Abstract:
A liquid crystal display (LCD) device includes an LCD panel having an exterior surface with a first area and an interior surface; a light filter layer having an exterior surface provided at the interior surface of the LCD panel and an interior surface; a light guide assembly provided behind the interior surface of the light filter layer, the light guide assembly including a plurality of light pipes; a light source including a plurality of selectively illuminated lamps arranged at a lateral side of the light guide assembly, each of the lamps being respectively associated with a different one of the light pipes for emitting light into the respective light pipe; a plurality of diffusion surfaces, each of the diffusion surfaces being provided on a selected area of a respective one of the plurality of the light pipes, the selected area being smaller than the first area; wherein each of the diffusion surfaces causes light to be emitted from the selected area of the respective light pipe when the light pipe is illuminated by the lamp associated therewith.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a backlight assembly and a display device using the same, and more particularly, to a backlight assembly for a thin portable liquid crystal display (LCD) device, which is capable of selectively lighting up different screen areas of the portable LCD device without increasing the thickness of the portable LCD device. 
         [0003]    2. Discussion of the Related Art 
         [0004]    With rapid development of information technology, flat panel display devices are in great demand because of their superior characteristics such as thin profile, light weight, and low power consumption. Among those flat panel display devices, liquid crystal display (LCD) devices having excellent color reproduction are being aggressively researched and developed. 
         [0005]    The LCD device includes an LCD panel having a thin film transistor (TFT) substrate, a color filter substrate and a liquid crystal layer disposed therebetween. Since the LCD panel does not emit light by itself, the LCD device includes a backlight assembly at a rear side of the LCD panel as a light source for providing light. The transmittance of the light generated from the backlight assembly is adjusted according to an alignment of the liquid crystal layer. The LCD panel and the backlight assembly are accommodated in a chassis of the LCD device. Depending on a location of the light source, the backlight assembly may be classified as an edge-type or direct-type backlight assembly. The edge-type backlight assembly is provided with a light source at a lateral side of a light guiding plate and is typically used for relatively small sized LCDs. The edge-type backlight assembly provides high light uniformity and good endurance and is suitable for use in thin profile LCDs, such as lap tops, portable TVs and DVD players. 
         [0006]    Hereinafter, an LCD device with a backlight assembly according to the related art will be described with reference to  FIGS. 1 and 2 .  FIG. 1  is a view schematically illustrating a related art LCD device  1 , and  FIG. 2  schematically illustrates a vertical section of the related art LCD device  1  of  FIG. 1 . Referring to  FIGS. 1 and 2 , the related art LCD device  1  includes an LCD panel  10 , a light filter layer  20  arranged behind the LCD panel  10 , a light guide plate  30  arranged behind the light filter layer  20 , and a light source  40  arranged laterally at the side of the light guide plate  30 . The light guide plate  30  may have a thickness usually from 2 mm to more than 10 mm. The light guide plate  30  may be made of a transparent plastic material. The light source  40  may include one or a plurality of lamps. 
         [0007]    As shown in  FIG. 2 , there are a plurality of diffusion lines or surfaces  50  painted on a rear surface of the light guide plate  30 . These diffusion lines or surfaces  50  serve to diffuse light, which is emitted from the light source  40  and then guided by the light pipes of the light guide plate  30 . When the light source  40  turns ON to emit light beams  60  through the edge of the light guide plate  30 , the light beams  60  bounce inside the light guide plate  30  until they hit the diffusion lines or surfaces  50  painted on the rear surface of the light guide plate  30 . Some of the diffused light beams  60  will go through a front surface of the light guide plate  30  to be guided toward the LCD panel  10 , when the angles between the light beams  60  and the perpendicular of the front surface are small enough. Moreover, the reference numeral  70  denotes that the light beams  60  make specular reflection inside the light guide plate  30 . 
         [0008]    The LCD panel  10  includes a plurality of the pixels (not shown) arranged in a matrix of rows (lines) and columns. The pixels are “refreshed” line by line. Since changing a pixel state from ON to OFF takes time, if the back light is ON at all time, it can cause some undesirable picture artifacts. For this reason, it would be good to turn off the light in the area of the screen of the LCD panel  10 , in which the pixels are being “refreshed”. 
         [0009]    It is also possible to create a software program in a TV using the LCD panel  10 , which analyzes the image to decide if all areas of the picture need full brightness or if the back light for some areas can be turned off. This can be an energy saving feature for the TV, but it means that some lamps of the light source can be turned off independently of the other lamps. 
         [0010]    In the direct-type backlight assembly, a light source is arranged right behind a screen of the LCD panel, and therefore can be designed and controlled to light up different parts of the screen of the LCD panel independently. However, this manner of mounting the light source in the direct-type backlight assembly may objectively increase the thickness of the LCD device, which is not desirable for portable LCD devices, such as lap tops, portable TVs, and the like. On the other hand, the related art LCD device using the edge-type backlight assembly cannot selectively illuminate areas of the screen of the LCD device. 
       SUMMARY OF THE INVENTION 
       [0011]    Accordingly, the present invention is directed to a backlight assembly and an LCD device using the same which substantially obviate one or more problems due to limitations and disadvantages of the related art. 
         [0012]    An object of the present invention is to provide a backlight assembly for an LCD device, which is capable of selectively illuminating areas of the screen of the LCD device. 
         [0013]    Another object of the present invention is to provide a backlight assembly for an LCD device, which is capable of selectively illuminating areas of the screen, thereby reducing or cancelling undesirable artifacts displayed on the screen of the LCD device. 
         [0014]    Another object of the present invention is to provide a backlight assembly for an LCD device with a lower energy consumption by providing different lighting energy for different parts of the screen depending on the image contents displayed on the LCD device. 
         [0015]    Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
         [0016]    To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the LCD device includes an LCD panel having an exterior surface with a first area and an interior surface, a light filter layer having an exterior surface provided at the interior surface of the LCD panel and an interior surface, a light guide assembly provided behind the interior surface of the light filter layer, the light guide assembly including a plurality of light pipes, a light source including a plurality of selectively illuminated lamps arranged at a lateral side of the light guide assembly, each of the lamps being respectively associated with a different one of the light pipes for emitting light into the respective light pipe, a plurality of diffusion surfaces, each of the diffusion surfaces being provided on a selected area of a respective one of the plurality of the light pipes, the selected area being smaller than the first area, wherein each of the diffusion surfaces causes light to be emitted from the selected area of the respective light pipe when the light pipe is illuminated by the lamp associated therewith. 
         [0017]    In another aspect of the present invention, the backlight assembly for the LCD device includes a light guide assembly including a plurality of light pipes, a light source arranged at a lateral side of the light guide assembly, a plurality of diffusion surfaces, each of the diffusion surfaces being provided on a selected area of a respective one of the plurality of the light pipes, wherein each of the diffusion surfaces causes light to be emitted from the selected area of the respective light pipe when the light pipe is illuminated by the light source. 
         [0018]    It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]    The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
           [0020]      FIG. 1  is a view schematically illustrating a liquid crystal display (LCD) device having a backlight assembly according to the related art; 
           [0021]      FIG. 2  schematically illustrates a vertical section of the related art LCD device of  FIG. 1 ; 
           [0022]      FIGS. 3(   a ) to  3 ( c ) are cross-sectional views schematically illustrating an LCD device including a backlight assembly according to a first exemplary embodiment of the present invention; 
           [0023]      FIG. 4  is a view schematically illustrating a light pipe configuration of the backlight assembly of the LCD device according to the first exemplary embodiment of the present invention; 
           [0024]      FIG. 5  is a view schematically illustrating one light pipe of the backlight assembly of the LCD device according to the first embodiment of the present invention; 
           [0025]      FIGS. 6(   a ) to  6 ( c ) are cross-sectional views schematically illustrating an LCD device including a backlight assembly according to a second exemplary embodiment of the present invention; 
           [0026]      FIG. 7  is a view schematically illustrating a light pipe configuration of the backlight assembly of the LCD device according to the second exemplary embodiment of the present invention; 
           [0027]      FIG. 8  is a view schematically illustrating the light pipe configuration of the backlight assembly of the LCD device of  FIG. 7  according to the second exemplary embodiment of the present invention; and 
           [0028]      FIG. 9  is a view schematically illustrating the light pipe configuration of the backlight assembly of the LCD device of  FIG. 7  according to the second exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0029]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
         [0030]      FIGS. 3(   a ) to  3 ( c ) are cross-sectional views schematically illustrating an LCD device including a backlight assembly according to a first exemplary embodiment of the present invention.  FIG. 3(   a ) is a cross-sectional view illustrating the backlight assembly including a plurality of light pipes with different lengths,  FIG. 3(   b ) is a cross-sectional view illustrating a portion X of the backlight assembly of  FIG. 3(   a ), and  FIG. 3(   c ) is a cross-sectional view illustrating one light pipe of the backlight assembly of the LCD device of  FIG. 3(   b ). 
         [0031]    Referring to  FIGS. 3(   a ) to  3 ( c ), the LCD device of the first exemplary embodiment includes an LCD panel  100 , a light filter layer  200  arranged behind the LCD panel  100 , and the backlight assembly arranged behind the light filter layer  200 . The backlight assembly includes a light guide plate  300  arranged behind the light filter layer  200 , and a light source  400  arranged laterally at two sides of the light guide plate  300 . The light guide plate  300  may include a plurality of light pipes, which are stacked together, thereby forming the light guide plate  300 . The light pipes may be made of a transparent plastic material. The light source  40  includes a plurality of lamps. The light pipes are designed to have different configurations. That is, the light pipes may be formed with different lengths, thicknesses or shapes depending on image contents to be displayed. Also, the plurality of lamps may be provided with different types and powers depending on the image contents to be displayed or the light pipes with which they are associated. 
         [0032]    As shown in  FIG. 3(   b ), which corresponds to the portion X of  FIG. 3(   a ), in this exemplary embodiment, there are three light pipes  300 A,  300 B and  300 C, and three lamps  400 A,  400 B and  400 C that respectively correspond to the light pipes  300 A,  300 B and  300 C of the light guide plate  300 . The light pipes  300 A,  300 B and  300 C may be formed at least with different lengths. The lamps  400 A,  400 B and  400 C may be provided with different powers. Each light pipe has at least a portion thereof covered by a diffusion surface  500 . The diffusion surface  500  may be made of white paint, white line, or a surface texture of the light pipe. The diffusion surface  500  may also be made of any other materials that allow the diffusion of light. Because each of the light pipes  300 A,  300 B and  300 C has at least a portion of its rear surface covered by the diffusion surface  500 , the covered portion serves to illuminate the LCD panel  100 . Moreover, the diffusion surfaces  500  covered on the different light pipes may be formed with different configurations, for example, different shapes and thicknesses. 
         [0033]    In the first exemplary embodiment, as shown in  FIG. 3(   a ), the light guide plate  300  includes an upper part and a lower part, which are symmetrical about the center of the LCD panel  100 , or a center  301  of the light pipe  300 A, such that each of the upper and lower parts includes the light pipes  300 A,  300 B and  300 C of different lengths stacked together. As shown in  FIG. 3(   b ), which illustrates the upper part X of the light guide plate  300 , the longest light pipe  300 A is on the front, and a portion  500 A thereof is covered by the diffusion surface  500 , thereby serving to illuminate the LCD panel  100  in the area A. The second longest light pipe  300 B is stacked on the light pipe  300 A, and a portion  500 B of the light pipe  300 B is covered by the diffusion surface  500 , thereby serving to illuminate the LCD panel  100  in the area B through the light pipe A. The shortest light pipe  300 C is stacked on the light pipe  300 B, and a portion  500 C thereof is covered by the diffusion surface  500 , thereby serving to illuminate the LCD panel  100  in the area C through the light pipes  300 A and  300 B. Moreover, as shown in  FIG. 3(   b ), the diffusion surfaces  500  attached to the respective light pipes  300 A to  300 C are arranged without overlapping with each other. Also, in the first exemplary embodiment, the longest light pipe is the one closest to the light filter layer  200 , and the shortest light pipe is the one farthest from the light filter layer  200 . 
         [0034]    As shown in  FIG. 3(   c ), a light beam  600  emitted from the lamp  400 B of the light source  400  is guided by the light pipe  300 B and diffused at the portion  500 B of the light pipe  300 B, on which the diffusion surface  500  is attached. The light beam  600  diffused at the portion  500 B of the light pipe  300 B passes through the light pipe  300 A and the light filter layer  200  to illuminate the LCD panel  100  in the area B (of  FIG. 3(   b )). 
         [0035]      FIG. 4  is a view schematically illustrating a configuration of the light pipes  300 A,  300 B and  300 C of the backlight assembly of the LCD device according to the first exemplary embodiment of the present invention. As shown in  FIG. 4 , the plurality of light pipes  300 A,  300 B and  300 C are stacked up with different lengths, and are arranged to be symmetrical about the center of the LCD panel  100  or the center  301  of the longest light pipe  300 A.  FIG. 5  is a view schematically illustrating only the light pipe  300 A of the backlight assembly of the LCD device according to the first embodiment of the present invention. As shown in  FIG. 5 , the light pipe  300 A has the portion  500 A covered by the diffusion surface  500 , so that when the lamp  400 A turns ON and emits light beams, the portion  500 A serves to diffuse the light beams. Thus, the diffused light beams pass through the light filter layer  200  to illuminate the LCD panel  100  in the area A (of  FIG. 3(   b )). 
         [0036]    According to the first exemplary embodiment, since the above-described arrangement can illuminate different areas of the screen of the LCD panel  100  independently by selective energization of the lamps  400 A,  400 B and  400 C, the undesirable artifacts attached to the LCD panel  100  can be reduced or canceled. Also, when compared with the LCD device of the related art, less energy can be used because the light lamps  400 B and  400 C can be chosen with less power than the light lamp  400 A-because the light lamps  400 B and  400 C illuminate smaller areas of the display than the light lamp  400 A. 
         [0037]      FIGS. 6(   a ) to  6 ( c ) are cross-sectional views schematically illustrating an LCD device including a backlight assembly according to a second exemplary embodiment of the present invention.  FIG. 6(   a ) is a cross-sectional view of the LCD device including the backlight assembly having a plurality of light pipes  300 A,  300 B and  300 C with different configurations,  FIG. 6(   b ) is a cross-sectional view illustrating a portion Y of the backlight assembly of  FIG. 6(   a ), and  FIG. 6(   c ) is a cross-sectional view illustrating one light pipe of the backlight assembly of the LCD device of  FIG. 6(   b ). 
         [0038]    Referring to  FIGS. 6(   a ) to  6 ( c ), the LCD device includes an LCD panel  100 , a light filter layer  200  arranged behind the LCD panel  100 , and the backlight assembly arranged behind the light filter layer  200 . The backlight assembly includes a light guide plate  300  arranged behind the light filter layer  200 , and a light source  400  arranged laterally at two sides of the light guide plate  300 . The light guide plate  300  includes a plurality of light pipes, which are stacked up together, thereby forming the light guide plate  300 . The light pipes may be made of a transparent plastic material. The light pipes may be designed to have different configurations. That is, the light pipes may be formed with different lengths, thicknesses and/or shapes depending on image contents to be displayed. The light source  400  includes a plurality of lamps. The plurality of lamps may be provided with different types and/or different powers depending on the image contents to be displayed. 
         [0039]    As shown in  FIG. 6(   b ), in this exemplary embodiment, there are three light pipes  300 A,  300 B and  300 C, and three lamps  400 A,  400 B and  400 C respectively associated with the light pipes  300 A,  300 B and  300 C of the light guide plate  300 . The light pipes  300 A,  300 B and  300 C may be formed at least with different lengths. The lamps  400 A,  400 B and  400 C may be provided at least with different powers with the lamp  400 A being the lowest power and the lamp  400 C being the highest power. Each of the light pipes  300 A,  300 B and  300 C has a portion thereof covered by a diffusion surface  500 . The diffusion surface  500  may be made of white paint, white line, or texture on the surface of the light pipe. The diffusion surface  500  may also be made of any other materials that allow the diffusion of light. Because each of the light pipes  300 A,  300 B and  300 C has a portion of its rear surface covered by the diffusion surface  500 , the covered portions serve to illuminate the LCD panel  100 . Moreover, the diffusion surfaces  500  attached to the respective light pipes may be formed with different shapes and/or thicknesses, and are particularly arranged not to overlap one another. 
         [0040]    In this second exemplary embodiment, as shown in  FIG. 6(   a ), the light guide plate  300  includes an upper part and a lower part, which are symmetrical about the center of the LCD panel  100  or a center  301  of the light pipe  300 C such that each of the upper and lower parts includes the light pipes  300 A,  300 B and  300 C stacked up together with different lengths. As shown in  FIG. 6(   b ), which illustrates the upper part Y of the light guide plate  300 , the shortest light pipe  300 A is on the front, and a portion  500 A thereof is covered by a diffusion surface  500  to serve to illuminate the LCD panel  100  in the area A. The second light pipe  300 B, which is longer than the light pipe  300 A, is stacked on the light pipe  300 A, and a portion  500 B of the light pipe  300 B is covered by a diffusion surface  500  to serve to illuminate the area B of the LCD panel  100 . The longest light pipe  300 C is stacked on the light pipe  300 B, and a portion  500 C thereof is covered by a diffusion surface  500  to serve to illuminate the area C of the LCD panel  100 . In such an arrangement, the shortest light pipe is the one closest to the light filter layer  200 , and the longest light pipe is the one farthest from the light filter layer  200 . Thus, in the second exemplary embodiment, light coming from the portions  500 A,  500 B and  500 C goes through only one light pipe before reaching the light filter layer  200 . Moreover, as shown in  FIG. 6(   b ), reflective coating layers (or a reflective sheet)  550  may be arranged among the light pipes  300 A,  300 B and  300 C to avoid diffusion or light leaks. Each of the reflective coating layers is formed to cover a rear surface of its corresponding light pipe including the diffusion surface  500  attached to the corresponding light pipe. 
         [0041]    As shown in  FIG. 6(   c ), a light beam  600  emitted from the lamp  400 B is guided by the light pipe  300 B and diffused at the portion  500 B of the light pipe  300 B, on which the diffusion surface  500  is attached. The light beam  600  diffused at the portion B of the light pipe  300 B passes through the light filter layer  200  to illuminate the LCD panel  100 . 
         [0042]      FIG. 7  is a view schematically illustrating the configuration of the light pipes  300 A to  300 C of the backlight assembly of the LCD device according to the second exemplary embodiment of the present invention. As shown in  FIG. 7 , in the backlight assembly of the second exemplary embodiment, the plurality of light pipes  300 A,  300 B and  300 C are stacked up in the adverse order to those shown in  FIG. 4  of the first exemplary embodiment, and are arranged to be symmetrical about the center  301  of the longest light pipe  300 C. Also, the portion  500 C of the light pipe  300 C is covered by the diffusion surface  500 , so that the light beams, which are emitted from the lamp  400 C of the light source  400  and diffused by the diffusion surface  500  at the portion  500 C, passes through the light filter layer  200  to illuminate the LCD panel  100  in the area C (of  FIG. 6(   b )). 
         [0043]      FIG. 8  is a view schematically illustrating a configuration in which the light pipe  300 C of the upper part of the light guide plate is removed according to the second embodiment of the present invention. As shown in  FIG. 8 , the portions  500 B of the light pipe  300 B are covered by the diffusion surface  500 , so that the light beams, which are emitted from the lamp  400 B of the light source  400  and diffused by the diffusion surface  500  at the portion  500 B, passes through the light filter layer  200  to illuminate the LCD panel  100  in the area B (of  FIG. 6(   b )). 
         [0044]      FIG. 9  is a view schematically illustrating a configuration in which the light pipes  300 B and  300 C of the upper part of the light guide plate are removed according to the second embodiment of the present invention. As shown in  FIG. 9 , the portion  500 A of the light pipe  300 A is covered by the diffusion surface  500 , so that the light beams, which are emitted from the light source  400  and diffused by the diffusion surface  500  at the portion  500 A, passes through the light filter layer  200  to illuminate the LCD panel  100  in the area A (of  FIG. 6(   b )). 
         [0045]    According to the second exemplary embodiment, since the above-described arrangement is capable of illuminating different areas of the screen of the LCD panel  100  independently, the undesirable artifacts attached to the LCD panel  100  can be reduced or canceled by using the backlight assembly with different lighting configurations of the second exemplary embodiment. Also, energy consumption can be reduced by using the backlight assembly having lamps with different lighting powers for different areas of the screen of the LCD device depending on the image contents to be displayed. 
         [0046]    It will be apparent to those skilled in the art that various modifications and variations can be made in the backlight assembly and the LCD device using the backlight assembly of the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.