OLED Cathode Mask Layout for Under-Screen Imaging Transmittance
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Solution Overview
Problem
Existing OLED panels face challenges in achieving high transmittance in imaging areas due to the design of top-emitting devices, where factors such as polyimide substrates, thin film transistor metal traces, and emissive layer cathodes affect light transmission, leading to reduced screen ratio and increased complexity in manufacturing.
Innovation Solution
A mask plate group comprising multiple mask plates with specific opening areas is used to perform sequential evaporation processes, allowing for varying cathode thicknesses across different areas of the OLED panel, including a precision mask area for the imaging area, to enhance transmittance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the cathode thickness is reduced to increase transmittance in the imaging area, then the light transmission performance is improved, but the OLED device efficiency is significantly affected
Solution Approach 1:
The patent applies local quality by differentiating the cathode structure into two regions: the imaging area with reduced cathode thickness for high transmittance, and the non-imaging area with standard cathode thickness for normal emission performance. This is achieved through the second mask plate with a special-shaped opening that covers only the non-imaging area during selective evaporation, allowing localized optimization without compromising overall device function.
Solution Approach 2:
The patent segments the cathode evaporation process into multiple steps using different mask plates. The first mask plate covers the entire substrate for initial cathode formation, the second mask plate selectively covers the non-imaging area for additional cathode deposition, and the third mask plate precisely defines the imaging area boundaries. This segmentation enables precise control of cathode thickness distribution to resolve the transmittance-efficiency contradiction.
2Ease of manufacture
If a single mask plate is used for cathode evaporation, then the manufacturing process is simple, but it cannot achieve varying cathode thicknesses in different areas
Solution Approach 1:
The patent segments the mask plate system into three distinct mask plates, each with specific opening patterns corresponding to different evaporation stages. This segmentation allows precise control of cathode thickness in different areas while maintaining a systematic and manageable manufacturing process through sequential evaporation steps.
Solution Approach 2:
The patent employs preliminary action by using the first mask plate to pre-form a uniform cathode layer across the entire substrate before applying the second mask plate for selective thickening in the non-imaging area. This preliminary uniform deposition simplifies subsequent selective evaporation steps and ensures baseline coverage before localized modification.
3Illumination intensity
If the cathode thickness is uniformly reduced across the entire display area, then transmittance is improved, but the light-emitting efficiency of the OLED device is significantly impacted
Solution Approach 1:
The patent implements local quality by creating spatial variation in cathode thickness: the imaging area has reduced cathode thickness (50-150 nm) for high transmittance, while the non-imaging area maintains standard cathode thickness (150-250 nm) for adequate emission. This is achieved through the second mask plate that selectively deposits additional cathode material only in the non-imaging area, resolving the contradiction between transmittance and light-emitting 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 method increases transmittance in the imaging area without significantly affecting the overall efficiency of the OLED device, reducing manufacturing complexity and risk of damage, and supports a real full-screen design with under-screen modules.
Implementation Method 1
performing a first evaporation process and a second evaporation process of a cathode of the OLED panel using a first mask plate and a second mask plate
Data Source
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AI summary
A mask plate group of an organic light emitting diode (OLED) panel, a cathode evaporation method thereof and an OLED panel are provided. The OLED panel includes a display area having an imaging area, and the mask plate group includes a first mask plate and a second mask plate. The first mask plate includes a common mask opening area. The common mask opening area covers an entire of the display area. The second mask plate includes a special-shaped mask opening area. The special-shaped mask opening area covers all the display area except the imaging area.