Copper Foil Surface Treatment for Low-Temperature Polyvinyl Acetal Lamination

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Solution Overview

Problem

The challenge lies in achieving strong adhesion between a polyvinyl acetal resin film and a copper foil, which is difficult due to low reactivity under low temperature and low pressure conditions typically required for laminating these materials.

Innovation Solution

By controlling the amount of nitrogen on the treated surface of the copper foil to be between 3.0 atomic % and 20.0 atomic %, preferably with a nitrogen-containing compound like silane coupling agents, the adhesion between the copper foil and the polyvinyl acetal resin film is enhanced, allowing for effective lamination under low temperature and low pressure conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a polyvinyl acetal resin film and copper foil are laminated under low temperature and low pressure conditions, then the resin film maintains its transparency and mechanical properties, but the adhesion between the copper foil and resin film is insufficient due to low reactivity

Engineering Contradiction:
Improveadhesion between copper foil and resin filmVSAvoidlamination temperature
Core Design Contradiction:
ReliabilityVSTemperature

Solution Approach 1:

The copper foil surface is treated in advance with a nitrogen-containing compound before lamination to enhance reactivity. This preliminary surface treatment creates a more reactive copper surface that can form stronger chemical bonds with the polyvinyl acetal resin film under low temperature and pressure conditions, thereby improving adhesion without requiring high energy input

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The chemical composition of the copper foil surface is modified by introducing nitrogen-containing compounds. This changes the surface parameters (chemical reactivity, surface energy) of the copper foil, enabling it to exhibit higher reactivity toward the resin film while maintaining the low temperature and pressure lamination process

Inventive Principle:
Principle #35Parameter changes

2Reliability

If a nitrogen-containing compound is used to treat the copper foil surface to improve adhesion, then the chemical reactivity and adhesion are enhanced, but the manufacturing process complexity increases

Engineering Contradiction:
Improveadhesion between copper foil and resin filmVSAvoidsurface treatment process complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The nitrogen-containing compound treatment serves multiple functions simultaneously: it enhances the chemical reactivity of the copper surface for better adhesion, and it can also provide corrosion resistance and surface uniformity. This multi-functionality reduces the need for separate treatment steps, thereby limiting the increase in manufacturing complexity while achieving improved adhesion

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 results in a laminate with improved adhesion, enabling the formation of a heating element with better visibility and efficiency, suitable for defrosters in vehicles.

Implementation Method 1

By controlling the amount of nitrogen on the treated surface of the copper foil to be between 3.0 atomic % and 20.0 atomic %, preferably with a nitrogen-containing compound like silane coupling agents, the adhesion between the copper foil and the polyvinyl acetal resin film is enhanced

Methodology Applied
Scientific EffectChemical bonding: Chemical Bonding

Data Source

PatentEP4296052B1Methods for manufacturing a laminated plate, a heat generator, and a defroster
Publication Date: 2025.08.20 MITSUI MINING & SMELTING CO LTD

AI summary

Provided is a method for manufacturing a laminate that is excellent in adhesion between the copper foil and the resin film while using a polyvinyl acetal resin having low reactivity with the copper foil. This method includes the steps of providing a copper foil having on at least one side a treated surface on which an amount of nitrogen is 3.0 atomic % or more and 20.0 atomic % or less, and attaching or forming a polyvinyl acetal resin film on the treated surface of the copper foil to form a laminate. The amount of nitrogen is a proportion of N in a total amount of N, O, Si, P, S, Cl, Cr, Ni, Cu, Zn, Mo, Co, W, and Fe when the treated surface is subjected to elemental analysis by X-ray photoelectron spectroscopy (XPS).