Abstract:
A display device includes a plurality of pixels in matrix, a substrate on which the plurality of pixels are formed, and a support member under the substrate. The substrate is arranged on a front surface of the support member and a plurality of recesses are formed on a rear surface of the support member. Each of the substrate and the support member is formed in substantially rectangular shape and has a first side, a second side, a third side facing to the first side, and a fourth side facing to the second side. Each of the plurality of recesses extends in a first direction extending substantially in parallel to the first side and the third side.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation of U.S. application Ser. No. 12/836,714, filed Jul. 25, 2010, the contents of which are incorporated herein by reference. 
         [0002]    The present application claims priority from Japanese application JP 2009-168085 filed on Jul. 16, 2009, the content of which is hereby incorporated by reference into this application. 
     
    
     BACKGROUND OF THE INVENTION 
       [0003]    1. Field of the Invention 
         [0004]    The present invention relates to a display device, and more particularly to a display device using a substrate which is liable to be deformed two-dimensionally such as a plastic substrate or a thin glass substrate. 
         [0005]    2. Description of the Related Art 
         [0006]    Various kinds of display devices such as a liquid crystal display device and an organic EL display device have been put into practice. Further, mobile phones and personal digital assistants which incorporate these display devices also have been provided. In display devices developed and used in recent years, to enhance the reduction of thickness, to enhance the reduction of weight or to increase the flexibility of the display device, a substrate which constitutes a part of the display device is formed using a plastic substrate or a thin glass substrate. 
         [0007]    With respect to a display device which uses a plastic substrate, as disclosed in JP-A-2002-184959 (patent document 1) or the like, there has been proposed a flexibly deformable display device in which functional elements such as thin film transistors (TFTs) are formed on a glass substrate and, thereafter, glass is removed or the glass substrate is formed into a thin film, and functional elements are adhered to (or transferred to) a plastic substrate. 
         [0008]    However, to use the plastic substrate in the display device such as a liquid crystal display device or an organic EL display device, the plastic substrate is required to possess high size stability (low thermal expansion property or high heat resistant property) and hence, the plastic substrate exhibits characteristics that the plastic substrate exhibits high resistance against bending but is liable to be broken when elongation deformation is applied to the plastic substrate. In fact, when a liquid crystal display panel which uses a plastic substrate is deformed, the liquid crystal display panel has a drawback that although the liquid crystal display panel exhibits high flexibility with respect to one-dimensional bending (one-dimensional deformation) such as a four-point bending test, the liquid crystal display panel is liable to be broken with respect to a point load which easily causes the two-dimensional bending (two-dimensional deformation) of the liquid crystal display panel such as a load falling test. Even when the liquid crystal display panel uses a thin glass substrate which is made thin enough to be bendable, in the same manner as the plastic substrate, the liquid crystal display panel exhibits more brittleness against the two-dimensional deformation than one-dimensional deformation. 
       SUMMARY OF THE INVENTION 
       [0009]    The present invention has been made to overcome the above-mentioned drawbacks, and it is an object of the present invention to provide a display device which can prevent a display panel from being broken even when a substrate which constitutes the display panel is formed of a substrate which is brittle to two-dimensional deformation. 
         [0010]    To overcome the above-mentioned drawbacks, the display device according to the present invention is characterized by following constitutions. 
         [0011]    (1) According to one aspect of the present invention, there is provided a display device which includes a display panel in which a plurality of pixels are arranged on a substrate two-dimensionally and which is configured to display an image thereon, and a support member which supports the display panel, wherein the support member possesses anisotropy in bending strength so as to encourage one-dimensional deformation of the display panel while suppressing two-dimensional deformation of the display panel. 
         [0012]    (2) In the display device having the constitution described in (1), the support member is a frame member which is configured to support only two opposite sides of the display panel. 
         [0013]    (3) In the display device having the constitution described in (2), the frame member is provided with a folded portion which projects toward a side where the display panel is arranged at portions thereof outside positions where two sides of the display panel are supported. 
         [0014]    (4) In the display device having the constitution described in (1), the support member is a casing member which houses the display panel, an optical sheet and a backlight member. 
         [0015]    (5) In the display device having the constitution described in (4), the casing member includes a bottom surface, and two side surface support portions which are formed on edge portions of the bottom surface by being bent from the bottom surface such that the side surface support portions support two opposite sides of the display panel. 
         [0016]    (6) In the display device having the constitution described in (5), a plurality of grooves which are arranged parallel to the side surface support portions are formed on the bottom surface of the casing member. 
         [0017]    (7) In the display device having the constitution described in (5) or (6), a plurality of auxiliary support portions which are bent from the bottom surface and support portions of two other sides of the display panel different from two opposite sides of the display panel are formed on the edge portions on a side where the side surface support portions are not formed out of the edge portions of the bottom surface. 
         [0018]    (8) In the display device having the constitution described in (1), the support member has a support surface which overlaps with the display panel as viewed in a plan view, and the support member is a back surface support member which supports a back surface of the display panel on a side opposite to a display screen of the display panel by the support surface. 
         [0019]    (9) In the display device having the constitution described in (8), the back surface support member has a plurality of beams which are arranged parallel to two opposite sides of the display panel. 
         [0020]    (10) In the display device having the constitution described in (9), the beams are formed on the back surface support member on a side opposite to a side where the display panel is arranged on the support surface. 
         [0021]    (11) In the display device having the constitution described in (8), the back surface support member has a plurality of grooves which are arranged parallel to two opposite sides of the display panel on the support surface. 
         [0022]    (12) In the display device having the constitution described in (8), a recessed portion whose thickness is continuously changed in the direction perpendicular to two opposite sides of the display panel is formed on the support surface. 
         [0023]    (13) In the display device having the constitution described in (12), the recessed portion is formed on the back surface support member on a side opposite to a side where the display panel is arranged on the support surface. 
         [0024]    According to the present invention, even when an external force such as a point load which causes the two-dimensional deformation is applied to a display panel, a support member which supports the display panel is deformed so as to suppress the two-dimensional deformation and accelerate the one-dimensional deformation of the display panel and hence, it is possible to prevent the display panel from being broken. Further, since the breaking of the display panel can be prevented, it is possible to enhance the mechanical strength of the whole display device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a plan view for explaining an embodiment of a display device which uses a frame member as a support member; 
           [0026]      FIG. 2A  and  FIG. 2B  are cross-sectional views taken along a chain double-dashed line A-A′ in  FIG. 1 ; 
           [0027]      FIG. 3  is a plan view for explaining an embodiment of the display device using a frame member which can suppress the deformation as a support member; 
           [0028]      FIG. 4A  and  FIG. 4B  are cross-sectional views taken along a chain double-dashed line B-B′ in  FIG. 3 ; 
           [0029]      FIG. 5  is a view for explaining the constitution of a liquid crystal display device which is one example of the display device; 
           [0030]      FIG. 6  is a perspective view for explaining an embodiment where a casing member is used as a support member of the display device; 
           [0031]      FIG. 7  is a perspective view for explaining another embodiment where a casing member is used as a support member of the display device; 
           [0032]      FIG. 8  is a perspective view for explaining an embodiment where a back surface support member possessing strength anisotropy due to a plurality of beams is used as a support member; 
           [0033]      FIG. 9  is a perspective view for explaining another embodiment where a back surface support member possessing strength anisotropy due to a plurality of beams is used as a support member; 
           [0034]      FIG. 10  is a perspective view for explaining an embodiment where a back surface support member possessing strength anisotropy due to a plurality of beams is used as a support member; and 
           [0035]      FIG. 11  is a perspective view for explaining an embodiment where a back surface support member possessing strength anisotropy due to the continuous curved structure formed by continuously changing a thickness of the back surface support member is used as a support member. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0036]    Hereinafter, a display device according to the present invention is explained in detail.  FIG. 5  is a view for explaining the constitution of a liquid crystal display device which is one example of the display device according to the present invention. Hereinafter, the explanation is made by focusing on the liquid crystal display device. However, the display device of the present invention is not limited to the liquid crystal display device, and is applicable to an organic EL display device or the like. Particularly, the present invention is preferably applicable to a display device which uses a plastic substrate or a thin glass substrate as a display panel. 
         [0037]    The liquid crystal display device shown in  FIG. 5  includes: a liquid crystal display panel PNL; a backlight BL; and an optical sheet OS for making an illumination light radiated from the backlight BL to the whole liquid crystal display panel PNL uniform. The optical sheet OS is constituted of a prism sheet and a diffusion sheet. The backlight BL is constituted of a light source formed of a light emitting diode (LED), a light guide plate, a reflection sheet and the like, for example. These parts are integrally held by an upper frame member URM, a lower frame member SRM and a back surface support member BSM. Further, there may be a case where the back surface support member BSM is omitted and the lower frame member SRM also functions as a back surface support member or a case where the upper frame member URM is omitted and a casing member is formed by adding the support structure for a display panel to a portion of the lower frame member SRM. 
         [0038]    The liquid crystal display panel has the structure where liquid crystal is sealed in a space defined between two substrates, and a thin film transistor (TFT) layer, a color filter layer and the like are formed on inner surfaces of the substrates. Usually, when the substrate is formed of a glass plate having a thickness of approximately 500 μm, the glass substrate per se possesses high rigidity and hence, the substrate is hardly deformed whereby there is no possibility that the substrate is broken by deformation thereof particularly. However, when the substrate is formed of a plastic substrate, a thin glass substrate having a thickness of 100 μm or less or a composite substrate of a plastic substrate and a thin glass substrate, the substrate is liable to be deformed. Particularly, the substrate is easily broken by the two-dimensional deformation attributed to a point load or the like. 
         [0039]    The liquid crystal display panel PNL is laminated to the optical sheet OS and backlight BL using an adhesive layer or the like and, at the same time, as shown in  FIG. 5 , is structurally fixed using the frame members and the casing member. Accordingly, conventionally, by improving a connection portion between the frame members and the display panel or improving the structure of the casing member, the deformation of the display device is restricted so as to prevent the display panel from being broken. 
         [0040]    However, as a result of extensive studies made by inventors of the present invention, the inventors have found that, rather than preventing all deformations, by suppressing the generation of two-dimensional deformation and by limiting the deformation to one-dimensional bending even when a point load is applied to the display panel, the elongation and shrinkage of the display panel become the circumference difference dependent on a plate thickness of the substrate and hence, the substrate is hardly broken. The present invention is made based on such finding. 
         [0041]    In the display device of the present invention which includes: the display panel in which a plurality of pixels are arranged on a substrate two-dimensionally and is configured to display an image thereon; and a support member which supports the display panel, the improvement is characterized in that the support member possesses anisotropy in bending strength (strength anisotropy) so as to encourage one-dimensional deformation while suppressing two-dimensional deformation of the display panel. 
         [0042]    The “strength anisotropy” in the present invention implies that bending strength of the support member with respect to an external force applied to the support member differs depending on the bending direction. To be more specific, “strength anisotropy” implies the structure in which easily bendable direction is intentionally imparted to a die-cast member such as the frame member exemplified by the upper frame member and the lower frame member constituting the support member and the back surface support member. 
         [0043]    Hereinafter, the explanation is made with respect to embodiments where the present invention is applied to various kinds of support members. 
         [0044]      FIG. 1  is a view showing an embodiment in which the present invention is applied to a frame member which is one of the support members, and more particularly to an upper frame member URM 1 . Different from the upper frame member URM shown in  FIG. 5  which covers the liquid crystal display panel PNL together with the optical sheet OS and the backlight BL, with respect to the upper frame member URM 1  shown in  FIG. 1 , the liquid crystal display panel PNL is arranged on an upper surface of the upper frame member URM 1 . The upper frame member URM 1  which supports the display panel PNL indicated by a chained line has support lugs  1  which support only two opposite sides of the display panel PNL. Further, the display panel PNL is fixed to the support lugs  1  using an adhesive agent or the like. 
         [0045]      FIG. 2A  and  FIG. 2B  are cross-sectional views taken along a chain double-dashed line A-A′ in  FIG. 1 .  FIG. 2A  and  FIG. 2B  show a state where the upper frame member URM 1  supports the display panel PNL, wherein  FIG. 2A  shows a state where a load such as an external force is not applied to the display panel PNL, and  FIG. 2B  shows a state where an external force F is applied to the display panel PNL so that the display panel PNL is deformed one-dimensionally. 
         [0046]    As shown in  FIG. 1 ,  FIG. 2A  and  FIG. 2B , by adopting the structure where the support structure for supporting the display panel PNL on the upper frame member URM 1  is provided to only two opposite sides of the display panel PNL, it is possible to provide the structure which allows the display panel PNL to perform only one-dimensional deformation in  FIG. 2B  where the display panel PNL is bent only vertically. In such support structure, due to the structure of the upper frame member URM 1  which uses the support lugs  1 , the display panel PNL is hardly bent in the direction parallel to two supported sides (Y direction in  FIG. 1 ), while only small resistance is generated in the display panel PNL in the direction perpendicular to the supported sides (X direction in  FIG. 1 ) so that the display panel PNL is easily bent in the X direction. Accordingly, it is possible to impart bending strength anisotropy to the display panel PNL. Particularly, by forming bent portions  3  (stepped portions shown in  FIG. 2 ) which are arranged parallel to the support lugs  1  on the upper frame member URM 1  in the vicinity of support portions of the upper frame member URM 1 , the display panel PNL is hardly bent in the Y direction so that it is possible to impart higher strength anisotropy to the display panel PNL. Here, the structure for supporting the display panel PNL is not limited to the upper frame member. That is, for example, the structure according to the present invention may be applied to a frame-shaped member (middle frame, mold frame) not shown in  FIG. 5  which supports the display panel PNL from an optical sheet OS side and a backlight BL side respectively. 
         [0047]      FIG. 3 ,  FIG. 4A  and  FIG. 4B  show another embodiment of the present invention where an upper frame member is used as the support member. To be more specific,  FIG. 3  and  FIG. 4  show the structure where the deformation of an upper frame member per se is suppressed.  FIG. 4A  and  FIG. 4B  are cross-sectional views taken along a chain double-dashed line B-B′ in  FIG. 3 . This embodiment is characterized in that a folded portion  2  which projects toward a side where the display panel PNL is arranged is formed on portions of the upper frame member URM 2  arranged around support lugs  1  respectively so that the deformation of the frame member per se is suppressed. 
         [0048]    By constituting the upper frame member URM 2  so as to prevent the deformation of the fame structure and to allow only the support lugs  1  to be deflected by an external force F, the deformation of the display panel PNL in the Y direction in  FIG. 3  can be surely suppressed thus allowing the display panel PNL to be deformed only in the X direction. Further, as another method for preventing the deformation of the frame structure, a thickness of a peripheral portion of the frame may be increased. Since it is often the case that the frame member, the casing member or the like described later is formed by press forming, it is easier to adjust the strength of the frame structure by the folded structure which is formed by folding or the like. 
         [0049]      FIG. 6  and  FIG. 7  show the improvement of the lower frame member SRM shown in  FIG. 5  where the lower frame member SRM is constituted of a casing member having strength anisotropy. A casing member SRM 1  is a casing member which covers a display panel. The display panel, an optical sheet and a backlight not shown in the drawing are housed in the inside of the casing member SRM 1 . The casing member SRM 1  includes integrally-formed folded portions (side surface support portions  11 ) at portions thereof corresponding to only two opposite sides of the display panel. 
         [0050]    The side surface support portion  11 , in the same manner as the frame member shown in  FIG. 1  to  FIG. 4 , supports the display panel by fixing such as adhesion. In a case where the display panel is deflected by its own weight, as shown in  FIG. 6 , it is preferable to provide auxiliary support portions  12  which support the display panel at intervals at positions other than the sides on which the side surface support portion  11  is formed. Such auxiliary support portions  12  are not continuously formed and hence, the display panel can be easily bent in the arrangement direction of the auxiliary support portions  12  (in the lateral direction in  FIG. 6 ) thus assisting the one-dimensional deformation of the display panel. 
         [0051]    A casing member SRM 2  in  FIG. 7  is configured such that a plurality of grooves  13  are formed on a bottom surface  10  of the casing member SRM 1  in  FIG. 6 , and a bottom surface of the casing member SRM 2  is constituted of planar portions  14  and a plurality of grooves  13 . Since the grooves  13  are formed parallel to the side surface support portions  11 , the casing member SRM 2  is characterized by being hardly bent in the direction along the grooves  13  and being easily bent in the direction perpendicular to the grooves  13  (in the lateral direction in  FIG. 7 ) with respect to the whole bottom surface of the casing member SRM 2 . Due to such a constitution, it is possible to impart strength anisotropy to the casing member SRM 2  which constitutes the support member. Here, in the same manner as the constitution shown in  FIG. 6 , the casing member SRM 2  in  FIG. 7  may also include auxiliary support portions  12 . 
         [0052]    Next, the explanation is made with respect to an embodiment in which strength anisotropy is imparted to a back-surface support member which supports a display panel from a back surface side. For example, the back-surface support member BSM shown in  FIG. 5  includes a support surface which supports the display panel PNL and overlaps with the display panel PNL as viewed in a plan view. The back-surface support member BSM mounts the display panel PNL, the optical sheet OS and the backlight BL thereon, and supports a back surface of the display panel PNL on a side opposite to a display screen of the display panel PNL by the support surface thereof. Such a back-surface support member is formed by a die-casting manufacturing method using a magnesium alloy or the like as a material. In the present invention, a thickness of the back-surface support member is adjusted to impart strength anisotropy to the back-surface support member, as shown in  FIG. 8  to  FIG. 11 . 
         [0053]    In  FIG. 8  and  FIG. 9 , the back-surface support members BSM 1  and BSM 2  respectively have the structure where a plurality of beams  21  (beam structure) are arranged parallel to two opposite sides of the display panel (not shown in the drawings). By forming the back surface support member by combining a planar plate portion  20  which constitutes a support surface and the beams  21  with each other, the back-surface support member BSM 1  or BSM 2  having partially thick portions and partially thin portions is formed. Due to such a constitution, the back-surface support members BSM 1  or BSM 2  is hardly bent in the direction along the beams  21  and is easily bent in the direction perpendicular to the beams  21  (in the lateral direction in  FIG. 8  and  FIG. 9 ). 
         [0054]    Further, in addition to the formation of the beams on the back-surface support member on a side opposite to the display panel, as indicated by symbol  22  in  FIG. 9 , the beams may be also formed on the back-surface support member on a display-panel side at edge portions of the back-surface support member. Due to such a constitution, the back-surface support member can house the display panel, the backlight and the like therein. 
         [0055]      FIG. 10  shows a back-surface support member BSM 3  where a plurality of grooves  31  are formed on the back-surface support member BSM 3  parallel to two opposite sides of a display panel. With the formation of the grooves  31 , a thickness of the plate member  30  which constitutes the back-surface support member is adjusted so that the plate member  30  is hardly bent in the direction along the grooves  31  and is easily bent in the direction perpendicular to the grooves  31  thus ensuring bending strength anisotropy. The grooves  31  may be formed either on a side of the back-surface support member BSM 3  on which the display panel is held or on a side of the back-surface support member BSM 3  opposite to the side of the back-surface support member BSM 3  on which the display panel is held. 
         [0056]      FIG. 11  shows a back-surface support member BSM 4  on which a recessed portion  41  is formed by continuously changing a thickness of the back-surface support member BSM 4  in the direction perpendicular to two opposite sides of the display panel. The recessed portion  41  is formed on a back surface of a back plate  40  (on a side opposite to a side on which the display panel is arranged) such that a thickness of the recessed portion  41  is gradually and continuously changed. With the formation of the recessed portion  41 , the back-surface support member BSM 4  is hardly bent in the extending direction of the recessed portion  41  and is easily bent in the direction perpendicular to the recessed portion  41  (in the lateral direction in  FIG. 11 .) 
         [0057]    By using the above-mentioned various kinds of support members, it is possible to impart strength anisotropy to the display panel. Accordingly, even when an external force is applied to the display panel which is supported by the support member, it is possible to encourage the display panel to be deformed one-dimensionally while suppressing the two-dimensional deformation of the display panel. 
         [0058]    As has been explained heretofore, according to the present invention, even when the substrate which is brittle to two-dimensional deformation is used as the substrate which constitutes the display panel, it is possible to provide the display device which can suppress the breaking of the display panel. 
         [0059]    While there have been described what are at present considered to be certain embodiments of the invention, it will be understood that various modifications may be made thereto, and it is intended that the appended claims cover all such modifications as fall within the true spirit and scope of the invention.