TFT Display Brightness Uniformity via Electrode Gap Variation
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Solution Overview
Problem
Conventional liquid crystal display devices face brightness unevenness due to inconsistent write current values in TFTs, leading to increased manufacturing costs and larger drive circuit volumes, especially when using three-level scanning signals to address this issue.
Innovation Solution
The solution involves arranging pixel electrodes and counter electrodes in a comb-like fashion on the same surface of an insulating layer, with varying gaps between them based on the thickness of the gate insulating film and channel width-to-length ratios of TFTs, allowing for uniform brightness without converting scanning signals to three-level signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a three-level scanning signal is used to reduce brightness unevenness, then display uniformity is improved, but drive circuit volume and manufacturing cost increase
Solution Approach 1:
The patent applies local quality by varying the gap between pixel electrodes and counter electrodes in different regions of the display panel. Specifically, the gap is adjusted according to the position-dependent write current characteristics of TFTs, with larger gaps in regions where write current is stronger and smaller gaps where write current is weaker. This spatially differentiated structure compensates for brightness unevenness without requiring complex three-level signal conversion circuits.
2Reliability
If the gap between pixel electrode and counter electrode is increased, then overwriting prevention is improved, but liquid crystal response speed decreases
Solution Approach 1:
The patent implements local quality by setting different gap sizes between pixel electrodes and counter electrodes in different display regions. The gap is locally optimized to be larger in regions prone to overwriting (improving reliability) while maintaining smaller gaps in regions requiring fast response, thereby achieving both overwriting prevention and acceptable response speed through spatially differentiated design.
Solution Approach 2:
The patent applies parameter changes by systematically varying the gap dimension between pixel electrodes and counter electrodes as a key geometric parameter. This parameter optimization allows tuning of the electric field distribution to prevent overwriting while maintaining response characteristics, demonstrating how parameter adjustment can resolve conflicting performance requirements.
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 reduces brightness unevenness and manufacturing costs by optimizing the gap between pixel electrodes and counter electrodes, enhancing display quality and enabling narrower picture frames without the need for three-level signal conversion.
Implementation Method 1
the pixel electrode and the counter electrode in a shape of comb are arranged in an opposing manner, so that the teeth of the two comb-shaped electrodes may be placed alternately. The liquid crystal display panel, in which the pixel electrode and the counter electrode in a shape of comb are arranged in an opposing manner, drives a liquid crystal generally by the method called a lateral electric field drive method (or simply called in-plane switching method).
Data Source
AI summary
A display device which can reduce easily the brightness unevenness produced by the insufficient writing of TFT, wherein, the display device having: a display panel which, over a surface of an insulating substrate, includes plural scanning signal lines; plural picture signal lines; plural TFTs; plural pixel electrodes coupled to sources of the TFTs; and a counter electrode, wherein the pixel and counter electrodes are arranged over the same surface of an insulating layer overlying the surface of the insulating substrate, and when a gate insulating film provided at one TFT among the TFTs is thinner than a gate insulating film provided at another TFT among the TFTs, a gap between a pixel electrode coupled to the source of the one TFT and the counter electrode is set to be wider than a gap between a pixel electrode coupled to the source of the another TFT and the counter electrode.