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JP2005347907

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DESCRIPTION JP2005347907
PROBLEM TO BE SOLVED: To provide a speaker diaphragm having excellent features such as
excellent workability at the time of molding and high strength and rigidity. SOLUTION: The
acrylic foam 1 is obtained by mixing fibers 5 and is obtained by molding the acrylic foam plate 1
in which the fibers 5 are mixed with a die for a speaker diaphragm. The acrylic foam board 1
with which the fiber 5 was mixed is obtained by mixing the fiber 5 at the time of acrylic resin
superposition | polymerization, and making it heat-foam after that. The length of the fibers 5 is
preferably 0.1 to 50 mm. Further, as the fibers 5, various types of fibers can be used, such as
flexible ones such as aramid, PEN and polyester fibers, and rigid ones such as carbon fibers and
glass fibers. [Selected figure] Figure 2
Speaker diaphragm
[0001]
The present invention relates to a speaker diaphragm, for example, to a speaker diaphragm
having excellent features such as excellent workability at the time of molding and high strength.
[0002]
As a reinforcing material of the speaker diaphragm or the speaker diaphragm (with a skin layer
on both sides or one side), it is possible to use a rigid foam made of a continuous foam acrylic
foam which is shaped by heat press molding (See, for example, Patent Document 1).
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1
For example, the outline of the cross section of the acrylic foam 1 is shown to (a) of FIG. In FIG.
1A, 2 is an acrylic resin portion, and 3 is an open cell portion. Such acrylic foam 1 is processed
into the speaker diaphragm 10 by a manufacturing process including preheating, mold lowering,
molding, mold opening, inside and outside diameter cutting, etc. as shown in FIG. 1B. The
Numeral 4 in FIG. 1 (b) is a mold used for heat press molding.
[0003]
JP-A-61-19299 (page 3)
[0004]
However, although acrylic foam is a hard and rigid material, it has the disadvantage of being
brittle.
For example, as shown in FIG. 1C, the acrylic foam 1 is easily broken even when the amount of
deformation is small. Therefore, when the speaker diaphragm 10 is processed from the acrylic
foam 1 by the process as shown in FIG. 1 (b), the workability at the time of molding is bad, and
even if the inner and outer diameters are removed in the later process Possibilities are mentioned
as an example.
[0005]
That is, the invention according to claim 1 is characterized in that it comprises an acrylic foam
mixed with fibers.
[0006]
Hereinafter, the speaker diaphragm of the present invention will be described in more detail.
The speaker diaphragm of the present invention can be obtained by molding an acrylic foam
plate mixed with fibers with a mold for a speaker diaphragm. The acrylic foam board with which
the said fiber was mixed can be obtained by mixing a fiber at the time of acrylic resin
superposition | polymerization, and making it heat-foam after that. The fibers used in the present
invention are not particularly limited, and may be flexible or rigid. Although it does not
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2
specifically limit as a flexible fiber, Aramid fiber, PEN fiber or polyester fiber etc. are mentioned.
The rigid fiber is not particularly limited, and carbon fiber, glass fiber and the like can be
mentioned. Other fibers that can be used include PBO fibers, liquid crystal fibers, acrylic fibers,
metal fibers, ceramic fibers, silicon carbide fibers, boron fibers, amorphous fibers, acetate fibers,
silk fibers and the like. The length of the fibers used in the present invention is not particularly
limited, but is preferably 0.1 to 50 mm.
[0007]
Next, the above-mentioned "liquid acrylic resin before foaming" will be described. Although the
"acrylic resin" of "liquid acrylic resin before foaming" is not particularly limited, for example, one
or more monomers selected from the group consisting of acrylamide, methacrylamide, acrylic
acid and methacrylic acid (Hereinafter, also referred to as an acrylic monomer) and, as required,
a polymer obtained by polymerizing a monomer copolymerizable with the acrylic monomer
(hereinafter, also simply referred to as another monomer), etc. .
[0008]
In this case, any other monomer may be used as long as it can be copolymerized with the abovementioned acrylic monomer, and in particular, styrene, acrylonitrile, vinyl acetate, various acrylic
esters, methacrylic esters, etc. Of vinyl compounds and diallyl phthalate, triallyl cyanurate,
triallylamine, diallylamine, diallyl citracolate, triallyl phosphonate, diallylia itaconate, triallyl
ascorbate, divinyl benzene, ethylene glycol dimethacrylate and the like. Preferred are compounds
having two or more bonds.
[0009]
As a method of polymerizing the above-mentioned acrylic monomer and, if necessary, other
monomers, known methods are used.
Examples of known polymerization methods include catalytic polymerization, thermal
polymerization, ionizing radiation, polymerization by irradiation with ultraviolet light or light,
polymerization by the action of ultrasonic waves, etc. A method or catalyst by which
polymerization is performed by ionizing radiation irradiation The method of first polymerizing by
polymerization and further performing ionizing radiation irradiation is the one which gives the
best result.
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[0010]
Moreover, the "acrylic resin before foaming" used in the present invention contains the above
"acrylic resin" and a foaming agent. As the above-mentioned foaming agent, all of the foaming
agents which are vaporized by heating to become gas or are decomposed to generate gas are
used, but in addition, urea which is not well known as a conventional foaming agent Substances
which decompose to generate gas at a temperature at which heating and foaming occur, such as
citric acid and itaconic acid, are also used. However, preferred blowing agents used are
dinitrosopentamethylenetetramine, amidoguanidine, trimethylene triamine, paratoluene sulfone
hydrazine, azodicarbonamide, itaconic acid, maleic anhydride, urea, thiourea, ammonium
chloride, dicyandiamide, There are dioxane, hexane, chloral hydrate and citric acid, etc., among
which urea, itaconic acid, maleic anhydride, thiourea, chloral hydrate and citric acid are
preferable.
[0011]
Such a foaming agent is mixed uniformly only by mixing the two when it is compatible with the
above-mentioned acrylic polymer, or uniformly mixed by appropriately using a medium when the
two are not compatible. . Furthermore, with respect to the addition amount of the abovementioned foaming agent, generally, the expansion ratio of the foaming agent is proportionally
increased if the addition amount of the foaming agent is increased until the addition amount of
the foaming agent is increased to some extent. When the expansion ratio is reached, the
expansion ratio hardly changes even if the addition amount of the foaming agent is further
increased. Therefore, industrially, it is meaningless to add more than the amount of the foaming
agent at the maximum expansion ratio. The amount of the foaming agent at this time varies
depending on the type of monomer, the type of the foaming agent, the pressure at the time of
foaming, the temperature, etc., but usually 60% by weight or less, preferably 0.1 -30 (weight)% is
used and is used suitably according to the use.
[0012]
The fiber is mixed with the liquid acrylic resin before the polymerization, and after the
completion of the polymerization, it is possible to obtain an acrylic foam board mixed with the
fibers by heating and foaming. The temperature at the time of heating and foaming varies
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4
depending on the nature of the unfoamed acrylic resin, the type of the foaming agent, etc., but
usually 100 to 300 ° C., particularly preferably 130 to 230 ° C. The outline of the cross
section of "the acrylic foam board with which the fiber was mixed" obtained by said process is
shown in FIG. (A) uses flexible fibers, and (b) uses rigid fibers. In FIG. 2 (a) and (b), 5 is a fiber and
others are the same as that of FIG. 1 (a). In the case of using flexible fibers, mixed fibers are
formed along the inside of the foam cells to improve the strength between the cells. Further, in
the case of using rigid fibers, the fibers are disposed in the hollow portion of the foam cell, and
the rigidity of the cell is improved.
[0013]
The above-mentioned "acrylic foam plate mixed with fibers" is subjected to steps including die
lowering, (heating) molding, mold opening, inside and outside diameter cutting, etc. as shown in
(b) of FIG. It is processed into a speaker diaphragm. The heating temperature and time during
molding are not particularly limited, but 100 to 200 ° C. and 5 seconds to 5 minutes are
preferable.
[0014]
In addition, the speaker diaphragm of the present invention may contain nano-sized (5-500 nm)
inorganic fillers such as alumina and silica, and carbon nanotubes. The inorganic filler and the
carbon nanotube can be added at the same time as the addition of the fiber during the
production of the speaker diaphragm of the present invention.
[0015]
The above-described speaker diaphragm is improved in strength or rigidity by containing fibers,
so that the workability at the time of molding when processing the speaker diaphragm from an
acrylic foam is improved, and the inner and outer diameters are removed in the post process. But
I was not cramped.
[0016]
EXAMPLES The present invention will be more specifically described below by way of Examples,
but the scope of the present invention is of course not limited by these.
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[Example 1] 100 parts of acrylamide, 100 parts of acrylic acid, 60 parts of maleic anhydride, 100
parts of acrylonitrile, 50 parts of methyl methacrylate, 50 parts of styrene, 35 parts of
concentrated sulfuric acid are mixed, and 1% tertiary butyl hydroperper is mixed Oxide and 1%
dimethylaniline are added to form a homogeneous solution, which is polymerized at 35 ° C for
40 hours, and then 30 parts of urea and 30 parts of aramid fibers of 0.1 to 50 mm in length are
mixed, 200 It shape | molded in plate shape, heating at (degreeC), and obtained the "acrylic foam
with which the fiber was mixed." As shown in FIG. 1 (b), this “acrylic foam mixed with fibers”
was molded while being heated to 120 ° C. with a mold for a speaker diaphragm. After that, the
mold was opened to obtain a speaker diaphragm. Example 2 A speaker diaphragm was prepared
in the same manner as in Example 1 except that glass fibers were substituted for aramid fibers.
[0017]
It is a manufacturing-process schematic of the conventional speaker diaphragm which consists of
acrylic foams. It is the cross-sectional schematic of the acrylic foam used for the speaker
diaphragm of this invention.
Explanation of sign
[0018]
Reference Signs List 1 acrylic foam 2 acrylic resin portion 3 continuous air bubble portion 4
speaker diaphragm mold 5 fiber 10 speaker diaphragm
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