JP2005311443A - Acoustic damping cloth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic damping cloth having also the electromagnetic wave shield performance without losing the acoustic damping performance at all, which the acoustic damping cloth has to substantially have. <P>SOLUTION: The acoustic damping cloth is formed by forming a metallic coating film to the surface of fibers of meshed fabric comprising synthetic fiber filament yarns, and preferably the diameter of the synthetic fiber filament yarn configuring the meshed fabric is 20 to 500 μm, the warp desnity and the weft density of the meshed fabric are respectively 50 to 500 lines / inch, the uppermost face of the metallic coating film is colored in black, and a low surface energy compound coating film is laminated on an upper part of the metallic coating film. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acoustic braking cloth used for an electroacoustic transducer. More specifically, the present invention relates to an acoustic braking cloth that has both acoustic braking properties and electromagnetic wave shielding properties and is preferably used for an electroacoustic transducer incorporated in an electronic device such as a mobile phone, a personal digital assistant (PDA), or a digital camera. is there.

  In recent years, it has been pointed out that with the rapid spread of electronic devices in various fields such as homes and offices, electromagnetic waves leaking from electronic devices may cause other electronic devices to malfunction or affect the human body. Has been. In particular, mobile phones are not only carried around all the time, but are also used in the state of being close to the head, so there are concerns about health problems.

To prevent leakage of electromagnetic waves from the case, cover the case of the mobile phone with metal foil, apply conductive paint, or place an electromagnetic shielding material at the case joint. ing.
However, leakage from an opening provided for transmitting sound from the speaker to the outside of the housing or collecting external sound to the microphone inside the housing is unavoidable. Moreover, since it is defenseless against electromagnetic waves flying from the outside, a speaker or a microphone picks up electromagnetic noise and degrades sound quality.

  For this problem, various accessories such as a cover and a case having electromagnetic shielding properties have been proposed. For example, Patent Document 1 uses a telephone case in which an electromagnetic wave shielding woven fabric is provided in a portion covering a telephone receiving part of a telephone, and an electromagnetic wave shielding woven cloth as a main component and is attached to a telephone receiving part. An electromagnetic wave shielding seal for a telephone is disclosed. However, a mobile phone equipped with a case is difficult to hold and has a heavy burden, and the electromagnetic wave shielding seal is easily peeled off by an external force. Furthermore, since these are retrofitted to a mobile phone, there is a problem that the appearance and sound transmission are impaired. Patent Document 1 also describes that an electromagnetic wave shielding seal is attached to the back surface of the receiving part of the mobile phone body to provide a mobile phone incorporating an electromagnetic shielding fabric, but the number of parts is increased. However, there is a problem that the mobile phone is not suitable for lightening and downsizing.

  Patent Document 2 discloses a pad made of a radio wave absorber that is formed to have the same dimensions as a voice transmission opening formed in a casing of a mobile phone and is used by filling the opening. However, the radio wave absorber has a narrow frequency range to be absorbed and cannot sufficiently prevent leakage of electromagnetic waves from the casing, and has a thickness of about 1 mm. there were.

  On the other hand, electroacoustic transducers such as speakers (sounding bodies) and microphones (sound receiving bodies) incorporated in electronic devices such as mobile phones are usually acoustic braking cloths so as to close the openings provided in the exterior containers. By arranging the above, an appropriate acoustic resistance is provided, the frequency characteristics are flattened, and the frequency bandwidth is improved. Then, the electroacoustic transducer is incorporated into the electronic device in a state where the opening provided in the exterior container communicates with the opening provided in the housing of the electronic device. At this time, if water or dust enters from the opening, the life of the electroacoustic transducer is shortened. Therefore, a protective material is installed on the inner surface of the casing of the electronic device so as to block the opening. There is also a case. If the acoustic braking cloth has a drip-proof and dust-proof function, it is not necessary to provide a protective material, and the number of parts of the electronic device can be reduced.

  If the acoustic braking cloth used in this way can be provided with electromagnetic shielding properties, the above-mentioned problems in the prior art can be solved all at once. For example, in Patent Document 3, a conductive sound transmitting plate such as a metal net or an insulating sound transmitting plate such as a cloth is coated with a conductive material powder such as metal with a binder on the outer surface thereof. A microphone screen that is coated with a highly water-repellent material and satisfies acoustic characteristics, drip-proof properties, and electrostatic shielding effects is disclosed. However, the conductive sound transmission plate is not only very expensive, but also has a problem of poor flexibility and poor workability. Also, the surface of the insulating sound transmitting plate coated with conductive material powder has a problem that the conductivity is small and sufficient electromagnetic wave shielding properties cannot be obtained.

Utility Model Registration No. 3035244 Japanese Patent Laid-Open No. 2002-16994 JP 2004-7330 A

  The present invention has been made in view of such a current situation, and an object of the present invention is to provide an acoustic braking cloth having electromagnetic shielding properties without impairing the acoustic braking ability that the acoustic braking cloth should originally have. Is to provide.

The present invention
(1) An acoustic braking cloth characterized in that a metal coating is formed on the fiber surface of a mesh-like woven fabric composed of synthetic fiber filament yarns.
(2) An acoustic braking cloth characterized in that the diameter of the synthetic fiber filament yarn constituting the mesh fabric is 20 to 500 μm, and the warp density and weft density of the mesh fabric is 50 to 500 yarns / inch. is there.
(3) The acoustic braking cloth is characterized in that the outermost surface of the metal coating is black.
(4) An acoustic braking cloth characterized in that a low surface energy compound film is laminated on the metal film.

According to the present invention, it is possible to provide an acoustic braking cloth having both acoustic braking properties and electromagnetic shielding properties. The acoustic braking cloth of the present invention is used for an electroacoustic transducer and incorporated into an electronic device such as a mobile phone, a personal digital assistant (PDA), a digital camera, etc. Since leakage can be effectively prevented, the influence on other electronic devices and the human body can be reduced. In addition, since the entry of electromagnetic waves from the outside can be effectively prevented, the sound quality is not deteriorated. Furthermore, the acoustic braking cloth of the present invention can prevent the intrusion of dust by controlling the area of the hole formed between the yarns. In addition, it is possible to prevent electrification due to its conductivity and to prevent dust from adhering due to electrostatic action.
Furthermore, if a low surface energy compound film is laminated on top of the metal film, a protective material is disposed in the opening provided in the casing of the electronic device in order to exhibit drip-proof properties due to its water repellency. There is no need to do this, and the time and effort can be omitted, and the number of parts of the electronic device can be reduced.

Hereinafter, the present invention will be described in detail.
The acoustic braking cloth of the present invention is formed by forming a metal coating on the fiber surface of a mesh-like woven fabric composed of synthetic fiber filament yarns.

  Examples of fiber materials used in the present invention include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyamides such as nylon 6 and nylon 66, polyolefins such as polyethylene and polypropylene, polyacrylonitriles, polyvinyl alcohols, polyurethanes, Examples thereof include synthetic fibers such as polyvinyl chloride, and two or more of these may be combined. Of these, polyester fibers or polyamide fibers are preferable in consideration of processability and durability.

  Moreover, in order to suppress generation | occurrence | production of a fluff etc., it is requested | required that it is a thread | yarn which consists of a long fiber, ie, a filament. The form may be either a monofilament yarn or a multifilament yarn, or a combination thereof. Among these, monofilament yarns that are free from fraying of the yarn during cutting and generate less chips are preferable.

  In the present invention, a synthetic fiber spun yarn, semi-synthetic fiber, regenerated fiber, natural fiber, inorganic fiber, metal fiber, or the like may be included within a range that does not impair the characteristics of the synthetic fiber filament yarn.

  In the present invention, the mesh-like woven fabric refers to a woven fabric having a larger thread interval and having both air permeability and translucency as compared with a woven fabric usually used for clothing.

  The structure of the mesh woven fabric is not particularly limited, and examples thereof include plain weave, satin weave, and twill weave. Of these, plain weave is preferably used because warps and wefts are alternately crossed one by one, so that the binding force at the intersection of the warp and weft is high, the form stability is increased, and the handling is excellent.

  The acoustic braking cloth of the present invention is formed by forming a metal film on the fiber surface of the mesh-like woven fabric. In order to satisfy both the acoustic braking property and the electromagnetic wave shielding property, the synthetic fiber constituting the mesh-like woven fabric is used. It is preferable that the diameter of the filament yarn and the warp density and the weft density of the mesh fabric are within a specific numerical range.

That is, the diameter of the synthetic fiber filament yarn is preferably 20 to 500 μm, more preferably 30 to 200 μm, and still more preferably 30 to 60 μm. If the diameter is less than 20 μm, weaving is difficult and expensive. When the diameter exceeds 500 μm, the thickness of the mesh-like woven fabric increases, making it unsuitable as an acoustic braking cloth used for an electroacoustic transducer incorporated in an electronic device having a limited installation space.
Although the fineness of the synthetic fiber filament yarn having a diameter of 20 to 500 μm varies depending on the fiber material, it usually corresponds to 4 to 2700 dtex (decitex).

  Further, the warp density and the weft density of the mesh woven fabric are preferably 50 to 500 yarns / inch, more preferably 80 to 300 yarns / inch, and further preferably 100 to 300 yarns / inch. When the warp density and / or the weft density is less than 50 yarns / inch, the area of the hole formed between the yarns and the aperture ratio increase, and sufficient electromagnetic wave shielding properties cannot be obtained. When the warp density and / or the weft density exceeds 500 yarns / inch, the area of the hole formed between the yarns and the opening ratio are reduced, so that sufficient sound permeability cannot be obtained and the sound quality is deteriorated.

When the diameter of the synthetic fiber filament yarn constituting the mesh woven fabric, and the warp density and weft density of the mesh woven fabric are within the specific numerical range, the area per hole formed between the yarns is as follows: Usually, it is 600 to 62500 μm ² , and the aperture ratio is usually 18 to 80%.

  Thus, by controlling the area of the hole formed between the yarns and the opening ratio, it is possible to effectively prevent the intrusion of dust. In addition, since a metal coating is formed on the fiber surface of the mesh-like woven fabric, it is provided with conductivity, so that charging can be prevented and dust adhesion due to electrostatic action can be prevented.

  In order to ensure the fixing of the metal film formed on the fiber surface of the mesh-like woven fabric, impurities such as glue, oil, dust, etc. adhering to the fiber surface in advance are used as surfactants (so-called scouring agents). It is preferable to remove it using an organic solvent or the like.

The metal used for forming the metal film is not particularly limited as long as it has conductivity, and examples thereof include gold, silver, copper, zinc, nickel, and alloys thereof. Of these, copper and nickel are preferable in view of conductivity and manufacturing cost.
The conductivity is closely related to the electromagnetic wave shielding property, and if the diameter of the synthetic fiber filament yarn constituting the mesh woven fabric and the warp density and the weft density of the mesh woven fabric are the same, the higher the conductivity, Electromagnetic shielding properties tend to be high. Further, as described above, it also contributes to dust resistance.

  In order to form a metal film on the fiber surface of the mesh fabric, a conventionally known method such as a vapor deposition method, a sputtering method, an electroplating method, or an electroless plating method can be employed. Among these, in consideration of the uniformity and productivity of the formed metal film, the electroless plating method or the combined use of the electroless plating method and the electroplating method is preferable.

  As is well known, electroless plating is performed by chemical plating after applying a catalyst. To apply the catalyst, after sensitization with a tin chloride solution, activation with a palladium chloride solution, after applying a one-part catalyst with a colloidal tin palladium colloid, the tin ions on the colloid surface layer are removed and used as a catalyst. The method for exposing effective palladium is not particularly limited. Next, the metal is deposited by treatment in a chemical plating bath comprising a metal salt, a reducing agent, a buffering agent, a pH adjusting agent and the like.

Metal deposition amount is preferably 0.1 to 50 g / ^{m 2,} more preferably from 1 to 20 g / ^{m 2.} When the precipitation amount is less than 0.1 g / m ² , sufficient electromagnetic wave shielding properties cannot be obtained. Even if the amount of precipitation exceeds 50 g / m ² , the electromagnetic wave shielding property exceeding that is not obtained, which is uneconomical, and the inherent flexibility of the fabric is impaired, and the metal film is easily peeled off.
The thickness of the metal coating when the amount of deposited metal is 0.1 to 50 g / m ² is usually 0.01 to 1 μm, although it varies depending on the metal species.

  The metal coating is preferably one layer or two layers. When the number of layers is three or more, the thickness of the metal coating increases, which is not preferable for the above reason. When two layers of metal films are used, the same kind of metal may be stacked in two layers, or different metals may be stacked. These may be set appropriately in consideration of the required electromagnetic shielding properties and durability.

  The outermost surface of the metal coating is preferably a black layer from the viewpoint of design. In order to make the outermost surface a black layer, a method of coating with a black metal or a black pigment, a method of oxidation or sulfuration treatment, and the like can be mentioned, and among them, there is little influence on conductivity, particularly surface conductivity. For reasons, the method of coating with black metal is preferred. To cover with black metal, for example, black nickel plating treatment or chromate plating treatment, black ternary alloy plating treatment using tin, nickel and copper, black ternary alloy plating treatment using tin, nickel and molybdenum, etc. Good. In order to coat with a black pigment, for example, spray coating, brush coating, electrodeposition coating, or the like may be performed using a black paint in which a black pigment is dispersed. Examples of the black pigment include carbon black, and among them, those having conductivity are preferable. It can also be blackened by oxidizing or sulfurating the outermost surface of the metal coating, and these can be performed by a conventionally known method.

  Thus, the acoustic braking cloth of the present invention in which the metal coating is formed on the fiber surface of the mesh-like woven fabric can be obtained. Hereinafter, in the present specification, a mesh-like woven fabric in which a metal film is formed on the fiber surface may be simply referred to as a metal-coated woven fabric.

  The acoustic braking cloth of the present invention can be evaluated for its braking performance by measuring the sound pressure level in the used voice band. Here, it can be said that the more the flat frequency-sound pressure characteristic is obtained over a wide range of the used voice band while suppressing the rapid fluctuation of the frequency-sound pressure characteristic without impairing the sound pressure level, the better the braking performance is. I can say that.

  The acoustic braking cloth of the present invention preferably has an electromagnetic wave shielding property at a frequency of 10 MHz to 1 GHz measured by the KEC method of 20 dB or more, more preferably 40 dB or more. If the electromagnetic wave shielding property is less than 20 dB, leakage of electromagnetic waves from the housing cannot be sufficiently prevented.

  The conductivity of the acoustic braking cloth is preferably 1000Ω / sq or less, more preferably 1Ω / sq, as the surface resistance value. If the surface resistance value exceeds 1000 Ω / sq, when used in an electroacoustic transducer and incorporated in an electronic device, the grounding effect with the housing of the electronic device cannot be obtained, and the original electromagnetic shielding properties cannot be obtained. There is a case.

  In the acoustic braking cloth of the present invention, it is preferable that a film made of a compound having a low surface energy is further laminated on the metal film. Thereby, the acoustic braking cloth of the present invention can have drip-proof properties due to the water repellency of the compound. If the acoustic braking cloth has drip-proof properties, it is not necessary to arrange a protective material in the opening provided in the casing of the electronic device, and the labor can be omitted. The number can be reduced.

  In order to laminate the low surface energy compound film on the metal film, the treatment liquid containing the compound is applied to the metal-coated fabric, followed by drying and, if necessary, heat treatment. A cross-linking agent, an emulsifying dispersant, a penetrating agent and the like may be added to the treatment liquid.

  Examples of the low surface energy compound include conventionally known compounds that can be used as so-called water repellents (water and oil repellents) such as silicone compounds and fluorine-containing compounds. Among these, since the fluorine-containing compound itself has a low polarizability, the intermolecular cohesive force and the surface energy are remarkably low, thereby having a property that it is difficult to wet a liquid or solid having a high intermolecular cohesive force. It also has excellent heat resistance, chemical resistance, and oxidation resistance, is electrically neutral, and has a low dielectric constant. For these reasons, fluorine-containing compounds are preferably used. Specifically, a polymer having a structural unit derived from a monomer having a fluoroalkyl group, for example, acrylate, methacrylate, maleate, fumarate having a fluoroalkyl group, or urethane having a fluoroalkyl group is exemplified. Can do. Two or more of these may be used in combination.

  In the present invention, a commercially available fluorine-based water repellent can be used as the fluorine-containing compound, and such a water-repellent is emulsified (emulsion type) and dispersed (dispersion type) in water or an organic solvent. ) Or in dissolved form. Any type can be used in the present invention, but an organic solvent type is preferably used from the viewpoint of quality. When the water type (water-based emulsion type) is used, yellowing or spotting may occur depending on the molecular structure, ionicity, pH, etc. of the fluorine-containing compound.

The amount of the fluorine-containing compound applied to the metal-coated fabric is preferably 0.1 to 10% by weight, more preferably 0.3 to 1% by weight. If the applied amount is less than 0.1% by weight, sufficient drip-proof property cannot be obtained. Even if the application amount exceeds 10% by weight, a drip-proof property exceeding that cannot be obtained.
In order for the acoustic braking cloth to exhibit sufficient drip-proof properties, the water repellency measured by the spray test of JIS L 1092 is required to be 4th grade or more, preferably 5th grade.
The amount of the fluorine-containing compound applied to the metal-coated woven fabric can be applied in an appropriate amount by adjusting the concentration of the processing liquid and the amount of the processing liquid applied to the mesh-shaped woven fabric.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example. “%” In the examples is based on weight. The performance of the obtained acoustic braking cloth was evaluated by the following method.
(1) Conductivity (surface conductivity)
The resistance value of the sample surface was measured using a Loresta-EP MCP-T360 ESP type resistance value measuring instrument manufactured by Mitsubishi Chemical Corporation.
(2) Electromagnetic wave shielding property Based on the KEC method by Kansai Electronics Industrial Promotion Center, the attenuation of electromagnetic waves at 10 MHz to 1 GHz was measured using a spectrum analyzer HP8591EM with tracking generator manufactured by Hewlett-Packard Japan.
(3) Acoustic braking performance The sound pressure level at a frequency of 100 Hz to 5 kHz was measured using a B & K audio analyzer 2012 as a sound source, a Bose 101MM & GCW4 as a speaker, and a B & K 4192 as a microphone.
(4) Water repellency: Measured by the water repellency test (spray test) of JIS L 1092.
(5) Quality Visually determined according to the following criteria.
○ No yellowing and good quality △ Slightly yellowing, slightly inferior quality × Extremely yellowing, poor quality

[Example 1]
Both the warp and weft are made of polyethylene terephthalate monofilament yarn with a diameter of 35μm (fineness 13dtex), and both the warp density and weft density are 300 yarns / inch (per hole formed between the yarns). of the area 2401μm ^2), was heat-treated at 190 ° C. (preset).
This was immersed in an aqueous solution at 40 ° C. containing palladium chloride 0.3 g / L, stannous chloride 30 g / L, and 36% hydrochloric acid 300 ml / L for 2 minutes and then washed with water. Subsequently, it was immersed in borohydric acid having an acid concentration of 0.1 N and 30 ° C. for 5 minutes and then washed with water.
Next, it was immersed in an electroless copper plating solution containing 35 g of copper sulfate 7.5 g / L, 37% formalin 30 ml / L, and Rochelle salt 85 g / L for 15 minutes and then washed with water. As a result, a copper film having a thickness of 1 μm was formed on the fiber surface of the mesh plain fabric.
Next, it was immersed in an electric nickel-tin alloy plating solution containing nickel sulfate 100 g / L and stannous sulfate 50 g / L at 40 ° C. for 10 minutes at a current density of 1 A / dm ² and then washed with water. Thereby, a nickel-tin alloy film having a thickness of 0.1 μm was laminated.

[Example 2]
Using the metal-coated plain fabric obtained in Example 1 as a turpentine, Dickguard SDF-20 (manufactured by Dainippon Ink & Chemicals, Inc., fluorinated water repellent (organic solvent type), solid content 10%) 5% It was immersed in the dispersed treatment solution, squeezed to a pick-up rate of 60% at a mangle roll pressure of 3 kg / cm ² , dried at 105 ° C. for 4 minutes, and then heat treated at 160 ° C. for 1 minute. Thereby, the fluorine-containing compound film was laminated on the upper part of the metal film.

[Example 3]
The metal-coated plain fabric obtained in Example 1 was immersed in a treatment solution containing 5% Asahi Guard AG-7000 (manufactured by Meisei Chemical Industry Co., Ltd., fluorine-based water repellent (water type), solid content 20%). The solution was squeezed to a pick-up rate of 60% at a mangle roll pressure of 3 kg / cm ² , dried at 105 ° C. for 4 minutes, and then heat-treated at 160 ° C. for 1 minute. Thereby, the fluorine-containing compound film was laminated on the upper part of the metal film.

[Example 4]
Both warp and weft are composed of polyethylene terephthalate monofilament yarns with a diameter of 40μm (fineness 17dtex), and both the warp density and the weft density are 135 mesh / inch (per hole formed between the yarns) of the area 21904μm ^2), was heat-treated at 190 ° C. (preset).
This was immersed in an aqueous solution at 40 ° C. containing palladium chloride 0.3 g / L, stannous chloride 30 g / L, and 36% hydrochloric acid 300 ml / L for 2 minutes and then washed with water. Subsequently, it was immersed in borohydric acid having an acid concentration of 0.1 N and 30 ° C. for 5 minutes and then washed with water.
Next, it was immersed in an electroless copper plating solution containing 35 g of copper sulfate 7.5 g / L, 37% formalin 30 ml / L, and Rochelle salt 85 g / L for 15 minutes and then washed with water. As a result, a copper film having a thickness of 1 μm was formed on the fiber surface of the mesh plain fabric.
Next, it was immersed in an oxidation treatment solution at 80 ° C. containing 10% sodium chlorite and 3% sodium hydroxide for 5 minutes and then washed with water. Thereby, a black copper oxide film was formed.

[Example 5]
The metal-coated plain weave obtained in Example 4 was treated in the same manner as in Example 2, and a fluorine-containing compound film was laminated on top of the metal film.

[Comparative Example 1]
Both the warp and weft are made of polyethylene terephthalate monofilament yarn with a diameter of 35μm (fineness 13dtex), and both the warp density and weft density are 300 yarns / inch (per hole formed between the yarns). of the area 2401μm ^2), was heat-treated at 190 ° C. (preset).
Next, it dye | stained for 30 minutes at 130 degreeC using the dyeing liquid containing 5% (vs. fiber weight) of Miketon Polyester Black PBSF u / c (black disperse dye, the Daistar Japan KK make). Subsequently, after reducing and washing by a conventional method, it was washed with water.

  For the samples obtained in the above examples and comparative examples, the results of (1) surface conductivity, (2) electromagnetic wave shielding, (3) acoustic braking, (4) water repellency, (5) quality were evaluated. It is shown in Table 1 together with the area per hole formed between the yarns (which is an index of dust resistance).

Claims (4)

  An acoustic braking cloth characterized in that a metal coating is formed on a fiber surface of a mesh-like woven fabric composed of synthetic fiber filament yarns.   2. The acoustic braking according to claim 1, wherein the diameter of the synthetic fiber filament yarn constituting the mesh fabric is 20 to 500 [mu] m, and the warp density and the weft density of the mesh fabric is 50 to 500 yarns / inch. cloth.   The acoustic braking cloth according to claim 1 or 2, wherein the outermost surface of the metal coating is black. The acoustic braking cloth according to any one of claims 1 to 3, wherein a low surface energy compound film is laminated on the metal film.