Polyimide Film Drying Process for Transparency and Heat Resistance
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Solution Overview
Problem
Conventional production methods of polyimide films face challenges in achieving high colorless transparency and heat resistance, leading to suboptimal performance in optical and display device applications.
Innovation Solution
A solution flow casting method involving specific drying steps, including evaporating organic solvents with controlled oxygen content and temperature, is employed to produce a polyamic acid or polyimide film with enhanced transparency and heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the solution is exposed to high temperature exceeding 240°C upon evaporating the solvent by drying, then the solvent is completely evaporated, but the resulting resin film suffers decrease in total light transmittance and increase in haze
Solution Approach 1:
The drying process is divided into multiple stages with different temperature conditions. The first drying stage uses high temperature (exceeding 240°C) to evaporate most of the solvent, while the second drying stage uses lower temperature (200°C or lower) to remove residual solvent without causing resin degradation. This segmentation resolves the contradiction by separating the solvent evaporation function from the resin protection function into distinct process stages.
Solution Approach 2:
The drying temperature parameter is changed dynamically during the process. Initially, high temperature is applied to achieve rapid solvent evaporation, then the temperature is reduced to 200°C or lower for the final drying stage. This parameter change allows complete solvent removal while preventing resin film degradation that would cause haze and reduce light transmittance.
2Temperature
If conventional polyimide production methods are used, then heat resistance is achieved, but high colorless transparency cannot be provided stably
Solution Approach 1:
The drying temperature parameter is optimized to 200°C or lower in the second drying stage, which prevents resin degradation and maintains colorless transparency while still achieving complete solvent evaporation. This parameter optimization resolves the contradiction by finding the optimal temperature window that satisfies both heat resistance requirements and optical transparency requirements.
Solution Approach 2:
The two-stage drying process ensures continuous and complete solvent removal without interruption. The first stage removes the majority of solvent rapidly, and the second stage completes the evaporation of residual solvent under controlled conditions. This continuous action ensures both heat resistance and stable colorless transparency are achieved.
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 method results in a polyimide film with high colorless transparency, excellent heat resistance, and flatness, suitable for use in liquid crystal display devices and organic EL display devices.
Implementation Method 1
the solution in the solvent solution is evaporated by drying to provide a resin film
Implementation Method 2
a drying step of heating the resin film by using at least one infrared radiation heater
Data Source
AI summary
A method for producing a colorless transparent resin film by a solution flow casting method containing: flow-casting an organic solvent solution of a polyamic acid or a polyimide on a support; and drying, the method containing at least the following step (1), step (2) and step (3) in this order, and an apparatus therefor:(1) a step of flow-casting an organic solvent solution of a polyamic acid or polyamide on a support,(2) a step of evaporating the organic solvent while blowing a gas having an oxygen content of from 0.001 to 15% by volume at a temperature of from 100 to 170° C. onto the flow-cast material, and releasing as a self-supporting film from the support, and(3) a step of performing the following step (3-1) and step (3-2) in this order:(3-1) a step of lowering a residual ratio of the organic solvent in the self-supporting film while blowing a gas having an oxygen content of 15% by volume or less at a temperature of from 100 to 250° C. onto the film by using at least one dryer of a type of blowing a heated gas, and(3-2) a step of lowering the residual ratio of the organic solvent in the self-supporting film while blowing a gas having an oxygen content of 5% by volume or less at a temperature of from 150 to 400° C. onto the film by using at least one dryer of a type of blowing a heated gas.