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Description 1, title of the invention
Diaphragm for audio equipment and method of manufacturing the same
4 Detailed Description of the Invention The present invention is based on a diaphragm for an
acoustic device represented by a speaker, and a manufacturing method of an array number, in
particular, an acoustic device whose elastic modulus and internal loss are both large and whose
manufacturing process is easy. It has its main feature in obtaining the diaphragm for vibration.
The speaker diaphragm is preferably made of a material having a large Young's modulus, a light
weight, and an appropriate internal loss. Conventionally, as the diaphragm material, paper, resin,
resin mixed with reinforcing fiber, aluminum, titanium, beryllium, foamed nickel, a single plate of
metal such as honeycomb, a laminate thereof, etc. have been used. Some have poor performance
on the rigid surface such as Young's modulus, others have excellent stiffness, but some loss is
small and inconvenient, and others have good physical properties but poor processability. There
is a problem that there is no mass productivity and cost increase, and each has its own
drawbacks. The diaphragm according to the present invention uses carbon fibers having a
particularly high elastic modulus to improve the rigidity of the diaphragm, while using scale-like
mica to increase the internal loss of the diaphragm, which are made of heat such as
polypropylene It is characterized in that the resin is uniformly dispersed and filled in the plastic
resin. Polypropylene and the like are commonly used as diaphragms made of a resin alone.
However, these resins alone are insufficient in rigidity as a diaphragm and are generally
unsuitable for use except for speakers with a very small diameter of 1 inch or 2 inches. In view of
this point, a method is proposed in which the resin is filled with a reinforcing material to increase
the rigidity of the diaphragm. For example, a composite material filled with a high elastic fiber as
a resin number and a reinforcing material has a large elastic modulus, but has a small internal
loss and is therefore insufficient as a characteristic of a diaphragm of a speaker. On the other
hand, there is known a method of mixing scaly materials such as mica flakes and graphite flakes
in a resin in order to increase internal loss. However, although some of these scaly materials may
increase the internal loss, if it is necessary to obtain the elastic modulus necessary for the
speaker diaphragm, it is necessary to fill a considerable amount of scaly materials into the resin,
in this case In addition, it becomes difficult to mix the resin uniformly with the resin, and at the
same time, voids are easily generated in the resin. As a result, problems arise in terms of the
strength of the resin itself, and disadvantages such as deterioration in moldability occur.
Therefore, it is said that the compounding ratio of the filler to the resin needs to be kept below a
certain limit depending on the kind of filler. On the other hand, as a method of increasing the
content of scale-like substances, for example, as shown in JP-A-55-20029, one sheet is formed,
and for example, mica flakes are dispersed in water, precipitated, filtered and laminated. After
that, there is a special method of impregnating the resin, but the so-called laminated mica
obtained in this way has a high mica content, a large Young's modulus, a large internal loss, and
is satisfactory as a diaphragm. Is.
However, this diaphragm has a new problem that mass productivity is poor and it is fragile. As
another example in which the content of the serpentine scale-like substance is increased, as
described in JP-A-55-150698, scaly aluminum hydride (m / B2) is similarly produced by the
paper-making method. After precipitation and laminating, a method of bonding with a resin may
be mentioned. However, the diaphragm manufactured by this method also has no problem in
characteristics, but since the manufacturing process is complicated and the material itself is an
integrated product, it is difficult to form into a diaphragm shape by press processing etc. Missing,
there is a big problem in cost. The present invention has been made in view of such a point, and
comprises a scale-like material, a special No. Mica flake, and a diaphragm having a reinforced IiR
fiber, particularly a carbon Ia fiber filled in a resin, and having high elasticity, and an internal By
mixing with mica flakes that can increase loss, it is characterized in that these characteristics and
defects are simultaneously used, and at the same time, the elastic modulus and the internal loss
are both enhanced in a well-balanced manner. Other than mica flakes, graphite flakes, aluminum
boride flakes, boron nitride flakes and the like can be considered as scale-like substances, but
when they are all mixed in the diaphragm, they are effective in increasing the elastic modulus of
the diaphragm. Although the effect of increasing the internal loss is small compared to mica, and
all of these materials are expensive, they have the disadvantage of EndPage: 2. As other scaly
materials, glass flakes, shell-pieces, lead pieces and the like are also proposed, but these are
disadvantageous because they have a lower specific modulus ('/ p') than mica pieces. For these
reasons, it has been concluded that mica flakes are the most preferable as scaly materials for
reducing internal loss. Here, we will consider the physical properties of various fillers. The details
are shown in the following table: 70 parts by weight of polyamide resin filled with 30 parts by
weight of scale-like mica (sample A), one filled with 30 parts by weight of graphite piece (sample
B), and The ones loaded with 30 parts by weight of glass flakes (Sample C), as well as those of
100% polyamide (Sample D) are shown. However, the unit of Young's modulus is Kp / d, and as
reinforcing fibers mixed into the resin, boron fiber, alumina fiber, asbestos ring, aromatic
polyamide fiber, etc. can be considered in addition to carbon fiber. The carbon fiber was selected
in view of the size of 1 / p, cost, difficulty of obtaining, etc. The physical properties of carbon
fiber and other twill weaves and fillings are shown in the following table for reference.
However, as a unit of Young's modulus, a unit of 1-1 density is 1 / d sound velocity, and a unit of
In / sec. Another object of the present invention is to provide a diaphragm material which is
relatively inexpensive and capable of mass production. That is, the carbon fibers and mica flakes
are mixed in a thermoplastic resin and uniformly dispersed, and then made into a sheet, and the
sheet is pressed with a mold as necessary to obtain a diaphragm. It is a thing. According to this
method, there is no complicated process such as dispersion, paper making, lamination, and heat
forming in water as seen in the conventional manufacturing method of laminated mica, and the
sheet is preheated and then press-formed with a die. Since the diaphragm can be easily formed
by vacuum forming or pressure forming, the mass productivity is extremely high, and the cost
can be reduced as compared with the conventional diaphragm having the same level of
performance. In addition, when obtaining a sheet-like material, it is obtained by stretching such
as calendering, and the scaly mica and carbon fibers are oriented in the surface direction of the
sheet to increase the rigidity of the sheet-like material, so that preferable ligation is obtained. Be
As the thermoplastic resin, resins such as polyamide, polyester, polypropylene, polyvinyl
chloride, polyacrylonitrile, polystyrene and polymethyl methacrylate are used. Next, a specific
example of the method of manufacturing the diaphragm of the present invention will be
described. First of all, the weight ratio of mica flakes with an average particle diameter of 100μ
and an average aspect ratio of 50, and an average diameter of 8μ and a Young's modulus of
20000? After thoroughly mixing and stirring 20 parts of a carbon fiber (hereinafter abbreviated
as σ) chopped to a degree of mycorrhiza of 0.5 / − and 60 parts of polypropylene (hereinafter
abbreviated as PP), an extruder is used. Make a beret. At this time, in order to increase the
adhesion to PP, mica flakes are treated in a 60% aqueous nitric acid solution, and CF is immersed
in nitric acid, washed with water, treated with potassium permanganate and washed with water,
and sodium hypophosphite in addition. It is processed by. The bellet thus obtained is processed
into a sheet having a thickness of about L00μ by calendering. When a cross section of this sheet
is microscopically observed, CF and mica flakes are oriented parallel to the sheet surface, and No
void was found. This sheet is cut into 1501 corners, the periphery is fixed with a gold rod, and
the front and back sides are preheated for about 15 seconds with Far EndPage: 3 infrared heater,
and then press molded with a cone-shaped die of Nikkei 120yi at room temperature. A speaker
diaphragm was obtained. Furthermore, in order to compare the physical properties of the
diaphragms here, a sample in which only 40 parts of mica flakes were mixed in the PP6 Q part
((転), a sample in which 40 parts of CP only was mixed in the PP60 area The diaphragm was
press-formed from the sheet-like material as in the case of the diaphragm in the sample (C).
The physical properties of each sample prepared in this manner were measured by the vibration
lead method. The respective values are shown in the table below. However, the unit of Young's
modulus is the unit of I & / j density, the unit of 1 / d sound velocity is-/ 8 @ C, and the internal
loss is represented by the reciprocal of the Q value. As apparent from this table, in the case of the
sample in which only mica flakes were mixed in 40 weight percent PP, the internal loss was
large, but the speed of sound did not increase so much as compared with the filling amount. On
the other hand, 40 weight percent PP # of CF alone (Sample B mixed has an increased sound
velocity but extremely small internal loss, which is not preferable as a speaker diaphragm.
Compared to this, cy 20 weight percent and mica flake 20 weight The diaphragm mixed with the
percentage has an increased sound velocity and a large internal loss, and both are well balanced
and can be said to be ideal as a speaker diaphragm. Next, physical properties were examined
when the blending ratio of each filler was changed relative to the resin. Samples were prepared
in the same manner as described above, and the following sample types were prepared. That is,
the compounding ratio of pp to the composite material is 10, 40. 90 in weight percent, and the
compounding ratio of cy and mica flakes is 100: 0. in weight ratio with respect to each
compounding ratio of these 6PF. A total of 15 samples of 80: 20.50: 50.20: 80.0: 100 5N were
prepared. The internal loss (1A) and the speed of sound <01 port C1i> of these samples were
measured by the vibration lead method. Based on this value, when the blending ratio of CIP and
PP (horizontal axis) 'is changed with the blending □ ratio of PP as a parameter, the Q value and
the speed of sound (longitudinal axis) are plotted as shown in the figure. . In this figure, a solid
line indicates a curve in which the Q value is plotted, and a broken line indicates a curve in which
the speed of sound is plotted. As for the Q value, it is shown that the more the compounding ratio
of mica, that is, the less the compounding ratio of CF, the lower the amount of PP for the same PP
amount. The sound velocity is shown to increase as the blending ratio of CF increases, and
further increases as the view of the filler increases. Considering the compounding ratio of PP, if
the amount of PP is less than 10, the filler is too much, and the binding effect as a resin and the
moldability are extremely deteriorated to cause inconvenience. If the blending ratio of the
continuous ball filter PF exceeds 90%, the effect of the filler decreases, and the sound velocity
can not be used as a speaker diaphragm at a sound velocity of 1.3 Km / sec or less. From these
things, it is preferable that the compounding ratio of PP is in the range of 10 to 901 (weight)
with respect to the composite material.
Next, an appropriate range of the mixing ratio of CF and mica flakes when the mixing ratio of PP
is set in the range of 10 to 90 is examined. First, with regard to the sound velocity, at least 1.3 Im
/ s @ a or more is considered necessary in consideration of the physical properties of a normal
speaker diaphragm. Therefore, in the figure, in the dotted curve representing the velocity of
sound, the upper part of the curve of 90 俤 for the blending ratio of pp is a range limited from
the point of the velocity of sound. Next, with regard to the Q value, it is generally unsuitable as a
speaker diaphragm unless Q indicated by a dashed dotted line is 35 or less. Therefore, in the
figure, of the solid line representing the Q value, within the range surrounded by the curve with
90% of PP and the curve with PP = 10%, the range below the one-dot broken line of Q) 35 is
limited by the Q value It becomes. Therefore, the optimum compounding ratio between cy and
mica flakes is limited to the common part defined by the speed of sound and the Q value
regardless of PP, that is, the shaded part in the figure. That is, it is in the range of C a; mica flakes
g $ 90; 10 to 30 near 0, but it may be said to be appropriate. EndPage: 4 As apparent from the
above description, since the carbon fiber and the mica flakes are filled and bonded in the
thermoplastic resin, the carbon fiber acts to increase the elastic modulus of the diaphragm, and it
is scaly Mica is extremely useful as a diaphragm for acoustic equipment without reducing
internal loss even when the elastic modulus of the resin increases. In addition, a sheet of
thermoplastic resin filled with carbon fibers and mica flakes can be thermoformed continuously
in volume J4, and a diaphragm with high mass productivity and low cost can be obtained.
4. A simple illustration of the drawing is a relationship curve diagram between the Q value of the
diaphragm and the speed of sound with respect to the respective blending ratios of carbon fiber,
mica flakes and polypropylene. EndPage: 5
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