Double-Layered Source Drain Electrodes in LCD Array Substrates
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Solution Overview
Problem
The existing methods for fabricating array substrates for liquid crystal display (LCD) devices face challenges such as high production costs and electrical conductivity issues when using flexible substrates and organic semiconductor materials, particularly due to the difficulty in forming semiconductor layers at temperatures lower than 200°C and the use of gold electrodes which are prone to diffusion and wastage.
Innovation Solution
The solution involves forming a double-layered structure for source and drain electrodes using a low-resistant metal layer and a transparent conductive material layer, such as ITO, with the transparent conductive material covering the upper surface of the metal layer to improve electrical characteristics and reduce production costs, while using a buffer layer to enhance adhesion and uniformity of the organic semiconductor layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold is used for source and drain electrodes, then electrical conductivity is improved, but production cost increases and material diffusion occurs
Solution Approach 1:
The patent applies composite materials by creating a double-layered electrode structure combining a metal layer (Al, Mo, or Cu) and a transparent conductive material layer (ITO, IZO, or ZnO). This composite structure provides both the electrical conductivity needed for functionality and the adhesion prevention benefits, eliminating gold diffusion issues while maintaining performance.
Solution Approach 2:
The patent replaces expensive gold electrodes with cheaper alternative materials such as aluminum, molybdenum, copper for the metal layer and ITO, IZO, or ZnO for the transparent conductive layer. This substitution significantly reduces production costs while achieving the required electrical conductivity and adhesion properties.
2Temperature
If organic semiconductor material is used, then low-temperature fabrication is enabled, but adhesion and uniformity of semiconductor layer deteriorate
Solution Approach 1:
The patent introduces a buffer layer as an intermediary between the substrate and the organic semiconductor layer. This buffer layer mediates the interaction between the substrate and semiconductor material, providing improved adhesion and uniformity formation while enabling low-temperature fabrication processes.
Solution Approach 2:
The patent uses composite materials in the buffer layer, combining organic and inorganic components to achieve both low-temperature processing capability and improved adhesion/uniformity properties for the organic semiconductor layer.
3Reliability
If transparent conductive material covers metal layer, then adhesion of semiconductor layer is improved, but electrode structure complexity increases
Solution Approach 1:
The patent segments the electrode into two distinct functional layers: a metal layer for electrical conductivity and a transparent conductive material layer for adhesion enhancement. This segmentation allows each layer to perform its specific function optimally while maintaining a relatively simple overall structure that can be integrated into existing LCD manufacturing processes.
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 production costs and improves the electrical characteristics of the thin-film transistors (TFTs) by using ITO instead of gold, maintaining the integrity of the electrode structure and preventing undercutting issues, thus enhancing the overall performance and efficiency of the LCD device.
Implementation Method 1
a second source electrode and a second drain electrode of a transparent conductive material formed on the first source electrode and the first drain electrode, respectively, such that the second source electrode covers an upper surface of the first source electrode, and the second drain electrode covers an upper surface of the first drain electrode
Data Source
AI summary
An array substrate for a liquid crystal display device includes a first source electrode and a first drain electrode on a substrate, wherein the first source electrode and the first drain electrode are separated from each other and formed of a metallic material, a second source electrode and a second drain electrode on the first source electrode and the first drain electrode, respectively, and are formed of a transparent conductive material, wherein the second source electrode covers an upper surface of the first source electrode, and the second drain electrode covers an upper surface of the first drain electrode, a pixel electrode on the substrate and contacting the second drain electrode on the substrate, an organic semiconductor layer on the substrate, a gate insulating layer on the organic semiconductor layer, and a gate electrode on the gate insulating layer.