WATER-PROOF SOUND-TRANSMITTING MEMBRANE, METHOD FOR PRODUCING WATER-PROOF SOUND-TRANSMITTING MEMBRANE, AND ELECTRICAL APPLIANCE USING THE MEMBRANE

• US 20100206660A1
• Filed: 07/11/2008
• Published: 08/19/2010
• Est. Priority Date: 07/18/2007
• Status: Active Grant

• Current Assignee: Nitto Denko Corporation
• Original Assignee: Nitto Denko Corporation
• Inventors: Horie, Yuri, Furuuchi, Kouji
• Granted Patent: US 8,695,812 B2
• Time in Patent Office: Days
• US Class Current: 181/175
• CPC Class Codes: B29C 48/08 flexible, e.g. films
• CPC Class Codes: B29C 48/305 having a wide opening, e.g. for forming sheets
• CPC Class Codes: B29C 48/32 with annular openings, e.g. for forming tubular articles
• CPC Class Codes: B29C 55/005 characterised by the choice of materials
• CPC Class Codes: B29C 55/023 using multilayered plates or sheets
• CPC Class Codes: B29C 55/12 biaxial
• CPC Class Codes: B29C 55/18 by squeezing between surfaces, e.g. rollers
• CPC Class Codes: B29K 2027/18 PTFE, i.e. polytetrafluorethene , e.g. ePTFE, i.e. expanded polytetrafluorethene
• CPC Class Codes: B29K 2105/04 cellular or porous
• CPC Class Codes: B29K 2105/256 Sheets, plates, blanks or films
• CPC Class Codes: B29K 2105/258 Tubular
• CPC Class Codes: B29K 2995/0001 having particular acoustical properties
• CPC Class Codes: B29K 2995/0069 non-permeable
• CPC Class Codes: B29L 2031/755 Membranes, diaphragms
• CPC Class Codes: B32B 27/06 as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a layer of a particular substance B32B9/045; next to a bituminous or tarry layer B32B11/046; next to a water setting substance layer B32B13/12; next to a metal layer B32B15/08; next to a glass layer B32B17/10; next to a layer formed of natural mineral fibres or particles B32B19/045; next to a wood layer B32B21/08; next to a cellulosic plastic layer B32B23/08; next to a natural or synthetic rubber layer B32B25/08
• CPC Class Codes: B32B 27/08 of synthetic resin
• CPC Class Codes: B32B 27/30 comprising vinyl (co)polymers; comprising acrylic (co)polymers
• CPC Class Codes: B32B 5/32 at least two layers being foamed and next to each other
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 5/2237 containing fluorine

Abstract

A water-proof sound-transmitting membrane 10 includes a polytetrafluoroethylene porous membrane 1 and has a surface density of 1 to 20 g/m². The polytetrafluoroethylene porous membrane 1 includes a first porous layer 1a, and a second porous layer 1b stacked on and integrated with the first porous layer 1a by a binding force acting between polytetrafluoroethylene matrices.

Claims

1. A water-proof sound-transmitting membrane comprising a polytetrafluoroethylene porous membrane,

wherein the polytetrafluoroethylene 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 polytetrafluoroethylene matrices, and

the water-proof sound-transmitting membrane has a surface density of 1 to 20 g/m².

2. The water-proof sound-transmitting membrane according to claim 1,

wherein the first porous layer and the second porous layer each are stretched biaxially, and

stretching ratios at which the first porous layer is stretched are the same as stretching ratios at which the second porous layer is stretched.

3. The waterproof sound-transmitting membrane according to claim 2, wherein the first porous layer is stretched in stretching directions conforming to those of the second porous layer, respectively, and the stretching ratios at which the first porous layer is stretched are the same, with respect to the respective stretching directions, as the stretching ratios at which the second porous layer is stretched.

4. The water-proof sound-transmitting membrane according to claim 1,

wherein the first porous layer and the second porous layer have an average pore size of 1 μ

m or less, respectively, and

the surface density of the water-proof sound-transmitting membrane is 10 g/m² or less.

5. The waterproof sound-transmitting membrane according to claim 1, further comprising a support body stacked on at least one selected from the first porous layer and the second porous layer.

8. An electrical appliance with a sound function, comprising at least one selected from a sound emitting part for outputting sound and a sound receiving part for inputting sound, and a water-proof sound-transmitting membrane for protecting the sound emitting part and/or the sound receiving part from water and dust,

wherein the water-proof sound-transmitting membrane according to claim 1 is used as the water-proof sound-transmitting membrane.

6. A method for producing a water-proof sound-transmitting membrane, comprising the steps of

extrusion-molding a paste containing a polytetrafluoroethylene fine powder and a processing aid;

stretching a sheet as a molded product of the paste or a sheet obtained by roll-pressing the molded product of the paste, in a first direction at a lower temperature than a melting point of polytetrafluoroethylene;

stacking a plurality of the sheets;

stretching the stacked sheets in a second direction intersecting with the first direction at a lower temperature than the melting point of polytetrafluoroethylene; and

firing the stacked sheets at a temperature equal to or higher than the melting point of polytetrafluoroethylene so that the stacked sheets are integrated with each other by a binding force acting between polytetrafluoroethylene matrices, the steps being performed in this order,

wherein stretching ratios at which the sheets are stretched in the first direction and the second direction are adjusted so that the water-proof sound-transmitting membrane has a surface density of 1 to 20 g/m².

7. A method for producing a water-proof sound-transmitting membrane, comprising the steps of

extrusion-molding a paste containing a polytetrafluoroethylene fine powder and a processing aid;

stretching biaxially a sheet as a molded product of the paste or a sheet obtained by roll-pressing the molded product of the paste, at a lower temperature than a melting point of polytetrafluoroethylene;

stacking a plurality of the sheets; and

firing the stacked sheets at a temperature equal to or higher than the melting point of polytetrafluoroethylene so that the stacked sheets are integrated with each other by a binding force acting between polytetrafluoroethylene matrices, the steps being performed in this order,

wherein stretching ratios of the sheets are adjusted so that the water-proof sound-transmitting membrane has a surface density of 1 to 20 g/m².