Switchable Window Pretilt Angle Optimization
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Solution Overview
Problem
Existing switchable window technologies using liquid crystal cells with homeotropic alignment often experience non-uniform optical states and grainy appearances during electrical switching, particularly when overdrive voltages are applied, leading to delayed uniformity in the desired optical state.
Innovation Solution
By setting a pretilt angle in the range of 84° to 86° at the alignment layers of the liquid crystal cells, the switching performance is improved, reducing unwanted inhomogeneities and allowing for faster and more reliable transitions between optical states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If homeotropic alignment with conventional pretilt angles (88°-89°) is used, then vertical alignment and viewing angle dependence are achieved, but grainy appearances and non-uniform optical states occur during electrical switching
Solution Approach 1:
The patent changes the pretilt angle parameter from the conventional range of 88°-89° to a specific range of 84°-86°. This parameter modification eliminates the grainy appearance and non-uniform optical states that occur during electrical switching, while maintaining the vertical alignment and viewing angle dependence characteristics of homeotropic alignment. The optimized pretilt angle range resolves the contradiction by improving switching uniformity without sacrificing appearance quality.
2Speed
If overdrive voltages are applied to accelerate switching, then switching speed is improved, but non-uniform optical states and grainy appearances are exacerbated
Solution Approach 1:
The patent applies preliminary anti-action by pre-setting the liquid crystal molecules at an optimized pretilt angle of 84°-86° before switching occurs. This preliminary configuration creates a more stable initial state that resists the destabilizing effects of overdrive voltages. When overdrive voltages are applied to accelerate switching, the optimized pretilt angle prevents the formation of non-uniform optical states and grainy appearances, allowing high switching speed to be achieved without sacrificing optical state uniformity.
3Reliability
If conventional alignment layers are used, then homeotropic alignment is achieved, but delayed uniformity and inhomogeneities occur during switching transitions
Solution Approach 1:
The patent modifies the alignment layer parameters to produce liquid crystal molecules with a pretilt angle of 84°-86° instead of the conventional 88°-89°. This parameter change in the alignment layer configuration enables the liquid crystal to achieve uniform optical states more quickly during switching transitions. The optimized pretilt angle reduces the stabilization time by eliminating delayed uniformity and inhomogeneities, thereby improving overall switching performance without sacrificing reliability.
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 approach enables quick and uniform switching between bright and dark states, maintaining high contrast and efficient electro-optical performance, thus addressing the issues of non-uniformity and delayed stabilization in previous technologies.
Implementation Method 1
Such liquid crystal-based devices in principle employ a change in the orientation of liquid crystal (LC) molecules between two conductive electrodes by applying an electric field which results in a change of the transmittance.
Implementation Method 2
by purposively controlling the alignment of the liquid crystalline medium in the switchable layer and in particular by specifically setting at least at one of the alignment layers, preferably at both alignment layers, a pretilt angle in the range of from 84° to 86°
Implementation Method 3
WO 2015/090506 A1 describes the use of dichroic dye-doped liquid crystalline media having a negative dielectric anisotropy in devices for regulating the passage of light.
Data Source
AI summary
The present invention relates to devices for the regulation of light transmission and in particular switchable windows. The present invention in particular relates to window elements comprising a switchable optical cell having a homeotropically aligned liquid crystal layer wherein a pretilt angle in the range of from 77° to 88° is set.