Flexible Display Substrate Structure for Heat-Resistant Insulation

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Solution Overview

Problem

Plastic substrates used in flexible displays suffer from inferior heat resistance, thermal conductivity, and electrical insulation compared to glass substrates, leading to issues like deformation and afterimages during high-temperature manufacturing processes.

Innovation Solution

A substrate for display devices comprising a first polyimide resin layer with a Td1% of 570°C or more and a yellowness index of 25 to 60, a second polyimide resin layer with a yellowness index of less than 25, and inorganic material layers of specific thicknesses positioned between and on these resin layers to enhance heat resistance and electrical insulation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a plastic substrate is used to achieve lightweight and flexible properties, then adaptability and ease of manufacture are improved, but heat resistance and electrical insulation deteriorate

Engineering Contradiction:

ImproveflexibilityVSAvoidheat resistance

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs a composite structure consisting of multiple polyimide resin layers with different yellowness indices and inorganic material layers. This composite material approach combines the flexibility and light weight of plastic substrates with the heat resistance and electrical insulation properties of inorganic materials, resolving the contradiction between adaptability and reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies local quality by using polyimide resin layers with different yellowness indices (25-60 for the first layer, less than 25 for the second layer) and positioning inorganic material layers at specific locations. This creates zones with different functional properties within the same substrate, allowing the substrate to exhibit both flexibility and heat resistance in different regions.

Inventive Principle:

Principle #3Local quality

2Productivity

If a plastic substrate is used to enable continuous manufacturing process, then productivity is improved, but manufacturing precision deteriorates due to deformation in high-temperature processes

Engineering Contradiction:

Improvecontinuous manufacturing capabilityVSAvoidfilm deformation control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent controls the yellowness index parameter of polyimide resin layers (first layer: 25-60, second layer: less than 25) and the thickness of inorganic material layers (100-700 nm for first layer, 100-500 nm for second layer). These parameter optimizations enable the substrate to maintain dimensional stability during high-temperature continuous manufacturing processes while preserving flexibility.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The composite structure of multiple polyimide layers with different optical properties and inorganic material layers provides both the flexibility needed for continuous manufacturing and the thermal stability required to prevent deformation, thereby resolving the contradiction between productivity and manufacturing precision.

Inventive Principle:

Principle #40Composite materials

3Temperature

If polyimide resin layers are used to achieve heat resistance, then temperature resistance is improved, but optical quality deteriorates due to high yellowness index

Engineering Contradiction:

Improveheat resistanceVSAvoidoptical quality

Core Design Contradiction:

TemperatureVSIllumination intensity

Solution Approach 1:

The patent applies local quality by using a first polyimide resin layer with a higher yellowness index (25-60) that provides heat resistance, combined with a second polyimide resin layer having a lower yellowness index (less than 25) that maintains optical quality. This spatial differentiation of material properties allows the substrate to exhibit both heat resistance and good optical characteristics.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The composite structure combines polyimide resin layers with different yellowness indices and inorganic material layers to achieve a balance between heat resistance and optical quality. The inorganic material layers further enhance heat resistance while the second polyimide layer with low yellowness index ensures good optical properties.

Inventive Principle:

Principle #40Composite 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 substrate maintains optical and mechanical stability during high-temperature processes, reducing deformation and afterimages, while ensuring high resistance and device stability by blocking air and moisture, thus providing a high-quality display device substrate.

Implementation Method 1

blocking air and moisture

Methodology Applied

Scientific EffectBarrier effect:

Implementation Method 2

heat resistance characteristics, without causing a film deformation even in high-temperature processes

Methodology Applied

Scientific EffectThermal resistance: Thermal Insulation

Implementation Method 3

electrical insulation property

Methodology Applied

Scientific EffectElectrical insulation: Electrical Resistance

Data Source

PatentEP4137469B1Board for display device or flexible display device, and display device or flexible display device

Publication Date: 2026.01.07 LG CHEM LTD

AI summary

The present disclosure relates to a substrate for a display device or a flexible display device that realizes low dielectric properties and excellent heat resistance, and a display device or a flexible display device using the same.