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Conventionally, polypropylene (tan δ: 0.097) and polyethylene (tan δ: 0.08), which have
relatively large vibration loss in physical properties, are often used as raw materials of plastic
film diaphragms. Thus, there are the following methods for forming such a crystalline plastic film
into a diaphragm. First, the plastic film is heated to a temperature close to the melting point, and
then the position of the mold is raised while drawing air with a vacuum pump through a die
provided with minute holes or slits to raise the plastic position on the mold A vacuum forming
method of bringing a film into close contact and further cooling it to obtain a molded product.
Next, are plastic films expensive? A pressure forming method in which softened with ul and
pressed against a die with compressed air to form. And, 2) 431 month method of vacuum
forming method and pressure forming method. A method of pressing and heating a plastic film
that has been heated and softened with a mold having a humidity close to room temperature, and
then cooling and solidifying it using the mold. などである。 In any of these methods, it takes
several seconds from the heated state of the plastic film to the cooled and solidified state
necessary for shape retention, and the so-called annealed state occurs, and the main chain of the
plastic film is crystallized. Crystallization takes place with the cooling time required to align them
in the proper position to make iiJ function. That is, as shown by the dotted line in FIG. 1 due to
crystallization, many characteristics of polypropylene having a cutting angle and a large value of
δ of polyethylene are lost. The manufacturing method of the present invention will be described
taking polyethylene as an example, and as shown in FIG. 4, the diaphragm 1 made of
polyethylene film obtained by the above-mentioned method is used in a mold 3 "2 having a hole
2 for intake. After placing it, suction it with the vacuum pump 4 to make the diaphragm 1 in
close contact with the mold 3, listen to the valve 21 and shake the heated air of about 125 ° C
from the hot air source 5 + fi! Blow the 2 plate to activate the molecular activity of polyethylene
and release the formation of crystals, and then close the valve 21 and open the valve 22 at the
same time as water from a cold water source 6 to 2 to 3 ° C. Is sprayed onto the vibrating plate
1 to quench the vibrating plate 1 and to cool and solidify before the formation of crystals occurs
to obtain an amorphous polyethylene diaphragm. Since such a manufacturing method performs
heating and quenching while being placed on the mold 3, even if the plastic material softens near
the melting point, it does not lose its shape retention degree, and the Buddha heart of the
temperature rapidly It has the advantage that it is carried out and material amorphisation is
realized uniformly throughout the feed. The used cold water is collected in a drainage tank, sent
to a cold water source, and reused.
Thus, although there is a slight decrease in, The effect on the performance is small and
practically negligible, whereas the solid line in FIG. 1 and FIG. As shown, it has excellent values,
and has a significant advantage in eliminating the peak dip and making it flat characteristics,
especially in the high tone range.
Brief description of the drawings
1, 2 and 3 are characteristic diagrams of the theory δ, Young's modulus and output sound
pressure level (S, P, L) of the diaphragm of the present invention and the diaphragm of the prior
art, respectively, and FIG. It is explanatory drawing of this invention manufacturing method.
1 is a diaphragm, 2 is an intake hole, 3 is a mold, 4 is an exhaust pump, 5 is a hot air source, and
6 is a cold water source. Fig. 1 Fig. 2 Frequency-10 (Hz) Fig. 3