Chiral Smectic Liquid Crystal Cell for Fast Response
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Solution Overview
Problem
Liquid crystal display devices based on field-sequential color mixing require significantly faster operating speeds than traditional additive color mixing processes, especially for achieving high-resolution and continuous gray scale, while also being insensitive to driving voltage polarity and frequency.
Innovation Solution
The implementation of a liquid crystal cell using a chiral smectic liquid crystal with a helix pitch less than the thickness of the liquid crystal layer, placed between two polarizers, and subjected to a voltage source with an amplitude below the critical unwinding voltage, allowing for electro-optical responses with continuous gray scale and high frequency operation, utilizing ferroelectric or antiferroelectric liquid crystals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional nematic liquid crystals are used in field-sequential color displays, then the manufacturing complexity is reduced, but the response time is too slow to achieve the required operating speed of at least three times 60 Hz
Solution Approach 1:
The patent changes the fundamental parameter of liquid crystal response mechanism by transitioning from nematic to ferroelectric liquid crystal phase, achieving sub-millisecond response times necessary for field-sequential color operation at frequencies of 180 Hz or higher
Solution Approach 2:
The patent utilizes the phase transition properties of ferroelectric liquid crystals, which exhibit spontaneous polarization and fast switching between stable states, enabling the rapid response required for successive additive color mixing while maintaining manufacturing feasibility
2Ease of manufacture
If three color filters are used in simultaneous additive color mixing, then color reproduction is achieved, but the manufacturing process becomes very complex and expensive
Solution Approach 1:
The patent extracts and eliminates the complex three-color-filter manufacturing process by using field-sequential color mixing with a single liquid crystal cell, achieving color reproduction through temporal rather than spatial separation of color components
Solution Approach 2:
The patent employs periodic switching of the liquid crystal state synchronized with sequential illumination by red, green, and blue light sources, creating the perception of full-color images through temporal multiplexing at frequencies above the human eye's persistence threshold
3Use of energy by moving object
If three color filters are used in simultaneous additive color mixing, then color images are produced, but the light transmission is reduced requiring higher power consumption
Solution Approach 1:
The patent removes the three color filters from the optical path, eliminating their light-absorbing effect and achieving up to three times higher light transmission efficiency, which directly reduces power consumption for the same display brightness
Solution Approach 2:
The patent uses time-sequential activation of red, green, and blue light sources combined with corresponding liquid crystal state switching, allowing each wavelength to pass through the cell during its active period without being absorbed by stationary color filters, thereby maximizing overall light transmission efficiency
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 solution enables liquid crystal display cells with fast response times, hysteretic-free and non-polarity-sensitive light transmission, and high-frequency operation, suitable for applications in fast photonics devices and displays, such as modulators and filters, with reduced power consumption.
Implementation Method 1
allowing for electro-optical responses with continuous gray scale and high frequency operation
Implementation Method 2
a chiral smectic liquid crystal whose helix pitch is less than thickness of liquid crystal layer placed between two polarizers
Implementation Method 3
utilizing ferroelectric or antiferroelectric liquid crystals
Implementation Method 4
utilizing ferroelectric or antiferroelectric liquid crystals
Data Source
AI summary
The invention relates to liquid crystal display cells with fast response and continuous gray scale. The liquid crystal cell is based on a field-sequential color system (“FSC”) and comprises a chiral smectic liquid crystal whose helix pitch is less than thickness of liquid crystal layer placed between two polarizers, as well as a source of voltage applied to electrodes of the cell, wherein the amplitude of the applied voltage is less than the critical voltage amplitude of the helix unwinding. The liquid crystal has one steady state corresponding to twisted helix without applied voltage. In this case, the principal optical axis coincides with the helical axes, but deviates from steady state under the action of a driving voltage, providing thereby an electro-optical response of the display which exhibits gray scale in light transmission or reflection that is continuous, hysteretic-free and non-sensitive to the driving voltage polarity, if the steady orientation of the principle axes is parallel or perpendicular to the light polarization plane and the driving voltage frequency is between 10 Hz and 5 kHz. In embodiments with very short helix pitches, the cells may be free from selective reflection and diffraction in the visible spectral range. Different embodiments of the invention may use ferroelectric liquid crystal, ferroelectric liquid crystal, or antiferroelectric liquid crystal.