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JP2002291092

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DESCRIPTION JP2002291092
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
speaker diaphragm. More particularly, the present invention relates to a speaker diaphragm
formed by molding a cast film made of an aromatic polysulfone resin.
[0002]
2. Description of the Related Art In addition to the low density for maintaining the acoustic
radiation sound pressure level and the large rigidity for suppressing distortion and maintaining a
large allowable input resistance, the speaker diaphragm has a reproduction frequency band. It is
required that the specific elastic modulus is large in order to expand, and that the internal loss is
large in order to suppress the divided vibration of the diaphragm and flatten the frequency
characteristic. As a speaker diaphragm, although what impregnated resin in paper pulp is known,
since a specific elastic modulus and rigidity are low, the reproduction | regeneration frequency
band was narrow and it was not able to hold | maintain large tolerance input tolerance. In order
to solve these problems, it is known that carbon fiber woven fabric is impregnated with an epoxy
resin and thermoformed, but it is not practical because the raw material cost is high and the
molding takes a long time. Further, from the viewpoint of the acoustic radiation sound pressure
level, polyethylene terephthalate films, which are lower in density and cheaper than metals and
ceramics, have recently been used. However, when used in the vicinity of a voice coil which is a
driving source of a speaker or a speaker for car listing, etc., the diaphragm is exposed to a high
temperature for a long time, but the heat resistance which can sufficiently withstand under such
use conditions is I did not.
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[0003]
Then, the speaker diaphragm using the polyether sulfone resin film excellent in heat resistance is
examined. For example, JP-A-59-63897 discloses a sheet-like film having a thickness of 100 μm,
which is obtained by heating and pressing a film made of polyether sulfone. Japanese Patent
Application Laid-Open No. 60-139099 discloses a film having a thickness of 50 μm obtained by
vacuum forming a film made of polyether sulfone. However, polyether sulfone films
manufactured by these melt extrusion methods are prone to generation of bumps and die lines,
and there is a problem that it is difficult to obtain a speaker diaphragm having excellent
thickness accuracy.
[0004]
SUMMARY OF THE INVENTION An object of the present invention is to provide a diaphragm of a
speaker having excellent heat resistance, a large specific elastic modulus, a wide reproduction
frequency band, and a large internal loss and a flat frequency characteristic. It is.
[0005]
SUMMARY OF THE INVENTION As a result of intensive studies to find a speaker diaphragm free
from the problems as described above, the present inventors manufactured from an aromatic
polysulfone resin having a specific reduced viscosity. A speaker diaphragm obtained by molding
a cast film having a specific average film thickness and thickness accuracy is found to be high in
specific modulus and internal loss and excellent in acoustic characteristics, and the present
invention has been completed. The
[0006]
That is, the present invention comprises an aromatic polysulfone resin having a reduced viscosity
of 0.60 to 1.0 dl / g and containing 80 mol% or more of a repeating structural unit represented
by the following structural formula (I) per molecule, A speaker diaphragm characterized in that a
cast film having an average film thickness of 40 μm or less and a thickness accuracy within 10%
of the average film thickness is formed.
[0007]
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BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in
detail below.
The aromatic polysulfone resin used in the present invention is a resin containing a repeating
structural unit represented by the following general formula (I).
In addition, the aromatic polysulfone resin may contain at least one of a structure represented by
the following general formula (II) or a structure represented by the following general formula
(III), and the above-mentioned formula (II) and It may be a random copolymer or an alternating
copolymer containing a repeating structural unit represented by the formula (III).
[0008]
[In formula (I), R1 represents a C1-C6 alkyl group, a C2-C10 alkenyl group, a phenyl group, or a
halogen atom, and p is an integer of 0-4.
Each R1 on the same or different nucleus may be different from each other. Each p may be
different from one another. ]
[0009]
[In formula, R1 represents the same thing as the above-mentioned, p is an integer of 0-4. m and n
indicate the average number of repeating structural units, and m and n are positive numbers
from 0.1 to 100. Each R1 on the same or different nucleus may be different from each other.
Each p may be different from one another. X represents an organic group having 1 to 20 carbon
atoms, a carbonyl group, a divalent sulfur atom or a divalent oxygen atom. ]
[0010]
...... (III) [In formula, R1 represents the same thing as the above, p is an integer of 0-4. q is an
integer of 1 to 5; m and n indicate the average number of repeating structural units, and m and n
are positive numbers from 0.1 to 100. Each R1 on the same or different nucleus may be different
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from each other. Each p may be different from one another. Each q may be different from one
another. ]
[0011]
Here, as a C1-C6 alkyl group, a methyl group, an ethyl group, t-butyl group, a cyclohexyl group
etc. are mention | raise | lifted, for example. Moreover, as a C2-C10 alkenyl group, an ethynyl
group, an iso-propenyl group, etc. can be illustrated, for example. Examples of the halogen atom
include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. Examples of the
organic group having 1 to 20 carbon atoms include saturated aliphatic alkylene groups such as
isopropylidene group, ethylidene group and methylene group, unsaturated aliphatic alkylene
groups such as ethynylene group, and aroma such as xylylene group and phenylmethylene group
Group alkylene groups and the like.
[0012]
When the aromatic polysulfone resin used in the present invention contains the structure
represented by (II) or (III), (m / m + n) is 0.8 or more. Further, q in the structure of (III) is
preferably 1 or 2, and more preferably 2. In the present invention, a resin containing a structure
comprising a repeating structural unit represented by (I), a resin containing a structure
represented by (II) is preferably used, and more preferably a resin comprising a repeating
structural unit represented by (I) Resins containing structures are used. Among them, resins in
which all p is 0, that is, a resin containing a structure comprising repeating structural units
represented by the following formula are more preferable, and 80 mol% or more of repeating
structural units represented by the following formula per one molecular chain Resins are
particularly preferred.
[0013]
The reduced viscosity of the aromatic polysulfone resin used in the present invention is 0.6 to
1.0 dl / g, preferably 0.60 to 0.90 dl / g, more preferably 0.70 to 0.80 dl / g It is. When this resin
is used at less than 0.6 dl / g, it is difficult to obtain a stable aromatic polysulfone resin solution
composition suitable for casting, and it is difficult to prepare a uniform solution at more than 1.0
dl / g. In addition, filtration and degassing become difficult, causing problems in the appearance
of the film. Here, the reduced viscosity is a value obtained by dissolving 1 g of aromatic
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polysulfone in 100 cm 3 of N, N-dimethylformamide and then measuring the viscosity of this
solution at 25 ° C. using an Ostwald viscosity tube.
[0014]
A known method can be adopted as a method of producing the aromatic polysulfone resin used
in the present invention. Alternatively, commercially available aromatic polysulfone resins may
be used as they are. Examples of commercially available aromatic polysulfone resins include
those comprising the above structural unit (I) such as Sumika Excel PES 7600P by Sumitomo
Chemical Co., Ltd., and above structural units (I) such as UDELP-1700 by AMOCO. And (II).
Moreover, the terminal structure is decided according to the manufacturing method of each
resin, Although it does not specifically limit, For example, -Cl, -OH, -OR (R is an alkyl group) etc.
are mentioned.
[0015]
As a solvent used to dissolve the aromatic polysulfone resin of the present invention, amides such
as N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide; sulfoxides such as
dimethyl sulfoxide; cresol etc. Such as phenols of the above; halogenated carbons such as
methylene chloride; esters such as .gamma.-butyrolactone; and good solvents for aromatic
polysulfone resins. These solvents may be used alone or in combination of two or more. Further,
it is preferable to add a poor solvent or non-solvent for aromatic polysulfone resins such as
hydrocarbons, ketones, esters, ethers and acetals. Preferred are hydrocarbons such as
cyclohexane and toluene, ketones such as acetone and cyclopentanone, esters such as ethyl
acetate, and ether acetals such as methylal. By adding these poor solvents or non-solvents, not
only can the storage stability of the solution of the aromatic polysulfone resin be further
improved, but also solutions at the same concentration as compared with the case where good
solvents are used alone. Since the viscosity is reduced, high solid differentiation can be achieved,
which is very advantageous in practical use.
[0016]
The concentration of the aromatic polysulfone resin in the solution is preferably 10% by weight
to 50% by weight, and more preferably 20% by weight to 40% by weight. If the concentration is
less than 10% by weight, the effective concentration is low, and particularly when producing a
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thick film, the film tends to have orange peel caused by convection in the early stage of drying,
and the surface smoothness tends to be deteriorated. At a concentration of 50% by weight or
more, the solution is gelled by crystallization of the aromatic polysulfone resin during storage
and is inferior in stability, and furthermore, in this region, the solution has high viscosity and is
thus filterable. And tend to be inferior to defoaming properties. The method for producing the
solution is not particularly limited, and the solvent may be added to the resin or the resin may be
added to the solvent. In order to increase the dissolution rate, it is preferable to use powder as
the form of the resin, but it is not particularly limited.
[0017]
In addition, various additives such as a leveling agent, a plasticizer, and an antistatic agent can be
added to the solution, as necessary. As the leveling agent, those of acrylic type, silicone type and
fluorine type can be used. The plasticizer is preferably one which is compatible with the aromatic
polysulfone resin, does not cause phase separation or bleed out, and does not cause coloring. For
example, plasticizers such as phthalic acid type, phosphoric acid type, adipic acid type, citric acid
type and glycolic acid type can be mentioned, and butyl benzyl phthalate, tricresyl phosphate,
methyl phthalyl ethyl glycolate and the like are preferably used. There are two types of antistatic
agents, one for surface coating and one for internal kneading. Examples of antistatic agents for
surface coating include polymers containing quaternary ammonium salt esters of acrylic acid and
methacrylic acid, copolymers containing polyethylene glycol (meth) acrylate, polyethylene glycol
and terephthalic acid. In addition to polyethers and polyesters, epoxy resins with polyethylene
glycol diglycidyl ether and amine compounds, urethanes with polyethylene glycol and
diisocyanate, etc., quaternary ammonium salts, betaine type, imidazoline type, alanine type,
sulfonic acid, sulfuric acid ester, Conventional surfactants such as phosphoric acid esters can also
be used. As antistatic agents for kneading, fatty acid monoglycerides, sorbitan fatty acid esters,
nitrogen-free non-ionic surfactants such as polyoxyethylene derivatives are used. Alternatively,
the surface may be subjected to hydrophilization treatment using corona treatment or the like
without using an antistatic agent.
[0018]
Next, an aromatic polysulfone resin film and a method for producing the same will be described.
In the film, a solution of an aromatic polysulfone resin is cast on a support to form a cast film
containing a solvent (hereinafter sometimes referred to as a cast step), and then the solvent is
evaporated from the cast film ( Hereinafter, it may be easily produced by the drying step).
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[0019]
The casting step is a step of forming a cast film containing a solvent on a support. In this step, a
solution of an aromatic polysulfone resin is cast on a support such as an endless band or a drum
using a comma coater, a lip coater, a doctor blade coater, a bar coater, a roll coater or the like. In
addition, although it is preferable to use metals, such as stainless steel which performed mirror
surface processing, resin films, such as a polyethylene terephthalate, glass etc. for a support
body, it is not limited to these.
[0020]
The drying step is a step of evaporating the solvent from the cast film to form an aromatic
polysulfone resin film. The evaporation of the solvent is preferably carried out by heating in
order to improve the efficiency. The heating may be performed at a constant temperature, but it
is preferable to change the temperature over several stages or more from the viewpoint of
economy and the smoothness of the surface of the film.
[0021]
The amount of residual solvent in the aromatic polysulfone resin film after drying is preferably
5% by weight or less, more preferably 1% by weight or less, and still more preferably 0.5% by
weight or less. When the amount of residual solvent is large, not only the glass transition
temperature (Tg) of the aromatic polysulfone resin film is significantly lowered, but also there is
a tendency to cause dimensional change or curling or to absorb moisture when heat is applied in
post-processing. Furthermore, the residual solvent may affect the peripheral parts of the film at
the practical stage. In order to efficiently produce an aromatic polysulfone resin film having a Tg
substantially equal to that of the raw material aromatic polysulfone resin, the aromatic
polysulfone resin is heated at a temperature of Tg or higher after the drying step. Is preferred.
[0022]
The formed aromatic polysulfone resin film is usually used by peeling from the support. Although
the method of peeling is not particularly limited, a long aromatic polysulfone resin film can be
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obtained by continuously peeling the film-like material from the support, and a sheet-like support
is used to obtain a short length by a batch method. An aromatic polysulfone resin film can also be
obtained.
[0023]
The cast film obtained in this manner is superior to the film produced by the extrusion method
without producing streaks such as die lines on the film surface and is excellent in film thickness
accuracy, and further, the MD direction of the film Because there is no anisotropy in the physical
properties in the and TD directions, it is suitable for the application of the speaker diaphragm.
The film thickness accuracy needs to be within ± 10% of the average film thickness and within
± 8% of the average film thickness from the viewpoint of acoustic performance such as
reproduction frequency band and frequency characteristics. Preferably, it is more preferably
within ± 6% of the average film thickness. Here, the thickness accuracy can be determined by
the following equation. Thickness accuracy (%) = [(film thickness-average film thickness) /
(average film thickness)] × 100
[0024]
The cast film is further processed as a speaker diaphragm. Although the processing method is
not particularly limited, the film is pressed at a temperature above the glass transition point, and
the film is given a shape suitable as a speaker diaphragm such as a dome shape. At this time, the
film thickness of the aromatic polysulfone resin film is required to be 40 μm or less, preferably
25 μm or less, more preferably 20 μm or less from the viewpoint of processability. When the
film thickness exceeds 40 μm, when the film is used for forming, problems occur in
processability, such as the desired shape can not be applied in a given time cycle. Further, after
shaping a desired shape, processing such as vapor deposition of metal may be further performed
on the surface of the diaphragm. The speaker diaphragm thus obtained is excellent in heat
resistance, and has a wide reproduction frequency band because of a large specific elastic
modulus, and is excellent in acoustic characteristics such as a flat frequency characteristic
because of a large internal loss. It is a thing.
[0025]
The present invention will be described based on examples, but it goes without saying that the
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present invention is not limited by the examples. The aromatic polysulfone resin, Sumica Excel
PES 5200 P, and Sumica Excel PES 7600 P used in the Examples substantially consist of the
following repeating structural units.
[0026]
Moreover, the measuring method of the various properties of an aromatic polysulfone resin film
is as follows. The thickness was measured using an Eriksen foil thickness gauge model 497. (2)
Glass transition temperature (Tg) The film was heated from 25 ° C. to 300 ° C. at 10 (°
C./min) and measured using a thermal analysis system SSC / 5200 manufactured by Seiko
Instruments Inc. (3) Specific modulus of elasticity obtained by cantilever beam bending vibration
method. (4) The internal loss was determined by the cantilever beam bending vibration method.
[0027]
Example 1 Sumika Excecel PES 7600 P (Sumitomo Chemical Industry Co., Ltd., polyether sulfone,
reduction) using trade name Multi Test Coater NCR 230 (made by YASU SEIKI Co., Ltd.) with a
knife coater having a clearance of 200 μm. A 20% N, N-dimethylformamide solution of viscosity
0.76 dl / g) was cast on a polyethylene terephthalate film. At this time, the line speed was 0.5 m /
min, and the temperature in the drying furnace was 100 ° C. Furthermore, this continuous film
was cut out into A4 size, dried in a ventilated oven at 200 ° C. for 2 hours, and peeled off from
the support to obtain a polyethersulfone film for evaluation. The Tg of this film was 223 ° C.,
the average film thickness was 18 μm (minimum 17 μm, maximum 19 μm), and the thickness
accuracy was ± 5.6%. Specific modulus of elasticity and internal loss are shown in Table 1.
[0028]
Comparative Example 1 A trade name Sumika Excel 5200P (manufactured by Sumitomo
Chemical Co., Ltd., polyether sulfone, reduced viscosity 0.52 dl / g) is dissolved in N, Ndimethylformamide to prepare a solution having a solid content of 25% by weight did. This
solution was cast on a glass plate using a bar coater (clearance 500 μm), placed in a heating
oven at 100 ° C., and left for 10 minutes. Then, when the surface state of the film was observed,
orange peel was generated on the entire surface.
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[0029]
Comparative Example 2 Using GS65-25 (single shaft, L / D = 25) manufactured by Ikegai Co.,
Ltd., screw rotation number 15 rpm, discharge amount 10.9 kg / h, pick-up speed 6.67 m / min,
trade name Sumika Excel An extruded film of 4100 G (manufactured by Sumitomo Chemical Co.,
Ltd., polyether sulfone, reduced viscosity 0.41 dl / g) was produced. As a result of measuring the
film thickness of this film, the average film thickness is 45 μm, the minimum value is 43 μm,
and the maximum value is 51 μm, and the thickness accuracy is −4.4% and + 13.3%.
[0030]
Comparative Example 3 The specific elastic modulus and the internal loss of trade name Emblet
S-50 (polyethylene terephthalate film manufactured by Unitika Co., Ltd., average film thickness
55 μm) were measured. The results are shown in Table 1.
[0032]
According to the present invention, it is possible to provide a speaker diaphragm excellent in
heat resistance and excellent in acoustic characteristics having a wide reproduction frequency
band and flat frequency characteristics.
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