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JP2011109664

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JP2011109664
The present invention relates to a diaphragm and a speaker using the same, and more
particularly to a diaphragm using a carbon nanotube and a speaker using the same. A diaphragm
according to the present invention includes a central portion and an edge portion joined around
the central portion, the central portion including a plurality of carbon nanotubes connected by
intermolecular force. The speaker of the present invention includes a voice coil and a diaphragm.
The voice coil is connected to the diaphragm, and the diaphragm includes a central portion and
an edge portion joined to surround the central portion, and the central portions are connected by
an intermolecular force. Containing carbon nanotubes. [Selected figure] Figure 1
Diaphragm and speaker using it
[0001]
The present invention relates to a diaphragm and a speaker using the same, and more
particularly to a diaphragm using a carbon nanotube and a speaker using the same.
[0002]
The speaker can convert an electrical signal to sound as an electroacoustic transducer.
According to the principle of operation, speakers are classified into various types such as
dynamic speakers, magnetic speakers, electrostatic speakers, and piezoelectric speakers. The
various types of speakers all produce mechanical sound by means of mechanical vibration, that
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is, they realize electro-mechanical force-sound conversion. Here, dynamic speakers are widely
used.
[0003]
In the conventional speaker, a diaphragm is directly connected to the voice coil, and the
diaphragm vibrates together to emit a sound having a waveform equal to that of the audio signal
into the air. The volume of the speaker is related to the power of the electrical signal input to the
speaker and the efficiency of converting the electrical signal into sound. However, if the power of
the electrical signal input to the speaker is too high, the diaphragm may be deformed or
damaged. Therefore, the toughness and Young's modulus of the diaphragm are related to the
rated output of the speaker. That is, the rated output of the speaker is the maximum power input
to the speaker to the extent that deformation or damage of the diaphragm does not occur. If the
weight per unit of the diaphragm is small, the energy for vibrating the diaphragm is small, the
energy conversion efficiency of the speaker is high, and the output volume of the speaker is
large.
[0004]
Chinese Patent Application Publication No. 101300895
[0005]
Kaili Jiang, Qunqing Li, Shoushan Fan, "Spinning continuous carbon nanotube yarns", Nature, Vol.
419, p.801
[0006]
However, the diaphragm of a conventional speaker is made of polymer, metal, ceramic or paper.
Since the toughness and Young's modulus of the diaphragm made of polymer or paper are very
low and the weight of the diaphragm made of metal or ceramic is large, the rated output of the
speaker using the diaphragm is low (eg, 0.3 W to There is a problem of 0.5 W).
In addition, since the density of the conventional diaphragm is high, the energy conversion
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efficiency of the speaker is low. Therefore, in order to increase the rated output and energy
conversion efficiency of the speaker, it is necessary to increase the Young's modulus and
toughness of the diaphragm and to reduce the density of the diaphragm.
[0007]
In Patent Document 1, a diaphragm is manufactured using a composite material formed by
dispersing carbon nanotubes in a film (stearic acid or fatty acid) with a surfactant. However,
since the specific surface area of carbon nanotubes is very large, carbon nanotubes tend to be
concentrated in the film. When the number of carbon nanotubes added to the film increases, it
becomes difficult to disperse the carbon nanotubes. In addition, since an additive such as a
surfactant is used, there is a problem that the vibration plate has many impurities. Also, it is
difficult to install carbon nanotubes only at predetermined positions of the diaphragm.
[0008]
The present invention provides a diaphragm having high toughness and Young's modulus and a
speaker using the same in order to solve the problems.
[0009]
The diaphragm of the present invention includes a central portion and an edge portion joined
and joined to the central portion.
The central portion includes a plurality of carbon nanotubes connected by intermolecular force.
[0010]
The central portion includes a carbon nanotube structure formed of a plurality of carbon
nanotubes.
[0011]
The central portion includes a carbon nanotube structure and a substrate.
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[0012]
The speaker of the present invention includes a voice coil and a diaphragm.
The voice coil is connected to the diaphragm, and the diaphragm includes a central portion and
an edge portion joined and joined to the central portion, and the central portion is connected by
a plurality of intermolecular forces. Contains carbon nanotubes.
[0013]
Compared with the prior art, the diaphragm of the present invention has the following
advantages.
First, since the carbon nanotube composite structure is used for the diaphragm of the present
invention, and carbon nanotubes have high toughness, Young's modulus and small density, the
toughness and Young's modulus of the diaphragm are high. Second, since carbon nanotubes are
very light, diaphragms utilizing carbon nanotube structures or carbon nanotube composite
structures are much thinner than conventional diaphragms. Third, since the carbon nanotube
structure or the carbon nanotube composite structure is used in the central portion of the
diaphragm, the volume and energy conversion can be enhanced.
[0014]
It is a schematic diagram of the speaker in Example 1 of this invention. It is an upper view of the
speaker in Example 1 of this invention. It is sectional drawing of the speaker in Example 1 of this
invention. It is sectional drawing of the speaker in Example 1 of this invention. It is a scanning
electron micrograph of the drone structure carbon nanotube film of this invention. It is a
schematic diagram of the carbon nanotube segment in the drawn structure carbon nanotube film
of this invention. It is a scanning electron micrograph of the carbon nanotube film of the fluff
structure of this invention. It is a scanning electron micrograph of the presid structure carbon
nanotube film of this invention. It is a scanning electron micrograph of the non-twisted carbon
nanotube wire of this invention. It is a scanning electron micrograph of the twist-like carbon
nanotube wire of this invention. It is sectional drawing of the diaphragm in Example 2 of this
invention. It is sectional drawing of the diaphragm in Example 3 of this invention.
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[0015]
Hereinafter, embodiments of the present invention will be described with reference to the
drawings.
[0016]
Embodiment 1 Referring to FIG. 1, the speaker 100 of the present embodiment includes a frame
10, a magnet 11, an reinforcement plate 12, a voice coil 13, and a diaphragm 14.
[0017]
The frame 10 is formed by pressing a circular metal plate.
The frame 10 includes an upper plate 10a, a side wall 10b and an edge 10c.
The side wall 10b extends from the periphery of the upper plate 10a. The side wall 10 b and the
upper plate 10 a form a chamber 101. The chamber 101 has an opening (not shown) directed to
the upper plate 10a. The edge 10 c is provided perpendicularly to the side wall 10 b so as to
surround one periphery of the side wall 10 b. A plurality of ventilating openings 103 are
provided at the edge 10 c to introduce air into the chamber 101. In order to install the magnet
11, a fixed pillar 104 is installed vertically to the upper plate 10a at its center.
[0018]
The magnet 11 is in the form of a ring having a central hole 11 a, and the fixing post 104 is fixed
through the central hole 11 a of the magnet 11. The outer diameter of the magnet 11 is smaller
than the inner diameter of the chamber 101. Since the thickness of the magnet 11 is smaller than
the length of the fixed column 104, the fixed column 104 can be fixed by the reinforcing plate
12.
[0019]
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In order to prevent the magnet 11 from being detached from the fixed column 104, the
reinforcing plate 12 is preferably fixed to the end of the fixed column 104. Since the reinforcing
plate 12 is made of an impact absorbing material, damage to the magnet 11 can be prevented.
The outer diameter of the reinforcing plate 12 is slightly larger than the outer diameter of the
magnet 11. The magnet 11 can be fixed to the chamber 101 by the reinforcing plate 12, the
upper plate 10 a, and the fixing post 104.
[0020]
The voice coil 13 is installed in a gap formed between the magnet 11 and the side wall 10 b as
an element for driving the speaker 100. The voice coil 13 is made of a conductive wire. When an
electrical signal is input to the voice coil 13, the voice coil 13 can generate a magnetic field. The
voice coil 13 is vibrated by the interaction of the magnetic field generated by the voice coil 13
and the magnet 11.
[0021]
The diaphragm 14 is installed as a sound emitting element of the speaker 100. The shape of the
diaphragm 10 is formed into a shape such as a rectangle, an ellipse, a circle, or a triangle. When
applied to the large-sized speaker 100, the diaphragm 14 is formed in a cone shape. When
applied to the small-sized speaker 100, the diaphragm 14 is formed in a flat plate-like circle or
rectangle.
[0022]
Referring to FIGS. 2 and 3, the diaphragm 14 includes a convex central portion 142 and a
circular edge 141. The back edge portion of the edge portion 141 is joined to the outer periphery
of the central portion 142, and the outer periphery of the edge portion 141 is fixed to the edge
portion 10c of the frame 10. It is fixed to the frame 10. In this case, the central portion 142 of
the central portion 142 of the diaphragm 14 may cover the opening of the chamber 101.
Furthermore, the voice coil 13 may be joined to the outer periphery of the central portion 142 of
the diaphragm 14 and may be joined to the joint of the central portion 142 and the edge portion
141 of the diaphragm 14. Thus, the central portion 142 and the edge portion 141 of the
diaphragm 14 are vibrated together with the voice coil 13.
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[0023]
The edge 141 of the diaphragm 14 is cloth, paper, paper-like wool or polypropylene. The central
portion 142 of the diaphragm 14 is made of a carbon nanotube composite structure having a
thickness of 1 μm to 1 mm. In the present embodiment, the central portion 142 of the
diaphragm 14 includes a substrate and a carbon nanotube structure composited with the
substrate. The carbon nanotube composite structure can be classified as follows according to the
relationship between the substrate and the carbon nanotube structure.
[0024]
First, the material of the base material is infiltrated into the carbon nanotube structure to form a
carbon nanotube composite structure. In the carbon nanotube composite structure, the base
material is any one polymer of polypropylene, polyacrylonitrile, bitumen, tenasco, phenol fiber
polyvinyl chloride, phenol resin, epoxide resin, and polyester.
[0025]
In the second type, the substrate is a layered structure, and carbon nanotube structures are
dispersed in the layered substrate. The substrate is a cloth, paper or paper-like wool, or a
polymer of cellulose, polyethylene terephthalate, polyethylene, styrene resin, phenol resin,
epoxide resin or polyester.
[0026]
Referring to FIG. 3, as one example, the central portion 142 of the diaphragm 14 is a carbon
nanotube composite structure. The edge 141 of the diaphragm 14 is cloth, paper, paper-like wool
or polypropylene. The edge 141 of the diaphragm 14 is bonded to the outer periphery of the
central portion 142 of the diaphragm 14 with an adhesive.
[0027]
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Referring to FIG. 4, as another example, the central portion 142 of the diaphragm 14 includes a
base 143 and a carbon nanotube structure 144. The carbon nanotube structure 144 is disposed
on one surface of the substrate 143. A part of the base material 143 is infiltrated into the carbon
nanotube structure 144 to form a carbon nanotube composite structure.
[0028]
The base 143 and the edge 141 of the diaphragm 14 may be made of the same material. In this
case, the above-described material is integrally molded to form one plate-like structure, and then
the carbon nanotube structure 144 is placed at the central portion of the plate-like structure.
Finally, the carbon nanotube structure 144 and the plate-like structure are hot-pressed to
permeate a portion of the plate-like structure into the carbon nanotube structure 144 to form the
central portion 142 of the diaphragm 14. Do.
[0029]
The carbon nanotube structure 144 has a plurality of holes and has a free standing structure
including a plurality of carbon nanotubes. Here, the self-supporting structure is a form in which
the carbon nanotube structure 144 can be used independently without using a support material.
That is, it means that the carbon nanotube structure 144 can be suspended by supporting the
carbon nanotube structure 144 from opposite sides without changing the structure of the carbon
nanotube structure 144.
[0030]
The plurality of carbon nanotubes are uniformly dispersed in the carbon nanotube structure 144.
The plurality of carbon nanotubes are arranged or not oriented. When the plurality of carbon
nanotubes are arranged without orientation, the carbon nanotubes are arranged or entangled in
different directions. When the plurality of carbon nanotubes are oriented, the plurality of carbon
nanotubes are arranged along the same direction. The carbon nanotube is a single-walled carbon
nanotube, a double-walled carbon nanotube, or a multi-walled carbon nanotube. When the
carbon nanotube is a single-walled carbon nanotube, the diameter is set to 0.5 nm to 50 nm, and
when the carbon nanotube is a double-walled carbon nanotube, the diameter is set to 1 nm to 50
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nm, and the carbon nanotube is a multilayer carbon In the case of nanotubes, the diameter is set
to 1.5 nm to 50 nm.
[0031]
Examples of the carbon nanotube structure of the present invention include the following (1) to
(4).
[0032]
(1) Drone-Structured Carbon Nanotube Film The carbon nanotube structure includes at least one
carbon nanotube film.
The carbon nanotube film may be a drawn carbon nanotube film shown in FIG. The carbon
nanotube film is obtained by drawing from a super-aligned carbon nanotube array (see NonPatent Document 1). In the single carbon nanotube film, a plurality of carbon nanotubes are
connected end to end along the same direction. That is, the single carbon nanotube film includes
a plurality of carbon nanotubes whose ends in the longitudinal direction are connected by an
intermolecular force. The single carbon nanotube film comprises a plurality of carbon nanotube
segments. The plurality of carbon nanotube segments are connected end-to-end with
intermolecular force along the length direction. Each carbon nanotube segment includes a
plurality of carbon nanotubes connected by intermolecular force in parallel to one another. The
lengths of the plurality of carbon nanotubes are the same in the single carbon nanotube segment.
Toughness and mechanical strength of the carbon nanotube film can be enhanced by immersing
the carbon nanotube film in an organic solvent. The carbon nanotube film immersed in the
organic solvent has a low heat capacity per unit area. The carbon nanotube film has a width of
100 μm to 10 cm and a thickness of 0.5 nm to 100 μm.
[0033]
The carbon nanotube structure 144 may include a plurality of stacked carbon nanotube films. In
this case, the adjacent carbon nanotube films are bonded by an intermolecular force. The carbon
nanotubes in the adjacent carbon nanotube film cross each other at an angle of 0 ° to 90 °.
When the carbon nanotubes in the adjacent carbon nanotube film intersect at an angle larger
than 0 °, a plurality of micro holes are formed in the carbon nanotube structure 144.
Alternatively, the plurality of carbon nanotube films may be juxtaposed without gaps.
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[0034]
The method of manufacturing the carbon nanotube film includes the following steps.
[0035]
The first step provides a carbon nanotube array.
The carbon nanotube array is a super aligned carbon nanotube array (see Super Aligned Array of
Carbon Nanotubes, Non-Patent Document 1), and a method of manufacturing the super aligned
carbon nanotube array employs a chemical vapor deposition method. The manufacturing method
includes the following steps. In step (a), a flat substrate is provided, which is any one of a P-type
silicon substrate, an N-type silicon substrate and a silicon substrate on which an oxide layer is
formed. In the present example, it is preferred to select a 4 inch silicon substrate. In step (b), a
catalyst layer is uniformly formed on the surface of the substrate. The material of the catalyst
layer is any one of iron, cobalt, nickel and alloys of two or more thereof. In step (c), the substrate
on which the catalyst layer is formed is annealed in air at 700 ° C. to 900 ° C. for 30 minutes
to 90 minutes. In step (d), the annealed substrate is placed in a reactor and heated with a
protective gas at a temperature of 500 ° C. to 740 ° C., and then a gas containing carbon is
introduced to react for 5 minutes to 30 minutes. To grow super aligned carbon nanotube arrays
(Non-Patent Document 1). The height of the carbon nanotube array is 100 micrometers or more.
The carbon nanotube array is composed of a plurality of carbon nanotubes parallel to each other
and growing perpendicularly to the substrate. The carbon nanotubes are partially intertwined
with one another because of their long length. By controlling the growth conditions, the carbon
nanotube array is free of impurities such as, for example, amorphous carbon and metal particles
as remaining catalyst.
[0036]
In the present embodiment, as the gas containing carbon, for example, active hydrocarbons such
as acetylene, ethylene, methane and the like are selected, and ethylene is preferably selected. The
protective gas is nitrogen gas or inert gas, preferably argon gas.
[0037]
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The carbon nanotube array provided by the present example is not limited to being
manufactured by the above manufacturing method, and may be manufactured by an arc
discharge method or a laser evaporation method.
[0038]
In the second step, at least one carbon nanotube film is stretched from the carbon nanotube
array.
First, it has a plurality of carbon nanotube ends using tools such as tweezers. For example, a tape
having a certain width is used to have the ends of a plurality of carbon nanotubes. Next, the
plurality of carbon nanotubes are drawn at a predetermined speed to form a continuous carbon
nanotube film composed of a plurality of carbon nanotube segments.
[0039]
In the step of drawing the plurality of carbon nanotubes, when the plurality of carbon nanotubes
are respectively detached from the base, the carbon nanotube segments are joined end to end by
an intermolecular force to form a continuous carbon nanotube film ( See Figure 5). 5 and 6, a
single carbon nanotube film 143a includes a plurality of carbon nanotube segments 143b. The
plurality of carbon nanotube segments 143b are connected end to end by intermolecular force
along the length direction. Each carbon nanotube segment 143b includes a plurality of carbon
nanotubes 145 connected by intermolecular force in parallel to each other. The lengths of the
plurality of carbon nanotubes 145 are the same in the single carbon nanotube segment 143b.
Toughness and mechanical strength of the carbon nanotube film 143a can be enhanced by
immersing the carbon nanotube film 143a in an organic solvent. The heat capacity per unit
volume of the carbon nanotube film immersed in the organic solvent is reduced.
[0040]
In order to enhance mechanical strength and toughness of the carbon nanotube structure, two or
more carbon nanotube films may be laminated to form the carbon nanotube structure. In this
case, the carbon nanotubes in the adjacent carbon nanotube film intersect at 0 to 90 °. The light
transmittance of the carbon nanotube structure is related to the number of laminated carbon
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nanotube films. That is, as the number of stacked carbon nanotube films increases, the carbon
nanotube structure becomes thicker and the light transmittance thereof becomes lower. In the
present embodiment, the carbon nanotube structure has a thickness of 0.5 nm to 1 mm. When
the thickness of the carbon nanotube structure is in the range of 0.5 nm to 99 nm, the light
transmittance of the carbon nanotube structure may reach 86% to 95%.
[0041]
(2) Fluff Structure Carbon Nanotube Film The carbon nanotube structure 144 includes at least
one carbon nanotube film. The carbon nanotube film may be a flocculated carbon nanotube film.
Referring to FIG. 7, in the single carbon nanotube film, a plurality of carbon nanotubes are
entangled and arranged isotropically. In the carbon nanotube structure, the plurality of carbon
nanotubes are uniformly distributed. The plurality of carbon nanotubes are arranged without
orientation. The length of the single carbon nanotube is 100 nm or more, preferably 100 nm to
10 cm. The plurality of carbon nanotubes are formed close to each other by intermolecular force
and mutually intertwined to form a carbon nanotube network. The plurality of carbon nanotubes
are arranged without being oriented to form many minute holes. Here, the diameter of the single
minute hole is 10 μm or less. Since the carbon nanotubes in the carbon nanotube structure are
arranged to be entangled with each other, the carbon nanotube structure is excellent in flexibility
and can be formed to be curved in an arbitrary shape. Depending on the application, the length
and width of the carbon nanotube structure can be adjusted. The carbon nanotube structure 144
has a thickness of 0.5 nm to 1 mm.
[0042]
The method of manufacturing the carbon nanotube film includes the following steps.
[0043]
In the first step, a carbon nanotube raw material (a carbon nanotube to be the basis of a fluff
structured carbon nanotube film) is provided.
[0044]
The carbon nanotubes are peeled off from the substrate with a tool such as a knife to form a
carbon nanotube material.
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The carbon nanotubes are intertwined to some extent.
In the raw material of the carbon nanotube, the length of the carbon nanotube is 100
micrometers or more, and preferably 10 micrometers or more.
[0045]
In the second step, the carbon nanotube material is immersed in a solvent, and the carbon
nanotube material is treated to form a fluff structure carbon nanotube structure.
[0046]
After immersing the carbon nanotube raw material in the solvent, the carbon nanotube is formed
into a fluff structure by ultrasonic dispersion, high intensity stirring, vibration or the like.
The solvent is water or a volatile organic solvent. The solvent containing the carbon nanotubes is
treated for 10 to 30 minutes by the ultrasonic dispersion method. Since carbon nanotubes have a
large specific surface area and a large intermolecular force is generated between carbon
nanotubes, the carbon nanotubes are entangled and formed into a fluff structure.
[0047]
In the third step, the solution containing the fluff structure carbon nanotube structure is filtered
to take out the final fluff structure carbon nanotube structure.
[0048]
First, provide a funnel on which filter paper is placed.
The solvent containing the fluff structure carbon nanotube structure is added to the funnel on
which the filter paper is placed, and left for a while to be dried, whereby the fluff structure
carbon nanotube structure is separated. Referring to FIG. 7, carbon nanotubes in the fluff carbon
nanotube structure are entangled with each other to form an irregular fluff structure.
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[0049]
The separated carbon nanotube structure of the fluff structure is placed in a container, the
carbon nanotube structure of the fluff structure is developed into a predetermined shape, and a
predetermined pressure is applied to the expanded carbon nanotube structure of the fluff
structure, If the solvent remaining in the fluff structure carbon nanotube structure is heated or
the solvent evaporates spontaneously, a fluff structure carbon nanotube film is formed.
[0050]
The thickness and area density of the fluff structure carbon nanotube film can be controlled by
the area where the fluff structure carbon nanotube structure is developed.
That is, in the fluff structure carbon nanotube structure having a certain volume, the thickness
and the surface density of the fluff structure carbon nanotube film decrease as the developed
area increases.
[0051]
In addition, a fluff structure carbon nanotube film is formed using a microporous membrane and
an air-pumping funnel. Specifically, a microporous membrane and an air pump funnel are
provided, a solvent containing the fluff structure carbon nanotube structure is added to the air
pump funnel through the microporous membrane, and the air pump funnel is bled and dried.
Then, a fluff structure carbon nanotube film is formed. The microporous membrane has a smooth
surface. In the microporous membrane, the diameter of a single micropore is 0.22 micrometers.
Since the microporous membrane has a smooth surface, the carbon nanotube film can be easily
peeled off from the microporous membrane. Furthermore, since the air is applied to the fluff
structure carbon nanotube film by using the air pump, it is possible to form a uniform fluff
structure carbon nanotube film.
[0052]
(3) Presidated carbon nanotube film The carbon nanotube structure 144 includes at least one
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carbon nanotube film. The carbon nanotube film may be a pressed carbon nanotube film shown
in FIG. The plurality of carbon nanotubes in the single carbon nanotube film may be arranged
isotropically, arranged along a predetermined direction, or arranged along different directions.
The carbon nanotube film has a sheet-like free-standing structure formed by pressing the carbon
nanotube array by applying a predetermined pressure by using a pressing tool, and tilting the
carbon nanotube array by pressure. is there. The arrangement direction of carbon nanotubes in
the carbon nanotube film is determined by the shape of the pressing device and the direction in
which the carbon nanotube array is pushed.
[0053]
The carbon nanotubes in the single carbon nanotube film can be arranged without orientation.
The carbon nanotube film includes a plurality of carbon nanotubes arranged isotropically.
Adjacent carbon nanotubes attract and connect to each other by intermolecular force. The carbon
nanotube structure has planar isotropy. The carbon nanotube film is formed by pressing the
carbon nanotube array along a direction perpendicular to the substrate on which the carbon
nanotube array is grown, using a flat tool.
[0054]
The carbon nanotubes in the single carbon nanotube film may be oriented and arranged. The
carbon nanotube film includes a plurality of carbon nanotubes arranged along the same
direction. When simultaneously pressing the carbon nanotube array along the same direction
using a pressing device having a roller shape, a carbon nanotube film including carbon
nanotubes aligned in basically the same direction is formed. In addition, when simultaneously
pressing the carbon nanotube array along different directions by using a pressing device having
a roller shape, a carbon nanotube film including carbon nanotubes arranged in selective
directions along the different directions. Is formed.
[0055]
The degree of tilt of the carbon nanotubes in the carbon nanotube film is related to the pressure
applied to the carbon nanotube array. The carbon nanotubes in the carbon nanotube film and the
surface of the carbon nanotube film form an angle α, and the angle α is 0 ° or more and 15 °
or less. Preferably, carbon nanotubes in the carbon nanotube film are parallel to the surface of
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the carbon nanotube film. The greater the pressure, the greater the degree of inclination. The
thickness of the carbon nanotube film is related to the height of the carbon nanotube array and
the pressure applied to the carbon nanotube array. That is, as the height of the carbon nanotube
array increases and the pressure applied to the carbon nanotube array decreases, the thickness
of the carbon nanotube film increases. Conversely, the smaller the height of the carbon nanotube
array and the greater the pressure applied to the carbon nanotube array, the smaller the
thickness of the carbon nanotube film.
[0056]
(4) Carbon Nanotube Wire The carbon nanotube structure may include at least one carbon
nanotube wire. The heat capacity of one carbon nanotube wire is 0 (not 0 included) to 2 × 10 <4> J / cm <2> · K, 5 × 10 <-5> J / cm <2> -It is preferable that it is K. The diameter of one carbon
nanotube wire is 4.5 nm to 1 cm. Referring to FIG. 9, the carbon nanotube wire comprises a
plurality of carbon nanotubes connected by intermolecular force. In this case, one carbon
nanotube wire (non-twisted carbon nanotube wire) includes a plurality of carbon nanotube
segments (not shown) connected end to end. The carbon nanotube segments have the same
length and width. Furthermore, a plurality of carbon nanotubes of the same length are arranged
in parallel to each of the carbon nanotube segments. The plurality of carbon nanotubes are
arranged parallel to the central axis of the carbon nanotube wire. In this case, the diameter of
one carbon nanotube wire is 1 μm to 1 cm. Referring to FIG. 10, the carbon nanotube wire may
be twisted to form a twisted carbon nanotube wire. Here, the plurality of carbon nanotubes are
arranged in a spiral shape with the central axis of the carbon nanotube wire as an axis. In this
case, the diameter of one carbon nanotube wire is 1 μm to 1 cm. The carbon nanotube structure
may be formed of any one of the non-twisted carbon nanotube wire, the twisted carbon nanotube
wire, or a combination thereof.
[0057]
The method of forming the carbon nanotube wire utilizes a carbon nanotube film drawn from a
carbon nanotube array. There are the following three methods for forming the carbon nanotube
wire. In the first type, the carbon nanotube film is cut at a predetermined width along the
longitudinal direction of the carbon nanotube in the carbon nanotube film to form a carbon
nanotube wire. In the second type, the carbon nanotube film may be immersed in an organic
solvent to shrink the carbon nanotube film to form a carbon nanotube wire. In the third type, the
carbon nanotube film is machined (for example, a spinning process) to form a twisted carbon
nanotube wire. Specifically, first, the carbon nanotube film is fixed to a spinning device. Next, the
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spinning device is operated to rotate the carbon nanotube film to form a twisted carbon
nanotube wire.
[0058]
When the carbon nanotube structure includes a plurality of carbon nanotube wires, the plurality
of carbon nanotube wires may be parallelly juxtaposed, or crosswise woven or twisted.
[0059]
In order to enhance mechanical strength and toughness of the carbon nanotube structure, two or
more carbon nanotube films may be laminated to form the carbon nanotube structure.
However, if the carbon nanotube structure is too thick, its specific surface area decreases, and its
heat capacity increases. On the other hand, if the carbon nanotube structure is too thin, its
toughness decreases and its service life becomes short. Accordingly, the thickness of the carbon
nanotube structure is preferably set to 0.5 nm to 1 mm. In the present embodiment, the carbon
nanotube structure is formed by laminating four sheets of the carbon nanotube films, and the
thickness thereof is 40 nm to 100 μm. The carbon nanotubes in the adjacent carbon nanotube
film are arranged in parallel.
[0060]
Second Embodiment Referring to FIG. 11, the diaphragm 24 of the present embodiment is
different from the diaphragm 14 of the first embodiment in the following points. The diaphragm
24 includes a convex central portion 242 and a circular edge 241. The central portion 242 and
the edge portion 241 of the diaphragm 24 are made of the carbon nanotube composite structure
of Example 1, and are integrally molded.
[0061]
Third Embodiment Referring to FIG. 12, the diaphragm 34 of the present embodiment is different
from the diaphragm 14 of the first embodiment in the following points. The diaphragm 34
includes a convex central portion 342 and a circular edge 341. The central portion 342 of the
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diaphragm 34 includes the carbon nanotube composite structure of the first embodiment. The
central portion 342 of the diaphragm 34 is formed by laminating the carbon nanotube films of a
plurality of examples 1 and has a thickness of 1 μm to 1 mm.
[0062]
DESCRIPTION OF SYMBOLS 100 Speaker 10 frame 10a upper board 10b side wall 10c edge 101
chamber 103 ventilating hole 104 fixed pillar 11 magnet 12 force board 13 voice coil 14
diaphragm 141 edge 142 center 143 base 144 carbon nanotube structure 24 diaphragm 241
edge Part 242 Center 34 Diaphragm 341 Edge 342 Center
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