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JPH07131888

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DESCRIPTION JPH07131888
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
edge for a speaker, and more particularly to an edge for a speaker which can fully exhibit
responsiveness and vibration absorption characteristics and can reduce manufacturing time.
[0002]
2. Description of the Related Art In a so-called cone type speaker, an annular edge formed of a
rubber elastic body is fixed to a peripheral portion of a cone. The speaker edge is required to be
able to emit vibration of the vibrator as a sound wave with high responsiveness. Furthermore, the
speaker edge can exert a sufficient damping function so that the previous vibration does not
affect the next transmitted vibration in a state where the vibration of the vibrator is continuously
transmitted to the edge. In other words, a large loss factor is required.
[0003]
However, in order to satisfy high responsiveness, the material needs to have a property close to a
rigid body, and conversely, the material has sufficient viscosity to increase the loss factor. There
is a need. That is, two opposing performances need to be imparted to the material of the speaker
edge, and there is a problem that if one is to be satisfied, the other performance can not be
sufficiently secured.
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[0004]
By the way, conventionally, there is one using a rubber elastic body as a speaker edge, and for
example, a speaker edge formed by molding a rubber material having butyl rubber as a main
component is known (Japanese Patent Application Laid-Open No. 52) -127227)). However, in the
case of forming the speaker edge by the rubber elastic body, the vulcanization step is essential in
order to accelerate the reaction or to maintain the predetermined shape as the edge. In the
vulcanization process, it is necessary to mix various compounding agents including a vulcanizing
agent and a vulcanization accelerator under highly accurate compounding conditions, and to
perform long-term heating and pressurization in a vulcanizing apparatus. There is also a problem
that the working environment is polluted, because the time and economic disadvantages are
inevitable.
[0005]
SUMMARY OF THE INVENTION An object of the present invention is to provide a speaker edge
which can exhibit high response and high vibration absorption characteristics, and has excellent
precision that can be formed in a shortened operation process.
[0006]
SUMMARY OF THE INVENTION The present invention has been proposed to achieve the above
object, and is characterized by the following constitution.
That is, according to the present invention, it is characterized by being formed of a thermoplastic
elastomer which is a block copolymer of a segment capable of providing a function as a viscous
body and a segment capable of imparting a function close to a rigid body. A speaker edge is
provided.
[0007]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The technical feature of the
present invention is that the speaker edge is formed not by a rubber elastic body in which a
vulcanization process is indispensable for expressing physical properties but by a thermoplastic
elastomer which does not require a vulcanization process. Specifically, the thermoplastic
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elastomer may be a segment capable of exhibiting a function as a viscous material (hereinafter
referred to as a soft segment) and a segment capable of exhibiting a function similar to a rigid
body (hereinafter referred to as a hard segment). And the block copolymer of
[0008]
That is, the speaker edge can exhibit sufficient viscosity by having the soft segment, and can also
exhibit a function close to a rigid body by having the hard segment, and the speaker edge of the
present invention is It has both the characteristic of sufficiently damping the vibration and the
characteristic of well transmitting the vibration.
[0009]
In the present invention, the segment capable of imparting the function as a viscous material
means a segment belonging to at least one of the following categories.
The degree of interaction between the molecules is high, and the degree to which the segment
can freely rotate around its bond (hereinafter referred to as the degree of rotational freedom) is
low.
[0010]
Further, in the present invention, a segment capable of giving a function close to a rigid body
means a segment belonging to the following at least one category.
It has low rotational freedom, large steric hindrance, long side chains with relatively long chain
length, and ends with large atomic radius such as halogen. In the present invention, a segment
means a unit which constitutes a part of a block copolymer and exhibits common characteristics.
[0011]
Examples of the hard segment include polystyrene and polyvinyl chloride (TPVC), and
polystyrene is particularly preferable. Further, as the soft segment, vinyl polyisoprene,
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polyisoprene and the like can be exemplified, and vinyl poly isoprene is particularly preferable. In
addition, the thermoplastic elastomer in the present invention means a polymer substance which
is melted or softened to show plasticity when heated and exhibits rubber elasticity at around
normal temperature.
[0012]
The polymer of the present invention may contain a compounding agent known per se, such as a
foaming agent, a crosslinking agent, a filler, and a softening agent. Examples of the foaming
agent include silicone, DCP (dicumyl peroxide) as the crosslinking agent, mica as the filler, and
DOP (dioctyl phthalate) as the softening agent.
[0013]
According to the present invention, according to the present invention, high response and high
vibration absorption characteristics can be exhibited, and no vulcanization step is required.
Therefore, for speakers for high precision in molding in a short time economically. Can provide
an edge. (2) Furthermore, in the present invention, the edge for the speaker is formed not by
rubber but by thermoplastic elastomer, and the molding material can be supplied as pellets, so
that an almost unmanned molding process in which a working robot is disposed can be realized .
Therefore, the productivity of the speaker edge can be improved, and the manufacturing cost can
also be reduced.
[0014]
The invention will now be described by way of example. A triblock copolymer consisting of
polystyrene and vinyl-polyisoprene having a styrene content of 20% and a vinyl bond content of
55% is injection molded under conditions of a cylinder temperature of 220 ° C. and a mold
temperature of 40 ° C. The speaker edge which is a polymer was obtained. The loss factor of the
obtained speaker edge is shown in Table 1, and the frequency characteristic is shown by curve A
in FIG. As shown in FIG. 1, in Example 1, the curve is substantially flat in the range of about 40
Hz to 20 KHz, which indicates that the frequency characteristic is good. In addition, the speaker
edge of Example 1 is positioned on the sound pressure level side where the flat portion of the
curve is higher than the edge of a comparative example (curve indicated by symbol B in FIG. 1)
described later. Is also superior to the edge of the comparative example. Furthermore, in the
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comparative example, as shown by the curve B, the natural vibration was generated at about 800
Hz, but in Example 1, it was found that the edge was a good edge free of the natural vibration.
[0015]
Example 2 5 parts by weight of azodicarbonamide (foaming agent), 0.8 parts by weight of DCP
(crosslinking agent), 110 parts by weight of calcium carbonate with respect to 85 parts by
weight of a block copolymer having the same composition as in Example 1. One part by weight of
stearic acid and 15 parts by weight of EVA resin were blended respectively. The mixture was
kneaded on a roll at a temperature of 115 ° C. to obtain a batch, and the batch was put into a
mold and pressed at 170 ° C. for 10 minutes to form a foam. Then, the foam was sliced to a
predetermined thickness and punched into a predetermined shape by a press to obtain a speaker
edge. The loss factor of this speaker edge is shown in Table 1.
[0016]
EXAMPLE 3 30 parts by weight of polybutene was blended with 100 parts by weight of a block
copolymer having the same composition as in Example 1, and the barrel was kneaded at a
temperature of 200 ° C. by a twin-screw extruder. Next, pellets were obtained with a grinder,
and injection molding was performed using the pellets under conditions of a cylinder
temperature of 220 ° C. and a mold temperature of 40 ° C. to obtain an edge for a speaker.
The loss factor of this edge is shown in Table 1. Although polybutene is added to the block
copolymer in Example 3, even if an elastomer such as butyl rubber, styrene-butadiene rubber or
isoprene rubber is added in place of this to obtain desired temperature characteristics. Good. The
addition amount is preferably 50 phr or less, although it depends on the required temperature
characteristics.
[0017]
Comparative Example 1 50 parts by weight of carbon, 10 parts by weight of softener and 1 part
by weight of sulfur are kneaded with a roll with respect to 100 parts by weight of styrenebutadiene rubber with a roll and vulcanized at 170 ° C. for 10 minutes with a press I got an
edge for it. The loss coefficient of the obtained speaker edge is shown in Table 1, and the
frequency characteristic is shown by curve B in FIG.
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[0018]
As shown in Table 1 above, the loss coefficients of Examples 1 to 3 were all greater than the loss
coefficient of the comparative example, and it became clear that they were excellent as the
speaker edge. In addition, the value of each column of the loss factor in Table 1 has shown the
value in 25 degreeC.
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