1. Field of the Invention
The present invention relates to a light emission device, a method of manufacturing the light emission device, and a display device using the light emission device as a backlight unit. More particularly, the present invention relates to a driving electrode of the light emission device.
2. Discussion of Related Art
A liquid crystal display, which is one of a variety of flat panel display devices, displays an image by varying a light transmission amount at each pixel using a dielectric anisotropy property of liquid crystal whose twisting angle varies according to a voltage applied.
The liquid crystal display includes a liquid crystal panel assembly and a backlight unit for emitting light toward the liquid crystal panel assembly. The liquid crystal panel assembly receives light emitted from the backlight unit and allows the light to be transmitted or blocked by a liquid crystal layer.
Backlight units can be classified according to their light sources into different types (or light source types), one of which is a cold cathode fluorescent lamp (CCFL) type. The CCFL is a linear light source that can uniformly emit light to the liquid crystal panel assembly through optical members such as a diffusion sheet, a diffuser plate, and a prism sheet.
However, in the CCFL type backlight unit, since the light emitted from the CCFL travels through the optical members, there may be a light loss. Considering the light loss, a relatively high intensity of light is emitted from the CCFL. This causes an increase in power consumption. Furthermore, since it is difficult to increase the size of the CCFL type backlight unit due to a structural limitation of the CCFL type backlight unit, the CCFL type backlight unit may not be applied to a large-size liquid crystal display (e.g., a liquid crystal display that is over 30 inches).
A light emission diode (LED) type backlight unit is another light source type that may be used to provide light to a liquid crystal display. The LED type backlight unit includes a plurality of LEDs and optical members such as a reflection sheet, a waveguide plate, a diffusion sheet, a diffuser plate, a prism sheet, and the like. The LED type backlight unit has fast response time and relatively good color reproduction characteristics. However, the LED is costly and increases an overall thickness of the liquid crystal display.
Therefore, recently, a field emission type backlight unit that emits light using an electron emission property of an electric field has been developed to replace the CCFL and LED type backlight units.
Since the field emission type backlight unit should provide a relatively high luminance, a relatively high voltage is applied to an anode electrode of the field emission type backlight unit. As such, there may be a short circuit between the driving electrode formed on a first substrate of the field emission type backlight unit and the anode electrode formed on a second substrate of the field emission type backlight unit. In addition, an arc discharge may be generated in a vacuum envelope (or chamber) of the field emission type backlight unit. The arc discharge may damage the driving electrodes.
Furthermore, among the driving electrodes, cathode and gate electrodes should be insulated from each other. However, the cathode and gate electrodes may be short-circuited during a manufacturing process.
When the driving electrodes are short-circuited or damaged as described above, the pixels controlled by the driving electrodes cannot properly emit light. That is, in a conventional field emission type light emission device (or backlight unit), when one driving electrode is damaged, all of the pixels that are controlled by the damaged driving electrode are defective in the emission of light.
In addition, the conventional backlight units are maintained at a constant (or predetermined) brightness when the liquid crystal display is driven. Therefore, it is difficult to improve the display quality of the liquid crystal display to a sufficient level.
For example, when the liquid crystal panel assembly intends to display an image having a high luminance portion and a low luminance portion in response to an image signal, it will be possible to realize an image having a more improved dynamic contrast if the backlight unit can emit lights having different intensities to the respective high and low luminance portions.
However, since the conventional backlight units may not achieve the above function, the liquid crystal display has a limitation in how much the dynamic contrast of an image can be improved.