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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for acoustic equipment having a small specific gravity <<, a large Young's modulus, a
good frequency characteristic with a large internal loss, and an excellent vibration damping
characteristic. Generally, the material of this type of diaphragm is required to have a small
specific gravity, a large Young's modulus, and a large internal loss. By the way, in the
conventional diaphragm, paper subjected to various processing is widely used, and the above
conditions are not necessarily satisfied. Although a diaphragm made of aluminum or the like has
recently been used as a substitute for this paper, this diaphragm has a large Young's modulus,
but because the specific gravity is large and the internal loss is small, flattening of the frequency
band is difficult. And therefore not desirable in terms of acoustic characteristics. Therefore,
attention was paid to materials with large internal loss for flattening of the frequency band, but
materials with large internal loss generally have lower Young's modulus and lower efficiency
with decreasing output level at high frequencies understood. For example, a synthetic resin foam
can be exemplified as the above-mentioned material, and it can not be said to be a diaphragm
having satisfactory performance. Recently, diaphragms made of olefin resins such as
polypropylen and polyethylene have also been used, but all of specific gravity, Young's modulus
and internal loss can not be simultaneously satisfied, and especially Young's modulus at low
temperatures. There was a problem. Therefore, in order to solve the above problems, the present
applicant has previously described JP-A-58-64896 as an olefin resin such as polypropylene and
polyethylene, an ethylene α-olefin copolymer, a foaming agent and a filler. The diaphragm which
formed the composite material which consists of by injection molding was provided. However,
although this diaphragm was very excellent, the vibration damping characteristics were slightly
inferior, and furthermore, the composite material showed a unidirectional shrinkage and it was
found that the performance was not good. There was a problem with In the present invention, in
view of the above problems, the specific gravity is small, the Young's modulus is thick <<, and
while it has a good frequency characteristic with a large internal loss, the vibration damping
characteristic is further excellent and isotropic contraction. The purpose is to provide the
frequency of operation. (Means for Solving the Problems) In order to achieve the above object,
the present invention is configured such that the diaphragm for acoustic equipment is made of a
composite material of an olefin resin such as boliproylene and polyethylene and an aramid fiber.
(Example) The olefin resin used in the present invention is a general commercially available
product such as polypropylene and polyethylene. On the other hand, chopped fiber is used as the
aramid fiber, and a commercially available trade name "Kevlar" (registered trademark) is
Hereinafter, more specific examples will be described. A raw material bellet is prepared by
blending 5 to 30 parts by weight of aramid fiber (chopped fiber) with 100 parts by weight of
boriblovirene, and this is injection-molded into a mold cavity of an appropriate shape using a
conventional injection molding machine to obtain a diaphragm I got The thickness of this
diaphragm is 0.17 to 0.61 IIII1, and aramid fibers are uniformly dispersed in polypropylene as a
base material to constitute a composite reinforced with aramid fibers. As a result of the test, this
diaphragm has a large Young's modulus, a large internal loss, a good vibration damping
characteristic, a flat frequency characteristic up to Takashiro, and a high frequency range can be
reproduced. is there. In addition, since no unidirectional shrinkage after molding was observed,
the performance was greatly improved compared to the conventional one. (Effect of the
Invention) The diaphragm for audio equipment according to the present invention is made of a
composite material of an olefin resin and an aramid fiber, has a small specific gravity, a large
Young's modulus, and has particularly large frequency characteristics of internal loss. It has
excellent characteristics and isotropic shrinkage due to injection molding, so it is an excellent one
that does not degrade the performance even in long-term use.