In-Cell Phase Difference Layer for Photo-Luminescent LCD Contrast
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Solution Overview
Problem
Photo-luminescent liquid crystal displays (LCDs) face challenges in achieving high contrast ratios and display characteristics due to the scattering characteristics of light emitting elements, leading to deteriorated performance compared to LCDs using color filters.
Innovation Solution
The implementation of a liquid crystal display structure that includes a color conversion layer with a light emitting element, a first phase difference layer with specific refractive indices and retardation values between the liquid crystal layer and the polarizing layer, and a second phase difference layer with specific refractive indices and retardation values between the light source and the lower substrate, optimizing the refractive index relationships and retardation values to enhance contrast ratio and display characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a color filter is used to display color, then color display is achieved, but light absorption increases and photo-efficiency decreases
Solution Approach 1:
The patent changes the fundamental mechanism from light absorption (color filter) to light emission (photo-luminescent material). By using quantum dots or phosphors that emit light when excited by a blue light source, the system achieves color display without absorbing significant light, thereby improving photo-efficiency and reducing energy loss.
2Reliability
If a polarizing plate is disposed on the light emitting element, then polarization control is achieved, but contrast ratio deteriorates due to scattering characteristics
Solution Approach 1:
The patent introduces a scattering layer as an intermediary between the light emitting element and the polarizing plate. This scattering layer diffuses the scattered light from the quantum dots or phosphors, enabling effective interaction with the polarizing plate and improving contrast ratio while maintaining the benefits of photo-luminescent color display.
3Illumination intensity
If conventional LCD structure is used with photo-luminescent elements, then color display without color filter is achieved, but contrast ratio and display characteristics deteriorate
Solution Approach 1:
The patent creates a composite structure combining photo-luminescent materials (quantum dots or phosphors) with a scattering layer and polarizing plate. This composite approach integrates the high photo-efficiency of photo-luminescent elements with the contrast enhancement capabilities of the scattering layer and polarizer, achieving both improved photo-efficiency and contrast ratio simultaneously.
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 improves the contrast ratio and display characteristics of photo-luminescent LCDs by reducing light leakage and unnecessary light emission, thereby increasing photo-efficiency and maintaining high color purity and viewing angle characteristics.
Implementation Method 1
the first phase difference layer has a refractive index satisfying Inequality 1 and the second phase difference layer has refractive indexes satisfying Inequality 2
Implementation Method 2
a color conversion layer on the liquid crystal layer, a first polarizing layer and a first phase difference layer between the liquid crystal layer and the color conversion layer
Data Source
AI summary
A liquid crystal display includes a lower substrate and an upper substrate facing each other, a liquid crystal layer disposed between the lower substrate and the upper substrate, a color conversion layer disposed on the liquid crystal layer, a first polarizing layer and a first phase difference layer disposed between the liquid crystal layer and the color conversion layer, and a second polarizing layer and a second phase difference layer disposed between a light source and the lower substrate, wherein the first phase difference layer has a refractive index satisfying Inequality 1 and the second phase difference layer has refractive indexes satisfying Inequality 2.nx1≥ny1≥nz1 [Inequality 1]nx2>nz2>ny2 [Inequality 2]In Inequalities 1 and 2, nx1, nx2, ny1, ny2, nz1, and nz2 are the same in the detailed description.