Patent Publication Number: US-2020292870-A1

Title: Display device

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. Provisional Patent Application No. 62/818,719 filed on Mar. 14, 2019. The entire contents of the priority application are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The technology described herein relates to a display device. 
     BACKGROUND 
     A thin display device in a flat shape for an electronic product includes at least a display panel for displaying images and a backlight unit for applying light to the display panel from a back side. A method for fixing the display panel and the backlight unit together may use an adhesive double-sided tape. The double-sided tape is attached to a frame-shaped outer edge area of the display panel corresponding to a non-display area. The double-sided tape is provided in black to have a light blocking property to block light to the non-display area NAA. 
     As a reduction in frame width progresses in recent years, structural difficulty arises to reserve a sufficient area for the double-sided tape. An increase in retention force is expected. 
     SUMMARY 
     The technology described herein was made in view of the above circumstances. An object is to provide a display device including a display panel and a backlight unit solidly fixed together. 
     A display device includes a display panel, a backlight unit, and a fixing member. The display panel includes a display area. in which images are displayed and a non-display area disposed to surround the display area. The backlight unit is disposed opposite a back surface of the display panel. The fixing member is fixed between the display panel and the backlight unit to fix the display panel and the backlight together. The fixing member includes a blocking portion and a light passing portion. The light blocking portion has a light blocking property. The light blocking portion is disposed in an area overlapping the non-display area. The light passing portion has light transmissivity. The light passing portion is disposed inner than the light blocking portion. 
     According to the technology described herein, a display device including a display panel and a backlight unit solidly fixed together. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a liquid crystal display device according to an embodiment. 
         FIG. 2  is a cross-sectional side view of the liquid crystal display device. 
         FIG. 3  is a plan view of a fixing sheet. 
         FIG. 4  is a cross-sectional side view of the fixing sheet. 
         FIG. 5  is a plan view of a fixing member according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An embodiment will be described in detail with reference to  FIGS. 1 to 4 . In this section, a liquid crystal display device  10  (an example of a display device) including a liquid crystal panel  11  will be described. In the drawings, X-axes, Y-axes, and Z-axes may be present. The axes in each drawing correspond to the respective axes in other drawings. A vertical direction is defined based on  FIG. 2 . An upper side and a lower side in  FIG. 2  correspond to a front side and a rear side of the liquid crystal display device  10 , respectively. 
     The liquid crystal display device  10  has a block shape with a rectangular shape in a plan view. As illustrated in  FIG. 1 , the liquid crystal display device  10  includes the liquid crystal panel  11  and a backlight unit  20 . The liquid crystal panel  11  is formed in a plate shape and configured to display images. The backlight unit  20  is disposed behind the liquid crystal panel  11  and configured to apply light to the liquid crystal panel  11 . The liquid crystal display device  10  according to this embodiment may be used for an electronic device such as a portable digital assistant (e.g., a mobile phone, a smartphone, and a tablet personal computer), an onboard digital assistant a built-in car navigation system and a portable car navigation system), and a handheld gate console. 
     The liquid crystal panel  11  has a rectangular plate shape. The liquid crystal panel  11  has a known configuration including a pair of transparent glass substrates (having high transmissivity)  11 A and  11 B and a liquid crystal layer. The glass substrates  11 A and  11 E are bonded together with a predefined gap therebetween. The liquid crystal layer is disposed between the glass substrates  11 A and  11 B. 
     On the glass substrate  11 A on the front side, color filters, a common electrode, and an alignment film are disposed. The color filters include red (R), green (C), and blue (B) color portions arranged in predefined sequence. On the glass substrate  11 B on the back side, switching components (e.g., TFTs) connected to source lines and gate lines that are perpendicular to each other, pixel electrodes connected to the switching components, and an alignment film are disposed. Image data and various control signals are transmitted from a driver circuit board to the source lines, the gate lines, and the common electrode for displaying images. 
     The glass substrate  11 B of the pair of glass substrates  11 A and  11 B on the back side has a short dimension larger than a short dimension of the glass substrate  11 A on the front side. The glass substrate  11 B is bonded to the glass substrate  11 A with one of edges at an end of the short dimension (on the upper side in  FIG. 1 ) aligned with that of the glass substrate  11 A. Front and back surfaces of section of the glass substrate  11 B including the other edge at an end of the short dimension (on the lower side in  FIG. 1 ) is exposed without the glass substrate  11 A thereon. A driver  13  for driving the liquid crystal panel  11  is mounted on the section of the glass substrate  11 B. 
     Polarizing plates  12  are disposed on outer surfaces (a front surface and a back surface) of the glass substrates  11 A and  11 B. Each of the polarizing plates  12  has a sheet shape slightly smaller than an overall size of the glass substrates  11 A and  11 B. The polarizing plates  12  cover the outer surfaces of the glass substrates  11 A and  11 B such that edge areas of the front surface and the back surface of the liquid crystal panel  11  in frame shapes are exposed. The polarizing plates  12  are components of the liquid crystal panel  11 . 
     The liquid crystal panel  11  includes a display area (an active area) AA and a non-display area (a non-active area) NAA. The display area AA is located. closer to a first long edge (on the upper side in  FIG. 1 ) extending in a lengthwise direction (the X-axis direction). The non-display area NAA is a frame-shaped area surrounding the display area AA and in which images are not displayed. A section of the non-display area NAA along a second long edge (on the lower side in  FIG. 1 ) has a width larger than widths of other sections. The driver  13  is mounted on the wide section and a flexible circuit board  14  that is connected to a control circuit board is connected to the wide section. 
     The liquid crystal panel  11  is configured to display images using light supplied by the backlight unit  20 . A front side of the liquid crystal panel  11  is defined as a fight exiting side. The lengthwise direction and the widthwise direction of the liquid crystal panel  11  correspond with the X-axis direction and the Y-axis direction, respectively. Further, a thickness direction of the liquid crystal panel  1  corresponds with the Z-axis direction. 
     The backlight unit  20  has a block shape with a rectangular shape in a plan view. The backlight unit  20  includes a chassis  21 , light emitting diodes (LEDs), an LED substrate, a light guide plate  22 , an optical sheet  23 , a reflection sheet  24 , and a pair of holders  25 . The chassis  21  has a box shape with an opening on a liquid crystal panel  11  side. The LEDs are light sources and mounted on the LED substrate. The light guide plate  22  is configured to guide light emitted by the LEDs. The optical sheet  23  is stacked on a front surface of the light guide plate  22 . The reflection sheet  24  is stacked on a back surface of the light guide plate  22 . The holders  25  are disposed along short edges of the chassis  21 . 
     In the backlight unit  20 , the LEDs are disposed at an end surface of the light guide plate  22  on one of long edge sides (on the lower side in  FIG. 1  and light enters the light guide plate  22  from one side. That is, the backlight unit  20  is a one-side edge-lit (a side-lit) backlight. The backlight unit  20  is configured to convert the light from the LEDs into planar light and output the light toward the liquid crystal panel  11  on the front side through the opening of the backlight unit  20 . The front side of the backlight unit  20  is defined as the light exiting side. The components of the backlight unit  20  will be described in sequence. 
     The chassis  21  is made of a metal material such as an aluminum sheet and an electro galvanized sheet (SECC). The chassis  21  has a rectangular shape in a plan view and a box shape with the opening on the front side. The chassis  21  holds the LED substrate and the light guide plate  22  therein (see  FIG. 2 ). The chassis  21  includes a bottom plate  21 A and sidewalls  21 B. The bottom plate  21 A has a rectangular shape. The sidewalls  21 B project from edges (two long edges and two short edges) of the bottom plate  21 A toward the front side, respectively. A lengthwise direction and a widthwise direction of the bottom plate  21 A of the chassis  21  correspond with the X-axis direction and the Y-axis direction, respectively direction perpendicular to the plate surface of the bottom plate  21 A corresponds with the Z-axis direction. 
     The bottom plate  21 A supports the components held in the chassis  21  from the back side. The sidewalls  21 B are disposed to surround the components held in the chassis  21  from outer sides, that is, the sidewalls  21 B form a rectangular frame. 
     Each of the LEDs includes an LED chip (a LED component) disposed on a substrate fixed to a plate surfaced of the LED substrate and sealed by a resin material. The LED chip mounted on the substrate is configured to emit light with one main emission wavelength, specifically, in single color of blue. The rein material that seals the LED chip contains phosphors dispersed in a resin. The phosphors are configured to emit light in a specific color when exited. by the blue light emitted by the LED chip. The phosphors are configured to emit light in substantially white. 
     The LED substrate includes a base film, conductive lines, a thermoplastic layer, and the LEDs. The base film is made of thermosetting resin such as a urethane resin and an epoxy resin. The conductive lines are patterned on the base film for supplying power to the LEDs. The thermoplastic layer having a thermoplastic property such as a polyimide resin is stacked on the base film. The LEDs arranged at intervals are surface-mounted on the thermoplastic layer. 
     The LED substrate is disposed along an inner surface of the sidewall  21 B of the chassis  21  such that light emitting surfaces of the LEDs are opposed to and parallel to the end surface of the light guide plate  22 , which will be described later, on the long edge side. The LED substrate includes a base portion. and an external circuit connecting portion  26 . The base portion has an elongated band shape and a long dimension (a dimension in the X-axis direction) about equal to a long dimension of the light guide plate, which will be described later. The external circuit connecting portion  26  extend from the base portion in the vertical direction (the Y-axis direction). The external circuit connecting portion  26  is connected to an external circuit. The external circuit connecting portion  26  is drawn out of the chassis  21  through a cutout in the sidewall  21 B. The LEDs are arranged in line on the base portion having the band shape and mounted on the base portion. 
     The light guide plate  22  is made of a transparent synthetic resin such as an acrylic-based resin and a polycarbonate. The light guide plate  22  has a rectangular plate shape slightly smaller than the bottom plate  21 A of the chassis  21  in a plan view. The light guide plate  22  is disposed parallel to the bottom plate  21 A of the chassis  21 . The lengthwise direction and the widthwise direction of the light guide plate  22  correspond with the X-axis direction and the Y-axis direction, respectively. The thickness direction of the light guide plate  22  perpendicular to the plate surface of the light guide plate  22  corresponds with the Z-axis direction. The light guide plate  22  is held in the chassis  21  to be surrounded by the sidewalls  21 B. 
     An upper surface (a front surface) of a pair of plate surfaces of the light guide plate is defined as a light exiting surface  22 A through which light that has entered the light guide plate  22  exits toward the liquid crystal panel  11 . The optical sheet  23  is stacked on the light exiting surface  22 A. 
     The optical sheet  23  is a rectangular flat sheet. The lengthwise direction and the widthwise direction of the optical sheet  23  correspond with the X-axis direction and the Y-axis direction, respectively. The optical sheet  23  is disposed immediately behind the liquid crystal panel. The optical sheet  23  is disposed between the light guide plate  22  and the liquid crystal panel  11 . The optical sheet  23  passes the from the light guide plate  22 , exerts predefined optical effects on the passing light, and directs the light to the liquid crystal panel  11 . 
     The optical sheet  23  in this embodiment has a triple-layer structure. The optical sheet  23  includes a diffuser sheet  23 A, a lens sheet  23 B, and a reflective polarizing sheet  23 C stacked in this sequence from a lower layer side. 
     The reflection sheet  24  is stacked on the back surface of the light guide late  22 . The reflection sheet  24  is made of a synthetic resin sheet material having a white surface with high light reflectivity. The reflection sheet  24  efficiently direct light rays traveling through the light guide plate  22  and exiting through a reflective surface  22 B on an opposite side from the light exiting surface  22 A toward the front side (the light exiting surface  22 A). The reflection sheet  24  has a rectangular shape in a plan view. A large area of a middle portion of the reflection sheet  24  is sandwiched between the light guide plate  22  and the bottom plate  21 A of the chassis  21 . Edge sections of the reflection sheet  24  project outer than the outer end surfaces of the light guide plate  22 . 
     The holders  25  are made of a white synthetic resin. Each holder  25  has an elongated square bar shape extending in the widthwise direction of the chassis  21  (the Y-axis direction). The holders  25  are disposed inside the chassis  21  along the sidewalls  21 B adjacent to the short edges of the chassis  21 . Upper inner edges of the holders  25  are cut such that each holder  25  has an L shaped edge in a cross-sectional view to form receiving portions  25 A on which edge sections of the fixing sheet  30 , which will be described later, can be placed, respectively. Lower inner edges of the holders  25  are cut such that each holder  25  has an L shaped edge in a cross-sectional view to form pressing portions  25 B with which the edge sections of the reflection sheet  24  projecting from the edges of the light guide plate  22  are pressed toward the chassis  21 . 
     The liquid crystal panel  11  is fixed to the backlight unit  20  with the fixing sheet  30  (an example of the fixing member), which will be described next. 
     The fixing sheet  30  is made of a synthetic resin. The fixing sheet  30  includes a base having a sheet shape slightly larger than the liquid crystal panel  11  and adhesives applied to surfaces of the base. The base of the fixing sheet  30  is made of a material having highlight transmissivity such as a polycarbonate or an acrylic resin. The adhesives applied to the surfaces of the base may be acrylic-based adhesives, urethane-based adhesives, or silicone-based adhesives having high light transmissivity. The acrylic-based adhesives may be preferred to other the adhesives because polymers thereof have high tackiness and because of their high modifiability, high resistance to heat and weather, and high adherend selectivity. 
     A light blocking portion  31  that does not pass the light is provided in an outer edge portion, that is, a frame-shaped region of the fixing sheet  30  including section overlapping the non-display area (NAA) of the liquid crystal panel  11 . The light blocking portion  31  includes a light blocking layer  33  having a light blocking property printed on the back surface (a surface on a backlight unit  20  side) of the base of the fixing sheet  30  (see  FIG. 4 ). A portion of the fixing sheet  30  in which the light blocking layer  33  is not provided inner than the light blocking portion  31  is defined as a light passing portion  32  having light transmissivity (see  FIG. 3 ). 
     As illustrated in  FIG. 2 , the outer edge portion (the light blocking portion  31 ) of the fixing sheet  30  that is attached to a predefined attachment position on the back surface of the liquid crystal panel  11  projects slightly outer than the outer edges of the liquid crystal panel  11 . The light blocking portion  31  of the fixing sheet  30  that is attached to a predefined attachment position on the back surface of the liquid crystal panel  11  extends inner than the edges of the liquid crystal panel  11  to overlap the non-display area NAA of the liquid crystal panel  11 . 
     The liquid crystal display device  10  according to this embodiment has the configuration described above. Operation and Effect of the liquid crystal display device  10  will be described. 
     The liquid crystal display device  10  according to this embodiment includes the liquid crystal panel  11 , the backlight unit  20 , and the fixing sheet  30 . The liquid crystal panel  11  includes the display area AA in which images are displayed and the non-display area NAA surrounding the display area. The backlight unit  20  is disposed opposite the back surface of the liquid crystal panel  11 . The fixing sheet  30  is fixed between the liquid crystal panel  11  and the backlight unit  20  to fix the liquid crystal panel  11  and the backlight unit  20  together. The fixing sheet  30  includes the light blocking portion  31  and the light passing portion  32 . The light blocking portion  31  is disposed in the area overlapping the non-display area NAA. The light passing portion  32  having the light transmissivity is disposed inner than the light blocking portion  31 . 
     According to the configuration, the fixing sheet  30  includes joint plane areas larger than the non-display area NAA regardless of an area of the non-display area NAA. Therefore, high cohesion (a large retention force) can be achieved. Further, leakage of light from the edges of the display area AA is reduced by the light blocking portion  31 . 
     The light passing portion  32  entirely covers the display area AA. According to the configuration, higher cohesion (a larger retention force) can be achieved. 
     The light blocking portion  31  includes the light blocking layer  33  printed on one of the surfaces of the base light having the transmissivity. According to the configuration, the fixing sheet  30  including the light blocking portion  31  and the light passing portion  32  that are integrally provided can be prepared by a simple method that includes printing the light blocking layer  33  at the predefined position on the base sheet having high light transmissivity. 
     Other Embodiments 
     The technology described herein is not limited to the embodiments described above and illustrated by the drawings. For example, the following embodiments will be included in the technical scope of the technology described herein. 
     (1) In the above embodiment, the edge sections of the fixing sheet  30  for fixing the liquid crystal panel  11  and the backlight unit  20  together are placed on the receiving portions  25 A of the holders  25  in the backlight unit  20  and fixed. However, the configuration of the backlight unit  20  is not limited to the configuration in the above embodiment and may be altered where appropriate. The edge sections of the fixing sheet may be fixed to components other than the holders as long as the liquid crystal panel  11  and the backlight unit  20  are fixed together with fixing members having adhesiveness. 
     (2) In the above embodiment, the fixing sheet  30  covers the entire area of the liquid crystal panel  11 . However, the fixing sheet  30  may not cover the entire area of the liquid crystal panel  11 . For example, a fixing member having a frame shape illustrated in  FIG. 5  may be provided. The fixing member  130  includes a light blocking portion  131  and a light passing portion  132 . The light blocking portion  131  has a frame shape to overlap the non-display area NAA. The light passing portion  132  has a frame shape to extend inwardly from the light blocking portion  131 . According to such a configuration, an area of the liquid panel and an area of the backlight unit  20  bonded together are larger than the non-display area NAA. Therefore, cohesion (a retention force) increases. 
     (3) In the above embodiment, the light blocking portion  31  of the fixing sheet  30  is disposed in areas between the outer edges of the liquid crystal panel  11  and borders between. the non-display area NAA and the display area AA. However, the areas may be altered as long as the light blocking portion is not disposed in the display area AA because a sufficient fixing area can be provided by the light passing portion.