Cholesteric Liquid Crystal Reflection Film Side Lobe Suppression
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Solution Overview
Problem
Cholesteric liquid crystalline layers often generate side lobes, which are undesirable as they reflect light outside the intended wavelength range, reducing selective reflectivity.
Innovation Solution
A reflection film is created by laminating two cholesteric liquid crystalline layers with specific properties, where the second layer has a smaller birefringence and half or less helical pitch number than the first layer, positioned on its surfaces, to interfere and weaken side lobes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cholesteric liquid crystalline layer is used for selective reflection, then reflection properties are improved, but side lobes are generated that reflect unwanted wavelengths
Solution Approach 1:
The single cholesteric liquid crystalline layer is segmented into multiple layers with different helical pitch numbers. The first layer has a higher helical pitch number and reflects the target wavelength, while the second layer has a lower helical pitch number (half or less) and selectively suppresses side lobes without significantly affecting the main reflection peak.
Solution Approach 2:
Different regions of the reflection film have different optical properties tailored to specific functions. The first cholesteric liquid crystalline layer is optimized for main reflection with higher helical pitch number, while the second layer is optimized for side lobe suppression with lower helical pitch number and smaller birefringence, creating local quality differentiation.
2Stability of the object's composition
If the helical pitch number is increased to improve reflection bandwidth, then more side lobes are generated
Solution Approach 1:
The reflection function is segmented between two layers: the first layer with higher helical pitch number provides the main reflection bandwidth, while the second layer with lower helical pitch number (half or less) specifically targets and suppresses side lobe frequencies without compromising the main reflection bandwidth.
Solution Approach 2:
The invention uses a composite structure of two cholesteric liquid crystalline layers with different optical properties (different helical pitch numbers and birefringence values). This composite approach combines the advantages of both layers to achieve broad reflection bandwidth while suppressing side lobes.
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 configuration effectively suppresses the generation of side lobes, enhancing selective reflectivity by ensuring that only intended wavelengths are reflected, improving the performance of the film in applications like transparent screens, color filters, and decorative films.
Implementation Method 1
A layer obtained by fixing a cholesteric liquid crystalline phase (hereinafter, also referred to as a 'cholesteric liquid crystalline layer') is known as a layer having properties of selectively reflecting any one of right circularly polarized light or left circularly polarized light in a specific wavelength range
Implementation Method 2
selectively reflecting any one of right circularly polarized light or left circularly polarized light in a specific wavelength range
Implementation Method 3
a second cholesteric liquid crystalline layer which is disposed at least on one surface of the first cholesteric liquid crystalline layer and formed of a composition including a second liquid crystal compound... to interfere and weaken side lobes
Implementation Method 4
a birefringence Δn2 of the second liquid crystal compound is smaller than a birefringence Δn1 of the first liquid crystal compound
Data Source
AI summary
The invention provides a reflection film in which generation of side lobes derived from a cholesteric liquid crystalline layer is suppressed. A reflection film of the invention includes: a first cholesteric liquid crystalline layer which is formed of a composition including a first liquid crystal compound; and a second cholesteric liquid crystalline layer which is disposed at least on one surface of the first cholesteric liquid crystalline layer and formed of a composition including a second liquid crystal compound, in which a helical pitch length of the first cholesteric liquid crystalline layer is constant, a birefringence Δn2 of the second liquid crystal compound is smaller than a birefringence Δn1 of the first liquid crystal compound, and a helical pitch number of the second cholesteric liquid crystalline layer is a half or less of a helical pitch number of the first cholesteric liquid crystalline layer.