Organic EL Display Polarization Separation Layer for Oblique Light Leakage
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Solution Overview
Problem
Organic EL image display devices face issues with reduced brightness due to the visible light blocking black matrix and blurring caused by the cholesteric liquid crystal layer, especially when viewed obliquely, due to light leakage and external light reflection.
Innovation Solution
Incorporating a polarization separation layer with a cholesteric liquid crystalline phase and a positive C region-containing layer between the organic electroluminescent layer and the circularly polarizing plate, which includes a visible light transmission region and polarization separation regions that reflect and transmit light of specific polarization states, respectively, to enhance light utilization and reduce blurring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a visible light blocking black matrix is provided between the organic electroluminescent layer and the circularly polarizing plate, then light leakage and blurring are reduced, but brightness is reduced
Solution Approach 1:
The black matrix is divided into multiple segments corresponding to different sub-pixels (red, green, blue regions). Each segment is positioned to block light leakage from specific adjacent sub-pixels while allowing light from the corresponding sub-pixel to pass through. This segmentation approach reduces light leakage and blurring without blocking all light, thereby maintaining brightness.
2Illumination intensity
If a cholesteric liquid crystal layer is arranged without a visible light blocking layer, then brightness is improved, but blurring is observed in the image
Solution Approach 1:
The black matrix is designed with different optical properties in different regions. The regions corresponding to sub-pixel boundaries have light-blocking properties to prevent blurring, while the central regions maintain high light transmission. This local differentiation of optical properties allows the system to achieve both high brightness and clear images without requiring a complete visible light blocking layer.
3Loss of energy
If the polarization separation layer reflects light of one polarization state, then light utilization efficiency is improved, but light leakage at oblique observation occurs
Solution Approach 1:
A phase compensation layer is introduced as an intermediary between the polarization separation layer and the circularly polarizing plate. This layer has specific optical compensation properties that correct the phase differences caused by oblique light passing through the cholesteric liquid crystal layer. By compensating for these phase differences, the phase compensation layer prevents light leakage at oblique observation while maintaining the high light utilization efficiency of the polarization separation layer.
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 results in an organic EL image display device with improved brightness and reduced light leakage and blurring when viewed obliquely, by optimizing the optical properties of the cholesteric liquid crystal layer and the positive C region-containing layer.
Implementation Method 1
the polarization separation region includes a layer formed by immobilizing a cholesteric liquid crystalline phase, and the polarization separation region reflects light of one polarization state in light emitted from the organic electroluminescent layer, and transmits light of another polarization state
Implementation Method 2
a phase compensation layer that functions as a refractive index ellipsoid having almost no refractive index difference in an in-plane direction and having a refractive index in a thickness direction different from a refractive index in the in-plane direction
Data Source
AI summary
The present invention provides an organic EL image display device including a light emitting element substrate, and a circularly polarizing plate, in which the light emitting element substrate includes a reflecting layer and an organic electroluminescent layer on the reflecting layer, the reflecting layer, the organic electroluminescent layer, and the circularly polarizing plate are arranged in this order, a polarization separation layer is provided between the organic electroluminescent layer and the circularly polarizing plate, the polarization separation layer includes a polarization separation region that reflects light of one polarization state in light emitted from the organic electroluminescent layer, and transmits light of another polarization state, and a visible light transmission region, the polarization separation region is formed of a layer formed by immobilizing a cholesteric liquid crystalline phase, and a positive C region-containing layer is provided between the organic electroluminescent layer and the circularly polarizing plate. The organic EL image display device according to the present invention has high brightness and little light leakage and blurring at the time of oblique observation.