Patent Publication Number: US-10768702-B2

Title: Display device

Description:
BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a display device presenting a tactile sense using vibration. 
     2. Description of the Related Art 
     In recent years, a touch panel presenting an operator with a tactile sense using vibration has been mounted in portable information devices such as a smartphone and a tablet PC, various consumer devices including home appliances such as a microwave oven, a television and lighting equipment, and various industrial equipment such as an automated teller machine, an automatic ticket machine, and a vending machine. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP-A 2014-6672 
       
    
     SUMMARY 
     An object of the present disclosure is to provide a highly reliable tactile sense transmission type display device in which a good tactile sense is presented with the degradation of the vibration efficiency suppressed. 
     A display device of the present disclosure includes: a substrate having a display section; a vibrating body disposed on the substrate; a support disposed so as to face the substrate apart therefrom; an elastic supporting member disposed between the substrate and the support, the elastic supporting member being elastically deformable in accordance with vibration of the vibrating body; and a wall member disposed across the substrate and the support so as to externally surround the display section, the wall member including a pressure variation relaxation section which relaxes pressure variation caused by the vibrating body in a space surrounded by the wall member. 
     In addition, a display device of the present disclosure includes: a display panel having a display section; an operation panel disposed so as to cover the display panel, the operation panel having an operation surface which is located on an opposite side to a side facing the display panel; a vibrating body disposed on the operation panel; a support disposed on the side facing the display panel so as to face the operation panel apart therefrom; an elastic supporting member disposed between the operation panel and the support, the elastic supporting member being elastically deformable in accordance with vibration of the vibrating body; and a wall member disposed across the operation panel and the support so as to externally surround the display section, the wall member including a pressure variation relaxation section which relaxes pressure variation caused by the vibrating body in a space surrounded by the wall member. 
     According to the display device of the present disclosure, since the wall member including the pressure variation relaxation section is provided, pressure variation caused by the vibrating body in a space surrounded by the wall member can be suppressed, and decrease of the efficiency of the vibration generated by the vibrating body can be suppressed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Other and further objects, features, and advantages of the present disclosure will be more explicit from the following detailed description taken with reference to the drawings wherein: 
         FIG. 1  is a plan view of an example of a display device according to a first embodiment; 
         FIG. 2  is a cross-sectional view of an example of the display device according to the first embodiment; 
         FIG. 3  is an enlarged cross-sectional view for explaining an air flow in the vicinity of a wall member; 
         FIG. 4  is a plan view of an example of a display device according to a second embodiment; 
         FIG. 5  is a cross-sectional view of an example of the display device according to the second embodiment; 
         FIG. 6  is an enlarged cross-sectional view for explaining an air flow in the vicinity of a wall member; 
         FIG. 7  is a cross-sectional view of an example of a display device according to a third embodiment; 
         FIG. 8  is an enlarged cross-sectional view for explaining an air flow in the vicinity of a wall member; and 
         FIG. 9  is an enlarged cross-sectional view for explaining movement of the wall member. 
     
    
    
     DETAILED DESCRIPTION 
     Now referring to the drawings, preferred embodiments of the present disclosure is described below. 
       FIG. 1  is a plan view of an example of a display device according to a first embodiment.  FIG. 2  is a cross-sectional view of the exemplified display device according to the first embodiment, and schematically illustrates a cross-section including vibrating bodies  13   a  and  13   b  of the display device of  FIG. 1 . In  FIG. 2 , a thickness direction of the display device is enlargedly illustrated for purposes of explanation. A liquid crystal display device  1 , which is an example of a display device, includes a liquid crystal display panel  20  which is a display panel, on a rear surface of a transparent touch panel  10  which is an operation panel, and a backlight unit  30  which is a support, is further disposed on a rear surface of the liquid crystal display panel  20 , and the liquid crystal display device  1  is constituted by housing the touch panel  10 , the liquid crystal display panel  20  and the backlight unit  30  in a housing  40 . 
     In the display device of the present disclosure illustrated in  FIGS. 1 and 2 , a substrate having a display section has a complex structure in which a touch detection section  12  and the liquid crystal display panel  20  are stacked on one main surface (a rear surface) of a transparent protection plate  11  formed of, for example, a glass substrate or a plastic substrate. 
     The display panel including the display section can be, for example, the liquid crystal display panel  20  including a liquid crystal display section as the display section, but the display panel of the present disclosure is not limited to the liquid crystal display panel  20 , but may be a self light emitting display panel such as an organic EL (Electroluminescence) display panel, an inorganic EL display panel, or a light emitting diode (LED) display panel. 
     The vibrating bodies  13   a  and  13   b  are disposed in an peripheral portion (an edge portion) on the rear surface of the transparent protection plate  11  included in the substrate in positions outside the liquid crystal display panel  20  in a plan view thereof. Besides, the vibrating bodies  13   a  and  13   b  are disposed in positions opposing each other. In this case, vibration generated by the vibrating bodies  13   a  and  13   b  can easily occur uniformly in the entire substrate. Alternatively, the vibrating bodies  13   a  and  13   b  may be disposed on the other main surface (a front surface) of the transparent protection plate  11 . 
     The support is a supporting substrate composed of a light guiding panel  31  of the backlight unit  30 . In a peripheral portion on a surface (a light irradiation surface) of the light guiding panel  31  opposing a non-display surface  20   b  of the liquid crystal display panel  20 , a projected portion (a flange portion) of a frame body  32  is disposed, and the transparent protection plate  11  is supported on the projected portion via elastic supporting members  50   a ,  50   b ,  50   c  and  50   d.    
     A wall member  60  is disposed across the substrate and the support so as to externally surround the display section, is deformable in accordance with the vibration generated by the vibrating bodies  13   a  and  13   b , and has void portions which are constituted by a mesh structure to be ventilatable. The wall member  60  specifically has void portions constituted by a mesh structure such as non-woven fabric, a flocculent material, an air filter, or an HEPA (high efficiency particulate air) filter, and the size of an opening can be adjusted to be ventilatable. The size of the opening can be adjusted, with the mesh structure caused to contain, for example, fiber and an adhesive, by adjusting a combination of the contents or the like of the fiber and the adhesive. In this manner, the wall member  60  having a suitable ventilation property can be obtained. In the wall member  60 , there may be or may not be a gradient in the density of the void portions (openings) in a ventilating direction. 
     In the ventilatable wall member  60  of the present disclosure, a pressure loss of air passing through the wall member  60  during the vibration of the substrate (for example, a pressure loss caused assuming that an air passing speed is 20 cm/sec.) is preferably in a range of 0.1 pascal to 100 pascals (Pa). If the pressure loss is less than 0.1 Pa, dust and dirt tend to easily pass through the wall member  60 . If the pressure loss exceeds 100 Pa, the wall member  60  is degraded in the ventilation property, and hence, resistance of the wall member  60  to the air passing through the wall member  60  easily becomes large. As a result, the wall member  60  impairs the vibration of the substrate, and thus, the efficiency of the vibration is easily lowered. The pressure loss is more preferably 0.1 Pa to 50 Pa, and further preferably 0.1 Pa to 40 Pa. Incidentally, the passing speed of the air passing through the wall member  60  during the vibration of the substrate is about 1 cm/sec. to 100 cm/sec., and the pressure loss may be 0.1 Pa to 100 Pa within this range of the passing speed. 
     The pressure loss can be measured as follows. When the air passes through the wall member  60 , the wall member  60  serves as the resistance to the air, and hence, a difference is caused between a pressure on an inlet side of the wall member  60  and a pressure on an outlet side of the wall member  60 . This pressure difference can be measured with a manometer (such as a U-tube manometer or an inclined manometer) connected to a measurement duct. The difference between the pressure on the inlet side of the wall member  60  (an upstream static pressure) and the pressure on the outlet side of the wall member  60  (a downstream static pressure) caused when the wall member  60  is used at a predetermined air passing speed (of, for example, 20 cm/sec.) is defined as the pressure loss (unit: Pa). 
     The touch detection section  12  constituting the touch panel  10  is disposed in parallel to and apart, in a thickness direction of the light guiding panel  31 , from the light guiding panel  31  of the backlight unit  30  which is the supporting substrate. In the touch panel  10 , an operation surface  11   a  is a surface of the transparent protection plate  11  which is located on the opposite side to the light guiding panel  31  (i.e., a surface on the side of an operator, or a surface on the side of a viewer), and the touch detection section  12  is disposed on the rear surface  11   b  of the transparent protection plate  11  which is located on the opposite side to the operation surface  11   a.    
     The touch panel  10  includes the touch detection section  12  disposed on the rear surface  11   b  of the transparent protection plate  11 . The transparent protection plate  11  is, for example, in a rectangular shape in a plan view thereof, and can be formed of a glass plate, a plastic plate or the like. The shape in a plan view of the transparent protection plate  11  is not limited to the rectangular shape, but may be a polygonal shape such as a triangular shape or a pentagonal shape, a trapezoidal shape, any of these shapes having rounded corners, or a wholly curved shape such as a circular shape or an elliptical shape. The transparent protection plate  11  has the operation surface  11   a  that can be operated by touching with a finger F or a stylus by an operator. There is a gap between the edge of the transparent protection plate  11  and the housing  40 , through which the air can pass. 
     On the rear surface  11   b  of the transparent protection plate  11  which is located on the opposite side of the operation surface  11   a , the touch detection section  12  is disposed. The touch detection section  12  is in the shape of a thin film, and in a plan view thereof, is in a rectangular shape smaller than the transparent protection plate  11 . The shape in a plan view of the touch detection section  12  may be a shape similar to any of the above-described various shapes in a plan view of the transparent protection plate  11 . The touch detection section  12  can detect a position on the operation surface  11   a  touched with the finger F or the stylus. As a detection method, a capacitance sensing method, a resistance film method or the like can be employed. Although the touch detection section  12  is disposed between the transparent protection plate  11  and the liquid crystal display panel  20  in the present embodiment, the touch detection section  12  may be built in the liquid crystal display panel  20 , or disposed outside the liquid crystal display device. 
     The display device of the present disclosure does not necessarily include the touch detection section  12 , and the touch detection section  12  may be omitted. The touch detection section  12  may be omitted if, for example, the vibrating bodies  13   a  and  13   b  formed of a piezoelectric material themselves have a structure for detecting position change of a touch with the finger F or the stylus. 
     On the rear surface  11   b  of the transparent protection plate  11 , the vibrating bodies  13   a  and  13   b  (hereinafter, generically referred to as the “vibrating body (vibrating bodies)  13 ” with the indexes a and b omitted), which are a plurality of vibrating bodies, are disposed. The vibrating bodies  13   a  and  13   b  are disposed, for example, respectively along two opposing sides of the rectangular operation surface  11   a  of the transparent protection plate  11 . Besides, the vibrating bodies  13   a  and  13   b  are disposed, in a plan view thereof, at positions point-symmetrical about a center P of the operation surface  11   a  of the rectangular transparent protection plate  11 . The vibrating bodies  13   a  and  13   b  may be disposed in direct contact with the transparent protection plate  11  so as to directly transmit the vibration to the transparent protection plate  11 , or may be disposed above the transparent protection plate  11  with another member disposed therebetween so as to indirectly transmit the vibration. Besides, when an operator touches the operation surface  11   a  with the finger F or the stylus, the touch detection section  12  detects the position of the touch, and the operation surface  11   a  is vibrated by the vibrating bodies  13  on the basis of detected information, so that the operator can sense the vibration via the finger F or the stylus. 
     The vibrating body  13  is composed of a piezoelectric body such as a ceramic piezoelectric body or a polymer piezoelectric body, an eccentric motor, a linear vibrator, a shape memory alloy or the like. As a material of the ceramic piezoelectric body, barium titanate (BaTiO 3 ), lead titanate (PbTiO 3 ), lead zirconate titanate (Pb[Zr x Ti 1-x ]O 3 , wherein 0&lt;x&lt;1, mixed crystal: PZT), potassium niobate (KNbO 3 ), lithium niobate (LiNbO 3 ), lithiumtantalate (LiTaO 3 ), sodium tungstate (Na x WO 3 ), zinc oxide (ZnO, Zn 2 O 3 ), Ba 2 NaNb 5 O 5 , Pb 2 KNb 5 O 15 , lithium tetraborate (Li 2 B 4 O 7 ), sodium potassium niobate ((K,Na)NbO 3 ), sodium bismuth titanate (Na 0.5 Bi 0.5 TiO 3 ) or the like can be employed. As a material of the polymer piezoelectric body, polyvinylidene fluoride (1,1-2 ethane fluoride polymer: PVDF) or the like can be employed. 
     The frequency of the vibration generated by the vibrating bodies  13  is about 30 Hz to 300 Hz, and as tactile vibration for providing a good tactile sense to a human finger, the frequency is preferably about 150 Hz to 250 Hz. The amplitude of the vibration is about 30 μm to 1000 μm, and as the tactile vibration for providing a good tactile sense to a human finger, the amplitude is preferably about 50 μm to 150 μm. Each vibrating body  13  can be in an appearance shape of a rectangular parallelepiped, a cube, a plate, or a columnar body such as a cylinder. The vibrating body  13  may be directly attached to the transparent protection plate  11 , or may be indirectly attached via a vibration transmission member formed of a metal, a resin or the like. Besides, as long as the touch panel  10  can be vibrated, the vibrating body  13  may be attached to any position, for example, on a side surface of the transparent protection plate  11 . 
     The liquid crystal display panel  20 , which is the display panel, is disposed on the opposite side to the operation surface  11   a  of the touch panel  10 . The liquid crystal display panel  20  is, for example, in the shape of a rectangle smaller than the touch panel  10  in a plan view thereof, and the touch panel  10  is disposed so as to cover the liquid crystal display panel  20 . The shape in a plan view of the liquid crystal display panel  20  may be a shape similar to any of the above-described various shapes in a plan view of the transparent protection plate  11 . The liquid crystal display panel  20  includes a display surface  20   a  and the non-display surface  20   b . The liquid crystal display panel  20  includes the display section (the liquid crystal display section)  20   c  in a center portion thereof, and the touch detection section  12  is positioned so as to cover at least the display surface  20   a  corresponding to the display section  20   c . Besides, although the liquid crystal display panel  20  is in contact with the rear surface of the touch panel  10  in the present embodiment, the liquid crystal display panel  20  may be disposed to be spaced from the touch panel  10 . 
     The backlight unit  30 , which is the support, is disposed so as to face the non-display surface  20   b  of the liquid crystal display panel  20  apart therefrom. The backlight unit  30  includes the light guiding panel  31 , the frame body  32  disposed in the periphery of the guiding panel  31 , and a conductor plate  33  on which the light guiding panel  31  is placed and which also serves as a ground conductor. The backlight unit  30  is configured so that light from a light source which is built therein and composed of an LED or the like can be emitted toward the liquid crystal display panel  20  via the light guiding panel  31 . The frame body  32  and the conductor plate  33  are formed of a metal such as aluminum. 
     In order to avoid that the liquid crystal display panel  20  and the backlight unit  30  impede the vibration generated by the vibrating bodies  13 , a distance (a height) of a space provided between the liquid crystal display panel  20  and the backlight unit  30  is preferably about 1 mm to 5 mm, and more preferably about 1 mm to 3 mm from the viewpoint of thickness reduction. 
     The housing  40  is, for example, in a rectangular shape in a plan view thereof, and has a bottom surface  40   a  in the center thereof, and a frame portion  40   b  which is the periphery of the bottom surface  40   a . On the bottom surface  40   a , the backlight unit  30 , the liquid crystal display panel  20  and the touch panel  10  are stacked in the stated order. The backlight unit  30  is placed and fixed to the bottom surface  40   a  of the housing  40 . The frame portion  40   b  corresponding to the periphery of the bottom surface  40   a  protects the side surfaces of the backlight unit  30 , the liquid crystal display panel  20  and the touch panel  10 . As a material of the housing  40 , for example, a plastic or a metal can be used. 
     On the rear surface  11   b  of the transparent protection plate  11  of the touch panel  10 , the elastic supporting members are disposed. In the present embodiment, the elastic supporting members  50   a ,  50   b ,  50   c  and  50   d  (hereinafter, generically referred to as the elastic supporting member(s)  50  with the indexes a, b, c and d omitted) are disposed in the four corners of the rectangular transparent protection plate  11 . As the elastic supporting members  50 , it is possible to use a member having a property to be displaced in accordance with the vibration of the vibrating bodies  13  so as to little attenuate the vibration of the operation panel, the member being formed of a rubber such as urethane rubber or silicone rubber, a resin or the like. Alternatively, a spring member such as a spring coil or a leaf spring may be used. 
     These elastic supporting members  50  are disposed between the frame body  32  of the backlight unit  30  which is the support and the transparent protection plate  11  which is the operation panel. The elastic supporting members  50  support the transparent protection plate  11 . Besides, each elastic supporting member  50  has one end in contact with the frame body  32  and the other end in contact with the rear surface  11   b  of the transparent protection plate  11 . The elastic supporting members  50  are held and fixed, with an adhesive or the like, onto the frame body  32  and the transparent protection plate  11  so as not to move from the disposed positions. If the operation panel and the display panel are integrally formed, a structure in which one end of each elastic supporting member  50  is fixed to the non-display surface of the display panel with the other end fixed to the support can be employed. 
     If the liquid crystal display panel  20  is used as the display panel, the backlight unit  30  can be used as the support, but if a display panel not requiring a backlight unit including a light guiding panel, such as a self light emitting display panel like an organic EL (Electroluminescence) display panel or a light emitting diode (LED) display panel, is used, the housing  40  may be used as the support. 
     The wall member  60  is disposed across the rear surface  11   b  of the transparent protection plate  11  and the frame body  32  of the backlight unit  30 . The wall member  60  is disposed so as to surround the liquid crystal display panel  20  serving as the display section. In other words, the wall member  60  is disposed across the operation panel and the support so as to externally surround the display section. Although the wall member  60  serves as a partition between a space inside the wall member  60  including the display section and a space outside the wall member  60 , the wall member  60  includes a large number of void portions which are a pressure variation relaxation section, and hence, the space inside the wall member  60  and the space outside the wall member  60  communicate with each other through the void portions. The wall member  60  is composed of a member having a large number of continuous pores, and can be formed by using, for example, an ultra-high molecular weight polyethylene porous film (trade name: “SUNMAP”, manufactured by Nitto Denko Corporation), or any of the above-described deformable members such as non-woven fabric, a flocculent material, an air filter, and an HEPA filter. Thus, the space inside the wall member  60  and the space outside the wall member  60  communicate with each other to be ventilatable through the void portions such as pores. An ultra-high molecular weight polyethylene porous film is produced, for example, by preparing a sintered porous molded body of an ultra-high molecular weight polyethylene powder, and cutting the resultant into a desired shape and size. Incidentally, a pressure loss of the wall member  60  formed of the ultra-high molecular weight polyethylene porous film (trade name: “SUNMAP”, manufactured by Nitto Denko Corporation) was measured, and found to be 40 Pa when the wall member  60  had a thickness of 0.32 mm and an air passing speed was 20 cm/sec. 
       FIG. 3  is an enlarged cross-sectional view for explaining an air flow in the vicinity of the wall member  60 . The space between the liquid crystal display panel  20  and the backlight unit  30  is configured to have such a high airtight structure as to prevent dust from entering the space between the liquid crystal display panel  20  and the backlight unit  30 , in many cases. If the vibrating bodies  13  are attached to such a display device to construct a display device presenting a tactile sense, however, an air pressure within a high airtight space between the liquid crystal display panel  20  and the backlight unit  30  is largely varied due to the vibration of the vibrating bodies  13 . Besides, the air pressure variation thus occurring in the space between the liquid crystal display panel  20  and the backlight unit  30  may affect components such as the housing  40 , in addition to the operation panel in which the tactile sense is to be presented, and it is apprehended that sense of use of a tactile sense and the like may be impaired. Furthermore, the vibration is diffused and attenuated, and hence, the display device is difficult to be efficiently vibrated. 
     Therefore, as the wall member  60 , the member which is deformable in accordance with the vibration of the vibrating bodies  13  and includes the void portions is used. Since the wall member  60  deforms in accordance with the vibrating bodies  13 , the vibration of the vibrating bodies  13  is difficult to be transmitted to the housing  40  via the wall member  60 . Therefore, the vibration of the vibrating bodies  13  is not diffused to the component such as the housing  40 , and hence, the touch panel  10  can be efficiently vibrated. 
     Besides, although slight volume change is caused in the space S inside the wall member  60  owing to the vibration of the transparent protection plate  11 , if the space S has a high airtightness, the air pressure variation in the space S is increased, and hence, the vibration may be transmitted to the housing  40 , or the vibration energy may be easily diffused and attenuated through the pressure loss or the like. Therefore, the wall member  60  is provided with the void portions so as to make the space S communicate with the space outside the wall member  60  through the void portions. Thus, air corresponding to the volume change of the space S flows through the wall member  60 , so as to suppress the air pressure variation in the space S. In this manner, the air pressure variation in the space inside the wall member  60  caused by the vibration of the vibrating bodies  13  is relaxed so that attenuation of the vibration of the transparent protection plate  11  included in the operation panel can be suppressed. Therefore, the transparent protection plate  11  can be efficiently vibrated. Accordingly, increase of the electric power for driving the vibrating bodies  13  can be suppressed. 
     Besides, since the wall member  60  need not support the touch panel  10  or the liquid crystal display panel  20  differently from the elastic supporting members  50 , the wall member  60  need not have rigidity as that of the elastic supporting members  50 , and may have a small thickness as long as dust can be prevented from entering the space S inside the wall member  60 , and preferably has lower rigidity than the elastic supporting members  50  because the air pressure variation in the space S inside the wall member  60  can be thus reduced. For example, a volume occupancy ratio of the void portions, that is, a volume ratio of a portion of the wall member  60  where the void portions are present in a region of the wall member  60  including the void portions, is preferably 40% or more and less than 100%. In other words, a ratio of a resin or fiber constituting walls of the void portions is preferably 60% or less of the portion where the void portions are present. If the volume occupancy ratio of the void portions is less than 40%, the ventilation property of the wall member  60  is degraded, and hence, the efficiency of the vibration generated by the vibrating bodies  13  tends to be easily lowered. The volume occupancy ratio of the void portions is more preferably 80% or more and less than 100%, and further preferably 90% or more and less than 100%. 
     As long as the ventilation between the space S inside the wall member  60  and the space outside the wall member  60  is sufficiently attained, the region including the void portions may be provided in merely a part of the wall member  60  with the remaining region constituted by a member having no void portions. Besides, if the whole wall member  60  is constituted by a material having the void portions, the ventilation between the space inside the wall member  60  and the space outside the wall member  60  can be improved. In this manner, the air pressure variation in the space S inside the wall member  60  can be reduced, and the attenuation of the vibration of the transparent protection plate  11  included in the operation panel can be further suppressed, so as to more efficiently vibrate the transparent protection plate  11 . 
     In the wall member  60 , the void portions are constituted by a mesh structure, and the mesh structure is a structure in which a large number of mesh-shaped voids are formed by entangling a linear material or a fibrous material, or a structure in which a large number of regular mesh-shaped voids are formed by a linear material, a fibrous material or a wall material continuous as a whole, and for example, is a structure of non-woven fabric, a flocculent material, woven fabric, a fishing net, an insect net, a honeycomb or the like. The wall member  60  may include such a mesh structure in at least a part thereof. The mesh structure used in the display device of the present disclosure does not embrace a dense material having a porous structure in which a large number of pores are formed in a base formed by using a dense material of a flexible continuous structure made of a resin such as polyurethane foam rubber, or the like. If the wall material  60  is formed by using such a flexible dense material as a base, although it is ventilatable, it is difficult to obtain a ventilation property sufficient for suppressing the air pressure variation in the space S inside the wall member  60  caused by the vibration of the transparent protection plate  11 , and hence, the vibration energy may be easily diffused and attenuated through the pressure loss. A specific example of the mesh structure includes an air cleaning filter (trade name: “Filtrete”, manufactured by 3M Company). Besides, the mesh structure may be an electrostatic charged material such as an electrostatic charged filter, and a dust collecting effect can be thus improved. The mesh structure has, for example, the pressure loss of 0.1 Pa to 100 Pa (as a value obtained at an air passing speed of 20 cm/sec.), and a thickness of about 0.5 mm to 5 mm. If the wall member  60  including such a mesh structure is used, the flow passage resistance of the void portions of the wall member  60  can be reduced, and hence, the attenuation of the vibration of the transparent protection plate  11  included in the operation panel is further suppressed, and the transparent protection plate  11  can be more efficiently vibrated. Incidentally, the pressure loss of two types (different in the density of the voids) of wall members  60  using the air cleaning filter (trade name: “Filtrete”, manufactured by 3M Company) was measured, and found to be 5 Pa to 7 Pa when the wall member  60  had a thickness of 2 mm and the air passing speed was 20 cm/sec. 
     Further, in the case where the mesh structure constituting the void portions of the wall member  60  is a structure in which a large number of regular mesh-shaped voids are formed by a linear material, a fibrous material or a wall material continuous as a whole, the mesh structure is preferably a structure having a regular mesh portion and a large number of branch portions extending in a branch shape from the regular mesh portion. In this case, since the large number of branch portions are present in the voids, dust and the like are easily trapped by the large number of branch portions. 
     Besides, each void of the wall member  60  preferably has a structure in which an opening facing the space inside the wall member  60  and an opening facing the space outside the wall member  60  are connected to each other in a straight tubular shape. In other words, in at least one of the opening of the void facing the space inside the wall member  60  and the opening of the void facing the space outside the wall member  60 , when the inside of the wall member  60  is seen from the opening of the void, the substance of the wall member  60  is preferably present to obstruct at least a part of the opening. Incidentally, a structure in which the substance of the wall member  60  obstructs at least a part of the opening includes a structure in which a portion of the void present inside the wall member  60  is narrower than the opening. By having such a structure, the substance of the wall member  60  present to obstruct at least a part of the opening easily traps dust and the like. Each of the opening facing the space inside the wall member  60  and the opening facing the space outside the wall member  60  formed by each void of the wall member  60  has a size, for example, in terms of an average opening diameter in a unit area (1 cm 2 ), of about 10 μm to 300 μm, but the size is not limited to this range. 
     For example, if the amplitude of the vibration of the transparent protection plate  11  generated by the vibrating bodies  13  is about 150 μm to 300 μm, which is large (namely, has large vibration energy) as the tactile vibration, an HEPA filter having particle removal efficiency of 99.97% or more for dust having a particle size of about 0.3 μm, and having performance (defined in JIS 28122) of an initial pressure loss of 245 Pa or less may be used as the wall member  60 . An HEPA filter is a kind of air filters used for purposes of removing dust and dirt from air to obtain clean air, and is used as a filter for an air cleaner or a clean room. 
       FIG. 4  is a plan view of an example of a display device according to a second embodiment.  FIG. 5  is a cross-sectional view of an example of the display device according to the second embodiment, and schematically illustrates a cross-section including vibrating bodies  13   a  and  13   b  of the display device of  FIG. 4 . In  FIG. 5 , a thickness direction of the display device is enlargedly illustrated for purposes of explanation. A liquid crystal display device  1 A which is an example of the display device includes a liquid crystal display panel  20 , that is, a display panel, on a rear surface of a transparent touch panel  10  which is an operation panel, and further includes a backlight unit  30  which is a support, disposed on a rear surface of the liquid crystal display panel  20 , and is constituted by housing the touch panel  10 , the liquid crystal display panel  20  and the backlight unit  30  in a housing  40 . 
     The liquid crystal display device  1 A according to the second embodiment is similar to the liquid crystal display device  1 , and corresponding parts are denoted by the same reference numerals and descriptions thereof will be omitted. The liquid crystal display device according to the second embodiment is provided with a wall member  160 , instead of the wall member provided in the liquid crystal display device according to the first embodiment. 
     The wall member  160  is disposed across the rear surface  11   b  of the transparent protection plate  11  and the frame body  32  of the backlight unit  30 . The wall member  160  is disposed to surround the display section  20   c  of the liquid crystal display panel  20 . In other words, the wall member  160  is disposed across the operation panel and the support so as to externally surround the display section. The wall member  160  serves as a partition between a space inside the wall member  160  including the display section  20   c  and a space outside the wall member  160 , and at least a part of the wall member  160  includes a flexible wall member  61 , which is the pressure variation relaxation section, formed of a material that can easily bent by the vibration of the vibrating bodies  13   a  and  13   b . Needless to say, the entire wall member  160  may be the flexible wall member  61 . In a space surrounded by the transparent protection plate  11 , the backlight unit  30  and the wall member  160 , the transparent protection plate  11  is vibrated in accordance with the vibration generated by the vibrating bodies  13   a  and  13   b , so as to displace the position of the transparent protection plate  11  against the backlight unit  30 . The flexible wall member  61  is formed of a flexible material that can be bent. Besides, there is a gap between the housing  40  and the touch panel  10 , and the space outside the wall member  160  is in communication with outside air. 
     The flexible wall member  61  includes, for example, a base member  61   a , and flexible linear materials  61   b  extending from the base member  61   a  toward the backlight unit  30 . The base member  61   a  is fixed to the transparent protection plate  11  on the side of the transparent protection plate  11  as a fixed end of the flexible wall member  61 . One end of each flexible linear material  61   b  is fixed to the base member  61   a , and the other end thereof is a free end, and is in contact with the backlight unit  30 . The flexible linear materials  61   b  are composed of a plurality of fibrous members each having a thickness of 10 μm or more and 300 μm or less. As a material of the flexible linear materials  61   b , resins such as polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyvinyl chloride (PVC), polyvinyl alcohol (PVA), and polypropylene (PP), and rubbers such as a silicone rubber, a urethane rubber, and an acrylic rubber can be used. 
     In the present embodiment, the base member  61   a  is formed of a flexible material such as a resin of polyurethane, silicone or the like, or cloth, is in a frame-like shape in a plan view thereof, and is fixed to the transparent protection plate  11  which is the operation panel with an adhesive or the like. A large number of the flexible linear materials  61   b , which extend from the base member  61   a  toward the backlight unit  30 , are disposed in a brush-like shape on the base member  61   a , and are disposed across the base member  61   a  fixed to the transparent protection plate  11  and the backlight unit  30  so as to externally surround the liquid crystal display panel  20  which is the display section. Besides, the flexible wall member  61  including the flexible linear materials  61   b  has a natural length larger than a distance between the transparent protection plate  11  and the backlight unit  30  in a standard state where no specific operation is performed, and therefore, at least some of the flexible linear materials  61   b  are in contact with the backlight unit  30 . A distance between adjacent ones of the flexible linear materials  61   b  is 10 μm or more and 300 μm or less. Owing to gaps among the flexible linear materials  61   b , the space inside the wall member  160  and the space outside the wall member  160  are in communication with each other. The wall member  160  has a thickness of about 0.01 mm to 0.3 mm. Since the flexible linear materials  61   b  are thus densely disposed over a prescribed thickness, the wall member  160  having both a ventilation property and a dust proof property can be obtained. Incidentally, in the display device of the present disclosure, the base member  61   a  may be formed of a resin having no flexibility, a metal, a ceramic or the like, and the flexible linear materials  61   b  may be fixed to the base member  61   a  with an adhesive or the like. 
     Although some of the flexible linear materials  61   b  constituting the flexible wall member  61  are arranged along a direction parallel to a direction of air passing in a plan view thereof, they are preferably arranged along a direction inclined to the direction of air passing in a plan view thereof. In this case, a flow passage of air passing through the flexible wall member  61  becomes complex, and dust and the like are easily trapped. 
     The flexible linear materials  61   b  constituting the flexible wall member  61  is preferably configured to have a stem portion and a large number of branch portions extending in a branch shape from the stem portion. In this case, dust and the like are easily trapped by the large number of branch portions. 
       FIG. 6  is an enlarged cross-sectional view for explaining an air flow in the vicinity of the wall member  160 . The space between the liquid crystal display panel  20  and the backlight unit  30  is configured to have such a high airtight structure as to prevent dust from entering the space S between the liquid crystal display panel  20  and the backlight unit  30 , in many cases. If the vibrating bodies  13   a  and  13   b  are attached to such a display device to construct a display device presenting a tactile sense, however, an air pressure within a high airtight space S between the liquid crystal display panel  20  and the backlight unit  30  is largely varied due to the vibration of the vibrating bodies  13   a  and  13   b . Besides, the air pressure variation thus occurring in the space S between the liquid crystal display panel  20  and the backlight unit  30  may affect a component, such as the housing  40 , in addition to the panel in which the tactile sense is to be presented, and it is apprehended that sense of use may be impaired. Furthermore, the vibration is diffused and attenuated, and hence, the display device is difficult to be efficiently vibrated. 
     Therefore, the wall member  160  has the structure including the flexible wall member  61  having one end which is a fixed end fixed to either of the operation panel or the support, and the other end which is a free end. Although the touch panel  10  is displaced in a direction vertical to the operation surface  11   a  by the vibrating bodies  13   a  and  13   b , the flexible wall member  61  having a ventilation property is deformed in accordance with the displacement of the transparent protection plate  11 , so as to suppress the air pressure variation caused by the volume change of the space S surrounded by the operation panel, the support and the wall member  60 . Besides, since one end of the flexible wall member  61  is a free end and is not fixed, the vibration of the vibrating bodies  13   a  and  13   b  is difficult to be transmitted to the housing  40  or the like via the wall member  60  or the space S. Therefore, the vibration of the vibrating bodies  13   a  and  13   b  is not diffused to the component such as the housing  40 , and hence the touch panel  10  can be efficiently vibrated. 
     Furthermore, although slight volume change is caused in the space S inside the wall member  160  owing to the vibration of the vibrating bodies  13   a  and  13   b  disposed on the transparent protection plate  11 , if the space S has a high airtightness, the air pressure variation in the space S is increased, and hence, the vibration may be transmitted to the housing  40 , or the vibration energy may be easily diffused and attenuated through the pressure loss or the like. Therefore, the flexible wall member  61  includes the base member  61   a  and the flexible linear materials  61   b  each having one end fixed to the base member  61   a  and the other end which is a free end, so that the space S can be in communication with the space outside the wall member  160 . Thus, air corresponding to the volume change of the space S flows through the wall member  160  as illustrated with arrows in  FIG. 6 , so as to suppress the air pressure variation in the space S. 
     In this manner, the air pressure variation in the space inside the wall member  160  caused by the vibration of the vibrating bodies  13   a  and  13   b  is relaxed so that attenuation of the vibration of the transparent protection plate  11  which is the operation panel can be suppressed. Therefore, the transparent protection plate  11  can be efficiently vibrated. Accordingly, increase of the electric power for driving the vibrating bodies  13   a  and  13   b  can be suppressed. 
     Although the entire wall member  160  corresponds to the flexible wall member  61  in the present embodiment, the air pressure variation in the space S can be suppressed as long as the flexible wall member  61  is included in at least a part of the wall member  160 . Besides, in the present embodiment, the base member  61   a  is fixed to the transparent protection plate  11 , the flexible linear materials  61   b  extend from the base member  61   a  toward the backlight unit  30 , and the flexible linear materials  61   b  are in contact with the backlight unit  30 . Alternatively, a structure in which the base member  61   a  is fixed to the backlight unit  30 , the flexible linear materials  61   b  extend toward the transparent protection plate  11 , and the flexible linear materials  61   b  are in contact with the transparent protection plate  11  can be employed. Further alternatively, a structure in which the wall member  160  has, in a part thereof, the structure in which the base member  61   a  is fixed to the transparent protection plate  11 , the flexible linear materials  61   b  extend toward the backlight unit  30 , and the flexible linear materials  61   b  are in contact with the backlight unit  30 , and has, in another part thereof, the structure in which the base member  61   a  is fixed to the backlight unit  30 , the flexible linear materials  61   b  extend toward the transparent protection plate  11 , and the flexible linear materials  61   b  are in contact with the transparent protection plate  11  may be employed. Alternatively, the wall member  160  may include both the flexible wall member  61  having the base member  61   a  fixed to the transparent protection plate  11  and the flexible linear members  61   b  extending toward the backlight unit  30 , and the flexible wall member  61  having the base member  61   a  fixed to the backlight unit  30  and the flexible linear materials  61   b  extending toward the transparent protection plate  11 , with these flexible linear materials  61   b  disposed to overlap each other in a plan view thereof. 
       FIG. 7  is a cross-sectional view illustrating an example of a display device according to a third embodiment. With respect to a liquid crystal display device  1 B which is an example of the display device, an aspect of a wall member  260  is different from the wall member  160  of  FIG. 5 . At least a part of the wall member  260  includes a flexible wall member  62 , which is the pressure variation relaxation section, formed of a material that can be easily bent. The flexible wall member  62  includes a base member  62   a  and a curtain-shaped wall material  62   b . The base member  62   a  is fixed to an outer circumferential surface of the transparent protection plate  11  which is the operation panel. The curtain-shaped wall member  62   b  extends from the base member  62   a  toward the backlight unit  30 . An end of the curtain-shaped wall member  62   b  on the opposite side to the base member  62   a  reaches an upper surface or a side surface of the backlight unit  30 , and the flexible wall member  62  is disposed across the transparent protection plate  11  and the backlight unit  30  so as to externally surround the liquid crystal display panel  20 . Therefore, enter of dust can be inhibited from entering the space S between the liquid crystal display panel  20  and the backlight unit  30 . The curtain-shaped wall member  62   b  can be formed of a lightweight material little attenuating the vibration of the vibrating bodies  13   a  and  13   b , and for example, the base member  62   a  and the curtain-shaped wall member  62   b  can be composed of a film-shaped or sheet-shaped member formed of a polyethylene terephthalate (PET) resin. It is noted that the base member  62   a  and the curtain-shaped wall member  62   b  may be integrally formed. 
       FIG. 8  is an enlarged cross-sectional view for explaining an air flow in the vicinity of the wall member  260  according to the third embodiment. The curtain-shaped wall member  62   b  has a free end on the side opposite to the base member  62   a , and there is a gap between the curtain-shaped wall member  62   b  and the side surface of the backlight unit  30 , through which air can flow. As illustrated with an arrow in  FIG. 8 , the air can flow through the gap, and hence, the air pressure change in the space S caused by the vibration of the vibrating bodies  13   a  and  13   b  can be relaxed, attenuation of the vibration of the transparent protection plate  11  which is the operation panel can be further suppressed, and the transparent protection plate  11  can be more efficiently vibrated. 
     In the structure of  FIG. 8 , the curtain-shaped wall member  62   b  may have a protrusion in a portion of its free end facing the side surface of the backlight unit  30 . In this case, the free end of the curtain-shaped wall member  62   b  can be inhibited from adhering to the side surface of the backlight unit  30  due to static electricity, and a gap between the free end of the curtain-shaped wall member  62   b  and the side surface of the backlight unit  30  can be secured. As a result, passing of air can be secured. 
     In addition, the curtain-shaped wall member  62   b  may have a single-piece structure, but may be divided into plural pieces in a vertical direction thereof. In this case, when the curtain-shaped wall member  62   b  vibrates by the vibration of the vibrating bodies  13   a  and  13   b , since a new gap is produced between divided portions of the curtain-shaped wall member  62   b , air passing property is improved. Further, since the new gap is produced only when the vibration is generated, decrease of the dust proofing effect can be suppressed. 
       FIG. 9  is an enlarged cross-sectional view for explaining movement of the wall member  260  in the third embodiment. The end of the curtain-shaped wall member  62   b  on the opposite side to the base member  62   a  may be in contact with the backlight unit  30 . Even in such a case, since the end of the curtain-shaped wall member  62   b  on the opposite side to the base member  62   a  is a free end, the wall member is deformed by deflection as illustrated with a two-dot chain line in accordance with the vibration of the transparent protection plate  11 . Therefore, the air pressure change in the space S can be relaxed by the shape change of the curtain-shaped wall member  62   b . Accordingly, attenuation of the vibration of the transparent protection plate  11  can be further suppressed, and the transparent protection plate  11  can be further efficiently vibrated. 
     Although the base member  62   a  is fixed to the transparent protection plate  11  in the third embodiment, a structure in which the base member  62   a  is fixed to the backlight unit  30  with the curtain-shaped wall member  62   b  extending to the transparent protection plate  11  may be employed. Also in employing this structure, the air pressure change in the space S caused by the vibrating bodies  13   a  and  13   b  can be relaxed, attenuation of the vibration of the transparent protection plate  11  which is the operation panel can be further suppressed, and the transparent protection plate  11  can be further efficiently vibrated. 
     In the display device of the present disclosure, the liquid crystal display panel  20  is disposed in the space S inside the wall member  60 ,  160 ,  260 , and the wall member  60 ,  160 ,  260  functions as a protection member for the liquid crystal display panel  20 , and functions also as a dust proofing member. Besides, the elastic supporting members  50  and the vibrating bodies  13  are preferably disposed in the space S inside the wall member  60 ,  160 ,  260 , and the wall member  60 ,  160 ,  260  functions as a protection member therefor, and functions also as the dust proofing member. Incidentally, the elastic supporting members  50  and the vibrating bodies  13  need not be always disposed in the space S inside the wall member  60 ,  160 ,  260 , but may be disposed outside the wall member  60 ,  160 ,  260 . 
     As mentioned above, although the present disclosure has been described in detail, the present disclosure is not limited to the above-described embodiments, and various modifications and improvements are possible without departing from the scope of the disclosure.