Organic Light-Emitting Device Hole Transport Layer Ink Application
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Solution Overview
Problem
In organic light emitting device manufacturing, differences in ink application among groove regions lead to biased film thickness distribution, causing uneven current density and potential degradation during device operation.
Innovation Solution
A method is developed to form functional layers by defining groove region groups with varying ink and solvent application per unit surface area, ensuring homogenized ink and solvent amounts across regions, thereby controlling solvent vapor pressure and drying time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ink is applied to groove regions with different amounts per unit surface area to account for varying film thickness requirements, then the film thickness can be adjusted for different sub-pixel colors, but bias in film thickness distribution occurs within each groove region due to uneven drying speed
Solution Approach 1:
The patent applies different amounts of solvent to different groove regions based on their specific requirements. By controlling the solvent amount locally in each groove region, the drying speed is adjusted to compensate for the varying ink amounts, ensuring uniform film thickness distribution across all sub-pixels despite different initial ink application quantities.
Solution Approach 2:
The patent changes the solvent amount parameter for each groove region to control the drying process. By adjusting the solvent quantity, the drying speed is modified to achieve consistent evaporation rates across regions with different ink amounts, thereby eliminating film thickness bias and preventing device degradation.
2Ease of manufacture
If uniform ink amount per unit surface area is applied to all groove regions, then manufacturing process is simplified, but film thickness distribution becomes biased when different sub-pixels require different thicknesses
Solution Approach 1:
The patent implements local quality control by applying different solvent amounts to different groove regions. This allows the manufacturing process to maintain simplicity in ink application while achieving precise film thickness control through localized solvent adjustment, ensuring each sub-pixel receives the appropriate film thickness.
Solution Approach 2:
The patent performs preliminary action by adjusting the solvent amount before the drying process begins. This pre-adjustment ensures that regions requiring thicker films receive more solvent to slow drying, while regions requiring thinner films receive less solvent, thereby achieving the desired film thickness distribution before evaporation occurs.
3Device complexity
If solvent is applied uniformly to all groove regions, then the drying process is simplified, but film thickness bias persists due to different initial ink amounts
Solution Approach 1:
The patent applies local quality control to the drying process by varying the solvent amount in each groove region. This localized approach allows the drying process to compensate for different initial ink amounts, ensuring uniform film thickness distribution across all sub-pixels while maintaining a relatively simple overall process structure.
Solution Approach 2:
The patent changes the solvent amount parameter for each groove region to control evaporation rates. By adjusting this parameter locally, the drying process achieves consistent film thickness despite varying ink application amounts, eliminating the need for complex multi-step drying procedures.
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 eliminates film thickness bias, ensuring homogeneous current density and prolonged device lifespan by maintaining consistent brightness across light emitting elements.
Implementation Method 1
applying a solvent able to dissolve the ink to the subset of the groove regions
Implementation Method 2
drying ink layers formed in the groove regions by the application of the ink and the solvent
Data Source
AI summary
A method of forming a hole transport layer in which an amount of ink per unit surface area to be applied to a plurality of groove regions is set so as to decrease in an order R, G, B. Prior to applying the ink, a nozzle head is scanned across while applying only solvent to each of the groove regions. At this time, an amount of the solvent to be applied to the groove regions is set so as to increase in the order R, G, B.