Liquid-Crystalline Medium for IPS Displays
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Solution Overview
Problem
In-plane switching (IPS) and fringe field switching (FFS) liquid-crystal display technologies face limitations in achieving high transmission, a good black state, and high contrast ratio due to issues with rotational viscosity, low-temperature stability, and response times, as well as the trade-offs between dielectric anisotropy, elastic constants, and operating voltage.
Innovation Solution
A liquid-crystalline medium comprising specific compounds of formulas I, II, and III, which provide positive dielectric anisotropy, high elastic constants, low rotational viscosity, and good low-temperature stability, optimizing the parameters for improved contrast and response times in IPS and FFS displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid-crystalline media with high elastic constants and suitable Δn are used to achieve good black state and low light scattering, then rotational viscosity increases and low-temperature stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid-crystalline medium by incorporating specific compounds (cyclohexane derivatives with cyanobiphenyl or fluorinated benzoic acid ester groups, pyrimidine derivatives, and terphenyl derivatives) in controlled proportions. This compositional parameter change enables simultaneous achievement of high elastic constants (for good black state) and low rotational viscosity (for low-temperature stability and fast response), resolving the technical contradiction.
2Illumination intensity
If electrode separation is increased to improve transmission, then dielectric anisotropy must be increased to maintain operating voltage, but this increases rotational viscosity and reduces low-temperature stability
Solution Approach 1:
The patent achieves the required dielectric anisotropy through specific chemical compound selection and proportioning rather than increasing electrode separation. The formulated liquid-crystalline medium provides high dielectric anisotropy values that enable maintenance of operating voltage levels even with increased electrode separation, thereby improving transmission while maintaining low-temperature stability through appropriate compositional parameters.
3Illumination intensity
If dielectric anisotropy is increased to improve transmission, then elastic constants decrease which reduces black state and reaction time
Solution Approach 1:
The patent achieves the required dielectric anisotropy through specific chemical compound selection and proportioning rather than increasing electrode separation. The formulated liquid-crystalline medium provides high dielectric anisotropy values that enable maintenance of operating voltage levels even with increased electrode separation, thereby improving transmission while maintaining low-temperature stability through appropriate compositional parameters.
4Speed
If rotational viscosity is decreased to improve response time, then low-temperature stability deteriorates
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid-crystalline medium by incorporating specific compounds (cyclohexane derivatives with cyanobiphenyl or fluorinated benzoic acid ester groups, pyrimidine derivatives, and terphenyl derivatives) in controlled proportions. This compositional parameter change enables simultaneous achievement of low rotational viscosity (for fast response times) and good low-temperature stability, resolving the technical contradiction.
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 medium achieves high elastic constants, low rotational viscosity, and good low-temperature stability, enabling fast response times and high contrast ratios, suitable for modern display applications such as mobile devices and tablets, with enhanced dielectric anisotropy and specific resistance values.
Implementation Method 1
A liquid-crystalline medium having positive dielectric anisotropy... which comprises at least one compound of the formula I, at least one compound of the formula II and at least one compound of the formula III
Implementation Method 2
Liquid-crystalline medium and electro-optical liquid-crystal display having a re-alignment layer for the re-alignment of the liquid crystals whose field has a component, crucial for the re-alignment, parallel to the liquid-crystal layer
Data Source
AI summary
The invention relates to an electro-optical liquid-crystal display having a re-alignment layer for the re-alignment of the liquid crystals whose field has a component, crucial for the re-alignment, parallel to the liquid-crystal layer, containing a liquid-crystalline medium, characterized in that it contains at least one compound of the formula (I), at least one compound of the formula (II), and at least one compound of the formula (III), in which the parameters R11 to R31, X11 and X21 have the meanings indicated in Claim 1.