Optically Anisotropic Laminate Crack Suppression
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Solution Overview
Problem
Existing laminates composed of optically anisotropic layers are prone to cracking when exposed to sudden changes in temperature, such as during a heat shock resistance test.
Innovation Solution
A laminate configuration where a first optically anisotropic layer and a second optically anisotropic layer are laminated directly or through an alignment film, with an endothermic peak temperature of 125° C. or lower, as observed by differential scanning calorimetry, to suppress the occurrence of cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If optically anisotropic layers are laminated directly or through an alignment film, then the number of attachment times is reduced and thinning is achieved, but cracks occur when exposed to sudden temperature changes
Solution Approach 1:
The patent applies parameter changes by controlling the endothermic peak temperature of the laminate to be 125°C or lower through careful selection of polymerizable compounds and liquid crystal compounds. This temperature parameter control prevents excessive thermal stress during heating processes, thereby suppressing crack formation while maintaining the direct lamination structure that reduces attachment times
Solution Approach 2:
The patent uses composite materials by combining specific polymerizable compounds (with polymerization conversion rates of 90% or higher) with liquid crystal compounds to create optically anisotropic layers with enhanced thermal stability. The composite structure of multiple optically anisotropic layers with controlled interlayer bonding also forms a composite laminate that resists crack propagation
2Manufacturing precision
If the endothermic peak temperature is increased to improve optical performance, then optical properties are enhanced, but crack occurrence increases under thermal stress
Solution Approach 1:
The patent optimizes the endothermic peak temperature parameter to be 125°C or lower, which balances optical performance requirements with thermal stress resistance. This parameter control is achieved by selecting polymerizable compounds and liquid crystal compounds with appropriate glass transition temperatures and polymerization characteristics, preventing crack formation while maintaining necessary optical properties
Solution Approach 2:
The patent applies local quality by ensuring uniform distribution of polymerizable compounds and liquid crystal compounds within each optically anisotropic layer, creating localized regions with consistent thermal and optical properties. This uniformity prevents localized stress concentration that could lead to crack initiation during temperature changes
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 laminate configuration effectively suppresses the occurrence of cracks when exposed to temperature changes, thereby enhancing the thermal stability and reliability of the laminate.
Implementation Method 1
an endothermic peak temperature of the laminate observed by differential scanning calorimetry is 125° C. or lower
Data Source
AI summary
A laminate in which the occurrence of cracks is suppressed, and a laminate with a pressure-sensitive adhesive layer, a polarizing plate, and an image display device which use the laminate. The laminate includes a first optically anisotropic layer; and a second optically anisotropic layer, the first optically anisotropic layer and the second optically anisotropic layer being laminated directly or through an alignment film, in which the first optically anisotropic layer satisfies Expression (A) nx>ny, the second optically anisotropic layer satisfies Expression (B) nx<nz, the laminate satisfies Expressions (1) 100 nm≤Re(550)≤180 nm, Expression (2) Re(450)/Re(550)<1.0, Expression (3) Re(650)/Re(550)>1.0, Expression (4)−40 nm≤Rth(550)≤70 nm, Expression (5) Rth(550)<Re(550)/2, and an endothermic peak temperature of the laminate observed by differential scanning calorimetry is 125° C. or lower.