Patent Publication Number: US-2005134765-A1

Title: Dual display panel

Description:
FIELD OF THE INVENTION  
      This invention relates in general to a display device and, more particularly, to a flat panel display device including a dual display panel.  
     BACKGROUND OF THE INVENTION  
      Flat panel display devices are typically backlit by a backlight assembly or alternatively front-lit by a front-light assembly. The backlight or front-light assembly generally includes a lamp and a light guide plate to provide uniform illumination to a display panel of a display device. Electronic products which use flat panel display devices may include lap-top computers, televisions, digital watches, calculators, telephones and cellular phones.  
      Certain electronic products, for example, cellular phones, are designed with a shell-type outlook. An exemplary shell-type electronic product  10  in the art is shown in  FIGS. 1A and 1B . Referring to  FIG. 1A , electronic product  10  includes an operation member  12  and a display panel  14  foldable with respect to operation member  14 . Operation member  12  allows a user  16  of electronic product  10  to enter information through, for example, a keyboard (not shown). Display panel  14  may include a main panel  14 - 2  and a sub-panel  144 . Generally, main panel  14 - 2  serves to provide main display functions of electronic product  10 , and sub-panel  14 - 4  serves to provide subsidiary display functions such as caller identity display or clock display. When display panel  14  is held at an unfolded position, user  16  views an image on display from main panel  14 - 2 . On the other hand, referring to  FIG. 1B , when display panel  14  is held at a folded position, user  16  views an image on display from sub-panel  144 .  
       FIG. 2  is a cross-sectional view of an electronic product  20  in the art.  
      Electronic product  20  includes a main panel  22 , a sub-panel  24 , a backlit assembly  26  common to main panel  22  and sub-panel  24 , and a frame  28 . Main panel  22  and sub-panel  24  are generally independent of each other, and include individual driving circuits (not shown). Referring to  FIG. 2 , main panel  22  includes a first polarizer  22 - 2 , a color filter  224 , a transparent substrate  22 - 6  and a second polarizer  22 - 8 .  
      Similarly, sub-panel  24  includes a first polarizer  24 - 2 , a color filter  244 , a transparent substrate  24 - 6 , and a second polarizer  24 - 8 . Backlight assembly  26  includes a light source  26 - 2 , a light guide plate  264 , a first optical film  26 - 6  associated with main panel  22 , and a second optical film  26 - 8  associated with sub-panel  24 . Each of first and second optical films  26 - 6  and  26 - 8  may further include a layer structure of a diffuser (not shown) and prism sheets (not shown). Since panels and driving circuits are individually and severally required in electronic product  20 , manufacturing cost and overall product size disadvantageously increase as a result.  
     SUMMARY OF THE INVENTION  
      Accordingly, the present invention is directed to a display device and a method of display that obviate one or more of the problems due to limitations and disadvantages of the related art.  
      To achieve these and other advantages, and in accordance with the purpose of the invention as embodied and broadly described, there is provided a display device that comprises a first viewing face allowing viewing of a first image on display from a first direction, a second viewing face allowing viewing of a second image on display from a second direction, a light source, a transparent substrate, a light guide plate receiving light provided by the light source, a surface of the light guide plate that transmits the light toward the first viewing face, and a plurality of reflective regions provided over the transparent substrate that reflect the light transmitted from the surface toward the second viewing face.  
      In one aspect, each of the reflective regions further comprises a metal electrode formed thereon.  
      In another aspect, the reflective regions are separated from each other by transmissive regions provided over the transparent substrate.  
      Also in accordance with the present invention, there is provided a display device that comprises at least one light source, a transparent substrate, a light guide plate receiving light provided by the at least one light source, a surface of the front light guide plate that transmits the light received from the light source toward the transparent substrate, a plurality of transmissive regions disposed between the light guide plate and the transparent substrate that allow the light to pass the transparent substrate, and a plurality of reflective regions disposed between the light guide plate and the transparent substrate that reflect the light toward the light guide plate.  
      In one aspect, the at least one light source further comprises a light emitting diode, a cold cathode ray tube and an ambient light.  
      Still in accordance with the present invention, there is provided a display device that comprises a single display panel including a first side and a second side, a transparent substrate formed in the single display panel, a transparent light guide plate receiving light provided by a light source, a surface of the light guide plate that transmits the light from the light source toward the single display panel, a plurality of transmissive regions disposed between the transparent light guide plate and the transparent substrate that allow the light to pass the first side of the display panel, and a plurality of reflective regions separated from each other by the transmission regions that reflect the light toward the second side of the display panel.  
      Yet still in accordance with the present invention, there is provided a method of displaying an image that comprises providing a single display panel with a first side and a second side, providing a transparent substrate disposed between the first and second sides, providing light from a light source, providing a transparent light guide plate receiving the light provided by the light source, providing the transparent light guide plate with a surface, transmitting the light via the surface toward the display panel, providing a plurality of transmissive regions disposed between the transparent light guide plate and the transparent substrate, providing a plurality of reflective regions disposed between the transparent light guide plate and the transparent substrate, passing the light transmitted from the surface through the transmissive regions through the first side of the display panel, and reflecting the light transmitted from the surface by the reflective regions toward the second side of the display panel.  
      Additional objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.  
      The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description, serve to explain the principles of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A and 1B  are schematic diagrams of an electronic product in the art;  
       FIG. 2  is a cross-sectional view of an electronic product in the art;  
       FIG. 3  is a cross-sectional view of a display device in accordance with one embodiment of the present invention; and  
       FIGS. 4A and 4B  are diagrams illustrating the operation of a display device in accordance with one embodiment of the present invention. 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
      Reference will now be made in detail to the present embodiment of the invention, an example of which is illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.  
       FIG. 3  is a cross-sectional view of a display device  50  in accordance with one embodiment of the present invention. Referring to  FIG. 3 , display device  50  includes a light source  52 , a light guide plate  54 , a single display panel  56 , and a frame  58 . Light source  52  may include a lamp (not shown) and a reflector (not shown) surrounding the lamp. In one embodiment according to the invention, light source  52  includes a light emitting diode (“LED”). In another embodiment, light source  52  includes a cold cathode ray tube (“CRT”). In addition to a LED or a cold CRT, display device  50  may use ambient light  72  such as indoor luminescent light or sunlight as a light source. Display device  50  further includes a single integrated circuit (“IC”)  70  corresponding to single display panel  56 . IC  70  functions to drive display panel  56  and can be made in the form of a flexible printed circuit (“FPC”).  
      Light guide plate  54  serves to transmit light  52 - 2  provided by light source  52  toward display panel  56 . In one embodiment, light guide plate  54  is made of acrylic species resin, which is transparent to ambient light  72 . Light guide plate  54  includes a first surface  54 - 2  and a second surface  54 - 4 . In one embodiment according to the invention, first surface  54 - 2  is formed with a plurality of prisms  54 - 6  (shown as saw-tooth projections) thereon which constitute a micro-mirror structure to transmit light  52 - 2  from light source  52  toward display panel  56 . Second surface  54 - 4  may be provided with anti-reflection coating (“ARC”) thereon to secure the transmission of light  52 - 2  toward display panel  56 .  
      Display panel  56  includes a first polarizer  56 - 2 , a color filter  56 - 4 , a transparent substrate  56 - 6 , and a second polarizer  56 - 8 . A plurality of reflective regions  60  and transmissive regions  62  are formed over transparent substrate  56 - 6 . Reflective regions  60  are separated from each other by transmissive regions  62  such that each of reflective regions  60  is surrounded by transmissive regions  62 . Meanwhile, transmissive regions  62  are separated from each other by reflective regions  60  such that each of transmissive regions  60  is surrounded by reflective regions  60 . Each of reflective regions  60  is formed with a metal electrode  60 - 2  thereon to reflect light  52 - 2  transmitted from light guide plate  54  away from transparent substrate  56 - 6 . In one embodiment according to the invention, metal electrode  60 - 2  includes a metal material such as aluminum. Each of transmissive regions  62  allows light  52 - 2  transmitted from light guide plate  54  to pass transparent substrate  56 - 6 . In one embodiment according to the invention, each of transmissive regions  62  is formed with a transparent electrode (not shown) thereon. The transparent electrode can further include an indium tin oxide (“ITO”).  
       FIGS. 4A and 4B  are diagrams illustrating the operation of display device  50  in accordance with one embodiment of the present invention. Referring to  FIG. 4A , a part of light  52 - 2  or ambient light  72  transmitted by light guide plate  54  passes through transmissive regions  62 . A user  80  of display device  50  views an image on display at a first viewing face  50 - 2  of display device  50  from a first direction. In this particular embodiment, single display panel  56  serves to provide the main display function.  
      Referring to  FIG. 4B , a part of light  52 - 2  or ambient light  72  transmitted by light guide plate  54  is reflected by reflective regions  60 . User  80  views an image on display at a second viewing face  50 - 4  of display device  50  from a second direction substantially opposite to the first direction. In this particular embodiment, single display panel  56  serves to provide sub-display function. Metal electrode  60 - 2  formed on reflective region  60  further includes a roughened surface  60 - 4  to enhance reflectivity.  
      The present invention also provides a method of displaying an image. A single display panel  56  including a first side  56 - 8  and a second side  56 - 2  is provided. Both first side  56 - 8  and second side  56 - 2  are made of transparent materials. A transparent substrate  56 - 6  such as a glass substrate is disposed between the first and second sides  56 - 8  and  56 - 2 . A light source  52  is provided to illuminate single display panel  56 . Alternately, ambient light  72  such as indoor luminescent light or sunlight is used for luminescence if conditions permit. A light guide plate  54  made of transparent material such as acrylic species resin is provided to receive light provided by light source  52  or ambient light  72 . Light guide plate  54  is provided with a surface  54 - 2  to transmit light  52 - 2  toward single display panel  56 . A plurality of transmissive regions  62  disposed between light guide plate  54  and transparent substrate  56 - 6  are provided. A plurality of reflective regions  60  disposed between light guide plate  54  and transparent substrate  56 - 6  are also provided. Reflective regions  60  are separated from each other by transmissive regions  62 . A part of the light transmitted from light guide plate  54  passes through transmissive regions  62  toward first side  56 - 8  of single display panel  56 . Another part of the light transmitted from light guide plate  54  is reflected by reflective regions  60  toward second-side  56 - 2  of single display panel  56 . User  80  of display device  50  may choose to view an image on display from first side  56 - 8 , in which single display panel functions to serve as a main panel. User  80  may alternately choose to view an image on display from second side  56 - 2 , in which single display panel  56  functions to serve as a sub-panel.  
      Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.