JPH0341182A - Water-proof sound-permeable material - Google Patents

Abstract

PURPOSE:To prepare a sheet excellent not only in the sound permeability but also in the waterproofness by specifying both the value of aerial transmission and that of resistance to water pressure of a sheet material wherein a great number of continuous micropores are dispersed. CONSTITUTION:A microporous polymer sheet, which is obtd. by stretching, etching, interfacial polymerization, etc., and in which a great number of continuous micropores are dispersed, is made to have an aerial transmission (measured by Frazil tester) and resistance to water pressure of 0.1cc/cm<2>.sec or higher and 30cm aq. or higher, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a waterproof sound-permeable material used for protecting the sound oscillator of a watch, the speaker of a cordless telephone, a microphone, etc.

[Conventional technology and its problems]

Wristwatches are often exposed to water during use, and to protect their internal mechanisms, wristwatches have traditionally been backed with highly water-resistant rubber or polyethylene sheets.

By the way, recently there are many types of wristwatches that can be thrown away without replacing the batteries. In such watches,
In order to extend the life of the battery, the sound oscillator is designed to oscillate with low power consumption, and an important issue is to make the sound audible to the outside even if the sound pressure is low. However, since the rubber gaskets and the like conventionally used do not have sound permeability, it is not preferable to apply them as they are to wristwatches with low sound pressure as described above.

Therefore, a sheet-like material made of a non-woven fabric with excellent sound permeability and a water-repellent surface is sometimes used as a protective material, but the above-mentioned non-woven fabric is not optimal because it is inferior in waterproofness no matter how much water-repellent treatment is applied. do not have. Therefore, it is desired to develop a new protective material that has both sound permeability and water resistance.

In addition, some of the cordless phones that are now on the market have radio wave reception ranges of nearly 300 meters, and can be used not only indoors but also outdoors, so some speakers and microphones need to be water resistant. It's coming. Therefore, as in the case of the above-mentioned wristwatch, there is a desire to develop a new protective material that has both sound permeability and water resistance.

The present invention was made in view of the above circumstances, and an object thereof is to provide a waterproof sound-permeable material that has both sound-permeability and water resistance.

[Means for solving problems]

In order to achieve the above object, the waterproof sound-permeable material of the present invention has the following features:
A sheet-like body in which a large number of fine holes are dispersed, and the air permeability measured by a Frazier type tester is 0.1.
cc/cl, seconds or more, and water pressure resistance is 30cma
The configuration is such that it is set to q or more.

[Effect]

In other words, the present inventors recognized that it is impossible to overturn the fact that protective materials with good sound permeability have high air permeability, which means that they are inferior in water resistance. If so, we carefully considered whether it would have good sound permeability in practical terms and be waterproof enough to withstand normal use. As a result, when the airflow rate is 0゜lcc/c+fl・sec or more, the waterproofness is 3.
The present invention was achieved by finding that a sheet-like membrane with fine perforations of 0 cmaq or more has no problem in normal use with respect to both sound permeability and water resistance.

Next, this invention will be explained in detail.

The waterproof sound-permeable material of the present invention is a sheet-like body in which a large number of fine holes are dispersed. As such a sheet-like body,
A porous polymer membrane (film) obtained by a known method such as a stretching method, an etching method, or an interfacial polymerization method is suitable. Examples of such porous polymer membranes include polytetrafluoroethylene and ultra-high density polyethylene porous membranes.

However, these membranes have a ventilation rate of 0.1 cc/c
It is necessary that it is rM·sec or more. These conditions were obtained by the inventors from the following experiment. That is, first, as shown in Fig. 1, in a noisy room comparable to a 23°C1 office room, place the volume measuring device 2 at 3CI11 from the oscillation source 1 with a volume of 80 dB, and place it 1 cm from the oscillation source 1. The sound pressure was measured by stretching the sample membrane 3 to be measured.

Furthermore, the sound quality was evaluated by human ears at a distance of 59 cm from the oscillation source 1. And set the frequency to 20
The sound pressure was measured using the sound volume measuring device 2 while changing the frequency between 20,000 Hz and 20,000 Hz, and the sound quality was also evaluated in the practical range of 00 to 15,001 (z). It was found that as the volume increases, the sound pressure decreases, and the crackling and muffled sound also decrease.Especially, when the volume increases to 3D, the sound pressure decreases.
It was found that when the frequency is below B, cracking and muffled sounds occur, making it difficult to hear, and it is difficult to distinguish between sounds between 700 and 1500 Hz. When this 3 dB boundary is converted into air flow rate, it is approximately 0.1 cc/ctM·sec (measured with a Frazier type tester). Therefore, the ventilation amount is O, l
It was found that a film of cc/cl·sec has practical compatibility. In addition, the above pulse oscillation sound is 700~
It is divided into 12 stages at 1500 Hz, and this oscillation sound ranges from 0 to 9. It is designed to identify * and #.

Further, the above-mentioned membrane also needs to have a water pressure resistance of 30 cmaq or more. These conditions were also obtained through the following experiment independently conducted by the present inventors. That is, first, the water pressure resistance of the sample membrane was measured using method A of JISL 1092, and this membrane was placed and fixed on the surface of a predetermined block, and then water droplets were dropped on it to determine whether or not the water droplets had penetrated into the membrane. Observed. The results are shown in Table 1 below.

From the above results, it was found that if the water pressure resistance is 30 cmaq or more, water droplets on the membrane surface do not penetrate into the membrane, and the membrane has practical water resistance.

Note that the thickness of the membrane material used in this invention is preferably 1 mm or less. That is, if the film thickness exceeds one plate, the sound quality heard through the film tends to deteriorate.

Next, Examples will be explained together with Comparative Examples [Examples 1 to 5, Comparative Examples 1.2] As shown in Table 2 below, polytetrafluoroethylene membranes with different pore sizes (manufactured by Nitto Denko Corporation) were used. was prepared, and the suitability of the conductive membrane as a waterproof sound-permeable material was evaluated according to the method described above. The results are shown in Table 2 below.

(Left below) [Examples 6 to 10, Comparative Examples 3 and 4] As shown in Table 3 below, ultra-high molecular weight polyethylene porous membrane water-repellent products with different thicknesses (Bresslon) were used.

(manufactured by Nitto Denko Corporation) was prepared, and the suitability of the conductive membrane as a waterproof sound-permeable material was evaluated according to the method described above. The results are shown in Table 3 below.

(Left below) [Comparative Examples 5 to 11] As shown in Table 4 below, non-woven water-repellent products made of various materials (
(manufactured by Nippon Hylene Co., Ltd.) was prepared, and the suitability of the conductive membrane as a waterproof sound-permeable material was evaluated according to the method described above. The results are shown in Table 4 below.

(Left below) [Example 11.12, Comparative Example 12] As a practical test of waterproofness, three commercially available digital clocks with DTMF signal emitting speakers were prepared, and the following three types of membrane materials were used in the transmitting part. Each was equipped with 7r.

Ratio IH+'l 12 Product: Non-woven fabric D S 40 S
ta water products (Nippon Vilene Inc.!!!!) Example 11 product Nibrethron ultra-high molecular weight polyethylene porous membrane (thickness 60 μm) 1B crystal (manufactured by Nitto Denko Corporation) Example 12 product: NTF membrane (thickness 30 μm) (Nitto Denko Corporation) Then, as shown in FIG. 2, the digital clock 12 was fixed in a space 30 cm away from the shower spout lO and 20 cm away from the wall 11 with the speaker part 12a facing the wall 11 side. 1 °C water at a rate of 2.21/min
The presence or absence of water infiltration into the transmitting part was examined by applying the test for 0 minutes. In addition, a wash bowl with a depth of about 22 C11 is
The watch was filled with water at a temperature of .degree. C., and the watch was submerged in the water and left for 24 hours.The watch was then pulled out and examined to see if water had penetrated into the inside. These results are shown in Table 5 below.

In addition, as a result of attaching the above comparative example words and example words to some commercially available telephone speakers and conducting the same test as above,
The comparative example word had water intrusion, and the example word had no water intrusion.

[Effects of the Invention] As described above, the waterproof sound-permeable material of the present invention has good practical sound permeability and waterproofness that can withstand normal use, so it can be used in watches, cordless telephones, etc. When used as an internal protection material, it can prevent water from entering the interior without impairing the proper sound function.

[Brief explanation of drawings]

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

Claims (2)

[Claims] (1) A sheet-like material in which a large number of fine pores are dispersed, and the air permeability measured by a Frazier type tester is 0.
．． 1cc/cm^2・sec or more, and water pressure resistance is 30cm
A waterproof sound-permeable material characterized by having a setting of aq or higher. (2) The waterproof sound-permeable material according to claim (1), wherein the sheet-like body has a practical thickness of 1 mm or less.