Polyester Film UV Absorbent Migration Control
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Solution Overview
Problem
Low-priced polymer films used in polarizing plates for liquid crystal displays, such as polyester and (meth)acrylate films, suffer from variations in retardation, haze, and transmittance due to UV absorbent migration when stretched, leading to image quality deterioration.
Innovation Solution
A polarizing plate comprising a polyester film with a UV absorbent content of 0.1% to 5% by weight, where the film includes a polyester base film and a primer layer, is stretched in the transverse direction to prevent UV absorbent migration and maintain stable optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If low-priced polyester films are used as protective films in polarizing plates, then cost is reduced, but the films suffer from UV absorbent migration during stretching causing variations in retardation, haze, and transmittance
Solution Approach 1:
The patent introduces a silane coupling agent as an intermediary substance between the UV absorbent and polyester base film. This coupling agent forms a chemical bridge that prevents UV absorbent migration while maintaining the low-cost advantage of polyester films. The silane coupling agent reacts with both the UV absorbent and the polyester matrix, creating a stable interface that eliminates the migration problem without requiring expensive alternative films like TAC.
2Object-affected harmful factors
If PET film is stretched to high elongation to prevent rainbow spots, then image quality improves, but UV absorbent migration increases causing deterioration in optical properties
Solution Approach 1:
The silane coupling agent serves as a mediator that anchors the UV absorbent molecules to the polyester matrix during high-elongation stretching. This intermediary connection prevents UV absorbent migration even under the mechanical stress of high elongation, allowing the film to achieve the necessary optical uniformity without compromising compositional stability.
Solution Approach 2:
The patent modifies the chemical parameters of the polyester film system by incorporating silane coupling agents. This chemical modification changes the interaction parameters between UV absorbent and polymer matrix, increasing the binding strength and preventing migration during the high-elongation stretching process required to eliminate rainbow spots.
3Object-affected harmful factors
If UV absorbent is added to protect liquid crystals from UV light, then UV protection is provided, but the UV absorbent migrates during stretching causing variations in optical properties
Solution Approach 1:
The silane coupling agent acts as an intermediary that chemically bonds the UV absorbent to the polyester matrix. This intermediary connection ensures that the UV absorbent remains fixed in position during stretching and processing, maintaining both UV protection functionality and optical property stability throughout the film's lifecycle.
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 solution results in a polarizing plate with reduced variation rates in retardation, haze, and transmittance, preventing rainbow spots and maintaining image quality, while effectively blocking UV light and enhancing the durability of the film.
Implementation Method 1
the PET film contains a UV absorbent to protect the liquid crystals
Data Source
AI summary
A polarizing plate includes a polarizer and a polyester film formed on at least one surface of the polarizer. The polyester film includes a polyester base film and a primer layer formed on at least one surface of the polyester base film. The polyester film contains about 0.1 wt % to about 5 wt % of a UV absorbent. In addition, a liquid crystal display includes the polarizing plate. A method of fabricating a polarizing plate includes preparing a multilayer film containing about 0.1 wt % to about 5 wt % of a UV absorbent, stretching the multilayer film to about 2 to about 10 times its initial length in a transverse direction (TD) to prepare a polyester film, and attaching the polyester film to at least one surface of a polarizer. The multilayer film comprises a polyester base film and a primer layer on at least one surface of the polyester base film.