JP2005260899A - High-quality function microphone apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively and easily manufacture a high-function microphone comprising a high-quality function windshield having both electrostatic shielding property and water repellency. <P>SOLUTION: A conductive coating having thickness of ≤50 microns is applied to a sound-transmissible windshield to be attached to an opening on the front face of a microphone, and its outer surface is coated with a water repellent agent having thickness of ≤50 microns and a contact angle with water of ≥120°. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

Detailed Description of the Invention

Industrial application fields

  The present invention is highly resistant to interference by electrostatic induction, can operate without causing problems such as water wetting failure due to rainfall, etc., and can be installed close to an electrostatic induction source such as an electronic circuit. To improve the convenience of communication equipment, acoustic devices, measuring devices and systems, such as miniaturization, high functionality, high reliability, relaxation of restrictions on use conditions, and ease of maintenance It is.

Capacitor microphones that are often used for communication, especially for mobile phones, etc., electrically insulate the conductive diaphragm, which is the main component, the back electrode that is placed in parallel to the conductive diaphragm, and both. Insulators that are mechanically fixed are the main elements of electroacoustic conversion, and the electric signals converted from acoustic waves through vibrations of the vibrating membrane and changes in the capacitance between the membrane and electrode based on the vibrations are efficiently used. In general, the preamplifier is integrally housed in a housing for detection and transmission (1).
FIG. 1 is a schematic example of a microphone that has been widely used in the past. In FIG. 1, a cylindrical one is shown as a cross-sectional view along the diameter. In FIG. Is a back electrode of a conductor, one side of which faces the vibrating membrane and is installed in parallel at an interval of about 1 to 100 microns to form a capacitor. 14 has a function of fixing as much as possible and electrically insulating. As for output 14, an amount by which the potential difference between the back electrode and the diaphragm is changed by the vibration of the diaphragm due to the sound pressure is extracted as an output. And is connected to the preamplifier 15. 16 is a connector for connecting to the outside, 17 is a front opening for introducing an acoustic wave, 18 is a housing, 19 is a front protective film, and a capacitor formed by a microphone is described in FIG. As described above, it has a parallel disk shape, and its diameter is several centimeters at the maximum. As can be seen from the distance between the electrodes of the diaphragm as described above, the capacitance is about 100 pF at the maximum. Between several hertz to several tens of kilohertz which is the frequency band of acoustic measurement, the impedance is high impedance of several megohms or more. For this reason, in order to efficiently connect the converted electrical signal to the outside, if moisture adheres to this high impedance part connected to the built-in preamplifier, problems such as reduced sensitivity and generation of noise occur. In addition, as is well known, a condenser microphone detects vibration of the vibrating membrane due to an acoustic signal as a change in the capacitance of the capacitor, and converts it into an electrical signal. Therefore, it is necessary to charge the capacitor in advance, but a film such as FEP (fluoroethylene propylene) is formed on one of the vibration film or the opposed surface of the fixed electrode, and the film is formed by applying a permanent charge to the film. In so-called electret type condenser microphones, the function of the electret-forming layer is impaired by water. Furthermore, as mentioned above, the electrical impedance of the microphone body and the connection from the microphone to the preamplifier is as low as several megohms, even small ones at 1 gigaohm. This is one of the reasons why the preamplifier is installed in close proximity, but this high impedance part is the part before amplification, so even in parts where the signal level is very low is there. As can be easily understood from this, it is vulnerable to noise contamination due to electrostatic induction, and a strict electrostatic shield is required. Although it is easy and widely used, there is no problem, but in order to efficiently introduce an acoustic signal wave into the vibrating membrane, a substantial part of the opening is required, and electrostatic induction from this part is prevented. Therefore, a lot of means such as electrical blockage of the opening by the metal mesh was necessary.

Problems to be solved by the invention

As described above, the solution to the present invention is to efficiently realize a method for improving the functionality of a condenser microphone that prevents damage caused by moisture and prevents electrostatic induction from the opening at low cost. Is an issue

Means for solving the problem

In the present invention, a so-called windshield (hereinafter referred to as a windshield), which is often used for the front opening of a condenser microphone, is used to prevent dust and wind from entering and protect from damage from the outside. It is intended to form a high-performance windshield (hereinafter referred to as a high-function windshield) that has an electrostatic shielding effect and a water-repellent effect by a simple surface treatment without impairing sound properties.

Composition and action

Used in the present invention. A high function windshield is shown in FIG. In FIG. 2, reference numeral 21 denotes a windshield base material. For example, non-woven fabric and urethane foam are frequently used, and are generally mounted on a casing 24 of a microphone. Reference numeral 22 denotes a conductive coating, which is a so-called conductive coating such as an epoxy resin mixed with a conductive agent powder such as carbon or nickel. 23 is a water repellent mainly composed of PTFE or the like, and in the present invention, a material having a water repellency of 120 degrees or more as a contact angle is used. This water repellent needs to be applied to the outside of the conductive coating. Each of these coatings needs to be 50 microns or less, and when it is thicker than this, the acoustic characteristics of the high-performance windshield are impaired. The conductive coating can be either single-sided or double-sided and can be arbitrarily selected depending on the convenience of the manufacturing process, but part or all of it must be in contact with the conductive casing. In FIG. 2, the conductive coating is applied to the outside of the periphery of the base material, and the portion is in contact with the casing and is electrically connected to provide an electrostatic shielding effect. The high-performance windshield of the high-frequency amplifier is close to electrostatic induction sources such as high-frequency amplifiers, while maintaining the acoustic characteristics of the windshield substrate, and by the electrostatic shielding by the conductive coating and the water-repellent action by the water-repellent coating provided on the outside. It has a function that can be installed and that can prevent obstacles due to the ingress of moisture from the opening.

As an example of the present invention, a DS-15SS (thickness 0.15 mm, weight 45 g / square meter) manufactured by Nippon Vilene Co., Ltd., which is one of commercially available non-woven fabrics, is used as a substrate, and Fujikura Kasei Co., Ltd. is used as a conductive coating. A high-performance windshield was prepared by coating 20-micron coating of Dotite XC-12 and coating it with a low-molecular-weight polymerized PTFE with a binder added as a water repellent, and when applied to an electret condenser microphone, it was 20 cm for a 20 W fluorescent lamp. Even if it is close to the distance, no guidance is received, and even if it is submerged for 30 minutes at a depth of water depth, no performance deterioration is observed, confirming the effectiveness of the present invention.

The invention's effect

The application of the present invention greatly contributes to the expansion of the degree of freedom of design of equipment such as voice communication and acoustic measurement and the relaxation of restrictions on use.

References

(1) The Acoustical Society of Japan, Electroacoustic Engineering Corona Company, 1979

Fig. 1

Schematic diagram of typical structure of condenser microphone

Fig. 2

High-performance windshield according to the present invention

Explanation of symbols

11 is a vibrating membrane, 12 is a back electrode, 13 is an insulator, 14 is a lead wire, 15 is a preamplifier, 16 is a connector, 17 is a front opening, 18 is a housing, 19 is a front protective film, 21 is a windshield base Material 22 is a conductive coating part 23 is a water repellent agent 24 is a microphone housing

Claims (2)

In a condenser microphone mainly composed of a conductive vibration film installed in a casing having a shielding effect, a fixed electrode installed in parallel with the diaphragm and an insulator that is electrically insulated while fixing both, The sound receiving opening is provided with a conductive or non-conductive sound-permeable film with a conductive coating on one or both sides, and a water repellent containing PTFE as a main component is 1 to 50 microns on the outer surface. Microphone device characterized by thickness coating 2. The microphone device according to claim 1, further comprising: an electret forming layer fixed on either one of the vibrating membrane and the fixed electrode.

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