PDLC Display Oblique Lighting Uniformity
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Solution Overview
Problem
Existing see-through liquid crystal display devices face challenges in achieving high contrast ratio and luminance, especially on larger screens, due to light loss through diffraction and scattering, leading to non-uniform luminance and inadequate front characteristics.
Innovation Solution
A display device design featuring a polymer dispersed liquid crystal panel with a light source positioned behind and emitting light obliquely, varying the refractive index and twist angle across the panel to optimize light scattering and transmission, utilizing a chiral agent and different polymer network densities in specific regions to achieve uniform front characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a light-guiding type backlight is used to reduce display device thickness, then the profile becomes thinner, but light loss due to diffraction increases and front characteristics (contrast ratio and luminance) deteriorate
Solution Approach 1:
The patent applies different optical properties to different regions of the liquid crystal layer. Specifically, the central portion has a first optical property (higher refractive index anisotropy) while the end portions have a second optical property (lower refractive index anisotropy). This local differentiation optimizes light transmission in the central region while managing diffraction effects at the edges, thereby improving overall light efficiency without increasing device thickness.
Solution Approach 2:
The patent changes the refractive index anisotropy parameter across different regions of the liquid crystal layer. By controlling the refractive index anisotropy to be higher in the central portion and lower in the end portions, the system optimizes light transmission characteristics. This parameter variation allows the thin-profile design to maintain adequate luminance and contrast ratio by reducing light loss through strategic optical property modulation.
2Area of stationary object
If the display screen area is increased, then the display capacity improves, but light loss due to scattering increases and uniformity of luminance deteriorates
Solution Approach 1:
The patent implements local quality differentiation by setting distinct optical properties for the central portion versus the end portions of the liquid crystal layer. The central portion uses a first optical property optimized for light transmission, while the end portions use a second optical property that accounts for increased scattering paths. This regional optimization ensures uniform luminance distribution across large display areas.
Solution Approach 2:
The patent introduces spatial variation in optical properties across the liquid crystal layer thickness dimension. By controlling the refractive index anisotropy in the thickness direction and creating regional differences, the system addresses luminance uniformity issues in large-area displays. This dimensional approach to optical property control compensates for increased scattering effects in larger screens.
3Illumination intensity
If a polymer dispersed liquid crystal material is used to achieve see-through functionality, then transparency is improved, but light scattering loss increases and contrast ratio deteriorates
Solution Approach 1:
The patent optimizes the refractive index anisotropy parameter of the polymer dispersed liquid crystal material to balance transparency and light scattering loss. By carefully controlling this optical parameter, the system achieves adequate transparency for see-through functionality while minimizing excessive light scattering that would reduce contrast ratio and overall light efficiency.
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 enables a thin-profile see-through display with high contrast ratio and luminance across large areas, reducing light loss and improving uniformity by strategically controlling light interaction with the polymer dispersed liquid crystal layer.
Implementation Method 1
Application of voltage to the PDLC material changes the alignment of the liquid crystal components and produces a difference in refractive index between the liquid crystal components and the polymer network
Implementation Method 2
Light emitted from the light source and incident on the side surface of the light guide plate is reflected in the light guide plate multiple times, and then emitted from the front surface
Implementation Method 3
The liquid crystal display devices use this difference to switch between a transparent state and a scattering state
Data Source
AI summary
The display device includes a liquid crystal panel including a polymer dispersed liquid crystal (PDLC) layer and a light source, the PDLC layer containing a polymer network and liquid crystal components dispersed in the polymer network, the light source being apart from the liquid crystal panel with an air layer, and configured to emit light toward the liquid crystal panel from an oblique direction, the end portion and the central portion of the PDLC layer each having, in the scattering state, an angle dependence which changes a transmittance of light to be emitted from a front surface based on an angle at which light is incident on a back surface of the PDLC layer, with the angle dependence of the end portion being different from the angle dependence of the central portion, the light source irradiating the end portion and the central portion with light at different angles.