JP4426941B2 - Diaphragm, condenser microphone unit using the same, and method for forming diaphragm - Google Patents

Description

  The present invention relates to a diaphragm that can effectively contribute to improving the sensitivity of a condenser microphone by reducing the stray capacitance and stabilizing the effective capacitance, a condenser microphone unit using the diaphragm, and a method for forming the diaphragm. is there.

The condenser microphone unit has a predetermined gap defined by the thickness of an electrically insulating spacer including a diaphragm formed by attaching a diaphragm to a diaphragm ring as shown in Patent Document 1 below. In this case, it is arranged to face the back electrode plate, and this configuration can exhibit a kind of capacitor function.
JP 2003-209899 A

  4 is a longitudinal sectional view showing an example of the structure of a conventional condenser microphone unit, and FIG. 5 is an enlarged view of a main part of FIG. According to these drawings, the condenser microphone unit 1 includes a diaphragm 2 formed by attaching a diaphragm 3 to a diaphragm ring 4 with a predetermined tension, and a thickness of an electrically insulating spacer 5 having a diaphragm 2 interposed therebetween. It is formed by disposing it so as to face the back electrode plate 6 with a predetermined gap defined by the above, and this configuration makes it possible to exhibit the kind of capacitor function already described. In addition, the code | symbol 7 in a figure shows the support stand which supports the diaphragm 2 side via the back pole board 6. FIG.

  The condenser microphone unit 1 having such a configuration can output a displacement of the diaphragm 3 due to the sound pressure as an electric signal by applying a bias voltage by a DC power supply or an electret under the condenser function. . In this case, the electric signal has a very high impedance because the signal source is derived from the capacitor function. For this reason, an impedance converter composed of a field effect transistor (FET) is arranged at the subsequent stage of the condenser microphone unit 1, and the signal output can be taken out after the impedance is converted to be low by the impedance converter. Yes.

  In addition, the condenser microphone unit 1 having the above-described configuration is easily adopted in the flatness of the diaphragm ring 4 and the back electrode plate 6, and is used in many relatively inexpensive condenser microphones.

  However, in the condenser microphone unit 1 having the above-described structure, as shown in FIG. 5, the portion located between the outer diameter edge 6 a of the back electrode plate 6 and the inner diameter edge 4 a of the diaphragm ring 4 is overlapped in a ring shape. The electrostatic capacity becomes the stray capacity, resulting in a decrease in sensitivity.

This will be described in detail by taking as an example the case where the back electrode plate is of the back electret type. The condenser microphone unit 1 having a diameter of 16 mm is formed with the structure shown in FIG. 4 under the following conditions. It shall be.
-Diaphragm ring 4 inner diameter: 11.5 mm
・ Outer diameter of back electrode plate 6: 13.4 mm
・ Thickness of diaphragm 3 (relative dielectric constant: 3): 2.0 μm
-Spacer 5 (relative dielectric constant: 3) thickness: 50.0 μm
・ Thickness of electret material (dielectric constant: 2): 12.5 μm
In the condenser microphone unit 1 formed under such conditions, the diaphragm ring 4, the diaphragm 3, the spacer 5, and the back electrode plate 6 overlap each other, that is, due to the stray capacitance. It was confirmed that a sensitivity reduction of 4 dB occurred.

  On the other hand, FIG. 6 is an explanatory view showing the behavior of the adhesive interposed when the diaphragm 3 is attached to the diaphragm ring 4 in the example shown in FIG. 4, and (a) of which the adhesive is cured. The previous state (b) shows the state after the adhesive has hardened. That is, according to FIG. 6A, a part of the adhesive 8 made of epoxy or ultraviolet curable resin protrudes from the inner diameter edge 4a side of the diaphragm ring 4 onto the diaphragm 3 before the curing. Variations in the effective capacitance will occur.

  Further, when the adhesive 8 protrudes on the vibration plate 3 in this way, the adhesive 8 contracts at the time of curing, and due to the contracting action at that time, the original position indicated by the broken line in FIG. The diaphragm 3 is attracted and displaced toward the diaphragm ring 4 (upward in the figure).

  Moreover, since the adhesive 8 has wettability, the inner peripheral wall surface of the diaphragm ring 4 may rise by, for example, about 0.2 mm. In this case, the displacement of the diaphragm 3 reaches 10 μm. Become.

  That is, although it varies depending on the thickness of the spacer 5, when the spacer 5 having a thickness of 50.0 μm is used, the displacement amount of the diaphragm 3 by the protruding adhesive 8 is 10 μm. As a result, a sensitivity difference of about 2 dB is generated as compared with the case where the amount of protrusion is small. Further, when the diaphragm 3 is displaced in this manner and the dimension of the gap with the back electrode plate 6 is changed, the frequency response in the high frequency range and the inherent noise are varied.

  That is, in the case of the prior art, there is a disadvantage in that the sensitivity is reduced due to the stray capacity generated by the overlapping part of the condenser microphone unit in a ring shape. Further, as shown in FIG. 6B, when the diaphragm is attracted and displaced, the sensitivity is lowered, and there is also a problem that the frequency response in high frequency and the inherent noise are varied.

  In view of the above-mentioned problems of the prior art, the present invention eliminates sensitivity reduction due to stray capacity, eliminates displacement of the diaphragm when the adhesive is cured, prevents sensitivity reduction, and provides high frequency response and uniqueness. An object of the present invention is to provide a diaphragm capable of effectively preventing noise variation and contributing to improvement in sensitivity of a condenser microphone, a condenser microphone unit using the diaphragm, and a method of forming the diaphragm.

  The present invention has been made to achieve the above object, and the invention according to claim 1 (diaphragm) is a diaphragm in which a diaphragm is attached to one side face of a diaphragm ring via an adhesive. The diaphragm ring includes a ring-shaped flat surface left on the inner diameter edge side of the one side surface, and a stepped portion formed by recessing a surface region of the one side surface excluding the ring-shaped flat surface, The most important feature is that it is attached to the step portion side through an adhesive supplied into the step portion.

  The invention according to claim 2 (condenser microphone unit) has a gap defined by the thickness of the electrically insulating spacer interposed with respect to the one side surface of the diaphragm ring in the diaphragm according to claim 1. The most important feature is that the back electrode plates are opposed to each other.

  Furthermore, the invention (formation method) according to claim 3 includes a step of leaving a ring-shaped flat surface on the inner diameter edge side of one side surface of the diaphragm ring and forming a stepped portion by recessing the remaining portion, and the diaphragm ring A step of supplying an adhesive into the stepped portion, a step of fixing the position of the vibration sheet forming the vibration plate by adjusting its tension, and the one side faced to face the adhesive sheet to the vibration sheet side. Placing the diaphragm ring on the vibration sheet, and cutting the vibration sheet protruding from the outer diameter edge of the diaphragm ring together with the adhesive attached to the diaphragm ring after curing of the adhesive The main feature is that it includes at least a step of leaving it.

  Among the present inventions, according to the invention according to claim 1, since it is possible to avoid the displacement of the diaphragm when the adhesive is cured, it is possible to eliminate a cause of a decrease in sensitivity, and in the high range. It is possible to eliminate variations in the frequency response and natural noise.

  According to the second aspect of the present invention, the portion of the condenser microphone unit that is overlapped in a ring shape can be narrowed, so that the stray capacity can be reduced and the sensitivity reduction can be suppressed.

  Furthermore, according to the invention which concerns on Claim 3, the diaphragm which a displacement does not produce in a diaphragm at the time of adhesive hardening can be formed by eliminating the protrusion of the adhesive agent from the internal diameter edge side of a diaphragm ring.

  FIG. 1 is an enlarged view of a main part corresponding to FIG. 5 showing a condenser microphone unit (second invention) according to the present invention as a conventional example. According to the figure, the condenser microphone unit 11 includes a diaphragm 12 formed by adhering the diaphragm 13 to one side face 16 of the diaphragm ring 15 via an adhesive 26, and one diaphragm ring 15 in the diaphragm 12. A back electrode plate 24 disposed opposite to the side surface 16 with a gap t defined by the thickness of the interposed electrically insulating spacer 22, and the back electrode plate 24 via its outer peripheral edge 25. And a support base 28 having a concave support surface 29 for supporting the support. And a kind of capacitor | condenser function can be exhibited under such a structure.

  Among these, the metal diaphragm ring 15 constituting the diaphragm 12 according to the first invention is a ring-shaped flat that remains on the inner diameter edge 16a side of the one side surface 16 as is apparent from FIG. The surface 17 and a surface area of one side surface excluding the ring-shaped flat surface 17 are recessed from the outer edge 17a side of the ring-shaped flat surface 17 through an inclined surface 19 with appropriate dimensions to reach the outer diameter edge 16b. And a flat stepped portion 18.

  In the diaphragm 12 according to the first invention, the diaphragm 13 is connected to the diaphragm 13 via the adhesive 26 supplied in the stepped portion 18 of the diaphragm ring 15 having the above-described configuration under the state shown in FIG. It is formed by sticking to the ring 15 side. The diaphragm 13 is formed using a very thin metal foil such as aluminum, titanium, or gold of the order of several μm, Mylar, or a plastic film.

  On the other hand, the electrically insulating spacer 22 having a thickness of about 50 μm has an inner diameter that is larger than the inner diameter of the diaphragm ring 15 and an outer diameter that is smaller than the outer diameter of the diaphragm ring 15. It is formed in size.

  The back electrode plate 24 having an appropriate thickness includes an electret layer (not shown) having a thickness of about 12.5 μm on the surface facing the diaphragm 13, and the outer diameter thereof is larger than the outer diameter of the diaphragm ring 15. It is formed in an appropriate size with a small diameter.

  Next, a method for forming a diaphragm according to the third invention will be described below with reference to FIG. 2 and FIGS. 3A to 3D shown as end views according to processes.

  That is, in the diaphragm manufacturing method, first, in the first step, the ring-shaped flat surface 17 is left on the inner diameter edge 16a side of the one side surface 16 of the diaphragm ring 15 as shown in FIG. Is flattened to reach the outer diameter edge 16b, and a flat step portion 18 is formed.

  In the second step, as shown in FIG. 2 (b), an appropriate amount of an adhesive 26 made of epoxy or UV curable resin or the like is applied to the stepped portion 18 of the diaphragm ring 15 by, for example, a rotary glue machine. Supplied. In this case, the adhesive 26 is preferably supplied in an amount sufficient to be substantially equal to the height of the ring-shaped flat surface 17 in the step portion 18 of the diaphragm ring 15.

  In the third step, as shown in FIG. 3 (a), the vibration sheet 14 forming the diaphragm 13 is adjusted in position and fixed, and the diaphragm ring 15 shown in FIG. The adhesive 26 is made to face the vibration sheet 14 side by disposing in reverse.

  In the fourth step, as shown in FIG. 3B, the diaphragm sheet 14 is moved relatively by moving the diaphragm ring 15 side down or raising the diaphragm sheet 14 side. A diaphragm ring 15 with one side face 16 facing the side is placed on the vibration sheet 14. At this time, although a part of the adhesive 26 protrudes from the outer diameter edge 16b side of the diaphragm ring 15, the slope 19 becomes a barrier plate and does not protrude to the ring-shaped flat surface 17 side of the diaphragm ring 15. Absent.

  In the fifth step, the adhesive 26 is cured. By curing the adhesive 26 in this way, the diaphragm 14 is diaphragmed in a contracted state as shown in FIG. It can be made to stick to the level difference part 18 side including the slope 19 of the ring 15.

  In the sixth process as the final process, the vibration sheet 14 protruding from the outer diameter edge 16b of the diaphragm ring 15 as shown in FIG. The diaphragm 12 in which the diaphragm 13 is left is formed by cutting with the cutting means.

  By forming the diaphragm 12 in this way, the adhesive 26 does not enter between the ring-shaped flat portion 17 of the diaphragm ring 15 and the vibration sheet 14. Accordingly, since the adhesive 26 does not protrude from the inner diameter edge 16a of the diaphragm ring 15, unlike the case of FIG. 6B, the vibration plate 13 can be prevented from being displaced after the adhesive 26 is cured.

  Moreover, since the adhesive 26 in the stepped portion 18 of the diaphragm ring 15 maintains the thickness of the recessed portion as the stepped portion 18, it shrinks as shown in FIG. For this reason, since the diaphragm 12 formed as shown in FIG. 3D can be separated from the outer peripheral edge 25 of the back electrode plate 24 as shown in FIG. 1, the stray capacity can be reduced accordingly. it can.

  Therefore, when the condenser microphone unit 11 shown in FIG. 1 (the dimension of the diaphragm 12 in contact with the spacer 22 is 0.2 mm) is formed under the conditions shown in the paragraph number “0007”, the stray capacitance As a result, the sensitivity was improved by about 1.4 dB (S / N was also improved by 1.4 dB). Therefore, it was possible to form the condenser microphone unit 11 with little performance variation and improved sensitivity.

The principal part enlarged view shown corresponding to FIG. 5 which shows the capacitor | condenser microphone unit (2nd invention) which concerns on this invention as a prior art example. (A) is a longitudinal cross-sectional view about an example of the diaphragm ring in this invention, (b) shows the longitudinal cross-sectional view in the state which supplied the adhesive agent to the diaphragm ring of (a), respectively. The end view which shows the formation method (3rd invention) of the diaphragm based on this invention as (a)-(d) according to process. The longitudinal cross-sectional view which shows the structural example of the conventional condenser microphone unit. The principal part enlarged view about the prior art example shown in FIG. FIG. 5 is an explanatory view showing the behavior of the adhesive interposed when the diaphragm is attached to the diaphragm ring in the example shown in FIG. 4, (a) of which shows the state before the adhesive is cured, (b) Indicates the state after the adhesive is cured.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Condenser microphone unit 12 Diaphragm 13 Diaphragm 14 Vibrating sheet 15 Dia or diaphragm ring 16 One side surface 16a Inner diameter edge 16b Outer diameter edge 17 Ring-shaped flat part 17a Outer edge 18 Step part 19 Slope 22 Spacer 24 Back electrode plate 25 Outer peripheral edge part 26 Adhesive 28 Support base 29 Recessed support surface t Gap

Claims (3)

In the diaphragm formed by attaching a diaphragm to one side of the diaphragm ring via an adhesive,
The diaphragm ring includes a ring-shaped flat surface left on the inner diameter edge side of the one side surface, and a stepped portion formed by recessing a surface region of the one side surface excluding the ring-shaped flat surface, A diaphragm attached to the step portion side through an adhesive supplied into the step portion.   The capacitor according to claim 1, wherein a back electrode plate is disposed opposite to the one side surface side of the diaphragm ring in the diaphragm according to claim 1 with a gap defined by the thickness of the interposed electrically insulating spacer. Microphone unit. Leaving a ring-shaped flat surface on the inner diameter edge side of one side surface of the diaphragm ring, and forming a stepped portion by recessing the remaining portion;
Supplying an adhesive into the step portion of the diaphragm ring;
Adjusting the position of the vibrating sheet forming the diaphragm by adjusting its tension; and
Placing the diaphragm ring having the one side faced on the vibration sheet such that the adhesive side faces the vibration sheet side;
Forming a diaphragm, comprising at least a step of removing a vibration sheet protruding from an outer peripheral edge of the diaphragm ring after curing of the adhesive together with leaving the vibration plate together with the adhesive attached thereto Method.

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