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JP2003274484

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DESCRIPTION JP2003274484
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for an electroacoustic transducer used for a speaker, a microphone, etc., which is a
kind of acoustic equipment, and more specifically to paper electroacoustics having improved
flame retardancy and waterproofness. The present invention relates to a transducer diaphragm.
[0002]
2. Description of the Related Art The physical properties required of a diaphragm for an
electroacoustic transducer such as a speaker are as follows: specific elastic modulus, specific
flexural rigidity, large appropriate internal loss, resistance to mechanical fatigue, good weather
resistance It is.
[0003]
As the diaphragm material, there are various metals, ceramics, synthetic fibers, carbon, aramid
fibers, synthetic resins, paper mainly made of paper, and the like.
Among them, the paper diaphragm has a merit that it has a small mass, a high degree of freedom
in design, and an advantage in cost. For this reason, generally, a paper diaphragm is often used.
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1
[0004]
In recent years, there is much demand as a use of a diaphragm as a vehicle, and it has become an
important issue to provide excellent waterproofness for use as a vehicle. In addition, since the
voice coil peripheral portion is exposed to high temperature due to the large input of the speaker
and the abnormal current, it is necessary to prevent the ignition of the cone paper provided in
the vicinity, so the flame retardancy of the cone paper becomes an important issue. It is coming.
[0005]
However, since the paper diaphragm is easily burned and has low waterproofness, it is necessary
to perform the waterproofing process together with the flameproofing process. As the flame
retardant treatment, there is a method of impregnating a boron compound, a halogen compound,
a phosphoric acid compound or the like. As the waterproofing process, for example, there is a
method of impregnating a highly waterproof resin, coating the surface, or forming a film layer on
the surface by thermocompression bonding or heat adsorption of a synthetic film.
[0006]
However, when a boron-based compound is impregnated as a flame-retardant treatment, the
strength is greatly reduced due to its hygroscopicity, and in the case of a halogen-based
compound, the flame-retardant effect is low. In addition, there is a problem that it must be used
in large quantities, and a large amount of toxic gas is generated at the time of smoke generation.
As a waterproofing treatment, a method of impregnating a fluorine resin or the like has no
persistence in the waterproofing effect, and in order to coat the surface, it is necessary to prepare
a coating agent and coat it, and the production is complicated.
[0007]
Furthermore, the method of heat-pressing and heat-adsorbing a synthetic resin film and
providing a film layer on the surface has the problem that pinholes can be formed by heating the
film, and water may infiltrate from there, and the paper vibration It was very difficult to
simultaneously satisfy the flame retardancy and the waterproofness at the same time with the
board.
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[0008]
The present invention solves the above-mentioned problems, and while having a high
waterproofness sufficient for in-vehicle use, a diaphragm made of a paper-made electroacoustic
transducer, which is satisfied with flame retardancy and has improved acoustic characteristics.
Intended to provide.
[0009]
[Means for Solving the Problems] In order to achieve the above object, the present invention is to
mix cellulose fibers or cellulose fibers and synthetic fibers, to make a wet sheet-forming method,
to heat and dry under pressure, After forming into the shape of, the composition formed by
impregnating and drying the salt of a cyanamide derivative and the fluorine-based resin, and
further heat treatment is adopted.
[0010]
Further, the synthetic fiber is characterized in that poly-para-phenylene-terephthal-amide fiber,
carbon fiber and polybenzazole fiber are used.
The salt of the cyanamide derivative is characterized in that it is a flame retardant of guanidine
phosphate type.
The fluorine-based resin is characterized in that it is a block copolymer of methacrylic acid ester
and fluorinated alkyl acrylate.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION The diaphragm for an electroacoustic
transducer in the present invention is made of a cellulose fiber as a main component to produce
a paper-made product.
Thereafter, it is subjected to heat press drying to be formed into a predetermined shape. The
vibration plate is impregnated with a cyanamide derivative salt, dried, impregnated with a
fluorine resin, dried again, and heated again.
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[0012]
Furthermore, synthetic fibers are mixed with a substance mainly composed of cellulose fibers to
produce a paper-made product, which is then heat-pressed and formed into a predetermined
shape, and then impregnated and dried with a salt of cyanamide derivative in this vibration plate,
Further, when the fluorine resin is impregnated and dried, and heat treatment is performed
again, higher performance can be secured.
[0013]
EXAMPLE 1 100% NBKP (25 ° SR) was used as cellulose fiber.
[0014]
A solution (slurry) obtained by dispersing the above NBKP in water was cut into a predetermined
shape on a wire mesh or the like, and adjusted to an appropriate water content in a dehydration
step.
[0015]
The sheet-formed product obtained above is pressurized, heated and dried using a mold having a
predetermined shape, and then this diaphragm is a guanidine phosphate flame retardant which is
a salt of a cyanamide derivative (trade name: P-Z401 three) A mixed solution of 10 parts of
guanidine carbonate (PH adjuster), 10 parts of 1,3 aminotriazole (copper rust inhibitor) and 300
parts of methanol is impregnated and dried in 200 parts of Sum Chemical Co., Ltd. After
impregnating and drying 200 parts of ethyl acetate in 100 parts of a block copolymer of ester
and fluorinated alkyl acrylate (trade name: Modiper F110 Nippon Oil and Fats Co., Ltd.), heat
treatment is performed again at 120 ° C. for 20 minutes to prepare a 16 cm diaphragm did.
[0016]
In this case, 100% NBKP (25 ° SR) of flammable cellulose fiber was used as the base pulp, but
carbon fiber and polybenzazole fiber other than poly-para-phenylene-terephthal-amide fiber are
used as the synthetic fiber. You may mix | blend suitably and use it.
[0017]
Physical properties, such as Young's modulus, of the diaphragm of the present invention are as
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follows when compared with the untreated one to which neither flame retardancy nor fire
prevention treatment is added nor to which only the flame retardant treatment is added, and is
untreated Compared with the ones, the physical properties are significantly reduced by
impregnating and drying the flame retardant of guanidine phosphate type, but the block
copolymer of methacrylic acid ester and fluorinated alkyl acrylate, which is a fluorocarbon resin,
is further impregnated and dried again. The heat treatment improves the physical properties.
Young's modulus (GPa) Speed of sound (m / s) Specific bending rigidity Tan δ Inventive product
2.44 1812 2.44 0.1 Flame retardant treatment only 1.02 1244 1.89 0.1 Untreated 1.56 1586 2
.56 0.
0
[0018]
The flame retardancy of the product of the present invention was evaluated according to the
method of MVSS No. According to 302 and (JIS 1201), it was confirmed that the flame
disappears immediately after the gas burner is extinguished, and the self-extinguishing ability is
excellent.
[0019]
According to the evaluation of the waterproofness of the product of the present invention, after
leaving for 30 hours with 30 mm of water accumulated on the back surface of the diaphragm,
the exudation of water to the diaphragm surface and the deformation of the diaphragm were
observed. Was not seen and there was no deformation of the diaphragm.
[0020]
As described above, it is possible to obtain a paper-made diaphragm with low hygroscopicity as
well as flame retardancy with a small amount of adhesion, just by impregnating with a guanidine
phosphate flame retardant, Young's modulus, sound velocity, specific flexural rigidity In addition,
the method of impregnating a fluorine-based resin or the like, which has been conventionally
used as a waterproofing treatment, does not have sufficient water repellency and does not
provide sufficient waterproofness.
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In the present invention, a guanidine phosphate flame retardant is impregnated and dried, and a
block copolymer of a methacrylate and a fluorinated alkyl acrylate is impregnated and dried as a
fluorocarbon resin, and then heat treated again at 120 ° C. for 20 minutes. Therefore, it is
possible to achieve improvement in various physical properties while achieving both excellent
flame retardancy and waterproofness without requiring special equipment.
[0021]
In particular, the improvement of the waterproofness and physical properties is achieved by the
capture of the compatible segment of the fluorine-based block copolymer of methacrylic acid
ester and fluorinated alkyl acrylate with the substrate to enhance the bonding between fibers. At
the same time, it is considered that the fluorine group is transferred to the surface and oriented.
[0022]
Further, as shown in FIG. 1, the second harmonic distortion 11 in the middle and high
frequencies is reduced and the frequency at the sound pressure 12 is lower than that in the case
where the flame retardant treatment and the waterproof treatment are not performed (see FIG.
2). The sound pressure characteristics became flat and good sound quality could be obtained.
This is largely due to the function of the block copolymer of the fluorine-based resin
methacrylate and the fluorinated alkyl acrylate, as the impregnating agent used in the present
invention as described above.
[0023]
In the above examples, 100% of cellulose fibers are shown, but those obtained by mixing
cellulose fibers and synthetic fibers are impregnated and dried with a guanidine phosphate flame
retardant, and further impregnated and dried with a fluorine-based resin, If it heat-processes
again, while being able to acquire the same effect about flame retardance and waterproofness, an
acoustic characteristic will also be improved further.
[0024]
As described above, according to the present invention, in production, cellulose fiber or a mixture
of cellulose fiber and synthetic fiber is paper-made, and then impregnated with a guanidine
phosphate flame retardant and then dried. Furthermore, the flame resistance and waterproofness
of the diaphragm mainly made of paper can be improved, and the acoustic characteristics can be
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improved by means such as impregnating with a fluorine resin, drying again, and heat drying
again without increasing the cost. Can also achieve the effect of improving.
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