Reflective Sheet Pitch Gradient Wavy Structure
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Solution Overview
Problem
Cholesteric liquid crystal layers with pitch gradients exhibit varying tint when viewed from different angles due to shifts in reflection wavelength with incidence angle, leading to inconsistent visual appearance.
Innovation Solution
A reflective sheet with a pitch gradient layer where the helical pitch changes in thickness direction, incorporating a wavy structure in the stripe pattern and specific optical properties to maintain consistent tint across angles, achieved through a chiral agent with changing helical twisting power and photopolymerization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a pitch gradient layer is used to broaden the reflection wavelength range, then the selective reflection bandwidth is improved, but the tint consistency across different viewing angles deteriorates
Solution Approach 1:
The patent applies parameter changes by carefully controlling the pitch gradient distribution and introducing a wavy structure with specific parameters (amplitude 1-10 μm, wavelength 10-100 μm) to modify the reflection characteristics. This resolves the contradiction by adjusting structural parameters to achieve both broad wavelength reflection and consistent tint appearance.
Solution Approach 2:
The patent introduces a wavy structure (curved morphology) in the pitch gradient layer to diffuse reflected light and reduce angle-dependent tint variations. The wavy configuration transforms the flat surface into a curved structure that scatters light more uniformly across different viewing angles, thereby maintaining tint consistency while preserving the broad reflection bandwidth.
2Illumination intensity
If a cholesteric liquid crystal layer is used to achieve high reflection brightness, then the visual appearance is improved, but the environmental burden and radio disturbance risk worsen
Solution Approach 1:
The patent replaces heavy metal particles (environmentally harmful and non-renewable) with cholesteric liquid crystal layers that are environmentally friendly and can be regenerated. This substitution eliminates the environmental burden while maintaining high reflection brightness through the optical properties of the liquid crystal structure.
3Adaptability or versatility
If elements using external light are mounted on devices to improve functionality, then the device capability is improved, but the design unity and aesthetic appearance worsen
Solution Approach 1:
The patent utilizes the color-changing and light-reflecting properties of cholesteric liquid crystal layers to create decorative surfaces that can mask or blend the appearance of functional elements like cameras and sensors. The liquid crystal layer changes its optical characteristics based on viewing angle and light conditions, allowing functional elements to be visually integrated into the overall design, thereby maintaining design unity while preserving functionality.
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 a reflective sheet with selective reflection in a wide wavelength range and minimal tint variation when viewed from different angles, ensuring consistent visual appearance and enhanced brilliance.
Implementation Method 1
a cholesteric liquid crystalline phase exhibits selective reflection having a reflection center wavelength correlating to a helical pitch of the cholesteric liquid crystalline phase
Implementation Method 2
a broadband reflection film having selective reflection in a wide wavelength range can be obtained in which the wavelength range of selective reflection becomes wider than that of a layer obtained by immobilizing a cholesteric liquid crystalline phase having a uniform helical pitch using a layer (also referred to as 'pitch gradient layer' or 'PG layer') in which a helical pitch changes in a thickness direction of the layer
Implementation Method 3
obtained by immobilizing a cholesteric liquid crystalline phase
Data Source
AI summary
Provided are a reflective sheet having selective reflection in a wide wavelength range and a small change in tint depending on angles at which light is visually recognized, a decorative sheet, and a method of manufacturing a reflective sheet, the reflective sheet including a pitch gradient layer in which a helical pitch changes in a thickness direction of the layer. The reflective sheet includes at least one cholesteric liquid crystal layer having wavelength selective reflection properties, in which at least one of the cholesteric liquid crystal layers is a pitch gradient layer in which a helical pitch changes in a thickness direction, a half-width of an integral reflection spectrum of the reflective sheet is 100 nm or longer, and in a case where a wavelength on a short wavelength side that defines the half-width is represented by λα, a wavelength on a long wavelength side that defines the half-width is represented by λβ, a center wavelength that defines the half-width is represented by λC, λ1=(λα+λC/2, and λ2=(λC+λβ)/2, the following Expressions (1) and (2) are satisfied.I−R(λ1)>I−R(λ2) Expression (1)SCE(λ1)/I−R(λ1)>SCE(λ2)/I−R(λ2) Expression (2)