This application claims the benefit of Korean Patent Application No. 1999-51143, filed on Nov. 17, 1999, under 35 U.S.C. xc2xa7119, the entirety of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a transflective liquid crystal display device and a method of manufacturing the same.
2. Description of Related Art
Liquid crystal display (LCD) devices are in wide use as display devices capable of being reduced in weight, size and thickness. In general, the LCD device includes upper and lower substrates with a liquid crystal layer interposed therebetween. The upper substrate includes a common electrode and a color filter, and the lower substrate includes a pixel electrode and TFTs. An upper polarizer is arranged on a front surface of the upper substrate, and a lower polarizer is arranged on a bottom surface of the lower substrate. A back light device is arranged under the lower substrate as a light source.
The LCD device is divided into a transmissive LCD device and a reflective LCD device. The typical transmissive LCD device displays images using light from the back light device. However, the transmissive LCD device is a non-effective light converter that merely transmits about 3% to about 8% of light from the back light device. In other words, as shown in FIG. 1, the observer gets to see about 7% of light from the back light device. Therefore, the transmissive LCD device requires a back light device having high brightness, leading to high power consumption.
In order to achieve a back light device having high brightness, sufficient power must be supplied to the back light device, thereby increaseing battery weight. However, such a back light device cannot be used for a long time.
To overcome the problems described above, the reflective LCD device has been introduced. Since the reflective LCD device is possible to use the device for a long time, and it is easy to carry due to its light weight.
FIG. 2 is a plan view illustrating a lower array substrate of a conventional reflective LCD device. As shown in FIG. 2, data lines 2 and 4 are arranged in a longitudinal direction, and gate lines 6 and 8 are arranged in a transverse direction perpendicular to the data lines 2 and 4. A reflective electrode 10 is arranged on a region defined by the gate and data lines. TFTs are arranged at a cross point of the gate and data lines. Each of the TFTs includes a gate electrode 18, a source electrode 12 and a drain electrode 14. The gate electrode 18 extends from the gate line 8, and the source electrode 12 extends from the data line 2. The drain electrode 14 is spaced apart from the source electrode 12 and contacts the reflective electrode 10 through a contact hole 16.
FIG. 3 is a cross sectional view taken along line IIIxe2x80x94III of FIG. 2. As shown in FIG. 2, the gate electrode 18 is formed on a substrate 1, and a gate insulating layer 20 is formed on the gate electrode 18 and an exposed surface of the substrate 1. A semiconductor layer 22 is formed on the gate insulating layer 20. The source and drain electrodes 12 and 14 overlap both end portions of the semiconductor layer 22. A passivation film 24 is formed over the whole surface of the substrate 1 while covering the source and drain electrodes 12 and 14. The passivation film 24 has the contact hole 16 on a portion of the drain electrode 14. The reflective electrode 10 is formed on the passivation film and contacts the drain electrode 14 through the contact hole 16. The reflective electrode is made of a reflective material having a good reflectance.
As described above, since the reflective LCD device uses ambient light other than an internal light source such as a back light device, it can be used for a long time. In other words, the reflective LCD device is driven using light reflected from the reflective electrode 10.
However, ambient light such as natural light and external light does not exist always. In other words, the reflective LCD device can be used during the day or in office where external light exists, but it can not be used during the night or in a dim place.
For the foregoing reasons, there is a need for a liquid crystal display device that its weight is light and that power consumption is low and that can be used during both the day and the night.
To overcome the problems described above, preferred embodiments of the present invention provide a transflective liquid crystal display device that can be used during both the day and the night.
In order to achieve the above object, the preferred embodiments of the present invention provide a transflective liquid crystal display device, including: a liquid crystal panel including: a) a first substrate having a color filter; b) a second substrate spaced apart from the first substrate, having a switching element, a reflective electrode, and a pixel electrode, the reflective electrode having at least one transmitting hole and reflecting ambient light, the transmitting hole transmitting light and being covered by the pixel electrode, the reflective electrode and the pixel electrode being electrically insulated from each other; and c) a liquid crystal layer interposed between the upper and lower substrates; and a back light device providing light toward the transmitting hole.
The preferred embodiment of the present invention provides a transflective liquid crystal display device, including: a first substrate; a second substrate spaced apart from the first substrate, including: a) a gate electrode formed on the second substrate: b) a first insulating layer formed over the whole surface of the second substrate and covering the gate electrode; c) a semiconductor layer formed on the first insulating layer; d) source and drain electrodes spaced apart from each other and overlapping both end portions of the semiconductor layer; e) a second insulating layer formed over the whole surface of the second substrate and covering the source and drain electrodes; f) a pixel electrode formed on the second insulating layer and contacting the drain electrode; g) a third insulating layer formed ove the whole surface of the second substrate and covering the pixel electrode; and h) a reflective electrode formed on the thrid insulating layer and having at least one transmitting hole, the transmitting hole being covered by the pixel electrode; and a liquid crystal layer interposed between the first and second substrates.
The preferred embodiment of the present invention provides a method of manufacturing an array substrate of a transflective liquid crystal display device, the method including: forming a gate electrode on the substrate forming a first insulating layer, over the whole surface of the substrate while covering the gate electrode; forming a semiconductor layer on the first insulating layer; forming source and drain electrodes, the source and drain electrodes being spaced apart from each other and overlapping both end portions of the semiconductor layer; forming a second insulating layer over the whole surface of the substrate while covering the source and drain electrodes; forming a pixel electrode on the second insulating layer, the pixel electrode contacting the drain electrode; forming a third insulating layer over the whole surface of the substrate while covering the pixel electrode; and forming a reflective electrode on the third insulating layer, the reflective electrode having at least one transmitting hole, the transmitting hole being covered by the pixel electrode.
The reflective electrode is a made of an opaque metal. The pixel electrode is made of one of ITO and IZO. The first and third insulating layers are made of SiNx or SiO2. The second insulating layer is made of BCB (benzocyclobutene). The reflective electrode and the pixel electrode are electrically insulated by an insulating layer.
As described herein before, since the transflective LCD device according to the preferred embodiment of the present invention has both the reflective mode and the transmissive mode, it can be used in anytime and it everywhere regardless of a time and a place.