Via-Hole Geometry for Polyimide Coating Uniformity
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Solution Overview
Problem
The abnormal coating of polyimide film due to via-holes in the path layer network (PLN) leads to uneven display brightness (Mura) in liquid crystal display panels, caused by poor precision in film thickness and surface quality during the manufacturing process.
Innovation Solution
The design of an array substrate with via-holes in the non-display area having specific dimensions and shapes, such as lengths not exceeding 12.5 microns, distances between adjacent via-holes of at least 30 microns, and cross-sectional areas facilitating fluid flow and electrical connections, guides the polyimide film coating and prevents backflow accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the polyimide film is coated using a printing method with conventional via-holes, then the encapsulation layer can be formed, but the polyimide film gathers at the edge of the via-hole causing abnormal coating and Mura phenomenon
Solution Approach 1:
The via-holes are designed with non-uniform cross-sectional areas along their length, creating different local properties. The cross-sectional area varies from the first end to the second end, which guides the polyimide film flow locally and prevents abnormal gathering at specific locations, thereby eliminating the Mura phenomenon while maintaining proper encapsulation layer formation.
2Reliability
If the via-hole length close to the display area is long, then the electrical connection can be ensured, but the polyimide film backflow is obstructed causing thickness variation
Solution Approach 1:
The via-hole parameters are optimized by controlling the cross-sectional area variation along its length. The cross-sectional area at different positions is specifically designed to balance electrical connection requirements with polyimide film flow characteristics, ensuring both reliable electrical connection and uniform film thickness without abnormal gathering.
3Reliability
If the via-hole cross-sectional area is large, then the electrical connection between common electrode and source-drain is improved, but the polyimide film flow is obstructed
Solution Approach 1:
The via-hole structure implements local quality optimization by having different cross-sectional areas at different positions. This allows the via-hole to provide sufficient electrical connection area where needed while maintaining appropriate flow characteristics in other regions, preventing polyimide film gathering and coating abnormalities.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach reduces the occurrence of Mura phenomena by ensuring smooth fluid flow and preventing film thickness variations, resulting in uniform liquid crystal alignment and improved display quality.
Implementation Method 1
Due to an effect of surface tension and a longer length of one end of the via-hole close to a display area, the polyimide film will gather at an edge of the via-hole and its backflow will be obstructed.
Data Source
AI summary
An array substrate and a liquid crystal display panel are provided, wherein the array substrate includes a display area and a non-display area, and a length of one end of via-holes close to the display area is not greater than 12.5 microns. By reducing a length of one end of the via-holes positioned at a boundary position between the display area and the non-display area close to the display area, a flow of polyimide fluid is guided and enables an edge of a polyimide film to cover an area where the via-holes are located.