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JP2018152740

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DESCRIPTION JP2018152740
Abstract: PROBLEM TO BE SOLVED: To provide a speaker diaphragm having a good balance of
physical properties of elastic modulus and internal loss. A speaker diaphragm is provided with a
coating layer (1B) composed of chitin nanofibers (12) on a substrate layer (1A) molded into a
diaphragm shape, and a coating layer (1B) While increasing the elastic modulus, the
intermolecular distance of the coating layer after curing is wide, and the molecule is easy to
move as compared to the diaphragm in which the coating layer (1B) is composed of cellulose
nanofibers, and the hardness is ensured by the hard main skeleton And molecular motion can
increase internal loss. [Selected figure] Figure 1
Speaker diaphragm, method of manufacturing the same, and speaker using the same
[0001]
The present invention relates to a speaker diaphragm used for a speaker.
[0002]
The speaker diaphragm is required to be lightweight, highly rigid, and have a suitable internal
loss.
Patent Document 1 discloses a speaker diaphragm in which a coating layer of cellulose
nanofibers is provided on at least one side of a cellulose-containing base layer containing natural
fibers.
10-05-2019
1
[0003]
The natural fibers of the base layer are described as wood pulp and non-wood pulp, and wood
pulp and non-wood pulp can also be used in combination. Non-wood pulp is a fiber obtained
from bamboo or the like. The cellulose nanofiber of a coating layer is a fiber of the nano level
containing cellulose, and the thing using the nata de coco powder and the bamboo fiber refined
to the nano level is disclosed.
[0004]
WO2015/011903
[0005]
In the speaker diaphragm in which the coating layer of cellulose nanofibers is provided in the
base layer, even if the elastic modulus of the base layer can be increased, the internal loss is a
value that is considered to be an appropriate internal loss in the obtained rigidity. It tends to be
lower than it is, and improvement of the physical property balance of the speaker diaphragm is
expected.
[0006]
Therefore, the speaker using this diaphragm has high rigidity and can extend the high frequency
limit frequency as the frequency characteristic, so that the sound quality with high clarity can be
obtained.
[0007]
However, when the internal loss is low, peaks and dips tend to be generated as frequency
characteristics, and this is a factor that generates a reverberation of sound, so the sound quality
tends to be distorted and lacking in expressive power.
[0008]
An object of the present invention is to provide a speaker diaphragm having a good balance of
physical properties, which can increase the elastic modulus by providing a coating layer on a
base material layer, and can approach an appropriate internal loss.
10-05-2019
2
[0009]
In the speaker diaphragm of the present invention, at least one surface of the base layer
containing natural fibers is provided with a coating layer composed of chitin nanofibers having a
modulus of elasticity larger than that of the base layer. It features.
[0010]
In addition, the coating layer is provided on both sides of the base layer.
[0011]
Further, the coating layer is provided at the center of the diaphragm.
[0012]
Further, the coating layer is provided on a portion of the diaphragm where the unnecessary
resonance is likely to occur.
[0013]
In addition, the chitin nanofiber is a polysaccharide in which acetylglucosamine is linked in a
linear manner, and has an average diameter of 10 to 20 nm.
[0014]
The natural fiber is characterized in that it is a cellulose fiber.
[0015]
Further, the natural fiber is a bamboo cellulose fiber.
[0016]
In addition, the natural fiber is characterized in that it comprises bamboo cellulose nanofibers.
[0017]
The material thickness of the coating layer is 3% or more and 20% or less of the material
thickness of the entire diaphragm.
10-05-2019
3
[0018]
In the method of manufacturing a diaphragm for a speaker according to the present invention, an
aqueous dispersion of chitin nanofibers is spray-coated on at least one surface of a base layer
containing natural fibers, and heat-pressed to form a diaphragm. It is characterized by
[0019]
The speaker according to the present invention comprises a speaker diaphragm, a magnetic
circuit comprising a yoke, a magnet and a plate, and an outer periphery of the speaker
diaphragm via an edge attached to the yoke in the vicinity of the magnetic gap of the magnetic
circuit. And a voice coil having one end attached to the back surface of the speaker diaphragm
and a coil wound on the magnetic gap at the other end, and the speaker diaphragm being
provided with a natural fiber And a coating layer composed of chitin nanofibers having a
modulus of elasticity greater than that of the substrate layer.
[0020]
According to this configuration, the coating layer is composed of a chitin nanofiber composed of
an OH group less than that of the conventional cellulose nanofiber and having an OH group and
an acetyl group having a weaker hydrogen bond than the OH group. Since the intermolecular
distance of the coating layer after curing is wide, the molecule can move easily, the hardness can
be secured by the hard main skeleton, and the internal loss can be increased by the molecular
motion.
[0021]
Cross-sectional view of a speaker using the speaker diaphragm according to the first embodiment
of the present invention A schematic view of a cross-section of the speaker diaphragm according
to the embodiment Cross-sectional view showing a manufacturing process of the speaker
diaphragm according to the embodiment Chemical structure diagram of nanofibers Chemical
structure diagram of chitin nanofibers Cross-sectional view of a speaker according to another
embodiment of the present invention A plan view of a speaker according to another embodiment
of the present invention
[0022]
Hereinafter, embodiments of the present invention will be described based on the drawings.
[0023]
10-05-2019
4
FIG. 1 shows a cross-sectional view of a speaker using the speaker diaphragm of the present
invention.
[0024]
This speaker is attached to the yoke 2 in the vicinity of the magnetic gap 6 of the cone-shaped
diaphragm 1, the magnetic circuit 5 formed of the yoke 2, the magnet 3 and the plate 4, and the
outer periphery of the diaphragm 1 It comprises a frame 7 to be supported, and a voice coil 9
having one end attached to the back surface of the diaphragm 1 and the other end wound with a
coil 8 positioned in the magnetic gap 6.
10はエッジである。
A magnetic gap 6 having a uniform gap is formed between the inner periphery of the yoke 2 and
the outer periphery of the plate 4.
The lower end of the frame 7 is joined to the outer periphery of the yoke 2.
A voice coil 9 is joined to the center of the diaphragm 1.
The outer periphery of the diaphragm 1 is joined to the upper end of the frame 7 via an edge 10.
A damper 13 is joined between the voice coil 9 and the frame 7.
In the vicinity of the center of the diaphragm 1, a dust cap 14 is provided to prevent dust from
entering the magnetic gap 6.
[0025]
FIG. 2 shows an enlarged sectional view of the diaphragm 1.
10-05-2019
5
[0026]
The diaphragm 1 has a base layer 1A having natural fibers and a coating layer 1B formed on the
surface of the base layer 1A opposite to the magnetic circuit 5.
[0027]
The natural fibers 11 of the base layer 1A can be used alone or in combination of wood pulp and
non-wood pulp with wood pulp or non-wood pulp which is cellulose fiber.
Non-wood pulp is a fiber obtained from bamboo or the like.
The coating layer 1B is composed of chitin nanofibers 12 having a modulus of elasticity greater
than that of the base layer 1A.
The chitin nanofibers used here are polysaccharides in which acetylglucosamine is linked in a
linear manner, and more specifically, they are chicken nanofibers derived from crab shells, and
have an average diameter of 10 to 20 nm.
[0028]
3 (a), (b) and (c) show the manufacturing process of the speaker diaphragm of the embodiment.
[0029]
In the first step, wood pulp and non-wood pulp are beaten to prepare a stock having a fiber
diameter of about 13 μm, which is cut out and deposited in a sheet form as shown in FIG. 3 (a).
Furthermore, suction dehydration is performed to obtain the substrate layer 1A in which the
surface is wet to some extent.
[0030]
10-05-2019
6
The beating in the first step is to add a waterproofing agent of at least one of a fluorine emulsion
and a paraffinic emulsion simultaneously with the pulp to be beaten while adsorbing the
waterproofing agent to the pulp.
A resin emulsion may be added to the beating machine to further improve the waterproofness.
The mixing ratio of the waterproofing agent to the stock was 5 to 10% by weight.
As a waterproofing agent which can be used besides the above, a silicone / silane type thing can
be used.
[0031]
The resin emulsion is epoxy, acrylic, ester, or synthetic resin, for example, vinyl acetate polymer,
acrylic acid ester copolymerization, ethylene / vinyl acetate / acrylic acid copolymerization.
[0032]
In the second step, chitin nanofiber aqueous dispersion (1 wt%) 12A is spray-coated on the base
material layer 1A to form a coating layer 1B as shown in FIG. 3 (b).
The chitin nanofibers of the coating layer 1B are polysaccharides in which acetylglucosamine is
linearly linked, and have an average diameter of 10 to 20 nm.
[0033]
In the third step, the one shown in FIG. 3 (b) in which the coating layer 1B is formed on one side
of the base material layer 1A is heat-pressed to form a cone-shaped diaphragm with drying.
The film thickness of the coating layer 1B was 3.5% to 6% of the total thickness.
10-05-2019
7
[0034]
Thereafter, the voice coil 9 and the edge 10 are attached and set in the frame 7 to complete the
speaker.
[0035]
The diaphragm, the elastic modulus and the internal loss of Comparative Examples 1 and 2 were
measured using the diaphragm of the speaker configured as described above as an example.
The comparative example 1 is a case where the coating layer 1B is a cellulose nanofiber, in the
case of only the base layer 1A not having the coating layer 1B.
The film thickness of the coating layer 1B of Comparative Example 2 was the same as that of the
embodiment at 3.5% to 6% of the total thickness.
The other conditions were the same between the example and the comparative examples 1 and 2.
[0036]
The measurement results are as follows.
[0037]
Elastic Modulus Internal Loss Comparative Example 1 (Base Layer Only) 2.0 GPa 0.040
Comparative Example 2 (Base Layer + Cellulose Nanofiber) 2.7 GPa 0.035 Example (Base Layer +
Chitin Nanofiber) 3. Thus, the elastic modulus of the embodiment is 3.5 GPa, which is higher than
the elastic modulus of 2.7 GPa of Comparative Example 2 in which the cellulose nanofiber is used
for the coating layer 1B, and the internal loss of the embodiment is It is 0.040 same as the
comparative example 1 of a base material layer alone, and it can be made higher than the
internal loss 0.035 of comparative example 2 which uses a cellulose nanofiber for coating layer
1B, and an elastic modulus is 3.5 GPa An internal loss of a reasonable size could be realized for a
rigid diaphragm.
10-05-2019
8
[0038]
In addition, hydrophobic acetyl groups remained on the surface of the coating layer 1B, and a
better waterproofness than in Comparative Example 2 was obtained.
[0039]
FIG. 4 shows the chemical structure of cellulose nanofibers.
FIG. 5 shows the chemical structure of chitin nanofibers.
[0040]
Since chitin nanofibers are composed of OH groups less than cellulose nanofibers, less hydrogen
bonds, and acetyl groups less OH bonds and hydrogen bonds than OH groups, chitin nanofibers
12 can be used as coating layer 1B. In the diaphragm 1 of the embodiment used, the
intermolecular distance of the coating layer after curing is wide, the molecule is easy to move,
the hardness is secured by the hard main skeleton, and the internal loss can be increased by the
molecular motion. It can be considered.
[0041]
In the above embodiment, the coating layer composed of chitin nanofibers is provided on one
side of the base layer, but the coating layer composed of chitin nanofibers may be provided on
both sides of the base layer. it can.
[0042]
With this configuration, the effect of the coating layer by chitin nanofibers can be exhibited more
strongly, so that the high frequency limit frequency can be extended, and sound quality with high
clarity can be obtained.
[0043]
Further, although the coating layer 1B is provided on the entire area of the base material layer
1A of the diaphragm 1 in FIG. 1, the coating layer 1B may be provided only on the central
portion of the diaphragm 1.
10-05-2019
9
An example is shown in FIG.
In FIG. 6, the coating layer 1 </ b> B is annularly provided only at the central portion of the base
layer 1 </ b> A of the diaphragm 1.
[0044]
With this configuration, the coating layer 1B is not formed around the central portion of the base
material layer 1A of the diaphragm 1, so the coating layer is applied only to the highly effective
portion without increasing the weight of the entire diaphragm. Can be provided, so that the
upper limit frequency can be expanded while realizing the improvement of the sound pressure
level, and the sound quality with high clarity can be obtained.
[0045]
Furthermore, although the coating layer 1B is provided on the entire area of the base material
layer 1A of the diaphragm 1 in FIG. 1, the coating layer 1B may be provided only on the portion
of the diaphragm 1 where unnecessary resonance is likely to occur.
An example is shown in FIG.
In FIG. 7, the coating layer 1B is partially provided on the base material layer 1A at a position
close to the outer periphery of the diaphragm 1 and at the same distance from the center of the
diaphragm 1.
[0046]
With this configuration, the coating layer can be provided only on the highly effective portion
without increasing the weight of the entire diaphragm, so that unnecessary resonance can be
reduced while the improvement of the sound pressure level is realized. Can be obtained to obtain
high definition sound quality.
[0047]
10-05-2019
10
The material thickness of the coating layer constituted by chitin nanofibers is preferably 3% or
more and 20% or less of the material thickness of the entire diaphragm.
[0048]
Note that a bamboo cellulose nanofiber may be included.
[0049]
Furthermore, when the natural fiber used as a base material layer of the diaphragm 1 contains
bamboo, the cellulose fiber may be a cellulose nanofiber.
[0050]
By adopting these configurations, not only the effect generated from the coating layer but also
the base material layer of the diaphragm becomes strong in the entanglement of fibers, so that a
greater effect can be exhibited.
Therefore, by the synergetic effect, it is possible to further extend the high frequency limit
frequency, and to obtain the sound quality with high clarity.
[0051]
The present invention contributes to the realization of a speaker with a good balance of physical
properties.
[0052]
1 diaphragm 1A base layer 1B coating layer 5 magnetic circuit 11 natural fiber 12 chitin
nanofiber
10-05-2019
11
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