sheet
(A). In addition, the internal fibers sandwiched by the surface fiber layers are simultaneously
entangled to form the internal fiber layers, and the fibers present in the surface fiber layers and
the internal fiber layers are intertwined and integrated, and the present invention is realized. A
speaker cone sheet (A) of the invention is formed.
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[0031]
The degree of division of the acrylic synthetic fiber can be adjusted by changing the magnitude
of the external force applied to the fiber, and the dispersion state of the obtained fine fibers and
the degree of interlacing of the fibers are also the magnitude of the external force. Can be
adjusted. 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 in
terms of shape retention of the speaker cone, and 30 to 60 mm fibers are more preferred.
[0032]
Although the weight per unit area of the non-woven fabric varies depending on the intended use
of the speaker cone, 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 columnar 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
columnar flow is 20 to 100 kg / cm 2, preferably 40 to 80 kg It is / cm2.
[0033]
The speaker cone of the present invention is obtained by heat and pressure molding a laminate
of the sheet (A) and a sheet (B) such as a nonwoven fabric, a knitted fabric, a woven fabric, etc.,
which is composed of heat melting fibers. This sheet (B) is used by laminating with the sheet (A),
thereby improving the shape retention, strength and handleability of the speaker cone, and
changing the shape of the speaker cone when used in a high temperature, high humidity
environment As a result, it is possible to prevent the deterioration of quality due to noise, to
change other acoustic characteristics without causing a change in internal loss, and to cope with
a wider range of timbre.
[0034]
The sheet (B) is preferably a non-woven fabric from the easiness of production of the sheet (B)
and of the laminate of the sheet (B) and the sheet (A), easiness of molding of the speaker cone,
uniformity thereof and the like. The fibers forming the sheet (B) are heat fusible fibers which
melt at the molding temperature and pressure of the speaker cone. The fibers are polyethylene
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fibers, polyolefin fibers such as polypropylene fibers, polyamide fibers, polyester fibers, polyvinyl
alcohol fibers, vinyl chloride fibers, vinylidene chloride fibers and the like, and polyolefin fibers
are preferable, but polypropylene is particularly preferable. Fiber is preferred.
[0035]
The fineness of the heat-meltable fiber is preferably 10 deniers or less, and in particular, ultrafine
fibers of 0.5 deniers or less are preferable in terms of the uniformity of the speaker cone. The
length of these fibers is not particularly limited, and both long fibers and short fibers can be
used. The weight per unit area of the sheet (B) made of the above fiber is usually 10 to 300 g /
cm 2, preferably 20 to 100 g / cm 2 in order to prevent deformation of the speaker cone in high
temperature and high humidity environments. The proportion of the sheet (B) in is 5% to 50%,
preferably 10 to 30% by weight.
[0036]
When the sheet weight of the sheet (B) decreases, the adhesive strength for fixing the acrylic
synthetic fiber forming the sheet (A) is weak, and when it increases, the adhesive strength
becomes stronger and at the same time, the internal loss of the speaker cone almost changes.
Young's modulus is high and the speed of sound is fast. Therefore, by appropriately selecting the
weight of the sheet (B) made of the heat melting fiber, the adhesive strength of the fiber can be
easily improved and, at the same time, the acoustic characteristics of the speaker cone can be
improved.
[0037]
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. The speaker cone of the present invention can be
manufactured by placing the laminate in a mold of a predetermined shape and molding the
laminate at a predetermined temperature and pressure. The molding temperature 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 to 2 10 seconds.
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[0038]
When the molding temperature exceeds 250 ° C., denaturation and decomposition of the acrylic
synthetic fiber occur and the molding becomes difficult, and when the pressure exceeds 30 kg /
cm 2, fusion of the acrylic synthetic fiber on each surface of the sheet (A) takes place It becomes
intense and molding becomes difficult. If the 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.
[0039]
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. FIG. 3 is a
speaker cone manufactured by pressure heating molding of a three-layered laminate obtained by
sandwiching a sheet (A) of a sheet (B) made of a non-woven fabric of polypropylene fibers of 0.1
denier with a sheet (A) The form of the inner surface of (Example 1) is shown, FIG. 4: is an
electron micrograph (236x and 234x, respectively) which shows the form of the outer surface.
[0040]
Acrylic synthetic fibers present on the inner and outer surfaces of this speaker cone are divided
into finer fine fibers along the length direction, these fibers are mutually entangled, and indicated
by the symbol c. It is fixed by the melt of the polypropylene fiber. In addition, these fine fibers
present on the inner and outer surfaces of the speaker cone are in intimate contact and may be
partially fused and bonded by heat and pressure (shown in FIG. 3 as black) Part d).
[0041]
FIG. 5 is an electron photomicrograph (177 ×) showing the form of the cross section of the
speaker cone shown in FIGS. 3 and 4 described above. In FIG. 5, the upper surface corresponds to
the inner side surface of the speaker cone, and the lower surface corresponds to the outer side
surface. As can be seen from FIG. 5, undivided acrylic synthetic fibers are present inside in the
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thickness direction of the sheet that has become the speaker cone.
[0042]
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. The undivided acrylic synthetic fiber present in
the inside of the sheet (A) is an acrylic synthetic fiber which has almost the same structure as
before being molded into a speaker cone.
[0043]
The undivided fibers and the divided fine fibers present inside the thickness direction are not
fused but only the fibers are in close contact with each other and merely strongly crimped.
Furthermore, many spaces (for example, e) are included between fibers. When manufacturing the
nonwoven fabric consisting of the above-mentioned acrylic synthetic fiber as a sheet (A) for
speaker cones in the present invention, other fibers such as natural wood pulp, carbon fiber,
aromatic polyamide fiber or mineral fiber are used as a speaker It can be mixed in amounts of up
to 10% depending on the properties required of the corn. It is also possible to add additives such
as carbon powder, resin powder, coloring agent and ceramic. Further, the molded speaker cone
can be processed by resin impregnation or coating, metal deposition, coloring, and the like to
impart various characteristics to the acoustic characteristics and design of the speaker cone.
[0044]
[Regarding Shape Retentivity] In the sheet (A) of the present invention, the acrylic synthetic fiber
has a special fiber structure, and this sheet (A) itself has a special structure. Because it does not
depend on this, it is characterized in that physical properties such as tensile strength of the sheet
(A) are greatly improved by factors such as being a uniform sheet using fibers with a long fiber
length.
[0045]
The structural and physical factors of the sheet (A) and the thermal properties of the acrylic
synthetic fiber originally possessed by the acrylic synthetic fiber such as being non-meltable but
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thermoplastic are combined When the laminate of the sheet (A) and the sheet (B) is formed into a
speaker cone by a mold, the sheet (A) can sufficiently cope with the stretching force acting on the
sheet (A) .
Therefore, when the laminate 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. In
addition, since the heat-meltable fibers are firmly bonded to form the sheet (A) by melting, the
shape retention is remarkably improved.
[0046]
On at least one surface of the surface of the speaker cone, a fusion of finely divided acrylic
synthetic fibers (sometimes divided fibers, including undivided fibers) present on the surface of
the sheet (A) A portion may be present, in which case the fused portion is preferably present, as
its shape retention is further improved. The above-described bonding of fibers by melting of the
heat-melting fibers and the fusion-bonded portion greatly contribute to the shape retention of the
speaker cone, and the undivided acrylic within the sheet (A) formed into a cone Despite the
presence of synthetic fibers and many spaces between the fibers, they are a major factor in
holding the speaker cone shape firmly even in high humidity and high temperature
environments.
[0047]
The fused portion of the fibers present on the surface of the speaker cone is formed by forming a
laminate of the sheet (A) and the 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 By doing this, it can be formed on at least one surface of
the surface. FIG. 6 is an electron photomicrograph (236 ×) showing the form of the inner
surface of a speaker cone manufactured from natural pulp, as can be seen from a comparison of
this figure with FIG. 3 (of the present invention): It can be seen that the pulp fibers are thicker
than the fibers of the inner surface of the speaker cone of the present invention, and the fibers
are not fused to each other.
[0048]
[About acoustic characteristics] Even after being formed into a speaker cone, the speaker cone of
the present invention has a large number of elongated gaps extending along the length direction
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which are almost the same as before being formed. And an acrylic synthetic fiber whose crosssectional shape of the void is not specified.
[0049]
In addition, on the surface of the speaker cone of the present invention, fine fibers obtained by
dividing the above-mentioned 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 .
[0050]
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 a value equivalent to the internal loss of natural pulp which is supposed to be
ideal, and this internal loss is hardly changed by these processes.
[0051]
FIG. 7 is an electron photomicrograph (176 ×) showing the morphology of the cross section of
the speaker cone tissue produced from natural pulp, but as described above, the speaker cone of
the present invention has a fine and uniform space While a compact uniform layer is formed as a
whole (see FIG. 5), the speaker cone made of natural pulp has rough and uneven spaces, as can
be seen from FIG. As a whole, a rough nonuniform layer is formed.
[0052]
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.
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From this, in the speaker cone of the present invention, the sound velocity which is another
characteristic of the speaker cone can be changed by changing the processing pressure such as
the molding pressure, the temperature or the metal laminate.
At this time, the internal loss hardly changes as described above.
[0053]
The present invention will be described in more detail by way of the following examples. First, an
acrylic synthetic fiber forming a 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). .
[0054]
The spinning stock solution is then allowed to stand for 6 hours, and then extruded through a
spinneret having a diameter of 0.08 mm into an aqueous coagulating solution consisting of a
mixture of 75% dimethylformamide and 25% water at 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.
[0055]
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.
[0056]
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The fibers were formed into a web with a basis weight of 100 g / m @ 2 using a spinning carder.
The web is placed on a wire mesh moving at a speed of 4 m / min, and water is jetted at a
pressure of 60 kg / cm 2 from a nozzle having 0.1 mm diameter pores arranged in a row at 0.8
mm intervals. It was processed. After repeating this process ten times alternately on the front and
back of the web, the obtained non-woven fabric was dried in hot air at 80 ° C.
[0057]
In the non-woven fabric produced by the above method, the fibers present on the front and back
surfaces are divided into a large number of finer fine fibers, and the fine fibers are dispersed and
spread in one part and in a bundle in another part. Also, undivided acrylic synthetic fibers are
present between the front and back of the non-woven fabric, and these fibers entangle with one
another to form a non-woven fabric as a whole by fiber entanglement. Integration of all the
fibers.
[0058]
Various speaker cones were formed using the non-woven fabric obtained in this manner.
[0059]
[Example 1] A three-layered laminate in which a non-woven fabric having a basis weight of 40 g
/ m2 consisting of 0.5 denier poly-polypropylene fiber is sandwiched between the non-woven
fabrics (sheet (A)) as a speaker cone manufacturing mold And molded for 5 seconds at a
temperature of 150 DEG C. and a pressure of 2 kg / cm @ 2 to produce a large number of
speaker cones.
[0060]
FIG. 3 is an electron photomicrograph (236 ×, 234 ×) showing the form of its inner side and
FIG. 4 its outer side.
FIG. 5 is an electron micrograph (magnification of 177) showing the cross-sectional form of the
above speaker cone.
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In FIG. 5, the upper surface corresponds to the inner side surface of the speaker cone, and the
lower surface corresponds to the outer side surface.
The undivided acrylic synthetic fibers exist inside in the thickness direction of the speaker cone,
and these undivided acrylic synthetic fibers are intertwined with one another and also with the
divided fine filaments. The undivided acrylic synthetic fibers and the divided fine fibers existing
inside the thickness direction are in close contact with each other. 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 polypropylene fiber melts and acts as an
adhesive. For this reason, the shape holding strength of the speaker cone is greatly improved,
and the handling thereof is improved, and the strength enough to withstand use in high
temperature and high humidity environments such as automobiles and outdoors is provided.
Met.
[0061]
Furthermore, no abnormality such as deformation or breakage of the laminate was observed at
the time of molding, and the moldability was extremely good. The variation in weight between
the speaker cones and the variation in adhesion of the melt of the polypropylene fiber were
within ± 4% and ± 3%, respectively. Table 1 shows the characteristics of the speaker cones
(Nos. 1 to 3).
[0062]
Example 2 No. 1 produced in Example 1 A modified silica-based resin solution 100H clear (trade
name, manufactured by Ron Chemical Co., Ltd.) containing 20% of solid content was coated on
the entire surface of the speaker cone 1 and naturally dried to produce a ceramic-containing
speaker cone. The weight variation among the speaker cones was within ± 4%.
[0063]
Table 2 shows the characteristics of the speaker cones (Nos. 4 to 6). As can be seen from Table 2,
this speaker cone is improved in Young's modulus and sound speed without changing the
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internal loss.
[0064]
[Example 3] No. 1 produced in Example 1 A large number of speaker cones were manufactured
by laminating an aluminum foil having a thickness of 50 μm with an adhesive on 1 speaker
cone. 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).
[0065]
As can be seen from Table 3, this speaker cone has substantially the same internal loss (tan δ) as
that of a natural pulp speaker cone, and the Young's modulus and the speed of sound are greatly
improved.
[0066]
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%.
[0067]
Table 4 shows the characteristics of an example (No. 10) of these speaker cones.
[0068]
Comparative Example 2 The acrylic synthetic fiber was cut to 15 mm, and 10 parts by weight of
the fiber was dispersed in 90 parts by weight of water.
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Next, this fiber was beaten to a freeness of 450 cc with a papermaking paper refiner adjusted to
a disk interval of 0.1 mm to produce an acrylic synthetic pulp-like fiber.
[0069]
In this pulp, many fine beard-like fibers branched from this trunk were generated on the surface
of the thick fiber portion (the original acrylic synthetic fiber trunk). In addition, there was a part
where the fiber serving as the trunk was partially divided in its length direction and separated
into thin fibers. 90 parts of this synthetic acrylic pulp fiber and 10 parts by weight of natural
wood pulp (N-BKP) are dispersed in water and made into paper through a normal paper making
process, and then dried with hot air at 85 ° C. to obtain 300 g / m 2 A sheet was produced.
[0070]
In this production process, the dispersibility of the acrylic synthetic pulp-like fiber in water was
poor, fiber lumps were generated vigorously, and a uniform sheet could not be produced. For this
reason, the obtained sheet-like material had many spots of a fiber lump. When this sheet was
formed into speaker cone paper under the conditions of 6 kg / cm 2, 120 ° C., 3 seconds,
although the form of the speaker cone could be maintained to some extent, partial breakage
occurred at the bent portion of the sheet And acoustic characteristics could not be measured.
[0071]
As can be seen from the results of each of the above Examples and Comparative Examples, in the
speaker cone of the present invention, the variation in weight among the speaker cones
manufactured under the same conditions is within ± 5%, and the comparison obtained from
natural pulp It can be half or less compared to Example 1 (± 10%). Moreover, when a speaker
cone manufactured from conventional natural pulp laminates aluminum foil, the value of tan δ
representing internal loss changes significantly by an order of magnitude, but with the speaker
cone of the present invention, as can be seen from Example 3. The velocity of sound and the
Young's modulus can be increased without changing the value of tan δ so much.
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[0072]
Also, as can be seen from Comparative Example 2, when the acrylic synthetic fiber of the present
invention is processed into a pulp, it is more difficult to produce a sheet-like material than when
using conventional natural pulp as a raw material. It is not possible to produce corn.
[0077]
According to the present invention, the speaker cone of the present invention is a sheet having a
special structure (A) formed of acrylic synthetic fiber having a special structure, and a sheet (B)
made of heat melting fiber as a speaker cone. It is molded. Therefore, the speaker cone can be
manufactured without performing the paper making process, and the working environment at
the speaker cone manufacturing site can be remarkably improved and the generation of waste
can be suppressed. Further, since the thickness unevenness 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.
[0078] Furthermore, it is possible to provide a speaker cone with less deterioration in quality
even in high temperature and high humidity environments. In addition, 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 after molding, but in the speaker cone
of the present invention, such treatment Do not need
[0079] In addition to this, in the speaker cone of the present invention, since the internal loss of
the acoustic characteristics hardly changes due to the change of the manufacturing conditions,
the resin processing, the lamination of the metal foil, etc. There is also an effect that it is possible
to change in a well-balanced manner over a wide range by changing processing conditions.
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