Registered Color Filter Sub-Pixel Architecture for Reflective Displays
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Solution Overview
Problem
Reflective image displays experience significant lateral displacement of light rays, leading to loss of resolution and efficiency, particularly in color displays with smaller sub-pixels, where proper alignment of light reflection sites is crucial for maintaining high-quality images.
Innovation Solution
The implementation of a registered color filter sub-pixel architecture with electrodes, electrophoretically mobile particles, and convex protrusions for total internal reflection, which redirects incident light back through the same color filter, minimizing lateral displacement and maintaining uniform particle distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional reflective image display is used, then the display structure is simple, but lateral displacement of light rays causes loss of resolution and efficiency
Solution Approach 1:
The display is divided into individual sub-pixels, each with its own light redirecting structure. This segmentation allows each sub-pixel to independently control light reflection, ensuring that light entering through one sub-pixel exits through the same sub-pixel, thereby eliminating lateral displacement and improving alignment precision without requiring complex global structures.
Solution Approach 2:
The patent introduces a vertical dimension to light control by using microlens arrays and light redirecting structures positioned at specific depths within the display. This three-dimensional arrangement of optical elements allows precise control over light paths, enabling light to be redirected back through the same sub-pixel aperture while maintaining a relatively simple overall display structure.
2Manufacturing precision
If the sub-pixel size is reduced to improve resolution, then the display resolution increases, but the tolerance to lateral displacement decreases
Solution Approach 1:
By segmenting the display into smaller sub-pixels with dedicated light redirecting structures, the patent ensures that even though individual sub-pixels are small, each one independently manages its own light reflection. This prevents lateral displacement from affecting adjacent sub-pixels, thereby maintaining high resolution while preserving sufficient tolerance to lateral displacement through localized control.
Solution Approach 2:
The patent changes the optical parameters by introducing microlens arrays with specific focal lengths and light redirecting structures with optimized geometries. These parameter changes enable efficient light redirection within each small sub-pixel, ensuring that light paths are precisely controlled even at reduced sub-pixel sizes, thus maintaining both high resolution and adequate lateral displacement tolerance.
3Productivity
If light enters through one color sub-pixel and exits through an adjacent sub-pixel, then the display structure is simple, but resolution and efficiency are lost
Solution Approach 1:
The patent segments the light reflection function to each individual sub-pixel by incorporating dedicated light redirecting structures within each sub-pixel. This ensures that light entering through a specific color sub-pixel is reflected back through the same sub-pixel, preventing color mixing and improving both reflection efficiency and color accuracy without requiring complex registration mechanisms between different color filter layers.
Solution Approach 2:
The light redirecting structures serve multiple functions: they reflect light back through the same sub-pixel, maintain uniform particle distribution in electrophoretic displays, and prevent lateral displacement. This multi-functionality improves light reflection efficiency and color accuracy without adding separate complex registration systems, thereby enhancing productivity without proportionally increasing device complexity.
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 solution effectively reduces lateral displacement, enhances light redirection efficiency, and maintains high-quality image appearance and contrast in reflective displays, particularly in color displays with smaller sub-pixels, by ensuring light is reflected back through the same color sub-pixel, thereby improving resolution and contrast.
Implementation Method 1
convex protrusions for total internal reflection, which redirects incident light back through the same color filter
Implementation Method 2
light absorbing electrophoretically mobile particles suspended in an optically clear fluid
Data Source
AI summary
A high efficiency, long life, video rate, electrophoretic display comprises fluid containing sub-pixel structures that are periodic, and aligned with a color filter array. A fluid comprising of electrophoretically mobile particles is compartmentalized at the size scale of the individual filters (one per filter) such that the particles may be moved to either allow light to be returned through the same filter back towards the viewer by total internal reflection (TIR) or conventional reflection to create a light state or to be absorbed by the particles to create a dark state. High reflectance is achieved through the use of structures that avoid ITO layers in the light path and reflecting most light, by virtue of a dual control of light by TIR and transmission to a reflector. In one embodiment the structures are in the shape of truncated pyramids.