Abstract
Improvements in electro-optical responses of LC devices by doping organic N-benzyl-2-methyl-4-nitroaniline (BNA) and Morpholinium 2-chloro-4-nitrobenzoate (M2C4N) in nematic liquid crystals (LCs) have been reported in this study. BNA and M2C4N-doped LC cells have the fall time that is fivefold and threefold faster than the pristine LC cell, respectively. The superior performance in fall time of BNA-doped LC cell is attributed to the significant decrements in the rotational viscosity and threshold voltage by 44% and 25%, respectively, and a strong additional restoring force resulted from the spontaneous polarization electric field of BNA. On the other hand, the dielectric anisotropy (Δε) of LC mixture is increased by 16% and 6%, respectively, with M2C4N and BNA dopants. M2C4N dopant induces a large dielectric anisotropy, because the phenyl-amine/hydroxyl in M2C4N induces a strong intermolecular interaction with LCs. Furthermore, BNA dopant causes a strong absorbance near the wavelength of 400 nm that filters the blue light. The results indicate that M2C4N doping can be used to develop a high Δε of LC mixture, and BNA doping is appropriate to fabricate a fast response and blue-light filtering LC device. Density Functional Theory calculation also confirms that BNA and M2C4N increase the dipole moment, polarization anisotropy, and hence Δε of LC mixture.
Highlights
Nematic liquid crystals (LCs) have been successfully conquered in every corner of our modern world because of their electro-optic applications such as micro-displays [1], flat panel and flexible displays [2,3], and focusing systems [4]
The results indicate that Morpholinium 2-chloro-4-nitrobenzoate (M2C4N) doping can be used to develop a high ∆ε of LC mixture, and BNA
Nanoparticle (NP) dispersion in the LC matrix has been considered as a promising technique for achieving fast response time, low power consumption, or bright display colors [16]
Summary
Nematic liquid crystals (LCs) have been successfully conquered in every corner of our modern world because of their electro-optic applications such as micro-displays [1], flat panel and flexible displays [2,3], and focusing systems [4]. The sub-millisecond switching time is required to implement the field sequential color technology of LC displays (LCDs) [7]. Various technologies have been proposed to improve the response time of LCs, such as thin cell gap [8], tuning the optical phase shift [9], an overdrive/undershoot drive scheme [10], new switching modes [11], and using LCs with ultralow viscosity [12]. Some researchers have attempted to accelerate the LC response by incorporating the guest entities, i.e., polymer dispersed liquid crystal (PDLC). Polymer network liquid crystal (PNLC), which are the most efficient routes to achieve the fast. Nanoparticle (NP) dispersion in the LC matrix has been considered as a promising technique for achieving fast response time, low power consumption, or bright display colors [16]. NP doping is still a challenging issue because of the nonuniform dispersion and NP aggregation
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