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Organic thin film transistor array substrate and liquid crystal display including the same

Organic thin film transistor array substrate and liquid crystal display including the same description/claims

1. Field of the Invention

The present invention relates to an organic thin film transistor array substrate, and more particularly to an organic thin film transistor array substrate in which the dielectric layer underlying the pixel electrode has an uneven structure.

2. Description of the Prior Art

In recent years, organic semiconducting material has drawn many researchers' attention and has proven to be one of the most popular candidates in fabrication of thin film transistors (TFTs) and various electronic and optoelectronic devices. Organic semiconducting material is easy to fabricate, increasing the chance of its future application in flexible displays.

An organic thin film transistor (OTFT) is a TFT that uses an organic layer to serve as the active layer and has been used to drive liquid crystal displays (LCDs). In recent years, in order to simplify the process and decrease production cost, some researchers have developed integration technology that fabricates the LCD and OTFT monolithically (i.e., on the same substrate).

For example, Kabushiki Kaisha Toshiba in U.S. Pat. No. 5,355,235 discloses an integrated device of LCD and bottom-gate OTFT, in which two organic layers are used in the OTFT structure.

Mitshubishi Denki Kabushiki Kaisha in U.S. Pat. No. 6,060,333 discloses a bottom-gate OTFT structure combined with a transmissive or reflective type LCD. For the reflective LCD, the reflector sheet is simply a mirror surface; therefore, the display effect (reflectivity and contrast) is inferior.

Hitachi, Ltd. in U.S. Pat. No. 6,300,988 B1 uses a bottom-gate OTFT combined with an LCD. A patterned insulating layer is used to make the overlying deposited organic semiconducting layer have a pattern, thus separating into a channel region and a non-channel region. Thus, current leakage and crosstalk between devices decreases.

For the above-mentioned reflective or transflective LCD driven by OTFT, the display effect requires improvement.

An object of the present invention is to solve the above-mentioned problems and provide an organic thin film transistor (OTFT) array substrate and a liquid crystal display (LCD) including the OTFT array substrate, in which the LCD exhibits good display effect.

To achieve the above object, the OTFT array substrate of the present invention includes:

a substrate divided into a liquid crystal display (LCD) region and an organic thin film transistor (OTFT) region;

a first dielectric layer formed on the substrate in the LCD region and having a first uneven portion;

an organic semiconducting layer formed on the substrate in the OTFT region;

a gate, source, and drain formed in the OTFT region, wherein the source and drain are in contact with the organic semiconducting layer to form a channel between the source and drain; and

a pixel electrode formed on the first uneven portion of the first dielectric layer in the LCD region.

According to the present invention, the process for fabricating the organic thin film transistor array substrate includes the following steps. A substrate divided into an LCD region and an OTFT region is provided. A first dielectric layer having a first uneven portion is formed on the substrate in the LCD region. An organic semiconducting layer is formed on the substrate in the OTFT region. A gate, a source, and a drain are formed in the OTFT region, such that the source and the drain are in contact with the organic semiconducting layer to form a channel between the source and the drain. A pixel electrode is formed on the first uneven portion of the first dielectric layer in the LCD region.

When the OTFT is a bottom-gate type, the process for fabricating the OTFT array substrate includes the following steps. A substrate divided into an LCD region and an OTFT region is provided. A gate is formed on the substrate in the OTFT region, and a dielectric layer is formed in the LCD and OTFT regions to cover the gate. The dielectric layer is patterned to concurrently form a first dielectric layer having a first uneven portion in the LCD region and a second dielectric layer in the OTFT region. An organic semiconducting layer is formed on the second dielectric layer in the OTFT region. A conductive layer is formed in the LCD and OTFT regions, and the conductive layer is patterned to concurrently form a pixel electrode on the first uneven portion of the first dielectric layer in the LCD region and a source and drain in the OTFT region, such that the source and drain are in contact with the organic semiconducting layer to form a channel between the source and drain.

When the OTFT is a top-gate type, the process for fabricating the OTFT array substrate includes the following steps. A substrate divided into an LCD region and an OTFT region is provided. An organic semiconducting layer is formed on the substrate in the OTFT region. A source and drain are formed on the organic semiconducting layer in the OTFT region to form a channel between the source and drain. A dielectric layer is formed on the substrate to cover the source and drain. The dielectric layer is patterned to form a first dielectric layer having a first uneven portion in the LCD region and to form a second dielectric layer on the source and drain in the OTFT region. A metal layer is formed on the first and second dielectric layer, and the metal layer is patterned to form a pixel electrode on the first dielectric layer in the LCD region and to form a gate on the second dielectric layer in the OTFT region.

The present invention also provides a liquid crystal display including an OTFT array substrate. The liquid crystal display includes an OTFT array substrate, a color filter substrate, and liquid crystal interposed between the OTFT array substrate and the color filter substrate. The OTFT array substrate includes:

a substrate divided into an LCD region and an OTFT region;

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