LCD Alignment Layer Resistivity Gradient for Afterimage Reduction
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Solution Overview
Problem
Liquid crystal displays (LCDs) with field generating electrodes on one substrate experience afterimages due to residual electric fields after voltage is turned off, caused by undischarged molecular ions and impurities from the color filter.
Innovation Solution
The LCD design includes a first and second electrode on a shared substrate with an insulating layer, where the first alignment layer has a lower resistivity and larger thickness, and the second alignment layer has a higher resistivity and smaller thickness, preventing the flow of unnecessary charges and reducing capacitance to minimize afterimages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two field generating electrodes are disposed on one substrate, then device complexity is reduced and manufacturing is simplified, but afterimage is generated due to undischarged molecular ions
Solution Approach 1:
The patent applies different resistivity values to different alignment layers: the first alignment layer has a lower resistivity value to facilitate discharge of molecular ions and prevent afterimage, while the second alignment layer has a higher resistivity value to maintain its alignment function. This local differentiation of material properties resolves the contradiction by addressing the specific need for ion discharge in the first alignment layer without compromising the overall device structure.
2Object-generated harmful factors
If the first alignment layer has lower resistivity, then discharge of molecular ions is enhanced and afterimage is prevented, but capacitance increases
Solution Approach 1:
The patent changes the resistivity parameter of the first alignment layer to a lower value compared to the second alignment layer. This parameter change enables enhanced discharge of molecular ions and prevention of afterimage. The patent accepts this capacitance increase as a trade-off, noting that the lower resistivity layer is specifically positioned where ion discharge is most critical, and the benefit of eliminating afterimage outweighs the capacitance penalty.
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 effectively discharges charged ions and reduces the flow of impurity-generated charges, preventing afterimages by minimizing the application of unnecessary electric fields to the liquid crystal layer.
Implementation Method 1
a first resistivity value of the first alignment layer is smaller than a second resistivity value of the second alignment layer
Implementation Method 2
applying voltages to field-generating electrodes to generate an electric field in an LC layer that determines orientations of LC molecules therein to adjust polarization of incident light
Implementation Method 3
displays images by applying voltages to field-generating electrodes to generate an electric field in an LC layer that determines orientations of LC molecules
Data Source
AI summary
A liquid crystal display includes a first substrate, a first electrode disposed on the first substrate, a second electrode which is disposed on the first substrate and overlaps the first electrode, an insulating layer interposed between the first electrode and the second electrode, a first alignment layer disposed on the first electrode and the second electrode, a second substrate facing the first substrate, and a second alignment layer disposed on the second substrate, where a first resistivity value of the first alignment layer is smaller than a second resistivity value of the second alignment layer.