Cholesteric Optical Film for Low-Haze Polarized Eyewear
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Solution Overview
Problem
Existing optical films for polarized sunglasses struggle to achieve a high degree of polarization and low haze value while maintaining a metallic color tone, and they face issues with adhesion and durability due to the use of inorganic multilayer films and cholesteric liquid crystal layers.
Innovation Solution
An optical film comprising two or more light reflection layers with different center wavelengths of selective reflection, each having a cholesteric liquid crystal phase with opposite spiral structures, and a polarizing element layer, where the layers are laminated with a specific wavelength shift and thickness to achieve a maximum reflectance of 50% or less and a polarization degree of 90% or more, with a haze value of less than 0.5%.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a multilayer film is deposited on the surface of polarized sunglasses to impart metallic color tone and improve visibility, then the reflected light can be seen by others and glare is reduced, but sebum is difficult to be removed and the film may peel off in places exposed to moisture
Solution Approach 1:
The patent embeds the light-reflecting layer inside the support material (between the support material and polarizing element) rather than depositing it on the surface. This nesting approach protects the light-reflecting layer from environmental exposure, preventing peeling and sebum accumulation while maintaining metallic color tone and designability.
2Reliability
If a multilayer film is arranged inside the support material to improve adhesion, then the film peeling problem is solved, but the reflection performance is reduced due to refractive index difference and adhesion issues with organic polarizing elements
Solution Approach 1:
The patent changes the material parameter of the light-reflecting layer from inorganic multilayer film to cholesteric liquid crystal. This material substitution enables the light-reflecting layer to achieve both good adhesion to organic polarizing elements and high reflection performance with metallic color tone, as cholesteric liquid crystals naturally reflect circularly polarized light with high efficiency.
Solution Approach 2:
The patent uses a composite structure combining cholesteric liquid crystal with the polarizing element and support material. This composite approach leverages the unique optical properties of cholesteric liquid crystals (circularly polarized light reflection) to achieve both adhesion compatibility with organic materials and superior reflection performance.
3Illumination intensity
If a cholesteric liquid crystal layer is used to impart metallic color tone, then the reflection performance is improved and adhesion is enhanced, but the transmitted light becomes circularly polarized which conflicts with the linearly polarized light function of the polarizing element
Solution Approach 1:
The patent segments the optical film into distinct functional layers: a light-reflecting layer with cholesteric liquid crystal for metallic color tone and glare reduction, and a polarizing element layer for linearly polarized light transmission. This segmentation allows each layer to perform its specific function without interfering with the other, as the light-reflecting layer reflects external glare while the polarizing element transmits polarized light to the wearer's eyes.
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 provides an optical film with enhanced polarization and reduced haze, ensuring effective glare reduction and improved visibility without compromising designability and durability.
Implementation Method 1
The cholesteric liquid crystal is in a state where the liquid crystal molecules are spirally oriented, and has a function of selectively reflecting a circularly polarized light component in the same direction as the spiral direction of the liquid crystal molecules in a specific wavelength region depending on the length of the spiral pitch.
Implementation Method 2
the polarized sunglasses are designed to effectively absorb the light in its polarization direction, it is possible to reduce glare and improve visibility without significantly reducing the amount of light incident on the eyes.
Implementation Method 3
the reflected light on the surface of the sunglasses can be seen by others who are not wearing polarized sunglasses in metallic tones such as blue, green, and red, and due to the specific reflected light, the glare is reduced
Data Source
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AI summary
The present invention relates to an optical film (9) including an optical laminate (1) in which two or more light reflection layers having center wavelengths of reflection different from each other are laminated and a polarizing element layer (8). The two or more light reflection layers are selected from at least one light reflection layer RPRL (2, 3, 4) having a center wavelength of selective reflection in the range of 400 nm or more and 850 nm or less, in which a cholesteric liquid crystal phase with a right-handed spiral structure having right-handed circularly polarized light reflectivity is fixed, and at least one light reflection layer LPRL (2, 3, 4) having a center wavelength of selective reflection in the range of 400 nm or more and 900 nm or less, in which a cholesteric liquid crystal phase with a left-handed spiral structure having left-handed circularly polarized light reflectivity is fixed. Light reflection layer RPRL and light reflection layer LPRL (2, 3, 4) each have a center wavelength of selective reflection shifted from that of a light reflection layer adjacent to each other by an interval of 40 nm or more and 500 nm or less, and the maximum reflectance of optical laminate (1) is 50% or less.