Optical Plastic Film Hardness via Phase Difference Control
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Solution Overview
Problem
Conventional plastic films used in image display devices have insufficient pencil hardness, leading to scratches and mechanical weaknesses, particularly when used as touch panel surfaces, and increasing thickness to improve hardness results in thicker, more prone to breakage devices.
Innovation Solution
An optical plastic film with an in-plane phase difference of 300 nm to 1,450 nm and an average erosion rate of 1.4 μm/g within 20 μm depth, along with a ratio of variation in erosion rate of 0.100 or less, providing enhanced pencil hardness without increasing in-plane phase difference, suitable for use in polarization plates and image display devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the thickness of the plastic film is increased to improve pencil hardness, then the pencil hardness is improved, but the device becomes thicker and the film becomes more prone to breakage
Solution Approach 1:
The patent changes the optical parameters of the plastic film, specifically controlling the in-plane phase difference to 300 nm or more and 1,450 nm or less, to achieve improved pencil hardness while maintaining thin film thickness. This parameter optimization allows the film to exhibit enhanced surface properties without increasing thickness.
Solution Approach 2:
The patent utilizes composite material properties by combining specific plastic resin compositions with controlled molecular orientation achieved through stretching. The composite structure of the stretched plastic film creates a material that simultaneously provides mechanical strength, appropriate optical phase difference, and improved pencil hardness while maintaining thin profile.
2Length of stationary object
If a conventional plastic film is used to maintain thin profile, then the device remains thin, but the film has insufficient pencil hardness and is easily scratched
Solution Approach 1:
The patent optimizes the in-plane phase difference parameter to 300-1,450 nm and controls the erosion rate to 1.4 μm/g or more, which fundamentally changes the surface properties of the thin film to achieve adequate pencil hardness without requiring additional protective layers or increased thickness.
3Strength
If a uniaxially stretched plastic film is used to improve mechanical strength, then the mechanical strength is improved, but the film has a tendency to break in the stretch direction
Solution Approach 1:
The patent controls the in-plane phase difference parameter and erosion rate to optimize the molecular orientation and crystalline structure of the stretched film, reducing the anisotropy that causes breakage in the stretch direction while maintaining mechanical strength.
Solution Approach 2:
The patent creates a composite material structure through controlled stretching and composition that distributes stress more evenly throughout the film, reducing the tendency to break in the stretch direction while maintaining overall mechanical strength.
Data Source
AI summary
The present disclosure addresses the problem of providing an optical plastic film having favorable pencil hardness without an increase in the in-plane phase difference. Disclosed is an optical plastic film comprising a first surface and a second surface that is a surface on a side opposite to the first surface, wherein the plastic film has an in-plane phase difference of 300 nm or more and 1,450 nm or less, and in a region within a depth of 20 μm from the first surface in a direction from the first surface to the second surface, an average of an erosion rate is 1.4 μm/g or more.