Liquid Crystal Display Unit Light Shielding TFTs
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Solution Overview
Problem
Existing liquid crystal display units face challenges in minimizing size and cost while maintaining image quality under strong light exposure, as current methods to reduce light leakage currents in poly-Si TFTs either increase panel size or require high assembly accuracy, leading to increased costs and operational failures.
Innovation Solution
The integration of a peripheral circuit with TFTs on the same substrate as pixels, using a top-gate structure with light shielding metals at specific positions to prevent light exposure, and employing a package member that covers the substrate but includes an opening to expose the pixel matrix, allowing for reduced panel size and cost-effective production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a light shielding film is disposed beneath a TFT channel section to reduce light leakage current, then light leakage current is reduced, but threshold voltage fluctuates causing circuit malfunction
Solution Approach 1:
The patent applies different structures to different regions: pixel section TFTs use a light shielding film beneath the channel section to block light, while peripheral circuit TFTs use a top-gate structure with the light shielding film positioned to shield the channel without causing threshold voltage fluctuation. This localized differentiation resolves the contradiction by adapting the light shielding approach to the specific requirements of each circuit region.
Solution Approach 2:
Instead of placing the light shielding film beneath the channel section as in conventional structures, the patent inverts the approach by using a top-gate structure where the light shielding film is positioned to shield from the opposite direction, preventing light-induced threshold voltage fluctuation while still blocking light leakage current.
2Object-affected harmful factors
If the peripheral circuit is covered with a package member to shield from light, then light leakage current is reduced, but the liquid crystal panel size increases
Solution Approach 1:
The patent transitions from a conventional planar light shielding approach to a three-dimensional top-gate structure. By positioning the light shielding film in the vertical dimension above the TFT channel section and connecting it to the gate electrode, the patent achieves effective light shielding without increasing the horizontal footprint of the liquid crystal panel.
Solution Approach 2:
The light shielding film serves multiple functions simultaneously: it blocks light from reaching the TFT channel section to prevent light leakage current, connects to the gate electrode to provide electrical potential, and integrates with the existing TFT structure without requiring additional space. This multi-functionality resolves the contradiction by achieving light shielding without panel size increase.
3Speed
If poly-Si TFTs are used to achieve high field-effect mobility and reduce light sensitivity, then device performance improves, but light leakage current increases under strong light irradiation
Solution Approach 1:
The patent applies preliminary protection by positioning the light shielding film to block light before it can reach the TFT channel section. The light shielding film is placed in the light path and connected to the gate electrode, creating a barrier that prevents light-induced carrier generation in the channel, thereby counteracting the light leakage current issue before it occurs.
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 prevents image quality deterioration and operational failures under strong light conditions while minimizing the liquid crystal display unit's size and cost by effectively shielding TFTs from light and optimizing the placement of light shielding films.
Implementation Method 1
a light shielding metal (or a light shielding film) disposed at an insulating-substrate side of the pixel TFT in each of the pixels, and a light shielding metal disposed at an insulating-substrate side of each of the TFTs at least in the output section among the TFTs in the peripheral circuit
Data Source
AI summary
A liquid crystal display unit includes: an insulating substrate; a counter insulating substrate; a liquid crystal put between the insulating substrate and the counter insulating substrate; a pixel matrix including plural pixels; and a peripheral circuit including a control section and an output section, for driving a gate line of a pixel TFT in each of the pixels. The pixel matrix and the peripheral circuit are integrally formed above the insulating substrate such that the output section is located closer to the pixel matrix than the control section. The liquid crystal display unit further comprises a light shielding metal disposed at an insulating-substrate side of the pixel TFT in each pixel, and a light shielding metal disposed at an insulating-substrate side of each TFT at least in the output section among TFTs in the peripheral circuit.