Optically Anisotropic Layer Curing via UV Wavelength Shift
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Solution Overview
Problem
The optically anisotropic layer in display devices, formed by polymerizing a polymerizable liquid crystal compound, experiences incomplete curing due to UV absorption, leading to a decrease in optical characteristics when exposed to high temperatures, as the unreacted compound melts and diffuses into the adhesive layer.
Innovation Solution
A laminated body structure comprising an optically anisotropic layer, an alignment film, and an adhesive agent layer, where the optically anisotropic layer is formed with specific absorption properties and contains a photopolymerization initiator, ensuring adequate curing and maintaining optical characteristics even at high temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a UV absorbent is added to the optically anisotropic layer to protect against UV deterioration, then UV resistance is improved, but the polymerizable liquid crystal compound cannot be sufficiently cured due to UV absorption, leading to decreased optical characteristics at high temperatures
Solution Approach 1:
The patent changes the wavelength parameter of UV irradiation to 300nm or less, which corresponds to the absorption peak of the photopolymerization initiator but is absorbed less by the UV absorbent. This parameter change enables sufficient curing while maintaining UV resistance.
Solution Approach 2:
The patent introduces a photopolymerization initiator as an intermediary substance that mediates between the UV absorbent and the polymerizable liquid crystal compound. The initiator absorbs UV light at 300nm or less to generate radicals that trigger polymerization, while the UV absorbent protects against longer wavelength UV damage.
2Weight of moving object
If the optically anisotropic layer is made thinner to reduce weight and meet display device requirements, then weight reduction is achieved, but UV penetration and curing effectiveness may be compromised
Solution Approach 1:
The patent changes the UV wavelength parameter to 300nm or less, which has higher energy and better penetration capability. This enables effective curing even in thinner optically anisotropic layers, allowing weight reduction while maintaining curing effectiveness.
3Ease of manufacture
If conventional UV irradiation is used for curing, then the process is simple, but incomplete curing occurs in deep parts of the optically anisotropic layer, causing polymerizable liquid crystal compound to melt and diffuse at high temperatures
Solution Approach 1:
The patent changes the UV wavelength parameter to 300nm or less and adjusts irradiation conditions to ensure complete curing throughout the optically anisotropic layer. This maintains manufacturing simplicity while achieving thorough curing that prevents high-temperature degradation.
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 proposed laminated body structure effectively prevents the decrease in optical characteristics of the optically anisotropic layer when exposed to high temperatures, maintaining its performance and wavelength dispersion properties.
Implementation Method 1
the optically anisotropic layer is formed by polymerizing a polymerizable liquid crystal compound
Implementation Method 2
the optically anisotropic layer having a maximum absorption at a wavelength in a range of not less than 300 nm and not more than 380 nm
Implementation Method 3
an alignment film... wherein the optically anisotropic layer satisfies specific P value ratios derived from infrared total reflection absorption spectrum measurement
Data Source
AI summary
The laminated body of the present invention includes an optically anisotropic layer, an alignment film, and an adhesive agent layer which are laminated in this order. The optically anisotropic layer has maximum absorptions at a wavelength in a range of not less than 300 nm and not more than 380 nm and satisfies Formula (Y) below. “50<(1−P′/P0)×100<85 . . . (Y)” wherein: P′ represents a P value in a surface of the optically anisotropic layer on which surface the alignment film is laminated and which surface is perpendicular to a thickness direction; and P0 represents the P value of the polymerizable liquid crystal compound.