LCD Column Spacer Design for Cell Gap Reliability
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Solution Overview
Problem
The reliability of maintaining a cell gap in liquid crystal display (LCD) panels is compromised due to the expansion of liquid crystals at high temperatures, particularly when using organic passivation films, which prevents the dual spacer structure from functioning effectively.
Innovation Solution
A liquid crystal display panel design featuring a color filter array substrate with a first column spacer partially inserted in a first hole and a thin film transistor (TFT) array substrate with a protective organic passivation film, where the main column spacer maintains contact with the TFT array substrate, and the auxiliary column spacer floats above with a designated distance, forming a step difference to prevent defects caused by liquid crystal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a dual spacer structure is used to maintain cell gap, then the reliability of maintaining cell gap is improved, but the structure becomes more complex and difficult to manufacture
Solution Approach 1:
The single column spacer is divided into two separate spacers: a first column spacer positioned over the TFT and a second column spacer positioned over the storage capacitor. This segmentation allows each spacer to independently maintain cell gap in different regions, improving overall reliability while keeping each individual spacer simple in structure.
Solution Approach 2:
Different spacers are assigned to different functional regions: the first column spacer serves the TFT region while the second column spacer serves the storage capacitor region. Each spacer is optimized for its specific location, with the first spacer having first height and the second spacer having second height, creating local quality variations that improve cell gap maintenance throughout the display panel.
2Reliability
If organic passivation film is used to protect TFT, then the TFT reliability is improved, but the liquid crystal expansion at high temperature causes defects
Solution Approach 1:
The dual spacer structure acts as an intermediary mechanism between the organic passivation film and the liquid crystal material. The spacers physically separate and support the substrates, preventing direct contact between the expanding liquid crystals and the passivation film, thereby eliminating the defect chain while preserving the protective function of the organic layer.
Solution Approach 2:
The spacers are positioned beforehand to create protective gaps and support structures before the liquid crystal material is fully injected. This prior cushioning arrangement prevents the liquid crystal expansion from causing defects in the organic passivation film, as the spacers absorb and distribute the expansion forces before they can reach the sensitive TFT region.
3Reliability
If column spacer is made tall to maintain cell gap, then the cell gap maintenance is improved, but the liquid crystal material expands and causes defects
Solution Approach 1:
The tall column spacer is segmented into two spacers of different heights positioned at different locations. The first column spacer has first height and the second column spacer has second height, allowing each to provide appropriate cell gap maintenance in its specific region without creating excessive expansion pressure that would cause defects.
Solution Approach 2:
Different spacer heights are assigned to different functional regions: the first column spacer over the TFT has first height optimized for that region, while the second column spacer over the storage capacitor has second height optimized for its region. This local quality approach ensures optimal cell gap maintenance while preventing liquid crystal expansion defects through region-specific design.
Data Source
AI summary
A liquid crystal display panel includes a color filter array substrate having a first column spacer and a second column spacer, the first column spacer being partially inserted in a first hole, and a thin film transistor (TFT) array substrate facing the color filter array substrate having a protective passivation film.