Polyimide Film Processing for Hard, Bendable Cover Substrates
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Solution Overview
Problem
Existing polyimide-based films struggle to achieve significant improvements in bending characteristics while maintaining surface hardness, optical properties, and moisture barrier properties, limiting their application in flexible electronic devices.
Innovation Solution
A manufacturing method involving roll-to-roll processing with controlled elongation and shrinkage in specific directions, followed by heat treatments at precise temperatures and tensions, enhances the polyimide film's bending characteristics and surface hardness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional transparent plastic substrates are used to achieve high hardness at small thickness, then surface hardness is improved, but bending characteristics deteriorate (curvature radius of 1 mm or less cannot be achieved)
Solution Approach 1:
The patent applies parameter changes by precisely controlling heat treatment temperature (250-330°C), elongation percentage (100-135% in MD), shrinkage percentage (75-100% in TD), and tension (30-160 N/mm²) to transform the polyimide film structure. These parameter adjustments enable simultaneous achievement of high surface hardness and excellent bending characteristics that cannot be obtained by conventional methods
Solution Approach 2:
The patent uses composite materials by combining polyimide base resin with specific additives and creating a multi-layered molecular structure through controlled heat treatment and mechanical deformation. This composite approach enhances both surface hardness and flexibility, resolving the contradiction between hardness and bendability
2Strength
If heat treatment is applied to improve surface hardness, then abrasion resistance is improved, but bending characteristics deteriorate
Solution Approach 1:
The patent applies preliminary action by performing elongation and shrinkage treatments before the final heat treatment to pre-organize the molecular structure. This preliminary mechanical deformation creates a structure that can subsequently withstand heat treatment while maintaining bending flexibility, preventing the deterioration of bendability that would occur with heat treatment alone
Solution Approach 2:
The patent applies periodic action through multiple sequential heat treatment steps (first heat treatment, second heat treatment) with intermediate mechanical treatments. This periodic cycling of thermal and mechanical processes allows progressive improvement of surface hardness while preserving bending characteristics, avoiding the adverse effects of single prolonged heat treatment
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 polyimide-based film exhibits excellent bending characteristics, surface hardness, and optical properties, making it suitable for flexible electronic devices with rollability or foldability, particularly as a cover substrate for devices with a radius of curvature of 1 mm or less.
Implementation Method 1
a polyimide-based film obtained as a gel state formed by being cast on a support
Implementation Method 2
conducting first heat treatment (S1) on a polyimide-based film obtained as a gel state
Implementation Method 3
conducting second heat treatment (S2) on the first heat-treated polyimide-based film
Implementation Method 4
elongating the polyimide-based film at an elongation percentage of not less than 100% and less than 135% in a machine direction (MD)
Implementation Method 5
shrinking the polyimide-based film at a shrinkage percentage of more than 75% and not more than 100% in a transverse direction (TD)
Implementation Method 6
conducting second heat treatment (S2) on the first heat-treated polyimide-based film while further elongating the polyimide-based film in the machine direction (MD) at a tension not less than 30 N/mm2 and less than 160 N/mm2
Data Source
AI summary
The present invention relates to a method for manufacturing a polyimide-based film and a polyimide-based film manufactured thereby and, particularly, to a method for manufacturing a polyimide-based film and a polyimide-based film manufactured thereby, wherein the polyimide-based film is useful as a cover substrate for a flexible electronic device since flexure characteristics thereof, represented by yield elongation, are excellent.