Symmetric Slit Electrodes for LCD Brightness Uniformity
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Solution Overview
Problem
Liquid crystal display devices employing lateral electric field methods, such as FFS and IPS, face issues with brightness unevenness due to displacement between the optical axis of the polarizing plate and the alignment controlling direction of the alignment film, particularly in larger devices and during halftone displays.
Innovation Solution
A liquid crystal display device configuration with four sub-pixel regions, each divided by orthogonal axes, where slit electrodes are symmetrically arranged to generate electric fields that rotate liquid crystal molecules in specific directions, compensating for alignment errors and maintaining uniform brightness across adjacent regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If slit electrodes are arranged symmetrically with respect to the optical axis of the polarizing plate, then alignment accuracy is improved, but device complexity increases due to the need for four divided display regions and multiple axes of symmetry
Solution Approach 1:
The patent applies asymmetry by intentionally introducing a tilt angle between the optical axis of the polarizing plate and the alignment controlling direction of the alignment film. This deliberate asymmetric arrangement allows the liquid crystal molecules to rotate in specific directions that compensate for brightness unevenness, resolving the technical contradiction by transforming what would normally be an error (misalignment) into a functional feature for view angle compensation and brightness uniformity.
2Adaptability or versatility
If the rubbing direction is tilted with respect to the optical axis of the polarizing plate, then view angle is improved, but brightness uniformity deteriorates due to brightness differences between adjacent display regions
Solution Approach 1:
The patent divides each pixel electrode into four distinct display regions (first, second, third, and fourth display regions) based on the tilt direction of the rubbing direction relative to the optical axis. This segmentation allows different rotation directions of liquid crystal molecules in different regions, compensating for brightness unevenness and achieving both wide view angle and uniform brightness through coordinated operation of all four regions.
3Area of stationary object
If pixel electrodes are made larger to increase display size, then display area is improved, but brightness unevenness worsens due to increased displacement effects
Solution Approach 1:
The patent applies local quality by configuring different display regions within each pixel electrode with specific tilt directions tailored to their local positions. The first and second display regions have one tilt direction while the third and fourth display regions have another tilt direction, allowing each region to be optimized for its specific location and contribute to overall brightness uniformity across the entire large display area.
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 ensures uniform brightness and wide view angles by compensating for voltage-transmissivity characteristics across adjacent regions, preventing display deterioration caused by alignment errors and enhancing image quality.
Implementation Method 1
A method for controlling alignment of liquid crystal molecules by applying an electric field to a liquid crystal layer in a direction of a substrate surface is known (hereinafter referred to as a 'lateral electric field method').
Implementation Method 2
Liquid crystal molecules rotate within a substrate horizontal plane from the rubbing direction to directions of the electric fields.
Implementation Method 3
A rubbing direction of an alignment film (alignment controlling direction) is substantially orthogonal to the arrangement axis AX
Implementation Method 4
an optical axis of a polarizing plate (for example, a transmission axis) is substantially parallel to the rubbing direction of the alignment film
Data Source
AI summary
A liquid crystal display device includes two substrates, liquid crystal therebetween, and sub-pixel regions. Each sub-pixel region is divided into first to fourth display regions by a first axis extending orthogonal to an optical axis of a polarizing plate and a second axis extending orthogonal to the first axis. Each first to fourth display region includes slit electrodes on the second electrodes along the first axis. First slit electrodes in the first display region and second slit electrodes in the second display region are symmetric relative to the first axis. Third slit electrodes in the third display region and fourth slit electrodes in the fourth display region are symmetric relative to the first axis. The first and fourth slit electrodes are symmetric relative to the second axis. The second and third slit electrodes are symmetric relative to the second axis.