Resin-Coated Metal Sheet Surface Roughness for Bubble-Free Adhesion

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Coated metal sheets face issues with air bubbles forming between the metal sheet and the coating layer, leading to poor adhesion and appearance, especially when using chromium-free adhesive layers.

Innovation Solution

A resin-coated metal sheet with a resin layer having a reduced peak height Rpk of 0.46 µm or more, formed on a metal base with controlled surface roughness, using direct roll coating with an aqueous dispersion containing a resin material at a concentration of 15% by weight or more, to enhance adhesion properties and prevent air bubbles.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If chromate conversion coating is performed to improve adhesion, then adhesion properties are improved, but environmental load increases

Engineering Contradiction:

Improveadhesion propertiesVSAvoidenvironmental load

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention changes the surface roughness parameter of the resin layer to achieve good adhesion without chromate conversion coating. By controlling the reduced peak height Rpk to be 0.46 μm or more, the resin layer provides sufficient mechanical interlocking for adhesive bonding while eliminating the need for environmentally harmful chromate treatments.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention replaces the environmentally harmful chromate conversion coating with a simpler resin layer that achieves equivalent adhesion functionality. This substitution eliminates the need for complex chromate processing while maintaining the essential bonding performance.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

2Object-affected harmful factors

If adhesive layer is disposed without chromate conversion coating to reduce environmental load, then environmental load is reduced, but adhesion properties worsen due to peel-off

Engineering Contradiction:

Improveenvironmental loadVSAvoidadhesion properties

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The invention optimizes the surface roughness parameters of the resin layer, specifically setting the reduced peak height Rpk to 0.46 μm or more and the arithmetic mean height Sa1 to 0.5 μm or more. These parameter changes create sufficient mechanical anchoring effects that prevent peel-off while maintaining eco-friendly production.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The resin layer is formed in advance with controlled surface roughness characteristics before the adhesive coating is applied. This preliminary preparation of the resin layer surface ensures that subsequent adhesive bonding will have excellent adhesion properties without requiring chromate conversion coating.

Inventive Principle:

Principle #10Preliminary action

3Shape

If resin layer surface is made smooth to improve appearance, then appearance is improved, but adhesion properties worsen due to reduced mechanical interlocking

Engineering Contradiction:

ImproveappearanceVSAvoidadhesion properties

Core Design Contradiction:

ShapeVSReliability

Solution Approach 1:

The invention precisely controls the surface roughness parameters to balance appearance and adhesion. By setting Rpk to 0.46 μm or more and Sa1 to 0.5 μm or more, the resin layer surface maintains sufficient mechanical interlocking for adhesion while presenting an acceptably smooth appearance for aesthetic purposes.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The resin layer is designed with specific local surface quality characteristics - the surface roughness is controlled to provide mechanical interlocking in the bulk while maintaining visual acceptability. The surface profile creates micro-anchoring effects that are invisible from a distance, providing both aesthetic and functional performance.

Inventive Principle:

Principle #3Local quality

4Reliability

If air bubbles are present between metal sheet and coating layer to indicate proper coating formation, then coating formation is confirmed, but appearance deteriorates

Engineering Contradiction:

Improvecoating formationVSAvoidappearance

Core Design Contradiction:

ReliabilityVSShape

Solution Approach 1:

The invention controls the resin layer surface roughness parameters (Rpk ≥ 0.46 μm, Sa1 ≥ 0.5 μm) to prevent air bubble formation during coating application. The optimized surface profile ensures complete wetting and adhesion of the adhesive coating without trapping air bubbles, thereby achieving both proper coating formation and good appearance.

Inventive Principle:

Principle #35Parameter changes

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

The solution provides excellent adhesion properties and a good appearance by ensuring the resin layer spreads uniformly, effectively preventing air bubbles and enhancing the bond with adhesive resins.

Implementation Method 1

applying an aqueous dispersion onto the metal base by direct roll coating

Methodology Applied

Scientific EffectDirect roll coating:

Implementation Method 2

drying the layer formed from the aqueous dispersion to form the resin layer

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentEP4691760A1Resin-coated metal sheet and resin-coated metal sheet production method

Publication Date: 2026.02.11 TOYO KOHAN CO LTD

Figure 1
Figure 2(a)~2(b)
Figure 3

AI summary

Provided is a resin-coated metal sheet comprising a metal base, and a resin layer formed on the metal base, wherein the resin layer has a surface with a reduced peak height Rpk of 0.46 µm or more.