Liquid-Crystal Display Element Substrate Contact Hole Profile
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Solution Overview
Problem
In liquid-crystal displays, contact holes lead to light leakage due to the arrangement of liquid-crystal molecules, resulting in decreased contrast and aperture ratio, and conventional solutions to cover the issue with larger source electrodes compromise illumination.
Innovation Solution
The design of an element substrate with a metal layer and planarization layer, where the contact hole's dimensions and slope are optimized to minimize light leakage, with the first width and second width of the contact hole satisfying a specific equation to maintain acceptable contrast and aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the source electrode area at the bottom of the contact hole is increased to cover light-leaking liquid-crystal molecules, then the contrast of the liquid-crystal display is improved, but the aperture ratio and illumination are decreased
Solution Approach 1:
The patent applies local quality by creating a planarization layer with different thicknesses in different regions. The planarization layer has a first thickness in the first region (away from contact hole) and a second thickness in the second region (above contact hole), allowing different functional optimizations in different areas - improving contrast where needed while maintaining aperture ratio in other areas
Solution Approach 2:
The patent transitions from a two-dimensional problem (enlarging source electrode area in the plane) to a three-dimensional solution by adding vertical thickness variation through the planarization layer. This allows the electrode to maintain its original planar area for high aperture ratio while the added vertical dimension provides the necessary coverage for light leakage prevention
2Ease of manufacture
If the contact hole is designed with a funnel structure, then the manufacturing process is simplified, but light leakage occurs due to liquid-crystal molecules arranged along the profile of the contact hole
Solution Approach 1:
The patent introduces the planarization layer as an intermediary element between the contact hole structure and the liquid-crystal molecules. This intermediate layer with its specific thickness profile prevents liquid-crystal molecules from aligning along the contact hole profile, thereby blocking the light leakage pathway while maintaining the simple funnel-shaped contact hole structure
Solution Approach 2:
The patent changes the thickness parameter of the planarization layer spatially - using a first thickness in the first region and a second thickness in the second region. This parameter variation allows the structure to maintain ease of manufacture while preventing the specific molecular alignment that causes light leakage
Data Source
AI summary
An element substrate is provided, including a substrate, a metal layer and a planarization layer. The metal layer is located on the substrate. The metal layer has a first edge in a first direction. The planarization layer is located on the metal layer. The planarization layer includes a contact hole. The contact hole has a contiguous wall and a bottom side. The metal layer is exposed in the bottom side. A contour line of the contiguous wall on a vertical plane is a curved line. The first edge corresponds vertically with a critical point on the contour line. The slope of a tangent line on the critical point of the contour line is smaller than 0.176.