Grating Light Guide for Electrophoretic Display Color Mode
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Solution Overview
Problem
Conventional electrophoretic display devices can only exhibit black-white images and lack the ability to switch between black-white and color modes, with the addition of color filters significantly reducing brightness due to light absorption by pigments or dyes.
Innovation Solution
A light guide with a light-emitting surface featuring multiple gratings with different orientations and pitches, which selectively transmits and blocks specific wavelength ranges of light to enable an electrophoretic display apparatus to switch between black-white and color modes without the need for conventional color filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If color filters with pigment or dye are added to conventional electrophoretic display devices to provide colorful images, then color display capability is improved, but brightness is significantly decreased due to light absorption
Solution Approach 1:
The patent replaces the conventional color filter system (based on light absorption by pigments/dyes) with a diffraction grating system that separates wavelengths through diffraction and interference. The grating structure directs different wavelengths to different sub-pixels without absorbing light, thereby maintaining brightness while achieving color display.
Solution Approach 2:
The patent changes the wavelength separation mechanism from absorption-based (color filters) to diffraction-based (gratings). By adjusting the grating period and orientation, different wavelengths are directed to appropriate sub-pixels, achieving color display without the brightness penalty of absorption.
2Ease of manufacture
If conventional electrophoretic display devices use color filters to display color images, then color mode is achieved, but the ability to switch between black-white mode and color mode is lost
Solution Approach 1:
The diffraction grating structure serves multiple functions: it enables color display by separating wavelengths to different sub-pixels, and it allows black-white mode operation by directing all wavelengths uniformly when needed. This single structure provides both color and monochrome display capabilities, enabling mode switching without requiring separate color filter systems.
3Ease of manufacture
If color filters are added to electrophoretic display devices, then color images can be displayed, but device complexity increases
Solution Approach 1:
The patent merges the wavelength separation function and the color display function into a single diffraction grating structure integrated with the display panel. Instead of adding separate color filters for each sub-pixel, the grating pattern across the entire display area performs wavelength routing, simplifying the overall structure while achieving color display.
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 allows for the display of color images without reducing brightness, as the light guide's gratings effectively transmit desired wavelengths to sub-pixels, enabling the electrophoretic display apparatus to operate in both color and black-white modes.
Implementation Method 1
The light-emitting surface includes a first region having a plurality of gratings spaced apart from each other by a spacing interval. Each of the gratings has a respective pre-determined direction and includes a plurality of prisms extending in the respective pre-determined direction.
Implementation Method 2
Each of the gratings has a respective pre-determined direction and includes a plurality of prisms extending in the respective pre-determined direction. The gratings of the first region cooperate together to transmit a light having a wavelength in a first wavelength range, and to block a light having a wavelength in another wavelength range.
Data Source
AI summary
Disclosed herein is a light guide, which includes a light-receiving surface and a light-emitting surface. The light-emitting surface includes a plurality of gratings spaced apart from each other by a spacing interval. Each grating has a number of prisms extending in a predetermined direction. The predetermined direction of at least one grating is different from that of another grating. These gratings cooperate together to allow light in a wavelength range to transmit the gratings, and to restrict light in another wavelength range to transmit the gratings. An electrophoretic display apparatus switchable between black-white mode and color mode is disclosed as well.