Transflective LCD Contrast via Segmented Liquid Crystal Thickness
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Solution Overview
Problem
In transflective liquid crystal display devices using IPS technology, the reflective portions operating in normally white mode face challenges in achieving complete black display, leading to higher luminance and decreased contrast ratio due to the inversion of bright and dark parts between transmissive and reflective portions.
Innovation Solution
The implementation of a transflective liquid crystal display device design where the reflective portions operate in normally white mode with a thicker liquid crystal layer than the transmissive portions, using independent counter electrodes and specific voltage applications to prevent inversion, and optionally omitting retardation films to enhance contrast ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the reflective portions operate in normally white mode with the same liquid crystal layer thickness as transmissive portions, then the device structure is simple, but the contrast ratio decreases and complete black display cannot be achieved
Solution Approach 1:
The patent applies different liquid crystal layer thicknesses to different functional regions: the reflective portions use a thicker liquid crystal layer (5.0-7.0 μm) while the transmissive portions use a thinner layer (3.0-5.0 μm). This local differentiation allows the reflective portions to achieve complete black display and high contrast ratio, while the transmissive portions maintain their optimal performance, resolving the contradiction between structural simplicity and display quality.
2Manufacturing precision
If the liquid crystal layer thickness in reflective portions is increased to improve black display, then the contrast ratio improves, but the device structure becomes more complex
Solution Approach 1:
The liquid crystal layer is segmented into two distinct thickness zones corresponding to the reflective and transmissive portions. The thicker liquid crystal layer in reflective portions (5.0-7.0 μm) enables complete black display by achieving the necessary optical path difference, while the thinner layer in transmissive portions (3.0-5.0 μm) maintains optimal transmission characteristics. This segmentation resolves the contradiction by allowing each region to have optimized thickness without requiring overall structural complexity.
3Manufacturing precision
If independent counter electrodes are used for transmissive and reflective portions, then bright and dark inversion is prevented, but the device complexity increases
Solution Approach 1:
The counter electrode is segmented into two independent electrodes: a first counter electrode for the transmissive portions and a second counter electrode for the reflective portions. This segmentation allows independent voltage control of each region, preventing bright and dark inversion between portions. Although it increases electrode structure complexity, it enables precise display accuracy by allowing separate optimization of electrical characteristics for each functional region.
Solution Approach 2:
Different counter electrodes are assigned to different functional regions with different electrical requirements. The first counter electrode is optimized for transmissive portion characteristics while the second counter electrode is optimized for reflective portion characteristics. This local quality differentiation allows each region to operate at optimal performance, resolving the contradiction between display accuracy and electrode structure complexity.
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 improves the contrast ratio of the reflective portions by allowing for better control of the liquid crystal layer thickness and voltage differences, resulting in enhanced display quality and reduced light leakage.
Implementation Method 1
Brightness/darkness levels are controlled by rotating the liquid crystal material within the plane of the substrates
Implementation Method 2
An electric field is produced by the pixel electrodes and the counter electrode
Implementation Method 3
light passes through the liquid crystal layer twice in the region A that is a light reflective part
Data Source
AI summary
There is disclosed a transflective liquid crystal display device having reflective portions having an improved contrast ratio. At each subpixel of the display device, a pixel electrode is shared between transmissive and reflective portions. Independent counter electrodes are used respectively for the transmissive and reflective portions. Different potentials are applied to the counter electrodes for the transmissive and reflective portions. The transmissive portion operates in normally black mode. That is, the transmissive portion displays black when no voltage is applied. The reflective portion operates in normally white mode. That is, the reflective portion displays white when no voltage is applied. The liquid crystal layer in the reflective portion is thicker than the liquid crystal layer in the transmissive portion.