TFT Substrate Electrode Slit Layout for Uniform FFS Electric Fields
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Solution Overview
Problem
FFS liquid crystal displays suffer from afterimage and flicker defects due to non-uniform electric fields caused by differences in alignment layer resistance and residual DC components between inner and edge areas, leading to noticeable image persistence and momentary screen shaking.
Innovation Solution
A thin film transistor substrate design with specific slit configurations and a floating conductive layer or common electrode slits to ensure uniform electric field distribution by aligning the resistance and residual DC components across different areas, using slits with defined width ratios to synchronize the dissipation of residual DC components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the alignment layer length in edge area is increased to cover the data line region, then the liquid crystal coverage is improved, but the resistance difference between inner area and edge area increases causing non-uniform electric fields
Solution Approach 1:
The alignment layer is designed with different lengths in different regions: longer in edge areas (A2) to cover the data line region and improve liquid crystal coverage, and shorter in inner areas (A1) to maintain uniform resistance characteristics. This local differentiation resolves the contradiction by allowing each region to have the specific alignment layer length suited to its functional requirements.
2Reliability
If the alignment layer resistance is increased in edge area to improve liquid crystal alignment, then the residual DC component increases causing afterimage defects
Solution Approach 1:
Different alignment layer lengths are used in different regions to balance alignment quality and residual DC control. The edge area alignment layer is extended to ensure proper liquid crystal alignment in the data line region, while the inner area alignment layer is kept shorter to minimize residual DC accumulation and prevent afterimage defects.
3Area of stationary object
If the common electrode is positioned closer to the pixel electrode to create fringe field, then the aperture ratio is improved, but the electric field non-uniformity between inner and edge areas increases
Solution Approach 1:
The alignment layer length is locally optimized for edge areas (A2) to be longer than in inner areas (A1), compensating for the electric field non-uniformity caused by the close positioning of common and pixel electrodes. This ensures that the fringe field benefits are achieved while maintaining sufficient liquid crystal coverage and uniform resistance characteristics in the edge regions.
Data Source
AI summary
Disclosed is a display device having a thin film transistor substrate, which may prevent afterimage and flicker defects by reducing the non-uniformity of an electric field. In the thin film transistor substrate, a pixel electrode includes a transparent edge electrode and a transparent inner electrode, which are spaced apart from each other with a first slit having a first width interposed therebetween, and a common electrode is exposed from the other-side end of the transparent edge electrode by a second width, which is smaller than the first width, in the width direction of a data line. As such, an inner area and an edge area in each sub pixel have uniform electric field distribution.