Liquid Crystal Display Light Shielding Layer and Spacer Integration
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Solution Overview
Problem
Liquid crystal display devices face issues with light leakage and reduced aperture ratio due to misalignment during the manufacturing process, which is exacerbated by the need for separate photolithographic processes for forming black matrices and color filters, leading to parasitic capacitors with high capacitance that distort gate and data signals.
Innovation Solution
A method is introduced to form a light shielding layer using a mask process that simultaneously creates a spacer, overlapping with the thin film transistor and maintaining a cell gap between substrates, thereby reducing the number of fabrication steps and preventing light leakage while improving the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a black matrix with wide width is used to prevent light leakage, then light leakage is reduced, but aperture ratio is lowered
Solution Approach 1:
The light shielding function is segmented from the black matrix and transferred to a separate light shielding layer formed by the spacer structure. This allows the black matrix to be narrowed to improve aperture ratio while the spacer-based light shielding layer prevents light leakage through its opaque material and geometric configuration.
Solution Approach 2:
The spacer acts as an intermediary structure that serves dual functions: maintaining the cell gap between substrates and providing light shielding through its opaque material. This mediator eliminates the need for a wide black matrix while preventing light leakage.
2Manufacturing precision
If separate photolithographic processes are used for black matrix and color filter, then each layer can be precisely formed, but manufacturing complexity increases and parasitic capacitors are generated
Solution Approach 1:
The formation of the light shielding layer and spacer is merged into a single photolithographic process. The light shielding layer is formed by depositing opaque material in the spacer pattern, allowing both structures to be created simultaneously without additional process steps, thereby reducing manufacturing complexity while maintaining precision.
Solution Approach 2:
The spacer structure serves multiple functions: maintaining cell gap, providing light shielding, and defining the pixel electrode pattern. This multi-functionality eliminates the need for separate processes for black matrix formation and light shielding, reducing the number of photolithographic steps.
3Manufacturing precision
If separate processes are used for forming black matrix and color filter, then alignment can be controlled, but production yield decreases due to increased process steps
Solution Approach 1:
By combining the light shielding layer formation with the spacer formation in a single photolithographic process, the number of alignment steps is reduced. This merging of processes maintains alignment precision while improving production yield by eliminating additional process steps where misalignment could occur.
Data Source
AI summary
A liquid crystal display device includes opposing substrates. One of the substrates has a thin film transistor and a color filter formed thereon. A spacer formed between the substrates maintains a cell gap. A light shielding layer is formed at a lower portion of the spacer and overlaps the thin film transistor. The light shielding layer has a pattern substantially identical to the spacer. The light shielding layer and the spacer are simultaneously formed using the same photolithographic process steps.