Thin Film Transistor Array Substrate with Inclined Common Electrode
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Solution Overview
Problem
Conventional thin film transistor array substrates for IPS mode LCD devices face challenges in increasing the aperture ratio of the pixel region and preventing short defects between common electrodes and channel layer patterns, while also dealing with light leakage issues due to the width of the black matrix and arrangement of electrodes.
Innovation Solution
The solution involves a thin film transistor array substrate design where a second common electrode is formed to cover the data line and protective film, with inclined surfaces connected to the protective film within the pixel region, and the use of a half tone or diffractive mask during contact hole formation to prevent short defects, along with an organic insulation film to reduce parasitic capacitance and signal delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the black matrix width is increased to prevent light leakage, then light leakage is reduced, but the aperture ratio of the pixel region decreases
Solution Approach 1:
The patent extracts the light shielding function from the black matrix and relocates it to the common electrode structure. The common electrode is extended to overlap with the data line and black matrix region, creating a separate light shielding layer that no longer requires increasing the black matrix width, thus preserving the aperture ratio while preventing light leakage.
Solution Approach 2:
The patent transitions from a planar black matrix structure to a three-dimensional electrode overlap structure. By extending the common electrode in the vertical dimension to overlap with the data line and black matrix region, the solution prevents light leakage through vertical field lines rather than horizontal black matrix extension.
2Object-affected harmful factors
If first common electrodes are arranged at both sides of the data line to prevent light leakage, then light leakage is reduced, but the aperture ratio cannot be increased above a critical value
Solution Approach 1:
The patent merges the light shielding function with the common electrode structure. Instead of having separate first common electrodes at both sides of the data line, the common electrode is continuously extended to overlap the data line and black matrix region, combining the shielding and common electrode functions into a single structure.
3Ease of manufacture
If conventional electrode arrangement is used, then manufacturing is simpler, but short defects occur between common electrodes and channel layer patterns
Solution Approach 1:
The patent introduces an organic insulation film as an intermediary layer between the common electrode and the channel layer pattern. This thin film mediator prevents direct contact and potential short defects while maintaining the simplified electrode arrangement and reducing parasitic capacitance.
4Object-affected harmful factors
If black matrix width is increased, then light leakage is prevented, but device complexity increases
Solution Approach 1:
Instead of increasing the black matrix width horizontally to prevent light leakage, the patent inverts the approach by extending the common electrode vertically to overlap the black matrix region. This reverses the conventional solution and achieves light shielding through electrode extension rather than black matrix expansion.
Data Source
AI summary
A thin film transistor array substrate including a substrate, a gate line intersecting a data line to define a pixel region on the substrate, a switching element disposed at an intersection of the gate line and the data line, a plurality of pixel electrodes and a plurality of first common electrodes alternately arranged on a protective film in the pixel region, a second common electrode overlapping the data line, a first storage electrode on the substrate, a second storage electrode overlapping the first storage electrode, and an organic insulation film on the switching element, the second storage electrode, the data line, a gate pad, and a data pad, wherein the second common electrode covers the data line, the protective film and the organic insulation film, and has inclined surfaces connected to the protective film within the pixel region.