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JPH0423597

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DESCRIPTION JPH0423597
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
acoustic diaphragm used for a speaker or the like and a method of manufacturing the same, and
more particularly to an acoustic diaphragm using microfibrillated cellulose and a method of
manufacturing the same. [Summary of the Invention] The present invention is intended to
provide an acoustic diaphragm excellent in physical properties such as Young's modulus and
tensile strength by forming microfibrillated cellulose. Furthermore, according to the present
invention, by reinforcing the microfibrillated cellulose with a reinforcing member placed on a
papermaking network, it is possible to handle even if the wet strength of the paper product is low
by making it into a paper, and an acoustic diaphragm having excellent physical characteristics.
Can be manufactured with high productivity. PRIOR ART Conventionally, cone paper made of
pulp is widely used as an acoustic diaphragm such as a speaker. Corn paper is prepared through
a process of beating pulp, a process of dispersing and swelling the beaten pulp in water, and a
process of making pulp into a shape requiring the pulp dispersed in water, etc. When the
resulting pulp is dispersed in water for papermaking, it has not only a crisp feel but also a low
strength and can not withstand use as a diaphragm. This is because the fibers constituting the
pulp and the fibers are not firmly fixed to each other. The adhesion is obtained by softening the
fibers and further loosening the fibers into fibrils forming fibers, so-called fibrillation to increase
contact points between the fibers and increasing hydrogen bonding. Such mechanical fibrillation
of fibers is referred to as beating and is usually performed by a device called a beater. By the
way, the acoustic diaphragm is required to have a high longitudinal wave propagation velocity
(sound velocity C), and therefore, it is preferable to use a material which is light and has a large
Young's modulus. Physical properties such as Young's modulus and tensile strength of corn
paper are determined by the degree of beating as described above, and in order to make corn
paper having a large Young's modulus, it is preferable to use as highly fibrillated cellulose with a
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high degree of beating There is a need. That is, in corn paper used as an acoustic diaphragm, it is
considered that the higher the beating degree of cellulose used for papermaking, the higher the
Young's modulus. (Problems to be Solved by the Invention) However, when the beating degree of
cellulose used for papermaking of corn paper becomes high, the strength in the wet state at the
time of papermaking is extremely reduced, so that handling and shape maintenance are difficult,
for example, If it is attempted to transfer the machined paper product to another mold while it is
wet, there is a risk that the form may collapse.
In addition, when cellulose tends to be intricately incorporated into the papermaking mesh and it
is attempted to peel off the papermaking product (corn paper) from the papermaking mesh after
drying, the rigidity of the papermaking mesh is high and therefore excessive force is applied at
one time. There is a risk of damaging the paper. Alternatively, if papermaking is carried out in the
form of a flat plate and molding into a desired shape is carried out by press processing using a
mold, it is also highly possible that an excessive force is locally applied to cause breakage.
Therefore, although it is expected to be advantageous in terms of characteristics, it is difficult to
make cellulose with high degree of fibrillation into an acoustic diaphragm due to manufacturing
problems, and it is particularly difficult to use a thin diaphragm. The realization is said to be very
difficult. Then, this invention is proposed in view of the above-mentioned conventional actual
condition, Comprising: It aims at providing the acoustic diaphragm excellent in physical
characteristics, such as Young's modulus and tensile strength. Another object of the present
invention is to make it possible to handle even a low wet strength sheet-formed product, and to
efficiently produce an acoustic diaphragm of Young's modulus made of microfibrillated cellulose.
[Means for Solving the Problems] In order to achieve the above-mentioned object, the acoustic
diaphragm of the present invention is characterized by being made of a microfibrillated cellulosemade paper product, and further microfibrillated. It is characterized in that a cellulose-made
product and a reinforcing member are laminated. Further, the manufacturing method of the
present invention is characterized in that a reinforcing member is placed on a papermaking net
and cellulose having a Canadian standard freeness of 300 ml or less is formed on the reinforcing
member. In the present invention, the cellulose used in papermaking is a highly microfibrillated
cellulose, which here is a cellulose having a Canadian standard freeness of 300 ml or less. If the
Canadian standard freeness is 300 ml or less, if the Canadian standard freeness exceeds 300 d,
the Young's modulus of the acoustic diaphragm to be made is insufficient, and the problem due
to the wet strength is also reduced during paper making . The cellulose (hereinafter referred to
as microfibril cellulose) having a Canadian standard freeness of 300 ml or less. Examples of)
include those obtained by mechanically refining pulp with a beater or the like. In this case, it is
possible to easily set the Canadian standard freeness to 300 ml or less by appropriately setting
the beating conditions by the beater (for example, the strength of the force applied at the beating
time). Alternatively, bacterial cellulose which is microbiologically produced by cultivating certain
types of bacteria under predetermined conditions is also suitable.
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The bacterial cellulose is composed of highly crystalline ?-cellulose, has extremely high surface
orientation, and has extremely high strength, and its thickness is as fine as 200 to 500 people. As
bacteria producing bacterial cellulose, acetic acid bacteria are typical. For example, Acetobacter
aceti (eight cetobacter aceti), Acetobacter xylinum (eight cetobacter xylinum), Acetobacter 0
Lansense (Acetobacter rancens) + Zaltina pentricli (Sarcina ventriculi) + Bacterium xyloides.
Examples thereof include Acetobacter pavilianus (eight cebacter terpasteurianus) +
Agrobacterium tumefaciens (Agrobacterium tumefaciens) and the like, and further, a genus
Rhizobium and the like of Pseudomonas (Pseudomonas). The above-mentioned bacterial cellulose
can be obtained as a gel-like substance having a certain thickness at the interface between the
culture medium and air, or by aeration stirring culture method, etc. However, the obtained
bacterial cellulose is disintegrated into water. It can be made into paper. At the time of
papermaking, it is also possible to mix carbon fiber and glass fiber as a reinforcing material with
the above-mentioned microfibril cellulose, and further, polymer fiber such as aramid fiber,
polyolefin fiber, super-stretched polyolefin fiber, polyester fiber and the like. In addition, paper
additives such as so-called sizing agents and fillers may be added as necessary. On the other
hand, the reinforcing member placed on the papermaking mesh is used to compensate for the
wet strength of the microfibrillated cellulose-made paper and has a void of about 100 mesh (pore
diameter of about 200 ?m) and is flexible to some extent. A woven or non-woven fabric or the
like is preferred. The material, thickness, etc. of these woven fabrics and non-woven fabrics are
optional when they are simply used as reinforcement for papermaking, but as described later,
they are integrated as they are with microfibril cellulose papermaking to make an acoustic
diaphragm. May be selected according to the characteristics of the target acoustic diaphragm. In
addition, when using a reinforcement member only as a reinforcement of a papermaking thing as
mentioned above, the said reinforcement member. That is, it is preferable that the woven or nonwoven fabric is a material which is easily peeled off from the microfibril cellulose, and when it is
integrated with the paper of micro fibril cellulose as it is, a material having high strength and
high elastic modulus. Is preferred.
Specifically, woven or non-woven fabric of carbon fiber, glass fiber, polyester fiber, aramid fiber,
silk or the like can be used, and it may be selected from these in consideration of the abovementioned requirements. In the present invention, in order to make microfibril cellulose, first, as
shown in FIG. 1, a paper mesh (2) is attached to the bottom of the paper machine (1) and the
above-mentioned reinforcing member (3) is made. The sheet (1) is placed on a net (2), and a
suspension (4) in which microfibril cellulose is dispersed is supplied thereon to make a
papermaking product (5). Subsequently, the process proceeds to a drying step to dry the
papermaking product (5), and at this time, the papermaking product (5) made of microfibril
cellulose is placed on the papermaking net (2) together with the reinforcing member (3). It may
be transferred to the drying step while being placed, or may be removed from the papermaking
net (2) together with the reinforcing member (3), transferred to another mold and transferred to
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the drying step. In the latter case, since the papermaking product (5) made of microfibril
cellulose is handled together with the reinforcing member (3), there is little possibility of
breakage or deformation even if the wet strength of the papermaking product (5) is low. In
addition, after drying, the reinforcing member may be peeled off from the paper (corn paper) of
microfibril cellulose, and only the paper made of the micro fibril cellulose may be used as an
acoustic diaphragm, or integrated as it is. It may be a non-woven composite diaphragm.
According to the above-mentioned method, the shape of the obtained corn paper is determined
by the shape of papermaking WI (2). In the present invention, for example, after microfibril
cellulose is made into a flat plate, it is drawn by a die or the like. It is also possible to give the
desired shape. In any case, a usual papermaking net can be used as the papermaking net (2), and
for example, a metal sheet or the like which has been subjected to processing such as wire
netting or punching called punching is used. [Function] In the acoustic diaphragm of the present
invention, since the corn paper is composed of microfibrillated cellulose, the contact points
between the fibers increase and hydrogen bonds increase, and physical properties such as
Young's modulus and tensile strength Characteristics are enhanced. Moreover, mechanical
strength is further improved by laminating and integrating with the reinforcing member. On the
other hand, in the production method of the present invention, microfibril cellulose is papermade on a reinforcing member placed on a paper-making net. Here, the paper-made product
made of microfibril cellulose has low wet strength, but since it is reinforced by the reinforcing
member, it becomes easy to handle even in the wet state, and its shape is maintained.
In addition, when the reinforcing member is peeled off from the papermaking after drying, the
reinforcing member has flexibility so that it can be gradually peeled off from the papermaking,
and carelessly in the paper-making (acoustic diaphragm) There is no big force. EXAMPLES
Specific examples to which the present invention is applied will be described below. Actually,
first, bacterial cellulose produced by acetic acid bacteria is deaggregated using a mixer and then,
as shown in FIG. 2A, papermaking is carried out on a papermaking wire mesh (11) attached with
a polyester fiber woven fabric (12). Then, a composite of cellulose (13) and woven fabric (12)
was prepared. The papermaking conditions, the type of the polyester fiber woven fabric (12) as a
reinforcing member, and the drying conditions are as follows. Microfibril cellulose: Flocculated
product of bacterial cellulose produced by acetic acid bacteria Concentration of paper: 1 g / 42
polyester fiber woven fabric: 100 mesh (pore diameter 200 ?m) manufactured by NBC, No 120
S Drying conditions: mold temperature 140 ░ C., 5 minutes Next, as shown in FIG. 2B, a mold
(14A) having a hemispherical concave portion and a convex portion corresponding to the shape
of the concave portion with respect to the composite consisting of the cellulose (13) and the
woven fabric (12) The draw forming process was carried out with a mold (14B) having the
following, to obtain a dome-shaped composite diaphragm as shown in FIG. Paper making and
draw forming were carried out under the same conditions as in Example 1 of Example 1, and
then the polyester fiber woven fabric (12) was peeled off to obtain a dome-shaped diaphragm
made of only cellulose (13). Actually, I beat 1 softwood bleached kraft pulp (N, B, KP) with a
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Horender-type beater to a Canadian standard freeness of 300 m, then perform the same
papermaking and drawing as in Example 1, and use cellulose and A composite diaphragm made
of polyester fiber woven fabric was obtained. In Examples 1 and 3 described above, in order to
improve the adhesion between the cellulose and the polyester fiber woven fabric, a binder
(NIPOL Latex, manufactured by Nippon Zeon Co., Ltd.) is used for the cellulose suspension before
paper making. 10% by weight of a solid matter ratio of LX-300) and 5% by weight of a retention
aid (wet strength agent) (Daick Burcules Co., Ltd., Kaimen 557-H) at a solid matter ratio of
cellulose. The internal loss (tan ?), Young's modulus E and sound speed C were measured by the
vibration lead method for the diaphragm obtained by the above method. The results are shown in
the following table. In addition, the measurement results are shown in the following table as a
comparative example also for a -fishing paper diaphragm (a diaphragm made of cellulose with a
Canadian standard freeness of 560).
When comparing the characteristics of the diaphragm obtained in each of the examples and the
general paper diaphragm, the diaphragm obtained in each of the Examples has a Young's
modulus 2 to 3 times that of the general paper diaphragm. It is understood that it has. In
addition, the diaphragm obtained in each of the embodiments is different from the conventional
paper diaphragms in film form and has no pinholes, so that the coating J2 of a material called as
a blocking which is indispensable in the paper diaphragm is used. No impregnation was
necessary, and it was possible to form a thin film diaphragm of about 10 ?m in thickness.
[Effects of the Invention] As apparent from the above description, (-in the acoustic diaphragm of
the present invention, since microfibrillated cellulose is paper-made, and further, since it is
laminated and integrated with a reinforcing member, It is possible to significantly improve the
physical properties, and to provide an acoustic diaphragm excellent in Young's modulus, tensile
strength, and the like. Further, in the manufacturing method of the present invention, since the
reinforcing member is placed on the papermaking net and cellulose is made on this, 0, when
cellulose having a low wet strength such as microfibril cellulose is made. Can also be easy to
handle. Therefore, it is possible to efficiently manufacture an acoustic diaphragm having a high
Young's modulus. Furthermore, in the manufacturing method of the present invention, a
diaphragm made of a composite material in which various materials are mixed with
microfibrillated cellulose can be easily prepared, and diaphragms of various characteristics are
manufactured according to the application etc. It is possible.
[0002]
Brief description of the drawings
[0003]
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FIG. 1 is a schematic cross-sectional view showing a papermaking process using a cone-shaped
papermaking net.
2A to 2C show the manufacturing steps of a dome-shaped diaphragm by drawing, and FIG. 2A is
a schematic cross-sectional view of a flat cellulose-woven fabric composite, and FIG. FIG. 2C is a
schematic cross-sectional view of a cellulose woven fabric composite formed into a dome shape.
2 иии Papermaking network 3 иии Reinforcing member 5 иии Paper making (cellulose)
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