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JPS59161200

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DESCRIPTION JPS59161200
[0001]
The present invention relates to an acoustic diaphragm used for a speaker or the like, and in
particular, a thin film of silicon (hereinafter referred to as Si) or boron (hereinafter referred to as
B) and a diamond like carbon film on an acoustic diaphragm substrate made of beryllium
(hereinafter referred to as Be). An acoustic diaphragm is provided in which the acoustic
characteristics are significantly improved as compared to the prior art by forming a three-layer
structure in which. Be Be or 3e alloy is known to be most suitable for an acoustic diaphragm such
as a speaker because it is light-weight and has high rigidity and extremely high ratio Young
(Young's modulus / density). Since such e and Be alloys are relatively weak in an atmosphere
containing chlorine ions, it is common to use the surface coated with SiO or 5i02 used for surface
protection of semiconductor IC for an acoustic diaphragm. The sound properties of SiO and SiO 2
are significantly inferior to that of ie, for example, the sound velocity of 3e is approximately
120001 / sec or more while the sound velocity of SiO is extremely low at 6000 m / sec or less.
Therefore, the Be diaphragm on which the protective film of SiO.sub.9 SiO.sub.2 is formed is
inferior in acoustic characteristics to the case of 3e alone, and the fact is that the original
excellent characteristics of 3e are not sufficiently utilized. Therefore, recently, it has been
considered to form a thin film of a diamond-like carbon film having better acoustic
characteristics than Be on Be. A diamond-like carbon film is a diamond-like carbon molding
which is also called pseudo-diamond, and has a crystal structure close to that of diamond, or
physical properties (especially Young's modulus, density, others, dielectric constant, refractive
index, specific resistivity) Etc.) means a carbon molding having properties close to diamond, but
such a diamond-like carbon film is made of Be or 3e alloy because the sound velocity reaches
183001 / s and has better acoustic properties than Be. An acoustic diaphragm in which a
diamond-like carbon film is formed on an acoustic diaphragm substrate is expected to exhibit
extremely good acoustic characteristics. However, in practice, it is extremely difficult to form a
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diamond-like carbon film by ion deposition or the like on an @ moving plate substrate made of Be
or 3e alloy, and there is a problem that productivity is extremely low. The adhesion of the carbon
film to the substrate is low, so that it can not sufficiently withstand excessive input or impact
during operation as an acoustic diaphragm, causing a problem that the diamond-like carbon film
peels off, and Since the adhesion between the diamond-like carbon film and the diaphragm
substrate is weak and the adhesion between the two is often not sufficient, it has been found that
the acoustic characteristics do not actually become as good as intended.
It is also conceivable to form a thin film of SiO 2 or SiO on a diaphragm substrate made of Be or
Be alloy, and to form a diamond-like carbon film on the thin film. It has been found that there is a
problem that the formation is quite difficult in practice and that the adhesion of the formed
diamond-like carbon film to the SiO or 5102 thin film is weak. As described above, it is actually
quite difficult to form a diamond-like carbon film on a diaphragm substrate made of Be or Be
alloy, or on a SiO or Si 3-002 thin film, and its adhesion The cause of weakness is considered to
be as follows. That is, generally, a diamond-like carbon film of this type is generally formed by a
method such as ion deposition, and in this ion deposition, a substrate is placed at a target portion
of a sputtering apparatus and a negative voltage is applied thereto. At the same time, methane
gas as a carbon source is supplied into the sputtering apparatus, and positive ions are
accelerated to be attached to the substrate. It is apparent that the acceleration energy of the
positive ions also causes sputtering on the film surface of the substrate. Focusing on the energy
at this time, the CH bond energy of methane as a carbon source is 80. . Statistically, H is
sputtered first, and the remaining C forms C and C bonds of the film, while the C-C bond energy
of 9 kcal / mol is 144 kcal / mol on one side. It is thought that a diamond-like carbon film will
grow. However, since 3e is extremely easily oxidized, oxides of the Be or 4- or Be alloy etc. are
often present on the surface, while the SiO and 5iO 211 films themselves are oxides. Thus, when
ion deposition is performed on a substrate in which oxygen is present in the form of oxides etc.
on the surface, the binding energy of c?o is lower than the binding energy of 120 kcal / ?01
and C?C, so methane is It is considered that C which is decomposed is CO and exhausted as
carbon, and the growth of the carbon film is not smoothly performed, and the generated carbon
film also has weak adhesion. Since the present invention has been made based on the
background described above, the present invention practically provides an extremely excellent
acoustic diaphragm in which a diamond-like carbon film is formed with strong adhesion to the
surface without inhibiting productivity. The purpose is to
That is, the acoustic diaphragm of the present invention has a thin film of 81 or 8 formed on an
acoustic diaphragm substrate made of metal such as 13e, and a diamondlike carbon film formed
on the Si or B III thereof. It is characterized by Hereinafter, the acoustic diaphragm of the present
invention will be described in more detail. The acoustic diaphragm according to the present
invention is, for example, as shown in FIG. 1 and FIG. A diamond-like carbon film 3 is formed on
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the Si or B thin film 2 by forming 2 as an undercoat film. The diamond-like carbon film 3 is
usually formed by ion deposition as in the prior art, but unlike the prior art, the diamond-like
carbon film 3 is formed by ion deposition on the Si or B thin film 2 Be done. Si and B have a
much lower affinity to oxygen than Be, which is a typical example of an acoustic diaphragm
substrate, and therefore there is little oxide present on the surface of the Sl or B thin film during
ion deposition. A diamond like carbon film can be smoothly grown, and a diamond like carbon
film having a desired thickness can be formed with high adhesion. On the other hand, the Si or B
thin film 2 itself can be formed on the acoustic diaphragm substrate with high adhesion by vapor
deposition, sputtering, CVD or the like. Therefore, in the present invention, a thin film of Si or B is
formed as an undercoat film, and a diamond-like carbon film is formed thereon, thereby forming
a diamond-like carbon film with high adhesion without inhibiting productivity. It became possible
industrially. In addition, the sound velocity of Si or B is about 7000 gn / s, about 12000 m / s,
respectively, which is higher than that of SiO or SiO2, and therefore there is little risk of
impairing the acoustic characteristics due to the presence of these thin films 2. It is desirable to
use Be, Be alloy, titanium (hereinafter, referred to as Ti) alloy, aluminum (J: J, 18 g) alloy or the
like as the acoustic diaphragm substrate 1 from the point of acoustic characteristics. Among
these, it is most desirable from the viewpoint of acoustic characteristics to use Be or Be alloy, and
the effect of the present invention is most effectively exhibited when using a base 1 made of Be
or 13e alloy. However, since the affinity to oxygen is stronger than that of Si or B in the case of Ti
alloy or g alloy, the effect of undercoating a thin film of Si or B can be obtained also in the case of
this 7-et al.
The thickness of the thin film 2 made of Si or B is preferably in the range of 500 to 10000A. If
the thickness is less than 500 A, a diamond-like carbon film having sufficient adhesion can not be
formed. If the thickness exceeds 10000, Si and B thin films having relatively poor acoustic
characteristics occupy the entire thickness of the acoustic diaphragm. There is a possibility that
the rate may be increased and the acoustic characteristics may be degraded. On the other hand, it
is desirable that the thickness of the diamond-like carbon film 3 be in the range of 5000 to
50000 A. If it is less than 5000 A, the effect of the acoustic property improvement by the
formation of the diamond-like carbon film can not be sufficiently obtained. On the other hand, if
it exceeds 5 oooo A, the effect is not further increased and the ion deposition takes a long time
Cost increase. In FIG. 3, the frequency characteristics of the acoustic diaphragm of the present
invention and the conventional acoustic diaphragm are compared and shown. Here, as the
acoustic diaphragm according to the invention 8-, a 5iiil film having a thickness of 1000 A is
formed on a 2591-thick Be diaphragm substrate, and a diamond-like carbon film is further
formed thereon to a thickness of 9,000 people. In addition, as the conventional acoustic
diaphragm, one having a SiO film formed to a thickness of 100OOA on a Be-made diaphragm
substrate of 25 voices was used as a conventional acoustic diaphragm. As apparent from FIG. 3,
in the acoustic diaphragm of the present invention, the high sound range limit is extended and
the sound pressure level is improved to improve the conversion efficiency as compared with the
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conventional SiO coated 3e diaphragm. Is recognized. Examples of the present invention will be
shown below. Si was deposited to a thickness of 5000 A on the diaphragm substrate of Example
1 Bell, and a diamond-like carbon film with a thickness of 2 was formed thereon by ion
deposition to form a diaphragm for a speaker. When the acoustic characteristics of this
diaphragm were examined, it was confirmed to be extremely excellent, and it was also confirmed
that the adhesion of the diamond-like carbon film was sufficient. Example 2 A speaker diaphragm
was prepared in the same manner as in Example 1 except that B was used instead of Si in
Example 1. It was confirmed that the diaphragm had the same acoustic characteristics and
adhesion as in the case of using Si as the thin film of the undercoat (Example 1). Example 3 A
5iliI film is formed to a thickness of 2000 A by sputtering on a diaphragm substrate formed by
press-molding 8g into a dome shape, and a diamondlike carbon film of 1JjI11 thickness is
formed thereon by ion deposition. , And a dome-shaped diaphragm.
When the acoustic characteristics of the diaphragm were examined, it was confirmed that the
diaphragm was excellent in elongation in the high frequency range, and it was also found that the
adhesion of the diamond-like carbon film was high. Example 4 A dome-shaped perturbation plate
was produced in the same manner as in Example 3 except that 8 was used instead of Si in
Example 3. The acoustic characteristics and adhesion of this diaphragm were also confirmed to
be substantially the same as in Example 3. As is apparent from the above description, the
acoustic diaphragm of the present invention is obtained by undercoating a thin film of Si or B on
a diaphragm substrate made of Be or the like, and forming a diamond-like carbon film thereon.
The adhesion of the diamond-like carbon film is strong, so that it can sufficiently withstand
excessive input and impact during use, and the diamond-like carbon film can be efficiently and
smoothly produced in its production. In addition, the acoustic diaphragm of the present invention
has a high sound expansion, a high sound pressure level, and an excellent conversion efficiency
as compared with a conventional diaphragm coated with SiO or SiO2 on a diaphragm substrate
such as 3e. The acoustic characteristics are also extremely excellent.
[0002]
Brief description of the drawings
[0003]
1 is a longitudinal sectional view showing an example of the acoustic diaphragm according to the
present invention, FIG. 2 is an enlarged view of part A of FIG. 1, and FIG. 3 is a frequency of the
acoustic diaphragm of the present invention and a conventional acoustic diaphragm. -It is a
microphotograph which compares and shows a sound pressure level characteristic.
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11-1 иии Acoustic diaphragm, 2 иии Thin film of Si or B, 3 иии Diamond-like carbon film. Assignee:
Nippon Musical Instruments Manufacturing Co., Ltd. Attorney Patent Attorney 1) Takehisa
Hisashi (1 fool) 12-
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