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JPH01282999

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DESCRIPTION JPH01282999
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic diaphragm and a method of manufacturing the same. [Prior Art] A number of methods
for treating the surface of a diaphragm base material and its material have been proposed as
diaphragms for use in acoustic diaphragms, in particular as speakers for high sound and medium
sound speakers. However, among them, as a method of forming a diamond film having a small
amount of amorphous (non-crystal) on the surface of the diaphragm substrate, as shown in FIGS.
14 (A) to (C), a thermal filament method, electron impact There are a chemical transport method
(EACVD method) and a microwave chemical transport method (MCVD method), and further,
although not shown in FIG. 1, there are a plasma jet method, a DC plasma method and the like.
Further, as a method of obtaining a diaphragm by using only a diamond film, Japanese Patent
Application Laid-Open No. 81-128700 is known, and as shown in FIG. 15 (A), the single crystal
silicon 40 formed in a diaphragm shape is used. As shown in FIG. 15 (B), a diamond film 41 is
deposited on the mixed gas of methane (CH 4) and hydrogen (H 2) by the 2 45 GHz MCVD
method described above, and then single crystal boron is dissolved. This is a method of
manufacturing the diamond diaphragm 42. [Problems to be Solved by the Invention] However,
the above-described conventional acoustic diaphragm and the method of manufacturing the
same have the following problems. First, the thermal filament method and the EACVD method
have a small area for obtaining a film, a short distance to the diaphragm substrate which is an
adherend, and a poor film thickness distribution, and in the MCVD method, the adhesion area is
It is known that the size is determined by the size of the quartz tube and plasma that react with
the wave tube, and the diameter of the deposition surface is 3 to 10 cm by either method, so a
diaphragm of 1 inch in diameter is 1 to 5 There is a disadvantage that it has only the ability to
process sheets, and that the deposited film thickness per hour is a rate of 1-10 g / cm ', which is
expensive and is poor in mass productivity. Second, since any of the above-described methods is
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a method of obtaining a diamond film by heating a filament, direct current discharge or high
frequency microwave discharge, heat is applied to the diaphragm substrate to a temperature of
1000 ° C. It is necessary to improve the heat dissipation because the deformation and damage
of the Thirdly, in the method of manufacturing a diaphragm of only a dyamond film, the method
described in the above-mentioned Japanese Patent Application Laid-Open No. 81-128700 makes
it difficult to process the single crystal boron 40 into a target shape, and Since the diameter is 3
to 10 c + s and the deposition rate per time is 1 or less, it takes several tens of hours to obtain a
diaphragm made of a diamond film of several tens of microns, and there is a problem of lack of
mass productivity. .
The first object of the present invention is to provide an acoustic diaphragm in which a diamond
film is formed on the surface of a diaphragm base and a diamond film having a uniform thickness
is formed even if the diaphragm has a large diameter. It is to do. The second object of the present
invention is to form a diamond film on the surface of the diaphragm base in a short period of
time, so that the film can be reliably formed in a short period of time. It is an object of the
present invention to provide a method of manufacturing an acoustic diaphragm which is not
restricted. A third object of the present invention is to provide an acoustic diaphragm which can
be manufactured in a short time, has high mass productivity, and is not limited by the size of the
diaphragm when manufacturing an acoustic diaphragm having only a diamond film. Is to provide
a manufacturing method of [Means for Solving the Problems] In order to achieve the above
object, in the acoustic diaphragm according to the present invention, argon, hydrocarbon and
hydrogen are formed on at least one side of a diaphragm substrate made of ceramics formed in a
diaphragm shape. A crystalline diamond film is formed by thermal plasma emission of the mixed
gas of In this case, the diaphragm substrate may be made of carbide-based ceramics such as
boron carbide, oxide-based ceramics such as aluminum oxide or zirconium oxide, or nitride-based
ceramics such as titanium nitride or boron nitride. it can. Furthermore, the above-mentioned
diaphragm substrate can be used as a metal diaphragm substrate, and this metal diaphragm
substrate is made of titanium, and thermal plasma radiation of argon and hydrocarbon gas is
performed on the diaphragm substrate surface. A titanium carbide layer is formed, and hydrogen
is added to the above argon and hydrocarbon gas and thermal plasma radiation is performed on
the titanium carbide layer to form a crystalline diamond film, thereby forming a titanium,
titanium carbide and diamond three-layer structure. A material layer can be formed. In the
method of manufacturing an acoustic diaphragm according to the present invention, a diamond
film is formed on the surface of a metal substrate formed in the shape of a diaphragm, and then
the metal substrate is dissolved to form an acoustic diaphragm formed of only a diamond film. In
the production of diamond, a diamond substrate is formed by depositing crystalline diamond by
thermal plasma emission of a mixed gas of argon, hydrocarbon and hydrogen on a metal base
formed into a diaphragm shape with titanium, tantalum or molybdenum. Form and dissolve the
metal substrate. In this case, boron or titanium carbide may be vapor-deposited on the surface of
the metal substrate, and a crystalline diamond film may be formed thereon by the above-
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described means, and then the metal substrate may be dissolved.
On the other hand, in the method of manufacturing a diaphragm for 99 by forming a diamond
film on the root of vibration root, a ceramic powder is filled between the diaphragm base and the
radiator to which the diaphragm base is to be set to vibrate. While cooling the plate, a mixed gas
of argon, hydrocarbon and hydrogen is thermally plasma-emitted to form a crystalline diamond
film on the vibrating root substrate. In this case, the ceramic powder to be filled can be a ceramic
of diamond, cubic boron nitride and boron carbide. In addition, a mixed gas of argon,
hydrocarbon and hydrogen is mixed on the above-mentioned vibration root base village while
water cooling is performed by setting the diaphragm substrate to a radiator provided with a set
portion having a shape corresponding to the shape of the diaphragm substrate. A method of
thermal plasma radiation to form a crystalline diamond film can be employed. In this case,
diamond, cubic boron nitride and boron carbide can be deposited on the surface of the set
portion of the radiator to form a ceramic film, thereby enhancing the cooling effect of the
diaphragm base. [Operation] Of the diaphragms for sound according to the present invention, the
diaphragm formed by forming a crystalline diamond film on the diaphragm substrate is excellent
in the velocity of sound, as will be described in detail later. The unique characteristics of high
hardness and high rigidity unique to diamond reduce split vibration and make an excellent
diaphragm. The diaphragm made of only the crystalline diamond film has a uniform film
thickness, and the sound velocity is further excellent. In the method of manufacturing an acoustic
diaphragm according to the present invention, a thermal plasma chemical transport method
(thermal plasma CVD method) for supplying a large amount of mixed gas is used when forming a
diamond film on a substrate, and the mixed gas is used as the mixed gas. And argon,
hydrocarbons and hydrogen are used. In this method, high temperature plasma can be generated,
and since the electrode of the direct current discharge is in the plasma torch, there is freedom in
the distance from the substrate as the adherend. In addition, many substrates can be processed
by moving the substrate about the plasma torch, and the deposition rate per hour is also
excellent. Therefore, a crystalline diamond film having a uniform film thickness can be rapidly
formed on the substrate, and the size of the substrate, which is an adherend, is not limited.
Therefore, a crystalline diamond diaphragm of a predetermined thickness can be mass-produced
also by the method of forming a diamond film on a metal substrate and then dissolving the metal
substrate to manufacture a diaphragm made of only a diamond film. Since the thermal plasma
CVD method generates high temperature plasma as described above, there is a risk that melting
or extreme deformation of the diaphragm substrate may occur or carbonization may be
promoted to form a diamond film, The desired purpose can be achieved by forming a crystalline
diamond film while cooling the diaphragm substrate.
[Embodiment] An embodiment of a diaphragm for acoustics according to the present invention
and a method of manufacturing the same will be described based on FIGS. 1 to 13 and FIG. 1 is a
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mechanism diagram used for carrying out a thermal plasma CVD method. The inside of the
plasma torch (gun) 1 and the chamber 2 for generating a thermal plasma is kept in vacuum by
the vacuum evacuation 5, and the source gas 3 is supplied. The diaphragm substrate 4 which is
an adherend is formed in a dome shape in the embodiment, and the cooling water 6 is set on the
radiator 7 which is a wI ring. The radiator 7 is adapted to rotate. The plasma torch 1 discharges
from the torch a plasma in which methane and hydrogen of hydrocarbon gas are decomposed by
a direct current discharge between electrodes composed of an anode (anode) 8 and a cathode
(cathode) 9, and a diaphragm by a chemical transport method (CVD) A grained diamond film is
deposited on the substrate 4. In this method, a large amount of mixed gas can be supplied to the
plasma torch 1 to generate high temperature plasma, and since the electrode of the DC discharge
is in the plasma torch, the distance between the electrode and the diaphragm substrate 4 which
is the adherend There is freedom. Also, by moving the diaphragm base 4 around the plasma
torch, many processes can be performed, which is an advantage over the conventional method.
Furthermore, since this thermal plasma CVD method is a method of supplying a large amount of
gas to the formation of a diamond film, a deposition rate of 10 to 50 times the conventional one
can be obtained, which is suitable for mass production. FIG. 2 is a temperature distribution chart
of plasma jet by the above-mentioned thermal plasma CVD method, but since the arc column is
squeezed by the induction magnetic field generated by the arc discharge current, it reaches
10000 to 20000 degrees at the outlet of the plasma torch l. Since the diaphragm substrate 4 set
in the radiator 7 is exposed to this high temperature, it is necessary to efficiently cool the
diaphragm substrate 4. As an experimental example, the mixing ratio of the raw material gas
(mixed gas) to be supplied is argon 100% methane 0.1% hydrogen 7%, and the other conditions
are vacuum degree 20 Torr diaphragm substrate silicon carbide (Sin) 40 JL When the abovementioned dome-shaped diaphragm substrate is set in a conventional supporting device having a
flat supporting surface with the size of the deposition substrate being 2.5 cm, and the thermal
plasma is emitted without cooling, the temperature of the surface of the diaphragm substrate
Reached 2000 to 3000 degrees, and the diaphragm base material was melted and extreme
deformation occurred. In addition, carbonization was promoted because of the high temperature,
and a diamond film was not formed. Then, the radiator 7 as shown to FIG. 3 and FIG. 4 is
provided.
The heat sink 7 made of copper is provided with a pressing jig 10 for fixing the hinge portion of
the diaphragm base material 4 and is cooled by circulating the cooling water 6 through the water
passage 11 inside. ing. In FIG. 3 (A), a hemispherical set portion 12 slightly smaller in diameter
than the dome diameter of the diaphragm substrate 4 is formed, and the diaphragm substrate 4
is set in the set portion 12; 4 and the ceramic powder 13 is filled. The surface temperature of the
diaphragm substrate could be maintained at 800 to 1000 ° C. when the plasma substrate was
cooled by the cooling means of FIG. 3 (A). In the case shown in FIG. 3 (B), in the case where the
dome-shaped diaphragm base 4 is set in a radiator having a flat mounting portion, the ceramic
powder 14 is placed between the mounting portion and the diaphragm base. Is filled with The
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ceramic powder is a powder of diamond, cubic boron nitride (CBN), and boron carbide (Sin).
Materials having a melting point of 1500 ° C. or higher and a thermal conductivity equal to or
higher than that of copper which is a material of the radiator 7 are preferable. The thermal
conductivity of these materials is as follows: . Copper 3.85 W / cra * ° C Diamond 20.0 Cubic
Boron Nitride 8.0 Boron Carbide 2.7 Ceramic Particle Size 0.5 to 2 Place Even when cooled in the
above FIG. 3 (B) FIG. 3 (A) In the same manner as in the above, the surface temperature of the
diaphragm substrate could be maintained at 800 to 1000 degrees. When the diaphragm
substrate is cooled using the cooling means shown in FIGS. 3 (A) and 3 (B) as described above,
the surface temperature of the diaphragm substrate may be cooled to 1/3 to 4 minutes. As a
result, the heat resistance of the surface of the radiator can be improved, deformation due to heat
fusion with the diaphragm substrate is eliminated, and deterioration in the quality of the
diamond film due to generation of gas can be prevented. The radiator 7 shown in FIG. 4 (A) forms
a hemispherical set portion 15 corresponding to the dome shape of the diaphragm substrate 4,
and the diaphragm substrate is fitted and set to this, and is water-cooled. is there. Also by this,
the surface temperature of the diaphragm substrate could be maintained at 800 to 1000
degrees. In the case shown in FIG. 4 (B), the surface of the set portion 15 is 1. S) A ceramic film
16 of diamond, cubic boron nitride, or boron carbide is formed with a thickness of 2 to 4 by
plasma CVD. Accordingly, the diaphragm substrate 4 is set to the set portion 15 through the
ceramic film 16, and the diaphragm surface temperature can be lowered to 800 to 1000 degrees
also by this.
Next, the specific example will be described. In the example, the mixing ratio of the raw material
gas (mixed gas) to be supplied is as follows, which is the same as the above-mentioned
experimental example. Argon 100% Methane 0.1% Hydrogen 7% Other conditions are as follows.
Example 1 Vacuum degree 20 Tarr diaphragm substrate Silicon carbide (Sin) 40μ Evaporated
substrate surface temperature 800-1000 degrees substrate size 2.5 cm diamond film thickness
formed 2 Note that in Example 1, time The adhesion film thickness was 50 to 100 g / crrr '. The
dome-shaped diaphragm 21 obtained in this Example 1 is shown in FIG. 5 (A), and a crystalline
diamond film 22 is formed on the diaphragm substrate 4. When analysis of this diamond film 22
is conducted by Raman spectroscopy and X-ray diffraction, as shown in the Raman spectroscopy
characteristic diagram of FIG. 8, a peak peculiar to diamond is obtained at 1333 cm 'and the Xray is also diamond similarly It is identified and identified. Further, in Example 1, as the
diaphragm base 4, it is possible to use a ceramic of oxide type or nitride type, which is low in
density and high in elasticity, and has a sound velocity of 10000 + s / s or more. The
manufactured dome-shaped diaphragms are shown in FIGS. 5 (B) and 5 (C) respectively. Of these
dome-shaped diaphragms 21, in the diaphragm of FIG. 5 (A) obtained in Example 1, the velocity
of sound is 10000 to 12000 + 1/3, and in the diaphragm of FIG. 5 (B), 9000 to 2000 A
loudspeaker of 11,000 intestines / g and a diaphragm of FIG. 5 (C) can provide 8000-10000 m /
s, which is about the frequency characteristic of the conventional loudspeaker and capable of
high frequency reproduction of S to 2.4 times. It can be done. FIG. 11 shows the frequency
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characteristic A (indicated by a solid line) of the dome-shaped diaphragm of FIG. 5 (A) obtained
according to Example 1 and the frequency characteristic B (indicated by a broken line) of the
dome-shaped diaphragm made of only titanium It is a frequency characteristic figure compared,
and it turns out that thing A of Drawing 5 (A) is remarkably improved especially in a high region.
Example 2 In Example 1, a metal base is used as the diaphragm base 4. Under the conditions of
Example 1, the surface temperature of the base is 600 to 1000 degrees. Others are the same as
in the first embodiment. The dome-shaped diaphragm 21 obtained by this Example 2 is shown in
FIG. 6 (A), and the analysis of the diamond film 22 was conducted in the same manner as in
Example 1.
The Raman spectral characteristic is shown in FIG. 9, and as is clear from this spectral
characteristic chart, as in Example 1, a peak unique to diamond was obtained at 1333 cm 'and
was also identified by X-ray diffraction. In Example 2, titanium is used as the metal diaphragm
substrate 4 and thermal plasma radiation of argon and hydrocarbon gas is formed on the surface
to form a titanium carbide layer, and then hydrogen is added to the argon and hydrocarbon. By
forming a crystalline diamond film on the surface of the above-mentioned titanium carbide layer,
as shown in FIG. 6 (B), a dome-shaped diaphragm consisting of three layers of a titanium
substrate 4, a titanium carbide layer 23 and a diamond film 22. It can be 21. In the dome-shaped
diaphragm 21 shown in FIG. 6 (A) obtained according to the second embodiment, the sound
velocity is 8000-1000011 / S, and in the case shown in FIG. -1 1000 m / s can be obtained. FIG.
12 is a frequency characteristic diagram comparing the frequency characteristic A of the domeshaped diaphragm of FIG. 6 (A) obtained in Example 2 with the frequency characteristic B of the
dome-shaped diaphragm made of only titanium. EXAMPLE 3 In Example 1, a crystalline diamond
film was formed on the surface of a metal base 20 (FIG. 7 (A)) formed of titanium (Ti) in a domeshaped diaphragm shape as the base 4 . The conditions in this case are as follows. Vacuum
degree 100 Torr base material Titanium 3 (14 as the base surface temperature 800 to 1000
degree base size 2.5 cm deposition time 45 minutes diamond film thickness formed 40 minutes
as described above on the metal base 20 In the case where the crystalline diamond film 22 was
formed, 1 to 5 grains of diamond were deposited, and a film having a pole-like crystal face was
obtained. When Raman spectroscopy and X-ray diffraction similar to Example 1 were performed,
as shown in FIG. 1O (A), the Raman spectrum characteristic showed a peak unique to diamond at
1333 cs ′ ′ ′ I as in Example 1. And were also identified by X-ray diffraction. The metal base
20 on which the diamond film 22 is formed as described above is dissolved using a 1: 1 mixed
solution of hydrogen fluoride (HF) and nitric acid, and the thickness 40. The dome-shaped
diaphragm 21 of only the diamond film was obtained. In Example 3 above, as shown in FIG. 7B,
boron (Si) was vapor-deposited on the surface of the metal base 20 to form a vapor-deposited
film 24, and a diamond film 22 was formed thereon.
In this case, the deposited film 24 of boron serves to prevent the reaction with the metal
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substrate 20, and the quality of the diamond film 22 is improved. Moreover, this vapor
deposition film is characterized by being able to be dissolved in the above-mentioned mixed
solution. Diamond is similar to the above example in that 1 to 5 crystal grains are deposited, but
a film having a crystal orientation of 100 orientation is obtained. The analysis of diamond I] I
222 is the same as in the above example, and the Raman spectral characteristics are as shown in
FIG. 10 (B). As shown in FIG. 7 (B), the metal base 20 and the vapor deposition film 24 were
dissolved by the same method as in the above example to obtain a dome-shaped diaphragm 21
having only the diamond film 22. Although titanium is used as the metal base in the third
embodiment, tantalum (Ta) can also be used, and furthermore, high melting point materials such
as tungsten and niobium can be used. Also, the M film deposition 24 can be made of boron
carbide. The acoustic constants of the diamond dome diaphragm 21 shown in FIGS. 7 (A) and 7
(B) obtained by Example 3 have densities of 3-3.4 (g / crn "), Young's modulus of 5.9-8. 2 × 10
11 (Pa) is obtained, and the speed of sound can be 1300 to 15000 tags in the case of FIG. 7 (A),
and 1400 to 1θ 000 tags in the case shown in FIG. 7 (B). This characteristic makes it possible to
obtain a speaker capable of high frequency reproduction up to 100 KHz, which is about 2 to 6
times the frequency characteristic of the conventional speaker. According to the diaphragm for
sound of the present invention, the acoustic constant is excellent, and in particular, the frequency
characteristic in the high region can be greatly improved, and it is most suitable as a speaker for
high sound and medium sound. It is. In addition, divided vibration can be reduced by the high
strength and high rigidity features unique to diamond, and a speaker with less distortion can be
obtained. According to the method of manufacturing an acoustic diaphragm according to the
present invention, a thermal plasma CVD method of supplying a large amount of gas is used to
generate a diamond film, and plasma radiation is performed while cooling the diaphragm
substrate. A diamond film of a predetermined film pressure can be formed on the vibrating root
substrate without melting or deforming the diaphragm substrate, and the formation rate thereof
is 10 to 50 times the conventional adhesion rate In addition, since a large number of sheets can
be processed by moving the diaphragm substrate, the acoustic diaphragm having excellent mass
productivity and excellent characteristics can be manufactured at low cost. Further, since the
diamond film having a predetermined film pressure can be rapidly formed on the substrate as
described above, the diamond film is formed using the substrate as a metal material, and then the
metal substrate is dissolved to vibrate only the diamond film. Abrasive production is also possible
in the case of obtaining a plate, and it is most suitable as a method for producing this type of
acoustic diaphragm.
[0002]
Brief description of the drawings
[0003]
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1 to 13 show an embodiment of an acoustic diaphragm according to the present invention and a
method of manufacturing the same, wherein FIG. 1 is a mechanism diagram used for carrying out
a thermal plasma CVD method, and FIG. 2 is a plasma jet temperature. 3 and 4 are sectional
views of the radiator, FIG. 5 and FIG. 6 are sectional views of the acoustic diaphragm, and FIG. 7
is a process of manufacturing the acoustic diaphragm of only the diamond film. FIGS. 8 to 10 are
Raman spectral characteristic diagrams, and FIGS. 11 to 13 are frequency characteristic
diagrams of a speaker incorporating an acoustic diaphragm, showing a base material and a
diamond film.
FIG. 14 is a mechanism diagram of a conventional diamond film forming method, and FIG. 15 is a
cross-sectional view showing a base material and a diamond film in the conventional method of
manufacturing an acoustic diaphragm using only a diamond film. ■ == plasma torch, 2: chamber,
3: mixed gas 4: diaphragm base material, 5: evacuation, 6: cooling water, 7: radiator 8 near node,
9: cathode, 10: holding jig 11: water passage , 12: set portion, 15: set portion 13: ceramic powder
14: ceramic powder, 18: ceramic film 20: metal base, 21: dome-shaped diaphragm 22: diamond
film, 23: titanium carbide layer 24: vapor deposited film patent Applicant: Kenwood Co., Ltd. Fig.
1 Fig. 2 m bar Y-Fig. 6 Fig. 9 + 800 1600 1400 1200 1000 shell (Cm-I) 12 Fig. 10 (A)
Temperature length (cm) -1) (B) Liquid length (cm- ') Fig. 11 B Fig. 12 B Fig. 13 B ° [R back
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