TN LCD Light Leakage Prevention via Asymmetric Electrode Tilting
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Solution Overview
Problem
Liquid crystal display devices using dot inversion or column inversion driving methods experience light leakage due to alignment disturbances, particularly when the colorscale inversion direction is set to three o'clock or nine o'clock, leading to reduced contrast and image quality.
Innovation Solution
The implementation of a TN-type liquid crystal display device structure where the rubbing process on substrates prevents colorscale inversion in the three o'clock or nine o'clock direction, with strategically positioned and angled video signal lines and light-shielding films to minimize alignment disturbances and light leakage, including specific overlap configurations and tilting of pixel electrodes and video signal lines to reduce reverse tilt domains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dot inversion or column inversion driving method is used, then image quality is improved, but light leakage occurs due to alignment disturbances at pixel periphery
Solution Approach 1:
The patent applies different structural configurations to different regions of the pixel electrode. Specifically, the pixel electrode has a first region with a first tilt angle and a second region with a second tilt angle relative to the video signal line. This local differentiation allows the electrode to compensate for alignment disturbances in specific areas where they occur most frequently, thereby reducing light leakage while maintaining the dot inversion or column inversion driving method for high image quality.
Solution Approach 2:
The patent introduces asymmetric tilt angles between the pixel electrode and the video signal line. The pixel electrode is designed with specific tilt angles (first tilt angle in a first direction, second tilt angle in a second direction) that are not symmetric relative to the video signal line. This asymmetric configuration counteracts the asymmetric alignment disturbances that occur at the pixel periphery during dot inversion or column inversion driving, effectively reducing light leakage.
2Object-generated harmful factors
If video signal line overlaps pixel electrode to prevent alignment disturbance, then light leakage is reduced, but aperture ratio decreases
Solution Approach 1:
The patent implements selective overlap between the video signal line and pixel electrode only in specific regions where alignment disturbances occur. The pixel electrode is divided into a first region where overlap with the video signal line prevents alignment disturbance and a second region with different tilt characteristics. This localized approach ensures light leakage prevention is applied only where necessary, maximizing the aperture ratio in non-problem areas.
Solution Approach 2:
The patent applies the overlap configuration partially - only in the first region of the pixel electrode where alignment disturbances are most problematic. The second region maintains different tilt angles without excessive overlap, thereby preventing light leakage in critical areas while preserving aperture ratio in areas where alignment disturbances are less severe.
3Measurement precision
If rubbing process prevents colorscale inversion in three o'clock or nine o'clock direction, then contrast is improved, but device complexity increases
Solution Approach 1:
The patent modifies the rubbing process parameters to control the initial alignment direction of liquid crystal molecules. By adjusting the rubbing direction and angle during manufacturing, the device prevents colorscale inversion in the three o'clock or nine o'clock direction. This parameter change during the manufacturing process achieves improved contrast without adding operational complexity to the device structure or driving circuitry.
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 effectively prevents light leakage and enhances contrast and image quality by shielding alignment disturbances and optimizing the overlap between video signal lines and pixel electrodes, maintaining a high aperture ratio and brightness.
Implementation Method 1
a rubbing process is applied to a first substrate and a second substrate so that a colorscale inversion does not tend to occur in a three o'clock direction or in a nine o'clock direction
Implementation Method 2
positive type liquid crystal molecules aligned parallel to the substrate are twisted by 90 degrees between two opposing substrates, and the alignment of the liquid crystal molecules are switched between horizontal and vertical with respect to the substrate by switching an electric field ON and OFF
Implementation Method 3
the alignment of the liquid crystal molecules are switched between horizontal and vertical with respect to the substrate by switching an electric field ON and OFF
Implementation Method 4
a light-shielding film is formed over the second substrate, the light-shielding film overlaps the first pixel electrode and the second pixel electrode
Implementation Method 5
the alignment of the liquid crystal molecules are switched between horizontal and vertical with respect to the substrate by switching an electric field ON and OFF, so that the optical rotation state of the light is changed
Data Source
AI summary
Light leakage between pixel electrodes over a video signal line in a TN-type liquid crystal display device in which a dot inversion driving is applied with a three o'clock viewing angle is prevented. Pixel electrodes (PX) are formed on both sides of a video signal line (DL) of a first substrate (SUB1), and an end of the pixel electrode (PX) and the video signal line (DL) overlap each other. Over a second substrate (SUB2), a black matrix (BM) is formed in a portion corresponding to the video signal line (DL). By shifting the black matrix BM and the video signal line DL to the left with respect to a gap G between the pixel electrodes PX, it is possible to prevent light leakage caused by a disclination line (DS) which occurs by a horizontal electric field between pixel electrodes (PX).