Patent Publication Number: US-2021191210-A1

Title: Display device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Continuation Application of PCT Application No. PCT/JP2019/025257, filed Jun. 25, 2019 and based upon and claiming the benefit of priority from Japanese Patent Application No. 2018-166061, filed Sep. 5, 2018, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD 
     Embodiments described herein relate generally to a display device. 
     BACKGROUND 
     Liquid crystal display devices, organic EL display devices, and the like are widely used as display devices for smartphones, tablet computers, car navigation systems, and the like. In recent years, there has been a demand for narrower frames in order to reduce the size of these display devices or to enlarge the display area for displaying images. For example, the liquid crystal display device comprises a liquid crystal display panel and a backlight device which illuminates the liquid crystal display panel. The backlight device includes a casing (or bezel) attached to the liquid crystal display panel, and various optical members arranged in the casing. One end of a flexible printed circuit (FPC) is joined to the liquid crystal display panel. The FPC extends outward from the liquid crystal display panel, and is bent, for example, toward the bottom of the casing. 
     SUMMARY 
     The present disclosure generally relates to a display device. 
     According to one embodiment, a display device includes a display panel, a first wiring board mounted on the display panel, and a backlight unit located on a back surface side of the display panel to illuminate the display panel. The backlight unit includes a casing which includes a bottom plate including a first slit and a side plate standing at the bottom plate, and a light guide arranged in the casing. The first wiring board passes between the side plate and the light guide and through the first slit and is bent toward a back surface side of the casing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view showing a display device of the embodiments. 
         FIG. 2  is a perspective view showing a back surface side of the display device. 
         FIG. 3  is a plan view showing a backlight unit of the embodiments. 
         FIG. 4  is a plan view showing a part of the backlight unit shown in  FIG. 3 . 
         FIG. 5  is a plan view showing a display panel arranged on the backlight unit shown in  FIG. 4 . 
         FIG. 6  is a sectional view of the display device taken along line AB shown in  FIG. 5 . 
         FIG. 7  is a cross-sectional view of the display device taken along line CD shown in  FIG. 5 . 
         FIG. 8  is a cross-sectional view showing a modified example of the display device shown in  FIG. 6 . 
         FIG. 9  is a plan view showing a modified example of the display device shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, there is provided a display device including a display panel, a first wiring board mounted on the display panel, and a backlight unit located on a back surface side of the display panel to illuminate the display panel. The backlight unit includes a casing which includes a bottom plate including a first slit and a side plate standing at the bottom plate, and a light guide arranged in the casing. The first wiring board passes between the side plate and the light guide and through the first slit and is bent toward a back surface side of the casing. 
     Embodiments will be described hereinafter with reference to the accompanying drawings. The disclosure is merely an example, and proper changes in keeping with the spirit of the invention, which are easily conceivable by a person of ordinary skill in the art, come within the scope of the invention as a matter of course. In addition, in some cases, in order to make the description clearer, the widths, thicknesses, shapes and the like, of the respective parts are illustrated schematically in the drawings, rather than as an accurate representation of what is implemented. However, such schematic illustration is merely exemplary, and in no way restricts the interpretation of the invention. In addition, in the specification and drawings, structural elements which function in the same or a similar manner to those described in connection with preceding drawings are denoted by like reference numbers, detailed description thereof being omitted unless necessary. 
       FIG. 1  is an exploded perspective view showing a display device DSP of the embodiments. 
     The display device DSP can be used by being incorporated in various electronic devices such as smartphones, tablet terminals, mobile phones, notebook PCs, portable game machines, electronic dictionaries, television devices, and car navigation systems. 
     The display device DSP comprises an active-matrix display panel PNL, a cover member CM arranged so as to be overlaid on the display surface PNLa which is one surface of the display panel PNL and to cover the entire display surface PNLa, a backlight unit BL arranged to be opposed to a back surface PNLb which is the other surface of the display panel PNL and to illuminate the display panel PNL, a first wiring board  23 , and a sub-wiring board  25 . 
     The display panel PNL comprises a first substrate SUB 1  having a rectangular plate shape, and a second substrate SUB 2  having a rectangular plate shape and arranged to be opposed to the first substrate SUB 1 . A peripheral portion of the second substrate SUB 2  is stuck on the first substrate SUB 1  with a sealing member SE. In  FIG. 1 , the sealing member SE is located in a region represented by hatching. Each of the first substrate SUB 1  and the second substrate SUB 2  is formed of a transparent insulating substrate such as a glass plate or a resin plate. 
     The display panel PNL includes a rectangular display region DA in a region which becomes an inner side of the sealing member SE in a state of plainly viewing the display surface PNLa (i.e., hereinafter referred to as a state in which the display panel is visually recognized from the normal direction of the surface of the display panel). An image is displayed in the display region DA. A non-display region NDA having a rectangular frame shape is provided around the display region DA. The display panel PNL has a transmissive display function of displaying an image by selectively transmitting light from the backlight unit BL to the display region DA. 
     The display device DSP includes the first wiring board  23  mounted on the display panel PNL. The first wiring board  23  has flexibility. A mounting portion MA which is not overlaid on the second substrate SUB 2  is provided on one shorter side of the first substrate SUB 1 , and one end of the first wiring substrate  23  is joined to the mounting portion MA. A width W 1  of one end of the first wiring substrate  23  is smaller than a width W 2  of the first substrate SUB 1 . 
     A semiconductor element such as a driver IC chip  24  which functions as a signal supply source for driving the display panel PNL is mounted on the first wiring board  23 . The sub-wiring board  25  is joined to the extending end of the first wiring board  23 . A capacitor  28 , connectors  26  and  27  and the like are mounted on the sub-wiring board  25 . 
     The cover member CM is formed of, for example, a glass plate or an acrylic transparent resin and has a rectangular plate shape. A frame-shaped light-shielding layer RS is formed on a peripheral portion of the back surface of the cover member CM (i.e., a surface on the display panel PNL side or a surface opposite to the surface facing an observer). 
     The backlight unit BL comprises a casing  18 , a plurality of optical members (not shown) arranged in the casing  18 , a light source unit  22  which supplies light made incident on the optical members, and a frame-shaped double-sided tape TP 1 . 
     The casing  18  includes a rectangular bottom plate  17  to be described later with reference to  FIG. 2 , and a plurality of side plates  18   a ,  18   b ,  18   c , and  18   d  rising from side edges of the bottom plate  17 . The light source unit  22  comprises a plurality of light sources  21  arranged at predetermined intervals along the side plate  18   d , and a second wiring board  32  extending along the side plate  18   d  and supporting the light source  21 . The second wiring board  32  is formed to have a length substantially equal to the side plate  18   d . In addition, the second wiring board  32  integrally includes a connection end portion  32   c.    
       FIG. 2  is a perspective view showing the back surface side of the display device DSP. 
     In the embodiments, the casing  18  includes a first slit SL 1  and a second slit SL 2  formed in the bottom plate  17 . The first wiring board  23  passes through the first slit SL  1  and is arranged to be overlaid on the bottom plate  17 . In addition, the connection end portion  32   c  passes through the second slit SL 2  and is arranged to be overlaid on the bottom plate  17 . The connection end portion  32   c  is connected to a connector  27 . Incidentally, in the example illustrated, the first wiring board  23  and the connection end portion  32   c  pass through different slits, respectively. However, the first slit SL 1  and the second slit SL 2  may be one connected slit. 
       FIG. 3  is a plan view showing the backlight unit BL of the embodiments. 
     The backlight unit BL further comprises a frame (reinforcement member)  16  having a rectangular frame shape, which is arranged inside the side plates  18   a  to  18   d , and a light guide LG arranged inside the frame  16 . The frame  16  includes a first portion  16   a , a second portion  16   b , a third portion  16   c , and a fourth portion  16   d  that are in contact with the side plates  18   a  to  18   d , respectively, and functions as a reinforcing member for the casing  18 . The frame  16  includes a recess portion  101  and a recess portion  102  in the fourth portion  16   d . The recess portion  101  and the recess portion  102  are formed on the side of the fourth portion  16   d  on a side opposed to the side plate  18   d , and form a gap between the fourth portion  16   d  and the side plate  18   d.    
     Both the frame  16  and the casing  18  can be integrally formed of resin or metal. Alternatively, either of them can be formed of resin and the other can be formed of metal. In the embodiments, the bottom plate  17  and the side plates  18   a  to  18   d  are formed of metal such as stainless steel (SUS), and the frame  16  is formed of resin. The frame  16  is integrated with the side plates  18   a  to  18   d  by insert molding or the like. Incidentally, the frame  16  is formed in a frame shape in the embodiments. However, a configuration is adopted in which only the third portion  16   c  and the fourth portion  16   d  are formed and the first portion  16   a  and the second portion  16   b  are not formed. In this case, only the third portion  16   c  and the fourth portion  16   d  function as a reinforcing member. In addition, a configuration in which only the fourth portion  16   d  is provided in the casing  18  as a reinforcing member can be adopted. 
       FIG. 4  is a plan view showing a part of the backlight unit BL shown in  FIG. 3 . In  FIG. 4 , in addition to  FIG. 3 , the second wiring board  32 , and the first slit SL 1  and the second slit SL 2  of the bottom plate  17  are illustrated, and the frame  16  is represented by hatching. 
     A recess portion  101  is overlaid on the first slit SL 1 . A recess portion  102  is overlaid on the second slit SL 2 . The connection end portion  32   c  of the second wiring board  32  is folded back to the back surface side of the casing  18  as shown in  FIG. 2  through the space between the recess portion  102  and the side plate  18   d  and through the second slit SL 2 . The inner edges of the first slit SL 1  and the second slit SL 2  are located more closely to the light guide LG than the inner surface of the fourth portion  16   d  accommodated in the casing  18 . 
       FIG. 5  is a plan view showing the display panel PNL arranged on the backlight unit BL shown in  FIG. 4 . 
     The first substrate SUB 1  is overlaid on the side plates  18   a  and  18   b , the first portion  16   a , and the second portion  16   b . In addition, the first substrate SUB 1  is overlaid on a part of the fourth portion  16   d . On the side plate  18   d  side, the side edge of the backlight unit BL is located slightly on an outer side than the side edge of the first substrate SUB 1 . 
     The first wiring board  23  is folded back to the back surface side of the casing  18  as shown in  FIG. 2  between the recess portion  101  and the side plate  18   d  and through the first slit SL 1 . The connection end portion  32   c  of the second wiring board  32  extends to the outside of the first board SUB 1 . 
       FIG. 6  is a cross-sectional view of the display device DSP taken along line AB shown in  FIG. 5 . 
     The display panel PNL comprises a first substrate SUB 1 , a second substrate SUB 2 , and a liquid crystal layer LC sealed with a sealing member SE. A polarizer PL 1  is stuck on a lower surface of the first substrate SUB 1 . A polarizer PL 2  is stuck on the upper surface of the second substrate SUB 2 . 
     A lower surface of the cover member CM is stuck on the polarizer PL 2  of the display panel PNL with an adhesive AD or a tackiness agent having optical transparency. 
     The backlight unit BL further comprises a reflection sheet RE arranged on the bottom plate  17 , and a plurality of first optical sheets OS 1  and second optical sheets OS 2  arranged to be overlaid on the light guide LG. The members constituting the backlight unit BL such as the reflection sheet RE, the light guide LG, the first optical sheet OS 1  and the second optical sheet OS 2 , the light source  21 , the second wiring board  32 , and the frame  16  are accommodated in the casing  18 . 
     The light source  21  is fixed to the light guide LG by, for example, a fixing tape TP 2  provided to extend from the lower surface of the light source  21  to the lower surface of the light guide LG. Incidentally, the fixing tape TP 2  is not bonded to the bottom plate  17 . The light source  21  is arranged between an incident surface EF of the light guide LG and the side plate  18   d , and the light emitting surface  21   a  of the light source  21  faces the incident surface EF or abuts on the incident surface EF. The light emitted from the light source  21  is made incident on the light guide LG from the incident surface EF, propagates in the light guide LG, or is reflected on the reflection sheet RE, and is emitted from the upper surface of the light guide LG to the display panel PNL side. 
     The second wiring board  32  is stuck on the fourth portion  16   d  of the frame  16  with a double-sided tape  42 . The second wiring board  32  is located on substantially the same plane as the first optical sheet OS 1  and is opposed to the bottom plate  17  with the light source  21  interposed therebetween. A side edge  32   a  of the second wiring board  32  is opposed to the end of the first optical sheet OS 1  with a gap interposed therebetween. A plurality of connection pads  41  formed of a conductive layer are provided on one surface of the second wiring substrate  32 . The light sources  21  are mounted on the connection pads  41 . 
     The backlight unit BL is attached to the display panel PNL with a double-sided tape TP 1 . An inner peripheral part of the double-sided tape TP 1  is stuck on the polarizer PL 1 , and an outer peripheral part is stuck on the first substrate SUB 1  with the spacer SP 2  interposed therebetween. In addition, the double-sided tape TP 1  is stuck on the second wiring board  32  via the spacer SP 1  and is further stuck on a light-shielding tape  45 . 
     The first wiring board  23  includes a layered or sheet-shaped base  23   a , a conductive layer  23   b  formed on one surface of the base  23   a  and constituting a plurality of lines, connection pads, and the like, and a protective layer  23   c  covering the conductive layer  23   b . The base  23   a  and the protective layer  23   c  are formed of, for example, a synthetic resin such as polyimide or polyurethane, and the conductive layer  23   b  is formed of a conductive metal layer, for example, a copper foil. 
     The first wiring board  23  passes between the side plate  18   d  and the light guide LG and through the first slit SL 1  and is bent toward the back surface side of the casing  18 . That is, the first wiring substrate  23  constitutes a curved portion  31  which is curved from the display panel PNL to the bottom plate  17  side of the casing  18 . The first wiring board  23  is arranged in a direction in which the protective layer  23   c  side is opposed to the display panel PNL. The protective layer  23   c  and the conductive layer  23   b  are located on the inner peripheral side of the curved portion  31 , and the base  23   a  is located on the outer peripheral side of the curved portion  31 . 
     A plurality of connection terminals  23   d  formed by parts of the conductive layer  23   b  are provided at one end of the first wiring board  23 . The plurality of connection terminals  23   d  are electrically connected to the plurality of pads PD of the first substrate SUB 1 , respectively, by thermally compressing one end of the first wiring substrate  23  on the first substrate SUB 1 . The driver IC chip  2  is mounted on the protective layer  23   c  side, and is electrically connected to the conductive layer  23   b  of the first wiring board  23  via an opening or connection pad (not shown) provided in the protective layer  23   c.    
     A width W 11  of the first slit SL 1  is desirably large enough to allow the first wiring board  23  to pass therethrough, for example, in a state in which the driver IC chip  2  and the connector are mounted on the first wiring board  23 . In the embodiments, for example, the width W 11  of the first slit SL 1  is approximately 2 mm or more. In addition, the thickness of the first wiring board  23  is, for example, approximately 0.1 mm. Therefore, when the frame is attached after the first wiring board  23  passes through the slit SL 1 , a width W 12  between the side plate  18   d  and the frame  16  may be approximately 0.3 mm or more. Furthermore, since the first wiring board  23  is bent so as to surround the upper and lower parts of the frame  16 , a width W 13  from the side plate  18   d  to the inner circumference of the frame  16  is, for example, approximately 0.5 mm or more. In contrast, the width W 12  between the side plate  18   d  and the frame  16  needs to be approximately 2 mm or more in order to first mount the frame  16  in the casing  18  and then pass the first wiring board  23  through the first slit SL 1 . In this case, the width of the first slit SL 1  is also increased as necessary. 
     According to the embodiments, the casing  18  includes the first slit SL 1  in the bottom plate  17 , and the first wiring board  23  is bent from the inside of the side plate  18   d  through the first slit SL 1 . For this reason, even if a force that expands toward the outside of the side plate  18   d  is generated in the curved portion  31  due to the repulsive force of bending, the swelling of the curved portion  31  can be suppressed by the side plate  18   d . Therefore, an increase in the frame width of the display device DSP caused by the swelling of the curved portion  31  can be suppressed. The frame width can be reduced by, for example, approximately 0.5 mm as compared to a configuration in which the curved portion  31  is located outside the side plate  18   d . Therefore, the frame on the mounting portion side of the display device DSP can be narrowed. 
       FIG. 7  is a sectional view of the display device DSP taken along line CD shown in  FIG. 5 . 
     The connection end portion  32   c  passes between the side plate  18   d  and the light guide LG and through the second slit SL 2  and is bent toward the back surface side of the casing  18 . That is, the second wiring substrate  32  forms a curved portion  33  that is curved from the display panel PNL to the bottom plate  17  side of the casing  18 . Similarly to the case shown in  FIG. 6 , even if a force that expands toward the outside of the side plate  18   d  due to the repulsive force of bending is generated at the curved portion  33 , the swelling of the curved portion  33  can be suppressed by the side plate  18   d . The frame of the display device DSP can be therefore narrowed. 
       FIG. 8  is a cross-sectional view showing a modified example of the display device DSP shown in  FIG. 6 . The configuration shown in  FIG. 8  is different from the configuration shown in  FIG. 6  with respect to a feature that the frame  16  enters the first slit SL 1 . 
     The bottom plate  17  includes an upper surface S 1  on the light guide LG side, a side surface S 2  in the first slit SL 1 , and a lower surface S 3  on a side opposite to the upper surface S 1 . The frame  16  is in contact with the upper surface S 1 , the side surface S 2 , and the lower surface S 3 . That is, the frame  16  is located between the side surface S 2  and the first wiring board  23 , and the side surface S 2  is covered with the frame  16 . For this reason, abutment of the first wiring board  23  on the bottom plate  17  inside the first slit SL 1  can be suppressed. Therefore, even when the conductive layer  23   b  of the first wiring board  23  is exposed, conduction between the conductive layer  23   b  and the casing  18  can be suppressed. Incidentally, in order to suppress the first wiring board  23  abutting on the side surface S 2 , a member  103  such as a sponge may be arranged between the first wiring board  23  and the bottom plate  17  as shown in the figure. 
       FIG. 9  is a plan view showing a modified example of the display device DSP shown in  FIG. 5 . The configuration shown in  FIG. 9  is different from the configuration shown in  FIG. 5  with respect to a feature that the first substrate SUB 1  includes a recess portion  104  at a position overlaid on the first slit SL 1 . The recess portion  104  is formed by shaving a central part of the mounting portion MA of the first substrate SUB 1  by a predetermined width from an edge. The first wiring board  23  passes through the recess portion  104 . The first substrate SUB 1  includes extending portions E 1  and E 2  that extend to the side plate  18   d  at both ends of the recess portion  104 . The extending portions E 1  and E 2  are overlaid on the fourth portion  16   d  of the frame  16 . Incidentally, the extending portions E 1  and E 2  may also be overlaid on the side plate  18   d . By forming such extending portions E 1  and E 2 , the area of the mounting portion MA can be enlarged and a margin can be given to a space for arranging the lines and the like. 
     As described above, according to the embodiments, a display device capable of narrowing the frame can be obtained. 
     Incidentally, in the embodiments, the configuration in which the frame  16  includes the recess portion  101  and the recess portion  102  has been described. However, the configuration is not limited to this example. For example, the frame  16  may not include the recess portion  101  or the recess portion  102 . In this case, after the first wiring substrate  23  and the second wiring substrate  32  are passed through the first slit SL 1  and the second slit SL 2 , the frame  16  may be arranged at a position overlaid on the slit SL 1  and the second slit SL 2 . In addition, for example, the frame  16  may not be interrupted and arranged at a position overlaid on the first slit SL 1  and the second slit SL 2 . 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.