1. Technical Field
The present invention relates to a light guiding plate, and to a backlight assembly and a display device having the light guiding plate. More particularly, the present invention relates to a light guiding plate that may be capable of enhancing uniformity of brightness, and to a backlight assembly and a display device containing the light guiding plate.
2. Related Art
A liquid crystal display (LCD) device has various advantageous characteristics in thickness, durability, weight, power consumption, etc. The LCD device is a type of flat panel display device that includes a LCD panel that has two substrates and a liquid crystal layer interposed therebetween. Generally, in the LCD device, an arrangement of liquid crystals of the liquid crystal layer vary in response to an applied electric field, and thus, a light transmittance can be changed to thereby display an image.
However, a conventional liquid crystal display is typically not a self-luminescent display device. Therefore, the liquid crystal display needs to use an outside light source unit for illuminating uniformly the viewing plane of the liquid crystal panel to display an image. A backlight assembly is used to provide light to the viewing plane of the liquid crystal panel. The backlight assembly is classified as an edge type or a direct type in accordance with the location of a light source.
The edge type backlight has at least one light source installed at one or both side edges of a light guiding plate and irradiates incident light from the light source to a liquid crystal display panel through the light guiding plate and a plurality of optical sheets. The direct type backlight has a plurality of light sources disposed under the liquid crystal display panel and irradiates incident light from the light sources to the liquid crystal display panel through a diffusion plate and a plurality of optical sheets. Thus, increasing luminance uniformity of the light emitted from the backlight assembly toward the liquid crystal display panel is an important technical problem.
FIG. 1 represents one example of an edge type backlight assembly adopting LEDs (i.e., light emitting diodes) as a light source.
Referring to FIG. 1, a plurality of LEDs 1, acting as point light sources, are disposed at one side edge of a light guiding plate 2 along the light incident portion of the light guiding plate 2 in a line. Light emitted from the LEDs 1 is input through the incident surface of the light guiding plate 2, converted as plane light source at the inside of the light guiding plate and emitted toward the liquid crystal panel (not shown).
The LEDs emanate a light within a particular angle range. Therefore, the backlight assembly, as shown in FIG. 1, has a brightness that appears higher where the lights incident from the LEDs 1 to a light guiding plate 2 cross than in other parts of the plate 2. A bright spot occurs where the light from the different LEDs 1 cross in the light guiding plate 2. The bright spot appears in the shape of a ring, circle, or ellipse and is known as a “hot spot” (corresponds to the part 3, in FIG. 1) in accordance with the shape.
Due to this phenomenon, in the backlight assembly and the liquid crystal display device of the related art, the brightness of the display picture is non-uniform because some part of the light guiding plate 2 appears to be brighter than another part.