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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for a speaker, and more particularly to a diaphragm for a speaker in which a surface
material obtained by blending graphite with thermoplastic resin is attached to front and back
surfaces of a core material. 2. Description of the Related Art Generally, the physical properties
required of a speaker diaphragm are lightweight, have a large elastic modulus, and have a large
loss coefficient tan δ. FIG. 3 shows a cross-sectional view of a conventional sandwich structure
diaphragm, in which aluminum Pi (20 to 60 μm) as a surface material 2 is bonded to both
surfaces of a honeycomb core la as a core material as shown in FIG. Also, there have been those
in which a plastic composite material such as fiber reinforced plastic (FRP) is bonded to both
surfaces of the honeycomb core 1a as a surface material. In addition, there is also one using a
foam material as a core material (see Japanese Patent Publication No. 59-7278). [Problems to be
Solved by the Invention] Although the conventional speaker diaphragms as described above are
relatively light in weight and rich in specific elastic modulus, they have the problem that they
have a small loss coefficient and are expensive. It was The present invention has been made to
solve such problems, and by using a thermoplastic resin containing graphite as the surface
material of the core material, it is lightweight, has a large specific elastic modulus, and has a
large loss coefficient. An object of the present invention is to provide an inexpensive speaker
diaphragm. [Means for Solving the Problems] The speaker diaphragm according to the present
invention is constructed by adhering a surface material formed by blending a thermoplastic resin
with graphite on the surface of a core material. [Function] In the present invention, since the
thermoplastic resin in which the surface material is blended with graphite is used, the
characteristic loss coefficient is also increased. FIG. 1 shows a cross-sectional view as a first
embodiment of a speaker diaphragm according to the present invention. The same reference
numerals as in the above-mentioned prior art denote the same constituent elements in the first
embodiment, and a description thereof will be omitted. In the figure, 3 is a surface material made
of a thermoplastic resin compounded with graphite. In the present embodiment, the surface
material 3 is provided on both sides of the honeycomb core 1a, and a sheet of 170 μm in
thickness is formed of composite polypropylene resin as a thermoplastic resin containing 30% by
weight of graphite as the surface material. , And bonded to the honeycomb core 1a having a
thickness 31 with an adhesive to form a diaphragm. Further, FIG. 2 shows a second embodiment
in which the foam material 1b is used for the core material 1, and the same effect as the above
embodiment can be realized. The following table shows the above conventional example and the
above first example. The respective physical property values of the second embodiment are
shown, and as is apparent from the table, according to the present embodiment, the loss factor is
increased as compared with the conventional example.
The thermoplastic resin used in the present invention is polyethylene (low, medium, high density,
linear low density). Poly α-olefins such as polypropylene, poly (4-methylpentene-1), propylene /
ethylene block or random copolymer; polystyrene; acrylic resins such as acrylonitrile / butadiene
/ styrene terpolymer, poly (methyl methacrylate); poly chloride Polyhalogenated vinyl such as
vinyl: Polyamide such as nylon 6, nylon 66; Saturated polyester such as polyethylene
terephthalate polybutylene terephthalate; Polyether such as Poniphenylene oxide; Polysulfone;
Polyphenylene sulfide; Polyvinylidene fluoride; Combination, α-olefin / vinyl monomer
copolymer such as ethylene / acrylic acid copolymer; maleic anhydride modified polypropylene,
maleic anhydride modified polyethylene, anhydrous A modified resin such as maleic acid
modified polystyrene; a modified resin such as styrene; a mixture of a hydrogenated substance of
styrene / butadiene block copolymer may be used. Among the above-mentioned thermoplastic
resins, preferred resins for the present invention are poly α-olefins and modified poly α-olefins,
and particularly preferred are polypropylene, propylene / ethylene block or random copolymer
and maleic anhydride modified polypropylene It is. In the present invention, the graphite used is
artificial graphite produced by graphitizing at a high temperature of 2000 ° C. or more, using
natural graphite produced by purifying natural products produced in Srilan power, Madagascar
island, etc., or petroleum coke, etc. Is used. The blending ratio of graphite in the composite resin
formed by blending the thermoplastic resin and the graphite in the present invention is in the
range of 5 to 50% by weight, preferably in the range of 20 to 40% by weight. In the present
invention, an inorganic or organic filler can be added as an additional component in the range of
20% by weight or less, preferably 15% by weight or less, in addition to the above components.
Talc and mica as inorganic fillers. Glass fiber, potassium titanate, carbon fiber and the like can be
used, and as the organic filler, aromatic polyamide fiber and the like can be used. As the core
material used in the present invention, expanded polystyrene, expanded polypropylene,
expanded phenolic resin, 1-part expanded acrylic resin, honeycomb core, etc. can be used. [Effect
of the Invention] As described above, according to the present invention, the surface material to
be adhered to the surface of the core material is formed by blending the thermoplastic resin with
the graphite, thereby improving the sound quality at low cost and efficiently. Have the effect of
Brief description of the drawings
FIG. 1 is a partial sectional view as a first embodiment of a speaker diaphragm according to the
present invention, FIG. 2 is a partial sectional view showing a second embodiment according to
the present invention, and FIG. 3 is a conventional speaker diaphragm FIG. 4 is a plan view
showing the configuration of the honeycomb core of the embodiment.
1 ... core material, 1 a ... plate material of honeycomb structure, 1 b ... foam material, 2, 3 ...
surface material. The same reference numerals are used for the same or corresponding parts in
the drawings.
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