Ink Drying Device for Organic EL Panels
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Solution Overview
Problem
Existing methods for manufacturing organic electroluminescence (EL) display panels face challenges in achieving uniform film thickness across the substrate, leading to in-plane luminance unevenness due to differences in solvent evaporation rates and ink surface tension, particularly as panel resolution increases.
Innovation Solution
A method involving the application of ink with multiple solvents between column banks on a substrate, where the atmosphere pressure is gradually reduced in a controlled manner to equalize film thickness, including a first period at a pressure higher than the highest vapor pressure and a second period at a pressure lower than the lowest vapor pressure, ensuring uniform drying and reducing ink convection effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If ink is applied to substrate and dried under atmospheric pressure, then drying process is simple, but film thickness becomes uneven across substrate due to different evaporation rates in peripheral and central portions
Solution Approach 1:
The patent changes the pressure parameter during the drying process, transitioning from atmospheric pressure to reduced pressure. This parameter change equalizes the evaporation rates across the substrate by reducing the overall vapor pressure gradient, thereby achieving uniform film thickness while maintaining process simplicity through automated pressure control.
Solution Approach 2:
The patent implements a dynamic pressure reduction process where the pressure is gradually reduced from atmospheric pressure to a lower pressure level. This dynamic adjustment allows the system to adapt to the evaporation process, maintaining uniform drying conditions across the substrate throughout the drying cycle.
2Manufacturing precision
If reduced pressure is applied during drying, then film thickness uniformity improves, but device complexity increases due to vacuum system requirements
Solution Approach 1:
The patent integrates the pressure reduction function into the existing drying device architecture, allowing the same device to perform both drying and pressure control functions. This multi-functionality approach reduces overall device complexity by eliminating the need for separate vacuum system components while achieving uniform film thickness.
3Manufacturing precision
If ink contains multiple solvents with different vapor pressures, then drying control becomes complex, but film uniformity can be improved through selective evaporation
Solution Approach 1:
The patent performs preliminary pressure reduction to a level between the vapor pressures of the different solvents before complete drying occurs. This preliminary action allows selective evaporation of higher vapor pressure solvents first, controlling the drying sequence to achieve uniform film formation while simplifying the overall control process through staged pressure management.
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 enhances luminance uniformity by equalizing film thickness across the substrate, reducing variations caused by ink ejection and surface tension imbalances, thereby improving display panel performance.
Implementation Method 1
drying the ink includes evaporating and drying the solvent
Implementation Method 2
Solvent vapor pressure is lower in a peripheral portion of a film forming area than in a central portion thereof
Implementation Method 3
an effect of equalizing film thicknesses of the light emitting layers within the column application regions is small. Due to this, film thicknesses of functional layers across a substrate plane are uneven
Implementation Method 4
reducing, during a second period after the first period, pressure of the atmosphere to a second pressure that is lower than vapor pressure of solvent having the lowest vapor pressure among the solvents
Data Source
AI summary
An ink drying process includes exhausting gas from atmosphere surrounding a substrate and drying ink through placing the substrate in a predefined pressure or less to form organic functional layers. Exhausting of gas includes: reducing, during a first period, pressure of the atmosphere from standard atmospheric pressure to a first pressure higher than vapor pressure of solvent having the highest vapor pressure among solvents of the ink; and subsequently reducing, during a second period, the pressure of the atmosphere to a second pressure lower than vapor pressure of solvent having the lowest vapor pressure among the solvents. Where pressure of the atmosphere is 10x Pa (X indicating a real number), a change amount average of X per unit time has a greater absolute value during the second period than during the first period.