LCD Through-Hole Taper Structure for Uniform Alignment Films
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Solution Overview
Problem
In high definition liquid crystal display devices, the increased taper angle of through holes in the organic passivation film prevents alignment film material from entering, leading to display defects like light leakage and uneven brightness due to poor initial alignment and irregular film thickness.
Innovation Solution
The through hole in the organic passivation film is designed with a smaller taper angle on the upper base and a steeper taper angle on the lower base, allowing the alignment film material to easily flow into the through hole, even when the pixel area is reduced for high definition screens.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the pixel size is reduced for high definition screens, then the definition is improved, but the ratio of the through hole diameter to pixel size increases, reducing bonding strength and causing interlayer insulating film removal
Solution Approach 1:
The through hole is designed with non-uniform taper angles at different locations: a first taper angle in the upper portion and a second taper angle in the lower portion. This local differentiation allows the upper portion to have a smaller opening for reduced bonding strength issues, while the lower portion maintains adequate width for proper alignment film formation, thus resolving the contradiction between high definition requirements and bonding strength
Solution Approach 2:
The through hole structure is segmented into distinct regions with different geometric characteristics - an upper region with smaller diameter and first taper angle, and a lower region with larger diameter and second taper angle. This segmentation enables each region to fulfill its specific function: the upper region minimizes bonding strength reduction, while the lower region ensures proper alignment film formation
2Area of stationary object
If the taper angle of the through hole is increased to reduce its diameter, then the area occupied by the through hole is reduced, but the alignment film material cannot enter the through hole, causing display defects
Solution Approach 1:
Different taper angles are applied to different sections of the through hole: the first taper angle in the upper portion is designed to be smaller than the second taper angle in the lower portion. This local quality differentiation ensures that the alignment film material can flow into the through hole through the wider lower opening while maintaining a compact overall structure, thus resolving the contradiction between reducing through hole area and ensuring proper alignment film formation
Solution Approach 2:
The through hole geometry is pre-designed with a wider lower opening (second taper angle) before the alignment film formation process. This preliminary structural preparation ensures that when the alignment film material is applied, it can easily enter the through hole without requiring excessive force or causing defects, thus preventing display issues before they occur
3Illumination intensity
If the through hole diameter is reduced to maintain transmittance in high definition screens, then the transmittance is maintained, but the alignment film thickness becomes irregular, causing uneven brightness
Solution Approach 1:
The through hole is designed with a smaller opening in the upper portion (first taper angle) to maintain transmittance for high definition screens, while the lower portion has a larger opening (second taper angle) that is sufficient for the alignment film material to enter and form a uniform layer. This local differentiation resolves the contradiction by allowing the critical transmittance area to be small while the film formation area remains adequate
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 configuration ensures stable formation of the alignment film within the through hole, preventing display defects such as uneven brightness and light leakage, while maintaining the required transmittance for high definition screens.
Implementation Method 1
the alignment film material can easily flow into the through hole
Implementation Method 2
rotate liquid crystal molecules by the electric field generated between the pixel electrode and the common electrode
Data Source
AI summary
In a liquid crystal display device, a common electrode is formed on an organic passivation film, an interlayer insulating film is formed on the common electrode, a pixel electrode with a slit is formed on the interlayer insulating film, and a through hole is formed in the organic passivation film and the interlayer insulating film, so that the pixel electrode is connected to a source electrode of a TFT through the through hole. Further, the taper angle around the upper base of the through hole is smaller than the taper angle around the lower base. Thus, the alignment film material can easily flow into the through hole when the diameter of the through hole is reduced to connect the pixel and source electrodes, preventing display defects such as uneven brightness due to the absence of the alignment film or due to the alignment film irregularity around the through hole.