LCD Array Substrate Gate Electrode Active Layer Coverage
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Solution Overview
Problem
The existing liquid crystal display (LCD) array substrates fabricated using four mask processes suffer from wavy noise and reduced aperture ratio due to light leakage currents caused by exposed active layers, which are not adequately covered by electrodes, and the protrusion of intrinsic amorphous silicon layers beyond data lines.
Innovation Solution
The array substrate is designed with a gate line and data line intersection, featuring a thin film transistor (TFT) with an active layer fully covered by the gate electrode and an etch stopper, preventing light exposure and using transparent conductive materials for electrodes to reduce resistance and prevent light reflection, while the data line includes opaque and transparent conductive layers to maintain integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the active layer is not fully covered by the gate electrode, then the fabrication process is simpler, but light leakage currents occur causing wavy noise
Solution Approach 1:
The gate electrode is designed to extend beyond the data line in the planar view, proactively covering the active layer before light exposure can occur. This preliminary coverage prevents light leakage currents and wavy noise before they can be generated, resolving the contradiction between fabrication simplicity and light leakage prevention.
2Illumination intensity
If the aperture ratio is increased, then the light transmission is improved, but the active layer protrusion causes wavy noise
Solution Approach 1:
The gate electrode extends beyond the data line to preemptively cover the active layer, preventing light leakage currents that would cause wavy noise. This allows the aperture ratio to be maximized for improved light transmission without sacrificing display quality.
3Object-affected harmful factors
If transparent conductive materials are used for electrodes, then light reflection is reduced, but electrode resistance increases
Solution Approach 1:
The electrode is constructed as a composite structure with multiple layers including transparent conductive materials and metal materials. This composite configuration balances the conflicting requirements by reducing light reflection through transparency while maintaining acceptable resistance through the conductive metal layers.
4Object-affected harmful factors
If the gate electrode fully covers the active layer, then light leakage is prevented, but the device complexity increases
Solution Approach 1:
The gate electrode is designed with extended coverage beyond the data line in a straightforward manner, preemptively preventing light leakage currents. This simple extension design achieves comprehensive active layer coverage without significantly increasing device complexity.
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 wavy noise and enhances the aperture ratio by shielding the active layer from light, reducing light leakage currents and improving TFT performance, allowing for thinner active layers and maintaining data line integrity.
Implementation Method 1
the gate electrode and an etch stopper, thereby preventing light from being irradiated into the active layer
Implementation Method 2
using transparent conductive materials for electrodes to reduce resistance
Data Source
AI summary
An array substrate for a liquid crystal display device includes a gate and a data lines on a substrate intersecting each other, the data line includes a first layer formed of a transparent conductive material and a second layer under the first layer; a thin film transistor including a gate electrode connected to the gate line formed at respective intersection of the gate and data lines, an insulating layer on the gate electrode, an active layer on the insulating layer disposed within the gate electrode, an etch stopper on the active layer, an ohmic contact layer on the etch stopper, a source electrode on the ohmic contact layer and connected to the first layer, a drain electrode spaced apart from the source electrode; a pixel electrode connected to the drain electrode, wherein the source, drain and pixel electrodes are formed of the same layer and material as the first layer.