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BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method of manufacturing an acoustic transducer used for calling a portable telephone or the like.
2. Description of the Related Art A conventional acoustic transducer will be described with
reference to the half sectional view of FIG. In FIG. 3, reference numeral 1 denotes a magnetic
circuit, and the magnetic circuit 1 is configured of a plate 3, a yoke 4, and a columnar magnet 2.
A frame 6 is coupled to such a magnetic circuit 1, and a gasket 7 is formed so that the voice coil
5 joined to the central portion of the frame 6 fits into the magnetic gap 9 of the magnetic circuit
1 without eccentricity. At the same time, the peripheral portion of the acoustic diaphragm 8 is
Among the acoustic transducers of such construction, there have conventionally been those
using a polyethylene terephthalate film, a polycarbonate film, a polyethylene naphthalate film, a
polyetherimide film, a polyimide film as the plastic acoustic diaphragm 8 and these film
vibrations The plates are generally bonded using a solvent rubber adhesive to assemble the
acoustic transducer.
However, since a rubber-based adhesive containing a solvent is used as the adhesive as described
above, it takes time to cure, and the acoustic diaphragm 8 and the voice coil 5, the acoustic In
order to bond the diaphragm 8 and the frame 6 to each other, it is necessary to fix the object so
as not to move, and it is necessary to hold the adhesive by means of jigs until it hardens. It was
an inhibiting factor.
In addition, although productivity was considered to be raised by heating at a temperature of 50
° C. to 60 ° C., adhesion strength is considered to be lowered due to foaming of the adhesive,
and thus it has not been adopted so much.
SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the invention
according to claim 1 of the present invention is an acoustic film diaphragm of a joint portion
between a frame and an acoustic film diaphragm and / or a voice coil. It is possible to cure for a
short period of time by irradiating the light with an adhesive that cures with visible light, curing
the adhesive by bonding light, and improving the productivity of the acoustic converter
(automation of production). It is a thing.
The invention according to claim 2 of the present invention relates to the method for producing
an acoustic transducer according to claim 1, wherein an acrylic resin is used as an adhesive
which is cured by visible light and benzyl is used as a photopolymerization initiator. Using a
butylamine-based sensitizer as a sensitizer and using a metal halide lamp having a spectral
energy distribution from an ultraviolet region to a visible light region as a light irradiation device,
curing can be performed in a short time, and productivity is excellent It is possible to provide a
manufacturing method.
In the invention according to claim 3 of the present invention, the addition amount of benzyl
according to claim 2 is 0.1 to 2%, and the addition amount of butylamine based sensitizer is 0.1
to 2.0%. Thus, it is possible to provide a method of manufacturing an acoustic transducer which
is stabilized by visible light and has stable curing characteristics and is suitable for mass
Hereinafter, an embodiment of the present invention will be described.
In the description, the same parts as in the prior art will be assigned the same reference
numerals and descriptions thereof will be omitted.
(First Embodiment) FIG. 1 is a half sectional view of an acoustic transducer according to the
present invention. A difference from the prior art will be described with reference to FIG. 1. A is
an adhesive that cures with visible light. It is applied between the diaphragm 8a and the frame 6
and between the acoustic film diaphragm 8a and the voice coil 5, and is cured by visible light.
In addition, although the polyethylene terephthalate film, a polycarbonate film, a polyethylene
naphthalate film, a polyether imide film, and a polyimide film are used as the film diaphragm 8a
for acoustics, the film diaphragm for acoustics using a polyethylene terephthalate and a
polyether imide film 8a can not be used because it does not transmit UV rays and curing
becomes poor with UV-curable adhesives, but in this case a voice coil is cured by using an
adhesive that cures with visible light having a light wavelength of 370 nm and 440 nm. Bonding
with 5 and 6 is possible.
Next, an adhesive that cures with visible light will be described. While an acrylic resin as an
adhesive that cures with visible light is used as a base with benzyl as a photopolymerization
initiator and a butylamine as a sensitizer, ultraviolet light as a light irradiation device By using a
metal halide lamp having a spectral energy distribution from the region to the visible light
region, mass productivity can be more efficiently achieved.
The addition amount of the photopolymerization initiator is about 0.1 to 2%, and the butylamine
type used as the sensitizer is about 0.1 to 2.0%.
It was confirmed that the curing speed became extremely slow if both were 0.1% or less, and that
the adhesive became unstable if it was 2.0% or more.
Therefore, 0.5 to 1.0% is desirable (in the following specific experimental examples, the sensitizer
is in the range of 0.5 to 1.0%).
Using the adhesive that cures with visible light according to the present embodiment configured
as described above, polyether ether ketone (hereinafter referred to as PEEK) that is a raw
material of galvanized steel plate that is a raw material of frame 6 and a diaphragm ),
Polyetherimide (hereinafter referred to as PEI), 30 micron thick film of polyether sulfone
(hereinafter referred to as PES) and 30 micron thick film of polycarbonate (hereinafter referred
to as PC) and polyethylene naphthalate Bonding each to 38 microns thick (hereinafter referred to
as PEN), irradiating for about 5 seconds with a light irradiation device using a 100 milliwatt
metal halide lamp, and irradiating 500 millijoules of heat to the bonded portion The peel
strength is shown in (Table 1) (adhesive application amount is 0.015 to 0.02 mg).
The peel strength of the conventional rubber-based adhesive is about 0.75 kg / 25 mm, and the
above-mentioned (Table 1) is not inferior to the peel strength of this rubber-based adhesive and
is cured. It has been confirmed that it can contribute to mass productivity since the time is only a
few seconds.
Also, PEEK, PES and PC have conventionally reacted with rubber-based adhesives and
deteriorated, and could not be used, but use as an acoustic film diaphragm by making the
adhesive of this embodiment This has made it possible to expand the options for obtaining
predetermined acoustic characteristics.
Although PEN films are excellent in acoustic characteristics, in general, it was considered difficult
to bond by light irradiation due to poor light transmittance, but as shown in FIG. By using a
photopolymerization initiator which cures and reacts with light in the sensitized region of 330
nm to 440 nm in the form and using a metal halide lamp having spectral energy from the
ultraviolet region to the wavelength of the visible light region, visible light irradiation It was
confirmed that joining by
As described above, the present invention enables bonding by irradiation with visible light, which
has not been conventionally used for bonding with other parts of acoustic film diaphragms, and it
is possible to cure adhesive in a short time. By making it possible, the production efficiency of the
acoustic transducer can be improved, and it can greatly contribute to the automation of