Wavy Substrate Surface for LED Light Extraction
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Solution Overview
Problem
Existing organic LED substrates suffer from low light extraction efficiency due to total reflection at the interface between the organic layer and the translucent electrode, and mechanical waviness in glass substrates can lead to short circuits and undesirable appearance.
Innovation Solution
A substrate with a glass substrate and a scattering layer formed on its surface, featuring waviness with a wavelength greater than 50 μm and a specific roughness ratio, which enhances light scattering and prevents short circuits while maintaining a flat surface for adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a glass substrate is mechanically polished to achieve flatness, then the surface flatness is improved, but fine polishing scratches are formed on the surface which become a cause of short-circuit
Solution Approach 1:
Instead of polishing the glass substrate to remove waviness (which causes scratches), the invention inverts the approach by intentionally forming a wavy structure on the substrate surface. This wavy structure controls specular reflection to prevent mirror-like appearance while avoiding the harmful scratches caused by mechanical polishing, thus resolving the contradiction between flatness and short-circuit prevention.
Solution Approach 2:
The invention changes the surface morphology parameters by controlling the wavelength and amplitude of the wavy structure. By optimizing these parameters (wavelength greater than 50 μm, specific roughness ratio), the substrate achieves both adequate flatness for device fabrication and sufficient surface variation to prevent specular reflection and short-circuits, without requiring mechanical polishing.
2Shape
If the substrate surface is made completely flat, then the appearance is improved, but the reflective electrode is visually recognized as a mirror surface which has undesirable outward appearance
Solution Approach 1:
The invention inverts the conventional approach by not making the surface completely flat, but instead introducing controlled waviness. This wavy structure with specific parameters (wavelength > 50 μm, controlled roughness) prevents the substrate from acting as a mirror while maintaining adequate flatness, thus eliminating the harmful mirror-like reflection without sacrificing overall surface quality.
Solution Approach 2:
The invention applies local quality by creating a wavy structure with specific characteristics (wavelength and amplitude) that is optimized for controlling specular reflection. The wavy structure is distributed across the substrate surface with controlled parameters, providing local surface variation that prevents mirror effects while maintaining global flatness for device fabrication.
3Object-generated harmful factors
If a light-scattering region is provided on the substrate surface, then the reflective electrode appearance is improved, but the scattering ability may be lowered which affects light extraction efficiency
Solution Approach 1:
The invention changes the parameters of the light-scattering structure by controlling the wavelength and roughness ratio of the wavy surface. By optimizing these parameters (wavelength > 50 μm, roughness ratio within specific range), the substrate provides sufficient scattering ability to prevent mirror-like appearance while maintaining adequate light extraction efficiency, avoiding the energy loss associated with excessive scattering structures.
Solution Approach 2:
Instead of adding a separate light-scattering layer that may reduce light extraction efficiency, the invention inverts the approach by forming the wavy structure directly on the substrate surface. This integrated wavy structure provides the necessary scattering function with optimized parameters, preventing mirror effects while minimizing energy loss and maintaining high light extraction efficiency.
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 significantly improves light extraction efficiency and prevents short circuits, ensuring a long life and high effective area for the organic LED device with a superior scattering property and aesthetically pleasing appearance.
Implementation Method 1
the waviness of the surface has a wavelength Rλa of greater than 50 μm, and a ratio Ra/Rλa of waviness roughness Ra of the surface which forms waviness to the wavelength Rλa of the waviness is from 1.0×10−4 to 3.0×10−2
Data Source
AI summary
Provided is an electronic device having a long life and a large effective area. Furthermore, provided is an optical device capable of controlling specular visibility. And provided is a substrate for the optical device, which includes a scattering layer having excellent scattering properties and having a desired refractive index while retaining surface smoothness. Further, there is provided a substrate for the electronic device, which includes a substrate having first and second main surfaces facing each other and an electrode pattern formed on the first main surface of the substrate, in which the first main surface of the first and second main surfaces is a surface which forms waviness made up of curved faces, the waviness of the surface has a wavelength Rλa of greater than 50 μm and a ratio Ra/Rλa of waviness roughness Ra of the surface which forms waviness to the wavelength Rλa of the waviness is from 1.0×10−4 to 3.0×10−2.