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JPH0193999

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DESCRIPTION JPH0193999
[0001]
FIELD OF THE INVENTION The present invention relates to a loudspeaker diaphragm having
excellent acoustic characteristics. More specifically, the present invention relates to a speaker
diaphragm having high sound quality and high durability because both the specific elastic
modulus and the internal loss are large and the heat resistance is good. <Prior Art> In order to
faithfully reproduce the characteristics of the speaker diaphragm, the material and the shape are
improved. As a material to be used, corn paper and aluminum are generally used. On the other
hand, in recent years, liquid crystalline polyester is known as a thermoplastic resin having a large
specific elastic modulus. For example, in JP-A-49-72395, a liquid crystal polyester obtained by
copolymerizing p-hydroxybenzoic acid and polyethylene terephthalate is disclosed in JP-A-54
77691'3, and p-hydroxybenzoic acid and 6-hydroxy- A liquid crystalline polyester of 2-naphthoic
acid is disclosed. <Problems to be Solved by the Invention> However, while the above-mentioned
cone paper has a large internal loss, it has a defect that the specific elastic modulus is small,
while the above-mentioned aluminum has a large specific elastic modulus, on the contrary Had.
Therefore, as a result of examining the speaker cone using the liquid crystal polyester, the
present inventors have found that the liquid crystal polyester obtained by copolymerizing phydroxybenzoic acid and polyethylene terephthalate described in the above-mentioned JP-A-4972395 has heat resistance. Due to the shortage, there is a defect in durability at high
temperature, and the liquid crystalline polyester of p-hydroxybenzoic acid and 6-hydroxy-2naphthoic acid described in JP-A-54-77691 lacks a specific elastic modulus It also turned out
that the heat resistance is not always sufficient. In other words, the liquid crystal polyesters that
have been studied so far have ■ poor durability under high temperatures such as in automobiles
due to insufficient heat resistance ■ ■ still lacks in specific elastic modulus ■ resin toughness
is There was a disadvantage that the durability was poor because of the shortage. Therefore, an
object of the present invention is to provide a speaker diaphragm having high specific modulus
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and high internal loss, good heat resistance, and excellent durability. Means for Solving the
Problems> The present inventors arrived at the present invention as a result of intensive studies
to solve the various problems of the existing speaker diaphragm. That is, this invention is a
speaker diaphragm which consists of following structural unit (I)-(I [[), and makes aromatic
polyester which can form an anisotropic molten phase as an essential component. Represents
one or more groups selected from -CH 2 CH 2-, and the unit (I> is 40 to 90 mol% of the whole,
the unit [(II) t (III)] whole whole 0 to 10 T: t%% When the molar ratio of structural unit (It) / (III)
is 1/9 to 9/1, and X is -CH2CH2-, the structural unit (I [[) is 5 to 23 mol% of the total. .
The carbonyl groups of the dicarboxylic acid components of the structural units (n) and (I) are in
the relation of para-position and / or meta-position to each other. In the aromatic polyester used
in the present invention, the above-mentioned Wi structural unit I) represents a structural unit of
a polyester formed from p-hydroxy anhydride, wax, and aromatic acid. The structural unit (II)
represents a cross unit of polyester formed from 4.4-monodihydroxybiphenyl and terephthalic
acid and / or isophthalic acid. Horizontal road unit <m> is hydroquinone, t-butyl hydroquinone,
4.4-hydroxybiphenyl ether, 2.6-hydroxynaphthalene, 2.7-hydroxynaphthalene,
chlorhydroquinone, methylhydroquinone, phenylhyde 17 quinone, ethylene Indicates a structural
unit of a polyester comprising one or more dihydroxy compounds selected from glycols,
preferably one or more dihydroxy compounds selected from hydroquinone, t-butylhydroquinone,
phenylhydroquinone, ethylene glycol and terephthalic acid and / or isophthalic acid . It is
essential that the structural unit (I) is 40 to 90 mol% of the whole, preferably 60 to 85 mol%, and
if the lateral unit (I) exceeds 90 mol% of the whole or 40 mol% In the case of ungrooved, the
flowability is poor and not practical. In addition, the molar ratio of the etM structural unit ■) /
(■) is 1-9 to 9/1, and if it is greater than 9/1 or less than 1/8, the flow and damage are defective
or the heat resistance is poor and it is not practical. . Furthermore, when X is -CH2CH2-, it is 523 mol% of a structural unit (I [[) or the whole. If the structure J clearance (II [) is less than 5
mol% of the whole, the flowability is poor, and if it exceeds 23 mol%, the heat resistance becomes
poor and it is not practical. The aromatic polyester used in the present invention can be produced
according to the conventional polycondensation method of polyester, and the production method
is not particularly limited, but in the cases other than the structural unit X or -CH2CH2-, (1) to (4)
When the structural unit X is -CH2CH2-, the method of (5) may be mentioned. (1) A method of
producing from an acylated product of p-acetoxybenzoic acid, an acylated product of an aromatic
hydroxy compound such as 4 ° -diacetoxybiphenyl and the like and an aromatic dicarboxylic
acid such as terephthalic acid by a deacetic acid polycondensation reaction. (2) A method of
production from an aromatic dihydroxy compound such as p-hydroxybenzoic acid or 4.4′dihydroxybiphenyl and an aromatic dicarboxylic acid such as terephthalic acid and acetic
anhydride by a deacetic acid polycondensation reaction.
(3) It is prepared by dephenolic polycondensation from an aromatic dihydroxy compound such
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as −-hydroxyanhydride, Q, phenyl ester of aromatic acid and 4.4-monodioxybiphenyl and
diphenyl ester of aromatic dicarboxylic acid such as terephthalic acid Method. (4) A desired
amount of diphenyl carbonate is reacted with an aromatic dicarboxylic acid such as Phydroxybenzoic acid and terephthalic acid to obtain diphenyl esters, and then an aromatic
dihydroxy compound such as 4.4-dihydroxybiphenyl is added to A method of producing by
phenol polycondensation reaction. (5) In the above-mentioned methods (1) and (2), polyethylene
terephthalate is allowed to coexist, and the acid decomposition of polyethylene terephthalate is
followed by production by a deacetic acid polycondensation reaction. Typical catalysts used for
the polycondensation reaction are metal compounds such as stannous acetate, tetrabutyl titanate,
lead # acid, antimony trioxide, magnesium, sodium acetate, potassium acetate and sodium
phosphate, among others, especially phenol-free phenols. It is effective at the time of
polycondensation. Also, the aromatic polyester used in the present invention forms an
anisotropic melt phase, but! having a melt viscosity of 10 to 15,000 boise measured at a shear
rate of 1.000 (1 / sec) at a temperature 40 ° C. higher than the temperature at which l ′ ′
begins to exhibit unilaterality (liquid crystal onset temperature) In particular, those of 20 to
5,000 voices can be used more preferably. The speaker diaphragm of the present invention can
be molded by molding the above-mentioned liquid crystalline aromatic polyester by a commonly
used method such as injection molding and press molding. Further, as the 0 reinforcing agent
which can be used by blending the above-mentioned aromatic polyester and a reinforcing agent,
inorganic or spinach fibers such as carbon fiber, glass fiber, aramid fiber, alumina fiber are
preferable, and specific elastic modulus High carbon fibers are particularly good. The shape of
the reinforcing agent is not particularly limited, and any of long fibers, crosses, short fibers and
the like can be used. In the case of molding by injection molding, a method in which a short fiber
reinforcing agent is mixed in advance with a liquid crystal polymer and injected is preferable, and
there is an advantage that the cost is low. In the case of molding by press molding, a crossshaped reinforcing agent is favorably used, and a diaphragm can be obtained by mixing a resin at
the time of pressing or by press molding a prepreg integrally fixed beforehand. According to, it is
possible to make a speaker diaphragm with a high-class feeling in which the color of the
reinforcing fiber is emphasized.
When a reinforcing agent is used, the amount thereof is preferably 60% by weight or less based
on the total weight, and particularly preferably in the range of 10 to 50% by weight. The speaker
diaphragm of the present invention can be made into various shapes and sizes by utilizing the
property of good fluidity of liquid crystal polymer. The shape can be an arc shape, a flat plate
shape, an irregular shape, or a complex shape, and the thickness is usually 0.05 to 10 mm, more
preferably 0.1 to 2 mm. Moreover, the control method of the diaphragm in the present invention
does not limit this. EXAMPLES The present invention will be described in more detail by way of
the following examples. Reference Example 1 519 Zff of p-acetoxybenzoic acid, 184 parts of 4,4diacetoxybiphenyl, 85 parts of t-butyl hydroquinone diacetate, 19.4 parts of hydroquinone
diacetate and 186 parts of terephthalic acid are stirred. Charge into a reaction vessel equipped
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with a wing and a distillation tube, react for 3.0 hours at 250-340 ° C under nitrogen gas
atmosphere, raise the temperature to 350 ° C, and reduce the pressure inside the system to 1 °
5 nonlliJ The reaction mixture was further heated for 1 hour for polycondensation reaction to
obtain a resin [A] having the following theoretical structural formula. -Buj, / m / n 10 = 72/17 /
8.5 / 2.5, put this resin A on the sample table of 1 ha light microscope ,! 71. When the optical
anisotropy was confirmed by heating, good optical anisotropy was shown at 307 ° C. or higher.
Reference Example 2 54 parts by weight of P-acetoxybenzoic acid, 184 parts by weight of 4,4diacetoxybiphenyl, 62 parts by weight of hydroquinone diacetate and 124 parts by weight of
terephthalic acid, 42 parts by weight of isophthalic acid, stirring blade, distillation pipe The
reaction vessel is charged with a reaction vessel under a nitrogen gas atmosphere for 3 hours at
250 to 360 "C. The pressure is reduced to 1 mHQ and heating is further performed for 1 hour to
complete the polycondensation, and has the following theoretical structural formula Resin [B]
was obtained. This polyester was placed on a sample stage of a polarizing microscope, and the
temperature was raised to confirm the optical anisotropy. As a result, no satisfactory optical
anisotropy was exhibited at 3O 5 ° C. or higher. Reference Example 3 608 parts by weight of pacetoxybenzoic acid, 122 parts by weight of 4,4-diacetoxybiphenyl, 75 parts by weight of
terephthalic acid and 130 parts by weight of polyethylene terephthalate having an intrinsic
viscosity of about 0.6 The reaction mixture was charged with the reaction mixture to carry out
deacetic acid polymerization. First, after reacting at 250 to 300 ° C. for 25 hours under a
nitrogen gas atmosphere, the pressure is reduced to 0.2 n + ml; l at 300 ° C., and the reaction is
further continued for 3.25 hours to complete the polycondensation. The theoretical amount of
acetic acid is distilled off, and the resin [C] having the following theoretical structural formula is
111.
j / m / n = 75/10. As a result of confirming the optical anisotropy by placing the polyester on a
sample stage of a polarizing microscope and confirming the optical anisotropy, the liquid crystal
start temperature was 264 ° C., and the optical anisotropy was excellent. EXAMPLE 1 The resin
[A] synthesized according to Reference Example 1 was injection-molded into an arc-shaped cone
having a diameter of 16 mm and a thickness of 0.4. As a result, a good speaker diaphragm
having a smooth surface and a white glossy appearance was obtained. Further, in order to
investigate the vibration characteristics, a flat plate was separately injection molded to a
thickness of 1/32 inch. The resin plate was cut into 180 m × 30 mm, and the vibration damping
coefficient (η) in the bending mode was determined by the vibration reed method using a
“complex elastic modulus measuring device” manufactured by Brüel & Kea. In addition, the
specific elastic modulus (E / e) was determined from the resonant frequency. These values are
listed in Table 1. Also, HDT (heat distortion temperature) was measured according to ASTM D648 and is shown in Table 1. Example 2 The resin [A 170 parts by weight of Reference Example
1] and 30 parts by weight of a cut fiber (3 inch length) of carbon fiber T-300 manufactured by
Higashi Shikko Co., Ltd. were melt-blended using an extruder. The extruded product was injection
molded into an arc cone and a flat plate in the same manner as in Example 1, and the physical
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properties were measured. In addition, the arc-shaped cone uniformly dispersed carbon fibers,
and the appearance was good. Examples 3 to 5 The same tests as in Example 1 were conducted
using the polymers [B] and [0] of Reference Example 2.3 and the above carbon fiber, and the
results are shown in Table 1. Comparative examples 1 to 3 or less! Using the resins [D] to [F]
shown by the I4 molding method, molding was performed in the same manner as in Example 1.
However, in Comparative Example 3, which is an example of molding using resin [F], the
formability was poor and a satisfactory diaphragm could not be obtained. Further, the
diaphragms molded using the resins [D] and [E] were tested in the same manner as in Example 1,
and the results are shown in Table 1. Resin [D] Resin [E Co-Resin [F] Comparative Example 4
Casting was carried out using an aluminum metal as a material and using a mold from which an
arc-shaped cone and a flat plate having the same shape as in Example 1 were obtained. The metal
was melted to 680 "C and the mold was at 250 ° C. After casting, cooling was performed to
obtain cones and flat plates and the same test was performed. As shown in Table 1, Comparative
Example 1.2 is inferior in specific elastic modulus to Examples 1 to 5 of the present invention.
Moreover, although the specific elastic modulus is high, the vibration damping coefficient of
Comparative Example 4 is significantly inferior to Examples 1 to 5 and Comparative Example 1.2.
It is also understood that Comparative Example 1.2 has a lower HDT compared to the present
example.
As described above, it is apparent that the speaker diaphragm in the present invention is
excellent in any of the specific elastic modulus, the vibration damping coefficient, and the HDT.
<Effect of the Invention> According to the present invention, it is possible to obtain a speaker
diaphragm in which both the specific elastic modulus and the vibration damping coefficient are
high and the high heat resistance is maintained.
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