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JPS61186098

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DESCRIPTION JPS61186098
[0001]
The present invention relates to a method of producing a carbon-based vibration plate, wherein a
thermosetting resin powder is used as a carbon source, which is dispersed by means of dispersal,
heat pressing, etc., and then heating and carbonization. Further, graphitization enables
adjustment of the length of the diaphragm to be freely performed and measures distortion of the
diaphragm to be measured. [Prior art and its problems] Generally, the materials constituting the
imaging plate for sound use are: ? light weight (low density), high rigidity (high Young's
modulus), ? moderate The requirement of having an internal loss of Cm?) is needed. Carbonbased materials such as carbon and graphite are known as one of the acoustic diaphragm
materials that satisfy such conditions. This carbon-based material has an extremely high rigidity
of 120 to 3000 P &, a density of 1.3 to 1-8, and! It is small as i '/ c-, and is particularly suitable
for the middle to high range diaphragm. One of the manufacturing methods of such a diaphragm
made of a carbon-based material is disclosed in Japanese Patent Publication No. 55-32318. This
method is to heat, plasticize or graphitize a plastic film or sheet without stretching or under
stretching. However, in this manufacturing method, since a plastic film or sheet is used as a
carbon source, an internal strain that remains as it is formed during formation of the film or
sheet remains until after carbonization or graphitization, and this distortion is There is a problem
that affects the sound transmission and adversely affects the sound quality. In addition, since the
film or sheet is similarly used, the thickness of the diaphragm can not be adjusted, and for
example, the edge portion may be integrally formed thicker than the dome portion like an edgeintegrated dome-shaped diaphragm. There was also a problem that is impossible. [Means for
Solving the Problems] Therefore, in the present invention, a thermosetting resin powder is used
as a carbon source, which is dispersed in a mold having the shape of a diaphragm and heated to
form a plate, The above problem is solved by further heating and carbonizing or graphitizing this.
Details will be described below. The thermosetting resin to be used here needs to be solid in a
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semi-cured state and capable of being powdered or powdered. The type of resin is not
particularly limited, but those of high carbonization yield such as phenol resin and polyimide d
fat are preferable in view of dimensional accuracy after carbonization or graphitization.
Specifically, when using a phenol resin, 10 to 15 wt% of hexamethylene tetrat as a curing agent
is mixed with a novolak resin, heated and kneaded at 120 to 130 ░ C., and this is pulverized to
form a powder.
The particle size of the resin powder is 100 ?m or less, preferably 50 ?m or less in average
particle size, and the dispersion of the particle size is within ▒ 10 ?m. When the powder
particle size exceeds 100 ?m, when the resin powder is melted in the mold, a local difference
occurs in the melting speed, the thickness of the molded article partially fluctuates, the thickness
accuracy decreases, and the sound quality is adversely affected. give. Next, prepare a mold as
shown in FIG. This type 1 is for producing a dome-shaped diaphragm, and is composed of a
convex lower type IA and a concave upper WIB. The mold 1 is preheated to a predetermined
temperature, and the resin powder 2 is dispersed uniformly on the lower mold IA using a sieve or
the like. In the case of a phenolic resin powder, the mold temperature is about 140 to 150 ░ C.
Then, the upper ffl1 B is placed on the lower WIA, and heat and pressure treatment is performed
at a pressure of about 1.0 to 2.0 M Pa. The time and temperature at the time of heat and
pressure treatment can be appropriately adjusted depending on the type of resin, etc. In addition,
the resin powder is squeezed appropriately in consideration of the thickness of the finished
diaphragm and the volume reduction rate due to carbonization or graphitization. By this heat and
pressure treatment, the resin powder 2 is melted, cured and integrated to form a dome-shaped
resin molded body 3 as shown in FIG. Then, the compact 3 is taken out of the mold 1 and placed
in a heating furnace, and is heated under a non-oxidative atmosphere to carbonize or graphitize.
The compact 3 is accommodated in a high temperature furnace such as a resistance heating
furnace in a stress-free state by a method such as suspending it, and the inside of the furnace is
evacuated or replaced with Nt + Ar gas. Then, the temperature is raised to 800 to 1500 ░ C. at a
temperature rising rate of 30 to 60 ░ C./hour, and held for several hours. By this heating, the
resin is carbonized by a thermal decomposition reaction to obtain a carbonized diaphragm.
Further, if the carbonized diaphragm is further heated to 2500 to 3000 ░ C. at a temperature
rising rate of 50 to 100 ░ C./hour and held for several hours, carbon is crystallized and a
graphitized diaphragm can be obtained. The mold 1 can also be heated from normal temperature
after the resin powder 2 is dispersed, and this method can also be adopted in the case of
obtaining a flat diaphragm. Furthermore, it is also possible to heat and carbonize or graphitize in
a non-oxidizing atmosphere while pressing the resin molded body 3 to the mold 1. In addition, a
small amount of carbon short fibers can be added to the resin powder and processed in the same
manner, and a diaphragm with high mechanical strength can be obtained. The characteristics of
the carbonized diaphragm thus obtained and the graphitized diaphragm will be described next in
comparison with a conventional titanium diaphragm. Dense If (9 / cta) Rigidity (GPIL) "Loss (-?)
carbonized diaphragm 1.50 140 ?04 graphitized #R moving plate 1.80 210 ?055 cut
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diaphragm 4.54 100 ?004 [action] like this In the production method, by using the
thermosetting resin powder, a distortion does not remain in the carbonized or graphitized
diaphragm, and a diaphragm with good sound quality can be obtained.
In addition, by changing the amount of resin powder applied partially, the thickness can be
changed at any part in one diaphragm, and as shown in FIG. It can be made at once and in a fully
integrated manner. Furthermore, since a thermosetting resin is used, the shape given by the mold
is held without thermal deformation in the next heating step, and post-processing and the like
can be made unnecessary. [Example] 15 parts by weight of hexamethylenetetramine was added
to 100 parts by weight of novolac type phenol resin, and the mixture was ground by a ball mill at
80 to 100 ░ C to obtain a powder having an average particle diameter of 50 ?m. This powder
was spread on the lower mold shown in FIG. The lower mold had been preheated to 140 ░ C.
The portion of the lower die that hits the edge portion of the lower mold is sprayed with a larger
amount than the portion on the central dome portion to make it thicker. After spraying, the
upper mold of the same crucible was placed and subjected to heat and pressure treatment for 5
minutes at a pressure of 0 MPa to obtain a dome-shaped compact. The thickness of the dome
portion of this molded article was 200 ?m, and the variation thereof was ▒ 7 ?m, and the
thickness of the edge portion was 300 ?m, and the thickness thereof was ▒ 10 ?m. Next, the
compact was placed in a resistance heating furnace, the inside of the furnace was replaced with
N, gas, and then heated at 1200C for 1 hour at 60C / hour to obtain a carbonized WtM plate.
When the frequency characteristics of this carbonized vibration plate were determined, the
characteristics represented by curve 1 of the graph in FIG. 3 were obtained. Moreover, the
diaphragm was similarly manufactured using the thing of average particle diameter 150 pTL to a
phenol resin powder. The thickness of the molded body was 200 ?m at the dome portion, with a
variation of ▒ 20 ?m, and at the edge portion of 300 ?m, the variation was ▒ 30 ?m. Further,
the frequency characteristic of the obtained carbonized vibration plate is indicated by a curve 1
in FIG. Furthermore, a semi-cured phenolic resin sheet is placed in the same mold and heat
treated at 140 ░ C. for 22 minutes, OMP & for 5 minutes to form a 300 ?m thick dome-like
shaped body, which is similarly carbonized and carbonized I left the diaphragm. The frequency
characteristic of this product is shown by curve in FIG. 3. From the graph of FIG. 3, according to
the resin powder of the present invention, it is possible to vibrate at high sound pressure level up
to high frequency range and further smaller particle size In the case of using the above, flat
frequency characteristics are shown, and it can be seen that it is particularly suitable as a
diaphragm for sound transmission. [Effects of the Invention] As described above, in the method
of manufacturing the diaphragm of the present invention, the thermosetting resin powder is
dispersed in a mold, heat pressed to form a compact, and this is heated to carbonize or
graphitize. Since there is no distortion associated with the formation on the diaphragm, a
diaphragm with good sound quality can be obtained.
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In addition, by changing the powder application rate, the thickness in a single + is plate can be
freely and easily changed, and for example, an edge-integrated diaphragm can be easily
manufactured (2).
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a cross-sectional view showing an example of a mold used in the manufacturing method
of the present invention, FIG. 2 is a cross-sectional view showing an example of a molded product
which is an intermediate product, and FIG. 3 is a carbonized diaphragm obtained in the example.
It is a graph which shows the frequency characteristic of.
1 (IA, IB) ииииииииииииииииииииииииииииии Thermosetting resin powder 3 иииииииииииии
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