Segmented Light-Shielding Layer for LCD Flicker Reduction
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Solution Overview
Problem
In liquid crystal display devices, the proximity of light-shielding layers to source lines leads to increased parasitic capacitance, altering the potential of the light-shielding layer and degrading display quality and touch sensor sensitivity due to flicker issues caused by light leaks, especially in high-definition displays using low-temperature polysilicon thin-film transistors.
Innovation Solution
The light-shielding layer is divided into parts corresponding to each drive unit electrode, and source lines of equal positive and negative polarity are arranged to minimize potential changes, reducing parasitic capacitance and flicker, while also using a double-gate structure for switching elements to reduce leak currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a light-shielding layer is provided to prevent light leaks and reduce flicker in LTPS TFTs, then display quality is improved, but parasitic capacitance increases due to proximity with source lines, causing potential changes and sensitivity degradation
Solution Approach 1:
The light-shielding layer is divided into multiple segments along the source line direction. Each segment corresponds to a specific pixel column and is electrically connected to the source line at its both ends, creating multiple smaller capacitive couplings instead of one large coupling, thereby reducing the overall parasitic capacitance effect
Solution Approach 2:
Conductive layers are introduced as intermediary elements between the light-shielding layer and source line. These conductive layers electrically connect the light-shielding layer segments to the source line while providing a controlled interface that manages the parasitic capacitance coupling
2Area of stationary object
If the light-shielding layer is positioned close to source lines to save space in high-definition displays, then aperture ratio is improved, but touch sensor sensitivity decreases due to potential changes from parasitic capacitance
Solution Approach 1:
The light-shielding layer is segmented into multiple sections that are electrically connected to the source line at both ends of each segment. This segmentation approach allows the light-shielding layer to be positioned close to source lines for high aperture ratio while reducing the parasitic capacitance effect through multiple smaller coupling points
Solution Approach 2:
The light-shielding layer segments are electrically connected to the source line at both ends, creating equipotential regions that minimize potential differences and reduce the impact of parasitic capacitance on touch sensor sensitivity
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 enhances display quality by reducing flicker and maintaining touch sensor sensitivity, preventing potential changes in the light-shielding layer from degrading the display and touch detection performance.
Implementation Method 1
a light-shielding layer arranged in an underlying layer of the switching elements
Implementation Method 2
a liquid crystal layer held between the array substrate and the counter-substrate
Data Source
AI summary
According to one embodiment, a liquid crystal display device includes touch-sensor electrodes, an array substrate including pixel electrodes, gate lines, source lines, switching elements, a light-shielding layer, and a plurality of stripe-like common electrodes, a counter-substrate, and a liquid crystal layer, wherein the common electrodes included in the array substrate are used not only as electrodes for display, but also as touch-sensor electrodes and, in a touch operation, a touch drive signal is input to each drive unit electrode including a plurality of common electrodes, and the light-shielding layer is divided into parts each of which corresponds to the drive unit electrode, and is provided to extend across a region opposed to a region of the drive unit electrode.