Abstract:
A portable display device includes a display panel, a backlight assembly having a light source for supplying light to the liquid crystal display panel and having a mold frame with a periphery step platform. A bottom chassis is combined with the mold frame, the bottom chassis having a bent unit surrounding the periphery step platform.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to and the benefit of Korean Patent Application Nos. 2005-117178, filed on Dec. 2, 2005, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to an improved portable display device, and more particularly to a portable display device with an enhanced stiffness. 
     2. Discussion of Related Art 
     Recently, various flat display devices have been developed having reduced weight and size. Exemplary flat display devices include a liquid crystal display, a field emission display, a plasma display panel, an organic light emitting display, etc. Specifically, liquid crystal displays have become popular due to their small size, light weight, and low power consumption. Liquid crystal displays may be mounted in large-sized television monitors as well as mobile phones and personal digital assistant (PDA). 
       FIG. 1  is an exploded prospective view illustrating a conventional portable display device.  FIG. 2  is an assembled sectional view taken along line A-A′ of the portable display device shown in  FIG. 1 . 
     Referring to  FIGS. 1 and 2 , the conventional portable display device includes a liquid crystal display panel  4 , a backlight assembly  50 , a bottom chassis  22 , a first printed circuit board  24 , a second printed circuit board  26 , and a light-emitting display panel  30 . 
     The liquid crystal display panel  4  displays predetermined images and includes a first substrate  4   a , a second substrate  4   b  and a liquid crystal (not shown) injected between the first substrate  4   a  and the second substrate  4   b.    
     The second substrate  4   b  includes a plurality of thin film transistors (TFTs) arranged in matrix form. A source electrode of the TFT is connected to a data line, and a gate electrode thereof is connected to a scan line. A drain electrode of the TFT is connected to a pixel electrode made of transparent indium tin oxide (ITO) of a conductive material. The TFT is turned on when the scan line is supplied with a scan signal, and supplies a data signal from the data line to the pixel electrode. 
     An integrated circuit  6  is inserted on one side of the second substrate  4   b , and the data signal and scan signal are supplied from the integrated circuit  6 . A protective layer  8  is deposited around the integrated circuit  6 . 
     The first substrate  4   a  is arranged facing the second substrate  4   b . A common electrode made of ITO is applied on a front surface of the first substrate  4   a . The common electrode is applied with a predetermined voltage, to generate an electric field between the common electrode and the pixel electrode. The array angle of the liquid crystal injected between the first substrate  4   a  and the second substrate  4   b  varies with the electric field, and the optical transparency varies according to the array angle to thereby display desired images. 
     The backlight assembly  50  includes a mold frame  16 , light emitting diodes (LEDs)  12 , a LED substrate  14 , a light guide plate  18 , a reflective plate  20  and optical sheets  10 . 
     The LEDs  12  emit a predetermined amount of light corresponding to a drive signal from the LED substrate  14 . The light guide plate  18  supplies the light from the LEDs  12  to the liquid crystal display panel  4 . 
     The reflective plate  20  arranged on the back surface of the light guide plate  18  reflects incidence light from the light guide plate  18  back onto the light guide plate, thereby improving optical efficiency. 
     The optical sheets  10  enhance the amount of light from the light guide plate  18  to the liquid crystal display panel  4 . 
     The LED substrate  14  connected to the first printed circuit board  24  supplies the drive signal to the LEDs  12  corresponding to control signal from the first printed circuit board  24 . 
     The LED substrate  14  mounted with LEDs  12  is fixed to the mold frame  16 , and the liquid crystal display panel  4 , a light guide plate  18 , a reflective plate  20  and optical sheets  10  are fixed to and supported by a step unit formed in the inner side surface of the mold frame  16 . The bottom chassis  22  is fixed to the mold frame  16  in the lower side and outer side surface thereof as shown in  FIG. 2  and an opening is formed in the part of the bottom chassis  22  such that a light emitting display panel  30  can be inserted therein. 
     The second printed circuit board  26  is supplied with the drive signal from a drive circuit (not shown) located in the mobile phone side and includes a mobile phone connector  28 . The mobile phone connector  28  is combined with and fixed to another connector attached to the drive circuit located in the mobile phone side to be supplied with the drive signal from the drive circuit located in the mobile phone side. The second printed circuit board  26  supplied with the drive signal generates various control signals corresponding to the drive signal. 
     The first printed circuit board  24  is connected to the second printed circuit board  26  through a first pad unit  38  provided in the second printed circuit board  26 . Additionally, the first printed circuit board  24  is connected to the integrated circuit  6  of the first liquid crystal display panel  4  and LED substrate  14  by a flexible printed circuit board (not shown). The first printed circuit board  24  connected to the integrated circuit  6  and LED substrate  14  drives the integrated circuit  6  and LED substrate  14  corresponding to the control signals supplied from the second printed circuit substrate  26 . 
     The light emitting display panel  30  includes a first substrate  30   a  and a second substrate  30   b . Organic LEDs (not shown) are arranged on the first substrate  30   a  in matrix form. The organic LEDs generate a predetermined amount of light corresponding to the amount of current supplied. The light emitting display panel  30  is connected to the second printed circuit board  26  by the second pad unit  36  of the flexible printed circuit board  32 . An integrated circuit  34  is mounted on the flexible printed circuit board  32 . The integrated circuit  34  lets the light emitting display panel  30  display a predetermined image in response to the control signals supplied from the second printed circuit board  26 . 
     The portable display device may be exposed to various environments, making the display device susceptible to being impacted from the outside. Due to the recent trend of smaller and slimmer portable display devices, portable display devices are more likely to be damaged by impact. Thus, there is a need for a stiffer portable display device. 
     SUMMARY OF THE INVENTION 
     Accordingly, a portable display device is provided having enhanced stiffness due to a bottom chassis formed to surround the upper side and inner side surface of a mold frame. 
     A portable display device includes a display panel, a backlight assembly having a light source for supplying light to the display panel and having a mold frame with a periphery step platform. The periphery step platform has peripheral side walls and a step portion, the peripheral side walls having an outer sidewall surface, a top sidewall surface and an inner sidewall surface, the step portion having a step portion top surface and a step portion side surface. The portable display device also includes a bottom chassis supporting the mold frame, the bottom chassis having a peripheral bent unit enclosing the outer sidewall surface, the top sidewall surface, the inner sidewall surface and the step portion top surface. The bent unit may also be formed to enclose the outer sidewall surface, the top sidewall surface, the inner sidewall surface, the step portion top surface and the step portion side surface. 
     The bottom chassis is formed of Steel Use Stainless (SUS) material. The bottom chassis has 0.1 mm to 0.2 mm in thickness. The backlight assembly is configured to include LEDs as a light source, a LED substrate, a light guide plate, a reflective plate and optical sheets. The portable display device of the present invention further includes a second printed circuit board connected to an external drive circuit, a first printed circuit board connected to the second printed circuit board, the first printed circuit board controlling the liquid crystal display panel and light source, and a light-emitting display panel connected to the second printed circuit board in the lower side thereof, the light-emitting display panel displaying images. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded prospective view illustrating a conventional portable display device. 
         FIG. 2  is an assembled sectional view taken along line A-A′ of the portable display device shown in  FIG. 1 . 
         FIG. 3  is an exploded prospective view illustrating a portable display device according to an embodiment of the present invention. 
         FIG. 4  is a view for illustrating an embodiment of a bottom chassis shown in  FIG. 3 . 
         FIG. 5  is an assembled sectional view taken along line B-B′ of the portable display device of  FIG. 3 , having the bottom chassis shown in  FIG. 4 . 
         FIG. 6  is a view for illustrating another exemplary embodiment of the bottom chassis shown in  FIG. 3 . 
         FIG. 7  is an assembled sectional view taken along line B-B′ of the portable display device of  FIG. 3  having the bottom chassis shown in  FIG. 6 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 3 ,  4  and  5 , a portable display device according to an embodiment of the present invention includes a liquid crystal display panel  104 , a backlight assembly  150 , a bottom chassis  122 , a first printed circuit board  124 , a second printed circuit board  126 , and a light-emitting display panel  130 . The bottom chassis  122  may be formed so as to surround the upper side and the step unit S 1  of the inner side surface of a mold frame  116  included in the backlight assembly  150 . 
     The liquid crystal display panel  104  displays images and includes a first substrate  104   a , a second substrate  104   b  and a liquid crystal (not shown) injected between the first substrate  104   a  and the second substrate  104   b.    
     The second substrate  104   b  includes a plurality of TFTs arranged in matrix form. A source electrode of the TFT is connected to a data line, and a gate electrode thereof is connected to a scan line. A drain electrode of the TFT is connected to a pixel electrode made of transparent ITO. The TFT is turned on when the scan line is supplied with a scan signal, and supplies a data signal from the data line to the pixel electrode. 
     An integrated circuit  106  is inserted to one side of the second substrate  104   b , and the data signal and scan signal are supplied from the integrated circuit  106 . A protective layer  108  is deposited around the integrated circuit  106 . 
     The first substrate  104   a  is arranged facing the second substrate  104   b . A common electrode made of ITO is applied on the front surface of the first substrate  104   a . The common electrode is applied with a predetermined voltage, and thus a predetermined electric field is generated between the common electrode and the pixel electrode. The array angle of the liquid crystal injected between the first substrate  104   a  and the second substrate  104   b  varies with the electric field. The optical transparency also may vary according to the array angle to thereby display desired images. 
     The backlight assembly  150  includes a mold frame  116 , LEDs  112 , a LED substrate  114 , a light guide plate  118 , a reflective plate  120  and optical sheets  110 . The LEDs  112  emit a predetermined amount of light corresponding to a drive signal from the LED substrate  114 . The light guide plate  118  supplies the light from the LEDs  112  to the liquid crystal display panel  104 . 
     The reflective plate  120 , located on a rear surface of the light guide plate  118 , supplies incidence light from the light guide plate  118  back to the light guide plate  118  thereby improving optical efficiency. 
     The optical sheets  110  enhance the brightness of light from the light guide plate  118  to supply light to the liquid crystal display panel  104 . The LED substrate  114 , which is connected to the first printed circuit board  124 , supplies the drive signal to the LEDs  112  corresponding to control signal from the first printed circuit board  124 . 
     The LED substrate  114  mounted with LEDs  112  is received in and fixed to the mold frame  116 , and the liquid crystal display panel  104  and backlight assembly  150  are fixed and supported in the mold frame  116 . A step unit S 1  is formed in the inner side surface of the mold frame  116  and the bottom chassis  122  is combined with the mold frame  116  in the lower side and side surface thereof. An opening is formed in the part of the bottom chassis  122  such that a light emitting display panel  130  is insertable therein. 
     The bottom chassis  122  of the present invention may surround the upper side and step unit S 1  of the inner side surface of the mold frame  116 . More specifically, the bottom chassis  122  is provided with a bent unit  122   a  extending from the side surface thereof and formed to correspond to the upper side and inner side surface formed with a step unit S 1  of the mold frame  116 . 
     The second printed circuit board  126  includes a mobile phone connector  128  and is supplied with the drive signal from a drive circuit (not shown) located in the mobile phone side. The mobile phone connector  128  is fixed to another connector attached to the drive circuit located in the mobile phone side to thus be supplied with the drive signal from the drive circuit located in the mobile phone side. The second printed circuit board  126  supplied with the drive signal generates various control signals corresponding to the drive signal. 
     The first printed circuit board  124  is connected to the second printed circuit board  126  through a first pad unit  138  formed in the second printed circuit board  126 . The first printed circuit board  124  is connected to the integrated circuit  106  of the liquid crystal display panel  104  and LED substrate  114  by a flexible printed circuit board (not shown). The first printed circuit board  124  connected to the integrated circuit  106  and LED substrate  114  drives the integrated circuit  106  and LED substrate  114  corresponding to the control signals supplied from the second printed circuit substrate  126 . 
     The light emitting display panel  130  includes a first substrate  130   a  and a second substrate  130   b . Organic LEDs (not shown) are arranged on the first substrate  130   a  in matrix form. The organic LEDs generate a predetermined amount of light corresponding to the amount of current supplied. The light emitting display panel  130  is connected to the second printed circuit board  126  by the second pad unit  136  of the flexible printed circuit board  132 . An integrated circuit  134  is mounted on the flexible printed circuit board  132 . The integrated circuit  134  allows the light emitting display panel  130  display a predetermined image in response to the control signals supplied from the second printed circuit board  126 . 
     In the above mentioned portable display device, the bottom chassis  122  surrounds the upper side and step unit of the inner side surface of the mold frame  116  and thereby enhances the combination with the mold frame  116  and protects the mold frame  116 . 
     Referring to  FIGS. 4 and 5 , the bottom chassis  122  according to a first embodiment of the present invention is configured to be combined to the lower side and side surface of the mold frame  116 . The bottom chassis  122 , which serves to fix the backlight assembly  150  and liquid crystal display panel  104  along with a top chassis (not shown), is generally form of SUS material having, in one exemplary embodiment, a thickness of between about 0.1 mm to 0.2 mm. 
     Because the portable display device according to an embodiment of the present invention is embodied in a dual type, an opening is formed in the middle surface of the bottom chassis  122  so that the light-emitting display panel  130  can be inserted therein. 
     The bottom chassis, which also called a bezel, is formed to surround the upper side and step unit S 1  of the inner side surface, as well as the lower side and the outer side surface of the mold frame  116  in the embodiment. The bottom chassis  122  is provided with a bent unit  122   a  extending from a side surface of the bottom chassis and formed to correspond to the bent part between the upper side and the first step unit S 1  of the mold frame  116 . 
     As mentioned above, the side surface part of the bent unit  122   a  is formed to surround the upper side and step unit of the inner side surface of the mold frame  116  and thus enhances the combination with the mold frame  116  and the like, and protects the mold frame  116 . 
     The bottom chassis  122 ′ may also be formed to surround the entire inner side surface as well as the step unit S 1  of the mold frame  116 , as shown in  FIGS. 6 and 7  by being extended. Thus, the bent unit  122   a ′ is formed to surround the entire inner side surface of the mold frame  116  receiving the optical sheets  110 , the light guide plate  118 , and the reflective plate  120 . As shown in  FIGS. 6 and 7 , the bent unit  122   a ′ of the bottom chassis  122 ′ is in contact with the bottom surface of the bottom chassis, but is not adhered thereto. Since the bottom chassis  122 ′ is flexible and the bent unit  122   a ′ is separable from the bottom surface, the mold frame  116  is insertable into the bottom chassis by force. 
     As mentioned above, in a portable display device of the present invention, the stiffness of the portable display device is enhanced by being provided with a bottom chassis formed to surround the upper side and inner side surface of a mold frame. 
     Although exemplary embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes might be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.