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JPS5760798

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DESCRIPTION JPS5760798
Description 1, title of the invention
Manufacturing method of polyimide diaphragm for audio equipment
3. Detailed Description of the Invention The present invention relates to a method for producing
a polyimide diaphragm for an acoustic device such as a speaker, a micro horn or a hel horn.
Conventionally, a diaphragm r1 pyromellitic acid polyimide film (Kapton, trade name)
manufactured for 7f sound equipment is bonded to a metal foil with an adhesive such as epoxy
or urethane, and then the metal foil is fully etched It is manufactured by the method to do.
However, in the above-mentioned conventional method V, the polyimide film and the metal '76
are completely adhered and / or an adhesive is used, and the heat resistance of this adhesive is
inferior to that of the polyimide film, There is a problem that the power of the acoustic device
can not be increased to the allowable limit of the polyimide film, and the acoustic device can be
used only in a low power state below the allowable limit of the adhesive. The development of
acoustic equipment in recent years is remarkable, and along with it, the requirements of the
power amplifier for the diaphragm are more severe than before (this requirement is particularly
noticeable in the ribbon tweeter diaphragm), but conventionally The fact is that if you use an
adhesive like a law, you can not meet the requirements of EndPage: 1. Furthermore, in addition
to the requirement of the power amplifier, there is also a demand for improvement of acoustic
characteristics such as frequency characteristics, impedance characteristics or frequency division
characteristics in the imaging plate for acoustic equipment. It is known that the acoustic
properties of the diaphragm can be improved by using a film which reduces the thickness of the
whole film or which has elastic properties such as to follow the Hooke's law as much as possible
as the film to be joined to the metal foil. It is difficult in the conventional method to obtain a film
having a thickness of 7.5 μm or less in view of the level of film forming technology, and
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according to the conventional method, much improvement in acoustic characteristics VC can not
be desired. The present invention solves the problems of the above-mentioned conventional
methods, and provides a method of manufacturing a polyimide diaphragm for an audio device
which can not only be power-up but also thin articles. That is, the method for producing a
polyimide diaphragm for an audio device according to the present invention comprises reacting a
biphenyltetracarboxylic acid dianhydride (hereinafter referred to as BPDA) represented by a
general formula% with an aromatic diamine in an organic polar solvent A polyamic acid solution
with an intrinsic viscosity of 0.5 or more obtained by coating is coated on at least one side of a
metal foil and then heat dried to remove the solvent. In the present invention, a diaphragm
material comprising a foil and a polyimide layer is obtained, and then etching is performed on
the metal foil of the diaphragm material 1 to 1 to form a conduction circuit of a predetermined
shape. First, a substantially equivalent molar amount of BPDA represented by the above general
formula and an aromatic diamine is reacted in an organic polar solvent to obtain a polyamic acid
solution having an intrinsic viscosity of 0.5 or more, and then a limb polya Doric acid solution is
coated on at least one side of all metal foils and then heated and dried to evaporate and remove
the solvent and convert the polyamic acid to polyimide to obtain a diaphragm material in which
the metal foil and the polyimide layer are directly bonded to each other. Be
As specific examples of BPDA used in this process, i; t, 3, 4, 3.4-BPDA, 2, 3 ° is M, and among
these 3,4, 3 ° is preferable. On the other hand, of the above aromatic diamine to be reacted with
the above BPf) A! "! Body side! Rn-phenylenediamine, p-phenylenediamine, 4,4diaminodiphenylmethane, 4.4-diaminodiphenylether, 4.4-diaminodiphenylpropane, 4 °
aminodiphenylsulfone, 3,3-diaminodiphenylsulfone And 1,5-diaminonaphthalene, 2.6diaminonaphthalene, 3,4-diaminobenzanilide and the like. In the present invention ((wherein the
BPDA and the aromatic diamine are N, N-dimethylformamide, N, N-diethylformamide, N, Ndimethylacetamide, N, N-diethylacetamide, N, N-dimethylmethyacetamide) Etc. in an organic
polar solvent such as N, N-dialkylcarboxamides, dimethylsulfoxide, N-methyl-2-pyrrolidone,
dimethylsulfone, hexamethylphosphoramide etc., BPDA and aromatic diamine during this
reaction The concentration of the organic polar solvent in the organic polar solvent may be set
according to various conditions, but it is usually 5 to 30 times the width, preferably 10 to 25
parts by weight. The reaction temperature is usually 80 ° C. or less, preferably 5 to 50 ° C.,
and the reaction time is usually about 1 to 10 hours. In the present invention, BPDA, aromatic
diamine and organic polar solvent may be used alone or in combination of two or more. Further,
as organic polar solvents, aromatic hydrocarbons such as benzene, toluene and xylene, ethers
such as dioxane, ketones such as methyl ethyl ketone, alcohols such as methanol, EndPage: 2
ethanol, and phenols such as phenol and cresol. It is also possible to use a mixture of various
solvents3 or 7) BPDA and an aromatic diamine are reacted in an organic tetrametallic W solution;
polyamic acid is formed when the medium is reacted f +, solution viscosity accompanying the
progress of the reaction In the present invention, the solution of polyamic acid on which C.sub.f'i
intrinsic viscosity is 0.5 is increased. When the intrinsic viscosity of the polyamic acid solution is
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(1,5 ′ ′ under (−), conversion of the polyamic acid makes the polyimide layer worn by a
thousand metal foils 1,000 Km brittle and is easily cracked, cracked, etc. , As a diaphragm, since
the practicality of this is reduced, it is not good.
The intrinsic viscosity of the polyamic acid solution in the present invention is determined by
taking out the polyamic acid from the polyamic acid solution, dissolving the polyamic acid
component in a predetermined solvent, determining its viscosity, 1) Calculated by the equation
1). C) where C is the number of grams of polymer in 100 mg of solution. The polyamic acid
solution thus obtained is used for viscosity 4 and its solution viscosity is measured at a
temperature of 30 ° C. by B-type viscosity autopsy (the value of 7 is usually 5 to 30 times the
concentration of polyamic acid). Show about 10 to 10 a poise. In the present invention, as
described above, the solution of polyamic acid obtained by reacting PDADA aromatic diamine in
organic cedar solvent as described above has a thickness of ili 50 .mu. For example, it is coated
on at least one side of aluminum foil, copper foil, etc. 1) -F1. ZIO Application of sigma novoliamic
acid solution to these metal foil surfaces vC is a variety of methods applied, for example, A1 For
example, immersing @ metal foil in polyamic acid solution 1 to 1, transfer the excess polyamic
acid with a doctor knife A method of taking it, a method of transferring and applying a polyamic
acid solution to a metal foil surface by a reverse roll coater, and a method of extruding a metal
foil surface and a VC polyamic acid solution by a T die can be exemplified as a fighting example.
In this coating process, a solution of polyamic acid is applied onto the sweetened metal foil and 0
surface VC. However, it is also possible to dilute the solution with an appropriate solvent or to
warm the solution to adjust its viscosity for coating. The coating thickness of the polyamic acid
solution on the metal foil is such that the thickness of the polyimide layer formed by the
conversion of the polyamic acid is usually 50 μm or less and preferably 2 to 25 μm. The metal
foil 111 coated with the polyamic acid solution on the surface at 12 as described above is then
heat-dried. This heat drying is performed to convert the polyamic acid in the polyamic acid
solution applied to the metal foil surface to a polyimide and to evaporate and remove volatile
components such as a solvent. The heating temperature in this case may vary depending on
various conditions, but is usually 50 to 500 ° C., preferably after predrying at 50 to 200 ° C.,
then raising the temperature to 200 to 500 ° C. Post drying is preferred. This two-stage I!
iji¥7. According to the drying method, most of the solvent is evaporated and removed in
the pre-drying stage, and volatile components such as residual solvent are evaporated and
removed in the post-drying stage, and conversion of polyamic acid to polyimide is performed.
Even when a polyamic acid solution containing many layers is used or when the coating
thickness is increased, the foaming phenomenon due to evaporation of volatile components can
be completely prevented, and there is an advantage that a uniform polyimide layer without voids
can be formed.
By this heating and drying, a polyimide layer having a volatile content of 5 parts by weight or
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less and preferably 1% by weight or less is formed on the surface of the gold pA foil, or a
diaphragm material is formed. The volatile matter content (% by weight) of the polyimide layer in
the diaphragm material is a value calculated by the following formula (] I). In the above formula
(n), W indicates the weight before drying of the diaphragm material, Wd indicates the weight
after heat-drying the material at 350 ° C. for 2 hours 1, and wb indicates the weight of the
metal foil. . In the present invention, etching is applied to the metal foil of the diaphragm material
obtained as described above to form a conduction circuit of a predetermined shape, and the
conduction circuit of the metal foil is directly formed on the polyimide layer EndPage: 3. A
bonded polyimide diaphragm is obtained. This etching process can be performed by a
photoetching method or a spanta etching method, and in the case of the photoetching method,
for example, the diaphragm material is cut into all predetermined dimensions, degreased, washed
with water, dried and then photographed on a metal foil. The entire resist (photosensitive resin)
layer is formed, and predetermined portions thereof are masked L, exposed, developed, removed
of the unexposed (uncured) photoresist layer portion, etched, removed of the unexposed (cured)
photoresist layer By sequentially working, a polyimide diaphragm in which a conductive circuit
of metal foil is formed on the polyimide layer is obtained. In the present invention, in order to
etch the metal foil of the diaphragm material having the polyimide layer formed on both sides of
the metal foil, one polyimide layer is etched with an aqueous solution of hydrazide or sodium
hydroxide, A portion of the foil is exposed and then the exposed metal foil is etched. The present
invention is constructed as described above, and since the polyimide layer and the metal foil are
joined in contact with each other in 15 layers, a polyimide diaphragm which can be used with
high power is obtained. Since the layer is formed, a thin layer can be formed as the polyimide
layer, and a polyimide diaphragm having excellent acoustic characteristics can be obtained.
Hereinafter, the present invention will be described in more detail by way of examples. In the
examples, all 1% or 1% by weight is shown. Example 13.4.3 ′, 4′BPT) A1176F (4 moles) and
4.4′-diaminodiphenylether 8009 (4 moles) in N-methyl-2-pyrrolidone 14.5 Ks + at a
temperature of 5-30 ° C. The reaction is carried out for 5 hours to obtain a polyamic acid
solution with an inherent viscosity of 2.5. Next, this polyamic acid solution is continuously
applied using a knife coater on one side of a long hard aluminum foil having a thickness of 20
μm and a width of 400 m, passed through a dryer at 150 ° C., and reserved for 10 minutes.
Dry, evaporate most of the N-methyl-2-pyrrolidone, and pass through a 250 to 300 ° C. dryer
for 20 minutes and dry again to evaporate remaining volatile components such as pi IJ ton Once
removed, conversion of the polyamic acid to polyimide is carried out, and a 12.5 μm polyimide
layer is formed on one side of the aluminum foil, and the next long diaphragm material is carried
out.
The content of volatile components in the polyimide layer was (1, 2). Thereafter, this diaphragm
material was cut into dimensions of 150 × 15 (ltrm, and photo etching 7111 was applied to
aluminum foil to obtain a polyimide diaphragm having a conduction circuit of a predetermined
shape. When a pair 1 to power test (Sin wave input test at 5 KHz) was performed on this
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diaphragm, no deterioration occurred even at 40 W for 20 minutes. For comparison, a
diaphragm in which a polyimide film of 12.5 voice thickness (made by Devon, trade name
Kapton) and the same aluminum foil as that described above are joined by an epoxy adhesive
(the shape of the conduction circuit is the diaphragm of the present invention) Same as with K) 1
to K, when the power test was conducted under the same conditions, the adhesive was
carbonized after 20120 minutes. In order to fully understand the acoustic characteristics of the
polyimide diaphragm obtained according to the present invention, the polyamic acid is cast on a
glass plate, and the plate is pre-dried and post-dried under the same conditions as in the case of
the diaphragm. When removed from the plate, 79.125.mu., a volatile component-containing
gi'0.2% BPDA-based polyimide film was obtained, subjected to a tensile test, and all stressdistortion lines were formed. Thus, it was found that the Hook's law was followed more faithfully
than the pyromellitic acid-based Kapton film (curve B), and the acoustic characteristics were also
improved compared to the conventional products. The tensile test was conducted under the
conditions of a sample width of 20 wn, a tensile speed of 50 m + n / −, a chuck interval 1 (lo + a,
a load of 100 to a temperature of 25 ° C.). Furthermore, after casting this polyamic acid on a
glass plate using the above-mentioned polyamic acid, pre-drying, post-drying and peeling from
the glass plate are sequentially carried out to obtain polyimide films of various thicknesses, and
these films are The relationship between the film thickness and the breaking load obtained by
conducting the tensile test under the same conditions as described above is shown in FIG. 2
EndPage: 41- () The polyimide layer used in the present invention (straight line C It can be seen
that the change in breaking load with thickness is smaller than the Kapton film (straight line D)
used in the conventional product. The diaphragm is usually stretched by a predetermined tension
on a tension frame and silked into a speaker etc. This tensioning operation changes the tension
even if the length of the L polyimide layer fluctuates a little The work efficiency is better if there
is no line 'λ. In addition, the change in breaking load due to the thickness of the BPDA-based
polyimide layer U used in the present invention is smaller than that of the conventional
pyromellitic acid-based Kapton film, and the diaphragm during stretching work on a tension
frame The workability is excellent because the thickness of the polyimide layer in (4) slightly
changes and it is not necessary to change the tension.
Example 2 Extruded from the polyamic acid solution eT Gui used in Example 1, coated on one
side of a long hard aluminum foil having a thickness of 1 () μ and a width of 400 mm, and heatdried under the same conditions as Example 1. Then, a long-sized moving plate having a
thickness of 4 .mu.m and a 0.05% volatile content polyimide layer is formed on one side of the
aluminum foil. Next, this diaphragm material is cut into dimensions of 150X] ',> Orra, and
subjected to aluminum foil r and photo Jitching 11 processing to form a 2% conductive circuit of
a predetermined shape. / R,. This diaphragm is paired with 1. Example 1 and Diffraction 1. Power
tests were conducted, 1 nW, 't for 20 minutes, (1' every 11 days of deterioration). For
comparison, the diaphragm (conduction circuit Q) shape joined with a 7.5 μm thick polyimide
film (made by Devon, trade name Kapton) with the same aluminum foil all urethane adhesive as
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above is the vibration of the above-mentioned invention. Conduct the power test under the same
conditions as for the plate), and the adhesive carbonizes in 15 W for 20 minutes. てし1つ
/C,。
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 and FIG. 2 show the stress-strain curve of the
polyimide layer used in the present invention and the polyimide film of the conventional product
(tC and the relationship between the film thickness and the breaking load) FIG. Patent issued Ha
f) Person Nitto Denki Industry Co., Ltd. Representative upper three parts: /: · · · 1 '? ... Fill 4
thickness (1 ') EndPage: 5
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