Organic Dichroic Dye Polarizing Plate for Thin Organic EL Displays
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Solution Overview
Problem
Iodine-PVA polarizing plates used in organic EL image displaying devices face issues such as iodine sublimation, denaturation, color change, warpage, and difficulty in forming thin films, limiting their application in devices requiring reduced profiles and high heat resistance.
Innovation Solution
A polarizing plate with a substrate and a polarizer having a dichroic dye-oriented layer of 5 μm or less, exhibiting high absorbance in the absorption axis direction and low absorbance in the transmission axis direction, utilizing organic dyes and polymerizable liquid crystal compounds, specifically smectic liquid crystal phases, and showing Bragg peaks in X-ray diffraction, combined with a ¼ wavelength plate for circular polarization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If iodine concentration is reduced to lower absorbance, then light absorption from organic EL element is reduced, but iodine sublimates and denatures causing color change and warpage
Solution Approach 1:
The patent changes the chemical composition parameters by replacing iodine with organic dichroic dyes (azo compounds, triphenylmethane compounds, etc.) and adjusts the polymer matrix composition using polymerizable liquid crystal compounds. This parameter change allows achieving low absorbance (A2 ≤ 0.15) while maintaining high heat resistance through the stable molecular structure of organic dyes and the rigid polymer matrix, eliminating iodine sublimation issues.
Solution Approach 2:
The patent creates a composite polarizing layer combining organic dichroic dyes with polymerizable liquid crystal compounds (smectic phase). This composite structure provides both the light absorption properties needed for polarization and the thermal stability of the polymer matrix, preventing warpage while maintaining optical performance. The composite material approach allows tuning of both optical and mechanical properties simultaneously.
2Length of stationary object
If iodine-PVA polarizing plate is made thinner to reduce profile, then device thickness is reduced, but iodine sublimation and warpage become more severe
Solution Approach 1:
The patent changes the material composition to organic dyes dispersed in a polymerizable liquid crystal matrix, which maintains structural integrity at thin dimensions. The polymer matrix provides mechanical strength and thermal stability even when the film thickness is reduced to 5 μm or less, preventing the warpage and sublimation issues that plague thinner iodine-PVA plates.
Solution Approach 2:
The patent replaces the unstable iodine-PVA system with a more stable organic dye-polymer composite that can be made thinner without sacrificing reliability. The organic dye molecules are covalently bonded or strongly associated with the polymer matrix, creating a stable structure that can be manufactured as a thin film without the sublimation and warpage problems of iodine-based systems.
3Manufacturing precision
If iodine concentration is increased to improve polarizing performance, then light absorbing selectivity is improved, but absorbance in transmission axis increases and heat resistance decreases
Solution Approach 1:
The patent achieves high light absorbing selectivity by orienting the dichroic dye molecules in a specific direction within the polymer matrix. The dye molecules are aligned during the stretching process to create anisotropic absorption properties, allowing strong absorption in the absorption axis direction while maintaining high transmission in the perpendicular direction. This local orientation of molecular dipoles provides selective light absorption without requiring high dye concentration.
Solution Approach 2:
The composite structure of organic dichroic dyes in a polymerizable liquid crystal matrix allows independent optimization of optical and thermal properties. The organic dyes provide the polarization function with high selectivity, while the polymer matrix provides structural stability and heat resistance, preventing the trade-off between polarizing performance and heat resistance that limits iodine-PVA systems.
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 polarizing plates with high light absorbing selectivity and heat resistance even in thin film form, addressing the limitations of iodine-PVA plates by maintaining performance and preventing warpage under heat stress.
Implementation Method 1
a polarizing layer having a thickness of 5 μm or less in which a dichroic dye is oriented, and an absorbance in the absorption axis direction (A1) of the polarizer at a wavelength of 380 to 760 nm is 0.3 or more and 1.5 or less, and an absorbance in a transmission axis direction (A2) is 0.001 or more and 0.15 or less
Implementation Method 2
the polarizing layer comprises a polymer of a polymerizable liquid crystal compound. wherein the polymerizable liquid crystal compound is a compound exhibiting a smectic liquid crystal phase
Implementation Method 3
the polarizer exhibits a Bragg peak in X-ray diffraction measurement
Implementation Method 4
a birefringence of the 1⁄4 wavelength plate to light having a wavelength of 450 nm, a birefringence to light having a wavelength of 550 nm, and a birefringence to light having a wavelength of 650 nm have reverse wavelength dispersibility
Data Source
AI summary
A polarizing plate including a substrate and a polarizer is provided. The polarizer has a polarizing layer having a thickness of 5 μm or less in which a dichroic dye is oriented. The absorbance in the absorption axis direction (A1) of the polarizer at a wavelength of 380 to 760 nm is 0.3 or more and 1.5 or less, and the absorbance in the transmission axis direction (A2) is 0.001 or more and 0.15 or less.