JPS5972300

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DESCRIPTION JPS5972300
[0001]
TECHNICAL FIELD The present invention relates to a method of manufacturing a diaphragm used
in a capacitor type microphone, and more particularly to a method of manufacturing a
diaphragm having a low fundamental resonance frequency. [Prior art and its problems j As is
well known, the majority of microphones manufactured industrially at present are occupied by
small microphones built into cassette tape recorders, and most of these small microphones are It
is an electret condenser type microphone. With the miniaturization of cassette-type tape
recorders and the spread of micro-cassette-type tape recorders, technology to miniaturize
microphones has progressed, but nowadays recording and playback technology has improved,
while microphones have become smaller as well. Improved performance of small microphones
has been strongly desired. For example, microphones for video tape recorders and microphones
for use in micro cassette type tape recorders are excellent in directivity of microphone sensitivity
so that they can be miniaturized as much as possible and at the same time, selective recording of
only the sound desired to be recorded can be performed. There is a need. On the other hand, if
the diameter of the diaphragm of the microphone is reduced in order to miniaturize the
microphone, the resonance frequency of the imaging film increases, and the sensitivity to lowfrequency sound decreases in the unidirectional microphone, and the usable frequency of the
microphone There is a disadvantage that the band narrows. As is well known, the fundamental
resonant frequency of the circular film whose periphery is fixed is fO, using the radius a of the
vibratable part of the film, the tension T applied to the film and the quality 91 m per unit area of
the film The following equation is used: a: [cm] T: (dyne / crrL) m: (g / r, w1) The radius of the
diaphragm is kept small and the fundamental resonance frequency is low. There are two ways to
reduce the tension T applied to the film or increase the mass m per unit area of vibrating
membrane, but the quality of the vibrating part 1j · increase is the decrease in the sensitivity of
the buoy chromone and the microphone In fact, it is necessary to lower the fundamental
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resonance frequency by lowering the tension T applied to the photographing movement v.
However, as shown in FIG. 1 ', in the conventional manufacturing method of the condenser type
microphone], the material film 3 for a diaphragm is fixed to the frame 1 for 1 diaphragm film
stretching in the manufacturing method of the peristaltic film After that, it is placed on the
vibrating membrane stretching stand 2 to remove the wrinkles of the vibrating membrane
material film 3 and keep the uniform tension applied to the film, and for the vibrating membrane
stretching ring 4 and the vibrating membrane A method of bonding the material film 3 with an
adhesive is adopted. In this method, since it is necessary to remove the wrinkles on the vibrating
membrane stretching base film 3, the tension T applied to the vibrating membrane stretching
base is made less than a certain value. It was not possible to do so and therefore the frequency of
seizing could not be reduced below a certain value.
For this reason, a microphone which is small and excellent in frequency characteristics and Qioriented at the same time has not been commercialized at present. SUMMARY OF THE
INVENTION It is an object of the present invention to provide a method of manufacturing an
imaging film for a condenser type microphone having a small I peristaltic film radius and a low
fundamental resonance frequency. [Summary of the Invention] The present invention disperses
conductive fine particles in an organic solvent, then dissolves a polymer substance in the organic
solvent in which the '4 electroconductive fine particles are dispersed, and disperses the
conductive fine particles in a polymer solution. The first step of obtaining a conductive filmforming liquid, and the obtained conductive film-forming liquid is applied to a metal plate used as
a four-layer membrane forming material forming material forming material former and
conductive on the metal plate Process of providing a composite conductive film consisting of
conductive fine particles and a polymer material, and a surface of the metal plate for forming a
vibrating membrane stretching ring having a composite conductive film formed on one side
which is not provided with the composite conductive film It is carried out by the third step of
forming a vibrating membrane tension ring by processing. That is, at the end of the abovementioned second step, as shown in FIG. 2 (a), the metal plate 41 for forming the VC diaphragm
ring and the combined conductive skin B! Aai is an ・ k layer, and internal stress is generated in
the composite conductive film 31 due to the evaporation of the organic solvent and the cohesion
of the polymer itself. The shape of FIG. 2 (a) is maintained by using a polymer having high
adhesive strength with the metal region plate for forming the film stretching ring, and then the
metal plate 41 for forming the vibrating film stretching ring is formed. If a photoresist is applied
to the metal surface side and etching material is formed on the vibrating membrane stretching
ring in the shape of a tension ring of vibration 1, the diaphragm for a condenser type
microphone shown in FIG. 2 (1) is formed. Is obtained. Make the thickness of the composite
conductive film as thin as possible in order to lighten the mass per unit area of the imaging film,
and as the conductive fine particles for forming the composite conductive film, those with a
specific gravity as light as possible, For example, it is preferable to use conductive carbon fine
particles such as acetylene φ blank kettin black. Further, as schematically shown in FIG. 3 as an
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example of the cross-sectional structure of an electret condenser type microphone using a
diaphragm according to the present invention, the moving surface of the condenser type
microphone is always grounded. It is preferable that the 7-resistance of the composite conductive
film be 10 M.OMEGA. Or less, preferably 1 M.OMEGA. Or less. The j peristaltic membrane for a
condenser type microphone obtained by the practice of the present invention is a combination of
a polymer and an organic solvent to be used, speed and temperature conditions for volatilizing a
mixed proportion solvent of the polymer and 4αα particle, 41 combined conductive film The
internal stress in the composite conductive film changes with the thickness of the film, and the
noise per unit area of the vibrating film changes with the thickness of the a composite conductive
film and the proportion of the polymer and 441'Il: fine particles. By appropriately setting the
manufacturing conditions described above, it is possible to obtain a diaphragm for a capacitor
type microphone having a desired fundamental resonance frequency.
Effect of the Invention According to the practice of the present invention, it is possible to obtain
an imaging film with a low fundamental resonance frequency which can not be obtained by the
conventional manufacturing method. In the manufacturing method according to the present
invention, there is no process requiring skill, such as stretching the thin film for forming the
vibrating film uniformly on the vibrating film stretching frame, so that vibration with uniform coimaging frequency can be easily obtained. g + earn or not. BEST MODE FOR CARRYING OUT THE
INVENTION The contents of the present invention will be specifically described based on the
following examples. Example 1 30 parts by weight of acetylene-black was dispersed in 100 parts
by weight of toluene, and then mixed with a solution of ethylene-vinyl acetate copolymer 10 ()
heavy-weight portion dissolved in 400 parts by weight of toluene At 74, a liquid film forming
liquid was obtained. This liquid was applied to a brass plate having a thickness of IM at room
temperature F to obtain a composite conductive film having a thickness of about 5 μm. Next,
this lead plate was chemically etched to obtain a vibrating membrane stretching ring (ring outer
diameter 6 mmφ, ring inner diameter 3.5 mmφ) having the composite conductive film adhered
to one side. The fundamental resonance frequency of the obtained moving film was 5.2 kHz.
Example-2: A phenol resin 70t obtained by condensation reaction of 1.2 moles of formalin with 1
mol of フェノール phenol using an alkali catalyst! Acetylene black was dispersed in a resin
solution by adding 30 parts by weight of acetylene black and 400 parts by weight of butyl
carbitol アセテート acetate to parts thereof to obtain a liquid composite liquid film forming
liquid. The liquid was applied to a brass plate having a thickness of t mm, and heated at 160 ° C.
for 1 hour to obtain a cured film. Next, in the same manner as in Example 1, the brass plate was
chemically etched to obtain an eye movement film (vibration partial diameter 3.5 mmφ) for a
condenser type microphone. The fundamental resonance frequency of this vibration 1 摸 was 5.7
kHz. Example 3 Same as Example 1, 2 in the same manner as Example 1, except that an acrylicbutadiene-styrene terpolymer was used as the polymer for forming the 1 ° composite layer 1D
film. I got an animated film. The fundamental resonant frequency of this vibrating membrane was
5.4 kHz. EXAMPLE 4-A composite conductive film-forming article, a child and 1. In the same
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manner as in Examples 1 and 3 except that a styrene-butadiene O rubber was used, a
photographing motion M having the same shape as in Examples 1 and 2 was obtained. The
fundamental resonant frequency of this vibrating membrane was about 3, 8 kHz. Comparative
Example A polyethylene prephthalate film having a thickness of 4 μm in which aluminum is
vacuum-deposited on one side is fixed to a film stretching frame 1 having an inner diameter of
13 cffi as shown in FIG. 1 and an outer diameter of 12 ctn. The sheet was placed on a vibrating 1
+ 9 stretching stand 2 to remove wrinkles on the polyethylene terephthalate)% I surface.
The weight of the vibrating membrane stretching frame 1 required to remove wrinkles on the
polyethylene terephthalate film surface was 300 g. The outer diameter f 3 mm φ inner diameter
3.5 mm φ, 1 mm thick X brass peristaltic membrane tension ring is attached to the aluminum
deposition surface of polyethylene terephthalate which has been strained) j), 4 The adhesive film
was fixed using an adhesive to obtain a diaphragm for a condenser type microphone: 2. The
fundamental resonance frequency of this vibrating membrane was 7 kl (z. When the weight of
the vibrating membrane stretching frame 1 is 300 g or less, there are many wrinkles in the
polyethylene terephthalate 1 pattern fixed by the jif + I return stretching frame 1, for 9%
recondenser type micro bon As [a heavy-duty vibrating membrane was not obtained, After that,
as explained 体 L in the history example, according to the present invention, it is difficult to
obtain a diaphragm for a capacitor type microphone of a basic frequency of 4 辰 which is not
obtained by the conventional method. it can. [Another Example of the Invention] In the example
of the invention, n: in the example, for the purpose of imparting conductivity to a polymer
substance, an example in which acetylene black which is 4 pentagonal 1 @ particles is added is
shown 17 However, if it is possible to add to a polymer and to provide 4 conductivity. It is
possible to use instead of acetylene black and kettin black shown in the examples. For example,
when conductive metal fine particles such as fine particles of silver or nickel are added to i1 + to
obtain a composite conductive film, the minimum 1 d-addition within the range in which the
conductivity can be given by 11]. The film is used as a vibrating film for capacitor type
microphones by reducing the thickness of the film by a small amount of 11 μm, and conductive
or semiconductive ultrafine particles such as tin oxide or titanium oxide according to the present
invention Can be used to implement Ji-k +: the component -r- itself is conductive or
semiconductive and capable of forming a wave film, such as a vinyl-pyridine polymer or an
alkylvinyl-pyridine polymer,. · A thin semiconductive or conductive α-type 1iQ is obtained by
using the radical I4 forming composition obtained by reacting with the rogenized alkyl (a
vibrating membrane stretching frame by etching as shown in the examples. I unite with it and
process it into a bowling activity I pattern 41. For example, it is obvious that a diaphragm of a
condenser type microphone having a low oscillation frequency can be obtained. In addition, as is
known in the art for producing printing inks and paints, as is conventionally known, a surfactant
is added which uniformly disperses carbon and other fine particles in a surface molecule and
forms a homogeneous film. The composite conductive film forming liquid can reduce the internal
residual stress of the formed skin 6 and increase it to the practical effect 1 of the present
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invention A.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a schematic view showing an embodiment of a method of manufacturing a diaphragm
for a condenser Φ microphone, which has been conventionally used.
FIG. 2 is a schematic view of a process of manufacturing a vibration nu for a gondensa type
microphone according to the present invention, and FIG. 3 is a schematic sectional view of an
electret condenser type microphone using a l peristaltic film according to the present invention.
31 ・・・ Complex film
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