Thin Polarizer Manufacturing via Low-Temperature Stretching
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Solution Overview
Problem
Current methods for manufacturing thin polarizers face limitations in achieving high-ratio stretching, optical characteristics, and low-temperature processing due to the use of polyethylene terephthalate resins, which result in increased costs and difficulties in separating the polarizer from the base film, and polyvinyl alcohol films are prone to breakage and damage during high-temperature stretching processes.
Innovation Solution
A stretched laminate is formed using a non-stretched thermoplastic polyurethane film with a polyvinyl alcohol-based film attached, allowing for high-ratio stretching at low temperatures (20°C to 80°C) with either a dry or wet boric acid solution process, enabling a thin polarizer with a thickness of 10 µm or less and superior optical characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If polyethylene terephthalate resin is used as base film, then stretching ratio is limited to 5-5.5 times, but optical characteristics cannot be improved further
Solution Approach 1:
The patent changes the material parameter of the base film from polyethylene terephthalate to polypropylene. This material substitution enables stretching ratios of 6 times or more while maintaining film integrity, thereby resolving the limitation on stretching ratio and allowing further improvement of optical characteristics through higher stretching ratios.
Solution Approach 2:
The patent creates a composite structure consisting of a polypropylene base film and a polyvinyl alcohol-based film. The polypropylene base film provides mechanical strength and stretchability, while the polyvinyl alcohol-based film provides optical functionality. This composite structure enables high-ratio stretching while maintaining good optical characteristics.
2Ease of manufacture
If polyethylene terephthalate resin is used as base film, then high-temperature dry stretching (120°C to 170°C) is required, but additional heating process and increased costs are incurred
Solution Approach 1:
The patent changes the material parameter of the base film from polyethylene terephthalate to polypropylene, which has different thermal properties. This allows the stretching process to be conducted at lower temperatures (below the glass transition temperature of polyvinyl alcohol), eliminating the need for additional heating processes and reducing energy consumption.
Solution Approach 2:
The patent performs the stretching process before the polyvinyl alcohol-based film undergoes cross-linking. This preliminary stretching action is performed at lower temperatures using the polypropylene base film's mechanical properties, avoiding the need for high-temperature heating that would be required if stretching were performed after cross-linking.
3Productivity
If high-temperature dry stretching is performed, then stretching ratio can be increased, but polyvinyl alcohol film may be damaged or properties changed
Solution Approach 1:
The patent changes the material parameter of the base film to polypropylene, which has a lower melting point and different thermal behavior compared to polyethylene terephthalate. This enables stretching to be performed at temperatures below the glass transition temperature of polyvinyl alcohol, preventing film damage while achieving high stretching ratios of 6 times or more.
Solution Approach 2:
The patent performs stretching as a preliminary action before the polyvinyl alcohol-based film undergoes cross-linking and other heat treatments. The polypropylene base film provides sufficient mechanical strength during this preliminary stretching, enabling high-ratio stretching without damaging the polyvinyl alcohol film, which then undergoes cross-linking to fix the stretched structure.
4Ease of manufacture
If polyethylene terephthalate resin is used as base film, then separation of polarizer from base film becomes difficult
Solution Approach 1:
The patent changes the material parameter of the base film from polyethylene terephthalate to polypropylene. The polypropylene base film exhibits different surface properties and adhesion characteristics that facilitate easier separation from the polyvinyl alcohol-based film after stretching, simplifying the manufacturing process and improving peelability.
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 enables the production of thin polarizers with high-ratio stretchability, superior optical characteristics, and reduced manufacturing costs by using a thermoplastic polyurethane film as a base, allowing for easy separation and minimizing film damage, while achieving a thickness of 10 µm or less.
Implementation Method 1
a stretched laminate which is processable using either of a low-temperature dry stretching process and a wet stretching process using an aqueous boric acid solution, stretchable with a high stretching ratio
Implementation Method 2
wet stretching process using an aqueous boric acid solution
Data Source
Figure 1~2
AI summary
There is provided a stretched laminate formed by stretching a laminate including: a non-stretched thermoplastic polyurethane film; and a non-stretched polyvinyl alcohol-based film attached to at least one surface of the thermoplastic polyurethane film, wherein the polyvinyl alcohol-based film has a thickness of 10 µm or less after stretching. In addition, there are provided a method of manufacturing a thin polarizer using the stretched laminate, a thin polarizer manufacturing by the method, and a polarizing plate including the thin polarizer.