Wet-on-Wet Multilayer Coating Conformability Control

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Solution Overview

Problem

Existing multilayer coating processes face challenges in achieving controlled conformability of skin coating layers on structured surfaces, leading to inconsistent surface and bulk coating properties, which affects the performance of coated articles.

Innovation Solution

A wet-on-wet coating method is employed, where a first coating fluid forms a skin layer on a structured substrate, and a second coating fluid is applied over it to create a bulk layer, with the residence time and environmental factors controlled to adjust the conformability of the skin layer, allowing for desired surface and bulk properties.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If a single layer coating process is used with sequential drying and curing, then the coating process is simple and easy to control, but the conformability of the skin coating layer on structured surfaces cannot be adequately controlled, leading to inconsistent surface and bulk coating properties

Engineering Contradiction:
Improveconformability control of skin coating layerVSAvoidcoating process complexity
Core Design Contradiction:
Manufacturing precisionVSDevice complexity

Solution Approach 1:

The coating process is segmented into two distinct coating layers applied in sequence without intermediate drying: a skin layer first, then a bulk layer. This segmentation allows independent optimization of surface properties (skin layer conformability) and bulk properties (coating thickness, material distribution), resolving the contradiction between manufacturing precision and process complexity.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The skin layer is applied first as a preliminary action to establish the desired surface conformability on structured substrates. This preliminary coating creates a controlled interface that guides subsequent bulk layer application, ensuring consistent surface properties before the bulk material is deposited.

Inventive Principle:
Principle #10Preliminary action

2Manufacturing precision

If the skin layer is applied with high conformability to structured surfaces, then surface coating properties are improved, but the interface between skin and bulk layers becomes sharp and distinct, potentially compromising bond performance

Engineering Contradiction:
Improvesurface coating conformabilityVSAvoidbond performance at skin-bulk interface
Core Design Contradiction:
Manufacturing precisionVSStrength

Solution Approach 1:

The residence time of the skin layer on the structured surface is controlled as a critical parameter. By optimizing this time, the skin layer achieves sufficient conformability to structured features while maintaining material properties that facilitate strong bonding with the subsequent bulk layer, creating an ideal intermediate state that satisfies both surface quality and bond strength requirements.

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The skin layer serves as an intermediary between the structured substrate and the bulk coating layer. By controlling its application parameters, it acts as a transition zone that ensures both conformal coverage of surface features and strong adhesive bonding to the bulk layer, mediating between surface geometry and bulk material properties.

Inventive Principle:
Principle #24Intermediary (Mediator)

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 method enables the production of dual-layer coatings with improved conformability and performance attributes, such as enhanced peel resistance and debonding forces, by creating a diffuse interface between the skin and bulk layers, resulting in better bond performance and stability of micro-structured features.

Implementation Method 1

a first coating fluid is applied from a first coating applicator on to a structured substrate surface to form a skin layer directly over the pattern of structured features on the substrate surface

Methodology Applied
Scientific EffectDeposition: Deposition (physical)

Implementation Method 2

a second coating fluid is applied from a second coating applicator on to the skin layer to form a bulk layer directly over the skin layer

Methodology Applied
Scientific EffectDeposition: Deposition (physical)

Implementation Method 3

creating a diffuse interface between the skin and bulk layers, resulting in better bond performance

Methodology Applied
Scientific EffectDiffusion: Diffusion

Data Source

PatentEP4084956B1Multilayer articles via wet-on-wet processing
Publication Date: 2024.12.04 3M INNOVATIVE PROPERTIES CO
  • EP4084956B1 patent drawingFigure 1
  • EP4084956B1 patent drawingFigure 2A~2C
  • EP4084956B1 patent drawingFigure 2D~3

AI summary

Wet-on-wet coating processes are provided to produce multilayer articles. First and second coating materials are sequentially applied on to a structured substrate surface to form a skin layer directly over the structured substrate surface and a bulk layer over the skin layer. The conformability of the skin layer can be adjusted to provide desired surface and bulk properties.