Light Control Sheet UV Protective Layer Color Stability
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Solution Overview
Problem
Existing light control sheets with liquid crystal compounds and dichroic dyes face challenges in maintaining color stability and light resistance, particularly due to the degradation of dichroic dyes under ultraviolet and visible light exposure.
Innovation Solution
A light control sheet and device comprising a laminate structure with a light control layer containing a liquid crystal compound and a dichroic dye, sandwiched between transparent electrode layers and supported by transparent support layers. A protective layer is added on one of the support layers, absorbing light in the ultraviolet region and having specific chromaticity values to enhance light resistance and color stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a light control sheet uses a liquid crystal compound and dichroic dye to achieve transparent and opaque states, then light transmittance control is improved, but color stability deteriorates due to dichroic dye degradation under ultraviolet and visible light exposure
Solution Approach 1:
The patent introduces a protective layer as an intermediary between the light control sheet and the external environment. This protective layer specifically absorbs ultraviolet light and visible light in the 380-430 nm wavelength range, preventing these harmful wavelengths from reaching and degrading the dichroic dye in the light control layer, thereby maintaining color stability while preserving light transmittance control functionality
Solution Approach 2:
The patent converts the potentially harmful ultraviolet and visible light (380-430 nm) that would otherwise degrade the dichroic dye into a beneficial protective function. By designing the protective layer to specifically absorb these wavelengths, the harmful radiation is transformed into a shielding mechanism that protects the light control sheet's color stability
2Reliability
If the protective layer absorbs light in the ultraviolet region to protect against degradation, then light resistance is improved, but the chromaticity range becomes more restricted
Solution Approach 1:
The patent precisely controls the optical parameters of the protective layer by specifying its chromaticity values (a* between -10 to 0, b* between 0 to 15) and absorption wavelength range (360 nm or less to 410-430 nm). This parameter optimization ensures the protective layer provides adequate ultraviolet and visible light protection while maintaining chromaticity within acceptable ranges that do not significantly interfere with the overall visual appearance and functionality of the light control sheet
3Stability of the object's composition
If the laminate structure includes multiple layers with specific chromaticity values, then color stability is improved, but device complexity increases
Solution Approach 1:
The patent divides the light control device into distinct functional layers: a light control layer containing liquid crystal compound and dichroic dye for transparent/opaque state switching, transparent electrode layers for applying electric fields, transparent support layers for structural support, and a protective layer for light absorption and color stability. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall system performance
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 effectively suppresses color fading of the dichroic dye by absorbing ultraviolet light and maintains a black or near-black color in the opaque state, while ensuring high transparency in the transparent state, thus enhancing both light resistance and privacy protection.
Implementation Method 1
a protective layer positioned on a surface of one of the transparent support layers of the laminate such that the protective layer absorbs light in an absorption wavelength range including an ultraviolet region
Implementation Method 2
A change in an orientation state of a liquid crystal compound contained in the light control layer changes the light transmittance of the light control sheet, following a change in a potential difference between the transparent electrode layers
Implementation Method 3
The light control layer in the laminate includes a liquid crystal compound and a dichroic dye such that orientations of the liquid crystal compound and the dichroic dye change in response to a change in a potential difference between the transparent electrode layers
Data Source
AI summary
A light control sheet includes: a laminate having a light control layer containing a liquid crystal compound and a dichroic dye; and a first protective layer and a second protective layer that are disposed to the laminate and absorb light in an absorption wavelength range including an ultraviolet region. The laminate in an opaque state has a chromaticity a* of −15 to 15 and a chromaticity b* of −16 to 15 in a CIE1976 (L*a*b*) color system in accordance with JIS-Z-8781-4. The smallest value of the absorption wavelength range is 360 nm or less, and the upper limit of the absorption wavelength range is 410 nm to 430 nm within the visible region. The protective layers have a chromaticity a* of −10 to 0 and a chromaticity b* of 0 to 15 in a CIE1976 (L*a*b*) color system in accordance with JIS-Z-8781-4.