Patent Application
20080297691
This application claims priority to and the benefit of Korean Patent Application No. 10-2007-0051995, filed on May 29, 2007, in the Korean Intellectual Property Office, the entire content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a back light unit for a liquid crystal display device.
2. Discussion of Related Art
With the rapid development of the information and communication industries, the use of display devices has rapidly expanded. Recently, there is demand for a display device having relatively low power, light weight, a thin profile, and high resolution. To meet such a demand, liquid crystal display devices or display devices using organic luminescence properties have been developed.
A thin film transistor-liquid crystal display (TFT-LCD) having excellent color reproduction properties and low power consumption is an example of a flat panel display device. The TFT-LCD includes a liquid crystal display panel, a back light unit, and an LCD drive IC (LDI). In the liquid crystal display panel, a liquid crystal is injected between two substrates. The back light unit is located under the liquid crystal display panel, and is used as a light source. The LDI drives the liquid crystal display panel.
In some back light units, a reflection sheet includes a dielectric substance such as a polymer compound, that complicates manufacturing of the reflection sheet. Furthermore, since a space is required between the reflection sheet and the light guide plate, a thickness of the back light unit is greater than it otherwise would be without the space.
An aspect of an embodiment of the present invention is directed toward a back light unit that can increase light efficiency by improving a reflection structure of a light guide plate, and also simplify manufacturing of a thin liquid crystal display device by making the back light unit relatively thin.
In an exemplary embodiment of the present invention, a back light unit for a liquid crystal display panel is provided to include a light source, a light guide plate for receiving light from the light source, a lower surface of the light guide plate including a reflection sheet, a diffuser for diffusing the light from the light guide plate, and an optical sheet for providing the light from the diffuser to the liquid crystal display panel. In one exemplary embodiment, the reflection sheet may be metal, such as aluminum or silver.
In one exemplary embodiment, an entire lower surface of the light guide plate may be directly coated with the reflection sheet such that there is no space between the reflection sheet and the light guide plate. Additionally, the back light unit may be incorporated into a liquid crystal display device.
The accompanying drawings, together with the specification, illustrate exemplary embodiments of the present invention, and, together with the description, serve to explain the principles of the present invention.
In the following detailed description, only certain exemplary embodiments of the present invention are shown and described, by way of illustration. As those skilled in the art will recognize, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Like reference numerals designate like elements throughout the specification.
With reference to
The back light unit 130 is supported by the bottom chassis 162 located below the back light unit, the bottom chassis 162 being fixed within the mold frame 110. The back light unit 130 includes a light guide plate 131 for directing light emitted from a lamp. In one embodiment, the lamp is a light emitting diode (LED). However, other suitable light sources, such as a surface light source or a line light source, can be used as the lamp. A lower portion of the light guide plate 131 is coated with a reflection sheet 131b (
The liquid crystal display panel unit 140 includes a liquid crystal display panel 150, a printed circuit board (PCB) 142, and a tape carrier package (TCP) 144. The liquid crystal display panel 150 includes a TFT substrate 151 having a thin film transistor, a color filter substrate 153 on an upper portion of the TFT substrate 151, and a liquid crystal between the TFT substrate 151 and the color filter substrate 153. Polarizers are attached to an upper portion of the color filter substrate 153 and a lower portion of the TFT substrate 151 for determining a polarized direction of visible light emitted from the back light unit 130.
In the TFT substrate 151, a thin film transistor is formed on a transparent substrate in a matrix. A source of the thin film transistor is coupled to a data line, a drain of the thin film transistor coupled to a pixel electrode, and a gate of the thin film transistor is coupled to a scan line. Here, the pixel electrode includes an indium tin oxide (ITO) conductive material. A scan signal transferred through the scan line determines on/off of the TFT to transfer an electric signal from the source thereof to the drain. An arrangement of a liquid crystal is changed according to the electric signal to thereby determine the transmittance of light.
In the color filter substrate 153, when light passes through a liquid crystal, the light passes through a color filter to indicate a specific color, and a gradation us expressed according to the transmittance of the light.
The PCB 142 transfers a data signal and a scan signal to the TFT substrate 151, and is fixed to the TFT substrate 151 by the TCP 144.
Referring to
A general reflection sheet is formed of polymer material. The reflection sheet 131b in one exemplary embodiment of the present invention includes metal, thereby simplifying the manufacturing of the reflection sheet 131b as well as decreasing the cost of manufacture. Because the lower surface of the light guide plate 131a is directly coated with the reflection sheet 131b, there is no space between the light guide plate 131a and the reflection sheet 131b, thereby preventing (or reducing) a dispersion of light and increasing the light efficiency. Furthermore, the lack of a space between the light guide plate 131a and the reflection sheet 131 allows for a thinner liquid crystal display device.
The light source 132 includes a lamp adjacent a light guide plate. At least one LED or cold cathode tube (fluorescent lamp) may be used as the lamp. In the liquid crystal display device according an exemplary embodiment of the present invention, the reflection sheet is located at a lower surface of the light guide plate to prevent or reduce light loss. Furthermore, when the reflection sheet is composed of metal such as silver or aluminum, the manufacturing of the liquid crystal display device is simplified and the cost is reduced as compared to using a dielectric (or polymer) substance. In addition, since the reflection sheet is in direct contact with the light guide plate, there is no space between the light guide plate and the reflection sheet, allowing a thinner back light unit, and therefore a thinner liquid crystal display device.
While the present invention has been described in connection with certain exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims, and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2007-0051995 | May 2007 | KR | national |
