Liquid Crystal Display Device with Inclined Substrate Step
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Solution Overview
Problem
Semi-transmissive liquid crystal display devices with a double-electrode structure and multiple-gap structure suffer from yellowish white display and significant changes in reflection chromaticity due to variations in cell gap, leading to reduced yield and unfavorable dark impressions.
Innovation Solution
A liquid crystal display device with a specific surface structure on the substrate, featuring a reflection region, transmission region, and inclined portion, where the lengths of the inclined and lower step portions satisfy a particular relationship (L1+L2≤1.81·L1), and a liquid crystal layer with a twist angle of 0 degrees, to minimize yellow shift and chromaticity changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a double-electrode structure with separated reflecting electrode and transparent electrode is used, then reflectance is improved, but yellow shift in reflection whiteness occurs and display appears dark
Solution Approach 1:
The patent applies parameter changes by optimizing the thickness of the liquid crystal layer in the reflection region and adjusting the twist angle to substantially 0 degree. These parameter adjustments modify the optical path and phase difference of reflected light, thereby reducing the yellow shift while maintaining high reflectance through the double-electrode structure.
Solution Approach 2:
The patent implements local quality by creating different liquid crystal layer thicknesses for different regions: a first thickness in the reflection region and a second thickness in the transmission region. This regional differentiation allows the reflection region to optimize for minimal yellow shift while the transmission region maintains its display performance, thus resolving the contradiction locally without compromising overall device function.
2Illumination intensity
If cell gap is varied to optimize display performance, then brightness is improved, but chromaticity changes significantly and yield reduces
Solution Approach 1:
The patent uses parameter changes by establishing a specific relationship between the liquid crystal layer thickness and cell gap variation. By controlling the thickness to substantially 0 degree twist angle and optimizing the numerical relationship between thickness and cell gap, the patent achieves brightness improvement while maintaining chromaticity consistency across manufacturing variations.
Solution Approach 2:
The patent applies beforehand cushioning by pre-compensating for cell gap variations through the designed thickness configuration. The specific thickness relationship acts as a buffer that compensates for manufacturing tolerances in cell gap, thereby cushioning against chromaticity changes and maintaining yield without sacrificing brightness.
3Illumination intensity
If liquid crystal layer thickness in transmission region is increased, then transmission display performance is improved, but reflection display chromaticity becomes unstable
Solution Approach 1:
The patent implements local quality by differentiating the liquid crystal layer thickness between transmission and reflection regions. The transmission region has a greater thickness optimized for transmission display brightness, while the reflection region maintains a specific thickness relationship that ensures chromaticity stability. This local differentiation resolves the contradiction by allowing each region to optimize for its specific function.
Solution Approach 2:
The patent applies segmentation by dividing the liquid crystal layer into functionally distinct regions with different thickness characteristics. The reflection region and transmission region are segmented with different thickness optimizations, allowing independent optimization of reflection chromaticity stability and transmission brightness without mutual interference.
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 reduces yellow shift in reflection whiteness and chromaticity variations, maintaining high reflectance and transmittance while ensuring consistent display quality across varying cell gaps.
Implementation Method 1
a liquid crystal layer provided between the first substrate and the second substrate. The liquid crystal layer has a twist angle of substantially 0 degree
Implementation Method 2
A thickness of the liquid crystal layer in the transmission region is greater than a thickness of the liquid crystal layer in the reflection region
Implementation Method 3
The first substrate includes a reflecting layer including a portion located in the reflection region of each pixel
Data Source
AI summary
A liquid crystal display device includes a first substrate, a second substrate, and a liquid crystal layer. Each pixel includes a reflection region and a transmission region. The first substrate includes a reflecting layer, a first insulating layer, and a pixel electrode. The thickness of the liquid crystal layer in the transmission region is greater than the thickness of the liquid crystal layer in the reflection region, and the liquid crystal layer has a twist angle of substantially 0 degree. A surface of the first substrate that faces the liquid crystal layer includes an upper step portion, a lower step portion, and an inclined portion. The length L1 of a portion of the inclined portion included in the reflection region and the length L2 of a portion of the lower step portion included in the reflection region satisfy the relationship L1+L2≤1.81·L1.