FFS Liquid Crystal Display Pixel Switch with Floating Gate
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Solution Overview
Problem
Current liquid crystal display devices face challenges in reducing power consumption and maintaining display quality while performing both display and sensing functions, particularly in the fringe field switching mode, due to high off-leak current and potential variations at the pixel switch.
Innovation Solution
The implementation of a liquid crystal display device with a pixel switch comprising serially connected first and second switching elements, where the second switching element is in a floating gate state, and a control electrode is opposed to the second gate electrode, reducing off-leak current and energy consumption by maintaining the pixel electrode voltage during sensing periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pixel switch is used in fringe field switching mode liquid crystal display devices, then display quality can be maintained, but off-leak current increases and power consumption rises
Solution Approach 1:
The pixel switch is divided into two separate switching elements connected in series between the signal line and pixel electrode. This segmentation allows each switching element to have optimized gate electrode configurations, where the first switching element's gate electrode is connected to the scanning line and the second switching element's gate electrode is in a floating state, thereby reducing off-leak current while maintaining display quality
Solution Approach 2:
Different gate electrode connection configurations are applied to different parts of the pixel switch structure. Specifically, the first switching element uses a conventional scanning line connection while the second switching element employs a floating gate electrode configuration. This local differentiation optimizes the electrical characteristics at each position, reducing overall off-leak current without compromising the lateral electric field generation needed for FFS mode operation
2Adaptability or versatility
If sensing operations are performed in liquid crystal display devices, then touch detection capability is improved, but potential variations at the pixel switch increase and display quality degrades
Solution Approach 1:
The pixel switch structure with two series-connected switching elements is designed to fulfill multiple functions: it serves as the pixel switch for display operation in FFS mode while simultaneously enabling sensing operations. The floating gate electrode of the second switching element can be utilized for sensing without significantly affecting display performance, allowing the same structure to support both display and touch detection functions
Solution Approach 2:
The floating gate electrode of the second switching element acts as an intermediary structure that facilitates sensing operations. During sensing periods, this floating gate can detect touch inputs through capacitance changes while the series connection configuration isolates the impact on the pixel electrode voltage, thereby enabling sensing functionality with minimal degradation to display quality
3Use of energy by moving object
If frame frequency is reduced below 60 Hz to save power, then energy consumption decreases, but image quality may be degraded
Solution Approach 1:
The display device operates at reduced frame frequencies below 60 Hz, utilizing periodic refresh cycles. The optimized pixel switch structure with two series-connected switching elements maintains adequate voltage holding capability during these extended periods between refreshes, enabling power-saving operation at lower frame rates while preserving image quality through the reduced off-leak current characteristics
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 suppresses off-leak current and potential variations, allowing for reduced power consumption and improved display quality, enabling efficient display and sensing operations with a frame frequency lower than 60 Hz without degrading image quality.
Implementation Method 1
a structure using a lateral electric field (including a fringe field) such as fringe field switching (FFS) mode
Implementation Method 2
a structure using a lateral electric field (including a fringe field) such as fringe field switching (FFS) mode
Data Source
AI summary
According to one embodiment, a display device includes a first substrate including a scanning line, a control line, a control electrode, a signal line, a pixel electrode, a first switching element, and a second switching element. The first switching element includes a first semiconductor layer, a first gate electrode, and a first insulating film. The second switching element includes a second semiconductor layer, a second gate electrode, and a second insulating film. The control electrode is overlapped with the second gate electrode.