Optical Laminate UV-Blocking Substrate for Retardation Stability
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Solution Overview
Problem
Liquid crystal cured layers in optical films used in image display devices with touch panels tend to deteriorate due to outside light, leading to changes in optical properties, particularly in environments with high exposure to sunlight.
Innovation Solution
An optical layered body is developed with a substrate layer having low light transmittance at 390 nm and a liquid crystal cured layer, which maintains optical properties by using a combination of a substrate layer with a low ultraviolet transmittance and an optically anisotropic layer containing the liquid crystal cured layer, ensuring stability even after exposure to xenon lamp light for 300 hours.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a liquid crystal cured layer is used in an optical film to reduce thickness, then the optical film can achieve specific optical properties with reduced thickness, but the liquid crystal cured layer deteriorates due to outside light exposure causing changes in optical properties
Solution Approach 1:
A substrate layer is introduced as an intermediary between the external environment and the liquid crystal cured layer. This substrate layer absorbs ultraviolet light with a wavelength of 390 nm or less, acting as a protective mediator that prevents direct exposure of the liquid crystal cured layer to harmful UV radiation, thereby maintaining the stability of optical properties while allowing the use of thin optical films
Solution Approach 2:
The invention converts the harmful effect of ultraviolet light into a beneficial protective mechanism. By designing the substrate layer to specifically absorb UV light at 390 nm or less, the previously harmful radiation is transformed into a selective filtering mechanism that protects the liquid crystal cured layer while allowing visible light to pass through, thus maintaining display quality
2Reliability
If the optical film is exposed to outside light in environments with high sunlight exposure, then the liquid crystal cured layer deteriorates, but maintaining protection requires additional layers that increase device complexity
Solution Approach 1:
The substrate layer is designed to perform multiple functions simultaneously: it serves as the structural base for the optical film, provides UV protection to the liquid crystal cured layer, and maintains optical transparency for visible light. This multi-functionality achieves reliable protection against light exposure without increasing device complexity, as a single layer accomplishes what would otherwise require multiple specialized layers
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 changes in optical properties, maintaining the retardation ratios within specific limits before and after exposure, thereby enhancing the durability and performance of the optical layered body in image display devices.
Implementation Method 1
a light transmittance of the substrate layer at a wavelength of 390 nm is 1% or less
Implementation Method 2
an optically anisotropic layer containing at least one liquid crystal cured layer
Implementation Method 3
an in-plane retardation Re0(450) at a wavelength 450 nm, an in-plane retardation Re0(550) at a wavelength 550 nm
Data Source
AI summary
An optical layered body including a substrate layer, and an optically anisotropic layer containing at least one liquid crystal cured layer, wherein a light transmittance of the substrate layer at a wavelength of 390 nm is 1% or less, and an in-plane retardation Re0(450) at a wavelength 450 nm before the optical layered body is exposed to the xenon lamp, an in-plane retardation Re0(550) at a wavelength 550 nm before the optical layered body is exposed to the xenon lamp, an in-plane retardation Re300(450) at the wavelength 450 nm after the optical layered body was exposed to the xenon lamp for 300 hours, and an in-plane retardation Re300(550) at the wavelength 550 nm after the optical layered body was exposed to the xenon lamp for 300 hours satisfy the following formulae (1) and (2):0.95≤Re300(450)/Re0(450)≤1.05 (1),0.95≤Re300(550)/Re0(550)≤1.05 (2).