Organic EL Panel Substrate Refractive Index Anisotropy Control
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Solution Overview
Problem
Organic EL panels using resin substrates face issues with refractive index anisotropy leading to color gaps and coloring due to wavelength dependence, particularly when viewed from oblique angles, as existing solutions like cyclic olefin thermoplastic resins do not effectively control thickness direction retardation.
Innovation Solution
The development of organic EL panel translucent substrates that are either substantially optically isotropic in both in-plane and thickness directions or have controlled refractive index anisotropy in these directions, utilizing a combination of negative and positive birefringent polymers through lamination, mixture, random copolymerization, block copolymerization, or graft copolymerization to cancel out birefringence and refractive index anisotropy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a resin film is used as the translucent substrate instead of sheet glass, then the substrate can be bent easily and is unbreakable, but refractive index anisotropy causes color gaps and coloring when viewed from oblique angles
Solution Approach 1:
The patent changes the optical parameters of the resin substrate by controlling its refractive index anisotropy. Specifically, it uses resins with specific in-plane retardation values (Rs) and thickness direction retardation values (Rth) to compensate for the natural birefringence of resin materials, thereby reducing color gaps and coloring when viewed from oblique angles while maintaining the flexibility and unbreakability of resin substrates
Solution Approach 2:
The patent employs composite material strategies by combining resin substrates with specific optical properties. It uses combinations of different resin materials (e.g., PEN, PET, PES, PMMA, PC, norbornene resin) with complementary refractive index characteristics to create a substrate that achieves both mechanical flexibility and optimal optical isotropy, effectively canceling out harmful birefringence effects
2Manufacturing precision
If cyclic olefin thermoplastic resin is used to reduce in-plane retardation, then in-plane isotropy is improved, but thickness direction retardation is not controlled and color gaps still occur
Solution Approach 1:
The patent extends the parameter control approach to include both in-plane retardation (Rs) and thickness direction retardation (Rth). It specifies that while in-plane retardation should be reduced (Rs ≤ 100 nm), the thickness direction retardation must be controlled within specific ranges (5 nm ≤ Rth ≤ 50 nm or -50 nm ≤ Rth ≤ 5 nm) to simultaneously achieve in-plane isotropy and control oblique viewing color gaps
Solution Approach 2:
The patent addresses the limitation of prior art by adding control in the thickness direction dimension. While previous solutions only controlled in-plane retardation, this invention introduces control of thickness direction retardation as an additional dimensional parameter, thereby achieving comprehensive optical isotropy in both in-plane and thickness directions to eliminate color gaps from all viewing angles
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
This approach effectively reduces or prevents color gaps and coloring from any angle by ensuring the organic EL panel remains optically isotropic, improving the viewing angle dependence and wavelength stability of the substrate.
Implementation Method 1
the substrate has refractive index anisotropy in at least one of its in-plane direction and thickness direction, and when the substrate is used for an organic EL panel, the whole organic EL panel becomes substantially optically isotropic
Data Source
AI summary
Disclosed is an organic EL panel translucent substrate that can prevent or reduce the color gap/coloring of an organic EL panel. In order to achieve the above object, organic EL panel translucent substrate 201 is formed of resins 203 and 204 and is substantially optically isotropic in its in-plane direction and thickness direction.