Organic EL Mask Rib Segmentation for Sagging
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Solution Overview
Problem
Organic electroluminescent (EL) device manufacturing faces challenges with mask sagging and reduced opening area, leading to inferior visibility and increased defect rates due to the mask sagging phenomenon and shadowing between pixels, especially as display device sizes increase.
Innovation Solution
A method of depositing a light emitting layer using a mask with a shield portion and patterned opening portions, including a rib between upper and lower pixels to prevent sagging, and adjusting the mask's position to separate black spots and reduce visibility issues, thereby improving the aperture ratio and visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a slit type shadow mask is used with large opening portions, then the opening area is increased, but mask sagging occurs due to the weight of the mask causing separation from the substrate
Solution Approach 1:
The mask structure is segmented by dividing it into multiple regions with ribs positioned between upper and lower pixels. These ribs act as structural supports that segment the large continuous opening into smaller effective spans, preventing mask sagging while preserving the overall large opening area needed for high aperture ratio.
2Reliability
If cross ribs are added to prevent mask sagging, then mask stability is improved, but shadowing phenomenon occurs between upper and lower pixels reducing the opening area
Solution Approach 1:
The rib structure is designed with local quality optimization where ribs are positioned specifically between upper and lower pixels rather than forming a complete grid. The ribs have optimized dimensions and positioning that provide structural support exactly where needed to prevent sagging, while minimizing their presence in areas that would cause shadowing between pixels.
3Area of stationary object
If the display device size is increased, then the display area is expanded, but mask sagging phenomenon is deteriorated due to the increased size of the shadow mask
Solution Approach 1:
The rib structure divides the large mask into smaller effective spans by positioning ribs between upper and lower pixels. This segmentation allows the mask to maintain stability even as the overall display device size increases, as each rib supports a smaller section of the mask rather than relying on a single continuous support structure across the entire large area.
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 effectively prevents mask sagging, reduces opening area, and minimizes inferior visibility caused by neighboring black spots, enhancing the display quality and reducing defect rates in organic EL devices.
Implementation Method 1
the mask sags due to the weight thereof so that the substrate and the mask can be separated from each other
Implementation Method 2
a deposition process of depositing an organic material for emitting light
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4C
AI summary
A method of depositing a light emitting layer (210,220,230) of an organic EL device in which a subpixel combination having a plurality of different colors is set as a unit pixel, a plurality of subpixels are sequentially and alternately arranged in a row direction, and a plurality of subpixels of the same color are arranged in a column direction, includes first depositing the light emitting layer using a mask (110) having a plurality of opening portions (112) corresponding to positions of the subpixels of the same color arranged in any of an odd-numbered row and an even-numbered column of the subpixels, and second depositing the light emitting layer by moving the mask to prevent the light emitting layer from being deposited at a subpixel adjacent to the subpixel where the light emitting layer is deposited during the first deposition operation, using the same opening portion of the mask used for the first deposition operation of the light emitting layer.