Dual-Gate Oxide TFT Structure for High-Aperture LCD Reliability
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Solution Overview
Problem
Liquid crystal display devices face challenges in maintaining high pixel density and reliability due to complex layer structures and exposure of metal wiring, which leads to moisture infiltration and reduced long-term reliability.
Innovation Solution
A liquid crystal display device structure featuring a dual-gate transistor with an oxide semiconductor layer sandwiched between first and second gate electrodes, and insulating layers, along with oxide conductive layers, which simplifies the layer structure while preventing exposure of metal wiring and enhancing reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shield electrodes are laminated to shield the electric field from signal lines, then the electric field shielding effect is improved, but the layer structure becomes complicated and the aperture ratio of the pixel is lowered
Solution Approach 1:
The patent combines the shield electrode function with the common electrode by forming both on the same substrate using the same transparent conductive film material. This merging eliminates the need for separate shield electrode layers, simplifying the overall layer structure while maintaining the electric field shielding effect through the common electrode's positioning and the transparent insulator's dielectric properties.
Solution Approach 2:
The common electrode is designed to serve dual functions: as the common electrode for liquid crystal modulation and as a shield electrode to protect signal lines from electric field interference. This multi-functionality reduces the number of required components and simplifies the display device structure while maintaining both liquid crystal control and electromagnetic shielding capabilities.
2Reliability
If shield electrodes are laminated to shield the electric field from signal lines, then the electric field shielding effect is improved, but the aperture ratio of the pixel is lowered
Solution Approach 1:
The patent combines the shield electrode function with the common electrode by forming both on the same substrate using the same transparent conductive film material. This merging eliminates the need for separate shield electrode layers, simplifying the overall layer structure while maintaining the electric field shielding effect through the common electrode's positioning and the transparent insulator's dielectric properties.
3Area of stationary object
If the layer structure is simplified without shield electrodes, then the aperture ratio is improved, but the electric field of the signal line acts on the liquid crystal layer lowering long-term reliability
Solution Approach 1:
The patent introduces a transparent insulator with a dielectric constant of 3.3 or less as an intermediary layer between the signal line and the liquid crystal layer. This intermediary prevents direct electric field interaction between the signal line and liquid crystal while maintaining optical transparency, thus protecting the liquid crystal from harmful electric field effects without compromising the aperture ratio.
4Reliability
If transparent insulator with low dielectric constant is used to shield signal lines, then the electric field shielding is improved, but manufacturing complexity increases
Solution Approach 1:
The patent uses the same transparent conductive film material (such as ITO, IZO, or AZO) for both the shield electrode/common electrode and the pixel electrode, ensuring material homogeneity. This approach simplifies the manufacturing process by eliminating the need for different material deposition techniques and reduces production complexity while maintaining effective electric field shielding through the consistent material properties and the transparent insulator's dielectric characteristics.
Data Source
AI summary
A liquid crystal display device includes a transistor, a pixel electrode, and a common electrode. The transistor includes a first gate electrode on a first substrate, a second gate electrode having a region overlapping the first gate electrode, an oxide semiconductor layer between the first gate electrode and the second gate electrode, a first insulating layer between the first gate electrode and the oxide semiconductor layer, a second insulating layer between the oxide semiconductor layer and the second gate electrode, and a first oxide conductive layer and a second oxide conductive layer disposed between the first insulating layer and the oxide semiconductor layer and disposed with the first gate electrode and the second gate electrode sandwiched from both sides. The pixel electrode is disposed between the first and the second insulating layer; the common electrode is disposed a region overlapping with the pixel electrode and on the second insulating layer.