Reflective LCD Flicker Suppression via Polarity Inversion
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Solution Overview
Problem
Reflective liquid crystal display devices experience flicker issues when driven at low frequencies, such as 1 Hz or less, which affects their contrast ratio and power consumption, particularly in wearable devices where low power consumption is crucial.
Innovation Solution
A reflective liquid crystal display device with a liquid crystal layer using a nematic material with negative dielectric anisotropy and a chiral agent, aligned nearly vertically without voltage and twisted with voltage, along with a polarizing layer and retarder layers, is driven at a frame rate of 1 fps or less, with white voltage polarity inversion across the liquid crystal layer to suppress flicker.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the reflective liquid crystal display device is driven at a low frame rate of 1 fps or less to reduce power consumption, then power consumption is reduced, but flicker occurs in the display
Solution Approach 1:
The patent applies periodic action by inverting the polarity of the white display voltage for each frame when white voltage is applied over multiple frames. This periodic polarity inversion prevents the accumulation of residual voltage and resulting liquid crystal alignment changes that cause flicker, enabling stable display at low frame rates of 1 fps or less while maintaining low power consumption
Solution Approach 2:
The patent changes the voltage parameter by applying different voltages (black voltage or white voltage) across the liquid crystal layer, and specifically inverts the polarity of the white display voltage for each frame. This parameter change prevents flicker by ensuring that the liquid crystal layer does not accumulate residual voltage effects, allowing stable operation at low frame rates
2Illumination intensity
If a liquid crystal layer with nearly vertical alignment and twist alignment is used to improve contrast ratio, then contrast ratio is improved, but flicker occurs when applied to memory liquid crystal device configuration
Solution Approach 1:
The patent changes the voltage parameter by applying different voltages (black voltage or white voltage) across the liquid crystal layer, and specifically inverts the polarity of the white display voltage for each frame. This parameter change prevents flicker while maintaining the high contrast ratio performance of the liquid crystal layer with nearly vertical alignment and twist alignment
Solution Approach 2:
The patent applies periodic polarity inversion of the white display voltage for each frame, which prevents the liquid crystal layer from developing residual voltage effects that would cause flicker, thereby maintaining display stability while preserving the high contrast ratio
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 achieves a contrast ratio of 20:1 or more while reducing flicker and maintaining low power consumption, suitable for wearable devices.
Implementation Method 1
a liquid crystal layer provided between the first electrode and the second electrode, including a nematic liquid crystal material having negative dielectric anisotropy Δε and a chiral agent, having nearly vertical alignment when no voltage is applied, and having twist alignment or hybrid alignment when white voltage is applied
Implementation Method 2
a liquid crystal layer provided between the first electrode and the second electrode, including a nematic liquid crystal material having negative dielectric anisotropy Δε and a chiral agent, having nearly vertical alignment when no voltage is applied, and having twist alignment or hybrid alignment when white voltage is applied
Implementation Method 3
assuming that a natural pitch of the nematic liquid crystal material including the chiral agent is p, that a thickness of the liquid crystal layer is d, and that a birefringence of the nematic liquid crystal material is Δn
Implementation Method 4
a first substrate having a first electrode that reflects light
Implementation Method 5
a polarizing layer provided on the observer side of the second substrate and at least one retarder layer disposed between the polarizing layer and the second substrate
Data Source
AI summary
A reflective liquid crystal display device has a first substrate having a first electrode that reflects light; a second substrate having a second electrode that transmits light; a liquid crystal layer provided between the first electrode and the second electrode, including a nematic liquid crystal material having negative dielectric anisotropy Δε and a chiral agent, having nearly vertical alignment when no voltage is applied, and having twist alignment or hybrid alignment when white voltage is applied; and a polarizing layer provided on the observer side of the second substrate and at least one retarder layer disposed between the polarizing layer and the second substrate, wherein the reflective liquid crystal display device has a drive circuit that applies black voltage or white voltage across the liquid crystal layer at a frame rate of 1 fps or less, and when applying white voltage across the liquid crystal layer over a plurality of frames, the drive circuit applies the white display voltage whose polarity is inverted for each frame with respect to the potential of the second electrode, and assuming that a natural pitch of the nematic liquid crystal material including the chiral agent is p, that a thickness of the liquid crystal layer is d, and that a birefringence of the nematic liquid crystal material is Δn, 60°<β60°·d/p|<180° and 237 nm≤Δnd≤≤331 nm are established.