Element Substrate Contact Hole Geometry for LCD Transmittance
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Solution Overview
Problem
Conventional liquid crystal displays face issues with transmittance loss, contact short-circuiting, and insufficient capacitance due to the radius of the contact hole affecting the reliability of the display.
Innovation Solution
The design of an element substrate with a specific relationship between the first and second widths of the contact hole, where the first width and second width satisfy a derived equation, ensuring a continuous wall and optimal curvature to minimize transmittance loss and prevent short-circuiting while maintaining sufficient capacitance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the radius of the contact hole at the location of the bottom conductive layer is decreased, then the short-circuiting problem is avoided, but the capacitance between the bottom conductive layer and the pixel conductive layer becomes insufficient
Solution Approach 1:
The patent transitions from controlling only the bottom radius to controlling both bottom and top radii of the contact hole, adding a dimensional parameter (top radius) to the design space. This allows simultaneous optimization of capacitance (bottom radius) and short-circuit prevention (top radius), resolving the contradiction by operating in a higher-dimensional parameter space.
Solution Approach 2:
The patent changes the geometric parameters of the contact hole from a single radius to two distinct radii (bottom radius and top radius), allowing independent optimization. By establishing specific relationships between these parameters (L1/2L2 ratio and curvature radius), the design achieves both sufficient capacitance and short-circuit prevention simultaneously.
2Ease of manufacture
If the contact hole has a funnel structure, then the manufacturing is simplified, but the liquid crystal molecules are arranged along the profile causing transmittance loss
Solution Approach 1:
The patent applies different geometric characteristics to different parts of the contact hole: the bottom portion has a larger radius for capacitance, while the top portion has a controlled radius for alignment. The continuous wall provides localized structural support, creating different functional zones within a single contact hole structure that simultaneously achieves manufacturing simplicity and optical performance.
Solution Approach 2:
The patent introduces curvature control through the continuous wall with a specified curvature radius (0.05L2 ≤ R ≤ 0.15L2). This curvature modification optimizes the liquid crystal molecule alignment at the contact hole edges, reducing transmittance loss while maintaining the overall funnel structure for ease of manufacture.
3Quantity of substance
If the opening of the first conductive layer is made larger, then the capacitance is increased, but the short-circuiting risk increases
Solution Approach 1:
The patent segments the contact hole geometry into distinct bottom and top portions with different radius characteristics. The bottom conductive layer opening (L1) and first conductive layer opening (L2) are independently controlled, allowing the capacitance-determining bottom opening to be optimized separately from the short-circuit-risk top opening, thus resolving the contradiction through spatial segmentation of functional requirements.
Data Source
AI summary
An element substrate is provided, including a substrate, a metal layer, a planarization layer and a first conductive layer. The metal layer is disposed on the substrate. The planarization layer is located on the metal layer, wherein the planarization layer includes a contact hole, the contact hole has a continuous wall and a bottom, the bottom exposes the metal layer, and the bottom of the contact hole has a first width. The first conductive layer is located on the planarization layer, wherein the first conductive layer includes an opening, the opening exposes the contact hole, and the opening has a second width above the contact hole, wherein the relationship of the first width and the second width is modified to decrease illumination loss and to prevent problems of shot-circuiting and insufficient capacitance.