Capping Layer Design for LCD Color Filter Stress Relief
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In liquid crystal displays, the capping layer generates stress on color filters, leading to defects like active unfilled area (AUA) defects and light leakage due to gas entrapment, which can cause color coordinate changes over time.
Innovation Solution
The capping layer is designed with specific openings and coverages over red, green, and blue color filters, reducing stress and preventing separation, with the green color filter being completely covered to avoid damage during the dry etching process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a solid capping layer is formed on the color filter, then the color filter is protected from lifting or separating, but significant stress is generated in the capping layer causing AUA defects and light leakage
Solution Approach 1:
The capping layer is designed with through-holes that extend from the upper surface to the lower surface, creating a porous structure. This allows the capping layer to maintain protection functionality while reducing stress accumulation by providing stress relief pathways, preventing AUA defects and light leakage that would occur with a solid capping layer.
Solution Approach 2:
The capping layer is segmented into multiple regions with through-holes distributed across its area. This segmentation divides the continuous solid structure into separate zones, allowing differential stress distribution and preventing the buildup of significant stress that would occur in a uniform solid capping layer.
2Reliability
If openings are created in the capping layer to reduce stress, then AUA defects are prevented, but the color filter may be damaged during dry etching process
Solution Approach 1:
The capping layer has different structures in different regions: regions with through-holes for stress relief and regions without through-holes for protection. Specifically, the green color filter region is completely covered while red and blue regions have selective coverage, allowing each area to have the quality needed for its specific function.
Solution Approach 2:
The capping layer acts as an intermediary protective layer during the dry etching process. By strategically placing openings and coverage regions, it mediates between the etching process and the color filter, allowing necessary stress relief while preventing direct exposure of the color filter to damaging etching conditions.
3Reliability
If the capping layer completely covers all color filters, then protection is maximized, but stress accumulation causes separation and AUA defects
Solution Approach 1:
The capping layer incorporates through-holes creating a porous structure that allows stress to be relieved while maintaining overall coverage and protection. The porous design enables the capping layer to accommodate thermal and mechanical stress without separating from the color filter, preventing interface instability.
Solution Approach 2:
The structure of the capping layer is changed from a solid continuous layer to one with controlled porosity and selective coverage. This parameter change allows the material to maintain protective functionality while fundamentally altering its stress characteristics to prevent accumulation and separation.
Data Source
AI summary
A thin film transistor includes: a substrate; a thin film transistor formed on the substrate; a first color filter and a second color filter formed on the thin film transistor and each having a through hole; a capping layer formed on the first color filter and the second color filter; and a pixel electrode formed on the capping layer and connected to the thin film transistor through the through hole, wherein the capping layer formed on the first color filter has a first opening exposing the through hole of the first color filter, the size of the first opening is larger than the size of the through hole, the capping layer formed on the second color filter has a second opening disposed inside the through hole of the second color filter, and the size of the second opening is smaller than the size of the through hole. Accordingly, the capping layer completely covers the green color filter which prevents damage to the green color filter in a dry etching process, and also prevents changes of a color coordinate.