JP2004274530

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DESCRIPTION JP2004274530
The present invention provides a film for a speaker diaphragm, which is excellent in acoustic
characteristics and can be suitably used as an on-vehicle speaker or a mobile phone speaker. A
speaker diaphragm in which a resin resin coating layer having a loss tangent (tan δ frequency 1
Hz, tensile method) higher at room temperature 23 ° C. higher than that of polyetherimide is
provided on one side or both sides of a polyetherimide film substrate. Film. [Selected figure]
None
Film for speaker diaphragm
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
film for a speaker diaphragm, and more particularly to a film for a speaker diaphragm having
excellent acoustic characteristics, which can be suitably used for a car-mounted speaker or a
mobile phone speaker. [0002] A polyetherimide speaker diaphragm made of polyetherimide
excellent in heat resistance has been used in place of a polyethylene terephthalate speaker for
vehicles, speakers for mobile phones, etc. (See, for example, Patent Document 1). Usually,
polyetherimide has an elastic modulus smaller than that of polyethylene terephthalate and
polyethylene naphthalate, so that it is possible to relatively increase the thickness of the film
necessary to obtain the same frequency characteristics, and it is advantageous in that it is easy to
handle at the time of processing There is. Moreover, the polyetherimide film used for the speaker
diaphragm made of polyetherimide is usually an amorphous non-oriented film, and since the
thermoforming property is very good, the processing when forming into various speaker shapes
It has the advantage of being excellent in sex. However, the polyetherimide speaker diaphragm is
prone to rolling and chattering due to the shape of the speaker diaphragm and the like, which is
a weak point in sound quality. In addition, there is a disadvantage that the sound pressure level
in the low temperature range is low, and it is demanded to further improve the sound quality by
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using a polyetherimide diaphragm. Patent Document 1: Japanese Patent Publication No. 4-68839
Patent Document 1: Means for Solving the Problems The present invention is to find a film for a
speaker diaphragm that can solve the above problems. A speaker having a resin resin coating
layer having a loss tangent (tan δ frequency of 1 Hz, tensile method) higher at room
temperature 23 ° C. than polyetherimide on one side or both sides of a polyetherimide film
substrate It is in the diaphragm film. It is preferable that the storage elastic modulus (E
'frequency of 1 Hz, tensile method) at room temperature of 23 ° C. of the resin resin coating
layer is lower than that of the polyetherimide film substrate. The resin coating layer preferably
has a thickness of 5% to 100% of the thickness of the base on one side, and the resin is
preferably made of a polyurethane resin. Furthermore, according to the present invention, a
speaker vibration having a film surface resistance of 10 <13> Ω or less, which is obtained by
adding a substance having an antistatic effect to the resin coating layer or coating the resin
coating layer with a metal layer. Includes board film.
DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in detail
below. In the film of the present invention, the sound quality improvement is improved while
maintaining the formability of the polyetherimide by providing a resin coating layer having
specific viscoelastic properties on one side or both sides of the polyetherimide which is the base
film. be able to. The polyetherimide used for the base film is an amorphous thermoplastic resin
containing an aromatic nucleus bond, an ether bond and an imide bond in its structural unit, and
is not particularly limited. Specifically, they are commercially available under the trade names
“Ultem CRS 5001” and “Ultem 1000” manufactured by General Electric Company, and can
be used together. The method for producing the polyetherimide resin is not particularly limited,
but usually, the weight of 4,4 '-[isopropylidene bis (p-phenylene oxy) diphthalic dianhydride and
p-phenylene diamine is used. It is synthesized as a condensate and as a polycondensate of 4,4 '[isopropylidene bis (p-phenyleneoxy) diphthalic dianhydride and m-phenylenediamine, by a
known method. Further, another copolymerizable monomer unit such as a polyimide unit may be
introduced into the above-mentioned amorphous polyetherimide resin. In addition, the polyether
imide resin to be used can be used individually by 1 type or in combination of 2 or more types. In
the present invention, it is necessary to provide a resin coating layer having a loss tangent higher
than that of polyetherimide on one side or both sides of the above-mentioned base film. C, tensile
method, measured at a frequency of 1 Hz. The loss tangent of the polyetherimide of the substrate
is usually about 0.02, which is higher than that, preferably 0.03 or more. If the loss tangent of
the resin coating layer is less than the loss tangent of the base film, rolling and chattering easily
occur. Examples of the above-mentioned resin for coating include urethanes, nylons, silicones,
polyamideimides, etc. From the viewpoint of heat resistance of molding process, specific gravity
and the like, it is preferable to use urethanes. Specific examples of the urethane resin include a
two-component curing type such as a polyol / isocyanate urethane resin. The thickness of the
resin coating layer depends on the selected resin, but if the layer thickness is large, the physical
properties will be close to the physical properties of the coating resin and the loss tangent etc.
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can be largely controlled, but conversely the heat resistance and formability of polyetherimide
There is a risk of being sacrificed.
Therefore, the thickness of the resin coating layer is suitably 5% to 100%, preferably 5% to 50%
of the base film. Here, in the resin-coated layer, it is preferable to use a material whose storage
elastic modulus is lower than that of the polyetherimide of the base film. The method of
measuring the storage elastic modulus is the same as the method of measuring the loss tangent
described above. The storage elastic modulus of the polyetherimide of the base material is
usually 3.5 × 10 <9> MPa, which is lower than that, preferably 3.0 × 10 <9> MPa or less. When
the storage elastic modulus of the resin coating layer is higher than that of the base film, there is
a problem that the sound pressure level in the low frequency range tends to decrease. The abovementioned urethane resin can be used as resin to be used. In the present invention, a film
satisfying all the above visco-elastic characteristics is obtained with excellent performance as a
speaker diaphragm. The method for providing the resin coating layer on the base film is not
particularly limited as long as it is a method such as gravure coating, reverse coating, etc. that
can be uniformly applied to the surface of the film. The resin coating layer may be one side or
both sides of the substrate film, but in consideration of curling of the film after coating, both
sides are preferable. Furthermore, it is preferable that a substance having an antistatic effect be
added to the resin coating layer, or a metal layer be coated on the resin coating layer to set the
surface resistance of the film to 10 <13> Ω or less. By setting it as 10 <13> Ω or less, it is
possible to improve the release of the film from the mold for molding at the time of speaker
molding, and to improve the handling property of the molded article (one sheet is easily peeled
off) As the substance having the antistatic effect described above, conductive carbon, metal
compounds, surfactants and the like can be used, and further, a mat for roughening the surface
to ensure slipperiness. A modifier such as an agent can be added as appropriate. Moreover,
aluminum, chromium, titanium etc. can be used suitably as a metal used for the metal layer coat |
covered to said resin coating layer, As a covering method, it may be according to the usual vapor
deposition method and sputtering method. By providing the metal layer, there is also an effect
that the heat resistance is improved and the designability is enhanced, as well as the releasability
of the film at the time of molding. The thickness of the metal layer is preferably about 100 to
1000 angstroms. If the thickness is less than 100 angstroms, the effect of improving the heat
resistance is small, and if it exceeds 1,000 angstroms, the formability tends to be reduced.
EXAMPLES Examples of the present invention will be described below, but the present invention
is not limited thereto. Example 1 A polyurethane-based ink (“Lamistar R-92” matte black ink
manufactured by Toyo Ink Mfg. Co., Ltd.) on one side of a 25 μm thick polyetherimide film
(“Ultem CRS 5001-1000” manufactured by GE Plastics) Was coated on the entire surface
(thickness 5 μm) by the gravure coating method. Example 2 A reverse coating method is
performed on a polyurethane-based ink (“N1038 LAMINASTER” manufactured by Toyo Ink
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Mfg. Co., Ltd.) on one side of a 25 μm-thick polyetherimide film (“Ultem CRS 5001-1000”
manufactured by GE Plastics) By the above method (thickness 17 .mu.m). Example 3 Metal
aluminum was formed on the surface of the polyurethane resin layer of the film used in Example
1 to a thickness of 400 angstrom by evaporation. Comparative Example 1 A film of 25 μm thick
polyether imide film (“Ultem CRS 5001-1000” manufactured by GE Plastics), the surface of
which is not coated. The elastic modulus and loss tangent of the above four types of films are
measured by a measurement method using a dynamic visco-elasticity measuring apparatus
“DVA-200” manufactured by IT Measurement & Control Co., Ltd. at a measurement
temperature of 23 ° C. and a measurement frequency of 1 Hz. The data measured in Table 1 are
shown in Table 1. The sound quality is evaluated according to JIS C 5532. The frequency
characteristics are measured, and there is no chattering, the sound pressure level in the low
temperature range is high, the speaker is extremely good as ◎, the good one is ○, chatter etc.
The inferior one was marked x. It can be seen from Table 1 that the film of the present invention
has good sound quality. Table 1 <img class = "EMIRef" id = "198371184-00002" /> In addition,
when the film of Example 1 was molded with a male and female mold having a mold temperature
of 200 ° C. under a pressure of 0.4 MPa for a time of 15 seconds, it could be molded without
problems such as deformation. Furthermore, the antistatic property was improved by the effect
of the carbon contained in the ink, the peeling from the mold was improved, and the separation
was easy even when the molded articles were stacked. Furthermore, in the film of Example 3, the
heat resistance was good and there was no fusion to the mold without lowering the cooling
temperature of the mold (a pressure of 0.4 MPa for a male and female mold with a mold
temperature of 230 ° C., time 15 seconds) Molding and cooling condition to 180 ° C.).
It was necessary to lower the cooling temperature to 150 ° C. without the metal layer, and it
was found that the molding cycle tended to be reduced. According to the present invention, a film
for a speaker diaphragm having excellent acoustic characteristics can be obtained without
impairing formability.
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