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JPH04261299

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DESCRIPTION JPH04261299
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm for a carbonaceous acoustic device and a method of manufacturing the same.
Specifically, as a diaphragm for a speaker and a microphone, a carbonaceous acoustic device
having excellent acoustic characteristics because it has high hardness, high strength, high elastic
modulus and is lightweight as compared with a conventional diaphragm material The present
invention relates to a diaphragm for a disk and a method of manufacturing the same.
[0002]
2. Description of the Related Art Generally, it is desirable that the following conditions be
satisfied as a diaphragm such as a speaker. ■ Low density. ■ A large Young's modulus. ■ The
propagation speed of longitudinal waves is high. ■ The internal loss of vibration is moderately
large. ■ Stable against changes in ambient conditions, and free from deformation or degradation.
■ The manufacturing method is simple and inexpensive.
[0003]
That is, in order to reproduce a wide frequency band faithfully, to have a good energy conversion
efficiency of electric single sound, and to express clear sound quality, it is highly rigid and
lightweight, and there is no distortion such as creep due to external stress. Further, to increase
the speed of sound from the equation of V = (E / ρ) (where V: speed of sound E: Young's
coefficient == density), a material having a small density and a high Young's modulus is required.
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[0004]
Conventional diaphragm materials include materials such as paper (pulp), plastics, aluminum,
titanium, beryllium, boron and the like as a base material, and further composites of glass fibers
and carbon fibers with these, metal alloys, etc. , Processed into metal carbides, metal borides and
the like.
[0005]
However, paper, plastics and their materials have a small ratio of Young's modulus to density and
low rigidity, so that they cause split vibration in a specific mode and the frequency characteristics
particularly in the high frequency band are significantly reduced. It is difficult to obtain clear
sound quality, and moreover, it is easily influenced by the external environment such as
temperature and humidity, and has disadvantages such as qualitative deterioration of the
material and fatigue over time to deteriorate the characteristics. .
In addition, carbon fiber reinforced plastic (CFRP) is a composite material that has excellent
properties such as high strength and high elasticity and high sound propagation speed in the
fiber orientation direction, but the high anisotropy of carbon fiber makes the fiber It has the
disadvantage that the physical properties in the orientation direction and in the other direction
differ significantly.
[0006]
On the other hand, when a metal plate such as aluminum or titanium is used, the sound velocity
is fast and it has excellent properties, but the internal damage of the diaphragm is small, sharp
resonance phenomenon occurs in the high frequency region, creep of material, etc. There is a
drawback that the fatigue with the passage of time occurs to deteriorate the characteristics.
Also, boron, beryllium and their nitrides, carbides, borides and the like are materials having
excellent physical properties, and the tweeter for high-range reproduction using these for the
diaphragm has a reproduction limit up to the audio frequency band or more Because it is
stretched, the high frequency distortion exceeds the audio frequency band, so that the signal in
the audio frequency band can be faithfully reproduced and natural sound quality can be
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expressed.
[0007]
However, these materials are extremely expensive, and their processing is extremely difficult
industrially, and the conventional diaphragm manufacturing method by roll rolling and press
forming is not practical. V. D. And P.I. V. D. And so on, so that the processing cost is extremely
expensive, and there are disadvantages such as difficulty in manufacturing a large speaker for
reproducing the low range.
[0008]
As is well known, carbon has a very wide range of physical and chemical properties, from
crystalline carbon of diamond and graphite to amorphous carbon such as carbon black and
charcoal. The inventors of the present invention have intensively studied to express desired
various functional characteristics by designing and combining these carbon materials according
to the required functions.
[0009]
First, the theoretical elastic modulus of graphite is 1020 GPa and extremely high as compared
with the elastic modulus of other materials, the density is small, and glassy carbon exhibits high
physical properties as compared with resin and metal materials. Focusing on the point, by
making a composite of carbon powder such as natural graphite having glassy carbon as a matrix
and high elastic modulus, manufacturing a carbonaceous diaphragm made of a graphite / carbon
composite material having excellent physical properties all in all A method was invented and a
patent application was filed (Japanese Patent Application Laid-Open No. 60-121895).
[0010]
Furthermore, noting that glassy hard carbon made only of resin has high precision and free
processability, it is a glass which can be industrially mass-produced and which can be
manufactured at low cost. Invented and patented a method for producing a solid hard
carbonaceous acoustic diaphragm (JP-A-61-65596).
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However, although a carbonaceous diaphragm made of a graphite / carbon composite material
has extremely excellent physical properties, it has a drawback that it is somewhat poor in
formability and lacks industrial mass productivity, while it is glassy. Carbonaceous diaphragms
made only of hard carbon can be easily mass-produced industrially, but have the disadvantage
that physical properties are inferior to those made of graphite / carbon composite materials .
[0011]
SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the conventional
diaphragm materials, the object of the present invention is to make use of the excellent physical
properties of carbon and to control the external environment such as temperature and humidity.
To provide a diaphragm which can reproduce a wide range of frequencies from the low range to
the high range without causing fatigue with time such as creep of the material, and can express
clear sound quality. An object of the present invention is to provide a method of manufacturing
inexpensively industrially.
[0012]
Means for Solving the Problems The inventors of the present invention have conducted intensive
studies to obtain a method of producing a carbonaceous diaphragm which can be easily massproduced industrially and has excellent physical properties. The
As a result, carbonaceous vibration made of glassy hard carbon is formed by orienting and
forming in the surface direction graphite which has developed crystals with high elastic modulus
on the surface of the vibration plate base material made of glassy hard carbon. A diaphragm for a
carbonaceous acoustic device according to the present invention, which has physical properties
superior to that of a plate, and mass productivity superior to that of a carbon diaphragm made of
a graphite / carbon composite material, and a method for producing the same. It came to
[0013]
That is, according to the present invention, (1) a carbonaceous acoustic material in which a
crystalline graphite having a high elastic modulus has been oriented in the surface direction and
fixedly formed on the surface of a vibrating plate substrate made of glassy hard carbon. It is a
diaphragm for equipment,
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[0014]
(2) A monomer and / or an initial condensation product of a thermosetting resin is shaped into a
diaphragm shape, and a mixture of highly crystalline graphite having an average particle size of
1.0 to 200 μm and a thermosetting resin is formed on the surface thereof. Is cast in a coating or
mold, and a curing reaction is allowed to proceed to obtain a formed form, and the formed form
is subjected to a carbon precursor treatment, and then 900 ° in an inert atmosphere while
controlling the temperature rising rate. A method of manufacturing a diaphragm for a
carbonaceous acoustic device, characterized in that the carbon is heated by heating to C or more,
[0015]
(3) On the back sheet having a release agent on the surface, a film of a monomer of
thermosetting resin and / or an initial condensation product, highly crystalline graphite of an
average particle size of 1.0 to 200 μm and a thermosetting resin The composite film of the
mixture of (1) and (2) is formed into a composite film, and is precured to obtain a preformed
sheet still having soft plasticity, the back sheet is removed, the preformed sheet is shaped into a
diaphragm shape, and the curing reaction proceeds Carbon is obtained by subjecting the formed
form to a carbon precursor treatment and then carbonizing by heating to 900 ° C. or higher in
an inert atmosphere while controlling the temperature rising rate. It is a manufacturing method
of the diaphragm for quality sound equipment.
[0016]
In the present invention, the diaphragm substrate made of glassy hard carbon is prepared using
only a thermosetting resin as a raw material.
This is because the thermosetting resin can be used as a raw material to increase the degree of
freedom in shaping, to be able to perform molding extremely easily, to easily eliminate firing
distortion, etc. (2) The density of glassy hard carbon after firing is extremely low at 1.35 to 1.50
g / cm 3, and it is possible to use a lot of shaping means industrially, which enables weight
reduction of the diaphragm. {Circle around (2)} This is because it is possible to simplify the
process without requiring complicated pretreatment for carbonization.
[0017]
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On the other hand, the graphite layer on the surface of the vibration plate base material is
prepared using as a raw material a graphite powder and a thermosetting resin for bonding the
same.
This makes it possible to obtain a diaphragm that exhibits high physical properties by using a
graphite powder having an extremely high theoretical elastic modulus as compared to other
materials, and by using a thermosetting resin, graphite The reason is that, even if it is mixed, the
degree of freedom in shaping can be maintained, so that the forming can be easily performed,
and the graphite can be oriented.
[0018]
Next, a method of manufacturing a diaphragm for a carbonaceous acoustic device according to
the present invention will be specifically described.
In the present invention, as a raw material for a diaphragm substrate, a thermosetting resin is
added with a predetermined amount of a curing agent as necessary, dispersed by a high-speed
agitator, etc., and then air bubbles are removed by a vacuum degassing device. Use
[0019]
On the other hand, as a raw material for the graphite layer portion on the surface of the
diaphragm substrate, it is sufficiently kneaded and dispersed using a graphite powder, a
thermosetting resin, a high speed agitator, a triple roll, etc. The mixture is dispersed again, and
the bubbles are removed by a vacuum degassing apparatus.
[0020]
Here, as thermosetting resins that can be used, phenol resins, furan resins, xylene resins, toluene
resins, COPNA resins, etc. are preferable. In particular, the monomers and / or precondensates
thereof are preferable, and they flow when heated. In addition, it is possible to use one which
exhibits high carbon residue yield without causing intermolecular crosslinking, threedimensionalizing and curing, and performing special carbon precursor conversion treatment.
[0021]
Preferred examples of the highly crystalline graphite include crystalline natural graphite, kish
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graphite, highly oriented gas phase cracked graphite, and graphite whiskers. The particle size of
the graphite powder is preferably 1.0 to 200 μm. Be
[0022]
In the present invention, as a method of forming and shaping a diaphragm shape, a hand lay-up
method, a spray-up method, a cast molding method, an injection molding method, a vacuum
forming method which is a conventional method of shaping plastic Or simple and quick forming
means such as a blow molding method are used alone or in combination.
[0023]
At this time, when using the hand lay-up method, the spray-up method, the cast molding method,
the injection molding method or the like as a method of forming and shaping the diaphragm
shape, first, the glassy hard carbon layer portion and The raw material liquid obtained for the
part to be used is coated or poured into a mold surface, and after hardening reaction proceeds
and solidified at normal temperature or under heating, it is obtained for the part to be a graphite
layer part from above The raw material liquid is applied onto the mold surface or poured into a
mold, and the curing reaction is sufficiently allowed to proceed at normal temperature or under
heating, and then the molded product is obtained by releasing the mold.
[0024]
In the case of using a vacuum forming method, a blow molding method, etc., it is first obtained
for the glassy hard carbon layer portion by using a coater or a calender roll on a back sheet
having a release agent on the surface. A film comprising a layer of the desired thickness and a
layer of the desired thickness obtained for the graphite layer portion is preformed and then the
film is still cured. The back sheet is removed in a region having plasticity (B-stage), and molded
into a desired diaphragm shape using each molding method.
At this time, it is possible to appropriately heat to increase the plasticity or to advance the curing
reaction.
After the material is sufficiently cured, it is released and the formed body is taken out.
[0025]
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Next, the obtained formed body is subjected to carbon precursor treatment in a normal
temperature or heated air oven, and then stored in a firing container to be in an inert atmosphere
such as nitrogen gas or argon gas. The carbonization is finished by heating to 900 ° C. or higher
while controlling the temperature rise rate, and then naturally cooled and allowed to complete
firing to complete the surface of the diaphragm base material made of glassy hard carbon. Thus,
there is obtained a diaphragm for a carbonaceous acoustic device, in which the developed
graphite of a crystal having a high elastic modulus is oriented and formed in the plane direction.
Further, if necessary, heat treatment may be performed from 2500 ° C. to 3000 ° C. in vacuum
or in an argon gas phase to graphitize the whole.
[0026]
EXAMPLES The present invention will be specifically described by way of examples; however, the
present invention is not limited by these examples.
(Example 1) As a raw material liquid for a glassy hard carbon layer portion, p- as a curing agent
with respect to 100% by weight of an initial condensation product of furfuryl alcohol / furfural
resin (VF-302 manufactured by Hitachi Chemical Co., Ltd.) 3% by weight of toluenesulfonic acid
and 3% by weight of methanol solution were added, and a product subjected to a vacuum
degassing operation while sufficiently stirring at room temperature using a high speed
homomixer was prepared.
[0027]
Further, 85% by weight of initial condensation product of furfuryl alcohol / furfural resin (VF302 manufactured by Hitachi Chemical Co., Ltd.) as a raw material liquid for the graphite layer
portion. 5% by weight of p-toluenesulfonic acid as a curing agent and 5% by weight of a
methanol solution are added to a product obtained by sufficiently kneading and dispersing 15%
by weight of 5 μm) using a triple roll, and using a high speed homomixer at room temperature.
A material subjected to a vacuum degassing operation with sufficient stirring was prepared.
[0028]
Next, using a coater having a doctor blade capable of double layer coating, on a back sheet
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provided with a release film on the surface, a film of 100 μm thickness made of a raw material
liquid for glassy hard carbon layer and graphite A composite film with a 15 μm-thick film
composed of the layer material liquid was prepared and pre-cured to obtain a preformed sheet
still having sufficiently flexible plasticity (B-stage state).
[0029]
Next, the back sheet of the obtained film is removed, and it is molded into a dome shape by a
vacuum molding machine using a dome-shaped molding die having a bore of 30 mmφ, and is
heated and cured by hot air at 80 ° C. Demolding gave a product form.
[0030]
This molded product is further post-cured in an air oven at 150 ° C. for 5 hours, and then put in
a firing case and heated to 500 ° C./15° C./hour in a nitrogen gas atmosphere furnace. After
heating at a speed, heating from 500 ° C. to 1000 ° C. at a temperature rising rate of 50 °
C./hour, holding at 1000 ° C. for 3 hours, natural cooling was carried out to complete firing.
[0031]
A diaphragm for a carbonaceous acoustic device, in which the graphite having a high elastic
modulus developed on the surface of the diaphragm base material made of glassy hard carbon
thus obtained is oriented in the plane direction and formed. The film had an aperture 24 mmφ
thickness 55 μm, weight 30 mg, Young's modulus 102 GPa, speed of sound 8.3 km / sec,
density 1.46 g / cm 3 and internal loss tan δ of 0.01 with equal physical properties in all
directions.
[0032]
Example 2 A resol type phenol resin (RM-300A manufactured by Asahi Organic Materials Co.,
Ltd.) is prepared as a raw material liquid for a glassy hard carbon layer portion, and a transfer
type injection forming machine is prepared using this. Thus, a dome-shaped living body having a
diameter of 60 mm was obtained.
[0033]
Next, as a raw material liquid for the graphite layer, 85% by weight of resol type phenol resin
(RM-300A manufactured by Asahi Organic Materials Co., Ltd.) and well-developed natural scaly
graphite (average particle size 5 μm) 15 weight % Was subjected to vacuum degassing with
sufficient stirring at room temperature using a high speed homomixer.
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[0034]
Then, the formed body obtained above was held in a jig capable of planetary movement, and on
the surface thereof, a uniform layer composed of a raw material liquid for the graphite layer
portion was constructed using a spray-up method.
[0035]
Thereafter, this molded product is post-cured for 5 hours in an air oven at 180.degree. C., and
then placed in a firing case in a nitrogen gas atmosphere furnace at 500.degree. C.-15.degree.
After heating at a temperature rising rate, heating at 500 ° C. to 1000 ° C. at a temperature
rising rate of 50 ° C./hour, holding at 1000 ° C. for 3 hours, natural cooling was carried out to
complete firing.
[0036]
The diaphragm for a carbonaceous acoustic device, in which a graphite layer having crystals
developed with high elastic modulus is formed on the surface of a glassy hard carbon diaphragm
base material thus obtained, has a diameter of 50 mmφ. It had physical properties of thickness
105 μm, weight 600 mg, Young's modulus 91 GPa, speed of sound 8.0 km / sec, density 1.41 g
/ cm 3 and internal loss tan δ of 0.015 equally in all directions.
[0037]
According to the diaphragm for a carbonaceous acoustic device of the present invention and the
method of manufacturing the same, ■ the highly crystalline graphite powder layer that
expresses high elastic modulus is oriented on the surface of the substrate of the diaphragm -As
constructed, a diaphragm having excellent physical properties can be obtained.
(2) Since a thermosetting resin is used as the main raw material for forming the diaphragm, it is
possible to use many shaping means industrially, and it is excellent in industrial mass
productivity.
(2) Since a thermosetting resin is used as the main raw material, complicated pretreatment is not
required in carbonization, so that the process can be simplified, it is easy to eliminate firing
distortion and the like, and quality control is easy. .
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[0038]
Therefore, the diaphragm of the present invention makes it possible to exhibit the capabilities of
a digital audio device with a clear sound quality and a wide dynamic range at high performance.
Moreover, since the manufacturing method can be manufactured very cheaply by a simple
process, the industrial effect is large.
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