Surface Light Emitting Device with Light Extraction Structure
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Solution Overview
Problem
Current surface light emitting devices face challenges in improving light extraction efficiency due to high refractive index differences between the light emitting layer and the light transmitting substrate, leading to significant total reflection losses, and existing solutions either increase production costs or compromise on weatherproof and waterproof properties.
Innovation Solution
A surface light emitting device configuration that includes an organic electroluminescent element with a light extraction structure part interposed between the light emitting layer and a protection substrate, featuring a recessed and protruded structure with a refractive index equal to or higher than the light transmitting substrate, and a glass protection substrate with enhanced weatherproof and waterproof properties, reducing total reflection and Fresnel losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a light transmitting substrate with high refractive index is used to improve light extraction efficiency, then light extraction efficiency is improved, but production cost increases
Solution Approach 1:
A light extraction structure part (micro-lens array or diffuser) is introduced as an intermediary component between the light emitting layer and the light transmitting substrate. This intermediary structure redirects and scatters light that would otherwise be totally reflected, enabling effective light extraction using a cost-effective standard glass substrate (refractive index 1.5) instead of expensive high refractive index glass.
2Ease of manufacture
If a plastic substrate is used as light transmitting substrate to reduce cost, then production cost is reduced, but weatherproof and waterproof properties deteriorate
Solution Approach 1:
The device is segmented into distinct functional layers: a standard glass light transmitting substrate provides structural support and weatherproof properties, while a separate light extraction structure part ( positioned between the organic EL element and the glass substrate) performs the light extraction function. This segmentation allows each component to be optimized for its specific function.
Solution Approach 2:
The light extraction structure part serves multiple functions: it extracts light from the organic EL element, interfaces with the glass substrate, and can be designed with refractive index matching properties to minimize reflection losses. This multi-functional component enables the use of standard glass substrates while maintaining high light extraction efficiency.
3Productivity
If the interface between light emitting layer and light transmitting substrate is optimized to reduce total reflection, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The light extraction structure part employs curved surfaces (micro-lenses or diffuser patterns) to redirect light paths. These curved structures are manufactured as standardized optical components that can be integrated into the device, providing effective light extraction without requiring complex custom interface structures.
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 configuration significantly enhances light extraction efficiency while maintaining cost-effectiveness and improving the device's reliability and durability by reducing total reflection and Fresnel losses, and enhancing weatherproof and waterproof properties.
Implementation Method 1
total reflection at an interface between materials having different refractive indices and light absorption caused by materials are likely to inhibit effective transmission of light to an outside as a light emission observation side
Implementation Method 2
loss caused by total reflection at the interface between the transparent electrode and the light transmitting substrate reaches about 50% of totally reflected light
Data Source
AI summary
The surface light emitting device includes an organic EL element, a protection substrate, a protection part, and a light extraction structure part. The element has a first face and a second face opposite to the first face, and emits light from the first face. The substrate has transparency for light emitted from the element, and is placed facing the first face, and has a primary surface facing the first face of the element. The protection part is placed facing the second face of the element, and constitutes a housing in combination with the substrate and accommodates the element so as to protect the element from water. The structure part is interposed between the first face of the element and the substrate, and suppresses reflection of light emitted from the element on at least one of the first face of the element and the primary surface of the substrate.