Optical Film with Cellulose Ester and Polyester for LCD Durability
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Solution Overview
Problem
Current optical films for liquid crystal display devices face challenges in achieving a thin film thickness with low retardation and high durability under high temperature and high humidity environments, as existing solutions either deteriorate display performance or fall short in durability.
Innovation Solution
An optical film comprising cellulose ester and a polyester with a specific recurring unit and blocked terminal, combined with a durability improving agent, is developed to achieve a thickness of 10-45 μm, with in-plane retardation and thickness direction retardation within specific ranges, enhancing both optical characteristics and polarizer durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If the film thickness is reduced to meet the thinning demand of liquid crystal display devices, then the device thickness is reduced, but the durability of the polarizer under high temperature and high humidity environment deteriorates
Solution Approach 1:
The patent uses a composite material system consisting of cellulose acylate as the base polymer and polyester resin as a modifier. This composite structure allows the film to achieve both thinness and durability by combining the advantages of different materials: cellulose acylate provides good optical properties and processability, while polyester resin enhances durability and moisture resistance. The specific composition ratio and molecular structure of the composite enable the thin film to maintain polarizer protection capability.
2Reliability
If conventional optical films are used to ensure polarizer durability, then the durability is maintained, but the retardation is high which deteriorates display performance of IPS liquid crystal display devices
Solution Approach 1:
The patent optimizes specific parameters of the cellulose acylate and polyester resin, including degree of substitution, molecular weight, and compositional ratio. By precisely controlling these parameters, the film achieves low retardation (Re ≤ 5 nm and Rth ≤ 5 nm) while maintaining high polarizer durability. The modified parameters enable the material to simultaneously satisfy optical performance requirements for IPS displays and durability requirements for polarizer protection.
3Length of stationary object
If the film thickness is reduced, then the device becomes thinner, but the optical characteristics such as retardation control become more difficult
Solution Approach 1:
The patent introduces polyester resin as a local modifier within the cellulose acylate matrix. This local quality adjustment allows specific regions of the film to have enhanced properties that compensate for the reduced overall thickness. The polyester resin components are strategically incorporated to provide localized structural support and optical property control, enabling precise retardation management in thin films.
Data Source
AI summary
An optical film having a thickness of from 10 to 45 μm and containing a cellulose ester, a polyester having a recurring unit represented by the formula 1A and having a blocked terminal, and a durability improving agent for a polarizer wherein Re and Rth are from −5 to 5 nm at a wavelength of 590 nm can be used as an polarizing plate protective film and is capable of ensuring the durability of the polarizer under a high temperature and high humidity environment. X represents an acyclic divalent linking group, R represents an alkyl, alkenyl, alkynyl or aryl group, and m represents an integer of from 0 to 4.