Organic EL Display Optical Stack Retardation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current organic electroluminescence (organic EL) display devices face issues with reduced contrast and background reflections due to internal light reflections, particularly when viewed from oblique angles, and existing solutions for polarizing plates are cumbersome and prone to quality degradation, misalignment, and increased costs.
Innovation Solution
An organic EL display device configuration incorporating a polarizer layer, a λ/2 plate, and a λ/4 plate, where the in-plane retardation of the λ/4 plate is between 115 and 155 nm, and the λ/2 plate's retardation is twice that of the λ/4 plate, with specific angle alignments and using discotic or rod-like liquid crystal compounds to enhance viewing angle characteristics and productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transparent conductive material having a high refractive index (e.g., ITO) and metal materials having high reflectance are used in the organic EL display device, then the display performance is improved, but external light is reflected at the interfaces of the layers, causing reduction of contrast and background reflections
Solution Approach 1:
A circular polarizing plate is introduced as an intermediary component between the viewer and the display. This plate converts linearly polarized light from the display into circularly polarized light, allowing light to pass through the display interfaces without being reflected back to the viewer, thereby eliminating background reflections while maintaining display brightness
Solution Approach 2:
The optical properties of the display system are changed by introducing materials with specific optical anisotropy (retardation plates with specific Re and Rth values). By controlling the retardation parameters and orientation angles of the polarizing components, the system transforms the polarization state of light to prevent harmful reflections
2Object-affected harmful factors
If absorption type linear polarizing plates and circular polarizing plates made from λ/4 plates are used to inhibit external light reflection, then background reflections are reduced, but the production process becomes cumbersome and quality degradation occurs due to chip cutting and sticking
Solution Approach 1:
The patent combines multiple optical functions (polarization, retardation, and circular polarization conversion) into a single integrated optical stack structure. This unified design eliminates the need for separate chip cutting and sticking processes, as the entire optical assembly can be manufactured as one continuous component, thereby simplifying production while maintaining the ability to reduce background reflections
3Adaptability or versatility
If the slow axis of the λ/4 plate is set at an angle neither parallel nor orthogonal to the absorption axis of the polarizing plate, then circular polarizing function is achieved, but the production process requires cutting and sticking chips which reduces productivity and increases cost
Solution Approach 1:
The patent transitions from a two-dimensional chip assembly approach to a continuous film-based optical stack. By using continuously formed retardation plates with controlled optical axes throughout the entire film area, the system achieves circular polarizing function without requiring cutting and sticking operations, thereby maintaining productivity while enabling versatile optical functionality
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 effectively reduces background reflections across all viewing angles, improving display performance and productivity while maintaining durability.
Implementation Method 1
The λ/4 plate or λ/2 plate is required that the slow axis thereof is set at an angle which is neither parallel nor orthogonal to the absorption axis of the polarizing plate. Most of the λ/4 plates or λ/2 plates currently used are retardation plates which exhibit optical anisotropy by stretching a polymer film
Implementation Method 2
a proposal of using an absorption type linear polarizing plate and a circular polarizing plate made from a λ/4 plate
Implementation Method 3
using discotic or rod-like liquid crystal compounds to enhance viewing angle characteristics and productivity
Implementation Method 4
a proposal of using an absorption type linear polarizing plate
Data Source
AI summary
An organic EL display device includes at least a polarizer layer, a λ/2 plate, a λ/4 plate and an organic EL panel in this order, and an in-plane retardation Re2(550) of the λ/4 plate at 550 nm satisfies 115≦Re2(550)≦155, and an in-plane retardation Re1(550) of the λ/2 plate at 550 nm satisfies Re1(550)=2×Re2(550)±50 nm.