Superposed OLED and Reflective LCD Display Assembly
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Solution Overview
Problem
Display devices for portable objects like wristwatches face challenges in readability and energy efficiency across varying ambient lighting conditions, with transflective liquid crystal displays losing light efficiency at night and emissive displays consuming excessive power in bright conditions.
Innovation Solution
A display assembly combining a partially transparent emissive organic light-emitting diode (OLED) display with a reflective liquid crystal display that can switch between transparent and reflective modes, using a circular polarizer and quarter-wave plate to minimize stray light and optimize energy use.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a transflective liquid crystal display cell is optimised for reflection of sunlight to ensure good readability in bright ambient conditions, then readability in daytime is improved, but transmission efficiency is greatly restricted causing poor energy efficiency when backlight is activated for twilight display
Solution Approach 1:
The display system is segmented into two separate display devices: a reflective display device optimized for daytime operation and an emissive display device optimized for twilight/night operation. Each device is independently optimized for its specific operating conditions, eliminating the compromise required by transflective displays. The segmented architecture allows each display type to operate at peak efficiency in its intended environment.
2Illumination intensity
If emissive display devices supply increased current to ensure minimum readability in outdoor conditions, then readability in bright conditions is improved, but electrical power consumption increases making permanent operation difficult in portable objects
Solution Approach 1:
Different display technologies are applied to different operational contexts: the reflective display device handles bright outdoor conditions with minimal power consumption, while the emissive display device handles twilight and night conditions. This local quality assignment ensures that each display type operates in its optimal performance range without unnecessary power consumption, as the emissive device only activates when needed for low-light conditions.
3Adaptability or versatility
If a single display device attempts to compromise between reflectivity mode and transmissive mode operation, then both daytime and nighttime operation becomes possible, but the optical qualities and energy efficiency of neither mode is optimized
Solution Approach 1:
The display system dynamically switches between two display devices based on ambient lighting conditions. The reflective display device is activated for daytime operation to maximize energy efficiency, while the emissive display device is activated for twilight and night operation. This dynamic switching strategy allows the system to adapt to changing environmental conditions while maintaining optimal energy efficiency at all times, avoiding the permanent power consumption penalty of keeping an emissive display always on.
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 readable information display in both bright and dark environments with reduced energy consumption, maintaining high optical quality and readability independent of viewing angle.
Implementation Method 1
a first, at least partially transparent, emissive display device (2) located on the side of an observer (4), preferably a transparent emissive organic light-emitting diode display cell (20)
Implementation Method 2
a first, at least partially transparent, emissive display device (2) located on the side of an observer (4), preferably a transparent emissive organic light-emitting diode display cell (20)
Implementation Method 3
the second reflective display device (6), arranged underneath the first emissive display device (2), capable of switching between a transparent state, when at rest, and a reflective state, when activated
Implementation Method 4
liquid crystal display cells capable of displaying information that will be visible in daytime by exploiting the phenomenon of ambient light reflection, and which will also be visible at night by transmission using a backlight device
Data Source
AI summary
Display assembly for a portable object, wherein the display assembly includes a first, at least partially transparent, emissive display device located on the side of an observer, a second reflective display device being arranged underneath the first emissive display device, wherein said second reflective display device is capable of switching between a transparent state, in which the device does not display any information, and a reflective state, when the device is activated.