Liquid crystal display panel

A liquid crystal display panel including an active device array substrate, an opposite substrate, and a liquid crystal layer is provided. The active device array substrate has at least one pixel unit including two active devices, two first pixel electrodes, and two common lines. Each of the active devices has a gate, a source, and a drain. The gates are connected with one another, the sources are connected with one another, and the pixel electrodes are connected with the drains. A first signal source connected with one of the common lines is different from a second signal source connected with the other one of the common lines. The opposite substrate has a common electrode connected with the first signal source. The liquid crystal layer is disposed between the active device array substrate and the opposite substrate.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the priority benefit of Taiwan application serial No. 97115368, filed on Apr. 25, 2008. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND OF THE INVENTION

1. Field of the Invention

In the conventional transflective LCD (TR-LCDs), each of the pixel units has a transparent region and a reflective region. The transparent region uses a backlight as a light source, and the reflective region uses an external ambient light as the light source. In order to present similar display effect at both the reflective region and the transparent region, usually, an organic layer may be disposed on the reflective region to elevate a reflective pixel electrode, so as to form the TR-LCD having a dual cell gap.

The thickness of the organic layer formed in the reflective region is likely to be nonuniform; therefore, the transmittance of the LCD panel, the contrast of the image, and colors of the image are nonuniform.

SUMMARY OF THE INVENTION

Accordingly, an embodiment of the present invention is directed to a transflective LCD panel, adapted to reduce a color shift effect of an image.

Another embodiment of the present invention is directed to a transflective LCD panel having a single cell gap.

An embodiment of the present invention provides an LCD panel, which includes an active device array substrate, an opposite substrate, and a liquid crystal layer. The active device array substrate has multiple pixel units. Each of the pixel unit includes a first active device, a second active device, a first pixel electrode, a second pixel electrode, a first common line, and a second common line. The first active device has a first gate, a first source, and a first drain. The second active device has a second gate, a second source, and a second drain. The first gate is connected to the second gate, and the first source is connected to the second source. The first pixel electrode is connected to the first drain, and the second pixel electrode is connected to the second drain. The first common line is connected to a first signal source, the second common line is connected to a second signal source, and the first signal source is different from the second signal source. The opposite substrate has a common electrode connected to the first signal source. The liquid crystal layer is disposed between the active device array substrate and the opposite substrate.

In an embodiment of the present invention, the first signal source is adapted to provide a first voltage ΔVcom1, such that a coupling voltage ΔV1 of the first pixel electrode is equal to

Δ⁢⁢V⁢⁢1=Δ⁢⁢Vcom⁢⁢1·Clc+CstCgs+Clc+Cst,wherein Cst is a storage capacitance formed by the first common line and the first drain, Cgs is a parasitic capacitance formed by the first gate and the first source, and Clc is a liquid crystal capacitance formed by the first pixel electrode and the common electrode.

In an embodiment of the present invention, the first signal source is adapted to provide a first voltage ΔVcom1, and the second signal source is adapted to provide a second voltage ΔVcom2, such that a coupling voltage ΔV2 of the second pixel electrode is equal to

Δ⁢⁢V⁢⁢2=Δ⁢⁢Vcom⁢⁢1·ClcCgs+Clc+Cst+Δ⁢⁢V⁢⁢com⁢⁢2·CstCgs+Clc+Cst,wherein Cst is a storage capacitance formed by the second common line and the second drain, Cgs is a parasitic capacitance formed by the second gate and the second source, and Clc is a liquid crystal capacitance formed by the second pixel electrode and the common electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode is a reflective pixel electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a first transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode includes a second transparent pixel electrode and a reflective pixel electrode. The second transparent pixel electrode is disposed on the reflective pixel electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a first transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode includes a second transparent pixel electrode and a reflective pixel electrode. The reflective pixel electrode is disposed on the second transparent pixel electrode.

In an embodiment of the present invention, the active device array substrate further includes a cover layer. The cover layer covers the first active device, the second active device, the first common line, the second common line, a part of the first transparent pixel electrode and the second transparent pixel electrode. The reflective pixel electrode covers the cover layer and passes through the cover layer, so as to connect the second transparent pixel electrode.

In an embodiment of the present invention, the active device array substrate further includes a cover layer. The cover layer covers the first active device, the second active device, the first common line, the second common line, the first transparent pixel electrode, and the second transparent pixel electrode. Further, the reflective pixel electrode covers a part of the cover layer and passes through the cover layer, so as to connect the second transparent pixel electrode.

An embodiment of the present invention further provides an LCD panel, which includes an active device array substrate, an opposite substrate, and a liquid crystal layer. The active device array substrate has multiple pixel units. Each of the pixel unit includes a first active device, a second active device, a first pixel electrode, a second pixel electrode, a first common line, and a second common line. The first active device has a first gate, a first source, and a first drain. The second active device has a second gate, a second source, and a second drain. The first gate is connected to the second gate, and the first source is connected to the second source. The first pixel electrode is connected to the first drain, and the second pixel electrode is connected to the second drain. The first common line is connected to a first signal source, the second common line is connected to a second signal source, and the first signal source is different from the second signal source. The opposite substrate has a common electrode, and the common electrode includes a first common sub-electrode and a second common sub-electrode. The first common sub-electrode is connected to the first signal source, the second common sub-electrode is connected to a third signal source, and the third signal source is different from the first signal source and the second signal source. The liquid crystal layer is disposed between the active device array substrate and the opposite substrate.

In an embodiment of the present invention, the first signal source is adapted to provide a first voltage ΔVcom1, such that a coupling voltage ΔV1 of the first pixel electrode is equal to

Δ⁢⁢V⁢⁢1=Δ⁢⁢Vcom⁢⁢1·Clc+CstCgs+Clc+Cst,wherein Cst is a storage capacitance formed by the first common line and the first drain, Cgs is a parasitic capacitance formed by the first gate and the first source, and Clc is a liquid crystal capacitance formed by the first pixel electrode and the common electrode.

In an embodiment of the present invention, the second signal source is adapted to provide a second voltage ΔVcom2, and the third signal source is adapted to provide a third voltage ΔVcom3, such that a coupling voltage ΔV2 of the second pixel electrode is equal to

Δ⁢⁢V⁢⁢2=Δ⁢⁢Vcom⁢⁢2·ClcCgs+Clc+Cst+Δ⁢⁢Vcom⁢⁢3·CstCgs+Clc+Cst,wherein Cst is a storage capacitance formed by the second common line and the second drain, Cgs is a parasitic capacitance formed by the second gate and the second source, and Clc is a liquid crystal capacitance formed by the second pixel electrode and the common electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode is a reflective pixel electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a first transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode includes a second transparent pixel electrode and a reflective pixel electrode. The second transparent pixel electrode is disposed on the reflective pixel electrode.

In an embodiment of the present invention, one of the first pixel electrode and the second pixel electrode is a first transparent pixel electrode, and the other one of the first pixel electrode and the second pixel electrode includes a second transparent pixel electrode and a reflective pixel electrode. The reflective pixel electrode is disposed on the second transparent pixel electrode.

In an embodiment of the present invention, the active device array substrate further has a cover layer. The cover layer covers the first active device, the second active device, the first common line, the second common line, a part of the first transparent pixel electrode and the second transparent pixel electrode. The reflective pixel electrode covers the cover layer and passes through the cover layer, so as to connect the second transparent pixel electrode.

In an embodiment of the present invention, the active device array substrate further has a cover layer. The cover layer covers the first active device, the second active device, the first common line, the second common line, the first transparent pixel electrode, and the second transparent pixel electrode. The reflective pixel electrode covers a part of the cover layer and passes through the cover layer, so as to connect the second transparent pixel electrode.

In the present invention, the first common line and the second common line receive different voltages, such that the first pixel electrode and the second pixel electrode may have different coupling voltages. Therefore, the color shift effect of the image may be compensated, since a rotating angle of the liquid crystals of the first pixel electrode in the liquid crystal layer is different from a rotating angle of the liquid crystals of the second pixel electrode.

DESCRIPTION OF THE EMBODIMENTS

FIG. 1Ais a schematic structural view of an LCD panel according to an embodiment of the present invention, andFIG. 1Bis an equivalent circuit diagram of the LCD panel inFIG. 1A. Referring toFIGS. 1A and 1B, in this embodiment, the LCD panel is, for example, a transflective LCD (TR-LCD) panel with a single cell gap. However, the present invention is not limited to the following embodiments.

The LCD panel10A includes an active device array substrate100, an opposite substrate200, and a liquid crystal layer300disposed between the active device array substrate100and the opposite substrate200. The liquid crystal layer300has a plurality of liquid crystals310, and the active device array substrate100has at least one pixel unit110. The pixel unit110may be divided into a reflective sub-pixel unit110aand a transparent sub-pixel unit110b. In order to simplify the drawings, only one pixel unit110is shown in the following embodiment.

In this embodiment, the reflective sub-pixel unit110amay include a first active device112a, a first pixel electrode114a, and a first common line116a. Further, the transparent sub-pixel unit110bmay include a second active device112b, a second pixel electrode114b, and a second common line116b.

The first active device112ais, for example, a thin film transistor (TFT), and has a first gate G1, a first source S1, and a first drain D1. Further, the second active device112bis, for example, also a TFT, and has a second gate G2, a second source S2, and a second drain D2. The first gate G1and the second gate G2are connected to a scan line SL, and the first source S1and the second source S2are connected to a data line DL. Further, the first gate G1and the first source S1may form a first parasitic capacitance Cgs1, and the second gate G2and the second source S2may form a second parasitic capacitance Cgs2. The first parasitic capacitance Cgs1and the second parasitic capacitance Cgs2may have the same capacitance value Cgs.

In addition, the first pixel electrode114ais, for example, a reflective pixel electrode and is connected to the first drain D1, and the second pixel electrode114bis, for example, a transparent pixel electrode and is connected to the second drain D2. Further, the first common line116ais connected to a first signal source P1and may form a first storage capacitance Cst1with the first drain D1, and the second common line116bis connected to a second signal source P2and may form a second storage capacitance Cst2with the second drain D2. The first signal source P1is different from the second signal source P2, and the first storage capacitance Cst1and the second storage capacitance Cst2may have the same capacitance value Cst.

In addition, the opposite substrate200is, for example, a color filter substrate, and has a color filter pattern210and a common electrode220. The common electrode220is disposed on the color filter pattern210, and is connected to the first signal source P1. Further, the first pixel electrode114amay form a first liquid crystal capacitance Clc1with the common electrode220, and the second pixel electrode114bmay form a second liquid crystal capacitance Clc2with the common electrode220. The first liquid crystal capacitance Clc1and the second liquid crystal capacitance Clc2may have the same capacitance value Clc.

When the first gate G1receives a voltage through the scan line SL to conduct the first source S1and the first drain D1, the first liquid crystal capacitance Clc1and the first storage capacitance Cst1may be charged through the data line DL. At the same time, the second gate G2may also receive the same voltage through the scan line SL to conduct the second source S2and the second drain D2, such that the second liquid crystal capacitance Clc2and the second storage capacitance Cst2are charged through the data line DL.

At this time, if the first signal source P1and the second signal source P2respectively provide a first voltage ΔVcom1and a second voltage ΔVcom2, a coupling voltage ΔV1 of the first pixel electrode114aand a coupling voltage ΔV2 of the second pixel electrode114bmay be respectively equal to

It may be known from the embodiment that when the first voltage ΔVcom1 is different from the second voltage ΔVcom2, the coupling voltage ΔV1 of the first pixel electrode114amay be different from the coupling voltage ΔV2 of the second pixel electrode114b. At this time, the potential difference between two ends of the first liquid crystal capacitance Clc1may be different from the potential difference between two ends of the second liquid crystal capacitance Clc2. In this manner, the rotating angle of the liquid crystals310located between the first pixel electrode114aand the common electrode220may be different from the rotating angle of the liquid crystals310located between the second pixel electrode114band the common electrode220, such that the transmittance of the reflective sub-pixel unit110ais different from the transmittance of the transparent sub-pixel unit110b. Therefore, two different characteristic curves are created. That is, applied voltage vs. the transmittance of the reflective sub-pixel unit (V-R) characteristic curve correspond to the reflective sub-pixel unit110aand applied voltage vs. the transmittance of the transparent sub-pixel unit (V-T) characteristic curve respectively correspond to transparent sub-pixel unit110b. The two different characteristic curves can be respectively adjusted to meet design requirement. In another embodiment, when the reflective sub-pixel unit110ais substituted by another transparent sub-pixel unit, two different characteristic curves can be utilized to compensate the color shift effect of the image in large viewing angle.

FIG. 2Ais a schematic structural view of an LCD panel according to another embodiment of the present invention, andFIG. 2Bis an equivalent circuit diagram of the LCD panel inFIG. 2A. Referring toFIGS. 2A and 2B, the structure and the circuit layout of the LCD panel10B inFIGS. 2A and 2Bare similar to the structure and the circuit layout of the LCD panel10A inFIGS. 1A and 1B, except that the common electrode220is formed by a first common sub-electrode220aand a second common sub-electrode220b. The first common sub-electrode220amay correspond to the first pixel electrode114aand connect to the first signal source P1. The second common sub-electrode220bmay correspond to the second pixel electrode114band connect to a third signal source P3. The third signal source P3is different from the first signal source P1and the second signal source P2.

When the first signal source P1, the second signal source P2, and the third signal source P3respectively provide a first voltage ΔVcom1, a second voltage ΔVcom2, and a third voltage ΔVcom3. A coupling voltage ΔV1 of the first pixel electrode114aand a coupling voltage ΔV2 of the second pixel electrode114bmay be respectively equal to

In this embodiment, when the first voltage ΔVcom1, the second voltage ΔVcom2, and the third voltage ΔVcom3 are different, the coupling voltage ΔV1 of the first pixel electrode114amay be different from the coupling voltage ΔV2 of the second pixel electrode114b. Therefore, in this embodiment, the color shift effect of the image may be compensated.

FIGS. 3 to 6are schematic structural views of an LCD panel according other embodiments of the present invention. First, referring toFIG. 3, the structure of the LCD panel10C inFIG. 3is similar to the structure of the LCD panel10A inFIG. 1, except that the first pixel electrode114aof the LCD panel10C is formed by a reflective pixel electrode R and a transparent pixel electrode T covered on the reflective pixel electrode R.

Further, referring toFIG. 4, the structure of the LCD panel10D inFIG. 4is similar to the structure of the LCD panel10C inFIG. 3, except that the transparent pixel electrode T is disposed below the reflective pixel electrode R.

In addition, referring toFIG. 5, the LCD panel10E inFIG. 5is a TR-LCD panel with a dual cell gap. In this embodiment, the first pixel electrode114ais formed by a reflective pixel electrode R and a transparent pixel electrode T electrically connected to the reflective pixel electrode R, and the second pixel electrode114bis another transparent pixel electrode. In addition, the active device array substrate100further has a cover layer118covering the first active device114a, the second active device114b, the first common line116a, the second common line116b, the transparent pixel electrode T, and a part of the second pixel electrode114b. The reflective pixel electrode R disposed on the cover layer118and connects the transparent pixel electrode T.

In addition, referring toFIG. 6, the structure of the LCD panel10F inFIG. 6is similar to the structure of the LCD panel10E inFIG. 5, except that the cover layer118of the LCD panel10F covers the overall second pixel electrode114b, and the reflective pixel electrode R only covers a part of the cover layer118.

Similarly, in the embodiments ofFIGS. 3 to 6, when the first voltage ΔVcom1 is different from the second voltage ΔVcom2, the coupling voltage ΔV1 of the first pixel electrode114amay be different from the coupling voltage ΔV2 of the second pixel electrode114b. Therefore, in this embodiment, the color shift effect of the image may be compensated.

To sum up, each pixel structure of the present invention may have two common lines and two pixel electrodes, and the two common lines are connected to different signal sources. Therefore, when the common lines are provided with difference voltages from different signal sources, the pixel electrodes may have different coupling voltages.

In addition, the common electrode may be divided into two different common sub-electrodes, and the two common sub-electrodes may correspond to different pixel electrodes and connect to different signal sources. Therefore, when the common lines and the common sub-electrodes are provided with difference voltages from different signal sources, the pixel electrodes may also have different coupling voltages.