Flexible Plastic Substrate with Hard Coating for Display Devices

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Solution Overview

Problem

Current portable display devices face challenges in finding a flexible plastic film that balances mechanical properties like hardness and flexibility with optical properties, making it difficult to replace rigid glass substrates without compromising performance.

Innovation Solution

A flexible plastic substrate is developed with a poly(amide-imide) copolymer and a hard coating layer containing a crosslinked siloxane copolymer, which provides a pencil hardness of at least 2H and total light transmittance of over 89% in the 350 nm to 750 nm wavelength range, along with improved flexural characteristics.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a rigid glass substrate is used for the protective window, then hardness and optical properties are improved, but flexibility and impact resistance deteriorate

Engineering Contradiction:

ImprovehardnessVSAvoidflexibility

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The patent replaces the rigid glass substrate with a flexible plastic film as the protective window. The plastic film maintains adequate hardness while providing the required flexibility and impact resistance for portable display devices, directly resolving the contradiction between hardness and flexibility.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent uses a composite structure consisting of a plastic film substrate with a hard coating layer applied to its surface. This composite material combines the flexibility of the plastic substrate with the enhanced surface hardness of the coating layer, simultaneously achieving both flexibility and hardness requirements.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If a plastic film is used to substitute glass, then flexibility is improved, but hardness deteriorates

Engineering Contradiction:

ImproveflexibilityVSAvoidhardness

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The patent applies a hard coating layer on the plastic film substrate to create a composite structure. The coating layer provides the necessary surface hardness (pencil hardness ≥2H) while the underlying plastic film maintains flexibility, thus resolving the hardness deficiency of plain plastic films.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent applies the hard coating layer specifically on the surface of the plastic film where hardness is required for protection, while the bulk plastic film retains its flexible properties. This localized application of different properties resolves the contradiction between surface hardness and overall flexibility.

Inventive Principle:

Principle #3Local quality

3Strength

If a hard coating layer is applied on plastic substrate, then hardness is improved, but optical properties (light transmittance) may deteriorate

Engineering Contradiction:

ImprovehardnessVSAvoidlight transmittance

Core Design Contradiction:

StrengthVSIllumination intensity

Solution Approach 1:

The patent optimizes the parameters of the hard coating layer, including its composition (siloxane copolymer with specific functional groups), thickness (5-50 μm), and curing conditions, to achieve the balance between hardness (≥2H) and light transmittance (≥89%). By carefully controlling these parameters, both hardness and optical properties are maintained.

Inventive Principle:

Principle #35Parameter changes

4Reliability

If plastic film is used instead of glass, then impact resistance is improved, but mechanical properties (hardness) deteriorate

Engineering Contradiction:

Improveimpact resistanceVSAvoidhardness

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent creates a composite structure with a plastic film substrate providing impact resistance and flexibility, combined with a hard coating layer providing surface hardness. This composite approach simultaneously achieves both impact resistance and adequate hardness that neither material could provide alone.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent uses a flexible plastic film as the base structure that inherently provides impact resistance through its flexibility, then adds a hard coating layer to compensate for the surface hardness deficiency, achieving both impact resistance and hardness.

Inventive Principle:

Principle #30Flexible shells and thin films

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 achieves a balance of high hardness, flexibility, and optical clarity, making it suitable for use as a protective window in flexible display devices without the fragility of glass.

Implementation Method 1

a hard coating layer disposed on a first surface of the film, wherein the hard coating layer includes a crosslinked siloxane copolymer

Methodology Applied

Scientific EffectCrosslinking: Chemical Bonding

Data Source

PatentEP3312220B1Plastic substrate and display device including same

Publication Date: 2020.04.15 SAMSUNG ELECTRONICS CO LTD

Figure 1~2

AI summary

A plastic substrate includes a film including a poly(amide-imide) copolymer and a hard coating layer disposed on one surface of the film including the poly(amide-imide), wherein the hard coating layer includes a siloxane copolymer cross-linked through a cross-linkable functional group thereof, and the plastic substrate has pencil scratch hardness of greater than or equal to 2H measured at a vertical load of about 1 kg according to ASTM D3363, transmittance of greater than or equal to about 89 % in about 350 nm to about 750 nm wavelength region, and flexural characteristics.