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DESCRIPTION JPH02202800

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DESCRIPTION JPH02202800
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
diaphragm of an electroacoustic transducer for converting vibration such as voice to an electric
signal, and in particular, it can be supported with low tension and disposed in close proximity to
a back electrode plate. The present invention relates to a diaphragm of an electroacoustic
transducer capable of [Prior Art] An electroacoustic transducer such as a condenser microphone
which captures the vibration of a diaphragm as a capacitance by a back electrode plate provided
on its back surface and outputs a change in the capacitance as an electric signal is for business
use. It is widely used not only in homes but also in homes. For example, in a polarization-type
compatible condenser microphone, the diaphragm is required to place the lower limit at a low
frequency, and-it is required to have fishing sensitivity, and in terms of miniaturization, the
diaphragm tension is low. It is required to set. However, a back electrode plate is located on the
back of the diaphragm, and a polarization voltage is present between them, so that an
electrostatic attractive force is applied to the diaphragm, and so-called adsorption on the back
electrode plate of the so-called diaphragm. I have a problem. Therefore, the tension must be set
in advance to sufficiently counter electrostatic attraction, and since the tension of the diaphragm
slightly changes due to changes in environmental conditions such as temperature and humidity,
such changes in environmental conditions In addition to setting the stability with a margin, the
above-mentioned problems are improved by performing aging with temperature and humidity.
On the other hand, such a diaphragm usually forms a thin film thermoplastic synthetic resin film
such as polyethylene terephthalate or polyphenylene sulfide having a thickness of 3 to 6 μm
into a desired shape by a heat forming apparatus as schematically shown in FIG. I'm making it.
That is, the diaphragm material 2 made of a synthetic resin film is placed on the mold 1 designed
in a desired shape, the pressure pot 3 is lowered, and between the pressure pot 3 and the mold 1
Next, the diaphragm material 2 is brought into close contact with the forming die 1 by injecting
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pressurized air into the pressure pot 3, and the forming die 1 is heated and cooled to perform the
forming. ing. An O-ring 4 is provided on the lower end periphery of the pressure pot 3 to prevent
leakage of the pressurized air. In this method, when the diaphragm 2 is placed on the mold 1, air
stagnation tends to occur between the back surface of the diaphragm 2 and the top surface of
the mold 1, and when molded as it is, it is molded in an expanded form as shown in the figure. I
will. Therefore, an air vent hole 5 penetrating to the lower part is provided at a substantially
central portion of the mold 1 so that air between the diaphragm 2 and the mold 1 can be
released to the outside through the hole 5.
[Problems to be Solved by the Invention] However, a part of the diaphragm material 2 protrudes
into the air vent hole 5 at the time of pressure molding, and an unnecessary convex portion is
formed on one surface of the diaphragm after molding. In particular, in a condenser microphone,
the gap between the diaphragm and the back plate is extremely small, and the height of the
convex portion is higher than the length of the gap, and it is necessary to separate the diaphragm
and the back plate by at least a distance equivalent to this height. Is the cause of the
deterioration of the performance of the diaphragm. Furthermore, the diaphragm material 2 has a
strong adhesion to the surface of the mold 1 and has the disadvantage that the diaphragm may
be damaged when it is peeled off after molding, or deformation may occur, resulting in poor
production. Therefore, an object of the present invention is to provide a diaphragm of an
electroacoustic transducer which does not adsorb in a planar manner to a static suction force and
does not cause extreme sensitivity deterioration even if the peripheral edge is fixed at low
tension. To provide. According to the present invention, there is provided a diaphragm of an
electro-acoustic transducer for converting vibration such as voice to an electric signal, wherein a
plurality of irregularities are formed on the surface of the diaphragm. It is [Embodiments] The
present invention will be described hereinbelow by taking a diaphragm of a condenser
microphone as an example and showing an embodiment shown in the drawings. First, an
example of the construction of the condenser microphone 11 will be described with reference to
FIG. 1. The back electrode plate 14 is located on the back surface of the diaphragm 13 whose
circumferential edge is fixed by the support ring 12 at a predetermined distance. A conductive
contact plate 15 is disposed in close contact with the surface of the back electrode plate 14
opposite to the vibrating plate 13. A plurality of through holes 16 forming a sound wave passage
are bored in the back electrode plate 14, and a dielectric 17 such as F, E, 'P or the like is crimped
on the top surface of the back electrode plate 14. The back electrode plate 14 is attached to the
upper end of the recess 19 of the support base 18 made of an electrically insulating material
such that the surface opposite to the surface of the dielectric 17 is in close contact with the
contact plate 15 having conductivity. . The contact plate 15 is also preceded by the through hole
21 communicating with the through hole 16, and the connection terminal 23 of the impedance
converter 22 disposed at the bottom of the recess 19 is electrically connected to the lower
surface of the contact plate 15 by the solder 24. It is done. Reference numeral 25 denotes a
spacer for setting the gap between the diaphragm 13 and the back electrode plate 14, and
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reference numeral 27 denotes a rear acoustic terminal. The diaphragm 13 is provided with a
plurality of fine asperities 26 on its surface. FIG. 2 is a photomicrograph showing the uneven
portion 26 of the diaphragm 13 at 200 times magnification. The depression of the uneven
portion 26 in this embodiment is about 8 μI at the maximum.
FIG. 3 shows a molding apparatus for molding such a diaphragm 13. A support base 33 is
provided on the lower base 31 so as to be vertically movable via an elastic member 32 such as a
spring. There is. A forming die 34 is placed substantially in the middle of the support table 33,
and a heating means 35 on which a heating wire or the like is disposed is attached to the lower
surface of the forming die 34. On the lower base 31 below the heating means 35, a cooling
means 36 is attached which cools the heating means 35 in contact when the heating means 35
descends. The heating means 35 is set in advance so that the power is turned off at the time of
lowering and the heating is stopped. The cooling means 36 is implemented, for example, by
laying a cooling pipe and passing cooling water through the pipe. An upper base 38 is provided
on the upper end of the column 37 standing on the lower base 31 so as to be substantially
parallel to the lower base 31. An air cylinder 42 is attached to the middle base of the upper base
38 so that the cylinder rod 41 moves up and down substantially vertically. A pressure pot 44,
which is formed in a substantially U-shaped cross section at the tip of the cylinder rod 41 and in
which a pressure chamber 43 is provided, is mounted with its open portion facing downward. An
airtight リ ン グ ring 45 is attached to the open end of the pressure pot 44. A pressurized air
supply port 46 for connecting to a pressurized air supply source (not shown) is formed on the
side surface of the pressurized pot 44. Since these structures are the same as the conventional
thermoforming apparatus, the description of those detailed structures is abbreviate | omitted. On
the upper surface of the mold 34, a synthetic resin or metal, such as nylon, having sufficient
flexibility to be compatible with the surface of the mold 34, for example, a mesh material having
a fine mesh such as # 300, nickel, An unevenness forming member 47 formed of a metal fiber
sintered body or woven fabric of titanium, copper, brass, monel metal, stainless steel or the like is
placed. In order to form the diaphragm 13 having the concavo-convex portion 26, first, the
forming die 34 which has been cooled down by the cooling means 36 is lowered to the position
shown in FIG. The diaphragm material 48 made of a thermoplastic film such as polyethylene
terephthalate or polyphenylene sulfide as described above is placed on the unevenness forming
member 47 of the mold 34 that has been cooled. Next, the heating means 35 is operated to heat
the mold 34, and the heating means 35 is stopped when the preset molding temperature is
reached. Next, the air cylinder 42 is operated to lower the cylinder rod 41 so that the diaphragm
material 48 is held between the open end of the mold 34 and the open end of the pressure pot
44 and fixed.
Then, pressurized air is supplied from the pressurized air supply port 46 into the pressurizing
chamber 43, and the forming die 34 is brought into contact with the cooling means 36 to cool
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the forming die 34. The diaphragm material 48 is molded according to the mold formed on the
mold 34 by air pressure and heat. The diaphragm material 48 is provided with the concavoconvex portion 26 in accordance with the mesh, the hole and the texture of the concavo-convex
forming member 47 positioned therebelow. By the supply of pressurized air, the air existing
between the diaphragm material 48 and the concavo-convex forming member 47 is discharged
to the outside directly from the side edge through the mesh, the holes and the weave of the
concavo-convex forming member 47. Or the gap between the unevenness forming member 47
and the molding die 34 is discharged to the outside. Therefore, no air accumulation can occur
between the diaphragm material 48 and the mold 34. When the diaphragm material 48 is
formed into a predetermined shape and the concavo-convex portion 26 is formed by the
concavo-convex forming member 47, the supply of the pressurized air is stopped. Next, when the
cylinder rod 41 is moved to the upper side, the diaphragm material 48 is positioned on the
forming die 34 in a state of being attached to the unevenness forming member 47. Finally, the
diaphragm material 48 is peeled off from the unevenness forming member 47. Unlike the case
where the diaphragm material 48 peels off from the portion with high adhesiveness such as the
surface of the conventional molding die, it peels from the unevenness-forming member 47 with
low adhesiveness, so it can be peeled off with extremely weak force. There is no damage or
deformation to the diaphragm during peeling. The photomicrograph shown in FIG. 2 shows the
case where the unevenness forming member 47 is made of # 308 nylon mesh. By providing the
fine asperities 26 on the surface of the diaphragm 13 in this manner, the R shape of the
asperities 26 changes with the back and forth movement of the diaphragm 13, so that the
tension can be lowered. These asperities 26. Even if the peripheral edge of the diaphragm is fixed
with low tension, the static attraction force of the back electrode plate 14 does not attract flatly
to the back electrode plate 14, and only the apexes of the uneven portion 26 are adsorbed. Only.
In addition, even when the stability is set low for adsorption, the absence of planar contact does
not cause extreme deterioration of sensitivity and the like. Therefore, it is possible to set the
stiffness lower than that of a conventional diaphragm of the same diameter, which can be a great
advantage when requiring a low tension in a small-diameter diaphragm. 4a to 4d are graphs
showing frequency response characteristics of a unidirectional microphone unit, and FIGS. 4a
and 4b show cases where the diameter of the diaphragm is 7 m +, and FIGS. 4c and 4d. Shows
the case where the diameter of the diaphragm is 5 m, and FIGS. 4a and 4c respectively use the
case of the conventional diaphragm and FIGS. 4b and 4d use the diaphragm made according to
the present invention The case is shown.
Note that a shows the case where the sound source is O 'b, 180' '' for the sound source, and C
shows 90 @ for the sound source. From a comparison of these two characteristics, it can be seen
that the low frequency response is improved and the flatness near 1.5 KHz is improved in the
diaphragm of the present invention. Although the above-described embodiment exemplifies a
condenser microphone, the present invention is not limited to this, and it is needless to say that
the present invention can be applied to diaphragms of various electroacoustic transducers such
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as dynamic microphones and headphones. As described above, the diaphragm of the
electroacoustic transducer according to the present invention has an extremely simple structure
having a plurality of irregularities on its surface, but this makes it possible to obtain a flat surface
by a static suction force. Thus, it is possible to provide a diaphragm which has no planar contact
even when the stability is set low for adsorption. Therefore, it is possible to set the stiffness low
by immersing in a conventional diaphragm of the same diameter, which provides a diaphragm
suitable for a microphone that requires low tension in a diaphragm with a small diameter. it can.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing an
example of a microphone using the diaphragm of the present invention, FIG. 2 is a
photomicrograph for showing the irregularities of the diaphragm, and FIG. 4a to 4d are graphs
showing the frequency response characteristics of the diaphragm according to the prior art and
the present invention, and FIG. 5 is a prior art vibration showing an example of a device for
producing a plate. It is an explanatory view showing roughly an example of a board
manufacturing device. In the drawings, 11 is a condenser microphone, 13 is a diaphragm, 26 is
an uneven portion, 47 is an unevenness forming member, and 48 is a diaphragm material. Patent
Assignee Audio-Technica Co., Ltd. Patent Attorney Takuya Ohara Figure 1 Figure 2 Figure 6 Day
6 Figure 4C Figure 4d Figure 6b Figure 4b Figure 4b Corrected Description Patent Office
Secretary吉 1) 毅 表示 1, display of the case Heisei year patent application No. 23253 2, the
name of the invention the diaphragm 3 of the electrostatic type electroacoustic transducer, the
relationship with the person making the correction Technica 5 Date of correction order
(spontaneous) Date of Showa month (shipping date: 6th month of the same year) 6 "Name of
invention", "claim" 1 in the specification subject to correction, name of invention Electrostatic In
the diaphragm 2 of the second electroacoustic transducer, the diaphragm of the tm
electroacoustic transducer for converting vibration of a voice or the like into an electric signal, a
plurality of irregularities are formed on the surface of the diaphragm Electrostatic electroacoustic transducer characterized by being formed Vibration plate of the vessel.
3. Detailed description of the invention [Industrial field of application] The present invention
relates to a diaphragm of an electroacoustic transducer for converting vibration such as voice to
an electric signal, and in particular, in particular, single-point supported with low tension. The
present invention relates to a diaphragm of an electrostatic electroacoustic transducer that can
be disposed in close proximity to a back plate in a capacitive electrostatic electroacoustic
transducer. [Prior Art] An electroacoustic transducer such as a condenser microphone which
captures the vibration of a diaphragm as a capacitance by a back electrode plate provided on its
back surface and outputs a change in the capacitance as an electric signal is for business use. It is
widely used not only in homes but also in homes. In general, in the polarization-type compatible
condenser microphone, the diaphragm is required to place the lower limit at a low frequency,
and-it is required to have fishing sensitivity, and in terms of miniaturization, the diaphragm
tension is low. It is required to set. However, a back electrode plate is located on the back of the
diaphragm, and a polarization voltage is present between them, so that an electrostatic attractive
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force is applied to the diaphragm, and so-called adsorption on the back plate of the diaphragm I
have a problem. したがって。 The tension must be set in advance to sufficiently counter
electrostatic attraction, and since the tension of the diaphragm slightly changes due to changes
in environmental conditions such as temperature and humidity, such changes in environmental
conditions are also taken into consideration. The above-mentioned problems are improved by
setting the stability with a margin and performing aging with temperature and humidity. Also, as
a special application such as a hearing aid, or a very rare example, a diaphragm may be formed
by heat molding. The thermoplastic synthetic resin such as 3 to 6 μm polyethylene
terephthalate or polyphenylene sulfide is formed into a shape according to the purpose.
[Problems to be Solved by the Invention] When molding such a thermoplastic resin, a heat
molding apparatus as schematically shown in FIG. 5 is generally used. The structure of the heat
forming apparatus will be described together with the forming process thereof. The diaphragm
material 2 made of a synthetic resin film is placed on the forming die 1 designed in a desired
shape, and the pressure pot 3 is lowered. The diaphragm material 2 is held between the pressure
pot 3 and the mold 1 and sealed. Then, by injecting pressurized air into the pressure pot 3, the
diaphragm material 2 is in close contact with the mold 1, and the mold 1 is heated and cooled to
perform molding. An O-ring 4 is provided on the lower end periphery of the pressure pot 3 to
prevent leakage of the pressurized air.
In this method, the diaphragm 2 is placed on the mold 1. Air stagnation is likely to occur between
the back surface of the diaphragm 2 and the top surface of the mold 1, and if molded as it is, it
will be molded in a bulging shape as shown. Therefore, an air vent hole 5 penetrating to the
lower part is provided at a substantially central portion of the mold 1 so that air between the
diaphragm 2 and the mold 1 can be released to the outside through the hole 5. However, a part
of the diaphragm material 2 protrudes into the air vent hole 5 at the time of pressure molding,
and an unnecessary convex portion is formed on one surface of the diaphragm after molding. In
particular, in a condenser microphone, the gap between the diaphragm and the back plate is
extremely small, and the height of the convex portion is higher than the length of the gap, and it
is necessary to separate the diaphragm and the back plate by at least a distance equivalent to this
height. Is the cause of the deterioration of the performance of the diaphragm. In addition, even if
this convex portion is formed to be located in the opposite direction to the back electrode plate,
the deterioration of the performance due to the non-uniformity of the diaphragm is inevitable.
Furthermore, the diaphragm material 2 has strong adhesion with the surface of the molding die
1, and there is a disadvantage that the diaphragm may be damaged by peeling off after molding,
or deformation may occur and productivity is not good. . Therefore, it is an object of the present
invention to provide an electrostatic electroacoustic transducer which does not adsorb planarly
to static suction force and does not cause extreme sensitivity deterioration even if the peripheral
edge is fixed with low tension. To provide a diaphragm of the [Means for Solving the Problems]
The present invention is a diaphragm of an electrostatic electroacoustic transducer for
converting vibration such as voice to an electric signal, wherein a plurality of continuous
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irregularities are formed on the surface of the diaphragm. It is characterized by [Embodiments]
The present invention will be described hereinbelow by taking a diaphragm of a condenser
microphone as an example and showing an embodiment shown in the drawings. First, an
example of the structure of the condenser microphone 11 will be described with reference to FIG.
1. The back electrode plate 14 is positioned on the back surface of the diaphragm 13 whose
circumferential edge is fixed by the support ring 12 with a predetermined distance. A conductive
contact plate 15 is disposed in close contact with the surface of the back electrode plate 14
opposite to the vibrating plate 13. A plurality of through holes 16 forming a sound wave passage
are bored in the back electrode plate 14, and a dielectric 17 such as F, E, P, etc. is crimped on the
upper surface of the back electrode plate 14. The back electrode plate 14 is attached to the
upper end of the recess 19 of the support base 18 made of an electrically insulating material
such that the surface opposite to the surface of the dielectric 17 is in close contact with the
contact plate 15 having conductivity. . The contact plate 15 is also preceded by the through hole
21 communicating with the through hole 16, and the connection terminal 23 of the impedance
converter 22 disposed at the bottom of the recess 19 is electrically connected to the lower
surface of the contact plate 15 by the solder 24. It is done.
Reference numeral 25 denotes a spacer for setting the gap between the diaphragm 13 and the
back electrode plate 14, and reference numeral 27 denotes a rear acoustic terminal. The
diaphragm 13 is provided with a fine uneven portion 26 continuous on its surface. The height of
the uneven portion 26 from the bottom of the recess to the top of the convex is preferably at
least the thickness of the diaphragm 13 or the like. FIG. 2 is a photomicrograph showing a
specific example of the concavo-convex part 26 of the diaphragm 13 at 200 times magnification,
and the height from the bottom of the concavo-convex part 26 to the top of the convex part in
this specific example is at maximum It is about 8 # I11. FIG. 3 shows a molding apparatus for
molding such a diaphragm 13. A support base 33 is provided on the lower base 31 so as to be
vertically movable via an elastic member 32 such as a spring. There is. A forming die 34 is placed
substantially in the middle of the support table 33, and a heating means 35 on which a heating
wire or the like is disposed is attached to the lower surface of the forming die 34. On the lower
base 31 below the heating means 35, a cooling means 36 is attached which cools the heating
means 35 in contact when the heating means 35 descends. The heating means 35 is set in
advance so that the power is turned off at the time of lowering and the heating is stopped. The
cooling means 36 is implemented, for example, by laying a cooling pipe and passing cooling
water through the pipe. An upper base 38 is provided on the upper end of the column 37
standing on the lower base 31 so as to be substantially parallel to the lower base 31. An air
cylinder 42 is attached to the middle base of the upper base 38 so that the cylinder rod 41
moves up and down substantially vertically. A pressure bot 44, which is formed in a substantially
U-shaped cross section at the tip of the cylinder rod 41 and in which a pressure chamber 43 is
provided, is mounted with its open portion directed downward. An air-tight O-ring 45 is attached
to the open end edge of the pressure bot 44. A pressurized air supply port 46 for connecting to a
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pressurized air supply source (not shown) is formed on the side surface of the pressurizing bot
44. Since these structures are the same as the conventional thermoforming apparatus, the
description of those detailed structures is abbreviate | omitted. On the upper surface of the
forming die 34, a synthetic resin such as nylon or the like having sufficient flexibility to be
compatible with the surface of the forming die 34 or a mesh material such as a mesh formed
with fine meshes such as 1,300 for example. An uneven member 47 made of a sintered metal
fiber or woven fabric of copper, brass, monel metal, stainless steel or the like is placed. In order
to form the diaphragm 13 having the continuous uneven portion 26, first, the forming die 34
which has been cooled down by the cooling means 36 is lowered to the position shown in FIG.
6. Place the diaphragm material 48 made of a thermoplastic film such as polyethylene
terephthalate or polyphenylene sulfide as described above on the uneven member 47 of the mold
34 that has been cooled 6 Next, the heating means 35 is operated to perform molding The mold
34 is heated, and the heating means 35 is stopped when reaching a preset molding temperature.
0 Next, the air cylinder 42 is operated to lower the cylinder rod 41 and the mold 34 and the
pressure pot 44 The diaphragm material 48 is held and fixed between the open end edges of the
plate. Then, pressurized air is supplied from the pressurized air supply port 46 into the
pressurizing chamber 43, and the forming die 34 is brought into contact with the cooling means
36 to cool the forming die 34. The diaphragm material 48 is molded according to the mold
formed on the mold 34 by air pressure and heat. The diaphragm material 48 is provided with
continuous irregularities 26 in accordance with the mesh, holes and texture of the concavoconvex member 47 located therebelow. Due to the supply of pressurized air, the air existing
between the diaphragm material 48 and the concavo-convex member 47 is discharged through
the mesh, hole and weave of the concavo-convex member 47 directly from the side edge to the
outside, The gap between the uneven member 47 and the mold 34 is discharged to the outside.
Therefore, no air accumulation can occur between the diaphragm material 48 and the mold 34.
When the diaphragm material 48 is formed in a predetermined shape and the concavo-convex
portion 26 is formed by the concavo-convex member 47, the supply of pressurized air is stopped.
0 Next, when the cylinder rod 41 is raised, the diaphragm material 48 It is positioned on the
forming die 34 in a state of being attached to the uneven member 47. Finally, the diaphragm
material 48 is peeled off from the uneven member 47. The diaphragm material 48 is peeled off
from the uneven member 47 having low adhesion, unlike the case where the diaphragm material
48 is peeled off from the high adhesion portion of the surface of the conventional molding die, so
it can be peeled off with extremely weak force. The diaphragm is not damaged or deformed at
the time of peeling. The photomicrograph shown in FIG. 2 shows the case where the concavoconvex member 47 is made of # 508 nylon mesh. By providing the fine asperities 26 on the
surface of the diaphragm 13 in this manner, the R shape of the asperities 26 changes with the
back and forth movement of the diaphragm 13, so that the tension can be lowered. These
asperities 26. Even if the peripheral edge of the diaphragm is fixed with low tension, the static
attraction force of the back electrode plate 14 does not attract flatly to the back electrode plate
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14, and only the apexes of the uneven portion 26 are adsorbed. Only. In addition, even when the
stability is set low for adsorption, the absence of planar contact does not cause extreme
deterioration of sensitivity and the like.
Therefore, it is possible to set the stiffness lower than that of a conventional diaphragm of the
same diameter, which can be a great advantage when requiring a low tension in a small-diameter
diaphragm. FIGS. 4a to 4d are graphs showing frequency response characteristics of the
unidirectional microphone unit, and FIGS. 4a and 4b show the case where the diameter of the
diaphragm is 711 n 5 and FIGS. 4c and 4d. Shows the case where the diameter of the diaphragm
is 5 m, and FIGS. 4a and 4c respectively use the case of the conventional diaphragm and FIGS. 4b
and 4d use the diaphragm made according to the present invention The case is shown. Note that
a indicates the case of 06 for the sound source, b indicates 180 @ for the sound source, and C
indicates 90 "for the sound source. From a comparison of these two characteristics, it can be seen
that the low frequency response of the diaphragm of the present invention is improved. [Effects
of the Invention] As described above, although the diaphragm of the electrostatic type
electroacoustic conversion quantity of the present invention has a very simple structure having a
plurality of continuous irregularities on its surface, static suction is thereby achieved. The force
does not cause planar adsorption, and a diaphragm having no planar contact can be provided
even when the stability is set low for adsorption. Therefore, it is possible to set the stiffness lower
than that of the conventional diaphragm of the same diameter, which provides an optimum
diaphragm for condenser microphones that require low tension in a small-diameter diaphragm.
can do.
[0002]
Brief description of the drawings
[0003]
FIG. 1 is a longitudinal sectional view showing an example of a microphone using the diaphragm
of the present invention, FIG. 2 is a photomicrograph for showing irregularities of the diaphragm,
and FIG. 3 is a device for producing this diaphragm. Fig. 4a to Fig. 4d are graphs showing the
frequency response characteristics of the diaphragm according to the prior art and the present
invention, and Fig. 5 is a schematic view of an example of the conventional diaphragm
manufacturing apparatus. It is explanatory drawing shown.
In the drawings, 11 is a condenser microphone, 13 is a diaphragm, 26 is an uneven portion, 47 is
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an uneven member, and 48 is a diaphragm material.
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