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The present invention relates to a diaphragm for a speaker having a sandwich structure in which
a surface material is attached to the surface of a flat plate-shaped core material having a large
number of irregularities formed by molding a thermoplastic resin film. It is an object of the
present invention to provide a diaphragm for a speaker which is easy to manufacture and has
high rigidity by using a bisphenol phthalate type resin film comprising an aromatic dicarboxylic
acid and a dihydric phenol as φ. In general, most of the speaker diaphragms are formed by
forming paper pulp and have a cone shape. Therefore, a phase difference occurs because the
position 1d of the sound source deviates between the inner and outer peripheral portions of the
diaphragm, and a speaker having a flat frequency characteristic is difficult to obtain. On the other
hand, a loudspeaker in which the diaphragm is a flat plate and the positions im of the sound
sources are equalized is advantageous for realizing flattening of the frequency characteristics.
However, when paper pulp is simply used as a flat diaphragm, rigidity against bending is small,
division vibration is likely to occur, and flat frequency characteristics are not wide across a wide
band. On the other hand, even when a plastic foam such as expanded polystyrene is used as a flat
diaphragm, its rigidity is small and it is not suitable as a diaphragm. Therefore, a flat plate
diaphragm having a sandwich structure capable of obtaining high bending rigidity can be
considered. However, in the case where the conventional structural member of aluminum
honeycomb → is used as a flat plate diaphragm, its processing is very complicated. Because of
this, the manufacturing cost is significantly reduced. The present invention does not have these
conventional drawbacks. ! Molding a bisphenol phthalate resin film consisting of an aromatic
dicarboxylic acid such as isophthalic acid, terephthalic acid, or a mixture of isophthalic acid and
terephthalic acid and a divalent fe // such as bisphenol A A flat core material having a large
number of irregularities is formed, and a surface facing material is attached to the surface of the
flat core material. The bisphenol phthalate resin used as the core material has the following basic
structure, and is a film of this resin. 0 0 (-0-0-RC-0-1 ('R:' Or <from isophthalic acid) or ゝ 0,
(from terephthalic acid) or Rt koni-) 6 = ()-(bisphenol A The resin film has an elastic modulus of
about 12 × 10 10 dyn / stripes and a density of about 1.2 y / ci. The polyethylene terephthalate
resin (Mylar (trademark)), which has been used as a plastic diaphragm for small speakers in the
past, has a density of about 1.41- / crd, which makes it possible to reduce the weight of the
diaphragm of the present invention It is possible.
The above resin film is excellent in heat resistance and has a heat distortion temperature of 176
° C. (test method ASTM-D648), which is higher than that of polyethylene terephthalate (mylar)
at 85 ° C. (ASTM-Da 48) It is also self-extinguishing. Therefore, the diaphragm formed of this
film is excellent in reliability at high temperatures. Since the above-mentioned resin film is nondefective, it is easy to perform thermoforming and mass production as compared to crystalline
polyethylene terephthalate (Mylar). Further, the above-mentioned resin film is made of nonquality polystyrene (heat deformation temperature 74 ° C.), acrylonitrile-butadiene-styrene
copolymer (heat deformation temperature 88 ′ ′ C) polyvinyl chloride (heat deformation (M If
75 ° C.), Compared to resins such as polycarbonate (heat distortion temperature 140 ° C). The
heat distortion temperature is high, and thermoforming is easy and mass production is possible
compared with these resins. Therefore, the core material of the sandwich structure can be easily
manufactured by vacuum molding or the like by using a polybisphenol phthalate resin film as the
core material, and a high-performance speaker diaphragm can be realized. Hereinafter, examples
of the present invention will be described. EXAMPLE A film having a molecular structure shown
below was used as a core forming film. C starvation: A film having a thickness of 100 μm was
heat-melted to about 3 (η ° C.), and a flat core material having a diameter of 28 mm and a
depth of 1 mm was formed by vacuum forming. At this time, as shown in FIG. 1, there is a large
number of asperities, and a mold 2f provided with suction holes 1 in its concave surface!
Between the press mold 3 and the press lower mold 6 provided with the press mold 3 and the
heater 6, the resin film 7 described above is held by the heater 5 in a state where the resin film 7
is held. The resin film 7 is heated when the resin film 7 is softened, and the resin film 7 is
suctioned into the mold 2 by means of a vacuum pump (not shown) which is provided in the
press upper die 3 and a suction hole 8 is formed. did. By vacuum forming in this manner, as
shown in FIGS. 2 and 3, there is obtained a flat core 9 in which concave surfaces and convex
surfaces 9B are alternately arranged in the radial and circumferential directions. Next, on both
sides of the core material 9 obtained as described above, a polyamide-based filo, 1-tonning agent
(Diamide # 3200. A surface material with a thickness of 30 μm and a G-grade is attached by
adhesion to make a diaphragm for tweeter.
The circumferential V-number characteristic when this is assembled into a speaker unit is shown
in FIG. In addition, the concavo-convex pattern of the core material is considered to be other than
those in the embodiments (ball-shaped, 9-circle, rhombus, cross, etc.). The diaphragm using the
core material of the concavo-convex pattern has the same effects and characteristics as the above
embodiment. Further, the diameter of the core material can be appropriately set by enlarging or
decreasing the size of the mold according to the diameter of the diaphragm such as woofer or
squawker. The forming method may be pressure forming or vacuum pressure forming in addition
to vacuum forming. As described above, according to the present invention, isophthalic acid. A
poly-bisphenol phthalate resin film consisting of terephthalic acid or an aromatic dicarboxylic
acid such as a mixture of isophthalic acid and terephthalic acid and a dihydric phenol such as
bisphenol is vacuum-formed, pressure-formed and vacuum-pressure formed Since the surface
material is attached to the surface of the flat-plate core having, it can be made a flat diaphragm
with a sandwich structure with high bending rigidity, and 1, the resin film can be easily
manufactured by vacuum forming etc. It has an easy advantage.
Brief description of the drawings
FIG. 1 is an explanatory view of a forming process of a core material for a speaker diaphragm
showing one embodiment of the present invention, FIG. 2 is a plan view of a concentric material,
FIG. 3 is a cross sectional view of the concentric material, FIG. These are the pressure-one
frequency characteristic figures of the speaker diaphragm which used the concentric material.
9A · · · · · · Concave, 9B · · · · · · · · · · · · · · · · · · · · Name of Agent Attorney Nakao Toshio 71) 1 person
Figure 1 Figure 12 Figure 13