Circularly Polarizing Plate for Reducing Tint Changes in Bent Organic EL Displays
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Solution Overview
Problem
Conventional organic electroluminescent display devices experience significant changes in tint when bent, particularly due to the application of forces on circularly polarizing plates, which affect their optical properties and visibility.
Innovation Solution
The implementation of a circularly polarizing plate configuration with a linear polarizer, a λ/4 plate, and a λ/2 plate, where the λ/4 plate exhibits reverse wavelength dispersibility, and at least one of these plates is formed using a liquid crystal compound, along with a positive C-plate and specific adhesion layers to manage the absorption axis and elasticity, reducing tint changes in bent portions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a circularly polarizing plate is used to suppress external light reflection, then visibility is improved, but the optical properties change when bent with small curvature diameter
Solution Approach 1:
The patent changes the orientation parameter of the linear polarizer's absorption axis relative to the bending direction. By setting the absorption axis at specific angles (0°±30° or 90°±30°) with respect to the ridge line extension direction, the patent optimizes the configuration to minimize optical property changes during bending while maintaining visibility enhancement.
2Stability of the object's composition
If the phase difference film is adjusted to reduce tint change, then optical stability is improved, but further improvement in visibility and tint consistency is still required
Solution Approach 1:
The patent employs a composite circularly polarizing plate structure consisting of a linear polarizer layer and a phase difference layer (λ/4 plate). This composite configuration combines the light-blocking function of the linear polarizer with the phase modulation function of the phase difference layer, achieving both improved visibility and reduced tint change during bending.
Solution Approach 2:
The patent introduces a new parameter - the angle between the absorption axis and the ridge line extension direction - and optimizes it to specific ranges (0°±30° or 90°±30°). This parameter optimization enables further improvement in visibility and tint consistency beyond what was achieved by previous phase difference film adjustments alone.
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 configuration significantly reduces tint changes in bent portions of the organic EL display device, enhancing visibility and durability while maintaining optical performance even at small curvature diameters.
Implementation Method 1
a linear polarizer
Implementation Method 2
a phase difference layer functioning as a λ/4 plate
Implementation Method 3
at least one of the λ/2 plate or the λ/4 plate is a layer formed by using a liquid crystal compound
Data Source
AI summary
An organic EL display device is provided in which a change in tint is reduced in a bent portion. This organic EL display device is an organic electroluminescent display device including, from a viewing side, a circularly polarizing plate, a first adhesion layer, and a bendable organic electroluminescent display panel, in which the circularly polarizing plate includes, from the viewing side, a linear polarizer, a second adhesion layer, and a phase difference layer functioning as a λ/4 plate, a complex modulus of elasticity of the first adhesion layer is 2.50×105 Pa or less, the first adhesion layer is thicker than the second adhesion layer, and an absorption axis of the linear polarizer is positioned at an angle of 0°±30° or 90°±30° with respect to an extension direction of a ridge line formed in a case where the organic electroluminescent display device is bent.