Zero–Zero Birefringence Cellulose Acetate-Based Optical Films by Benzoylation

Abstract

Zero−zero birefringence film is one of the key components in optical displays, and its design and preparation remain a challenge nowadays. Here, we report the synthesis of benzoylated cellulose acetate (BCA), the preparation of BCA films by solution casting, and the birefringent properties of unstretched and stretched BCA films. It is found that zero−zero birefringence films can be fabricated using both unstretched and stretched BCA films. As the degree of substitution of benzoyl (DS Bz ) increases, the out-of-plane birefringence (Δn th ) gradually decreases and changes from positive to negative. Particularly, for DS Bz = 0.511, both the in-plane birefringence (Δn in ) and out-of-plane birefringence (Δn th ) of stretched BCA films are close to zero. The orientations of the acetyl and benzoyl groups under stretching are measured to interpret the underlying compensation mechanisms. Finally, we show that the wavelength dispersion of BCA films with DS Bz = 0.511 varies significantly with the increase in draw ratio, and formulize the normalized birefringence with the relative orientation degree of the benzoyl and acetyl groups. Our results suggest that the birefringence and wavelength dispersion of cellulose acetate-based optical films can be well regulated by a combination of chemical modification and stretching, and have potential significance to the industrial production of zero−zero birefringence films.

Effect of propionyl group on birefringence and wavelength dispersion of propionylated cellulose acetate optical compensation films

“…Figure 1(a) illustrates the chemical structure of PCA. The synthesis mechanism of PCA with different degrees of propionyl substitution is similar to our previous work (Min et al 2022). Firstly, the raw material CA was completely dissolved in DMF.…”

“…Chemical modi cation is a method to improve one aspect of the properties of the original material without affecting other properties, which may be a good method to prepare VA-LCD compensation lm. In the previous work (Min et al 2022), we have successfully prepared IPS-LCD compensation lm by using the method of chemical modi cation.…”

Dual Ionic Liquid-Functionalized Cellulosic Materials: Thermal, Conductive, and Morphological Properties

“…Regardless of the degree of crystallinity, cellulose can be chemically altered to adopt more favorable morphologies due to the biopolymer’s multiple hydroxyl groups on each glucose unit. For example, cellulose can be acetylated, which can alter the extent of chain stiffness, cross-linking, and intermolecular interactions between the polymer chains. , Chemically modifying cellulose has led to several new applications in polymer and biomedical research as many of the resulting materials have been used in drug delivery and tissue engineering, as well as serving as optical films, and energy storage. ,,,, …”

“…1,2 Chemically modifying cellulose has led to several new applications in polymer and biomedical research as many of the resulting materials have been used in drug delivery and tissue engineering, as well as serving as optical films, and energy storage. 2,5,6,8,9 A relatively recent method for modifying cellulose is utilizing the "click" azide−alkyne 1,3-dipolar cycloaddition strategy. The hydroxyl groups on cellulose (in particular the primary alcohol) can be converted to azides or alkyne-containing groups and then undergo cyclization to yield a substituted 1,2,3-triazole ring, typically under copper-catalyzed conditions.…”

Spiro-Fluorene-Containing Cyclic Olefin Polymers

“…These hydrocarbon polymers are expected to be superior to the condensation polymers in terms of low hygroscopicity and excellent chemical and dimensional stability under harsh and humid conditions. Thus, by controlling the absolute value of birefringence to a low level, they can be applied to retardation films − used in polarizers, in which the retardation value (product of birefringence and film thickness) remains unchanged under various environments.…”