PVA Polarizer Drying Process for Optical Stability
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Solution Overview
Problem
Conventional polarizer production methods fail to achieve both high durability and stable optical properties over a wide band, especially under heating or humidifying conditions, due to insufficient crosslinking of polyvinyl alcohol films during the drying process.
Innovation Solution
A method involving a polyvinyl alcohol film subjected to dyeing, crosslinking, and stretching processes, followed by a drying process with a quick drying stage that reduces water content by at least 15% in ½ to 1/30 of the total drying time, using a heating roller to stabilize the iodine complex and enhance crosslinking, resulting in a polarizer with improved durability and optical stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional drying process is used to remove water from the polyvinyl alcohol film, then the film can be dried, but the crosslinking is insufficient and optical properties degrade under heating or humidifying conditions
Solution Approach 1:
The patent applies preliminary action by performing a quick drying stage at the beginning of the drying process to rapidly remove surface water before the film structure sets. This preliminary water removal prevents subsequent water-related optical property changes and ensures stable crosslinking, resolving the contradiction between durability and optical stability.
Solution Approach 2:
The patent implements periodic action by dividing the drying process into distinct stages: a quick drying stage followed by a slow drying stage. This multi-stage approach allows different drying rates at different times, ensuring both rapid initial water removal for stability and gradual completion for thorough drying, thereby achieving both durability and optical property stability.
2Manufacturing precision
If the drying time is extended to ensure thorough water removal, then the film can be completely dried, but the production efficiency decreases
Solution Approach 1:
The patent applies periodic action by implementing a two-stage drying process with different drying rates. The quick drying stage rapidly removes the majority of water, and the slow drying stage completes the process, achieving thorough water removal in less total time than conventional uniform drying, thus improving productivity while maintaining water content control.
Solution Approach 2:
The patent uses parameter changes by varying the drying rate throughout the drying process. By changing from a high drying rate in the initial stage to a lower drying rate in the later stage, the process achieves both efficient water removal and precise water content control, resolving the contradiction between manufacturing precision and productivity.
3Productivity
If the water content is reduced too rapidly, then the drying time is shortened, but the crosslinking becomes insufficient and optical properties become unstable
Solution Approach 1:
The patent implements periodic action by structuring the drying process into sequential stages with different rates. The quick drying stage operates at high speed for a limited period to remove surface water, followed by a slow drying stage that completes water removal gradually, ensuring both high productivity and optical property stability through controlled temporal variation in drying rate.
Solution Approach 2:
The patent applies preliminary action by performing rapid water removal at the beginning when the film structure is still flexible and can accommodate the quick drying without compromising crosslinking. This preliminary high-speed drying is followed by slower drying to complete the process, achieving both speed and stability.
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 produces a polarizer with stable optical properties and low crossed transmittance over a wide band, maintaining hue consistency under various conditions, and when integrated into a polarizing plate with a low water-vapor permeable protective film, it exhibits minimal changes in optical properties during durability tests.
Implementation Method 1
the quick drying stage may be performed by bringing the film into contact with a heating roller
Data Source
AI summary
A method for producing a polarizer of the present invention includes: subjecting a polyvinyl alcohol film to at least a dyeing process, a crosslinking process and a stretching process, then subjecting the film, in which all of the processes have been performed, having a water content of 25 to 55% by weight to a drying process, wherein in the drying process, the water content of the film is reduced by at least 15% by weight, so that the film has a water content of 5 to 35% by weight, and the drying process has a quick drying stage in which the water content of the film is reduced by at least 10% by weight in a time period of ½ to 1/30 of the total drying time of the drying process. The polarizer obtained by the production method has durability and has good optical properties over a wide band.