Thermoset Polyurethane Films for High-Temperature Electronics

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Solution Overview

Problem

Current polymeric films used in the electronics industry, such as those made from polyesters and polycarbonates, have low glass transition temperatures, limiting their thermal stability and requiring additional coatings for chemical resistance, which complicates the application of conductive layers and increases production costs.

Innovation Solution

A composition of polyisocyanates and polyols, specifically using isophorondiisocyanate trimer with diols and triols, is developed to produce thermoset polyurethane films with high glass transition temperatures, enabling the use as substrates for transparent conductive oxides, and a method involving solvent casting and thermal curing to achieve films with high transparency, flexibility, and chemical resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If thermoplastic films with low glass transition temperature are used, then production cost is reduced through melt extrusion, but thermal stability is insufficient and additional coatings are required for chemical resistance

Engineering Contradiction:

Improveproduction costVSAvoidglass transition temperature

Core Design Contradiction:

Ease of manufactureVSTemperature

Solution Approach 1:

The patent changes the fundamental parameter of glass transition temperature by transitioning from thermoplastic to thermoset polyurethane formulation. This enables the film to achieve high thermal stability (Tg > 100°C) while maintaining manufacturability through solution casting process, eliminating the need for additional protective coatings

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The invention uses a composite formulation combining polyisocyanates and polyols to create thermoset polyurethane films with enhanced thermal and chemical resistance properties, while maintaining optical transparency and flexibility required for electronic applications

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If melt extrusion is used for low Tg polymers, then production cost is reduced, but optical quality deteriorates due to gel formation and high optical retardation

Engineering Contradiction:

Improveproduction costVSAvoidoptical quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent replaces the mechanical melt extrusion process with a chemical solution casting approach. This substitution eliminates the high-temperature mechanical stress that causes gel formation and optical defects, while maintaining production efficiency through a simplified processing route

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If additional coatings are applied to improve chemical resistance, then chemical resistance is improved, but device complexity and production cost increase

Engineering Contradiction:

Improvechemical resistanceVSAvoidstructure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thermoset polyurethane film performs multiple functions simultaneously: it provides the structural substrate, ensures optical transparency, delivers chemical resistance, and offers thermal stability. This multi-functionality eliminates the need for separate protective coatings and simplifies the overall device structure

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

The resulting polyurethane films exhibit high glass transition temperatures, allowing for improved thermal stability and reduced electric resistivity of conductive coatings, enhancing their suitability for electronic devices like touch panels and photo-voltaic cells while maintaining transparency and flexibility.

Implementation Method 1

A composition of polyisocyanates and polyols, specifically using isophorondiisocyanate trimer with diols and triols, is developed to produce thermoset polyurethane films

Methodology Applied

Scientific EffectPolymerization: Chemical Bonding

Implementation Method 2

a method involving solvent casting and thermal curing to achieve films with high transparency, flexibility, and chemical resistance

Methodology Applied

Scientific EffectEvaporation: Evaporation

Implementation Method 3

a method involving solvent casting and thermal curing to achieve films with high transparency, flexibility, and chemical resistance

Methodology Applied

Scientific EffectThermal treatment: Heating

Data Source

PatentEP3197678B1Colorless, transparent and heat resistant polyurethane films and methods for manufacturing the same

Publication Date: 2020.04.08 COVESTRO DEUTSCHLAND AG

Figure 1

AI summary

The present inventions concerns compositions for producing thermoset polyurethanes, comprising polyisocyanates and polyols selected from a list consisting of allicyclic, aromatic compounds and branched polyesters. The films obtained from these compositions exhibit a high transparency, high thermal stability and good chemical resistance, and a method to produce the same. The said polyurethane films can be widely used in electronics industry where high transparency, high thermal resistance and good chemical resistance are the main requirements. Particularly, these films can be used as the substrates for conductive coatings and barrier coatings. These functionally coated films are particularly useful in applications such as touch panels or photo-voltaic cells.