Switchable Liquid Crystal Screen for Transparent Display
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Solution Overview
Problem
Existing see-through display technologies face challenges in achieving transparency and image visibility without using strong light sources, which can cause discomfort and safety issues due to strong light projection, and often result in a trade-off between image clarity and background transmissivity.
Innovation Solution
An image display device featuring a switchable screen with a liquid crystal light modulating layer containing a chiral nematic liquid crystal phase and polymeric resin, synchronized with an image projector to project images only when the screen is in a light-scattering state, reducing the need for strong light sources and enhancing transparency and image visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the screen is in a light-scattering state for a longer proportion of time to enhance image visibility, then image clarity is improved, but background transmissivity deteriorates causing blur
Solution Approach 1:
The screen is driven to periodically switch between light-transmitting and light-scattering states using burst voltage with specific frequency (40-100 Hz) and duty ratio (0.01-0.20). This periodic switching allows the image projector to project only during light-scattering phases while maintaining high background transmissivity during light-transmitting phases, resolving the contradiction between image visibility and background clarity.
Solution Approach 2:
The screen's optical state is dynamically controlled through voltage application, transitioning between transparent and scattering states. This dynamic control enables precise timing coordination with the image projector, allowing the system to optimize both image visibility and background transmissivity by adjusting the duty ratio and frequency of the switching cycle.
2Illumination intensity
If a strong light source is used to display a clear sharp image while ensuring background transmissivity, then image visibility is improved, but user comfort deteriorates due to strong light obstruction and potential safety issues
Solution Approach 1:
The system uses periodic switching of the screen with low duty ratio (0.01-0.20) to display images only during brief light-scattering intervals. This eliminates the need for continuous strong light projection, reducing light obstruction for background viewing and minimizing safety concerns while maintaining adequate image clarity during active display periods.
Solution Approach 2:
The invention changes the operating parameters of the screen by using specific burst voltage frequencies (40-100 Hz) and duty ratios (0.01-0.20) that enable effective image display with minimal light scattering time. This parameter optimization allows clear image projection without requiring strong continuous light sources, thereby improving user comfort and safety.
3Ease of manufacture
If conventional liquid crystal materials are used, then ease of manufacture is improved, but performance deteriorates due to large temperature dependence and viewing angle dependence
Solution Approach 1:
The invention uses a composite liquid crystal system comprising chiral nematic liquid crystal molecules with positive dielectric anisotropy combined with polymeric resin in a phase-separated structure. This composite material provides both manufacturability and superior optical stability with minimal temperature and viewing angle dependence, while maintaining the switchable light-transmitting/light-scattering functionality.
Solution Approach 2:
The invention changes the material parameters by selecting chiral nematic liquid crystal with positive dielectric anisotropy and specific chiral pitch (0.3-3 μm), combined with polymeric resin. This material parameter selection achieves optimal balance between manufacturability and optical stability, eliminating the drawbacks of conventional liquid crystal materials.
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 allows for clear image visibility and high background transmissivity without the use of strong light sources, improving user comfort and safety by synchronizing image projection with the screen's light-scattering state, thereby achieving desirable visibility and transparency simultaneously.
Implementation Method 1
a liquid crystal light modulating layer provided between the pair of substrates having an electrode, the liquid crystal light modulating layer containing a complex that contains a chiral nematic liquid crystal phase of positive dielectric constant anisotropy, and a solid phase of polymeric resin, wherein the screen is in a light-transmitting state under no applied voltage, and is switchable to a light-scattering state in response to applied voltage
Implementation Method 2
the liquid crystal light modulating layer containing a complex that contains a chiral nematic liquid crystal phase of positive dielectric constant anisotropy
Implementation Method 3
a solid phase of polymeric resin
Data Source
Figure 1~2
Figure 3(a)~4(c)
Figure 5(a)~6
AI summary
An image display device is provided that can satisfy both transparency of a non-displaying portion and visibility of a projected image. The screen of and the image projector of the image display device are synchronized such that the image projector projects an image on a part of the screen or on the whole screen when the screen is in a light-scattering state, and projects no image when the screen is in a light-transmitting state. The screen is driven to periodically switch between a light-transmitting state and a light-scattering state at a switching frequency of 40 Hz to 100 Hz and a periodic switching duty ratio of 0.01 to 0.20.