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JP2013042405

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DESCRIPTION JP2013042405
The present invention relates to a method of manufacturing a diaphragm for an electroacoustic
transducer, which has a high elastic modulus and is excellent in rigidity and difficult to be
realized by the conventional pulp, and which can be manufactured inexpensively and easily
compared to bacterial cellulose. Provide a board. Further, by using the diaphragm for electroacoustic transducer, the reproduction frequency band can be further expanded to a higher
frequency side than the diaphragm using bacterial cellulose fiber, and an electro-acoustic
transducer having excellent high-frequency characteristics and good sound quality. I will provide
a. In the present invention, first, wood is pulped, TEMPO oxidation treatment is performed to
produce TEMPO oxidized cellulose, the TEMO oxidized cellulose is dispersed in a liquid
dispersion medium, and a diaphragm element serving as a raw material of the diaphragm is
produced. A diaphragm was manufactured through a forming step of forming the disc into a
predetermined shape, and an electroacoustic transducer was configured using the diaphragm.
[Selected figure] Figure 1
Method of manufacturing diaphragm for electro-acoustic transducer, diaphragm manufactured
thereby, and electro-acoustic transducer provided with the diaphragm
[0001]
The present invention provides a method of manufacturing a diaphragm for an electroacoustic
transducer using a cellulose fiber oxidized by 2,2,6,6-tetramethylpepyridinyl-1-oxy radical
(TEMPO), and a method of manufacturing the same. The present invention relates to a vibrating
plate and an electro-acoustic transducer provided with the vibrating plate.
[0002]
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1
A microphone, a speaker, and the like have a magnetic circuit, a voice coil, a diaphragm, and the
like, and convert the electrical signal into mechanical vibration by the voice coil and the magnetic
circuit, and transmit it to the diaphragm to emit it as sound. It is
The diaphragm used in such an electroacoustic transducer is required to have an operation in
which the phase and amplitude are uniform as a whole, but in the high region, the diaphragm
resonates and splits to generate unevenness in the frequency characteristics, and Sound pressure
decreases gradually. It is necessary to increase the rigidity of the diaphragm in order to prevent
the occurrence of the resonance and the divided vibration of the diaphragm to as high frequency
as possible and widen the region where the frequency characteristic is flat.
[0003]
The rigidity of the diaphragm for electro-acoustic transducer is due to the shape and elastic
modulus of the material, etc. When the elastic modulus is improved, the high frequency limit
frequency is increased and the distortion is also reduced. Important element.
[0004]
Various materials such as paper, metal and resin are used as materials for diaphragms for
electro-acoustic transducers. Among them, paper has low density and high shape freedom, and it
is possible to use pretreatment or sizing agent. Since physical properties can be adjusted in small
lots, it has long been used as a diaphragm for electroacoustic transducers such as speakers.
In addition, there is also an advantage that natural materials are excellent in environmental
responsiveness and the cost can be reduced because the supply amount is large.
[0005]
However, paper diaphragms mainly composed of cellulose fibers have problems in terms of
rigidity, so carbon fibers, aramid fibers, etc. are mixed as reinforcing fibers, for example, but a
binder is added to bond with cellulose fibers. It is necessary to make the process complicated,
and the additives make it difficult to obtain desired physical properties, and the sound quality
inherent to the paper diaphragm is also impaired.
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2
[0006]
Therefore, a diaphragm made mainly of bacterial cellulose has been developed as one in which
the rigidity is enhanced while maintaining the characteristics of the paper-made diaphragm
mainly made of cellulose fiber and the regeneration frequency band is broadened.
The bacterial cellulose is a microbial cellulose produced by a microorganism such as acetic acid
bacteria, and is composed of highly crystalline cellulose, so that good rigidity can be obtained
(Patent Document 1).
[0007]
Further, there are a sheet in which another sheet is laminated on a sheet made of bacterial
cellulose to further improve physical properties (Patent Document 2), and a sheet in which
carbon nanotubes are added and reinforced in bacterial cellulose (Patent Document 3). .
[0008]
The present inventor uses cellulose fiber of wood which is abundant in nature, has high elastic
modulus while taking advantage of the original characteristics of paper diaphragm, is easy to
manufacture, is excellent in economy, and widely spreads generally The research of the
diaphragm which can be made is repeated.
During the research process, cellulose in pulp is oxidized by 2,2,6,6-tetramethylpiperidinyl-1-oxy
radical (hereinafter also referred to as TEMPO), which is used as a catalyst for oxidation reaction
in organic synthesis, Attention was focused on the technology for producing TEMPO oxidized
cellulose (Patent Document 4).
[0009]
Patent Document 1: Japanese Patent Application Laid-Open No. 61-281800 Patent Document 3:
Japanese Patent No. 3073608 Patent No. 3827153 Patent Document 2: Japanese Patent
Application Publication No. 2008-001728
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3
[0010]
In the above, although the diaphragm mainly composed of bacterial cellulose has high elasticity,
since acetic acid bacteria as the raw material are aerobic bacteria, it has to be cultured while
supplying oxygen in a medium containing organic substances, inorganic salts and the like. In
addition, it takes time and effort, and it takes a long time to produce, and it is very expensive.
Therefore, it is difficult to spread widely, and it is only used for some high-end machines.
[0011]
On the other hand, the present inventors have found that TEMPO oxidized cellulose is easy to
obtain because it is made from wood pulp which is abundant in the natural world, and is suitable
as a diaphragm for an electroacoustic transducer.
[0012]
The present invention has been proposed in view of the foregoing, and the object of the present
invention is to provide a high modulus of elasticity which is difficult to achieve with conventional
pulps and to be excellent in rigidity and inexpensive and easily compared to bacterial cellulose. A
method of manufacturing a diaphragm for an electroacoustic transducer that can be
manufactured, and a diaphragm manufactured thereby.
[0013]
Further, by using the diaphragm for electro-acoustic transducer, the reproduction frequency
band can be further expanded to a higher frequency side than the diaphragm using bacterial
cellulose fiber, and an electro-acoustic transducer having excellent high-frequency characteristics
and good sound quality. To provide.
[0014]
The invention according to claim 1 is characterized in that the diaphragm is manufactured
through a forming step of dispersing TEMPO oxidized cellulose in a liquid dispersion medium,
and forming a dispersion to be a raw material of the diaphragm into a predetermined shape.
The invention according to claim 2 is the method for producing a diaphragm for an
electroacoustic transducer according to claim 1, wherein the dispersion liquid (a) to (f), (a) pulp
or cellulose other than TEMPO oxidized cellulose (B) at least one of a sizing agent for imparting
water resistance and a paper strengthening agent as a general medicinal material as paper (c) a
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polymer soluble in the dispersion medium for obtaining a predetermined physical property d)
Particulate or fibrous filler as a reinforcing agent (e) Clay mineral for obtaining predetermined
physical properties (f) A cation interacting with a carboxyl group for bonding between fibers,
preferably a divalent or higher value A diaphragm is manufactured by adding at least any one or
more or all of additives of ions having positive charge or two or more arrangement numbers.
The invention according to claim 3 is the method for manufacturing a diaphragm for an
electroacoustic transducer according to claim 1 or 2, wherein the forming step directly forms the
dispersion into a predetermined shape, or (g) casting, coating Step of dripping or spreading and
drying (h) step of filtering and forming (i) forming into a sheet, film or structure by any of the
steps of forming into a fiber by electrospinning and forming the diaphragm It is characterized by
producing.
According to a fourth aspect of the present invention, in the method for manufacturing a
diaphragm for an electroacoustic transducer according to the first or second aspect, the
dispersion used as a raw material of the diaphragm is molded into a diaphragm shape different in
composition from the raw material. Alternatively, it is characterized in that a diaphragm is
manufactured by casting, coating, dropping or spreading on an unformed sheet, film or structure.
The invention according to claim 5 is the method for manufacturing a diaphragm for an
electroacoustic transducer according to claim 1 or 2, wherein the dispersion used as the raw
material of the diaphragm is molded into a diaphragm shape different in composition from the
raw material. Alternatively, it is characterized in that it is impregnated into an unformed sheet,
film or structure to produce a diaphragm.
The invention according to claim 6 is the method for manufacturing a diaphragm for an
electroacoustic transducer according to claim 1 or 2, wherein the dispersion used as the raw
material of the diaphragm is formed into a diaphragm shape and then laminated on another
molded body. It is characterized in that a vibrating plate is produced. The diaphragm according
to the invention of claim 7 is characterized in that it is manufactured by the manufacturing
method according to any one of claims 1 to 6. An electro-acoustic transducer according to the
invention of claim 8 is characterized by comprising the diaphragm according to claim 7.
[0015]
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According to the production method of the present invention, it is not necessary to use a culture
facility to take a time-consuming and labor-intensive microorganism culture step, and to use
TEMPO oxidized cellulose made from pulp which is abundant in nature as a raw material to form
a diaphragm. It is easy to manufacture, superior in productivity, and economical compared with
those using. Also, TEMPO oxidized cellulose fibers are hydrophilic fibers and can be easily
dispersed in a liquid dispersion, and they are excellent in dispersibility at the time of mixing with
a pulp in general, difficult to be nonuniform, easy to manufacture, stable without variation A
product (diaphragm) can be produced. Moreover, since it is a cellulose derived from wood, it is
carbon neutral (does not increase carbon dioxide in the atmosphere during the use cycle), and is
excellent in environmental properties.
[0016]
According to the diaphragm of the present invention, since pulp is used as the main raw material,
it is easy to obtain and inexpensive, and it is possible to use TEMPO oxidized cellulose which has
high crystallinity and long proportions of cellulose microfibrils. High modulus can be realized.
[0017]
According to the electro-acoustic transducer of the present invention, by using TEMPO oxidized
cellulose having a high ratio of cellulose microfibrils having high crystallinity and long fiber
length, the diaphragm is improved in rigidity with high elastic modulus, and the regeneration
frequency band Can be extended to the higher frequency side, and good sound quality can be
obtained.
[0018]
The example of a manufacturing process of the diaphragm which concerns on this invention is
shown.
The specific example of manufacture of the diaphragm raw material of this invention is shown.
(A), (b) shows the example which drips and shape | molds the diaphragm raw material of this
invention on a type | mold. An example of the type | mold used for this invention is shown. An
example of the process of filtering used by this invention is shown. An example of the
electrospinning method in this invention is shown. BRIEF DESCRIPTION OF THE DRAWINGS The
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cross-sectional view of an example of the diaphragm shape | molded using the dispersion liquid
in this invention is shown. An example of the cone-shaped diaphragm manufactured by this
invention is shown. Fig. 2 shows a schematic cross-sectional view of an electroacoustic
transducer incorporating a diaphragm manufactured according to the invention.
[0019]
The diaphragm for an electroacoustic transducer of the present invention contains TEMPO
oxidized cellulose formed by oxidizing cellulose of wood pulp with TEMPO. TEMPO is obtained
by oxidizing 2,2,6,6-tetrapiperidine, and functions as a reoxidizing agent and a catalyst for the
oxidation reaction in organic synthesis, and is used for oxidizing cellulose in the present
invention, TEMPO oxidized cellulose This was taken as the main component of the diaphragm
material. TEMPO oxidized cellulose is highly crystalline and excellent in heat resistance. Although
it was difficult to uniformly loosen fibers and fibers of cellulose fibers of wood because they are
firmly bonded by hydrogen bonding, it can be easily loosened by using TEMPO to make cellulose
nanofibers be able to. TEMPO oxidized cellulose is dispersed as nanofibers at least once during
production in a liquid dispersion medium such as water.
[0020]
Wood as a raw material of pulp is composed of cellulose, lignin, hemicellulose and the like.
Although pulping removes a considerable amount of components other than cellulose, lignin,
hemicellulose, etc. remain, and these greatly affect the strength of the paper.
[0021]
The TEMPO-oxidized cellulose selectively oxidizes the surface of highly crystalline cellulose
microfibrils in the pulp, and facilitates the dissociation of the microfibrils by carboxylation.
Thereby, components other than cellulose microfibrils, such as hemicellulose and cellulose with
low crystallinity, can be removed while maintaining the crystallinity of the cellulose microfibrils.
[0022]
According to the present invention, after dispersing this as nanofibers in a dispersion medium, it
is formed into a film, for example, to form a diaphragm for an electroacoustic transducer.
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[0023]
When the tensile test and dynamic viscoelasticity measurement (DMA) of the diaphragm for
electroacoustic transducer manufactured in this way were performed, it was confirmed that a
high elastic modulus exceeding bacterial cellulose was obtained.
In addition, since wood pulp can be used as a raw material and the reaction can be performed
under mild conditions, the production is easier than bacterial cellulose, and the production cost
can be significantly reduced.
[0024]
Hereinafter, an embodiment of the present invention will be described based on the drawings.
[0025]
FIGS. 1A to 1D are process diagrams showing a method of manufacturing a diaphragm for an
electroacoustic transducer according to a first embodiment of the present invention.
The original main raw material of the diaphragm according to the present invention is wood. This
wood is composed of cellulose, lignin, hemicellulose and the like. Wood chips are pulped through
a cooking process, a washing and dewatering process, and the like. Although considerable
components other than cellulose are removed in this process, lignin, hemicellulose, etc. remain.
[0026]
The pulp is then TEMPO oxidized using a TEMPO catalyst. That is, the pulp is dispersed in water,
and TEMPO is charged as a catalyst for the oxidation reaction, whereby the cellulose fibers of the
pulp are oxidized to form TEMPO oxidized cellulose. Pulp cellulose fibers are aggregates of
cellulose microfibrils, which are nanofibers. When the pulp is oxidized using TENPO catalyst,
primary hydroxyl groups on the surface of cellulose microfibrils are selectively converted to
carboxyl groups, resulting in separation of microfibrils. Ease and complete nanodispersion are
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possible and TEMPO oxidized cellulose is produced. And in this process, components other than
cellulose micro fibrils are removed and purity increases.
[0027]
In the present invention, as shown in FIG. 1 (a), the produced TEMPO oxidized cellulose is
dispersed at least once or more as nanofibers in a dispersion medium consisting of a liquid such
as water by the dispersion step shown in (b). To make it nanofibre. In this dispersion step, a
predetermined amount of dispersion medium is injected into a tank having a rotatable stirring
blade such as a screw mixer inside, a predetermined amount of TEMPO oxidized cellulose is
charged therein, and the mixture is stirred for a predetermined time. As an example, TEMPO
oxidized pulp containing water is put into water so as to have a pulp concentration of 0.1 to 1
wt% and dispersed by stirring with a screw mixer. In this case, TEMPO oxidized cellulose has
hydrophilicity and therefore has good dispersibility. This dispersion liquid becomes a raw
material of a diaphragm. The TEMPO oxidized cellulose nanofibers are as thin as carbon
nanotubes. If necessary, various additives such as the following (a) to (f) may be mixed into the
dispersion used as the raw material of the above-mentioned vibration plate, thereby obtaining the
desired physical properties required as the vibration plate. be able to. (A) Pulp and cellulose (at
least one) other than TEMPO oxidized cellulose. Here, suitable pulps such as softwood pulp,
hardwood pulp, non-wood pulp and the like are used as the pulp. As cellulose, for example, plant
and bacterial cellulose are used. (A) As a general medicine material as paper, sizing agent for
imparting water resistance and a paper strengthening agent (at least one) (c) PVC (polyvinyl
chloride) or PVA (for obtaining unique physical properties) Polymer soluble in solution or
dispersion medium such as polyvinyl alcohol) (d) Reinforcing particles or fibrous filler (c) Clay
mineral to obtain desired physical properties (c) Carboxylic acid for bonding between fibers A
cation which interacts with a group, preferably an ion having a positive charge of 2 or more or a
divisor of 2 or more
[0028]
The above additives may be used alone or in any combination, or all of them may be contained.
[0029]
As shown in the steps (c) and (d), the diaphragm element may be formed directly into a target
shape such as a flat plate shape or a cone shape by using a mold having an appropriate shape,
and the diaphragm may be manufactured. .
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[0030]
The production of this diaphragm may apply the conventional paper making process used in the
manufacture of an electroacoustic transducer.
Alternatively, the dispersion can be injected into a chamber having a predetermined diaphragm
shape between the lower mold and the upper mold and dried, for example.
The drying can be easily performed by providing a heater in the mold and by heating the heater
by energization. Of course, other drying means may be used.
[0031]
Alternatively, the dispersion may be formed into a sheet, film or thin structure. This molding can
be realized by any of the following methods (i) to (ii). (G) The dispersion is cast on a
predetermined device, that is, flowed, applied, dripped, spread, and dried. (G) The dispersion is
filtered and formed. (G) The dispersion is fiberized by electrospinning and deposited. Let
[0032]
FIG. 2 shows an example of an apparatus and a manufacturing process for casting the dispersion
on a belt and winding the vibrating plate element having a thin structure in a roll shape, of the
above (ii).
[0033]
This apparatus comprises a tank 20 filled with the dispersion 1, a first belt device 21 receiving
the dispersion 1 flowed from the nozzle 20a of the tank 20 on a mesh-like belt surface 21 ', and a
belt surface 21'. And a rotatable roller 22 for dewatering the felt to make it into a sheet, a second
belt device 23 for transporting the sheet to the drying device 24, and a roll of the dried one. A
take-up roller 25 is provided.
[0034]
Although not shown in the figure, it is preferable to provide the tank 20 with a stirring device for
stirring the dispersion liquid 1 to achieve uniformity.
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[0035]
The first belt device 21 is provided with an evacuation device (not shown) for evacuating the
dispersion 1 cast on the belt surface 21 ′.
In addition, an auxiliary roller 21b is provided at a roller 21a for driving the belt and at an
appropriate position.
[0036]
The second belt device 23 is also provided with a belt drive roller 23a and an auxiliary roller
23b, and a drying device 24 for delivering hot air via, for example, a built-in heater or blowing
means, provided at appropriate positions.
[0037]
In preparation of the diaphragm material, the dispersion 1 is first injected into the tank 20, and
the dispersion 1 is allowed to flow to the mesh belt surface 21 'through the nozzle 20a to form a
pulp web while drawing in vacuum, and a thick line is drawn. The felt shown below is pressed by
a roller 22 and dewatered into a sheet.
[0038]
It is transferred to the second belt device 23, and after passing through a drying process through
the drying device 24, the thin diaphragm element is wound onto the winding roller 25.
[0039]
Although the second belt device 23 having the drying device 24 is used in the example of FIG. 2,
the drying device 24 is provided on the extension in the rotational direction of the first belt
device 21 and the second belt device 23 is omitted. Of course it is also possible.
[0040]
FIGS. 3A and 3B show a state in which the dispersion liquid 1 is dropped on the upper surface of
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the mold 2 through the nozzle 3.
In the case of spreading, the dispersion liquid 1 may be ejected through the nozzle 3.
[0041]
For example, a cone-shaped mold 1A as shown in FIG. 4 may be used.
Of course, molds of other shapes may be used.
[0042]
FIG. 5 is a process explanatory view corresponding to the above (G), and shows an example of
filtering the dispersion 1 through the filter 4 and forming it on the filter 4.
[0043]
FIG. 6 shows an example of the electrospinning method described above in (iv).
In this case, the polymer is mixed into the dispersion to form a polymer solution.
5 is a container containing a dispersion liquid containing a polymer, 5a is a discharge port
thereof, 1B is a shaped body of a predetermined shape, 6 is a high pressure generator, for
example, the container 5 is added via the high pressure generator 6, a shaped body Charge 1B
negatively.
Then, when the electrospinning reaches a high voltage, the dispersion charged positively through
the container 5 is discharged from the discharge port 5a of the container 5 to form, for example,
a conical droplet, which flows out as a trickle. The fiber is fibrillated in the nanofiber state and
scattered toward the flat mold surface 1b of the negatively charged mold 1B as shown by the
flight line 1a, and is deposited on the mold surface 14.
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[0044]
FIG. 7 shows an example in which the dispersion liquid 1 is molded into a balance drive type
speaker diaphragm 11A through a predetermined mold.
The diaphragm 11A includes a dome-shaped diaphragm portion 11a at a central portion and a
cone-shaped diaphragm portion 11b formed on the outer periphery thereof.
[0045]
After forming into a sheet, film or thin structure as described above, it is laminated and
integrated, and / or press molded using a mold having a desired shape, and then molded into a
desired shape to vibrate. A plate can be made.
[0046]
A dispersion used as a raw material of the diaphragm is molded into a diaphragm having a
suitable shape different from that of the dispersion, or is not formed into a predetermined
diaphragm shape, and the dispersion has a composition It is also possible to prepare a diaphragm
by applying, dropping, spreading it on a different (for example, PET film, aluminum etc.) sheet,
film or thin structure, drying it, and forming a film sheet.
[0047]
The dispersion used as the raw material of the diaphragm is one that has already been formed
into a diaphragm of an appropriate shape (for example, cloth, ordinary paper not containing
nanofibers) that is different in composition from this, or is not molded into a predetermined
diaphragm shape Alternatively, the dispersion liquid may be impregnated into a sheet (eg, PET
film, aluminum, etc.) having a different composition (for example, PET film, aluminum, etc.), a
film or a thin structure, dried and shaped to prepare a diaphragm.
[0048]
A sheet, a film or a thin structure is used as a dispersion to be a raw material of a diaphragm, and
a formed body is bonded to a sheet, a film or a thin structure made of the same or other
composition (for example, PET film, aluminum etc.) It is also possible to produce a diaphragm by
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[0049]
FIG. 9 shows an example of an electroacoustic transducer using the diaphragm manufactured by
the process as described in the above embodiment.
In this example, a cone-shaped diaphragm is provided.
In the figure, 11 is a diaphragm, 12 is a cylindrical bobbin, 13 is a damper, 14 is a substantially
conical frame, 15 is a magnetic circuit, 16 is an edge, and 17 is a dust cover.
[0050]
According to the electro-acoustic transducer of the above configuration, by using the diaphragm
of high elastic modulus comprising TEMPO oxidized cellulose, the reproduction frequency band
can be further extended to the higher frequency side while being inexpensive, and the sound
quality is excellent. It becomes.
[0051]
In the above example, the case of applying to a general-purpose speaker using a conical
diaphragm has been described as an example, but the present invention is not limited to this
example, and diaphragms of various shapes such as planar shape are provided. Of course, it can
be applied to an electroacoustic transducer.
Further, the present invention is not limited to the above example, and can be variously modified
in the implementation stage without departing from the scope of the invention.
[0052]
Reference Signs List 1 dispersion 1a flight line 1b flat type surface 1A, 1B type 2 type 3 nozzle 4
filter 5 container 5a discharge port 6 high pressure generator 11 diaphragm 12 voice coil 13
damper 14 type surface 15 magnetic circuit 16 edge 20 tank 20a nozzle 21 First belt device 21a
Drive roller 21b Auxiliary roller 21 'Belt surface 22 Roller 23 Second belt device 23a Drive roller
23b Auxiliary roller 24 Drying device 25 Roller for take-up
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