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JPH01146498

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DESCRIPTION JPH01146498
[0001]
FIELD OF THE INVENTION The present invention relates to a method of manufacturing a
diaphragm for an all-carbon loudspeaker. Specifically, the present invention has high hardness,
high elasticity, high strength, and is lightweight as compared with the conventional speaker
diaphragm, and has a moderate internal loss, so that deformation due to external force is small.
Manufactures diaphragms for all-carbon speakers suitable for the digital audio age, with small
distortion of sound, wide reproduction range, and clear sound quality, at low cost using an
industrially simple method It is about how to do it. (Prior Art) Generally, a diaphragm such as a
speaker is required to satisfy the following conditions. (11 sound propagation speed is large, (2)
internal loss of vibration is moderately large, (3) bending rigidity is large, (4) stable against
changes in external air conditions, deformation or deterioration There is no. That is, in order to
be able to faithfully reproduce a wide frequency band as a diaphragm, to be efficient in sound
and express clear sound quality, the material constituting the diaphragm is highly rigid and
lightweight, and creep due to external stress No distortion such as is required. Conventionally,
paper, plastics and metals have been used as the material. However, although paper and plastic
have a moderately high internal loss, they have the disadvantage that sound propagation speed is
low and they are unstable against changes in external air conditions, and metals have a higher
sound velocity than plastic, but still There is a drawback that it is not sufficient and the internal
loss is extremely small. In recent years, focusing on the excellent characteristics of carbon
materials, ie, light weight, high rigidity, having appropriate internal loss, and stability against
environmental changes such as temperature and humidity, etc., vibration for a carbonaceous
speaker Various proposals have been made to use plates. That is, a carbonizable organic binder
may be sheet-processed alone, or carbon fine powder may be mixed and mixed with it, and this
may be sheet-processed and formed into a diaphragm shape using deformation due to heating. ,
Carbonized and fired. Among the characteristics of the diaphragm, it is important that the
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propagation velocity of sound is particularly high, but as a carbonaceous diaphragm, it has a fine
carbon powder, particularly a high elastic modulus, than a carbonized material with an organic
binder alone. It is well known that composite materials obtained by blending short fibers of
carbon fibers, crystalline graphite powder, graphite whiskers or the like give better results
according to the composite law. (Problems to be Solved by the Invention) However, since the
carbon fine powder, in particular, the crystal structure in which carbon elements are regularly
arranged as the modulus of elasticity increases, the surface energy is very small, so the surface of
the organic binder Poor affinity with
Therefore, simply by dispersing, mixing, and kneading the organic binder and the carbon fine
powder filler as a matrix, the bond between the two is weak, and as a result, in the fine structure
of the diaphragm obtained by carbonization, the mechanical binder carbonized It is unlikely that
a large bonding force exists between the interface of the binder carbon and the carbon fine
powder. For the above reasons, the composite law can not be established in the conventional
diaphragm, and the excellent characteristics of the carbon fine powder can not be utilized. In
addition, when the organic binder is filled with a filler, the viscosity of the compounded
composition is increased, so that the flexibility and elongation of the preformed sheet are
reduced, and the formability is inferior compared to the non-filled one. It is well known that there
is. Therefore, there is a disadvantage that the amount of filler added is limited. Therefore, the
object of the present invention is to blend a large amount of carbon fine powder by bringing
about a chemical bonding state or a physical bonding state between the interface of binder
carbon and carbon fine powder which can not be obtained by the conventional method. High
hardness, high elasticity, high strength, and light weight, and because it has appropriate internal
loss, it has little deformation due to external force, and it is Abstract: A method for industrially
simply and inexpensively manufacturing an all-carbon speaker diaphragm suitable for the digital
audio age with small distortion, wide reproduction range and clear sound quality is provided. It
is. (Means for Solving the Problems) The inventors of the present application have intensively
studied to solve the above-mentioned object, and a carbon fine powder is blended with an
organic binder to be carbonized after firing, and the composition is uniformly mixed and
dispersed. Material is kneaded and then preformed into a sheet, and the preform is molded into a
diaphragm shape, subjected to an insolubilizing treatment and then fired in an inert atmosphere
to obtain a diaphragm for a total carbonaceous speaker In the production method of the present
invention, by incorporating a titanate coupling agent in the compounded composition, first, a
strong bonding force is caused to intervene between the interface of the organic binder and the
carbon fine powder in the green state of the compounded composition, By firing as it is, it is
thought that the above object will be achieved, and the present invention has been completed.
Next, the present invention will be specifically described. The titanate coupling agent used in the
present invention is an organic titanium compound and has the following structure. (RO) M Tt (0X + Rz Y) N-Inorganic phase--Organic phase-Titanate coupling agents are variously selected
depending on the type of functional group or hydrocarbon group which determines the structure
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as shown in the above structural formula. Although various products can be obtained, in the
present invention, it is preferable to appropriately select the organic phase according to the type
of the organic binder used and the inorganic phase according to the carbon fine powder.
The addition ratio of the titanate coupling agent to the compounding composition depends on the
types of the organic binder and carbon fine powder used and the quality characteristics of the
desired product, but 0.1 to 5% by weight, preferably It is good to mix 0.5 to 2% by weight. As a
method of adding the titanate coupling agent to the compounded composition of the organic
binder and the carbon fine powder, the integral may be dissolved and added to the plasticizer of
the organic binder, the process oil and the solvent when mixing and kneading the compound.
Blending method, dry pretreatment method of dissolving necessary amount of titanate coupling
agent directly or in a small amount of solvent and stirring carbon fine powder under stirring, or
spray treatment, dissolving titanate coupling agent in large amount of solvent After stirring and
mixing with carbon fine powder, there is a wet pretreatment method in which the solvent is
removed by drying or used as it is, but in the present invention, the addition method is not
particularly limited, and it is preferable to select an optimum method as appropriate. . Next, other
configurations of the present invention will be described. The organic binder in the present
invention is selected from thermoplastic resins which carbonize in an inert atmosphere,
thermosetting resins, pitches, and natural or synthetic compounds having condensed polycyclic
aromatic groups in the basic structure of the molecule. Select one or two or more. As fine carbon
powder used in the present invention, it is preferable to use man-made or fine powder such as
natural graphite, carbon black, coke, carbon fiber, graphite whisker and the like in the range of
10 to 90% by weight of the composition. As the type thereof, in consideration of the acoustic
characteristics of the obtained diaphragm for a carbonaceous speaker, it is preferable to select a
short fiber of carbon fiber having a high elastic modulus, or a crystalline graphite powder or a
graphite whisker. More preferably, as a reinforcing material of a speaker diaphragm having a
theoretical elastic modulus of 1020 GPa, which is an extremely high value as compared with
other carbon fine powders, and having a plate-like and flat crystal form and a two-dimensional
spread. It is preferable to use crystalline graphite powder having ideal characteristics. With
regard to the size of the powder particles, better results can be obtained by using particles with
an average particle diameter of 50 μm or less, preferably 20 μm or less. In the present
invention, when adding the titanate coupling agent into the compounded composition, mixing of
the organic binder and the carbon fine powder, kneading characteristics, sheeting characteristics
as preforming, and molding characteristics to form a diaphragm are also included. For the
purpose of raising, DOP, DBP, if necessary. Plasticizers such as TCP, DOAXDO3, DAP, propylene
carbonate, N-methyl pyrrolidone, etc., or one or more solvents, and / or chlorinated polyolefin,
ethylene-vinyl acetate copolymer, ethylene-acrylic copolymer, metal soap, fat It is also possible to
add a small amount of one or two or more of molding assistants such as family soaps, natural
waxes, petroleum waxes and the like.
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Next, a method of manufacturing the all-carbon speaker diaphragm using the above-described
material will be specifically described. First, an organic binder, carbon fine powder, a plasticizer
optionally added, or a solvent, a molding aid, and a carbonization regulator are weighed, and a
titanate coupling agent treatment is performed by any of the methods described above, Disperse
and mix uniformly using a mixer. Next, the obtained mixture is kneaded. Preferably, a kneader
capable of imparting high elasticity to the organic binder and the carbon fine powder in the
compounding composition in order to form a strong chemical bond or a physical bond via a
titanate coupling agent. It is good to use As a result, it is possible to obtain a kneaded product in
which the binder to be subjected to the calcination and recarbonization is chemically and
physically bonded to the surface of the carbon fine powder by the mechanochemical reaction
generated by the mechanical energy. In particular, when the surface uses a relatively stable and
inert carbon fine powder as compared to other fillers, the high shear strength makes the surface
of the powder particles attrition or very active. This method is effective because the bonding
strength with the titanate coupling agent is large. In addition, when using carbon fiber as a
carbon fine powder, it must be careful not to cut | disconnect a fiber too much. As a kneader
giving high shear force, a two-roll mill, a three-roll mill, a pressurized Nigu, a Banbury mixer, a
two-screw extruder, a ball mill, etc. are used. Next, the kneaded material is formed into a sheet
having a uniform thickness using a rolling roll, an extrusion molding machine with a T-die at the
tip, and another film forming machine with a crucible. Next, the sheet is placed in a mold in
which the shrinkage after carbonization is read in a target diaphragm shape, and molded into a
desired diaphragm shape using a vacuum molding method, a compression molding method, a
blow molding method, etc. by a conventional method. . Next, the green molded body is subjected
to an insoluble and infusible treatment. In the case of producing a conventional carbon material,
the method of heat treatment to 150 to 400 ° C. in an oxidizing atmosphere such as air or
ozone is a method of this insoluble and infusible treatment, and corrosion of ammonia gas,
chlorine gas, etc. There are a method of heat treatment to 50 to 400 ° C. in a hydrogen gas
atmosphere, a method of irradiating radiation, and the like, but in the present invention, the
method of the insoluble and infusible treatment is not particularly limited. In addition, depending
on the type of the organic binder used, the insoluble and infusible treatment may be omitted.
Next, the molded product subjected to the above treatment is gradually heated from room
temperature in an inert atmosphere such as nitrogen or argon gas and heated to 700 ° C. or
higher, preferably 1000 ° C. or higher to be carbonized. Then, cool it and take it out to make a
product.
The speaker diaphragm obtained by the present invention has the following excellent
advantages. (1) A fine structure of a diaphragm obtained by carbonizing the organic binder and
the carbon fine powder filler in a green state chemically and physically between the two through
a titanate coupling agent as a result. In the above, by providing a large bonding strength between
the carbonized binder carbon and the interface of the carbon fine powder in the organic binder, a
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composite law is established and the excellent properties of the carbon fine powder are utilized.
(2) The viscosity of the blended composition is reduced by the action of the titanate coupling
agent. As a result, the following improvements can be made. a) Since the ratio of the carbon fine
powder in the compounded composition can be made larger than before, the characteristics of
the diaphragm are further improved. b) Even if the proportion of carbon fine powder added is the
same as in the prior art, the degree of freedom in formability is increased, and a diaphragm with
a more complicated shape or deep drawing can be obtained. C) Even if the ratio of carbon fine
powder added is the same as in the prior art, the amount of plasticizer and solvent added can be
reduced as necessary to achieve the plasticity of the blended composition. This also works
advantageously for the insoluble and infusible treatment performed before firing, leading to
energy saving and cost saving. EXAMPLES The present invention will be described more
specifically by the following examples. 40 parts by weight of a chlorinated vinyl chloride resin
(Nippon Carbide Industries Co., Ltd .: Nicaten T-742 manufactured by Nippon Carbide Industries
Co., Ltd.) 65 parts by weight, 60 parts by weight of natural scaly graphite powder (C3P
manufactured by Japan Graphite Industry Co., Ltd.) While dispersing a compounded composition
consisting of 1 part by weight of acid amide using a Henschel mixer, 0.5 part by weight of an
acylate based titanate coupling agent (Nippon Soda & Co., Ltd .; Chitako) S-181 ') is dissolved in 0
parts by weight of DBP1. The resulting solution was added dropwise and dispersed for another
10 minutes. The mixture was kneaded under heating using a pressure kneader, and then fully
kneaded using a three-roll mill. Next, the kneaded material was taken out and preformed into a
sheet of 150 μ in thickness using a rolling roll. Next, the obtained sheet was formed into a dome
having a diameter of 36 mm using a vacuum forming machine equipped with a heated mold.
Thereafter, the molded product is released from the mold and placed in a heating oven at 200 °
C. to perform insoluble and infusible processing, and then the temperature is gradually raised
from room temperature to 1000 ° C. in a nitrogen gas atmosphere to carbonize After
processing, the product was taken out after cooling. The obtained diaphragm for all-carbon
speaker has a thickness of 90μ and accurately maintains a dome shape with a diameter of 35
mm, a specific gravity of 1.65, a Young's modulus of 280 GPa, an acoustic velocity of 13 Km /
See, and an internal loss of 0.03. Show the characteristics of
Husband "I (-1 natural scaly graphite powder [Nippon Graphite Industry side type C3P) 25 parts
by weight, PAN based carbon short fiber (East Tori made Torekachosopudo fiber TOO 8A) carbon
fine powder consisting of 5 parts by weight While dispersing using a mixer, a solution of a
monoalkoxy-based titanate coupling agent [10.5 parts by weight of BLANAC 1-TTS 'made by
Ajinomoto Co.] in 5 parts by weight of IPA is added dropwise, and after dispersion for 10
minutes, The IPA was volatilized. Then, 70 parts by weight of furan resin (Hitachi Kasei Co., Ltd.,
Hitafuran VF-302) was added, and the mixture was kneaded for 40 minutes at room temperature
using a Warner mixer, and then kneaded using a water-cooled three-roll mill for ink. Next, the
kneaded material was taken out, 4 parts by weight of a 50 wt% methanol solution of p-)-ruene
sulfonic acid was added, and a vacuum degassing operation was performed while sufficiently
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stirring at room temperature using a high speed homomixer. Next, a 150 μm thick sheet was
formed on the back sheet using a coating machine equipped with an air-heated drying zone. Next,
the obtained sheet was peeled off from the hack sheet, and formed into a dome having a
diameter of 40 mm using a vacuum forming machine equipped with a heated mold. Thereafter,
the molded product is peeled off from the mold and placed in a heating oven at 200 ° C. to
perform insoluble and infusible processing, and then the temperature is gradually raised from
room temperature to 1000 ° C. in a nitrogen gas atmosphere to carbonize After processing, the
product was taken out after cooling. The obtained diaphragm for all-carbon speaker has a
thickness of 90μ and accurately maintains a dome shape with a diameter of 35 mm, a specific
gravity of 1.50, a Young's modulus of 120 GPa, an acoustic velocity of 8.9 Km / sec, and an
internal loss of 0 The characteristic of .01 was shown. When the same composition as in Example
1 was used except that the titanate coupling agent was removed from the compounded
composition in Example 1 of the resin, it was molded under the same conditions as in Example 1,
and the flexibility of the sheet and Due to the low elongation, the top of the forming stage dome
was cracked and no product was obtained. Therefore, when the compounding ratio of the organic
binder and the carbon fine powder is changed, that is, 50 parts by weight of the chlorinated vinyl
chloride resin and 50 parts by weight of the natural scaly graphite powder are prepared and
molded, a product is obtained. Therefore, thereafter, a diaphragm was obtained under the same
conditions as in Example 1. The diaphragm for all-carbon loudspeakers obtained had a thickness
of 90μ and correctly maintained a dome shape with a diameter of 35 mm, but a specific gravity
of 1.65, Young's modulus of 100 GPa, sound velocity of 7.8 Km / sec, internal loss It shows a
characteristic of 0.03 and is inferior to that of Example 1.
Comparative example of the composition of Example 2 using the same composition as Example 2
except that the titanate coupling agent was removed, the sheet was softened and stretched when
it was formed under the same conditions as Example 2. Because of the small size, the dome top of
the dome was cracked at the molding stage and no product was obtained. Therefore, the blending
ratio of the organic binder and the carbon fine powder is changed, that is, 85 parts by weight of
furan resin, 12 parts by weight of natural scaly graphite powder, 12 parts by weight, and 3 parts
by weight of PAN-based carbon short fibers After adjustment and molding, a product was
obtained. Thereafter, a diaphragm was obtained under the same conditions as in Example 2. The
diaphragm for all-carbon loudspeakers obtained had a thickness of 90μ and correctly
maintained a dome shape with a diameter of 35IIII11. However, the specific gravity of 1.50,
Young's modulus of 70 GPa, sound velocity of 6.8 Km / sec, internal loss It shows a characteristic
of 0.01 and is inferior to that of Example 2. (Effects of the Invention) As shown in the examples,
the diaphragm for the all-carbon speaker according to the present invention differs from the
conventional method in that the organic binder and the carbon fine powder filler which are the
matrix are used as a titanate coupling agent in the green state. Bond between the two chemically
and physically, and as a result, in the microstructure of the diaphragm obtained by carbonization,
a large bonding force is generated between the interface between the carbon binder and the
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carbon fine powder where the organic binder has carbonized. By being present, the composite
side is established, the blending ratio of the carbon fine powder is increased, and the excellent
characteristics of the carbon fine powder are utilized. Therefore, the present invention has high
hardness, high elasticity, high strength and light weight, and has adequate internal loss, so that
deformation due to external force is small, distortion of sound is small, reproduction range is
wide, and clear. It is possible to inexpensively provide an improved all-carbon diaphragm suitable
for the digital audio age capable of producing sound quality using an industrially simple method.
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