Curtain Coating Dynamic Surface Tension Control
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Solution Overview
Problem
Conventional thermosensitive recording material production methods using simultaneous multilayer curtain coating often result in 'white spots' due to curtain splitting, leading to areas without the thermosensitive recording layer and subsequent printing defects, as existing methods fail to effectively control the dynamic surface tension between layers.
Innovation Solution
Adjusting the dynamic surface tension difference between the thermosensitive recording layer and adjacent layers to 4 mN/m or less, ensuring the thermosensitive recording layer has a higher or lower dynamic surface tension than the adjacent layer, to stabilize the curtain and prevent splitting during the curtain coating process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simultaneous multilayer curtain coating is used to improve production efficiency, then coating speed and productivity increase, but curtain splitting occurs causing white spots and coating defects
Solution Approach 1:
The patent changes the physical-chemical parameter of dynamic surface tension to resolve the contradiction. By controlling the dynamic surface tension of the thermosensitive recording layer coating liquid to be higher than that of adjacent layers by 3 mN/m or more at coating speeds of 1000 m/min or more, the curtain stability is improved while maintaining high productivity. This parameter change prevents curtain splitting and white spot defects even at high coating speeds.
2Reliability
If conventional blade coating or wire bar coating is used to maintain coating quality, then coating uniformity is preserved, but production efficiency and coating speed decrease
Solution Approach 1:
The patent enables the use of curtain coating method (which is inherently faster) by changing the dynamic surface tension parameter. This allows achieving both high coating speed and good coating uniformity, resolving the contradiction between productivity and reliability that existed when using slower blade or wire bar coating methods.
3Reliability
If dynamic surface tension difference between layers is increased to stabilize the curtain, then coating uniformity improves, but formulation complexity increases
Solution Approach 1:
The patent specifies a quantitative parameter range (dynamic surface tension difference of 3 mN/m or more) that provides clear formulation guidance. This resolves the contradiction by transforming a complex formulation challenge into a specific parameter control task, making it easier to achieve curtain stability while managing formulation complexity.
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 stabilizes the curtain coating process, preventing 'white spots' and ensuring continuous, uniform application of the thermosensitive recording material, thereby maintaining print quality by ensuring the thermosensitive recording layer is consistently deposited across the web.
Implementation Method 1
a coating liquid contained in a curtain coating head 1 is ejected from a nozzle slit 1a, a coating liquid film 3 which has been ejected and tends to shrink in the width direction due to the surface tension, is allow to free fall in the form of a curtain by being guided by a curtain edge guide 2
Implementation Method 2
a coating liquid film 3 which has been ejected and tends to shrink in the width direction due to the surface tension
Data Source
AI summary
A method containing: ejecting a coating liquid for a thermosensitive recording material from a slit, the coating liquid being formed of at least two layers; allowing the coating liquid to free-fall while guiding in the form of a curtain with a curtain edge guide; applying the coating liquid on a web which continuously travels; and drying the coating liquid to form a coated film, wherein the method uses a curtain coating method, the coating liquid contains a coating liquid of a thermosensitive recording layer and that of a layer adjacent to the thermosensitive recording layer, and dynamic surface tension A of the coating liquid of the thermosensitive recording layer and that B of the coating liquid of the layer has a difference (A−B) of 4 mN/m or less.