Flexible Flat Cable Coating Film for Heat-Humidity Adhesion
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Solution Overview
Problem
Flexible flat cables face issues with insufficient moisture and heat resistance due to the use of polyester-based resin compositions, leading to peeling of the laminate and exposure of conductors in high temperature and humidity environments, and there are challenges with interlayer adhesive strength between polyolefin-based resin compositions and alternative insulating substrate films.
Innovation Solution
A coating material comprising acid-modified polypropylene, an organic solvent blend with aromatic hydrocarbon and ester/ketone/alcohol solvents, and a curing agent with multiple functional groups, applied to form a coating film that enhances adhesive strength on polyethylene naphthalate, polyimide, and polyphenylene sulfide resin films, improving interlayer bonding in high temperature and humidity conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyester-based resin composition is used as adhesive resin composition, then good initial adhesion is achieved, but moisture and heat resistance becomes insufficient in high temperature and humidity environments
Solution Approach 1:
The patent changes the chemical composition parameters of the adhesive resin from polyester-based to polyolefin-based resin, and further modifies it by grafting polar groups (carboxyl, hydroxyl, or amine groups) to enhance both adhesion and environmental resistance. This parameter transformation resolves the contradiction by maintaining initial adhesion while significantly improving moisture and heat resistance in high temperature and humidity conditions.
2Temperature
If polyethylene naphthalate resin film, polyimide resin film, or polyphenylene sulfide resin film is used as insulating substrate film to achieve higher rated temperatures, then heat resistance is improved, but interlayer adhesive strength becomes insufficient
Solution Approach 1:
The patent uses composite materials by combining polyolefin-based resin with grafted polar groups to create an adhesive layer that effectively bonds to high-temperature resistant substrate films like polyethylene naphthalate, polyimide, and polyphenylene sulfide. The polar groups on the polyolefin resin form strong interfacial bonds with these substrates, resolving the adhesion problem while maintaining heat resistance.
Solution Approach 2:
The patent modifies the adhesive resin composition by introducing polar functional groups (carboxyl, hydroxyl, or amine groups) with specific content ranges (0.1-10 mmol/g, preferably 0.5-5 mmol/g). This parameter change enables the adhesive to effectively bond to high-temperature substrate films while maintaining flexibility and adhesion performance.
3Reliability
If polyolefin-based resin composition is used as adhesive resin composition to improve moisture and heat resistance, then environmental stability is improved, but interlayer adhesive strength on alternative substrate films becomes insufficient
Solution Approach 1:
The patent modifies the polyolefin-based resin by grafting polar functional groups (carboxyl, hydroxyl, or amine groups) to change its surface energy and chemical reactivity parameters. This transformation maintains the inherent moisture and heat resistance of polyolefin while adding the ability to form strong bonds with alternative substrate films like polyethylene naphthalate and polyimide.
Solution Approach 2:
The polar groups on the polyolefin resin act as intermediaries that facilitate bonding between the non-polar polyolefin matrix and the polar substrate films. These functional groups form strong interfacial bonds with the substrate while maintaining compatibility with the polyolefin base, effectively mediating the adhesion between incompatible materials.
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 proposed coating material and film exhibit excellent storage stability and adhesive strength, effectively addressing the peeling issues and enhancing interlayer bonding in high temperature and humidity environments, making them suitable for use in flexible flat cables.
Implementation Method 1
a coating material comprising: (A) 100 parts by mass of an acid-modified polypropylene; and (B) 450 parts by mass or more of an organic solvent
Implementation Method 2
WO 2016/047289 A, WO 2014/185332 A, and WO 2019/171709 A (Patent Literatures 3 to 5) also disclose other polyolefin-based resin compositions used as adhesive resin compositions
Data Source
AI summary
Disclosed is a coating material comprising 100 parts by mass of an acid-modified polypropylene (A) and at least 450 parts by mass of organic solvents (B), wherein the acid-modified polypropylene has a melting point of 90° C. or lower and the organic solvents (B) comprises 80-99 mass % aromatic hydrocarbon solvent (B1) and 20-1 mass % one or more solvents (B2) selected from the group consisting of ester-based solvents, ketone-based solvents, and alcohol-based solvents, the sum of the proportion of the ingredient (B1) and the proportion of the ingredient (B2) being 100 mass %. The coating material may further contain a compound (C) having, in the molecule, two or more functional groups capable of forming a chemical bond with a carboxyl group, in an amount of 0.1-20 parts by mass. The compound (C) having, in the molecule, two or more functional groups capable of forming a chemical bond with a carboxyl group may be one having no hydrolyzable group. Also disclosed are: a coating film formed from the coating material; a layered product comprising the coating film and a substrate film; and a flexible flat cable including the layered product.