Optical Plastic Film Hardness Gradient for Dual Scratch Resistance

Solution Overview

Problem

Oriented plastic films with high elastic modulus exhibit good scratch resistance against hard materials but are easily scratched by soft materials, while those with low elastic modulus provide better resistance to soft materials but are vulnerable to hard materials, creating a trade-off in scratch resistance.

Innovation Solution

An optical plastic film with specific indentation hardness ratios and controlled orientation of slow axis directions, in-plane and thickness direction retardations, ensuring balanced scratch resistance against both hard and soft materials.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If oriented plastic films with high elastic modulus are used, then scratch resistance against hard materials is improved, but scratch resistance against soft materials deteriorates

Engineering Contradiction:

Improvescratch resistance against hard materialsVSAvoidscratch resistance against soft materials

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent applies local quality by creating different hardness characteristics at different locations within the plastic film thickness. The surface layer is formulated to have lower indentation hardness for resistance against soft materials, while the inner layer maintains higher hardness for resistance against hard materials. This is achieved by controlling the composition and crystallinity at different depths, allowing each layer to perform its specific protective function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining multiple resin components with different properties in a single plastic film structure. Specifically, it uses a first resin with high elastic modulus and a second resin with lower elastic modulus, creating a composite structure where the combination of materials provides both scratch resistance against hard materials and flexibility against soft materials.

Inventive Principle:

Principle #40Composite materials

2Reliability

If oriented plastic films with low elastic modulus are used, then scratch resistance against soft materials is improved, but scratch resistance against hard materials deteriorates

Engineering Contradiction:

Improvescratch resistance against soft materialsVSAvoidscratch resistance against hard materials

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent applies local quality by creating different hardness characteristics at different locations within the plastic film thickness. The surface layer is formulated to have lower indentation hardness for resistance against soft materials, while the inner layer maintains higher hardness for resistance against hard materials. This is achieved by controlling the composition and crystallinity at different depths, allowing each layer to perform its specific protective function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining multiple resin components with different properties in a single plastic film structure. Specifically, it uses a first resin with high elastic modulus and a second resin with lower elastic modulus, creating a composite structure where the combination of materials provides both scratch resistance against hard materials and flexibility against soft materials.

Inventive Principle:

Principle #40Composite materials

3Strength

If the elastic modulus is increased to improve mechanical strength, then scratch resistance against hard materials is improved, but the film becomes more susceptible to scratching by soft materials

Engineering Contradiction:

Improvemechanical strengthVSAvoidscratching by soft materials

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The patent applies local quality by creating different hardness characteristics at different locations within the plastic film thickness. The surface layer is formulated to have lower indentation hardness for resistance against soft materials, while the inner layer maintains higher hardness for resistance against hard materials. This is achieved by controlling the composition and crystallinity at different depths, allowing each layer to perform its specific protective function optimally.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent applies parameter changes by varying the elastic modulus and indentation hardness parameters across different layers of the plastic film. The surface layer has lower elastic modulus and lower indentation hardness, while the inner layer has higher elastic modulus and higher indentation hardness. This gradient in parameters allows the film to simultaneously resist both hard and soft material scratching while maintaining overall mechanical strength.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12422594B2Plastic film for optical applications, polarizing plate, and image display device

Publication Date: 2025.09.23 DAI NIPPON PRINTING CO LTD

AI summary

Provided is an optical plastic film that can have good scratch resistance against both a hard material and a soft material. An optical plastic film has a first surface and a second surface located on the opposite side to the first surface, wherein the indentation hardness of the cross section on the first surface side, the indentation hardness of the cross section on the second surface side, and the indentation hardness of the cross section in the middle in the thickness direction satisfy a predetermined relationship in the conveyance direction and the transverse direction of the plastic film.