FFS-LCD Pixel Structure Transparent Gate Electrode
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Solution Overview
Problem
Current fringe field switching liquid crystal display (FFS-LCD) pixel structures require six patterning processes for fabrication, making the process complex and costly due to the use of a bottom-gate type thin film transistor.
Innovation Solution
A pixel structure and fabrication method where both the gate and common electrode are formed using a transparent conductive layer, simplifying the process to four patterning steps and allowing for simultaneous fabrication, reducing costs and improving transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a bottom-gate type thin film transistor is used in FFS-LCD pixel structure, then the device functionality is achieved, but the fabrication process complexity increases requiring six patterning processes
Solution Approach 1:
The patent merges the gate electrode and common electrode into a single transparent conductive layer structure. The transparent conductive layer is patterned to simultaneously form both the gate electrode (in the active region) and the common electrode (in the non-active region), reducing the number of patterning processes from six to four while maintaining the bottom-gate transistor functionality required for FFS-LCD operation.
2Manufacturing precision
If multiple patterning processes are used to fabricate the pixel structure, then the device structure is achieved, but the fabrication cost increases
Solution Approach 1:
The patent combines the formation of gate electrode and common electrode into a single patterning process. By using one transparent conductive layer that is patterned to create both electrodes simultaneously, the number of patterning steps is reduced from six to four, directly lowering fabrication costs while maintaining the required structural precision for FFS-LCD pixels.
Solution Approach 2:
The transparent conductive layer serves multiple functions: it acts as both the gate electrode material and the common electrode material. This multi-functional approach eliminates the need for separate conductive layers for each electrode, simplifying the fabrication process and reducing material and process costs.
3Reliability
If opaque conductive materials are used for the gate electrode, then the electrical conductivity is sufficient, but the display transmittance decreases
Solution Approach 1:
The patent changes the material parameter of the gate electrode from opaque conductive material to transparent conductive material. This parameter change maintains sufficient electrical conductivity for gate operation while significantly improving the light transmittance of the display, enabling better display quality and potential applications in transparent displays.
Solution Approach 2:
The patent uses transparent conductive materials (such as ITO - indium tin oxide) that combine the electrical conductivity properties of metals with the optical transparency of dielectrics. This composite material approach allows the gate electrode to perform its electrical function while being optically transparent, resolving the contradiction between conductivity and transmittance.
Data Source
AI summary
A pixel structure includes a first patterned transparent conductive layer, an active layer, an insulating layer and a second patterned transparent conductive layer. The first patterned transparent conductive layer is disposed on a substrate and includes a source, a drain and a pixel electrode connected to the drain. The active layer connects the source and the drain. The insulating layer covers the source, the drain and the active layer. The second patterned transparent conductive layer is disposed on the insulating layer and includes a gate disposed above the active layer and a common electrode disposed above the pixel electrode. A fabrication method of a pixel structure is also provided.