FFS Liquid Crystal Device Two-Terminal Switching Element
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Solution Overview
Problem
The complexity and high manufacturing cost of liquid crystal devices using three-terminal switching elements, such as TFTs, in FFS mode, due to intricate configurations and the risk of short-circuiting between second electrodes and wiring lines, necessitate a simpler configuration that ensures electrical insulation without compromising the device's performance.
Innovation Solution
A liquid crystal device configuration with a dielectric film covering electrodes and wiring lines, allowing the second electrode to extend beyond the film and connect with the wiring line directly or through a contact hole, ensuring electrical insulation and simplifying the manufacturing process by eliminating the need for additional insulation structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a three-terminal switching element (TFT) is used as a switching element for controlling voltage applied to pixels in FFS mode, then the device can achieve proper switching control, but the configuration of elements on substrates becomes complex, manufacturing processes become complicated, and manufacturing cost increases
Solution Approach 1:
The patent extracts and removes the gate electrode and gate insulating layer from the TFT structure, retaining only the source and drain regions to form a simplified two-terminal switching element. This extraction eliminates the complex gate control structure while maintaining the essential switching function through direct voltage application to the source and drain regions.
Solution Approach 2:
The patent employs a simplified two-terminal switching element that is easier and cheaper to manufacture compared to the full TFT. The simplified structure requires fewer manufacturing steps and fewer precise alignment processes, reducing both manufacturing complexity and cost while achieving the necessary switching control for the liquid crystal device.
2Device complexity
If multiple second electrodes and wiring lines are disposed on the same substrate in FFS mode, then the device configuration is simplified, but the second electrodes may be short-circuited according to the configuration of wiring lines
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the wiring lines and second electrodes. This dielectric layer acts as an electrical insulator that prevents direct contact and potential short-circuits between the conductive wiring lines and the second electrodes, while still allowing the overall simplified configuration to be maintained.
Solution Approach 2:
The dielectric layer is selectively formed in specific regions where wiring lines and second electrodes are in close proximity or potential overlap. This localized application of the dielectric layer provides electrical insulation exactly where needed to prevent short-circuits, without requiring complete isolation throughout the entire substrate, thus maintaining the simplified configuration.
3Reliability
If electrical insulation configuration is provided only for wiring lines and second electrodes, then short-circuiting is prevented, but the configuration of the liquid crystal device is not sufficiently simplified and restrictions on wiring line and electrode configuration arise
Solution Approach 1:
The patent merges the dielectric layer formation with the existing manufacturing process steps for forming wiring lines and second electrodes. The dielectric layer is deposited and patterned in the same or adjacent process steps, combining multiple functions (insulation, structural support, and electrical isolation) into a unified approach that does not significantly increase manufacturing complexity.
Solution Approach 2:
The dielectric layer serves multiple functions simultaneously: it provides electrical insulation between wiring lines and second electrodes, acts as a protective barrier, and can serve as part of the overall device structure. This multi-functionality reduces the need for separate dedicated insulation structures, thereby preventing short-circuits without proportionally increasing device complexity.
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 configuration enables reliable electrical connection between the second electrode and wiring line while maintaining the high contrast and wide viewing angle characteristics of the FFS mode, reducing manufacturing complexity and cost by using a two-terminal switching element like TFD, and effectively preventing short-circuiting.
Implementation Method 1
a dielectric film covering the first electrode, the switching element, and the wiring line
Implementation Method 2
a liquid crystal layer interposed therebetween
Implementation Method 3
the second electrode is drawn from the dielectric film toward an area where the dielectric film does not exist and is electrically connected to the wiring line through the area where the dielectric film does not exist
Data Source
AI summary
A liquid crystal device includes a first substrate and a second substrate opposite each other with a liquid crystal layer interposed therebetween, wherein the first substrate includes a signal line, a switching element electrically connected to the signal line, a first electrode electrically connected to the switching element, a wiring line, a dielectric film covering the first electrode, the switching element, and the wiring line, and a second electrode disposed on the dielectric film so as to be opposite the first electrode, and wherein the second electrode is drawn from the dielectric film toward an area where the dielectric film does not exist and is electrically connected to the wiring line through the area where the dielectric film does not exist.