Nitto-denko Corporation

Kousei Takiishi

Kouji Furuuchi

Yuuichi Abe

Masaaki Mori

Yuri Horie

Yuichi Abe

A waterproof sound-transmitting membrane () includes a sound-transmitting region () having a porous polytetrafluoroethylene (PTFE) membrane (). The porous PTFE membrane () has a through-thickness air permeability of 2 cm/cm/s or more. Thus, it is possible to provide a waterproof sound-transmitting membrane that is suitable for reducing crackling noise while ensuring waterproofness required for at least daily use. The porous PTFE membrane () has a water entry pressure of 3 kPa or more, preferably 20 kPa or more and 50 kPa or less. The waterproof sound-transmitting membrane () may include an edge region () having an adhesive layer ().

Waterproof sound-transmitting membrane and waterproof sound-transmitting structure using the same

The present invention provides a sound-transmitting membrane for a microphone, to be disposed to a sound-collecting opening of the microphone so as to allow sound to transmit through the membrane while preventing a foreign matter from entering into the microphone through the opening. This membrane for a microphone prevents the entry of a foreign matter, such as fine dust and water vapor, that is difficult for conventional sound-transmitting membranes to block, and ensures the microphone performance. This membrane for a microphone is composed of a nonporous film or a multilayer membrane including a nonporous film, has a surface density of 30 g/mor less, and has a sound transmission loss of less than 3 dB in a frequency range of 300 to 4000 Hz.

Sound-transmitting membrane for microphone, sound-transmitting membrane member for microphone provided with the membrane, microphone, and electronic device provided with microphone

The present invention provides a water-proof sound-transmitting membrane including a polytetrafluoroethylene (PTFE) porous membrane, in which the waterproofness is enhanced further with little lowering of the sound transmittance. The water-proof sound-transmitting membrane includes the PTFE porous membrane. The PTFE porous membrane includes a first porous layer, and a second porous layer stacked on and integrated with the first porous layer by a binding force acting between PTFE matrices. The first porous layer and the second porous layer each are composed of PTFE with a number-average molecular weight of 5.0&#xd7;10or more determined by a standard specific gravity method. At least one layer selected from the first porous layer and the second porous layer has an average pore diameter of 1 &#x3bc;m or less. The water-proof sound-transmitting membrane has a surface density of 1 g/mto 10 g/m.

Water-proof sound-transmitting membrane, method for producing the water-proof sound-transmitting membrane, and electrical appliance including the water-proof sound-transmitting membrane

First, a mixture of a polytetrafluoroethylene fine powder and a liquid lubricant into a sheet-form body extending in a first direction. Next, the liquid lubricant is removed from the sheet-form body. Then, the sheet-form body is stretched by a factor of 40 to 250 in the longitudinal direction at a temperature equal to or higher than a melting point of polytetrafluoroethylene, and the stretched sheet-form body is further stretched by a factor of 3 to 40 in the width direction. Thus, a highly air-permeable porous polytetrafluoroethylene membrane is obtained.

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Osaka, Japan

Kousei Takiishi