Flexible Front Light System for Reflective Displays
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Solution Overview
Problem
Existing front lighting systems for reflective displays suffer from non-uniform lighting, are prone to defects from scratches or dirt, and require complex prism structures, making them unsuitable for flexible applications.
Innovation Solution
A front light system comprising light emitting sources sandwiched between a cathode and an anode, optionally with a light shield film, built on a thin and flexible substrate, using materials like LEDs or OLEDs, which provides uniform and efficient lighting suitable for flexible reflective displays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a light guide film with total internal reflection is used, then light can be guided along the display, but light intensity falls off rapidly away from the source
Solution Approach 1:
The patent extracts the light scattering function from the light guide film itself and places discrete light scattering elements at specific locations. This allows the light guide to maintain its guiding function while adding controlled scattering points to redistribute light uniformly, eliminating the need for complex prism structures throughout the entire film.
Solution Approach 2:
The patent introduces light scattering elements as intermediary components between the light source and the display surface. These elements act as mediators that redirect light from areas of high intensity to areas of low intensity, achieving uniform illumination without requiring the light guide film itself to be structurally complex.
2Illumination intensity
If a light scattering structure is used to distribute light, then lighting uniformity improves, but scratches and dirt in the light guide film create visible defects
Solution Approach 1:
The patent extracts the light scattering function from the bulk light guide material and concentrates it in discrete, removable light scattering elements. This separation allows the light guide film to remain smooth and defect-free while the scattering function is performed by dedicated elements that can be independently managed.
Solution Approach 2:
The patent applies light scattering only at specific locations where light scattering elements are positioned, rather than throughout the entire light guide film. This localized approach maintains uniform lighting where needed while keeping the rest of the light guide surface smooth and resistant to showing defects.
3Length of moving object
If a thin light guide film is used for flexible displays, then flexibility is achieved, but lighting uniformity deteriorates
Solution Approach 1:
The patent introduces light scattering elements as intermediary components that compensate for the reduced light redistribution capability of thin films. These elements act as localized light redistribution centers that maintain uniform illumination even when the overall film thickness is reduced for flexibility.
Solution Approach 2:
The patent changes the lighting system from relying on the inherent thickness and refractive index properties of the light guide film to using discrete light scattering elements with controllable parameters. This allows uniform lighting to be achieved through the positioning and optical properties of scattering elements rather than film thickness.
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 achieves satisfactory lighting uniformity with low power requirements, is cost-effective, and is suitable for keymat applications, enhancing the functionality of flexible reflective displays while minimizing defects.
Implementation Method 1
one or more light emitting sources each of which is sandwiched between a cathode and an anode
Implementation Method 2
the light is guided within the film by total internal reflection of the surface along the light guide film
Implementation Method 3
Part of the surface of the light guide has a light scattering structure which causes light inside the light guide film to be scattered out of the film
Data Source
AI summary
The present invention relates to a front light system which can be built with thin film light emitting diodes (LEDs), such as organic light emitting diodes (OLEDs) or electro-luminescent light emitting diodes. The front light system may be built on a thin and flexible substrate and can generate lighting of satisfactory uniformity and with high efficiency. The system also can potentially be inexpensive. The front light system of the present invention is particularly suitable for keymat applications wherein a flexible reflective display on top of a touch sensitive surface or device, is used as an output device.