Abstract:
Provided is a water-proof sound transmitting member that is less likely to be bonded to a housing at a position other than a normal attachment position. The present invention provides a waterproof sound transmitting member ( 2 ) having a multilayer structure. This water-proof sound transmitting member ( 2 ) includes: a water-proof sound transmitting membrane ( 11 ) to be attached to a housing having a hole that allows sound to pass therethrough; a support layer ( 12 ) to be attached to the housing together with the waterproof sound transmitting membrane ( 11 ), the support layer ( 12 ) allowing sound to pass therethrough; and a housing-side adhesive layer ( 21 ) for bonding the waterproof sound transmitting membrane ( 11 ) to the housing. The entire peripheral portion of the support layer ( 12 ) extends outwardly beyond the housing-side adhesive layer ( 21 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a water-proof sound transmitting member having a multilayer structure, in which a support layer is provided on or above a water-proof sound transmitting membrane for a housing of an electronic apparatus equipped with sound devices such as a speaker and a microphone. 
     BACKGROUND ART 
     In electronic apparatuses such as a cellular phone, a cordless phone, and a digital camera, sound devices are placed in housings. The housing has an opening for allowing sound to pass therethrough. In order to prevent water from entering the housing through this opening, a water-proof sound transmitting membrane that blocks passage of water through the opening while allowing passage of sound therethrough is attached to the opening. For example, Patent Literature 1 describes a water-proof sound transmitting member including a water-proof sound transmitting membrane. In this water-proof sound transmitting member, a housing-side adhesive layer for bonding the water-proof sound transmitting member to the housing, the water-proof sound transmitting membrane, and a support layer for reinforcing the water-proof sound transmitting membrane are laminated in this order. 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2008-237949 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the water-proof sound transmitting member of Patent Literature 1, the housing-side adhesive layer, the water-proof sound transmitting membrane, and the support layer are laminated so that the end faces of these components are aligned with one another. However, the water-proof sound transmitting member configured as described above may cause the following problem when the water-proof sound transmitting member is attached to the housing. If the end face of the water-proof sound transmitting member accidentally comes into contact with the housing, the end face of the housing-side adhesive layer is bonded to the housing, and thereby the end face of the water-proof sound transmitting member is bonded to the housing at a position other than the normal attachment position. With the recent reduction in size and thickness of electronic apparatuses, the distance between the attachment position and the wall surface of the housing has been reduced. Therefore, the above-mentioned problem has become apparent. 
     Under these circumstances, it is an object of the present invention to provide a water-proof sound transmitting member that is less likely to be bonded to the housing at a position other than the normal attachment position. 
     Solution to Problem 
     The present invention provides a waterproof sound transmitting member having a multilayer structure. This waterproof sound transmitting member includes: a water-proof sound transmitting membrane to be attached to a housing having a hole that allows sound to pass therethrough; a support layer to be attached to the housing together with the waterproof sound transmitting membrane, the support layer allowing sound to pass therethrough; and a housing-side adhesive layer for bonding the water-proof sound transmitting membrane to the housing. The entire peripheral portion of the support layer extends outwardly beyond the housing-side adhesive layer. 
     Advantageous Effects of Invention 
     In the water-proof sound transmitting member of the present invention, the entire peripheral portion of the support layer extends outwardly beyond the housing-side adhesive layer. Therefore, even if the end face of the waterproof sound transmitting member accidentally comes into contact with the housing when the water-proof sound transmitting member is attached to the housing, only the end face of the support layer contacts the housing and the end face of the housing-side adhesive layer never contacts the housing. This means that the present invention reduces the risk of causing the water-proof sound transmitting member to be bonded to the housing at a position other than the normal attachment position. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram for explaining a waterproof sound transmitting member according to an embodiment of the present invention. (A) is a cross-sectional view parallel to the thickness direction of a water-proof sound transmitting membrane, and (B) is a top view observed from the side of a support layer. 
         FIG. 2  is a diagram for explaining a water-proof sound transmitting member according to a first modification, and is a cross-sectional view parallel to the thickness direction of a water-proof sound transmitting membrane. 
         FIG. 3  is a diagram for explaining a waterproof sound transmitting member according to a second modification, and is a cross-sectional view parallel to the thickness direction of a waterproof sound transmitting membrane. 
         FIG. 4  is a diagram for explaining a water-proof sound transmitting member according to a third modification, and is a cross-sectional view parallel to the thickness direction of a waterproof sound transmitting membrane. 
         FIG. 5  is a diagram for explaining a waterproof sound transmitting member according to a fourth modification, and is a cross-sectional view parallel to the thickness direction of a water-proof sound transmitting membrane. 
         FIG. 6  is a diagram for explaining a waterproof sound transmitting member according to a fifth modification, and is a cross-sectional view parallel to the thickness direction of a waterproof sound transmitting membrane. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, an embodiment of the present invention is described with reference to the accompanying drawings. 
       FIG. 1  is a diagram for explaining a water-proof sound transmitting member according to the embodiment of the present invention.  FIG. 1  (A) is a cross-sectional view thereof, and  FIG. 1  (B) is a top view thereof. A water-proof sound transmitting member  2  of the present embodiment includes a water-proof sound transmitting membrane  11  and a support layer  12 . A housing-side adhesive layer  21  for bonding the water-proof sound transmitting member  2  to a housing is provided on the side of one surface of the waterproof sound transmitting membrane  11 . The support layer  12  is bonded to the other surface of the water-proof sound transmitting membrane  11  by a support layer-side adhesive layer  22 . As shown in  FIG. 1 , at the time of shipment from the factory, the water-proof sound transmitting member  2  is bonded to a release paper  13  using the housing-side adhesive layer  21  and thus is supported on the release paper  13 . 
     The water-proof sound transmitting membrane  11  is a membrane that blocks passage of foreign matters, such as liquid and dust, while allowing passage of sound. In the present embodiment, the water-proof sound transmitting membrane  11  has a rectangular shape, but it may have another shape such as a square, a polygon other than a square, or a circle. 
     In the present embodiment, the water-proof sound transmitting membrane  11  is formed of a polymer film. The material of the polymer film is, for example, a polymer material. Examples of the polymer material suitable for the water-proof sound transmitting membrane  11  include polyethylene (PE), polyimide (PI), polypropylene (PP), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE). Preferably, the water-proof sound transmitting membrane  11  is porous and contains fluorine (preferably, the water-proof sound transmitting membrane  11  is composed of a fluororesin). Porous polytetrafluoroethylene is particularly suitable as the material of the water-proof sound transmitting membrane  11 . The water-proof sound transmitting membrane  11  may be a nonwoven fabric, or may be formed of an assembly of nanofibers. The waterproof sound transmitting membrane  11  may be subjected to water-repellent treatment. 
     The support layer  12  is a layer containing no adhesive component, and increases the rigidity of the water-proof sound transmitting member  2  when it is bonded to the waterproof sound transmitting membrane  11 . That is, the support layer  12  has the effect of stabilizing the shape of the water-proof sound transmitting member  2 . 
     The support layer  12  has a structure through which sound can pass. In the present embodiment, the support layer  12  has a rectangular frame shape conforming to the four sides of the water-proof sound transmitting membrane  11 , and has an opening for allowing passage of sound therethrough in the center of the rectangle. The support layer  12  is bonded to the peripheral portion of the water-proof sound transmitting membrane  11  by the support layer-side adhesive layer  22 . The support layer  12  may have an annular frame shape, for example, depending on the shape of the water-proof sound transmitting membrane  11 . The frame shape includes a hollow rectangular shape and an annular shape. When the material of the support layer  12  is selected from materials that are unlikely to block passage of sound, the support layer  12  may have a plate shape that covers the entire surface of the waterproof sound transmitting membrane  11 . 
     In the present embodiment, the peripheral edge of the support layer  12  lies beyond the peripheral edge of the water-proof sound transmitting membrane  11  (that is, the entire peripheral portion of the support layer  12  also extends outwardly beyond the water-proof sound transmitting membrane  11 ). In this description, the term “peripheral edge” refers to the outline. 
     The support layer  12  can be formed of a polymer film. Examples of the material of the polymer film include polymer materials such as polyethylene (PE), polyimide (PI), polypropylene (PP), and polyethylene terephthalate (PET). Foamed polymer materials (such as PORON and SCF (registered trademark)) and urethane materials having a cushioning property can be used suitably as the material of the support layer  12 . The material of the support layer  12  may be a mixture of the above-mentioned materials. 
     The housing-side adhesive layer  21  and the support layer-side adhesive layer  22  are each a layer containing an adhesive component. As shown in  FIG. 1 , in the present embodiment, the housing-side adhesive layer  21  and the support layer-side adhesive layer  22  have a rectangular frame shape having the same outline as that of the water-proof sound transmitting membrane  11  and having an opening of the same shape as the opening of the support layer  12 . That is, the entire peripheral portion of the support layer  12  extends outwardly beyond the housing-side adhesive layer  21  and the support layer-side adhesive layer  22 . 
     The specific dimensions of the support layer  12 , the housing-side adhesive layer  21 , and the support layer-side adhesive layer  22  are not particularly limited. The portion of the support layer  12  extending outwardly beyond the housing-side adhesive layer  21  has a width (“I s ” in  FIG. 1  (A)) of 1.0 mm, for example. The ratio (r s /r a ) of the distance (“r s ” in  FIG. 1  (A)) from the center of the support layer  12  to the peripheral edge thereof to the distance (“r a ” in  FIG. 1  (A)) from the center of the housing-side adhesive layer  21  to the peripheral edge thereof is, for example 1.1 to 3.0. The portion of the support layer  12  extending outwardly beyond the support layer-side adhesive layer  22  also has a width of 1.0 mm. The ratio of the distance from the center of the support layer  12  to the peripheral edge thereof to the distance from the center of the support layer-side adhesive layer  22  to the peripheral edge thereof is also 1.1 to 3.0. 
     In the present embodiment, the housing-side adhesive layer  21  and the support layer-side adhesive layer  22  have the same rectangular frame shape. However, they may have an annular frame shape, for example. Their outlines may be different from each other. In the present embodiment, the support layer  12 , the housing-side adhesive layer  21 , and the support layer-side adhesive layer  22  each have a frame shape with an opening. The openings of these layers have the same shape, but they may have different shapes. 
     In the waterproof sound transmitting member  2  of the present embodiment, the housing-side adhesive layer  21  is provided on the opposite side of the waterproof sound transmitting membrane  11  from the support layer  12 . However, the housing-side adhesive layer  21  and the support layer  12  may be provided on the same side of the water-proof sound transmitting membrane  11 . 
     Examples of the housing-side adhesive layer  21  and the support layer-side adhesive layer  22  include adhesive tapes containing an acrylic or silicone adhesive. 
     In the present embodiment, the entire peripheral portion of the support layer  12  extends outwardly beyond the housing-side adhesive layer  21 . Therefore, even if the end face of the water-proof sound transmitting member  2  accidentally comes into contact with the housing when the water-proof sound transmitting member  2  is attached to the housing, only the end face of the support layer  12  contacts the housing and the end face of the housing-side adhesive layer  21  never contacts the housing. This means that the present embodiment reduces the risk of causing the end face of the water-proof sound transmitting member  2  to be bonded to the housing by the end face of the housing-side adhesive layer  21 . In addition, the present embodiment reduces the risk of adhesion of foreign matters such as dust to the end face of the housing-side adhesive layer  21  after the water-proof sound transmitting member  2  is attached to the housing. 
     Furthermore, since the entire peripheral portion of the support layer  12  also extends outwardly beyond the support layer-side adhesive layer  22 , the risk of causing the end face of the waterproof sound transmitting member  2  to be bonded to the housing by the end face of the support layer-side adhesive layer  22  also can be reduced. 
     Moreover, the support layer-side adhesive layer  22  is not provided on the peripheral portion of the support layer  12 . Therefore, even if this peripheral portion is held with a tool such as tweezers, the adhesive component derived from the support layer-side adhesive layer  22  does not adhere to the tool. In addition, since the peripheral edge of the support layer  12  of the present embodiment lies beyond the peripheral edge of the water-proof sound transmitting membrane  11 , the water-proof sound transmitting membrane  11  is kept out of the way of the tool such as tweezers used to hold the peripheral portion of the support layer  12 . That is, the support layer  12  of the present embodiment suitably serves also as a holding portion. 
     In the water-proof sound transmitting member  2  of the present embodiment, the housing-side adhesive layer  21  is provided on the opposite side of the water-proof sound transmitting membrane  11  from the support layer  12 . This means that the support layer  12  can be easily held and easily attached to the housing because a space between the support layer  12  and the release paper  13  on which the water-proof sound transmitting member  2  is supported and a space between the support layer  12  and the housing to which the water-proof sound transmitting member  2  is to be attached can be provided. Accordingly, the risk of causing the end face of the water-proof sound transmitting member  2  to come into contact with the housing accidentally is reduced when the water-proof sound transmitting member  2  is attached to the housing. 
     Thus, the embodiment of the present invention has been described. However, the present invention is not limited to this embodiment. Hereinafter, the other embodiments of the present invention are described collectively. 
     In the water-proof sound transmitting member  2  of the previously-described embodiment, the end faces of the housing-side adhesive layer  21 , the water-proof sound transmitting membrane  11 , and the support layer-side adhesive layer  22  are aligned with one another, but the water-proof sound transmitting member may be configured in other ways. For example, as shown in  FIG. 2 , a water-proof sound transmitting member  102  may be configured by replacing the water-proof sound transmitting membrane  11  in  FIG. 1  by a water-proof sound transmitting membrane  111  (first modification). The peripheral edge of the membrane  111  in  FIG. 2  lies within the peripheral edge of the membrane  11  in  FIG. 1 . In the water-proof sound transmitting member  102  shown in  FIG. 2 , the peripheral edge of the water-proof sound transmitting membrane  111  lies within the peripheral edge of the housing-side adhesive layer  21  and that of the support layer-side adhesive layer  22 . In other words, the entire peripheral portion of the housing-side adhesive layer  21  and that of the support layer-side adhesive layer  22  extend outwardly beyond the water-proof sound transmitting membrane  111 . The water-proof sound transmitting member  102  shown in  FIG. 2  has the same effects as the water-proof sound transmitting member  2  shown in  FIG. 1 . Furthermore, the water-proof sound transmitting membrane  111  of the water-proof sound transmitting member  102  shown in  FIG. 2  is smaller in size than the water-proof sound transmitting membrane  11  of the waterproof sound transmitting member  2  shown in  FIG. 1 . Therefore, the water-proof sound transmitting member  102  configured as shown in  FIG. 2  saves the material of the water-proof sound transmitting membrane. 
     As shown in  FIG. 3 , a water-proof sound transmitting member  202  may be configured by replacing the housing-side adhesive layer  21  in  FIG. 2  by a housing-side adhesive layer  221  (second modification). The peripheral edge of the adhesive layer  221  in  FIG. 3  lies within the peripheral edge of the adhesive layer  21  in  FIG. 2 . In the water-proof sound transmitting member  202  shown in  FIG. 3 , the peripheral edge of the water-proof sound transmitting membrane  111  and the peripheral edge of the housing-side adhesive layer  221  coincide with each other. In other words, the end face of the water-proof sound transmitting membrane  111  and the end face of the housing-side adhesive layer  221  are aligned with each other. That is, in the water-proof sound transmitting member  202  shown in  FIG. 3 , the housing-side adhesive layer  221  does not extend outwardly beyond the water-proof sound transmitting membrane  111 . Therefore, the risk of causing the end face of the water-proof sound transmitting member  202  to be bonded to the housing by the end face of the housing-side adhesive layer  221  is lower than the risk of causing the end face of the water-proof sound transmitting member  102  to be bonded to the housing by the end face of the housing-side adhesive layer  21 . Furthermore, the housing-side adhesive layer  221  of the water-proof sound transmitting member  202  shown in  FIG. 3  is smaller in size than the housing-side adhesive layer  21  of the water-proof sound transmitting member  102  shown in  FIG. 2 . Therefore, the water-proof sound transmitting member  202  configured as shown in  FIG. 3  saves the material of the housing-side adhesive layer. 
     As shown in  FIG. 4 , a water-proof sound transmitting member  302  may be configured by replacing the housing-side adhesive layer  221  in  FIG. 3  by a housing-side adhesive layer  321  (third modification). The peripheral edge of the adhesive layer  321  in  FIG. 4  lies within the peripheral edge of the adhesive layer  221  in  FIG. 3 . In the water-proof sound transmitting member  302  shown in  FIG. 4 , the peripheral edge of the housing-side adhesive layer  321  lies within the peripheral edge of the waterproof sound transmitting membrane  111 . That is, the entire peripheral portion of the water-proof sound transmitting membrane  111  extends outwardly beyond the housing-side adhesive layer  321 . Therefore, the risk of causing the end face of the water-proof sound transmitting member  302  to be bonded to the housing by the end face of the housing-side adhesive layer  321  is lower than the risk of causing the end face of the water-proof sound transmitting member  202  to be bonded to the housing by the end face of the housing-side adhesive layer  221 . Furthermore, the housing-side adhesive layer  321  of the waterproof sound transmitting member  302  shown in  FIG. 4  is smaller in size than the housing-side adhesive layer  221  of the water-proof sound transmitting member  202  shown in  FIG. 3 . Therefore, the water-proof sound transmitting member  302  configured as shown in  FIG. 4  further saves the material of the housing-side adhesive layer. 
     As shown in  FIG. 5 , a water-proof sound transmitting member  402  may be configured by replacing the water-proof sound transmitting membrane  111  in  FIG. 4  by the waterproof sound transmitting membrane  11  in  FIG. 1  (fourth modification). In the waterproof sound transmitting member  402  shown in  FIG. 5 , the peripheral edge of the water-proof sound transmitting membrane  11  and the peripheral edge of the support layer-side adhesive layer  22  coincide with each other. In other words, the end face of the waterproof sound transmitting membrane  11  and the end face of the support layer-side adhesive layer  22  are aligned with each other. That is, in the water-proof sound transmitting member  402  shown in  FIG. 5 , the support layer-side adhesive layer  22  does not extend outwardly beyond the water-proof sound transmitting membrane  11 . Therefore, the risk of causing the end face of the water-proof sound transmitting member  402  to be bonded to the housing by the end face of the support layer-side adhesive layer  22  is lower than the risk of causing the end face of the water-proof sound transmitting member  302  to be bonded to the housing by the end face of the support layer-side adhesive layer  22 . 
     As shown in  FIG. 6 , a water-proof sound transmitting member  502  may be configured by bringing a support layer  512  into direct contact with the water-proof sound transmitting membrane  11  provided with the housing-side adhesive layer  221  (fifth modification). In the water-proof sound transmitting member  502  shown in  FIG. 6 , the peripheral edge of the water-proof sound transmitting membrane  11  and the peripheral edge of the support layer  512  coincide with each other (in other words, the end face of the water-proof sound transmitting membrane  11  and the end face of the support layer  512  are aligned with each other), and the entire peripheral portion of the water-proof sound transmitting membrane  11  and the entire peripheral portion of the support layer  512  extend outwardly beyond the housing-side adhesive layer  221 . Therefore, the risk of causing the end face of the water-proof sound transmitting member  502  to be bonded to the housing by the end face of the housing-side adhesive layer  221  is low for the same reasons as in the case of the configuration of the water-proof sound transmitting member  302  and the water-proof sound transmitting member  402 . Furthermore, the water-proof sound transmitting member  502  does not have an adhesive layer between the water-proof sound transmitting membrane  11  and the support layer  512 . Therefore, the risk of causing the end face of the water-proof sound transmitting member  502  to be bonded to the housing at a position other than the normal attachment position is lower than the risk in the case where an adhesive layer is provided between the water-proof sound transmitting membrane  11  and the support layer  512 . The method for bonding the support layer  512  directly to the water-proof sound transmitting membrane  11  as shown in  FIG. 6  is, for example, heat lamination. 
     INDUSTRIAL APPLICABILITY 
     The water-proof sound transmitting member of the present invention can be suitably attached to housings of electronic apparatuses such as a cellular phone, a cordless phone, and a digital camera.