LCD Storage Capacitor Transparent Electrode Aperture Ratio
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Solution Overview
Problem
The existing thin film transistor substrates for liquid crystal display devices have a complex fabrication process and a storage capacitor design that reduces the aperture ratio when attempting to increase capacitance, leading to higher manufacturing costs and inefficient signal retention.
Innovation Solution
A thin film transistor substrate with a double-layered gate line structure, where the gate line consists of a first transparent conductive layer and a second opaque conductive layer with step coverage, and a storage capacitor with a lower storage electrode formed from a transparent conductive layer, allowing for increased capacitance without reducing the aperture ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the storage capacitor is designed with opaque electrodes to increase capacitance, then the capacitance value increases, but the aperture ratio is reduced
Solution Approach 1:
The invention changes the optical property of the storage capacitor electrodes from opaque to transparent. The lower storage electrode is formed of a transparent conductive layer (first transparent conductive layer) and the upper storage electrode is formed of a transparent conductive layer (second transparent conductive layer), allowing light to pass through the storage capacitor region, thereby increasing the aperture ratio while maintaining the capacitance function.
2Manufacturing precision
If a five-mask process is used for thin film transistor fabrication, then the manufacturing precision is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The invention merges the gate line and lower storage electrode into a single patterned structure formed by one mask process. The gate line includes a first transparent conductive layer and a second opaque conductive layer, where the first transparent conductive layer also serves as the lower storage electrode. This integration allows both the gate line and storage capacitor to be formed simultaneously in one masking step, reducing the total mask processes from five to four.
Solution Approach 2:
The first transparent conductive layer of the gate line serves dual functions: as the gate electrode conductor and as the lower storage electrode. This multi-functional design eliminates the need for separate electrode layers, simplifying the fabrication process while maintaining both gate control and capacitance storage functions.
3Ease of manufacture
If the gate line uses a single opaque layer, then the fabrication process is simplified, but the signal retention capability is reduced
Solution Approach 1:
The gate line is constructed as a composite structure with a first transparent conductive layer and a second opaque conductive layer. The transparent layer provides capacitance storage function while the opaque layer provides effective light shielding and signal isolation. This composite structure enhances signal retention capability by preventing light-induced signal leakage while maintaining fabrication feasibility.
Data Source
AI summary
A thin film transistor substrate of a LCD device and a fabricating method thereof are disclosed for simplifying a fabricating process and enlarging a capacitance value of a storage capacitor without any reduction of aperture ratio. The LCD device includes: a double-layered gate line having a first transparent conductive layer and a second opaque conductive layer, the second opaque conductive layer have a step coverage; a gate insulation layer film on the gate line; a data line crossing the gate line to define a pixel region; a TFT connected to the gate line and the data line; a pixel electrode connected to the TFT via a contact hole of a protective film on the TFT; and a storage capacitor overlapping the pixel electrode and having a lower storage electrode formed of the first transparent conductive layer.