1. Field of the Invention
The present invention relates to a liquid crystal display device and a method of fabricating a liquid crystal display device, and more particularly, to a transflective liquid crystal display device having through holes in color filters and a method of fabricating the same.
2. Description of Related Art
As the use of information technology increases, the need for flat panel displays with thin profiles, light weight, and lower power consumption has increased. Accordingly, various flat panel display (FPD) devices, such as liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display devices, and electro-luminescence display (ELD) devices, have been developed.
Presently, liquid crystal display (LCD) devices with light weight, thin profiles, and low power consumption are commonly used in office automation equipment and video units. LCD devices typically use a liquid crystal (LC) interposed between upper and lower substrates and make use of optical anisotropy of the LC. Because molecules of the LC are thin and long, an alignment direction of the LC molecules may be controlled by the application of an electric field to the LC molecules. When the alignment direction of the LC molecules is properly adjusted, the LC may be aligned such that light is refracted along the alignment direction of the LC molecules to display images.
In general, LCD devices are divided into transmissive-type LCD devices and reflective-type LCD devices according to whether the display device uses an internal or external light source. The transmissive-type LCD device includes an LCD panel and a backlight device, wherein the incident light produced by the backlight device is attenuated during transmission so that the actual transmittance is only about 7%. As a result, the transmissive-type LCD device requires a relatively high initial brightness, whereby the electrical power consumption required by the backlight device increases. Accordingly, a relatively heavy battery, which cannot be used for an extended period of time, is needed to supply sufficient power to the backlight device.
The reflective-type LCD has been developed, which overcomes these problems. Because the reflective-type LCD device uses ambient light instead of a backlight device and a reflective opaque material is used as a pixel electrode, the reflection-type LCD device is light and easy to carry. In addition, because the power consumption of the reflective-type LCD device is reduced, it may be used in a personal digital assistant (PDA). However, the reflective-type LCD device is easily affected by its surroundings. For example, because ambient light in an office differs largely from that outdoors, the reflective-type LCD device can not be used where the ambient light is weak or does not exist. In order to overcome the problems described above, a transflective-type LCD device has been developed, wherein the device has both a transmissive mode and a reflective mode.
FIG. 1 is a cross-sectional view illustrating a transflective liquid crystal display device according to the related art.
The transflective liquid crystal display device according to the related art includes an array substrate 10, a color filter substrate 50, and a liquid crystal layer 80 interposed between the array and color filter substrates 10 and 50. The color filter substrate 50 includes a black matrix 53 on a rear surface of a transparent substrate 51. Red (R), green (G) and blue (B) color filters 55a, 55b and 55c are also formed on the rear surface of the transparent substrate 51 while covering the black matrix 53. An overcoat layer 63 is formed on a rear surface of the red (R), green (G) and blue (B) color filters 55a, 55b and 55c. The overcoat layer 63 protects the color filters 55a, 55b and 55c. Additionally, a common electrode 65 is formed on a rear surface of the overcoat layer 63.
The array substrate 10 includes a thin film transistor T including a gate electrode 15, a semiconductor layer 20, a source electrode 23 and a drain electrode 25 on a transparent substrate 11 where a gate line (not shown) and a data line 21 cross. A gate insulating layer 17 is interposed between the gate electrode 15 and the semiconductor layer 20 and contacts the transparent substrate 11. A passivation layer 30 is formed on the gate insulating layer 17, covers the thin film transistor T, and has a drain contact hole 35 exposing a portion of the drain electrode 25. A pixel electrode 40 is formed on the passivation layer 30 and contacts the drain electrode 25 through the drain contact hole 35. A reflector 45 is formed on peripheral portions of the pixel electrode 40. In the array substrate, an area where the reflector 45 is formed becomes a reflective portion RA, and an area where the reflector 45 is not formed becomes a transmissive area TA.
Column spacers 70, which are interposed between the array and color filter substrates 10 and 50, form a cell gap where the liquid crystal layer is interposed. Each column spacer 70 corresponds in position to the black matrix 53 of the color filter substrate 50.
The transflective liquid crystal display device having the structure of FIG. 1 has a disadvantage due to the difference in the light efficiency between reflective mode and transmissive mode operation. Thus, the aforementioned liquid crystal display device produces unstable brightness and color reproduction, which are different between the reflective mode and the transmissive mode.
When the transflective liquid crystal display device operates in a transmissive mode, a backlight (not shown) disposed underneath the array substrate 10 generates light directed toward the array substrate 10 such that the light from the backlight passes only once through the color filters 55a, 55b and 55c. However, when the transflective liquid crystal display device operates in a reflective mode, ambient light incident from the surroundings passes through the color filters 55a, 55b and 55c, and then is reflected by the reflector 45 back towards the color filters 55a, 55b and 55c. Therefore, the ambient light passes twice through the color filters 55a, 55b and 55c. This two-time passage through the color filters 55a, 55b and 55c results in the reflective mode reproducing better color than the transmissive mode. However, the two-time passage decreases the brightness in the reflective mode versus the transmissive mode.
To overcome those problems, it has been suggested that the liquid crystal layer between the array and color filter substrates have two different cell gaps and/or that each color filter is formed to have a different thickness between the reflective portion and the transmissive portion. Thus, the color reproduction and the brightness are adjusted to be the same regardless of whether the transflective liquid crystal display device is operated in the reflective mode or in the transmissive mode. However, these modifications also have some disadvantages.
Today when a transflective liquid crystal display device is utilized in mobile phones or PDAs, the image quality becomes an important issue in satisfying buyer's demands. For good image quality, a high resolution is required in the transflective liquid crystal display device. Thus, the transflective liquid crystal display device needs to have many pixels per unit area such that individual pixels are smaller as compared to the pixels in a conventional liquid crystal display device. However, if the pixel size for the transflective liquid crystal display device is reduced, the reflective portion in the transflective liquid crystal display device is also reduced and a decrease in brightness results.