Slit-Type Die Coater Lip Groove for Stable Thin Film
Solution Overview
Problem
Conventional extrusion coating methods using slit-type die coaters face challenges in achieving stable coating thickness and width uniformity, especially when coating low viscosity solutions at thin film thicknesses, due to issues with wet expansion and air pressure, leading to non-uniformity and instability in forming stripe-shaped coatings.
Innovation Solution
The method involves using a slit-type die coater with a lip tip having at least one groove in the coating region, operating at a pressure where the slit outlet pressure is negative or zero, with a coater gap that is 30 to 300 times the wet coating thickness, and a coating speed that prevents air generation, allowing for stable formation of non-coating and coating portions in a stripe pattern.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the coater gap is enlarged to reduce pressure upstream of the slit-type die coater, then the coating thickness distribution is improved, but the bead cannot maintain its shape due to negative pressure atmosphere caused by accompanying air, resulting in poor coating stability
Solution Approach 1:
The invention applies preliminary anti-action by introducing a pressure regulation mechanism that preemptively counteracts the negative pressure atmosphere caused by accompanying air during substrate transport. The pressure upstream of the slit-type die coater is regulated to maintain positive pressure conditions, preventing the bead from losing its shape before the coating process is completed. This resolves the contradiction by anticipating and preventing the harmful effect of negative pressure on bead stability.
Solution Approach 2:
The invention changes the pressure parameter from negative to positive by regulating the pressure upstream of the slit-type die coater. This parameter change ensures that the bead maintains its shape under positive pressure conditions while still achieving acceptable coating thickness distribution. The coater gap is optimized to work effectively under positive pressure, transforming the operating conditions to resolve the contradiction between coating precision and stability.
2Manufacturing precision
If the pressure upstream of the slit-type die coater is reduced to prevent air generation, then the coating thickness distribution improves, but the bead shape stability deteriorates under negative pressure atmosphere
Solution Approach 1:
The invention applies preliminary anti-action by preemptively maintaining positive pressure upstream of the slit-type die coater to counteract the tendency toward negative pressure and accompanying air generation. This prevents bead shape distortion before it occurs, while still achieving improved coating thickness distribution through optimized coater gap settings under positive pressure conditions.
Solution Approach 2:
The invention changes the pressure parameter from negative to positive, fundamentally altering the operating conditions. By regulating pressure to remain positive, the bead shape is maintained while coating thickness distribution is improved through optimized coater gap parameters under the new positive pressure regime.
3Productivity
If a low viscosity coating solution is used to achieve thin film coating, then the coating speed increases, but the coating thickness uniformity deteriorates due to wet expansion and air pressure effects
Solution Approach 1:
The invention changes the pressure parameter from negative to positive, which fundamentally alters the behavior of low viscosity coating solutions. Under positive pressure, wet expansion and air pressure effects are controlled, allowing thin film coating with low viscosity solutions to maintain thickness uniformity while achieving high coating speeds.
Solution Approach 2:
The invention effectively creates a stable coating film structure by maintaining positive pressure conditions that prevent excessive wet expansion of low viscosity coating solutions. This allows the formation of uniform thin films at high coating speeds, as the positive pressure regime stabilizes the coating process despite the low viscosity of the coating solution.
Data Source
AI summary
Disclosed are a coating method of forming a coating with a stable thickness from a coating solution with a low viscosity employing a slit-type die coater and an organic electroluminescence element prepared employing the coating method. The coating method employing a slit-type die coater comprises the steps of allowing a lip tip of the slit-type die coater to bring close to the substrate to form a coating solution bead between the lip tip and the substrate, and coating on the substrate a coating solution ejected from a slit outlet at the lip tip while relatively moving the slit-type die coater and the substrate, thereby forming at least two coating layers in the stripe shape, featured in that the lip tip has at least one groove in the coating region in the coating width direction, and a pressure at the slit outlet of the coating solution of the bead is negative or zero.