Fringe Field Switching LCD Cell Gap Layout for Uniform Transmittance
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Solution Overview
Problem
Conventional fringe field switching mode LCDs exhibit differences in electro-optical characteristics between the center and edge of the pixel electrode, leading to suboptimal driving voltage and phase delay values, resulting in decreased transmittance.
Innovation Solution
A multi-cell gap fringe field switching mode LCD is implemented, where the overcoat film is patterned to create different cell gaps between the center and edge of the pixel electrode, with concave and convex patterns on the surface to optimize driving voltage and phase delay values, achieving Δnd values of 0.34-0.38 at the center and 0.42-0.46 at the edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform cell gap is used in the fringe field switching mode LCD, then the structure is simple and easy to manufacture, but the electro-optical characteristics differ between center and edge of the pixel electrode, resulting in suboptimal driving voltage and phase delay values
Solution Approach 1:
The patent applies local quality by creating different cell gap regions within the same liquid crystal cell. The overcoat film is formed with varying thickness: a first thickness in the first region (center area) and a second thickness in the second region (edge area). This allows each region to have optimized electro-optical characteristics suitable for its specific position, resolving the contradiction between structural simplicity and characteristic uniformity.
Solution Approach 2:
The patent segments the cell gap into multiple regions with different characteristics. By dividing the pixel electrode area into a first region and a second region, and providing different cell gaps for each region through the overcoat film thickness variation, the patent achieves optimized driving voltages and phase delay values for each segment while maintaining a single integrated cell structure.
2Manufacturing precision
If the cell gap is optimized for the center of the pixel electrode, then the driving voltage and phase delay value are optimized at the center, but the edge position cannot achieve maximum transmittance
Solution Approach 1:
The patent applies local quality by creating different cell gap regions within the same liquid crystal cell. The overcoat film is formed with varying thickness: a first thickness in the first region (center area) and a second thickness in the second region (edge area). This allows each region to have optimized electro-optical characteristics suitable for its specific position, resolving the contradiction between structural simplicity and characteristic uniformity.
3Illumination intensity
If the cell gap is optimized for the edge of the pixel electrode, then the transmittance is improved at the edge, but the center position cannot achieve optimal driving voltage and phase delay value
Solution Approach 1:
The patent applies local quality by creating different cell gap regions within the same liquid crystal cell. The overcoat film is formed with varying thickness: a first thickness in the first region (center area) and a second thickness in the second region (edge area). This allows each region to have optimized electro-optical characteristics suitable for its specific position, resolving the contradiction between structural simplicity and characteristic uniformity.
4Ease of manufacture
If a single phase delay value is used for the entire pixel electrode, then the manufacturing process is simple, but it is impossible to achieve maximum transmittance at both center and edge positions simultaneously
Solution Approach 1:
The patent applies local quality by creating different cell gap regions within the same liquid crystal cell. The overcoat film is formed with varying thickness: a first thickness in the first region (center area) and a second thickness in the second region (edge area). This allows each region to have optimized electro-optical characteristics suitable for its specific position, resolving the contradiction between structural simplicity and characteristic uniformity.
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 optimizes the driving voltage and phase delay values, enhancing average transmittance by aligning the edge's driving voltage with the center's, reducing transmittance reduction slope, and stabilizing liquid crystal power, resulting in increased maximum transmittance without altering the center's driving voltage.
Implementation Method 1
a liquid crystal (not shown) interposed between them... to arrange the liquid crystal molecules in the liquid crystal layer in a batch mode before an electric field is established
Implementation Method 2
the spacing between them is smaller than that of upper and lower substrates to establish a fringe field above them
Data Source
AI summary
A multi-cell gap fringe field switching mode LCD includes an upper substrate having an overcoat film and a lower substrate having a counter electrode and a pixel electrode successively formed thereon with a gate insulation film interposed between them. The overcoat film is patterned in such a manner that the cell gap at the center of the pixel electrode is different from that at the edge thereof and the overcoat film has a convex pattern formed on a part thereof corresponding to the center of the pixel electrode in a slanted profile and a concave pattern formed on a part thereof corresponding to the edge of the pixel electrode to optimize the driving voltage and phase delay value (Δnd) in each position of the pixel electrode.