IPS LCD Electrode Sequence and Gate Structure
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Solution Overview
Problem
The existing IPS mode liquid crystal display devices face issues with low production yield and reliability due to cell reactions between ITO and MoCr, leading to potential disconnection of source and drain electrodes and image signal lines, especially when patterning the pixel electrode, which increases production costs and reduces viewing angle characteristics.
Innovation Solution
The solution involves forming the pixel electrode first, followed by the source, drain, and image signal lines, ensuring these electrodes are not present during ITO patterning, thus preventing cell reactions and maintaining electrical contact, and using a two-layer gate electrode structure to prevent ITO reactions with underlying layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the source and drain electrodes are formed before patterning the pixel electrode, then the production process follows conventional IPS mode, but cell reactions occur between ITO and MoCr causing electrode disconnection and low production yield
Solution Approach 1:
The pixel electrode is patterned before the source and drain electrodes are formed. This preliminary action prevents MoCr from being present during ITO patterning, thereby preventing cell reactions between ITO and MoCr that would cause electrode disconnection and reduce production yield.
Solution Approach 2:
The conventional formation sequence is inverted: instead of forming source/drain electrodes first and then patterning the pixel electrode, the patent patterns the pixel electrode first and then forms the source/drain electrodes. This inversion eliminates the harmful cell reaction between ITO and MoCr.
2Adaptability or versatility
If multiple layers including common electrode and insulating films are disposed on TFT substrate, then IPS mode functionality is achieved, but production cost increases
Solution Approach 1:
The gate electrode and common electrode are merged into a single conductive layer formed on the TFT substrate. This merging reduces the number of separate layers and production steps while maintaining the necessary IPS mode functionality, thereby reducing production cost.
Solution Approach 2:
The gate insulating film serves multiple functions: it acts as an insulator for the gate electrode, provides a base for the pixel electrode formation, and prevents direct contact between the gate electrode and subsequent layers. This multi-functionality reduces the need for additional specialized layers.
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 enhances production yield and reliability by preventing electrode disconnection and reducing production costs while maintaining excellent viewing angle characteristics by minimizing the number of layers in the IPS liquid crystal display device.
Implementation Method 1
the liquid crystal molecules are rotated by an electric field generated between the pixel electrode and the common electrode
Implementation Method 2
A gate insulating film 102 is formed by sputtering SiN on the gate electrode 101
Implementation Method 3
the passivation film 107 is formed from SiN by CVD
Data Source
AI summary
In a liquid crystal display which includes a liquid crystal layer between a TFT substrate and a counter substrate, a gate electrode, a gate insulator and a semiconductor layer are laminated. A pixel electrode is formed on the gate insulator and metal source and drain electrodes are formed on the semiconductor layer and gate insulator. At least upper surfaces of the source and drain electrode contain Mo. The source is directly laminated on a portion of the pixel electrode, which portion is disposed on the gate insulating film.