Vapor Deposition Mask Curved Ends for EL Display Accuracy
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Solution Overview
Problem
Conventional vapor deposition masks in organic electroluminescence (EL) display devices suffer from poor accuracy and limited design freedom due to stress concentration at the mask's end portions, leading to suboptimal film deposition and increased cathode contact resistance, which affects the overall performance and power consumption of the devices.
Innovation Solution
A vapor deposition mask with a triangular-shaped end portion and rounded vertex is designed to disperse stress, improving deposition accuracy and allowing for more precise control over the vapor deposition area, while also incorporating an organic layer to mitigate film stress and reduce cathode contact resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional vapor deposition mask with rectangular end portions is used, then the mask structure is simple and easy to manufacture, but stress concentrates at the vertexes causing poor vapor deposition accuracy (±10 μm)
Solution Approach 1:
The mask end portions are designed with curved surfaces instead of sharp rectangular corners. Specifically, the end portions have radii of curvature R1 and R2 at different locations, which distributes stress more evenly across the mask structure during vapor deposition, thereby improving deposition accuracy to ±5 μm while maintaining manufacturing feasibility
Solution Approach 2:
The mask design employs asymmetric curvature radii (R1 ≠ R2) at different end portion locations. This asymmetric configuration optimizes stress distribution for the specific vapor deposition geometry and substrate arrangement, achieving improved accuracy without excessive structural complexity
2Manufacturing precision
If the vapor deposition area is extended beyond pixel areas to ensure uniform film deposition, then film uniformity is improved, but the area requiring high precision deposition increases making it harder to maintain accuracy
Solution Approach 1:
The curved end portions with optimized radii R1 and R2 create a more favorable stress distribution pattern that maintains deposition accuracy even when the vapor deposition area is extended beyond the pixel boundaries, enabling uniform film formation over larger areas without sacrificing precision
3Reliability
If cathode contacts are positioned near pixels to reduce cathode voltage and improve performance, then device performance is improved, but the already limited design freedom is further constrained due to poor mask accuracy
Solution Approach 1:
The curved mask end portions provide the precision needed to position cathode contacts near pixels without compromising overall mask performance. This enables optimized electrical performance while maintaining the flexibility to explore different contact configurations and designs
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 improved mask design enhances vapor deposition accuracy from ±10 μm to ±5 μm, reduces cathode contact resistance, and decreases power consumption by allowing for more efficient vapor deposition beyond pixel areas, thereby improving the overall performance and design flexibility of organic EL display devices.
Implementation Method 1
When a thermal stress is applied to the vapor deposition mask in a vapor deposition process, there occurs a fine deformation, causing a vapor deposition displacement.
Implementation Method 2
incorporating an organic layer to mitigate film stress and reduce cathode contact resistance
Implementation Method 3
As methods for forming a film of an organic layer of an organic EL display device there are known a printing method and a vapor deposition method.
Data Source
AI summary
An organic electroluminescence display device is disclosed wherein plural organic electroluminescence elements each having an anode, a cathode and an organic layer sandwiched in between the anode and the cathode, the plural organic electroluminescence elements including organic electroluminescence elements developing different colors in a row direction, and at least one of the organic layers having an outer edge of a conic section at an end portion in a column direction thereof, the outer edge of the conic section becoming narrower gradually in its width in a row direction of vapor deposition thereof toward an extreme end at an end portion in a column direction thereof. The organic electroluminescence display device can improve the vapor deposition accuracy and the degree of design freedom.