C-PSA Liquid-Crystal Display With Third-Electrode Field Shaping
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Solution Overview
Problem
Existing liquid crystal displays (LCDs) in polymer stabilized alignment (PSA) modes suffer from reduced transmittance due to dark trunk and edge lines caused by inhomogeneous electric fields, particularly in chiral polymer-stabilized alignment (C-PSA) displays, which affect image quality and energy efficiency.
Innovation Solution
Incorporating a third electrode layer between the second and third electrode, separated by an isolation layer, to create a uniform electric field that aligns liquid crystal molecules more uniformly, thereby improving transmittance and reducing dark lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a patterned electrode structure is used in C-PSA displays, then individual pixel switching is enabled, but dark trunk lines and dark edge lines appear due to inhomogeneous electric fields, reducing transmittance
Solution Approach 1:
The electrode structure is segmented into multiple functional layers: a first patterned electrode for pixel addressing, a second patterned electrode with different pattern for field generation, and a third patterned electrode with isolated regions. This segmentation allows each electrode to perform its specific function while collectively eliminating the inhomogeneous field effects that cause dark lines.
Solution Approach 2:
An isolation layer is introduced as an intermediary between the second and third electrodes. This isolation layer prevents direct electrical interaction between the electrodes while allowing the third electrode to generate a uniform electric field that compensates for the inhomogeneous fields from the second electrode, thereby eliminating dark trunk and edge lines.
2Manufacturing precision
If UV polymerization is performed in two steps with voltage application, then tilt angle is generated and polymerization is completed, but the process complexity increases
Solution Approach 1:
The first UV exposure step applies voltage during polymerization to pre-establish the desired tilt angle and initial alignment. This preliminary action ensures that the LC molecules are oriented correctly before the second UV step completes the polymerization, simplifying the overall process while maintaining precision.
Solution Approach 2:
Voltage is applied continuously across both UV exposure steps, ensuring that the electric field effect is maintained throughout the entire polymerization process. This continuous action ensures consistent alignment quality without requiring complex separate processing steps.
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
The additional electrode layer enhances the alignment of liquid crystal molecules, leading to improved transmittance and energy efficiency by reducing dark lines and allowing for energy savings through lower backlight power consumption.
Implementation Method 1
The UV polymerization process, also referred to as 'PSA process', is usually carried out in two steps, a first UV exposure step ('UV1 step'), with application of a voltage, to generate the tilt angle, and a second UV exposure step ('UV2 step'), without application of a voltage, to complete polymerization of the RMs.
Implementation Method 2
In the C-PSA mode a small amount, typically from 0.1 to 1% of one or more polymerizable mesogenic compounds, also known as RMs (reactive mesogens), is added to the LC medium. After filling the LC medium into the display the RMs are then polymerized in situ by UV photopolymerization
Implementation Method 3
a layer comprising a nematic LC medium having negative dielectric anisotropy
Data Source
AI summary
A liquid crystal display (LCD) of the chiral polymer stabilized alignment (C-PSA) mode, a method of its production and its use as an energy-saving display.