Pixel Defining Layer Slope Control for OLED Cathode Uniformity
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Solution Overview
Problem
In OLED display panel manufacturing, the large slope angles between adjacent sub-pixels lead to poor connection of the cathode, abnormal light reflection, and organic film defects, such as mura, due to differences in flowability and pre-baking processes, especially between green and other colored sub-pixels.
Innovation Solution
The array substrate design includes a pixel defining layer (PDL) with strategically arranged openings and slope angles, where the ratio of slope angles between adjacent openings is controlled between 0.8 to 1.25, and a mask plate with a pattern and filling portion to form openings that reduce slope angles and improve flowability during the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the slope angles between adjacent sub-pixels are large, then the cathode connection is poor and light reflection is abnormal, but reducing the slope angles requires precise control of the pixel defining layer structure
Solution Approach 1:
The patent applies parameter changes by controlling the slope angles of the pixel defining layer openings within a specific range (0.8 to 1.25 ratio between adjacent openings). This parameter optimization ensures that the slope angles are not too large, preventing cathode connection issues and abnormal light reflection, while maintaining manufacturability through precise but achievable angular control during the photolithography process.
Solution Approach 2:
The patent implements local quality by making the slope angles of different pixel defining layer openings non-uniform yet controlled. Specifically, adjacent openings have slope angles with a ratio between 0.8 and 1.25, meaning they are locally optimized to prevent excessive angular differences that cause manufacturing defects, while each opening maintains its own characteristic slope angle suitable for its position and function.
2Reliability
If the slope angles of pixel defining layer openings are not uniform, then flowability and pre-baking processes differ causing organic film defects, but making them uniform increases device complexity
Solution Approach 1:
The patent uses parameter changes by establishing a controlled non-uniformity in slope angles. Rather than making all openings identical, it specifies that adjacent openings have slope angles with a ratio between 0.8 and 1.25. This controlled variation allows each opening to be optimized for its local requirements while preventing excessive differences that would cause flowability and pre-baking inconsistencies leading to organic film defects.
Data Source
AI summary
Provided are an array substrate and a manufacturing method therefor, a display device, and a mask plate. The array substrate includes a pixel defining layer having a first opening, a second opening, and a third opening passing through the pixel defining layer. Every two of the first to third openings are adjacent to each other. The pixel defining layer includes first to third opening denning portions. At least one of the ratio of the slope angle of a portion of the first opening defining portion located between the first opening and the second opening to the slope angle of the third opening defining portion, and the ratio of the slope angle of a portion of the second opening defining portion located between the first opening and the second opening to the slope angle of the third opening defining portion is from 0.8 to 1.25.