LCD Common Electrode Finger Design for Crosstalk Reduction
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Solution Overview
Problem
In liquid crystal displays (LCDs), the parasitic capacitance between the common electrode and data line leads to unstable potential and crosstalk, requiring increased spacing that reduces pixel transmittance and area.
Innovation Solution
A liquid crystal display design with a common electrode having a finger-shaped section that overlaps the data line with a low dielectric passivation layer between them, along with a second inorganic passivation layer, and a pixel electrode with a similar finger shape, allowing for reduced parasitic capacitance and increased transmittance by minimizing the black matrix width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the common electrode is spaced apart from the data line by a predetermined distance to suppress crosstalk, then the parasitic capacitance is reduced, but the open block area in the pixel is decreased and transmittance is reduced
Solution Approach 1:
The patent changes the dielectric constant parameter of the passivation layer from high (conventional) to low (k≤3.5), specifically using materials like acrylic resin. This parameter change allows the common electrode to be positioned closer to the data line while maintaining low parasitic capacitance, thereby increasing the open block area and transmittance without compromising potential stability
Solution Approach 2:
The patent introduces a low dielectric material as an intermediary substance between the common electrode and the data line. This intermediary layer with k≤3.5 acts as a mediator that reduces the electric field coupling between the two conductors, suppressing parasitic capacitance formation while allowing closer spacing, thus resolving the contradiction between crosstalk suppression and area maximization
2Reliability
If the distance between the common electrode and data line is increased to reduce parasitic capacitance, then crosstalk is suppressed, but the black matrix must be broadened which much reduces transmittance
Solution Approach 1:
By changing the dielectric constant parameter to a low value (k≤3.5) for the passivation layer, the patent enables closer spacing between the common electrode and data line. This eliminates the need to broaden the black matrix, thereby maintaining high transmittance while still suppressing parasitic capacitance and crosstalk through the low dielectric material's inherent capacitance-reducing properties
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 increases the open block area in pixels, enhancing transmittance while maintaining stable potential and reducing crosstalk, thereby improving the display's viewing angle and image quality.
Implementation Method 1
the parasitic capacitance Cap is formed. The parasitic capacitance reflects a voltage variation in the common electrode Ec on the common electrode Ec to make the potential in the common electrode Ec unstable
Implementation Method 2
a first passivation layer having a low dielectric and placed between the common electrode and the data line
Implementation Method 3
drives an in plane switch ('IPS') mode LC layer by a horizontal electric field generated between a pixel electrode Ep and a common electrode Ec arranged in parallel
Implementation Method 4
displays images by adjusting a light transmittance of an LC layer using an electric field
Data Source
AI summary
A liquid crystal display comprises a gate line formed on a first substrate, a data line formed on the substrate intersecting the gate line to define a pixel area, a common line partially surrounding the pixel area and formed along with the gate line by the same process, a thin film transistor formed at the intersection of the gate line and the data line, a common electrode having a common electrode horizontal section connected to the common line, and a common electrode finger section extending from the common electrode horizontal section with a finger shape, and a pixel electrode connected to the thin film transistor and generating a horizontal electric field along with the common electrode, wherein a part of the common electrode finger section overlaps the data line with a first passivation layer having a low dielectric and placed between the common electrode and the data line.