Organic EL Display Mask Thermal Expansion Compensation
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Solution Overview
Problem
The existing vapor deposition methods for forming organic EL layers in organic EL display devices suffer from chromaticity and brightness irregularities due to film forming misalignment, which is not adequately addressed by current techniques, particularly in mass production where thermal expansion of masks leads to positioning errors.
Innovation Solution
The solution involves designing a vapor deposition mask and process that analyzes and accounts for film forming misalignment by ensuring the angles and magnitudes of misalignment vectors between organic EL layer centers and sub pixel openings are within 90°, applicable to both top-emission and bottom-emission types, using a mask with specific vector distributions to minimize thermal expansion effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a mask is used for vapor deposition to form organic EL layers, then the organic EL layer can be formed on sub pixel openings, but thermal expansion of the mask causes film forming misalignment leading to chromaticity and brightness irregularities
Solution Approach 1:
The patent applies preliminary action by pre-calculating and compensating for mask thermal expansion before the actual vapor deposition process. The mask is designed with expanded dimensions at high temperature to account for thermal expansion during vapor deposition, ensuring that the organic EL layer forms with correct alignment despite the mask's dimensional changes during the process.
Solution Approach 2:
The patent applies parameter changes by adjusting the mask's physical dimensions based on temperature conditions. The mask is designed with different dimensions for low-temperature processes (such as ITO formation) versus high-temperature processes (such as organic EL layer formation), with the high-temperature mask dimensions being larger to compensate for thermal expansion during vapor deposition.
2Manufacturing precision
If the mask size is reduced to minimize thermal expansion effects, then alignment improves, but the area for forming organic EL layers is reduced
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the mask size parameter based on the process temperature. For low-temperature processes, a smaller mask is used, while for high-temperature vapor deposition processes, a larger mask is used to compensate for thermal expansion. This allows the mask to provide adequate coverage area while maintaining alignment precision through temperature-appropriate sizing.
3Quantity of substance
If multiple vapor deposition processes are performed sequentially, then complete organic EL layer formation is achieved, but cumulative misalignment increases
Solution Approach 1:
The patent applies preliminary action by pre-establishing accurate alignment references (such as alignment marks or reference patterns) on the mother glass before any vapor deposition processes. These references remain stable throughout multiple deposition steps, allowing each subsequent layer to be aligned to the same reference, thereby preventing cumulative misalignment errors from building up across multiple sequential processes.
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 effectively suppresses chromaticity and brightness irregularities by optimizing the vapor deposition process, ensuring accurate alignment and consistent color reproduction across the display panel.
Implementation Method 1
a vapor deposition method of forming an organic EL layer on an organic EL panel by masking
Implementation Method 2
forming an organic EL material which corresponds to a large number of organic EL panels on a large-sized glass (mother glass) by vapor deposition
Implementation Method 3
misalignment of a film forming position is generated due to the thermal expansion of the mask
Data Source
AI summary
The present invention aims at the suppression of chromaticity irregularities and brightness irregularities by reflecting a result of an analysis of film forming misalignment of an organic EL layer. For this end, a drive circuit chip 6 is mounted on a lower side of a display panel 4, and a terminal portion 7 for connection with an external device (a host device) is mounted on an end edge of the lower side of a display panel 4. Film forming misalignment vectors (indicated by arrows) of sub pixels at an arbitrary point in a display region 5 fall within a first quadrant and an angle made between the vectors falls within 90°.