Active Matrix Pixel Electrode Layout for LCD Light Leakage
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Solution Overview
Problem
In liquid crystal display apparatuses with active matrix substrates, the contact holes formed in the organic insulating layer lead to misalignment of liquid crystal molecules and light leakage, resulting in decreased contrast ratio and transmittance, especially in high-definition displays where the area occupied by contact holes is significant.
Innovation Solution
The active matrix substrate design includes a light-blocking layer and a multi-layered pixel electrode structure with transparent conductive materials, where the second organic insulating layer fills the contact holes, reducing the need for optical shielding and minimizing the impact of contact holes on transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light-blocking layer is provided to suppress light leakage around contact holes, then contrast ratio and display quality are improved, but transmittance decreases because the light-blocking layer reduces the effective display area
Solution Approach 1:
The patent moves the light-blocking function from the optical path plane to the substrate plane by providing a light-blocking layer between the substrate and the oxide semiconductor layer. This spatial relocation allows the light-blocking layer to suppress light leakage around contact holes without interfering with light transmission through the pixel electrode, thereby resolving the contradiction between improving contrast ratio and maintaining transmittance.
2Reliability
If contact holes are formed in the organic insulating layer to connect the pixel electrode to the drain electrode, then electrical connection is achieved, but liquid crystal molecule alignment is disrupted causing light leakage and decreased contrast ratio
Solution Approach 1:
The patent segments the insulating structure into multiple layers: an organic insulating layer formed after the oxide semiconductor layer (avoiding contact hole formation in it) and a separate light-blocking layer positioned at the substrate interface. This segmentation eliminates the need to form contact holes through the organic insulating layer, thereby preventing liquid crystal molecule misalignment and light leakage while maintaining electrical connection through alternative pathways.
3Manufacturing precision
If the pixel structure is optimized for high definition (1000 ppi or higher), then definition is improved, but the proportion of contact hole area in the pixel region increases causing significant transmittance decrease
Solution Approach 1:
The patent relocates the light-blocking function to the substrate dimension rather than the optical path dimension. By positioning the light-blocking layer between the substrate and oxide semiconductor layer, the solution enables high-definition pixel structures with smaller contact holes to achieve adequate light leakage suppression without sacrificing transmittance, as the light-blocking layer does not occupy space in the optical path.
Data Source
AI summary
An active matrix substrate includes, in order, a pixel TFT including an oxide semiconductor layer, a first interlayer insulating layer covering the oxide semiconductor layer and a gate electrode, a first organic insulating layer, and a pixel electrode. A first pixel contact hole is formed in the first interlayer insulating layer, and a second pixel contact hole is formed in the first organic insulating layer. The pixel electrode is made of a transparent conductive material, a first electrode layer includes a first portion in contact with a drain contact region of the oxide semiconductor layer in the first pixel contact hole and a second portion located in the second pixel contact hole, a second electrode layer includes a third portion in contact with the second portion and a fourth portion located on the first organic insulating layer, and a third electrode layer includes a fifth portion in contact with the fourth portion and a sixth portion located on the second organic insulating layer. A length of the second electrode layer in a row direction is less than or equal to a length of the third electrode layer in the row direction. The active matrix substrate further includes a second organic insulating layer filling the second pixel contact hole.