OLED Mask Plate Assembly for Shadow Width Compensation
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Solution Overview
Problem
In the manufacturing process of OLEDs, the uneven thickness of film layers due to radial diffusion of evaporated materials leads to shadow areas with thickness less than the preset threshold, causing issues like abnormal pixel display at the edge of the display area and non-uniform brightness.
Innovation Solution
The proposed solution involves determining specific minimum distances between the boundaries of different layers and the display area boundaries, using formulas that incorporate alignment accuracy, position accuracy of the mask plate, and shadow widths of the layers. These distances are used to calculate the sizes of openings in mask plates for evaporating functional, pixel defining, cathode, and covering layers, ensuring uniform layer thickness and preventing shadow areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the mask plate opening size is reduced to minimize shadow areas, then the display area utilization is improved, but the manufacturing precision required increases due to alignment and position accuracy constraints
Solution Approach 1:
The patent calculates and determines the minimum distances between layer boundaries and display area boundaries before manufacturing the mask plate. By performing this calculation in advance using the formula d=√(a²+b²)+c, the design parameters are optimized beforehand, allowing the mask plate to be manufactured with precise dimensions that account for shadow effects, thus improving display area utilization while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the design parameter from a fixed mask plate opening size to a dynamically calculated minimum distance that incorporates alignment accuracy (a), position accuracy (b), and shadow width (c). This parameter transformation allows the system to optimize the balance between display area and manufacturing precision by adjusting the calculated minimum distance based on actual equipment capabilities
2Length of stationary object
If the functional layer is evaporated closer to the display area boundary to reduce frame size, then the OLED equipment frame is reduced, but shadow areas with non-uniform thickness are formed
Solution Approach 1:
The patent applies preliminary anti-action by calculating the shadow width (c) in advance and incorporating it into the minimum distance formula. This pre-calculated shadow compensation distance is designed into the mask plate specifications before evaporation, creating a buffer zone that prevents shadow areas from forming in the display region. The functional layer is evaporated at a distance that anticipates and counteracts the radial diffusion effect, thus reducing frame size while maintaining thickness uniformity
Solution Approach 2:
The calculated minimum distance acts as an intermediary parameter between the display area boundary and the functional layer boundary. This intermediate distance incorporates the shadow width as a mediating factor, allowing the system to achieve optimal positioning that balances frame reduction with prevention of shadow area formation during evaporation
3Length of stationary object
If multiple layers are stacked with minimal spacing to reduce device thickness, then the overall device thickness is reduced, but the complexity of maintaining uniform thickness across all layers increases
Solution Approach 1:
The patent establishes a universal minimum distance calculation method that can be applied to multiple different layers (functional layer, pixel defining layer, cathode layer, covering layer) using the same formula d=√(a²+b²)+c. This multi-functional approach allows consistent thickness control across all layers by applying the same shadow compensation principle, reducing the complexity of maintaining uniform thickness despite having multiple stacked layers with minimal spacing
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
This approach improves the display yield of the active area while reducing the frame of the OLED equipment, effectively preventing issues like abnormal pixel display and non-uniform brightness by ensuring uniform layer thickness across the substrate.
Implementation Method 1
a related material is evaporated in an opening area of the mask plate to form an OLED device
Data Source
AI summary
A display substrate and a mask plate assembly includes a base substrate, a pixel defining layer, a functional layer, a cathode layer, and a covering layer that are sequentially stacked in a direction away from the base substrate, wherein the size of orthographic projection of the functional layer on the base substrate is jointly determined by the size of a display area and a first minimum distance. The first minimum distance is the minimum distance in a direction from the display area to a non-display area and between the boundary of the display area and the boundary of the functional layer, and is determined by a first shadow width of the functional layer extending from the display area to the non-display area. The first shadow width is the maximum width of a shadow area formed within a preset region when the functional layer is vapor deposited in the preset region.