JP2815618B2 - Waterproof sound-permeable material - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waterproof sound-permeable material used for protecting a sound oscillating portion of a watch, a speaker of a cordless telephone, a microphone, and the like.

[Related Art and Problems Thereof] Wristwatches are often exposed to water during use, and packing with rubber or polyethylene sheets having excellent water resistance has been conventionally performed to protect the internal mechanism.

By the way, recently, there are many wristwatches that are disposable without replacing batteries. In such a wristwatch, the sound oscillating section oscillates with low power consumption in order to maintain the life of the battery, and it is important that the sound can be easily heard outside even when the sound pressure is low. Will be an issue. However, since the rubber packing and the like conventionally used do not have sound permeability, it is not preferable to apply them as they are to a wristwatch having a small sound pressure as described above.
Therefore, a sheet-like body obtained by performing surface water repellency on a nonwoven fabric having excellent sound permeability may be used as a protective material. However, the above nonwoven fabric is inferior in waterproofness, no matter how much water repellency is applied. Absent. Therefore, development of a new protective material having both sound permeability and water resistance is desired.

Also, in recent cordless phones,
Some telephone reception ranges are close to 300 m, and not only indoor use but also outdoor use are considered. Therefore, water resistance is required for the speaker unit and the microphone unit. Therefore, as in the case of the wristwatch, development of a new protective material having both sound permeability and water resistance is desired.

The present invention has been made in view of such circumstances,
An object of the present invention is to provide a waterproof sound-permeable material having both sound permeability and water resistance.

[Means for solving the problem]

In order to achieve the above object, the waterproof sound-permeable material of the present invention is a sheet made of a polytetrafluoroethylene film or an ultra-high-molecular-weight polyethylene film having a large number of fine pores dispersed therein. in O aeration amount of connexion measured 0.1 cc / cm ² · sec or more, and water pressure resistance 30c
It has a configuration that is set to m aq or more.

[Action]

In other words, the present inventors have recognized that the better the sound-permeable protective material is, the higher the air permeability, that is, the fact that it is inferior in water resistance is irreversible. If so, we conducted a thorough study to determine whether or not it had good sound permeability in practical use and also had waterproofness that could withstand normal use. As a result, the water pressure in the aeration amount is 0.1 cc / cm ² · sec or more is more than 30 cm aq, if polytetrafluoroethylene membrane or ultra high molecular weight composed of polyethylene film fine holes with sheet product sound permeability and The present inventors have found that there is no problem in normal use in any of the water resistance, and reached the present invention.

 Next, the present invention will be described in detail.

The waterproof sound-permeable material of the present invention is a sheet-like body in which a large number of fine through holes are dispersedly formed. Such a sheet-like body is a porous polymer film (film) obtained by a known method such as a stretching method, an etching method, or an interfacial polymerization method, and is made of polytetrafluoroethylene or ultra-high molecular weight polyethylene. Things are used.

However, these membranes need to have a ventilation rate of 0.1 cc / cm ² · second or more. This condition, the present inventors,
It was obtained from the following experiment. That is, first, in a noise room at about 23 ° C. and in an office room, as shown in FIG. 1, the sound volume measuring device 2 is placed at a position 3 cm from the oscillation source 1 having a volume of 80 dB, and the measurement is made at a position 1 cm from the oscillation source 1. The target sample film 3 was stretched, and the sound pressure was measured. The sound quality was evaluated by a human ear at a distance of 59 cm from the oscillation source 1. And the frequency is 20 ~
The sound pressure was measured with the sound volume meter 2 while varying between 20,000 Hz, and the sound quality was also evaluated especially in the practical range of 700 to 1500 Hz. As a result, it was found that the sound pressure was reduced when the amount of gas flow through the sample film 3 was increased, and that cracks and muffled sounds were reduced. In particular, it was found that when the volume was less than 3 dB, the sound was cracked or muffled, making it difficult to hear, and it was difficult to distinguish the difference between 700 and 1500 Hz. When this 3 dB boundary is converted into a ventilation volume, it is approximately 0.1 cc / cm ² · second (measured with a Frazier-type testing machine). Therefore, the ventilation rate is 0.1c
It was found that a film having a c / cm ² · sec has practical sound permeability. Note that the above pulse oscillation sound is 1 at 700 to 1500 Hz.
It is divided into two stages, and this oscillation sound identifies 0-9, *, and #.

Further, it is necessary that the film has a water pressure resistance of 30 cm aq or more. This condition was also obtained by the following experiments independently performed by the present inventors. That is, first, the water pressure resistance of a sample film is measured by the method A of JISL 1092, the film is fixed on a predetermined block surface, and a water droplet is dropped on the film to allow the water droplet to penetrate into the film. The presence or absence was observed. The results are shown in Table 1 below.

From the above results, it was found that if the water pressure was 30 cm aq or more, water droplets on the film surface did not penetrate into the inside, and the film had practical water resistance.

The thickness of the film material used in the present invention is preferably 1 mm or less. That is, when the film thickness exceeds 1 mm, the sound quality heard through the film tends to be deteriorated.

 Next, examples will be described together with comparative examples.

[Examples 1 to 5 and Comparative Examples 1 and 2] As shown in Table 2 below, polytetrafluoroethylene membranes (manufactured by Nitto Denko Corporation) having different pore diameters were prepared, and each membrane was used as a waterproof sound-permeable material. Suitability was evaluated according to the method described above. The results are shown in Table 2 below.

[Examples 6 to 10, Comparative Examples 3 and 4] As shown in Table 3 below, water-repellent products of ultra-high molecular weight polyethylene porous membranes (Breslon, manufactured by Nitto Denko Corporation) having different thicknesses were prepared. The suitability as a waterproof sound-permeable material was evaluated according to the method described above. The results are shown in Table 3 below.

[Comparative Examples 5 to 11] As shown in Table 4 below, nonwoven water-repellent products of various materials (manufactured by Nippon Vilene Co., Ltd.) were prepared, and the suitability of each membrane as a waterproof sound-permeable material was determined by the method described above. Therefore, it was evaluated. The results are shown in Table 4 below.

[Examples 11 and 12 and Comparative Example 12] As a practical test of waterproofness, three digital clocks having commercially available DTMF signal transmission speakers were prepared, and the transmission section thereof was provided with:
The following three types of film materials were respectively mounted.

Comparative Example 12: Non-woven fabric DS-40S water repellent product (manufactured by Nippon Vilene Co., Ltd.) Example 11 product: Breslon ultra high molecular weight polyethylene porous membrane (thickness: 60 μm) Water repellent product (manufactured by Nitto Denko Corporation) Example 12 product: NTF membrane (Thickness: 30 μm) (manufactured by Nitto Denko Corporation) Then, as shown in FIG.
Digital clock 12 above in a space 30 cm, 20 cm away from wall 11
With the speaker part 12a facing the wall 11 side 2
By applying 0 ° C water at a rate of 2.2 / min for 10 minutes,
The presence or absence of water permeation into the transmitting part was examined. In addition, about 22 depth
A wash bowl of 20 cm was filled with water at 20 ° C., and the watch was immersed therein and allowed to stand for 24 hours. Then, the watch was pulled up to check whether or not water had penetrated into the inside. The results are shown in Table 5 below.

In addition, the above comparative example product and the example product were attached to a commercially available telephone speaker unit, and a test similar to the above was performed. As a result, water infiltration occurred in the comparative example product, and no water entered the example product. Was.

〔The invention's effect〕

As described above, the waterproof sound-permeable material of the present invention has a ventilation rate of 0.
1 cc / cm ² seconds or more, water resistance is 30 cm aq or more, because it is a sheet-like body with fine pores formed of polytetrafluoroethylene film or ultra-high molecular weight polyethylene film,
It has good sound permeability in practical use and has waterproofness that can withstand normal use. Therefore, when used as an internal protective material for a watch or a cordless telephone, it is possible to prevent water or the like from entering the inside without impairing the sound-passing function.

[Brief description of the drawings]

FIG. 1 is an explanatory view of a method for measuring the sound permeability of a membrane, and FIG. 2 is an explanatory view of a method for measuring the waterproofness of the membrane. 3 .... sample film

Continuation of the front page (58) Fields investigated (Int. Cl. ⁶ , DB name) C09K 3/18 C08J 9/00 N04R 1/00 N04B 7/26 H05K 5/02-5/03 WPI / L (QUESTEL)

Claims (2)

(57) [Claims] 1. A sheet made of a polytetrafluoroethylene film or an ultra-high molecular weight polyethylene film in which a large number of fine pores are dispersed and formed, and the air flow rate measured by a Frazier type testing machine is 0.1 cc / cm. cm ² at-seconds, and waterproof sound material the water pressure, characterized in that it is set to at least 30 cm aq. 2. The waterproof sound-permeable material according to claim 1, wherein the sheet-like body has a practical thickness of 1 mm or less.