Liquid crystal display device having a common electrode substrate

A common electrode substrate for use in a liquid crystal display (LCD) device includes a substrate body, a common electrode disposed on the substrate body, and a peripheral first circuit disposed on the substrate body. The peripheral first circuit and the common electrode are electrically separate from each other, and the peripheral first circuit extends along at least a portion of a peripheral region of the substrate body.

CROSS-REFERENCE TO RELATED APPLICATION

This claims priority under 35 U.S.C. §119 of Taiwan Patent Application No. 96112819, filed Apr. 12, 2007, which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a common electrode substrate for use in a liquid crystal display device.

BACKGROUND

Liquid crystal display (LCD) devices exhibit various desirable characteristics, including, as examples, high definition, good space utilization, low power consumption, and no or low radiation.FIG. 1is a schematic sectional view of a conventional LCD device100. The LCD device100includes a pixel electrode array substrate110, a color filter substrate120, and a liquid crystal layer130between substrates110and120. The liquid crystal layer130is encapsulated between the pixel electrode array substrate110and the color filter substrate120by use of a sealant140. Conventionally, a portion of the pixel electrode array substrate110that is in a non-display (peripheral) region R10has peripheral circuits such as driving line(s), repair line(s), and bus line(s). However, due to reduction of sizes of parts of conventional LCD devices, including parts in the non-display region R10, it can be difficult to accommodate the various lines noted above in the non-display region R10. Moreover, the impedance of the lines may be greatly increased as line widths are reduced to achieve size reduction of LCD device parts. Also, if the space available to accommodate electrical lines in the non-display region R10is too small, then that may lead to low yield during manufacturing.

DETAILED DESCRIPTION

FIG. 2is a top view of a common electrode substrate according to an embodiment of the present invention that is part of a liquid crystal display (LCD) device (not shown).FIG. 3is a cross-sectional view of the common electrode substrate ofFIG. 2taken along line A-A. The common electrode substrate200includes a substrate body210, a common electrode220, and a peripheral first circuit230. As explained further below, the peripheral first circuit230can include various electrical lines. The common electrode220and peripheral first circuit230are disposed on the substrate body210. The common electrode220and first circuit230are considered to be “disposed on” the substrate body210if the common electrode220and first circuit have some fixed arrangement (e.g., over, under, in contact with) with respect to the substrate body210, whether directly or indirectly.

The first circuit230and the common electrode220are electrically separated from each other. As depicted inFIG. 2, the peripheral portion of the common electrode substrate200can be used as wiring space to accommodate the first circuit230. The peripheral portion of the common electrode substrate200refers to a portion that extends along a periphery (or peripheral region) of the common electrode substrate200. By using the common electrode substrate200in an LCD device to accommodate the peripheral first circuit230in accordance with some embodiments, the overall size of the LCD device can be reduced, and issues associated with layout and high impedance of electrical lines in peripheral regions of substrates in an LCD device can be reduced or eliminated.

As depicted further below, the common electrode substrate200, in an LCD device, is disposed opposite a pixel electrode array substrate, with a liquid crystal layer between the common electrode substrate200and the pixel electrode array substrate. The common electrode220can be set at a predetermined voltage to provide a reference for pixel electrodes, such that electric fields can be generated between the pixel electrodes and common electrode to control tilt angles of liquid crystal molecules in the liquid crystal layer.

In one embodiment, the common electrode220is “complete”; in other words, the common electrode220is a complete conductive layer (without the presence of openings or slits). However, in a multi-domain vertical alignment (MVA) LCD device, the common electrode220is designed to have a plurality of jagged slits (or other openings)222, as shown inFIG. 4. The material of the common electrode220can be ITO (indium tin oxide) or other suitable transparent material.

The common electrode substrate200can further include a color filter layer240(FIG. 3) disposed between the substrate body210and the common electrode220, such that an LCD device incorporating the common electrode substrate200can display full color. However, in other embodiments, the color filter layer240may also be formed on another substrate in the LCD device.

In addition, the common electrode substrate200can further include a passivation layer250disposed between the color filter layer240and the common electrode220to protect the color filter layer240.

Further, the common electrode220and the first circuit230can be made of the same material. In other words, the common electrode220and the first circuit230can be formed by performing one photolithography etching process on the same material layer without adding other processes. However, in other embodiments, the common electrode220and the first circuit230can also be made of different material layers. As examples, the material of the first circuit230can be ITO, metal, or other suitable materials.

The first circuit230can include one or more electrical lines, such as a repair line (to use for repairing defective lines), a bus line (e.g., a common bus line for providing one of the potentials of pixel storage capacitors on a pixel electrode array substrate), a driving line (to drive pixel data signals), and/or other lines. Basically, the first circuit230provides line(s) that are typically provided in the periphery of a pixel electrode array substrate. However, by providing the first circuit230on the common electrode substrate instead, various benefits can be achieved, as noted above.

InFIG. 2, the first circuit230extends along each of three sides of the substrate body210. In alternative embodiments, the first circuit230can extend along just one side of the substrate body210, two sides of the substrate body210, or around the entire periphery of the substrate body210. As noted above, the first circuit230can be a single electrical line or a combination of multiple lines.

FIG. 5is a top view of an LCD device that incorporates the common electrode substrate inFIG. 2, andFIG. 6is a cross-sectional view of the LCD device ofFIG. 5taken along line B-B. The LCD device500includes the common electrode substrate200described above, a pixel electrode array substrate510, a first conductive structure520, a second conductive structure522, and a liquid crystal layer530(FIG. 6). The components of the common electrode substrate200are assigned the same reference numerals as inFIGS. 2 and 3. The pixel electrode array substrate510is opposite to the common electrode substrate200, and has a pixel electrode array514, a peripheral second circuit512, and a third circuit516(FIG. 6). The first conductive structure520is disposed between and electrically connected to the peripheral first circuit230and the peripheral second circuit512. The second conductive structure522is disposed between and electrically connected to the third circuit516and the common electrode220. The common electrode220is set by the third circuit516to a common potential through the second conductive structure522. The liquid crystal layer530is disposed between the pixel electrode array substrate510and the common electrode substrate200.

Since the peripheral first circuit230is located on the periphery of the common electrode substrate200, and the peripheral first circuit230is electrically connected to the peripheral second circuit512through the first conductive structure520, some of the functions of the peripheral second circuit512in conventional LCD devices can at least be partially carried out by the peripheral first circuit230. In other words, the peripheral portions of the pixel electrode array substrate510and the common electrode substrate200can both be used together to provide peripheral circuits of an LCD device. Also, the overall size of the LCD device500can be reduced due to the presence of the peripheral first circuit230disposed on the common electrode substrate200. Moreover, since additional wiring space is available due to use of both peripheral portions of the common electrode substrate and pixel electrode array substrate for peripheral circuits, line width can be increased or more lines can be connected in parallel to reduce impedance.

In the embodiment ofFIGS. 5 and 6, the LCD device500further includes a sealant540for encapsulating the liquid crystal layer530between the pixel electrode array substrate510and the common electrode substrate200.

Moreover, the first conductive structure520and the second conductive structure522can be formed of one or more metallic balls (e.g., gold balls). The second conductive structure522can be positioned by the sealant540when the sealant540is coated around the second conductive structure522. The first conductive structure520can also be positioned by a sealant around the first conductive structure520. Alternatively, the first conductive structure520and the second conductive structure522can be positioned by use of metallic (e.g., silver) paste or other suitable conductive substances.

FIG. 7is a sectional view of the LCD device inFIG. 5taken along line C-C. Referring toFIGS. 5 and 7, the LCD device500may further include a third conductive structure524disposed between and electrically connected to the first circuit230and the peripheral second circuit512. Moreover, the peripheral second circuit512of this embodiment is not a continuous circuit, but can include a first portion512aand a second portion512bseparated from each other. The first portion512ais electrically connected with the peripheral first circuit230through the first conductive structure520, and the second portion512bis electrically connected with the peripheral first circuit230through the third conductive structure524. In other words, the pixel electrode array substrate510only has to provide a very small space for the first portion512aand the second portion512bof the second circuit512, as the signal can be transmitted through the peripheral first circuit230between the first conductive structure520and the third conductive structure524. As such, the area of the pixel electrode array substrate510can be reduced. In addition, the third conductive structure524is similar to the first conductive structure520, and can be gold ball, silver paste, or other suitable conductive substance.

FIG. 8is a partial sectional view of an LCD device according to another embodiment of the present invention, in which the position of the section depicted inFIG. 8is similar to that ofFIG. 7. Referring toFIG. 8, the LCD device800is similar to the LCD device500inFIG. 7, except that the peripheral second circuit812ofFIG. 8is a continuous circuit. In other words, the peripheral first circuit230and the peripheral second circuit812can be connected with each other through the first conductive structure520and the third conductive structure524. As a result, the equivalent resistance of the lines can be reduced, so as to reduce the power loss of a signal transmitted across the lines. Moreover, the line width of the peripheral first circuit230can be reduced to reduce the overall area of the common electrode substrate200.

FIGS. 9-11are partial sectional views of LCD devices according to other embodiments. Referring toFIG. 9, the LCD device900is similar to the LCD device500inFIG. 6, except that the second conductive structure522is independent of the sealant940. The third circuit516is still electrically connected to the common electrode220through the second conductive structure522.

Referring toFIG. 10, the LCD device1000of this embodiment is similar to the LCD device500inFIG. 6, except that the line width of the peripheral first circuit1030is greater than the line width of the peripheral second circuit512. As a result, the resistance of the peripheral first circuit1030is reduced. Such a design is especially useful when the material of the first circuit1030has poor conductivity.

Referring toFIG. 11, the LCD device1100of this embodiment is similar to the LCD device500inFIG. 6, except that the pixel electrode array substrate1110further has a peripheral fourth circuit1112. Meanwhile, the peripheral fourth circuit1112is also electrically connected to a peripheral fifth circuit1122on the common electrode substrate1120through a fourth conductive structure1130. However, the peripheral fourth circuit1112does not necessarily have to be electrically connected to the peripheral fifth circuit1122. Moreover, the common electrode substrate1120can also not be provided with the peripheral fifth circuit1122.FIG. 11shows an embodiment in which a plurality of other circuits can be disposed on the pixel electrode array substrate1110besides the peripheral second circuit512and the third circuit516. The peripheral fourth circuit1112can serve as a repair line, bus line, or other type of line.

FIG. 12is an exploded view of the LCD device ofFIG. 6after being modified. Referring toFIGS. 12 and 6, the LCD device1200includes a backlight module1210and a common electrode substrate200, a pixel electrode array substrate510, a first conductive structure520, a second conductive structure522, and a liquid crystal layer530ofFIG. 6. The common electrode substrate200, the pixel electrode array substrate510, the first conductive structure520, the second conductive structure522, and the liquid crystal layer530are disposed above the backlight module1210. In alternative embodiments, the above components can be replaced by other components.

In addition, the LCD device1200may further have a front frame1220for firmly attaching the common electrode substrate200, the pixel electrode array substrate510, the first conductive structure520, the second conductive structure522, and the liquid crystal layer530on the backlight module1210.

In accordance with any of the foregoing embodiments, a common electrode substrate of an LCD device provides a peripheral portion to add additional layout space for peripheral circuitry. Therefore, assuming that the overall size of the LCD device stays the same, layout difficulties and impedance issues that exist in conventional LCD devices can be avoided or reduced. According to some embodiments, some lines or other circuitry typically provided on the pixel electrode array substrate can be moved to the common electrode substrate to reduce the overall size of the LCD device.