Abstract:
Provided is a waterproof sound-permitting sheet, including: a porous substrate having a plurality of pores; and a porous nanoweb, which is stacked on the porous substrate, has a plurality of pores, and is formed by electrospinning a polymer material to which a black or a different color pigment is added, thereby improving waterproofing performance and sound penetration performance by forming on a porous substrate, such as non-woven fabric, the porous web having the black or the different color by using the electrospinning method, and can shorten a production process by eliminating a pigment coating step by means of adding the pigment to the polymer material when manufacturing the porous nanoweb according to the electrospinning method.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part application of PCT Application No. PCT/KR2013/004062, filed on May 9, 2013, which claims priority to and the benefit of Korean Application Nos. 10-2012-0053143 filed on May 18, 2012 and 10-2013-0051383 filed on May 7, 2013, the entire contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a technology that is provided for sound holes or air vents of a speaker or microphone of an electronic device so that sound and air is passed but water is blocked, and more particularly, to a waterproof sound-permitting sheet that is produced by an electrospinning method, a manufacturing method thereof, and an electronic device provided with the waterproof sound-permitting sheet. 
       BACKGROUND ART 
       [0003]    Recently, since it is easy to carry and use portable electronic devices, the use of the portable electronic devices is increasing day by day. These portable electronic devices such as portable terminals, digital cameras, or notebook computers may be required to have a waterproof function due to they are carried and used with the portability. However, sound holes are formed to emit sound at a portion where a speaker or microphone is installed, and accordingly water and dust are penetrated into an electronic device through the sound holes. 
         [0004]    Thus, a waterproof sound-permitting sheet is provided in the sound holes to pass the sound but to block water or dust. For water resistance of the waterproof sound-permitting sheet, it is advantageous to reduce an average diameter of fine holes, and for sound-permittivity of the waterproof sound-permitting sheet, it is advantageous to enlarge the size of the fine holes. Therefore, it is important to maintain the average diameter of the fine holes as appropriate so as to satisfy two conditions such as the sound-permittivity and the waterproof. 
         [0005]    As disclosed in Korean Patent Application Publication No. 10-2010-0041839 (published on Apr. 22, 2010), a conventional waterproof sound-permitting film includes a polytetrafluoroethylene porous film, in which the polytetrafluoroethylene porous film includes: a first porous layer; and a second porous layer stacked on and integrated with the first porous layer based on a settlement force acting between a matrix of polytetrafluoroethylene, surface density of the waterproof sound-permitting film is 1 to 20g/m2, the first porous layer and the second porous layer are biaxially oriented, and a draw ratio of the first porous layer is equal to that of the second porous layer. 
         [0006]    Such a waterproof sound-permitting film is configured to have a double layer structure formed of the first porous layer and the second porous layer, to thereby improve the waterproof performance However, since the conventional waterproof sound-permitting film is formed of only a polytetrafluoroethylene porous film, fine holes of the porous film will increase gradually in size due to the pressure of the shock or sound externally applied due to the long use, and thus there is a problem that waterproof performance is reduced. 
       SUMMARY OF THE INVENTION 
       [0007]    To solve the above problems or defects, it is an object of the present invention to provide a waterproof sound-permitting sheet that is produced by an electrospinning method to thus have a plurality of pores in a nanoweb form, a manufacturing method thereof, and an electronic device provided with the waterproof sound-permitting sheet. 
         [0008]    In addition, it is another object of the present invention to provide a waterproof sound-permitting sheet, a manufacturing method thereof, and an electronic device provided with the waterproof sound-permitting sheet, in which a pigment is added in a polymer material when a porous nanoweb is manufactured by an electrospinning method, to thereby delete an operation of coating the pigment, and to thus shorten a production process and improve waterproof performance and sound-permitting performance 
         [0009]    In addition, it is still another object of the present invention to provide a waterproof sound-permitting sheet, a manufacturing method thereof, and an electronic device provided with the waterproof sound-permitting sheet, in which a porous nanoweb is manufactured on a porous substrate by an electrospinning method, to thereby improve the sheet strength, and adjust the thickness of the nanoweb, the average diameter of the pores, and the number of pores, and to thus be applicable for various products. 
         [0010]    The technical problems to be solved in the present invention are not limited to the above-mentioned technical problems, and the other technical problems that are not mentioned in the present invention may be apparently understood by one of ordinary skill in the art in the technical field to which the present invention belongs. 
         [0011]    To accomplish the above and other objects of the present invention, according to an aspect of the present invention, there is provided a waterproof sound-permitting sheet comprising: a porous substrate having a plurality of pores; and a porous nanoweb, which is stacked on the porous substrate, has a plurality of pores, and is formed by electrospinning a polymer material to which a black or different color pigment is added. 
         [0012]    According to another aspect of the present invention, there is provided a method of manufacturing a waterproof sound-permitting sheet, the method comprising: supplying a porous substrate having a plurality of pores; and spinning a spinning solution to the porous substrate, thereby forming a porous nanoweb having a plurality of pores and having a black or different color. 
         [0013]    According to another aspect of the present invention, there is provided a method of manufacturing a waterproof sound-permitting sheet, the method comprising: supplying a porous substrate having a plurality of pores; spinning a spinning solution to one surface of the porous substrate, thereby forming a first nanoweb layer having a plurality of pores and having a black or different color; and spinning the spinning solution to the other surface of the porous substrate, thereby forming a second nanoweb layer having a plurality of pores and having the black or different color. 
         [0014]    According to another aspect of the present invention, there is provided a method of manufacturing a waterproof sound-permitting sheet, the method comprising: supplying a first porous substrate having a plurality of pores; spinning a spinning solution to one surface of the first porous substrate, thereby forming a porous nanoweb having a plurality of pores and having a black or different color; and stacking a second porous substrate having a plurality of pores on the other surface of the porous nanoweb. 
         [0015]    As described above, the waterproof sound-permitting sheet according to the present invention is configured by forming a porous nanoweb having a black or different color on a porous substrate such as a nonwoven fabric by a spinning method, thereby having advantages of improving strength of the waterproof sound-permitting sheet, and improving the waterproof performance and the sound-permitting performance. 
         [0016]    In addition, the waterproof sound-permitting sheet according to the present invention is configured by forming a porous nanoweb by an electrospinning method, thereby having advantages of adjusting the thickness of the nanoweb, an average diameter of pores, and the number of pores and being applied to a wide range of products. 
         [0017]    Further, the waterproof sound-permitting sheet according to the present invention is configured by adding a pigment to a polymer material when manufacturing a porous nanoweb on a nonwoven fabric by an electrospinning method, to thereby delete an operation of coating the pigment, to thus shorten a production process, and to improve the waterproof performance and the sound-permitting performance. 
     
    
     
       DESCRIPTION OF DRAWINGS 
         [0018]      FIG. 1  is a cross-sectional view of a waterproof sound-permitting sheet according to a first embodiment of the present invention. 
           [0019]      FIG. 2  is an enlarged close-up photograph of a waterproof sound-permitting sheet according to the first embodiment of the present invention. 
           [0020]      FIG. 3  is a configuration diagram of an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the first embodiment of the present invention. 
           [0021]      FIG. 4  is a cross-sectional view of a waterproof sound-permitting sheet according to a second embodiment of the present invention. 
           [0022]      FIG. 5  is a configuration diagram of an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the second embodiment of the present invention. 
           [0023]      FIG. 6  is a cross-sectional view of a waterproof sound-permitting sheet according to a third embodiment of the present invention. 
           [0024]      FIG. 7  is a configuration diagram of an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the third embodiment of the present invention. 
           [0025]      FIG. 8  is a cross-sectional view of a waterproof sound-permitting sheet according to a fourth embodiment of the present invention. 
           [0026]      FIG. 9  is a cross-sectional view of a double-sided adhesive tape applied to a waterproof sound-permitting sheet of the present invention. 
           [0027]      FIG. 10  is a partial sectional view of an electronic device to which a waterproof sound-permitting sheet according to the present invention is applied. 
           [0028]      FIG. 11  is an enlarged view of essential elements of  FIG. 10 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0029]    Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. Here, the size or shape of the components illustrated in the drawings may be shown to be exaggerated for convenience and clarity of illustration. In addition, specifically defined terms may be changed according to the intention or practices of users or operators in consideration of the construction and operation of the present invention. The definition of the terms should be made based on contents throughout the present specification. 
         [0030]    As shown in  FIGS. 1 and 2 , a waterproof sound-permitting sheet according to a first embodiment of the present invention includes: a porous substrate  20  having a plurality of pores; and a porous nanoweb  10 , which is stacked on one surface of the porous substrate  20 , has a plurality of pores, and is formed by electrospinning a polymer material to which a black or different color pigment is added. 
         [0031]    Any one of a thermal bond nonwoven fabric, a spun bond nonwoven fabric, a chemical bond nonwoven fabric, an air-laid nonwoven fabric, and a mixture thereof may be used as the porous substrate  20 . Further, a cloth, styrofoam, paper, or a mesh that has pores may be used as the porous substrate  20 , in addition to the nonwoven fabric. 
         [0032]    The porous substrate  20  may have a black or different color, and a method of coating the pigment may employ gravure printing, coating, and may also employ a dope-dye scheme. 
         [0033]    The porous nanoweb  10  is formed into a shape having a plurality of pores  12 , by making ultra-fine fiber strands  14  by electrospinning the polymer material to which the black or different color pigment is added, and accumulating the ultra-fine fiber strands. 
         [0034]    The polymer material used to make the porous nanoweb  10  in the present invention may be a resin that may be dissolved in an organic solvent for electrospinning, and that may be capable of forming nanofibers by electrospinning, but are not specifically limited thereto. 
         [0035]    For example, the polymer materials used in the present invention may be: polyvinylidene fluoride (PVdF), poly(vinylidene fluoride-co-hexafluoropropylene), a perfluoropolymer, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof; a polyethylene glycol derivative containing polyethylene glycol dialkylether and polyethylene glycol dialkylester; poly(oxymethylene-oligo-oxyethylene); polyoxide containing polyethylene oxide and polypropylene oxide; polyvinyl acetate, poly(vinyl pyrrolidone-vinyl acetate), polystyrene, and a polystyrene acrylonitrile copolymer; a polyacrylonitrile copolymer containing polyacrylonitrile (PAN) and a polyacrylonitrile methyl methacrylate copolymer; or polymethyl methacrylate, a poly methyl methacrylate copolymer, or a mixture thereof 
         [0036]    Further, the polymer material used in the present invention may be: aromatic polyester such as polyamide, polyimide, polyamideimide, poly(meta-phenylene isophthal amide), polyester sulfone (PES), polyether ketone, polyetherimide (PEI), polyethylene terephthalate, polytrimethylene terephthalate, or polyethylene naphthalate; polyphosphazene such as polytetrafluoroethylene, polydifenoxiphosphazene, or poly{bis[2-(2-methoxyethoxy) phosphazene]}; polyurethane, and polyurethane copolymer containing polyether urethane; or cellulose acetate, cellulose acetate butyrate, or cellulose acetate propionate. 
         [0037]    The polymer material that may be particularly desirably used to make a porous nanoweb according to the present invention may be polyacrylonitrile (PAN), polyvinylidene fluoride (PVdF), polyester sulfone (PES), and polystyrene (PS), alone or a mixture of polyvinylidene fluoride (PVdF) and polyacrylonitrile (PAN), a mixture of PVdF and PES, or a mixture of PVdF and thermoplastic polyurethane (TPU). 
         [0038]    Thus, the polymer that may be used in the present embodiment is not particularly limited to thermoplastic and thermosetting polymers that may be air-electrospinnable. 
         [0039]    The solvent that may be used in the present embodiment may be any one of DMAc(N, N-Dimethyl acetoamide), DMF(N, N-Dimethylformamide), NMP(N-methyl-2-pyrrolidinone), DMSO (dimethyl sulfoxide), THF (tetra-hydrofuran), EC (ethylene carbonate), DEC (diethyl carbonate), DMC (dimethyl carbonate), EMC (ethyl methyl carbonate), PC (propylene carbonate), water, acetic acid, formic acid, chloroform, dichloromethane, and acetone or a mixture thereof. 
         [0040]    Since the porous nanoweb  10  is produced by an electrospinning method, the thickness of the porous nanoweb  10  is determined according to the dose of the electrospun polymer material. Thus, it is advantageously easy to make the thickness of the porous nanoweb  10  into a desired thickness. That is, if the dose of the electrospun polymer material is made less, the thickness of the porous nanoweb  10  may be made thin, and since the dose of the electrospun polymer material is little, the production cost can be reduced that much. 
         [0041]    Here, it is determined that the porous nanoweb  10  has the number of pores and an average diameter of pores, depending on the thickness of the porous nanoweb  10 . Accordingly, the thickness of the porous nanoweb  10  is made thicker in order to improve the waterproof performance, and the thickness of the porous nanoweb  10  is made thinner in order to improve the sound-permitting performance. 
         [0042]    Thus, a variety of different types of waterproof sound-permitting sheets whose waterproof and sound-permitting features vary according to functions and types of electronic devices can be made. 
         [0043]    The diameters of the fiber strands  14  are in the range of 0.3˜1.5 μm. Then, the average pore size is up to 1.5˜2 μm, and the minimum pore size is not limited. That is, the average pore size is preferably not more than 2 μm. 
         [0044]    In addition, since the ultra-fine fiber strands  14  are formed in the case of the porous nanoweb  10 , a myriad of irregular pores are formed, which is more effective in improving the waterproof performance and the sound-permitting performance at the same time. 
         [0045]    The pigments are used to prepare the waterproof sound-permitting sheet of black or another color, in which a variety of colors or tones can be implemented in accordance with the amount and the type of the applied pigment. 
         [0046]    In this embodiment, a pigment is added in the polymer material to then be electrospun. Accordingly, an operation of coating a pigment on the surface of the porous nanoweb can be removed, to thus provide an effect of reducing the manufacturing process, and to make the average diameter of pores precisely. 
         [0047]    Gravure printing, coating, etc., may be used as the existing method of applying a pigment on the surface of the porous nanoweb. When a pigment is coated in this way to thus implement a color, problems such as degradation of the air permeability and low color fastness may occur. In this embodiment, a pigment is added in the polymer material to thus prepare nanowebs. Accordingly, the fastness of the color can be inherently improved, the waterproof performance, the sound-permitting performance, and the air-permitting performance can be improved, and air permeability can be prevented from being lowered. 
         [0048]    Then, the waterproof sound-permitting sheet according to the present embodiment is oil-repellent finish treated on the surface thereof so as to further improve the waterproof performance. Here, the oil-repellent finish is formed by treating an organic fluorine compound on the surface of the porous nanoweb  10  or the surface of a porous substrate. Besides, in addition to the above oil-repellent finish treatment, various ways can be applied for the oil-repellent finish treatment. 
         [0049]    Then, the waterproof sound-permitting sheet according to the present embodiment can be used a waterproof air-permitting sheet that passes heat or air but blocks water or dirt. 
         [0050]    As shown in  FIG. 3 , an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the first embodiment of the present invention includes: a spinning solution tank  30  that stores a spinning solution that is formed by mixing a polymer material to which s black or different color pigment is added with a solvent; a plurality of spinnerets  34  that are connected to a high voltage generator and connected to the spinning solution tank  30 , to thus spin ultra-fine fiber strands  14 ; and a collector  36  on which the ultra-fine fiber strands  14  spun from the spinnerets  34  are accumulated to thereby produce a porous nanoweb  10 . 
         [0051]    The spinning solution tank  30  is provided with a stirrer  32  that mixes evenly the polymer material, the pigment, and the solvent, and that also prevents phase separation of the spinning solution  32 . 
         [0052]    A high voltage electrostatic force of 90˜120 Kv is applied between the collector  36  and the spinnerets  34 , and the ultra-fine fiber strands  14  are spun from the spinnerets  34 . Accordingly, the porous nanoweb  10  is formed on the collector  36 . 
         [0053]    The plurality of the spinnerets  34  are arranged at intervals along the traveling direction of the collector  36 , and also the plurality of the spinnerets  34  are arranged at intervals along a direction perpendicular to the traveling direction of the collector  36 , i.e., along the width direction of the collector  36 .  FIG. 3  shows that there are three spinnerets for convenience of explanation, which are arranged at intervals along the traveling direction of the collector  36 . 
         [0054]    For example, 30 to 60 or more of the spinnerets may be arranged along the travelling direction of the collector  36 , as necessary. In the case that a plurality of the spinnerets are used as described above, productivity can be enhanced by increasing the rotational speed of the collector  36 . 
         [0055]    An air injection device  38  is provided to each of the spinnerets  34 , to spray air to the fiber strands  14  that are spun from the spinnerets  34 , to thereby guide the fiber strands  14  to be collected toward the collector  36 . 
         [0056]    If a multi-hole spin pack having a number of holes is applied for mass production, mutual interference occurs between multiple holes, and thus fibers not collected while As a result, since the porous nanoweb  10  that is obtained by using the multi-hole spin pack become too bulky, it may be difficult to form the porous nanoweb  10  and may act as a cause of the trouble of the spin. 
         [0057]    Therefore, in the present embodiment to solve this problem, a multi-hole spin pack is used and an air injection device  38  is provided at each spinneret. Accordingly, when the fiber strands  14  are spun, air is injected so that the fiber strands  14  are well collected on the collector  36 . 
         [0058]    An air pressure of an air injection device of a multi-hole spin pack nozzle is set in the range of 0.1 to 0.6 Mpa. In this case, the air pressure that is less than 0.1 MPa does not contribute to a trapping/accumulation, and the air pressure that exceeds 0.6 Mpa hardens cone of the spin nozzle firmly to thus raise a phenomenon of blocking the needle thereby causing a spin trouble. 
         [0059]    The collector  36  may be configured to employ a conveyor for transporting nanowebs such that the ultra-fine fiber strands  14  spun from the plurality of spinnerets  34  are sequentially accumulated on the conveyor. 
         [0060]    A substrate roll  44  around which a porous substrate  20  is wound is provided in the front side of the collector  36  to supply the porous substrate  20  for the collector  36 , and a pressing roller  40  is provided in the rear of the collector  36 , in which the pressing roller  40  presses the nanoweb  10  fabricated by an electrospinning method to make the nanoweb  10  to a predetermined thickness. In addition, a nanoweb roll  42  is provided in which the porous nanoweb  10  pressed through the pressing roller  40  is wound on the nanoweb roll  42 . 
         [0061]    The process of manufacturing the waterproof sound-permitting sheet by using the electrospinning device will follow. When the collector  36  is driven, the porous substrate  20  is moved on the upper surface of the collector  36 . That is, the porous substrate  20  wound on the substrate roll  44  is unrolled to then be supplied to the collector  36 . 
         [0062]    In addition, a high voltage electrostatic force is applied between the collector  36  and the spinnerets  34 , and thus the polymer material to which the pigment is added is made into the ultra-fine fiber strands  14  to then be spun to the porous substrate. Then, the ultra-fine fiber strands  14  are accumulated on the porous substrate  20  to thus form a porous nanoweb  10  having a black or different color and having a plurality of pores  12 . 
         [0063]    Here, since air is sprayed on each of the spinnerets  34  from the air injection device  38 , the spun fiber strands are not trapped in the collector  36  but are prevented from blowing. 
         [0064]    In addition, while a composite sheet in which the porous nanoweb  10  is formed on the porous substrate  20  is made into a certain thickness while passing through the pressure roller  40 , and is wound around the nanoweb roll  42 . 
         [0065]    As shown in  FIG. 4 , a waterproof sound-permitting sheet according to a second embodiment of the present invention includes: a porous nanoweb  10  that has a plurality of pores and that is formed by electrospinning a polymer material to which a black or different color pigment is added; a first porous substrate  22  that has a plurality of pores and that is formed on one surface of the porous nanoweb  10 ; and a second porous substrate  24  that has a plurality of pores and that is formed on the other surface of the porous nanoweb  10 . 
         [0066]    The porous nanoweb  10  according to a second embodiment of the present invention has the same configuration as the porous nanoweb  10  according to the first embodiment of the present invention, and a configuration of the first porous substrate  22  and the second porous substrate  24  are the same as the configuration of the porous substrate  20  that is described in the first embodiment. 
         [0067]    The waterproof sound-permitting sheet according to the second embodiment is formed into a three-layer structure where the first porous substrate  22  and the second porous substrate  24  are stacked on both side surfaces of the porous nanoweb  10 , respectively, to thereby enhance the strength of the waterproof sound-permitting sheet. 
         [0068]    As shown in  FIG. 5 , an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the second embodiment of the present invention includes: a spinning solution tank  30  that stores a spinning solution that is formed by mixing a polymer material to which s black or different color pigment is added with a solvent; a plurality of spinnerets  34  that are connected to a high voltage generator and connected to the spinning solution tank  30 , to thus spin ultra-fine fiber strands  14 ; and a collector  36  on which the ultra-fine fiber strands  14  spun from the spinnerets  34  are accumulated to thereby produce a porous nanoweb  10 . 
         [0069]    The electrospinning apparatus according to the second embodiment is the same as the electrospinning apparatus described in the first embodiment, but a first substrate roll  45  around which a first porous substrate  22  is wound is arranged in front side of the collector  36 , and a second substrate roll  46  around which a second porous substrate  24  is wound is arranged in the rear side of the collector  36 . 
         [0070]    The process of manufacturing the waterproof sound-permitting sheet by using the electrospinning device according to the second embodiment will follow. When the collector  36  is driven, the first porous substrate  22  is moved on the upper surface of the collector  36 . 
         [0071]    In addition, a high voltage electrostatic force is applied between the collector  36  and the spinnerets  34 , and thus the polymer material to which the pigment is added is made into the ultra-fine fiber strands  14  to then be spun to the first porous substrate  22 . Then, the ultra-fine fiber strands  14  are accumulated on the first porous substrate  22  to thus form a porous nanoweb  10  having a black or different color and having a plurality of pores  12 . 
         [0072]    Here, since air is sprayed on each of the spinnerets  34  from the air injection device  38 , the spun fiber strands are not trapped in the collector  36  but are prevented from blowing. 
         [0073]    Then, the second porous substrate  24  wound on the second substrate roll  46  disposed in the rear side of the collector  36  is supplied to the rear side of the collector  36 , to thus make the second porous substrate  24  stacked on the other surface of the porous nanoweb  10 . 
         [0074]    In addition, the composite sheet of a laminated three-layer structure where the first porous substrate  22  and the second porous substrate  24  are stacked on both side surfaces of the porous nanoweb  10 , respectively, is made into a certain thickness while passing through the pressure roller  40 , and is wound around the nanoweb roll  42 . 
         [0075]    As shown in  FIG. 6 , a waterproof sound-permitting sheet according to a third embodiment of the present invention includes: a porous substrate  20  that has a plurality of pores; a first nanoweb layer  50  that is stacked on one surface of the porous substrate  20 , that has a plurality of pores, and that is formed by electrospinning a polymer material to which a black or different color pigment is added; and a second nanoweb layer  52  that is stacked on the other surface of the porous substrate  20 , that has a plurality of pores, and that is formed by electrospinning a polymer material to which a black or different color pigment is added. 
         [0076]    The porous substrate  20  according to the third embodiment is the same as the porous substrate  10  described in the first embodiment, and the first nanoweb layer  50  and the second nanoweb layer  52  are the same as the porous nanoweb  10  described in the first embodiment. 
         [0077]    The waterproof sound-permitting sheet according to the third embodiment is configured to have a three-layer structure where the first nanoweb layer  50  is stacked on one surface of the porous substrate  20  and the second nanoweb layer  52  is stacked on the other surface of the porous substrate  20 . 
         [0078]    As shown in  FIG. 7 , an electrospinning apparatus for producing a waterproof sound-permitting sheet according to the third embodiment of the present invention includes: a plurality of first spinnerets  60  that spin a spinning solution that is formed by mixing a polymer material to which s black or different color pigment is added with a solvent, to thus form the first nanoweb layer  50 ; a first collector  62  on which ultra-fine fiber strands spun from the first spinnerets  60  are accumulated; a plurality of second spinnerets  66  that are disposed at the lower side of the first collector  62  and that spin a spinning solution that is formed by mixing a polymer material to which s black or different color pigment is added with a solvent, to thus form the second nanoweb layer  52 ; and a second collector  68  on which ultra-fine fiber strands spun from the second spinnerets  66  are accumulated. 
         [0079]    Here, the first spinnerets  60  and the second spinnerets  66  are connected to a spinning solution tank (not shown) that contains a spinning solution that is formed by mixing a polymer material to which s black or different color pigment is added with a solvent. 
         [0080]    A substrate roll  64  around which a porous substrate  20  is wound is provided in the front side of a first collector  62  to thus supply the porous substrate for the first collector  62 , and a pressing roller  72  is provided in the rear side of a second collector  68  in which the pressing roller  72  presses the sheet of the three-layer structure prepared by the electrospinning method to then be made into a predetermined thickness while passing through the pressing roller  72  and to then be wound on a sheet roll  70 . 
         [0081]    The process of manufacturing the waterproof sound-permitting sheet by using the electrospinning device according to the third embodiment will follow. When the first collector  62  is driven, the porous substrate  20  is moved on the upper surface of the first collector  62 . 
         [0082]    In addition, a high voltage electrostatic force is applied between the first collector  62  and the first spinnerets  60 , and thus the polymer material to which the pigment is added is made into the ultra-fine fiber strands  14  in the first spinnerets  60 , to then be spun to one surface of the porous substrate  20 . Then, the ultra-fine fiber strands  14  are accumulated on one surface of the porous substrate  20  to thus form a first nanoweb layer  50  having a black or different color and having a plurality of pores  12 . 
         [0083]    Then, the porous substrate on which the first nanoweb layer  50  is formed is guided to the second collector  68 . Here, the other surface of the porous substrate is disposed facing up. Then, a high voltage electrostatic force is applied between the second collector  68  and the second spinnerets  66 , and thus the polymer material to which the pigment is added is made into the ultra-fine fiber strands  14  in the second spinnerets  66 , to then be spun to the other surface of the porous substrate  20 . Then, the ultra-fine fiber strands  14  are accumulated on the other surface of the porous substrate  20  to thus form a second nanoweb layer  52  having a black or different color and having a plurality of pores  12 . 
         [0084]    In addition, while a composite sheet in which the nanoweb layers are formed on both surfaces of the porous substrate is made into a certain thickness while passing through the pressure roller  72 , and is wound around the sheet roll  70 . 
         [0085]    As illustrated in  FIG. 8 , a waterproof sound-permitting sheet according to a fourth embodiment of the present invention, includes: a porous substrate  20  having a plurality of pores; a porous nanoweb  10  that is formed on one surface of the porous substrate, that has a plurality of pores, and that is formed by electrospinning a polymer material to which a black or different color pigment is added; and a double-sided adhesive tape  160  that is formed on one surface of the porous substrate  20  or the porous nanoweb  10 . 
         [0086]    Since the structure of the porous substrate  20  and the porous nanoweb  10  is the same as that of the porous nanoweb  10  described in the first embodiment, the detailed description thereof will be omitted. 
         [0087]    The double-sided adhesive tape  160  is formed along the edge of the porous nanoweb  10  or the porous substrate  20  and serves to attach the waterproof sound-permitting sheet on a portion of the sound holes of an electronic device. Here, the double-sided adhesive tape  160  may be configured to employ a non-substrate type or a substrate type, a conventional double-sided adhesive tape, or a double-sided adhesive tape that is formed by an electrospinning method. 
         [0088]    As shown in  FIG. 9 , the double-sided adhesive tape  160  which is formed by the electrospinning method includes: a substrate  162  that is formed into a nanoweb type having a plurality of pores by an electrospinning method; a first adhesive layer  164  that is formed into a nanoweb type by spinning an adhesive material on one surface of the substrate  162 ; and a second adhesive layer  166  that is formed into a nanoweb type by spinning the adhesive material on the other surface of the substrate  162 . 
         [0089]    Here, the substrate  162  is formed into a nanoweb type having a plurality of pores, in which a polymer material is made into ultra-fine fiber strands by an electrospinning method, and the ultra-fine fiber strands are accumulated on the substrate  162 . 
         [0090]    Then, the first adhesive layer  164  and the second adhesive layer  166  are formed by spinning the adhesive material on one surface and the other surface of the substrate  162 , respectively. Here, the adhesive material is introduced into the pores of the substrate  162 , to thus increase the amount of the adhesive in the pores. Thus, even if the double-sided adhesive tape  160  has the same thickness as the conventional double-sided adhesive tape, the amount of the adhesive is more than the conventional double-sided adhesive tape to thereby increase the adhesive force. 
         [0091]    The double-sided adhesive tape  160  can be integrally formed in the electrospinning apparatus for forming the porous nanoweb  10 , or can be prepared separately from another electrospinning apparatus to then be laminated on the other surface of the porous nanoweb. 
         [0092]      FIG. 10  is a partial sectional view of an electronic device to which a waterproof sound-permitting sheet according to the present invention is applied.  FIG. 11  is an enlarged view of essential elements of  FIG. 10 . 
         [0093]    The electronic device according to the present invention includes: a main body  110 ; a speaker  120  that is provided in the main body  110 , and through which a sound is discharged to the outside from the main body  110 ; and a microphone  130  that is provided in the main body  110 , and through which the sound is input to the main body  110 , wherein sound holes  140  and  150  through which the sound passes are formed at portions where the speaker  120  and the microphone  130  are mounted in the main body  110 . 
         [0094]    Then, the waterproof sound-permitting sheets  100  and  200  according to the invention are provided on the sound holes  140  and  150 , to thus block water or dust and pass the sound. Here, the waterproof sound-permitting sheets  100  and  200  may employ the waterproof sound-permitting sheets explained in the first to fourth embodiments described above. A ring-shaped double-sided adhesive tape  160  is mounted on the inner surface of the sound holes  140  and  150  to thus secure the waterproof sound-permitting sheets  100  and  200  on the inner surfaces of the sound holes  140  and  150 . 
         [0095]    The waterproof sound-permitting sheet according to the present embodiment, is installed on air vent holes through which the heat of the electronic device or air is passed, in addition to the sound holes  140  and  150 , and serves to pass air or heat but block water or dust. 
         [0096]    As described above, the present invention has been described with respect to particularly preferred embodiments. However, the present invention is not limited to the above embodiments, and it is possible for one who has an ordinary skill in the art to make various modifications and variations, without departing off the spirit of the present invention. Thus, the protective scope of the present invention is not defined within the detailed description thereof but is defined by the claims to be described later and the technical spirit of the present invention. 
         [0097]    The waterproof sound-permitting sheet according to the present invention is mounted in an electronic device to pass air or heat but block water or dust. The waterproof sound-permitting sheet according to the present invention is applied for the electronic device such as a mobile terminal that is carried and used to perform a water resistance function. In addition, the waterproof sound-permitting sheet according to the present invention is formed into a nanoweb type having a plurality of pores to be formed by an electrospinning method to thereby improve the waterproof performance and sound-permitting performance.