Thin Polarizer Preparation via Segmented Stretching
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Solution Overview
Problem
Existing methods for manufacturing thin polarizers face challenges in achieving high magnification stretching and process stability, often resulting in defects such as fractures and uneven adhesion due to inadequate water resistance in adhesives, which deteriorate the optical properties of polyvinyl alcohol-based films.
Innovation Solution
A method involving the formation of a film laminate by bonding a non-stretched polyvinyl alcohol-based film to a base film using an adhesive containing an amine-based metal compound crosslinking agent and a polyvinyl alcohol-based resin with an acetoacetyl group, followed by stretching to achieve a thickness of 10 μm or less, while maintaining sufficient water resistance and peeling strength for stable separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a polyvinyl alcohol-based film with thickness exceeding 60 μm is used for stretching, then the film can be stretched without breakage, but the final polarizer thickness cannot be reduced to 10 μm or less
Solution Approach 1:
The invention divides the stretching process into two distinct stages: a preliminary stretching stage performed on the thick film (60 μm or more) to prevent breakage, followed by a final stretching stage performed on the thinner film after it has been bonded to the base film. This segmentation allows each stage to be optimized independently - the first stage ensures process stability while the second stage achieves the target thickness of 10 μm or less.
2Length of moving object
If a coating or co-extruding method is used to manufacture the polyvinyl alcohol layer, then the film can be made thin, but the polyvinyl alcohol layer and base layer cannot be easily separated after stretching
Solution Approach 1:
The invention performs preliminary bonding of the polyvinyl alcohol film to the base film before the stretching process. This preliminary action ensures that the film is securely attached during stretching, preventing defects. The bonding is designed to allow easy separation after stretching is complete, resolving the contradiction between making the film thin and enabling easy separation.
3Ease of manufacture
If general polyvinyl alcohol-based adhesive is used for bonding, then the adhesive initially bonds the films, but water resistance is degraded causing adhesive to melt and flow during stretching and cleaning processes
Solution Approach 1:
The invention modifies the adhesive composition by incorporating specific additives or crosslinking agents that enhance water resistance while maintaining initial bonding capability. This parameter change in the adhesive's chemical properties allows it to resist melting and flowing during the stretching and cleaning processes, while still providing adequate initial bonding between the films.
4Length of moving object
If the polyvinyl alcohol film is made thin to reduce polarizer thickness, then the final product is thinner, but the degree of swelling increases and breakage occurs easily during stretching
Solution Approach 1:
The invention segments the stretching process into two stages: first stretching the thick film (60 μm or more) to reduce swelling and increase strength, then bonding to the base film, and finally stretching the combined structure to achieve the target thickness of 10 μm or less. This segmentation allows the film to maintain sufficient strength during each stage while achieving the final thin dimension.
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
This approach enables the production of thin polarizers with excellent optical properties, including a single body transmittance of 40 to 45% and a degree of polarization of 99.9% or more, while reducing the occurrence of fractures and maintaining process stability.
Implementation Method 1
bonding a non-stretched polyvinyl alcohol-based film having a thickness of 10 to 60 μm to at least one surface of a non-stretched base film using an adhesive including an amine-based metal compound crosslinking agent and a polyvinyl alcohol-based resin containing an acetoacetyl group
Implementation Method 2
stretching the film laminate so as to allow the polyvinyl alcohol-based film to have a thickness of 10 μm or less
Data Source
AI summary
Provided are a method for preparing a thin polarizer, including forming a film laminate by bonding a non-stretched polyvinyl alcohol-based film having a thickness of 10 to 60 μm to at least one surface of a non-stretched base film using an adhesive including an amine-based metal compound crosslinking agent and a polyvinyl alcohol-based resin containing an acetoacetyl group, and stretching the film laminate so as to allow the polyvinyl alcohol-based film to have a thickness of 10 μm or less, and a thin polarizer manufactured through the same.