LCD Flicker Suppression via Mixed Dielectric Anisotropy LC
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Solution Overview
Problem
Liquid crystal display devices in the transverse electric field mode experience flickers during low-frequency driving due to the polarity reversal of pixel voltage, which causes alignment polarization variations and perceived luminance changes.
Innovation Solution
A liquid crystal display device with a liquid crystal layer containing a mixture of positive and negative liquid crystal compounds, where the pixel electrode has linear portions and slits, applies alternating positive and negative pixel voltages at frequencies lower than 60 Hz, specifically using a negative liquid crystal compound in proportions of 2-30 volume % to reduce flicker rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If low-frequency driving is performed in transverse electric field mode liquid crystal display devices, then power consumption is reduced and responsiveness is improved, but flickers occur due to polarity reversal causing alignment polarization variations
Solution Approach 1:
The patent changes the composition parameter of the liquid crystal material by introducing a mixture of positive and negative dielectric anisotropy liquid crystal compounds. Specifically, it uses a liquid crystal material containing a positive liquid crystal compound (Δε1) and a negative liquid crystal compound (Δε2) in a weight ratio of 9:1 to 1:9, with the negative compound comprising 1-40 wt%. This parameter change in material composition suppresses the flexoelectric effect and alignment polarization variations that cause flicker during low-frequency driving.
Solution Approach 2:
The patent employs a composite liquid crystal material system combining liquid crystal compounds with opposite dielectric anisotropy signs. The composite material consists of positive liquid crystal compounds (with positive dielectric anisotropy) and negative liquid crystal compounds (with negative dielectric anisotropy), creating a balanced system that reduces net alignment polarization and suppresses flicker while maintaining fast response characteristics suitable for low-frequency driving.
2Stability of the object's composition
If only positive liquid crystal compounds are used, then the liquid crystal display device achieves good alignment, but flicker rate increases during low-frequency driving
Solution Approach 1:
The patent applies the counterweight principle by introducing negative liquid crystal compounds that produce opposite alignment polarization effects to counterbalance the positive liquid crystal compounds. The negative liquid crystal compound acts as a counterweight to the alignment polarization generated by the positive compound, reducing net polarization variations and suppressing flicker while maintaining alignment stability.
3Object-affected harmful factors
If only negative liquid crystal compounds are used, then flicker rate is reduced, but transmittance and responsiveness deteriorate
Solution Approach 1:
The patent optimizes the compositional parameters of the liquid crystal mixture to achieve a balance between flicker suppression and optical performance. By controlling the weight ratio of positive to negative liquid crystal compounds within 9:1 to 1:9 (with negative compound at 1-40 wt%), the patent maintains sufficient transmittance and responsiveness while achieving effective flicker suppression through the composite material effect.
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
The solution effectively suppresses flicker occurrence during low-frequency driving in transverse electric field mode liquid crystal display devices without compromising responsiveness or transmittance, significantly reducing the flicker rate compared to devices using only positive or negative liquid crystal materials.
Implementation Method 1
the liquid crystal layer containing one or more types of positive liquid crystal compounds whose dielectric anisotropy is positive and one or more types of negative liquid crystal compounds whose dielectric anisotropy is negative
Implementation Method 2
A polarization change which can be caused by such spatial unevenness of the arrangement of dipoles (liquid crystal molecules) is called 'Flexo-electric Effect'
Data Source
AI summary
A liquid crystal display device (100) includes: a liquid crystal layer (42) held between a pair of substrates (10, 30), the liquid crystal layer containing one or more types of positive liquid crystal compounds whose dielectric anisotropy is positive and one or more types of negative liquid crystal compounds whose dielectric anisotropy is negative, a total content of the positive liquid crystal compounds not being smaller than a total content of the negative liquid crystal compounds; a pixel electrode (24) provided in the pair of substrates, the pixel electrode having a plurality of linear portions and a slit; and a common electrode (22) insulated from the pixel electrode, wherein the pixel electrode and the common electrode apply across the liquid crystal layer a pixel voltage of positive polarity and a pixel voltage of negative polarity alternately at a frequency lower than 60 Hz.