OLED Mask Plate with Variable Opening Slope for Brightness Uniformity
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Solution Overview
Problem
In OLED display devices, the voltage difference between the proximal and distal ends of the IC leads to ununiform long-run display brightness, especially as screen size increases, making it difficult to achieve high-quality displays, particularly for monochrome grayscale images.
Innovation Solution
A mask plate with varying opening widths and slope angles is used to create a pixel definition layer on the OLED display substrate, allowing for a controlled resistance variation in the cathode, which compensates for the voltage drop along the data line, maintaining consistent driving voltage across the display.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the screen size is increased to improve display area, then the average brightness increases, but the long run uniformity (LRU) becomes worse due to voltage drop along the data line
Solution Approach 1:
The pixel definition layer is designed with different slope angles in different regions: the first region (near IC) has a smaller slope angle while the second region (far from IC) has a larger slope angle. This local variation in geometric properties compensates for the voltage drop along the data line, ensuring uniform driving voltage across the entire display area.
Solution Approach 2:
The slope angle parameter of the pixel definition layer is changed across different regions to compensate for voltage drop. By adjusting this geometric parameter, the effective cathode area is modified to balance the voltage distribution, thereby maintaining consistent driving voltage despite the increased screen size.
2Power
If the data line impedance is present, then the Vdd signal experiences voltage drop at the distal end of the IC, but this causes difference in driving voltage between distal and proximal ends
Solution Approach 1:
The pixel definition layer is pre-designed with compensatory slope angle variations before the OLED device operates. This preliminary geometric adjustment creates a counter-effect that offsets the voltage drop caused by data line impedance, ensuring uniform driving voltage across different regions during operation.
Solution Approach 2:
Different regions of the pixel definition layer are assigned different slope angles: the first region near the IC has a smaller slope angle, while the second region farther from the IC has a larger slope angle. This local differentiation compensates for the voltage drop, maintaining consistent driving voltage and display brightness uniformity.
Data Source
AI summary
The present disclosure provides a mask plate, an OLED display substrate and a method for manufacturing the OLED display substrate, and a display device. The mask plate comprises a plurality of openings arranged as an array and configured to prepare patterns of a pixel definition layer, wherein a width of the opening close to a first side of the mask plate in a first direction is greater than that of the opening away from the first side of the mask plate, and the first direction is a direction from the opening close to the first side of the mask plate to the opening away from the first side of the mask plate. A slope angle of the pattern of the pixel definition layer close to a second side of the OLED display substrate is smaller than that away from the second side of the OLED display substrate.